392 research outputs found
Trophoniella radesiensis Chaibi & Antit & Bouhedi & Meca & Gillet & Azzouna & Martin 2019, n. sp.
No full textTrophoniella radesiensis n. sp. Chaibi and Gillet Figures 3–6 urn:lsid:zoobank.org:act: D7C85C70-87FF-4AF4-8599-A8462B3FB8B1 Material examined. Holotype: MNCN16.01 /18453, collected on 25 Nov 2015 in Radés Station, Gulf of Tunis (15°55′ N, 97°41′ W) by the first author. Paratypes: MNCN 16.01 /18454. 6 specimens, same data as for holotype; UCO T FLA 025.1specimen, same data as for holotype. Diagnosis. Body covered by sediments of different grain size (50–1000 µm of long axe) embedded on tunic, completely concealed except in posterior region. Tunic pale, dorsally smooth, ventrally rough, with large papillae, carrying sediment grains and particles. Body papillae arranged in two dorsal and four ventral rows. Branchial plate tongue-shaped. Unidentate anchylosed neurohooks from chaetiger 20. Description. Holotype with some chaetae broken, non-reproductive adult, unknown sex. 35 mm long, 4 mm wide, with 60 chaetigers; paratypes varying from 30–43 mm long and 1–4 mm wide for 43–74 chaetigers (Fig. 3 A– E). Anterior body sub-cylindrical in cross-section, tapering towards pygidium. Tunic transparent, dorsally smooth, ventrally rough with large papillae, carrying sediment grains and particles with long axes ranging from 50 to 1000 µm, totally embedded in tunic, completely concealing it dorsally and ventrally, absent in posterior region. Pale brown, slightly reddish anteriorly. Cephalic cage 12 mm long, with chaetae ca. 1.5 times longer than body width, formed by chaetigers 1–5; chaetiger 2 dorsolateral, chaetiger 3–4 lateral. Chaetal transition from cephalic cage to body chaetae gradual (Fig. 3A, 3 C–E). Body papillae similar in colour to body wall, mostly eroded, arising in two dorsal and four ventral longitudinal rows from first chaetiger to posterior end, better preserved anterior-most body region (Fig. 3A, 3 C–E). Parapodia well developed. Noto and neuropodia have four prechaetal papillae and five postchaetal papillae (Fig. 3C). Especially long papillae absent from anterior chaetigers. Gonopodial papillae not seen. Chaetiger 1 with about six notochaetae and eight neurochaetae; anterior dorsal margin with dorsal papillae, arising as a multifid cephalic veil (Fig. 4A). Chaetiger 5 widening posteriorly. Cephalic hood not exposed. Caruncle short and triangular (Fig. 4C, 4D). Branchiae cirriform, arising from tongue-shaped branchial plate, arranged in two lateral lobes (Fig. 4A, 4D), thin, long (0.5–3mm), whitish once preserved in ethanol, with ca. 60 filaments. Palp, long, corrugated, pale, as long as largest branchiae, 6 mm long (Fig. 4B, 4C). Prostomium lowcone, with two large and two small black eyes (Fig. 3D, 3E). Lateral lip expanded; dorsal and ventral lips not well developed (Fig. 3D, 3E). Notochaetae all multiarticulated capillaries; articles progressively longer towards falcate tips; medial ones in short longitudinal series, 4–7 per bundle; some yellowish some dark brown; unidentate tips (Fig. 5 A–5D). Multiarticulated capillary neurochaeta from chaetiger 2 to 5, then short unidentate neurohooks from chaetiger 6 to 19 (Fig. 6A) and anchylosed hooks from chaetiger 20 to body end (Fig. 6B), darker than preceding ones, arranged in transverse series of 4–6 units per bundle, similarly wide along their length, subdistally not or slightly expanded, with short rings continued up to a subdistal, non-annulated hyaline region, hooked, tapering to roughly pointed, unidentate tips (Fig. 5A, 6B). Pygidium simple, with single anal cirrus. No intra-specific variability in morphological characters was observed, except for lacking sediment gains in some specimens. Distribution. Known only from the type locality, Radés Station (Gulf of Tunisia, Mediterranean Sea). Collected from both soft and rocky bottoms, from 3–4 m to 10 m depth. Etymology. The species name radesiensis refers to the type locality, Radés Station.Published as part of Chaibi, Marwa, Antit, Mouna, Bouhedi, Marwa, Meca, Miguel A., Gillet, Patrick, Azzouna, Atf & Martin, Daniel, 2019, A new species of Flabelligeridae (Annelida), Trophoniella radesiensis n. sp., from Tunisia, pp. 551-561 in Zootaxa 4571 (4) on pages 554-556, DOI: 10.11646/zootaxa.4571.4.7, http://zenodo.org/record/261426
New and renewable energy and environmental engineering
No full textThere is an acute scarcity of potable water in many parts of the world, and especially in most of the Middle East region. Important advances have been made in desalination technology but its wide application is restricted by relatively high capital and input energy costs, even when solar energy is used. Until recently, flat-plate solar collectors have usually been employed to distill water in compact desalination systems. Currently, it is possible to replace these collectors by the more advanced evacuated tube collectors, which are now available on the market at a similar price. The research which is concerned with the development of a novel small scale solar water desalination technology, consists of experimental and theoretical investigations of the operation of a multi stage solar still desalination system coupled with a heat pipe evacuated tube solar collector with an aperture area of about 1.7 m(^2). The multi stage still was tested to recover latent heat from the evaporation and condensation processes in each of its four stages. A