Directions for new developments on statistical design and analysis of small population group trials

Most statistical design and analysis methods for clinical trials have been developed and evaluated where at least several hundreds of patients could be recruited. These methods may not be suitable to evaluate therapies if the sample size is unavoidably small, which is usually termed by small populations. The specific sample size cut off, where the standard methods fail, needs to be investigated. In this paper, the authors present their view on new developments for design and analysis of clinical trials in small population groups, where conventional statistical methods may be inappropriate, e.g., because of lack of power or poor adherence to asymptotic approximations due to sample size restrictions

randomizeR: An R Package for the Assessment and Implementation of Randomization in Clinical Trials

Randomization in clinical trials is the key design technique to ensure the comparability of treatment groups. Although there exist a large number of software products which assist the researcher to implement randomization, no tool which would cover a wide range of procedures and allow the comparative evaluation of the procedures under practical restrictions has been proposed in the literature so far. The R package randomizeR addresses this need. The paper includes a detailed description of the randomizeR package that serves as a tutorial for the generation of randomization sequences and the assessment of randomization procedures

ERDO - a framework to select an appropriate randomization procedure for clinical trials

Background: Randomization is considered to be a key feature to protect against bias in randomized clinical trials. Randomization induces comparability with respect to known and unknown covariates, mitigates selection bias, and provides a basis for inference. Although various randomization procedures have been proposed, no single procedure performs uniformly best. In the design phase of a clinical trial, the scientist has to decide which randomization procedure to use, taking into account the practical setting of the trial with respect to the potential of bias. Less emphasis has been placed on this important design decision than on analysis, and less support has been available to guide the scientist in making this decision.Methods: We propose a framework that weights the properties of the randomization procedure with respect to practical needs of the research question to be answered by the clinical trial. In particular, the framework assesses the impact of chronological and selection bias on the probability of a type I error. The framework is applied to a case study with a 2-arm parallel group, single center randomized clinical trial with continuous endpoint, with no-interim analysis, 1:1 allocation and no adaptation in the randomization process.Results: In so doing, we derive scientific arguments for the selection of an appropriate randomization procedure and develop a template which is illustrated in parallel by a case study. Possible extensions are discussed.Conclusion: The proposed ERDO framework guides the investigator through a template for the choice of a randomization procedure, and provides easy to use tools for the assessment. The barriers for the thorough reporting and assessment of randomization procedures could be further reduced in the future when regulators and pharmaceutical companies employ similar, standardized frameworks for the choice of a randomization procedure

Synthesis of glycolide by depolimerization of glycolic acid oligomers modified by polyhydric alcohols

Oligomers of glycolic acid esterified by ethylene glycol, propylene glycol, glycerin were obtained. These samples were depolymerized with various oxide catalysts such as MgO, ZnO, SnO[2] and Sb[2]O[3]. The resulting glycolide was analyzed by gas chromatography in different eluents - acetonitrile and hexafluoroisopropanol. It was shown that modification of glycolic acid oligomers by polyhydric alcohols reduces the content of hydroxyl containing impurities in raw glycolide

Aluminosis – Detection of an almost forgotten disease with HRCT

The aim of this study was to investigate whether it is possible to detect high-resolution computed tomography (HRCT) findings in aluminium powder workers, which are consistent with early stages of aluminosis. 62 male workers from 8 departments of two plants producing aluminium (Al) powder were investigated using a standardized questionnaire, physical examination, lung function analysis, biological monitoring of Al in plasma and urine, chest X-ray, HRCT and immunological tests. Chronic bronchitis was observed in 15 (24.2%) of the workers, and four workers (6.5%) reported shortness of breath during exercise. HRCT findings in 15 workers (24.2%) were characterized by ill-defined centrilobular nodular opacities. Workers with ill-defined centrilobular nodular opacities had a lower vital capacity than workers who had no such HRCT-findings (90.9 % pred. vs. 101.8 % pred., p = 0.01). Biological monitoring in plasma and urine revealed higher internal exposure to Al in affected workers (33.5 μg/l plasma to 15.4 μg/l plasma, p = 0.01) and (340.5 μg/g creat. to 135.1 μg/g creat., p = 0.007). Years of exposure and concentration of aluminum in urine and plasma appear to be the best predictors for HRCT findings. Age and decreased vital capacity show borderline significance. We conclude that aluminosis is still relevant in occupational medicine. With HRCT it is possible to detect early stages of aluminosis and biological monitoring can be used to define workers at high risk

Автоматизация электропривода холодильной установки

При разработке проекта рассматривается низкотемпературная компрессионная холодильная установка, для улучшения и надежности работы которой предлагается замена одного полугерметичного поршневого компрессора Frascold S10-52Y на компрессор открытого поршневого типа Bitzer 4P.2Y для подбора и расчета асинхронного двигателя АИС160М4 общепромышленного назначения соединенного на основе муфты с коническим замком с валом компрессора и подключенного через частотник Danfoss VLT.When developing the project, a low-temperature compression refrigeration unit is considered, for improvement and reliability of which a replacement of one semi-hermetic piston compressor Frascold S10-52Y with an open piston type compressor Bitzer 4P.2Y is proposed for the selection and calculation of the asynchronous AIS160M4 engine of a general industrial purpose connected on the basis of a coupling with a conical lock with the shaft of the compressor and connected through chastotnik Danfoss VLT

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Требования к узлу сопряжения секций геохода

Проведен анализ работы узла сопряжения секций (УСС) геохода. Сформированы требования к узлу сопряжения секций геохода.The analysis of the operation of the bearing unit of the geokhod is carried out. The requirements for the bearing unit of the geokhod are formed