bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monte Carlo Modelling of Secondary Electron Yield from Rough Surfaces
Authors: Russ John C. 
Published: June 2020

Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.
Analytical Self-Consistent Theory of Three Dimensional Image Reconstruction from Projections
Authors: Ximen Jiye 
Published: June 2020

Image reconstruction techniques have been widely applied to electron microscopy and computerized tomography. The classic algebraic reconstruction problem is to reconstruct the three dimensional (3D) objects from experimentally measured two dimensional (2D) projections. In literature, only approximate algorithm and iterative procedure have been investigated. Recently, an analytical self-consistent reconstruction method has been proposed by the author. A discrete/continuous object is given:whlie 2D projections are
Prospect for HEW Applications of Multivariate Statistical Analysis in Microscopy and Spectroscopy
Authors: Bonnet N. , Simova E. , Lebonvallet S. 
Published: June 2020

Multivariate Statistical Analysis has been developed in order to process large data sets and to extract from them the significant information.It has been introduced in electron microscopy in order to process image series of macromolecules and to classify individual images into several subsets of the series. This kind of series can be considered as a spatial series.In fact, electron microscopy and spectroscopy are using more and more image sequences in order to be able to access more precisely the content of the object studied. Among the different types of sequences which are already used and which will be used more extensively in the near future, one can mention :
—spatial series (several slightly different objects, whose images are to be classified and combined ; or several microanalytical spectra recorded at different places of the object).—time series : in order to study changes induced in the object, one has to record successive images or spectra.—series in energy : one possibility to study the behavior of a specimen is to vary the accelerating voltage, to record several images or spectra and process the whole data set. Another exemple of series in energy is given by energy loss elemental mapping (or Auger elemental mapping) where several energy filtered images must be recorded (below and above the edge of interest) in order to get a “true” elemental map.—more “exotic” series can also be obtained, for instance series obtained by varying the spot size in MEB, series obtained with different configured detectors in STEM...
Electron Microscopy of Selfassembling Lipids With Carbohydrate Headgroups and Their Stereochemical Interactions
Authors: Boettcher Christoph 
Published: June 2020

The spontaneous aggregation of amphiphilic molecules into ordered structures plays an important role in many biological and chemical systems. The stereochemistry of headgroups and their interaction in the mixed systems strongly influence the size and shape of the formed membranous aggregates .Upon cooling of the aqueous solution, containing D-Glu-8, micellar fibers of at least bimolecular diameter (4 nm) are formed and then converted within seconds into complex helical ropes of uniform screw sense. The preliminary structure, identified as a double stranded helix, could be detected by EM (a) after stabilisation in the presence of 2% phosphotungstic acid (Fig.1) and (b) using frozen hydrated specimens (Fig.2), which were prepared under controlled environment conditions at 60°C before plunging into liquid ethane. Small differences in the size and shape of the fibers, which were confirmed by image analysis, were traced back to adsorption effects on the carbon film and can be neglected, if frozen hydrated specimens are used.In an equimolar mixture of gluconamides, differentiated in the chain length, the formation of fibers is retarded and intermediate structures, such as micellar clusters are detectable (Fig.3). Racemic mixtures of hexonamides usually produce bilayer platelets (“Chiral Bilayer Effect”); if the enantiomers are again differentiated in the chain length, a spontaneous racemate resolution is observed (Fig.4, left-(M) and right-(P)handed helices!) and the formation of platelets (Fig.5) is retarded.
On the Use of POCS for Restoring the “Missing Wedge” in Electron Tomography
Authors: Zhang Neng-Yu , McEwen Bruce F. , Frank Joachim 
Published: June 2020

Reconstructions of asymmetric objects computed by electron tomography are distorted due to the absence of information, usually in an angular range from 60 to 90°, which produces a “missing wedge” in Fourier space. These distortions often interfere with the interpretation of results and thus limit biological ultrastructural information which can be obtained. We have attempted to use the Method of Projections Onto Convex Sets (POCS) for restoring the missing information. In POCS, use is made of the fact that known constraints such as positivity, spatial boundedness or an upper energy bound define convex sets in function space. Enforcement of such constraints takes place by iterating a sequence of function-space projections, starting from the original reconstruction, onto the convex sets, until a function in the intersection of all sets is found. First applications of this technique in the field of electron microscopy have been promising.To test POCS on experimental data, we have artificially reduced the range of an existing projection set of a selectively stained Golgi apparatus from ±60° to ±50°, and computed the reconstruction from the reduced set (51 projections). The specimen was prepared from a bull frog spinal ganglion as described by Lindsey and Ellisman and imaged in the high-voltage electron microscope.
A UHV-Compatible Photobmission Microscope for Applications in Surface Science
Authors: Engel W. , Rotermund H.H. , Kordesch M. , Kubala S. , Oertzen A.v. , Jakubith S. 
Published: June 2020

