122 research outputs found
Quasicondensation reexamined
We study in detail the effect of quasicondensation. We show that this effect
is strictly related to dimensionality of the system. It is present in one
dimensional systems independently of interactions - exists in repulsive,
attractive or in non-interacting Bose gas in some range of temperatures below
characteristic temperature of the quantum degeneracy. Based on this observation
we analyze the quasicondensation in terms of a ratio of the two largest
eigenvalues of the single particle density matrix for the ideal gas. We show
that in the thermodynamic limit in higher dimensions the second largest
eigenvalue vanishes (as compared to the first one) with total number of
particles as whereas goes to zero only logarithmically in
one dimension. We also study the effect of quasicondensation for various
geometries of the system: from quasi-1D elongated one, through spherically
symmetric 3D case to quasi-2D pancake-like geometry
Statistical properties of one dimensional attractive Bose gas
Using classical field approximation we present the first study of statistical
properties of one dimensional Bose gas with attractive interaction. The
canonical probability distribution is generated with the help of a Monte Carlo
method. This way we obtain not only the depletion of the condensate with
growing temperature but also its fluctuations. The most important is our
discovery of a reduced coherence length, the phenomenon observed earlier only
for the repulsive gas, known as quasicondensation.Comment: 4 pages, 4 figure
Star forming galaxies in the AKARI deep field south : identifications and spectral energy distributions
Aims. We investigate the nature and properties of far-infrared (FIR)
sources in the AKARI deep field south (ADF-S).
Methods. We performed an extensive search for the counterparts to 1000Â ADF-S objects brighter than 0.0301Â Jy in the WIDE-S (90Â ÎŒm)
AKARI band in the public databases (NED and SIMBAD). We analyzed the properties of the resulting sample: statistics of the identified objects, quality of position determination of the ADF-S sources, their number counts, redshift distribution, and comparison of morphological types, when the corresponding information was available. We performed a simplifield analysis of the clustering properties of the ADF-S sources and compliled spectral energy distributions (SEDs) of objects with the highest quality photometry, using three different models.
Results. Among 1000Â investigated ADF-S sources, 545 were identified with sources at other wavelengths in public databases. From them, 518 are known galaxies and 343 of these were previously known as infra-red sources. Among the remaining sources, there are two quasars and both infrared and radio sources of unknown origin. Among six stellar identifications, at least five are probably the effect of contamination. We measured the redshifts of 48Â extragalactic objects and determined the morphological types of 77Â galaxies. We present SED models of 47Â sources with sufficiently good photometric data.
Conclusions. We conclude that the bright FIR point sources observed in the ADF-S are mostly nearby galaxies. Their properties are very similar to the properties of the local population of optically bright galaxies, except for unusually high ratio of peculiar or interacting objects and a lower percentage of elliptical galaxies. The percentage of lenticular galaxies is the same as in the optically bright population, which suggests that galaxies of this type may frequently contain a significant amount of cool dust. It is possible that source confusion plays a significant role in more than 34% of measurements. The SEDs correspond to a variety of galaxy types, from very actively star forming to very quiescent. The AKARI long wavelength bands data have enabled us to determine for the first time that these galaxies are objects with very cool dust
Isthmus Dependent Atrial Flutter Cycle Length Correlates with Right Atrial Cross-Sectional Area
