bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of nonradiative centers on localized excitons in InGaN quantum well structures
Authors: Gotoh H. , Akasaka T. , Tawara T. , Kobayashi Y. , Makimoto T. , Nakano H.
Published: November 2006

The authors report the effects of nonradiative recombination on the properties of spatially localized excitons in InGaN quantum well structures studied using a microphotoluminescence (PL) technique. Sharp PL lines (linewidth of less than 1meV) are clearly obtained by combining the PL and nanolithographic techniques. The PL originates from localized excitons induced by quantum-dot-like local potential minima where indium is accumulated. A systematic study with various kinds of samples reveals that suppressing the density of the nonradiative centers is crucially important in terms of observing the exciton localization effects rather than increasing the effects of indium accumulation.
Acousto-optic-modulator-stabilized low-threshold mode-locked Nd:YVO4 laser
Authors: Ray Aniruddha , Das Susanta Kumar , Mukhopadhyay Sourabh , Datta Prasanta Kumar
Published: November 2006

A substantially low-threshold, kilohertz repetition rate and laser-diode-array pumped Nd:YVO4 laser, actively Q switched by an acousto-optic modulator and passively mode locked by a nonlinear mirror consisting of a KTiOPO4, second harmonic generating crystal, and a dichroic output coupler, is demonstrated with enhanced efficiency. The mode-locked pulses with a width of 11.5ps lie underneath a Q-switched envelope having a width of 58ns with a Q-switched modulation frequency of 40kHz. For 10W of pump power, a peak power of 719kW is obtained under stable Q-switched and mode-locked operation, which is a marked improvement compared to the earlier reports.
Scanning x-ray excited optical luminescence microscopy in GaN
Authors: Martínez-Criado G. , Alen B. , Homs A. , Somogyi A. , Miskys C. , Susini J. , Pereira-Lachataignerais J. , Martínez-Pastor J.
Published: November 2006

In this work, an imaging tool to investigate optical inhomogeneities with site and chemical sensitivities has been integrated in a hard x-ray microprobe. Freestanding GaN and epitaxially grown GaN:Mn on α-Al2O3 are used to exploit the unprecedented scanning x-ray excited luminescence technique. Optical images of the radiative recombination channels are reported for several impurities and defect centers in sapphire and GaN compounds. Within the experimental accuracy, a visible nonuniformity characterizes the Mn centers in good correlation with former x-ray fluorescence map. Expanding the microprobe versatility, x-ray absorption spectroscopy in both photon collection modes (x-ray excited luminescence and x-ray fluorescence) is finally presented from a freestanding GaN layer.
Large magnetoresistance in Ni50Mn34In16 alloy
Authors: Sharma V. K. , Chattopadhyay M. K. , Shaeb K. H. B. , Chouhan Anil , Roy S. B.
Published: November 2006

The authors report the observation of large magnetoresistance in Ni50Mn34In16 alloy. This alloy undergoes an austenite-martensite phase transformation which can be strongly affected by the applied magnetic field. This latter effect produces very large magnetoresistance at relatively high temperatures (e.g., 250K). Signature of field induced shape memory effect is also observed in the magnetoresistance results. Above 225K, the field induced shape memory effect is found to be affected by the path traversed in the H-T phase space to reach the target temperature.
Oxygen induced strong green light emission from low-temperature grown amorphous silicon nitride films
Authors: Huang Rui , Chen Kunji , Qian Bo , Chen San , Li Wei , Xu Jun , Ma Zhongyuan , Huang Xinfan
Published: November 2006

Luminescent amorphous silicon nitride films were fabricated by plasma-enhanced chemical vapor deposition at room temperature followed by thermal oxidation at 100°C. Very bright green emissions were clearly observed with the naked eye in a bright room after the samples had been oxidized. The emission peak is located at 495nm. Fourier-transform infrared absorption spectra and results of depth profiling with x-ray photoelectron spectroscopy indicate that the introduction of oxygen is of a key role in enhancing the photoluminescence intensity of the films. Emission and excitation spectra analyses suggest that the green emission is originated from the radiative recombination in the localized states related to the Si–O bonds.
Experimental observation of evanescent-wave amplification and propagation in microwave regime
Authors: Liu Ruopeng , Zhao Bo , Lin Xian Qi , Cui Tie Jun
Published: November 2006

Surface plasmon can lead to wave propagation not only along the surface as a dielectric waveguide but also in the normal direction to the surface because of the evanescent-wave amplification by metamaterial. In this letter, the authors design a surface plasmon structure to implement the electric and magnetic plasma resonances in microwave regime. Near the plasma resonant frequency, they directly observe the strong surface plasmon by experiments. The evanescent waves can be transmitted in an exponentially increasing and decreasing distribution, which is the evanescent-mode propagation by the tunneling effect.
Implementation of a symplectic multiple-time-step molecular dynamics algorithm, based on the united-residue mesoscopic potential energy function
Authors: Rakowski Franciszek , Grochowski Paweł , Lesyng Bogdan , Liwo Adam , Scheraga Harold A.
Published: November 2006

