bluuebunny/crossref_metadata_2025 huggingface dataset:
Allozymic Variation and Species Diversity in North American Bosminidae
Authors: Melo Rita De , Hebert Paul D. N.
Published: October 2008

North American members of the genus Bosmina show marked morphological variation and integradation, which have been attributed to the occurrence of both phenotypic plasticity and occasional hybridization between a small number of species. We employed allozyme analysis on 72 bosminid populations from 62 North American habitats to ascertain the validity of species boundaries and to verify the occurrence of hybridization. Results showed that levels of genetic variability (15.8% polymorphic loci, 10% individual heterozygosities) in bosminids were comparable with those reported in other zooplankton groups. Significant Hardy–Weinberg deviations were detected at 38% of polymorphic loci and were usually due to heterozygote deficiency. No clear evidence of interspecific hybridization was obtained, although some cases of heterozygote excess require further investigation. While prior morphological studies indicated the occurrence of only six species, the allozyme data revealed the presence of eight assemblages showing allelic substitutions at one or more loci. Each assemblage corresponded to a different species belonging to one of four subgenera (Bosmina, Eubosmina, Neobosmina, or Sinobosmina). Within two assemblages, individuals could be further partitioned into two morphologically distinct, but genetically similar species, leading to the recognition of 10 species in this study.
Long-term Invertebrate Community Response to Toxaphene Treatment in Two Lakes: 50-yr Records Reconstructed from Lake Sediments
Authors: Miskimmin Brenda M. , Schindler David W.
Published: October 2008

Analysis of sediment cores from two toxaphene-treated and one untreated lake basin demonstrates both the short-term effect of toxaphene applied in 1961–62 and the longer term effect of subsequent trout stocking on invertebrates. In Chatwin Lake (higher toxaphene concentration), planktonic cladocerans decreased in abundance, and dominance quickly changed from small- to large-bodied types. Bosmina was reduced by 88% at the time of toxaphene application and was eliminated during the 1970's as invertebrate predators like Chaoborus americanus increased in response to the poor survival of stocked fish. Short-term toxic effects were not detectable in cores from Peanut Lake (lower toxaphene concentration). In both treated lakes, large invertebrates became dominant with the absence of native fish and during trout stocking. Chaoborus spp. remained at low levels throughout the 1960's in both treated lakes compared with the untreated lake, possibly due to residual toxaphene toxicity and/or to predation by stocked fish. Toxicity to total chironomids was not detected, although genera-specific responses were not analysed. While the higher toxaphene dosage caused residual toxicity in Chatwin Lake for at least a decade, the manipulation of fish communities was primarily responsible for long-term changes in the invertebrates of both lakes.
Induced Cytochrome P4501A in Winter Flounder,Pleuronectes americanus, from Offshore and Coastal Sites
Authors: Monosson Emily , Stegeman John J.
Published: October 2008

Cytochrome P4501A (CYP1A), Aroclor 1254 (A1254), and 3,3′,4,4′-tetrachlorobiphenyl (TCB) were measured in liver of winter flounder, Pleuronectes americanus, from Boston Harbor, Mass., Hempsted Harbor, N.Y., Niantic, Conn., and an offshore site, Georges Bank. We also measured CYP1A content and activity in flounder from Passamaquoddy Bay, N.B. Concentrations of A1254 and TCB were the least in fish from Georges Bank (0.46 and 0.002 μg∙g dry weight−1, respectively); concentrations in fish from Boston, Niantic, and Hempsted ranged from 7.6 to 11.3 μg∙g−1and from 0.013 to 0.024 μg∙g−1. Immunodetected microsomal CYP1A contents (expressed as scup P450E equivalents) were 0.17 and 0.19 nmol∙mg−1in fish from Georges Bank and Passamaquoddy and 0.25–0.41 nmol∙mg−1in fish from Boston, Niantic, and Hempsted. Ethoxyresorufin-O-deethylase specific activities likewise were greater in fish from Boston, Niantic, and Hempsted (1.7–2.4 nmol∙min−1∙mg−1) than in fish from Georges Bank or Passamaquoddy (0.83 and 0.61 nmol∙min−1∙mg−1). CYP1A content and activity were correlated with hepatic concentrations of A1254 and TCB. These data, together with data reported in previous studies, indicate that strong induction of CYP1A protein occurs in winter flounder populations along most of the industrialized east coast and that induction of CYP1A is common, but less strong, at sites distant from the urban centers of the Northeast.
Placing Odds on Sustainable Catch Using Virtual Population Analysis and Survey Data
Authors: Walters Carl , Punt Andre
Published: October 2008

Virtual population analysis (VPA) is often used in conjunction with survey data to provide estimates of current stock size and an allowable catch that is sustainable in the sense that it is expected to produce some desired trend (or stability) in stock size. But these estimates are generally very uncertain, and should be accompanied by statements about the odds of sustainability for a range of allowable catch options. The odds can be expressed as an easily understood short-term risk function, but potential cumulative risks associated with the function should be simulated as a long-term guide for management. Bayesian estimates of the odds of sustainability can be calculated using the likelihood function of the survey data for different current stock size and natural mortality rate possibilities, with estimates of expected recruitment and recruitment variability. Prerecruitment year classes in the survey are included in the calculation of expected recruitment and its uncertainty, allowing use of survey data from gears with different (arbitrary) age selectivity from the main fishery gear. Application of the calculations to a yellow perch (Perca flavescens) fishery illustrates how critical it is to have a well-designed survey, even when much age composition data for VPA are also available.
Infection with the Piroplasm Haemohormidium terranovae in Relation to Haematocrit and Mortality of American Plaice (Hippoglossoides platessoides)
Authors: Siddall Mark E. , Measures Lena N. , Desser Sherwin S.
Published: October 2008

