bluuebunny/crossref_metadata_2025 huggingface dataset:
Length-scale distribution functions and conditional means for various fields in turbulence
Authors: WANG LIPO , PETERS NORBERT
Published: July 2008

Dissipation elements are identified for various direct numerical simulation (DNS) fields of homogeneous shear turbulence. The fields are those of the fluctuations of a passive scalar, of the three components of velocity and vorticity, of the second invariant of the velocity gradient tensor, turbulent kinetic energy and viscous dissipation. In each of these fields trajectories starting from every grid point are calculated in the direction of ascending and descending gradients, reaching a local maximum and minimum point, respectively. Dissipation elements are defined as spatial regions containing all the grid points from which the same pair of minimum and maximum points is reached. They are parameterized by the linear length between these points and the difference of the field variable at these points.

In analysing the changes that occur during one time step in the linear length as well as in the number of grid points contained in the elements, it is found that rapid splitting and attachment processes occur between elements. These processes are much more frequent than the previously identified processes of cutting and reconnection. The model for the length-scale distribution function that had previously been proposed is modified to include these additional processes. Comparisons of the length-scale distribution function for the various fields with the proposed model show satisfactory agreement.

The conditional mean difference of the field variable at the minimum and maximum points of dissipation elements is calculated for the passive scalar field and the three components of velocity. While the conditional mean difference follows the 1/3 inertial-range Kolmogorov scaling for the passive scalar field, the scaling exponent differs from the 1/3 law for each of the three components of velocity. This is thought to be due to the relatively high shear rate of the DNS calculations.

The conditional mean viscous dissipation shows, differently from all other field variables analysed, a pronounced dependence on the linear length of elements. This is explained by intermittency. This finding is used to evaluate the production and the dissipation term of the empirically derived ϵ-equation that is often used in engineering calculations.
Time-dependent force acting on a particle moving arbitrarily in a rotating flow, at small Reynolds and Taylor numbers
Authors: CANDELIER FABIEN
Published: July 2008

The arbitrary motion of a solid sphere released in a solid-body rotating fluid is investigated theoretically in the limit of small Reynolds and Taylor numbers. The angular velocity of the fluid is assumed to be constant and under the premise that Ta1/2 ≫ Re, the simplicity of the unperturbed flow enables us to calculate analytically the force acting on a particle moving with a harmonic slip velocity (by means of matched asymptotic expansions), when both inertia and unsteady effects are taken into account. Subsequently, these single-frequency results are used in order to determine the temporal expression of the force acting on an arbitrarily moving sphere, since the problem under study is linear. This force is first determined in a co-rotating reference frame and takes the form of two convolution products involving the particle acceleration and the particle velocity. For convenience, the corresponding expression of this force is also derived in the laboratory reference frame, and the particle motion equation obtained is thereafter illustrated by dealing with two practical situations, where unsteady and inertia effects must be taken into account to predict the particle dynamics accurately.
Flow-induced forces in sphere doublets
Authors: DERKSEN J. J.
Published: July 2008

Motivated by applications in solids formation and handling processes we numerically investigate the force and torque required for maintaining a fixed contact between two equally sized solid spheres immersed in fluid flow. The direct numerical procedure applied is based on solving the Navier–Stokes equations by means of the lattice-Boltzmann method, with no-slip conditions at the surfaces of the moving spheres. It is validated by means of the analytical results due to Nir & Acrivos (1973) for sphere doublets in creeping flow. Subsequently, doublets are released in turbulent flows. In these cases, the contact force and torque strongly fluctuate, with peak levels much higher than would follow from simple dimensional analysis. The force fluctuation levels have been quantified by a linear relation in the ratio of sphere radius over Kolmogorov length scale.
Low-Reynolds-number fountain behaviour
Authors: WILLIAMSON N. , SRINARAYANA N. , ARMFIELD S. W. , McBAIN G. D. , LIN W.
Published: July 2008

Experimental evidence for previously unreported fountain behaviour is presented. It has been found that the first unstable mode of a three-dimensional round fountain is a laminar flapping motion that can grow to a circling or multimodal flapping motion. With increasing Froude and Reynolds numbers, fountain behaviour becomes more disorderly, exhibiting a laminar bobbing motion. The transition between steady behaviour, the initial flapping modes and the laminar bobbing flow can be approximately described by a function FrRe2/3=C. The transition to turbulence occurs at Re > 120, independent of Froude number, and the flow appears to be fully turbulent at Re≈2000. For Fr > 10 and Re≲120, sinuous shear-driven instabilities have been observed in the rising fluid column. For Re≳120 these instabilities cause the fountain to intermittently breakdown into turbulent jet-like flow. For Fr≲10 buoyancy forces begin to dominate the flow and pulsing behaviour is observed. A regime map of the fountain behaviour for 0.7≲Fr≲100 and 15≲Re≲1900 is presented and the underlying mechanisms for the observed behaviour are proposed. Movies are available with the online version of the paper.
Ear, nose and throat manifestations of Behçet's disease: a review
Authors: Webb C J , Moots R J , Swift A C
Published: July 2008

Objective:

To review Behçet's disease and to describe its clinical features in the head, neck and upper respiratory tract.

Method:

A literature review was undertaken, following a Medline search of publications over a 30-year period, and utilising the expert knowledge of one of the authors (RJM) with a specialist interest in Behçet's disease.

