Frequency-Dependent Viscosity of Membrane Solutions

It is shown that dilute suspensions of membranes have strongly frequency-dependent viscosities. This behaviour should be seen in a variety of measurements such as capillary flow, mechanical impedance and ultrasound damping.

Photocytotoxic and anaerobic DNA cleavage activity of binuclear 3,3 '-dithiodipropionic acid cobalt(II) complexes having phenanthroline bases

Dicobalt(II) complexes [{(B)Co-11)(2)(mu-dtdp)(2)] (1-3) of 3,3'-dithiodipropionic acid (dtdp) and phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2) and dipyrido13,2-a:2',3'-clphenazine (dppz in 3), have been prepared, characterized and their photo-induced anaerobic DNA cleavage activity studied. The elemental analysis and mass spectral data suggest binuclear formulation of the complexes. The redox inactive complexes have magnetically non-interacting dicobalt(II) core showing magnetic moment of similar to 3.9 p per cobalt(II) center. The complexes show good binding propensity to calf thymus DNA giving K-b values within 4.3 x 10(5)-4.0 x 10(6) M-1. Thermal melting and viscosity data predict DNA groove binding and/or partial intercalative nature of the complexes. The complexes show significant anaerobic DNA cleavage activity in green light under argon atmosphere possibly involving radical species generated from the disulfide moiety in a type-I pathway. The DNA cleavage reaction under aerobic medium in green light is found to involve hydroxyl radical species. The dppz complex 3 exhibits significant photocytotoxicity in HeLa cervical cancer cells with an IC50 value of 2.31 mu M in UV-A light of 365 nm, while it is essentially non-toxic in dark giving an IC50 value of >200 mu M. A significant reduction of the dark toxicity of the organic dppz base (IC50 = 8.3 mu M in dark) is observed on binding to the cobalt(II) center while essentially retaining its photocytotoxicity in UV-A light (IC50 = 0.4 mu M). (C) 2010 Elsevier Ltd. All rights reserved.

Marketing and the Logic of Service: Value Facilitation, Value Creation and Co-creation, and Their Marketing Implications

The discussion of a service-dominant logic has made the findings of decades of service marketing research a topic of interest for marketing at large. Some fundamental aspects of the logic such as value creation and its marketing implications are more complex than they have been treated as so far and need to be further developed to serve marketing theory and practice well. Following the analysis in the present article it is argued that although customers are co-producers in service processes, according to the value-in-use notion adopted in the contemporary marketing and management literature they are fundamentally the creators of value for themselves. Furthermore, it is concluded that although by providing goods and services as input resources into customers’ consumption and value-generating processes firms are fundamentally value facilitators, interactions with customers that exist or can be created enable firms to engage themselves with their customers’ processes and thereby they become co-creators of value with their customers. As marketing implications it is observed that 1) the goal of marketing is to support customers’ value creation, 2) following a service logic and due to the existence of interactions where the firm’s and the customer’s processes merge into an integrated joint value creation process, the firm is not restricted to making value propositions only, but can directly and actively influence the customer’s value fulfilment as well and extend its marketing process to include activities during customer-firm interactions, and 3) although all goods and services are consumed as service, customers’ purchasing decisions can be expected to be dependant of whether they have the skills and interest to use a resource, such as a good, as service or want to buy extended market offerings including process-related elements. Finally, the analysis concludes with five service logic theses.

International Portfolio Investments and The Informational Value of Trade

A large volume of literature suggests that information asymmetry resulting from the spatial separation between investors and investments have a significant impact on the composition of investors’ domestic and international portfolios. I show that institutional factors affecting trading in tangible goods help explain a substantial portion of investors’ spatial bias. More importantly, I demonstrate that an information flow medium with breadth and richness directly linked to the bilateral commitment of resources between countries, that I measure by their trading intensity in tangible goods, is consistent with the prevailing country allocation in investors’ international portfolios.

Towards Service Logic: The Unique Contribution of Value Co-Creation

The underpinning logic of value co-creation in service logic is analysed. It is observed that three of the ten foundational premises of the so-called service-dominant logic are problematic and do not support an understanding of value-co-creation and creation that is meaningful for theoretical development and decision making in business and marketing practice. Without a thorough understanding of the interaction concept, the locus and nature of value co-creation cannot be identified. Based on the analysis in the present article it is observed that a unique contribution of a service perspective on business (service logic) is not that customers always are co-creators of value, but that under certain circumstances the service provider gets opportunities to co-create value together with its customers. Finally, the three problematic premises are reformulated accordingly.

