bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Decomposition of Pentaerythritol Tetranitrate
Authors: Tarver Craig M. , Tran Tri D. , Whipple Richard E. 
Published: August 2003

AbstractA chemical kinetic model for the thermal decomposition of the solid high explosive pentaerythritol tetranitrate (PETN) is developed for prediction of times to thermal explosion using the Chemical TOPAZ heat transfer computer code. The model is based on times to thermal explosion measured in a new One Dimensional Time to Explosion (ODTX) apparatus. ODTX experiments are reported for pure PETN and for Semtex 1A. The pure PETN results are accurately modeled using a four reaction decomposition process in which an autocatalytic process produces intermediate reaction product gases, which subsequently react in a second order gas phase process to produce the final reaction products. Semtex 1A exhibits longer times to explosion than PETN at low temperatures, indicating that its endothermic binder decomposition absorbs heat produced by PETN decomposition. This binder reaction is modeled as a first order endothermic process. Three experiments on 5.08 cm diameter unconfined cylinders of PETN ramp heated to explosion at different rates are reported. The PETN model accurately predicts the thermocouple records and explosion times for these unconfined experiments in which only intermediate gaseous products can form.
Voids and Density Distributions in 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐Hexaazaisowurtzitane (CL‐20) Prepared Under Various Conditions
Authors: Hoffman D. Mark 
Published: August 2003

AbstractThe density distributions of six samples of CL‐20 were measured using the density gradient technique. This technique was used to determine which preparation procedure produced the highest average CL‐20 density. Assuming crystals with fewer flaws result in reduced sensitivity to shock initiation, higher average crystal density (closest to the theoretical maximum density) would imply the least number of voids or inclusions. Based on hot‐spot theory, better crystals, i.e., smaller number of flaws will reduce the shock sensitivity and perhaps other impact initiation mechanisms as well. Six samples from different synthesis and crystallization procedures gave average densities from 2.042 to 2.0230 g/cm3 as measured by density gradient. Assuming the voids have no density, the crystals were between 99.90 to 98.98% of the theoretical maximum density (TMD for ε‐CL‐20 is 2.044 g/cm3). An attempt was made to account for the density difference by identifying voids in the crystals using polarized light microscopy. This method also gave some insight into the different morphologies produced by different crystallization techniques. In 3 cases voids on the order of several micrometers could be resolved in large CL‐20 crystals.
Properties of Gas‐Generating Mixtures Related to Different Fuel and Oxidizer Compositions
Authors: Engelen Karen , Lefebvre Michel H. 
Published: August 2003

AbstractThis work focuses on solid energetic materials designed to produce high‐pressure gas for pressurizing or inflating devices. In small gas generators sodium azide is often used. Unfortunately, this chemical exhibits drawbacks concerning toxicity and yield of gas. Other classical gas‐generating agents are double base propellants. However, they deliver toxic and reactive gases and their combustion temperatures are high. In previous work a series of alternative gas‐generating compositions have been proposed, fuelled with double base propellants, azodicarbonamide, nitroguanidine or guanidine nitrate and oxidized with potassium nitrate or potassium perchlorate. They were theoretically and experimentally evaluated on a series of combustion properties, such as ignition delay, burning rate, vivacity, specific energy, etc. The purpose of this paper is to experimentally examine the gas production of the previously proposed compositions. The yield of gas is determined through static pressure measurements after a closed vessel test, while the composition of the combustion gases is investigated through gas analysis. The addition of an oxidizer causes a significant drop in the yield of gas, but avoids the formation of hazardous gases, such as H2 and CO, in most of the studied cases. The only exception is the mixture of a double base propellant with potassium nitrate: potassium nitrate does not fully react with the double base propellant and therefore the formation of CO and H2 is not prevented.
Polymer Nanocomposites from Energetic Thermoplastic Elastomers and Alex®
Authors: Diaz Emmanuela , Brousseau Patrick , Ampleman Guy , Prud'homme Robert Emery 
Published: August 2003

