Use of Heat Transfer Enhancement Techniques in the Design of Heat Exchangers

Heat transfer enhancement refers to application of basic concepts of heat transfer processes to improve the rate of heat removal or deposition on a surface. In the flow of a clean fluid through the tube of a heat exchanger, the boundary layer theorem establishes that a laminar sublayer exists where the fluid velocity is minimal. Heat transfer through this stagnant layer is mainly dominated by thermal conduction, becoming the major resistance to heat transfer. From an engineering point of view, heat transfer can be enhanced if this stagnant layer is partially removed or eliminated. In single-phase heat transfer processes, three options are available to increase the heat transfer rate. One of them is the choice of smaller free flow sectional area for increased fluid velocity bringing about a reduction of the thickness of the laminar sublayer. A second option is the engineering of new surfaces which cause increased local turbulence, and the third option consists in the use of mechanical inserts that promote local turbulence. The application of these alternatives is limited by the pressure drop. This chapter describes the concept of heat transfer enhancement and the ways it is applied to the development of new heat exchanger technology

Characterization, Classification and Authentication of Honey by Non-Targeted UHPLC-HRMS Chromatographic Fingerprints and Chemometric Methods

Honey is a natural substance produced by bees of the genus Apis. Depending on the raw material used for its production, honey can be classified into two large groups: blossom honey, which results from the metabolization of nectar extracted from flowers; and honeydew honey, in which bees use plant or insect secretions for its production. The physicochemical characteristics are different between these two types of honey. For example, honeydew honey is darker and is characterized by a high content of phenolic acids. On the contrary, blossom honey stands out for its abundance of flavonoids. Blossom honey can be also classified based on the pollen origin. Thus, honey with more than 45% of the pollen coming from the same species can be considered monofloral; otherwise, it is considered multifloral. Honey is one of the food products with the highest level of fraudulent practices. Most of the adulterations consist of ingredient dilution, adding sweet substances, such as syrups, sugar cane, or corn syrup, among others. In the market, this was reflected in the dubious drop in prices for this product. In the last few years, several instance of honey fraud have come to light. This work aimed to develop a non-targeted ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) fingerprinting method to address the characterization, classification, and authentication of Spanish honey samples considering their botanical and geographical origin. A total of 136 kinds of honey from different Spanish production regions belonging to different botanical varieties were analyzed, including: blossom honey (orange blossom, rosemary, thyme, eucalyptus, and heather) and honeydew honey (holm oak, forest, and mountain). A simple sample treatment was carried out, consisting of dissolving 1 g of honey in 10 mL of water, followed by a 1:1 dilution with methanol. The chromatographic separation of the obtained extracts was performed using a Kinetex® C-18 core-shell column (100 × 4.6 mm I.D., 2.6 μm), working under gradient elution, using an aqueous solution of 0.1% formic acid and acetonitrile as the mobile phase components. HRMS acquisition was performed using electrospray in negative ionization mode (−2500 V) in an LTQ-Orbitrap working in full scan MS (m/z 100-1000) at a resolution of 50,000 full-width at half maximum (FWHM). The obtained non-targeted UHPLC-HRMS fingerprints (peak signals as a function of retention time and m/z) were considered as chemical descriptors of the analyzed honey samples for principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). PLS-DA revealed good discrimination between blossom and honeydew honey. Furthermore, the obtained chemometric models allowed the achievement of very good classification among the different botanical varieties under study for both blossom and honeydew honey. The discrimination of honey regarding the different Spanish climate production regions was more limited, although some trends were observed. Thus, the non-targeted UHPLC-HRMS fingerprinting approach proved to be an appropriate methodology to address honey characterization, classification, and authentication based on their different botanical origin

Analytical simulation of RBS spectra of nanowire samples

Almost all, if not all, general purpose codes for analysis of Ion Beam Analysis data have been originally developed to handle laterally homogeneous samples only. This is the case of RUMP, NDF, SIMNRA, and even of the Monte Carlo code Corteo. General-purpose codes usually include only limited support for lateral inhomogeneity. In this work, we show analytical simulations of samples that consist of a layer of parallel oriented nanowires on a substrate, using a model implemented in NDF. We apply the code to real samples, made of vertical ZnO nanowires on a sapphire substrate. Two configurations of the nanowires were studied: 40 nm diameter, 4.1 μm height, 3.5% surface coverage; and 55 nm diameter, 1.1 μm height, 42% surface coverage. We discuss the accuracy and limits of applicability of the analysisAuthors thank funding from projects CTQ2014-53334-C2-2-R (MINECO, Spain) and NANOAVANSENS S2013/MIT 3029 (Comunidad de Madrid). A.R.C. acknowledges Juan de la Cierva program (under contract number JCI-2012-14509). This work was partially funded by Fundação para a Ciência e Tecnologia under grant UID/Multi/04349/201

