Effects Of Changes In Parameters Research Articles

Factors affecting the isolation of CCC DNA from Streptomyces lividans and Escherichia coli

Based on the results of a systematic study of factors affecting plasmid yield and purity, a procedure suitable for the rapid screening for and isolation of covalently closed circular DNA from Streptomyces lividans and Escherichia coli was developed. The method consists of lysis of lysozyme-treated bacteria combined with alkaline denaturation of DNA at high temperature. Renaturation of CCC DNA and precipitation of single-stranded DNA together with protein is achieved by the addition of a minimal amount of phenol/chloroform. The screening procedure uses only a single tube and the samples can be analyzed by agarose gel electrophoresis about 30 min after lysis. Removal of phenol and further purification of the plasmid preparation is achieved by consecutive precipitations with isopropanol and spermine, followed by extraction with ethanol, producing samples suitable for restriction endonuclease digestion, ligation, and transformation of S. lividans protoplasts or competent E. coli cells in about 2 h. All steps of the procedure are explained in detail with information about the effects of changing parameters. This should help the experimenter to obtain reproducible results and may be useful if the method has to be adapted to new strains or plasmids.

A Method for Minimizing the Impact of Distributional Assumptions in Econometric Models for Duration Data

Conventional analyses of single spell duration models control for unobservables using a random effect estimator with the distribution of unobservables selected by ad hoc criteria. Both theoretical and empirical examples indicate that estimates of structural parameters obtained from conventional procedures are very sensitive to the choice of mixing distribution. Conventional procedures overparameterize duration models. We develop a consistent nonparametric maximum likelihood estimator for the distribution of unobservables and a computational strategy for implementing it. For a sample of unemployed workers our estimator produces estimates in concordance with standard search theory while conventional estimators do not. ECONOMIC THEORIES of search unemployment (Lippman and McCall [34]; Flinn and Heckman [14]), job turnover (Jovanovic [25]), mortality (Harris [17]), labor supply (Heckman and Willis [23]) and marital instability (Becker [3]) produce structural distributions for durations of occupancy of states. These theories generate qualitative predictions about the effects of changes in parameters on these structural distributions, and occasionally predict their functional forms.2 In order to test economic theories about durations and recover structural parameters, it is necessary to account for population variation in observed and unobserved variables unless it is assumed a priori that individuals are homogeneous.3 In every microeconomic study in which the hypothesis of heterogeneity is subject to test, it is not rejected. Temporally persistent unobserved components are an empirically important fact of life in microeconomic data (Heckman [19]). Since the appearance of papers by Silcock [39] and Blumen, Kogan, and McCarthy [5], social scientists have been aware that failure to adequately control for population heterogeneity can produce severe bias in structural estimates of duration models. Serious empirical analysts attempt to control for these unob

A model for the fouling of M.S.F. plants based on data from operating units

The behaviour of a number of large plants treated with a high performance additive and operated under steady conditions for long periods has been carefully monitored. In time the build-up of insulating deposits (fouling) in the brine heater stopped, the resistance to heat transfer reaching a steady value. Changes in operating conditions resulted in rapid reversible changes in the degree of fouling i.e. this regained its steady value when the operating conditions were returned to their original values. The most important parameter changed was identified as the brine circulating rate or velocity which sets the shear stress at the brine-deposit boundary. The commonly used linear relationship between fouling and time clearly does not explain these plant results. The use of such linear rates to predict the progress of fouling, particularly those obtained over short periods of operation, is shown to be invalid. The observations that a plant will come to different steady values of fouling which change reversibly with specific changes in operating conditions can only be sensibly explained by a two step process of deposition and subsequent removal. Models embracing this behaviour have been proposed in other fields of heat transfer and this approach has proved to be a more meaningful and acceptable technique to describe the plant behaviour. The theory of the model is introduced and the effect of changing parameters on the rate of fouling and steady state value is examined. More research is needed to quantify the factors which control the deposition and removal terms in operating plant. This model is shown to be applicable to plants treated with a polyphosphate based system as well as high performance additives such as ALBRIVAP DSB.

Sequential Bargaining with Incomplete Information

This paper describes a simple two-person, two-period bargaining game, and solves it using the concept of perfect Bayesian equilibrium, in which the actions of each player convey information which is used by his opponent. The paper examines the effects of changes in bargaining costs, the size of the contract zone, and the length of the bargaining process on such aspects of the solution as the probability of impasse and the likelihood of concessions. The combination of information transfer and the lack of pre-commitment embodied in perfectness yields many surprising results. Common perceptions about the effects of parameter changes on bargaining processes are suspect, and should be checked in the particular game being discussed.

The impact of adenine and inventory utilization decisions on blood inventory management.

