Vacuum Value Research Articles

Oscillation effects on high-energy neutrino fluxes from astrophysical hidden sources

High-energy neutrinos are expected to be produced in a variety of astrophysical sources as well as in optically thick hidden sources. We explore the matter-induced oscillation effects on emitted neutrino fluxes of three different flavors from the latter class. We use the ratio of electron and tau induced showers to muon tracks, in upcoming neutrino telescopes, as the principal observable in our analysis. This ratio depends on the neutrino energy, density profile of the sources, and on the oscillation parameters. The largely unknown flux normalization drops out of our calculation and only affects the statistics. For the current knowledge of the oscillation parameters we find that the matter-induced effects are non-negligible and the enhancement of the ratio from its vacuum value takes place in an energy range where the neutrino telescopes are the most sensitive. Quantifying the effect would be useful to learn about the astrophysics of the sources as well as the oscillation parameters. If the neutrino telescopes mostly detect diffuse neutrinos without identifying their sources, then any deviation of the measured flux ratios from the vacuum expectation values would be most naturally explained by a large population of hidden sources for which matter-induced neutrino oscillation effects are important.

SU(2) Yang–Mills quantum mechanics of spatially constant fields

Abstract As a first step towards a strong coupling expansion of Yang–Mills theory, the SU ( 2 ) Yang–Mills quantum mechanics of spatially constant gauge fields is investigated in the symmetric gauge, with the six physical fields represented in terms of a positive definite symmetric 3 × 3 matrix S. Representing the eigenvalues of S in terms of elementary symmetric polynomials, the eigenstates of the corresponding harmonic oscillator problem can be calculated analytically and used as orthonormal basis of trial states for a variational calculation of the Yang–Mills quantum mechanics. In this way high precision results are obtained in a very effective way for the lowest eigenstates in the spin-0 sector as well as for higher spin. Furthermore I find, that practically all excitation energy of the eigenstates, independently of whether it is a vibrational or a rotational excitation, leads to an increase of the expectation value of the largest eigenvalue 〈 ϕ 3 〉 of S, whereas the expectation values of the other two eigenvalues, 〈 ϕ 1 〉 and 〈 ϕ 2 〉 , and also the component 〈 B 3 〉 = g 〈 ϕ 1 ϕ 2 〉 of the magnetic field, remain at their vacuum values.

DLC solid lubricant coatings on ball bearings for space applications

The environment of space offers special challenges for the lubrication of components in sliding and rolling mechanisms. Hydrogenated diamond-like carbon (DLC) films are being studied as solid lubricant coatings to simultaneously fulfil specifications regarding wear resistance and low friction behaviour under ambient atmosphere and in vacuum. In this paper, the tribological behaviour of highly hydrogenated DLC coatings ( ∼ 50 at% hydrogen) is assessed. Coating composition was optimised on flat AISI 52100 steel substrates based on ball-on-disc tribotest results in air, vacuum and dry nitrogen environments. The developed DLC coatings can be tailored to yield ultra-low friction values in vacuum ( μ = 0.008 ) . The average friction coefficient range obtained in humid air, dry nitrogen and vacuum for the range of applied loads were, respectively, 0.22 to 0.27, 0.02 to 0.03, and 0.007 to 0.013. New in this work is that optimised DLC coatings were applied to ball bearings for space applications. The torque and life tests of coated pairs of angular contact bearings in air revealed that relatively high bearing torques are generated which increase with time, but the amount of coating wear generated during in-air operation appears relatively light. In vacuum, low torques are generated after a prolonged running-in period. Low-torque life exceeds that observed for MoS 2 by a factor of about two. It is concluded that, in contrast to MoS 2 coated bearings, DLC-coated bearings for space applications might therefore be capable of undergoing in-air ground testing without too much disruption of the subsequent in-space performance.

