1H nuclear magnetic resonance study of polyurethane prepolymers from toluene diisocyanate and polypropylene glycol

Polyurethane prepolymers prepared from toluene 2,4‐diisocyanate, toluene 2,6‐diisocyanate, and polypropylene glycol with a ratio between the isocyanate and hydroxyl groups equal to 2 were analyzed by ¹H nuclear magnetic resonance (NMR) spectroscopy in acetone‐d₆. Different temperatures and concentrations were used. Toluene 2,4‐dimethylurethane and toluene 2,6‐dimethylurethane were synthesized and used as model compounds to assign prepolymers signals. Measurements of spin–lattice relaxation time T₁ by “inversion recovery” experiments were carried out on toluene 2,4‐diisocyanate, toluene 2,6‐diisocyanate, toluene 2,4‐dimethylurethane, toluene 2,6‐dimethylurethane, and polyurethane prepolymers. Differences in T₁ times were used to interpret prepolymers spectra, by means of the strong observed effect on protons due to the presence of adjacent isocyanate groups. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 347–357, 2003     

Two is better than one: A diploid genotype for neural networks

In nature the genotype of many organisms exhibits diploidy, i.e., it includes two copies of every gene. In this paper we describe the results of simulations comparing the behavior of haploid and diploid populations of ecological neural networks living in both fixed and changing environments. We show that diploid genotypes create more variability in fitness in the population than haploid genotypes and buffer better environmental change; as a consequence, if one wants to obtain good results for both average and peak fitness in a single population one should choose a diploid population with an appropriate mutation rate. Some results of our simulations parallel biological findings.     

The fluid-filling system for the Borexino solar neutrino detector

The system for controlled filling of the nested flexible scintillator containment vessels in the Borexino solar neutrino detector is described. The design and operation principles of pressure and shape monitoring systems are presented for gas filling, gas displacement by water, and water displacement by scintillator. System specifications for safety against overstressing the flexible nylon vessels are defined as well as leak-tightness and cleanliness requirements. The fluid-filling system was a major engineering challenge for the Borexino detector.     

Impact of interface and bulk trapped charges on transistor reliability

Oxide reliability is a key issue and the main topic of several recent works. We study the impact of gate oxide stress on transistor performances following a methodology similar to oxide lifetime characterisation in capacitors. A universal trend for degradation of the threshold voltage and drain saturation current with injected charge is observed and the impact of boron on trapping enhancement has been separated by comparing n-MOS and p-MOS.     

Program assists economic life determination

An interactive computer program is described for economic life determination using the revenue requirement technique. This program can also be used to compare different financial strategies.     

Development of muscle pathology in canine X-linked muscular dystrophy. I. Delayed postnatal maturation of affected and normal muscle as revealed by myosin isoform analysis and utrophin expression

Canine X-linked muscular dystrophy (CXMD) is genetically homologous to Duchenne muscular dystrophy and shares the severe myopathy and lethal clinical development of the human disease. We used immunohistochemistry to characterize the time course of postnatal expression of adult fast, adult slow and developmental myosin in the muscle of CXMD dogs, carriers and healthy controls. We also characterized the expression of utrophin and dystrophin. This detailed immunolocalization study confirmed that postnatal muscle maturation is delayed in normal dogs compared to other animals and humans, and is only achieved at around 60 days. In CXMD dogs major derangement of myosin expression became evident from about 15 days; there was a selective loss of fibers expressing fast myosin and persistence of developmental fibers compared to controls. In carriers, the proportion of dystrophin-deficient fibers, which mainly expressed fast myosin, decreased with age. In controls and carriers utrophin was absent from muscle fiber surfaces in 2-day-old animals but present between 15 and 30 days, to mostly disappear by 60 days. In dystrophic animals, sarcolemmal expression of utrophin was more marked and persistent. That immature neonatal muscle from control dogs normally contains sarcolemmal utrophin may have implications for the success of utrophin up-regulation therapy to correct the dystrophic phenotype. The data of this study provide important baseline information for further studies on the development and progression of pathological changes in the muscle of CXMD dogs.     

Flow pattern transition for vertical downward two-phase flow in capillary tubes. Inlet mixing effects

Experimental results of flow pattern for vertical downward two-phase flow in capillary tubes are reported and flow pattern regime maps are presented. In addition theoretically based transition criteria for the flow pattern are presented. The experimental results and theory seem to match each other fairly well. When results given in this paper are compared with empirical ones presented in literature stratified flow has not been reported in this study. Additional experiments were undertaken and inlet mixing effects have been found to be extremely important for the existence of fully developed flow.     

Targeted downregulation of caveolin-1 is sufficient to drive cell transformation and hyperactivate the p42/44 MAP kinase cascade

Caveolin-1 is a principal component of caveolae membranes in vivo. Caveolin-1 mRNA and protein expression are lost or reduced during cell transformation by activated oncogenes. Interestingly, the human caveolin-1 gene is localized to a suspected tumor suppressor locus (7q31.1). However, it remains unknown whether downregulation of caveolin-1 is sufficient to mediate cell transformation or tumorigenicity. Here, we employ an antisense approach to derive stable NIH 3T3 cell lines that express dramatically reduced levels of caveolin-1 but contain normal amounts of caveolin-2. NIH 3T3 cells harboring antisense caveolin-1 exhibit anchorage-independent growth, form tumors in immunodeficient mice and show hyperactivation of the p42/44 MAP kinase cascade. Importantly, transformation induced by caveolin-1 downregulation is reversed when caveolin-1 protein levels are restored to normal by loss of the caveolin-1 antisense vector. In addition, we show that in normal NIH 3T3 cells, caveolin-1 expression levels are tightly regulated by specific growth factor stimuli and cell density. Our results suggest that upregulation of caveolin-1 may be important in mediating contact inhibition and negatively regulating the activation state of the p42/44 MAP kinase cascade.     

Protein oriented ligation on nanoparticles exploiting O6-alkylguanine-DNA transferase (SNAP) genetically encoded fusion

A bimodular genetic fusion comprising a delivery module (scFv) and a capture module (SNAP) is proposed as a novel strategy for the site-specific covalent conjugation of targeting peptides to nanoparticles. An scFv mutant selective for HER2 tumor antigen is chosen as the targeting ligand. SNAP-scFv is immobilized on magnetofluorescent nanoparticles and its targeting efficiency against HER2-positive cells is assessed by flow cytometry and immunofluorescence.     

Carbon carbon detection: Diamond detectors and AMS

¹⁴C ions (290 keV) have been detected with chemically vapour deposited diamond. Potential benefits of diamond detectors are radiation hardness, high charge collection and very fast response time/high bandwidth.