Free-running Conditions Research Articles

Daily Light Exposure Patterns Reveal Phase and Period of the Human Circadian Clock.

Light is the most potent time cue that synchronizes (entrains) the circadian pacemaker to the 24-h solar cycle. This entrainment process is an interplay between an individual’s daily light perception and intrinsic pacemaker period under free-running conditions. Establishing individual estimates of circadian phase and period can be time-consuming. We show that circadian phase can be accurately predicted (SD = 1.1 h for dim light melatonin onset, DLMO) using 9 days of ambulatory light and activity data as an input to Kronauer’s limit-cycle model for the human circadian system. This approach also yields an estimated circadian period of 24.2 h (SD = 0.2 h), with longer periods resulting in later DLMOs. A larger amount of daylight exposure resulted in an earlier DLMO. Individuals with a long circadian period also showed shorter intervals between DLMO and sleep timing. When a field-based estimation of tau can be validated under laboratory studies in a wide variety of individuals, the proposed methods may prove to be essential tools for individualized chronotherapy and light treatment for shift work and jetlag applications. These methods may improve our understanding of fundamental properties of human circadian rhythms under daily living conditions.

Simultaneous oscillations of twelve wavelengths around 1.3 μm in quasi-CW Nd:YAG laser

In this work, a simple cavity configuration for simultaneous observation of twelve oscillating wavelengths around 1.3µm in a quasi-CW side pumped Nd:YAG laser is proposed and demonstrated experimentally. The experiment has been studied in free running condition and by placing a position tunable Brewster plate within a linear cavity where new wavelengths viz. 1318.71nm, 1338.14nm, 1338.16nm, 1338.18nm, 1338.21nm, 1338.23nm, 1338.25nm and 1338.27nm have been observed. By introducing a Brewster plate within the cavity it is possible to maintain almost equal spectral contributions around 1318nm and 1338nm wavelength’s regions at the highest as well as lowest pump power levels. The maximum average output power of 20W and 13.87W at slope efficiencies of 42.22% and 35.37% are obtained in both conditions respectively. In this work it is also possible to measure the average output powers around 1319nm and 1338nm regions simultaneously at different average pump powers. The experimental results indicate the higher and better stability of power contributions of observed oscillating wavelengths around 1.3µm. The beam quality factor varies from 1.11 to 1.44 with the rise in average pump power simultaneously. The proposed work may enhance the application of 1.3µm laser in spectroscopic field and tunable laser generation. Moreover, by difference frequency mixing within these closely spaced wavelengths this configuration may also be a good source of coherent THz generation.

Emission Characteristics of Laser-Induced Plasma Using Collinear Long and Short Dual-Pulse Laser-Induced Breakdown Spectroscopy (LIBS).

Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.

Disrupted Ultradian Activity Rhythms and Differential Expression of Several Clock Genes in Interleukin-6-Deficient Mice.

The characteristics of the cycles of activity and rest stand out among the most intensively investigated aspects of circadian rhythmicity in humans and experimental animals. Alterations in the circadian patterns of activity and rest are strongly linked to cognitive and emotional dysfunctions in severe mental illnesses such as Alzheimer’s disease (AD) and major depression (MDD). The proinflammatory cytokine interleukin 6 (IL-6) has been prominently associated with the pathogenesis of AD and MDD. However, the potential involvement of IL-6 in the modulation of the diurnal rhythms of activity and rest has not been investigated. Here, we set out to study the role of IL-6 in circadian rhythmicity through the characterization of patterns of behavioral locomotor activity in IL-6 knockout (IL-6 KO) mice and wild-type littermate controls. Deletion of IL-6 did not alter the length of the circadian period or the amount of locomotor activity under either light-entrained or free-running conditions. IL-6 KO mice also presented a normal phase shift in response to light exposure at night. However, the temporal architecture of the behavioral rhythmicity throughout the day, as characterized by the quantity of ultradian activity bouts, was significantly impaired under light-entrained and free-running conditions in IL-6 KO. Moreover, the assessment of clock gene expression in the hippocampus, a brain region involved in AD and depression, revealed altered levels of cry1, dec2, and rev-erb-beta in IL-6 KO mice. These data propose that IL-6 participates in the regulation of ultradian activity/rest rhythmicity and clock gene expression in the mammalian brain. Furthermore, we propose IL-6-dependent circadian misalignment as a common pathogenetic principle in some neurodegenerative and neuropsychiatric disorders.

