bluuebunny/crossref_metadata_2025 huggingface dataset:
Vesicle deformations by clusters of transmembrane proteins
Authors: Bahrami Amir Houshang , Jalali Mir Abbas
Published: February 2011

We carry out a coarse-grained molecular dynamics simulation of phospholipid vesicles with transmembrane proteins. We measure the mean and Gaussian curvatures of our protein-embedded vesicles and quantitatively show how protein clusters change the shapes of their host vesicles. The effects of depletion force and vesiculation on protein clustering are also investigated. By increasing the protein concentration, clusters are fragmented to smaller bundles, which are then redistributed to form more symmetric structures corresponding to lower bending energies. Big clusters and highly aspherical vesicles cannot be formed when the fraction of protein to lipid molecules is large.
Improved germanium n+/p junction diodes formed by coimplantation of antimony and phosphorus
Authors: Kim Jeehwan , Bedell Stephen W. , Sadana Devendra K.
Published: February 2011

Obtaining heavily-doped n-type germanium (Ge) is difficult since n-type dopant activation in Ge is limited to less than 5×1019 cm−3 which is far below the solid solubility limit of phosphorus (P) in Ge. Such poor activation has limited the rectifying properties of n+/p Ge diodes. This work is aimed at understanding the challenge of forming highly rectifying n+/p diode as well as enhancing rectification of n+/p diode by using antimony (Sb) and P coimplantation process. Enhanced n+ doping of greater than 1020 cm−3 in Ge obtained by Sb/P codoping results in enhanced rectification in Ge n+/p junction diode.
Tunnel field-effect transistor using InAs nanowire/Si heterojunction
Authors: Tomioka Katsuhiro , Fukui Takashi
Published: February 2011

We report on fabrication of tunnel field-effect transistor with III-V nanowire (NW)/Si heterojunction and surrounding-gate structure. The device fabricated by selective-area growth of an n+-InAs/undoped-InAs axial NW on a p+-Si(111) substrate showed switching behavior with an average subthreshold slope (SS) of 104 mV/dec under reverse bias condition. The switching behavior appeared under small supply voltage (Vds=50 mV). Transmission electron microscopy revealed misfit dislocation formed at the interface degraded the SS and ON-state current. Coherent growth without misfit dislocations would promise realization of steep-slope transistor with a SS of <60 mV/dec.
Design of effective kernels for spectroscopy and molecular transport: Time-dependent current–density-functional theory
Authors: Gatti Matteo
Published: February 2011

Time-dependent current–density-functional theory (TDCDFT) provides an, in principle, exact scheme to calculate efficiently response functions for a very broad range of applications. However, the lack of approximations valid for a range of parameters met in experimental conditions has so far delayed its extensive use in inhomogeneous systems. On the other side, in many-body perturbation theory accurate approximations are available, but at a price of a higher computational cost. In the present work, the possibility of combining the advantages of both approaches is exploited. In this way, an exact equation for the exchange-correlation kernel of TDCDFT is obtained, which opens the way for a systematic improvement of the approximations adopted in practical applications. Finally, an approximate kernel for an efficient calculation of spectra of solids and molecular conductances is suggested and its validity is discussed.
Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowire
Authors: Fukami S. , Suzuki T. , Nakatani Y. , Ishiwata N. , Yamanouchi M. , Ikeda S. , Kasai N. , Ohno H.
Published: February 2011

Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowires with a stack structure of Ta(1.0 nm)/CoFeB(1.2 nm)/MgO(2.0 nm)/Ta(1.0 nm) was investigated. Domain wall motion driven by adiabatic spin-transfer torque was observed at a current of about 74 μA, corresponding to a current density of 6.2×107 A/cm2. The obtained results were compared with those of a micromagnetic simulation and the spin polarization of the CoFeB was estimated to be 0.72.
Raman scattering from Ti3SiC2 single crystals
Authors: Mercier Frédéric , Chaix-Pluchery Odette , Ouisse Thierry , Chaussende Didier
Published: February 2011

The lack of single crystalline Ti3SiC2 samples is currently limiting the accurate measurement of its basic properties as its layered crystalline structure presents a very strong anisotropy. In this letter, we report the growth of pure Ti3SiC2 single crystals after a careful study of the Ti3SiC2 liquidus surface extent through thermodynamical calculations. From a Raman scattering study on those single crystals, an unambiguous assignment of most of the phonon modes has been established, giving an answer to the discrepancies existing in the literature.
A large Kerr constant polymer-stabilized blue phase liquid crystal
Authors: Rao Linghui , Yan Jin , Wu Shin-Tson , Yamamoto Shin-ichi , Haseba Yasuhiro
Published: February 2011

A polymer-stabilized blue phase liquid crystal (BPLC) composite with a large Kerr constant (K∼13.7 nm/V2) is developed and its electro-optic properties characterized. In addition to the reduced operating voltage, this BPLC also exhibits a fast response time (∼1 ms), high contrast ratio (>1000:1), and relatively small hysteresis (<6%). It will undoubtedly accelerate the emergence of BPLC for next-generation display and photonic devices.
AlGaN based deep ultraviolet light emitting diodes with high internal quantum efficiency grown by molecular beam epitaxy
Authors: Liao Yitao , Thomidis Christos , Kao Chen-kai , Moustakas Theodore D.
Published: February 2011

