bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyber-Diplomacy: Managing Foreign Policy in the Twenty-First
Century
Authors: Mutimer David
Published: August 2005

Cyber-Diplomacy: Managing Foreign Policy in the Twenty-First
Century, Evan H. Potter, ed., Montreal & Kingston: McGill-Queen's
University Press, 2002, xii, 208.

We are repeatedly told that we live in a revolutionary age, a time in
which dramatic new developments in information and communication
technologies (ICTs) will fundamentally transform the ways in which we live
and work. Even the collapse of the dot.com bubble in 2000 has not much
dampened the spirits of the techno-utopians. Given these often-exaggerated
claims, I approached Cyber-Diplomacy with some trepidation, as
the editor cites Marshall McLuhan's ‘global village’ in
the first line of his introduction, and speaks of an information
revolution in his second paragraph. However, as I pressed on in the text I
was very pleasantly surprised to find that the editor and authors of this
short volume are well aware of the dangers of overstatement in relation to
ICTs, and work very hard throughout to avoid techno-utopianism. Instead,
the authors attempt to take a fairly sober look at “how diplomacy is
adapting to the new global information order” (7).
‘Choice’ Discourse in BC Child Care: Distancing Policy from Research
Authors: Kershaw Paul
Published: August 2005

Abstract.The gap between child care research and policy is growing in BC. While policy changes are what one would expect from the right-of-centre Liberal government, the gap runs contrary to its expressed commitment to the design of early childhood development policy on the basis of ‘science.’ The BC child care domain thus provides a rich context in which to examine how ideology mediates the consumption of research in the political arena. This article argues that the government's ‘choice’ discourse facilitates the articulation of neoliberal principles in a rhetorically neutral way while casting doubt on scholarship that illuminates gender and class inequalities.

Résumé.L'écart entre les recherches au sujet de soins d'enfant et la politique s'élargit en Colombie-Britannique. Pendant qu'on prévoit ces changements d'un gouvernement libéral droit-du-centre, l'écart dément son engagement de concevoir la politique de development de la petite enfance d'après la “science”. Ainsi la domaine de soins d'enfant en Colombie-Britannique fournit un contexte riche pour examiner comment l'idéologie s'interpose dans la consommation de recherches dans l'arène politique. Cet article soutient que la soi-disant dialogue de “choix” du gouvernement facilite l'articulation des principes néolibéraux d'une manière neutraliste pendant qu'on soulève du doute à l'érudition qui illumine des inégalités de genre et de classe sociale.
The Spouse in the House: What Explains the Marriage Gap in
Canada?
Authors: Wilson J. Matthew , Lusztig Michael
Published: August 2005

Abstract. A literature has emerged in American voting studies
noting a “marriage gap”—the propensity for married
voters to support the Republican party. Using Canadian Election Study
data, we establish the existence of a significant marriage gap in Canada.
We also seek to determine if the marriage gap is driven by
socio-demographic factors or attitudinal ones. We find that while
socio-demographic factors contribute to the marriage gap, they explain
relatively little variance. In probing the attitudinal basis of the
marriage gap further, we find that married Canadians differ from the unwed
very strongly on issues of moral traditionalism, but much less so on other
issues that measure generalized conservatism.

Résumé. Des travaux sont apparus dans les
études américaines sur le vote remarquant l'existence
d'un “écart mariage” (marriage gap) – la
tendance des électeurs mariés à soutenir le parti
républicain. Utilisant des données sur les élections
nationales canadiennes, nous établissons l'existence d'un
écart significatif au Canada. Nous cherchons aussi à
déterminer si ce phénomène est poussé par les
facteurs socio-démographiques ou les facteurs d'attitude. Nous
constatons que bien que les facteurs socio-démographiques
contribuent à cet écart, ils n'expliquent que
relativement peu de variation. En recherchant davantage la base
attitudinale, nous constatons que les canadiens mariés
diffèrent très fortement de ceux qui ne sont pas
mariés sur les questions de traditionalisme moral, mais cependant
beaucoup moins sur les questions de conservatisme géneral.
La Bruyère as Quietist: A Straussian Reading of La Bruyère's Caractères and Dialogues sur le quiétisme
Authors: Ford Ed
Published: August 2005

In October 1687, the Parisian publisher Michallet was granted the right to produce an anonymous work entitled Les Caractères de Théophraste traduits du grec avec les Caractères ou les mœurs de ce siècle. The first edition of the Caractères went on sale in March 1688, and the work became an instant classic. By 1696, Parisian readers hadpurchased eight editions, while an additional three editions had ap-peared in Lyon, and yet another in Brussels. In these later editions, the identity of the author was revealed: Jean de La Bruyère (1645–1696), who had been hired by the Duke of Condé as a tutor for his son and stayed on as librarian in the duke's palace at Chantilly.
First look at the 20 November 2003 superstorm with TIMED/GUVI: Comparisons with a thermospheric global circulation model
Authors: Meier R. R. , Crowley G. , Strickland D. J. , Christensen A. B. , Paxton L. J. , Morrison D. , Hackert C. L.
Published: August 2005

