On the geometry of Petrov type II spacetimes

In general, geometries of Petrov type II do not admit symmetries in terms of Killing vectors or spinors. We introduce a weaker form of Killing equations which do admit solutions. In particular, there is an analog of the Penrose-Walker Killing spinor. Some of its properties, including associated conservation laws, are discussed. Perturbations of Petrov type II Einstein geometries in terms of a complex scalar Debye potential yield complex solutions to the linearized Einstein equations. The complex linearized Weyl tensor is shown to be half Petrov type N. The remaining curvature component on the algebraically special side is reduced to a first order differential operator acting on the potential

Motion analysis of a trapped ion chain by single photon self-interference

We present an optical scheme to detect the oscillations of a two-ion string confined in a linear Paul trap. The motion is detected by analyzing the intensity correlations in the fluorescence light emitted by one or two ions in the string. We present measurements performed under continuous Doppler cooling and under pulsed illumination. We foresee several direct applications of this detection method, including motional analysis of multi-ion species or coupled mechanical oscillators, and sensing of mechanical correlations.Comment: 6 pages, 5 figure

Clonamiento y expresion del canal de cloruro CI-5 en epitelio intestinal de cobayo

71 p.Los canales de cloruro están presentes en la membrana celular de todas las células y en organelos intracelulares cumpliendo diferentes funciones. Algunos de estos canales han sido identificados molecularmente siendo la familia de canales de cloruro activados por voltaje o C1C la más numerosa. Hasta ahora, se han identificado 9 miembros de esta familia en mamíferos, estando establecida la función solamente para algunos de ellos. Además, mutaciones en algunos de estos canales han revelado ser causa de patologías humanas. Es así, como la enfermedad de Dent, caracterizada por proteinuria de bajo peso molecular y nefrolitiasis hipercalciúrica, es causada por mutaciones en el gen que codifica para el canal C1C-5. Estos hallazgos, previos al conocimiento de la función de este canal, han despertado gran interés en dilucidar los mecanismos por los que alteraciones en un canal de cloruro pueden generar un fenotipo caracterizado por proteinuria e hipercalciuria. Estudios de la presencia del RNA mensajero y de la proteína en diferentes especies coinciden en que la mayor expresión de C1C-5 ocurre en el riñón. En las células del túbulo proximal del nefrón C1C-5 se ubica intracelularmente en la membrana de vesículas endociticas tempranas, colocalizando con la bomba protón ATPasa vacuolar. De esta manera, el funcionamiento adecuado de este canal aniónico es necesario para lograr la acidificación intravesicular óptima requerida para la reabsorción de proteínas. Mutaciones en el gen que codifica a C1C-5, han demostrado causar ausencia o déficit en la actividad del canal, lo cual origina una falla en la disipación de cargas en las vesículas alterando la acidificación intravesicular y por ende la reabsorción de proteínas generando así proteinuria. Sin embargo, los mecanismos que llevan a la hipercalciuria en esta enfermedad son menos conocidos. Una hipótesis plantea que los cambios en el metabolismo del calcio son secundarios al trastorno de la endocitosis en el túbulo proximal. Alternativamente se ha sugerido que la hiperacalciuria seria secundaria a un aumento en la absorción intestinal de calcio. Considerando que el riñón no es el único órgano que participa en el metabolismo de proteínas y de calcio, se estudió la expresión del RNA mensajero de C1C-5 en el intestino delgado, órgano esencial en la absorción de ambos nutrientes desde la dieta. Además, existen antecedentes de que en el epitelio intestinal ocurre transporte vesicular tanto de proteínas como de calcio, lo cual hace más interesante estudiar la expresión de este canal en este órgano para posteriormente determinar cuál seria el papel fisiológico de C1C-5 en este tejido epitelial. En esta tesis se describe el clonamiento por homología del canal C1C-5 desde epitelio intestinal de cobayo mediante reacción en cadena de la polimerasa (PCR) y la distribución de su RNA mensajero en duodeno, yeyuno e ileon de cobayo. Para el clonamiento se utilizaron partidores apropiados con los que se obtuvo una secuencia parcial de 1144 pares de bases y los extremos 5 y 3 prima se obtuvieron mediante la técnica de amplificación rápida de los extremos de cDNA (RACE). Finalmente con partidores específicos diseñados a partir de las regiones 5 y 3 prima no traducidas se amplificó DNA complementario (cDNA), mediante la reacción de transcripción reversa del RNA obtenido del epitelio duodenal. Como resultado del clonamiento se obtuvo un cDNA cuya secuencia predice una proteína de 746 aminoácidos con un mínimo de un 95% de identidad con sus homólogos de otras especies. El análisis de hidrofobicidad de la secuencia aminoacídica, predice 10 a 12 dominios de transmembrana los cuales son comunes en todos los miembros de la familia C1C. Se detectaron sitios putativos de glicosilación y fosforilación por PKA y PKC que también han sido descritos en su homólogo de rata. La presencia del RNA mensajero en epitelio intestinal se estudió mediante transcripción reversa seguida de PCR (RT-PCR), Northern blot e Hibridación in situ. Mediante RTPCR se estableció la presencia del transcrito en las 3 porciones estudiadas. Mediante el análisis de Northern blot además de comprobar lo anterior, se estableció el tamaño del principal transcrito en aproximadamente 9,5 kilobases, equivalente a lo descrito en otras especies. Finalmente, la localización del mensajero se estudió mediante hibridación in situ utilizando una sonda de 662 pares de bases sintetizada por transcripción in vitro marcada con digoxigenina. Con esta técnica se demostró la presencia del mensajero de C1C-5 en las células del epitelio que conforman tanto las criptas como las vellosidades del duodeno yeyuno e ileon. La localización del RNA mensajero exclusivamente en las células epiteliales del intestino delgado sugiere la posible participación de este canal en el transporte transepitelial lo cual debe ser resuelto mediante futuros estudios

