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In present study, a novel biocarrier was fabricated from wood and high density polyethylene (HDPE) using a single screw extruder. The effect of wood:plastic mass ratio on physico-chemical properties of the obtained wood plastic composite (WPC) was evaluated. While the tensile and flexural strengths were decreased, the sample density was increased with higher wood contents. The wood:plastic mass ratio of 1:1 was considered as the best for the production of WPC biocarriers. The role of this material in moving bed biofilm system was tested in a batch mode reactor having volume of 2 L with 20% filling by the biocarrier. The treatment efficiencies of organic matter, ammonia and phosphate were enhanced nearly two times. The results are attributed to heterogenous and porous surface of WPC, which enhances bacteria adhesion and pollutant removal. It demonstrates that WPC can be a potential biocarrier for use in moving bed biofilm reactors (MBBRs).

In this research, the commercial PVDF/PVP membrane was irradiated at 10 and 100 kGy with electron beam (EB) to improve its fouling resistance capacity. Membrane irradiation was conducted in the presence of zwitterionic molecules ( L -Cysteine, Phosphocholine) and with 2-(Dimethylamino)ethyl methacrylate). The main goal was to investigate the impact of irradiation in presence of zwitterions on the modification route of PVP within the polymer blend and to relate it to filtration performances. Globally, EB irradiation enhanced the membrane’s filtration performance but this improvement cannot be sustained after several filtration cycles. Membranes irradiated with the lower absorbed dose (10 kGy) displayed higher permeate flux and lower cake resistance than membranes irradiated with the 100 kGy dose. The best sustainable anti-fouling capacity was observed for the membrane irradiated with 10 kGy in the presence of L -Cysteine. Membrane characterization showed that the membrane surface was modified by EB irradiation, with features such as smoother surface, modification of PVP and increased amount of crosslinking emphasizing the potential formation of PVP hydrogels. Despite obvious changes observed on membrane surface depending on the chosen compounds used for irradiation, membranes’ analyses failed to identify sulphur, phosphorous grafted moieties. From this study, it is confirmed that membranes EB irradiation in presence of zwitterionic molecules is a promising technique to modify the PVDF/PVP blended polymer.

Electron bifurcation plays a key role in anaerobic energy metabolism, but it is a relatively new discovery, and only limited mechanistic information is available on the diverse enzymes that employ it. Herein, we focused on the bifurcating electron transfer flavoprotein (ETF) from the hyperthermophilic archaeon Pyrobaculum aerophilum. The EtfABCX enzyme complex couples NADH oxidation to the endergonic reduction of ferredoxin and exergonic reduction of menaquinone. We developed a model for the enzyme structure by using nondenaturing MS, cross-linking, and homology modeling in which EtfA, -B, and -C each contained FAD, whereas EtfX contained two [4Fe-4S] clusters. On the basis of analyses using transient absorption, EPR, and optical titrations with NADH or inorganic reductants with and without NAD(+), we propose a catalytic cycle involving formation of an intermediary NAD(+)-bound complex. A charge transfer signal revealed an intriguing interplay of flavin semiquinones and a protein conformational change that gated electron transfer between the low- and high-potential pathways. We found that despite a common bifurcating flavin site, the proposed EtfABCX catalytic cycle is distinct from that of the genetically unrelated bifurcating NADH-dependent ferredoxin NADP(+) oxidoreductase (NfnI). The two enzymes particularly differed in the role of NAD(+), the resting and bifurcating-ready states of the enzymes, how electron flow is gated, and the two two-electron cycles constituting the overall four-electron reaction. We conclude that P. aerophilum EtfABCX provides a model catalytic mechanism that builds on and extends previous studies of related bifurcating ETFs and can be applied to the large bifurcating ETF family.

Introduction et but de l’etude De juillet 2008 a decembre 2018, plus de 2000 evenements significatifs de radioprotection ont ete declares a l’Agence de surete nucleaire (ASN). Durant cette periode, 57 evenements significatifs de radioprotection ont ete classes aux niveaux 2 ou 2+ de l’echelle ASN-SFRO, soit moins de 3 % des evenements declares, et ont concerne un total de 139 patients. Aucun evenement de niveau 3 ou plus n’a ete reporte. Notre etude propose une analyse de ces evenements ainsi que du suivi des patients concernes, a l’occasion des 10 ans d’utilisation de l’echelle ASN-SFRO. Materiel et methodes A partir du registre anonymise des evenements significatifs de radioprotection de l’ASN, les centres concernes ont ete contactes afin de recueillir les donnees concernant les patients pour lesquels un evenement de niveau 2 ou 2+ a ete declare de juillet 2008 a decembre 2018. Les donnees ont ete recueillies de juin 2019 a octobre 2020 et analysees en novembre 2020, si un refus de patient n’a pas ete emis et si le centre acceptait de participer a l’etude. Resultats et analyse statistique Les evenements etaient principalement dus a des erreurs de calculs dosimetriques (25 %), de positionnement (19 %), de fractionnement (19 %) et de lateralite (14 %). Les principales techniques concernees etaient la radiotherapie conformationnelle tridimensionnelle (39 %), la radiotherapie en conditions stereotaxiques (21 %), la curietherapie (14 %) et la radiotherapie conformationnelle avec modulation d’intensite (12 %). Apres exclusion des patients ou des centres ayant emis un refus, 112 patients ont ete analyses. Les patients ont recu un traitement a visee curative dans 61,9 % des cas. La dose mediane prescrite etait de 45 Gy (intervalle : 6–145 Gy) et la dose mediane delivree etait de 47,8 Gy (intervalle : 6–146 Gy), avec un surdosage relatif median de 6,3 % (intervalle : 0,4–100 %). A la date de l’analyse, 53 patients (soit 51,8 %) etaient decedes en raison d’une evolution carcinologique dans 79 % des cas ou d’une autre cause non liee au cancer dans 9 % des cas. Aucun deces n’a ete du a l’evenement significatif de radioprotection, sous reserve de 12 % de deces de cause inconnue, et de 29,5 % de patients perdus de vue. Le suivi median etait de 20 mois (intervalle : 0–123 mois), avec un suivi superieur a 6 mois pour 86 patients (soit 76,8 %). Pour ces 86 patients, 72 % ne presentaient pas de toxicite tardive a la date de dernieres nouvelles et 10,5 % ont presente une toxicite tardive de grade 1. Les taux de toxicite tardive de grade 2, 3 et 4 etaient respectivement de 7,5 %, 2,3 % et 1,2 %. Conclusion Meme si le taux de complications tardives se veut rassurant, l’heterogeneite des evenements significatifs de radioprotection, le delai insuffisant de suivi et la part non negligeable de patients perdus de vue rendent difficile l’evaluation de l’impact reelle de ces evenements. La constitution d’une base de donnees nationale de suivi serait une solution pertinente afin de permettre un suivi prospectif regulier et rigoureux du patient.

