Experimental measurements of the phase and group velocities of body waves in a transversely isotropic medium

In this study, we perform an experimental result for measurements of the body wave phase and group velocities in transversely isotropic media (TIM) by through-transmission technique. After comparing the experimental and theoretical first arrival times of the waves, a difference between the phase velocity and group velocity is observed. When the ratio between propagation distance (d) of the wave and the diameter (D) of transducer is 2.4 for measuring phase velocity and the point probes configuration for measuring group velocity, the accuracy in velocity estimation can reach the limit of system's resolution. However if d/D is 7.8, the wave will propagate with an intermediate velocity between the phase and group velocities. The rapid change of the wave velocity and waveform for qSV-wave propagation with the group velocity has been observed at the propagation direction near the cusps. Therefore, in order to reduce the error in group velocity estimation of qSV-waves, the optimum directions are suggested at 20 and 60°.     

Grain boundary effect on electron-beam-induced current in La3Ga5.5Ta0.5O14 crystal

La₃Ga_5.5Ta_0.5O₁₄ crystal recently attracted more attention due to its superior electromechanical properties and high Q × f product. We report that the first electron-beam-induced current experiment on La₃Ga_5.5Ta_0.5O₁₄ single crystal. This method is employed to study the effect of the crystal's grain boundary on the incident electron beam. The experimental results clearly show that when the electron beam scans over the grain boundary of the crystal, a fraction of the carriers recombine at the grain boundary and is unavailable for the current generation. This recombination rate will be enhanced when the electron beam was close to the boundary and cause a dip in the collected current. Although the crystal is an insulator, this effect still can be observed if the coating metal is proper to be chosen. It is also pointed out that the different diffusion lengths of the crystal might be due to the tilted grain boundary.     

Favorable effects of weak acids on negative-ion electrospray ionization mass spectrometry

Despite widespread use in pharmacokinetic, drug metabolism, and pesticide residue studies, little is known about the factors governing response during reversed-phase liquid chromatography coupled with negative-ion electrospray ionization (ESI(-)) mass spectrometry. We examined the effects of various mobile-phase modifiers on the ESI(-) response of four selective androgen receptor modulators using a postcolumn infusion system. Acetic, propionic, and butyric acid improved the ESI(-) responses of analytes to varying extents at low concentrations. Formic acid suppressed ionization, as did neutral salts (ammonium formate, ammonium acetate) and bases (ammonium hydroxide, triethylamine) under most conditions. Two modifiers (2,2,2-trifluoroethanol, formaldehyde) that produce anions with high gas-phase proton affinity increased ESI(-) responses. However, the concentrations of these modifiers required to enhance ESI(-) response were higher than that of acidic modifiers, which is a phenomenon likely related to their low pK(a) values. 2,2,2-Trifluoroethanol increased response of more hydrophobic compounds but decreased response of a more hydrophilic compound. Formaldehyde improved response of all the compounds, especially the hydrophilic compound with lower surface activity. In summary, these results suggest that an ideal ESI(-) modifier should provide cations that can be easily electrochemically reduced and produce anions with small molecular volume and high gas-phase proton affinity.     

Continuous monitoring of a restriction enzyme digest of DNA on a microchip with automated capillary sample introduction

Continuous analysis of a DNA restriction enzyme digest on a microfabricated device is demonstrated with minimal intervention and enhanced time resolution. A 62-base-pair fragment of dsDNA containing a KpnI site was used to demonstrate this process. A capillary was used to transfer sample from a single reaction mix to a microfabricated chip with parallel separation lanes. The 6-carboxyfluorescein-labeled DNA fragments were detected with a CCD camera as they separated in the lanes, which were filled with linear polyacrylamide. The products of the restriction enzyme digest were monitored for up to 60 min at an average sampling rate of 1 injection/46 s, with consecutive injections as short as 1 injection/14 s. The digest was injected directly into the chip, eliminating the need for any sample-handling steps after addition of the enzyme to the reaction mix. The effects of temperature and restriction enzyme concentration were briefly examined, as well. This work shows the potential of this method to provide valuable information about the process of restriction enzyme cleavage.     

