bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine tuning of coenzyme specificity in family 2 aldo‐keto reductases revealed by crystal structures of the Lys‐274 → Arg mutant of Candida tenuis xylose reductase (AKR2B5) bound to NAD+ and NADP+
Authors: Leitgeb Stefan , Petschacher Barbara , Wilson David K. , Nidetzky Bernd
Published: January 2005

Aldo‐keto reductases of family 2 employ single site replacement Lys → Arg to switch their cosubstrate preference from NADPH to NADH. X‐ray crystal structures of Lys‐274 → Arg mutant of Candida tenuis xylose reductase (AKR2B5) bound to NAD+ and NADP+ were determined at a resolution of 2.4 and 2.3 Å, respectively. Due to steric conflicts in the NADP+‐bound form, the arginine side chain must rotate away from the position of the original lysine side chain, thereby disrupting a network of direct and water‐mediated interactions between Glu‐227, Lys‐274 and the cofactor 2′‐phosphate and 3′‐hydroxy groups. Because anchoring contacts of its Glu‐227 are lost, the coenzyme‐enfolding loop that becomes ordered upon binding of NAD(P)+ in the wild‐type remains partly disordered in the NADP+‐bound mutant. The results delineate a catalytic reaction profile for the mutant in comparison to wild‐type.
Histopathological and immunophenotyping studies on normal and sarcoma 180-bearing mice treated with a complex homeopathic medication
Authors: Sato D.Y.O. , Wal R. , de Oliveira C.C. , Cattaneo R.I.I. , Malvezzi M. , Gabardo J. , de F Buchi D.
Published: January 2005

Canova is a homeopathic complex medicine, used as an immune modulator. We studied its effects in normal and sarcoma 180-bearing mice. Three control groups were also evaluated. The mice were examined at daily intervals and the tumours observed histologically. Peripheral blood was analysed by flow cytometry.

A delay in the development, and a reduction in size of the tumours, and increased infiltration by lymphoid cells, granulation tissue, and fibrosis surrounding the tumour were observed with active treatment compared to control. All animals from the treated group survived, 30% of control groups died. In 30% of treated animals, a total regression of the tumour was confirmed using light microscopy, no regression was found in the control groups. Treatment with Canova increased total numbers of leukocytes and lymphocytes. Among lymphocytes, TCD4, increased in normal-treated group and B and NK cells in S180-treated groups. The results reflect enhanced immune response of the host after treatment with Canova.
The Distribution of Arctic Lichens and Thoughts Concerning Their Origin
Authors: Thomson J. W.
Published: January 2005

The distribution of many Arctic lichens is well known but their place and time of origin is still conjectural. Land bridges are often suggested but continental drift suggests a possible tie to Gondwanaland and Pangaea. This review suggests consideration of the available evidence for such ideas and emphasizes the need for more exact data from molecular studies of living and amber materials to determine the antiquity of the lichen species involved.
Phytogeography of Continental Antarctic Lichens
Authors: Seppelt R.D.
Published: January 2005

The northern and southern polar regions differ substantially in topography, climate, terrestrial habitats and in their biota. The Arctic flora comprises around 900 flowering plants, 600–700 bryophytes and 2000 lichens. The Antarctic flora is depauperate by comparison with only two flowering plants, 100–120 bryophytes, and probably only around 200 lichens. Despite considerable taxonomic uncertainty, broad phytogeographic patterns can be outlined, with species having a Maritime Antarctic, Peninsula and Lesser Antarctic, Circum-Antarctic, and Disjunct distribution pattern. The extent of endemism in the flora is unclear. The origin of the Antarctic lichen flora appears ancient in pan, although there is ample evidence for post-Pleistocene or Holocene colonization and invasion.
Alpine Lichens of Tasmania' s South West Wilderness
Authors: Kantvilas Gintaras
Published: January 2005

The climate, geology and vegetation of Tasmania's South West wilderness are described briefly, with particular reference to lichens. One hundred and sixty-two lichens are recorded from alpine altitudes in the region and the major habitats for alpine lichens are discussed. The flora differs significantly from that of other Tasmanian mountain systems, and this is attributed in part to geology and macroclimate. The region is rich in Tasmanian endemics and distinctly austral species with restricted geographical distributions.
Short-Term Effects of Enhanced Uv-B and CO2 on Lichens at Different Latitudes
Authors: Sonesson M. , Callaghan T.V. , Björn L.O.
Published: January 2005

Interaction effects of UV-B and CO2 on three lichens species, Cladonia arbuscula, Cetraria islandica and Stereocaulon paschale, from two latitudinal sites, 68°N and 56°N, were studied in a laboratory experiment. The response of the plants was recorded by measuring their chlorophyll fluorescence. All species had a similar response to enhanced UV-B depending on the latitude from which the population came and the time of the season when they were sampled. Overall, there was a significant increase in photosystem II yield (as measured by a fluorescence technique) due to UV-B and no separate effect due to enhanced CO2, although there was a significant interaction between CO⊂2 and UV-B. The increase due to UV-B was at the low CO2 level. There were also significant differences in response due to latitude. The results contradict our hypotheses that negative effects of UV-B would be larger in the North than in the South and that a negative response hould be especially large during the early season.
Poisson brackets for guiding-centre and gyrocentre theories
Authors: CORREA-RESTREPO DARÍO , PFIRSCH DIETER
Published: January 2005

