Molecular state interpretation of charmed baryons in the quark model

Stimulated by the observation of $\Lambda_c(2910)^+$ by the Belle Collaboration, the $S$-wave $qqq\bar{q}c~(q=u~\text{or}~d)$ pentaquark systems with $I$ = 0, $J^P$ = $\frac{1}{2}^-,~\frac{3}{2}^- and~\frac{5}{2}^-$ are investigated in the framework of quark delocalization color screening model(QDCSM). The real-scaling method is utilized to check the bound states and the genuine resonance states. The root mean square of cluster spacing is also calculated to study the structure of the states and estimate if the state is resonance state or not. The numerical results show that $\Lambda_{c}(2910)$ cannot be interpreted as a molecular state, and $\Sigma_{c}(2800)$ cannot be explained as the $ND$ molecular state with $J^P=1/2^-$. $\Lambda_{c}(2595)$ can be interpreted as the molecular state with $J^P=\frac{1}{2}^-$ and the main component is $\Sigma_{c}\pi$. $\Lambda_{c}(2625)$ can be interpreted as the molecular state with $J^P=\frac{3}{2}^-$ and the main component is $\Sigma_{c}^{*}\pi$. $\Lambda_{c}(2940)$ is likely to be interpreted as a molecular state with $J^P=3/2^-$, and the main component is $ND^{*}$. Besides, two new molecular states are predicted, one is the $J^P=3/2^-$ $\Sigma_{c}\rho$ resonance state with the mass around 3140 MeV, another one is the $J^P=\frac{5}{2}^-$ $\Sigma_{c}^*\rho$ with the mass of 3188.3 MeV.Comment: 12 pages, 3 figure

Monetary Policy in a Schumpeterian Growth Model with Two R&D Sectors

We explore the growth and welfare effects of monetary policy in a two-sector Schumpeterian economy with cash-in-advance (CIA) constrained R&D investment in both sectors. We show that a nominal interest rate increase generates two effects on equilibrium labor allocation: a manufacturing-R&D-reallocation effect and a cross-R&D-sector effect. The former reduces economic growth by shifting labor from R&D to production, whereas the latter can enhance it by shifting labor from the less productive R&D sector to the more productive one. Unless the high productivity R&D sector is severely more CIA-constrained than the low productivity one, aggregate R&D overinvestment is sufficient but not necessary for the Friedman rule of monetary policy to be suboptimal. Our benchmark parameterization suggests that a positive nominal interest rate is optimal despite that it exacerbates the aggregate R&D underinvestment problem

Managerial rents vs. shareholder value in delegated portfolio management: the case of closed-end funds

We examine the dynamics of assets under management (AUM) and management fees at the portfolio manager level in the closed-end fund industry. We find that managers capitalize on good past performance and favorable investor perception about future performance, as reflected in fund premiums, through AUM expansions and fee increases. However, the penalties for poor performance or unfavorable investor perception are either insignificant, or substantially mitigated by manager tenure. Long tenure is generally associated with poor performance and high discounts. Our findings suggest substantial managerial power in capturing CEF rents. We also document significant diseconomies of scale at the manager level

Market Discipline and Internal Governance in the Mutual Fund Industry

We develop a continuous-time model in which a portfolio manager is hired by a management company. On the basis of observed portfolio returns, all agents update their beliefs about the manager's skills. In response, investors can move capital into or out of the mutual fund, and the management company can fire the manager. Introducing firing rationalizes several empirically documented findings, such as the positive relation between manager tenure and fund size or the increase of portfolio risk before a manager replacement and the following risk decrease. The analysis predicts that the critical performance threshold that triggers firing increases significantly over a manager's tenure and that management replacements are accompanied by capital inflows when a young manager is replaced but may be accompanied by capital outflows when a manager with a long tenure is fired. Our model yields much lower valuation levels for management companies than simple applications of discounted cash flow (DCF) methods and is thus more consistent with empirical observations. , Oxford University Press.

STRATEGIES OF FABRICATING GRAPHENE AND GRAPHENE-ANALOGOUS 2D NANOSHEETS

Due to the unique structures and properties of graphene and graphene-analogous two-dimensional (2D) nanosheets, such as MoS₂, C₃N₄, black phosphorus nanosheets, numerous methods were developed to prepare these 2D nanosheets, however, it is still a challenge to fabricate high quality 2D nanosheets cost-effectively on a large scale. This paper reviewed the recent progress of the strategies when fabricating graphene and graphene-analogous 2D nanosheets. These strategies were divided into five main categories based on the basic principles: physical exfoliation, chemical exfoliation, electrochemical exfoliation, chemical synthesis and chemical vapour deposition (CVD). The merits of each category were summarised and analysed, and the drawbacks were highlighted as well in detail. It provides an avenue to design and fabricate different kinds of high quality 2D nanosheets cost-effectively on a large scale for energy storage and conversion, catalysis, sensors, electronics, and so on

Study of Hidden-Charm and Hidden-Bottom Pentaquark Resonances in the Quark Model

Inspired by the LHCb observation of hidden-charm pentaquarks, i.e., Pc(4312), Pc(4440), and Pc(4457) in the J/ψp invariant mass spectrum, a calculation of the J/ψp scattering cross-section was performed using the quark-delocalization color screening model. The results show that Pc(4312) can be identified as a hidden-charm molecular state ΣcD with JP=12−. The two-peak structure can be reproduced around 4450 MeV, which corresponds to Pc(4440) and Pc(4457). They are the resonances molecular states ΣcD* of JP=12− and JP=32−. Moreover, the Σc*D* of both JP=12− and JP=32− are possible molecular pentaquarks. Moreover, in the same theoretical frame, the calculation is extended to the Pc-like molecular pentaquarks, denoted as Pb. Several hidden-bottom pentaquarks with masses above 11 GeV and narrow widths were obtained. All of these heavy pentaquarks are worth exploring in future experiments

Epidural Filling with Crystal-colloid Solution for Post Accidental Dural Puncture Headache: A Case Series

Purpose: Post dural puncture headache (PDPH) is a common anesthetic complication caused by expected spinal puncture or accidental dural puncture during intraspinal anesthesia operation. The purpose of this study was to retrospectively analyze the clinical features and outcomes of parturients with accidental dural punctures (ADP). Methods: (All cesarean sections at the Chongqing Health Center for Women and Children (Chongqing, China) carried out under neuraxial anesthesia from January 1, 2017 to December 31, 2018 were reviewed and data from 20 parturients with ADP were collected and analyzed. Results: Seventeen individuals received crystal-colloid solution fillers and three did not. The median epidural catheter retaining time was 40 hours; the median frequency of epidural filling was three times, with a median total volume of 60 ml. One patient developed tinnitus and three complained of head swelling during filling. The median bed-stay duration was 73 hours, with total intravenous infusion volume of 7.3 L in the first three postoperative days. Two patients complained of slight dizziness and mitigation, and five felt weak. One individual had intermittent headaches and dizziness till the seventh postoperative day. Conclusions: Epidural injection of crystal-colloid solution, combined with hydration, maybe a useful preven-tive strategy for ADP-induced headache after cesarean section