Study of Bootstrap Estimates in Cox Regression Model with Delayed Entry

summary:In most clinical studies, patients are observed for extended time periods to evaluate influences in treatment such as drug treatment, approaches to surgery, etc. The primary event in these studies is death, relapse, adverse drug reaction, or development of a new disease. The follow-up time may range from few weeks to many years. Although these studies are long term, the number of observed events is small. Longitudinal studies have increased the importance of statistical methods for time-to event data that can incorporate time-dependent covariates. The Cox proportional regression model is a widely used method. It is a statistical technique for exploring the relationship between the survival of a patient and several explanatory variables. We apply Cox regression models when right censoring and delayed entry survival data are considered. Su and Wang (2012) stated that delayed entry produced biased sample. In the paper we present how re-sampling together with effect of delayed entry affect estimated parameters. The possibilities as well as limitations of this approach are demonstrated through the retrospective study of mitral valve replacement in children under 18 years

Gestational surrogacy in the Czech Republic

BACKGROUND: Gestational surrogacy, is a treatment option for women with certain clearly defined medical problems, usually an absent uterus, to help them have their own genetic children. The aim of our study was to review, evaluate and share our experience and outcomes over the last 13 years of the largest surrogacy program in the Czech republic. METHODS: A total of 75 intended mothers and 82 surrogate mothers participated in this study. A retrospective cohort study was performed. Anonymized data were collected on 130 cycles of gestational surrogate (2004-2017) directly from the Clinic database. RESULTS: We performed 130 in vitro fertilization cycles with gestational surrogacy which involved 73 fresh embryo transfers and 57 frozen embryo transfers. We achieved 57 (43.9%) pregnancies and 42 (32.3%) live births. The rate of multiple pregnancies was only 2.3 %. The most common indication for using was an absent or damaged uterus (65%), followed by medical conditions precluding pregnancy (23%) and repeated in vitro fertilization cycles or pregnancy failure (12%). CONCLUSION: In the 14 years of our experience, we have shown that treatment of young women with specific indications for gestational surrogacy is beneficial, successful and relatively free of complications. However, it is imperative to follow the medical indications for this treatment and specialist recommendations.National Program of Sustainability II (MEYS CR) [LQ1605]; GACRGrant Agency of the Czech Republic [17-07753S

Survival analysis of factors influencing cyclic fatigue of nickel-titanium endodontic instruments

Objective. The aim of this study was to validate a survival analysis assessing the effect of type of rotary system, canal curvature, and instrument size on cyclic resistance. Materials and Methods. Cyclic fatigue testing was carried out in stainless steel artificial canals with radii of curvature of 3 or 5 mm and the angle of curvature of 60 degrees. All the instruments were new and 25 mm in working length, and ISO colour coding indicated the instrument size (yellow for size 20; red for size 25). Wizard Navigator instruments, Mtwo instruments, ProTaper instruments, and Revo-S instruments were passively rotated at 250 rotations per minute, and the time fracture was being recorded. Subsequently, fractographic analysis of broken tips was performed by scanning electron microscope. The data were then analysed by the Kaplan-Meier estimator of the survival function, the Cox proportional hazards model, the Wald test for regression covariates, and the Wald test for significance of regression model. Conclusion. The lifespan registered for the tested instruments was Mtwo > Wizard Navigator > Revo-S > ProTaper; 5 mm radius > 3 mm radius; and yellow > red in ISO colour coding system.Ministry of Education, Youth and Sports of the Czech Republic [CZ.1.07/2.3.00/20.0170, CZ.1.07/2.3.00/30.0041

Mathematization of the death-moment determination process of laboratory biological material

The article presents results of scientific research in the field of mathematization of the algor mortis process in death-moment determination of biological laboratory material. It describes in a clear form the basic mathematization models of the algor mortis process using mathematical regression, for calculation of the death moment based on acquired temperature values of the liver mass of biological laboratory material, for open and closed examined area of the peritoneal cavity of the left liver lobe, lobus sinister. The liver has a large functional reserve; even one third of its tissue is able to provide its basic functions, they also have a large regenerative ability and are located far from the body surface. © Tomáš Návrat, Vladimír Fuis, Lubomír Houfek and Miloš Vlk, 2011

Device for contactless sensing and regression of non-stationary temperature fields, especially in biological objects