Poisson brackets in the phase space of averaging Kruskal coordinates are obtained in a clear and straightforward way. The derivation makes use of the equations of motion of guiding centres and gyrocentres derived from a gyroangle-independent Lagrangian, and from generally valid relations of Hamiltonian mechanics. The usual procedure of matrix inversion to obtain the Poisson tensor from the Lagrange tensor is not required.
A study of ion-acoustic solitons and double layers in a multispecies collisionless weakly relativistic plasma
Authors: GILL TARSEM SINGH , KAUR HARVINDER , SAINI NARESHPAL SINGH
Published: January 2005

The effect on the propagation of ion-acoustic solitons and double layers has been studied in collisionless weakly relativistic plasma consisting of two-electron temperature with isothermal electrons and finite ion temperature. The Korteweg de-Vries (KdV) equation is derived for ion-acoustic solitons propagating in a collisionless plasma. This equation is solved in a stationary frame to obtain the expression for soliton phase velocity, soliton width and peak soliton amplitude. It is observed that these quantities are significantly influenced by the relativistic effect, ion temperature, low-temperature electron density and ratio of cold to hot electron temperatures. Many features expected from hot ion theory and two species electron plasmas automatically emerge. The analysis is further extended to higher order nonlinearity and modified Korteweg de-Vries (mKdV) equation is derived. Even though compressive and rarefactive ion-acoustic solitons are obtained, only rarefactive ion-acoustic double layers are obtained in the present investigation.
The magnetic entropy concept
Authors: MINARDI E.
Published: January 2005

The magnetic entropy concept is an interpretative and predictive tool based on probability and information, defined in a suitably coarse-grained possibility space of all current density distributions under testable constraints. This paper develops the concept starting from its statistical foundations and then proceeds illustrating its potentiality in the description of the global behavior of macroscopic plasma configurations with practical interest. Finally, the paper discusses the relations of the concept to the dynamics of the underlying system of particles.
International society, the International Criminal Court and American foreign policy
Authors: Ralph Jason
Published: January 2005

The discipline of International Relations has been slow to assess the ICC and American opposition to it. This article uses the English School approach to assess the impact of the ICC on international society. The Rome Statute's definition of core crimes and its provision of an independent prosecutor help to legally constitute world society which transcends the society of states. The US opposes this development by arguing that international criminal justice should remain within the framework of international society. This is because the society of states accommodates a strong exceptionalist discourse and furthers America's particular interests in a way world society does not.
Design of a novel 5-DOF parallel kinematic machine tool based on workspace
Authors: Gao Feng , Peng Binbin , Li Weimin , Zhao Hui
Published: January 2005

In this paper an inverse concept idea is presented to determine the main configuration dimensional parameters of a novel 5-DOF parallel kinematic machine tool. By the new described orientation workspace, the motion of the passive joints on the moving platform can be expressed in the fixed coordinate analytically. Some relationships between the reachable workspace and the dimensional parameters of the parallel machine tool have been obtained with graphical representation.
Design of an adaptive control law using trigonometric functions for robot manipulators
Authors: Burkan Recep
Published: January 2005

In this study, a new approach of adaptive control law for controlling robot manipulators using the Lyapunov based theory is derived, thus the stability of an uncertain system is guaranteed. The control law includes a PD feed forward part and a full dynamics feed forward compensation part with the unknown manipulator and payload parameters. The novelty of the obtained result is that an adaptive control algorithm is developed using trigonometric functions depending on manipulator kinematics, inertia parameters and tracking error, and both system parameters and adaptation gain matrix are updated in time.
Editor's Introduction: I. Writing Modern Art and Science – An Overview; II. Cubism, Futurism, and Ether Physics in the Early Twentieth Century
Authors: Henderson Linda Dalrymple
Published: January 2005

This issue of Science in Context presents a sampling of current work by art historians examining modern artists' engagement with science as well as the relationship of photography to both science and art. The essays' topics span the mid-to-later nineteenth century to the 1960s and, thus, in a series of case studies provide an introduction to aspects of artistic modernism. Indeed, it is impossible to understand fully many of the radical innovations of modern art without some knowledge of an artist's cultural context, and developments in science have often played a critical role in defining that milieu. Collected together, these essays also represent methodological models of historical work on art and science that serve as useful examples in this developing field.
Odilon Redon and the Pasteurian Revolution: Health, Illness, and le monde invisible
Authors: Larson Barbara
Published: January 2005

Argument

Odilon Redon's dark-spirited charcoals and lithographs of the last quarter of the nineteenth century responded to developments in science, including the Pasteurian revolution. Rather than celebrating the progressive potential of science, Redon's noirs engaged national anxieties that attended scientific advances. His position was close to the Decadents of the 1880s who dwelled on themes of illness and decay. While the artist's original biographer André Mellerio referred to the artist's fascination with Pasteur and his microbial world, where in a single drop of water “there arises the spectacle of giants of a gripping horror and a frightful, predatory nature,” the topic has virtually disappeared from Redon literature. By recovering the scientific/medical issues that stimulated Redon's creation, this article restores the subjects of pathogenic organisms and contagious illness to their rightful place in Redon's oeuvre. Further, it provides the reader with a discussion of the cultural context in which Redon's interest was generated.
Gyorgy Kepes, Billy Klüver, and American Art of the 1960s: Defining Attitudes Toward Science and Technology
Authors: Goodyear Anne Collins
Published: January 2005

