bluuebunny/crossref_metadata_2025 huggingface dataset:
Haemodynamic changes due to delayed sternal closure in newborns after surgery for congenital cardiac malformations
Authors: Vojtovič Pavel , Reich Oleg , Selko Marek , Tláskal Tomáš , Hostaša Jiří , Matějka Tomáš , Gebauer Roman , Gabriel Otakar , Chaloupecký Václav
Published: October 2009

Background

Delayed sternal closure is used to prevent low cardiac output syndrome in selected newborns shortly after cardiac surgery for congenital cardiac defects. Sternal closure itself often causes haemodynamic and ventilatory instability that cannot be entirely assessed by standard monitoring means. Therefore, we used transpulmonary thermodilution technique for an exact evaluation of the haemodynamic changes.

Patients and methods

Between April, 2006, and December, 2008, 23 neonates aged from 1 to 30 days, with a median of 7 days, and weighing from 1.9 to 4.2 kilograms, with a median of 3.25 kilograms, were studied after biventricular corrections. Residual intracardiac shunts were excluded by echocardiography. Haemodynamic and ventilatory parameters, along with those obtained by the transpulmonary thermodilution technique, were recorded before and immediately after the sternal closure, and then at 0.5, 1, 2, 6, 12, 24, and 48 hours.

Results

Chest closure caused significant decrease in systolic arterial pressure from 80.04 ± 11.48 to 69.48 ± 9.63 mmHg (p < 0.001), cardiac index from [median (25th/75th centile)] 2.640 (2.355/2.950) to 2.070 (1.860/2.420) l/min/m2 (p < 0.001), stroke volume index from 18.50 (16.00/20.00) to 14.00 (11.00/17.00) ml/m2 (p < 0.001), and dynamic lung compliance from 2.45 (2.31/3.00) to 2.30 (2.14/2.77) ml/cmH2O (p = 0.007). Stroke volume variation increased from 14.00 (9.25/16.75) to 18.00 (15.00/21.00) % (p < 0.001). The oxygenation index transitorily increased from 2.50 (2.14/3.15) to 3.36 (2.63/4.29) (p < 0.001). Serum lactate decreased from 1.40 (1.12/2.27) to 1.0 (0.8/1.3)mmol/l, p < 0.001 in coincidence with a haemodynamic stabilisation at a later time after chest closure. Cardiopulmonary instability caused by the sternal closure necessitated therapeutic intervention in 18 of 23 patients (78.3%).

Conclusion

Delayed sternal closure causes a significant transitory decrease in stroke volume, cardiac output and arterial blood pressure. Also lung compliance and blood oxygenation are temporarily significantly compromised.
Innovation in Basic Science: Stem Cells and their role in the treatment of Paediatric Cardiac Failure – Opportunities and Challenges
Authors: Kaushal Sunjay , Jacobs Jeffrey Phillip , Gossett Jeffrey G. , Steele Ann , Steele Peter , Davis Craig R. , Pahl Elfriede , Vijayan Kalpana , Asante-Korang Alfred , Boucek Robert J. , Backer Carl L. , Wold Loren E.
Published: October 2009

Heart failure is a leading cause of death worldwide. Current therapies only delay progression of the cardiac disease or replace the diseased heart with cardiac transplantation. Stem cells represent a recently discovered novel approach to the treatment of cardiac failure that may facilitate the replacement of diseased cardiac tissue and subsequently lead to improved cardiac function and cardiac regeneration.

A stem cell is defined as a cell with the properties of being clonogenic, self-renewing, and multipotent. In response to intercellular signalling or environmental stimuli, stem cells differentiate into cells derived from any of the three primary germ layers: ectoderm, endoderm, and mesoderm, a powerful advantage for regenerative therapies. Meanwhile, a cardiac progenitor cell is a multipotent cell that can differentiate into cells of any of the cardiac lineages, including endothelial cells and cardiomyocytes.

Stem cells can be classified into three categories: (1) adult stem cells, (2) embryonic stem cells, and (3) induced pluripotential cells. Adult stem cells have been identified in numerous organs and tissues in adults, including bone-marrow, skeletal muscle, adipose tissue, and, as was recently discovered, the heart. Embryonic stem cells are derived from the inner cell mass of the blastocyst stage of the developing embryo. Finally through transcriptional reprogramming, somatic cells, such as fibroblasts, can be converted into induced pluripotential cells that resemble embryonic stem cells.

