bluuebunny/crossref_metadata_2025 huggingface dataset:
Peer Review of Teaching: Multiple Raters
Authors: Prezas Raul , Shaver Mark , Carlson Tara , Taylor J. Scott , Scudder Rosalind
Published: October 2009

Peer review of teaching is relatively new in many academic programs. Primarily focused on formative, rather than summative, assessment, peer reviews differ in types of artifacts and teaching behaviors observed during the review. The purpose of this study was to begin a preliminary investigation of peer review of teaching among internal faculty. Two faculty members in the Department of Communication Sciences and Disorders (CSD) at Wichita State University participated in this study. Both instructors agreed to have one class session each videotaped within the same week. Two comparable 10-minute presentation segments were selected and edited from the recordings. The recordings were then viewed and rated in counter-balanced order by 17 faculty peers in CSD programs. Ratings were collected using a 5-point Likert scale rating form, which was created for the study. Results were found to be generally positive with mean ratings of 2.23 (s.d = 1.19) and 2.41 (s.d. = 1.19) for the two instructors. Interestingly, both videotapes exhibited an order effect when low responses were removed. These findings are presented as well as questions to be examined in future studies.
Language for Scholars: A Communication Skills Building Program
Authors: Lybolt John , Gottfred Kate , Anderson Roger , Olszewski Abbie
Published: October 2009

In this article we discuss a communication skills building program Leap Learning Systems calls Language for Scholars (LFS), a program developed at the request of a not-for-profit agency in 1994 to help 8th grade urban students who had received scholarships to private high schools. The LFS program focuses on building classroom communication skills called Academic English.
Förster resonance energy transfer enhanced color-conversion using colloidal semiconductor quantum dots for solid state lighting
Authors: Nizamoglu Sedat , Demir Hilmi Volkan
Published: October 2009

In this paper, we present Förster resonance energy transfer (FRET)-enhanced color-conversion using colloidal semiconductor quantum dot nanocrystals (NCs) to make reddish-orange light-emitting diodes for use in ultraefficient solid state lighting. To achieve FRET enhancement at 614 nm, we use an energy gradient hybrid structure made of cyan- and orange-emitting CdSe/ZnS NCs (λPL=492 and 588 nm in solution, respectively). This enables recycling of trapped excitons using FRET and achieves a relative quantum efficiency enhancement of 15.1% in reddish-orange full color-conversion for the integrated hybrid cyan-orange NC layer with respect to the case of full color-conversion using only orange NCs without FRET.
Discrete self-similarity in ultrarelativistic type-II strong explosions
Authors: Oren Yonatan , Sari Re’em
Published: October 2009

A solution to the ultrarelativistic strong explosion problem with a nonpower law density gradient is delineated. We consider a blast wave expanding into a density profile falling off as a steep radial power law with small, spherically symmetric, and log-periodic density perturbations. We find discretely self-similar solutions to the perturbation equations and compare them to numerical simulations. These results are then generalized to encompass small spherically symmetric perturbations with arbitrary profiles.
Coherent single-electron transfer in coupled quantum dots
Authors: Fountoulakis Antonios , Terzis Andreas F. , Paspalakis Emmanuel
Published: October 2009

We theoretically investigate the coherent transfer of one electron between the ground states of a double coupled quantum dot structure. The coherent transfer of the electron is externally controlled by applied electromagnetic fields with on- or close-resonance driving frequencies and various shapes and duration. We derive the analytical expressions for the parameters of the external fields by approximating the quantum dot system as a three-level Λ-type system. The analytical solutions are compared with numerical results and good agreement is found. The control methods developed here are applicable in symmetric and asymmetric quantum dot nanostructures.
Engineering of low-loss metal for nanoplasmonic and metamaterials applications
Authors: Bobb D. A. , Zhu G. , Mayy M. , Gavrilenko A. V. , Mead P. , Gavrilenko V. I. , Noginov M. A.
Published: October 2009

We have shown that alloying a noble metal (gold) with another metal (cadmium), which can contribute two electrons per atom to a free electron gas, can significantly improve the metal’s optical properties in certain wavelength ranges and make them worse in the other parts of the spectrum. In particular, in the gold-cadmium alloy we have demonstrated a significant expansion of the spectral range of metallic reflectance to shorter wavelengths. The experimental results and the predictions of the first principles theory demonstrate an opportunity for the improvement and optimization of low-loss metals for nanoplasmonic and metamaterials applications.
Dielectric function of zinc-blende AlN from 1 to 20 eV: Band gap and van Hove singularities
Authors: Röppischer M. , Goldhahn R. , Rossbach G. , Schley P. , Cobet C. , Esser N. , Schupp T. , Lischka K. , As D. J.
Published: October 2009

The dielectric function (DF) of phase-pure cubic AlN films is determined by ellipsometry. The sharp onset of the imaginary part of the DF defines the direct absorption edge corresponding to a conduction-to-valence band spacing at the center of the Brillouin zone (BZ) of 5.93 eV. Phonon-assisted transitions lead to the pronounced absorption tail below this edge from which the indirect gap of zinc-blende AlN is estimated with 5.3 eV. Transitions due to four additional critical points of the BZ are resolved at higher photon energies. The high-frequency and static dielectric constants are determined with 4.25 and 8.07, respectively.
Modeling spin transport with current-sensing spin detectors
Authors: Li Jing , Appelbaum Ian
Published: October 2009

