Extending a model of shift-work tolerance

The present study contributes to theory and practice through the development of a model of shift-work tolerance with the potential to indicate interventions that reduce nurses' intention toward turnover and increase job satisfaction in hospital-based settings. Survey data from 1257 nurses were used to conduct structural equation modeling that examine the direct and indirect effects of supervisor and colleague support, team identity, team climate, and control over working environment on time-based work/life conflict, psychological well-being, physical symptoms, job satisfaction, and turnover intention. The analysis of the proposed model revealed a good fit The chi-square difference test was non-significant (chi2(26) = 338.56), the fit indices were high (CFI = .923, NFI = .918, and NNFI = .868), the distribution of residuals was symmetric and approached zero, the average standardized residual was low (AASR = .04), and the standardized RMR was .072. In terms of the predictor variable, the final model explained 48% of the variance in turnover intention. The data revealed considerable evidence of both direct effects on adjustment and complex indirect links between levels of adjustment and work-related social support, team identity, team climate, and control. Nurses with high supervisor and coworker support experienced more positive team climates, identified more strongly with their team, and increased their perceptions of control over their work environment. This in turn lowered their appraisals of their time-based work/life conflict, which consequently increased their psychological well-being and job satisfaction and reduced their physical health symptoms and turnover intention. The type of shift schedule worked by the nurses influenced levels of turnover intention, control over work environment, time-based work/life conflict, and physical symptoms.     

红褐斑腿蝗的耐寒能力及其季节性变化

用测定过冷却点的方法研究了红褐斑腿蝗(Catantops pinguis (Stal))在不同季节的抗寒能力,并就虫体含水量、粗脂肪、总蛋白和总糖等成分在不同季节的变化及其对过冷却点的影响进行了探讨.结果表明,红褐斑腿蝗的过冷却点存在显著的季节性差异,依次为秋季种群((-23.1 ± 0.2 )℃)＜ 越冬后种群((-19.3 ± 0.1) ℃)＜ 夏季种群((-4.0 ± 0.1) ℃).含水率在生长期极显著高于越冬期,越冬初期和越冬后期变化不大,说明红褐斑腿蝗在越冬准备期已排出了体内多余的游离水.越冬后蝗虫体内总糖含量和脂肪含量均显著低于越冬初期,说明蝗虫在越冬时主要靠消耗体内的碳水化合物和脂肪物质来维持体温,体内的营养物质消耗极大,导致越冬后过冷却点显著上升.含水率和含脂率在两性间差异不显著,雌性蝗虫的总蛋白含量在夏季种群略高于雄性,越冬期显著低于雄性,可能与雌蝗孕卵过程中动用了大量营养物质有关.     

A study of weekly and seasonal variation of stroke onset

A registry based study was conducted to assess the variation in first-onset stroke with weekdays and seasons, in relation to the effects of age. Between 1 December 1991 and 30 November 1998, 10,729 first-onset stroke patients aged 25 or more were registered in Toyama Prefecture, Japan. We compared the weekly and seasonal variation in first-onset stroke by a one-way goodness-of-fit chi(2)-test. The relationship between seasonal variation in stroke onset and age was also evaluated by the method of Kendall's tau-b R x C tables with ordered categories. The frequency of onset of all strokes and cerebral infarctions (CI) was significantly higher on weekdays than at weekends (P < 0.01). More men had strokes and CI on a Monday (P < 0.01), and more women had cerebral hemorrhage (CH) on a Monday and CI at the end of the week. Stroke incidence was higher in patients aged less than 60 years (20.6%) than in those aged 60 years or over (18.7%) on a Monday compared to the weekend. By chi(2)-test, comparing observed with expected numbers of stroke onsets, weighted by the number of days in each 3-month period, the incidence of all strokes, CI and CH was significantly higher in winter and spring than in summer. The seasonal variation in the onset of stroke declined with age: all strokes (P < 0.001) and CH (P < 0.001) in both genders; subarachnoid hemorrhage (P < 0.001) only in men. Our study shows that the onset of stroke is more frequent on weekdays than on weekends, and may be associated with changes in psychophysiological stresses between working days and the weekend. We also observed a clear negative dose response relationship between seasonal variations in occurrence and age. It may be speculated that younger people have more change to work outdoors, exposing themselves to the winter environment. Their lifestyle and physiological condition may be different from those of older people.     

