Multifactor Approach Research Articles

The influence of season, photoperiod, and pineal melatonin on immune function.

: In addition to the well‐documented seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among many animal populations. Challenging winter conditions (i.e., low ambient temperature and decreased food availability) can directly induce death via hypothermia, starvation, or shock. Coping with these challenges can also indirectly increase morbidity and mortality by increasing glucocorticoid secretion, which can compromise immune function. Many environmental challenges are recurrent and thus predictable; animals could enhance survival, and presumably increase fitness, if they could anticipate immunologically challenging conditions in order to cope with these seasonal threats to health. The annual cycle of changing photoperiod provides an accurate indicator of time of year and thus allows immunological adjustments prior to the deterioration of conditions. Pineal melatonin codes day length information. Short day lengths enhance several aspects of immune function in laboratory studies, and melatonin appears to mediate many of the enhanced immunological effects of photoperiod. Generally, field studies report compromised immune function during the short days of autumn and winter. The conflict between laboratory and field data is addressed with a multifactor approach. The evidence for seasonal fluctuations in lymphatic tissue size and structure, as well as immune function and disease processes, is reviewed. The role of pineal melatonin and the hormones regulated by melatonin is discussed from an evolutionary and adaptive functional perspective. Finally, the clinical significance of seasonal fluctuations in immune function is presented. Taken together, it appears that seasonal fluctuations in immune parameters, mediated by melatonin, could have profound effects on the etiology and progression of diseases in humans and nonhuman animals. An adaptive functional perspective is critical to gain insights into the interaction among melatonin, immune function, and disease processes.

Corporate Risk Management: A Multi-factor Approach

Corporate Risk Management: A Multi-factor Approach

Macroeconomic variables and the Johannesburg Stock Exchange: A multifactor approach

This study estimates the simultaneous relationship between a number of selected macroeconomic variables and share prices on the Johannesburg Stock Exchange (JSE). A linear factor model identical in form to that assumed by the arbitrage pricing theory (APT) is estimated. ‘Candidate’ macroeconomic variables are selected on the basis of prior research and theoretical considerations.The estimated sensitivities to these macroeconomic variables are compared across market sectors. The models estimated are evaluated for explanatory power beyond that of the ‘market model’ and are tested for robustness and extra-sample predictive power through a succession of Chow forecast tests.A tentative and ‘preparatory’ insight into the nature of the APT factors operational on the JSE is offered. Furthermore, it is hoped that the models estimated in this paper will be of interest to practitioners in terms of suggesting a methodology to estimate the macroeconomic risk profiles of their investment portfolios.

Community and edaphic analysis of upland northern hardwood communities, central Vermont, USA

An ecological multifactor approach was used to identify and describe upland northern hardwood site types and species groups on the central Green Mountains, Vermont. Seven ecological types and ten species groups were identified by a method combining plot sampling of vegetative and soil-site variables and numerical analysis. Two-way indicator species analysis and canonical correspondence analysis (CCA) were used to evaluate the distinctness of the identified ecological types and species groups and to compare the discriminating abilities of different ecosystem components (landscape position, vegetation, and soil). Each ecological type was a characteristic combination of physiography, landscape position, soil, and vegetation. Descriptions of the relationships of species groups to gradients of soil moisture and fertility, inferred from landscape position and substrate are presented. CCA demonstrated that most species within defined groups had similar ecological responses. Few groups occurred in only one ecological type. In all cases evaluation of topographic and soil factors in conjunction with species groups facilitated identification of ecological types.

