Diurnal Trajectory Research Articles

Investigating the Diurnal Variation in Coastal Boundary Layer Winds on Hainan Island Using Three Tower Observations

This study analyzes wind structures up to 509 m in the atmospheric boundary layer in the coastal area of Hainan Island, using a dataset obtained from ultrasonic anemometers housed in three towers. The wind profile, consisting of the measurements from the three towers, followed logarithmic law. In a diurnal variation, the maximum wind speed occurred at night, with a greater component of northerly wind, while the minimum wind speed was observed at noon, with a greater component of easterly wind. The variation in wind speed suggests that the measurements were representative of the wind field in the upper part of the atmospheric boundary layer, and the variation in wind direction might be affected by sea and land breezes, which can be induced by the different thermal conditions of underlying surfaces. The diurnal variation in average wind speed ranged from 0.5 to 1.5 m s−1, and the diurnal variation in wind direction was 10–20 degrees. In our measurements, the diurnal trajectory of the wind vector was observed to be counterclockwise, which differs from previous studies conducted over uniform and flat underlying surfaces. This is partially due to the different thermodynamic conditions of the underlying land and sea surfaces. The impact of topographic relief on wind measurement is also discussed. The measurements suggest that wind speeds at altitudes above 50 m are less influenced by terrain. The height of the reversal layer, which is generated by the different diurnal variations in wind speed in the upper and lower parts of the boundary layer, was estimated to be around 300 m.

Evidence for a modulating effect of transcutaneous auricular vagus nerve stimulation (taVNS) on salivary alpha-amylase as indirect noradrenergic marker: A pooled mega-analysis

BackgroundNon-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has received tremendous attention as a potential neuromodulator of cognitive and affective functions, which likely exerts its effects via activation of the locus coeruleus-noradrenaline (LC-NA) system. Reliable effects of taVNS on markers of LC-NA system activity, however, have not been demonstrated yet. MethodsThe aim of the present study was to overcome previous limitations by pooling raw data from a large sample of ten taVNS studies (371 healthy participants) that collected salivary alpha-amylase (sAA) as a potential marker of central NA release. ResultsWhile a meta-analytic approach using summary statistics did not yield any significant effects, linear mixed model analyses showed that afferent stimulation of the vagus nerve via taVNS increased sAA levels compared to sham stimulation (b = 0.16, SE = 0.05, p = 0.001). When considering potential confounders of sAA, we further replicated previous findings on the diurnal trajectory of sAA activity. Conclusion(s)Vagal activation via taVNS increases sAA release compared to sham stimulation, which likely substantiates the assumption that taVNS triggers NA release. Moreover, our results highlight the benefits of data pooling and data sharing in order to allow stronger conclusions in research.

Characterizing and Evaluating Diurnal Salivary Uric Acid Across Pregnancy Among Healthy Women.

Uric acid levels during pregnancy have been examined as a potential indicator of risk for gestational diabetes mellites, hypertension, and related adverse birth outcomes. However, evidence supporting the utility of serum uric acid levels in predicting poor maternal and fetal health has been mixed. The lack of consistent findings may be due to limitations inherent in serum-based biomeasure evaluations, such as minimal repeated assessments and variability in the timing of these assessments. To address these gaps, we examined repeated measurements of diurnal salivary uric acid (sUA) levels in a sample of 44 healthy women across early-mid and late pregnancy. We assessed potential covariates and confounds of sUA levels and diurnal trajectories, as well as associations between maternal weight gain and blood pressure during pregnancy and sUA concentrations. Using multilevel linear models, we found sUA increased across pregnancy and displayed a robust diurnal pattern with the highest concentrations at waking, a steep decline in the early morning, and decreasing levels across the day. Maternal pre-pregnancy BMI, age, prior-night sleep duration, and fetal sex were associated with sUA levels and/or diurnal slopes. Maternal blood pressure and gestational weight gain also showed significant associations with sUA levels across pregnancy. Our results expand upon those found with serum UA measurements. Further, they demonstrate the feasibility of using at-home, minimally-invasive saliva sampling procedures to track UA levels across pregnancy with potential applications for the long-term monitoring of maternal cardiometabolic risk.

