858 research outputs found
Detection of a Superconducting Phase in a Two-Atom Layer of Hexagonal Ga Film Grown on Semiconducting GaN(0001)
The recent observation of the superconducting state at atomic scale has motivated the pursuit of exotic condensed phases in two-dimensional (2D) systems. Here we report on a superconducting phase in twomonolayer crystalline Ga films epitaxially grown on wide-band-gap semiconductor GaN(0001). This phase exhibits a hexagonal structure and only 0.552 nm in thickness, nevertheless, brings about a superconducting transition temperature Tc as high as 5.4 K, confirmed by in situ scanning tunneling spectroscopy and ex situ electrical magnetotransport and magnetization measurements. The anisotropy of critical magnetic field and Berezinski-Kosterlitz-Thouless-like transition are observed, typical for the 2D superconductivity. Our results demonstrate a novel platform for exploring atomic-scale 2D superconductors, with great potential for understanding the interface superconductivit
Evaluating the impact of decentralising tuberculosis microscopy services to rural township hospitals in gansu province, china
<p>Abstract</p> <p>Background</p> <p>In 2004, the Ministry of Health issued the policy of decentralising microscopy services (MCs) to one third of all township hospitals in China. The study was conducted in Gansu Province, a poor western one in China. Ganzhou was one county in Gansu Province. Ganzhou County was identified as a unique case of further decentralisation of tuberculosis (TB) treatment services in township hospitals. The study evaluated the impact of the MC policy on providers and patients in Gansu Province. The second objective was to assess the unique case of Ganzhou County compared with other counties in the province.</p> <p>Methods</p> <p>Both quantitative and qualitative methods were used. All 523 MCs in the province completed an institutional survey regarding their performance. Four counties were selected for in-depth investigation, where 169 TB suspects were randomly selected from the MC and county TB dispensary registers for questionnaire surveys. Informant interviews were conducted with 38 health staff at the township and county levels in the four counties.</p> <p>Results</p> <p>Gansu established MCs in 39% of its township hospitals. From January 2006 to June 2007, 8% of MCs identified more than 10 TB sputum smear positive patients while 54% did not find any. MCs identified 1546 TB sputum smear positive patients, accounting for 9% of the total in the province. The throughputs of MCs in Ganzhou County were eight times of those in other counties. Interviews identified several barriers to implement the MC policy, such as inadequate health financing, low laboratory capacity, lack of human resources, poor treatment and management capacities, and lack of supervisions from county TB dispensaries.</p> <p>Conclusion</p> <p>Microscopy centre throughputs were generally low in Gansu Province, and the contribution of MCs to TB case detection was insignificant taking account the number of MCs established. As a unique case of full decentralisation of TB service, Ganzhou County presented better results. However, standards and quality of TB care needed to be improved. The MC policy needs to be reviewed in light of evidence from this study.</p
One-Pot Green Synthesis and Bioapplication ofl-Arginine-Capped Superparamagnetic Fe3O4 Nanoparticles
Water-solublel-arginine-capped Fe3O4 nanoparticles were synthesized using a one-pot and green method. Nontoxic, renewable and inexpensive reagents including FeCl3,l-arginine, glycerol and water were chosen as raw materials. Fe3O4 nanoparticles show different dispersive states in acidic and alkaline solutions for the two distinct forms of surface bindingl-arginine. Powder X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the structure of Fe3O4 nanocrystals. The products behave like superparamagnetism at room temperature with saturation magnetization of 49.9 emu g−1 and negligible remanence or coercivity. In the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride, the anti-chloramphenicol monoclonal antibodies were connected to thel-arginine-capped magnetite nanoparticles. The as-prepared conjugates could be used in immunomagnetic assay
Measurements of Born Cross Sections for and at 4918.0 and 4950.9 MeV
Using collision data collected with the BESIII detector operating at
the BEPCII collider, the Born cross sections of and are measured for the first time at
center-of-mass energies of and 4950.9 MeV. Non-zero cross
sections are observed very close to the production threshold. The measured Born
