scholarly journals Progress in semi-empirical modelling of main-sequence stellar chromospheres

1996 ◽  
Vol 176 ◽  
pp. 547-555
Author(s):  
E.R. Houdebine
Keyword(s):  
Main Sequence ◽  
Radiation Transfer ◽  
Research Programme ◽  
Significant Progress ◽  
Wave Dissipation ◽  
Empirical Modelling ◽  
Spectral Signatures ◽  
Outer Atmosphere ◽  
Semi Empirical

We present the results of a long term research programme on the outer atmospheres of main-sequence dwarfs. Combining NLTE-radiation transfer calculations with high resolution spectroscopic observations have led to significant progress in understanding chromospheric physical properties and spectral signatures. We emphasize that in order to unravel the extremely complex physics of the outer atmosphere and its energy source, magnetic field and acoustic wave dissipation, one must isolate the influence of all stellar parameters.

scholarly journals Reconstruction of long-term dynamics of Chernobyl-derived <sup>137</sup>Cs in the Upa River using bottom sediments in the Scheckino reservoir and semi-empirical modelling

2019 ◽  
Vol 381 ◽  
pp. 95-99
Author(s):  
Alexei V. Konoplev ◽  
Maxim M. Ivanov ◽  
Valentin N. Golosov ◽  
Evgenyi A. Konstantinov
Keyword(s):  
Bottom Sediments ◽  
Chernobyl Accident ◽  
137Cs Activity ◽  
Time Dependency ◽  
Empirical Modelling ◽  
Activity Concentrations ◽  
Order Of Magnitude ◽  
Time Dependencies ◽  
Semi Empirical

Abstract. Two cores of bottom sediments were collected in 2018 to a depth of ∼200 cm in the deepest part of the Scheckino reservoir on the Upa River (9500 km2), Tula region, Russia. This area was severely contaminated by radiocesium (r-Cs) after the Chernobyl accident in 1986. The fact that 137Cs activity concentrations in a specific horizon of the bottom sediments correspond to 137Cs concentrations associated with suspended matter delivered to the reservoir, provides a basis for constructing the dynamics of particulate 137Cs activity concentrations in the Upa River catchment from 1986 to 2017. Over the time since the Chernobyl accident, the particulate 137Cs concentrations have decreased by more than an order of magnitude, with only minor changes occurring during the last 15 years. Using a typical value for the distribution coefficient Kd for the rivers of the Chernobyl contamination zone, dissolved 137Cs activity concentrations in the Upa River have been estimated and their changes over the past 30 years since the accident have been studied. The resulting estimates of dissolved 137Cs concentrations in the Upa River have been found to be in good agreement with measured data over the period 1987–1991. The proposed and tested method provides a basis for reconstructing the long-term dependence of radionuclide concentrations in rivers and reservoirs based on their vertical distribution in bottom sediments. Reconstructed time dependencies of particulate and dissolved 137Cs activity concentrations in the Upa River were found to be described well by the proposed semi-empirical “diffusion” model based on an assumption that the time dependency of particulate r-Cs in the river corresponds to the time dependency of its concentration in top soil layers across the catchment which can be approximated by a dispersion-convection equation with physically meaningful parameters.

scholarly journals A Study of UVER in Santiago, Chile Based on Long-Term In Situ Measurements (Five Years) and Empirical Modelling

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 368
Author(s):  
Lisdelys González-Rodríguez ◽  
Amauri Pereira de Oliveira ◽  
Lien Rodríguez-López ◽  
Jorge Rosas ◽  
David Contreras ◽  
...  
Keyword(s):  
Urban Areas ◽  
Solar Spectrum ◽  
Sun Exposure ◽  
Great Accuracy ◽  
In Situ Measurements ◽  
Uv Index ◽  
Empirical Modelling ◽  
The People

Ultraviolet radiation is a highly energetic component of the solar spectrum that needs to be monitored because is harmful to life on Earth, especially in areas where the ozone layer has been depleted, like Chile. This work is the first to address the long-term (five-year) behaviour of ultraviolet erythemal radiation (UVER) in Santiago, Chile (33.5° S, 70.7° W, 500 m) using in situ measurements and empirical modelling. Observations indicate that to alert the people on the risks of UVER overexposure, it is necessary to use, in addition to the currently available UV index (UVI), three more erythema indices: standard erythemal doses (SEDs), minimum erythemal doses (MEDs), and sun exposure time (tery). The combination of UVI, SEDs, MEDs, and tery shows that in Santiago, individuals with skin types III and IV are exposed to harmfully high UVER doses for 46% of the time that UVI indicates is safe. Empirical models predicted hourly and daily values UVER in Santiago with great accuracy and can be applied to other Chilean urban areas with similar climate. This research inspires future advances in reconstructing large datasets to analyse the UVER in Central Chile, its trends, and its changes.

