Value Of Αs Research Articles

A relativistic structure of one-meson and one-gluon exchange forces and a lower excitation spectrum of the nucleon and Δ

A lower excitation spectrum of the nucleon and Δ is calculated in a relativistic chiral quark model. Corrections to the baryon mass spectrum from the second-order self-energy and exchange diagrams induced by pion and gluon fields are estimated in the field-theoretical framework. Convergent results for the self-energy terms are obtained when including the intermediate quark and antiquark states with a total momentum up to j = 25/2. Relativistic one-meson and color-magnetic one-gluon exchange forces are shown to generate spin 0, 1, 2, etc operators, which couple the lower and the upper components of the two interacting valence quarks and yield reasonable matrix elements for the lower excitation spectrum of the nucleon and Δ. The only contribution to the ground-state nucleon and Δ comes from the spin-1 operators, which correspond to the exchanged pion or gluon in the l = 1 orbit, thus indicating that both pion exchange and color-magnetic gluon exchange forces can contribute to the spin of baryons. Is is shown also that the contribution of the color-electric component of the gluon fields to the baryon spectrum is enormously large (more than 500 MeV with a value of αs = 0.65) and one needs to restrict to very small values of the strong coupling constant or to exclude completely the gluon-loop corrections to the baryon spectrum. With this restriction, the calculated spectrum reproduces the main properties of the data; however it needs further contribution from the two-pion exchange and instanton-induced exchange (for the nucleon sector) forces in consistence with the realistic NN-interaction models.

Enantioselectivity in aquatic toxicity of synthetic pyrethroid insecticide fenvalerate

Synthetic pyrethroids (SPs) are a family of chiral insecticides with a large number of stereoisomers. Fenvalerate (FV) is one of the most potent pyrethroid insecticides, controlling a wide range of insect pests in agricultural fields, public health situations and animal houses. FV contains two chiral centers. In this study, four stereoisomers of FV were absolutely separated by high-performance liquid chromatography with a commercial chiral column, CHIRALCEL ® OJ-H, using n-hexane containing 1,2-dichloroethane and ethanol as mobile phase. Toxicity assays of each isomer and racemate of FV were performed using Daphnia magna ( D. magna), zebrafish ( Danio rerio) and zebrafish embryo-larval. In the acute toxicity of D. magna, significant differences were observed: the 24 h EC 50 of αS-2S-FV was 51 times more toxic than the αR-2R-FV, and the 48 h LC 50 results showed that the αS-2S-FV was 99 times more toxic than αR-2R-FV. In the toxicity assay of D. rerio, dramatic differences were also found: the LC 50 value of αS- 2S-FV was 17, 22, 39 and 56 times more toxic than the αR-2R-FV at 24, 48, 72 and 96 h, respectively. The assays of 4-day-old zebrafish embryo-larval showed that the exposure to FV enantioselectively induced crooked body, yolk sac edema and pericardial edema and that the αS-2S-FV was 3.8 times stronger than the other isomers in 96-h mortality. The results indicate that the enantiomeric differences should be taken into consideration in assessing the ecological effects of SPs.

On the effects of compressibility in marginally separated flows

AbstractIf the angle of attack α of a slender airfoil reaches a critical value αs flow separation is known to occur at the upper surface. Further increase of α initially leads to the formation of a short laminar separation bubble which has an extremely weak influence on the external flow field — a phenomenon known as marginal separation — but then rather rapidly causes a severe change of the flow behaviour (leading edge stall). According to the asymptotic theory of marginal separation holding in the limit of large Reynolds numbers t→∞ the flow in the neighbourhood of the separation bubble is governed by an integro–differential equation exhibiting a single controlling parameter Γ which relates the angle of attack to the Reynolds number, with a value Γs corresponding to αs. Numerical investigations have shown that solutions to this equation exist up to a critical value Γc>Γs only and this has been taken as an indication that a substantial change of the flow field must take place if Γ exceeds Γc. In the case of unsteady three–dimensional perturbations of a two–dimensional steady marginally separated boundary layer in the limit Γ→Γc, the (generalized form of the) integro–differential equation reduces to a nonlinear diffusion equation of Fisher type. This asymptotic description serves as a basis for the investigations concerning compressibility effects, also in respect of the mechanism through which the hydromechanic motion inside the boundary layer could be transformed into aerodynamic sound. A modified interaction equation is obtained, which in addition to Γ, contains the Mach number at the point of separation as a second controlling parameter. The unsteady changes of the boundary layer displacement thickness in the limit ΔΓ=Γc−Γ→0, again governed by Fisher's equation, then are identified to act as a quadrupole source for sound radiation. The most surprising outcome is the fact that in the three–dimensional case, the second derivative with respect to the lateral direction contained in the Fisher equation changes its sign and becomes negative if the Mach number exceeds a certain value. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of Thomson effect on the resultant local Seebeck coefficient in thermoelectric composite materials

