3,563 research outputs found
Electroneutrality and Phase Behavior of Colloidal Suspensions
Several statistical mechanical theories predict that colloidal suspensions of
highly charged macroions and monovalent microions can exhibit unusual
thermodynamic phase behavior when strongly deionized. Density-functional,
extended Debye-H\"uckel, and response theories, within mean-field and
linearization approximations, predict a spinodal phase instability of charged
colloids below a critical salt concentration. Poisson-Boltzmann cell model
studies of suspensions in Donnan equilibrium with a salt reservoir demonstrate
that effective interactions and osmotic pressures predicted by such theories
can be sensitive to the choice of reference system, e.g., whether the microion
density profiles are expanded about the average potential of the suspension or
about the reservoir potential. By unifying Poisson-Boltzmann and response
theories within a common perturbative framework, it is shown here that the
choice of reference system is dictated by the constraint of global
electroneutrality. On this basis, bulk suspensions are best modeled by
density-dependent effective interactions derived from a closed reference system
in which the counterions are confined to the same volume as the macroions.
Linearized theories then predict bulk phase separation of deionized suspensions
only when expanded about a physically consistent (closed) reference system.
Lower-dimensional systems (e.g., monolayers, small clusters), depending on the
strength of macroion-counterion correlations, may be governed instead by
density-independent effective interactions tied to an open reference system
with counterions dispersed throughout the reservoir, possibly explaining
observed structural crossover in colloidal monolayers and anomalous
metastability of colloidal crystallites.Comment: 12 pages, 5 figures. Discussion clarified, references adde
Freezing of Simple Liquid Metals
Freezing of simple liquid metals and the relative stabilities of competing
crystalline solids are investigated using thermodynamic perturbation theory,
the interactions between ions being modeled by effective pair potentials
derived from pseudopotential theory. The ionic free energy of the solid phase
is calculated, to first order in the perturbation potential, using classical
density-functional theory and an accurate approximation to the hard-sphere
radial distribution function. Free energy calculations for Na, Mg, and Al yield
well-defined freezing transitions and structural free energy differences for
bcc, fcc, and hcp crystals in qualitative agreement with experiment.Comment: 8 pages, 4 figures, LaTeX with elsart.st
The Transition from Good to Poor Health: An Econometric Study of the Older Population
This is a study of the influence of socioeconomic factors on the state of health of older Canadians. Three years of panel data from the Survey of Labour and Income Dynamics are used to model the transition probabilities between good and poor health. Care is taken to avoid the problem of endogeneity of income in modelling its effects, and to adjust reported income to free it from its strong association with age at the time of the survey. Of particular note are the significant effects found for income, in spite of universal public health care coverage. Significant effects are found also for age, education, and other variables.Socioeconomic factors and health; older population; panel data
Socioeconomic Influence on the Health of Older People: Estimates Based on Two Longitudinal Surveys
There is a strong positive relationship between socioeconomic status (SES) and health, but identifying the direction of causation is difficult. This study exploits the longitudinal nature of two Canadian surveys, the Survey of Labour and Income Dynamics and the National Population Health Survey, to study the link from SES to health. For people aged 50 and older who are initially in good health we examine whether changes in health status over the next two to four years are related to prior SES, as represented by income and education. Although the two surveys were designed for quite different purposes the evidence they yield with respect to the probability of remaining in good health is strikingly similar. Both suggest that SES does play a role, that the differences across SES groups are quantitatively significant, that the differences increase with age, and that they are much same for men and women.health; socioeconomic status; SLID; NPHS
Socioeconomic Influence on the Health of Older People: Estimates Based on Two Longitudinal Surveys
There is a strong positive relationship between socioeconomic status (SES) and health, but identifying the direction of causation is difficult. This study exploits the longitudinal nature of two Canadian surveys, the Survey of Labour and Income Dynamics and the National Population Health Survey, to study the link from SES to health. For people aged 50 and older who are initially in good health we examine whether changes in health status over the next two to four years are related to prior SES, as represented by income and education. Although the two surveys were designed for quite different purposes the evidence they yield with respect to the probability of remaining in good health is strikingly similar. Both suggest that SES does play a role, that the differences across SES groups are quantitatively significant, that the differences increase with age, and that they are much same for men and women.health; socioeconomic status; SLID; NPHS
Socioeconomic Influences on the Health of Older Canadians: Estimates Based on Two Longitudinal Surveys
It is well established that there is a positive statistical relationship between socioeconomic status (SES) and health but identifying the direction of causation is difficult. This study exploits the longitudinal nature of two Canadian surveys, the Survey of Labour and Income Dynamics and the National Population Health Survey, to study the link from SES to health (as distinguished from the health-to-SES link). For people aged 50 and older who are initially in good health we examine whether changes in health status over the next two to four years are related to prior SES, as represented by income and education. Although the two surveys were designed for different purposes and had different questions for income and health, the evidence they yield with respect to the probability of remaining in good health is similar. Both suggest that SES does play a role and that the differences across SES groups are quantitatively significant, increase with age, and are much the same for men and women.health transitions, income, education
Healthy Aging at Older Ages: Are Income and Education Important?
Being higher on the socioeconomic scale is correlated with being in better health, but is there is a causal relationship? Using three years of longitudinal data for individuals aged 50 and older from the Canadian Survey of Labour and Income Dynamics, we study the health transitions for those who were in good health in the first year, focussing especially on income and education. The initial good health restriction removes from the sample those whose incomes may have been affected by a previous history of poor health, thus avoiding a well known problem of econometric endogeneity. We then ask, for those in good health, whether later transitions in health status are related to socioeconomic status. We find that they are that changes in health status over the subsequent two years are related in particular to income and education.aging, health, income, education
Healthy Aging at Older Ages: Are Income and Education Important?
Being higher on the socioeconomic scale is correlated with being in better health, but is there is a causal relationship? Using three years of longitudinal data for individuals aged 50 and older from the Canadian Survey of Labour and Income Dynamics, we study the health transitions for those who were in good health in the first year, focussing especially on income and education. The initial good health restriction removes from the sample those whose incomes may have been affected by a previous history of poor health, thus avoiding a well known problem of econometric endogeneity. We then ask, for those in good health, whether later transitions in health status are related to socioeconomic status. We find that they are -- that changes in health status over the subsequent two years are related in particular to income and education.aging, health, income, education
The Transition from Good to Poor Health: An Econometric Study of the Older Population
This is a study of the influence of socioeconomic factors on the state of health of older Canadians. Three years of panel data from the Survey of Labour and Income Dynamics are used to model the transition probabilities between good and poor health. Care is taken to avoid the problem of endogeneity of income in modelling its effects, and to adjust reported income to free it from its strong association with age at the time of the survey. Of particular note are the significant effects found for income, in spite of universal public health care coverage. Significant effects are found also for age, education, and other variables.Socio-economic factors and health; older population; panel data; SLID
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