Night Cycle Research Articles

Mice deficient of glutamatergic signaling from intrinsically photosensitive retinal ganglion cells exhibit abnormal circadian photoentrainment.

Several aspects of behavior and physiology, such as sleep and wakefulness, blood pressure, body temperature, and hormone secretion exhibit daily oscillations known as circadian rhythms. These circadian rhythms are orchestrated by an intrinsic biological clock in the suprachiasmatic nuclei (SCN) of the hypothalamus which is adjusted to the daily environmental cycles of day and night by the process of photoentrainment. In mammals, the neuronal signal for photoentrainment arises from a small subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) that send a direct projection to the SCN. ipRGCs also mediate other non-image-forming (NIF) visual responses such as negative masking of locomotor activity by light, and the pupillary light reflex (PLR) via co-release of neurotransmitters glutamate and pituitary adenylate cyclase-activating peptide (PACAP) from their synaptic terminals. The relative contribution of each neurotransmitter system for the circadian photoentrainment and other NIF visual responses is still unresolved. We investigated the role of glutamatergic neurotransmission for circadian photoentrainment and NIF behaviors by selective ablation of ipRGC glutamatergic synaptic transmission in mice. Mutant mice displayed delayed re-entrainment to a 6 h phase shift (advance or delay) in the light cycle and incomplete photoentrainment in a symmetrical skeleton photoperiod regimen (1 h light pulses between 11 h dark periods). Circadian rhythmicity in constant darkness also was reduced in some mutant mice. Other NIF responses such as the PLR and negative masking responses to light were also partially attenuated. Overall, these results suggest that glutamate from ipRGCs drives circadian photoentrainment and negative masking responses to light.

A multi-imaging approach to study the root-soil interface.

Dynamic processes occurring at the soil-root interface crucially influence soil physical, chemical and biological properties at a local scale around the roots, and are technically challenging to capture in situ. This study presents a novel multi-imaging approach combining fluorescence and neutron radiography that is able to simultaneously monitor root growth, water content distribution, root respiration and root exudation. Germinated seeds of white lupins (Lupinus albus) were planted in boron-free glass rhizotrons. After 11 d, the rhizotrons were wetted from the bottom and time series of fluorescence and neutron images were taken during the subsequent day and night cycles for 13 d. The following day (i.e. 25 d after planting) the rhizotrons were again wetted from the bottom and the measurements were repeated. Fluorescence sensor foils were attached to the inner sides of the glass and measurements of oxygen and pH were made on the basis of fluorescence intensity. The experimental set-up allowed for simultaneous fluorescence imaging and neutron radiography. The interrelated patterns of root growth and distribution in the soil, root respiration, exudation and water uptake could all be studied non-destructively and at high temporal and spatial resolution. The older parts of the root system with greater root-length density were associated with fast decreases of water content and rapid changes in oxygen concentration. pH values around the roots located in areas with low soil water content were significantly lower than the rest of the root system. The results suggest that the combined imaging set-up developed here, incorporating fluorescence intensity measurements, is able to map important biogeochemical parameters in the soil around living plants with a spatial resolution that is sufficiently high enough to relate the patterns observed to the root system.

Starch productivity in cyclically operated photobioreactors with marine microalgae—effect of ammonium addition regime and volume exchange ratio

Large-scale production of microalgal storage compounds will likely involve marine microalgae. Previously, we described a method to enrich microalgae with a high storage compound productivity from a natural inoculum. Here, this strategy was implemented under marine conditions in a sequencing batch reactor. The influence of the volume exchange ratio and the moment of ammonium addition in the day–night cycle on the storage compound productivity are described. Storage compound productivity was maximal if ammonium was supplied at the start of the dark period rather than the light period, irrespective of the volume exchange ratio. Increasing the volume exchange ratio from 33 to 50 % per cycle induced a decrease in storage compound production if ammonium was supplied in the light whereas the storage compound productivity was comparable when ammonium was supplied in the dark. The latter indicates a shift of cell division processes to the light period at increasing volume exchange ratio, although ammonium uptake completely occurred in the dark period.