The relationship between infection with Haemohormidium terranovae and the health of captive American plaice (Hippoglossoides platessoides) was investigated for over a 1-yr period. Intensity of infection and haematocrit were not significantly correlated at any of the sampling periods, although there was a moderately negative relationship between these parameters when data from all periods were pooled. Intensity and haematocrit varied inversely in time; intensities rose gradually during the winter months and dropped off significantly in the summer, while haematocrit values fell significantly until March and increased significantly by June. Only haematocrit showed a significant correlation with water temperature. Fish harboured higher intensities and lower haematocrit values prior to death than was apparent in fish that survived. The greatest differences between the mortality-group and the survivor-group occurred just prior to the greatest number of deaths, between March and June. The presence of infection in all captive plaice at all sampling periods, in the absence of leeches, is discussed in relation to possible mechanisms for long-term maintenance of infection and to possible routes of transmission of this parasite.
Physiological and Growth Differences in Three Stocks of Underyearling Sockeye Salmon (Oncorhynchus nerka) on Early Entry into Seawater
Authors: Rice Stanley D. , Thomas Robert E. , Moles Adam
Published: October 2008

We compared the impact of exposure to seawater on three sockeye salmon (Oncorhynchus nerka) stocks: one that normally migrates to sea as underyearlings (sea-type) and two with the more common life history strategies of 1 (river-type) or 2 (lake-type) yr of freshwater residence prior to seaward migration. Innate differences in survival, ability to regulate tissue chlorides, and oxygen consumption when first introduced into salt water were more evident in April and May when fish were less than 50 mm in length. In fish longer than 50 mm, the only significant differences among the stocks were in saltwater growth. Between June and August, sea-type fish showed faster growth than river-type fish which in turn grew faster than lake-type fish. When introduced into salt water in October, virtually no growth occurred in any stock, regardless of fish size. River-type and lake-type sockeye, which normally overwinter 1 and 2 yr, respectively, in freshwater, can be reared in seawater if underyearlings are raised to a length of 50 mm before release into salt water, similar to the normal life history of sea-type underyearlings. Early life history appears to be influenced more by habitat than by genetics.
ERp57 and PDI: multifunctional protein disulfide isomerases with similar domain architectures but differing substrate–partner associationsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease.
Authors: Maattanen P. , Kozlov G. , Gehring K. , Thomas D.Y.
Published: October 2008

Secretory proteins become folded and acquire stabilizing disulfide bonds in the endoplasmic reticulum (ER). Correct disulfide bond formation is a key step in ER quality control (ERQC). Proteins with incorrect disulfide bonds are recognized by the quality control machinery and are retrotranslocated into the cytosol where they are degraded by the proteasome. The mammalian ER contains 17 disulfide isomerases and at least one of them, ERp57, works in conjunction with the ER lectin-like chaperones calnexin and calreticulin. The targeting of ERp57 to calnexin–calreticulin is mediated by its noncatalytic b′ domain, and analogous domains in other disulfide isomerases likely determine their substrate and partner preferences. This review discusses some explanations for the multiplicity of disulfide isomerases and highlights structural differences in the b′ domains of PDI and ERp57 as an example of how noncatalytic domains define specialized roles in oxidative folding.
Investigating membrane protein dynamics in living cellsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease.
Authors: Bates Ian R. , Wiseman Paul W. , Hanrahan John W.
Published: October 2008

Live cell imaging is a powerful tool for understanding the function and regulation of membrane proteins. In this review, we briefly discuss 4 fluorescence-microscopy-based techniques for studying the transport dynamics of membrane proteins: fluorescence-correlation spectroscopy, image-correlation spectroscopy, fluorescence recovery after photobleaching, and single-particle and (or) molecule tracking. The advantages and limitations of each approach are illustrated using recent studies of an ion channel and cell adhesion molecules.
Stimulatory effect of insecticides on partially purified P-glycoprotein ATPase from the resistant pestHelicoverpa armigeraThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease.
Authors: Aurade Ravindra , Jayalakshmi Senigala K. , Sreeramulu Kuruba
Published: October 2008

A P-glycoprotein-like protein (Ha-Pgp) was detected in a membrane preparation from the insecticide-resistant pest Helicoverpa armigera (Lepidoptera: Noctüidae) using C219 antibodies that are directed towards an epitope in the nucleotide-binding domains. This protein was partially purified and found to be a glycoprotein displaying ATPase activity. SDS–PAGE confirmed that a high molecular mass glycoprotein (150 kDa) was overexpressed in resistant pests, but was not detected in susceptible pests. The partially purified Ha-Pgp ATPase was reconstituted into proteoliposomes and it was found that some insecticides, namely, monocrotophos, endosulfan, cypermethrin, fenvalerate, and methylparathion, stimulated the ATPase activity. The effect of various inhibitors on partially purified Ha-Pgp showed that orthovanadate is a potent inhibitor of its ATPase activity, inhibiting it by 90% at a concentration of 2 mmol/L. Other inhibitors, such as EDTA, sodium azide, and molybdate resulted in only a 20% decrease in activity. Details of the structure and function of Ha-Pgp will be important in the development of strategies to overcome insecticide resistance in this pest.
Fractality feature in incompressible three-dimensional magnetohydrodynamic turbulence
Authors: Momeni M , Moslehi-Fard M
Published: October 2008

