General maximum likelihood empirical Bayes estimation of normal means

We propose a general maximum likelihood empirical Bayes (GMLEB) method for the estimation of a mean vector based on observations with i.i.d. normal errors. We prove that under mild moment conditions on the unknown means, the average mean squared error (MSE) of the GMLEB is within an infinitesimal fraction of the minimum average MSE among all separable estimators which use a single deterministic estimating function on individual observations, provided that the risk is of greater order than $(\log n)^5/n$. We also prove that the GMLEB is uniformly approximately minimax in regular and weak $\ell_p$ balls when the order of the length-normalized norm of the unknown means is between $(\log n)^{\kappa_1}/n^{1/(p\wedge2)}$ and $n/(\log n)^{\kappa_2}$. Simulation experiments demonstrate that the GMLEB outperforms the James--Stein and several state-of-the-art threshold estimators in a wide range of settings without much down side.Comment: Published in at http://dx.doi.org/10.1214/08-AOS638 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

An Empirical Study of Evaluation Index System and Measure Method on City’s Soft Power: 17 Cities in Shandong Province

Based on the research of city’s soft power at home and abroad, the current study was intended to build an evaluation index system and analyzed the city’s soft power of 17cities in Shandong Province in 2010. Both the qualitative and quantitative methods were adopted. Frequency statistical method was used to build the evaluation index system of city’s soft power, and AHP and CRITIC methods were used to determine index weight. By using the evaluation system, data from Shandong 2010 statistic yearbook and SPSS18.0, the researchers analyzed the soft power of 17 cities in Shandong province, and finally constructed a measure model for city’s soft power. Results indicated that this model is practically viable and consistent with the real situation of the soft power of 17cities in Shandong Province. It is the researchers hope that this measure model would provide reference for government’s decision-making in the development of promoting urbanization

Singly authored papers contribute the most to scientists’ impact

Utilizing citation data for 100,000 most-cited scientists in the Scopus database, this paper investigated how citations received by an author in different authorship affect his/her academic impact differently. Using a linear regression model as an estimation, it shows that the citations received as the single author of a paper elevates the academic impact the most, followed by that as the first (but not single) author, last author, and middle author. Differences also emerged when we probed into different research fields separately as in some fields citations in the four types of authorship do not differ a lot, and also in some fields, the last-authored citations could 'outweigh' the first-authored ones

The Hydrodynamic Interaction in Polymer Solutions Simulated with Dissipative Particle Dynamics

We analyzed extensively the dynamics of polymer chains in solutions simulated with dissipative particle dynamics (DPD), with a special focus on the potential influence of a low Schmidt number of a typical DPD fluid on the simulated polymer dynamics. It has been argued that a low Schmidt number in a DPD fluid can lead to underdevelopment of the hydrodynamic interaction in polymer solutions. Our analyses reveal that equilibrium polymer dynamics in dilute solution, under a typical DPD simulation conditions, obey the Zimm model very well. With a further reduction in the Schmidt number, a deviation from the Zimm model to the Rouse model is observed. This implies that the hydrodynamic interaction between monomers is reasonably developed under typical conditions of a DPD simulation. Only when the Schmidt number is further reduced, the hydrodynamic interaction within the chains becomes underdeveloped. The screening of the hydrodynamic interaction and the excluded volume interaction as the polymer volume fraction is increased are well reproduced by the DPD simulations. The use of soft interaction between polymer beads and a low Schmidt number do not produce noticeable problems for the simulated dynamics at high concentrations, except that the entanglement effect which is not captured in the simulations.Comment: 27 pages, 13 page

Prevalence of COPD and its association with socioeconomic status in China: Findings from China Chronic Disease Risk Factor Surveillance 2007

<p>Abstract</p> <p>Background</p> <p>Socioeconomic status is likely an independent risk factor for Chronic Obstructive Pulmonary Disease (COPD), but little research has been done in China to study this association in a nationwide sample.</p> <p>Methods</p> <p>We used data from the 2007 China Chronic Disease Risk Factor Surveillance of 49,363 Chinese men and women aged 15-69 years to examine the association between the prevalence of self-reported physician diagnosed COPD and socioeconomic status defined by both educational level and annual household income. Multivariable logistic regression modelling was performed with adjustement for potential confounders.</p> <p>Results</p> <p>Both low educational attainment and low household income were independently associated with higher risk of physician-diagnosed COPD. Compared to subjects with high educational level, subjects with low educational level had a significantly increased risk of COPD (OR 1.67, 95%CI 1.32-2.13, p for trend< 0.001 for urban, OR 1.76, 95%CI 1.34-2.30, p for trend < 0.001 for rural) after adjusting for age, sex, smoking status, passive smoking and geographic regions. Similarly increased risk was observed for household income and COPD in urban (OR 1.64, 95%CI 1.28-2.09, P for trend< 0.001) but not rural areas. Among never smokers, low educational level and household income were still associated with a significant higher prevalence of COPD (OR 1.77, 95%CI 1.40-2.25, OR 1.31, 95%CI 1.05-1.62). Removal of those with asthma diagnosis did not alter the observed associations.</p> <p>Conclusions</p> <p>Socioeconomic status is a risk factor for self-reported physician-diagnosed COPD independently of current or passive smoking. Prospective studies are needed in China to better understand the association between socioeconomic status and COPD.</p