An insight into light as a chronobiological therapy in affective disorders

The field of chronobiology has vastly expanded over past few decades, bringing together research from fields of circadian rhythms and sleep. The importance of environmental day–night cycle on our health is becoming increasingly evident as we evolve into a 24-hour society. Reducing or changing sleep times against our natural instincts to rest at night has a detrimental impact on our well-being. The mammalian circadian clock, termed the suprachiasmatic nucleus, is responsible for synchronizing our behavioral and physiological outputs to environment. It utilizes light transcoded by specialized retinal photoreceptors as its cue to set internal rhythms to be in phase with light–dark cycle. Misalignment of these outputs results in symptoms such as altered/disturbed sleep patterns, changes in mood, and physical and mental exhaustion – symptoms shared by many affective clinical disorders. Key links to circadian abnormalities have been found in a number of disorders, such as seasonal affective disorder, nonseasonal depression, and bipolar affective disorder. Furthermore, therapies developed through chronobiological research have been shown to be beneficial in treatment of these conditions. In this article, we discuss impact of circadian research on management of affective disorders, giving evidence of how a misaligned circadian system may be a contributor to symptoms of depression and how moderating circadian rhythms with light therapy benefits patients.

Environmental and ecological controls of coral community metabolism on Palmyra Atoll

Accurate predictions of how coral reefs may respond to global climate change hinge on understanding the natural variability to which these ecosystems are exposed and to which they contribute. We present high-resolution estimates of net community calcification (NCC) and net community production (NCP) from Palmyra Atoll, an uninhabited, near-pristine coral reef ecosystem in the central Pacific. In August–October 2012, we employed a combination of Lagrangian and Eulerian frameworks to establish high spatial (~2.5 km2) and temporal (hourly) resolution coral community metabolic estimates. Lagrangian drifts, all conducted during daylight hours, resulted in NCC estimates of −51 to 116 mmol C m−2 h−1, although most NCC estimates were in the range of 0–40 mmol C m−2 h−1. Lagrangian drift NCP estimates ranged from −7 to 67 mmol C m−2 h−1. In the Eulerian setup, we present carbonate system parameters (dissolved inorganic carbon, total alkalinity, pH, and pCO2) at sub-hourly resolution through several day–night cycles and provide hourly NCC and NCP rate estimates. We compared diel cycles of all four carbonate system parameters to the offshore surface water (0–50 m depth) and show large departures from offshore surface water chemistry. Hourly Eulerian estimates of NCC aggregated over the entire study ranged from 14 to 53 mmol C m−2 h−1, showed substantial variability during daylight hours, and exhibited a diel cycle with elevated NCC in the afternoons and depressed, but positive, NCC at night. The Eulerian NCP range was very high (−55 to 177 mmol C m−2 h−1) and exhibited strong variability during daylight hours. Principal components analysis revealed that NCC and NCP were most closely aligned with diel cycle forcing, whereas the NCC/NCP ratio was most closely aligned with reef community composition. Our analysis demonstrates that ecological community composition is the primary determinant of coral reef biogeochemistry on a near-pristine reef and that reef biogeochemistry is likely to be responsive to human behaviors that alter community composition.

A fast line-scanning-based detection algorithm for real-time SAR ship detection

Synthetic aperture radar (SAR) provides a powerful surveillance capability allowing the observation of target, independently from weather effects and from the day and night cycle. Unfortunately, the automatic interpretation of SAR images is often complicated and time consuming. In support of real-time vessel monitoring, a fast line-scanning detector designed for detecting ships from SAR imagery is proposed in this paper. The detector does not require any prior knowledge about ships and background observation. It uses a novel local gray-level gathering degree algorithm to detect potential targets and then a complementary filtering scheme to reject false alarms. The performance analysis over real SAR images confirms that the proposed detector works well in various circumstances with high detection rate, fast detection speed and perfect shape preservation.