We report the development of AlGaN based deep ultraviolet light emitting diodes (UV-LEDs) by molecular beam epitaxy. By growing the AlGaN well layer under Ga-rich conditions to produce strong potential fluctuations, internal quantum efficiency of a quantum well structure emitting at 300 nm was found to be 32%. By combining such Ga-rich growth condition in the active region with polarization field enhanced carrier injection layers, deep UV-LEDs emitting at 273 nm were obtained with output power of 0.35 mW and 1.3 mW at 20 mA continuous wave and 100 mA pulsed drive current, respectively. The maximum external quantum efficiency was 0.4%.
Change Detection in Complex Scenes: Hemispheric Contribution and the Role of Perceptual and Semantic Factors
Authors: Spotorno Sara , Faure Sylvane
Published: February 2011

The perceptual salience and semantic relevance of objects for the meaning of a scene were evaluated with multiple criteria and then manipulated in a change-detection experiment that used an original combination of one-shot and tachistoscopic divided-visual-field paradigms to study behavioural hemispheric asymmetry. Coloured drawings that depicted meaningful situations were presented centrally and very briefly (120 ms) and only the changes were lateralised by adding an object in the right or in the left visual hemifield. High salience and high relevance improved both response times (RTs) and accuracy, although the overall contribution of salience was greater than that of relevance. Moreover, only for low-salience changes did relevance affect speed. RTs were shorter when a change occurred in the left visual hemifield, suggesting a right-hemisphere advantage for detection of visual change. Also, men responded faster than women. The theoretical and methodological implications are discussed.
Object Salience is Transiently Represented Whereas Object Presence is Not: Evidence from Temporal Order Judgment
Authors: Donk Mieke , Soesman Leroy
Published: February 2011

We investigated the temporal dynamics in the processing of object salience and object presence by using a temporal-order-judgment task. In two experiments, observers were presented with displays containing one or two orientation singletons embedded in a background of homogeneously oriented lines. Observers had the task to indicate the temporal order of two colour changes which occurred either at two singleton locations differing in salience (experiment 1) or at two locations differing in singleton presence (experiment 2). Singleton displays were presented for a short or a long duration prior to the colour changes. The results demonstrated that salience affects the perceived temporal order of two colour changes more strongly after a short than after a long presentation duration (experiment 1). Singleton presence affects the perceived temporal order of two colour changes equally after a short and a long presentation duration (experiment 2). The results suggest that object salience and object presence are differently represented in the visual system.
Exploring a Brightness-Drag Illusion
Authors: Habota Tina , Chappell Mark
Published: February 2011

A sudden luminance increment on a moving stimulus was perceived significantly along the trajectory, in the direction of motion, from its displayed position. A nonlinear relationship with stimulus speed, for a Fröhlich-like illusion, but not for the luminance-increment illusion, challenges certain models of spatial mislocalisation and argues for different processes underlying the two illusions.
Amodal Causal Capture in the Tunnel Effect
Authors: Bae Gi Yeul , Flombaum Jonathan I
Published: February 2011

In addition to identifying individual objects in the world, the visual system must also characterize the relationships between objects, for instance when objects occlude one another or cause one another to move. Here we explored the relationship between perceived causality and occlusion. Can one perceive causality in an occluded location? In several experiments, observers judged whether a centrally presented event involved a single object passing behind an occluder, or one object causally launching another (out of view and behind the occluder). With no additional context, the centrally presented event was typically judged as a non-causal pass, even when the occluding and disoccluding objects were different colors—an illusion known as the ‘tunnel effect’ that results from spatiotemporal continuity. However, when a synchronized context event involved an unambiguous causal launch, participants perceived a causal launch behind the occluder. This percept of an occluded causal interaction could also be driven by grouping and synchrony cues in the absence of any explicitly causal interaction. These results reinforce the hypothesis that causality is an aspect of perception. It is among the interpretations of the world that are independently available to vision when resolving ambiguity, and that the visual system can ‘fill in’ amodally.
Depth Interval Estimates from Motion Parallax and Binocular Disparity beyond Interaction Space
Authors: Gillam Barbara , Palmisano Stephen A , Govan Donovan G
Published: February 2011

Static and dynamic observers provided binocular and monocular estimates of the depths between real objects lying well beyond interaction space. On each trial, pairs of LEDs were presented inside a dark railway tunnel. The nearest LED was always 40 m from the observer, with the depth separation between LED pairs ranging from 0 up to 248 m. Dynamic binocular viewing was found to produce the greatest (ie most veridical) estimates of depth magnitude, followed next by static binocular viewing, and then by dynamic monocular viewing. (No significant depth was seen with static monocular viewing.) We found evidence that both binocular and monocular dynamic estimates of depth were scaled for the observation distance when the ground plane and walls of the tunnel were visible up to the nearest LED. We conclude that both motion parallax and stereopsis provide useful long-distance depth information and that motion-parallax information can enhance the degree of stereoscopic depth seen.
Signaling by vitamin A and retinol-binding protein regulates gene expression to inhibit insulin responses
Authors: Berry Daniel C. , Jin Hui , Majumdar Avijit , Noy Noa
Published: February 2011