Argument

This essay aims to broaden our understanding of relationships between art, science, and technology during the 1960s by juxtaposing two of the most important, and under-examined, figures of this period, the artist Gyorgy Kepes and the engineer Billy Klüver. While these two are generally linked due to their similarities, a closer examination demonstrates significant differences in their outlook. Comparing the organizations they nurtured, Kepes, the Center for Advanced Visual Studies at the Massachusetts Institute of Technology, and Klüver, Experiments in Art and Technology, provides unique insight into the distinct origins of such organized collaborations between art, science, and technology. It reveals both how the cultural conditions of the 1960s contributed to the perceived need for such agencies and how interactions between art, science, and technology reflected, at once, the culmination of aspirations reaching back to the opening decades of the twentieth century, and a perceived break with the past.
Wavelet Analysis For Improving INS and INS/DGPS Navigation Accuracy
Authors: Nassar Sameh , El-Sheimy Naser
Published: January 2005

The integration of the Global Positioning System (DGPS) with an Inertial Navigation System (INS) has been implemented for several years. In an integrated INS/DGPS system, the DGPS provides positions while the INS provides attitudes. In case of DGPS outages (signal blockages), the INS is used for positioning until the DGPS signals are available again. One of the major issues that limit the INS accuracy, as a stand-alone navigation system, is the level of sensor noise. The problem with inertial data is that the required signal is buried into a large window of high frequency noise. If such noise component could be removed, the overall inertial navigation accuracy is expected to improve considerably. The INS sensor outputs contain actual vehicle motion and sensor noise. Therefore, the resulting position errors are proportional to the existing sensor noise and vehicle vibrations. In this paper, wavelet techniques are applied for de-noising the inertial measurements to minimize the undesirable effects of sensor noise and other disturbances. To test the efficiency of inertial data de-noising, two road vehicle INS/DGPS data sets are utilized. Compared to the obtained position errors using the original inertial measurements, the results showed that the positioning performance using de-noised data improves by 34%–63%.
GPS Navigation Solutions by Analogue Neural Network Least-Squares Processors
Authors: Jwo Dah-Jing
Published: January 2005

The solution for the receiver's position and clock bias using four or more GPS pseudorange measurements involve nonlinear quadratic equations. One of the popular techniques attempts to linearise the equations and solve them by the least-squares (LS) scheme based on an iterative gradient approach. For real-time applications when the solution is to be obtained within a time of the order of a hundred nanoseconds, a digital computer often cannot comply with the desired computation time, or its use is too expensive. In this paper, two ordinary differential equation formulation schemes and corresponding circuits of neuron-like analog processors will be employed for GPS navigation processing. The circuits of simple neuron-like analog processors are employed essentially for solving systems of linear equations based on the criterion of mean square error minimization, which is commonly utilized for determining positioning solutions in the GPS receivers. Experiments on single epoch and thereafter dynamic positioning will be conducted by computer simulation to validate the usefulness of the proposed scheme. The solutions will be assessed and compared to those provided by the conventional method in which pseudo-inverse matrix calculation by digital computer is involved.
A Method of Over Bounding Ground Based Augmentation System (GBAS) Heavy Tail Error Distributions
Authors: Braff Ronald , Shively Curtis
Published: January 2005

The purpose of this paper is to describe a statistical method for modelling and accounting for the heavy tail fault-free error distributions that have been encountered in the Local Area Augmentation System (LAAS), the FAA's version of a ground-based augmentation system (GBAS) for GPS. The method uses the Normal Inverse Gaussian (NIG) family of distributions to describe a heaviest tail distribution, and to select a suitable NIG family member as a model distribution based upon a statistical observability criterion applied to the FAA's LAAS prototype error data. Since the independent sample size of the data is limited to several thousand and the tail probability of interest is of the order of 10−9, there is a chance of mismodelling. A position domain monitor (PDM) is shown to provide significant mitigation of mismodelling, even for the heaviest tail that could be encountered, if it can meet certain stringent accuracy and threshold requirements. Aside from its application to GBAS, this paper should be of general interest because it describes a different approach to navigation error modelling and introduces the application of the NIG distribution to navigation error analysis.
Designing Usable Marine Interfaces: Some Issues and Constraints
Authors: Mills Stella
Published: January 2005

Although there have been improvements to the interface design of marine systems, there are still calls for increased usability as designers are blamed for systems that users find difficult to operate. This paper examines some of the issues and constraints that the designer faces when attempting to design a usable interface. The approach to designing that the developer may take is considered as well as more practical issues such as the limitations of using design principles. The importance of domain and context knowledge is stressed as well as other issues such as safety and culture. The paper concludes that design is a complex compromise but user involvement throughout the lifecycle can improve the ease of using marine systems.
Concerning Cross Track Distance at Mid-Longitude (3)
Authors: Hickley Paul
Published: January 2005

