Sedimentología de los yesos del sector central de la Depresión del Duero

En el sector central de la Depresión del Duero afloran sedimentosneógenos, terrígenos, carbonatados y yesíferos. En los depósitos yesiferos se han diferenciado facies de yeso primario, secundario y retrabajado que junto a las facies carbonatadas se ordenan en secuencias y megasecuencias positivas y negativas. Las megasecuencias se interpretan como retracciones o expansiones del sistema lacustre. Se relacionan las secuencias con los modelos paleogeográficos establecidos y se analizan los factores que controlaron la evolución de los depósitos yesíferos en el tiempo

A detailed two-dimensional stellar population study of M32

We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region of M32 obtained with the 2D_FIS fibre spectrograph installed at the William Herschel Telescope. From these spectra line strength maps have been reconstructed for about 20 absorption lines, mostly belonging to the Lick system. We find good agreement with long-slit line strength profiles in the literature. In contrast with previous studies, indices were azimuthally averaged along continuum isophotes of M32. A remarkable result is that no gradients are presented in the spectral indices. So, we have fitted the mean values of each spectral index and central colours to the models of Vazdekis et al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and metallicity similar to solar (Z=0.02) are the best fitted values for the innermost region of M32.Comment: accepted in MNRA

Short-timescale Fluctuations in the Difference Light Curves of QSO 0957+561A,B: Microlensing or Noise?

From optical R band data of the double quasar QSO 0957+561A,B, we made two new difference light curves (about 330 days of overlap between the time-shifted light curve for the A image and the magnitude-shifted light curve for the B image). We observed noisy behaviours around the zero line and no short-timescale events (with a duration of months), where the term event refers to a prominent feature that may be due to microlensing or another source of variability. Only one event lasting two weeks and rising - 33 mmag was found. Measured constraints on the possible microlensing variability can be used to obtain information on the granularity of the dark matter in the main lensing galaxy and the size of the source. In addition, one can also test the ability of the observational noise to cause the rms averages and the local features of the difference signals. We focused on this last issue. The combined photometries were related to a process consisting of an intrinsic signal plus a Gaussian observational noise. The intrinsic signal has been assumed to be either a smooth function (polynomial) or a smooth function plus a stationary noise process or a correlated stationary process. Using these three pictures without microlensing, we derived some models totally consistent with the observations. We finally discussed the sensitivity of our telescope (at Teide Observatory) to several classes of microlensing variability.Comment: MNRAS, in press (LaTeX, 14 pages, 22 eps figures

El paleógeno del sector suroccidental de la Cuenca del Duero: nueva división estratigráfica y controles sobre su sedimentación