The resultant local Seebeck coefficient αR (=αS−αT) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric efficiency, where αS is the local Seebeck coefficient and αT is the one caused by the Thomson effect. It is shown in this paper that αS, αT, and αR of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of αS at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite, respectively, while those of αT are less than 8% of αS all over the composite and are so small that the relation αR≈αS can be held. We thus succeeded in measuring αR at the interfaces of the composite.

Direct quantification of CSF α-synuclein by ELISA and first cross-sectional study in patients with neurodegeneration

Because accumulation of α-synuclein (αS) in the brain is a hallmark of Parkinson disease (PD) and related disorders, we examined its occurrence in human cerebrospinal fluid (CSF). Following affinity enrichment and trypsin digestion of CSF collected from a neurologically healthy donor, we identified several αS-derived peptides by mass spectrometry. The concentration of αS amounted to <0.001% of the CSF proteome. We then built, validated and optimized a sandwich-type, enzyme-linked immunoadsorbent assay (ELISA) to measure total αS levels in unconcentrated CSF. In a cross-sectional study of 100 living donors, we examined cell-free CSF samples from subjects clinically diagnosed with advanced PD, dementia with Lewy bodies (DLB), Alzheimer disease (AD), and a group of non-neurodegenerative disease controls (NCO). In these four groups the CSF αS concentrations ranged from 0.8 to 16.2 pg/μl. Mean CSF αS values were lower in donors with a primary synucleinopathy (PD, DLB: n=57) than in the other two groups (AD, NCO: n=35; p=0.025). By contrast, living Creutzfeldt–Jakob disease patients showed markedly elevated CSF αS levels (n=8; mean, 300 pg/μl; p<0.001). Our results unequivocally confirm the presence of αS in adult human CSF. In a first feasibility study employing a novel ELISA, we found relatively low CSF αS concentrations in subjects with parkinsonism linked to synucleinopathy, PD and DLB. In definite prion disease cases, we recorded a marked rise in total CSF αS resulting from rapid cell death. Our results will likely aid future biomarker explorations in neurodegenerative conditions and facilitate target validation studies.

SU-GG-T-218: Measurements of X-Ray Spectra Emergent From Low-Energy Photon- Emitting Brachytherapy Sources

Purpose: To investigate changes in the emergent spectra of low‐energy photon‐emitting brachytherapy sources as a function of angle in the plane of the source long axis. Method and Materials: X‐ray spectrometry was performed utilizing a high‐purity germanium detector, having a 1 cm diameter aperture, located at a distance of 177 cm from the center of the source. The source, with the long axis parallel to the floor of the laboratory, was mounted on a rotating vertical post. Emergent spectra were measured at rotation intervals that varied from 5 degrees to 15 degrees for a total of forty spectra per source. The intensity ratio of Kβ to Kαx rays from the decay of the radionuclide, the intensity ratio of Ag Kαfluorescencex rays to the 35 keV emission line from I‐125 sources that contained silver, and the air‐kerma strength were all calculated from the measuredspectra as a function of source rotation angle. Results: The degree of anisotropy about the axis perpendicular to the mid‐point of the long axis of the source was characterized by calculating the ratio of the air‐kerma strength of the source positioned perpendicular to and parallel to the detector face. Values of this “air‐anisotropy ratio”, αS, varied from 0.05 for a Pd‐103 source with thick end caps to about 1 for an I‐125 source with a uniform encapsulation thickness. Sources with low values of αS showed a significant increase in the Kβ‐to‐Kα intensity ratio for emissions from the seed ends. Conclusion: Variations in the designs of brachytherapy sources significantly influence their emergent spectra.Measuring the spectra around these sources has lead to an understanding of the response of well‐ionization chambers, used in therapy clinics to verify source air‐kerma strength prior to treatment, relative to the NIST Wide‐Angle Free‐Air Chamber (WAFAC) primary standard.