A symplectic multiple-time-step (MTS) algorithm has been developed for the united-residue (UNRES) force field. In this algorithm, the slow-varying forces (which contain most of the long-range interactions and are, therefore, expensive to compute) are integrated with a larger time step, termed the basic time step, and the fast-varying forces are integrated with a shorter time step, which is an integral fraction of the basic time step. Based on the split operator formalism, the equations of motion were derived. Separation of the fast- and slow-varying forces leads to stable molecular dynamics with longer time steps. The algorithms were tested with the Ala10 polypeptide chain and two versions of the UNRES force field: the current one in which the energy components accounting for the energetics of side-chain rotamers (Urot) can lead to numerically unstable forces and a modified one in which the the present Urot was replaced by a numerically stable expression which, at present, is parametrized only for polyalanine chains. With the modified UNRES potential, stable trajectories were obtained even when extending the basic time step to 15fs and, with the original UNRES potentials, the basic time step is 1fs. An adaptive multiple-time-step (A-MTS) algorithm is proposed to handle instabilities in the forces; in this method, the number of substeps in the basic time step varies depending on the change of the magnitude of the acceleration. With this algorithm, the basic time step is 1fs but the number of substeps and, consequently, the computational cost are reduced with respect to the MTS algorithm. The use of the UNRES mesoscopic energy function and the algorithms derived in this work enables one to increase the simulation time period by several orders of magnitude compared to conventional atomic-resolution molecular dynamics approaches and, consequently, such an approach appears applicable to simulating protein-folding pathways, protein functional dynamics in a real molecular environment, and dynamical molecular recognition processes.
The straining effect on tunneling resistance of Co∕AlOx∕Co∕IrMn junctions
Authors: Jen S. U. , Chen Yuan-Tsung , Wu Jenn-Ming , Chen Wen-Chih , Cheng Wei-Chun , Yao Y. D.
Published: November 2006

The authors have fabricated a series of Co∕AlOx(d0)∕Co∕IrMn magnetic tunnel junctions (MTJs), with d0=12–30Å. They can be used as ultrasensitive strain gauges. From the resistance (R) versus strain (Δε) curve, the authors find that the maximum value of the gauge factor (γmax) is as large as 5000–20000 in the low-strain (∣Δε∣⩽25×10−6) range. Furthermore, the response is linear. Two mechanisms are proposed to explain the piezoresistance behavior of these MTJs: one is due to the tunneling magnetoresistance effect (the magnetic origin) and the other due to the ordinary tunneling effect (the nonmagnetic origin).
Structural and electrical characteristics of thin erbium oxide gate dielectrics
Authors: Pan Tung-Ming , Chen Chun-Lin , Yeh Wen Wei , Hou Sung-Ju
Published: November 2006

A high-k erbium oxide thin film was grown on silicon substrate by reactive rf sputtering. It is found that the capacitance value of Er2O3 gate dielectric with TaN metal gate annealed at 700°C is higher compared to other annealing temperature and exhibits a lower hysteresis voltage as well as interface trap density in C-V curves. They also show negligible charge trapping under high constant voltage stress. This phenomenon is attributed to a rather well-crystallized Er2O3 and the decrease of the interfacial layer and Er silicate thickness observed by x-ray diffraction and x-ray photoelectron spectroscopy, respectively.
Surface phase transitions in athermal mixtures of hard rods and excluded volume polymers investigated using a density functional approach
Authors: Bryk Paweł
Published: November 2006

Using fundamental measures’ density functional framework based on Wertheim’s first order perturbation theory [J. Chem. Phys. 87, 7323 (1987)] we study the surface phase transitions in athermal polymer-needle mixtures, which demix in bulk into the isotropic polymer-rich (rod-poor) and polymer-poor (rod-rich) phases. We find that the polymer-rich (rod-poor) phase wets the hard wall at coexistence and the wetting transition is of first order. In the partial wetting regime we find a sequence of layerings but these transitions are gradually suppressed as the chain length increases. For long enough chains we detect the prewetting line. Rods exhibit pronounced ordering at the wall in the polymer-rich phases. Our results imply that experiments on the (isotropic) wetting transition for colloidal rod-polymer mixtures should be easier to carry out than those for the colloidal rod-sphere mixtures because the wetting transition occurs at lower rod densities. On the other hand, layerings in sphere-needle mixtures may turn out to be difficult to observe experimentally because some of them will be metastable with respect to the freezing transition, whereas the remaining ones are located very close to the binodal.
Density functional theory study of water adsorption at reduced and stoichiometric ceria (111) surfaces
Authors: Kumar Santosh , Schelling Patrick K.
Published: November 2006

We study the structure and energetics of water molecules adsorbed at ceria (111) surfaces for 0.5 and 1.0 ML coverages using density functional theory. The results of this study provide a theoretical framework for interpreting recent experimental results on the redox properties of water at ceria (111) surfaces. In particular, we have computed the structure and energetics of various absorption geometries at the stoichiometric ceria (111) surface. We find that single hydrogen bonds between the water and the oxide surface are favored in all cases. At stoichiometric surfaces, the water adsorption energy depends rather weakly on coverage. We predict that the observed coverage dependence of the water adsorption energy at stoichiometric surfaces is likely the result of dipole-dipole interactions between adsorbed water molecules. When oxygen vacancies are introduced in various surface layers, water molecules are attracted more strongly to the surface. We find that it is very slightly energetically favorable for adsorbed water to oxidized the reduced (111) surface with the evolution of H2. In the event that water does not oxidize the surface, we predict that the effective attractive water-vacancy interaction will result in a significant enhancement of the vacancy concentration at the surface in agreement with experimental observations. Finally, we present our results in the context of recent experimental and theoretical studies of vacancy clustering at the (111) ceria surface.
Suppression of transmission minima and maxima with structured metal surface
Authors: Wang Qian-Jin , Huang Cheng-Ping , Li Jia-Qi , Zhu Yong-Yuan
Published: November 2006