The NASA TIMED/GUVI experiment obtained unprecedented far ultraviolet images of thermospheric composition and temperature during the intense geomagnetic storm on 20–21 November 2003. Geographic maps of the atomic oxygen to molecular nitrogen column density ratio show severe depletions that extend to the equator near the peak of the storm. This ratio is a key indicator of how the thermospheric composition is disrupted at high latitudes and how the perturbed air moves globally as a result of dynamical forcing. For example, migrating regions of low oxygen‐to‐nitrogen air are invariably found to correlate with high thermospheric temperatures. As well, GUVI obtained altitudinal‐latitudinal (limb) images of temperature and composition, which show how the disturbances vary at different heights. The ASPEN thermospheric global circulation model was used to test our understanding of these remarkable images. The resulting simulations of thermospheric response show good agreement with GUVI data prior to the peak of the storm on 20 November. During the peak and recovery phases, serious discrepancies between data and model are seen. Although this initial attempt to model the storm is encouraging, much more detailed analysis is required, especially of the high‐latitude inputs. The GUVI images demonstrate that far ultraviolet imaging is becoming a crucial component of space weather research and development.
Relict subduction zones in Canada
Authors: van der Velden Arie J. , Cook Frederick A.
Published: August 2005

Relict subduction zones that are interpreted on 10 Lithoprobe deep seismic reflection profiles in Canada provide key observational evidence that lithosphere plate interactions have operated with essentially the same resultant geometry for at least 2.7 Gyr. Subduction zone reflections are generally found beneath known collisional belts, and their orientations are often consistent with the locations of exposed arcs, sutures, and subduction complexes. They project from the lower crust into the upper mantle and provide key geometric relationships between the crust, Moho, and upper mantle. The interpretation of subduction zone reflections as being syntectonic establishes a minimum age for the overlying lower crust and mantle wedge and precludes inferred formation of the Moho and upper mantle by postorogenic delamination in these areas. The orientation of subduction zone reflections may be synthetic or antithetic to exposed sutures, indicating juxtaposition by subcretion or by delamination, respectively. The mantle wedge above the subduction zone reflections may exhibit sparse reflectivity. Subduction zone reflections commonly dip toward the craton, indicating a preferred dip of subduction during the last stages of convergence within an orogen, or else a higher likelihood of preservation beneath older domains. Interpreted ages of the Canadian examples range from Recent to Neoarchean (∼2.7 Ga), providing observational evidence that plate tectonics or similar processes have been active since at least the Neoarchean. The locations and geometries of these relict subduction zones provide a snapshot of accretion boundaries in the mantle and establish a framework for the Neoarchean‐Recent accretionary architecture of the North American lithosphere.
Yellow Sea ocean‐acoustic solitary wave modeling studies
Authors: Warn‐Varnas A. C. , Chin‐Bing S. A. , King D. B. , Hawkins J. A. , Lamb K. G. , Teixeira M.
Published: August 2005

This study is in an area south of the Shandong peninsula, near the region where Zhou et al. (1991) observed anomalous drops in acoustical intensity. Solitary wave generation and propagation simulations are performed using the Lamb (1994) nonhydrostatic model. The model simulations show that, for summer conditions, the existing semi‐diurnal tidal flow over the topographic variations formed internal bores and solitary waves. For the Shandong area, we analyzed summer observations from Synthetic Aperture Radar (SAR) that tracked solitary wave trains from their surface roughness signatures. The images contained seven events consisting of internal bores and solitary waves that traveled in a well‐defined direction for 2.5 days. The origin of the trains appeared at a well‐defined point along a steep topographic drop. The SAR observations guided and tuned the model simulations, by comparing spectra of observed and modeled wavelengths. The tuned model yields wavelengths within factors of 2, or less, of those derived from SAR data. Wavelength and amplitude dispersion analysis showed two dispersion regimes. Modeled phase speeds were at the lower limit of phase speeds deduced from SAR data, from about 0.8 to 1.0 m/s. Acoustical intensity calculations in the presence of solitary wave trains will be undertaken in a subsequent paper using a parabolic equation acoustical model along the path of solitary wave train propagation.
Seasonal variations of polygonal thermal contraction crack patterns in a south polar trough, Mars
Authors: van Gasselt S. , Reiss D. , Thorpe A. K. , Neukum G.
Published: August 2005

We present observations of seasonal variations in polygonal crack patterns located in a polar trough on the south polar cap of Mars; previously, there was no direct observation showing that these patterns change. Polygonal patterns on Mars are attributed to thermal contraction cracking, which is commonly observed in periglacial environments on Earth. In this paper we discuss observations based upon the high‐resolution image data of the Mars Orbiter Camera and focus on the reconstruction of the seasonal development. The image‐based observations are further supported by temperature data. We show that the south polar trough pattern is located in an active geologic unit, which undergoes seasonal variations and annual crack formation. Furthermore, there are strong indications showing these contraction‐crack processes take place in a thin layer that might be composed of water‐ice and is located beneath the seasonal carbon dioxide ice cover.
Glacier surge dynamics of Sortebræ, east Greenland, from synthetic aperture radar feature tracking
Authors: Pritchard Hamish , Murray Tavi , Luckman Adrian , Strozzi Tazio , Barr Stuart
Published: August 2005