Application of the Acoustic Emission Method for Diagnosis of On-Load Tap Changer

Abstract This paper provides an example of the application of the acoustic emission (AE) method for the diagnosis of technical conditions of a three-phase on-load tap-changer (OLTC) GIII type. The measurements were performed for an amount of 10 items of OLTCs, installed in power transformers with a capacity of 250 MVA. The study was conducted in two different OLTC operating conditions during the tapping process: under load and free running conditions. The analysis of the measurement results was made in both time domain and time-frequency domain. The description of the AE signals generated by the OLTC in the time domain was performed using the analysis of waveforms and determined characteristic times. Within the time-frequency domain the measured signals were described by short-time Fourier transform spectrograms.

Amplification of a nanosecond laser pulse chain via dynamic injection locking of a laser diode.

We report a novel optical pulse generation method for high-speed wavelength switching of amplified nanosecond (ns) laser pulses resonant to atomic transitions. Under free-running conditions, a slave laser diode is blue-detuned with tens of GHz relative to the master laser. A nanosecond pulse chain generated by modulating the continuous-wave master laser with a fiber-pigtailed electro-optical intensity modulator is injected into the slave laser diode to fast switch the slave laser's wavelength back and forth. The output beam of the slave laser is filtered by a temperature-controlled etalon to get the amplified pulse chain. Based on our dynamic injection locking scheme, we produce an ns-scale square pulse chain with an effective ON/OFF ratio ∼108, considering at least the 60 dB scattering suppression by tuning the light-atom interactions with far off-resonance detuning and the 26.7 dB suppression ratio of the etalon. By studying the dynamic processes of injection locking, we determine the dependence of injection locking on both the injection power and the frequency detuning.

Impact of Ataxin-2 knock out on circadian locomotor behavior and PER immunoreaction in the SCN of mice

ABSTRACTIn Drosophila melanogaster, Ataxin-2 is a crucial activator of Period and is involved in the control of circadian rhythms. However, in mammals the function of Ataxin-2 is unknown despite its involvement in the inherited neurogenerative disease Spinocerebellar Ataxia type 2 in humans. Therefore, we analyzed locomotor behavior of Atxn2-deficient mice and their WT littermates under entrained- and free-running conditions as well as after experimental jet lag. Furthermore, we compared the PER1 and PER2 immunoreaction (IR) in the SCN. Atxn2−/− mice showed an unstable rhythmicity of locomotor activity, but the level of PER1 and PER2 IR in the SCN did not differ between genotypes.

Investigation of PCM as retrofitting option to enhance occupant thermal comfort in a modern residential building

This study investigated the feasibility of PCM as a retrofitting option to reduce the zone air temperature and improve occupant thermal comfort under free running condition in an existing house in Melbourne, Australia. Both the experimental and numerical approach were applied in this study. In the experimental study, PCM was installed in the ceiling of one of the rooms and indoor air temperatures of two rooms (one with PCM and the other without PCM) were recorded. A simulation model was developed using building simulation software EnergyPlus and validated using the recorded experimental temperature data. The results showed up to 1.1°C reduction in BED 2 indoor air temperature during daytime and 34% reduction in thermal discomfort hours through the passive installation of PCM on the ceilings. Several simulations including different user behaviour scenario (windows and internal door operations) were carried out to identify the influence of user behaviour on the effectiveness of PCM. It was observed that integration of PCM is more effective in reducing thermal discomfort hours if windows are kept open at night for night purging and the internal doors are remained closed at all time to prohibit any mixing with surrounding zones without PCM. Further improvement in PCM effectiveness was observed when similar amount of PCM was spread in the ceiling and walls.

