2,137 research outputs found

    \u3cem\u3eAlectryon vitiensis\u3c/em\u3e: A New Species of Sapindaceae Endemic to Fiji

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    A new species of Alectryon Gaertn. (Sapindaceae) endemic to the Fijian archipelago is described as A. vitiensis Buerki, Lowry, Munzinger & Callm. based on morphological and molecular evidence. It can easily be distinguished from the two congeners currently known from Fiji by its smaller leaves, subsessile leaflets, apetalous flowers, and crested fruits. A phylogenetic analysis using ITS sequence data shows that the new species is closely related to two Australian endemics, A. diversifolius (F. Muell.) S. T. Reynolds and A. oleifolius (Desf.) S. T. Reynolds, but differs in having compound leaves covered with a golden indument. Moreover, the Australian taxa are associated with dry habitats, whereas the new species from Fiji is confined to evergreen humid forests. Among apetalous species (all of which belong to a well-supported clade), A. vitiensis morphologically most closely resembles the generic type, A. excelsus Gaertn., endemic to New Zealand, but they differ from one another in the type of indument covering their branches and leaves and the arrangement, shape, and nature of the indument on their leaflets; and they belong to different clades. The new species is provisionally assigned a conservation status of “Endangered” according to the IUCN Red List criteria

    Visual perception system and method for a humanoid robot

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    A robotic system includes a humanoid robot with robotic joints each moveable using an actuator(s), and a distributed controller for controlling the movement of each of the robotic joints. The controller includes a visual perception module (VPM) for visually identifying and tracking an object in the field of view of the robot under threshold lighting conditions. The VPM includes optical devices for collecting an image of the object, a positional extraction device, and a host machine having an algorithm for processing the image and positional information. The algorithm visually identifies and tracks the object, and automatically adapts an exposure time of the optical devices to prevent feature data loss of the image under the threshold lighting conditions. A method of identifying and tracking the object includes collecting the image, extracting positional information of the object, and automatically adapting the exposure time to thereby prevent feature data loss of the image

    Similarity to peroxisomal-membrane protein family reveals that Sinorhizobium and Brucella BacA affect lipid-A fatty acids

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    Sinorhizobium meliloti, a legume symbiont, and Brucella abortus, a phylogenetically related mammalian pathogen, both require the bacterial-encoded BacA protein to establish chronic intracellular infections in their respective hosts. We found that the bacterial BacA proteins share sequence similarity with a family of eukaryotic peroxisomal-membrane proteins, including the human adrenoleukodystrophy protein, required for the efficient transport of verylong- chain fatty acids out of the cytoplasm. This insight, along with the increased sensitivity of BacA-deficient mutants to detergents and cell envelope-disrupting agents, led us to discover that BacA affects the very-long-chain fatty acid (27-OHC28:0 and 29-OHC30:0) content of both Sinorhizobium and Brucella lipid A. We discuss models for how BacA function affects the lipid-A fatty-acid content and why this activity could be important for the establishment of chronic intracellular infections. Originally published Proceedings of the National Academy of Sciences, Vol. 101, No. 14, Apr 200

    Trans-mitochondrial coordination of cristae at regulated membrane junctions

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    Reminiscent of bacterial quorum sensing, mammalian mitochondria participate in inter-organelle communication. However, physical structures that enhance or enable interactions between mitochondria have not been defined. Here we report that adjacent mitochondria exhibit coordination of inner mitochondrial membrane cristae at inter-mitochondrial junctions (IMJs). These electron-dense structures are conserved across species, resistant to genetic disruption of cristae organization, dynamically modulated by mitochondrial bioenergetics, independent of known inter-mitochondrial tethering proteins mitofusins and rapidly induced by the stable rapprochement of organelles via inducible synthetic linker technology. At the associated junctions, the cristae of adjacent mitochondria form parallel arrays perpendicular to the IMJ, consistent with a role in electrochemical coupling. These IMJs and associated cristae arrays may provide the structural basis to enhance the propagation of intracellular bioenergetic and apoptotic waves through mitochondrial networks within cells

    Perilipin regulates the thermogenic actions of norepinephrine in brown adipose tissue

