bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular and molecular physiopathology of congenital toxoplasmosis: The dual role of IFN-γ
Authors: PFAFF A. W. , ABOU-BACAR A. , LETSCHER-BRU V. , VILLARD O. , SENEGAS A. , MOUSLI M. , CANDOLFI E.
Published: October 2007

Toxoplasma gondiiis one of the few pathogens that can cross the placenta. Frequency and severity of transmission vary with gestational age. While the control of acquired toxoplasmosis is already well explored, the control of materno-foetal transmission of the parasite remains almost unknown. This is partly due to the lack of an animal model to study this process. This review summarises the studies which have been undertaken and shows that the mouse is a valuable model despite obvious differences to the human case. The paramount role of the cellular immune response has been shown by several experiments. However, IFN-γ has a dual role in this process. While its beneficial effects in the control of toxoplasmosis are well known, it also seems to have transmission-enhancing effects and can also directly harm the developing foetus. The ultimate goal of these studies is to develop a vaccine which protects both mother and foetus. Therefore, it is useful to study the mechanisms of natural resistance against transmission during a secondary infection. In this setting, the process is more complicated, involving both cellular and also humoral components of the immune system. In summary, even if the whole process is far from being elucidated, important insights have been gained so far which will help us to undertake rational vaccine research.
Building simply: ethic or aesthetic? Thinking and making in an era of specialisation
Authors: Murray Gordon
Published: October 2007

The recent history of architecture can be characterised as a battle between attention-grabbing, ‘iconic’ buildings and a counteracting tendency towards the aesthetically reduced, even avowedly ‘minimal’. But beneath the surface appearance of these contrasting formal tendencies – restless or serene, as demanded by their aesthetic ideals – the means of building have become relentlessly more complex to meet ever more demanding environmental and other performance requirements. It was against this background that the Design Research Unit at Cardiff University convened a one-day symposium to explore the possibility of ‘Building Simply’: the topic proved, not unexpectedly, elusive. Below we publish some reflections by Gordon Murray on some of the issues raised, and these are followed by three design papers – by Pierre d'Avoine, Roland Raderschall and the organisers – that addressed the topic from differing perspectives.
Building simply: challenges and dilemmas
Authors: Forster Wayne , Heal Amanda , Thomas Rhian
Published: October 2007

Driven by our interest in sustainability, the vernacular architecture of Wales and a preference for ‘rational’ over wilfully expressive form, the determination to ‘build simply’ has become an abiding aspiration in the work of the Design Research Unit (dru) at the Welsh School of Architecture, Cardiff University. Established in 1998, dru aims both to apply the School's wider research to architectural commissions and to develop design as a medium of research in its own right. In this paper, various themes that recur in the Unit's recent work are discussed in the context of two current schemes that exemplify this research-based approach to design.
Rhetorical space – the hunting lodge at Venaria Reale
Authors: Cullum Hugh
Published: October 2007

Venaria Reale was built by the Savoy Duke Carlo Emanuele II on a marshy site about six miles north-east of Turin. It comprised a large palace cum hunting-lodge, gardens, a hunting wood and a small city through which the palace was approached. Designed by the architect Amadeo di Castellamonte, it was built almost entirely ex novo between about 1655 and 1675. The entire project was thematically structured around an elaborate programme of emblems (essentially mottos with illustrative paintings) drawn from contemporary rhetorical practice. This iconographic scheme was devised by the court philosopher and eminent theorist of rhetoric, Emanuele Tesauro. It is also clear that the Duke himself was involved in both the architecture and decoration of the scheme.
Cross-linguistic influence in the interpretation of anaphoric and cataphoric pronouns in English–Italian bilingual children
Authors: SERRATRICE LUDOVICA
Published: October 2007

This study reports the results of a picture verification task assessing the interpretation of intra-sentential anaphora and cataphora in Italian by a group of English–Italian bilingual eight-year-olds, a group of age-matched Italian monolinguals, and a group of Italian monolingual adults. No significant differences between the groups were observed in the choice of a subject antecedent for null anaphoric pronouns, and only marginally significant differences were reported between the adults and the two groups of children for the interpretation of null cataphoric pronouns. By contrast, overt pronominal subjects were accepted as co-referential with a subject antecedent significantly more often by the bilingual children than by the monolingual children and the adults in the anaphoric condition, and both groups of children accepted a subject as the antecedent of an overt cataphoric pronoun significantly more often than the adults. These results are interpreted in the context of language-universal and language-specific processing strategies in anaphora resolution in bilingual and monolingual acquisition.
Behaviours of wh-words in English speakers' L2 Chinese wh-questions: Evidence of no variability, temporary variability and persistent variability in L2 grammars
Authors: YUAN BOPING
Published: October 2007

