bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the natural attenuation of benzene in groundwater impacted by ethanol‐blended fuels: Effect of ethanol content on the lifespan and maximum length of benzene plumes
Authors: Gomez Diego E. , Alvarez Pedro J. J.
Published: March 2009

A numerical model was used to evaluate how the concentration of ethanol in reformulated gasoline affects the length and longevity of benzene plumes in fuel‐contaminated groundwater. Simulations considered a decaying light nonaqueous phase liquid source with a total mass of ∼85 kg and a groundwater seepage velocity of 9 cm d−1 and corroborated previous laboratory, field, and modeling studies showing benzene plume elongation due to the presence of ethanol. Benzene plume elongation reached a maximum of 59% for 20% ethanol content (E20) relative to regular gasoline without ethanol. Elongation was due to accelerated depletion of dissolved oxygen during ethanol degradation and to a lower specific rate of benzene utilization caused by metabolic flux dilution and catabolite repression. The lifespan of benzene plumes was shorter for all ethanol blends compared to regular gasoline (e.g., 17 years for regular gasoline, 15 years for E10, 9 years for E50, and 3 years for E85), indicating greater natural attenuation potential for higher‐ethanol blends. This was attributed to a lower mass of benzene released for higher‐ethanol blends and increased microbial activity associated with fortuitous growth of benzene degraders on ethanol. Whereas site‐specific conditions will determine actual benzene plume length and longevity, these decaying‐source simulations imply that high‐ethanol blends (e.g., E85) pose a lower risk of benzene reaching a receptor via groundwater migration than low‐ethanol blends such as E10.
An Exchange Theory of Money and Self-Esteem in Decision Making
Authors: Zhang Liqing
Published: March 2009

This article addresses the relationship between money and self-esteem, both of which human beings desire. Money is used to purchase products. It may also indicate its owner's competence. Self-esteem is the subjective evaluation of the self, and people want to maintain their good self-image. The exchange between money and self-esteem may follow 3 principles: augmentation, substitution, and competition. A superior payoff augments utility of self-esteem. Money and self-esteem partially compensate for one another when an option contains an abundance of one type of utility and lacks the other. Money and self-esteem compete against each other when decision makers have to choose between the two. Empirical evidence has shown that meaning of money, situational need for money, self-esteem boost, and ego threat influence the exchange between money and self-esteem. The theory presented in this article bridges research in psychology and findings in economics and provides an integrative perspective on understanding human decision making.
The Perennial Debate: Nature, Nurture, or Choice? Black and White Americans’ Explanations for Individual Differences
Authors: Jayaratne Toby Epstein , Gelman Susan A. , Feldbaum Merle , Sheldon Jane P. , Petty Elizabeth M. , Kardia Sharon L. R.
Published: March 2009

The authors examine 3 common explanations for human characteristics: genes, the environment, and choice. A representative sample of White and Black Americans indicated how much they believed each factor influenced individual differences in athleticism, nurturance, drive to succeed, math ability, tendency toward violence, intelligence, and sexual orientation. Results show that across traits (a) Black respondents generally favored choice and rejected genetic explanations, whereas White respondents indicated less causal consistency; (b) although a sizable subset of respondents endorsed just 1 factor, most reported multiple factors as at least partly influential; and (c) among White respondents, greater endorsement of genetic explanations was associated with less acceptance of choice and the environment, although among Black respondents a negative relationship held only between genes and choice. The social relevance of these findings is discussed within the context of the attribution, essentialism, and lay theory literature. The results underscore the need to consider more complex and nuanced issues than are implied by the simplistic, unidimensional character of the nature–nurture and determinism–free will debates—perennial controversies that have significance in the current genomic era.
High-temperature characteristics up to 590 °C of a pnp AlGaN/GaN heterojunction bipolar transistor
Authors: Kumakura Kazuhide , Makimoto Toshiki
Published: March 2009

We investigated the temperature dependence of the common-emitter I-V characteristics of a pnp AlGaN/GaN heterojunction bipolar transistor (HBT) at temperatures ranging from RT to 590 °C. The HBT operated at 590 °C in air with a current gain of 3. Even at 590 °C, the collector-emitter leakage current was as low as 9 μA at the collector-emitter voltage of 40 V. Although there is no significant degradation of the HBT characteristics only by annealing in air at 400 °C for 2 h, the current gain reduced to 30% of the initial one after the common-emitter operation at 400 °C for 2 h.
Observation of L1-like chemical ordering in a decahedral FePt nanoparticle by Cs-corrected high resolution transmission electron microscopy
Authors: Hu Xuerang , Xie Lin , Zhu Jing , Poudyal Narayan , Liu J. Ping , Yuan Jun
Published: March 2009

The state of the chemical ordering in a decahedral FePt nanoparticle was studied using aberration corrected high resolution transmission electron microscopy. With the reduced image delocalization effect as a result of spherical aberration correction, it is possible to directly correlate the image intensity with the local state of chemical ordering through the help of a multislice image simulation. We have found direct evidence for the image intensity oscillation from one atomic layer to another. It is interpreted as L10-like chemical ordering, i.e., the alternate occupation of Fe and Pt atoms in the (002) planes. The result suggests that chemical ordering survives even in decahedral nanoparticles down to 3 nm size despite the possible surface effects.
Chemical ordering and magnetic properties of L10 CoPt–SiO2 nanocomposite
Authors: Yang Yang , Pandey K. K. M. , Chen J. S. , Chow G. M. , Hu J. F.
Published: March 2009

