bluuebunny/crossref_metadata_2025 huggingface dataset:
Antioxidant and Acetylcholinesterase Response to Repeated Malathion Exposure in Rat Cerebral Cortex and Hippocampus
Authors: Trevisan Rafael , Uliano‐Silva Marcela , Pandolfo Pablo , Franco Jeferson L. , Brocardo Patrícia S. , Santos Adair R. S. , Farina Marcelo , Rodrigues Ana Lúcia S. , Takahashi Reinaldo N. , Dafre Alcir L.
Published: March 2008

Abstract:  The wide use of the organophosphate insecticide malathion is accompanied by the risk of human exposure, especially in developing countries, which underlines the need of basic studies in this area. Some reports have shown that low doses of malathion, in a repeated treatment regimen, are unable to reduce acetylcholinesterase (AChE) activity in the rat brain, in contrast to the inhibitory effect in acute treatment. In order to investigate if AChE activity is affected by repeated low‐level malathion administration, female Wistar rats were exposed to malathion (50 and 100 mg/kg, intraperitoneally) for 3 consecutive days. Exposure to malathion 50 mg/kg did not affect AChE activity, as previously observed. Contrary to expectation, 100 mg/kg malathion produced a significant increase in AChE activity in both cerebral cortex and hippocampus. Besides AChE inhibition, malathion may act as a pro‐oxidative agent by interfering with antioxidant defences, as shown by a decrease of glutathione peroxidase and glutathione reductase activity in the cerebral cortex (100 mg/kg malathion). These effects are in contrast to response in the hippocampus where the increase in AChE activity correlates positively with the antioxidant defences, while the opposite was found in the cerebral cortex. These data indicate that, with low doses, and after a short period of exposure, malathion induces an up‐regulation of AChE activity, a pattern similar to that found in the hippocampus for the antioxidant defences studied. The cerebral cortex was more vulnerable to malathion, as reflected in a decrease of two antioxidant enzymes. This study indicates that (i) alternatively to AChE inhibition, interference with the antioxidant defence system may be another important target for malathion toxicity; (ii) hippocampal and cortical AChE activity in rats can be increased after repeated low‐dose malathion exposure. This response suggests the occurrence of a pathophysiological response in order to maintain the homeostasis of the cholinergic system in these cerebral structures.
Redshift-dependent lag—luminosity relation in 565 BATSE gamma-ray bursts
Authors: Tsutsui Ryo , Nakamura Takashi , Yonetoku Daisuke , Murakami Toshio , Tanabe Sachiko , Kodama Yoshiki
Published: March 2008

We compared redshifts zY measured from the Yonetoku relation and zlag from the lag–luminosity relation for 565 BATSE gamma-ray bursts (GRBs) and were surprised to find that the correlation between these two redshifts is very low. Assuming that the luminosity is a function of both zY and the intrinsic spectral lag τlag, we found a new redshift-dependent lag–luminosity relation L= 7.5 × 1050 erg s−1 (1 +z)2.53τ−0.282lag with the correlation coefficient of 0.77 and the chance probability of 7.9 × 10−75. Although the spectral lag is computed from two channels of the Burst and Transient Source Experiment (BATSE), our new lag–luminosity relation suggests that a future lag–luminosity relation defined in the Swift data should also depend on the redshift.
X-ray line ratio 3C/3D in Fe xvii
Authors: Chen G. X.
Published: March 2008

The X-ray line intensity ratio 3C/3D in Fe xvii is potentially one of the most useful plasma diagnostic line ratios for X-ray astronomy. Based on our recent converged and highly accurate atomic calculations for electron impact excitation of Fe xvii using the fully relativistic close-coupling method, we demonstrate that 3C/3D in Fe xvii is not a constant with respect to electron temperature/energy. The cascade effects (including the excitation and recombination population pumping) on 3C/3D as a function of temperature (for Maxwellian plasmas) or electron beam energy (for some laboratory plasmas) are studied and elaborated. For Maxwellian plasmas prevailing in astrophysical sources under the condition of collisional ionization equilibrium, a new and highly accurate 3C/3D line ratio is reported. The values of 3C/3D reported in this work are 2.66, 2.76, 2.81, 2.88 and 2.94 for electron temperatures of 2, 3, 4, 6 and 10 MK, respectively. The uncertainty in our new line ratio is estimated to be about 5 per cent. These new 3C/3D values are expected to have immediate applications for a wide range of X-ray spectra observed from both point sources as well as extended sources.
Effects of Assigning Raters to Items
Authors: Sykes Robert C. , Ito Kyoko , Wang Zhen
Published: March 2008

Student responses to a large number of constructed response items in three Math and three Reading tests were scored on two occasions using three ways of assigning raters: single reader scoring, a different reader for each response (item‐specific), and three readers each scoring a rater item block (RIB) containing approximately one‐third of a student's responses. Multiple group confirmatory factor analyses indicated that the three types of total scores were most frequently tau‐equivalent. Factor models fitted on the item responses attributed differences in scores to correlated ratings incurred by the same reader scoring multiple responses. These halo effects contributed to significantly increased single reader mean total scores for three of the tests. The similarity of scores for item‐specific and RIB scoring suggests that the effect of rater bias on an examinee's set of responses may be minimized with the use of multiple readers though fewer than the number of items.
Spinal and supraspinal adaptations associated with balance training and their functional relevance
Authors: Taube W. , Gruber M. , Gollhofer A.
Published: March 2008