By incorporating the proper boundary conditions, we analytically derive the impulse response (or “Green’s function”) of a current-sensing spin detector. We also compare this result to a Monte Carlo simulation (which automatically takes the proper boundary condition into account) and an empirical spin transit time distribution obtained from experimental spin precession measurements. In the strong drift-dominated transport regime, this spin current impulse response can be approximated by multiplying the spin density impulse response by the average drift velocity. However, in weak drift fields, large modeling errors up to a factor of 3 in most-probable spin transit time can be incurred unless the full spin current Green’s function is used.
Benchmarking density-functional-theory calculations of rotational g tensors and magnetizabilities using accurate coupled-cluster calculations
Authors: Lutnæs Ola B. , Teale Andrew M. , Helgaker Trygve , Tozer David J. , Ruud Kenneth , Gauss Jürgen
Published: October 2009

An accurate set of benchmark rotational g tensors and magnetizabilities are calculated using coupled-cluster singles-doubles (CCSD) theory and coupled-cluster single-doubles-perturbative-triples [CCSD(T)] theory, in a variety of basis sets consisting of (rotational) London atomic orbitals. The accuracy of the results obtained is established for the rotational g tensors by careful comparison with experimental data, taking into account zero-point vibrational corrections. After an analysis of the basis sets employed, extrapolation techniques are used to provide estimates of the basis-set-limit quantities, thereby establishing an accurate benchmark data set. The utility of the data set is demonstrated by examining a wide variety of density functionals for the calculation of these properties. None of the density-functional methods are competitive with the CCSD or CCSD(T) methods. The need for a careful consideration of vibrational effects is clearly illustrated. Finally, the pure coupled-cluster results are compared with the results of density-functional calculations constrained to give the same electronic density. The importance of current dependence in exchange–correlation functionals is discussed in light of this comparison.
ZnO-based metal-semiconductor field-effect transistors on glass substrates
Authors: Frenzel H. , Lorenz M. , Lajn A. , von Wenckstern H. , Biehne G. , Hochmuth H. , Grundmann M.
Published: October 2009

We investigate the influence of quartz glass and borosilicate glass substrates on the electrical properties of ZnO-based metal-semiconductor field-effect transistors (MESFETs). The n-type ZnO thin-film channels were grown by pulsed-laser deposition and MESFETs were processed by reactive dc sputtering of AgxO-Schottky gate contacts. All devices are in the normally-off state. They exhibit very low off-currents in the range of 10−13A and on/off ratios of maximum 6 decades. The channel mobilities are highest for ZnO on quartz with 1.3cm2/Vs. The glass substrates introduce a compensating effect on the conduction of the ZnO channel resulting in higher on/off-voltages and lower on-current.
Decomposition of energy and free energy changes by following the flow of work along reaction path
Authors: Haas Kevin , Chu Jhih-Wei
Published: October 2009

To extract mechanistic information of activated processes, we propose to decompose potential energy and free energy differences between configurations into contributions from individual atoms, functional groups, or residues. Decomposition is achieved by calculating the mechanical work associated with the displacements and forces of each atom along a path that connects two states, i.e., following the flow of work. Specifically, we focus on decomposing energy or free energy differences along representative pathways such as minimum energy paths (MEPs) and minimum free energy paths (MFEPs), and a numerical metric is developed to quantify the required accuracy of the reaction path. A statistical mechanical analysis of energy decomposition is also presented to illustrate the generality of this approach. Decomposition along MEP and MFEP is demonstrated on two test cases to illustrate the ability to derive quantitative mechanistic information for different types of activated processes. First, the MEP of alanine dipeptide isomerization in vacuum and the MFEP of isomerization in explicit water is studied. Our analysis shows that carbonyl oxygen and amide hydrogen contribute to most of the energetic cost for isomerization and that explicit water solvation modulates the free energy landscape primarily through hydrogen bonding with these atoms. The second test case concerns the formation of tetrahedral intermediate during a transesterification reaction. Decomposition analysis shows that water molecules not only have strong stabilization effects on the tetrahedral intermediate but also constitute a sizable potential energy barrier due to their significant structural rearrangement during the reaction. We expect that the proposed method can be generally applied to develop mechanistic understanding of catalytic and biocatalytic processes and provide useful insight for strategies of molecular engineering.
The nonrelativistic limit of (central-extended) Poincaré group and some consequences for quantum actualization
Authors: Ardenghi Juan S. , Castagnino M. , Campoamor-Stursberg R.
Published: October 2009

The nonrelativistic limit of the centrally extended Poincaré group is considered and their consequences in the modal Hamiltonian interpretation of quantum mechanics are discussed [O. Lombardi and M. Castagnino, Stud. Hist. Philos. Mod. Phys 39, 380 (2008); J. Phys, Conf. Ser. 128, 012014 (2008)]. Through the assumption that in quantum field theory the Casimir operators of the Poincaré group actualize, the nonrelativistic limit of the latter group yields to the actualization of the Casimir operators of the Galilei group, which is in agreement with the actualization rule of previous versions of modal Hamiltonian interpretation [Ardenghi et al., Found. Phys. (submitted)].
Chaos and crises in a model for cooperative hunting: A symbolic dynamics approach
Authors: Duarte Jorge , Januário Cristina , Martins Nuno , Sardanyés Josep
Published: October 2009

