Estudio geológico de las concentraciones de Co- (Ni-Cu-Fe) en el Silúrico de San Juan de Plan, Valle de Gistaín (Pirineo de Huesca)

Se estudian las mineralizaciones -explotadas en el pasado- de sulfuros, arseniuros y sulfoarseniuros de Co-( Ni-Cu-Fe) existentes en el Paleozoico autóctono de San Juan de Plan, estableciéndose la estructura y los controles (litológico y tectónico) de las mismas a fin de esclarecer su génesis. Se trata de mineralizaciones estratoligadas que se ubican en el seno de un horizonte bien caracterizado mineralógica y petrográficamente (<<brecha ankerítica») y que están ligadas al Sistema Silúrico (pizarras ampelíticas). Los indicios de «brecha ankerítica» no se limitan a dicho Sistema, sino que aparecen también en relación con otras litologías (rocas pelíticas y carbonatadas ordovícicas), pero en este caso son estériles. La distribución espacial de dicha roca ankeritica está controlada por una familia de fracturas E-O cuyo origen se supone relacionado con la intrusión granodiorítica de Bielsa. La roca ankerítica se explica por las acciones metasomáticas debidas a fluidos hidrotermales emanados de dicha intrusión. El horizonte mineralizado, en particular, procede de la ankeritización de calizas folisíferas dolomitizadas, intercaladas entre las pizarras ampelíticas silúricas. Su contenido metálico se supone derivado de estas pizarras. A todos estos episodios, ligados al ciclo hercínico, se superpone una intensa tectónica alpina de fracturación y cabalgamiento que trastorna e interrumpe las estructuras mineralizadas, previamente truncadas por el juego pre-alpino de las fracturas E-O

Las mineralizaciones argentíferas de Plasenzuela, Cáceres. España

En el distrito de Plasenzuela, constituido por cinco minas reconocidas y numerosas labores menores, se desarrolló, especialmente en el siglo XIX y a comienzos del XX, una intensa actividad minera para la extracción de menas de plata y plomo. Estas cementan brechas y rellenan fracturas, principalmente de dirección N-S, con buzamientos fuertes al oeste, que ocupan una faja N-S, de unos 10 X 3 Km., próxima al borde occidental del macizo granítico de Plasenzuela. Los materiales encajantes están escasamente metamorflzados y forman parte del Complejo Esquisto-Grauváquico, de edad precámbrica y composición predominantemente pelitica, con preferencia esporádica de niveles volcanogénicos. Aunque se observan variaciones locales, las menas pueden caracterizarse por la paragénesis: arsenopirita, sulfuros BGPC y sulfosales argentiferas (especialmente freieslebenita, freibergita, Ag-tennantita, con polibasita, miargirita, etc., escasas), en ganga cuarzo-sideritica. Se trata de mineralizaciones meso-epitermales, que muestran típicas texturas de relleno, zonadas y ocasionalmente cataclásticas. Las alteraciones en el encajante (siliclflcación, carbonatación esporádica, sulfidización) son poco acusadas; la más típica del distrito es la definida por la difusión de arsenopirita en el encajante, restringida a la proximidad inmediata de las vetas mineralizadas. Se observan numerosas analogías con el distrito de Coeur d'Alene, Idaho. Se propone un modelo genético que implica fracturación repetida asociada a circulación de fluidos hidrotermales (probablemente relacionados con el granito de Plasenzuela, cuyo contenido metálico podría derivarse de los aportes volcano- sedimentarios sulfurados observados en el encajante