We have measured the surface flow rate of the large east Greenland glacier, Sortebræ, through both the initiation and termination of a major surge using synthetic aperture radar (SAR) feature tracking, optimized to minimize error. The Sortebræ surge began between November and January 1992–1993, after at least 6 weeks of subfreezing temperatures over the whole glacier, and propagated rapidly up‐glacier from a central nucleus. Sortebræ reached sustained fast flow rates of up to 24 m d−1, and the active phase lasted for 28–32 months before terminating in June 1995. Termination was abrupt, coinciding with the arrival of the spring thaw and the apparent release of a large volume of stored water from a single outlet at the front. The surge mechanism is interpreted as a switch from channelized to distributed drainage, which at present is best explained by Kamb's linked cavity sliding model.
Intensity and spatial extent of droughts in southern Africa
Authors: Rouault Mathieu , Richard Yves
Published: August 2005

The standardized precipitation index allows for monitoring the intensity and spatial extent of droughts at different time scales. We used it to do a retrospective analysis of the spatial extent of droughts in Southern Africa (South of 10°S), from 1901 to 1999. Accordingly, the 8 most severe droughts at the 6‐month scale (October–April) for the summer rainfall region of Southern Africa ended in 1916, 1924, 1933, 1949, 1970, 1983, 1992 and 1995. At the 2‐year scale, they ended in 1906, 1933, 1983, 1984, 1992, 1993, 1995 and 1996. Areas affected by those droughts ranged from 3.4 to 2 106 km2. Eight of those 12 years are El Niño years. Preliminary data indicates that 2001/2002, 2002/2003 and 2003/2004 experienced severe droughts at a number of scales. This confirms the increase in the spatial extent of drought in Southern Africa since the 1970's due to stronger ENSO Southern African rainfall relationship
Variability in Saturn's bow shock and magnetopause from Pioneer and Voyager: Probabilistic predictions and initial observations by Cassini
Authors: Hendricks S. , Neubauer F. M. , Dougherty M. K. , Achilleos N. , Russell C. T.
Published: August 2005

Probability distributions for the location of the Saturnian bow shock and magnetopause have been derived by extrapolating observations of dynamic solar wind pressures to the position of Saturn's orbit. These observations are those made by the Pioneer 11, Voyager 1 and 2 spacecraft near Saturn's orbit and by the Ulysses spacecraft near its aphelion. The magnetopause subsolar distance (measured from Saturn's center) is obtained using pressure equilibrium. The bow shock standoff distance is determined using empirical relations between bow shock size and solar wind dynamic pressure. Simple 2‐D geometric models of the magnetopause and bow shock surfaces have been used to determine their morphologies over a large range in local time. Three cases have been studied: (1) An Earth‐type magnetosphere with low internal plasma pressure; (2) An intermediate case calibrated with Voyager 1 observations; and (3) A Jupiter‐like inflated magnetosphere. The comparison of these models with initial observations from the initial sunward orbits of the Cassini spacecraft indicates a more inflated magnetosphere than postulated by the previous modelling of the Pioneer‐Voyager encounters.
An analysis of potential cloud artifacts in MODIS over ocean aerosol optical thickness products
Authors: Zhang Jianglong , Reid Jeffery S. , Holben Brent N.
Published: August 2005

Using spatially and temporally collocated MODerate Resolution Imaging Spectroradiometer (MODIS) products and data from seven AErosol RObotic NETwork (AERONET) sun‐photometer sites, we explored the relationship between MODIS aerosol optical depth and cloud fraction over remote oceans that have been recently reported in the literature. We show that artifacts such as cloud contamination or adjacency effect contribute to the majority of the relationship in clean marine conditions. This cloud fraction effect could result in a 10–20% overestimation in monthly mean aerosol optical depth or aerosol direct forcing values that are derived using MODIS aerosol products over cloud free oceans. It may also explain some of the high optical depth values derived in the mid‐latitude southern oceans. We also suggest that covariances of meteorological phenomenon such as wind or humidity in cloudy regions while logical might only account for a minor portion of the ensemble relationship.
Response of the ocean, climate and terrestrial carbon cycle to Holocene freshwater discharge after 8 kyr BP
Authors: Wang Yi , Mysak Lawrence A.
Published: August 2005

The “green” McGill Paleoclimate Model is run from 8 to 0 kyr BP under variable insolation (Milankovitch forcing), Taylor Dome CO2 (radiative forcing) and four prescribed meltwater scenarios (freshwater forcing) due to the retreat of the Laurentide Ice Sheet (LIS). For each scenario, we constrain the total volume of meltwater to be 1.62 × 1015 m3 (sea level‐equivalent of 4.62 m), which is obtained from the work of Paterson (1972) and the reconstructed sea level increase between 8 and 6 kyr BP. During each freshwater perturbation, the simulated maximum Atlantic meridional overturning circulation (MOC) intensity is reduced, by amounts of up to 8 Sv. During the time of a weakened MOC, the sea surface temperature is reduced in the high‐latitude North Atlantic and increased in the Southern Ocean. Our model results indicate that the freshwater impact on the Holocene climate and terrestrial carbon cycle is likely negligible after the 8.2‐kyr cold event. Only a large freshwater perturbation (>0.1 Sv) has a significant impact on the Holocene climate and terrestrial carbon cycle; it results in an enhanced cooling of about 1°C in the Northern Hemisphere (NH) and notable drops in the global net primary productivity (2 PgC/yr) and total land carbon storage (40 PgC).
Heterogeneous Oxygen Extraction in the Visual Cortex during Activation in Mild Hypoxic Hypoxia Revealed by Quantitative Functional Magnetic Resonance Imaging
Authors: Tuunanen Pasi I , Murray Ian J , Parry Neil RA , Kauppinen Risto A
Published: August 2005

