Towards the understanding of the molecular weight dependence of essential work of fracture in semi-crystalline polymers: A study on poly(ε-caprolactone)

The plane-stress ductile fracture of poly(#-caprolactone) (PCL) has been investigated as a function of molecular weight and related crystalline structure. Because of the interacting effects in semi-crystalline polymers a separate study of a given structural parameter is rather challenging. Nevertheless, this polymer seems to be a good model material to study the effect of molecular weight on the essential work of fracture, as the interactions between the separate parameters, at room temperature, are negligible. The molecular characteristics of PCL were determined by size exclusion chromatography. To confirm the entangled molecular structure of studied polymers rheological measurements were performed. The crystalline morphology has been characterized by differential scanning calorimetry and wide angle X-ray diffraction. Quasi-static tensile tests and essential work of fracture tests were performed to study the mechanical behavior. Based on the experimental observations an empirical model has been proposed to outline the molecular weight and crystallinity dependence of the essential work of fracture in this semi-crystalline polymer

Development of high efficiency (14 percent) solar cell array module

Most effort was concentrated on development of procedures to provide large area (3 in. diameter) high efficiency (16.5 percent AM1, 28 C) P+NN+ solar cells. Intensive tests with 3 in. slices gave consistently lower efficiency (13.5 percent). The problems were identified as incomplete formation of and optimum back surface field (BSF), and interaction of the BSF process and the shallow P+ junction. The problem was shown not to be caused by reduced quality of silicon near the edges of the larger slices

Development of High Efficiency (14%) Solar Cell Array Module

High efficiency solar cells required for the low cost modules was developed. The production tooling for the manufacture of the cells and modules was designed. The tooling consisted of: (1) back contact soldering machine; (2) vacuum pickup; (3) antireflective coating tooling; and (4) test fixture

Arene oxidation with malonoyl peroxides

Malonoyl peroxide 7, prepared in a single step from the commercially available diacid, is an effective reagent for the oxidation of aromatics. Reaction of an arene with peroxide 7 at room temperature leads to the corresponding protected phenol which can be unmasked by aminolysis. An ionic mechanism consistent with the experimental findings and supported by isotopic labeling, Hammett analysis, EPR investigations and reactivity profile studies is proposed

Methanol-to-Olefins Catalysis with Hydrothermally Treated Zeolite SSZ-39

Zeolite SSZ-39 is evaluated for catalyzing the methanol-to-olefins (MTO) reaction. By steaming NH_4–SSZ-39, Al can be removed from framework positions, resulting in an increase in framework-Si/AlT and thus a lowered active acid site density. The Si/Al_T ratios can be controlled by the steaming temperatures. SSZ-39 steamed at 750 °C, with preserved pore volume and morphology, is an excellent MTO catalyst, as high, stable olefin selectivities, long time-on-stream activity, and low alkane production are observed. Moreover, interesting propylene/ethylene/butylene ratios of 2.8/1/1.1 are obtained, likely related to the shape of the AEI cage. By Cu^(2+)-exchanging SSZ-39, evidence is provided to show that Al_T sites in close proximity (high AlT density) produce the unwanted effects (higher alkane-make and carbonaceous deposits) in nonsteamed materials during MTO

Magnetic spectra analysis of dielectrics

Method of magnetic spectroscopy is used to analyze and to interpret the experimental data obtained by magnetic measurement of the complex permeability spectra of Mg ferrite and NiZn ferritepolymers. Ferritepolymers were prepared from various concentration of NiZn ferrite particles as a soft magnetic fillers dispersed in PVC polymer matrix. Effect of the filler content on the permeability spectra of NiZn ferritepolymers was examined and compared with presented sintered ferrite samples. The variations of permeability and relaxation frequency due to ferrite filler concentration in composite are presented and discussed from point of view the magnetization processes in samples

SEVERE OSTEOPOROSIS DUE TO SYSTEMIC MAST CELL DISEASE: SUCCESSFUL TREATMENT WITH INTERFERON ALPHA-2B

We describe a 33-yr-old man suffering from severe vertebral osteoporosis and urticaria pigmentosa due to systemic mast cell disease (SMCD). Because i.v. clodronate therapy could not prevent further vertebral fractures, an additional treatment with interferon alpha-2b was initiated. During 24 months of treatment, our patient had no further pain episodes, no new vertebral fractures were discovered, trabecular bone mineral density (BMD) increased significantly and urticarial symptoms improved. Nevertheless, the extent of skin lesions remained unchanged. On histological examination, a remarkable decrease of mast cells was observed in the bone marrow, but not in the skin. Five months after discontinuation of interferon alpha-2b, trabecular BMD decreased and urticarial symptoms deteriorated. These findings illustrate a beneficial effect of interferon alpha-2b on SMCD-induced osteoporosis as well as urticarial symptoms, and raise the question whether this treatment may have a diverse impact on mast cell populations in different tissue

The design of organic catalysis for epoxidation by hydrogen peroxide

The potential of various organic species to catalyze epoxidation of ethene by hydrogen peroxide is explored with B3LYP/6-31G* DFT calculations