Laser-fired contact optimization in c-Si solar cells

In this work we study the optimization of laser-fired contact (LFC) processing parameters, namely laser power and number of pulses, based on the electrical resistance measurement of an aluminum single LFC point. LFC process has been made through four passivation layers that are typically used in c-Si and mc-Si solar cell fabrication: thermally grown silicon oxide (SiO2), deposited phosphorus-doped amorphous silicon carbide (a-SiCx/H(n)), aluminum oxide (Al2O3) and silicon nitride (SiNx/H) films. Values for the LFC resistance normalized by the laser spot area in the range of 0.65–3 mΩ cm2 have been obtained

Evaluación de la madera estructural para la rehabilitación de las Naves Cros (Valencia, España) por medio de diferentes técnicas no destructivas

El proyecto de rehabilitación de una de las naves del complejo fabril de la industria química ?CROS? en Valencia se llevó a cabo con el criterio de mantener, en la medida de lo posible, los elementos estructurales presentes en la nave. Con este objetivo se realizaron una serie de ensayos no destructivos (END) in situ. Estos ensayos permitieron evaluar la calidad de la madera, determinar qué elementos estructurales debían ser sustituidos y comprobar la aptitud de los que iban a ser reutilizados. Los END empleados en este estudio fueron los siguientes: (1) Identificación de la especie por técnicas anatómicas, (2) Clasificación resistente por método visual, (3) Estimación de humedad por la técnica de resistencia eléctrica; (4) Obtención de velocidades de propagación ultrasónicas (5) Resistógrafía y (6) Alteración de la propagación de ondas electromagnéticas por medio de Georradar. Para la calibración de estos END se tomó una muestra de piezas y se hicieron ensayos destructivos bajo condiciones controladas en laboratorio. En el trabajo que aquí se presenta se muestra la metodología empleada durante el proceso de toma de datos, de análisis de resultados y de cruce de la información obtenida a partir de cada uno de los ensayos hasta llegar a un diagnóstico para los elementos analizados. The assessment of structural timber was requested in the rehabilitation project of the Naves of the chemical industry "CROS". The criterion was to maintain as much as possible timber of the structure and to make only partial replacements. In order not to damage the existing structure and to assess the quality of the existing timber, a series of non-destructive testing (NDT) in the entire structure were performed: (1) Identification of the species by anatomical techniques, (2) Strength grading by visual method, (3) Estimation of moisture content by the technique of electrical resistance, (4) Acquisition of ultrasonic propagation velocities (5) Resistography and (6) Record of the propagation of electromagnetic waves by means of Ground-penetrating radar. Following, a sample group was chose to carry out destructive testing in the lab and compare the NDT results with those obtained with the standard UNE-EN408 (modules of strength, stiffness and density). In the present work, the results provided by each of the NDT techniques are detailed and above all, what is more important, the validity of these after they have been contrasted with the destructive standard tests.

Fabrication process of Mo/Au TES at RT

We report on the fabrication details of TES based on Mo/Au bilayers. The Mo layer is deposited by radio frequency (RF) sputtering and capped with a sputter deposited thin Au protection layer. Afterwards, a second Au layer of suitable (lower) resistivity is deposited ex‐situ by e‐beam evaporation, until completion of the total desired Au thickness. The deposition was performed at room temperature (RT) on LPCVD Si3 N4 membranes. Such a deposition procedure is very reproducible and allow controlling the critical temperature (Tc) and normal electrical resistance (RN ) of the Mo/Au bilayer. The process is optimized to achieve low stress bilayers, thus avoiding the undesirable curvature of the membranes. Bilayers are patterned using photolithographic techniques and wet etching procedures. Mo superconducting paths are used to contact the Mo/Au bilayers, thus ensuring good electrical conductivity and thermal isolation. The entire fabrication process let to stable and reproducible sensors with required and tunable functional properties

