1,085 research outputs found

    Electric Field Controlled Magnetic Anisotropy in a Single Molecule

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    We have measured quantum transport through an individual Fe4_4 single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties, and moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition / subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled

    Viabilidad del modelo de confort térmico adaptativo bajo condiciones de clima cálido subhúmedo: Ahorro energético en refrigeración en Campeche, México

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    The conventional approach to achieve thermal comfort generally focuses on modifying the setpoint temperature in fully air-conditioned buildings. However, the adaptive thermal comfort approach is an alternative that considers the interaction between buildings, the local climate, and the users to allow significant improvements in energy savings. This paper analyzes the feasibility of implementing adaptive thermal comfort strategies, comparing adaptive models based on the ASHRAE 55-2020 Standard and a regional model for the tropical climate typology of Mexico, and contrasting the results with the static approach. Thirteen locations in the State of Campeche were thermally analyzed, seeing that the ventilation strategies are applicable throughout the State and that both models ensure improvements in energy consumption. In addition, the results suggest that it is necessary to develop more local adaptive models to propose strategies with better potential impact in the region.A abordagem convencional para alcançar o conforto térmico geralmente se concentra em modificar a temperatura de referência em edifícios totalmente climatizados. No entanto, a abordagem do conforto térmico adaptativo é uma alternativa que considera a interação entre os edifícios, o clima local e os usuários, a fim de permitir melhorias significativas na economia de energia. Este trabalho analisa a viabilidade de implementar estratégias de conforto térmico adaptativo, comparando modelos adaptativos baseados na norma ASHRAE 55-2020 e um modelo regional para a tipologia climática tropical do México, contrastando os resultados com a abordagem estática. Foram analisados termicamente 13 locais no estado de Campeche, concluindo-se que as estratégias de ventilação são aplicáveis em todo o estado e que ambos os modelos garantem melhorias no consumo de energia. Além disso, os resultados sugerem a necessidade de desenvolver mais modelos adaptativos locais para propor estratégias com maior potencial de impacto na região.El enfoque convencional para alcanzar el confort térmico generalmente se centra en modificar la temperatura de consigna en edificios totalmente climatizados. Sin embargo, el enfoque del confort térmico adaptativo es una alternativa que considera la interacción entre los edificios, el clima local y los usuarios para permitir mejoras significativas en el ahorro de energía. El trabajo analiza la viabilidad de implementar estrategias de confort térmico adaptativo, comparando modelos adaptativos basados en la norma ASHRAE 55-2020 y un modelo regional para la tipología climática tropical de México, contrastando los resultados respecto del enfoque estático. Se analizó térmicamente 13 locaciones del Estado de Campeche obteniendo que las estrategias de ventilación son aplicables en todo el Estado y que ambos modelos aseguran mejoras en el consumo de energía. Además, los resultaron siguieren que es necesario desarrollar más modelos adaptativos locales para proponer estrategias con mejor potencial de impacto en la región

    A Gamma-Herpesvirus Glycoprotein Complex Manipulates Actin to Promote Viral Spread

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    Viruses lack self-propulsion. To move in multi-cellular hosts they must therefore manipulate infected cells. Herpesviruses provide an archetype for many aspects of host manipulation, but only for alpha-herpesviruses in is there much information about they move. Other herpesviruses are not necessarily the same. Here we show that Murine gamma-herpesvirus-68 (MHV-68) induces the outgrowth of long, branched plasma membrane fronds to create an intercellular network for virion traffic. The fronds were actin-based and RhoA-dependent. Time-lapse imaging showed that the infected cell surface became highly motile and that virions moved on the fronds. This plasma membrane remodelling was driven by the cytoplasmic tail of gp48, a MHV-68 glycoprotein previously implicated in intercellular viral spread. The MHV-68 ORF58 was also required, but its role was simply transporting gp48 to the plasma membrane, since a gp48 mutant exported without ORF58 did not require ORF58 to form membrane fronds either. Together, gp48/ORF58 were sufficient to induce fronds in transfected cells, as were the homologous BDLF2/BMRF2 of Epstein-Barr virus. Gp48/ORF58 therefore represents a conserved module by which gamma-herpesviruses rearrange cellular actin to increase intercellular contacts and thereby promote their spread

    Transarterial embolization of renal cell carcinoma as an adjunctive therapy prior to cryoablation: a propensity score matching analysis

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    PURPOSE:We aimed to assess the safety and effectiveness of transarterial embolization (TAE) prior to percutaneous cryoablation (PCA) in the management of renal cell carcinoma (RCC) compared with PCA alone using a propensity score matching analysis to minimize confounding factors.METHODS:A retrospective review of all PCAs performed for renal masses identified 9 patients who underwent TAE prior to PCA. These patients were matched in a 2:1 ratio with patients who underwent PCA only using age, gender, and tumor size to create the propensity score model for matching. Other demographic, clinical, and outcomes data were collected.RESULTS:The TAE+PCA group included 5 males and 4 females with a mean age of 67.9 years and mean tumor diameter of 51.7 mm. The PCA only group included 11 males and 7 females with a mean age of 66.8 years and mean tumor diameter of 46.2 mm. No significant differences in these propensity score matched characteristics were identified. Further, the groups had no significant differences in tumor geometry (P = 0.831), R.E.N.A.L. nephrometry scores (P = 0.144), or comorbidity indices (P = 0.392). TAE was technically successful and without complication in all cases. PCA was technically successful in 8 of 9 patients in the TAE+PCA group and in 14 of 18 patients in the PCA only group (P = 0.483). No significant differences in the rate of complications (P = 0.483), change in eGFR (P = 0.691), or change in hematocrit (P = 0.152) were identified between the two groups.CONCLUSION:TAE of RCC prior to PCA is safe and technically feasible; however, no objective benefits over PCA alone were identified by propensity score matching analysis. Due to small sample size and limitations of the study, no definite conclusions should be drawn. Larger, prospective studies of this therapeutic approach are warranted

