Experimental Evaluation of Thermal Conductivity and Other Thermophysical Properties of Nanofluids Based on Functionalized (-OH) Mwcnt Nanoparticles Dispersed in Distilled Water

A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).

Analysis of Daily Rainfall in São Carlos/SP, Brazil over 1979-2017 Using Laplace Trend Test

Rainfall expresses one of the most complex climate factors in Southeastern Brazil. Understanding the dynamics and temporal trends of rainfall represents a significant challenge due to regional and even global mechanisms, such as FS (Frontal Systems) and the SACZ (South Atlantic Convergence Zone), and the interaction with the Atlantic and Pacific Oceans. The present study aimed at analyzing the pluviometric tendencies in São Carlos/SP, in the countryside of São Paulo State. Laplace trend test was used to comprehend the temporal evolution of daily rainfall in the region in the historical series 1979-2017, in seven pluviometric stations (climatological or surface stations). Significant fluctuations in interannual trends and between seasons were observed. However, it was noted that the beginning of the 1980s showed positive trends, whereas, as of the year 2000, most of the stations demonstrated negative trends, indicating a reduction in daily rainfall volume due to the great tropical climatic variability of Brazil. Emphasis should also be given to the regional and local effects, such as elevation and urbanization, respectively, which corroborate such differences among the analyzed stations. This methodology is of considerable value for the observation of pluviometric trends, and future studies can validate such a tool in climatological studies.

Understanding bark thickness variations for Araucaria angustifolia in southern Brazil

This study aimed to understand bark thickness variations of Araucaria angustifolia(Bertol.)Kuntze trees growing in natural forest remnants in southern Brazil,and their relationship with quantitative and qualitative attributes.Bark thickness must be accurately estimated in order to determine timber volume stocks.This is an important variable for the sustainable management and conservation of araucaria forests.In spite of its importance and visibility,bark thickness variations have not been evaluated for this key species in southern Brazil.A total of 104 trees were selected,and their qualitative and quantitative attributes such as diameter at breast height(D_(BH)),height(H),crown base height(C_(BH)),crown length(C_(L)),social position(S_(P)),stoniness(S_(T)),position on the relief(P_(R)),vitality(V_T)and branch arrangement(B_(A))were measured.The trees were categorized into two groups:red bark or gray bark.Regression analysis and artificial neural networks(ANN)were used for modelling bark thickness.The results indicate that:(1)bark thickness showed good correlation to D_(BH),with 0.76 as coefficient of determination(RS_P),0.540 as Mean Absolute Error(M_(AE))and 22.4 root-meansquare error in percentage(R_(MSE%));(2)the trend changed according to bark colour,with significant differences for the intersection(_0–Pr>F:p=0.0124)and slope(β_(1)–Pr>F:p=0.0126)of bark thickness curves between groups;(3)the highest correlation of bark thickness was found with:D_(BH)(ρ=0.88),H(ρ=0.58),C_(BH)(ρ=0.46),S_(P)(ρ=-0.52),and B_(A)(ρ=-0.32);(4)modelling with ANN confirmed high adjustment(R^(2)=0.99)and accuracy(R_(MSE%)=3.0)of the estimates.ANN is an efficient and robust technique for the modelling of various qualitative and quantitative attributes commonly used in forest mensuration.The effective use of ANN to estimate araucaria bark in natural forests reinforces its potential,besides the possibility of application for other forest species.

Effects of probiotic supplementation on abdominal pain severity in pediatric patients with irritable bowel syndrome:a systematic review and meta-analysis of randomized clinical trials

Background Probiotic supplementation has been used to alleviate abdominal pain in children and adolescents with irritable bowel syndrome(IBS),but the evidence is not compelling.Thus,a systematic review and meta-analysis of randomized clinical trials(RCTs)were performed to investigate the effects of probiotic supplementation on abdominal pain in pediatric patients with IBS.Methods PubMed/MEDLINE,Web of Science,Scopus,Cochrane Library,and Embase were the available databases searched to find relevant randomized clinical trials up to April 2021.The effect size was expressed as weighted mean differenee(WMD)and 95% confidence interval(CI).Results Seven RCTs with 441 participants were included,from which the meta-analysis demonstrated that probiotic supplementation has a significant effect on reducing abdominal pain in pediatric patients with IBS(WMD=-2.36:95%CI-4.12 to-0.60;P=0.009).Although our study involved children and adolescents(≤18 years),the effects of probiotic supplementation seem to be more potent in patients under 10 years old(WMD=-2.55;95%CI-2.84 to -2.27)compared to patients aged 10-18 years(WMD=-1.70;95%CI-2.18 to -1.22).The length of supplementation longer than four weeks was more effective(WMD=-2.43;95%CI-2.76 to -2.09).Conclusion Probiotic supplementation can reduce abdominal pain in pediatric patients with IBS.