Sunrise Period Research Articles

Performance analysis of integrating photovoltaic-radiative sky cooling and humidification-dehumidification for combined power and all-day desalination

Although the state-of-the-art photovoltaic-thermal-driven humidification-dehumidification desalination has a high potential for electricity and freshwater cogeneration, this technology can only operate when there is sunlight and has zero output during the night. This research exploits the photovoltaic cell's nighttime radiative sky-cooling ability to achieve dehumidification of ambient humid air and subsequently nighttime desalination. By combining this with the usual daytime operation, the proposed system increases the all-day productivity while keeping the system structure simple. The proposed system is analyzed via steady-state thermodynamic models of the photovoltaic panel, radiative sky cooling, seawater flow, and humidification-dehumidification subsystems. A series of parametric studies and a time-dependent analysis are conducted to evaluate its cogeneration performance. Results reveal that the nighttime and daytime freshwater productivities are a maximum of 0.13 kg/(h m2 PV area) and 0.6 kg/(h m2 PV area), respectively. The corresponding all day productivities are 1.114 kg/(day m2) and 5.371 W h/(day m2), respectively, which demonstrate that the photovoltaic cell's radiative sky cooling ability can offer an additional 20% of productivity. Notably, desalination is weakest during the sunset and sunrise periods because the radiative cooling and solar irradiance effects cancel each other here.

The Unified Patent Court’s Opt-Out Option – A General Introduction

Abstract With the entry into force of the Agreement on a Unified Patent Court (UPCA) on 1 June 2023, a common patent court will be created for 17 Member States of the European Union. It will be competent for disputes concerning the infringement and revocation of Unitary Patents and classic European patents. At the request of the users, a so-called opt-out mechanism was introduced, which allows the jurisdiction of the Court to be excluded by a corresponding notification. Such opt-outs can be filed via the Court’s case management system as of the start of the ‘sunrise period’ on 1 March 2023. This article provides a first general practical overview concerning the recording of such notifications.***

Thermal Model of a Parabolic Trough Solar Field With a Closed-Loop Operation During Sunrise Period

Abstract This work presents a numerical simulation of a thermal model for a solar loop with parabolic trough collectors (PTCs) considering fluid recirculation at closed-loop (CL) operation during sunrise. At the beginning of the day, the heat transfer fluid (HTF) is recirculated in a CL to obtain the inlet loop operating temperature without resorting to additional preheating energy. Energy balances are carried out on the HTF, the absorber tube, and the glass envelope as a function of optical and thermo-physical parameters of the heat collector element (HCE). A system of second-order differential equations was established, and mathematical model was resolved by finite difference and Newton–Raphson methods for solution. This model has been well validated by comparing the results with the existing experimental and numerical data. Three typical days of winter, spring, and summer were simulated for the solar loop operation considering a CL fluid recirculation at start-up conditions. Results show a more flexible CL operation at relatively large flowrates compared to the open-loop (OL) operation, which requires substantial preheating energy at the same conditions; the start-up solar field using the CL strategy allows us both operational autonomy and significant energy savings. Solar loop thermal and optical powers gained and lost are plotted for the typical days considered; we observe that maximum thermal efficiency of 66.53% is achieved at 2.27 p.m. for the summer day.

Turbulence characteristics within the atmospheric surface layer of the coastal region of Qatar

The atmospheric turbulence characteristics in the coastal region of Qatar are analyzed using the measurements conducted on the shoreline (26.08 N, 51.36 E). The micrometeorological data were collected, from August 2015 to September 2016, using sonic anemometers (20 Hz) at three heights and a weather station atop a 9-m tower. The turbulence characteristics are studied within the framework of Monin–Obukhov similarity theory (MOST), in the presence of the coastal inhomogeneities generated by the sea and land surfaces coming together. The results show the wind from the north-west prevails during the entire test period, with the wind speed higher than that from other directions. The non-dimensional standard deviations of velocity components are found to be consistent the results reported around the world and match suggested MOST scaling, with a relatively greater value for the dissipation rate of turbulent kinetic energy. The flux Richardson number shows a larger scatter under the super-stable and super-unstable regimes. Moreover, the non-dimensional standard deviation of temperature does not align with the suggested model under near-neutral and very stable regimes, and the gradient Richardson number shows some negative values under stable regimes. Two different atmospheric daily stability patterns, ‘orderly’ and ‘disheveled,’ are identified based on the wind conditions. The orderly stability pattern shows a daily descending and ascending trend during the sunrise and sunset periods, respectively, while the disheveled days follow a random pattern with no clear order. The two patterns are then related to the wind continuity and direction relative to the shoreline.

