bluuebunny/crossref_metadata_2025 huggingface dataset:
Generic error model for calibration and uncertainty estimation of hydrological models
Authors: Götzinger Jens , Bárdossy András
Published: November 2008

Because of the necessary simplification of the complex natural processes and the limited availability of observations, model simulations are always uncertain and this uncertainty should be quantified. In this contribution, the model error is quantified using a combined procedure. For the uncertainty of discharge due to meteorological input, a stochastic simulation method is used. To quantify the effect of process representation and parameterization, a sensitivity analysis is carried out. It is assumed that the model error due to process uncertainty is proportional to the sensitivity. The final model error variance can thus be calculated from the stochastic errors and the process sensitivities. The coefficients used for the quantification are estimated simultaneously with the model parameters. The methodology presented produces error series that are normally distributed and that represent the varying importance of different processes in time. This uncertainty time series can be used as a weighting factor to normalize the model residuals during calibration so that the assumptions of least squares optimization are fulfilled. Calibration and uncertainty estimation are demonstrated with an example application of a distributed Hydrological Bureau Waterbalance (HBV) model of three watersheds in the Neckar basin in southwest Germany. The model residual distributions are presented and compared to a standard calibration method. Further, it is shown that the new methodology leads to more realistic confidence intervals for model simulations. Although applied to the HBV model as an example, the method is general and can be applied to any model and also in conjunction with other uncertainty estimation techniques.
Resolving Stressful Relationships in Prehistory: Macroscopic and Histological Indicators of Growth Disruption in Subadult Long Bones
Authors: Robbins Gwen
Published: November 2008

This poster provides a set of quadratic formulas for predicting body mass using the femoral midshaft in subadult skeletons. This age-structured method has lower %SEE and is more efficient than estimating body mass from the bone ends (Ruff, 2007). This poster demonstrates that estimates of body mass in subadult skeletons can be compared with stature to look at biocultural stress levels in prehistoric populations. Finally a qualitative assessment of histological markers of growth disruption is provided for individuals that demonstrate low bone mass for body size.
Kardiologische Diagnostik mit Hilfe der Farb-Doppler-Echokardiographie
Authors: Redel D. A. , Wippermann C. F. , Lu J.-H. , Knyphausen E. G. von
Published: November 2008

Mit der Farb-Doppler-Echokardiographie steht eine neue nicht-invasive Methode zur Verfügung, die für die kardiologische Diagnostik von Herzfehlern neue Per-spektiven hinsichtlich diagnostischer Zuverlässigkeit, Anschaulichkeit der Darstellung und Erfassung komplexer kardialer Blutströmungsverhältnisse eroffnet. Diese Methode kann ferner dazu dienen, bereits etablierte Verfahren wie die CW-Doppler-Methode in der Anwendung zu optimieren und damit auch für die quantitative Druckmessung bei Kindern verfügbar zu machen. Schließlich wird die Quantifizierbarkeit von Regurgitationen und Shuntläsionen erheblich verbessert werden durch die Einführung des Digitalen Flow-Mappings, mit dem in absehbarer Zeit zu rechnen ist.
Azido-derivatized compounds as IR probes of local electrostatic environment: Theoretical studies
Authors: Choi Jun-Ho , Oh Kwang-Im , Cho Minhaeng
Published: November 2008

A variety of spectroscopic probe molecules have been used to study the local electrostatic environment in proteins. Particularly, a few IR probes such as nitrile- and thiocyanate-derivatized amino acids were found to be quite useful not just because they are small but also because their IR absorption frequencies strongly depend on the strengths of hydrogen bonds with the surrounding protic solvent molecules. Recently, we experimentally demonstrated that azido-derivatized alanine is an excellent IR probe for studying structural change in protein in solution. The asymmetric stretching mode frequency of N3-group becomes blueshifted when it is dissolved in water. Such a blueshifting behavior upon hydrogen-bonding interaction with protic solvent molecules was commonly found in other IR probes containing a triple bond such as CN and SCN groups. In this paper, theoretical descriptions on the solvatochromic frequency shift and fluctuation of the azido stretch frequency are presented by carrying out ab initio calculations and both classical and quantum mechanical/molecular mechanical dynamics simulation studies for azidomethane and azidoalanine dipeptide dissolved in water. Two different methods developed here are based on the distributed multipole interaction models, and they are shown to be useful to describe site-specific hydrogen-bonding interaction-induced red- or blueshift of the azido stretch frequency. To test the validity of thus obtained interpolation formula, numerically simulated IR spectra of azidomethane and azidoalanine dipeptide in water are directly compared with experimental results. We anticipate that the present theoretical approaches will be of use in connecting experimentally measured azido stretch frequency to conformational change in protein containing this azido-derivatized alanine residue.
A model for hybrid simulations of molecular dynamics and computational fluid dynamics
Authors: Yasuda Shugo , Yamamoto Ryoichi
Published: November 2008

