Optimal Time Of Day Research Articles

Methodology for measuring fAPAR in crops using a combination of active optical and linear irradiance sensors: a case study in Triticale (X Triticosecale Wittmack)

The amount of photosynthetically active radiation (PAR, 0.4–0.7 μm) absorbed by plants for photosynthesis relative to incident radiation is defined as the fraction of absorbed photosynthetically active radiation (fAPAR). This is an important variable in both plant biomass production and plant growth modeling. This study investigates the application of a newly developed, linear irradiance sensor (LightScout Quantum Bar Sensor, LightScout, Spectrum Technologies, Inc. USA), to quantify fAPAR for a demonstrator crop, Triticale (X Triticosecale Wittmack). A protocol was devised for sensor placement to determine reflected PAR components of fAPAR and to determine the optimal time of day and sensor orientation for data collection. Coincident, top of canopy, normalized difference vegetation index (NDVI) measurements were also acquired with a CropCircle™ ACS-210 sensor and measurements correlated with derived fAPAR values. The optimum height of the linear irradiance sensor above soil or plant canopy was found to be 0.4 m while measuring reflected PAR. Measurement of fAPAR was found to be stable when conducted within 1 h of local solar noon in order to avoid significant bidirectional effects resulting from diurnal changes of leaf orientation relative to the vertically-placed sensor. In the row crop studied, averaging fAPAR readings derived from the linear irradiance sensor orientated across and along the plant row provided an R2 = 0.81 correlation with above-canopy NDVI. Across row sensor orientation also gave a similar correlation of R2 = 0.76 allowing the user to reduce sampling time.

Validity of Midday Total Testosterone Levels in Older Men with Erectile Dysfunction

Based on studies showing the circadian rhythmicity of testosterone the optimal time of day to draw total testosterone in men has classically been reported as between 8 and 11 a.m. However, further studies demonstrated that the testosterone circadian rhythmicity becomes blunted with age. We retrospectively reviewed the charts of 2,569 men who presented with erectile dysfunction for total testosterone and draw times. We compared the men by age group, including less than 40 years and 5-year groupings after age 40 years. Total testosterone was analyzed for variability during the most common draw time hours (7 a.m. to 2 p.m.). Mean total testosterone at 7 to 9 a.m. and 9 a.m. to 2 p.m. clinically and statistically differed only in men younger than 40 vs 40 to 44 years old (mean difference 207 ng/dl, 95% CI 98-315, p = 0.0004 vs 149 ng/dl, 95% CI 36-262, p = 0.01). No other group showed a clinically and statistically significant difference between those periods. Total testosterone in men with erectile dysfunction who are younger than 45 years should be drawn as close to 7 a.m. as possible because a statistically and clinically relevant decrease in testosterone will occur during the course of the day. Men older than 45 years with erectile dysfunction can have total testosterone drawn at any time before 2 p.m. without misleading results.

The Optimal Time of Day for Training during Ramadan: A Review Study

Literature concerning the effects of Ramadan fasting on sports performance presents conflicting results. In this context, some studies reported a significant impairment of sports performance during the month of Ramadan. However, other studies suggested that Ramadan fasting has no significant effect on physical performance. The discrepancies between the studies could be explained by time-of-day variations in testing. In this regard, recent studies reported that Ramadan negatively affects the afternoon sports performance; however, the morning and the evening (after breaking the fast) performances were not affected by fasting. This suggests that the optimal time of day for training during Ramadan is the morning or the evening. Therefore, coaches should schedule the training sessions in the morning or evening during the month of Ramadan. However, further studies should investigate the effect of training at a specific time of day on sports performance during Ramadan.