High-resolution direct numerical simulation data for three-dimensional magnetohydrodynamic (MHD) turbulence based on the 10243-modes in a periodic box are used to study the statistical properties of turbulence. In this paper, the presence of intermittency in MHD turbulence is investigated through the analysis of the Probability Distribution Function (PDF) for Elsässer fields and total energy fluctuations. The energy PDFs exhibit similarity over all scales of the turbulent system since they show no substantial qualitative change in shape as the scale of the fluctuations varies. This is in sharp and surprising contrast to the well-known behavior of PDFs of turbulent field fluctuations of, for example, velocity, and magnetic and Elsässer fields. The PDFs have exponential tails and satisfy the function P(| δX |) ~ exp(–A | δX | μ). Numerically, we extract the exponent μ and find that it is constant for monofractal behavior as the scale of length varies. The compensated structure functions exhibit self-similarity for the respective fluctuations, and it is a reliable way in turbulence.

PACS Nos.: 52.30.–q , 52.30.Cv , 52.35.Ra , 52.65.–y
Effects of chemical reaction and thermophoresis on magneto-hydrodynamic mixed convective heat and mass transfer flow along an inclined plate in the presence of heat generation and (or) absorption with viscous dissipation and Joule heating
Authors: Alam M S , Rahman M M , Sattar M A
Published: October 2008

The present paper deals with the effects of thermophoresis and the homogeneous chemical reactions of first order on magneto-hydrodynamic mixed convective flow past a heated inclined permeable flat plate in the presence of heat generation or absorption considering the viscous dissipation and Joule heating. The resulting governing partial differential equations are transformed into non-dimensional ordinary differential equations using the usual similarity transformations and then solved numerically by applying the Nachtsheim–Swigert shooting iteration technique together with the sixth-order Runge–Kutta integration scheme. Comparison with previously published work is performed and very good agreement is obtained. A parametric study of the governing parameters is carried out and the results are displayed graphically. The results show that viscous drag, rate of heat transfer, and wall deposition flux decreases as the angle of inclination increases. It is also observed that due to the presence of the first-order homogeneous chemical reaction, the concentration decreases with increasing values of the chemical reaction parameter.PACS Nos.: 44.20.+b, 47.65.–d, 47.70.Fw
Unsteady boundary-layer viscous flow due to an impulsively started porous plate
Authors: Mehmood A , Ali A , Shah T
Published: October 2008

In this paper, we investigate the unsteady boundary-layer flow of an incompressible viscous fluid over an impulsively started porous flat plate in a constant velocity free-stream flow. The governing nonlinear partial-differential equations are simplified by the use of suitable similarity transformations. The resulting equation is then solved analytically using the homotopy analysis method. The present analytic solution is uniformly valid for all time 0 ≤ τ < ∞ in the whole spatial domain. The effect of the suction on the dynamic drag at the moving wall is studied. Also, the behavior of the dynamic drag is studied for different values of the parameter λ. Results are presented as graphs. PACS No.: 47.15.Cb
Solutions of the Duffin–Kemmer–Petiau equation for a pseudoscalar potential step in (1 + 1) dimensions
Authors: Boumali A
Published: October 2008

We solve the Duffin–Kemmer–Petiau equation in the presence of a pseudoscalar potential step in (1 + 1) dimensions. We show that the paradox of Klein is not found for particles of spin-1, contrary to the case of the particles of spin-0 where it always persists. The absence of this paradox in the vector bosons is explained with the arguments based on effective mass.PACS Nos.: 03.65.Pm; 03.65.Ge
Application of the exact quantization rule for some noncentral separable potentials
Authors: Kasri Y , Chetouani L
Published: October 2008

The energy spectrum of some noncentral separable potentials are obtained using the exact quantization rule in r and θ dimensions. The results are consistent with those obtained by other methods. PACS Nos.: 03.65.Ca, 03.65.Ge
Spherical Couette flow of Oldroyd 8-constant model. Part II. Third-order approximation and the stream function Ψ(3)
Authors: Hassan A Abu-El
Published: October 2008

In the previous work, Part I, Abu-El Hassan (Can. J. Phys. 84, 345 (2006)), the steady flow of an incompressible Oldroyd 8-constant fluid in the annular region between two concentric spheres is investigated up to the second-order approximation. Hence, the normalized second-order velocity field, V is seen to be V = W(0)[Formula: see text]+λU[Formula: see text](1)+λ(2)W(2)[Formula: see text]+O(λ3) with U[Formula: see text](1) = –[Formula: see text][Formula: see text](Ψ(1)/r sin θ) =  [Formula: see text]U(1) + [Formula: see text]V(1). The leading velocity term represents the Newtonian flow in the ϕ-direction, while the first-order term denoted by the stream function Ψ(1)(r,θ), produces a secondary flow field that divides the flow region into four parts symmetric about the z-axis, which is the axis of rotation. The second-order approximation gives a viscoelastic contribution W(2)(r,θ) in the ϕ-direction. λ is the retardation time parameter. The present work is devoted to the solution of the third-order approximation of the same problem treated in Abu-El Hassan (Can. J. Phys. 84, 345 (2006)). The solution produces a stream function Ψ(3)(r, θ), which being a secondary flow field divides the domain of flow into two similar regions symmetric about an axis perpendicular to the axis of rotation. The streamlines Ψ(3)(r,θ) = const. are sketched for Maxwell, Oldroyd-B, and Oldroyd-8 constant model fluids, respectively. The results show that the distribution of flow for these fields is mainly affected by the values of the field's elastic parameters.PACS No.: 47.15.Rq
Power laws and production of direct photons in high-energy physics
Authors: Biswas S K , Sau G , Guptaroy P , De B , Bhattacharya A , Bhattacharyya S
Published: October 2008