Electron bifurcation has recently gained acceptance as the third mechanism of energy conservation in which energy is conserved through the coupling of exergonic and endergonic reactions. A structure-based mechanism of bifurcation has been elucidated recently for the flavin-based enzyme NADH-dependent ferredoxin NADP+ oxidoreductase I (NfnI) from the hyperthermophillic archaeon Pyrococcus furiosus. NfnI is thought to be involved in maintaining the cellular redox balance, producing NADPH for biosynthesis by recycling the two other primary redox carriers, NADH and ferredoxin. The P. furiosus genome encodes an NfnI paralog termed NfnII, and the two are differentially expressed, depending on the growth conditions. In this study, we show that deletion of the genes encoding either NfnI or NfnII affects the cellular concentrations of NAD(P)H and particularly NADPH. This results in a moderate to severe growth phenotype in deletion mutants, demonstrating a key role for each enzyme in maintaining redox homeostasis. Despite their similarity in primary sequence and cofactor content, crystallographic, kinetic, and mass spectrometry analyses reveal that there are fundamental structural differences between the two enzymes, and NfnII does not catalyze the NfnI bifurcating reaction. Instead, it exhibits non-bifurcating ferredoxin NADP oxidoreductase-type activity. NfnII is therefore proposed to be a bifunctional enzyme and also to catalyze a bifurcating reaction, although its third substrate, in addition to ferredoxin and NADP(H), is as yet unknown.

Flavin-based electron transfer bifurcation is emerging as a fundamental and powerful mechanism for conservation and deployment of electrochemical energy in enzymatic systems. In this process, a pair of electrons is acquired at intermediate reduction potential (i.e. intermediate reducing power), and each electron is passed to a different acceptor, one with lower and the other with higher reducing power, leading to “bifurcation.” It is believed that a strongly reducing semiquinone species is essential for this process, and it is expected that this species should be kinetically short-lived. We now demonstrate that the presence of a short-lived anionic flavin semiquinone (ASQ) is not sufficient to infer the existence of bifurcating activity, although such a species may be necessary for the process. We have used transient absorption spectroscopy to compare the rates and mechanisms of decay of ASQ generated photochemically in bifurcating NADH-dependent ferredoxin-NADP+ oxidoreductase and the non-bifurcating flavoproteins nitroreductase, NADH oxidase, and flavodoxin. We found that different mechanisms dominate ASQ decay in the different protein environments, producing lifetimes ranging over 2 orders of magnitude. Capacity for electron transfer among redox cofactors versus charge recombination with nearby donors can explain the range of ASQ lifetimes that we observe. Our results support a model wherein efficient electron propagation can explain the short lifetime of the ASQ of bifurcating NADH-dependent ferredoxin-NADP+ oxidoreductase I and can be an indication of capacity for electron bifurcation.

Summary Ethanol is an important target for the renewable production of liquid transportation fuels. It can be produced biologically from pyruvate, via pyruvate decarboxylase, or from acetyl-CoA, by alcohol dehydrogenase E (AdhE). Thermophilic bacteria utilize AdhE, which is a bifunctional enzyme that contains both acetaldehyde dehydrogenase and alcohol dehydrogenase activities. Many of these organisms also contain a separate alcohol dehydrogenase (AdhA) that generates ethanol from acetaldehyde, although the role of AdhA in ethanol production is typically not clear. As acetyl-CoA is a key central metabolite that can be generated from a wide range of substrates, AdhE can serve as a single gene fuel module to produce ethanol through primary metabolic pathways. The focus here is on the hyperthermophilic archaeon Pyrococcus furiosus, which grows by fermenting sugar to acetate, CO2 and H2. Previously, by the heterologous expression of adhA from a thermophilic bacterium, P. furiosus was shown to produce ethanol by a novel mechanism from acetate, mediated by AdhA and the native enzyme aldehyde oxidoreductase (AOR). In this study, the AOR gene was deleted from P. furiosus to evaluate ethanol production directly from acetyl-CoA by heterologous expression of the adhE gene from eight thermophilic bacteria. Only AdhEs from two Thermoanaerobacter strains showed significant activity in cell-free extracts of recombinant P. furiosus and supported ethanol production in vivo. In the AOR deletion background, the highest amount of ethanol (estimated 61% theoretical yield) was produced when adhE and adhA from Thermoanaerobacter were co-expressed.