Traditionally, balance training has been used to rehabilitate ankle injuries and postural deficits. Prospective studies have shown preventive effects with respect to ankle and knee joint injuries. Presently, balance training is not only applied for rehabilitation and prevention but also for improving motor performance, especially muscle power. The recent application of noninvasive electrophysiological and brain imaging techniques revealed insights into the central control of posture and the adaptations induced by balance training. This information is important for our understanding of the basic control and adaptation mechanisms and to conceptualize appropriate training programmes for athletes, elderly people and patients. The present review presents neurophysiological adaptations induced by balance training and their influence on motor behaviour. It emphasizes the plasticity of the sensorimotor system, particularly the spinal and supraspinal structures. The relevance of balance training is highlighted with respect to athletic performance, postural control within elderly people as well as injury prevention and rehabilitation.
Leadership, task and relationship: Orpheus, Prometheus and Janus
Authors: Cowsill Rhys , Grint Keith
Published: March 2008

The idea that the major division in leadership or management styles is a preference for either task or relationship orientation has long prevailed in the literature. This article proposes an alternative orientation for leaders; that, while in pursuit of achieving the task, the leader is focused either on the needs of superordinates or subordinates, or both. A large‐scale evaluation of leadership in the Royal Air Force from the perspective of followers suggests that although there is some surface support for the task/relationship dichotomy, the more important division is threefold: between people who only look upwards to satisfy the demands of their superordinates (Orpheans), those that tend to focus downwards at the demands of their subordinates (Prometheans) and those that try to look both ways (Janusians). The latter appear to have the greatest chance of sustained success at the more senior levels of the organisation.
Fresh‐Cut Lettuce in Modified Atmosphere Packages Stored at Improper Temperatures Supports Enterohemorrhagic E. coli Isolates to Survive Gastric Acid Challenge
Authors: Chua D. , Goh K. , Saftner R.A. , Bhagwat A.A.
Published: March 2008

ABSTRACT:  Incidences of foodborne outbreaks involving enterohemorrhagic Escherichia coli strains with mutations in a key regulatory gene, rpoS, have been reported. Incentives, if any, for losing this regulatory function are not clear since the RpoS regulator is required for the expression of several environmental stress tolerance genes. RpoS also positively regulates 2 of the 3 acid‐resistance systems of E. coli under aerobic growth conditions and enables the pathogen to survive gastric acid challenge. We selected 7 enterohemorrhagic E. coli isolates, 6 of which are known to carry defective rpoS gene, and then analyzed resistance to synthetic gastric juice after the strains were inoculated on fresh‐cut lettuce and stored under modified atmosphere packaging (MAP) conditions. Subatmospheric oxygen partial pressures in MAP enabled all 6 rpoS‐defective isolates to induce acid resistance over the 8‐d storage period if the temperature was ≥ 15 °C. No acid resistance was induced for MAP‐stored lettuce left at temperatures ≤ 10 °C or for lettuce packed and stored under aerobic conditions. The data underscore the impending danger of abusive storage temperatures especially with regard to the application of MAP to extend the shelf life of fresh produce. The results also highlight the biological significance of having multiple acid‐resistance pathways and the complex regulatory network of enterohemorrhagic E. coli strains.
Signal Transfer in Haloarchaeal Sensory Rhodopsin– Transducer Complexes†
Authors: Sasaki Jun , Spudich John L.
Published: March 2008

Membrane‐inserted complexes consisting of two photochemically reactive sensory rhodopsin (SR) subunits flanking a homodimer of a transducing protein subunit (Htr) are used by halophilic archaea for sensing light gradients to modulate their swimming behavior (phototaxis). The SR–Htr complexes extend into the cytoplasm where the Htr subunits bind a his‐kinase that controls a phosphorylation system that regulates the flagellar motors. This review focuses on current progress primarily on the mechanism of signal relay within the SRII–HtrII complexes from Natronomonas pharaonis and Halobacterium salinarum. The recent elucidation of a photoactive site steric trigger crucial for signal relay, advances in understanding the role of proton transfer from the chromophore to the protein in SRII activation, and the localization of signal relay to the membrane‐embedded portion of the SRII–HtrII interface, are beginning to produce a clear picture of the signal transfer process. The SR–Htr complexes offer unprecedented opportunities to resolve first examples of the chemistry of signal relay between membrane proteins at the atomic level, which would provide a major contribution to the general understanding of dynamic interactions between integral membrane proteins.
Protein Diffusion Probed by the Transient Grating Method with a New Type of Photochromic Molecule†
Authors: Eitoku Takeshi , Terazima Masahide
Published: March 2008

A new type of photochromic molecule that can be used for diffusion coefficient (D) measurements of various proteins in solution is described. The absorption spectrum of this molecule is changed upon photoexcitation by the trans–cis isomerization reaction. Target proteins were labeled by this photochromic molecule in the dark and the translational motion of the proteins was detected by the transient grating (TG) method. The TG signal was simple enough to determine D accurately and was stable even for long‐time irradiation by the laser light. The TG method using this probe molecule improves many drawbacks of the other techniques.
Role of Ocular Melanin in Ophthalmic Physiology and Pathology†
Authors: Hu Dan‐Ning , Simon John D. , Sarna Tadeusz
Published: March 2008