This paper presents an empirical study of how different wh -words behave in English speakers' L2 Chinese wh-questions. Our results indicate that L2 Chinese wh-questions are specified by the Chinese wh -particle ne and that there is neither variability nor L1 transfer in this aspect of L2 grammars as no wh -movement is found in English speakers' L2 Chinese. However, wh -words do not develop in a uniform fashion and different wh -words behave differently both synchronically and developmentally in English speakers' L2 Chinese. There is evidence for both temporary variability and persistent variability in some aspects of English speakers' L2 Chinese wh-questions. This is believed to result from breakdowns at the lexical morphology–syntax interface and morphosyntax–semantics interface levels in L2 Chinese grammars. We will provide an account for the no variability, temporary variability as well as persistent variability in English speakers' L2 Chinese wh-questions.
Factors influencing L2 gender processing
Authors: BORDAG DENISA , PECHMANN THOMAS
Published: October 2007

In four experiments we explored processes underlying L2 gender retrieval. We focused on L1 interference and on the influence of the L2 noun's termination. In Experiments 1 and 2 we tried to manipulate the intensity of L1 interference. We found that L2 speakers cannot eliminate or substantially reduce the interlingual interference neither when they know the response language long in advance in a situation in which code-switching is required (Experiment 1), nor when they are close to the monolingual mode (Experiment 2). Experiments 3 and 4 yielded evidence that gender typicality of the L2 noun's termination also exerts an influence on L2 processing, both in production and comprehension. L2 gender thus does not seem to be stored as a fixed feature as it is assumed for L1. Rather, our data support the assumption that it is computed anew each time when needed for processing. Further implications for modeling are discussed.
Parent and child perspectives on physician communication in pediatric palliative care
Authors: Hsiao Jennifer L. , Evan Elana E. , Zeltzer Lonnie K.
Published: October 2007

Objective:

Despite growing recognition of the importance of communication with children with life-limiting illnesses and their families, there has been limited research that includes the child's perspective. The purpose of the current study was to identify the aspects of physician communication that children with life-limiting illnesses and their parents perceived to be facilitative or obstructive in pediatric palliative care.

Methods:

This qualitative study reports on the first 20 parent and child pairs of pediatric oncology and cardiology patients (mean age 14.25 years, range 9-21 years) with a poor prognosis (physician reported likely <20% chance of survival beyond 3 years) from two children's hospitals and one pediatric hospice in Los Angeles, California. Perspectives on physician communication were elicited from children's and parents' individual narratives, recorded, coded, and analyzed using qualitative grounded theory methodology.

Results:

Both children and parents identified five domains of physician communication deemed to be highly salient and influential in quality of care. These included relationship building, demonstration of effort and competence, information exchange, availability, and appropriate level of child and parent involvement. Parents identified coordination of care as another important communication domain. The characteristics of physicians that were deemed most harmful to satisfying communication included having a disrespectful or arrogant attitude, not establishing a relationship with the family, breaking bad news in an insensitive manner, withholding information from parents and losing their trust, and changing a treatment course without preparing the patient and family.

Significance of results:

The six positive communication domains are areas for clinicians to recognize and monitor in communicating with children and families in the pediatric palliative care setting. Knowledge of the qualities of communication that are satisfying to and valued by children and their parents have the potential to lead to more effective communication around the difficult decisions faced by physicians, parents, and children with life-threatening conditions.
Facing uncertainty: The lived experience of palliative care
Authors: Mckechnie Roz , Macleod Rod , Keeling Sally
Published: October 2007

Objective:

This qualitative research study listens to the narratives of people experiencing the dying process who attended the Otago Community Hospice, Dunedin, New Zealand.

Methods:

Ten people, aged between 51 and 65, were approached; two declined and one died sooner than expected. All were women (although this was not part of the original design) and all had carcinoma. Data for the study was sought through qualitative research interviews, considering the development of each participant's illness in relation to her perception of her embodiment in the palliative care setting, and concluding with questions about what she wants the people who care for and about her to learn from her experience. Consistent with this phenomenological approach, the method of analysis was thematic and interpretive.

Results:

The main theme was the uncertainty that all participants felt throughout the diagnostic process and during treatment. Uncertainty, too, was a factor in how they managed their day, whether they would be able to sustain an outing or an activity or not and whether they would be pain free. None were afraid of dying but hoped that when they did die, they would do so comfortably. The relationship with their general practitioners varied. Where fatigue or the effects of medication were not an issue, they could think clearly, but their bodies were experienced as letting them down and limiting their activities. The ideal of “living until you die” was not able to be fulfilled. The increasing approach of social death as they withdrew from their employment and social responsibilities affected them.