The hyperthermophilic archaeon, Pyrococcus furiosus, grows optimally near 100°C by fermenting sugars to acetate, carbon dioxide and molecular hydrogen as the major end products. The organism has recently been exploited to produce biofuels using a temperature-dependent metabolic switch using genes from microorganisms that grow near 70°C. However, little is known about its metabolism at the lower temperatures. We show here that P. furiosus produces acetoin (3-hydroxybutanone) as a major product at temperatures below 80°C. A novel type of acetolactate synthase (ALS), which is involved in branched-chain amino acid biosynthesis, is responsible and deletion of the als gene abolishes acetoin production. Accordingly, deletion of als in a strain of P. furiosus containing a novel pathway for ethanol production significantly improved the yield of ethanol. These results also demonstrate that P. furiosus is a potential platform for the biological production of acetoin at temperatures in the 70-80°C range.

Although the extremely thermophilic archaea (T(opt) ≥ 70°C) may be the most primitive extant forms of life, they have been studied to a limited extent relative to mesophilic microorganisms. Many of these organisms have unique biochemical and physiological characteristics with important biotechnological implications. These include methanogens that generate methane, fermentative anaerobes that produce hydrogen gas with high efficiency, and acidophiles that can mobilize base, precious and strategic metals from mineral ores. Extremely thermophilic archaea have also been a valuable source of thermoactive, thermostable biocatalysts, but their use as cellular systems has been limited because of the general lack of facile genetics tools. This situation has changed recently, however, thereby providing an important avenue for understanding their metabolic and physiological details and also opening up opportunities for metabolic engineering efforts. Along these lines, extremely thermophilic archaea have recently been engineered to produce a variety of alcohols and industrial chemicals, in some cases incorporating CO(2) into the final product. There are barriers and challenges to these organisms reaching their full potential as industrial microorganisms but, if these can be overcome, a new dimension for biotechnology will be forthcoming that strategically exploits biology at high temperatures.

Recent investigations into ferredoxin-dependent transhydrogenases, a class of enzymes responsible for electron transport, have highlighted the biological importance of flavin-based electron bifurcation (FBEB). FBEB generates biomolecules with very low reduction potential by coupling the oxidation of an electron donor with intermediate potential to the reduction of high and low potential molecules. Bifurcating systems can generate biomolecules with very low reduction potentials, such as reduced ferredoxin (Fd), from species such as NADPH. Metabolic systems that use bifurcation are more efficient and confer a competitive advantage for the organisms that harbor them. Structural models are now available for two NADH-dependent ferredoxin-NADP+ oxidoreductase (Nfn) complexes. These models, together with spectroscopic studies, have provided considerable insight into the catalytic process of FBEB. However, much about the mechanism and regulation of these multi-subunit proteins remains unclear. Using hydrogen/deuterium exchange mass spectrometry (HDX-MS) and statistical coupling analysis (SCA), we identified specific pathways of communication within the model FBEB system, Nfn from Pyrococus furiosus, under conditions at each step of the catalytic cycle. HDX-MS revealed evidence for allosteric coupling across protein subunits upon nucleotide and ferredoxin binding. SCA uncovered a network of co-evolving residues that can provide connectivity across the complex. Together, the HDX-MS and SCA data show that protein allostery occurs across the ensemble of iron‑sulfur cofactors and ligand binding sites using specific pathways that connect domains allowing them to function as dynamically coordinated units.

This paper proposes an integrated numerical approach to model the thin-film deposition of amorphous silicon in the afterglow of argon plasma. The investigated plasma enhanced chemical vapor deposition (PECVD) process is governed by gas flow equations, chemical kinetics equations and surface reaction equations. Nineteen species, i.e. Ar, Ar*, Ar+, Si2H6, Si2H4, SiH4, SiH3, SiH2, SiH, H2, H, Si, Si+, SiH 3 + , SiH 2 + , SiH+, H 2 + , H+ and electron (e) are considered, where 52 chemical reaction equations are adopted to describe the reactions in space among silane, hydrogen and argon plasma. Continuity, momentum and energy equations are solved to describe the velocity, pressure and temperature field of gas flow in the process chamber, while the density of neutral species is calculated from the corresponding transport equation considering its convection and diffusion effect, as well as the production and destruction due to chemical reactions. The transport equations of charged species are modeled by a drift–diffusion approximation. The ambipolar diffusion is assumed for charged species in the afterglow of argon plasma due to the vanishing of external electrical field. The equation of energy balance for electron is applied to the estimation of the electron temperature in the process chamber. In this study, ten reaction mechanisms of thin film growth are taken into account. The species considered in the deposition process on substrates are silane, the free radicals of silane, hydrogen, hydrogen atom, silicon atom, the species with dangling bond on the substrate surface covered by active and the passive site. All governing equations are discretized by using a finite volume method and solved by an iterative approach. The variables, such as position, velocity and moment, are expressed by Cartesian coordinates, where the non-staggered variable arrangement is adopted to define field variables. The deferred correction approach is employed to approximate for both diffusion and source terms, where SIMPLE algorithm is used to decouple pressure and velocity. A parallelized numerical scheme is implemented via MPI library. Numerical simulations with different operation parameters are performed to show their influence on the deposition rate. The numerical results indicate the deposition rate exhibits a double-peak characteristic on the substrate and give an average value varying between 5 A/s and 10 A/s for the studied PECVD process in the afterglow of argon plasma.