The mammalian eye consists of several layers of pigmented tissues that contain melanin. The eye is a unique organ for pigment cell research because one can isolate and compare melanosomes from different tissues and embryonic origins. Retinal, iris and ciliary pigment epithelial cells are derived from the neural ectoderm, more specifically from the extremity of the embryonic optical cup, which is also the origin of the retina. In contrast, the pigment‐generating cells in the choroid and in the stroma of the iris and ciliary body, uveal melanocytes, are developed from the neural crest, the same origin as the melanocytes in skin and hair. This review examines the potential functions of ocular melanin in the human eye. Following a discussion of the role of melanins in the pigment epithelium and uveal melanocytes, three specific topics are explored in detail—photo‐screening protective effects, biophysical and biochemical protective effects, and the biologic and photobiologic effects of the two main classes of melanins (generally found as mixtures in ocular melanosomes)—eumelanin and pheomelanin.
Alpha‐retinals as Rhodopsin Chromophores—Preference for the 9‐Z Configuration and Partial Agonist Activity†
Authors: Wang Yajie , Bovee‐Geurts Petra H. M. , Lugtenburg Johan , DeGrip Willem J.
Published: March 2008

The visual pigment rhodopsin, the photosensory element of the rod photoreceptor cell in the vertebrate retina, shows in combination with an endogenous ligand, 11‐Z retinal, an astonishing photochemical performance. It exhibits an unprecedented quantum yield (0.67) in a highly defined and ultrafast photoisomerization process. This triggers the conformational changes leading to the active state Meta(rhodopsin) II. Retinal is covalently bound to Lys‐296 of the protein opsin in a protonated Schiff base. The resulting positive charge delocalization over the terminal part of the polyene chain of retinal creates a conjugation defect that upon photoexcitation moves to the opposite end of the polyene. Shortening the polyene as in 4,5‐dehydro,5,6‐dihydro (alpha), 5,6‐dihydro or 7,8‐dihydro‐analogs might facilitate photoisomerization of a 9‐Z and a 11‐Z bond. Here we describe pigment analogs generated with bovine opsin and 11‐Z or 9‐Z 4,5‐dehydro,5,6‐dihydro‐retinal that were further characterized by UV–Vis and FTIR spectroscopy. The preference of opsin for native 11‐Z retinal over the 9‐Z isomer is reversed in 4,5‐dehydro,5,6‐dihydro‐retinal. 9‐Z 4,5‐dehydro,5,6‐dihydro‐retinal readily generated a photosensitive pigment. This modification has no effect on the quantum yield, but affects the Batho↔blueshifted intermediate (BSI) equilibrium and leads to a strong decrease in the G‐protein activation rate because of a downshift of the pKa of the Meta I↔Meta II equilibrium.
The Photoreaction of the Photoactive Yellow Protein Domain in the Light Sensor Histidine Kinase Ppr is Influenced by the C‐terminal Domains†
Authors: Kamikubo Hironari , Koyama Tomonori , Hayashi Michihiro , Shirai Kumiko , Yamazaki Yoichi , Imamoto Yasushi , Kataoka Mikio
Published: March 2008

To study the role of the C‐terminal domains in the photocycle of a light sensor histidine kinase (Ppr) having a photoactive yellow protein (PYP) domain as the photosensor domain, we analyzed the photocycles of the PYP domain of Ppr (Ppr‐PYP) and full‐length Ppr. The gene fragment for Ppr‐PYP was expressed in Escherichia coli, and it was chemically reconstituted with p‐coumaric acid; the full‐length gene of Ppr was coexpressed with tyrosine ammonia‐lyase and p‐coumaric acid ligase for biosynthesis in cells. The light/dark difference spectra of Ppr‐PYP were pH sensitive. They were represented as a linear combination of two independent difference spectra analogous to the PYPL/dark and PYPM/dark difference spectra of PYP from Halorhodospira halophila, suggesting that the pH dependence of the difference spectra is explained by the equilibrium shift between the PYPL‐ and PYPM‐like intermediates. The light/dark difference spectrum of Ppr showed the equilibrium shift toward PYPL compared with that of Ppr‐PYP. Kinetic measurements of the photocycles of Ppr and Ppr‐PYP revealed that the C‐terminal domains accelerate the recovery of the dark state. These observations suggest an interaction between the C‐terminal domains and the PYP domain during the photocycle, by which light signals captured by the PYP domain are transferred to the C‐terminal domains.
Culture and Biology: The Foundation of Pathways of Development
Authors: Keller Heidi
Published: March 2008

This paper develops the argument that the relationship of biology and culture is systematic: evolved predispositions and learning devices allow individuals to acquire contextually relevant information to become competent in particular environments. It is proposed to synthesize evolutionary theory with cultural and indigenous approaches defining cultural contexts on the basis of shared practices and shared beliefs. Human development can be understood as a series of evolved developmental tasks that need to be solved locally to define adaptive life histories. Early parenting strategies are defined for two prototypical sociocultural contexts: rural farmers in traditional non‐Western villages and urban Western middle‐class families. Parenting strategies are supposed to lay the foundation during the brain imprint period of infancy for different developmental pathways of self‐development.
Building Boxes and Policing Boundaries: (De)Constructing Intersexuality, Transgender and Bisexuality
Authors: Lucal Betsy
Published: March 2008

