bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Cartilage and Bone During Formation of Phalanges by Tissue Engineering
Authors: Landis W , Isogai N , Vacanti J 
Published: July 2020

Abstract
Treatment of human congenital malformations and for loss of tissue or organ function is a serious clinical concern, frequently supported by harvesting autogenous tissue for reconstructive surgery. This paper summarizes an alternate approach through novel tissue engineering methods and describes cell-polymer composites that could be fundamental in developing advances for digit and joint replacement. The work utilizes cells from different sources transplanted on biodegradable polymer matrices to form structures with defined shape, morphological features and composition resembling those of human phalanges and intact joints.
Polyglycolic acids (PGA) fibers (Albany International, Mansfield, MA) 15 μm in diameter were used as a mesh support for cell attachment and matrix formation. For cartilage and tendon cells, PGA alone served as a flat surface without specific shape. For bone cells, PGA was copolymerized with poly-L-lactic acid (PLLA) (Polysciences, Warrington, PA) and shaped after a human phalanx molded from cadaveric distal and middle phalangeal bones. Polymers were sterilized with ethylene oxide before use.
Elastin-Mimetic Covalently Crosslinked Synthetic Protein Networks: Solvent and Temperature Dependent Morphological Features Imaged by SEM
Authors: McMillan R A , Apkarian R P , Conticello V P 
Published: July 2020

Abstract
Gel networks that mimic the properties of naturally occurring mammalian elastin have been synthesized for the development of novel biomaterials. Hydrogels with controllable and predictable mechanical properties are pursued for use in drug encapsulation and delivery systems, as scaffolds for tissue engineering and for the development of prosthetic implantable devices. The techniques of genetic engineering and microbial expression have been used to produce a 90KD recombinant protein based starting material that was polymerized into a solvent swollen gel network by the introduction of covalent bifunctional crosslinks at regularly spaced lysyl residues. SEM methods have been used to describe solvent and temperature dependent structural features.
The polypeptide precursor to the elastin-mimetic gels, poly[(VPGVG)4VPGKG], was obtained through bacterial expression (pET system) of an oligomerized gene coding for tandem repeats of the monomer. Gel networks were formed by crosslinking the protein with a bifunctional NHS-ester in both water and anhydrous DMSO. For conventional below-lens SEM studies, samples were dehydrated in an ethanol gradient, critical point dried from CO2(l), mounted on stubs with carbon tape and sputter coated with a 4-6 nm layer of Au/Pd.
Use of Single Particle Methods to Reconstruct Helical Reca and F-Actin Filaments
Authors: Egelman EH , Orlova A , Yu X 
Published: July 2020

Abstract
RecA has been the most intensively studied enzyme in homologous genetic recombination. Actin is one of the most abundant and conserved eukaryotic proteins, and is central to muscle contraction, cell motility, and the control of cell shape. Both form helical filaments, and we have been studying both for many years, primarily using negatively stained specimens. We and others have used cryo-EM of frozen-hydrated RecA and F-actin samples, but the resolution obtained by this method is actually worse than that obtained from negatively stained specimens. The criterion for resolution that we have used is the match with an atomic model for F-actin, since this is a much better standard than statistical measures such as Fourier ring correlations or phase residuals, which can only measure the internal consistency of the data.
F-actin is a flexible structure, both with respect to bending and torsional motions of subunits. The RecA filament is 10 times more flexible than F-actin. The bending of RecA and F-actin require that images be straightened, and the ability of a user to fit a spline function to the filament axis limits the precision of the method. The method is only valid for small perturbations from a rigid rod, and thus will introduce artifacts for real filaments. In order to straighten filament images obtained in ice, one needs sufficient contrast (obtained by a large defocus) to be able to apply such algorithms. The torsional motions of the actin subunits, which may be as large as 5-6° per subunit, limit the resolution that can be obtained as one averages over long lengths.
Imaging Considerations for Cryo-Tomography of Organelles and Whole Cells at High Accelerating Voltage
Authors: Marko M , Hsieh C-E , Mannella CA , McEwen BF 
Published: July 2020

