Differential Effects of Human P301L Tau Expression in Young versus Aged Mice

The greatest risk factor for developing Alzheimer’s disease (AD) is increasing age. Understanding the changes that occur in aging that make an aged brain more susceptible to developing AD could result in novel therapeutic targets. In order to better understand these changes, the current study utilized mice harboring a regulatable mutant P301L human tau transgene (rTg(TauP301L)4510), in which P301L tau expression can be turned off or on by the addition or removal of doxycycline in the drinking water. This regulatable expression allowed for assessment of aging independent of prolonged mutant tau expression. Our results suggest that P301L expression in aged mice enhances memory deficits in the Morris water maze task. These behavioral changes may be due to enhanced late-stage tau pathology, as evidenced by immunoblotting and exacerbated hippocampal dysregulation of glutamate release and uptake measured by the microelectrode array technique. We additionally observed changes in proteins important for the regulation of glutamate and tau phosphorylation that may mediate these age-related changes. Thus, age and P301L tau interact to exacerbate tau-induced detrimental alterations in aged animals.     

Odd-Stoichiometry and Secondary Phase Relations in Higher Manganese Silicides

Higher manganese silicides (denoted as MnSi_γ) are a prominent class of intermetallic compound for thermoelectric applications that crystallizes into a Nowotny Chimney Ladder (NCL) phase and constitutes a higher concentration of silicon with odd stoichiometry, typically represented by an irrational number. In this work, the genesis of Si odd stoichiometry and secondary phase relations in silicon-rich and silicon-deficient MnSi_x is presented to clarify the significance of labile (i.e., easily alterable) Si-subsystem in inheriting the modulated lattice structure with characteristic anharmonicity. The transport properties show an interrelation to the presence of a secondary phase, which is driven by the odd stoichiometry, where the thermoelectric figure of merit (zT) is found to be optimal for MnSi_1.74. The structural characterization of rapidly solidified melt-spun ribbons and spark plasma sintered bulk specimens reveal a characteristic presence of MnSi and Si as secondary phases in Si-deficient (x ≈ 1.5) and Si-excess (x ≈ 2) compositions of nominal MnSi_x, respectively, that coexists with the major MnSi_γ based NCL phase. This study provides the fundamental basis of phase evolution and the relevance of odd stoichiometry in silicon-rich manganese silicides which exhibit fascinating phonon dynamics in optimal MnSi_1.74 stoichiometry.     

Study of diffusion and sorption of bis-(2-chloroethyl)sulfide (SM) and bis-(2-chloroethyl)ether (OM) through polypropylene (PP) and biaxial-oriented polypropylene (bopp) films by the FTIR–ATR spectroscopic method

The diffusion of sulfur mustard (SM) and oxygen mustard (OM) in polypropylene (PP) and biaxial-oriented PP (BOPP) was measured using Fourier transform infrared–attenuated total reflectance (FTIR–ATR) spectroscopy, which allows one to study the diffusion of liquid through thin polymer films in situ. The temperature-dependent diffusion coefficients of OM and SM for PP and BOPP are also reported; these are in good agreement with the values obtained by the weight gain method. The activation energy of diffusion is determined by both methods. The polymer–penetrant interaction parameter (K) and transport number (n) are calculated for the system PP/OM and BOPP/OM by weight gain method. The “n” values indicate a Fickian mode of diffusion. © 1996 John Wiley & Sons, Inc.     

Evaporation of multicomponent liquid fuel droplets

A theoretical investigation on evaporation of a two-component liquid fuel droplet in high-temperature quiescent gaseous surroundings has been made from the numerical solution of conservation equations of heat, mass and momentum transports in the carrier and droplet phases. Liquid fuel droplets containing (i) components of widely varying volatilities, namely, n-hexane and n-hexadecane and (ii) components of closely spaced volatilities, namely, n-hexane and benzene, have been considered for the studies. The evaporation characteristics, namely mass depletion, droplet temperature and droplet composition histories with time, have been evaluated in terms of the pertinent input parameters, namely the initial composition of the drop constituents and the free stream temperature. The present studies have been made on the basis of both (i) the interdiffusion (finite diffusion in the droplet phase) model, and (ii) the rapid mixing (infinite diffusion in the droplet phase) model. The results from both the models have been compared to ascertain the accuracy of the rapid mixing model.     