Extraordinary optical transmission through perforated metal films has received much attention recently. In this letter, the authors propose a method for studying the transmission properties, in which the Fourier coefficient of reciprocal lattice vectors is manipulated. Especially, due to a zero Fourier coefficient, the suppression of transmission minima and maxima has been experimentally observed. The results open a way to tailor the transmission properties of light.
Impacts of intrinsic defects on luminescence properties of CuAlS2
Authors: Kuroki Yuichiro , Okamoto Tomoichiro , Takata Masasuke , Osada Minoru
Published: November 2006

The authors report on Raman scattering of CuAlS2 in order to study the influences of intrinsic defects on luminescence properties. The A1 mode is dominated in stoichiometric samples, whereas sulfur-poor conditions prepared at high temperatures (⩾800°C) cause defect-specific shift and broadening. They also find that additional mode (at 330cm−1) caused by antisite defects is resonated at 2.16eV excitation, in accordance with visible luminescence attributed to donor-acceptor pair (DAP) emission in photoluminescence. These results suggest that the DAP emissions may be caused by the defect complexes such as AlCu–VCu and VS–VCu, which reduces ultraviolet excitonic emission in this system.
Bursts in single-file motion mediated conduction
Authors: Majumder Shashwati Roy , Bandyopadhyay Tusar , Ghosh Swapan K.
Published: November 2006

We present a cellular automaton (CA) model of particles in a single-file motion with free particle exchange at the boundaries of a one-dimensional channel connected to two infinite reservoirs in order to study the self-transmission of particles with excluded mutual passage. The parallel, local and homogeneous rule sets of the CA algorithm consider two different interactions of varying strength between particles, without any specific particle-channel interaction. CA model results suggest that one hallmark of single-file motion is the conduction bursts at a particular time scale, which have thus far only been discovered for hydrogen bond networked water translocation. The cumulative transport probabilities of particles through single-file channels of different length follow a single profile, which can be obtained through proper scaling of time. The universal features of our results suggest new experiments in single-file channel with fluids other than water.
Counterflow drag reduction by supersonic jet for a blunt body in hypersonic flow
Authors: Venukumar Balla , Jagadeesh G. , Reddy K. P. J.
Published: November 2006

Counterflow drag reduction by supersonic jet for a large angle blunt cone at hypersonic Mach number is investigated in a shock tunnel. The flowfields around the test model in the hypersonic flow with an opposing supersonic jet emanating from the stagnation point of the model are visualized by high speed schlieren technique. The aerodynamic drag force is measured using the accelerometer based force balance system. The experimental measurements show about 30%–45% reduction in drag coefficient for different jet pressures.
Many-electron self-interaction error in approximate density functionals
Authors: Mori-Sánchez Paula , Cohen Aron J. , Yang Weitao
Published: November 2006

One of the most important challenges in density functional theory (DFT) is the proper description of fractional charge systems relating to the self-interaction error (SIE). Traditionally, the SIE has been formulated as a one-electron problem, which has been addressed in several recent functionals. However, these recent one-electron SIE-free functionals, while greatly improving the description of thermochemistry and reaction barriers in general, still exhibit many of the difficulties associated with SIE. Thus we emphasize the need to surpass this limit and shed light on the many-electron SIE. After identifying the sufficient condition for functionals to be free from SIE, we focus on the symptoms and investigate the performance of most popular functionals. We show that these functionals suffer from many-electron SIE. Finally, we give a SIE classification of density functionals.
Molecular orientation and alignment of rubbed poly(vinyl cinnamate) surfaces
Authors: Pagliusi P. , Chen C. Y. , Shen Y. R.
Published: November 2006

We observed that weakly and strongly rubbed polyvinyl-cinnamate surfaces align liquid crystal films perpendicular and parallel to the rubbing direction, respectively. Surface-specific sum-frequency vibrational spectroscopy was used to probe molecular orientations and alignments of the rubbed surfaces and provide a molecular-level understanding of the observation.
Long-term flowering patterns of melliferous Eucalyptus (Myrtaceae) species
Authors: Birtchnell Melanie J. , Gibson Maria
Published: November 2006

The flowering patterns of 28 Victorian melliferous (honey-producing) eucalypts were investigated by using long-term observations of highly experienced, commercial apiarists. Frequency, timing, duration and intensity of flowering were determined, as were spatial differences within and among species. Data were obtained by face-to-face interviews with 25 Victorian apiarists, each of whom had operated a minimum of 350 hives for a minimum of 30 years. Flowering frequency ranged from 1 to 7 years, and most species flowered once every 2–4 years. Long-term flowering frequency, timing and duration were reported as constant, although short-term perturbations could occur. Most melliferous species flowered during spring and summer for a period of 3 months or more. Only few species had shorter flowering periods. Information provided by apiarists compared well with available published information (e.g. flowering period reported in field guides) and revealed a reliable, largely untapped source of long-term data, the use of which could benefit many ecological research endeavours.
Hydraulically based stomatal oscillations and stomatal patchiness in Gossypium hirsutum
Authors: Marenco Ricardo A. , Siebke Katharina , Farquhar Graham D. , Ball Marilyn C.
Published: November 2006