Relationship between sociometric types and academic goals in a sample of Spanish students of Secondary Education

El objetivo de este estudio fue analizar la relación entre tipos sociométricos, categorías conductuales y metas académicas en una muestra de 1349 estudiantes (51.7% chicos) de educación secundaria obligatoria. La identificación sociométrica de los estudiantes se realizó mediante el Programa Socio y las metas académicas fueron evaluadas mediante el AGTQ (Achievement Goals Tendencies Questionnaire). El AGTQ es una medida de autoinforme diseñada para medir tres orientaciones de metas: aprendizaje, logro y refuerzo social. Los resultados muestran que los estudiantes nominados positivamente por sus compañeros presentaron mayores puntuaciones en metas de aprendizaje y de logro que los estudiantes nominados negativamente. Además, los tipos sociométricos fueron predictores significativos de las metas académicas, ya que los estudiantes nominados positivamente por sus compañeros presentaron mayor probabilidad de alcanzar altas metas de aprendizaje y de logro que los estudiantes nominados negativamente.The aim of this study was to analyze the relationship between sociometric types, behavioral categories and academic goals in a sample of 1349 students (51.7% boys) of compulsory secondary education. The students’ sociometric identification was performed by the Programa Socio and academic goals was measured by the AGTQ (Achievement Goals Tendencies Questionnaire). The AGTQ is a self-report measure designed to measure three tendencies of goals: Learning goals, Achievement goals and Reinforcement Social goals. Results show that students nominated by their peers positively had higher scores on Learning and Achievement goals than students negatively nominated. Furthermore, sociometric types were significant predictors of academic goals, as students nominated by their peers positively were more likely to achieve high Learning goals and Achievement goals that students negatively nominated.Este trabajo ha sido realizado a través del Proyecto SEJ 2004-07311/EDUC perteneciente al Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica del MEC concedido al primer autor

Student Perception of Teacher and Parent Involvement in Homework and Student Engagement: The Mediating Role of Motivation

Currently, there is much debate about the value of assigning homework. Organizations such as the OECD have concluded that doing more homework is not synonymous with better performance. This study was designed to analyze the mediating role of student motivation in the relationship between the involvement of parents and teachers in homework and the engagement of students in these tasks. Seven hundred and thirty students in Compulsory Secondary Education (7th–10th grade) participated from 14 schools in the north of Spain. Three competing models were developed and tested to study motivational mediation: a non-motivational mediation model (direct effects model); a total motivational mediation model (indirect effects model); and a partial motivational mediation model (mixed effects model). The best model was adjusted according to gender and school year variables. The total mediation motivational model demonstrated the best fit (indirect effects model). The results suggest the total mediation of student motivation in the relationship between the perception of parents’ and teachers’ involvement in homework and student cognitive engagement in these tasks. Some differences, albeit slight, were observed with respect to gender and school year. The results have clear theoretical and educational implications.Ministerio de Economía y Competitividad; EDU2013-44062-PMinisterio de Economía y Competitividad; EDU2017-82984-PGobierno de Asturias; FC-GRUPIN-IDI/2018/00019

Strong enhancement of superconductivity at high pressures within the charge-density-wave states of 2H-TaS 2 and 2H-TaSe 2

We present measurements of the superconducting and charge density wave critical temperatures (Tc and TCDW) as a function of pressure in the transition metal dichalchogenides 2H-TaSe2 and 2H-TaS2. Resistance and susceptibility measurements show that Tc increases from temperatures below 1 K up to 8.5 K at 9.5 GPa in 2H-TaS2 and 8.2 K at 23 GPa in 2H-TaSe2. We observe a kink in the pressure dependence of TCDW at about 4 GPa that we attribute to the lock-in transition from incommensurate CDW to commensurate CDW. Above this pressure, the commensurate TCDW slowly decreases coexisting with superconductivity within our full pressure range.Comment: Published in Phys. Rev B 93, 184512 (2016

Identification of differentially expressed key genes of Longissimus lumborum samples from Portuguese Alentejano and Bísaro local pig breeds

