Early stages of growth of gold layers sputter deposited on glass and silicon substrates

Extremely thin gold layers were sputter deposited on glass and silicon substrates, and their thickness and morphology were studied by Rutherford backscattering (RBS) and atomic force microscopy (AFM) methods. The deposited layers change from discontinuous to continuous ones for longer deposition times. While the deposition rate on the silicon substrate is constant, nearly independent on the layer thickness, the rate on the glass substrate increases with increasing layer thickness. The observed dependence can be explained by a simple kinetic model, taking into account different sticking probabilities of gold atoms on a bare glass substrate and regions with gold coverage. Detailed analysis of the shape of the RBS gold signal shows that in the initial stages of the deposition, the gold layers on the glass substrate consist of gold islands with significantly different thicknesses. These findings were confirmed by AFM measurements, too. Gold coverage of the silicon substrate is rather homogeneous, consisting of tiny gold grains, but a pronounced worm-like structure is formed for the layer thickness at electrical continuity threshold. On the glass substrate, the gold clusters of different sizes are clearly observed. For later deposition stages, a clear tendency of the gold atoms to aggregate into larger clusters of approximately the same size is observed. At later deposition stages, gold clusters of up to 100 nm in diameter are formed.     

Polarized recombination of acoustically transported carriers in GaAs nanowires

ABSTRACT: : The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited electrons and holes in GaAs nanowires deposited on a SAW delay line on a LiNbO3 crystal. The carriers generated in the nanowire by a focused light spot are acoustically transferred to a second location where they recombine. We show that the recombination of the transported carriers occurs in a zinc blende section on top of the predominant wurtzite nanowire. This allows contactless control of the linear polarized emission by SAWs which is governed by the crystal structure. Additional polarization-resolved photoluminescence measurements were performed to investigate spin conservation during transport.     

Resting energy expenditure and carbohydrate oxidation are higher in elderly patients with COPD: a case control study

ABSTRACT: BACKGROUND: Elderly patients with chronic obstructive pulmonary disease (COPD) usually have a compromised nutritional status which is an independent predictor of morbidity and mortality. To know the Resting Energy Expenditure (REE) and the substrate oxidation measurement is essential to prevent these complications. This study aimed to compare the REE, respiratory quotient (RQ) and body composition between patients with and without COPD. METHODS: This case-control study assessed 20 patients with chronic obstructive pulmonary disease attending a pulmonary rehabilitation program. The group of subjects without COPD (control group) consisted of 20 elderly patients attending a university gym, patients of a private service and a public healthy care. Consumption of oxygen (O2) and carbon dioxide (CO2) was determined by indirect calorimetry and used for calculating the resting energy expenditure and respiratory quotient. Body mass index (BMI) and waist circumference (WC) were also measured. Percentage of body fat (%BF), lean mass (kg) and muscle mass (kg) were determined by bioimpedance. The fat free mass index (FFMI) and muscle mass index (MMI) were then calculated. Results: The COPD group had lower BMI than control (p=0.02). However, WC, % BF, FFMI and MM-I did not differ between the groups. The COPD group had greater RQ (p=0.01), REE (p=0.009) and carbohydrate oxidation (p= 0.002). Conclusions: Elderly patients with COPD had higher REE, RQ and carbohydrate oxidation than controls.     

Polymer anion-selective membranes for electrolytic splitting of water. Part II: Enhancement of ionic conductivity and performance under conditions of alkaline water electrolysis

An attempt was made to increase the ionic conductivity of novel, heterogeneous, anion-selective membranes by increasing the porosity of their surface skin. This was based on the addition of a water-soluble component, namely poly(ethylene-ran-propylene glycol), to an inert polymer matrix, based on low-density polyethylene, while mixing it with the ion-exchange particles. A series of membranes was prepared, consisting of 66 wt% of anion-exchange phase represented by a styrene-divinyl benzene copolymer matrix with quaternary ammonium functional groups and an inert polymer matrix in a mixture with variable amounts of water-soluble component added. The membranes were subsequently tested with respect to their morphology, mechanical properties, apparent ion-exchange capacity, ionic conductivity, and performance under conditions of alkaline water electrolysis. When added in the appropriate amount, the addition of a water-soluble component was found to improve the electrochemical properties of the resulting membrane efficiently, while at the same time not reducing its mechanical properties to below a critical level.     

The influence of electrolyte composition on electrochemical ferrate(VI) synthesis. Part III: anodic dissolution kinetics of a white cast iron anode rich in iron carbide

The anolyte composition and process temperature could improve the kinetics of iron anode dissolution and subsequent ferrate(VI) production significantly. This also holds for the anode composition. Following pure iron and silicon-rich steel (SRS), white cast iron (WCI) was the last representative of anode material tested that is typically used to produce ferrate(VI). Using anolytes 14 M NaOH, 14 M KOH, and mixtures thereof, the systems were studied by potentiodynamic methods, electrochemical impedance spectroscopy, and batch electrolysis experiments. Additionally, metallographic analysis of the material was performed. The dissolution kinetics increases with increasing temperature and also, at 60 °C, with increasing K⁺ content in the anolyte, but less progressively than in the case of SRS. Similar to SRS, WCI also easily dissolves into ferrate(VI) even at 20 °C in pure NaOH, thus indicating the inferior protective properties of oxo-hydroxide surface layers. In general, a maximum current efficiency of approx. 60 % was obtained at 60 °C in pure KOH solution. The authors conclude that, at 60 °C, the high efficiency of the synthesis is caused by the low protective properties of the oxo-hydroxide surface layer caused by the preferential dissolution of cementite and at the same time by the precipitation of the potassium salt of the product in the electrolyte immediately after its formation. This minimizes the effect of its decomposition.     