Chemical ordering and magnetic properties of L10 CoPt–SiO2 nanocomposite were investigated. The chemical ordering increased with SiO2 addition, showed maximum at 10 vol % SiO2, and decreased with further increase in SiO2 compositions. It was observed that coercivity was directly related to the degree of chemical ordering and showed maximum corresponding to 10 vol % SiO2 composition. The large volume fraction of SiO2 increased the grain isolation but deteriorated chemical ordering and magnetic properties.
ac susceptibility of (Ga,Mn)As probed by the anomalous Hall effect
Authors: Nishitani Y. , Chiba D. , Matsukura F. , Ohno H.
Published: March 2009

ac susceptibility of a ferromagnetic semiconductor (Ga,Mn)As was measured using microscaled Hall bar through the anomalous Hall effect. The synchronous component of the Hall resistance with applied ac magnetic field (∼1 mT) was detected using a lock-in technique. The temperature dependence of the ac Hall resistance shows a clear peak in the vicinity of the Curie temperature TC, when an offset dc field, whose magnitude is comparable to that of the ac field, is superimposed. We applied this method to detect the change of TC as a function of hole concentration by applying electric fields.
The effect of oxygen on the surface coercivity of Nd-coated Nd–Fe–B sintered magnets
Authors: Fukagawa T. , Hirosawa S. , Ohkubo T. , Hono K.
Published: March 2009

We have investigated the effect of oxygen on the surface coercivity of Nd-coated Nd–Fe–B sintered magnets as a model experiment to understand the coercivity mechanism. The coercivity values of the surface Nd2Fe14B grains of Ta-coated and uncoated Nd(2 μm)/Nd–Fe–B magnets were compared after annealing at 400 to 600 °C in vacuum. The coercivity of the Ta coated sample did not recover after the heat treatment, whereas that of uncoated sample recovered to a bulk value. Transmission electron microscopy indicated that most of the phases near the Nd/Nd–Fe–B interface were double hcp Nd (metallic Nd) in the coated sample, while an fcc phase was dominant in the uncoated sample, suggesting that the cubic NdOx phase is effective to suppress the nucleation of reverse magnetic domains on the surface of an Nd2Fe14B grain. This suggests that a certain amount of oxygen is an indispensable ingredient to achieve a high coercivity in Nd–Fe–B sintered magnets.
Effect of transcranial magnetic stimulation on force of finger pinch
Authors: Odagaki Masato , Fukuda Hiroshi , Hiwaki Osamu
Published: March 2009

Transcranial magnetic stimulation (TMS) is used to explore many aspects of brain function, and to treat neurological disorders. Cortical motor neuronal activation by TMS over the primary motor cortex (M1) produces efferent signals that pass through the corticospinal tracts. Motor-evoked potentials (MEPs) are observed in muscles innervated by the stimulated motor cortex. TMS can cause a silent period (SP) following MEP in voluntary electromyography (EMG). The present study examined the effects of TMS eliciting MEP and SP on the force of pinching using two fingers. Subjects pinched a wooden block with the thumb and index finger. TMS was applied to M1 during the pinch task. EMG of first dorsal interosseous muscles and pinch forces were measured. Force output increased after the TMS, and then oscillated. The results indicated that the motor control system to keep isotonic forces of the muscles participated in the finger pinch was disrupted by the TMS.
Temperature dependence of magnetic anisotropy of germanium/cobalt cosubstituted cobalt ferrite
Authors: Ranvah N. , Melikhov Y. , Nlebedim I. C. , Jiles D. C. , Snyder J. E. , Moses A. J. , Williams P. I.
Published: March 2009

The variations in magnetization and magnetic anisotropy of Ge4+/Co2+ cosubstituted cobalt ferrite with temperature were investigated for a series of compositions Co1+xGexFe2−2xO4 (0≤x≤0.4). The magnetization at 5 T and low temperature were observed to increase for all Ge/Co cosubstituted samples compared to pure CoFe2O4. Hysteresis loops were measured for each sample over the magnetic field range of −5 T to +5 T for temperatures in the range of 10–400 K. The high field regions of these loops were modeled using Law of Approach to saturation, which represents the rotational and forced magnetization processes. The first order cubic magnetocrystalline anisotropy coefficient K1 was calculated from these fits. K1 decreased with increasing Ge content at all temperatures. Anisotropy increased substantially as temperature decreased. Below 150 K, for certain compositions (x=0, 0.1, 0.2, and 0.3), the maximum applied field of μ0H=5 T was less than the anisotropy field and therefore insufficient to saturate the magnetization. In these cases, the use of the Law of Approach model can give values of K1 that are lower than the correct values and this method cannot be used to estimate anisotropy accurately under these conditions.
The relationship between material properties, device design, and the sensitivity of resonant mechanical sensors
Authors: Waggoner Philip S. , Craighead Harold G.
Published: March 2009

