A Mean Field Analysis of Pairing in Asymmetric Fermi Systems at Finite Temperature

We study the phase diagram of a two component Fermi system with a weak attractive interaction. Our analysis includes the leading order Hartree energy shifts and pairing correlations at finite temperature and chemical potential difference between the two fermion species. We show that in an asymmetric system, the Hartree shift to the single particle energies are important for the phase competition between normal and superfluid phase and can change the phase transition curve qualitatively. At large asymmetry we find that a novel but somewhat fragile superfluid state can be favored due to finite temperature effects. We also investigate the transition between the normal phase and an inhomogeneous superfluid phase to study how gradient instabilities evolve with temperature and asymmetry. Finally, we adopt our analysis to study the density profiles of similar asymmetric Fermi systems that are being observed in cold atom experiments.Comment: 17 pages, 7 figure

Electronic screening and damping in magnetars

We calculate the screening of the ion-ion potential due to electrons in the presence of a large background magnetic field, at densities of relevance to neutron star crusts. Using the standard approach to incorporate electron screening through the one-loop polarization function, we show that the magnetic field produces important corrections both at short and long distances. In extreme fields, realized in highly magnetized neutron stars called magnetars, electrons occupy only the lowest Landau levels in the relatively low density region of the crust. Here our results show that the screening length for Coulomb interactions between ions can be smaller than the inter-ion spacing. More interestingly, we find that the screening is anisotropic and the screened potential between two static charges exhibits long range Friedel oscillations parallel to the magnetic field. This long-range oscillatory behavior is likely to affect the lattice structure of ions, and can possibly create rod-like structures in the magnetar crusts. We also calculate the imaginary part of the electron polarization function which determines the spectrum of electron-hole excitations and plays a role in damping lattice phonon excitations. We demonstrate that even for modest magnetic fields this damping is highly anisotropic and will likely lead to anisotropic phonon heat transport in the outer neutron star crust.Comment: 14 pages, 5 Figure

Evaluation of 976 nm Multimode Single Emitter Laser Diodes for Efficient Pumping of 100 W+ Yb-doped Fiber Laser

Experimental evaluation of spectral and power-current (P-I) characteristics of fiber coupled single emitter multimode laser diodes used for development of efficient pumping assembly is reported. Fiber coupled laser diodes emitting around 976 nm are best suited for pumping Yb-doped fiber lasers because of excellent coupling efficiency and reduced thermal load. We have experimentally investigated emission spectrum of fiber coupled multimode laser diodes at different temperatures and drive currents. It is found that peak emission wavelength shifts towards the longer wavelength with increase in temperature and drive current. P-I characteristics of fiber coupled laser diodes have been obtained and presented for drive current from 0.4 A to 11.5 A. Based on experiment, we have constructed spectrally matched laser diode assembly for efficient pumping of 100 W fiber laser. It requires very precise control of temperature and drive current to maintain the emission spectrum. Total 162 W power is pumped in to the Yb-doped fiber laser cavity through multi-mode pump combiners and we have obtained 110 W fiber laser output power @1070 nm. The achieved optical-to-optical efficiency is 68 per cent

Testing the Ginzburg-Landau approximation for three-flavor crystalline color superconductivity

It is an open challenge to analyze the crystalline color superconducting phases that may arise in cold dense, but not asymptotically dense, three-flavor quark matter. At present the only approximation within which it seems possible to compare the free energies of the myriad possible crystal structures is the Ginzburg-Landau approximation. Here, we test this approximation on a particularly simple "crystal" structure in which there are only two condensates $\sim \Delta \exp(i {\bf q_2}\cdot {\bf r})$ and $\sim \Delta \exp(i {\bf q_3}\cdot {\bf r})$ whose position-space dependence is that of two plane waves with wave vectors ${\bf q_2}$ and ${\bf q_3}$ at arbitrary angles. For this case, we are able to solve the mean-field gap equation without making a Ginzburg-Landau approximation. We find that the Ginzburg-Landau approximation works in the $\Delta\to 0$ limit as expected, find that it correctly predicts that $\Delta$ decreases with increasing angle between ${\bf q_2}$ and ${\bf q_3}$ meaning that the phase with ${\bf q_2}\parallel {\bf q_3}$ has the lowest free energy, and find that the Ginzburg-Landau approximation is conservative in the sense that it underestimates $\Delta$ at all values of the angle between ${\bf q_2}$ and ${\bf q_3}$.Comment: 16 pages, 6 figures. Small changes only. Version to appear in Phys. Rev.