Most of the swine industry nowadays is about productive and profitable fast-growing lean breeds raised under intensive conditions leading to meat and fat rich in saturated fatty acids. The Portuguese local Alentejano (AL) and Bísaro (BI) pig breeds present high intramuscular fat (IMF) content which contributes to highly appreciated pork products. These breeds have different ancestors: AL belongs to the Iberian group, presenting lower growth rates and higher lipid accretion and unsaturated fatty acids level when compared to BI, which belongs to the Celtic group, sharing ancestors with leaner breeds such as Large White and Landrace. The goal of this work was to compare the muscle gene expression profiles of AL and BI pig breeds to better understand the influence of the genetic background in the main metabolic processes occurring in the Longissimus lumborum (LL) muscle, namely in terms of lipid synthesis, muscle tissue formation, protein synthesis and cell proliferation. LL samples were obtained at slaughter, from adult AL and BI pigs with ~150kg body weight. Total RNA was extracted and sequenced for a transcriptome comparison analysis. A total of 250 genes were found to be differentially expressed (DE) in LL samples (q<0.05) conditional on breed, with 174 DE genes up-regulated in AL (log2(fold_change) = 0.65 to 7.03) and 76 in BI (log2(fold_change) = 0.63 to 4.53). Genes related to skeletal muscle development and function, such as MYH3, MYH13 or ACTN4, were significantly up-regulated in BI when compared to AL, which is in agreement with the higher muscle mass of the former breed. Genes involved in lipid metabolism were up-regulated in AL, including SCD (q=0.05), responsible for catalysing the reaction that introduces the first double bond into saturated fatty acyl-CoA substrates, which agrees with the higher unsaturation of fat tissues generally associated with the former breed. A functional enrichment analysis (metabolic pathways and GO enrichment) was performed for the DE genes and the identified functions included tissue development, cellular growth and proliferation, quantity of connective tissue and lipid metabolism. Potential regulators found that explain the observed gene expression changes in the dataset included molecules such as: ADORA2A, CEBPA, SMAD3 and PPARG (predicted to be activated in AL); HDAC and ASXL1 (predicted to be inhibited in AL)

Zinc nitride thin films: Basic properties and applications

A. Redondo-Cubero, M. Gómez-Castaño, C. García Núñez, M. Domínguez, L. Vázquez, J. L. Pau , "Zinc nitride thin films: basic properties and applications", Oxide-based Materials and Devices VIII, Proc. SPIE 10105, 101051B (24 February 2017); doi: 10.1117/12.2253044. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibitedProceedings of VIII Oxide-based Materials and Devices Conference (San Francisco, California, United States)Zinc nitride films can be deposited by radio frequency magnetron sputtering using a Zn target at substrate temperatures lower than 250°C. This low deposition temperature makes the material compatible with flexible substrates. The asgrown layers present a black color, polycrystalline structures, large conductivities, and large visible light absorption. Different studies have reported about the severe oxidation of the layers in ambient conditions. Different compositional, structural and optical characterization techniques have shown that the films turn into ZnO polycrystalline layers, showing visible transparency and semi-insulating properties after total transformation. The oxidation rate is fairly constant as a function of time and depends on environmental parameters such as relative humidity or temperature. Taking advantage of those properties, potential applications of zinc nitride films in environmental sensing have been studied in the recent years. This work reviews the state-of-the-art of the zinc nitride technology and the development of several devices such as humidity indicators, thin film (photo)transistors and sweat monitoring sensors.This research is supported by the MINECO (CTQ2014-53334-C2-2-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029). ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047

Luxación anterior de codo en la infancia : a propósito de 1 caso

La luxación anterior de codo es una lesión excepcional que suele ocurrir cuando existen factores facilitadores como una hiperlaxitud articular, una hipoplasia de olécranon o deformidades adquiridas por traumatismo previo. El propósito de este artículo es presentar un nuevo caso con esta lesión en un niño de 8 años de edad sin factores facilitadores aparentes, así como analizar la fisiopatología de la lesión, las opciones terapéuticas y el pronóstico futuroAnterior dislocation of the elbow is a rare lesion. Hipermobility of joint, olecranon hipoplasy or elbow postraumatic deformities predisposed to the anterior dislocation of the elbow. The purpose of this paper is to point out a new case with this rare lesion in a child of 8 years old, without predisponent factors. We analized the injury phisiopathology, therapeutic options and future pronostic