bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Post Weld Treatment of a Repair Weld in an Austenitic Header
Authors: Brown T. B. , Dauda T. A. , Truman C. E. , Smith D. J.
Published: August 2008

The repair or replacement of nuclear power components outwith code is a very cumbersome, costly and time consuming exercise which is responsible for long plant shut down time and corresponding loss of electricity production. The aim of the European Union sponsored project ENPOWER was to produce advanced repair techniques and procedures for application in such circumstances to improve the integrity and life of the component and eliminate the need for expensive and sometimes difficult to execute global Post Weld Heat Treatment (PWHT). This paper describes the development and validation of an Alternative Post Weld Treatment (APWT) for a repair weld in an austenitic header component consisting of a 217mm outside diameter by 202mm thick tube plate welded to a 64mm thick cylindrical header. The development of the method using finite element (FE) analysis and the predicted residual stresses before and after application of the APWT are given. Application of the method to a full size mock up of the header is described. Comparison is made between the FE predictions and Deep Hole Drilling through thickness residual stress measurements. This leads to the conclusion that the APWT method is a suitable alternative to a standard PWHT for the control of residual stress in repair welds.
Application of Modified Damage Potential (ψ-Integral) to Predict Crack Initiation in Welded Pipes and Experimental Verification
Authors: Dutta B. K. , Saini Shekhar , Arora Navneet
Published: August 2008

The mesh dependency of Rice and Tracey cavity growth factor (CGF) is overcome by integrating the CGF over a process zone surrounding the crack tip. This integral represents a modified damage potential. The critical value of the integral for crack initiation in weld material has been determined analyzing a welded CT specimen and comparing the computed crack initiation J with experimentally measured J-initiation value. This critical value is then employed to predict crack initiation load in 8” and 12” welded pipes having different measure of through-wall cracks at the center to predict the loads under four point bending loads. The computed values are compared with the experimentally measured values. A close agreement between the computed crack initiation loads with the experimentally measured values justifies the usefulness of the present modified damage potential.
Construction of Web-Accessible Materials Handbook for Generation IV Nuclear Reactors
Authors: Ren Weiju , Rittenhouse Philip
Published: August 2008

The development of a web-accessible materials handbook in support of the materials selection and structural design for the Generation IV nuclear reactors is being planned. Background of the reactor program is briefly introduced. Evolution of materials handbooks for nuclear reactors over years is reviewed in light of the trends brought forth by the rapid advancement in information technologies. The framework, major features, contents, and construction considerations of the web-accessible Gen IV Materials Handbook are discussed. Potential further developments and applications of the handbook are also elucidated.
Mechanical Properties and Cracking Behavior of High-Temperature Heat-Exchanger Materials
Authors: Roy Ajit K. , Savalia Lalit , Kothapalli Narendra , Karamcheti Raghunandan
Published: August 2008

The structural materials selected for high-temperature heat-exchanger applications are expected to withstand very severe operating conditions including elevated temperatures and aggressive chemical species during hydrogen generation using nuclear power. Three different cycles namely sulfur-iodine, calcium-bromine and high temperature electrolysis have been identified for hydrogen generation. Three different structural materials namely Alloy C-22, Alloy C-276 and Waspaloy have been tested to evaluate their high-temperature tensile properties and stress corrosion cracking (SCC) resistance in an acidic solution. The data indicate that all three alloys are capable of maintaining appreciably high tensile strength upto a temperature of 600°C. The results of SCC testing indicate that all three materials are highly resistant to cracking in an acidic solution retaining much of their ductility and time to failure in the tested environment. Fractographic evaluation by scanning electron microscopy revealed dimple microstructure indicating significant ductility in all three alloys.
Susceptibility of Carbon Steel to Stress Corrosion Cracking in Sodium Hydroxide
Authors: Ziomek-Moroz M. , Flis J.
Published: August 2008

Stress corrosion cracking susceptibility of carbon steel and decarburized steel was studied in 8.5 M sodium hydroxide at 100 °C. Potentiodynamic experiments were performed to determine the potential values to be applied in slow strain rate (ssr) experiments. Optical and scanning electron microcopy were used to investigate the surfaces of corroded samples. Severe intergranular stress corrosion cracking was observed on the carbon steel samples in comparison to the decarburized steel samples.
Current Status of R&D Activities on Low Emission Gland Packings in Japan
Authors: Kobayashi Takashi
Published: August 2008

Attention has been paid on emission from valves in piping system to meet the regulations such as TA-LUFT in Europe and Clean Air Act Amendment of 1990 in USA. In this presentation, discussions are made on R&D activities in Japanese industries regarding low emission gland packings. New structure and material used in those applications are shown. A test method for gland packings in Japan is also shown.
Laser Peening Technology for Remote Processing of Pressure Vessels
Authors: Hackel Lloyd A. , Dane C. Brent , Rankin Jon , Harris Fritz
Published: August 2008

