5,486 research outputs found

    Gauge Equivalence in Two--Dimensional Gravity

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    Two-dimensional quantum gravity is identified as a second-class system which we convert into a first-class system via the Batalin-Fradkin (BF) procedure. Using the extended phase space method, we then formulate the theory in most general class of gauges. The conformal gauge action suggested by David, Distler and Kawai is derived from a first principle. We find a local, light-cone gauge action whose Becchi-Rouet-Stora-Tyutin invariance implies Polyakov's curvature equation ∂−R=∂−3g++=0\partial_{-}R=\partial_{-}^{3}g_{++}=0, revealing the origin of the SL(2,R)SL(2,R) Kac-Moody symmetry. The BF degree of freedom turns out be dynamically active as the Liouville mode in the conformal gauge, while in the light-cone gauge the conformal degree of freedom plays that r{\^o}le. The inclusion of the cosmological constant term in both gauges and the harmonic gauge-fixing are also considered.Comment: 30 pages, KANAZAWA 93-

    High-fructose corn-syrup-sweetened beverage intake increases 5-hour breast milk fructose concentrations in lactating women

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    This study determined the effects of consuming a high-fructose corn syrup (HFCS)-sweetened beverage on breast milk fructose, glucose, and lactose concentrations in lactating women. At six weeks postpartum, lactating mothers (n = 41) were randomized to a crossover study to consume a commercially available HFCS-sweetened beverage or artificially sweetened control beverage. At each session, mothers pumped a complete breast milk expression every hour for six consecutive hours. The baseline fasting concentrations of breast milk fructose, glucose, and lactose were 5.0 ± 1.3 µg/mL, 0.6 ± 0.3 mg/mL, and 6.8 ± 1.6 g/dL, respectively. The changes over time in breast milk sugars were significant only for fructose (treatment × time, p < 0.01). Post hoc comparisons showed the HFCS-sweetened beverage vs. control beverage increased breast milk fructose at 120 min (8.8 ± 2.1 vs. 5.3 ± 1.9 µg/mL), 180 min (9.4 ± 1.9 vs. 5.2 ± 2.2 µg/mL), 240 min (7.8 ± 1.7 vs. 5.1 ± 1.9 µg/mL), and 300 min (6.9 ± 1.4 vs. 4.9 ± 1.9 µg/mL) (all p < 0.05). The mean incremental area under the curve for breast milk fructose was also different between treatments (14.7 ± 1.2 vs. −2.60 ± 1.2 µg/mL × 360 min, p < 0.01). There was no treatment × time interaction for breast milk glucose or lactose. Our data suggest that the consumption of an HFCS-sweetened beverage increased breast milk fructose concentrations, which remained elevated up to five hours post-consumption

    Hybridization Mechanism for Cohesion of Cd-based Quasicrystals

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    Cohesion mechanism of cubic approximant crystals of newly discovered binary quasicrystals, Cd6_6M (M=Yb and Ca), are studied theoretically. It is found that stabilization due to alloying is obtained if M is an element with low-lying unoccupied dd states. This leads to conclusion that the cohesion of the Cd-based compounds is due to the hybridization of the dd states of Yb and Ca with a wide spsp band. %unlike known stable quasicrystals without transition elements %such as Al-Li-Cu and Zn-Mg-RE (RE:rare earth). Although a diameter of the Fermi sphere coincides with the strong Bragg peaks for Cd-Yb and Cd-Ca, the Hume-Rothery mechanism does not play a principal role in the stability because neither distinct pseudogap nor stabilization due to alloying is obtained for isostructural Cd-Mg. In addition to the electronic origin, matching of the atomic size is very crucial for the quasicrystal formation of the Cd-based compounds. It is suggested that the glue atoms, which do not participate in the icosahedral cluster, play an important role in stabilization of the compound.Comment: 4 pages, 2 figure

    A Phase-Space Approach to Collisionless Stellar Systems Using a Particle Method

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    A particle method for reproducing the phase space of collisionless stellar systems is described. The key idea originates in Liouville's theorem which states that the distribution function (DF) at time t can be derived from tracing necessary orbits back to t=0. To make this procedure feasible, a self-consistent field (SCF) method for solving Poisson's equation is adopted to compute the orbits of arbitrary stars. As an example, for the violent relaxation of a uniform-density sphere, the phase-space evolution which the current method generates is compared to that obtained with a phase-space method for integrating the collisionless Boltzmann equation, on the assumption of spherical symmetry. Then, excellent agreement is found between the two methods if an optimal basis set for the SCF technique is chosen. Since this reproduction method requires only the functional form of initial DFs but needs no assumptions about symmetry of the system, the success in reproducing the phase-space evolution implies that there would be no need of directly solving the collisionless Boltzmann equation in order to access phase space even for systems without any special symmetries. The effects of basis sets used in SCF simulations on the reproduced phase space are also discussed.Comment: 16 pages w/4 embedded PS figures. Uses aaspp4.sty (AASLaTeX v4.0). To be published in ApJ, Oct. 1, 1997. This preprint is also available at http://www.sue.shiga-u.ac.jp/WWW/prof/hozumi/papers.htm

