bluuebunny/crossref_metadata_2025 huggingface dataset:
a study of mathematical modelling of the competitions of flow in the cavopulmonary anastomosis with persistent forward flow
Authors: migliavacca francesco , pennati giancarlo , dubini gabriele , de leval marc r.
Published: September 2005

among the operations which lead to a partial rerouting of the systemic venous return into the pulmonary arteries, the bidirectional cavopulmonary anastomosis is frequently utilised in the staged surgical management of patients with functionally univentricular hearts. whereas some surgeons insist on closing any other source of pulmonary blood flow while performing a bidirectional cavopulmonary anastomosis, others maintain patency of either a stenosed native pulmonary outflow tract, or of a systemic-to-pulmonary arterial shunt. it remains controversial as to whether an additional source of pulmonary arterial blood flow can safely and usefully be left at the time of the bidirectional cavopulmonary anastomosis to increase systemic saturation, or whether it should be eliminated to reduce the volume load on the ventricle.
the clinical impact of antegrade pulmonary blood flow on the bidirectional cavopulmonary shunt in infants
Authors: migliazza lucia , seddio francesco , annecchino francesco paolo , crupi giancarlo
Published: September 2005

the bidirectional cavopulmonary anastomosis is commonly used in the palliation of patients with a functionally univentricular physiology. the management of alternative sources of flow of blood to the lungs, as well as the magnitude of acceptable accessory blood flow at the time of surgery, nonetheless, remains controversial. these issues are particularly significant when a cavopulmonary anastomosis is performed in infants who may become candidates for a fontan procedure. indeed, a long-standing volume overload, which is invariably associated with the maintenance of accessory sources of pulmonary blood flow, may result in systemic ventricular dysfunction. these observations prompted us to review the influence of antegrade pulmonary blood flow in the management of infants undergoing a cavopulmonary anastomosis.
ten years of modelling to achieve haemodynamic optimisation of the total cavopulmonary connection
Authors: dubini gabriele , migliavacca francesco , pennati giancarlo , de leval marc r. , bove edward l.
Published: September 2005

the techniques of computational fluid dynamics are among the most powerful tools available to engineers dealing with the motion of fluids and the exchange of mass, momentum, and energy. they have recently been shown to have an increasing number of applications to the human cardiovascular system, including the fluid dynamics of surgical reconstruction of congenitally malformed parts of the cardiovascular system. in vitro models are the alternative laboratory tools with which to study fluid dynamics. the advantages of computational fluid dynamics over the in vitro models are the easy quantification of haemodynamic variables, such as rates of flow, pressure, and distribution of shear stress, and changes in geometric and fluid dynamics parameters. furthermore, using computational fluid dynamics allows the development of three-dimensional models to reproduce both the complex anatomy of the investigated region and the details of the surgical reconstruction, especially with the recent developments in magnetic resonance imaging. on the basis of the results, it is possible quantitatively to evaluate the surgical correction. this technology, which benefits greatly from the continuous improvement in hardware and software, enables cardiovascular experts and bioengineers to look at the fluid dynamics of various cardiovascular regions with increasing sophistication.
should we attempt functionally univentricular or partial biventricular repair for patients with complex congenital cardiac anomalies and hypoplasia of the subpulmonary ventricle?
Authors: vida vladimiro l. , rubino maurizio , bottio tomaso , milanesi ornella , pittarello giorgio , stellin giovanni
Published: September 2005

hypoplasia, with or without dysplasia, of the subpulmonary ventricle is found in association with a wide spectrum of complex congenital cardiac anomalies. in these cardiac defects, the systemic ventricle is usually normal, while the subpulmonary one, usually of right morphology, is incapable of supporting the entire flow of blood to the lungs. there is now an alternative to the more classical functionally univentricular type of repair, which can be achieved by means of the total cavopulmonary connection, namely the partial biventricular, or the so called “one and a half ventricle” repair. in selected cases, by reducing the preload on the subpulmonary ventricle by construction of a bi-directional cavo-pulmonary shunt, it is possible to achieve complete separation of the pulmonary and systemic circulations, whilst still maintaining pulsatile flow of blood to the lungs. in this review, we describe our experience with the “one-and-a-half ” ventricular option, analysing the role of preoperative evaluation of the subpulmonary ventricle, and describing our results over the short and intermediate term.
global mathematical modelling of the norwood circulation: a multiscale approach for the study of the pulmonary and coronary arterial perfusions
Authors: migliavacca francesco , laganà katia , pennati giancarlo , de leval marc r. , bove edward l. , dubini gabriele
Published: September 2005

the norwood procedure involves three separate stages of operative corrections. the first stage involves re-fashioning the pulmonary trunk into a neo-aorta so that it is possible to establish an unrestricted systemic circulation. an interpositional, or systemic-to-pulmonary arterial, shunt is then created between the neo-aorta and the pulmonary arteries to allow pulmonary perfusion and gas exchange. two of the available options for the systemic-to-pulmonary shunt are the central shunt and the right modified blalock-taussig shunt. in the setting of a central shunt, pulmonary perfusion is derived from a conduit placed between the pulmonary arterial bed and the neo-aorta whereas, in the modified blalock-taussig shunt, the conduit is interposed between one of the pulmonary arteries and the brachiocephalic artery. in subsequent stages, pulmonary perfusion is provided directly by deoxygenated blood. this is achieved by connecting, first, the superior caval vein, and then the inferior caval vein, to the pulmonary arteries. it is usually during the second stage that the systemic-to-pulmonary shunt is removed.
hypoplasia of the left ventricle and the physiology of the norwood circulation
Authors: sidi daniel
Published: September 2005