Eradication of introduced fish allows successful recovery of a stream-dwelling amphibian

Introduction of alien fish is a major problem for the conservation of amphibians inhabiting originally fishless mountain streams. While fish eradication programs in lakes and ponds have proven successful for the recovery of amphibian populations, there is no such information for stream-dwelling amphibians, possibly because fish removal from streams is difficult and costly. Here, we show the first case of successful recovery of a stream-dwelling amphibian (Rana iberica) in a mountain area of central Spain, following eradication of introduced brook trout (Salvelinus fontinalis) and native brown trout (Salmo trutta) translocated from downstream reaches by local anglers. Electrofishing for 12 consecutive years eradicated both fish species in the introduced area, and allowed the recovery of the R. iberica population as a result of natural recolonization from nearby streams and reintroduction of captive-reared individuals. Our results demonstrate how electrofishing can be a costly but effective method for the eradication of introduced fish and the conservation of stream-dwelling amphibians

Anti-interleukin 2 receptor monoclonal antibodies spare phenotypically distinct T suppressor cells in vivo and exert synergistic biological effects.

The therapeutic efficacies of ART-18, ART-65, and OX-39, mouse antibodies of IgG1 isotype recognizing distinct epitopes of the p55 beta chain of the rat IL-2-R molecule, were probed in LEW rat recipients of (LEW X BN)F1 heterotopic cardiac allografts (acute rejection in untreated hosts occurs within 8 d). A 10-d course with ART-18 prolongs graft survival to approximately 21 d (p less than 0.001). Therapy with ART-65, but not with OX-39, was effective (graft survival approximately 16 and 8 d, respectively). Anti-IL-2-R mAb treatment selectively spared T cells with donor-specific suppressor functions; the CD8+ (OX8+ W3/25-) fraction from ART-18-modified recipients, and primarily the CD4+ (W3/25+ OX8-) subset from ART-65-treated hosts conferred unresponsiveness to naive syngeneic rats after adoptive transfer, increasing test graft survival to approximately 16 and 45 d, respectively. Concomitant administration of ART-18 and ART-65 to recipient animals in relatively low doses exerted a strikingly synergistic effect, with 30% of the transplants surviving indefinitely and 50% undergoing late rejection over 50 d. These studies provide evidence that anti-IL-2-R mAbs selectively spare phenotypically distinct T cells with suppressor functions. The data also suggest that in vivo targeting of functionally different IL-2-R epitopes may produce synergistic biological effects