Impact of loneliness on diurnal cortisol in youth

Loneliness is associated with multiple forms of psychopathology in youth. However, we do not yet know how loneliness gets “under the skin” in ways that may impact the long-term health and development of early adolescents. In particular, loneliness may influence youths’ patterns of diurnal cortisol, an index of hypothalamic-pituitary-adrenal (HPA) axis functioning and a central predictor of health across the lifespan. The current severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, or COVID-19) pandemic represents a salient period in which to study the consequences of loneliness, as recent work has provided evidence that the physical-distancing measures put in place to contain the virus have resulted in greater loneliness, particularly among youth. Thus, the current study aimed to examine the prospective association between loneliness during the COVID-19 pandemic and diurnal cortisol in early adolescents. We found that greater loneliness was associated with higher levels of cortisol at waking and a blunted cortisol awakening response (CAR). These results held even when controlling for covariates that can influence diurnal trajectories of cortisol. Critically, this pattern of HPA-axis functioning increases risk for adverse mental and physical health outcomes across adolescence and into adulthood. This study is the first to examine the prospective association between loneliness and diurnal cortisol in early adolescence, and the first to identify mechanisms that contribute to biological markers of distress during the COVID-19 pandemic. Findings underscore the importance of developing and distributing strategies to mitigate feelings of loneliness among youth.

Urban Nature Experiences Reduce Stress in the Context of Daily Life Based on Salivary Biomarkers.

Stress reduction through contact with nature is well established, but far less is known about the contribution of contact parameters – duration, frequency, and nature quality. This study describes the relationship between duration of a nature experience (NE), and changes in two physiological biomarkers of stress – salivary cortisol and alpha-amylase. It is the first study to employ long-term, repeated-measure assessment and the first evaluation wherein study participants are free to choose the time of day, duration, and the place of a NE in response to personal preference and changing daily schedules. During an 8-week study period, 36 urban dwellers were asked to have a NE, defined as spending time in an outdoor place that brings a sense of contact with nature, at least three times a week for a duration of 10 min or more. Their goal was compliance within the context of unpredictable opportunity for taking a nature pill. Participants provided saliva samples before and after a NE at four points over the study period. Before-NE samples established the diurnal trajectory of each stress indicator and these were in line with published outcomes of more closely controlled experiments. For salivary cortisol, an NE produced a 21.3%/hour drop beyond that of the hormone’s 11.7% diurnal drop. The efficiency of a nature pill per time expended was greatest between 20 and 30 min, after which benefits continued to accrue, but at a reduced rate. For salivary alpha-amylase, there was a 28.1%/h drop after adjusting for its diurnal rise of 3.5%/h, but only for participants that were least active sitting or sitting with some walking. Activity type did not influence cortisol response. The methods for this adaptive management study of nature-based restoration break new ground in addressing some complexities of measuring an effective nature dose in the context of normal daily life, while bypassing the limitations of a clinical pharmacology dose–response study. The results provide a validated starting point for healthcare practitioners prescribing a nature pill to those in their care. This line of inquiry is timely in light of expanding urbanization and rising healthcare costs.

What in the World Is North? Translating Cardinal Directions across Languages, Cultures and Environments

What in the World Is North? Translating Cardinal Directions across Languages, Cultures and Environments

Latent virus reactivation in astronauts on the international space station

Reactivation of latent herpes viruses was measured in 23 astronauts (18 male and 5 female) before, during, and after long-duration (up to 180 days) spaceflight onboard the international space station . Twenty age-matched and sex-matched healthy ground-based subjects were included as a control group. Blood, urine, and saliva samples were collected before, during, and after spaceflight. Saliva was analyzed for Epstein–Barr virus, varicella-zoster virus, and herpes simplex virus type 1. Urine was analyzed for cytomegalovirus. One astronaut did not shed any targeted virus in samples collected during the three mission phases. Shedding of Epstein–Barr virus, varicella-zoster virus, and cytomegalovirus was detected in 8 of the 23 astronauts. These viruses reactivated independently of each other. Reactivation of Epstein–Barr virus, varicella-zoster virus, and cytomegalovirus increased in frequency, duration, and amplitude (viral copy numbers) when compared to short duration (10 to 16 days) space shuttle missions. No evidence of reactivation of herpes simplex virus type 1, herpes simplex virus type 2, or human herpes virus 6 was found. The mean diurnal trajectory of salivary cortisol changed significantly during flight as compared to before flight (P = 0.010). There was no statistically significant difference in levels of plasma cortisol or dehydoepiandosterone concentrations among time points before, during, and after flight for these international space station crew members, although observed cortisol levels were lower at the mid and late-flight time points. The data confirm that astronauts undertaking long-duration spaceflight experience both increased latent viral reactivation and changes in diurnal trajectory of salivary cortisol concentrations.

