bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of cryo-electron microscopic and x-ray data and compensation of the contrast transfer function
Authors: Cheng R. Holland 
Published: June 2020

Cryo-electron microscopy (cryoEM) along with image reconstruction techniques can produce vivid images of biological macromolecules in their “native” state, although objective interpretation of these images is influenced by the fact that the contribution of phase contrast greatly exceeds that of amplitude contrast in such weakly scattering objects. The microscope contrast transfer function (CTF), which is strongly dependent on the defocus level of objective lens, modulates images of the object density distribution as a function of spatial frequency. Compensation for the effects of phase contrast transfer is important because underweighting of the low spatial frequencies usually causes difficulties in evaluating absolute mass distributions in objects.Correct compensation for the CTF is difficult to achieve. This is due, in part, to ambiguities in measuring the exact defocus level in noisy micrographs, and in knowing the relative contributions of amplitude and phase contrast, beam coherence, and inelastic scattering. The availability of atomic resolution determinations for a few viruses allows one to determine empirically how to correct the cryoEM images to best fit the x-ray data.
Analysis of time-varying imaging from phase-contrast microscopy
Authors: Gwydir Stacy , Kirgios Christos , Buettner Helen , Dunn Stanley 
Published: June 2020

Quantitative analysis of neurite outgrowth and growth cone (filopodia and lamellipodia) motility provides key information for developing new therapeutic strategies for treating peripheral nerve injury and disease. Neurite outgrowth and growth cone properties will be measured for neurons taken from the dorsal root ganglia of 8-day old chick embryos. Ganglia will be enzymatically dissociated into single neurons and cultured in a serum-free medium. Cultures will be grown on glass coverslips coated with the basement membrane protein laminin. Following a brief incubation period of 4 hr to allow the initiation of neurites from the nerve cell bodies, cultures will be moved to an incubated microscope stage maintained at 37 C. Subsequent growth of the neurites will be recorded at a rate of 2 frames/sec with a time-lapse videocassette recorder connected to the phase-contrast microscope through a high-resolution (800 lines) video camera.The videotaped growth sequence will be digitized at a specified time interval, using a frame grabber.
AFM, LVHRSEM, and cross-sectional TEM of the near-surface morphology of diblock copolymers
Authors: Schwark D. W. , Vezie D. L. , Reffner J. R. , Thomas E. L. , Annis B. K. , Wunderlich B. 
Published: June 2020

Application of block copolymers as adhesives and biomedical devices requires an understanding of the surface composition and morphology of these materials. Microscopy techniques offer excellent depth and lateral resolution and therefore can provide direct microstructural and compositional surface data. Previous workers frequently used only a single microscopy technique to investigate the influence of an external surface constraint on the morphology. The implementation of several different microscopy techniques, each with its own strengths, affords a very complete characterization of the surface composition and morphology of self-assembling diblock copolymers.The investigation of solvent-cast and annealed thick (1 mm) films of two poly(styrene-b-butadiene) (SB) diblock copolymers, which usually self-assemble to form alternating poly(styrene) (PS) and poly (butadiene) (PB) lamellar microdomains, by three complementary microscopy techniques: cross-sectional transmission electron microscopy (CSTEM), low-voltage high-resolution scanning electron microscopy (LVHRSEM), and atomic force microscopy (AFM) is discussed. For CSTEM and LVHRSEM imaging, contrast between the PS and PB phases was enhanced by preferential staining of the PB phase with the vapors of a 4% aqueous osmium-tetroxide (OsO4) solution for 24 hours.
Evaluation of stereo imaging capabilities and parameters when using personal computers: Defining a low-cost high-quality system
Authors: Mackenzie John M. 
Published: June 2020

