The elusive role of the N-terminal extension of {beta}A3- and {beta}Al-crystallin

ß-Crystallins are structural lens proteins with aconserved two-domain structure and variable N- and C-terminalextensions. These extensions are assumed to be involved in quaternaryinteractions within the ß-crystallin oligomers orwith other lens proteins. Therefore, the production of ßA3-and ßAl-crystallin from the single ßA3/A1mRNA by dual translation initiation is of interest. These crystallinsare identical, except that ßAl has a much shorterN-terminal extension than ßA3. This rare mechanismhas been conserved for over 250 million years during the evolutionof the ßA3/A1 gene, suggesting that the generationof different N-terminal extensions confers a selective advantage.We therefore compared the stability and association behaviourof recombinant ßA3- and ßAl-crystallin.Both proteins are equally stable in urea- and pH-induced denaturationexperiments. Gel filtration and analytical ultracentrifugationestablished that ßA3 and ßA1 both form homodimers.In the water-soluble proteins of bovine lens, ßA3and ßA1 are present in the same molecular weight fractions,indicating that they oligomerize equally with other ß-crystallins.¹H-NMR spectroscopy showed that residues Met1 to Asn22 of theN-terminal extension of ßA3 have great flexibilityand are solvent exposed, excluding them from protein interactionsin the homodimer. These results indicate that the differentN-terminal extensions of ßA3 and ßA1 donot affect their homo- or heteromeric interactions.     

Electrochemical lithiation synthesis of nanoporous materials with superior catalytic and capacitive activity

Nanoporous materials have attracted great technological interest during the past two decades, essentially due to their wide range of applications: they are used as catalysts, molecular sieves, separators and gas sensors as well as for electronic and electrochemical devices. Most syntheses of nanoporous materials reported so far have focused on template-assisted bottom-up processes, including soft templating (chelating agents, surfactants, block copolymers and so on) and hard templating (porous alumina, carbon nanotubes and nanoporous materials) methods. Here, we exploit a mechanism implicitly occurring in lithium batteries at deep discharge to develop it into a room-temperature template-free method of wide applicability in the synthesis of not only transition metals but also metal oxides with large surface area and pronounced nanoporosity associated with unprecedented properties. The power of this top-down method is demonstrated by the synthesis of nanoporous Pt and RuO2, both exhibiting superior performance: the Pt prepared shows outstanding properties when used as an electrocatalyst for methanol oxidation, and the RuO2, when used as a supercapacitor electrode material, exhibits a distinctly better performance than that previously reported for non-hydrated RuO2 (refs 19,20).     

Modelling brittle crack formation at geometrical and material discontinuities using a finite fracture mechanics approach

In this study, finite fracture mechanics procedures are employed to predict crack formation at geometrical and material discontinuities in brittle elastic structures. A hybrid failure model is utilised taking into account the stress field in the undamaged structure and the energy balance for the formation of cracks. Asymptotic formulations are compared to a direct numerical implementation. Experiments carried out on notched brittle specimens exhibiting various geometries and loading-modes are analysed by means of both approaches. Additionally, free-edge effects in composite laminates are analysed. It is found that the predictions from the model agree well with experimental results.     

Logarithmic Mean Pressure Difference—A New Concept in the Analysis of the Flow Distribution in Parallel Channels of Plate Heat Exchangers

This paper deals with a new concept of logarithmic mean pressure difference (LMPD) to find an accurate mean or true friction coefficient for variable flow in parallel flow channels of the plate heat exchangers while considering the first and the last channel pressure drops. This is analogous to the log mean temperature difference (LMTD) used for the computation of heat transfer in heat exchangers. A method has been suggested to improve the computation of mean or a newly defined “true friction factor” and the mean velocity for considerable flow variations in the channels. A comparative study has been made between the conventional average friction factor and the true mean friction factor for large parallel channels. The results have also been compared between the mean channel pressure drop and LMPD for different sizes of the channels. The analysis shows that the mean channel pressure drop of parallel channels can be predicted accurately by using the so-called true mean friction factor rather than the average friction factor. Using the LMPD method, one can find the last channel pressure drop by knowing the first channel pressure drop of the plate package. Hence, the nature of flow distribution in parallel channels can be predicted easily.     

Über Beiträge geophysikalischer Forschungen zum Umbruch der klassischen zur modernen Physik vor 100 Jahren

In 1897 physicists took the first e/m measurements at electrons, the consequence was a revival of the atomistic ideas in physics. The researches in geophysics also contributed to the construction of the modern physics. Four examples are dealt with this essay. 1) In 1899 J. J. Thomson was able to carry out the first direct determination of elementary electric charge with the help of the conformity with the natural laws at the formation of fog, found by C. T. R. Wilson. 2) The cloud-chamber, called after C. T. R. Wilson, was the result of various constructions of for- or cloud-chambers, in it there were shown for the first time the tracks of α- and β-particles. 3) At the exploration of the photoelectric effect of the sunlight (especially of the ultraviolet share) Elster and Geitel made essential preliminary studies for the lightquanta-hypothesis of Einstein. 4) Elster and Geitel detected radioactive substances in the atmosphere and in the soil to be the main source of the atmospheric electricity.      

Diffusion of ammonia in silicalite studied by QENS and PFG NMR

Ammonia diffusivities in silicalite have been studied by quasi-elastic neutron scattering (QENS) and pulsed-field gradient (PFG) NMR for temperatures between 200 and 500 K and loadings from 1.5 up to 4.3 molecules per unit cell. The diffusion coefficients obtained by both techniques increase with increasing ammonia concentration. The QENS diffusivities refer to only a certain fraction of molecules, because during the time scale of the measurement the other part of molecules is essentially immobile, in interaction with silanol groups. During the much larger time scale of the PFG NMR experiment, ammonia molecules assume both states of mobility, leading to an average diffusivity which is smaller than the diffusivity of the mobile molecules recorded by QENS. The difference between the diffusivities derived from both techniques decreases when the proportion of immobile molecules is taken into account. The residence time of ammonia in interaction with silanol groups is about two orders of magnitude longer than with oxygen atoms.