In this work we investigate the population dynamics of cooperative hunting extending the McCann and Yodzis model for a three-species food chain system with a predator, a prey, and a resource species. The new model considers that a given fraction σ of predators cooperates in prey’s hunting, while the rest of the population 1−σ hunts without cooperation. We use the theory of symbolic dynamics to study the topological entropy and the parameter space ordering of the kneading sequences associated with one-dimensional maps that reproduce significant aspects of the dynamics of the species under several degrees of cooperative hunting. Our model also allows us to investigate the so-called deterministic extinction via chaotic crisis and transient chaos in the framework of cooperative hunting. The symbolic sequences allow us to identify a critical boundary in the parameter spaces (K,C0) and (K,σ) which separates two scenarios: (i) all-species coexistence and (ii) predator’s extinction via chaotic crisis. We show that the crisis value of the carrying capacity Kc decreases at increasing σ, indicating that predator’s populations with high degree of cooperative hunting are more sensitive to the chaotic crises. We also show that the control method of Dhamala and Lai [Phys. Rev. E 59, 1646 (1999)] can sustain the chaotic behavior after the crisis for systems with cooperative hunting. We finally analyze and quantify the inner structure of the target regions obtained with this control method for wider parameter values beyond the crisis, showing a power law dependence of the extinction transients on such critical parameters.
A simple, analytical model of collisionless magnetic reconnection in a pair plasma
Authors: Hesse Michael , Zenitani Seiji , Kuznetsova Masha , Klimas Alex
Published: October 2009

A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region and to impart thermal energy to the plasma by means of quasiviscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative procedure. The solutions show expected features such as dominance of enthalpy flux in the reconnection outflow, as well as combination of adiabatic and quasiviscous heating. Furthermore, the model predicts a maximum reconnection electric field of E∗=0.4, normalized to the parameters at the inflow edge of the diffusion region.
Numerical simulation of high-current vacuum arc characteristics under combined action of axial magnetic field and external magnetic field from bus bar
Authors: Wang Lijun , Jia Shenli , Liu Ke , Wang Liuhuo , Shi Zongqian
Published: October 2009

In this paper, the two-dimensional high-current vacuum arc (HCVA) model under the combined action of axial magnetic field (AMF) and external magnetic field from bus bar (EMFBB) is established. Based on this model, the influence of AMF and EMFBB on HCVA characteristics can be simulated and analyzed. Simulation results show that the HCVA column will be deflected by the Lorentz force generated by EMFBB and higher arc current. Moreover, the deflection level will be increased with the increase in external EMFBB strength. For HCVA, due to the smaller axial velocity near cathode side, the deflection of plasma parameters (such as ion number density, ion temperature, electron temperature, plasma pressure, and so on) near cathode side is more significant than that near anode side. The current deflection near cathode side toward direction of Lorentz force is more significant than that near anode side.
Axisymmetric instabilities in electrospinning of highly conducting, viscoelastic polymer solutions
Authors: Carroll Colman P. , Joo Yong Lak
Published: October 2009

In this paper the axisymmetric instabilities observed during the electrospinning of highly electrically conducting, viscoelastic poly(ethylene oxide) (PEO)/water solutions are investigated. In our theoretical study, a linear stability analysis is coupled with a model for the stable electrospun jet. The combined model is used to calculate the expected bead growth rate and wave number for given electrospinning conditions. In the experimental section of the study, PEO/water solutions are electrospun and the formation of axisymmetric beads is captured using high-speed photography. Experimental values for the bead growth rate and wave number are extracted and compared with the model predictions. An energy analysis is then carried out on the stability results to investigate the mechanism of instability via the coupling between base flow and perturbation. The analysis reveals that the unstable axisymmetric mode for electrically driven, highly conducting jets is not a capillary mode, but is mainly driven by electrical forces due to the interaction of charges on the jet. We note that this axisymmetric, conducting mode often exhibits a growth rate too small to be observed during electrospinning. However, both our experiments and stability analysis demonstrate that the axisymmetric instability with a high growth rate can be seen in practice when the electrical force is effectively coupled with viscoelastic forces.
Characterization of tips for spin-polarized scanning tunneling microscopy
Authors: Rodary G. , Wedekind S. , Oka H. , Sander D. , Kirschner J.
Published: October 2009

We propose a conclusive characterization of the magnetic configuration of tips for spin-polarized scanning tunneling microscopy studies. We show that both careful tip preparation and characterization by tunneling spectroscopy need to be augmented by in-field measurements to ensure a reliable analysis of a magnetic contrast in spin-polarized scanning tunneling microscopy studies.
Anisotropic electronic properties of Ni nanowires in oriented mesoporous silica film
Authors: Cui Wei , Lu Xuemin , Su Bin , Lu Qinghua , Wei Yen
Published: October 2009

The electronic behavior of Ni nanowires in an oriented mesoporous silica thin film was reported. The hybrid film was prepared using a facile method of airflow-induced mesopore orientation from silica sol solution containing Ni2+ cation, followed by H2 reduction. Because of the confinement effect, the Ni nanowires were aligned in the oriented mesochannels, which resulted in anisotropic electronic responses. Such a property would be of great importance in the design of nanodevices for advanced photoelectric applications.
Sheath and presheath in plasma with warm ions
Authors: Robertson Scott
Published: October 2009

