Clasificación textural del cuarzo epitermal (Au-Ag) de relleno filoniano del área volcánica de Cabo de Gata, Almería

El estudio de filones epitermales, particularmente del tipo low-sulphidation o adularia-sericita, pone de manifiesto la existencia, en el relleno hidrotermal, de frecuentes manifestaciones de cuarzo anómalo, por sus texturas y características petrográficaso La interpretación de estos tipos de cuarzo plantea problemas a la hora de establecer su origen y para cualquier estudio de inclusiones fluidas, al obligar a cuestionar el carácter primario de asociaciones de inclusiones que en otras condiciones sería indudable (por ejemplo, las asociadas a zonado de crecimiento). El campo filoniano de Cabo de Gata (Almería) ofrece un amplio muestrario de este tipo de manifestaciones de cuarzo epitermal, el cual ha servido de base para proponer una clasificación de dichas texturas, como primer paso para abordar, con el rigor y precisión debidos, ulteriores estudios mineralógicos, geoquímicos y, en particular, microtermométricos por inclusiones fluidas. Se recogen de la literatura internacional y se aplican las ideas derivadas de otros campos similares y se propone una clasificación -Cuadros 1 y 2- que distingue las generaciones de cuarzo estrictamente primario (es decir, no transformadas por procesos ulteriores) y las modificadas, recristalizadas, secundarias, etc... Todas ellas se documentan gráficamente. Las texturas recristalizadas son particularmente engañosas, ya que pueden mostrar rasgos aparentemente primarios, como zonado de crecimiento, que inducen a error al interpretar las inclusiones correspondientes como primarias. Dicha clasificación tiene por objeto no sólo el asegurar el rigor necesario para abordar la petrografía de inclusiones fluidas, sino también el apoyo a la exploración y a la caracterización tipológica de las concentraciones de metales preciosos. Se aportan criterios para facilitar la interpretación y reconocimiento de procesos epitermales en general y, particularmente, mediante la caracterización de las texturas de relleno en campo y laboratorio, para distinguir ambientes epitermales de otros (vbgr. metamórficos, mesotermales o ligados a zonas de cizalla), relevantes o no para la exploración. Se ha hecho el esfuerzo de referir las texturas a términos castellanos, evitando la repetición "ad infinitum", no siempre necesaria, de términos anglosajones. Lo que en algunos casos obliga a innovar, pero, para evitar toda confusión, se ha reducido al mínimo indispensable la terminología nueva. Para mayor precisión y para facilitar la comparación con otros trabajos, se propone -Cuadro 3- una tabla de equivalencias entre la terminología (española) empleada y definida en este trabajo y la más extendida en la literatura internacional (inglés, francés)

The radon anomaly of Porcheresse (Ardennes, Belgium). A case study

From a very high radon concentration in a dwelling of the village of Porcheresse, one discusses on of the significance of the numerous radon indoor anomalies detected in the southern part of Belgium

Genetic Analyses in Small for Gestational Age Newborns

Context: Small for gestational age (SGA) can be a result of fetal growth restriction, associated with perinatal morbidity and mortality. Mechanisms that control prenatal growth are poorly understood. Objective: The aim of the present study was to gain more insight into prenatal growth failure and determine an effective diagnostic approach in SGA newborns. We hypothesized that one or more CNVs and disturbed methylation and sequence variants may be present in genes known to be associated with fetal growth. Design: A prospective cohort study of subjects with a low birthweight for gestational age. Setting: The study was conducted at an academic pediatric research institute. Patients: A total of 21 SGA newborns with a mean birthweight below the 1st centile and a control cohort of 24 appropriate for gestational age newborns were studied. Intervention: Array comparative genomic hybridization, genome-wide methylation studies and exome sequencing were performed. Main Outcome Measures The numbers of copy number variations, methylation disturbances and sequence variants. Results: The genetic analyses demonstrated three CNVs, one systematically disturbed methylation pattern and one sequence variant explaining the SGA. Additional methylation disturbances and sequence variants were present 20 patients. In 19 patients, multiple abnormalities were found. Conclusion: Our results confirm the influence of a large number of mechanisms explaining dysregulation of fetal growth. We conclude that copy number variations, methylation disturbances and sequence variants all contribute to prenatal growth failure. Such genetic workup can be an effective diagnostic approach in SGA newborns

