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PubMedDate not supplied

Is it resources, habit or both: interpreting twenty years of hospital strategic response to prospective payment.

The 1983 Tax Equity and Fiscal Responsibility Act (TEFRA) transformed acute care from a benevolent to malevolent environment. A dual-paradigm of resource dependency and institutional theories that balances isomorphic with economic variables has emerged to better explain hospital strategic response to the resultant constraint on resources than a traditional single paradigm approach. Using the population of non-rural, non-federal acute-care hospitals, strategic response from 1982 to 2001 is studied; distinct cost and service changes occur. Cost strategy is linked primarily to Medicare utilization, a resource dependence response. Service strategy favors high technology regardless of prospective payment diffusion, an institutional theory perspective. Strategic implications are discussed.

Acute Disease↗
PubMed2001

Start right-eat right award scheme: implementing food and nutrition policy in child care centers.

The Start Right-Eat Right award scheme implemented in Western Australia has been used to provide the incentive to bring about improvement in food service in line with government policy and regulations in the child care industry. Theories of organizational change were used to identify processes and strategies to support the industry in translating policy into practice. A baseline survey of food service management practices, as well as process evaluation, informed action and identified barriers. Impact evaluation demonstrated that the award scheme could bring about improvements in the quality of food service; 80% of centers made changes to their menus as a result of participating. Two years postlaunch, 40% of centers have registered in the scheme. The diffusion of innovation theory is used to explain uptake and discuss results. The success of the scheme was based on four factors: an understanding of the industry, collaboration between the child care industry and government, supporting resources, and incentives.

Certification↗
PubMed2006

Percolative transport and cluster diffusion near and below the percolation threshold of a porous polymeric matrix.

PURPOSE: The purpose of this research was to develop a quantitative mass transport model to describe the release of a drug from a porous inert matrix dosage form near and below the percolation threshold for the system. METHODS: Cumulative release profiles were generated for a series of tablets composed of a binary mixture of varying amounts of non-conducting (poly(vinyl stearate)) and conducting (benzoic acid) components. The porous microstructure was analyzed using re-constructed three-dimensional images of leached microtomed tablet sections. Poly(vinyl stearate) was characterized for transport properties, molecular weight and thermal properties. RESULTS: Based on percolation theory, the binary matrix was determined to have a percolation threshold of 0.09 +/- 0.02. Transport, which could not be explained by "classical" percolation theory or surface diffusion alone, was observed below the percolation threshold for the system. CONCLUSIONS: A model describing transport near and below the percolation threshold in matrices composed of two phases, polymer and drug, was developed. The percolation model developed accounts for diffusion within the porous structure and through the inert, insoluble polymeric amorphous regions of the matrix. The low percolation threshold and subsequently high coordination was concluded to be due to the biphasic classical porous and nonclassical polymeric diffusional transport mechanisms associated with the system studied.

Algorithms↗
PubMed2003

Modeling of neutral solute transport in a dynamically loaded porous permeable gel: implications for articular cartilage biosynthesis and tissue engineering.

A primary mechanism of solute transport in articular cartilage is believed to occur through passive diffusion across the articular surface, but cyclical loading has been shown experimentally to enhance the transport of large solutes. The objective of this study is to examine the effect of dynamic loading within a theoretical context, and to investigate the circumstances under which convective transport induced by dynamic loading might supplement diffusive transport. The theory of incompressible mixtures was used to model the tissue (gel) as a mixture of a gel solid matrix (extracellular matrix/scaffold), and two fluid phases (interstitial fluid solvent and neutral solute), to solve the problem of solute transport through the lateral surface of a cylindrical sample loaded dynamically in unconfined compression with frictionless impermeable platens in a bathing solution containing an excess of solute. The resulting equations are governed by nondimensional parameters, the most significant of which are the ratio of the diffusive velocity of the interstitial fluid in the gel to the solute diffusivity in the gel (Rg), the ratio of actual to ideal solute diffusive velocities inside the gel (Rd), the ratio of loading frequency to the characteristic frequency of the gel (f), and the compressive strain amplitude (epsilon 0). Results show that when Rg > 1, Rd < 1, and f > 1, dynamic loading can significantly enhance solute transport into the gel, and that this effect is enhanced as epsilon 0 increases. Based on representative material properties of cartilage and agarose gels, and diffusivities of various solutes in these gels, it is found that the ranges Rg > 1, Rd < 1, correspond to large solutes, whereas f > 1 is in the range of physiological loading frequencies. These theoretical predictions are thus in agreement with the limited experimental data available in the literature. The results of this study apply to any porous hydrated tissue or material, and it is therefore plausible to hypothesize that dynamic loading may serve to enhance solute transport in a variety of physiological processes.