Numerical solutions are found for the potential profile of the presheath and sheath in plasma with a Maxwellian ion source distribution. Solutions are obtained for ratios of the electron temperature to ion source temperature from 0.1 to 10 for plasmas that are 20, 50, and 100 Debye lengths from the midplane to the wall. With increasing ion source temperature, the potential profile falls less rapidly in the presheath and the current density of ions to the wall increases and approaches the random ion current calculated for the source temperature. Ion distribution functions at the midplane, the sheath-presheath boundary, and at the wall are found and are more sharply peaked than Maxwellian distributions. At the midplane, the effective ion temperature is much less than the ion source temperature.
Coupled flows and oscillations in asymmetric rotating plasmas
Authors: Karimov A. R. , Stenflo L. , Yu M. Y.
Published: October 2009

Nonlinear coupling among the radial, axial, and azimuthal flows in an asymmetric cold rotating plasma is considered nonperturbatively. Exact solutions describing an expanding or contracting plasma with oscillations are then obtained. It is shown that despite the flow asymmetry the energy in the radial and axial flow components can be transferred to the azimuthal component but not the vice versa, and that flow oscillations need not be accompanied by density oscillations.
Monte Carlo investigation of terahertz plasma oscillations in gated ultrathin channel of n-InGaAs
Authors: Millithaler J.-F. , Pousset J. , Reggiani L. , Ziade P. , Marinchio H. , Varani L. , Palermo C. , Mateos J. , González T. , Perez S. , Pardo D.
Published: October 2009

By numerical simulations we investigate the dispersion of the plasma frequency in a gated channel of n-type InGaAs layer of thickness W and submicron length L at T=300 K. In the presence of a source-drain voltage and for a carrier concentrations of 1018 cm−3 the spectra evidences a peaked shape with two main bumps, the former at high frequency corresponding to the three-dimensional plasma frequency and the latter at a low frequency. The frequency value of the latter peak exhibits a dispersion as the inverse of the channel length in agreement with the predictions of gradual channel approximation. At increasing drain voltages the instabilities associated with the presence of Gunn domains are responsible for a suppression of the plasma peak in favor of the onset of a peak in the subterahertz domain associated with transit time effects.
Two routes to the one-dimensional discrete nonpolynomial Schrödinger equation
Authors: Gligorić G. , Maluckov A. , Salasnich L. , Malomed B. A. , Hadžievski Lj.
Published: October 2009

The Bose–Einstein condensate (BEC), confined in a combination of the cigar-shaped trap and axial optical lattice, is studied in the framework of two models described by two versions of the one-dimensional (1D) discrete nonpolynomial Schrödinger equation (NPSE). Both models are derived from the three-dimensional Gross–Pitaevskii equation (3D GPE). To produce “model 1” (which was derived in recent works), the 3D GPE is first reduced to the 1D continual NPSE, which is subsequently discretized. “Model 2,” which was not considered before, is derived by first discretizing the 3D GPE, which is followed by the reduction in the dimension. The two models seem very different; in particular, model 1 is represented by a single discrete equation for the 1D wave function, while model 2 includes an additional equation for the transverse width. Nevertheless, numerical analyses show similar behaviors of fundamental unstaggered solitons in both systems, as concerns their existence region and stability limits. Both models admit the collapse of the localized modes, reproducing the fundamental property of the self-attractive BEC confined in tight traps. Thus, we conclude that the fundamental properties of discrete solitons predicted for the strongly trapped self-attracting BEC are reliable, as the two distinct models produce them in a nearly identical form. However, a difference between the models is found too, as strongly pinned (very narrow) discrete solitons, which were previously found in model 1, are not generated by model 2—in fact, in agreement with the continual 1D NPSE, which does not have such solutions either. In that respect, the newly derived model provides for a more accurate approximation for the trapped BEC.
Plasmon enhanced light emission from InGaN quantum wells via coupling to chemically synthesized silver nanoparticles
Authors: Henson John , Heckel John C. , Dimakis Emmanouil , Abell Josh , Bhattacharyya Anirban , Chumanov George , Moustakas Theodore D. , Paiella Roberto
Published: October 2009

Chemically synthesized single-crystal silver nanoparticles are used to demonstrate plasmon enhanced visible light emission from nitride semiconductor quantum wells. For ease of assembly and testing, the nanoparticles are embedded onto the surface of flexible resin films, which are then simply adhered on top of the light emitting samples. Large enhancements in photoluminescence efficiency are correspondingly measured at emission wavelengths near the nanoparticle plasmonic resonance. At the same time, when samples emitting at a sufficiently far detuned wavelength are used, the measured efficiency is not affected by the nanoparticles, which confirms the plasmonic origin of the observed enhancement.
High temperature strain glass in Ti50(Pd50−xCrx) alloy and the associated shape memory effect and superelasticity
Authors: Zhou Yumei , Xue Dezhen , Ding Xiangdong , Otsuka Kazuhiro , Sun Jun , Ren Xiaobing
Published: October 2009

