Automated,Ultra‐Fast Laser‐Drilling of Nanometer Scale Pores and Nanopore Arrays in Aqueous Solutions

The ability to quickly and reliably fabricate nanoscale pore arrays in ultra‐thin membranes such as silicon nitride (Si_xN) is extremely important for the growing field of nanopore biosensing. Laser‐based etching of thin Si_xN membranes immersed in aqueous solutions has recently been demonstrated as a method to produce stable functional pores. Herein, the principal mechanism governing material etching and pore formation using light is investigated. It is found that the process is extremely sensitive to the relative content of Si over N atoms in the amorphous membrane, produced by chemical vapor deposition. Commonly, Si_xN membranes are made to be Si‐rich to increase their mechanical stability, which substantially reduces the material's bandgap and increases the density of Si‐dangling bonds. Hence, even minimal batch‐to‐batch variation may lead to remarkably different etch rates. It is shown that higher Si content results in orders of magnitude faster etching rates. This rate is further accelerated in an alkaline environment allowing on‐demand controlled nanopore formation in about 10 s time even at low laser radiation intensities. These results highlight that photoactivation of the Si_xN by the incident beam is critical to the chemical etching process and can be used to readily produce nanopore arrays at any specific location.     

The Vibration Behavior of Sub‐Micrometer Gas Vesicles in Response to Acoustic Excitation Determined via Laser Doppler Vibrometry

The ability to monitor sub‐micrometer gas vesicles' (GVs) vibration behavior to nonlinear buckling and collapse using laser Doppler vibrometry is reported, providing a precise noncontact technique for monitoring the motion of sub‐micrometer objects. The fundamental and first harmonic resonance frequencies of the vesicles are found to be 1.024 and 1.710 GHz, respectively. An interparticle resonance is furthermore identified at ≈300 MHz, inversely dependent upon the agglomerated GV size of around 615 nm. Most importantly, the vesicles amplify and broaden input acoustic signals at far lower frequencies—for example, 7 MHz—associated with medical and industrial applications, and they are found to transition from a linear to nonlinear response at 150 kPa and to collapse at 350 kPa or greater.     

Semi-supervised fuzzy neighborhood preserving analysis for feature extraction in hyperspectral remote sensing images

Neural Computing and Applications - Semi-supervised feature extraction methods are an important focus of interest in data mining and machine learning areas. These methods are improved methods based...     

美国电池市场小考

通过对1994年1—5月间美国从世界各地进口各种一次电池、二次电池总贸易额的分析,结合近年来对美国日本电池工业发展动向的观察,本文试图阐明中国电池出口美国应努力的目标。     

Effects of ceramic-based CrN,TiN, and AlCrN interlayers on wear and friction behaviors of AlTiSiN+TiSiN PVD coatings

In this study, the wear and friction behavior of cathodic arc physical vapor deposited AlTiSiN+TiSiN coatings on H13 tool steels were investigated by using CrN, TiN and AlCrN interlayers with tribometer tests both under unlubricated and boundary lubricated conditions. 6 mm alumina balls were used as counter surfaces to test ceramic hard coatings. Surface coatings were characterized through nanoindentation, scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer (SEM/EDXS), optical profilometry, and atomic force microscopy (AFM) techniques. The results showed that especially AlTiSiN+TiSiN coating with TiN interlayer resulted in a much more enhanced tribological performance of the tool steels at both unlubricated and the boundary lubricated conditions even at elevated contact pressures.     

Methodological approach to identify chemical oviposition stimulants from maize for European corn borer

The noncontingent distribution ofO. nubilalis Hbn. eggs on various corn varieties has allowed their classification as either favorable or nonfavorable hybrids. This classification is based on a chemical communication system using volatile compounds active at a distance from the insect or active when in contact with the insect as soluble sugar components. Under this hypothesis, gas chromatography is the best way of investigating for the chemical differences between corn silk extracts from the two types of hybrids. A first experiment, using a desorption-trapping system on Tenax coupled to a gas chromatograph showed a quantitative difference between two compounds from the two hybrids. A second experiment showed the advantages and disadvantages of this method and allowed the development of two complementary techniques: (1) direct extraction of corn silk with trichlorofluo-romethane and direct injection into a capillary column with an apolar stationary phase using an on-column system; and (2) extraction under vacuum of volatile compounds from corn silk and their trapping on Tenax, followed by a second desorption. This allows a direct injection on the same capillary column. The first technique allows identification by mass spectrometry of many alkanes with high molecular weights. The second technique seems to confirm the presence of phenylacetaldehyde. Both techniques show quantitative differences in the composition of corn silk extracts from favorable and nonfavorable hybrids; however, the biologically active chemicals remain unknown.     

