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Even as the company rolls out more features for its cameras and software, it will still sell Tasers, which made up about three-quarters of the company's sales last year.

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This research was supported in part by the Ministry of Education, Culture, Sports, Science and Technology of Japan (Grant-in-Aid for Scientific Research (KAKENHI): 20117003 and 23249004 to Y.U., 23113504 and 25113707 to M.K., 23710108 to M.C.T., 24659092, 25113723 and 25293046 to Y.O. and 21121004 to T. F.), by The Daiichi-Sankyo Foundation of Life Science (to Y.U.), by the Uehara memorial Foundation (to Y.O.), by The Mochida Memorial Foundation for Medical and Pharmaceutical Research (to M.K.) and by a JSPS stipend (to S.U.). The authors thank D. Toomre for many useful discussions, K. Johnsson and G. Lukinavičius for β-tubulin–SNAP plasmid, N. Imamoto for HeLa cell lines expressing nuclear pore proteins, R. Wong for POM121 plasmid, J. Asada and S. Dan Xu for the construction of plasmids and experimental assistance, and Y. Arai for the ImageJ script for analysing projection profiles of the localization of super-resolution images. The African green monkey kidney normal cell line Vero (JCRB0111) was obtained from the Japanese Collection of Research Bioresources (JCRB) cell bank.

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Axon and its body-camera competitor Vievu say their products will save time for law enforcement agencies by, for example, making it easier to review footage. Axon's Evidence.com platform offers automated facial redaction and tools to share evidence with prosecutors; Vievu said it will integrate with an AI platform that offers facial recognition and sentiment analysis.

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How to pronouncespontaneously

Funakoshi, T. et al. Two distinct human POM121 genes: requirement for the formation of nuclear pore complexes. FEBS Lett. 581, 4910–4916 (2007).

Along with the name change, Axon announced a free trial program for its body cameras: It will send law enforcement agencies one body camera per sworn officer to use for a year. The company is also offering a year of free data storage on its Evidence.com service.

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A patrol officer in West Valley City, Utah, starts a body camera recording by pressing a button on his chest in March 2015. The West Valley City Police Department issued 190 Axon Flex body cameras for all its sworn officers to wear.

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Lukinavičius, G. et al. A near-infrared fluorophore for live-cell super-resolution microscopy of cellular proteins. Nature Chem. 5, 132–139 (2013).

A patrol officer in West Valley City, Utah, starts a body camera recording by pressing a button on his chest in March 2015. The West Valley City Police Department issued 190 Axon Flex body cameras for all its sworn officers to wear. George Frey/Getty Images hide caption

Sales of body cameras have boomed since the national uproar over a number of police-involved shootings, including the 2014 shooting of Michael Brown in Ferguson, Mo. A recent Pew study found broad support for police-worn body cameras, with a majority of both police officers (66 percent) and the public (93 percent) in favor of their use.

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After the free trial is up, Axon's Body 2 camera has a one-time cost of $399, while use of the company's Evidence.com platform costs $15 to $89 per month, per officer.

S.U., M.K., T.Y., Y.O., S.T. and Y.U. conducted experiments and performed analyses. S.U., M.K., Y.O. and Y.U. co-wrote the manuscript. K.S., K.O., M.C.T., T.F. and H.F. contributed materials/analysis tools. M.K. and Y.U. planned and initiated the project, designed experiments, and supervised the entire project.

Officers are increasingly getting used to recording their interactions with the public, and now a key question is what police departments should do with all that footage, as NPR's Martin Kaste has reported.

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Center for International Research on Micronano Mechatronics, Institute of Industrial Science, The University of Tokyo, Tokyo, 153-8505, Japan

Taser International has sold a whole lot of stun guns since its founding in 1993. By the company's estimation, nearly two-thirds of all law enforcement patrol officers in the U.S. carry a Taser.

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Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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An investigation by The Washington Post in November 2015 found that about one person a week that year had died in incidents in which they were Tasered by police. More than half of them suffered from mental illness or had illegal drugs in their system when they died, according to the newspaper.

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"At least 10 were Tasered while handcuffed or shackled," the report found. "Only one was female. Nearly 55 percent of the people who died were minorities."

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Axon spokesman Steve Tuttle says law enforcement agencies using body cameras have seen "improved behavior on both sides of the badge," citing decreases in both use of force and complaints from the public.

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Single-molecule localization microscopy is used to construct super-resolution images, but generally requires prior intense laser irradiation and in some cases additives, such as thiols, to induce on–off switching of fluorophores. These requirements limit the potential applications of this methodology. Here, we report a first-in-class spontaneously blinking fluorophore based on an intramolecular spirocyclization reaction. Optimization of the intramolecular nucleophile and rhodamine-based fluorophore (electrophile) provide a suitable lifetime for the fluorescent open form, and equilibrium between the open form and the non-fluorescent closed form. We show that this spontaneously blinking fluorophore is suitable for single-molecule localization microscopy imaging deep inside cells and for tracking the motion of structures in living cells. We further demonstrate the advantages of this fluorophore over existing methodologies by applying it to nuclear pore structures located far above the coverslip with a spinning-disk confocal microscope and for repetitive time-lapse super-resolution imaging of microtubules in live cells for up to 1 h.

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Axon says it has the answer: Use its cameras to capture the footage, and then use its service to upload it directly to the cloud, where artificial intelligence technology will analyze the video and audio.

So when the company announced this week that it was changing its name to Axon — the name of its line of body cameras — it signaled where the company thinks its future lies: in becoming a device-connected platform for law enforcement data.

Kamiya, M. et al. β-Galactosidase fluorescence probe with improved cellular accumulation based on a spirocyclized rhodol scaffold. J. Am. Chem. Soc. 133, 12960–12963 (2011).

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But since 2009, Taser has also been selling body cameras worn by police officers. The company says its cameras are now used by 36 of the 68 major law enforcement agencies across America, including the Los Angeles Police Department, which bought more than 7,500 of the devices.

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