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In this paper, we quantify an important management problem, which is how a company should respond to cyclical shocks of different amplitudes and duration when time delays are present in the factor input adjustment process. Our objective is to show how different shock profiles affect the amplitude and wavelength of the production path. We also consider the extent to which cyclical shocks generate long-run persistence in the time-path of output. Finally, our analysis suggests a scheme, which is not based simply on calendar time, for classifying different shock profiles as short or long.

A CKNOWLEDGED more than understood, the I752 reform of the calendar in colonial America illustrates nicely Norbert Elias's observation that "knowledge of calendar time . . . is taken for granted to the point where it escapes reflection." Indeed, in contrast to the British experience, there is virtually no work on the way the calendar shift affected colonial America. Instead, historians have focused on the form and content of colonial calendars (primarily through celebrations) and their implications for American national identity and have overlooked the larger temporal or calendrical framework in which these celebrations occurred and this identity was formed.1 Even specialists fail to examine fully colonial America's reaction to

This paper concentrates on the contextual diffusion of flexible automation production and design/engineering technologies in the Italian metalworking industry. The authors use duration data analysis with explanatory covariates to point out the role of complementarities between the technologies examined and learning by using effects matured with experience of previously available technologies in shaping diffusion paths. The impact of industry- and plant-specific control variables, as well as that of the stock of previous adopters, on adoption probabilities is also taken into account. In addition, the authors analyze duration versus calendar time dependence of adoption probabilities. Copyright 1995 by Blackwell Publishing Ltd.

Businesses of the future will rely more than ever on the work of teams. Making better use of the team times spend in meetings will be a high priority, as will being able to adapt rapidly to change. Electronic meeting systems (EMS), which apply information technology to support the meeting process, can help accomplish these goals. This paper describes and discusses the implementation of EMS at IBM in an alliance with the University of Arizona. During the past three years, the project has grown from initial support for a single site to 33 IBM sites, with more on the way. Over 15,000 people have used the ever-expanding and evolving EMS tool kit. Use of EMS has improved group performance by an average of 55 percent, with even more dramatic reductions in project calendar time. The lessons learned and success factors at IBM can assist managers in effectively introducing EMS to their organizations.

Owing to the inadequacy of conventional laboratory windshield qualification testing methods, it is not unusual for unforeseen problems to develop in the real world of flight service. Aircraft windshields are normally subjected to static, material, environmental, and, in some instances, to limited service condition testing before being incorporated into prototype hardware. In‐service monitoring is used to compare the prototype to previous designs. Determining the relative effectiveness of corrective “fixes” or design improvements by in‐service testing can take months or even years of calendar time. To overcome these prob‐lems, Sierracin has developed and constructed an advanced Windshield Flight Environment Simulator (WFES), that duplicates the total operating environment of electrically‐heated, pressurized windshields, on a highly compressed time scale.

This paper examines the turn-of-the-year effect, the firm size effect, and the relation between these two effects for a sample of OTC stocks traded via the NASDAQ reporting system over the period 1973-1985. We find results similar to those based solely on listed stocks. The importance of these findings stems from the existence of nontrivial differences between the characteristics of the OTC/NASDAQ sample and the samples of listed firms examined previously in the literature. We also find that NASDAQ quoted bid-ask spreads are highly negatively correlated with firm size, are not highly seasonal, and are large enough to preclude trading profits based upon a knowledge of the seasonality of small firms' returns. BOTH THE "SIZE EFFECT" and the "turn-of-the-year effect" have received much recent attention in the finance literature. Wachtel (1942), Rozeff and Kinney (1976), Branch (1977), and Dyl (1977) have all documented calendar time seasonalities in U.S. stock returns. Particularly striking are the large, regularly observed January returns. Banz (1981) and Reinganum (1981) found that, on average, small capitalization firms experience significantly higher risk-adjusted (vis 'a vis CAPM) returns than large firms. Keim (1983) showed that the two effects are related. A large part of the annual excess risk-adjusted return earned by small firms accrues in January, and in particular during the first few trading days in January.1 Conversely, large firms earn significantly negative excess riskadjusted returns in January.