A quantitative study of the climate-responsive design strategies of ancient timber-frame halls in northern China based on field measurements

The risks of global warming and the depletion of fossil fuels call for a re-examination of traditional buildings, which have shown satisfactory climate adaptability. Although vernacular dwellings have received considerable attention, few studies investigate other building types. In this paper, the thermal environments of ancient timber-frame halls in northern China were investigated based on field measurements to obtain more evidence of traditional ecological ideology and related strategies. As one of the main types of public buildings in ancient China, six typical halls with different orientations, openings, and ceilings but similar spatial scales and materials were selected; their air temperature, relative humidity (RH), air speed, surface temperature, and globe temperature on typical summer and winter days were measured. The results show that the indoor air temperature of the ancient halls under free-running conditions fluctuated between 22.52 and 29.46°C in summer and between −8.91 and −2.64°C in winter, meaning that the indoor environments are comfortable in summer but too cold in winter according to GB/T 50785-2012, which is the Chinese standard for evaluating indoor thermal environments. Further analysis shows that the key strategy for comfort in summer is to have high heat capacity to provide shelter from hot air and solar gains; natural ventilation is considered to be merely an auxiliary approach. Climate-responsive design strategies for winter consist of a south-facing orientation with a maximum window-to-wall ratio and significant thermal insulation to utilize solar gains and to provide shelter from cold air. In addition, the results reveal that ancient halls are limited in their ability to use climatic resources due to technical restrictions.

Genomic Analysis Reveals Contrasting PIFq Contribution to Diurnal Rhythmic Gene Expression in PIF-Induced and -Repressed Genes

Members of the PIF quartet (PIFq; PIF1, PIF3, PIF4, and PIF5) collectively contribute to induce growth in Arabidopsis seedlings under short day (SD) conditions, specifically promoting elongation at dawn. Their action involves the direct regulation of growth-related and hormone-associated genes. However, a comprehensive definition of the PIFq-regulated transcriptome under SD is still lacking. We have recently shown that SD and free-running (LL) conditions correspond to “growth” and “no growth” conditions, respectively, correlating with greater abundance of PIF protein in SD. Here, we present a genomic analysis whereby we first define SD-regulated genes at dawn compared to LL in the wild type, followed by identification of those SD-regulated genes whose expression depends on the presence of PIFq. By using this sequential strategy, we have identified 349 PIF/SD-regulated genes, approximately 55% induced and 42% repressed by both SD and PIFq. Comparison with available databases indicates that PIF/SD-induced and PIF/SD-repressed sets are differently phased at dawn and mid-morning, respectively. In addition, we found that whereas rhythmicity of the PIF/SD-induced gene set is lost in LL, most PIF/SD-repressed genes keep their rhythmicity in LL, suggesting differential regulation of both gene sets by the circadian clock. Moreover, we also uncovered distinct overrepresented functions in the induced and repressed gene sets, in accord with previous studies in other examined PIF-regulated processes. Interestingly, promoter analyses showed that, whereas PIF/SD-induced genes are enriched in direct PIF targets, PIF/SD-repressed genes are mostly indirectly regulated by the PIFs and might be more enriched in ABA-regulated genes.

Yb-fiber laser pumped high-power, broadly tunable, single-frequency red source based on a singly resonant optical parametric oscillator.

