Revisión de los elementos de ajuar conservados del sepulcro megalítico de Unón (Clavijo, La Rioja)

En este artículo se procede a la revisión de los materiales conservados del megalito desaparecido de Uñón (Clavijo, La Rioja), entre los que destacan varios recipientes campaniformes

Enhancement of photoacoustic detection of inhomogeneities in polymers

We report a series of experiments on laser pulsed photoacoustic excitationin turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon(R) samples in different situations and we show the limitations of the method.Comment: 8 pages, 7 figure

Experimental Test of a Two-dimensional Approximation for Dielectric Microcavities

Open dielectric resonators of different shapes are widely used for the manufacture of microlasers. A precise determination of their resonance frequencies and widths is crucial for their design. Most microlasers have a flat cylindrical geometry, and a two-dimensional approximation, the so-called method of the effective index of refraction, is commonly employed for numerical calculations. Our aim has been an experimental test of the precision and applicability of a model based on this approximation. We performed very thorough and accurate measurements of the resonance frequencies and widths of two passive circular dielectric microwave resonators and found significant deviations from the model predictions. From this we conclude that the model generally fails in the quantitative description of three-dimensional dielectric resonators.Comment: 10 pages, 13 figure

The Post-Common Envelope and Pre-Cataclysmic Binary PG 1224+309

We have made extensive spectroscopic and photometric observations of PG 1224+309, a close binary containing a DA white dwarf primary and an M4+ secondary. The H alpha line is in emission due to irradiation of the M-star by the hot white dwarf and is seen to vary around the orbit. From the radial velocities of the H alpha line we derive a period of P = 0.258689 +/- 0.000004 days and a semi-amplitude of K_Halpha = 160 +/- 8 km/s. We estimate a correction Delta_K = 21 +/- 2 km/s, where K_M = K_Halpha + Delta_K. Radial velocity variations of the white dwarf reveal a semi-amplitude of K_WD = 112 +/- 14 km/s. The blue spectrum of the white dwarf is well fit by a synthetic spectrum having T_eff = 29,300 K and log(g) = 7.38. The white dwarf contributes 97% of the light at 4500 Angstroms and virtually all of the light blueward of 3800 Angstroms. No eclipses are observed. The mass inferred for the white dwarf depends on the assumed mass of the thin residual hydrogen envelope: 0.40 < M_WD < 0.45 solar masses for hydrogen envelope masses of 0 < M_H < 4.0E-4 solar masses. We argue that the mass of the white dwarf is closer to 0.45 solar masses, hence it appears that the white dwarf has a relatively large residual hydrogen envelope. The mass of the M-star is then M_M = 0.28 +/- 0.05 solar masses, and the inclination is i = 77 +/- 7 degrees. We discuss briefly how PG 1224+309 may be used to constrain theories of close binary star evolution, and the past and future histories of PG 1224+309 itself. The star is both a ``post-common envelope'' star and a ``pre-cataclysmic binary'' star. Mass transfer by Roche-lobe overflow should commence in about 10 Gyr.Comment: 17 pages, 8 figures, AAS LaTeX, to appear in AJ, March 199

Human activities, biostratigraphy and past environment revealed by small-mammal associations at the chalcolithic levels of El Portalón de Cueva Mayor (Atapuerca, Spain)

The Chalcolithic levels of El Portalón de Cueva Mayor (Atapuerca, Burgos, Spain) offer a good opportunity to test whether the small-mammal contents of different archaeo-stratigraphical units may be useful to characterize them as independent entities. With that purpose, we studied representative samples of small-mammal remains from the two main contexts identified: the Early Chalcolithic (EC) funerary context and the Late Chalcolithic (LC) habitat/stabling context, with the latter comprising three different archaeological units according to their origin, namely prepared floors, activity floors and stabling surfaces or fumiers. Following the distribution of taxa in their respective contexts, we performed several statistical tests to check for significant discrepancies between archaeological units. The exclusive presence of certain taxa, together with the statistical difference in relative taxonomic ratios, points to the integrity and unpolluted condition of the EC context. The interspersed arrangement of the different LC context’s units made them prone to inter-pollution as they are not statistically different. The unexpected presence of Pliomys lenki and Chionomys nivalis in the prepared floors evidences their Upper Pleistocene allochthonous origin. The EC levels of El Portalón contribute the first Holocene records of nine taxa in the Sierra de Atapuerca. An environment dominated by woodland, shrubland and wet meadows, with moderate presence of grassland, inland wetlands and rocky areas, is inferred from the small-mammal association of the EC levels

Filogeografía de la pescadilla de red Cynoscion guatucupa (Perciformes: Sciaenidae) del Atlántico suroccidental