Laser peening technology has matured into a fully qualified production process that is now in routine and reliable use for a broad range of metal alloys. Deep compressive stress developed in metal surfaces extends the fatigue life and stress corrosion cracking life of components, and will enable designers to consider higher stress levels in certain life limited designs. This technology has been applied to critical stress areas of military aircraft engine fan blades and to over 12,000 wide cord fan blades and blade hubs for operation in high performance commercial jet engines. A broad range of materials are in production or development, including but not limited to Ti 6/4 (alpha and beta and BSTOA), 300M and 9310 steels, A1 7050, and A1 2023. Enhancement to the life of components with complex geometries and welds has been demonstrated. The processing capability is being extended with the introduction of a transportable laser peening system including a moveable beam that can go out in the field to treat large pressure vessel systems allowing applications not previously possible.
Model for Predicting Laser Peening Residual Stresses in Arbitrary 3D Bodies
Authors: DeWald Adrian T. , Hill Michael R.
Published: August 2008

This paper presents a methodology for predicting the residual stress resulting from laser peening treatment of arbitrary 3D bodies. The model consists of three basic steps. First, the inputs to the model are derived from residual stress measurements made on laser peened blocks of the pertinent material. The measured residual stress in the blocks consists of residual stress caused directly by laser peening and residual stress required for equilibrium. The laser peening induced residual stress is converted into an equivalent strain distribution that reproduces the stress state in an elastic model of the original body (called eigenstrain). Second, a finite element model representing the geometry of the actual part is constructed. Third, the laser peening induced eigenstrain is input into the finite element model at the locations where laser peening is to be applied (arbitrary coverage area). Solving for equilibrium provides a prediction for the residual stress resulting from laser peening treatment. The modeling procedure is verified using comparisons with residual stress measurements for specimens containing corner fillets of various sizes. The model predictions correlate well with the residual stress measurements over the range of conditions studied.
Panel Discussion of User Requirements for the Web-Accessible Gen IV Materials Handbook
Authors: Ren Weiju
Published: August 2008

Development for a web-accessible, interactive materials handbook has been planned for materials selection, design, and construction of the Generation IV Nuclear Reactors. A panel discussion will be held among potential users and the handbook development planners on functionality requirements for the handbook.
ABC of Statistics for Verification and Validation (V&V) of Simulations of High-Consequence Engineering Systems
Authors: Fong Jeffrey T.
Published: August 2008

We begin this expository essay by reviewing, with examples from the materials and fabrication testing literature, what a typical engineer already knows about statistics. We then consider a central question in engineering decision making, i.e., given a computer simulation of high-consequence systems, how do we verify and validate (V & V) and what are the margins of errors of all the important predicted results? To answer this question, we assert that we need three basic tools that already exist in statistical and metrological sciences: (A) Error Analysis. (B) Experimental Design. (C) Uncertainty Analysis. Those three tools, to be known as A B C of statistics, were developed through a powerful linkage between the statistical and metrological sciences. By extending the key concepts of this linkage from physical experiments to numerical simulations, we propose a new approach to answering the V & V question posed earlier. The key concepts are: (1) Uncertainty as defined in ISO Guide to the Expression of Uncertainty in Measurement (1993). (2) Design of experiments prior to data collection in a randomized or orthogonal scheme to evaluate interactions among model variables. (3) Standard reference benchmarks for calibration, and inter-laboratory studies for “weighted” consensus mean. To illustrate the need for and to discuss the plausibility of this metrology-based approach to V & V, two example problems are presented: (a) the verification of 12 simulations of the deformation of a cantilever beam, and (b) the calculation of a mean time to failure for a uniformly loaded 100-column single-floor steel grillage on fire.
Shaking Table Tests on a Spherical Tank Mock-Up Provided With Seismic Isolation and Flexible Piping Connections
Authors: Forni Massimo
Published: August 2008

The Project INDEPTH (Development of INnovative DEvices for Seismic Protection of PeTrocHemical Facilities), supported by the European Commission, has the objective of developing and applying innovative seismic isolation and/or dissipation devices for critical structures at petrochemical facilities. In the framework of INDEPTH, integrated seismic protection systems have been conceived, developed and tested. They are aimed at protecting liquid-filled structures (product storage, spherical and LNG tanks), with new devices (fiber-reinforced isolators, buckling reinforced braces) specific for each application and new flexible piping couplings, to compensate the displacements resulting from the use of isolation systems. The research program has been focused on the selection of critical structures, the design and manufacturing of the devices, the numerical assessment and the experimental validation through shaking table tests. A quantification of technical/economical/safety benefits with respect to the conventional state-of-the-art measures presently adopted and potential application to retrofitting has been performed. Validation through shaking table tests of the effectiveness of the isolation systems on the spherical mock-up (Figure 1), and the related piping system equipped with flexible joints (Figure 2), had been performed. Two types of seismic input have been applied, both synthesized from the 5% damping spectra of EC8 (medium and soft soils); the target peak acceleration value of the time histories was 0.4 g. Different configurations of the mock-up have been tested, such as: fixed base, isolated base with High Damping Rubber Bearings, Fiber Reinforced Rubber Bearings and Lead Rubber Bearings. Furthermore, each configuration has been tested for both time histories and at three different level of filling to verify the sloshing behavior in the sphere and the effectiveness of the isolation systems at levels of filling different from the design one (full sphere). Comparison among all the above mentioned conditions could be done. The presentation will show the main results of the shaking table campaign.
Perception of silent-center syllables by native and non-native English speakers
Authors: Rogers Catherine L. , Lopez Alexandra S.
Published: August 2008

