Ultrasonic evaluation of delamination in quasi-isotropic CFRP laminates subjected to low-velocity impact

Ultrasonic C-Scan is used very often to detect flaws and defects in the composite components resulted during fabrication and damages resulting from service conditions. Evaluation and characterization of defects and damages of composites require experience and good understanding of the material as they are distinctly different in composition and behavior as compared to conventional metallic materials. The failure mechanisms in composite materials are quite complex. They involve the interaction of matrix cracking, fiber matrix interface debonding, fiber pullout, fiber fracture and delamination. Generally all of them occur making the stress and failure analysis very complex. Under low-velocity impact loading delamination is observed to be a major failure mode. In composite materials the ultrasonic waves suffer high acoustic attenuation and scattering effect, thus making data interpretation difficult. However these difficulties can be overcome to a greater extent by proper selection of probe, probe parameter settings like pulse width, pulse amplitude, pulse repetition rate, delay, blanking, gain etc., and data processing which includes image processing done on the image obtained by the C-Scan.

Extent of Structural Asymmetry in Homodimeric Proteins: Prevalence and Relevance

Most homodimeric proteins have symmetric structure. Although symmetry is known to confer structural and functional advantage, asymmetric organization is also observed. Using a non-redundant dataset of 223 high-resolution crystal structures of biologically relevant homodimers, we address questions on the prevalence and significance of asymmetry. We used two measures to quantify global and interface asymmetry, and assess the correlation of several molecular and structural parameters with asymmetry. We have identified rare cases (11/223) of biologically relevant homodimers with pronounced global asymmetry. Asymmetry serves as a means to bring about 2:1 binding between the homodimer and another molecule; it also enables cellular signalling arising from asymmetric macromolecular ligands such as DNA. Analysis of these cases reveals two possible mechanisms by which possible infinite array formation is prevented. In case of homodimers associating via non-topologically equivalent surfaces in their tertiary structures, ligand-dependent mechanisms are used. For stable dimers binding via large surfaces, ligand-dependent structural change regulates polymerisation/depolymerisation; for unstable dimers binding via smaller surfaces that are not evolutionarily well conserved, dimerisation occurs only in the presence of the ligand. In case of homodimers associating via interaction surfaces with parts of the surfaces topologically equivalent in the tertiary structures, steric hindrance serves as the preventive mechanism of infinite array. We also find that homodimers exhibiting grossly symmetric organization rarely exhibit either perfect local symmetry or high local asymmetry. Binding of small ligands at the interface does not cause any significant variation in interface asymmetry. However, identification of biologically relevant interface asymmetry in grossly symmetric homodimers is confounded by the presence of similar small magnitude changes caused due to artefacts of crystallisation. Our study provides new insights regarding accommodation of asymmetry in homodimers.

Ramachandran analysis of conserved glycyl residues in homologous proteins of known structure

High conservation of glycyl residues in homologous proteins is fairly frequent. It is commonly understood that glycine tends to be highly conserved either because of its unique Ramachandran angles or to avoid steric clash that would arise with a larger side chain. Using a database of aligned 3D structures of homologous proteins we identified conserved Gly in 288 alignment positions from 85 families. Ninety-six of these alignment positions correspond to conserved Gly residue with (phi, ) values allowed for non-glycyl residues. Reasons for this observation were investigated by in-silico mutation of these glycyl residues to Ala. We found in 94% of the cases a short contact exists between the C atom of the introduced Ala with the atoms which are often distant in the primary structure. This suggests the lack of space even for a short side chain thereby explaining high conservation of glycyl residues even when they adopt (phi, ) values allowed for Ala. In 189 alignment positions, the conserved glycyl residues adopt (phi, ) values which are disallowed for Ala. In-silico mutation of these Gly residues to Ala almost always results in steric hindrance involving C atom of Ala as one would expect by comparing Ramachandran maps for Ala and Gly. Rare occurrence of the disallowed glycyl conformations even in ultrahigh resolution protein structures are accompanied by short contacts in the crystal structures and such disallowed conformations are not conserved in the homologues. These observations raise the doubt on the accuracy of such glycyl conformations in proteins.

