bluuebunny/crossref_metadata_2025 huggingface dataset:
Cascaded systems analysis of charge sharing in cadmium telluride photon‐counting x‐ray detectors
Authors: Tanguay Jesse , Cunningham Ian A.
Published: March 2018

Purpose

Single‐photon‐counting (SPC) and spectroscopic x‐ray detectors are under development in academic and industry laboratories for medical imaging applications. The spatial resolution of SPC and spectroscopic x‐ray detectors is an important design criterion. The purpose of this article was to extend the cascaded systems approach to include a description of the spatial resolution of SPC and spectroscopic x‐ray imaging detectors.

Methods

A cascaded systems approach was used to model reabsorption of characteristic x rays, Coulomb repulsion, and diffusion in SPC and spectroscopic x‐ray detectors. In addition to reabsorption, diffusion, and Coulomb repulsion, the model accounted for x‐ray conversion to electron‐hole (e‐h) pairs, integration of e‐h pairs in detector elements, electronic noise, and energy thresholding. The probability density function (PDF) describing the number of e‐h pairs was propagated through each stage of the model and was used to derive new theoretical expressions for the large‐area gain and modulation transfer function (MTF) of CdTe SPC x‐ray detectors, and the energy bin sensitivity functions and MTFs of CdTe spectroscopic detectors. Theoretical predictions were compared with the results of MATLAB‐based Monte Carlo (MC) simulations and published data. Comparisons were also made with the MTF of energy‐integrating systems.

Results

Under general radiographic conditions, reabsorption, diffusion, and Coulomb repulsion together artificially inflate count rates by 20% to 50%. For thicker converters (e.g. 1000 μm) and larger detector elements (e.g. 500 μm pixel pitch) these processes result in modest inflation (i.e. ∼10%) in apparent count rates. Our theoretical and MC analyses predict that SPC MTFs will be degraded relative to those of energy‐integrating systems for fluoroscopic, general radiographic, and CT imaging conditions. In most cases, this degradation is modest (i.e., ∼10% at the Nyquist frequency). However, for thicker converters, the SPC MTF can be degraded by up to 25% at the Nyquist frequency relative to EI systems. Additionally, unlike EI systems, the MTF of spectroscopic systems is strongly dependent on photon energy, which results in energy‐bin‐dependent spatial resolution in spectroscopic systems.

Conclusions

The PDF‐transfer approach to modeling signal transfer through SPC and spectroscopic x‐ray imaging systems provides a framework for understanding system performance. Application of this approach demonstrated that charge sharing artificially inflates the SPC image signal and degrades the MTF of SPC and spectroscopic systems relative to energy‐integrating systems. These results further motivate the need for anticharge‐sharing circuits to mitigate the effects of charge sharing on SPC and spectroscopic x‐ray image quality.
Acute hypertensive stress imaged by cardiac hyperpolarized [1‐13C]pyruvate magnetic resonance
Authors: Tougaard Rasmus Stilling , Hansen Esben Søvsø Szocska , Laustsen Christoffer , Lindhardt Jakob , Schroeder Marie , Bøtker Hans Erik , Kim Won Yong , Wiggers Henrik , Stødkilde‐Jørgensen Hans
Published: March 2018

Purpose

Deranged metabolism is now recognized as a key causal factor in a variety of heart diseases, and is being studied extensively. However, invasive methods may alter metabolism, and conventional imaging techniques measure tracer uptake but not downstream metabolism. These challenges may be overcome by hyperpolarized MR, a noninvasive technique currently crossing the threshold into human trials. The aim of this study was to image metabolic changes in the heart in response to endogastric glucose bolus and to acute hypertension.

Methods

Five postprandial pigs were scanned with hyperpolarized [1‐13C]pyruvate cardiac MR at baseline, after oral glucose bolus, and after infusion of angiotensin‐II.

Results

No effect of glucose bolus was seen using hyperpolarized [1‐13C]pyruvate MR despite changes in circulating substrates. During angiotensin‐II infusion, blood pressure increased 179% (P = 0.008) and ejection fraction decreased from 54 ± 2% to 47 ± 6% (P = 0.03) The hemodynamic changes were accompanied by increases in the hyperpolarized [1‐13C]pyruvate MR derived ratios of lactate/alanine (from 0.58 ± 0.13 to 0.78 ± 0.06, P = 0.03) and bicarbonate/alanine (from 0.55 ± 0.12 to 0.91 ± 0.14, P = 0.007).

Conclusion

Glucose loading did not alter cardiac metabolism, but during acute hypertensive stress, cardiac aerobic, carbohydrate metabolism, and pyruvate‐lactate exchange was altered. Hyperpolarized MR allows noninvasive evaluation of acute changes in cardiac metabolism. However, hemodynamics must be taken into account when interpreting the results.
Highly accurate equilibrium structure of the C2h symmetric N1‐to‐O2 hydrogen‐bonded uracil‐dimer
Authors: Kruse Holger , Šponer Jiří
Published: March 2018