Strain glass has recently been reported in Ti50−xNi50+x (x≥1.5 at %) alloys and caused by the existence of point defects. This strain glass alloy, being nonmartensitic, exhibits shape memory effect (SME) and superelasticity (SE) around the freezing temperature T0. However, the T0 of Ti50−xNi50+x (x≥1.5 at %) strain glass alloy is very low (∼160 K), thus restricting its potential applications. In the present letter, we report a strain glass system, Ti50(Pd50−xCrx) (x≥9 at %), which has a significantly higher freezing temperature. It is based on a high-temperature martensitic system TiPd (with Ms∼810 K) and dopant Cr (as point defect). For Ti50(Pd40Cr10) strain glass, the freezing transition occurs at T0∼250 K, being close to the room temperature. Correspondingly, it exhibits SME and SE around its high T0. We further clarified that T0 of strain glass alloy is controlled by the martensitic transformation temperature Ms (i.e., martensite stability) of its corresponding host alloy without point defect. Our work provides insight into how to develop strain glass with desired T0 and the associated SME and SE for applications.
Estimating genetic diversity in Greek durum wheat landraces with RAPD markers
Authors: Mantzavinou Anna , Bebeli Penelope J. , Kaltsikes Pantouses J.
Published: October 2009

Using the random amplified polymorphic DNA (RAPD) method, the genetic diversity of 19 Greek landraces and 9 cultivars of durum wheat [Triticum turgidum L. var. durum (Desf.)] was studied. Two commercial bread wheat (Triticum aestivum L.) cultivars and one genotype of Triticum monococcum L. were also included in the study. Eighty-seven arbitrary primers (10-mer) were evaluated in a preliminary experiment and 15 of them were selected for the main experiments based on the quality and reliability of their amplification and the polymorphism they revealed. A total of 150 DNA bands were obtained, 125 (83.3%) of which were polymorphic. On average, 10 DNA bands were amplified per primer, 8.3 of which were polymorphic. The genetic similarity between all pairs of genotypes was evaluated using the Jaccard’s or Nei and Li’s coefficients; the values of the former ranged from 0.153 to 0.973 while those of the latter were slightly higher (0.265–0.986). Cluster analysis was conducted by the UPGMA and the Njoin methods. Both methods broadly placed 26 durum genotypes into 1 branch while the other branch consisted of 2 subgroups: 1 included the 2 bread wheat cultivars; the other 1 consisted of 2 durum landraces, ‘Kontopouli’ and ‘Mavrotheri-Chios’, which showed an intruiging behaviour sharing bands with the bread wheat cultivars. The T. monococcum cultivar stood apart from all other genotypes.
Hindered Rotation in New Air-Stable Ruthenium Olefin Metathesis Catalysts with Chromanylmethylidene Ligands
Authors: Hryniewicka Agnieszka , Morzycki Jacek W. , Siergiejczyk Leszek , Witkowski Stanisław , Wójcik Jacek , Gryff-Keller Adam
Published: October 2009

Three new ruthenium complexes with chromanylmethylidene ligands were synthesized and dynamic NMR analysis of these compounds was carried out. The activation energy for the C–Ru rotation was measured for the first time and found to be of ~60 kJ mol–1. The complexes may potentially serve as latent catalysts for olefin metathesis – they promote the simple ring-closing metathesis reactions very slowly at room temperature, but are much more active at slightly elevated temperatures. No asymmetric induction was observed when the chiral α-tocopherol-derived catalyst was used.
Hidden dynamic allostery in a PDZ domain
Authors: Petit Chad M. , Zhang Jun , Sapienza Paul J. , Fuentes Ernesto J. , Lee Andrew L.
Published: October 2009

Structure–function relationships in proteins are predicated on the spatial proximity of noncovalently interacting groups of atoms. Thus, structural elements located away from a protein's active site are typically presumed to serve a stabilizing or scaffolding role for the larger structure. Here we report a functional role for a distal structural element in a PDZ domain, even though it is not required to maintain PDZ structure. The third PDZ domain from PSD-95/SAP90 (PDZ3) has an unusual additional third alpha helix (α3) that packs in contiguous fashion against the globular domain. Although α3 lies outside the active site and does not make direct contact with C-terminal peptide ligand, removal of α3 reduces ligand affinity by 21-fold. Further investigation revealed that the difference in binding free energies between the full-length and truncated constructs is predominantly entropic in nature and that without α3, picosecond-nanosecond side-chain dynamics are enhanced throughout the domain, as determined by
2
H methyl NMR relaxation. Thus, the distal modulation of binding function appears to occur via a delocalized conformational entropy mechanism. Without removal of α3 and characterization of side-chain dynamics, this dynamic allostery would have gone unnoticed. Moreover, what appeared at first to be an artificial modification of PDZ3 has been corroborated by experimentally verified phosphorylation of α3, revealing a tangible biological mechanism for this novel regulatory scheme. This hidden dynamic allostery raises the possibility of as-yet unidentified or untapped allosteric regulation in this PDZ domain and is a very clear example of function arising from dynamics rather than from structure.
Spatiotemporal precision and hemodynamic mechanism of optical point spreads in alert primates
Authors: Sirotin Yevgeniy B. , Hillman Elizabeth M. C. , Bordier Clemence , Das Aniruddha
Published: October 2009