Effects of hypodontia on craniofacial structures and mandibular growth pattern

Introduction This study was performed to examine craniofacial structures in persons with hypodontia and to reveal any differences, that may occur, when agenetic teeth are only found in the maxilla, the mandible or in both jaws. The groups consistent of 50 children (33 girls, 17 boys) aged between 9 and 13.5 years were analyzed and assigned to three subgroups. Group 1= upper jaw hypodontia. Group 2= lower jaw hypodontia. Group 3= hypodontia in both jaws. Material and methods Eleven angular and three index measurements from lateral encephalographs and two linear measurements from dental blaster casts were calculated. All data was statistically analyzed, parameters with p<5% were investigated for each subgroup respectively. Results In comparison with standards the study group showed bimaxillary retrognathism and a reduction of the lower anterior facial height. Moreover both overbite and overjet significantly increased. Other values laid within the normal ranges. Evaluating results of the subgroups, differences in the means of SNA, SNB and overjet between the groups were observed. Analysis of the mandibular growth pattern revealed, that neither vertical nor horizontal patterns are dominant in hypodontia patients. Conclusions In certain dentofacial parameters differences between persons with hypodontia and such with full dentition exist. According to our findings agenetic teeth may have a negative influence on the saggital development of a jaw and the lower face and may be responsible for increased overbites. This should receive attention in orthodontic treatment of hypodontia patients

Relationship between PPI and baseline startle response

Prepulse inhibition (PPI) of the startle response to a sudden noise is the reduction in startle observed when the noise is preceded shortly by a mild sensory event, which is often a tone. A part of the literature is based on the assumption that PPI is independent of the baseline startle. A simple model is presented and experimental validation provided. The model is based on the commonly accepted observation that the neuronal circuit of PPI differs from that of startle. But, by using a common output, the measures of both phenomena become linked to each other. But, how can we interpret the numerous experimental data showing PPI to be independent of the startle level? It is suggested that in a number of such cases the baseline startle would have been stabilized by a ceiling effect in the startle/PPI neuronal networks. Reducing the startle level, for example in a PPI evaluation procedure, may disclose properties of startle masked by this ceiling effect. Disclosure of habituation to the startle eliciting noise produced an increase of PPI along its initial measurements. Taken together, even if the neuronal process that sustains startle and PPI are distinct, separating them experimentally requires careful parametric methods and caution in the interpretation of the corresponding observations

Effect of Audiovisual Training on Monaural Spatial Hearing in Horizontal Plane

The article aims to test the hypothesis that audiovisual integration can improve spatial hearing in monaural conditions when interaural difference cues are not available. We trained one group of subjects with an audiovisual task, where a flash was presented in parallel with the sound and another group in an auditory task, where only sound from different spatial locations was presented. To check whether the observed audiovisual effect was similar to feedback, the third group was trained using the visual feedback paradigm. Training sessions were administered once per day, for 5 days. The performance level in each group was compared for auditory only stimulation on the first and the last day of practice. Improvement after audiovisual training was several times higher than after auditory practice. The group trained with visual feedback demonstrated a different effect of training with the improvement smaller than the group with audiovisual training. We conclude that cross-modal facilitation is highly important to improve spatial hearing in monaural conditions and may be applied to the rehabilitation of patients with unilateral deafness and after unilateral cochlear implantation

Aminocronology of the Middle Pleistocene deposits of Redueña (Madrid)

This paper deals with Redueña alluvial fan deposits amino acid (aspartic acid and leucine ) racemization dating. Redueña deposits and faunal and archaeological Middle Paleolithic remains can be correlated with the 8th oxigen episode (ca.350 k.a.). Method usefullness to determine thermal story data was also checked

The descending corticocollicular pathway mediates learning-induced auditory plasticity.

Descending projections from sensory areas of the cerebral cortex are among the largest pathways in the brain, suggesting that they are important for subcortical processing. Although corticofugal inputs have been shown to modulate neuronal responses in the thalamus and midbrain, the behavioral importance of these changes remains unknown. In the auditory system, one of the major descending pathways is from cortical layer V pyramidal cells to the inferior colliculus in the midbrain. We examined the role of these neurons in experience-dependent recalibration of sound localization in adult ferrets by selectively killing the neurons using chromophore-targeted laser photolysis. When provided with appropriate training, animals normally relearn to localize sound accurately after altering the spatial cues available by reversibly occluding one ear. However, this ability was lost after eliminating corticocollicular neurons, whereas normal sound-localization accuracy was unaffected. The integrity of this descending pathway is therefore critical for learning-induced localization plasticity