bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatiotemporal variability of interdecadal sea level oscillations in the North Pacific
Authors: Senjyu Tomoharu
Published: July 2006

The interdecadal variations in the North Pacific sea level field were investigated on the basis of two historical tide‐gauge data sets: long‐term sea level records spanning 100 years but spatially limited in the midlatitudes (the CL data set) and records from a wider area but with a data length of about 50 years (the HCL data set). A seesaw‐like sea level oscillation between the eastern and the western Pacific was extracted as the first mode of empirical orthogonal functions (EOF) from the CL data set. This mode shows a 22.5‐year period of variation that has continued throughout the 20th century. A similar variation was found in the HCL data set as the first mode of complex EOF (CEOF), though its dominant period was 14.5 years. This interdecadal sea level oscillation is the steric sea level change associated with the Pacific Inter‐Decadal Oscillation (PDO) in the upper ocean temperature field, because the temporal evolution and spatial structure in the interdecadal oscillation resemble those of the dominant modal pattern in the temperature field. However, this mode shows a standing wave characteristic in the midlatitudes rather than propagating, though the clockwise phase propagation around the subtropical gyre has been reported in the temperature field. Another interdecadal oscillation is found in the CEOF second mode, which was dominant in the 1960s when the first mode was relatively weak. The second mode shows a 15‐ to 16‐years period of variation and phase lags of 3–4 years at the subtropical stations relative to those in the midlatitudes.
Neutral air temperatures at 90 km and 70°N and 78°N
Authors: Hall C. M. , Aso T. , Tsutsumi M. , Höffner J. , Sigernes F. , Holdsworth D. A.
Published: July 2006

Meteor radars are employed to determine neutral air temperatures at 90 km altitude above Adventdalen, Spitsbergen (78°N, 16°E) and Ramfjordmoen, mainland Norway (70°N, 19°E). The philosophy underlying the temperature derivation including choice of appropriate pressure model and calibration against independent observations is discussed. Average annual variations at each of the two geographic locations are presented, indicating that current models overestimate the summer temperatures by as much as 20 K. The seasonal variation of variability of these temperatures, indicative of corresponding variation in planetary wave activity, is investigated, and in particular, we see that wave activity at 78°N is largely suppressed during summer and is otherwise characterized by a quasi 27‐day oscillation during late autumn and winter. The monthly average temperatures for 78°N presented here are proposed as a viable alternative to current semiempirical models.
Bistatic observations of Titan's surface with the Huygens probe radio signal
Authors: Pérez‐Ayúcar M. , Lorenz R. D. , Floury N. , Prieto‐Cerdeira R. , Lebreton J.‐P.
Published: July 2006

Huygens provided an unanticipated bistatic radio scattering experiment from Titan's surface. After a successful entry and descent on Titan, on 14 January 2005, the probe remarkably survived the landing and continued radioing from the surface to the overflying Cassini, until the orbiter set below Titan's local horizon. Here we report high‐quality measurements of the 2098 MHz (14.3 cm) postlanding radio signal, focusing on the striking variations observed in signal strength. The mechanism that creates this fading pattern is physically interpreted as multipath interference between the direct signal and the signal reflected on Titan's surface. The geophysical aspects that could bear on the signal analysis are described.
Characterization of permeability anisotropy using wavelet analysis
Authors: Neupauer Roseanna M. , Powell Kaye L. , Qi Xing , Lee Douglas H. , Villhauer Danylo A.
Published: July 2006

Wavelet analysis is an image analysis technique that can extract local information at multiple scales. Because of this capability, wavelet analysis can be used to identify dominant scales in statistically heterogeneous and anisotropic random fields. We develop and test a wavelet analysis method for identifying dominant scales and orientations in permeability fields and for identifying boundaries between regions with different dominant orientations. We evaluate three different wavelets (fully anisotropic Morlet wavelet, Mexican hat wavelet, and Cauchy wavelet) and show that the Morlet wavelet is the most effective of these three wavelets in identifying dominant orientations. We also investigate the use of several different quantitative wavelet measures in identifying dominant scales and orientations in permeability fields. The technique is demonstrated using both a synthetic data set with known characteristics and a laboratory‐collected permeability data set from Massillon sandstone.
Seasonal and latitudinal variation of atmospheric methane: A ground‐based and ship‐borne solar IR spectroscopic study
Authors: Warneke T. , Meirink J. F. , Bergamaschi P. , Grooß J.‐U. , Notholt J. , Toon G. C. , Velazco V. , Goede A. P. H. , Schrems O.
Published: July 2006

Column‐averaged volume mixing ratios of CH4 were retrieved with a precision of better than 0.5% from infrared solar absorption spectra obtained at Ny‐Alesund (Spitsbergen, 79°N) between 1997 and 2004 and during two ship cruises (54°N–34°S) on the Atlantic in 2003. The retrieval has been performed in a spectral region available to all operational FTIR (Fourier Transform InfraRed) spectrometers performing solar absorption measurements. The seasonality and the long‐term increase of the tropospheric volume‐mixing ratio, derived from the infrared measurements agree well with data from surface sampling at this site. The latitudinal variation of ship‐borne measurements between 54°N and 34°S is in agreement with inverse model simulations which are optimized vs. the global NOAA/ESRL measurements.
Atorvastatin inhibits inflammatory hypernociception
Authors: Santodomingo‐Garzón T , Cunha T M , Verri W A , Valério D A R , Parada C A , Poole S , Ferreira S H , Cunha F Q
Published: July 2006

Background and purpose:

Atorvastatin is an inhibitor of the enzyme 3‐hydroxyl‐3‐methylglutaryl coenzyme A reductase used to prevent coronary heart disease. We have studied the analgesic effect of atorvastatin in inflammatory models in which a sequential release of mediators (bradykinin, (BK), tumour necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β) and the chemokine, KC/CXCL) links the stimulus with release of directly acting hypernociceptive mediators such as prostaglandin E2 (PGE2).

