A Relic Neutrino Detector

Probably the most promising way of detecting cosmic neutrinos is measuring the mechanical force exerted by elastic scattering of cosmic neutrinos from macroscopic targets. The expected acceleration is $\sim 10^{-23} cm/s^2$ for Dirac neutrinos of mass $\sim 10 eV$ and local density $\sim 10^7/ cm^3$. A novel torsion balance design is presented. which addresses the sensitivity-limiting factors of existing balances, such as seismic and thermal noise, and angular readout resolution and stability.Comment: 4 pages, 2 figures. In proceedings of the COSMO-98 Int'l Workshop on Particle Physics and the Early Universe, edited by D. Caldwell (AIP Press, New York, 1999

Axions from wall decay

We discuss the decay of axion walls bounded by strings and present numerical simulations of the decay process. In these simulations, the decay happens immediately, in a time scale of order the light travel time, and the average energy of the radiated axions is $\simeq 7 m_a$ for $v_a/m_a\simeq 500$. $$ is found to increase approximately linearly with $\ln(v_a/m_a)$. Extrapolation of this behaviour yields $\simeq 60 m_a$ in axion models of interest.Comment: 6 pages, 7 figures, to be published in the Proc. of the 5th IFT Axion workshop Gainesville FL, Mar 13-15 199

A 1 GHz RF Trigger Unit implemented in FPGA logic

Applications of Trigger Units (TU) can be found in almost all accelerators at CERN. The requirements in terms of operating frequencies, configuration or modes of operation change from one application to another, how-ever, in terms of design requirements for the Trigger Unit, the operating frequency is probably the most demanding one. In this work, we present an implementation of a Trigger Unit almost fully embedded in the FPGA logic operating at a maximum frequency of 1 GHz using the internal serializer/deserializer circuitry to simplify the timing constraints of the design. This implementation allows easy reconfiguration of the module and the development of new modes of operation, which are described in this paper.Comment: Poster presented at LLRF Workshop 2017 (LLRF2017, arXiv:1803.07677

Critical examination of the inherent-structure-landscape analysis of two-state folding proteins

Recent studies attracted the attention on the inherent structure landscape (ISL) approach as a reduced description of proteins allowing to map their full thermodynamic properties. However, the analysis has been so far limited to a single topology of a two-state folding protein, and the simplifying assumptions of the method have not been examined. In this work, we construct the thermodynamics of four two-state folding proteins of different sizes and secondary structure by MD simulations using the ISL method, and critically examine possible limitations of the method. Our results show that the ISL approach correctly describes the thermodynamics function, such as the specific heat, on a qualitative level. Using both analytical and numerical methods, we show that some quantitative limitations cannot be overcome with enhanced sampling or the inclusion of harmonic corrections.Comment: published Physical Review E, vol. 80, 061907-1-11 (2009

Characterization of the low temperature properties of a simplified protein model

Prompted by results that showed that a simple protein model, the frustrated G\=o model, appears to exhibit a transition reminiscent of the protein dynamical transition, we examine the validity of this model to describe the low-temperature properties of proteins. First, we examine equilibrium fluctuations. We calculate its incoherent neutron-scattering structure factor and show that it can be well described by a theory using the one-phonon approximation. By performing an inherent structure analysis, we assess the transitions among energy states at low temperatures. Then, we examine non-equilibrium fluctuations after a sudden cooling of the protein. We investigate the violation of the fluctuation--dissipation theorem in order to analyze the protein glass transition. We find that the effective temperature of the quenched protein deviates from the temperature of the thermostat, however it relaxes towards the actual temperature with an Arrhenius behavior as the waiting time increases. These results of the equilibrium and non-equilibrium studies converge to the conclusion that the apparent dynamical transition of this coarse-grained model cannot be attributed to a glassy behavior

Probing Axions with Radiation from Magnetic Stars

Recent experiments suggest that polarized photons may couple significantly to pseudoscalar particles such as axions. We study the possible observational signatures of axion-photon coupling for radiation from magnetic stars, with particular focus on neutron stars. We present general methods for calculating the axion-photon conversion probability during propagation through a varying magnetized vacuum as well as across an inhomogeneous atmosphere. Partial axion-photon conversion may take place in the vacuum region outside the neutron star. Strong axion-photon mixing occurs due to a resonance in the atmosphere, and depending on the axion coupling strength and other parameters, significant axion-photon conversion can take place at the resonance. Such conversions may produce observable effects on the radiation spectra and polarization signals from the star. We also apply our results to axion-photon propagation in the Sun and in magnetic white dwarfs. We find that there is no appreciable conversion of solar axions to photons during the propagation.Comment: 12 pages, 11 figures. Minor changes. PRD accepte