Functional magnetic resonance imaging (fMRI) techniques were used to study haemodynamic and metabolic responses in human visual cortex during varying arterial blood oxygen saturation levels ( Ysat, determined by pulse-oximeter) and stimulation with contrast-reversing checkerboards. The visual-evoked potential amplitude remained constant at lowered Ysat of 0.82 ± 0.03. Similarly, fMRI cerebral blood flow ( CBF) responses were unchanged during reduced Ysat. In contrast, visual cortex volume displaying blood oxygen level-dependent (BOLD) fMRI response decreased as a function of Ysat, but the BOLD signal change of 3.6% ± 1.4% was constant. Oxygen extraction ratio ( OER) during visual activation showed values of 0.26 ± 0.03 for normal Ysat. At lowered Ysat, two OER patterns were observed. Firstly, a reduced OER of 0.14 ± 0.03 in the visual cortex structures showing BOLD in hypoxia was observed. Secondly, signs of much higher OER in other parts of visual cortex were obtained. T2*-weighted magnetic resonance imaging revealed signal increases by 0.8% ± 0.4% with visual activation during lowered Ysat in the visual cortex structures, which showed BOLD of 3.6% in magnitude under normoxia. Because the CBF response in the visual cortex was quantitatively similar during stimulation in normoxia and hypoxia, attenuated T2*-weighted signal increase in parts of visual cortex indicated high OER during visual activation in hypoxia, which was close to that encountered in the resting brain. These spatially localised regions of tissue oxygen extraction and metabolism argue for dissociation between CBF and BOLD fMRI signals in mild hypoxia. The findings point to heterogeneity with regard to oxygen requirement and its coupling to the haemodynamic response in the brain.
Acute Hypertension Induces Oxidative Stress in Brain Tissues
Authors: Poulet Roberta , Gentile Maria T , Vecchione Carmine , Distaso Maria , Aretini Alessandra , Fratta Luigi , Russo Giovanni , Echart Cinara , Maffei Angelo , De Simoni Maria G , Lembo Giuseppe
Published: August 2005

Arterial hypertension is not only a major risk factor for cerebrovascular accidents, such as stroke and cerebral hemorrhage, but is also associated to milder forms of brain injury. One of the main causes of neurodegeneration is the increase in reactive oxygen species (ROS) that is also a common trait of hypertensive conditions, thus suggesting that such a mechanism could play a role even in the onset of hypertension-evoked brain injury. To investigate this issue, we have explored the effect of acute-induced hypertensive conditions on cerebral oxidative stress. To this aim, we have developed a mouse model of transverse aortic coarctation (TAC) between the two carotid arteries, which imposes acutely on the right brain hemisphere a dramatic increase in blood pressure. Our results show that hypertension acutely induced by aortic coarctation induces a breaking of the blood–brain barrier (BBB) and reactive astrocytosis through hyperperfusion, and evokes trigger factors of neurodegeneration such as oxidative stress and inflammation, similar to that observed in cerebral hypoperfusion. Moreover, the derived brain injury is mainly localized in selected brain areas controlling cognitive functions, such as the cortex and hippocampus, and could be a consequence of a defect in the BBB permeability. It is noteworthy to emphasize that, even if these latter events are not enough to produce ischemic/hemorrhagic injury, they are able to alter mechanisms fundamental for maintaining normal brain function, such as protein synthesis, which has a prominent role for memory formation and cortical plasticity.
Model Selection in Magnetic Resonance Imaging Measurements of Vascular Permeability: Gadomer in a 9L Model of Rat Cerebral Tumor
Authors: Ewing James R , Brown Stephen L , Lu Mei , Panda Swayamprava , Ding Guangliang , Knight Robert A , Cao Yue , Jiang Quan , Nagaraja Tavarekere N , Churchman Jamie L , Fenstermacher Joseph D
Published: August 2005

Vasculature in and around the cerebral tumor exhibits a wide range of permeabilities, from normal capillaries with essentially no blood-brain barrier (BBB) leakage to a tumor vasculature that freely passes even such large molecules as albumin. In measuring BBB permeability by magnetic resonance imaging (MRI), various contrast agents, sampling intervals, and contrast distribution models can be selected, each with its effect on the measurement's outcome. Using Gadomer, a large paramagnetic contrast agent, and MRI measures of T1, over a 25-min period, BBB permeability was estimated in 15 Fischer rats with day-16 9L cerebral gliomas. Three vascular models were developed: (1) impermeable (normal BBB); (2) moderate influx (leakage without efflux); and (3) fast leakage with bidirectional exchange. For data analysis, these form nested models. Model 1 estimates only vascular plasma volume, vD, Model 2 (the Patlak graphical approach) vD and the influx transfer constant K1- Model 3 estimates vD, Ki and the reverse transfer constant, kb, through which the extravascular distribution space, ve, is calculated. For this contrast agent and experimental duration, Model 3 proved the best model, yielding the following central tumor means (±s.d.; n = 15): vD = 0.07±0.03 for Ki = 0.0105±0.005 min −1 and ve = 0.10±0.04. Model 2 Ki estimates were approximately 30% of Model 3, but highly correlated ( r 0.80, P<0.0003). Sizable inhomogeneity in vD, Ki and kb appeared within each tumor. We conclude that employing nested models enables accurate assessment of transfer constants among areas where BBB permeability, contrast agent distribution volumes, and signal-to-noise vary.
Positron Emission Tomography Quantification of [11C]-Harmine Binding to Monoamine Oxidase-A in the Human Brain
Authors: Ginovart Nathalie , Meyer Jeffrey H , Boovariwala Anahita , Hussey Doug , Rabiner Eugenii A , Houle Sylvain , Wilson Alan A
Published: August 2005

