Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures

At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO(3)/SrTiO(3) system . Although this state has been predicted and reported to be confined at the interface, some studies indicate a much broader spatial extension, thereby questioning its origin. Here, we provide for the first time a direct determination of the carrier density profile of this system through resistance profile mappings collected in cross-section LaAlO(3)/SrTiO(3) samples with a conducting-tip atomic force microscope (CT-AFM). We find that, depending on specific growth protocols, the spatial extension of the high-mobility electron gas can be varied from hundreds of micrometres into SrTiO(3) to a few nanometres next to the LaAlO(3)/SrTiO(3) interface. Our results emphasize the potential of CT-AFM as a novel tool to characterize complex oxide interfaces and provide us with a definitive and conclusive way to reconcile the body of experimental data in this system.     

Estimation of polyvinyl alcohol cryogel mechanical properties with four ultrasound elastography methods and comparison with gold standard testings

Tissue-mimicking phantoms are very useful in the field of tissue characterization and essential in elastography for the purpose of validating motion estimators. This study is dedicated to the characterization of polyvinyl alcohol cryogel (PVA-C) for these types of applications. A strict fabrication procedure was defined to optimize the reproducibility of phantoms having a similar elasticity. Following mechanical stretching tests, the phantoms were used to compare the accuracy of four different elastography methods. The four methods were based on a one-dimensional (1-D) scaling factor estimation, on two different implementations of a 2-D Lagrangian speckle model estimator (quasistatic elastography methods), and on a 1-D shear wave transient elastography technique (dynamic method). Young's modulus was investigated as a function of the number of freeze-thaw cycles of PVA-C, and of the concentration of acoustic scatterers. Other mechanical and acoustic parameters-such as the speed of sound, shear wave velocity, mass density, and Poisson's ratio-also were assessed. The Poisson's ratio was estimated with good precision at 0.499 for all samples, and the Young's moduli varied in a range of 20 kPa for one freeze-thaw cycle to 600 kPa for 10 cycles. Nevertheless, above six freeze-thaw cycles, the results were less reliable because of sample geometry artifacts. However, for the samples that underwent less than seven freeze-thaw cycles, the Young's moduli estimated with the four elastography methods showed good matching with the mechanical tensile tests with a regression coefficient varying from 0.97 to 1.07, and correlations R2 varying from 0.93 to 0.99, depending on the method.     

A highly conserved intraspecies homolog of the Saccharomyces cerevisiae elongation factor-3 encoded by the HEF3 gene

A paralog (intraspecies homolog) of the Saccharomyces cerevisiae YEF3 gene, encoding elongation factor-3, has been sequenced in the course of the yeast genome project, and identified by database searching; this gene has been designated HEF3. Bioinformatic and Northern blot analysis indicate that the HEF3 gene is not expressed during vegetative growth. Deletion of the HEF3 gene reveals no growth defects, nor any defects in mating or sporulation. A high copy 2μ clone of HEF3 was constructed, and was shown to be unable to complement a null allele of yef3. Finally, an in vitro assay for ribosome-stimulated ATPase activity was performed with isogenic HEF3 and Δhef3 strains; no difference in biochemical activity could be detected in these strains. From these results, we conclude that the HEF3 gene does not encode a functional homolog of YEF3. © 1998 John Wiley & Sons, Ltd.     

Synthesis of conducting transparent few-layer graphene directly on glass at 450 °C

Post-growth transfer and high growth temperature are two major hurdles that research has to overcome to get graphene out of research laboratories. Here, using a plasma-enhanced chemical vapour deposition process, we demonstrate the large-area formation of continuous transparent graphene layers at temperatures as low as 450?°C. Our few-layer graphene grows at the interface between a pre-deposited 200 nm Ni catalytic film and an insulating glass substrate. After nickel etching, we are able to measure the optical transmittance of the layers without any transfer. We also measure their sheet resistance directly and after inkjet printing of electrical contacts: sheet resistance is locally as low as 500 Ω sq?1. Finally the samples equipped with printed contacts appear to be efficient humidity sensors.     