in this review, i will first consider the general physiology induced by hypoplasià of the left ventricle, examining in particular its practical consequences in the fetus and the neonate. i will then explore the particularity of the physiology after the first stage of the norwood sequence of operations, comparing the two approaches of an aorta-pulmonary shunt versus a conduit placed from the right ventricle to the pulmonary arteries.
results of the norwood operation for hypoplastic left heart syndrome
Authors: bove edward l.
Published: September 2005

efforts to treat babies with hypoplastic left heart syndrome began over 30 years ago, when surgeons first reported limited success with palliative surgery. cayler et al. performed an anastomosis between the ascending aorta and the right pulmonary artery, bilateral banding of the pulmonary arteries, and an atrial septectomy. their follow-up extended for only 7 months, but the authors predicted that the rapid advances being made in cardiac surgery at the time heralded a new era where hypoplastic left heart syndrome would be cured. unfortunately, that prediction remains far from true today, although dramatic advances have been made in the therapy of this otherwise lethal condition.
experience over five years using a shunt placed between the right ventricle and the pulmonary arteries during initial reconstruction of hypoplasia of the left heart
Authors: sano shunji , ishino kozo , kawada masaaki , yoshizumi ko , takeuchi mamoru , ohtsuki shin-ichi
Published: September 2005

the hypoplastic left heart syndrome includes a spectrum of underdevelopment of the left-sided cardiac structures, characterized by aortic valvar atresia or severe stenosis with a small ascending aorta and hypoplasia of the left ventricle. without surgical treatment, practically all infants with this complex cardiac anomaly die within the first month of life. since norwood et al. reported successful surgical palliation in 1981, multi-staged reconstructive surgery, involving the norwood procedure as the first stage, followed by a bi-directional glenn anastomosis and subsequent completion of the fontan circulation, has become the established surgical treatment.
closing remarks
Authors: giusti sandra
Published: September 2005

in the 17th century, william harvey discovered the circulation of the blood, describing at this time the pumping function of the heart and the “in series” disposition of the pulmonary and systemic circulations. these concepts provided the foundation for the development of modern cardiac physiology. during the three centuries that followed the discovery of circulation, many scientists studied and expanded our knowledge of cardiac and pulmonary function. with the description of complex congenital cardiac diseases, in particular functionally univentricular hearts, and with the development of their palliative surgical treatment, we have uncovered another type of cardiac physiology. in these cases, the circulation of the blood is characterized by an “in parallel” disposition of the pulmonary and systemic circulations, with direct venous–arterial connections in the absence of one pumping ventricle.
Global modeling of aerosol dynamics: Model description, evaluation, and interactions between sulfate and nonsulfate aerosols
Authors: Liu Xiaohong , Penner Joyce E. , Herzog Michael
Published: September 2005

The IMPACT global chemistry and transport model has been updated to include an aerosol dynamics module. Here it is used to simulate the dynamics of sulfate aerosol and its interaction with nonsulfate aerosol components: carbonaceous aerosol (organic matter (OM) and black carbon (BC)), dust, and sea salt. The sulfate aerosol dynamics is based on the method of modes and moments. In the current implementation, two modes are used for sulfate aerosol (nuclei and accumulation mode), and two moments are predicted within each mode (sulfate aerosol number and mass concentration). The aging of carbonaceous aerosol and dust particles from hydrophobic to hydrophilic depends on the surface coating of sulfate which occurs as a result of the condensation of sulfuric acid gas H2SO4 (g) on their surface, and coagulation with pure sulfate aerosol. The model predicts high sulfate aerosol number concentrations in the nuclei mode (over 104 cm−3) in the tropical upper troposphere, while accumulation mode sulfate number concentrations are generally within 50–500 cm−3 in most parts of the free troposphere. The model predicted mass concentrations of sulfate, OM, BC, dust, and sea salt, H2SO4 (g) concentration, aerosol number, and size distributions are compared with measurement data. Our model predicts ∼80% of global sulfate existing as a pure sulfate aerosol (9.7% in nuclei and 69.8% in accumulation mode), with 14.3% on carbonaceous aerosol, 3.3% on dust, and 2.7% on sea salt. In the boundary layer, over 40% of sulfate is associated with nonsulfate aerosols in many regions of the world whereas less than 10% of sulfate is associated with nonsulfate aerosols in the upper troposphere. The model predicted mass fraction of sulfate in the sulfate‐carbonaceous aerosol mixture suggests that carbonaceous aerosol in most of the troposphere is internally mixed with sulfate and thus generally hygroscopic except near the source regions where the mass fraction is less than 5%. On the global mean, 54% and 93% of carbonaceous aerosol are coated with sulfate in the boundary layer and in the upper troposphere, respectively. Our result suggests that carbonaceous aerosols have a shorter lifetime (3∼4 days) than predicted (4∼8 days) using models that treat these aerosols as partly hydrophobic with an arbitrary e‐folding time from hydrophobic to hydrophilic.
Impacts of integrated crop‐livestock systems on nitrogen dynamics and soil erosion in western Iowa watersheds
Authors: Burkart M. , James D. , Liebman M. , Herndl C.
Published: September 2005

