Absorption Heat Transfer Performance of Ammonia-Water Mixture in 116 Tube Mini-Channel Heat Exchanger

It is known that decreasing the channel size in heat exchangers increases its heat and mass transfer performance. Using such heat exchangers offers the opportunity to reduce the size and cost of industrial heat pumps, what should lead to better market acceptance. In the past, many experiments have been done for air/water mixtures (adiabatic) and refrigerants like CO2, R134a and water (diabatic). A variety of models predicting heat transfer coefficients for these refrigerants are available in literature, but for certain systems they are not in agreement with each other. Currently data for ammonia/water mixtures, a fluid used in absorption and compression-resorption heat pumps is missing. A novel mini channel shell and tube heat exchanger with 116 tubes with an inner diameter of 0.5 mm, an outer diameter of 1.0 mm and a length of 0.655 m has been developed to increase the heat transfer performance in industrial compression-resorption heat pumps working with ammonia-water as refrigerant. In the current research the tube side heat transfer performance is investigated using the ammonia-water mixture, while water is used in the shell side of the heat exchanger. The influence of mass flow rate, heat load and vapor quality on the heat transfer performance and pressure drop are investigated. The heat load was varied between 200 and 1800 W, with the refrigerant mass flux varied between 20 and 75 kg m-2 s-1 with the average vapor quality ranging between 0.2 and 0.6 kg kg 1 and operating pressures between 5 and 13 bar. Overall heat transfer coefficients, based on the outer diameter of the tubes, between 70 and 700 W m-2 s-1 have been obtained. The approach temperature at the absorber inlet, after calibrating the PT-100 elements, ranged between 0.3 and 4 K and the average temperature driving force is determined to be between 8 and 25 K. The measured pressure drop ranges between 0.02 and 0.2 bar. Trends show an increasing pressure drop and heat transfer coefficient with increasing mass flux and vapor quality. The heat transfer coefficient on the shell side appears to be the limiting factor at higher measured mass fluxes. The heat load was limited by the maximum flow of the water pumps on the shell side as well as the maximum available heating power of 3.5 kW

Prenatal exposure to endocrine disrupting chemicals in relation to thyroid hormone levels in infants – a Dutch prospective cohort study

Background: Endocrine disrupting chemicals (EDCs) present in the environment may disrupt thyroid hormones, which in early life are essential for brain development. Observational studies regarding this topic are still limited, however as the presence of chemicals in the environment is ubiquitous, further research is warranted. The objective of the current study was to assess the association between exposure markers of various EDCs and thyroxine (T4) levels in newborns in a mother-child cohort in the Netherlands. Methods: Exposure to dichlorodiphenyldichloroethylene (DDE), three di-2-ethylhexyl phthalate (DEHP) metabolites, hexachlorobenzene (HCB), polychlorinated biphenyl (PCB)-153, perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) was determined in cord plasma or breast milk, and information on T4 levels in heel prick blood spots was obtained through the neonatal screening programme in the Netherlands. Linear regression models were composed to determine associations between each of the compounds and T4, which were stratified for gender and adjusted for a priori defined covariates. Results: Mean T4 level was 86.9 nmol/L (n = 83). Girls in the highest quartile of DDE and PFOA exposure showed an increased T4 level compared to the lowest quartile with both crude and fully adjusted models (DDE > 107.50 ng/L, +24.8 nmol/L, 95% CI 0.79, 48.75; PFOA > 1200 ng/L, +38.6 nmol/L, 95% CI 13.34, 63.83). In boys a lower T4 level was seen in the second quartile of exposure for both PFOS and PFOA, however after fully adjusting the models these associations were attenuated. No effects were observed for the other compounds. Conclusion: DDE and perfluorinated alkyl acids may be associated with T4 in a sex-specific manner. These results should however be interpreted with caution, due to the relatively small study population. More research is warranted, as studies on the role of environmental contaminants in this area are still limited

First year growth in relation to prenatal exposure to endocrine disruptors - A dutch prospective cohort study