Effects of wax coatings and postharvest storage on sensory quality and aroma volatile composition of ‘Mor’ mandarins

BACKGROUND: Mandarins suffer from accumulation of off‐flavours after harvest. In this study the sensory quality and aroma profile composition of homogenised segments of untreated (control) and wax‐coated ‘Mor’ mandarins after 7 days at 20 °C or 3 or 6 weeks of cold storage at 5 °C were examined. RESULTS: Fruit taste score decreased during storage and following wax coating, and this was attributed to decreases in sourness and mandarin flavour and accumulation of off‐flavours. Aroma profiling identified 31 volatiles that decreased by at least 50% during storage and after waxing and thus may be involved in the observed flavour loss. In contrast, 13 volatiles, mostly belonging to ethanol fermentation and fatty acid and amino acid catabolism pathways, significantly increased at least twofold and probably contributed to off‐flavour enhancement. CONCLUSION: The results showed that after harvest there was a progressive decrease in sensory quality of ‘Mor’ mandarins. It is proposed that observed decreases in contents of sesqui‐ and monoterpenes and short‐chain oxygenated fatty acids may contribute to the decrease in mandarin flavour, whereas increases in the contents of ethanol fermentation metabolites and derivates of fatty acid and amino acid catabolism are most likely involved in causing the enhanced sensation of off‐flavours. Copyright © 2010 Society of Chemical Industry     

Modal Parameter Identification of Hagia Sophia Bell-Tower via Ambient Vibration Test

Many of historical structures have degenerated in time by environmental effects, earthquakes, and winds because of the inadequate preservation. The preservation of historical heritage is considered a fundamental issue in the cultural life of modern societies. The protective measures can be supplied if the actual behaviour of the structures is known. The paper presents the results of ambient vibration test and operational modal analysis carried out on the historical masonry bell-tower of the Hagia Sophia church in Trabzon, Turkey. The bell-tower is about 23 m high and dates back to the XIII century. The study includes also the initial analytical model of the tower constituted by the geometrical survey. The experimental measurements are performed using two measurement setups in different times. In the first setup twelve uniaxial accelerometers are used, while in the second setup four triaxial accelerometers with one uniaxial reference are used with the aim of determining the bending and torsional mode shapes as well as natural frequencies and modal damping ratios of the tower. The analytical model of the tower is developed by using solid brick elements, and a relatively large number of finite elements have been used in the model to obtain a regular distribution of mass. The first five natural frequencies and corresponding mode shapes are determined from both theoretical and experimental modal analyses and compared with each other. A good harmony is attained between mode shapes, but there are some differences between natural frequencies. The sources of the differences are introduced in terms of variations in the elasticity modulus of walls, cracks on upper walls, and boundary conditions on base level.     

Gastrointestinal tolerance of γ-cyclodextrin in humans

The gastrointenstinal tolerance of γ-cyclodextrin (γ-CD) was examined in 24 healthy human volunteers. In a double-blind, placebo-controlled, randomized crossover study, single acute doses of 8g maltodextrin (placebo) or 8g γ-CD (test) were consumed as a mid-morning snack after addition to 100g yogurt. Gastrointenstinal symptoms as well as frequency and consistency of stools were recorded before and after lunch at between 3-4 and 7-8h after intake respectively. The perception of the symptoms was rated on a subjective scale ranging from 1 ('more than normal') to 3('exceptionally more than normal'). Following consumption of maltodextrin, five subjects reported a total of 12 symptoms of which seven, two and three were rated as having grade 1, 2 and 3, respectively. Following consumption of γ-CD, five subjects reported six symptoms all of which were graded as 1. Two subjects reported flatulence, which is a frequent consequence of the consumption of malabsorbed carbohydrates, after placebo and test treatment. The incidence of individual and combined side-effects as well as the number and consistency of faeces passed was not significantly different between placebo and test treatment. It is concluded that single doses of 8g γ-CD and maltodextrin are tolerated equally well. This is in keeping with a good digestibility of γ-CD by salivary and pancreatic amylase.