Agricultural land uses impact leachable nitrogen (N) and erosion, indicators of the potential for nitrate and sediment contamination of water resources. This paper evaluates the potential impact of alternative land uses on leachable N, soil organic nitrogen (SON) and erosion in western Iowa watersheds using a combination of widely available models and georeferenced data. The alternative land uses increase land area under perennial cover, integrate livestock with cropping systems, and reduce inorganic fertilizer use. We used the Water Erosion Prediction Program (WEPP) to estimate erosion and a N‐budget model to estimate leachable N and changes in SON. The N model described here is widely applicable because it utilizes commonly available georeferenced data on soils, crops, and livestock. Maximum annual erosion rates were estimated to be 22 Mg ha−1 under current conditions, double the regional maximum at which soil is maintained as a medium for plant growth (T). Under alternative land uses, erosion was between 1.1 Mg ha−1 and 5.5 Mg ha−1, well below T. Annual leachable N was as much as 43 kg ha−1 for current conditions, but consistently less than15 kg ha−1 under alternative land uses. Maximum SON losses were 23 kg N ha−1 under current conditions while SON increased by as much as 18 kg N ha−1 under alternative land uses. These results indicate that erosion may be minimized, leachable N could be decreased and SON may be increased by better accounting of N inputs and altering the distribution and species composition of crop and pasture systems.
Variability of the altitude of the Martian sheath
Authors: Brain D. A. , Halekas J. S. , Lillis R. , Mitchell D. L. , Lin R. P. , Crider D. H.
Published: September 2005

Using electron energy spectra, we identify time periods when the Mars Global Surveyor (MGS) spacecraft is in or above the Martian magnetic pileup boundary (MPB). We use more than five years of data to develop a statistical picture of the location of the MPB relative to the MGS mapping altitude near 400 km. We show for the first time that the MPB location is sensitive to interplanetary magnetic field (IMF) orientation and to Martian season, and confirm a dependence upon solar wind pressure. We confirm that crustal magnetic sources raise the altitude of the MPB, and demonstrate that sheath electrons populate magnetic cusp regions in the southern hemisphere. During southern summer strong crustal fields near the subsolar point raise the altitude of the MPB over the entire dayside, implying that Martian crustal fields modify the solar wind interaction globally.
Tilt recorded by a portable broadband seismograph: The 2003 eruption of Anatahan Volcano, Mariana Islands
Authors: Wiens Douglas A. , Pozgay Sara H. , Shore Patrick J. , Sauter Allan W. , White Randall A.
Published: September 2005

The horizontal components of broadband seismographs are highly sensitive to tilt, suggesting that commonly deployed portable broadband seismic sensors may record important tilt information associated with volcanic eruptions. We report on a tilt episode that coincides with the first historical eruption of Anatahan volcano on May 10, 2003. The tilt was recorded by a Strekheisen STS‐2 seismograph deployed in an underground insulated chamber 7 km west of the active vent. An ultra‐long period signal with a dominant period of several hours was recorded on the E‐W component beginning at 06:20 GMT on May 10, which coincides with the onset of continuous volcano‐tectonic (VT) seismicity and is one hour prior to the eruption time estimated by the Volcanic Ash Advisory Center. The signal is much smaller on the N‐S component and absent on the vertical component, suggesting it results from tilt that is approximately radial with respect to the active vent. An estimate of tilt as a function of time is recovered by deconvolving the record to acceleration and dividing by the acceleration of gravity. The record indicates an initial episode of tilt downward away from the volcanic center from 06:20–09:30 GMT, which we interpret as inflation of the shallow volcanic source. The tilt reverses, recording deflation, from 09:30 until 17:50, after which the tilt signal becomes insignificant. The inflation corresponds to a period of numerous VT events, whereas fewer events were recorded during the deflation episode, and the VT events subsequently resumed after the end of the deflationary tilt. The maximum tilt of 2 microradians can be used to estimate the volume of the source inflation (∼2 million m3), assuming a simple Mogi source model. These calculations are consistent with other estimates of source volume if reasonable source depths are assumed. Examination of broadband records of other eruptions may disclose further previously unrecognized tilt signals.
Thermoremanent magnetization of multidomain hematite
Authors: Özdemir Özden , Dunlop David J.
Published: September 2005