Experimental approach:

The effects of orally administered atorvastatin on inflammatory mechanical hypernociception in mouse paws were evaluated with an electronic pressure‐meter. Cytokines and PGE2 were measured by ELISA and RIA.

Key results:

Treatment with atorvastatin for 3 days dose‐dependently reduced hypernociception induced by lipopolysaccharide (LPS) or that following antigen challenge in sensitized animals. Atorvastatin pre‐treatment reduced hypernociception induced by bradykinin and cytokines (TNF‐α, IL‐1β and KC), and the release of IL‐1β and PGE2 in paw skin, induced by lipopolysaccharide. The antinociceptive effect of atorvastatin on LPS‐induced hypernociception was prevented by mevalonate co‐treatment without affecting serum cholesterol levels. Hypernociception induced by PGE2 was inhibited by atorvastatin, suggesting intracellular antinociceptive mechanisms for atorvastatin. The antinociceptive effect of atorvastatin upon LPS‐ or PGE2‐induced hypernociception was prevented by non‐selective inhibitors of nitric oxide synthase (NOS) but not by selective inhibition of inducible NOS or in mice lacking this enzyme.

Conclusions and implications:

Antinociceptive effects of atorvastatin depend on inhibition of cytokines and prostanoid production and on stimulation of NO production by constitutive NOS. Our study suggests that statins may constitute a novel class of analgesic drugs.

British Journal of Pharmacology (2006) 149, 14–22. doi:10.1038/sj.bjp.0706836
Theory and experiment agree: Single-walled carbon nanotube caps grow catalyst-free with chirality preference on a SiC surface
Authors: Irle Stephan , Wang Zhi , Zheng Guishan , Morokuma Keiji , Kusunoki Michiko
Published: July 2006

High-temperature quantum chemical molecular dynamics simulations have been performed on model systems of thin SiC crystal surfaces with two graphene sheets placed on top of either C or Si face. In agreement with experiment, we find that (a) the C-face-attached graphene layer warps readily to form small diameter, stable nanocaps, suitable for further perpendicular growth of nanotubes, (b) the Si-face-attached graphene sheet does not readily wrap and forms more volatile Si-graphene bonds, and (c) C face nanocaps appear to anneal to dome-shape structures with zigzag chirality.
Structure-property relationships for three-photon absorption in stilbene-based dipolar and quadrupolar chromophores
Authors: Zhu Lingyun , Yi Yuanping , Shuai Zhigang , Brédas Jean-Luc , Beljonne David , Zojer Egbert
Published: July 2006

Based on essential-state models for three-photon absorption (3PA), we have investigated the structure-property relationships for stilbene-based dipolar and quadrupolar chromophores. The emphasis lies on the evolution of the 3PA cross section with the degree of ground-state polarization. For dipolar systems, we find a dominant role played by Δμ, which expresses the change in dipole moment between the ground state and the 3PA active excited state. Thus, the strategies usually applied to maximize the second-order polarizability β are also applicable to optimize the 3PA cross section. For quadrupolar systems, the 3PA response is dominated by contributions from channels including various low-lying two-photon allowed states, which limits the applicability of essential-state models. Optimization strategies can be proposed but vary for different ranges of ground-state polarization.
Valence band structure and band offset of 3C- and 4H-SiC studied by ballistic hole emission microscopy
Authors: Park K.-B. , Ding Y. , Pelz J. P. , Neudeck P. G. , Trunek A. J.
Published: July 2006

p -type Schottky barriers in Pt∕3C-SiC contacts have been measured using ballistic hole emission microscopy (BHEM) and estimated to be ∼0.06eV higher than identically prepared Pt∕p-type 4H-SiC contacts. This indicates the 3C-SiC valence band maximum (VBM) is ∼0.06eV below the 4H-SiC VBM, consistent with the calculated ∼0.05eV type-II valence band offset between these polytypes. We also observe no evidence of an additional VBM in 3C-SiC, which supports the proposal that the second VBM observed in BHEM spectra on 4H-SiC is a crystal-field split VBM located ∼110meV below the highest VBM.
All-atom multiscaling and new ensembles for dynamical nanoparticles
Authors: Miao Yinglong , Ortoleva Peter
Published: July 2006

Viruses and other nanoparticles have mixed microscopic/macroscopic character. Thus it is natural to develop an understanding of their dynamics via a multiscale analysis of the Liouville equation following prescriptions introduced for the study of Brownian motion. However, the internal dynamics of the atoms constituting a nanoparticle introduces conceptual and technical difficulties associated with a description involving both the atomistic and nanometer scale properties of these systems and the potential overcounting of degrees of freedom. To overcome these difficulties we introduce a “nanocanonical” ensemble method to facilitate the multiscale analysis of the all-atom Liouville equation. Our approach overcomes technical difficulties associated with the removal of secular behavior, which leads to Fokker-Planck-type equations. Our approach ensures removal of all secular behavior in the N-atom probability density and not just that of a reduced distribution. Being based on a calibrated interatomic force field, our method has the potential to yield parameter-free universal models for nanoparticle dynamics including viral migration in complex media and viral phase transitions and disassembly.
The path topology and the causal completion
Authors: Kim Do-Hyung
Published: July 2006