Bond performance analysis

40 w P erformance analysis focuses on the central goal 9 f: S of investment management: achieving superior performance. Most simply, was the portfolio up or down? More sophisticated, did the portfolio beat the market? Most sophisticated, what specific bets paid off, does the pattern of winning bets show evidence of manager skill, and, given some demonstrated level of skill, did the manager add value? Performance analysis is important both for pension fund sponsors and for investment managers. Sponsors use performance analysis to monitor their investment managers. They need to know the skill and value-added of their managers. They also need to monitor manager styles to insure a proper fit between different managers. Investment managers use performance analysis to monitor and hone their investment strategies. This article presents a rigorous and systematic multi-factor approach to performance analysis as applied to fixed-income investments. A multi-factor model can measure the return generated by each factor, and can forecast the ex ante risk of each factor's return.' Such an approach to bond performance analysis allows detailed identification of the sources of return, as well as analysis of the statistical significance of those returns. Previous approaches to bond performance analysis have focused on a limited attribution of return to different investment factors, and have not 4 attempted a statistical analysis of the significance of the returns. (See, for example, Fong, Pearson, and Vasicek [19831, and Fong et al. [19911.) After briefly introducing the multi-factor framework, I present two separate components of performance analysis in turn: single-period performance attribution and multi-period performance analysis. Single-period performance attribution identifies the sources of exceptional return in each period. Multiperiod performance analysis investigates the series of single-period attributed re turns in order to separate skill from luck.

Landscape ecosystems of disturbed oak forests of southeastern Michigan, U.S.A.

An ecological multifactor approach was used to identify and describe oak ecosystem types in highly disturbed landscapes and fragmented forests in an area of over 19 000 km2 in southeastern Michigan, United States. Eleven upland ecosystems and 1 wetland ecosystem were identified in the field using reconnaissance, plot sampling, and test mapping. Each ecosystem type was a characteristic combination of physiography, soil, and climax vegetation (overstory and ground-cover vegetation). The ecological approach emphasized physiographic and soil factors because of the disturbed state of the vegetation. Of 222 species of ground-cover vegetation, only 68 were used in forming the 13 ecological species groups. White oak (Quercusalba L.) exhibited the largest ecological amplitude of the three major oak species; it occurred on dry to mesic sites. Red oak (Q. rubra L.) occurred on dry-mesic to mesic sites, and black oak (Q. velutina Lam.) was restricted to dry sites. Discriminant analysis was used to examine the distinctness of the upland ecosystems and to compare the error rates of different ecosystem components. The misclassification rates obtained by using all ecosystem components (physiography, soil, ecological species groups, and overstory vegetation) were the lowest: 20% in highly dissected terrain and 34% in flat to gently rolling terrain. However, results obtained with physiography–soil and ecological species group variables were nearly as good as results that added the overstory vegetation. More overlap among ecosystem types and higher misclassification rates were found than in ecosystems of old-growth forests of northern Michigan and oak forests in southwestern Wisconsin where similar methods were used. Nevertheless, for the highly disturbed forests of southern Michigan, the ecological, multifactor landscape approach is a useful and effective method of identifying, describing, and mapping ecosystem types.

A multifactor approach to selecting computer generated electronics assembly facility layouts

This research proposes a method for comparing computer generated electronics assembly facility layouts. CRAFT, ALDEP, and CORELAP outputs are disccused in terms of quantitative measures such as flow inefficiency, distance between functional areas and growth capacity. Flow linearity, access to functional areas, and maintenance of critical relationships between functional areas are examined for qualitative layout comparison. Although 3 software packages' output were compared, the approach could easily be applied to comparing the outputs dervied from one layout software package. Results taken from the implementation of the comparison method at a Fortune 500 electronics manufacturing firm are presented. An algorithmic method is presented which has not been developed into software and in which the authors have no commercial interest. Use of the method, MASL, Multifactor Approach for Selecting Layouts, enhanced the utility and performance measurement of the computer generated layouts for the electronics assembly area of the plant.

Multifactor classification and analysis of upland hardwood forest ecosystems of the Kickapoo River watershed, southwestern Wisconsin

An ecological multifactor approach was used to develop a hierarchical classification of upland hardwood forest ecosystems of the Kickapoo River watershed, southwestern Wisconsin. This method was chosen from among the variety available because of its utility in this area of heavily disturbed forests. Eleven major ecosystem units were distinguished for the 67 plot areas sampled. Each ecosystem unit is characterized by a distinct combination of physiography (aspect and slope position and steepness), soil (parent material depth and type), and vegetation (canopy tree species and groups of ground cover species), and occurs in a unique position in the landscape. The canopies of most units are dominated by combinations of northern red oak (Quercusrubra L.), white oak (Q. alba L.), and sugar maple (Acersaccharum Marsh.). The results of several discriminant analyses indicate a high level of association between plots within some units. A combination of physiographic, soil, and vegetational variables resulted in the highest overall percentage of correct classification of the plots. These 11 ecosystem units ranged in estimated productivity (average site index for northern red oak) from 12 to 21 m, with the two extremes significantly different at the 5% level.