The highly accurate ab initio equilibrium geometry of the hydrogen‐bonded uracil dimer is derived using a composite geometry extrapolation scheme based on all‐electron, complete basis set extrapolated Møller–Plesset perturbation theory using the jun‐pwCV[T,Q]Z basis sets combined with a valence CCSD(T)/cc‐pVTZ high‐level correction. Geometrical changes on dimerization are discussed and the performance of the several density functional approximations (among others SCAN, ωB97M‐V, DSD‐PBEP86‐D3(BJ), and DSD‐PBEP86‐NL) is evaluated. Orbital‐optimized MP2.5 is discussed as a reduced‐cost alternative to the CCSD(T) gradient in the composite scheme. A new reference interaction energy is calculated with explicitly correlated F12‐CCSD(T).
Whistleblowing on accountingy-related misconduct: A synthesis of the literature
Authors: Lee Gladys , Xiao Xinning
Published: March 2018

Whistleblowers have been credited for uncovering financial scandals in companies globally, including Enron, Olympus Corporation, and WorldCom. Despite increasing support and incentives for whistleblowing, there generally remains reluctance to blow the whistle. Thus, the purpose of this study is to review: (1) the determinants of internal and external whistleblowing on accounting-related misconduct, (2) U.S. whistleblowing legislation on accounting-related misconduct and related research, and (3) the effects of whistleblowing on firms and whistleblowers. Within each area, suggestions for future research are offered.
Creating Pseudocolor Images using ImageJ
Authors: Sheffield Joel B
Published: March 2018

It is common for microscopists to examine fluorescent samples that have been exposed to a mixed set of fluorophores with specific staining properties. Images are often captured from these samples as a set, using different filter sets to isolate specific elements of the sample. Sometimes the images are captured in gray scale, and in other cases, they are captured with color cameras. In either case, one would often like to combine the images to create a single image that presents the information from all fluorophores at once. This kind of display is particularly useful for determining the relative locations of different components.
Nanoparticle Visualization with an AFM
Authors: West Paul , Starostina Natasha
Published: March 2018

It is often said that: “…a picture is worth a thousand words… ” This can be certainly true for images from an Atomic Force Microscope.

Although we often know that nanoparticles exist and we have a mental picture of what they look like, it is often helpful to be able to “see” the particles to verify that they are morphologically what we imagine they are. When the particles are much less than a micron in diameter, they cannot be directly visualized with an optical microscope. At best, sub micron particles appear as “diffraction spots” in an optical microscope. It is possible to visualize nanoparticles with SEM or TEM.
Protect Your Detectors
Authors: Michael Stanley C
Published: March 2018

Excessive light to detectors can be very harmful. Too much light, either monochromatic or wide band, can easily destroy photomultiplier tubes (PMTs). Charge-coupled devices (CCDs) cameras, of modern design, are typically made with cut-outs so that saturation beyond several pixels will cause them to shut off. Unfortunately, the detectors in the back of your eyes do not have automatic shut-off mechanisms, and can be easily destroyed with excessive light.

As a review of filters and cubes, keep in mind that the primary job for the excitation filter is to block all light other than the desired band being used to excite the fluorochrome. The primary job of the emission filter is to block the excitation source. If these two optics are chosen correctly and inserted in the beam path, the only light reaching the detector is the fluorescence emission from the fluorochrome. Nothing from the source should make it to the detector. This very weak emission intensity has no chance of harming the detectors. If these two optics are not perfectly matched, the excitation light may reach the detector and cause all sorts of problems.
Digital Image Tips: Adjusting Brightness And Contrast In Micrographs Using Adobe PhotoshopÆ
Authors: Johnson Bradley R
Published: March 2018

Recently on the microscopy list server, a question came up as to how to compensate for charging in SEM micrographs. Several good answers were suggested. Some of them were 1) recoating the sample to prevent the build up of charge on the sample in the first place, and image it again, 2) use an environmental SEM (ESEM) in the “wet” mode to eliminate the charging phenomena, 3) use a different detector, such as a backscattered electron detector, which is much less sensitive to charging phenomena, and 4) apply adjustments to the digital image using software such as Adobe PhotoshopÆ to minimize the effect of the charging problem.
Applicability of Freeze-Fracture and Cryo-TEM to Complex Liquids
Authors: Burns Janet L , Spontak Richard J
Published: March 2018

Traditional methods of sample preparation and analysis in conventional transmission electron microscopy (TEM) are not readily applicable to multicomponent complex liquids which may contain a wealth of microstructural information. Two techniques which facilitate the study of structure in such liquids are freeze-fracture (FF) TEM and cryo-TEM.
Microscopy Reveals Early Neolithic Dentistry
Authors: Carmichael Stephen W
Published: March 2018

Many people dread the visit to their dentist when they have their teeth drilled, but how long has this been going on? The most ancient evidence to date was recently described by Alfredo Coppa, Luca Bondioli, Andrea Cucian, David Frayer, Catherine Jarrige, Jean-François Jarrige, Guivron Quivron, Massimo Rossi, Massimo Vidale, and Roberto Macchiarelli and microscopy provided the convincing proof. The specimens were recovered from Mehrgarh, Pakistan, an area known to be occupied by farmers as long as 9,000 years ago. They identified four females, two males, and three individuals of undetermined gender who had a total of eleven drilled permanent teeth, all from adults. No drilled teeth from children were found. Four of the teeth were from the maxilla and seven from the mandible. All the drilling had been in the first or second molars. This led Coppa et al. to conclude that the drilling was not done for decorative purposes because on these teeth the holes, with or without decorative material inserted into them, would have been hardly visible.
Why Pressure Scales Cause So Much Confusion
Authors: Buonaquisti Anthony D
Published: March 2018

Pressure scales can be extremely confusing to new operators. This is not surprising. To my mind, there are three primary areas of confusion.

