Noves tècniques per estudiar la cromatina

En el nucli de les cèl·lules el DNA no està lliure, es troba associat amb unes proteïnes bàsiques molt abundoses que s'anomenen histones. El complex resultant és la cromatina. Mitjançant una tècnica microscòpica que permet visualitzar les mostres en el seu entorn aquós natural, investigadors de la UAB han trobat que la cromatina en les condicions iòniques corresponents a la interfase del cicle cel·lular és molt més compacta del que es considera actualment en molts altres laboratoris.En el núcleo de las células el ADN no está libre, se encuentra asociado con unas proteínas básicas muy abundantes que se denominan histonas. El complejo resultante es la cromatina. Mediante una técnica microscópica que permite visualizar las muestras en su entorno acuoso natural, investigadores de la UAB han encontrado que la cromatina en las condiciones iónicas correspondientes a la interfase del ciclo celular es mucho más compacta de lo que se considera actualmente en muchos otros laboratorios

Apodized Lyot Coronagraph for VLT-SPHERE: Laboratory tests and performances of a first prototype in the visible

We present some of the High Dynamic Range Imaging activities developed around the coronagraphic test-bench of the Laboratoire A. H. Fizeau (Nice). They concern research and development of an Apodized Lyot Coronagraph (ALC) for the VLT-SPHERE instrument and experimental results from our testbed working in the visible domain. We determined by numerical simulations the specifications of the apodizing filter and searched the best technological process to manufacture it. We present the results of the experimental tests on the first apodizer prototype in the visible and the resulting ALC nulling performances. The tests concern particularly the apodizer characterization (average transmission radial profile, global reflectivity and transmittivity in the visible), ALC nulling performances compared with expectations, sensitivity of the ALC performances to misalignments of its components

Les proteïnes específiques dels nuclis en els espermatozoides dels mol.luscs

El present treball revisa els estudis efectuats sobre les proteïnes bàsiques específiques en els nuclis espermàtics dels mol·luscs. En la primera part (Característiques de les SBP) fem un repàs de la informació disponible, mentre que en la segona part (Aspectes evolutius de les molècules i de la seva funció) intentem expressar una visió integrada de tals proteïnes i de llurs possibles relacions evolutives

Photometric quality of Dome C for the winter 2008 from ASTEP South

ASTEP South is an Antarctic Search for Transiting Exo- Planets in the South pole field, from the Concordia station, Dome C, Antarctica. The instrument consists of a thermalized 10 cm refractor observing a fixed 3.88\degree x 3.88\degree field of view to perform photometry of several thousand stars at visible wavelengths (700-900 nm). The first winter campaign in 2008 led to the retrieval of nearly 1600 hours of data. We derive the fraction of photometric nights by measuring the number of detectable stars in the field. The method is sensitive to the presence of small cirrus clouds which are invisible to the naked eye. The fraction of night-time for which at least 50% of the stars are detected is 74% from June to September 2008. Most of the lost time (18.5% out of 26%) is due to periods of bad weather conditions lasting for a few days ("white outs"). Extended periods of clear weather exist. For example, between July 10 and August 10, 2008, the total fraction of time (day+night) for which photometric observations were possible was 60%. This confirms the very high quality of Dome C for nearly continuous photometric observations during the Antarctic winter

Thermalizing a telescope in Antarctica: Analysis of ASTEP observations

The installation and operation of a telescope in Antarctica represent particular challenges, in particular the requirement to operate at extremely cold temperatures, to cope with rapid temperature fluctuations and to prevent frosting. Heating of electronic subsystems is a necessity, but solutions must be found to avoid the turbulence induced by temperature fluctua- tions on the optical paths. ASTEP 400 is a 40 cm Newton telescope installed at the Concordia station, Dome C since 2010 for photometric observations of fields of stars and their exoplanets. While the telescope is designed to spread star light on several pixels to maximize photometric stability, we show that it is nonetheless sensitive to the extreme variations of the seeing at the ground level (between about 0.1 and 5 arcsec) and to temperature fluctuations between --30 degrees C and --80 degrees C. We analyze both day-time and night-time observations and obtain the magnitude of the seeing caused by the mirrors, dome and camera. The most important effect arises from the heating of the primary mirror which gives rise to a mirror seeing of 0.23 arcsec K--1 . We propose solutions to mitigate these effects.Comment: Appears in Astronomical Notes / Astronomische Nachrichten, Wiley-VCH Verlag, 2015, pp.1-2

A Successful TOD Will Reinforce Both The Community & The Transit System?

The three cases of transit-oriented development (TOD) were selected either because they represent comparable rail station types (and/or physical settings) or because certain types of implementation tools were used to make transit-oriented development happen. In looking for comparable examples of TOD in Perth City, specific station area characteristics were evaluated: • whether the station is underground, at-grade or elevated • how many people use the station • surrounding urban form and land us, and, • other transportation connections that are provided This paper presents detailed case studies of representative TOD projects throughout Perth. The experiences of transit operators, and local authorities, with TOD will help Perth establish a planning framework and to take action toward station-area development. This paper provides background for the case studies by defining transit-oriented development, describing the methodology for choosing the specific case study areas and establishing the framework for analysing individual station areas. This analysis of TOD case studies looks at a variety of transit operators and suburban station types throughout Perth. Although the case studies make reference to many exemplary station-area projects within the transit corridors served the following stations are reviewed in the most detail: 1. Esplanade 2. Murdoch 3. Cockburn Central The selected stations are located in dense urban areas, with limited provision for parking and ride, consistent with the proposed characteristics of Perth’s transit system.Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne