bluuebunny/crossref_metadata_2025 huggingface dataset:
A double-panel active segmented partition module using decoupled analog feedback controllers: Numerical model
Authors: Sagers Jason D. , Leishman Timothy W. , Blotter Jonathan D.
Published: June 2009

Low-frequency sound transmission has long plagued the sound isolation performance of lightweight partitions. Over the past 2 decades, researchers have investigated actively controlled structures to prevent sound transmission from a source space into a receiving space. An approach using active segmented partitions (ASPs) seeks to improve low-frequency sound isolation capabilities. An ASP is a partition which has been mechanically and acoustically segmented into a number of small individually controlled modules. This paper provides a theoretical and numerical development of a single ASP module configuration, wherein each panel of the double-panel structure is independently actuated and controlled by an analog feedback controller. A numerical model is developed to estimate frequency response functions for the purpose of controller design, to understand the effects of acoustic coupling between the panels, to predict the transmission loss of the module in both passive and active states, and to demonstrate that the proposed ASP module will produce bidirectional sound isolation.
Lamb mode spectra versus the Poisson ratio in a free isotropic elastic plate
Authors: Royer Daniel , Clorennec Dominique , Prada Claire
Published: June 2009

The variation, with material parameters, of Lamb modes is investigated. Vibration spectra of traction-free elastic plates are generally presented, for a given isotropic material, as a set of dispersion curves corresponding to the various Lamb mode branches. Here, the spectrum variations, with the Poisson ratio ν, are plotted in a dimensionless co-ordinate system in the form of a bundle of curves for each Lamb mode. Except for the fundamental anti-symmetric mode A0, this representation highlights the same behavior for all Lamb modes. VT denoting the shear wave velocity, the (ω,k) plane can be divided into two angular sectors separated by the line of slope VT2. In the upper one, corresponding to a phase velocity V=ω∕k larger than VT2, dispersion curves are very sensitive to the plate material parameters. In the lower sector (V<VT2) all the branches, whatever the value of the Poisson ratio (0≤ν<0.5), are gathered into a thin pencil. Moreover, curves of a given bundle cross the boundary line at coincidence points equally spaced. These properties and a specific behavior observed for ν=0 are explained in terms of Lamé wave solutions of the characteristic equations of Lamb modes.
A model for sound absorption by spheroidal particles
Authors: Hipp Alexander K.
Published: June 2009

This paper describes a mathematical model for the scattering of acoustic waves in dispersions of prolate or oblate non-spherical particles. Based on fundamental equations of change for mass, momentum, and energy, wave equations are derived and solved in spheroidal coordinates. The examination of the boundary-value problem of an aligned spheroidal particle in a continuous medium, excited by a plane wave, leads to a description of the viscoinertial, thermal, and diffractive phenomena. The model is analogous to the Epstein–Carhart–Allegra–Hawley theory for spherical particles, and suggests itself for studying non-sphericity in the acoustic analysis of industrial dispersions.
Radiation force of a helicoidal Bessel beam on a sphere
Authors: Marston Philip L.
Published: June 2009

The partial-wave series for the scattering of an acoustic helicoidal Bessel beam by a sphere centered on the axis of the beam is applied to the calculation of the acoustic radiation force by the beam on the sphere in an inviscid fluid. The term “helicoidal” refers to a type of beam having an axial amplitude null and an azimuthal phase gradient. Such a beam is known as an acoustic vortex and only the case of a vortex having a unit magnitude topological charge is considered. There is no monopole contribution to the radiation force. Radiation force examples are computed for a soft sphere, a fixed rigid sphere, a movable rigid sphere, an aluminum sphere in water, and an acrylic sphere in water. Beam parameters are found for the rigid sphere and the aluminum and acrylic cases in which the radiation force is directed opposite the propagation direction of the beam. Negative radiation forces appear to be associated with relatively weak scattering into the backward hemisphere. Some aspects of the low frequency scattering of plane waves and helicoidal Bessel beams are examined for movable rigid spheres.
Gaussian-noise discrimination and its relation to auditory object formation
Authors: Goossens Tom , van de Par Steven , Kohlrausch Armin
Published: June 2009

This study used a same/different experiment to assess the ability of human listeners to discriminate Gaussian-noise tokens with a spectral range of 350–850 Hz and a duration of 50 ms. For this duration, discrimination ability is high. However, when an identical 200-ms noise fringe with the same statistical properties as the 50-ms target tokens is appended to the end of the two target tokens, listeners show very poor discrimination. It was investigated whether altering the properties of the fringes with respect to those of the target improved the ability to discriminate the target tokens. This method was used to investigate the influence of changing fringe properties such as spectral range, level, interaural level difference, and interaural time delay on discrimination performance for the target. Spectral and temporal separation showed the strongest improvements, whereas no effect was found for doubling the fringe bandwidth, 5-dB level increases or decreases, or 10 dB interaural level differences. In the second experiment, subjects were asked to indicate whether they perceived one or two auditory objects for these stimuli. The results of the two experiments indicate that perceiving two objects is a necessary but not sufficient condition for good target discrimination.
Interaural correlation and the binaural summation of loudness
Authors: Edmonds Barrie A. , Culling John F.
Published: June 2009

