Ultra High Resolution Transmission Electron Microscopy of Matrix Mineral Grains in CM Chondrites: Preaccretionary or Parent Body Aqueous Processing?

CM chondrites are highly hydrated meteorites associated with a parent asteroid that has experienced significant aqueous processing. The meteoritic evidence indicates that these non-differentiated asteroids are formed by fine-grained minerals embedded in a nanometric matrix that preserves chemical clues of the forming environment. So far there are two hypothesis to explain the presence of hydrated minerals in the content of CM chondrites: one is based on textural features in chondrule-rim boundaries [1-3], and the other ‘preaccretionary’ hypothesis proposes the incorporation of hydrated phases from the protoplanetary disk [4-6]. The highly porous structure of these chondrites is inherited from the diverse materials present in the protoplanetary disk environment. These bodies were presumably formed by low relative velocity encounters that led to the accretion of silicate-rich chondrules, refractory Ca- and Al-rich inclusions (CAIs), metal grains, and the fine-grained materials forming the matrix. Owing to the presence of significant terrestrial water in meteorite finds [7], here we have focused on two CM chondrite falls with minimal terrestrial processing: Murchison and Cold Bokkeveld. Anhydrous carbonaceous chondrite matrices are usually represented by highly chemically unequilibrated samples that contain distinguishable stellar grains. Other chondrites have experienced hydration and chemical homogeneization that reveal parent body processes. We have studied CM chondrites because these meteorites have experienced variable hydration levels [8-10]. It is important to study the textural effects of aqueous alteration in the main minerals to decipher which steps and environments promote bulk chemistry changes, and create the distinctive alteration products. It is thought that aqueous alteration has particularly played a key role in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials [7, 11, 12]. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive [5, 11]

Ancient Martian Floods in a Plausible Variable Climatic Environment as Revealed from the Sequential Growth of Allan Hills 84001 Carbonate Globules

No abstract available

Ultra High Resolution Transmission Electron Microscopy of Matrix Mineral Grains in CM Chondrites: Preaccretionary or Parent Body Aqueous Processing?

CM chondrites are highly hydrated meteorites associated with a parent asteroid that has experienced significant aqueous processing. The meteoritic evidence indicates that these non-differentiated asteroids are formed by fine-grained minerals embedded in a nanometric matrix that preserves chemical clues of the forming environment. So far there are two hypothesis to explain the presence of hydrated minerals in the content of CM chondrites: one is based on textural features in chondrule-rim boundaries [1-3], and the other ‘preaccretionary’ hypothesis proposes the incorporation of hydrated phases from the protoplanetary disk [4-6]. The highly porous structure of these chondrites is inherited from the diverse materials present in the protoplanetary disk environment. These bodies were presumably formed by low relative velocity encounters that led to the accretion of silicate-rich chondrules, refractory Ca- and Al-rich inclusions (CAIs), metal grains, and the fine-grained materials forming the matrix. Owing to the presence of significant terrestrial water in meteorite finds [7], here we have focused on two CM chondrite falls with minimal terrestrial processing: Murchison and Cold Bokkeveld. Anhydrous carbonaceous chondrite matrices are usually represented by highly chemically unequilibrated samples that contain distinguishable stellar grains. Other chondrites have experienced hydration and chemical homogeneization that reveal parent body processes. We have studied CM chondrites because these meteorites have experienced variable hydration levels [8-10]. It is important to study the textural effects of aqueous alteration in the main minerals to decipher which steps and environments promote bulk chemistry changes, and create the distinctive alteration products. It is thought that aqueous alteration has particularly played a key role in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials [7, 11, 12]. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive [5, 11]

A Simple Method to Check the Reliability of Annual Sunspot Number in the Historical Period 1610-1847

A simple method to detect inconsistencies in low annual sunspot numbers based on the relationship between these values and the annual number of active days is described. The analysis allowed for the detection of problems in the annual sunspot number series clustered in a few specific periods and unambiguous, namely: i) before Maunder minimum, ii) the year 1652 during the Maunder minimum, iii) the year 1741 in Solar Cycle -1, and iv) the so-called "lost" solar cycle in 1790s and subsequent onset of the Dalton Minimum.Comment: 15 pages, 3 figures, to be published in Solar Physic

Ancient Martian Floods in a Plausible Variable Climatic Environment as Revealed from the Sequential Growth of Allan Hills 84001 Carbonate Globules

No abstract available

Genetic identification and pedigree control on horses through microsatellite DNA sequences