Biomechanics of smart wings in a bat robot: morphing wings using SMA actuators

This paper presents the design of a bat-like micro aerial vehicle with actuated morphing wings. NiTi shape memory alloys (SMAs) acting as artificial biceps and triceps muscles are used for mimicking the morphing wing mechanism of the bat flight apparatus. Our objective is twofold. Firstly, we have implemented a control architecture that allows an accurate and fast SMA actuation. This control makes use of the electrical resistance measurements of SMAs to adjust morphing wing motions. Secondly, the feasibility of using SMA actuation technology is evaluated for the application at hand. To this purpose, experiments are conducted to analyze the control performance in terms of nominal and overloaded operation modes of the SMAs. This analysis includes: (i) inertial forces regarding the stretchable wing membrane and aerodynamic loads, and (ii) uncertainties due to impact of airflow conditions over the resistance–motion relationship of SMAs. With the proposed control, morphing actuation speed can be increased up to 2.5 Hz, being sufficient to generate lift forces at a cruising speed of 5ms−1.

Investigación sobre la aplicación de energía solar a una depuradora convencional de fangos activos

El consumo de energía es responsable de una parte importante de las emisiones a la atmósfera de CO2, que es uno de los principales causantes del efecto invernadero en nuestro planeta. El aprovechamiento de la energía solar para la producción de agua caliente, permite economizar energía y disminuir el impacto del consumo energético sobre el medio ambiente y por tanto un menor impacto medioambiental. El objetivo de la presente investigación consiste en estudiar el aprovechamiento solar para el calentamiento de los fangos en los digestores anaerobios mediante agua caliente circulando en el interior de un serpentín que rodea la superficie de dicho digestor, como apoyo a los métodos convencionales del calentamiento de fangos como la resistencia eléctrica o el intercambiador de calor mediante la energía obtenida por el gas metano producido en la digestión anaerobia. Para el estudio se utilizaron 3 digestores, dos delos cuales se calentaron con agua caliente en el interior de un serpentín (uno aislado mediante una capa de fibra de vidrio y poliuretano y otro sin aislar).El tercer digestor no tenía calentamiento exterior con el objetivo de observar su comportamiento y comparar su evolución con el resto de los digestores .La comparación de los digestores 1 y 2 nos permitió estudiar la conveniencia de proveer de aislamiento al digestor. La transferencia de calor mediante serpentín de cobre dio valores comprendidos entre 83 y 92%. La aplicación de la instalación a una depuradora a escala real para mantenimiento en el interior del digestor a T=32ºC en diferentes climas: climas templados, cálidos y fríos, consistió en el cálculo de la superficie de colectores solares y superficie de serpentín necesario para cubrir las necesidades energéticas anuales de dicho digestor, así como el estudio de rentabilidad de la instalación, dando los mejores resultados para climas cálidos con períodos de retorno de 12 años y una tasa interna de rentabilidad (TIR) del 16% obteniendo una cobertura anual del 79% de las necesidades energéticas con energía solar térmica. Energy consumption accounts for a significant part of the emissions of CO2, which is one of the main causes of the greenhouse effect on our planet. The use of solar energy for hot water production. can save energy and reduce the impact of energy consumption on the environment and therefore a reduced environmental impact. The objective of this research is to study the solar utilization for heating the sludge in anaerobic digesters by hot water circulating inside a coil surrounding the surface of digester, to support conventional heating methods sludge as the electrical resistance or heat exchanger by energy generated by the methane gas produced in the anaerobic digestion. To study 3 digesters used two models which are heated with hot water within a coil (one insulated by a layer of fiberglass and polyurethane and other uninsulated) .The third digester had no external heating in order to observe their behavior and compare their evolution with the rest of the .The comparison digesters digesters 1 and 2 allowed us to study the advisability of providing insulation to the digester. Heat transfer through copper coil gave values between 83 and 92%. The installation application to a treatment for maintaining full scale within the digester at T = 32ºC in different climates: temperate, warm and cold climates, consisted of calculating the surface area of solar collectors and coil required to cover the annual energy needs of the digester, and the study of profitability of the installation, giving the best results for hot climates with return periods of 12 years and an internal rate of return (IRR) of 16% achieving an annual coverage of 79 % of energy needs with solar energy.

