TORCH: A Cherenkov Based Time-of-Flight Detector

TORCH is a novel high-precision time-of-flight detector suitable for large area applications and covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors. For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners. The development is divided into three phases. Phase 1 addresses the lifetime requirements for TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial tests show stable gain performance for integrated anode current >5 C/cm2 and a single photon time resolution of ≤ 30 ps. Initial simulations indicate the single photon timing resolution of the TORCH detector will be ∼70 ps

Enhanced Joule Heating in Umbral Dots

We present a study of magnetic profiles of umbral dots (UDs) and its consequences on the Joule heating mechanisms. Hamedivafa (2003) studied Joule heating using vertical component of magnetic field. In this paper UDs magnetic profile has been investigated including the new azimuthal component of magnetic field which might explain the relatively larger enhancement of Joule heating causing more brightness near circumference of UD.Comment: 8 pages, 1 figure, accepted in Solar Physic

Oscillation Induced Neutrino Asymmetry Growth in the Early Universe

We study the dynamics of active-sterile neutrino oscillations in the early universe using full momentum-dependent quantum-kinetic equations. These equations are too complicated to allow for an analytical treatment, and numerical solution is greatly complicated due to very pronounced and narrow structures in the momentum variable introduced by resonances. Here we introduce a novel dynamical discretization of the momentum variable which overcomes this problem. As a result we can follow the evolution of neutrino ensemble accurately well into the stable growing phase. Our results confirm the existence of a "chaotic region" of mixing parameters, for which the final sign of the asymmetry, and hence the SBBN prediction of He(4)-abundance cannot be accurately determined.Comment: 23 pages, 9 eps-figs, Latex, uses JHEP clas

Phase-space analysis of interacting phantom cosmology

We perform a detailed phase-space analysis of various phantom cosmological models, where the dark energy sector interacts with the dark matter one. We examine whether there exist late-time scaling attractors, corresponding to an accelerating universe and possessing dark energy and dark matter densities of the same order. We find that all the examined models, although accepting stable late-time accelerated solutions, cannot alleviate the coincidence problem, unless one imposes a form of fine-tuning in the model parameters. It seems that interacting phantom cosmology cannot fulfill the basic requirement that led to its construction.Comment: 6 figures, use revtex, v2: minor corrections, references added, accepted for publication in JCA

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for colorectal neuroendocrine tumours.

This ENETS guidance paper, developed by a multidisciplinary working group, provides an update on the previous colorectal guidance paper in a different format. Guided by key clinical questions practical advice on the diagnosis and management of neuroendocrine tumours (NET) of the caecum, colon, and rectum is provided. Although covered in one guidance paper colorectal NET comprises a heterogeneous group of neoplasms. The most common rectal NET are often small G1 tumours that can be treated by adequate endoscopic resection techniques. Evidence from prospective clinical trials on the treatment of metastatic colorectal NET is limited and discussion of patients in experienced multidisciplinary tumour boards strongly recommended. Neuroendocrine carcinomas (NEC) and mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN) are discussed in a separate guidance paper

TORCH: A Cherenkov Based Time-of-Flight Detector

TORCH is a novel high-precision time-of-flight detector suitable for large area applications and covering the momentum range up to 10 GeV/c. The concept uses Cherenkov photons produced in a fused silica radiator which are propagated to focussing optics coupled to fast photodetectors. For this purpose, custom MCP-PMTs are being produced in collaboration with industrial partners. The development is divided into three phases. Phase 1 addresses the lifetime requirements for TORCH, Phase 2 will customize the MCP-PMT granularity and Phase 3 will deliver prototypes that meet the TORCH requirements. Phase 1 devices have been successfully delivered and initial tests show stable gain performance for integrated anode current >5 C/cm2 and a single photon time resolution of ≤ 30 ps. Initial simulations indicate the single photon timing resolution of the TORCH detector will be ∼70 ps

The Relationship Between Plasma Flow Doppler Velocities and Magnetic Field Parameters During the Emergence of Active Regions at the Solar Photospheric Level