Structural analysis and spectroscopy elucidate how pairs of electrons are bifurcated in a flavoenzyme by generating an unstable flavin semiquinone, thus coupling exergonic and endergonic oxidation–reduction reactions. The recently realized biochemical phenomenon of energy conservation through electron bifurcation provides biology with an elegant means to maximize utilization of metabolic energy. The mechanism of coordinated coupling of exergonic and endergonic oxidation–reduction reactions by a single enzyme complex has been elucidated through optical and paramagnetic spectroscopic studies revealing unprecedented features. Pairs of electrons are bifurcated over more than 1 volt of electrochemical potential by generating a low-potential, highly energetic, unstable flavin semiquinone and directing electron flow to an iron–sulfur cluster with a highly negative potential to overcome the barrier of the endergonic half reaction. The unprecedented range of thermodynamic driving force that is generated by flavin-based electron bifurcation accounts for unique chemical reactions that are catalyzed by these enzymes.

The electrical and thermal conductivities of a silver flake/thermosetting polymer matrix composite were studied experimentally and analytically in terms of silver flake size and size distribution. The electrical volume resistivity and the steady-state thermal conductivity of the composite were measured at various silver flake loading. The analytical study was based on a three-dimensional resistor network model, which takes into account percolation and microscopic conduction mechanisms. The predictions based on the resistor network model were compared with the experimental data, resulting in a reasonably good agreement. It was found that flakes with smaller mean value in size and broader size distribution yield smaller threshold volume fraction of silver flake. It was shown that the predictions by the present thermal resistor network model yields better agreement with the experimental data than those by the effective medium theory such as Eshelby’s model, for a composite with high thermal conductivity ratio of filler to matrix.

The Power Systems Development group at SLAC has developed an improved design for the H-bridge switch plates of the High Voltage Converter Modulators at the Spallation Neutron Source. This integral modulator component has been identified as the source of numerous modulator faults. This paper presents the design and implementation of the alternative switch plate, which is based upon press-pack IGBTs.

Carbon monoxide (CO) is an important intermediate in anaerobic carbon fixation pathways in acetogenesis and methanogenesis. In addition, some anaerobes can utilize CO as an energy source. In the hyperthermophilic archaeon Thermococcus onnurineus, which grows optimally at 80°C, CO oxidation and energy conservation is accomplished by a respiratory complex encoded by a 16-gene cluster containing a carbon monoxide dehydrogenase, a membrane-bound [NiFe]-hydrogenase and a Na+/H+ antiporter module. This complex oxidizes CO, evolves CO2 and H2, and generates a Na+ motive force that is used to conserve energy by a Na+-dependent ATP synthase. Herein we used a bacterial artificial chromosome to insert the 13.2 kb gene cluster encoding the CO-oxidizing respiratory complex of T. onnurineus into the genome of the heterotrophic archaeon, Pyrococcus furiosus, which grows optimally at 100°C. P. furiosus is normally unable to utilize CO, however, the recombinant strain readily oxidized CO and generated H2 at 80°C. Moreover, CO also served as an energy source and allowed the P. furiosus strain to grow with a limiting concentration of sugar or with peptides as the carbon source. Moreover, CO oxidation by P. furiosus was also coupled to the re-utilization, presumably for biosynthesis, of acetate generated by fermentation. The functional transfer of CO utilization between Thermococcus and Pyrococcus species demonstrated herein is representative of the horizontal gene transfer of an environmentally-relevant metabolic capability. The transfer of CO utilizing, hydrogen-producing genetic modules also has applications for biohydrogen production and a CO-based industrial platform for various thermophilic organisms.

The visible burrow system (VBS) is a model used to study chronic social stress in colony-housed rats. A hierarchy develops among the males resulting in dominant (DOM) and subordinate (SUB) animals. Hierarchy-associated changes in body weight, body composition, behavior, and neuroendocrine measures have been observed. After 14 d of VBS housing, SUB animals have decreased body weight, elevated corticosterone, and decreased testosterone (T), compared with DOM animals and controls, placing SUB animals in an ideal endocrine state to regain lost body weight as adipose tissue. It is hypothesized that maintaining constant androgen concentrations in SUB males during stress will prevent body weight loss by maintaining more lean body mass. To test this, animals were gonadectomized and implanted with SILASTIC implants containing T, 5α-dihydrotestosterone (DHT), or cholesterol. Implants maintained constant physiological levels of T. Standard intact, T, and DHT implant colonies formed hierarchies, whereas cholesterol colonies did not. Androgen manipulations significantly altered offensive and defensive behaviors only on the first day of VBS housing. After VBS stress, intact, T, and DHT SUB animals weighed less and lost more adipose and lean tissue than DOM and control males, whereas DOM animals primarily lost adipose tissue. However, on recovery, DHT SUB animals maintained more lean tissue than intact SUB animals. Oral glucose tolerance tests revealed that glucose clears faster in stressed T-implanted males that have increased adipose tissue. Overall, these data suggest that constant androgen concentrations in SUB animals do not prevent weight loss and changes in body composition during stress but do so during recovery.