This study presents the clinical-epidemiological analysis of data from 769 individuals, representing greater than 95% of all cases of diabetes mellitus diagnosed during the first 20 years of life among the Danish male birth cohorts 1949-1956 inclusive. It is concluded that except for a very few, all cases of diabetes developing during the first 20 years of life are insulin-dependent with a duration of symptoms less than 2 months before diagnosis in greater than 75% of the cases. The cases were evenly distributed within Denmark at the time of birth as well as of diagnosis, and greater than 98% were admitted to hospital at diagnosis. A relatively higher proportion of cases diagnosed during autumn and winter periods was found, but was not statistically significant. Incidence was analysed in a regression model with age and calendar time as variables; the variation of age at onset was similar to previous studies with a peak at pre-school age and at puberty. Contrary to previous Danish analyses, we found a significant calendar time variation with steadily increasing age-specific incidences from the beginning of 1950s until an apparent maximum in mid-1970s.

Evidence of weekend effects on the distribution of security returns suggests that returns are generated by a process operating closer to trading time rather than calendar time. In contrast, accumulation of interest over the weekend follows a calendar-time process. Since both the variance of returns and the interest rate are important parameters of the Black-Scholes option pricing model, this paper suggests that the model be stated to account for this by utilizing a trading-time variance and a calendar-time interest rate. Empirical evidence indicates that this allows the model to better explain market option prices.

Cumulative replicative lifespan (CRLS) was determined in replicates for skin fibroblasts from ten non-diabetic and 11 diabetic donors. The results show that CRLS 1. 1. decreases as function of donor age for controls but not for diabetics 2. 2. is not different for random subsites of the same biopsy 3. 3. is not affected by freeze-thawing of either tissues or cells or by the calendar time during which the cells were tested 4. 4. is affected by different lots of fetal bovine sera. The data also shows that variation of CRLS among diabetic donors is greater than among controls and that cells from some diabetics may have decreased CRLS.

This reminiscence group helped disoriented old people find intimacy with others in the present time. Telling of loss, group members resolved grief by seeking meaning in their experience. Folktales allowed the group to reminisce even when memories failed. The group's time limited structure helped the worker empathize with old people's life tasks. But time limits were not useful to a group whose members had little awareness of calendar time.

The importance of resistance has increased in the last decade, together with the increasing use of site-specific fungicides. Mathematical models have been developed to deal with disruptive selection that occurs when the initial population of the target organism in terms of fungicide sensitivity consists of two or more distinct, non-overlapping distributions around widely different central values. Whether these models are static or dynamic, they lead to the same basic conclusions as to what factors would accelerate resistance build-up, namely the initial incidence of the resistant mutants, the efficacy of the fungicide at risk and the degree of resistance to it, and the degree of control pursued in the field. Dynamic models add to those factors the speed of the pathogen spread in the field, the fitness of the resistant mutants and the size of the pathogen population exposed to the fungicide. Resistance build-up can be delayed by the use of mixtures. In such a case, the higher the efficacy of the companion fungicide, the greater the delay. Alternation of fungicides will delay resistance build-up in calendar time: however, in the case of fit resistant mutants it will not extend the useful life of the fungicide at risk. No models have been developed to deal with the directional selection that occurs when, in terms of fungicide sensitivity, the population of the pathogen consists of one wide unimodal frequency distribution. Further research is recommended towards verifying the disruptive selection models, creating models to deal with directional selection and generating baseline sensitivity data for new fungicides before their commercial introduction.

For most cancer sites there is a linear log-log relationship between incidence and age. This relationship does not hold for breast cancer, and certain 'key' breast cancer risk factors suggest that breast tissue does not 'age' in step with calendar time. A quantitative description of 'breast tissue age' is suggested which brings the age-incidence curve of breast cancer into line with the common log-log cancers and explains quantitatively the known key risk factors. The model also explains the 'anomalous' finding that although early first birth is protective, late first birth carries a higher risk than nulliparity. US breast cancer rates are some four to six times the rates in Japan--the model suggests that the key risk factors, when considered jointly with weight, can explain about 85% of the difference.