Abstract
Cryo-electron tomography can be used to obtain highly-detailed 3-D reconstructions of micrometer-sized biological structures which are unfixed, unstained and embedded in vitreous ice. Important practical considerations for acquiring the requisite tilt-series images are the choice of electron dose and defocus value, and the effects of contamination and ice thickness.
It is essential to reduce the total dose enough to prevent excessive ice radiolysis and damage to the specimen itself. To reduce the dose, a sensitive cooled CCD camera and microscope automation system are all but required. Because the specimens are thick, it is advantageous to use a high accelerating voltage, and/or energy filtering to reduce inelastic scattering. At high accelerating voltage, it is important to keep the dose high enough so that the signal is above the “scintillator noise” generated by the interaction of the high-energy electrons with the phosphor scintillator of the CCD camera. Initial test reconstructions indicate that scintillator noise, unlike electron shot noise, cannot be mitigated using dose fractionation. Fortunately, we find that large objects embedded in a thick (ca. 1 μm) vitrified ice layer are more resistant to beam damage (as well as charging) compared to smaller objects embedded in ice 100-200nm thick.
FESEM and Cryo-Techniques in the Study of Marine Diatom A. Longipes
Authors: Chen Ya , Wang Yan , Gretz Michael 
Published: July 2020

Abstract
Field emission scanning electron microscopy (FESEM) provides a direct view of a biological sample with high spacial resolution. Combining FESEM with cryo-techniques, macromolecular structures have been obtained from single SEM image successfully (Hermann & Müller, 1992; Chen et al., 1995, 1997). This protocol is now applied to study the extracellular matrix of the diatom A. longipes.
Stalk, which is originated from the terminal region of diatom cells, consists of 3 regions: a surfaceadhered pad, a shaft that separates the cell from the substratum, and a ring-like collar (Fig. 1). Investigating the structure and function of the stalk will help to understand the adhesion and interaction of diatom with the external environment. The extracellular matrix of diatom is highly hydrated, it is difficult to preserve them for EM. It will be easily extracted and collapse during specimen preparation (e.g. fixation, dehydration). In order to preserver the stalk structures close to their native condition and observer them with high fidelity, cryo-preparation techniques are implemented. Cryo-technique is widely used in the plant biology. However, to our knowledge, it has not been used in the diatom research.
Nuclear Envelope and Nuclear Pore Complex Dynamjcs in vitro, Visualised by FEISEM
Authors: Allen TD , Cotter LA , Cronshaw JM , Wilson KL , Goldberg MW 
Published: July 2020

Abstract
As the defining structure in eukaryote cells, the nuclear envelope is completely dismantled and reformed within an hour or so at each cell division (open mitosis). In yeast and some insect tissues, closed mitosis occurs, in which the nuclear envelope is maintained largely intact throughout chromosome separation. Use of cell free systems has allows us access to the mechanisms of cell division and NE dynamics in vitro by FEISEM (Field Emission In Lens Scanning Electron Microscopy. We have used demembranated Xenopus sperm heads as a source of DNA, which is incubated in an extract of Xenopus egg cytoplasm, where it becomes assembled into a normal nucleus with functional nuclear envelope (1-4). DNA replication proceeds under normal cell cycle controls, followed by an in vitro mitosis in suitable conditions. The cytoplasmic extract can be separated into membrane and soluble fractions that can be supplemented with, or depleted of, specific proteins. Inhibitors and other effectors can be.added to modulate both assembly and transport (5). Using the lectin WGA we have depleted Xenopus cytoplasmic extract of the major nucleoporins, CAN, Nup 98 and p62 and their associated proteins, whose removal effectively inhibits three aspects of nuclear formation, namely NPC formation, nuclear growth, and the reorganisation of the DNA in the depleted nuclei. Adding back these eluted nucleoporins restores normality with respect to nuclear growth, DNA reorganisation and NPC assembly. Current work involves purification of complexes containing these proteins by HPLC to allow add back of the complexes singly and in combination, to characterise their individual roles in NPC assembly, structure and transport (Figures 1,2,3).
High-Pressure Frozen Mouse Lung: Cryo Scanning Electron Microscopy
Authors: Bastacky Jacob , Walther Paul , Goerke Jon , Clausnitzer Eve , Lee Charles , Müller Martin 
Published: July 2020

