GaN reactive ion etching using SiCl<Subscript>4</Subscript>:Ar:SF<Subscript>6</Subscript> chemistry

Reactive ion etching with SiCl₄:Ar:SF₆ mixtures of gallium nitride epitaxial layers grown by metal organic chemical vapour deposition (MOCVD) has been studied. The effects of several factors such as gas mixture, chamber pressure, and drive power on the etch rate and etched profile have been investigated. A strong dependence of both properties with the amount of SF₆ present in the mixture has been found. High etch rates (> 50 nm/min) and controllable sidewall angles and smoothness have been achieved.     

Capturing Solvation Effects at a Liquid/Nanoparticle Interface by Ab Initio Molecular Dynamics: Pt201 Immersed in Water

Solvation can substantially modify the adsorption properties of heterogeneous catalysts. Although essential for achieving realistic theoretical models, assessing such solvent effects over nanoparticles is challenging from a computational standpoint due to the complexity of those liquid/metal interfaces. This effect is investigated by ab initio molecular dynamics simulations at 350 K of a large platinum nanoparticle immersed in liquid water. The first solvation layer contains twice as much physisorbed water molecules above the terraces, than chemisorbed ones located only at edges and corners. The solvent stabilizes the binding energy of chemisorbates: 66% of the total gain comes from interactions with physisorbed molecules and 34% from the influence of bulk liquid.     

Differential actions of the dopamine agonist bromocriptine on growth of SMtTW tumors exhibiting a prolactin and/or a somatotroph cell phenotype: relation to dopamine D2 receptor expression

We have studied microtubule-associated protein 2 (MAP2) expression in anterior horn neurons in the cervical and lumbar spinal cords of 19 cases of adult-onset sporadic amyotrophic lateral sclerosis (ALS) using immunohistochemistry. Specimens from 7 patients without neurological disease served as controls. MAP2 expression decreased in the anterior gray horn of all ALS cases and in the intermediate gray of several ALS cases. Such reduction correlated with the degree of degeneration or neuronal loss in anterior horn cells and with the clinical symptoms of limb weakness. Cytopathologically, the MAP2 immunoreactivity decreased corresponding to the occurrence of individual signs of neuronal degeneration, such as chromatolytic neurons, shrunken neurons and pigmented neurons. MAP2 expression was relatively well preserved in the specimens in which spheroids are conspicuous. The findings of this study demonstrate MAP2 to be an excellent marker for the detection and quantification of anterior horn degeneration in ALS.     

Optimized silicon antiresonant reflecting optical waveguides forsensing applications

The development of an evanescent field sensor with an integrated Mach-Zehnder interferometric (MZI) configuration requires the fabrication of optical waveguides with two main characteristics: (1) monomode behavior and (2) high surface sensitivity for sensing biomolecular interactions in a direct way (without labels). In this paper, we present an experimental study for the optimization of the different parameters of the waveguides that will be the basis of a highly sensitive optical sensor. After optimization, an MZI sensor has been fabricated and some sensing applications are shown. The designed waveguides are based on antiresonant reflecting optical waveguide (ARROW) structures and are fabricated with standard silicon technology     

Effects of N2 Plasma Pretreatment on the SiN Passivation of AlGaN/GaN HEMT

The impact of in situ low-power plasma pretreatment, prior to silicon-nitride (SiN) deposition, was investigated in AlGaN/GaN high-electron mobility transistors (HEMTs). These studies reveal that the use of plasma in HEMT passivation reduces current-collapse and gate-lag effects. Such treatment is also beneficial to improve gate leakage, and from RF measurements, no degradation of was observed. These beneficial effects of the plasma pretreatment seem to be due to a significant reduction in interface charge density, as shown in this letter using GaN MIS devices, where a decrease of 60% was observed.     

