Low-dimensional procedure for the characterization of human faces

A method is presented for the representation of (pictures of) faces. Within a specified framework the representation is ideal. This results in the characterization of a face, to within an error bound, by a relatively low-dimensional vector. The method is illustrated in detail by the use of an ensemble of pictures taken for this purpose.

Bias in indirectly adjusted comparisons due to taking the total study population as the reference group

It is well known that comparisons of indirectly adjusted statistics, such as standardized morbidity ratios (SMRs), can be biased when the joint effect of the study exposure and the covariates is not multiplicative. This paper describes a related bias in SMR comparisons, one that can arise if the total study population is used as the referent. This bias can occur even if the exposure-covariate effects are multiplicative.

Effect of fetal growth on maternal protein metabolism in postabsorptive rat

Rates of protein synthesis were measured in whole fetuses and maternal tissues at 17 and 20 days of gestation in postabsorptive rats using continuous infusion of L-[1-14C]leucine. Fetal protein degradation rates were derived from the fractional rates of synthesis and growth. Whole-body (plasma) leucine kinetics in the mother showed a significant reduction of the fraction of plasma leucine oxidized in the mothers bearing older fetuses, a slight increase in the plasma flux, with total leucine oxidation and incorporation into protein remaining similar at the two gestational ages. Estimates of fractional protein synthesis in maternal tissues revealed an increase in placental and hepatic rates at 20 days of gestation, whereas the fractional synthetic rate in muscle remained unchanged. A model for estimation of the redistribution of leucine between plasma and tissues is described in detail. This model revealed a more efficient utilization of leucine in fetal protein synthesis in comparison with other maternal tissues, a greater dependency of the fetus on plasma supply of leucine, and a significant increase (2-fold) in the release of leucine from maternal muscle as the fetal requirements increased proportionately with its size. The latter conclusion, supported by nitrogen analysis and the ratio of bound-to-free leucine in maternal tissues, confirms the importance of maternal stores in maintaining the homeostasis of essential amino acids during late pregnancy.

Screening for colorectal cancer in a high-risk population. Results of a mathematical model

A mathematical model was used to estimate the cost-effectiveness of colorectal cancer screening strategies for people who are at high risk because of a first-degree relative with colorectal cancer. The model uses indirect evidence about such factors as cancer incidence, sensitivity and specificity of different tests, and treatment effectiveness. The analysis indicates that for screening people over 40 yr old an annual fecal occult blood test may reduce colorectal cancer mortality by about one-third, either colonoscopy or barium enema may reduce mortality by approximately 85%, a 3-5-yr frequency for endoscopies or barium enemas preserves 70%-90% of the effectiveness of an annual frequency, and beginning screening at age 50 reduces effectiveness by 5%-10%. Although both barium enemas and colonoscopies appear to be effective in reducing mortality, the lower cost of the barium enema makes it a more cost-effective strategy. All of these estimates depend on the baseline estimates of each of the factors incorporated in the model; the conclusions are most sensitive to assumptions about the natural history of adenomatous polyps, the bleeding of adenomas and presymptomatic cancers, and the sensitivity of the fecal occult blood test. Recommendations about colorectal cancer screening must also consider factors such as discomfort, inconvenience, and the availability of various technologies.

Fluorescence quenching dynamics of tryptophan in proteins. Effect of internal rotation under potential barrier

In many proteins fluorescence from single tryptophan exhibits a nonexponential decay function. To elucidate the origin of this nonexponential decay, we have examined the fluorescence decay function and time-resolved fluorescence anisotropy of a fluorophore covalently bound to a macromolecule by solving a rotational analogue of the Smoluchowski equation. An angular-dependent quenching constant and potential energy for the fluorophore undergoing internal rotation were introduced into the equation of motion for fluorophore. Results of numerical calculations using the equations thus obtained predict that both the fluorescence decay function and time-resolved anisotropy are dependent on rotational diffusion coefficients of fluorophore and potential energy for the internal rotation. The method was applied to the observed fluorescence decay curve of the single tryptophan in apocytochrome c from horse heart. The calculated decay curves fit the observed ones well.