While an earlier report on the Texaco Mortality Study cohort showed no statistically significant elevations for any cause of death for the white males, it did not preclude any excess risk of mortality within subgroups of workers. In this study, an employee's complete job history was used to determine his work categories, and patterns of mortality were examined for the more common job categories. All of the job categories examined showed deficits for mortality overall, and the patterns seen were similar to those for the entire cohort. Significant elevations were seen in pancreas cancer mortality for office and managerial people and in leukemia mortality for pipefitters and boilermakers. Other elevations of particular interest based on five or more deaths were brain cancer for laboratory workers and benign neoplasms in pipefitters and boilermakers. These associations were examined by latency and years worked, and no consistently positive associations were seen. It was not possible to take into account calendar time of exposure in this type of analysis, nor could any specific chemicals or levels of exposure be associated with the job categories where the standardized mortality ratios were elevated.

The Operational Readiness concept differs from the conventional Availability concept and must be modelled differently mathematically. Operational Readiness analyses are appropriate for systems which carry out missions as the demand for their operation arrives. These systems are normally in the dormant state. They operate when they are called upon to do so. Typical examples are emergency safety systems. The conventional Availability concept applies only to systems which are subject to a continuous demand to operate and which only stop to carry out preventive or corrective maintenance actions. Typical examples are electric power generating systems, pumping systems, etc. The Operational Readiness of a system is the probability that, at any time, the system is either operating satisfactorily or ready to operate on demand, when used under stated conditions. The total calendar time is the basis for computational Operational Readiness. This paper develops a mathematical Operational Readiness model for safety systems which are regularly tested (and repaired if necessary) during its dormant state.

Published information about the effects of ozone on plants and ecosystems is synthesized into a conceptual model to explain the response of evergreen conifers, deciduous hardwoods and agricultural crops to ambient levels of ozone pollution. The effects of ozone on carbon balance and growth of individual plants can be quantified on the basis of concentration, external dose (concentration x duration of exposure), or uptake. For an equivalent dose within a single growing season, agricultural crops are the most sensitive to ozone, with hardwoods intermediate and conifers least sensitive. In contrast, all species display a similar decline in photosynthesis and growth in response to equivalent total uptake or uptake per leaf life span, with trees somewhat less sensitive than agricultural crops on a calendar time scale, but slightly more sensitive on a relative (leaf life span) time scale. Among species, differences in ozone uptake and response can be predicted from differences in the inherent leaf diffusive conductance.

Firms in the same industry exhibit systematic differences in the organization of production and the structure of employment. Entrepreneurial ability is the specific scarce input that limits the size of a firm. This input must be allocated to two activities, coordinating production and monitoring workers. Able entrepreneurs can convert calendar time into larger supplies of coordinating effort that enable them to assemble large firms. Greater ability implies a higher shadow price of time which increases the implicit costs of monitoring. A dispersion of entrepreneurial abilities generates an equilibrium size distribution of firms. Differences in monitoring costs affect the choice of worker productivities, the design of products, and the organization of production. The monitoring cost hypothesis advanced in this paper goes a long way in explaining the equilibrium of an industry containing heterogeneous firms that differ in size and behavior.

The current system for overhauling soaking pits within a steel production plant is reviewed with the objective of improving the overall cost effectiveness of the pits. It is concluded that this may be improved by regularly phased overhauls where the time scale is based upon tonnes throughput of steel and not, as at present, upon calendar time. The proposed solution is sufficiently robust to accommodate expected interruptions in the phasing of overhauls without losing its effectiveness.