The process of social differentiation, or the process of creating boxes in which we can place other people and in which we can place ourselves, is key to the existence and persistence of social inequality. The focus of this article is on the construction and maintenance of boxes and boundaries with respect to sex, gender and sexuality. We take the existence of these boxes and boundaries for granted, organizing our lives around them in a variety of ways. Exceptions to them call our categorizations and the decisions we make based upon them into question. Particularly interesting in this context are intersexuality, transgender and bisexuality. Intersexuality, transgender and bisexuality have in common the fact that they challenge our easy reliance on categories and the boundaries between those categories. Our responses to, treatment of and understanding of these exceptions provides striking insights into our system of boxes and boundaries and, correspondingly, to sex‐, gender‐ and sexuality‐based inequalities.
Micro‐Analytical Zircon and Monazite U‐Pb Isotope Dating by Laser Ablation‐Inductively Coupled Plasma‐Quadrupole Mass Spectrometry
Authors: Alagna Keegan E. , Petrelli Maurizio , Perugini Diego , Poli Giampiero
Published: March 2008

In this study we evaluated the capability of a 213 nm laser ablation system coupled to a quadrupole‐based ICP‐MS in delivering accurate and precise U‐Pb ages on zircons and monazites. Four zircon samples (ca. 50 Ma to ca. 600 Ma) and four monazite samples (ca. 30 Ma to ca. 1390 Ma) of known ages were analysed utilising laser ablation pits with diameters of 20 μm and 60 μm. Instrument mass bias and laser induced time‐dependent elemental fractionation were corrected for by calibration against a matrix‐matched reference material. Tera‐Wasserburg plots of the calculated U‐Pb data were employed to assess, and correct for, common Pb contributions. The results indicated that the LA‐ICP‐MS technique employed in this study allowed precise and accurate U‐Pb isotope dating of zircon and monazite on sample areas 20 μm in diameter. At this spot size, the precisions achieved for single spot 206Pb/238U ages, were better than 5% (2s) for monazites and zircons with ages down to 30 Ma and 50 Ma, respectively. The precisions reported are comparable to those generally reported in SIMS and LA‐MC‐ICP‐MS U‐Pb isotope determinations.
Psychological Adjustment to Chronic Illness: The Role of Prototype Evaluation in Acceptance of Illness
Authors: Dijkstra Arie , Buunk Abraham P. , Tóth Gabriella , Jager Nienke
Published: March 2008

Acceptance of chronic illness refers to psychological adjustment to the chronic illness. We propose that patients' prototype evaluations provide patients with information to evaluate themselves and to accept their illness. In cross‐sectional Study 1 (n = 149), diabetic patients' prototype evaluations predicted self‐evaluations and acceptance, explaining about 10% and 20%, respectively. Study 2 was a field experiment (n = 255) among diabetic patients designed to test whether prototype evaluations are causally related to acceptance, and whether this relation is moderated by individual differences. The results showed that the effects of positive prototype information on acceptance depended on the individual's prototype evaluation at pretest and on the individual's social comparison orientation. These results support the idea that prototype perceptions play a role in the psychological adjustment to a chronic illness.
Cavitation Resonance
Authors: Li S. C. , Zuo Z. G. , Liu S. H. , Wu Y. L. , Li S.
Published: March 2008

This article deals with a phenomenon named as cavitation resonance. Cavitation-associated pressure fluctuations in hydraulic systems affect their design, operation, and safety. Under certain conditions, the amplitude of a particular component of these fluctuations will be significantly magnified, causing a resonance. Here, the observed phenomenon from three different flow systems is briefly introduced. Based on the coupling of two subsystems, a hypothesis of (macroscopic) mechanism reduced from these experimental observations is presented.
Numerical and Experimental Studies of Oscillatory Airflows Induced by Rotation of a Grass-Cutting Blade
Authors: Abbasian F. , Cao J. , Yu S. D.
Published: March 2008

Three-dimensional oscillatory airflows induced by a rotating grass-cutting blade in a cylindrical chamber are studied experimentally and numerically in this paper. Experimental pressure results are obtained using a sound pressure transducer and a data acquisition system. The measured pressure data contain background noise and high-frequency sound signals due to the blade vibrations. The background noise is separately measured; its effect on the signal is determined from a spectral subtraction algorithm. A time-accurate finite volume numerical solution to the three-dimensional incompressible unsteady Navier–Stokes equations is also sought using the sliding frame technique and the unstructured tetrahedral mesh. Convergence studies are conducted using various combinations of mesh sizes and time increments to ensure the stability of the numerical scheme. The experimental and numerical pressure results are in good agreement.
Analysis of the Deterministic Unsteady Flow in a Low-Speed Axial Fan With Inlet Guide Vanes
Authors: Oro Jesús Manuel Fernández , Díaz Katia María Argüelles , Morros Carlos Santolaria , Marigorta Eduardo Blanco
Published: March 2008