Results:

Twenty-seven articles with ENT relevance were obtained. Otorhinolaryngological manifestations included symptoms and signs in the mouth, nose, sinus, larynx and ear.

Conclusion:

Behçet's disease is usually considered to be a condition affecting the oral cavity, eyes and genitals. This article shows that most patients will also exhibit other ENT symptoms, hearing loss in particular. Indeed, Behçet's disease may present with features other than the classic triad of symptoms. Raised awareness of the clinical features within the head and neck region will hopefully enable early diagnosis and treatment of this potentially serious condition.
Numerical investigations on the effects of geometrical parameters on free electron laser instability
Authors: SHARMA B. S. , JAIMAN N. K.
Published: July 2008

In this paper we numerically investigate the effects of various geometrical parameters of a backward wave oscillator (BWO), filled with a magnetized plasma of uniform density and driven by a mild relativistic solid electron beam, on the instability growth rate (Γ) of a free electron laser (FEL). The FEL instability is numerically calculated and the result is compared with the instability growth rate of an annular electron beam for the same set of parameters. The instability growth for a solid electron beam scales inversely to the seventh power of relativistic gamma factor γ0 and directly proportional to the corrugation amplitude.
Host-cell apoptosis inTaenia solium-induced brain granulomas in naturally infected pigs
Authors: SIKASUNGE C. S. , PHIRI I. K. , JOHANSEN M. V. , WILLINGHAM A. L. , LEIFSSON P. S.
Published: July 2008

To assess whether apoptosis occurs in pig brain granulomas due toTaenia soliumcysticerci, brain tissues from 30 pigs naturally infected withT. soliumcysticercosis were evaluated by terminal deoxynucleotidyl transferase-end labelling (TUNEL) staining. In addition, tissues were stained with CD3 marker to identify T lymphocytes. Examination of TUNEL-stained tissues showed apoptotic cells in early lesions that contained viable cysticerci. Apoptotic cells were primarily found interspersed with normal cell types, and were mostly located in the inflammatory infiltrate. Late or advanced granulomas with disintegrated scolices did not show TUNEL-positive cells. CD3+ cells were found in both early and advanced lesions and apoptosis mainly co-localized with CD3+ T lymphocytes. This suggests that these cells are constantly undergoing apoptosis and thus die as soon as they arrive at the site of infection. Apoptosis indeed may be one way by whichT. soliumcysticerci down-regulate the host's cellular immune response in early cysticercosis. Therefore, further research is needed to establish if other cells besides T-lymphocytes are also a target for destruction by cysticerci in early cysticercosis as well as studies to assess if cysteine protease is expressed by viable cysticerciin situ.
Some counterexamples in topological dynamics
Authors: PAVLOV RONNIE
Published: July 2008

In this paper, we exhibit, for any sparse-enough increasing sequence {pn} of integers, totally minimal, totally uniquely ergodic, and topologically mixing systems (X,T) and (X′,T′) and f∈C(X) for which the averages $({1}/{N}) \sum _{n=0}^{N-1} f(T^{p_n} x)$ fail to converge on a residual set in X, and where there exists x′∈X′ with $x' \notin \overline {\{T'^{p_n} x'\}}$.
An algebraic generalization of Kripke structures
Authors: MARCELINO SÉRGIO , RESENDE PEDRO
Published: July 2008

The Kripke semantics of classical propositional normal modal logic is made algebraic via an embedding of Kripke structures into the larger class of pointed stably supported quantales. This algebraic semantics subsumes the traditional algebraic semantics based on lattices with unary operators, and it suggests natural interpretations of modal logic, of possible interest in the applications, in structures that arise in geometry and analysis, such as foliated manifolds and operator algebras, via topological groupoids and inverse semigroups. We study completeness properties of the quantale based semantics for the systems K, T, K4, S4 and S5, in particular obtaining an axiomatization for S5 which does not use negation or the modal necessity operator. As additional examples we describe intuitionistic propositional modal logic, the logic of programs PDL and the ramified temporal logic CTL.
A combinatorial formula for Earle's twisted 1-cocycle on the mapping class group
Authors: KUNO YUSUKE
Published: July 2008

We present a formula expressing Earle's twisted 1-cocycle on the mapping class group of a closed oriented surface of genus ≥ 2 relative to a fixed base point, with coefficients in the first homology group of the surface. For this purpose we compare it with Morita's twisted 1-cocycle which is combinatorial. The key is the computation of these cocycles on a particular element of the mapping class group, which is topologically a hyperelliptic involution.
Surjectivity of the Taylor map for complex nilpotent Lie groups
Authors: DRIVER BRUCE K. , GROSS LEONARD , SALOFF-COSTE LAURENT
Published: July 2008

A Hermitian formqon the dual space,*, of the Lie algebra,, of a simply connected complex Lie group,G, determines a sub-Laplacian, Δ, onG. Assuming Hörmander's condition for hypoellipticity, there is a smooth heat kernel measure, ρt, onGassociated toetΔ/4. In a companion paper [6], we proved the existence of a unitary “Taylor” map from the space of holomorphic functions inL2(G, ρt) ontoJt0(a subspace of) the dual of the universal enveloping algebra of. Here we give a very different proof of the surjectivity of the Taylor map under the assumption thatGis nilpotent. This proof provides further insight into the structure of the Taylor map. In particular we show that the finite rank tensors are dense inJt0when the Lie algebra is graded and the Laplacian is adapted to the gradation. We also show how the Fourier–Wigner transform produces a natural family of holomorphic functions inL2(G, ρt), for appropriatet, whenGis the complex Heisenberg group.
Domination of operators on function spaces
Authors: DEFANT A. , PÉREZ E. A. SÁNCHEZ
Published: July 2008