The measured data on transverse momentum spectra for production of direct photons in hadron–hadron, hadron–nucleus, and nucleus–nucleus interactions at high energies are compiled. Besides, data on some other aspects related to these pT-spectra are also assorted in the present work. The pT-spectra for production of direct photons at pT > 1 GeV/c are, then, fitted here by using two parameterizations, which essentially approach the power-law dependence at high transverse momenta. The power indices range between 16 to 7 depending on the interacting particles and the centre-of-mass energy of the system. The power index decreases gradually with increasing energy, with a variation of the rate of fall for various energy ranges. The formulae applied here phenomenologically bring out the main features of the data characteristics in a modestly satisfactory manner. This provokes us to raise some serious questions about the existing “theoretical” approaches, all, or most of which, lack in the first-principle derivations of the actual working expressions used to finally describe the nature of the measured data on direct photons, or for that matter, on any other secondary particle.PACS Nos.: 25.75.–q, 12.38.Mh, 13.85.Ni
Interplay between field-induced and frustration-induced quantum criticalities in the frustrated two-leg Heisenberg ladder
Authors: Ramakko B , Azzouz M
Published: October 2008

The antiferromagnetic Heisenberg two-leg ladder in the presence of frustration and an external magnetic field is a system that is characterized by two sorts of quantum criticalities, not only one. One criticality is the consequence of intrinsic frustration, and the other one is a result of the external magnetic field. So the behaviour of each of them in the presence of the other deserves to be studied. Using the Jordan–Wigner transformation in dimensions higher than one and the bond-mean-field theory we examine the interplay between the field-induced and frustration-induced quantum criticalities in this system. The present work could constitute a prototype for those systems showing multiple, perhaps sometimes competing, quantum criticalities. We calculate several physical quantities such as magnetization and spin susceptibility as functions of field and temperature.PACS Nos.: 75.10.Jm 73.43.Nq 75.10.Pq 75.10.Dg
A first course in the Yang–Baxter equation
Authors: Karanth D , Richmond D , Schmidt J R
Published: October 2008

A crash course on the Yang–Baxter equation and its applications in the statistical mechanics of lattice vertex models is presented. Using the simple example of a one-dimensional lattice gas, the basic terminology and standard mathematical procedures of statistical mechanics are illustrated. The coproduct notation is introduced via a discussion of the two-dimensional dimer model, and the transfer matrix formulation is elaborated further. The algebraic Bethe Ansatz (ABA) is introduced in the context of the ice model, leading to the Yang–Baxter equations. The motivation for introducing the ABA is developed, emphasizing the similarity to the quantum oscillator problem, in features such as the generation of “excited states”, and the determination of the eigenvalue spectrum. Finally, these methods from the theory of lattice models are applied to the case of a quantum many-body problem, the Heisenberg chain. From the condition that the monodromy matrices satisfy the Yang–Baxter equation, a complete set of mutually commuting operators is derived, and the Heisenberg chain problem is completely solved.PACS Nos.: 02.20.Uw, 24.10.Cn, 87.10.Hk, 05.20.–y
Calibration concepts for load and resistance factor design (LRFD) of reinforced soil walls
Authors: Bathurst Richard J. , Allen Tony M. , Nowak Andrzej S.
Published: October 2008

Reliability-based design concepts and their application to load and resistance factor design (LRFD or limit states design (LSD) in Canada) are well known, and their adoption in geotechnical engineering design is now recommended for many soil–structure interaction problems. Two important challenges for acceptance of LRFD for the design of reinforced soil walls are (i) a proper understanding of the calibration methods used to arrive at load and resistance factors, and (ii) the proper interpretation of the data required to carry out this process. This paper presents LRFD calibration principles and traces the steps required to arrive at load and resistance factors using closed-form solutions for one typical limit state, namely pullout of steel reinforcement elements in the anchorage zone of a reinforced soil wall. A unique feature of this paper is that measured load and resistance values from a database of case histories are used to develop the statistical parameters in the examples. The paper also addresses issues related to the influence of outliers in the datasets and possible dependencies between variables that can have an important influence on the results of calibration.
On equivalent granular void ratio and steady state behaviour of loose sand with fines
Authors: Rahman M. M. , Lo S. R. , Gnanendran C. T.
Published: October 2008