A statistical study has been carried out of the relationship between plasma flow Doppler velocities and magnetic field parameters during the emergence of active regions at the solar photospheric level with data acquired by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). We have investigated 224 emerging active regions with different spatial scales and positions on the solar disc. The following relationships for the first hours of the emergence of active regions have been analysed: i) of peak negative Doppler velocities with the position of the emerging active regions on the solar disc; ii) of peak plasma upflow and downflow Doppler velocities with the magnetic flux growth rate and magnetic field strength for the active regions emerging near the solar disc centre (the vertical component of plasma flows); iii) of peak positive and negative Doppler velocities with the magnetic flux growth rate and magnetic field strength for the active regions emerging near the limb (the horizontal component of plasma flows); iv) of the magnetic flux growth rate with the density of emerging magnetic flux; v) of the Doppler velocities and magnetic field parameters for the first hours of the appearance of active regions with the total unsigned magnetic flux at the maximum of their development.Comment: 14 pages, 8 figures. The results of article were presented at the ESPM-13 (12-16 September 2011, Rhodes, Greece, Abstract Book p. 102-103, P.4.13, http://astro.academyofathens.gr/espm13/documents/ESPM13_abstract_programme_book.pdf

Nonlinear electrodynamics and CMB polarization

Recently WMAP and BOOMERanG experiments have set stringent constraints on the polarization angle of photons propagating in an expanding universe: $\Delta \alpha = (-2.4 \pm 1.9)^\circ$. The polarization of the Cosmic Microwave Background radiation (CMB) is reviewed in the context of nonlinear electrodynamics (NLED). We compute the polarization angle of photons propagating in a cosmological background with planar symmetry. For this purpose, we use the Pagels-Tomboulis (PT) Lagrangian density describing NLED, which has the form $L\sim (X/\Lambda^4)^{\delta - 1}\; X$, where $X=1/4 F_{\alpha\beta} F^{\alpha \beta}$, and $\delta$ the parameter featuring the non-Maxwellian character of the PT nonlinear description of the electromagnetic interaction. After looking at the polarization components in the plane orthogonal to the ($x$)-direction of propagation of the CMB photons, the polarization angle is defined in terms of the eccentricity of the universe, a geometrical property whose evolution on cosmic time (from the last scattering surface to the present) is constrained by the strength of magnetic fields over extragalactic distances.Comment: 17 pages, 2 figures, minor changes, references adde

Observational constraints on holographic dark energy with varying gravitational constant

We use observational data from Type Ia Supernovae (SN), Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and observational Hubble data (OHD), and the Markov Chain Monte Carlo (MCMC) method, to constrain the cosmological scenario of holographic dark energy with varying gravitational constant. We consider both flat and non-flat background geometry, and we present the corresponding constraints and contour-plots of the model parameters. We conclude that the scenario is compatible with observations. In 1$\sigma$ we find $\Omega_{\Lambda0}=0.72^{+0.03}_{-0.03}$, $\Omega_{k0}=-0.0013^{+0.0130}_{-0.0040}$, $c=0.80^{+0.19}_{-0.14}$ and $\Delta_G\equiv G'/G=-0.0025^{+0.0080}_{-0.0050}$, while for the present value of the dark energy equation-of-state parameter we obtain $w_0=-1.04^{+0.15}_{-0.20}$.Comment: 12 pages, 2 figures, version published in JCA

Non-minimally coupled canonical, phantom and quintom models of holographic dark energy

We investigate canonical, phantom and quintom models, with the various fields being non-minimally coupled to gravity, in the framework of holographic dark energy. We classify them and we discuss their cosmological implications. In particular, we examine the present value of the dark energy equation-of-state parameter and the crossing through the phantom divide, and we extract the conditions for a future cosmological singularity. The combined scenarios are in agreement with observations and reveal interesting cosmological behaviors.Comment: 9 pages, 5 figures, version published in Phys. Lett.