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Objectives: To report the prevalence and distribution of nonsyndromic dental anomalies in children in eastern Saudi Arabia.Methods: This retrospective records review study involved radiographic examination of 6-18 years old pediatric patients who attended the Dental Hospital of the College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. Four calibrated examiners recorded nonsyndromic dental anomalies from patients' digital orthopantomograms (OPG). The anomalies recorded were related to tooth number, shape, and location. Descriptive statistics, chi-square test, and Fisher exact tests were used to report prevalence and differences by gender, nationality, and medical history at the 5% significance level.Results: Of 2226 reviewed patients' records, 1897 met the inclusion criteria and were included in the study. The study sample had equal distribution of males (52.6%) and females (47.4%) and comprised 81.2% Saudi children with a mean age of 8.8 ± 1.84 years. Most study subjects (97.8%) were in mixed dentition and 88.7% were healthy. The prevalence of dental anomalies was as follows: teeth rotations (24.5%), ectopically erupted teeth (6%), congenitally missing permanent teeth (5.4%), peg lateral (1.1%), supernumerary (0.5%), gemination (0.3%), and fusion (0.1%). No statistically significant differences were found in the distribution of dental anomalies by patients' gender, medical history, and nationality (p value ≥0.05).Conclusion: This study showed that teeth rotations were the most common dental anomalies followed by ectopic eruptions and congenitally missing teeth. The study findings may guide dental practitioners to better diagnose and manage children with dental anomalies in eastern Saudi Arabia. [ABSTRACT FROM AUTHOR]

Ionizing radiation (IR) can result in serious genomic instability and genotoxicity by causing DNA damage. Carbon ion (CI) beams and X-rays are typical IRs and possess high-linear energy transfer (LET) and low-LET, respectively. In this article, a comet assay that was optimized by decreasing the electrophoresis time (8 minutes) and voltage (0.5 V/cm) was performed to elucidate and quantify the DNA damage induced by CI or X-rays radiation. Two quantitative methods for the comet assay, namely, comet score and olive tail moment, were compared, and the appropriate means and parameter values were selected for the present assay. The dose-effect relationship for CI or X-rays radiation and the DNA repair process were studied in yeast cells. These results showed that the quadratic function fitted the dose-effect relationship after CI or X-rays exposure, and the trend for the models fitted the dose-effect curves for various repair times was precisely described by the cubic function. A kinetics model was also creatively used to describe the process of DNA repair, and equations were calculated within repairable ranges that could be used to roughly evaluate the process and time necessary for DNA repair. [ABSTRACT FROM AUTHOR]

3D woven composite materials have been recently used to design some engine structures in order to improve their impact resistance. The aim of this work is to study experimentally and numerically low-velocity/energy impact damage in such recent composites. Impact tests at different energy levels have been performed and analysed using microscopic observations and X-ray tomography in order to understand damage mechanisms occurring in this material. Finite element simulations have been performed using the continuum damage model, ODM-PMC, developed at Onera for 3D woven composites under static loadings. Through comparisons with the available experimental data, it has been demonstrated that the damage mechanisms are described correctly by the present model. Moreover, the residual depth after impact is also accurately predicted, allowing to generate, numerically, relations between impact energy, damaged area and residual depth, currently determined experimentally in aeronautical industries. [ABSTRACT FROM AUTHOR]

In mineral beneficiation, the mineral liberation spectrum of the plant feed conveys valuable information for adjusting operations, provided that it is available in minutes from particulate sampling. X-ray micro-tomography is the only technique available for unbiased measurement of composite particle composition (on a 3D basis). The bottleneck of current micro-tomographic systems is the X-ray scanning time (data acquisition) rather than the slice reconstruction time (data processing). An algorithm capable of reconstructing tomographic slices of composite mineral particles from a limited number of radiographic projections, thus significantly reducing the overall measurement time, is presented and demonstrated with numerical examples. The algorithm is cast around the discrete algebraical reconstruction technique and requires less than one tenth of the projection data needed by the currently used filtered back-projection methods, thus allowing a dramatic reduction of the scanning time. [ABSTRACT FROM AUTHOR]