Animals↗
PubMed1995

Simultaneous diffusion and metabolism of betamethasone 17-valerate in the living skin equivalent.

Simultaneous diffusion and metabolism of betamethasone 17-valerate was studied using betamethasone 17-valerate, betamethasone 21-valerate, and betamethasone as permeants. These corticosteroids were suspended in silicone adhesive and applied to an artificial living skin equivalent (LSE) for 72 h. When betamethasone was applied, no metabolites were detected in the receptor medium. Conversely, with betamethasone 21-valerate application, only betamethasone but no betamethasone 21-valerate was detected in the receptor medium indicating the metabolism of the latter by skin esterases. When tested with the theory for simultaneous diffusion and metabolism, the result is consistent with the enzyme rate constant in the LSE homogenate measured in a previous study. When betamethasone 17-valerate was applied to the LSE, more than half of the total amount of corticosteroids detected in the receptor medium was unchanged, consistent with the previously reported chemical (as opposed to enzymatic) degradation half-life of about 8 h. This result also indicated that very little metabolism of betamethasone 17-valerate occurred in the skin.

Betamethasone↗
PubMed2006

Determination of the capacitance of solid-state potentiometric sensors: An electrochemical time-of-flight method.

A dual microelectrode electrochemical time-of-flight technique in which diffusion flux of Ag+, Cl-, or H+ ions electrochemically produced at a generator electrode is measured by recording potential-time transients with Ag, Ag/AgCl, or iridium oxide potentiometric microsensors, respectively, is developed. The generator and microsensor electrodes are typically spaced by 50-100 microm and are incorporated in the lithographically fabricated thin-layer-type devices. Under conditions of moderate rates of the ion electrogeneration, the potential-time (E-t) transients recorded with the three microsensors show excellent agreement with theory involving linear diffusion equations and the experimentally determined Nernstian slopes of the microsensors. However, when the generator current, or the initial concentration of the primary ion of interest is low, appreciable delays in the recorded E-t transients are observed due to the finite capacitance of the micropotentiometric sensors. The recorded delay in the E-t transients can be quantitatively accounted for by including the sensor capacitance (C) in the theoretical description of the transients. Direct comparison between the theoretical and the experimental E-t transients yields the sensor's capacitance. This capability of our new technique is unique in that it allows determination of the capacitance of a potentiometric sensor at open circuit. In the cases of silver electrodes, this method results in C = 31 +/- 2 microF/cm2, a value that is in agreement with those obtained by other methods. The results for silver chloride sensors yield a C in the range of 100-140 +/- 10 microF/cm2. The specific values depend on sensor preparation and the resulting roughness of the Ag/AgCl interface. Iridium oxide sensors show a capacitance that linearly depends on the thickness of the film. Specific capacitance of these microporous films was determined to be 59 +/- 6 F/cm3.

Electric Capacitance↗
PubMed2001

Modeling of drug release from delivery systems based on hydroxypropyl methylcellulose (HPMC).

The objective of this article is to review the spectrum of mathematical models that have been developed to describe drug release from hydroxypropyl methylcellulose (HPMC)-based pharmaceutical devices. The major advantages of these models are: (i) the elucidation of the underlying mass transport mechanisms; and (ii) the possibility to predict the effect of the device design parameters (e.g., shape, size and composition of HPMC-based matrix tablets) on the resulting drug release rate, thus facilitating the development of new pharmaceutical products. Simple empirical or semi-empirical models such as the classical Higuchi equation and the so-called power law, as well as more complex mechanistic theories that consider diffusion, swelling and dissolution processes simultaneously are presented, and their advantages and limitations are discussed. Various examples of practical applications to experimental drug release data are given. The choice of the appropriate mathematical model when developing new pharmaceutical products or elucidating drug release mechanisms strongly depends on the desired or required predictive ability and accuracy of the model. In many cases, the use of a simple empirical or semi-empirical model is fully sufficient. However, when reliable, detailed information are required, more complex, mechanistic theories must be applied. The present article is a comprehensive review of the current state of the art of mathematical modeling drug release from HPMC-based delivery systems and discusses the crucial points of the most important theories.