Imbalance in the diurnal salivary testosterone/cortisol ratio in men with severe obstructive sleep apnea: an observational study

IntroductionThe complex relationship between sleep disorders and hormones could lead to alterations in the production of cortisol and testosterone in obstructive sleep apnea (OSA) patients. ObjectiveThe purpose of this study was to determine the diurnal trajectories of salivary free-testosterone, free-cortisol and their ratio (T/C). MethodsTen subjects newly diagnosed with OSA, based on nocturnal polysomnography evaluation and excessive daytime sleepiness, and seven matched controls were consecutively recruited. Cortisol and testosterone were measured in salivary samples collected upon awakening, at noon and in the evening. The psychometric evaluation of anxiety/depression and referred sexual function disturbances was performed to evaluate the presence of neuropsychological comorbidities. Results and conclusionThe main finding was that OSA subjects displayed hypocortisolism upon awakening and a significant reduction in testosterone concentration in the evening in comparison with the control group, which has maintained the physiological testosterone and cortisol diurnal fluctuation, with higher hormone concentrations in the morning and lower concentrations in the evening. The use of data from multiple diurnal measurements rather than a single point allowed the detection of T/C ratio changes of opposite signs at the beginning and end of the day: the OSA subjects had a higher T/C ratio than the controls in the morning, while their T/C ratio was significantly lower than that of the controls in the evening. The imbalances in the anabolic-catabolic diurnal equilibrium suggest that OSA is associated with a dysregulation of the hypothalamic–pituitary–adrenal and hypothalamic–pituitary–gonadal axes, potentially an underlying cause of some of the neuropsychological comorbidities observed in OSA patients.

Salivary α-amylase and cortisol after exercise in menopause: influence of long-term HRT

Objectives This observational prospective study analyzed the effect of an incremental cardiopulmonary exercise test (CPET) on the secretion of salivary biomarkers of the adrenergic nervous system and hypothalamus–pituitary–adrenal (HPA) axis activity by measuring salivary α-amylase and cortisol diurnal trajectories in the setting of long-term hormone replacement therapy (HRT).Methods Fifteen healthy sedentary postmenopausal women who were current HRT users and 15 women who had never used HRT were consecutively recruited. α-Amylase and cortisol were measured in salivary samples collected on the CPET day and on a rest day. Cardiovascular and respiratory fitness parameters were recorded during the CPET challenge.Results The participants had very homogeneous somatic characteristics, and they were all in generally good health. The postmenopausal never-HRT users presented an abnormal diurnal pattern of α-amylase at baseline and a flattened response to CPET. In contrast, women on HRT had a physiological α-amylase diurnal pattern and increased salivary α-amylase production during the CPET-induced challenge. The CPET challenge physiologically activated the HPA axis activity, as shown by the increase in the concentration of salivary cortisol during the effort test. HPA axis activity was not affected by long-term HRT. Postmenopausal women using HRT exhibited a cardiorespiratory functional capacity that was significantly (p < 0.05) higher than that of non-users.Conclusions Our findings show that healthy postmenopausal women present an asymmetry between adrenergic nervous system and HPA axis activities under both basal and stress conditions. HRT was able to modify the abnormal adrenergic nervous system activity, most likely by reducing the sympathetic hyperactivity that characterizes menopause.

Optochemical Self-Organisation of Functional Microstructures

Our group previously reported an optochemical organization route to 3-D optical and microstructural lattices that combines the spontaneity of self-organisation to the precision and directionality of lithography. This method exploits the inherent instability of a broad, uniform beam of white light propagating in a photopolymer and its consequent division into identical filaments of light. By imposing spatially controlled noise on the light beam, the self-organizing filaments can be coaxed into 2-D and 3-D lattices. Unlike any other known self-organised or lithographically constructed structure, these lattices comprise functional, multimode and multi-wavelength cylindrical waveguides.The objective of the work presented here is to apply multidirectional waveguide lattices (MWGLs) as wide-angled, light-capturing coatings that increase the intensity of light that is incident on optical devices including photovoltaic (PV) cells. Our approach is strongly motivated by the fact that even small increments of energy conversion efficiency (<1%) of PV modules are critical in the field. Furthermore, wide-angled, light-capture could eliminate (expensive) mechanised rotation of solar panels to track the Sun’s diurnal trajectory. We employ optochemical organization to prepare elastomer films comprising up to 5 intersecting arrays of waveguide lattices, which are oriented over a large range of angles with respect to the surface normal. When integrated into solar cell devices for example, the MWGLs could capture light seamlessly over a large range of angles and deliver intensity to the photovoltaic module and in this way, could increase conversion efficiencies.

Salivary biomarkers of obstructive sleep apnea syndrome in children

The present pilot study was performed to evaluate the HPA axis and ANS activity by measuring salivary cortisol and α-amylase diurnal trajectory and production, respectively, in mild or moderate-to-severe (MS) OSA-affected, but otherwise healthy, children. Moreover, a correlative analysis was performed between the salivary biomarker concentrations and the PSG variables characterizing the OSA severity. We studied 27 consecutive OSA patients (13 mild OSA; 14 MS OSA) and seven healthy children who were enrolled as controls by collecting salivary samples and measuring cortisol and α-amylase levels using enzyme-linked bioassays. Compared with controls, both mild and MS OSA children showed: (1) increased salivary cortisol diurnal production, (2) maintenance of the physiological circadian activity of the HPA axis, and (3) no changes in α-amylase diurnal trajectory and production. In addition, morning salivary cortisol concentrations was negatively associated with the disease severity in the MS OSA group. OSA is associated with dysregulation of the HPA axis activity in children, the latter potentially underlying some of the adverse consequences of the disease.

