Brownian molecular motors driven by rotation-translation coupling

We investigated three models of Brownian motors which convert rotational diffusion into directed translational motion by switching on and off a potential. In the first model a spatially asymmetric potential generates directed translational motion by rectifying rotational diffusion. It behaves much like a conventional flashing ratchet. The second model utilizes both rotational diffusion and drift to generate translational motion without spatial asymmetry in the potential. This second model can be driven by a combination of a Brownian motor mechanism (diffusion driven) or by powerstroke (drift driven) depending on the chosen parameters. In the third model, elements of both the Brownian motor and powerstroke mechanisms are combined by switching between three distinct states. Relevance of the model to biological motor proteins is discussed.Comment: 11 pages, 8 figure

Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surfaces near monoatomic step edges

We measured the electronic local density of states (LDOS) of graphite surfaces near monoatomic step edges, which consist of either the zigzag or armchair edge, with the scanning tunneling microscopy (STM) and spectroscopy (STS) techniques. The STM data reveal that the $(\sqrt{3} \times \sqrt{3}) R 30^{\circ}$ and honeycomb superstructures coexist over a length scale of 3-4 nm from both the edges. By comparing with density-functional derived nonorthogonal tight-binding calculations, we show that the coexistence is due to a slight admixing of the two types of edges at the graphite surfaces. In the STS measurements, a clear peak in the LDOS at negative bias voltages from -100 to -20 mV was observed near the zigzag edges, while such a peak was not observed near the armchair edges. We concluded that this peak corresponds to the graphite "edge state" theoretically predicted by Fujita \textit{et al.} [J. Phys. Soc. Jpn. {\bf 65}, 1920 (1996)] with a tight-binding model for graphene ribbons. The existence of the edge state only at the zigzag type edge was also confirmed by our first-principles calculations with different edge terminations.Comment: 20 pages, 11 figure

Effect of La Doping on Microstructure and Critical Current Density of MgB2

In the present study, La-doped MgB_2 superconductors with different doping level (Mg1-xLaxB2; x=0.00, 0.01, 0.03 & 0.05) have been synthesized by solid-state reaction route at ambient pressure. Effect of La doping have been investigated in relation to microstructural characteristics and superconducting properties, particularly intragrain critical current density (Jc). The microstructural characteristics of the as synthesized Mg(La)B2 compounds were studied employing transmission electron microscopic (TEM) technique. The TEM investigations reveal inclusion of LaB6 nanoparticles within the MgB2 grains which provide effective flux pinning centres. The evaluation of intragrain Jc through magnetic measurements on the fine powdered version of the as synthesized samples reveal that Jc of the samples change significantly with the doping level. The optimum result on Jc is obtained for Mg0.97La0.03B2 at 5K, the Jc reaches ~1.4x107A/cm2 in self field, ~2.1 x 106A/cm2 at 1T, ~2.5 x 105A/cm2 at 2.5T and ~1.8 x 104 A/cm2 at 4.5T. The highest value of intragrain Jc in Mg0.97La0.03B2 superconductor has been attributed to the inclusion of LaB6 nanoparticles which are capable of providing effective flux pinning centres

Fabrication and transport critical currents of multifilamentary MgB2/Fe wires and tapes

Multifilamentary MgB2/Fe wires and tapes with high transport critical current densities have been fabricated using a straightforward powder-in-tube (PIT) process. After annealing, we measured transport jc values up to 1.1 * 105 A/cm2 at 4.2 K and in a field of 2 T in a MgB2/Fe square wire with 7 filaments fabricated by two-axial rolling, and up to 5 * 104 A/cm2 at 4.2 K in 1 T in a MgB2/Fe tape with 7 filaments. For higher currents these multifilamentary wires and tapes quenched due to insufficient thermal stability of filaments. Both the processing routes and deformation methods were found to be important factors for fabricating multifilamentary MgB2 wires and tapes with high transport jc values.Comment: 13 pages, 7 figure