EXPERIMENTAL EXPERIENCE IN STUDYING THE WEIGHT DYNAMICS OF ROTATING GYROSCOPES AND THEIR ROTATION FEATURES AT CRITICALLY LOW SPEEDS, INCLUDING AT SUNRISE AND DURING A LUNAR-SOLAR ECLIPSE

The cycle of experiments with free-rolling gyroscopes at different angular velocity intervals including those on scales with continuous-discrete weight registration was carried out. We concluded that the free-running time of gyroscopes in one interval of angular velocities can vary greatly (within hundreds of percent). Measuring the free running time of a gyroscope during a solar eclipse has shown a connection between registered fluctuations in the gyroscope behavior and the eclipse stroke. The data obtained during the periods of sunrise indicate that the gyroscope can react at the moment of the sunrise while recording the true ascent, as well as the ascent preceding the true one with a difference of 8 minutes. Statistical analysis of the graphs of weight changes of the disk at right and left-hand free rotation in the speed range from 5000 to 250 rpm showed that the abnormal weight changes recorded at certain “critical” frequencies with different directions of rotation reliably differ in amplitude characteristics.

Enhancement of single solar still integrated with solar dishes: An experimental approach

The current experimental work targets to progress in the daily production of fresh water of a single solar still. Two identical solar parabolic dishes were equipped with two conical tanks were integrated with a single solar still and four modules of PV with total power output 1000 W. Each PV module is about 1650 mm × 992 mm × 46 mm dimensions. The proposed system was constructed and tested for three months under the weather conditions of Ismailia, Egypt. The area ratio of the receiver to the absorber is 100. The solar parabolic dish is of 2000 mm diameter. The modified system is used to increase the water basin temperature during the sunrise period. The basin water is recirculated to the cone tanks and sprayed in the solar still to increase the evaporation rate. The proposed system is controlled with a control unit which receives the input signals from various sensors and operates the output. The effect of basin water depths is studied at two values 10 and 20 mm. The experimental results were conducted in three cases that represent the conventional solar still, one solar parabolic dish, and two solar parabolic dishes. The experimental results showed that, the daily distillate productivity in case of one solar dish is 8.8 and 5.45 kg/day at the two water depths 10 and 20 mm, respectively. The usage of the two solar dishes integrates with the solar still increase the daily productivity to reach 13.63 and 7.69 kg/day at the two water depths 10 and 20 mm respectively.

Morphology of GPS and DPS TEC over an equatorial station: validation of IRI and NeQuick 2 models

Abstract. We investigated total electron content (TEC) at Ilorin (8.50∘ N 4.65∘ E, dip lat. 2.95) for the year 2010, a year of low solar activity in 2010 with Rz=15.8. The investigation involved the use of TEC derived from GPS, estimated TEC from digisonde portable sounder data (DPS), and the International Reference Ionosphere (IRI) and NeQuick 2 (NeQ) models. During the sunrise period, we found that the rate of increase in DPS TEC, IRI TEC, and NeQ TEC was higher compared with GPS TEC. One reason for this can be attributed to an overestimation of plasmaspheric electron content (PEC) contribution in modeled TEC and DPS TEC. A correction factor around the sunrise, where our finding showed a significant percentage deviation between the modeled TEC and GPS TEC, will correct the differences. Our finding revealed that during the daytime when PEC contribution is known to be absent or insignificant, GPS TEC and DPS TEC in April, September, and December predict TEC very well. The lowest discrepancies were observed in May, June, and July (June solstice) between the observed values and all the model values at all hours. There is an overestimation in DPS TEC that could be due to extrapolation error while integrating from the peak electron density of F2 (NmF2) to around ∼1000 km in the Ne profile. The underestimation observed in NeQ TEC must have come from the inadequate representation of contribution from PEC on the topside of the NeQ model profile, whereas the exaggeration of PEC contribution in IRI TEC amounts to overestimation in GPS TEC. The excess bite-out observed in DPS TEC and modeled TEC indicates over-prediction of the fountain effect in these models. Therefore, the daytime bite-out observed in these models requires a modifier that could moderate the perceived fountain effect morphology in the models accordingly. The daytime DPS TEC performs better than the daytime IRI TEC and NeQ TEC in all the months. However, the dusk period requires attention due to the highest percentage deviation recorded, especially for the models, in March, November, and December. Seasonally, we found that all the TECs maximize and minimize during the March equinox and June solstice, respectively. Therefore, GPS TEC and modeled TEC reveal the semiannual variations in TEC.