The amount of acoustic information that native and non-native listeners need for syllable identification was investigated by comparing the performance of monolingual English speakers and native Spanish speakers with either an earlier or a later age of immersion in an English-speaking environment. Duration-preserved silent-center syllables retaining 10, 20, 30, or 40ms of the consonant-vowel and vowel-consonant transitions were created for the target vowels /i, ɪ, eɪ, ε, æ/ and /ɑ/, spoken by two males in /bVb/ context. Duration-neutral syllables were created by editing the silent portion to equate the duration of all vowels. Listeners identified the syllables in a six-alternative forced-choice task. The earlier learners identified the whole-word and 40ms duration-preserved syllables as accurately as the monolingual listeners, but identified the silent-center syllables significantly less accurately overall. Only the monolingual listener group identified syllables significantly more accurately in the duration-preserved than in the duration-neutral condition, suggesting that the non-native listeners were unable to recover from the syllable disruption sufficiently to access the duration cues in the silent-center syllables. This effect was most pronounced for the later learners, who also showed the most vowel confusions and the greatest decrease in performance from the whole word to the 40ms transition condition.
Guided wave propagation and mode differentiation in hollow cylinders with viscoelastic coatings
Authors: Mu Jing , Rose Joseph L.
Published: August 2008

Guided wave propagation theories have been widely explored for about one century. Earlier theories on single-layer elastic hollow cylinders have been very beneficial for practical nondestructive testing on piping and tubing systems. Guided wave flexural (nonaxisymmetric) modes in cylinders can be generated by a partial source loading or any nonaxisymmetric discontinuity. They are especially important for guided wave mode control and defect analysis. Previous investigations on guided wave propagation in multilayered hollow cylindrical structures mostly concentrate on the axisymmetric wave mode characteristics. In this paper, the problem of guided wave propagation in free hollow cylinders with viscoelastic coatings is solved by a semianalytical finite element (SAFE) method. Guided wave dispersion curves and attenuation characteristics for both axisymmetric and flexural modes are presented. Due to the fact that dispersion curve modes obtained from SAFE calculations are difficult to differentiate from each other, a mode sorting method is established to distinguish modes by their orthogonality. Theoretical proof of the orthogonality between guided wave modes in a viscoelastic coated hollow cylinder is provided. Wave structures are also calculated and discussed in view of wave mechanics in multilayered cylindrical structures containing viscoelastic materials.
Coding of intonational meanings beyond F0: Evidence from utterance-final /t/ aspiration in German
Authors: Niebuhr Oliver
Published: August 2008

An acoustic analysis of a German read-speech corpus showed that utterance-final /t/ aspirations differ systematically depending on the accompanying nuclear accent contour. Two contours were included: Terminal-falling early and late F0 peaks in terms of the Kiel Intonation Model. They correspond to H+L*L−% and L*+HL−% within the autosegmental metrical (AM) model. Aspirations in early-peak contexts were characterized by (a) “short”, (b) “high-intensity” noise with (c) “low” frequency values for the spectral energy maximum above the lower spectral energy boundary. The opposite holds for aspirations accompanying late-peak productions. Starting from the acoustic analysis, a perception experiment was performed using a variant of the semantic differential paradigm. The stimuli were varied in the duration and intensity pattern as well as the spectral energy pattern of the final /t/ aspiration. Results revealed that the different noise patterns found in connection with early and late peak productions were able to change the attitudinal meaning of the stimuli toward the meaning profile of the respective F0 peak category. This suggests that final aspirations can be part of the coding of meanings, so far solely associated with intonation contours. Hence, the traditionally separated segmental and suprasegmental coding levels seem to be more intertwined than previously thought.
Classification of live, untethered zooplankton from observations of multiple-angle acoustic scatter
Authors: Roberts Paul L. D. , Jaffe Jules S.
Published: August 2008

A broadband, multiple-angle acoustic array was used to classify millimeter to centimeter sized live zooplankton in a laboratory tank. Reflections in the frequency range from 1.5to2.5MHz were recorded from untethered 1–4mm calanoid copepods and 8–12mm mysids over an angular range of 0°–47°. A synchronized, coregistered video system recorded animal location and orientation. To highlight differences between animals, a frequency correlation matrix was computed from the observed wide-band power spectra of the scattered sound. Significant differences in the slopes and shapes of the eigenvalue spectra of this matrix were found for mysids versus copepods. These results support the idea that broadband, multiple-angle scatter can be used to classify organisms of different sizes and shapes.
Analysis of time delay effects on a linear bubble chain system
Authors: Ooi Andrew , Nikolovska Aneta , Manasseh Richard
Published: August 2008

