TEM of Dislocations in AIN

Sintered AIN specimens were deformed by Vickers hardness (HV) indentations. Compared with Al₂O₃ the HV hardness values indicate a much higher plasticity of AIN at room temperature, but above 600°C a higher ductility for Al₂O₃. Deformed AIN specimens were examined by transmission electron microscopy. Basal and prismatic glide with the slip systems (0001) 〈1120〉 and {1 1 00}〈11 2 0〉 were frequently observed. This results in four linearly independent slip systems. The critical resolved shear stress for single prismatic slip seems to be even smaller than for basal slip. However, thermally activated dislocation reactions are frozen up to at least 1000°C. Thus, prismatic slip is suppressed as soon as more than one slip direction is activated.     

Structure-function studies of an IGF-I analogue that can be chemically cleaved to a two-chain mini-IGF-I

The structure and biological activities of two disulphide isomersof a C-region deletion mutant of insulin-like growth factor-I(IGF-I) which has an Asn–Gly link engineered at the junctionof the A- and B-regions were studied before and after chemicalcleavage. Circular dichroism (CD) spectra and binding affinityto IGF binding protein 3 (IGFBP3) indicated that the treatmentwith hydroxylamine did not disrupt the overall tertiary foldof the hormones. Cleavage restored some binding affinity forthe IGF-I receptor in both isomers and weakly restored the abilityto stimulate incorporation of tritiated thymidine into DNA inNIH 3T3 fibroblasts transfected with the human IGF-I receptor.Cleavage also restored metabolic capacity, as measured by theability of the isomers to promote lipogenesis in isolated ratadipocytes through the insulin receptor. These results are consistentwith the theory that binding of IGF-I to the IGF-I receptorrequires a conformational change similar to that involved ininsulin binding the insulin receptor. The weak affinity forthe IGF-I receptor after cleavage is consistent with the beliefthat residues in the C-region interact with the IGF-I receptor.This structural difference between insulin and IGF-I gives eacha higher binding affinity for its own receptor.     

Gradient high-performance liquid chromatography of statistical and block copolymers of styrene and t-butyl methacrylate

Copolymers of styrene (S) and tert-butyl methacrylate (TBMA) containing 24–92 mass % of the latter monomer were investigated using a silica column with isooctane/tetrahydrofuran (THF) gradients and on a phenyl bonded-phase column by methanol (MeOH)/THF gradients using UV detection. In both cases, retention decreased with increasing TBMA content of the sample. This is in contrast to the behavior of copolymers of S and methyl methacrylate (MMA) whose retention in gradient elution on silica columns increases with MMA content due to the polarity of this unit. The inversion of elution order is a result of the bulky TBMA residues shielding the polar groups of the ester units. For copolymers of varying composition, the gradation in retention on retention on silica is quite sufficient for separating S/MMA but not for S/TBMA mixtures. The latter could be separated by composition on phenyl packings through MeOH/THF gradient elution. Block copolymers containing 80 or 92% TBMA could be baseline-separated. It was also possible to separate these samples from admixed PTBMA or PS homopolymers. Under the conditions used, the retention of a given block copolymer was somewhat higher than that of a statistical copolymer having the same composition. A block copolymer containing 80% TBMA was converted by transesterification into a S/MMA block copolymer. The elution of the latter fitted well in the sequence of S/MMA copolymers on silica column.     

Ultraviolet lithography on sloped surfaces utilizing diamond turned holograms

A lithography method by means of a diamond turned hologram (DTH) is presented, that allows patterning of sloped surfaces. The DTH is manufactured by a modified diamond turning process, using a piezoelectric actuator, the nano fast tool servo, which modulates the depth of cut within submicrometer range at a frequency up to 10 kHz. In order to machine a DTH to be applied as phase masks for ultraviolet lithography, workpiece materials have to feature a sufficient reflectivity and excellent machinability. Ultra-fine grained aluminium was identified as most suitable workpiece material, since its reflectivity measures around 80 % and a homogenous structure can be machined. The employed DTH is used in a lithography setup in conjunction with a helium cadmium laser emitting at a wavelength of λ = 325 nm. Patterns up to a linewidth of 30 μm were successfully and consistently transferred on a photoresist coated planar substrate with a tilt angle of 30° with respect to the optical axis.     

Fatigue strength of welded joints in austenitic Cr-Ni steels

Abstract

High quality corrosion resistant Cr-Ni steels are used in many branches of industry. Constructors are faced with the problem of correctly dimensioning statically and dynamically loaded parts, but have little data available for dynamically loaded welded constructions of high alloy austenitic steels. To close this gap fatigue strength tests were carried out on three different steels and five different welded joints.     