It currently is believed that vitamin A, retinol, functions through active metabolites: the visual chromophore 11-
cis
-retinal, and retinoic acids, which regulate gene transcription. Retinol circulates in blood bound to retinol-binding protein (RBP) and is transported into cells by a membrane protein termed “stimulated by retinoic acid 6” (STRA6). We show here that STRA6 not only is a vitamin A transporter but also is a cell-surface signaling receptor activated by the RBP–retinol complex. Association of RBP-retinol with STRA6 triggers tyrosine phosphorylation, resulting in recruitment and activation of JAK2 and the transcription factor STAT5. The RBP–retinol/STRA6/JAK2/STAT5 signaling cascade induces the expression of STAT target genes, including suppressor of cytokine signaling 3 (
SOCS3
), which inhibits insulin signaling, and peroxisome proliferator-activated receptor gamma (
PPARγ
), which enhances lipid accumulation. These observations establish that the parental vitamin A molecule is a transcriptional regulator in its own right, reveal that the scope of biological functions of the vitamin is broader than previously suspected, and provide a rationale for understanding how RBP and retinol regulate energy homeostasis and insulin responses.
Arid5a cooperates with Sox9 to stimulate chondrocyte-specific transcription
Authors: Amano Katsuhiko , Hata Kenji , Muramatsu Shuji , Wakabayashi Makoto , Takigawa Yoko , Ono Koichiro , Nakanishi Masako , Takashima Rikako , Kogo Mikihiko , Matsuda Akio , Nishimura Riko , Yoneda Toshiyuki
Published: February 2011

SRY-box–containing gene 9 (Sox9) is an essential transcription factor in chondrocyte lineage determination and differentiation. Recent studies demonstrated that Sox9 controls the transcription of chondrocyte-specific genes in association with several other transcriptional regulators. To further understand the molecular mechanisms by which Sox9 influences transcriptional events during chondrocyte differentiation, we attempted to identify transcriptional partners of Sox9 and to examine their roles in chondrocyte differentiation. We isolated AT-rich interactive domain–containing protein 5a (Arid5a; also known as Mrf1) as an activator of the Col2a1 gene promoter from an ATDC5 cDNA library. Arid5a was highly expressed in cartilage and induced during chondrocyte differentiation. Furthermore, Arid5a physically interacted with Sox9 in nuclei and up-regulated the chondrocyte-specific action of Sox9. Overexpression of Arid5a stimulated chondrocyte differentiation in vitro and in an organ culture system. In contrast, Arid5a knockdown inhibited Col2a1 expression in chondrocytes. In addition, Arid5a binds directly to the promoter region of the Col2a1 gene and stimulates acetylation of histone 3 in the region. Our results suggest that Arid5a may directly interact with Sox9 and thereby enhance its chondrocyte-specific action.
Nestin as a regulator of Cdk5 in differentiating myoblasts
Authors: Pallari Hanna-Mari , Lindqvist Julia , Torvaldson Elin , Ferraris Saima E. , He Tao , Sahlgren Cecilia , Eriksson John E.
Published: February 2011

Many types of progenitor cells are distinguished by the expression of the intermediate filament protein nestin, a frequently used stem cell marker, the physiological roles of which are still unknown. Whereas myogenesis is characterized by dynamically regulated nestin levels, we studied how altering nestin levels affects myoblast differentiation. Nestin determined both the onset and pace of differentiation. Whereas depletion of nestin by RNAi strikingly accelerated the process, overexpression of nestin completely inhibited differentiation. Nestin down-regulation augmented the early stages of differentiation, at the level of cell-cycle withdrawal and expression of myogenic markers, but did not affect proliferation of undifferentiated dividing myoblasts. Nestin regulated the cleavage of the Cdk5 activator protein p35 to its degradation-resistant form, p25. In this way, nestin has the capacity to halt myoblast differentiation by inhibiting sustained activation of Cdk5 by p25, which is critical for the progress of differentiation. Our results imply that nestin regulates the early stages of myogenesis rather than maintains the undifferentiated state of progenitor cells. In the bidirectional interrelationship between nestin and Cdk5, Cdk5 regulates the organization and stability of its own nestin scaffold, which in turn controls the effects of Cdk5. This nestin–Cdk5 cross-talk sets the pace of muscle differentiation.
PKCθ signaling is required for myoblast fusion by regulating the expression of caveolin-3 and β1D integrin upstream focal adhesion kinase
Authors: Madaro Luca , Marrocco Valeria , Fiore Piera , Aulino Paola , Smeriglio Piera , Adamo Sergio , Molinaro Mario , Bouché Marina
Published: February 2011