Clarifying a "Pattern" of Confusion: A Multi-Factor Approach to Civil RICO's Pattern Requirement

Clarifying a "Pattern" of Confusion: A Multi-Factor Approach to Civil RICO's Pattern Requirement

A Multifactor Matrix Approach to Evaluating Circulation Markets

The article develops a framework for market evaluation and strategic planning by newspaper circulation departments with emphasis on identifying opportunities for circulation growth, allocation of resources and market targeting based on priority. The matrix approach has the advantage of using terms and questions familiar to managers without being overly mathematical; its weakness is relying on subjective judgments.

A multifactor model for international plant location and financing under uncertainty

This paper presents a model for analyzing international plant location and financing decisions under uncertainty. The model diverges from the usual plant location problem in that location and financing decisions are considered simultaneously. This approach is necessary since subsidized financing as well as preferential tax treatment can be significant influences on international location decisions. In addition, financing in different currencies can be used to hedge uncertain price and exchange rate movements. Risk aversion enters via a mean-variance objective function in firm profit. The resulting problem is mixedinteger quadratic and would generally present severe computational difficulties. However, we show that a multifactor approach can be used to transform this problem into one which can be solved fairly readily. The result is a model which is computationally feasible for problems of reasonable size while still including the effects of uncertainty, financial subsidies and hedging strategies on international location decisions. Computational experience is discussed for two solution procedures. One approach uses the quadratic programming package of LINDO coupled to a branch-and-bound procedure. The other approach used a gradient search procedure plus branch-and-bound.

Application of a Multifactor Approach to Transfer of Training Research

A multifactor, multicriterion transfer of training experiment involving a computer-generated horizontal tracking task was conducted to establish relationships among training and transfer scores for manual control of a maneuvering vehicle, to determine the response surfaces for training and transfer, and to demonstrate a new transfer research paradigm that makes economically feasible the simultaneous investigation of the effects of a large number of training-equipment and use variables on transfer to multiple-criterion vehicle configurations. There were 80 experimental participants, 48 of whom were trained and tested on individually unique combinations of training and transfer conditions. This study was the first to measure the training and transfer effects of as many as six training equipment and use factors in a single experiment, to examine as many as 25 training-vehicle configurations in the same experiment, to train a single individual on each of 48 training conditions, to employ multiple (3) transfer vehicle configurations, and to provide data suitable for deriving multiple-regression equations for estimating the transfer effectiveness of configurations not directly studied.

Directions for Leisure Research: A Critique of the Radical View

This article is divided into two main parts. The first provides an account of the radical view of leisure research as it has emerged in recent literature. This focuses upon views of social class as the main dimension of social composition in leisure groups, explanations of change which stress the causal significance of class conflict, and theories relating to the social significance of leisure groups for ideological control and class domination. The second section of the article provides a critique of the radical view and suggests an alternative formulation of research orientations and issues. In particular, a range of significant dimensions in the social composition of leisure groups is postulated, and conceptual formulations are proposed for the study of change which take account of configurational and multifactor approaches. The suggestion is made that the nature of the satisfactions derived by participants from their pursuit of leisure activities should be an essential feature of any analysis of the s...

Simulation and Training for Aircraft Carrier Landings: An Economical Multifactor Approach

The Visual Technology Research Simulator (VTRS) at the Naval Training Equipment Center was used to study the effects of six factors on carrier-landing training. An in-simulator fractional factorial transfer design was chosen, in which students were trained under various conditions, and then tested under a standard condition that represented maximum realism. The experimental design permitted a relatively large number of variables to be studied, using a relatively small number of student subjects. The subjects were pilots who had no prior carrier-landing experience: 16 recent graduates of Air Force T-38 training, and 16 highly experienced Navy P-3 pilots. Factors investigated were field-of-view, scene detail, platform motion, descent-rate cuing and training task (straight-in approaches vs. circling approaches). Turbulence was included as a factor and pilot type (Navy P-3 vs. Air Force T-38) was also included as a factor to control this source of subject variability. After training under a certain factor-level combination, students were tested on the day, wide field-of-view, circling task with motion and without descent-rate cuing. Results showed that the simulator and training factors generally produced small or no differences in transfer effectiveness. There were some advantages of the wide field-of-view and high-detail conditions, but these effects were small and/or short-lived, generally disappearing after a few transfer trials. Training with straight-in approaches resulted in transfer performance that was equal to or better than that produced by training with circling approaches. There were no motion or descent-rate cuing effects on the transfer task.

