First-principles study of the electronic structures and absorption spectra for the PbMoO4 crystal with lead vacancy

The electronic structures and absorption spectra for the perfect PbMoO4 crystal and the crystal containing lead vacancy V-Pb(2-) with lattice structure optimized are calculated using density functional theory code CASTEP. The calculated absorption spectra of the PbMoO4 crystal containing V-Pb(2-) exhibit three absorption bands peaking at 2.0 eV (620 nm), 3.0 eV (413 run) and 3.3 eV (375 nm), which are in good agreement with experimental values. The theory predicts that the 390 nm, 430 nm and 580 run absorption bands are related to the existence of V-Pb(2-) in the PbMoO4 crystal.

Trypsin inhibitory loop is an excellent lead structure to design serine protease inhibitors and antimicrobial peptides

The disulfide-bridged hendecapeptide ( CWTKSIPPKPC) loop, derived from an amphibian skin peptide, is found to have strong trypsin inhibitory capability. This loop, called the trypsin inhibitory loop ( TIL), appears to be the smallest serine protease inhib

Concentration and distribution of heavy metals (lead, cadmium, chromium, copper, nickel, zinc) in Karachi shore and offshore sediments

A study to measure the heavy metal pollution level in the sediment of coastal and offshore area indicates that high concentration of heavy metals were found around Manora channel and eastern coast of Karachi. In comparison with coastal areas, relatively low concentration of heavy metals was recorded in the offshore area. The result shows that sewage and industrial wastes are the main source of heavy metal pollution in the coastal area. The concentration of heavy metals in the sediments is as follows: Chromium 10.4-33.69, nickel 13.3-47.6, lead 10.0-39.04, cadmium 0.08-0.21, zinc 7.4-73.2 and copper 9.44-18.56 mg/kg. In the offshore areas strong correlation was observed between copper and organic carbon, and calcium carbonate and cadmium. In the shore area such correlation has been recorded among nickel, chromium, zinc, and chromium and copper. The Karachi. coast is viewed as moderately polluted when compared to other continental coastal areas.

Calcium-permeable acid-sensing ion channel is a molecular target of the neurotoxic metal ion lead

Acid-sensing ion channels (ASICs) are emerging as fundamental players in the regulation of neural plasticity and in pathological conditions. Here we showed that lead (Pb2+), a well known neurotoxic metal ion, reversibly and concentration-dependently inhib

Chemical forms of copper, zinc, lead and cadmium in sediments of the northern part of the Red Sea, Egypt

Total concentrations and chemical forms of heavy metals in sediment samples from the Gulf of Suez and the northern part of the Red Sea, collected during January 2003, were determined by atomic absorption spectrometry. Maximum concentrations of 49.56, 65.42, 33.52 and 3.52 µg/g were recorded for total Cu, Zn, Pb and Cd respectively at Adabiya location. These may reflect the high contribution of land-based activities in the northern part of the Gulf. Also, high percentages of heavy metals were found in the residual fraction (Cu=78.61, Zn=77.10 and Pb=66.80%) while a high percentage of Cd was found in the carbonate fraction (45.82%). However, few or negligible percentages were recorded in the exchangeable fractions (Cu=0.51, Zn=1.57 and Pb=1.74%). Concentration of Cd in the exchangeable fraction was too low to be detected.

Lead exposure through gestation-only caused long-term learning/memory deficits in young adult offspring

Numerous observations in clinical and preclinical studies indicate that the developing brain is particular sensitive to lead (Pb)'s pernicious effects. However, the effect of gestation-only Pb exposure on cognitive functions at maturation has not been studied. We investigated the potential effects of three levels of Pb exposure (low, middle, and high Pb: 0.03%, 0.09%, and 0.27% of lead acetate-containing diets) at the gestational period on the spatial memory of young adult offspring by Morris water maze spatial learning and fixed location/visible platform tasks. Our results revealed that three levels of Pb exposure significantly impaired memory retrieval in male offspring, but only female offspring at low levels of Pb exposure showed impairment of memory retrieval. These impairments were not due to the gross disturbances in motor performance and in vision because these animals performed the fixed location/visible platform task as well as controls, indicating that the specific aspects of spatial learning/memory were impaired. These results suggest that exposure to Pb during the gestational period is sufficient to cause long-term learning/memory deficits in young adult offspring. (C) 2003 Elsevier Inc. All rights reserved.

A study of capacitance-voltage characteristics of lead zirconate titanate ferroelectric thin films and their usage to investigate polarization and coercive field.

Capacitance-voltage (C-V) characteristics of lead zirconate titanate (PZT) thin films with a thickness of 130 nm were measured between 300 and 533 K. The transition between ferroelectric and paraelectric phases was revealed to be of second order in our case, with a Curie temperature at around 450 K. A linear relationship was found between the measured capacitance and the inverse square root of the applied voltage. It was shown that such a relationship could be fitted well by a universal expression of C/A = k(V+V(0))(-1/2) and that this expression could be derived by expanding the Landau-Devonshire free energy at an effective equilibrium position of the Ti/Zr ion in a PZT unit cell. By using the derived equations in this work, the free energy parameters for an individual material can be obtained solely from the corresponding C-V data, and the temperature dependences of both remnant polarization and coercive voltage are shown to be in quantitative agreement with the experimental data.

Magnetic sensor with compensation for lead and coil resistance

A measurement system for magnetic fields or electric currents uses a single-core fluxgate, magneto-inductive or magneto-impedance device driven from a radio frequency excitation source. Flux nulling feedback circuitry is provided to maintain the core of the sensor at substantially zero net flux and improve the linearity and dynamic response of the sensor system. A high pass filter is provided for reducing the dc effects of the ohmic resistance of the coil and lead wires on the effectiveness of the flux nulling feedback.