1,545 research outputs found
A comparison of different cluster mass estimates: consistency or discrepancy ?
Rich and massive clusters of galaxies at intermediate redshift are capable of
magnifying and distorting the images of background galaxies. A comparison of
different mass estimators among these clusters can provide useful information
about the distribution and composition of cluster matter and their dynamical
evolution. Using a hitherto largest sample of lensing clusters drawn from
literature, we compare the gravitating masses of clusters derived from the
strong/weak gravitational lensing phenomena, from the X-ray measurements based
on the assumption of hydrostatic equilibrium, and from the conventional
isothermal sphere model for the dark matter profile characterized by the
velocity dispersion and core radius of galaxy distributions in clusters. While
there is an excellent agreement between the weak lensing, X-ray and isothermal
sphere model determined cluster masses, these methods are likely to
underestimate the gravitating masses enclosed within the central cores of
clusters by a factor of 2--4 as compared with the strong lensing results. Such
a mass discrepancy has probably arisen from the inappropriate applications of
the weak lensing technique and the hydrostatic equilibrium hypothesis to the
central regions of clusters as well as an unreasonably large core radius for
both luminous and dark matter profiles. Nevertheless, it is pointed out that
these cluster mass estimators may be safely applied on scales greater than the
core sizes. Namely, the overall clusters of galaxies at intermediate redshift
can still be regarded as the dynamically relaxed systems, in which the velocity
dispersion of galaxies and the temperature of X-ray emitting gas are good
indicators of the underlying gravitational potentials of clusters.Comment: 16 pages with 7 PS figures, MNRAS in pres
Application of RetCamâ…ˇ in the screening of neonatal fundus disease
AIM: To investigate the safe and reliable examination method for neonatal fundus screening.<p>METHODS: Fundus information of 2 836 neonates performed by RetCamâ…ˇ in our hospital from January 1, 2012 to December 31, 2012 were retrospectively analyzed, including 1 625 cases(57.30%)of premature infants which were first examined 1-4 weeks after birth and 1 211 cases(42.70%)of term infants which were first examined within 4 weeks after birth.<p>RESULTS: Totally 454 cases of abnormalfundus were found, including 207 cases(12.74%)of retinopathy of prematurity(ROP), ROPâ… in 118 cases(57%), ROPâ…ˇ in 58 cases(28.02%), ROPâ…˘ in 23 cases(11.11%), ROPâ…Ł in 8 cases(3.86%), no case of ROPV. A total of 247(20.40%)term infants had abnormal fundus, of which 68 cases(27.53%)were developmental or hereditary disease, retinoblastoma in 1 case(0.40%), retinal hemorrhage in 102 cases(41.30%), retinal exudative changes in 68 cases(27.53%), optic atrophy in 5 cases(2.02%)and optic disc edema in 3 cases(1.21%).<p>CONCLUSION: Neonatal fundus diseases were so various and harmful that early screening should be attended to. Premature infants and term infants with high risk are treated as focus group of fundus screening and RetCamII examination is safe and effective
Electroneutrality Breakdown and Specific Ion Effects in Nanoconfined Aqueous Electrolytes Observed by NMR
Ion distribution in aqueous electrolytes near the interface plays critical
roles in electrochemical, biological and colloidal systems and is expected to
be particularly significant inside nanoconfined regions. Electroneutrality of
the total charge inside nanoconfined regions is commonly assumed a priori in
solving ion distribution of aqueous electrolytes nanoconfined by uncharged
hydrophobic surfaces with no direct experimental validation. Here, we use a
quantitative nuclear magnetic resonance approach to investigate the properties
of aqueous electrolytes nanoconfined in graphitic-like nanoporous carbon.
Substantial electroneutrality breakdown in nanoconfined regions and very
asymmetric responses of cations and anions to the charging of nanoconfining
surfaces are observed. The electroneutrality breakdown is shown to depend
strongly on the propensity of anions toward the water-carbon interface and such
ion-specific response follows generally the anion ranking of the Hofmeister
series. The experimental observations are further supported by numerical
evaluation using the generalized Poisson-Boltzmann equationComment: 26 pages, 3 figure
A Robust Quantum Random Access Memory
A "bucket brigade" architecture for a quantum random memory of memory
cells needs times of quantum manipulation on control circuit nodes
per memory call. Here we propose a scheme, in which only average times
manipulation is required to accomplish a memory call. This scheme may
significantly decrease the time spent on a memory call and the average overall
error rate per memory call. A physical implementation scheme for storing an
arbitrary state in a selected memory cell followed by reading it out is
discussed.Comment: 5 pages, 3 figure
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