Amplitude of the oral temperature circadian rhythm and the tolerance to shift-work

The aim of the study was to test the hypothesis of a relationship between the tolerance to shift-work and the amplitude of the oral temperature circadian rhythm. Forty eight shift-workers (Rh?ne-Alpes Region) volunteered for this chronophysiological investigation: a) 23 steel-industry workers (SI); shift-duration: 7 days (weekly rotation); b) 25 chemical-industry workers (CI); shift-duration 2 days. The subjects' ages were roughly similar with regard to groups (SI and CI) as well as sub-groups (good and poor tolerance of shift-work). The tolerance was evaluated conventionally, according to both the existence and intensity of 3 types of medical complaint: (1) digestive troubles: gastritis, colitis, peptic ulcer etc.; (2) persisting fatigue, unusual nerviness, etc.; (3) sleep alterations. The poor tolerance was observed mostly in subjects shift-working for 10 years or more. Regular large-scaled and retested medical Hg thermometers (1/20 Celsius precision) were used. Data were recorded 2-hourly, at fixed clock hours in order to obtain individual time series. Both conventional and cosinor statistical analysis show that, in both groups, the oral temperature circadian amplitude is larger in subjects tolerant to shift-work than in subjects that have become intolerant.     

A biometric study of seasonal variation in worker wasps (Hymenoptera: Vespidae)

The seasonal changes in some morphometric characters of worker wasps of Vespula vulgaris and Vespula germanica are described and discussed in relation to colony populations and economics.     

A multi-lake study of seasonal variation in lake surface evaporation using MODIS satellite-derived surface temperature

Knowledge of the evaporative loss from lakes and reservoirs is critical to water resources managers as well as to the overall understanding of the water balance in a given basin, geographical region, or continent. Existing methods for ascertaining evaporation from lakes and reservoirs include point measurements, water balance and mass transfer calculations, and proxy measurements using a pan. Point measurements using the eddy flux covariance method can be accurate, but are resource intensive and unsuited for determining spatial variation over a lake, or for obtaining measurements over many lakes. Mass balance methods cannot provide spatial variability and their accuracy depends on other portions of the water balance that can be challenging to obtain, such as leakage. Similarly, relatively recently deployed scintillation methods provide only an average for a strip across a lake and are also resource intensive and not suited for multi-lake studies. Evaporation pan measurements can also be used, though their accuracy is poor. Herein, we use a combination of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite measurements of water surface temperature, measurements of wind speed, air temperature, and relative humidity from local NWS stations, and a mass transfer method, to demonstrate multi-lake evaporation measurements. Specifically, the seasonal variation in evaporation is obtained for the five major lakes in the Savannah River Basin (in South Carolina, USA): Lakes Jocassee, Keowee, Hartwell, Russell, and Thurmond. Since this approach requires only an existing satellite resource with global coverage and existing NWS stations, this method can potentially be ported to any lake where there is a nearby meteorology station. Hence, this method could be used by both water resource managers and limnologists alike. The possibility is discussed of extending this approach beyond a single basin to encompass an entire geographical region or continent.     

Biometeorological study of the seasonal variation of mortality in Japan and other countries on the seasonal disease calendar

The results of previously published statistical evaluations of morbidity and mortality statistics from 1900 to 1960 for various diseases in Japan,the United States, Egypt and several European countries are summarized. It was found that for all the diseases considered there is a monthly change in frequency distribution which led to the elaboration of a seasonal disease calendar. For Japan it was noted that the mortality peak has gradually moved from summer to winter for most diseases.This pattern has been found to exist in the highly industrialized European countries and the USA for some time, while a high summer mortality and typical seasonal disease distribution is still found in little industrialized countries such as Egypt. The deseasonality of diseases seems to be typical of industrialized countries with highly developed public health and medical services.

