Assessing the macroporous structure of monolithic columns by transmission electron microscopy

A set of monolithic stationary phases representing a broad span of monomers and porogens have been characterized directly in their capillary chromatographic format by computational assessment of their pore structure from transmission electron micrographs obtained after in situ embedment of the monoliths in contrast resin, followed by dissolution of the fused-silica tubing, further encasement of the resin-embedded monolith, and microtomy. This technique has been compared to mercury intrusion, a more conventional technique for macroporosity estimation. Supplementing the embedding resin by lead methacrylate gave a negative staining, and the resulting micrographs showed a good contrast between the polymeric monoliths and the embedding resin that allowed studies on the pore formation and polymer development. The technique was also applied to a commercial monolithic silica column.     

Electrochemical impedance spectroscopy for investigations on ion permeation in omega-functionalized self-assembled monolayers

Electrochemical impedance spectroscopy was employed to explore the possibility of relating the permeation of electrolyte ions in omega-functionalized self-assembled monolayers to structural or polarity changes induced by interaction with metal ions. The monolayers were based on alkanethiols modified with a phosphorylated tyrosine analogue, which from previous work are known to drastically change their organization on gold surfaces upon interaction with aluminum and magnesium ions. The ion permeation was evaluated by using relatively low excitation frequencies, 1000 to 2 Hz, and quantified by an extra resistive component in the equivalent circuit (RSAM). The extent of ion permeation influenced by the dc potential, the electrolyte concentration, the functional group, and the thiol length were also investigated. It was, for example, found that RSAM decreased approximately 20% when the thiol organization collapsed and that RSAM increased approximately 4-5 times when the electrolyte concentration was decreased by 1 order of magnitude. Interesting observations were also made regarding the potential dependence of RSAM and the double layer capacitance. The evaluation of the ion permeation can be used to indirectly detect whether the organization of a SAM is influenced by, for example, electric fields or chemical and biological interactions. This analysis can be performed without addition of redox species, but is on the other hand complicated by the fact that other factors also influence the presence of ions within the monolayer. In addition, a second parallel RC process was obtained in some of the impedance spectra when using even lower frequencies, and its resistive component revealed different results compared to RSAM. Such data may be useful for the understanding of complex double layer phenomena at modified electrodes.     

Electrophysiological and Behavioral Responses of <Emphasis Type="Italic">Ips subelongatus</Emphasis> to Semiochemicals from Its Hosts,Non-hosts,and Conspecifics in China

Volatiles from hosts, non-hosts, interspecifics, and conspecifics of the Asian larch bark beetle, Ips subelongatus Motsch., were analyzed using both gas chromatographic-electroantennographic detection (GC-EAD) and gas chromatography/mass spectrometry (GC-MS) techniques, and field trapping bioassays in Inner Mongolia, China. GC-EAD experiments indicated that I. subelongatus antennae (both sexes) strongly responded not only to the major male-produced conspecific components, ipsenol, and ipsdienol, but also to other bark beetle compounds (cis-verbenol and verbenone), host monoterpenes (α-pinene, β-pinene, and para-cymene) from Larix sp. logs, and non-host leaf (green leaf volatiles and geranyl acetone) and bark (C₈-alcohols and trans-conophthorin) volatiles. Repeatable EAD responses were also found to two compounds from hindgut extracts that are undetectable by GC. One of these minor compounds was identified as amitinol. Field trapping experiments showed that the EAD-active, major male-hindgut component, racemic ipsenol, is the only individual compound that significantly attracted both sexes of I. subelongatus, whereas all other compounds, including previously reported pheromone components of European Ips cembrae, ipsdienol and 3-methyl-3-buten-1-ol, were unattractive. Ipsdienol, 3-methyl-3-buten-1-ol, or their binary blend had no synergistic or antagonistic effects on I. subelongatus attraction when combined with ipsenol, whereas cis-verbenol (a synomone) and verbenone (the antiaggregation semiochemical) inhibited its attraction to the ipsenol-containing attractive blend. A mixture of three EAD-active host monoterpenes, α-pinene, β-pinene, and para-cymene, was unattractive, but interrupted the pheromone response of I. subelongatus. Geranyl acetone, one of the strong EAD-active non-host volatiles also significantly reduced the number of I. subelongatus captured in traps baited with ipsenol-containing attractive blend. Our results add support to the recent phylogenetic finding that European and Asian larch bark beetles should be regarded as two distinct species: I. cembrae infecting larch in Europe and I. subelongatus infesting larch in Asia.     

Leaf Volatiles from Nonhost Deciduous Trees: Variation by Tree Species, Season and Temperature, and Electrophysiological Activity in Ips typographus

The leaf volatiles emitted from four nonhost tree species of Ips typographus, i.e. Betula pendula, B. pubescens, Populus tremula, and Sambucus nigra, were collected outdoors by headspace sampling in situ and analyzed by GC-MS. Three major classes of compounds, aliphatics [mainly green-leaf volatiles (GLVs)], monoterpenes, and sesquiterpenes, existed in all the deciduous tree species investigated. In June, when the bark beetles are searching in flight for host trees, GLVs mainly consisting of (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol were the dominant constituents in B. pendula and S. nigra. In B. pubescens and P. tremula, sesquiterpenes (and their derivatives) and monoterpenes made up the major part of whole volatile blends, respectively. Surprisingly, sesquiterpene alcohols and other oxides released from B. pubescens in considerable amounts were not found in the closely related species, B. pendula. By August, both the total volatiles and individual compounds significantly decreased, mainly due to the maturation of leaves, since the light intensity and temperatures during sampling were the same as in June. There were almost no volatiles detected from P. tremula and S. nigra leaves in August. The total emissions from these deciduous species were significantly different among the species, with B. pubescens releasing 5–10 times more than other species. Under the conditions of constant light intensity and humidity, emissions of both total volatiles and most individual components of severed B. pendula and S. nigra branches (with fresh leaves) increased according to a saturation curve from 16°C to 40°C. Ips typographus antennae responded strongly to green leaf alcohols: (Z)-3-hexen-1-ol, 1-hexanol, and (E)-2-hexen-1-ol, but not to aldehydes or acetates in GC-EAD analyses of B. pendula and B. pubescens leaf volatiles. No antennal responses to monoterpenes, sesquiterpenes, or sesquiterpene oxides were found. These three antennally active GLVs emitted from nonhost tree leaves might be indicators of a wrong habitat in the host selection of conifer bark beetles.     

