Transesterification of Poly(Ethylene Terephthalate) and Bisphenol-A-Polycarbonate

Blends of Poly(ethylene terephthalate) (PET) and bisphenol-A-polycarbonate (PC) have been made by solution and melt blending and these blends were subject to isothermal heating to induce a transesterification reaction. The raw materials and products of this reaction have been studied by a variety of different methods to ascertain the chemical, physical and mechanical properties they possess. The conclusions drawn are listed below. PET and PC are immiscible but are compatibilised by transesterification. Transesterification is a second order reversible process and is fast only when water is present, when absent the rate of transesterification is so slow that little or no reaction is observed in after 60 minutes at 300 c. When water is present in the blend significant chain scission and degradation takes place, this is not observed in the absence of water• The material obtained from melt blending has a molecular weight higher than that of commercial PET and it is possible to increase it further by standard solid state polymerization techniques. The PC concentration in PET is critical to the existence and extent of crystallisation. PET blends containing 10% PC are not significantly stronger or weaker than commercial PET and perform very similarly to the yield point. PET blends containing 10% PC are less ductile than commercial PET and will therefore fail sooner when they have yielded under tension. PET blends containing 10% PC do not injection mould as well as commercial PET under conventional procedures for PET, surface crazing and voiding is observe

Improving SRAM FPGA Radiation Reliability Through Low-Level TMR Implementation

Mitigation techniques, such as TMR with repair, are used to reduce the negative effects of radiation on FPGAs deployed in space environments. While these techniques increase the robustness of the device, there is still room for improvement in the range of 100 to 1,000x. These improvements can be realized through the low-level implementation of the placement and routing on the device. This work has implemented a wide variety of techniques to realize these gains, achieving an overall improvement of 57,443x through fault-injection testing and an improvement of 350x in radiation testing

A Solution Hiding in Plain Sight: Special Education and Better Outcomes for Students with Social, Emotional, And Behavioral Challenges

This Article will contribute to the ongoing dialogue about special education and the IDEA in two ways. First, it will describe patterns that have emerged from our work with individual children and families that shed light on how common IDEA implementation failures increase the risk of poor outcomes for students with social, emotional and behavioral challenges. Critiques of the law and proposals to amend it should be grounded in an understanding of exactly how and why it is falling short of meeting its promise to these children. Our hope is that mapping the common implementation failures we have seen in our cases will advance this understanding - at least with respect to the particular population of students for whom we advocate - and will help guide the development of public policy. Second, this Article will assert that fixing these common implementation failures is a critical reform and a worthwhile investment of public time, money and attention. While proposing specific legislative remedies or strategies is beyond the scope of this Article, we will suggest some priorities for reform that appear warranted based on our work

Automatic structures, rational growth and geometrically finite hyperbolic groups

We show that the set $SA(G)$ of equivalence classes of synchronously automatic structures on a geometrically finite hyperbolic group $G$ is dense in the product of the sets $SA(P)$ over all maximal parabolic subgroups $P$. The set $BSA(G)$ of equivalence classes of biautomatic structures on $G$ is isomorphic to the product of the sets $BSA(P)$ over the cusps (conjugacy classes of maximal parabolic subgroups) of $G$. Each maximal parabolic $P$ is a virtually abelian group, so $SA(P)$ and $BSA(P)$ were computed in ``Equivalent automatic structures and their boundaries'' by M.Shapiro and W.Neumann, Intern. J. of Alg. Comp. 2 (1992) We show that any geometrically finite hyperbolic group has a generating set for which the full language of geodesics for $G$ is regular. Moreover, the growth function of $G$ with respect to this generating set is rational. We also determine which automatic structures on such a group are equivalent to geodesic ones. Not all are, though all biautomatic structures are.Comment: Plain Tex, 26 pages, no figure

The antioxidant action of tamoxifen and its metabolites Inhibition of lipid peroxidation