Pressure Driven Flow of Polymer Solutions in Nanoscale Slit Pores

Polymer solutions subject to pressure driven flow and in nanoscale slit pores are systematically investigated using the dissipative particle dynamics approach. We investigated the effect of molecular weight, polymer concentration and flow rate on the profiles across the channel of the fluid and polymer velocities, polymers density, and the three components of the polymers radius of gyration. We found that the mean streaming fluid velocity decreases as the polymer molecular weight or/and polymer concentration is increased, and that the deviation of the velocity profile from the parabolic profile is accentuated with increase in polymer molecular weight or concentration. We also found that the distribution of polymers conformation is highly anisotropic and non-uniform across the channel. The polymer density profile is also found to be non-uniform, exhibiting a local minimum in the center-plane followed by two symmetric peaks. We found a migration of the polymer chains either from or towards the walls. For relatively long chains, as compared to the thickness of the slit, a migration towards the walls is observed. However, for relatively short chains, a migration away from the walls is observed.Comment: 11 pages, 13 figure

Room Temperature Ferromagnetic and Optical Properties of Chrome Doped ZnS Nanorods Prepared by Hydrothermal Method

Cr doped Zn1-xCrxS nanorods with different concentration ratio (x=0, 0.01, 0.03, and 0.05) were successfully synthesized by hydrothermal method. The crystal microstructure, morphology, chemical composition, and optical and magnetic properties of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS), diffuse-reflectance spectroscopy (DRS), photoluminescence (PL) spectra, and the vibrating sample magnetometer (VSM). All the samples synthesized by this method exhibited single-phase wurtzite structure with good crystallization as demonstrated by XRD studies, which indicated that all Cr ions successfully substituted for the lattice site of Zn2+ and generated single-phase Zn1-xCrxS. DRS revealed the band gap of doped Zn1-xCrxS underwent blue shift compared to that of the bulk ZnS. PL spectra showed obvious ultraviolet emission peak at 375 nm and two blue emissions appear about 500 and 580 nm. The blue emissions intensity of doped samples improved with the increase of Cr concentration, comparing to pure ZnS. Magnetic measurements indicated that the undoped and doped ZnS nanorods exhibited well-defined ferromagnetic behavior at room temperature. The saturation magnetization weakened significantly with increasing Cr concentration comparing to pure ZnS and reached minimum for 3% Cr

Cost-effectiveness of the Da Qing Diabetes Prevention program : a modelling study

Objective The Da Qing Diabetes Prevention program (DQDP) was a randomized lifestyle modification intervention conducted in 1986 for the prevention and control of type 2 diabetes in individuals with impaired glucose tolerance. The current study estimated long-term cost-effectiveness of the program based on the health utilities from the Chinese population. Methods A Markov Monte Carlo model was developed to estimate the impact of the intervention from the healthcare system perspective. The analysis was run over 30-year and lifetime periods and costs were estimated respectively as health management service costs. Baseline characteristics and intervention effects were assessed from the DQDP. Utilities and costs were generated from relevant literature. The outcome measures were program cost per quality-adjusted life-years (QALYs) gained and incremental cost-effectiveness ratio (ICER) of the intervention. Sensitivity analyses and threshold analyses were performed. Results Using a 30-year horizon, the intervention strategy was cost-saving and was associated with better health outcomes (increase of 0.74 QALYs per intervention participant). Using a lifetime horizon, the intervention strategy was cost-saving and was associated with additional 1.44 QALYs. Sensitivity analyses showed that the overall ICER was most strongly influenced by the hazard ratio of cardiovascular disease event. Conclusions The Da Qing lifestyle intervention in a Chinese population with impaired glucose tolerance is likely to translate into substantial economic value. It is cost-saving over a 30-year time and lifetime frame