Revisiting 2D numerical models for the 19th century outbursts of eta Carinae

We present here new results of two-dimensional hydrodynamical simulations of the eruptive events of the 1840s (the great) and the 1890s (the minor) eruptions suffered by the massive star eta Carinae (Car). The two bipolar nebulae commonly known as the Homunculus and the little Homunculus (LH) were formed from the interaction of these eruptive events with the underlying stellar wind. We assume here an interacting, non-spherical multiple-phase wind scenario to explain the shape and the kinematics of both Homunculi, but adopt a more realistic parametrization of the phases of the wind. During the 1890s eruptive event, the outflow speed decreased for a short period of time. This fact suggests that the LH is formed when the eruption ends, from the impact of the post-outburst eta Car wind (that follows the 1890s event) with the eruptive flow (rather than by the collision of the eruptive flow with the pre-outburst wind, as claimed in previous models; Gonzalez et al.). Our simulations reproduce quite well the shape and the observed expansion speed of the large Homunculus. The LH (which is embedded within the large Homunculus) becomes Rayleigh-Taylor unstable and develop filamentary structures that resemble the spatial features observed in the polar caps. In addition, we find that the interior cavity between the two Homunculi is partially filled by material that is expelled during the decades following the great eruption. This result may be connected with the observed double-shell structure in the polar lobes of the eta Car nebula. Finally, as in previous work, we find the formation of tenuous, equatorial, high-speed features that seem to be related to the observed equatorial skirt of eta Car.

Paleomagnetism of the Santa Fe Group, central Brazil: Implications for the late Paleozoic apparent polar wander path for South America

Paleomagnetic and rockmagnetic data are reported for the Floresta Formation (Santa Fe Group) of the Sanfranciscana Basin, central Brazil. This formation represents the Permo-Carboniferous glacial record of the basin and comprises the Brocoto (diamictites and flow diamictites), Brejo do Arroz (red sandstones and shales with dropstones and invertebrate trails), and Lavado (red sandstones) members, which crop out near the cities of Santa Fe de Minas and Canabrava, Minas Gerais State. Both Brejo do Arroz and Lavado members were sampled in the vicinities of the two localities. Alternating field and thermal demagnetizations of 268 samples from 76 sites revealed reversed components of magnetization in all samples in accordance with the Permo-Carboniferous Reversed Superchron. The magnetic carriers are magnetite and hematite with both minerals exhibiting the same magnetization component, suggesting a primary origin for the remanence. We use the high-quality paleomagnetic pole for the Santa Fe Group (330.9 degrees E 65.7 degrees S; N = 60; alpha(95) = 4.1 degrees; k = 21) in a revised late Carboniferous to early Triassic apparent polar wander path for South America. On the basis of this result it is shown that an early Permian Pangea A-type fit is possible if better determined paleomagnetic poles become available.

Low doses of hydrogen peroxide impair glucose-stimulated insulin secretion via inhibition of glucose metabolism and intracellular calcium oscillations

The inhibitory effect of hydrogen peroxide (H(2)O(2)) on glucose-stimulated insulin secretion was previously reported. However, the precise mechanism involved was not systematically investigated. In this study, the effects of low concentrations of H(2)O(2) (5-10 mu mol/L) on glucose metabolism, intracellular calcium ([Ca(2+)](i)) oscillations, and dynamic insulin secretion in rat pancreatic islets were investigated. Low concentrations of H(2)O(2) impaired insulin secretion in the presence of high glucose levels (16.7 mmol/L). This phenomenon was observed already after 2 minutes of exposure to H(2)O(2). Glucose oxidation and the amplitude of [Ca(2+)](i); oscillations were dose-dependently suppressed by H(2)O(2). These findings indicate that low concentrations of H(2)O(2) reduce insulin secretion in the presence of high glucose levels via inhibition of glucose metabolism and consequent impairment in [Ca(2+)](i); handling. (C) 2010 Elsevier Inc. All rights reserved.