Feasibility and simulation model of a pilot scale membrane bioreactor for wastewater treatment and reuse from Chinese traditional medicine

The lack and pollution of water resource make wastewater reuse necessary. The pilot scale long-term tests for submerged membrane bioreactor were conducted to treat the effluents of anaerobic or aerobic treatment process for the high-strength Chinese traditional medicine wastewater. This article was focused on the feasibility of the wastewater treatment and reuse at shorter hydraulic retention time (HRT) of 5.0, 3.2 and 2.13 h. MLSS growth, membrane flux, vacuum values and chemical cleaning periods were also investigated. The experimental results of treating two-phase anaerobic treatmenl effluent demonstrated that the COD filt was less than 100 mg/L when the influent COD was between 500–10000 mg/L at HRT of 5.0 h, which could satisfy the normal discharged standard in China. The experimental results to treat cross flow aerobic reactor effluent demonstrated that the average value of COD filt was 17.28 mg/L when the average value of influent COD was 192.84 mg/L at HRT of 2.13 h during 106 d, which could completely meet the normal standard for water reuse. The maximum MLSS and MLVSS reached 24000 and 14500 mg/L at HRT of 3.2 h respectively. Membrane flux had maximal resume degrees of 94.7% at vacuum value of 0.02 MPa after cleaning. Chemical cleaning periods of membrane module were 150 d. A simulation model of operational parameters was also established based on the theory of back propagation neural network and linear regression of traditional mathematical model. The simulation model showed that the optimum operational parameters were suggested as follows: HRT was 5.0 h, SRT was 100 d, the range of COD loading rate was between 10.664–20.451 kg/(m 3-d), the range of MLSS was between 7543–13694 mg/L.

Isospin mode splitting and mixing in asymmetric nuclear matter

We estimate exclusive density and asymmetry parameter dependent dispersion relations of various charged states of pions in asymmetric nuclear matter. The possibility of matter induced mixing of {pi}{sup 0} with {eta} is clearly exposed with the further mass modification of {pi}{sup 0} meson due to mixing. Asymmetry driven mass splitting and mixing amplitude are of the same order as the corresponding values in vacuum. Closed form analytic results for the mass shifts and dispersion relations with and without mixing are presented. Furthermore, we discuss the sensitivity of our results on the scalar mean field within the framework of quantum hadrodynamics.

Influence of oxygen exclusion and temperature on pathogenic bacteria levels and sensory characteristics of packed ostrich steaks throughout refrigerated storage

Ostrich steaks (290) were obtained from Iliofibularis muscles. For microbiological and pH determinations, samples were inoculated with Listeria monocytogenes NCTC 11994 (80 steaks) or Escherichia coli ATCC 12806 (80), then air- or vacuum-packed and stored at either 4 ± 1 °C or 10 ± 1 °C. Analyses were carried out on days 0, 3, 6 and 9 of storage. For sensory evaluation, samples (130) were air- or vacuum-packed and stored at 4 ± 1 °C or at 10 ± 1 °C. Sensory attributes (odour, colour, drip loss, texture and general acceptability) were scored by six untrained judges using an unstructured nine-point hedonic scale on eleven sampling days (0, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30). Increases in microbial counts (log 10 cfu/g) were observed throughout storage in all groups of samples for both L. monocytogenes (from 6.39 ± 0.43–6.62 ± 0.32 at day 0 to 8.87 ± 0.19–9.64 ± 0.43 at day 9) and E. coli (from 5.57 ± 0.15–5.68 − 0.40 to 7.79 ± 0.96–9.64 ± 0.17). Gas atmosphere influenced microbial counts from day 3 of storage with lower ( P < 0.05) values observed in vacuum- than in air-packed samples at 10 °C ( L. monocytogenes) or at 4 and 10 °C ( E. coli). Storage temperature significantly influenced bacterial counts throughout storage, especially in air-packed samples. Lower pH values in vacuum- than in air-packed samples were observed from day 6. Both effects (gas atmosphere and temperature) influenced the hedonic scores, with higher values assigned to vacuum-packed samples for most attributes (with the exception of drip loss) and sampling days. A marked influence of storage temperature on sensorial scores was obtained in air-packaged ostrich steaks. The shelf-life (time until the average general acceptability score fell below 5) was 6 (air-packed samples), 9 (vacuum-packed, 10 °C), or 12 days (vacuum-packed, 4 °C). The results being reported here suggest the importance of both oxygen exclusion and storage at low temperatures to reduce microbiological risks and improve the acceptability of ostrich meat. However, the short shelf-life of this product highlights the need to keep the time between slaughter and sale to a minimum.

