Search results for "PRESSURE"

Segregation of lipid in Ir-dye/DMPA mixed monolayers as strategy to fabricate 2D supramolecular nanostructures at the air–water interface

2008

A novel pseudospherical fluorinated iridium(III) derivative, Ir-dye/PF6, [Ir(F2-ppy)2(bpy)]PF6 (F2-ppy = 2-(2,4-difluoro)phenylpyridine, bpy = 2,2′-bipyridine), has been organized by using a lipid matrix, DMPA (dimyristoyl-phosphatidic acid), in several molar ratios at the air–water interface. The molecular organization of both components and the degree of miscibility in the different mixed films have been inferred by surface techniques such as π–A isotherms, ellipsometry, reflection spectroscopy, Brewster angle microscopy (BAM), and IR spectroscopy for the LB films, additionally the results have been discussed according to the additivity rule. The equimolecular Ir-dye/DMPA mixture leads to…

Zinc-blende AlN and GaN under pressure: structural, electronic, elastic and piezoelectric properties

2004

In this paper we report a theoretical study of the structural, elastic, electronic and piezoelectric properties of zinc-blende AlN and GaN under the pressure effect. The study is focused on the first-principles all electron full-potential augmented plane wave plus local orbitals calculations within the density-functional theory. The results of bulk properties, including lattice constants, bulk modulus and derivatives and band structures are obtained and compared using both the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation functional. We find that the GGA does not give a significant improvement over LDA. We also report calcula…

High-pressure structural study of the scheelite tungstatesCaWO4andSrWO4

2005

Angle-dispersive x-ray-diffraction and x-ray-absorption near-edge structure measurements have been performed on ${\mathrm{CaWO}}_{4}$ and ${\mathrm{SrWO}}_{4}$ up to pressures of approximately 20 GPa. Both materials display similar behavior in the range of pressures investigated in our experiments. As in the previously reported case of ${\mathrm{CaWO}}_{4}$, under hydrostatic conditions ${\mathrm{SrWO}}_{4}$ undergoes a pressure-induced scheelite-to-fergusonite transition around 10 GPa. Our experimental results are compared to those found in the literature and are further supported by ab initio total-energy calculations, from which we also predict the instability at larger pressures of the …

Characterization of theTiSiO4structure and its pressure-induced phase transformations: Density functional theory study

2009

Theoretical investigations concerning the possible titanium silicate polymorphs have been performed using density functional theory at B3LYP level. Total-energy calculations and geometry optimizations have been carried out for all phases involved. The following sequence of pressure-driven structural transitions has been found: ${\text{CrVO}}_{4}$-type, $Cmcm$ (in parenthesis the transition pressure), $\ensuremath{\rightarrow}$ zircon-type, $I{4}_{1}/amd$ (0.8 GPa), $\ensuremath{\rightarrow}$ scheelite-type, $I{4}_{1}/a$ (3.8 GPa). At higher pressure the last phase is found to be stable at least up to 25 GPa. The equation of state of the different polymorphs is also reported. We found that t…

Determination of bupivacaine in human plasma by high-performance liquid chromatography.

1984

Comparison of the performance of butanol and pentanol as modifiers in the micellar chromatographic determination of some phenethylamines

2000

Abstract A procedure was developed for the determination of several phenethylamines (amphetamine, arterenol, ephedrine, phenylephrine, phenylpropanolamine, mephentermine, methoxyphenamine, pseudoephedrine and tyramine), using micellar mobile phases of sodium dodecyl sulfate (SDS), a C18 column and UV detection. The drugs were eluted at short retention times with conventional acetonitrile–water or methanol–water mobile phases. In contrast, in the micellar system, they were strongly retained due to association with the surfactant adsorbed on the stationary phase, and needed the addition of butanol or pentanol to be eluted from the column. These modifiers allowed a simple way of controlling th…

Experimental „Luxury Perfusion” in the Cerebral Cortex of the Cat

1968

Publisher Summary Preliminary studies have been performed, on the changes of cortical rCBF (Krypton- 85 Beta clearance technique) in response to a localized pressure applied to the cerebral cortex (suprasylvian gyrus) of 8 cats under Nembutal anesthesia (30 to 40 mg/kg bodyweight). No change in rCBF is found at regions as distant as the contralateral hemisphere. The increase of rCBF at the compressed site, during the compression, seems to be more marked in animals with higher blood (i.e. perfusion) pressure, and may be absent in cats with blood pressure of about 80 mm Hg. The augmentation of rCBF around the compressed area during the compression is always very marked, and after some time fl…

Carbonyl reductase 1 is a predominant doxorubicin reductase in the human liver.

2008

A first step in the enzymatic disposition of the antineoplastic drug doxorubicin (DOX) is the reduction to doxorubicinol (DOX-OL). Because DOX-OL is less antineoplastic but more cardiotoxic than the parent compound, the individual rate of this reaction may affect the antitumor effect and the risk of DOX-induced heart failure. Using purified enzymes and human tissues we determined enzymes generating DOX-OL and interindividual differences in their activities. Human tissues express at least two DOX-reducing enzymes. High-clearance organs (kidney, liver, and the gastrointestinal tract) express an enzyme with an apparent Km of approximately 140 microM. Of six enzymes found to reduce DOX, Km valu…

CARS spectroscopy of CH4 for implication of temperature measurements in supercritical LOX/CH4 combustion

2007

International audience; Experimental and theoretical investigations of coherent anti-Stokes Raman spectroscopy of CH4 have been carried out. Experimental spectra were measured in a heated high-pressure test cell and compared with numerical simulations. Good agreement was obtained for the temperature and the pressure dependence of CARS spectra in the ranges 300-1100 K and 0.1-5.0 MPa. The observed dependencies provide useful guidance for CARS thermometry, allowing quantitative measurements of temperature in high-pressure combustors. Application of multiplex CH4 CARS thermometry for single-shot measurements in a LOX/CH4 combustion at high pressure was demonstrated at supercritical conditions …

How far are we from the valorization of waste-CO2 to formic acid via electrochemical routes for the applicative scale?

To date, the decarbonization of the world economy and storage and production of energy from alternative C-based sources is considered a relevant topic. The electrochemical conversion of CO2 has been widely investigated since the 1870s as a promising strategy to convert waste-CO2 into value-added chemicals [1,2]. Recently, it was highlighted that, among the several emerging technologies for CO2 conversion to value-added products on an applicative scale, electrochemical technologies are the closest to commercialization due to the numerous start-ups and established companies being invested in this area (e.g., Opus-12, Dioxide Material, and Carbon Recycling International) [3]. These technologie…