Zařízení je tvořeno mikrobolometrickou maticí, snímací jednotkou parametrů prostředí a vyhodnocovací jednotkou, která je spojena s mikrobolometrickou maticí a snímací jednotkou parametrů prostředí a je vybavena zadávacím systémem korekčních parametrů měřeného objektu. Zařízení má s výhodou mikrobolometrickou matici obsahující vybavení pro vyhodnocení četnosti jednotlivých teplot a jejich časové závislosti. Snímací jednotka parametrů prostředí pak s výhodou obsahuje snímač teploty prostředí. Zařízení může mít mikrobolometrickou matici spojenou s vyhodnocovací jednotkou kartou nebo kabelem. Snímací jednotka parametrů prostředí může být spojena s vyhodnocovací jednotkou bezdrátově nebo kabelem.In the present invention, there is disclosed a device consisting of a microbolometric matrix, an ambient environment parameter scanning device as well as an evaluation and assessment unit, which is linked to the microbolometric matrix as well as to the ambient environment parameter scanning device. The evaluation and assessment unit is provided with a data-entry system of the measured object's parameters correction. The microbolometric matrix preferably contains equipment for the evaluation of the frequency of individual temperatures and their time-courses. The ambient environment parameter-scanning device is preferably equipped with an ambient environment temperature scanner. The microbolometric matrix can be linked to the assessment unit using a card or cable. The ambient environment parameter-scanning device can be linked with the evaluation and assessment unit either wirelessly or by a cable

Gait Patterns for Crime Fighting: Statistical Evaluation

The criminality is omnipresent during the human history. Modern technology brings novel opportunities for identification of a perpetrator. One of these opportunities is an analysis of video recordings, which may be taken during the crime itself or before/after the crime. The video analysis can be classed as identification analyses, respectively identification of a person via externals. The bipedal locomotion focuses on human movement on the basis of their anatomical-physiological features. Nowadays, the human gait is tested by many laboratories to learn whether the identification via bipedal locomotion is possible or not. The aim of our study is to use 2D components out of 3D data from the VICON Mocap system for deep statistical analyses. This paper introduces recent results of a fundamental study focused on various gait patterns during different conditions. The study contains data from 12 participants. Curves obtained from these measurements were sorted, averaged and statistically tested to estimate the stability and distinctiveness of this biometrics. Results show satisfactory distinctness of some chosen points, while some do not embody significant difference. However, results presented in this paper are of initial phase of further deeper and more exacting analyses of gait patterns under different conditions

Synthesis of control rule for synthesized chaotic system by means of evolutionary techniques

The paper deals with a synthesis of control law for a discrete chaotic system, both synthesized by means of analytic programming. This is a preliminary study in which the aim is to show that tool for symbolic regression analytic programming - is possible to use for such kind of problems. The paper consists of description of analytic programming as well as a chaotic system. This article contents 52 successful simulations in the result section and will be extended within future tests in this field. SOMA (Self-Organizing Migrating Algorithm) with analytic programming was used for experiments in this case

AMH levels and IVF stimulation

The goal of this study was to evaluate the utility of anti-Mullerian hormone (AMH) serum levels for prediction of gonadotropin dose for stimulation prior to an IVF cycle. In conclusion, AMH is a good predictor for the dose of gonadotropins. A lower value of AMH corresponds with the high consumption of gonadotropins during the stimulation process. A low level of AMH predicts a high dose of gonadotropins, required during stimulation and also predicts a poorer yield of oocytes

Comparison of intracytoplasmic sperm injection and preselected intracytoplasmic sperm injection by time-lapse monitoring

OBJECTIVE: To compare the methods of fertilization using intracytoplasmic sperm injection (ICSI) and preselected intracytoplasmic sperm injection (PICSI) via the assessment of time parameters during an early development of embryos by the timelapse monitoring system. STUDY DESIGN: In total, 258 embryos destined for embryo transfer by 136 couples undergoing in vitro fertilization (IVF) cycle with donated oocytes were evaluated retrospectively. The first patient group underwent the PICSI fertilization method and the second group the ICSI method. Exact time parameters of early embryo development were compared. RESULTS: The chance of clinical pregnancy is slightly decreased with the increasing time when the embryo has reached the 8-cell stage (p=0.017). Clinical pregnancy rate for the PICSI method was 54.9% and 50% for the ICSI method (odds ratio=1.216, 95% CI 0.611-2.42, p=0.065). By using the PICSI method there was a 22% greater chance of clinical pregnancy. This increase is not statistically significant. CONCLUSION: Our findings noted an important contribution of the PICSI method. We will continue to monitor the development of the pregnancy arising from this study, in order to contribute to a clarification whether the sperm bound to hyaluronic acid increases the chance of maintaining a pregnancy and carrying the fetus to term