Fusion of mononucleated myoblasts to form multinucleated myofibers is an essential phase of skeletal myogenesis, which occurs during muscle development as well as during postnatal life for muscle growth, turnover, and regeneration. Many cell adhesion proteins, including integrins, have been shown to be important for myoblast fusion in vertebrates, and recently focal adhesion kinase (FAK), has been proposed as a key mediator of myoblast fusion. Here we focused on the possible role of PKCθ, the PKC isoform predominantly expressed in skeletal muscle, in myoblast fusion. We found that the expression of PKCθ is strongly up-regulated following freeze injury–induced muscle regeneration, as well as during in vitro differentiation of satellite cells (SCs; the muscle stem cells). Using both PKCθ knockout and muscle-specific PKCθ dominant-negative mutant mouse models, we observed delayed body and muscle fiber growth during the first weeks of postnatal life, when compared with wild-type (WT) mice. We also found that myofiber formation, during muscle regeneration after freeze injury, was markedly impaired in PKCθ mutant mice, as compared with WT. This phenotype was associated with reduced expression of the myogenic differentiation program executor, myogenin, but not with that of the SC marker Pax7. Indeed in vitro differentiation of primary muscle-derived SCs from PKCθ mutants resulted in the formation of thinner myotubes with reduced numbers of myonuclei and reduced fusion rate, when compared with WT cells. These effects were associated to reduced expression of the profusion genes caveolin-3 and β1D integrin and to reduced activation/phosphorylation of their up-stream regulator FAK. Indeed the exogenous expression of a constitutively active mutant form of PKCθ in muscle cells induced FAK phosphorylation. Moreover pharmacologically mediated full inhibition of FAK activity led to similar fusion defects in both WT and PKCθ-null myoblasts. We thus propose that PKCθ signaling regulates myoblast fusion by regulating, at least in part, FAK activity, essential for profusion gene expression.
Actin depolymerizing factor controls actin turnover and gliding motility inToxoplasma gondii
Authors: Mehta Simren , Sibley L. David
Published: February 2011

Apicomplexan parasites rely on actin-based gliding motility to move across the substratum, cross biological barriers, and invade their host cells. Gliding motility depends on polymerization of parasite actin filaments, yet ∼98% of actin is nonfilamentous in resting parasites. Previous studies suggest that the lack of actin filaments in the parasite is due to inherent instability, leaving uncertain the role of actin-binding proteins in controlling dynamics. We have previously shown that the single allele of Toxoplasma gondii actin depolymerizing factor (TgADF) has strong actin monomer–sequestering and weak filament-severing activities in vitro. Here we used a conditional knockout strategy to investigate the role of TgADF in vivo. Suppression of TgADF led to accumulation of actin-rich filaments that were detected by immunofluorescence and electron microscopy. Parasites deficient in TgADF showed reduced speed of motility, increased aberrant patterns of motion, and inhibition of sustained helical gliding. Lack of TgADF also led to severe defects in entry and egress from host cells, thus blocking infection in vitro. These studies establish that the absence of stable actin structures in the parasite are not simply the result of intrinsic instability, but that TgADF is required for the rapid turnover of parasite actin filaments, gliding motility, and cell invasion.
Interactions between a luteovirus and the GroEL chaperonin protein of the symbiotic bacterium Buchnera aphidicola of aphids
Authors: Bouvaine Sophie , Boonham Neil , Douglas Angela E.
Published: February 2011

Luteoviruses and poleroviruses are important plant viruses transmitted exclusively by aphids in a circulative manner via the aphid haemolymph. A chaperonin protein, GroEL, synthesized in aphids by a symbiotic bacterium, Buchnera aphidicola, is hypothesized to bind to virus particles in the haemolymph, thereby promoting transmission. To investigate this hypothesis, the GroEL-binding site for barley yellow dwarf virus (BYDV) was determined in vitro, and the abundance of GroEL protein in different aphid tissues was investigated. Virus binding to a peptide library representing the full GroEL molecule revealed a single binding site that coincides with the site that anchors two GroEL rings to form the native GroEL tetradecamer. In the functional form of the GroEL protein, virus binding would compete with the formation of the two GroEL rings. Using a mAb raised against a Buchnera-specific GroEL epitope, GroEL was detected in Buchnera cells by immunoblotting and immunocytochemistry, but not in the aphid haemolymph, fat body or gut. From the prediction here that GroEL–virus interactions are probably severely limited by competition with other GroEL molecules, and the evidence that GroEL is not available to interact with virus particles in vivo, it is concluded that GroEL–virus interactions are unlikely to contribute to virus transmission by aphids.
Structural and sequence integrity are essential for the replication of the viroid-like satellite RNA of lucerne transient streak virus
Authors: Gellatly Duncan , Mirhadi Kayvan , Venkataraman Srividhya , AbouHaidar Mounir G.
Published: February 2011

Lucerne transient streak virus (LTSV, genus Sobemovirus) supports the replication and encapsidation of a 322 nt untranslated small-circular RNA (scLTSV). Since scLTSV does not code for any proteins or share sequence similarity with its helper virus (LTSV), it is presumed that it uses structural and sequence motifs to signal the helper virus (and host) machinery for its replication and encapsidation. Insertion and deletion mutations were introduced at various locations within the scLTSV molecule. Our results showed that most mutants were not infectious, with only two exceptions, a (−1) nucleotide deletion and a 9 nt, palindromic insertion mutant which preserved the overall rod-like structure of the scLTSV. Sequence analysis of cDNA clones revealed that the palindromic sequence was replicated for up to 12 days of infection, before the sequence reverted back to its wild-type form. Our results indicate that scLTSV has an optimal sequence and secondary structure for replication, movement and/or packaging within the LTSV helper virus.
Feedback Mechanisms, Judgment Bias, and Trust Formation in Online Auctions*
Authors: Wolf James R. , Muhanna Waleed A.
Published: February 2011