The effect of interaural correlation (ρ) on the loudness for noisebands was measured using a loudness-matching task in naïve listeners. The task involved a sequence of loudness comparisons for which the intensity of one stimulus in a given comparison was varied using a one-up-one-down adaptive rule. The task provided an estimate of the level difference (in decibels) for which two stimulus conditions have equal loudness, giving measures of loudness difference in equivalent decibel units (dBequiv). Concurrent adaptive tracks measured loudness differences between ρ=1, 0, and −1 and between these binaural stimuli and the monaural case for various noisebands. For all noisebands, monaural stimuli required approximately 6dB higher levels than ρ=1 for equal loudness. For most noisebands, ρ=1 and ρ=−1 were almost equal in loudness, with ρ=−1 being slightly louder in the majority of measurements, while ρ=0 was about 2dBequiv louder than ρ=1 or ρ=−1. However, noisebands with significant high-frequency energy showed smaller differences: for 3745–4245Hz, ρ=0 was only about 0.85dBequiv louder than ρ=±1, and for 100–5000Hz it was non-significantly louder (perhaps 0.7dBequiv).
The acquisition of Korean word-initial stops
Authors: Kim Minjung , Stoel-Gammon Carol
Published: June 2009

A number of studies have investigated acquisition of stop voicing contrast in various languages by voice onset time measurement. Korean stops, however, are all voiceless word-initially and are differentiated by multiple acoustic-phonetic parameters resulting in a three-way contrast (fortis, aspirated, and lenis). The present study examines developmental patterns of Korean word-initial stops produced by 40 Korean children aged 2;6 (year; month), 3;0, 3;6, and 4;0 years, and compare the children’s productions to those of 10 female adults. Voice onset time, fundamental frequency, and amplitude difference between the first and second harmonics of the post-stop vowel are obtained from monosyllabic near-minimal triplets at three places of articulation (labial, alveolar, and velar). Acoustic measures of children’s productions reveal both universal phonetic patterns and phonetic variation associated with articulatory complexity specific to Korean. Language-specific fundamental frequency variation begins to emerge as early as 2;6, but appears to be mastered later than the voice onset time distinction. In comparison to the adults, young Korean children exhibit greater overlap across stop categories, and the acoustic overlap decreases over age. Results suggest that language-specific phonetic details as well as universal patterns should be examined to provide a better understanding of the speech sound development of a given language.
Modeling the dynamics of a vibrating string with a finite distributed unilateral constraint: Application to the sitar
Authors: Vyasarayani Chandrika P. , Birkett Stephen , McPhee John
Published: June 2009

The free vibration response of an ideal string impacting a distributed parabolic obstacle located at its boundary has been analyzed, the goal being to understand and simulate a sitar string. The portion of the string in contact with the obstacle is governed by a different partial differential equation (PDE) from the free portion represented by the classical string equation. These two PDEs and corresponding boundary conditions, along with the transversality condition that governs the dynamics of the moving boundary, are obtained using Hamilton’s principle. A Galerkin approximation is used to convert them into a system of nonlinear ordinary differential equations, with lower mode-shapes parametrized with respect to the location of the moving boundary as basis functions. This system is solved numerically and the behavior of the string studied from simulations. The advantages and disadvantages of the proposed method are discussed in comparison to the penalty approach for simulating wrapping contacts. Simulations with bridge-string parameters consistent with the configuration of a real sitar show that any degree of obstacle wrapping may occur during normal playing. Finally, the model is used to investigate the mechanism behind the generation of the buzzing tone in a sitar.
Active noise control in a pure tone diffuse sound field using virtual sensing
Authors: Moreau D. J. , Ghan J. , Cazzolato B. S. , Zander A. C.
Published: June 2009

Local active noise control systems generate a zone of quiet at the physical error sensor using one or more secondary sources to cancel acoustic pressure and its spatial derivatives at the sensor location. The resulting zone of quiet is generally limited in size and as such, placement of the error sensor at the location of desired attenuation is required, which is often inconvenient. Virtual acoustic sensors overcome this by projecting the zone of quiet away from the physical sensor to a remote location. The work described here investigates the effectiveness of using virtual sensors in a pure tone diffuse sound field. Stochastically optimal virtual microphones and virtual energy density sensors are developed for use in diffuse sound fields. Analytical expressions for the controlled sound field generated with a number of control strategies are presented. These expressions allow the optimal control performance to be predicted. Results of numerical simulations and experimental measurements made in a reverberation chamber are also presented and compared.
Homogeneous and sandwich active panels under deterministic and stochastic excitation
Authors: Rohlfing J. , Gardonio P.
Published: June 2009

In this paper an element-based model is used to predict the structural response and sound radiation of two smart panels excited by (a) an acoustic plane wave, (b) a stochastic acoustic diffuse field, and (c) a turbulent boundary layer. The first panel is made of aluminum, while the second is a composite sandwich panel with equivalent static stiffness but four times lower mass per unit area. The panels are equipped with 16 decentralized velocity feedback control loops using idealized point force actuators. In contrast to previous studies on smart panels, the analysis is extended to the upper end of the audio frequency range. In this frequency region the response and sound radiation of the panels strongly depend on the spatial characteristics of the excitation field and the sound radiation properties with respect to the bending wavelength on the panels. Considerable reduction in structural response and sound radiation is predicted for the low audio frequency range where the panel response is dominated by well separated resonances of low order structural modes. It is also found that some reduction can be achieved around acoustic and convective coincidence regions.
Controller design and consonantal contrast coding using a multi-finger tactual display
Authors: Israr Ali , Meckl Peter H. , Reed Charlotte M. , Tan Hong Z.
Published: June 2009

