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Studies of changes in the flexural strength and phase composition of castable refractories are being carried out in simulated coal gasification reactor environments. This paper describes a pressure vessel in which x-ray powder diffraction measurements can be made by an energy dispersive method while the specimen is being heated to temperatures as high as 1000°C in atmospheres containing H2O, CO2, CO, H2, CH4, NH3 , and H2S at pressures up to 7 MPa (1000 psig).
Comparing genotype results of tuberculosis (TB) isolates from individuals diagnosed with TB can support or refute transmission; however, these conclusions are based upon the criteria used to define a genotype match. We used a genotype-match definition which allowed for variation in IS6110 restriction fragment length polymorphism (RFLP) to support transmission between epidemiologically linked persons. Contacts of individuals with infectious TB (index cases) diagnosed in New York City from 1997 to 2003 who subsequently developed TB (contact cases) from 1997 to 2007 were identified. For each contact case and index case (case-pair), isolate genotypes (spoligotype and RFLP results) were evaluated. Isolates from case-pairs were classified as exact or non-exact genotype match. Genotypes from non-exact match case-pairs were reviewed at the genotyping laboratory to determine if the isolates met the near-genotype-match criteria (exactly matching spoligotype and similar RFLP banding patterns). Of 118 case-pairs identified, isolates from 83 (70%) had exactly matching genotypes and 14 (12%) had nearly matching genotypes (supporting transmission), while the remaining 21 (18%) case-pairs had discordant genotypes (refuting transmission). Using identical genotype-match criteria for isolates from case-pairs epidemiologically linked through contact investigation may lead to underestimation of transmission. TB programmes should consider the value of expanding genotype-match criteria to more accurately assess transmission between such cases.
The program has been continued thanks to the financial help of IAU, Unesco, and of local authorities. A school has been held in Lembang, Indonesia from May 16 to June 2, 1983, with students from India, Indonesia, Malaysia, Philippines, and Thailand. The Local Organizing Committee, chaired by B. Hidayat was very efficient, and the school is considered to be one of the most successful held to date. Both teachers and students expressed their appreciation to the School Secretary, Dr J. Kleczek, and to the IAU Executive Committee. Another school, foreseen in Venezuela for September 1983, had to be cancelled due to the lack of support of the Venezuelan Research Council. There are plans to hold several schools during the 1985-1988 period.
The undergraduate program at the University of Texas has grown into the largest astronomy teaching program in the world, with some 7000 students per year (almost 20,000 credit hours). The department has 22.5 Ph.D.-level teaching faculty, about 45 graduate students, and about 40 pre-professional undergraduate majors. But most of the enrollment is in courses that satisfy the science requirements of students in liberal arts and non-technical majors. In 1985–86, 96.4 per cent of our undergraduate credit hours taught were in such classes. It is instructive to examine the historical reasons for our growth and its educational consequences, and to draw some conclusions from both for other programs.
You might be somewhat surprised by the presentations [as delivered] so far, in that there has been relatively little discussion of pedagogical matters (e.g., what should be the content of a text and what should be its order and manner of presentation). It seems that rather personal factors are in the foreground of everyone’s thinking. But I think that is probably inevitable, because the process of writing a textbook is not only a huge undertaking that comes to dominate the life of the author, but it is also an endeavor that places the author directly at the interface between the idealistic world of education and the very practical world of economics as dictated by the realities of the publishing markets. In addition, a textbook has a strong effect on an astronomy class. It has been suggested that an important reason why so many educational research studies fail to come to a definite conclusion is that the textbook is such a dominant influence that it swamps all the other factors!
Arboviruses are pathogens that widely affect the health of people in different communities around the world. Recently, a few successful approaches toward production of effective vaccines against some of these pathogens have been developed, but treatment and prevention of the resulting diseases remain a major health and research concern. The arbovirus infection and replication processes are complex, and many factors are involved in their regulation. Apoptosis, autophagy and the unfolded protein response (UPR) are three mechanisms that are involved in pathogenesis of many viruses. In this review, we focus on the importance of these pathways in the arbovirus replication and infection processes. We provide a brief introduction on how apoptosis, autophagy and the UPR are initiated and regulated, and then discuss the involvement of these pathways in regulation of arbovirus pathogenesis.