We present an efficient and tunable source generating multi-watt single-frequency red radiation by intra-cavity frequency doubling of the signal in a MgO-doped periodically poled LiNbO3 (MgO:PPLN)-based singly resonant optical parametric oscillator (SRO). By optimally designing the SRO cavity in a six-mirror configuration, we generate ≈276 nm tunable idler radiation in mid-infrared with a maximum power of Pi=2.05 W at a pump power of Pp=14.0 W. The resonant signal is frequency doubled using a 10 mm-long BiB3O6 (BiBO) crystal which resulted in tunability of a red beam from ≈753 to 780 nm band with maximum power Pr≈4.0 W recorded at λr≈756 nm. The deployment of a six-mirror SRO ensures single-frequency generation of red across the entire tuning range by inducing additional losses to Raman modes of LiNbO3 and, thus, inhibiting their oscillation. Using a scanning Fabry-Perot interferometer (FPI), nominal linewidth of the red beam is measured to ≈3 MHz which changes marginally over the entire tuning range. Long-term (over 1 h) peak-to-peak frequency fluctuation of the generated red beam is estimated to be about 3.3 GHz under free-running conditions at Pp=14.0 W. The generated red beam is delivered in a TEM00 mode profile with M2≤1.32 at maximum power in a red beam.

Spectrum Improvement of a High-Power Broad-Area Laser Diode Based on a Grating Semi-Feedback External Cavity Scheme

We propose a grating semi-feedback external cavity (GSFEC) scheme for high-power broad-area laser diodes for improving the spectrum characteristics of high-power semiconductor lasers. We design this scheme as two crossed cylindrical resonators employing a holographic diffraction grating and a rectangular highly reflecting mirror. In our experiments, we obtain stable spectrum characteristics over a tuning range of 5 nm, with maximum output power up to 764 mW at an operating current of 3.5 A. The wavelength drift rate with injection current decreases from 0.59 nm/A of free-running condition to 0.2 nm/A, and the laser bandwidth is compressed to 21.5% at 2 A.

Timed food availability affects circadian behavior but not the neuropeptide Y expression in Indian weaverbirds exposed to atypical light environment

We tested the hypothesis whether daily food availability period would restore rhythmicity in individuals with disrupted circadian behavior with no effect on appetite regulation. Particularly, we investigated the effects of timed food availability on activity behavior, and Fos and neuropeptide Y expressions in Indian weaverbirds (Ploceus philippinus) under atypical light conditions. Initially, weaverbirds in 3 groups of 7–8 each were entrained to 7L:17D (25: <0.3lx) with food ad libitum. Thereafter, food availability was restricted for 7h such that it overlapped with the light period. After a week, 7L:17D was replaced with 3.5L: 3.5D (T7, group 1), 3.5L: 20.5D (T24, group 2) or constant dim light, LLdim (<0.3lx, group 3) for 5weeks. Food cycles synchronized the circadian activity behavior, albeit with group differences, but did not affect body mass, blood glucose levels or testis size. Further, Fos, not NPY mRNA or peptide, expression measured at ZT2 and ZT14 (ZT0=time of food given) showed significant group differences in the hippocampus, dorsomedial hypothalamus and infundibular nuclear complex. Another identical experiment examined after-effects of the 3 light conditions on persistence of the circadian rhythms. Weaverbirds exposed for 4weeks to identical food but different light conditions, as above, were released into the free-running condition of food ad libitum and LLdim. Circadian rhythms were decayed in birds previously exposed to T7 LD cycle. Overall, these results show that timed meal restores rhythmicity in individuals with circadian rhythm disruptions without involving neuropeptide Y, the key appetite regulatory molecule.

The adoption of green roofs for the retrofitting of existing buildings in the Mediterranean climate

AbstractIn recent years, the demand for air conditioning systems has increased considerably. Consequentially, the energy demand for building cooling has become a serious concern. In particular, the energy peak demand that is intensified by the urban heat island (UHI) effect is often a critical issue for the outdated electricity infrastructure in many countries. In order to rationalize the building energy consumption while ensuring indoor thermal comfort, this paper explores the possibilities offered by the retrofitting of existing uninsulated roofs in combination with night natural cooling strategies. To this end, a case study was selected in order to investigate the performance of an extensive green roof (GR) with and without natural ventilation (NV). The selected building is located in Catania, southern Italy, in a very mild climate. Free-running conditions were evaluated together with air conditioning conditions during the daytime and free cooling via natural ventilation at night. The hourly variation ...

