162 research outputs found
New Neighbours: Modelling the Growing Population of Gamma-ray Millisecond Pulsars
The Fermi Large Area Telescope, in collaboration with several groups from the
radio community, have had marvellous success at uncovering new gamma-ray
millisecond pulsars (MSPs). In fact, MSPs now make up a sizable fraction of the
total number of known gamma-ray pulsars. The MSP population is characterized by
a variety of pulse profile shapes, peak separations, and radio-to-gamma phase
lags, with some members exhibiting nearly phase-aligned radio and gamma-ray
light curves (LCs). The MSPs' short spin periods underline the importance of
including special relativistic effects in LC calculations, even for emission
originating from near the stellar surface. We present results on modelling and
classification of MSP LCs using standard pulsar model geometries.Comment: 4 pages, 2 figures, proceedings of the ICREA Workshop on The
High-Energy Emission from Pulsars and their Systems (HEEPS), Sant Cugat,
Spai
Fermi Large Area Telescope observations of PSR J1836+5925
The discovery of the gamma-ray pulsar PSR J1836+5925, powering the formerly
unidentified EGRET source 3EG J1835+5918, was one of the early accomplishments
of the Fermi Large Area Telescope (LAT). Sitting 25 degrees off the Galactic
plane, PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8
million years, a spindown luminosity of 1.1 erg s, and a
large off-peak emission component, making it quite unusual among the known
gamma-ray pulsar population. We present an analysis of one year of LAT data,
including an updated timing solution, detailed spectral results and a long-term
light curve showing no indication of variability. No evidence for a surrounding
pulsar wind nebula is seen and the spectral characteristics of the off-peak
emission indicate it is likely magnetospheric. Analysis of recent XMM
observations of the X-ray counterpart yields a detailed characterization of its
spectrum, which, like Geminga, is consistent with that of a neutron star
showing evidence for both magnetospheric and thermal emission.Comment: Accepted to Astrophysical Journa
Ultrasensitive gold micro-structured electrodes enabling the detection of extra-cellular long-lasting potentials in astrocytes populations
Ultra-sensitive electrodes for extracellular recordings were fabricated and electrically characterized. A signal detection limit defined by a noise level of 0.3-0.4 mu V for a bandwidth of 12.5 Hz was achieved. To obtain this high sensitivity, large area (4 mm(2)) electrodes were used. The electrode surface is also micro-structured with an array of gold mushroom-like shapes to further enhance the active area. In comparison with a flat gold surface, the micro-structured surface increases the capacitance of the electrode/electrolyte interface by 54%. The electrode low impedance and low noise enable the detection of weak and low frequency quasi-periodic signals produced by astrocytes populations that thus far had remained inaccessible using conventional extracellular electrodes. Signals with 5 mu V in amplitude and lasting for 5-10 s were measured, with a peak-to-peak signal-to-noise ratio of 16. The electrodes and the methodology developed here can be used as an ultrasensitive electrophysiological tool to reveal the synchronization dynamics of ultra-slow ionic signalling between non-electrogenic cells.Portuguese Foundation for Science and Technology (FCT), through the project "Implantable organic devices for advanced therapies" (INNOVATE) [PTDC/EEI-AUT/5442/2014]; Instituto de Telecomunicacoes [UID/Multi/04326/2013]; Associated Laboratory - Institute of Nanoscience and Nanotechnology [POCI-01-0145-FEDER-016623]; [PTDC/CTM-NAN/3146/2014
Binary and Millisecond Pulsars at the New Millennium
We review the properties and applications of binary and millisecond pulsars.
Our knowledge of these exciting objects has greatly increased in recent years,
mainly due to successful surveys which have brought the known pulsar population
to over 1300. There are now 56 binary and millisecond pulsars in the Galactic
disk and a further 47 in globular clusters. This review is concerned primarily
with the results and spin-offs from these surveys which are of particular
interest to the relativity community.Comment: 59 pages, 26 figures, 5 tables. Accepted for publication in Living
Reviews in Relativity (http://www.livingreviews.org
Binary and Millisecond Pulsars
We review the main properties, demographics and applications of binary and
millisecond radio pulsars. Our knowledge of these exciting objects has greatly
increased in recent years, mainly due to successful surveys which have brought
the known pulsar population to over 1700. There are now 80 binary and
millisecond pulsars associated with the disk of our Galaxy, and a further 103
pulsars in 24 of the Galactic globular clusters. Recent highlights have been
the discovery of the first ever double pulsar system and a recent flurry of
discoveries in globular clusters, in particular Terzan 5.Comment: 77 pages, 30 figures, available on-line at
http://www.livingreviews.org/lrr-2005-
Lighting Up Clostridium Difficile: Reporting Gene Expression Using Fluorescent Lov Domains
The uses of fluorescent reporters derived from green fluorescent protein have proved invaluable for the visualisation of biological processes in bacteria grown under aerobic conditions. However, their requirement for oxygen has limited their application in obligate anaerobes such as Clostridium difficile. Fluorescent proteins derived from Light, Oxygen or Voltage sensing (LOV) domains have been shown to bridge this limitation, but their utility as translational fusions to monitor protein expression and localisation in a strict anaerobic bacterium has not been reported. Here we demonstrate the utility of phiLOV in three species of Clostridium and its application as a marker of real-time protein translation and dynamics through genetic fusion with the cell division protein, FtsZ. Time lapse microscopy of dividing cells suggests that Z ring assembly arises through the extension of the FtsZ arc starting from one point on the circumference. Furthermore, through incorporation of phiLOV into the flagella subunit, FliC, we show the potential of bacterial LOV-based fusion proteins to be successfully exported to the extracellular environment
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