Optimum deposition conditions of ultrasmooth silver nanolayers

Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2).

PACS

63.22.Np Layered systems; 68. Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization     

Changes in the contents of mono-, di- and oligosaccharides in leek plants stored in cold room

The aim of this work is to present the results of the analysis of composition of mono-, di- and oligosaccharides, including the content of fructooligosaccharides as well as rafinose, stachyose in pseudo stalk of leek plants of the following cultivars: Shelton F1, Belton F1 and Parton F1. Leek plants were stored in cold room at the temperature 0 °C and relative humidity around 98% in the period from December to May. Fructose, glucose, saccharose, fructooligosaccharides (FOS) as well as α-galactosides were determined with the HPLC method with the application of water-alcohol extracts. It was shown that some of the studied parameters have changed during storage, i.e., the glucose content increased from 4.4 ± 0.3 to 16.2 ± 1.6, fructose from 4.7 ± 0.2 to 23.8 ± 0.4, saccharose from 5.1 ± 0.7 to 18.7 ± 0.1, depending on the cultivar and the storage period. The largest increase in the content of fructose and glucose took place between 60th and 90th day of storage which testifies to intensive hydrolysis of fructans. Leek cv. Parton F1 was characterised by the largest content of fructans and the lowest susceptibility to hydrolysis. The amount of kestose, nystose and rafinose after the period of storage changed from 0.3 ± 0.0 to 0.9 ± 0.2, 0.5 ± 0.1 to 1.8 ± 0.1, 0.8 ± 0.1 to 1.8 ± 0.2 g/100 g of dry mass, respectively. The content of stachyose, in turn, remained at a constant level and amounts to around 0.5 g/100 g of dry mass. Leek plants kept in typical refrigeration conditions are characterised by good durability and constitute a valuable merchandise. However, due to ongoing hydrolysis processes, the content of prebiotic substances decreased what lowered the health-promoting value.     

metaXCMS: second-order analysis of untargeted metabolomics data

Mass spectrometry-based untargeted metabolomics often results in the observation of hundreds to thousands of features that are differentially regulated between sample classes. A major challenge in interpreting the data is distinguishing metabolites that are causally associated with the phenotype of interest from those that are unrelated but altered in downstream pathways as an effect. To facilitate this distinction, here we describe new software called metaXCMS for performing second-order ("meta") analysis of untargeted metabolomics data from multiple sample groups representing different models of the same phenotype. While the original version of XCMS was designed for the direct comparison of two sample groups, metaXCMS enables meta-analysis of an unlimited number of sample classes to facilitate prioritization of the data and increase the probability of identifying metabolites causally related to the phenotype of interest. metaXCMS is used to import XCMS results that are subsequently filtered, realigned, and ultimately compared to identify shared metabolites that are up- or down-regulated across all sample groups. We demonstrate the software's utility by identifying histamine as a metabolite that is commonly altered in three different models of pain. metaXCMS is freely available at http://metlin.scripps.edu/metaxcms/.     

Automated iterative MS/MS acquisition: a tool for improving efficiency of protein identification using a LC-MALDI MS workflow

We have developed an information-dependent, iterative MS/MS acquisition (IMMA) tool for improving MS/MS efficiency, increasing proteome coverage, and shortening analysis time for high-throughput proteomics applications based on the LC-MALDI MS/MS platform. The underlying principle of IMMA is to limit MS/MS analyses to a subset of molecular ions that are likely to identify a maximum number of proteins. IMMA reduces redundancy of MS/MS analyses by excluding from the precursor ion peak lists proteotypic peptides derived from the already identified proteins and uses a retention time prediction algorithm to limit the degree of false exclusions. It also increases the utilization rate of MS/MS spectra by removing "low value" unidentifiable targets like nonpeptides and peptides carrying large loads of modifications, which are flagged by their "nonpeptide" excess-to-nominal mass ratios. For some samples, IMMA increases the number of identified proteins by ～20-40% when compared to the data dependent methods. IMMA terminates an MS/MS run at the operator-defined point when "costs" (e.g., time of analysis) start to overrun "benefits" (e.g., number of identified proteins), without prior knowledge of sample contents and complexity. To facilitate analysis of closely related samples, IMMA's inclusion list functionality is currently under development.     