[Comparative evaluation of mathematical models of the process for the biological treatment of the wastes from antibiotic manufacture]

The main kinetic relationships of the process of biological oxidation of antibiotic production sewage were studied in laboratory models of mixer aerotanks. A relationship between the specific rates of BOD (biological oxygen demand) decreasing and BOD concentration in aerotanks was developed on the basis of the results relating to treatment of 8 types of the sewage within the ranges of the pure water BOD equal to 18-220 mg/l and the loads of 0.18-3.85 g BOD/g X day. To describe this relationship the following models were tested for their adequacy: Michaelis-Menten and Mozer models, a general model and a model of the first order reaction equation. The Mozer model with the relative root-mean-square deviation of 18.3 per cent proved to be the best in description of wide ranges of pure water BOD changing. The first order model with deviation of 12 per cent was the best in describing the process with low loads.

Guideline report. Projecting MRI utilization: two new approaches

In today's competitive marketplace, hospitals must carefully analyze the financial impact of acquiring new technologies. The high cost of magnetic resonance imaging (MRI), one of the most prominent new technologies, makes it critical for hospitals to evaluate thoroughly the financial risks of providing this service. To determine whether it is likely to generate a sufficient number of MRI scans to break even financially, a hospital must carefully analyze its patient case mix. In 1984, the American Hospital Association (AHA) developed a method, the AHA MRI Utilization Model, for performing such an analysis. The original AHA model projected a hospital's potential demand for MRI procedures based on an analysis of that hospital's inpatient discharge data. The widespread use of the original AHA MRI Utilization Model by over 500 hospitals and a number of state health planning agencies has significantly influenced the diffusion of MRI throughout the United States. The original AHA model had several limitations, however: it ignored scans that might be performed to evaluate secondary diagnoses; its estimate of follow-up scans and replacement of CT by MRI was based on information from 1978; and it lacked a mechanism for considering outpatient scans. These limitations, together with the rapid evolution in clinical applications for MRI, led the AHA to improve its original MRI utilization projection methodology. In 1986, the AHA developed a new second generation MRI Utilization Model that employs two independently derived methodologies. The AHA's revised ICD-9-CM Projection method was developed by Richard diMonda, M.S.B.M.E., M.B.A.; the Diagnosis Related Groups (DRG) Projection Method was developed by Earl P. Steinberg, M.D., M.P.P. The second generation model has several advantages over the original model: it utilizes the opinions of a greater number of experts, as well as experts from more varied backgrounds; experts' opinions were obtained in 1986, rather than 1984, and so are more relevant to current patterns of practice; experts' opinions are employed to project CT, as well as MRI volume when both technologies are available, and the extent to which MRI will replace CT; total inpatient and outpatient scans are calculated; and hospital-specific adjustment factors are used to adjust for variations in patterns of practice across institutions. The DRG projection method also adds the ability to consider MRI and CT scans used to evaluate comorbid conditions and complications, as well as scans performed on patients who turned out to have no pathology. In addition, the DRG method provides a projection of potential MRI and CT volume in 1990, as well as currently.

Relations between tablet properties

With the aid of simple mathematical models the relations between specific crushing strength (i.e. crushing strength divided by the breaking surface), friability and disintegration time of a tablet can be given. The friability is related to the porosity of the tablets and the specific crushing strength, independent of the process conditions. For the disintegration time two models have been used, depending on the disintegration mechanism. In the first one the disintegration time is only dependent on the porosity, in the second on the specific surface by weight of the granules of which the tablets are made. The theoretical relationships were verified for two tablet formulations, made under varying process conditions.

Radioepidemiological tables. Council on Scientific Affairs

In 1983, the Federal Orphan Drug Act was passed. This act included a rider intended as a foundation for compensating individuals with cancers allegedly caused by radiation exposures during certain nuclear events. In response, a National Institutes of Health working group was established that prepared the National Institutes of Health Radioepidemiological Tables. The tables permit computation of a "probability of causation" (otherwise known as "assigned share") that an individual's cancer was caused by earlier estimated exposure to radiation. However, several limitations have been noted in the accuracy of the computations and in the conditions under which the computations are applicable. These limitations have caused the Council on Scientific Affairs of the American Medical Association to recommend that the probability of causation approach not be applied to occupational radiation exposures or to diagnostic or therapeutic exposures in medicine.