Significance of results:

Whether one has a “good death” or not is determined not only by the progression and management of the disease process by health professionals, but also by the way in which one is perceived, by self and others. There are no guidelines for the dying role; everybody dies differently and individually.
Cell Separator Operation within Temperature Ranges To Minimize Effects on Chinese Hamster Ovary Cell Perfusion Culture
Authors: Drouin Hans , Ritter Joachim B. , Gorenflo Volker M. , Bowen Bruce D. , Piret James M.
Published: October 2007

A cell retention device that provides reliable high‐separation efficiency with minimal negative effects on the cell culture is essential for robust perfusion culture processes. External separation devices generally expose cells to periodic variations in temperature, most commonly temperatures below 37 °C, while the cells are outside the bioreactor. To examine this phenomenon, aliquots of ∼5% of a CHO cell culture were exposed to 60 s cyclic variations of temperature simulating an acoustic separator environment. It was found that, for average exposure temperatures between 31.5 and 38.5 °C, there were no significant impacts on the rates of growth, glucose consumption, or t‐PA production, defining an acceptable range of operating temperatures. These results were subsequently confirmed in perfusion culture experiments for average exposure temperatures between 31.6 and 38.1 °C. A 25−1 central composite factorial design experiment was then performed to systematically evaluate the effects of different operating variables on the inlet and outlet temperatures of a 10L acoustic separator. The power input, ambient temperature, as well as the perfusion and recycle flow rates significantly influenced the temperature, while the cell concentration did not. An empirical model was developed that predicted the temperature changes between the inlet and the outlet of the acoustic separator within ±0.5 °C. A series of perfusion experiments determined the ranges of the significant operational settings that maintained the acoustic separator inlet and outlet temperatures within the acceptable range. For example, these objectives were always met by using the manufacturer‐recommended operational settings as long as the recirculation flow rate was maintained above 15 L day−1 and the ambient temperature was near 22 °C.
Induction of Zone‐Like Liver Function Gradients in HepG2 Cells by Varying Culture Medium Height
Authors: Camp James P. , Capitano Adam T.
Published: October 2007

In most laboratory‐scale mammalian cell cultures, the primary mode of oxygen delivery to cultured cells is by passive diffusion through a thin layer of culture medium, and the height of culture medium chosen may therefore have a significant effect on the phenotype of oxygen‐sensitive cell types. Many of the liver functions performed by hepatocytes are thought to be regulated into zones by the local oxygen concentration; of particular interest to in vitro toxicologists, the cytochrome P450 family of detoxification enzymes is known to be preferentially expressed by hepatocytes at low (perivenous) oxygen concentrations. Using an array of different medium heights in a 12‐well plate format, we show that the height of culture medium has a significant effect on cytochrome P450 1A1 detoxification activity, glucose metabolism, and cell morphology of HepG2 hepatocellular carcinoma cultures. In particular, cytochrome P450 activity exhibits a maximum at medium heights corresponding to perivenous oxygen concentrations. This work demonstrates that optimizing cell culture performance is not always the same as maximizing oxygen delivery.
Bayesian modeling of hydrographs
Authors: Merleau James , Perreault Luc , Angers Jean‐François , Favre Anne‐Catherine
Published: October 2007

This article presents a new approach to model yearly hydrographs with daily or weekly streamflow measurements. The method considers yearly hydrographs as a sample of functions to be modeled nonparametrically in a Bayesian setting. The functional data analysis framework provides great flexibility to reproduce the features of yearly hydrographs, while the Bayesian probabilistic model ensures statistical coherence between the flood variables and the shapes of flood events. The proposed methodology is applied to two samples of hydrographs from two watersheds in the province of Quebec.
Stream gains and losses across a mountain‐to‐valley transition: Impacts on watershed hydrology and stream water chemistry
Authors: Covino Timothy P. , McGlynn Brian L.
Published: October 2007

The mountain to alluvial valley transition is a dominant landscape of the American West, and of mountainous regions around the world, and is crucial to water resources in these regions. We combined stream water and groundwater (GW) hydrometric methods with geochemical hydrograph separations to investigate stream gains and losses across a mountain to alluvial valley transition in southwestern Montana to address the following questions: (1) How do alpine to valley bottom transitions affect stream discharge? (2) How do stream gains and losses change across alpine to valley bottom transitions? There was an annual 23% net loss in stream discharge across the transition zone, which we refer to as the mountain front recharge (MFR) zone. Gross stream gains were minimal in the MFR zone. Gross stream losses across the valley bottom equaled ∼140,000 m3 while gross gains equaled ∼70,000 m3, resulting in a net loss of ∼70,000 m3 in the valley bottom zone. Stream discharge was 97% alpine runoff (AL) in the MFR zone, whereas downstream discharge in the valley bottom was 48% AL and 52% valley groundwater. These large spatial and long temporal scale exchanges of water across the mountain‐to‐valley transition affected stream discharge magnitude, valley aquifer storage state, and valley stream water chemistry. This work suggests that streams do not simply lose or gain over a particular reach, but rather many streams are both gaining and losing and that net differences yield an incomplete depiction of stream hydrology.
Resistivity‐based monitoring of biogenic gases in peat soils
Authors: Slater Lee , Comas Xavier , Ntarlagiannis Dimitrios , Moulik Maitry Roy
Published: October 2007