I am grateful to both Dr Ponsonby and Sqn Ldr Hoare for their responses to my original article and would like to thank them for replying. It is interesting that they have come up with such different approaches, one based on solid geometry (but not spherical trigonometry) and the other based on a map projection, which both give exact or near-exact answers.
Definition of a Fast and Manoeuvrable Craft and Amendments to the Collision Regulations
Authors: Undrum Rolf Johannes
Published: January 2005

This paper is presented as a think piece and poses the introduction of a new type of high-speed craft to represent the growing number of fast manoeuvrable craft that could safely maintain their speed in heavy traffic areas. A method of defining such craft is introduced and a proposal made for a corresponding amendment to the COLREGS.
Flow performance of horizontal wells with inflow control devices
Authors: ATKINSON C. , MONMONT F. , ZAZOVSKY A. F.
Published: January 2005

This paper presents a powerful approximate method for modelling the steady single-phase flow into a horizontal well completed with an Inflow Control Device (ICD) in an anisotropic reservoir. Two types of problems are investigated: the forward problem, which allows the user to find the flux distribution along the wellbore for a specified pressure drawdown, and the inverse problem to determine the ICD properties when the flux or reservoir pressure drawdown along the wellbore is given. The method is based on structuring the flow patterns around and, inside the wellbore and across the ICD and on the reduction of the dimensionality of the problem by using boundary integral equations. The resulting one dimensional singular nonlinear integro-differential equation is solved numerically, using the appropriate quadrature formula for singular integrals with Cauchy kernels.
When Less is More: The Dominance of Subject-Content in the Teaching of Undergraduate Social Policy
Authors: Irving Zoë , Young Pat
Published: January 2005

This article explores the implications of expanding content in undergraduate Social Policy. Although the problem of curriculum content is not unique to Social Policy, particular features exacerbate the issue. These include the relationship of the subject to other disciplines, and to wider political and social issues. Dominance of content is argued to limit the aims of teaching, squeezing out skills development. It also restricts the methods employed. Content dominance also contributes to the development of a deficit model of students. The article is based on data drawn from semi-structured interviews with 46 lecturers working in universities across the UK.
Geochemical segmentation of the Mid‐Atlantic Ridge north of Iceland and ridge–hot spot interaction in the North Atlantic
Authors: Blichert‐Toft Janne , Agranier Arnaud , Andres Magdalena , Kingsley Richard , Schilling Jean‐Guy , Albarède Francis
Published: January 2005

Hafnium, Nd, and Pb isotope data are reported for mid‐ocean ridge basalts (MORB) from the Mid‐Atlantic Ridge between 50°N and 78°N. Treating Pb isotopes separately from Sr, Nd, and Hf isotopes drastically reduces the number of end‐members required to account for mixing properties in the investigated basalt population. Three geochemical end‐members account for >99.95% of the observed Pb isotope variability. The isotopic compositions of Pb are somewhat decoupled from those of other isotopic systems due to nonlinear mixing relationships between isotopic compositions of different elements and elemental fractionation by magmatic processes. The first principal component reflects a mixture of two geochemical end‐members, DM and the common component C. The third end‐member (EM) is enriched and its Th/U ratio substantially higher than that of the first two end‐members. The HIMU end‐member apparently is missing. Iceland and Jan Mayen divide the northern Mid‐Atlantic Ridge into three isotopically distinct segments. The strong first Pb principal component present in Icelandic basalts expands southward into the Reykjanes Ridge, but not northward into the Kolbeinsey Ridge. Similar features are observed for Hf and Nd isotope compositions. By contrast, the second Pb principal component shows a smooth transition between Kolbeinsey MORB and subaerial Iceland data. The distribution of the two Pb principal components present in the basalts around Jan Mayen likewise is contrasted: the first Pb principal component and its Nd and Hf counterparts flow northward into the Mohns Ridge but are arrested southward by the Jan Mayen fracture zone. Basalts north of Jan Mayen display the most radiogenic Hf reported so far for any MORB worldwide. For ∼1000 km along the Mohns and Knipovich Ridges, Hf isotope compositions fail to correlate linearly with ɛNd, but instead define a hyperbolic array between the C component and an end‐member unusually depleted in Hf. The latter carries a strong garnet signature and may appear by disequilibrium melting of streaks of subcontinental lithosphere left by continental rifting. The presence of continental crust beneath Jan Mayen is not supported by either Ce/Pb, Nb/U, or Hf/Sm. If Jan Mayen is a hot spot, its material is injected along a major mantle discontinuity separating distinct convective domains.
Sr‐Nd isotope systematics in 14–28 Ma low‐temperature altered mid‐ocean ridge basalt from the Australian Antarctic Discordance, Ocean Drilling Program Leg 187
Authors: Krolikowska‐Ciaglo Sylwia , Hauff Folkmar , Hoernle Kaj
Published: January 2005