We have studied thermoremanent magnetization (TRM) produced by fields of 10–140 μT in the (0001) basal plane of a 10 × 6 × 2 mm natural single crystal of hematite, both before and after zero‐field cycling through the Morin transition at TM = 260 K. Stepwise thermal demagnetization of TRM indicated high‐unblocking temperatures between 680°C and the Curie‐Néel temperature TN = 690°C. In contrast, TRM was easily demagnetized by alternating fields, TRM intensity decreasing exponentially with increasing field in typical multidomain fashion. The observed 100‐μT MTRM is 1.1 kA/m. This strong TRM, almost equal to the saturation remanence, results from hematite's weak internal demagnetizing field. Domain walls move almost unhindered to their limiting positions, and TRM intensity approaches saturation. On cooling through TM, spins rotate to the antiferromagnetic c axis, and hematite's weak ferromagnetism is largely lost. However, on reheating in zero field through TM, as the spins rotate back into the basal plane, a “memory” remanence is regenerated in the original TRM direction. This TRM memory was about 25% of MTRM for our crystal and was even more resistant to thermal demagnetization than the original TRM. The 25% memory of TRM is similar to that of 0.12‐ to 0.42‐μm single‐domain hematites. High‐unblocking‐temperature TRM and TRM memory must be due to magnetoelastic pinning of spins in the basal plane by lattice defects, because both TRM and memory decrease with high‐temperature treatment, which anneals out defects. The memory phenomenon seems to be in essence an amplification of residual magnetism that survives below the Morin transition. Remanence produced in a demagnetized sample below TM and room temperature remanence that has been cooled through TM increase in identical ways on warming through the transition. We propose that small regions of canted spins, pinned by crystal defects, remain below TM when the bulk of spins have aligned with the antiferromagnetic c axis. These nuclei serve to regenerate room temperature domain structure and remanence in warming through TM.
Ozarks Isoprene Experiment (OZIE): Measurements and modeling of the “isoprene volcano”
Authors: Wiedinmyer Christine , Greenberg Jim , Guenther Alex , Hopkins Brian , Baker Kirk , Geron Chris , Palmer Paul I. , Long Bryan P. , Turner Jay R. , Pétron Gabrielle , Harley Peter , Pierce Thomas E. , Lamb Brian , Westberg Hal , Baugh William , Koerber Mike , Janssen Mark
Published: September 2005

The Ozarks Isoprene Experiment (OZIE) was conducted in July 1998 in Missouri, Illinois, Indiana, and Oklahoma. OZIE was designed to investigate the presumed strong isoprene emission rates from the Missouri Ozarks, where there is a high density of oak trees that are efficient isoprene emitters. Ground, balloon, and aircraft measurements were taken over a three‐week study period; 0‐D and 3‐D chemical models were subsequently used to better understand the observed isoprene emissions from the Ozarks and to investigate their potential regional‐scale impacts. Leaf‐level measurements for two oak tree species yielded normalized average isoprene emission capacities of 66 mgC g−1 h−1, in good agreement with values used in current biogenic emissions models. However, the emission capacities exhibited a temperature dependence that is not captured by commonly used biogenic emission models. Isoprene mixing ratios measured aloft from tethered balloon systems were used to estimate isoprene fluxes. These measurement‐derived fluxes agreed with BEIS3 estimates within the relatively large uncertainties in the estimates. Ground‐level isoprene mixing ratios exhibited substantial spatial heterogeneity, ranging from <1 to 35 ppbv. The agreement between measured isoprene mixing ratios and regional‐scale chemical transport model estimates was improved upon averaging the ground‐level isoprene data observed at several sites within a representative area. Ground‐level formaldehyde (HCHO) mixing ratios were very high (up to 20 ppbv) and were consistently higher than mixing ratios predicted by a regional chemical transport model. The spatial distribution and magnitude of the elevated HCHO concentrations showed good agreement with GOME satellite column observations of HCHO.
Martian megaflood‐triggered chaos formation, revealing groundwater depth, cryosphere thickness, and crustal heat flux
Authors: Coleman Neil M.
Published: September 2005

Ravi Vallis is an outflow channel complex that emerged from Aromatum Chaos, a region of collapsed ground in Xanthe Terra, Mars. I propose that the megaflood that carved Ravi Vallis incised the crust more than 700 m, penetrated the cryosphere, and triggered the release of groundwater and genesis of secondary chaos zones in the deepest parts of the channel system. Discharge rates of 4 × 106 to 5 × 107 m3 s−1 are estimated for early overland flooding. Assuming bank‐full flow would yield unrealistic discharge rates of >3 × 108 m3 s−1. Waning stage flooding in an inner channel had a discharge rate on the order of ≲1 × 106 m3 s−1. The cryosphere thickness and groundwater depth are estimated as the sum of the channel incision depth and the thickness of residual cryosphere beneath the channel floor that could be disrupted by high artesian pressure. The surface elevation (−1231 m) of a transient water body in Aromatum Chaos would have controlled the maximum potentiometric heads in confined aquifers to the east. Where Iamuna Chaos was spawned, the floor of Ravi Vallis would have experienced upward hydraulic pressures of ≤2.4 MPa, enough to rupture a basaltic rock layer ≤255 m thick. At the time of the flood the cryosphere thickness and groundwater depth would have been 700 to 1000 m at this location on the equator, indicating a relatively cold, long‐term climate trend similar to that of present‐day Mars. The crustal heat flux likely exceeded 50 mW m−2 at Iamuna Chaos. If deep lakes existed at that time in the ancestral Valles Marineris, their ice covers are estimated to have been less than 3 km thick. The fluvial incision and groundwater breakout model described here can fully account for the inception of Iamuna Chaos, Oxia Chaos, and a smaller unnamed chaos. Therefore a locally enhanced crustal heat flux was not required to initiate the formation of these chaotes.
On the Psychometric Principles of Affect
Authors: Carroll James M. , Yik Michelle S. M. , Russell James A. , Barrett Lisa Feldman
Published: September 2005