Chronotype-dependent circadian rhythmicity of driving safety

Among the factors associated with driving safety, sleep-related variables constitute a leading cause of road accidents. Circadian fluctuations of driver’s somnolence has been previously linked to road safety. However, the role of chronotype in this relationship has been poorly investigated. Thus, the aim of the present work was to address whether driving performance is influenced by circadian patterns, in turn modulated by the driver’s chronotype and the time of day (i.e. synchrony effect). We assessed 47 healthy young adults with specific chronotypes in several simulated driving sessions, both in the morning and in the evening. We collected driving performance data, along with self-reported levels of activation prior to each driving session and other sleep-related variables. Participants drove less safely when testing times took place outside their optimal time of day, as determined by their chronotype and confirmed by self-reported levels of activation. These differences were more pronounced in the morning, when morning types shown a better driving performance. Our results suggest that chronotype plays an important role as a modulator of the relationship between the time of day and driving safety. Therefore, it is necessary to acknowledge this variable in theoretical models of driving behavior, and for the improvement of occupational accidents prevention programs.

Influence of Circadian Typology and Time of Day on Temporal Preparation

The present study addressed the interactions between processes of circadian and millisecond timing by testing whether the ability for temporal preparation is influenced both by individual differences in circadian rhythmicity and by the time of day at which a task is performed. A temporal preparation task that measures temporal orienting and sequential effects was administered to morning-type and evening-type groups of participants, both in morning and evening sessions. The results confirmed a synchrony effect on overall reaction time (RT), indicating that participants were most vigilant at their optimal time of day according to their specific chronotype. This synchrony effect, however, did not influence temporal orienting or sequential effects. These findings suggest that only processes mediating overall RT (vigilance) but not processes related to temporal preparation are susceptible to circadian influence. The current research thus supports the dissociation between circadian timing and temporal preparation.

N2O emissions from a cultivated mollisol: optimal time of day for sampling and the role of soil temperature

The correct use of closed field chambers to determine N2O emissions requires defining the time of day that best represents the daily mean N2O flux. A short-term field experiment was carried out on a Mollisol soil, on which annual crops were grown under no-till management in the Pampa Ondulada of Argentina. The N2O emission rates were measured every 3 h for three consecutive days. Fluxes ranged from 62.58 to 145.99 ∝g N-N2O m-2 h-1 (average of five field chambers) and were negatively related (R² = 0.34, p < 0.01) to topsoil temperature (14 - 20 ºC). N2O emission rates measured between 9:00 and 12:00 am presented a high relationship to daily mean N2O flux (R² = 0.87, p < 0.01), showing that, in the study region, sampling in the mornings is preferable for GHG.

Appropriate frequency and time of day to measure methane emissions from an irrigated rice paddy in Japan using the manual closed chamber method

Rice agriculture is a large anthropogenic source of atmospheric methane (CH4). The reliable estimation of CH4 emissions requires frequent measurements to trace diurnal and seasonal variations. To evaluate the appropriate intervals and optimal time of day to measure CH4 emissions using the manual closed chamber method, this study analysed four datasets of CH4 fluxes in a Japanese irrigated rice paddy measured at 2-hour intervals using the automated closed chamber method. The typical diurnal variation in the CH4 flux was observed after the rice's heading stage, during which the daily time-weighted mean CH4 flux was observed twice, in the 08:00–11:59 and 18:00–21:59 time windows. During the flooded rice-growing period, the CH4 emissions, which were estimated by weekly measurements once per day during the 10:00–11:59 time window, corresponded to 93–106% of the emissions calculated using the automated measurement method. In contrast, no regular measurement strategies produced a satisfactory estimate of the CH4...

Light Acts on the Zebrafish Circadian Clock to Suppress Rhythmic Mitosis and Cell Proliferation

A fundamental role of the circadian clock is to control biochemical and physiological processes such that they occur an optimal time of day. One of the most significant clock outputs from a clinical as well as basic biological standpoint is the timing of the cell cycle. Here we show that the circadian clock regulates the timing of mitosis in a light-responsive, clock-containing zebrafish cell line. Disrupting clock function, using a CLOCK1 dominant-negative construct or constant light, blocks the gating of cell division, demonstrating that this mitotic rhythm is cell autonomous and under control of the circadian pacemaker. Quantitative PCR reveals that several key mitotic genes, including Cyclin B1, Cyclin B2, and cdc2, are rhythmically expressed and clock-controlled. Peak expression of these genes occurs at a critical phase required to gate mitosis to the late night/early morning. Using clock and cell cycle luminescent reporter zebrafish cell lines, we show that light strongly represses not only circadian clock function, but also mitotic gene expression, and consequently slows cell proliferation.

