Local partial likelihood estimation in proportional hazards regression

Fan, Gijbels and King [Ann. Statist. 25 (1997) 1661--1690] considered the estimation of the risk function $\psi (x)$ in the proportional hazards model. Their proposed estimator is based on integrating the estimated derivative function obtained through a local version of the partial likelihood. They proved the large sample properties of the derivative function, but the large sample properties of the estimator for the risk function itself were not established. In this paper, we consider direct estimation of the relative risk function $\psi (x_2)-\psi (x_1)$ for any location normalization point $x_1$. The main novelty in our approach is that we select observations in shrinking neighborhoods of both $x_1$ and $x_2$ when constructing a local version of the partial likelihood, whereas Fan, Gijbels and King [Ann. Statist. 25 (1997) 1661--1690] only concentrated on a single neighborhood, resulting in the cancellation of the risk function in the local likelihood function. The asymptotic properties of our estimator are rigorously established and the variance of the estimator is easily estimated. The idea behind our approach is extended to estimate the differences between groups. A simulation study is carried out.Comment: Published at http://dx.doi.org/10.1214/009053606000001299 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Investigation of microstructure and liquid lead corrosion behavior of a Fe-18Ni-16Cr-4Al base alumina-forming austenitic stainless steel

The microstructure of an alumina-forming austenitic stainless steel with a composition design of Fe-18Ni-16Cr-4Al-2Mo-0.4 Nb (in wt%) is characterized. The steel contains about 75 vol% austenitic phase and 25 vol% ferritic phase. B2-NiAl precipitates with round shape can be found only in the ferritic phase in the as-rolled sample. The corrosion behavior in static liquid lead with different oxygen content of 10−9 and 10−6% by mass at 700 °C for 1000 h is investigated. After exposure for 1000 h in liquid lead with oxygen content of 10−9%, obvious lead penetration combined with nickel dissolution is found. In the case of liquid lead with 10−6% oxygen content, a thin oxide layer can be formed on the surface, thus protecting the steel from liquid lead attack. After the corrosion test, significant precipitations are found in both austenitic and ferritic phases in the matrix of the steel

Photometry of Variable Stars from THU-NAOC Transient Survey I: The First 2 Years

In this paper, we report the detections of stellar variabilities from the first 2-year observations of sky area of about 1300 square degrees from the Tsinghua University-NAOC Transient Survey (TNTS). A total of 1237 variable stars (including 299 new ones) were detected with brightness < 18.0 mag and magnitude variation >= 0.1 mag on a timescale from a few hours to few hundred days. Among such detections, we tentatively identified 661 RR Lyrae stars, 431 binaries, 72 Semiregular pulsators, 29 Mira stars, 11 slow irregular variables, 11 RS Canum Venaticorum stars, 7 Gamma Doradus stars, 5 long period variables, 3 W Virginis stars, 3 Delta Scuti stars, 2 Anomalous Cepheids, 1 Cepheid, and 1 nove-like star based on their time-series variability index Js and their phased diagrams. Moreover, we found that 14 RR Lyrae stars show the Blazhko effect and 67 contact eclipsing binaries exhibit the O'Connell effect. Since the period and amplitude of light variations of RR Lyrae variables depend on their chemical compositions, their photometric observations can be used to investigate distribution of metallicity along the direction perpendicular to the Galactic disk. We find that the metallicity of RR Lyrae stars shows large scatter at regions closer to the Galactic plane (e.g., -3.0 < [Fe/H] < 0) but tends to converge at [Fe/H]~ -1.7 at larger Galactic latitudes. This variation may be related to that the RRAB Lyrae stars in the Galactic halo come from globular clusters with different metallicity and vertical distances, i.e. OoI and OoII populations, favoring for the dual-halo model.Comment: 18 pages, 19 figures, published in AJ, 150, 10

Evaluation of production and environmental efficiency in each country by DEA

departmental bulletin pape

Outcome Predictors in Patients Presenting With Acute Aortic Dissection

ObjectiveTo investigate the role of thyroid hormones and other factors in acute aortic dissection and an association with in-hospital adverse events.DesignA retrospective analysis.SettingA university-affiliated cardiac center.ParticipantsA total of 151 patients with aortic dissection admitted to the authors’ hospital between January 2011 and May 2015.InterventionNone.Measurements and ResultsThe total in-hospital mortality rate was 12.6%. Triiodothyronine (T3) level was lower in nonsurviving than surviving patients (0.8±0.3 v 1.0±0.4 nmol/L, p<0.05). T3 independently predicted in-hospital mortality (hazard ratio [HR] 0.07, 95% CI 0.01-0.43, p<0.01) and in-hospital acute renal failure (HR 0.22, 0.05-0.89, p<0.05) for all patients. Other independent predictors of in-hospital mortality were pericardial effusion (HR 8.18, 2.11-31.67, p<0.01), conservative treatment (HR 82.12, 12.49-540.09, p<0.01) and Stanford type-A aortic dissection (HR 3.86, 1.06-14.09, p<0.05). Inpatient conservative treatment, T3 (HR 0.01, 0.00-0.18, p<0.01) as well as pericardial effusion (HR 11.80, 2.46-56.59, p<0.01), Stanford type-A dissection (HR 22.35, 3.15-158.40, p<0.01), and in-hospital acute renal failure (HR 16.95, 2.04-140.86, p<0.01) were predictors for in-hospital mortality. In nonconservatively treated patients, T3 (HR 0.02, 0.00-0.88, p<0.05) as well as cardiac care unit stay (HR 0.74, 0.59-0.94, p<0.01) and postoperative acute renal failure (HR 21.32, 3.07-147.88, p<0.01) were predictors for in-hospital mortality.ConclusionT3 was downregulated in acute aortic dissection. Low T3 level was a risk factor for in-hospital death and acute renal failure in patients with acute aortic dissection