Effect of isothermal aging and electromigration on the microstructural evolution of solder interconnections during thermomechanical loading

The effect of different pre-aging treatments on the microstructural evolution of lead-free solder and growth of interfacial intermetallic compound layers under thermal cycling has been investigated in this work. The results show that there are distinct differences in the microstructural changes between samples with no pretreatment, samples that have experienced thermal annealing at 125A degrees C for 750 h before thermal cycling, and those that have had direct current (DC) stressing for 750 h as pretreatment. The microstructural evolution of the solder matrix is rationalized by utilizing the science of microstructures and analysis of the influence of electron flow on the precipitation phenomena. The finite-element method is utilized to understand the loading conditions imposed on the solder interconnections during cyclic stressing. The growth of intermetallic reaction layers is further analyzed by utilizing quantitative thermodynamic calculations coupled with kinetic analysis. The latter is based on the changes in the intrinsic diffusion fluxes of elements induced by current flow and alloying elements present in the system. With this concurrent approach the differences seen in thermal cycling behavior between the different pre-aging treatments can be explained.

A Single-Stage Water-Gas Shift Reaction over Highly Active and Stable Si- and Al-Substituted Pt/CeO2 Catalysts

Ce0.88Si0.1Pt0.02O2-d and Ce0.88Al0.1Pt0.02O2-d catalysts were synthesized by using a low-temperature sonochemical method and characterized by using XRD, TEM, XPS, FTIR, and BET surface analyzer. The catalytic activities of these compounds were investigated for the watergas shift reaction in the temperature range of 140-440 degrees C. The substitution of Si in Ce0.98Pt0.02O2-d increased the releasing capacity of lattice oxygen, whereas the substitution of Al decreased the reducibility of Ce0.98Pt0.02O2-d, as evidenced by hydrogen temperature-programmed reduction studies. However, both the catalysts showed a considerable improvement in terms of activity and stability compared to Ce0.98Pt0.02O2-d. The combined activity measurement and characterization results suggest that the increase in the oxygen vacancy, which acts as a dissociation center for water, is the primary reason for the improvement in the activity of modified Ce0.98Pt0.02O2-d. Both the catalysts are 100?% selective toward H2 production, and approximately 99?% conversion of CO to CO2 was observed at 260 and 270 degrees C for Ce0.88Si0.1Pt0.02O2-d and Ce0.88Al0.1Pt0.02O2-d, respectively. These catalysts do not deactivate during the daily startup/shutdown operations and are sustainable even after prolonged reaction. Notably, these catalysts do not require any pretreatment or activation during startup/shutdown operations.

An Efficient Probe for Rapid Detection of Cyanide in Water at Parts per Billion Levels and Naked-Eye Detection of Endogenous Cyanide

A new molecular probe based on an oxidized bis-indolyl skeleton has been developed for rapid and sensitive visual detection of cyanide ions in water and also for the detection of endogenously bound cyanide. The probe allows the naked-eye detection of cyanide ions in water with a visual color change from red to yellow ((max)=80nm) with the immediate addition of the probe. It shows high selectivity towards the cyanide ion without any interference from other anions. The detection of cyanide by the probe is ratiometric, thus making the detection quantitative. A Michael-type addition reaction of the probe with the cyanide ion takes place during this chemodosimetric process. In water, the detection limit was found to be at the parts per million level, which improved drastically when a neutral micellar medium was employed, and it showed a parts-per-billion-level detection, which is even 25-fold lower than the permitted limits of cyanide in water. The probe could also efficiently detect the endogenously bound cyanide in cassava (a staple food) with a clear visual color change without requiring any sample pretreatment and/or any special reaction conditions such as pH or temperature. Thus the probe could serve as a practical naked-eye probe for in-field experiments without requiring any sophisticated instruments.