It is shown that the path topology of Hawking, King, and McCarthy can be extended to the causal completion of a globally hyperbolic Lorentzian manifold. The suggested topology T is defined only in terms of chronological structures and T is finer than the extended Alexandrov topology. It is also shown that a T-homeomorphism induces a conformal isomorphism and a homeomorphism in the extended Alexandrov topology.
Diffusion damping during adiabatic z-rotation pulses for NMR spectroscopy in inhomogeneous magnetic fields
Authors: Topgaard Daniel , Sakellariou Dimitris
Published: July 2006

High-resolution nuclear magnetic resonance spectra from samples located in inhomogeneous static and radio frequency magnetic fields can be obtained by applying a train of z-rotation radio frequency pulses to repeatedly refocus the inhomogeneous broadening during signal detection. z-rotation pulses based on an adiabatic double passage are effective over wide bandwidths using a limited amount of radio frequency power at the expense of being time consuming and, consequently, sensitive to motion of the spin bearing molecules. The signal damping resulting from molecular self-diffusion during the pulse was studied experimentally and using Brownian dynamics simulations. The results show that the analytical expression for diffusion damping during a double spin echo is a reasonable approximation for the signal decay during an adiabatic z-rotation pulse. Methods to alleviate the effects of diffusion are discussed.
Analysis of methane-to-methanol conversion on clean and defective Rh surfaces
Authors: Fratesi Guido , de Gironcoli Stefano
Published: July 2006

We investigate by density-functional theory simulations several elementary reactions associated to direct methane-to-methanol conversion on clean Rh(111) surfaces and on Rh adatoms on Rh(111). Energy barriers and reaction paths have been determined by the nudged elastic band method. The rate-limiting step in the process, C–O bond formation, has higher activation energy than the one for complete methane dehydrogenation. Our analysis enables us to understand the effect of defects on the reactivity and rules out Rh as candidate catalyst for methanol synthesis.
First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures
Authors: Goldman Nir , Fried Laurence E.
Published: July 2006

We have conducted ab initio molecular dynamics simulations of hydrogen fluoride (HF) at pressures of 5–66GPa along the 900K isotherm. We predict a superionic phase at 33GPa, where the fluorine atoms are fixed in a bcc lattice while the hydrogen atoms diffuse rapidly with a diffusion constant between 2×10−5 and 5×10−5cm2∕s. We find that a transformation from asymmetric to symmetric hydrogen bonding occurs in HF at 66GPa and 900K. With superionic HF we have discovered a model system where symmetric hydrogen bonding occurs at experimentally achievable conditions. Given previous results on superionic H2O [Goldman et al., Phys. Rev. Lett. 94, 217801 (2005)] and NH3 [Cavazzoni et al., Science 283, 44 (1999)], we conclude that high P, T superionic phases of electronegative element hydrides could be common.
Time-resolved broadband analysis of split ring resonators in terahertz region
Authors: Quan B. G. , Xu X. L. , Yang H. F. , Xia X. X. , Wang Q. , Wang L. , Gu C. Z. , Li C. , Li F.
Published: July 2006

Split ring resonators (SRRs) in micrometer scale were fabricated by photolithography and lift-off technologies. The transmission and dispersion characteristics of SRR were measured by terahertz spectroscopy in broadband time domain. Significant resonances at about 0.88 and 2.01THz have been observed, where two stop-band gaps are formed in the dispersion spectrum of SRR. It is suggested that these two minimum dips in the transmission spectrum are induced by dipole and magnetodipole resonances. The results show good agreement with the effective medium theory and the numerical calculation of electromagnetic propagation using finite-difference time-domain method.
Atomic layer etching of InP using a low angle forward reflected Ne neutral beam
Authors: Park S. D. , Oh C. K. , Bae J. W. , Yeom G. Y. , Kim T. W. , Song J. I. , Jang J. H.
Published: July 2006

In this study, the atomic layer etching characteristics and the etch mechanism of (100) InP as functions of Cl2 pressure and Ne neutral beam irradiation dose were investigated. When Cl2 pressure and Ne neutral beam irradiation dose were lower than the critical values of 0.4mTorr and 7.2×1015at.∕cm2cycle, respectively, the InP etch rate (Å/cycle) and the InP surface roughness varied with Cl2 pressure and Ne neutral beam irradiation dose. However, when the Cl2 pressure and Ne neutral beam irradiation dose were higher than the critical values, the InP etch rate remained as 1.47Å∕cycle, corresponding to one monolayer per cycle, and the surface roughness and the surface stoichiometry remained similar to those of InP before etching.
Infinite-order quasirelativistic density functional method based on the exact matrix quasirelativistic theory
Authors: Liu Wenjian , Peng Daoling
Published: July 2006

