The role of microstructure in the thermal fatigue of solder joints.

Thermal fatigue is a common failure mode in electronic solder joints, yet the role of microstructure is incompletely understood. Here, we quantify the evolution of microstructure and damage in Sn-3Ag-0.5Cu joints throughout a ball grid array (BGA) package using EBSD mapping of localised subgrains, recrystallisation and heavily coarsened Ag3Sn. We then interpret the results with a multi-scale modelling approach that links from a continuum model at the package/board scale through to a crystal plasticity finite element model at the microstructure scale. We measure and explain the dependence of damage evolution on (i) the ß-Sn crystal orientation(s) in single and multigrain joints, and (ii) the coefficient of thermal expansion (CTE) mismatch between tin grains in cyclic twinned multigrain joints. We further explore the relative importance of the solder microstructure versus the joint location in the array. The results provide a basis for designing optimum solder joint microstructures for thermal fatigue resistance.

Restrictions and distress in daily, social, and sexual functioning, and intimate relationships in women with pelvic floor complaints: A mixed-method study.

Women with pelvic floor complaints experience restrictions and distress in their daily, social, and sexual functioning, and their intimate relationships. We interviewed forty-eight women to unravel differences between women receiving and not receiving pelvic physical therapy and between pregnant, parous, and nulliparous women in preparation for theory development. We analyzed data in a mixed-method design using NVivo and Leximancer. Sexual dysfunction, relationship dynamics, the nature and severity of restrictions and distress, and coping strategies appear to vary between women receiving and not receiving therapy. Specific combinations of restrictions and distress are present in pregnant, parous, and nulliparous women, and might influence women's decision to seek help.

Spectroscopic and in silico study on the conversion of N,N'-disubstituted hydrazone derivatives of 5-nitrobenzimidazole-2-thione into anion and radical anion products: Implications in hepatotoxicity.

The conversion of N,N'-disubstituted hydrazone derivatives of 5-nitrobenzimidazole-2-thione into radical anion and dianion products was studied through infrared (IR) spectroscopy and computational methods. The electrochemical reduction of 3,3'-(5-nitro-2-thioxo-1H-benzo[d]imidazole-1,3(2H)-diyl)bis(N'-(2-methoxybenzylidene))propane-hydrazide was performed directly in the IR cell and the spectral changes were monitored over time in order to identify the spectral bands originating from the reduction product. In order to clarify whether the reduction leads to the generation of radical anion or deprotonated radical dianion, a second spectroscopic experiment was carried out where deprotonation was achieved by treatment with sodium methoxide. Both experiments resulted in distinctly different spectral features, giving evidence that the reduction to radical anion is not accompanied by deprotonation. In order to explain the experimentally observed differences in the hepatotoxicity within the series of N,N'-disubstituted derivatives of 5-nitrobenzimidazole-2-thione, several molecular electronic parameters such as frontier molecular orbitals, spin and charge distribution over fragments, and electron affinities of the studied hydrazone derivatives were compared to those of a previously studied ester derivative. Based on the estimated electronic parameters, it was shown that the type of the side chains (ester, hydrazone etc.) attached to the N-atoms in the nitrobenzimidazole derivatives do not change significantly the propensity of the compounds towards nitro reduction, but however the generated radical anions are characterized by different reactivity accounting for the different hepatotoxicity.

Foamability of aqueous solutions: Role of surfactant type and concentration.

In this paper we study the main surface characteristics which control the foamability of solutions of various surfactants. Systematic series of experiments with anionic, cationic and nonionic surfactants with different head groups and chain lengths are performed in a wide concentration range, from 0.001 mM to 100 mM. The electrolyte (NaCl) concentration is also varied from 0 up to 100 mM. For all surfactants studied, three regions in the dependence of the foamability, VA, on the logarithm of surfactant concentration, lgCS, are observed. In Region 1, VA is very low and depends weakly on CS. In Region 2, VA increases steeply with CS. In Region 3, VA reaches a plateau. To analyse these results, the dynamic and equilibrium surface tensions of the foamed solutions are measured. A key new element in our interpretation of the foaming data is that we use the surface tension measurements to determine the dependence of the main surface properties (surfactant adsorption, surface coverage and surface elasticity) on the surface age of the bubbles. In this way we interpret the results from the foaming tests by considering the properties of the dynamic adsorption layers, formed during foaming. The performed analysis reveals a large qualitative difference between the nonionic and ionic surfactants with respect to their foaming profiles. The data for the nonionic and ionic surfactants merge around two master curves when plotted as a function of the surface coverage, the surface mobility factor, or the Gibbs elasticity of the dynamic adsorption layers. This difference between the ionic and nonionic surfactants is explained with the important contribution of the electrostatic repulsion between the foam film surfaces for the ionic surfactants which stabilizes the dynamic foam films even at moderate surface coverage and at relatively high ionic strength (up to 100 mM). In contrast, the films formed from solutions of nonionic surfactants are stabilized via steric repulsion which becomes sufficiently high to prevent bubble coalescence only at rather high surface coverage (> 90%) which corresponds to related high Gibbs elasticity (> 150 mN/m) and low surface mobility of the dynamic adsorption layers. Mechanistic explanations of all observed trends are provided and some important similarities and differences with the process of emulsification are outlined.