Delayed-Action Preparations↗
PubMed2001

Predicting migration of trace amounts of styrene in poly(styrene) below the glass transition temperature.

The use of general purpose polystyrene (GPPS) as food packaging material is widespread. Therefore, the rate of migration of the styrene in GPPS is of interest in order to predict the potential exposure of consumers to styrene. Studies have shown a relatively weak dependence of the diffusion coefficient on the residual styrene content, and a strong dependence on temperature. We have compared the predictions of the free-volume theory with experimentally measured diffusivity data. The predictions and the measured values are observed to be consistent with each other. These results illustrate the capability of the free-volume theory of transport to predict the diffusivity of trace amounts of impurity in a glassy polymer.

Diffusion↗
PubMed2005

Dynamics in dialysis process for liquid crystalline gel formation.

The processes of gelation and liquid crystalline formation in the dialysis of Curdlan solution have been observed under crossed nicols, and the calcium concentration and pH of the inner solution were traced. The results showed that the gelation and the liquid crystalline formation occurred simultaneously to form liquid crystalline gel (LCG), but the birefringence of the LCG increased even after the gelation, suggesting further ordering of the Curdlan molecules. On the basis of the calcium ion diffusion, a simple theory for the time development of the thickness of the LCG layer was developed. The experimental and theoretical results agree very well until an amorphous gel (AG) ring appears. The whole process was expressed by a master curve by reducing time and distance data for different radius dialysis tubes by those at the final state; a scaling behavior with respect to the dialysis tube radius was found. The experimental analysis for the calcium concentrations and the pH indicates that forming Curdlan LCG with high ordering of Curdlan molecules consists of two steps: the diffusion of calcium ions inducing the ordering of Curdlan molecules and yielding cross-links simultaneously, and the local relaxation of the Curdlan molecules increasing the ordering degree further.

Crystallization↗
PubMedDate not supplied

A conceptual framework to increase usability of outcome research for evidence-based practice.

Although evidence-based practice is the current practice approach recommended for use in occupational therapy, practitioners often report difficulties in using research evidence because of its content and presentation. This paper discusses a conceptual model that researchers can use to create research evidence that is easier for practitioners to understand and use. The Diffusion of Innovations Theory is used as a framework to identify desirable characteristics that may facilitate practitioners' adoption and utilization of research evidence. The concepts of social validity, ecological validity, and clinical significance are presented and discussed as ways to create those desirable characteristics that could make research information more usable for evidence-based practice. Examples for implementation of the conceptual model are also discussed.

Diffusion of Innovation↗
PubMed2005

On the validity of the quasi-steady state approximation of bimolecular reactions in solution.

Two-step binding kinetics are extensively used to study the relative importance of diffusion in biochemical reactions. Classical analysis of this problem assumes ad hoc that the encounter complex is at quasi-steady state (QSS). Using scaling arguments we derive a criterion for the validity of this assumption in the limit of irreversible product formation. We find that the QSS approximation (QSSA) of two-step binding is only valid if the total ligand and receptor concentrations are much smaller than (k2+k-1)/k1, where k1 and k-1 are, respectively, the forward and reverse diffusion encounter rate constants and k2 is the chemical association rate constant. This criterion can be shown to imply that the average time between encounters is much longer than the half-life of the encounter complex and also guarantees that the concentration of the encounter complex is negligible compared to the reactant and product concentrations. Numerical examples of irreversible and reversible cases corroborate our analysis and illustrate that the QSS may be invalid even if k-2<<k2. Our analysis of the irreversible case is shown to carry through to the more rigorous framework of the Smoluchowski theory of diffusion-controlled reactions. This work underscores the need for exercising greater caution in invoking the QSSA.

Animals↗
PubMed2002

The diffusion of innovation: factors influencing the uptake of telehealth.

The actual use of telehealth, particularly for clinical consultations, has in many cases been less than anticipated. The literature identifies a number of factors or barriers. These include legal issues, technical difficulties, time and convenience, cost and training/familiarity with the equipment. No single factor has been identified as being consistently present. Rogers' diffusion of innovation theory suggests that organizational structures and cultures will affect health professionals' perceptions of telehealth. The introduction of telehealth services affects existing work practices and workflows. We believe that it is necessary to develop strategies for the introduction of telehealth applications which take into account the idiosyncrasies of the health service sector, and the particular structures and cultures of individual organizations within that sector.

