Universal properties and the first law of black hole inner mechanics

We show by explicit computations that the product of all the horizon areas is independent of the mass, regardless of the topology of the horizons. The universal character of this relation holds for all known five dimensional asymptotically flat black rings, and for black strings. This gives further evidence for the crucial role that the thermodynamic properties at each horizon play in understanding the entropy at the microscopic level. To this end we propose a "first law" for the inner Cauchy horizons of black holes. The validity of this formula, which seems to be universal, was explicitly checked in all cases.Comment: 4 pages, 1 figure; v2: minor corrections, references added; v3: minor corrections, references adde

Black Hole Monodromy and Conformal Field Theory

The analytic structure of solutions to the Klein-Gordon equation in a black hole background, as represented by monodromy data, is intimately related to black hole thermodynamics. It encodes the "hidden conformal symmetry" of a non-extremal black hole, and it explains why features of the inner event horizon appear in scattering data such as greybody factors. This indicates that hidden conformal symmetry is generic within a universality class of black holes.Comment: 20 pages, v2 minor corrections, updated reference

Restrictions on the coherence of the ultrafast optical emission from an electron-hole pairs condensate

We report on the transfer of coherence from a quantum-well electron-hole condensate to the light it emits. As a function of density, the coherence of the electron-hole pair system evolves from being full for the low density Bose-Einstein condensate to a chaotic behavior for a high density BCS-like state. This degree of coherence is transfered to the light emitted in a damped oscillatory way in the ultrafast regime. Additionally, the photon field exhibits squeezing properties during the transfer time. We analyze the effect of light frequency and separation between electron and hole layers on the optical coherence. Our results suggest new type of ultrafast experiments for detecting electron-hole pair condensation.Comment: 4 pages,3 figures, to be published in Physical Review Letters. Minor change

Extraction of wood compounds by use of subcritical fluids

A study of the extraction of oak wood compounds with subcritical water-ethanol mixtures as extractant, with an ethanol content between 0-60%, is reported. Identification and characterisation of the extracted compounds have been made by spectrophotometry and gas chromatography with either flame ionisation or mass detectors. Extraction was performed statically manner by use of a single cycle or repeated cycles. All variables affecting the extraction process were studied and optimised. Extraction time and temperature are 60 min and 200ºC, respectively. Comparison of the extract thus obtained with commercial extracts showed the former to be rich in compounds characteristic of the commercial extracts. The method enables manipulation of the extract composition by changing the temperature and water/ethanol ratio used. It is faster than the traditional procedures for obtaining wood extracts

Method for the simultaneous determination of total polyphenol and anthocyan indexes in red wines using a flow injection approach

A simultaneous and fast method for the determination of total polyphenol index (t.p.i.) and total anthocyan index (t.a.i.) has been developed by a flow injection approach and a diode array spectrophotometer for monitoring at 280 nm and 520 nm, respectively. Linear ranges were obtained from 20 to 70 index units and from 20 to 500 mg l-1 for t.p.i. and t.a.i., respectively. The results provided by the proposed method agree with those obtained using the polyphenol index at 280 nm and the Ribereau-Gayon method for the determination of total anthocyans. The sample throughput was 25-30 samples per hour. Analytical features such as repeatability, reproducibility and detection and quantification limits as well as the results of a robustness study based on the Steiner-Younden procedure are also given

Sequential Spectrophotometric determination of methanol and iron in vinegar by a flow injection-pervaporation method

An easily automatable sequential flow-injection-pervaporation method is proposed for the photometric determination of methanol and iron in vinegar. The method is based on separation of the methanol from the sample matrix by pervaporation followed by its oxidation to formaldehyde with permanganate, decolouration of the latter with S2O5-2 and subsequent reaction of formaldehyde with p-rosaniline to yield a violet reaction product with maximum absorption at 567 nm. Iron is determined by an existing method based on reaction with thiocyanate in acidic medium and monitoring at 508 nm. After optimisation by either the univariate or multivariate approaches, as required, the linear range was established for methanol (4-1000 mg L-1) and iron (0.18-20 mg L-1); The proposed method was then compared with reference methods for methanol and iron in terms of repeatability (2.452 mg L-1 and 0.245 mg L-1, respectively), reproducibility (4.435 mg L-1 and 0.356 mg L-1, respectively), detection limit (LOD=82 and 0.234 mg L-1, respectively) and traceability. The throughput was nine samples per hour

Detection of magnetic field in the B2 star ρ\rho Oph A with ESO FORS2

Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them ($\sim$ 10 %) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star $\rho$ Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyzed FORS2 ESO VLT spectra of $\rho$ Oph A taken at two epochs and detected a longitudinal component of the magnetic field of order of $\sim500$ G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of $\rho$ Oph A and further constrained its age. We conclude that $\rho$ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.Comment: 4 pages, 1 figure, 2 tables, accepted as a "Letter to the Editor" to Astronomy & Astrophysic