Neutral pion condensation and magnetic field in the chiral model

It has been suggested that, in the chiral model of nucleons and pions, the neutral pions form a spatially non-uniform condensate and the spins of nucleons are polarized; therefore, the matter is magnetized at high density. Because of the magnetic moment and/or electric charge, the motion of a proton is controlled by the magnetic field, which is generated by the motion and magnetic moments of other nucleons. We re-examine this phenomenon in a neutron–proton–electron–muon system by taking the magnetic field into account in a self-consistent way. The vacuum values for the magnetic moments are assumed. We find that the protons do not occupy the Landau level with the lowest principal quantum number. The magnetic flux density in matter is of the order of 1015 G, whose effect on the equation of state is very small compared with the pion condensation. The equation of state is softened further as compared to the case in which a pion condensate is absent.

Green's dyadic approach of the self-stress on a dielectric–diamagnetic cylinder with non-uniform speed of light

We present a Green's dyadic formulation to calculate the Casimir energy for a dielectric-diamagnetic cylinder with the speed of light differing on the inside and outside. Although the result is in general divergent, special cases are meaningful. It is pointed out how the self-stress on a purely dielectric cylinder vanishes through second order in the deviation of the permittivity from its vacuum value, in agreement with the result calculated from the sum of van der Waals forces.

Moduli-mixing racetrack model

We study supersymmetric models with double gaugino condensations in the hidden sector, where the gauge couplings depend on two light moduli of superstring theory. We perform a detailed analysis of this class of model and show that there is no stable supersymmetric minimum with finite vacuum values of moduli fields. Instead, we find that the supersymmetry breaking occurs with moduli stabilized and negative vacuum energy. That yields moduli-dominated soft supersymmetry breaking terms. To realize slightly positive (or vanishing) vacuum energy, we add uplifting potential. We discuss uplifting does not change qualitatively the vacuum expectation values of moduli and the above feature of supersymmetry breaking.

Environmental stability and cryogenic thermal cycling of low-temperature plasma-deposited silicon nitride thin films

Stress in low-temperature plasma-enhanced chemical vapor deposited silicon nitride (SiNx) thin films subject to cryogenic thermal cycling (100–323K) has been measured. It is observed that the SiNx deposition temperature strongly influences the thin film characteristics. For films deposited between 200 and 300°C, the thermal expansion coefficient is similar to that of silicon over the 180–323K temperature range. The room temperature thermal expansion coefficient of SiNx films is found to decrease sublinearly from 5.2×10−6to2.6×10−6K−1 as the temperature of the deposition process is increased from 50to300°C. The negative correlation between deposition temperature and thin film thermal expansion coefficient, and the positive correlation between deposition temperature and the thin film Young’s modulus inferred from nanoindentation are postulated to be associated with the local bonding environment within the thin film. The stress state of SiNx films deposited above 150°C is stable under atmospheric conditions, in contrast to SiNx films deposited below 100°C, which under atmospheric storage conditions become more tensile with time due to oxidation. In addition, SiNx thin films deposited below 100°C exhibit higher tensile stress values in vacuum than at atmospheric pressure, and vacuum annealing at 50°C of films deposited below 100°C introduces further tensile stress changes. These stress changes have been shown to be fully reversible upon reexposure to high purity nitrogen, helium, argon, oxygen, or laboratory atmosphere, and are likely to be associated with thin film porosity.

