J08069+1527: A newly discovered high amplitude, hybrid subdwarf B pulsator

We present our discovery of a new hybrid pulsating subdwarf B star, J08069+1527. The effective temperature and surface gravity of 28,500$\pm$400\,K and 5.37$\pm$0.04\,dex, respectively, place this object inside the instability strip and also among other pulsating hot subdwarfs of a hybrid nature, right next to another fascinating star: Balloon\,090100001. From this proximity, we anticipated this star could pulsate in both high and low frequency modes. Indeed, our analysis of photometric data confirmed our prediction. We detected two peaks in the high frequency region and two other peaks at low frequencies. In addition, the amplitude of the dominant mode is very high and comparable to the dominant peaks in other hybrid subdwarf B stars. Since this star is bright, we performed time-series low resolution spectroscopy. Despite a low signal-to-noise (S/N) ratio, we were able to detect the main peak from these data. All our results strongly indicate that J08069+1527 is a high amplitude pulsating hot subdwarf B star of hybrid nature. By analogy to the other pulsating sdB star, we judge that the dominant mode we detected here has radial nature. Future stellar modeling should provide us with quite good constrains as p- and g-modes presented in this star are driven in different parts of its interior.Comment: 7 pages, 10 figures, accepted for publication in MNRA

RAT J0455+1305: A rare hybrid pulsating subdwarf B star

We present results on the second-faintest pulsating subdwarf B (sdB) star known, RAT J0455+1305, derived from photometric data obtained in 2009. It shows both short and long periods oscillations, theoretically assigned as pressure and gravity modes. We identify six short-period frequencies (with one being a combination) and six long-period frequencies. This star is the fourth hybrid sdB star discovered so far which makes it of special interest as each type of mode probes a different part of the star. This star is similar to the sdB hybrid pulsator Balloon 090100001 in that it exhibits short-period mode groupings, which can be used to identify pulsation parameters and constrain theoretical models.Comment: published in MNRA

Vibrational Spectroscopy of Selected Natural Uranyl Vanadates

Raman spectroscopy has been used to study a selection of uranyl vanadate minerals including carnotite, curienite, francevillite, tyuyamunite and metatyuyamunite. The minerals are characterised by an intense band in the 800 to 824 cm-1 region, assigned to the ν1 symmetric stretching vibrations of the (UO2)2+ units. A second intense band is observed in the 965 to 985 cm-1 range and is attributed to the ν1 (VO3) symmetric stretching vibrations in the (V2O8) units. This band is split with a second component observed at around 963 cm-1. A band of very low intensity is observed around 948 cm-1 and is assigned to the ν3 antisymmetric stretching vibrations of the (VO3) units. Bands in the range 608-655 cm-1 may be attributed to molecular water librational modes or the stretching modes ￮(V2O2) units. Bands in the range 573-583 cm-1 may be connected with the ￮ (U-Oequatorial) vibrations or ￮ (V2O2) units. Bands located in the range 467-539 cm-1 may be also attributed to the ￮ (U-Oequatorial) units vibrations. The bending modes of the (VO3) units are observed in the 463 to 480 cm-1 range – there may be some coincidence with ￮ (U-Oequatorial). The bending modes of the (V2O2) in the (V2O8) units are located in a series of bands around 407, 365 and 347 cm-1 (ν2). Two intense bands are observed in the 304 to 312 cm-1 range and 241 to 264 cm-1 range and are assigned to the doubly degenerate ν2 modes of the (UO2)2+ units. The study of the vibrational spectroscopy of uranyl vanadates is complicated by the overlap of bands from the (VO3) and (UO2)2+ units. Raman spectroscopy has proven most useful in assigning bands to these two units since Raman bands are sharp and well separated as compared with infrared bands. The uranyl vanadate minerals are often found as crystals on a host matrix and Raman spectroscopy enables their in-situ characterisation without sample preparation

On the mechanical behaviour of a butt jointed thermoplastic composite under bending

