Nitric oxide and the release of lipoprotein lipase from white adipose tissue

Background/Aim: Lipoprotein lipase (LPL) is the main enzyme responsible for the distribution of circulating triacylglycerides in tissues. Its regulation via release from active sites in the vascular endothelium is poorly understood. In a previous study we reported that in response to acute immobilization (IMMO), LPL activity rapidly increases in plasma and decreases in white adipose tissue (WAT) in rats. In other stress situations IMMO triggers a generalized increase in nitric oxide (NO) production. Methods/Results: Here we demonstrate that in rats: 1) in vivo acute IMMO rapidly increases NO concentrations in plasma 2) during acute IMMO the WAT probably produces NO via the endothelial isoform of nitric oxide synthase (eNOS) from vessels, and 3) epididymal WAT perfused in situ with an NO donor rapidly releases LPL from the endothelium. Conclusion: We propose the following chain of events: stress stimulus / rapid increase of NO production in WAT (by eNOS) / release of LPL from the endothelium in WAT vessels. This chain of events could be a new mechanism that promotes the rapid decrease of WAT LPL activity in response to a physiological stimulus.

Reduced microwave losses of YBa2Cu3O7_thin films on electro-optic LiNbO3 crystals

We report on the growth of epitaxial YBa2Cu3O7 thin films on X-cut LiNbO3 single crystals. The use of double CeO2/YSZ buffer layers allows a single in-plane orientation of YBa2Cu3O7, and results in superior superconducting properties. In particular, surface resistance Rs values of 1.4 m¿ have been measured at 8 GHz and 65 K. The attainment of such low values of Rs constitutes a key step toward the incorporation of high Tc materials as electrodes in photonic and acoustic devices.

Temperature dependence of the magnetization processes in Co/Al oxide/Permalloy trilayers

The magnetization process of Co/Al oxide/Py trilayers and its evolution with the temperature have been analyzed. The particular behavior of the Co layers, including the shift of the hysteresis loops and a coercivity increase with the decrease of temperature, is related with the apparition of a CoO layer at the Co/Al-oxide interface.

Quasi real-time Raman studies on the growth of Cu-In-S thin films

In this work annealing and growth of CuInS2 thin films is investigated with quasireal-time in situ Raman spectroscopy. During the annealing a shift of the Raman A1 mode towards lower wave numbers with increasing temperature is observed. A linear temperature dependence of the phonon branch of ¿2 cm¿1/100 K is evaluated. The investigation of the growth process (sulfurization of metallic precursors) with high surface sensitivity reveals the occurrence of phases which are not detected with bulk sensitive methods. This allows a detailed insight in the formation of the CuInS2 phases. Independent from stoichiometry and doping of the starting precursors the CuAu ordering of CuInS2 initially forms as the dominating ordering. The transformation of the CuAu ordering into the chalcopyrite one is, in contrast, strongly dependent on the precursor composition and requires high temperatures.

Study of post-deposition contamination in low-temperature deposited polysilicon films

The presence of hydrogen in polysilicon films obtained at low temperatures by hot-wire CVD and the post-deposition oxidation by air-exposure of the films are studied in this paper. The experimental results from several characterization techniques (infrared spectroscopy, X-ray photoelectron spectroscopy, secondary ion mass spectrometry and wavelength dispersive spectroscopy) showed that hydrogen and oxygen are homogeneously distributed at grain boundaries throughout the depth of the films. Hydrogen is introduced during the growth process and its concentration is higher in samples deposited at lower temperatures. Oxygen diffuses along the grain boundaries and binds to silicon atoms, mainly in Si 2O groups.

Spectroscopic ellipsometry study of the In1-x Gax Asy P1-y / InP Heterojunctions grown by metalorganic chemical-vapor deposition

The dielectric functions of InP, In0.53Ga0.47As, and In0.75Ga0.25As0.5P0.5 epitaxial layers have been measured using a polarization modulation spectroscopic ellipsometer in the 1.5 to 5.3 eV region. The oxide removal procedure has been carefully checked by comparing spectroscopic ellipsometry and x ray photoelectron spectroscopy measurements. These reference data have been used to investigate the structural nature of metalorganic chemical vapor deposition grown In0.53Ga0.47As/InP and In0.75Ga0.25As0.5P0.5/InP heterojunctions, currently used for photodiodes and laser diodes. The sharpness of the interfaces has been systematically compared for the two types of heterojunctions: In1 xGaxAsy/InP and InP/In1 xGaxAsyP1 y. The sharpest interface is obtained for InP growth on In0.75Ga0.25As0.5P0.5 where the interface region is estimated to be (10±10) Å thick. The importance of performing in situ SE measurements is emphasized.