AbstractPolymer Nanocomposites (PNs) obtained from linear energetic copolyurethane thermoplastic elastomers (ETPEs) based on GAP and a commercially available nanometric aluminum (Alex) were characterized. Two methods were performed to prepare the PNs: in‐situ and by solvent evaporation. The thermal and mechanical properties of the pure ETPEs, of the composite ETPE/Al (micrometric) and of the nanocomposite ETPE/Alex were studied. The percentage of Alex was adjusted to obtain the optimum mechanical properties. The beneficial effects of the nanopowder on the material properties are highlighted. The introduction of nanoaluminum improves the elasticity and strength of the original ETPE and, consequently, makes it easier to use, to handle, and to process. It indicates that PNs can be considered for future applications in energetic material, such as in gun propellants, rocket propellants and insensitive melt‐cast explosive formulations.
Why Wild Values Occur in Pyrotechnic Sensitivity Analysis
Authors: Chao Min‐Te , Fuh Cheng‐Der 
Published: August 2003

AbstractIn sensitivity studies when estimating the location and scale parameters for the underlying latent distribution “wild values” are often encountered. This is typically caused by the non‐existence of the corresponding estimates. A simple condition is developed, which is both necessary and sufficient for the existence of the Maximum Likelihood Estimates (MLE) in all types of sensitivity studies we are aware of. This condition can thus be employed in an iteration procedure to ensure proper convergence.
Off‐shell supergravity in five dimensions and supersymmetric brane world scenarios
Authors: Zucker M. 
Published: August 2003

AbstractWe review the construction of${\cal N}=2$off‐shell Poincaré supergravity in five dimensions. We describe in detail the minimal multiplet, which is the basic building block, containing the propagating fields of supergravity. All matter multiplets containing (8 + 8) components, being the smallest matter multiplets in five dimensions, are constructed. Using these multiplets the complete tensor calculus for supergravity is developed. As expected it turns out, that there exist three distinct minimal (i.e. containing (48 + 48) field components) off‐shell supergravities. The lagrangians for these theories and their gauged variants are given explicitly. These results are used in the second part to develop a tensor calculus on the orbifold\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$S^1/\mathbb{Z}_2$\end{document}. Gauged supergravity on the orbifold\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$S^1/\mathbb{Z}_2$\end{document}with additional cosmological constants at the fixpoints, is constructed. This generalizes the work of Randall‐Sundrum to local supersymmetry. The developed tensor calculus is used to extend this model to include matter located at the fixpoints. Chiral and super Yang‐Mills multiplets at the fixpoints are considered.
Decreased gene expression of steroid 5 alpha‐reductase 2 in human prostate cancer: Implications for finasteride therapy of prostate carcinoma
Authors: Luo Jun , Dunn Thomas A. , Ewing Charles M. , Walsh Patrick C. , Isaacs William B. 
Published: August 2003

AbstractBACKGROUNDSteroid 5α‐reductase 2 (SRD5A2) catalyzes the conversion of testosterone to the more potent androgen, DHT, in the prostate. The therapeutic influence of SRD5A2 inhibitor finasteride on prostate cancer is currently unknown. The direction and extent of changes in SRD5A2 expression in disease tissues is a relevant issue in this regard.METHODSThe expression differences of SRD5A2 in tissues representative of normal, benign, and malignant growth in the human prostate were examined in parallel by comparative analysis of relevant microarray gene expression data. Semiquantitative RT‐PCR was used to further verify the gene expression differences of SRD5A2.RESULTSConsistently decreased expression of SRD5A2 was observed in 25 prostate cancer samples when compared to 25 matched normal samples and nine BPH samples. Expression differences among these samples for six other genes were presented in parallel as indicators of the direction and extent of expression changes. These additional genes include SRD5A1, Hepsin (overexpressed in prostate cancer), AMACR (overexpressed in prostate cancer), Keratin 8 (epithelial marker), smooth muscle actin (stromal marker), Nell2 (overexpressed in BPH). Semiquantitative RT‐PCR verified the expression differences for SRD5A2 in six normal, six BPH, and six prostate cancer samples.CONCLUSIONSResults from this study, combined with those from previous studies, indicate an association of prostate cancer with reduced 5α‐reductase enzymatic activity as a result of remarkably decreased expression of the SRD5A2 gene. The implications of this study for finasteride therapy of prostate cancer are discussed. Prostate 57: 134–139, 2003. © 2003 Wiley‐Liss, Inc.
Inhibition of prostate cancer cell growth by activated eosinophils
Authors: Furbert‐Harris Paulette , Parish‐Gause Debra , Laniyan Ibrahim , Hunter Keith A. , Okomo‐Awich Josephine , Vaughn Theresa R. , Forrest Kesha C. , Howland Christina , Abdelnaby Abier , Oredipe Oladipo A. 
Published: August 2003