A chain of vertically rising discrete air bubbles represents a transition phenomenon from individual to continuum behavior in a bubbly liquid. Previous studies have reported that there is a preference for acoustic energy to propagate along the bubble chain and that this behavior could be explained by a coupled-oscillator model. However, it has recently been demonstrated that quantitative results from the coupled-oscillator model do not match experimental data. In this paper, it is shown how adding time delays to the coupled-oscillator model can produce results that are in better agreement with experimental data. In addition, the effects of time delays on the natural frequencies and damping of individual eigenmodes of the vertical bubble chain are also investigated. It was found that adding time delays can dramatically change the damping of the different modes of the system while having less dramatic impact on the natural frequencies of the individual eigenmodes. Counterintuitively, it is found that the effects of time delays appear to be more important when the bubbles are closer together than when they are farther apart.
Influence of wall vibrations on the behavior of a simplified wind instrument
Authors: Nief Guillaume , Gautier François , Dalmont Jean-Pierre , Gilbert Joël
Published: August 2008

The issue of the influence of wall vibrations on the behavior of wind instruments is still under debate. The mechanisms of vibroacoustic couplings involved in these vibrations are difficult to investigate, as fluid-structure interactions are weak. Among these vibroacoustic interactions, the present study is focused on the coupling between the internal acoustic field and the mechanical behavior of the duct. For this purpose, a simplified single reed instrument consisting of a brass tube connected to a clarinet mouthpiece has been studied. A theoretical model of coupling between the plane inner acoustic wave and mechanical modes is developed and suggests that in order to obtain measurable effects of wall vibrations, the geometrical parameters of the studied tube have to be unusual compared to that of real instruments. For a slightly oval-shaped and very thin brass tube, it is shown theoretically and experimentally that a coupling between the inner plane acoustic wave and ovalling mechanical modes occurs and results in disturbances of the input impedance, which can slightly affect the tone color of the sound produced. It is concluded that the reported effects are unlikely to occur in real instruments except for some organ pipes.
Cue-specific effects of categorization training on the relative weighting of acoustic cues to consonant voicing in English
Authors: Francis Alexander L. , Kaganovich Natalya , Driscoll-Huber Courtney
Published: August 2008

In English, voiced and voiceless syllable-initial stop consonants differ in both fundamental frequency at the onset of voicing (onset F0) and voice onset time (VOT). Although both correlates, alone, can cue the voicing contrast, listeners weight VOT more heavily when both are available. Such differential weighting may arise from differences in the perceptual distance between voicing categories along the VOT versus onset F0 dimensions, or it may arise from a bias to pay more attention to VOT than to onset F0. The present experiment examines listeners’ use of these two cues when classifying stimuli in which perceptual distance was artificially equated along the two dimensions. Listeners were also trained to categorize stimuli based on one cue at the expense of another. Equating perceptual distance eliminated the expected bias toward VOT before training, but successfully learning to base decisions more on VOT and less on onset F0 was easier than vice versa. Perceptual distance along both dimensions increased for both groups after training, but only VOT-trained listeners showed a decrease in Garner interference. Results lend qualified support to an attentional model of phonetic learning in which learning involves strategic redeployment of selective attention across integral acoustic cues.
Fast affine projections and the regularized modified filtered-error algorithm in multichannel active noise control
Authors: Wesselink J. M. , Berkhoff A. P.
Published: August 2008

In this paper, real-time results are given for broadband multichannel active noise control using the regularized modified filtered-error algorithm. As compared to the standard filtered-error algorithm, the improved convergence rate and stability of the algorithm are obtained by using an inner–outer factorization of the transfer path between the actuators and the error sensors, combined with a delay compensation technique using double control filters and a regularization technique that preserves the factorization properties. The latter techniques allow the use of relatively simple and efficient adaptation schemes in which filtering of the reference signals is unnecessary. Results are given for a multichannel adaptive feedback implementation based on the internal model control principle. In feedforward systems based on this algorithm, colored reference signals may lead to reduced convergence rates. An adaptive extension based on the use of affine projections is presented, for which real-time results and simulations are given, showing the improved convergence rates of the regularized modified filtered-error algorithm for colored reference signals.
Compensation strategies for a lip-tube perturbation of French [u]: An acoustic and perceptual study of 4-year-old children
Authors: Ménard Lucie , Perrier Pascal , Aubin Jerôme , Savariaux Christophe , Thibeault Mélanie
Published: August 2008

The relations between production and perception in 4-year-old children were examined in a study of compensation strategies for a lip-tube perturbation. Acoustic and perceptual analyses of the rounded vowel [u] produced by twelve 4-year-old French speakers were conducted under two conditions: normal and with a 15-mm-diam tube inserted between the lips. Recordings of isolated vowels were made in the normal condition before any perturbation (N1), immediately upon insertion of the tube and for the next 19 trials in this perturbed condition, with (P2) or without articulatory instructions (P1), and in the normal condition after the perturbed trials (N2). The results of the acoustic analyses reveal speaker-dependent alterations of F1, F2, and/or F0 in the perturbed conditions and after the removal of the tube. For some subjects, the presence of the tube resulted in very little change; for others, an increase in F2 was observed in P1, which was generally reduced in some of the 20 repetitions, but not systematically and not continuously. The use of articulatory instructions provided in the P2 condition was detrimental to the achievement of a good acoustic target. Perceptual data are used to determine optimal combinations of F0, F1, and F2 (in bark) related to these patterns. The data are compared to a previous study conducted with adults [Savariaux et al., J. Acoust. Soc. Am. 106, 381–393 (1999)].
Defect detection and localization in orthotropic wood slabs by inversion of dynamic surface displacements
Authors: Romano Anthony J. , Bucaro Joseph A. , Dey Saikat
Published: August 2008