Time of Day and Accurate Weights for Patients With Heart Failure

Heart failure (HF) is a significant health problem in the United States. It is estimated that 5.8 million Americans currently live with a diagnosis of HF (American Heart Association, 2010). Despite the fact that daily weight monitoring of patients with HF in the hospital has long been a standard part of monitoring effectiveness of treatment, the literature is lacking recommendations based on evidence specific to the optimal time of day for weighing inpatients. The clinical question under consideration is the following: In hospitalized patients with HF, does consistently measuring weights in the evening compared to early morning accurately reflect differences in net weight gain or loss?In this quasi-experimental, prospective cohort pilot study, 29 patients who met inclusion criteria were weighed in the morning and again in the evening. Results of this study revealed predictable differences for morning (M = 3.09, SD = 2.06) and evening weights (M = 2.47, SD = 1.80); t(28) = −2.602, p = .015. For study patients with three consecutive days of weights (N = 24), Pearson product-moment correlations revealed a statistically significant correlation between individual differences/changes in a.m. and p.m. weights, r(22) = .752, p < .001.The implication for clinical practice is that weights should be measured at a consistent time of day. This may be the morning or evening.

PROTOCOL: Systematic Review Protocol: Later School Start Times for Supporting the Education, Health and Well‐being of High School Students

PROTOCOL: Systematic Review Protocol: Later School Start Times for Supporting the Education, Health and Well‐being of High School Students

Time of day effects on problem solving: When the non-optimal is optimal

In a study examining the effects of time of day on problem solving, participants solved insight and analytic problems at their optimal or non-optimal time of day. Given the presumed differences in the cognitive processes involved in solving these two types of problems, it was expected that the reduced inhibitory control associated with non-optimal times of the day would differentially impact performance on the two types of problems. In accordance with this expectation, results showed consistently greater insight problem solving performance during non-optimal times of day compared to optimal times of day but no consistent time of day effects on analytic problem solving. The findings indicate that tasks involving creativity might benefit from a non-optimal time of day.

Individual Differences in the Influence of Time of Day on Executive Functions

Previous research has documented the impact of time of day on vigilance and memory and the moderating influence of circadian typology (morningness-eveningness) on the relationship between time of testing and cognitive processes. This study examined the impact of circadian typology and time of testing on executive functions. Morning-type and evening-type people were randomly assigned to a morning or afternoon testing time, and their performance on neuropsychological tests, including the Conners Continuous Performance Test (CPT), the Digit Span test, the Controlled Oral Word Association Test (COWAT), and the Wisconsin Card Sorting Test (WCST) was compared. No interactions between circadian typology and time of day were observed on the CPT or Digit Span test. A time of day effect was found on the letter generation portion of the COWAT. More words were generated in the afternoon than in the morning. In contrast, performance on the WCST was best when morning-type participants were tested at their optimal time of day. These findings suggest that circadian typology should be considered when scheduling neuropsychological assessments, rehabilitation training, and critical job tasks.

PO23-782 THE EFFECTIVENESS AND SAFETY OF EXTENDED RELEASE FLUVASTATIN

Evidence about the optimal time of day at which to administer statins is lacking.The objective of this study is to synthesize evidence about effects of morning vs evening statin administration on lipid profile.We searched PubMed, SCOPUS, Web of Science, and Embase databases (from inception up to July 24, 2016) to identify the relevant studies. Mean differences (MDs) between the change scores in lipid parameters were pooled using a fixed-effect model.Eleven articles with 1034 participants were eligible for the analysis. The pooled analysis comparing effects of morning vs evening administration of statins on plasma total cholesterol (TC; P = .10), high-density lipoprotein cholesterol (P = .90), and triglycerides (P = .45) was not statistically significant. Low-density lipoprotein cholesterol (LDL-C) lowering was statistically greater in the evening-dose group (MD: 3.24 mg/dL, 95% CI: 1.23–5.25, P = .002). Subgroup analysis according to statin half-lives showed that evening dose of statins was significantly superior to morning dose for lowering LDL-C in case of both short and long half-life statins (MD: 9.68 mg/dL, 95% CI: 3.32–16.03, P = .003 and MD: 2.53 mg/dL, 95% CI: 0.41–4.64, P = .02, respectively) and also for TC reduction in case of short half-life statins only (P = .0005).LDL-C and TC lowering was significantly greater in the evening dose than in the morning dose in case of short-acting statins. Besides slight but significant effect on LDL-C, the efficacy of long-acting statins was equivalent for both regimens. Therefore, long-acting statins should be given at a time that will best aid compliance. Short-acting statins should be given in the evening.