Slow stomatal oscillations (70–95 min), associated with feedback within the plant hydraulic systems, were studied in cotton (Gossypium hirsutum L.). Oscillations were only evident when the whole plant was exposed to light, and were not influenced by reductions in intercellular CO2 concentrations (Ci) in intact, attached leaves. Oscillations were synchronised among different leaves of the same plant, even when the leaf-to-air vapour pressure difference (VPD) was reduced in a cuvette enclosing one of the leaves. In the trough phase of stomatal oscillations the apparent Ci was higher than expected from the combination of the observed assimilation rate and the A(Ci) relationship measured in the absence of oscillations. Using chlorophyll fluorescence imaging we found evidence of stomatal heterogeneity in this phase. Finally, we found that stomatal oscillations appeared to be correlated with xylem embolism, with more vessels filled with gas at the peak than at the troughs of stomatal oscillations.
Measurement of (carbon) kinetic isotope effect by Rayleigh fractionation using membrane inlet mass spectrometry for CO2-consuming reactions
Authors: McNevin Dennis B. , Badger Murray R. , Kane Heather J. , Farquhar Graham D.
Published: November 2006

Methods for determining carbon isotope discrimination, Δ, or kinetic isotope effects, α, for CO2-consuming enzymes have traditionally been cumbersome and time-consuming, requiring careful isolation of substrates and products and conversion of these to CO2 for measurement of isotope ratio by mass spectrometry (MS). An equation originally derived by Rayleigh in 1896 has been used more recently to good effect as it only requires measurement of substrate concentrations and isotope ratios. For carboxylation reactions such as those catalysed by d-ribulose-1,5-bisphosphate carboxylase / oxygenase (RuBisCO, EC 4.1.1.39) and PEP carboxylase (PEPC, EC 4.1.1.31), this has still required sampling of reactions at various states of completion and conversion of all inorganic carbon to CO2, as well as determining the amount of substrate consumed. We introduce a new method of membrane inlet MS which can be used to continuously monitor individual CO2 isotope concentrations, rather than isotope ratio. This enables the use of a simplified, new formula for calculating kinetic isotope effects, based on the assumptions underlying the original Rayleigh fractionation equation and given by: --> The combination of inlet membrane MS and this formula yields measurements of discrimination in less than 1 h. We validate our method against previously measured values of discrimination for PEP carboxylase and RuBisCO from several species.
Alternation of wet and dry sides during partial rootzone drying irrigation alters root-to-shoot signalling of abscisic acid
Authors: Dodd Ian C. , Theobald Julian C. , Bacon Mark A. , Davies William J.
Published: November 2006

Partial rootzone drying (PRD) is an irrigation technique where water is distributed unevenly to the root system such that part is irrigated while the remainder is allowed to dry the soil. Tomato (Lycopersicon esculentum Mill.) plants were grown with their roots in two soil columns to compare the physiological consequences of alternation of wet and dry columns during PRD irrigation (alternate PRD, PRD-A) with retention of the same wet and dry columns (fixed PRD, PRD-F). When PRD plants received 50% less water than well-watered (WW) plants, xylem ABA concentration ([X-ABA]) increased and stomatal conductance decreased relative to WW plants. Although both sets of PRD plants received the same amount of water, [X-ABA] of PRD-A plants increased up to 2-fold above that of PRD-F plants, which further decreased stomatal conductance. Differences in [X-ABA] were detected within an hour of alternation, but did not persist beyond the photoperiod of alternation. [X-ABA] increased linearly as whole-pot soil water content (θpot) and leaf water potential (Ψleaf) declined, but the difference in [X-ABA] between the two sets of PRD plants was not due to differences in either θpot or Ψleaf. In PRD-F plants, the unwatered part of the root system contributes proportionally less to the transpiration stream as the soil progressively dries (Yao et al. 2001, Plant, Cell & Environment 24, 227–235). In PRD-A plants, we hypothesise that re-watering the dry part of the root system allows these roots to contribute proportionally more to total sap flux, thus liberating a pulse of ABA to the transpiration stream as the root ABA pool accumulated during soil drying is depleted. Since the enhancement of [X-ABA] caused by PRD-A increased as θpot and Ψleaf declined, an optimal frequency of alternation to maximise the cumulative physiological effects of this ABA pulse must consider possible negative impacts of leaf water deficit as soil water status declines.
Viewpoint: The perils of pot experiments
Authors: Passioura John B.
Published: November 2006