Abstract
High-pressure facilitates freezing of biological specimens: pressurizing to 2000 bar before cooling retards growth and reduces size of ice crystals in the specimen. Although the lung is 80% air and is generally difficult to freeze, we report here good cellular ultrastructure in high-pressure frozen lung when: 1) the lung is allowed to collapse (empty of air) prior to sampling, or 2) air-filled lung is allowed to compress during pressurization in the high-pressure freezer prior to freezing or 3) airspaces are filled with relatively incompressible fluorocarbon liquid.
Small Balb mice (28-30g) were anaesthetized and ventilated via endotracheal tube. The chest was opened and a 2mm diameter disk of lung at the thin anterior margin of the right lung was clamped between two aluminum tophats (200μm wells), sealing in air. In other experiments, the lung was allowed to collapse to 0 cm water transpulmonary pressure prior to clamping. In the third series of experiments, air was gradually replaced with fluorocarbon liquid (FC5312, 3M, Minneapolis MN) and the lung inflated with liquid to functional residual capacity. The top hat assembly containing the sealed lung was transferred to the high-pressure freezer (HPM 010, Bal-Tec, Balzers, Lichtenstein) where they were pressurized and frozen.
Time-Dependent Structural Changes in Porcine Stratum Corneum Following an Electroporating Pulse
Authors: Gallo SA , Sen A , Hensen ML , Chow B , Hui SW 
Published: July 2020

Abstract
Electroporation has been used to permeabilize the skin to enhance the transdermal delivery of molecules. The mechanism is generally believed to be based on the temporary breakdown and permeabilization of the stratum corneum by the applied pulsed electric field. The kinetics of recovery are believed to be in the millisecond range. However, no structural changes within this time scale have been observed.
We studied the morphological changes to heat stripped porcine stratum corneum following an electroporating pulse by time-resolved freeze fracture electron microscopy. Pulses at a supraelectroporation threshold of 80 volts and 300 μsec were applied across the stratum corneum with a pair of copper plate electrodes, which also served as cooling contacts. The pulse timing was accomplished through the time-of-flight of a trigger bar attached to the plunging rod holding the sample.. The trigger bar passes through two optical switches. As the sample was propelled towards the liquid propane coolant container, the first switch triggered the pulse generator and the second marked the precise time at which the sample was frozen. The sample was pulsed at set times of 0.5 ms, 12ms, 5 sec, 60 sec, and 300 sec before freezing.
Bugscope: a Sustainable Web-Based Telemicroscopy Project for K-12 Classrooms
Authors: Potter CS , Carragher B , Ceperley M , Conway C , Grosser B , Hanlon J , Hoyer C , Kisseberth N , Robinson S , Sapp J , Soskin P , Stone D , Thakkar U , Weber D 
Published: July 2020

Abstract
Bugscope is a new educational project in the World Wide Laboratory. The World Wide Laboratory provides Web browser based control of scientific imaging instrumentation using the Internet [1]. Providing K-12 classrooms with web based remote access to sophisticated scientific imaging systems was initially demonstrated by us in 1996 in the Chickscope project [2,3]. Chickscope allowed students to study chicken embryo development using a remotely controlled magnetic resonance imaging (MRI) system from their classrooms. While the Chickscope project was highly successful, the resources required to provide operational support for the remote imaging aspects of the project for a small number of classrooms were enormous and the project was not sustainable. The Bugscope project builds on the methods developed and the lessons learned from the Chickscope project. The primary goal is to demonstrate that relatively low cost, sustainable access to an environmental scanning electron microscope (ESEM) can be made available to K-12 classrooms to examine arthropods.
Methods: Classrooms use a standard web browser over the Internet to control and acquire images from a Philips XL-30FEG ESEM. The architecture to support remote acquisition is shown in fig. 1. The client/server control architecture for the ESEM remote control server is based on the emScope control library [4].
From 3-D Light Microscopic Images to Quantitative Insight
Authors: Roysam B , Can A , Shen H , Al-Kofahi K , Turner JN 
Published: July 2020