Investigation on slab-thickness and B0 over an equatorial station in Africa and comparison with IRI model

The present study investigates the simultaneous morphologies of slab-thickness (τ) and thickness parameter (Bo) over Ilorin (8.500 N, 4.680 E; dip lat. 2.95), an equatorial station, during a year of low solar activity (2010). The τ is deduced from global positioning system total electron content (GPS-TEC) while the F2 peak electron density (NmF2), from digisonde portable sounder (DPS). The use of measured TEC for this type of investigation takes care of the inclusion of plasmaspheric electron content (PEC). The PEC distributions on the topside and bottomside electron density (Ne) profile add considerably to the genuine signatures of τ and Bo. Therefore, the dynamic contributions of the PEC need to be emphasized for the accurate prediction of the ionospheric models. Apart from daytime signatures of the τ and Bo which are not primarily influenced by PEC, we found that between two and 3 h of pre-sunrise and dusk periods are mainly controlled by PEC which manifests as huge peaks in the τ and Bo. Also, our investigation reveals that the Bo profile is thicker than the τ profile during the pre-sunrise periods in June indicating partial flow or halt in PEC. The result revealed approximately the same values of τ and Bo around the sunrise period suggesting the absence or negligible PEC contributions. Our investigation also shows that there are maximum and minimum of the thickness in Bo and τ during the December solstice and June solstice, respectively. We also observed a moderate sunrise enhancement in τ that is not conspicuous in the Bo signature. On the relationship between the τ and Bo, we found a significant association between τ and Bo with the highest coefficient value observed during the June seasons indicating the possibility of predicting τ in the absence of Bo and vice-versa, especially during the June season. The validation of International Reference Ionosphere (IRI) model with observed τ and Bo revealed appreciable discrepancies between the model and observed values, particularly between the IRI-τ and observed τ values. Our result revealed the underestimation of IRI-τ with respect to observed τ value in November and December.

Numerical investigation of thermal and optical performance of window units filled with nanoparticle enhanced PCM

Filling window units with phase change material (PCM) improves the thermal performance of windows, but on the other hand it has a deteriorative effect on the optical performance due to poor heat conductivity of PCM. A novel method to tackle this drawback of PCM is to disperse nanoparticles in the PCM. In this study, a model was developed to evaluate the thermal and optical performances of window units filled with nanoparticle enhanced PCM (NePCM). The effect of different types of nanoparticles, volume fractions of nanoparticles and sizes of nanoparticles on the thermal and optical performances of windows such as temperature, heat flux, solar transmittance, absorptance and reflectance were numerically investigated and compared with the referent case (i.e. pure PCM). The results showed that the optical and thermal performances of window units filled with nanoparticle dispersed paraffin wax are improved compared to that of with pure paraffin. However, the improvement is nearly the same regardless of nanoparticle type. The effect of volume fraction and size of nanoparticle is significant during the sunset and sunrise periods. Considering both thermal and optical performances of window units, it is recommended to disperse CuO nanoparticles with the volume fraction of below 1% and nanoparticle size of below 15 nm in PCM.

Simultaneous response of NmF2 and GPS-TEC to storm events at Ilorin

A comparative study of both TEC and NmF2 variations during quiet and disturbed conditions has been investigated using simultaneous measurements from dual frequency Global Positioning System (GPS) receiver and a DPS-4 Digisonde co-located at Ilorin (Geog. Lat. 8.50°N, Long. 4.50°E, dip. – 7.9°). The results of the quiet time variations of the two parameters show some similarities as well as differences in their structures. The values of both parameters generally increase during the sunrise period attaining a peak around the noon and then decaying towards the night time. The onset time of the sunrise growth is observed to be earlier in TEC than in NmF2. The rate of decay of TEC was observed to be faster than that of the NmF2 in most cases. Also, the noon ‘bite-outs’, leading to the formation of pre-noon and post-noon peaks, are prominent in the NmF2 structure and was hardly noticed in TEC. Results of the variations of both TEC and NmF2 during the 5 April, 10 May and 3 August 2010 geomagnetic storm events showed a simultaneous deviations of both parameters from the quiet time behavior. The magnitude of the deviations is however most pronounced in NmF2 structure than in TEC. We also found that the enhancement observed in the two parameters during the storm events generally corresponds to decrease in hmF2.

