The use of mineral interfaces in sand-sized volcanic rock fragments to infer mechanical durability

AbstractThe use of mineral interfaces, in sand-sized rock fragments, to infer the influence exerted by mechanical durability on the generation of siliciclastic sediments, has been determined for plutoniclastic sand. Conversely, for volcaniclastic sand, it has received much less attention, and, to our knowledge, this is the first attempt to make use of the volcaniclastic interfacial modal mineralogy of epiclastic sandy fragments, to infer mechanical durability control at a modern beach environment. Volcaniclastic sand was collected along five beaches developed on five islands, of the southern Tyrrhenian Sea (Alicudi, Filicudi, Salina, Panarea and Stromboli) from the Aeolian Archipelago, and one sample was collected near the Stromboli Island volcanic crater. Each sample was sieved and thin sectioned for petrographic analysis. The modal mineralogy of the very coarse, coarse and medium sand fractions was determined by point-counting of the interfacial boundaries discriminating 36 types of interfaces categories, both no-isomineralic and/or no iso-structural (e.g., phenocrystal/glassy groundmass or phenocrystal/microlitic groundmass boundaries) and iso-mineralic interfaces, inside volcanic lithic grains with lathwork and porphyric textures. A total of 47,386 interfacial boundaries have been counted and, the most representative series of interfaces, from the highest to the lowest preservation, can be grouped as: a) ultrastable interfaces, categorized asPl (Plagioclase)/Glgr (Glassy groundmass) > > Px (Pyroxene)/Glgr > > Ol (Olivine)/Glgr > > Op (Opaque)/Glgr > > Hbl (Hornblende)/Glgr> > Bt (Biotite)/Glgr > > Idd (Iddingsite)/Glgr > > Rt (Rutile) / Glgr; b) stable interfaces, categorized asPl/Migr (Microlitic groundmass) > > Op/Migr > > Px/Migr > > Ol/Migr; c) moderately stable interfaces, categorized asOp/Px > > Op/Hbl > > Px/P > > Ol/Pl> > Bt/Op; and d) unstable interfaces, categorized asPl/Pl > > Px/Px > > Ol/Ol > > Op/Op > > Hbl/Hbl > > Bt/Bt.Grains, eroded from the volcanic bedrock, if affected solely by abrasion, developed a rounded and smoothed form, with prevailing no-isostructural interfaces such as Plagioclase/Glassy groundmass, Pyroxene/Glassy groundmass and Olivine/Glassy groundmass interfaces. Grains that during transport suffered fracturing and percussion have a sharp and angular form: these combined transport mechanisms produce mainly volcanic sandy grains with iso-structural interfaces, such as Pl/Pl, Px/Px, Hbl/Hbl, and, to a lesser extent, Bt/Op and Bt/Glgr interfaces

Petrography of Middle Jurassic to Early Cretaceous sandstones in the Kutch Basin, western India: Implications on provenance and basin evolution

Abstract This paper investigates the provenance of Middle Jurassic to Early Cretaceous sediments in the Kutch Basin, western India, on the basis of mineralogical investigations of sandstones composition (Quartz–Feldspar–Lithic (QFL) fragment), Zircon–Tourmaline–Rutile (ZTR) index, and mineral chemistry of heavy detrital minerals of the framework. The study also examines the compositional variation of the sandstone in relation to the evolution of the Kutch Basin, which originated as a rift basin during the Late Triassic and evolved into a passive margin basin by the end Cretaceous. This study analyzes sandstone samples of Jhumara, Jhuran and Bhuj Formations of Middle Jurassic, Upper Jurassic and Lower Cretaceous, respectively, in the Kutch Mainland. Sandstones record a compositional evolution from arkosic to subarkosic as the feldspar content decreases from 68% in the Jhumara Formation to 27% in the Bhuj Formation with intermediate values in the Jhuran Formation. The QFL modal composition indicates basement uplifted and transitional continental settings at source. Heavy mineral content of these sandstones reveals the occurrence of zircon, tourmaline, rutile, garnet, apatite, monazite and opaque minerals. Sub-rounded to well-rounded zircon grains indicate a polycyclic origin. ZTR indices for samples in Jhumara, Jhuran and Bhuj Formations are 25%, 30% and 50% respectively. Chemistry of opaque minerals reveals the occurrence of detrital varieties such as ilmenite, rutile, hematite/magnetite and pyrite, in a decreasing order of abundances. Chemistry of ilmenites in the Jhumara Formation reveals its derivation from dual felsic igneous and metabasic source, while those in Jhuran and Bhuj Formations indicate a metabasic derivation. Chemistry of garnet reveals predominantly Fe-rich (almandine) variety of metabasic origin. X-ray microscopic study provides the percentage of heavy minerals ranging from 3% to 5.26%. QFL detrital modes reflect the evolution of the basin from an active rift to a passive margin basin during the Mesozoic. Integration of results from QFL modal composition of the sandstones, heavy mineral analysis and mineral chemistry, suggests sediment supply from both northern and eastern highlands during the Middle Jurassic. The uplift along the Kutch Mainland Fault in the Early Cretaceous results in curtailment of sediment input from north

