The Effects of Inhomogeneities on Evaluating the Deceleration Parameter q0_0

Analytic expressions for distance-redshift relations which have been corrected for the effects of some inhomogeneities in the Friedmann-Robertson-Walker (FRW) mass density are used to illustrate the significance of inhomogeneities on a determination of $q_0$ made by using Type Ia supernovae. The value of $q_0$ inferred from a given set of observations depends on the fractional amount of matter in inhomogeneities and is up to 50 percent larger than that obtained by using the standard Mattig $m$-$z$ result for pure dust FRW models.Comment: 16 pages, 7 figures in separate uuencoded fil

Development of fire-resistant wood structural panels

Structural panels made with Xylok 210 resin as the binder had a burn-through resistance at least equal to the structural panels made with Kerimid 500. Therefore, because of its comparative ease of handling, Xylok 210 was selected as the resin binder to provide the baseline panel for the study of a means of improving the flame-spread resistance of the structural panels. The final resin-filler system consisted of Xylok 210 binder with the addition of ammonium oxalate and ammonium phosphate to the strands of the surface layers, using 24% of each salt based upon the air-dry weight of the strands. This system resulted in a panel with a flame-spread code of about 60, a Class 2 classification. A standard phenolic based structural panel had a flame-spread greater than 200 for laboratory prepared panels. The burn-through tests indicated an average burn-through time of 588 seconds for the specimens made with the final system. This compares to an average burn-through time of 287 seconds for the standard phenolic base structural specimen. One full-size panel was made with the final system

Nonlinear soil-structure interaction calculations simulating the SIMQUAKE experiment using STEALTH 2D

Transient, nonlinear soil-structure interaction simulations of an Electric Power Research Institute, SIMQUAKE experiment were performed using the large strain, time domain STEALTH 2D code and a cyclic, kinematically hardening cap soil model. Results from the STEALTH simulations were compared to identical simulations performed with the TRANAL code and indicate relatively good agreement between all the STEALTH and TRANAL calculations. The differences that are seen can probably be attributed to: (1) large (STEALTH) vs. small (TRANAL) strain formulation and/or (2) grid discretization differences

The effect of material processing on the dielectric properties of polystyrene boron nitride nanocomposites

Extensive experimental work in the area of polymer nanocomposites has been done over the past two decades to explore their potential. In this study, a range of related polymer nanocomposite materials was prepared using a solvent blending method, using dichloromethane (DCM), toluene (TOL) and chlorobenzene (CB) to dissolve the polymer, atactic polystyrene (a-PS), and disperse the filler, hexagonal boron nitride (hBN). Where TOL and CB were used, heat was used in material processing, whereas the material was processed at room temperature with DCM. The largest increase in breakdown strength is observed in the materials processed with TOL and CB. The hBN appears to be well dispersed in these systems and more agglomerated in the DCM system as shown from SEM

Electrical breakdown strength of boron nitride polyethylene nanocomposites

There is a growing demand for the design of high-performance insulators for high voltage applications. It was proposed that the addition of nanofillers to a polymer could potentially enhance the electrical properties of insulators when compared to the conventional unfilled or microfilled polymers [1]. These materials have captured the interest of many researchers worldwide since then, as present dielectric materials could benefit from improvements in properties such as dielectric strength, dielectric loss, electrical and thermal conductivity, and permittivity that nanodielectrics offer. However, many of the underlying principles remain uncertain, such as the polymer/nanofiller interface, and researchers are still exploring solutions to common challenges faced by nanodielectrics such as nanoparticle agglomeration [2].The work presented in this paper is based on a hexagonal boron nitride nanocomposite in a polyethylene blend host polymer. A polyethylene blend composed of 80% low density polyethylene (LDPE) and 20% high density polyethylene (HDPE) is chosen as the polymer matrix since it has a higher electrical breakdown strength than pure LDPE. Hexagonal boron nitride was chosen as a nanofiller because of its attractive properties for high voltage applications such as high dielectric strength, high thermal conductivity, and mechanical robustness [3]. A solution blending method is used to mix the nanoparticles in the polymer as better quality materials and nanoparticle dispersion are achieved.This paper will investigate the AC electrical breakdown behaviour of the prepared polymer nanocomposite materials. The electrical breakdown strength of the unfilled polymer will be compared to the untreated hexagonal boron nitride filled polymer at different loading levels. The addition of this nanofiller is expected to alter the dielectric strength due to changes in the material’s structure. The chemical structure of hexagonal boron nitride is illustrated in Figure 1, where there is an equal number boron and nitrogen atoms firmly bound together. The breakdown results will then be analysed using a two-parameter Weibull distributio