Multi-year comparisons of ground-based and space-borne Fourier transform spectrometers in the high Arctic between 2006 and 2013

Abstract. This paper presents 8 years (2006–2013) of measurements obtained from Fourier transform spectrometers (FTSs) in the high Arctic at the Polar Environment Atmospheric Research Laboratory (PEARL; 80.05° N, 86.42° W). These measurements were taken as part of the Canadian Arctic ACE (Atmospheric Chemistry Experiment) validation campaigns that have been carried out since 2004 during the polar sunrise period (from mid-February to mid-April). Each spring, two ground-based FTSs were used to measure total and partial columns of HF, O3, and trace gases that impact O3 depletion, namely, HCl and HNO3. Additionally, some tropospheric greenhouse gases and pollutant species were measured, namely CH4, N2O, CO, and C2H6. During the same time period, the satellite-based ACE-FTS made measurements near Eureka and provided profiles of the same trace gases. Comparisons have been carried out between the measurements from the Portable Atmospheric Research Interferometric Spectrometer for the InfraRed (PARIS-IR) and the co-located high-resolution Bruker 125HR FTS, as well as with the latest version of the ACE-FTS retrievals (v3.5). The total column comparison between the two co-located ground-based FTSs, PARIS-IR and Bruker 125HR, found very good agreement for most of these species (except HF), with differences well below the estimated uncertainties ( ≤ 6 %) and with high correlations (R ≥ 0. 8). Partial columns have been used for the ground-based to space-borne comparison, with coincident measurements selected based on time, distance, and scaled potential vorticity (sPV). The comparisons of the ground-based measurements with ACE-FTS show good agreement in the partial columns for most species within 6 % (except for C2H6 and PARIS-IR HF), which is consistent with the total retrieval uncertainty of the ground-based instruments. The correlation coefficients (R) of the partial column comparisons for all eight species range from approximately 0.75 to 0.95. The comparisons show no notable increases of the mean differences over these 8 years, indicating the consistency of these datasets and suggesting that the space-borne ACE-FTS measurements have been stable over this period. In addition, changes in the amounts of these trace gases during springtime between 2006 and 2013 are presented and discussed. Increased O3 (0. 9 % yr−1), HCl (1. 7 % yr−1), HF (3. 8 % yr−1), CH4 (0.5 % yr−1), and C2H6 (2. 3 % yr−1, 2009–2013) have been found with the PARIS-IR dataset, the longer of the two ground-based records.

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

Abstract. The study of diurnal and seasonal variations in total electron content (TEC) over Nigeria has been prompted by the recent increase in the number of GPS continuously operating reference stations (CORSs) across Nigeria as well as the reduced costs of microcomputing. The GPS data engaged in this study were recorded in the year 2012 at nine stations in Nigeria located between geomagnetic latitudes – 4.33 and 0.72° N. The GPS data were used to derive GPS TEC, which was analysed for diurnal and seasonal variations. The results obtained were used to produce local GPS TEC maps and bar charts. The derived GPS TEC across all the stations demonstrates consistent minimum diurnal variations during the pre-sunrise hours 04:00 to 06:00 LT, increases with sharp gradient during the sunrise period (∼ 07:00 to 09:00 LT), attains postnoon maximum at about 14:00 LT, and then falls to a minimum just before sunset. Generally, daytime variations are found to be greater than nighttime variations, which range between 0 and 5 TECU. The seasonal variation depicts a semi-annual distribution with higher values (∼ 25–30 TECU) around equinoxes and lower values (∼ 20–25 TECU) around solstices. The December Solstice magnitude is slightly higher than the June Solstice magnitude at all stations, while March Equinox magnitude is also slightly higher than September Equinox magnitude at all stations. Thus, the seasonal variation shows an asymmetry in equinoxes and solstices, with the month of October displaying the highest values of GPS TEC across the latitudes.