The use of citrate-phosphate-dextrose-adenine as an anticoagulant for whole blood increases the storage period permitted for whole blood and red cells from 21 to 35 days. A simulation model was used to analyze the possible consequences for outdates and shortages of the addition of adenine. The model accepts as input (1) the maximum age (21 or 35 days), (2) parameters describing the demand and supply distributions, and (3) parameters describing inventory control (crossmatch recycle period, transfusion fraction, deviation from optimal target inventory levels). These parameters were varied over wide ranges, and a full factorial design was carried out. The observed shortage and outdate rates were then related (via multiple regression) to the parameter values. The resulting shortage and outdate functions indicated the effect of parameter changes, including extending the lifetime from 21 to 35 days, and the joint effect of changing more than one parameter. Conclusions indicate that, while the contribution of an increased lifetime to reducing shortages and outdates can be substantial, this contribution can be easily dissipated by relaxing the tightness of other inventory management controls.

A Simple Tool for the Design of Passive Solar Buildings

The design tools that are presently available for use by designers of passive solar heating or cooling systems include detailed simulation codes, correlations derived from the detailed codes, and simulations that may be used for short-term analyses using programmable handheld calculators or desktop computers. An alternative method is based on classical frequency response techniques and yields results that are in close agreement with those that are obtained from detailed computer simulations. The method may be used to quickly determine the average temperature and the magnitude of the diurnal temperature variation in a passive solar building. The effects of parameter changes may also be quickly and easily determined by this method. The method is described in the paper and results are presented for a slab-on-grade building having a thermal storage wall and a thermal storage floor incorporating off-peak load management.

ChemInform Abstract: ALKALOID PRODUCTION IN CATHARANTHUS ROSEUS CELL CULTURES. VII. EFFECT OF PARAMETER CHANGES AND CATABOLISM STUDIES ON CELL LINE PRL NO. 953

Chemischer InformationsdienstVolume 13, Issue 1 Natural Products ChemInform Abstract: ALKALOID PRODUCTION IN CATHARANTHUS ROSEUS CELL CULTURES. VII. EFFECT OF PARAMETER CHANGES AND CATABOLISM STUDIES ON CELL LINE PRL NO. 953 J. P. KUTNEY, J. P. KUTNEYSearch for more papers by this authorL. S. L. CHOI, L. S. L. CHOISearch for more papers by this authorP. KOLODZIEJCZYK, P. KOLODZIEJCZYKSearch for more papers by this authorS. K. SLEIGH, S. K. SLEIGHSearch for more papers by this authorK. L. STUART, K. L. STUARTSearch for more papers by this authorB. R. WORTH, B. R. WORTHSearch for more papers by this authorW. G. W. KURZ, W. G. W. KURZSearch for more papers by this authorK. B. CHATSON, K. B. CHATSONSearch for more papers by this authorF. CONSTABEL, F. CONSTABELSearch for more papers by this author J. P. KUTNEY, J. P. KUTNEYSearch for more papers by this authorL. S. L. CHOI, L. S. L. CHOISearch for more papers by this authorP. KOLODZIEJCZYK, P. KOLODZIEJCZYKSearch for more papers by this authorS. K. SLEIGH, S. K. SLEIGHSearch for more papers by this authorK. L. STUART, K. L. STUARTSearch for more papers by this authorB. R. WORTH, B. R. WORTHSearch for more papers by this authorW. G. W. KURZ, W. G. W. KURZSearch for more papers by this authorK. B. CHATSON, K. B. CHATSONSearch for more papers by this authorF. CONSTABEL, F. CONSTABELSearch for more papers by this author First published: January 5, 1982 https://doi.org/10.1002/chin.198201318AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue1January 5, 1982 RelatedInformation

Interactive electromagnetic launcher simulation

The mathematical model, usage, and documentation of an interactive computer simulation for an electromagnetic launcher is presented. The launcher is modeled as an electrical circuit. Three slight variations of the program permit studies of a launcher with (1) rail skin effects, (2) rail skin effects and approximated storage coil skin effects, or (3) neither of these effects. Usage of the program as currently implemented on the Westinghouse R&D Univac 1106 is described, with a sample session shown. The implementation of the program permits rapid scoping of the effects of parameter changes.

Design of Modal Control of Structures

A structure with active control possesses a mechanism to apply forces on the structure by prestressing cables or other suitable devices to reduce the structure response. This mechanism is controlled by current or voltage produced by sensors located at various points of the structure, and this current or voltage is related to the response of the structure at the sensor location. The modal approach is a technique for designing this mechanism. When using the modal technique, the effect of the active control mechanism on the structure response can be presented by the so-called influence matrix. This matrix indicates the effect of the active control mechanism on the different modes of the structure. By studying the properties of this matrix, the effect of changing parameters in the active control mechanism on the response of the structure can be seen clearly and the matrix can be of great help in the designing of the active control mechanism.

