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PubMed1998

Marketing innovations to nurses, Part 1: How people adopt innovations.

This article is the first in a two-part series that explores marketing techniques to enhance nurse's adoption of innovations in practice. Introducing new policies and procedures and persuading colleagues to implement them constitute an important part of the WOC nurse role. Nursing research reveals a lag of 8 to 30 years between the time new ideas are generated and nurses use them in practice. This article presents a theoretic grounding based on the Everett Rogers Diffusion of innovation Theory and uses the author's experiences introducing a research-based practice innovation to illustrate concrete and practice-relevant examples of innovation adoption theory and marketing principles in action.

Decision Support Techniques↗
PubMed1982

Viscosity dependence of the kinetics of the diffusion-controlled reaction of carbon monoxide and myoglobin.

The kinetics of the reaction of CO with myoglobin have been studied by laser flash photolysis in glycerol-water as a function of solvent viscosity and temperature. At high viscosities and low temperatures the second-order rate constant is inversely proportional to the viscosity raised to approximately the 0.5 power. This result parallels the behavior of the oxygen diffusion coefficient in glycerol-water. It is concluded that the reaction kinetics in high viscosity glycerol-water are largely diffusion controlled. At higher temperatures, though, the effect of simultaneous chemical activation control of the reaction is observed. The diffusion-controlled rate constant is 1.4 X 10(-3) of that predicted from simple von Smoluchowski theory based on diffusion coefficients and molecular radii. Several models with steric requirements for diffusion-controlled reactions are examined.

Carbon Monoxide↗
PubMed2000

Overdamped van hove function of colloidal suspensions

The generalized-hydrodynamic theory for collective diffusion of a monodisperse colloidal suspension is developed in the framework of the Onsager-Machlup theory of time-dependent fluctuations. The time evolution of the intermediate scattering function F(k,t) is derived as a contraction of the description involving the instantaneous particle number concentration, the particle current, and the stress tensor of the Brownian fluid as state variables. We show that the proper overdamped limit of this equation requires the explicit separation of the stress tensor in its mutually orthogonal kinetic and configurational contributions. Analogous results also follow for the self-intermediate scattering function F(s)(k,t). We show that neglecting the non-Markovian part of the configurational stress tensor memory, one recovers the single exponential memory approximation (based on sum rules derived from the Smoluchowski equation) for both F(s)(k,t) and F(k,t). We suggest simple approximate manners to relate the collective and the self-memory functions, leading to Vineyard-like approximate relations between F(s)(k,t) and F(k,t).

Journal Article↗
PubMed2007

The special theory of Brownian relativity: equivalence principle for dynamic and static random paths and uncertainty relation for diffusion.

The theoretical basis of a recent theory of Brownian relativity for polymer solutions is deepened and reexamined. After the problem of relative diffusion in polymer solutions is addressed, its two postulates are formulated in all generality. The former builds a statistical equivalence between (uncorrelated) timelike and shapelike reference frames, that is, among dynamical trajectories of liquid molecules and static configurations of polymer chains. The latter defines the "diffusive horizon" as the invariant quantity to work with in the special version of the theory. Particularly, the concept of universality in polymer physics corresponds in Brownian relativity to that of covariance in the Einstein formulation. Here, a "universal" law consists of a privileged observation, performed from the laboratory rest frame and agreeing with any diffusive reference system. From the joint lack of covariance and simultaneity implied by the Brownian Lorentz-Poincaré transforms, a relative uncertainty arises, in a certain analogy with quantum mechanics. It is driven by the difference between local diffusion coefficients in the liquid solution. The same transformation class can be used to infer Fick's second law of diffusion, playing here the role of a gauge invariance preserving covariance of the spacetime increments. An overall, noteworthy conclusion emerging from this view concerns the statistics of (i) static macromolecular configurations and (ii) the motion of liquid molecules, which would be much more related than expected.

Journal Article↗
PubMed2006

Diffusion of spheres in isotropic and nematic suspensions of rods.