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Zusammenfassung Die in früheren Arbeiten veröffentlichten Ergebnisse statistischer Untersuchungen von Morbiditäts- und Mortalitätsstatistiken von 1900 bis 1960 für verschiedene Krankheiten in Japan, den Vereinigten Staaten,Ägypten und mehreren europäischen Ländern wurden hier im Zusammenhang beschrieben. Es war gefunden worden, dass die Häufigkeitsverteilung aller berücksichtigten Krankheiten sich von Monat zu Monat ändert. Dies wurde in einem Kalender über die jahreszeitliche Verteilung der Krankheiten zusammengefasst. In Japan hat sich die Spitze der Mortalität bei den meisten Krankheiten langsam vom Sommer in die Winterperiode verschoben. Diese Verschiebung ist in den hochindustrialisierten Ländern Europas und in den Vereinigten Staaten schon früher erfolgt. Dagegen wird in den wenig industrialisierten Ländern wie Ägypten noch eine hohe Sommer-Mortalität und die typische jahreszeitliche Krankheitsverteilung gefunden. Das Verschwinden der jahreszeitlichen Häufigkeitsverteilung von Krankheiten scheint typisch zu sein für industrialisierte Länder, in denen Medizin und Gesundheitsdienst einen hohen Stand aufweisen.

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Resume On a réuni ici les résultats de recherches statistiques publiées antérieurement sur la morbidité et la mortalité de 1900 à 1960 et concernant diverses maladies au Japon, aux Etats-Unis, en Egypte et en de nombreux pays d'Europe.On constate que la répartition des fréquences de toutes les maladies considérées varie de mois en mois. On a résumé cette constatation en un calendrier de la répartition des maladies au cours de l'année. Au Japon,le maximum de la mortalité s'est lentement déplacé de l'été vers l'hiver et cela pour la plupart des maladies. Ce décalage s'est manifesté antérieurement dans les pays hautement industrialisés d'Europe ainsi au'aux Etats-Unis. Par contre, dans les pays moins industrialisés, comme l'Egypte par exemple, on constate encore une très forte mortalité en été'et une répartition typique des maladies au cours de l'année. La disparition de la répartition des fréquence des maladies au cours de l'année semble un phénomène typique des pays industrialisés dans lesquels la médecine et les services d'hygiène publique ont atteint un niveau élevé.

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This is a summary of my previous studies published in Japan.     

A community-based study of seasonal variation in the onset of chronic fatigue syndrome and idiopathic chronic fatigue

One proposed hypothesis regarding the etiology of chronic fatigue syndrome (CFS) is that there is a subgroup of patients in which symptom onset is precipitated by a viral infection. If this is indeed true, then one would anticipate a greater incidence of the emergence of CFS symptoms during months when viral infections occur with the greatest frequency. The current community-based epidemiology study examined the month of symptom onset for 31 patients with CFS and 44 others with idiopathic chronic fatigue (ICF). It was determined that the distribution of the month of illness onset for the CFS and ICF groups was nonrandom, with greater numbers of participants than expected reporting an onset of CFS and ICF during January. (Chronobiology International, 18(2), 315-319, 2001)     

Methodological aspects of shift-work research

A major issue in shift-work research is to understand the possible ways in which shift work can impact performance and health. Nearly all body functions, from those of the cellular level to those of the entire body, are circadian rhythmic. Disturbances of these rhythms as well as the social consequences of odd work hours are of importance for the health and well-being of shift workers. This article reviews a number of common methodological issues which are of relevance to epidemiological studies in this area of research. It discusses conceptual problems regarding the use of the term "shift work," and it underscores the need to develop models that explain the mechanisms of disease in shift workers.     