Social stress resulting from dominant-subordinate relationships is associated with body weight loss and altered body composition in subordinate (SUB) male rats. Here, we extend these findings to determine whether stress-induced changes in energy homeostasis persist when the social stress is removed, and the animal is allowed to recover. We examined body weight (BW), body composition, and relevant endocrine measures after one or two cycles of 14 days of social stress, each followed by 21 days of recovery in each rat's individual home cage. SUB lost significantly more BW during social housing in a visible burrow system (VBS) compared with dominant (DOM) animals. Weight loss during social stress was attributable to a decrease in adipose tissue in DOM and SUB, with an additional loss of lean tissue in SUB. During both 21-day recovery periods, DOM and SUB regained lost BW, but only SUB were hyperphagic. Following recovery, SUB had a relatively larger increase in adipose tissue and plasma leptin compared with DOM, indicating that body composition changes were dependent on social status. Control animals that were weight matched to SUB or male rats exposed to the VBS environment without females, and that did not form a social hierarchy, did not exhibit changes in body composition like SUB in the VBS. Therefore, chronic social stress causes social status-dependent changes in BW, composition and endocrine measures that persist after repeated stress and recovery cycles and that may ultimately lead to metabolic disorders and obesity.

The next linear collider (NLC) accelerator proposal at Stanford Linear Accelerator Center (SLAC, Menlo Park, CA), requires a highly efficient and reliable, low cost, pulsed-power modulator to drive the klystrons. A solid-state induction modulator has been developed at SLAC to power the klystrons; this modulator uses commercial high voltage and high current insulated gate bipolar transistor (IGBT) modules. Testing of these IGBT modules under pulsed conditions was very successful; however, the IGBTs failed when tests were performed into a low inductance short circuit. The internal electrical connections of a commercial IGBT module have been analyzed to extract self- and mutual partial inductances for the main current paths as well as for the gate structure. The IGBT module, together with the partial inductances, has been modeled using PSpice. Predictions for electrical paths that carry the highest current correlate with the sites of failed die under short circuit tests. A similar analysis has been carried out for a SLAC proposal for an IGBT module layout. This paper discusses the mathematical model of the IGBT module geometry and presents simulation results.

Bioethanol production is achieved by only two metabolic pathways and only at moderate temperatures. Herein a fundamentally different synthetic pathway for bioalcohol production at 70 °C was constructed by insertion of the gene for bacterial alcohol dehydrogenase (AdhA) into the archaeon Pyrococcus furiosus. The engineered strain converted glucose to ethanol via acetate and acetaldehyde, catalyzed by the host-encoded aldehyde ferredoxin oxidoreductase (AOR) and heterologously expressed AdhA, in an energy-conserving, redox-balanced pathway. Furthermore, the AOR/AdhA pathway also converted exogenously added aliphatic and aromatic carboxylic acids to the corresponding alcohol using glucose, pyruvate, and/or hydrogen as the source of reductant. By heterologous coexpression of a membrane-bound carbon monoxide dehydrogenase, CO was used as a reductant for converting carboxylic acids to alcohols. Redirecting the fermentative metabolism of P. furiosus through strategic insertion of foreign genes creates unprecedented opportunities for thermophilic bioalcohol production. Moreover, the AOR/AdhA pathway is a potentially game-changing strategy for syngas fermentation, especially in combination with carbon chain elongation pathways.

A novel snap curable organic die attach adhesive has been developed for hermetic packages. This thermoset die-attach paste is suitable for use on conventional dispensing equipment. This material can be cured in less than 60 s at 200 degrees C and does not generate any appreciable weight loss during cure. The authors review the chemical and physical characteristics of the material along with its functional performance as a die-attach medium. The combination of a glass transition temperature around 260 degrees C and high thermal stability up to 400 degrees C provides significant performance enhancement over conventional epoxies. In addition, the material exhibits high adhesive strengths while imparting low stress on the die. Experimental results show that the moisture content in the cavity of a Au-Sn solder sealed ceramic package is less than 1000 ppm. The low moisture characteristic is found to be an inherent property of the material. Reliability tests such as thermal cycling and high temperature storage have shown that the low moisture level is still maintained after 1000 cycles or 1000 h at 150 degrees C. >

The bed nucleus of the stria terminalis (BST) plays a prominent role in brain integration of acute responses to stressful stimuli. This study tests the hypothesis that the BST plays a complementary role in regulation of physiological changes associated with chronic stress exposure. Male Sprague-Dawley rats received bilateral ibotenate lesions or sham lesions of the posterior medial region of the BST (BSTpm), an area known to be involved in inhibition of HPA axis responses to acute stress. Chronic stress was induced by 14-day exposure to twice daily stressors in an unpredictable sequence (chronic variable stress, CVS). In the morning after the end of CVS, stressed and non-stressed controls were exposed to a novel restraint stress challenge. As previously documented, CVS caused adrenal hypertrophy, thymic involution, and attenuated body weight gain. None of these endpoints were affected by BSTpm lesions. Chronic stress exposure facilitated plasma corticosterone responses to the novel restraint stress and elevated CRH mRNA. Lesions of the BSTpm increased novel stressor-induced plasma ACTH and corticosterone secretion and enhanced c-fos mRNA induction in the paraventricular nucleus of the hypothalamus (PVN). In addition, lesion of the BSTpm resulted in an additive increase in CVS-induced facilitation of corticosterone responses and PVN CRH expression. Collectively these data confirm that the BSTpm markedly inhibits HPA responses to acute stress, but do not strongly support an additional role for this region in limiting HPA axis responses to chronic drive. The data further suggest that acute versus chronic stress integration are subserved by different brain circuitry.

