On the stability of the primordial closed string gas

We recast the study of a closed string gas in a toroidal container in the physical situation in which the single string density of states is independent of the volume because energy density is very high. This includes the gas for the well known Brandenberger-Vafa cosmological scenario. We describe the gas in the grandcanonical and microcanonical ensembles. In the microcanonical description, we find a result that clearly confronts the Brandenberger-Vafa calculation to get the specific heat of the system. The important point is that we use the same approach to the problem but a different regularization. By the way, we show that, in the complex temperature formalism, at the Hagedorn singularity, the analytic structure obtained from the so-called F-representation of the free energy coincides with the one computed using the S-representation.Comment: 20 pages and 1 figure. The final version that appeared in JHE

Juvenile wood in Populus deltoides 'Stoneville 67': analysis of density variation in the stem.

El objetivo del presente trabajo fue determinar la edad de transición de madera juvenil a madura a partir del estudio de la variación axial y radial de la densidad y realizar modelos descriptivos de distribución de madera juvenil y madura en el fuste de Populus deltoides, clon `Stoneville 67 ́ de 20 años de edad. La densidad presentó un aumento de sus valores de médula a corteza y desde la base hacia el ápice. La edad de transición se determinó entre los 10-12 años de edad, el volumen de madera juvenil y madura fue del 40 % y 60 % respectivamente. La distribución de la madera juvenil coincidió con el modelo de cilindro central.The objective of the present work was to determine the age of transition from juvenile to mature wood from the study of the axial and radial variation of density and to carry out descriptive models of distribution of juvenile and mature wood in the stem of Populus deltoides, clone `Stoneville 67´ of 20 years of age. The density presented an increase in its values from the medulla to the cortex and from the base to the apex. The transition age was determined between 10-12 years of age, the volume of juvenile and mature wood was 40% and 60%, respectively. The distribution of juvenile wood coincided with the central cylinder model.Fil: Cobas, Ana Clara. Universidad Nacional del Noroeste de la Provincia de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iurritia, Elisabet. Universidad Nacional del Noroeste de la Provincia de Buenos Aires; ArgentinaFil: Tortoriello, Miguel Antonio. Universidad Nacional del Noroeste de la Provincia de Buenos Aires; Argentin

Metatranscriptomic Approach to Analyze the Functional Human Gut Microbiota

The human gut is the natural habitat for a large and dynamic bacterial community that has a great relevance for health. Metagenomics is increasing our knowledge of gene content as well as of functional and genetic variability in this microbiome. However, little is known about the active bacteria and their function(s) in the gastrointestinal tract. We performed a metatranscriptomic study on ten healthy volunteers to elucidate the active members of the gut microbiome and their functionality under conditions of health. First, the microbial cDNAs obtained from each sample were sequenced using 454 technology. The analysis of 16S transcripts showed the phylogenetic structure of the active microbial community. Lachnospiraceae, Ruminococcaceae, Bacteroidaceae, Prevotellaceae, and Rickenellaceae were the predominant families detected in the active microbiota. The characterization of mRNAs revealed a uniform functional pattern in healthy individuals. The main functional roles of the gut microbiota were carbohydrate metabolism, energy production and synthesis of cellular components. In contrast, housekeeping activities such as amino acid and lipid metabolism were underrepresented in the metatranscriptome. Our results provide new insights into the functionality of the complex gut microbiota in healthy individuals. In this RNA-based survey, we also detected small RNAs, which are important regulatory elements in prokaryotic physiology and pathogenicity

Propiedades tecnológicas de la madera de obinia pseudoacacia "acacia blanca" implantada en la provincia de Buenos Aires