A low energy theory for superfluid and solid matter and its application to the neutron star crust

We formulate a low energy effective theory describing phases of matter that are both solid and superfluid. These systems simultaneously break translational symmetry and the phase symmetry associated with particle number. The symmetries restrict the combinations of terms that can appear in the effective action and the lowest order terms featuring equal number of derivatives and Goldstone fields are completely specified by the thermodynamic free energy, or equivalently by the long-wavelength limit of static correlation functions in the ground state. We show that the underlying interaction between particles that constitute the lattice and the superfluid gives rise to entrainment, and mixing between the Goldstone modes. As a concrete example we discuss the low energy theory for the inner crust of a neutron star, where a lattice of ionized nuclei coexists with a neutron superfluid.Comment: 21 pages, 1 figur

Adjuvant drugs in management of osteoarthritis: spotlight on type II collagen

Osteoarthritis (OA) is a common musculoskeletal disorder that affects large and small joints and is seen in all ages due to diverse aetiologies. Pain, joint stiffness and limitation of daily activities affects the quality of life of individuals with OA. Conventional analgesics like non-steroidal anti-inflammatory drugs affect pain and inflammatory component but do not target the disease pathogenesis. Damage to the joint cartilage is central to the pathogenesis of OA. Better understanding of the pathogenesis has led to evolution of various adjuvant drugs in management of OA. Among them, undenatured type II collagen induces immune tolerance and thereby provide benefits by reducing the joint damage. Studies assessing efficacy and safety of undenatured type II collagen in OA have shown to reduce clinical symptoms like pain, joint stiffness and improvement in physical activities, and thus improving the quality of life. It is well tolerated and safe for use in OA. This article discusses the pathophysiology of OA with inflammation and beyond, and overviews the various drugs that are used as adjuvants in the management of OA with special focus on the use of type 2 collagen

EBBIOT: A Low-complexity Tracking Algorithm for Surveillance in IoVT Using Stationary Neuromorphic Vision Sensors

In this paper, we present EBBIOT-a novel paradigm for object tracking using stationary neuromorphic vision sensors in low-power sensor nodes for the Internet of Video Things (IoVT). Different from fully event based tracking or fully frame based approaches, we propose a mixed approach where we create event-based binary images (EBBI) that can use memory efficient noise filtering algorithms. We exploit the motion triggering aspect of neuromorphic sensors to generate region proposals based on event density counts with >1000X less memory and computes compared to frame based approaches. We also propose a simple overlap based tracker (OT) with prediction based handling of occlusion. Our overall approach requires 7X less memory and 3X less computations than conventional noise filtering and event based mean shift (EBMS) tracking. Finally, we show that our approach results in significantly higher precision and recall compared to EBMS approach as well as Kalman Filter tracker when evaluated over 1.1 hours of traffic recordings at two different locations.Comment: 6 pages, 5 figure

Superfluid Heat Conduction and the Cooling of Magnetized Neutron Stars

We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superfluid neutron matter, called superfluid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field B \gsim 10^{13} G. At density $\rho \simeq 10^{12}-10^{14}$ g/cm$^3$ the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity when temperature $\simeq 10^8$ K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction could show observationally discernible differences.Comment: 4 pages, 3 figure

Who funded the research behind the Oxford-AstraZeneca COVID-19 vaccine?

Objectives The Oxford-AstraZeneca COVID-19 vaccine (ChAdOx1 nCoV-19, Vaxzevira or Covishield) builds on two decades of research and development (R&D) into chimpanzee adenovirus-vectored vaccine (ChAdOx) technology at the University of Oxford. This study aimed to approximate the funding for the R&D of ChAdOx and the Oxford-AstraZeneca vaccine and to assess the transparency of funding reporting mechanisms. Methods We conducted a scoping review and publication history analysis of the principal investigators to reconstruct R&D funding the ChAdOx technology. We matched award numbers with publicly accessible grant databases. We filed freedom of information (FOI) requests to the University of Oxford for the disclosure of all grants for ChAdOx R&D. Results We identified 100 peer-reviewed articles relevant to ChAdOx technology published between January 2002 and October 2020, extracting 577 mentions of funding bodies from acknowledgements. Government funders from overseas (including the European Union) were mentioned 158 times (27.4%), the UK government 147 (25.5%) and charitable funders 138 (23.9%). Grant award numbers were identified for 215 (37.3%) mentions; amounts were publicly available for 121 (21.0%). Based on the FOIs, until December 2019, the biggest funders of ChAdOx R&D were the European Commission (34.0%), Wellcome Trust (20.4%) and Coalition for Epidemic Preparedness Innovations (17.5%). Since January 2020, the UK government contributed 95.5% of funding identified. The total identified R&D funding was £104 226 076 reported in the FOIs and £228 466 771 reconstructed from the literature search. Conclusion Our study approximates that public and charitable financing accounted for 97%-99% of identifiable funding for the ChAdOx vaccine technology research at the University of Oxford underlying the Oxford-AstraZeneca vaccine until autumn 2020. We encountered a lack of transparency in research funding reporting