Nuclear hourglass technique: An approach that detects electrically open nuclear pores in Xenopus laevis oocyte

Nuclear pore complexes (NPCs) mediate both active transport and passive diffusion across the nuclear envelope (NE). Determination of NE electrical conductance, however, has been confounded by the lack of an appropriate technical approach. The nuclear patch clamp technique is restricted to preparations with electrically closed NPCs, and microelectrode techniques fail to resolve the extremely low input resistance of large oocyte nuclei. To address the problem, we have developed an approach for measuring the NE electrical conductance of Xenopus laevis oocyte nuclei. The method uses a tapered glass tube, which narrows in its middle part to 2/3 of the diameter of the nucleus. The isolated nucleus is sucked into the narrow part of the capillary by gentle fluid movement, while the resulting change in electrical resistance is monitored. NE electrical conductance was unexpectedly large (7.9 ± 0.34 S/cm2). Evaluation of NPC density by atomic force microscopy showed that this conductance corresponded to 3.7 × 106 NPCs. In contrast to earlier conclusions drawn from nuclear patch clamp experiments, NPCs were in an electrically “open” state with a mean single NPC electrical conductance of 1.7 ± 0.07 nS. Enabling or blocking of active NPC transport (accomplished by the addition of cytosolic extracts or gp62-directed antibodies) revealed this large NPC conductance to be independent of the activation state of the transport machinery located in the center of NPCs. We conclude that peripheral channels, which are presumed to reside in the NPC subunits, establish a high ionic permeability that is virtually independent of the active protein transport mechanism.

Regulated assembly of tight junctions by protein kinase C.

We have previously shown that protein phosphorylation plays an important role in the sorting and assembly of tight junctions. We have now examined in detail the role of protein kinases in intercellular junction biogenesis by using a combination of highly specific and broad-spectrum inhibitors that act by independent mechanisms. Our data indicate that protein kinase C (PKC) is required for the proper assembly of tight junctions. Low concentrations of the specific inhibitor of PKC, calphostin C, markedly inhibited development of transepithelial electrical resistance, a functional measure of tight-junction biogenesis. The effect of PKC inhibitors on the development of tight junctions, as measured by resistance, was paralleled by a delay in the sorting of the tight-junction protein, zona occludens 1 (ZO-1), to the tight junction. The assembly of desmosomes and the adherens junction were not detectably affected, as determined by immunocytochemical analysis. In addition, ZO-1 was phosphorylated subsequent to the initiation of cell-cell contact, and treatment with calphostin C prevented approximately 85% of the phosphorylation increase. Furthermore, in vitro measurements indicate that ZO-1 may be a direct target of PKC. Moreover, membrane-associated PKC activity more than doubled during junction assembly, and immunocytochemical analysis revealed a pool of PKC zeta that appeared to colocalize with ZO-1 at the tight junction. A preformed complex containing ZO-1, ZO-2, p130, as well as 330- and 65-kDa phosphoproteins was detected by coimmunoprecipitation in both the presence and absence of cell-cell contact. Identity of the 330- and 65-kDa phosphoproteins remains to be determined, but the 65-kDa protein may be occludin. The mass of this complex and the incorporation of ZO-1 into the Triton X-100-insoluble cytoskeleton were not PKC dependent.

A chemically diverse conducting polymer-based "electronic nose".

We describe a method for generating a variety of chemically diverse broadly responsive low-power vapor sensors. The chemical polymerization of pyrrole in the presence of plasticizers has yielded conducting organic polymer films whose resistivities are sensitive to the identity and concentration of various vapors in air. An array of such sensing elements produced a chemically reversible diagnostic pattern of electrical resistance changes upon exposure to different odorants. Principal component analysis has demonstrated that such sensors can identify and quantify different airborne organic solvents and can yield information on the components of gas mixtures.