Composition of modern stream sand derived from a mixture of sedimentary and metamorphic source rocks (Henares River, Central Spain)

The Henares River, central Spain, flows westward from the Iberian Range (Mesozoic sedimentary rocks) under semiarid climatic conditions. In the middle and lower reaches, the Henares River receives sediment from three tributaries (Cañamares, Bornova and Sorbe rivers) that drain the Central System (Paleozoic crystalline rocks, low-grade metamorphic rocks, and minor amounts of Mesozoic sedimentary rocks). Modern sands from the Henares River and its tributaries offer an excellent opportunity to evaluate the importance of lithology and physiography in determining detrital modes from mixed metamorphic and sedimentary source terrain. Sand modes from the Henares River and its tributaries are quartzolithic. They plot in a restricted area on a QmFLt diagram, with low contents of feldspar and variable amounts of quartz, and carbonate, metamorphic and minor siliciclastic lithic fragments. Higher feldspar abundances in the Cañamares and Bornova stream sands are related to the erosion of gneissic rocks. By contrast, sands from Sorbe River are low in feldspar, reflecting the absence of coarse metamorphic sources. Thus, proportions of bedrock lithologies in the drainage sub-basins are the main control on detrital modes of the tributaries. In addition, slope acts on the sand productivity of source rocks. Sedimentary source rocks in the upper reaches of the three tributaries have a poor productivity in the carbonate lithic fragments (Lsc), compared with the Lsc productivity of sedimentary sources located downstream, with higher relief. The percentage of bedrock types in the source area versus petrographic indices (Lm/L, Lss/L and Lsc/L) provide a useful contrast between source and sand composition in the tributaries. Thus, the high content of metamorphic lithic grains in the lithic grain population over-represents this lithology (slate plus schist) at the source terrain. Lithic grains from sedimentary clastic sources generate few recognizable grains (Lss) in the lithic grain population. Local supplies from carbonate sources may produce important increases of Lsc in short reaches of the channels. Sand compositions in the Henares River seem to be very homogeneous in a QmFLt diagram, with only minor differences caused by the supplies from the tributaries. These differences can be modeled in terms of end-member mixing processes between Henares detritus and detritus from the relevant tributary. These mixing processes are more evident when lithic grain contents (LmLvLs and LmLssLsc diagrams) are compared. Changes produced by inputs from the Cañamares, Bornova and Sorbe rivers are not permanent along the Henares course. An important homogenization of Henares sand composition takes place by the mixing of tributary deposits with previously deposited Henares River terraces. Abrasion during transport does not appear to cause significant changes in the sand composition along the Henares River

La Contabilidad acumulativa y por lo devengado: Necesidad apremiante para los gobiernos

El tema seleccionado por la XXIV CIC corresponde al Sistema de Contabilidad Gubernamental. Contabilidad es uno de los sistemas componentes del Macrosistema de Administración Financiera y Control del Sector Público. Por lo tanto resulta conveniente recordar brevemente los conceptos de Teoría General de Sistemas. Luego se analiza en especial al Sistema de Contabilidad Gubernamental para entrar luego de lleno en el tema de XXIV CIC Contabilidad acumulativa y por lo devengado: necesidad apremiante para los gobiernos

Structure and Emplacement of the Giant Okavango Dike Swarm in Northern Botswana: a New Perspective from Airborne Geophysical Data

The mode of emplacement of continental dike swarms extending across large distances remains enigmatic and the subject of debate. Here we examine the 1500 km long WNW-trending Okavango Dike Swarm (ODS) in Botswana, Africa suggested as representing a ~180Ma magmatic-tectonic event associated with the initial thermal weakening phase of Gondwana breakup. Historically, the ODS has been interpreted as a failed rift segment of a triple junction based on its geometric relationship with two other prominent dike swarms. Recent studies suggest instead that the ODS was emplaced along a preexisting Precambrian basement lineament. This work examines the lithospheric structural controls on the emplacement of the ODS using gravity and magnetic data. For this we have established the relationship between crustal heterogeneities and the swarm, identified variations in crustal thickness below the ODS, and determined along-strike variations in Curie point depth. Our results show: (1) no apparent basement structures with the same 110� orientation as the ODS, (2) crustal thickness below the swarm ranges from 39-45 km with an average of 42�3 km, indicating the lack of crustal thinning typically associated with rifting, (3) the magnetic basement beneath the swarm extends to a depth of about 24 km and is discontinuous along strike. These high susceptibility axial anomalies conceivably represent fossilized mid-crustal feeder chambers, similar to those found in continental spreading centers such as Afar and Iceland. The lack of significant thinning below the ODS and lack of parallelism with the Precambrian basement fabric suggest the ODS was not associated with a failed rift system and did not actively follow preexisting structures. The ODS is thus interpreted to have been emplaced within the upper crust through magma-enhanced fractures coupled with the presence of a ENE-WSW tensile stress orientation, induced by thermal insulation of the mantle below a stagnant supercontinent and uplift of the asthenosphere.Geolog

Cicerón y el accionista controlante

Fil: Le Pera, Sergio. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho Comercial. Buenos Aires, Argentin

Surgical anatomy of the facial nerve: from middle cranial fossa approach to endoscopic approach. A pictorial review.