scholarly journals Fine-scale multiannual survey of benthic invertebrates in a glacier-fed stream used for hydropower generation

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Alberto Scotti ◽  
Roberta Bottarin
Keyword(s):  
Research Programme ◽  
Eastern Alps ◽  
Hydropower Plant ◽  
Research Network ◽  
Small Hydropower ◽  
Hydropower Plants ◽  
Before And After ◽  
Long Term Ecological Research ◽  
Research Facilities

AbstractThe present dataset contains information about aquatic macroinvertebrates and environmental variables collected before and after the implementation of a small “run-of-river” hydropower plant on the Saldur stream, a glacier-fed stream located in the Italian Central-Eastern Alps. Between 2015 and 2019, with two sampling events per year, we collected and identified 34,836 organisms in 6 sampling sites located within a 6 km stretch of the stream. Given the current boom of the hydropower sector worldwide, and the growing contribution of small hydropower plants to energy production, data here included may represent an important – and long advocated – baseline to assess the effects that these kinds of powerplants have on the riverine ecosystem. Moreover, since the Saldur stream is part of the International Long Term Ecological Research network, this dataset also constitutes part of the data gathered within this research programme. All samples are preserved at Eurac Research facilities.

scholarly journals Towards reducing variations in infant mortality and morbidity: a population-based approach

2016 ◽  
Vol 4 (1) ◽  
pp. 1-218 ◽  
Author(s):  
David Field ◽  
Elaine Boyle ◽  
Elizabeth Draper ◽  
Alun Evans ◽  
Samantha Johnson ◽  
...  
Keyword(s):  
Infant Mortality ◽  
Early Life ◽  
Developmental Outcomes ◽  
Research Programme ◽  
Mortality Rates ◽  
Population Based ◽  
Childhood Mortality ◽  
Mortality And Morbidity ◽  
Future Work

BackgroundOur aims were (1) to improve understanding of regional variation in early-life mortality rates and the UK’s poor performance in international comparisons; and (2) to identify the extent to which late and moderately preterm (LMPT) birth contributes to early childhood mortality and morbidity.ObjectiveTo undertake a programme of linked population-based research studies to work towards reducing variations in infant mortality and morbidity rates.DesignTwo interlinked streams: (1) a detailed analysis of national and regional data sets and (2) establishment of cohorts of LMPT babies and term-born control babies.SettingCohorts were drawn from the geographically defined areas of Leicestershire and Nottinghamshire, and analyses were carried out at the University of Leicester.Data sourcesFor stream 1, national data were obtained from four sources: the Office for National Statistics, NHS Numbers for Babies, Centre for Maternal and Child Enquiries and East Midlands and South Yorkshire Congenital Anomalies Register. For stream 2, prospective data were collected for 1130 LMPT babies and 1255 term-born control babies.Main outcome measuresDetailed analysis of stillbirth and early childhood mortality rates with a particular focus on factors leading to biased or unfair comparison; review of clinical, health economic and developmental outcomes over the first 2 years of life for LMPT and term-born babies.ResultsThe deprivation gap in neonatal mortality has widened over time, despite government efforts to reduce it. Stillbirth rates are twice as high in the most deprived as in the least deprived decile. Approximately 70% of all infant deaths are the result of either preterm birth or a major congenital abnormality, and these are heavily influenced by mothers’ exposure to deprivation. Births at < 24 weeks’ gestation constitute only 1% of all births, but account for 20% of infant mortality. Classification of birth status for these babies varies widely across England. Risk of LMPT birth is greatest in the most deprived groups within society. Compared with term-born peers, LMPT babies are at an increased risk of neonatal morbidity, neonatal unit admission and poorer long-term health and developmental outcomes. Cognitive and socioemotional development problems confer the greatest long-term burden, with the risk being amplified by socioeconomic factors. During the first 24 months of life each child born LMPT generates approximately £3500 of additional health and societal costs.ConclusionsHealth professionals should be cautious in reviewing unadjusted early-life mortality rates, particularly when these relate to individual trusts. When more sophisticated analysis is not possible, babies of < 24 weeks’ gestation should be excluded. Neonatal services should review the care they offer to babies born LMPT to ensure that it is appropriate to their needs. The risk of adverse outcome is low in LMPT children. However, the risk appears higher for some types of antenatal problems and when the mother is from a deprived background.Future workFuture work could include studies to improve our understanding of how deprivation increases the risk of mortality and morbidity in early life and investigation of longer-term outcomes and interventions in at-risk LMPT infants to improve future attainment.FundingThe National Institute for Health Research Programme Grants for Applied Research programme.

