Three-dimensional silicon inverse photonic quasicrystals for infrared wavelengths

Quasicrystals are a class of lattices characterized by a lack of translational symmetry. Nevertheless, the points of the lattice are deterministically arranged, obeying rotational symmetry. Thus, we expect properties that are different from both crystals and glasses. Indeed, naturally occurring electronic quasicrystals (for example, AlPdMn metal alloys) show peculiar electronic, vibrational and physico-chemical properties. Regarding artificial quasicrystals for electromagnetic waves, three-dimensional (3D) structures have recently been realized at GHz frequencies and 2D structures have been reported for the near-infrared region. Here, we report on the first fabrication and characterization of 3D quasicrystals for infrared frequencies. Using direct laser writing combined with a silicon inversion procedure, we achieve high-quality silicon inverse icosahedral structures. Both polymeric and silicon quasicrystals are characterized by means of electron microscopy and visible-light Laue diffraction. The diffraction patterns of structures with a local five-fold real-space symmetry axis reveal a ten-fold symmetry as required by theory for 3D structures.     

Auto-ignition of toluene-doped n-heptane and iso-octane/air mixtures: High-pressure shock-tube experiments and kinetics modeling

Toluene is often used as a fluorescent tracer for fuel concentration measurements, but without considering whether it affects the auto-ignition properties of the base fuel. We investigate the auto-ignition of pure toluene and its influence on the auto-ignition of n-heptane and iso-octane/air mixtures under engine-relevant conditions at typical tracer concentrations. Ignition delay times τ_ign were measured behind reflected shock waves in mixtures with air at φ = 1.0 and 0.5 at p = 40 bar, over a temperature range of T = 700–1200 K and compared to numerical results using two different mechanisms. Based on the models, information is derived about the relative influence of toluene on τ_ign on the base fuels as function of temperature. For typical toluene tracer concentrations ?10%, the ignition delay time τ_ign changes by less than 10% in the relevant pressure and temperature range.     

基于主观评价的非织造布质量客观评价方法——QualiVlies

非织造布在世界范围内广泛生产.全球标准是非织造布生产的一个竞争因素.目前,非织造布在市场中的优势不仅是价格便宜,而且质量优良.因此,为了保持非织造布的市场,有必要提高非织造布质量.在线检测系统可检测破洞、薄区、厚区等疵点,但影响非织造布质量的不仅仅是疵点,还取决于其光学均匀性.尤其对于面密度较小(如15 g/m2)的非织造布,明显的不规则纤维分布会影响顾客的主观评价.阐述了一种代表主观评价的客观图像分析方法.     

Modelocked integrated external-cavity surface emitting laser

A modelocked integrated external-cavity surface emitting laser (MIXSEL) is a novel type of ultrafast semiconductor laser that integrates a saturable absorber directly into a vertical external cavity surfaceemitting laser. The saturable absorber requirements and integration challenges to obtain self-starting and stable pulse formation are discussed. One single quantum dot absorber layer was optimised for this application. Since the first feasibility demonstration of an optically pumped MIXSEL, the authors have further improved the average output power to 185 mW with 32 ps pulses at around 3 GHz pulse repetition rate at a centre wavelength of ∼957 nm. The authors analyse and discuss the challenges for further power scaling and pulse shortening. The MIXSEL concept appears suitable for cost-efficient wafer-scale mass production when the external cavity is defined by a transparent wafer into which the curved output coupler can be etched. The semiconductor MIXSEL structure would then be glued to such a transparent wafer. The potential for electrically pumped MIXSELs will make this laser technology even more attractive.     

Metal Decontamination of Soil, Sediment, and Sewage Sludge by Means of Transition Metal Chelant [S,S]-EDDS

The biodegradable strong transition metal chelant [S,S] stereoisomer of ethylenediamine disuccinate was investigated for its applicability for the washing extraction of heavy metals from soil, sewage sludge, and harbor sediment. Heavy metals Pb, Zn, Cu, and Cd were extracted from authentically polluted samples by means of an ex situ washing procedure at the laboratory scale. The exposure time necessary to achieve maximum metal extraction from the authentically polluted solids used in this study was longer than that reported elsewhere with solids polluted artificially in the laboratory. Required exposure time was 1 day for the extraction of Pb, 3 days for Zn, and 6 days for Cu, irrespective of solid type. Speed and extent of metal extraction were increased by facilitating mass transfer from the solids to the liquid (e.g., by lowering calcium concentration, increasing temperature, adding fatty acid soap, and most of all, by using intermittent but intense agitation). Slightly alkaline pH was necessary to eliminate the interference by iron. This pH effect as well as observed metal selectivity was explained with a speciation model. It was feasible to achieve 70–90% extraction of Zn, Pb, and Cu from all three solids tested. These extraction efficiencies were equal or superior to those obtained with the benchmark chelants, ethylenediamine tetraacetic acid and nitrilotriacetate, provided extraction time was sufficient.     

DNA extraction and Escherichia coli quantification of anaerobically digested biosolids using the competitive touchdown PCR method

Accurate enumeration of indicator organisms such as Escherichia coli is important for assessing the safety of water and wastewater samples. Recent research has shown that E. coli can enter a viable but non-culturable state; therefore, traditional cultivation methods could potentially underestimate the quantities of the organisms. The goals of the research were to develop and verify a DNA extraction protocol and a quantitative polymerase chained reaction (PCR) method for E. coli enumeration in digested biosolids. A solvent-based DNA extraction protocol with extensive cell lysis recovered approximately 78-84% of spiked DNA. In comparison, a commercial kit only recovered 28-42% of DNA, likely from inefficient cell lysis. The developed competitive touchdown PCR (cPCR) method for E. coli enumeration was comparable to both real-time PCR (rt-PCR) and cultivation methods with sensitivity of approximately 50,000-500,000 E. coli per gram dry solids (DS), which is suitable for Class B biosolids monitoring in the US and "conventional" biosolids in the European Union. The cPCR protocol provides a less expensive alternative than the rt-PCR as a culturing independent method for enumerating E. coli.     

A rapid sample preparation method for the determination of sulfamethazine in swine tissues by high-performance liquid chromatography

A rapid procedure for the determination of sulfamethazine in swine muscle and kidney is described. The method comprises sonication-aided extraction with dichloromethane, cleaning-up of the extract on a combination of silica and reversed-phase C18 Sep-Pak cartridges and analysis by high-performance liquid chromatography on a Hypersil ODS column using acetonitrile/ammonium acetate solution (10 mmol X 1(-1), pH 6.8) 1 + 3 v/v as the mobile phase. Detection was performed at 254 nm. Mean recoveries of added sulfamethazine from swine muscle and kidney, at levels of 0.05 to 0.5 micrograms X g-1, were 89.5 and 80.5%, respectively. After intramuscular injection of sulfamethazine into swine, residues in tissues were also determined. The application of ultrasonic energy for the extraction of sulfamethazine residues from animal tissues is also discussed.     

High velocity contact properties

It is noted that electrical contacts have not been experimentally investigated at velocities above a few hundred meters per second. The authors describe a ballistic technique which can be used to measure friction coefficient and contact resistance at velocities up to several kilometers per second (i.e. at railgun armature operating conditions). The theoretical basis of the technique is described, and the experimental hardware is presented