Electron tunneling in heavily In-doped polycrystalline CdS films

The electrical properties of heavily In‐doped polycrystalline CdS films have been studied as a function of the doping level. The films were prepared by vacuum coevaporation of CdS and In. Conductivity and Hall measurements were performed over the temperature range 77-400 K. The conductivity decreases weakly with the temperature and shows a tendency towards saturation at low temperatures. A simple relationship σ=σ0(1+βT2) is found in the low‐temperature range. The temperature dependence of the mobility is similar to that of the conductivity since the Hall coefficient is found to be a constant in the whole temperature range. We interpret the experimental results in terms of a modified version of grain‐boundary trapping Seto"s model, taking into account thermionic emission and tunneling of carriers through the potential barriers. The barriers are found to be high and narrow, and tunneling becomes the predominating transport mechanism.

Properties of amorphous silicon thin films grown in square wave modulated silane rf discharges.

Hydrogenated amorphous silicon (a‐Si:H) thin films have been obtained from pure SiH4 rf discharges by using the square wave modulation (SQWM) method. Film properties have been studied by means of spectroellipsometry, thermal desorption spectrometry, photothermal deflection spectroscopy and electrical conductivity measurements, as a function of the modulation frequency of the rf power amplitude (0.2-4000 Hz). The films deposited at frequencies about 1 kHz show the best structural and optoelectronic characteristics. Based upon the experimental results, a qualitative model is presented, which points up the importance of plasma negative ions in the deposition of a‐Si:H from SQWM rf discharges through their influence on powder particle formation.

Structural factors impacting carrier transport and electroluminescence from Si nanocluster-sensitized Er ions.

We present an analysis of factors influencing carrier transport and electroluminescence (EL) at 1.5 µm from erbium-doped silicon-rich silica (SiOx) layers. The effects of both the active layer thickness and the Si excess content on the electrical excitation of erbium are studied. We demonstrate that when the thickness is decreased from a few hundred to tens of nanometers the conductivity is greatly enhanced. Carrier transport is well described in all cases by a Poole-Frenkel mechanism, while the thickness-dependent current density suggests an evolution of both density and distribution of trapping states induced by Si nanoinclusions. We ascribe this observation to stress-induced effects prevailing in thin films, which inhibit the agglomeration of Si atoms, resulting in a high density of sub-nm Si inclusions that induce traps much shallower than those generated by Si nanoclusters (Si-ncs) formed in thicker films. There is no direct correlation between high conductivity and optimized EL intensity at 1.5 µm. Our results suggest that the main excitation mechanism governing the EL signal is impact excitation, which gradually becomes more efficient as film thickness increases, thanks to the increased segregation of Si-ncs, which in turn allows more efficient injection of hot electrons into the oxide matrix. Optimization of the EL signal is thus found to be a compromise between conductivity and both number and degree of segregation of Si-ncs, all of which are governed by a combination of excess Si content and sample thickness. This material study has strong implications for many electrically driven devices using Si-ncs or Si-excess mediated EL.

Surface passivation of crystalline silicon by Cat-CVD amorphous and nanocrystalline thin silicon films

In this work, we study the electronic surface passivation of crystalline silicon with intrinsic thin silicon films deposited by Catalytic CVD. The contactless method used to determine the effective surface recombination velocity was the quasi-steady-state photoconductance technique. Hydrogenated amorphous and nanocrystalline silicon films were evaluated as passivating layers on n- and p-type float zone silicon wafers. The best results were obtained with amorphous silicon films, which allowed effective surface recombination velocities as low as 60 and 130 cms -1 on p- and n-type silicon, respectively. To our knowledge, these are the best results ever reported with intrinsic amorphous silicon films deposited by Catalytic CVD. The passivating properties of nanocrystalline silicon films strongly depended on the deposition conditions, especially on the filament temperature. Samples grown at lower filament temperatures (1600 °C) allowed effective surface recombination velocities of 450 and 600 cms -1 on n- and p-type silicon.