Behavioural and physiological responses of birds to environmentally relevant concentrations of an antidepressant.

Many wildlife species forage on sewage-contaminated food, for example, at wastewater treatment plants and on fields fertilized with sewage sludge. The resultant exposure to human pharmaceuticals remains poorly studied for terrestrial species. On the basis of predicted exposure levels in the wild, we administered the common antidepressant fluoxetine (FLUOX) or control treatment via prey to wild-caught starlings (Sturnus vulgaris) for 22 weeks over winter. To investigate responses to fluoxetine, birds were moved from their group aviaries into individual cages for 2 days. Boldness, exploration and activity levels showed no treatment effects but controls and FLUOX birds habituated differently to isolation in terms of the concentration of corticosterone (CORT) metabolites in faeces. The controls that excreted higher concentrations of CORT metabolites on day 1 lost more body mass by day 2 of isolation than those which excreted lower levels of CORT metabolites. CORT metabolites and mass loss were unrelated in FLUOX birds. When we investigated the movements of birds in their group aviaries, we found the controls made a higher frequency of visits to food trays than FLUOX birds around the important foraging periods of sunrise and sunset, as is optimal for wintering birds. Although individual variability makes interpreting the sub-lethal endpoints measured challenging, our data suggest that fluoxetine at environmentally relevant concentrations can significantly alter behaviour and physiology.

The New .Africa Top Level Domain: An African Initiative in Ensuring Africa's Rightful Place on the Global Network

The new gTLD programme of the Internet Corporation for Assigned Names and Numbers (ICANN) is the single most important development since the privatisation of the DNS in 1998. The management of the Domain Name System (DNS) has developed from a modest undertaking to its current explosive expansion through the new gTLD programme. Africa has boldly entered the arena through the delegation of the .Africa gTLD. This new development heralds an innovative era in the management of the DNS, especially for Africa. The dotAfrica gTLD launch strategy offers several advantages to African governments and traders alike. One of the innovative features of the management of dotAfrica is the fact that a broader set of rights including commercial, cultural, linguistic, religious and personal rights will be protected. Furthermore, African trade mark proprietors and other rights holders are protected, initially at least, by various innovative rights-protection mechanisms. This development is important for African governments and it should form an integral part of right holders' intellectual property management strategy. Keywords: dotAfrica; new gTLD programme; trade mark rights; sunrise period; priority rights; dispute resolution; ICANN; ZACR; mark validation system; rights protection mechanisms; land rush phase; reserve names list; trademark clearing house; African Union Commission.

Research of Ship Communication in the Atmospheric Turbulence at Sea

With the application of the Rytov method proposed by Tatarskii, the light intensity scintillation probability distribution equation of marine atmospheric turbulence is established. Using the signal detection theory, the relationship between light intensity fluctuation and BER resulting from the marine atmospheric turbulence is deduced. The result shows that 2 n C has obvious diurnal variation, it will reach to the extremum in the afternoon and will show a downward trend with the height increases in the coastal area with its minimum around sunrise period. With the increase of 2 n C , and the decrease of transmission range, when 3 / 2 15 2 10 3     m C n , the effective transmission range is m 2900 , and allows a s 95 adjustment time to APT（ acquisition 、pointing and tracking） system; The system adjustment time will increase as the 2 n C value decreases and the wavelength increases.

Four Fourier transform spectrometers and the Arctic polar vortex: instrument intercomparison and ACE-FTS validation at Eureka during the IPY springs of 2007 and 2008

