9,012 research outputs found
Star Formation and Relaxation in 379 Nearby Galaxy Clusters
We investigate the relationship between star formation (SF) and level of
relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the
Sloan Digital Sky Survey to measure cluster membership and level of relaxation,
and to select star-forming galaxies based on mid-infrared emission detected
with the Wide-Field Infrared Survey Explorer. For galaxies with absolute
magnitudes M_r < -19.5, we find an inverse correlation between SF fraction and
cluster relaxation: as a cluster becomes less relaxed, its SF fraction
increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed
clusters (0.117 +/- 0.003) is higher than that in all relaxed clusters (0.097
+/- 0.005). We verify the validity of our SF calculation methods and membership
criteria through analysis of previous work. Our results agree with previous
findings that a weak correlation exists between cluster SF and dynamical state,
possibly because unrelaxed clusters are less evolved relative to relaxed
clusters.Comment: 6 pages, 4 figures, accepted for publication in Ap
Star Formation and Substructure in Galaxy Clusters
We investigate the relationship between star formation (SF) and substructure
in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky
Survey (SDSS). Several past studies of individual galaxy clusters have
suggested that cluster mergers enhance cluster SF, while others find no such
relationship. The SF fraction in multi-component clusters (0.228 +/- 0.007) is
higher than that in single-component clusters (0.175 +/- 0.016) for galaxies
with M^0.1_r < -20.5. In both single- and multi-component clusters, the
fraction of star-forming galaxies increases with clustercentric distance and
decreases with local galaxy number density, and multi-component clusters show a
higher SF fraction than single-component clusters at almost all clustercentric
distances and local densities. Comparing the SF fraction in individual clusters
to several statistical measures of substructure, we find weak, but in most
cases significant at greater than 2 sigma, correlations between substructure
and SF fraction. These results could indicate that cluster mergers may cause
weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit
slightly stronger SF due to their less evolved states relative to relaxed
clusters.Comment: 10 pages, 6 figures, accepted for publication in Ap
High-Resolution Imaging and Optical Control of Bose-Einstein Condensates in an Atom Chip Magnetic Trap
A high-resolution projection and imaging system for ultracold atoms is
implemented using a compound silicon and glass atom chip. The atom chip is
metalized to enable magnetic trapping while glass regions enable high numerical
aperture optical access to atoms residing in the magnetic trap about 100
microns below the chip surface. The atom chip serves as a wall of the vacuum
system, which enables the use of commercial microscope components for
projection and imaging. Holographically generated light patterns are used to
optically slice a cigar-shaped magnetic trap into separate regions; this has
been used to simultaneously generate up to four Bose-condensates. Using
fluorescence techniques we have demonstrated in-trap imaging resolution down to
2.5 micronsComment: 4 pages, 5 figures, 12 reference
Variability of Objectively Measured Sedentary Behavior
The primary purpose of this study was to evaluate variability of sedentary behavior (SB) throughout a 7-d measurement period and to determine if G7 d of SB measurement would be comparable with the typical 7-d measurement period. Methods: Retrospective data from Ball State University_s Clinical Exercise Physiology Laboratory on 293 participants (99 men, 55 T 14 yr, body mass index = 29 T 5 kgImj2; 194 women, 51 T 12 yr, body mass index = 27 T 7 kgImj2) with seven consecutive days of data collected with ActiGraph accelerometers were analyzed (ActiGraph, Fort Walton Beach, FL). Time spent in SB (either G100 counts per minute or G150 counts per minute) and breaks in SB were compared between days and by sex using a two-way repeated-measures ANOVA. Stepwise regression was performed to determine if G7 d of SB measurement were comparable with the 7-d method, using an adjusted R2 of Q0.9 as a criterion for equivalence. Results: There were no differences in daily time spent in SB between the 7 d for all participants. However, there was a significant interaction between sex and days, with women spending less time in SB on both Saturdays and Sundays than men when using the 100 counts per minute cut-point. Stepwise regression showed using any 4 d would be comparable with a 7-d measurement (R2 9 0.90). Conclusions: When assessed over a 7-d measurement period, SB appears to be very stable from day to day, although there may be some small differences in time spent in SB and breaks in SB between men and women, particularly on weekend days. The stepwise regression analysis suggests that a measurement period as short as 4 d could provide comparable data (91% of variance) with a 1-wk assessment. Shorter assessment periods would reduce both researcher and subject burden in data collection