cross sections of are about times greater than those of , thereby indicating that
the exotic structure potentially exists in the excited charmed baryons. The
Born cross sections are pb and pb for
, and are
pb and pb for at and 4950.9 MeV,
respectively. Based on the polar angle distributions of the
and , the form-factor ratios
are determined for for the first time, which
are and at and
4950.9 MeV, respectively. All of these first uncertainties are statistical and
second systematic.Comment: 10 pages, 6 figure
Amplitude Analysis of the Decays and
Using annihilation data corresponding to an integrated luminosity of
2.93 taken at the center-of-mass energy ~GeV with
the BESIII detector, a joint amplitude analysis is performed on the decays
and (non-). The
fit fractions of individual components are obtained, and large interferences
among the dominant components of ,
, and
are found in both channels. With the obtained amplitude
model, the -even fractions of and
(non-) are determined to be and , respectively. The branching fractions of and (non-) are measured
to be and
, respectively. The
amplitude analysis provides an important model for binning strategy in the
measurements of the strong phase parameters of when used to
determine the CKM angle via the decay
Updated measurements of the M1 transition with
Based on a data sample of events
collected with the BESIII detector at the BEPCII collider, the M1 transition
with is
studied, where is or
. The mass and width of the are
measured to be MeV/
and MeV, respectively. The
product branching fraction is determined to be . Using , we obtain the branching fraction of the
radiative transition to be , where the third uncertainty is due to the quoted
Partial Wave Analysis of
Using a sample of events collected with
the BESIII detector at the BEPCII collider, a partial wave analysis on the
decay is performed to investigate the intermediate
resonances in . The
resonances , , , ,
, , , , and
are observed with statistical significance greater than 5.
The product branching fractions are reported. The resonance parameters of
and are also measured
Improved measurements of the Dalitz decays
Based on a data sample of 10 billion events collected with the
BESIII detector, improved measurements of the Dalitz decays
are performed, where the and
are produced through the radiative decays . The branching fractions of and
are measured to be and , respectively.
Within the single pole model, the parameter of electromagnetic transition form
factor for is determined to be
. Within the
multi-pole model, we extract the electromagnetic transition form factors for
to be and . The results are consistent with both theoretical predictions and
previous measurements. The characteristic sizes of the interaction regions for
the and are calculated to be and , respectively. In addition, we
search for the dark photon in ,
and the upper limits of the branching fractions as a function of the dark
photon are given at 90\% confidence level
Search for an axion-like particle in radiative decays
We search for an axion-like particle (ALP) through the process
, ,
in a data sample with
events collected by the BESIII detector. No significant ALP signal
is observed over the expected background, and the upper limits on the branching
fraction of the decay and the ALP-photon coupling
constant are set at the 95\% confidence level in the mass
range of 0.165\leq m_a\leq2.84\,\mbox{GeV}/c^2. The limits on
range from to
over the search region, and the constraints on the
ALP-photon coupling are the most stringent to date for 0.165\leq
m_a\leq1.468\,\mbox{GeV}/c^2.Comment: 10 pages, 5 figure
Measurement of the Electromagnetic Transition Form-factors in the decays
With a sample of events accumulated with
the BESIII detector, we analyze the decays
via the process
. The branching fractions are measured to be
and
,
and the ratio is
. In addition, by combining the
and
decays, the slope parameter of the electromagnetic transition form factor is
measured to be , which is
consistent with previous measurements from BESIII and theoretical predictions
from the VMD model. The asymmetry in the angle between the and
decay planes, which has the potential to reveal the -violation
originating from an unconventional electric dipole transition, is also
investigated. The asymmetry parameters are determined to be
and
,
implying that no evidence of -violation is observed at the present
statistics. Finally, an axion-like particle is searched for via the decay
, and upper limits of the
branching fractions are presented for the mass assumptions of the axion-like
particle in the range of
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