Abstract. The Canadian Arctic Atmospheric Chemistry Experiment Validation Campaigns have been carried out at Eureka, Nunavut (80.05° N, 86.42° W) during the polar sunrise period since 2004. During the International Polar Year (IPY) springs of 2007 and 2008, three ground-based Fourier transform infrared (FTIR) spectrometers were operated simultaneously. This paper presents a comparison of trace gas measurements of stratospherically important species involved in ozone depletion, namely O3, HCl, ClONO2, HNO3 and HF, recorded with these three spectrometers. Total column densities of the gases measured with the new Canadian Network for the Detection of Atmospheric Change (CANDAC) Bruker 125HR are shown to agree to within 3.5% with the existing Environment Canada Bomem DA8 measurements. After smoothing both of these sets of measurements to account for the lower spectral resolution of the University of Waterloo Portable Atmospheric Research Interferometric Spectrometer for the Infrared (PARIS-IR), the measurements were likewise shown to agree with PARIS-IR to within 7%. Concurrent measurements of these gases were also made with the satellite-based Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) during overpasses of Eureka during these time periods. While one of the mandates of the ACE satellite mission is to study ozone depletion in the polar spring, previous validation exercises have identified the highly variable polar vortex conditions of the spring period to be a challenge for validation efforts. In this work, comparisons between the CANDAC Bruker 125HR and ACE-FTS have been used to develop strict criteria that allow the ground- and satellite-based instruments to be confidently compared. When these criteria are taken into consideration, the observed biases between the ACE-FTS and ground-based FTIR spectrometer are not persistent for both years and are generally insignificant, though small positive biases of ~5%, comparable in magnitude to those seen in previous validation exercises, are observed for HCl and HF in 2007, and negative biases of −15.3%, −4.8% and −1.5% are seen for ClONO2, HNO3 and O3 in 2008.

Low latitude E-region irregularities studied using Gadanki radar, ionosonde and in situ measured electron density

In this paper, we attempt to identify the driving forces responsible for the generation of low-latitude E-region field-aligned irregularities (FAIs). It is evident that the low-latitude E-region FAIs occur both during the day and night with preferential occurrence being most during local sunrise period. Simultaneous measurements are made with Gadanki radar and nearby located Ionosonde for understanding the low-latitude Es–FAIs relationship. The observations suggest that the occurrence and SNR of FAIs have a close relationship with ftEs−−fbEs. Finally, using the past electron density profiles and reasonable values of electric field, we have shown that it is generally difficult with the gradient drift instability to explain low-latitude E-region FAIs when electric field alone is considered as driving agency. We hypothesize that neutral winds play important role for the generation of irregularities at low latitudes outside the electrojet belt either by forming sharp Es layers or by enhancing the differential drift of electrons and ions or by both.

GPS observations of TID events generated by the moving solar terminator

GPS-TEC data from the International GNSS Services (IGS) were used in this paper to analyze the medium scale traveling ionospheric disturbances (MSTIDs) which are generated by the moving solar terminator (ST) during the quiet days in 2005. We collected the most comprehensive and dense GPS network's data from North-America region and introduce here a strategy that combines polynomial fitting and multi-channel maximum entropy spectral analysis to obtain TID parameters. The results of our study are summarized as follows: (1) MSTIDs stimulated by the moving ST (ST-MSTIDs) are detected at mid-latitudes after the passage of the solar terminator with the life time of 2 similar to 3 h and the variation amplitude of 0.2 similar to 0.8 TECU. Spectral analysis indicated that the horizontal wavelength, average period, horizontal phase velocity of the MSTIDs are around 300 +/- 150 km,150 +/- 80 m/s, and 25 +/- 15 min, respectively. In addition, ST-MSTIDs have wavefronts elongated in the moving ST direction and almost parallel to ST. (2) The statistical results demonstrate that the dusk MSTIDs stimulated by ST is more obvious than the dawn MSTIDs in summer days. On the contrary, the more-pronounced dawn MSTIDs occur in winter days. Further analysis indicates that the seasonal variations of ST-MSTIDs occurrence frequency are most probably related to the seasonal differences of the variations of EUV flux in the ionosphere region and recombination process during sunrise and sunset period at mid-latitudes.

Feeding ecology and predation impact of the recently established amphipod, Themisto libellula, in the St. Lawrence marine system, Canada