Renminbi Internationalisation: Precedents and Implications

While it is commonly assumed that there are no known precedents against which to benchmark the internationalisation of the Renminbi (RMB), this paper argues that the PRCs own development experience provides a useful perspective on the internationalisation debate. In particular it indicates that lessons can be learnt from both the successes and the shortcomings of efforts to internationalise the RMB in the 1970s. During this period state-owned banks in Hong Kong played a central role in mobilising finance for foreign trade. Access to Hong Kong’s developed financial institutions allowed the PRC to maximise receipts from foreign trade as well as minimise the risks of undue swings in capital flows. The paper shows that although China no longer faces foreign exchange scarcity, economic reforms have not yet resolved vulnerabilities in China’s financial institutions and as such Hong Kong’s role in mitigating the risk of undue capital swings remains

GSDMD is critical for autoinflammatory pathology in a mouse model of Familial Mediterranean Fever

Pyroptosis is an inflammasome-induced lytic cell death mode, the physiological role of which in chronic inflammatory diseases is unknown. Familial Mediterranean Fever (FMF) is the most common monogenic autoinflammatory disease worldwide, affecting an estimated 150,000 patients. The disease is caused by missense mutations in Mefv that activate the Pyrin inflammasome, but the pathophysiologic mechanisms driving autoinflammation in FMF are incompletely understood. Here, we show that Clostridium difficile infection of FMF knock-in macrophages that express a chimeric FMF-associated Mefv(V726A) Pyrin elicited pyroptosis and gasdermin D (GSDMD)-mediated interleukin (IL)-1 beta secretion. Importantly, in vivo GSDMD deletion abolished spontaneous autoinflammatory disease. GSDMD-deficient FMF knock-in mice were fully protected from the runted growth, anemia, systemic inflammatory cytokine production, neutrophilia, and tissue damage that characterize this autoinflammatory disease model. Overall, this work identifies pyroptosis as a critical mechanism of IL-1 beta-dependent autoinflammation in FMF and highlights GSDMD inhibition as a potential antiinflammatory strategy in inflammasome-driven diseases

Magnetic characterization of sintered MgB2 samples: effect of the substitution or doping with Li, Al and Si

Powdered and sintered MgB2 samples have been characterized through magnetic measurements performed from T = 5 K up to few degrees above the transition temperature of about 39 K. We found that the sintered samples behave as well-connected bodies, showing no trace of granularity. In order to obtain the critical current density value Jc the Critical State Model has been therefore employed in a straightforward way. With the aim either to decrease the electron mean free path or to increase its Jc we have attempted to introduce defects in the MgB2 structure by different procedures: substitution of Lithium on the Magnesium site and doping of the precursor Boron powders with Aluminum and Silicon. The best result in terms of Jc has been achieved by Silicon doping that, moreover, does not significantly affect the transition temperature.Comment: 10 pages, 6 figures, 1 tabl

Oxidation and magnetic states of chalcopyrite CuFeS2: a first principles calculation

The ground state band structure, magnetic moments, charges and population numbers of electronic shells of Cu and Fe atoms have been calculated for chalcopyrite CuFeS2 using density functional theory. The comparison between our calculation results and experimental data (X ray photoemission, X ray absorption and neutron diffraction spectroscopy) has been made. Our calculations predict a formal oxidation state for chalcopyrite as Cu1+Fe3+S. However, the assignment of formal valence state to transition metal atoms appears to be oversimplified. It is anticipated that the valence state can be confirmed experimentally by nuclear magnetic and nuclear quadrupole resonance and Mössbauer spectroscopy methods

Muon spin rotation and relaxation in magnetic materials

A review of the muon spin rotation and relaxation ($\mu$SR) studies on magnetic materials published from July 1993 is presented. It covers the investigation of magnetic phase diagrams, of spin dynamics and the analysis of the magnetic properties of superconductors. We have chosen to focus on selected experimental works in these different topics. In addition, a list of published works is provided.Comment: Review article, 59 pages, LaTeX with IoP macro

Performance studies of the Belle II Silicon Vertex Detector with data taken at the DESY test beam in April 2016

Belle II is a multipurpose detector currently under construction which will be operated at the next generation B-factory SuberKEKB in Japan. Its main devices for the vertex reconstruction are the Silicon Vertex Detector (SVD) and the Pixel Detector (PXD). In April 2016 a sector of the Belle II SVD and PXD have been tested in a beam of high energetic electrons at the test beam facility at DESY Hamburg (Germany). We report here the results for the hit efficiency estimation and the measurement of the resolution for the Belle II silicon vertex etector. We find that the hit efficiencies are on average above 99.5% and that the measured resolution is within the expectations