We develop a method for multiscale hybrid simulations of molecular dynamics (MD) and computational fluid dynamics (CFD). In this method, the usual lattice-mesh based simulations are applied for the CFD level, but each lattice is associated with a small MD cell that generates a “local stress” according to a “local flow field” given from CFD instead of using any constitutive functions at the CFD level. We carried out hybrid simulations for some elemental flow problems involving simple Lennard-Jones liquids and compared the results with those obtained by usual CFD with a Newtonian constitutive relation in order to examine the validity of our hybrid simulation method. It is demonstrated that our hybrid simulations successfully reproduce the correct flow behavior obtained from usual CFD as long as the mesh size Δx and the time step Δt of CFD are not too large compared to the system size lMD and the sampling duration tMD of MD simulations performed at each time step of the CFD. Otherwise, the simulations are affected by large fluctuations due to poor statistical averages taken in the MD part. Properties of the fluctuations are analyzed in detail.
Interfacial spin order in exchange biased systems
Authors: Fernandez-Outon L. E. , Vallejo-Fernandez G. , Manzoor Sadia , Hillebrands B. , O’Grady K.
Published: November 2008

The phenomenon of exchange bias in which a ferromagnet is grown in intimate contact with an antiferromagnet leads to a shifted hysteresis loop. All analytical theories developed to explain this effect predict values of the shift of the loop that are too large, often by an order of magnitude. In many numerical models an interface exchange coupling constant C∗ is introduced to account for these discrepancies. In this work we describe a series of experiments, which reveals the temperature and field dependence of this interfacial spin order that account for the weakened coupling between the layers. We also show that this order has a marked temperature dependence at temperatures down to ∼50 K. At temperatures below 50 K we observe a sudden marked increase in the observed exchange bias of up to a factor of 2, which we attribute to a spontaneous spin ordering of the interfacial spins analogous to that which occurs in spin-glass systems.
Influence of high-temperature GaN annealed surface on the electrical properties of Ni/GaN Schottky contacts
Authors: Iucolano Ferdinando , Roccaforte Fabrizio , Giannazzo Filippo , Raineri Vito
Published: November 2008

In this work, the electrical properties of Ni/GaN Schottky contacts formed on high-temperature annealed (1100–1200 °C) GaN surfaces were studied. Although the morphology of the GaN surface was not changing after annealing, a worsening of the electrical behavior of the Schottky contact occurred, with a reduction in the barrier height and an increase in the leakage current. Moreover, a different temperature dependence of the reverse electrical characteristics of the Schottky diodes was observed. In particular, for the sample annealed at 1150 °C for 5 min, one-dimensional variable-range-hopping conduction was one of the dominant carrier transport mechanisms. The presence of a high density of interface states was indicated as a possible reason of this electrical behavior.
Magnetic field effect for cellulose nanofiber alignment
Authors: Kim Jaehwan , Chen Yi , Kang Kwang-Sun , Park Young-Bin , Schwartz Mark
Published: November 2008

Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the exposure time of the magnetic field increased.
Charge injection and charge separation as revealed by dynamic space charge measurement in poly(propylene-ethylene) copolymer films
Authors: Zheng Feihu , Teyssedre Gilbert , Laurent Christian , Thomas Cécilien , Hoyos Mario , Zhang Yewen
Published: November 2008

The time resolved fast pulsed electroacoustic method is used to investigate the space charge characteristics in an additive-free poly(propylene-ethylene) copolymer in film form. The 190 μm thick films, sandwiched by aluminum (at the lower electrode) and semiconducting material (at the upper electrode), were submitted to dc and low frequency ac stress for various durations at various temperatures. The results show that under dc stress, homocharges accumulate near the lower electrodes and heterocharge near the upper electrode at 25 °C whereas at 50 °C, besides the similar space charge behavior as at 25 °C in the vicinity of the electrodes, a region of symmetric separation of charges of opposite polarity is detected in the bulk. In addition, the time for the symmetric separation emergence under high voltage application depends on the field intensity, being shorter for higher field. Similar charging characteristics were also found at 50 °C under low frequency (5 mHz) square 50 kV/mm rms stress, with surprisingly periodical feature, while only injected charge was observed at 0.1 Hz square rms 50 kV/mm stress. Combining dc data with ac data, it is shown that the space charge build up results from two contributing processes: the space charge formation adjacent to the electrode is due to electronic carriers injection and drift, whereas the symmetric space charge in the bulk shows ionic transport characteristics, which can be well fitted with an ionic transport model.
A simple calculation of energy changes upon stacking fault formation or local crystalline phase transition in semiconductors
Authors: Glas Frank
Published: November 2008

We use a simple scheme to calculate the energies of stacking faults, polytypes, and arbitrary stacking sequences in elementary and compound semiconductors. The scheme is based on the calculation of two elementary energies, which can be obtained for each material from the computed difference of energy between its cubic and hexagonal modifications and from the measured or computed energy of a single kind of stacking fault. Formulas are given for faults in both zinc blende and wurtzite structures and for the stacking sequences that occur during the transformation of one phase into the other. This applies in particular to nanowires, where such faults and sequences are frequently encountered.
Brillouin light scattering observation of the transition from the superparamagnetic to the superferromagnetic state in nanogranular (SiO2)Co films
Authors: Stashkevich A. A. , Roussigné Y. , Djemia P. , Billet D. , Stognij A. I. , Novitskii N. N. , Wurtz G. A. , Zayats A. V. , Viau G. , Chaboussant G. , Ott F. , Gautrot S. , Kostylev M. P. , Lutsev L. V. , Belotelov V.
Published: November 2008