Biogenic free‐phase gas (FPG) formation was induced in a peat block (dimensions 0.28 × 0.21 × 0.21 m) extracted from a peatland in Maine. Electrical resistivity (ER), surface deformation, and methane (CH4) flux from the peat surface was monitored over a 48‐day period during which the temperature remained constant at 21 ± 1°C. ER measurements were made on 5 vertical electrode arrays, each containing 20 electrodes spaced at 0.01‐m intervals. Surface deformation was monitored using 30 elevation rods equally spaced across the surface of the block, and average CH4 flux from the peat surface estimated by integration of measurements obtained with a portable gas detector over a 20‐min time period. Pore water conductivity was recorded at three depths (0.06, 0.09, and 0.15 m) at a single point in the block. ER measurements were inverted for the ratio resistivity change relative to a background data set and corrected for changes in pore fluid conductivity, permitting an estimate of equivalent change in gas content assuming (1) insignificant surface conduction, (2) porosity changes estimated from peat surface expansion, and (3) an Archie saturation exponent n of 1.3 based on results from a parallel block experiment. The resistivity ratios reveal a pattern of FPG evolution consistent with surface deformation and CH4 flux data. During the first part of the experiment (approximately the first 24 days), a gradual buildup in FPG within a layer 4–6 cm below the peat surface (water table) occurs concurrent with modest surface deformation and low CH4 fluxes. In contrast, during the latter half of the experiment (approximately 25–48 days), a complex pattern of more pronounced gas buildup and release at multiple depths occurs concurrent with large rates of surface deformation and higher CH4 fluxes. The experiment demonstrates that ER monitoring is a viable geophysical technology for imaging and monitoring biogenic gas fluxes in peat soils. Here the resistivity clearly shows that FPG is preferentially generated in layers about 0.04–0.06 m below the peat surface and that the buildup of gas is spatially nonuniform even in a relatively small peat block. Furthermore, the experimental results suggest that factors other than temperature and atmospheric pressure must control biogenic gas accumulation and release. As the method is readily deployable at the field scale, possibly in an autonomous monitoring mode, resistivity measurements may permit significant improvements in understanding of carbon gas generation and release from northern peatlands.
Nonlinear excitation of temperature waves in He3–He4 superfluid solutions due to absorption of light waves
Authors: Pushkina N. I.
Published: October 2007

The nonlinear excitation of temperature waves in superfluid solutions of He3 in He4 through the absorption of optical waves is considered. A nonlinear equation which describes such an interaction is derived, an expression for the nonlinear interaction length is obtained, and the necessary value of the interaction length for which second sound excited by two light waves can be amplified from fluctuations to observable values is estimated in order of magnitude.
Features of the phase separation kinetics for solutions of He4 in He3 under conditions of coexistence of the liquid and solid phases
Authors: Grigor’ev V. N. , Degtyaryov I. A. , Sokolov S. S.
Published: October 2007

A discussion of the nucleation kinetics in the phase separation of a solution of He4 in He3 under conditions of coexistence of the liquid and solid phases, when solid inclusions of a new phase enriched in He4 form in the liquid matrix, is presented. The growth rate of the new phase is determined by the probability of penetration of the particles into the new phase. Equations are formulated and solved to find the size of the inclusions and the change of pressure in the volume as functions of time. The times characterizing the phase separation process are estimated under the assumption of homogeneous nucleation.
The Al+–H2 cation complex: Rotationally resolved infrared spectrum, potential energy surface, and rovibrational calculations
Authors: Emmeluth C. , Poad B. L. J. , Thompson C. D. , Weddle G. , Bieske E. J. , Buchachenko A. A. , Grinev T. A. , Kłos J.
Published: October 2007

The infrared spectrum of the Al+–H2 complex is recorded in the H–H stretch region (4075–4110cm−1) by monitoring Al+ photofragments. The H–H stretch band is centered at 4095.2cm−1, a shift of −66.0cm−1 from the Q1(0) transition of the free H2 molecule. Altogether, 47 rovibrational transitions belonging to the parallel Ka=0-0 and 1-1 subbands were identified and fitted using a Watson A-reduced Hamiltonian, yielding effective spectroscopic constants. The results suggest that Al+–H2 has a T-shaped equilibrium configuration with the Al+ ion attached to a slightly perturbed H2 molecule, but that large-amplitude intermolecular vibrational motions significantly influence the rotational constants derived from an asymmetric rotor analysis. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 3.03Å, decreasing by 0.03Å when the H2 subunit is vibrationally excited. A three-dimensional potential energy surface for Al+–H2 is calculated ab initio using the coupled cluster CCSD(T) method and employed for variational calculations of the rovibrational energy levels and wave functions. Effective dissociation energies for Al+–H2(para) and Al+–H2(ortho) are predicted, respectively, to be 469.4 and 506.4cm−1, in good agreement with previous measurements. The calculations reproduce the experimental H–H stretch frequency to within 3.75cm−1, and the calculated B and C rotational constants to within ∼2%. Agreement between experiment and theory supports both the accuracy of the ab initio potential energy surface and the interpretation of the measured spectrum.
Hydrated hydride anion clusters
Authors: Lee Han Myoung , Kim Dongwook , Singh N. Jiten , Kołaski Maciej , Kim Kwang S.
Published: October 2007