In functional brain imaging there is controversy over which hemodynamic signal best represents neural activity. Intrinsic signal optical imaging (ISOI) suggests that the best signal is the early darkening observed at wavelengths absorbed preferentially by deoxyhemoglobin (HbR). It is assumed that this darkening or “initial dip” reports local conversion of oxyhemoglobin (HbO) to HbR, i.e., oxygen consumption caused by local neural activity, thus giving the most specific measure of such activity. The blood volume signal, by contrast, is believed to be more delayed and less specific. Here, we used multiwavelength ISOI to simultaneously map oxygenation and blood volume [i.e., total hemoglobin (HbT)] in primary visual cortex (V1) of the alert macaque. We found that the hemodynamic “point spread,” i.e., impulse response to a minimal visual stimulus, was as rapid and retinotopically specific when imaged by using blood volume as when using the initial dip. Quantitative separation of the imaged signal into HbR, HbO, and HbT showed, moreover, that the initial dip was dominated by a fast local increase in HbT, with no increase in HbR. We found only a delayed HbR decrease that was broader in retinotopic spread than HbO or HbT. Further, we show that the multiphasic time course of typical ISOI signals and the strength of the initial dip may reflect the temporal interplay of monophasic HbO, HbR, and HbT signals. Characterizing the hemodynamic response is important for understanding neurovascular coupling and elucidating the physiological basis of imaging techniques such as fMRI.
War Crimes and Genocide in History, and the Evolution of Responsive International Law
Authors: Crowe David M.
Published: October 2009

War crimes and genocide are as old as history itself. So are regulations and laws that protect individuals during time of war, whether they be combatants or civilians. The Chinese philosopher Sun Tzu wrote in the fifth century BCE that it was important to treat “captured soldiers well in order to nurture them [for our use]. This is referred to as ‘conquering the enemy and growing stronger.'” Yet several centuries later, Qin Shi Huangdi, China's first emperor, committed horrible atrocities during his military campaigns to unite China. Eric Yong-Joon Lee adds that it should be remembered that the Qin emperor also created that country's “first managed international legal order.” But, according to Robert Cryer, it was the West, not Asia, that created the world's first “international criminal law regime.” This “regime,” R. P. Anand argues, was, in many ways, a form of“Victor's Justice“ or “ruler's law,” since it was forced on Asia and Africa by the West in the nineteenth century.
Justice 30 Years Later? The Cambodian Special Tribunal for the Punishment of Crimes against Humanity by the Khmer Rouge
Authors: Form Wolfgang
Published: October 2009

After a two-year tug-of-war between the US, the UN, and Phnom Penh, the Cambodian government, supported by massive international intervention, brought some of those accused of committing Khmer Rouge atrocities to trial before an independent court. The atrocities, which verged on genocide, were perpetrated between 1975 and 1979. The plan was to create a special tribunal consisting of both indigenous and foreign judges to try the perpetrators. Newspapers from 2002 reported that the first indictment would be issued some time during that year. As we know today, this proved to be a rosily optimistic prediction.
Teaching and Learning in the Social Context: A Meta-Analysis of Service Learning's Effects on Academic, Personal, Social, and Citizenship Outcomes
Authors: Conway James M. , Amel Elise L. , Gerwien Daniel P.
Published: October 2009

Service learning places teaching and learning in a social context, facilitating socially responsive knowledge. The purposes of this meta-analysis were to summarize evidence on (a) extent and types of change in participants in service learning programs, (b) specific program elements (moderators) that affect the amount of change in participants, and (c) generalizability of results across educational levels and curricular versus noncurricular service. We included 103 samples and found positive changes for all types of outcomes. Changes were moderate for academic outcomes, small for personal outcomes and citizenship outcomes, and in between for social outcomes. Programs with structured reflection showed larger changes and effects generalized across educational levels. We call for psychologists to increase their use of service learning, and we discuss resources for doing so.
A Strategy to Reduce Plagiarism in an Undergraduate Course
Authors: Belter Ronald W. , du Pré Athena
Published: October 2009

This study evaluated how effective an online academic integrity module was at reducing the occurrence of plagiarism in a written assignment for a university course. In a preintervention comparison group, plagiarism was detected in 25.8% of papers submitted, compared with only 6.5% in the group that completed the academic integrity module. The grades for plagiarized papers were significantly lower than grades for nonplagiarized papers, suggesting that a substantial amount of plagiarism occurs among students who produce relatively poor quality work. These findings indicate that a substantial proportion of plagiarism encountered was the result of inadequate knowledge about proper quotation and citation. The self-instruction module successfully reduced the occurrence of plagiarism.
Oxidative Stress Inhibits Nuclear Protein Export by Multiple Mechanisms That Target FG Nucleoporins and Crm1
Authors: Crampton Noah , Kodiha Mohamed , Shrivastava Sanhita , Umar Rehan , Stochaj Ursula
Published: October 2009