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 373:53-70 (2008) - DOI: https://doi.org/10.3354/meps07716 Feeding ecology and predation impact of the recently established amphipod, Themisto libellula, in the St. Lawrence marine system, Canada Alexandra Marion1,2, Michel Harvey2,*, Denis Chabot3, Jean-Claude Brêthes1 1Institut des Sciences de la Mer (ISMER), Université du Québec à Rimouski (UQAR), 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 2Direction des Sciences Océaniques et Environnementales, Ministère des Pêches et des Océans, Institut Maurice-Lamontagne, CP 1000, Mont-Joli, Québec G5H 3Z4, Canada 3Direction des Sciences Halieutique et de l’Aquaculture, Ministère des Pêches et des Océans, Institut Maurice-Lamontagne, CP 1000, Mont-Joli, Québec G5H 3Z4, Canada *Corresponding author. Email: Michel.Harvey@dfo-mpo.gc.ca ABSTRACT: Themisto libellula was virtually absent from the St. Lawrence marine system (SLMS) before 1990. Since then, it has become an abundant, full-time resident of this system. Hyperiid amphipods of the genus Themisto are principally carnivorous and represent an essential link in the trophic pathway from secondary production to higher trophic levels. Sampling of T. libellula was carried out in the lower St. Lawrence Estuary (LSLE) and the northwest Gulf of St. Lawrence (NWGSL) in the fall of 1998, 2003 and 2004 to study the feeding dynamics and predation impact of this species on mesozooplankton and macrozooplankton communities. Our results showed that T. libellula was an opportunistic predator with a circadian feeding cycle; activity was higher during the second part of the night and the sunrise period. Stomach content analyses showed that these amphipods consumed chiefly copepods, in particular, the copepodite stages CIV and CV of Calanus finmarchicus. Euphausiids, chaetognaths, amphipods and mysids constituted other important prey. Digestion time was estimated at 13 h. The daily ingestion rate of T. libellula was estimated using 2 approaches: (1) stomach fullness index and (2) mean number of prey removed per unit of time and converted to prey biomass using the stage-species dry masses of each prey item. We found that the daily ingestion rate of T. libellula ranged from 6.32 to 16.82% of body dry mass per day in both study areas (LSLE and NWGSL). Concerning predation impact, T. libellula consumed between 0.14 and 1.79% of the combined mesozooplankton and macrozooplankton standing stock per day and between 0.43 and 2.48% of the C. finmarchicus standing stock. Themisto libellula may thus exert a significant control on the mesozooplankton and macrozooplankton communities in the SLMS through direct predation. KEY WORDS: Hyperiid amphipod · Themisto libellula · Feeding ecology · Ingestion rate · Digestion time · Predation impact · Gulf of St. Lawrence Full text in pdf format PreviousNextCite this article as: Marion A, Harvey M, Chabot D, Brêthes JC (2008) Feeding ecology and predation impact of the recently established amphipod, Themisto libellula, in the St. Lawrence marine system, Canada. Mar Ecol Prog Ser 373:53-70. https://doi.org/10.3354/meps07716Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 373. Online publication date: December 23, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Diurnal, seasonal, latitudinal and solar cycle variation of electron temperature in the topside F-region of the Indian zone ionosphere

Abstract. Electron temperature Te observed by the SROSS C2 satellite at equatorial and low latitudes during the low to high solar activity period of 1995–2001 at the height of ~500 km is investigated in terms of local time, season, latitude, solar sunspot number Rz and F10.7 cm solar flux. The satellite covered the latitude belt of 31° S–34° N and the longitude range of 40°–100° E. The average nighttime (20:00–04:00 LT) Te varies between 750–1200 K and then rises sharply in the sunrise period (04:00–06:00 LT) to the morning high from 07:00 to 10:00 LT and attains a daytime (10:00–14:00 LT) average of 1100–2300 K. The morning enhancement is more pronounced in the equinoxes. A secondary maximum in Te is also observed around 16:00–18:00 LT in the June solstice and in the equinoxes. Daytime electron temperature was found to be higher in autumn compared to that in spring in all latitudes. Between the solstices, the amplitude of the morning enhancement is higher in winter compared to that in summer. Both day and nighttime Te observed by the SROSS C2 satellite bears a positive correlation with solar activity when averaged on a shorter time scale, i.e. over the period of a month. But on a longer time scale, i.e. averaged over a year, the daytime electron temperature gradually decreases from 1995 till it reaches the minimum value in 1997, after which Te again continues to rise till 2001. The variations are distinctly seen in summer and in the equinoxes. The sunspot activity during solar cycle 23 was minimum in 1996 and maximum in 2000. Annual average electron temperature, therefore, appears to follow the variation of solar activity with a time lag of about one year, both at the bottom and top of solar cycle 23, indicating an inherent inertia of the ionosphere thermosphere regime to variations in solar flux.