The effects of low‐temperature alteration on the Rb‐Sr and Sm‐Nd isotope systems were investigated in 14–28 Ma mid‐ocean ridge basalts recovered during Ocean Drilling Program (ODP) Leg 187 from the Australian Antarctic Discordance through comparison of pristine glass and associated variably altered basalts. Both Nd and Sm are immobile during low‐temperature alteration, and 143Nd/144Nd displays mantle values even in heavily altered samples. In contrast, 87Sr/86Sr and Rb concentrations increase during seawater‐rock interaction, which is especially apparent in single samples with macroscopically zoned alteration domains. The increase in 87Sr/86Sr roughly correlates with the visible degree of alteration, indicating a higher seawater/rock ratio in the more altered samples. Sr concentrations, however, do not systematically increase with increasing degree of alteration, most likely reflecting exchange of Sr in smectite interlayer sites. The degree of alteration in the uppermost oceanic crust of the Australian Antarctic Discordance is independent of crustal age. A comparison with literature data for young and old altered oceanic crust suggests that most low‐temperature alteration occurs within a few million years after formation of the oceanic crust, probably reflecting greater fluid flux through the crust during its early history as a result of higher permeability and increased fluid circulation near the ridge.
Synoptic conditions causing nonmonsoon snowfalls in the Tibetan Plateau
Authors: Ueno Kenichi
Published: January 2005

The characteristics of atmospheric circulations in Asia causing snowfalls over the central Tibetan Plateau (TP) were investigated during the nonmonsoon season. During 1994–2004, a clear pattern of a barotropic pressure anomaly was found over northeast Asia by means of composite analysis. NCEP reanalysis data and METEOSAT images were examined for snowfall events detected by in‐situ surface albedo measurements during Nov.–May, 1998/99, and the possible mechanisms causing precipitation in the TP and the influence of mid‐latitude large‐scale meandering flow were discussed.
A 220 kyr record of Pb isotopes at Dome C Antarctica from analyses of the EPICA ice core
Authors: Vallelonga P. , Gabrielli P. , Rosman K. J. R. , Barbante C. , Boutron C. F.
Published: January 2005

Pb isotopic compositions and Pb and Ba concentrations are reported in EPICA Dome C ice core samples dating to 220 kyr BP, indicating that Pb isotopic compositions in Antarctic ice vary with changing climate. 206Pb/207Pb ratios decrease during glacial periods, with the lowest values occurring during colder climatic periods (stages 2, 4 and 6) and the Holocene. Low Pb concentrations (<1 pg/g) were found during the Holocene and the last interglacial (climate stage 5.5) while higher Pb concentrations (>10 pg/g) were found during cold climatic periods. Ba, a proxy for mineral dust, was used to determine that dust usually accounts for ∼70% of Pb in Dome C ice, while the remaining ∼30% was attributed to volcanic emissions. Pb isotopic compositions at Dome C differ from those reported in pre‐industrial ice from other Antarctic locations, due to greater proportions of dust Pb at Dome C.
Observations of mesospheric ozone depletion during the October 28, 2003 solar proton event by OSIRIS
Authors: Degenstein D. A. , Lloyd N. D. , Bourassa A. E. , Gattinger R. L. , Llewellyn E. J.
Published: January 2005

One of the largest solar proton events in the past thirty years took place on October 28, 2003 and had a significant impact on the Earth's middle atmosphere. The incoming protons produce significant amounts of HOx constituents in the mesosphere and upper stratosphere that lead to ozone depletion. For 11 hours during the solar proton event the OSIRIS instrument on Odin measured high spatial resolution profiles of the oxygen infrared atmospheric band at 1.26 microns which under sunlit conditions can be used as a direct proxy for ozone. Ozone depletion is observed across the southern polar cap for the duration of the observations and extends to latitudes as far north as 45°S. OSIRIS observed significant ozone depletion between 50 and 80 km with a maximum value of 75% around 65 km. The actual maximum depletion could have been even greater as observations ceased while the depletion was still increasing.
Plasma sheet turbulence observed by Cluster II
Authors: Weygand James M. , Kivelson M. G. , Khurana K. K. , Schwarzl H. K. , Thompson S. M. , McPherron R. L. , Balogh A. , Kistler L. M. , Goldstein M. L. , Borovsky J. , Roberts D. A.
Published: January 2005

Cluster fluxgate magnetometer (FGM) and ion spectrometer (CIS) data are employed to analyze magnetic field fluctuations within the plasma sheet during passages through the magnetotail region in the summers of 2001 and 2002 and, in particular, to look for characteristics of magnetohydrodynamic (MHD) turbulence. Power spectral indices determined from power spectral density functions are on average larger than Kolmogorov's theoretical value for fluid turbulence as well as Kraichnan's theoretical value for MHD plasma turbulence. Probability distribution functions of the magnetic fluctuations show a scaling law over a large range of temporal scales with non‐Gaussian distributions at small dissipative scales and inertial scales and more Gaussian distribution at large driving scales. Furthermore, a multifractal analysis of the magnetic field components shows scaling behavior in the inertial range of the fluctuations from about 20 s to 13 min for moments through the fifth order. Both the scaling behavior of the probability distribution functions and the multifractal structure function suggest that intermittent turbulence is present within the plasma sheet. The unique multispacecraft aspect and fortuitous spacecraft spacing allow us to examine the turbulent eddy scale sizes. Dynamic autocorrelation and cross correlation analysis of the magnetic field components allow us to determine that eddy scale sizes fit within the plasma sheet. These results suggest that magnetic field turbulence is occurring within the plasma sheet resulting in turbulent energy dissipation.
Deficiency of PAR-2 Gene Increases Acute Focal Ischemic Brain Injury
Authors: Jin Guang , Hayashi Takeshi , Kawagoe Junichi , Takizawa Toshiaki , Nagata Tetsuya , Nagano Isao , Syoji Mikio , Abe Koji
Published: January 2005