Analysis of seasonal variation of birth defects in Atlanta

BACKGROUND: Compared with analyses of temporal trends, analyses of seasonal variations in the prevalence of birth defects have been more limited and have provided less consistent information. Possible reasons for this lack of consistency in findings include differences in populations, underlying factors, seasons or climates, and methods of ascertainment and analysis between studies. This study examines possible seasonal variation in the prevalence of selected birth defects in a defined study population using graphical displays and three statistical methods. METHODS: Cases were infants and fetal deaths in nine birth defect groups born to residents of mothers in five counties of metropolitan Atlanta during the period of 1978-2001 and ascertained by the Metropolitan Atlanta Congenital Defects Program. These birth defect groups were anencephaly, spina bifida, total neural tube defects, cleft palate, cleft lip with or without cleft palate, anomalies of the pulmonary valve, anomalies of the aortic valve, hypoplastic left heart syndrome, and congenital dislocation of the hip. We pooled monthly case counts and calculated monthly rates for each of these birth defect groups for five different birth periods: 1978-2001, 1978-1989, 1990-2001, 1990-1994, and 1995-2001. We applied the Cochran-Armitage test for trend to rule out homogeneity in pooled monthly rates. Data for each defect group were examined for possible seasonal (i.e., cyclical) variation overall and within the cited birth periods using the Hewitt-Rogerson test and the Walter-Elwood test. RESULTS: Graphical analyses of the pooled monthly rates showed no apparent seasonal patterns for any of the nine defect groups examined. Statistical tests for seasonality suggested possible seasonality for three defect groups: the Hewitt-Rogerson test was statistically significant for anencephaly (peak March-August, p = 0.048),while the Walter-Elwood test was significant for anomalies of the pulmonary valve (peak September, p = 0.02), and anomalies of the aortic valve (peak July, p = 0.039). With both methods, the results appeared to be influenced by the choice of time (i.e., birth) period. Results for anomalies of the pulmonary valve were statistically significant and more consistent with all tests in most of the time periods examined. CONCLUSIONS: Graphical analyses and basic statistical tests for seasonality showed no consistent evidence of seasonality for any of the nine defect groups examined, except for anomalies of the pulmonary valve. The two basic statistical methods coupled by a trend test for exploring seasonal patterns of the prevalence of birth defects can be useful for preliminary analyses of possible seasonal patterns. However, these methods have some limitations: (1) an assumption of no strong temporal trend over the study years, and (2) the results can vary by time period chosen. For specific hypotheses regarding seasonality, a more robust analytical approach such as time-series analysis might be more appropriate.     

Statistical analysis of the seasonal variation in demographic data

There has been little agreement as to whether reproduction or similar demographic events occur seasonally and, especially, whether there is any universal seasonal pattern. One reason is that the seasonal pattern may vary in different populations and at different times. Another reason is that different statistical methods have been used. Every statistical model is based on certain assumed conditions and hence is designed to identify specific components of the seasonal pattern. Therefore, the statistical method applied should be chosen with due consideration. In this study we present, develop, and compare different statistical methods for the study of seasonal variation. Furthermore, we stress that the methods are applicable for the analysis of many kinds of demographic data. The first approaches in the literature were based on monthly frequencies, on the simple sine curve, and on the approximation that the months are of equal length. Later, "the population at risk" and the fact that the months have different lengths were considered. Under these later assumptions the targets of the statistical analyses are the rates. In this study we present and generalize the earlier models. Furthermore, we use trigonometric regression methods. The trigonometric regression model in its simplest form corresponds to the sine curve. We compare the regression methods with the earlier models and reanalyze some data. Our results show that models for rates eliminate the disturbing effects of the varying length of the months, including the effect of leap years, and of the seasonal pattern of the population at risk. Therefore, they give the purest analysis of the seasonal pattern of the demographic data in question, e.g., rates of general births, twin maternities, neural tube defects, and mortality. Our main finding is that the trigonometric regression methods are more flexible and easier to handle than the earlier methods, particularly when the data differ from the simple sine curve.     

Detecting seasonal variation in composition of adult Coccinellidae communities

1. Following its recent global spread, Harmonia axyridis (Coleoptera: Coccinellidae), an aphid predator of East Palearctic origin, dominated local coccinellid communities. While long‐term trends in this change are well documented, little is known about seasonal changes. 2. Seasonal changes in communities of adult Coccinellidae were investigated in central Europe (Prague), from April to November in 2010–2014. The beetles were collected at 2‐weekly intervals by net‐sweeping particular stands of trees (Tilia spp., Acer spp. and Betula sp.). The numbers of beetles caught were recalculated per unit effort, and average species abundance and community richness, dominance and diversity were calculated for each 2‐week period. 3. Frequencies of 21 established species varied throughout the vegetative season and general trends in this variation were similar in each of the 5 years of this study. In May–June the abundant species was Adalia decempunctata, which was later replaced by Harmonia axyridis as the most abundant species in late summer. Coccinella septempunctata colonized trees occasionally in summer. This sequence of species substitution occurred every year and was reset during winter. Species richness decreased and dominance increased during the course of each vegetative season. The diversity of the coccinellid community (Shannon index H′) significantly decreased during the course of the vegetative season. This was caused by a gradual increase in the dominance of H. axyridis, the abundance of which explained 88% of variation in H′. 4. The existence of a significant seasonal difference indicates that it is important to take this into consideration when comparing coccinellid communities.     