Numerical Design of Megawatt Gyrotron with 120 GHz Frequency and 50% Efficiency for Plasma Fusion Application

The design of 120 GHz, 1 MW gyrotron for plasma fusion application is presented in this paper. The mode selection is carried out considering the aim of minimum mode competition, minimum cavity wall heating, etc. On the basis of the selected operating mode, the interaction cavity design and beam-wave interaction computation are carried out by using the PIC code. The design of triode type Magnetron Injection Gun (MIG) is also presented. Trajectory code EGUN, synthesis code MIGSYN and data analysis code MIGANS are used in the MIG designing. Further, the design of MIG is also validated by using the another trajectory code TRAK. The design results of beam dumping system (collector) and RF window are also presented. Depressed collector is designed to enhance the overall tube efficiency. The design study confirms >1 MW output power with tube efficiency around 50% (with collector efficiency).     

A study on a multi-stage hybrid gasifier-engine system

This paper presents the results of a study on a multi-stage hybrid biomass–charcoal gasification to produce low tar content gas for engine application using coconut shell as a fuel. The performance of a gasifier-engine system consisting of the hybrid biomass–charcoal gasifier, a gas cleaning/cooling system and a diesel engine is also discussed.

The lowest tar content found in hybrid coconut shell-charcoal gasification was 28 mgNm⁻³. Using a spray tower, producer gas could be cooled down to 40°C; almost tar-free gas was obtained after cooling the producer gas from the hybrid gasifier system. A three-cylinder Perkins diesel engine was tested at a constant speed of 1500 rpm on diesel alone and dual fuel modes of operation. A maximum of 81% of the total heat energy input was replaced by the producer gas at an electricity generation of 11.44 kWe.     

Renewable energy education at the university level

The rapid growth in global enrolment of students for higher education observed in recent decades is expected to continue in the early next century. However, the role of the universities and their approach to education may undergo substantial transformation in the future. The Internet is expected to play a significant role in university-level education in general and renewable energy education (REE) in particular. Currently, REE at different universities is characterized by a lack of uniformity in terms of duration, coursework, emphasis on research, etc. There is a need to establish guidelines and standards regarding academic programs and to establish a system of accreditation, preferably global, of REE in different academic disciplines and departments.     

Submicron scaling of HBTs

The variation of heterojunction bipolar transistor (HBT) bandwidth with scaling is reviewed. High bandwidths are obtained by thinning the base and collector layers, increasing emitter current density, decreasing emitter contact resistivity, and reducing the emitter and collector junction widths. In mesa HBTs, minimum dimensions required for the base contact impose a minimum width for the collector junction, frustrating device scaling. Narrow collector junctions can be obtained by using substrate transfer or collector-undercut processes or, if contact resistivity is greatly reduced, by reducing the width of the base ohmic contacts in a mesa structure. HBTs with submicron collector junctions exhibit extremely high f_max and high gains in mm-wave ICs. Transferred-substrate HBTs have obtained 21 dB unilateral power gain at 100 GHz. If extrapolated at -20 dB/decade, the power gain cutoff frequency f_max is 1.1 THz. f_max will be less than 1 THz if unmodeled electron transport physics produce a >20 dB/decade variation in power gain at frequencies above 110 GHz. Transferred-substrate HBTs have obtained 295 GHz f_T. The substrate transfer process provides microstrip interconnects on a low-ϵ_r polymer dielectric with a electroplated gold ground plane. Important wiring parasitics, including wiring capacitance, and ground via inductance are substantially reduced. Demonstrated ICs include lumped and distributed amplifiers with bandwidths to 85 GHz and per-stage gain-bandwidth products over 400 GHz, and master-slave latches operating at 75 GHz     

Deformation behavior of a Ni3Al(B,Zr) alloy during cold rolling: Part I. changes in order and structure

A hypostoichiometric Ni₃Al(B,Zr) alloy was homogenized and cold rolled by amounts ranging from 25 to 73 pct. The alloy consisted of two phases—a partially ordered γ′ phase (L1₂) and a Ni-rich fcc solid solution (γ). On deforming the alloy by rolling at room temperature, the order parameter showed a gradual change. In fact, between 35 and 45 pct deformation, the order characteristic of the L1₂ structure changed into that of a DO₂₂ structure. The possibility of transition from L1₂ to DO₂₂ structure is also corroborated from strain parameter, microhardness, and detailed x-ray diffraction (XRD) measurements. This structural transformation is accompanied by a change in the deformation mode (from slip to twinning), as is evident from the relevant microstructures.     

Premature fatigue failure of a spring due to quench cracks

The premature fatigue failure of a compression spring during service has been analysed. Optical and scanning electron microscopy, hardness and tensile testing and X-ray diffraction techniques were employed. Quench cracks, presumably due to improper quenching, were observed across the cross-section of the spring. It is established theoretically that the diameter of the spring rod was smaller than the critical diameter for this composition of steel. X-ray diffraction showed the presence of a small amount of retained austenite (average grain size of 2 μm).