Enhanced hydrogen reversibility of nanoconfined LiBH4–Mg(BH4)2

This study shows the hydrogen desorption kinetics and reversible hydrogen storage properties of 0.55LiBH₄–0.45Mg(BH₄)₂ melt-infiltrated in different nanoporous carbon aerogels with different BET surface areas of 689 or 2660 m²/g and pore volumes of 1.21 or 3.13 mL/g. These investigations clearly show a significantly improved hydrogen storage capacity after four cycles of hydrogen release and uptake for bulk 0.55LiBH₄–0.45Mg(BH₄)₂ and infiltrated in carbon aerogel and the high surface area scaffold, where 22, 36 and 58% of the initial hydrogen content remain after four cycles of hydrogen release and uptake, respectively. Nanoconfinement in high surface area carbon aerogel appears to facilitate hydrogen release illustrated by release of 13.3 wt% H₂ (93%) and only 8.4 wt% H₂ (58%) from bulk hydride in the first cycle using the same physical condition. Notably, nanoconfinement also appear to have a beneficial effect on hydrogen uptake, since 8.3 wt% H₂ (58%) is released from the high surface area scaffold and only 3.1 wt% H₂ (22%) from the bulk sample during the fourth hydrogen release.     

Detection of the voltage distribution in photovoltaic modules by electroluminescence imaging

We introduce an approach to determine the operating voltage of individual solar cells in photovoltaic (PV) modules by electroluminescence (EL) imaging. The highest EL signal of each solar cell is proportional to its operating voltage. Moreover the sum of all operating voltages equals the externally applied module voltage. Thus the operating voltage of individual solar cells is determined from the measured EL signal. The reliability of this relation is verified by measurements on specially prepared PV modules allowing us to measure the individual operating cell voltage. The experimentally measured cell voltages are deduced with an uncertainty of ±1% from an EL image. Moreover, the operating cell voltages determined from the EL image are used to calculate the module series resistance. Comparing experimentally determined values from the operating cell voltage and the total current flowing supplied to the module with calculated module series resistances using tabulated material and typical solar cell parameters, a very good correspondence is found. Copyright © 2010 John Wiley & Sons, Ltd.     

Surface-Enhanced Raman Scattering Detection of pH with Silica-Encapsulated 4-Mercaptobenzoic Acid-Functionalized Silver Nanoparticles

Sensors based upon surface-enhanced Raman spectroscopy (SERS) are attractive because they have narrow, vibrationally specific spectral peaks that can be excited using red and near-infrared light which avoids photobleaching, penetrates tissue, and reduces autofluorescence. Several groups have fabricated pH nanosensors by functionalizing silver or gold nanoparticle surfaces with an acidic molecule and measuring the ratio of protonated to deprotonated Raman bands. However, a limitation of these sensors is that macromolecules in biological systems can adsorb onto the nanoparticle surface and interfere with measurements. To overcome this interference, we encapsulated pH SERS sensors in a 30 nm thick silica layer with small pores which prevented bovine serum albumin (BSA) molecules from interacting with the pH-indicating 4-mercaptobenzoic acid (4-MBA) on the silver surfaces but preserved the pH-sensitivity. Encapsulation also improved colloidal stability and sensor reliability. The noise level corresponded to less than 0.1 pH units from pH 3 to 6. The silica-encapsulated functionalized silver nanoparticles (Ag-MBA@SiO(2)) were taken up by J774A.1 macrophage cells and measured a decrease in local pH during endocytosis. This strategy could be extended for detecting other small molecules in situ.     

Conversion of the maltogenic {alpha}-amylase Novamyl into a CGTase

Novamyl is a thermostable five-domain maltogenic     

Self‐Limiting Galvanic Growth of MnO2 Monolayers on a Liquid Metal—Applied to Photocatalysis

Liquid metals offer unprecedented chemistry. Here it is shown that they can facilitate self‐limiting oxidation processes on their surfaces, which enables the growth of metal oxides that are atomically thin. This claim is exemplified by creating atomically thin hydrated MnO₂ using a Galvanic replacement reaction between permanganate ions and a liquid gallium–indium alloy (EGaIn). The “liquid solution”–“liquid metal” process leads to the reduction of the permanganate ions, resulting in the formation of the oxide monolayer at the interface. It is presented that under mechanical agitation liquid metal droplets are established, and simultaneously, hydrated gallium oxides and manganese oxide sheets delaminate themselves from the interfacial boundaries. The produced nanosheets encapsulate a metallic core, which is found to consist of solid indium only, with the full migration of gallium out of the droplets. This process produces core/shell structures, where the shells are made of stacked atomically thin nanosheets. The obtained core/shell structures are found to be an efficient photocatalyst for the degradation of an organic dye under simulated solar irradiation. This study presents a new research direction toward the modification and functionalization of liquid metals through spontaneous interfacial redox reactions, which has implications for many applications beyond photocatalysis.     