Interlocked grain in wood of Nyssa sylvatica Marsh. is a lapse-time record of cyclical changes in inclination (rightward or leftward) of fusiform initial cells in the cambium. Typically the inclination cycles have periods of a decade or more. Such cycles can be interpreted as manifestations of long-term endogenous rhythms. Interlocked grain in N. sylvatica is not the result of whole-stem spiral grain that reverses periodically. As wavy grain in other species is a record of wavelike migration of orientational domains along the cambium, interlocked grain in N. sylvatica can be interpreted as being related to a more complex system of domains having long axial dimensions. These domains migrate or change their efficacy and directional sense in place in such a way that some regularity of inclination cycles is maintained at the various stem levels. Inclination cycle lengths have a closer relation to calendar time than they do to the amount of radial growth of the stem. This is affirmed by data from paired stems of similar ages but which grew in diameter at widely different rates. IN IDEAL TREES the long axes of the cambial fusiform initial cells are parallel to the stem axis, and wood derived from their progeny is straight grained. In real trees the wood grain is sometimes straight, but more often there are deviations. Commonly, fusiform initials are slightly inclined to the stem axis and the wood grain has a spiral course. Often the inclination of the initials in the same cambial locality changes with time. The scale and temporal aspects of these cell inclination changes in the cambium determine whether the wood grain is straight, spiral, wavy, or interlocked, or whether it has a more complex pattern (Braun, 1854; Bannan, 1966; Hejnowicz, 1968; Hejnowicz and Krawczyszyn, 1969; Hejnowicz and Romberger, 1973, 1979; Pyszynski, 1977). If grain inclination of the wood produced by the same area of cambium changes cyclically from left (S) to right (Z) repeatedly during the life of a tree, it is possible to determine the cycle length, axially and radially, by study of the wood. When the axial cycles are short, millimeters to a few decimeters, the grain is "wavy"; when axial cycles are long, several decimeters to many meters, we interpret the 1 Received for publication 23 April 1979; revision accepted 19 June 1979. The senior author expresses his appreciation and indebtedness to the Kosciuszko Foundation (New York) for a postdoctoral fellowship at the Forest Physiology Laboratory in Beltsville, Maryland, during the tenure of which some of the work reported here was accomplished. 2 Present address: Department of Botany, Bialystok Division of Warsaw University, Lipowa Street 41, 15424 Bialystok, Poland. grain as "interlocked." Among investigated woods there exists, however, a near-continuous spectrum of cycle lengths; hence it can be shown that both wavy grain and interlocked grain have a similar relation to orientational domains in the cambium (Krawczyszyn, 1972; Hejnowicz, 1973; Hejnowicz and Romberger, 1979). Although interlocked grain has long been recognized as a phenomenon of interest (Martley, 1920; Limaye, 1954; Kadambi, 1956), its spatial and temporal aspects in tree stems have only recently been given serious study. Krawczyszyn (1972, 1977) found that interlocked grain of Platanus can be interpreted as resulting from the upward migration of broad bands of successive S and Z orientational domains in the cambium. These interpretations are compatible with those of Hejnowicz and Romberger (1973) regarding wavy grain. Hejnowicz and Zagorska-Marek (1974) found that similar interpretations of interlocked grain formation apply to storied as well as nonstoried cambia. Recently we (Krawczyszyn and Romberger, 1979) reported that cyclical changes in cell length may accompany the inclination cycles of interlocked grain in woods with storied structure, but we found no such relation in woods with nonstoried structure. Economically both wavy grain and interlocked grain have positive and negative aspects. For decorative uses the figured or striped appearance of wavy or interlockedgrain wood is highly prized, though machining is difficult. These same features may be considered as defects in construction timber (Weddell, 1960; Webb, 1967).

The paper begins with a review of some of the approaches which have in the past been adopted for the study of residential mobility. The limitations are then identified which arise from approaches which either concentrated upon the individual to the exclusion of the institutional context of mobility or, as is currently tending to happen, concentrate upon the institutional analysis to the exclusion of the individual actor. From this discussion an attempt is made to bring together the two aspects of analysis and provide a model which relates the institutional and the individual aspects of residential mobility. In the final section of the paper, material is presented from a New Zealand study of residential mobility to demonstrate the utility of the approach and the range and variety of material it can provide.

SOME RESEARCHERS HAVE APPARENTLY been surprised to discover that the distribution of stock returns depends on the day of the week.' Kenneth French [3], for example, in testing whether daily stock returns are generated by a trading time or calendar time hypothesis, provided convincing evidence of a negative market return on Mondays. As French carefully notes, this finding runs counter to both hypotheses, since a trading time view would have expected stock returns equal on different days, and a calendar time view would have higher expected returns on Monday to compensate for the longer holding period. In this paper we offer a partial explanation for the apparently puzzling discovery of different daily returns. We argue that the expected stock returns as measured, for example, from closing to closing prices, should depend on the day of the week. In general, we argue that the expected returns on Mondays should be lower than would be implied simply by a trading time or calendar time model, and the returns on Fridays should be higher. In addition, we anticipate that holidays will have complex effects on stock returns on other days of the week. Our argument is based on the delay between trading and settlements in stocks and in clearing checks. The explanation that we offer for different measured daily returns does not contradict the efficient market hypothesis, as correctly adjusted expected returns should not differ according to the day of the week.

