Development of research on the physiological mechanisms of auditory localization.

Early work on the perception of location of a sound source was considered to be a judgment arrived at by comparing differences in the stimulation at the 2 ears. This view gave way to the dichotic time hypothesis which led to many speculations concerning the neurological mechanisms involved in localization. More recently ablation and electrophysiological techniques have been employed but as yet there is not a completely satisfactory neurological model. From Psyc Abstracts 36:01:3DI76R. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A dry electrochemical cell containing cupric chloride supported by γ-alumina

An electrochemical cell was formed by enclosing a commercial catalyst containing cupric chloride supported by γ-alumina between electrodes of copper and iron. The voltage obtained is a logarithmic function of the vapour pressure of the water sorbed by the support. Voltages of a few hundred millivolts are obtained at relative pressures between 0.1 and 0.8 and temperatures between 25 and 170°C.     

Pharmacokinetics and bioavailability of a sustained-release diltiazem formulation (Mono-Tildiem LP 300 MG) after repeated administration in healthy volunteers

The usual dosage regimen of diltiazem (Tildiem) is 60 mg 3-4 times a day. A sustained-release formulation has been developed (Mono-Tildiem LP 300 mg) in order to allow a single daily administration. Two repeated dosing studies were performed in healthy volunteers. The absolute bioavailability of sustained-release diltiazem LP 300 mg was investigated using concomitant i.v. administration of 13C-labelled drug: absolute bioavailability of the "once a day" formulation was 35%. The second study compared sustained-release diltiazem LP 300 mg with the standard formulation of diltiazem. The results showed that the diltiazem plasma concentrations obtained after the LP formulation remained stable between 2 and 14 h after administration and were compatible with a once a day administration. Relative bioavailability of sustained-release diltiazem LP 300 mg was 79.3% compared with diltiazem. Therefore, a unitary dose of sustained-release diltiazem LP 300 mg was chosen as the dose equivalent to the daily dose administered with the standard diltiazem formulation.     

Dimensional variations of two spherical polymeric particles during sintering

A quantitative “Round Neck” (RN) model based upon volume balances and considerations of surface tension phenomena is proposed for simulation of coalescence of two spherical polymeric particles; during sintering. This model and an early model developed by Frenkel are compared and evaluated against experimental data to show their suitability to simulate geometrical variations of a particle pair during sintering.     

Luminescent quantum dots fluorescence resonance energy transfer-based probes for enzymatic activity and enzyme inhibitors

The paper describes the development and characterization of analytical properties of quantum dot-based probes for enzymatic activity and for screening enzyme inhibitors. The luminescent probes are based on fluorescence resonance energy transfer (FRET) between luminescent quantum dots that serve as donors and rhodamine acceptors that are immobilized to the surface of the quantum dots through peptide linkers. Peptide-coated CdSe/ZnS quantum dots were prepared using a one-step ligand exchange process in which RGDC peptide molecules replace trioctylphosphine oxide (TOPO) molecules as the capping ligands of the quantum dots. The peptide molecules were bound to the surface of the CdSe/ZnS quantum dots through the thiol group of the peptide cysteine residue. The peptide-coated quantum dots were labeled with rhodamine to form the FRET probes. The emission quantum yield of the quantum dot FRET probes was 4-fold lower than the emission quantum yield of TOPO-capped quantum dots. However, the quantum dot FRET probes were sufficiently bright to enable quantitative enzyme and enzyme inhibition assays. The probes were used first to test the enzymatic activity of trypsin in solution based on FRET signal changes of the quantum dot-based enzymatic probes in the presence of proteolytic enzymes. For example, exposure of the quantum dot FRET probes to 500 microg/mL trypsin for 15 min resulted in 60% increase in the photoluminescence of the quantum dots and a corresponding decrease in the emission of the rhodamine molecules. These changes resulted from the release of rhodamine molecules from the surface of the quantum dots due to enzymatic cleavage of the peptide molecules. The quantum dot FRET-based probes were used to monitor the enzymatic activity of trypsin and to screen trypsin inhibitors for their inhibition efficiency.     