Void ratio has traditionally been used as a state variable for predicting the liquefaction behaviour of soils under the critical state soil mechanics framework. Recent publications show that void ratio may not be a good state variable for characterizing sand with fines. An alternative state variable referred to as the equivalent granular void ratio has been proposed to resolve this problem. To calculate this alternative state variable, a b parameter is needed. This b parameter represents the fraction of fines that actively participate in the force structure of the solid skeleton. However, predicting the value of b is problematic. Most, if not all, of the b values reported were determined by case-specific back-analysis, that is, the b value was selected so that a single correlation between equivalent granular void ratio and the measured steady state strength (or cyclic resistance) could be achieved. This paper examines the factors affecting the b value based on published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based on fines size and fines content. Published data appear to be in support of the proposed equation. A series of experiments were conducted on a specially designed sand–fines type to provide additional validation of the proposed equation and to reinforce the use of equivalent granular void ratio in a more generalized context.
Instability caused by a seepage impediment in layered fill slopes
Authors: Lee Y. S. , Cheuk C. Y. , Bolton M. D.
Published: October 2008

The underlying cause of loose fill slope failures in Hong Kong has been attributed to static liquefaction during heavy rainfall. A series of centrifuge model tests and numerical analyses were conducted to illustrate that instability of a fill slope inclined at approximately the internal friction angle of the soil can be triggered by confined groundwater flow due to soil layering in the fill slope. The results also showed that slope failure could occur irrespective of the density of the fill material when seepage was sufficiently impeded leading to a localised buildup of pore-water pressure in the slope. A numerical parametric study was carried out to examine the effect of variations in hydraulic conductivity in the layered fill slopes. The results showed that the excess pore pressure distribution and hence the failure mode were strongly dependent on the location of the inhomogeneous soil layers and their hydraulic properties. It was also demonstrated that layered fill slopes with spatial variation in hydraulic conductivity of as small as one order of magnitude were vulnerable to global failure under confined groundwater flow.
Three-dimensional numerical investigation of multifaced tunneling in water-bearing soft ground
Authors: Yoo Chungsik , Kim Sun-Bin
Published: October 2008

This paper presents the results of a numerical investigation of the performance of multifaced tunneling under a pile-supported building in water-bearing soft ground. Special attention was paid to the effect of tunneling and groundwater interaction on the tunneling performance. A fully coupled three-dimensional (3D) stress – pore pressure finite element model was adopted to realistically capture the mechanical and hydrological interaction between the tunneling and groundwater. The results indicate that the groundwater drawdown during tunneling yields a considerably larger settlement-affected zone than for cases with no groundwater drawdown, with a tendency for large portions of ground settlement and groundwater drawdown to be completed before the tunnel passes a monitoring section. Also revealed is that the presence of a building tends to reduce the ground settlements and cause subsurface settlements more or less uniformly with depth. It is shown that the lining deformation, and thus its stresses are not significantly affected by the presence of the building for the multifaced tunneling considered in this study. Axial loads in the piles supporting the building tend to either increase or decrease depending on the pile location relative to the tunnel axis. The patterns of changes in pile axial loads are different from the results of previous studies concerning a single pile.
Factors affecting germination of Myricagale seeds
Authors: Schwintzer Christa R. , Ostrofsky Andrea
Published: October 2008

Several factors affecting seed germination were investigated in Myricagale L., a nitrogen fixing shrub common on wet soils. Light was essential: seeds failed to germinate in the dark and required four 16-h photoperiods (one per day) for maximum germination. There was no absolute requirement for prechilling, but prechilling increased germination by 75% in 2-month-old seeds and by 164% in 4.5 year-old seeds. Leaching did not affect germination and 500 ppm gibberellic acid enhanced germination only 20%. The seeds were long-lived: there was no decrease in percent germination during 6 years of dry storage at 5 °C and germination remained high after 1 year of wet storage at 5 °C. Because M. gale seeds often germinate on water-worked substrates, the requirement for extended exposure to light for germination may serve as a mechanism to prevent unsuccessful germination of seeds that are reburied after brief exposure to light as sediments are worked by water.
Asymbiotic nitrogen fixation and denitrification in a mature forest in coastal British Columbia
Authors: Cushon G. H. , Feller M. C.
Published: October 2008

Gaseous nitrogen inputs due to asymbiotic nitrogen fixation and outputs due to biological denitrification were estimated for a mature mid-successional Pseudotsugamenziesii (Mirb.) Franco–Thujaplicata Donn–Tsugaheterophylla (Raf.) Sarg. forest in southwestern British Columbia. Forest floor material, mineral soil, decaying wood, foliage, and bark were incubated in an atmosphere of 10 kPa C2H2 to allow the simultaneous measurement of N2O production by denitrifying bacteria and C2H2 reduction by free-living bacteria and blue-green algae. Forest floor material accounted for 70% of an estimated total annual nitrogen fixation of 0.3 kg N•ha−1•year −1.•Relatively small amounts of nitrogen were fixed in mineral soil, decaying wood, and foliage, and no indication of nitrogen fixation activity in bark was detected. Some denitrification was found; it was essentially negligible, although possibly underestimated. The net gaseous nitrogen input into the mid-successional forests of the study area is likely to be < 5% of the total net nitrogen inputs, which are primarily from precipitation.
Growth response of young slash pine trees to simulated acid rain and ozone stress
Authors: Dean Thomas J. , Johnson Jon D.
Published: October 2008