Firstly, the pressure of gas inside an instrument changes over many orders of magnitude during pump-down. The change is about 9 orders of magnitude for a traditional Scanning Electron Microscope and about 13 orders of magnitude for an ultra-high vacuum instrument such as a Scanning Auger Microprobe.
Towards Optimal Imaging and Microanalysis in Variable Pressure and Low Voltage SEM
Authors: Griffin Brendan J
Published: March 2018

Image quality of 'secondary electron imaging' has been an ongoing operational issue with the variable pressure range of scanning electron microscopes (VPSEM), including the extended pressure range environmental or SEM. A second question that has received considerable attention concerns charge cancellation on insulators in VPSEM with particular reference to effects of charging on x-ray microanalytical results.
Digital Scanning, Archiving, and Transmitting Electron Micrographs
Authors: Cartwright Joiner
Published: March 2018

The primary responsibility of the clinical electron microscopy laboratory is to produce, and deliver to the pathologist or clinician, high quality ultrastructural images of pathological specimens in a timely manner. In order to facilitate this process, medical EM labs are converting from traditional chemical processing of photographic film and paper to the acquisition and transmission of electron images by computer. Ideally the electron microscope would incorporate a digital camera in the column to collect the images, thus bypassing chemical processing of film and paper altogether. However, due mainly to the high cost of the in-column cameras, many labs continue to use film, but replace the time consuming enlarging/printing in the darkroom with digital techniques at the computer.
"Objects Worthy of Notice" Microscopical Anatomy of Selected Plants Collected by The Lewis & Clark Expedition
Authors: Alden Harry A , Cunningham Roland H , Ryan Kevin , Jantzen Paul T , Dobbins David R
Published: March 2018

Plants that are used for taxonomic research are generally preserved by drying them out while they are being pressed flat for easy storage. This pressed plant material, is placed in a herbarium, in phylogenetic order, based on the species, genus, family and order designations.

Herbaria are essential for the study and verification of plant classification, the study of geographic distributions, and the standardizing of taxonomic nomenclature. Lately, herbarium materials have been utilized in biochemical and genetic studies. The key to these studies is the state of preservation of the plant material. The preservation of the reproductive and vegetative structures (hairs, stomata, cuticle, etc.), internal anatomy (vascular tissue size and arrangement), biochemistry and genetic material is essential to make accurate observations, to collect representative data and answer pertinent research questions.
Correlating Fluorescence Microscopy with Electron Microscopy
Authors: Carmichael Stephen W , Charlesworth Jon
Published: March 2018

The use of fluorescent probes is becoming more and more common in cell biology. It would be useful if we were able to correlate a fluorescent structure with an electron microscopic image. The ability to definitively identify a fluorescent organelle would be very valuable. Recently, Ying Ren, Michael Kruhlak, and David Bazett-Jones devised a clever technique to correlate a structure visualized in the light microscope, even a fluorescing cell, with transmission electron microscopy (TEM).

Two keys to the technique of Ren et al are the use of grids (as used in the TEM) with widely spaced grid bars and the use of Quetol as the embedding resin. The grids allow for cells to be identified between the grid bars, and in turn the bars are used to keep the cell of interest in register throughout the processing for TEM. Quetol resin was used for embedding because of its low auto fluorescence and sectioning properties. The resin also becomes soft and can be cut and easily peeled from glass coverslips when heated to 70°C.
Comments on Cryo High Resolution Scanning Electron Microscopy
Authors: Apkarian Robert P
Published: March 2018

Stephen Carmichael wrote about Cryoelectron Tomography in the May 2003 issue of Microscopy Today. Citing new preparation methods, small cells can be vitrified, observed frozen in the TEM and a series of digital images captured while the specimen is being rotated around the axis perpendicular to the electron beam producing a 3-D tomogram. Gina Sosinski and Maryann Martone wrote about imaging big and messy biological structures using cryo-electron Tomography in the July issue of Microscopy Today. Cryo-HRSEM now also seeks to provide 3-D information approaching the molecular level from frozen hydrated cell and molecular systems. Vitrification procedures for small specimens such as platelets and biomolecules on grids are accomplished by plunge freezing in liquefied etiiane as is done with cryo-TEM procedures. Bulk specimens such as organic hydrogels and tissues are routinely high pressure frozen (HPF) in 3mm gold planchets. Employing an in-lens cryostage, identical to those used in cryo-TEM, cryo-HRSEM provides 3-D high-resolution images because secondary electrons are efficiently collected above the lens in a single scan thus minimizing specimen irradiation.
New Adhesion Mechanism in Giardia: Role of the Ventrolateral Flange in the Attachment of Trophozoites to Rough and Porous Surfaces
Authors: Erlandsen SL , Russo AP , Turner JN
Published: March 2018

