9,393 research outputs found

    Violation of the London Law and Onsager-Feynman quantization in multicomponent superconductors

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    Non-classical response to rotation is a hallmark of quantum ordered states such as superconductors and superfluids. The rotational responses of all currently known single-component "super" states of matter (superconductors, superfluids and supersolids) are largely described by two fundamental principles and fall into two categories according to whether the systems are composed of charged or neutral particles: the London law relating the angular velocity to a subsequently established magnetic field and the Onsager-Feynman quantization of superfluid velocity. These laws are theoretically shown to be violated in a two-component superconductor such as the projected liquid metallic states of hydrogen and deuterium at high pressures. The rotational responses of liquid metallic hydrogen or deuterium identify them as a new class of dissipationless states; they also directly point to a particular experimental route for verification of their existence.Comment: Nature Physics in print. This is an early version of the paper. The final version will be posted 6 months after its publication Nature Physics, according to the journal polic

    Reprogramming of lysosomal gene expression by interleukin-4 and Stat6.

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    BACKGROUND: Lysosomes play important roles in multiple aspects of physiology, but the problem of how the transcription of lysosomal genes is coordinated remains incompletely understood. The goal of this study was to illuminate the physiological contexts in which lysosomal genes are coordinately regulated and to identify transcription factors involved in this control. RESULTS: As transcription factors and their target genes are often co-regulated, we performed meta-analyses of array-based expression data to identify regulators whose mRNA profiles are highly correlated with those of a core set of lysosomal genes. Among the ~50 transcription factors that rank highest by this measure, 65% are involved in differentiation or development, and 22% have been implicated in interferon signaling. The most strongly correlated candidate was Stat6, a factor commonly activated by interleukin-4 (IL-4) or IL-13. Publicly available chromatin immunoprecipitation (ChIP) data from alternatively activated mouse macrophages show that lysosomal genes are overrepresented among Stat6-bound targets. Quantification of RNA from wild-type and Stat6-deficient cells indicates that Stat6 promotes the expression of over 100 lysosomal genes, including hydrolases, subunits of the vacuolar H⁺ ATPase and trafficking factors. While IL-4 inhibits and activates different sets of lysosomal genes, Stat6 mediates only the activating effects of IL-4, by promoting increased expression and by neutralizing undefined inhibitory signals induced by IL-4. CONCLUSIONS: The current data establish Stat6 as a broadly acting regulator of lysosomal gene expression in mouse macrophages. Other regulators whose expression correlates with lysosomal genes suggest that lysosome function is frequently re-programmed during differentiation, development and interferon signaling

    North Atlantic Deep Water Production during the Last Glacial Maximum.

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    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial-interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ(13)C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters.Sample material was provided by the Godwin Laboratory for Paleoclimate Research at the University of Cambridge, the International Ocean Discovery Program, the GeoB Core Repository at the MARUM – Center for Marine Environmental Sciences, University of Bremen and Petrobras. Jo Kerr and Aurora Elmore are thanked for providing additional samples. The data reported in this paper are listed in supplementary information and archived in Pangaea (www.pangaea.de). Thiago Pereira dos Santos is thanked for providing the unpublished age model data for GL1090; Jo Clegg and Vicky Rennie are thanked for technical support and Natalie Roberts for helpful discussions. Radiocarbon analyses were supported by NERC radiocarbon grant 1752.1013 and Nd isotope analyses by NERC grant NERC NE/K005235/1 and NERC NE/F006047/1 to AMP. JNWH was supported by a Rutherford Memorial Scholarship. SM was funded through the DFG Research Center/Cluster of Excellence “The Ocean in the Earth System”. CMC acknowledges financial support from FAPESP (Grant 2012/17517-3).This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Nature Publishing Group

    Coherent Single Charge Transport in Molecular-Scale Silicon Nanowire Transistors

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    We report low-temperature electrical transport studies of molecule-scale silicon nanowires. Individual nanowires exhibit well-defined Coulomb blockade oscillations characteristic of charge addition to a single nanostructure with length scales up to at least 400 nm. Further studies demonstrate coherent charge transport through discrete single particle quantum levels extending the whole device, and show that the ground state spin configuration follows the Lieb-Mattis theorem. In addition, depletion of the nanowires suggests that phase coherent single-dot characteristics are accessible in a regime where correlations are strong.Comment: 4 pages and 4 figure

    Clocking the Lyme Spirochete

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    In order to clear the body of infecting spirochetes, phagocytic cells must be able to get hold of them. In real-time phase-contrast videomicroscopy we were able to measure the speed of Borrelia burgdorferi (Bb), the Lyme spirochete, moving back and forth across a platelet to which it was tethered. Its mean crossing speed was 1,636 µm/min (N = 28), maximum, 2800 µm/min (N = 3). This is the fastest speed recorded for a spirochete, and upward of two orders of magnitude above the speed of a human neutrophil, the fastest cell in the body. This alacrity and its interpretation, in an organism with bidirectional motor capacity, may well contribute to difficulties in spirochete clearance by the host