This paper is conceived as an extension in the analysis of the periodic stator-rotor interaction in a low-speed axial fan with inlet guide vanes. Here, the present work focuses on the deterministic fluctuations that occur in the axial gap between the blade rows. In particular, we present experimental data on the phase averaged velocity in the stator frame of reference. Detailed measurements of the flow field were obtained using hot-wire anemometry in a traverse sector that covered the whole span of the stage for a complete stator pitch. The blade-to-blade velocity gradient in the rotor passage is observed as an unsteady flow in the stator frame of reference due to the relative motion of the blades. As a consequence, this periodic fluctuation is superimposed on the steady vane-to-vane velocity distribution, resulting in a nonuniform unsteadiness with additional phase-dependent wake-blockage interaction. This phase-dependent interaction is determined by the difference between the overall deterministic fluctuation and the rotating spatial blade-to-blade distribution, when the latter is accurately transformed to the stator reference frame. The results revealed that high unsteadiness in the tip region is mainly derived from the radial increase of the blade-to-blade nonuniformities in the rotor, whereas the wake-blockage interaction exhibits a spanwise uniform distribution. Hence, the hub-to-tip torsion of the blades is responsible for setting off a major spatial distortion between the rows. Complementarily, we observed that a reduction in the rows’ spacing or an increase in the blade loadings leads to a higher wake-blockage interaction, modifying the impingement of the incoming stator wakes. In addition, the deterministic stresses were calculated by time averaging the phase-dependent velocity correlations and compared to the turbulent stresses. The deterministic stresses were also segregated in temporal, spatial, and spatial-temporal correlations in order to analyze the dominant mechanisms involved in their generation. At this point, the deterministic kinetic energy levels were found to be generally lower than turbulent kinetic energy levels, with both temporal and spatial correlations being the most significant terms of the tensor.
Inhomogeneous Multifluid Model for Prediction of Nonequilibrium Phase Transition and Droplet Dynamics
Authors: Gerber A. G.
Published: March 2008

A pressure based Eulerian multifluid model for application to phase transition with droplet dynamics in transonic high-speed flows is described. It is implemented using an element-based finite-volume method, which is implicit in time and solves mass and momentum conservation across all phases via a coupled algebraic multigrid approach. The model emphasizes treatment of the condensed phases, with their respective velocity and thermal fields, in inertial nonequilibrium and metastable gas flow conditions. The droplet energy state is treated either in algebraic form or through transport equations depending on appropriate physical assumptions. Due to the complexity of the two-phase phenomena, the model is presented and validated by exploring phase transition and droplet dynamics in a turbine cascade geometry. The influence of droplet inertia on localized homogeneous nucleation is examined.
A Numerical and Experimental Study on the Effect of the Cone Angle of the Spindle in Murata Vortex Spinning Machine
Authors: Guo Huifen , An Xianglong , Yu Zhaosheng , Yu Chongwen
Published: March 2008

To study the effect of the cone angle of the hollow spindle in the nozzle of Murata vortex spinning (MVS) on yarn properties, the k‐ε turbulence model is employed to simulate the airflow patterns inside the different nozzles with different spindle cone angles. A set of corresponding spinning experiments is designed to verify numerical predictions. The simulation results show that some factors, such as the counter-rotating vortex pair (CVP) over the spindle, high supersonic zone in the inlet of the swirling chamber, and the distribution of wall shear stress (WSS) along the outer wall of the spindle caused by variation of the cone angle of the spindle, are significantly related to fluid flow, and consequently to MVS yarn properties. A rational cone angle (Case 2) can form an axisymmetric CVP and high WSS, which can ensure sufficient twisting of the yarn and produce high quality yarn. The experimental results, which yarn properties spun using 100% cotton, 100% polyester, and polyester 70∕cotton 30 blends with different nozzles, are well consistent with the numerical study.
Design of the Dense Gas Flexible Asymmetric Shock Tube
Authors: Colonna P. , Guardone A. , Nannan N. R. , Zamfirescu C.
Published: March 2008

This paper presents the conceptual design of the flexible asymmetric shock tube (FAST) setup for the experimental verification of the existence of nonclassical rarefaction shock waves in molecularly complex dense vapors. The FAST setup is a Ludwieg tube facility composed of a charge tube that is separated from the discharge vessel by a fast-opening valve. A nozzle is interposed between the valve and the charge tube to prevent disturbances from the discharge vessel to propagate into the tube. The speed of the rarefaction wave generated in the tube as the valve opens is measured by means of high-resolution pressure transducers. The provisional working fluid is siloxane D6 (dodecamethylcyclohexasiloxane, C12H36O6Si6). Numerical simulations of the FAST experiment are presented using nonideal thermodynamic models to support the preliminary design. The uncertainties related to the thermodynamic model of the fluid are assessed using a state-of-the-art thermodynamic model of fluid D6. The preliminary design is confirmed to be feasible and construction requirements are found to be well within technological limits.
Oersted Medal Lecture 2007: Interactive simulations for teaching physics: What works, what doesn’t, and why
Authors: Wieman Carl E. , Perkins Katherine K. , Adams Wendy K.
Published: March 2008

We give an overview of the Physics Educational Technology (PhET) project to research and develop web-based interactive simulations for teaching and learning physics. The design philosophy, simulation development and testing process, and range of available simulations are described. The highlights of PhET research on simulation design and effectiveness in a variety of educational settings are provided. This work has shown that a well-designed interactive simulation can be an engaging and effective tool for learning physics.
Calculation of phonon dispersion in semiconductor nanostructures: An undergraduate computational project
Authors: Zou Jie
Published: March 2008