Diurnal variation in rumination.

The present study investigated the daily fluctuation of ruminative thinking and its individual differences by using the experience sampling method. Participants recorded their thought contents and negative affect eight times a day for a week at semirandom intervals. High-trait ruminators showed high levels of self-focus, unpleasantness, and uncontrollability in their thoughts over the sampling course. These variables were interacted to predict the levels of concurrent negative affect: Self-focus was strongly associated with increased levels of negative affect when the thought was highly unpleasant and uncontrollable. A composite measure of rumination, including self-focus, unpleasantness, and uncontrollability, exhibited diurnal variation, which was assimilated by a quadratic function of time of day. However, there were differences in the estimated parameters of diurnal trajectories between high and low levels of depression, which indicated that individuals with higher levels of depression are more likely to engage in rumination in the evening, not in the morning, than those with lower levels of depression. These findings suggest that rumination in the evening would play an important role in the exacerbation and maintenance of depression.

Causes and consequences of mass loss upon predator encounter: feeding interruption, stress or fit‐for‐flight?

Abstract1. Birds have been shown to lose mass upon predator encounters. This mass loss has generally been assumed to be caused by the feeding interruption the birds experience upon encountering the predator. However, birds may lose this mass because of predator stress and because they prepare themselves for flight (fit‐for‐flight). In this experiment the aim was to distinguish between effects of feeding interruptions and stress or fit‐for‐flight on the mass loss of Yellowhammers (Emberiza citrinella L.) upon predator exposure.2. When exposed to a 45‐min feeding interruption, the birds lost only a quarter of the mass they lost when they were moved to another room and exposed to a stuffed Sparrowhawk (Accipiter nisus) for 1 min at that beginning of the feeding interruption. This indicates that mass loss upon predator exposure is not just due to the feeding interruption birds experience upon encountering a predator, but is probably, to a large extent, due to both predator stress and fit‐for‐flight.3. When the stuffed Sparrowhawk was replaced with a dummy (an opaque plastic bottle), mass loss upon exposure was similar to the loss in the Sparrowhawk treatment. This indicates that moving the birds to another room, which occurred in both these treatments, may to a large extent be the cause of the mass loss.4. During the same day, the birds regained 92% of their losses. However, regaining those losses was partly postponed to the end of the day, which indicates that the birds faced a trade‐off between starvation and predation risk, and were able to respond to that trade‐off by altering their diurnal trajectory of mass increase. By postponing foraging to the end of the day, the birds decreased the mass‐dependent costs of predation risk.

Comparison of Polar and Equatorial Magnetic Fields Near Sunspot Minimum

We investigate the polar magnetic fields near sunspot minimum using high-resolution videomagnetograph data from Big Bear Solar Observatory. To avoid the problem of center-to-limb variation of the projected longitudinal field, we compare polar with equatorial field strengths for the same limb distance. Polar fields are stronger than the quiet equatorial field, but no greater than equatorial limb data containing unipolar regions. The difference is entirely in the stronger field elements. The polar background fields are of mixed polarity but show a net weak field opposite in sign to that of the stronger polar elements. We believe this to be the first evidence of widespread background field. No dependence of the measured signal on the B-angle was found, so the high-latitude fields do not change strength near the pole. Further, there was no significant change in the polar fields in the 15-month period studied. We tried to derive a high-latitude rotation rate; our data show motion of high-latitude magnetic elements, but the diurnal trajectory is not much bigger than random motions and field changes, so the result is inconclusive. We suggest that the polar fields represent the accumulation of sunspot remnants, the elements of which last for years in the absence of other fields.

Insolation Topoclimates and Potential Ablation in Alpine Snow Accumulation Basins: Front Range, Colorado

Measurements of insolation during the Indian Peaks snowmelt season indicate that the average diurnal trajectory of solar transmission is highly asymmetric with lower values occuring in the afternoon when cloud coverage is maximum. A statistical analysis of simulated insolation suggests that topographic factors interact with prevailing sky conditions to produce a complex pattern of topoclimates within the study area. Differences between insolation topoclimates are not stationary; they depend upon timing and degree of cloud coverage as reflected in the diurnal trends of solar transmission. On an average summer day (clear morning‐cloudy afternoon), simulated insolation to north and south facing basins is roughly equivalent, while east facing basins receive the largest daily totals. These findings are important to snow hydrologists because relative (intramountain) differences in glacier ablation, and therefore potential basin melt, appear to be adjusted to the pattern of radiation that occurs on partly cloudy (not cloudless) days.