The exact one-electron matrix quasirelativistic theory [Kutzelnigg and Liu, J. Chem. Phys. 123, 241102 (2005)] is extended to the effective one-particle Kohn-Sham scheme of density functional theory. Several variants of the resultant theory are discussed. Although they are in principle equivalent, consideration of computational efficiency strongly favors the one (F¯+) in which the effective potential remains untransformed. Further combined with the atomic approximation for the matrix X relating the small and large components of the Dirac spinors as well as a simple ansatz for correcting the two-electron picture change errors, a very elegant, accurate, and efficient infinite-order quasirelativistic approach is obtained, which is far simpler than all existing quasirelativistic theories and must hence be regarded as a breakthrough in relativistic quantum chemistry. In passing, it is also shown that the Dirac-Kohn-Sham scheme can be made as efficient as two-component approaches without compromising the accuracy. To demonstrate the performance of the new methods, atomic calculations on Hg and E117 are first carried out. The spectroscopic constants (bond length, vibrational frequency, and dissociation energy) of E1172 are then reported. All the results are in excellent agreement with those of the Dirac-Kohn-Sham calculations.
Second harmonic generation of continuous wave ultraviolet light and production of β-BaB2O4 optical waveguides
Authors: Degl’Innocenti R. , Guarino A. , Poberaj G. , Günter P.
Published: July 2006

We report on the generation of continuous-wave (cw) ultraviolet (UV) laser light at λ=278nm by optical frequency doubling of visible light in β-BaB2O4 waveguides. Ridge-type waveguides were produced by He+ implantation, photolithography masking, and plasma etching. The final waveguides have core dimension of a few μm2 and show transmission losses of 5dB∕cm at 532nm and less than 10dB∕cm at 266nm. In our first experiments, a second harmonic power of 24μW has been generated at 278nm in an 8mm long waveguide pumped by 153mW at 556nm.
Intrinsic current-voltage properties of nanowires with four-probe scanning tunneling microscopy: A conductance transition of ZnO nanowire
Authors: Lin X. , He X. B. , Yang T. Z. , Guo W. , Shi D. X. , Gao H.-J. , Ma D. D. D. , Lee S. T. , Liu F. , Xie X. C.
Published: July 2006

We report intrinsic current-voltage properties of ZnO nanowire measured by a four-tip scanning tunneling microscopy (F-STM). It is found that after bending the nanowire with the F-STM the conductance is reduced by about five orders of magnitude. The cathodoluminescent spectra indicate that the ZnO nanowires contain a sizable amount of defects in the surface region, responsible for their conduction. It is suggested that the observed huge conductance changes are caused by the shifting of the surface defect states in the ZnO nanowires in response to the applied surface strain.
Formation of SrTiO3 nanocrystals in amorphous Lu2O3 high-k gate dielectric for floating gate memory application
Authors: Yuan C. L. , Darmawan P. , Setiawan Y. , Lee P. S. , Ma J.
Published: July 2006

We have developed a method based upon pulsed laser deposition to produce SrTiO3 nanocrystals embedded in amorphous Lu2O3 high-k dielectric. The high resolution transmission electron microscopy study revealed the complete isolation of SrTiO3 nanocrystals embedded in Lu2O3 matrix with 4nm diameter and well distributed with an area density estimated to be about 8×1011cm−2. A pronounced capacitance-voltage hysteresis is observed with a memory window of ∼1.5V under the 6V programming. In addition, the retention characteristics are tested to be robust.
Role of delocalized charges in the pyroelectric effect
Authors: Evans D. R. , Basun S. A. , Cook G. , Meltzer R. S.
Published: July 2006

The temperature dependence of the pyroelectric effect is investigated. An increase in dark conductivity resulting from either trap depopulation or proton migration is shown to suppress the pyroelectric-generated high voltage. Electrically shorting crystal z surfaces coated with a transparent conductive layer is shown to be effective in eliminating the breakdown of the surface charge in air and thus provides a means to study weak thermoluminescence in pyroelectric crystals. In addition, a new method to measure proton migration and dark conductivity is proposed; a direct correlation between the emitted light intensity resulting from ionization of air and the pyroelectric current is observed.
Metal precipitation at grain boundaries in silicon: Dependence on grain boundary character and dislocation decoration
Authors: Buonassisi T. , Istratov A. A. , Pickett M. D. , Marcus M. A. , Ciszek T. F. , Weber E. R.
Published: July 2006

Synchrotron-based analytical microprobe techniques, electron backscatter diffraction, and defect etching are combined to determine the dependence of metal silicide precipitate formation on grain boundary character and microstructure in multicrystalline silicon (mc-Si). Metal silicide precipitate decoration is observed to increase with decreasing atomic coincidence within the grain boundary plane (increasing Σ values). A few low-Σ boundaries contain anomalously high metal precipitate concentrations, concomitant with heavy dislocation decoration. These results provide direct experimental evidence that the degree of interaction between metals and structural defects in mc-Si can vary as a function of microstructure, with implications for mc-Si device performance and processing.
Multipeak solitons and nonlinear modulated solutions in plasma under relativistic electromagnetic field
Authors: Xie Bai-Song , Du Shu-Cheng
Published: July 2006

Multipeak solitons and nonlinear modulated solutions in plasma under relativistic electromagnetic field are investigated. The incident electromagnetic field is allowed to have a nonzero initial constant amplitude. Some interesting numerical results are obtained including multipeak laser pulse and a single or/and multipeak plasma wave structure. It is also found that there exists a combination of soliton-like and oscillation waves for the plasma electrostatic field.
Unpinned metal gate/high-κ GaAs capacitors: Fabrication and characterization
Authors: Shahrjerdi Davood , Oye Michael M. , Holmes Archie L. , Banerjee Sanjay K.
Published: July 2006