En la provincia de Buenos Aires, Argentina, existen plantaciones dispersas de dicha especie que a su vez no han sido manejadas silvícolamente. Actualmente, esta madera se utiliza en carpintería de obra y construcciones rurales, presentando buenos resultados. En la actualidad no se cuenta con una base mínima de recurso en cantidad y calidad produciéndose la sustitución de la madera redonda de acacia blanca por productos de pino y de eucalipto impregnados. El objetivo de este trabajo fue caracterizar tecnológicamente la madera de acacia blanca, de manera de aportar datos que permitan revalorizar su madera hacia productos de mayor valor e incentivar su plantación y comercialización. Se determinaron: densidad normal, relación T/R, flexión estática, compresión paralela a las fibras y dureza Brinell. La densidad media tuvo valores de 0,625 ±0,05 g/cm3 que la clasifica como madera semi-pesada. El ensayo de flexión arrojo valores de 154,80 N/mm2 (MOR) y 10390,29 N/mm2 (MOE) mientras que en compresión paralela a las fibras los valores obtenidos fueron 66,82 N/mm2 (MOR) y 5878,68 N/mm2 (MOE). De acuerdo a los valores de dureza Brinell y relación T/R obtenidos (8,87 ±0,8 HB y 1,51 ±0,25 respectivamente), se la puede considerar una madera dura y estable.Fil: Doblari, Victoria. Argentina. Universidad Nacional del Noroeste.Fil: Aragón, Paula. Argentina. Universidad Nacional del Noroeste.Fil: Cobas, Ana Clara. Argentina. Universidad Nacional del Noroeste.Fil: Gallo, Jacqueline. Argentina. Universidad Nacional del Noroeste.Fil: Tortoriello, Miguel. Argentina. Universidad Nacional del Noroeste.Fil: Zorrilla, Lautaro. Argentina. Universidad Nacional del Noroeste

Occurrence of persistent and mobile chemicals and other contaminants of emerging concern in Spanish and Portuguese wastewater treatment plants, transnational river basins and coastal water

This work investigated, during one year, the occurrence and fate of 52 contaminants of emerging concern (CECs) in transnational river basins and coastal areas of the North of Portugal and Galicia (NW Spain) and the wastewater treatment plants (WWTPs) discharging on these environments. The different CECs investigated included pharmaceuticals, personal care products, industrial chemicals, among others, of which ca. 90 % would fulfill the persistence, mobility and toxicity criteria proposed by the German Environmental Agency. The results showed the ubiquitous presence of these CECs and an incomplete removal of over 60 % of them with current conventional WWTPs. These findings highlight the requirement of a prominent and coordinated upgrade of WWTP treatments in order to meet the future European Union regulations on urban wastewater treatment and surface water quality. In fact, even some compounds exhibiting high removals, such as caffeine or xylene sulfonate, were frequently detected in river and estuarine waters at the high ng L−1 level. Thus, our preliminary risk assessment study concluded that 18 of the CECs presented a potential risk for the environment, being caffeine, sulpiride, perfluorooctanoic acid (PFOA), diclofenac, fipronil and perfluorobutanoic acid (PFBA) the most concerning ones. Yet, additional toxicity data as well as a more robust information on persistence and mobility of CECs are necessary for better estimating the magnitude of the problem and improve risk assessment. As an example, in the case of the antidiabetic metformin, recent research has revealed toxicity for model fish species at concentration levels below those found in 40 % of the river water samples analyzed in this workThis work was financed by the European Regional Development Fund through the Interreg V-A Spain-Portugal Programme (POCTEP) 2014-2020 (ref. 0725_NOR_WATER_1_P), the Agencia Estatal de Investigación MCIN/AEI/10.13039/501100011033 (ref. PID2020-117686RB-C32) and the Consellería de Cultura, Educación y Universidades da Xunta de Galicia (ref. ED431C 2021/06). The study was also supported by the Portuguese Foundation for Science and Technology (FCT) under the projects [UIDB/04423/2020 and UIDP/04423/2020]. R.M. acknowledges Banco Santander and Universidade de Santiago de Compostela for her outstanding researcher contract, N. A. acknowledges the FCT for his Ph.D. grant DFA/BD/6218/2020 and T.N. acknowledges FCT Individual Call to Scientific Employment Stimulus 2022 (2022.02925.CEECIND). The authors also want to acknowledge Agilent Technologies for providing the equipment described in Section 2.4 and the different entities which have collaborated in the sampling campaign: VIAQUA, Augas de Galicia, Confederación Hidrográfica do Miño-Sil, Águas do Porto, Efacec and Águas do NorteS

Plan estratégico de la Empresa Chancadora Excálibur

La presente tesis es un planeamiento estratégico para la Empresa Chancadora Excálibur, dedicada al servicio de chancado y triturado de minerales y materiales pétreos desde abril de 2013; y con operaciones, en la actualidad, de producción y venta de agregados en el sur de Lima. El planeamiento propuesto para Chancadora Excálibur se inicia con la revisión de la visión, la misión, los valores y el código de ética, que están emparejados con los objetivos de largo y corto plazo; y el desarrollo de diversas matrices que permiten diagnosticar el panorama actual de la organización. Finalmente, se formulan y evalúan estrategias y acciones a realizar en el futuro. La recuperación del Sector Construcción y el déficit de infraestructura en el país impulsarán el crecimiento y la demanda de insumos básicos para la construcción, ofreciendo perspectivas favorables para la Empresa Chancadora Excálibur. Por esto, el presente plan se orienta a la identificación de oportunidades y desafíos que el contexto plantea a la organización, en su tarea de consolidarse como fabricante de agregados y sentar las bases de una futura operación de concreto premezcladoThis thesis is a strategic plan for Chancadora Excalibur, company that specializes in the service of crushing and grinding of sand and stone materials since April 2013. It currently has a production and sale of milling stones in the South of Lima. The geographic position of this plant, give it advantages against their competitors and give the possibilities to considerer additional investment in order to become one of the biggest companies in their influence area. This work begins with the review of the vision, mission, values and code of ethics of the company. These should be consistent with short and long-term objectives through the development of many analytical matrices, providing a diagnosis of the current situation of the organization. Finally, based on this diagnosis we proceed to formulate and evaluate strategies to be perform in the future. The recovery of the construction sector and the infrastructure deficit in the country will develop the demand for basic construction materials, offering favorable prospects for the Company Chancadora Excálibur. Therefore, this plan identifies the opportunities and challenges posed to the organization to consolidate its position as manufacturer of aggregates and to promote future his operation of ready-mix concreteTesi

Screening of contaminants of emerging concern in surface water and wastewater effluents, assisted by the Persistency-Mobility-Toxicity Criteria

Contaminants of emerging concern (CECs) are compounds of diverse origins that have not been deeply studied in the past which are now accruing growing environmental interest. The NOR-Water project aimed to identify the main CECs and their sources in the water environment of Northern Portugal–Galicia (located in northwest Spain) transnational region. To achieve these goals, a suspect screening analytical methodology based on the use of liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) was applied to 29 sampling sites in two campaigns. These sampling sites included river and sea water, as well as treated wastewater. The screening was driven by a library of over 3500 compounds, which included 604 compounds prioritized from different relevant lists on the basis of the persistency, mobility, and toxicity criteria. Thus, a total of 343 chemicals could be tentatively identified in the analyzed samples. This list of 343 identified chemicals was submitted to the classification workflow used for prioritization and resulted in 153 chemicals tentatively classified as persistent, mobile, and toxic (PMT) and 23 as very persistent and very mobile (vMvP), pinpointing the relevance of these types of chemicals in the aqueous environment. Pharmaceuticals, such as the antidepressant venlafaxine or the antipsychotic sulpiride, and industrial chemicals, especially high production volume chemicals (HPVC) such as ε-caprolactam, were the groups of compounds that were detected at the highest frequencies.This research was funded by Xunta de Galicia (ED431C 2021/06) and the European Regional Development Fund through the Interreg V-A Spain-Portugal Programme (POCTEP) 2014-2020 (ref. 0725_NOR_WATER_1_P). R. M. acknowledges Banco Santander and Universidade de Santiago de Compostela for her outstanding researcher contract and N. A. acknowledges the Portuguese Foundation for Science and Technology (FCT) for his Ph.D. grant DFA/BD/6218/2020.S

Microestructura de una aleación níquel-cromo-molibdeno soldada con electrodos revestidos

Las aleaciones de níquel-cromo-molibdeno fundamentalmente se usan en la fabricación de componentes para el sector aeronáutico y la industria petroquímica. Este artículo se enfocó en determinar el comportamiento microestructural de una aleación de este tipo, soldada con electrodo E NiCrFe-3 de 3,25 mm de diámetro. La unión se obtuvo a tope con preparación de los bordes a 60o. Las variaciones microestructurales se evaluaron mediante la microscopía óptica y se realizó el análisis de la dureza en las zonas afectadas por el ciclo térmico de soldadura. Para la determinación del cromo y el níquel equivalente se utilizó el diagrama de Schaeffler, lo que posibilitó obtener la composición química resultante del depósito. Se determinó que la estructura de esta aleación en la unión es austenítica, con transformaciones estructurales consistentes en ferrita de morfología tipo esqueleto, alineadas en dirección a la fuente de calor del arco eléctrico. Se evidencia la formación de fases de austenita primaria, austenita Widmanstátten y la precipitación de austenita secundaria al interior de la ferrita, donde la estructura de austenita Widmanstátten es la más frágil