Abstract
This presentation will describe a common core set of widely applicable image analysis techniques for automated quantitative analysis of volumetric microscope image data. Volumetric (as distinct from stereoscopic) three-dimensional (3-D) Microscopy is a rapidly maturing field offering the ability to image thick (compared to the depth of field) specimens using a variety of instrumentation techniques, and producing arrays of brightness values in three spatial dimensions. Also well developed are methods to correct the acquired images for a variety of physical effects including blur and attenuation.
Commonly, what is of interest is the best-possible visualization of thick specimens. The next step, increasingly being considered in view of growing computational resources, and progress in image analysis techniques, seeks to quantify many of the processes and effects being studied. In some mainstream fields, such quantitation is essential. For instance, various assays for substance testing in pharmaceutical and chemical industries involve quantitative end points. As an illustration, the Draize assay for ocular irritancy testing of drugs and biochemical products for human use requires counting of live and dead cells that stain differently. Another example is the mouse lymphoma test that requires a 3-D counting of bacterial colonies. Neurobiological assays require morphometry, as well as quantification of changes in neurons as a function of time and various applied stimuli such as drugs, heat, and radiation. Angiogenesis assays require quantification of changes in vascular morphometry. Computerized image analysis is a powerful tool for extracting quantitative data from 3-D images for statistical analysis.
Scanning Electron Microscopy at a Distance: A Nuts-and-Bolts Discussion
Authors: Barlow S B 
Published: July 2020

Abstract
Not everyone can afford to own and operate a scanning electron microscope. Everyone can, however, access images and instruments in a variety of ways, depending on the objective. Remote access capability is a result of recent developments in desktop computers, software, and the World Wide Web. Some of these developments and some suggestions for future resource development will be reviewed here.
With the arrival of commercially available, digitally controlled SEMs in the 1980s, it became possible to control microscope operation with a desktop computer and the appropriate software. By connecting a desktop computer to the microscope via the Internet or dedicated data lines such as ATMs, remote control of microscopes became a reality. Although analog microscopes are not as readily controllable over the Internet, their video data stream is easily captured, digitized, and dispatched to remote observers using low-cost consumer video conferencing programs. These approaches enable users at one location to observe their samples in a microscope located elsewhere. However, transfer rates over the Internet fluctuate wildly depending on network traffic, at times making remote access or control almost impossible. Dedicated data lines ensure a relatively stable transfer rate, but at a significantly higher cost.
50 Years of EPMA / Today’s and Tomorrow’s Instruments.
Authors: Conty C 
Published: July 2020

Abstract
The Sepia years. 1951. Castaing’s thesis(1) : Genesis of a Non-Destructive and truly Quantitative Microanalysis method. 1958. The beginning of commercial microprobes : Early instruments had no computers and were lacking special analyzing crystals, but overall they were well designed. Modern features we are familiar with today, such as light element analysis, field emission gun, Energy Dispersive analysis, analysis of insulated material and scanning analysis, although not widely implemented, were discussed in scientific reviews even then(2) 1963. One of my early personal experience: The daring job of obtaining Castaing’s acceptance for his Cameca-buih EPMA at the University of Paris/Orsay.
From early models to present microprobes Early microprobes were developed, after WWII, in a world driven by metallurgy. They had few WD spectrometers, usually at low take off angle. However, the need for light element analysis and the fast growing use of EPMA in geology have sent the manufacturers back to the drawing board. Why ? The design of modern microprobes was a compromise between light optics, electron optics and higher take off angle X-ray spectrometry. There were three possible designs of X-ray path geometry : X-rays through the(final) lens, X-rays through the gap of the lens, X-rays outside the lens, hence three suppliers arose based on these concepts.
Present and future EPMA improvements. As in the initial era of EPMA newer applications will point the direction in which the electron microprobe of the future should evolve.
Minimally Invasive (ENERGY) Dispersive Analytical Spectroscopy (MIDAS). The Golden Touch for In-Situ X-Ray Microanalysis of Bulk Bio-Organic Samples
Authors: Echlin Patrick 
Published: July 2020

