Evaluation of leakage through labyrinth seals with analytical models

Secondary flows in turbo machinery highly affect the overall efficiency and rotor stability. A prime example of such a phenomenon are leakage flows. Despite their complexity,they can often be estimated with simple semi-empirical formulae, solved with hand calculations.Such an approach is much more cost and time effective during the design process. The formulae consists of a carry-over coefficient and a discharge coefficient elements. To evaluate the leakage properly, an adequate model of the carry-over coefficient has to be developed. This paper presents show the flow conditions and the cavity geometry changes in a straight through labyrinth seal affect the amount of leakage. The effect of the number of teeth, the gap size, the Reynolds number and the pressure ratio are considered. The data to validate the results was obtained from an in-house experiment, where a vast number of cases was tested. Additionally, the study was supported by a two-dimensional steady-state CFD study. Eleven analytical models,Including both very simple as well as more sophisticated methods, were solved according to the experimental case and compared. Six different seal configurations were examined. They included straight through seals with two and three straight knives for various gap sizes.The comparison highlighted differences in the results for models – a certain group presented underestimated results. However, another group of models – presented an excellent agreement with the experimental data. Based on this study, a group of models representing the results within the 10% uncertainty band was selected

Birth status and twin birth weight discordance

Abstract Objectives: The aim of the research was to estimate the influence of birth weight discordance on birth status of twins. Material and methods: Material of the research consisted of 560 foetuses derived from successful twin pregnancies. In the analysis the following factors were taken into consideration: birth status, gasometry, and birth weight discordance. Results: The degree of birth weight discordance under 10% was noted in 50% of twin pregnancies (n=140), discordance of 10%-20% was observed in 30.7% (n=86), and >20 % - in 19,3% (n=54). Conclusions: Birth weight discordance is an important risk factor for fetal and neonatal morbidity which is higher in smaller twins than in larger ones. Along with the degree of birth weight discordance, an increased risk of neonatal complications was observed

Retinoic Acid and Its Derivatives in Skin

The retinoids are a group of compounds including vitamin A and its active metabolite all-trans-retinoic acid (ATRA). Retinoids regulate a variety of physiological functions in multiple organ systems, are essential for normal immune competence, and are involved in the regulation of cell growth and differentiation. Vitamin A derivatives have held promise in cancer treatment and ATRA is used in differentiation therapy of acute promyelocytic leukemia (APL). ATRA and other retinoids have also been successfully applied in a variety of dermatological conditions such as skin cancer, psoriasis, acne, and ichthyosis. Moreover, modulation of retinoic acid receptors and retinoid X (or rexinoid) receptors function may affect dermal cells. The studies using complex genetic models with various combinations of retinoic acid receptors (RARs) and retinoid X (or rexinoid) receptors (RXRs) indicate that retinoic acid and its derivatives have therapeutic potential for a variety of serious dermatological disorders including some malignant conditions. Here, we provide a synopsis of the main advances in understanding the role of ATRA and its receptors in dermatology

Classical and quantum molecular dynamics in NMR spectra

The book provides a detailed account of how condensed-phase molecular dynamics are reflected in the line shapes of NMR spectra. The theories establishing connections between random, time-dependent molecular processes and lineshape effects are exposed in depth. Special emphasis is placed on the theoretical aspects, involving in particular intermolecular processes in solution, and molecular symmetry issues. The Liouville super-operator formalism is briefly introduced and used wherever it is beneficial for the transparency of presentation. The proposed formal descriptions of the discussed problems are sufficiently detailed to be implemented on a computer. Practical applications of the theory in solid- and liquid-phase studies are illustrated with appropriate experimental examples, exposing the potential of the lineshape method in elucidating molecular dynamics NMR-observable molecular phenomena where quantization of the spatial nuclear degrees of freedom is crucial are addressed in the last part of the book. As an introduction to this exciting research field, selected aspects of the quantum mechanics of isolated systems undergoing rotational tunnelling are reviewed, together with some basic information about quantum systems interacting with their condensed environment. The quantum theory of rate processes evidenced in the NMR lineshapes of molecular rotors is presented, and illustrated with appropriate experimental examples from both solid- and liquid-phase spectra. In this context, the everlasting problem of the quantum-to-classical transition is discussed at a quantitative level. The book will be suitable for graduate students and new and practising researchers using NMR techniques

Evaluation of leakage through labyrinth seals with analytical models

Secondary flows in turbomachinery highly affect the overall efficiency and rotorstability. A prime example of such a phenomenon are leakage flows. Despite their complexity, they can often be estimated with simple semi-empirical formulae, solved with hand calculations.Such an approach is much more cost and time effective during the design process. The formula econsists of a carry-over coefficient and a discharge coefficient elements. To evaluate the leakage properly, an adequate model of the carry-over coefficient has to be developed. This paper presents how the flow conditions and the cavity geometry changes in a straight through labyrinth sea laffect the amount of leakage. The effect of the number of teeth, the gap size, the Reynolds number and the pressure ratio are considered. The data to validate the results was obtained from an in-house experiment, where a vast number of cases was tested. Additionally, the study was supported by a two-dimensional steady-state CFD study. Eleven analytical models, including both very simple as well as more sophisticated methods, were solved according to the experimental case and compared. Six different seal configurations were examined. They included straight through seals with two and three straight knives for various gap sizes.The comparison highlighted differences in the results for models – a certain group presented underestimated results. However, another group of models – presented an excellent agreement with the experimental data. Based on this study, a group of models representing the results within the 10% uncertainty band was selected

The effect of Foley catheter preinduction on the birth state of a newborn compared to a spontaneous birth. Wpływ preindukcji cewnikiem Foleya na stan urodzeniowy noworodka w porównaniu z porodem samoistnym.