Experiments with plants in pots can be beset by several often-unrecognised artefacts. The soil or other medium at the bottom of a freshly watered and drained pot is inevitably saturated with water; if the pot is short the whole of the medium may have such little air-filled porosity that it becomes hypoxic. This is an especial problem with field soils used in pots, for these typically do not contain many pores large enough to be drained at the small water suctions that prevail. Such suctions are zero at the bottom of a freshly drained pot and rise by 1 kPa for every 100-mm increment in height, leading to suctions at the top of a typical pot that are much less than the 10–30 kPa that occurs in soils in the field that have drained to ‘field capacity’. Commercial potting mixes overcome this problem by using coarse materials in the mix, which create many large pores (>1 mm diameter) that drain at small suctions. Fine potting mixes used for growing Arabidopsis in small pots are likely to lead to hypoxia throughout the pot. Pots in glasshouses may experience temperatures that are substantially higher or lower than the air temperature. Sun striking the sides of dark pots can raise the temperature by several degrees. In heated glasshouses cold tap water added to warm pots can greatly affect the growth of plants in those pots. Simple precautions can at least partly ameliorate these difficulties.
Soil assessment of apple orchards under conventional and organic management
Authors: Vogeler Iris , Cichota Rogerio , Sivakumaran Siva , Deurer Markus , McIvor Ian
Published: November 2006

To determine the effect of wheel traffic and two different management practices on soil compaction and its consequences on physical and chemical soil properties, we measured penetration resistance, water infiltration, bulk density, macroporosity, chemical mobility, air permeability, and soil strength in a conventional orchard (integrated fruit-production program) with bare (sprayed with herbicides) rows and an organic apple orchard with grassed rows. Resistance measurements were taken both within the tree row and the wheel track, down to a depth of 0.35 to 0.40 m. The results indicate that compaction is greater in the wheel tracks under both management methods. Compaction in the wheel track was higher under organic than conventional management. Organic management resulted in a higher macroporosity in both the row and the wheel-track than conventional management. The ‘close-to-saturation’ infiltration rate was significantly greater within the row of the organic orchard (0.06 m/h) compared with the row of the conventional orchard (0.02 m/h), and compared with the wheel tracks (0.01 m/h). The precompression stress value in the top 100 mm, a measure of the soil strength, was low on all sites. The chemical mobilities were 57 and 50% in the organic orchard, and 86 and 93% in the conventional orchard, respectively, for wheel track and row. Apart from the compaction in the wheel track of the organic orchard, physical and chemical soil characteristics were in a better condition compared with the conventional orchard.
Sleep deprivation inhibits adult neurogenesis in the hippocampus by elevating glucocorticoids
Authors: Mirescu Christian , Peters Jennifer D. , Noiman Liron , Gould Elizabeth
Published: November 2006

Prolonged sleep deprivation is stressful and has been associated with adverse consequences for health and cognitive performance. Here, we show that sleep deprivation inhibits adult neurogenesis at a time when circulating levels of corticosterone are elevated. Moreover, clamping levels of this hormone prevents the sleep deprivation-induced reduction of cell proliferation. The recovery of normal levels of adult neurogenesis after chronic sleep deprivation occurs over a 2-wk period and involves a temporary increase in new neuron formation. This compensatory increase is dissociated from glucocorticoid levels as well as from the restoration of normal sleep patterns. Collectively, these findings suggest that, although sleep deprivation inhibits adult neurogenesis by acting as a stressor, its compensatory aftereffects involve glucocorticoid-independent factors.
Dynamics of allosteric transitions in GroEL
Authors: Hyeon Changbong , Lorimer George H. , Thirumalai D.
Published: November 2006

The chaperonin GroEL-GroES, a machine that helps proteins to fold, cycles through a number of allosteric states, the
T
state, with high affinity for substrate proteins, the ATP-bound
R
state, and the
R
″ (
GroEL
–
ADP
–
GroES
) complex. Here, we use a self-organized polymer model for the GroEL allosteric states and a general structure-based technique to simulate the dynamics of allosteric transitions in two subunits of GroEL and the heptamer. The
T
→
R
transition, in which the apical domains undergo counterclockwise motion, is mediated by a multiple salt-bridge switch mechanism, in which a series of salt-bridges break and form. The initial event in the
R
→
R
″ transition, during which GroEL rotates clockwise, involves a spectacular outside-in movement of helices K and L that results in K80-D359 salt-bridge formation. In both the transitions there is considerable heterogeneity in the transition pathways. The transition state ensembles (TSEs) connecting the
T
,
R
, and
R
″ states are broad with the TSE for the
T
→
R
transition being more plastic than the
R
→
R
″ TSE.
Note on the energy density in the solvent induced by a solute
Authors: Widom B. , Ben-Amotz Dor
Published: November 2006

The question of how far the effect of the presence of a solute molecule propagates into the solvent is studied in a lattice model that had been used earlier to describe hydrophobic interactions. The local energy density in the model solvent is obtained as an explicit function of distance from the solute and is found to decay to its bulk-phase value with the same decay length as that of the solvent-mediated part of the potential of mean force between a pair of solute molecules. The integrated deviation of the energy density from its bulk-phase value is evaluated in Bethe-Guggenheim approximation and shown to be identical to the energy change accompanying the dissolution of the solute as obtained from the temperature dependence of its solubility.
Human cytomegalovirus pUL37x1 induces the release of endoplasmic reticulum calcium stores
Authors: Sharon-Friling Ronit , Goodhouse Joseph , Colberg-Poley Anamaris M. , Shenk Thomas
Published: November 2006