The nondestructive evaluation inversion and generalized force-mapping techniques developed and demonstrated for isotropic thin plates by Bucaro et al. [(2004). “Detection and localization of inclusions in plates using inversion of point actuated surface displacements,” J. Acoust. Soc. Am. 115, 201–206] are extended to the case of orthotropic plates. The extended techniques are applied to a finite-element generated numerical database for point excited wooden slabs with and without an internal defect at 5 and 10kHz. Operation of the original isotropic algorithms on the wood surface displacements is shown to fail in recovering the uniform elastic parameters or in detecting and locating the defect. The new algorithms based on the wave equation for a thin, orthotropic plate successfully convert the surface displacements on the uniform wooden slab to elastic parameter maps which serve to detect and localize the defect in the flawed plate. The results, particularly at the higher frequency, indicate that the onset of failure in the thin plate approximation impacts both the inversion and the generalized force-mapping accuracy. However, in this case use of the inversion algorithm to obtain modified wave equation coefficients followed by operation of the force-mapping algorithm with these new parameters inserted is shown to successfully mitigate this effect.
The inner ears of Northern Canadian freshwater fishes following exposure to seismic air gun sounds
Authors: Song Jiakun , Mann David A. , Cott Peter A. , Hanna Bruce W. , Popper Arthur N.
Published: August 2008

An earlier study examined the effects of exposure to seismic air guns on the hearing of three species of fish from the Mackenzie River Delta in Northern Canada [Popper et al. (2005). “Effects of exposure to seismic airgun use on hearing of three fish species,” J. Acoust. Soc. Am. 117, 3958–3971]. The sound pressure levels to which the fishes were exposed were a mean received level of 205–209dB re 1μPa (peak) per shot and an approximate received mean SEL of 176–180dB re 1μPa2s per shot. In this report, the same animals were examined to determine whether there were effects on the sensory cells of the inner ear as a result of the seismic exposure. No damage was found to the ears of the fishes exposed to seismic sounds despite the fact that two of the species, adult northern pike and lake chub, had shown a temporary threshold shift in hearing studies.
Effects of modulation wave shape on modulation frequency discrimination with electrical hearing
Authors: Landsberger David M.
Published: August 2008

Amplitude modulations of pulsitile stimulation can be used to convey pitch information to cochlear implant users. One variable in designing cochlear implant speech processors is the choice of modulation waveform used to convey pitch information. Modulation frequency discrimination thresholds were measured for 100Hz modulations with four waveforms (sine, sawtooth, a sharpened sawtooth, and square). Just-noticeable differences (JNDs) were similar for all but the square waveform, which often produced larger JNDs. The results suggest that a sine, sawtooth, and sharpened sawtooth waveforms are likely to provide similar pitch discrimination within a speech processing strategy.
Order of presentation asymmetry in intonational contour discrimination in English.
Authors: Hwang Hyekyung , Schafer Amy J. , Anderson Victoria B.
Published: August 2008

In the work of Hwang et al. (2007), native English speakers showed overall poor accuracy in distinguishing initially rising versus level (e.g., L*L*H- H*L-L% vs L*L*L- H*L-L%) or initially falling versus level (e.g., H*H*L- H*L-L% vs H*H*H- H*L-L%) contour contrasts on English phrases in an AX discrimination task. Results not reported in that paper found that it was easier to discriminate when a more complex F0 contour occurred second than when it occurred first. Several orders of presentation effects in the perception of intonation have been reported (e.g., L. Morton (1997); S. Lintfert (2003); Cummins et al. (2006)] but no satisfying account has been provided. This study investigated these asymmetries more systematically. The order effect was significant for falling-level contrast pairs: pairs with a more complex F0 contour last were discriminated more easily than the reverse order. Rising versus level contrasts showed a similar tendency. The results thus extend intonational discrimination asymmetries to these additional contours. They suggest that the cause of the asymmetries may depend more on F0 complexity than on F0 peak.
Amylase-Binding Protein B of
Streptococcus gordonii
Is an Extracellular Dipeptidyl-Peptidase
Authors: Chaudhuri Biswendu , Paju Susanna , Haase Elaine M. , Vickerman M. Margaret , Tanzer Jason M. , Scannapieco Frank A.
Published: August 2008