Evolution of magnetic excitations from purely magnetostatic modes to dipole-exchange spin waves in the Damon–Eshbach geometry in nanocomposite (SiO2)100−xCox (50 at. %<x<80 at. %) films during a transition from superparamagnetic to superferromagnetic state has been studied by Brillouin light scattering. It has been shown that removal of the degeneracy of backward volume magnetostatic waves due to nonzero exchange constant manifests itself in more pronounced Stokes/anti-Stokes asymmetry. Accompanying static characterization by means of magnetic force microscopy imaging and grazing incidence small angle neutron scattering has demonstrated the presence of weak stripe domains in the superferromagnetic phase.
Low frequency noise in 4H-SiC metal oxide semiconductor field effect transistors
Authors: Rumyantsev S. L. , Shur M. S. , Levinshtein M. E. , Ivanov P. A. , Palmour J. W. , Das M. K. , Hull B. A.
Published: November 2008

The low frequency noise was studied in 4H-SiC metal oxide semiconductor field effect transistors (MOSFETs) in the frequency range from 1 Hz to 100 kHz. 1/f (flicker) noise dominated in output noise over the entire frequency range and for a wide range of drain and gate biases. The dependence of the relative spectral noise density, SI/Id2, on the drain current, Id (at constant drain voltage, Vd), was qualitatively different from typical dependences for n-channel Si MOSFETs. In Si MOSFETs, in strong inversion, SI/Id2 usually decreases as ∼1/Id2 and tends to saturate in the subthreshold region, whereas in SiC MOSFETs under study, SI/Id2∝Id−0.5 for the currents varying from the deep subthreshold regime to the strong inversion. [Similar dependences were often observed in amorphous and polycrystalline thin film transistors (TFTs).] The effective field effect mobility of 3–7 cm2/V s extracted from the measured I-V characteristics is almost as low as that in amorphous Si TFTs. This result might be explained by a high density of localized states near the conduction band in the thin ion implanted silicon carbide layer. The energy dependence of trap density responsible for the noise was extracted for the states located close to the bottom of conduction band.
Magnetization induced dielectric anomaly in multiferroic LaFeO3–PbTiO3 solid solution
Authors: Singh Anupinder , Chatterjee Ratnamala
Published: November 2008

Coexistence of both typically ferroelectric (Tc1∼434 K) and frequency dependent broad transitions (650 K≤Tc2≤800 K) in έ versus T is demonstrated in a multiferroic candidate [(Pb0.8La0.2)(Ti0.8Fe0.2)O3]. The sample shows spontaneous magnetization and enhancement of magnetization on electrical poling. We demonstrate clearly that although the frequency dependent broad transition has no origin in ferroelectricity and is instead driven by a corresponding magnetic ordering at ∼650 K, the solid solution shows magnetoelectric coupling due to its pure ferroelectric behavior at and below 434 K.
Self-extrusion of Te nanowire from Si–Sb–Te thin films
Authors: Cheng Y. , Han X. D. , Liu X. Q. , Zheng K. , Zhang Z. , Zhang T. , Song Z. T. , Liu B. , Feng S. L.
Published: November 2008

A crystallized Si2Sb2Te5 thin film was observed to extrude single-crystalline [0001] oriented tellurium nanowires at room temperature. The single crystalline Te nanowires nucleation and extruded outgrowth can be greatly accelerated by electron-beam-illumination (EBI) in a transmission electron microscope by an order as high as four. The EBI-enhanced outgrowth speed of Te nanowires is a function of electron beam flux and can be described as v=k ln(J+m). This Te nanowires self-outflow phenomenon comes from a decomposition process of the Si2Sb2Te5 matrix and provides an interesting model and mechanism of the nanowires’ growth, which is distinctive to the vapor-liquid-solid (VLS) mechanism.
Ge–Si separate absorption and multiplication avalanche photodiode for Geiger mode single photon detection
Authors: Carroll M. S. , Childs K. , Jarecki R. , Bauer T. , Saiz K.
Published: November 2008

A Ge–Si separate absorption and multiplication avalanche photodiode (SAM-APD) is reported. The structure is grown using a low temperature in situ clean and epitaxy process, Tinsitu and Tepitaxy<∼460°C, resulting in a Ge layer with a dislocation density of ∼5×1010cm−2. The SAM-APD has a responsivity of 3.2×10−4A∕W (1310nm) and a dark current density at punch-through of 0.2mA∕cm2. In Geiger mode (GM) at 206K, the dark count rates (DCRs) are ∼280kHz, which is within an order of magnitude of DCR reported for InGaAs∕InP GM APDs despite the high defect density in the Ge.
Electro-optically tuned defect mode in structurally chiral materials
Authors: Palomares Laura O. , Reyes Juan Adrian
Published: November 2008

We considered an orthorhombic mm2 structurally chiral material, susceptible to the Pockels effect having a twist defect and subjected to a dc electric field oriented along the nonhomogeneity axis. We found that its localized mode can be tuned and the scaling of the inverse relative linewidth can be largely enhanced when the magnitudes of the field and the tilt angle of the structure are near the pseudoisotropic curve. This tuning gives rise to a dramatic variation in the behavior of the photon dwell time for the defect mode, which never reaches a maximum by increasing the sample thickness.
Long luminescence lifetime in self-assembled InGaAs/GaAs quantum dots at room temperature
Authors: Xu Zhangcheng , Zhang Yating , Hvam Jørn M.
Published: November 2008