The ultrafast electron beam X-ray tomography scanner ROFEX is used for the investigation of multiphase flows. Its functional principle allows us to obtain sequences of cross-sectional flow images, which shows local attenuation properties of the flow. Hence, the X-ray CT images mainly reveal the shape and interfaces of flow constituents, such as gas, liquid and solids via their X-ray contrast. It is, however, more difficult to obtain velocity information from multiphase flows. In this article we discuss different methods to extract information on the velocities of particles or interfaces as well as for continuous phase. For disperse phase velocity measurement, e.g. in gas–liquid or gas–solids flows, we employ cross-correlation based techniques using two imaging planes. Apart from the standard cross-correlation technique we developed a method and algorithm, which is capable to identify identical bubbles in the two planes giving us a unique Lagrangian particle-related velocity information. Eventually we give an example of velocity measurement in the continuous liquid phase using an X-ray contrast agent. [ABSTRACT FROM AUTHOR]

We report recent progress made in a complete fiber-optic, high-precision, long-term stable timing distribution system for synchronization of next generation X-ray free-electron lasers. Timing jitter characterization of the master laser shows less than 170-as RMS integrated jitter for frequencies above 10 kHz, limited by the detection noise floor. Timing stabilization of a 3.5-km polarization-maintaining fiber link is successfully achieved with an RMS drift of 3.3 fs over 200 h of operation using all fiber-coupled elements. This all fiber-optic implementation will greatly reduce the complexity of optical alignment in timing distribution systems and improve the overall mechanical and timing stability of the system. [ABSTRACT FROM AUTHOR]

Two-dimensional meso-scale finite element models with realistic aggregates, cement paste and voids of concrete are developed using microscale X-ray Computed Tomography images. Cohesive elements with traction–separation laws are pre-embedded within cement paste and aggregate–cement interfaces to simulate complex nonlinear fracture. Tension tests using a large number of images were simulated with statistical analysis. The very different load-carrying capacities and crack patterns demonstrate the effects of random distribution of phases. It is found that the tensile strength decreases as the void fraction increases, and the relative strength of cement paste and interfaces dominates the microcracking behaviour, which in turn affects macrocracking and load-carrying capacity. [ABSTRACT FROM AUTHOR]

Abstract: Physically small cracks in a ferritic martensitic steel were analyzed in the SPring-8 synchrotron facility. Change in the crack shape under static and cyclic loading could be determined in addition to the crack shape by mounting micro-specimens in an in- beam loading stage. Additional information can be gained by comparing three-dimensional images of the crack faces using volumetric digital image correlation. The displacement field on the crack faces is then available which, in turn, can be correlated to the microstructure determined by serial sectioning and orientation microscopy. [Copyright &y& Elsevier]

We present a method to calculate the harmonic spectrum of the radiation emitted at the interactions between intense laser beams and atoms. Our relations describe accurately, in good agreement with the experiment, important features of the harmonic spectrum and the evolution of its shape with the increase of the laser beam intensity. More specifically, for low intensities, of the order of 10^13~W/cm^2, the spectrum has the well-known plateau shape, after which follows a sharp decrease at the cutoff edge. When the beam intensity is increased, toward 10^15~W/cm^2, the slope of the plateau increases, corresponding to a decrease by one or two orders of magnitude of the harmonic intensities. When the beam intensity is increased more, toward 10^17~W/cm^2, there is a maximum at the left edge of the spectrum, which is followed by a strong decrease of many orders of magnitude, and the spectrum concentrates in a very limited domain, under a certain frequency, far lower than the theoretical cutoff frequency. These theoretical results are in good agreement with numerous experimental data from the literature, for many atoms and ions, and for a large spectrum of intensities of laser beams. This result has important implications in the emerging field of generation of high intensity hard X-rays. [ABSTRACT FROM PUBLISHER]

Leaf venation networks mediate many plant resource fluxes and are therefore of broad interest to research questions in plant physiology, systematics, paleoecology, and physics. However, the study of these networks is limited by slow and destructive imaging methods. X-ray imaging of leaf veins is potentially rapid, of high resolution, and nondestructive., Here, we have developed theory for absorption- and phase-contrast X-ray imaging. We then experimentally test these approaches using a synchrotron light source and two commercially available X-ray instruments., Using synchrotron light, we found that major veins could be consistently visualized using absorption-contrast imaging with X-ray energies < 10 keV, while both major and minor veins could be consistently visualized with the use of an iodine contrast agent at an X-ray energy of 33.269 keV. Phase-contrast imaging at a range of energies provided high resolution but highlighted individual cell walls more than veins. Both approaches allowed several hundred samples to be processed per d. Commercial X-ray instruments were able to resolve major veins and some minor veins using absorption contrast., These results show that both commercial and synchrotron X-ray imaging can be successfully applied to leaf venation networks, facilitating research in multiple fields. [ABSTRACT FROM AUTHOR]