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    In response to cold, norepinephrine (NE)-induced triacylglycerol hydrolysis (lipolysis) in adipocytes of brown adipose tissue (BAT) provides fatty acid substrates to mitochondria for heat generation (adaptive thermogenesis). NE-induced lipolysis is mediated by protein kinase A (PKA)-dependent phosphorylation of perilipin, a lipid droplet-associated protein that is the major regulator of lipolysis. We investigated the role of perilipin PKA phosphorylation in BAT NE-stimulated thermogenesis using a novel mouse model in which a mutant form of perilipin, lacking all six PKA phosphorylation sites, is expressed in adipocytes of perilipin knockout (Peri KO) mice. Here, we show that despite a normal mitochondrial respiratory capacity, NE-induced lipolysis is abrogated in the interscapular brown adipose tissue (IBAT) of these mice. This lipolytic constraint is accompanied by a dramatic blunting (∼70%) of the in vivo thermal response to NE. Thus, in the presence of perilipin, PKA-mediated perilipin phosphorylation is essential for NE-dependent lipolysis and full adaptive thermogenesis in BAT. In IBAT of Peri KO mice, increased basal lipolysis attributable to the absence of perilipin is sufficient to support a rapid NE-stimulated temperature increase (∼3.0°C) comparable to that in wild-type mice. This observation suggests that one or more NE-dependent mechanism downstream of perilipin phosphorylation is required to initiate and/or sustain the IBAT thermal response

    Identification of priority areas for plant conservation in Madagascar using Red List criteria: rare and threatened Pandanaceae indicate sites in need of protection

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    A major problem in establishing effective protocols for conserving Madagascar's biodiversity is the lack of reliable information for the identification of priority sites in need of protection. Analyses of field data and information from herbarium collections for members of the plant family Pandanaceae (85 spp. of Pandanus; 6 spp. of Martellidendron) showed how risk of extinction assessments can inform conservation planning. Application of IUCN Red List categories and criteria showed that 91% of the species are threatened. Mapping occurrence revealed centres of richness and rarity as well as gaps in Madagascar's existing protected area network. Protection of 10 additional sites would be required to encompass the 19 species currently lacking representation in the reserve network, within which east coast littoral forests are particularly under represented and important. The effect of scale on assessments of risk of extinction was explored by applying different grid cell sizes to estimate area of occupancy. Using a grid cell size within the range suggested by IUCN overestimates threatened status if based solely upon specimen data. For poorly inventoried countries such as Madagascar measures of range size based on such data should be complemented with field observations to determine population size, sensitivity to disturbance, and specific threats to habitat and therefore potential population decline. The analysis of such data can make an important contribution to the conservation planning process by identifying threatened species and revealing the highest priority sites for their conservatio

    Integer and half-integer flux-quantum transitions in a niobium/iron-pnictide loop

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    The recent discovery of iron-based superconductors challenges the existing paradigm of high-temperature superconductivity. Owing to their unusual multi-orbital band structure, magnetism, and electron correlation, theories propose a unique sign reversed s-wave pairing state, with the order parameter changing sign between the electron and hole Fermi pockets. However, because of the complex Fermi surface topology and material related issues, the predicted sign reversal remains unconfirmed. Here we report a novel phase-sensitive technique for probing unconventional pairing symmetry in the polycrystalline iron-pnictides. Through the observation of both integer and half-integer flux-quantum transitions in composite niobium/iron-pnictide loops, we provide the first phase-sensitive evidence of the sign change of the order parameter in NdFeAsO0.88F0.12, lending strong support for microscopic models predicting unconventional s-wave pairing symmetry. These findings have important implications on the mechanism of pnictide superconductivity, and lay the groundwork for future studies of new physics arising from the exotic order in the FeAs-based superconductors.Comment: 23 pages, including 4 figures and supplementary informatio

    NLL soft and Coulomb resummation for squark and gluino production at the LHC

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    We present predictions of the total cross sections for pair production of squarks and gluinos at the LHC, including the stop-antistop production process. Our calculation supplements full fixed-order NLO predictions with resummation of threshold logarithms and Coulomb singularities at next-to-leading logarithmic (NLL) accuracy, including bound-state effects. The numerical effect of higher-order Coulomb terms can be as big or larger than that of soft-gluon corrections. For a selection of benchmark points accessible with data from the 2010-2012 LHC runs, resummation leads to an enhancement of the total inclusive squark and gluino production cross section in the 15-30 % range. For individual production processes of gluinos, the corrections can be much larger. The theoretical uncertainty in the prediction of the hard-scattering cross sections is typically reduced to the 10 % level.Comment: 45 pages, 16 Figures, LaTex. v2: published version. Grids with numerical results for the NLL cross sections for squark and gluino production at the 7/8 TeV LHC are included in the submission and are also available at http://omnibus.uni-freiburg.de/~cs1010/susy.htm
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