The protozoan parasite Giardia, an intestinal flagellate, has evolved an unique attachment organelle called the ventral adhesive disk (VAD). This attachment organelle mediates attachment of the trophozbite to the microviUous border (MVB) of intestinal absorptive cells, and production of lesions via attachment are thought to lead to diarrheal disorder characteristic of giardiasis. The VAD has contractile proteins arranged around it's circumference and it has been suggested that contraction of this area might function like a purse-string suture. The resemblance of the VAD to a suction cup has led to the hypothesis that suction or a negative pressure produced under the VAD by a grasping action might produce the adhesive force regulating attachment. To test whether or not the generation of a negative pressure is necessary for attachment, experiments were designed in which the substratum was fabricated to have an uneven surface, or the substratum was composed of different arrangement of pores.
Membrane Leftovers after Fusion of Vacuoles
Authors: Carmichael Stephen , McNiven Mark
Published: March 2018

In a clever application of time-lapse fluorescence microscopy, Li Wang, Scott Seeley, William Wickner, and Alexey Merz looked to see if there was membrane left over after vacuoles fused within a cell. Specifically, It is not known what happens when two vacuoles come together (this is referred to as “docking” ) and join together as one larger vacuole (“fusion“). For reference, the surfaces of the vacuoJes where they have joined is the “boundary” membrane, the membranes on the outside are the “outside” membranes, and the circular junction of the boundary and outside membranes is the “vertex.“
Photoshop™ Tutorials Selecting ROIs from Brightfield Images
Authors: Sedgewick Jerry
Published: March 2018

This column is, perhaps, a departure from many techniques papers because the accompanying image chosen as “representative“ really is representative, rather than what is seen in many published papers in which the representative image is the one perfect image among hundreds of those that are biologically messy. The image used in this article to illustrate methods is not the best to use when creating regions of interest with Photoshop toots, for it contains elements which make the separation into regions of interest difficult to accomplish without reacquiring the image using better microscope techniques. I'm assuming that an image of this sort CAN bereacquired; if that isn't possible, some head-scratching and, perhaps a shift from a position of absolute accuracy to statistical accuracy might occur, and many would argue, should occur (since the whole matter is statistical anyway). Hopefully the investigator understands that, in some instances, human error can be as confounding as image processing error, except that image processing can create consistency. In other instances, artifacts in the images themselves cart cause too many wrong features to be measured, leaving humans as the best instrument.
When is a Microscope MORE than a Microscope?
Authors: Piano Robert J , Leckenby Jezz
Published: March 2018

Traditionally the field of microscopy has centered on the creation of highly magnified images of things too small to be seen with the eye alone. This was certainly the case with scanning probe microscopy, which burst on to the scene some 15 years ago with dramatic images of individual atoms. We are visual beings and the rapid acceptance of SPM followed directly from its ability to represent physical interactions in an intuitive image format. However, much of the vaiue of SPM today derives from its ability detect and measure a wide variety of specific interactions between its scanning probe and the sample. As the technology continues to mature, emphasis is shifting from its ability to display these signals as images to its ability to quantify and measure them.
Microwave Immunohistochemistry On Mohs Cryostat Sections
Authors: Miller Diane G
Published: March 2018

With the advent of Mohs surgery in the dermatology clinics, making sure the margins are clear of any cancer is of the utmost importance to both patient and dermatopathologist. While the patient is stiil in the surgery suite, immunohistochemistry staining can be done in the laboratory microwave (Pelco microwave with waiter load cooler wattage controller arid temperature probe). The immunohistochemistry procedure takes only 25-30 minutes as compared to the more conventional methods that take 2 hours or more.

The microwave needs to be checked for hot spots using the Pelco #36140 microwave bulb array. Make sure the area in which you are going to put your slides has no hot spots, indicated by no illuminating bulbs. Using a Sigma Diagnostics #H6644 Humid Chamber; place a paper towel in the bottom of the chamber and fill with 1/4 inch of water.
Taking Correlative Microscopy to a New Level
Authors: Carmichael Stephen W
Published: March 2018

We are all familiar with the concept of correlating an image acquired by light microscopy (LM) with one obtained by transmission electron microscopy (TEM). This allows us to take advantage of the “wide angle” view of LM and the high resolution of TEM. Correlative microscopy has been taken to a new level by Alvin Lin and Cynthia Goh who have designed a clever device. This device allows repetitive correlative microscopy between TEM and atomic force microscopy (AFM).
A New Capability for Light Microscopes: Mid infrared Molecular Analysis
Authors: Rein Alan J
Published: March 2018

The merger of molecular spectroscopy with microscopy is certainly not a new concept. Microscope attachments for FT-IR spectrometers have been available for nearly two decades and there are literally thousands of FT-IR spectrometers with these devices currently installed. The vast majority of them are applied to contaminant or forensic oriented problems. As such, the microscopes are often used as sophisticated beam condensers, enabling the spectrometer to focus infrared radiation on the samples that are typically larger than 10 microns.
M&M 2002: Core Facility Management Session Maintaining Major Equipment in the Core Microscopy Facility
Authors: Sherman Debby
Published: March 2018

D. Sherman: This session centers on approaches to maintaining major equipment—primarily electron microscopes. I thought we ought to look at how effective it is to seivice with onsite engineers. So with that I would like to start us out with Pat McGinley from JEOL.