Spanish adaptation and validation of the Mobile Application Rating Scale questionnaire.

INTRODUCTION AND AIM: In recent years, numerous health-related apps have appeared on the market, and assessing their quality has become crucial. A very popular tool worldwide, created especially for this purpose, is the Mobile Application Rating Scale (MARS). However, there are no similar tools in Spanish. Therefore, the aim of this paper is to adapt MARS to the Spanish language and validate the resultant version. METHOD: The design consists of three processes: cross-cultural adaptation, translation, and metric evaluation. 46 mobile applications, 23 of which were for Apple telephones and 23 of which were for telephones running Android, were included in the study. The main objective of these applications was to promote physical activity. The internal factor structure and reliability of MARS were examined. RESULTS: No major differences were observed in the two Spanish translations, which were carried out independently. The blind back-translation, reviewed by the original author of MARS, suggested minor edits. Discrimination indices (item-scale correlation) obtained appropriate results for both raters. The reliability of the scores was found to be appropriate both in terms of internal consistency (α > 0.77), temporal stability (r > 0.72), and inter-rater reliability (IC > 0.76). The correlations between the subscales have shown high values with range between 0.47 and 0.83. CONCLUSION: The Spanish version of MARS was shown to have appropriate metric properties to assess the quality of health apps.

Saponin Adsorption at the Air-Water Interface-Neutron Reflectivity and Surface Tension Study.

Saponins are a large group of glycosides present in many plant species. They exhibit high surface activity, which arises from a hydrophobic scaffold of triterpenoid or steroid groups and attached hydrophilic saccharide chains. The diversity of molecular structures, present in various plants, gives rise to a rich variety of physicochemical properties and biological activity and results in a wide range of applications in foods, cosmetics, medicine, and several other industrial sectors. Saponin surface activity is a key property in such applications and here the adsorption of three triterpenoid saponins, escin, tea saponins, and Quillaja saponin, is studied at the air-water interface by neutron reflectivity and surface tension. All these saponins form adsorption layers with very high surface visco-elasticity. The structure of the adsorbed layers has been determined from the neutron reflectivity data and is related to the molecular structure of the saponins. The results indicate that the structure of the saturated adsorption layers is governed by densely packed hydrophilic saccharide groups. The tight molecular packing and the strong hydrogen bonds between the neighboring saccharide groups are the main reasons for the unusual rheological properties of the saponin adsorption layers.

Colloids in Flatland: a perspective on 2D phase-separated systems, characterisation methods, and lineactant design.

In 1861 Thomas Graham gave birth to a new field of science, today known as colloid science. Nowadays, the notion "colloid" is often used referring to systems consisting of two immiscible phases, one of which is finely dispersed into the other. Research on colloids deals mostly with sols (solids dispersed in a liquid), emulsions (liquids dispersed in liquid), and foams (gas dispersed in a liquid). Because the dispersed particles are small, there is a lot of interface per unit mass. Not surprisingly, therefore, the properties of the interface have often a decisive effect on the behaviour of colloids. Water-air interfaces have a special relevance in this field: many water-insoluble molecules can be spread on water and, given the right spreading conditions and enough available surface area, their spreading proceeds until a monolayer (a one-molecule thick layer) eventually remains. Several 2D phases have been identified for such monolayers, like "gas", "liquid expanded", "liquid condensed", and "solid". The central question of this review is whether these 2D phases can also exist as colloidal systems, and what stabilizes the dispersed state in such systems. We shall present several systems capable of yielding 2D phase separation, from those based on either natural or fluorinated amphiphiles, to polymer-based ones. We shall seek for analogies in 3D and we shall try to clarify if the lines between these 2D objects play a similar role as the interfaces between 3D colloidal systems. In particular, we shall consider the special role of molecules that tend to accumulate at the phase boundaries, that is, at the contact lines, which will therefore be denoted "line-actants" (molecules that adsorb at a 1D interface, separating two 2D colloidal entities), by analogy to the term "surfactant" (which indicates a molecule that adsorbs at a 2D interface separating two 3D colloidal entities).