We prove a domination theorem for operators on Köthe function spaces by probability measures which includes both the Maurey–Rosenthal domination theorem and the Pisier domination theorem as special cases.
Oocyte activation procedures and influence of serum on porcine oocyte maturation and subsequent parthenogenetic and nuclear transfer embryo development
Authors: García-Mengual E. , Alfonso J. , Salvador I. , Duque C-C. , Silvestre M-A.
Published: July 2008

The viability of SCNT embryos is poor, with an extremely low cloned piglet production rate. In the present work, we studied the effect of three activation protocols based on ionomycin treatment (5 μM ionomycin for 5 min and incubated in 2 mM 6-DMAP for 3.5 h) or electric stimuli (two square wave electrical DC pulses of 1.2 kV/cm for 30 μs) combined or not with 6-DMAP on parthenogenetic embryo development. Oocytes activated by ionomycin plus 6-DMAP showed lower cleavage (47.2 vs. 78.5–81.5; p < 0.05) and blastocyst rates (11.3 vs. 29.2–32.1; p < 0.05) than those activated by electrical and electrical plus 6-DMAP treatments. Also, we studied the effect of addition of serum to maturation medium (0% vs. 10%) on nuclear maturation and further parthenogenetic and SCNT embryo development. We observed in the parthenogenetic embryos that cleavage rates in the serum-free group were significantly higher than in the serum-supplemented group (81.8 vs. 69.6% respectively; p < 0.05), although these differences were not detected in blastocyst rates or blastocyst nuclei numbers. Regarding SCNT embryos, no significant differences were observed in cleavage or blastocyst rates between different experimental groups of SCNT embryos. In conclusion, electrical pulse followed or not by 6-DMAP was found to be an efficient procedure to artificially activate MII porcine oocytes. Moreover, the addition of serum to oocyte maturation media did not seem to improve parthenogenetic or SCNT porcine embryo development.
Sex identification of pigs using polymerase chain reaction amplification of the amelogenin gene
Authors: Sembon Shoichiro , Suzuki Shun-ichi , Fuchimoto Dai-ichiro , Iwamoto Masaki , Kawarasaki Tatsuo , Onishi Akira
Published: July 2008

The amelogenin (AMEL) gene exists on both sex chromosomes of various mammalian species and the length and sequence of the noncoding regions differ between the two chromosome-specific alleles. Because both forms can be amplified using a single primer set, the use of AMEL in polymerase chain reaction (PCR)-based methods has facilitated sex identification in various mammalian species, including cattle, sheep and humans. In this study, we designed PCR primers to yield different-sized products from the AMEL genes on the X (AMELX) and Y (AMELY) chromosomes of pigs. PCR amplification of genomic DNA samples collected from various breeds of pigs (European breeds: Landrace, Large White, Duroc and Berkshire; Chinese breeds: Meishan and Jinhua and their crossbreeds) yielded the expected products. For all breeds, DNA from male pigs produced two bands (520 and 350 bp; AMELX and AMELY, respectively), whereas samples from female pigs generated only the 520 bp product. We then tested the use of PCR of AMEL for sex identification of in vitro-produced (IVP) porcine embryos sampled at 2 or 5 to 6 days after fertilization; germinal vesicle (GV)-stage oocytes and electroactivated embryos were used as controls. More than 88% of the GV-stage oocytes and electroactivated embryos yielded a single 520 bp single band and about 50% of the IVP embryos tested produced both bands. Our findings show that PCR analysis of the AMEL gene is reliable for sex identification of pigs and porcine embryos.
Determinants of low birth weight in urban Pakistan
Authors: Janjua Naveed Zafar , Delzell Elizabeth , Larson Rodney R , Meleth Sreelatha , Kristensen Sibylle , Kabagambe Edmond , Sathiakumar Nalini
Published: July 2008

Objective

To identify determinants of low birth weight (LBW) in Karachi, Pakistan, including environmental exposures and nutritional status of the mother during pregnancy.

Design

Cross-sectional study.

Participants

Five hundred and forty mother–infant pairs. We interviewed mothers about obstetric history, diet and exposure to Pb. We measured birth weight and blood lead level (BLL). We performed multiple log binomial regression analysis to identify factors related to LBW.

Results

Of 540 infants, 100 (18·5 %) weighed ≤2·5 kg. Umbilical cord BLL was not significantly associated with LBW. Maternal poor self-rated health (adjusted prevalence ratio (adjPR) = 1·83; 95 % CI 1·09, 3·07) and none or one prenatal visit (adjPR = 2·18; 95 % CI 1·39, 3·43) were associated with LBW. A statistically significant interaction between mothers’ mid upper-arm circumference (MUAC) and dietary vitamin C intake was noted. Compared with mothers with MUAC above the median and dietary vitamin C intake above the 3rd quartile (>208·7 mg/d), infants of mothers with MUAC less than or equal to the median and dietary vitamin C intake >208·7 mg/d (adjPR = 10·80; 95 % CI 1·46, 79·76), mothers with MUAC above the median and vitamin C intake ≤208.7 mg/d (adjPR = 10·67; 95 % CI 1·50, 76·02) and mothers with MUAC less than or equal to the median and vitamin C intake ≤208·7 mg/d (adjPR = 13·19; 95 % CI 1·85, 93·79) more likely to give birth to an LBW infant.