The sintering characteristics of a silver-filled lead borate glass composite were studied since it influences die stresses. This is especially true for very-large-area die attachments. The kinetics of silver particle sintering in the presence of liquid-phase glass was examined by dilatometry and electron microscopy. During heat treatment, the sintering rate is significantly increased after the glass becomes liquid. This can cause excessive die stresses, resulting in cracks, typically at the die-bond interface, and/or poor adhesion. The sintering process is influenced by material parameters such as silver flake surface area, glass transition temperature, and additives, and by process profiles such as temperature ramp rate and dwell time. It was found that, by adding a small amount of appropriate additives, it is possible to either increase or decrease the sintering rate significantly. Thus, stress relief in large-area dice can be achieved by using additives in silver-glass to control the sintering rate. >

To facilitate a rapid response to the International Linear Collider (ILC) L-band development program at SLAC, a spare converter-modulator was shipped from LANL. This modulator was to be a spare for the spallation neutron source (SNS) accelerator at ORNL. The ILC application requires a 33% higher peak output power (15 MW) and output current (120 Amp). This presents significant design challenges to modify the existing hardware and yet maintain switching parameters and thermal cycling within the semiconductor component ratings. To minimize IGBT commutation and free-wheeling diode currents, a different set of optimizations, as compared to the SNS design, were used to tune the resonant switching networks. Additional complexities arose as nanocrystalline cores with different performance characteristics (as compared to SNS), were used to fabricate the resonant "boost" transformers. This paper will describe the electrical design, modelling efforts, and resulting electrical performance as implemented for the ILC L-band test stand.

Summary form only given. A solid state induction modulator was designed and operated for the Next Linear Collider accelerator project at SLAC (Stanford Linear Accelerator Center) to drive 8 X-band klystron. With the redirection of the NLC physics program, the remaining hardware from the DFM (Design for Manufacturability) modulator was combined with existing pulse transformers to fabricate two hybrid solid state induction modulators, one to drive two XK5 klystrons at 420 kV 400 A 1.5 mus and a second modulator to drive a single 5045 klystron to 360 kV 430 A 3.5 mus. These modulators use induction cells to drive a conventional pulse transformer. Both modulator are smaller and operate at a lower operating voltage than a equivalent modulator using thyratron and PFN. The modulator have been fabricated, tested, and are in operation. The design, implementation, and results will be describe in the paper.

Evanescently coupled waveguide arrays are written in fused silica using femtosecond laser pulses. Array supermodes are tailored by adjusting the writing conditions of a common central core and agree with scattering matrix method simulations.

Social stress is prevalent in many facets of modern society. Epidemiological data suggest that stress is linked to the development of overweight, obesity and metabolic disease. Although there are strong associations between the incidence of obesity with stress and elevated levels of hormones such as cortisol, there are limited animal models to allow investigation of the etiology of increased adiposity resulting from exposure to stress. Perhaps more importantly, an animal model that mirrors the consequences of stress in humans will provide a vehicle to develop rational clinical therapy to treat or prevent adverse outcomes from exposure to chronic social stress. In the visible burrow system (VBS) model of chronic social stress mixed gender colonies are housed for 2 week periods during which male rats of the colony quickly develop a dominance hierarchy. We found that social stress has significant effects on body weight and body composition such that subordinate rats progressively develop characteristics of obesity that occurs, in part, through neuroendocrine alterations and changes in food intake amount. Although subordinate rats are hyperphagic following social stress they do not increase their intake of sucrose solution as control and dominants do suggesting that they are anhedonic. Consumption of a high fat diet does not appear to affect development of a social hierarchy and appears to enhance the effect that chronic stress has on body composition. The visible burrow system (VBS) model of social stress may be a potential laboratory model for studying stress-associated metabolic disease, including the metabolic syndrome.

A compact, water cooled, high power switch for the Superconducting Module Test Facility (SMTF) long-pulse klystron modulator has been constructed and implemented at the Fermi National Accelerator Laboratory (FNAL). This solid-state switch is composed of six series devices, each having a rating of 4.5 kV and 2000 Adc. Latest generation, press-pack IGBT modules are utilized to reduce the physical size and complexity of the switch assembly. The new switch and its associated controller provide a high degree of redundancy and fail-safe operation, which meets the modulator requirements. This paper describes the general switch assembly, IGBT protection and control schemes, and test results.

Prolonged social subjugation produces physiological indices of chronic stress in rats. In the current study, we examined the impact of social stress on glutamic acid decarboxylase (GAD) isoforms, corticotropin-releasing hormone (CRH) and vasopressin mRNA expression in forebrain stress circuitry, using the visible burrow system model of dominance–subordination. Subordinate male rats develop behavioral and neuroendocrine changes consistent with exposure to chronic stress, including marked loss of body weight and elevation of basal plasma corticosterone relative to dominant rats. Forebrain GAD65, GAD67, CRH and vasopressin mRNA expression in central stress-regulatory circuits were examined by in situ hybridization. Elevated CRH mRNA was observed in the oval nucleus of the bed nucleus of the stria terminalis (BST) of subordinate males. In contrast, GAD67 expression was decreased in the interfascicular nucleus of the BST in both the subordinate and dominant rats compared to non-burrow control rats. No changes in CRH, GAD or vasopressin were observed in amygdaloid nuclei, other BST nuclei or in the hypothalamic paraventricular nucleus. Collectively, these data suggest that exposure to the visible burrow system attenuates BST GAD expression regardless of social status, whereas the enhanced physiological responses to social stress seen in subordinates may be associated with enhanced CRH expression in the oval nucleus of the BST.