Diffusion of a small tracer sphere (apoferritin) in isotropic and nematic networks [of fd virus] is discussed. For a tracer sphere that is smaller than the mesh size of the network, screened hydrodynamic interactions between the sphere and the network determine its diffusion coefficient. A theory is developed for such interactions as well as their relation to the long-time self-diffusion coefficient. Fluorescence correlation spectroscopy measurements on mixtures of apoferritin and fd virus are presented. The long-time self-diffusion coefficient of apoferritin is measured as a function of the fd-virus concentration, both in the isotropic and nematic state, in directions parallel and perpendicular to the nematic director. The hydrodynamic screening length of the fd-virus network as a function of fd concentration is obtained by combining these experimental data with the theory. Surprisingly, the screening length increases with increasing concentration in nematic networks. This is due to the increase in the degree of alignment, which apparently leads to a strong increase of the screening length. Hydrodynamic screening is thus strongly diminished by alignment. A self-consistent calculation of the screening length does not work at higher concentrations, probably due to the strong variation of the typical incident flow fields over the contour of a rod.

Algorithms↗
PubMed2005

Separating the contribution of translational and rotational diffusion to protein association.

The association of two proteins is preceded by a mutual diffusional search in solution. The role of translational and rotational diffusion in this process has been studied theoretically for many years. However, systematic experimental verification of theoretical results is still lacking. We report here measurements of association rates of the proteins beta-lactamase (TEM) and beta-lactamase inhibitor protein (BLIP) in solutions of glycerol and poly(ethylene glycol) of increasing viscosity. We also measured translational and rotational diffusion in the same solutions, using fluorescence correlation spectroscopy and fluorescence anisotropy, respectively. It is found that in glycerol both translational and rotational diffusion rates are inversely dependent on viscosity, as predicted by the classical Stokes-Einstein relations, while the association rate depends nonlinearly on viscosity. In contrast, the association rate depends only weakly on the viscosity of the polymer solutions, which results in a similar weak dependence of k(on) on viscosity. The data are modeled using the theory of diffusion-limited association. Deviations from the theory are explained by a short-range solute-induced repulsion between the proteins in glycerol solution and an attractive depletion interaction generated by the polymers. These results open the way to the creation of a unified framework for all nonspecific effects involved in the protein association process, as well as to better theoretical understanding of these effects. Further, they reflect on the complex factors controlling protein association within the crowded environment of cells and suggest that a high concentration of macromolecules does not significantly impede protein association.

Diffusion↗
PubMed2006

Modeling water diffusion anisotropy within fixed newborn primate brain using Bayesian probability theory.

An active area of research involves optimally modeling brain diffusion MRI data for various applications. In this study Bayesian analysis procedures were used to evaluate three models applied to phase-sensitive diffusion MRI data obtained from formalin-fixed perinatal primate brain tissue: conventional diffusion tensor imaging (DTI), a cumulant expansion, and a family of modified DTI expressions. In the latter two cases the optimum expression was selected from the model family for each voxel in the image. The ability of each model to represent the data was evaluated by comparing the magnitude of the residuals to the thermal noise. Consistent with previous findings from other laboratories, the DTI model poorly represented the experimental data. In contrast, the cumulant expansion and modified DTI expressions were both capable of modeling the data to within the noise using six to eight adjustable parameters per voxel. In these cases the model selection results provided a valuable form of image contrast. The successful modeling procedures differ from the conventional DTI model in that they allow the MRI signal to decay to a positive offset. Intuitively, the positive offset can be thought of as spins that are sufficiently restricted to appear immobile over the sampled range of b-values.

Animals↗
PubMed1999

General solution for diffusion-controlled dissolution of spherical particles. 1. Theory.

Three classical particle dissolution rate expressions are commonly used to interpret particle dissolution rate phenomena. Our analysis shows that an assumption used in the derivation of the traditional cube-root law may not be accurate under all conditions for diffusion-controlled particle dissolution. Mathematical analysis shows that the three classical particle dissolution rate expressions are approximate solutions to a general diffusion layer model. The cube-root law is most appropriate when particle size is much larger than the diffusion layer thickness, the two-thirds-root expression applies when the particle size is much smaller than the diffusion layer thickness. The square-root expression is intermediate between these two models. A general solution to the diffusion layer model for monodispersed spherical particles dissolution was derived for sink and nonsink conditions. Constant diffusion layer thickness was assumed in the derivation. Simulated dissolution data showed that the ratio between particle size and diffusion layer thickness (a0/h) is an important factor in controlling the shape of particle dissolution profiles. A new semiempirical general particle dissolution equation is also discussed which encompasses the three classical particle dissolution expressions. The success of the general equation in explaining limitations of traditional particle dissolution expressions demonstrates the usefulness of the general diffusion layer model.

