A dedicated photometric system for the detection of Wolf-Rayet stars

We present here tests of a five-filter photometric system aimed at WR classification. In addition to the well-known easy separation between the WN and WC spectral types, these tests indicate interesting potentialities in the discrimination of subgroups among the WN and the WC which look well related to the classical subtypes. The proposed combinations of filters (or derived ones) bear enough discriminating power to satisfy some evolutionary studies in crowded fields where spectroscopic follow-up is not possible.Comment: 10 pages, 7 figures, uses l-aa.sty and psfig for figure inclusion. Also available at http://vela.astro.ulg.ac.be/preprint/P10 Accepted for publication in Astronomy & Astrophysics Supp

Solenoidal Optics

Preliminary studies on neutrino factories se solenoids at di .erent stages. Often quoted is the adiabatic device,a long solenoid with a slowly decreas- ing .eld sed to capture pions behind the target.In cooling sections as well, design reports show lattices using solenoids with alternating .eld to contain the beam.This note describes the transverse behaviour of charged parti- cles in a solenoidal .eld.First,a general description of the magnetic .eld is reviewed with emphasis on particular features,s ch as the canonical momen- tum formalism.Then,a complete study of the adiabatic device is presented, along with tracking simulations based on hamiltonian mechanics.Eventu- ally,the case of solenoidal focusing within the short lens approximation is discussed following either the paraxial ray equation approach or the matrix formalism

Compact star clusters of the LMC HII region N11C

Based on imaging and spectroscopy obtained at the ESO NTT telescope and using an efficient image analysis algorithm, we study the core of the LMC OB association LH13, particularly the two compact stellar clusters Sk-6641 and HNT in the HII, region N11C. We resolve Sk-6641 into 15 components and for the first time the HNT cluster into 70 stars, and derive photometry for the members. Moreover, from medium resolution spectroscopy we determine the spectral types for sixteen stars in N11C. We compare the color-magnitude diagrams of the clusters with that of the field stars and discuss the cluster ages. With an age of ~100 Myr, the HNT cluster appears significantly older than the very young (< 5 Myr) Sk-6641 starburst. We suggest that most of the `field' O-stars in the core of N11C have actually been ejected from Sk-6641 through dynamical interactions in the compact cluster. The properties of the Sk-6641 and HNT clusters suggest that we are viewing different star formation regions lying at different distances along the same line of sight.Comment: 12 pages, 8 figure

Lumen Maintenance and Light Loss Factors: Consequences of Current Design Practices for LED's

Synopsis: Light loss factors are used to help lighting systems meet quantitative design criteria throughout the life of the installation, but they also influence energy use. As the light sources currently being specified continue to evolve, it is necessary to reevaluate the methods used in calculating light loss factors, as well as carefully consider the consequences of different product performance attributes. Because of the unique operating characteristics of LEDs and lack of a comprehensive lifetime rating—as well as the problematic relationship between lifetime and lumen maintenance—determining an appropriate lamp lumen depreciation (LLD) factor for LED products is difficult. As a result, a unique solution has been advocated: when quantity of light is an important design consideration, the IES recommends using an LLD of not greater than 0.70. This method deviates from the typical practice for conventional sources of using the ratio of mean to initial lumen output, and can misrepresent actual performance, increase energy use, and inhibit comparisons between products. This paper discusses the complications related to LLD and LEDs, compares the performance of conventional and LED products, and examines alternatives to a maximum LLD of 0.70 for LEDs

Optimum Optical Systems

The characteristics of complex optical systems required by modern accelerators and storage rings result from the optimization of many variable function, usually of c2-type. The search for the minimum of the function is very sensitive to the initial values of the variables. The route towards a safe determination of the initial conditions is described. First, fully analytical solutions for thin lens models are derived using symbolic computing. Then, for thick lens systems, the equations become transcendent and numerical techniques are applied. It is shown that, under rather general conditions, the optimization converges towards a single solution located in the neighbourhood of the thin lens approximation. The example of betatron matching with a doublet is described, as well as the case of an isochronous periodic structure

The atypical emission-line star Hen3-209

We analyse observations, spanning 15 years, dedicated to the extreme emission-line object Hen3-209. Our photometric data indicate that the luminosity of the star undergoes marked variations with a peak-to-peak amplitude of 0.65mag. These variations are recurrent, with a period of 16.093+-0.005d. The spectrum of Hen3-209 is peculiar with many different lines (HI, HeI, FeII,...) showing P Cygni profiles. The line profiles are apparently changing in harmony with the photometry. The spectrum also contains [OIII] lines that display a saddle profile topped by three peaks, with a maximum separation of about 600km/s. Hen3-209 is most likely an evolved luminous object suffering from mass ejection events and maybe belonging to a binary system.Comment: 6p, 5 fig, accepted for publication in MNRAS (www.blackwell-synergy.com

Electron beam combination by RF deflectors: Tolerance and requirements

In the framework of the new Compact Linear Collider (CLIC) Test Facility CTF3, it is planned to perform a demonstration of the bunch frequency multiplication process on which the CLIC drive beam generation scheme is based. This process relies on the combination of electron bunch trains in isochronous rings using RF deflecting cavities. Specific requirements are imposed on both the beam characteristics and the RF amplitude and phase in the deflectors. In this paper, we study and specify these requirements in the case of the Preliminary Phase of CTF3

Transverse collection of pions

The early stages of a neutrino factory are critical to fulfil physics requirements in the final muon storage ring. The transverse collection of pions behind the target is therefore a crucial feature for which different options exist. In this article, two collection systems using either quadrupoles or a transition solenoid between the target and the downstream channel are studied. The transition optics from the solenoid to a quadrupole channel is also discussed. Some figures of merit such as maximum transverse momentum captured or radial acceptance are compared as well as the technical challenges for each solution

Collagen V Promotes Fibroblast Contractility, And Adhesion Formation, And Stability

Ehlers-Danlos syndrome, classical type, (cEDS) is a hereditary connective tissue disorder causing excessive elasticity and fragility of the connective tissue and problems with wound healing. Most cases of cEDS are caused by haploinsufficiency for collagen V. Collagen V regulates collagen fibril diameter. In cEDS fibroblast migration is impaired and integrin expression is altered. The effects of collagen V on collagen gel ultrastructure and how it alters its mechanical properties were measured using scanning electron microscopy (SEM) and rheology respectively. Fibroblast contractility and adhesion dynamics were investigated to better understand the role of fibroblast disfunction in wound healing in cEDS. To quantify these, traction force microscopy (TFM) and time lapse imaging were used. Collagen V decreased fibril diameter and curvature, and increased gel stiffness, indicating that the fibrils themselves were likely stiffer. Cells cultured on collagen V were more contractile and adhesions assembled faster