The effects of changing a unit time length of a planning horizon from a month to a week on the optimum planning horizon were examined by calculating the optimum planning horizon through the methods proposed by Nagasawa, Nishiyama, and Hitomi (1982). It was found that the optimum planning horizon decreased by 20-30% in calendar time when the unit time length was changed from a month (monthly scheduling) to a week (weekly scheduling). However, the degree of this decrease was much smaller than the (65% shown by Bernardo (1978), and it followed that the optimum planning horizon largely increased in the number of periods with this change of the unit time length. It was also clarified that the large amount of the decrease shown by Bernardo was derived on the basis of the erroneous analysis of the relation between cost coefficients and the unit time length. Consequently, weekly scheduling was not always preferred to monthly scheduling

We studied the periods of time that newly emerged southern pine beetles, Dendroctonus frontalis Zimmermann, lived without food at 10 constant temperatures between 10 and 41°C. Two hundred or more adults were tested at each temperature to obtain mean longevities and longevity distributions. At 10 and 12.5°C, average longevity was about 18 days. Above 12.5°C, these times decreased exponentially to about 1 day at 41°C. Females lived longer than males held at the same temperature. There was considerable variability in average longevity for replicate experiments; the causes for this variability are discussed. Longevity distributions changed from near uniform at the lower temperatures to peaked at the higher temperatures. The data were described mathematically using a two-component model. First, an exponential function described adult dying rates (inverse of mean longevities) as a function of temperature. Second, an empirical distribution function described the cumulative percentage of beetles dying over physiological time. It is noteworthy that on a physiological time scale, one temperature-independent distribution described the data reasonably well. The combined rate and distribution functions adequately predicted the percentage of mortality of a cohort over calendar time.

This paper develops a new distribution theory for common stock returns. The model is composed of a calendar time diffusion process and a jump process where the magnitudes of the jumps may be autocorrelated. Empirical tests are performed on a month of transactions returns for twenty New York Stock Exchange securities. The data analysis supports the validity of the proposed theory.

K. W Schaie's 1965 (Psychological Bulletin, 64, 91–107) general developmental model was designed to explicate research strategies that permit the separation of age, cohort, and period (time-of-measurement) effects. Because of the dependency of each one of these constructs upon the remaining two, it has been necessary to impose restrictive assumptions to permit unconfounding of sources of developmental influences. This paper examines conditions under which the parameters of cohort and period can be freed from their dependency upon calendar time. Expanded definitions, thought to have increased explanatory power, are offered for the concepts of cohort and time-of-measurement. Implications for developmental research that might employ sequential strategies are examined, and future directions for the measurement of developmental context are sketched.

Performances on the Benton Visual Retention Test were collected for 894 men 17 to 96 years of age between 1960 and 1976 and were analyzed using slopes to estimate time-of-measurement effects. For each of the nine birth cohorts and eight age groups, performance (errors) was plotted on calendar time. Comparisons of the within-birth-cohort slopes showed an increase in slope with age (rho = 0.92); earlier born (older) cohorts had larger slopes indicating increased errors per year. Comparisons of within-age-group slopes showed no difference among age groups. Slopes of four of the five oldest cohorts were larger (p less than .05) than the common age-group slope. Whether the common age-group slope was a secular effect, a cohort effect, or some combination of the two, the data were consistent with age changes in performance late in life confirming longitudinal results of direct measures of change previously reported.

This paper explores the distinction between physical age and experience within the context of the human capital model of earnings determination. We extend the human capital model to distinguish the investment behavior of age-experience cohorts and to incorporate the effects of calendar time. Several alternative models are developed which are empirically tested based on a unique body of data (on Swedish engineering graduates) reflecting the earnings of cohorts with identical educational qualifications cross-classified by age and experience for a 10-year period. The results clearly indicate the necessity for distinguishing between experience and age in analyses of investment in human capital and are consistent with the interpretation that younger members of the same experience cohort are more efficient in producing human capital. The analysis also indicates the sensitivity of investment profiles to a priori restrictions on functional form and detects an inflection point in earnings increases consistent with...