Four classes of stem cells that may lead to cardiac regeneration are: (1) Embryonic stem cells, (2) Bone Marrow derived stem cells, (3) Skeletal myoblasts, and (4) Cardiac stem cells and cardiac progenitor cells. Embryonic stem cells are problematic because of several reasons: (1) the formation of teratomas, (2) potential immunologic cellular rejection, (3) low efficiency of their differentiation into cardiomyocytes, typically 1% in culture, and (4) ethical and political issues. As of now, bone marrow derived stem cells have not been proven to differentiate reproducibly and reliably into cardiomyocytes. Skeletal myoblasts have created in vivo myotubes but have not electrically integrated with the myocardium. Cardiac stem cells and cardiac progenitor cells represent one of the most promising types of cellular therapy for children with cardiac failure.
The Gerbode Defect: The Significance of a Left Ventricular to Right Atrial Shunt
Authors: Kelle Angela M. , Young Luciana , Kaushal Sunjay , Elise Duffy C. , Anderson Robert H. , Backer Carl L.
Published: October 2009

Background

The so-called Gerbode ventriculo-atrial defect is a rare defect that permits shunting from the left ventricle to the right atrium. It takes 2 forms, either a deficiency of the atrioventricular membranous septum, or shunting initially through a ventricular septal defect, with atrial shunting occurring through a deficiency in the septal leaflet of the tricuspid valve. In this review, we describe the natural history and outcomes of surgical repair for the variant with shunting through a deficiency at the site of the atrioventricular membranous septum.

Methods

From 1990 to 2008, we identified 6 patients from our departmental database who had undergone surgical closure of a congenital defect of the atrioventricular component of the membranous septum. Median age at repair was 1.6 years, with a range, from 0.4 to 19 years. All patients were symptomatic, with 3 having congestive cardiac failure, 2 failing to thrive, and 2 having intolerance to exercise. All had a dilated right atrium demonstrated by echocardiogram, with a mean preoperative gradient measured by echocardiogram to be 109 millimetres of mercury, with a range from 65 to 150 millimetres of mercury.

Results

There was no operative or late mortality. The mean size of the defect was 6.2 ± 2.0 millimetres, with a range from 4 to 8 millimetres. All were closed by insertion of a patch. The mean period of cardiopulmonary bypass was 90.5 ± 11.3 minutes, the mean time of aortic cross-clamping 54.8 ± 6.9 minutes, and the mean length of stay in hospital 4.3 ± 1.0 days. No patient had a residual defect, and only trivial regurgitation of the tricuspid valve was evident by postoperative echocardiography. There were no complications or reoperations.

Conclusion

The membranous ventriculo-atrial defect can be recognized echocardiographically on the basis of dilation of the right atrium in the setting of an unusually high Doppler echocardiogram gradient compared to the ventricular septal defect with shunting only at ventricular level. Since all patients in our series were symptomatic, we recommend surgical closure of all these defects.
Index flood–based multivariate regional frequency analysis
Authors: Chebana F. , Ouarda T. B. M. J.
Published: October 2009

Because of their multivariate nature, several hydrological phenomena can be described by more than one correlated characteristic. These characteristics are generally not independent and should be jointly considered. Consequently, univariate regional frequency analysis (FA) cannot provide complete assessment of true probabilities of occurrence. The objective of the present paper is to propose a procedure for regional flood FA in a multivariate framework. In the present paper, the focus is on the estimation step of regional FA. The proposed procedure represents a multivariate version of the index flood model and is based on copulas and a multivariate quantile version with a focus on the bivariate case. The model offers increased flexibility to designers by leading to several scenarios associated with the same risk. The univariate quantiles represent special cases corresponding to the extreme scenarios. A simulation study is carried out to evaluate the performance of the model in a bivariate framework. Simulation results show that bivariate FA provides the univariate quantiles with equivalent accuracy. Similarity is observed between results of the bivariate model and those of the univariate one in terms of the behavior of the corresponding performance criteria. The procedure performs better when the regional homogeneity is high. Furthermore, the impacts of small variations in the record length at gauged sites and the region size on the performance of the proposed procedure are not significant.
Flexure due to the Messinian‐Pontian sea level drop in the Black Sea
Authors: Bartol J. , Govers R.
Published: October 2009

Paleowater depth observations suggest that a large sea level drop occurred in the Black Sea coeval with the Messinian salinity crisis in the Mediterranean Sea. This sea level drop would have induced vertical motions of the solid earth, which influenced strait dynamics with major implications for the hydrological regime of the region. Using three‐dimensional flexure models we find that a sea level drop between 1730 and 2230 m is required to reproduce the observed paleowater depths. The models predict that uplift reduced the seaway connectivity between the Black Sea and the Mediterranean Sea (Aegean region) and between the Black Sea and the Caspian Sea (Stavropol Highlands). The Miocene Paratethys Sea consequently became fragmented, and the remaining subseas likely became more sensitive to climate change. This agrees with the discovery of erosional surfaces in the Caspian Sea and in the Pannonian Basin. To explain the synchronicity of the sea level lowering in the Black Sea and the Mediterranean, we speculate that a regional shift toward a drier climate occurred in response to the Messinian salinity crisis in the Mediterranean, which led to a fall in sea level within the Black Sea.
Waveform inversion for D″ structure beneath northern Asia using Hi‐net tiltmeter data
Authors: Kawai Kenji , Sekine Shutaro , Fuji Nobuaki , Geller Robert J.
Published: October 2009