A population dynamics simulation model with application to health planning

Despite the increasing emphasis on computers and quantitative methods in health services programs, health services administration students are denied access to many of the most powerful tools of systems analysis, including discrete event simulation, because they lack the necessary background in computer programming, simulation methodology, and stochastic processes. This article presents an approach to the modeling of the growth and decline of population groups and their attributes that can be used by students who do not have the extensive quantitative background required to develop the usual discrete event simulation models. The underlying theory, which is based on the behavior of the expectation process of vector Galton-Watson branching processes, can be explained quite easily. An example is presented that uses an age and sex specific model of population growth to investigate policy questions related to the feasibility of the construction of a long-term care facility for a defined population group. Planning decisions are based on the growth and decline of the numbers of individuals in the various age and sex groups. Extensions of the basic methodology are possible that would include projections of the variance-covariance matrix of the population sizes for each year of the projection process. In addition, the model can be extended to include projections of the impact of infectious and communicable diseases on a defined population group together with the effect of categorical disease screening and control programs. Given the basic data utilized in the model, the implementation of the calculations required by the model can be made on modern microcomputer hardware using any of the standard spreadsheet programs.

An introduction to national health care systems

There are many different types of health care delivery systems throughout the world. The purpose of this article is to introduce the reader to the various factors that will influence both the health care system and the overall health status of the individual. These factors include: social; economic; political and historical elements. Finally, this article lists the major worldwide health organizations that operate within the health arena and notes the major sources of health statistics.

Illegal aliens, unemployment and immigration policy

"This paper develops a simple two-country model of illegal immigration in an attempt to examine the interaction among variables such as the stock of migrant labor, the unemployment rates of the two economies, and the rate of spending by the host country on the enforcement of its immigration restrictions. The focus of the analysis is on the dynamics of immigration policy and on its role in determining the nature of the mechanism by which disturbances to the labor market of one country are transmitted to that of the other in the short run and in the long run."

Effects of brackets and ties on stiffness of an arch wire

Beam theory was used to evaluate the stiffness of a simulated orthodontic model as affected by the type of bracket, interbracket distance, type of ligature tie, and size of segment. For a given deflection, the model generated greater force (increased stiffness) as the beam constant (N) increased. N increased as interbracket distance increased. Metal ties were as rigid or more rigid than o-rings. Four bracket segments were more rigid than two-bracket segments when tied with o-rings but not metal ligatures. Values of N of Lewis and narrow twin brackets with metal ties were similar and greater than the N of wide twin and medium single brackets. Wide twin brackets were more rigid than others with o-rings.

Contrasting the models. Reflections on the pattern of geriatric evaluation unit care

In order to understand geriatric assessment programs better, it is necessary to understand some of the general subgroups of such programs. This article compares various aspects of geriatric evaluation units.

Individual and population sex allocation patterns

A variety of sex allocation models is considered in which the reproductive returns on investment in males differ from the returns on investment in females, the amounts of resources available for reproduction vary in the population, the costs of making male and female reproductive structures differ, and the conception sex ratio may be fixed and there may be an initial minimum investment per offspring. Results of these models include quantitative predictions for both individual- and population-level sex allocation, an opportunity to study the magnitude of changes in predicted patterns as key variables change, and therefore an analysis of the robustness of Fisher's equal investment theory. One example is that Fisher's argument is extremely robust for high fecundity organisms, but, in low fecundity organisms, is sensitive to differences between the sexes in reproductive returns on investment per offspring, a situation that occurs in many vertebrates to which Fisher's theory is often applied. A second example is that individual- and population-level patterns often depend strongly on the distribution of resources available for reproduction among individuals in the population.

Strategic financial planning: a balance sheet perspective

This paper presents an easily comprehended approach to the strategic financial planning process. It utilizes a balance sheet approach that focuses attention on three key business policy decisions: asset growth rates, debt policy, and equity growth policy. Because the approach taken here does not get involved with the numerous assumptions and projections involved in a typical funds flow approach to financial planning, it is easier to understand and use by both boards and top management. A financial plan is defined as a bridge between two balance sheets.

Increase in life expectancy at birth in Japan: some implications for variable patterns of decrease in mortality

The characteristics of the increase in life expectancy at birth (eo) in Japan were analyzed using the life tables of developed countries in which the values of eo were almost the same. When the decrease in age-specific probability of dying (qx) and its contribution to total gain in eo in Japan were compared to those of other developed countries, the decline in qx in prime, middle and old age groups accounts for much of the change; the decrease in this variable for males aged 50 years and over accounted for 35% of the recent increase in eo. Well-organized medical care and public services are discussed in relation to this unique and unusually rapid increase in eo for the Japanese population.