The effects of optimal time of day on persuasion processes in older adults

AbstractPast research demonstrates that the majority of older adults (60 years and older) perform resource‐demanding tasks better in the morning than in the afternoon or evening. The authors ask whether this time‐of‐day effect also impacts persuasion processes performed under relatively high involvement. The data show that the attitudes of older adults are more strongly affected by an easy‐to‐process criterion, picturerelatedness, at their non‐optimal time of day (afternoon) and by a more‐difficult‐to‐process criterion, argument strength, at their optimal time of day (morning). In contrast, the attitudes of younger adults are affected primarily by argument strength at both their optimal (afternoon) and non‐optimal (morning) times of day. Process‐level evidence that accords with these results is provided. The results accentuate the need for matching marketing communications to the processing styles and abilities of older adults. © 2007 Wiley Periodicals, Inc.

Maternal sensitivity concerning aetiological research into childhood cancer: results of preliminary focus groups

We and others have postulated that modifications to epidemiological methods and tools could improve understanding of childhood cancer aetiology. We describe features of paediatric cancer that influence study design and data collection strategies, and examine determinants of the reproducibility and accuracy of mothers' responses to questionnaires, which are the primary source of risk factor information. Two focus group sessions with mothers of children with acute lymphoblastic leukaemia (ALL) and two with mothers of children with brain tumours were conducted to explore: the optimal time of day, method of administration, and location for the interview; the availability of alternative data sources; the interval between paediatric cancer diagnosis and epidemiological interview; and other features which may affect maternal interview responses. Mothers of children with both types of cancer preferred being interviewed at home during the evening and were willing to provide complete access to their offsprings' medical records. Emotional, socio-economic and perhaps cultural differences between the groups of mothers were exemplified by the willingness of mothers of children with ALL to participate in epidemiological interviews earlier in their child's treatment course and to provide greater access to maternal reproductive history records compared with mothers of children with brain tumours. Parental concerns about the difficult disease and treatment course of children with brain tumours were a key element in their decision to defer participating in epidemiological interviews for many months after their child's cancer diagnosis. We conclude that the focus group approach can contribute to a broad strategy for improving questionnaires and methods for conducting paediatric cancer epidemiological research.

A ‘polarisation sun‐dial’ dictates the optimal time of day for dispersal by flying aquatic insects

Summary1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood.2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid‐morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid‐morning; (ii) in the evening; (iii) both in mid‐morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic.3. We found experimental evidence that the proportion (%) P(θ) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (θ) for dark reflectors while P(θ) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies.4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(θ) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations θ. The θ‐dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid‐morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun‐dial’ of dispersing aquatic insects.

Life time—circadian clocks, mitochondria and metabolism

A functional circadian clock has long been considered a selective advantage. Accumulating evidence shows that the clock coordinates a variety of physiological processes in order to schedule them to the optimal time of day and thus to synchronize metabolism to changes in external conditions. In mitochondria, both metabolic and cellular defense mechanisms are carefully regulated. Abnormal clock function, might influence mitochondrial function, resulting in decreased fitness of an organism.

Persistent twenty-four hour changes in liver and bone marrow despite suprachiasmatic nuclei ablation in mice.