Purpose: The pathology of the facial nerve is extremely varied and extensive knowledge of the surgical anatomy in different approaches is required to manage it. During the last 15 years, the development of endoscopic ear surgery has significantly changed anatomical concepts, introducing new surgical approaches. The aim of this review is to illustrate five different surgical approaches to the facial nerve: the endoscopic approach, the middle cranial fossa approach, two translabyrinthine approaches (one simple and one endoscopic-assisted) with decompression of the whole petrous portion of the facial nerve, and a transotic approach with temporal craniotomy. Methods: Representative cases of middle and/or inner ear pathologies, surgically treated at our ENT Department, were selected to illustrate each of the five different approaches involving the facial nerve throughout its course. Results: In all cases, the pathology was removed with effective decompression of the facial nerve. The surgical anatomy in each surgical approach is described and illustrated. Conclusions: Facial nerve surgery is challenging for ENT specialists. An excellent knowledge of facial nerve anatomy is needed to eradicate pathology, avoiding nerve injuries and providing a good outcome after surgery

PICMI: mapping point mutations on genomes

Motivation: Several international collaborations and local projects are producing extensive catalogues of genomic variations that are supplementing existing collections such as the OMIM catalogue. The flood of this type of data will keep increasing and, especially, it will be relevant to a wider user base, including not only molecular biologists, geneticists and bioinformaticians, but also clinical researchers. Mapping the observed variations, sometimes only described at the amino acid level, on a genome, identifying whether they affect a gene and—if so—whether they also affect different isoforms of the same gene, is a time consuming and often frustrating task

Adherence to triage among women with HPV-positive self-collection: A study in a middle-low income population in Argentina

Introduction: Screening for cervical cancer (CC) prevention has substantially changed with the introduction of human papillomavirus (HPV) tests. This technology compared to cytology has increased the detection of pre-malignant and malignant cervical lesions in real-world programmes in different settings. Very importantly, through self-collection, HPV testing can reduce barriers to screening and increase coverage. However, when using HPV self-collection, triage tests are a key step in the CC prevention process, and high adherence to triage has been difficult to obtain in low-middle income settings. The aim of this study was to measure adherence to triage among women with HPV+ self-collection and analysed factors associated with this adherence in a middle-low resource setting in Argentina. We also evaluated key indicators related to the implementation of the HPV self-collection strategy. Methods: We analysed data on screening/triage/diagnosis/treatment from women aged 30+ who performed self-collection between 2015 and 2017 (n = 15,763), in the public health system in Tucuman, Argentina. We analysed secondary data from the national screening information system. The primary outcomes were: 1) adherence to cytology triage within the recommended timeframe (120 days) and 2) overall adherence to cytology triage including data at 18 months after screening. Multivariable regression was used to examine the association between age group, year of the screening test, record of the previous Pap-based screening and health insurance status with adherence to triage test as a primary outcome. We reported odds ratios, 95% confidence intervals and p-value of 0.05, which was considered the threshold for p-values). Results: We analysed data of 2,389 HPV+ women. The overall adherence to triage at 18 months was 42.9%. The percentage of women completing cytology triage within the recommended timeframe of 120 days was lower (25.2%). Women with the record of a previous Pap-based screening had 1.86 times the odds of having a triage compared to women without a record of a previous Pap-based screening (95% CI: 1.64-2.64, p <0.001). Furthermore, the probability of having triage at the recommended timeframe was higher among women who were older and women with public health insurance. Conclusions: Our results showed that adherence to triage in the recommended timeframe was low. In addition, the probability of having triage at the recommended timeframe was higher among women with a record of a previous Pap-based screening, a proxy of the use of health services. Our results showed that adherence to triage in the context of the HPV-self-collection strategy is challenging. The implementation of alternative approaches that might facilitate adherence to triage should be further investigated.Fil: Paolino, Melisa Delia. Centro de Estudio de Estado y Sociedad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gago, Juan. University Of New York. School Of Medicine.; Estados UnidosFil: Le Pera, Anabella Hebe. Centro de Estudio de Estado y Sociedad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cinto, Oscar. Provincia de Tucuman. Ministerio de Salud; ArgentinaFil: Thouyaret, Laura. Ministerio de Salud. Instituto Nacional del Cáncer; ArgentinaFil: Arrossi, Silvina. Centro de Estudio de Estado y Sociedad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin