Mishchenko, M. I., Travis, L. D. & Mackowski, D. W. T-matrix computations of light scattering by nonspherical particles: a review. J. Quant. Spectrosc. Radiat. Transfer 55, 535–575 (1996).

Yahia-Ammar, A., Sierra, D., Mérola, F., Hildebrandt, N. & Guével, X. L. Self-assembled gold nanoclusters for bright fluorescence imaging and enhanced drug delivery. ACS Nano 10, 2591–2599 (2016).

Mishchenko, M. I. & Travis, L. D. Capabilities and limitations of a current FORTRAN implementation of the T-matrix method for randomly oriented, rotationally symmetric scatterers. J. Quant. Spectrosc. Radiat. Transfer 60, 309–324 (1998).

Gustav Mie in his celebrated work27 showed that the expansion of incident and scattered electric fields in vector-spherical harmonic functions yields an exact solution for light scattering by spherical particles. In the far field, this approach relates the incident and the scattered electric fields through the Jones formalism by \(E_{s} = {\mathbf{J}}E_{i}\) where \({\mathbf{J}}\) is the 2 × 2 amplitude scattering Jones matrix, \(E_{i}\) and \(E_{s}\) are the incident and the scattered electric fields, respectively. Since the Mie theory is based on spherical symmetry, various extensions to non-spherical particles have also been proposed28,29,30,31,32,33. Among these, the T-matrix method has been the most widely used for modeling particles with an axis of symmetry, such as ellipsoids, spheroids, and cylinders31. Using the T-matrix framework, the incident, and the scattered fields from a long cylindrical scattered (length \(\gg\) diameter) can be expressed as30:

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Here, \(l\) is the water medium thickness (1-cm-thick glass cuvette in our experiments), \(\left\langle {C_{ext} } \right\rangle = \pi a_{0}^{2} \left\langle {Q_{ext} } \right\rangle\) is the extinction cross section, the averaging over GNR orientations is represented by the angular brackets, \(\rho_{g} \left( {19.3\,\hbox{gm/cc}} \right)\) is the density of gold, \(N = c_{g} /V\rho_{g}\) is the “numerical concentrations” (number of GNRs per unit volume of water suspension), \(a_{0} = \left( {{{3V} \mathord{\left/ {\vphantom {{3V} {4\pi }}} \right. \kern-\nulldelimiterspace} {4\pi }}} \right)^{1/3}\) is the equi-volume radius, and \(V\) is the volume of all the GNRs sampled by light in the water suspension.

Unfortunately, many ccd and cmos camera manufacturers do not conform with the standard DSLR spacing of 55 mm. So you need to know your camera's total back focus ...

Sun, H. et al. Cancer cell membrane-coated gold nanocages with hyperthermia-triggered drug release and homotypic target inhibit growth and metastasis of breast cancer. Adv. Func. Mater. 27(3), 1604300 (2017).

It has previously been shown that for a single isolated plasmonic GNR, the differential scattering cross-section between horizontally and vertically polarized light approaches unity in the vicinity of GNR’s longitudinal plasmon resonance (and occurs at longer wavelength than the transverse plasmon resonance)19,22,23. This suggests that isolated plasmonic GNRs can act as a nearly perfect linear diattenuator19,23. However, this idealized scenario does not account for (1) large background tissue depolarization, and (2) the potential loss of GNRs’ polarization signatures due to their random 3D spatial orientation. It is thus crucial to understand detailed polarization response from random distributions of multiple GNRs inside heterogeneous media such as biological systems. There have only been a few works on the use of depolarization mapping approach in this context23,24. For example, Lippok et al. has illustrated the diffusion and distribution of GNRs in biologically relevant scenarios24. The authors described the statistics of polarization states using the density matrix formalism and the Mueller matrix-derived depolarization coefficient. However, such advanced analysis may be limited to gated detection of ballistic-like photons scenarios, necessitating the use of complex partially coherent imaging systems for its practical realization. The MM derived polarimetry parameters such as diattenuation, retardance and (importantly) its orientation provide anisotropic organizational information on the tissue collagen fibre network25. Such polarization parameters may serve as additional metrics for characterizing various biological tissues and their pathologies, for example with significant connective tissue (stromal) involvement such as cancer development26.

On May 6, In Shanghai, which is entering its second month of lockdown, city officials said cases have been declining since Apr 22 and its outbreak is under control.[45]

In late April to early May, online personality Dawn Wong produced Fake News with Alison Alison (爱丽森假新闻), an English-language, Chinese-subtitled satirical news show about lockdown conditions, from her residence in Shanghai. She posted two episodes to Weibo and YouTube, both being censored on the former. She was arrested on May 11 shortly after posting the second episode and was released after a two-hour "talk" resulting in the unlisting of these videos from YouTube.[83]

After confirming a positive diagnosis, the risk levels of some areas of Shanghai were raised from "low risk" to "middle risk".[1][16] According to Shanghai's information office, the main source for the spread of the outbreak was the Huating Hotel, a previously designated quarantine site for inbound travelers.[17] In response, the Shanghai World Expo Exhibition & Convention Center was converted into a temporary hospital on March 26, 2022.[18] By March 27, just before Shanghai started area-separated testing, a total of 16,013 people had tested positive for COVID-19. Additional temporary quarantine centers in the Shanghai New International Expo Center opened on 29 March 2022.[19][20]

On April 7, the infected owner of a cat called the CDC about bringing their cat to quarantine. The CDC bluntly responded that the "only thing they could do was to wait to be taken away and to give up on their cat".[99]

Polystyrene microsphere phantom systems of three different diameters (\(0.42,0.65\) and \(0.92\,\upmu\)m) at varying concentrations were investigated to determine polarization effects in turbid media. Mueller metrices were experimentally recorded from the phantoms and were subsequently analyzed by the Mueller matrix decomposition method to extract and quantify the medium polarimetry parameters (depolarization \(\Delta\), diattenuation \(D\) and retardance \(R\)), following the procedure discussed in “Mueller matrix inverse analysis to quantify depolarization, diattenuation and retardance signatures of GNRs” section. Similar analysis was also performed on the corresponding Mueller metrices generated by the PSMC model. The extracted diattenuation and retardance parameters are shown for both approaches in Fig. 2a,b. Linear diattenuation values for three different microsphere diameters obtained from PSMC simulation are observed to be negligible. The corresponding experimental diattenuation values are also quite low, within the typical elemental error (\(\sim 0.05\)) and thus agree well with the results of the simulations. Indeed, the scattering from spherically symmetric dielectric microspheres is not expected to produce any diattenuation effect in the backscattering configuration, as seen both theoretically and experimentally here. However, it is known that scattering from large dielectric spheres (size parameters \(x > 1,\)\(x = 2\pi an/\lambda\), where \(a\) is the radius of the scatterer, \(N\) is its refractive index and \(\lambda\) is the wavelength of light) can lead to significant linear retardance effects that depend on the particle diameter and detection angle19,38. This has been previously attributed to the excitation of the different higher order transverse magnetic (\(TM - a_{n}\)) and transverse electric (\(TM - b_{n}\)) Mie modes of dielectric spheres and their complex interference effects that depend on light’s polarization state19. Thus, both the theoretical and experimental Mueller metrices yielded finite linear retardance values, of the order of \(\sim 1.5\) radians for all three microsphere diameters.

To put such GNR loadings into context, we note that typical concentrations of GNRs ranges from \(\sim 25\) to 80 mg/ml for optical imaging in vivo40. However other methods such as computed tomography, photoacoustic and fluorescence imaging techniques typically report lower GNR concentrations (5–25  mg/ml)40,41,42,43,44. Our simulated and experimental results with GNR concentration range of \(0.03\) to 2.5  mg/ml is typically \(10\) to 100× lower than the in-vivo levels reported in the literature above. This is particularly promising as it demonstrates significant polarization contrast at rather modest GNR levels, at least in our controlled examined phantom system.

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where \(E_{\parallel i}\), \(E_{ \bot i}\) and \(E_{\parallel s}\), \(E_{ \bot s}\) represent incident and the scattered electrical fields polarized parallel and perpendicular to the scattering plane, \(r\) and \(z\) are the cylindrical polar coordinates, \(k\) is the wave number, \(\xi\) is the oblique incident angle between the incident light and the longitudinal axis of the cylinder. The elements \(T^{11} ,T^{12} ,T^{21}\) and \(T^{22}\) form the amplitude scattering matrix (“the T matrix”). However, slight deviation from ideal finite cylindrical shape of GNRs may results in significant changes in the scattering, absorption, and extinction properties. To obtain a more realistic model for non-ideal finite cylinders, we incorporated a more generalized T-matrix model33 into our PSMC simulation engine. Specifically, this model allows one to incorporate five modified parameters for individual GNRs: length, central diameter, end-cap diameter, end-cap elliptical thickness and the shape of the generating line between the end caps. The details of these modifications to Eq. (1) are described in Supplemental Materials. The resultant differential scattering, absorption, and extinction cross-sections of individual GNRs were then used to calculate 3D-orientation-averaged scattering, absorption and extinction cross-sections for multiple GNRs, as described in “Simulation of polarized light propagation in turbid media containing dielectric microspheres and GNRs” section below.