Como resultado de un detallado trabajo cartográfico, estratigráfico y sedimentológico, se propone la división del Paleógeno del sector suroccidental de la Cuenca del Duero en cuatro U.T.S. limitadas por discordancias. Estas D.T.S., que abarcan desde el tránsito Cretácico superior-Paleoceno hasta el Oligoceno, incluyen distintas unidades litoestratigráficas que sonreordenadas, modificando la sucesión estratigrática propuesta por los autores anteriores. Se asigna a la U.T.S. Me una edad Cretácico superior-Paleoceno. Se individualiza el Eoceno inferior (U.T.S. PI) en la zona de Salamanca. Se reinterpreta la relación existente entre los materiales del Eoceno mediosuperior y los del Eoceno superior-Oligoceno considerándolos en tránsito por lo que se asignan a una única U.T.S. (UT.S. P2, Eoceno medio Oligoceno inferior). Se incluyen en la U.T.S. P3 (Oligoceno superior) los sedimentos arcósicos anterionnente considerados como Vatlesienses. Así mismo, se considera que gran parte de los materiales asignados al mioceno inferior son sedimentos paleógenos afectados por un proceso de alteración de edad Miocena, lo que implica una variación en la extensión y límites de la cuenca neógena en su extremo SO. Se analiza la evolución de las distintas U.T.S. deduciendo un carácter tectónico para las megasecuencias propuestas relacionado con el progresivo levantamiento de las áreas fuente. El clima muestra un tránsito desde condiciones tropicales sin estaciones contrastadas (U,T.S. MC) hasta un clima mediterráneo árido (U.T.S. P3) con una estación seca muy marcada y una corta estación húmeda caracterizada por violentas avenidas. [ABSTRACT] A Paleogene four-fold stratigraphical division is proposed here as result fram the detailed studies carried out during the elaboration of 22 sheets of the Geological Map of Spain (E. 1 :50.000). This units (T.S.U.) are limited by regional discordances and they have a Upper Cretaceous to Oligocene ages. The previous stratigraphical schemes are rearranged due to the different stratigraphical relations observed between the lithostratigraphical units proposed by other workers (Jiménez, 1970; Corrochano, 1977; Alonso, 1981...). An Upper Cretaceous-Paleocene age is assumed to T.S.U. MC which is mainly composed by siliciclastic sediments strongly silicified forming a FU megasequence. It is intcrpretated as braided streams that flowed downslope filling paleovalleys erodcd onto Paleozoic materiaIs. Mineralogical features point to a tropical climate. Lower Eocene (T.S.U. P I ) is identified in the Salamanca area, where ir was considered as lacking. It is composed by arkosic sediments forming a CU megasequence. Fossil faunas of this T.S.U. record a subtropical clima te. It is observed a transition from high sinuosity streams to braided ones. T.S.U. P2 (Middle Eocene-Lower Oligocene) is composed of two lithostratigraphical units previously considered as bounded by a discordance (Alonso, 1981).It has a subarkosic to lithic nature and forms a CU megasequence. This unit records a subtropical climate with short arid periods and is interpretated as braided streams showing an increasing stability and enviromental energy to the topo T.S. U. P3 (Upper Oligocene) is composed by arkosic sediments previously considered of Vallesian (Middle to Upper Miocene) age. They form a CU megasequence that records braided streams prograding basinwardfrom higher arcas. Palinological associations and pedological features indicate an arid mediterranean climate with long arid periods and a short rainy season with strong floods. We consider that most of Lower Miocene sediments are of Paleogene age. They are afected by a widespread alteration profile developed along Lower Miocene that masked its more significative features. Sedimentological analysis of T.S.U. shows that its megasequentiality is related to the rates of tectonical uplift of source arcas whereas a distensive regime developed in the sedimentation basin

A Large Brightness Enhancement of the QSO 0957+561 A Component

We report an increase of more than 0.2 mag in the optical brightness of the leading image (A) of the gravitational lens Q0957+561, detected during the 09/2000 -- 06/2001 monitoring campaign (2001 observing season). The brightening is similar to or even greater than the largest change ever detected during the 20 years of monitoring of this system. We discuss two different provisional explanations to this event: intrinsic source variability or microlensing (either short timescale microlensing or cessation of the historical microlensing). An exhaustive photometric monitoring of Q0957+561 is needed until summer of 2002 and during 2003 to discriminate between these possibilities.Comment: 13 pages including 3 figures and 1 table. Accepted for publication in ApJ Let

Spectroscopy of the Lens Galaxy of Q0957+561A,B. Implications of a possible central massive dark object

We present new long-slit William Herschel Telescope spectroscopic observations of the lens galaxy G1 associated with the double-imaged QSO 0957+561A,B. The obtained central stellar velocity dispersion, sigma_l = 310 +/- 20 km/s, is in reasonable agreement with other measurements of this dynamical parameter. Using all updated measurements of the stellar velocity dispersion in the internal region of the galaxy (at angular separations < 1".5) and a simple isotropic model, we discuss the mass of a possible central massive dark object. It is found that the data of Falco et al. (1997) suggest the existence of an extremely massive object of (0.5-2.1) x 10E10/h M_\odot (80% confidence level), whereas the inclusion of very recent data (Tonry & Franx 1998, and this paper) substantially changes the results: the compact central mass must be $\le$ 6 x10E9/h M_\odot at the 90% confidence level. We note that, taking into account all the available dynamical data, a compact nucleus with a mass of 10E9/h M_\odot (best fit) cannot be ruled out.Comment: 20 pages, 10 figures ApJ, in pres

Luxación esternoclavicular posterior: a propósito de un caso y revisión de la literatura

