304 research outputs found
Effect of B-site Dopants on Magnetic and Transport Properties of LaSrCoRuO
Effect of Co, Ru and Cu substitution at B and B' sites on the magnetic and
transport properties of LaSrCoRuO have been investigated. All the doped
compositions crystallize in the monoclinic structure in the space group
indicating a double perovskite structure. While the magnetization and
conductivity increase in Co and Ru doped compounds, antiferromagnetism is seen
to strengthen in the Cu doped samples. These results are explained on the basis
of a competition between linear Co-O-Ru-O-Co and perpendicular Co-O-O-Co
antiferromagnetic interactions and due to formation of Ru-O-Ru ferromagnetic
networks
Horava-Lifshitz Dark Energy
We formulate Horava-Lifshitz cosmology with an additional scalar field that
leads to an effective dark energy sector. We find that, due to the inherited
features from the gravitational background, Horava-Lifshitz dark energy
naturally presents very interesting behaviors, possessing a varying
equation-of-state parameter, exhibiting phantom behavior and allowing for a
realization of the phantom divide crossing. In addition, Horava-Lifshitz dark
energy guarantees for a bounce at small scale factors and it may trigger the
turnaround at large scale factors, leading naturally to cyclic cosmology.Comment: 17 pages, no figures, version published at EJP
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
Outbreak of COVID-19 and SARS in mainland China: a comparative study based on national surveillance data
Objective To compare the epidemiological characteristics
and transmission dynamics in relation to interventions
against the COVID-19 and severe acute respiratory
syndrome (SARS) outbreak in mainland China.
Design Comparative study based on a unique data set of
COVID-19 and SARS.
Setting Outbreak in mainland China.
Participants The final database included 82 858
confirmed cases of COVID-19 and 5327 cases of SARS.
Methods We brought together all existing data sources
and integrated them into a comprehensive data set.
Individual information on age, sex, occupation, residence
location, date of illness onset, date of diagnosis and
clinical outcome was extracted. Control measures
deployed in mainland China were collected. We
compared the epidemiological and spatial characteristics
of COVID-19 and SARS. We estimated the effective
reproduction number to explore differences in transmission
dynamics and intervention effects.
Results Compared with SARS, COVID-19 affected more
extensive areas (1668 vs 230 counties) within a shorter
time (101 vs 193 days) and had higher attack rate (61.8 vs
4.0 per million persons). The COVID-19 outbreak had only
one epidemic peak and one epicentre (Hubei Province),
while the SARS outbreak resulted in two peaks and two
epicentres (Guangdong Province and Beijing). SARSCoV-2 was more likely to infect older people (median
age of 52 years), while SARS-CoV tended to infect young
adults (median age of 34 years). The case fatality rate
(CFR) of either disease increased with age, but the CFR of
COVID-19 was significantly lower than that of SARS (5.6%
vs 6.4%). The trajectory of effective reproduction number
dynamically changed in relation to interventions, which
fell below 1 within 2 months for COVID-19 and within 5.5
months for SARS.
Conclusions China has taken more prompt and effective
responses to combat COVID-19 by learning lessons from
SARS, providing us with some epidemiological clues to
control the ongoing COVID-19 pandemic worldwid
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays
By analyzing about 33 data sample collected at and around 3.773
GeV with the BES-II detector at the BEPC collider, we directly measure the
branching fractions for the neutral and charged inclusive semimuonic decays
to be and , and determine the ratio of the two branching
fractions to be
A study of charged kappa in
Based on events collected by BESII, the decay
is studied. In the invariant mass
spectrum recoiling against the charged , the charged
particle is found as a low mass enhancement. If a Breit-Wigner function of
constant width is used to parameterize the kappa, its pole locates at MeV/. Also in this channel,
the decay is observed for the first time.
Its branching ratio is .Comment: 14 pages, 4 figure
Partial Wave Analysis of
BES data on are presented. The
contribution peaks strongly near threshold. It is fitted with a
broad resonance with mass MeV, width MeV. A broad resonance peaking at 2020 MeV is also required
with width MeV. There is further evidence for a component
peaking at 2.55 GeV. The non- contribution is close to phase
space; it peaks at 2.6 GeV and is very different from .Comment: 15 pages, 6 figures, 1 table, Submitted to PL
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