858 research outputs found

    Detection of a Superconducting Phase in a Two-Atom Layer of Hexagonal Ga Film Grown on Semiconducting GaN(0001)

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    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

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    <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

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    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 e+eΛc+Λˉc(2595)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2595)^- + {\rm c.c.} and e+eΛc+Λˉc(2625)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2625)^- + {\rm c.c.} at s=\sqrt{s}=4918.0 and 4950.9 MeV

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    Using e+ee^+e^- collision data collected with the BESIII detector operating at the BEPCII collider, the Born cross sections of e+eΛc+Λˉc(2595)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2595)^- + \rm{c.c.} and e+eΛc+Λˉc(2625)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2625)^- + \rm{c.c.} are measured for the first time at center-of-mass energies of s=4918.0\sqrt{s}=4918.0 and 4950.9 MeV. Non-zero cross sections are observed very close to the production threshold. The measured Born cross sections of e+eΛc+Λˉc(2625)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2625)^- + \rm{c.c.} are about 232\sim3 times greater than those of e+eΛc+Λˉc(2595)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2595)^- + \rm{c.c.}, thereby indicating that the exotic structure potentially exists in the excited charmed baryons. The Born cross sections are 15.6±3.1±0.915.6\pm3.1\pm0.9 pb and 29.4±3.7±2.729.4\pm3.7\pm2.7 pb for e+eΛc+Λˉc(2595)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2595)^- + \rm{c.c.}, and are 43.4±4.0±4.143.4\pm4.0\pm4.1 pb and 76.8±6.5±4.276.8\pm6.5\pm4.2 pb for e+eΛc+Λˉc(2625)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2625)^- +\rm{c.c.} at s=4918.0\sqrt s=4918.0 and 4950.9 MeV, respectively. Based on the polar angle distributions of the Λˉc(2625)\bar{\Lambda}_{c}(2625)^- and Λc(2625)+\Lambda_{c}(2625)^+, the form-factor ratios GE2+3GM2/GC\sqrt{|G_{E}|^2 + 3|G_{M}|^2}/|G_{C}| are determined for e+eΛc+Λˉc(2625)+c.c.e^+e^-\to \Lambda_{c}^+ \bar{\Lambda}_{c}(2625)^- + \rm{c.c.} for the first time, which are 5.95±4.07±0.155.95\pm4.07\pm0.15 and 0.94±0.32±0.020.94\pm0.32\pm0.02 at s=4918.0\sqrt s=4918.0 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 D0π+ππ+πD^0\to\pi^+\pi^-\pi^+\pi^- and π+ππ0π0\pi^+\pi^-\pi^0\pi^0

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    Using e+ee^+e^- annihilation data corresponding to an integrated luminosity of 2.93 fb1\rm fb^{-1} taken at the center-of-mass energy s=3.773\sqrt{s}=3.773~GeV with the BESIII detector, a joint amplitude analysis is performed on the decays D0π+ππ+πD^0\to\pi^+\pi^-\pi^+\pi^- and D0π+ππ0π0D^0\to\pi^+\pi^-\pi^0\pi^0(non-η\eta). The fit fractions of individual components are obtained, and large interferences among the dominant components of D0a1(1260)πD^{0}\to a_{1}(1260)\pi, D0π(1300)πD^{0}\to\pi(1300)\pi, D0ρ(770)ρ(770)D^{0}\to\rho(770)\rho(770) and D02(ππ)SD^{0}\to2(\pi\pi)_{S} are found in both channels. With the obtained amplitude model, the CPCP-even fractions of D0π+ππ+πD^0\to \pi^+\pi^-\pi^+\pi^- and D0π+ππ0π0D^0\to\pi^+\pi^-\pi^0\pi^0(non-η\eta) are determined to be (75.2±1.1stat.±1.5syst.)%(75.2\pm1.1_{\rm stat.}\pm1.5_{\rm syst.})\% and (68.9±1.5stat.±2.4syst.)%(68.9\pm1.5_{\rm stat.}\pm 2.4_{\rm syst.})\%, respectively. The branching fractions of D0π+ππ+πD^0\to \pi^+\pi^-\pi^+\pi^- and D0π+ππ0π0D^0\to\pi^+\pi^-\pi^0\pi^0(non-η\eta) are measured to be (0.688±0.010stat.±0.010syst.)%(0.688\pm0.010_{\rm stat.}\pm 0.010_{\rm syst.})\% and (0.951±0.025stat.±0.021syst.)%(0.951\pm0.025_{\rm stat.}\pm 0.021_{\rm syst.})\%, respectively. The amplitude analysis provides an important model for binning strategy in the measurements of the strong phase parameters of D04πD^0 \to 4\pi when used to determine the CKM angle γ(ϕ3)\gamma (\phi_{3}) via the BDKB^{-}\to D K^{-} decay

    Updated measurements of the M1 transition ψ(3686)γηc(2S)\psi(3686) \to \gamma \eta_{c}(2S) with ηc(2S)KKˉπ\eta_{c}(2S) \to K \bar{K} \pi