A study of ethanol tolerance in yeast

The ethanol tolerance of yeast and other microorganisms has remained a controversial area despite the many years of study. The complex inhibition mechanism of ethanol and the lack of a universally accepted definition and method to measure ethanol tolerance have been prime reasons for the controversy. A number of factors such as plasma membrane composition, media composition, mode of substrate feeding, osmotic pressure, temperature, intracellular ethanol accumulation, and byproduct formation have been shown to influence the ethanol tolerance of yeast. Media composition was found to have a profound effect upon the ability of a yeast strain to ferment concentrated substrates (high osmotic pressure) and to ferment at higher temperatures. Supplementation with peptone-yeast extract, magnesium, or potassium salts has a significant and positive effect upon overall fermentation rates. An intracellular accumulation of ethanol was observed during the early stages of fermentation. As fermentation proceeds, the intracellular and extracellular ethanol concentrations become similar. In addition, increases in osmotic pressure are associated with increased intracellular accumulation of ethanol. However, it was observed that nutrient limitation, not increased intracellular accumulation of ethanol, is responsible to some extent for the decreases in growth and fermentation activity of yeast cells at higher osmotic pressure and temperature.     

Glucose tolerance in patients with cystic fibrosis: five year prospective study.

OBJECTIVES--To study prevalence and incidence of diabetes mellitus in patients with cystic fibrosis. DESIGN--Five year prospective study with annual oral glucose tolerance tests. SETTING--CF Center Copenhagen, Denmark. SUBJECTS--191 patients with cystic fibrosis aged above 2 years. MAIN OUTCOME MEASURES--Glucose tolerance, plasma glucose concentrations after fasting and after glucose loading, and haemoglobin A1c levels. RESULTS--Prevalence of diabetes increased from 11% (n = 21) to 24% (n = 46) during study, with annual age dependent incidence of 4-9%. Diabetes was diagnosed at median age of 21 (range 3-40). At diagnosis of diabetes, symptoms of hyperglycaemia were present in 33% of patients, fasting hyperglycaemia (> or = 7.8 mmol/l) was seen in 16%, and increased haemoglobin A1c levels (> 6.4%) were seen in 16%. Impaired glucose tolerance implied higher risk for development of diabetes than normal glucose tolerance (odds ratio 5.6). In 58% of cases with impaired glucose tolerance, however, glucose tolerance was normal at next annual test. Normal glucose tolerance was found in only 37% of patients at all five tests. Within this group of patients, median plasma glucose concentrations after fasting and after glucose loading and haemoglobin A1c levels increased by 6-8% during study. CONCLUSIONS--Prevalence and incidence of diabetes in cystic fibrosis patients was high and increased with age. Since hyperglycaemic symptoms, fasting hyperglycaemia, and increased levels of glycated haemoglobin did not reliably identify diabetes mellitus, we recommend annual oral glucose tolerance tests in all cystic fibrosis patients aged over 10 years.     