Investigation of biotin-streptavidin binding interactions using microcantilever sensors

We report the investigation of biotin-streptavidin binding interactions using microcantilever sensors. A symmetric cantilever construction is employed to minimize the effects of thermal drift and the control of surface chemistry on the backside of the cantilever is demonstrated to reduce the effects of non-specific binding interactions on the cantilever. Three structurally different biotin modified cantilever surfaces are used as a model system to study the binding interaction with streptavidin. The cantilever response to the binding of streptavidin on these biotin sensing monolayers is compared. The lowest detection limit of streptavidin using biotin-HPDP is found to be between 1 and 10 nM limited by the optical measurement setup. Surface characterization using quartz crystal microbalance (QCM) and high-resolution atomic force microscope (AFM) is used to benchmark the cantilever sensor response. In addition, the QCM and AFM studies reveal that the surface density of bound streptavidin on biotin modified surfaces was low, thereby implying that effects other than steric hindrance are responsible for defining cantilever response. (c) 2006 Elsevier B.V. All rights reserved.

用相似准数统计方法处理装药撞击起爆模拟实验数据

用相似准数构造刺激量，根据不同撞击条件起爆的实验结果，用最大似然法在正态假设下估计刺激量的期望和方差，并对处理结果进行讨论。把炸药装药撞击起爆实验数据视同刺激量不重复的感度试验数据，用最大似然法处理炸药实验数据。结果表明炸药装药撞击起爆模拟实验相似律存在；用相似准数统计方法可以处理实验数据。

Experimental investigation on low-temperature fatigue crack propagation in offshore structural steel A131 under random sea ice loading

An apparatus of low-temperature controlling for fatigue experiments and its crack measuring system were developed and used for offshore structural steel A131 under conditions of both low temperature and random sea ice. The experimental procedures and data processing were described, and a universal random data processing software for FCP under spectrum loading was written. Many specific features of random ice-induced FCP which differed with constant amplitude FCP behaviours were proposed and temperature effect on ice-induced FCP was pointed out with an easily neglected aspect in designing for platforms in sea ice emphasized. In the end, differences of FCP behaviours between sea ice and ocean wave were presented.

Distribution of catch-per-unit-of-effort and fishing effort for tuna in the Eastern Tropical Pacific Ocean by months of the year 1951-1960

ENGLISH: Comparison of physical and biological environmental factors affecting the aggregation of tunas with the success of fishing by the commercial fleets, requires that catch and effort data be examined in greater detail than has been presented in these publications. Consequently, the United States Bureau of Commercial Fisheries Biological Laboratory, San Diego, to serve the needs of its program of research on causes of variations in tuna abundance, made arrangements with the Tuna Commission to summarize these catch and effort data by month, by one-degree area, by fishing vessel size-class, for the years 1951-1960 for bait boats and 1953-1960 for purse-seiners. The present paper describes the techniques employed in summarizing these data by automatic data processing methods. It also presents the catch and effort information by months, by five-degree areas and certain combinations of five-degree areas for use by fishermen, industry personnel, and research agencies. Because of space limitations and other considerations, the one-degree tabulations are not included but are available at the Tuna Commission and Bureau laboratories. SPANISH: La comparación de los factores ambientales físicos y biológicos que afectan la agrupación del atún, con el éxito obtenido en la pesca por las flotas comerciales, requiere que los datos sobre la captura y el esfuerzo sean examinados con mayor detalle de lo que han sido presentados en estas publicaciones. En consecuencia, el Laboratorio Biológico del Buró de Pesquerías Comerciales de los Estados Unidos, situado en San Diego, a fin de llenar los requisitos de su programa de investigación sobre las causas de las variaciones en la abundancia del atún, hizo arreglos con la Comisión del Atún para sumarizar esos datos sobre la captura y el esfuerzo por meses, por áreas de un grado, por clases de tamaño de las embarcaciones de pesca durante los años 1951-1960 en lo que concierne a los barcos de carnada y durante el período 1953-1960 en lo que respecta a los barcos rederos. El presente trabajo describe la técnica empleada en la sumarización de dichos datos mediante métodos automáticos de manejo de datos. También se da aquí la información sobre la captura y el esfuerzo por meses, por áreas de cinco grados y ciertas combinaciones de áreas de cinco grados para el uso de los pescadores, del personal de la industria y de las oficinas de investigación. Por falta de espacio y otras razones, las tabulaciones de las áreas de un grado no han sido incluídos en este trabajo, pero están a la disposición de quien tenga interés en los laboratorios de la Comisión del Atún y del Buró.

Mitigation Techniques to Reduce the Impact of Wind Turbines on Radar Services

Radar services are occasionally affected by wind farms. This paper presents a comprehensive description of the effects that a wind farm may cause on the different radar services, and it compiles a review of the recent research results regarding the mitigation techniques to minimize this impact. Mitigation techniques to be applied at the wind farm and on the radar systems are described. The development of thorough impact studies before the wind farm is installed is presented as the best way to analyze in advance the potential for interference, and subsequently identify the possible solutions to allow the coexistence of wind farms and radar services.

