1,552 research outputs found
Monte Carlo Study of the Inflation-Deflation Transition in a Fluid Membrane
We study the conformation and scaling properties of a self-avoiding fluid
membrane, subject to an osmotic pressure , by means of Monte Carlo
simulations. Using finite size scaling methods in combination with a histogram
reweighting techniques we find that the surface undergoes an abrupt
conformational transition at a critical pressure , from low pressure
deflated configurations with a branched polymer characteristics to a high
pressure inflated phase, in agreement with previous findings
\cite{gompper,baum}. The transition pressure scales with the system
size as , with . Below
the enclosed volume scales as , in accordance with the
self-avoiding branched polymer structure, and for our data
are consistent with the finite size scaling form ,
where .
Also the finite size scaling behavior of the radii of gyration and the
compressibility moduli are obtained. Some of the observed exponents and the
mechanism behind the conformational collapse are interpreted in terms of a
Flory theory.Comment: 20 pages + postscript-file, Latex + Postscript, IFA Report No. 94/1
The Future of Codetermination After Centros: Will German Corporate Law Move Closer to the U.S. Model?
Mesoscopic modeling of the rtm process for homogenization
Intrinsic hybrids can be manufactured in a modified resin transfer molding (RTM) process
for fibre reinforced polymers. Our work concentrates on mesoscopic modeling for
temperature-dependent visco-elastic effects accompanied by curing within the RTM process.
During hybridization and later thermal loading the periodic mesostructure defined
by resin and fibres is taken into account as a representative volume element (RVE) subjected
to thermo-mechanical loading. Homogenization leads to results on the less resolved
macroscale. In the examples we illustrate the characteristic behavior of the mesoscopic
model, such as shrinking due to curing and temperature dependence and simulate the
RTM process as well as thermal loading of the cured composite with the finite-element-method
Resuscitation Endpoints in Traumatic Shock: A Focused Review with Emphasis on Point-of-Care Approaches
Trauma resuscitation is a blend of art and science, with the traumatologist at the helm of a large, multidisciplinary team, making split-second decisions and overseeing various parallel processes. Despite tremendous progress over the past few decades, the âartâ component continues to play a large part in the overall trauma resuscitation process, with the âscienceâ part slowly but steadily increasing its footprint as a determinant of processes and decisions. Thus, it becomes critical for all clinicians to be able to recognize the evidence-based factors which can be most valuable in guiding trauma resuscitations. This chapter serves as an overview of the current clinical findings, resuscitative endpoints, imaging techniques, and physiologic indices that are most helpful in order to promptly recognize and treat traumatic shock as well as projecting forward to look at novel techniques and biomarkers. Though a single universal marker that accurately and consistently identifies traumatic shock has yet to be discovered, certain factors discussed, such as lactate and base deficit, have been proven to be much more reliable than others
FPGA basierte, konfigurierbare OFDM Sender-Plattform fĂŒr die Positionsbestimmung mittels TDoA
FĂŒr die Evaluierung von Algorithmen zur Positionsbestimmung nach dem Time Difference of Arrival â Verfahren wird eine frei konfigurierbare OFDM Sender-Plattform benötigt. Da die Berechnung in Echtzeit erfolgen soll, ist eine Implementierung in rekonfigurierbarer Hardware (FPGA) erforderlich. Das Manuskript
gibt sowohl einen Ăberblick ĂŒber die HintergrĂŒnde und die Architektur des Sendesystems, als auch einen tieferen Einblick in verschiedene Lösungsdetails
Presenilin-1 processing of ErbB4 in fetal type II cells is necessary for control of fetal lung maturation
AbstractMaturation of pulmonary fetal type II cells to initiate adequate surfactant production is crucial for postnatal respiratory function. Little is known about specific mechanisms of signal transduction controlling type II cell maturation. The ErbB4 receptor and its ligand neuregulin (NRG) are critical for lung development. ErbB4 is cleaved at the cell membrane by the Îł-secretase enzyme complex whose active component is either presenilin-1 (PSEN-1) or presenilin-2. ErbB4 cleavage releases the 80kDa intracellular domain (4ICD), which associates with chaperone proteins such as YAP (Yes-associated protein) and translocates to the nucleus to regulate gene expression. We hypothesized that PSEN-1 and YAP have a development-specific expression in fetal type II cells and are important for ErbB4 signaling in surfactant production. In primary fetal mouse E16, E17, and E18 type II cells, PSEN-1 and YAP expression increased at E17 and E18 over E16. Subcellular