Human diploid fibroblasts from an embryonic and an adult donor were maintained in an essentially nonmitotic state for extended periods of time by reducing the serum concentration of the growth medium from 10 to 0.5%. These cells could be returned to the rapidly proliferating state by subcultivation with medium containing 10% serum. Cells treated in such a manner took a proportionately longer calendar time to reach phase III than did controls that had been continuously cultured on growth medium. The division potential of cells from the adult donor was unaffected by the arrested state; however, that of cells from the embryonic donor was extended beyond that of growth controls. The extension of division potential in cells from the embryonic donor never exceeded the maximum passage level reported for these cells. During 21 days of cultivation with medium containing 0.5% serum, cell losses ranged from 15 to 35% and the protein content of the remaining cells decreased by 15 to 20%. It was concluded that division potential and not total calendar time was the primary determinant of the in vitro lifespan of these human diploid cells and that arresting cells from younger donors increased their ability to attain the maximum limit of their lifespan.

This paper describes the relationship between information time and calendar time in the use of group sequential procedures to monitor interim analyses of clinical trials. Information time is the proportion of maximum subjects or events already observed. Interim analyses often occur at specified calendar times while the definition of classic group sequential procedures occurs in terms of information time. We extend the general group sequential approach of Lan and DeMets to include this situation as well.

The principles of cohort analysis have been previously applied predominantly to the problem of the clarification of the pattern of change in disease incidence or mortality rates with age. However, many chronic diseases, including neoplastic diseases, show no peak in their age incidence curves, such as that exhibited by tuberculosis rates, which can be utilized to enable a decision as to whether mortality rates are characteristic of a cohort or of current time. It is shown that in such situations, where there has been a change in the direction of the mortality trend over time, the pattern of changes in age-specific rates may assist in this decision. For a number of sites of cancer examined in this way changes in mortality rates in England and Wales during the period 1911–1955 appear to be characteristic of successive cohorts rather than of particular periods of calendar time. This finding is relevant to the interpretation of the pattern of such changes, to the interpretation of age-risk curves in these conditions, and to hypotheses concerning the nature of the influences responsible for the changes over time.

The present status of interactive graphic displays in the application environment is reviewed. Although graphics data processing is still largely experimental, several applications have come into productive use--especially in the areas of data and design analysis. The primary benefit from enhancing such applications with graphic displays is the savings in calendar time. Before surveying several application areas, user aspects and application characteristics are discussed.

Human embryonic diploid fibroblast cultures (WI-38) were maintained for periods of 3 and 5 weeks in a stationary phase by low (0.1 percent) serum medium. Upon subcultivation, these cultures underwent fewer cell doublings than continuously subcultivated controls. All the cultures reached the degenerative Phase III state at approximately the same calendar time regardless of the number of cell doublings. Limited culture lifespan of WI-38 may not be directly related to cell doubling potential, as previously reported, but may be a function of total metabolic time in vitro .

Men drafted into the Army, hospitalized during 1944–1945 for service-connected trauma to the extremities, and consequently separated for disability were followed for mortality from January 1946 to April 1977. Three groups were established consisting of those whose injury resulted in: 1. (a) limb amputation; 2. (b) disfigurement without loss of body part; 3. (c) loss of part of hand or part of foot. Group (a) had a mortality, standardized for age and calendar time, 1.4 times that of group (b), matched on age and length of service at admission, and 1.3 times that of group (c), similar in age and length of service to group (a). The excess mortality of limb amputees was statistically significant (p

Except for a few brief years in the 1930s, the development of monetary theory and international trade theory has been dominated by a pre-Keynesian, i.e. neoclassical, logic. This analytical approach may have been useful as a rough approximation a century or more ago when agricultural products made up a large proportion of the gross national product and economic and financial affairs were organised on a significantly different basis than currently.

This paper reviews the sources of apparent time trends in effect. Apparent changes in effect may arise from changes in covariate distributions, background rates, exposure distribution, measurement quality, or selection factors. As with time trends in rates, time trends in effect must have at least one of these sources, since time itself has no effect. If background incidence is changing, however, time trends in effect become dependent on choice of effect measure, and interpretation must take this into account. Evidence that a trend arises from age-, cohort-, or period-related phenomena can indicate the relative plausibility of different explanations of the trend. Conversely, the relative plausibility of each explanation may indicate whether the trend is most appropriately viewed over the axis of age, birth cohort, or calendar time. Nevertheless, studies of short duration relative to an apparent trend (such as most case-control studies) must invoke strong assumptions to justify focusing on a particular axis. Illustrations are given from studies of electronic fetal monitoring and of smoking and lung cancer.