The intention was to develop a low-cost reliable photoemission microscope (Fig.l) which gives only modest lateral resolution but allows full advantage to be taken of its ability to reveal small variations of the sample‘s work function with high contrast. Another important point was its applicability in the field of heterogeneous catalysis, i.e. the possibility of observing catalyst surfaces during catalitic reactions.The microscope can be attached to any vacuum chamber which has been provided with a port for a standard LEED system. It is mounted on an 8-inch OD CF flange, and the flange-to-sample distance has the standard length of 10 inches. The sample is at ground potential whereas the microscope column is at +20 kV. The microscope is connected to an auxiliary pump, and a fixed aperture (diameter 300 μn) in the back focal plane of the objective lens permits differential pumping. Pressures in the sample area even approaching 10−3 Torr do not effect the operation of the microscope and its channel-plate image intensifier.
Methods and Applications of UV Photoelectron Microscopy in Surface Science
Authors: Mundschau M. , Bauer E. , ᔒwięch W. 
Published: June 2020

Photoelectron microscopy is sensitive to single atomic or molecular layers on surfaces at submonolayer coverages. A significant advance for fundamental studies in surface science has been the construction of ultra-high vacuum versions of classical photoelectron microscopes and the combination with other techniques of surface analysis - most notably low-energy electron diffraction and microscopy. This is essential for the proper interpretation of the micrographs. The technique is well suited for in situ studies of large flat samples such as silicon wafers, single crystals and polished metallurgical samples.One of the most promising fields for application of the photoelectron microscope is in the area of epitaxial growth.In epitaxy a crystalline substance grows as an oriented overgrowth atop a substrate. It has widespread use in the semiconductor industry and in the field of quantum electronics, in which epitaxially grown structures have the dimensions of the same order of magnitude as the wavelengths of the conducting electrons.
Images and Applications of Ion Explosion Spike Pits
Authors: Fraundorf P. , Tentschert J. 
Published: June 2020

Since the discovery of their etchability in the early 1960‘s, nuclear particle tracks in insulators have had a diverse and exciting history of application to problems ranging from the selective filtration of cancer cells from blood to the detection of244Pu in the early solar system. Their usefulness stems from the fact that they are comprised of a very thin (e.g. 20-40Å) damage core which etches more rapidly than does the bulk material. In fact, because in many insulators tracks are subject to radiolysis damage (beam annealing) in the transmission electron microscope, the body of knowledge concerning etched tracks far outweighs that associated with latent (unetched) tracks in the transmission electron microscope.With the development of scanned probe microscopies with lateral resolutions on the near atomic scale, a closer look at the structure of unetched nuclear particle tracks, particularly at their point of interface with solid surfaces, is now warranted and we think possible. The ion explosion spike model of track formation, described loosely, suggests that a burst of ionization along the path of a charged particle in an insulator creates an electrostatically unstable array of adjacent ions which eject one another by Coulomb repulsion from substitutional into interstitial sites. Regardless of the mechanism, the ejection process which acts to displace atoms along the track core seems likely to operate at track entry and exit surfaces, with the added feature of mass loss at those surfaces as well. In other words, we predict pits whose size is comparable to the track core width.
Molecular imaging of Organo-Calcium salts by High Resolution Electron Microscopy and Image Processing
Authors: Miller G. , Fryer J.R. , Kunath W. , Weiss K. 
Published: June 2020

Unfortunatly Wolfgang Kunath died January 1990High resolution electron microscopy and image processing are being used to determine the molecular packing within the crystal unit cell of the, organic-azo calcium salt. Due to the beam sensitive nature of the organic moiety which contains both aromatic and and aliphatic components, low dose techniques were used. This concisted of, searching the sample in the diffraction mode to find single crystals exibiting point like reflection to at least .2nm resolution, (fig. 1). Focusing and astigmatism correction was performed by moving the beam of the crystal (off axis). The beam was then moved on axis and a series of four, 10 e/A images taken, (fig. 2). Images were primarily recorded using an on line T.V. recording device. These images were then available for processing using the Semper image processing system. Two crystal orientations were found. Type 1 consisted of thin plate like crystals up to 5um diameter and generally 10nm to 20nm thick. Type 2 were thicker crystals with a 3.2nm lattice spacing. The power specrta of the first low dose images were calculated to asses the quality of the of the structural information present. For the type 1 crystal the power spectrum had to show at least second order reflections in two directions ( fig. 3 ). Type 2 crystals showed the 3.2nm reflection often down to the fith order. These crystals also showed parallel side bands corresponding to a d-spacing of about .8nm. With these results the unit cell was found to be tetragonal with a= .78nm b= 3.2nm c= .78nm. In accordance with the diffraction patterns exibited.
Accuracy of Stereoscopic Technique in S.E.M.
Authors: Wang D. , Feng Y. , Lu H. 
Published: June 2020