This article describes the kinetic modeling of [11C]-harmine binding to monoamine oxidase A (MAO-A) binding sites in the human brain using positron emission tomography (PET). Positron emission tomography studies were performed in healthy volunteers at placebo conditions and after treatment with clinical doses of moclobemide. In either condition, a two-tissue compartment model (2CM) provided better fits to the data than a one-tissue model. Estimates of k3/ k4 values from an unconstrained 2CM were highly variable. In contrast, estimates of the specifically bound radioligand distribution volume ( DVB) from an unconstrained 2CM were exceptionally stable, correlated well with the known distribution of MAO-A in the brain (cerebellum <frontal cortex ≈ putamen <temporal cortex ≈ cingulate <thalamus) and thus provided reliable indices of MAO-A density. Total distribution volume (DV) values were also highly stable and not different from those estimated with the Logan approach. Fixing the DV of free and nonspecifically bound radiotracer ( DVF + NS) or coupling DVF + NS between brain regions enabled more stable estimates of k3/ k4 as compared with an unconstrained 2CM. Moclobemide treatment leads to a 64% to 79% MAO-A blockade across brain regions, a result that supports the specificity of [11C]-harmine binding to MAO-A. The stability and reliability of DVB values obtained from an unconstrained 2CM, together with the computational simplicity associated with this method, support the use of DVB as an appropriate outcome measure for [11C]-harmine. These results indicate the suitability of using [11C]-harmine for quantitative evaluation of MAO-A densities using PET and should enable further studies of potential MAO-A dysregulation in several psychiatric and neurologic illnesses.
Computer simulation of polymer networks: Swelling by binary Lennard-Jones mixtures
Authors: Oyen Enno , Hentschke Reinhard
Published: August 2005

The swelling of regular, tightly meshed model networks is investigated by a molecular-dynamics–Monte Carlo hybrid technique. The chemical equilibrium between two simulation boxes representing the gel phase and a solvent bath, respectively, is obtained by subjecting the Lennard-Jones particles of a binary mixture, serving as explicit solvent, to the particle transfer step of Gibbs ensemble-Monte Carlo. The swelling behavior, especially preferential absorption of a single component, whose dependence on temperature, pressure, and fluid composition is studied, also depends significantly on the size of the central simulation cell. These finite-size effects correlate well with those exhibited by the density of solvent-free (dry) networks. A theoretical expression, whose derivation is based on network elasticity (of dry networks) yields finite-size scaling behavior in good accord with simulation results for both dry networks and gels in contact with solvent baths. This expression can be used to extrapolate the swelling behavior of simulated finite systems to infinite system size.
Femtosecond degenerate four-wave mixing of cyclopropane
Authors: Kummli Dominique S. , Frey Hans M. , Keller Michael , Leutwyler Samuel
Published: August 2005

Femtosecond degenerate four-wave mixing (fs-DFWM) is applied for the measurement of rotational constants of cyclopropane (C3H6). The rotational coherence method yields a very accurate B0=20093.322(12)MHz and centrifugal distortion constants DJ and DJK. To exploit the full resolution of the fs-DFWM method, the accuracy of the optical delay measurement was increased by nearly two orders of magnitude, including elimination of effects from the refractive index of air. The fs-DFWM molecular constants are comparable in accuracy to those from high-resolution infrared spectroscopy and are only surpassed by those of dipole distortion microwave spectroscopy. In parallel, the equilibrium structure, vibrationally averaged structure parameters and rotational constants were calculated using high-level ab initio methods and large basis sets. Combining these with the results of previous calculations and the measured rotational constants yields re(C–C)=1.5034(3)Å, re(C–H)=1.0775(5)Å, and αe(H–C–H)=115.09(10)°.
Ar
n
HF
van der Waals clusters revisited: II. Energetics and HF vibrational frequency shifts from diffusion Monte Carlo calculations on additive and nonadditive potential-energy surfaces for n=1-12
Authors: Jiang Hao , Xu Minzhong , Hutson Jeremy M. , Bačić Zlatko
Published: August 2005

