Using fourier transform infrared spectroscopy to examine structure in bisurea organogels

The structure of two bisurea organogels was examined by Fourier-transform infrared (FT-IR) spectroscopy. Organogels were prepared in benzene at different concentrations of gelator in order to determine the effect of concentration on the assembly of organogelator molecules. This work examined two types of bisurea organogelators, both with dodecyl alkyl tail groups. The two molecules differ only in the length of an alkyl chain separating their two urea groups: 6 carbons in the C6C12 organogelator (1,6-bis(3(3,5-didodecoxybinzyl)-urea-hexane) and 12 carbons in the C12C12 organogelator (1,12-bis(3(3,5-didodecoxybinzyl)-urea-dodecane). The degree of urea hydrogen bonding was determined from the position of the amide II band, and the conformational order of the alkyl chains in the organogelator was determined in the methylene bending region. Both gels showed a general trend of less hydrogen bonding and greater conformational disorder in the alkyl chains as the concentration of organogelator increased; however, the changes were smaller in the C12C12 gels. This decrease in structural order with increasing organogelator concentration is explained by the kinetics of gel formation; more concentrated gels solidify too quickly to assemble perfectly. The observed differences between the two organogelators are caused by the different structures into which these two similar molecules assemble. The C6C12 organogelator only assembles linearly, while the C12C12 organogelator can form sheets through brick-like packing, and these packing motifs were confirmed by scanning electron microscopy.     

Esorex 2005

The European Study on Occupational Radiation Exposure called ESOREX was initiated by the European Commission in the 1997 year. The objectives of this European study are: (1) to provide the European Commission and the national competent radiation protection authorities with reliable information on how personal radiation monitoring, reporting and recording of dosimetric results is structured in European countries; (2) to collect reliable and directly comparable data on individual and collective radiation exposure in all occupational sectors where classified workers are employed. Therefore, it is important to receive information about the levels of individual personal radiation doses to workers in the different sectors and the trends and developments of these doses over a period of several years; (3) at present, all 25 European Union Member States, plus Bulgaria, Iceland, Norway, Romania and Switzerland, participate in the study; and (4) the study was executed under the leadership of German BfS in co-operation with Czech SUJB. First results and analyses based on the data collected in the previous studies are presented in the paper 'Frasch, Petrová: Dose trends in occupational radiation exposure in Europe-Results from the ESOREX project'. As a result of a call for tender of the European Commission/DGTREN in the year 2003, the new ESOREX study called 'ESOREX2005' has been initiated. This study will end at the year 2007 and its main objectives are-to finalise the updating of the country-wise reports by describing the current situation in the field of occupational exposure control, evaluation and registration of personal doses of radiation workers and as a second part of the study, to collect dosimetric data for the period 2001-2005.     

Individually addressable crystalline conducting polymer nanowires in a microelectrode sensor array

An efficient, site-specific and scalable approach has been developed to produce high-quality and individually addressable conducting polymer nanowire electrode junctions (CPNEJs) in a parallel-oriented array. Polypyrrole and PEDOT conducting polymer nanowires (CPNWs) with uniform diameters (ca. 60-150?nm) were introduced into the desired electrode junctions in a precise manner by performing a three-step constant-current electrochemical process at a low current density and a low concentration of monomers. A low scan rate, cyclic voltammetric method was also employed and gave similar results. These CPNEJ arrays function as a miniaturized sensor for the parallel and real-time detection of gas and organic vapour. The electrochemical approaches utilized allow the conducting polymer chains to self-organize in the CPNWs to form novel polycrystalline structures, observed by high resolution TEM. The weak diffraction rings at 4.88?? and 4.60?? were observed for PEDOT and polypyrrole CPNWs, respectively.     

Cyclic energy harvesting from pyroelectric materials

A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 μW/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 μW/cm(3), which is 40% larger than the density of 4.48 μW/cm3 obtained from standard PZT.     

Structural and pharmacological characterization of phenylalanine-based AMPA receptor antagonists at kainate receptors

Continued efforts into the discovery of ligands that target ionotropic glutamate receptors (iGluRs) are important for studies of the physiological roles of the various iGluR subtypes as well as for the search for drugs that can be used in the treatment of diseases of the central nervous system. A new series of phenylalanine derivatives that target iGluRs was reported to bind AMPA receptors. Herein we report our studies of these compounds at the kainate receptors GluK1-3. Several compounds bind with micromolar affinity at GluK1 and GluK3, but do not bind GluK2. The crystal structure of the most potent compound in the ligand binding domain of GluK1 revealed different modes of binding to GluK1 and GluA2, due primarily to residues Ser741 (GluK1) and Met729 (GluA2). The compound was shown to be slightly more potent at GluK1 than at AMPA receptors and to induce a domain closure similar to that observed in GluK1 structures with partial agonists.     

Compacted artificially cemented soil-acid leachate contaminant interactions: breakthrough curves and transport parameters

The transport of contaminants through compacted artificially cemented soil subjected to acid leachate contaminant percolation was analyzed by means of laboratory column tests. The effect of cement content, degree of acidity and hydraulic gradient were evaluated after permeation of several pore volumes of acid leachate contaminant flow through the soil. The pH, electric conductivity and solute breakthrough curves were considered throughout the study. The results showed that the increase of cement content increases the solute pore volumes needed before breakthrough occurred. An increase of the degree of acidity of the percolate and of the hydraulic gradient cause a reduction in the pore volumes needed before breakthrough occurred. The larger the soil cement content, the longer the time required to reach maximum effluent solute concentration. The hydraulic conductivity slightly increased due to cement addition and reduced with increasing degree of acidity of the percolate. Finally, it is possible to state that cement addition to the soil was responsible for increasing retardation coefficient (R) and distribution coefficient (k_d) values, meaning that the artificially cemented soils have higher capability to retard the propagation of the contamination and amplified affinity with dissolved acid contaminant.     