Conclusions

In Pakistan, poor nutritional status and inadequate prenatal care were major determinants of LBW in this setting. Environmental factors including umbilical cord BLL were not significantly associated with LBW.
Preconceptional folic acid supplement use in Lebanon
Authors: Tamim H , Harrison G , Atoui M , Mumtaz G , El-Kak F , Seoud M , Yunis K ,   for the National Collaborative Perinatal Neonatal Network (NCPNN)
Published: July 2008

Objective

The objective of the present study was to assess the prevalence and determinants of preconceptional folic acid supplement use among pregnant women in Lebanon.

Design/setting/subjects

The study was a descriptive epidemiological study. Analysis was performed on 5280 deliveries admitted to twelve member hospitals of the National Collaborative Perinatal Neonatal Network during the period September 2003–January 2005. Information on folic acid intake and maternal and neonatal characteristics were obtained from obstetric charts along with direct interviews performed by trained personnel. Logistic regression was performed to determine the predictors of preconceptional folic acid use.

Results

The overall use of preconceptional folic acid supplementation was 14·0 % (18·6 % in urban hospitals v. 2·7 % in rural hospitals). Higher socio-economic status, lower parity and having a history of previous spontaneous abortions were significantly associated with preconceptional folic acid use.

Conclusion

Our study shows that Lebanon currently has a low rate of preconceptional folic acid supplement use. Intervention through the means of awareness campaigns needs to be implemented on a national level.
Identifying ‘unhealthy’ food advertising on television: a case study applying the UK Nutrient Profile model
Authors: Jenkin Gabrielle , Wilson Nick , Hermanson Nicole
Published: July 2008

Objectives

To evaluate the feasibility of the UK Nutrient Profile (NP) model for identifying ‘unhealthy’ food advertisements using a case study of New Zealand television advertisements.

Design

Four weeks of weekday television from 15.30 hours to 18.30 hours was videotaped from a state-owned (free-to-air) television channel popular with children. Food advertisements were identified and their nutritional information collected in accordance with the requirements of the NP model. Nutrient information was obtained from a variety of sources including food labels, company websites and a national nutritional database.

Results

From the 60 h sample of weekday afternoon television, there were 1893 advertisements, of which 483 were for food products or retailers. After applying the NP model, 66 % of these were classified as advertising high-fat, high-salt and high-sugar (HFSS) foods; 28 % were classified as advertising non-HFSS foods; and the remaining 2 % were unclassifiable. More than half (53 %) of the HFSS food advertisements were for ‘mixed meal’ items promoted by major fast-food franchises. The advertising of non-HFSS food was sparse, covering a narrow range of food groups, with no advertisements for fresh fruit or vegetables.

Conclusions

Despite the NP model having some design limitations in classifying real-world televised food advertisements, it was easily applied to this sample and could clearly identify HFSS products. Policy makers who do not wish to completely restrict food advertising to children outright should consider using this NP model for regulating food advertising.
Logic programming with social features
Authors: BUCCAFURRI FRANCESCO , CAMINITI GIANLUCA
Published: July 2008

In everyday life it happens that a person has to reason out what other people think and how they behave, in order to achieve his goals. In other words, an individual may be required to adapt his behavior by reasoning about the others' mental state. In this paper we focus on a knowledge-representation language derived from logic programming which both supports the representation of mental states of individual communities and provides each with the capability of reasoning about others' mental states and acting accordingly. The proposed semantics is shown to be translatable into stable model semantics of logic programs with aggregates.
A dynamical model for generating Eurasian lithospheric stress and strain rate fields: Effect of rheology and cratons
Authors: Hieronymus C. F. , Goes S. , Sargent M. , Morra G.
Published: July 2008

For most continents, stress models driven by plate boundary forces have successfully reproduced the main characteristics of the stress field. However, Eurasia has remained a challenge due to its large areas of intraplate deformation. We present a set of three‐dimensional models of the upper mantle lithosphere system for a simplified geometry of the Eurasian plate where we try to match the first‐order characteristics of the stress and strain rate fields simultaneously. For typical elastic, viscous, or plastic rheologies, high stress levels are required in order to produce realistic convergence rates between India and Asia. Our models show robustly that such stresses are transmitted throughout most of the plate, dominating locally generated stresses even in distal regions such as Europe in a manner that is not compatible with observations. Cratons with roots that extend deep into the mantle are unable to provide a significant stress‐shielding effect unless the viscosity contrast between the asthenosphere and the underlying mantle is around 100 or greater. A damage rheology for the lithosphere with history‐dependent behavior and material softening by a viscosity reduction of several orders of magnitude is shown to eliminate this conundrum. Continental convergence at high velocity but low stress is facilitated by the formation of long‐lived shear zones similar to those observed north of the Himalayas. The low stress associated with the collision, together with the decoupling effect of the shear zones, causes the distal stress field in Europe to be controlled by the effects of the neighboring boundaries in agreement with observations.
An annual study of inorganic and organic nitrogen and phosphorus and silicic acid in the southeastern Beaufort Sea
Authors: Simpson Kyle G. , Tremblay Jean‐Éric , Gratton Yves , Price Neil M.
Published: July 2008