The expression profile of the protease-activated receptor-2 (PAR-2) and effects of PAR-2 gene knockout (PAR-2 KO) on the infarct size were investigated after 60 minutes of transient middle cerebral artery occlusion (tMCAO) in mice in relation to phosphorylated extracellular signal-regulated kinase (p-ERK) and astrocyte activation. PAR-2 was normally distributed mainly in neurons of the central nervous system (CNS), and strongly upregulated at 8–24 hours after tMCAO. Deficiency of PAR-2 gene significantly increased the infarct volume and the number of TUNEL-positive cells at 24 hours of reperfusion. The strong neuronal expression of p-ERK was induced at 5 minutes as a peak after reperfusion in wild-type mice, but the signal change was significantly reduced in PAR-2 KO mice. Astroglial activation was also greatly inhibited at 24 hours after tMCAO in PAR-2 KO mice. These results show that the deficiency of PAR-2 gene increases the acute ischemic cerebral injury associating with suppression of neuronal ERK activation and reactive astroglial activation.
Doxycycline Reduces Cleaved Caspase-3 and Microglial Activation in An Animal Model of Neonatal Hypoxia-Ischemia
Authors: Jantzie Lauren L , Cheung Po-Yin , Todd Kathryn G
Published: January 2005

Neonatal hypoxia-ischemia (HI) is a major contributor to many perinatal neurologic disorders and, thus, the search for therapies and effective treatments for the associated brain damage has become increasingly important. The tetracycline derivative, doxycycline (DOXY), has been reported to be neuroprotective in adult animal models of cerebral ischemia. To investigate the putative neuroprotective effects of DOXY in an animal model of neonatal HI, a time-course study was run such that pups received either DOXY (10 mg/kg) or VEH immediately before hypoxia, 1, 2, or 3 hours after HI ( n=6). At 7 days after injury, the pups were euthanized, and the brains were removed and processed for immunohistochemical and Western blot analyses using antibodies against specific markers for neurons, apoptotic markers, microglia, oligodendrocytes, and astrocytes. Results showed that in vulnerable brain regions including the hippocampal formation, thalamus, striatum, cerebral cortex and white matter tracts, DOXY significantly decreased caspase-3 immunoreactivity (a marker of apoptosis), promoted neuronal survival, inhibited microglial activation and reduced reactive astrocytosis compared with VEH-treated HI pups. These effects were found to occur in a time-dependent manner. Taken together, these results strongly suggest that doxycycline has potential as a pharmacological treatment for mild HI in neonates.
Thermal decomposition of RDX from reactive molecular dynamics
Authors: Strachan Alejandro , Kober Edward M. , van Duin Adri C. T. , Oxgaard Jonas , Goddard William A.
Published: January 2005

We use the recently developed reactive force field ReaxFF with molecular dynamics to study thermal induced chemistry in RDX [cyclic-[CH2N(NO2)]3] at various temperatures and densities. We find that the time evolution of the potential energy can be described reasonably well with a single exponential function from which we obtain an overall characteristic time of decomposition that increases with decreasing density and shows an Arrhenius temperature dependence. These characteristic timescales are in reasonable quantitative agreement with experimental measurements in a similar energetic material, HMX [cyclic-[CH2N(NO2)]4]. Our simulations show that the equilibrium population of CO and CO2 (as well as their time evolution) depend strongly of density: at low density almost all carbon atoms form CO molecules; as the density increases larger aggregates of carbon appear leading to a C deficient gas phase and the appearance of CO2 molecules. The equilibrium populations of N2 and H2O are more insensitive with respect to density and form in the early stages of the decomposition process with similar timescales.
Theoretical investigation of the SO2+ dication and the photo-double ionization spectrum of SO
Authors: Ben Houria A. , Ben Lakhdar Z. , Hochlaf M. , Kemp F. , McNab I. R.
Published: January 2005

Highly correlated ab initio methods were used in order to generate the potential energy curves of the electronic states of the SO2+ dication and of the electronic ground state of the neutral SO molecule. These curves were used to predict the spectroscopic properties of this dication and to perform forward calculations of the double photoionization spectrum of SO. In light of spin-orbit calculations, the metastability of this doubly charged ion is discussed: for instance, the rovibrational levels of the X 1Σ+ and A 3Σ+ states are found to present relatively long lifetimes. In contrast, the other electronic excited states should predissociate to form S+ and O+ in their electronic ground states. The simulated spectrum shows structures due to transitions between the v=0 vibrational level of SO (X 3Σ−) and the vibrational levels below the barrier maximum of 11 of the calculated electronic states. The 2 1Σ+ electronic state of SO2+ received further treatment: in addition to vibrational bands due to the below barrier energy levels of this electronic state, at least nine continuum resonances were predicted which are responsible for the special shape of the spectrum in this energy region. This work is predictive in nature and should stimulate future experimental investigations dealing with this dication.
van der Waals interactions of polycyclic aromatic hydrocarbon dimers
Authors: Chakarova Svetla D. , Schröder Elsebeth
Published: January 2005