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    Based on a data sample of (27.08±0.14)×108 ψ(3686)(27.08 \pm 0.14 ) \times 10^8~\psi(3686) events collected with the BESIII detector at the BEPCII collider, the M1 transition ψ(3686)γηc(2S)\psi(3686) \to \gamma \eta_{c}(2S) with ηc(2S)KKˉπ\eta_{c}(2S) \to K\bar{K}\pi is studied, where KKˉπK\bar{K}\pi is K+Kπ0K^{+} K^{-} \pi^{0} or KS0K±πK_{S}^{0}K^{\pm}\pi^{\mp}. The mass and width of the ηc(2S)\eta_{c}(2S) are measured to be (3637.8±0.8(stat)±0.2(syst))(3637.8 \pm 0.8 (\rm {stat}) \pm 0.2 (\rm {syst})) MeV/c2c^{2} and (10.5±1.7(stat)±3.5(syst))(10.5 \pm 1.7 (\rm {stat}) \pm 3.5 (\rm {syst})) MeV, respectively. The product branching fraction B(ψ(3686)γηc(2S))×B(ηc(2S)KKˉπ)\mathcal{B}\left(\psi(3686) \rightarrow \gamma \eta_{c}(2 S)\right) \times \mathcal{B}(\eta_{c}(2 S) \rightarrow K \bar{K} \pi) is determined to be (0.97±0.06(stat)±0.09(syst))×105(0.97 \pm 0.06 (\rm {stat}) \pm 0.09 (\rm {syst})) \times 10^{-5}. Using BR(ηc(2S)KKˉπ)=(1.860.49+0.68)%\mathcal{BR}(\eta_{c}(2S)\to K\bar{K}\pi)=(1.86^{+0.68}_{-0.49})\%, we obtain the branching fraction of the radiative transition to be BR(ψ(3686)γηc(2S))=(5.2±0.3(stat)±0.5(syst)1.4+1.9(extr))×104\mathcal{BR}(\psi(3686) \to \gamma \eta_{c}(2S)) = (5.2 \pm 0.3 (\rm {stat}) \pm 0.5 (\rm {syst}) ^{+1.9}_{-1.4} (extr)) \times 10^{-4}, where the third uncertainty is due to the quoted BR(ηc(2S)KKˉπ)\mathcal{BR}(\eta_{c}(2S) \to K\bar{K}\pi)

    Partial Wave Analysis of J/ψγγϕJ/\psi\rightarrow \gamma \gamma \phi

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    Using a sample of (10087±44)×106(10087\pm44)\times10^{6} J/ψJ/\psi events collected with the BESIII detector at the BEPCII collider, a partial wave analysis on the decay γγϕ\gamma\gamma\phi is performed to investigate the intermediate resonances in J/ψγX,XγϕJ/\psi\rightarrow\gamma X, X\rightarrow\gamma\phi. The resonances f1(1285)f_{1}(1285), η(1405)\eta(1405), f1(1420)f_{1}(1420), f1(1510)f_{1}(1510), f2(1525)f_{2}(1525), X(1835)X(1835), f2(1950)f_{2}(1950), f2(2010)f_{2}(2010), f0(2200)f_{0}(2200) and ηc\eta_{c} are observed with statistical significance greater than 5σ\sigma. The product branching fractions B(J/ψγX,Xγϕ)\mathcal{B}(J/\psi\rightarrow\gamma X, X\rightarrow \gamma \phi) are reported. The resonance parameters of η(1405)\eta(1405) and X(1835)X(1835) are also measured

    Improved measurements of the Dalitz decays η/ηγe+e\eta/\eta'\rightarrow\gamma e^{+}e^{-}

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    Based on a data sample of 10 billion J/ψJ/\psi events collected with the BESIII detector, improved measurements of the Dalitz decays η/ηγe+e\eta/\eta'\rightarrow\gamma e^+e^- are performed, where the η\eta and η\eta' are produced through the radiative decays J/ψγη/ηJ/\psi\rightarrow\gamma \eta/\eta'. The branching fractions of ηγe+e\eta\rightarrow\gamma e^+e^- and ηγe+e\eta'\rightarrow\gamma e^+e^- are measured to be (7.07±0.05±0.23)×103(7.07 \pm 0.05 \pm 0.23)\times10^{-3} and (4.83±0.07±0.14)×104(4.83\pm0.07\pm0.14)\times10^{-4}, respectively. Within the single pole model, the parameter of electromagnetic transition form factor for ηγe+e\eta\rightarrow\gamma e^+e^- is determined to be Λη=(0.749±0.027±0.007) GeV/c2\Lambda_{\eta}=(0.749 \pm 0.027 \pm 0.007)~ {\rm GeV}/c^{2}. Within the multi-pole model, we extract the electromagnetic transition form factors for ηγe+e\eta'\rightarrow\gamma e^+e^- to be Λη=(0.802±0.007±0.008) GeV/c2\Lambda_{\eta'} = (0.802 \pm 0.007\pm 0.008)~ {\rm GeV}/c^{2} and γη=(0.113±0.010±0.002) GeV/c2\gamma_{\eta'} = (0.113\pm0.010\pm0.002)~ {\rm GeV}/c^{2}. The results are consistent with both theoretical predictions and previous measurements. The characteristic sizes of the interaction regions for the η\eta and η\eta' are calculated to be (0.645±0.023±0.007) fm(0.645 \pm 0.023 \pm 0.007 )~ {\rm fm} and (0.596±0.005±0.006) fm(0.596 \pm 0.005 \pm 0.006)~ {\rm fm}, respectively. In addition, we search for the dark photon in η/ηγe+e\eta/\eta^\prime\rightarrow\gamma e^{+}e^{-}, 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 J/ψJ/\psi radiative decays