D. Watson and L. A. Clark (1997) announced “two fundamental psychometric principles” (p. 282) of affect: The positive correlation between affects with the same valence tends to be substantial, whereas the negative correlation between affects with opposite valence tends to be weak. These allegedly robust empirical generalizations underlie various conceptual models of affect (such as those that posit an independence between positive and negative affect) and various scales of affect. The authors offer an alternative analysis: The correlation between two affects is a function of the angle between them within a circular ordering. Two data sets were reanalyzed and showed predicted exceptions to Watson and Clark's principles: same-valenced pairs with weak correlations and oppositely valenced pairs with substantial correlations.
Self-Threat Magnifies the Self-Serving Bias: A Meta-Analytic Integration
Authors: Campbell W. Keith , Sedikides Constantine
Published: September 2005

Experiments testing the self-serving bias (SSB; taking credit for personal success but blaming external factors for personal failure) have used a multitude of moderators (i.e., role, task importance, outcome expectancies, self-esteem, achievement motivation, self-focused attention, task choice, perceived task difficulty, interpersonal orientation, status, affect, locus of control, gender, and task type). The present meta-analytic review established the viability and pervasiveness of the SSB and, more important, organized the 14 moderators just listed under the common theoretical umbrella of self-threat. According to the self-threat model, the high self-threat level of each moderator is associated with a larger display of the SSB than the low self-threat level. The model was supported: Self-threat magnifies the SSB.
Unifying Psychology Requires New Infrastructure, Theory, Method, and a Research Agenda
Authors: Staats Arthur W.
Published: September 2005

Conduct of a long-term research program with a focus on constructing an overarching, unified theory of psychology revealed characteristics of psychology as a science that (a) encourage disunity of its endeavors and (b) impede attaining the unification and consequent power attained by older natural sciences. Considered a “would-be science” because of its disunity, psychology lacks knowledge of theory, theory methodology, and theory needs with respect to changing from a disunified to unified science, as well as the infrastructure needed for this fundamentally important change. These are critical and general deficits. This analysis outlines key developments necessary for psychology to begin its advancement to the powerful unification characteristics of advanced science.
Mood Induction in Children: Methodological Issues and Clinical Implications
Authors: Brenner Eliot
Published: September 2005

The author reviews 7 different types of mood induction procedures for use with children and discusses these procedures in light of a number of critical methodological issues. The issues considered are administration, participant characteristics, measurement, mood quality, and demand characteristics. The author proposes a broad framework for the future investigation of mood induction procedures for children that includes comparative outcome studies, parametric studies, and more comprehensive mood measurement. Several issues are outlined that investigators might consider when designing experiments to test the generality of negative mood induction studies to clinical depression, including specificity or comorbidity, intensity or severity, age, and sex.
On the Impact of Mood on Behavior: An Integrative Theory and a Review
Authors: Gendolla Guido H. E.
Published: September 2005

Empirical evidence for effects of moods (both naturally occurring and experimentally manipulated) on behavior is reviewed in terms of an integrative theory: the mood–behavior model (MBM). It is posited that moods can influence behavior via 2 processes: (a) by informational effects on behavior-related judgments and appraisals, which in turn will result in behavioral adjustments (i.e., the informational mood impact on behavior), and (b) by influencing behavioral preferences and interests in compliance with a hedonic motive (i.e., the directive mood impact on behavior). The strength of the informational mood impact depends on moods' effective informational weight for behavior-related judgments and on mood-primed associations. The strength of the directive mood impact is predicted to be jointly determined by 2 variables: the strength of a hedonic motive and the instrumentality of possible acts for affect regulation.
Reversion of lethality and growth defects in Fatiga oxygen‐sensor mutant flies by loss of Hypoxia‐Inducible Factor‐α/Sima
Authors: Centanin Lázaro , Ratcliffe Peter J , Wappner Pablo
Published: September 2005

Hypoxia‐Inducible Factor (HIF) prolyl hydroxylase domains (PHDs) have been proposed to act as sensors that have an important role in oxygen homeostasis. In the presence of oxygen, they hydroxylate two specific prolyl residues in HIF‐α polypeptides, thereby promoting their proteasomal degradation. So far, however, the developmental consequences of the inactivation of PHDs in higher metazoans have not been reported. Here, we describe novel loss‐of‐function mutants of fatiga, the gene encoding the Drosophila PHD oxygen sensor, which manifest growth defects and lethality. We also report a null mutation in dHIF‐α/sima, which is unable to adapt to hypoxia but is fully viable in normoxic conditions. Strikingly, loss‐of‐function mutations of sima rescued the developmental defects observed in fatiga mutants and enabled survival to adulthood. These results indicate that the main functions of Fatiga in development, including control of cell size, involve the regulation of dHIF/Sima.
The RING‐finger scaffold protein Plenty of SH3s targets TAK1 to control immunity signalling in Drosophila
Authors: Tsuda Manabu , Langmann Caillin , Harden Nicholas , Aigaki Toshiro
Published: September 2005