Abstract
The matrix of bio-organic samples is composed primarily of carbon, hydrogen, oxygen and nitrogen. Dispersed within this matrix there is a wide spectrum of other elements whose local concentration can be measured in situ by x-ray spectroscopy. The analysis continues to present a challenge because most samples are highly hydrated, beam sensitive and of low density. In light of these restrictions there is only one sensible approach to the use of an analytical procedure which depends on the intereaction of high energy beam electrons with a labile specimen. Samples must be prepared by the least invasive preparative procedure and irradiated with the minimum amount of energy in order to obtain the maximun amount of chemical information. Low temperature sample preparation and low voltage electron beam instruments are central to these processes. By way of example, a brief description will be given of an on-going biological investigation which makes full use of these processes.
Quantitative Elemental Analysis of Heavy Metal Exposed Cells of Synechococcus Leopoliensis Using Regular and Overplus Cells: An Energy Disspersive X-Ray Spectroscopy Study
Authors: Goldberg JJ , Jensen TE 
Published: July 2020

Abstract
It has previously been shown that microbial polyphosphate bodies are the main sites of metal sequestration. In our present study, we have exposed Synechococcus leopoliensis, grown to log phase and to overplus phase, to five different heavy metals, Al, Cu, Cd, Pb, and Zn, independently. The cells were analyzed using the STEM mode of a transmission electron microscope in conjunction with a PGT IMIX energy dispersive x-ray spectrometer.
Cells of Synechococcus leopoliensis were grown for two weeks at 21°C on a 12-hour light/dark cycle in modified Fizgerald’s medium The second cell type were the overplus cells, which were grown as previously described. The cells were exposed to 100PPM of each metal for two hours, then were fixed and embedded in EPON according to Luff’s procedure.
For x-ray analysis, cells of interest were first located using the TEM mode. The microscope was then switched to the STEM mode.
Observing the Chemical State of Elements With Z=21 To 28 From L Alpha1 To L L Ratios With Energy Dispersive Spectroscopy (EDS)
Authors: Sandborg A , Anderhalt R 
Published: July 2020

Abstract
It is well known that chemical bonding affects elemental x-ray emission spectra. The spectra of low atomic number elements show energy shifts which depend on the bonding of the element. To observe these shifts, a high resolution wavelength dispersive (WDS) x-ray spectrometer is required. Intensity variations of the L series can be observed with an EDS system which also show chemical effects.
The L Alphal and the L L radiations are produced from a vacancy in the L III shell. Normally the L L line is about 5 to 6% of the intensity of the L Alphal line. However, in the atomic number range of Z=21 to 28, it is easily observed that the L L line becomes more intense. The L Alphal is no longer present at Z=20. These intensity changes are due to the outer electron shells of these atoms being unfilled. The L Alphal comes from the L3-M5 transition, while the L L comes from L3-M1 transition. The M5 (3d level) of the M shell is partially filled for Z=21 to 28; empty for Z&lt;21and full for Z&gt; 28. Holliday observed a Ti LL which was 17% greater than the Ti L Alphal.
Microstructural Evaluation and Quantitative Analysis in the Unleaded Solder Joint
Authors: Duh JG , Lee YG , Wu FB 
Published: July 2020

Abstract
Solder joints provide mechanical and electronic connections between solders and components for various levels in microelectronic package. However, due to different thermal expansion coefficients and elastic modulus of the associated materials, solder joints are susceptible to fatigue degration, microcracks and fracture. The solder joint reliability is, therefore, critical in the evalution of the joint quality. Recently, the employment of lead-free solder is attractive due to the environmental concern of the Pb-containing solder. Hence, the investigation on the unleaded solder joint is of practical importance in the field of microelectronic package.
Intermetallic compounds (IMC), which form and grow between solders and metallizations, are considered to be a source of mechanical weakness for its brittleness and different coefficient of thermal expansion from the metallization or the solder.