System partial inverses for sensitivity, adaptivity and estimation

In this paper we consider the common analytic characteristics of the system sensitivity, adaptivity and parameter estimation problems. We emphasize the applicability of the concept of partial inverses. The partial inverses are developed in both the input-output and state format. The latter approach leads into the theory of finite memory partial inverses. As an illustration vehicle we analyze in detail one particular sensitivity reduction algorithm. It is shown that in some cases it produces a complete reduction of the effect of parameter changes. The algorithm can be used for the case of time varying parameters. The approach that we follow uses the Hilbert resolution space concepts. The input-output relationship is then modelled by linear bounded causal maps. Since the results are established in this general framework, they are applicable, and can be specialized, to a wide variety of systems.

Sensitivity analysis of goal programming with pre-emption

Abstract Empirical applications of goal programming with pre-emption to-date have failed to deal with the effects of changes in parameters after the optimal solution has been obtained. A few studies that attempted to do this employed the existing linear programming packages as the basic tool for the analysis, with numerical weights assigned in place of the pre-emptive priority factors. Here an attempt is made to extend the duality theory of linear programming and to relate it to the analysis c f po8t-optimality, especially regarding changes in the priority structure. To this end, the dual problem is constructed and interpreted. It is shown that a duality-based sensitivity analysis helps a decision maker have a better feel for the soundness of bis priority structure of goals.

A Comprehensive Model for C02 Assimilation in Leaves

ABSTRACT A model of C02 assimilation in leaves is presented which includes consideration of the size and distribution of cells and biochemical kinetics. The model, which includes the effects of distributed sources and sinks on the diffusion process, is formulated as a nonlinear boundary value problem involving two coupled ordinary differential equations. An approximate analytic solution is presented and its validity is checked by finite differences. The qualitative effects of parameter changes are discussed.

A mathematical model of tractor overturning and impact behaviour

A mathematical model was developed based on the force and displacement equations of equilibrium at each point where the tractor or cab makes contact with the ground during overturning. This allowed incorporation of non-linear force-deflection characteristics describing deformation of the soil, cab and parts of the tractor, giving a more accurate representation than is possible if impacts are assumed to be pure plastic impulses. The model was used to cover the overturning phase, in addition to impact, by including tyre side force relationships and damping terms. A computer program based on the model was written in Fortran IV for the simulation of overturns down steep banks and multiple rolls on continuous slopes, the two most severe types found in a survey of overturning accidents. Validation of the model by a series of full scale experiments, and use of the simulation in predicting the effect of parameter changes are described in other papers (References (2) and (3)). A brief review of the literature is given.

SEASONALITY AND THE REQUIREMENTS FOR PERPETUATION AND ERADICATION OF VIRUSES IN POPULATIONS

Perpetuation of a virus in a population is distinct from the ability to persist in a cell culture or individual host. Parameters which determine perpetuation include: 1) the size of the population; 2) the turnover of the population; 3) the proportion of immunes in the population; 4) the transmissibility of the infection; and 5) the generation time between sequential infections. These parameters may be grouped into two composite factors which most directly affect transmission dynamics and perpetuation: (a) population turnover per generation period, and (b) transmissibility or the fraction of susceptibles infected per existing infection. Perpetuation in small populations usually requires either the ability to persist in individuals or rapid population turnover. Conversely, human viruses which initiate only acute infections require larger populations to persist. Seasonal variation in transmissibility can greatly increase the minimum population size in which persistence is possible, and we argue that the population size of 500,000 for measles persistence (described by Bartlett) is primarily a consequence of seasonal variation. Computer modelling can be used to examine the effect of changes in parameters which determine the seasonal cycle of virus perpetuation and fadeout. Finally, human infections are reviewed to indicate those which have been eradicated (smallpox), are on the threshold of eradication (poliomyelitis), are possibly eradicable (measles), or could be candidates for future efforts (hepatitis A and hepatitis B). In developing a strategy for eradication two points are of great potential utility: first, the seasonal trough should be exploited as a time for effective intervention; and, second, containment efforts should be directed at epidemiologically important population groupings such as schools.