We invert shear‐wave waveform data for the radial variation of (isotropic) shear‐velocity in D″ beneath Northern Asia. We reduce source and receiver effects by using data for intermediate and deep events beneath Italy and Japan recorded respectively at stations in East Asia and Europe. Relative to PREM, we find a significantly higher S‐wave velocity in the depth range from 150 to 300 km above the core‐mantle boundary (CMB) and a slightly lower S‐wave velocity in the depth range 0–150 km above the CMB. As our previous studies of D″ structure beneath Central America and the Arctic obtained similar S‐wave velocity models, we suggest that this pattern of vertical dependence of shear wave velocity in D″ may be a general phenomenon, at least in relatively cold regions.
THEMIS observation of multiple dipolarization fronts and associated wave characteristics in the near‐Earth magnetotail
Authors: Zhou Meng , Ashour‐Abdalla Maha , Deng Xiaohua , Schriver David , El‐Alaoui Mostafa , Pang Ye
Published: October 2009

Multiple dipolarization fronts were observed by THEMIS spacecraft in the near‐Earth magnetotail during a substorm. The dipolarization fronts were located at the leading edge of earthward propagating plasma bubbles. Major energetic electron flux enhancements were observed at the dipolarization fronts, which were also associated with large wave fluctuations extending from below the lower hybrid frequency to above the electron cyclotron frequency. Intense electric field wave packets, primarily contributed by the Hall electric field and lower hybrid drift (LHD) wave, were observed right at the front, which was a thin current layer with size of the order of the ion inertial length. The LHD wave was believed to be generated by a diamagnetic current in the presence of density and temperature gradients. Electrostatic electron cyclotron harmonic (ECH) waves were detected slightly after the front. The ECH waves were probably generated by the positive slope of the electron perpendicular velocity distribution. Both of these waves are suggested to be able to heat electrons. The observation of these waves at the dipolarization front could be important for the understanding of electron energization during substorm injection, as well as the mechanism of current disruption.
Global surface cooling: The atmospheric fast feedback response to a collapse of the thermohaline circulation
Authors: Laurian A. , Drijfhout S. S. , Hazeleger W. , van Dorland R.
Published: October 2009

In the ECHAM5/MPI‐OM model a collapse of the Atlantic thermohaline circulation results in a global surface cooling of 0.72 K. The mechanisms that are responsible for this cooling are investigated. Additional experiments were performed with a one‐dimensional radiative convective model in which anomalies from the climate model were prescribed. Fast atmospheric feedbacks are essential to maintain and strengthen the global surface cooling caused by a THC collapse. Reduced downward long wave radiation exceeds the decreased upward long wave radiation. This decreased downward long wave radiation is caused by reduced water vapor content rather than by ice‐albedo feedbacks. Also, the decrease in water vapor is much stronger than suggested by the water vapor feedback expected from the simulated albedo change. The large decrease in water vapor is the main feedback. On the regional scale, changes in cloud water and cloud radiative forcing further modify the surface cooling.
Changes in synoptic weather patterns and Greenland precipitation in the 20th and 21st centuries: 1. Evaluation of late 20th century simulations from IPCC models
Authors: Schuenemann Keah C. , Cassano John J.
Published: October 2009

Using the self‐organizing map (SOM) technique, the sea level pressure synoptic climatology and precipitation of 15 Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) models are compared to that of the ERA‐40 reanalysis for the North Atlantic region for the period 1961 to 1999. Three of the models, the CCCMA‐CGCM3.1(T63), the MIROC3.2(hires), and the MPI‐ECHAM5, best reproduce the ERA‐40 synoptic climatology and are chosen for further analysis of precipitation over Greenland. The MIROC3.2(hires) is the best single performing model, in that it best matches ERA‐40. Although the three‐model ensemble simulates the same mean annual precipitation over Greenland as ERA‐40, the ensemble simulates the mean annual precipitation differently than ERA‐40. A dry bias in the CCCMA‐CGCM3.1(T63) and a wet bias from the MPI‐ECHAM5 cancel in the ensemble average. The mean annual precipitation difference between the model ensemble, as well as each individual model, and ERA‐40 is then attributed to differences in intrapattern variability and pattern frequency components in the models that make up the ensemble. Pattern frequency differences between the model and ERA‐40 indicate a difference in the occurrence of synoptic weather patterns, while intrapattern variability differences denote differences in the amount of precipitation produced when a given synoptic weather pattern occurs. Intrapattern variability differences between the models and ERA‐40 are predominantly responsible for Greenland precipitation differences, but pattern frequency (circulation) differences in the models also play a small role. Part 2 of this paper uses this three‐model ensemble to analyze and attribute predicted increases in precipitation over the Greenland ice sheet for the 21st century.
Predicting CD62L expression during the CD8+ T‐cell response in vivo
Authors: Schlub Timothy E , Badovinac Vladimir P , Sabel Jaime T , Harty John T , Davenport Miles P
Published: October 2009