Epidemic threshold determined by the first moments of network with alternating degree distributions

During the alternating day–night cycle, people have differing behavior and hence different connection patterns—such as going to work or home, shopping and so on. Hence, the true topological structure of human contact networks are not only time-varying but also exhibit certain distribution regularity. In this paper, we will investigate epidemic spreading on time-varying human contact networks, which follow one degree distribution during daytime, but another at night. Based on SIS (susceptible/infected/susceptible) propagation mechanism, we study the epidemic threshold of this network with alternating distributions. A surprising result is that for the discrete-time case the epidemic threshold is determined only by the first moments of the two alternating degree distributions, if the degree of each node is constant for all nights. A similar result is valid for the continuous-time case if the duration is sufficiently small. This work shows that the spreading dynamics of time-varying networks with alternating distributions is completely different from the widely studied case of static spreading networks.

Running on time: the role of circadian clocks in the musculoskeletal system.

The night and day cycle governs the circadian (24 hourly) rhythm of activity and rest in animals and humans. This is reflected in daily changes of the global gene expression pattern and metabolism, but also in the local physiology of various tissues. A central clock in the brain co-ordinates the rhythmic locomotion behaviour, as well as synchronizing various local oscillators, such as those found in the musculoskeletal system. It has become increasingly recognized that the internal molecular clocks in cells allow a tissue to anticipate the rhythmic changes in their local environment and the specific demands of that tissue. Consequently, the majority of the rhythmic clock controlled genes and pathways are tissue specific. The concept of the tissue-specific function of circadian clocks is further supported by the diverse musculoskeletal phenotypes in mice with deletions or mutations of various core clock components, ranging from increased bone mass, dwarfism, arthropathy, reduced muscle strength and tendon calcification. The present review summarizes the current understanding of the circadian clocks in muscle, bone, cartilage and tendon tissues, with particular focus on the evidence of circadian rhythms in tissue physiology, their entrainment mechanisms and disease links, and the tissue-specific clock target genes/pathways. Research in this area holds strong potential to advance our understanding of how circadian rhythms control the health and disease of the musculoskeletal tissues, which has major implications in diseases associated with advancing age. It could also have potential implications in sports performance and sports medicine.

Relative roles of endolithic algae and carbonate chemistry variability in the skeletal dissolution of crustose coralline algae

Abstract. The susceptibility of crustose coralline algae (CCA) skeletons to dissolution is predicted to increase as oceans warm and acidify. Skeletal dissolution is caused by bioerosion from endolithic microorganisms and by chemical processes associated with undersaturation of carbonate minerals in seawater. Yet, the relative contribution of algal microborers and seawater carbonate chemistry to the dissolution of organisms that cement reefs under projected pCO2 and temperature (pCO2-T) scenarios have not been quantified. We exposed CCA skeletons (Porolithon onkodes) to four pCO2-T treatments (pre-industrial, present-day, SRES-B1 "reduced" pCO2, and SRES-A1FI "business-as-usual" pCO2 emission scenarios) under natural light cycles vs. constant dark conditions for 8 weeks. Dissolution rates of skeletons without photo-endoliths were dramatically higher (200%) than those colonized by endolithic algae across all pCO2-T scenarios. This suggests that daytime photosynthesis by microborers counteract dissolution by reduced saturation states resulting in lower net erosion rates over day–night cycles. Regardless of the presence or absence of phototrophic microborers, skeletal dissolution increased significantly under the spring A1FI "business-as-usual" scenario, confirming the CCA sensitivity to future oceans. Projected ocean acidity and temperature may significantly disturb the stability of reef frameworks cemented by CCA, but surficial substrates harbouring photosynthetic microborers will be less impacted than those without algal endoliths.

Effect of temperature on growth and paralytic toxin profiles in isolates of Gymnodinium catenatum (Dinophyceae) from the Pacific coast of Mexico

