Lichtinitiierte Polymer- und Polymerisationsreaktionen. 14. Radikalische Photopolymerisation mit Kaliumtrisoxalatocobaltat-Aryloniumsalz-Systemen

Light Induced Polymer and Polymerization Reactions. 14. Radical Photopolymerization by Potassium Trisoxalato Cobaltate Arylonium Salts Systems. The photopolymerization of acrylamide (AA) by trisoxalato cobaltate ([Co(ox)₃]³⊖) is inefficient because the produced nucleophilic ·CO₂⊖-radicals are oxidized or they terminate with polymer radicals. If onium compounds are added to this system the initiation efficiency is increased as follows : p-CH₃OC₆H₄N₂⊕>Ph₂I⊕>PhCOCH₂S(CH₃)₂⊕>Ph₃S⊕. By means of quantum yield measurements a mechanism was proposed including the electron transfer from ·CO₂⊖ to onium compounds. The produced radicals also initiate the polymerization of AA. The exponent m of the polymerization rate (v_p ≈︁ [AA]^m) is decreased from 1.4 to 1.1 in the presence of Ph₂I⊕, deciding the decrease of termination reaction between ·CO₂⊖ and polymer radicals. In comparison with K₃[Fx(ox)₃] the corresponding cobalt complex possesses higher polymerization quantum yields for AA.     

Atopic Dermatitis: The Fate of the Fat

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease in which dry and itchy skin may develop into skin lesions. AD has a strong genetic component, as children from parents with AD have a two-fold increased chance of developing the disease. Genetic risk loci and epigenetic modifications reported in AD mainly locate to genes involved in the immune response and epidermal barrier function. However, AD pathogenesis cannot be fully explained by (epi)genetic factors since environmental triggers such as stress, pollution, microbiota, climate, and allergens also play a crucial role. Alterations of the epidermal barrier in AD, observed at all stages of the disease and which precede the development of overt skin inflammation, manifest as: dry skin; epidermal ultrastructural abnormalities, notably anomalies of the lamellar body cargo system; and abnormal epidermal lipid composition, including shorter fatty acid moieties in several lipid classes, such as ceramides and free fatty acids. Thus, a compelling question is whether AD is primarily a lipid disorder evolving into a chronic inflammatory disease due to genetic susceptibility loci in immunogenic genes. In this review, we focus on lipid abnormalities observed in the epidermis and blood of AD patients and evaluate their primary role in eliciting an inflammatory response.     

在铅焊料的标准流程中用无铅元件

随着欧洲的RoHS和WEEE指令已于2006年7月1日开始执行,许多元件供应商面临着使其产品符合无铅环境的挑战。两个指令都要解决将铅从元件中去除的问题。半导体公司必须选择高性价比、与含铅焊料逆向兼容,并与无铅焊料前向兼容的无铅镀层策略。逆向兼容表示无铅元件能够用锡铅（SnPb）焊料回流工艺安放在PCB上。前向兼容表示目前的锡铅工艺能够在面板组装中,与无铅焊料一起使用。     

Characterization of an Invertebrate-Type Dopamine Receptor of the American Cockroach,Periplaneta americana

We have isolated a cDNA coding for a putative invertebrate-type dopamine receptor (Peadop2) from P. americana brain by using a PCR-based strategy. The mRNA is present in samples from brain and salivary glands. We analyzed the distribution of the PeaDOP2 receptor protein with specific affinity-purified polyclonal antibodies. On Western blots, PeaDOP2 was detected in protein samples from brain, subesophageal ganglion, thoracic ganglia, and salivary glands. In immunocytochemical experiments, we detected PeaDOP2 in neurons with their somata being located at the anterior edge of the medulla bilaterally innervating the optic lobes and projecting to the ventro-lateral protocerebrum. In order to determine the functional and pharmacological properties of the cloned receptor, we generated a cell line constitutively expressing PeaDOP2. Activation of PeaDOP2-expressing cells with dopamine induced an increase in intracellular cAMP. In contrast, a C-terminally truncated splice variant of this receptor did not exhibit any functional property by itself. The molecular and pharmacological characterization of the first dopamine receptor from P. americana provides the basis for forthcoming studies focusing on the significance of the dopaminergic system in cockroach behavior and physiology.     