We have examined the kinetics of chick cell population aging in vitro using the percentage of labeled nuclei, the number of colonies formed from a low density inoculum and the number of cells/colony to monitor culture age. The results from these studies showed a gradual age-associated decline in each of the parameters which was first detected early in the culture lifespan and well in advance of changes in total cell number at confluency. Our results also indicated that each of the above parameters, in addition to the calendar time cells had been in culture, could be used to estimate the percentage of lifespan completed by the culture. A comparison of the methods used to estimate the remaining culture lifespan indicated that the percentage of labeled nuclei was the most accurate in describing cell age.

To understand the potential health effects of a chemical on humans, epidemiologists, industrial engineers, toxicologists, physiologists, as well as other laboratory scientists must interrelate the information gathered from their areas of expertise in order to interpret the overall risks related to chemicals. Before presenting the data from epidemiology studies of 1,3-butadiene, a brief summary of the types of studies which have been done and the weight of evidence which can be determined from each type will be discussed.

After maintenance in a confluent state, human diploid fibroblasts were returned to a proliferative state by serial subcultivation. Their total metabolic time was greater than that of the continuously subcultivated controls. When the cells were serially subcultivated with low inoculation densities, their total metabolic time decreased considerably, while their total population doublings were slightly increased over cells split at 1:4 ratio. Thus, lifespan depends on the cumulative number of population doublings rather than on the total calendar time in vitro. The low-density inoculation method of the serial subcultivation is efficiently and economically advantageous in studying cellular aging in vitro.

Sidney Weintraub died on 19 June 1983. Until his last breath he had hoped and planned that his health would permit him to address the conference. This is especially significant since he had already rejected an invitation to attend the Royal Economic Society’s ‘Keynes’ Centenary Conference’ at Cambridge in July 1983, despite Lord Kaldor’s generous offer to relinquish his own place on that programme to give Sidney time to set the record straight, or as Sidney would have said ‘to keep the American Keynesians honest’.

This is a semi-annual progress report, and it presents a specialized summary of the data in the counting accelerometer program. Statistics describing Navy and Marine aircraft cumulative g-count exceedances are calculated and tabulated. These tabulations are separated by calendar time and into four major categories of fleet experience: (1) Navy Training, (2) Navy Combat, (3) Marine Training, and (4) Marine Combat. These data show that the load rate distributions (counts at 1000 hours) for most models and most g-levels have a non-normal distribution. Within a model (F-4B, F-8H, etc.) differences in the average load rates exist when data are separated by calendar time or mission category.

The ratio of cancer occurrence among smokers compared to nonsmokers has been generally reported to be greatest for carcinomas arising in the lung and larynx. This report presents the results of an investigation into mechanisms underlying the temporal trends in the incidence of these two forms of cancer in Scotland over the 20-year period, 1960-1979. The purpose of the study was to establish the independent effects of age, calendar time, and birth cohort on the observed pattern of incidence by adopting an alternative approach to this classical problem which can be employed when data are available as individual records. The most economic model found to explain the data involved the independent effects of site, sex, and age and different cohort effects in each sex. The cohort effect was more pronounced in men than women in older cohorts but, conversely, stronger in women than in men in younger cohorts, i.e., among those born most recently. This observation accords with the observed increase in the use of cigarettes in young women relative to young men. There appeared to be a small effect of calendar time which was the same in both sexes and both sites, although this main effect, it must be emphasized, could be eliminated from the model on statistical grounds. The effect can be interpreted to indicate the increase in the coverage of cancer registration in Scotland which has taken place since 1960. These results indicate that lung cancer risk in Scottish males will continue to fall, with the risk in women lagging 20 years behind, although the levels in women will probably not reach those attained by men.

The ASMR for cancer of the oesophagus in men was 5.3 in 1963 and 4.7 in 1982, while the respective figures for women were 1.5 and 0.8. Cancers of the oesophagus are more frequent in men than in women. Mortality of men increases rapidly after the age of 40 to reach the maximum of 50 cases per 100000 in men aged about 75. The mortality rate in younger age groups has declined with calendar time only for women; in men, especially after 1970, we observe an increase. In the 50–64 age group, the mortality rate has declined for both sexes with calendar time. A decreasing risk of cancer of the oesophagus is also observed in the successive birth cohorts of men and women alike, though not in cohorts born after 1920.