Polymer compatibility in two dimensions. Modeling of phase behavior of mixed polymethacrylate Langmuir films.

We analyze the possibility of polymer blends undergoing phase separation in two dimensions. To this end, we investigate a model system consisting of water-supported Langmuir monolayers, obtained from binary polyalkyl-methacrylate mixtures (PXMA, where X stands for any of the type of ester side groups used: M, methyl-; E, ethyl-; B, butyl-; H, hexyl-; O, octyl-; L, lauryl-methacrylate), by means of self consistent field (SCF) calculations. In particular, we address the conditions which determine demixing and phase separation in the two-dimensional system, showing that a sufficient chain length mismatch in the ester side group moieties is able to drive the polymer demixing. When the difference in length of the alkyl chain of the ester moieties on the two types of polymers is progressively reduced, from 11 carbon atoms (PMMA/PLMA) to 4 carbons only (POMA/PLMA), the demixing tendency is also reduced. The polymer/subphase interactions affect more the distribution of the polymer coils in the POMA/PLMA blend monolayer. Mixing of the two polymers is observed, but also a partial layering along the vertical direction. We also add, to a PMMA/PLMA blended monolayer, a third component, namely, a symmetrical diblock copolymer of the type PLMA-b-PMMA. We observe adsorption of the diblock copolymer exclusively at the contact line between the two homopolymer domains, and a concomitant lowering of the line tension. The line tension varies with the chemical potential of the diblock copolymer according to Gibbs' law, which demonstrates that PLMA-b-PMMA can act as a "lineactant" (the equivalent of a surfactant in two-dimensional systems) in the binary demixed PMMA/PLMA Langmuir monolayer.

3D-RISM-KH molecular theory of solvation and density functional theory investigation of the role of water in the aggregation of model asphaltenes.

We applied a multiscale modeling approach that involves the statistical-mechanical three-dimensional reference interaction site model with the Kovalenko-Hirata closure approximation (3D-RISM-KH molecular theory of solvation) as well as density functional theory (DFT) of electronic structure to study the role of water in aggregation of the asphaltene model compound 4,4'-bis(2-pyren-1-yl-ethyl)-2,2'-bipyridine (PBP) [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2008, 22, 715]. The solvation free energy and potential of mean force predicted by 3D-RISM-KH reveal favorable pathways for disaggregation of PBP dimers in pure versus water-saturated chloroform solvent. The water density distribution functions elucidate hydrogen bonding preferences and water bridge formation between PBP monomers. The ΔG(298) values of -5 to -7 kcal mol(-1) for transfer of water molecules in chloroform to a state interacting with PBP molecules are in agreement with experimental results. Geometry optimization and thermochemistry analysis of PBP dimers with and without water bridges using WB97Xd/6-31G(d,p) predict that both PBP dimerization and dimer stabilization by water bridges are spontaneous (ΔG(298) < 0). The (1)H NMR chemical shifts of PBP monomers and dimers predicted using the gauge-independent atomic orbital method and polarizable continuum model for solvation in chloroform are in an excellent agreement with the experimental results for dilute and concentrated PBP solutions in chloroform, respectively [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2009, 23, 3687]. The DFT calculations of PBP dimers with explicit water show that bridges containing 1-3 water molecules lead to stabilization of PBP dimers. Additional water molecules form hydrogen bonds with these bridges and de-shield the PBP protons, negating the effect of water on the (1)H(C3) NMR chemical shift of PBP, in agreement with experiment. The ΔG(298) results show that hydrogen bonding to water and water-promoted polynuclear assembly bridging is as important as π-π interactions for asphaltene aggregation.

Surface rheology of saponin adsorption layers.