The oral commensal bacterium
Streptococcus gordonii
interacts with salivary amylase via two amylase-binding proteins, AbpA and AbpB. Based on sequence analysis, the 20-kDa AbpA protein is unique to
S. gordonii
, whereas the 82-kDa AbpB protein appears to share sequence homology with other bacterial dipeptidases. The aim of this study was to verify the peptidase activity of AbpB and further explore its potential functions. The
abpB
gene was cloned, and histidine-tagged AbpB (His-AbpB) was expressed in
Escherichia coli
and purified. Its amylase-binding activity was verified in an amylase ligand binding assay, and its cross-reactivity was verified with an anti-AbpB antibody. Both recombinant His-AbpB and partially purified native AbpB displayed dipeptidase activity and degraded human type VI collagen and fibrinogen, but not salivary amylase. Salivary amylase precipitates not only AbpA and AbpB but also glucosyltransferase G (Gtf-G) from
S. gordonii
supernatants. Since
Streptococcus mutans
also releases Gtf enzymes that could also be involved in multispecies plaque interactions, the effect of
S. gordonii
AbpB on
S. mutans
Gtf-B activity was also tested. Salivary amylase and/or His-AbpB caused a 1.4- to 2-fold increase of
S. mutans
Gtf-B sucrase activity and a 3- to 6-fold increase in transferase activity. An enzyme-linked immunosorbent assay verified the interaction of His-AbpB and amylase with Gtf-B. In summary, AbpB demonstrates proteolytic activity and interacts with and modulates Gtf activity. These activities may help explain the crucial role AbpB appears to play in
S. gordonii
oral colonization.
Antibiotic-Induced Perturbations of the Intestinal Microbiota Alter Host Susceptibility to Enteric Infection
Authors: Sekirov Inna , Tam Nicola M. , Jogova Maria , Robertson Marilyn L. , Li Yuling , Lupp Claudia , Finlay B. Brett
Published: August 2008

Intestinal microbiota comprises microbial communities that reside in the gastrointestinal tract and are critical to normal host physiology. Understanding the microbiota's role in host response to invading pathogens will further advance our knowledge of host-microbe interactions.
Salmonella enterica
serovar Typhimurium was used as a model enteric pathogen to investigate the effect of intestinal microbiota perturbation on host susceptibility to infection. Antibiotics were used to perturb the intestinal microbiota. C57BL/6 mice were treated with clinically relevant doses of streptomycin and vancomycin in drinking water for 2 days, followed by oral infection with
Salmonella enterica
serovar Typhimurium. Alterations in microbiota composition and numbers were evaluated by fluorescent in situ hybridization, differential plating, and Sybr green staining. Antibiotics had a dose-dependent effect on intestinal microbiota composition. The chosen antibiotic regimen did not significantly alter the total numbers of intestinal bacteria but altered the microbiota composition. Greater preinfection perturbations in the microbiota resulted in increased mouse susceptibility to
Salmonella
serovar Typhimurium intestinal colonization, greater postinfection alterations in the microbiota, and more severe intestinal pathology. These results suggest that antibiotic treatment alters the balance of the microbial community, which predisposes the host to
Salmonella
serovar Typhimurium infection, demonstrating the importance of a healthy microbiota in host response to enteric pathogens.
Enhanced Innate Immune Responsiveness to PulmonaryCryptococcus neoformansInfection Is Associated with Resistance to Progressive Infection
Authors: Guillot Loïc , Carroll Scott F. , Homer Robert , Qureshi Salman T.
Published: August 2008

Genetically regulated mechanisms of host defense againstCryptococcus neoformansinfection are not well understood. In this study, pulmonary infection with the moderately virulentC. neoformansstrain 24067 was used to compare the host resistance phenotype of C57BL/6J with that of inbred mouse strain SJL/J. At 7 days or later after infection, C57BL/6J mice exhibited a significantly greater fungal burden in the lungs than SJL/J mice. Characterization of the pulmonary innate immune response at 3 h after cryptococcal infection revealed that resistant SJL/J mice exhibited significantly higher neutrophilia, with elevated levels of inflammatory cytokine tumor necrosis factor alpha (TNF-α) and keratinocyte-derived chemokine (KC)/CXCL1 in the airways, as well as increased whole-lung mRNA expression of chemokines KC/CXCL1, MIP-1α/CCL3, MIP-1β/CCL4, MIP-2/CXCL2, and MCP-1/CCL2 and cytokines interleukin 1β (IL-1β) and IL-1Ra. At 7 and 14 days after infection, SJL/J mice maintained significantly higher levels of TNF-α and KC/CXCL1 in the airways and exhibited a Th1 response characterized by elevated levels of lung gamma interferon (IFN-γ) and IL-12/IL-23p40, while C57BL/6J mice exhibited Th2 immunity as defined by eosinophilia and IL-4 production. Alveolar and resident peritoneal macrophages from SJL/J mice also secreted significantly greater amounts of TNF-α and KC/CXCL1 following in vitro stimulation withC. neoformans. Intracellular signaling analysis demonstrated that TNF-α and KC/CXCL1 production was regulated by NF-κB and phosphatidylinositol 3 kinase in both strains; however, SJL/J macrophages exhibited heightened and prolonged activation in response toC. neoformansinfection compared to that of C57BL/6J. Taken together, these data demonstrate that an enhanced innate immune response against pulmonaryC. neoformansinfection in SJL/J mice is associated with natural resistance to progressive infection.
Enumeration of Cytotoxic CD8 T Cells Ex Vivo during the Response toListeria monocytogenesInfection
Authors: Zaiss Dietmar M. W. , Sijts Alice J. A. M. , Mosmann Tim R.
Published: August 2008