fractionation showed a strong cytosolic and a weaker membrane location of both PSEN-1 and YAP. This was enhanced by NRG stimulation. Co-immunoprecipitations showed ErbB4 associated separately with PSEN-1 and with YAP. Their association, phosphorylation, and co-localization were induced by NRG. Confocal immunofluorescence and nuclear fractionation confirmed these associations in a time-dependent manner after NRG stimulation. Primary ErbB4-deleted E17 type II cells were transfected with a mutant ErbB4 lacking the Îł-secretase binding site. When compared to transfection with wild-type ErbB4, the stimulatory effect of NRG on surfactant protein mRNA expression was lost. We conclude that PSEN-1 and YAP have crucial roles in ErbB4 signal transduction during type II cell maturation
Genomic biomarkers of prenatal intrauterine inflammation in umbilical cord tissue predict later life neurological outcomes
Preterm birth is a major risk factor for neurodevelopmental delays and disorders. This study aimed to identify genomic biomarkers of intrauterine inflammation in umbilical cord tissue in preterm neonates that predict cognitive impairment at 10 years of age
Cerebral palsy and placental infection: a case-cohort study
BACKGROUND: The association between cerebral palsy in very preterm infants and clinical, histopathologic and microbiological indicators of chorioamnionitis, including the identification of specific micro-organisms in the placenta, was evaluated in a case-cohort study. METHODS: Children with a diagnosis of cerebral palsy at five years of age were identified from amongst participants in a long-term follow-up program of preterm infants. The comparison group was a subcohort of infants randomly selected from all infants enrolled in the program. The placentas were examined histopathologically for chorioamnionitis and funisitis, and the chorioamnionic interface was aseptically swabbed and comprehensively cultured for aerobic and anaerobic bacteria, yeast and genital mycoplasmas. Associations between obstetric and demographic variables, indicators of chorioamnionitis and cerebral palsy status were examined by univariate analysis. RESULTS: Eighty-two infants with cerebral palsy were compared with the subcohort of 207 infants. Threatened preterm labor was nearly twice as common among the cases as in the subcohort (p < 0.01). Recorded clinical choroamnionitis was similar in the two groups and there was no difference in histopathologic evidence of infection between the two groups. E. coli was cultured from the placenta in 6/30 (20%) of cases as compared with 4/85 (5%) of subcohort (p = 0.01). Group B Streptococcus was more frequent among the cases, but the difference was not statistically significant. CONCLUSIONS: The association between E. coli in the chorioamnion and cerebral palsy in preterm infants identified in this study requires confirmation in larger multicenter studies which include microbiological study of placentas
Placental CpG methylation of infants born extremely preterm predicts cognitive impairment later in life
Abstract: Background The placenta is the central regulator of maternal and fetal interactions. Perturbations of placental structure and function have been associated with adverse neurodevelopmental outcomes later in life. Placental CpG methylation represents an epigenetic modification with the potential to impact placental function, fetal development and child health later in life. Study design Genome-wide placental CpG methylation levels were compared between spontaneous versus indicated deliveries from extremely preterm births (EPTBs) (n = 84). The association between the identified differentially methylated CpG sites and neurocognitive outcome at ten years of age was then evaluated. Results Spontaneous EPTB was associated with differential CpG methylation levels in 250 CpG sites (217 unique genes) with the majority displaying hypermethylation. The identified genes are known to play a role in neurodevelopment and are enriched for basic helix-loop-helix transcription factor binding sites. The placental CpG methylation levels for 17 of these sites predicted cognitive function at ten years of age. Conclusion A hypermethylation signature is present in DNA from placentas in infants with spontaneous EPTB. CpG methylation levels of critical neurodevelopment genes in the placenta predicted..
The Dynamic Exponent of the Two-Dimensional Ising Model and Monte Carlo Computation of the Sub-Dominant Eigenvalue of the Stochastic Matrix
We introduce a novel variance-reducing Monte Carlo algorithm for accurate
determination of autocorrelation times. We apply this method to two-dimensional
Ising systems with sizes up to , using single-spin flip dynamics,
random site selection and transition probabilities according to the heat-bath
method. From a finite-size scaling analysis of these autocorrelation times, the
dynamical critical exponent is determined as (12)
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