Comparative study of seasonal and intradiurnal variation of airborne herbaceous pollen in urban and rural areas

The content of herbaceous pollen in the atmosphere depends on the vegetal cover, climate and the weather and geographical conditions. The aim of the study reported here was to compare aerobiological data obtained from pollen monitoring stations located at sites differing with respect to their flora and microclimate – i.e. a town and a rural area. A volumetric method was used for sampling. In each microscopic preparation 12 vertical strips corresponding with 2-h intervals were analysed. A 90% method was used to determine the pollen season. The results were statistically verified using the u test and the Kolmogorov-Smirnov, Spearman and Wilcoxon tests. Higher values of the Seasonal Pollen Index (SPI), higher daily average concentrations and higher peak values were recorded in the rural area. An analysis of intradiurnal variations of airborne pollen showed that apart from the Poaceae the number of pollen grains in the air began to increase earlier in the day in the rural area; in the case of Rumex and Ambrosia, the maximum values also appeared a few hours earlier. For all the taxa investigated, the analysis of correlation showed a significant association between the daily average concentrations at both sites. The weakest association occurred for Plantago lanceolata; for all other taxa, the determination coefficients (R ²) were high. The results of the Wilcoxon test showed that, despite the strong positive association between daily concentrations of the pollen types investigated, there were differences in mean pollen concentrations in the overlapping pollen season. Mean concentrations of Poaceae and Rumex airborne pollen were significantly higher in the rural area in both years, and those of Urtica and P. lanceolata were significantly higher only in 2002.     

Modelling of seasonal variation in nitrogen retention and in-lake concentration: A four-year mass balance study in 16 shallow Danish lakes

The mass balance for total nitrogen (N) was studied over a four-year period in 16 shallow mainly eutrophic 1st order Danish lakes. Water was sampled in the main inlet of each lake 18–26 times annually, and from the outlets and the lake 19 times annually. Water was also sampled from minor inlets, although less frequently. N input and output were calculated using daily data on discharge (Q), the latter being obtained either from the Q/H relationship based on automatic recordings of water level (H) for the main in- and outlet, or by means of Q/Q relationships for the minor inlets. Annual mean N retention in the lakes ranged from 47 to 234 mg N m^–2 d^–1, and was particularly high in lakes with high N loading. Annual percentage retention (N _ret –y%) ranged from 11 to 72%. Non-linear regression analysis revealed that hydraulic retention time and mean depth accounted for 75% of the variation in annual mean N _ret –y% and, in combination with inlet N concentration, accounted for 84% of the variation in the in-lake N concentration. N _ret % varied according to season, being higher in the second and third quarter than in the first and fourth quarter (median 18–19%). A simple model was developed for predicting monthly nitrogen retention (N _ret –m) on the basis of external N loading, the lake water pool of nitrogen N _pool , hydraulic loading and lake water temperature. Calibration of only two parameters on data from the randomly selected 8 out of 16 lakes rendered the model capable of accurately simulating seasonal dynamics of the in-lake N concentration and N _ret –m in all 16 lakes. We conclude that with regard to shallow, eutrophic lakes with a relatively low hydraulic retention time, it is now possible to determine not only annual mean nitrogen retention, but also the seasonal variation in N _ret–m . Prediction of seasonal variation in N loading of downstream N-limited coastal areas is thereby rendered much more reliable.     

Intraspecific variation in tolerance of warming in fishes

Intraspecific variation in key traits such as tolerance of warming can have profound effects on ecological and evolutionary processes, notably responses to climate change. The empirical evidence for three primary elements of intraspecific variation in tolerance of warming in fishes is reviewed. The first is purely mechanistic that tolerance varies across life stages and as fishes become mature. The limited evidence indicates strongly that this is the case, possibly because of universal physiological principles. The second is intraspecific variation that is because of phenotypic plasticity, also a mechanistic phenomenon that buffers individuals’ sensitivity to negative impacts of global warming in their lifetime, or to some extent through epigenetic effects over successive generations. Although the evidence for plasticity in tolerance to warming is extensive, more work is required to understand underlying mechanisms and to reveal whether there are general patterns. The third element is intraspecific variation based on heritable genetic differences in tolerance, which underlies local adaptation and may define long-term adaptability of a species in the face of ongoing global change. There is clear evidence of local adaptation and some evidence of heritability of tolerance to warming, but the knowledge base is limited with detailed information for only a few model or emblematic species. There is also strong evidence of structured variation in tolerance of warming within species, which may have ecological and evolutionary significance irrespective of whether it reflects plasticity or adaptation. Although the overwhelming consensus is that having broader intraspecific variation in tolerance should reduce species vulnerability to impacts of global warming, there are no sufficient data on fishes to provide insights into particular mechanisms by which this may occur.