The human CMV UL37x1-encoded protein, also known as the viral mitochondria-localized inhibitor of apoptosis, traffics to the endoplasmic reticulum and mitochondria of infected cells. It induces the fragmentation of mitochondria and blocks apoptosis. We demonstrate that UL37x1 protein mobilizes Ca
2+
from the endoplasmic reticulum into the cytosol. This release is accompanied by cell rounding, cell swelling, and reorganization of the actin cytoskeleton, and these morphological changes can be substantially blocked by a Ca
2+
chelating agent. The UL37x1-mediated release of Ca
2+
from the endoplasmic reticulum likely has multiple consequences, including induction of the unfolded protein response, modulation of mitochondrial function, induction of mitochondrial fission, and protection against apoptotic stimuli.
Magnetic resonance imaging and radiographic findings of seal finger
Authors: Marjelund S. , Tikkakoski T. , Isokangas M. , Räisänen S.
Published: November 2006

Purpose: To describe the magnetic resonance imaging (MRI) and radiographic findings of five patients with seal finger.

Material and Methods: The MR images and radiographs of five patients with seal finger were retrospectively evaluated. MRI was performed on four patients in the subacute phase, and follow-up imaging was done on one of them at 5 months. One patient had MRI only at a later stage 5 years after onset. Radiographs were taken three times in the subacute phase and once at a later stage. One patient had had seal finger in another finger previously.

Results: Short-tau inversion-recovery (STIR) sequence showed extensive subcutaneous soft tissue edema in all four patients in the subacute phase and tenosynovitis of the flexion tendons in two cases. Three patients had edema in 2–3 phalanges, and effusion in the distal interphalangeal (DIP) joint was seen in one case. At the later stage, no signal pathology in soft tissues or bones was seen in STIR images. In the subacute phase, radiographs showed digital soft-tissue swelling in three patients, and one patient had a narrowed DIP joint, periarticular osteoporosis, and a periosteal reaction. At the later stage, flexion contracture of the finger was seen.

Conclusion: In addition to soft-tissue infection, seal finger causes bone marrow edema, tenosynovitis, and effusion in the interphalangeal joints visible as increased signal intensity in STIR images. Radiographs reveal periarticular osteoporosis with loss of cartilage in the subacute phase and flexion contracture at the later stage. MRI (STIR) allows more precise delineation of the inflammatory process compared to radiography.
Arrangement of fiber tracts forming probst bundle in complete callosal agenesis: report of two cases with an evaluation by diffusion tensor tractography
Authors: Utsunomiya H. , Yamashita S. , Takano K. , Okazaki M.
Published: November 2006

We report two patients with complete callosal agenesis in whom Probst bundles in both hemispheres could be depicted by diffusion tensor tractography (DTT). While one patient had no associated telencephalic anomaly other than callosal agenesis, the other had cortical dysplasia in the right frontal lobe. Although Probst bundles in the three normal hemispheres were well developed, that in the hemisphere which was affected by cortical dysplasia was small and poorly developed. DTT also showed that the fibers from the frontal pole ran more on the inner side of the Probst bundle than those from a more caudal region of the frontal lobe. Furthermore, fibers from the orbital gyri ran along the outermost side of Probst bundle. The arrangement of these fiber tracts in Probst bundle may reflect the developmental process of callosal fibers in their normal formation.
Novel diffusion-weighted magnetic resonance imaging findings in leptomeningeal carcinomatosis: a case report
Authors: Hu Y.-F. , Chang F.-C. , Hu H.-H. , Hsu L.-C.
Published: November 2006

This report presents a rare case of leptomeningeal carcinomatosis initially presenting with mental impairment and rapidly progressing to coma without any history of malignancy. In addition to highlighting the diagnostic difficulties, the linear high signal intensity along the cortex on the diffusion-weighted imaging (DWI) sequence of magnetic resonance (MR) imaging was identified accidentally. High signal change in the corresponding areas was also noted on unenhanced fluid-attenuated inversion recovery (FLAIR) MR imaging, which may be a novel method of diagnosing leptomeningeal carcinomatosis, which should be studied further.
Quantification of global left ventricular function: comparison of multidetector computed tomography and magnetic resonance imaging. a meta-analysis and review of the current literature
Authors: van der Vleuten P. A. , Willems T. P. , Götte M. J. W. , Tio R. A. , Greuter M. J. W. , Zijlstra F. , Oudkerk M.
Published: November 2006

Cardiac morbidity and mortality are closely related to cardiac volumes and global left ventricular (LV) function, expressed as left ventricular ejection fraction. Accurate assessment of these parameters is required for the prediction of prognosis in individual patients as well as in entire cohorts. The current standard of reference for left ventricular function is analysis by short-axis magnetic resonance imaging. In recent years, major extensive technological improvements have been achieved in computed tomography. The most marked development has been the introduction of the multidetector CT (MDCT), which has significantly improved temporal and spatial resolutions. In order to assess the current status of MDCT for analysis of LV function, the current available literature on this subject was reviewed. The data presented in this review indicate that the global left ventricular functional parameters measured by contemporary multi-detector row systems combined with adequate reconstruction algorithms and post-processing tools show a narrow diagnostic window and are interchangeable with those obtained by MRI.
Percutaneous transluminal cutting-balloon angioplasty for hemodialysis access stenoses resistant to conventional balloon angioplasty
Authors: Kariya S. , Tanigawa N. , Kojima H. , Komemushi A. , Shomura Y. , Shiraishi T. , Kawanaka T. , Sawada S.
Published: November 2006

Purpose: To examine the value of cutting-balloon percutaneous transluminal angioplasty (PTA) for hemodialysis access with residual stenosis after conventional balloon PTA.