Pat is a long—time JEOL employee. He started out as a service engineer in 1976 and is currently Vice President of Service and a member of the Board of Directors for JEOL USA.
Adding Color to Grayscale Images
Authors: Sedgewick Jerry
Published: March 2018

In the world of fluorescent imaging, the need to colorize grayscale images can be an everyday task. Yet, when all too many of these colorized images go to publication, the results appear to contain undifferentiated blobs of a saturated color, rather than images that contain gradations of color.

While very small objects need to be as bright as possible in order to make these objects apparent (e.g. bacteria under low magnification), and while too many push the gain on photomultiplier tubes in order to top grayscale values off at 255 (on an 8-bit range) in order to show unquestionable colocalization, only the former can be defended on the basis of revealing lost features.
Sub-Ångstrom Resolution
Authors: Carmichael Stephen W
Published: March 2018

Antoni van Leeuwenhoek showed the practical use of the light microscope in the 1600s after much effort to improve the quality of optical lenses. Pioneering microscopists such as Ernst Abbé, Hermann Ludwig Ferdinand von Helmholtz, Lord John Rayleigh, Carl Zeiss, and August Köhler then brought us to the brink of optimal performance of the light microscope approximately a century ago, Ernst Ruska and Max Knoll showed in the 1930s that high-energy electrons could be used in place of light, giving greatly improved resolution. In the 1970's Albert Crewe and co-workers developed the scanning transmission electron microscope (STEM) and used the Z-contrast method to improve resolution in the electron microscope by about a factor of two. The scanning probe (nonoptical) microscopes aside, there hasn't been a significant advance in spatial resolution since.
Cellulose Acetate Replication of Plant Surfaces for SEM
Authors: Ahlstrand Gib
Published: March 2018

Replicas of botanical surfaces are sometimes preferred for imaging in the SEM, instead of original surfaces, in cases where it is not possible or desirable, for a variety of reasons, to prepare originais using conventional techniques (chemical fixation followed by dehydration and critical point drying, freeze drying, or cryo-SEM). Samples may be rare (herbarium specimens), or impossible to bring into the lab for processing, and field replication may be the only alternative.
Is An Atomic Microscope In Our Future?
Authors: Carmichael Stephen W
Published: March 2018

When you read the header to this article, you probably thought I made a mistake. Doesn't he mean atomic force microscope, the familiar AFM? And isn't that microscope in our present, not in our future? Well, I'm not confused. The reference is to a beam of atoms that some day may be used in an atomic microscope, just like a beam of electrons is used in an electron microscope. It would be even more accurate to refer to an “atomic de Broglie microscope,” but that's a rather awkward label.
Part 3: Justification Of Cost, Cost Recovery: Electronic Bookkeeping And Billing
Authors: Sherman Debby
Published: March 2018

This article is the third of a series transcribed from the discussion taped during the Facility Management session at M&M 2000. it is printed with permission of the Microscopy Society of America, Bulleted paragraphs indicate comments by individuals attending the session.

D. Sherman: I am sure that there are many different schemes to try to recoup some costs in facilities we manage. Probably very few of us are really happy with the schemes we have at present. Hopefully this discussion will provide us with information that will be useful in refining the financial management of our different facilities.
A Pump For Liquid Nitrogen
Authors: Couger Gordon
Published: March 2018

On the Microscopy ListServer, a thread came up about problems with safety when loading cold traps from ladders. Working from a ladder is not a very safe proposition and being up there with a Dewar full of liquid nitrogen brings the safety officer to attention.

An alternative to trying to climb a ladder with a Dewar flask and pour the liquid nitrogen into the trap would be to have a pump for the liquid nitrogen in a Dewar flask on the ground that could be controlled from the top of a ladder.
A Fool-Proof Method For Mounting Serial Sections On Single Hole Grids
Authors: Sherman Debbie
Published: March 2018

I did serial sectioning for years on large single hole grids using a very simple technique that made the potential problems of film thickness, wrinkles and section loss very minor. I was not the original developer of the method and do not remember who originally gave it to me. It goes as follows:

1) Have your machine shop cut some thin pieces of Plexiglas into the size of glass slides. At one end, drill about a dozen holes, roughly 5 mm in diameter, in an area about the size of a formvar film cast on glass slides. These slides will serve as your template for holding your films.
Right at Your Fingertips
Authors: Carmichael Stephen W
Published: March 2018

They're right at your fingertips, but how often do you consider the microscopic anatomy of your fingernails? How is their form fitted to function? Primates, including humans, use fingernails to maintain the anatomic integrity at the distal end of our phalanges, which often serves as the leading edge of our physical sensory apparatus. The nails serve as a stiff backing to the soft pads of our fingers, helping to improve the grip and sensitivity by allowing the pad to “push back” on the object we are touching. Nails also serve specific functions in maneuvering within cracks, scratching, and fighting.

