Seasonal distribution of bloater (Coregonus hoyi) in the waters of Lake Huron surrounding the Bruce Peninsula

Information about bloater (Coregonus hoyi) habitat in Lake Huron was limited to correlations between commercial yield and fishing depth, despite available information from other Great Lakes. We identified seasonal patterns of bloater habitat use in hypolimnetic waters surrounding the Bruce Peninsula, Lake Huron. We applied a delta-lognormal model to fisheries-independent survey data to evaluate whether bloater catch-per-unit-effort was related to depth, temperature, and bathymetric slope. A Bayesian variable selection technique indicated that bloater distribution was most strongly related to bottom depth and water temperature. Our study also reconfirmed a previously-described pattern of seasonal inshore movement during warmer months followed by a return to deeper offshore waters during cooler months. By focusing our sampling within the hypolimnion, we characterized intra-annual patterns of bloater habitat use with respect to a temperature gradient near the minimum thermal requirements reported for this species. Bloater distribution under these thermal conditions has not been previously reported.     

SilentKnock: practical, provably undetectable authentication

Port knocking is a technique to prevent attackers from discovering and exploiting vulnerable network services, while allowing access for authenticated users. Unfortunately, most work in this area suffers from a lack of a clear threat model or motivation. To remedy this, we introduce a formal security model for port knocking, show how previous schemes fail to meet our definition, and give a provably secure scheme. We also present SilentKnock, an implementation of this protocol that is provably secure under the assumption that AES and a modified version of MD4 are pseudorandom functions, and integrates seamlessly with existing applications.     

3G将拉近移动运营商与企业的距离

随着西欧3G部署的提速,整个产业将更多的目光投向了企业市场,因为3G能够为运营商带来更多的企业市场的收入,比如促进基础和增值企业应用的增长;推动更低廉的语音服务,从而加速对固网业务的替代;提供与设备紧密联系的业务等。然而与大众消费市场不同的是,3G能为运营商带来的企业应用比2.5G多不了太多。事实上,3G可能充其量只是通过提升现有基于GPRS的企业应用的质量,从而提升在企业移动应用市场的机会。虽然如此,3G对于繁荣西欧企业移动应用市场还是十分必要的。目前,西欧的这一市场还处于起步阶段。2004年底,西欧的4600万企业用户对一些…     

An optical technique to measure distortion in heat-treated parts in-situ

Improvements in the properties of aluminum alloys have made them more popular for structural applications. Using the different heat treatments that are available, aluminum alloys can have a wide variation in properties for different types of applications. The appropriate heat treatments of these alloys are vital in providing the properties needed for their particular applications. Moreover, understanding the effects of heat treatments that may cause distortion to a part is critical. Most of the work carried out in this field is in the form of pre- and post-treatment analysis of a part. In this study, in-situ measurements of the distortions that a heat-treated part undergoes when subjected to rapid heating to temperatures near melting followed by slow cooling were carried out. A numerical model was built to simulate the experiment and the results are compared. This study will provide much-needed insight into the complex occurrences that aluminum parts undergo during heat treatment. For more information, contact Federico Sciammarella, Thermal Processing Technology Center, Illinois Institute of Technology, 10 W. 32nd St. Chicago, IL 60616; (312) 927-0596; fax (312) 664-5758; e-mail sciammarellaf@itt.edu.     

High pressure unfolding of ovalbumin

Summary The effects of high pressure processing of ovalbumin have been investigated. After treatment with pressures in excess of 400 MPa at pH 6.5, circular dichroism (CD) and Fourier transform infra-red spectroscopy (FTIR) spectroscopy showed limited irreversible changes in secondary structure. Fluorescence and derivative spectroscopy as well as fluorescence-quenching experiments indicated greater solvent exposure of aromatic residues in pressure-treated protein. Pressure treatment also caused enhanced binding of anilino-1-naphthalene-8-sulphonic acid (ANS). The pressure necessary to cause these changes was lower at low pH. These data indicate a pressure-induced molten-globule formation. The pressurized protein may be structurally similar to forms of the protein found at acid pH or as intermediates in protein folding.     