Over the past several years the capabilities of personal computers have advanced at a staggering rate. At the same time, the cost of the hardware has dropped to such a degree that one wonders whether such inexpensive hardware can perform adequately.The purpose of this discussion is to look at the minimum hardware necessary to do quality stereo imaging on CRT display devices and to discuss several important evaluation criteria in producing these stereo images.The most important criteria for producing high quality stereo pairs lies in the quality of the digitization of the image. Most TV rate imaging systems even after multiple frames are averaged are quite distorted and lack sufficient image detail. Slow scan imaging systems such as the one developed in this laboratory which use a gated integrator and can digitize at over one thousand pixels square with 256 gray levels produce images which are extremely close to photographic quality.
Application of an image management system in microscopy
Authors: Chemock Richard S. 
Published: June 2020

One of the most common tasks in a typical analysis lab is the recording of images. Many analytical techniques (TEM, SEM, and metallography for example) produce images as their primary output. Until recently, the most common method of recording images was by using film. Current PS/2R systems offer very large capacity data storage devices and high resolution displays, making it practical to work with analytical images on PS/2s, thereby sidestepping the traditional film and darkroom steps. This change in operational mode offers many benefits: cost savings, throughput, archiving and searching capabilities as well as direct incorporation of the image data into reports.The conventional way to record images involves film, either sheet film (with its associated wet chemistry) for TEM or PolaroidR film for SEM and light microscopy. Although film is inconvenient, it does have the highest quality of all available image recording techniques. The fine grained film used for TEM has a resolution that would exceed a 4096x4096x16 bit digital image.
Reconstruction of intracellular and extracellular networks from stereo IVEM images using computer graphic methods
Authors: Peachey Lee D. , Haselgrove John C. , Baradet Timothy , Weisel John , Haselgrove Christian , Porter Keith R. 
Published: June 2020

High and intermediate voltage electron microscopes can be used to get good images of many types of thick biological specimens, including sections of embedded material up to several micrometers thick, whole cells, or isolated cellular components mounted on support films, stereoscopic pairs of images can be obtained by tilting the specimen between exposures, and this requires only relatively small tilt angles, often less than 15°. With a high tilt specimen holder, images covering a wider range of tilt angles can be obtained, increasing the amount of 3D information. Computer graphic methods for extracting quantitative 3D information from such images have been under development and use in this laboratory for several years.Many cellular structures take the form of networks. Examples that we study are transverse tubular networks in muscle, fibrin clots, and the microtrabecular lattice of the cytoplasm. We perform quantitative, 3D reconstruction and analysis of such networks from multiple stereoscopic image sets obtained using a JEOL 4000-EX TEM.
Multi-dimensional microscopy and analysis
Authors: Echlin Patrick 
Published: June 2020

Our natural world is multi-dimensional in which the spatial coordinates of an object are, for a given moment of time, fixed relative to each other. These fixed points change, either very rapidly as in the case of most living material, or very slowly as with metals and rocks. The rates of change are influenced by environmental factors such as temperature, pressure, humidity and electromagnetic radiation.Sight together with the coupled neuro-physiological processes is the most powerful of our noninvasive senses for detecting, imaging and analysing what is happening in our environment. Our memory serves us reasonably well as a short term archiving mechanism. The images we see arise as a consequence of selective scattering and absorption of a small portion of the electromagnetic spectrum as it interacts with the specimen. We quickly learn how to interpret the information-rich images we are presented with in our daily life; we can perceive motion, minute changes in patterns and the three dimensional location of objects.
Applications of AFM and STM: Solvation forces in liquids and inelastic photon excitation
Authors: Welland M. E. , O'Shea S. , McKinnon A. W. , Wong T. M. H. 
Published: June 2020

We describe here non-standard applications of scanned probe microscopy; one application making use of the force sensitivity of the AFM to measure solvation forces at the liquid-solid interface and the other application based on the STM where the tunnelling current is used to excite photon emission from a surface.An interesting aspect of the solid-liquid interface is the molecular order induced in the liquid by the solid surface. This order can give rise to observable changes in the short range forces acting between two solids in a liquid medium; so called “solvation” or “structural” forces. As a first investigation of the local variation of short range forces in liquids we have used an AFM to observe solvation forces near a graphite surface. The AFM is ideal for this work as it can typically measure very small forces (∼10-10N) with high lateral (∼0.3nm) and vertical resolution (∼0.03nm). In this study, an optical deflection type AFM is used in which the movement of a small cantilever is sensed by measuring the deflection of a laser beam focussed on the back of the lever.
The impact of confocal microscopy in biomedical research
Authors: Amos William B. 
Published: June 2020