Diffusion↗
PubMed1979

Electrostatic interactions at charged lipid membranes. Calcium binding.

A quantitative study of calcium-ion binding by the negatively-charged phospholipid methylphosphatidic acid is presented. Experimental results are compared with the predictions of the Gouy-Chapman theory, taking into account both the ions bound at the membrane surface and the ions held in the diffuse layer. This theory suffices to explain the titration of the calcium/lipid system, but fails to explain completely the behaviour of the ordered-fluid transition temperature, which shows a splitting that according to electrostatic theory alone should not occur. The dependence of the calcium-lipid binding constant. upon 1: 1 electrolyte concentration is correctly predicted by the theory; the latter however gives equations which can only be solved numerically. A simple, approximate equation is therefore given (in the text, eq. 34) for the prediction of the degree of calcium binding to a negatively-charged lipid membrane.

Journal Article↗
PubMed1998

Effect of diffusion potential, osmosis and ion-exchange on transdermal drug delivery: theory and experiments.

Equations expressing the effect of the diffusion potential on the trace ion transfer across a porous charged membrane have been derived. These equations have been tested with experiments with human cadaver skin. The transfer of sotalol and salicylate was measured varying the salt (NaCl) concentration in the donor and receiver compartments. It appears that osmotic pressure and ion-exchange make a significant contribution to the flux enhancement by the diffusion potential.

Administration, Cutaneous↗
PubMed1980

Vehicle effects in percutaneous absorption: in vitro study of influence of solvent power and microscopic viscosity of vehicle on benzocaine release from suspension hydrogels.

The release through silicone rubber membranes of benzocaine suspended in carbomer hydrogels containing different concentrations of low molecular weight polysols (ethylene glycol, propylene glycol, glycerol, and sorbitol) was studied to establish general principles and procedures for control of the effects on percutaneous absorption caused by changes in drug solubility and/or diffusivity in the vehicle. The effect of the additives on the release is expressed in terms of the relative released amount, i.e., the ratio, Q/Qw, of the amount of drug released from each additive-containing gel to the amount released at the same time from the additive-free gel. The experimental Q/Qw values are correlated with values calculated by a simple equation involving known or readily measurable parameters such as the drug concentration in the gel, the drug solubility in the pure liquid phase, and the viscosity of this phase. Derivation of such a relationship from a known equation describing the vehicle-controlled relase of suspended drugs was possible because an inverse proportionality was observed between drug diffusivity in the gels and the viscosity of the respective solvents. This relationship is interpreted with respect to current theories on drug diffusion in diluted gels.

Benzocaine↗
PubMed1981

Anisotropic rotation of bacteriorhodopsin in lipid membranes. Comparison of theory with experiment.

Rotational diffusion of bacteriorhodopsin in dimyristoyl phosphatidylcholine vesicles has been measured at different temperatures and lipid; protein ratios by the technique of flash-induced transient linear dichroism. The data are used to evaluate critically the theory of anisotropy decay due to protein rotation in the lipid bilayer. The theoretical model assumes that rotation of the protein occurs only around the membrane normal. Under conditions favoring completely monomeric bacteriorhodopsin, namely at molar lipid; protein ratios greater than or approximately 100 and for temperatures sufficiently above the lipid phase transition, it is found that the theoretical model provides an excellent description of the experimental data. Curve-fitting analyses of the experimental decay curves show that the retinal is oriented at an angle of 78 +/- 2 degrees with respect to the membrane normal. Between 25 and 37 degrees C, the protein rotates with a relaxation time of 15 +/- 5 micros in the lipid liquid crystalline phase, corresponding to the membrane viscosity of 3.7 +/- 1.3 P. The curve analysis also provides a sensitive test for the presence of protein aggregates in the lipid bilayer.

Bacteriorhodopsins↗
PubMed2000

Chart it once: innovation in public health documentation.