Dynamic Control Over Electronic Transport in 3D Bulk Nanographene via Interfacial Charging

Electrochemical surface charge‐induced variation of physical properties in interface‐dominated bulk materials is a rapidly emerging field in material science. The recently developed three‐dimensional bulk nanographene (3D‐BNG) macro‐assemblies with ultra‐high surface area and chemical inertness offer new opportunities in this area. Here, the electronic transport in centimeter‐sized 3D‐BNG monoliths can be dynamically controlled via electrochemically induced surface charge density. Specifically, a fully reversible variation in macroscopic conductance up to several hundred percent is observed with ≤1 V applied gate potential. The observed conductivity change can be explained in the light of the electrochemically‐induced accumulation or depletion of charge carriers in combination with a large variation in the carrier mobility; the latter, being highly affected by the defect density modulations resulting from the interfacial charge injection, sharply decreases with an increase in defect concentrations. The phenomenon presented in this study is believed to open the door to novel applications of bulk graphene materials such as, for example, low voltage and high power tunable resistors.     

First steps in developing a multimetric macroinvertebrate index for the Ohio River

The causes of degradation of aquatic systems are often complex and stem from a variety of human influences. Comprehensive, multimetric biological indices have been developed to quantify this degradation and its effect on aquatic communities, and measure subsequent recovery from anthropogenic stressors. Traditionally, such indices have concentrated on small‐to medium‐sized streams. Recently, however, the Ohio River Fish Index (ORFIn) was created to assess biotic integrity in the Ohio River. The goal of the present project was to begin developing a companion Ohio River multimetric index using benthic macroinvertebrates. Hester–Dendy multiplate samplers were used to evaluate benthic macroinvertebrate assemblages in relation to a gradient of water quality disturbance, represented by varying distances downstream of industrial and municipal wastewater outfalls in the Ohio River. In August 1999 and 2000, samplers were set every 100 m downstream of outfalls (12 outfalls in 1999, 22 in 2000) for 300–1000 m, as well as at upstream reference sites. Candidate metrics (n = 55) were examined to determine which have potential to detect changes in water quality downstream of outfalls. These individual measures of community structure were plotted against distance downstream of each outfall to determine their response to water quality disturbance. Values at reference and outfall sites were also compared. Metrics that are ecologically relevant and showed a response to outfall disturbance were identified as potentially valuable in a multimetric index. Multiple box plots of index scores indicated greater response to outfall disturbance during periods of low‐flow, and longitudinal river‐wide trends. Evaluation of other types of anthropogenic disturbance, as well as continued analysis of the effects of chemical water quality on macroinvertebrate communities in future years will facilitate further development of a multimetric benthic macroinvertebrate index to evaluate biotic integrity in the Ohio River. Copyright © 2007 John Wiley & Sons, Ltd.     

Thin film lithium niobate for use in silicon based devices

The incorporation of a thin film of lithium niobate (LiNbO3) in a conventional MOS (metal-oxide-semiconductor) structure gives the possibility of two fundamentally different types of computer memory architectures. One, based on ferroelectric switching involves the reorganization of charge in the transistor channel to compensate for the change in polarization. Another, based on the bulk photovoltaic effect, involves a shift in the transistor threshold with exposure to differing intensities of incident light. With the use of a molybdenum liftoff process, transistors have been fabricated in which LiNbO3 replaces the usual gate oxide of an MOS transistor. Transistor parameters such as the transconductance, output conductance, and amplification for these devices are reported.     

SiC ceramic micropatterns from polycarbosilanes

Micropatterned SiC ceramics were fabricated from polycarbosilanes applying a softlithographic replication technique. A polydimethylsiloxane mould replicated from a photolithographic microstructured silicon wafer was used as master structure. The polydimethylsiloxane mould was coated with a solution containing a mixture of two different polycarbosilanes in n-octane. After treatment at 200–400 °C the cross-linked polycarbosilane films were debonded and pyrolysed at 900 °C in nitrogen and subsequently crystallised at temperatures up to 1500 °C in argon. The cross-linking and thermal degradation behaviour of the polycarbosilanes was investigated by Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. X-ray diffractrometry showed the expected development of a nanocrystalline β-SiC (3 nm) as the main phase with increasing temperature. However, traces of α-SiO₂ derived from the polycarbosilane precursors were also detected by X-ray analysis. Removal of the α-SiO₂ dioxide with hydrofluoric acid in the pyrolysed samples and subsequent increased the crystallite size to 7 nm. The Young's modulus determined by nanoindentation was increased from 3 GPa after cross-linking to 110 GPa after crystallisation. Scanning electron microscopy revealed, that the initial micropatterns were fully retained in the pyrolysed and crystallised SiC ceramics. The micropatterned cross-linked and crystallised β-SiC based substrates exhibited light scattering characteristics, which qualify them as promising candidates for diffractive optical elements in microoptical applications.