Rest-activity or cortisol rhythms can be altered in cancer patients, a condition that may impair the benefits from a timed delivery of anticancer treatments. In rodents, the circadian pattern in rest-activity is suppressed by the destruction of the suprachiasmatic nuclei (SCN) in the hypothalamus. We sought whether such ablation would result in a similar alteration of cellular rhythms known to be relevant for anticancer drug chronopharmacology. The SCN of 77 B6D2F(1) mice synchronized with 12 h of light and 12 h of darkness were destroyed by electrocoagulation [SCN(-)], while 34 animals were sham operated. Activity and body temperature were recorded by telemetry. Blood and organs were sampled at one of six circadian times for determinations of serum corticosterone concentration, blood leukocyte count, reduced glutathione (GSH), and dihydropyrimidine dehydrogenase (DPD) mRNA expression in liver and cell cycle phase distribution of bone marrow cells. Sham-operated mice displayed significant 24-h rhythms in rest-activity and body temperature, whereas such rhythms were found in none and in 15% of the SCN(-) mice, respectively. SCN lesions markedly altered the rhythmic patterns in serum corticosterone and liver GSH, which became nonsinusoidal. Liver DPD mRNA expression and bone marrow cell cycle phase distribution displayed similar 24-h sinusoidal patterns in sham-operated and SCN(-) mice. These results support the existence of another light-dark entrainable pacemaker that can coordinate cellular functions in peripheral organs. They suggest that the delivery of anticancer treatments at an optimal time of day may still be beneficial, despite suppressed rest-activity or cortisol rhythms.

Attention, Scholastic Achievement and Timing of Lessons

Previous research has revealed that lower grade elementary school pupils who differ in their ability to learn to read also differ with respect to the optimal time of day for reading achievement. The present study strove to determine the hours of optimal attention in older pupils who varied in their apparent aptitude for mathematics. A sample of 204 fifth graders and 202 tenth graders were divided into three groups (high, average and low ability) on the basis of their mean yearly mathematics achievement scores. The subjects were asked to report on their attention levels throughout the day. The findings showed that fifth graders' attention levels were especially high in the afternoon, whereas tenth graders reported increased concentration during the morning hours. Among tenth graders, but not among fifth graders, there was a significant interaction between mathematics achievement and attention levels at various times of day. The practical implications of these findings for the planning of school schedules are discussed.

Chronotolerance of experimental radioimmunotherapy: clearance, toxicity, and maximal tolerated dose of 131I-anti-carcinoembryonic antigen (CEA) IgG as a function of time of day of dosing in a murine model

The temporal variation in bone marrow proliferation has been used to help define the optimal time of day to dose with approximately 30 chemotherapeutic agents, so that treatment efficacy is maximised and toxicity is minimised. Since myelosuppression is also the dose-limiting toxicity for most forms of radioimmunotherapy, we hypothesised that time of day of administration might also influence tolerance for radioantibody therapy. Bone marrow proliferative activity in BALB/c mice was determined using cell cycle analysis of propidium iodide-stained bone marrow samples collected at 3 h intervals. Myelosuppression was determined at weekly intervals after a therapeutic dose of 131I-NP-4 anti-CEA (carcinoembryonic antigen) intact IgG at either 0900 h (2 h after light onset [HALO]), 1300 h (6 HALO) or 1600 h (9 HALO). The highest bone marrow proliferative activity was noted between 20 HALO (0300 h) and 4 HALO (1100 h), and the lowest activity could be measured at 10–13 HALO (1700–2000 h). Seven days after a maximal tolerated dose (MTD) of radioantibody, granulocyte reduction was 50% at both 2 and 6 HALO and only 32% at 9 HALO ( P<0.003). Fourteen days after radioantibody therapy, an 87% granulocyte suppression was observed in mice treated at 2 HALO and only a 64% granulocyte loss was noted in the 9 HALO treated group ( P<0.001). The 2 HALO group recovered earlier than the 9 HALO group ( P<0.013; 22% loss from the 2 HALO dose and 40% loss from the 9 HALO dose) on day 28 post-radioimmunotherapy. The difference in magnitude of neutropenia, rather than duration, was critical for establishing the MTD. A 30% increase in the MTD was possible if mice were dosed at 9 HALO (320 μCi) versus 2 HALO (240 μCi). These studies suggest that principles of chronobiology may govern the magnitude of toxicity and the highest dose tolerated in radioantibody therapy in the same way that it does for cytotoxic drug therapy.