Fabrication of GaAs metal-oxide-semiconductor capacitors (MOSCAPs) with an unpinned interface is reported. The MOSCAP structure consists of a few monolayers of germanium grown in a molecular beam epitaxy (MBE) system in order to terminate an MBE-grown silicon-doped (100) GaAs layer. An ex situ HfO2 high-κ dielectric with an equivalent oxide thickness of 12Å was deposited by using a dc magnetron sputtering system. A midgap interface state density (Dit) of 5×1011eV−1cm−2 was measured using the high-frequency conductance technique. A rapid thermal annealing study was performed in order to examine the integrity of the gate stack at different temperatures. In addition, a forming gas anneal at 400°C appears to significantly reduce the midgap Dit revealed by probing the frequency dispersion behavior of the MOSCAPs.
Field emission of one-dimensional micro- and nanostructures of zinc oxide
Authors: Yang Y. H. , Wang B. , Xu N. S. , Yang G. W.
Published: July 2006

A variety of one-dimensional (1D) micro- and nanostructures of zinc oxide (ZnO) were self-assembled on amorphous carbons using thermal chemical vapor transport and condensation without any metal catalysts. The low turn-on electronic field and the higher current density were achieved on these 1D ZnO micro- and nanostructural emitters. It was found that the geometry of the micro- and nanostructural emitters plays a crucial role in the field emission of ZnO.
Tritiation of amorphous and crystalline silicon using T2 gas
Authors: Liu Baojun , Chen Kevin P. , Kherani Nazir P. , Kosteski Tome , Costea Stefan , Zukotynski Stefan , Antoniazzi Armando B.
Published: July 2006

Incorporation of tritium in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) at 250°C using tritium (T2) gas at pressures of up to 120atm is reported. The tritium is stored in a surface layer which is approximately 150 and 10nm for a-Si:H and c-Si, respectively. The concentration of tritium occluded in planar and textured c-Si is linearly dependent on the total surface area. The tritium is stable and the dominant tritium evolution occurs at temperatures above 300°C. The concentration of tritium locked in a-Si:H and c-Si was 20 and 4at.%, respectively. Self-catalysis appears to be important in the tritiation process.
Density peaking and turbulent pinch in DIII-D discharges
Authors: Estrada-Mila C. , Candy J. , Waltz R. E.
Published: July 2006

A study of density peaking and particle flow in low confinement (L-mode) DIII-D discharges [G. R. McKee, C. C. Petty, R. E. Waltz et al., Nucl. Fusion 41, 1235 (2001)], using global gyrokinetic simulations, is presented. It is found that under experimental conditions, in particular when realistic collisionality is included, a turbulent pinch driven by electron temperature and density gradients can occur.
The appearance of accessory growth centres in adult whiting Merlangius merlangus otoliths
Authors: Tomás J.
Published: July 2006

The appearance of accessory growth centres (AGCs) in the otoliths of adult whiting Merlangius merlangus reared in the laboratory for 2 years is reported. The causes and implications of AGCs appearing in otoliths of adult fish are discussed.
Ascorbic acid reduces the effects of hypoxia on the Amazon fish tambaqui
Authors: Chagas E. C. , Val A. L.
Published: July 2006

Juveniles of tambaqui Colossoma macropomum were fed diets containing 0, 100 and 500 mg of L‐ascorbic acid (AA) per kg of feed for 10 weeks. Subsequently exposed to acute hypoxia for 6 h, the animals fed with high levels of AA exhibited no changes in blood pH and plasma glucose and reduced levels of lipid peroxidation. Thus, AA‐enriched diets reduce the effects of hypoxia insult on juveniles of C. macropomum.
Morphological development and allometric growth patterns in the juvenile seahorseHippocampus kudaBleeker
Authors: Choo C. K. , Liew H. C.
Published: July 2006

The morphological development and allometric growth patterns in the juvenile spotted seahorseHippocampus kudawere studied under hatchery rearing conditions. Newborn spotted seahorses [mean ±s.d. standard length (LS) 9·33 ± 0·79 mm] were raised till the age of 124 days (119·35 ± 6·04 mm). Growth was characterized by three stages with two inflexion points occurring at day 21 and 76. The mean growth rates in the first, second and third stages were 0·68, 1·16 and 0·71 mm day−1, respectively. The growth rate was most rapid in the second stage and was probably influenced by a behavioural shift from pelagic to benthic form. The mass (M) andLSrelationship was exponential (M= 7·14 × 10−6LS2·76), but the slope,b= 2·76, reflected negative allometric growth. Sexes could be distinguished atc.110 days, and the sex ratio was unbiased. TheLSin males and females did not differ significantly. Morphological stageing series is proposed, which dividesH. kudajuvenile development into eight stages based on the development of coronet, cheek and eye spines, keel and pigmentation. The morphometric ratios for all the body parts, except trunk length, showed considerable changes at a transition point occurring atc.25 mmLS. The high proportional growth in head length, head depth, pectoral fin base length, dorsal fin base length, snout length, snout depth and eye diameter at the initial stages, and the abrupt increase in tail length only after the first 2 weeks, possibly reflect development priorities during early development where important organs are being developed first for the enhancement of juvenile survival.
Blood‐chemistry indicators of nutritional status in juvenile salmonids
Authors: Congleton J. L. , Wagner T.
Published: July 2006