Water column samples from the Mackenzie Shelf, the Beaufort Sea, and the Amundsen Gulf were obtained during 2003–2004 to investigate nutrient dynamics in an Arctic ecosystem influenced by a large river and flaw lead polynya. Nutrient inventories in the upper water column showed a significant seasonal drawdown of nitrate (NO3−) and silicic acid (Si(OH)4) (1:1.75 mol/mol) and subsequent accumulation of nitrite (NO2−) and ammonium (NH4+). Dissolved organic nitrogen and phosphorus concentrations (DON and DOP) were elevated in surface waters during the time of peak phytoplankton growth (bloom and postbloom phases) and covaried in a 17:1 molar ratio. Vertical profiles showed the typical middepth maxima in NO3−, PO43−, and Si(OH)4 at salinity 32–33.1. The concentration of DOP (0.76 ± 0.27 μmol P L−1) was also 2 times higher in this layer compared to the surface average and inversely correlated with the water mass tracer N* [N* = (NO3− − 16 × PO43− + 2.9) × 0.87], suggesting that Pacific‐derived waters were a source of the enrichment. Below the mixed layer, DON was generally constant with depth, although averaged profiles (like those of urea) suggested the presence of subsurface maxima at 50 m and between 250 and 300 m. Regeneration ratios varied with depth and were approximately 9.0 mol −O2/mol NO3− and 122.5 mol −O2/mol PO43− in shallow Pacific‐derived waters (halocline layer) and 17.4 and 193.5 in deep Atlantic waters (Atlantic layer), respectively. Deep waters of the Amundsen Gulf contained an excess of 1.7 μmol NO3− L−1, 0.12 μmol PO43− L−1, and 6.2 μmol Si(OH)4 L−1 and a deficit in O2, relative to waters of similar density in the Beaufort Sea, in proportions consistent with the remineralization ratios derived from oxygen‐nutrient regressions. Enhanced export of particulate matter from the overlying polynya and subsequent remineralization at depth are hypothesized to create this nutrient enrichment.
Aboveground biomass and leaf area index (LAI) mapping for Niassa Reserve, northern Mozambique
Authors: Ribeiro Natasha S. , Saatchi Sassan S. , Shugart Herman H. , Washington‐Allen Robert A.
Published: July 2008

Estimations of biomass are critical in miombo woodlands because they represent the primary source of goods and services for over 80% of the population in southern Africa. This study was carried out in Niassa Reserve, northern Mozambique. The main objectives were first to estimate woody biomass and Leaf Area Index (LAI) using remotely sensed data [RADARSAT (C‐band,λ= 5.7‐cm)] and Landsat ETM+ derived Normalized Difference Vegetation Index (NDVI) and Simple Ratio (SR) calibrated by field measurements and, second to determine, at both landscape and plot scales, the environmental controls (precipitation, woody cover density, fire and elephants) of biomass and LAI. A land‐cover map (72% overall accuracy) was derived from the June 2004 ETM+ mosaic. Field biomass and LAI were correlated with RADARSAT backscatter (rbiomass= 0.65,rLAI= 0.57,p< 0.0001) from July 2004, NDVI (rbiomass= 0.30,rLAI= 0.35;p< 0.0001) and SR (rbiomass= 0.36,rLAI= 0.40,p< 0.0001). A jackknife stepwise regression technique was used to develop the best predictive models for biomass (biomass = −5.19 + 0.074 * radarsat + 1.56 * SR,r2= 0.55) and LAI (LAI = −0.66 + 0.01 * radarsat + 0.22 * SR,r2= 0.45). Biomass and LAI maps were produced with an estimated peak of 18 kg m−2and 2.80 m2m−2, respectively. On the landscape‐scale, both biomass and LAI were strongly determined by mean annual precipitation (F = 13.91,p= 0.0002). On the plot spatial scale, woody biomass was significantly determined by fire frequency, and LAI by vegetation type.
A modeling approach for upscaling gross ecosystem production to the landscape scale using remote sensing data
Authors: Hilker Thomas , Coops Nicholas C. , Hall Forrest G. , Black T. Andrew , Chen Baozhang , Krishnan Praveena , Wulder Michael A. , Sellers Piers J. , Middleton Elizabeth M. , Huemmrich Karl F.
Published: July 2008