scholarly journals Nanoparticulate Adjuvants and Delivery Systems for Allergen Immunotherapy

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Juliana De Souza Rebouças ◽  
Irene Esparza ◽  
Marta Ferrer ◽  
María Luisa Sanz ◽  
Juan Manuel Irache ◽  
...  
Keyword(s):  
Allergen Immunotherapy ◽  
Allergic Diseases ◽  
Delivery Systems ◽  
Efficacy And Safety ◽  
Significant Progress ◽  
Reduced Dose ◽  
Promising Strategy ◽  
Polymeric Carriers ◽  
Local Side

In the last decades, significant progress in research and clinics has been made to offer possible innovative therapeutics for the management of allergic diseases. However, current allergen immunotherapy shows limitations concerning the long-term efficacy and safety due to local side effects and risk of anaphylaxis. Thus, effective and safe vaccines with reduced dose of allergen have been developed using adjuvants. Nevertheless, the use of adjuvants still has several disadvantages, which limits its use in human vaccines. In this context, several novel adjuvants for allergen immunotherapy are currently being investigated and developed. Currently, nanoparticles-based allergen-delivery systems have received much interest as potential adjuvants for allergen immunotherapy. It has been demonstrated that the incorporation of allergens into a delivery system plays an important role in the efficacy of allergy vaccines. Several nanoparticles-based delivery systems have been described, including biodegradable and nondegradable polymeric carriers. Therefore, this paper provides an overview of the current adjuvants used for allergen immunotherapy. Furthermore, nanoparticles-based allergen-delivery systems are focused as a novel and promising strategy for allergy vaccines.

scholarly journals Characteristics of Solidified Products Containing Radioactive Molten Salt Waste

2007 ◽  
Author(s):  
In-Tae Kim ◽  
Hwan-Seo Park ◽  
Yong-Zun Cho ◽  
Kwang-Wook Kim ◽  
Seong-Won Park ◽  
...  
Keyword(s):  
Molten Salt ◽  
Material System ◽  
Leaching Test ◽  
Spent Fuel ◽  
Micro Hardness ◽  
Chemical Route ◽  
Rich Phase ◽  
Stable Chemical ◽  
Semi Empirical

For a treatment of molten salt wastes generated from a pyroprocessing of oxide spent fuel, we had suggested a stable chemical route, named GRSS (Gel-Route Stabilization & Solidification), and a subsequent consolidation method. By using this method, a series of monolithic wasteforms with different conditions were fabricated, and then their physicochemical properties were investigated. A simulated salt containing 90wt% LiCl, 6.8wt% CsCl, and 3.2wt% SrCl2 was treated with a gel-forming material system, Si/Al/P = 0.4/0.4/0.2 and 0.35/0.35/0.3, and the gel-products were treated at 1100C° after mixing with borosilicate glass powder, where the salt loadings were about 16∼20wt%. The solidified products had a density of 2.3∼2.35g/cm3, a micro-hardness of 4.69∼4.72GPa, a glass transition temperature of 528∼537C°, and a thermal expansion coefficient of 1.65×10−7∼3.38×10−5/C°. Leaching results by the PCT-A method revealed leached rates, 10−3∼10−2g/m2day and 10−4∼10−3g/m2day for Cs and Sr, respectively. From the long-term ISO leaching test, the 900day-leached fraction of Cs and Sr predicted by a semi-empirical model were 0.89% and 0.39%. The leaching behaviors indicated that Cs would be immobilized into a Si-rich phase while Sr would be in a P-rich phase. The experimental results revealed that the GRSS method could be an alternative method for a solidification of radioactive molten salt wastes.