In this work we study three distinct resonant micromechanical sensor geometries and their ability to detect the addition of material at different locations on the devices. Small regions of gold were patterned on the resonators, and changes in frequency due to the presence of gold were measured as a function of position, device geometry, and the resonant mode. We have demonstrated the conditions under which micromechanical resonators are sensitive to the mechanical properties of added material as well as its mass and have quantified how these qualities have competing effects on resonant frequency using finite element analysis and analytical techniques. In cases where this competition significantly reduces frequency shift amplitudes, localized binding of the analyte is required, and we will compare different sensor designs and their frequency responses. When material is uniformly added to resonators, however, device geometry has little to no effect on sensitivity. While cantilevers may be the most commonly used geometry in this field, we show that they are not necessarily the most sensitive in all situations. In most biosensing applications, flexural rigidity is not expected to have an impact on resonant frequency, suggesting that all available resonator surface area should be used for analyte binding.
Effect of nonisothermal electrons on dressed soliton in ion beam plasma system
Authors: Tiwari R. S.
Published: March 2009

Using the reductive perturbation method (RPM) evolution equations, governing the first and second order potentials for ion acoustic wave in an ion beam plasma system with nonisothermal electrons, are derived. Adopting renormalization procedure of Kodama and Taniuti [J. Phys. Soc. Jpn. 45, 298 (1978)] nonsecular dressed soliton solution of these coupled equations is determined. An alternative approach is also used to obtain large amplitude soliton solution, retaining higher order nonlinearities in the expansion of the Sagdeev potential and integrating the resulting energy equation for the system. For small amplitude approximation, this solution reduces to dressed soliton solution obtained for the system using the renormalization in the RPM. Variation of the amplitude (A), velocity (λ), width (W), and the product amplitude×width4 (AW4) are numerically studied for the Korteweg–de Vries, dressed and large amplitude soliton for different values of parameters of the beam-plasma system, and results are summarized.
Building a polarizable pair interaction potential for lanthanoids(III) in liquid water: A molecular dynamics study of structure and dynamics of the whole series
Authors: Duvail Magali , Vitorge Pierre , Spezia Riccardo
Published: March 2009

In this work we have extended our previously presented polarizable pair interaction potential for La3+-water [Duvail et al., J. Chem. Phys. 127, 034503 (2007)] to the whole lanthanoid(III) series (Ln3+) interacting with water. This was performed taking into account known modification of ionic radius and atomic polarizability across the series and thus changing potential parameters according to that. Our procedure avoids the hard task of doing expensive high level ab initio calculations for all the atoms in the series and provides results in good agreement with experimental data and with ab initio calculations performed on the last atom in the series (Lu3+, the atom for which the extrapolation should be in principle much crude). Thus we have studied the hydration properties of the whole Ln3+ series by performing classical molecular dynamics in liquid phase. This systematic study allows us to rationalize from a microscopic point of view the different experimental results on Ln3+-water distances, first shell coordination numbers and first shell water self-exchange reactivity. In particular, we found that across the series the coordination number decreases from 9 for light lanthanoids to 8 for heavy lanthanoids in a continuous shape. This is due to the continuous changing in relative stability of the two forms that can be both populated at finite temperature with different probabilities as a function of the Ln3+ atomic number. The changeover of the Ln3+ ionic radius across the series resulted to be the main driving physical properties governing not always the Ln3+-water distance changing across the series but also the observed coordination number and consequently ligand dynamics.
Depletion effects in a mixture of hard and attractive colloids
Authors: Lajovic A. , Tomšič M. , Jamnik A.
Published: March 2009

Monte Carlo simulation and theory were used to study the potential of mean force (PMF) between a pair of big colloidal (solute) particles suspended in a sea of smaller particles (solvent) interacting via Baxter’s sticky hard sphere (SHS) potential. Simulation results were obtained by applying a special simulation technique developed for sampling the hard sphere collision force, while the theoretical predictions were calculated from the analytic solution of the Percus–Yevick/Ornstein–Zernike integral equation for spatial correlations in a two-component mixture at vanishing solute concentration. Both theory and simulation revealed oscillations of the solute-solute PMF with a period equal to the diameter of the solvent molecules. Further, the attractive PMF between solute particles in the SHS fluid decays slower than in a hard sphere solvent. Upon increasing the strength of attraction (stickiness) between the molecules of solvent, these oscillations gradually disappear, the PMF becoming long ranged and attractive at all separations.
Hydrogen induced antiferromagnetic ordering and structural changes in U(Co0.3Ni0.7)AlH2.2
Authors: Shashikala K. , Sathyamoorthy A. , Raj P. , Dhar S. K. , Kundaliya D. , Malik S. K.
Published: March 2009

Hydrogen absorption studies have been carried out on the intermetallic compound U(Co0.3Ni0.7)Al. Unlike UNiAl which forms a hydride with composition UNiAlH2.3, the isostructural UCoAl does not absorb hydrogen under moderate conditions. However, hydrogen absorption is found to take place in the Ni substituted U(Co1−xNix)Al alloys, where the Ni content (x) is >0.5. For x=0.7, we find that U(Co0.3Ni0.7)Al forms the hydride U(Co0.3Ni0.7)AlH2.2. The hexagonal structure of the parent compound is retained on hydrogen absorption, but there is a shifting of the transition elements from the U plane to the Al plane in the unit cell. While the parent compound U(Co0.3Ni0.7)Al is paramagnetic down to 2 K, U(Co0.3Ni0.7)AlH2.2 is an antiferromagnet with a relatively high Néel temperature TN=70 K. Heat capacity measurements show a decrease in the electronic specific heat coefficient (γ) on hydrogenation, implying a reduction in the electronic density of states at the Fermi level.
Energy partitioning for generalized product functions: The interference contribution to the energy of generalized valence bond and spin coupled wave functions
Authors: Cardozo Thiago Messias , Nascimento Marco Antonio Chaer
Published: March 2009