This paper presents the design and evaluation of a new controller for a multi-finger tactual display in speech communication. A two-degree-of-freedom controller consisting of a feedback controller and a prefilter and its application in a consonant contrasting experiment are presented. The feedback controller provides stable, fast, and robust response of the fingerpad interface and the prefilter shapes the frequency-response of the closed-loop system to match with the human detection-threshold function. The controller is subsequently used in a speech communication system that extracts spectral features from recorded speech signals and presents them as vibrational-motional waveforms to three digits on a receiver’s left hand. Performance from a consonantal contrast test suggests that participants are able to identify tactual cues necessary for discriminating consonants in the initial position of consonant-vowel-consonant (CVC) segments. The average sensitivity indices for contrasting voicing, place, and manner features are 3.5, 2.7, and 3.4, respectively. The results show that the consonantal features can be successfully transmitted by utilizing a broad range of the kinesthetic-cutaneous sensory system. The present study also demonstrates the validity of designing controllers that take into account not only the electromechanical properties of the hardware, but the sensory characteristics of the human user.
A recency effect in sound localization?
Authors: Stecker G. Christopher , Hafter Ervin R.
Published: June 2009

In a free-field pointing task, listeners localized trains of 4–32 spatially distributed Gabor clicks (narrowband impulses) centered at 4-kHz carrier frequency and repeating at an interval of 5ms. Multiple regression coefficients estimated the perceptual “weight” applied to each click in a train during location judgments. Temporal weighting functions obtained in this way exhibited two key features: onset dominance, as evidenced by high weight on the initial click, and “upweighting” of late-arriving sound, as evidenced by weights that gradually increased over the duration of each click-train. Across all tested click-train durations, and despite randomly varying the durations from trial to trial, the greatest post-onset weights were consistently found for clicks at or near the offset. The results imply a special importance of late-arriving sound rather than feedforward recovery from onset dominance, and are broadly consistent with recency effects resulting from temporal integration.
Attenuation and dispersion of antiplane shear waves due to scattering by many two-dimensional cavities
Authors: Kawahara Jun , Ohno Taichi , Yomogida Kiyoshi
Published: June 2009

Propagation and scattering of antiplane shear waves within media with two-dimensional cavities are numerically simulated, and the attenuation and phase velocities are experimentally determined. The results are compared with the predictions by the Foldy theory and its three corrected versions. If the cavity concentrations are small such as 0.02, the differences among the theoretical predictions are insignificant, and every theory is consistent with the experimental results. For higher concentrations such as 0.1, the differences become significant, but there are no objective grounds to say that any of the corrected versions of the Foldy theory works better than the original. If the error tolerance is as high as 10%, the simple Foldy formula may remain useful for concentrations up to about 0.1.
Acoustical model and theory for predicting effects of environmental noise on people
Authors: Kryter Karl D.
Published: June 2009

The Schultz [(1978). J. Acoust. Soc. Am. 64, 377–405]; Fidell et al. [(1991). J. Acoust. Soc. Am. 89, 221–233] and Finegold et al. [(1994). Noise Control Eng. 42, 25–30] curves present misleading research information regarding DENL/DENL levels of environmental noises from transportation vehicles and the impact of annoyance and associated adverse effects on people living in residential areas. The reasons are shown to be jointly due to (a) interpretations of early research data, (b) plotting of annoyance data for noise exposure from different types of transportation vehicles on a single set of coordinates, and (c) the assumption that the effective, as heard, levels of noise from different sources are proportional to day, night level (DNL)/day, evening night level (DENL) levels measured at a common-point outdoors. The subtraction of on-site attenuations from the measured outdoor levels of environmental noises used in the calculation of DNL/DENL provides new metrics, labeled EDNL/EDENL, for the calculation of the effective exposure levels of noises perceived as equaling annoying. Predictions of judged annoyance in residential areas from the noises of transportation vehicles are made with predicted errors of <1dB EDNL/EDENL, compared to errors ranging from ∼6to∼14dB by DNL/DENL. A joint neurological, physiological, and psychological theory, and an effective acoustical model for the prediction of public annoyance and related effects from exposures to environment noises are presented.
Design optimization of condenser microphone: A design of experiment perspective
Authors: Tan Chee Wee , Miao Jianmin
Published: June 2009

A well-designed condenser microphone backplate is very important in the attainment of good frequency response characteristics—high sensitivity and wide bandwidth with flat response—and low mechanical-thermal noise. To study the design optimization of the backplate, a 26 factorial design with a single replicate, which consists of six backplate parameters and four responses, has been undertaken on a comprehensive condenser microphone model developed by Zuckerwar. Through the elimination of insignificant parameters via normal probability plots of the effect estimates, the projection of an unreplicated factorial design into a replicated one can be performed to carry out an analysis of variance on the factorial design. The air gap and slot have significant effects on the sensitivity, mechanical-thermal noise, and bandwidth while the slot/hole location interaction has major influence over the latter two responses. An organized and systematic approach of designing the backplate is summarized.
General perceptual contributions to lexical tone normalization
Authors: Huang Jingyuan , Holt Lori L.
Published: June 2009