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Khlebtsov, B., Khanadeev, V., Pylaev, T. & Khlebtsov, N. A new T-matrix solvable model for nanorods: TEM-based ensemble simulations supported by experiments. J. Phys. Chem. C 115, 6317–6323 (2011).

In principle, Mueller matrix \(M\) can be determined from experimental \(M_{i}\), by using theoretical forms of \(A\) and \(W\) metrices (obtained by using the standard Mueller metrices of the polarizer and the quarter wave plates). However, this is confounded by the complex nature of the polarization effects caused by non-ideal behavior of polarization optical elements, slight misalignments, excitation/collection/focusing geometry details and so forth. These can lead to significant deviations in the actual experimentally determined \(W\) and \(A\) metrices from their ideal theoretical forms. We have taken care of these issues through a robust eigenvalue calibration method (ECM) yielding accurate information of the polarization response of the PSG and the PSA units by determining the exact experimental forms of the \(W\) and \(A\) matrices45. Using this approach, \(W\) and \(A\) are determined by performing measurements on ideal calibration samples with known polarization properties, such as pure attenuators (polarizers) and retarders (wave plates). The ensuing calibration results are presented in Fig. 1, demonstrating good \(MM\) polarimeter performance and enabling robust and accurate measurements in the complex turbid media as described above.

The outbreak and the strict response had significant economic impacts.[72] Oil prices fell globally.[73] By mid-April, the lockdown had led to Shanghai residents complaining of food shortages.[74]

Most used phantom systems to study the optical effects in turbid media are suspensions of solid scattering particles in a transparent background44. When the particles are of uniform size and shape and known refractive index (e.g., polystyrene microspheres and plasmonic GNRs in our study), the optical properties (e.g., scattering coefficient) and polarization effects (e.g., \(\Delta ,R\) and \(D\)) can be calculated, the latter through Monte Carlo modelling. For our experiments, three different diameters of \(0.42,0.65\) and \(0.92\,\upmu \hbox{m}\) polystyrene microspheres (PM; Bangs Laboratories Inc.) suspension in water were used to mimic the turbidity of tissue, to which different concentrations of GNRs were then added. Mie theory for spherical scatterer was used to calculate the scattering cross-section of an individual microsphere σ, and suspensions with a precise number of microspheres per unit volume N were prepared to yield the desired medium scattering coefficient µs (via µs = σ · N). Therefore, we have prepared a stock solution of 0.1 (w/w) of polystyrene microspheres to get scattering coefficient \(\upmu_{S} = 621\,\hbox{cm}^{ - 1}\). Sequential dilutions were performed by precisely adding distilled water aliquots to get the desired scattering coefficient down to \(\upmu_{S} = 16\,\hbox{cm}^{ - 1}\). Similar process was followed for the \(0.65\,\upmu \hbox{m}\) and \(0.92\,\upmu \hbox{m}\) polystyrene microspheres. Then, the effects of the addition of GNRs were systematically investigated. For this purpose, we chose \(d = 0.42\,\upmu \hbox{m}\) diameter microsphere suspension with \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\) and added GNRs in 0.03 to 2.5 mg/ml concentration range. Keeping the microsphere suspension’s \(\upmu_{S}\) fixed, appropriate addition of GNRs concentration and water were decided using the relation \(C_{\% } (w/w) = m_{Solt} /m_{so\ln } *100\), here \(C_{\% } (w/w)\),\(m_{Solt}\) and \(m_{so\ln }\) represents % concentration of the solid content, total mass of the solute (GNRs and microspheres) and mass of water respectively. We have considered the linear addition of the total mass of GNRs, PM and water to get the desired % concentration, thereafter the desired scattering coefficient. To ensure uniform distribution of added particles in the resultant suspensions, we sonicated each of the samples for 1 h, and the experiments were subsequently performed within 15 min of the preparation.

Experimental polarimetry set up and system calibration for exact backscattering configuration. (a) Schematic diagram of the experimental polarimetry system for measurements in exact backscattering configuration, comprised of an excitation laser (λ = 633 nm), a polarization state generator unit (PSG: rotating linear polarizer P1 and quarter wave plate Q1), a polarization state analyzer unit (PSA: rotating quarter wave plate Q2 and linear polarizer P2), beam splitter (BS), collection lenses and a photodetector. Actual experimental form of the (b) PSG matrix W and (c) PSA matrix A. (d) The experimental Mueller matrix from a cuvette filled with distilled water resembles an identity matrix as expected, with individual elements exhibiting an error \(\le 0.05\).

Chen, M., Cao, S. H. & Li, Y. Q. Surface plasmon–coupled emission imaging for biological applications. Anal. Bioanal. Chem. https://doi.org/10.1007/s00216-020-02635-3 (2020).

Purwar, H., Soni, J., Lakhotia, H., Chandel, S., Banerjee, C., & Ghosh, N. Development and eigenvalue calibration of an automated spectral Mueller matrix system for biomedical polarimetry. In Biomedical Applications of Light Scattering VI 2012 Feb 2 (Vol. 8230, p. 823019). International Society for Optics and Photonics.

Mishchenko, M. I., Travis, L. D. & Lacis, A. A. Scattering, Absorption, and Emission of Light by Small Particles (Cambridge University Press, Cambridge, 2002).

We now proceed to investigate the interesting polarization effects due to the presence of plasmonic GNRs in a turbid phantom with fixed microsphere concentration (scattering coefficient \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\)). Once again, the Mueller matrix-derived polarization parameters obtained using the polarization sensitive Monte Carlo simulations will be compared to those from experimental Mueller matrix measurements. As noted in “Simulation of polarized light propagation in turbid media containing dielectric microspheres and GNRs” section, we have modeled the orientation-averaged extinction, scattering and absorption cross sections for an ensemble of randomly oriented GNRs with constant mass-volume concentrations of gold per unit volume of water suspension containing microspheres, using Eq. (4). The polarization signature of randomly oriented nanorods was studied by determining all the sixteen scattering Mueller matrix elements \(M_{ij}\), which transform the Stokes parameters (\(I,Q,U,V\)) of the incident light into the corresponding set of scattering Stokes’s parameters. The averaging over random orientations was performed numerically as described in “Simulation of polarized light propagation in turbid media containing dielectric microspheres and GNRs” section by taking the ensemble average of scattering matrix elements. The Mueller matrix-derived diattenuation, retardance and degree of polarization parameters are summarized in Fig. 3. The diameter of the microspheres was kept fixed as 0.42 µm, and geometrical dimensions of GNRs ranged in length \(l = 71\) to 105 nm and \(d = 25\) to 70 nm. The concentration and the aspect ratios \(\left( { \in = l/d} \right)\) of the GNRs were systematically varied to study the corresponding changes in the polarization parameters.

The general form of a Mueller matrix of an arbitrary sample is given by \(M\left( \theta \right)\), where the angular dependence emphasizes that the polarization response varies with the measurement geometry:

Following the linear diattenuation and retardance results, we now present the corresponding depolarization in Fig. 3e. Depolarization here appears to stem from (1) multiple scattering effects and (2) random orientation of the non-spherical metal nanorods. Both effects lead to incoherent addition of scattered polarized Stokes vectors of light (or incoherent addition of Mueller matrices of individual scatterers), eventually manifesting as net depolarization. However, unlike multiple scattering-induced depolarization from dielectric microspheres, the depolarization induced by scattering from the GNRs exhibit distinct spectral characteristics which strongly depends on their aspect ratios, previously reported by our group19. It is important to note that the wavelength corresponding to strongest depolarization does not coincide with the peak of linear diattenuation as shown in Supplementary Figure S1. Specifically, while the magnitude of diattenuation is maximum at wavelength corresponding to the peak of the longitudinal plasmon resonance of the GNR, the depolarization peak is observed at the overlap spectral region of the longitudinal and the transverse plasmon resonances, which is at a shorter wavelength. With increasing GNR aspect ratio, the depolarization peak further shifts spectrally away from the peak of the longitudinal resonance (and the wavelength peak of diattenuation also) towards shorter wavelength. Thus, with the choice of wavelength λ = 633 nm closer to the longitudinal plasmon resonance peak, one may obtain weak depolarization but strong diattenuation, even for randomized 3D orientation of GNRs, as is observed here.

Ghosh, N., Wood, M. F. & Vitkin, I. A. Polarimetry in turbid, birefringent, optically active media: a Monte Carlo study of Mueller matrix decomposition in the backscattering geometry. J. Appl. Phys. 105, 102023 (2009).

Numerical simulations and experiments were performed in the backscattering configuration on polystyrene microspheres suspensions of water without and with the additions of the GNRs. The utility of the proposed approach was demonstrated by decoupling and quantifying the polarization response of the dielectric background of the optically turbid samples and the important polarization effects of localized surface plasmon resonances (LSPRs) of the GNRs.

Shanghai residents were required to undertake nucleic acid tests throughout the lockdown, ranging from multiple times per week to once per day. Tests were initially posted on the Health Cloud APP, but over the course of the lockdown migrated to mini programs on Alipay or WeChat. Tests were required for all regions regardless of risk, and would generate a colored health code (jian4kang1 ma3 健康码). Each district was responsible for implementing their own system around the code[57][58] Green codes were issued to people with negative antigen tests, yellow for close contacts of positive cases or those who did not test, and red for positive cases. Enforcement of health codes was left up to individual districts and communities; some locations forbade residents from leaving their neighborhoods regardless of the health code.

Since 2020, nearly 40% of international arrivals to China came through Shanghai.[11] Shanghai also had a relatively large number of imported cases. By March 14, the number of cases reported as coming from outside mainland China was 4345, compared to 473 local cases.[12] Shanghai authorities had previously taken a "more relaxed" approach to the pandemic compared to other Chinese cities.[13] Doctor Zhang Wenhong of the Shanghai Medical Treatment Expert Group, said the control of COVID-19 in Shanghai is like "catching a mouse in the ceramic shop", and said maintaining a normal manufacturing industry and public life is important. Due to the Omicron variant, Shanghai's COVID-19 response had been challenged.[14][15]

In general, propagation of polarized light through optically turbid biological medium results in depolarization, diattenuation, and retardance effects. Multiple scattering is often the primary source of depolarization, although other inhomogeneities—for example, randomly oriented birefringent domains—also contribute to polarization loss20,21. Whatever the mechanism, the unique scattering asymmetries of GNRs imbedded in such a random inhomogeneous medium may get completely washed out due to strong multiple scattering background. Additionally, random orientations of GNRs invariably introduce stochastic variation of polarization states, increasing decoherence and entropy, thus leading to further depolarization and weakening of the intrinsic diattenuation and retardance effects.

After the outbreak, artist Wang Yuanchao created the Shanghainese-language song "Steamed Eggs with Clams" (Chinese: 蛤蜊炖蛋),[c] which described how people in Shanghai work together to prevent the spread of COVID-19. The song got considerable attention on the internet upon its publication.[77] On March 27, the song "First Snap Up Groceries, Then Do Nucleic Acid" (Chinese: 先抢菜，再做核酸) was published on the WeChat Public Account; it got over 100,000 views in the first ten minutes after being published. Afterwards, the three authors renamed the song to "Buy Groceries" and uploaded it to NetEase Cloud Music, where it received more than 200,000 views. The song uses with humorous Shanghainese lyrics.[78]

By April 17, according to China National Radio, Shanghai had 16 severe cases, all having pre-existing health conditions, with only 1 of them being vaccinated.[24] On the same day, officials reported 3 deaths of COVID-19 infected patients, with all deaths also being linked to other underlying health conditions, such as diabetes.[25][26][27] On April 18, officials reported 7 more deaths with ages ranging from 60 to 101; 6 of them were aged above 70.[28]

An April 22 montage called The Sounds of April (四月之声) featured clips of government announcers and events such as pet-killing, child separation, and medical delays. The author also included some positive events like people sharing foods with in area and stated it was meant to be neutral. Many posts, including the original one, containing the montage were quickly taken down and netizens attempted to fight its removal on WeChat by various edits.[80] Some users even tried to change their username on platforms like Weibo to protest.[81] The original video had been played more than 5 million times before it was taken down.[82]

On March 22, two people posted information on a group chat saying Shanghai was about to perform a "city closure"(feng1cheng2 封城). The next day, the public security bureau of Shanghai investigated both for the crime of posting false information intentionally.[65] On March 26, Wu Fan, the vice-principal of Shanghai Medical College stated that Shanghai would not go into lockdown because of how much the city contributed to the economy of China.[66]

As previously discussed, in addition to multiple scattering effects, the other prominent mechanism of depolarization in the composite heterogeneous system is the randomization of the scattering-induced phase retardance effects (between the two orthogonal dipolar plasmon polarizabilities) due to the random orientation of the GNRs. Overall then, judicious choices of the GNR concentrations, their aspect ratios and the choice of the wavelength will be key optimization parameters for contrast enhancement in polarimetric imaging of biological tissues.

In this study, we examined polarization effects in optically turbid media containing polystyrene microspheres and GNRs, using both polarization sensitive Monte Carlo simulations and experimental Mueller matrix measurements. Backscattering geometry was chosen for both scientific and practical reasons (non-diminishing polarization signals and biological relevance, respectively). T-matrix formalism was incorporated into the existing polarization-sensitive Monte Carlo code to enable accurate modeling of GNR polarization effects. Parameters of the complex scattering medium—micro-and nano-particle sizes, shapes, concentrations—were systematically varied to quantify the resultant effects on medium polarization properties such as linear diattenuation, linear retardance, and depolarization. GNR-induced polarization preservation and increases in linear diattenuation and retardance were noted as a function of the various examined medium parameters. Importantly, significant GNR-enabled polarization contrast was observed despite their random 3D orientation. A notable finding was a decrease in GNR-induced polarization contrast effects with increasing nanorod concentration; in other words, GNR polarization contrast effects were more significant at generally lower nanorod concentrations. In all examined cases, simulation and experimental results showed excellent agreement, lending credence to the presented framework for examining model turbid media and showing promise for enabling GNR polarimetric studies in real biological tissues.

Ghosh, N. et al. Mueller matrix decomposition for polarized light assessment of biological tissues. J. Biophoton. 2, 145–156 (2009).

Garoli, D., Yamazaki, H., Maccaferri, N. & Wanunu, M. Plasmonic nanopores for single-molecule detection and manipulation: toward sequencing applications. Nano Lett. 19(11), 7553–7562 (2019).

On April 18, the Public Security Bureau of Shanghai posted that the message "The women who gave preterm birth failed to ask for help and died because of hemorrhage" was false information. The women gave natural birth and were sent to a hospital on time and successfully gave birth. The publisher Zhang had been captured.[69][clarification needed]

Polarization effects in a composite microsphere + GNRs phantom system. Mueller matrix simulated (red symbols) and experimentally obtained (black symbols) variation of the (a) diattenuation and (b) retardance with GNR's aspect ratio \(\in\) for a fixed scattering coefficient of the composite system(\(\upmu_{{_{S} }} = 102\,\hbox{cm}^{ - 1}\) due to microspheres plus \(16\,\hbox{cm}^{ - 1}\) due to GNRs). Increasing diattenuation and retardance with aspect ratio suggests size-dependent increase of the optically anisotropic nature of GNRs. Simulated (red symbols) and experimental (black symbols) variation of diattenuation and retardance with GNRs concentration in a turbid phantom of fixed microsphere scattering properties (diameter = \(0.42\,\upmu\)m, \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\)). The geometrical parameters of GNRs were length \(l = 70\,\hbox{nm}\) diameter \(d = 25\,\hbox{nm}\)(aspect ratio \(\in = 2.8\)). Both \(D\) and \(R\) exhibit significantly higher values (better contrast) at lower nanorod concentrations (\(\upmu_{S} = 16\,\hbox{cm}^{ - 1}\)), implying strong orthogonal dipolar plasmon polarizabilities even for 3D random orientations of GNRs (for details, see text). The corresponding variation of the simulated and experimental degree of polarization on the GNR concentration shown in (e).

We therefore pursue a more direct polarimetric study of turbid media based on optical polarization signatures (linear diattenuation and retardance) of plasmonic GNRs derived from Mueller matrix measurements, in carefully designed tissue phantoms comprised of scattering polystyrene microspheres and GNRs. The experimental results are supported by numerical simulations of T-matrix-modified polarization sensitive Monte-Carlo (PSMC) model. Importantly, both theory and experiments reveal significant magnitude of linear diattenuation and retardance effects stemming from the longitudinal and transverse plasmon resonances of the GNRs, despite their random orientation and the presence of strong multiple scattering backgrounds.

