The “cost” of obtaining a higher NA is that the working distance (WD) of the lens becomes much shorter. Working distance is “… the distance between the objective front lens and the top of the cover glass when the specimen is in focus. In most instances, the working distance of an objective decreases as magnification increases.” (1) A smaller working distance can be a problem when you cannot see an object with a high magnification lens, even though you could see it with a low magnification lens. A 10x objective can have a WD of several millimeters (4-10mm, or 4000-10,000um). A well corrected, high NA 20x dry objective will have a WD of slightly less than 1mm (1000um). Most well corrected, high NA 40x and 60x oil objectives have working distances on the order of 0.1mm (100um).

In 1849, the method of producing an I-beam, as rolled from a single piece of wrought iron,[1] was patented by Alphonse Halbou of Forges de la Providence in Marchienne-au-Pont, Belgium.[2]

High magnification without high NA does not give the resolving power that most people expect from a research grade microscope.  Using a high NA objective lens means that you are most likely sacrificing working distance (how deep into the sample that you can focus) for higher optical resolution. In most instances this is a very acceptable trade off.

However, these ideal conditions can never be achieved because material is needed in the web for physical reasons, including to resist buckling. For wide-flange beams, the section modulus is approximately

In India, I-beams are designated as ISMB, ISJB, ISLB, ISWB. ISMB: Indian Standard Medium Weight Beam, ISJB: Indian Standard Junior Beams, ISLB: Indian Standard Light Weight Beams, and ISWB: Indian Standard Wide Flange Beams. Beams are designated as per respective abbreviated reference followed by the depth of section, such as for example ISMB 450, where 450 is the depth of section in millimetres (mm). The dimensions of these beams are classified as per IS:808 (as per BIS).[citation needed]

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A volunteer and collaborative effort to bring information about shared microscopy facilities to the University of Arizona and the community.

HPshapeSteel

A beam under bending sees high stresses along the axial fibers that are farthest from the neutral axis. To prevent failure, most of the material in the beam must be located in these regions. Comparatively little material is needed in the area close to the neutral axis. This observation is the basis of the I-beam cross-section; the neutral axis runs along the center of the web which can be relatively thin and most of the material can be concentrated in the flanges.

Bethlehem Steel, headquartered in Bethlehem, Pennsylvania, was a leading supplier of rolled structural steel of various cross-sections in American bridge and skyscraper work of the mid-20th century.[3] Rolled cross-sections now have been partially displaced in such work by fabricated cross-sections.

Numerical Aperture (NA) is “… a critical value that indicates the light acceptance angle, which in turn determines the light gathering power, the resolving power, and depth of field of the objective.”(1) As light passes through a sample, the information describing the highest resolution information in the sample is diffracted at a very wide angle. Low magnification lenses typically have low NAs, meaning that they cannot capture the highest resolution information. To capture the widely diffracted information, high NA lenses move the front of the lens closer to the sample (increases the light acceptance angle). Dry lenses can only have NAs of up to 1.0. By using specially formulated oil and oil lenses, NAs of up to 1.4 can be achieved.

Reviewed & updated 06/16/2017. Creation of this web page was originally supported as part of the Southwest Environmental Health Sciences Center at the University of Arizona, NIEHS P30 ES006694.

In the United Kingdom, these steel sections are commonly specified with a code consisting of the major dimension, usually the depth, -x-the minor dimension-x-the mass per metre-ending with the section type, all measurements being metric. Therefore, a 152x152x23UC would be a column section (UC = universal column) of approximately 152 mm (6.0 in) depth, 152 mm width and weighing 23 kg/m (46 lb/yd) of length.[10]

2021621 — The diameter of the field of view is 3mm and that they are 10 cells across the field of view, the total magnification was 100x.

The UArizona Microscopy Alliance is a volunteer and collaborative effort to bring information about shared microscopy facilities to the University of Arizona and the community.

Sshape beam

For a beam of cross-sectional area a and height h, the ideal cross-section would have half the area at a distance ⁠h/2⁠ above the cross-section and the other half at a distance ⁠h/2⁠ below the cross-section.[4] For this cross-section,

In Mexico, steel I-beams are called IR and commonly specified using the depth and weight of the beam in metric terms. For example, a "IR250x33" beam is approximately 250 mm (9.8 in) in depth (height of the I-beam from the outer face of one flange to the outer face of the other flange) and weighs approximately 33 kg/m (22 lb/ft).[9]

I-joists, I-beams engineered from wood with fiberboard or laminated veneer lumber, or both, are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden joists. However, there has been some concern as to their rapid loss of strength in a fire if unprotected.

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Ibeamsizes

I-beams are commonly made of structural steel but may also be formed from aluminium or other materials. A common type of I-beam is the rolled steel joist (RSJ), sometimes incorrectly rendered as reinforced steel joist. British and European standards also specify Universal Beams (UBs) and Universal Columns (UCs). These sections have parallel flanges, shown as "W-Section" in the accompanying illustration, as opposed to the varying thickness of RSJ flanges, illustrated as "S-Section", which are seldom now rolled in the United Kingdom. Parallel flanges are easier to connect to and do away with the need for tapering washers. UCs have equal or near-equal width and depth and are more suited to being oriented vertically to carry axial load such as columns in multi-storey construction, while UBs are significantly deeper than they are wide are more suited to carrying bending load such as beam elements in floors.

