The study of the thermal behavior of a new semicrystalline polyimide

Thermal properties of a new semicrystalline polyimide synthesized from 3,3',4,4' benzophenone tetracarboxylic dianhydride (BTDA) and 2,2 dimethyl 1,2-(4 aminophenoxy) propane (DMDA) were studied. Heat capacities in the solid and liquid states of BTDA-DMDA were measured. The heat capacity increase at the glass transition temperature (T sub g = 230 C) is 145 J/(C mol) for amorphous BTDA-DMDA. The equilibrium heat of fusion of the BTDA-DMDA crystals was obtained using wide angle X ray diffraction and differential scanning calorimetry measurements, and it is 75.8 kJ/mol. Based on the information of crystallinity and the heat capacity increase at T sub g, a rigid amorphous fraction is identified in semicrystalline BTDA-DMDA samples. The rigid amorphous fraction represents an interfacial region between the crystalline and amorphous states. In particular, this fraction increases with the crystallinity of the sample which should be associated with crystal sizes, and therefore, with crystal morphology. It was also found that this polymer has a high temperature crystal phase upon annealing above its original melting temperature. The thermal degradation activation energies are determined to be 154 and 150 kJ/mol in nitrogen and air, respectively

EFFICIENT ANALYTIC COMPUTATION OF HIGHER-ORDER QCD AMPLITUDES

We review techniques simplifying the analytic calculation of one-loop QCD amplitudes with many external legs, for use in next-to-leading-order corrections to multi-jet processes. Particularly useful are the constraints imposed by perturbative unitarity, collinear singularities and a supersymmetry-inspired organization of helicity amplitudes. Certain sequences of one-loop helicity amplitudes with an arbitrary number of external gluons have been obtained using these constraints.Comment: Talk given at Beyond the Standard Model IV, December 13-18 1994, Lake Tahoe, CA. Latex, 4 pages, no figures

Reason and eros

This study is not intended as a work of research into any existing body of philosopny. It is, rather, an independent inquiry into the origins and the objective of philosophical activity. In this it assumes the somewhat enigmatic role of a philosophy of philosophy

Measurement of aberrations of photographic lenses

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ICU admission and severity assessment in community-acquired pneumonia

The past 15 years have seen major advances in our understanding of severity assessment in community-acquired pneumonia (CAP). Prognostic tools have been promoted to guide all major management decisions in CAP, including admission to the critical care unit. Several recent studies, including the study by Renaud and colleagues, have challenged us to re-evaluate how we consider severe CAP, a concept for which there is still no universally accepted definition. Existing severity scores such as the Pneumonia Severity Index and the CURB65 score are designed to predict 30-day mortality. As a result, they are heavily weighted by age and co-morbidity. They perform less well when predicting other outcomes such as requirement for ICU admission and are of limited use in the critical care environment. This commentary discusses recent attempts to develop useful severity criteria to guide the use of ICU resources in patients with severe CAP

A Survey of Quality of Service in Mobile Computing Environments

Accepted versio