Effect of renoguanylin on hydrogen/bicarbonate ion transport in rat renal tubules

Renoguanylin (REN) is a recently described member of the guanylin family, which was first isolated from eels and is expressed in intestinal and specially kidney tissues. In the present work we evaluate the effects of REN on the mechanisms of hydrogen transport in rat renal tubules by the stationary microperfusion method. We evaluated the effect of 1 mu M and 10 mu M of renoguanylin (REN) on the reabsorption of bicarbonate in proximal and distal segments and found that there was a significant reduction in bicarbonate reabsorption. In proximal segments, REN promoted a significant effect at both 1 and 10 mu M concentrations. Comparing control and REN concentration of 1 mu M, JHCO(3)(-) . nmol cm(-2) s(-1) -1,76 +/- 0.11(control) x 1,29 +/- 0,08(REN) 10 mu m: P<0.05, was obtained. In distal segments the effect of both concentrations of REN was also effective, being significant e.g. at a concentration of 1 mu M (JHCO(3)(-), nmol cm(-2) s(-1) -0.80 +/- 0.07(control) x 0.60 +/- 0.06(REN) 1 mu m; P<0.05), although at a lower level than in the proximal tubule. Our results suggest that the action of REN on hydrogen transport involves the inhibition of Na(+)/H(+) exchanger and H(+)-ATPase in the luminal membrane of the perfused tubules by a PKG dependent pathway. (c) 2009 Elsevier B.V. All rights reserved.

Differing effects of exogenous and endogenous hydrogen sulphide in carrageenan-induced knee joint synovitis in the rat

Background and purpose: Recent findings suggest that the noxious gas H(2)S is produced endogenously, and that physiological concentrations of H(2)S are able to modulate pain and inflammation in rodents. This study was undertaken to evaluate the ability of endogenous and exogenous H(2)S to modulate carrageenan-induced synovitis in the rat knee. Experimental approach: Synovitis was induced in Wistar rats by intra-articular injection of carrageenan into the knee joint. Sixty minutes prior to carrageenan injection, the rats were pretreated with indomethacin, an inhibitor of H(2)S formation (dl-propargylglycine) or an H(2)S donor [Lawesson`s reagent (LR)]. Key results: Injection of carrageenan evoked knee inflammation, pain as characterized by impaired gait, secondary tactile allodynia of the ipsilateral hindpaw, joint swelling, histological changes, inflammatory cell infiltration, increased synovial myeloperoxidase, protein nitrotyrosine residues, inducible NOS (iNOS) activity and NO production. Pretreatment with LR or indomethacin significantly attenuated the pain responses, and all the inflammatory and biochemical changes, except for the increased iNOS activity, NO production and 3-NT. Propargylglycine pretreatment potentiated synovial iNOS activity (and NO production), and enhanced macrophage infiltration, but had no effect on other inflammatory parameters. Conclusions and implications: Whereas exogenous H(2)S delivered to the knee joint can produce a significant anti-inflammatory and anti-nociceptive effect, locally produced H(2)S exerts little immunomodulatory effect. These data further support the development and use of H(2)S donors as potential alternatives (or complementary therapies) to the available anti-inflammatory compounds used for treatment of joint inflammation or relief of its symptoms.

Hydrogen peroxide is a novel mediator of inflammatory hyperalgesia, acting via transient receptor potential vanilloid 1-dependent and independent mechanisms

