3,129 research outputs found
Understanding the internal structures of the , , and
We investigate the newly observed and based on the
diquark-antidiquark configuration within the framework of QCD sum rules. Both
of them may be interpreted as the -wave tetraquark states
of , but with opposite color structures, which is remarkably similar
to the result obtained in Ref.~\cite{Chen:2010ze} that the and
can be both interpreted as the -wave tetraquark
states of , also with opposite color structures. However, the
extracted masses and these suggested assignments to these states do depend
on these running quark masses where m_s (2 \mbox{ GeV}) = 95 \pm 5 MeV and
GeV. As a byproduct, the masses of the
hidden-bottom partner states of the and are extracted to be
both around 10.64 GeV, which can be searched for in the
invariant mass distribution.Comment: 6 pages, 4 figures. Accepted by Eur. Phys. J.
QCD sum rule Study of the
We systematically construct six-quark local interpolating
currents without derivative operators. We discuss the best choice of operator,
and select three - like operators to perform QCD sum rule
analyses to calculate the mass of the . The mass extracted from this
analysis is GeV, consistent with the mass
observed by the WASA detector at COSY. We also obtain a sum-rule lower mass
bound GeV. We also consider the effect of mixing of singlet
dibaryon fields with the same quantum numbers, and perform the QCD sum rule
analysis of the mixed interpolating current and extract the mass of the
and its lower mass bound. With optimized mixing parameters, we find
that the mixed current does not change the numerical result significantly.Comment: 9 pages, 4 figure
resonance as a tetraquark state and its isospin partner
We systematically construct tetraquark currents of and
classify them into types (antisymmetric), (symmetric)
and (mixed), based on flavor symmetries of diquarks and
antidiquarks composing the tetra quark currents. We use tetraquark currents of
type to perform QCD sum rule analyses, and find a tetraquark
current with quark contents ( or )
leading to a mass of GeV consistent with the state
recently observed by the COMPASS collaboration. Our results support tetraquark
explanations for both and , assuming that they are
isospin partners. We also study their possible decay patterns. As tetraquark
candidates, the possible decay modes of are -wave and -wave while
the possible decay patterns of are -wave and -wave . We speculate that
is partly responsible for the large isospin violation in the
decay mode which is reported by BESIII
collaboration in the process.Comment: 15 pages, 8 figures. Accepted by Phys. Rev.
miR-638 is a new biomarker for outcome prediction of non-small cell lung cancer patients receiving chemotherapy.
MicroRNAs (miRNAs), a class of small non-coding RNAs, mediate gene expression by either cleaving target mRNAs or inhibiting their translation. They have key roles in the tumorigenesis of several cancers, including non-small cell lung cancer (NSCLC). The aim of this study was to investigate the clinical significance of miR-638 in the evaluation of NSCLC patient prognosis in response to chemotherapy. First, we detected miR-638 expression levels in vitro in the culture supernatants of the NSCLC cell line SPC-A1 treated with cisplatin, as well as the apoptosis rates of SPC-A1. Second, serum miR-638 expression levels were detected in vivo by using nude mice xenograft models bearing SPC-A1 with and without cisplatin treatment. In the clinic, the serum miR-638 levels of 200 cases of NSCLC patients before and after chemotherapy were determined by quantitative real-time PCR, and the associations of clinicopathological features with miR-638 expression patterns after chemotherapy were analyzed. Our data helped in demonstrating that cisplatin induced apoptosis of the SPC-A1 cells in a dose- and time-dependent manner accompanied by increased miR-638 expression levels in the culture supernatants. In vivo data further revealed that cisplatin induced miR-638 upregulation in the serum derived from mice xenograft models, and in NSCLC patient sera, miR-638 expression patterns after chemotherapy significantly correlated with lymph node metastasis. Moreover, survival analyses revealed that patients who had increased miR-638 levels after chemotherapy showed significantly longer survival time than those who had decreased miR-638 levels. Our findings suggest that serum miR-638 levels are associated with the survival of NSCLC patients and may be considered a potential independent predictor for NSCLC prognosis
Polychronicity, Decision-making and Entrepreneurial Self-efficacy of Venture Team Founders: An Exploratory Study
Purpose - This study explores the role of polychronic temporal orientation and decision-making decentralization on founders\u27 perceptions of entrepreneurial self-efficacy (ESE).