Material and Methods: Angioplasty with conventional balloons was performed on 48 hemodialysis access stenoses in 28 patients. If the balloon waist still remained at the rated burst pressure, the balloon was reinflated up to three times. Fifteen of 48 stenoses had residual stenoses of more than 30% after conventional balloon PTA. In these 15 stenoses, additional cutting-balloon PTA was performed.

Results: The mean residual percent diameter stenoses before and after conventional balloon PTA were 77.6±3.4% and 48.6±8.5%, respectively. Additional cutting-balloon PTA decreased the mean residual percent diameter to 27.9±10.0%, and the cutting balloon was completely inflated without complication. In 12 patients, the 6-month primary patency rate (±SE) was 90.0% (9.5), and the 1-year primary patency rate (±SE) was 25.0% (14.8).

Conclusion: Additional cutting-balloon PTA was found useful for reducing residual stenosis.
O-(2-[18F]fluoroethyl)-l-tyrosine (18F-FET) uptake in mouse thymoma cells, and its biodistribution in mice and human volunteers
Authors: Abe K. , Hayashi K. , Sasaki M. , Koga H. , Kaneko K. , Sawamoto H. , Himuro K. , Honda H.
Published: November 2006

Purpose: To evaluate O-(2-[18F]fluoroethyl)-l-tyrosine (18F-FET) uptake in mouse malignant thymoma (EL4), and its biodistribution in mice and humans.

Material and Methods: First, 18F-FET uptake in EL4 cells was examined in an in vitro study. Second, the kinetics of 18F-FET uptake and its biodistribution were examined in mice after subcutaneous injection of EL4 cells and complete Freund's adjuvant. Finally, the kinetics of 18F-FET uptake and its biodistribution in healthy human volunteers were examined.

Results: In an in vitro study, 18F-FET was extensively incorporated in EL4 cells. In an animal study, 18F-FET accumulation in normal organs peaked within 30 min postinjection. The mean ratios of 18F-FET uptake in tumors and in inflammatory lesions to that in muscle tissue at 60 min postadministration were 2.18 (range 2.00–2.29) and 1.04 (range 0.95–1.14), respectively. In a human study, static images were taken 60 min after 18F-FET administration. Mean standardized uptake values (SUVs) of the liver (1.52, range 1.38–1.71) and kidneys (1.90, range 1.74–2.24) were nearly equal or slightly higher than that of muscle tissue (1.19, range 0.99–1.33).

Conclusion: This study demonstrates that 18F-FET accumulation in thymoma is significantly higher than in normal organs. 18F-FET could be a useful tracer for tumor imaging.
Corpus callosum hematoma secondary to isolated inferior sagittal sinus thrombosis
Authors: Erbaş G. , Oner A. Y. , Akpek S. , Tokgoz N.
Published: November 2006

A 45-year-old female was admitted with headache and vomiting. Cranial computed tomography (CT) demonstrated a callosal hematoma. Magnetic resonance imaging (MRI) showed no venous flow and thrombus replacing the inferior sagittal sinus (ISS) lumen. Under appropriate medical treatment and close follow-up she recovered quickly and, after 2 years, was doing well with corpus callosum infarcts. Isolated inferior sagittal sinus thrombosis is an extremely rare condition with only one previously reported case in the literature. Although it is very rare, isolated inferior sagittal sinus thrombosis should be considered in the differential diagnosis of non-traumatic corpus callosum hematoma.
Sex-specific suicide mortality in the South African urban context: The role of age, race, and geographical location
Authors: Burrows Stephanie , Vaez Marjan , Laflamme Lucie
Published: November 2006

Aims: This study investigates the importance of sociodemographic and geographical characteristics for suicide risks in the South African urban context. Suicide epidemiology is under-researched in low- and middle-income countries, and such knowledge is important not only for local and national policy, but also for a global understanding of the phenomenon. Methods: Sex-specific crude and adjusted odds ratios (95% confidence intervals) for suicide by age, race, and city are assessed using logistic regression. Cases aged 45+ years, classified as ``Coloured'' (a category denoting mixed racial origin), and living in Cape Town are used as reference groups. Additionally, the proportion of leading suicide methods within groups was estimated (95% confidence intervals). Results: For males, compared with each reference group, the odds of suicide are significantly higher during middle adulthood, among Asians and particularly among Whites, and among residents of all but one city. Patterns for women differ in magnitude and distribution. Suicide odds are significantly higher in all age groups, particularly 15—24 years, among Whites, and among residents of all other cities, particularly Nelson Mandela or Buffalo City. Males living in Tshwane and Black females have lower odds of suicide. The distribution of methods across age, race, and city groups varies little for males but substantially for females. Conclusions: Age, race, and city play independent roles in sex-specific suicide rates. As for high-income settings, age, race, method and city are important in sex-specific suicide in the urban South African context. Possible underlying mechanisms deserve greater attention for context-relevant preventive efforts.
Intrusion Detection for Routing Attacks in Sensor Networks
Authors: Loo Chong Eik , Ng Mun Yong , Leckie Christopher , Palaniswami Marimuthu
Published: November 2006