The effects of temperature on growth, cell toxicity, toxin content, and profile of paralytic shellfish toxins was determined in eight isolates of Gymnodinium catenatum from several localities along the Pacific Coast of Mexico. The isolates were cultivated in modified f/2 media with Se (10−8 M), and a reduced concentration of Cu (10−8 M), under a 12 h:12 h day–night cycle with an irradiance of 150 μE m−2 s−1. Isolates were progressively adapted for three generations to each of the temperatures (16, 19, 22, 24, 27, 30, and 33 °C). The cultures were grown in 125 mL Erlenmeyer flasks with 60 mL of media and harvested by filtration in late exponential growth. Toxins were analyzed by HPLC with a post-column oxidation and fluorescent detection (FLD). G. catenatum isolates tolerate temperatures between 16 and 33 °C, with maximum growth rates of 0.32 and 0.39 div day−1 at 21 °C and 24 °C, respectively; maximum cell densities of 4700 and 5500 cells mL−1 were obtained at 27 and 21 °C, respectively. No effect of toxicity per cell with temperature was observed, varying between 10.10 and 28.19 pgSXTeq cell−1. Ten saxitoxin analogues were detected in all isolates, observing changes in the toxin profile with temperature. C1/2 toxins decreased from 80% mol at 16 °C to 20% mol at 33 °C, B1/2 toxins increased from 19% mol at 16 °C to 42% mol at 33 °C, and decarbamoyl toxins were more abundant at 21 °C. These results show that G. catenatum isolates from different regions of the Pacific coast of Mexico have a similar response to temperature and that this parameter can modify growth rate, cell density, and toxin profile of the species, particularly the decarbamoyl and sulfocarbamoyl toxins.

Recognizing changes in cognition in sub types of acute confusional state.

Delirium or acute confusional state is an acute neuropsychiatric syndrome, with varied cognitive dysfunctions. However, no comprehensive studies about this common condition have been carried out in India. To assess cognitive dysfunctions in hypoactive and hyperactive delirium. Forty cases of delirium including hypoactive and hyperactive delirium and 40 other patients (neuropsychiatric patients) were studied as controls. Cognitive status estimation test, mini mental state examination and memorial delirium assessment scale were administered to each patient. All assessments were carried out three times in 24 hour cycle of day and night. The data was analysed using two sample independent t-test. The mean age (standard deviation) of study and control group was 27.85 (13.73) and 33.10 (11.26) years respectively. 70% patients had hyperactive delirium while 30% were having hypoactive delirium. Hypoactive delirium had more cognitive impairment compared to hyperactive delirium (p=0.001). The difference between highest and lowest score of MMSE in both types of delirium (day to night) was found to be statically significant (p=0.001). The fluctuation in intensity of cognitive symptoms varies from day to night in both types of delirium, but more in hypoactive delirium and wider fluctuation in cognitive dysfunctions was noted in delirium cases with psychosis.

Inter- and intra-specific diurnal habitat selection of zooplankton during the spring bloom observed by Video Plankton Recorder

Diel vertical migration (DVM) is a common behavior adopted by zooplankton species. DVM is a prominent adaptation for avoiding visual predation during daylight hours and still being able to feed on surface phytoplankton blooms during night. Here, we report on a DVM study using a Video Plankton Recorder (VPR), a tool that allows mapping of vertical zooplankton distributions with a far greater spatial resolution than conventional zooplankton nets. The study took place over a full day–night cycle in Disko Bay, Greenland, during the peak of the phytoplankton spring bloom. The sampling revealed a large abundance of copepods performing DVM (up during night and down during day). Migration behavior was expressed differently among the abundant groups with either a strong DVM (euphausiids), an absence of DVM (i.e., permanently deep; ostracods) or a marked DVM, driven by strong surface avoidance during the day and more variable depth preferences at night (Calanus spp.). The precise individual depth position provided by the VPR allowed us to conclude that the escape from surface waters during daytime reduces feeding opportunities but also lowers the risk of predation (by reducing the light exposure) and thereby is likely to influence both state (hunger, weight and stage) and survival. The results suggest that the copepods select day and night time habitats with similar light levels (~10−9 μmol photon s−1 m−2). Furthermore, Calanus spp. displayed state-dependent behavior, with DVM most apparent for smaller individuals, and a deeper residence depth for the larger individuals.