Density functional theory is in principle exact and includes also long-range interactions, such as the van der Waals interactions. These are, however, part of the exchange-correlation energy functional that needs to be approximated, and are absent in the local and semilocal standard implementations. Recently a density functional which includes van der Waals interactions for planar systems has been developed [Phys. Rev. Lett. 91, 126402 (2003)], which we show can be extended to provide a treatment of planar molecules. We use this functional to calculate binding distances and energies for dimers of three of the smallest polycyclic aromatic hydrocarbons (PAHs)—naphthalene, anthracene, and pyrene.
The E⊗e dynamic Jahn-Teller problem: A new insight from the strong coupling limit
Authors: Sato Tohru , Chibotaru Liviu F. , Ceulemans Arnout
Published: January 2005

Correct boundary conditions for the E⊗e dynamic Jahn-Teller problem are considered explicitly for the first time to obtain approximate analytical solutions in the strong coupling limit. Numerical solutions for the decoupled equations using the finite difference method are also presented. The numerical solutions for the decoupled equations exhibit avoided crossings in the weak coupling region, which explains the oscillating behavior of the solutions obtained by Longuet-Higgins et al. for the coupled equations. The obtained analytical energy expressions show improved agreement with the numerical calculations as compared with the previous treatment in which the potentials were assumed to be harmonic. We demonstrate that the pseudorotational energy j2/(2g2), where g is the dimensionless vibronic coupling constant, and j total angular momentum: j=±1/2,±3/2,…, in the conventional strong coupling expression for the vibronic levels of the lower sheet is exact. Non-Hermitian first-order perturbation theory gives the energy which is correct up to 1/g4. The asymptotic behavior of the wave function at the origin does not influence the corrected energy up to order of 1/g4. At the same time the treatment of the upper sheet with correct boundary conditions gives solutions which are entirely different from the corresponding Slonczewski’s solutions. Besides, the correct boundary conditions enable us to evaluate the nonadiabatic coupling between the lower and upper potential sheets. The energy correction due to the nonadiabatic coupling is estimated to be of order 1/g6.
Isomolar semigrand ensemble molecular dynamics: Development and application to liquid-liquid equilibria
Authors: Morrow Timothy I. , Maginn Edward J.
Published: January 2005

An extended system molecular dynamics method for the isomolar semigrand ensemble (fixed number of particles, pressure, temperature, and fugacity fraction) is developed and applied to the calculation of liquid-liquid equilibria (LLE) for two Lennard-Jones mixtures. The method utilizes an extended system variable to dynamically control the fugacity fraction ξ of the mixture by gradually transforming the identity of particles in the system. Two approaches are used to compute coexistence points. The first approach uses multiple-histogram reweighting techniques to determine the coexistence ξ and compositions of each phase at temperatures near the upper critical solution temperature. The second approach, useful for cases in which there is no critical solution temperature, is based on principles of small system thermodynamics. In this case a coexistence point is found by running N-P-T-ξ simulations at a common temperature and pressure and varying the fugacity fraction to map out the difference in chemical potential between the two species A and B (μA−μB) as a function of composition. Once this curve is known the equal-distance/equal-area criterion is used to determine the coexistence point. Both approaches give results that are comparable to those of previous Monte Carlo (MC) simulations. By formulating this approach in a molecular dynamics framework, it should be easier to compute the LLE of complex molecules whose intramolecular degrees of freedom are often difficult to properly sample with MC techniques.
Mechanisms of lithium transport in amorphous polyethylene oxide
Authors: Duan Yuhua , Halley J. W. , Curtiss Larry , Redfern Paul
Published: January 2005

We report calculations using a previously reported model of lithium perchlorate in polyethylene oxide in order to understand the mechanism of lithium transport in these systems. Using an algorithm suggested by Voter, we find results for the diffusion rate which are quite close to experimental values. By analysis of the individual events in which large lithium motions occur during short times, we find that no single type of rearrangement of the lithium environment characterizes these events. We estimate the free energies of the lithium ion as a function of position during these events by calculation of potentials of mean force and thus derive an approximate map of the free energy as a function of lithium position during these events. The results are consistent with a Marcus-like picture in which the system slowly climbs a free energy barrier dominated by rearrangement of the polymer around the lithium ions, after which the lithium moves very quickly to a new position. Reducing the torsion forces in the model causes the diffusion rates to increase.
An investigation of valence shell orbital momentum profiles of difluoromethane by binary (e,2e) spectroscopy
Authors: Su G. L. , Ning C. G. , Zhang S. F. , Ren X. G. , Zhou H. , Li B. , Huang F. , Li G. Q. , Deng J. K.
Published: January 2005