η mesons in nuclear matter

The $\eta$-nucleon ($\eta$N) interactions are deduced from the heavy baryon chiral perturbation theory up to the next-to-leading-order terms. Combining the relativistic mean-field theory for nucleon system, we have studied the in-medium properties of $\eta$-meson. We find that all the elastic scattering $\eta$N interactions come from the next-to-leading-order terms. The $\eta $N sigma term is found to be about 280$\pm$130 MeV. The off-shell terms are also important to the in-medium properties of $\eta$-meson. On application of the latest determination of the $\eta$N scattering length, the ratio of $\eta$-meson effective mass to its vacuum value is near $0.84\pm0.015$, while the optical potential is about $-(83\pm5)$ MeV, at the normal nuclear density.

Anisotropic muonium centers in aluminum nitride

An atomic-like neutral muonium center with a small anisotropy is inferred from hyperfine decoupling curves and longitudinal relaxation data on AlN. The isotropic contribution of A = 4422 MHz , 99% of the full vacuum value, is accompanied by a weak dipolar term with D = 144 MHz as average values extracted from complete decoupling curves at a few temperatures. Simulations assuming the four nitrogen antibonding sites well reproduce the decoupling data. The hyperfine constants are consistent with those previously obtained from fitting temperature-dependent longitudinal relaxation rates to a simple model for Mu 0 motion.

NEAR FORWARD pp ELASTIC SCATTERING AT LHC AND NUCLEON STRUCTURE

High energy pp and [Formula: see text] elastic scattering carried out at CERN ISR and SPS Collider and at Fermilab Tevatron are studied first in a model where the nucleon has an outer cloud and an inner core. Elastic scattering is viewed as primarily due to two processes: (a) diffraction scattering originating from cloud–cloud interaction; (b) a hard or large |t| scattering originating from one nucleon core scattering off the other via vector meson ω exchange, while their outer clouds interact independently. For small |t| diffraction dominates, but the hard scattering takes over as |t| increases. The ω-exchange amplitude shows that ω behaves like an elementary vector meson at high energy, contrary to a regge pole behavior. This behavior, however, can be understood in the nonlinear σ-model where ω couples to a topological baryonic current like a gauge boson, and the nucleon is described as a topological soliton. Further investigation shows that the underlying effective field theory model is a gauged Gell-Mann–Levy type linear σ-model that has not only the pion sector and the Wess–Zumino–Witten action of the nonlinear σ-model, but also a quark sector where quarks and antiquarks interact via a scalar field. The scalar field vanishes near the center of the nucleon, but rises sharply at some critical distance to its vacuum value fπ leading to a [Formula: see text] condensate analogous to a BCS condensate in superconductivity. The nucleon structure that emerges then is that the nucleon has an outer cloud of [Formula: see text] condensed ground state, an inner core of topological baryonic charge probed by ω, and a still smaller quark-bag containing massless valence quarks. Large |t|pp elastic scattering is attributed to valence quark–quark elastic scattering, which is taken to be due to the hard pomeron (BFKL pomeron with next to leading order corrections). The parameters in the model are determined by requiring that they satisfactorily describe the known asymptotic behavior of σ tot (s) and ρ(s), and the measured [Formula: see text] at [Formula: see text], 630 GeV, and 1.8 TeV. The model is then used to predict pp elastic differential cross-section at LHC at [Formula: see text] and |t| = 0–10 GeV 2. Our predicted dσ/dt at 14 TeV is found to be very different from those predicted by the impact-picture model and the eikonalized pomeron–reggeon model. Precise measurement of dσ/dt at LHC by the TOTEM group will be able to distinguish between these models. If our predicted dσ/dt is quantitatively confirmed, then it will indicate that various novel ideas developed to describe the nucleon combine and lead to a unique physical description of its structure.

