9,952 research outputs found
Evidence for a Mid-Atomic-Number Atmosphere in the Neutron Star 1E1207.4-5209
Recently Sanwal et al. (2002) reported the first clear detection of
absorption features in an isolated neutron star, 1E1207.4-5209. Remarkably
their spectral modeling demonstrates that the atmosphere cannot be Hydrogen.
They speculated that the neutron star atmosphere is indicative of ionized
Helium in an ultra-strong (~1.5x10^{14} G) magnetic field. We have applied our
recently developed atomic model (Mori & Hailey 2002) for strongly-magnetized
neutron star atmospheres to this problem. We find that this model, along with
some simp le atomic physics arguments, severely constrains the possible
composition of the atmosphere. In particular we find that the absorption
features are naturally associated with He-like Oxygen or Neon in a magnetic
field of ~10^{12} G, comparable to the magnetic field derived from the spin
parameters of the neutron star. This interpretation is consistent with the
relative line strengths and widths and is robust. Our model predicts possible
substructure in the spectral features, which has now been reported by
XMM-Newton (Mereghetti et al. 2002). However we show the Mereghetti et al.
claim that the atmosphere is Iron or some comparable high-Z element at ~
10^{12} G is easily ruled out by the Chandra and XMM-Newton data.Comment: 5 pages, AASTeX, Revised version. Accepted for publication in ApJ
Letter
Stabilization of Extra Dimensions at Tree Level
By considering the effects of string winding and momentum modes on a time
dependent background, we find a method by which six compact dimensions become
stabilized naturally at the self-dual radius while three dimensions grow large.Comment: 15 pages, 2 figures, minor typos correcte
Effect of wood aging on wine mineral composition and 87Sr/86Sr isotopic ratio
The evolution of mineral composition and wine strontium isotopic ratio 87Sr/86Sr (Sr IR) during wood aging were
investigated. A red wine was aged in stainless steel tanks with French oak staves (Quercus sessiliflora Salisb.), with three industrial
scale replicates. Sampling was carried out after 30, 60, and 90 days of aging, and the wines were evaluated in terms of general
analysis, phenolic composition, total polysaccharides, multielement composition, and Sr IR. Li, Be, Mg, Al, Sc, Ti, V, Mn, Co, Ni,
Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Mo, Sb, Cs, Ba, Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb, Lu, Tl, and Pb elements and 87Sr/86Sr were
determined by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) and Na, K, Ca, and Fe by flame atomic
absorption spectrometry (FAAS). Two-way ANOVA was applied to assess wood aging and time effect on Sr IR and mineral
composition. Wood aging resulted in significantly higher concentrations of Mg, V, Co, Ni, and Sr. At the end of the aging period,
wine exhibited statistically identical Sr IR compared to control. Study suggests that wood aging does not affect 87Sr/86Sr, not
precluding the use of this parameter for wine traceability purposesinfo:eu-repo/semantics/publishedVersio
On Winding Branes and Cosmological Evolution of Extra Dimensions in String Theory
We consider evolution of compact extra dimensions in cosmology and try to see
whether wrapped branes can prevent the expansion of the internal space. Some
difficulties of Brandenberger and Vafa mechanism for decompactification are
pointed out. In both pure Einstein and dilaton gravities, we study cosmology of
winding brane gases in a continuum approximation. The energy momentum tensor is
obtained by coupling the brane action to the gravity action and we present
several exact solutions for various brane configurations. T-duality invariance
of the solutions are established in dilaton gravity. Our results indicate that
phenomenologically the most viable scenario can be realized when there is only
one brane wrapping over all extra dimensions.Comment: 17 pages, RevTex4, 2 figures, a paragraph added, to appear in
Classical and Quantum Gravit
Origins of Chevron Rollovers in Non-Two-State Protein Folding Kinetics
Chevron rollovers of some proteins imply that their logarithmic folding rates
are nonlinear in native stability. This is predicted by lattice and continuum
G\=o models to arise from diminished accessibilities of the ground state from
transiently populated compact conformations under strongly native conditions.
Despite these models' native-centric interactions, the slowdown is due partly
to kinetic trapping caused by some of the folding intermediates' nonnative
topologies. Notably, simple two-state folding kinetics of small single-domain
proteins are not reproduced by common G\=o-like schemes.Comment: 10 pages, 4 Postscript figures (will appear on PRL
Pertumbuhan dan Produksi Tanaman Jagung (Zea Mays L.) Akibat Pemberian Kompos Ela Sagu dan Pupuk Organik Cair (POC) pada Tanah Ultisol
The purpose of this study is to determine the growth and yield of maize (Zea mays L) as responses of organic fertilizer sago palm waste compost and liquid organic fertilizer (LOF) on Ultisols. The research was conducted on the field in the village of Telaga Kodok. The treatments were carried out in a factorial experiment using randomized block design in which the sago palm waste compost consisted of 4 dose levels: 0, 30, 45, and 60 tons/Ha and liquid organic fertilizer (LOF) was composed of 3 dose levels: 0, 10, and 20 mL/L solution which is repeated three times, so that there were 36 treatment combinations. The results showed that the application of sago palm waste compost and LOF independently promote plant growth (height and stem diameter) of corn, as well as the production of plant (length, diameter, and weight of cobs) of Corn. While the sago palm waste application together with LOF could improve corn dry seed weight as much as 121.33 g per plant or 5.8 ton/Ha on soil Ultisol
Volume Stabilization and Acceleration in Brane Gas Cosmology
We investigate toy cosmological models in (1+m+p)-dimensions with gas of
p-branes wrapping over p-compact dimensions. In addition to winding modes, we
consider the effects of momentum modes corresponding to small vibrations of
branes and find that the extra dimensions are dynamically stabilized while the
others expand. Adding matter, the compact volume may grow slowly depending on
the equation of state. We also obtain solutions with winding and momentum modes
where the observed space undergoes accelerated expansion.Comment: 20 pages, 3 figures, v2: comments and references added, to appear in
JCA
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