The main driving force for the formation of the covalent bond is the quantum-mechanical interference effect among one-electron states, as has been suggested in several works by the use of partition schemes to calculate the interference contributions to the energy. However, due to some difficulties associated with the original approaches, calculations were only carried out for a few, mostly diatomic molecules. In this work, we propose a general approach of partitioning based on generalized product functions with generalized valence bond at the perfect pairing approximation and spin-coupled groups, which should allow the investigation of a broader array of molecules, and hopefully, shed light on the nature of the chemical bond in molecules with unusual chemical features. Among other things, this approach lends itself naturally to the investigation of interference in individual bonds or groups of bonds in a molecule.
Inverse spectral results for Schrödinger operators on the unit interval with partial information given on the potentials
Authors: Amour L. , Faupin J. , Raoux T.
Published: March 2009

We pursue the analysis of the Schrödinger operator on the unit interval in inverse spectral theory initiated in the work of Amour and Raoux [“Inverse spectral results for Schrödinger operators on the unit interval with potentials in Lp spaces,” Inverse Probl. 23, 2367 (2007)]. While the potentials in the work of Amour and Raoux belong to L1 with their difference in Lp (1≤p<∞), we consider here potentials in Wk,1 spaces having their difference in Wk,p, where 1≤p≤+∞, k∊{0,1,2}. It is proved that two potentials in Wk,1([0,1]) being equal on [a,1] are also equal on [0,1] if their difference belongs to Wk,p([0,a]) and if the number of their common eigenvalues is sufficiently high. Naturally, this number decreases as the parameter a decreases and as the parameters k and p increase.
Population inversion induced by Landau–Zener transition in a strongly driven rf superconducting quantum interference device
Authors: Sun Guozhu , Wen Xueda , Wang Yiwen , Cong Shanhua , Chen Jian , Kang Lin , Xu Weiwei , Yu Yang , Han Siyuan , Wu Peiheng
Published: March 2009

Microwave resonances between discrete macroscopically distinct quantum states with single photon and multiphoton absorption are observed in a strongly driven radio frequency superconducting quantum interference device flux qubit. The amplitude of the resonant peaks and dips are modulated by the power of the applied microwave irradiation and a population inversion is generated at low flux bias. These results, which can be addressed with Landau–Zener transition, are useful to develop an alternative means to initialize and manipulate the flux qubit, as well as to do a controllable population inversion used in a micromaser.
The open cloak
Authors: Ma Hua , Qu Shaobo , Xu Zhuo , Wang Jiafu
Published: March 2009

By adopting the coordinate transformation theory and the corresponding numerical approach, we investigated the method of designing open cloaks that have one or more windows to exchange information and matter with the outer environment. Compared with close cloaks, open cloaks have the quasiperfect cloaking performance and are applied to any objects especially to the moving ones that must communicate and exchange matter with the outer region, which thus opens up possibilities for practical applications of cloak technologies developed recently.
Phase stability of cubic Mg0.55Zn0.45O thin film studied by continuous thermal annealing method
Authors: Ju Z. G. , Shan C. X. , Yang C. L. , Zhang J. Y. , Yao B. , Zhao D. X. , Shen D. Z. , Fan X. W.
Published: March 2009

The phase stability of cubic Mg0.55Zn0.45O thin film grown by metal-organic chemical vapor deposition was studied through continuous thermal annealing. The crystal quality and surface smoothness were greatly improved after a continuous thermal annealing at 750 °C. It is attributed to the reducing of interstitial Zn by thermal annealing. However, phase segregation occurred when the sample was annealed at a higher temperature (850 °C), which is identified from both x-ray diffraction patterns and optical transmission spectra.
Highly efficient single-emitting-layer white organic light-emitting diodes with reduced efficiency roll-off
Authors: Wang Qi , Ding Junqiao , Ma Dongge , Cheng Yanxiang , Wang Lixiang
Published: March 2009

By codoping blue and orange phosphorescent dyes into a single host material, a highly efficient white organic light-emitting diode (WOLED) with Commission Internationale de L’Eclairage coordinates of (0.38, 0.43) at 12 V is demonstrated. Remarkably, this WOLED achieves reduced current efficiency roll-off, which slightly decreases from its maximum value of 37.3–31.0 cd/A at 1000 cd/m2. The device operational mechanism is subsequently investigated in order to unveil the origin of the high performance.
The Politics of Landscape Value: A Case Study of Wind Farm Conflict in Rural Catalonia
Authors: Zografos Christos , Martínez-Alier Joan
Published: March 2009