Nuclear transport of macromolecules is regulated by the physiological state of the cell and thus sensitive to stress. To define the molecular mechanisms that control nuclear export upon stress, cells were exposed to nonlethal concentrations of the oxidant diethyl maleate (DEM). These stress conditions inhibited chromosome region maintenance-1 (Crm1)-dependent nuclear export and increased the association between Crm1 and Ran. In addition, we identified several repeat-containing nucleoporins implicated in nuclear export as targets of oxidative stress. As such, DEM treatment reduced Nup358 levels at the nuclear envelope and redistributed Nup98. Furthermore, oxidative stress led to an increase in the apparent molecular masses of Nup98, Nup214, and Nup62. Incubation with phosphatase or β-N-acetyl-hexosaminidase showed that oxidative stress caused the phosphorylation of Nup98, Nup62, and Nup214 as well as O-linked N-acetylglucosamine modification of Nup62 and Nup214. These oxidant-induced changes in nucleoporin modification correlated first with the increased binding of Nup62 to the exporter Crm1 and second with the reduced interaction of Nup62 with other FxFG-containing nucleoporins. Together, oxidative stress up-regulated the binding of Crm1 to Ran and affected multiple repeat-containing nucleoporins by changing their localization, phosphorylation, O-glycosylation, or interaction with other transport components. We propose that the combination of these events contributes to the stress-dependent regulation of Crm1-mediated protein export.
Phosphatidylserine Regulation of Ca2+-triggered Exocytosis and Fusion Pores in PC12 Cells
Authors: Zhang Zhen , Hui Enfu , Chapman Edwin R. , Jackson Meyer B.
Published: October 2009

The synaptic vesicle protein synaptotagmin I (Syt I) binds phosphatidylserine (PS) in a Ca2+-dependent manner. This interaction is thought to play a role in exocytosis, but its precise functions remain unclear. To determine potential roles for Syt I-PS binding, we varied the PS content in PC12 cells and liposomes and studied the effects on the kinetics of exocytosis and Syt I binding in parallel. Raising PS produced a steeply nonlinear, saturating increase in Ca2+-triggered fusion, and a graded slowing of the rate of fusion pore dilation. Ca2+-Syt I bound liposomes more tightly as PS content was raised, with a steep increase in binding at low PS, and a further gradual increase at higher PS. These two phases in the PS dependence of Ca2+-dependent Syt I binding to lipid may correspond to the two distinct and opposing kinetic effects of PS on exocytosis. PS influences exocytosis in two ways, enhancing an early step leading to fusion pore opening, and slowing a later step when fusion pores dilate. The possible relevance of these results to Ca2+-triggered Syt I binding is discussed along with other possible roles of PS.
Bayesian random-effects threshold regression with application to survival data with nonproportional hazards
Authors: Pennell Michael L. , Whitmore G. A. , Ting Lee Mei-Ling
Published: October 2009

In epidemiological and clinical studies, time-to-event data often violate the assumptions of Cox regression due to the presence of time-dependent covariate effects and unmeasured risk factors. An alternative approach, which does not require proportional hazards, is to use a first hitting time model which treats a subject's health status as a latent stochastic process that fails when it reaches a threshold value. Although more flexible than Cox regression, existing methods do not account for unmeasured covariates in both the initial state and the rate of the process. To address this issue, we propose a Bayesian methodology that models an individual's health status as a Wiener process with subject-specific initial state and drift. Posterior inference proceeds via a Markov chain Monte Carlo methodology with data augmentation steps to sample the final health status of censored observations. We apply our method to data from melanoma patients with nonproportional hazards and find interesting differences from a similar model without random effects. In a simulation study, we show that failure to account for unmeasured covariates can lead to inaccurate estimates of survival probabilities.
Contribution of Erwinia amylovora Exopolysaccharides Amylovoran and Levan to Biofilm Formation: Implications in Pathogenicity
Authors: Koczan Jessica M. , McGrath Molly J. , Zhao Youfu , Sundin George W.
Published: October 2009

Erwinia amylovora is a highly virulent, necrogenic, vascular pathogen of rosaceous species that produces the exopolysaccharide amylovoran, a known pathogenicity factor, and levan, a virulence factor. An in vitro crystal violet staining and a bright-field microscopy method were used to demonstrate that E. amylovora is capable of forming a biofilm on solid surfaces. Amylovoran and levan production deletion mutants were used to determine that amylovoran was required for biofilm formation and that levan contributed to biofilm formation. In vitro flow cell and confocal microscopy were used to further reveal the architectural detail of a mature biofilm and differences in biofilm formation between E. amylovora wild-type (WT), Δams, and Δlsc mutant cells labeled with green fluorescent protein or yellow fluorescent protein. Scanning electron microscopy analysis of E. amylovora WT cells following experimental inoculation in apple indicated that extensive biofilm formation occurs in xylem vessels. However, Δams mutant cells were nonpathogenic and died rapidly following inoculation, and Δlsc mutant cells were not detected in xylem vessels and were reduced in movement into apple shoots. These results demonstrate that biofilm formation plays a critical role in the pathogenesis of E. amylovora.
Analysis of the Accumulation of Pea enation mosaic virus Genomes in Seed Tissues and Lack of Evidence for Seed Transmission in Pea (Pisum sativum)
Authors: Timmerman-Vaughan Gail , Larsen Richard , Murray Sarah , McPhee Kevin , Coyne Clarice
Published: October 2009