Automatic control systems for the artificial heart and ventricular assist device

Automatic control systems for the artificial heart (AH) and ventricular assist device were developed using selected criteria of effectiveness, a mathematical model of regulation, and noninvasive measures of the hemodynamic parameters. The Sinus IS2 system was developed for control of the AH; its main component is a high-speed servomechanism that provides for the generation of pneumatic pulses. The servomechanism is controlled by automatic regulation with pressure feedback. Mean aortic pressure was used as the primary regulated hemodynamic parameter. The systems were tested using both a physical model and a physiologic experiment. Contractile insufficiency of the left ventricle was simulated in testing the control system for circulatory assistance. The studies demonstrate that automatic control systems function effectively by providing normal blood circulation in both the resting state and in certain transient processes occurring in a real, dynamic circulatory system.

A program for improving energy conservation behaviors in adults with rheumatoid arthritis

This paper presents the design and evaluation of an occupational therapy program developed at the National Institutes of Health for teaching energy conservation and joint protection to adults with rheumatoid arthritis. An existing model for educational diagnosis in health education was used to identify program, behavioral, and educational objectives for the new program. The use of this model resulted in measurable objectives, which were used as outcome measures in the randomized research evaluation of the new program. The dependent variables measured were activity-of-daily-living status, psychosocial adjustment to illness, knowledge, disease activity, pain, and fatigue. None were significantly different after the intervention. The independent variables measured included components of balancing rest and physical activity. After 3 months, a greater percentage of the subjects receiving the workbook-based occupational therapy program than those receiving traditional occupational therapy demonstrated an application of the behaviors the intervention was designed to change.

Influence of specific contacts on the stability and structure of proteins. Theory for the perturbation of a harmonic system

The question of how specific contacts within a protein influence its stability and structure is examined within a formal theoretical framework. A mathematical model is developed in which the potential energy of a protein is taken as a harmonic expansion of all of its internal or normal coordinates. With classical statistical mechanics the properties of the system can be derived from this potential energy function. A few new contacts are then introduced as additional energy terms, each having a quadratic dependence on a single internal coordinate. These terms are added as perturbations to the original potential energy, and the attendant changes in the properties of the system are obtained. Exact expressions can be derived for changes in the enthalpy, entropy, and for any arbitrary internal degree of freedom. These quantities are expressed in terms of the parameters of the potential energy functions of the new contacts, and the mean square displacements and positional correlation functions of the internal coordinates. These results provide qualitative insights into the role of contacts in stabilizing a particular conformation. Estimates are given for the entropy of formation of a hydrogen bond in a protein. A criterion is proposed for determining whether a contact is essential to the stability of a protein conformation. This model may be applicable to many experimental systems in which mutant or modified proteins are available that differ by one or a few amino acids. The results may also be useful in thermodynamic analyses of computer simulations.

The effects on Schild regressions of antagonist removal from the receptor compartment by a saturable process

A theoretical model of the effects of a saturable removal mechanism for an antagonist diffusing into the receptor compartment of a tissue is used to calculate expected deviations in Schild regressions. At concentrations of antagonist which do not saturate the removal mechanism, there can be a deficit of antagonist in the receptor compartment as compared to the concentration of antagonist bathing the tissue. This results in a shift to the right of the Schild regression and a corresponding underestimation of antagonist potency. The model predicts that as the concentration of antagonist exceeds the Km for removal (saturation of the removal process), this concentration deficit is eliminated, resulting in a proportionate increase in antagonist concentration at the receptor and a concomitant increase in receptor antagonism. This results in a steepening of the Schild regression; the slope in the region of saturation is greater than one. Experimental evidence in support of this model was found in studies of the antagonism of responses to bethanechol by atropine in rabbit ileum; this species is known to have an atropinesterase capable of hydrolyzing atropine. The Schild regression for atropine was curvilinear with an overall slope of 1.42 (1.34-1.5) and pKB = 8.5 (8.36-8.8); in the ileum from guinea pigs, a species which does not possess this enzyme, the Schild regression for atropine was linear, had a slope not significantly different from unity (1.1; 0.95-1.2) and a pKb of 9.0 (8.9-9.2). The slope of the regression in rabbit ileum was corrected to unity by the addition of an excess concentration of methylbutyrate, an alternate substrate for atropinesterase.(ABSTRACT TRUNCATED AT 250 WORDS)

The doctor-patient relationship and counseling for preventive care

Theories and research related to the doctor-patient relationship have developed in a context of therapeutic care. This context is an increasingly inadequate definition of the boundaries of the doctor-patient relationship, as expectations grow for the physician's role in counseling for disease prevention and health promotion. This paper reviews the literature of the doctor-patient relationship, and extends its application to this newer context. Suggestions are discussed for overcoming some of the obstacles to the successful incorporation of counseling for preventive care in daily medical practice. Doctors and patients will benefit from a clarified understanding of their counseling responsibilities in disease prevention and health promotion as the theoretical and practical complexities of providing health care in medical institutions are examined.