Cytotoxicity is a key effector function of CD8 T cells. However, what proportion of antigen-specific CD8 T cells in vivo exert cytotoxic activity during a functional CD8 T-cell response to infection still remains unknown. We used the Lysispot assay to directly enumerate cytotoxic CD8 T cells from the spleen ex vivo during the immune response to infection with the intracellular bacteriumListeria monocytogenes. We demonstrate that not all antigen-responsive gamma interferon (IFN-γ)-secreting T cells display cytotoxic activity. Most CD8 T cells detected at early time points of the response were cytotoxic. This percentage continuously declined during both the expansion and contraction phases to about 50% at the peak and to <10% of IFN-γ-producing cells in the memory phase. As described for clonal expansion, this elaboration of a program of differentiation after an initial stimulus was not affected by antigen or CD4 help but, like proliferation, could be influenced by later reinfection. These data indicate that cytotoxic effector function during the response to infection is regulated independently from IFN-γ secretion or expansion or contraction of the overall CD8 T-cell response.
Cultivation of Pseudoterranova decipiens (Sealworm) from Third-Stage Larvae to Egg-Laying Adults in Vitro
Authors: Likely C. G. , Burt M. D. B.
Published: August 2008

Third-stage larvae (L3) of Pseudoterranova decipiens from cod (Gadus morhua) developed to maturity at 35 °C in a two-step roller culture system. The medium was API-1 for step 1, and API-1 with bovine haem supplement for step 2. The gas phase was 85% N: 10% CO2:5% O2.
Factors Influencing the Abundance of Blue-Green Algae in Florida Lakes
Authors: Canfield Jr. Daniel E. , Phlips Edward , Duarte Carlos M.
Published: August 2008

Phytoplankton samples collected from 165 Florida lakes were examined to determine relationships between blue-green algal abundance and environmental conditions. Blue-green algal biomass in the Florida samples was weakly correlated (r = −0.34) with water transparency and the concentration of total nitrogen (TN) (r = 0.47) and total phosphorus (TP) (r = 0.33). The relative contribution of blue-green algae to total phytoplankton biomass, however, did not decrease with TN/TP > 29. Blue-green algal biomass was strongly correlated (r = 0.90) to total algal biomass, and blue-green algae became consistently dominant when total algal biomass exceeded 100 mg/L.
TIME TRANSFER BY LASER LINK – THE T2L2 EXPERIMENT ON JASON-2 AND FURTHER EXPERIMENTS
Authors: SAMAIN ÉTIENNE , WEICK JONATHAN , VRANCKEN PATRICK , PARA FRANCK , ALBANESE DOMINIQUE , PARIS JOCELYN , TORRE JEAN-MARIE , ZHAO CHENG , GUILLEMOT PHILIPPE , PETITBON ISABELLE
Published: August 2008

The new generation of optical time transfer will allow the synchronization of remote ultra stable clocks and the determination of their performances over intercontinental distances. The principle of T2L2 (Time Transfer by Laser Link) is based on the techniques of satellite laser ranging coupled with time-frequency metrology. It consists of synchronizing ground and space clocks using short laser pulses travelling between ground clocks and satellite equipment. The instrument will be integrated on the ocean altimetry satellite Jason-2 that is scheduled for launch in 2008. The experiment should enhance the performance of time transfer by one or two magnitudes compared to existing microwave techniques such as GPS and Two-Way Satellite Time and Frequency Transfer (TWSTFT).
Pleistocene pluvial lakes of the American West: a short history of research
Authors: Orme Antony R.
Published: August 2008

Scientific investigations of Pleistocene pluvial lakes in the American West occurred in five phases. The pioneer phase prior to 1870 saw former lakes identified by missionary priests, fur trappers, military expeditions and railroad surveyors. The classic phase, between 1870 and 1920, linked initially with independent surveys and, after 1879, with the United States Geological Survey and with irrigation and mining ventures, saw most lakes identified and described by such worthies as Gilbert, Russell, Gale, Waring and Thompson. A consolidation phase from 1920 to 1955 provided synthesis and new data but, in the absence of age controls, saw much speculation about temporal links between pluvial lakes, glacial stages, and climate forcing. The initial dating phase between 1955 and 1980 saw radiocarbon dating applied to late Pleistocene lakes and their Holocene relics and successors. The integrative phase since 1980, supported by enhanced field, remote sensing, laboratory and dating techniques, has seen an array of issues involving pluvial lakes linked to changes in regional ecology and global climate. In the above sequence, progress from one phase to the next reflected changes in the intellectual climate and advances in scientific methods. Today, we reflect on the episodic but cumulative increase in knowledge about late Pleistocene pluvial lakes, especially for Lake Bonneville, Lake Lahontan and the eastern California lake cascade. The record of earlier Pleistocene lakes, in some cases successors to Miocene and Pliocene lakes, is less certain because of deformation and erosion or burial. Continuing challenges involve evaluation of the Pleistocene lake record as a whole in the context of late Cenozoic tectonic and climate change, and of contemporary environmental and water-resource issues.
Piotr Alekseevich Kropotkin and his monograph
Researches on the Glacial Period
(1876)
Authors: Ivanova Tatiana K. , Markin Vyacheslav A.
Published: August 2008