Within tone languages that use pitch variations to contrast meaning, large variability exists in the pitches produced by different speakers. Context-dependent perception may help to resolve this perceptual challenge. However, whether speakers rely on context in contour tone perception is unclear; previous studies have produced inconsistent results. The present study aimed to provide an unambiguous test of the effect of context on contour lexical tone perception and to explore its underlying mechanisms. In three experiments, Mandarin listeners’ perception of Mandarin first and second (high-level and mid-rising) tones was investigated with preceding speech and non-speech contexts. Results indicate that the mean fundamental frequency (f0) of a preceding sentence affects perception of contour lexical tones and the effect is contrastive. Following a sentence with a higher-frequency mean f0, the following syllable is more likely to be perceived as a lower frequency lexical tone and vice versa. Moreover, non-speech precursors modeling the mean spectrum of f0 also elicit this effect, suggesting general perceptual processing rather than articulatory-based or speaker-identity-driven mechanisms.
Accuracy of acoustic ear canal impedances: Finite element simulation of measurement methods using a coupling tube
Authors: Schmidt Sebastian , Hudde Herbert
Published: June 2009

Acoustic impedances measured at the entrance of the ear canal provide information on both the ear canal geometry and the terminating impedance at the eardrum, in principle. However, practical experience reveals that measured results in the audio frequency range up to 20 kHz are frequently not very accurate. Measurement methods successfully tested in artificial tubes with varying area functions often fail when applied to real ear canals. The origin of these errors is investigated in this paper. To avoid mixing of systematical and other errors, no real measurements are performed. Instead finite element simulations focusing on the coupling between a connecting tube and the ear canal are regarded without simulating a particular measuring method in detail. It turns out that realistic coupling between the connecting tube and the ear canal causes characteristic shifts of the frequencies of measured pressure minima and maxima. The errors in minima mainly depend on the extent of the area discontinuity arising at the interface; the errors in maxima are determined by the alignment of the tube with respect to the ear canal. In summary, impedance measurements using coupling tubes appear questionable beyond 3 kHz.
Stability of monitoring weak changes in multiply scattering media with ambient noise correlation: Laboratory experiments
Authors: Hadziioannou Céline , Larose Eric , Coutant Olivier , Roux Philippe , Campillo Michel
Published: June 2009

Previous studies have shown that small changes can be monitored in a scattering medium by observing phase shifts in the coda. Passive monitoring of weak changes through ambient noise correlation has already been applied to seismology, acoustics, and engineering. Usually, this is done under the assumption that a properly reconstructed Green function (GF), as well as stable background noise sources, is necessary. In order to further develop this monitoring technique, a laboratory experiment was performed in the 2.5 MHz range in a gel with scattering inclusions, comparing an active (pulse-echo) form of monitoring to a passive (correlation) one. Present results show that temperature changes in the medium can be observed even if the GF of the medium is not reconstructed. Moreover, this article establishes that the GF reconstruction in the correlations is not a necessary condition: The only condition to monitoring with correlation (passive experiment) is the relative stability of the background noise structure.
The mode shapes of a tennis racket and the effects of vibration dampers on those mode shapes
Authors: Timme Nicholas , Morrison Andrew
Published: June 2009

The vibrational behavior of a tennis racket was studied using a speckle-pattern interferometry system. Specifically, the first 12 mode shapes of a racket are shown and discussed. In addition, the speckle-pattern interferometry system was used to compare the effects of four commercially available vibration damping systems. It was found that these vibration dampers produce a variety of effects on the vibrational behavior of the racket, though these effects may not be noticeable during play.
Effects of spectral smearing and temporal fine structure degradation on speech masking release
Authors: Gnansia Dan , Péan Vincent , Meyer Bernard , Lorenzi Christian
Published: June 2009

This study assessed the effects of spectral smearing and temporal fine structure (TFS) degradation on masking release (MR) (the improvement in speech identification in amplitude-modulated compared to steady noise observed for normal-hearing listeners). Syllables and noise stimuli were processed using either a spectral-smearing algorithm or a tone-excited vocoder. The two processing schemes simulated broadening of the auditory filters by factors of 2 and 4. Simulations of the early stages of auditory processing showed that the two schemes produced comparable excitation patterns; however, fundamental frequency (F0) information conveyed by TFS was degraded more severely by the vocoder than by the spectral-smearing algorithm. Both schemes reduced MR but, for each amount of spectral smearing, the vocoder produced a greater reduction in MR than the spectral-smearing algorithm, consistent with the effects of each scheme on F0 representation. Moreover, the effects of spectral smearing on MR produced by the two schemes were different for manner and voicing. Finally, MR data for listeners with moderate hearing loss were well matched by MR data obtained for normal-hearing listeners with vocoded stimuli, suggesting that impaired frequency selectivity alone may not be sufficient to account for the reduced MR observed for hearing-impaired listeners.
A new safety parameter for diagnostic ultrasound thermal bioeffects: Safe use time
Authors: Karagoz Irfan , Kartal Mustafa K.
Published: June 2009