This paper discusses an undergraduate research project that involves the numerical calculation of phonon dispersion in semiconductor nanostructures. Phonon dispersion is calculated in the elastic continuum approximation by applying a finite-difference method to solving the elastic wave equation with boundary conditions. Students did simulations for two nanostructures: a free-standing GaN thin film and a free-standing AlN∕GaN∕AlN heterostructure. A comparison of these two structures helps students understand the effect of boundary conditions on the nature of the phonon dispersion. The project is related to current research in phonon thermal transport in semiconductor nanostructures and nanodevices.
Computation in undergraduate physics: The Lawrence approach
Authors: Cook David M.
Published: March 2008

The physics program at Lawrence University has introduced sophisticated computational techniques throughout its curriculum. Distinguishing features of the Lawrence approach include a focus on flexible, general purpose computational packages; application to theory and experiment; extensive use for preparing reports; and distribution throughout the curriculum. Most importantly, computation is introduced early enough so that students subsequently use computers independently on their own initiative. A required sophomore course in computational mechanics provides a uniform orientation to symbolic and numerical tools, and an elective junior/senior course in computational physics is offered. Students’ use of computational resources in independent studies and summer research experiences and positive comments from recent graduates provide evidence of the success and value of these curricular inclusions.
A model-based view of physics for computational activities in the introductory physics course
Authors: Buffler Andy , Pillay Seshini , Lubben Fred , Fearick Roger
Published: March 2008

A model-based view of physics provides a framework within which computational activities may be structured so as to present to students an authentic representation of physics as a discipline. The use of the framework in teaching computation at the introductory physics level is illustrated by a case study based on the simultaneous translation and rotation of a disk-shaped spaceship. Student responses to an interactive worksheet are used to support guidelines for the design of computational tasks to enhance the understanding of physical systems through numerical problem solving.
Integrating computational activities into the upper-level Paradigms in Physics curriculum at Oregon State University
Authors: McIntyre David H. , Tate Janet , Manogue Corinne A.
Published: March 2008

The Paradigms in Physics project at Oregon State University has reformed the entire upper-level physics curriculum. The reform has involved a rearrangement of content to better reflect the way physicists think about the field and the use of several new pedagogies that place responsibility for learning more firmly in the hands of the students. In particular, we employ a wide variety of computational examples and problems throughout the courses. Students use MAPLE, MATHEMATICA, JAVA, and other software packages to do calculations, visualizations, and simulations that develop their intuition and physical reasoning. These computational activities are indispensable to the success of the curriculum.
Time development in quantum mechanics using a reduced Hilbert space approach
Authors: Belloni M. , Christian W.
Published: March 2008

We have created a suite of open source programs that numerically calculate and visualize the evolution of arbitrary initial quantum-mechanical bound states. The calculations are based on the expansion of an arbitrary wave function in terms of basis vectors in a reduced Hilbert space. The approach is stable, fast, and accurate at depicting the long-time dependence of complicated bound states. Several real-time visualizations, such as the position and momentum expectation values and the Wigner quasiprobability distribution for the position and momentum, can be shown. We use these computational tools to study the time-dependent properties of quantum-mechanical systems and discuss the effectiveness of the algorithm.
Simulation of quantum systems with the coupled channel method
Authors: Wang J. , Champagne J. D.
Published: March 2008

We describe a computational method for simulating time-dependent quantum mechanical systems interacting with external fields. In this method, the Schrödinger equation is solved by expanding the wave function in the basis set of the unperturbed Hamiltonian. The expansion yields a set of coupled ordinary differential equations for the expansion coefficients. This coupled channel method can be applied to many time-dependent problems. We apply the coupled channel method to a particle in a box interacting with a laser pulse. We show that if only two states are involved, the method leads naturally to the solutions for Rabi flopping, and that the system exhibits Rabi flopping behavior even with realistic, nonmonochromatic laser pulses. We also discuss instances where simulations could improve the understanding or address misconceptions of beginning students in quantum mechanics.
Resource Letter CP-2: Computational Physics
Authors: Landau Rubin H.
Published: March 2008

This Resource Letter provides a guide to print and electronic literature relevant to a computational physics course. The multidisciplinary aspect of computational physics and its relation to computational science is reflected in the sections Courses, Programs and Reviews, Journals, Conferences and Organizations, Books, Tools, Languages and Environments, Parallel Computing, and Digital Libraries.
Supercomputer based laboratories and the evolution of the personal computer based laboratory
Authors: Joiner David A. , Panoff Robert M. , Gray Paul , Murphy Tom , Peck Charlie
Published: March 2008

The increase in availability of open source research quality simulation software coupled with a reduction in barriers to high performance computer hardware access and new methods for adding interactivity to server-side web services have created a rich environment for the development of supercomputer based laboratories to augment the many personal computer based activities currently in use in the physics classroom. An exemplary supercomputer based laboratory is presented using the N-body problem applied to galactic structure.
Computer simulations: A window on the static and dynamic properties of simple spin models
Authors: Tsai Shan-Ho , Landau D. P.
Published: March 2008