Cationic and charge segregation in La2/3Ca1/3MnO3 thin films grown on (001) and (110) SrTiO3.

Electron energy-loss spectroscopy is used to map composition and electronic states in epitaxial La2/3Ca1/3MnO3 films grown on SrTiO3 001 and 110 substrates. It is found that in partially relaxed 110 films cationic composition and valence state of Mn3+/4+ ions are preserved across the film thickness. In contrast, in fully strained 001 films, the Ca/La ratio gradually changes across the film, being La rich at film/substrate interface and La depleted at free surface; Mn valence state changes accordingly. These observations suggest that a strongly orientation-dependent adaptative composition mechanism dominates stress accommodation in manganite films and provides microscopic understanding of their dissimilar magnetic properties.

Correlation between charge transport and electroluminescence properties of Si-rich oxide/nitride/oxide-based light emitting capacitors.

The electrical and electroluminescence (EL) properties at room and high temperatures of oxide/ nitride/oxide (ONO)-based light emitting capacitors are studied. The ONO multidielectric layer is enriched with silicon by means of ion implantation. The exceeding silicon distribution follows a Gaussian profile with a maximum of 19%, centered close to the lower oxide/nitride interface. The electrical measurements performed at room and high temperatures allowed to unambiguously identify variable range hopping (VRH) as the dominant electrical conduction mechanism at low voltages, whereas at moderate and high voltages, a hybrid conduction formed by means of variable range hopping and space charge-limited current enhanced by Poole-Frenkel effect predominates. The EL spectra at different temperatures are also recorded, and the correlation between charge transport mechanisms and EL properties is discussed.

Ferromagnetism in transparent thin films of MgO

We show both theoretical and experimental evidences of the appearance of ferromagnetism in MgO thin films. First-principles calculations allow predicting the possibility of the formation of a local moment in MgO, provided the existence of Mg vacancies which create holes on acceptor levels near the O 2p-dominated valence band. Magnetic measurements evidence of the existence of room-temperature ferromagnetism in MgO thin films. High-resolution transmission electron microscopy demonstrates the existence of cation vacancies in our samples. Finally, by applying the element specificity of the x-ray magnetic circular dichroism technique, we also demonstrate that the magnetic moments of the system arise from the spin polarization of the 2p electrons of oxygen atoms surrounding Mg vacancies.

Domain matched epitaxial growth of Bi1.5Zn1Nb1.5O7 thin films by pulsed laser deposition

Bi1.5Zn1Nb1.5O7 (BZN) epitaxial thin films were grown by pulsed laser deposition on Al2O3 with a double ZnO buffer layer through domain matching epitaxy (DME) mechanism. The pole figure analysis and reciprocal space mapping revealed the single crystalline nature of the thin film. The pole figure analysis also shows a 60º twinning for the (222) oriented crystals. Sharp intense spots in the SAED pattern also indicate the high crystalline nature of BZN thin film. The Fourier filtered HRTEM images of the BZN-ZnO interface confirms the domain matched epitaxy of BZN with ZnO buffer. An electric field dependent dielectric tunability of 68% was obtained for the BZN thin films with inter digital capacitors patterned over the film.

MgO/Ag(001) interface structure and STM images from first principles

The interface of MgO/Ag(001) has been studied with density functional theory applied to slabs. We have found that regular MgO films show a small adhesion to the silver substrate, the binding can be increased in off-stoichiometric regimes, either by the presence of O vacancies at the oxide film or by a small excess of O atoms at the interface between the ceramic to the metal. By means of theoretical methods, the scanning tunneling microscopy signatures of these films is also analyzed in some detail. For defect free deposits containing 1 or 2 ML and at low voltages, tunnelling takes place from the surface Ag substrate, and at large positive voltages Mg atoms are imaged. If defects, oxygen vacancies, are present on the surface of the oxide they introduce much easier channels for tunnelling resulting in big protrusions and controlling the shape of the image, the extra O stored at the interface can also be detected for very thin films.