Thick PECVD Germanium films for MEMS Application

Plasma enhanced chemical vapour deposition (PECVD) of thick germanium (Ge) films (similar to 1 mu m) on silicon dioxide (SiO2) at low temperatures is described. A diborane pretreatment on SiO2 films is done to seed the Ge growth, followed by the deposition of thick Ge films using germane (GeH4) and argon (Ar). Further, the effect of hydrogen (H-2) dilution on the deposition rate is also investigated. The film thickness and morphology is characterized using SEM. Use of high RF power and substrate temperature show increased deposition rate. EDS analysis indicates that these films contain 97-98 atomic percentage of Ge. A recipe for anisotropic dry etching of the deposited Ge films with 10nm/ min etch rate is also suggested.

Macroporous three-dimensional graphene oxide foams for dye adsorption and antibacterial applications

Several reports illustrate the wide range applicability of graphene oxide (GO) in water remediation. However, a few layers of graphene oxide tend to aggregate under saline conditions thereby reducing its activity. The effects of aggregation can be minimized by having a random arrangement of GO layers in a three dimensional architecture. The current study emphasizes the potential benefits of highly porous, ultralight graphene oxide foams in environmental applications. These foams were prepared by a facile and cost effective lyophilization technique. The 3D architecture allowed the direct use of these foams in the removal of aqueous pollutants without any pretreatment such as ultrasonication. Due to its macroporous nature, the foams exhibited excellent adsorption abilities towards carcinogenic dyes such as rhodamine B (RB), malachite green (MG) and acriflavine (AF) with respective sorption capacities of 446, 321 and 228 mg g(-1) of foam. These foams were also further investigated for antibacterial activities against E. coli bacteria in aqueous and nutrient growth media. The random arrangement of GO layers in the porous foam architecture allowed it to exhibit excellent antibacterial activity even under physiological conditions by following the classical wrapping-perturbation mechanism. These results demonstrate the vast scope of GO foam in water remediation for both dye removal and antibacterial activity.

Application of laser cladding technology to improve the interface of thermal barrier coatings

The present study is focused on improvement of the adhesion properties of the interface between plasma-sprayed coatings and substrates by laser cladding technology (LCT), Within the laser-clad layer there is a gradient distribution in chemical composition and mechanical properties that has been confirmed by SEM observation and microhardness measurement. The residual stress due to mismatches in thermal and mechanical properties between coatings and substrates can be markedly reduced and smoothed out. To examine the changes of microstructure and crack propagation in the coating and interface during loading, the three-point bending test has been carried out in SEM with a loading device. Analysis of the distribution of shear stress near the interface under loading has been made using the FEM code ANSYS, The experimental results show clearly that the interface adhesion can be improved with LCT pretreatment, and the capability of the interface to withstand the shear stress as well as to resist microcracking has been enhanced.

Teología, 1984, Tomo XXI nº 044 (número completo)

La verdad del alma. Una lectura de la cuestión 10 “De Veritate” / Héctor Aguer -- Naturaleza teológica de los Nuevos Ministerios / Osvaldo D. Santagada -- Teoría de la evolución: actualización bibliográfica / Miguel de Asúa – Cecilia Demargasso Nuevos aportes bibliográficos I. Teología cristiana del judaísmo (Jorge Mejía) II. Ontología y libertad. A propósito de un libro de E. Briancesco sobre San Anselmo (José Pablo Martín) -- Crónica de la Facutad -- Notas bibliográficas -- Libros recibidos – Índice del volumen XXI

La economía familiar en sistemas de producción en comunidades del área de desarrollo territorial (ADT) del Municipio de Matigúas Matagalpa: Pasantías realizadas en Abril - Octubre en Fundación Ayuda en Acción proyecto " Desarrollo de la Economía Familiar (DEF.)"