Fractal scaling properties of heart rate dynamics following resistance exercise training

With aging and disease, there is a breakdown of the natural fractal-like organization of heart rate (HR). Fractal-like correlation properties of HR can be assessed with detrended fluctuation analysis (DFA). A short-time scaling exponent (alpha(s)) value of 1 is associated with healthy HR dynamics, whereas values that deviate away from 1, in either direction, indicate fractal collapse. The purpose of this study was to examine the effect of resistance exercise training (RT) on fractal correlation properties of HR dynamics. Resting ECG was collected at baseline, following a 4-wk time control period and 6 wk of RT (3 days per wk) in 34 men (23 +/- 1 years of age). Fractal properties of HR were assessed with DFA. There was no change in alpha(s) following either the time control period or RT (1.01 +/- 0.06 to 0.98 +/- 0.06 to 0.93 +/- 0.04, P > 0.05). Given the potential bidirectional nature of fractal collapse, subjects were retrospectively separated into two groups (higher alpha(s) and lower alpha(s)) on the basis of the initial alpha(s) by using cluster analysis. An interaction was detected for alpha(s) following RT (P < 0.05). There was no change in alpha(s) in either group following the time control, but alpha(s) increased following RT in the lower alpha(s) group (n = 18; 0.73 +/- 0.04 to 0.69 +/- 0.04 to 0.88 +/- 0.04) and alpha(s) decreased following RT in the higher alpha(s) group (n = 16; 1.20 +/- 0.04 to 1.24 +/- 0.04 to 0.98 +/- 0.04). In conclusion, RT improves fractal properties of HR dynamics.

Precision measurements of αs at hera

Recent determinations of αs (MZ) from the H1 and ZEUS Collaborations using inclusive-jet cross-section measurements in neutral current deep inelastic scattering at high Q2 are presented. A combined value of αs (MZ) = 0.1198±0.0019 (exp.)±0.0026 (th.) was obtained from these measurements. The determinations of αs at various scales clearly show the running of the coupling from HERA jet data alone and in agreement with the prediction of QCD.

Deconfinement Phase Transition Including Perturbative QCD Corrections in (Proto)neutron Star Matter

Deconfinement phase transition and neutrino trapping in (proto)neutron star matter are investigated in a chiral hadronic model (also referred to as the FST model) for the hadronic phase (HP) and in the color-flavor-locked (CFL) quark model for the deconfined quark phase. We include a perturbative QCD correction parameter αs in the CFL quark matter equation of states. It is shown that the CFL quark core with K0 condensation forms in neutron star matter with the large value of αs. If the small value of αs is taken, hyperons suppress the CFL quark phase and the HP is dominant in the high-density region of (proto)neutron star matter. Neutrino trapping makes the fraction of the CFL quark matter decrease compared with those without neutrino trapping. Moreover, increasing the QCD correction parameter αs or decreasing the bag constant B and the strange quark mass ms can make the fraction of the CFL quark matter increase, simultaneously, the fraction of neutrino in protoneutron star matter increases, too. The maximum masses and the corresponding radii of (proto)neutron stars are not sensitive to the QCD correction parameter αs.

NJL INTERACTION DERIVED FROM QCD

We apply Bogolubov approach to QCD with two light quarks to demonstrate a spontaneous generation of an effective interaction, leading to the Nambu–Jona-Lasinio model. The resulting theory contains two parameters: average low-energy value of αs and current light quark mass m0. All other low-energy parameters: the pion decay constant, mass of the π-meson, mass of the σ-meson and its width, the constituent quark mass, and the quark condensate are expressed in terms of the two input parameters in satisfactory correspondence to experimental data and chiral phenomenology. For example, in the approximation being used we have for αs = 0.67 and m0 = 20 MeV : fπ = 93 MeV , mπ = 135 MeV , mσ = 492 MeV , Γσ = 574 MeV , mq = 295 MeV , [Formula: see text].

Odderon and pomeron from the vacuum correlator method

Glueball masses with J⩽7 are computed both for C=+1 and C=−1 using the string Hamiltonian derived in the framework of the vacuum correlator method. No fitting parameters are used, and masses are expressed in terms of string tension σ and effective value of αs. We extend the calculations done for J⩽3 using the same Hamiltonian, which provided glueball masses in good agreement with existing lattice data, to higher mass states. It is shown that 3−−,5−− and 7−− states lie on the odderon trajectories with the intercept around or below 0.14. Another odderon trajectory with 3g glueballs of Y-shape, corresponds to 11% higher masses and low intercept. These findings are in agreement with recent experimental data, setting limits on the odderon contribution to the exclusive γp reactions.

