Turbulenzmodellierung für quasidimensionale Motorprozessrechnung

In dieser Arbeit wird ein quasidimensionales Ladungsbewegungs- und Turbulenzmodell für ottomotorische Motorprozessrechnung präsentiert. Die Grundlage bildet ein k-epsilon-Turbulenzmodell. Eine Beschreibung von spezifischer turbulenter kinetischer Energie und Dissipation im Zylinder erfolgt nulldimensional. Als Quellterme für Turbulenzproduktion werden die Einflüsse von einströmender kinetischer Energie, Tumble, Kolbenbewegung und Kompression berücksichtigt. Es wird ein Tumble-Modell mit quasidimensionaler Modellierung der Turbulenzproduktion innerhalb des Tumble-Wirbels vorgestellt. Dissipation wird auf Basis eines Turbulenz-Längenmaßes, in Abhängigkeit von Zylindergeometrie und Einlass-Ventilhub bestimmt. Zusätzlich wird die inhomogene Verteilung spezifischer kinetischer Energie während der Einströmphase berücksichtigt. Es wird eine Verbindung des präsentierten Turbulenzmodells mit einem Brennverlaufsmodell für homogene ottomotorische Verbrennung – Entrainmentmodell – gezeigt. Die Ergebnisse werden in Form von vorhergesagten und mittels Druckverlaufsanalyse ermittelten Brennverläufen auf Basis von Messdaten diskutiert

Changes in Heart Rate, Heart Rate Variability, Breathing Rate, and Skin Temperature throughout Pregnancy and the Impact of Emotions—A Longitudinal Evaluation Using a Sensor Bracelet

(1) Background: Basic vital signs change during normal pregnancy as they reflect the adaptation of maternal physiology. Electronic wearables like fitness bracelets have the potential to provide vital signs continuously in the home environment of pregnant women. (2) Methods: We performed a prospective observational study from November 2019 to November 2020 including healthy pregnant women, who recorded their wrist skin temperature, heart rate, heart rate variability, and breathing rate using an electronic wearable. In addition, eight emotions were assessed weekly using five-point Likert scales. Descriptive statistics and a multivariate model were applied to correlate the physiological parameters with maternal emotions. (3) Results: We analyzed data from 23 women using the electronic wearable during pregnancy. We calculated standard curves for each physiological parameter, which partially differed from the literature. We showed a significant association of several emotions like feeling stressed, tired, or happy with the course of physiological parameters. (4) Conclusions: Our data indicate that electronic wearables are helpful for closely observing vital signs in pregnancy and to establish modern curves for the physiological course of these parameters. In addition to physiological adaptation mechanisms and pregnancy disorders, emotions have the potential to influence the course of physiological parameters in pregnancy

Antibiotic Use During Pregnancy and Childbirth: Prospective Observational Study on Prevalence, Indications, and Prescribing Patterns in a German Tertiary Center

Introduction Antibiotics are powerful drugs to prevent and treat perinatal infections. Overuse of antibiotics leads to antibiotic resistance, has potential side effects and influences the maternal and neonatal microbiome. Patients and Methods We performed a prospective observational study on the prevalence, indications, and prescribing patterns of antibiotics during pregnancy and childbirth. We included women who had given birth after 23+0 weeks of gestation at a single tertiary center in Germany from January 2020 to March 2021. Descriptive statistics and binomial regression were performed to analyze the factors influencing the prescription of antibiotics. Results We included 522 postpartum women into our study. 337 (64.6%) were exposed to antibiotics during pregnancy and/or childbirth. 115 women received antibiotics during pregnancy, 291 during birth. Most antibiotics during pregnancy were prescribed for urinary tract infections (UTIs) (56.0%). Most prescriptions were issued by obstetrics and gynecology physicians (65.8%), followed by hospitals (16.7%) and family medicine physicians (8.8%). Most antibiotics during childbirth were given for a cesarean section (64.3%), followed by preterm rupture of membranes (41.2%). 95.3% of women who had a preterm birth were exposed to antibiotics. In logistic regression models, lower gestational age at birth, higher maternal body-mass-index and smoking were independently associated with antibiotic use during pregnancy and childbirth. Conclusion We found a high rate of antibiotic exposure during pregnancy and childbirth. Our results imply an urgent need for antibiotic stewardship programs in perinatal medicine as well as further research on the effects of perinatal antibiotic exposure on microbiome development and childhood health. // Einleitung Antibiotika sind potente Medikamente, die verschrieben werden, um perinatale Infektionen zu verhindern oder zu behandeln. Der übermäßige Einsatz von Antibiotika führt zur Antibiotikaresistenz, ist potenziell mit Nebenwirkungen behaftet und hat zudem Auswirkungen auf das mütterliche und neonatale Mikrobiom. Patientinnen und Methoden Wir führten eine prospektive Beobachtungsstudie durch, um die Prävalenz, die Indikationen und die Verschreibungsmuster für Antibiotika während der Schwangerschaft und der Geburt zu untersuchen. Eingeschlossen wurden Frauen, die nach 23+0 Schwangerschaftswochen zwischen Januar 2020 and März 2021 in einem deutschen universitären Perinatalzentrum Level I entbanden. Es wurden eine deskriptive statistische Analyse sowie binomiale Regressionsanalysen durchgeführt, um Faktoren, welche die Verschreibung von Antibiotika beeinflussen, zu identifizieren. Ergebnisse Insgesamt wurden 522 Frauen nach der Entbindung eingeschlossen. 337 (64,6%) erhielten Antibiotika während der Schwangerschaft und/oder der Geburt. 115 Frauen erhielten Antibiotika während der Schwangerschaft und 291 Frauen erhielten sie während der Geburt. Die meisten Antibiotika wurden während der Schwangerschaft zur Behandlung von Harnwegsinfektionen verschrieben (56,0%). Die meisten Verschreibungen wurden von Frauenärzten ausgestellt (65,8%), gefolgt von Krankenhäusern (16,7%) und Hausärzten (8,8%). Die meisten während der Geburt verabreichten Antibiotika wurden wegen eines Kaiserschnitts (64,3%) verschrieben; an zweiter Stelle war die Verschreibung wegen vorzeitigen Blasensprungs (41,2%). 95,3% der Frauen, die eine Frühgeburt hatten, wurden mit Antibiotika behandelt. In den Regressionsmodellen war ein niedriges Gestationsalter bei der Entbindung, ein hoher mütterlicher Body-Mass-Index und Rauchen unabhängig voneinander mit dem Einsatz von Antibiotika während der Schwangerschaft und der Geburt assoziiert. Schlussfolgerung Unsere Studie zeigt eine hohe Antibiotikaexposition von Frauen während Schwangerschaft und Geburt. Die Ergebnisse weisen darauf hin, dass ein Antibiotic-Stewardship-Programm in der Perinatalmedizin dringend nötig ist. Weitere Studien zu den Auswirkungen einer perinatalen Antibiotikaexposition auf die frühe Entwicklung des menschlichen Mikrobioms sowie auf die Gesundheit von Kindern werden benötigt