Although liquids typically flow around intruding objects, a counterintuitive phenomenon occurs in dense suspensions of micrometre-sized particles: they become liquid-like when perturbed lightly, but harden when driven strongly. Rheological experiments have investigated how such thickening arises under shear, and linked it to hydrodynamic interactions or granular dilation. However, neither of these mechanisms alone can explain the ability of suspensions to generate very large, positive normal stresses under impact. To illustrate the phenomenon, such stresses can be large enough to allow a person to run across a suspension without sinking, and far exceed the upper limit observed under shear or extension. Here we show that these stresses originate from an impact-generated solidification front that transforms an initially compressible particle matrix into a rapidly growing jammed region, ultimately leading to extraordinary amounts of momentum absorption. Using high-speed videography, embedded force sensing and X-ray imaging, we capture the detailed dynamics of this process as it decelerates a metal rod hitting a suspension of cornflour (cornstarch) in water. We develop a model for the dynamic solidification and its effect on the surrounding suspension that reproduces the observed behaviour quantitatively. Our findings suggest that prior interpretations of the impact resistance as dominated by shear thickening need to be revisited. [ABSTRACT FROM AUTHOR]

The effect of solidification velocity on nucleation and growth of porosity in a directionally solidified A356 alloy was investigated in situ using microfocus x-ray imaging and directional solidification technology. Increasing solidification velocity produces high hydrogen solute segregation in the solidification front, leading to a considerable reduction of nucleation temperature for porosity formation. When the solidification velocity increases from 0.1 mm/s to 0.2 mm/s, the average nucleation temperature decreases from 634.0°C to 614.6°C. The increased solidification velocity also increases the rate and fluctuation of pore growth. As a result, the average pore size in the fast solidified specimen is smaller than that with a slow velocity. [ABSTRACT FROM AUTHOR]

Abstract: The comprehensive diagnostics of melt pool and keyhole dynamics is crucial in the ambitious efforts of understanding the complex behaviour of laser welding and cutting processes. A major drawback of commonly used in-situ diagnostics is the fact that high-speed cameras and other optical sensors reveal only phenomena on the surface of the process. This paper describes a novel high-speed x-ray diagnostics system that enables the view inside the samples with high spatial as well as high temporal resolution. Calibration images demonstrated the detection of features well below 250μm in steel. In combination with maximum detection rates exceeding 10,000Hz it enables outstanding new possibilities for direct observation of the keyhole and fluid dynamics. [Copyright &y& Elsevier]

A comprehensive understanding of the sap flow dynamics and xylem hydraulic properties is essential to unravel the functional features of water transport from roots to shoots in vascular plants. To evaluate quantitatively the safety and efficiency of this system, nondestructive methods to assess the interactions between sap ascent kinetics and xylem structure are required. In this study, synchrotron X-ray microscopy was employed to observe anatomical structures and sap flow dynamics in rice (Oryza sativa) xylem simultaneously. The phase-contrast imaging technique allowed nondestructive observation of the xylem structural characteristics and the air-water interfaces generated by dehydration-rehydration cycles in excised leaves. This X-ray microimaging method provided a unique tool to characterize the perforated end walls of vessel elements and to evaluate their influence on hydraulic resistance during the refilling of embolized vessels. The real-time monitoring of the axial and radial sap flow under various environmental conditions highlighted the important role of perforation plates. In summary, we report a new methodology to study the sap flow dynamics and xylem hydraulic properties with lm spatial and ms temporal resolution using X-ray microscopy. The experimental procedure described herein provides a useful handle to understand key sap transport phenomena in xylem. [ABSTRACT FROM AUTHOR]