Self-heating and deicing conductive cement. Experimental study and modeling

This research studies the self-heating produced by the application of an electric current to conductive cement pastes with carbonaceous materials. The main parameters studied were: type and percentage of carbonaceous materials, effect of moisture, electrical resistance, power consumption, maximum temperature reached and its evolution and ice melting kinetics are the main parameters studied. A mathematical model is also proposed, which predicts that the degree of heating is adjustable with the applied voltage. Finally, the results have been applied to ensure that cementitious materials studied are feasible to control ice layers in transportation infrastructures.

A conceptual map about alternating current circuits

Teachers are deeply concerned on how to be more effective in our task of teaching. We must organize the contents of our specific area providing them with a logical configuration, for which we must know the mental structure of the students that we have in the classroom. We must shape this mental structure, in a progressive manner, so that they can assimilate the contents that we are trying to transfer, to make the learning as meaningful as possible. In the generative learning model, the links before the stimulus delivered by the teacher and the information stored in the mind of the learner requires an important effort by the student, who should build new conceptual meanings. That effort, which is extremely necessary for a good learning, sometimes is the missing ingredient so that the teaching-learning process can be properly assimilated. In electrical circuits, which we know are perfectly controlled and described by Ohm's law and Kirchhoff's two rules, there are two concepts that correspond to the following physical quantities: voltage and electrical resistance. These two concepts are integrated and linked when the concept of current is presented. This concept is not subordinated to the previous ones, it has the same degree of inclusiveness and gives rise to substantial relations between the three concepts, materializing it into a law: The Ohm, which allows us to relate and to calculate any of the three physical magnitudes, two of them known. The alternate current, in which both the voltage and the current are reversed dozens of times per second, plays an important role in many aspects of our modern life, because it is universally used. Its main feature is that its maximum voltage is easily modifiable through the use of transformers, which greatly facilitates its transfer with very few losses. In this paper, we present a conceptual map so that it is used as a new tool to analyze in a logical manner the underlying structure in the alternate current circuits, with the objective of providing the students from Sciences and Engineering majors with another option to try, amongst all, to achieve a significant learning of this important part of physics.

Establishment of a confluent monolayer model with human primary trophoblast cells: novel insights into placental glucose transport

STUDY HYPOTHESIS Using optimized conditions, primary trophoblast cells isolated from human term placenta can develop a confluent monolayer in vitro, which morphologically and functionally resembles the microvilli structure found in vivo. STUDY FINDING We report the successful establishment of a confluent human primary trophoblast monolayer using pre-coated polycarbonate inserts, where the integrity and functionality was validated by cell morphology, biophysical features, cellular marker expression and secretion, and asymmetric glucose transport. WHAT IS KNOWN ALREADY Human trophoblast cells form the initial barrier between maternal and fetal blood to regulate materno-fetal exchange processes. Although the method for isolating pure human cytotrophoblast cells was developed almost 30 years ago, a functional in vitro model with primary trophoblasts forming a confluent monolayer is still lacking. STUDY DESIGN, SAMPLES/MATERIALS, METHODS Human term cytotrophoblasts were isolated by enzymatic digestion and density gradient separation. The purity of the primary cells was evaluated by flow cytometry using the trophoblast-specific marker cytokeratin 7, and vimentin as an indicator for potentially contaminating cells. We screened different coating matrices for high cell viability to optimize the growth conditions for primary trophoblasts on polycarbonate inserts. During culture, cell confluency and polarity were monitored daily by determining transepithelial electrical resistance (TEER) and permeability properties of florescent dyes. The time course of syncytia-related gene expression and hCG secretion during syncytialization were assessed by quantitative RT-PCR and enzyme-linked immunosorbent assay, respectively. The morphology of cultured trophoblasts after 5 days was determined by light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Membrane makers were visualized using confocal microscopy. Additionally, glucose transport studies were performed on the polarized trophoblasts in the same system. MAIN RESULTS AND THE ROLE OF CHANCE During 5-day culture, the highly pure trophoblasts were cultured on inserts coated with reconstituted basement membrane matrix . They exhibited a confluent polarized monolayer, with a modest TEER and a size-dependent apparent permeability coefficient (Papp) to fluorescently labeled compounds (MW ∼400-70 000 Da). The syncytialization progress was characterized by gradually increasing mRNA levels of fusogen genes and elevating hCG secretion. SEM analyses confirmed a confluent trophoblast layer with numerous microvilli, and TEM revealed a monolayer with tight junctions. Immunocytochemistry on the confluent trophoblasts showed positivity for the cell-cell adhesion molecule E-cadherin, the tight junction protein 1 (ZO-1) and the membrane proteins ATP-binding cassette transporter A1 (ABCA1) and glucose transporter 1 (GLUT1). Applying this model to study the bidirectional transport of a non-metabolizable glucose derivative indicated a carrier-mediated placental glucose transport mechanism with asymmetric kinetics. LIMITATIONS, REASONS FOR CAUTION The current study is only focused on primary trophoblast cells isolated from healthy placentas delivered at term. It remains to be evaluated whether this system can be extended to pathological trophoblasts isolated from diverse gestational diseases. WIDER IMPLICATIONS OF THE FINDINGS These findings confirmed the physiological properties of the newly developed human trophoblast barrier, which can be applied to study the exchange of endobiotics and xenobiotics between the maternal and fetal compartment, as well as intracellular metabolism, paracellular contributions and regulatory mechanisms influencing the vectorial transport of molecules. LARGE-SCALE DATA Not applicable. STUDY FUNDING AND COMPETING INTERESTS This study was supported by the Swiss National Center of Competence in Research, NCCR TransCure, University of Bern, Switzerland, and the Swiss National Science Foundation (grant no. 310030_149958, C.A.). All authors declare that their participation in the study did not involve factual or potential conflicts of interests.