Gross ecosystem production (GEP) can be estimated at the global scale and in a spatially continuous mode using models driven by remote sensing. Multiple studies have demonstrated the capability of high resolution optical remote sensing to accurately measure GEP at the leaf and stand level, but upscaling this relationship using satellite data remains challenging. Canopy structure is one of the complicating factors as it not only alters the strength of a measured signal depending on integrated leaf‐angle‐distribution and sun‐observer geometry, but also drives the photosynthetic output and light‐use‐efficiency (ɛ) of individual leaves. This study introduces a new approach for upscaling multiangular canopy level reflectance measurements to satellite scales which takes account of canopy structure effects by using Light Detection and Ranging (LiDAR). A tower‐based spectro‐radiometer was used to observe canopy reflectances over an annual period under different look and solar angles. This information was then used to extract sunlit and shaded spectral end‐members corresponding to minimum and maximum values of canopy‐ɛ over 8‐d intervals using a bidirectional reflectance distribution model. Using three‐dimensional information of the canopy structure obtained from LiDAR, the canopy light regime and leaf area was modeled over a 12 km2 area and was combined with spectral end‐members to derive high resolution maps of GEP. Comparison with eddy covariance data collected at the site shows that the spectrally driven model is able to accurately predict GEP (r2 between 0.75 and 0.91, p < 0.05).
Ba/Ca evolution in water masses of the Mediterranean late Neogene
Authors: Sprovieri Mario , d'Alcalà Maurizio Ribera , Manta Daniela Salvagio , Bellanca Adriana , Neri Rodolfo , Lirer Fabrizio , Taberner Conxita , Pueyo Juan Josè , Sammartino Simone
Published: July 2008

A Mediterranean composite sedimentary record was analyzed for Ba/Ca ratios on carbonate shells of Orbulina universa planktonic foraminifer (Ba/Ca)carb providing the opportunity to study and assess the extent of freshwater inputs on the basin and possible impacts on its dynamics during the Tortonian to Recent period. A number of scanning electron microscope analyses and auxiliary trace element measurements (Mn, Sr, and Mg), obtained from the same samples, exclude important diagenetic effects on the studied biogenic carbonates and corroborate the reliability of (Ba/Ca)carb ratios in foraminifera calcite as indicators of seawater source components during the studied interval. A long‐term trend with (Ba/Ca)carb values shifting from ∼7 to 3 μmol mol−1 from the base of the Tortonian to the top of the Messinian is observed. The interval of the late Messinian salinity crisis, where biogenic carbonates are missing or strongly diagenized, represents a crucial passage not monitored in our record. At the base of the Pliocene, up to about 4.7 Ma, the (Ba/Ca)carb record shows a decreasing trend from ∼4 μmol mol−1 stabilizing itself to an about constant value of 0.9 ± 0.3 μmol mol−1 for the whole Plio‐Pleistocene interval. These results suggest a dramatic change in the continental runoff values, up to ∼3–16 times higher during part of the late Neogene (Tortonian–early Pliocene), with a possible profound modification in the physical dynamics of the Mediterranean basin. First‐order mass balance equations used to estimate barium and salinity budgets in the Mediterranean Sea during the late Miocene–early Pliocene interval support the hypothesis of an active connection of the basin with the Paratethys region and of a definitive restriction at the base of the Pliocene after about 0.7 Ma from the well‐known Messinian Lagomare phase. They also open intriguing scenarios on possible circulation shifts during the Neogene.
East Asian monsoon to El Niño/Southern Oscillation: A shift in the winter climate of Ishigaki Island accompanying the 1988/1989 regime shift, based on instrumental and coral records
Authors: Tsunoda Tomoaki , Kawahata Hodaka , Suzuki Atsushi , Minoshima Kayo , Shikazono Naotatsu
Published: July 2008

The relationship between the coral skeletal oxygen isotope ratio (δ18Ocoral) of a coral core (Porites sp.), which was collected from the inshore area of Ishigaki Island, Japan (24°N, 124°E) and represents 180 years of continuous growth, and sea surface temperature (SST) was examined for the last 30 years. A significant linear correlation was found between winter δ18Ocoral and SST measured at Ishigaki Port (SSTI), which suggests that the winter data from this coral sample is a good proxy for reconstructing past climate change. Furthermore, the winter instrumental SSTI shifted from being related to the East Asian Winter Monsoon to being dependent on the El Niño/Southern Oscillation in response to the 1988/1989 climate regime shift. Since this shift is also captured by the winter δ18Ocoral values, this 180‐year coral core record may provide insight into past climate regime shifts that occurred before instrumental records.
Evolution of the semidiurnal (M2) internal tide on the continental slope of the northern South China Sea
Authors: Xie Xiao‐Hui , Chen Gui‐Ying , Shang Xiao‐Dong , Fang Wen‐Dong
Published: July 2008

Kinetic energy spectra from a site on the continental slope in the South China Sea reveal that significant peaks appear at some nonlinear interaction frequencies, namely M3 (M1 + M2) and fM1 (M1 + f), where f is the inertial frequency, M1 is the diurnal internal wave, and M2 is the lunar semidiurnal internal tide. A possible generation mechanism of M3 is explored. Analysis of bicoherence and shear spectra suggests that strong M3 is indirectly associated with parametric subharmonic instability (PSI) of M2. In another word, under the effect of PSI the energy of M2 is first transferred to M1; then via other nonlinear coupling, some nonlinear waves (e.g. fM1, M3) are generated. Moreover, M1 is also present at another site near the bottom of the continental slope. The shear spectra from these two sites show, for the first time, that M1 can be significantly distinguished from lunar diurnal O1 and lunisolar diurnal K1.
Internal solitary waves in the northwestern South China Sea inferred from satellite images
Authors: Li Xiaofeng , Zhao Zhongxiang , Pichel William G.
Published: July 2008