number of experimental tests were carried out using a laboratory rig to investigate its water production capacity. Solar radiation (insolation) during a mid-summer day in the Middle East region was simulated by an array of 110 halogen flood lights. Computational Fluid Dynamics (CFD) modeling of the evaporation and condensation processes in one of the still's stages was conducted using FLUENT 6.2 software. The simulation results demonstrate the importance of the various parameters affecting the total production rate of the solar still and provide detailed information on the temperature distribution and condensate formation inside the solar still. However, it was found that the CFD technique at this stage does not provide accurate quantitative predictions and results obtained can be used only for qualitative analysis. Hence, the use of a lumped parameter mathematical model was preferred for analysis and design purpose. A lumped parameter model has been developed to describe the system's operation. It consists of a system of ordinary differential equations of energy and mass conservation written for each stage of the still. A MATLAB computer program was written to solve the system of governing equations to simulate the evaporation and condensation processes and the experimental results were used to validate numerical predictions. The experimental and theoretical values for the total daily distillate output were found to be closely correlated. The test results demonstrate that the system produces about 9 kg of clean water per day and has a distillation efficiency of 90%. The overall efficiency is 33% due to the presence of heat losses in the system. However, this level of efficiency is greater of that for conventional solar stills. Following the experimental calibration of the lumped parameter model, this was used for determination of rational design parameters of the still and it was demonstrated that the performance of the system could be considerably improved to produce 11 kg/m(^2) of water per day if the number of stages and evaporation area were 4 and 1 m(^2), respectively. A water quality analysis was performed for the distilled water and the levels of total dissolved solids, electrical conductivity and pH were well within the range defined by the World Health Organization guidelines for drinking water. An economic study was also conducted for the system and it was shown that the distilled water costs of 0.016 US$/litre with a payback period of 6 months in the Middle East region conditions. This research demonstrates, empirically and theoretically, the potential role in the field of solar desalination of the multistage solar still coupled to the evacuated tube solar collector. Not only is this system a promising new technology but it could prove to be particularly appropriate in remote and rural areas. Simultaneously this system also uses a completely clean energy source and contributes to tackling environmental pollution, global carbon emissions and climate change problems
Is Sustainable Development of Deserts Feasible?
No full textHot deserts that presently cover about one-fifth of the land area of our planet are rapidly devouring more and more arable lands mostly due to anthropogenic causes. We propose an interdisciplinary approach to revitalizing and commercializing hot deserts, which is based on systems thinking and Russian and NASA space technology experience in designing life-support systems for long-duration flights. We formulate ten principles for the design of sustainable life support systems in deserts, which can make the development of the deserts feasible. It is discussed how the principles can be employed to design and operate desert’s eco-industrial parks with greenhouses in which the transpired and evaporated moisture is collected and condensed. The potential benefits of setting up the eco-industrial parks in deserts include the slowdown and eventual reversal of the desertification trend, the migration of many industrial production facilities from mild-climate regions to deserts, the increased availability of potable water and food in deserts, the development of poor African countries, and the emergence of new investment markets
Calibration of advanced Virgo and reconstruction of the gravitational wave signal h(t) during the observing run O2
No full textIn August 2017, advanced Virgo joined advanced LIGO for the end of the O2 run, leading to the first gravitational waves detections with the three-detector network. This paper describes the advanced Virgo calibration and the gravitational wave strain h(t) reconstruction during O2. The methods are the same as the ones developed for the initial Virgo detector and have already been described in previous publications; this paper summarizes the differences and emphasis is put on estimating systematic uncertainties. Three versions of the h(t) signal have been computed for the Virgo O2 run, an online version and two post-run reprocessed versions with improved detector calibration and reconstruction algorithm. A photon calibrator has been used to establish the sign of h(t) and to make an independent partial cross-check of the systematic uncertainties. The uncertainties reached for the latest h(t) version are 5.1% in amplitude, 40 mrad in phase and 20 mu s in timing
Calibration of advanced Virgo and reconstruction of the detector strain h(t) during the observing run O3