Seasonality in circadian locomotor activity and serum testosterone level in the subtropical tree sparrow (Passer montanus)

Seasonality in daily locomotor activity pattern was investigated in the subtropical tree sparrow by exposing a group of birds to natural day lengths (NDL) for 30days and another group to 12L/12D for 14days followed by transfer to constant dim light (LLdim) for another 15days in four different seasons of the year. Serum testosterone levels were also measured during different seasons. Sparrows, under NDL, exhibited distinct circadian rhythmicity in their locomotor activity with almost similar general pattern in different seasons that restricted mainly to the light hours. However, they showed season-dependent differences in the characteristics of circadian locomotor activity rhythm. Birds, when exposed to 12L/12D, showed entrainment of their locomotor activity rhythm with the activity confined mainly during the light phase. Though, tau (τ) under free run conditions did not show any significant difference, the activity period varied significantly in different seasons. The highest level of testosterone was recorded in the spring season that corresponded with the maximum locomotor activity in spring months. The seasonality in daily locomotor activity correlates with the seasonal changes in testosterone levels suggesting the influence of gonadal steroids on endogenous circadian system which is indicative of adaptation of tree sparrow to local photoperiodic conditions.

Frequency stabilization of an optically pumped far-infrared laser to the harmonic of a microwave synthesizer.

Measurements of the frequency stability of a far-infrared molecular laser have been made by mixing the harmonic of an ultrastable microwave source with a portion of the laser output signal in a terahertz (THz) Schottky diode balanced mixer. A 3GHz difference-frequency signal was used in a frequency discriminator circuit to lock the laser to the microwave source. Comparisons of the short- and long-term laser frequency stability under free-running and locked conditions show a significant improvement with locking. Short-term frequency jitter was reduced by an order of magnitude, from approximately 40 to 4kHz, and long-term drift was reduced by more than three orders of magnitude, from approximately 250kHz to 80Hz. The results, enabled by the efficient Schottky diode balanced mixer downconverter, demonstrate that ultrastable microwave-based frequency stabilization of THz optically pumped lasers (OPLs) will now be possible at frequencies extending well above 4.0THz.

Specific Measurement of Tethered Running Kinetics and its Relationship to Repeated Sprint Ability.

Repeated sprint ability has been widely studied by researchers, however, analysis of the relationship between most kinetic variables and the effect of fatigue is still an ongoing process. To search for the best biomechanical parameter to evaluate repeated sprint ability, several kinetic variables were measured in a tethered field running test and compared regarding their sensitivity to fatigue and correlation with time trials in a free running condition. Nine male sprint runners (best average times: 100 m = 10.45 ± 0.07 s; 200 m = 21.36 ± 0.17 s; 400 m = 47.35 ± 1.09 s) completed two test sessions on a synthetic track. Each session consisted of six 35 m sprints interspersed by 10 s rest under tethered field running or free running conditions. Force, power, work, an impulse and a rate of force development were all directly measured using the sensors of a new tethered running apparatus, and a one-way ANOVA with Scheffé post-hoc test used to verify differences between sprints (p < 0.05). Pearson product-moment correlation measured the relationship between mechanical variables and free running performance. A total impulse, the rate of force development and maximum force did not show significant differences for most sprints. These three variables presented low to moderate correlations with free running performance (r between 0.01 and −0.35). Maximum and mean power presented the strongest correlations with free running performance (r = −0.71 and −0.76, respectively; p < 0.001), followed by mean force (r = −0.61; p < 0.001) and total work (r = −0.50; p < 0.001). It was concluded that under a severe work-to-rest ratio condition, power variables were better suited to evaluating repeated sprint ability than the other studied variables.

