Stable Umbral Chromospheric Structures

Aims. To understand the morphology of the chromosphere in sunspot umbra. We investigate if the horizontal structures observed in the spectral core of the Ca II H line are ephemeral visuals caused by the shock dynamics of more stable structures, and examine their relationship with observables in the H-alpha line. Methods. Filtergrams in the core of the Ca II H and H-alpha lines as observed with the Swedish 1-m Solar Telescope are employed. We utilise a technique that creates composite images and tracks the flash propagation horizontally. Results. We find 0"15 wide horizontal structures, in all of the three target sunspots, for every flash where the seeing was moderate to good. Discrete dark structures are identified that are stable for at least two umbral flashes, as well as systems of structures that live for up to 24 minutes. We find cases of extremely extended structures with similar stability, with one such structure showing an extent of 5". Some of these structures have a correspondence in H-alpha but we were unable to find a one to one correspondence for every occurrence. If the dark streaks are formed at the same heights as umbral flashes then there are systems of structures with strong departures from the vertical for all three analysed sunspots. Conclusions. Long-lived Ca II H filamentary horizontal structures are a common and likely ever-present feature in the umbra of sunspots. If the magnetic field in the chromosphere of the umbra is indeed aligned with the structures, then the present theoretical understanding of the typical umbra needs to be revisited.Comment: Accepted to Astronomy and Astrophysics. Online material (Fig3.mov and Fig4.mov) will be available at A&

Development of biocolonization resistant mortars: preliminary results

Restoration of Buildings and Monuments, vol. 13, nº 6 (2007), p.389-400The negative impact of biocolonization on buildings, particularly rendered ones, prompted the evaluation of a hydraulic mortar formulation to which copper metal, either as a powder or as fibres, was added as a means to control this problem. The study used in situ exposure in a location prone to biocolonization for over nine years. The results have proved that over this time period, no biocolonization occurred on samples containing 0.35 % by weight of copper powder with regards to the dry mortar mix. The mortar proved to acquire a slightly bluer-green hue which diminished after the nine year outdoor exposure. The mortars formulated with copper have a lower porosity as well as a lower capillary water absorption coefficient a definite advantage for their eventual life span. On the other hand, the mechanical resistance is slightly decreased but not significantly so. Further studies are envisioned to assess the performance with other types of binder, such as aerial lime

Magnetic ordering of EuTe/PbTe multilayers determined by x-ray resonant diffraction

In this work we use resonant x-ray diffraction combined with polarization analysis of the diffracted beam to study the magnetic ordering in EuTe/PbTe multilayers. The presence of satellites at the (1/2 1/2 1/2) magnetic reflection of a 50 /repetition EuTe/PbTe superlattice demonstrated the existence of magnetic correlations among the alternated EuTe layers. The behavior of the satellites intensity as T increases toward the Neel temperature T(N) indicates that these correlations persist nearly up to T(N) and suggests the preferential decrease of the magnetic order parameter of external monolayers of each EuTe layer within the superlattice. (C) 2008 American Institute of Physics.922

An Exact Calculation of the Energy Density of Cosmological Gravitational Waves

In this paper we calculate the Bogoliubov coefficients and the energy density of the stochastic gravitational wave background for a universe that undergoes inflation followed by radiation domination and matter domination, using a formalism that gives the Bogoliubov coefficients as continous functions of time. By making a reasonable assumption for the equation of state during reheating, we obtain in a natural way the expected high frequency cutoff in the spectral energy density.Comment: 12 pages+5 figures, uuencoded file,DF/IST-2.9

The incidence of cancer and potential role of sirolimus immunosuppression conversion on mortality among a single-center renal transplantation cohort of 1,816 patients

INTRODUCTION: The chronic use of immunosuppressive drugs in renal transplant recipients increases the risk of developing de novo malignancies. Herein we analyze the incidence of de novo tumors and the potential role of sirolimus to improve cancer-specific survival among a cohort at a single center. METHODS: This retrospective analysis of our 1,816 patients allografted between January 1983 and December 2009 sought subjects who developed de novo tumors. Epidemiological and clinical data were examined using Mann-Whitney and Pearson's chi-square or Fisher exact tests for statistical comparisons of continuous and categorical variables, respectively. Kaplan-Meier survival curves were used to determine cancer-specific survival according to type of neoplasia and immunosuppressive regimen, namely, conversion to sirolimus. RESULTS: One hundred patients (5.5%) were diagnosed with a de novo malignancy. The 110 different cancers were diagnosed at a median interval of 73 months after kidney transplantation. The overall cancer-specific survivals at 1 and 5 years after cancer diagnosis were 87.0% and 76.9%, respectively. The 15 patients converted to sirolimus showed no difference in survival. CONCLUSION: The observed frequencies of cancer in our center are consistent with the literature. Among our cohort, sirolimus did not significantly impact survival among subjects who had de novo malignancies

Efeito da temperatura no perfil de ácidos graxos do óleo de girassol.