It is widely accepted that diagnostic ultrasound has the potential to elevate the temperature of tissue being scanned. Because both the maximum value of the temperature rise and the temporal profile of that rise are necessary to estimate the risk correctly, the temperature rise [ΔT(t)] at an observation point for an exposure condition is presumed to have two components, that is, ΔT(t)=ΔTmaxX(t). The amplitude component ΔTmax is the maximum value of ΔT(t), and the exposure time component X(t) represents the time dependency of that ΔT(t). Ninety-six cases were investigated to obtain the proposed ΔT(t) model at six frequencies, four source diameters, and four f-numbers. Then, using the relative change in the rate of induction of a thermal effect due to ultrasound exposure that produces ΔT(t) different from a threshold exposure, the safe use time (SUT) model was constructed. SUT informs the user of the maximum duration of exposure in a region at a particular output level that would be no more hazardous than scanning at the threshold exposure. Using the SUT model, high power ultrasound can be applied for a short time so that the user can improve imaging performance while staying within safe limits.
Hole distribution in phononic crystals: Design and optimization
Authors: Romero-García V. , Sánchez-Pérez J. V. , García-Raffi L. M. , Herrero J. M. , García-Nieto S. , Blasco X.
Published: June 2009

An exhaustive study has been made into the potential improvement in attenuation and focusing of phononic crystal arrays resulting from the deliberate creation of vacancies. Use is made of a stochastic search algorithm based on evolutionary algorithms called the epsilon variable multi-objective genetic algorithm which, in conjunction with the application of multiple scattering theory, enables the design of devices for effectively controlling sound waves. Several parameters are analyzed, including the symmetries used in the distribution of holes and the optimum number of holes. The validity and utility of the general rules obtained have been confirmed experimentally.
Characterization of the trabecular bone structure using frequency modulated ultrasound pulse
Authors: Lin Wei , Xia Yi , Qin Yi-Xian
Published: June 2009

The objective of this study was to investigate the efficacy of modulated ultrasound signals in the measurement of bone properties as an early indicator of osteoporosis. Twenty-one trabecular bone cubes were harvested from sheep femoral condyles and the cube axes corresponded to the anatomic superior-inferior (SI), antero-posterior (AP), and medio-lateral (ML) orientations. Micro-CT measurements were made on those samples to obtain bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). Ultrasound tests were performed in the three orthogonal orientations using pulse and frequency modulated ultrasound. The comparison of the frequency modulated attenuation (FMA) with the broadband ultrasound attenuation (BUA) was made within the frequency band between 300 and 700kHz. Results showed that FMA demonstrated higher correlations to the trabecular structure properties in the SI orientation (R2=0.84 for BV/TV, R2=0.77 for Tb.Th, R2=0.7 for Tb.Sp) than BUA (R2=0.30 for BV/TV, R2=0.27 for Tb.Th, R2=0.33 for Tb.Sp). In the AP orientation, FMA had higher correlation to Tr.Sp (R2=0.64) than BUA (R2=0.48), and relatively lower correlation to BV/TV (R2=0.48) and Tb.Th (R2=0.31) than BUA (R2=0.64 for BV/TV and R2=0.58 for Tb.Th). The results suggested that FMA could be a new ultrasound index for bone properties assessment.
A sound field separation technique based on measurements with pressure-velocity probes
Authors: Zhang Yong-Bin , Chen Xin-Zhao , Jacobsen Finn
Published: June 2009

It has recently been shown that statistically optimized near field acoustic holography based on measurement with an array of pressure-velocity transducers makes it possible to distinguish between sources on the two sides of the array and thus suppress the influence of a disturbing source [F. Jacobsen and V. Jaud, J. Acoust. Soc. Am. 121, 1550–1558 (2007)]. However, the suggested technique uses a transfer matrix optimized for the source under test and may be expected to perform less well when the disturbing source is not placed symmetrically on the other side of the array, and this will usually be the case. In this letter, a modified method is presented.
Flow noise from spoilers in ducts
Authors: Mak Cheuk Ming , Wu Jia , Ye Chao , Yang Jun
Published: June 2009

Measurements of flow noise produced by strip spoilers in the air duct of a ventilation system and radiated from an open exhaust termination unit into a reverberation chamber have been made. The results agree with the previous work of Nelson and Morfey [J. Sound Vib. 79, 263–289 (1981)]. Prediction of flow noise produced by multiple spoilers requires the values of the ratio of the mean drag forces that act on the spoilers, the phase relationship between the fluctuating drag forces that act on the spoilers, and the coherence function of the noise sources. The latter is empirically derived from the measured results, where the predicted results agree well with the experimental results within 3dB at most frequencies except for very high frequencies.
A note on the effects of roughness on acoustic propagation past curved rough surfaces
Authors: Whelan Andrew , Chambers James P.
Published: June 2009

Previous work on sound propagation past curved rough rigid surfaces demonstrated substantial changes in the insertion loss in the shadow zone due to the roughness ranging from +6 to −20 dB from their smooth counterparts. These previous data also lead to new propagation modeling efforts to incorporate the effects of roughness via an impedance model but the data and modeling efforts were limited to a narrow range of roughness and hill sizes. The current effort was designed to expand the range of roughness and hill sizes in order to explore the range of influence of the roughness. The work presented here confirms the effects of surface roughness as observed in previous work and indicates where the effects of roughness begin to emerge as well as where they transition between decreasing the insertion loss to increasing the insertion loss.
Did Warfare Among Ancestral Hunter-Gatherers Affect the Evolution of Human Social Behaviors?
Authors: Bowles Samuel
Published: June 2009

War and Peace?