Direct-write soft x-ray lithography with an ∼50 nm diameter beam is used to pattern features in hydrogen silsesquioxane (HSQ) thin films. Scanning transmission x-ray microscopy of the undeveloped patterns (latent patterns) at the oxygen K-edge reveals a two-stage cross-linking mechanism. Oxygen and silicon near edge x-ray absorption fine structure spectra of latent patterns show an increase in oxygen content and no change in silicon content within exposed regions. A dose and thickness dependent spatial spread of the cross-linking reaction beyond the exposure boundaries is observed and quantified in detail. Strong area-dependent exposure sensitivity (attributed to cross-linking beyond the exposed region) is observed in latent patterns. A lateral spread in the cross-linking of >70 nm (full width at half maximum) is observed on both sides of the lines created with 580 eV x-rays (λ=2.14 nm) in 330±50 nm thick HSQ films at low dose (0.6±0.3 MGy, 27±12 mJ/cm2) (1 MGy=106 J/kg absorbed energy). At a higher dose (111±29 MGy, 5143±1027 mJ/cm2), this spread increased to 150 nm. Preliminary results indicate that latent line widths increased with increasing delay between film spin-coating and exposure. Sharper lines are observed after room temperature development of the latent HSQ patterns in NaOH/NaCl solution (onset dose of 3.9±1.0 MGy, 181±36 mJ/cm2) due to the removal of material below a critical degree of cross-linking. Given the short range of low energy secondary electrons in condensed media (<10 nm at ≤580 eV), the observed spread is likely due to the propagation of reactive ions or radicals beyond the exposed regions. [ABSTRACT FROM AUTHOR]

Abstract: Organic synthesis reactions demand improved characteristics of enzymes than wild type such as reactivity, thermostability, enantioselectivity and so on. Especially thermostability of enzyme is highly important since reaction at higher temperature has many advantages such as elevated reaction rate and increased solubility of substrates. Due to this requirement, a rational approach was employed to develop thermostable CalB. The first step of this approach was the selection of appropriate sites showing a high ‘B-factor’ value. These sites were chosen on the basis of atomic displacement parameters obtained from X-ray data. These selected sites were then substituted with other amino acids that were determined to be more rigid than the original amino acids by computational modeling using ‘RosettaDesign’. As a result of this rational approach, several thermostable CalB mutants including R249L were produced. The residual activity of R249L CalB was two times higher than that of wild type CalB at 55°C. Melting temperature (T m) of R249L mutant increased to 56.8°C compared with wild type CalB (T m: 54.5°C), which was determined by DSF (differential scanning fluorimetry). Additionally, packing analysis tool “Voronoia” pointed out that one cavity close to residue 249 of wild type CalB disappeared in CalB R249L, which could be the reason for the increase in thermal stability of CalB R249L mutant compared wild type CalB. [Copyright &y& Elsevier]

Abstract: The monitoring of heavy metals in industrial waste water effluents is an important activity in many laboratories. Of special interest is the screening of elemental composition of inlet effluents and quantitative analysis of outlet effluents to study the efficiency of chemical treatment process to eliminate metals and to comply with current established concentration limits, respectively. In this sense, fast analytical methodologies which entail simple sample preparation are desired. In the present work, the possibilities and drawbacks of a benchtop total reflection X-ray fluorescence spectrometer (TXRF) for the rapid and simple determination of some inorganic impurities (As, Ba, Cd, Cu, Cr, Sn, Fe, Mn, Ni, Pb, Se and Zn) in inlet and outlet industrial waste water effluents from metallurgical and tanning leather factories have been tested. An evaluation of different simple sample treatments is presented and it is followed by a discussion of spectral and chemical matrix effects when dealing with this type of samples. Analytical figures of merit such as accuracy, precision and limits of detection have also been carefully studied. Finally, the data obtained by direct TXRF analysis has been compared to that obtained by ICP-OES/ICP-MS after a microwave digestion. [Copyright &y& Elsevier]

A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the Hertzsprung-Russell (HR) diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, and evolution of X-ray activity with age), to X-ray generating processes (e.g., accretion, jets, magnetically confined winds) that were poorly understood in the preChandra/XMM-Newton era. I will discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysical context, focusing on the role of spectral diagnostics now accessible. [ABSTRACT FROM AUTHOR]