It is necessary to standardise the definition of the direction of the minor axes of spheroids used for geodetic computations. In view of polar motion, the definition “parallel to the axis of rotation” is ambiguous. Few countries have explicitly stated the direction adopted, and it has generally been implicitly defined by the corrections for polar motion applied to astronomical azimuths, latitudes, and longitudes. But these corrections have often been neglected or applied inconsistently, and errors of perhaps 0′′.5 of azimuth result. The choice for a recommended Geodetic Mean Pole, to which spheroidal minor axes can in future be defined to be parallel, seems to lie either with the Cecchini “new system, 1900–05” or with the Mean Pole of Epoch 1962·0.
Resilience is the capacity of individuals to resist mental disorders despite exposure to stress. Little is known about its neural underpinnings. The putative variation of white-matter microstructure with resilience in adolescence, a critical period for brain maturation and onset of high-prevalence mental disorders, has not been assessed by diffusion tensor imaging (DTI). Lower fractional anisotropy (FA) though, has been reported in the corpus callosum (CC), the brain's largest white-matter structure, in psychiatric and stress-related conditions. We hypothesized that higher FA in the CC would characterize stress-resilient adolescents.
Three groups of adolescents recruited from the community were compared: resilient with low risk of mental disorder despite high exposure to lifetime stress (n = 55), at-risk of mental disorder exposed to the same level of stress (n = 68), and controls (n = 123). Personality was assessed by the NEO-Five Factor Inventory (NEO-FFI). Voxelwise statistics of DTI values in CC were obtained using tract-based spatial statistics. Regional projections were identified by probabilistic tractography.
Higher FA values were detected in the anterior CC of resilient compared to both non-resilient and control adolescents. FA values varied according to resilience capacity. Seed regional changes in anterior CC projected onto anterior cingulate and frontal cortex. Neuroticism and three other NEO-FFI factor scores differentiated non-resilient participants from the other two groups.
High FA was detected in resilient adolescents in an anterior CC region projecting to frontal areas subserving cognitive resources. Psychiatric risk was associated with personality characteristics. Resilience in adolescence may be related to white-matter microstructure.
Impulsivity and compulsivity represent useful conceptualizations that involve dissociable cognitive functions, which are mediated by neuroanatomically and neurochemically distinct components of cortico-subcortical circuitry. The constructs were historically viewed as diametrically opposed, with impulsivity being associated with risk-seeking and compulsivity with harm-avoidance. However, they are increasingly recognized to be linked by shared neuropsychological mechanisms involving dysfunctional inhibition of thoughts and behaviors. In this article, we selectively review new developments in the investigation of the neurocognition of impulsivity and compulsivity in humans, in order to advance our understanding of the pathophysiology of impulsive, compulsive, and addictive disorders and indicate new directions for research.
Ever more agricultural economics departments are offering appointments for nine rather than twelve months but little if any analysis of the impact of this change has been done. Our research shows that converting to nine-month contracts is an effective way to raise salaries without an initial outlay of new funds and thus meets the retention criterion. Lower ranks do not suffer significantly lower salaries (without supplements) and professors earn more. Because the nine-month alternative costs more, justification for converting all twelve-month faculty members must rest on other factors, such as enhanced grants or comparability.
Obsessive-compulsive disorder (OCD) and related conditions (trichotillomania, pathological skin-picking, pathological nail-biting) are common and disabling. Current treatment approaches fail to help a significant proportion of patients. Multiple tiers of evidence link these conditions with underlying dysregulation of particular cortico-subcortical circuitry and monoamine systems, which represent targets for treatment. Animal models designed to capture aspects of these conditions are critical for several reasons. First, they help in furthering our understanding of neuroanatomical and neurochemical underpinnings of the obsessive-compulsive (OC) spectrum. Second, they help to account for the brain mechanisms by which existing treatments (pharmacotherapy, psychotherapy, deep brain stimulation) exert their beneficial effects on patients. Third, they inform the search for novel treatments. This article provides a critique of key animal models for selected OC spectrum disorders, beginning with initial work relating to anxiety, but moving on to recent developments in domains of genetic, pharmacological, cognitive, and ethological models. We find that there is a burgeoning literature in these areas with important ramifications, which are considered, along with salient future lines of research.