Modern behavior, including the development of advanced tools, musical instruments, and art, seems to have arisen in humans in stages. The earliest hints are seen in Africa about 70 to 90,000 years ago, but later in Europe about 45,000 years ago. An ongoing discussion centers on the origins and significance of human prosociality. During early human development, could the benefits of altruistic behavior have outweighed its costs (see the Perspective by

Mace

)?
Bowles
(p.
1293
) constructed a model of conflict between groups of humans and extracted estimates of the critical parameters from archaeological and ethnographic data sets. Provocatively, it appears that warfare might have enhanced the emergence and persistence of altruistic behavior.

Powell
et al.

(p.
1298
) present a population model that shows that the development of modern behaviors may rely on the attainment of critical population densities and migratory patterns required for stable cultural transmission. The model is consistent with genetic inferences of population dynamics in Africa and Europe and suggests that these cultural changes may not solely reflect increased cognitive evolution.
Regulation of Hypoxia-Inducible Factor 2α Signaling by the Stress-Responsive Deacetylase Sirtuin 1
Authors: Dioum Elhadji M. , Chen Rui , Alexander Matthew S. , Zhang Quiyang , Hogg Richard T. , Gerard Robert D. , Garcia Joseph A.
Published: June 2009

Coordinating Response to Stress

Sirtuin 1 (Sirt1) (a protein deacetylase implicated in aging), senses the metabolic state of the cell and modulates the activity of substrate proteins that in turn regulate cellular transcriptional responses. In response to hypoxia, cells activate the transcription factor hypoxia-inducible factor 2 alpha (HIF-2α), which promotes adaptive responses.

Dioum
et al.

(p.
1289
; see the Perspective by

Guarente

) discovered a link between these two important cellular stress response systems—HIF-2α is a substrate of Sirt1. Direct interaction between Sirt1 and HIF-2α results in deacetylation of HIF-2α and enhances its transcriptional activity. In mice lacking Sirt1, the ability of HIF-2α to promote synthesis of the growth factor erythropoietin is diminished. Thus, the regulation of HIF-2α helps to coordinate responses of cells to various stresses.
McsB Is a Protein Arginine Kinase That Phosphorylates and Inhibits the Heat-Shock Regulator CtsR
Authors: Fuhrmann Jakob , Schmidt Andreas , Spiess Silvia , Lehner Anita , Turgay Kürşad , Mechtler Karl , Charpentier Emmanuelle , Clausen Tim
Published: June 2009

Transcriptional Repressor Dissected

Living organisms have quality-control mechanisms to eliminate proteins damaged by environmental stresses. In the model organism
Bacillus subtilis
, the transcriptional repressor CtsR controls the expression of genes that are key to the heat-shock response. CtsR is activated by the kinase McsB to allow transcription of stress response genes, however, the mechanism of activation is unclear.

Fuhrmann
et al.

(p.
1323
) now describe structural and biochemical studies showing that McsB inhibits DNA binding of CtsR by specifically phosphorylating arginine residues in its DNA binding domain. This study provides a basis for exploring a potential wider role of arginine phosphorylation in prokaryotic and eukaryotic transcriptional regulation.
Late Pleistocene Demography and the Appearance of Modern Human Behavior
Authors: Powell Adam , Shennan Stephen , Thomas Mark G.
Published: June 2009

War and Peace?

Modern behavior, including the development of advanced tools, musical instruments, and art, seems to have arisen in humans in stages. The earliest hints are seen in Africa about 70 to 90,000 years ago, but later in Europe about 45,000 years ago. An ongoing discussion centers on the origins and significance of human prosociality. During early human development, could the benefits of altruistic behavior have outweighed its costs (see the Perspective by

Mace

)?
Bowles
(p.
1293
) constructed a model of conflict between groups of humans and extracted estimates of the critical parameters from archaeological and ethnographic data sets. Provocatively, it appears that warfare might have enhanced the emergence and persistence of altruistic behavior.

Powell
et al.

(p.
1298
) present a population model that shows that the development of modern behaviors may rely on the attainment of critical population densities and migratory patterns required for stable cultural transmission. The model is consistent with genetic inferences of population dynamics in Africa and Europe and suggests that these cultural changes may not solely reflect increased cognitive evolution.
Endogenous Activation Patterns of Cdc42 GTPase Within
Drosophila
Embryos
Authors: Kamiyama Daichi , Chiba Akira
Published: June 2009

Signaling Signature in Situ

Upon activation, signaling proteins trigger response pathways, but knowing when and where they are activated within animals has been difficult.
Kamiyama and Chiba
(p.
1338
) describe an in vivo bioprobe imaging technology that reveals the restricted pattern for endogenous activities of a ubiquitously expressed signaling protein Cdc42 within individual cells and in whole animals. Genetic experiments confirmed that it is the activation within individual cells and tissues, not simply the protein's presence, which defines its function during development.
Disulfide Formation in the ER and Mitochondria: Two Solutions to a Common Process
Authors: Riemer Jan , Bulleid Neil , Herrmann Johannes M.
Published: June 2009

Two Ways to Redox Regulation

Eukaryotic cells control the redox environment within their cytoplasm to be generally reducing. However, the endoplasmic reticulum provides an oxidizing environment for secretory and membrane proteins. In addition, a subcompartment of mitochondria—the powerhouses of the cell—also generates an oxidizing environment for constituent and itinerant proteins.