Group-housed male rats form social hierarchies, and under these conditions, it has been reported that subordinate (SUB) rats consume more alcohol than dominant (DOM) rats. We tested the hypothesis that a history of drinking alcohol would cause SUB rats to consume even greater amounts of alcohol.Male Long-Evans rats were trained to drink 10% alcohol or a sucrose/quinine solution equal in calories for 1 h/day using a sucrose-fading procedure. Subsequently, rats were housed in colonies (four males, two females) in a visible burrow system (VBS) for 14 days. Individual control male rats were housed in a tub cage with one female. Rats were removed from the VBS (or control environment) daily and given 1 h to drink alcohol or sucrose/quinine.Colonies given daily access to sucrose/quinine formed clear DOM/SUB relationships in all measured parameters. Alcohol-drinking colonies failed to establish a dominance hierarchy and displayed little aggression, with an average of 14.6 +/- 6.1 offensive attacks compared with 58.5 +/- 12.3 attacks carried out by DOM sucrose/quinine rats. During VBS housing, alcohol and sucrose/quinine intake decreased independent of housing environment or social status.Contrary to prior reports of the effect of alcohol on aggressive behavior, moderate daily alcohol intake before and during VBS housing reduced aggression and precluded the formation of a dominance hierarchy in rats.

As the switching capabilities of solid-state devices increase, these devices are being incorporated into modulator designs for high voltage accelerator applications. Solid-state modulators based on inductive adder circuit topology have demonstrated great versatility with regard to pulse width and pulse repetition rate while maintaining fast pulse rise and fall times. Additionally, these modulators are capable of being scaled to higher output voltage and power levels. An explanation of the basic circuit operation will be presented as well as test data of several different hardware systems.

The next linear collider (NLC) accelerator proposal at Stanford Linear Accelerator Center (SLAC) requires a high efficiency, highly reliable, and low cost pulsed power modulator to drive the X band klystrons. The present NLC RF compression technique needed a modulator to drive 4 Klystrons at 400 kV, 1300 A for 1.6 muS at 60 PPS (>500 megawatt pulse, 80 kW average). A prototype NLC solid-state induction modulator was modified to drive this new klystron array. The prototype induction modulator utilizes a three-turn secondary with 76 single "fraction turn" primary to produce the 400 kV pulse. The design, testing and operational experience will be discussed

Social stress is associated with development of many psychological and physiological disturbances in humans. Animal models are needed to determine the etiology of these diseases and to develop rational clinical therapies to treat those afflicted. Rodent and non-human primate models of social stress have been developed to address these needs and contribute in complementary ways to the understanding of social stress. In this review, we provide an overview of common rodent and non-human primate models of social stress used in the laboratory with a focus on social hierarchy models. The implications of the current findings on understanding of the development of stress-related disease will also be discussed.

At SLAC, research and development for the next linear collider (NLC) is progressing. The 8-Pack project is a test stand in which key NLC components will be developed. Presently the setup is such that an induction modulator [R. L. Cassel et al., The Prototype Solid State Induction Modulator for SLAC NLC] will generate 400 kV, 1200 A, and 1.6 /spl mu/s flattop pulse to drive four XL4 X-band klystrons. This requires the use of 76 high power IGBT modules operating in parallel at 3600 A and up to 2200 V each. IGBT switching speeds and short circuit protection from klystron arcs are major concerns. This paper describes a gate drive circuit with a new method to protect IGBT modules under short circuit conditions. Using a dI/dt control technique, the gate drive circuit enabled the Mitsubishi module CM600HB-90H to switch 4000 A at speeds up to 10 kA//spl mu/s in normal operation, while holding the short circuit peak-current to about 8000 A. Results from the single IGBT test and the 8-Pack Modulator prototype will be presented.

The Next Linear Collider accelerator proposal at SLAC requires a high efficiency, highly reliable, and low cost pulsed power modulator to drive the X band klystrons. The present NLC envisions a solid state induction modulator design to drive up to 8 klystrons to 500 kV for 3(S) at 120 PPS with one modulator (>1000 megawatt pulse, 500 kW average). A prototype modulator is under construction, which will power 4 each 5045 SLAC klystron to greater than 380 kV for 3(S) (>600 megawatt pulse, >300 kW ave.). The prototype induction modulator utilizes a three-turn secondary to produce the 500 kV pulse. The design, installation and testing of the three turn secondary and its effect on rise time and fault conditions is discussed. The design and implementation of a snubber to improve the arcing condition are covered.

The visible burrow system (VBS) is an ethologically relevant model of social stress, which has been used to study the aggression of male rats in a social context. Previous studies using the VBS have established physiological, endocrine, and neurochemical characteristics associated with chronic social stress in dominant and subordinate animals. A critical criterion in establishing an animal model for research is the replication of findings and the independent validation of the model. Here, we independently confirm previously reported findings and include novel control groups that are important in dissociating the effects of chronic social stress from those resulting from group-housing the male rats in an “enriched environment”. Furthermore, we show that whereas the VBS model is useful for males, it is not effective for studies of females because they do not form dominance hierarchies when housed in groups. We also extend the use of the VBS model to examine the etiology of stress-induced anorexia and obesity, finding that weight loss in subordinate rats is attributable to decreased adipose and lean tissue, whereas in dominant rats, it is associated only with adipose tissue loss. Consistent with this, the adiposity hormones leptin and insulin are decreased in subordinates and, to a lesser extent, in dominants, compared with the controls. In summary, the VBS model of chronic social stress is an ethologically relevant animal model and provides a valuable tool for studies of stress-related conditions and pathologies.