Time-resolved photoluminescence (PL) measurements of high-quality self-assembled small In0.5Ga0.5As/GaAs quantum dots (QDs) show that the PL decay time of the QD ground state transition is nearly constant when the temperature is below 80 K and increases monotonously from 1.0 to 5.5 ns when the temperature increases from 80 to 300 K. The increased radiative lifetime of the QD ground state at higher temperatures is attributed to the thermal population of the subwetting-layer continuum states and could be one of the fundamental reasons for the low modal gain of the QD ground state transition in single-layer self-assembled QD lasers.
Optical properties of pulsed laser deposited rutile titanium dioxide films on quartz substrates determined by Raman scattering and transmittance spectra
Authors: Hu Z. G. , Li W. W. , Wu J. D. , Sun J. , Shu Q. W. , Zhong X. X. , Zhu Z. Q. , Chu J. H.
Published: November 2008

Optical response of rutile TiO2 films grown under different laser energy by pulsed laser deposition has been investigated by Raman scattering and spectral transmittance. Dielectric functions in the photon energy range of 1.24–6.5 eV have been extracted by fitting the experimental data with the Adachi’s model [S. Adachi, Phys. Rev. B 35, 7454 (1987)]. The refractive index dispersion in the transparent region is mainly ascribed to the higher A1-A2 electronic transitions for the rutile TiO2 films. Owing to slightly different crystalline structures and film densities, the optical band gap linearly increases with increasing packing density. The phenomena were confirmed by different theoretical evaluation methods.
High hole concentration in Mg-doped a-plane Ga1−xInxN (<x<0.30) grown on r-plane sapphire substrate by metalorganic vapor phase epitaxy
Authors: Iida Daisuke , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu
Published: November 2008

The electrical properties of Mg-doped a-plane Ga1−xInxN (0<x<0.30) films on undoped GaN grown by sidewall-epitaxial-lateral overgrowth on +0.5°-off r-plane sapphire substrates by metalorganic vapor phase epitaxy were systematically investigated. The activation energy of Mg acceptors in a-plane Ga0.83In0.17N was as small as 48 meV. Therefore, highly Mg-doped a-plane GaInN with a high hole concentration can be realized. A maximum hole concentration of as high as 1.7×1019 cm−3 in Ga0.71In0.29N was reproducibly achieved at room temperature.
Finding stable α-quartz (0001) surface structures via simulations
Authors: Chen Yun-Wen , Cao Chao , Cheng Hai-Ping
Published: November 2008

Reconstruction of α-quartz (0001) surfaces is studied using combined classical molecular dynamics and density functional theory. Five reconstruction patterns are identified, including three (2×1) patterns and two (1×1) patterns. The energetically most stable surface structure is found to be a (2×1) reconstruction pattern, and several patterns can coexist in a large-scale surface. A combination of structures can explain the experimentally observed (2×2) diffraction pattern.
Efficient second harmonic generation in ZnO nanorod arrays with broadband ultrashort pulses
Authors: Das Susanta Kumar , Bock Martin , O'Neill Christopher , Grunwald Ruediger , Lee Kyung Moon , Lee Hwang Woon , Lee Soonil , Rotermund Fabian
Published: November 2008

Broadband frequency-doubling properties of c-axis oriented zinc oxide (ZnO) nanorod arrays grown by low-temperature chemical bath method on glass substrate were studied. The maximum effective nonlinearity was found to be about 7.5 times higher than that of a type-I beta-barium borate crystal for a pump intensity of 5.5×1010 W/cm2. The angular dependence of second harmonic generation (SHG) was determined experimentally. The measured spectral profile of SHG was found to be in good agreement with theoretical simulations.
Anomalous current-voltage behavior of CaCu3Ti4O12 ceramics
Authors: Cordeiro Marco A. L. , Souza Flavio L. , Leite Edson R. , Lanfredi Alexandre J. C.
Published: November 2008

This letter reports on an investigation of dc current-voltage measured in CaCu3Ti4O12 ceramics. The experimental results show unusual I-V behaviors associated with the electrically inhomogeneous nature of the grains (mixture of semiconducting and insulating regions) and dependence on delay time. The data strongly suggest that both the localization of current in the conductive region and local Joule self-heating effects are essential elements to explain the abrupt drop in the electric field. In addition, the hysteresis behavior recorded during the I-V measurements shows strong dependence on delay time, i.e., the time needed for the polarization phenomena to occur.
New melanic pigments in the human brain that accumulate in aging and block environmental toxic metals
Authors: Zecca Luigi , Bellei Chiara , Costi Patrizia , Albertini Alberto , Monzani Enrico , Casella Luigi , Gallorini Mario , Bergamaschi Luigi , Moscatelli Alberto , Turro Nicholas J. , Eisner Melvin , Crippa Pier Raimondo , Ito Shosuke , Wakamatsu Kazumasa , Bush William D. , Ward Weslyn C. , Simon John D. , Zucca Fabio A.
Published: November 2008

Neuronal pigments of melanic type were identified in the putamen, cortex, cerebellum, and other major regions of human brain. These pigments consist of granules 30 nm in size, contained in organelles together with lipid droplets, and they accumulate in aging, reaching concentrations as high as 1.5–2.6 μg/mg tissue in major brain regions. These pigments, which we term neuromelanins, contain melanic, lipid, and peptide components. The melanic component is aromatic in structure, contains a stable free radical, and is synthesized from the precursor molecule cysteinyl-3,4-dihydroxyphenylalanine. This contrasts with neuromelanin of the substantia nigra, where the melanic precursor is cysteinyl-dopamine. These neuronal pigments have some structural similarities to the melanin found in skin. The precursors of lipid components of the neuromelanins are the polyunsaturated lipids present in the surrounding organelles. The synthesis of neuromelanins in the various regions of the human brain is an important protective process because the melanic component is generated through the removal of reactive/toxic quinones that would otherwise cause neurotoxicity. Furthermore, the resulting melanic component serves an additional protective role through its ability to chelate and accumulate metals, including environmentally toxic metals such as mercury and lead.
Caffeine activates mouse TRPA1 channels but suppresses human TRPA1 channels
Authors: Nagatomo Katsuhiro , Kubo Yoshihiro
Published: November 2008