Generalized Burgers equations and Euler–Painlevé transcendents. III

It was proposed earlier [P. L. Sachdev, K. R. C. Nair, and V. G. Tikekar, J. Math. Phys. 27, 1506 (1986); P. L. Sachdev and K. R. C. Nair, ibid. 28, 977 (1987)] that the Euler–Painlevé equations  y(d2y/dη2)+a(dy/dη)2 +f(η)y(dy/dη)+g(η)y2+b(dy/dη) +c=0 represent generalized Burgers equations (GBE’s) in the same way as Painlevé equations represent the Korteweg–de Vries type of equations. The earlier studies were carried out in the context of GBE’s with damping and those with spherical and cylindrical symmetry. In the present paper, GBE’s with variable coefficients of viscosity and those with inhomogeneous terms are considered for their possible connection to Euler–Painlevé equations. It is found that the Euler–Painlevé equation, which represents the GBE ut+uβux=(δ/2)g(t)uxx, g(t)=(1+t)n, β>0, has solutions, which either decay or oscillate at η=±∞, only when −1value β=βn seems to bifurcate the families of solutions, which remain bounded at η=±∞. Other GBE’s considered here are also found to be reducible to Euler–Painlevé equations.

Electrocardiographic parameters of ventricular repolarization : modifiers and the prognostic value

Electric activity of the heart consists of repeated cardiomyocyte depolarizations and repolarizations. Abnormalities in repolarization predispose to ventricular arrhythmias. In body surface electrocardiogram, ventricular repolarization generates the T wave. Several electrocardiographic measures have been developed both for clinical and research purposes to detect repolarization abnormalities. The study aim was to investigate modifiers of ventricular repolarization with the focus on the relationship of the left ventricular mass, antihypertensive drugs, and common gene variants, to electrocardiographic repolarization parameters. The prognostic value of repolarization parameters was also assessed. The study subjects originated from a population of more than 200 middle-aged hypertensive men attending the GENRES hypertension study, and from an epidemiological survey, the Health 2000 Study, including more than 6000 participants. Ventricular repolarization was analysed from digital standard 12-lead resting electrocardiograms with two QT-interval based repolarization parameters (QT interval, T-wave peak to T-wave end interval) and with a set of four T-wave morphology parameters. The results showed that in hypertensive men, a linear change in repolarization parameters is present even in the normal range of left ventricular mass, and that even mild left ventricular hypertrophy is associated with potentially adverse electrocardiographic repolarization changes. In addition, treatments with losartan, bisoprolol, amlodipine, and hydrochlorothiazide have divergent short-term effects on repolarization parameters in hypertensive men. Analyses of the general population sample showed that single nucleotide polymorphisms in KCNH2, KCNE1, and NOS1AP genes are associated with changes in QT-interval based repolarization parameters but not consistently with T-wave morphology parameters. T-wave morphology parameters, but not QT interval or T-wave peak to T-wave end interval, provided independent prognostic information on mortality. The prognostic value was specifically related to cardiovascular mortality. The results indicate that, in hypertension, altered ventricular repolarization is already present in mild left ventricular mass increase, and that commonly used antihypertensive drugs may relatively rapidly and treatment-specifically modify electrocardiographic repolarization parameters. Common variants in cardiac ion channel genes and NOS1AP gene may also modify repolarization-related arrhythmia vulnerability. In the general population, T-wave morphology parameters may be useful in the risk assessment of cardiovascular mortality.

Aitosuklaa jäätelöpuikon kuorrutteena

Tutkimuksen kirjallisuuskatsauksessa keskityttiin jäätelöpuikkoihin, erilaisiin suklaakuorrutteisiin ja elintarvikkeiden kuorruttamiseen suklaalla. Lisäksi kirjallisuuskatsauksessa perehdyttiin suklaan koostumukseen, nestemäisen suklaan virtausominaisuuksiin ja koostumuksen ja virtausominaisuuksien välisiin vuorovaikutuksiin. Kokeellisessa osassa tavoitteena oli selvittää, miten maitosuklaakuorrutteen rasvapitoisuuden, emulgointiainepitoisuuden ja kuorrutteen lämpötilanvaihtelut vaikuttavat kuorrutteen viskositeettiin, myötöjännitykseen, jähmettymisaikaan ja jäätelöpuikon päälle jäävän kuorrutteen määrään. Erityisesti pyrittiin selvittämään, miten jäätelöpuikon päälle jäävän kuorrutteen määrää saadaan säädeltyä kuorrutteen rasvapitoisuutta, emulgointiainepitoisuutta ja lämpötilaa muuttamalla. Tutkimuksen koeasetelma tehtiin Box-Behnken-mallilla. Selittäviksi muuttujiksi tutkimukseen valittiin kuorrutteen rasvan määrä, emulgointiaineen määrä ja kuorrutteen lämpötila jäätelöpuikkoja kuorrutettaessa. Vastemuuttujina oli kuorrutteen jähmettymisaika, viskositeetti, myötöjännitys ja jäätelöpuikon päälle jäävän kuorrutteen määrä. Tulokset käsiteltiin regressioanalyysin avulla. Muuttujien välisiä vuorovaikutuksia tutkittiin vastepintamallilla. Vastemuuttujien välisiä korrelaatioita tutkittaessa käytettiin Pearsonin korrelaatiokerrointa. Kuorrutteen rasvan määrän lisääntyminen vähensi tilastollisesti merkitsevästi jäätelöpuikon päälle jäävän kuorrutteen määrää, kuorrutteen jähmettymisaikaa, viskositeettia ja myötöjännitystä. Emulgointiaineen määrän lisääminen kuorrutteessa pienensi kuorrutteen määrää jäätelöpuikon päällä, kuorrutteen jähmettymisaikaa ja kuorrutteen myötöjännitystä. Kuorrutteen lämpötilan lisääminen jäätelöpuikkoja kuorrutettaessa pienensi kuorrutteen määrää ja viskositeettia. Kuorrutteen jähmettymisaika sen sijaan piteni lämpötilaa lisättäessä. Tutkimuksen perusteella voidaan sanoa, että jäätelöpuikkoja kastettaessa suklaakuorrutteen lämpötila, rasvan määrä ja lesitiinin määrä vaikuttivat jäätelöpuikon päälle jäävän kuorrutteen määrään. Vastepintamallinnuksen käyttö soveltui hyvin suklaakuorrutteen määrän tutkimiseen. Sen avulla saatiin selvitettyä, miten jäätelöpuikon päälle jäävän kuorrutteen määrää saadaan säädeltyä muuttamalla kuorrutteen emulgointiainepitoisuutta, rasvapitoisuutta ja lämpötilaa.