Structural and mechanistic insights into methane oxidation by particulate methane monooxygenase

Particulate methane monooxygense (pMMO) is an integral membrane copper-containing enzyme that converts methane to methanol. Knowledge of how pMMO selectively oxidizes methane under ambient conditions could impact the development of new catalysts. The crystal structure of Methylococcus capsulatus (Bath) pMMO reveals the composition and location of three metal centers. Spectroscopic data provide insight into the coordination environments and oxidation states of these metal centers. These results, combined with computational studies and comparisons to relevant systems, are discussed in the context of identifying the most likely site for O 2 activation.     

Carrier capture and escape processes inIn0.25Ga0.75As-GaAs quantum-well lasers

We have extracted the ratio between the carrier capture and escape times, η, for In_0.25Ga_0.75As-GaAs lasers containing one, two, or three quantum wells, from high-frequency subthreshold impedance measurements at different temperatures. Our results show that the carrier capture process dominates over the diffusion along the confinement region in the overall transport/capture process. The obtained value for η is comparable to unity, and this fact has to be taken into account to obtain real material parameters, such as the carrier lifetime and the radiative recombination coefficient     

100-112.Gbit/s complete ETDM systems based on monolithically integrated transmitter and receiver modules

Traditional intensity modulated two-level electrical time-division multiplexing(ETDM)transmission systems working at 100-112Gbit/s were investigated.The complete ETDM systems based on monolithically integrated transmitter and receiver modules were demonstrated with bit-error-rate(BER)performance of 10-8 at 107Gbit/s,and near error-free standard forward error correction(FEC)threshold(2×10-3)at 112Gbit/s.The experiment results showed that directly modulated high-speed ETDM transmission systems with the symbol rates at 100Gbaud and beyond were promising candidate for cost-effective 100GbE applications and might be a preform of the next generation of Terabit/s Ethernet.     

Characterization of plasma accelerators with RF linac terminology

The physics of plasma acceleration is described by using RF linac terminology such as shunt impedance, filling time, transit time factor, etc. It is shown that some differences between conventional RF accelerators and plasma accelerators make it difficult to import the RF linac terminology directly into the new field. For example, the shunt impedance is of limited use and the filling time is no use in wake-field accelerators with single-drive beams or single-pump pulses. The beatwave accelerator, a driven oscillator system, has in a sense more similarity to RF linacs than wake-field accelerators. It was shown that plasma wave decay due to collisions and modulational instability seriously deteriorate the quality factor.     

Oleic acid and angiotensin II induce a synergistic mitogenic response in vascular smooth muscle cells

Oleic acid and angiotensin II (Ang II) are elevated and may interact to accelerate vascular disease in obese hypertensive patients. We studied the effects of oleic acid and Ang II on growth responses of rat aortic smooth muscle cells (VSMCs). Oleic acid (50 micromol/L) raised thymidine incorporation by 50% at 24 hours and cell number by 55% at 6 days (P<.05). Ang II (10(-11) to 10(-6) mol/L) did not significantly increase thymidine incorporation or VSMC number. Combining Ang II and 50 micromol/L oleic acid doubled thymidine incorporation and VSMC number. Losartan, an angiotensin type 1 (AT1) receptor antagonist, blocked the synergistic interaction between Ang II and oleic acid, whereas the AT2 receptor antagonist PD 123319 did not. Protein kinase C inhibition and downregulation, as well as inhibition of extracellular signal-regulated kinase (ERK) activation by PD 98059, eliminated the rise of thymidine incorporation in response to oleic acid and the synergistic interaction with Ang II. However, the response to 10% fetal bovine serum was unaffected. An antisense oligodeoxynucleotide to ERK-1 and ERK-2 reduced ERK protein expression and activation by 83% and 75%, respectively. Antisense prevented the rise of thymidine incorporation in response to oleic acid and the synergy with Ang II. Antisense reduced but did not prevent increased thymidine incorporation in response to serum. The data indicate that oleic acid and Ang II exert a synergistic mitogenic effect in VSMCs and suggest an important role for the AT1 receptor, PKC, and ERK in this synergy. The observations raise the possibility that a synergistic mitogenic interaction between oleic acid and Ang II accelerates vascular remodeling in obese hypertensive patients.