    The origin of defects induced in ultra-pure germanium by Electron Beam Deposition

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    The creation of point defects in the crystal lattices of various semiconductors by subthreshold events has been reported on by a number of groups. These observations have been made in great detail using sensitive electrical techniques but there is still much that needs to be clarified. Experiments using Ge and Si were performed that demonstrate that energetic particles, the products of collisions in the electron beam, were responsible for the majority of electron-beam deposition (EBD) induced defects in a two-step energy transfer process. Lowering the number of collisions of these energetic particles with the semiconductor during metal deposition was accomplished using a combination of static shields and superior vacuum resulting in devices with defect concentrations lower than 1011 10^{11}\,cm3^{-3}, the measurement limit of our deep level transient spectroscopy (DLTS) system. High energy electrons and photons that samples are typically exposed to were not influenced by the shields as most of these particles originate at the metal target thus eliminating these particles as possible damage causing agents. It remains unclear how packets of energy that can sometimes be as small of 2eV travel up to a μ\mum into the material while still retaining enough energy, that is, in the order of 1eV, to cause changes in the crystal. The manipulation of this defect causing phenomenon may hold the key to developing defect free material for future applications.Comment: 18 pages, 9 figure

    Protein Pattern Formation

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    Protein pattern formation is essential for the spatial organization of many intracellular processes like cell division, flagellum positioning, and chemotaxis. A prominent example of intracellular patterns are the oscillatory pole-to-pole oscillations of Min proteins in \textit{E. coli} whose biological function is to ensure precise cell division. Cell polarization, a prerequisite for processes such as stem cell differentiation and cell polarity in yeast, is also mediated by a diffusion-reaction process. More generally, these functional modules of cells serve as model systems for self-organization, one of the core principles of life. Under which conditions spatio-temporal patterns emerge, and how these patterns are regulated by biochemical and geometrical factors are major aspects of current research. Here we review recent theoretical and experimental advances in the field of intracellular pattern formation, focusing on general design principles and fundamental physical mechanisms.Comment: 17 pages, 14 figures, review articl

    Multisensory causal inference in the brain

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    At any given moment, our brain processes multiple inputs from its different sensory modalities (vision, hearing, touch, etc.). In deciphering this array of sensory information, the brain has to solve two problems: (1) which of the inputs originate from the same object and should be integrated and (2) for the sensations originating from the same object, how best to integrate them. Recent behavioural studies suggest that the human brain solves these problems using optimal probabilistic inference, known as Bayesian causal inference. However, how and where the underlying computations are carried out in the brain have remained unknown. By combining neuroimaging-based decoding techniques and computational modelling of behavioural data, a new study now sheds light on how multisensory causal inference maps onto specific brain areas. The results suggest that the complexity of neural computations increases along the visual hierarchy and link specific components of the causal inference process with specific visual and parietal regions

    Pelatihan Pliometrik Jump to Box Lebih Meningkatkan Daya Ledak Otot Tungkai Dari Pada Pelatihan Pliometrik Barrier Hops Pada Permainan Bola Basket

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    Penelitian ini bertujuan untuk membandingkan  pelatihan  jump to box dan barrier hops terhadap peningkatan daya ledak otot tungkai. Penelitian ini dilakukan terhadap 32 orang siswa SMK Negeri 1 Kuta Selatan yang dipilih secara acak sederhana yang telah memenuhi kriteria insklusi dan eksklusi. Sampel dibagi menjadi dua kelompok sehingga masing-masing kelempok berjumlah 16 orang dan diberikan perlakuan yang berbeda selama enam minggu. Kelompok satu  diberikan pelatihan jump to box dan kelompok dua diberikan pelatihan barrier hops. Data yang didapat dianalisis dengan uji t paired untuk mengethui perbedaan antara sebelum dan sesudah pelatihan pada kedua kelompok dan uji t-independent untuk menguji perbedaan daya ledak otot tungkai antar kelompok baik sebelum maupun sesudah pelatihan. Batas kemaknaan di pakai 0,05. Hasil penelitian menunjukan rerata daya ledak otot tungkai antar kelompok sesudah pelatihan sebesar 58,00±10,33 cm pada kelompok jump to box dan pada kelompok barrier hops sebesar 50,49±10,19 cm. Rerata daya ledak otot tungkai pelatihan jump to box lebih tinggi dibandingkan dengan pelatihan barrier hops yang secara statistik berbeda bermakna dengan nilai p=0,036 (p<0,05). Dengan demikian, pelatihan jump to box dan pelatihan barrier hops dapat meningkatkan daya ledak otot tungkai, di mana pelatihan jump to box lebih meningkatkan daripada pelatihan barrier hops
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