The electron binding energy spectra and momentum profiles of the valence orbitals of difluoromethane, also known as HFC32 (HFC—hydrofluorocarbon) (CH2F2), have been studied by using a high resolution (e,2e) electron momentum spectrometer, at an impact energy of 1200 eV plus the binding energy, and by using symmetric noncoplanar kinematics. The experimental momentum profiles of the outer valence orbitals and 4a1 inner valence orbital are compared with the theoretical momentum distributions calculated using Hartree–Fock and density functional theory (DFT) methods with various basis sets. In general, the shapes of the experimental momentum distributions are well described by both the Hartree–Fock and DFT calculations when large and diffuse basis sets are used. However, the result also shows that it is hard to choose the different calculations for some orbitals, including the methods and the size of the basis sets employed. The pole strength of the ionization peak from the 4a1 inner valence orbital is estimated.
Humidity sensing by fractally grown nanocomposites
Authors: Pal B. N. , Basu S. , Chakravorty D.
Published: January 2005

Fractal structure of α-iron was grown within gel-derived silica films. These were subjected to oxidation treatments at a temperature of 400K for durations varying from 1to4h. Nanoshells of Fe3O4 up to a thickness of 2nm were formed in the process. The electrical resistivity of these nanocomposites was shown to arise due to a small polaron hopping mechanism between Fe2+ and Fe3+ sites. The nanocomposite films exhibited about three to four orders-of-magnitude resistivity change for an increase of relative humidity from 35% to 95%. The decrease was found to be exponential in nature and is believed to arise due to the injection of electrons to the oxide nanoshell.
Mechanism of polarization enhancement in La-doped Bi4Ti3O12 films
Authors: Yau C. Y. , Palan R. , Tran K. , Buchanan R. C.
Published: January 2005

Bi 4 − x La x Ti 3 O 12 (La-doped BIT, x=0–0.6) thin films prepared by metalorganic decomposition method, were studied using x-ray diffraction (XRD), polarization hysteresis and Raman scattering techniques. The XRD and polarization studies showed that La substitution reduces structural distortion, relaxes internal strain and enhances polarization, while the Raman data indicate that the added La occupies mainly at A sites in the BIT films. Raman modes also indicate an increase in TiO6 symmetry, internal strain relaxation, lower Ti–O hybridization, and decrease in polarization along the a axis. Further, the polarization in the highly c-oriented BIT films significantly increases with the added La, hence a polarization tilt towards the c axis is implied. The higher polarization observed can be attributed, therefore, to microscopic changes involving decreased distortion in the TiO6 octahedra and a polarization tilt towards the c axis, caused by doping with the electronically less active ion (e.g., La, Y) onto the A sites in the BIT structure. This understanding is important to the commercialization of high-density ferroelectric random access memories.
Dust particle alignments and confinement in a radio frequency sheath
Authors: Samarian A. A. , Vladimirov S. V. , James B. W.
Published: January 2005

Stability of vertical and horizontal confinement of dust particles levitating in a rf sheath was studied experimentally. The experiments were carried out in an argon plasma discharge with micron-sized dust particles. Disruptions of particle arrangements were triggered by changing the discharge controlling parameters (pressure and peak-to-peak voltage) as well as by applying an additional bias to the confining electrode. Where the transition was triggered by changes of the discharge parameters, the transition from the horizontal to the vertical alignment has been found to be more pronounced than the reverse one. Clear hysteretic phenomena were observed for the transition triggered by changes of the confining voltage.
Electron-trap centers in ZnO layers grown by molecular-beam epitaxy
Authors: Oh D. C. , Suzuki T. , Kim J. J. , Makino H. , Hanada T. , Cho M. W. , Yao T.
Published: January 2005

We have investigated electron-trap centers in ZnO layers grown under different Zn∕O flux ratios by molecular-beam epitaxy. Frequency-dependent capacitance measurements show that ZnO layers grown under Zn-rich and stoichiometric flux conditions suffer from larger dispersion than a ZnO layer grown under an O-rich flux condition. Temperature-dependent capacitance measurements reveal that all the ZnO layers have shallow electron-trap centers ET1 and deep electron-trap centers ET2, while the Zn-rich ZnO layer has another shallow electron-trap center ET3 besides ET1 and ET2: the thermal activation energies of ET1, ET2, and ET3 are estimated to be 0.033–0.046, 0.12–0.15, and 0.065 eV, respectively. Moreover, it is exhibited that the trap density of ET2 is larger than those of ET1 or ET3 in all the cases and increases as the Zn∕O flux ratio increases. Consequently, it is suggested that the large dispersion effect observed in the Zn-rich and stoichiometric ZnO layers is ascribed to the large density of deep electron-trap center ET2.
Joint statistics of the scalar gradient and the velocity gradient in turbulence using linear diffusion models
Authors: Martín Jesús , Dopazo César , Valiño Luis
Published: January 2005

A model for the evolution of scalar gradients in turbulence is proposed. The molecular diffusion is approximated by a linear estimation, while the straining term is closed taking advantage of a previous model for velocity gradients [J. Martín, C. Dopazo, and L. Valiño, “Dynamics of velocity gradient invariants in turbulence: Restricted Euler and linear diffusion models,” Phys. Fluids 10, 2012 (1998)]. The joint statistics of the scalar gradients and velocity gradients obtained from this model are studied. In particular, the alignment of the scalar gradient with the principal strain axis, and the correlations between the strain rate and the scalar dissipation rate are investigated. The results show reasonably good agreement with data from direct numerical simulation, which indicates that this simple model captures the essential geometrical properties of the scalar-gradient/velocity-gradient coupling in turbulent flows.