No full textInternational audienceThe three advanced Virgo and LIGO gravitational wave detectors participated to the third observing run (O3) between 1 April 2019 15:00 UTC and 27 March 2020 17:00 UTC, leading to several gravitational wave detections per month. This paper describes the advanced Virgo detector calibration and the reconstruction of the detector strain h(t) during O3, as well as the estimation of the associated uncertainties. For the first time, the photon calibration technique as been used as reference for Virgo calibration, which allowed to cross-calibrate the strain amplitude of the Virgo and LIGO detectors. The previous reference, so-called free swinging Michelson technique, has still been used but as an independent cross-check. h(t) reconstruction and noise subtraction were processed online, with good enough quality to prevent the need for offline reprocessing, except for the two last weeks of September 2019. The uncertainties for the reconstructed h(t) strain, estimated in this paper in a 20–2000 Hz frequency band, are frequency independent: 5% in amplitude, 35 mrad in phase and 10 μs in timing, with the exception of larger uncertainties around 50 Hz
Calibration of advanced Virgo and reconstruction of the detector strain h( t) during the observing run O3
No full textThe three advanced Virgo and LIGO gravitational wave detectors participated to the third observing run (O3) between 1 April 2019 15:00 UTC and 27 March 2020 17:00 UTC, leading to several gravitational wave detections per month. This paper describes the advanced Virgo detector calibration and the reconstruction of the detector strain h(t) during O3, as well as the estimation of the associated uncertainties. For the first time, the photon calibration technique as been used as reference for Virgo calibration, which allowed to cross-calibrate the strain amplitude of the Virgo and LIGO detectors. The previous reference, so-called free swinging Michelson technique, has still been used but as an independent cross-check. h(t) reconstruction and noise subtraction were processed online, with good enough quality to prevent the need for offline reprocessing, except for the two last weeks of September 2019. The uncertainties for the reconstructed h(t) strain, estimated in this paper in a 20-2000 Hz frequency band, are frequency independent: 5% in amplitude, 35 mrad in phase and 10 μs in timing, with the exception of larger uncertainties around 50 Hz
GW231123:a binary black hole merger with total mass 190–265 <i>M</i><sub>⊙</sub>
No full textOn 2023 November 23, the two LIGO observatories both detected GW231123, a gravitational-wave signal consistent with the merger of two black holes with masses 137+23-18 M⊙ and 101+22-50 M⊙ (90% credible intervals), at a luminosity distance of 0.7–4.1 Gpc, a redshift of 0.40+0.27-0.25, and with a network signal-to-noise ratio of ∼20.7. Both black holes exhibit high spins— 0.90+0.10-0.19 and 0.80+0.20-0.52, respectively. A massive black hole remnant is supported by an independent ringdown analysis. Some properties of GW231123 are subject to large systematic uncertainties, as indicated by differences in the inferred parameters between signal models. The primary black hole lies within or above the theorized mass gap where black holes between 60–130 M⊙ should be rare, due to pair-instability mechanisms, while the secondary spans the gap. The observation of GW231123 therefore suggests the formation of black holes from channels beyond standard stellar collapse and that intermediate-mass black holes of mass ∼200 M⊙ form through gravitational-wave-driven mergers
Heat transfer and evaporation in geothermal desalination units
No full textThe heat transfer of air-water-vapour mixtures in a desalination plant, using the aero-evapo-condensation process, has been studied theoretically and experimentally. The present unit consists of a falling-film evaporator and condenser, made of polypropylene. It was designed to work at low temperatures (of 60-90°C) utilizing geothermal energy. A model for heat-and-mass transfers in the plant is developed, resulting in a set of classical equations. Two experimental pilot studies were used. The latter, installed in France and the south of Tunisia, were supplied by fuel and geothermal energy respectively. The influences of different thermal and hydrodynamic parameters on the unit performances were investigated. Experimental results were compared with the model predictions. From this comparison, it can be learnt that the model is well able to predict the trends of the heat-and-mass characteristics of the evaporator. The present process was compared with other desalination techniques. It was shown that in areas where geothermal water resources are available, the process is promising either for cooling or desalting geothermal water.Geothermal energy Desalination Evaporator Horizontal tubes Falling film Evaporation Heat transfer Economic evaluation
GW190521: a binary black hole merger with a total mass of 150 M⊙
No full textOn May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85+21−14 M⊙ and 66+17−18 M⊙ (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65 M⊙. We calculate the mass of the remnant to be 142+28−16 M⊙, which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is 5.3+2.4−2.6 Gpc, corresponding to a redshift of 0.82+0.28−0.34. The inferred rate of mergers similar to GW190521 is 0.13+0.30−0.11 Gpc−3 yr−1
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