Towards Understanding Directed Evolution: More than Half of All Amino Acid Positions Contribute to Ionic Liquid Resistance of Bacillus subtilis Lipase A

Ionic liquids (ILs) are attractive (co‐)solvents for biocatalysis. However, in high concentration (>10 % IL), enzymes usually show decreased activity. No general principles have been discovered to improve IL resistance of enzymes by protein engineering. We present a systematic study to elucidate general engineering principles by site saturation mutagenesis on the complete gene bsla. Screening in presence of four [BMIM]‐based ILs revealed two unexpected lessons on directed evolution: 1) resistance improvement was obtainable at 50–69 % of all amino acid positions, thus explaining the success of small sized random mutant libraries; 2) 6–13 % of substitutions led to improved resistance. Among these, 66–95 % were substitutions by chemically different amino acids (e.g., aromatic to polar/aliphatic/charged amino acids), thus indicating that mutagenesis methods introducing such changes should, at least for lipases like BSLA, be favored to improve IL resistance.     

Do investments in flexibility enhance sustainability? A simulative study considering the German electricity sector

Current research concerning industrial demand side management primarily focuses on monetary aspects. Herein, we extend this perspective by assessing whether economically driven measures increasing the flexibility also result in reduced contributions to the residual load. For this purpose, we conduct a simulative study using historic and projected time series for the German electricity sector. First, Fourier analysis are performed to show that the main oscillation in the electricity price time series has a period length of 12 hr, whereas the renewable generation is primarily characterized by an oscillation with a period length of 24 hr. Second, a generic process model with capabilities for load shiftings is used to evaluate how the fluctuation patterns can be exploited via scheduling optimizations. Most importantly, our results demonstrate that prevalent price fluctuations prevent adequate monetary incentives for providing storage capacities for bridging up to 24 hr, which are desired for reducing the residual load.     

Can the centre–periphery model explain patterns of international scientific collaboration among threshold and industrialised countries? The case of South Africa and Germany

As scientific collaboration is a phenomenon that is becoming increasingly important, studies on scientific collaboration are numerous. Despite the proliferation of studies on various dimensions of collaboration, there is still a dearth of analyses on the effects, motives and modes of collaboration in the context of developing countries. Adopting Wallerstein’s world-system theory, this paper makes use of bibliometric data in an attempt to understand the pattern of collaboration that emerges between South Africa and Germany. The key argument is that we can expect the collaborative relationship between South Africa and Germany to be one that is shaped by a centre–periphery pattern. The analyses show that a theory of scientific collaboration building on the notion of marginality and centre–periphery can explain many facets of South African–German collaboration, where South Africa is a semi-peripheral region, a centre for the periphery, and a periphery for the centre.     

Antagonist properties of a phosphono isoxazole amino acid at glutamate R1-4 (R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid receptor subtypes

All three subtypes of beta-adrenoceptors are coupled to stimulation of adenylyl cyclase activity via the stimulatory guanine-nucleotide-binding protein. Nevertheless, the beta3 adrenoceptor (beta3-AR) differs significantly from the other subtypes in terms of pharmacology. Most strikingly, it recognizes as agonists several compounds acting as potent beta1-AR and beta2-AR antagonists. Furthermore, the human beta3-AR is quite different from the animal beta3-AR. Molecular modelling studies followed by site-directed mutagenesis was used here to identify some of the amino acid residues which may be implicated in ligand binding and signal transduction of the beta3-AR. Three contiguous residues, valine-leucine-alanine, which are present in the first transmembrane domain at positions 48-50 of the human receptor but are absent in all known rodent sequences, were thought to be important for species specificity. When these three residues were deleted from the human receptor, no 'rodent-like' pharmacological profile was obtained in terms of either binding or adenylyl cyclase activation. Glycine at position 53, also in the first transmembrane domain in the human beta3-AR, has been suggested to participate in beta2-/beta3-AR subtype selectivity. Replacement of this glycine residue by phenylalanine, which is the residue present at the homologous position in the human beta2-AR, left the beta3-AR pharmacological profile unaltered in terms of specificity and selectivity. Aspartate residue 117, in the third transmembrane domain, has been found to be essential for ligand binding and consequently adenylyl cyclase activation in several bioamine receptors. When this residue was replaced by a leucine residue in the beta3-AR, ligand binding and signal transduction were suppressed. Finally, replacement of asparagine at position 312 in the sixth transmembrane domain by an alanine residue, led to alterations in the signal-transduction pathway.     

In vivo inhibition of aromatization by exemestane, a novel irreversible aromatase inhibitor, in postmenopausal breast cancer patients

The effect of exemestane (6-methylenandrosta-1,4-diene-3,17-dione) 25 mg p.o. once daily on in vivo aromatization was studied in 10 postmenopausal women with advanced breast cancer. Aromatization was determined before treatment and after 6-8 weeks on therapy by administering a bolus injection of [3H]androstenedione (500 microCi) and [14C]estrone (5 microCi) followed by measurement of the isotope ratio of urinary estrogens after high-performance liquid chromatography purification. In addition, plasma endogenous estrogens were measured with highly sensitive radioimmunoassays after separation with high-performance liquid chromatography. Treatment with exemestane suppressed whole body aromatization from a mean pretreatment value of 2.059% to 0.042% (mean suppression of 97.9%). Plasma levels of estrone, estradiol, and estrone sulfate were found to be suppressed by 94.5%, 92.2%, and 93.2%, respectively. This is the first study revealing near total aromatase inhibition in vivo with the use of a steroidal aromatase inhibitor. The observation that exemestane is a highly potent aromatase inhibitor, together with the fact that the drug is administered p.o. and causes limited side effects, suggests that exemestane is a promising new drug for the treatment of hormone sensitive breast cancer.