Vapor pressures and evaporation coefficients for melts of ferromagnesian chondrule-like compositions

To determine evaporation coefficients for the major gaseous species that evaporate from silicate melts, the Hertz–Knudsen equation was used to model the compositions of residues of chondrule analogs produced by evaporation in vacuum by Hashimoto [Hashimoto A. (1983) Evaporation metamorphism in the early solar nebula-evaporation experiments on the melt FeO–MgO–SiO 2–CaO–Al 2O 3 and chemical fractionations of primitive materials. Geochem. J. 17, 111–145] and Wang et al. [Wang J., Davis A. M., Clayton R. N., Mayeda T. K., Hashimoto A. (2001) Chemical and isotopic fractionation during the evaporation of the FeO–MgO–SiO 2–CaO–Al 2O 3–TiO 2 rare earth element melt system. Geochim. Cosmochim. Acta 65, 479–494], in vacuum and in H 2 by Yu et al. [Yu Y., Hewins R. H., Alexander C. M. O’D., Wang J. (2003) Experimental study of evaporation and isotopic mass fractionation of potassium in silicate melts. Geochim. Cosmochim. Acta 67, 773–786], and in H 2 by Cohen et al. [Cohen B. A., Hewins R. H., Alexander C. M. O’D. (2004) The formation of chondrules by open-system melting of nebular condensates. Geochim. Cosmochim. Acta 68, 1661–1675]. Vapor pressures were calculated using the thermodynamic model of Ghiorso and Sack [Ghiorso M. S., Sack R. O. (1995) Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid–solid equilibria in magmatic systems at elevated temperatures and pressures. Contrib. Mineral. Petrol. 119, 197–212], except for the late, FeO-free stages of the Wang et al. (2001) and Cohen et al. (2004) experiments, where the CMAS activity model of Berman [Berman R. G. (1983) A thermodynamic model for multicomponent melts, with application to the system CaO–MgO–Al 2O 3–SiO 2. Ph.D. thesis, University of British Columbia] was used. From these vapor pressures, evaporation coefficients ( α) were obtained that give the best fits to the time variation of the residue compositions. Evaporation coefficients derived for Fe (g), Mg (g), and SiO (g) from the Hashimoto (1983) experiments are similar to those found by Alexander [Alexander C. M. O’D. (2004) Erratum. Meteoritics Planet. Sci. 39, 163] in his EQR treatment of the same data and also adequately describe the FeO-bearing stages of the Wang et al. (2001) experiments. From the Yu et al. (2003) experiments at 1723 K, α Na = 0.26 ± 0.05, and α K = 0.13 ± 0.02 in vacuum, and α Na = 0.042 ± 0.020, and α K = 0.017 ± 0.002 in 9 × 10 −5 bar H 2. In the FeO-free stages of the Wang et al. (2001) experiments, α Mg and α SiO are significantly different from their respective values in the FeO-bearing portions of the same experiments and from the vacuum values obtained at the same temperature by Richter [Richter F. M., Davis A. M., Ebel D. S., Hashimoto A. (2002) Elemental and isotopic fractionation of Type B calcium-, aluminum-rich inclusions: experiments, theoretical considerations, and constraints on their thermal evolution. Geochim. Cosmochim. Acta 66, 521–540] for CMAS compositions much lower in MgO. When corrected for temperature, the values of α Mg and α SiO that best describe the FeO-free stages of the Wang et al. (2001) experiments also adequately describe the FeO-free stage of the Cohen et al. (2004) H 2 experiments, but α Fe that best describes the FeO-bearing stage of the latter experiment differs significantly from the temperature-corrected value derived from the Hashimoto (1983) vacuum data.

Laser nanotraps and nanotweezers for cold atoms: 3D gradient dipole force trap in the vicinity of scanning near-field optical microscope tip

Using a two-dipole model of an optical near-field of scanning near-field optical microscope tip, i.e., taking into account contributions of magnetic and electric dipoles, we propose and analyze a new type of 3D optical nanotrap found for certain relations between electric and magnetic dipoles. Electric field attains a minimum value in vacuum in the vicinity of the tip and hence such a trap is quite suitable for manipulations with cold atoms.

