245 research outputs found
Multi-disciplinary analysis of light shelves application within a student dormitory refurbishment
The achievement of sustainable cities and communities is closely linked to an accurate design of the buildings. In this context, the transparent elements of the building envelope have a crucial role since, on one hand, they are a bottleneck in regards to heat and mass transfers and sound propagation, while, on the other hand, they must allow daylight penetration. Thus, they are responsible for occupants' thermal and visual comfort and their health. Considering passive solutions for windows, the light shelves can improve natural light penetration, reducing the lights' electricity demand and controlling windows' related thermal aspects. The scientific literature is characterized by several studies that analyze this topic, which, however, focus only on the daylight field and sometimes the energy saving for lights. Moreover, they often refer to fixed sky type for the simulations. The aim of the present study is to analyze the application of the light shelves with a multi-disciplinary approach, by means of dynamic simulations, in the EnergyPlus engine, for a whole year. A new methodological approach is presented in order to investigate the technology under different fields of interest: daylight, lighting energy, cooling and heating needs, and thermo-hygrometric comfort. The case study chosen is an existing building, a student dormitory belonging to the University of Athens. It is subject to a deep energy renovation to conform to the "nearly Zero Energy Building" target, in the frame of a European research project called Pro-GET-onE (G.A No. 723747). By means of the calibrated numerical model of this HVAC-building system, ten different configurations of light shelves have been investigated. The best solution is given by the application of an internal horizontal light shelf placed at 50 cm from the top of the window with a depth of 90 or 60 cm. It has been found that despite the reduction in electricity demand for lighting, the variation in heating and cooling needs does not always lead to a benefit
Application of light shelves in a refurbished student dormitory: Energy, lightings and comfort aspects
The transparent elements of the building envelope have a crucial role not only in term of heat and mass transfers control, but also for natural light penetration, sound insulation, thermal and visual comfort of the occupants and their health. Among passive technologies, the light shelves could be architectural solutions for improving daylight penetration and for controlling thermal loads. The available research papers usually focus on one aspect. For this reason, the aim of the present study is to analyse the application of the light shelves with multidisciplinary approach and thus, taking into account: daylight, electricity for lighting, cooling and heating needs and thermo-hygrometric comfort. The case study is a real dormitory building placed in Athens and subject to a deep energy renovation toward the nearly zero energy building target. EnergyPlus, by means of DesignBuilder interface, has been used as dynamic simulation tool. Among ten different configurations, the optimal one turns out to be the internal horizontal light shelf placed at 50 cm from the top of the window with a depth of 90 cm or 60 cm. It has been found that in some cases the reduction of electricity for lighting cannot balance the variation in heating and cooling needs
Measurement of the neutron capture cross section of the s-only isotope 204Pb from 1 eV to 440 keV
The neutron capture cross section of 204Pb has been measured at the CERN
n_TOF installation with high resolution in the energy range from 1 eV to 440
keV. An R-matrix analysis of the resolved resonance region, between 1 eV and
100 keV, was carried out using the SAMMY code. In the interval between 100 keV
and 440 keV we report the average capture cross section. The background in the
entire neutron energy range could be reliably determined from the measurement
of a 208Pb sample. Other systematic effects in this measurement could be
investigated and precisely corrected by means of detailed Monte Carlo
simulations. We obtain a Maxwellian average capture cross section for 204Pb at
kT=30 keV of 79(3) mb, in agreement with previous experiments. However our
cross section at kT=5 keV is about 35% larger than the values reported so far.
The implications of the new cross section for the s-process abundance
contributions in the Pb/Bi region are discussed.Comment: 8 pages, 3 figures, article submitted to Phys. Rev.
New measurement of neutron capture resonances of 209Bi
The neutron capture cross section of Bi209 has been measured at the CERN n
TOF facility by employing the pulse-height-weighting technique. Improvements
over previous measurements are mainly because of an optimized detection system,
which led to a practically negligible neutron sensitivity. Additional
experimental sources of systematic error, such as the electronic threshold in
the detectors, summing of gamma-rays, internal electron conversion, and the
isomeric state in bismuth, have been taken into account. Gamma-ray absorption
effects inside the sample have been corrected by employing a nonpolynomial
weighting function. Because Bi209 is the last stable isotope in the reaction
path of the stellar s-process, the Maxwellian averaged capture cross section is
important for the recycling of the reaction flow by alpha-decays. In the
relevant stellar range of thermal energies between kT=5 and 8 keV our new
capture rate is about 16% higher than the presently accepted value used for
nucleosynthesis calculations. At this low temperature an important part of the
heavy Pb-Bi isotopes are supposed to be synthesized by the s-process in the He
shells of low mass, thermally pulsing asymptotic giant branch stars. With the
improved set of cross sections we obtain an s-process fraction of 19(3)% of the
solar bismuth abundance, resulting in an r-process residual of 81(3)%. The
present (n,gamma) cross-section measurement is also of relevance for the design
of accelerator driven systems based on a liquid metal Pb/Bi spallation target.Comment: 10 pages, 5figures, recently published in Phys. Rev.