Conflicts over the installation of wind farms constrain the potential to adopt an effective means for mitigating climate change. Although conventional wisdom attributes wind farm opposition to ‘not in my back yard’ attitudes, research shows that this explanation fails to incorporate the multiplicity of underlying motivations of opposition. Instead, distributional and institutional factors and procedural opportunities for public participation significantly influence support for wind farms. We consider the relevance of a political ecology explanation of wind farm conflicts by focusing on a case study in rural Catalonia, Spain. We argue that the conflict constitutes a recurrence of older and broader ‘centre’–‘periphery’ antagonisms and that two more explanatory elements are complementary to this political ecology explanation: the existence of alternative landscape valuations and the encouragement of instrumental rationality by the planning framework. We suggest that the absence of opportunities for meaningful deliberation in decision making and the predominance of decisional bottom lines curtail claims to fairer distribution of costs and benefits from locally hosted energy developments, as well as alternative landscape value claims, and that this fuels conflict.
Neonatal respiratory morbidity and mode of delivery in a population‐based study of low‐risk pregnancies
Authors: FARCHI SARA , DI LALLO DOMENICO , FRANCO FRANCESCO , POLO ARIANNA , LUCCHINI RENATO , CALZOLARI FLAMINIA , DE CURTIS MARIO
Published: March 2009

The aim of this study is to evaluate the association between the mode of delivery and the risk of neonatal respiratory complications in a cohort of term newborns in the Lazio region, Italy. Data on 139,379 term singleton infants born in 2003–2005 were retrieved from birth and hospital discharge database. Odds Ratios (ORs) adjusted by age, parity, birth weight, gestational age, and gender were calculated using logistic regression models. The rate of prelabor cesarean section (CS) was 26.2%. The rates of neonatal respiratory morbidity were 29.6/1,000 in infants delivered by prelabor CS and 17.4/1,000 in infants delivered vaginally or by CS in labor. The adjusted risk of neonatal respiratory morbidity associated with prelabor cesarean birth at 37 weeks is four times higher than in intended vaginal birth after 37 weeks. Prelabor cesarean delivery should be performed after at least 38 weeks’ of gestation in order to minimize neonatal respiratory morbidity.
Multicast Encryption Infrastructure for Security in Sensor Networks
Authors: Brooks R. R. , Pillai Brijesh , Pirretti Matthew , Weigle Michele C.
Published: March 2009

Designing secure sensor networks is difficult. We propose an approach that uses multicast communications and requires fewer encryptions than pairwise communications. The network is partitioned into multicast regions; each region is managed by a sensor node chosen to act as a keyserver. The keyservers solicit nodes in their neighborhood to join the local multicast tree. The keyserver generates a binary tree of keys to maintain communication within the multicast region using a shared key. Our approach supports a distributed key agreement protocol that identifies the compromised keys and supports membership changes with minimum system overhead. We evaluate the overhead of our approach by using the number of messages and encryptions to estimate power consumption. Using data from field tests of a military surveillance application, we show that our multicast approach needs fewer encryptions than pair-wise keying approaches. We also show that this scheme is capable of thwarting many common attacks.
Adaptive Optimizations for Surveillance Sensor Network Longevity
Authors: Brooks R. R. , Siddulugari Hemanth
Published: March 2009

Sensor networks are typically wireless networks composed of resource-constrained battery powered devices. In this paper, we present a criterion for determining whether or not a surveillance sensor network is viable. We use this criterion to compare methods for extending the effective lifetime of the sensor network. The life extension methods we consider are local adaptations that reduce the energy drain on individual nodes. They are communications range management, node repositioning, and data agreement. Simulations of a surveillance scenario quantify the utility of these methods. Our results indicate that data agreement provides the most improvement in network longevity, and communications range management is also useful. Repositioning nodes to reduce the power needed for communications is dependent on the amount of attenuation experienced by the node's communications signal and the volume of traffic between nodes. When these factors are considered, node repositioning is an effective strategy for network life extension. Synergies between the energy conservation approaches are also explored.
Power Assignment for Symmetric Communication in Wireless Sensor Networks
Authors: Park Joongseok , Sahni Sartaj
Published: March 2009

We show that two incremental power heuristics for power assignment in a wireless sensor network have an approximation ratio 2. Enhancements to these heuristics are proposed. It is shown that these enhancements do not reduce the approximation ratio of the considered incremental power heuristics. However, experiments conducted by us indicate that the proposed enhancements reduce the power cost of the assignment on average. Further, the two-edge switch enhancements reduce the power-cost reduction (relative to using minimum cost spanning trees) that is, on average, twice as much as obtainable from any of the heuristics proposed earlier.
An Interactive, Source-Centric, Open Testbed for Developing and Profiling Wireless Sensor Systems
Authors: Dalton Andrew R. , Hallstrom Jason O.
Published: March 2009

The difficulty of developing wireless sensor systems is widely recognized. Problems associated with testing, debugging, and profiling are key contributing factors. While network simulators have proven useful, they are unable to capture the subtleties of underlying hardware, nor the dynamics of wireless signal propagation and interference; and physical experimentation remains a necessity. To this end, developers increasingly rely on shared deployments exposed for physical experimentation. Sensor network testbeds are under development across the world.