Low Q^2 Jet Production at HERA and Virtual Photon Structure

The transition between photoproduction and deep-inelastic scattering is investigated in jet production at the HERA ep collider, using data collected by the H1 experiment. Measurements of the differential inclusive jet cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the transverse energy and the pseudorapidity of the jets in the virtual photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3 < y < 0.6. The interpretation of the results in terms of the structure of the virtual photon is discussed. The data are best described by QCD calculations which include a partonic structure of the virtual photon that evolves with Q2.Comment: 20 pages, 5 Figure

Hadron Production in Diffractive Deep-Inelastic Scattering

Characteristics of hadron production in diffractive deep-inelastic positron-proton scattering are studied using data collected in 1994 by the H1 experiment at HERA. The following distributions are measured in the centre-of-mass frame of the photon dissociation system: the hadronic energy flow, the Feynman-x (x_F) variable for charged particles, the squared transverse momentum of charged particles (p_T^{*2}), and the mean p_T^{*2} as a function of x_F. These distributions are compared with results in the gamma^* p centre-of-mass frame from inclusive deep-inelastic scattering in the fixed-target experiment EMC, and also with the predictions of several Monte Carlo calculations. The data are consistent with a picture in which the partonic structure of the diffractive exchange is dominated at low Q^2 by hard gluons.Comment: 16 pages, 6 figures, submitted to Phys. Lett.

Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA

An investigation of the hadronic final state in diffractive and non--diffractive deep--inelastic electron--proton scattering at HERA is presented, where diffractive data are selected experimentally by demanding a large gap in pseudo --rapidity around the proton remnant direction. The transverse energy flow in the hadronic final state is evaluated using a set of estimators which quantify topological properties. Using available Monte Carlo QCD calculations, it is demonstrated that the final state in diffractive DIS exhibits the features expected if the interaction is interpreted as the scattering of an electron off a current quark with associated effects of perturbative QCD. A model in which deep--inelastic diffraction is taken to be the exchange of a pomeron with partonic structure is found to reproduce the measurements well. Models for deep--inelastic $ep$ scattering, in which a sizeable diffractive contribution is present because of non--perturbative effects in the production of the hadronic final state, reproduce the general tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil

Measurement of D* Meson Cross Sections at HERA and Determination of the Gluon Density in the Proton using NLO QCD

With the H1 detector at the ep collider HERA, D* meson production cross sections have been measured in deep inelastic scattering with four-momentum transfers Q^2>2 GeV2 and in photoproduction at energies around W(gamma p)~ 88 GeV and 194 GeV. Next-to-Leading Order QCD calculations are found to describe the differential cross sections within theoretical and experimental uncertainties. Using these calculations, the NLO gluon momentum distribution in the proton, x_g g(x_g), has been extracted in the momentum fraction range 7.5x10^{-4}< x_g <4x10^{-2} at average scales mu^2 =25 to 50 GeV2. The gluon momentum fraction x_g has been obtained from the measured kinematics of the scattered electron and the D* meson in the final state. The results compare well with the gluon distribution obtained from the analysis of scaling violations of the proton structure function F_2.Comment: 27 pages, 9 figures, 2 tables, submitted to Nucl. Phys.

A Search for Selectrons and Squarks at HERA

Data from electron-proton collisions at a center-of-mass energy of 300 GeV are used for a search for selectrons and squarks within the framework of the minimal supersymmetric model. The decays of selectrons and squarks into the lightest supersymmetric particle lead to final states with an electron and hadrons accompanied by large missing energy and transverse momentum. No signal is found and new bounds on the existence of these particles are derived. At 95% confidence level the excluded region extends to 65 GeV for selectron and squark masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure

Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA

Deep--inelastic scattering events with a leading baryon have been detected by the H1 experiment at HERA using a forward proton spectrometer and a forward neutron calorimeter. Semi--inclusive cross sections have been measured in the kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T <= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV, or a neutron with energy E' >= 160 GeV. The measurements are used to test production models and factorization hypotheses. A Regge model of leading baryon production which consists of pion, pomeron and secondary reggeon exchanges gives an acceptable description of both semi-inclusive cross sections in the region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading neutron data are used to estimate for the first time the structure function of the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.