To assess the impact of acid rain and ozone stress on the growth and physiology of slash pine (Pinuselliottii Engelm. var. elliottii), four half-sib families of slash pine were planted in large open-top chambers and exposed 28 months to factorial combinations of three rain acidities (pH 3.3, 4.3, and 5.3) and four concentrations of ozone (subambient produced with carbon filtration, ambient, two times ambient, and three times ambient). Growth was assessed by seasonal stem diameter and height increments and by stem volume increment at steady-state conditions. Information on tree physiology was obtained indirectly from estimates of mean unit leaf rate, a measure of the net assimilation capacity of the tree. Among the growth variables, only volume increment showed a consistent year to year response to acid rain and ozone. The acid rain × ozone interaction was significant for volume increment each year and was the result of trees in the two times ambient ozone level having greater sensitivity to rain acidity. Both acid rain and ozone significantly affected mean unit leaf rate; however, this effect weakened with time, suggesting some degree of physiological acclimation. Increasing rain acidity significantly increased mean leaf area only during the first growth period. Ozone significantly decreased mean leaf area all three growth periods, with the effect intensifying each year. Complex family interactions with acid rain and ozone masked any clear family sensitivities to these pollutants.
Predicting water fluxes through forests from monthly precipitation and mean monthly air temperature records
Authors: Arp Paul A. , Yin Xiwei
Published: October 2008

A process-oriented computer model addressing all major water fluxes through forests is introduced. The model is driven by monthly mean air temperature, monthly precipitation, and mean snow fraction of that precipitation. Other data requirements are limited to latitude, proportions of coniferous and deciduous trees in the forest, thickness of each soil layer (forest floor, soil, and subsoil), and clay fraction (or texture) of each mineral soil layer. The number of parameters to be calibrated is kept at a minimum. Parameter calibration is applicable across sites without further modification unless warranted by outstanding physical differences. The model successfully reproduces available data on throughfall, snowpack, forest floor percolate, soil water content, and streamflow from a deciduous forest in Ontario (Turkey Lakes) and a coniferous forest in Quebec (Lake Laflamme).
Antidepressant-like effect of 17β-estradiol: involvement of dopaminergic, serotonergic, and (or) sigma-1 receptor systems
Authors: Dhir Ashish , Kulkarni S.K.
Published: October 2008

17β-estradiol has been reported to possess antidepressant-like activity in animal models of depression, although the mechanism for its effect is not well understood. The present study is an effort in this direction to explore the mechanism of the antidepressant-like effect of 17β-estradiol in a mouse model(s) of behavioral depression (despair behavior). Despair behavior, expressed as helplessness to escape from a situation (immobility period), as in a forced swim test in which the animals are forced to swim for a total of 6 min, was recorded. The antiimmobility effects (antidepressant-like) of 17β-estradiol were compared with those of standard drugs like venlafaxine (16 mg/kg, i.p.). 17β-estradiol produced a U-shaped effect in decreasing the immobility period. It had no effect on locomotor activity of the animal. The antidepressant-like effect was comparable to that of venlafaxine (16 mg/kg, i.p.). 17β-estradiol also exhibited a similar profile of antidepressant action in the tail suspension test. When coadministered with other antidepressant drugs, 17β-estradiol (5 μg/kg, i.p.) potentiated the antiimmobility effect of subeffective doses of fluoxetine (5 mg/kg, i.p.), venlafaxine (2 mg/kg, i.p.), or bupropion (10 mg/kg, i.p.), but not of desipramine (5 mg/kg, i.p.) or tranylcypromine (2 mg/kg, i.p.), in the forced swim test. The reduction in the immobility period elicited by 17β-estradiol (20 μg/kg, i.p.) was reversed by haloperidol (0.5 mg/kg, i.p.; a D2 dopamine receptor antagonist), SCH 23390 (0.5 mg/kg, i.p.; a D1 dopamine receptor antagonist), and sulpiride (5 mg/kg, i.p.; a specific dopamine D2 receptor antagonist). In mice pretreated with (+)-pentazocine (2.5 mg/kg, i.p.; a high-affinity sigma-1 receptor agonist), 17β-estradiol (5 μg/kg, i.p.) produced a synergistic effect. In contrast, pretreatment with progesterone (10 mg/kg, s.c.; a sigma-1 receptor antagonist neurosteroid), rimcazole (5 mg/kg, i.p.; another sigma-1 receptor antagonist), or BD 1047 (1 mg/kg, i.p.; a novel sigma-1 receptor antagonist) reversed the antiimmobility effects of 17β-estradiol (20 μg/kg, i.p.). Similarly, in mice pretreated with a subthreshold dose of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, a 5-HT1A serotonin receptor agonist), 17β-estradiol (5 μg/kg, i.p.) produced an antidepressant-like effect. These findings demonstrate that 17β-estradiol exerted an antidepressant-like effect preferentially through the modulation of dopaminergic and serotonergic receptors. This action may also involve the participation of sigma-1 receptors.
UNPARTICLE AS A PARTICLE WITH ARBITRARY MASS
Authors: NIKOLIĆ HRVOJE
Published: October 2008

The unparticle field operator can be expanded in terms of creation and destruction operators corresponding to particles with a continuous mass spectrum. Hence, when the four-momentum of an unparticle is measured, then the unparticle manifests as an ordinary particle with a definite (but arbitrary) mass.
DETERMINATION OF f0(980) STRUCTURE BY FRAGMENTATION FUNCTIONS
Authors: HIRAI M. , KUMANO S. , OKA M. , SUDOH K.
Published: October 2008