Three experiments were performed to determine the effects of food deprivation (21–35 days at 10–12° C) on selected blood‐chemistry variables in juvenile salmonids. The experimental groups were laboratory‐reared rainbow trout Oncorhynchus mykiss (RBT), laboratory‐reared Chinook salmon Oncorhynchus tshawytscha (LCS) and hatchery‐reared, actively migrating Chinook salmon (MCS). After fasting, RBT and LCS were refed for 10 days. In fasted fishes, plasma alkaline phosphatase (ALP) activities decreased relatively rapidly, differing significantly (P ≤ 0·05) from activities in fed control fishes after 1–2 weeks. Total protein (for all groups) and total cholesterol (for RBT and MCS) decreased relative to fed controls after 2–3 weeks, and total calcium (for RBT and MCS) after 3–4 weeks. Plasma ALP activities recovered after 10 days refeeding, but total protein, cholesterol and calcium concentrations did not. Triglyceride concentrations were highly variable and responded significantly to fasting only in the trial with RBT. Concentrations of some variables decreased (glucose and phosphorus) or increased (total magnesium) relative to control values during the initial days or weeks of fasting and then stabilized at new levels. Activities of four metabolic enzymes of intracellular origin (alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and creatine kinase) did not differ significantly in the plasma of fed and fasted fishes.
Sound production in two species of damselfishes (Pomacentridae): Plectroglyphidodon lacrymatus and Dascyllus aruanus
Authors: Parmentier E. , Vandewalle P. , Frédérich B. , Fine M. L.
Published: July 2006

Agonistic sounds of two pomacentrid species, Plectroglyphidodon lacrymatus and Dascyllus aruanus, were recorded in captivity. Plectroglyphidodon lacrymatus produced trains of 2–5 pops, each composed of 18–25 cycles, with an average duration of 56 ms; most energy ranged from c. 100 to 1000 Hz. Dascyllus aruanus produced pops and chirps. Pops were generally composed of a single pulse, with 2–14 peaks and an average duration of 6·7 ms. Pops contained energy >4 kHz, and peak frequency ranged from 680 to 1300 Hz. Chirps consisted of trains of 12–42 short pulses of three to six cycles, with durations varying from 0·6 to 1·27 ms; peak frequency varied from 3400 to 4100 Hz. Sound production in P. lacrymatus suggested that pomacentrids are derived from an ancestral taxon capable of sound production and that this capacity is a synapomorphy for the family. Although in the Pomacentridae, pops are typically composed of a single pulse, which is longer and higher pitched than chirps composed of a series of shorter pulses, D. aruanus chirps were higher pitched than its pops. Thus, acoustic variation in the genus Dascyllus is probably not more restricted than in the Pomacentridae.
Resource partitioning in a tropical stream fish assemblage
Authors: Herder F. , Freyhof J.
Published: July 2006

An assemblage of freshwater fishes inhabiting a medium‐sized stream in tropical central Vietnam was investigated with respect to spatial and trophic distribution. Point‐abundance sampling, gut content analysis and relative intestine length yielded interspecific differences in niche expression. Conspecific juvenile and adult habitat and feeding niches were also distinct. Niche differences arose mainly from differences in current velocity, substrata and foraging preferences. Extreme specializations, such as selective feeding on hard incustrations of cyanobacteria by adult Annamia normani, were present. The low niche overlap suggests that this tropical fish assemblage is structured by competitive interactions.
Depth and movement behaviour of the Pacific sleeper shark in the north‐east Pacific Ocean
Authors: Hulbert L. B. , Sigler M. F. , Lunsford C. R.
Published: July 2006

Satellite‐linked radio telemetry was used to study the geographic movements and vertical movement behaviour of the Pacific sleeper shark Somniosus pacificus. The fish were tagged near Steller sea lion Eumetopias jubatus rookeries in the Gulf of Alaska during periods when Steller sea lions pups were most vulnerable to predation; when Steller sea lion pups first enter the water (July to August) and when Steller sea lion pups are weaned (April to May). Final locations recovered from most Pacific sleeper sharks (76%) were within 100 km of release locations, 16% were within 100–250 km and 8% were within 250–500 km. The most striking behavioural feature was their extensive, nearly continuous vertical movements. Median daily depth range was 184 m; the most time (61%) was spent between 150 and 450 m, but ascents above 100 m were common (58% of days). Median vertical movement rate was 6 km day−1 and steady. The longest period of continuous vertical movement (> 60 m h−1) was 330 h. Systematic vertical oscillations were most common (60%), followed by diel vertical migrations (25%) and irregular vertical movements (15%). The Pacific sleeper sharks travelled below the photic zone during the day and approached the surface at night. Pacific sleeper sharks appear to employ a stealth and ambush hunting strategy that incorporates slow vertical oscillations to search for prey, and cryptic colouration and cover of darkness to avoid detection by potential prey. The depth and geographic range of Pacific sleeper shark and Steller sea lions overlap near four important Steller sea lion rookeries in the northern Gulf of Alaska, so the potential exists for predation to occur. None of the tissues in the stomachs of the 198 Pacific sleeper sharks collected during a companion diet study, however, were identified as Steller sea lion.
Characterization of Arabidopsis thaliana–Fusarium graminearum interactions and identification of variation in resistance among ecotypes
Authors: CHEN XINWEI , STEED ANDREW , HARDEN CLARE , NICHOLSON PAUL
Published: July 2006