Quantum Cryptography Approaching the Classical Limit
We consider the security of continuous-variable quantum cryptography as we
approach the classical-limit, i.e., when the unknown preparation noise at the
sender's station becomes significantly noisy or thermal (even by as much as
10,000 times the variance of the vacuum mode). We show that, provided the
channel transmission losses do not exceed 50%, the security of quantum
cryptography is not dependent on the channel transmission, and is therefore,
incredibly robust against significant amounts of excess preparation noise. We
extend these results to consider for the first time quantum cryptography at
wavelengths considerably longer than optical and find that regions of security
still exist all the way down to the microwave.Comment: Letter (4 pages) followed by appendix (4 pages). Updated from
published version with some minor correction
Botulinum toxin-A for the treatment of overactive bladder: UK contributions
Background: Botulinum toxin-A (BoNT/A) is now established second-line management for refractory overactivebladder (OAB) and recognised in many incontinence guidelines and pathways. For those with neurogenic detrusoroveractivity secondary to spinal cord injury or multiple sclerosis, the toxin is currently licensed in certain parts of theworld, including the UK. It is an effective treatment in those in whom antimuscarinics and conservative measures havefailed who have symptoms of OAB and or detrusor overactivity (DO). Methods: Treatment can be given in an outpatient setting and can be administered under local anaesthesia. Its efficacylasts for between six and 12 months. Results: It has an acceptable safety profile with the biggest risk being urinary tract infection and difficulty emptying thebladder, necessitating clean intermittent self-catheterisation (CISC). Medium-term follow-up suggests repeated injectionsare also safe and efficacious. Conclusions: The mechanism of action of the toxin is more complicated than originally thought, and it seems likelythat it affects motor and sensory nerves of the bladder. In the last 10 years much of the progress of this treatment fromearly experimental trials to mainstream clinical use, and a better understanding of how it works in the bladder, are as aresult of research conducted in the UK. This review summarises the significant and substantial evidence for BoNT/A totreat refractory OAB from UK centres. © British Association of Urological Surgeons 2013
Quantum private queries
We propose a cheat sensitive quantum protocol to perform a private search on
a classical database which is efficient in terms of communication complexity.
It allows a user to retrieve an item from the server in possession of the
database without revealing which item she retrieved: if the server tries to
obtain information on the query, the person querying the database can find it
out. Furthermore our protocol ensures perfect data privacy of the database,
i.e. the information that the user can retrieve in a single queries is bounded
and does not depend on the size of the database. With respect to the known
(quantum and classical) strategies for private information retrieval, our
protocol displays an exponential reduction both in communication complexity and
in running-time computational complexity.Comment: 4 pages, 1 figur
Collisional Transfer of Population and Orientation in NaK
We report current work to study transfer of population and orientation in collisions of NaK molecules with argon and potassium atoms using polarization labeling (PL) and laser- induced fluorescence (LIF) spectroscopy. In the PL experiment, a circularly polarized pump laser excites a specific NaK A1Σ +(v 0=16, J 0 ) ← X1Σ +(v 00=0, J 0 ± 1) transition, creating an orientation (non-uniform MJ0 level distribution) in both levels. The linearly polarized probe laser is scanned over various 31Π(v, J 0±1) ← A1Σ +(v 0=16, J 0 ) transitions. The probe laser passes through a crossed linear polarizer before detection, and signal is recorded if the probe laser polarization has been modified by the vapor (which occurs when it comes into resonance with an oriented level). Using both spectroscopic methods, analysis of weak collisional satellite lines adjacent to these directly populated lines, as a function of argon buffer gas pressure and cell temperature, allows us to discern separately the effects collisions with argon atoms and potassium atoms have on the population and orientation of the molecule. In addition, code has been written which provides a theoretical analysis of the process, through a solution of the density matrix equations of motion for the system
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