In order to understand optical specifications, it is important to first review what they mean. To simplify the ever-growing number, consider the most common ...

A 58-year-old male was found dead at home on May 1, with rumors of death by starvation. The city fact-checking service interviewed paramedics and confirmed that the actual cause was cardiac arrest. The community also said that they took good care of the man prior to his death, knowing that he was not in good health, having regularly delivered food during the pandemic.[92]

The COVID-19 pandemic is an ongoing viral pandemic of coronavirus disease 2019. It began in early 2020 as an outbreak in Hubei province, China, which prompted a strict lockdown. The Chinese government's response since then has been to pursue a zero-COVID strategy, aiming to eliminate the virus altogether. However, the increased transmissibility of the SARS-CoV-2 Omicron variant that emerged in late 2021 has posed challenges.[10]

where \(\sum\nolimits_{nn^{\prime},mm^{\prime},ij}^{\infty ,n,2} {\left| {T_{mn,m^{\prime}n^{\prime}}^{ij} } \right|}^{2} = \sum\nolimits_{nn^{\prime},mm^{\prime}}^{\infty ,n,2} {\left| {p_{mn} } \right|}^{2} + \left| {q_{mn} } \right|^{2} ;\) \({\text{Re}} \sum\nolimits_{n = 1,m = - n,i = 1}^{\infty ,n,2} {T_{mn,nmn}^{ij} } = {\text{Re}} \sum\nolimits_{n = 1,m = - n}^{\infty ,n,2} {\left[ {a_{mn} \left( {p_{mn} } \right)^{*} + b_{mn} \left( {q_{mn} } \right)^{*} } \right]} ;\) \(a_{mn} ,b_{mn}\) and \(P_{mn} ,q_{mn}\) are the expansion coefficients of the incident and scattered-field waves respectively. These two expansion coefficients are related as

This research was supported by grants from the Canadian Institute of Health Research (CIHR, PJT-156110), the Natural Sciences and Engineering Research Council of Canada (RGPIN-2018-04930).

On May 6, multiple areas (including "prevention areas") was put into a so-called "silent period" (静默期), banning all entry and exit, including delivery shipment. The stated rationale was that some positive cases appeared in prevention areas, and for a "final assault" (攻坚) on the case count.[42][43] On May 17, another wave of "silencing" started, this time spanning the entirety of multiple districts, again under the name of a "final assault".[44]

On April 12, Hongkou District Health Department IT lead Qian Wenxiong killed himself, leaving behind his cancer-ridden wife.[95] Many Chinese netizens believe his suicide was due to the stress under the zero-COVID policy.[79] (Previous rumors inaccurately attributed the death either to Qian's wife or to another official named Cai Yongqiang and were "dispelled" by official sources.)

2024812 — For a convex lens, the distance between the lens and its principal focus plays a significant role in determining the image formation ...

Liu, H. et al. Targated tumor computed tomography imaging using low-generation dendrimer-stabilized gold nanoparticles. Chem. Eur. J. 19, 6409–6416 (2013).

Since April 22, Shanghai officials said Shanghai have to follow the "static management" (静态管理) policy On April 27, Shanghai officials announced that some hospitals in Shanghai will temporarily suspend their service.[40][41]

Figures 3e clearly demonstrate the preservation of polarization through PSMC simulations and experimentally in a GNRs + microspheres phantom system. Here, the DOP is plotted against varying GNR-induced scattering coefficients for a fixed microsphere scattering coefficient (\(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\)). At the lowest GNR concentration examined (\(\upmu_{S} = 16\,\hbox{cm}^{ - 1}\)), depolarization reduced significantly compared to a microsphere-only system (cf. Fig. 2e): our theory and experiment yielded DOP values of ~ 70% compared to ~ 30% in the absence of GNRs at similar turbidity levels. This is particularly promising as a ‘polarization contrast enhancement effect’ in the biomedical context. As evident, one may obtain high magnitudes of polarization diattenuation and linear retardance (which act as the polarization contrast mechanism in this scenario) in the presence of considerably reduced depolarization effect with relatively small amount of added GNR as ‘contrast agent’. Thus, the exogenous in vivo additions of GNRs for polarization contrast may involve overall smaller amounts of injectable foreign substance, which is biomedically desirable. As expected, polarization loss scaled with increasing GNR concentrations, leading to DOP of \(\sim 10\%\) at the highest medium turbidity examined (\(\upmu_{S} = 195\,\hbox{cm}^{ - 1}\) due to GNRs, \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\) due to microspheres). Yet significant polarization preservation is noted in the backscattering direction even in this very high scattering model system scenario.

Mohd-Zahid, M. H. et al. Colorectal cancer stem cells: a review of targeted drug delivery by gold nanoparticles. RSC Adv. 10, 973–985 (2020).

All the medium polarization properties are contained in the various elements of the Mueller matrix in a complex, interrelated way. Extraction, quantification and unique interpretation of these is possible by mathematically decomposing the Mueller matrix into ‘basis’ metrices of elementary polarization properties. This is not a unique process, and several variants of this decomposition exist with their relative merits extensively discussed in the literature34,35,36,37. Among the different options, the Lu and Chipman’s Polar Decomposition Method is the most widely used and was also utilized here37. The extraction of \(D,R\) and \(DOP\) parameters via this decomposition approach is further described in the “Supplementary Materials” section.

The adjustments were made to "promote epidemic prevention and control as well as economic and social development, and resume work and a return to normal life," the city official added in the May 29 press conference.[46] City officials also emphasized that the term "lifting the lockdown" (解封) is not to be used, as "static management" is not "lockdown" (封城).[48]

Mi, P. et al. A pH-activatable nanoparticle with signal-amplification capabilities for non-invasive imaging of tumour malignancy. Nat. Nanotechnol. 11(8), 724–730 (2016).

shine上海

Large GNR-induced linear diattenuation and retardance values in the presence of large background turbidity suggest that these could be exploited for contrast enhancing mechanisms in polarimetric imaging of biological tissues. Specifically, diattenuation may prove easier and more amenable in clinical situations due to the ease of the measurement procedure; for example, one may directly obtain a tissue diattenuation image via a simple setup with suitable orientations of two linear polarizers in the excitation and detection paths. We are currently expanding our investigations towards in-vivo biomedical deployment of the proposed unique polarized light imaging strategy using GNRs for enhancing contrast in actual biological tissues, with potential applications in tumor margin detection, surgical guidance, and therapy monitoring.

Its outbreak marked the end of the Emperor of Mankind's Great Crusade to reunite the scattered colony worlds of Humanity in the Milky Way Galaxy under a single ...

The case of randomly oriented GNRs within the multiply scattering dielectric medium containing polystyrene microspheres were simulated next. First, unlike the symmetrical case of the microspheres, the scattering and polarization effects of light interactions with GNRs are dependent on the orientation of the latter. That is, the scattering matrix of finite cylindrically shaped GNRs varies with the angle \(\xi\) between the direction of the incident photon and the orientation of GNR’s cylindrical axis. To address this issue, we resort to the single scattering T-matrix formalism for GNRs (“Modelling single scattering from plasmonic Au GNRs” section above) to study polarization preservation in a collection of randomly oriented 3-dimensional distributions of finite GNRs inside a turbid medium. For a monodispersed (same sized) ensemble of randomly oriented GNRs with constant mass-volume concentration of gold \(c_{g}\) per unit water suspension volume, the extinction coefficient is given by33

On February 28, a 56-year-old vaccinated woman came to Tongji Hospital with a fever and was confirmed positive on March 1. This case became patient zero in the outbreak. After confirmation of her case, her dance group had at least 8 people test positive as well.

Polarization preservation in the exact backscattering direction is a well-known effect20,38 and is also quite evident from the results presented in Fig. 2e where excellent agreement between theory and experiment is once again seen. We also note that the circular depolarization was consistently observed to be stronger than linear depolarization in our backscattering investigations, both theoretically and experimentally (data not shown). These results agree with previous reports demonstrating that the characteristic length for depolarization of linearly polarized light is considerably higher than circularly polarized light for turbid media comprised of larger sized scatterers (typically for size parameters \(x > 1,\) in our case \(x \sim 3.3\))38. The nonzero values of \(DOP\) for large values of scattering coefficients suggest that even for a highly turbid medium, some polarization information is preserved and quantification of polarization parameters in backscattering geometry is possible.

The lockdown has caused a number of deaths due to an inability to receive appropriate medical care as COVID testing is required to access any emergency services and any hospital that has seen to a positive patient needed to undergo disinfection. High-profile individuals who died include a former Fudan University professor Yu Huizhong, a Dongfang Hospital nurse Zhou Shengni, and violinist Chun Shunping.[88] On April 14, an article on WeChat listed 12 deaths due to lockdown practices, but was deleted soon after.[89] A crowd-sourced continuation of the effort on Airtable listed 186 deaths as of April 30.[90][79]

Chinabusinessnews

Surface plasmon resonance (SPR) is the collective oscillation mode of free conduction electrons at the metal–dielectric interface irradiated by an electromagnetic (EM) wave, causing strong field enhancement and localization at the interface. SPR decays rapidly with distance, enabling precise localization of the process and furnishing a potentially effective tool for imaging, sensing, and optical manipulations1,2,3,4. For example, light incident onto a medium containing metallic nanoparticles causes excitation of localized surface plasmons, affecting the intensity and the spectral content of the reflected or transmitted light and thereby enhancing optical contrast5. Gold nanoparticles (GNPs) exhibit strong localized SPR effect and have thus been actively explored in biology and medicine6,7,8. Their strong confinement of EM waves and biocompatibility has spurred their use as multifunctional probes for molecular rulers9, single molecule detection10, photoactive drug delivery11, photodynamic therapy12, photothermal treatments13, stem cells targeting14, tumour and stromal microenvironment imaging15, and optical contrast enhancement16. In this context, plasmonic gold nanospheres have not proven particularly useful because their plasmon resonance effects occur at shorter wavelengths, which owing to basic tissue optics limits their biomedical use17. However, plasmonic gold nanorods (GNRs) have been found to be more useful due to their geometry and aspect ratio dependent tunable plasmon mode which falls within the visible and near infrared spectral regime suitable for biomedical imaging6,7,8. Several studies have therefore focused on GNR delivery mechanism, their interaction with biological media, and their photoactivity12,13,14,15,16,17.

Chandel, S. et al. Complete polarization characterization of single plasmonic nanoparticle enabled by a novel Dark-field Mueller matrix spectroscopy system. Sci. Rep. 6, 26466 (2016).

Kudryashov, S. I. et al. Deeply sub-wavelength laser nanopatterning of Si surface in dielectric fluids: manipulation by surface plasmon resonance. Appl. Surf. Sci. 519, 146204 (2020).

The strategy for constructing the sample Mueller matrix in the backscattering geometry involves recording sixteen polarization-resolved intensity measurements for four different combinations of the optimized elliptical polarization generator (using PSG) and analyzer (using PSA) basis states. The PSG unit consists of a linear polarizer (P1) and a quarter wave plate (Q1) whereas a PSA unit consist of a quarter wave plate (Q2) and a linear polarizer (P2) placed in reverse order. Sequential changes of the fast axis of Q1 to four angles (β = 35°, 70°, 105° and 140°) with respect to the axis of \(P_{1}\) leads to generation of four optimized input elliptical polarization states (Stokes vectors)42. These four sets of Stokes vectors (each a 4 × 1 array) are then grouped as column vectors to form the 4 × 4 generator matrix \(W\) for PSG. Likewise, the 4 × 4 analyzer matrix \(A\) was formed by the four elliptical polarization basis states obtained by changing the fast axis of \(Q_{2}\) to the same four angles (β = 35°, 70°, 105° and 140°). The sixteen sequential intensity measurements were grouped in a 4 × 4 measurement matrix \(M_{i}\) which is related to \(A\), \(W\) and the sample Mueller matrix \(M\) as \(M_{i} = AMW\). The sample Mueller matrix \(M\) was then determined from the known forms of \(A\) and \(W\) matrices via \(M = A^{ - 1} M_{i} W^{ - 1}\). Details on the optimization of the polarization basis states in the PSG and the PSA matrices, including optimization of the orientation angle of the quarter waveplates with respect to the polarizers, have been published45.

Zhan, Q., Zhang, X., Zhao, Y., Liu, J. & He, S. Tens of thousands-fold upconversion luminescence enhancement induced by a single gold nanorod. Laser Photonics Rev. 9(5), 479–487 (2015).

Shanghai authorities converted schools, residential buildings and other structures into quarantine facilities when designated facilities ran short on space.[59]

Figure 3 summarizes the results of the polarization characteristics of GNRs in turbid medium. Significant linear diattenuation and retardance effects were observed both in the simulated and in the experimentally recorded Mueller metrices. Specifically, the significant magnitude of diattenuation appears to be a characteristic polarization signature of the GNRs, given low diattenuation observed from the microsphere-only turbid phantoms (Fig. 2a–d). Comparison of the PSMC simulated and experimental Mueller matrix-derived linear diattenuation \(D\) and linear retardance \(R\) with varying aspect ratio \(\in\) are shown in Fig. 3a,b, respectively. The origin of the observed strong linear diattenuation and retardance effects due to scattering from GNRs is worth a brief mention here19,39.

Residents that refused COVID testing would see their health code turned red. Some neighborhoods threatened permanent red-code status for those who refused or resisted transportation to a quarantine center, with one location promising on April 12 that such people would "never be rehabilitated" (永不摘帽).

Soni, J., Purwar, H. & Ghosh, N. Quantitative polarimetry of plasmon resonant spheroidal metal nanoparticles: a Mueller matrix decomposition study. Opt. Commun. 285, 1599–1607 (2012).

Ghosh, N. & Vitkin, A. I. Tissue polarimetry: concepts, challenges, applications, and outlook. J. Biomed. Opt. 16, 110801 (2011).

Plasmonic gold nanorods (GNRs) are finding increasing use in biomedicine due to their unique electromagnetic properties, optical contrast enhancement and biocompatibility; they also show promise as polarization contrast agents. However, quantification of their polarization-enhancing properties within heterogeneous turbid media remains challenging. We report on polarization response in controlled tissue phantoms consisting of dielectric microsphere scatterers with varying admixtures of GRNs. Experimental Mueller matrix measurements and polarization sensitive Monte-Carlo simulations show excellent agreement. Despite the GNRs’ 3D random orientation and distribution in the strong multiply scattering background, significant linear diattenuation and retardance were observed. These exclusive measurable characteristics of GNRs suggest their potential uses as contrast enhancers for polarimetric assessment of turbid biological tissue.

ChineseNews

Gas fired infrared heating appliances are available from a variety of manufacturers, each with their own design nuances and performance claims. Although.

On March 4, Shanghai instituted a policy of mass COVID testing. In every building with a positive COVID-19 case, all residents were required to undertake individual "nucleic acid" COVID tests. Other areas undertook pooled COVID-19 testing.[55][56]

Darrigues, E. et al. Tracking gold nanorods’ interaction with large 3D pancreatic-stromal tumor spheroids by multimodal imaging: fluorescence, photoacoustic, and photothermal microscopies. Sci. Rep. 10, 1–14 (2020).

As the caseload in the outbreak was growing, there were messages like "Shanghai will stop school" on Weibo.[60] On March 8, a Shanghai official denied the possibility, but for students absent due to COVID-19 the platform "Air Class" would allow for education to continue. On March 12, in-person school was suspended, with students able to participate using platforms such as "Shanghai V-Class" or "Shanghai Education" instead.[61] On May 7, Official announced the National College Entrance Examination in Shanghai will be extended to June, Senior High School Entrance Examination in Shanghai will extend to July, with lab and English speaking test section being removed and counted as full credit toward final score.[62]

Zhao, T. et al. Gold nanorod-enhanced two-photon excitation fluorescence of conjugated oligomers for two-photon imaging guided photodynamic therapy. J. Mater. Chem. C 7, 14693–14700 (2019).

Figure 2c,d summarize the observed trends of scattering-induced linear diattenuation and retardance obtained through PSMC simulations and experiments from varying-turbidity for the 0.42 µm diameter microsphere suspensions. The scattering coefficients (\(\upmu_{S}\)) were varied from − 16 to 621 cm−1. Corresponding changes in the magnitude of diattenuation was in the range \(0.0113 - 0.0147\)(simulations) and \(0.0217 - 0.0412\) (experiment). Similarly, the observed changes in the magnitude of linear retardance spans 1.45–1.53 rads (theory) and 1.42–1.47 rads (experiment). Thus, theory and experiments show good agreement on the behavior of both these important polarization metrics with turbidity. As noted above, while diattenuation is consistently negligible from spherical scatterers, the non-zero magnitude of retardance is influenced by a number of factors like scatterer size, shape and concentration, signal collection angle etc. which affects the interference of the higher order \(TM\) and \(TE\) scattering modes in a complex way19,38.