Static potential and local color fields in unquenched latticeQCD3

String breaking by dynamical quarks in three-dimensional lattice QCD is analyzed through measurements of the potential and the local color-electric field strength generated by a static quark-antiquark pair. Simulations were done for unquenched SU(2) color with two flavors of staggered light quarks. An improved gluon action was used, which allows simulations to be done on coarse lattices, providing an extremely efficient means to access the large quark separations and long propagation times at which string breaking occurs. The static sources were generated using Wilson loop operators, hence no light valence quarks are present in the resulting trial states. Results give unambiguous evidence of string breaking. First the static potential is shown to saturate at twice the heavy-light meson mass at large separations. Then it is demonstrated that the local color-electric field strength in the region between the heavy quarks tends towards vacuum values at large separations, the first time that this most graphic effect of quark vacuum polarization on the confining flux-tube has been realized in lattice QCD. Implications of these results for unquenched simulations of four-dimensional QCD are drawn.

Casimir energy for a dielectric cylinder

In this paper, we calculate the Casimir energy for a dielectric–diamagnetic cylinder with the speed of light differing on the inside and outside. Although the result is in general divergent, special cases are meaningful. The well-known results for a uniform speed of light are reproduced. The self-stress on a purely dielectric cylinder is shown to vanish through second order in the deviation of the permittivity from its vacuum value, in agreement with the result calculated from the sum of van der Waals forces. These results are unambiguously separated from divergent terms.

The α Helix Dipole: Screened Out?

Aligned alpha helix peptide dipoles sum to a "macroscopic" dipole parallel to the helix axis that has been implicated in protein folding and function. However, in aqueous solution the dipole is counteracted by an electrostatic reaction field generated by the solvent, and the strength of the helix dipole may reduce drastically from its value in vacuum. Here, using atomic-detail helix models and Poisson-Boltzmann continuum electrostatics calculations, the net effective dipole moment, mu(eff), is calculated. Some initially surprising results are found. Whereas in vacuum mu(eff) increases with helix length, the opposite is found to be the case for transmembrane helices. In soluble proteins, mu(eff) is found to vary strongly with the orientation and position of the helix relative to the aqueous medium. A set of rules is established to estimate of the strength of mu(eff) from graphical inspection of protein structures.

Spontaneous Lorentz violation, Nambu-Goldstone modes, and gravity

The fate of the Nambu-Goldstone modes arising from spontaneous Lorentz violation is investigated. Using the vierbein formalism, it is shown that up to 10 Lorentz and diffeomorphism Nambu-Goldstone modes can appear and that they are contained within the 10 modes of the vierbein associated with gauge degrees of freedom in a Lorentz-invariant theory. A general treatment of spontaneous local Lorentz and diffeomorphism violation is given for various spacetimes, and the fate of the Nambu-Goldstone modes is shown to depend on both the spacetime geometry and the dynamics of the tensor field triggering the spontaneous Lorentz violation. The results are illustrated within the general class of bumblebee models involving vacuum values for a vector field. In Minkowski and Riemann spacetimes, the bumblebee model provides a dynamical theory generating a photon as a Nambu-Goldstone boson for spontaneous Lorentz violation. The Maxwell and Einstein-Maxwell actions are automatically recovered in axial gauge. Associated effects of potential experimental relevance include Lorentz-violating couplings in the matter and gravitational sectors of the Standard-Model Extension and unconventional Lorentz-invariant couplings. In Riemann-Cartan spacetime, the possibility also exists of a Higgs mechanism for the spin connection, leading to the absorption of the propagating Nambu-Goldstone modes into the torsion component of the gravitational field.

Transient photoconductivity of nanocrystalline TiO 2 sol–gel thin films

Thin TiO 2 sol–gel films were prepared using the dip-coating technique. The transient photoconductivity was studied in vacuum and in air as a function of temperature and light intensity. The dark conductivity in vacuum is much larger than that in air and they are both thermally activated. The transient photoconductivity rises slowly in vacuum saturating in days, and is much larger than that in air, which reaches a maximum within the first few minutes of illumination. The larger values in vacuum can be attributed to the reduced amount of adsorbed oxygen at the surface, which acts as electron scavenger.