Acute infection leads to CD8+ T‐cell activation, division and differentiation. Following clearance of infection, cells revert to two distinct subsets of memory, central (TCM) and effector (TEM) memory. Adoptive transfer of naive T‐cell receptor transgenic (TCR‐tg) T cells has been used to study the differentiation of these memory subsets, which are often discriminated by expression of CD62L. Naive CD8+ T cells are CD62Lhigh, and CD62L expression is lost during the ‘effector’ phase. Adoptive transfer studies show that higher transfer frequencies result in diminished T‐cell expansion and a higher proportion CD62Lhigh. This suggests a relationship between CD62L expression and cell division, where division leads to conversion from CD62Lhigh to CD62Llow phenotype. To address this hypothesis we adoptively transferred graded numbers of OT‐1 TCR‐tg T cells from naive donors and tracked the kinetics and phenotype of the immune response after infection. We developed a simple mathematical model of division‐linked CD62L differentiation, which we compared with the experimental data. Our results show that division‐linked differentiation predicts the differences in proportion of cells CD62Lhigh observed between responses of different adoptive transfer number and within individual mice. We calculate that approximately 20% of CD62Lhigh cells convert to CD62Llow during each division.
A conformal variational approach for helices in nature
Authors: Barros Manuel , Ferrández Angel
Published: October 2009

We propose a two step variational principle to describe helical structures in nature. The first one is governed by an energy action which is a linear function in both curvature and torsion allowing to describe nonclosed structures including elliptical, spherical, and conical helices. These appear as rhumb lines in right cylinders constructed over plane curves. The model is completed with a conformal alternative which, in particular, gives a description of closed structures. The energy action is linear in the curvatures when computed in a conformal spherical metric. Now, helices appear as making a constant angle with a Villarceau flow and so they are loxodromes in surfaces which are stereographic projections of Hopf tubes, in particular, anchor rings, revolution tori, and Dupin cyclides. The model satisfies the requirements of simplicity and beauty as reflected in the three main principles that head its construction: least action, topological, and quantization. According to the latter, the main entities and quantities associated with the model should not be multiplied unnecessarily but they are quantized. In this sense, a quantization principle, a la Dirac, is obtained for closed structures and also for the critical levels of energy.
Runaway electron transport via tokamak microturbulence
Authors: Hauff T. , Jenko F.
Published: October 2009

The mechanisms found for the magnetic transport of fast ions in the work of Hauff et al. [Phys. Rev. Lett. 102, 075004 (2009)] are extended to the diffusion of runaway electrons. Due to their smaller mass and larger energy, they behave strongly relativistically, for which reason the scaling laws defined previously have to be modified. It is found that due to these changes, the regime of constant magnetic transport does not exist anymore, but diffusivity scales with E−1 for magnetic transport, or even with E−2 in the case that finite gyroradius effects become important. It is shown that the modified analytical approaches are able to explain the surprisingly small values found in experiments, although it cannot be excluded that possibly other reduction mechanisms are present at the same time.
Trapping of Ce electrons in band gap and room temperature ferromagnetism of Ce4+ doped ZnO nanowires
Authors: Iqbal Javed , Liu Xiaofang , Zhu Huichao , Pan Chongchao , Zhang Yong , Yu Dapeng , Yu Ronghai
Published: October 2009

Rare-earth (RE) metal doped ZnO nanowires have been fabricated through a simple, quick, and versatile low temperature soft chemical method. The average length and diameter of nanowires lie in range of 5μm and 60nm, respectively. Raman and x-ray photoelectron spectroscopy studies demonstrate that Ce has 4+ oxidation state and successfully substitutes Zn up to 2.5% into ZnO single phase wurtzite structure. Doping of Ce shows a remarkably prominent large redshift of 22nm in the UV region of the band gap, with an increase in the intensity of green emission band due to charge transfer of Ce4+ dopant. In addition, it has been interestingly found that RE (Ce) doped ZnO nanowires exhibit room temperature ferromagnetism, which makes them potential for spintronic devices with excellent optical characteristics.
The nanoindentation applied to predict the interface delamination for the C/amorphous Si composite film
Authors: Han Chang-Fu , Huang Chao-Yu , Wu Bo-Hsiung , Lin Jen-Fin
Published: October 2009

In the present study, the indentation depth corresponding to the pop-in arising in the loading process is found to be quite close to the C/amorphous Si composite film thickness, regardless of the C-film thickness. This load-depth behavior gives a clue that the occurrence of pop-in is perhaps related to the buckling of the composite film, which had already delaminated from the silicon substrate. This indentation depth of buckling predicted by the present model is quite close to the pop-in depth obtained from experimental results, regardless of the change in the C-film thickness. This characteristic reveals that the present model is developed successfully to predict the pop-in depth of a specimen, and the pop-in is indeed created due to the buckling of the composite film under a compression stress.
Structure and dielectric properties of cubic Bi2(Zn1∕3Ta2∕3)2O7 thin films
Authors: Noh Jun Hong , Hong Hee Beom , Lee Jung-Kun , Cho Chin Moo , Kim Jin Young , Lee Sangwook , Cho In-Sun , Jung Hyun Suk , Hong Kug Sun
Published: October 2009