According to a 19-minute recording, a woman and her husband were forced to go to a mobile cabin hospital, even though none of their family members were positive for COVID-19. They consented to leaving if tested positive, but policies had forced them to leave home because officials already believed they were positive for COVID-19. Shanghai officials replied saying that person in question was a 13-year-old girl, and they had already communicated with the family many times previously. and they had agreed at first, but this time they disagreed; according to the policy, they need to take them to a mobile cabin hospital.[clarification needed] Officials also said that the results from the "Health Cloud" app may differ from the actual situation.[101][clarification needed]

S.K.R conceived the idea, performed all the simulations and experiments; N.G. and A.V. designed and supervise the research; All authors contributed in writing the manuscript.

Wu, Y., Ali, M. R., Chen, K., Fang, N. & El-Sayed, M. A. Gold nanoparticles in biological optical imaging. Nano Today 24, 120–140 (2019).

By April 8, there had been a total of 131,524 people tested positive, with a single severe case.[21] About 90 percent of the cases were "asymptomatic".[22][23]

There have been cases of fraud and illegal marketing during the Shanghai lockdown. On April 16, the legal representative of a medical company was arrested for selling 29,000 masks that did not meet health standards.[70] On April 19, a man was arrested for selling rotten pork for over 320,000 yuan.[71]

EO Precision Zoom Lenses ideal for inspecting small details, especially electronic components, and feature 0.37X-2.23X lens are available at Edmund Optics.

Chang, C. M., Lo, Y. L., Tran, N. K. & Chang, Y. J. Optical characterization of porcine articular cartilage using a polarimetry technique with differential Mueller matrix formulism. Appl. Opt. 57(9), 2121–2127 (2018).

Carmagnola, F., Sanz, J. M. & Saiz, J. M. Development of a Mueller matrix imaging system for detecting objects embedded in turbid media. J. Quant. Spectrosc. Radiat. Transfer 146, 199–206 (2014).

On April 6, a community guard beat a Corgi to death after refusing a request to allow the dog to be taken with the owner into isolation. Later, the local community stated that they were worried that the dog may have been infected but acknowledged that they didn't "think very carefully" and would compensate the owner.[97][98]

The lockdown was lifted at midnight June 1, with many rushing to the grocery store to restock on food.[50] Shanghai declared that it would do its best to recover the losses caused by the epidemic.[51][52]

Studinski, R. C. & Vitkin, I. A. Methodology for examining polarized light interactions with tissues and tissue-like media in the exact backscattering direction. J. Biomed. Opt. 5, 330–338 (2000).

On February 28, 2022, introduction of travel restrictions was announced by the Shanghai Municipal People's Government and negative PCR testing within 48 hours of the travel became mandatory.[citation needed] In addition to the negative PCR testing, travel from "control area" to "prevention area" was conditioned by the 14 days mandatory quarantine at its own residence (quarantine in commercial facilities such as hotel does not qualify) within the "prevention area". On March 15, Civil Aviation Administration of China announced that the international flights into Shanghai shall be diverted to other cities.

A previously developed and validated polarization sensitive Monte Carlo (“polMC”) model20,34 was used to track and record the polarization status of photon packets propagating in a turbid medium containing dielectric polystyrene microspheres and gold nanoparticles having the shape of finite cylinders (GNRs). For the turbid media comprising of aqueous suspension of dielectric microspheres-only, position and propagation direction of individual photon packets were tracked along with the polarization information using the Stokes vector. The final values of the different Stokes vector elements were computed as the sum of all the appropriate photon subpopulations exiting the sample. For this study, the photon collection geometry in the backscattering direction was chosen to have a detection area of 1 mm2 and an acceptance angle of 10°. These selected parameters mimic our experimental polarimetry configuration (Fig. 1a). The refractive index of the background medium was taken as 1.334 to represent water with no absorption. Spherical polystyrene microspheres with diameters \(0.42,\) \(0.65\) and \(0.92\) μm and refractive index \(1.59\) were used as dielectric scatterers. The photon wavelength was 632.8 nm. Using standard Mie theory calculations for spherical dielectric particles27,30, the scattering efficiency \(Q\) and scattering anisotropy parameter (\(g\), the average cosine of scattering angle) were calculated. The former value was used to scale the microsphere concentration to yield the medium scattering coefficient \(\upmu_{s} = 102\,\hbox{cm}^{ - 1}\), which is typical of mammalian tissues in the “optical window” spectral regime. The simulations were carried out with \(10^{9}\) photons. The incident polarizations were horizontal, vertical, + 45°, − 45°, left and right circular states using the standard Stokes vector description. The Stokes vector elements of the backscattered light emerging in the 10° cone centered on the backscattering direction were recorded for each of the input polarization states. The Mueller matrix of the medium was constructed by performing standard algebraic manipulations using the recorded output Stokes parameters for each respective input state20,34.

On June 3, four neighborhoods in Jing'an and Pudong were put back into "closed" lockdown and designated as "mid-risk" due to seven new cases found the prior day.[53] On June 7, some more areas are restricted to "closed" area.

Since April 1, most areas of Shanghai are under three-level control. The levels includes "closed area" (封控区), "control area" (管控区), and "prevention area" (防控区) and typically spans the size of a residential complex, later (in June) granulizing into individual buildings.

Barreda, Á. I., Gutiérrez, Y., Sanz, J. M., González, F. & Moreno, F. Light guiding and switching using eccentric core-shell geometries. Sci. Rep. 7(1), 1–10 (2017).

This system was described as a "humanitarian crisis" by a Radio France Internationale commentator.[104] On March 31, the Consulate of France in Shanghai issued a protest to the Shanghai Government on behalf of 24 EU states.[105]

The two different polarizabilities along the two orthogonal directions of the plasmonic GNRs allow free conduction electrons to oscillate and resonate along the radial (transverse mode) and the axial (longitudinal mode) direction. These produce transverse and longitudinal surface plasmon resonances with different resonance wavelengths within the biologically relevant spectral range. As a result, GNRs exhibit large differences in both intensity and phase of the scattered light depending on its incident polarization. This manifests as extremely large and resonance-enhanced polarization effects of the GNRs18,19. These intriguing polarization effects are manifested as (1) differential attenuations (absorption and scattering) between two orthogonal linear polarization states, (2) difference in phase between two orthogonal linear polarization states (retardance) and (3) incident-polarization-state-dependent degree of polarization (DOP). Importantly, these resonance-enhanced linear diattenuation and retardance effects are also wavelength tunable through the size and aspect ratio of the GNRs and can generally be observed even from a randomly dispersed collection of the GNRs, making them a promising candidate for polarization-optimized bioimaging.

The elements of \(M\) contain useful polarization information about the interrogated medium in terms of the sample polarization properties, namely, depolarization, retardance and diattenuation. Depolarization \(\Delta\) is a quantitative measure of the net decrease in the degree of polarization (\(DOP = \frac{{\sqrt {\left( {Q^{2} + U^{2} + V^{2} } \right)} }}{I}\)) where \(I,Q,U\) and \(V\) are the elements of the light’s Stokes vector, arising due to the heterogeneous nature of the scattering medium. The quantity depolarization is usually defined as \(\Delta = 1 - DOP\); for example, fully polarized light having net \(DOP = 1\) would correspond to no depolarization or \(\Delta = 0\), whereas unpolarized light with \(DOP = 0\) would imply complete depolarization with \(\Delta = 1\). Retardance \(R\) is defined by the phase shift between two orthogonal polarization states, arising from the directional asymmetries in the real part of the refractive index of the medium (e.g., in a birefringent crystal or striated biological tissues such as muscle fibers or collagenous connective tissue). Analogously, diattenuation \(D\) is defined as the differential attenuation of orthogonal polarization states, which arises due to difference in the imaginary part of the refractive index between orthogonal polarizations. Thus, whereas retardance quantifies difference in phase shifts, diattenuation reports on intensity differences (due to differential absorption and scattering) between orthogonal polarizations.

Mackey, M. A., Ali, M. R., Austin, L. A., Near, R. D. & El-Sayed, M. A. The most effective gold nanorod size for plasmonic photothermal therapy: theory and in vitro experiments. J. Phys. Chem. B 118(5), 1319–1326 (2014).