Final α s combinations from the LEP QCD Working Group

The LEP QCD Working Group has for several years produced combinations of αs values derived from eventshape distributions. The distributions are measured at scales below the mass of the Z boson up to 206 GeV. Values of αs are all extracted using the consistent application of O(αs2)+NLLA predictions with the modified Log(R) matching scheme. A combined αs is obtained for each experiment and observable using at least two experiments in each case for energies above at ad above the mass of the Z boson. A consistent treatment and controlled breakdown is made of the sources of uncertainty on the input values. The final combinations are now being performed, with the last of the definitive inpits being received for the Summer 2004 conferences The combined best value for LEP I is αs(MZ) = 0.1202 ± 0.0006(expt.) ± 0.0050(theo.) and for LEP II is α.(MZ) = 0.1202 ± 0.0011(expt.) ± 0.0046(theo.). The dominant theoretical uncertainty is due to the effects of missing higher order contributions in the perturbative predictions used.

Electron beam evaporated rigid optical solar reflectors for space applications

Rigid optical solar reflectors (OSRs) for space applications were developed by using the electron beam evaporation technique. The component layers of the full stack were optimised for their electrical and optical properties. Thin films of Ta2O5 show absorption in the ultraviolet–visible range at high substrate temperatures, which can be eliminated by deposition at an oxygen partial pressure of >4 × 10−5 torr. Under optimised deposition conditions, indium–tin oxide (ITO) films have a sheet resistance Rsh of <0·95 kΩ/□ and a transmittance of <95% in the visible region. The electrical and optical properties of the OSR stacks were investigated as a function of various deposition parameters, such as substrate temperature, thickness and deposition rate. It was found that the functional properties of the OSRs developed with the electron beam technique are equivalent to those of the rigid OSRs deposited by the sputtering technique. A solar absorptance αs value of <0·047 and a sheet resistance Rsh value of <3 kΩ/□ were obtained for the OSR deposited under the optimised conditions. The samples were found to be environmentally durable.

WE‐C‐T‐617‐07: Using X‐Ray Spectrometry to Quantify the Effects of Emission Anisotropy On Air‐Kerma‐Strength Measurements of Prostate Brachytherapy Seeds

Purpose: To utilize the results of prostate brachytherapy seed x‐ray spectrometry to quantify the effects of emission anisotropy on air‐kerma‐strength measurements. Method and Materials: Air‐kerma strength was calculated from x‐ray spectra measured with a high‐purity germanium detector with the seed rotated at 90‐degree intervals about an axis perpendicular to the mid‐point of the long axis of the seed. The “air‐anisotropy ratio”, αS, was formed by taking the quotient of the air‐kerma strength of the seed with the long axis perpendicular to the detector face and the air‐kerma strength of the seed with the long axis parallel to the detector face. The resulting quantity αS is a quantitative measure of in‐air anisotropy, which has a significant effect on the relative responses of secondary‐standard well chambers and the National Institute of Standards and Technology (NIST) Wide‐Angle Free‐Air Chamber (WAFAC) primary standard. Results: Values of αS for various seed models are influenced by the presence of end welds, seed internal geometry, and the incorporated radionuclide. In comparing αS among seeds, a lower value indicated that the output of the seed was more directional (along the transverse axis), such that less emission was “missed” by the WAFAC (8 degree half‐angle) that was detected by the well chamber (approximate 4π geometry). Conclusion: The quantity αS has proven to be a useful parameter for explaining differences in well‐chamber response observed for different seed models having the same emergent spectrum on their transverse axis. It also has been used to identify aberrantly produced seeds that are not representative of those calibrated previously by NIST. Characterization of seed anisotropy is necessary in order to maintain accuracy in the transfer of air‐kerma‐strength standards from NIST to the AAPM Accredited Dosimetry Calibration Laboratories and to seed manufacturers.

The gluon splitting function at moderately small x

It is widely believed that at small x, the BFKL resummed gluon splitting function should grow as a power of 1/x. But in several recent calculations it has been found to decrease for moderately small-x before eventually rising. We show that this ‘dip’ structure is a rigorous feature of the Pgg splitting function for sufficiently small αs, the minimum occurring formally at log(1/x)∼1/αs. We calculate the properties of the dip, including corrections of relative order αs, and discuss how this expansion in powers of αs, which is poorly convergent, can be qualitatively matched to the fully resummed result of a recent calculation, for realistic values of αs. Finally, we note that the dip position, as a function of αs, provides a lower bound in x below which the NNLO fixed-order expansion of the splitting function breaks down and the resummation of small-x terms is mandatory.