Internationales Otolithen-Symposium in Australien

The Third International Symposium on Fish Otolith Research and Application in Townsville, Australia, from 11 to 16 July 2004, gathered around 300 scientists from 30 nations (http://www.otolith2004.com). Mayor topics were: structure of otoliths and function; micro-Chemitry and composition; determination of age and growth and their validation; de-termination of age in fish from tropical habitats; influence of climate, ecology and population biology; statistik and modelling; stock assessment and fishery management; quality control in institutions carrying out age determinations, and data processing; and development of technologies. The symposium was preceeded by a workshop at the James Cook University, Townsville, to enhance the knowledge and skill of participants in theoretrical and practical aspects for prearation of otoliths and interpretation of annuli; difficulties in interpreting age in tropical fish; daily increments as well as shape and image analysis.

Gestión de datos de investigación en repositorios de acceso abierto: una visión panorámica y un caso práctico en la UPV/EHU

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Observational and theoretical advances in cosmological foreground emission

Observational and theoretical work towards the separation of foreground emission from the cosmic microwave background is described. The bulk of this work is in the design, construction, and commissioning of the C-Band All-Sky Survey (C-BASS), an experiment to produce a template of the Milky Way Galaxy's polarized synchrotron emission. Theoretical work is the derivation of an analytical approximation to the emission spectrum of spinning dust grains.

The performance of the C-BASS experiment is demonstrated through a preliminary, deep survey of the North Celestial Pole region. A comparison to multiwavelength data is performed, and the thermal and systematic noise properties of the experiment are explored. The systematic noise has been minimized through careful data processing algorithms, implemented both in the experiment's Field Programmable Gate Array (FPGA) based digital backend and in the data analysis pipeline. Detailed descriptions of these algorithms are presented.

The analytical function of spinning dust emission is derived through the application of careful approximations, with each step tested against numerical calculations. This work is intended for use in the parameterized separation of cosmological foreground components and as a framework for interpreting and comparing the variety of anomalous microwave emission observations.

Label-free detection of single biological molecules using microtoroid optical resonators

Being able to detect a single molecule without the use of labels has been a long standing goal of bioengineers and physicists. This would simplify applications ranging from single molecular binding studies to those involving public health and security, improved drug screening, medical diagnostics, and genome sequencing. One promising technique that has the potential to detect single molecules is the microtoroid optical resonator. The main obstacle to detecting single molecules, however, is decreasing the noise level of the measurements such that a single molecule can be distinguished from background. We have used laser frequency locking in combination with balanced detection and data processing techniques to reduce the noise level of these devices and report the detection of a wide range of nanoscale objects ranging from nanoparticles with radii from 100 to 2.5 nm, to exosomes, ribosomes, and single protein molecules (mouse immunoglobulin G and human interleukin-2). We further extend the exosome results towards creating a non-invasive tumor biopsy assay. Our results, covering several orders of magnitude of particle radius (100 nm to 2 nm), agree with the `reactive' model prediction for the frequency shift of the resonator upon particle binding. In addition, we demonstrate that molecular weight may be estimated from the frequency shift through a simple formula, thus providing a basis for an ``optical mass spectrometer'' in solution. We anticipate that our results will enable many applications, including more sensitive medical diagnostics and fundamental studies of single receptor-ligand and protein-protein interactions in real time. The thesis summarizes what we have achieved thus far and shows that the goal of detecting a single molecule without the use of labels can now be realized.

Parallel optical negabinary signed-digit computing: algorithm and optical implementation

Negabinary is a component of the positional number system. A complete set of negabinary arithmetic operations are presented, including the basic addition/subtraction logic, the two-step carry-free addition/subtraction algorithm based on negabinary signed-digit (NSD) representation, parallel multiplication, and the fast conversion from NSD to the normal negabinary in the carry-look-ahead mode. All the arithmetic operations can be performed with binary logic. By programming the binary reference bits, addition and subtraction can be realized in parallel with the same binary logic functions. This offers a technique to perform space-variant arithmetic-logic functions with space-invariant instructions. Multiplication can be performed in the tree structure and it is simpler than the modified signed-digit (MSD) counterpart. The parallelism of the algorithms is very suitable for optical implementation. Correspondingly, a general-purpose optical logic system using an electron trapping device is suggested. Various complex logic functions can be performed by programming the illumination of the data arrays without additional temporal latency of the intermediate results. The system can be compact. These properties make the proposed negabinary arithmetic-logic system a strong candidate for future applications in digital optical computing with the development of smart pixel arrays. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)00803-X].