Although stars and planets form in cold environments, X-rays are produced in abundance by young stars. This review examines the implications of stellar X-rays for star and planet formation studies, highlighting the contributions of NASA's (National Aeronautics and Space Administration) Chandra X-ray Observatory. Seven topics are covered: X-rays from protostellar outflow shocks, X-rays from the youngest protostars, the stellar initial mass function, the structure of young stellar clusters, the fate of massive stellar winds, X-ray irradiation of protoplanetary disks, and X-ray flare effects on ancient meteorites. Chandra observations of star-forming regions often show dramatic star clusters, powerful magnetic reconnection flares, and parsec-scale diffuse plasma. X-ray selected samples of premain sequence stars significantly advance studies of star cluster formation, the stellar initial mass function, triggered star-formation processes, and protoplanetary disk evolution. Although X-rays themselves may not play a critical role in the physics of star formation, they likely have important effects on protoplanetary disks by heating and ionizing disk gases. [ABSTRACT FROM AUTHOR]

A highly sensitive detection system for magnetic contaminants using a High-Tc superconducting quantum interference device (SQUID) was developed. Finding ultra-small metallic contaminants is a big issue for manufacturers producing commercial products such as lithium ion batteries. When the contamination does occur, the manufacturer of the product suffers a great loss to recall the tainted products. The outer dimension of metallic particles less than 100 microns can not be detected by X-ray imaging, which is commonly used as the inspection method. Inmost cases, the matrix of industrial products is magnetized and the magnetic signal from the matrix is large enough to mask the signal from contaminants. We developed a detection system based on a high-Tc SQUID gradiometer. A specially designed low noise planar gradiometer for the system was developed. The flux white noise level of the SQUID gradiometer was 8-16μø0/Hz1/2 at 1 kHz. Use of the gradiometer and horizontal magnetization could solve problem above. We tested the performances of the system and found that small iron particles as small as 50 μm × 50 μm on the electrode of the lithium ion battery could be clearly detect. This detection level is difficult to achieve using other methods. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure of cold rolled metals is highly complex, but characterization of its transformation to the recrystallized state is essential to design thermal–mechanical processing of sheet products. In this study recovery leading to continuous recrystallization was examined by both X-ray line broadening and measurement of activation volumes at 78K as a function of isochronal anneals to characterize the recovered structure wherein non-conservative motion of defects is not possible. The statistically stored dislocation density recovered without a large reduction in the flow stress. On the other hand, the typical decrease in hardness associated with recrystallization was observed with the inception of discontinuous grain growth when the geometrically necessary dislocation arrays started to disintegrate. Activation distance determinations of pre-rolled structure during micro-strain correlate with the Burgers vectors of stair-rod dislocations, indicating that the controlling mechanism is the dragging of jogs. [Copyright &y& Elsevier]

Abstract: X-ray and neutron reflectometry are used for structural characterization of self-assembled InAs quantum dot stacks on GaAs (100), grown by molecular beam epitaxy. The macroscopic density profile of uncapped InAs layer is extracted and shows a three-dimensional pyramidal structure of maximum height of 5nm. The ultra thin InAs buried layers are well approximated as a two-dimensional structure, indicating amalgamation between InAs and GaAs. The interface roughness of the capping layers is found smaller than 0.5nm, showing the high quality of the epitaxial surfaces. The thicknesses of the capping GaAs layers are extracted in atomic scale level and are found in fine agreement with the nominal values. [Copyright &y& Elsevier]

In order to improve the surface quality and formability of 3003 aluminum alloy sheet, laser-textured rolls are used in cold rolling. The influences of the cold rolling procedures with conventional and laser-textured rolls on the evolution of microstructure and texture were studied by the means of microstructural observations and X-ray texture analysis. Experimental results show that the microstructures are similar besides the samples rolled with laser-textured rolls containing a relatively larger amount of shear bands. The sheets deformed with conventional rolls have developed the typical rolling textures of FCC metals, which consist of Bs, Cu, and S components. However, the rolling textures of the sheets rolled with laser-textured rolls are comparatively weak, and the shear texture {001}⟨110⟩ is developed on the surface layer, but not observed in the intermediate layer of the sheet. The intensity of the rotated cube orientation increases with the increase of rolling reduction and then decreases after 90% rolling reduction. [ABSTRACT FROM AUTHOR]