    Induced Anisotropies in NiCo Obliquely Deposited Films and Their effect on Magnetic Domains

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    English Article: Oblique and in-plane anisotropies in obliquely evaporated NiCo thin films were investigated in order to understand their origin. All the compositions studied clearly show the effect of columnar grain morphology coupled with some intrinsic factors such as magnetostriction and crystallinity. Energy calculations are undertaken to explain the effect of

    Nonlinear Supersymmetry, Brane-bulk Interactions and Super-Higgs without Gravity

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    We derive the coupling of a hypermultiplet of N=2 global supersymmetry to the Dirac-Born-Infeld Maxwell theory with linear N=1 and a second nonlinear supersymmetry. At the level of global supersymmetry, this construction corresponds to the interaction with Maxwell brane fields of bulk hypermultiplets, such as the universal dilaton of type IIB strings compactified on a Calabi-Yau manifold. It displays in particular the active role of a four-form field. Constrained N=1 and N=2 superfields and the formulation of the hypermultiplet in its single-tensor version are used to derive the nonlinear realization, allowing a fully off-shell description. Exact results with explicit symmetries and supersymmetries are then obtained. The electric-magnetic dual version of the theory is also derived and the gauge structure of the interaction is exemplified with N=2 nonlinear QED of a charged hypermultiplet. Its Higgs phase describes a novel super-Higgs mechanism without gravity, where the goldstino is combined with half of the hypermultiplet into an N=1 massive vector multiplet.Comment: 42 page

    Magnetic properties of the Ag-In-rare-earth 1/1 approximants

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    We have performed magnetic susceptibility and neutron scattering measurements on polycrystalline Ag-In-RE (RE: rare-earth) 1/1 approximants. In the magnetic susceptibility measurements, for most of the RE elements, inverse susceptibility shows linear behaviour in a wide temperature range, confirming well localized isotropic moments for the RE3+^{3+} ions. Exceptionally for the light RE elements, such as Ce and Pr, non-linear behaviour was observed, possibly due to significant crystalline field splitting or valence fluctuation. For RE = Tb, the susceptibility measurement clearly shows a bifurcation of the field-cooled and zero-field-cooled susceptibility at Tf=3.7T_{\rm f} = 3.7~K, suggesting a spin-glass-like freezing. On the other hand, neutron scattering measurements detect significant development of short-range antiferromagnetic spin correlations in elastic channel, which accompanied by a broad peak at ℏω=4\hbar\omega = 4~meV in inelastic scattering spectrum. These features have striking similarity to those in the Zn-Mg-Tb quasicrystals, suggesting that the short-range spin freezing behaviour is due to local high symmetry clusters commonly seen in both the systems.Comment: 14 pages, 12 figure

    Timing of sea ice retreat can alter phytoplankton community structure in the western Arctic Ocean

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    This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. Distribution patterns of phytoplankton groups in the late summers of 2008–2010 were analysed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years–the sea ice retreat in 2008 was 1–2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure

    The effect of 1.0% tropicamide/2.5% phenylephrine and Paremyd on pupil diameter, accomodative amplitude and intraocular pressure

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    Background: The demand for a milder, yet effective dilation drop prompted Allergan to introduce Paremyd™ to the eye care community in 1993. This study sought to form clinical comparisons between Paremyd™ and the standard drug regimen for dilation of 1% tropicamide/2.5% phenylephrine. Methods: 23 subjects who ranged from 23-29 years of age were dilated with 1 drop each of 1% tropicamide and 2.5% phenylephrine in the right eye and 1 drop of Paremyd™ in the left eye. Pupil diameter and accommodative amplitude (using the push up method) was evaluated at 0, 10, 20, 30, 45, 60, 90, 120, 150 and 180 minute intervals while intraocular pressures were attained at 0, 30, 60, 120 and 180 minute intervals. Results: Analysis revealed that Paremyd™ had a slightly less mydriatic and cycloplegic effect than the standard drug regimen. There was also a difference in efficacy when segregating participants due to irides\u27 color with both dilation methods having a greater mydriatic effect on non-brown eyed vs. brown eyed subjects. The reverse was true when cycloplegic effect was analyzed. Conclusions: It is difficult to assess which regimen should be the drug or drugs of choice with regard to pupil dilation. Paremyd™ proves to be an effective, milder mydriatic agent. Although in brown eyed individuals, one drop of Paremyd™ may fall slightly short of the desired 7 mm dilated pupil
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