Implications of physical key factors in the early rearing of the long-snouted seahorse Hippocampus guttulatus

Abstract Although breeding conditions are rather well established for some seahorse species ( Hippocampus spp.), zootechnics and the effect of non-biological factors are still unknown for many species. The present study is focussed on the effects of aquarium type/design, photoperiod regime and aeration level on the early performance (growth and survival) of Hippocampus guttulatus juveniles. Three aquarium types were evaluated: pseudoKreisel, spherical and rectangular. Juveniles grown in pseudoKreisel aquaria showed lower growth rates but significantly higher survivals (69 ± 15%) at day 30 after male's pouch release (DAR) when compared to either spherical (30 ± 22%) or rectangular (16 ± 12%) aquaria. Survival enhancement in pseudoKreisel aquaria was mainly related to the very lower proportion of juveniles showing swim bladder hyperinflation during the first days of life. Conversely, the other aquarium types did not avoid juveniles to remain near water surface and to gulp air in excess for swim bladder inflation. The effects of light regime and aeration level were assayed in H. guttulatus juveniles reared in all three aquarium types or in pseudoKreisel aquaria only, respectively. In general, the application of extended (continuous light) or natural photoperiods (day–night cycle; 16 h light:8 h dark) did not affect survival nor growth significantly. On the other hand, aeration levels in pseudoKreisel aquaria significantly affected juvenile survival. Survivals in 30 day old seahorses reared under a strong aeration were significantly higher (41 ± 12%) than when reared under weak aeration (13 ± 0%). Strong aeration levels enhanced the distribution of juveniles in the aquaria and diminished both their over-exposition to water surface and the resulting appearance of hyperinflation problems. The overall results suggest that the best rearing conditions were met when H. guttulatus juveniles grew in pseudoKreisel aquaria under both a strong aeration level and, to a lesser extent, a natural photoperiod regime, due to a slight enhancement in seahorse juvenile performance.

Temporal and environmental influences on the vocal behaviour of a nocturnal bird

Temporal and environmental variation in vocal activity can provide information on avian behaviour and call function not available to short‐term experimental studies. Inter‐sexual differences in this variation can provide insight into selection effects. Yet factors influencing vocal behaviour have not been assessed in many birds, even those monitored by acoustic methods. This applies to the New Zealand kiwi (Apterygidae), for which call censuses are used extensively in conservation monitoring, yet which have poorly understood acoustic ecology. We investigated little spotted kiwi Apteryx owenii vocal behaviour over 3 yr, measuring influences on vocal activity in both sexes from time of night, season, weather conditions and lunar cycle. We tested hypotheses that call rate variation reflects call function, foraging efficiency, historic predation risk and variability in sound transmission, and that there are inter‐sexual differences in call function. Significant seasonal variation showed that vocalisations were important in kiwi reproduction, and inter‐sexual synchronisation of call rates indicated that contact, pair‐bonding or resource defence were key functions. All weather variables significantly affected call rates, with elevated calling during increased humidity and ground moisture indicating a relation between vocal activity and foraging conditions. A significant decrease in calling activity on cloudy nights, combined with no moonlight effect, suggests an impact of light pollution in this species. These influences on vocal activity provide insight into kiwi call function, have direct consequences for conservation monitoring of kiwi, and have wider implications in understanding vocal behaviour in a range of nocturnal birds.

Molecular mechanisms of the circadian clockwork in mammals.

Circadian rhythms enable organisms to co-ordinate biological processes with the predictable 24 h cycle of day and night. Given that molecular clocks that coordinate such biological timing have evolved in almost all organisms, it is clear that being synchronous with the external environment confers competitive advantage. Conversely, it is apparent that being out of phase is detrimental, resulting in a number of clinical conditions, many of which are linked to metabolic dysfunction. The canonical clockwork involves a core set of genes that negatively regulate themselves through a so-called transcription translation feedback loop. However, recent studies describing evolutionarily conserved oscillations in redox reactions link circadian rhythms to metabolic processes, and in particular, redox pathways. In this review we describe the evidence for the interaction between transcriptional loops, redox and metabolism in mammals and suggest the clock may be potential target for the treatment of disease.