In general, Mainland China has strict laws controlling crime related to pandemic management. According to Chinese jurist Luo Xiang's Criminal Law Textbook, people who don't obey basic isolation rules when they know they have tested positive for COVID-19 have committed the crime of harming public safety (Chinese: 以危险方法危害公共安全罪). Other people who don't obey isolation rules but caused heavy losses may get accused of the crime of distraction of disease prevention (Chinese: 妨碍传染病防治罪).[clarification needed] People who post allegedly false content about COVID-19 control policies may be accused of the crime of posting false information (Chinese: 编造、故意传播虚假信息罪).[67][68]

Figure 3c,d show the dependence of linear diattenuation and retardance parameters on the concentrations of GNRs. Here the scattering coefficient due to the fixed concentration of microspheres was \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\), whereas that induced by GNRs ranged from \(\upmu_{S} = 16\) to \(195\,\hbox{cm}^{ - 1}\). As noted above large magnitudes of linear diattenuation (\(D = 0.287\)) and retardance (\(R = 1.69\) rad) corresponding to the lowest examined concentration of GNR likely arise due to a large difference in the amplitude and phases respectively of the two orthogonal resonant dipolar plasmon polarizabilities (excited by orthogonal linear polarizations).

Yin, D., Li, X., Ma, Y. & Liu, Z. Targeted cancer imaging and photothermal therapy via monosaccharide-imprinted gold nanorods. Chem. Commun. 53, 6716–6719 (2017).

Shanghai decided to adopt "area-separated and batch-separated control" (Chinese: 分区分批防控) starting on March 28. On March 27, many markets got crowded, with some scholars arguing these conditions were due to city closure.[31][32][clarification needed] This was extended on April 1.[33] Some media suspected that cases were underreported.[34] Wang Keyu, a staff member at Huashan Hospital stated that (locally-available) COVID-19 vaccines offered weak protection against the Omicron variant, and that a wide range of COVID-19 testing control was important and necessary.[35] By March 29, over 9.1 million people had been tested by roughly 17,000 testers in roughly 6,300 testing areas. By April 1, over 18 million people had been tested.[36][37]

A system for quarantining children, including infants, away from adults was implemented. The site in Jinshan was first reported online by desperate parents. The separation was described officially on April 2 as a policy to "quickly help" minors and involves "temporary guardians".[102] On April 4, the health committee said that a system is in place to allow some children to be accompanied by their also COVID-positive parents. An online trend started where parents sought to become infected to stay with their children.[103]

Huang, X. H., Neretina, S. & El-Sayed, M. A. Gold nanorods: from synthesis and properties to biological and biomedical applications. Adv. Mater. 21, 4880–4910 (2009).

Depolarization peaks at wavelengths away from the peak of the longitudinal resonance (− 633 nm) whereas diattenuation peak coincides with the longitudinal resonance19. Therefore, depolarization peaks at the overlapped wavelength regions of the longitudinal and the transverse resonance. Thus, it sees the diattenuation peak near the longitudinal resonance and is spectrally away from the depolarization peak (which is at shorter wavelength). Therefore, with increasing GNR aspect ratio, depolarization peak shifts away from the longitudinal resonance and towards shorter wavelength. As a result, even for highly randomized 3D orientation of GNRs, we observed maximum preservation of polarization (less depolarization) near the peak of the longitudinal plasmon resonance.

Note that none of these intriguing trends were observed in the previous dielectric microspheres-only scenario (Fig. 2), where \(D\) and \(R\) did not show any appreciable variation with microsphere concentration. In contrast, here the magnitude of diattenuation and retardance is observed to drop off rapidly with increasing scattering coefficients (i.e., concentration) of GNRs. This interesting and somewhat counter-intuitive observation—GNR ‘anisotropic polarization signals’ getting weaker as their concentrations increases!—is likely due to the incoherent addition of the multiply scattered polarized light from the randomly oriented nanorods. As the size of the single GNR is very small compared to the focal spot size, the relative orientation of a large number of GNRs per unit volume (e.g., \(2.4 \times 10^{7}\) particles per microliter for GNR-induced scattering coefficient of 180 cm−1) can add up constructively or destructively, leading to high or low anisotropic polarization signal. Evidently the latter effect (destructive superposition) dominates here, as D and R values diminish with the increasing GNR concentration, and thus the resultant randomness of their orientation/superposition increases. In our case, we have achieved diattenuation value \(D = 0.28\) from the randomly oriented GNRs at the lowest studied value of nanorod-induced turbidity of \(\upmu_{S} = 16\,\hbox{cm}^{ - 1}\), over and above \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\) exhibited by the dielectric microspheres.

Digital Interface Cables · Length: 100 m · Robust dust-protected fibre optic connector system · OpticalCON DUO 2-pole field cable with multi-mode fibres.

On April 5, the lockdown was expanded to encompass the entire city, affecting the population of 25 million.[38] On April 11, Shanghai published the list of closed areas, control areas, and prevention areas.[39] On April 11, Shanghai officially announced all areas are under three-level control and clarified. Closed area contains people who tested positive for COVID-19 in the neighborhood, the "7-7" quarantine policy is required to follow, during 7-day closing period, if there was no people who tested positive, the restriction will be the same as the restrictions of a "control area". People in control areas can, with limit, collect essential supplies within the neighborhood. Neighborhoods which are listed as prevention areas have no reported case within 14 days. People in prevention areas should only travel within the street.[39] In practice, additional restrictions are levied by the local residents' committee.

On April 26, a French citizen is seen on a two-minute-long video asking quarantine workers for help with suicide in three languages. He was subdued and later became stabilized. The French embassy confirmed his identity and commented that food shortage is likely not the reason.[96]

Shanghai violinist Chen Shunping experienced a severe stomach ache and vomiting at night on April 13. Upon calling emergency services, he was told he would have to "wait in line". Later that night, he went to two different hospitals and was unable to receive medical service at either. Faced with immense pain, he committed suicide by jumping off a building.[91]

On March 26, an old man is seen having died after falling off a residential building. The original poster suggested that the death was due to lack of access to medical help, but the family clarified that the dead has been allowed to regularly go to the hospital to the government-run fact checker.[93]

In the presence of both microspheres and GNRs, the generalized extinction of a polydisperse ensemble consisting of \(n_{R}\) and \(n_{S}\) (number fractions of GNRs and microspheres, respectively) can be obtained from Eqs. (2) and (3) as

Tilt and decenter result in one side of the optical surface becoming closer to the wavefront than the other one - a recipe for coma, which is by far the ...

Chinaonline newspaper

Dolinnyi, A. I. Nanometric rulers based on plasmon coupling in pairs of gold nanoparticles. J. Phys. Chem. C 119(9), 4990–5001 (2015).

On May 9, live fish were recorded getting killed by ground impact at the entrance to a residential complex in Jingan. The local residents' committee explained that the group-buy organizer acquired permission for buying refrigerated fish, not the prohibited live fish actually delivered. The organizer chose to kill the fish outside the gate to comply.[100]

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Nangare, S. N. & Patil, P. O. Affinity-based nanoarchitectured biotransducer for sensitivity enhancement of surface plasmon resonance sensors for in vitro diagnosis: a review. ACS Biomater. Sci. Eng. 7(1), 2–30 (2020).

On April 13, the Public Security Bureau of Shanghai announced that people in prevention areas must not enter "closing areas"; nonessential automobiles would also be prohibited.[64]

Chen, Y. S., Zhao, Y., Yoon, S. J., Gambhir, S. S. & Emelianov, S. Miniature gold nanorods for photoacoustic molecular imaging in the second near-infrared optical window. Nat. Nanotechnol. 14, 465–472 (2019).

Jan 8, 2024 — Hello, I'm using LUXEON Z high power LED for my application. I would like to have many LEDs (~1000) in series and parallel connections.

Tong, L., Wei, Q., Wei, A. & Cheng, J. X. Gold nanorods as contrast agents for biological imaging: optical properties, surface conjugation and photothermal effects. Photochem. Photobiol. 85, 21–32 (2009).

By April 30, officially all of the deaths were caused by other severe symptoms. On the same day, the first fangcang quarantine hospital (fang1cang1 方舱, literally "portable building") was officially closed.[30]

We have set up and calibrated the polarization Mueller matrix measurement system in the backscattering configuration as shown in Fig. 1. It consists of a 633 nm laser whose emission, after passing through a polarization state generator (PSG), was incident on a 50–50 beam splitter. The reflected light beam from the beam splitter was then focused on to the sample cuvette and the backscattered light from the sample was subsequently collected using a10 × microscope objective. The thickness of the cuvette was 1 cm and the width of its glass wall was ~ 1 mm. The incident laser beam diameter was 5 mm and after passing through the microscope objective, the diameter of the focal spot was ~ 1 mm. The backscattered light was collected by the same low-NA microscope objective, corresponding to an acceptance angle of ~ 10°. The collected backscattered light then passed through the beam splitter again and its polarization state was analyzed using a polarization state analyzer (PSA) and the polarization-resolved intensity signal was detected by a high-SNR photo detector. Each detected polarization-resolved intensity signal was recorded by taking average over 25 times recorded intensity signal. Thereafter, collecting 16 sequential polarization-resolved intensity measurement, Mueller matrix was constructed as discussed above.