AbstractBACKGROUNDHost Immune response to prostate cancer primarily involves the CTL and NK effector cells. Recent immunotherapeutic strategies incorporating cytokine genes into the tumor cell and/or dendritic cells have had encouraging results. In this study, we describe the inhibitory activity of a third potential effector cell, the eosinophil, against DU 145 and PC‐3 prostate tumor cells growth in vitro.METHODSSubconfluent monolayer cultures of DU 145 and PC‐3 cells were incubated with peripheral blood eosinophils from allergic or asthmatic individuals and also with eosinophil cultured supernatants. Newly established eosinophil cell lines were also studied. After harvesting, the plates were washed and stained with Hematoxylin/eosin (H/E) then photographed. The combination of monolayer cell growth inhibition and colony formation inhibition assays were used to evaluate eosinophil inhibitory activity. In the colony formation inhibition assay one hundred cells per well in 6‐well plates were incubated overnight, after which peripheral blood eosinophils, conditioned media and cytokines, IL‐4 and TNF‐α were added. The plates were harvested after 10 days incubation period. Colonies were stained and counted.RESULTSHypo‐ and hyperdense peripheral blood eosinophils from allergic and asthmatic individuals as well as eosinophil cell lines established from these subpopulations inhibited both DU 145 and PC‐3 cell growth at 58–78% and 10–38%, respectively. IL‐5 up‐regulated eosinophil cell line activity by 21–24%. The conditioned media which contained the released mediators of activated eosinophils were potent in their actions on both DU 145 and PC‐3, inhibiting colony formation by as much as 90–100%.CONCLUSIONThese results clearly demonstrate the inhibitory potential of activated eosinophils and their released “soup” of mediators and therefore support the hypothesis that eosinophils may participate in host response to prostate cancer together with CTLs and NK cells. Furthermore, this study offers insights into possible strategies for enhancing eosinophilic activity in prostate cancer. Prostate 57: 165–175, 2003. © 2003 Wiley‐Liss, Inc.
Presence of neuroendocrine cells during postnatal development in rat prostate: Immunohistochemical, molecular, and quantitative study
Authors: Rodríguez Rosario , Pozuelo José M. , Martín Rocío , Henriques‐Gil Nuno , Haro María , Arriazu Riánsares , Santamaría Luis 
Published: August 2003

AbstractBACKGROUNDThis work was undertaken to study the prostate neuroendocrine cells (PNEC) during the post‐natal development of rats.METHODSForty male Wistar rats (pre‐pubertals, pubertals, young, and aged adults) were used for immunohistochemistry of chromogranin A (cgA), serotonin (SER), and protein gene product 9.5 (PGP9.5). They were also evaluated for numerical cell density (NV SER) and PNEC number per prostate (N SER). Five additional young adult rats were used for a RT‐PCR study (mRNA cgA detection).RESULTSWeak immunoreactivity to cgA was observed in pubertal rats. No PNEC immunostained to PGP 9.5 was observed. Cells expressing SER were detected in all the groups exclusively located in periurethral ducts. The NV SER increased significantly in pubertal animals. In aged animals, it decreased to levels observed in pre‐pubertal rats. The N SER increased significantly from pre‐pubertal to young adults, decreasing in aged adults. There was weak production of cgA mRNA, with more expression in the dorsal prostate.CONCLUSIONSPNEC differ in rats when compared to humans: they are weakly immunopositive to cgA, do not express PGP 9.5, only show immunoreactivity to SER, and do not appear in acini. The changes in the amount of rat PNEC during the post‐natal development suggest an androgenic influx. PNEC might regulate the contractility of periurethral ducts. Prostate 57: 176–185, 2003. © 2003 Wiley‐Liss, Inc.
1‐D random walk in presence of a totally reflecting barrier
Authors: Orlowski Marius 
Published: August 2003