WbeamSize chart

The American Institute of Steel Construction (AISC) publishes the Steel Construction Manual for designing structures of various shapes. It documents the common approaches, Allowable Strength Design (ASD) and Load and Resistance Factor Design (LRFD), (starting with 13th ed.) to create such designs.

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In Canada, steel I-beams are now commonly specified using the depth and weight of the beam in metric terms. For example, a "W250x33" beam is approximately 250 millimetres (9.8 in) in depth (height of the I-beam from the outer face of one flange to the outer face of the other flange) and weighs approximately 33 kg/m (22 lb/ft; 67 lb/yd).[8] I-beams are still available in US sizes from many Canadian manufacturers.

Steelbeamtypes and sizes

Though I-beams are excellent for unidirectional bending in a plane parallel to the web, they do not perform as well in bidirectional bending. These beams also show little resistance to twisting and undergo sectional warping under torsional loading. For torsion dominated problems, box beams and other types of stiff sections are used in preference to the I-beam.

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Hbeamsizes

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Mshape Beam

Many of us have looked though the eyepiece of a department store microscope and seen a fuzzy looking “something” with the highest magnification objective lens. It’s not completely surprising that an inexpensive lens would give a blurry image. There are many optical aberrations that need to be corrected to manufacture the expensive lenses that are used on research grade microscopes.

I-beams may be used both on their own, or acting compositely with another material, typically concrete. Design may be governed by any of the following criteria:

Cellular beams are the modern version of the traditional castellated beam, which results in a beam approximately 40–60% deeper than its parent section. The exact finished depth, cell diameter and cell spacing are flexible. A cellular beam is up to 1.5 times stronger than its parent section and is therefore utilized to create efficient large span constructions.[11]

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by JH Burnett · 2008 · Cited by 6 — We have made accurate measurements near 157 nm of the relative index of refraction, its dispersion, and its temperature dependence for two ...

In Australia, these steel sections are commonly referred to as Universal Beams (UB) or Columns (UC). The designation for each is given as the approximate height of the beam, the type (beam or column) and then the unit metre rate (e.g., a 460UB67.1 is an approximately 460 mm (18.1 in) deep universal beam that weighs 67.1 kg/m (135 lb/yd)).[6]

where I is the moment of inertia of the beam cross-section and c is the distance of the top of the beam from the neutral axis (see beam theory for more details).

When designing a symmetric I-beam to resist stresses due to bending the usual starting point is the required section modulus. If the allowable stress is σmax and the maximum expected bending moment is Mmax, then the required section modulus is given by:[4]

In the United States, the most commonly mentioned I-beam is the wide-flange (W) shape. These beams have flanges whose inside surfaces are parallel over most of their area. Other I-beams include American Standard (designated S) shapes, in which inner flange surfaces are not parallel, and H-piles (designated HP), which are typically used as pile foundations. Wide-flange shapes are available in grade ASTM A992,[5] which has generally replaced the older ASTM grades A572 and A36. Ranges of yield strength:

An I-beam is any of various structural members with an Ɪ- (serif capital letter 'I') or H-shaped cross-section. Technical terms for similar items include H-beam, I-profile, universal column (UC), w-beam (for "wide flange"), universal beam (UB), rolled steel joist (RSJ), or double-T (especially in Polish, Bulgarian, Spanish, Italian, and German). I-beams are typically made of structural steel and serve a wide variety of construction uses.

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Light microscopes can, under the best conditions, resolve objects that are approximately equal to half the size of the wavelength used. In the real world this comes out to objects that are 250-300nm in size, if you are using a NA=1.4 objective lens (under optimal conditions). This means that you can make out two adjacent objects in this size range, assuming that you can see at least a 25% dip in intensity between them (Rayleigh criterion). Sample preparation is especially important when you want to resolve structures this small.

In the United States, steel I-beams are commonly specified using the depth and weight of the beam. For example, a "W10x22" beam is approximately 10 in (254 mm) in depth with a nominal height of the I-beam from the outer face of one flange to the outer face of the other flange, and weighs 22 lb/ft (33 kg/m). Wide flange section beams often vary from their nominal depth. In the case of the W14 series, they may be as deep as 22.84 in (580 mm).[7]'

Steelbeamshapes

The ideal beam is the one with the least cross-sectional area (and hence requiring the least material) needed to achieve a given section modulus. Since the section modulus depends on the value of the moment of inertia, an efficient beam must have most of its material located as far from the neutral axis as possible. The farther a given amount of material is from the neutral axis, the larger is the section modulus and hence a larger bending moment can be resisted.

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I-beams are widely used in the construction industry and are available in a variety of standard sizes. Tables are available to allow easy selection of a suitable steel I-beam size for a given applied load. I-beams may be used both as beams and as columns.

The horizontal elements of the Ɪ are called flanges, and the vertical element is known as the "web". The web resists shear forces, while the flanges resist most of the bending moment experienced by the beam. The Euler–Bernoulli beam equation shows that the Ɪ-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web. On the other hand, the cross-section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion, for which hollow structural sections are often preferred.