Extracts of the Quillaja saponaria tree contain natural surfactant molecules called saponins that very efficiently stabilize foams and emulsions. Therefore, such extracts are widely used in several technologies. In addition, saponins have demonstrated nontrivial bioactivity and are currently used as essential ingredients in vaccines, food supplements, and other health products. Previous preliminary studies showed that saponins have some peculiar surface properties, such as a very high surface modulus, that may have an important impact on the mechanisms of foam and emulsion stabilization. Here we present a detailed characterization of the main surface properties of highly purified aqueous extracts of Quillaja saponins. Surface tension isotherms showed that the purified Quillaja saponins behave as nonionic surfactants with a relatively high cmc (0.025 wt %). The saponin adsorption isotherm is described well by the Volmer equation, with an area per molecule of close to 1 nm(2). By comparing this area to the molecular dimensions, we deduce that the hydrophobic triterpenoid rings of the saponin molecules lie parallel to the air-water interface, with the hydrophilic glucoside tails protruding into the aqueous phase. Upon small deformation, the saponin adsorption layers exhibit a very high surface dilatational elasticity (280 ± 30 mN/m), a much lower shear elasticity (26 ± 15 mN/m), and a negligible true dilatational surface viscosity. The measured dilatational elasticity is in very good agreement with the theoretical predictions of the Volmer adsorption model (260 mN/m). The measured characteristic adsorption time of the saponin molecules is 4 to 5 orders of magnitude longer than that predicted theoretically for diffusion-controlled adsorption, which means that the saponin adsorption is barrier-controlled around and above the cmc. The perturbed saponin layers relax toward equilibrium in a complex manner, with several relaxation times, the longest of them being around 3 min. Molecular interpretations of the observed trends are proposed when possible. Surprisingly, in the course of our study we found experimentally that the drop shape analysis method (DSA method) shows a systematically lower surface elasticity, in comparison with the other two methods used: Langmuir trough and capillary pressure tensiometry with spherical drops. The possible reasons for the observed discrepancy are discussed, and the final conclusion is that the DSA method has specific problems and may give incorrect results when applied to study the dynamic properties of systems with high surface elasticity, such as adsorption layers of saponins, lipids, fatty acids, solid particles, and some proteins. The last conclusion is particularly important because the DSA method recently became the preferred method for the characterization of fluid interfaces because of its convenience.

PMMA highlights the layering transition of PDMS in Langmuir films.

We report a system consisting of a mixed Langmuir monolayer, made of water-insoluble, spreadable, fluid-like polymers polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA) with a minority P(DMS-b-MMA) copolymer. We have performed both Langmuir trough pressure/area isotherm measurements and Brewster angle microscopy (BAM) observations and complement the experiments with molecularly detailed self-consistent field (SCF) calculations. PDMS undergoes a layering transition that is difficult to detect by BAM. Addition of PMMA gives contrast in BAM, now showing a two-phase system: if this would consist of separate two-dimensional (2D) PMMA and PDMS phases, a PDMS-PMMA diblock should accumulate at the phase boundary. However, the diblock copolymer of PDMS-PMMA failed to show the expected "lineactant" behavior, i.e., failed to accumulate at the phase boundary. The calculations point to a nontrivial arrangement of the polymer chains at the interface: in mixtures of the two homopolymers, in a rather wide composition ratio, we find a vertical (with respect to the air/water interfacial plane) configuration, with PMMA sitting preferably at the PDMS/water interface of the thicker PDMS film, during the PDMS layering phase transition. This also explains why the diblock copolymer is not a lineactant. Both PMMA and P(DMS-b-MMA) are depleted from the thin-thick PDMS film interface, and the line tension between the phases is, consequently, increased, in the binary mixtures as well as in the ternary ones.

Polymers at the water/air interface, surface pressure isotherms, and molecularly detailed modeling.

Surface pressure isotherms at the air/water interface are reproduced for four different polymers, poly-L-lactic acid (PLLA), poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), and poly(isobutylene) (PiB). The polymers have the common property that they do not dissolve in water. The four isotherms differ strongly. To unravel the underlying details that are causing these differences, we have performed molecularly detailed self-consistent field (SCF) modeling. We describe the polymers on a united atom level, taking the side groups on the monomer level into account. In line with experiments, we find that PiB spreads in a monolayer which smoothly thickens already at a very low surface pressure. PMMA has an autophobic behavior: a PMMA liquid does not spread on top of the monolayer of PMMA at the air/water interface. A thicker PMMA layer only forms after the collapse of the film at a relatively high pressure. The isotherm of PDMS has regions with extreme compressibility which are linked to a layering transition. PLLA wets the water surface and spreads homogeneously at larger areas per monomer. The classical SCF approach features only short-range nearest-neighbor interactions. For the correct positioning of the layering and for the thickening of the polymer films, we account for a power-law van der Waals contribution in the model. Two-gradient SCF computations are performed to model the interface between two coexistent PDMS films at the layering transition, and an estimation of the length of their interfacial contact is obtained, together with the associated line tension value.