Structure, thermal stability and electrical properties of Ca(V0.5Mo0.5)O3 as solid oxide fuel cell anode

The Ca(V_0.5Mo_0.5)O₃ perovskite has been prepared in order to study its potential use as anode in SOFC. The crystal structure has been refined, by neutron powder diffraction, in the orthorhombic Pbnm space group (no. 62). The electrical conductivity values were over 525 S cm⁻¹ in the studied temperature range (25-800 °C). The sample is stable under reducing working conditions (H₂/N₂ 10:90, 25-900 °C). This orthorhombic phase transforms at 500 °C in air to the tetragonal I4₁/a scheelite phase. This transition is reversible and, due to the fact that the thermal expansion coefficients of both, the reduced and oxidized phases, are very similar and match well with those of the other cell components ((10-13) × 10⁻⁶ K⁻¹) this materials are presented as excellent candidates as anodes in SOFCs.     

Occupation and breast cancer mortality in a prospective cohort of US women

We report the isolation of the functional form of the Ca-ATPase from porcine cardiac sarcoplasmic reticulum (SR) membranes, taking advantage of the ability of this enzyme to bind to the nucleotide site affinity dye, Reactive Red 120. Conditions that optimize the solubility and functional stability of the cardiac Ca-ATPase in detergent during the purification procedure are essential to its recovery. The purified Ca-ATPase migrates as a single band on Coomassie blue-stained polyacrylamide gels and exhibits high specific activity (2.5 IU at 25 degreesC) and functional stability. Similar enrichment of the Ca-ATPase estimated from either relative amounts of the 100-kDa protein band on polyacrylamide gels or steady-state concentrations of phosphorylated enzyme intermediate (E-P) demonstrate that neither nonfunctional Ca-ATPases nor non-Ca-ATPase proteins migrating with an apparent molecular weight of 100 kDa constitute a significant fraction of these preparations. Steady-state levels of E-P are 1.3 and 8.6 nmol/mg protein, respectively, for native cardiac SR membranes and the final purified fraction. These values, in comparison to the maximum value (9.1 nmol/mg) for the 110-kDa protein, agree well with estimates of total Ca-ATPase abundance from gel densitometry for both preparations and indicate full site reactivity, i.e., one phosphorylation site for each 110-kDa cardiac Ca-ATPase polypeptide chain.     

Differential regional and cellular distribution of dopamine D2-like receptors: an immunocytochemical study of subtype-specific antibodies in rat and human brain

Dopamine D2-like receptors (D2, D3, and D4) are major targets for action of typical and atypical neuroleptics, commonly used in the treatment of schizophrenia. To understand their individual functional contribution, subtype-selective anti-peptide antibodies were raised against D2, D3, and D4 receptor proteins. The antibodies were shown to be specific on immunoblots of rat brain membranes and immunoprecipitated the solubilized native dopamine receptors in an antibody concentration-dependent manner. In addition, they also bind selectively to the respective recombinant D2, D3, and D4 receptor membrane proteins from cDNA transfected cells. Immunolocalization studies show that the D2-like receptor proteins had differential regional and cellular distribution in the cerebral cortex, hippocampus, basal ganglia, cerebellum, and midbrain, thus providing anatomical substrate for area-specific regulation of the dopamine neurotransmission. In cortical neurons, D4 receptor protein was found in both pyramidal and nonpyramidal cells, whereas D2 and D3 seem to be mostly associated with nonpyramidal interneurons. In rat hippocampus, the expression pattern of D2-like receptors (D4>D3>D2) mirrored that obtained with immunoprecipitation studies. D2 and D4 receptor immunolabeling was observed in the thalamic reticular nucleus, which was negative for the D3 subtype. Species differences were also observed; for example, the D4 subtype receptor is the most highly expressed protein in the rat cortex, whereas it is significantly less in human cortex. Differential patterns of D2, D3, and D4 receptor expression in rat and human brain should shed light on the therapeutic actions of neuroleptic drugs and may lead to the development of more specifically targeted antipsychotic drugs.