The notable Russian scientist Piotr Alekseevich Kropotkin (1842–1921) is well known in Western countries for his writings on anarchist philosophy and various historical and political themes, but his geological and geographical work is less familiar, and his great treatise on Quaternary geology is virtually unknown in the Western world. The present paper provides a summary account of Kropotkin's Quaternary studies and his travels in the glaciated regions of Siberia and Scandinavia. He was an exponent of the ‘land-ice’ theory and traced the movements of glaciers in Scandinavia, paying particular attention to the form and structure of eskers.
Factoring repeated content within and among images
Authors: Wang Huamin , Wexler Yonatan , Ofek Eyal , Hoppe Hugues
Published: August 2008

We reduce transmission bandwidth and memory space for images by factoring their repeated content. A transform map and a condensed epitome are created such that all image blocks can be reconstructed from transformed epitome patches. The transforms may include affine deformation and color scaling to account for perspective and tonal variations across the image. The factored representation allows efficient random-access through a simple indirection, and can therefore be used for real-time texture mapping without expansion in memory. Our scheme is orthogonal to traditional image compression, in the sense that the epitome is amenable to further compression such as DXT. Moreover it allows a new mode of progressivity, whereby generic features appear before unique detail. Factoring is also effective across a collection of images, particularly in the context of image-based rendering. Eliminating redundant content lets us include textures that are several times as large in the same memory space.
Parallel Poisson disk sampling
Authors: Wei Li-Yi
Published: August 2008

Sampling is important for a variety of graphics applications include rendering, imaging, and geometry processing. However, producing sample sets with desired efficiency and blue noise statistics has been a major challenge, as existing methods are either sequential with limited speed, or are parallel but only through pre-computed datasets and thus fall short in producing samples with blue noise statistics. We present a Poisson disk sampling algorithm that runs in parallel and produces all samples on the fly with desired blue noise properties. Our main idea is to subdivide the sample domain into grid cells and we draw samples concurrently from multiple cells that are sufficiently far apart so that their samples cannot conflict one another. We present a parallel implementation of our algorithm running on a GPU with constant cost per sample and constant number of computation passes for a target number of samples. Our algorithm also works in arbitrary dimension, and allows adaptive sampling from a user-specified importance field. Furthermore, our algorithm is simple and easy to implement, and runs faster than existing techniques.
Backward steps in rigid body simulation
Authors: Twigg Christopher D. , James Doug L.
Published: August 2008

Physically based simulation of rigid body dynamics is commonly done by time-stepping systems
forward
in time. In this paper, we propose methods to allow time-stepping rigid body systems
back-ward
in time. Unfortunately, reverse-time integration of rigid bodies involving frictional contact is mathematically ill-posed, and can lack unique solutions. We instead propose time-reversed rigid body integrators that can sample
possible
solutions when unique ones do not exist. We also discuss challenges related to dissipation-related energy gain, sensitivity to initial conditions, stacking, constraints and articulation, rolling, sliding, skidding, bouncing, high angular velocities, rapid velocity growth from micro-collisions, and other problems encountered when going against the usual flow of time.
Real-time motion retargeting to highly varied user-created morphologies
Authors: Hecker Chris , Raabe Bernd , Enslow Ryan W. , DeWeese John , Maynard Jordan , van Prooijen Kees
Published: August 2008

Character animation in video games---whether manually keyframed or motion captured---has traditionally relied on codifying skeletons early in a game's development, and creating animations rigidly tied to these fixed skeleton morphologies. This paper introduces a novel system for animating characters whose morphologies are unknown at the time the animation is created. Our authoring tool allows animators to describe motion using familiar posing and key-framing methods. The system records the data in a morphology-independent form, preserving both the animation's structural relationships and its stylistic information. At runtime, the generalized data are applied to specific characters to yield pose goals that are supplied to a robust and efficient inverse kinematics solver. This system allows us to animate characters with highly varying skeleton morphologies that did not exist when the animation was authored, and, indeed, may be radically different than anything the original animator envisioned.
Animating oscillatory motion with overlap
Authors: Kass Michael , Anderson John
Published: August 2008

Oscillatory motion is ubiquitous in computer graphics, yet existing animation techniques are ill-suited to its authoring. We introduce a new type of spline for this purpose, known as a "Wiggly Spline." The spline generalizes traditional piecewise cubics when its resonance and damping are set to zero, but creates oscillatory animation when its resonance and damping are changed. The spline provides a combination of direct manipulation and physical realism. To create overlapped and propagating motion, we generate phase shifts of the Wiggly Spline, and use these to control appropriate degrees of freedom in a model. The phase shifts can be created directly by procedural techniques or through a paint-like interface. A further option is to derive the phase shifts statistically by analyzing a time-series of a simulation. In this case, the Wiggly Spline makes it possible to canonicalize a simulation, generalize it by providing frequency and damping controls and control it through direct manipulation.