We discuss internal structure of an exotic hadron by using fragmentation functions. The fragmentation functions for the f0(980) meson are obtained by a global analysis of e+ + e− → f0 + X data. Quark configuration of the f0(980) could be determined by peak positions and second moments of the obtained fragmentation functions.
SCALAR NONETS IN POLE-DOMINATED QCD SUM RULES
Authors: KOJO TORU , JIDO DAISUKE
Published: October 2008

The light scalar nonets are studied using the QCD sum rules for the tetraquark operators. The operator product expansion for the correlators is calculated up to dimension 12 and this enables us to perform analyses retaining sufficient pole-dominance. To classify the light scalar nonets, we investigate the dependence on current quark mass and flavor dynamics. Especially, to examine the latter, we study separately SU(3) singlet and octet states, and show that the number of annihilation diagrams is largely responsible for their differences, which is also the case even after the inclusion of the finite quark mass. Our results support the tetraquark picture for isosinglets, while that for octets is not conclusive yet.
STUDYING DIQUARK STRUCTURE OF HEAVY BARYONS IN RELATIVISTIC HEAVY ION COLLISIONS
Authors: YASUI S. , LEE S. H. , OHNISHI K. , YOO I.-K. , KO C. M.
Published: October 2008

We propose the enhancement of Λc yield in heavy ion collisions at RHIC and LHC as a novel signal for the existence of diquarks in the strongly coupled quark-gluon plasma produced in these collisions as well as in the Λc. Assuming that stable bound diquarks can exist in the quark-gluon plasma, we argue that the yield of Λc would be increased by two-body collisions between [ud] diquarks and c quarks, in addition to normal three-body collisions among u, d and c quarks. A quantitative study of this effect based on the coalescence model shows that including the contribution of diquarks to Λc production indeed leads to a substantial enhancement of the Λc/D ratio in heavy ion collisions.
SEA-QUARK FLAVOR ASYMMETRY IN THE NUCLEON FROM A RELATIVISTIC ANALYSIS OF THE DRELL–YAN SCATTERING OFF NUCLEI
Authors: MOLOCHKOV ALEXANDER
Published: October 2008

The study presented in this paper shows that accounting for the relativistic structure of the deuteron allows to explain the ratio of the Drell-Yan pair production cross-sections at the low Bjorken x off the deuteron and the proton. Thus, the sea quark distributions in the nucleon should be studied with accounting for the effects of the relativistic structure of the deuteron. The suggested approach reduces theoretical uncertainty in extracting the ratio [Formula: see text] from the data and it is important for the clarification of the nature of the sea quark asymmetry in the nucleon.
NUCLEAR INTERACTIONS: THE CHIRAL PICTURE
Authors: ROBILOTTA M. R.
Published: October 2008

Chiral expansions of the two-pion exchange components of both two- and three-nucleon forces are reviewed and a discussion is made of the predicted pattern of hierarchies. The strength of the scalar-isoscalar central potential is found to be too large and to defy expectations from the symmetry. The causes of this effect can be understood by studying the nucleon scalar form factor.
LATTICE QCD SIMULATION OF HYPERON-NUCLEON POTENTIAL
Authors: NEMURA H. , ISHII N. , AOKI S. , HATSUDA T.
Published: October 2008

We calculate pΞ0 potentials from the equal-time Bethe-Salpeter amplitude measured in the quenched QCD simulation with the spatial lattice volume, (4.4 fm)3. The standard Wilson gauge action with the gauge coupling β = 5.7 on 324 lattice together with the standard Wilson quark action is used. The hopping parameter κud = 0.1678 is chosen for u and d quarks, which corresponds to mπ ≃ 0.37 GeV . The physical strange quark mass is used by taking the parameter κs = 0.1643 which is deduced from the physical K meson mass. The lattice spacing a = 0.1420 fm is determined by the physical ρ meson mass. We find that the pΞ0 potential has sizable spin dependence. Strong repulsive core is found in 1S0 channel while the effective central potential in the 3S1 channel has relatively weak repulsive core. The potentials also have weak attractive parts in the medium to long distance region (0.6 fm ≲ r ≲ 1.2 fm ) in both of the 1S0 and 3S1 channels.
COUPLED-CHANNELS PARTIAL-WAVE ANALYSIS OF KAON PHOTOPRODUCTION
Authors: SCHOLTEN OLAF , USOV ALEXANDER
Published: October 2008

A coupled channels analysis is presented for photo-induced kaon production which is based on the K-matrix approach. Channel coupling effects are large and should not be ignored. It is shown that multiple solutions exist in a model independent analysis. An outlook is given to the possibilities to include constraints due to causality.
NEUTRINO-INDUCED WEAK PION PRODUCTION OFF THE NUCLEON
Authors: HERNÁNDEZ E. , NIEVES J. , VALVERDE M.
Published: October 2008

We study neutrino-induced one-pion production off the nucleon in and around the Delta resonance region. Apart from the Delta-pole mechanism we include background terms required by chiral symmetry. These background terms give sizeable contributions in all channels. To better reproduce the ANL q2-differential cross section data, we make a new fit of the [Formula: see text] axial nucleon to Delta form factor. The new result [Formula: see text] is some 30% smaller than the commonly accepted value. This correction is compatible with most quark model estimates and a recent lattice calculation.1
NUCLEAR EFFECTS IN NEUTRINO INDUCED REACTIONS
Authors: VICENTE VACAS M. J. , ALVAREZ-RUSO L. , GENG L. S. , NIEVES J. , VALVERDE M. , HIRENZAKI S.
Published: October 2008