Caffeine has various well-characterized pharmacological effects, but in mammals there are no known plasma membrane receptors or ion channels activated by caffeine. We observed that caffeine activates mouse transient receptor potential A1 (TRPA1) in heterologous expression systems by Ca
i
2+
imaging and electrophysiological analyses. These responses to caffeine were confirmed in acutely dissociated dorsal root ganglion sensory neurons from WT mice, which are known to express TRPA1, but were not seen in neurons from TRPA1 KO mice. Expression of TRPA1 was detected immunohistochemically in nerve fibers and bundles in the mouse tongue. Moreover, WT mice, but not KO mice, showed a remarkable aversion to caffeine-containing water. These results demonstrate that mouse TRPA1 channels expressed in sensory neurons cause an aversion to drinking caffeine-containing water, suggesting they mediate the perception of caffeine. Finally, we observed that caffeine does not activate human TRPA1; instead, it suppresses its activity.
Effects of petroleum and its derivatives in benthic communities at Baía de Todos os Santos/Todos os Santos Bay, Bahia, Brazil
Authors: Peso-Aguiar M.C. , Smith D.H. , Assis R.C.F. , Santa-Isabel L.M. , Peixinho S. , Gouveia E.P. , Almeida T.C.A. , Andrade W.S. , Carqueija C.R.G. , Kelmo F. , Carrozzo G. , Rodrigues C.V. , Carvalho G.C. , Jesus A.C.S.
Published: November 2008

Benthic community structure and diversity have been investigated to assess stress conditions of Todos os Santos Bay, Bahia, Brazil, as a possible result of the extraction, transportation and refining of petroleum, activities carried out in this area for more than 40 years. Samples were collected over two years, at four stations under the direct influence of stress-causing activities and at a control station. Benthic indices were calculated for all intertidal communities. The density, relative abundance, frequency of occurrence, diversity, similarity and occurrence of preferential species were recorded. Linear correlation indices were calculated to establish comparisons between ecological parameters of the studied communities and concentrations of heavy metals, hydrocarbons, petroleum pollution indicators and sediment mud percentages. The polychaete worms were the dominant group — up to 92% dominance in the community within the influence of refinery activities. Diversity indices indicated significant stress related spatial gradients tied to petroleum. The refinery sample station showed notable differences in its biodiversity figures compared to the other stations. Quantitative benthic indices showed negative correlations between the presence of cadmium, hydrocarbons, n-alkanes and the unresolved complex mixture in the intertidal zone marine sediments.
A biogeochemical comparison of Lakes Superior and Malawi and the limnological consequences of an endless summer
Authors: Hecky R.E.
Published: November 2008

Fundamental differences between tropical and temperate Great Lakes are the continuously high temperature throughout the water column in tropical lakes and high rates of annual photosynthesis possible under continuously high solar irradiance. These aspects not only lead to permanent stratification and hypolimnetic anoxia in the deepest tropical lakes, but also they have consequences for oxygen concentrations throughout the water column and can dramatically affect the biogeochemical cycles of carbon, nitrogen and phosphorus. Denitrification and enhanced regeneration of phosphorus from metal oxides cause low nitrogen:phosphorus ratios in the deep waters of tropical lakes and create a nitrogen deficit when deep waters mix into surface waters which is met through N-fixation. Comparison of the whole lake nutrient budgets of Lake Superior and Lake Malawi demonstrate the effects of the preferential regeneration of phosphorus in Lake Malawi and loss of nitrogen. In the upper 200 m of permanently stratified Lake Malawi, nitrogen has a residence time of 2 years while in dimictic Lake Superior the nitrogen residence time is over 50 years. This disparity in the residence time indicates that nitrogen is poorly recycled to the mixed layer of Malawi. The physical climate of tropical great lakes affects nutrient biogeochemical cycles differently and imposes biogeochemical characteristics different from temperate lakes on the water quality. In particular, tropical lakes have low nitrogen to phosphorus ratios and chronic, anoxia which will lead to rapid proliferation of nitrogen fixing filamentous cyanobacteria when nutrient loading increases. The chronic hypoxia of tropical lakes will also enhance release of phosphorus bound to metal oxides and allow soil erosion to induce eutrophication in tropical lakes.
Hydrodynamics as a limiting factor in the Lake Baikal ecosystem
Authors: Verkhozina V.A. , Kozhova O.M. , Kusner Yu.S.
Published: November 2008

The intense turbulent diffusion in the water body is one of the features of Lake Baikal, a deep-water, sea-like lake. In this paper we argue that the turbulent mixing of water determines the dynamics of intermediate gaseous nitrogen-containing products, and therefore may be regarded as the limiting factor for Lake Baikal as well as for other ecosystems of the oceanic type.
Ecological monitoring of phytoplankton in Lake Baikal
Authors: Popovskaya G.I.
Published: November 2008