We present a complementary testbed architecture that derives its novelty from three characteristics. First, the system is interactive; users can profile source and network level components across a network in real time, as well as inject transient state faults and external network traffic. Second, the system is source-centric; it enables automated source code analysis, instrumentation, and compilation. Finally, the design is open; developers can extend the set of exposed inter faces as appropriate to particular projects without modifying the underlying middleware. We present the testbed design and implementation, a graphical user interface, a shell-based macro programming interface, example scenarios that illustrate their use, and discuss the testbed's application in the research and teaching activities at client institutions.
Bryan Krantz: From folding to unfolding proteins
Authors: Savage Liz
Published: March 2009

Krantz analyzes anthrax toxin to understand the physics of protein unfolding and transport.
ER membrane–bending proteins are necessary for de novo nuclear pore formation
Authors: Dawson T. Renee , Lazarus Michelle D. , Hetzer Martin W. , Wente Susan R.
Published: March 2009

Nucleocytoplasmic transport occurs exclusively through nuclear pore complexes (NPCs) embedded in pores formed by inner and outer nuclear membrane fusion. The mechanism for de novo pore and NPC biogenesis remains unclear. Reticulons (RTNs) and Yop1/DP1 are conserved membrane protein families required to form and maintain the tubular endoplasmic reticulum (ER) and the postmitotic nuclear envelope. In this study, we report that members of the RTN and Yop1/DP1 families are required for nuclear pore formation. Analysis of Saccharomyces cerevisiae prp20-G282S and nup133Δ NPC assembly mutants revealed perturbations in Rtn1–green fluorescent protein (GFP) and Yop1-GFP ER distribution and colocalization to NPC clusters. Combined deletion of RTN1 and YOP1 resulted in NPC clustering, nuclear import defects, and synthetic lethality with the additional absence of Pom34, Pom152, and Nup84 subcomplex members. We tested for a direct role in NPC biogenesis using Xenopus laevis in vitro assays and found that anti-Rtn4a antibodies specifically inhibited de novo nuclear pore formation. We hypothesize that these ER membrane–bending proteins mediate early NPC assembly steps.
Unc5B associates with LARG to mediate the action of repulsive guidance molecule
Authors: Hata Katsuhiko , Kaibuchi Kozo , Inagaki Shinobu , Yamashita Toshihide
Published: March 2009

Neuronal axons are guided by attractive and repulsive cues in their local environment. Because the repulsive guidance molecule A (RGMa) was originally identified as an axon repellent in the visual system, diverse functions in the developing and adult central nervous system have been ascribed to it. RGMa binding to its receptor neogenin induces RhoA activation, leading to inhibitory/repulsive behavior and collapse of the neuronal growth cone. However, the precise mechanisms that regulate RhoA activation are poorly understood. In this study, we show that Unc5B, a member of the netrin receptor family, interacts with neogenin as a coreceptor for RGMa. Moreover, leukemia-associated guanine nucleotide exchange factor (LARG) associates with Unc5B to transduce the RhoA signal. Focal adhesion kinase (FAK) is involved in RGMa-induced tyrosine phosphorylation of LARG as well as RhoA activation. These findings uncover the molecular basis for diverse functions mediated by RGMa.
Unusual Long-Distance Movement Strategies of Potato mop-top virus RNAs in Nicotiana benthamiana
Authors: Torrance Lesley , Lukhovitskaya Nina I. , Schepetilnikov Mikhail V. , Cowan Graham H. , Ziegler Angelika , Savenkov Eugene I.
Published: March 2009

The Potato mop-top virus (PMTV) genome encodes replicase, movement, and capsid proteins on three different RNA species that are encapsidated within tubular rod-shaped particles. Previously, we showed that the protein produced on translational readthrough (RT) of the coat protein (CP) gene, CP-RT, is associated with one extremity of the virus particles, and that the two RNAs encoding replicase and movement proteins can move long distance in the absence of the third RNA (RNA-CP) that encodes the capsid proteins, CP and CP-RT. Here, we examined the roles of the CP and CP-RT proteins on RNA movement using infectious clones carrying mutations in the CP and CP-RT coding domains. The results showed that, in infections established with mutant RNA-CP expressing CP together with truncated CP-RT, systemic movement of the mutant RNA-CP was inhibited but not the movement of the other two RNAs. Furthermore, RNA-CP long-distance movement was inhibited in a mutant clone expressing only CP in the absence of the CP-RT polypeptide. CP-RT was not necessary for particle assembly because virions were observed in leaf extracts infected with the CP-RT deletion mutants. RNA-CP moved long distance when protein expression was suppressed completely or when CP expression was suppressed so that only CP-RT or truncated CP-RT was expressed. CP-RT but not CP interacted with the movement protein TGB1 in the yeast two-hybrid system. CP-RT and TGB1 were detected by enzyme-linked immunosorbent assay in virus particles and the long-distance movement of RNA-CP was correlated with expression of CP-RT that interacted with TGB1; mutant RNA-CP expressing truncated CP-RT proteins that did not interact with TGB1 formed virions but did not move to upper noninoculated leaves. The results indicate that PMTV RNA-CP can move long distance in two distinct forms: either as a viral ribonucleoprotein complex or as particles that are most likely associated with CP-RT and TGB1.
Conidiophore Stalk-less1 Encodes a Putative Zinc-Finger Protein Involved in the Early Stage of Conidiation and Mycelial Infection in Magnaporthe oryzae
Authors: Zhou Zhuangzhi , Li Guihua , Lin Chunhua , He Chaozu
Published: March 2009