The ground-state energies and HF vibrational frequency shifts of ArnHF clusters have been calculated on the nonadditive potential-energy surfaces (PESs) for n=2-7 and on the pairwise-additive PESs for the clusters with n=1-12, using the diffusion Monte Carlo (DMC) method. For n>3, the calculations have been performed for the lowest-energy isomer and several higher-lying isomers which are the closest in energy. They provide information about the isomer dependence of the HF redshift, and enable direct comparison with the experimental data recently obtained in helium nanodroplets. The agreement between theory and experiment is excellent, in particular, for the nonadditive DMC redshifts. The relative, incremental redshifts are reproduced accurately even at the lower level of theory, i.e., the DMC and quantum five-dimensional (rigid Arn) calculations on the pairwise-additive PESs. The nonadditive interactions make a significant contribution to the frequency shift, on the order of 10%–12%, and have to be included in the PESs in order for the theory to yield accurate magnitude of the HF redshift. The energy gaps between the DMC ground states of the cluster isomers are very different from the energy separation of their respective minima on the PES, due to the considerable variations in the intermolecular zero-point energy of different ArnHF isomers.
Mechanisms of fluorescence blinking in semiconductor nanocrystal quantum dots
Authors: Tang Jau , Marcus R. A.
Published: August 2005

The light-induced spectral diffusion and fluorescence intermittency (blinking) of semiconductor nanocrystal quantum dots are investigated theoretically using a diffusion-controlled electron-transfer (DCET) model, where a light-induced one-dimensional diffusion process in energy space is considered. Unlike the conventional electron-transfer reactions with simple exponential kinetics, the model naturally leads to a power-law statistics for the intermittency. We formulate a possible explanation for the spectral broadening and its proportionality to the light energy density, the −3∕2 power law for the blinking statistics of the fluorescence intermittency, the breakdown of the power-law behavior with a bending tail for the “light” periods, a lack of bending tail for the “dark” periods (but would eventually appear at later times), and the dependence of the bending tail on light intensity and temperature. This DCET model predicts a critical time tc (a function of the electronic coupling strength and other quantities), such that for times shorter than tc the exponent for the power law is −1∕2 instead of −3∕2. Quantitative analyses are made of the experimental data on spectral diffusion and on the asymmetric blinking statistics for the “on” and “off” events. Causes for deviation of the exponent from the ideal value of −3∕2 are also discussed. Several fundamental properties are determined from the present experimental data, the diffusion correlation time, the Stokes shift, and a combination of other molecular-based quantities. Specific experiments are suggested to test the model further, extract other molecular properties, and elucidate more details of the light-induced charge-transfer dynamics in quantum dots.
Magneto-optical additivity in ferromagnetic bilayers separated by nonferromagnetic spacers
Authors: Nývlt M. , Przybylski M. , Grabowski J. , Kirschner J.
Published: August 2005

We show that for some ultrathin multilayer structures the proportionality of the longitudinal Kerr ellipticity signal to the magnetic film thickness does not take place. Instead, thinner magnetic layers give even twice larger contributions than the thicker ones located a few monolayers deeper. This effect is demonstrated both experimentally and theoretically on ultrathin Fe∕Cr∕Fe sandwich systems prepared on GaAs(001) surfaces. Such a behavior is explained by a depth variation of phase relations between the optically reflected wave and the wave generated by the magneto-optical interaction. This mechanism becomes very effective close to the phase where the magneto-optical ellipticity cancels.
The influence of Cu∕Al ratio on properties of chemical-vapor-deposition-grown p-type Cu–Al–O transparent semiconducting films
Authors: Cai Jianling , Gong Hao
Published: August 2005

Transparent p-type copper aluminum oxide (Cu–Al–O) semiconducting thin films, with Cu∕Al atomic ratios ranging from 1.0 to 4.3, were deposited by plasma-enhanced metal-organic chemical-vapor deposition. The films were grown on z-cut single-crystal quartz substrates, at a substrate temperature of 450°C. Crystalline CuAlO2 was found dominant in the films, including small amounts of CuAl2O4, Al2O3, and amorphous Cu2O. The effect of varying Cu∕Al ratio on the structural, electrical, and optical properties of the films were studied by x-ray diffraction, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and Seebeck technique, and discussed. We were able to optimize the Cu∕Al ratio for the p-type conductivity and transmittance in copper aluminum oxide thin films, and the best conductive film, with a room-temperature conductivity of 0.289Scm−1 and a transparency of 80%, was found to have a Cu∕Al ratio of 1.4±0.3. In addition, the mechanism of the p-type conduction of copper aluminum oxide was discussed.
Anisotropy of optical absorption and fluorescence in Al2O3:C,Mg crystals
Authors: Sanyal Subrata , Akselrod Mark S.
Published: August 2005

Spectroscopic properties of recently discovered fluorescent sapphire single crystals (Al2O3:C,Mg), developed for volumetric optical data storage, are investigated. Polarized optical absorption, excitation-emission spectra, and quantum yield of fluorescence of the crystal in two different photochromic states are studied. The spatial distribution of intensity and polarization ratio of the fluorescence associated with the 435∕520- and 620∕750-nm excitation-emission bands, characteristic of the two photochromic states of the crystal, display strong anisotropy. The intensity distribution, and hence the spatially averaged quantum yield of fluorescence for the two states, measured relative to standard laser dyes are similar for different crystallographic orientations. The average quantum yield is found to be close to unity for both the states. The anisotropic properties of optical absorption and fluorescence suggest a model of double oxygen vacancy.
Phase-matched generation of a terahertz surface wave by a subluminous optical strip
Authors: Bakunov M. I. , Maslov A. V. , Bodrov S. B.
Published: August 2005