Fusarium graminearum causes fusarium head blight (FHB) of wheat and other cereals. Resistance of wheat to FHB is incomplete and the defence mechanisms involved are poorly understood owing to the complex genome and long life cycle of the host. A robust and reproducible bioassay system was established for the study of interactions between F. graminearum and Arabidopsis by wound inoculation of detached leaves embedded in agar medium. Amendment of the inoculum with deoxynivalenol enhanced symptom development and conidial production. Colonization of leaf tissue was by both inter‐ and intracellular growth and extensive cell death was observed ahead of advancing hyphae indicating the presence of phytotoxic compounds or host‐initiated programmed cell death. Expression of defence response genes associated with jasmonic acid/ethylene and salicylic acid pathways indicated that both pathways were activated in response to F. graminearum with expression of the jasmonic acid/ethylene pathways being more enhanced than that of the salicylic acid pathway, as expected for a necrotrophic pathogen. A large variation in resistance among Arabidopsis ecotypes was revealed. The ecotype Col‐0 was significantly more resistant than Ler using both the detached leaf and a detached flower assay. Foliar resistance was shown to be controlled largely by a single genetic factor on chromosome 4 near the RFLP marker O6455. The detached leaf assay described herein provides a means to enable fundamental studies on the defence mechanisms of Arabidopsis in response to F. graminearum.
Barriers to the recovery of aquatic insect communities in urban streams
Authors: BLAKELY TANYA J. , HARDING JON S. , MCINTOSH ANGUS R. , WINTERBOURN MICHAEL J.
Published: July 2006

1. Worldwide, increasing numbers of stream restoration projects are being initiated to rehabilitate waterways modified by urbanisation. However, many of these projects have limited success in restoring stream communities. Prompted by this, we investigated previously unrecognised barriers to aquatic insect colonisation in urban streams.

2. To investigate whether the availability of suitable substrata for oviposition limited the longitudinal distribution of caddisflies, large boulders were added to the upstream reaches of one stream. Prior to the addition, more egg masses were observed downstream and this longitudinal pattern persisted subsequently.

3. Malaise trapping revealed that adult caddisfly diversity and abundance was greater downstream than upstream. Furthermore, in a previous study the authors found larval caddisflies reflected the longitudinal distribution of adults.

4. The only obvious potential obstructions between reaches were roads beneath which the stream flowed through culverted crossings. Malaise trapping was used to examine the effect of road culverts and bridges on caddisfly dispersal. Numbers of caddisflies caught declined upstream and about 2.5 × more individuals were taken in traps immediately below than above five culverts.

4. Bridges, which had a more open structure than culverts, had no significant effect on the size of catches made above and below them.

5. Road culverts could act as partial barriers to upstream flight, with consequences for larval recruitment in urban streams. We recommend that urban planners and designers of restoration projects consider possible synergistic effects of poor oviposition habitat and barriers to aquatic insect dispersal, which may be critical for the colonisation of urban headwater streams and for the maintenance of stream insect populations.
Modeling dynamics of stable carbon isotopic exchange between a boreal forest ecosystem and the atmosphere
Authors: CHEN BAOZHANG , CHEN JING M. , HUANG LIN , TANS PIETER P.
Published: July 2006

Stable isotopes of CO2 contain unique information on the biological and physical processes that exchange CO2 between terrestrial ecosystems and the atmosphere. In this study, we developed an integrated modeling system to simulate dynamics of stable carbon isotope of CO2, as well as moisture, energy, and momentum, between a boreal forest ecosystem and the atmosphere, as well as their transport/mixing processes through the convective boundary layer (CBL), using remotely sensed surface parameters to characterize the surface heterogeneity. It has the following characteristics: (i) it accounts for the influences of the CBL turbulent mixing and entrainment of the air aloft; (ii) it scales individual leaf‐level photosynthetic discrimination up to the whole canopy (Δcanopy) through the separation of sunlit and shaded leaf groups; (iii) it has the capacity to examine the detailed interrelationships among plant water‐use efficiency, isotope discrimination, and vapor pressure deficit; and (iv) it has the potential to investigate how an ecosystem discriminates against 13C at various time and spatial scales. The monthly mean isotopic signatures of ecosystem respiration (i.e. δ13CR) used for isotope flux calculation are retrieved from the nighttime flask data from the intensive campaigns (1998–2000) at 20 m level on Fraserdale tower, and the data from the growing season in 1999 are used for model validation. Both the simulated CO2 mixing ratio and δ13C of CO2 at the 20 m level agreed with the measurements well in different phases of the growing season. On a diurnal basis, the greatest photosynthetic discrimination at canopy level (i.e. Δcanopy) occurred early morning and late afternoon with a varying range of 10–26‰. The diurnal variability of Δcanopy was also associated with the phases of growing season and meteorological variables. The annual mean Δcanopy in 1999 was computed to be 19.58‰. The monthly averages of Δcanopy varied between 18.55‰ and 20.84‰ with a seasonal peak during the middle growing season. Because of the strong opposing influences of respired and photosynthetic fluxes on forest air (both CO2 and 13CO2) on both the diurnal and seasonal time scales, CO2 was consistently enriched with the heavier 13C isotope (less negative δ13C) from July to October and depleted during the remaining months, whereas on a diurnal basis, CO2 was enriched with the heavier 13C in the late afternoon and depleted in early morning. For the year 1999, the model results reveal that the boreal ecosystem in the vicinity of Fraserdale tower was a small sink with net uptake of 29.07 g 12C m−2 yr−1 and 0.34 g 13C m−2 yr−1.
Hypoandrogenaemia is associated with subclinical hypothyroidism in men
Authors: Kumar Anand , Chaturvedi P. K. , Mohanty Bidut P.
Published: July 2006