Inflammatory diseases associated with pain are often difficult to treat in the clinic due to insufficient understanding of the nociceptive pathways involved. Recently, there has been considerable interest in the role of reactive oxygen species (ROS) in inflammatory disease, but little is known of the role of hydrogen peroxide (H(2)O(2)) in hyperalgesia. In the present study, intraplantar injection of H(2)O(2)-induced a significant dose- and time-dependent mechanical and thermal hyperalgesia in the mouse hind paw, with increased c-fos activity observed in the dorsal horn of the spinal cord. H(2)O(2) also induced significant nociceptive behavior Such as increased paw licking and decreased body liftings. H(2)O(2) levels were significantly raised in the carrageenan-induced hind paw inflammation model, showing that this ROS is produced endogenously in a model of inflammation. Moreover, superoxide dismutase and catalase significantly reduced carrageenan-induced mechanical and thermal hyperalgesia, providing evidence of a functionally significant endogenous role. Thermal, but not mechanical, hyperalgesia in response to H(2)O(2) (i.pl.) Was longer lasting in TRPV1 wild type mice compared to TRPV1 knockouts. It is unlikely that downstream lipid peroxidation was increased by H(2)O(2). In conclusion, we demonstrate a notable effect of H(2)O(2) in mediating inflammatory hyperalgesia, thus highlighting H(2)O(2) removal as a novel therapeutic target for anti-hyperalgesic drugs in the clinic. (C) 2008 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

MULTIPLICITY OF POSITIVE SOLUTIONS FOR A CLASS OF NONLINEAR SCHRODINGER EQUATIONS

This paper proves the multiplicity of positive solutions for the following class of quasilinear problems: {-epsilon(p)Delta(p)u+(lambda A(x) + 1)vertical bar u vertical bar(p-2)u = f(u), R(N) u(x)>0 in R(N), where Delta(p) is the p-Laplacian operator, N > p >= 2, lambda and epsilon are positive parameters, A is a nonnegative continuous function and f is a continuous function with subcritical growth. Here, we use variational methods to get multiplicity of positive solutions involving the Lusternick-Schnirelman category of intA(-1)(0) for all sufficiently large lambda and small epsilon.

Soliton solutions for quasilinear Schrodinger equations with critical growth

In this paper we establish the existence of standing wave solutions for quasilinear Schrodinger equations involving critical growth. By using a change of variables, the quasilinear equations are reduced to semilinear one. whose associated functionals are well defined in the usual Sobolev space and satisfy the geometric conditions of the mountain pass theorem. Using this fact, we obtain a Cerami sequence converging weakly to a solution v. In the proof that v is nontrivial, the main tool is the concentration-compactness principle due to P.L. Lions together with some classical arguments used by H. Brezis and L. Nirenberg (1983) in [9]. (C) 2009 Elsevier Inc. All rights reserved.

Schrodinger-Poisson equations without Ambrosetti-Rabinowitz condition

We prove the existence of ground state solutions for a stationary Schrodinger-Poisson equation in R(3). The proof is based on the mountain pass theorem and it does not require the Ambrosetti-Rabinowitz condition. (C) 2010 Elsevier Inc. All rights reserved.

Influence diagnostics in nonlinear mixed-effects elliptical models

In this work we propose and analyze nonlinear elliptical models for longitudinal data, which represent an alternative to gaussian models in the cases of heavy tails, for instance. The elliptical distributions may help to control the influence of the observations in the parameter estimates by naturally attributing different weights for each case. We consider random effects to introduce the within-group correlation and work with the marginal model without requiring numerical integration. An iterative algorithm to obtain maximum likelihood estimates for the parameters is presented, as well as diagnostic results based on residual distances and local influence [Cook, D., 1986. Assessment of local influence. journal of the Royal Statistical Society - Series B 48 (2), 133-169; Cook D., 1987. Influence assessment. journal of Applied Statistics 14 (2),117-131; Escobar, L.A., Meeker, W.Q., 1992, Assessing influence in regression analysis with censored data, Biometrics 48, 507-528]. As numerical illustration, we apply the obtained results to a kinetics longitudinal data set presented in [Vonesh, E.F., Carter, R.L., 1992. Mixed-effects nonlinear regression for unbalanced repeated measures. Biometrics 48, 1-17], which was analyzed under the assumption of normality. (C) 2009 Elsevier B.V. All rights reserved.