Improved thermal stability of oxide-supported naked gold nanoparticles by ligand-assisted pinning

We report a method to improve the thermal stability, up to 900 °C, of bare-metal (naked) gold nanoparticles supported on top of SiO(2) and SrTiO(3) substrates via ligand-assisted pinning. This approach leads to monodisperse naked gold nanoparticles without significant sintering after thermal annealing in air at 900 °C. The ligand-assisted pinning mechanism is described.     

Thermal stability of HfO2-on-GaAs nanopatterns

We have evaluated the effect of thermal annealing on the morphology, crystalline phase and elemental composition of high-k dielectric HfO(2)-on-GaAs nanopatterns at 500-620 °C by using atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). While the HfO(2)-GaAs interface continues to be atomically abrupt at 620 °C, we have found a gradual shrinkage in the pattern linewidth and period with increasing temperature. Facet formation triggered by a nanoscale-modulated sequence of tensile and compressive stresses on the GaAs substrate, observed at 620 °C, has been attributed to a volumetric expansion of the HfO(2) nanostructures, caused by the tetragonal/cubic to monoclinic HfO(2) phase transformation and, to a lesser extent, by solid-state diffusion of As into HfO(2).     

Prospective surveillance of multivariate spatial disease data

Surveillance systems are often focused on more than one disease within a predefined area. On those occasions when outbreaks of disease are likely to be correlated, the use of multivariate surveillance techniques integrating information from multiple diseases allows us to improve the sensitivity and timeliness of outbreak detection. In this article, we present an extension of the surveillance conditional predictive ordinate to monitor multivariate spatial disease data. The proposed surveillance technique, which is defined for each small area and time period as the conditional predictive distribution of those counts of disease higher than expected given the data observed up to the previous time period, alerts us to both small areas of increased disease incidence and the diseases causing the alarm within each area. We investigate its performance within the framework of Bayesian hierarchical Poisson models using a simulation study. An application to diseases of the respiratory system in South Carolina is finally presented.     

Salivary defense proteins: their network and role in innate and acquired oral immunity

There are numerous defense proteins present in the saliva. Although some of these molecules are present in rather low concentrations, their effects are additive and/or synergistic, resulting in an efficient molecular defense network of the oral cavity. Moreover, local concentrations of these proteins near the mucosal surfaces (mucosal transudate), periodontal sulcus (gingival crevicular fluid) and oral wounds and ulcers (transudate) may be much greater, and in many cases reinforced by immune and/or inflammatory reactions of the oral mucosa. Some defense proteins, like salivary immunoglobulins and salivary chaperokine HSP70/HSPAs (70 kDa heat shock proteins), are involved in both innate and acquired immunity. Cationic peptides and other defense proteins like lysozyme, bactericidal/permeability increasing protein (BPI), BPI-like proteins, PLUNC (palate lung and nasal epithelial clone) proteins, salivary amylase, cystatins, prolin-rich proteins, mucins, peroxidases, statherin and others are primarily responsible for innate immunity. In this paper, this complex system and function of the salivary defense proteins will be reviewed.     

Evaluating the In Vitro Metabolism of Docosahexaenoic Acid in Sheep Rumen Fluid

Rumen metabolism (e.g., biohydrogenation) of dietary unsaturated fatty acids (FA) is one of the main reasons why ruminant fats tend to be highly saturated and contain many isomerized FA intermediates. The process by which long-chain (20- to 24-carbon FA) polyunsaturated FA (LC-PUFA) are metabolized by rumen bacteria is not as well understood as that of linoleic or linolenic acids. In order to better understand the fate of LC-PUFA in the rumen several concentrations of docosahexaenoic acid (DHA) were evaluated in in vitro batch incubations ranging from 100 to 1,500 μg per 6 mL of incubation volume using rumen fluid from sheep and incubated for 0, 1, 2, 3, and 6 h. From the results, it was shown that DHA was extensively metabolized at low (100 to 300 μg/6 mL incubation volume), but not at high level of inclusion (800 μg). At 300 μg of DHA most of the depleted DHA was recovered as LC-DHA metabolites within the first 6 h of incubation, and at the lowest levels (100 μg of incubation volume) further metabolism is apparent at 6 h. Using SP-2560 GC columns several LC-DHA metabolites were shown to elute after 24:0 and just past DHA, a region generally free of interfering FA. The present in vitro study would appear to be a useful method to evaluate the production of DHA metabolites in combination with its depletion.