The results of the long-term investigations of phytoplankton of the whole of Lake Baikal summarizing almost 40 years of systematic observations are given in this paper. These studies draw attention to spatial heterogeneity of planktonic biomass across the basin during the spring maximal bloom. The research of vertical distribution of phytoplankton during different years allows us to specify the role of phytoplankton in the cycle of organic substances and in biological productivity of Lake Baikal. For the first time, Baikal picophytoplankton, peculiarities of its production, seasonal and inter-annual dynamics, biocoenotic interrelations and its role in the ecosystem of Lake Baikal have been described. Changes occurring in Baikal pelagial phytocoenoses during the 1970–1990s in comparison with those of 1950–1960s have been revealed.
Lake Baikal: biomonitoring of pulp and paper mill waste water
Authors: Stepanova L.I. , Lindström-Seppä P. , Hänninen O.O.P. , Kotelevtsev S.V. , Glaser V.M. , Novikov C.N. , Beim A.M.
Published: November 2008

The quality and biological effects of the waste waters released by Baikalsk Pulp and Paper Mill were monitored chemically and biologically. In 1:5 dilution, the treated waste water induced monooxygenase activity in the liver of grayling and bullhead in standardised laboratory conditions. The Ames test was used to monitor mutagenicity of waste waters of the mill and tissue extracts of fish, sponge, mollusc and plankton collected near the mill and of seals collected from the middle part of the lake. Mutagens were found in waste water produced during pulp chlorination before treatment and in a few samples of fully treated waste water during 10 years (1982–1993). Bottom sediments near the mill showed some mutagenicity. Mutagens were not found in tissues of most aquatic animals studied with the exception of zooplankton, roach and seals collected in Lake Baikal close to the discharge outlet of the mill.
A geomorphological framework for the assessment of instream flow requirements
Authors: Rowntree K. , Wadeson R.
Published: November 2008

As South African ecologists become increasingly aware of the possible long term impacts of river regulation schemes on channel structure and associated aquatic habitats, fluvial geomorphologists are being called upon to assist in recommending instream flow requirements for future river regulation schemes. In South Africa, the standard procedure for the assessment of Instream Flow Requirements (IFR) is the Building Block Methodology (BBM). Central to the BBM is the assumption that the flow regime can be divided into three groups of flow: the low flows, freshes and floods. Each group has a particular ecological (and geomorphological) significance. The IFR assessment are applied at selected sites, chosen to represent the river reaches downstream of the dam site. This paper presents a geomorphological framework developed as a component of the BBM. This framework recognises five important geomorphological issues which are addressed within an IFR exercise: (1) A general assessment is made of the catchment condition to determine the potential for morphological change within the river. (2) An evaluation of the geomorphological characteristics of the river network is carried out to aid the selection of IFR sites within representative reaches. (3) At each IFR site an assessment is made of the relationship between hydraulic diversity and discharge for the different morphological units present at the site. This assessment relates in particular to the low flow component of the BBM. (4) The freshes and floods required to maintain channel form and bed condition are determined at each IFR site. An assessment is also made of the likely pattern and direction of morphological change that are likely to result from the recommended flow regime. (5) In the case of interbasin transfers, an assessment should be made of the potential impact of transferred water on the receiving channel. To illustrate the practical application of the geomorphological framework to an IFR procedure, an example is given from a recently completed study carried out in the Tugela River in KwaZulu-Natal, commissioned by the Department of Water Affairs and Forestry. The underlying theoretical principles upon which decisions were made are outlined in this paper.
Water quality characteristics of a high altitude oligotrophic Mexican lake
Authors: Chacon-Torres A. , Rosas-Monge C.
Published: November 2008

Lake Zirahuen, a small (10.48 km2) tropical high-mountain lake located in the Mexican Neovolcanic Axis, is under severe anthropogenic pressure. Its maximum depth is 43 m. The annual water balance is controlled by differences between rainfall, plus seepage, watershed runoff, and the main stream ‘La Palma’ plus evaporation. Tropical latitudinal conditions and high altitude produce thermal characteristics intermediate between temperate and tropical lakes. Transparency is good (up to 7.0 m). The nutrient relationship for N:P suggests that phosphorus remains limiting to primary productivity. Maximum phytoplankton chlorophyll a occurs in September at the end of the rainy season. Trophic state models suggest that Lake Zirahuen is an oligotrophic system. However, increasing erosion loads and untreated sewage input indicate the need for compatible watershed and lake management strategies which will ensure the conservation of the system and its sustainable development.
Aquatic ecology and management assessment in Valle de Bravo reservoir and its watershed
Authors: Olvera-Viascán V. , Bravo-Inclán L. , Sánchez-Chávez J.
Published: November 2008

The Valle de Bravo reservoir provides 30% of Mexico City’s drinking water. Unfortunately, human activities in the watershed have affected the water quality in this reservoir. Its trophic state changed from oligotrophic in 1980 to mesotrophic in 1987. Research conducted from March 1992 to February 1993 defined the main limnological characteristics of the water body and identified the most highly polluted subbasins in the Amanalco River Watershed. For this purpose, water, sediments and vascular plants were sampled in the waterbody. In the Amanalaco River Watershed land use and nutrient loadings in each subbasin were quantified.