Neste trabalho são apresentados resultados de composição de óleos extraídos de girassóis, convencionais e alto oleico, semeados na safra e na safrinha, com o objetivo de investigar o efeito da temperatura na produção de óleo e na proporção dos principais ácidos graxos em sua composiçã

Dust-filled axially symmetric universes with a cosmological constant

Following the recent recognition of a positive value for the vacuum energy density and the realization that a simple Kantowski-Sachs model might fit the classical tests of cosmology, we study the qualitative behavior of three anisotropic and homogeneous models: Kantowski-Sachs, Bianchi type-I and Bianchi type-III universes, with dust and a cosmological constant, in order to find out which are physically permitted. We find that these models undergo isotropization up to the point that the observations will not be able to distinguish between them and the standard model, except for the Kantowski-Sachs model $(\Omega_{k_{0}}0)$ with $\Omega_{\Lambda_{0}}$ smaller than some critical value $\Omega_{\Lambda_{M}}$. Even if one imposes that the Universe should be nearly isotropic since the last scattering epoch ($z\approx 1000$), meaning that the Universe should have approximately the same Hubble parameter in all directions (considering the COBE 4-Year data), there is still a large range for the matter density parameter compatible with Kantowsky-Sachs and Bianchi type-III if $|\Omega_0+\Omega_{\Lambda_0}-1|\leq \delta$, for a very small $\delta$ . The Bianchi type-I model becomes exactly isotropic owing to our restrictions and we have $\Omega_0+\Omega_{\Lambda_0}=1$ in this case. Of course, all these models approach locally an exponential expanding state provided the cosmological constant $\Omega_\Lambda>\Omega_{\Lambda_{M}}$.Comment: 12 pages, 9 figures, 1 table. Published in Physical Review D 1

Intercomparison of aerosol optical depth measurements in the UVB using Brewer Spectrophotometers and a Li-Cor Spectrophotometer

The first Iberian UV radiation intercomparison was held at “El Arenosillo”-Huelva station of the Instituto Nacional de Técnica Aeroespatial (INTA) from September 1 to 10, 1999. During this campaign, seven Brewer spectrophotometers and one Li-Cor spectrophotometer measured the total column aerosol optical depth (AOD) at 306, 310, 313.5, 316.75 and 320 nm. The AOD calibration of one Brewer was transferred to all other Brewers using one day of intensive measurements. The remaining days were used to observe the stability and reproducibility of the AOD measurements by the different instruments. All Brewer spectrophotometers agreed to within an AOD of 0.03 during the whole measurement campaign. The differences in AOD between the Li-Cor spectrophotometer and the Brewer spectrophotometers were between −0.07 and +0.02 at 313.5, 316.75, and 320 nm. This investigation demonstrates the possibility of using the existing worldwide Brewer network as a global UV aerosol network for AOD monitoring.The first Iberian UV radiation intercomparison was supported by the CICYT, project CLI97- 0345-C05-05 under the coordination of INM

High magnetic field induced charge density wave states in a quasi-one dimensional organic conductor

We have measured the high field magnetoresistence and magnetization of quasi-one- dimensional (Q1D) organic conductor (Per)2Pt(mnt)2 (where Per = perylene and mnt = maleonitriledithiolate), which has a charge density wave (CDW) ground state at zero magnetic field below 8 K. We find that the CDW ground state is suppressed with moderate magnetic fields of order 20 T, as expected from a mean field theory treatment of Pauli effects[W. Dieterich and P. Fulde, Z. Physik 265, 239 - 243 (1973)]. At higher magnetic fields, a new, density wave state with sub-phases is observed in the range 20 to 50 T, which is reminiscent of the cascade of field induced, quantized, spin density wave phases (FISDW) observed in the Bechgaard salts. The new density wave state, which we tenatively identify as a field induced charge density wave state (FICDW), is re-entrant to a low resistance state at even higher fields, of order 50 T and above. Unlike the FISDW ground state, the FICDW state is only weakly orbital, and appears for all directions of magnetic field. Our findings are substantiated by electrical resistivity, magnetization, thermoelectric, and Hall measurements. We discuss our results in light of theoretical work involving magnetic field dependent Q1D CDW ground states in high magnetic fields [D. Zanchi, A. Bjelis, and G. Montambaux, Phys. Rev. B 53, (1996)1240; A. Lebed, JETP Lett. 78,138(2003)].Comment: 16 pages, 5 figure