The US Department of Agriculture uses many methods to screen incoming passenger baggage for agricultural quarantined materials (e.g. fresh fruits and meat). X-ray inspection is relied upon because it is a fast and non-invasive inspection method. This paper investigates a new image feature based approach to training for X-ray inspection that instructs subjects to search for particular patterns and textures in the X-ray image, rather than specific objects (e.g. an apple). The image feature based approach is found to have demonstrable potential as a training program and provides justification for further research into implementation in a computer pattern recognition program. [Copyright &y& Elsevier]

A breakthrough in understanding elastic grain interaction in massive polycrystalline bodies, a classical field of mechanical behavior of solids, has been possible due to recent, highly accurate x-ray (also synchrotron) diffraction stress analysis and theoretical development. Thereby, so-called surface anisotropy (i.e., the occurrence of grain-interaction constraints different along directions parallel and perpendicular to a free surface) was proven unambiguously for the first time to exist. [ABSTRACT FROM AUTHOR]

A new approach based on an improved genetic algorithm (GA) was proposed to implement the image reconstruction when using X-ray computed tomography (XCT) for the application of fast measurement of multiphase flow dynamics. Instead of directly using a traditional XCT, we pursued to develop a different discrete tomography (DT) method, aiming to achieve a high resolution in time during the measurements with only limited projection data. The proposed method assumed that the interested multiphase flow can be simplified as having distinct dense and dilute phases so that the local phase concentration can be binary-coded, e.g., 0 or 1 in a gas bubbling system. The mathematical problem under these circumstances is strongly ill-posed, and thus tackled with an optimization approach, i.e., a GA incorporated with the underlying physics as some constraints. The numerical simulations mimicking the physical measurements demonstrated the feasibility of the new approach, namely GA-XCT, especially with high robustness to the noise. Experiments were performed to simulate a transient measurement on the gas bubbles in water, with a portable X-ray tube and a 2D plane detector as the hardware and a static object rotating in between. The results further provided the validation of the GA-XCT being superior to the conventional algorithm, e.g., filtered back-projection (FBP) technique, in dealing with the tomography of multiphase system with binary local density field. [Copyright &y& Elsevier]

This paper presents a newly developed 3-Dimensional (3-D) simulation system for Moving Mask Deep X-ray Lithography (M²DXL) technique, and its validation. The simulation system named X-ray Lithography Simulation System for 3-Dimensional Fabrication (X3D) is tailored to simulate a fabrication process of 3-D microstructures by M²DXL. X3D consists of three modules: mask generation, exposure and resist development (hereafter development). The exposure module calculates a dose distribution in resist using an X-ray mask pattern and its movement trajectory. The dose is then converted to a resist dissolution rate. The development module adopted the "Fast Marching Method" technique to calculate the 3-D dissolution process and resultant 3-D microstructures. This technique takes into account resist dissolution direction that is required by 3-D X-ray lithography simulation. The comparison between simulation results and measurements of "stairs-like" dose deposition pattern by M²DXL showed that X3D correctly predicts the 3-D dissolution process of exposed PMMA. [ABSTRACT FROM AUTHOR]

Abstract: We have used in situ X-ray scattering and finite element modeling (FEM) to examine the micromechanics of deformation of in situ formed metallic-glass–matrix composites consisting of Ta-rich particles dispersed in an amorphous matrix. The strain measurements show that under uniaxial compression the second-phase particles yield at an applied stress of ∼325MPa. After yielding, the particles do not strain harden significantly; we show that this is due to an increasingly hydrostatic stress state arising from the lateral constraint on deformation of the particles imposed by the elastic matrix. Shear band initiation in the matrix is not due to the difference in elastic properties between the matrix and the particles. Rather, the development of a plastic misfit strain causes stress concentrations around the particles, resulting in localized yielding of the matrix by shear band formation at an applied stress of ∼1450MPa, considerably lower than the macroscopic yield stress of the composite (∼1725MPa). Shear bands do not propagate at the lower stress because the yield criterion of the matrix is only satisfied in the region immediately around the particles. At the higher stresses, the yield criterion is satisfied in large regions of the matrix, allowing extensive shear band propagation and significant macroscopic plastic deformation. However, the presence of the particles makes the stress state highly inhomogeneous, which may partially explain why fracture is suppressed in the composite, allowing the development of large plastic strains. [Copyright &y& Elsevier]