The study dam is warm and monomictic, with a nine-month period of stratification and an overturn in December. Bottom anoxia occurred during the stratified phase. The reservoir was eutrophic during summer and mesotrophic the rest of the year. In the Amanalco basin, the highest phosphorus and nitrogen loadings (P, N in t y-1) entered by way of the Becerra (4.9, 47.2), Pipioltepec (8.6, 61.9) and Candelaria (8.5, 69.5) subbasins. A good agreement was found in a comparison between the export coefficients estimates in the Amanalco River Watershed and the measured amounts of phosphorus and nitrogen transported to 38 US waterbodies. Nevertheless, the phosphorus export coefficients for the forested subbasins within the Amanalco River Watershed were rather high in relation to the typical values found in the literature, and the values for agricultural land were low in relation to the same source.

For the first time in Mexico, export coefficients for phosphorus and nitrogen were estimated, both of which will be useful in assigning priorities in land management. The export coefficients estimates presented in this study can be applied to other scenarios in Mexico which have the same temperate semihumid climate.
Saline lake ecosystems of Mexico
Authors: Alcocer J. , Hammer U.T.
Published: November 2008

This paper aims to draw attention to the need to better know and understand Mexican saline lakes. It does this by outlining their distribution, abundance and location and their physical, chemical and biological characteristics. The influence of climatic factors on saline lakes is discussed. To sharpen the focus of the general discussion, a few Mexican saline lakes are discussed in more detail in each of the indicated topics. Saline lakes are found throughout Mexico, with the greatest number in the northwest and the least in the southeast, and from sea level to altitudes above 2000 m. Mexican saline lakes widely fluctuate morphometrically. The majority are tiny, shallow, and temporal with small volumes. Some are large or deep, and perennial with large volumes. Polymixis is common in shallow lakes while deeper ones are monomictic. Temperature and dissolved oxygen fluctuate widely. Alkaline waters are frequent. Mirroring high primary productivity rates, water is often green and turbid but other colors (blue, sepia, purple, yellow) and clear water are also found. Most lakes are sodium chloride or alkali carbonate types. Salts resulting from the combination of sodium with chloride, carbonates and sulfates are common and, to a lesser extent, salts of calcium, potassium, magnesium, lithium and boron are present. Species richness in Mexican saline lakes decreases as salinity rises. Hyposaline lakes display a more diverse biota than hypersaline ones. Organisms commonly found in Mexican saline lakes are: blue-green algae (e.g., Spirulina geitleri, Phormidium tenue), rotifers (Brachionus spp.), anostracans (Artemia spp.), copepods (e.g., Diaptomus, Leptodiaptomus), corixid bugs (e.g., Corisella, Krizousacorixa, Trichocorixella), ephydrids (e.g., Ephydra hians), the neotenic salamander (e.g., Ambystoma spp.), atherinids (e.g., Chirostoma spp.), goodeids (e.g., Goodea spp.), cyprinodontids (e.g., Cyprinodon spp.), poecilids (e.g., Gambusia spp.), and the Caribbean pink flamingo (Phoenicopterus ruber ruber).
Role of major histocompatibility complex class I‐related molecules A*A5·1 allele in ulcerative colitis in Chinese patients
Authors: Lü Min , Xia Bing , Ge Liuqing , Li Yi , Zhao Jie , Chen Fan , Zhou Feng , Zhang Xiaolian , Tan Jinquan
Published: November 2008

The major histocompatibility complex (MHC) class I‐related molecules A (MICA) is a stress‐inducible cell surface antigen that is recognized by intestinal epithelial Vδ1 γδ T cells, natural killer (NK) cells and CD8+ T cells with NKG2D receptor participating in the immunological reaction in the intestinal mucosa. The present study aimed to investigate the functions of the MICA*A5.1 allele in the development of ulcerative colitis (UC) in the Chinese population. The microsatellite polymorphisms of MICA were genotyped in 124 unrelated Chinese patients with UC and 172 ethnically matched healthy controls using a semiautomatic fluorescently labelled polymerase chain reaction. MICA*A5.1‐expressing Raji cells were generated by gene transfection. Cytotoxicity of NK cells to Raji cells expressing different MICA molecules was detected using the lactate dehydrogenase method. Soluble MICA in the culture supernatant was detected by enzyme‐linked immunosorbent assay. The frequency of MICA*A5.1 was significantly higher in UC patients compared with the healthy controls (29·0% versus 17·4%, P = 0·001, corrected P = 0·005, OR = 1·936, 95% CI 1·310–2·863) and the frequency of a MICA*A5.1/A5.1 homozygous genotype was increased in UC patients (18·5% versus 7% in healthy controls, P = 0·0032, corrected P = 0·048, OR = 3·036, 95% CI 1·447–6·372). Raji cells with MICA*A5.1 expression produced more soluble MICA (t = 5·75, P < 0·01) than Raji cells with full‐length MICA expression in culture supernatant. Raji cells with MICA*A5.1 expression were more resistant to killing by NK cells than Raji cells with full‐length MICA expression. The MICA*A5.1 allele and MICA*A5.1/A5.1 genotype are significantly associated with Chinese UC patients in central China. MICA*A5.1 may play a role in the development of UC by producing more soluble MICA and resistance to NK cells.
Human CD4low CD25high regulatory T cells indiscriminately kill autologous activated T cells
Authors: Bryl Ewa , Daca Agnieszka , Jóźwik Agnieszka , Witkowski Jacek M.
Published: November 2008