Imd‐mediated innate immunity is activated in response to infection by Gram‐negative bacteria and leads to the activation of Jun amino‐terminal kinase (JNK) and Relish, a nuclear factor‐κB transcription factor responsible for the expression of antimicrobial peptides. Plenty of SH3s (POSH) has been shown to function as a scaffold protein for JNK activation, leading to apoptosis in mammals. Here, we report that POSH controls Imd‐mediated immunity signalling in Drosophila. In POSH‐deficient flies, JNK activation and Relish induction were delayed and sustained, which indicated that POSH is required for properly timed activation and termination of the cascade. The RING finger of POSH, possessing ubiquitin‐ligase activity, was essential for termination of JNK activation. We show that POSH binds to and degrades TAK1, a crucial activator of both the JNK and the Relish signalling pathways. These results establish a novel role for POSH in the Drosophila immune system.
Electronic relaxation of paramagnetic metal ions and NMR relaxivity in solution: Critical analysis of various approaches and application to a Gd(III)-based contrast agent
Authors: Fries Pascal H. , Belorizky Elie
Published: September 2005

The time correlation functions (TCFs) Gαα(t)≡⟨Sα(t)Sα(0)⟩ (α=x,y,z) of the electronic spin components of a complexed paramagnetic metal ion give information about the time fluctuations of its zero-field splitting (ZFS) Hamiltonian due to the random dynamics of the coordination polyhedron. These TCFs reflect the electronic spin relaxation which plays an essential role in the inner- and outer-sphere paramagnetic relaxation enhancements of the various nuclear spins in solution. When a static ZFS Hamiltonian is allowed by symmetry, its modulation by the random rotational motion of the complex has a great influence on the TCFs. We discuss several attempts to describe this mechanism and show that subtle mathematical pitfalls should be avoided in order to obtain a theoretical framework, within which reliable adjustable parameters can be fitted through the interpretation of nuclear-magnetic relaxation dispersion experimental results. We underline the advantage of the numerical simulation of the TCFs, which avoids the above difficulties and allows one to include the effect of the transient ZFS for all the relative magnitudes of the various terms in the electron-spin Hamiltonian and arbitrary correlation times. This method is applied for various values of the magnetic field taken to be along the z direction. At low field, contrary to previous theoretical expectations, if the transient ZFS has negligible influence, the longitudinal TCF G‖(t)≡Gzz(t) has a monoexponential decay with an electronic relaxation time T1e different from 1∕(2Dr), Dr being the rotational diffusion coefficient of the complex. At intermediate and high field, the simulation results show that G‖(t) still has a monoexponential decay with a characteristic time T1e, which is surprisingly well approximated by a simple analytical expression derived from the Redfield perturbation approximation of the time-independent Zeeman Hamiltonian, even in the case of a strong ZFS where this approximation is expected to fail. These results are illustrated for spins S=1, 3∕2, and 5∕2 in axial and rhombic symmetries. Finally, the simulation method is applied to the reinterpretation of the water-proton relaxivity profile due to P760–Gd(III), an efficient blood pool contrast agent for magnetic-resonance imaging.
Influence of vibrational energy flow on isomerization of flexible molecules: Incorporating non-Rice-Ramsperger-Kassel-Marcus kinetics in the simulation of dipeptide isomerization
Authors: Agbo Johnson K. , Leitner David M. , Evans David A. , Wales David J.
Published: September 2005

The conformational isomerization of a dipeptide, N-acetyl-tryptophan methyl amide (NATMA), is studied computationally by including important dynamical corrections to Rice-Ramsperger-Kassel-Marcus (RRKM) theory for the transition rate between pairs of isomers. The dynamical corrections arise from incomplete or sluggish vibrational energy flow in the dipeptide, a property suggested by the mode-selective chemistry that has been observed by Dian et al. [J. Chem. Phys. 120, 133 (2004)]. We compute the extent and rate of vibrational energy flow in NATMA quantum mechanically using local random matrix theory, which we then use to correct the RRKM theory rates. The latter rates are then introduced into a master equation to study the population dynamics of the dipeptide. Incomplete or slow vibrational energy flow is found to enhance the conformational selectivity of NATMA over RRKM estimates.
DFT-based chemical reactivity indices in the Hartree-Fock method. II. Fukui function, chemical potential, and hardness
Authors: Balawender Robert , Geerlings Paul
Published: September 2005

A derivation of the density-functional-theory- (DFT) based reactivity indices in the ensemble unrestricted Hartree-Fock (eUHF) method is presented. The comparison between the properties of the reactivity indices evaluated in one and two sets of spin-orbital approach of the eUHF and hyper-unrestricted Hartree-Fock (UHF) methods are shown. All approaches give similar Fukui function irrespective of methodology used, but significantly differ for the global indices, containing important chemical information, and so their interpretation in terms of DFT- based indices can be questionable. The calculation scheme for the indices using the first- and second-order coupled perturbed eHF equations is proposed. A method for the identification of the spinorbitals involved in the change of the total number of electrons is included. The illustrative examples (water and hydrogen cyanide) show that the ground-state (GS) properties of the (Z±1)-electron systems can be predicted from the GS properties of the Z-electron systems with an accuracy comparable with the UHF calculations. The relaxation effect, important for the HCN system in which a change in the symmetry of the highest-occupied spin-orbital occurs, is effectively predicted.
Dynamics of liquid benzene: A cage analysis
Authors: Magro Andrea , Frezzato Diego , Polimeno Antonino , Moro Giorgio J. , Chelli Riccardo , Righini Roberto
Published: September 2005