SUMMARYObjective: The aim of the study was to analyze the birth status of a newborn after a childbirth induced by a Foley catheter compared to a spontaneous birth.Materials and methods: The study involved 146 newborns after spontaneous deliveries (47.9%) or induced by Foley catheter (52.1%). The research methodology assumed the analysis of medical records. The calculations were carried out using the Statistica v 10.0 software from StatSoft. The Chi square Pearson and t-Student tests were used for statistical analysis. The significance level was assumed to be p£0.05.Results: The most common indications for Foley catheter pre-induction were pregnancy after term, gestational type 1 diabetes and oligohydramnios. The neonatal birth rate assessed according to the Apgar scale did not differ significantly in both groups. Differences in the values of umbilical blood gasometry parameters in both groups were not statistically significant.Conclusions: Induction of delivery with the Foley catheter is not associated with a worse birth condition of the newborn. The birth state of the newborn may also be dependent on pre-induction indications. The anthropometric parameters of the born fetuses, the Apgar score as well as the gasometric tests indicate that the Foley catheter can be considered as a cheap, but above all safe and effective method of labor induction.KEYWORDS: Scores on the Apgar's scale, umbilical cord blood gasometry, childbirth, induction of labor, Foley's catheter. STRESZCZENIE Cel: Celem pracy była analiza stanu urodzeniowego noworodka po porodzie indukowanym cewnikiem Foleya w porównaniu do porodu samoistnego.Materiały i Metody: Badaniu poddano 146 noworodków po porodach samoistnych (47,9%) lub indukowanych cewnikiem Foleya (52,1%). Metodyka badań zakładała analizę dokumentacji medycznej.  Obliczenia wykonano przy pomocy oprogramowania Statistica v 10.0 firmy StatSoft. Do analizy statystycznej użyto testu Chi kwadrat Pearsona  oraz t- Studenta. Za poziom istotności przyjęto p£0,05.Wyniki: Najczęstszymi wskazaniami do preindukcji cewnikiem Foleya były ciąża po terminie, cukrzyca ciążowa typu 1 oraz małowodzie.  Stan urodzeniowy noworodków oceniany  według skali Apgar  nie różnił się istotnie statystycznie w obu grupach. Różnice w wartościach parametrów gazometrii krwi pępowinowej w obu grupach nie były istotne statystycznie.Wnioski: Indukcja porodu cewnikiem Foleya nie wiąże się z gorszym stanem urodzeniowym noworodka. Stan urodzeniowy noworodka może także być uzależniony od wskazań do preindukcji. Parametry antropometryczne urodzonych płodów, punktacja w skali Apgar, jak i badania gazometryczne wskazują, że cewnik Foleya można uznać za tanią, ale przede wszystkim bezpieczną i skuteczną metodę indukcji porodu. SŁOWA KLUCZOWE:  punktacja w skali Apgar, gazometria krwi pępowinowej, poród, indukcja porodu, cewnik Foleya.

Neonatal thermal response to childbirth: Vaginal delivery vs. caesarean section.

Newborns, regardless of the method of termination of pregnancy, are exposed to the first exogenous stress factors during delivery. The purpose of the study was to evaluate the differences in newborns' thermal response to vaginal (VD) vs caesarean section (CS) delivery. The temperature was measured during the first minutes of life within 122 healthy full-term newborns, on the forehead, chest and upper-back by infrared camera (FLIR T1030sc HD). The lowest temperatures were recorded in the forehead of VD newborns (significantly difference with CS; p < 0.001), the warmest was the chest. A significant correlation was found between the duration of the second stage of natural childbirth and surface temperature and pO2 in the newborn blood. The temperatures of selected body surface areas correlate highly positively, regardless of the mode of delivery. In the case of healthy neonates, with normal birth weight and full-term, VD creates more favourable conditions stimulating the mechanisms of adaptation for a newborn than CS

Surface Body Temperature of Full-Term Healthy Newborns Immediately after Birth—Pilot Study

The aim of the study was to perform an evaluation of chosen body surface temperatures in neonates immediately after birth, and to seek a relationship between those temperatures and the factors related both to the mother and newborn. The study included 74 healthy newborns. Maternal age, body weight, body mass index before pregnancy and on delivery day, birth and pregnancy order, newborn sex, birth weight, body length, pregnancy week on delivery, as well as newborn gasometric test results were collected. The highest temperature values were observed in the chest of the newborn. Significant relationships between the temperature of the evaluated areas were found. The parameters that correlated positively with the temperature of the back region were maternal body weight (both before pregnancy and on delivery day) as well as weight gain during pregnancy. The core and surface temperatures of the body are one of the most important elements of neonatal homeostasis and any changes constitute a risk to the newborn&#8217;s health. It seemed that according to the surface temperature, the most important area that must be evaluated is the neonate&#8217;s back, as it is most affected by appropriate weight gain during pregnancy