The interest of the scientific community in regulatory CD4+ T cells has reached an enormously high level. Common agreement is that they inhibit not only the proliferation of CD4 and CD8 lymphocytes, but also the activities of natural killer cells and macrophages. However, very important issues concerning actual mechanism(s) and specificity of the action of regulatory T cells (Tregs) upon responder cells are still unsolved or vague. The best known marker for Tregs is the expression of transcription factor FoxP3, widely used for their enumeration. It is known that FoxP3 inhibits cytokine production so the most probable action of Tregs is direct. However, FoxP3 expression cannot be used for functional studies in humans. Therefore we identified human peripheral blood Tregs as a distinct, very well‐defined population of peripheral blood T cells with reduced CD4 and high CD25 expression (CD4low CD25high), which fulfils the current phenotypic criteria identifying the Tregs by simultaneously expressing high amounts of FoxP3. We conclude that the definition of a CD4low CD25high phenotype is enough to unambiguously detect and study the regulatory function of these cells. On the functional level, the CD4low Tregs are able to non‐specifically suppress the proliferation of autologous, previously polyclonally activated CD4+ and CD4− lymphocytes and to kill them by direct contact, probably utilizing intracellular granzyme B and perforin.
The decrease of regulatory T cells correlates with excessive activation and apoptosis of CD8+ T cells in HIV‐1‐infected typical progressors, but not in long‐term non‐progressors
Authors: Jiao Yanmei , Fu JunLiang , Xing Shaojun , Fu Baoyun , Zhang Zheng , Shi Ming , Wang Xicheng , Zhang Jiyuan , Jin Lei , Kang Fubiao , Wu Hao , Wang Fu‐Sheng
Published: November 2008

Persistent HIV infection results in a decrease in absolute counts of CD4+ CD25+ regulatory T cells (Treg). To investigate the role of decreased Treg counts in the regulation of excessive activation and apoptosis of CD8+ T cells in human immunodeficiency virus (HIV)‐1 infection, we characterized Treg in 83 HIV‐1‐infected individuals, including 19 long‐term non‐progressors (LTNPs) and 51 typical progressors (TPs) who were treatment‐naïve, and 13 AIDS patients on highly active antiretroviral therapy (HAART), of whom nine were complete responders (CRs) and the remaining four were non‐responders (NRs) to the treatment. TPs but not LTNPs had a significant decrease in absolute counts of circulating Treg, which was inversely correlated with the activation and apoptosis of CD8+ T cells. Efficient HAART was found to increase Treg counts in CR patients and temper the excessive activation and apoptosis of CD8+ T cells. Moreover, isolated Treg significantly inhibited the spontaneous and anti‐CD3‐induced apoptosis of CD8+ T cells in a dose‐dependent manner in vitro. Thus, our findings indicate that the decrease in Treg closely correlates with the increase in apoptotic CD8+ T cells and disease progression in chronic HIV‐1 infection, and that Treg may play a key role in maintaining the balance between the amount and quality of CD8+ T cells in HIV‐1 infection. Manipulation of Treg function may be a promising strategy for immune therapy of this disease.
Blattabacteria, the endosymbionts of cockroaches, have small genome sizes and high genome copy numbers
Authors: López‐Sánchez María José , Neef Alexander , Patiño‐Navarrete Rafael , Navarro Lara , Jiménez Ricardo , Latorre Amparo , Moya Andrés
Published: November 2008

Blattabacteria are intracellular endosymbionts of cockroaches and primitive termites that belong to the class Flavobacteria and live only in specialized cells in the abdominal fat body of their hosts. In the present study we determined genome sizes as well as genome copy numbers for the endosymbionts of three cockroach species, Blattella germanica, Periplaneta americana and Blatta orientalis. The sole presence of blattabacteria in the fat body was demonstrated by rRNA‐targeting techniques. The genome sizes of the three blattabacteria were determined by pulsed field gel electrophoresis. The resulting total genome sizes for the three symbionts were all approximately 650 ± 15 kb. Comparison of the genome sizes with those of free‐living Bacteroidetes shows extended reduction, as occurs in other obligatory insect endosymbionts. Genome copy numbers were determined based on cell counts and determination of DNA amounts via quantitative PCR. Values between 10.2 and 18.3 and between 323 and 353 were found for the symbionts of P. americana and B. orientalis respectively. Polyploidy in intracellular bacteria may play a significant role in the genome reduction process.
FACTIVE, IMPLICATIVE VERBS AND THE ORDER OF OPERATORS
Authors: Erdmann Peter
Published: November 2008

To account for the semanties of complement constructions requires meaning properties that are not restricted to individual lexical items and their sense relationships. In dealing with subject and object sentences one has to pay attention to semantic properties that define a subordinate clause in relation to the predicate of the main clause. The distinction between factives and implicatives, which has been drawn in recent studies on English complement constructions boils down to the question originally asked by Frege whether the complement is semantically a sentence or not. In case it is Frege distinguished between two groups. Sentences which have the truth value for their reference and sentences which have the truth value for their presup‐position. In case it is not the complement sentence has no reference at all. Factive and implicative predicates differ in that complement sentences of the former constitute a sentence semantically the truth value of which is its presupposition, while the latter do not. This difference shows up in various restrictions on operators like negation, tense, time and locative adverbials. Whereas the complement of an implicative falls within the scope of the operator of the main clause predicate, the order of main clause predicate and complement is reversed for factives.