39-GHz Millimeter-Wave Carrier Generation in Dual-Mode Colorless Laser Diode for OFDM-MMWoF Transmission

By using a nully biased MZM to modulate an incoming single-mode light into a double sideband (CCA-DSB or CCS-DSB) master with preserved or suppressed central carrier, the directly OFDM encoded dual-mode colorless laser diode is performed for a successful fusion between wired and wireless links to establish a 5G-based MMWoF system. The dual-mode L-band optical carrier successfully delivers a 36-Gb/s OFDM data with a BER of $3.2 \times 10^{-3}$ , while the stabilized 39-GHz mm-wave carrier can provide wireless 4-Gb/s 16-QAM OFDM data with 16.6-dB SNR. The in-situ 39-GHz mm-wave carrier can be synthesized by optically heterodyne mixing the dual-mode carrier at remote node. When injection-locking with the CCS-DSB master, the dual-mode slave colorless laser diode improves its central carrier suppression ratio and RIN to 38 dB and −104 dBc/Hz, respectively. In comparison, the dual-DFBLD master injection-locking mixed mm-wave carrier is relatively unstable due to the individual DFBLDs at free-running condition. With the CCS-DSB master, the mm-wave carrier self-beat from the dual-mode optical carrier exhibits a narrow linewidth of <3 kHz with high purity and stability. Such a dual-mode colorless laser diode-based MMWoF link is capable of fusing the fiber wired and the 5G wireless links demanded in the near future.

Seasonal changes of locomotor activity patterns in the desert isopod Hemilepistus reaumuri

The locomotor activity rhythm of the desert woodlouse Hemilepistus reaumurii was monitored as individuals over the four seasons, under entraining and constant darkness conditions. Results indicated that individuals exhibited an endogenous rhythm of locomotor activity with a circadian period longer in spring than the other seasons whatever the regimen. Due to the important inter-individual variability, no significant difference in period was found between seasons as well as between regimens. Periodogram analysis revealed also an ultradian period around 12 h. Activity was mostly confined to the hours of the photophase or to those of subjective day. The activity pattern showed two main peaks. This bimodal circadian rhythm persisted for as long as the experiments were run, and was clearer in summer and autumn than in winter. The most clearly defined rhythms were found in spring and summer recordings, respectively, under entraining and free running conditions. The variation of activity patterns according to the seasons will be discussed.

Exaggerated Nighttime Sleep and Defective Sleep Homeostasis in a Drosophila Knock-In Model of Human Epilepsy.

Despite an established link between epilepsy and sleep behavior, it remains unclear how specific epileptogenic mutations affect sleep and subsequently influence seizure susceptibility. Recently, Sun et al. (2012) created a fly knock-in model of human generalized epilepsy with febrile seizures plus (GEFS+), a wide-spectrum disorder characterized by fever-associated seizing in childhood and lifelong affliction. GEFS+ flies carry a disease-causing mutation in their voltage-gated sodium channel (VGSC) gene and display semidominant heat-induced seizing, likely due to reduced GABAergic inhibitory activity at high temperature. Here, we show that at room temperature the GEFS+ mutation dominantly modifies sleep, with mutants exhibiting rapid sleep onset at dusk and increased nighttime sleep as compared to controls. These characteristics of GEFS+ sleep were observed regardless of sex, mating status, and genetic background. GEFS+ mutant sleep phenotypes were more resistant to pharmacologic reduction of GABA transmission by carbamazepine (CBZ) than controls, and were mitigated by reducing GABAA receptor expression specifically in wake-promoting pigment dispersing factor (PDF) neurons. These findings are consistent with increased GABAergic transmission to PDF neurons being mainly responsible for the enhanced nighttime sleep of GEFS+ mutants. Additionally, analyses under other light conditions suggested that the GEFS+ mutation led to reduced buffering of behavioral responses to light on and off stimuli, which contributed to characteristic GEFS+ sleep phenotypes. We further found that GEFS+ mutants had normal circadian rhythms in free-running dark conditions. Interestingly, the mutants lacked a homeostatic rebound following mechanical sleep deprivation, and whereas deprivation treatment increased heat-induced seizure susceptibility in control flies, it unexpectedly reduced seizure activity in GEFS+ mutants. Our study has revealed the sleep architecture of a Drosophila VGSC mutant that harbors a human GEFS+ mutation, and provided unique insight into the relationship between sleep and epilepsy.