The Seattle-King County Department of Public Health implemented a revision in the charting for its Family Support programs with the goal of streamlining the entire charting process, reducing redundancy, improving quality, and improving productivity. This article applies diffusion of innovations theory to the process of changing documentation.

Diffusion of Innovation↗
PubMed2002

A framework for the dissemination and utilization of research for health-care policy and practice.

PURPOSE: The purpose of this paper is to construct a comprehensive framework of research dissemination and utilization that is useful for both health policy and clinical decision-making. ORGANIZING CONSTRUCT: The framework illustrates that the process of the adoption of research evidence into health-care decision-making is influenced by a variety of characteristics related to the individual, organization, environment and innovation. The framework also demonstrates the complex inter-relationships among these characteristics as progression through the five stages of innovation namely, knowledge, persuasion, decision, implementation and confirmation occurs. Finally, the framework integrates the concepts of research dissemination, evidence-based decision-making and research utilization within the diffusion of innovations theory. METHODS: During the discussion of each stage of the innovation adoption process, relevant literature from the management field (i.e., diffusion of innovations, organizational management and decision-making) and health-care sector (i.e., research dissemination and utilization and evidence-based practice) is summarized. Studies providing empirical data contributing to the development of the framework were assessed for methodological quality. CONCLUSIONS: The process of research dissemination and utilization is complex and determined by numerous intervening variables related to the innovation (research evidence), organization, environment and individual.

Clinical Nursing Research↗
PubMed1985

Translational diffusion of lipids in liquid crystalline phase phosphatidylcholine multibilayers. A comparison of experiment with theory.

A systematic study of the translational diffusion of the phospholipid derivative N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylethanolamine (NBD-PE) has been undertaken in liquid crystalline phase phosphatidylcholine bilayers by using the fluorescence recovery after photobleaching technique. This work was done with the intention of comparing the experimental results with the predictions of theoretical models for diffusion in membranes. The following is shown. For NBD-PE, the dependence of the translational diffusion coefficient (Dt) upon the acyl chain length of the diffusant is not that predicted by continuum fluid hydrodynamic models for diffusion in membranes [Saffman, P.G., & Delbrueck, M. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 3111-3113; Hughes, B. D., Pailthorpe, B. A., & White, L. R. (1981) J. Fluid Mech. 110, 349-372]. Plots of Dt vs. 1/T (Arrhenius plots) are nonlinear in dilauroyl-phosphatidylcholine (DLPC), dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) bilayers where the acyl chain composition of the NBD-PE is matched with that of the host bilayer lipid. This suggests that a "free volume" model may be appropriate for the description of lipid diffusion in lipid bilayers. In bilayers of phosphatidylcholines with saturated acyl chains at the same "reduced temperature", the magnitude of Dt follows the order distearoylphosphatidylcholine greater than DPPC greater than DMPC greater than DLPC. This is the inverse of what may be expected from the hydrodynamic model but is in agreement with the free volume in these bilayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Diffusion↗
PubMedDate not supplied

Measuring the diffusion of innovative health promotion programs.

Once a health promotion program has proven to be effective in one or two initial settings, attempts may be made to transfer the program to new settings. One way to conceptualize the transference of health promotion programs from one locale to another is by considering the programs to be innovations that are being diffused. In this way, diffusion of innovation theory can be applied to guide the process of program transference. This article reports on the development of six questionnaires to measure the extent to which health promotion programs are successfully disseminated: Organizational Climate, Awareness-Concern, Rogers's Adoption Variables, Level of Use, Level of Success, and Level of Institutionalization. The instruments are being successfully used in a study of the diffusion of health promotion/tobacco prevention curricula to junior high schools in North Carolina. The instruments, which measure the four steps of the diffusion process, have construct validity since they were developed within existing theories and are derived from the work of previous researchers. No previous research has attempted to use instruments like these to measure sequentially the stages of the diffusion process.

Adolescent↗
PubMed2000

Noise in hysteretic systems and stochastic processes on graphs

It is shown that the theory of stochastic diffusion processes on graphs is a natural tool for the analysis of noise in hysteretic systems. In particular, by using this theory, analytical expressions for stationary characteristics of random outputs of some hysteretic systems are derived.

Journal Article↗