Tetradecane and hexadecane binary mixtures as phase change materials (PCMs) for cool storage in district cooling systems

As the demand for refrigeration and air-conditioning has increased during the last decade, district cooling systems have been introduced in some major European cities. In a district cooling system, the combination of central cooling facilities and cool storage systems provides economic advantages over older conventional cooling plants. A cool storage system can meet the same total cooling load as a non-storage system over a given period of time with a smaller chiller. Cool storage systems using Phase Change Materials (PCMs) have a low temperature range and high energy density in the melting solidification of PCMs compared to sensible heat storage. Thus they are advantageous in reducing the storage volume, heat loss, and size of the chilling equipment. In this paper we describe some paraffin waxes and their binary mixtures. We discuss the thermal properties of laboratory-grade tetradecane, hexadecane and their binary mixtures, and we demonstrate their potential for use as PCMs for cool storage. The thermal properties include freezing point, the heat of fusion, thermal stability and volume expansion during the phase change process. In the study, a Differential Scanning Calorimeter (DSC) was used to determine the heat of fusion of these materials and to generate thermal data for study and analysis. The results show that these materials are attractive candidates as potential PCMs for cool storage in district cooling systems. However, because of the high cost of laboratory-grade materials, technical-grade materials must be used for cool storage.     

Analysis of an image processing method for fiber orientation in polymer composites

The errors in fiber orientation distribution measurements of compression molding materials have been investigated, for generated as well as for real distributions. Because of the size of the sample, only a finite number of fibers are visible in a picture leading to a statistical error in the measurement. A method is proposed to express this error as function of the number of visible fibers and the number of subintervals the distribution is divided into. Studies of the error In a Fraunhofer/FT based fiber orientation distribution analysis have been performed, including effects of increasing number of fibers (fiber‐fiber intersections) in generated pictures and investigation of the errors in real fiber images. All steps in a fiber orientation distribution analysis of SMC/GMT kind of material are described, including suitable equipment, image enhancement methods and investigation of the errors present in analysis of a real image as well as comparisons to hand–measured data.     

Leaf Apoplast of Field-Grown Potato Analyzed by Quantitative Proteomics and Activity-Based Protein Profiling

Multiple biotic and abiotic stresses challenge plants growing in agricultural fields. Most molecular studies have aimed to understand plant responses to challenges under controlled conditions. However, studies on field-grown plants are scarce, limiting application of the findings in agricultural conditions. In this study, we investigated the composition of apoplastic proteomes of potato cultivar Bintje grown under field conditions, i.e., two field sites in June–August across two years and fungicide treated and untreated, using quantitative proteomics, as well as its activity using activity-based protein profiling (ABPP). Samples were clustered and some proteins showed significant intensity and activity differences, based on their field site and sampling time (June–August), indicating differential regulation of certain proteins in response to environmental or developmental factors. Peroxidases, class II chitinases, pectinesterases, and osmotins were among the proteins more abundant later in the growing season (July–August) as compared to early in the season (June). We did not detect significant differences between fungicide Shirlan treated and untreated field samples in two growing seasons. Using ABPP, we showed differential activity of serine hydrolases and β-glycosidases under greenhouse and field conditions and across a growing season. Furthermore, the activity of serine hydrolases and β-glycosidases, including proteins related to biotic stress tolerance, decreased as the season progressed. The generated proteomics data would facilitate further studies aiming at understanding mechanisms of molecular plant physiology in agricultural fields and help applying effective strategies to mitigate biotic and abiotic stresses.     

Interface engineered ultrashort period Cr-Ti multilayers as high reflectance mirrors and polarizers for soft x rays of lambda = 2.74 nm wavelength

Cr-Ti multilayers with ultrashort periods of 1.39-2.04 nm have been grown for the first time as highly reflective, soft-x-ray multilayer, near-normal incidence mirrors for transition radiation and Cherenkov radiation x-ray sources based on the Ti-2p absorption edge at E = 452 eV (lambda = 2.74 nm). Hard, as well as soft, x-ay reflectivity and transmission electron microscopy were used to characterize the nanostructure of the mirrors. To achieve minimal accumulated roughness, improved interface flatness, and to avoid intermixing at the interfaces, each individual layer was engineered by use of a two-stage ion assistance process during magnetron sputter deposition: The first 0.3 nm of each Ti and Cr layer was grown without ion assistance, and the remaining 0.39-0.72 nm of the layers were grown with high ion-neutral flux ratios phi (phiTi = 3.3, phiCr = 2.2) and a low energy Eion (ETi = 23.7 and ECr = 21.2), ion assistance. A maximum soft-x-ray reflectivity of R = 2.1% at near-normal incidence (approximately 78.8 degrees) was achieved for a multilayer mirror containing 100 bilayers with a modulation period of 1.379 nm and a layer thickness ratio of tau = 0.5. For a polarizing multilayer mirror with 150 bilayers designed for operation at the Brewster angle, 45 degrees, an extinction ratio, Rs/Rp, of 266 was achieved with an absolute reflectivity of R = 4.3%.