The principle of 3-D reconstrution for SEM image is not so conplex, ie. the SEM image of polar project is treated with a rectangular coordinate, however, it accuracy is an attractatble topic. The accuracy of a stereopair is effected by following factors:(1) Sample’s position:Image’s field depth of SEM is determined bywhere, F4: the depth of fieldD0: resolution of imageβ : condence angle of E-beam (about 1 × 10−3 rad.)when the magnificaton is 1000 times, ie. Do = 0.1μm, then Ff = 100μm. To get an accurate stereopair, one should keep the interested points on the specimen in the same field depth before and after tilting operation. During the operation, a point displacement is sketched in Fig.1, where 0 is tilting axis. Ao is the original position of A, A, is tilted one, α is tilted angle and β is the angle betweem 0Ao and Z axis. After the tilt, the perpendicular displacement of A point isand the horizontal one isGenerally, the magnification is 1000X, ie. Ff=100μm, α≈10°, if β<=30° then, 0Ao<=700μm is the condition for that ZA < = 100 m.
Evaluation of human resources needed and comparison with human resources available to implement emergency vaccination in case of foot and mouth disease outbreaks in Tunisia
Authors: Marsot Maud , Durand Benoit , Ben Hammouda Wafa , Hadj Ammar Heni , Zrelli Malek , Khorchani Roukaya 
Published: June 2020

Abstract
Foot and mouth disease (FMD) is a highly contagious viral disease that affects domestic and wild artiodactyl animals and causes considerable economic losses related to outbreak management, production losses and trade impacts. In Tunisia, the last FMD outbreak took place in 2018–2019. The effectiveness of control measures implemented to control FMD depends, in particular, on the human resources used to implement them. Tunisia has the ultimate objective of obtaining OIE status as ‘FMD-free with vaccination’. The aim of this study was to determine and compare the necessary and available human resources to control FMD outbreaks in Tunisia using emergency vaccination and to assess the gaps that would play a role in the implementation of the strategy. We developed a resources-requirement grid of necessary human resources for the management of the emergency vaccination campaign launched after the identification of a FMD-infected premises in Tunisia. Field surveys, conducted in the 24 governorates of Tunisia, allowed quantifying the available human resources for several categories of skills considered in the resources-requirement grid. For each governorate, we then compared available and necessary human resources to implement vaccination according to eight scenarios mixing generalised or cattle-targeted vaccination and different levels of human resources. The resources-requirement grid included 11 tasks in three groups: management of FMD-infected premises, organisational tasks and vaccination implementation. The available human resources for vaccination-related tasks included veterinarians and technicians from the public sector and appointed private veterinarians. The comparison of available and necessary human resources showed vaccination-related tasks to be the most time-consuming in terms of managing a FMD outbreak. Increasing the available human resources using appointed private veterinarians allowed performing the emergency vaccination of animals in the governorate in due time, especially if vaccination was targeted on cattle. The overall approach was validated by comparing the predicted and observed durations of a vaccination campaign conducted under the same conditions as during the 2014 Tunisian outbreak. This study could provide support to the Tunisian Veterinary Services or to other countries to optimise the management of a FMD outbreak.
Tree‐Branching‐Based Enhancement of Kinetic Energy Models for Reproducing Channelization Processes of Pyroclastic Density Currents
Authors: Aravena A. , Cioni R. , Bevilacqua A. , de' Michieli Vitturi M. , Esposti Ongaro T. , Neri A. 
Published: June 2020