Cognitive set influences on Witkin's Rod-and-Frame Test.

Witkin's field-dependence theory is embroiled in conflict as research shows its primary assessment method, the Rod-and-frame Test, is influenced by situational events. This study explored the impact of an additional situational variable, locus of problem-solving data search, a cognitive set modified from Rotter's (1966) work. Two experimental groups of hospitalized alcoholics received standard Witkin instructions plus instructions emphasizing either an internal or external search for problem-solving cues. A control group received only Witkin's instructions. Aanlysis of variance showed the special instructions affected rod-and-frame scores in the predicted directions. The results were interpreted as indicating a need for a multi-factor approach to analyzing the complex relationships of the Rod-and-frame Test.

The Developmenal Learning Program at P.S. 78

A developmental learning program for first graders identified as poor learners was established in one of the New York City public schools. The children were seen on a daily basis in small groups for perceptual-motor, language, and other developmental experiences intended to foster their readiness for learning. Considerable differences were found in the degree of responsiveness to such help as revealed in the inventory of strengths and weaknesses and the retest results for the group. A multifactor approach utilizing an inventory of developmental strengths and weakness is advocated within this framework.

Single‐Factor Analysis in Population Dynamics

In the study of natural populations it is desirable btit not always feasible to measure the effects of all mortality factors. This requires frequent population sampling, supported by data on natural enemies, climate, and other factors, and leads to the compilation of detailed life tables for successive generations. These tables must be compiled simultaneously for a number of differentt environments if it is desired to learn why population density varies in place as well as in time. It is important to know, for example, why a forest insect periodically develops high populations in certain well-defined stand types but not in all types where it occurs. This multi-factor approach therefore demands much time and effort and, for species that are difficult to sample, is more suitable for a team of investigators than for the individual. A preliminary examination of rather extensive life-table data for the spruce budworm, Choristoneura fumniferana (Clem.), suggested that the factors affecting this species in any one place are of two types-those that cause a relatively constant mortality from year to year and contribute little to population variation, and those that cause a variable, though perhaps much smaller, mortality and appear to be largely responsible for the observed changes in population (Morris 1957). A factor of the latter type will here be called a 'key factor,' meaning simply that changes in population density from generation to generation are closely related to the degree of mortality caused by this factor, which therefore has predictive value. This leads to some interesting questions: Do these key factors exist for other species or are most populations affected by so many interacting factors that they behave like random numbers? If a key factor is suspected in a population, can its existence be demonstrated effectively by a very limited 'single-factor' approach in which only population density and the mortality caused by this factor are measured in each generation? If so it may be possible, with the expenditure of only a few man-days each season, to discover relationships of value for the prediction of population changes. This would be particularly useful for certain species of economic importance which, be-

Pregnancy changes in the uterine cervical ganglia (Frankenhäuser) as causative factors of vascular hypertension in toxemia

Recognition of the disturbed delicate balance in certain hormonal regulatory mechanisms and homeostatic adjustments of normal gestation seems to be the nearest visible approach to a coherent interpretation and resolution of the origin of hypertension and impairment of inner oxidation in pregnancy toxemia, and of the laboratory data available. The multifactor approach involves hyperactivity of the pituitary, the adrenal cortex, and the accessory medulla-like formations occurring in the cervical ganglia during gestation as interdependent members of a dynamic system which assumes etiological significance as the result of the inadequacy of its controlling factors. In pre-eclampsia, marked eosinopenia, sodium and chloride retention, increase in urinary 17-ketosteroids and uric acid excretion afford sensitive indicators of anterior pituitary-adrenal cortical stimulation, with the activation of pituitary ACTH secretion most likely due to epinephrine.