We discuss the relevance of nuclear medium effects in the analysis of some low and medium energy neutrino reactions of current interest. In particular, we study the Quasi-Elastic (QE) process, where RPA correlations and Final State Interactions (FSI) are shown to play a crucial role. We have also investigated the ν induced coherent pion production. We find a strong reduction of the cross section due to the distortion of the pion wave function and the modification of the production mechanisms in the nucleus. The sensitivity of the results to the axial NΔ coupling [Formula: see text] has been also investigated.
LATTICE QCD STUDY OF $g^{N^{\ast}N^{\ast}}_{A}$ WITH TWO FLAVORS OF DYNAMICAL QUARKS
Authors: TAKAHASHI TORU T. , KUNIHIRO TEIJI
Published: October 2008

We show the first lattice QCD result of the axial charge [Formula: see text] of N* (1535). We perform the measurements with two flavors of dynamical quarks employing the renormalization-group improved gauge action at β = 1.95 and the mean-field improved clover quark action with the hopping parameters, κ = 0.1375, 0.1390 and 0.1400. In order to avoid signal contaminations by N*(1650), we construct 2 × 2 correlation matrices and diagonalize them so that clear signal separation can be found. The wraparound contributions in the correlator, which can be another source of signal contamination, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of N*(1535) takes a small value, as [Formula: see text], which is almost independent of quark masses.
PROPERTIES OF SCALAR-QUARK SYSTEMS IN SU(3)c LATTICE QCD
Authors: IIDA HIDEAKI , TAKAHASHI TORU T. , SUGANUMA HIDEO
Published: October 2008

We perform the first study for the bound states of colored scalar particles ϕ (“scalar quarks”) in terms of mass generation with quenched SU (3)c lattice QCD. We investigate the bound states of ϕ, ϕ†ϕ and ϕϕϕ (“scalar-quark hadrons”), as well as the bound states of ϕ and quarks ψ, i.e., ϕ†ψ, ψψϕ and ϕϕψ (“chimera hadrons”). All these new-type hadrons including ϕ have a large mass of several GeV due to large quantum corrections by gluons, even for zero bare scalar-quark mass mϕ = 0 at a−1 ~ 1 GeV . We find a similar mψ-dependence between ϕ†ψ and ϕϕψ, which indicates their similar structure due to the large mass of ϕ. From this study, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluons.
CHIRAL SYMMETRY IN NUCLEI THEORETICAL EXPECTATIONS AND HARD FACTS
Authors: MOSEL ULRICH
Published: October 2008

It is widely believed that chiral symmetry is restored not only at high temperatures, but also at high nuclear densities. The drop of the order parameter of the chiral phase transition, the chiral condensate, with density has indeed been calculated in various models and is as such a rather robust result. In this talk I point out that the connection of this property with actual observables is far less clear. For this task a good hadronic description of the primary production of hadrons, their propagation inside the nuclear medium, their decay and the propagation of the decay products through the medium to the detector all have to be treated with equal accuracy and weight. In this talk I illustrate with the examples of ω production and π0π0 production how important in particular final state interactions are.
CHIRALLY SYMMETRIC BUT CONFINED HADRONS AT FINITE DENSITY
Authors: YA. GLOZMAN L. , WAGENBRUNN R. F.
Published: October 2008

At a critical finite chemical potential and low temperature QCD undergoes the chiral restoration phase transition. The folklore tradition is that simultaneously hadrons are deconfined and there appears the quark matter. We demonstrate that it is possible to have confined but chirally symmetric hadrons at a finite chemical potential and hence beyond the chiral restoration point at a finite chemical potential and low temperature there could exist a chirally symmetric matter consisting of chirally symmetric but confined hadrons. If it does happen in QCD, then the QCD phase diagram should be reconsidered with obvious implications for heavy ion programs and astrophysics.
THE STRUCTURE OF N(1535) IN THE ASPECT OF CHIRAL SYMMETRY
Authors: JIDO D. , HYODO T. , HOSAKA A.
Published: October 2008

The structure of N(1535) is discussed in dynamical and symmetry aspects based on chiral symmetry. We find that the N(1535) in chiral unitary model has implicitly some components other than meson-baryon one. We also discuss the N(1535) in the chiral doublet picture.
CHARMONIUM STATES IN QGP
Authors: LEE SU HOUNG , MORITA KENJI
Published: October 2008

Motivated by recent lattice gauge results that the quarkonium does not dissolve at the critical temperature, we report on recent developments in understanding the properties of charmonium states in the quark gluon plasma using perturbative QCD and QCD sum rule approaches. Using lattice results on the energy density and pressure of pure gauge theory as inputs to the operator product expansion in these theories, we find non trivial property changes of heavy quarkonium across the phase transition.
BARYON–BARYON INTERACTION IN THE EXTENDED CHIRAL SU(3) QUARK MODEL
Authors: DAI L. R. , ZHANG H. , FU Y. , ZHANG Z. Y. , YU Y. W.
Published: October 2008

The hyperon-nucleon scattering processes and some dibaryon states are studied both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model by solving the resonating group method (RGM) equation. We find that the short-range interaction could be described either by the one-gluon exchange or by the vector meson exchange for baryon-baryon system.