Growth in the first year of life may already be predictive of obesity later in childhood. The objective was to assess the association between prenatal exposure to various endocrine disrupting chemicals (EDCs) and child growth during the first year. Dichlorodiphenyldichloroethylene (DDE), mono(2-ethyl-5-carboxypentyl)phthalate (MECPP), mono(2-ethyl-5-hydroxyhexyl)phthalate (MEHHP), mono(2-ethyl-5-oxohexyl)phthalate (MEOHP), polychlorinated biphenyl-153, perfluorooctanesulfonic acid, and perfluorooctanoic acid were measured in cord plasma or breast milk. Data on weight, length, and head circumference (HC) until 11 months after birth was obtained from 89 mother-child pairs. Mixed models were composed for each health outcome and exposure in quartiles. For MEOHP, boys in quartile 1 had a higher BMI than higher exposed boys (p = 0.029). High DDE exposure was associated with low BMI over time in boys (0.8 kg/m2 difference at 11 m). Boys with high MECPP exposure had a greater HC (1.0 cm difference at 11 m) than other boys (p = 0.047), as did girls in the second quartile of MEHHP (p = 0.018) and DDE (p < 0.001) exposure. In conclusion, exposure to phthalates and DDE was associated with BMI as well as with HC during the first year after birth. These results should be interpreted with caution though, due to the limited sample size

Hyperbilirubinemie bij gezonde voldragen pasgeborenen: richtlijnen voor diagnostiek en behandeling

Contains fulltext : 26014___.PDF (publisher's version ) (Open Access

A Genetic Mosaic Screen Reveals Ecdysone-Responsive Genes Regulating Drosophila Oogenesis

Information about the supplemental materials can be found here: www.g3journal.org/lookup/suppl/doi:10.1534/g3.116.028951/-/DC1Multiple aspects of Drosophila oogenesis, including germline stem cell activity, germ cell differentiation, and follicle survival, are regulated by the steroid hormone ecdysone. While the transcriptional targets of ecdysone signaling during development have been studied extensively, targets in the ovary remain largely unknown. Early studies of salivary gland polytene chromosomes led to a model in which ecdysone stimulates a hierarchical transcriptional cascade, wherein a core group of ecdysone-sensitive transcription factors induce tissue-specific responses by activating secondary branches of transcriptional targets. More recently, genome-wide approaches have identified hundreds of putative ecdysone-responsive targets. Determining whether these putative targets represent bona fide targets in vivo, however, requires that they be tested via traditional mutant analysis in a cell-type specific fashion. To investigate the molecular mechanisms whereby ecdysone signaling regulates oogenesis, we used genetic mosaic analysis to screen putative ecdysone-responsive genes for novel roles in the control of the earliest steps of oogenesis. We identified a cohort of genes required for stem cell maintenance, stem and progenitor cell proliferation, and follicle encapsulation, growth, and survival. These genes encode transcription factors, chromatin modulators, and factors required for RNA transport, stability, and ribosome biogenesis, suggesting that ecdysone might control a wide range of molecular processes during oogenesis. Our results suggest that, although ecdysone target genes are known to have cell type-specific roles, many ecdysone response genes that control larval or pupal cell types at developmental transitions are used reiteratively in the adult ovary. These results provide novel insights into the molecular mechanisms by which ecdysone signaling controls oogenesis, laying new ground for future studies.ECU Open Access Publishing Support Fun

Volatilization of tri-allate, ethoprophos and parathion measured with four methods after spraying on a sandy soil

At about eleven times after application of tri-allate, ethoprophos and parathion to a sandy soil, their rates of volatilization were determined by the aerodynamic method (AD), the Bowen-ratio method (BR), the theoretical-profile method (TP) and the Box method. The volatilization was highest for tri-allate and lowest for parathion. On the first day after application, the volatilization rate decreased sharply, but thereafter the decrease was more gradual. The differences in volatilization rate as determined with the AD, BR and TP methods were comparatively small. The rates determined with the Box method were mostly lower than those determined with the other methods