Ponencia publicada en ITEA, vol.104El Laboratorio Central de Veterinaria de Algete (LCV) ha sido nombrado centro de referencia para la realización de análisis de marcadores genéticos y la homologación de las técnicas para la identificación y el control de filiación en équidos, con el fin de garantizar las genealogías de los animales inscritos en los libros genealógicos (Real Decreto 662/2007). A partir de ese momento, se ha desarrollado un protocolo de trabajo que cubre la totalidad de los pasos a seguir desde la recogida de muestras en el campo hasta la recepción final de los resultados por parte de la asociación de ganaderos. La metodología empleada utiliza los medios más avanzados y tiene establecidos una serie de puntos de control para poder detectar los errores que pudieran producirse tanto en la recogida de muestras como en la transmisión de la información que a éstas debe acompañar para su posterior análisis. La optimización de la metodología empleada posibilita procesar un número elevado de muestras en un corto espacio de tiempo con una gran fiabilidad en los resultados obtenidos. El análisis al que se someten las muestras incluye 18 marcadores microsatélite de ADN, amplificados en una reacción única de PCR, elegidos de la lista propuesta por la ISAG (Intenational Society for Animal Genetics). Se dispone, además, de dos paneles adicionales compuestos de 22 y 8 nuevos marcadores respectivamente, que son utilizados en los casos en que se necesita una mayor capacidad de exclusión o para llevar a cabo estudios de genealogías con datos de progenitores procedentes de otros laboratorios donde utilicen estos marcadores, algo bastante habitual en las razas equinas en las que existe gran movimiento de animales entre distintos países.Central Veterinary Laboratory of Algete (LCV) has been appointed as a referral center for the analysis of genetic markers and certification of techniques for the identification and genealogical control in horses, in order to guarantee the genealogies of the animals entered in studbooks (Royal Decree 662/2007). Since then, it has developed a working protocol covering all the steps to follow from the collection of samples in the field until receipt of the final results by the breeders’ association. The methodology uses the most advanced and has established a series of checkpoints in order to detect any errors that may occur in both the sample collection and transmission of information that must accompany them for later analysis. The optimization methodology enables to process a large number of samples in a short time with great reliability in the results. The analysis that the samples are submitted includes 18 microsatellite DNA markers, amplified in a single PCR reaction, chosen from the list proposed by the ISAG (International Society for Animal Genetics). It also provides two additional panels composed of 8 and 22 new markers, respectively, which are used in cases where there is a need for increased capacity of exclusion or to conduct studies pedigrees with data from parents from other laboratories where use these markers, which is quite common in horse races where there is great movement of animals between countries

155-day Periodicity in Solar Cycles 3 and 4

The near 155 days solar periodicity, so called Rieger periodicity, was first detected in solar flares data and later confirmed with other important solar indices. Unfortunately, a comprehensive analysis on the occurrence of this periodicity during previous centuries can be further complicated due to the poor quality of the sunspot number time-series. We try to detect the Rieger periodicity during the solar cycles 3 and 4 using information on aurorae observed at mid and low latitudes. We use two recently discovered aurora datasets, observed in the last quarter of the 18th century from UK and Spain. Besides simple histograms of time between consecutive events we analyse monthly series of number of aurorae observed using different spectral analysis (MTM and Wavelets). The histograms show the probable presence of Rieger periodicity during cycles 3 and 4. However different spectral analysis applied has only confirmed undoubtedly this hypothesis for solar cycle 3.Comment: 13 pages, 6 figures, to appear in New Astronom

Physical Disintegration of Biochar: An Overlooked Process

Data collected from both artificially and field (naturally) weathered biochar suggest that a potentially significant pathway of biochar disappearance is through physical breakdown of the biochar structure. Through scanning electron microscopy (SEM) we characterized this physical weathering which increased structural fractures and possessed higher numbers of liberated biochar fragments. This was hypothesized to be due to the graphitic sheet expansion accompanying water sorption coupled with comminution. These fragments can be on the micro and nano-scale, but are still carbon-rich particles with no detectable alteration in the oxygen to carbon ratio of the original biochar. However, these particles are now easily dissolved and could be moved by infiltration. There is a need to understand how to produce biochars that are resistant to physical degradation in order to maximize long-term biochar C-sequestration potential within soil systems

Unprecedented pathway of reducing equivalents in a diflavin-linked disulfide oxidoreductase

Flavoproteins participate in a wide variety of physiologically relevant processes that typically involve redox reactions. Within this protein superfamily, there exists a group that is able to transfer reducing equivalents from FAD to a redox-active disulfide bridge, which further reduces disulfide bridges in target proteins to regulate their structure and function. We have identified a previously undescribed type of flavin enzyme that is exclusive to oxygenic photosynthetic prokaryotes and that is based on the primary sequence that had been assigned as an NADPH-dependent thioredoxin reductase (NTR). However, our experimental data show that the protein does not transfer reducing equivalents from flavins to disulfides as in NTRs but functions in the opposite direction. High-resolution structures of the protein from Gloeobacter violaceus and Synechocystis sp. PCC6803 obtained by X-ray crystallography showed two juxtaposed FAD molecules per monomer in redox communication with an active disulfide bridge in a variant of the fold adopted by NTRs. We have tentatively named the flavoprotein “DDOR” (diflavin-linked disulfide oxidoreductase) and propose that its activity is linked to a thiol-based transfer of reducing equivalents in bacterial membranes. These findings expand the structural and mechanistic repertoire of flavoenzymes with oxidoreductase activity and pave the way to explore new protein engineering approaches aimed at designing redox-active proteins for diverse biotechnological applications