AbstractKinetic energy models, also called kinetic models, are simple tools able to provide a fast estimate of the inundation area of pyroclastic density currents (PDCs). They are based on the calculation of the PDC front kinetic energy as a function of the distance from a source point. On a three‐dimensional topography, the PDC runout distance is estimated by comparing the flow kinetic energy with the potential energy associated with the topographic obstacles encountered by the PDC. Since kinetic models do not consider the occurrence of channelization processes, the modeled inundation areas can be significantly different from those observed in real deposits. To address this point, we present a new strategy that allows improving kinetic models by considering flow channelization processes, and consists in the inclusion of secondary source points in the expected channelization zones, adopting a tree branch‐like structure. This strategy is based on the redistribution of a key physical variable, such as the flow energy or mass depending on the considered kinetic model, and requires the adoption of appropriate equations for setting the characteristics of the secondary sources. Two models were modified by applying this strategy: the energy cone and the box model. We tested these branching models by comparing their results with those derived from their traditional formulations and from a two‐dimensional depth‐averaged model, considering two specific volcanoes (Chaitén and Citlaltépetl). Thereby, we show the capability of this strategy of improving the accuracy of kinetic models and considering flow channelization processes without including additional, unconstrained input parameters.
Relative Dispersion of Surface Drifters in the North Sea: The Effect of Tides on Mesoscale Diffusivity
Authors: Meyerjürgens Jens , Ricker Marcel , Schakau Vanessa , Badewien Thomas H. , Stanev Emil V. 
Published: June 2020

AbstractWe examine the relative dispersion and the contribution of tides on the relative diffusivities of surface drifters in the North Sea. The drifters are released in two clusters, yielding 43 pairs, in the vicinity of a tidal mixing front in the German Bight, which is located in the southeastern area of the North Sea. Both clusters indicate decreasing dispersion when crossing the tidal mixing front, followed by exponentially increasing dispersion with e‐folding times of 0.5 days for Cluster 1 and 0.3 days for Cluster 2. A transition of the dispersion regimes is observed at scales of the order of the Rossby radius of deformation (10 km). After that, the relative dispersion grows with a power‐law dependency with a short period of ballistic dispersion (quadratic growth), followed by a Richardson regime (cubic growth) in the final phase. Scale‐dependent metrics such as the relative diffusivities are consistent with these findings, while the analysis of the finite‐scale Lyapunov exponents (FSLEs) shows contradictory results for the submesoscales. In summary, the analysis of various statistical Lagrangian metrics suggests that tracer stirring at the submesoscales is nonlocal and becomes local at separation scales larger than 10 km. The analysis of meridional and zonal dispersion components indicates anisotropic dispersion at the submesoscales, which changes into isotropic dispersion on the mesoscales. Spectral analysis of the relative diffusivity gives evidence that semidiurnal and shallow‐water tides influence relative diffusivity at the mesoscales, especially for drifter separations above 50 km.
Atmospheric Lifetimes of Halogenated Hydrocarbons: Improved Estimations From an Analysis of Modeling Results
Authors: Orkin Vladimir L. , Kurylo Michael J. , Fleming Eric L. 
Published: June 2020

AbstractDetailed results of computer modeling of halocarbon removal rates from the atmosphere are analyzed to find simple correlations useful for improving estimations of the atmospheric lifetimes of industrial chemicals based on the rate constants for their reactions with OH and O(1D) and their UV absorption spectra. This analysis is limited to relatively long‐lived chemicals that are well mixed in the troposphere.
Quantifying the Human Health Benefits of Using Satellite Information to Detect Cyanobacterial Harmful Algal Blooms and Manage Recreational Advisories in U.S. Lakes
Authors: Stroming Signe , Robertson Molly , Mabee Bethany , Kuwayama Yusuke , Schaeffer Blake 
Published: June 2020

AbstractSignificant recent advances in satellite remote sensing allow environmental managers to detect and monitor cyanobacterial harmful algal blooms (cyanoHAB), and these capabilities are being used more frequently in water quality management. A quantitative estimate of the socioeconomic benefits generated from these new capabilities, known as an impact assessment, was missing from the growing literature on cyanoHABs and remote sensing. In this paper, we present an impact assessment framework to characterize the socioeconomic benefits of satellite remote sensing for detecting cyanoHABs and managing recreational advisories at freshwater lakes. We then apply this framework to estimate the socioeconomic benefits of satellite data that were used to manage a 2017 cyanoHAB event in Utah Lake. CyanoHAB events on Utah Lake can pose health risks to people who interact with the blooms through recreation. We find that the availability of satellite data yielded socioeconomic benefits by improving human health outcomes valued at approximately $370,000, though a sensitivity analysis reveals that this central estimate can vary significantly ($55,000–$1,057,000 in benefits) as a result of different assumptions regarding the time delay in posting a recreational advisory, the number of people exposed to the cyanoHAB, the number of people who experience gastrointestinal symptoms, and the cost per case of illness.