On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.
Collisions, caging, thermodynamics, and jamming in the barrier hopping theory of glassy hard sphere fluids
Authors: Schweizer Kenneth S. , Yatsenko Galina
Published: October 2007

An ultralocal limit of the microscopic single particle barrier hopping theory of glassy dynamics is proposed which allows explicit analytic expressions for the characteristic length scales, energy scales, and nonequilibrium free energy to be derived. All properties are shown to be controlled by a single coupling constant determined by the fluid density and contact value of the radial distribution function. This parameter quantifies an effective mean square force exerted on a tagged particle due to collisions with its surroundings. The analysis suggests a conceptual basis for previous surprising findings of multiple inter-relationships between characteristics of the transient localized state, the early stages of cage escape, non-Gaussian or dynamic heterogeneity effects, and the barrier hopping process that defines the alpha relaxation event. The underlying physical picture is also relevant to fluids of nonspherical molecules and sticky colloidal suspensions. The possibility of a unified view of liquid dynamics is suggested spanning the range from dense gases to the zero mobility jammed state.
Soliton propagation in an inhomogeneous plasma at critical density of negative ions: Effects of gyratory and thermal motions of ions
Authors: Malik Hitendra K. , Kawata Shigeo
Published: October 2007

The effects of gyratory and thermal motions of ions on soliton propagation in an inhomogeneous plasma that contains positive ions, negative ions, and electrons are studied at a critical density of negative ions. Since at this critical negative ion density the nonlinear term of the relevant Korteweg–deVries (KdV) equation vanishes, a higher order of nonlinearity is considered by retaining higher-order perturbation terms in the expansion of dependent quantities together with the appropriate set of stretched coordinates. Under this situation, time-dependent perturbation leads to the evolution of modified KdV solitons, which are governed by a modified form of the KdV equation that has an additional term due to the density gradient present in the plasma. On the basis of the solution of this equation and obliquely applied magnetic field, the effects of gyratory and thermal motions of ions are analyzed on the soliton propagation for three cases, nn0ne0, together with nn0 (ne0) as the density of negative ions (electrons). The role of the negative ions in the evolution of the modes and the solitons is also discussed. Under the limiting cases, our calculations reduce to the ones obtained by other investigators in the past. This substantiates the generality of the present analysis.
Time dependent density functional theory investigation of the resonance Raman properties of the julolidinemalononitrile push-pull chromophore in various solvents
Authors: Guthmuller Julien , Champagne Benoît
Published: October 2007

The absorption and resonance Raman spectra have been investigated for the first excited state of the julolidinemalononitrile push-pull chromophore in cyclohexane, dichloromethane, and acetonitrile by means of time dependent density functional theory calculations. The effect of nonlocal exchange has been considered by using three different hybrid exchange-correlation functionals containing 20%, 35%, and 50% of exact Hartree-Fock exchange. The interactions with the solvent have been described by the polarizable continuum model. The short-time approximation expression has been used to evaluate the resonance Raman intensities, while the vibronic theory of resonance Raman spectroscopy has been employed to determine both the intensities and the excitation profiles. It is shown that a consistent description of the vibronic structure of the excited state and resonance Raman spectra can be obtained provided that an adequate amount, close to 35%, of exact exchange is included in the exchange-correlation functional. The effect of increasing the polarity of the solvent is well represented by the polarizable continuum model, both for the absorption spectra and resonance Raman intensities. In particular, these simulations can reproduce the observed variations of the 1560cm−1 band intensity and attribute them to elongations of a CC double bond upon electronic excitation. Moreover, the short-time approximation has been found sufficient to reproduce most of the results of the more evolved vibronic theory of resonance Raman spectroscopy, which includes summations over vibrational excited states, for both the spectral signatures and their solvent dependencies.
Fluid and kinetic parameters near the plasma-sheath boundary for finite Debye lengths
Authors: Jelić N. , Riemann K.-U. , Gyergyek T. , Kuhn S. , Stanojević M. , Duhovnik J.
Published: October 2007

