Carbon coating of the SPS dipole chambers

The Electron Multipacting (EM) phenomenon is a limiting factor for the achievement of high luminosity in accelerators for positively charged particles and for the performance of RF devices. At CERN, the Super Proton Synchrotron (SPS) must be upgraded in order to feed the Large Hadron Collider (LHC) with 25 ns bunch spaced beams. At such small bunch spacing, EM may limit the performance of the SPS and consequently that of the LHC. To mitigate this phenomenon CERN is developing a carbon thin film coating with low Secondary Electron Yield (SEY) to coat the internal walls of the SPS dipoles beam pipes. This paper presents the progresses in the coating technology, the performance of the carbon coatings and the strategy for a large scale production.Comment: 7 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.141-14

Detection of a variable ultra-fast outflow in the Narrow Line Seyfert 1 galaxy PG 1448+273

Relativistically blueshifted absorption features of highly ionised ions, the so-called ultra-fast outflows (UFOs), have been detected in the X-ray spectra of a number of accreting supermassive black holes. If these features truly originate from accretion disc winds accelerated to more than 10 per cent of the speed of light, their energy budget is very significant and they can contribute to or even drive galaxy-scale feedback from active galactic nuclei (AGN). However, the UFO spectral features are often weak due to high ionisation of the outflowing material, and the inference of the wind physical properties can be complicated by other spectral features in AGN such as relativistic reflection. Here we study a highly accreting Narrow Line Seyfert 1 galaxy PG 1448+273. We apply an automated, systematic routine for detecting outflows in accreting systems and achieve an unambiguous detection of a UFO in this AGN. The UFO absorption is observed in both soft and hard X-ray bands with the XMM-Newton observatory. The velocity of the outflow is (26900 +- 600) km/s (~0.09c), with an ionisation parameter of log ({\xi} / erg cm s^-1)=4.03_{-0.08}^{+0.10} and a column density above 10^23 cm^-2. At the same time, we detect weak warm absorption features in the spectrum of the object. Our systematic outflow search suggests the presence of further multi-phase wind structure, but we cannot claim a significant detection considering the present data quality. The UFO is not detected in a second, shorter observation with XMM-Newton, indicating variability in time, observed also in other similar AGN.Comment: Accepted for publication in MNRAS. 14 pages, 11 figures, 1 tabl

Bifurcation analysis of the twist-Freedericksz transition in a nematic liquid-crystal cell with pre-twist boundary conditions

Motivated by a recent investigation of Millar and McKay [Mol. Cryst. Liq. Cryst., 435, 277/[937]-286/[946] (2005)], we study the magnetic field twist-Fr´eedericksz transition for a nematic liquid crystal of positive diamagnetic anisotropy with strong anchoring and pre- twist boundary conditions. Despite the pre-twist, the system still possesses Z2 symmetry and a symmetry-breaking pitchfork bifurcation, which occurs at a critical magnetic-field strength that, as we prove, is above the threshold for the classical twist-Fr´eedericksz tran- sition (which has no pre-twist). It was observed numerically by Millar and McKay that this instability occurs precisely at the point at which the ground-state solution loses its monotonicity (with respect to the position coordinate across the cell gap). We explain this surprising observation using a rigorous phase-space analysis

Effective action in DSR1 quantum field theory

We present the one-loop effective action of a quantum scalar field with DSR1 space-time symmetry as a sum over field modes. The effective action has real and imaginary parts and manifest charge conjugation asymmetry, which provides an alternative theoretical setting to the study of the particle-antiparticle asymmetry in nature.Comment: 8 page

Probing BH mass and accretion through X-ray variability in the CDFS

Recent work on nearby AGNs has shown that X-ray variability is correlated with the mass and accretion rate onto the central SMBH. Here we present the application of the variability-luminosity relation to high redshift AGNs in the CDFS, making use of XMM-Newton observations. We use Monte Carlo simulations in order to properly account for bias and uncertainties introduced by the sparse sampling and the very low statistics. Our preliminary results indicate that BH masses span over the range from 10^5 to 10^9 solar mass while accretion rates range from 10^-3 up to values greater than 1, in unit of Eddington accretion rate.Comment: 2 pages, 2 figures,in press in the X-ray 2009 Conference Proceedings (Bologna, 7-11 September 2009

Easy and accurate estimation of grapevine leaf area with simple mathematical models

Empirical models for non-destructive estimation of primary and lateral leaf area are presented for cv. Aragonez, syn. Tempranillo. Primary leaf area of shoots is estimated by a model using a calculated variable obtained from the average of the largest and smallest primary leaf area multiplied by the number of primary leaves. For lateral leaf area estimation another model is presented which uses the same type of calculated variable plus the area of the largest leaf. Both models explain a high proportion of the leaf area variability and have a good predicting capability. Validation with 4 independent data sets periodically sampled during several seasons from different varieties shows that these models can predict primary and lateral leaf area independently of variety, year and growth stage, using a non-destructive, low cost, simple and accurate method. The models represent a powerful tool for grapevine research, for consultants and advanced growers allowing the evaluation of leaf area more frequently.

VESTIBULAR SYMPTOMS IN WORKERS EXPOSED TO OCCUPATIONAL NOISE IN A MATCHES COMPANY

Objective: To determine vestibular disorders in workers of a matches company, and identify the main risks associated with the development of these symptoms. Methods: The work included two groups: the experimental constituting the workers who were exposed to chronic occupational noise, and the control group corresponding to the administrative staff which were not exposed to occupational noise. The Irvine questionnaire  developed by the by Department of Otolaryngology at the University of California, and the Dizziness Questionnaire developed by the Center for Audio and Balance from the University of Maryland were used to evaluate the prevalence of vestibular symptoms. Tone audiometric evaluations were performed to all individuals in the population.Results: In the experimental group 9.7% of the employees showed hearing loss or acoustic trauma in both ears. In the control group 5.5% of the employees showed mild hearing loss. 60 % of the employees have any symptoms associated with a vestibular disorder either by noise or exposure (experimental group) to ergonomic risk factors (administrative staff).Conclusions: The prevalence of vestibular symptoms in individuals of the experimental group could be associated with exposure to occupational noise ≥ 85 decibels (dBA). The questionnaires are important tools because they could prevent occupational hearing loss and it does not involve onerous economic cost for the company. Questionnaires could be used in any type of business from craftwork to industrial plants. Keywords: Vestibular symptoms; Noise; safety and occupational health

A power management strategy for a stand-alone photovoltaic/fuel cell energy system for a 1kW application

In this paper a power management strategy is presented for a stand-alone photovoltaic (PV)/fuel cell (FC) energy system. PV is the primary power source of the system and an FC-electrolyzer combination is used as a backup and a long-term storage system. The energy in the hybrid system is balanced by the common dc bus voltage regulation. A simple hysteresis voltage control is used for dc bus voltage regulation. In this way, the fuel cell and the electrolyzer can be protected from unnecessary utilization or irregular operation (reduction of frequent start-ups and shutdowns). Simulation results obtained using Matlab and Simulink are presented to verify the effectiveness of the proposed control algorithm