Measurement of subjet multiplicities in neutral current deep inelastic scattering at HERA and determination of αs

The subjet multiplicity has been measured in neutral current e+p interactions at Q2>125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb−1. Jets were identified in the laboratory frame using the longitudinally invariant kT cluster algorithm. The number of jet-like substructures within jets, known as the subjet multiplicity, is defined as the number of clusters resolved in a jet by reapplying the jet algorithm at a smaller resolution scale ycut. Measurements of the mean subjet multiplicity, 〈nsbj〉, for jets with transverse energies ET,jet>15 GeV are presented. Next-to-leading-order perturbative QCD calculations describe the measurements well. The value of αs(MZ), determined from 〈nsbj〉 at ycut=10−2 for jets with 25<ET,jet<71 GeV, is αs(MZ)=0.1187±0.0017(stat.)+0.0024−0.0009(syst.)+0.0093−0.0076(th.).

ZEUS next-to-leading-order QCD analysis of data on deep inelastic scattering

Next-to-leading-order QCD analyses of the ZEUS data on deep inelastic scattering together with fixed-target data have been performed, from which the gluon and quark densities of the proton and the value of the strong coupling constant αs(MZ) were extracted. The study includes a full treatment of the experimental systematic uncertainties including point-to-point correlations. The resulting uncertainties in the parton density functions are presented. A combined fit for αs(MZ) and the gluon and quark densities yields a value for αs(MZ) in agreement with the world average. The parton density functions derived from ZEUS data alone indicate the importance of HERA data in determining the sea quark and gluon distributions at low x. The limits of applicability of the theoretical formalism have been explored by comparing the fit predictions to ZEUS data at very low Q2. Received 9 September 2002DOI:https://doi.org/10.1103/PhysRevD.67.012007©2003 American Physical Society

Solar absorber coatings based on CoCuMnOx spinels prepared via the sol–gel process: structural and optical properties

Abstract Titanium-doped and undoped CuCoMnOx spinel films were deposited on Al substrates from sols which were made from the following: Co-acetate, Cu-chloride and Mn-acetate (Ti:CoCuMnOx-I); and Co-acetate, Cu-nitrate and Mn-acetate (CoCuMnOx-II). The precursors’ ratio Co:Cu:Mn was equal to 1:3:3. The solar absorptance (αs) and the thermal emittance (eT) of the films, which were annealed at 450°C for 15 or 30 min, were determined from the corresponding diffuse reflectance spectra in the 0.32–20 μm range. The results show that the CoCuMnOx-II films with SiOx protective over-coatings exhibited values of αs=0.85–0.91 and eT below 0.036 after just a single dipping/annealing cycle. The structure of the films was studied with X-ray diffraction (XRD), infrared (IR) absorbance and near-grazing incidence angle (NGIA) reflection-absorption spectroscopy. Our results suggested that the films have a spinel structure with the composition CoCuMnOx. The stability of the films was tested by soaking them in boiling water for 2 h. NGIA IR spectra of the treated films confirmed the formation of the hydrated mixed oxide (Mn-, Co-, Cu-) phases. To improve the stability of the films two kinds of protective over-coatings were tested: one over-coating was based on polysiloxane resin and the other on high-density silica (T-resin). Films that were resistant to boiling water were obtained by applying the high-density silica protective over-coating, which was cured at 140°C for 30 min.

Flipping SU(5) out of trouble

Minimal supersymmetric SU(5) GUTs are being squeezed by the recent values of αs, sin2θW, the lower limit on the lifetime for p→ν̄K decay, and other experimental data. We show how the minimal flipped SU(5) GUT survives these perils, accommodating the experimental values of αs and sin2θW and other constraints, while yielding a p→e/μ+π0 lifetime beyond the present experimental limit but potentially accessible to a further round of experiments. We exemplify our analysis using a set of benchmark supersymmetric scenarios proposed recently in a constrained MSSM framework.

Inclusive jet cross sections in the Breit frame in neutral current deep inelastic scattering at HERA and determination of αs

Inclusive jet differential cross sections have been measured in neutral current deep inelastic e+p scattering for boson virtualities Q2>125 GeV2. The data were taken using the ZEUS detector at HERA and correspond to an integrated luminosity of 38.6 pb−1. Jets were identified in the Breit frame using the longitudinally invariant kT cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy (EBT,jet), jet pseudorapidity and Q2, for jets with EBT,jet>8 GeV. Next-to-leading-order QCD calculations agree well with the measurements both at high Q2 and high EBT,jet. The value of αs(MZ), determined from an analysis of dσ/dQ2 for Q2>500 GeV2, is αs(MZ)=0.1212±0.0017(stat.)+0.0023−0.0031(syst.)+0.0028−0.0027(th.).