Online markets, like eBay, Amazon, and others rely on electronic reputation or feedback systems to curtail adverse selection and moral hazard risks and promote trust among participants in the marketplace. These systems are based on the idea that providing information about a trader's past behavior (performance on previous market transactions) allows market participants to form judgments regarding the trustworthiness of potential interlocutors in the marketplace. It is often assumed, however, that traders correctly process the data presented by these systems when updating their initial beliefs. In this article, we demonstrate that this assumption does not hold. Using a controlled laboratory experiment simulating an online auction site with 127 participants acting as buyers, we find that participants interpret seller feedback information in a biased (non‐Bayesian) fashion, overemphasizing the compositional strength (i.e., the proportion of positive ratings) of the reputational information and underemphasizing the weight (predictive validity) of the evidence as represented by the total number of transactions rated. Significantly, we also find that the degree to which buyers misweigh seller feedback information is moderated by the presentation format of the feedback system as well as attitudinal and psychological attributes of the buyer. Specifically, we find that buyers process feedback data presented in an Amazon‐like format—a format that more prominently emphasizes the strength dimension of feedback information—in a more biased (less‐Bayesian) manner than identical ratings data presented using an eBay‐like format. We further find that participants with greater institution‐based trust (i.e., structural assurance) and prior online shopping experience interpreted feedback data in a more biased (less‐Bayesian) manner. The implications of these findings for both research and practice are discussed.
Why Competition from a Multi‐Channel E‐Tailer Does Not Always Benefit Consumers*
Authors: Jeffers Patrick I. , Nault Barrie R.
Published: February 2011

Empirical studies have delivered mixed conclusions on whether the widely acclaimed assertions of lower electronic retail (e‐tail) prices are true and to what extent these prices impact conventional retail prices, profits, and consumer welfare. For goods that require little in‐person pre‐ or postsales support such as CDs, DVDs, and books, we extend Balasubramanian's e‐tailer‐in‐the‐center, spatial, circular market model to examine the impact of a multichannel e‐tailer's presence on retailers' decisions to relocate, on retail prices and profits, and consumer welfare. We demonstrate several counter‐intuitive results. For example, when the disutility of buying online and shipping costs are relatively low, retailers are better off by not relocating in response to an e‐tailer's entry into the retail channel. In addition, such an entry—a multichannel strategy—may lead to increased retail prices and increased profits across the industry. Finally, consumers can be better off with less channel competition. The underlying message is that inferences regarding prices, profits, and consumer welfare critically depend on specifications of the good, disutility and shipping costs versus transportation costs (or more generally, positioning), and competition.
Building a Model of Technology Preference: The Case of Channel Choices
Authors: Muthitcharoen Achita (Mi) , Palvia Prashant C. , Grover Varun
Published: February 2011

Intention theories, such as the Theory of Reasoned Action, the Theory of Planned Behavior, and the Technology Acceptance Model (TAM), have been widely adopted to explain information system usage. These theories, however, do not explicitly consider the availability of alternative systems that users may have access to and may have a preference for. Recent calls for advancing knowledge in technology acceptance have included the examination of selection among competing channels and extending the investigation beyond adoption of a single technology. In this study, we provide a theoretical extension to the TAM by integrating preferential decision knowledge to its constructs. The concept of Attitude‐Based Preference and Attribute‐Based Preference are introduced to produce a new intention model, namely the Model of Technology Preference (MTP). MTP was validated in the context of alternative behaviors in adopting two service channels: one a technology‐based online store and the other a traditional brick‐and‐mortar store. A sample of 320 responses was used to run a structural equation model. Empirical results show that MTP is a powerful predictor of alternative behaviors. Furthermore, in the context of service channel selection, incorporating preferential decision knowledge into intention models can be used to develop successful business strategies.
Numerical Model of the Temperature Control Curve Linearity of HVAC Module in Automobile Air-Conditioning System and Applications
Authors: Qu Xiaohua , Qi Zhaogang , Shi Junye , Chen Jiangping , Zhou Hua
Published: February 2011

In the present work, a numerical model of the temperature control curve (TCC) linearity of the heating ventilating and air conditioning (HVAC) module in automobile air-conditioning system is established. The numerical model is composed of several higher precision submodels. The simulation results are validated by experimental data performed on a calorimeter test bench. It is found that the simulation data agree with the experimental data very well. The maximum deviations of the airflow rate and the temperature are 3% and 1.4°C, respectively. The factors, which influenced the TCC linearity, are numerically studied. The simulation results show that the different door configuration needs to be matched with the division type for vent ducts of the HVAC module outlet, which can decrease the temperature stratification of airflow at the outlets. Cold and hot air mixing ratio determines the slope of the linearity curve. In addition, the further the distance between the HVAC module outlet and the mixing chamber and the greater the turbulent intensity, the more the cold-hot airflow will fully mix. It contributes to the temperature uniformity at the outlets.
Recent Developments in Biotransport
Authors: Zhu Liang
Published: February 2011