    Food chain length and omnivory determine the stability of a marine subtidal food web

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    P\u3e1. Using a subtidal marine food web as a model system, we examined how food chain length (predators present or absent) and the prevalence of omnivory influenced temporal stability (and its components) of herbivores and plants. We held the density of top predators constant but manipulated their identity to generate a gradient in omnivory prevalence. 2. We measured temporal stability as the inverse of the coefficient of variation of abundance over time. Predators and omnivory could influence temporal stability through effects on abundance (the \u27abundance\u27 effect), summed variance across taxa (the \u27portfolio effect\u27) or summed covariances among taxa (the \u27covariance effect\u27). 3. We found that increasing food chain length by predator addition destabilized aggregate herbivore abundance through their cascading effects on abundances. Thus, predators destabilized herbivores through the overyielding effect. We also found that the stability of herbivore abundance and microalgae declined with increasing prevalence of omnivory among top predators. Aggregate macroalgae was not affected, but the stability of one algal taxon increased with the prevalence of omnivory. 4. Our results suggest that herbivores are more sensitive than plants to changes in food web structure because of predator additions by invasion or deletions such as might occur via harvesting and habitat loss

    Current State of Conservation Knowledge on Threatened Amphibian Species in Peru

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    This study documents the current state of conservation knowledge on threatened amphibian species in Peru. Following the International Union for the Conservation of Nature (IUCN) classification system, we considered species in the following categories: Critically Endangered, Endangered, Vulnerable, and Near Threatened. Even though only the first three categories are regarded as threatened by IUCN, we included the fourth category to make comparisons with the list of threatened species issued by the Peruvian government. We used the Global Amphibian Assessment\u27s database and the list issued in Peru for this comparison. We conducted separate field surveys in 17 regions of Peru to evaluate the presence/absence of threatened amphibian species and species that are potentially threatened. We also used the Declining Amphibian Database-DAPTF, to compare our results with previous assessments on population declines, and the World Wildlife Fund\u27s Wildfinder database, to determine in which Neotropical ecoregion each species occurs. We compiled data on 83 species, 44 of which are recognized as threatened by the IUCN and/or the Peruvian government. The remaining 39 species should be re-assessed as they face various threats. A re-evaluation of current estimates is needed as only 8% of all species recorded in Peru are recognized as threatened by the government, whereas the global estimate of threatened species is about 32%. In addition to using IUCN criteria, this re-assessment should follow national guidelines standardized in Peru and be in accordance with the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Because the habitat of almost 40% of threatened species reported herein still remains unprotected, and data on chytridiomycosis and other threats are lacking for most taxa, it is crucial to develop strategies for habitat conservation and research on disease dynamics in natural populations

    Rickettsia typhi en roedores de una comunidad con antecedentes de tifo murino, de Yucatán, México.

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    Objetivo. Determinar la presencia de Rickettsia typhi en roedores sinantrópicos capturados en la comunidad rural de Bolmay, Yucatán, México, con antecedentes de tifo murino en sus habitantes. Materiales y métodos. Se examinaron 37 roedores: 30 Mus musculus, 6 Rattus rattus y 1 Heteromys gaumeri. Se obtuvo ADN total del bazo de los roedores. La identificación de R. typhi se realizó a través de la amplificación de un fragmento del gen htrA (proteína 17-kDa) por PCR punto final. Los productos positivos fueron purificados y enviados a secuenciación para su análisis de alineamiento con la herramienta BLAST. Resultados. La identificación de ADN rickettsial se logró en un 27% (10/37) de los roedores: siete M. musculus y 3 R. rattus. El análisis de alineamiento obtuvo porcentajes de identidades y coberturas del 97 - 99% para R. typhi, respectivamente. Conclusiones. El presente estudio sugiere la participación de los roedores sinantrópicos en el ciclo de transmisión del tifo murino en la región. Se describe la primera evidencia molecular de R. typhi en M. musculus de Yucatán, México

    A domain insertion in Escherichia coli GyrB adopts a novel fold that plays a critical role in gyrase function

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    DNA topoisomerases manage chromosome supercoiling and organization in all forms of life. Gyrase, a prokaryotic heterotetrameric type IIA topo, introduces negative supercoils into DNA by an ATP-dependent strand passage mechanism. All gyrase orthologs rely on a homologous set of catalytic domains for function; however, these enzymes also can possess species-specific auxiliary regions. The gyrases of many gram-negative bacteria harbor a 170-amino acid insertion of unknown architecture and function in the metal- and DNA-binding TOPRIM domain of the GyrB subunit. We have determined the structure of the 212 kDa Escherichia coli gyrase DNA binding and cleavage core containing this insert to 3.1 Å resolution. We find that the insert adopts a novel, extended fold that braces the GyrB TOPRIM domain against the coiled-coil arms of its partner GyrA subunit. Structure-guided deletion of the insert greatly reduces the DNA binding, supercoiling and DNA-stimulated ATPase activities of gyrase. Mutation of a single amino acid at the contact point between the insert and GyrA more modestly impairs supercoiling and ATP turnover, and does not affect DNA binding. Our data indicate that the insert has two functions, acting as a steric buttress to pre-configure the primary DNA-binding site, and serving as a relay that may help coordinate communication between different functional domains
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