scholarly journals SIMULATION OF LONG-TERM SHORELINE CHANGE DRIVEN BY LONGSHORE AND CROSS-SHORE SEDIMENT TRANSPORT

2020 ◽  
pp. 31
Author(s):  
Yan Ding ◽  
Sung-Chan Kim ◽  
Richard B. Styles ◽  
Rusty L. Permenter
Keyword(s):  
Sediment Transport ◽  
Shoreline Change ◽  
Breaking Wave ◽  
Beach Profile ◽  
Shoreline Evolution ◽  
Longshore Sediment Transport ◽  
Wave Energy Flux ◽  
Semi Empirical ◽  
Evolution Modeling

Driven by wave and current, sediment transport alongshore and cross-shore induces shoreline changes in coasts. Estimated by breaking wave energy flux, longshore sediment transport in littoral zone has been studied for decades. Cross-shore sediment transport can be significant in a gentle-slope beach and a barred coast due to bar migration. Short-term beach profile evolution (typically for a few days or weeks) has been successfully simulated by reconstructing nonlinear wave shape in nearshore zone (e.g. Hsu et al 2006, Fernandez-Mora et al. 2015). However, it is still lack of knowledge on the relationship between cross-shore sediment transport and long-term shoreline evolution. Based on the methodology of beach profile evolution modeling, a semi-empirical closure model is developed for estimating phase-average net cross-shore sediment transport rate induced by waves, currents, and gravity. This model has been implemented into GenCade, the USACE shoreline evolution model.

Prediction of Hydraulic Conductivity of Fly Ash Built-in Mineral Sealing Layers

2017 ◽  
Author(s):  
Mariola Wasil
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Laboratory Tests ◽  
Physical Parameters ◽  
Low Permeability ◽  
Empirical Formulas ◽  
Semi Empirical ◽  
Sealing Layer ◽  
Compaction Method

Mineral barrier protects the groundwater and soil from contamination by insulating the leakage of harmful substances from landfill. One of the most important parameters, which decides about usefulness of material to built-in sealing layers, is hydraulic conductivity. Researchers have conducted investigations with the possibility of utilising fly ash as a mineral sealing layer material, which is justified by its low permeability and other properties. It is known that laboratory tests of hydraulic conductivity are often long-term and require expensive equipment. Therefore, to avoid this, researchers trying to assess permeability of tested material with empirical or semi empirical formulas. The aim of the paper is to compare the results of hydraulic conductivity of fly ash obtained from the laboratory tests and from estimation using different empirical formulas. Fly ash was compacted by the Standard Proctor compaction method at the optimum moisture content. The results obtained from empirical equations were variable. It was observed that the Kozeny-Carman formula and other, based on a few physical parameters of the soil, gave better results in prediction of hydraulic conductivity of fly ash than equations based on only one parameter.

scholarly journals Long‐Term Statistics of Observed Bubble Depth Versus Modeled Wave Dissipation

2020 ◽  
Vol 125 (2) ◽  
Author(s):  
Kjersti Opstad Strand ◽  
Øyvind Breivik ◽  
Geir Pedersen ◽  
Frode Bendiksen Vikebø ◽  
Svein Sundby ◽  
...  
Keyword(s):  
Wave Dissipation

scholarly journals Photometry of AM Her Stars – Line and Continuum Emission

1979 ◽  
Vol 53 ◽  
pp. 324-328
Author(s):  
Paula Szkody
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Main Sequence ◽  
Close Binary ◽  
Line Spectrum ◽  
Continuum Emission ◽  
Late Type ◽  
Emission Line Spectrum ◽  
Orbital Periods

The 4 known AM Her stars or polars (AM Her, ANUMa, W Pup, and 2A0311-227) are characterized by large circular polarizations of 10-35%, (Tapia 1977a, b, Krzeminski and Serkowski 1977), an emission line spectrum with strong H and He lines (Crampton and Cowley 1977, Greenstein et al. 1977), complex photometric variations (Szkody 1978, Priedhorsky and Krzeminski 1978, Warner & Nather 1972), long term high and low states and short orbital periods (80-180 min.). Models of these systems envision a close binary containing a magnetic white dwarf primary (B ~ 108G) and late type main sequence secondary transferring material into an accretion funnel over one or both poles of the white dwarf (Stockman et al. 1977, Lamb & Masters 1979, Liebert et al. 1978).

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