Aurora: a new model and architecture for data stream management

This paper describes the basic processing model and architecture of Aurora, a new system to manage data streams for monitoring applications. Monitoring applications differ substantially from conventional business data processing. The fact that a software system must process and react to continual inputs from many sources (e.g., sensors) rather than from human operators requires one to rethink the fundamental architecture of a DBMS for this application area. In this paper, we present Aurora, a new DBMS currently under construction at Brandeis University, Brown University, and M.I.T. We first provide an overview of the basic Aurora model and architecture and then describe in detail a stream-oriented set of operators.Received: 12 September 2002, Accepted: 26 March 2003, Published online: 21 July 2003Edited by Y. Ioannidis     

Suomi NPP/VIIRS: improving drought watch,crop loss prediction,and food security

Since 1990, the role of satellite observations for climate and land services increased considerably, especially with the introduction in 2011 of the new generation of NOAA operational satellites, called Suomi NPOSS Polar-Orbiting Partnership (S-NPP). S-NPP will continue as the Joint Polar Satellite System (JPSS) for the next two decades. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the S-NPP spacecraft is accommodating the best technical and scientific features of its predecessors and has several new important features. S-NPP and JPSS, in addition to data collection, will address the impacts of climate and weather on industries, water, energy, population health, and other resources and activities. This article discusses how these operational satellites improve early drought detection, monitoring its features (intensity, duration, area, etc.) and prediction of agricultural losses; how fast the Earth’s natural resources deteriorate; and whether the current warm climate intensifies droughts and increases its area and duration. These climate services have already become available to the global community (http://www.star.nesdis.noaa.gov/smcd/emb/vci/VH/index.php). The S-NPP/VIIRS data permits its users to enhance long-term environmental data records, thereby improving the ability to estimate global warming, land-cover changes, and better monitoring of environmental resources.     

Alcohol Consumption Moderates the Link Between Cannabis Use and Cannabis Dependence in an Internet Survey.

The link between cannabis use and cannabis dependence remains poorly understood. Some people use cannabis regularly without signs of dependence; others show dependence despite using less. This study examined alcohol consumption as a moderator of this association. A sample of 476 people (primarily Caucasian men) who used cannabis at least once per week reported their alcohol consumption, cannabis use, and cannabis dependence symptoms in an Internet survey. Regressions revealed significant interactions between measures of cannabis use and alcohol consumption when predicting cannabis dependence. Cannabis use covaried with cannabis dependence, particularly in people who consumed alcohol frequently or in large amounts per week. Despite limitations, these data suggest that alcohol may decrease the safety of cannabis consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

浅析移动多媒体的货币化进程

过去的一年，流行的视频网站、兴趣社区（Communities of interest）、社交网络的普及和个性化需求出现成倍增长。虽然以分钟计算，多媒体服务和使用率均创下历史新高，但服务提供商和内容提供者仍然在根据消费者和企业的需求，不断调整着他们的收益和推出新服务模式。     

Identifying correlates of breaks in occupational sitting: a cross-sectional study

Office workers are commonly targeted in interventions to modify their sitting behaviour, yet there is limited evidence of the correlates of breaks in sitting to inform intervention development. This study identifies the individual, workplace and spatial configuration correlates of the frequency of breaks in sitting (number/hour) in office workers (n?=?5531) stratified by office type (private-enclosed, shared, open plan). All behaviours and potential correlates were measured via self-report using an online cross-sectional survey. Regression analyses revealed age was the only socio-demographic characteristic associated with frequency of breaks in sitting in all office types. Greater job autonomy and local connectivity were positively associated with frequency of breaks in sitting in shared and open-plan offices. In open-plan offices co-worker proximity was negatively associated with frequency of breaks in sitting. Co-worker visibility was positively associated with frequency of breaks in sitting in all office types. This study demonstrates that individual, workplace and spatial configuration factors are all associated with the frequency of breaks in sitting and that these relationships differ by office type. These observations extend prior studies that have only examined correlates at a single level (e.g. the individual). This evidence could be useful to guide future interventions in the design of workplaces to increase breaks in sitting and workers’ physical activity.