• 제목/요약/키워드: Oxford University

검색결과 221건 처리시간 0.022초

DESIGN AND ANALYSIS OF RANDOMIZED CLINICAL TRIALS REQUIRING PROLONGED OBSERVATION OF EACH PATIENT I. INTRODUCTION AND DESIGN

  • Peto R.;Pike M.C.;Armitage P.;Breslow N.E.;Cox D.R.;Howard S.V.;Mantel N.;Mcpherson K.;Peto J.;Smith P.G.
    • 대한예방의학회:학술대회논문집
    • /
    • 대한예방의학회 1994년도 교수 연수회(역학)
    • /
    • pp.206-233
    • /
    • 1994
  • The Medical Research Council has for some years encouraged collaborative clinical trials in leukaemia and other cancers, reporting the results in the medical literature. One unreported result which deserves such publication is the development of the expertise to design and analyse such trials. This report was prepared by a group of British and American statisticians, but it is intended for people without any statistical expertise. Part!, which appears in this issue, discusses the design of such trials; Part II, which will appear separately in the January 1977 issue of the Journal, gives full instructions for the statistical analysis of such trials by means of life tables and the logrank test, including a worked example, and discusses the interpretation of trial results, including brief reports of particular trials. Both parts of this report are relevant to all clinical trials which study time to death, and would be equally relevant to clinical trials which study time to other particular classes of untoward event: first stroke, perhaps, or first relapse, metastasis, disease recurrence, thrombosis, transplant rejection, or death from a particular cause. Part I, in this issue, collects together ideas that have mostly already appeared in the medical literature, but Part II, next month, is the first simple account yet published for non-statistical physicians of how to analyse efficiently data from clinical trials of survival duration. Such trials include the majority of all clinical trials of cancer therapy; in cancer trials, however, it may be preferable to use these statistical methods to study time to local recurrence of tumour, or to study time to detectable metastatic spread, in addition to studying total survival. Solid tumours can be staged at diagnosis; if this, or any other available information in some other disease is an important determinant of outcome, it can be used to make the overall logrank test for the whole heterogeneous trial population more sensitive, and more intuitively satisfactory, for it will then only be necessary to compare like with like, and not, by chance, Stage I with Stage III.

  • PDF

Methyl Viologen Mediated Oxygen Reduction in Ethanol Solvent: the Electrocatalytic Reactivity of the Radical Cation

  • Lin, Qianqi;Li, Qian;Batchelor-McAuley, Christopher;Compton, Richard G.
    • Journal of Electrochemical Science and Technology
    • /
    • 제4권2호
    • /
    • pp.71-80
    • /
    • 2013
  • The study of methyl viologen ($MV^{2+}$) mediated oxygen reduction in electrolytic ethanol media possesses potential application in the electrochemical synthesis of hydrogen peroxide mainly due to the advantages of the much increased solubility of molecular oxygen ($O_2$) and high degree of reversibility of $MV^{2+/{\bullet}+}$ redox couple. The diffusion coefficients of both $MV^{2+}$ and $O_2$ were investigated via electrochemical techniques. For the first time, $MV^{2+}$ mediated $O_2$ reduction in electrolytic ethanol solution has been proved to be feasible on both boron-doped diamond and micro-carbon disc electrodes. The electrocatalytic response is demonstrated to be due to the radical cation, $MV^{{\bullet}+}$. The homogeneous electron transfer step is suggested to be the rate determining step with a rate constant of $(1{\pm}0.1){\times}10^5M^{-1}s^{-1}$. With the aid of a simulation program describing the EC' mechanism, by increasing the concentration ratio of $MV^{2+}$ to $O_2$ electrochemical catalysis can be switched from a partial to a 'total catalysis' regime.

EBSD를 이용한 $SrTiO_3$의 입자 크기 및 입자 배향 분포 (EBSD studies of the grain size and grain orientation distribution of $SrTiO_3$)

  • 박명범;;조남희
    • 한국전기전자재료학회:학술대회논문집
    • /
    • 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
    • /
    • pp.46-46
    • /
    • 2006
  • $SrTiO_3$ was annealed at two different annealing times (1 h and 16 h) to investigate the annealing effect on the grain size and orientation distribution. Electron backscattered diffraction (EBSD) was used to analyze the grain size and grain orientation distributions of the $SrTiO_3$. It is possible to understand the annealing effect on the microstructure evolution, by comparing the grain size and orientation distribution of the $SrTiO_3$ as a function of annealing time.

  • PDF

EFFECT OF SURFACE ROUGHNESS ON THE ADHESION OF SILICON WAFERS PRIOR TO BONDING

  • Lee, D. H.;B. Derby
    • 한국전기전자재료학회:학술대회논문집
    • /
    • 한국전기전자재료학회 1998년도 춘계학술대회 논문집
    • /
    • pp.497-502
    • /
    • 1998
  • To understand the effect of surface roughness on silicon wafer bonding, a continuum mechanical model is presented. This model is based on Obreimoff's experiment and the contact theory of rough surfaces. The surface energy of silicon was calculated to be much reduced than the theoretical value. Problems are discussed concerning surface film effects and the assumption of constant asperity radius and statistical distribution function.

  • PDF

Association between Smoking and Mortality: Khon Kaen Cohort Study, Thailand

  • Kamsa-ard, Siriporn;Promthet, Supannee;Lewington, Sarah;Burrett, Julie Ann;Sherliker, Paul;Kamsa-ard, Supot;Wiangnon, Surapon;Parkin, Donald Maxwell
    • Asian Pacific Journal of Cancer Prevention
    • /
    • 제14권4호
    • /
    • pp.2643-2647
    • /
    • 2013
  • Background: Despite anti-smoking campaigns, smoking prevalence among Thai males aged 30 or older is high, at around 50%. The purpose of this study was to determine the relationship between smoking and mortality in a rural Thai community. Materials and Methods: Subjects enrolled into the Khon Kaen cohort study between 1990 and 2001 were followed up for their vital status until $16^{th}$ March 2012. The death resource was from the Bureau of Policy and Strategy, Ministry of Interior, Thailand. A Cox proportional hazards model was used to analyse the association between smoking and death, controlling for age, education level and alcohol drinking, and confidence intervals were calculated using the floating risk method. Results: The study recruited 5,962 male subjects, of whom 1,396 died during a median 13.5 years of follow-up. Current smokers were more likely to die than never smokers after controlling for age, education level and alcohol drinking (HR, 95%CI: 1.41, 1.32-1.51), and the excess mortality was greatest for lung cancer (HR, 95%CI: 3.51, 2.65-4.66). However, there was no increased risk with increasing dose of tobacco, and no difference in risk between smokers of yamuan (hand-rolled cigarettes) and manufactured tobacco. Conclusion: Mortality from cancer, particularly lung cancer, and from all causes combined is dependent on smoking status among men in rural Thailand, but the relative risks are lower than have been reported from studies in high income countries, where the tobacco epidemic is more established.