Security is a critical challenge for creating robust and reliable sensor networks. For example, routing attacks have the ability to disconnect a sensor network from its central base station. In this paper, we present a method for intrusion detection in wireless sensor networks. Our intrusion detection scheme uses a clustering algorithm to build a model of normal traffic behavior, and then uses this model of normal traffic to detect abnormal traffic patterns. A key advantage of our approach is that it is able to detect attacks that have not previously been seen. Moreover, our detection scheme is based on a set of traffic features that can potentially be applied to a wide range of routing attacks. In order to evaluate our intrusion detection scheme, we have extended a sensor network simulator to generate routing attacks in wireless sensor networks. We demonstrate that our intrusion detection scheme is able to achieve high detection accuracy with a low false positive rate for a variety of simulated routing attacks.
Coverage Strategies in Wireless Sensor Networks
Authors: Commuri Sesh , Watfa Mohamed K.
Published: November 2006

An energy efficient cover of a region using Wireless Sensor Networks (WSNs) is addressed in this paper. Sensor nodes in a WSN are characterized by limited power and computational capabilities, and are expected to function for extended periods of time with minimal human intervention. The life span of such networks depends on the efficient use of the available power for sensing and communication. In this paper, the coverage problem in a three dimensional space is rigorously analyzed and the minimum number of sensor nodes and their placement for complete coverage is determined. Also, given a random distribution of sensor nodes, the problem of selecting a minimum subset of sensor nodes for complete coverage is addressed. A computationally efficient algorithm is developed and implemented in a distributed fashion.

Numerical simulations show that the optimized sensor network has better energy efficiency compared to the standard random deployment of sensor nodes. It is demonstrated that the optimized WSN continues to offer better coverage of the region even when the sensor nodes start to fail over time. A localized “self healing” algorithm is implemented that wakes up the inactive neighbors of a failing sensor node. Using the “flooding algorithm” for querying the network, it is shown that the optimized WSN with integrated self healing far outweighs the performance that is obtained by standard random deployment. For the first time, a “measure of optimality” is defined that will enable the comparison of different implementations of a WSN from an energy efficiency stand point.
Tightly Clustered Outbreak of Group A Streptococcal Disease at a Long-Term Care Facility
Authors: Arnold Kathryn E. , Schweitzer Jody L. , Wallace Barbara , Salter Monique , Neeman Ruth , Hlady W. Gary , Beall Bernard
Published: November 2006

Objective.

To describe investigation of a tightly clustered outbreak of invasive group A streptococcal (GAS) disease associated with a high mortality rate in a long-term care facility (LTCF).

Design.

Cross-sectional carriage survey and epidemiologic investigation of LTCF resident and employee cohorts.

Setting.

A 104-bed community LTCF between March 1 and April 7, 2004.

Patients.

A cohort of LTCF residents with assigned beds at the time of the outbreak.

Interventions.

Reinforcement of standard infection control measures and receipt of chemoprophylaxis by GAS carriers.

Results.

Four confirmed and 2 probable GAS cases occurred between March 16 and April 1, 2004. Four case patients died. The final case occurred during the investigation, before the patient was determined to be a GAS carrier. No case occurred during the 6 months after the intervention. Disease was caused by type emm3 GAS; 16.5% of residents and 2.4% of employees carried the outbreak strain. Disease was clustered in 1 quadrant of the LTCF and associated with nonintact skin. GAS disease or carriage was associated with having frequent personal visitors.

Conclusions.

Widespread carriage of a virulent GAS strain likely resulted from inadequate infection control measures. Enhanced infection control and targeted prophylaxis for GAS carriers appeared to end the outbreak. In addition to employees, regular visitors to LTCFs should be trained in hand hygiene and infection control because of the potential for extended relationships over time, leading to interaction with multiple residents, and disease transmission in such residential settings. Specific attention to prevention of skin breaks and proper wound care may prevent disease. The occurrence of a sixth case during the investigation suggests urgency in addressing severe, large, or tightly clustered outbreaks of GAS infection in LTCFs.
Bacterial and Fungal Counts in Hospital Air: Comparative Yields for 4 Sieve Impactor Air Samplers With 2 Culture Media
Authors: Gangneux Jean-Pierre , Robert-Gangneux Florence , Gicquel Guirec , Tanquerel Jean-Jacques , Chevrier Sylviane , Poisson Magali , Aupée Martine , Guiguen Claude
Published: November 2006

We compared the yields of 4 recently developed sieve impactor air samplers that meet international standard ISO 14698-1, using 2 growth media (tryptic soy agar and malt extract agar) in real conditions of use. Several hospital sites expected to have different densities of airborne microflora were selected in 2 hospitals. The Samplair MK2, Air Ideal, and Mas-100 samplers yielded higher bacterial counts than did the SAS Super-100 device (P<.05). No significant differences in fungal counts were noted between the 4 devices. The use of malt extract agar in addition to tryptic soy agar significantly improved the fungal yield.