Como una forma de culminación de estudios de la carrera de Licenciatura en Desarrollo Rural, las pasantías han sido realizadas en Fundación Ayuda en Acción (AeA), en el Área de Desarrollo Territorial (ADT) del Municipio de Matiguás-Matagalpa, en el período comprendido de Abril a Octubre del 2014. La Fundación AeA es una organización No Gubernamental de Desarrollo (ONGD) independiente, aconfesional y apartidista, fundada en España en 1981. Actualmente trabaja en 21 países en Asía, África y América Latina. En Nicaragua, la Fundación AeA está presente en: Matagalpa: Matiguás, Río Blanco y Tuma-La Dalia, Región Autónoma del Atlántico Sur (RAAS): Kukra Hill, León: Telica y Quezalguaque, Boaco: Boaco y Camoapa, Madriz: Totogalpa. Los proyectos que implementa son intersectoriales, articulando acciones en educación, salud, prevención de riesgos, gobernabilidad, seguridad y soberanía alimentaria entre otros, con la finalidad de impulsar cambios estructurales que contribuyan a la erradicación de la pobreza. El pasante a través de información primaria y secundaria consideró que la Fundación AeA era el organismo idóneo para realizar sus pasantías, ya que los proyectos que implementa se ajustan al perfil de la carrera de Licenciatura en Desarrollo Rural, al mismo tiempo se visualizó las condiciones favorables para su desempeño laboral. El área de trabajo asignada al pasante estuvo enfocada en proyectos productivos, dirigidos a mejorar los ingresos de las familias, dietas alimenticias, nutrición, así como la creación de conocimientos en diferentes temáticas a través capacitaciones. Entre las funciones asignadas al pasante se menciona: Realizar un estudio económico con productores sobre establecimiento de Sistemas Agroforestales (SAF) en cultivo de Cacao, fortalecer la organización comunitaria, levantar información primaria, elaborar herramientas para el levantamiento de base de datos, facilitar eventos de capacitación, reuniones, talleres e intercambios de experiencia, recolección de mensajes a niñez auspiciados, elaboración de informes, levantar información secundaria, coordinar y planificar con el equipo técnico. El análisis del estudio socioeconómico con productores sobre SAF en Cultivo de Cacao en el proyecto Desarrollo de Economía Familiar (DEF), demostró que el productor trabajando bajo un sistema técnico adecuado podrá obtener altos rendimientos productivos de hasta 15 quintales por manzana desde los 3 años. El pasante en el proyecto DEF, seleccionó en conjunto con el equipo técnico, 186 familias de 243 fichas analizadas los cuales trabajaron en componentes sobre establecimiento de SAF, hortalizas, cultivos en parra y crianza de especies menores. El proyecto de Soberanía y Seguridad Alimentaria y Nutricional (SSAN), ha estado enfocado en apoyar a 255 familias en 17 comunidades, estableciendo rubros, mejorando la calidad y consumo de agua (entrega de Rotoplas) a las familias y enriqueciendo sus conocimientos a través de capacitaciones en diferentes temas de género, comunicación asertiva, elaboración de alimentos, compartiendo experiencias con otras zonas de nuestro país. El pasante obtuvo lecciones como Identificación de diferentes actores locales en el municipio de Matiguás, como AeA, Alcaldía, Fundeser y Nitlapán, a través de iniciativa propia priorizó y gestionó las pasantías en la fundación AeA, relación con el equipo técnico recibiendo un proceso de inducción. La Fundación AeA debería continuar impartiendo talleres de capacitación en el ADT. En cuanto al desarrollo de las pasantías es necesario que desde un inicio se establezcan coordinaciones y planes entre la universidad y la institución donde el pasante desempeñara sus funciones.

A special method to evaluate the strong adhesion between brittle coating and ductile substrate

The evaluation of the interfacial adhesion of coating system has always been a rough task. In this paper, a special testing method of cross-sectional indentation is applied on a model coating system, i.e. electroplated chromium on a steel substrate which is generally regarded as an example of materials pair with strong adhesion. Based on fractography analysis with SEM and interfacial stress simulation with FEM, it is found that interfacial shear stress may induce coating spalling. More interestingly, spalling location is sensitive to substrate pretreatment process. This shows the feasibility of cross-sectional indentation to distinguish interfacial strength at a high level.

ATP Antagonizes Thrombin-Induced Signal Transduction through 12(S)-HETE and cAMP

15 p.