Pyrochlore Bi2(Zn1∕3Ta2∕3)2O7 (BZT) films were prepared by pulsed laser deposition on Pt∕TiO2∕SiO2∕Si substrates. In contrast to bulk monoclinic BZT ceramics, the BZT films have a cubic structure mediated by an interfacial layer. The dielectric properties of the cubic BZT films [ε∼177, temperature coefficient of capacitance (TCC) ∼−170ppm∕°C] are much different from those of monoclinic BZT ceramics (ε∼61, TCC ∼+60ppm∕°C). Increasing the thickness of the BZT films returns the crystal structure to the monoclinic phase, which allows the dielectric properties of the BZT films to be tuned without changing their chemical composition.
Changes to the network structure of Er–Yb doped phosphate glass induced by femtosecond laser pulses
Authors: Fletcher Luke B. , Witcher Jon J. , Reichman Wilbur B. , Arai Alan , Bovatsek Jim , Krol Denise M.
Published: October 2009

Changes to the glass network structure after modification with tightly focused 1043nm, 400fs laser pulses have been studied in Er–Yb doped phosphate glass using in situ confocal Raman microscopy. For femtosecond laser writing conditions that result in heat accumulation, the 710 and 1209cm−1 Raman peaks, which are due to the (POP)sym and (PO2)sym network vibration modes, respectively, shift to both higher and lower wavenumbers. The differences in refractive index are shown to correlate spatially with the 1209cm−1 Raman signal shifts. Systematic shifts in this Raman peak to higher and lower wavenumbers indicate an overall expansion and/or contraction of the phosphate network that depends on the femtosecond laser writing conditions.
Mechanical stress induced voltage shift in polycrystalline Bi3.25La0.75Ti3O12 thin films
Authors: Wu Xiumei , Zhai Ya , Kan Yi , Lu Xiaomei , Zhu Jinsong
Published: October 2009

Imprint behavior of polycrystalline Bi3.25La0.75Ti3O12 thin films under stress was studied. The voltage shift along the positive voltage axis can be depressed by tensile stress while increased by compressive stress. With the measured voltage increasing, the voltage shift referred above increases and the increase trend gets enhanced under both compressive and tensile stress compared with that at zero stress. The asymmetric distribution of the trapped charged in films, which is caused by the increase of the in-plane polarization component for the domain reorientation induced by stress or for the voltage-assisted domain walls depinning, was considered the contribution to the voltage shift.
Spectral features above LO phonon frequency in resonant Raman scattering spectra of small CdSe nanoparticles
Authors: Dzhagan V. M. , Lokteva I. , Valakh M. Ya. , Raevska O. E. , Kolny-Olesiak J. , Zahn D. R. T.
Published: October 2009

We report unusual spectral features in the resonant Raman scattering spectra of colloidal CdSe nanoparticles as small as 2–3 nm. High-frequency shoulders of the longitudinal optical phonon peak and its overtones were observed and their dependence on the excitation wavelength, temperature, nanoparticle size, and surface passivation with ZnS shell studied. As the probable origin of the uncommon spectral feature the participation of acoustic phonons and manifestation of the density of surface-related vibrational states is discussed.
Formation dynamics of hexadecanethiol self-assembled monolayers on (001) GaAs observed with photoluminescence and Fourier transform infrared spectroscopies
Authors: Kim Chan-Kyu , Marshall Gregory M. , Martin Matthieu , Bisson-Viens Michel , Wasilewski Zbigniew , Dubowski Jan J.
Published: October 2009

The dynamics of hexadecanethiol (HDT) [HS(CH2)15CH3] chemisorption and the formation of a self-assembled monolayer (SAM) on the GaAs(001) surface was studied in situ by monitoring the photoluminescence (PL) intensity over a 20 h period. Comparing the PL time series in HDT solution with that of the bare GaAs surface similarly exposed to the ethanol solvent, we observed a two-phased evolution of the associated PL enhancement. Time-commensurate changes in the absorption frequency and intensity of the C–H stretching mode vibrations were then recorded using Fourier transform infrared spectroscopy, supporting that the PL enhancement corresponds directly with known mechanisms of ordered SAM formation. These results highlight the sensitivity with which in situ PL monitoring can reflect surface processes and underscores its potential for use in sensor applications.
Second-order neutral impulsive stochastic evolution equations with delay
Authors: Ren Yong , Sun Dandan
Published: October 2009

In this paper, we study the second-order neutral stochastic evolution equations with impulsive effect and delay (SNSEEIDs). We establish the existence and uniqueness of mild solutions to SNSEEIDs under non-Lipschitz condition with Lipschitz condition being considered as a special case by the successive approximation. Furthermore, we give the continuous dependence of solutions on the initial data by means of corollary of the Bihari inequality. An application to the stochastic nonlinear wave equation with impulsive effect and delay is given to illustrate the theory.
Wavepacket approach to the cumulative reaction probability within the flux operator formalism
Authors: Garashchuk Sophya , Vazhappilly Tijo
Published: October 2009