大规模多级水力压裂技术在页岩油气藏开发中的应用

北美地区页岩气开发已经商业化,开发技术也逐步趋于成熟,而中国虽然有丰富的页岩气资源,但由于起步较晚,目前还处于探索阶段。有效开采页岩气通常需要在水平井中实施大规模的多级水力压裂,提出了低渗油气藏大规模水力压裂的关键岩石力学原则,介绍了微地震技术在水力压裂监测中的应用,并用离散单元法建立的数学模型对水力压裂的效果进行了评价,分析了中国页岩油气藏水力压裂方案优化的地质因素,并对大规模水力压裂的可持续性发展提出了一些建议。      

Removal of TDS from Cooling Tower Water by Using EDTA-Modified Bagasse Fibers

Modified by ethylenediaminetetraacetic acid (EDTA) salts and unmodified bagasse fibers were tested for the removal of total dissolved solids (TDSs) from cooling tower water. Parameters such as hydrogen ion concentration (pH), particle size of bagasse fibers, and the concentrations of adsorbent and adsorbate were studied to optimize the conditions to be applied on a commercial scale for the decontamination of effluents of cooling tower water. The optimum pH for TDS removal was between 6 and 6.5. The efficiency of TDS removal increased when the size of fiber particles decreased (100?μm) and when the concentration of EDTA salt increased to reach 78 mg/g of modified bagasse fibers. The adsorption parameters were determined using both Langmuir and Freundlich isotherms. The preferential mechanisms for the retention of TDSs are a complexation process between the TDSs and chemical functions present on the surface of fibers, and the chelation process with the EDTA attached to the fibers. The results obtained could be valuable for application to cooling tower water treatment and for the softening of hard drinking water.     

Two-dimensional scattering from a multilayered periodic structure of arbitrary shapes

A numerical approach is presented to analyze the two-dimensional scattering properties from a multilayered periodic dielectric structure of an arbitrary number of arbitrarily shaped unit cells. The approach is enhanced by the periodic moment method, the lattice sums technique, and the Poisson summation formula. The matrix element's evaluation accounts for the overall coupling between layers. The choosing of lattice parameters allows designs for a wide range of applications, including the electromagnetic bandgap filtering of an E-polarized wave, which is simulated and reported here.     

Sensory quality of unheated and heated Mozzarella‐style cheeses with different fat,salt and calcium levels

The current study evaluated the effects of reducing fat from 23w/w to 11w/w and salt from 1.8 to 1.0w/w on the texture profile attributes, volatile compounds and sensory characteristics of unheated and heated (95 °C) mozzarella‐style cheese after 15 and 35 days of storage at 4 °C. Reducing fat content significantly impaired sensory acceptability, mainly because of associated increases in firmness, rubberiness and chewiness, and reductions in fat flavour and cheese flavour in the unheated and heated cheeses. Reducing salt content had relatively minor effects. Reducing calcium content counteracted some of the negative sensory attributes associated with reduced‐fat cheese.     

Distraction and driving: Results from a case–control responsibility study of traffic crash injured drivers interviewed at the emergency room

Background

Use of cellular phones has been shown to be associated with crashes but many external distractions remain to be studied.

Objective

To assess the risk associated with diversion of attention due to unexpected events or secondary tasks at the wheel.

Design

Responsibility case–control study.

Setting

Adult emergency department of the Bordeaux University Hospital (France) from April 2010 to August 2011.

Participants

955 injured drivers presenting as a result of motor vehicle crash.

Main outcome measures

The main outcome variable was responsibility for the crash. Exposures were external distraction, alcohol use, psychotropic medicine use, and sleep deprivation. Potential confounders were sociodemographic and crash characteristics.

Results

Beyond classical risk factor found to be associated with responsibility, results showed that distracting events inside the vehicle (picking up an object), distraction due to driver activity (smoking) and distracting events occurring outside were associated with an increased probability of being at fault. These distraction-related factors accounted for 8% of injurious road crashes.

Limitations

Retrospective responsibility self-assessment.

Conclusions

Diverted attention may carry more risk than expected. Our results are supporting recent research efforts to detect periods of driving vulnerability related to inattention.