An XPS Investigation of Thermal degradation and Charring of Cross-linked Polyisoprene and Polychloroprene

Our interest in butadiene-containing polymers had led to an investigation of the thermal degradation of polyisoprene, PIP, and polychloroprene, PCP. The connection between cross-linking and thermal stability through an examination of PIP and PCP has been reported. Like the course of thermogravimetric analysis (TGA) the cross-linking and charring of polymers subjected to heat can also be experimentally observed as function of temperatures by the pseudo-in-situ XPS (X-ray Photoelectron Spectroscopy). Data acquisition of C1s spectra as function of temperature permits us to explore: (1) the extent of cross-linking and/or carbon accumulation of systems of PCP and PIP with/without initiators, BPO and DCP, via the analysis of the relative intensity versus temperature; and (2) the onset of charring by determining the limiting transition temperature (LTGRL) of the graphite-like structure and particularly the plasmon loss (ΔEL)

Upsilon Transverse Momentum at Hadron Colliders

We predict the shape of the transverse momentum p_T spectrum of Upsilon production. The distribution at low p_T is dominated by the region of small impact parameter b and may be computed reliably in perturbation theory. We resum to all orders in the strong coupling alpha_s the process-independent large logarithmic contributions that arise from initial-state gluon showers in the small p_T (< M_Upsilon) region. The cross section at large p_T is represented by the alpha_s^3 lowest-order non-vanishing perturbative contribution.Comment: 4 pages, 5 figures. Presented at the 2004 Meeting of the APS Division of Particles and Fields, University of California, Riverside, CA, Aug 26-31, 200

The Effects of Lexical Approach on non-English Majors’ Writing Proficiency: An Empirical Study

conducting an experiment of applying lexical approach for one semester in college English reading and writing course, this study aims to explore the effects of lexical approach on non-English major’s writing proficiency. There were 80 subjects involved in the experiment, and half of them were in controlled group (CG), the rest in experimental group (EG). Lexical approach was used in EG and traditional approach was applied in CG. All subjects attended both pre- and post-tests. The comparisons of composition scores of both tests were made between and within groups through independent and paired t tests. The findings are: 1) Students in EG have shown greater improvement than those students in CG in writing proficiency. They get higher composition scores on average than those in CG. 2) Students in EG have achieved significant progress in writing proficiency after the application of the lexical approach. 3) Students in CG show no significant progress in writing proficiency under the instruction of traditional teaching approach. So it can be concluded that the lexical approach has positive effects on non-English majors’ writing proficiency