La luxación esternoclavicular posterior es una patología poco frecuente. Se presenta sobre todo en varones jóvenes asociada a traumatismos de alta energía. Puede presentar complicaciones potencialmente letales por compresión de estructuras mediastínicas, por lo que es necesario su reducción urgente. El diagnóstico radiográfico puede ser difícil debido a la superposición de estructuras, siendo de gran utilidad la TC para determinar el tipo y grado de desplazamiento, así como la relación anatómica con las estructuras mediastínicas. Se presenta el caso de un paciente varón, de 23 años de edad, que presentó una luxación esternoclavicular posterior traumática aguda tras accidente de tráfico en el que se consiguió la reducción cerrada mediante manipulación bajo anestesia general y posterior inmovilización antiálgica durante 3 semanas, sin objetivarse inestabilidad esternoclavicular posterior que obligase a más procedimientos. Se realiza una revisión de la literatura médica al respecto de esta patología.Posterior sternoclavicular dislocation is a rare disease. It occurs mainly in young men associated with high-energy trauma. It can be life-threatening due to compression of mediastinal structures, so its reduction is urgently needed. The radiographic diagnosis can be difficult because of overlapping structures, CT is very helpful to determine the type and degree of displacement and the anatomic relationship with the mediastinal structures. We present the case of a male patient, aged 23, with an acute traumatic posterior sternoclavicular dislocation after accident, in which closed reduction was achieved by manipulation under general anesthesia, followed by analgesic immobilization for 3 weeks resulting in sternoclavicular healing without instability, so no more procedures were needed. A literature review is presented regarding to this case

New VR magnification ratios of QSO 0957+561

We present VR magnification ratios of QSO 0957+561, which are inferred from the GLITP light curves of Q0957+561A and new frames taken with the 2.56m Nordic Optical Telescope about 14 months after the GLITP monitoring. From two photometric approaches and a reasonable range for the time delay in the system (415-430 days), we do not obtain achromatic optical continuum ratios, but ratios depending on the wavelength. These new measurements are consistent with differential extinction in the lens galaxy, the Lyman limit system, the damped Ly-alpha system, or the host galaxy of the QSO. The possible values for the differential extinction and the ratio of total to selective extinction in the V band are reasonable. Moreover, crude probability arguments suggest that the ray paths of the two components cross a similar dusty environment, including a network of compact dust clouds and compact dust voids. As an alternative (in fact, the usual interpretation of the old ratios), we also try to explain the new ratios as caused by gravitational microlensing in the deflector. From magnification maps for each of the gravitationally lensed images, using different fractions of the surface mass density represented by the microlenses, as well as different sizes and profiles of the V-band and R-band sources, several synthetic distributions of V-band and R-band ratios are derived. In some gravitational scenarios, there is an apparent disagreement between the observed pair of ratios and the simulated distributions. However, several microlensing pictures work well. To decide between either extinction, or microlensing, or a mixed scenario (extinction + microlensing), new observational and interpretation efforts are required.Comment: PS and PDF versions are created from the LaTeX file and 5 EPS figures, two additional figues (Figs. 6 and 7) in JPEG format, scheduled for the ApJ 20 January 2005 issu

Scientific Basis for the Potential Use of Melatonin in Bone Diseases: Osteoporosis and Adolescent Idiopathic Scoliosis

The objective of this paper was to analyze the data supporting the possible role of melatonin on bone metabolism and its repercussion in the etiology and treatment of bone pathologies such as the osteoporosis and the adolescent idiopathic scoliosis (AIS). Melatonin may prevent bone degradation and promote bone formation through mechanisms involving both melatonin receptor-mediated and receptor-independent actions. The three principal mechanisms of melatonin effects on bone function could be: (a) the promotion of the osteoblast differentiation and activity; (b) an increase in the osteoprotegerin expression by osteoblasts, thereby preventing the differentiation of osteoclasts; (c) scavenging of free radicals generated by osteoclast activity and responsible for bone resorption. A variety of in vitro and in vivo experimental studies, although with some controversial results, point toward a possible role of melatonin deficits in the etiology of osteoporosis and AIS and open a new field related to the possible therapeutic use of melatonin in these bone diseases