Testing for the unintended or adventitious presence (AP) of genetically modified (GM) events in seed lots is a common practice to comply with regulatory requirements and good stewardship practices. A subsample of a seed lot is typically tested for AP levels, and then statistical methods are used to estimate the upper level of AP in the remainder of the lot with a given level of confidence. For large seed lots, a binomial distribution is typically assumed, but for seed lots where the tested sample is a substantial proportion of the overall seed lot, a hypergeometric distribution is typically assumed. Due to the destructive nature of AP seed testing, we suggest that this latter method may overestimate confidence of low AP in the remaining seed.
Spectral reflectance and spectroscopic ellipsometry measurements have been made on SOS wafers with haze ratings 1-5. The wavelength dependence of reflectance is dominated by surface scattering, but degraded crystallinity effects are also observed, and are significant in some samples. Analysis of dielectric function spectra using an effective medium approximation has indicated the presence of α-Si and voids in surface layers up to 300Å thick in medium haze wafers, with concentrations decreasing away from the surface. The assessment parameter normally used for SOS, UVR No., has been shown to includeboth crystallinity and scattering effects, and their relative importance cannot be determined without more detailed measurements.
In this paper we will describe the production, separation and characterization of the new all carbon molecules, C60 and C70. High performance liquid chromatography HPLC is used to obtain purified samples of C60 and C70, which are subsequently characterized by electron impact and chemical ionization mass spectrometry, IR and UV-visible absorption spectroscopy, NMR, ESR, scanning tunnelling microscopy, transmission electron microscopy and x-ray absorption fine structure measurements.
Ferroelectric thin films have been deposited on polycrystalline silicon micromechanical structures to form both physical microsensors and microactuator devices. These devices which include acoustic pressure sensors, infrared detectors, micropositioners, and stepper motors are based on either the piezoelectric or pyroelectric properties of sol-gel Pb(ZrxTi1-x)O3 or PbTiO3 deposited on surface-machined microelectromechanical structures. Several materials, micromachining, process integration, and performance issues are introduced in the description of these devices.
Light scattering has been used to characterise the periodic surface topography which develops on (001) Si epitaxial layers growing by a step flow mechanism. The periodicity provides a measure of the average kink density along the misorientation steps which develop a sawtooth form during growth. The diffracting properties of the layers have been determined after growth by angle-resolved scattering measurements. In-situ light scattering at fixed angle has been used to fol low the build-up of the periodic step arrays. The periodic structure is a metastable state of the surface maintained by the supersaturation during growth, and it decays on switching off the silane source gas or when the temperature is reduced below the point at which surface diffusion will support the sawtooth step shape.
Electrical, structural and diffusion characteristics of a solid phase reacted ohmic contact to n-GaAs are studied. Attempts were made to form a low band gap interfacial phase of InGaAs to reduce the barrier height at the conductor/semiconductor junction and thus yielding a low resistance, high reliablity contacts. The understanding of the interface is important from the point of view of device performance as well as device reliability. The contacts were fabricated by co-sputtering W, In and Te targets on n-GaAs with subsequent annealing. The as-deposited rectifying contacts became ohmic when annealed to 500°C, and showed a specific contact resistance of ∽5×10-6 ohm cm2. The Auger and Rutherford back scattering analysis of the interface revealed an InGaAs phase formation prior to the onset of ohmic conduction. The contacts were stable up to 500°C and the surface morphology was superior to presently used AuNiGe contacts. The contact pads were patterned by dry plasma etching without adversely affecting the GaAs substrate.
The first in-situ observations of initial stages of growth during Si vapour-phase homoepitaxy are reported, using the simultaneous measurement of dual-wavelength ellipsometry (364/488nm) and diffuse light scattering (488nm). Effective medium modelling shows that initial growth is nonuniform with pits present in the first 50–200Å of growth which rapidly fill in as growth proceeds. The sizes of the ellipsometric and scattering discontinuities are dependent on the extent of pre-growth roughening associated with oxide removal and finite wavelength effects become important for growth on roughened substrates.
In-situ dual-wavelength ellipsometry and laser light scattering have been used to monitor growth of Si/Si1−x,Gex heterojunction bipolar transistor and multi-quantum well (MQW) structures. The growth rate of B-doped Si0 8Ge0.2 has been shown to be linear, but that of As-doped Si is non-linear, decreasing with time. Refractive index data have been obtained at the growth temperature for x = 0.15, 0.20, 0.25. Interface regions ∼ 6-20Å thickness have been detected at hetero-interfaces and during interrupted alloy growth. Period-to-period repeatability of MQW structures has been shown to be ±lML.