Statistical analysis of proficiency testing results under elliptical distributions

The use of inter-laboratory test comparisons to determine the performance of individual laboratories for specific tests (or for calibration) [ISO/IEC Guide 43-1, 1997. Proficiency testing by interlaboratory comparisons - Part 1: Development and operation of proficiency testing schemes] is called Proficiency Testing (PT). In this paper we propose the use of the generalized likelihood ratio test to compare the performance of the group of laboratories for specific tests relative to the assigned value and illustrate the procedure considering an actual data from the PT program in the area of volume. The proposed test extends the test criteria in use allowing to test for the consistency of the group of laboratories. Moreover, the class of elliptical distributions are considered for the obtained measurements. (C) 2008 Elsevier B.V. All rights reserved.

Termination of diamond surfaces with hydrogen, oxygen and fluorine using a small, simple plasma gun

We have formed and characterized polycrystalline diamond films with surfaces having hydrogen terminations, oxygen terminations, or fluorine terminations, using a small, simple and novel plasma gun to bombard the diamond surface, formed by plasma assisted CVD in a prior step, with ions of the wanted terminating species. The potential differences between surface regions with different terminations were measured by Kelvin Force Microscopy (KFM). The highest potential occurred for oxygen termination regions and the lowest for fluorine. The potential difference between regions with oxygen terminations and hydrogen terminations was about 80 mV, and between regions with hydrogen terminations and fluorine terminations about 150 mV. Regions with different terminations were identified and imaged using the secondary electron signal provided by scanning electron microscopy (SEM). since this signal presents contrast for surfaces with different electrical properties. The wettability of the surfaces with different terminations was evaluated, measuring contact angles. The sample with oxygen termination was the most hydrophilic, with a contact angle of 75 degrees. hydrogen-terminated regions with 83 degrees, and fluorine regions 93 degrees, the most hydrophobic sample. (C) 2010 Elsevier B.V. All rights reserved.

Characterization and spectroscopic analysis of phenol-ethanol hydrogen bonded clusters

Different hydrogen bonded clusters involving phenol and ethanol are studied theoretically using MP2/aug-cc-pVDZ. Nine different 1: 1 clusters are obtained and analyzed according to their stability and spectroscopic properties. Different isomeric forms of ethanol are considered. Attention is also devoted to the spectral shift of the characteristic pi -> pi* transition of phenol. Using TDHF, CIS, CIS(D) and TDB3LYP in aug-cc-pVDZ basis set, all results agree that a red shift is obtained when phenol is the hydrogen donor and a blue shift is obtained in the opposite case. These results are used to rationalize the red shift observed for phenol in liquid ethanol. (C) 2010 Elsevier B.V. All rights reserved.

Electronic properties of liquid hydrogen fluoride: A sequential quantum mechanical/Born-Oppenheimer molecular dynamics approach

The electronic properties of liquid hydrogen fluoride (HF) were investigated by carrying out sequential quantum mechanics/Born-Oppenheimer molecular dynamics. The structure of the liquid is in good agreement with recent experimental information. Emphasis was placed on the analysis of polarisation effects, dynamic polarisability and electronic excitations in liquid HF. Our results indicate an increase in liquid phase of the dipole moment (similar to 0.5 D) and isotropic polarisability (5%) relative to their gas-phase values. Our best estimate for the first vertical excitation energy in liquid HF indicates a blue-shift of 0.4 +/- 0.2 eV relative to that of the gas-phase monomer (10.4 eV). (C) 2010 Elsevier B.V. All rights reserved.

Many-body energy decomposition of hydrogen-bonded glycine clusters in gas-phase

A detailed analysis of the many-body contribution to the interaction energies of the gas-phase hydrogen-bonded glycine clusters, (Gly)(N), N = 1-4 is presented. The energetics of the hydrogen-bonded dimer, trimer and tetramer complexes have been analyzed using density-functional theory. The magnitude of the two-through four-body energy terms have been calculated and compared. The relaxation energy and the two-body energy terms are the principal contributors to the total binding energy. Four-body contribution is negligible. However, the three-body contribution is found to be sizable and the formation of the cyclic glycine trimer presents geometric strains that make it less favorable. (C) 2010 Elsevier B.V. All rights reserved.