Diffusion of Innovation↗
PubMed2003

An angle-by-angle approach to predicting broadband high-frequency sound fields in rectangular enclosures with experimental comparison.

Experiments were performed on an elongated rectangular acoustic enclosure with different levels of absorptive material placed on side walls and an end wall. The acoustic source was a broadband high-frequency sound from a loudspeaker flush-mounted to an end wall of the enclosure. Measurements of sound-pressure levels were averaged in cross sections of the enclosure and then compared to theoretical results. Discrepancies between the experimental results and theoretical predictions that treated all incidence angles as equally probable led to the development of an angle-by-angle approach. The new approach agrees well with the experimentally obtained values. In addition, treating the absorptive material as bulk reacting rather than point reacting was found to significantly change the theoretical value for the absorption coefficient and to improve agreement with experiment. The new theory refines an earlier theory based on power conservation and locally diffuse assumptions. Furthermore, the new theory includes both the angle of incidence effects on the resistive and reactive properties of the absorptive material, and the effects of angle filtering, i.e., that reflecting waves associated with shallow angles become relatively stronger than those associated with steep angles as a function of distance from the source.

Journal Article↗
PubMed2004

Texas physicians' perceptions of genomic medicine as an innovation.

Primary care providers (PCPs) are believed to be the professionals who, in the near future, will be responsible for incorporating genomic medicine (GM) into primary care. Given the dearth of empirical data describing PCPs' beliefs about GM and the relationship between beliefs and the incorporation of GM into practice, this study assessed whether (and to what extent) PCPs' perceptions of GM as an innovation influence their likelihood of adopting this innovation into primary care. The study utilized diffusion of innovations theory as a framework. A state-wide representative sample of PCPs practicing in Texas responded to a mailed survey. The survey measured PCPs' perceptions of five characteristics of GM as an innovation. Findings suggest that among the five characteristics examined GM's relative advantage, compatibility with current practice, its complexity, and observability were the strongest predictors of likelihood to adopt GM tasks into primary care practice.

Adult↗
PubMed1979

Adsorption of monovalent cations to bilayer membranes containing negative phospholipids.

The electrophoretic mobilities of multilamellar phosphatidylserine vesicles were measured in solutions containing monovalent cations, and the xi potentials, the electrostatic potentials at the hydrodynamic plane of shear, were calculated from the Helmholtz--Smoluchowski equation. In the presence of 0.1 M lithium, sodium, ammonium, potassium, rubidium, cesium, tetraethylammonium, and tetramethylammonium chloride, the xi potentials were -60, -62, -72, -73, -77, -80, -82, and -91 mV, respectively. Similar results were obtained with phosphatidylglycerol vesicles; different results were obtained with cardiolipin, phosphatidylinositol, and phosphatidic acid vesicles. The phosphatidylserine results are interpreted in terms of the Stern equation, a combination of the Gouy equation from the theory of the diffuse double layer, the Boltzmann relation, and the Langmuir adsorption isotherm. Evidence is presented that suggests the hydrodynamic plane of shear is 2 A from the surface of the membrane in solutions containing the alkali metal cations. With this assumption, the intrinsic association constants of the above monovalent cations with phosphatidylserine are 0.8, 0.6, 0.17, 0.15, 0.08, 0.05, 0.03, and 0 M-1, respectively. The validity of this approach was tested in two ways. First, the xi potentials of vesicles formed from mixtures of phosphatidylserine and a zwitterionic lipid, phosphatidylcholine, were measured in solutions containing different concentrations of sodium. All the data could be described by the Stern equation if the "relaxation" of the ionic atmosphere, which is predicted by classic electrostatic and hydrodynamic theory to occur at low salt concentrations and high potentials, was circumvented by using only large (diameter greater than 13 micrometers) vesicles for these measurements. Second, the fluorescent probe 2-(p-toluidinyl)naphthalene-6-sulfonate was used to estimate the potential at the surface of phosphatidylserine and phosphatidylglycerol vesicles sonicated in 0.1 M NaCl. Reasonable agreement with the predicted values of the surface potential was obtained.

Cations, Monovalent↗
PubMed2001

Dopamine-mediated volume transmission in midbrain is regulated by distinct extracellular geometry and uptake.