Dynamics of single molecules in liquids, inspected in the picosecond time scale by means of spectroscopic measurements or molecular-dynamics (MD) simulations, reveals a complex behavior which can be addressed as due to local confinement (cage). This work is devoted to the analysis of cage structures in liquid benzene, obtained from MD simulations. According to a paradigm proposed for previous analysis of atomic and molecular liquids [see, for example, A. Polimeno, G. J. Moro, and J. H. Freed, J. Chem. Phys. 102, 8094 (1995)], the istantaneous cage structure is specified by the frame of axes which identifies the molecular configuration at the closest minimum on the potential-energy landscape. In addition, the modeling of the interaction potential between probe molecule and molecular environment, based on symmetry considerations, and its parametrization from the MD trajectories, allows the estimation of the structural parameters which quantify the strength of molecular confinement. Roto-translational dynamics of probe and related cage with respect to a laboratory frame, dynamics of the probe within the cage (vibrations, librations, re-orientational motions), and the restructuring processes of the cage itself are analyzed in terms of selected time self-correlation functions. A time-scale separation between the processes is established. Moreover, by exploiting the evidence of fast vibrational motions of the probe with respect to the cage center, an orientational effective potential is derived to describe the caging in the time scale longer than ∼0.2ps.
On the universal behavior of some thermodynamic properties along the whole liquid-vapor coexistence curve
Authors: Román F. L. , White J. A. , Velasco S. , Mulero A.
Published: September 2005

When thermodynamic properties of a pure substance are transformed to reduced form by using both critical- and triple-point values, the corresponding experimental data along the whole liquid-vapor coexistence curve can be correlated with a very simple analytical expression that interpolates between the behavior near the triple and the critical points. The leading terms of this expression contain only two parameters: the critical exponent and the slope at the triple point. For a given thermodynamic property, the critical exponent has a universal character but the slope at the triple point can vary significantly from one substance to another. However, for certain thermodynamic properties including the difference of coexisting densities, the enthalpy of vaporization, and the surface tension of the saturated liquid, one finds that the slope at the triple point also has a nearly universal value for a wide class of fluids. These thermodynamic properties thus show a corresponding apparently universal behavior along the whole coexistence curve.
Ion-induced nucleation in polar one-component fluids
Authors: Kitamura Hikaru , Onuki Akira
Published: September 2005

We present a Ginzburg-Landau theory of ion-induced nucleation in a gas phase of polar one-component fluids, where a liquid droplet grows with an ion at its center. By calculating the density profile around an ion, we show that the solvation free energy is larger in gas than in liquid at the same temperature on the coexistence curve. This difference much reduces the nucleation barrier in a metastable gas.
Influence of Si(001) substrate misorientation on morphological and optical properties of Ge quantum dots
Authors: Berbezier I. , Descoins M. , Ismail B. , Maaref H. , Ronda A.
Published: September 2005

We have investigated the correlation between morphological and optical properties of Ge dots deposited by molecular-beam epitaxy on a Si(001) surface and on a high-index Si(118) vicinal surface. Ge islands were confined on the top of an undulated Si0.5Ge0.5 template layer according to the Stranski-Krastanov growth mode. Atomic force microscopy measurements reveal that the main effect of the vicinal substrate is to transform hut islands on a nominal (001) substrate into wire-shaped islands on (118) substrates. We have observed a direct correlation between the elongated shape and polarization anisotropy of optical transitions in island. The island photoluminescence (PL) emission is partially (∼25%) polarized for dots deposited on a (118) substrate. PL spectroscopy investigations as a function of temperature and excitation power are reported. The results show that the PL of islands strongly depends on the pump excitation power: it broadens and is blueshifted by 28 and 14meV∕decade for structures grown on (001) and (118), respectively, as the excitation power density increases. The significant blueshift is interpreted in terms of band bending in type II recombination. Moreover, a detailed analysis of (118) island PL band shows the presence of two main peaks that could be attributed to the different island morphologies clearly identified by transmission electron and atomic force microscopies: wire islands and dome islands.
Perpendicular magnetization reversal, magnetic anisotropy, multistep spin switching, and domain nucleation and expansion in Ga1−xMnxAs films
Authors: Liu X. , Lim W. L. , Titova L. V. , Dobrowolska M. , Furdyna J. K. , Kutrowski M. , Wojtowicz T.
Published: September 2005

We present a comprehensive study of the reversal process of perpendicular magnetization in thin layers of the ferromagnetic semiconductor Ga1−xMnxAs. For this investigation we have purposely chosen Ga1−xMnxAs with a low Mn concentration (x≈0.02), since in such specimens contributions of cubic and uniaxial anisotropy parameters are comparable, allowing us to identify the role of both types of anisotropy in the magnetic reversal process. As a first step we have systematically mapped out the angular dependence of ferromagnetic resonance in thin Ga1−xMnxAs layers, which is a highly effective tool for obtaining the magnetic anisotropy parameters of the material. The process of perpendicular magnetization reversal was then studied by magnetotransport (i.e., Hall effect and planar Hall-effect measurements). These measurements enable us to observe coherent spin rotation and noncoherent spin switching between the (100) and (010) planes. A model is proposed to explain the observed multistep spin switching. The agreement of the model with experiment indicates that it can be reliably used for determining magnetic anisotropy parameters from magnetotransport data. An interesting characteristic of perpendicular magnetization reversal in Ga1−xMnxAs with low x is the appearance of double hysteresis loops in the magnetization data. This double-loop behavior can be understood by generalizing the proposed model to include the processes of domain nucleation and expansion.
Paleoclassical transport in low-collisionality toroidal plasmas
Authors: Callen J. D.
Published: September 2005