Internal solitary waves (ISWs) in the northwestern South China Sea are studied from three spaceborne synthetic aperture radar images. ISWs are observed in the same area 18.5–20.5°N, 112–114°E. The common characteristics of the ISWs are: 1) their propagation directions are 270 ∼ 300 degrees with respect to north; 2) the wavelength is about 1.2–1.6 km; 3) the distance between two neighboring ISW packets is about 10 km, but it is not a constant; 4) in two images, the easternmost ISWs evolve into multiple rank‐ordered soliton on the shelf (ISW fission); and 5) near Shenhu Shoal, a local uplift at 19.5°N, 112.9°E, one ISW packet splits into two ISW packets. Based on their propagation direction and barotropic tidal forcing analysis, we suggest that these ISWs originate from tide‐topography interactions in the Luzon Strait. It takes the internal tide about 100 hours to propagate 880 km from the Luzon Strait to the observation site.
New insights into dissipation in the electron layer during magnetic reconnection
Authors: Ji H. , Ren Y. , Yamada M. , Dorfman S. , Daughton W. , Gerhardt S. P.
Published: July 2008

Detailed comparisons are reported between laboratory observations of electron‐scale dissipation layers near a reconnecting X‐line and direct two‐dimensional full‐particle simulations. Many experimental features of the electron layers, such as insensitivity to the ion mass, are reproduced by the simulations; the layer thickness, however, is about 3–5 times larger than the predictions. Consequently, the leading candidate 2D mechanism based on collisionless electron nongyrotropic pressure is insufficient to explain the observed reconnection rates. These results suggest that, in addition to the residual collisions, 3D effects play an important role in electron‐scale dissipation during fast reconnection.
Effects of 5‐HT6 receptor antagonism and cholinesterase inhibition in models of cognitive impairment in the rat
Authors: Marcos B , Chuang T T , Gil‐Bea F J , Ramirez M J
Published: July 2008

Background and purpose:

The beneficial effect of 5‐HT6 receptor antagonism in cognition remains controversial. This study has been undertaken to reassess the cognition enhancing properties of acute vs subchronic treatment with the selective 5‐HT6 receptor antagonist SB‐271046 in unimpaired rats, as well as against scopolamine (cholinergic‐) or MK‐801 (glutamatergic‐mediated) deficits.

Experimental approach:

The Morris water maze was used, measuring behaviour acquisition and retention, and swim speed. Other behavioural measures included yawning and motor activity. SB‐271046 was given acutely before each trial or subchronically for 7 days before the trials. The AChE inhibitor galanthamine was also used alone or in combination with SB‐271046.

Key results:

Subchronic treatment with SB‐271046 improved acquisition in the Morris water maze, while the acute treatment only improved retention. Neither acute nor subchronic SB‐271046 treatment reversed scopolamine‐induced learning deficits. MK‐801 induced learning impairment associated with a behavioural syndrome, reversed by acute, but not subchronic, SB‐271046 treatment. Interestingly, combined treatment with galanthamine and SB‐271046 reversed the scopolamine‐ or MK‐801‐induced learning impairments. Subchronic treatment with SB‐271046 did not modify motor activity or the increased number of yawns, a cholinergic‐mediated behaviour, induced by single administration of SB‐271046.

Conclusions and implications:

These data suggest a potential therapeutic role of 5‐HT6 receptor antagonists such as SB‐271046, alone or in combination with galanthamine, in the treatment of cognitive dysfunction, such as those seen in Alzheimer's disease and schizophrenia.

British Journal of Pharmacology (2008) 155, 434–440; doi:10.1038/bjp.2008.281; published online 14 July 2008
Dynamic states of the DNA repair enzyme AlkB regulate product release
Authors: Bleijlevens Boris , Shivarattan Tara , Flashman Emily , Yang Yi , Simpson Pete J , Koivisto Pertti , Sedgwick Barbara , Schofield Christopher J , Matthews Steve J
Published: July 2008

The 2‐oxoglutarate (2OG)‐ and Fe2+‐dependent dioxygenase AlkB couples the demethylation of modified DNA to the decarboxylation of 2OG. Extensive crystallographic analyses have shown no evidence of significant structural differences between complexes binding either 2OG or succinate. By using nuclear magnetic resonance spectroscopy, we have shown that the AlkB–succinate and AlkB–2OG complexes have significantly different dynamic properties in solution. 2OG makes the necessary contacts between the metal site and the large β‐sheet to maintain a fully folded conformation. Oxidative decarboxylation of 2OG to succinate leads to weakening of a main contact with the large β‐sheet, resulting in an enhanced dynamic state. These conformational fluctuations allow for the replacement of succinate in the central core of the protein and probably contribute to the effective release of unmethylated DNA. We also propose that the inherent dynamics of the co‐product complex and the subsequent increased molecular ordering of the co‐substrate complex have a role in DNA damage recognition.
SUMO1 modification of NF‐κB2/p100 is essential for stimuli‐induced p100 phosphorylation and processing
Authors: Vatsyayan Jaya , Qing Guoliang , Xiao Gutian , Hu Jing
Published: July 2008