AbstractA rigorous analysis of counting paths for 1‐D random walk in the presence of a reflecting barrier is presented. This paper defines and distinguishes between partially and totally reflecting barriers. So far, in the literature only a special case of partially reflecting barrier has been dealt with. An exact combinatorial formula is proven which describes the probability distribution of a diffusing particle at a totally reflecting barrier, allowing computation of any random walk redistribution of a diffusing species near or at the totally reflecting barrier. The analysis shows that for a particle starting its random walk at the barrier, the probability of finding it at the interface is diminishing with the number of diffusion steps N as 1/(N/2 + 1) and that the peak of the probability distribution is moving away from the barrier with the increasing number of steps as . This analysis has implications on the treatment of diffusion of impurities and point defects in thin films and in subsurface layers.
Modeling ferroelectric properties of dipole planes
Authors: Farag Nayel , Kliem Herbert 
Published: August 2003

AbstractFerroelectric properties of a system of electric dipoles arranged in a plane are calculated with a Monte Carlo simulation, the importance‐sampling method. The plane is a substructure of the perovskite structure found in barium titanate. Two sorts of dipoles are simulated: 1) permanent dipoles with two possible antiparallel orientations, 2) induced point dipoles. The permanent dipoles represent the titanium ions, and the induced point dipoles represent the oxygen atoms of the dipole plane. The dipoles are located between two plane‐parallel electrodes of a capacitor. The effect of the electrodes to the local electric field is taken into account with the method of images. With the Monte Carlo simulation the polarization of the dipole plane in dependence on the applied field is calculated. For the case without applied field we find a spontaneous polarization if the values for the polarizabilities of the induced dipoles are chosen appropriate. The temperature dependence of the spontaneous polarization is computed. From the simulations with applied field we get hysteresis loops of the polarization. We calculate the temperature dependence of the coercive field and the remanent polarization. For the susceptibility a Curie–Weiss law is found.
Statistical fluctuation of universal mobility curves in sub‐100 nm MOSFETs due to random oxide interface
Authors: Kaya Savas 
Published: August 2003

AbstractWe explore the behavior of universal mobility in sub‐100 nm Si MOSFETs, using a novel 3D statistical simulation approach. Our approach is based on 3D Brownian dynamics in devices with realistic Si/SiO2interfaces reconstructed from a Gaussian or exponential correlation function. In this approach carrier trajectories in the bulk are treated via 3D Brownian dynamics, while the carrier‐interface roughness scattering is treated using a novel empirical model. Owing to the high efficiency of the transport kernel, effective mobility in 3D MOSFETs with realistic Si/SiO2can be simulated in a statistical manner. We first demonstrate a practical calibration procedure for the interface mobility and affirm the universal behaviour in the long channel limit, using single atomic steps and a correlation length of 6 nm. Next, effective mobility in ensembles of MOSFETs with gate length down to 10 nm is investigated. It is found that random‐discrete nature of the Si/SiO2interface leads to a distribution of carrier mobility below the interface, which can deviate considerably from universal mobility curves whenLgate< 6Λ, whereΛis the correlation length for the SiO2interface. Based on recent dataΛ= 2.8 nm, our simulations indicate that universal‐mobility curves should be reliable for MOSFET designs down to a gate length of 17 nm. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Green's function approach for transport calculation in a In0.53Ga0.47As/In0.52Al0.48As modulation‐doped heterostructure
Authors: Vasileska D. , Prasad C. , Wieder H. H. , Ferry D. K. 
Published: August 2003