Low-Molecular Weight Heparin Increases Circulating sFlt-1 Levels and Enhances Urinary Elimination

Rationale: Preeclampsia is a devastating medical complication of pregnancy which leads to maternal and fetal morbidity and mortality. While the etiology of preeclampsia is unclear, human and animal studies suggest that excessive circulating levels of soluble fms-like tyrosine-kinase-1 (sFlt-1), an alternatively spliced variant of VEGF-receptor1, contribute to the signs and symptoms of preeclampsia. Since sFlt-1 binds to heparin and heparan sulfate proteoglycans, we hypothesized that the anticoagulant heparin, which is often used in pregnancy, may interfere with the levels, distribution and elimination of sFlt-1 in vivo. Objective: We systematically determined serum and urine levels of angiogenic factors in preeclamptic women before and after administration of low molecular weight heparin and further characterized the interaction with heparin in biochemical studies. Methods and Results: Serum and urine samples were used to measure sFlt-1 levels before and after heparin administration. Serum levels of sFlt-1 increased by 25% after heparin administration in pregnant women. The magnitude of the increase in circulating sFlt-1 correlated with initial sFlt-1 serum levels. Urinary sFlt-1 levels were also elevated following heparin administration and levels of elimination were dependent on the underlying integrity of the glomerular filtration barrier. Biochemical binding studies employing cation exchange chromatography revealed that heparin bound sFlt-1 had decreased affinity to negatively charged surfaces when compared to sFlt-1 alone. Conclusion: Low molecular weight heparin administration increased circulating sFlt1 levels and enhanced renal elimination. We provide evidence that both effects may be due to heparin binding to sFlt1 and masking the positive charges on sFlt1 protein

Low-Molecular Weight Heparin Increases Circulating sFlt-1 Levels and Enhances Urinary Elimination

Rationale: Preeclampsia is a devastating medical complication of pregnancy which leads to maternal and fetal morbidity and mortality. While the etiology of preeclampsia is unclear, human and animal studies suggest that excessive circulating levels of soluble fms-like tyrosine-kinase-1 (sFlt-1), an alternatively spliced variant of VEGF-receptor1, contribute to the signs and symptoms of preeclampsia. Since sFlt-1 binds to heparin and heparan sulfate proteoglycans, we hypothesized that the anticoagulant heparin, which is often used in pregnancy, may interfere with the levels, distribution and elimination of sFlt-1 in vivo. Objective: We systematically determined serum and urine levels of angiogenic factors in preeclamptic women before and after administration of low molecular weight heparin and further characterized the interaction with heparin in biochemical studies. Methods and Results: Serum and urine samples were used to measure sFlt-1 levels before and after heparin administration. Serum levels of sFlt-1 increased by 25% after heparin administration in pregnant women. The magnitude of the increase in circulating sFlt-1 correlated with initial sFlt-1 serum levels. Urinary sFlt-1 levels were also elevated following heparin administration and levels of elimination were dependent on the underlying integrity of the glomerular filtration barrier. Biochemical binding studies employing cation exchange chromatography revealed that heparin bound sFlt-1 had decreased affinity to negatively charged surfaces when compared to sFlt-1 alone. Conclusion: Low molecular weight heparin administration increased circulating sFlt1 levels and enhanced renal elimination. We provide evidence that both effects may be due to heparin binding to sFlt1 and masking the positive charges on sFlt1 protein

Insights Into the Aerodynamic Versus Radiometric Surface Temperature Debate in Thermal-Based Evaporation Modeling

Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State-of-the-art one-source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non-parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio-temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research

Insights into the aerodynamic versus radiometric surface temperature debate in thermal-based evaporation modeling

Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State-of-the-art one-source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non-parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio-temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research