Over recent decades, many pathogenicity genes of Magnaporthe oryzae have been identified but only a very limited number of genes have been identified that encode components of the conidiogenesis pathway. We report here a T-DNA insertional mutant that completely lost conidiation ability. Further investigation revealed that this mutant did not develop any conidiophore, and that the T-DNA was integrated into an annotated gene designated as conidiophore stalk-less1 or COS1. Complementation experiments suggested that COS1 may be a determinant of conidiation. Sequence analysis revealed that COS1 putatively encodes a 491-amino-acid zinc-finger protein and the protein was revealed localized to nucleus. Reverse-transcriptase polymerase chain reaction (RT-PCR)-based expression analysis indicated that two homologues of conidiophore-related genes were affected by the cos1 mutation, suggesting that Cos1 may function as a transcriptional regulator controlling genes responsible for conidiation. Inoculations of rice roots and wounded leaves with mycelia suggested that COS1 is not required for pathogenicity. Moreover, mutation of COS1 may aggravate infection of wounded leaves. Interestingly, different from the wild-type strain, mycelia of the cos1 mutant successfully infected host cells and caused visible symptoms on unwounded leaf blades and sheaths, indicating that Cos1 may have a role in some unknown mechanism of mycelial infection of M. oryzae.
The Magnaporthe oryzae Avirulence Gene AvrPiz-t Encodes a Predicted Secreted Protein That Triggers the Immunity in Rice Mediated by the Blast Resistance Gene Piz-t
Authors: Li Wei , Wang Baohua , Wu Jun , Lu Guodong , Hu Yajun , Zhang Xing , Zhang Zhengguang , Zhao Qiang , Feng Qi , Zhang Hongyan , Wang Zhengyi , Wang GuoLiang , Han Bin , Wang Zonghua , Zhou Bo
Published: March 2009

The Magnaporthe oryzae avirulence gene AvrPiz-t activates immunity in a gene-for-gene fashion to rice mediated by the blast resistance gene Piz-t. To dissect the molecular mechanism underlying their recognition, we initiated the cloning of AvrPiz-t using a map-based cloning strategy. The AvrPiz-t gene was delimited to an approximately 21-kb genomic fragment, in which six genes were predicted. Complementation tests of each of these six candidate genes led to the final identification of AvrPiz-t, which encodes a 108-amino-acid predicted secreted protein with unknown function and no homologues in M. oryzae or in other sequenced fungi. We found that AvrPiz-t is present in the virulent isolate GUY11 but contains a Pot3 insertion at a position 462 bp upstream from the start codon. Complementation tests of AvrPiz-t genes driven by promoters of varying length revealed that a promoter larger than 462 bp is essential to maintain the AvrPiz-t function. These results suggest that a Pot3 insertion in GUY11 might interfere with the proper function of AvrPiz-t. Additionally, we found that AvrPiz-t can suppress the programmed cell death triggered by mouse BAX protein in Nicotiana benthamiana, identifying a mechanism by which AvrPiz-t may contribute virulence of M. oryzae.
Broad-Spectrum Resistance to Crown Rust, Puccinia coronata f. sp. avenae, in Accessions of the Tetraploid Slender Oat, Avena barbata
Authors: Carson M. L.
Published: March 2009

The use of race-specific seedling genes for resistance has been the primary means of controlling crown rust of oat (Puccinia coronata). As resistance genes from hexaploid cultivated oat, Avena sativa and, later, the wild hexaploid animated oat, A. sterilis, were deployed in oat cultivars, corresponding virulence in the crown rust population increased rapidly, such that the effective lifespan of a resistant cultivar in the United States is now 5 years or less. Introgression of resistance genes from diploid and tetraploid Avena spp. into hexaploid oat has been difficult due to differences in ploidy levels and the lack of homology of chromosomes between the two species. The wild tetraploid slender oat, A. barbata, has been a source of powdery mildew and stem rust resistance in cultivated oat but has largely been unexploited for crown rust resistance. In total, 359 accessions of A. barbata from the National Small Grains Collection were evaluated in seedling greenhouse tests. Of these accessions, 39% were at least moderately resistant when inoculated with a crown rust race with low virulence (DBBC). When tested further with a highly diverse bulk inoculum from the 2006 and 2007 St. Paul buckthorn nursery, 48 accessions (approximately 13%) were resistant. Many of these accessions were heterogeneous in reaction, but two accessions (PI320588 from Israel and PI337893 from Italy) were highly resistant (immune) and two others (PI337886 from Italy and PI367293 from Spain) consistently produced resistant reactions (chlorotic flecks) in all tests. Resistant accessions were found from throughout much of the natural range of A. barbata. Crosses of some of the better accessions have been made to cultivated oat.
Managing Foliar Blights on Carrot Using Copper, Azoxystrobin, and Chlorothalonil Applied According to TOM-CAST
Authors: Dorman E. A. , Webster B. J. , Hausbeck M. K.
Published: March 2009