Engineering thermostable fungal cellobiohydrolases

Meeting the world's growing energy demands while protecting our fragile environment is a challenging issue. Second generation biofuels are liquid fuels like long-chain alcohols produced from lignocellulosic biomass. To reduce the cost of biofuel production, we engineered fungal family 6 cellobiohydrolases (Cel6A) for enhanced thermostability using random mutagenesis and recombination of beneficial mutations. During long-time hydrolysis, engineered thermostable cellulases hydrolyze more sugars than wild-type Cel6A as single enzymes and binary mixtures at their respective optimum temperatures. Engineered thermostable cellulases exhibit synergy in binary mixtures similar to wild-type cellulases, demonstrating the utility of engineering individual cellulases to produce novel thermostable mixtures. Crystal structures of the engineered thermostable cellulases indicate that the stabilization comes from improved hydrophobic interactions and restricted loop conformations by proline substitutions. At high temperature, free cysteines contribute to irreversible thermal inactivation in engineered thermostable Cel6A and wild-type Cel6A. The mechanism of thermal inactivation in this cellulase family is consistent with disulfide bond degradation and thiol-disulfide exchange. Enhancing the thermostability of Cel6A also increases tolerance to pretreatment chemicals, demonstrated by the strong correlation between thermostability and tolerance to 1-ethyl-3-methylimidazolium acetate. Several semi-rational protein engineering approaches – on the basis of consensus sequence analysis, proline stabilization, FoldX energy calculation, and high B-factors – were evaluated to further enhance the thermostability of Cel6A.

Wastewater Electrolysis Cell for Environmental Pollutants Degradation and Molecular Hydrogen Generation

This study proposes a wastewater electrolysis cell (WEC) for on-site treatment of human waste coupled with decentralized molecular H₂ production. The core of the WEC includes mixed metal oxides anodes functionalized with bismuth doped TiO₂ (BiO_x/TiO₂). The BiO_x/TiO₂ anode shows reliable electro-catalytic activity to oxidize Cl- to reactive chlorine species (RCS), which degrades environmental pollutants including chemical oxygen demand (COD), protein, NH4⁺, urea, and total coliforms. The WEC experiments for treatment of various kinds of synthetic and real wastewater demonstrate sufficient water quality of effluent for reuse for toilet flushing and environmental purposes. Cathodic reduction of water and proton on stainless steel cathodes produced molecular H2 with moderate levels of current and energy efficiency. This thesis presents a comprehensive environmental analysis together with kinetic models to provide an in-depth understanding of reaction pathways mediated by the RCS and the effects of key operating parameters. The latter part of this thesis is dedicated to bilayer hetero-junction anodes which show enhanced generation efficiency of RCS and long-term stability.

Chapter 2 describes the reaction pathway and kinetics of urea degradation mediated by electrochemically generated RCS. The urea oxidation involves chloramines and chlorinated urea as reaction intermediates, for which the mass/charge balance analysis reveals that N₂ and CO₂ are the primary products. Chapter 3 investigates direct-current and photovoltaic powered WEC for domestic wastewater treatment, while Chapter 4 demonstrates the feasibility of the WEC to treat model septic tank effluents. The results in Chapter 2 and 3 corroborate the active roles of chlorine radicals (Cl•/Cl₂^-•) based on iR-compensated anodic potential (thermodynamic basis) and enhanced pseudo-first-order rate constants (kinetic basis). The effects of operating parameters (anodic potential and [Cl^-] in Chapter 3; influent dilution and anaerobic pretreatment in Chapter 4) on the rate and current/energy efficiency of pollutants degradation and H₂ production are thoroughly discussed based on robust kinetic models. Chapter 5 reports the generation of RCS on Ir_0.7Ta_0.3O_y/Bi_xTi_1-xO_z hetero-junction anodes with enhanced rate, current efficiency, and long-term stability compared to the Ir_0.7Ta_0.3O_y anode. The effects of surficial Bi concentration are interrogated, focusing on relative distributions between surface-bound hydroxyl radical and higher oxide.