A primary step in activating the alternative nuclear factor‐κB (NF‐κB) pathway requires NF‐κB2/p100 processing to generate p52. In most cases, stimuli‐induced p100 processing is dependent on NF‐κB‐inducing kinase/IκB kinase α‐mediated phosphorylation and ubiquitination. Here, we report that post‐translational modification of p100 at specific sites by the small ubiquitin‐like modifier (SUMO) is another determining factor for stimuli‐induced p100 processing. The results show that basal SUMO modification is required for stimuli‐induced p100 phosphorylation and that blocking SUMOylation of p100, either by site‐directed mutation or by short interfering RNA‐targeted diminution of E2 SUMO‐conjugating enzyme Ubc9, inhibits various physiological stimuli‐induced p100 processing and ultimate activation of the alternative NF‐κB pathway. Together, these findings show the crucial role of SUMO1 modification in p100 processing and provide mechanistic insights into the participation of SUMO1 modification in the regulation of signal transduction.
SUMO‐modified Sp3 represses transcription by provoking local heterochromatic gene silencing
Authors: Stielow Bastian , Sapetschnig Alexandra , Wink Christina , Krüger Imme , Suske Guntram
Published: July 2008

Modification of many transcription factors including Sp3 and steroidogenic factor 1 with the small ubiquitin‐like modifier (SUMO) is associated with transcriptional repression. Here, we show that SUMOylation of transcription factors bound to DNA provokes the establishment of compacted repressive chromatin with characteristics of heterochromatin. Chromatin immunoprecipitation experiments revealed SUMO‐dependent recruitment of the chromatin remodeller Mi‐2, MBT‐domain proteins, heterochromatic protein 1, and the histone methyltransferases SETDB1 and SUV4‐20H, concomitant with the establishment of histone modifications associated with repressed genes, including H3K9 and H4K20 trimethylation. These results indicate that SUMOylation has a crucial role in regulating gene expression by initiating chromatin structure changes that render DNA inaccessible to the transcription machinery.
The type VI secretion toolkit
Authors: Cascales Eric
Published: July 2008

Bacterial secretion systems are macromolecular complexes that release virulence factors into the medium or translocate them into the target host cell. These systems are widespread in bacteria allowing them to infect eukaryotic cells and survive or replicate within them. A new secretion system, the type VI secretion system (T6SS), was recently described and characterized in several pathogens. Genomic data suggest that T6SS exist in most bacteria that come into close contact with eukaryotic cells, including plant and animal pathogens. Many research groups are now investigating the underlying mechanisms and the way in which the effector proteins translocated through this machine subvert host defences. This review provides an overview of our current knowledge about type VI secretion, focusing on gene regulation, components of the secretion machine, substrate secretion and the cellular consequences for the host cell.
Substrate specificity and structure of human aminoadipate aminotransferase/kynurenine aminotransferase II
Authors: Han Qian , Cai Tao , Tagle Danilo A. , Robinson Howard , Li Jianyong
Published: July 2008

KAT (kynurenine aminotransferase) II is a primary enzyme in the brain for catalysing the transamination of kynurenine to KYNA (kynurenic acid). KYNA is the only known endogenous antagonist of the N-methyl-D-aspartate receptor. The enzyme also catalyses the transamination of aminoadipate to α-oxoadipate; therefore it was initially named AADAT (aminoadipate aminotransferase). As an endotoxin, aminoadipate influences various elements of glutamatergic neurotransmission and kills primary astrocytes in the brain. A number of studies dealing with the biochemical and functional characteristics of this enzyme exist in the literature, but a systematic assessment of KAT II addressing its substrate profile and kinetic properties has not been performed. The present study examines the biochemical and structural characterization of a human KAT II/AADAT. Substrate screening of human KAT II revealed that the enzyme has a very broad substrate specificity, is capable of catalysing the transamination of 16 out of 24 tested amino acids and could utilize all 16 tested α-oxo acids as amino-group acceptors. Kinetic analysis of human KAT II demonstrated its catalytic efficiency for individual amino-group donors and acceptors, providing information as to its preferred substrate affinity. Structural analysis of the human KAT II complex with α-oxoglutaric acid revealed a conformational change of an N-terminal fraction, residues 15–33, that is able to adapt to different substrate sizes, which provides a structural basis for its broad substrate specificity.
Regional Foreign Participation and Externalities: New Empirical Evidence from Mexican Regions
Authors: Jordaan Jacob A
Published: July 2008

Recent empirical research on externalities from foreign direct investment (FDI) is engaged with the identification of externalities along the dimensions of industry and geographical space. In this paper I explore these externality dimensions in the context of estimating FDI externalities in regional Mexican manufacturing industries. The main findings indicate that the presence of FDI creates a variety of externality effects. Intraregional foreign participation creates negative intraindustry and positive interindustry externalities. Furthermore, the estimations identify negative intraindustry externalities across regions and positive spatial interindustry FDI externalities. In addition, the estimations identify three different regional characteristics that have a negative or positive effect on spatial externalities from FDI.
An Evolutionary Perspective on Internet Adoption by Retailers in the Netherlands
Authors: Boschma Ron A , Weltevreden Jesse W J
Published: July 2008

The paper analyses from an evolutionary perspective how retailers respond and adapt to business-to-customer e-commerce. As such, the paper explores the diverse behavior of retailers with respect to the adoption of e-commerce. In particular, it empirically examines the extent to which the adoption of Internet strategies is affected by firm-specific features (eg habit of entrepreneur, routines of firms), network relationships, and geographical proximity. Logistic regression analyses of 643 independent retailers in the Netherlands suggest that geography matters, when other factors are controlled for. That is, the probability of having an Internet strategy increases significantly (a) when more relevant knowledge is locally available; (b) the more demanding local customers are; and (c) the less rivalry is present locally.