140 research outputs found

    Introducing the crystalline phase of dicalcium phosphate monohydrate

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    Calcium orthophosphates (CaPs) are important in geology, biomineralization, animal metabolism and biomedicine, and constitute a structurally and chemically diverse class of minerals. In the case of dicalcium phosphates, ever since brushite (CaHPO4·2H2O, dicalcium phosphate dihydrate, DCPD) and monetite (CaHPO4, dicalcium phosphate, DCP) were first described in 19th century, the form with intermediary chemical formula CaHPO4·H2O (dicalcium phosphate monohydrate, DCPM) has remained elusive. Here, we report the synthesis and crystal structure determination of DCPM. This form of CaP is found to crystallize from amorphous calcium hydrogen phosphate (ACHP) in water-poor environments. The crystal structure of DCPM is determined to show a layered structure with a monoclinic symmetry. DCPM is metastable in water, but can be stabilized by organics, and has a higher alkalinity than DCP and DCPD. This study serves as an inspiration for the future exploration of DCPM’s potential role in biomineralization, or biomedical applications

    Linear and Second-order Optical Response of the III-V Mono-layer Superlattices

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    We report the first fully self-consistent calculations of the nonlinear optical properties of superlattices. The materials investigated are mono-layer superlattices with GaP grown on the the top of InP, AlP and GaAs (110) substrates. We use the full-potential linearized augmented plane wave method within the generalized gradient approximation to obtain the frequency dependent dielectric tensor and the second-harmonic-generation susceptibility. The effect of lattice relaxations on the linear optical properties are studied. Our calculations show that the major anisotropy in the optical properties is the result of strain in GaP. This anisotropy is maximum for the superlattice with maximum lattice mismatch between the constituent materials. In order to differentiate the superlattice features from the bulk-like transitions an improvement over the existing effective medium model is proposed. The superlattice features are found to be more pronounced for the second-order than the linear optical response indicating the need for full supercell calculations in determining the correct second-order response.Comment: 9 pages, 4 figures, submitted to Phy. Rev.

    Market segmentation and ideal point identification for new product design using fuzzy data compression and fuzzy clustering methods

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    In product design, various methodologies have been proposed for market segmentation, which group consumers with similar customer requirements into clusters. Central points on market segments are always used as ideal points of customer requirements for product design, which reflects particular competitive strategies to effectively reach all consumers’ interests. However, existing methodologies ignore the fuzziness on consumers’ customer requirements. In this paper, a new methodology is proposed to perform market segmentation based on consumers’ customer requirements, which exist fuzziness. The methodology is an integration of a fuzzy compression technique for multi-dimension reduction and a fuzzy clustering technique. It first compresses the fuzzy data regarding customer requirements from high dimensions into two dimensions. After the fuzzy data is clustered into marketing segments, the centre points of market segments are used as ideal points for new product development. The effectiveness of the proposed methodology in market segmentation and identification of the ideal points for new product design is demonstrated using a case study of new digital camera design

    Measurements of Cabibbo Suppressed Hadronic Decay Fractions of Charmed D0 and D+ Mesons

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    Using data collected with the BESII detector at e+e−e^{+}e^{-} storage ring Beijing Electron Positron Collider, the measurements of relative branching fractions for seven Cabibbo suppressed hadronic weak decays D0→K−K+D^0 \to K^- K^+, π+π−\pi^+ \pi^-, K−K+π+π−K^- K^+ \pi^+ \pi^- and π+π+π−π−\pi^+ \pi^+ \pi^- \pi^-, D+→K0ˉK+D^+ \to \bar{K^0} K^+, K−K+π+K^- K^+ \pi^+ and π−π+π+\pi^- \pi^+ \pi^+ are presented.Comment: 11 pages, 5 figure

    Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

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    Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure

    BESII Detector Simulation

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    A Monte Carlo program based on Geant3 has been developed for BESII detector simulation. The organization of the program is outlined, and the digitization procedure for simulating the response of various sub-detectors is described. Comparisons with data show that the performance of the program is generally satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM

    Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons

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    The branching fractions for the inclusive Cabibbo-favored ~K*0 and Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with the BES-II detector at the BEPC collider. The branching fractions for the decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 -> \~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X) < 6.6%

    Study of J/ψ→ωK+K−J/\psi \to \omega K^+K^-

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    New data are presented on J/ψ→ωK+K−J/\psi \to \omega K^+K^- from a sample of 58M J/ψJ/\psi events in the upgraded BES II detector at the BEPC. There is a conspicuous signal for f0(1710)→K+K−f_0(1710) \to K^+K^- and a peak at higher mass which may be fitted with f2(2150)→KKˉf_2(2150) \to K\bar K. From a combined analysis with ωπ+π−\omega \pi ^+ \pi ^- data, the branching ratio BR(f0(1710)→ππ)/BR(f0(1710)→KKˉ)BR(f_0(1710)\to\pi\pi)/BR(f_0(1710) \to K\bar K) is <0.11< 0.11 at the 95% confidence level.Comment: 11 pages, 5 figures. Submitted to Phys. Lett.

    Direct Measurements of the Branching Fractions for D0→K−e+ÎœeD^0 \to K^-e^+\nu_e and D0→π−e+ÎœeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

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    The absolute branching fractions for the decays D0→K−e+ÎœeD^0 \to K^-e ^+\nu_e and D0→π−e+ÎœeD^0 \to \pi^-e^+\nu_e are determined using 7584±198±3417584\pm 198 \pm 341 singly tagged Dˉ0\bar D^0 sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged Dˉ0\bar D^0 meson, 104.0±10.9104.0\pm 10.9 events for D0→K−e+ÎœeD^0 \to K^-e ^+\nu_e and 9.0±3.69.0 \pm 3.6 events for D0→π−e+ÎœeD^0 \to \pi^-e^+\nu_e decays are observed. Those yield the absolute branching fractions to be BF(D0→K−e+Îœe)=(3.82±0.40±0.27)BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)% and BF(D0→π−e+Îœe)=(0.33±0.13±0.03)BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)%. The vector form factors are determined to be ∣f+K(0)∣=0.78±0.04±0.03|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03 and ∣f+π(0)∣=0.73±0.14±0.06|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06. The ratio of the two form factors is measured to be ∣f+π(0)/f+K(0)∣=0.93±0.19±0.07|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07.Comment: 6 pages, 5 figure
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