AbstractThe anti-oestrogen drug tamoxifen is an inhibitor of lipid peroxidation in rat liver microsomes and in phospholipid liposomes. Its cis isomer and N-desmethyl form are weaker inhibitors, but 4-hydroxytamoxifen is much more powerful. It is possible that the antioxidant property of tamoxifen might contribute to its biological actions

A Global Plate Model Including Lithospheric Deformation Along Major Rifts and Orogens Since the Triassic

Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 × 106 km2 in the Late Jurassic (~160–155 Ma), driven by a vast network of rift systems. After a mid‐Cretaceous drop in deformation, it reaches a high of 48 x 106 km2 in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plate‐mantle system

The Amateur Sky Survey Mark III Project

The Amateur Sky Survey (TASS) is a loose confederation of amateur and professional astronomers. We describe the design and construction of our Mark III system, a set of wide-field drift-scan CCD cameras which monitor the celestial equator down to thirteenth magnitude in several passbands. We explain the methods by which images are gathered, processed, and reduced into lists of stellar positions and magnitudes. Over the period October, 1996, to November, 1998, we compiled a large database of photometric measurements. One of our results is the "tenxcat" catalog, which contains measurements on the standard Johnson-Cousins system for 367,241 stars; it contains links to the light curves of these stars as well.Comment: 20 pages, including 4 figures; additional JPEG files for Figures 1, 2. Submitted to PAS

Receptor use by pathogenic arenaviruses

The arenavirus family contains several important human pathogens including Lassa fever virus (LASV), lymphocytic choriomeningitis virus (LCMV) and the New World clade B viruses Junin (JUNV) and Machupo (MACV). Previously, α-dystroglycan (α-DG) was identified as a receptor recognized by LASV and certain strains of LCMV. However, other studies have suggested that α-DG is probably not used by the clade B viruses, and the receptor(s) for these pathogens is currently unknown. Using pseudotyped retroviral vectors displaying arenavirus glycoproteins (GPs), we are able to explore the role played by the GP in viral entry in the absence of other viral proteins. By examining the ability of the vectors to transduce DG knockout murine embryonic stem (ES) cells, we have confirmed that LASV has an absolute requirement for α-DG in these cells. However, the LCMV GP can still direct substantial entry into murine ES cells in the absence of α-DG, even when the GP from the clone 13 variant is used that has previously been reported to be highly dependent on α-DG for entry. We also found that neither LASV or LCMV pseudotyped vectors were able to transduce human or murine lymphocytes, presumably due to the glycosylation state of α-DG in these cells. In contrast, the JUNV and MACV GPs displayed broad tropism on human, murine and avian cell types, including lymphocytes, and showed no requirement for α-DG in murine ES cells. These findings highlight the importance of molecules other than α-DG for arenavirus entry. An alternate receptor is present on murine ES cells that can be used by LCMV but not by LASV, and which is not available on human or murine lymphocytes, while a distinct and widely expressed receptor(s) is used by the clade B viruses.Facultad de Ciencias Exacta

Evolutionary ecology, resource depression, and niche construction theory: applications to central California hunter–gatherers and Mimbres-Mogollon Agriculturalists

Abstract Evolutionary ecology is a theoretical framework that has been widely applied to problems in human evolution and prehistory. Because the approach often focuses on how behavioral adjustments to changing socio-ecological conditions create novel selective pressures that in turn drive other changes in morphology and behavior, it draws on the same evolutionary logic that underlies niche construction theory. We illustrate here the important role that niche construction has played in archaeological applications of evolutionary ecology with two detailed case studies: one from Late Holocene hunter-gatherer populations in Central California and one from Mimbres-Mogollon agriculturalists in New Mexico. These examples illustrate that evolutionary ecology-based approaches, with an emphasis on formal predictive modeling, allow for the incorporation of niche construction as it affects model parameters with reference to specific problems involving past behavior. Further modeling and empirical applications will expand the synergies between these complementary approaches and advance our understanding of the human past