Background: Right atrial flutter cycle length can prolong in the presence of antiarrhythmic drug therapy. We hypothesized that the cycle length of right atrial isthmus dependent flutter would correlate with right atrial cross-sectional area measurements. Methods: 60 patients who underwent ablation for electrophysiologically proven isthmus dependent right atrial flutter, who were not on Class I or Class III antiarrhythmic drugs and had recent 2-dimensional echocardiographic data comprised the study group. Right atrial length and width were measured in the apical four chamber view. Cross-sectional area was estimated by multiplying the length and width. 35 patients had an atrial flutter rate â„250 bpm (Normal Flutter Group) and 25 patients had an atrial flutter rate < 250 bpm (Slow Flutter Group). Results: Mean atrial flutter rate was 283 bpm in the normal flutter group and 227 bpm in the slow flutter group. Mean atrial flutter cycle length was 213 ms in the Normal Flutter Group and 265 ms in the Slow Flutter Group (p<0.0001). Mean right atrial cross sectional area was 1845 mm2 in the Normal Flutter group and 2378 mm2 in the Slow Flutter Group, (p< 0.0001). Using linear regression, CSA was a significant predictor of cycle length (ÎČ =0.014 p = 0.0045). For every 1 mm2 increase in cross-sectional area, cycle length is 0.014 ms longer.Conclusion: In the absence of antiarrhythmic medications, right atrial cross sectional area enlargement correlates with atrial flutter cycle length. These findings provide further evidence that historical rate-related definitions of typical isthmus dependent right atrial are not mechanistically valid
Clinical and diagnostic features of Bartter and Gitelman syndromes
Background: Bartter and Gitelman syndromes are autosomal recessive disorders of renal tubular salt handling. Due to their rarity, limited long-term data are available to inform prognosis and management. / Methods: Long-term longitudinal data were analysed for 45 children with pathogenic variants in SLC12A1 (n = 8), KCNJ1 (n = 8), CLCNKB (n = 17), BSND (n = 2) and SLC12A3 (n = 10) seen at a single centre between 1984 and 2014. Median follow-up was 8.9 [interquartile range (IQR) 0.7â18.1]âyears. / Results: Polyhydramnios and prematurity were seen in children with SLC12A1 and KCNJ1 mutations. Patients with CLCNKB mutations had the lowest serum potassium and serum magnesium and the highest serum bicarbonate levels. Fractional excretion of chloride was >0.5% in all patients prior to supplementation. Nephrocalcinosis at presentation was present in the majority of patients with SLC12A1 and KCNJ1 mutations, while it was only present in one patient with CLCNKB and not in SLC12A3 or BSND mutations. Growth was impaired, but within the normal range (median height standard deviation score â1.2 at the last follow-up). Impaired estimated glomerular filtration rate (eGFR <90âmL/min/1.73 m2) at the last follow-up was seen predominantly with SLC12A1 [71âmL/min/1.73 m2 (IQR 46â74)] and KCNJ1 [62âmL/min/1.73 m2 (IQR 48â72)] mutations. Pathological albuminuria was detected in 31/45 children. / Conclusions: Patients with Bartter and Gitelman syndromes had a satisfactory prognosis during childhood. However, decreased eGFR and pathologic proteinuria was evident in a large number of these patients, highlighting the need to monitor glomerular as well as tubular function. Electrolyte abnormalities were most severe in CLCNKB mutations both at presentation and during follow-up. Fractional excretion of chloride prior to supplementation is a useful screening investigation in children with hypokalaemic alkalosis to establish renal salt wasting
Implementing a Fast Unbounded Quantum Fanout Gate Using Power-Law Interactions
The standard circuit model for quantum computation presumes the ability to
directly perform gates between arbitrary pairs of qubits, which is unlikely to
be practical for large-scale experiments. Power-law interactions with strength
decaying as in the distance provide an experimentally
realizable resource for information processing, whilst still retaining
long-range connectivity. We leverage the power of these interactions to
implement a fast quantum fanout gate with an arbitrary number of targets. Our
implementation allows the quantum Fourier transform (QFT) and Shor's algorithm
to be performed on a -dimensional lattice in time logarithmic in the number
of qubits for interactions with . As a corollary, we show that
power-law systems with are difficult to simulate classically
even for short times, under a standard assumption that factoring is classically
intractable. Complementarily, we develop a new technique to give a general
lower bound, linear in the size of the system, on the time required to
implement the QFT and the fanout gate in systems that are constrained by a
linear light cone. This allows us to prove an asymptotically tighter lower
bound for long-range systems than is possible with previously available
techniques.Comment: 6 pages, 1 figur
Exaggerated increase of exercise-induced pulmonary artery pressure in systemic sclerosis patients predominantly results from left ventricular diastolic dysfunction
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