Computational exploration of molecular receptive fields in the olfactory bulb reveals a glomerulus-centric chemical map

© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.Progress in olfactory research is currently hampered by incomplete knowledge about chemical receptive ranges of primary receptors. Moreover, the chemical logic underlying the arrangement of computational units in the olfactory bulb has still not been resolved. We undertook a large-scale approach at characterising molecular receptive ranges (MRRs) of glomeruli in the dorsal olfactory bulb (dOB) innervated by the MOR18-2 olfactory receptor, also known as Olfr78, with human ortholog OR51E2. Guided by an iterative approach that combined biological screening and machine learning, we selected 214 odorants to characterise the response of MOR18-2 and its neighbouring glomeruli. We found that a combination of conventional physico-chemical and vibrational molecular descriptors performed best in predicting glomerular responses using nonlinear Support-Vector Regression. We also discovered several previously unknown odorants activating MOR18-2 glomeruli, and obtained detailed MRRs of MOR18-2 glomeruli and their neighbours. Our results confirm earlier findings that demonstrated tunotopy, that is, glomeruli with similar tuning curves tend to be located in spatial proximity in the dOB. In addition, our results indicate chemotopy, that is, a preference for glomeruli with similar physico-chemical MRR descriptions being located in spatial proximity. Together, these findings suggest the existence of a partial chemical map underlying glomerular arrangement in the dOB. Our methodology that combines machine learning and physiological measurements lights the way towards future high-throughput studies to deorphanise and characterise structure-activity relationships in olfaction.Peer reviewe

Analysis of the association between spawning time QTL markers and the biannual spawning behavior in rainbow trout (Oncorhynchus mykiss)

The rainbow trout is a salmonid fish that occasionally exhibits broodstocks with biannual spawning behavior, a phenomenon known as a double annual reproductive cycle (DARC). Spawning time quantitative trait loci (SPT-QTLs) affect the time of the year that female rainbow trout spawn and may influence expression of the DARC trait. In this study, microsatellite markers linked and unlinked to SPT-QTLs were genotyped to investigate the underlying genetics of this trait. SPT-QTLs influenced the DARC trait since in two case-control comparisons three linked markers (OmyFGT12TUF, One3ASC and One19ASC) had significant levels of allelic frequency differentiation and marker-character association. Furthermore, alleles of One3ASC and One19ASC had significantly higher frequencies in populations that carried the DARC trait

Aquatic community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record

Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132′S–78°04.847′W) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328′S–78°09.175′W) is a glacially formed lake with an inflow and outflow in high Andean Páramo grasslands. In each lake we examined the dynamics of chironomids and other aquatic and semi-aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer-type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes

First 230 GHz VLBI Fringes on 3C 279 using the APEX Telescope

We report about a 230 GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT of the Arizona Radio Observatory (ARO). We installed VLBI equipment and measured the APEX station position to 1 cm accuracy (1 sigma). We then observed 3C 279 on 2012 May 7 in a 5 hour 230 GHz VLBI track with baseline lengths of 2800 M$\lambda$ to 7200 M$\lambda$ and a finest fringe spacing of 28.6 micro-arcseconds. Fringes were detected on all baselines with SNRs of 12 to 55 in 420 s. The correlated flux density on the longest baseline was ~0.3 Jy/beam, out of a total flux density of 19.8 Jy. Visibility data suggest an emission region <38 uas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 10^10 K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ~38 uas. With APEX the angular resolution of 230 GHz VLBI improves to 28.6 uas. This allows one to resolve the last-photon ring around the Galactic Center black hole event horizon, expected to be 40 uas in diameter, and probe radio jet launching at unprecedented resolution, down to a few gravitational radii in galaxies like M 87. To probe the structure in the inner parsecs of 3C 279 in detail, follow-up observations with APEX and five other mm-VLBI stations have been conducted (March 2013) and are being analyzed.Comment: accepted for publication in A&