Spacer grid effects on the heat transfer enhancement during a reflood

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.An experimental study using 6x6 and 2x2 square lattice rod bundles has been performed to investigate the effects of spacer grids on the heat transfer enhancement during a bottom-reflood phase. The spacer grids improve a turbulent mixing of flow and induces breakup of large droplets into smaller ones. These result in the heat transfer enhancement between the fuel rods and the surrounding fluid. Since the geometry of the spacer grid affects the turbulent mixing and droplet breakup behaviors, three types of spacer grids with different geometry were tested in the present study. In order to investigate the heat transfer enhancement by spacer grids, single-phase steam cooling and droplet breakup by spacer grid were separately investigated. For the convective heat transfer enhancement in singlephase steam flow, the heater rod surface temperatures were measured in the vicinity of the space grid. In single-phase steam cooling experiment, the heat transfer was enhanced at upstream and downstream of spacer grids. Downstream of the spacer, the heat transfer enhancement decays with the distance from the top end of the spacer grid exponentially. The heat transfer enhancement depends on the Reynolds number as well as the flow blockage ratio. A new empirical correlation was developed in order to account for the effect of the Reynolds number. For the droplet breakup experiment, the sizes and velocities of droplets were measured across the spacer grid. The droplet breakup ratio decreases with increasing the Weber number of the droplet impacting on the spacer grid. The droplet breakup ratio by spacer grids was relatively higher than conventional correlations.dc201

Microvasculature remodeling in the mouse lower gut during inflammaging

Inflammaging is defined as low-grade, chronic, systemic inflammation in aging, in the absence of overt infection. Age-associated deterioration of gastrointestinal function could be ascribed to the inflammaging, although evidence is yet to emerge. Here we show that microvessels in aging mouse intestine were progressively deprived of supportive structures, microvessel-associated pericytes and adherens junction protein vascular endothelial (VE)-cadherin, and became leaky. This alteration was ascribed to up-regulation of angiopoetin-2 in microvascular endothelial cells. Up-regulation of the angiopoietin-2 was by TNF-α, originated from M2-like residential CD206 + macrophages, proportion of which increases as animal ages. It was concluded that antigenic burdens encountered in intestine throughout life create the condition of chronic stage of inflammation, which accumulates M2-like macrophages expressing TNF-α. The TNF-α induces vascular leakage to facilitate recruitment of immune cells into intestine under the chronic inflammatory setting. © Author(s) 2017.1

Pregnancy-related knowledge, risk perception, and reproductive decision making of women with epilepsy in Korea

AbstractPurposeTo determine the influence of pregnancy-related knowledge and the risk perception on reproductive decision making in women with epilepsy.MethodsWe enrolled women with epilepsy, who were of reproductive age and were considering having children in the future. A questionnaire was used to assess the level of pregnancy-related knowledge, perception of the offspring's risk for developing epilepsy or for having a congenial anomaly, and discussion with a physician concerning pregnancy-related issues. We evaluated the following outcome variables: (1) the decision to discontinue anti-epileptic drug (AED) during a future pregnancy regardless of the medical indication; and (2) the decision to have fewer children because of epilepsy.ResultsWe enrolled a total of 186 women with epilepsy. (1) Fifty-eight percent of the women were considering discontinuing AED during a future pregnancy regardless of the medical indication, and 25% of the women decided to have fewer children because of epilepsy. (2) The decision to discontinue AED during a future pregnancy was associated with low-level pregnancy-related knowledge. (3) The decision to have fewer children because of epilepsy was associated with an exaggerated perception of the offspring's risk for developing epilepsy. (4) The women who had ever discussed pregnancy-related issues with their physician were less likely to decide to discontinue AED during a future pregnancy; however, a discussion on this issue had no impact on their decision to have fewer children because of epilepsy.ConclusionMore than 50% of the women would decide to discontinue AED during a future pregnancy, and 25% of the women stated that they would have fewer children because of epilepsy. These data highlight the importance of education on pregnancy-related issues and genetic risk counseling