AbstractThe gate voltage dependence of the low‐field electron mobility has been investigated in a In0.53Ga0.47As/In0.52Al0.48As modulation‐doped heterostructure using a real‐time Green's function formalism. All scattering mechanisms relevant for this material system have been incorporated in the theoretical model, including alloy disorder scattering, Coulomb scattering from the ionized impurities in the buffer layer, acoustic phonon and piezoelectric scattering. The simulation results for the subband structure suggest occupation of two subbands at VG = 0 V. Good agreement is observed between the simulated sheet electron densities and the experimentally extracted ones from Hall and Shubnikov‐De Haas oscillatory magnetoresistance measurements. The mobility results for the structure investigated suggest that alloy‐disorder scattering is the dominant mobility degradation mechanism. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proceedings of the 4th Motorola Workshop on Computational Materials and Electronics
Authors: Demkov Alex , Fonseca Leonardo , Liu Chun‐Li 
Published: August 2003

AbstractThe 4th Motorola Workshop on Computational Materials and Electronics was held on 14–15 November 2002 in Tempe, Arizona, USA. Focus areas were computational materials and quantum transport, including molecular electronics, and nanodevices. The cover picture shows a prototype 1 nm silicon quantum dot formed by high‐temperature synthesis which luminesces in the ultraviolet at 400 nm, taken from [1]. The proceedings of the workshop series are published in this journal for the third time, following the 2nd and 3rd Motorola Workshops in phys. stat. sol. (b) 226, No. 1 (2001), and phys. stat. sol. (b) 233, No. 1 (2002), respectively.This issue is completed by Original Papers including the Editor's Choice by M. Q. Weng and M. W. Wu, a many‐body study on spin dephasing in n‐type GaAs quantum wells in the presence of high magnetic fields [2].
A user‐assisted approach to component clustering
Authors: Sartipi Kamran , Kontogiannis Kostas 
Published: August 2003

AbstractIn this paper, we present a user‐assisted clustering technique for software architecture recovery based on a proximity measure that we call component association. The component association measure is computed on the shared properties among groups of highly related system entities. In this approach, the software system is modeled as an attributed relational graph with the software constructs (entities) represented as nodes and data/control dependencies represented as edges. The application of data mining techniques on the system graph allows us to generate a component graph where the edges are labeled by the association strength values among the components. An interactive partitioning technique is used to partition a system into cohesive components. Graph visualization tools and cluster quality evaluation metrics are applied by the user to assess and fine tune the partition result. Copyright © 2003 John Wiley & Sons, Ltd.
Theoretical framework and empirical evidence of students' cognitive processes in three dimensions of content, complexity, and time
Authors: von Aufschnaiter Claudia , von Aufschnaiter Stefan 
Published: August 2003

AbstractIn the literature, learners' cognitive development is mainly discussed with respect to changes in learners' content‐dependent knowledge (conceptual change or growth). Additional dimensions of time and complexity may also be taken into account to describe cognitive processes in at least three dimensions. We discuss these three dimensions of content, complexity, and time theoretically and show empirically what results can be found with such a framework. The primary database consists of 27 students who worked in groups of three on physics tasks during three sessions in an experimental setting. All activities were videotaped and analyzed in great detail. Results indicate that students' meanings always refer to a narrow area of content, are developed bottom‐up with respect to complexity, and show time‐dependent dynamics in which maxima of 30 seconds and 5 minutes are important time scales. Comparison with outcomes of additional experimental settings on the same topic with more and less advanced students indicate the results to have a greater validity. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 616–648, 2003
Development of chemistry attitudes and experiences questionnaire (CAEQ)
Authors: Dalgety Jacinta , Coll Richard K. , Jones Alister 
Published: August 2003

AbstractIn this article we describe the development of the Chemistry Attitudes and Experiences Questionnaire (CAEQ) that measures first‐year university chemistry students' attitude toward chemistry, chemistry self‐efficacy, and learning experiences. The instrument was developed as part of a larger study and sought to fulfill a need for an instrument to investigate factors that influence student enrollment choice. We set out to design the instrument in a manner that would maximize construct validity. The CAEQ was piloted with a cohort of science and technology students (n = 129) at the end of their first year. Based on statistical analysis the instrument was modified and subsequently administered on two occasions at two tertiary institutions (n = 669). Statistical data along with additional data gathered from interviews suggest that the CAEQ possesses good construct validity and will prove a useful tool for tertiary level educators who wish to gain an understanding of factors that influence student choice of chemistry enrolment. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 649–668, 2003