Design/methodology/approach - Longitudinal survey data were collected from 141 business founders in China.
Findings - Findings suggest that decision-making decentralization is positively associated with founders\u27 ESE. In addition, a polychronic temporal orientation is positively related to ESE, and this relationship is mediated by decision-making decentralization.
Originality/value - This study adds to existing knowledge on ESE and temporal related issues by presenting empirical evidence that explains how and why the temporal orientation context and the practice of decision-making decentralization can shape ESE perceptions among venture founders
Janus Monolayer Transition Metal Dichalcogenides
A novel crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe)
at the monolayer limit has been synthesized and carefully characterized in this
work. By controlled sulfurization of monolayer MoSe2 the top layer of selenium
atoms are substituted by sulfur atoms while the bottom selenium layer remains
intact. The peculiar structure of this new material is systematically
investigated by Raman, photoluminescence and X-ray photoelectron spectroscopy
and confirmed by transmission-electron microscopy and time-of-flight secondary
ion mass spectrometry. Density-functional theory calculations are performed to
better understand the Raman vibration modes and electronic structures of the
Janus SMoSe monolayer, which are found to correlate well with corresponding
experimental results. Finally, high basal plane hydrogen evolution reaction
(HER) activity is discovered for the Janus monolayer and DFT calculation
implies that the activity originates from the synergistic effect of the
intrinsic defects and structural strain inherent in the Janus structure.Comment: 22 pages, 12 figure
The D-wave heavy-light mesons from QCD sum rules
We study the D-wave c_bar s heavy meson doublets (1^-,2^-) and (2^-,3^-)
using the method of QCD sum rule in the framework of heavy quark effective
theory. Choosing the same threshold values omega_c around 2.7 Gev, we calculate
the masses of the 1^- and 3^- states. They are m_{D*_{s1}} = 2.81 \pm 0.10 GeV
and m_{D*_{s3}} = 2.85 \pm 0.08 GeV, consistent with the newly observed
D*_{s1}(2860) and D*_{s3}(2860) states by LHCb. The masses of their 2^-
partners are calculated to be 2.82 \pm 0.10 and 2.81 \pm 0.08 GeV. The mass
splittings within the same doublet are calculated to be m_{D_{s2}} -
m_{D*_{s1}} = 0.016 \pm 0.007 GeV and m_{D*_{s3}} - m_{D'_{s2}} = 0.039 \pm
0.014 GeV.Comment: 8 pages, 6 figures, accepted by PR
Three-Dimensional Spectral-Domain Optical Coherence Tomography Data Analysis for Glaucoma Detection
Purpose: To develop a new three-dimensional (3D) spectral-domain optical coherence tomography (SD-OCT) data analysis method using a machine learning technique based on variable-size super pixel segmentation that efficiently utilizes full 3D dataset to improve the discrimination between early glaucomatous and healthy eyes. Methods: 192 eyes of 96 subjects (44 healthy, 59 glaucoma suspect and 89 glaucomatous eyes) were scanned with SD-OCT. Each SD-OCT cube dataset was first converted into 2D feature map based on retinal nerve fiber layer (RNFL) segmentation and then divided into various number of super pixels. Unlike the conventional super pixel having a fixed number of points, this newly developed variable-size super pixel is defined as a cluster of homogeneous adjacent pixels with variable size, shape and number. Features of super pixel map were extracted and used as inputs to machine classifier (LogitBoost adaptive boosting) to automatically identify diseased eyes. For discriminating performance assessment, area under the curve (AUC) of the receiver operating characteristics of the machine classifier outputs were compared with the conventional circumpapillary RNFL (cpRNFL) thickness measurements. Results: The super pixel analysis showed statistically significantly higher AUC than the cpRNFL (0.855 vs. 0.707, respectively, p = 0.031, Jackknife test) when glaucoma suspects were discriminated from healthy, while no significant difference was found when confirmed glaucoma eyes were discriminated from healthy eyes. Conclusions: A novel 3D OCT analysis technique performed at least as well as the cpRNFL in glaucoma discrimination and even better at glaucoma suspect discrimination. This new method has the potential to improve early detection of glaucomatous damage. © 2013 Xu et al
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