Properties and preparation of ceramic insulators for spark plugs /

"Pre-print from fifth annual report."

Investigation of the absorption pathways of some poorly absorbed drugs using human intestinal (CAC0-2) cell monolayers

Absorption across the gastro-intestinal epithelium is via two pathways; the transcellular and paracellular pathway. Caco-2 cells, when cultured on polycarbonate filters, formed a confluent monolayer with many properties of differentiated intestinal epithelial cells, As a model of human gastro-intestinaJ tract epithelia they were used to elucidate and characterise the transepithelial transport of two protein kinase C inhibitors, N-(3-chlorophenyl)-4-[2-(3-hydroxypropylamino)-4-pyridyl]-2-pyrimidinamin (CHPP) and N-benzoyl-staurosporine (NBS), and the polypeptide, human calcitonin. Lanthanum ions are proposed as a paracellular pathway inhibitor and tested with D-mannitol permeability and transepithelial electrical resistance measurements. The effect La3+ has on the carrier-mediated transport of D-glucose and Sodium taurocholate as well as the vesicularly transcytosed horseradish peroxidase was also investigated. As expected, 2 mM apical La3+ increases transepithelial electrical resistance 1.S-fold and decreases mannitol permeability by 63.0 % ± 1.37 %. This inhibition was not repeated by other cations. Apical 2 mM La3+ was found to decrease carrier-mediated D-glucose and taurocholate permeability by only 8.7 % ± 1.6 %, 26.3 % ± 5.0 %. There was no inhibitory effect on testosterone or PEG 4000 permeability observed with La3+. However, for horseradish peroxidase and human calcitonin permeability was decreased by 98.7 % ± 11.7%, and 96.2 % ± 0.8 % respectively by 2 mM La3+. Indicating that human calcitonin could also be transported by vesicular transcytosis. The addition of 2 mM La3+ to the apical surface of Caco-2 monolayers produces a paracellular pathway inhibition. Therefore, La3+ could be a useful additional tool in delineating the transepithelial pathway of passive drug absorption.