A sufficient criterion for Rayleigh-Taylor instability of incompressible viscous three-layer flow

Using normal mode analysis Rayleigh-Taylor instability is investigated for three-layer viscous stratified incompressible steady flow, when the top 3rd and bottom 1st layers extend up to infinity, the middle layer has a small thickness δ. The wave Reynolds number in the middle layer is assumed to be sufficiently small. A dispersion relation (a seventh degree polynomial in wave frequency ω) valid up to the order of the maximal value of all possible Kj (j less-than-or-equals, slant 0, K is the wave number) in each coefficient of the polynomial is obtained. A sufficient condition for instability is found out for the first time, pursuing a medium wavelength analysis. It depends on ratios (α and β) of the coefficients of viscosity, the thickness of the middle layer δ, surface tension ratio T and wave number K. This is a new analytical criterion for Rayleigh-Taylor instability of three-layer fluids. It recovers the results of the corresponding problem for two-layer fluids. Among the results obtained, it is observed that taking the coefficients of viscosity of 2nd and 3rd layers same can inhibit the effect of surface tension completely. For large wave number K, the thickness of the middle layer should be correspondingly small to keep the domain of dependence of the threshold wave number Kc constant for fixed α, β and T.

Solution of a Boundary-Value Problem associated with Diffraction of Water Waves by a Nearly Vertical Barrier

An exact solution is derived for a boundary-value problem for Laplace's equation which is a generalization of the one occurring in the course of solution of the problem of diffraction of surface water waves by a nearly vertical submerged barrier. The method of solution involves the use of complex function theory, the Schwarz reflection principle, and reduction to a system of two uncoupled Riemann-Hilbert problems. Known results, representing the reflection and transmission coefficients of the water wave problem involving a nearly vertical barrier, are derived in terms of the shape function.

Chemical toughening of epoxies. I. Structural modification of epoxy resins by reaction with hydroxy-terminated poly (butadiene-co-acrylonitrile)

In an attempt to toughen the epoxy resin matrix for fiber-reinforced composite applications, a chemical modification procedure of a commercially available bisphenol-A-based epoxy resin using reactive liquid rubber HTBN [hydroxy-terminated poly(butadiene-co-acrylonitrile)] and TDI (tolylene diisocyanate) is described. The progress of the reaction and the structural changes during modification process are studied using IR spectroscopy, viscosity data, and chemical analysis (epoxy value determination). The studies support the proposition that TDI acts as a coupling agent between the epoxy and HTBN, forming a urethane linkage with the former and an oxazolidone ring with the latter. The chemical reactions that possibly take place during the modification are discussed.

Structural effects on the vaporization of high molecular weight esters

To understand the effect of molecular weight and branching on the heats of vaporization (AH,) and their flow behavior, AH, and viscosity (7) were measured at different temperatures in the high molecular weight ester series: linear flexible di-n-alkyl sebacates and compact branched triglycerides with molecular weight ranging from 300 to 900. AHv" values (AHv corrected to 298 K) have been obtained with experimental AH, and also computed according to the group additivity method; a smaller-CH,- group value of 3.8 kJ mol-' compared to the normal value of 5.0 kJ mol-' is found to give good agreement with the experimental data (within 2-5% error). Both ester series have the same AH," irrespective of their molecular features, namely,shape, flexibility, and polarity, suggesting the coiling of the molecules during vaporization. The segmental motion of these ester series during their flow and its dependence on their molecular features unlike AH,' are demonstrated by the correlation of the enthalpy of activation for viscous flow (AH*) and the ratio AE,/AH* = n (AE, is the energy of vaporization) with molecular weight.