The gross structure of nails helps to resist upward bending forces that are encountered in these functions. The convex curvature contributes, just like a curved piece of paper has more stiffness than a flat sheet. The composition of nails is also suitable. As with the outer layer of skin, and the structure of hair, nails are also composed of keratin.
Comments on the Use of Digital Filters
Authors: Walck Scott D
Published: March 2018

At the Microscopy and Microanalysis 2003 meeting, a member of the audience in one talk sharply criticized a speaker of a talk for his use of a Savitsky-Golay (S-G) digital filter for smoothing Electron Energy Loss Spectroscopy (EELS) data. The statement was made that the digital filter would decrease the resolution of the peak, i.e. widen the width, and that all digital filters do that, including the Top Hat filter. In support of this statement, he said to consider what would happen if the filter were applied to a Dirac delta function. I knew that his argument was not correct, but I didn't think of the reason until later. This interchange was on my mind because I was familiar with both of these filters due to implementing both the Top Hat and the Savitsky-Golay filters into my “Beerware” program, EELS-PLOT.
Gradient Reference Specimens for Advanced Scanned Probe Microscopy
Authors: Julthongpiput Duangrut , Fasolka Michael J , Amis Eric J
Published: March 2018

Scanned Probe Microscopy (SPM) techniques are attractive because they provide easily acquired micrographs that map specimen properties with nanometer scale resolution. SPM micrographs can be collected without the use of high vacuum (as opposed to many electron microscopies). Moreover, SPM methods allow in-situ imaging of specimens in a variety of environments, including under liquids and at higher temperatures. However, from a metrology perspective, the great promise of SPM must be balanced by the fact that SPM techniques generally provide qualitative data unless supplementary actions are taken. That is, quantification of SPM image contrast is difficult since it depends highly upon probe characteristics, probe/ sample interactions (both of which can be difficult Eo gauge), and instrument calibration.
Surveillance of Bioterrorism Agents: Considerations for EM Laboratories
Authors: Miller Sara E
Published: March 2018

Biowarfare was first documented in the eighteenth century during the French and Indian War when the British distributed smallpox-contaminated blankets to the American Indians. Smallpox is considered a likely agent even today because the USSR was known to have produced and stockpiled large amounts of the virus even after signing the 1972 treaty prohibiting such production. Because of the large number of workers involved and the poor economy, the security of these stockpiles is unclear [1, txtwriler.com/Backgrounders/Bioterrorism/bioterrar4.html]. Since the terrorist attacks in the United States in 2001, world attention has been drawn to terrorism and potential release of dangerous biological organisms. Considerable efforts are being made to establish methods for rapidly recognizing these agents. Numerous electron microscopy (EM) laboratories have been approached to join rapid response teams for the detection of viral agents. However, several issues should be carefully considered before an EM laboratory agrees to participate in surveillance.
Assessing Microalgal Morphology from Century-Old Herbarium Sheets using SEM
Authors: Linton E W , Farmer M A , Triemer R E
Published: March 2018

Traditionally, type specimens have not been deposited for most unicellular algae. There are few known holotypes and those that are available are often of limited use. Samples from taxa described before 1900 commonly consist of materials dried down on herbarium sheets or mica. Dried algal samples can be rehydrated, but preservation is very poor and little structure can be determined from them. Whether wet or dry, the amount of information that can be derived from such samples using conventional light microscopy is limited.
Microscopy in Ecuador
Authors: Eades Alwyn
Published: March 2018

The present situation in Ecuador is not a happy one. You would think that this ought not to be the case. There are seven electron microscopes in the country and all of them are in working order (although with problems - see below), so why then are things not good. The problem begins with geography. Unlike most smaller countries, Ecuador is not dominated by a single large city. There are two major cities, locked in a continuous rivalry: Quito, the capital, is in the mountains, and Guayaquil, the larger city, is on the coast. They are about seven hours apart by road. Both cities have electron microscopes. Worse, however, is the fact that, in each city, the microscopes are in two different locations - making a total of four microscopy centers. This is too many and Ecuador can not support them all effectively.
Making Replicas of Surfaces for TEM and SEM
Authors: Mager Mary
Published: March 2018

Before SEMs were invented and when they were still of relatively poor resolution, one way to see the fine details of a sample surface was to prepare an electron-transparent replica of the sample surface and view it in a TEM. The carbon-coated surface of the sample was shadowed with a heavy metal to make a replica that mimicked the topography of the original surface, in a sample that could be viewed in the TEM.

We have found some value in this old technique; to examine second-phase particles freed from the metal matrix for EDX, diffraction, and morphology studies—while preserving the original position and distribution of the particles, historically called “extraction replication.”
An Electron Optical Achromat
Authors: Carmichael Stephen W
Published: March 2018

Spherical and chromatic aberrations have been the bane of optical lenses ever since they were first ground from a piece of glass. As light travels through a convex (converging) lens, the rays at the center of the optical axis are refracted (bent) less than the peripheral rays, so that the central rays are focused behind the peripheral rays. This is the essence of spherical aberration. Light of differing wavelengths (colors) interact differently with the lens so that longer wavelengths (red) are focused behind shorter wavelengths (blue). This is chromatic aberration. In the early days of light microscopy, these two inherent flaws seriously limited the quality of images.
Pretreating Epoxy Thin Sections With Sodium Periodate Prior To Immunostaining
Authors: Crowley Hildegard H
Published: March 2018