Use of an immunoassay as a means to detect polychlorinated biphenyls in animal fat

In this paper we describe the validation and utilization of the Hybrizyme TM DELFIA immunoassay for detecting polychlorinated biphenyls (PCBs) in animal fat. The immunoassay incorporates a rapid sample processing protocol that has been optimized to detect concentrations of PCBs in animal fat at or above 200ng/g. The limit of detection of the assay was less than 50ng/g. When the action level for the DELFIA assay was set at 100ng/g to detect samples having 200ng/g or more PCBs, the false negative rate was estimated at 0.2% . The false positive rate depends on the concentration of PCBs in the sample population and was estimated at 4% and 7% for samples having 10ng/ g and 20ng/g PCBs, respectively. By utilizing the DELFIA assay system to select for positive samples and GC/MS analysis for confirmation analysis, an accurate and cost-effective programme has been established for the high throughput detection of PCBs in animal products.     

Introduction to the Asian Energy Security project: Project organization and methodologies

The spectacular recent economic growth in the Asia-Pacific region in general, and in many of the economies of Northeast Asia in particular, has spurred a vast expansion in the need for energy services, and an expansion in the demand for the fuels that help to supply these services. Future projections suggest that the growth of fossil fuel use in Northeast Asia, especially in China, will have major consequences for financial and fuel markets and pollution both regionally and globally. Before the project described in this paper was initiated, there was no ongoing forum for energy experts from all of the countries of the region to meet, informally and in an unofficial capacity, to discuss openly and in a targeted fashion the energy situations in their countries, and to work together to evaluate the energy efficiency costs and benefits of different ways of meeting regional demand. The Asian Energy Security (AES) project provides such a forum, and as such constitutes a unique resource in the engagement of the countries of Northeast Asia on the topic of energy security.     

CDM potential of solar water heating systems in India

The Clean Development Mechanism (CDM) provides industrialized countries with an incentive to invest in emission reduction projects in developing countries to achieve a reduction in CO₂ emissions at lowest cost that also promotes sustainable development in the host country. Solar water heating systems (SWHs) could be of interest under the CDM because they directly displace greenhouse gas emissions while contributing to sustainable development by reducing local pollutants. However, there are only three solar water heating projects under the CDM so far. An attempt has been made to estimate the CDM potential of SWHs in India in this study. Our estimates indicate that there is a vast theoretical potential of CO₂ mitigation by the use of SWHs in India. The annual CER potential of SWHs in India could theoretically reach 27 million tonnes. Under more realistic assumptions about diffusion of SWHs based on past experiences with the government-run programmes, annual CER volumes by 2012 could reach 4–9 million and 15–22 million by 2020. This would require that the government sets the subsidy level for SWHs at a level that allows them to become viable with the CER revenue. From a macro-economic point of view this makes sense if the sustainability benefits are deemed sufficiently high to warrant promotion of this project type.     

Performance analysis of the power conversion unit of a solar chimney power plant

The power conversion unit (PCU) of a large solar chimney power plant consists of one or several turbogenerators, power electronics, a grid interface and the flow passage from collector exit to chimney inlet. The main goals of this paper are to analyze the performance of the PCU and its interaction with the plant as well as to compare three configurations from an efficiency and energy yield point of view.First, a reference plant is defined and the plant performance data taken from simulations with a model found in the literature are analyzed, and the matching of the turbine(s) to the characteristic of the plant is discussed. It was found that a well designed turbine can be run at high efficiency over the entire operating range, as the plant performance data can be fitted using the ellipse law of Stodola.Loss models for all components of the power conversion unit are then defined, and the impact of the various losses on the overall performance is assessed. Three configurations of the PCU are compared, i.e. the single vertical axis, the multiple vertical axis and the multiple horizontal axis turbine configuration. It is found that the single vertical axis turbine has a slight advantage with regards to efficiency and energy yield because certain loss mechanisms are not present. But its output torque is tremendous, making its feasibility questionable. It is shown that with designing the flow passage in an appropriate manner the aerodynamic losses can be kept low. The assumption made by many other researchers that the total-to-total efficiency of the PCU is 80 % has been confirmed with the present model. Further, it has been shown that the PCU efficiency deteriorates significantly with increasing diffuser area ratio but improves only slightly with reducing the diffuser area ratio below unity.     

The statistics of the thermal motion of the atoms during imaging process in transmission electron microscopy and related techniques

The concern of this work is the influence of the thermal motion of the atoms on electron scattering simulations, used for quantitative interpretation of results in high-resolution electron microscopy. We distinguish between the influence of inelastic phonon excitation and the effect of a moving lattice on images generated by elastically scattered electrons. It is shown that, analog to aberrations, the impact of a moving lattice differs substantially with respect to different imaging conditions and cannot be described by the Debye–Waller damping applicable in XRD. We derive a new formalism, based on the frozen lattice and multislice approach, to incorporate the statistics of the thermal motion into elastic TEM imaging simulations, taking into account different imaging conditions. The averaging over different atom positions is generally performed within a density matrix framework, which can be linearized in the special case of off-axis electron holography. All findings are supported by explicit numerical simulations: molecular dynamics simulations are performed to get a realistic thermal motion and the electron scattering simulations are performed within the new multislice algorithm.