On the Distribution of Generating Functions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135518/1/blms0113.pd

THE PSOCOPTERA OF THE KRAKATAU ISLANDS, INDONESIA

At least 80 species of Psocoptera are represented in recent collections from the Krakatau Islands, Sunda Strait. They represent 15 families, and 29 species are described tu new. Twenty four species are known only from the Krahataus but. others are widespread in nearby regions of Sumatra and Java and a few are known to be more broadly distributed. Numbers of species recorded from each of the Krahatau Islands are : Rakata 58, Panjang 48, Sertung 27, Anak Krakatau 27

U-Pb Ages of Lunar Apatites

Apatite is one of the minerals that is rarely utilized in U-Pb geochronology, compared to some other U-rich accessory phases. Relatively low U concentration, commonly high proportion of common Pb and low closure temperature of U-Pb system of apatite inhibit its application as geochronological tool when other minerals such as zircon are widely available. However, zircon appear to be restricted to certain type of lunar rocks, carrying so called KREEP signature, whereas apatite (and whitlockite) is a common accessory mineral in the lunar samples. Therefore, utilizing apatite for lunar chronology may increase the pool of rocks that are available for U-Pb dating. The low stability of U-Pb systematics of apatite may also result in the resetting of the system during meteoritic bombardment, in which case apatite may provide an additional tool for the study of the impact history of the Moon. In order to investigate these possibilities, we have analysed apatites and zircons from two breccia samples collected during the Apollo 14 mission. Both samples were collected within the Fra Mauro formation, which is interpreted as a material ejected during the impact that formed the Imbrium Basin

The association of HLA-DRB genes and the shared epitope with rheumatoid arthritis in Pakistan

The association of particular HLA-DR alleles and the shared epitope with rheumatoid arthritis (RA) is now well established. The strength of these links varies between races. Furthermore, the proposition that the presence of the shared epitope is indicative of severe disease has been more difficult to sustain in non-Europeans. This study examines the frequency of HLA-DR and HLA-DRB1 amongst Pakistanis for the first time. Using the polymerase chain reaction (PCR) and sequence-specific oligonucleotide probes (PCR-SSOP) and primers (PCR-SSP), HLA-DR phenotype and genotype frequencies were ascertained in 86 RA hospital out-patients and 79 healthy controls matched for age, gender and ethnicity. HLA-DR1 and HLA-DR4 frequency was similar in patients and controls. HLA-DR10 occurred in 26 instances (15%) in RA and in eight (5%) controls (Pcorr = 0.048). HLA-DR2 was also increased in patients (P = 0.053) and its major subtype DR15 was significantly increased (Pcorr = 0.03). HLA-DR5 frequency was 5% in patients and 19% in controls (Pcorr = 0.002). The HLA-DR4 alleles possessing the shared epitope were more common in RA (Pcorr = 0.03) and this difference was enhanced by inclusion of other alleles possessing the shared epitope (Pcorr = 0.002). Shared epitope alleles were observed in 43 (50%) patients and 17 (22%) controls (Pcorr = 0.003). The shared epitope did not distinguish patients with more severe disease, as reflected by pain, joint deformities, disability, rheumatoid factor or X-ray damage. The distribution of HLA-DR alleles in Pakistanis with RA supports the shared epitope hypothesis. In common with other non-European racial groups, HLA-DR4 was not associated with RA. Unlike other groups, there was a weak link of RA with HLA-DR2. A protective effect of HLA-DR5 was apparent. In accord with some other studies, the shared epitope in this hospital out-patient population was not a marker for more severe disease