Riemer
et al.

(p.
1284
) review the current understanding of both eukaryotic redox machineries and highlight their implications for the biogenesis and regulation of protein function, focusing on the impact of these systems on health and disease.
Mechanoenzymatic Cleavage of the Ultralarge Vascular Protein von Willebrand Factor
Authors: Zhang Xiaohui , Halvorsen Kenneth , Zhang Cheng-Zhong , Wong Wesley P. , Springer Timothy A.
Published: June 2009

Dissecting VWF's Thrombogenic Potential

Von Willebrand factor (VWF) is secreted from cells in an ultralarge form (ULVWF) in response to thrombogenic stimuli. Shear forces expose a binding site for platelets, enabling formation of a hemostatic plug. The thrombogenic potential of VWF correlates with its length and is regulated by proteolytic cleavage of the A2 domain.

Zhang
et al.

(p.
1330
; see the Perspective by

Gebhardt and Rief

) now combine single molecule data and polymer dynamics theory to show that shear forces in the circulation are sufficient to unfold the A2 domain and allow cleavage of multimers with more than about 200 monomers. The A2 domain may thus represent the “shear bolt” of VWF, unfolding when multimers experience high forces to allow cleavage and down-regulation of thrombogenic potential.
Epigenetic Temporal Control of Mouse
Hox
Genes in Vivo
Authors: Soshnikova Natalia , Duboule Denis
Published: June 2009

Hox
Clocks

Homeobox
or
Hox
genes are historically significant for demonstrating evolutionary conservation and homology in developmentally important genes. In addition, in many species, the
Hox
genes are fundamental to the organization of the embryo. Modifications in the regulation of their colinear, temporal activation may represent a way of altering their expression patterns and to elaborate body plans during evolution.
Soshnikova and Duboule
(p.
1320
) now report highly dynamic modifications of chromatin marks along with progressive
Hox
gene activation during axial extension in the mouse. This work supports the proposal that the “
Hox
clock” may be controlled, at least in part, by epigenetic mechanisms.
Observation of Single Colloidal Platinum Nanocrystal Growth Trajectories
Authors: Zheng Haimei , Smith Rachel K. , Jun Young-wook , Kisielowski Christian , Dahmen Ulrich , Alivisatos A. Paul
Published: June 2009

Mergers and Acquisitions

The crystallization of small molecules or polymers is often described in terms of a nucleation stage, where initial clusters form, followed by a distinct growth stage. Growth can come from the addition of unbound molecules, or through “Ostwald ripening” where larger crystals grow at the expense of smaller ones due to thermodynamic effects.

Zheng
et al.

(p.
1309
) studied the growth of platinum nanocrystals inside a transmission electron microscope using a special liquid cell, allowing observation of crystal growth in situ. Both monomer addition to growing particles and the coalescence of two particles were observed. The specific growth mechanism appeared to be governed by the size of each of the particles. The combination of growth processes makes it possible for an initially broad distribution of particles to narrow into an almost uniform one.
Social Transmission of a Host Defense Against Cuckoo Parasitism
Authors: Davies Nicholas B. , Welbergen Justin A.
Published: June 2009

Defeating the Cuckoo

Brood parasite-host interactions show ongoing antagonistic coevolution. What mediates rapid behavioral changes that do not reflect genetic change?
Davies and Welbergen
(p.
1318
) show that reed warblers learn from their neighbors to behave aggressively toward models of the parasitic common cuckoo. Furthermore, reed warblers seem to be predisposed to learn to respond to cuckoos as enemies: Hosts that witnessed neighbors mobbing a harmless parrot model did not increase their aggression toward a cuckoo model. Thus, birds have templates for threats, and relevant antithreat behaviors can be turned on or off depending on social experience.
Rhes, a Striatal Specific Protein, Mediates Mutant-Huntingtin Cytotoxicity
Authors: Subramaniam Srinivasa , Sixt Katherine M. , Barrow Roxanne , Snyder Solomon H.
Published: June 2009

Rhes-olving Huntington's Disease?

Huntington's disease (HD) is caused by a single dominant mutation of huntingtin (Htt), a protein that occurs in all tissues of the body and that is uniformly distributed throughout the brain. How mutant Htt (mHtt) selectively damages striatal neurons with negligible alterations elsewhere has been a mystery.

Subramaniam
et al.