Expressions for the singular flux operator eigenfunctions and eigenvalues are given in terms of the Dirac δ-function representable as a localized Gaussian wavepacket. This functional form enables computation of the cumulative reaction probability N(E) from the wavepacket time-correlation functions. The Gaussian based form of the flux eigenfunctions, which is not tied to a finite basis of a quantum-mechanical calculation, is particularly useful for approximate calculation of N(E) with the trajectory based wavepacket propagation techniques. Numerical illustration is given for the Eckart barrier using the conventional quantum-mechanical propagation and the quantum trajectory dynamics with the approximate quantum potential. N(E) converges with respect to the Gaussian width parameter, and the convergence is faster at low energy. The approximate trajectory calculation overestimates tunneling in the low energy regime, but gives a significant improvement over the parabolic estimate of the tunneling probability.
Effects of viscosity ratio and three dimensional positioning on hydrodynamic interactions between two viscous drops in a shear flow at finite inertia
Authors: Singh Rajesh Kumar , Sarkar Kausik
Published: October 2009

Drops driven toward each other by shear at finite inertia follow two distinct types of trajectories. Type I trajectory is similar to the one in Stokes flow where drops slide past each other. However, at finite inertia, drops display a new type II trajectory, where they reverse their paths. Increasing viscosity ratio results in a transition from type II to type I trajectory. The transition is caused by decreased drop deformation and increased alignment with the flow at higher drop viscosity; both decrease the zone of reversed streamlines that accompanies a drop at finite inertia. The transition is delineated in a phase diagram of Reynolds number and viscosity ratio for different capillary numbers. The critical viscosity ratio, where a type II transitions into type I, increases with Reynolds number except at higher capillary numbers, where the critical viscosity ratio shows a slight nonmonotonic variation with Reynolds number. Also, it is nonmonotonic with capillary numbers in that for a fixed Reynolds number, the critical viscosity ratio first increases with increasing capillary number and then decreases. Similar to the Stokes regime, increased viscosity ratio leads to a decreased postcollision cross-stream separation effectively decreasing the shear induced diffusion. Higher viscosity ratio results in an increased separation between drops during encounter, which results in a smaller interaction time. With drops placed initially at different shear planes, drops come under the influence of the reversed flow zone around a single drop that broadens off the central shear plane. Consequently, the trajectory changes from type I to type II as the offset in the vorticity direction increases. The change depends on the initial offset in the shear direction as well. The final displacement in the shear direction varies linearly with the initial offset. The net relative displacement in the shear direction shows a gradual decrease with increasing offset. The net relative displacement in the vorticity direction with increasing offset first increases from a zero value when drops are placed at the same shear plane to a maximum and then decreases. For certain cases, it reaches a negative value.
Sedimentation of a sphere in a fluid channel
Authors: Pitois Olivier , Fritz Christelle , Pasol Laurentiu , Vignes-Adler Michèle
Published: October 2009

We studied both experimentally and numerically the sedimentation velocity of small solid particles through liquid channels merging at the intersection of three soap films. The wall mobility induces a nontrivial behavior for the particle drag coefficient, providing particular transport properties that are not observed for channels with rigid walls. It is shown that for sufficiently small particles, slow and fast motions are observed for the particle along the channel, depending on the particle position within the channel cross section and the sphere/channel size ratio. The velocity corresponding to fast motions can be as high as twice the Stokes velocity in an unbounded fluid. Moreover, the fast motions are not observed anymore when the size ratio exceeds a critical value, which has been found to be approximately equal to 0.5. As another major difference with the solid wall channel, the sphere velocity does not vanish when the size ratio reaches unity. Instead, the smallest value is found to be 14 of the Stokes velocity.
A diffusional bimolecular propensity function
Authors: Gillespie Daniel T.
Published: October 2009

We derive an explicit formula for the propensity function (stochastic reaction rate) of a generic bimolecular chemical reaction in which the reactant molecules move about by diffusion, as solute molecules in a bath of much smaller and more numerous solvent molecules. Our derivation assumes that the solution is macroscopically well stirred and dilute in the solute molecules. It effectively extends the physical rationale for the chemical master equation and the stochastic simulation algorithm from well-stirred dilute gases to well-stirred dilute solutions, with the former becoming a limiting case of the latter. This extension is important for cellular systems, where the solvent molecules are typically water and the solute (reactant) molecules are much larger organic structures, whose relatively low populations often require a discrete-stochastic formalism. In the course of our derivation, we illuminate some limitations on the ability of the classical diffusion equation to accurately describe how a diffusing molecule moves on spatial and temporal scales that are relevant to collision-induced chemical reactions.
Scalable arrays of rf Paul traps in degenerate Si
Authors: Britton J. , Leibfried D. , Beall J. A. , Blakestad R. B. , Wesenberg J. H. , Wineland D. J.
Published: October 2009

We report techniques for the fabrication of multizone linear radio frequency Paul traps that exploit the machinability and electrical conductivity of degenerate silicon. The approach was tested by trapping and laser cooling M24g+ ions in the two following trap geometries: a single-zone two-layer trap and a multizone surface-electrode trap. From the measured ion motional heating rate we determine an electric field spectral density at the ion’s position of approximately 1×10−10 (V/m)2⋅Hz−1 at ωz/2π=1.125 MHz when the ion lies 40 μm above the trap surface. One application of these devices is controlled manipulation of atomic ion qubits, the basis of one form of quantum information processing.
Regular surface grating on doped polymer induced by laser scanning
Authors: Lyutakov Oleksiy , Huttel Ivan , Siegel Jakub , Švorčík Václav
Published: October 2009