Somatodendritic release of dopamine (DA) in midbrain is, at least in part, nonsynaptic; moreover, midbrain DA receptors are predominantly extrasynaptic. Thus somatodendritic DA mediates volume transmission, with an efficacy regulated by the diffusion and uptake characteristics of the local extracellular microenvironment. Here, we quantitatively evaluated diffusion and uptake in substantia nigra pars compacta (SNc) and reticulata (SNr), ventral tegmental area (VTA), and cerebral cortex in guinea pig brain slices. The geometric parameters that govern diffusion, extracellular volume fraction (alpha) and tortuosity (lambda), together with linear uptake (k'), were determined for tetramethylammonium (TMA(+)), and for DA, using point-source diffusion combined with ion-selective and carbon-fiber microelectrodes. TMA(+)-diffusion measurements revealed a large alpha of 30% in SNc, SNr, and VTA, which was significantly higher than the 22% in cortex. Values for lambda and k' for TMA(+) were similar among regions. Point-source DA-diffusion curves fitted theory well with linear uptake, with significantly higher values of k' for DA in SNc and VTA (0.08--0.09 s(-1)) than in SNr (0.006 s(-1)), where DA processes are sparser. Inhibition of DA uptake by GBR-12909 caused a greater decrease in k' in SNc than in VTA. In addition, DA uptake was slightly decreased by the norepinephrine transport inhibitor, desipramine in both regions, although this was statistically significant only in VTA. We used these data to model the radius of influence of DA in midbrain. Simulated release from a 20-vesicle point source produced DA concentrations sufficient for receptor activation up to 20 microm away with a DA half-life at this distance of several hundred milliseconds. Most importantly, this model showed that diffusion rather than uptake was the most important determinant of DA time course in midbrain, which contrasts strikingly with the striatum where uptake dominates. The issues considered here, while specific for DA in midbrain, illustrate fundamental biophysical properties relevant for all extracellular communication.

Animals↗
PubMed2003

Influence of information sources on the adoption of uterine fibroid embolization by interventional radiologists.

OBJECTIVES: The purpose of the research was to (1) understand the influence of information sources on the awareness and adoption of uterine fibroid embolization (UFE) by interventional radiologists in Michigan and (2) to decipher communication relations in the social network of interventional radiologists that were most conducive to the flow of information about UFE. METHODS: Diffusion of innovations theory and constructs in social network analysis formed the basis for the development of an interview guide. Thirty-two interventional radiologists in Michigan were interviewed over the phone. Chi-square statistics were employed to analyze the awareness and adoption of UFE. Factor analysis was applied to decipher important communication relations in the social network of interventional radiologists. RESULTS: Conferences were found to be an initial source of information, creating awareness among early adopters (P < 0.05), but other individuals were found to be influential sources in the adoption of UFE by later adopters (P < 0.05). Radiologists rarely browsed Websites for information. Work relations in everyday clinical practice were the communication relations most conducive to the flow of information about UFE. Preliminary qualitative data indicated that opinion leaders in the diffusion of UFE in Michigan were located in hospitals primarily dedicated to practice rather than in hospitals affiliated with universities. CONCLUSIONS: Journals are important information sources for creating awareness and stimulating adoption of innovation among both early and late adopters of new procedures in interventional radiology. Conferences, however, are significantly more important for creating early awareness, while interactions with colleagues is the most important factor in stimulating use of the innovation among later adopters. Among colleagues, opinion leaders in nonacademic hospitals may be more influential than individuals in the academic community.

Adult↗
PubMed2006

Changing the work environment to promote wellness: a focus group study.

It is estimated that employers spend more than 75 billion dollars annually on obesity-attributable health care. Interventions to reduce or prevent the risk of obesity are increasingly common at worksites and include health fairs, weight loss and nutrition classes, and fitness programs. However, many companies lack the resources to plan and implement these types of programs. Environmental approaches offer companies a low-cost option. A community-based participatory research model was used to bring academic researchers, human resources personnel, and health department educators together to plan and implement an environmental program aimed at increasing healthy eating and physical activity at four small manufacturing companies. The Diffusion of Innovations Theory guided the development of focus group questions. A focus group study was then conducted to gather information from employees and managers at these four companies. The questions identified workplace strategies that would aid in reducing barriers and developing appropriate communication channels to enhance employee participation in the program. The researchers identified themes from manager and employee focus groups regarding the following five environmental components: signs, walking paths, food changes, educational strategies, and advisory groups.

Adolescent↗