As part of an improvement project on the linear accelerator at SLAC, it was necessary to replace the original thyratron trigger generator, which consisted of two chassis, two vacuum tubes, and a small thyratron. All solid-state, fast rise, and high voltage thyratron drivers, therefore, have been developed and built for the 244 klystron modulators. The rack mounted, single chassis driver employs a unique way to control and generate pulses through the use of an asymmetric SCR, a PFN, a fast pulse transformer, and a saturable reactor. The resulting output pulse is 2 kV peak into 50 /spl Omega/ load with pulse duration of 1.5 /spl mu/s FWHM at 180 Hz. The pulse risetime is less than 40 ns with less than 1 ns jitter. Various techniques are used to protect the SCR from being damaged by high voltage and current transients due to thyratron breakdowns. The end-of-line clipper (EOLC) detection circuit is also integrated into this chassis to interrupt the modulator triggering in the event of a high percentage of line reflections occurring.

Retrieval information about soil moisture and roughness from remotely sensed data is of great interest for agricultural soil management. In fact, these two physical parameters are crucial for predicting erosion rates within agricultural watersheds during the rainfall season. In this context, there exists a strong interest to assess the potential of SAR (synthetic aperture radar) images to provide information regarding to these two physical surface parameters with periodic acquisitions. Nevertheless, one major source of error in the quantitative estimate of these parameters is the presence of the speckle within the scene registered by SAR instruments. To overcome this difficulty many filtering techniques have been developed for reducing this multiplicative noise. However, as to the authors' knowledge, no study has analysed the sensitivity of these speckle filtering approaches on the estimates of soil moisture and roughness. Consequently, the authors propose in this paper to quantify the influence of several speckle filtering methods on the assessment of these agricultural soil parameters.

Recent experience with SLC (Stanford Linear Collider) has shown that very fast, ferrite-loaded, transmission-line, beam-kicker magnets can cause significant and undesirable distortion of a 1.5-2.5-kA, 20-40-kV pulse as it travels through the magnet. In general, there is a net lengthening of the pulse, with increases in its rise and fall times, a decrease in amplitude, and an unsymmetrical rounding of the flat top. A number of practical design considerations are discussed in terms of equivalent circuits, magnet circuit dispersion and dissipation, undesired circuit shunting and coupling, high-voltage breakdown problems and high-order-mode losses that lead to beam tube heating. These effects are linked to the properties of the materials, the presence of radiation, and realizable magnet topologies. Measurements and calculations of some of these characteristics for several magnet design are reviewed. >

EPOS (Expert system for PrOgram and System development) is a kernel software engineering environment, offering integrated software configuration management (CM) and process management. The EPOS process modelling (PM) support system runs on top of the versioned EPOS database (DB), operating in client-server mode. An extension of the EPOS PM is introduced for coping with cooperative, developing activities in an engineering environment. An EPOS DB transaction is connected to a change job or project activity (task). The cooperation model provides facilities for automatically or manually monitoring a set of evolving products, and negotiating to a protocol defining when/how changes will be both locally and globally propagated. The model also offers different policies for reconciliation of conflicting updates. The authors' cooperation model is built on top of versioned EPOS DB and regulated by EPOS PM. It indicates a good coupling of CM and PM for handling cooperation in a software development environment. >

Identifies a taxonomy to characterize meta-process categories, and their characteristics. The taxonomy is applied to several existing software process-centered support environments (PSEs) and their support technologies. Up to now, meta-processes have been poorly understood, and thus hardly exploited properly. In some PSEs, meta-processes are supported, but their properties are not reflected clearly in any systematic framework. In this paper, some typical characteristics of meta-processes are recognized by clarifying: (i) the reasons why meta-processes are necessary for software development and maintenance; (ii) which effects they have on other components or fragments of a software process; (iii) how and when they should be accomplished; and (iv) who is responsible for performing them. These characteristics also contribute to recognizing the phases of meta-processes in software engineering. Identified characteristics and phases, serving as a framework for assessment, are then applied to evaluate five European PSEs, namely Adele2, EPOS, SPADE, Process Weaver and Process Wise Integrator. The intention of this evaluation is to illustrate the strengths and weaknesses of the identified PSE systems, providing a motivation for their further research and enhancement. In addition, it is also an initial step to validate and demonstrate the usefulness of this proposed assessment framework w.r.t. studying software meta-processes. >

Silver filled epoxy is the most common type of adhesive used to attach Si chips to metal leadframes in plastic packages. However, with the attachment of larger die sizes (2 cm length on the side or larger) to thin copper lead frames now coming into routine use, most of the current adhesives were not reliable for these applications. Major technical issues of these materials are: stress-induced Si fracture; delamination at molding and post molding; device failures under pressure cooker tests and thermal shock tests; thermal/hydrolytic stability of adhesive; and narrow processing window. A novel thermoset cyanate ester die-attach paste has been developed to address the above issues. The paste is suitable for use on conventional dispensing equipment. This material can be cured in less than 60 seconds at 200/spl deg/C and does not generate any appreciable weight loss during cure. As a result, the same fast cure profile can be utilized for all die sizes. In this paper, we review the chemical and physical characteristics of the material and its functional performance as a die-attach media. The combination of a lower modulus of rigidity, about 400 MPa (vs. 1000 Mpa for conventional epoxies) and thermal stability at temperatures well above 300/spl deg/C has given the material excellent adhesive strength, even at 300/spl deg/C, as well as imparting very low stress on the die. Our data indicated the stress level is not sensitive to curing methods such as fast-curing on a heater block or slower-curing in a box oven. The stress level also does not change after long term high temperature at 150/spl deg/C or temperature cycles between -65/spl deg/C to 150/spl deg/C. >