In the past ten years, one has seen rapid advancements in heat and mass transport applications in biology and medicine. The research activities have been shifted from fundamental development of better theoretical models accurately describing the thermal effect of local vasculature geometry and blood perfusion rate in the 1980s and 1990s to emphases on biotransport research with clear clinical applications and on how to utilize theoretical simulation and imaging techniques for better designing treatment protocols in those applications. This review will first describe briefly technical advancements in bioheat and mass transfer in the past several decades and then focus on two important applications in bioheat and mass transport covering different temperature ranges: hypothermia in brain injury and hyperthermia in tissue thermal damage. The contributions of nanotechnology, imaging tools, and multiscale modeling to the advancements will be discussed in the review.
Articulatory–acoustic kinematics: The production of American English /s/
Authors: Iskarous Khalil , Shadle Christine H. , Proctor Michael I.
Published: February 2011

Due to its aerodynamic, articulatory, and acoustic complexities, the fricative /s/ is known to require high precision in its control, and to be highly resistant to coarticulation. This study documents in detail how jaw, tongue front, tongue back, lips, and the first spectral moment covary during the production of /s/, to establish how coarticulation affects this segment. Data were obtained from 24 speakers in the Wisconsin x-ray microbeam database producing /s/ in prevocalic and pre-obstruent sequences. Analysis of the data showed that certain aspects of jaw and tongue motion had specific kinematic trajectories, regardless of context, and the first spectral moment trajectory corresponded to these in some aspects. In particular contexts, variability due to jaw motion is compensated for by tongue-tip motion and bracing against the palate, to maintain an invariant articulatory–aerodynamic goal, constriction degree. The change in the first spectral moment, which rises to a peak at the midpoint of the fricative, primarily reflects the motion of the jaw. Implications of the results for theories of speech motor control and acoustic–articulatory relations are discussed.
Comparison of distortion-product otoacoustic emission growth rates and slopes of forward-masked psychometric functions
Authors: Rodríguez Joyce , Neely Stephen T. , Jesteadt Walt , Tan Hongyang , Gorga Michael P.
Published: February 2011

Slopes of forward-masked psychometric functions (FM PFs) were compared with distortion-product otoacoustic emission (DPOAE) input/output (I/O) parameters at 1 and 6 kHz to test the hypothesis that these measures provide similar estimates of cochlear compression. Implicit in this hypothesis is the assumption that both DPOAE I/O and FM PF slopes are functionally related to basilar-membrane (BM) response growth. FM PF-slope decreased with signal level, but this effect was reduced or reversed with increasing hearing loss; there was a trend of decreasing psychometric function (PF) slope with increasing frequency, consistent with greater compression at higher frequencies. DPOAE I/O functions at 6 kHz exhibited an increase in the breakpoint of a two-segment slope as a function of hearing loss with a concomitant decrease in the level of the distortion product (Ld). Results of the comparison between FM PF and DPOAE I/O parameters revealed only a weak correlation, suggesting that one or both of these measures may provide unreliable information about BM compression.
Optimized constraints for the linearized geoacoustic inverse problem
Authors: Ballard Megan S. , Becker Kyle M.
Published: February 2011

A geoacoustic inversion scheme to estimate the depth-dependent sound speed characteristics of the shallow-water waveguide is presented. The approach is based on the linearized perturbative technique developed by Rajan et al. [J. Acoust. Soc. Am. 82, 998–1017 (1987)]. This method is applied by assuming a background starting model for the environment that includes both the water column and the seabed. Typically, the water column properties are assumed to be known and held fixed in the inversion. Successful application of the perturbative inverse technique lies in handling issues of stability and uniqueness associated with solving a discrete ill-posed problem. Conventionally, such problems are regularized, a procedure which results in a smooth solution. Past applications of this inverse technique have been restricted to cases for which the water column sound speed profile was known and sound speed in the seabed could be approximated by a smooth profile. In this work, constraints that are better suited to specific aspects of the geoacoustic inverse problem are applied. These techniques expand on the original application of the perturbative inverse technique by including the water column sound speed profile in the solution and by allowing for discontinuities in the seabed sound speed profile.
The perception of Arabic and Japanese short and long vowels by native speakers of Arabic, Japanese, and Persian
Authors: Tsukada Kimiko
Published: February 2011

This study examines the perception of short and long vowels in Arabic and Japanese by three groups of listeners differing in their first languages (L1): Arabic, Japanese, and Persian. While Persian uses the same alphabet as Arabic and Iranian students learn Arabic in school, the two languages are typologically unrelated. Further, unlike Arabic or Japanese, vowel length may no longer be contrastive in modern Persian. In this study, a question of interest was whether Persian listeners’ foreign language learning experience or Japanese listeners’ L1 phonological experience might help them to accurately process short and long vowels in Arabic. In Experiment 1, Arabic and Japanese listeners were more accurate than Persian listeners in discriminating vowel length contrasts in their own L1 only. In Experiment 2, Arabic and Japanese listeners were more accurate than Persian listeners in identifying the length categories in the “other” unknown language as well as in their own L1. The difference in the listeners’ perceptual performance between the two experiments supports the view that long-term L1 representations may be invoked to a greater extent in the identification than discrimination test. The present results highlight the importance of selecting the appropriate test for assessing cross-language speech perception.
Wind noise measured at the ground surface
Authors: Yu Jiao , Raspet Richard , Webster Jeremy , Abbott JohnPaul
Published: February 2011