Thin polymer film doped with optical chromophore porphyrin are shown to respond to irradiation with laser light (λ=405 nm). By simultaneous scanning with laser beam and continual mechanical movement of the polymer film regular grating pattern is formed on the polymer surface. Parameters of the grating vary in wide range as a function of the movement velocity and the laser intensity. Submicron, periodically structures can be prepared using the proposed technique.
Refractive index dispersion deduced from lasing modes in ZnO microtetrapods
Authors: Ursaki V. V. , Zalamai V. V. , Tiginyanu I. M. , Burlacu A. , Rusu E. V. , Klingshirn C.
Published: October 2009

High optical quality, well end leg faceted ZnO microtetrapods sustaining lasing modes with quality factors of 2500–3000 have been grown by carbothermal chemical vapor deposition. It is shown that lasing is due to longitudinal Fabry–Pérot modes in individual tetrapod legs and the analysis of the wavelength position of these modes is an effective instrument for the investigation of temperature dependence of the refractive index dispersion in the region of exciton resonances. The dispersion of the ZnO refractive index is experimentally determined in the temperature interval from 10 to 300 K and is compared with available literature data.
Addressable photocharging of single quantum dots assisted with atomic force microscopy probe
Authors: Dokukin M. , Olac-Vaw R. , Guz N. , Mitin V. , Sokolov I.
Published: October 2009

Here we report on addressable photocharging of individual cadmium selenide quantum dots (QDs). The charging is a result of synergetic action of light and an atomic force microscope (AFM) probe. The probe squeezes the coating layer of QDs helping the photoelectron to tunnel to either conductive AFM probe or substrate. The charge can be induced on individual QDs by locating the QDs with AFM. The charges are stable in ambient conditions. These results may be of interest for QDs based sensors, memory, and solar cell applications. For instance, this method could provide recording information at a density of 1 Tb/cm2.
High optical quality InAs site-controlled quantum dots grown on soft photocurable nanoimprint lithography patterned GaAs substrates
Authors: Cheng Chien-Chia , Meneou K. , Cheng K. Y.
Published: October 2009

InAs site-controlled quantum dots (SCQDs) have been demonstrated on GaAs substrates patterned by soft photocurable nanoimprint lithography. The substrates are patterned with a dense array of 100 nm nanopores and then InAs is deposited by molecular beam epitaxy to form uniform single QD in each patterned nanopore. Strong room temperature photoluminescence (PL) obtained from uncapped sample with a single SCQD layer reveals a defect-free interface and high quality growth of QDs. A narrower PL linewidth indicates more uniformly distributed SCQDs on the patterned substrate than self-assembled QDs on an unpatterned substrate.
A room temperature 19-channel magnetic field mapping device for cardiac signals
Authors: Bison G. , Castagna N. , Hofer A. , Knowles P. , Schenker J.-L. , Kasprzak M. , Saudan H. , Weis A.
Published: October 2009

We present a multichannel cardiac magnetic field imaging system built in Fribourg from optical double-resonance Cs vapor magnetometers. It consists of 25 individual sensors designed to record magnetic field maps of the beating human heart by simultaneous measurements on a grid of 19 points over the chest. The system is operated as an array of second order gradiometers using sophisticated digitally controlled feedback loops.
Queer-Friendly Neighbourhoods: Interrogating Social Cohesion across Sexual Difference in Two Australian Neighbourhoods
Authors: Gorman-Murray Andrew , Waitt Gordon
Published: October 2009

This paper examines processes of social cohesion across sexual difference in ‘queer-friendly neighbourhoods’—localities that have a heterosexual majority in residential and commercial terms, but where a significant presence of gay and lesbian residents, businesses, and organisations are welcomed. This investigation advances a lineage of work on the development and maintenance of gay and lesbian neighbourhoods, and their role in residents' well-being. The findings also extend understandings of social cohesion, a key theme in neighbourhood and policy research across the West. The context of this study is Australia, where recent projects on social cohesion have focused on public order, economic benefits, and race tensions. However, given that gay men and lesbians are present in Australian social and political debates, sexuality should be integrated into studies about neighbourhood cohesion. To analyse processes of cohesion between heterosexual and same-sex-attracted people, we draw on data from case studies of two queer-friendly neighbourhoods in Australia—the inner-city suburb of Newtown, NSW, and the regional town of Daylesford, Victoria. We discuss the findings in three analytical categories to highlight common processes and characteristics of queer-friendly neighbourhoods: diversity and difference; symbolic landscapes; combating homophobia.
Measuring Inequality in Rural England: The Effects of Changing Spatial Resolution
Authors: Huby Meg , Cinderby Steve , White Piran , de Bruin Annemarieke
Published: October 2009