Measurements of high-energy neutron-induced fission of (nat)Pb and (209)Bi
This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial License 3.0, which permits unrestricted use, distribution, and reproduction in any noncommercial medium, provided the original work is properly citedThe CERN Neutron Time-Of-Flight (n_TOF) facility is well suited to measure low cross sections as those of neutron-induced fission in subactinides. The cross section ratios of (nat)Pb and (209)Bi relative to (235)U and (238)U were measured using PPAC detectors and a fragment coincidence method that allows us to identify the fission events. The present experiment provides first results for neutron-induced fission up to 1 GeV. Good agreement is found with previous experimental data below 200 MeV. The comparison with proton-induced fission indicates that the limiting regime where neutron-induced and proton-induced fission reach equal cross sections is close to 1 GeV
Measurement of the (90,91,92,93,94,96)Zr(n,gamma) and (139)La(n,gamma) cross sections at n_TOF
Open AccessNeutron capture cross sections of Zr and La isotopes have important implications in the field of nuclear astrophysics as well as in the nuclear technology. In particular the Zr isotopes play a key role for the determination of the neutron density in the He burning zone of the Red Giant star, while the (139)La is important to monitor the s-process abundances from Ba up to Ph. Zr is also largely used as structural materials of traditional and advanced nuclear reactors. The nuclear resonance parameters and the cross section of (90,91,92,93,94,96)Zr and (139)La have been measured at the n_TOF facility at CERN. Based on these data the capture resonance strength and the Maxwellian-averaged cross section were calculated
Covid-19 disease, women’s predominant non-heparin vaccine-induced thrombotic thrombocytopenia and kounis syndrome: A passepartout cytokine storm interplay
Coronavirus disease 2019 (COVID-19) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) constitute one of the deadliest pandemics in modern history demonstrating cardiovascular, gastrointestinal, hematologic, mucocutaneous, respiratory, neurological, renal and testicular manifestations and further complications. COVID-19-induced excessive immune response accompanied with uncontrolled release of cytokines culminating in cytokine storm seem to be the common pathogenetic mechanism of these complications. The aim of this narrative review is to elucidate the relation between anaphylaxis associated with profound hypotension or hypoxemia with pro-inflammatory cytokine release. COVID-19 relation with Kounis syndrome and post-COVID-19 vaccination correlation with heparin-induced thrombocytopenia with thrombosis (HITT), especially serious cerebral venous sinus thrombosis, were also reviewed. Methods: A current literature search in PubMed, Embase and Google databases was performed to reveal the pathophysiology, prevalence, clinical manifestation, correlation and treatment of COVID-19, anaphylaxis with profuse hypotension, Kounis acute coronary syndrome and thrombotic events post vaccination. Results: The same key immunological pathophysiology mechanisms and cells seem to underlie COVID-19 cardiovascular complications and the anaphylaxis-associated Kounis syndrome. The myocardial injury in patients with COVID-19 has been attributed to coronary spasm, plaque rupture and microthrombi formation, hypoxic injury or cytokine storm disposing the same pathophysiology with the three clinical variants of Kounis syndrome. COVID-19-interrelated vaccine excipients as polysorbate, polyethelene glycol (PEG) and trometamol constitute potential allergenic substances. Conclusion: Better acknowledgement of the pathophysiological mechanisms, clinical similarities, multiorgan complications of COVID-19 or other viral infections as dengue and human immunodeficiency viruses along with the action of inflammatory cells inducing the Kounis syndrome could identify better immunological approaches for prevention, treatment of the COVID-19 pandemic as well as post-COVID-19 vaccine adverse reactions
Measurement of the radiative neutron capture cross section of 206Pb and its astrophysical implications
The (n, gamma) cross section of 206Pb has been measured at the CERN n_TOF
facility with high resolution in the energy range from 1 eV to 600 keV by using
two optimized C6D6 detectors. In the investigated energy interval about 130
resonances could be observed, from which 61 had enough statistics to be
reliably analyzed via the R-matrix analysis code SAMMY. Experimental
uncertainties were minimized, in particular with respect to (i) angular
distribution effects of the prompt capture gamma-rays, and to (ii) the
TOF-dependent background due to sample-scattered neutrons. Other background
components were addressed by background measurements with an enriched 208Pb
sample. The effect of the lower energy cutoff in the pulse height spectra of
the C6D6 detectors was carefully corrected via Monte Carlo simulations.
Compared to previous 206Pb values, the Maxwellian averaged capture cross
sections derived from these data are about 20% and 9% lower at thermal energies
of 5 keV and 30 keV, respectively. These new results have a direct impact on
the s-process abundance of 206Pb, which represents an important test for the
interpretation of the cosmic clock based on the decay of 238U.Comment: 11 pages, 8 figures, paper to be submitted to Phys. Rev.
Resonance capture cross section of 207Pb
The radiative neutron capture cross section of 207Pb has been measured at the
CERN neutron time of flight installation n_TOF using the pulse height weighting
technique in the resolved energy region. The measurement has been performed
with an optimized setup of two C6D6 scintillation detectors, which allowed us
to reduce scattered neutron backgrounds down to a negligible level. Resonance
parameters and radiative kernels have been determined for 16 resonances by
means of an R-matrix analysis in the neutron energy range from 3 keV to 320
keV. Good agreement with previous measurements was found at low neutron
energies, whereas substantial discrepancies appear beyond 45 keV. With the
present results, we obtain an s-process contribution of 77(8)% to the solar
abundance of 207Pb. This corresponds to an r-process component of 23(8)%, which
is important for deriving the U/Th ages of metal poor halo stars.Comment: 7 pages, 3 figures, to be published in Phys. Rev.
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