The genetic structure of populations/species was established during the Quaternary glaciations. Over the last 250 ka (Pleistocene), the South American marine biogeographic history recorded three main glaciations: the most extensive one between 140 and 180 ka, a minor one between 60 and 70 ka, and the last glaciation approximately between 15 and 35 ka. With the aim of assessing the pattern of molecular diversity and historical demography of weakfish (Cynoscion guatucupa), a 365 bp sequence of the mitochondrial control region was amplified at four coastal sites located in the southwestern Atlantic. Haplotype diversity was high, whereas nucleotide diversity was low and similar at each sample site. AMOVA failed to detect population structure. This lack of differentiation was subsequently observed in the distribution of samples sites in the haplotype network. Fu’s Fs was negative and highly significant while the mismatch analysis yielded a unimodal distribution, indicating a global population expansion. The Bayesian skyline plot revealed a coalescence time of weakfish population at approximately 210 ka, and a very rapid expansion from 180-190 ka, probably caused by a habitat expansion, as these two events coincide in time.La estructura genética de las poblaciones/especies se ha establecido principalmente durante las glaciaciones del Cuaternario. La historia biogeográfica marina en Sudamérica en los últimos 250 ka registra durante el Pleistoceno tres glaciaciones importantes: la más extensa entre 140-180 ka, una menor entre 60-70 ka y la última glaciación aproximadamente entre 15-35 ka. Para evaluar el patrón de diversidad molecular y de demografía histórica en la pescadilla de red (Cynoscion guatucupa) se analizó una secuencia de 365 pb de la región control del ADN mitocondrial en cuatro zonas costeras del Atlántico suroccidental. La diversidad haplotípica fue alta mientras que la diversidad nucleotídica fue baja y ambos índices fueron similares en cada sitio de muestreo. El análisis de varianza molecular (AMOVA) no detectó estructura poblacional. Esta falta de diferenciación posteriormente se pudo observar en la distribución de los sitios de muestreo en la red de haplotipos. El test de Fu fue negativo y altamente significativo y el análisis de falta de coincidencia produjo una distribución unimodal indicando expansión poblacional. El skyline plot indicó un tiempo a la coalescencia de 210 ka y una expansión poblacional que comenzó hace 180-190 ka que probablemente se produjo por la expansión del hábitat ya que ambos eventos coinciden en el tiempo

Alpha and beta oscillatory activity during a sequence of two movements

OBJECTIVE: We studied movement-related electroencephalographic oscillatory changes in the alpha and beta range during a sequence of two movements in 7 healthy volunteers, in order to investigate the relationship between these changes and each component in the sequence. METHODS: The sequence consisted of a wrist active extension-passive flexion followed by a first and second finger pincer. A total of 10.5 s sweeps were recorded using the level of surface electromyographic (EMG) activity in wrist extensors as trigger, including a 7.5 s pre-stimulus. The sweeps were also realigned manually offline using as trigger the end of the first EMG burst, or the beginning of the second movement. An index of the changes in non-phase-locked energy in the 7-37 Hz range was obtained by averaging single-sweep time-frequency transforms. RESULTS: The duration of each of the movements in the sequence and the relationship between them were compatible with the use of two different motor programmes in the sequence. In the beta band, a decrease in energy (event-related desynchronisation, ERD) began 1.5 s before the onset of the first movement, and was sustained until the end of the second movement. No energy increases were observed until the end of the second movement. In the alpha band, the ERD began 0.5 seconds before the first movement and was sustained throughout the recording. CONCLUSION: These findings suggest that the beta-event-related synchronisation is related to the end of the whole motor process, and not to the end of each motor programme

Molecular characterization of KPC-2–positive Klebsiella pneumoniae isolates from a neurosurgical centre in Argentina

Carbapenem-resistant Enterobacteriaceae is a growing concern worldwide. Klebsiella pneumoniae is an important nosocomial pathogen with a high capacity for nosocomial spread. We described the occurrence of plasmid-encoded KPC-2–harbouring K. pneumoniae isolates recovered from a neurosurgical centre in Argentina. The blaKPC-2 gene was surrounded by ISkpn6 and ISkpn7.Fil: Montaña, Sabrina Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Hernandez, M.. California State University; Estados UnidosFil: Fernandez, J. S.. California State University; Estados UnidosFil: Penini, M.. Stamboulian Servicios de Salud; ArgentinaFil: Centron, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Sucari, A.. Stamboulian Servicios de Salud; ArgentinaFil: Iriarte, A.. Universidad de la República; UruguayFil: Ramirez, Maria Soledad. California State University; Estados Unido