Monte Carlo algorithms can provide detailed information about the static properties of magnets and spin dynamics simulations can be used to understand their dynamic properties. We present an introduction to these methods and discuss some simple examples, showing the insights that can be gained.
The kicked rotor: Computer-based studies of chaotic dynamics
Authors: Korsch H. J. , Graefe E. M. , Jodl Hans-Jörg
Published: March 2008

The kicked rotor is a prototype of a classical nonlinear system with regular and chaotic behavior. Its dynamics can be reduced to a simple and accessible two-dimensional area preserving map in phase space. Despite its simplicity, the kicked rotor is not merely a toy system but serves as a basis for recent research in quantum dynamics. We discuss the use of a computer program to simulate the kicked rotor and related systems.
Remotely controlled laboratories: Aims, examples, and experience
Authors: Gröber Sebastian , Vetter Martin , Eckert Bodo , Jodl Hans-Jörg
Published: March 2008

Remotely controlled laboratories are real experiments that can be controlled by users from their computers via the Internet. We present an overview of technical and pedagogical developments, describe the diversity and potential of our experiments, and comment on their acceptance by physics instructors.
Developing and researching PhET simulations for teaching quantum mechanics
Authors: McKagan S. B. , Perkins K. K. , Dubson M. , Malley C. , Reid S. , LeMaster R. , Wieman C. E.
Published: March 2008

Quantum mechanics is counterintuitive, difficult to visualize, mathematically challenging, and abstract. The Physics Education Technology (PhET) Project now includes 18 simulations on quantum mechanics designed to improve the learning of this subject. These simulations include several key features to help students build mental models and intuition about quantum mechanics: visual representations of abstract concepts and microscopic processes that cannot be directly observed, interactive environments that directly couple students’ actions to animations, connections to everyday life, and efficient calculations so that students can focus on the concepts rather than the mathematics. Like all PhET simulations, these are developed using the results of research and feedback from educators, and are tested in student interviews and classroom studies. This article provides an overview of the PhET quantum simulations and their development. We also describe research demonstrating their effectiveness and discuss some insights about student thinking.
Evidence for Karyogamy and Exchange of Genetic Material in the Binucleate Intestinal Parasite
Giardia intestinalis
Authors: Poxleitner Marianne K. , Carpenter Meredith L. , Mancuso Joel J. , Wang Chung-Ju R. , Dawson Scott C. , Cande W. Zacheus
Published: March 2008

The diplomonad parasite
Giardia intestinalis
contains two functionally equivalent nuclei that are inherited independently during mitosis. Although presumed to be asexual,
Giardia
has low levels of allelic heterozygosity, indicating that the two nuclear genomes may exchange genetic material. Fluorescence in situ hybridization performed with probes to an episomal plasmid suggests that plasmids are transferred between nuclei in the cyst, and transmission electron micrographs demonstrate fusion between cyst nuclei. Green fluorescent protein fusions of giardial homologs of meiosis-specific genes localized to the nuclei of cysts, but not the vegetative trophozoite. These data suggest that the fusion of nuclei, or karyogamy, and subsequently somatic homologous recombination facilitated by the meiosis gene homologs, occur in the giardial cyst.
Organic Molecules and Water in the Planet Formation Region of Young Circumstellar Disks
Authors: Carr John S. , Najita Joan R.
Published: March 2008

The chemical composition of protoplanetary disks is expected to hold clues to the physical and chemical processes that influence the formation of planetary systems. However, characterizing the gas composition in the planet formation region of disks has been a challenge to date. We report here that the protoplanetary disk within 3 astronomical units of AA Tauri possesses a rich molecular emission spectrum in the mid-infrared, indicating a high abundance of simple organic molecules (HCN, C
2
H
2
, and CO
2
), water vapor, and OH. These results suggest that water is abundant throughout the inner disk and that the disk supports an active organic chemistry.
On Ends and Means
Authors: Goldman Michael A.
Published: March 2008

Elizabeth Blackburn and the Story of Telomeres
. Deciphering the Ends of DNA.
By Catherine Brady
. MIT Press, Cambridge, MA, 2007. 412 pp. $29.95, £19.95. ISBN 9780262026222.

Drawing heavily on interviews with Blackburn, her colleagues, and her students, the author provides a "life and science" that addresses approaches to carrying out groundbreaking research and working for policies that nurture such science.
Single-Dose, Therapeutic Vaccination of Mice with Vesicular Stomatitis Virus Expressing Human Papillomavirus Type 16 E7 Protein
Authors: Liao John B. , Publicover Jean , Rose John K. , DiMaio Daniel
Published: March 2008

We are developing recombinant attenuated vesicular stomatitis virus (VSV) as a vaccine vector to generate humoral and cell-mediated immune responses. Here, we explore the use of VSV vaccines for cancer immunotherapy. Immunotherapy targeting high-risk human papillomavirus (HPV) lesions has the potential to benefit HPV-infected individuals and cervical cancer patients by generating cytotoxic T cells that kill tumor cells that express viral antigens. A single dose of VSV expressing the HPV type 16 (HPV16) E7 oncogene was used for therapeutic vaccination of mice bearing TC-1 syngeneic tumors, which express HPV16 E7. HPV16 E7-specific T cells were generated and displayed cytotoxic activity against the tumor cells. By 14 days postvaccination, average tumor volumes were 10-fold less in the vaccinated group than in mice that received the empty-vector VSV, and regression of preexisting tumors occurred in some cases. This antitumor effect was CD8 T-cell dependent. Our results demonstrate antitumor responses to HPV16 E7 and suggest that recombinant-VSV-based vaccination should be explored as a therapeutic strategy for cervical carcinoma and other HPV-associated cancers.
Recombinant AttenuatedSalmonella entericaSerovar Typhimurium Expressing the Carboxy-Terminal Domain of Alpha Toxin fromClostridium perfringensInduces Protective Responses against Necrotic Enteritis in Chickens
Authors: Zekarias Bereket , Mo Hua , Curtiss Roy
Published: March 2008

