Molecular dynamics calculation of heat dissipation during sliding friction

A novel method of calculation of heat dissipation during sliding between metals was presented by using molecular dynamics. Temperature distribution in the regions near the contact interface was calculated. The calculation results show that plastic deformation in the near-surface regions accounts for most of the friction heat and the temperature increase. Friction heat was built up in the regions subject to plastic deformation. In the case that no plastic deformation occurred, elastic waves contributed mainly to the energy dissipation so that no large heat buildup could take place in the vicinity of the contact regions.     

Fiber-device-fiber gain from a sol-gel erbium-doped waveguideamplifier

An erbium-doped silica-on-silicon planar waveguide optical amplifier is described. The active core is a topographic guide formed from aluminophosphosilicate glass doped with erbium and ytterbium. The buffer is formed from silica deposited by thermal oxidation and the cladding from borophosphosilicate glass obtained by plasma-enhanced chemical vapor deposition. The use of low process temperatures allows relatively heavy doping and careful control of the core etching allows low background insertion losses to be obtained. Spontaneous emission and gain measurements are given and 5.4-dB fiber-device-fiber gain is demonstrated using a 5-cm-long chip pumped using a 980-nm laser diode at 175-mW pump power     

Morphometric and neurodevelopmental outcome at age five years of the offspring of women who continued to exercise regularly throughout pregnancy

OBJECTIVE: To test the hypothesis that continuing regular, vigorous, sustained exercise throughout pregnancy adversely affects morphometric and neurodevelopmental outcome in offspring at 5 years of age. STUDY DESIGN: The offspring of 20 women who exercised were compared with those of 20 physically active control subjects. The women and their offspring were matched for multiple prenatal and postnatal variables known to influence outcome. All women were enrolled before the index pregnancy, monitored throughout, and had clinically normal antenatal, intrapartum, and postnatal courses. Morphometric measures were obtained at birth and at 5 years of age by a single, trained observer. Neurodevelopment was assessed by developmental psychologists masked to maternal exercise status. Data were analyzed with an unpaired Student t test. RESULTS: At birth, head circumference and length were similar, but the offspring of the exercising women weighed less (3.40 +/- 0.80 vs 3.64 +/- 0.70 kg) and had less fat (10.5% +/- 0.9% vs 15.1% +/- 0.6%). At 5 years of age, head circumference and height were similar, but the offspring of the women who exercised weighed less (18.0 +/- 0.5 vs 19.5 +/- 0.6 kg) and had a lower sum (sigma) of five site skinfolds (37 +/- 1 vs 44 +/- 2 mm). Motor, integrative, and academic readiness skills were similar. However, the exercise offspring performed significantly better on the Wechsler scales (125 +/- 2 vs 116 +/- 3) and tests of oral language skills (119 +/- 2 vs 109 +/- 3). CONCLUSIONS: These data refute the hypothesis and suggest that exercise during pregnancy reduces the subcutaneous fat mass of the offspring.     

Correction of Fanconi anemia type C phenotypic abnormalities using a clinically suitable retroviral vector infection protocol

Fanconi anemia (FA) is a complex autosomal recessive disease with hematologic manifestations characterized by a progressive hypoplastic anemia, hypersensitivity to clastogenic agents, and an increased incidence of acute myelogenous leukemia. The cDNA that corrects one of four FA complementation subtypes, named Fanconi anemia Type C (FAC) has recently been identified. We constructed a a simplified recombinant retrovirus (vMFGFAC) encoding only the FAC cDNA, and tested its ability to correct the FAC defect in a lymphocytic cell line and primary mobilized blood progenitor cells. In addition, the gene transfer efficiency using a clinically applicable gene transfer protocol into normal primitive hematopoietic progenitor cells, high proliferating potential colony forming cells (HPP-CFC), derived from CD34+ purified cord blood cells was examined. The gene transfer efficiency was significantly enhanced when cells were transduced with supernatant while adherent to a 30/35 KD fragment of fibronectin, FN30/35, and was similar to efficiency obtained by coculture with retrovirus packaging cells. Transduction of an FAC deficient lymphoid cell line with vMFGFAC supernatant resulted in an enhanced cell viability, and G-CSF mobilized peripheral blood cells from an FAC-deficient patient transduced with the vMFGFAC virus demonstrated enhanced progenitor cell colony formation. These data indicate that the vMFGFAC virus allows functional complementation of FAC in lymphoblasts and primary hematopoietic progenitors, and that primitive cord blood hematopoietic stem/progenitor cells can be transduced at an efficiency comparable to protocols using cocultivation if adherent to FN 30/35 fragment.     

Modeling flexural plate wave devices

A lumped-parameter model is derived for flexural plate wave (FPW) devices which are rectangular plates or diaphragms with structural layers, a piezoelectric layer, and with interdigitated conducting combs for driving and sensing. This configuration is often used in micromechanical chemical sensors. The model is based an a closed-form solution of a resonating beam; however, the results are applicable to plates supported on four edges. The model gives a voltage or charge output from the sense combs as a function of voltage applied to the drive combs. The analysis predicts the response of the multiple plate modes to axial tensions and to comb finger dimensions and position relative to the diaphragm eigenfunctions. These models are much more detailed than those described in the literature on acoustic chemical sensors and are difficult to obtain by finite-element solutions. Frequency responses of FPW devices constructed from silicon with deposited aluminum nitride as the piezoelectric compared well with analytic results. The effects of boundary conditions on the plate's lateral edges are discussed in both the analysis and testing     

Proteolytic activity monitored by fluorescence resonance energy transfer through quantum-dot-peptide conjugates

Proteases are enzymes that catalyse the breaking of specific peptide bonds in proteins and polypeptides. They are heavily involved in many normal biological processes as well as in diseases, including cancer, stroke and infection. In fact, proteolytic activity is sometimes used as a marker for some cancer types. Here we present luminescent quantum dot (QD) bioconjugates designed to detect proteolytic activity by fluorescence resonance energy transfer. To achieve this, we developed a modular peptide structure which allowed us to attach dye-labelled substrates for the proteases caspase-1, thrombin, collagenase and chymotrypsin to the QD surface. The fluorescence resonance energy transfer efficiency within these nanoassemblies is easily controlled, and proteolytic assays were carried out under both excess enzyme and excess substrate conditions. These assays provide quantitative data including enzymatic velocity, Michaelis-Menten kinetic parameters, and mechanisms of enzymatic inhibition. We also screened a number of inhibitory compounds against the QD-thrombin conjugate. This technology is not limited to sensing proteases, but may be amenable to monitoring other enzymatic modifications.     

Pretransformation effects of localized soft modes on neutron scattering,acoustic attenuation,and Mössbauer resonance measurements

The localized soft mode model of martensitic nucleation is used to predict pretransformation effects of such regions on inelastic neutron scattering, ultrasonic acoustic attenuation and Mössbauer resonance absorption. The theoretical predictions are compared with the available experimental data.     

Inappropriate antidiuretic hormone secretion. Occurrence in a patient with Rocky Mountain spotted fever

A 51-year-old man with serologically confirmed Rocky Mountain spotted fever was believed to have inappropriate antidiuretic hormone (ADH) secretion. He was observed for four days in the hospital until the correct diagnosis was made. During this period, he progressively became more hyponatremic, despite a low BUN level and the administration of large amounts of sodium and water. At the time, his serum sodium concentration was 117 mEq/liter, and his urine was hypertonic to that of serum. Thereafter, his serum sodium level rose with fluid restriction. Rickettsia-induced CNS damage may have lead to the inappropriate ADH release that was observed in this patient.