In a recent paper by Kuhn et al. [Phys. Plasmas 13, 013503 (2006)], it has been demonstrated that in a plasma, the polytropic coefficient γ is a spatially varying quantity rather than a global constant as usually assumed in fluid theory. Assuming cold ion sources and using the asymptotic two-scale approximation (in which the ratio of the Debye length over the characteristic presheath length, ε, is set to zero), it was found that the γ profile exhibits a sharp peak (with values roughly between 6 and 8) at the plasma-sheath boundary. In the present paper, it is shown that in a finite ε approach, this sharp peak is smoothed to a regular maximum, which for increasing ε (e.g., decreasing plasma density) decreases and finally disappears. In any case, assumptions like γ=1 and/or γ=3, which are customarily encountered in the context of fluid approaches, are disproved. Although the present results were obtained for collisionless plasmas, it is reasonable to assume that the behavior uncovered holds qualitatively for any plasma with cold ion sources. In addition to calculating time-independent theoretical solutions by means of an analytic-numerical approach, we primarily employ particle-in-cell (PIC) computer simulations, which intrinsically represent a time-dependent approach. It is confirmed that, although extreme care is required to separate physical from numerical effects, the PIC simulation method is a highly suitable tool also for future investigations of more demanding physical scenarios assuming, e.g., warm ion sources and other more complex aspects that cannot be treated realistically by analytic-numerical means alone. In addition, the extension from time-independent analytic-numerical calculation to time-dependent simulation permits us also to investigate the effect of collective plasma oscillations on the ion velocity distribution function (VDF). Although the ion VDFs obtained in our PIC simulations visibly differ in some details from the time-independent theoretical ones, the related ion-temperature and γ profiles turn out to fit their theoretical counterparts very well over significant parameter ranges. Hence, the two methods may to some extent be applied as alternative ones in future investigations on the plasma-sheath transition.
Evidence for mobility enhancement in double-gate silicon-on-insulator metal-oxide-semiconductor field-effect transistors
Authors: Rodriguez N. , Cristoloveanu S. , Gámiz F.
Published: October 2007

The methodology of mobility extraction from the Y-function or from the transconductance peak is revisited in the context of silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistors (MOSFETs). Based on a simple two-channel model, we discuss the biasing conditions that enable the Y-function to be applied to both single-gate (SG) and double-gate (DG) modes. Systematic mobility measurements in thick and ultrathin SOI transistors are presented for the front channel, back channel, and in quasi-double-gate mode. In SG-mode, the mobility is overestimated as soon as the opposite channel is activated. In partially depleted or relatively thick, fully depleted MOSFETs, the two channels are separated; hence, the total apparent mobility in DG mode is the sum of the front and back channel mobilities. By contrast, the two-channel model fails in ultrathin transistors, where the two channels become strongly coupled and volume inversion occurs. Volume inversion is reflected in a remarkable increase of the apparent mobility in DG mode.
A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit
Authors: Huang Yongxian , Tian Xiubo , Yang Shiqin , Chu Paul K.
Published: October 2007

A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289–2.984)×1016at.∕cm2s at an oxygen pressure of 1.5Pa and rf power of 400W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.
Size dependence in the magnetization reversal of Fe∕Gd multilayers on self-assembled arrays of nanospheres
Authors: Amaladass E. , Ludescher B. , Schütz G. , Tyliszczak T. , Eimüller T.
Published: October 2007

The size dependent magnetization reversal of Fe∕Gd multilayers on self-assembled silica nanospheres has been studied by scanning transmission x-ray microscopy. Caps on 800nm spherules show S-shaped hysteresis loops while the caps on 330 and 160nm spherules exhibit rectangular loops. This drastic change is attributed to a transition from a radial to a uniaxial magnetization distribution with decreasing diameter and results from the increasing exchange interaction between adjacent moments. Furthermore, element selective studies reveal a transition from an aligned to a twisted magnetic state with reducing size of the nanocaps.
Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography
Authors: Kim Tae Sun , Kim Sang-Mook , Jang Yun Hee , Jung Gun Young
Published: October 2007

The light extraction efficiency of light emitting diodes (LEDs) was enhanced by incorporating nanoscale patterns inside the LED structure. A hole patterned p-GaN layer and a pillar patterned indium-tin-oxide (ITO) contact layer were fabricated by using colloidal lithography with size-tunable polystyrene spheres. It was found that the light output power (at 20mA) of the LEDs with the hole patterned p-GaN layer and the pillar patterned ITO contact layer were enhanced by 21% and 10%, respectively, compared with the conventional LED due to the increase of the extraction probability of the internally reflected photons through the patterns.
Influence of quantum well and barrier composition on the spectral behavior of InGaAs quantum dots-in-a-well infrared photodetectors
Authors: Jolley G. , Fu L. , Tan H. H. , Jagadish C.
Published: October 2007

We report on the spectral behavior of two different quantum dots-in-a-well infrared photodetectors grown by low-pressure metal-organic chemical vapor deposition. In0.5Ga0.5As quantum dots embedded in an In0.15Ga0.85As∕GaAs quantum well (QW) or a GaAs∕Al0.2Ga0.8As QW have been incorporated into photodetectors and were characterized. A spectral response in the 3–5μm atmospheric window has been achieved by adopting the GaAs∕Al0.2Ga0.8As QW.
Thermal Elasticity in Glassy Alloys based on Topology of Metallic Clusters
Authors: Fukuhara Mikio , Wang Xinming , Inoue Akihisa
Published: October 2007