Clostridium perfringens-induced necrotic enteritis (NE) is a widespread disease in chickens that causes high mortality and reduced growth performance. Traditionally, NE was controlled by the routine application of antimicrobials in the feed, a practice that currently is unpopular. Consequently, there has been an increase in the occurrence of NE, and it has become a threat to the current objective of antimicrobial-free farming. The pathogenesis of NE is associated with the proliferation ofC. perfringensin the small intestine and the secretion of large amounts of alpha toxin, the major virulence factor. Since there is no vaccine for NE, we have developed a candidate live oral recombinant attenuatedSalmonella entericaserovar Typhimurium vaccine (RASV) that delivers a nontoxic fragment of alpha toxin. The 3′ end of theplcgene, encoding the C-terminal domain of alpha toxin (PlcC), was cloned into plasmids that enable the expression and secretion of PlcC fused to a signal peptide. Plasmids were inserted intoSalmonella entericaserovar Typhimurium host strain χ8914, which has attenuatingpabAandpabBdeletion mutations. Three-day-old broiler chicks were orally immunized with 109CFU of the vaccine strain and developed alpha toxin-neutralizing serum antibodies. When serum from these chickens was added intoC. perfringensbroth cultures, bacterial growth was suppressed. In addition, immunofluorescent microscopy showed that serum antibodies bind to the bacterial surface. The immunoglobulin G (IgG) and IgA titers in RASV-immunized chickens were low; however, when the chickens were given a parenteral boost injection with a purified recombinant PlcC protein (rPlcC), the RASV-immunized chickens mounted rapid high serum IgG and bile IgA titers exceeding those primed by rPlcC injection. RASV-immunized chickens had reduced intestinal mucosal pathology after challenge with virulentC. perfringens. These results indicate that oral RASV expressing an alpha toxin C-terminal peptide induces protective immunity against NE.
Mice with Pulmonary Tuberculosis Treated with
Mycobacterium vaccae
Develop Strikingly Enhanced Recall Gamma Interferon Responses to
M. vaccae
Cell Wall Skeleton
Authors: Rodríguez-Güell Elisabeth , Agustí Gemma , Corominas Mercè , Cardona Pere-Joan , Luquin Marina , Julián Esther
Published: March 2008

Whole heat-killed
Mycobacterium vaccae
is used as an immunotherapeutic agent in tuberculosis (TB), but the compound(s) that triggers its immunostimulatory ability is not known. Here, we show that among different subcellular fractions, the cell wall skeleton induced a prominent expression of gamma interferon in splenocytes from both non-TB and TB
M. vaccae
-treated mice.
Prospective Evaluation of Rapid Antigen Tests for Diagnosis of Respiratory Syncytial Virus and Human Metapneumovirus Infections
Authors: Aslanzadeh Jaber , Zheng Xiaotian , Li Haijing , Tetreault Janice , Ratkiewicz Irene , Meng Shufang , Hamilton Pamela , Tang Yi-Wei
Published: March 2008

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are two important viral pathogens that cause respiratory tract infections in the pediatric population. The rapid detection of these agents allows the prompt isolation and treatment of infected patients. In the present prospective study, we evaluated the performances of four rapid antigen detection assays, including a rapid chromatographic immunoassay (CIA) for RSV (Directigen EZ RSV; Becton Dickinson, Sparks, MD), a direct fluorescent-antibody assay (DFA) for RSV (Bartels; Trinity Biotech, Carlsbad, CA), and two DFAs for hMPV manufactured by Diagnostic Hybrids Inc. (DHI; Athens, OH) and Imagen (Oxoid Ltd., Basingstoke, Hampshire, United Kingdom). The clinical specimens tested comprised 515 nasopharyngeal aspirates submitted to the Clinical Microbiology Laboratory at Hartford Hospital from 1 November 2006 to 21 April 2007. Compared to the results of real-time reverse transcription-PCR (RT-PCR), the CIA had a sensitivity of 79.8% and a specificity of 89.5%. The RSV DFA with Bartels reagents showed a sensitivity of 94.1% and a specificity of 96.8%. For hMPV, the sensitivity and specificity were 62.5% and 99.8%, respectively, for the DHI DFA and 63.2% and 100%, respectively, for the Imagen DFA. The hands-on and test turnaround times for CIA were 10 and 30 to 60 min, respectively, and the hands-on and test turnaround times for the RSV and hMPV DFAs were 30 and 105 min, respectively. We conclude that while the RSV CIA is user-friendly, it lacks sensitivity and specificity, especially during off-peak months. In contrast, the RSV DFA is more sensitive and specific, but interpretation of its results is subjective and it demands technical time and expertise. Similarly, both hMPV DFAs are highly specific in comparison to the results of RT-PCR, but their sensitivities await further improvements.