In the present work, the mechanical behavior of a recently developed novel butt jointed thermoplastic composite was investigated under bending conditions. The laminated skin and the web were made of carbon fiber (AS4) and polyetherketoneketone (PEKK). The butt joint (filler) was injection molded from 20% short carbon fiber filled with PEKK thermoplastic. The skin and web were co-consolidated together with the butt joint in the form of a hybrid T-shaped structure. A three point bending (3 PB) set-up was used to investigate the mechanical response of the hybrid composite. The crack initiation and propagation mechanisms for the filler and the delamination at the skin-filler interface were captured using a high speed camera. It was found from the experimental observations that the crack initiated in the filler and then propagated towards the skin-filler interface. A numerical model was also developed using the finite element method in ABAQUS including the crack initiation and growth in the filler together with the delamination at the skin-filler interface. For this purpose the virtual crack closure technique (VCCT) was employed for the crack growth in the filler and the traction separation law was applied at the skin-filler interface using a cohesive surface. The residual stresses and deformations coming from the co-consolidation process were predicted by applying a thermal load and taken into account in the quasi-static analysis. A good agreement was found between the predicted and measured force-displacement curves. The developed numerical model was further employed to address the crack initiation and growth in the filler and delamination at the skin-filler interface using the mix mode effective fracture energies. A linear elastic behavior was found in the structure until the crack initiation in the filler

Infrared spectra and thermal behaviour of salts of the bis(malonato) oxovanadium(IV) anion

Infrared spectra of a series of anhydrous (Rb, Cs) and hydrated (Na, K, Ca, Sr, Ba, Pb, Ag, Tl) salts of the complex anion VO(C₃H₂O₄)₂]₂− were recorded and briefly discussed. The thermal behaviour of these compounds, as well as that of the corresponding diprotonated ethylenediamine cation, were investigated by TG- and DTA-methods in N₂-atmosphere and complemented with studies carried out in crucible furnaces in air. Pyrolysis intermediates and residues were characterized by IR spectroscopy and overall stoichiometries for the degradation processes were proposed. In most cases orthovanadate/VO₂ mixtures were obtained as final residues in N₂, whereas the corresponding divanadates were produced in air.Facultad de Ciencias Exacta

Symmetry Energy Effects on the Mixed Hadron-Quark Phase at High Baryon Density

The phase transition of hadronic to quark matter at high baryon and isospin density is analyzed. Relativistic mean field models are used to describe hadronic matter, and the MIT bag model is adopted for quark matter. The boundaries of the mixed phase and the related critical points for symmetric and asymmetric matter are obtained. Due to the different symmetry term in the two phases, isospin effects appear to be rather significant. With increasing isospin asymmetry the binodal transition line of the (T,\rho_B) diagram is lowered to a region accessible through heavy ion collisions in the energy range of the new planned facilities, e.g. the FAIR/NICA projects. Some observable effects are suggested, in particular an "Isospin Distillation" mechanism with a more isospin asymmetric quark phase, to be seen in charged meson yield ratios, and an onset of quark number scaling of the meson/baryon elliptic flows. The presented isospin effects on the mixed phase appear to be robust with respect to even large variations of the poorly known symmetry term at high baryon density in the hadron phase. The dependence of the results on a suitable treatment of isospin contributions in effective QCD Lagrangian approaches, at the level of explicit isovector parts and/or quark condensates, is finally discussed.Comment: 14 two column pages, 14 figures, new results with other hadron EoS. Accepted for publication in Phys.Rev.

Ibuprofen Blunts Ventilatory Acclimatization to Sustained Hypoxia in Humans.

Ventilatory acclimatization to hypoxia is a time-dependent increase in ventilation and the hypoxic ventilatory response (HVR) that involves neural plasticity in both carotid body chemoreceptors and brainstem respiratory centers. The mechanisms of such plasticity are not completely understood but recent animal studies show it can be blocked by administering ibuprofen, a nonsteroidal anti-inflammatory drug, during chronic hypoxia. We tested the hypothesis that ibuprofen would also block the increase in HVR with chronic hypoxia in humans in 15 healthy men and women using a double-blind, placebo controlled, cross-over trial. The isocapnic HVR was measured with standard methods in subjects treated with ibuprofen (400 mg every 8 hrs) or placebo for 48 hours at sea level and 48 hours at high altitude (3,800 m). Subjects returned to sea level for at least 30 days prior to repeating the protocol with the opposite treatment. Ibuprofen significantly decreased the HVR after acclimatization to high altitude compared to placebo but it did not affect ventilation or arterial O2 saturation breathing ambient air at high altitude. Hence, compensatory responses prevent hypoventilation with decreased isocapnic ventilatory O2-sensitivity from ibuprofen at this altitude. The effect of ibuprofen to decrease the HVR in humans provides the first experimental evidence that a signaling mechanism described for ventilatory acclimatization to hypoxia in animal models also occurs in people. This establishes a foundation for the future experiments to test the potential role of different mechanisms for neural plasticity and ventilatory acclimatization in humans with chronic hypoxemia from lung disease