Evaluation of sensory attributes of coffee brews from robusta coffee roasted under different conditions

Robusta coffee beans with a different initial moisture of 5, 7.5 and 10% were convectively roasted at 230 °C, microwaved at 700 W, and roasted by the coupled convective-microwave method. Sensory attributes of brews prepared from these coffee samples were evaluated. Final temperature of microwaved coffee beans was lower than that of the beans processed by the two other methods, which resulted in a higher content of volatile aroma compounds and a lesser degree of charring of their surface. Lower initial humidity of coffee beans shortened the time of roasting. However, the aroma developed upon roasting of the moistest beans was the most intense and pleasant. Modification of roasting conditions increased shifting of the overall acceptability of coffee infusions by 2 points in a 10-point hedonic scale, which implies that, if roasting conditions are adequate to the type of coffee, its sensory characteristics can be improved. Thus, optimization of roasting parameters can increase the share of robusta in well-accepted commercial coffee blends, a convenient fact because of the significant difference in price between the latter and arabica coffee.     

Large-scale multimedia content delivery over optical networks for interactive TV services

iTVP is a system built for delivery of live TV programming, video-on-demand and audio-on-demand with interactive access over IP networks. It has a nationwide range and is designed to provide service to a high number of concurrent users. Hence, scalability is one of the most important issues. In this paper we described how scalability is achieved in a two-level hierarchical architecture of the delivery system. We present the principles of content caching mechanisms and the management of the resulting distributed content repository. The system is implemented and currently operates in a test installation. Although the range of the test system operations is limited, as far as the number of users and the size of the content repository is concerned, the experience gained with iTVP so far provides an insight into the expected prototype performance. We present a system performance evaluation and describe the experience gained during the iGrid demonstration.     

Optimization of an industrial DC magnetron sputtering process for graded composition solar thermal absorbing layer

Optimization of an industrial DC magnetron sputtering process for thin graded index coatings for solar thermal absorbers is reported. The optimization concerned the main processing parameters: sputtering power, argon flow, oxygen flow, and system set-up for graded control. The purpose of the optimization was to achieve a surface with efficient solar-thermal energy conversion based on the concept graded index coating, using a metal-dielectric composite coating of nickel–nickel oxide with a continuous change in composition through the film depth profile. It was found that the optimization of the materials composition could be controlled by one parameter related to the sputtering process, the relative oxygen flow RO, defined as the ratio of applied oxygen flow to the critical oxygen flow. For optimized sputtering conditions a solar absorptance of 0.92 was obtained for a single graded index coating on aluminum for RO value of 0.8. From the materials characterization it was found that this gave a graded index coating of two thick sub-layers, a top layer of nano-sized nickel oxide grains and a base layer of nano-size metallic nickel grains with a very thin interface of a mixture of nickel and nickel oxide that was almost amorphous.     

Monitoring pH-dependent conformational changes in aqueous solutions of poly(methacrylic acid)-b-polydimethylsiloxane copolymer based on fluorescence spectra of pyrene and 1,3-bis(1-pyrenyl)propane

Aqueous solutions of poly(methacrylic acid)-b-polydimethylsiloxane copolymer (PMA-b-PDMS), and reference solutions of PMA homopolymer, were studied as a function of pH using fluorescent probes: pyrene (P) and 1,3-bis(1-pyrenyl)propane (P3P). In both polymers the conformational transition of PMA chains at pH>5 was reflected in the sharp increase of the intensity ratio of the first to the third vibronic band in emission spectra of P; an excimer emission appeared for P3P, as well as for P if the probe concentration was higher than its solubility limit in water. The excimer to monomer intensity ratio of both probes is a sensitive indicator of the conformational transitions of polymer chains, but P3P is significantly more sensitive compared to pyrene. The data clearly indicated that the presence of PDMS blocks markedly facilitated the transition, even though the ratio of dimethylsiloxane to methacrylic acid units in the copolymer was low, 1:34. The absence of the P3P excimer emission at pH≈3 was rationalized by assuming that clustering of sections of PMA chains around pyrene moieties imposes an extended conformation of the probe molecule.