Pea enation mosaic virus (PEMV) is an important virus disease of pea. International movement of commercial pea cultivars and germplasm can be problematic due to uncertainty about seed transmission of the viruses responsible for the disease. Whether PEMV is seedborne was assessed by collecting developing seed from infected plants and determining the relative concentrations of the PEMV-1 and PEMV-2 viral genomes using quantitative real-time reverse-transcription polymerase chain reaction. The relative accumulation of PEMV-1 and PEMV-2 was ≈1,240 and 13,000 times higher, respectively, in leaf than in embryo tissues. Accumulation of PEMV-1 and PEMV-2 RNA was also significantly higher in pod walls and seed coats than in cotyledons or embryo axes. No evidence was obtained for seed transmission of PEMV in pea. Although PEMV-1 and PEMV-2 genomic RNAs were found in developing seed, no PEMV symptoms were observed in the field on more than 50,000 plants from seed derived from PEMV-infected source plants. These data demonstrate that PEMV is seedborne in pea but do not support a previous report that PEMV is seed transmitted. Absence of seed transmission may result from the low abundance of PEMV viral genomes in embryo tissue.
Generation of Transgenic Papaya with Double Resistance to Papaya ringspot virus and Papaya leaf-distortion mosaic virus
Authors: Kung Yi-Jung , Bau Huey-Jiunn , Wu Yi-Ling , Huang Chiung-Huei , Chen Tsui-Miao , Yeh Shyi-Dong
Published: October 2009

During the field tests of coat protein (CP)-transgenic papaya lines resistant to Papaya ringspot virus (PRSV), another Potyvirus sp., Papaya leaf-distortion mosaic virus (PLDMV), appeared as an emerging threat to the transgenic papaya. In this investigation, an untranslatable chimeric construct containing the truncated CP coding region of the PLDMV P-TW-WF isolate and the truncated CP coding region with the complete 3′ untranslated region of PRSV YK isolate was transferred into papaya (Carica papaya cv. Thailand) via Agrobacterium-mediated transformation to generate transgenic plants with resistance to PLDMV and PRSV. Seventy-five transgenic lines were obtained and challenged with PRSV YK or PLDMV P-TW-WF by mechanical inoculation under greenhouse conditions. Thirty-eight transgenic lines showing no symptoms 1 month after inoculation were regarded as highly resistant lines. Southern and Northern analyses revealed that four weakly resistant lines have one or two inserts of the construct and accumulate detectable amounts of transgene transcript, whereas nine resistant lines contain two or three inserts without significant accumulation of transgene transcript. The results indicated that double virus resistance in transgenic lines resulted from double or more copies of the insert through the mechanism of RNA-mediated posttranscriptional gene silencing. Furthermore, three of nine resistant lines showed high levels of resistance to heterologous PRSV strains originating from Hawaii, Thailand, and Mexico. Our transgenic lines have great potential for controlling a number of PRSV strains and PLDMV in Taiwan and elsewhere.
Multidisciplinary fingerprints: forensic reconstruction of an insect reinvasion
Authors: Kim Kyung Seok , Jones Gretchen D. , Westbrook John K. , Sappington Thomas W.
Published: October 2009

An unexpected outbreak of boll weevils,Anthonomus grandis, an insect pest of cotton, across the Southern Rolling Plains (SRP) eradication zone of west-central Texas, USA, was detected soon after passage of Tropical Storm Erin through the Winter Garden district to the south on 16 August 2007. The synchrony and broad geographic distribution of the captured weevils suggest that long-distance dispersal was responsible for the reinvasion. We integrated three types of assessment to reconstruct the geographic origin of the immigrants: (i) DNA fingerprinting; (ii) pollen fingerprinting; and (iii) atmospheric trajectory analysis. We hypothesized the boll weevils originated in the Southern Blacklands zone near Cameron, or in the Winter Garden district near Uvalde, the nearest regions with substantial populations. Genetic tests broadly agree that the immigrants originated southeast of the SRP zone, probably in regions represented by Uvalde or Weslaco. The SRP pollen profile from weevils matched that of Uvalde better than that of Cameron. Wind trajectories supported daily wind-aided dispersal of weevils from the Uvalde region to the SRP from 17 to 24 August, but failed to support migration from the Cameron region. Taken together the forensic evidence strongly implicates the Winter Garden district near Uvalde as the source of reinvading boll weevils.
Reflectivity of the gyroid biophotonic crystals in the ventral wing scales of the Green Hairstreak butterfly,Callophrys rubi
Authors: Michielsen K. , De Raedt H. , Stavenga D. G.
Published: October 2009

We present a comparison of the computer simulation data of gyroid nanostructures with optical measurements (reflectivity spectra and scattering diagrams) of ventral wing scales of the Green Hairstreak butterfly,Callophrys rubi. We demonstrate that the omnidirectional green colour arises from the gyroid cuticular structure grown in the domains of different orientation. We also show that this three-dimensional structure, operating as a biophotonic crystal, gives rise to various polarization effects. We briefly discuss the possible biological utility of the green coloration and polarization effects.
Translation, Experimentation and the Spring of the Air: Richard Waller's
Essayes of Natural Experiments
Authors: Boschiero Luciano
Published: October 2009

In 1668, when the Royal Society of London received a copy of the book of experiments compiled by the Tuscan Accademia del Cimento, it was deemed by the Society to contain little that was new or innovative, and was seemingly soon forgotten. Yet 15 years later, Richard Waller's English translation of this book was licensed and published by the Society. The only reason offered by historians for this turnaround in the English attitude towards the book has been the social and political circumstances facing the Society in the early 1680s. However, a closer look at the reception of the translation and the intellectual interests of some of the Society's members at this time, especially the Society's temporary curator, Denis Papin, reveals that the Tuscans' work was re-evaluated for its significance to natural philosophical theories developed in the field of pneumatics.