Hypothyroidism has been shown to be associated with a reduction in serum testosterone level in males. This reduction in testosterone is reversible by thyroxine replacement therapy. However, to the best of our knowledge, it is not yet known, whether a similar reduction in serum testosterone level is observed in subclinically hypothyroid males [thyroid‐stimulating hormone (TSH) < 10 mIU/L] in whom the benefits of thyroxine replacement therapy are still controversial. Our goal was to investigate the putative connections between subclinical hypothyroidism and the circulating levels of gonadotrophins and gonadal steroids in males (mean age ± SEM, 34.67 ± 1.52 years; ranging from 20 to 54 years). The serum samples from patients showing normal euthyroid and subclinical hypothyroid profiles (TSH < 10 mIU/L) were further analysed for the levels of luteinizing hormone, follicle‐stimulating hormone, prolactin, testosterone, sex hormone‐binding globulin, progesterone and oestradiol. Subclinical hypothyroidism was associated with a decrease in the levels of serum testosterone and its precursor progesterone. The data suggest that serum testosterone declines because of the non‐availability of its precursor progesterone. The level of oestradiol was similar in both the groups, suggesting a greater conversion rate of testosterone to oestradiol in subclinically hypothyroid males, in order to maintain the oestradiol levels. Prolactin levels were slightly but significantly increased in subclinical hypothyroidism. To the best of our information this is a novel report, which shows a direct association between subclinical hypothyroidism and hypoandrogenaemia. Testosterone deficiency and its symptoms should be kept in view while managing subclinical hypothyroidism in male patients. Further studies are needed in order to reveal the physiological and molecular mechanisms leading to hypoandrogenaemia in subclinical hypothyroidism (TSH < 10 mIU/L).
Movement trajectories and habitat partitioning of small mammals in logged and unlogged rain forests on Borneo
Authors: WELLS KONSTANS , PFEIFFER MARTIN , LAKIM MAKLARIN B. , KALKO ELISABETH K. V.
Published: July 2006

Non‐volant animals in tropical rain forests differ in their ability to exploit the habitat above the forest floor and also in their response to habitat variability. It is predicted that specific movement trajectories are determined both by intrinsic factors such as ecological specialization, morphology and body size and by structural features of the surrounding habitat such as undergrowth and availability of supportive structures.

We applied spool‐and‐line tracking in order to describe movement trajectories and habitat segregation of eight species of small mammals from an assemblage of Muridae, Tupaiidae and Sciuridae in the rain forest of Borneo where we followed a total of 13 525 m path. We also analysed specific changes in the movement patterns of the small mammals in relation to habitat stratification between logged and unlogged forests. Variables related to climbing activity of the tracked species as well as the supportive structures of the vegetation and undergrowth density were measured along their tracks.

Movement patterns of the small mammals differed significantly between species. Most similarities were found in congeneric species that converged strongly in body size and morphology. All species were affected in their movement patterns by the altered forest structure in logged forests with most differences found in Leopoldamys sabanus. However, the large proportions of short step lengths found in all species for both forest types and similar path tortuosity suggest that the main movement strategies of the small mammals were not influenced by logging but comprised generally a response to the heterogeneous habitat as opposed to random movement strategies predicted for homogeneous environments.

Overall shifts in microhabitat use showed no coherent trend among species. Multivariate (principal component) analysis revealed contrasting trends for convergent species, in particular for Maxomys rajah and M. surifer as well as for Tupaia longipes and T. tana, suggesting that each species was uniquely affected in its movement trajectories by a multiple set of environmental and intrinsic features.
Collapse of Asian vulture populations: risk of mortality from residues of the veterinary drug diclofenac in carcasses of treated cattle
Authors: GREEN RHYS E. , TAGGART MARK A. , DAS DEVOJIT , PAIN DEBORAH J. , SASHI KUMAR C. , CUNNINGHAM ANDREW A. , CUTHBERT RICHARD
Published: July 2006

The populations of three species of South Asian vultures (Gyps bengalensis, Gyps indicus and Gyps tenuirostris) have declined rapidly within the last decade and all are now critically endangered. Veterinary use of the non‐steroidal anti‐inflammatory drug diclofenac appears to be a major cause of the declines. Vultures are likely to be exposed to the drug when they feed on carcasses of livestock that were treated with diclofenac before death.

We measured the concentration of diclofenac in the tissues of treated Indian humped and European cattle (Bos indicus and Bos taurus) in relation to the interval between dosing and death. We used a dose–response model to assess the risk posed to wild vultures if they feed on carcasses of treated livestock.

Diclofenac concentrations in fat, intestine, kidney and liver were considerably higher than those in muscle, but concentrations in the first four tissues initially depleted more rapidly (half‐life 6–8 h) with time since the last injection of the drug, compared with muscle (half‐life 15 h). Depletion rates became much slower in all tissues 25–98 h after the last injection.

Diclofenac concentration, averaged across the carcass, was enough to cause appreciable mortality (> 10% of birds per meal) if oriental white‐backed vultures G. bengalensis were to take a large meal from the carcass of an animal that was given its last dose of the drug within a day or two before death. Vultures that feed selectively on tissues with high concentrations of the drug, such as kidney, liver and intestine, would be exposed to a higher risk and for longer after dosing.

Synthesis and applications. The tissues of cattle treated with diclofenac are a hazard to wild vultures that feed on an animal that dies within a few days after treatment. Intestine, kidney and liver have the highest diclofenac concentrations, but the concentration averaged across all the edible tissues of the carcass is also hazardous. Withdrawal of diclofenac from veterinary use on animals whose carcasses may become available to scavenging vultures is recommended. In ex situ and in situ conservation projects, vultures should be fed on carcasses of animals that are known not to have been treated with diclofenac in the week before death.