Pretreatment of epoxy thin sections with strong oxidizing agents such as hydrogen peroxide, sodium methoxide, and sodium m-metaperiodate facilities the location of antigens with immunostaining procedures. Etching, or pretreatment, of sections unmasks antigenic sites on glutaraldehyde fixed and postosmicated tissue, partially removes osmium bonds, temporarily decreases the hydrophobicity of the epoxy surface layer of the section, reduces the electron density of the tissue and increases resistance to heavy rnetai poststaining.
High-Resolution Imaging with Atomic Force Microscopy
Authors: Magonov Sergei
Published: March 2018

The invention of scanning tunneling microscopy (STM) in 1982 revolutionized surface analysis by providing atomic-scale surface imaging of conducting and semiconducting materials. Shortly after that, atomic force microscopy (AFM) was introduced as an accessory of STM for high-resolution imaging of surfaces independent of their conductivity. Mechanical force interactions between a sharp tip placed at one end of a micro fabricated cantilever and a sample surface were employed for imaging in this method. In the past decade, AFM has developed into a leading scanning probe technique applied in many fields of fundamental and industrial research. The progress of AFM has been made possible by implementation of an optical level detection scheme, which allows precise measuring of the cantilever deflection caused by the tip-sample forces, by mass microfabrication of probes consisting of cantilevers, and by developments of oscillatory imaging modes, particularly, Tapping ModeTM.
Endogenous Fluorescence Identifies Dead Cells In Plants
Authors: Ryerse Jan S , Feng Paul C C , Sammons R Douglas
Published: March 2018

Various fluorescent stains and vital dyes have been used to identify dead cells in animal tissues and celi lines. In plants, fluorescein diacetate and propidium iodide have been used to label nuclei and to identify necrotic cells in plant protoplasts and 4,6-diamidino-2-phenylindole (DAPI) has been used to mark senescing cells in sections of roots. However, these dyes may be problematic when used with intact plant tissue with well-developed cells walls which may impede dye penetration. Endogenous fluorescence has been used to identify dead cells in intact and sectioned plant tissues. Published procedures typically employ ultraviolet (UV) excitation wavelengths of 340-380 nm and emission wavelengths of 400- 425 nm, thus requiring a UV filter set.
Fixing and Embedding Protocol for Octocorals and Their Sclerites
Authors: Bray Elizabeth
Published: March 2018

Many organisms are mostly soft tissue, with hard bits embedded within them. This includes many invertebrates, and vertebrates with calcified areas in their tissues. This procedure works well for soft-bodied corals which have hard pieces of calcium carbonate (sclerites) embedded in their tissues. It should also work for similar soft-tissue/calcified bits in other animals.
Physics of Impregnation
Authors: Nelson J Roy
Published: March 2018

There appears to be some confusion as to how materials are impregnated or dried. Without getting into the exciting mathematical details best suited for persons who second language is Greek, I offer the following short explanation as to how materials are impregnated or dried.

If the object is porous, the porosity is described in terms of macropores (>50 nm), mesopores (50 - 2 nm), and micropores (2 - 0.8 nm). These three size classes of pores represent different flow mechanisms for the impregnation of porous materials. Solvent penetration of a non-porous particle by imbibing is similar mathematically to solvent penetration of micropores although the actual mechanism is quite different.
An Affordable Digital Micrography to Interest Children (Of all Ages) in Science
Authors: Lazaroff Norman
Published: March 2018

Inexpensive fixed-focus digital cameras can be used with homemade lens attachments to obtain good quality close-up images and photomicrographs. The current availability of inexpensive digital cameras with resolutions of 1024 x 768 pixels or better is brought about by technical advance and the continual introduction of competing new models and accessories. The digital camera which I use costs less than $150 now

at a liquidation sale or internet auction, and the price continues to decrease. Although more expensive digital cameras are great to have, their advanced features are not necessary for introducing young students to the digital revolution in photography and for exploring the microscopic world.
BioFilm©
Authors: van Hook Lee
Published: March 2018

Photographic chemistry has long been a complex combination of inorganic metal-halide and organic chemistries and polymer science. We at the P.R.I, have managed to add biology to this stew.

Silver has long been known as a toxicelement to microbes, and so used as a drug to kill bacteria. But there are bacteria that can survive in environments high in silver. It has been reported that some bacteria can accumulate up to 25% of their dry biomass as silver, and so acquire resistance to the toxic effects of silver. Also, a recent article in the Proc. Nat. Acad.Sci. describes the intracellular deposition of silver grains in such shapes as hexagons and equilateral triangles.
A Comment on using FLIM with FRET
Authors: Garsha Karl
Published: March 2018

Depending on the nature of the study and what sort of information one is trying to gather through the use of FRET, FLIM has some compelling advantages in certain situations, and can provide a quantitative evaluation of the donor, acceptor and FRET pair stoichiometry. It does require access to specialized equipment and software. Different approaches to FLIM data acquisition have different strengths and weaknesses. For dynamic studies requiring high time resolution, FLIM acquisition times can fall well short of ideal.

If a yes/no answer to whether FRET is occurring is all that is required, then the polarization anisotropy of the acceptor can be used to determine FRET between fluorescent proteins (Rizzo and Piston, 2005). This is a relatively simple and robust method for confirming the presence/absence of FRET.
Microscopic Artifacts In The History Of Biology
Authors: Davis Alan Eugene
Published: March 2018

I am posting a summary of responses to my request to the Microscopy Listserver on 3 December 2001, for Information about any roles microscopic artifacts may have played in the history of biology. I posted my own experience regarding Sidney Hickson's description of reproductive events in Miliepora spp. (A copy of my somewhat lengthy post is enclosed at the end of this summary.)