Thermal elasticity of two kinds of bonding-type glassy alloys, Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20, during progressive devitrification was evaluated by Poisson’s ratio, Debye temperature, and internal frictions in terms of topological change in metallic clusters. Both alloys showed opposite behavior for thermal elasticity: thermal softening associated with relaxation of icosahedral clusters and thermal-induced entropy elasticity associated with the rotational and vibrational motions of polyhedral clusters, and an increment of internal friction based on electron-longitudinal phonon interaction derived from the variation amount of potential energy among atoms, showing vanishment of free electrons.
Ultrafast photoluminescence dynamics of nitride-passivated silicon nanocrystals using the variable stripe length technique
Authors: Chen Hui , Shin Jung H. , Fauchet Philippe M. , Sung Joo-Yeon , Shin Jae-Heon , Sung Gun Yong
Published: October 2007

The ultrafast photoluminescence dynamics of nitride-passivated silicon nanocrystals is investigated using the variable stripe length geometry with 200 femtosecond pump pulses. We find that the luminescence lifetimes are in the nanosecond range throughout the entire spectral range. However, no evidence for optical gain is observed even when the pump fluence is in excess of 40mJ∕cm2. A comparison with similarly prepared, oxide-passivated silicon nanocrystals suggests that oxide passivation plays an important role in providing optical gain from silicon nanocrystals.
Experimental evidence for the role of electrodes and oxygen vacancies in voltage nonlinearities observed in high-k metal-insulator-metal capacitors
Authors: El Kamel F. , Gonon P. , Vallée C.
Published: October 2007

This work reports on voltage nonlinearities in metal-insulator-metal (MIM) capacitors using amorphous barium titanate (a-BaTiO3) thin films. It is experimentally demonstrated that voltage nonlinearity is related to the formation of a double layer at electrodes (electrode polarization mechanism). The magnitude of nonlinearities is shown to be controlled by the nature of the metal contacts (Al, Cu, Au, and Ag), as well as by the presence of oxygen during film deposition. It is thought that oxygen vacancies are the defects responsible for the nonlinear character of high-k oxide-based MIM capacitors.
Estimating direct carbon emissions from Canadian wildland fires
Authors: de Groot William J. , Landry Robert , Kurz Werner A. , Anderson Kerry R. , Englefield Peter , Fraser Robert H. , Hall Ronald J. , Banfield Ed , Raymond Donald A. , Decker Vincent , Lynham Tim J. , Pritchard Janet M.
Published: October 2007

In support of Canada’s National Forest Carbon Monitoring, Accounting and Reporting System, a project was initiated to develop and test procedures for estimating direct carbon emissions from fires. The Canadian Wildland Fire Information System (CWFIS) provides the infrastructure for these procedures. Area burned and daily fire spread estimates are derived from satellite products. Spatially and temporally explicit indices of burning conditions for each fire are calculated by CWFIS using fire weather data. The Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) provides detailed forest type and leading species information, as well as pre-fire fuel load data. The Boreal Fire Effects Model calculates fuel consumption for different live biomass and dead organic matter pools in each burned cell according to fuel type, fuel load, burning conditions, and resulting fire behaviour. Carbon emissions are calculated from fuel consumption. CWFIS summarises the data in the form of disturbance matrices and provides spatially explicit estimates of area burned for national reporting. CBM-CFS3 integrates, at the national scale, these fire data with data on forest management and other disturbances. The methodology for estimating fire emissions was tested using a large-fire pilot study. A framework to implement the procedures at the national scale is described.
Cooperative DNA binding by CI repressor is dispensable in a phage λ variant
Authors: Babić Andrea C. , Little John W.
Published: October 2007

Complex gene regulatory circuits contain many interacting components. In principle, all of these components and interactions may be essential to the function of the circuit. Alternatively, some of them may be refinements to a simpler version of the circuit that improve its fitness. In this work, we have tested whether a particular property of a critical regulatory protein, CI, is essential to the behavior of the phage λ regulatory circuit. In the lysogenic state, CI represses the expression of the lytic genes, allowing a stable lysogenic state, by binding cooperatively to six operators. A mutant phage lacking cooperativity because of a change in
c
I could not form stable lysogens; however, this defect could be suppressed by the addition of mutations that altered two
cis
-acting sites but did not restore cooperativity. The resulting triple mutant was able to grow lytically, form stable single lysogens, and switch to lytic growth upon prophage induction, showing a threshold response in switching similar to that of wild-type λ. We conclude that cooperative DNA binding by CI is not essential for these properties of the λ circuitry, provided that suppressors increase the level of CI. Unlike wild-type lysogens, mutant lysogens were somewhat unstable under certain growth conditions. We surmise that cooperativity is a refinement to a more basic circuit, and that it affords increased stability to the lysogenic state in response to environmental variations.
A protein key to plant virus transmission at the tip of the insect vector stylet
Authors: Uzest Marilyne , Gargani Daniel , Drucker Martin , Hébrard Eugénie , Garzo Elisa , Candresse Thierry , Fereres Alberto , Blanc Stéphane
Published: October 2007