Structural,functional, thermal and rheological properties of nixtamalised and extruded blue maize (Zea mays L.) flour with different calcium sources

The effects of different concentrations of calcium hydroxide [Ca(OH)₂] and calcium lactate [C₆H₁₀O₆Ca] on the functional and physical properties of extruded (EF) and nixtamalised (NF) blue maize flours were evaluated. Calcium source and concentration showed no significant effects on the EF expansion index. The water absorption index (WAI) of EF decreased as the concentrations of both calcium sources increased, and NF with C₆H₁₀O₆Ca had the lowest WAI. The thermal and pasting properties of NFs were higher than those of EF. NF with C₆H₁₀O₆Ca showed the highest final viscosity (FinV), indicating less damage to the starch granules, and this was correlated with microscopic analysis. In contrast, the FinV of EFs was significantly affected by calcium source and concentration. Extrusion with 0.3% and nixtamalisation at 2.95% of C₆H₁₀O₆Ca yielded high WAI value and the best rheological properties in maize flour, respectively. These results suggest the use of C₆H₁₀O₆Ca in extrusion or nixtamalisation to produce blue maize flours for tortilla or snacks with antioxidants.     

The effect of transglutaminase-induced polymerization in the presence of cysteine on β-lactoglobulin antigenicity

The effect of polymerization by the enzyme transglutaminase (TG) on the antigenicity of β-lactoglobulin (β-Lg) was investigated. Polymerization was carried out using 7% heat treated β-Lg and 5–50 U TG g^?1 substrate or 7% untreated β-Lg in the presence of 0.05–0.4 mol L^?1 cysteine (Cys) and 25 U TG g^?1 substrate. The electrophoretic profile of polymerized samples showed bands corresponding to high molecular mass. For antigenicity evaluation, sera from BALB/c mice sensitized with native β-Lg, β-Lg polymerized by 25 U TG g^?1 (β-Lg HT TG) or polymerized in 0.25 mol L^?1 Cys (β-Lg Cys TG) were used. Animals sensitized with β-Lg Cys TG showed lower levels of IgG1 and IgE than those immunized with native β-Lg or β-Lg HT TG. These results suggested that polymerization in the presence of Cys modified or hid epitopes, reducing the potential antigenicity of β-Lg, whereas heat treatment followed by polymerization did not lead to a reduction in antigenicity.     

Passive-sampler derived air concentrations of persistent organic pollutants on a north-south transect in Chile

Passive air samplers consisting of polyurethane foam (PUF) disks, were deployed in six locations in Chile along a north-south transect to investigate gas-phase concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). The study provides new information on air concentrations of these persistent organic pollutants (POPs) which is lacking in this region. It also provides insight into potential sources and long-range transport (LRT). The samplers were deployed for a 2-month period in five remote sites and one site in the city of Concepción. Mean concentrations (pg m(-3)) for sigmaPCB were 4.7 +/- 2.7 at remote sites and 53 +/- 13 in Concepción. PCB levels at remote sites were related to proximity to urban source regions and/or air back trajectories. With the exception of endosulfan I, mean concentrations (pg m(-3)) of OCPs at background sites were consistently low: 5.4 +/- 1.4 for alpha-HCH, 7.0 +/- 1.1 for gamma-HCH, 2.5 +/- 0.5 for TC, 2.5 +/- 0.6 for CC, 1.9 +/- 1.2 for dieldrin, and less than 3.5 for toxaphene. Endosulfan I showed a decreasing concentration gradient from 99 to 3.5 pg m(-3) from the north to south of Chile. Concentrations of OCPs in the Concepción City were generally 10-20 times higher than at the background sites suggesting continued usage and/or re-emission from past use. For instance, at remote sites, the alpha/gamma ratio (0.76) was typical of background air, while the ratio in Concepción (0.12) was consistent with fresh use of gamma-HCH. Levels of sigmaPBDEs were below the detection limit of 6 pg m(-3) at all sites.     

Toward a global network for persistent organic pollutants in air: results from the GAPS study

The Global Atmospheric Passive Sampling (GAPS) study aims to demonstrate the feasibility of using passive samplers to assess the spatial distribution of persistent organic pollutants on a worldwide basis. The GAPS network includes more than 40 sites on 7 continents, mainly in background locations, with some representation of urban and agricultural areas. Here we present concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in polyurethane foam disk samplers, deployed from December 2004 to March 2005. Legacy OCPs such as alpha-HCH (hexachlorocyclohexane), Chlordanes (trans- and cis-Chlordane and trans-Nonachlor), Dieldrin, and dichlorodiphenyltrichloroethane isomers were detected at most sites with some high values that may be related to possible continued use and/or re-emissions related to historic use. Geometric mean (GM) air concentrations (pg/m3) were: 8.5 for sigmaHCH (sum of alpha- and gamma-isomers), 2.6 for sigmaChlordanes, 0.8 for Dieldrin, and 0.8 for p,p'-DDE. Current-use pesticides such as gamma-HCH (lindane) and especially Endosulfan I exhibited more variable and higher concentrations with GMs of 5 and 58, respectively. PCBs and PBDEs were elevated at urban/suburban sites consistent with their historical use pattern. GM concentrations (pg/m3) were 17 for PCBs and 4 for PBDEs. Sampling under GAPS will continue and will eventually allow seasonality effects and longer-term temporal and spatial trends to be evaluated.