(p.
1327
) show that Rhes, a small G protein very highly localized to the striatum, binds mHtt and augments its neurotoxicity. Rhes promotes sumoylation of mHtt, leading to its disaggregation and augmented cytotoxicity. The findings establish how mHtt selectively kills cells in the striatum and suggest that Rhes-Htt binding might provide a therapeutic target.
Watching Nanocrystals Grow
Authors: Murray Christopher B.
Published: June 2009

In situ transmission electron microscopy has revealed unprecedented detail in the growth of platinum nanocrystals.
Hypoxic Hookup
Authors: Guarente Leonard
Published: June 2009

The range of protective effects that a sirtuin deacetylase affords to cells and organisms under stressful conditions continues to grow.
Force Signaling in Biology
Authors: Christof J. , Gebhardt M. , Rief Matthias
Published: June 2009

Single-molecule studies are revealing the biomolecular processes initiated when biological systems sense mechanical forces.
A Story of Symbiosis
Beanworld
Book 1: Wahoolazuma!

by Larry Marder

Dark Horse, Milwaukie, OR, 2009. 272 pp., illus. $19.95. ISBN 9781595822406.
Beanworld
Book 2: A Gift Comes!

by Larry Marder

Dark Horse, Milwaukie, OR, August 2009. 272 pp., illus. $19.95. ISBN 9781595822994.
Authors: Boerner Leigh Krietsch
Published: June 2009

The adventures of the Beans in Marder's fanciful world reflect aspects of ecology, culture, invention, and the scientific method.
Chinese Scientists Hope to Make Deepest, Darkest Dreams Come True
Authors: Normile Dennis
Published: June 2009

After months of negotiations, on 8 May Tsinghua University in Beijing signed an agreement to build the deepest underground science facility in the world, edging out—by 100 meters or so—a planned U.S. project.
European Neutron Source Finally Finds a Home
Authors: Clery Daniel
Published: June 2009

After 15 years on the drawing board, the countries interested in funding the European Spallation Source picked a site last week on which to build it in Lund, Sweden.
The Bug and the Bacterium: Interdependent Genomes
Authors: Pennisi Elizabeth
Published: June 2009

The newly sequenced DNA of the pea aphid, a common pest of legume crops, reflects a long history of give-and-take between the genomes of the bug and a tiny bacterium called
Buchnera aphidicola
, scientists reported at the Biology of Genomes meeting.
Persevering Researchers Make a Splash With Farm-Bred Tuna
Authors: Normile Dennis
Published: June 2009

A 30-year effort has paid off in raising bluefin tuna in captivity, but the benefit for wild stocks of the embattled predator may be years more away.
Scientists Get No Respect From Fishery Managers
Authors: Normile Dennis
Published: June 2009

A 2008 report on the health of the bluefin tuna stock in the East Atlantic and Mediterranean recommended setting a catch quota of 15,000 tons starting in 2009. Fishery managers responded by setting quotas of 22,000 tons in 2010, 19,950 tons in 2011, and 18,500 tons in 2012.
The Tales Told by Lonely Galaxies
Authors: Cho Adrian
Published: June 2009

To what extent is a galaxy shaped by its surroundings? To find out, astronomers are seeking the rare ones that appear to be isolated.
Results From the Science Dance Match-Up Challenge
Authors: Bohannon John
Published: June 2009

How well did you do in the Science Dance Match-Up Challenge? Compare yourself to the hundreds of other people around the world who tried to guess which of four research papers inspired which of four modern dances commissioned by AAAS.
The Fcγ Receptor IIA-R/R131 Genotype Is Associated with Severe Sepsis in Community-Acquired Pneumonia
Authors: Endeman Henrik , Cornips Marie Claire A. , Grutters Jan C. , van den Bosch Jules M. , Ruven Hendrik J. T. , van Velzen-Blad Heleen , Rijkers Ger T. , Biesma Douwe H.
Published: June 2009

Community-acquired pneumonia (CAP) can be caused by a variety of microorganisms but is most frequently associated withStreptococcus pneumoniaeand gram-negative bacteria likeHaemophilus influenzae. Encapsulated bacteria are able to escape phagocytosis, unless they are bound by immunoglobulin G2 subclass antibodies. These antibodies interact with Fcγ receptor IIa (Fcγ-RIIa), thereby facilitating opsonophagocytosis of the encapsulated bacteria. We studied the relationship between the Fcγ-RIIa-R/H131 polymorphism and the clinical course of CAP and pathogen-specific susceptibility. Regarding methodology, the Fcγ-RIIa genotype R/H131 was determined in 200 patients with CAP and in 313 healthy controls and was correlated with the clinical course, laboratory parameters, and causative microorganism. The Fcγ-RIIa-R/R131 genotype was found more frequently in patients with severe sepsis (odds ratio [OR], 2.55; 95% confidence interval [CI], 1.30 to 5.00;P< 0.01). The majority of patients in this group suffered from invasive pneumococcal disease. The duration of hospital stay was longer for patients with the Fcγ-RIIa-R/R131 genotype. Fcγ-RIIa genotypes were not associated with an increased risk of CAP in general; however, the Fcγ-RIIa-R/R131 genotype was found more frequently in patients with CAP caused byH. influenzaethan in controls (OR, 3.03; CI, 1.04 to 9.09;P< 0.05). In conclusion, the Fcγ-RIIa-R/R131 genotype is associated with severity of CAP and is more frequent in CAP caused byH. influenzae.