Sensitivity of housekeeping genes in the suprachiasmatic nucleus of the mouse brain to diet and the daily light–dark cycle

The endogenous timing system within the suprachiasmatic nuclei (SCN) of the hypothalamus drives the cyclic expression of the clock molecules across the 24h day–night cycle controlling downstream molecular pathways and physiological processes. The developing fetal clock system is sensitive to the environment and physiology of the pregnant mother and as such disruption of this system could lead to altered physiology in the offspring. Characterizing the gene profiles of the endogenous molecular clock system by quantitative reverse transcription polymerase chain reaction is dependent on normalization by appropriate housekeeping genes (HKGs). However, many HKGs commonly used as internal controls, although stably expressed under control conditions, can vary significantly in their expression under certain experimental conditions. Here we analyzed the expression of 10 classic HKG across the 24h light–dark cycle in the SCN of mouse offspring exposed to normal chow or a high fat diet during early development and in postnatal life. We found that the HKGs glyceraldehyde-3-phosphate dehydrogenase, beta actin and adenosine triphosphate synthase subunit to be the most stably expressed genes in the SCN regardless of diet or time within the 24h light–dark cycle, and are therefore suitable to be used as internal controls. However SCN samples collected during the light and dark periods did show differences in expression and as such the timing of collection should be considered when carrying out gene expression studies.

White Rust of Echinacea angustifolia and E. purpurea in North America Caused by a Pustula Species.

In 2012 and 2013, foliar symptoms were observed in certified organic, 2- to 4-ha crops of Echinacea angustifolia and E. purpurea in Grant and Klickitat counties, WA. White pustules were predominant on the abaxial leaf surface, increased in number, and coalesced on E. angustifolia, with 100% infection by the end of the season; in contrast, symptoms remained sparse on E. purpurea. Symptomatic leaves of each species were collected in May 2013 in Grant Co. Sori and sporangia were typical of those of white rust on Asteraceae caused by Pustula obtusata (1), originally named Albugo tragopogonis, then P. tragopogonis (4). Hyaline sporangia (n = 50) averaged 21 ± 2 × 20 ± 2 μm (16 to 25 × 16 to 24 μm) with a 2.6 ± 0.8 μm (1.0 to 4.0 μm) thick wall. Honey-colored to dark brown oospores were embedded in the abaxial leaf surface surrounding sori on older leaves. Oospores (n = 50) averaged 75 ± 7 × 63 ± 6 μm (60 to 96 × 52 to 76 μm) and 52 ± 4 × 51 ± 4 μm (44 to 65 × 44 to 60 μm) with (including protruberances) and without the hyaline outer wall, respectively. Sori were excised and shaken in 100 ml cold (4°C), deionized water at 400 rpm for 15 min on a gyrotory shaker. DNA extracted from the resulting spore suspension was subjected to a PCR assay using oomycete specific primers (2) to amplify the cytochrome oxidase subunit II (cox2) region of mtDNA (3). The 511-nt consensus sequence of the PCR product (GenBank Accession No. KF981439) was 98% identical to a cox2 sequence of A. tragopogonis from sunflower (Helianthus annuus) (AY286221.1), and 96% identical to cox2 sequences of P. tragopogonis (GU292167.1 and GU292168.1) (= P. obtusata) (1,2,4). Pathogenicity of the white rust isolate was confirmed by inoculating 49-day-old plants of E. angustifolia and E. purpurea with a spore suspension prepared as described above. One plant/species was placed in each of six clear plastic bags in a growth chamber at 18°C with a 12-h day/12-h night cycle for 48 h. Five replicate sets of one plant/species were each inoculated with 2.2 × 105 spores/ml on the adaxial and abaxial leaf surfaces using an airbrush (8 psi). One plant/species was sprayed with water as a control treatment. The plants were resealed in the bags for 48 h. After 7 days, white pustules were observed on at least one plant species. The plants were placed in plastic bags again overnight, and re-inoculated with 2.9 × 105 spores/ml. In addition, two sunflower plants at the 4-true-leaf stage were incubated in each of two plastic bags overnight, and inoculated with the spore suspension. Two additional sunflower plants were treated with water as control plants. All plants were removed from the bags after 48 h. White rust sori with sporangia developed on all inoculated Echinacea plants within 10 days, but not on control plants of either species, nor inoculated and non-inoculated sunflower plants, verifying that the pathogen was not P. helianthicola (1,2). Since the cox2 sequence was closest to that of a sunflower white rust isolate, the pathogen appears to be closer to P. helianthicola than P. obtusata, and may be a new Pustula species. To our knowledge, this is the first documentation of white rust on E. angustifolia and E. purpurea in North America. The severity of white rust on E. angustifolia highlights the need for effective management practices.