Monopolistic Competition with Outside Goods

The Chamberlinian monopolistically competitive equilibrium has been explored and extended in a number of recent papers. These analyses have paid only cursory attention to the existence of an industry outside the Chamberlinian group. In this article I analyze a model of spatial competition in which a second commodity is explicitly treated. In this two-industry economy, a zero-profit equilibrium with symmetrically located firms may exhibit rather strange properties. First, demand curves are kinked, although firms make Nash conjectures. If equilibrium lies at the kink, the effects of parameter changes are perverse. In the short run, prices are rigid in the face of small cost changes. In the long run, increases in costs lower equilibrium prices. Increases in market size raise prices. The welfare properties are also perverse at a kinked equilibrium.

INFORMATIONAL ASYMMETRIES, FINANCIAL STRUCTURE, AND FINANCIAL INTERMEDIATION

NUMEROUS MARKETS ARE characterized by informational differences between buyers and sellers. In financial markets, informational asymmetries are particularly pronounced. Borrowers typically know their collateral, industriousness, and moral rectitude better than do lenders; entrepreneurs possess "inside" information about their own projects for which they seek financing. Lenders would benefit from knowing the true characteristics of borrowers. But moral hazard hampers the direct transfer of information between market participants. Borrowers cannot be expected to be entirely straightforward about their characteristics, nor entrepreneurs about their projects, since there may be substantial rewards for exaggerating positive qualities. And verification of true characteristics by outside parties may be costly or impossible. Without information transfer, markets may perform poorly. Consider the financing of projects whose quality is highly variable. While entrepreneurs know the quality of their own projects, lenders cannot distinguish among them. Market value, therefore, must reflect average project quality. If the market were to place an average value greater than average cost on projects, the potential supply of low quality projects may be very large, since entrepreneurs could foist these upon an uninformed market (retaining little or no equity) and make a sure profit. But this argues that the average quality is likely to be low, with the consequence that even projects which are known (by the entrepreneur) to merit financing cannot be undertaken because of the high cost of capital resulting from low average project quality. Thus, where substantial information asymmetries exist and where the supply of poor projects is large relative to the supply of good projects, venture capital markets may fail to exist. For projects of good quality to be financed, information transfer must occur. We have argued that moral hazard prevents direct information transfer. Nonetheless, information on project quality may be transferred if the actions of entrepreneurs ("which speak louder than words") can be observed. One such action, observable because of disclosure rules, is the willingness of the person(s) with inside information to invest in the project or firm. This willingness to invest may serve as a signal to the lending market of the true quality of the project; lenders will place a value

Team Production and the Dynamics of the Firm

This paper discusses the behavior of the firm when its nature as a nonmarket allocational device (a team) is taken into account. The activities of the firm are divided into team formation and team production in a dynamic model of the competitive firm. The determinants of stationary equilibrium and the optimal growth path are analyzed. Impact and long-run effects of parameter changes are also derived. It is concluded that textbook results largely continue to hold in stationary equilibrium, but that significant modifications may have to be made with respect to conjectures regarding the short-run behavior of growing firms.

SIMPAK —

A software system for continuous system simulation, having an interactive graphics capability, is described. Inasmuch as the system uses reasonably priced, commercially available graphics hardware, it has wide potential utility. The system uses the IBM 360 Continuous System Modeling Program (CSMP) and has a simple command language to control the CSMP problem. The user enters commands at the key board of the graphics terminal to initiate simulation runs, change parameter values, and display graphs of problem variables. The system maintains a file which permits the user to display curves from earlier runs and thereby to readily obtain insight into the effect of parameter changes.

SIMULATION OF INFORMATION CHOICE

ABSTRACTBeginning with the information economics framework and a multi‐period decision model [15], this paper considers the use of computer simulation methods within an information system choice environment. Actual decision behavior is replaced by optimal decision rules, and simulation is used to evaluate the effects of parameter changes in the environmental model. Simulation is shown to be functional (1) in estimating the value of alternative information structures within a fifteen period decision model and (2) in providing sensitivity and statistical data which would be useful both for different decision maker utility functions and for a variety of information system design questions.

Some Properties of the Variance of the Switch-Count Load

Under equilibrium conditions, the load carried by a service system is defined as the average amount of traffic handled per unit of time. An unbiased estimate of this parameter is provided by the switch-count load, which is obtained by recording the number of busy servers at regular time intervals and then taking the arithmetic mean of these observations. Formulas for the variance of this measurement (which are applicable to delay-and-loss systems with either finite- or infinite-source inputs and arbitrary defection rates) were derived in a previous paper1; a program for their computation is now available and has been used to explore effects of parameter changes on the switch-count load variance. The purpose of the present paper is to describe results of this investigation and, in particular, to draw attention to two properties which may be unexpected: (i) the variance of the switch-count load does not always decrease when waiting positions are added, and (ii) the variance of the carried-load estimate obtained from continuous observation over a given time interval is not a lower bound for the variance of load estimates calculated from a finite sequence of recording of the number of busy servers.