We show that a weakly focused ultrashort laser pulse with tilted intensity front can efficiently excite a terahertz surface wave via phase-matched optical rectification at the surface of a semiconductor. The surface wave is excited by a strip of nonlinear polarization moving along the semiconductor surface with subluminous velocity. The amplitude and power of the radiated surface wave are calculated. For a 90-fs optical pulse with a peak intensity of 2GW∕cm2, we estimate the energy conversion coefficient to be 10−7 at the surface of GaAs. The direct excitation of surface waves at terahertz frequencies can be particularly attractive for terahertz spectroscopy of semiconductor surfaces.
Diode calibration of a Langmuir probe system for measurement of electron energy distribution functions in a plasma
Authors: DeJoseph C. A. , Demidov V. I.
Published: August 2005

It is shown that a simple circuit consisting of a semiconductor diode, a resistor, and a dc voltage source can model a narrow-energy group of electrons in a plasma for the purpose of calibration of a Langmuir probe. The calibration is appropriate when the probe is used for measurement of the electron energy distribution function (EEDF). This simple circuit allows real-time determination of sensitivity, energy resolution, and signal-to-noise ratio for probe measurements of the EEDF.
Submicron periodic poling and chemical patterning of GaN
Authors: Pezzagna S. , Vennéguès P. , Grandjean N. , Wieck A. D. , Massies J.
Published: August 2005

Periodic polarity (PePo) GaN films are grown by molecular-beam epitaxy. A high Mg doping is used to reverse the film polarity from Ga to N. An etching step is then performed to define the PePo pattern. Ultrasharp inversion domain boundaries between Ga- and N-polar domains are shown by transmission electron microscopy. Moreover, it is demonstrated that three-dimensional (3D) patterned Ga-polarity GaN films can be obtained from these PePo samples by a simple wet chemical etching procedure. When combined with a focused ion beam (FIB) to define the initial PePo template, periodic poling as well as chemical 3D patterning is demonstrated down to the nanometer scale.
Roles of PSF protein and VL30 RNA in reversible gene regulation
Authors: Song Xu , Sun Ying , Garen Alan
Published: August 2005

The mammalian protein PSF contains a DNA-binding domain (DBD) that coordinately represses multiple oncogenic genes in human cell lines, indicating a role for PSF as a human tumor-suppressor protein. PSF also contains two RNA-binding domains (RBD) that form a complex with a noncoding VL30 retroelement RNA, releasing PSF from a gene and reversing repression. Thus, the DBD and RBD in PSF are linked by a mechanism of reversible gene regulation involving a noncoding RNA. This mechanism also could apply to other regulatory proteins that contain both DBD and RBD. The mouse genome has multiple copies of VL30 retroelements that are developmentally regulated, and mouse cells contain VL30 RNAs that have normal and pathological roles in gene regulation. Human chromosome 11 has a VL30 retroelement, and a VL30 EST was identified in human blastocyst cells, indicating that the PSF-VL30 RNA regulatory mechanism also could function in human cells.
PpATG9 Encodes a Novel Membrane Protein That Traffics to Vacuolar Membranes, Which Sequester Peroxisomes during Pexophagy inPichia pastoris
Authors: Chang Tina , Schroder Laura A. , Thomson J. Michael , Klocman Amy S. , Tomasini Amber J. , Strømhaug Per E. , Dunn William A.
Published: August 2005

When Pichia pastoris adapts from methanol to glucose growth, peroxisomes are rapidly sequestered and degraded within the vacuole by micropexophagy. During micropexophagy, sequestering membranes arise from the vacuole to engulf the peroxisomes. Fusion of the sequestering membranes and incorporation of the peroxisomes into the vacuole is mediated by the micropexophagy-specific membrane apparatus (MIPA). In this study, we show the P. pastoris ortholog of Atg9, a novel membrane protein is essential for the formation of the sequestering membranes and assembly of MIPA. During methanol growth, GFP-PpAtg9 localizes to multiple structures situated near the plasma membrane referred as the peripheral compartment (Atg9-PC). On glucose-induced micropexophagy, PpAtg9 traffics from the Atg9-PC to unique perivacuolar structures (PVS) that contain PpAtg11, but lack PpAtg2 and PpAtg8. Afterward, PpAtg9 distributes to the vacuole surface and sequestering membranes. Movement of the PpAtg9 from the Atg9-PC to the PVS requires PpAtg11 and PpVps15. PpAtg2 and PpAtg7 are essential for PpAtg9 trafficking from the PVS to the vacuole and sequestering membranes, whereas trafficking of PpAtg9 proceeds independent of PpAtg1, PpAtg18, and PpVac8. In summary, our data suggest that PpAtg9 transits from the Atg9-PC to the PVS and then to the sequestering membranes that engulf the peroxisomes for degradation.
Measuring the Stoichiometry and Physical Interactions between Components Elucidates the Architecture of the Vertebrate Kinetochore
Authors: Emanuele Michael J. , McCleland Mark L. , Satinover David L. , Stukenberg P. Todd
Published: August 2005