Shell-driven magnetic stability in core-shell nanoparticles.

The magnetic properties of ferromagnetic-antiferromagnetic Co-CoO core-shell nanoparticles are investigated as a function of the in-plane coverage density from 3.5% to 15%. The superparamagnetic blocking temperature, the coercivity, and the bias field radically increase with increasing coverage. This behavior cannot be attributed to the overall interactions between cores. Rather, it can be semiquantitatively understood by assuming that the shells of isolated core-shell nanoparticles have strongly degraded magnetic properties, which are rapidly recovered as nanoparticles come into contact.

Application of spectroscopic and computational methods in the study of the electronic excitations of partially silylated hydroxyquinones.

The silylation of hydroxynaphthoquinones and hydroxyanthraquinones with N-methyl-N-(tert-butyldimethylsilyl)-2,2,2-trifluoroacetamide, in one step reaction, under mild conditions, has led, in nearly quantitative yields, to the isolation of hydrolytically stable partially silylated products (only of the hydroxyl groups), which differ dramatically in color from the starting materials. The spectroscopic investigation of the silylated products in solution as well as the correlation of the observed data with computationally derived results have been carried out within a study aiming at the understanding of the visible maxima shift to either the ultraviolet or near-infrared region of the electromagnetic spectrum, which would imply availability of the silylated products in a variety of related applications.

Characterization of human, mouse and rabbit anti-gliadin antibodies by ELISA and western blotting.

Monoclonal, hyperimmune rabbit and human serum anti-gliadin antibodies were analyzed by ELISA and immunoblotting techniques. In Western blotting the difference in reactivity between monoclonal and human antibodies was quantitative rather than qualitative. Rabbit antisera differed in reactivity according to the protein used for immunization. The rabbits immunized by the peptic-tryptic pancreatic digest of gliadin reacted similarly to the patients. In ELISA, significantly higher reactivity with crude, A-, glyc-gli, alpha-, beta- and omega-gliadins was found in the patients' sera than in controls.

Photoinduced anisotropy: new photopolarimetric setup for real-time measurements.

We describe an experimental set up that measures material optical anisotropy and its eventual evolution in real time. The setup is based on a new photopolarimeter that measures the four Stokes parameters of quasi-monochromatic light quickly and simultaneously. The photoinduced anisotropy in the material optical constants is determined from the measured Stokes parameters. The features of the experimental setup are demonstrated by simultaneous measurement of the photoinduced changes in dichroism and birefringence of layers of rigid solutions of azodyes in polymethyl methacrylate, for which it is known that linearly polarized light orients the dye molecules.

Monoclonal antibodies reacting with gliadin as tools for assessing antigenic structure responsible for exacerbation of celiac disease.

Monoclonal antibodies reactive with gliadin were prepared by fusion of spleen cells isolated from gliadin-immunized BALB/c mice with myeloma cells. The reactivity of mAbs with different preparations of gliadin and their enzymatic digest were measured using ELISA method. The mAb produced by GL 1 clone was shown to react preferentially with alpha-gliadin and its enzymatic digest.

Monoclonal antibodies against human leucocyte antigens. II. Antibodies against CD45 (T200), CD3 (T3), CD43, CD10 (CALLA), transferrin receptor (T9), a novel broadly expressed 18-kDa antigen (MEM-43) and a novel antigen of restricted expression (MEM-74).

The specificities of several monoclonal antibodies described by us earlier were determined more exactly: (1) antibodies MEM-31 and MEM-32 are directed against CD8 and CD5 T cell antigens, respectively: (2) MEM-15 and MEM-18 react with the CD14 monocyte antigen; (3) MEM-28 recognizes the CD45 pan-leucocyte antigen. Several new monoclonal antibodies are described: (4) MEM-55 and MEM-58, reactive with subsets of CD45-related molecules; (5) MEM-43, recognizing a broadly expressed 18-kDa glycoprotein; (6) MEM-57, reacting with the CD3 antigen complex: (7) MEM-59 recognizing the CD43 leucocyte antigen; (8) MEM-74, which reacts with an unidentified antigen strongly expressed on several cell lines and many leukaemic cells but absent from most resting leucocytes; (9) MEM-75, directed against transferrin receptor, and (10) MEM-78, recognizing CD10 (CALLA) antigen.