Shear strength of chromia across multiple length scales: An LDA + U study

A method for predicting the shear strength of materials over multiple length scales is developed and tested. The method is based on renormalizing the energies and shear displacements obtained through electronic structure calculations of nanoscale models of the material of interest. All material- and size-dependent quantities are incorporated into the renormalization factors, yielding a universal model that can be applied to many materials and length scales. The model is used to predict the shear strength of Cr₂O₃ along three relevant slip planes and slip directions. The results demonstrate that the shear strengths of the nanoscale systems used in the calculations range from 19.4 to 29.4 GPa. These data are then renormalized to predict the shear strength of a grain that is 10 μm thick, yielding shear strengths ranging from 189 to 342 MPa. The large decrease in the shear strength with increasing grain size is consistent with the behavior of many materials. The ability to capture this change using electronic structure calculations that do not require experimental input may be useful in developing cohesive laws of novel materials for use in large-scale mechanical engineering simulations of materials failure.     

Flexural Capacity of Compact Composite I-Girders in Positive Bending

Current American Association of State Highway and Transportation Officials (AASHTO) bridge specifications for compact composite steel girders in positive bending with adjacent compact pier sections limit the allowable maximum strength to a value between the full plastic moment and the hypothetical yield moment of the cross section as a function of the depth of web in compression. The strength prediction equations derived using these methods provide conservative values when compared to the results of the parametric studies used to develop the equations. Recent experimental tests coupled with finite-element analysis and mechanistic evaluations of the cross-section flexural capacity suggest that larger capacities may be achieved than those determined from AASHTO’s prediction equations. This paper presents an assessment of the behavior of composite positive bending specimens. A summary of a comprehensive literature review is provided coupled with results of the analytical and experimental evaluation of the nominal moment capacity of composite girders. Lastly, a less conservative design moment capacity expression developed from this assessment is provided.     

Reduction of prelimbic inhibitory gating of auditory evoked potentials after fear conditioning.

Inhibitory gating (IG) is a basic central nervous system process for filtering repetitive sensory information. Although IG deficits coincide with cognitive and emotional dysfunction in a variety of neuropsychiatric disorders, limited research has been completed on the basic, functional nature of IG. Persistent IG occurs in rat prelimbic medial prefrontal cortex (mPFC), a crucial site for modulating emotional learning. To investigate the interaction of affect and IG, we recorded local field potentials (LFP) directly from prelimbic mPFC and examined the influence of tone-shock fear conditioning (FC) on IG. Behavioral reactions during IG were observed before and after FC, and increase of orienting response after FC indicated induction of tone-shock association. After FC, some components of LFP response exhibited short-term weakening of IG. On a subsequent day of recording, IG strengthened for all LFP components, but individual components differed in their particular changes. Affective regulation of IG represents an important factor influencing within-subject IG variability, and these results have implications for understanding the role of rapid, implicit neural coding involved in emotional learning and affective disruption in psychiatric disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance engineering - editorial

Imperial College London was host to the 24th Annual UK Performance Engineering Workshop in July 2008. UKPEW is an enjoyable workshop that brings together researchers in the performance engineering community to discuss quantitative aspects of, for instance, Grid computing, web and e-commerce, performance modelling techniques, power management and wireless network performance. In 2008, we had 29 papers presented over the two days of the workshop and this IET Software Special Issue represents significantly extended versions of the best selected papers from that workshop.     

Interpretation of full-scale strain data from wind pressures on a low-rise structure

This paper presents a study on the structural performance of a low-rise building under high-wind action, derived from the data analysis of a long-term full-scale monitoring program (1997–2000). Experimentation and full-scale measurements are critical in the study of wind-pressure-induced loading associated with complex phenomena such as three-dimensional flow fields and non-stationary winds. Recorded pressure data and corresponding deformations (strains) on selected portions of the structural frame in the proximity of the pressure transducers are evaluated and compared. The system under investigation is unique since it is located in a complex topography (coastal) environment, for which even the interpretation of basic wind and pressure data becomes challenging.The correspondence of the observed data with the United States wind load specifications (ASCE-7) is investigated both from the perspective of the loads (pressures) and of the deformation response predictions. The structural performance is evaluated through the comparison of the recorded strains with predicted deformations, derived from the application of the corresponding external wind pressure loading to a simplified structural model simulating the behavior of an instrumented region of the building.Results show good agreement between measured pressure coefficients and selected values estimated through the ASCE-7 specifications, especially in areas of positive pressures where the predictions are consistently larger than the recorded data. Reasonable and consistent correspondence was also found from the analysis of the strains in structural members.