Alternaria dauci and Cercospora carotae cause foliar blight on carrot, causing yield reductions in severely blighted fields. Currently, fungicides are used on either a 7-day schedule or according to the TOM-CAST disease forecasting system. Organic production prohibits applications of most fungicides for blight control but does allow select copper-based products. The objective of this study was to use the TOM-CAST weather forecasting system to (i) assess the efficacy of copper hydroxide treatments for organic operations and (ii) evaluate the efficacy of reduced-risk products in an alternating spray program. Chlorothalonil, azoxystrobin, and copper hydroxide were applied alone or in alternating programs in 2001 and 2002. Reapplications were made on a 7-day schedule or according to TOM-CAST using disease severity value (DSV) thresholds of 10, 15, and 20. Area under the disease progress curve (AUDPC) data revealed that all application intervals significantly limited disease incidence on the foliage and petioles, resulting in healthier petioles at harvest compared with the untreated. The 7-day and TOM-CAST 10 DSV programs had comparable rating values for all parameters assessed and were more effective than the TOM-CAST 15 and 20 DSV programs in limiting petiole disease and maintaining overall petiole health. Copper hydroxide treatments resulted in higher AUDPC values and significantly different petiole health ratings compared with other treatments, yet P values indicated significant disease control compared with the untreated. The TOM-CAST 15 DSV program reduced sprays up to 40% compared with a 7-day interval and produced mean savings of $127/ha in 2001 and $137/ha in 2002.
Identification of Soybean Genotypes Resistant to Cercospora sojina by Field Screening and Molecular Markers
Authors: Mian Rouf , Bond Jason , Joobeur Tarek , Mengistu Alemu , Wiebold William , Shannon Grover , Wrather Allen
Published: March 2009

Frogeye leaf spot (FLS) of soybean, caused by Cercospora sojina, has been a problem in the southern United States for many years and has recently become a greater problem in the northern United States. Cultivars resistant to FLS have been developed for planting in the southern United States and resistance in many of these cultivars is conditioned by the Rcs3 gene. This gene conditions immunity to all known races and isolates of the pathogen. Resistance to C. sojina in soybean genotypes (cultivars and breeding lines) adapted to north-central U.S. production region is unknown. The objectives of this study were to (i) identify maturity group (MG) III, IV, and V soybean genotypes resistant to C. sojina race 11 by field screening at multiple locations over years and (ii) determine whether FLS resistance in these genotypes is likely to be conditioned by the Rcs3 gene. In total, 1,350 genotypes were evaluated for resistance to race 11 in field trials, and 13 MG III, 45 MG IV, and 15 MG V genotypes did not develop symptoms of FLS. Of these, 54 were subsequently tested for the possible presence of Rcs3 using five molecular markers located within 2 centimorgans (cM) of the gene. None of the MG III genotypes tested had the Rcs3 haplotype of cv. Davis, the source of Rcs3; six of the MG IV genotypes and seven of the MG V genotypes had the Rcs3 haplotype. This is the first report of the presence of the Rcs3 haplotype in LN 97-15076 and S99-2281. The soybean genotypes predicted to have the Rcs3 gene and other genotypes with no FLS symptoms in field trials may be useful in developing soybean cultivars with broad resistance to FLS and adapted to the northern United States.
First Report of Cucumber mosaic virus in Anemone sp. in the United States
Authors: Tzanetakis I. E.
Published: March 2009

In the spring of 2008, more than a dozen, aphid-infested, anemone plants (Anemone sp.) grown at the campus of the University of Arkansas in Fayetteville showed stunting and mosaic, whereas only two were asymptomatic. Leaf homogenates from four symptomatic plants were inoculated onto Nicotiana benthamiana that became stunted and developed severe mosaic approximately 7 days postinoculation, whereas buffer-inoculated plants remained asymptomatic. Double-stranded RNA (dsRNA) extraction (4) from symptomatic anemone revealed the presence of four predominant bands of approximately 3.2, 2.9, 2.2, and 0.9 kbp, a pattern indicative of cucumovirus infection. Cucumber mosaic virus (CMV) is the only cucumovirus reported in anemone in Europe (2) and Israel (3), and for this reason, anemone and N. benthamiana plants were tested by Protein A ELISA with antisera against CMV developed by H. A. Scott. ELISA verified the presence of CMV in symptomatic anemone and inoculated N. benthamiana, while asymptomatic plants were free of the virus. Using cucumovirus degenerate primers, essentially as described by Choi et al. (1), a region of approximately 940 bases that includes the complete coat protein gene of the virus was amplified from symptomatic anemone and N. benthamiana but not asymptomatic plants of either species. This anemone isolate (GenBank Accession No. FJ375723) belongs to the IA subgroup of CMV because it shares 99% nucleotide and 100% amino acid sequence identities with the Fny isolates of the virus. To my knowledge, this is the first report of CMV infecting anemone in the United States and an important discovery for the ornamental industry since anemone is commonly grown together with several ornamental hosts of CMV in nursery and garden settings.

References: (1) S. K. Choi et al. J. Virol. Methods 83:67, 1999. (2) M. Hollings. Ann. Appl. Biol. 45:44, 1957 (3) G. Loebenstein. Acta Hortic. 722:31, 2006 (4) I. E. Tzanetakis and R. R. Martin, J. Virol. Methods 149:167, 2008.