Radial electron heat transport in a low-collisionality, current-carrying resistive plasma confined in an axisymmetric toroidal magnetic field is hypothesized to be caused by the paleoclassical collisional processes of parallel electron heat conduction and radial magnetic-field diffusion. The electron distribution is Maxwellianized and the electron temperature equilibrated over a long length L (⪢ the poloidal periodicity half-length πR0q) along helical magnetic-field lines that are diffusing radially with the resistivity-induced magnetic-field diffusivity Dη≡η‖nc∕μ0≃νe(c∕ωp)2. This produces a paleoclassical radial electron heat diffusivity χepc that is a multiple M≃L∕(πR0q)∼10⪢1 of the magnetic-field diffusivity: χepc≃(3∕2)MDη. New paleoclassical model developments in this paper include full axisymmetric toroidal magnetic-field geometry, evolution of toroidal, poloidal, and helical magnetic fluxes, effects of temporally varying magnetic fluxes, introduction of electron guiding center radial diffusion effects induced by poloidal magnetic-flux diffusion into electron drift kinetics via a Fokker-Planck procedure, and determination of both axisymmetric and the usually dominant helically resonant paleoclassical radial electron heat transport.
Creation of localized sheared flow by ion trapping
Authors: Ohkawa T. , Miller R. L.
Published: September 2005

Radially localized sheared toroidal flow may be driven in a toroidal plasma by using ion cyclotron heating to assymmetrically trap ions.
The neoclassical angular momentum flux in the large aspect ratio limit
Authors: Wong S. K. , Chan V. S.
Published: September 2005

The small rotation version of the neoclassical angular momentum flux is calculated in the large aspect ratio limit and in the banana regime. The method relies on solving an adjoint equation to the customary linearized drift kinetic equation, circumventing the difficulty of obtaining the ion distribution function that is second order in the ratio of poloidal gyroradius over plasma scale length. The result differs significantly from a long-standing result for circular cross-section flux surfaces.
Conditional mixing statistics in a self-similar scalar mixing layer
Authors: de Bruyn Kops Stephen M. , Mortensen Mikael
Published: September 2005

Conditional scalar mixing statistics from a three-dimensional direct numerical simulation (DNS) of a scalar mixing layer are presented in the context of modeling nonpremixed turbulent combustion. The simulation is closely matched to a particular laboratory experiment but with slight adjustments so that the simulated flow is very nearly self-similar. All statistics commonly used in mixing models are presented, along with comparisons to models and laboratory data where available. A model for the conditional scalar dissipation rate (CSD), recently introduced by Mortensen [“Consistent modeling of scalar mixing for presumed multiple parameter probability density functions,” Phys. Fluids 17, 018106 (2005)], is tested against the data set, as is a Lagrangian stochastic trajectory technique recently published by Sawford [“Conditional scalar mixing statistics in homogenous isotropic turbulence,” New J. Phys. 6, 1 (2004)]. It is concluded that (i) the DNS data set provides an excellent, high-resolution description of the scalar mixing layer that can be used for developing and verifying models for scalar mixing; (ii) the self-consistent CSD model of Mortensen is necessary for consistent implementations of the conditional moment closure, but for the current flow it gives only small adjustments to the more commonly adopted model of Girimaji [“On the modeling of scalar diffusion in isotropic turbulence,” Phys. Fluids A 4, 2529 (1992)]; and (iii) Sawford’s Lagrangian technique very closely predicts the DNS results.
Streamline topologies near nonsimple degenerate points in two-dimensional flows with double symmetry away from boundaries and an application
Authors: Gürcan F. , Deliceoğlu A.
Published: September 2005

Streamline patterns and their bifurcations in two-dimensional incompressible fluid near simple degenerate critical points away from boundaries have been investigated by Brøns and Hartnack [Phys. Fluids 11, 314 (1999)] using a normal form approach. In this study, their method is extended to a nonsimple degenerate point under certain conditions. A normal form transformation is used to simplify the differential equations of a Hamiltonian system that describes the streamlines. Bifurcations in the flow occur when parameters take certain degenerate values. When the degenerate configuration is perturbed slightly, an unfolding of the system is obtained. From this, we give a complete description of the bifurcations up to codimension two. New flow patterns are found that inflow saddles are connected by a single heteroclinic connection and an interaction of two vortices with opposite rotations appears in the flow. The theory is applied to the patterns and bifurcations found numerically in the studies of Stokes flow in a double-lid-driven rectangular cavity.
Bulk nanostructured alloys prepared by flux melting and melt solidification
Authors: Shen T. D. , Schwarz R. B. , Zhang X.
Published: September 2005

We have prepared bulk nanostructured Ag60Cu40 alloys by a flux-melting and melt-solidification technique. The flux purifies the melts, leading to a large undercooling and nanometer-sized microstructure. The as-prepared alloys are composed of nanolayered Ag and Cu within micrometer-sized grains. The bulk nanostructured alloys have an ultimate tensile strength of approximately 560MPa, similar yield strength in tension and compression, elongation of 7% in tension, strain hardening exponent of 0.1, and relatively high mechanical and thermal stability up to 400°C.