Measurements of the wind noise measured at the ground surface outdoors are analyzed using the mirror flow model of anisotropic turbulence by Kraichnan [J. Acoust. Soc. Am. 28(3), 378–390 (1956)]. Predictions of the resulting behavior of the turbulence spectrum with height are developed, as well as predictions of the turbulence-shear interaction pressure at the surface for different wind velocity profiles and microphone mounting geometries are developed. The theoretical results of the behavior of the velocity spectra with height are compared to measurements to demonstrate the applicability of the mirror flow model to outdoor turbulence. The use of a logarithmic wind velocity profile for analysis is tested using meteorological models for wind velocity profiles under different stability conditions. Next, calculations of the turbulence-shear interaction pressure are compared to flush microphone measurements at the surface and microphone measurements with a foam covering flush with the surface. The measurements underneath the thin layers of foam agree closely with the predictions, indicating that the turbulence-shear interaction pressure is the dominant source of wind noise at the surface. The flush microphones measurements are intermittently larger than the predictions which may indicate other contributions not accounted for by the turbulence-shear interaction pressure.
Behaviors of cubic distortion product otoacoustic emissions evoked by amplitude modulated tones
Authors: Bian Lin , Chen Shixiong
Published: February 2011

Distortion product otoacoustic emissions (DPOAEs) were measured using sinusoidal amplitude modulation (AM) tones. When one of the primary stimuli (f1 or f2, f1 < f2) was amplitude modulated, a series of changes in the cubic difference tone (CDT) were observed. In the frequency domain, multiple sidebands were present around the CDT and their sizes grew with the modulation depth of the AM stimulus. In the time domain, the CDT showed different modulation patterns between two major signal conditions: the AM tone was used as the f1 or the f2. The CDT amplitude followed the AM tone when the f1 was amplitude modulated. However, when the AM tone acted as the f2, the CDT showed a more complex modulation pattern with a notch present at the AM tone peak. The relatively linear dependence of CDT on f1 and the nonlinear relation with f2 can be explained with a variable gain-control model representing hair cell functions at the DPOAE generation site. It is likely that processing of AM signals at a particular cochlear location depends on whether the hair cells are tuned to the frequency of the carrier. Nonlinear modulation is related to on-frequency carriers and off-frequency carriers are processed relatively linearly.
Pekeris waveguide comparisons of methods for predicting acoustic field amplitude uncertainty caused by a spatially uniform environmental uncertainty (L)
Authors: James Kevin R. , Dowling David R.
Published: February 2011

Acoustic field calculations in underwater environments are often uncertain because the environmental parameters required for such calculations are uncertain. This letter compares the accuracy of direct simulations, the field shifting approximation, and polynomial chaos expansions for predicting acoustic amplitude uncertainty in 100-m-deep Pekeris waveguides having spatially uniform uncertain water-column sound speed. When this sound speed is Gaussian-distributed with a standard deviation of 1 m/s, direct simulations and polynomial chaos expansions, based on 21 field calculations, are more accurate than the field shifting approximation, based on two field calculations. This ranking reverses as the sound-speed standard deviation increases to 20 m/s.
The radiating part of circular sources
Authors: Carley Michael
Published: February 2011

An analysis is developed linking the form of the sound field from a circular source to the radial structure of the source, without recourse to far-field or other approximations. It is found that the information radiated into the field is limited, with the limit fixed by the wavenumber of the source multiplied by the source radius (Helmholtz number). The acoustic field is found in terms of the elementary fields generated by a set of line sources whose form is given by Chebyshev polynomials of the second kind and whose amplitude is found to be given by weighted integrals of the radial source term. The analysis is developed for tonal sources, such as rotors, and for Helmholtz number less than two, for random disk sources. In this case, the analysis yields the cross-spectrum between two points in the acoustic field. The analysis is applied to the problems of tonal radiation, random source radiation as a model problem for jet noise, and to noise cancellation, as in active control of noise from rotors. It is found that the approach gives an accurate model for the radiation problem and explicitly identifies those parts of a source which radiate.
Comment on “Mantle Flow Drives the Subsidence of Oceanic Plates”
Authors: Croon Marcel B. , Hillier John K. , Sclater John G.
Published: February 2011

Adam and Vidal (Reports, 2 April 2010, p. 83) reported sea-floor depth increasing as the square root of distance from the ridge along “mantle flow lines.” However, their data actually support a depth-age relationship and “flattening” at older ages. We argue that no plausible physical mechanism supports their proposal that mantle flow drives subsidence.
Direct Measurement of Long-Range Third-Order Coherence in Bose-Einstein Condensates
Authors: Hodgman S. S. , Dall R. G. , Manning A. G. , Baldwin K. G. H. , Truscott A. G.
Published: February 2011

Correlation of arrival times of metastable helium atoms is consistent with long-range coherence to higher orders.
Heisenberg in the “Public Sphere”
Heisenberg in the Atomic Age
Science and the Public Sphere

by Cathryn Carson

Cambridge University Press, Cambridge, and the German Historical Institute, Washington, DC, 2010. 565 pp. $88, £55. ISBN 9780521821704.
Authors: Seth Suman
Published: February 2011

Drawing on extensive research and interviews, Carson offers a detailed yet accessible consideration of Heisenberg's roles in postwar Germany.
Preference by Exclusion
Authors: Godley Lucy A. , Mondragón Alfonso
Published: February 2011