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    We search for an axion-like particle (ALP) aa through the process ψ(3686)π+πJ/ψ\psi(3686)\rightarrow\pi^+\pi^-J/\psi, J/ψγaJ/\psi\rightarrow\gamma a, aγγa\rightarrow\gamma\gamma in a data sample with (2708.1±14.5)×106(2708.1\pm14.5)\times10^6 ψ(3686)\psi(3686) 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 J/ψγaJ/\psi\rightarrow\gamma a and the ALP-photon coupling constant gaγγg_{a\gamma\gamma} 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 B(J/ψγa)\mathcal{B}(J/\psi\rightarrow\gamma a) range from 8.3×1088.3\times10^{-8} to 1.8×1061.8\times10^{-6} 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 ηπ+πl+l\eta'\rightarrow\pi^+\pi^-l^+l^-

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    With a sample of (10087±44)×106(10087\pm44)\times10^{6} J/ψJ/\psi events accumulated with the BESIII detector, we analyze the decays ηπ+πl+l(l=e,\eta'\rightarrow\pi^+\pi^-l^+l^-(l=e, μ)\mu) via the process J/ψγηJ/\psi\rightarrow\gamma\eta'. The branching fractions are measured to be B(ηπ+πe+e)=(2.45±0.02(stat.)±0.08(syst.))×103\mathcal{B}(\eta'\rightarrow\pi^+\pi^-e^+e^-)=(2.45\pm0.02(\rm{stat.})\pm0.08(\rm{syst.})) \times10^{-3} and B(ηπ+πμ+μ)=(2.16±0.12(stat.)±0.06(syst.))×105\mathcal{B}(\eta'\rightarrow\pi^+\pi^-\mu^+\mu^-)=(2.16\pm0.12(\rm{stat.})\pm0.06(\rm{syst.}))\times10^{-5}, and the ratio is B(ηπ+πe+e)B(ηπ+πμ+μ)=113.4±0.9(stat.)±3.7(syst.)\frac{\mathcal{B}(\eta'\rightarrow\pi^{+}\pi^{-}e^{+}e^{-})}{\mathcal{B}(\eta'\rightarrow\pi^{+}\pi^{-}\mu^{+}\mu^{-})} = 113.4\pm0.9(\rm{stat.})\pm3.7(\rm{syst.}). In addition, by combining the ηπ+πe+e\eta'\rightarrow\pi^+\pi^-e^+e^- and ηπ+πμ+μ\eta'\rightarrow\pi^+\pi^-\mu^+\mu^- decays, the slope parameter of the electromagnetic transition form factor is measured to be bη=1.30±0.19 (GeV/c2)2b_{\eta'}=1.30\pm0.19\ (\mathrm{GeV}/c^{2})^{-2}, which is consistent with previous measurements from BESIII and theoretical predictions from the VMD model. The asymmetry in the angle between the π+π\pi^+\pi^- and l+ll^+l^- decay planes, which has the potential to reveal the CPCP-violation originating from an unconventional electric dipole transition, is also investigated. The asymmetry parameters are determined to be ACP(ηπ+πe+e)=(0.21±0.73(stat.)±0.01(syst.))%\mathcal{A}_{CP}(\eta'\rightarrow\pi^+\pi^-e^+e^-)=(-0.21\pm0.73(\rm{stat.})\pm0.01(\rm{syst.}))\% and ACP(ηπ+πμ+μ)=(0.62±4.71(stat.)±0.08(syst.))%\mathcal{A}_{CP}(\eta'\rightarrow\pi^+\pi^-\mu^+\mu^-)=(0.62\pm4.71(\rm{stat.})\pm0.08(\rm{syst.}))\%, implying that no evidence of CPCP-violation is observed at the present statistics. Finally, an axion-like particle is searched for via the decay ηπ+πa,ae+e\eta'\rightarrow\pi^+\pi^-a, a\rightarrow e^+e^-, and upper limits of the branching fractions are presented for the mass assumptions of the axion-like particle in the range of 0500 MeV/c20-500\ \mathrm{MeV}/c^{2}
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