Preferred Temperature, Thermal Tolerance, and Metabolic Response of Tegula Regina (Stearns, 1892)

The preferred temperature of Tegula regina was determined in a horizontal thermal gradient with organisms acclimated to 16C, 19C, and 22C using to acute method, with a preferred temperature of 19.7± 1.8C for the day cycle and 18.8± 1.2C for the night cycle. The final preferred temperature determined for marine snails was 19.2 ± 1.5C. The displacement velocity decreased to an interval from 99.1 cm/h to 62.5 cm/h. During the third hour, when organisms detected the preferred temperature, the velocity diminished gradually from 25.8 cm/h to 7.5 cm/h. Critical temperature maxima (CTMax), which refers to the temperature at which at least 50% of the experimental group displays a loss of attachment, was measured at three acclimation temperatures (16C, 19C, and 22C). At the acclimation temperature (16C), 50% of the experimental group had an attachment loss at a CTMax of 29.3C. At a warmer acclimation temperature (22C), the observed CTMax was 31.2C. Marine snail oxygen consumption rate increased significantly (P < 0.05, 31%) from 16 Ct o 22C.

Current–voltage characteristics of a cathodic plasma contactor with discharge chamber for application in electrodynamic tether propulsion

This paper focuses on the net electron-emission current as a function of bias voltage of a plasma source that is being used as the cathodic element in a bare electrodynamic tether system. An analysis is made that enables an understanding of the basic issues determining the current–voltage (C–V) behaviour. This is important for the efficiency of the electrodynamic tether and for low impedance performance without relying on the properties of space plasma for varying orbital altitudes, inclinations, day–night cycles or the position of the plasma contactor relative to the wake of the spacecraft. The cathodic plasma contactor considered has a cylindrical discharge chamber (10 cm in diameter and ∼11 cm in length) and is driven by a hollow cathode. Experiments and a 1D spherical model are both used to study the contactor's C–V curves. The experiments demonstrate how the cathodic contactor would emit electrons into space for anode voltages in the range of 25–40 V, discharge currents in the range of 1–2.5 A, and low xenon gas flows of 2–4 sccm. Plasma properties are measured and compared with (3 A) and without net electron emission. A study of the dependence of relevant parameters found that the C–V behaviour strongly depends on electron temperature, initial ion energy and ion emission current at the contactor exit. However, it depended only weakly on ambient plasma density. The error in the developed model compared with the experimental C–V curves is within 5% at low electron-emission currents (0–2 A). The external ionization processes and high ion production rate caused by the discharge chamber, which dominate the C–V behaviour at electron-emission currents over 2 A, are further highlighted and discussed.

Time-restricted feeding and the realignment of biological rhythms: translational opportunities and challenges.

It has been argued that circadian dysregulation is not only a critical inducer and promoter of adverse health effects, exacerbating symptom burden, but also hampers recovery. Therefore understanding the health-promoting roles of regulating (i.e., restoring) circadian rhythms, thus suppressing harmful effects of circadian dysregulation, would likely improve treatment. At a critical care setting it has been argued that studies are warranted to determine whether there is any use in restoring circadian rhythms in critically ill patients, what therapeutic goals should be targeted, and how these could be achieved. Particularly interesting are interventional approaches aiming at optimizing the time of feeding in relation to individualized day–night cycles for patients receiving enteral nutrition, in an attempt to re-establish circadian patterns of molecular expression. In this short review we wish to explore the idea of transiently imposing (appropriate, but yet to be determined) circadian rhythmicity via regulation of food intake as a means of exploring rhythm-setting properties of metabolic cues in the context of improving immune response. We highlight some of the key elements associated with his complex question particularly as they relate to: a) stress and rhythmic variability; and b) metabolic entrainment of peripheral tissues as a possible intervention strategy through time-restricted feeding. Finally, we discuss the challenges and opportunities for translating these ideas to the bedside.