The structure of a methyltransferase indicates how the enzyme selects its DNA substrates.
The Meaning of the Human Genome Project for Neuropsychiatric Disorders
Authors: Hyman Steven E.
Published: February 2011

Human genome sequences as well as associated technologies and analytic approaches are providing new tools to understand neuropsychiatric disorders.
Advancing Regulatory Science
Authors: Hamburg Margaret A.
Published: February 2011

Ensuring the safety and quality of food and medical products has never been more complicated. Societies around the world face increasingly complex challenges that require harnessing the best available science and technology on behalf of patients and consumers. This effort requires a strong field of regulatory science to develop new tools, standards, and approaches that efficiently and consistently assess the safety, efficacy, quality, and performance of products. Yet, despite being a critical component of the scientific enterprise, regulatory science has long been underappreciated and underfunded.
Activists Go on Warpath Against Transgenic Crops—and Scientists
Authors: Stone Richard
Published: February 2011

Wu You Zhi Xiang, a loose-knit group known in English as Utopia, is gathering signatures on an open letter denouncing genetically modified (GM) crops. Few observers expect Utopia's petition to sway the Chinese government, which has enshrined transgenic crop R&D as a top priority. But Utopia's actions may well slow commercialization of GM foods.
Tracing the Tree of Life
Authors: Pennisi Elizabeth
Published: February 2011

With the help of next-generation sequencing, a team of evolutionary biologists is shining a scientific spotlight on little-studied organisms in order to refine the much-debated animal tree of life.
Tackling the Mystery of the Disappearing Frogs
Authors: Pennisi Elizabeth
Published: February 2011

The chytrid fungus,
Batrachochytrium dendrobatidis
, has wiped out amphibians around the globe. The results of new sequencing technologies that directly decipher all the active genes of a species suggest that in susceptible frogs, the immune system doesn't go on the defensive; the fungi somehow evades the body's defenses.
Probing Pronghorn Mating Preferences
Authors: Pennisi Elizabeth
Published: February 2011

Animal behaviorists suspect that female pronghorns choose mates with the lowest burden of so-called deleterious mutations. Thanks to the growing availability of next-generation DNA sequencing, they may finally have a chance to prove this theory.
Streptococcus pneumoniae Isolates from Middle Ear Fluid and Nasopharynx of Children with Acute Otitis Media Exhibit Phase Variation
Authors: Arai Jun , Hotomi Muneki , Hollingshead Susan K. , Ueno Yumi , Briles David E. , Yamanaka Noboru
Published: February 2011

Pneumococcal phase variation of 37 middle ear and 31 nasopharyngeal isolates obtained from children with acute otitis media was examined in the absence of intervening culture. The fraction of the opaque colonies was significantly higher in middle ear isolates than in nasopharyngeal isolates. The difference is probably the result of the pneumococci adapting to differential selective environments.
Evaluation of the Gen-Probe Aptima HIV-1 RNA Qualitative Assay as an Alternative to Western Blot Analysis for Confirmation of HIV Infection
Authors: Pierce Virginia M. , Neide Brandy , Hodinka Richard L.
Published: February 2011

The Gen-Probe Aptima HIV-1 RNA qualitative assay was evaluated as an alternative to Western blot analysis for the confirmation of HIV infection using serum samples that were repeatedly reactive for HIV antibodies. The Aptima HIV assay readily discriminated between HIV-1-infected and -uninfected individuals and effectively reduced the number of indeterminate results relative to Western blot analysis.
Evaluation of the Inaccurate Assignment of Mixed Infections by Mycobacterium tuberculosis as Exogenous Reinfection and Analysis of the Potential Role of Bacterial Factors in Reinfection
Authors: Martín Ana , Herranz Marta , Navarro Yurena , Lasarte Sandra , Ruiz Serrano María Jesús , Bouza Emilio , García de Viedma Darío
Published: February 2011

Molecular analysis of recurrent tuberculosis has revealed that a second episode may be caused by a strain ofMycobacterium tuberculosisother than that involved in the first infection, thus indicating that exogenous reinfection plays a role in recurrence. We focused on two aspects of reinfection that have received little attention. First, we evaluated whether a lack of methodological refinement could lead to inaccurate assignment of mixed infections as exogenous reinfection, in which a differential selection of each of the coinfecting strains occurred over time. We used the mycobacterial interspersed repetitive-unit–variable-number tandem-repeat (MIRU-VNTR) method to genotype 122 isolates from 40 patients with recurrent tuberculosis. We identified 11/40 (27.5%) cases with genotypic differences between the isolates involved in the sequential episodes. Major genotypic differences were found in 8/11 cases, suggesting exogenous reinfection; in the remaining 3 cases, subtle genotypic differences were observed, probably indicating microevolution from a parental strain. In all cases, only a single strain was detected for the isolate(s) from each episode, thus ruling out the possibility that reinfection could correspond to undetected mixed infection. Second, we analyzed the infectivity of a selection of 12 strains from six cases with genotypically different strains between episodes. No main differences were observed in anex vivomodel of infection between the strains involved in the first episodes and those involved in the recurrent episodes. In our setting, our results suggest the following: (i) the possibility of misassignment of mixed infection as exogenous reinfection is improbable, and (ii) bacterial infectivity does not seem to play a role in exogenous reinfection.