Mieszawska, A. J., Mulder, W. J. M., Fayad, Z. A. & Cormode, D. P. Multifunctional gold nanoparticles for diagnosis and therapy of disease. Mol. Pharm. 10, 831–847 (2013).

During late March, Zhang Wenhong, a doctor who made many speeches during the pandemic, has been absent for a few events, some media suspect that this is a "sign" made by Shanghai government.[76]

On April 3, a Shanghai woman wanted to send her grandfather meals, but the distance between their homes was very far. She found a man to deliver the meals for her to Qingpu but did not ask for money. The next day, the woman transferred him 200 yuan by phone but was later criticized for paying too little when she shared her story online. On April 6, she committed suicide. Her parents and other online commentators called for the people who bullied her to be sued or punished.[94]

Bonyar, A. Label-free nucleic acid biosensing using nanomaterial-based localized surface plasmon resonance imaging: a review. ACS Appl. Nano Mater. 3(9), 8506–8521 (2020).

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Lippok, N. et al. Quantitative depolarization measurements for fiber-based polarization-sensitive optical frequency domain imaging of the retinal pigment epithelium. J. Biophotonics 12(1), 201800156 (2019).

ChinaDaily

Here, \(c_{g}\) and \(\rho_{g}\) are mass-volume concentration and density of gold, \(V_{t}\) is the total volume of scatterers (GNRs and microspheres) per unit suspension volume, and \(w_{R/S} = \left( {n_{R/S} } \right)/n\). We have thus replaced the Mie scattering function with Eq. (4) in the PSMC simulation described in “Monte Carlo modeling of polarized light propagation in multiply scattering tissue-like turbid media containing dielectric microspheres” section above. Simulations were carried out for a fixed \(W_{S}\) (corresponding to microsphere-induced \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\) value with \(0.42\,\upmu \hbox{m}\) diameter microspheres), whereas the values of \(w_{R}\) (corresponding to GNR-induced \(\upmu_{S}\) in the 16 to 195 cm−1 range) were varied. Tracking the position, direction, and Stokes’s vector of each photon packet described above then enables the Mueller matrix elements of the backscattered detected light to be constructed.

Ray, S.K., Ghosh, N. & Vitkin, A. Diattenuation and retardance signature of plasmonic gold nanorods in turbid media revealed by Mueller matrix polarimetry. Sci Rep 11, 20017 (2021). https://doi.org/10.1038/s41598-021-99430-6

In early May, constitutional academic Tong Zhiwei [zh] expressed his opposition to forced quarantine transport and home disinfection, stating that the authorities' legal basis (Public Security Penalties Law, Art. 50(1)) is nil – the law requires a state of emergency to be declared, but none has been. Around the same time, financial lawyer Liu Dali expressed his opposition to procedural problems in quarantine transport, namely lack of paperwork and an overly liberal definition of "contact" involving whole floors or even buildings. Both articles were quickly taken down on the Chinese internet, their Weibo accounts suspended, and bar associations warned not to distribute these articles.[106]

Polarization effects in microspheres-only phantom system. Dependence of the Mueller matrix-derived polarization parameters of a controlled turbid media (microsphere phantom) on the diameter and scattering coefficient. MC-simulated (red symbols) and experimentally obtained (black symbols) variations of the (a) diattenuation and (b) retardance with microsphere diameters for a fixed scattering coefficient \(\upmu_{S} = 102\,\hbox{cm}^{ - 1}\). Near zero diattenuation stems from isotropic nature of the spherical scatterers, and non-zero retardance (\(\sim 1.5\) radians) likely arises from the detection geometry effects and particle diameters (for details, see text). The simulated (red symbols) and experimental (black symbols) variations of (c) diattenuation and (d) retardance with optical turbidity (\(\upmu_{S}\) range from 16 to 621 cm−1) for a fixed scatterer diameter (\(d = 0.42\,\upmu\)m) exhibit similar trends of near zero diattenuation and finite retardance (− 1.4 to 1.5 radians). The corresponding variation of the simulated and experimental degree of polarization with turbidity shown in (e). Note: in Figs. 2 and 3, symbols are experimental and simulations results, and lines are guides for the eye.

These effects arise due to the differences in amplitudes and phases, respectively, of the two orthogonal (longitudinal and transverse) dipolar plasmon polarizabilities of the GNRs. Strong linear diattenuation is thus manifested due to polarization-selective resonance of the two plasmon polarizabilities (longitudinal and transverse plasmon resonances excited by horizontal and vertical linear polarizations respectively) and subsequent differential scattering intensities for the two orthogonal linear polarizations. Such resonance-enhanced linear diattenuation in plasmonic nanorods is known to exhibit its maximum magnitude near the peak wavelength of the longitudinal plasmon resonance19,39. Linear retardance, on the other hand, arises due to the resonance-enhanced phase difference between the two orthogonal plasmon polarizabilities, which typically exhibits its maxima at wavelengths away from the peak of the longitudinal resonance and around the spectral overlap region of the longitudinal and the transverse resonances19,39. The excitation wavelength in our study is accordingly chosen at \(\lambda = 633\,\hbox{nm}\), close to the peak of the longitudinal plasmon resonance. Therefore, in general, we observed both resonance-enhanced linear diattenuation and retardance effects at this excitation wavelength. Since the magnitude and the phases of the two orthogonal dipolar plasmon polarizabilities are influenced by the aspect ratio \(\in\), changing \(\in\) could also control and optimize the magnitudes of both diattenuation and retardance (Fig. 3a,b). In our case, we varied the GNRs length \(l = 70\,\hbox{nm}\) to \(105\,\hbox{nm}\) and diameter \(d = 25\,\hbox{nm}\) to \(71\,\hbox{nm}\) to change the aspect ratio by keeping the peak of the longitudinal resonance close to the excitation wavelength 633 nm. Specifically, for an aspect ratio \(\in = 2.8\), maximum values of \(D = 0.3\) and \(R = 1.68\) were obtained through PSMC simulation, in excellent agreement with the experimental maximum values of \(D = 0.295\) and \(R = 1.71\). For value of aspect ratio \(\in > 2.8\), diattenuation also shows linear behavior. However, control and tuning of the diattenuation and retardance effects by changing the aspect ratio of the GNRs with appropriate choice of the excitation wavelength thus appears to be an effective means of isolating the polarization effects of the GNRs from the corresponding background scattering effects of turbid media. Further, the diattenuation and retardance effects of the GNRs exhibit sharp spectral characteristic of the longitudinal and the transverse plasmon resonances, whereas those due to scattering from dielectrics typically exhibits broader wavelength variations.

Big Eye High Intensity Magnifier Desk Lamp with 2X magnification is built with a flexible, chrome gooseneck to help manipulate the lamp to a desirable ...

A COVID-19 outbreak in the city of Shanghai, China began on February 28, 2022,[1] and ended on August 7, 2022.[2] The outbreak was caused by the Omicron variant and became the most widespread in Shanghai since the pandemic began two years prior.[7] Authorities responded with mass COVID-19 testing and a strict lockdown of the city in an effort to uphold China's zero-COVID policy;[8] the latter marked the largest one in the country since the lockdown of Hubei in early 2020.[9] The outbreak caused substantial economic and social disruption across Shanghai with consequences felt elsewhere, and led to the spread of COVID-19 to other parts of China, including Beijing, Guangdong, and Hunan.

Experimental calibration results are presented in Fig. 1, where a schematic of the experimental configuration is shown in Fig. 1a. Corresponding experimentally obtained PSG matrix W, PSA matrix A and the extracted blank Mueller matrix of the pure-water-filled cuvette are presented in Fig. 1b–d respectively. Each column of the PSG matrix W (Fig. 1b) represents a Stokes vector corresponding to the optimized orientation angles \(\theta = 35^{o} ,70^{o} ,105^{o}\) and \(140^{o}\)) of the quarter waveplate Q1. For example, first column of Fig. 1b represents the normalized Stokes vector for \(\theta = 35^{o}\). Similarly, each row of the PSA matrix A in Fig. 1c represents the top row of the combined Mueller matrix of the optical elements forming the PSA. Experimentally calibrated Mueller matrix for a non-depolarizing sample (blank cuvette filled with pure water) shown in Fig. 1d yields a 4 × 4 array that closely resembles an identity matrix with an elemental error \(\le 0.05\), which may be considered as the elemental accuracy of our Mueller matrix measurement system.

On April 22, officials announced they would escalate COVID lockdown restrictions and further tighten lockdown measures. Some of the new measures include evacuating people to disinfect their homes and placing electronic door alarms to warn if infected people are trying to leave.[29]