Vertebrate kinetochores contain over 50 different proteins organized into three distinct regions: the inner plate, outer plate, and fibrous corona. The present study characterizes numerous precursors of kinetochore assembly in a system free of centromeric chromatin, Xenopus extracts. Hydrodynamic analysis suggests there are a minimum of two monomeric proteins and six preassembled complexes that accumulate on centromeres to form the kinetochore. The inner and outer kinetochore assemble from at least two distinct kinetochore complexes containing the proteins Mis12, Zwint, and Ndc80, all of which interact by immunoprecipitation. There is also a network of interactions between the fibrous corona proteins that is dissociated by microtubules. We quantify the number of molecules of specific proteins assembled into a single kinetochore. There are between 800 and 1200 molecules of the measured inner and outer kinetochore proteins, demonstrating that the components in these regions are in similar stoichiometry. In contrast, the measured fibrous corona proteins are present at 250-300 molecules per kinetochore. Zwint, but not Mis12, requires the Ndc80 complex for assembly into the kinetochore. Further, Ndc80 requires Zwint for assembly, indicating a codependency for these two proteins. Our data provide a model for the structural architecture and assembly pathway of the vertebrate kinetochore.
Selective Modulation of Integrin-mediated Cell Migration by Distinct ADAM Family Members
Authors: Huang Jing , Bridges Lance C. , White Judith M.
Published: August 2005

A disintegrin and a metalloprotease (ADAM) family members have been implicated in many biological processes. Although it is recognized that recombinant ADAM disintegrin domains can interact with integrins, little is known about ADAM-integrin interactions in cellular context. Here, we tested whether ADAMs can selectively regulate integrin-mediated cell migration. ADAMs were expressed in Chinese hamster ovary cells that express defined integrins (α4β1, α5β1, or both), and cell migration on full-length fibronectin or on its α4β1 or α5β1 binding fragments was studied. We found that ADAMs inhibit integrin-mediated cell migration in patterns dictated by the integrin binding profiles of their isolated disintegrin domains. ADAM12 inhibited cell migration mediated by the α4β1 but not the α5β1 integrin. ADAM17 had the reciprocal effect; it inhibited α5β1- but not α4β1-mediated cell migration. ADAM19 and ADAM33 inhibited migration mediated by both α4β1 and α5β1 integrins. A point mutation in the ADAM12 disintegrin loop partially reduced the inhibitory effect of ADAM12 on cell migration on the α4β1 binding fragment of fibronectin, whereas mutations that block metalloprotease activity had no effect. Our results indicate that distinct ADAMs can modulate cell migration mediated by specific integrins in a pattern dictated, at least in part, by their disintegrin domains.
TOR Complex 2 Integrates Cell Movement during Chemotaxis and Signal Relay in Dictyostelium
Authors: Lee Susan , Comer Frank I. , Sasaki Atsuo , McLeod Ian X. , Duong Yung , Okumura Koichi , Yates John R. , Parent Carole A. , Firtel Richard A.
Published: August 2005

Dictyostelium cells form a multicellular organism through the aggregation of independent cells. This process requires both chemotaxis and signal relay in which the chemoattractant cAMP activates adenylyl cyclase through the G protein-coupled cAMP receptor cAR1. cAMP is produced and secreted and it activates receptors on neighboring cells, thereby relaying the chemoattractant signal to distant cells. Using coimmunoprecipitation and mass spectrometric analyses, we have identified a TOR-containing complex in Dictyostelium that is related to the TORC2 complex of Saccharomyces cerevisiae and regulates both chemotaxis and signal relay. We demonstrate that mutations in Dictyostelium LST8, RIP3, and Pia, orthologues of the yeast TORC2 components LST8, AVO1, and AVO3, exhibit a common set of phenotypes including reduced cell polarity, chemotaxis speed and directionality, phosphorylation of Akt/PKB and the related PKBR1, and activation of adenylyl cyclase. Further, we provide evidence for a role of Ras in the regulation of TORC2. We propose that, through the regulation of chemotaxis and signal relay, TORC2 plays an essential role in controlling aggregation by coordinating the two essential arms of the developmental pathway that leads to multicellularity in Dictyostelium.
FORCED INFORMATION DISCLOSURE AND THE FALLACY OF TRANSPARENCY IN MARKETS
Authors: Cason Timothy N. , Plott Charles R.
Published: August 2005

A theory advanced in regulatory hearings holds that market performance will be improved if one side of the market is forced to publicly reveal preferences. For example, wholesale electricity producers claim that retail electricity consumers would pay lower prices if wholesale public utility demand is disclosed to producers. Experimental markets studied here featured decentralized, privately negotiated contracts, typical of the wholesale electricity markets. Two conclusions emerge: (1) such markets generally converge to the competitive equilibrium and (2) forced disclosure works to the disadvantage of the disclosing side. Information disclosure would result in higher wholesale and thus higher retail electricity prices. (JEL L50, L94, D43)
SILENT AUCTIONS IN THE FIELD AND IN THE LABORATORY
Authors: Isaac R. Mark , Schnier Kurt
Published: August 2005

We analyze data from hundreds of auctions from three field silent auction sessions. We focus on the descriptive statistics and on a parametric model of jump bidding. We then report data from six laboratory sessions of silent auctions. As a controlled environment, this allows us to evaluate the auctions in ways not available within the field. The laboratory experiments capture essential features of the field sessions and thus comprise a credible laboratory testbed for further examination of institutional perturbations in the silent auction. (JEL D44, H41)