To be fair to Sidney Hickson, who drew and described the incredible, imagined sequence of reproductive events in Miliepora spp. as mentioned in my original, I believe that he did print a retraction of the findings in that paper.
Tips on Examining Metal-Coated Glass Beads for Cracks
Authors: Twilley John
Published: March 2018

I once had a problem looking for cracks in a graphite coating on quartz fibers. This problem is a good example of the general case of defining visible light microscopy inspection criteria. Since specimen lighting may influence critically what one can see. The answer to the question depends a bit on the size of the crack and the opacity and reflectivity of the oxide coated surface. First insure that the microscope has a lighting set up that allows one to dependably see the cracks before worrying about a camera. Most of the digital cameras that can be used with a microscope would probably be adequate to recording the crack, once the viewing situation is set up.
Some Thoughts on Vibrations in EM Laboratories
Authors: Garratt-Reed Anthony J
Published: March 2018

Sometimes a scientist or laboratory manager has the opportunity to be involved in the design of a new building for housing sensitive instruments, such as electron microscopes. Unfortunately, few of us are trained in the necessary skills, and “learning the hard way”, by making mistakes, is not really satisfactory, given the expected lifetime of the resulting structure. It has to “right first time”!

Vibration, sound and electromagnetic interference are all huge unknowns, when it comes to microscope performance. Each manufacturer will provide you with a set of specifications which are “required” for their instrument to meet its guaranteed performance criteria.
Resolution Confusion
Authors: Sedgewick Jerry
Published: March 2018

The most persistent misconception made in digital imaging among those who use our core facility involves the understanding of digital resolution; and the greatest mistakes result from a mis-use of the “Image Size” dialogue box in Adobe Photoshop. Add to that, an intractable desire to use Microsoft PowerPoint and to somehow make Photoshop and PowerPoint agree about the nature of images that open in both programs, weighted toward the miserable resolutions and compression required by PowerPoint, changes in original data become as common as dandelions on a lawn. Yet, changes in data that result from increasing or, more commonly, decreasing pixels (what is called re-sampling), can be avoided.

Resolution, as many of us have learned, is the ability to discriminate between two points in space, a phenomenon made easier by high contrast objects versus those that are low in contrast.
Calibration of Electron Microscopes: How to do this, how often, pit-falls and problems
Authors: Postek Michael T
Published: March 2018

SEM Instrument calibration is something most people don't always realize they need to do. Images look about right so the magnification seems close enough. Today, measurements are being done in specialized scanned beam metrology instruments everyday, so correct magnification calibration is very important. Calibration is probably more acknowledged from the point of the transmission electron microscope than for the scanning microscope. But, it still needs to be done. Today, people can buy SEM's that cost around $100,000 (refurbished ones somewhat less) to $2.5M with one instrument model from one manufacturer costing about $8M. Believe it or not, often the instrument buyer thinks that as soon as they get the instrument into their facility (since it is new and they paid a lot of money for it) that it is perfect and everything is correct.
Internet-Based Administration of Shared Instruments with Facility Online Manager
Authors: Li Shu-You , Dravid Vinayak P
Published: March 2018

Resource sharing has become an absolute necessity for modern scientific research because of the increasing expense and complexity of instruments, and the ever changing funding paradigm which often requires sharing of major instrumentation resource across multiple disciplines. Many universities and even large companies have set up centralized facilities to serve researchers from different departments, divisions and units to minimize expenses and maximizing usage.

Just in the materials research area alone, it is estimated that there are more than 500 mid-size facilities existing nationwide, as reported in 2005 by the Committee on Smaller Facilities of National Research Council. Resource sharing is also common in large research groups, between Principal Investigators, as well as in corporate/industrial laboratories.
Andrew Paul Leonard: Capturing the Cover of Time Magazine
Authors: Stevens Lise Millay
Published: March 2018

If beauty is in the eye of the beholder, then microscopic photographer Andrew Paul Leonard might have a lot to explain. After all, touting the aesthetic merits of an eosinophil (picture that let alone pronounce it) hardly brings to mind the rugged splendor of Ansel Adam's “El Capitan” or the quirky languidness of Richard Avedon's “Dovima with Elephants.” Yet, one look at these starkly detailed images reveals a textured, beautiful world reminiscent of the fancy of Yellow Submarine and the graphic logic of M.C.Escher.
Streamlining the Modern Lab
Authors: Subramanian Radhika
Published: March 2018

Imagine what a researcher 50 years ago would think of the technology available in today's modern research labs, where the ability to photograph and videotape live cell images in high resolution has spurred numerous advances in the sciences. Additionally, technology's shift from analog to digital image acquisition has enhanced scientific collaboration and analysis abilities, perhaps in ways our predecessors could never have imagined. However, the massive quantities of data that result from these image acquisition techniques, and subsequent storage requirements, have created unforeseen challenges. While we describe life science applications, the methods described in this article are equally applicable in physical sciences laboratories.