Nutrition priority system: a model for patient care

The criterion for the level of nutrition monitoring used by many hospitals and residential care facilities has traditionally been the patient's diet order. Patients on "regular" diets may receive minimal monitoring (if any) with little discharge instruction, and patients on "modified diets" receive a full assessment with specified routine follow-up by nutrition-care team members and detailed discharge planning. The concentration on the diet rather than the patient gives cause for concern, but in residential care facilities such concerns are magnified. While it is appropriate to monitor a 60-year-old patient with adult-onset diabetes whose disease of 20 years' duration is stable, the present diet order system insists that that patient be monitored intensely but ignores his 80-year-old neighbor on a general diet, despite her poor appetite and 87-lb weight. The authors developed a priority system that sets three levels of patient care and materials for teaching the system to treatment team members. The system is based on the patient's needs, not the diet order. Although reduction in staff time would have been an additional welcome result, use of the system does permit the more efficient utilization of the dietitian's and dietetic technician's time. The greatest effect has been individualized, monitored nutrition care for residential psychiatric patients.

Theory of sample translation in fluorescence correlation spectroscopy

New applications of the technique of fluorescence correlation spectroscopy (FCS) require lateral translation of the sample through a focused laser beam (Peterson, N.O., D.C. Johnson, and M.J. Schlesinger, 1986, Biophys. J., 49:817-820). Here, the effect of sample translation on the shape of the FCS autocorrelation function is examined in general. It is found that if the lateral diffusion coefficients of the fluorescent species obey certain conditions, then the FCS autocorrelation function is a simple product of one function that depends only on transport coefficients and another function that depends only on the rate constants of chemical reactions that occur in the sample. This simple form should allow manageable data analyses in new FCS experiments that involve sample translation.

Evaluation of electrical conductivity-temperature curves using a mathematical model: temperature-dependent changes during thawing of frozen aqueous pharmaceuticals

The information contained in the electrical conductivity curves of pharmaceuticals measured as a function of temperature can be represented by a small set of parameters. This is achieved by approximating the electrical conductivity curve as a number of consecutive steps, using a suitable empirical model. The three parameters describing each step are: transition temperature, slope factor and step height. The validity of the calculated transition temperatures was established by applying the model to electrical conductivity curves measured on aqueous solutions of KCl, NaCl and on a KCl-NaCl mixture. It appears that the transition temperatures calculated for these inorganic salts are in good agreement with the respective eutectic temperatures reported in the literature. Subsequently, the method was applied to the corticosteroids prednisolone sodium succinate and prednisolone disodium phosphate. The mathematical model yields a satisfactory fit for both experimental conductivity curves. The actual consequences of freeze-drying an aqueous solution of prednisolone sodium succinate below and above the respective transition temperatures calculated are discussed in relation to the experimental conductivity data.

Cost-benefit analysis: dealing with the problems of indivisible projects and fixed budgets

The use of cost-benefit analysis in option appraisals in health care when the decision-maker is faced with indivisible projects and a fixed budget is examined. It is argued that the methods used to overcome the problem of indivisibilities, benefit-cost ratios and the net benefit method, are not suitable for choosing between alternative projects for two reasons. Firstly, the values of benefit-cost ratios are sensitive to the specification of costs and benefits, and the literature abounds with examples of averted costs being added to the benefits of a project or reduced benefits being interpreted as an additional (psychic) cost. We show that such erroneous specification can lead to a relatively inefficient project being accepted as efficient, and vice versa. Secondly, practical applications of CBA have been performed in the absence of budget constraints on available resources. We show that once budget constraints are recognised the shadow price of resources required to implement a project may be affected by the amount of resources remaining in the budget after implementation. Once the budget constraint is recognised, a project which initially appeared to be the most efficient can be rendered relatively inefficient. It is suggested that alternative uses of remaining (or residual) resources should be identified and evaluated, thus ensuring the maximisation of benefits from the use of an overall budget.