The confocal optical microscope, using laser illumination, has now gained widespread acceptance (see volume edited by Pawley) Its advantage in providing clear optical sections, particularly with fluorescent specimens, is well known. Of the many confocal instruments now in use in cell biology, the applications can be classified into five different categories.The chief use is to give three-dimensional information about conventionally prepared fluorescent specimens. A notable example is the in vivo mapping of an identified neurone through several days of embryonic life by O'Rourke, Scott Fraser and colleagues at Irvine, USA. There has also been much work on in situ hybridisation, morphometry of solid tumours, oncogene product localisation and many aspects of the cytoskeleton.The second use has been in reflection imaging of cell surface contacts, of isolated microtubules and microorganisms, of parts of the eye and of reaction products such as peroxidase.The third application is the measurement of intracellular parameters such as pH and calcium ion concentration within a defined volume.
Structure refinement from systematic row integrated intensities and non-systematic critical voltages
Authors: Gjønnes J. , Ma Y. 
Published: June 2020

Renewed interest in the quantitative side of electron diffraction may be due to several factors:
•convergent beam diffraction is reckognized as a source for precise and useful intensity data for structure determination;•structural features where electron diffraction offers high sensitivity, e.g. disorder, defects, transformation structures and microstructures, charge distributions, receive increasing attention in solid state research.
Various approaches and applications of electron diffraction to structure determination and refinement have been reported in recent years,. In our lab we have concentrated on two methods: the non-systematical critical voltage effect applied to a inner reflections from small unit cells; intensity profiles and integrated intensities from reflections in a systematic row. Applications include charge distributions and ionicities, refinement of coordinates and thermal parameters, supplement to X-ray structure determinations.The studies of charge distribution combine two basic features of electron difraction: the high sensitivity of inner reflections to charge transfer, cf the Mott formula
Measurement of small structure factors by the critical-voltage effect in HEED: The superlattice reflections in β'nial, β'CoAl and γtial
Authors: Fox Alan G. , Tabbernor Mark A. 
Published: June 2020

The systematic critical voltage effect, Vc, in high energy electron diffraction has been used for some time to accurately measure low-angle x-ray structure factor structure factor amplitudes (see e.g. 1). It has a significant advantage over other methods for accurate structure factor measurement, such as systematic convergent beam rocking curve or x-ray Pendellösung techniques, in that it is capable of measuring very small structure factors such as the 222 ‘forbidden’ reflections in Si and Ge (see e.g. 2). In the present work the potential of the systematic Vc method for measuring small structure factor amplitudes and average Debye-Waller factors in the intermetallic alloys NiAl, CoAl and TiAl will be demonstrated.The structure factors, F, for ordered stoichiometric B2 alloys comprising A and B atoms such as Ni (Co)Al are given by
Segregation in a neutron-irradiated Type 316 stainless steel
Authors: Kenik E. A. , Burke M. G. 
Published: June 2020

Radiation-induced segregation (RIS) and associated irradiation-assisted stress corrosion cracking (IASCC) of austenitic alloys may be a major factor in limiting component lifetimes in water-cooled nuclear reactors. There are some similarities between radiation-induced sensitization/IASCC and thermally-induced sensitization/intergranular stress corrosion cracking. Both processes are associated with chromium depletion at grain boundaries. Segregation to boundaries in a neutron irradiated type 316 stainless steel has been investigated with both energy-dispersive X-ray spectrometry (EDXS) and parallel detection electron energy loss spectrometry (PEELS).All specimens were from the same heat of cold-worked type 316 stainless steel. Both unirradiated control material and material irradiated at ∼300°C to a range of fluences 0.3 - 5 × 1026 neutrons/m2 (E>0.1 MeV) were available. The mass of irradiated material was minimized by mechanically polishing 3-mm-diam. disks to ∼75 μm thickness prior to electropolishing. However, the specific radioactivity of the specimens, which increased with neutron fluence, limited the application of EDXS to the unirradiated and the lowest fluence irradiated materials.
Trace analysis of transition elements and rare earths by parallel EELS
Authors: Leapman R.D. , Newbury D.E. 
Published: June 2020

It has been realized for some years that electron energy loss spectroscopy (EELS) offers the potential for a highly sensitive microanalytical technique. Here, we present measurements from some NIST glass standard reference materials showing that EELS provides both high spatial resolution and trace sensitivity for a wide range of elements including the 3-d transition metals and the lanthanides.Specimens were prepared by grinding the glass and depositing the powder on to thin carbon support films. The energy loss spectra were collected by means of a Gatan 666 parallel-detection spectrometer attached to a VG Microscopes HB501 scanning transmission electron microscope (STEM) operating at 100 keV beam energy. This arrangement gave an energy resolution of approximately 0.4 eV limited by the spread of the field-emission source. Large spectral intensities were obtained by setting the probe current to about 8 nA and the collection semi-angle to 20 mrad. In order to eliminate possible hydrocarbon contamination the specimens were cooled to -160 C.
Energy-analyzing setup for backscattered electrons
Authors: Gérard Pascal , Balladore Jean Louis , Martinez Jean Paul , Ouabbou Abdelghafour 
Published: June 2020

We present in this paper an experimental device for determining for an electron beam incident normal to a target, the angular and energetic backscattered electron distribution as a function of the emission angle. The originality of our setup lies in the fact that under a normal incidence the particules reach the target which remains stationary. The detection system, placed on a rotating arm around the point of impact of the incident beam consists of a semiconductor detector (PIN diode). To enable its use as a detector of electron whose energy is comprised between 10 and 40 keV, a specially tailored electronic device was required. In order to enhance the energy resolution the PIN diode is cooled down at liquid nitrogen temperature.Figure 1 gives an example of the type of spectrum obtained. At a low energy, the electronic noise due the measurement setup appears in the form of the peak at 2 keV, irrespective of the nature of the target, the detection angle θ or the incident energy Eo chosen.
High-Resolution stereo imaging of frozen-hydrated biological samples by Cryo-SEM
Authors: Chen Ya , Walther Paul 
Published: June 2020

The introduction of cryo-techniques to SEM allowed the biologist to examine frozen-hydrated specimens at low temperatures on a cryo-stage in the SEM. The problems associated with conventional cryo-SEM included ice crystal formation caused by low cooling rate, poor resolution, limited magnification (<10 kX), specimen contamination, beam damage and charging. Recently, the effectiveness of this technique has been improved because a number of new cryo-preparation instruments have become commercially available. The high pressure freezer permits cryo-fixation of large biological specimens (diameter up to about 1mm) without ice crystal artifacts. Cryo-coating units permit fine-grain metal coating of fractured specimens. In addition, microscopes combining a short focal length lens with a fieldemission (FE) source permit high resolution imaging at low beam voltage (Vo). However, for high resolution cryo-SEM, especially for producing stereo pictures, the artifacts caused by electron irradiation remain a critical problem.The purpose of this work was to evaluate the extent to which beam damage varies with Vo, and to determine the most appropriate Vo for stereo imaging.
Imaging and analysis of submicron single-crystal aluminum whiskers in Al/Cu/Si deposited films
Authors: Schaper Jacob A. 
Published: June 2020

The formation of stress-relieving hillocks, also referred to as single-crystal whiskers is a well-known occurrence in the preparation of metallic thin films. In the manufacture of Application Specific Integrated Circuits, devices at the wafer level are often processed through the first metallic thin film process, coated with a plasma enhanced oxide (PEO), then stockpiled either at the manufacturer's site or the customer's to await final option-level programming. Whisker growth has been detected on wafers retrieved from the stockpile inventory. This paper describes the techniques employed for initial detection, subsequent sample preparation, and the composition analysis of submicron diameter whiskers in Al/Cu/Si thin films on inventoried product wafers.First indications of whisker growth are increased surface defect levels observed during high power optical microscope sample inspection. Typical appearance of the whiskers, as viewed with an optical microscope, are shown in Figure 1. Structures thought to be surface particles are later imaged in the SEM and confirmed to be oxide-covered whiskers, as shown in Figure 2. Imaging of the nonconductive oxide layer is accomplished via a Field Emission SEM.
Low-Voltage scanning electron microscope (LVSEM) determination of nevirapine Crystal Habit in a Pharmaceutical Suspension
Authors: Angel A. , Peischl R. , Hawi A. 
Published: June 2020

LVSEM permits the examination of materials with reduced radiation damage and high contrast, factors which are critical to the successful examination of organic crystals. In this study, LVSEM was applied to characterize the structure of a beam sensitive anhydrous crystal form and its subsequent conversion to the hemihydrate form in an aqueous suspension.Nevirapine, a dipyridodiazepenone compound, is a reverse transcriptase inhibitor currently being developed for the treatment of AIDS. Nevirapine exists as the hemihydrate stable form and as the anhydrous metastable form. The hemihydrate crystals are multifaceted blades (Fig. 1) whereas the anhydrous form exists predominately as large agglomerates of porous “coral like” crystals with high surface area (Fig. 2). When formulated in aqueous suspensions, anhydrous Nevirapine converted into the hemihydrate form, with eventual growth of the hemihydrate crystals. The extent of conversion and rate of growth have been determined to be a function of temperature and time. LVSEM was used to study the anhydrous-to-hemihydrate conversion as the two forms could easily be identified by their characteristic morphology.
Heterojunction band offsets in GE-SI alloys from EELS
Authors: Batson P.E. , Morar J.F. , Tersoff J. , LeGoues F.K. 
Published: June 2020

The positions of the band edges on either side of a semi-conductor heterojunction determine the electrical properties of the interface by defining the potential barrier to transport experienced by an electron or hole. This behavior dominates the function, the Schottky Barrier height, for instance, of semi-conductor structures. On the other hand, the band line-up is essentially a microscopic quantity. It depends on the atomic structure averaged over only two or three atomic spacings.Band offsets can be inferred from transport properties, such as capacitance. However, these methods are subject to problems of charge trapping and recombination effects because they average over large areas of the heterojunction. An alternate method is to measure some reference level on either side of an interface, a core level or a valence band edge, for instance, and then to measure the band edge relative to the reference using another technique. In an important simplification, Shih and Spicer proposed that some situations may occur where a core level is unchanged on either side of a heterojunction.
In situ crystallization of amorphous silicon
Authors: Batstone J.L. 
Published: June 2020

The solid state transformation of amorphous silicon (a-Si) to crystalline silicon (c-Si) is a first order phase transformation which is driven by the difference in free energy between the amorphous and crystalline phases. The crystallization occurs at temperatures of 500-700°C which are readily accessible with commercial specimen heating stages for the transmission electron microscope (TEM). In this paper we study the a-c phase transformation dynamically by utilizing the powerful technique of in-situ TEM to monitor the nucleation and growth kinetics of thin films of Si. The propagation of a moving a-c interface is presented and an activation energy for crystal growth is obtained.400Å of a-Si was prepared by electron beam deposition of Si at room temperature on amorphous Si3,N4 “window” substrates which required no additional sample preparation for TEM. The samples were examined in a plan view orientation to minimize surface effects on the crystallization process. The a-Si films were annealed by in-situ heating in a Gatan single-tilt hot stage which has a temperature accuracy of ±25°C. Crystallization occurred at ∼700°C with the formation of small crystallites which grew to consume the entire amorphous film. Fig. 1 shows a partially transformed region of a-Si after annealing at 710°C for 6 mins.