The relative mortality of Type 1 (insulin-dependent) diabetes in Denmark during the period 1933–1981 was studied using a modification of Cox's regression model on the basis of two patient populations, ascertained in different ways and independently of each other. Initial analysis showed that the two groups could be combined completely into one common analysis. Relative mortality was the same for both sexes. The additional variables studied were age at diagnosis, current age, calendar year at diagnosis and calendar time during follow-up. All these interrelated variables were accounted for in the analysis. The analysis showed that relative mortality (a) decreased with increasing age at diagnosis; (b) increased from 1933 to a maximum in about 1965, after which it decreased; (c) increased with increased duration of diabetes to a maximum at 15–25 years, after which it declined.

This paper discusses improvements to conventional software reliability analysis models by making the assumptions on which they are based more realistic. That is, for example, the mutual dependency of errors in a program.

A historical prospective mortality study was conducted on a cohort of 34 156 male members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions. This cohort comprised all individuals who were members of the International Union of Operating Engineers, Locals 3 and 3A, for at least one year between 1 January 1964 and 31 December 1978. The mortality experience of the entire cohort and several subcohorts was compared with that of United States white men, adjusted for age and calendar time. The comparison statistic was the commonly used standardised mortality ratio (SMR). Historical environmental measurements did not exist, but partial work histories were available for some cohort members through the union dispatch computer tapes. An attempt was made to relate mortality experience to the union members' dispatch histories. Overall mortality for the entire cohort and several subgroups was significantly lower than expected. When cause specific mortality was examined, however, the study provided suggestive evidence for the existence of several potential health problems in this cohort. Mortality from liver cancer for the entire cohort was significantly high. Although mortality from lung cancer for the entire cohort was similar to expected, a positive trend by latency was observed for lung cancer. A significant excess of mortality from lung cancer was found among the retirees and the group for whom no dispatch histories were available. Other dispatch groups showed no evidence of lung cancer excess. In addition, the total cohort experienced significant mortality excess from emphysema and accidental deaths.

This paper was prepared in support of a Project 7900 long-term analysis to better understand and define the integrated air/ground threat in central Europe. The paper provides a descriptive summary of environmental conditions in central Europe whose probability for recurrence in calendar time can be predicted broadly from a long statistical history of occurrence. The effect of the conditions on military operations is assessed in terms of the opportunities it provides and/or the limitations it imposes. (Author)

To explore the relative importance of mitotic versus non-mitotic (metabolic) factors in determining the finite lifespan of human fibroblasts, mass cultures and 5 clones from 2 normal adults were followed as cohort pairs monitoring calendar time, mean population doublings (MPD), plating efficiency and expression of HL-A antigens. One member of each pair was split serially while the other was held in relative stationary phase with weekly refeeding using standard medium and culture conditions throughout. First cohorts became senescent after 52–62 MPD and 105–170 days while plating efficiencies declined and some HL-A antigens lost reactivity with specific antisera. At this time second cohorts were released from stationary phase and split serially. After initial loss of viability they generally showed higher plating efficiencies and normal reactivity of HL-A antigens till cell death within a calendar time of 195–240 days. The total MPD were reduced only marginally if allowance was made for low grade mitosis occurring during prolonged stationary phase. The results indicate that continuously replicating cells lose viability significantly before mitotically inhibited but actively metabolizing cohorts and suggest that factors which increase cellular turnover accelerate senescence and its pathological sequelae.

This report is a specialized summary of normal acceleration data recorded by counting accelerometers. Data are separated by calendar time and mission category. Only data reported in the counting accelerometer program are included.

The ASMR for cancer of the colon in men was 3.0 in 1963 and 4.6 in 1982, while the respective figures for women were 2.8 and 3.4. The time trend for 1963–1982 was in two phases: an increase in mortality over the period 1963–1978 in males and females, and after that, in 1979–1982, a decrease for both sexes. The mortality rates increase rapidly with age starting from about 40. The extreme value for both sexes is about 45 deaths per 100000. Mortality increase with calendar time is also observed (usually by the end of the 1970s) in all single age groups and in both sexes.