The sustainability of rural development depends on the distribution of the social and environmental resources needed to maintain and improve the vitality of rural areas. Here we examine the complexity of measuring patterns of distribution using examples of socioeconomic data on rural poverty and affluence as well as data on environmental quality and species richness. We demonstrate how changes in the base spatial units used for analysis have different effects on different measures of inequality. The effects of such changes in spatial resolution also depend on the underlying processes that generate the data. The results of our investigations into the effects of scale on the assessment of inequality suggest that, where data come from both the social and natural science sources, the most appropriate level for analysis is that of the finest common resolution. This may result in redundancy of effort for some types of data but any such disadvantage is offset by the benefits of identifying inequalities that are masked at coarser resolutions.
Excess, Catastrophe, and Climate Change
Authors: Yusoff Kathryn
Published: October 2009

This paper seeks to give expression to notions of excess within economies of climate change. The paper begins by addressing the dominance of scientific modelling in the scientific and political constructions of climate change manifested through general circulation models and scientific visualisation. Considering this ‘digital earth’, the paper further investigates how the unit-based accumulation of earth data has actively secured the production of political responses that have both emulated and reinstated a model of accounting (such as the Stern Review and carbon trading). Considering the rendering of digital earth as a specific assemblage of globalisation produced through digitalisation, I argue that the digital realm is productive of its own forms of excess (expressed in aesthetics and globalism). I suggest how this excessive globality reveals its own fragmentation through negative presentation. Drawing from Georges Bataille's notion of expenditure and Maurice Blanchot's writing of the disaster I seek to describe a terrain of knowledge and loss that breaks with this aforementioned circuit of accounting, and instead considers another kind of relation (Bataille's concept of expenditure) to account for the wasting of the world. The paper concludes with a Bataillean ‘sketch’ to consider how this excess may be recuperated as an emergent ethic within the disaster yet to come.
Visual Reaction Time and Size Constancy
Authors: Sperandio Irene , Savazzi Silvia , Gregory Richard L , Marzi Carlo A
Published: October 2009

We carried out six experiments to find out whether simple manual reaction time (RT) to flux-equated visual stimuli of different size is modulated by size constancy or by the retinal angle subtended by the stimuli. We found that RT decreased with the increase in perceived stimulus size rather than retinal angle and that this relationship depended on the use of familiar 3-D-like stimuli and on the availability of other size-constancy cues. Thus, a stereotyped speeded motor response, such as that employed in a simple RT paradigm, is modulated by size constancy, as is the case with perceptual judgments. The present results provide original evidence on the relationship between simple RT and perception.
Detection of clusters using space - time scan statistics
Authors: Tonini Marj , Tuia Devis , Ratle Frédéric
Published: October 2009

This paper aims at detecting spatio-temporal clustering in fire sequences using space–time scan statistics, a powerful statistical framework for the analysis of point processes. The methodology is applied to active fire detection in the state of Florida (US) identified by MODIS (Moderate Resolution Imaging Spectroradiometer) during the period 2003–06. Results of the present study show that statistically significant clusters can be detected and localized in specific areas and periods of the year. Three out of the five most likely clusters detected for the entire frame period are localized in the north of the state, and they cover forest areas; the other two clusters cover a large zone in the south, corresponding to agricultural land and the prairies in the Everglades. In order to analyze if the wildfires recur each year during the same period, the analyses have been performed separately for the 4 years: it emerges that clusters of forest fires are more frequent in hot seasons (spring and summer), while in the southern areas, they are widely present during the whole year. The recognition of overdensities of events and the ability to locate them in space and in time can help in supporting fire management and focussing on prevention measures.
Climate, lightning ignitions, and fire severity in Yosemite National Park, California, USA
Authors: Lutz James A. , van Wagtendonk Jan W. , Thode Andrea E. , Miller Jay D. , Franklin Jerry F.
Published: October 2009

Continental-scale studies of western North America have attributed recent increases in annual area burned and fire size to a warming climate, but these studies have focussed on large fires and have left the issues of fire severity and ignition frequency unaddressed. Lightning ignitions, any of which could burn a large area given appropriate conditions for fire spread, could be the first indication of more frequent fire. We examined the relationship between snowpack and the ignition and size of fires that occurred in Yosemite National Park, California (area 3027 km2), between 1984 and 2005. During this period, 1870 fires burned 77 718 ha. Decreased spring snowpack exponentially increased the number of lightning-ignited fires. Snowpack mediated lightning-ignited fires by decreasing the proportion of lightning strikes that caused lightning-ignited fires and through fewer lightning strikes in years with deep snowpack. We also quantified fire severity for the 103 fires >40 ha with satellite fire-severity indices using 23 years of Landsat Thematic Mapper data. The proportion of the landscape that burned at higher severities and the complexity of higher-severity burn patches increased with the log10 of annual area burned. Using one snowpack forecast, we project that the number of lightning-ignited fires will increase 19.1% by 2020 to 2049 and the annual area burned at high severity will increase 21.9%. Climate-induced decreases in snowpack and the concomitant increase in fire severity suggest that existing assumptions may be understated – fires may become more frequent and more severe.