The nuclear and radiological safety regulatory framework in Cuba, until the year 2002, had not had a safety Guide for the industrial X-ray practice The improvement of our national regulatory framework, following the international recommendations and the national experience in the inspection and license activities of this practice led to the necessity of the existence of a safety Guide that would allow in an effective way to accomplish the safety criteria established in the Basic Safety Standards (BSS), during the operation of the industrial X-ray equipments. This paper exposes the main aspects that are included in this Safety Guide which are, in fact, specifications to the principles established in the BSS. [ABSTRACT FROM AUTHOR]

We discuss the fabrication of anodized aluminum nanopore arrays by electrochemical means using inexpensive and readily available equipment. The arrays of pores exhibit short-range hexagonal order, with diameters ranging from ∼7 nm to hundreds of nanometers. The pore diameter and spacing are varied by changing the anodization conditions. We have used nanopore arrays to fabricate arrays of bismuth nanowires and as masks for x-ray lithography. [ABSTRACT FROM AUTHOR]

Features equipment for industrial radiography. RID-Se4/R gamma-ray flaw detector with sharp-focus unique selenium 75 source; RID-K/100 mobile gamma-ray system; RID-KTM-6 gamma-ray flaw detector.

Low-voltage operation of millimeter-wave folded waveguide traveling-wave tube (TWT) was investigated using a 12 kV linear electron beam. Backward wave oscillation operated at second space harmonic was observed with output power of 20 W, linear tunability of 6% within 0.01 dB/MH.z, and voltage-frequency stability of 0.56 MHz/V The measured frequency and output power are in a good agreement with the predicted values using a particle-in-cell (PlC) code. In addition, backward-wave interaction at second-space harmonic as an amplifier was observed with a measured linear gain of 15 dB and a bandwidth of 03%. For forward wave Interaction, a linear gain of 25 dB, bandwidth of 17%, and efficiency of 7% were predicted for fundamental space harmonic using a PlC code. Improvement In efficiency was predicted for the forward-wave amplifier where It was operated as an oscifiator employing a delayed feedback. Output power was increased by 10 dB in the delayed feedback oscillator comparing with the backward-wave oscillator. The effect of period doubling due to potential fabrication inaccuracies on the stopband was studied experimentally. The folded waveguide TWT fabricated using the Lighographie, Galvanoformung, Abformung (LIGA) process operated at much higher frequencies is discussed. [ABSTRACT FROM AUTHOR]

Discusses the generation of femtosecond pulses from an electron storage ring. Application of x-ray pulses in investigating ultrafast structural dynamics in chemical reactions and biological processes; Determination of the duration of x-ray pulses generated by synchrotrons; Experiments on femtosecond x-rays.

Explores the efficacy of treating Escherichia coli O157:H7 in ground beef by irradiating frozen ground beef with high-dose-rate X-rays. Selection and description of accelerator; Preparation of beef samples; Discussion of the experimental protocol.

Discusses the use of radiation in industrial production. Description of electron beams and x-rays which are the types of high-energy radiation used in industry; Advantages and disadvantages of isotopes and beam-generating machines; Cost of most irradiation installations; Possibilities for radiation sterilization; Effects of radiation on plastic materials; Chemical applications; Preservation of food.

There appears to be enough evidence to support the desirability and feasibility of a study to record the diagnostic radiation exposure of radiation workers. A course of action to initiate a viable pro- gram of this type is described. [ABSTRACT FROM AUTHOR]

The article discusses the study which discovered the nanoimprint lithography (NIL) technique called substrate conformal imprint lithography (SCIL) using the equivalent tools on mask aligners from Suss MiroTec AG . It notes that the SCIL process can provide a larger area for imprinting with minimized resolutions. It implies that the SCIL technique can offer the potential reliability and efficiency in high volume production of patterned media storage and high brightness applications using light emitting diodes (LEDs).

To reduce excess radiation dosage to the population of the United States in diagnostic radiography it is necessary among other actions to reduce the size of the X-ray beam to the size of the hidden film. Two basic systems to do this automatically are available today and experience with them is discussed. [ABSTRACT FROM AUTHOR]