Amino acid, peptide and drug transport across monolayers of human intestinal (CAC0-2) cells in vitro

The properties of Caco-2 monolayers were compared on aluminium oxide and nitrocellulose permeable-supports. On nitrocellulose, Caco-2 cells displayed a higher rate of taurocholic acid transport than those cultured on aluminium oxide inserts. In addition, Caco-2 cells grown on these two inserts were not comparable with respect to cell morphology, cell numbers and transepithelial electrical resistance. The low adsorption potential of the aluminium oxide inserts, particularly for high molecular weight or lipophilic ligands, offers a distinct advantage over nitrocellulose inserts for drug transport studies. The carrier-mediated uptake and transport of the imino acid (L-proline) and the acidic amino acids (L-aspartate and L-glutamate) have been studied. At pH7.4, L-proline uptake is mediated via an A-system carrier. Elevated uptake and transport under acidic conditions occurs by activation of a distinct carrier population. Acidic amino acid transport is mediated via a X-AG system. The flux of baclofen, CGP40116 andCGP40117 across Caco-2 monolayers was described by passive transport. The transport of three peptides, thyrotrophin-releasing hormone, SQ29852 and cyclosporin were investigated. Thyrotrophin-releasing hormone transport acrossCaco-2 monolayers was characterised by a minor saturable (carrier-mediated,approximately 25%) pathway, superimposed onto a major non-saturable (diffusional)pathway. SQ29852 uptake into Caco-2 monolayers is described by a major saturable mechanism (Km = 0.91 mM) superimposed onto a minor passive component.However, the initial-rate of SQ29852 transport is consistent with a passive transepithelial transport mechanism. These data highlight the possibility that itsbasolateral efflux is severely retarded such that the passive paracellular transportdictates the overall transepithelial transport characteristics. In addition, modelsuitable for investigating the transepithelial transport of cyclosporin A has been developed. A modification of the conventional Caco-2 model has been developed which has a calcium-free Ap donor-solution and a Bl receiver-solution containing the minimumcalcium concentration required to maintain monolayer integrity (100 μM). The influence of calcium and magnesium on the absorption of [14C]pamidronate was evaluated by comparing its transport across the conventional and minimum calciumCaco-2 models. Ap calcium and magnesium ions retard the Ap-to-Bl flux of pamidronate across Caco-2 monolayers. The effect of self-emulsifying oleic acid-Tween 80 formulations on Caco-2monolayer integrity has been investigated. Oleic acid-Tween 80 (1 0:1) formulations produced a dose-dependent disruption of Caco-2 monolayer integrity. This disruption was related to the oleic acid content of the formulation.

Application of thermal neutron radiography for the mass transport of moisture through freezing soil

This thesis reports on the development of a technique to evaluate hydraulic conductivities in a soil (Snowcal) subject to freezing conditions. The technique draws on three distinctly different disciplines, Nuclear Physics, Soil Physics and Remote Sensing to provide a non-destructive and reliable evaluation of hydraulic conductivity throughout a freezing test. Thermal neutron radiography is used to provide information on local water/ice contents at anytime throughout the test. The experimental test rig is designed so that the soil matrix can be radiated by a neutron beam, from a nuclear reactor, to obtain radiographs. The radiographs can then be interpreted, following a process of remote sensing image enhancement, to yield information on relative water/ice contents. Interpretation of the radiographs is accommodated using image analysis equipment capable of distinguishing between 256 shades of grey. Remote sensing image enhancing techniques are then employed to develop false colour images which show the movement of water and development of ice lenses in the soil. Instrumentation is incorporated in the soil in the form of psychrometer/thermocouples, to record water potential, electrical resistance probes to enable ice and water to be differentiated on the radiographs and thermocouples to record the temperature gradient. Water content determinations are made from the enhanced images and plotted against potential measurements to provide the moisture characteristic for the soil. With relevant mathematical theory pore water distributions are obtained and combined with water content data to give hydraulic conductivities. The values for hydraulic conductivity in the saturated soil and at the frozen fringe are compared with established values for silts and silty-sands. The values are in general agreement and, with refinement, this non-destructive technique could afford useful information on a whole range of soils. The technique is of value over other methods because ice lenses are actually seen forming in the soil, supporting the accepted theories of frost action. There are economic and experimental restraints to the work which are associated with the use of a nuclear facility, however, the technique is versatile and has been applied to the study of moisture transfer in porous building materials and could be further developed into other research areas.