Easy Diagnosis of Asthma: Computer-Assisted, Symptom-Based Diagnosis

Diagnosis of asthma is often challenging in primary-care physicians due to lack of tools measuring airway obstruction and variability. Symptom-based diagnosis of asthma utilizing objective diagnostic parameters and appropriate software would be useful in clinical practice. A total of 302 adult patients with respiratory symptoms responded to a questionnaire regarding asthma symptoms and provoking factors. Questions were asked and recorded by physicians into a computer program. A definite diagnosis of asthma was made based on a positive response to methacholine bronchial provocation or bronchodilator response (BDR) testing. Multivariate logistic regression analysis was used to evaluate the significance of questionnaire responses in terms of discriminating asthmatics. Asthmatic patients showed higher total symptom scores than non-asthmatics (mean 5.93 vs. 4.93; p<0.01). Multivariate logistic regression analysis identified that response to questions concerning the following significantly discriminated asthmatics; wheezing with dyspnea, which is aggravated at night, and by exercise, cold air, and upper respiratory infection. Moreover, the presence of these symptoms was found to agree significantly with definite diagnosis of asthma (by kappa statistics). Receiver-operating characteristic curve analysis revealed that the diagnostic accuracy of symptom-based diagnosis was high with an area under the curve of 0.647±0.033. Using a computer-assisted symptom-based diagnosis program, it is possible to increase the accuracy of diagnosing asthma in general practice, when the facilities required to evaluate airway hyperresponsiveness or BDR are unavailable

Customized Asthma Control Test with Reflection on Sociocultural Differences

We evaluated the utility and feasibility of customizing Asthma Control Test (ACT) items to generate a Korean Asthma Control Test (KACT) specific for Korean patients. We surveyed 392 asthma patients with 19 items, selected to reflect the Korean sociocultural context. Guideline ratings were integrated with the evaluations of specialists (i.e., using both guide base rating together with specialist's rating), and items with the greatest discriminating validity were identified. Stepwise regression methods were used to select items. KACT scale scores showed significant differences between the asthma control ratings generated by integrating ratings (r=0.77, P<0.001), by specialist's evaluations (r=0.54, P<0.001), or by FEV1 percent predicted (r=0.39, P<0.001). Specialist's and guideline ratings detected 56% and 48.6% of patients with well-controlled asthma, respectively. However, the integrated ratings indicated that only 34.3% of the patients in the test sample were well controlled. The overall agreement between KACT and the integrated rating ranged from 45% to 78%, depending on the cut-off points used. It is possible to formulate a valid, useful country-specific diagnostic tool for the assessment of asthma patients based on the original ACT that reflect differences in sociocultural context

Easy diagnosis of asthma: computer-assisted, symptom-based diagnosis

Diagnosis of asthma is often challenging in primary-care physicians due to lack of tools measuring airway obstruction and variability. Symptom-based diagnosis of asthma utilizing objective diagnostic parameters and appropriate software would be useful in clinical practice. A total of 302 adult patients with respiratory symptoms responded to a questionnaire regarding asthma symptoms and provoking factors. Questions were asked and recorded by physicians into a computer program. A definite diagnosis of asthma was made based on a positive response to methacholine bronchial provocation or bronchodilator response (BDR) testing. Multivariate logistic regression analysis was used to evaluate the significance of questionnaire responses in terms of discriminating asthmatics. Asthmatic patients showed higher total symptom scores than non-asthmatics (mean 5.93 vs. 4.93; p<0.01). Multivariate logistic regression analysis identified that response to questions concerning the following significantly discriminated asthmatics; wheezing with dyspnea, which is aggravated at night, and by exercise, cold air, and upper respiratory infection. Moreover, the presence of these symptoms was found to agree significantly with definite diagnosis of asthma (by kappa statistics). Receiver-operating characteristic curve analysis revealed that the diagnostic accuracy of symptom-based diagnosis was high with an area under the curve of 0.647 +/- 0.033. Using a computer-assisted symptom-based diagnosis program, it is possible to increase the accuracy of diagnosing asthma in general practice, when the facilities required to evaluate airway hyperresponsiveness or BDR are unavailable