Hundreds of species of plant viruses, many of them economically important, are transmitted by noncirculative vector transmission (acquisition by attachment of virions to vector mouthparts and inoculation by subsequent release), but virus receptors within the vector remain elusive. Here we report evidence for the existence, precise location, and chemical nature of the first receptor for a noncirculative virus, cauliflower mosaic virus, in its insect vector. Electron microscopy revealed virus-like particles in a previously undescribed anatomical zone at the extreme tip of the aphid maxillary stylets. A novel
in vitro
interaction assay characterized binding of cauliflower mosaic virus protein P2 (which mediates virus–vector interaction) to dissected aphid stylets. A P2-GFP fusion exclusively labeled a tiny cuticular domain located in the bottom-bed of the common food/salivary duct. No binding to stylets of a non-vector species was observed, and a point mutation abolishing P2 transmission activity correlated with impaired stylet binding. The novel receptor appears to be a nonglycosylated protein deeply embedded in the chitin matrix. Insight into such insect receptor molecules will begin to open the major black box of this scientific field and might lead to new strategies to combat viral spread.
Gata2, Fli1, and Scl form a recursively wired gene-regulatory circuit during early hematopoietic development
Authors: Pimanda John E. , Ottersbach Katrin , Knezevic Kathy , Kinston Sarah , Chan Wan Y. I. , Wilson Nicola K. , Landry Josette-Renée , Wood Andrew D. , Kolb-Kokocinski Anja , Green Anthony R. , Tannahill David , Lacaud Georges , Kouskoff Valerie , Göttgens Berthold
Published: October 2007

Conservation of the vertebrate body plan has been attributed to the evolutionary stability of gene-regulatory networks (GRNs). We describe a regulatory circuit made up of Gata2, Fli1, and Scl/Tal1 and their enhancers,
Gata2-3
,
Fli1
+12, and
Scl
+19, that operates during specification of hematopoiesis in the mouse embryo. We show that the
Fli1
+12 enhancer, like the
Gata2-3
and
Scl
+19 enhancers, targets hematopoietic stem cells (HSCs) and relies on a combination of Ets, Gata, and E-Box motifs. We show that the
Gata2-3
enhancer also uses a similar cluster of motifs and that Gata2, Fli1, and Scl are expressed in embryonic day-11.5 dorsal aorta where HSCs originate and in fetal liver where they multiply. The three HSC enhancers in these tissues and in ES cell-derived hemangioblast equivalents are bound by each of these transcription factors (TFs) and form a fully connected triad that constitutes a previously undescribed example of both this network motif in mammalian development and a GRN kernel operating during the specification of a mammalian stem cell.
Molecular level stochastic model for competence cycles in
Bacillus subtilis
Authors: Schultz Daniel , Ben Jacob Eshel , Onuchic José N. , Wolynes Peter G.
Published: October 2007

The role of stochasticity and noise in controlling genetic circuits is investigated in the context of transitions into and from competence in
Bacillus subtilis
. Recent experiments have demonstrated that bistability is not necessary for this function, but that the existence of one stable fixed point (vegetation) and an excitable unstable one (competence) is sufficient. Stochasticity therefore plays a crucial role in this excitation. Noise can be generated by discrete events such as RNA and protein synthesis and their degradation. We consider an alternative noise source connected with the protein binding/unbinding to the DNA. A theoretical model that includes this “nonadiabatic” mechanism appears to produce a better agreement with experiments than models where only the adiabatic limit is considered, suggesting that this nonconventional stochasticity source may be important for biological functions.
Evaluation of coronary bypass graft occlusion and stenosis with 64-detector-row computed tomography angiography
Authors: Oncel D. , Oncel G. , Taştan A. , Tamci B.
Published: October 2007

Background: A noninvasive imaging modality is desirable for the evaluation of coronary bypass graft stenosis and occlusion.

Purpose: To prospectively evaluate the effectiveness of 64-detector-row computed tomography (DCT) for the assessment of coronary bypass grafts.

Material and Methods: Forty-two patients (35 male, seven female, mean age 66.3 years) with 103 bypass grafts (32 arterial, 71 venous) were examined with 64-DCT. The evaluations were done by two radiologists blinded to the results of quantitative coronary angiography (QCA), used as the reference standard.

Results: All of the 26 occluded grafts, nine of the 10 stenosed grafts, and 66 of the 67 patent grafts were correctly diagnosed with 64-DCT angiography. The sensitivity, specificity, and positive and negative predictive values for 64-DCT in detecting graft stenosis were 90%, 99%, 90%, and 99%, respectively. For graft occlusion, all were 100%. No statistically significant difference was found between 64-DCT and QCA for the evaluation of bypass grafts. Intermodality and interobserver agreement were excellent.

Conclusion: 64-DCT angiography is a reliable, noninvasive diagnostic method for the assessment of coronary bypass grafts. It can be considered as a useful tool for follow-up purposes and may function as a gatekeeper before invasive procedures.