3,569 research outputs found
Response to Comment on `Undamped electrostatic plasma waves' [Phys. Plasmas 19, 092103 (2012)]
Numerical and experimental evidence is given for the occurrence of the
plateau states and concomitant corner modes proposed in \cite{valentini12}. It
is argued that these states provide a better description of reality for small
amplitude off-dispersion disturbances than the conventional
Bernstein-Greene-Kruskal or cnoidal states such as those proposed in
\cite{comment
NEA TDBIV project : preparation of a state-of-the-art report on thermodynamic data for cement
The program of work of the fourth phase of the OECD NEA Thermochemical Database Project (TDB-IV) contemplates a line of activity on the preparation of a state of the art report on cements. The present work aims at presenting the project, its aims and its limits
The effects of reduced physical activity on the lipid profile in patients with high cardiovascular risk during covid-19 lockdown
Background: The COVID-19 pandemic is a serious global health problem. In Italy, to limit the infections, the government ordered lockdown from March 2020. This measure, designed to contain the virus, led to serious limitations on the daily life of the individuals it affected, and in particular in the limitation of physical exercise. The aim of this study was to evaluate the effects of reduced physical activity on the lipid profile in patients with high cardiovascular risk. Methods: We enrolled 38 dyslipidemic patients, 56% male, with an age range of 44–62 years, considered to be at high cardiovascular risk. All patients were prescribed statin drug therapy (atorvastatin 40 mg) and a vigorous physical activity program four times a week, 1 h per session. In addition, a personalized Mediterranean diet was prescribed to all the patients. Total cholesterol, LDL, HDL and triglycerides were measured in patients at T0 before lockdown and at T1 during lockdown. Results: Data showed a significant increase (p < 0.01) in total cholesterol (+6,8%) and LDL (+15,8%). Furthermore, the analysis of the data revealed a reduction in HDL (−3%) and an increase in triglycerides (+3,2%), although both were not significant (p > 0.05). Conclusions: Our study showed that the reduction in physical activity during lockdown led to an increase in LDL levels, and therefore, in the risk of ischemic heart disease in dyslipidemic patients with high cardiovascular risk
foF2 prediction in Rome observatory
A prediction procedure of the hourly values of the critical frequency of the F2 ionospheric layer, foF2, based on the local geomagnetic index ak, is presented. The geomagnetic index utilised is the time-weighted accumulation magnetic index ak(τ) based on recent past history of the index ak. It is utilised an empirical relationship between the log(NmF2(t)/ NmF2M), where NmF2(t) is the hourly maximum electron density at the F2 peak layer and NmF2M is its 'quiet' value, and the time weighted magnetic index. The prediction of foF2 is calculated during periods of severe magnetic activity in the current solar cycle 23 in Rome observatory
On the possible use of radio occultation middle latitude electron density profiles to retrieve thermospheric parameters
This paper investigates possible use of middle latitude daytime COSMIC and CHAMP ionospheric radio occultation (IRO)
electron density profiles (EDPs) to retrieve thermospheric parameters, based on the Mikhailov et al. (2012) method. The aim of
this investigation is to assess the applicability of this type of observations for the routine implementation of the method. According
to the results extracted from the analysis presented here, about half of COSMIC IRO EDP observed under solar minimum
(2007–2008) conditions gave neutral gas density with an inaccuracy close to the declared absolute inaccuracy ±(10–15)% of
CHAMP observations, with the results being better than the empirical models JB-2008 and MSISE-00 provide. For the other half
of IRO EDP, either the solution provided by the method had to be rejected due to insufficient accuracy or no solution could be
obtained. For these cases, the parameters foF2 and hmF2 extracted from the corresponding IRO profiles have been found to be
inconsistent with the classic mid-latitude daytime F2-layer formalism that the method relies on, and they are incompatible with
the general trend provided by the IRI model. For solar maximum conditions (2002) the method was tested with IRO EDP from
CHAMP and it is indicated that its performance is quite stable in the sense that a solution could be obtained for all the cases
analyzed here. However available CHAMP EDP are confined by ~ 400 km in altitude and this might be the reason for the
20% bias of the retrieved densities toward larger values in respect to the observed densities. IRO observations up to 600 km under
solar maximum are required to confirm the exact performance of the method
Collaboration between two COST actions. Ionosphere and space weather
In this paper, we describe the collaboration between two COST action: COST 724 devoted
to space weather and COST 296 devoted to the study of the ionosphere and its impact on communication
and positionning. Several colleagues work in the two actions. This resulted in an important input on
ionospheric models provided by the COST 296 action to COST 724
Retrieval of thermospheric parameters from routinely observed F2-layer Ne(h) profiles at the geomagnetic equator
A principal possibility to retrieve basic thermospheric parameters (neutral temperature Tex, atomic [O] and molecular [O2] oxygen as well as molecular nitrogen [N2] concentrations) from the observed daytime electron density profiles Ne(h) in the equatorial F2-region is demonstrated for the first time. The reduction of a 2D continuity equation for electron concentration in the low-latitude F2-region at the geomagnetic equator (I = 0) results in a simple 1D equation which can be efficiently solved. The method was tested using Jicamarca Incoherent Scatter Radar (ISR) and Digisonde Ne(h) profiles for the periods when CHAMP and GRACE neutral gas density observations are available in the vicinity of the Jicamarca Observatory. The retrieved from ISR Ne(h) neutral gas densities were shown to be close to the observed ones (MRD < 10%) being within the announced absolute uncertainty (10–15%) of the neutral gas density observations and more successful than the predictions of the empirical models JB-2008 (MRD = 32%) and MSISE-00 (MRD = 27%) for the analyzed cases. The implementation of the method with Jicamarca Digisonde Ne(h) profiles has also shown acceptable results especially for solar minimum conditions (MRD ~ 12%) and higher prediction accuracy than modern empirical models provide. This finding seems to open a way for the practical exploitation of the method for thermospheric monitoring purposes
Self-Organized Criticality model for Brain Plasticity
Networks of living neurons exhibit an avalanche mode of activity,
experimentally found in organotypic cultures. Here we present a model based on
self-organized criticality and taking into account brain plasticity, which is
able to reproduce the spectrum of electroencephalograms (EEG). The model
consists in an electrical network with threshold firing and activity-dependent
synapse strenghts. The system exhibits an avalanche activity power law
distributed. The analysis of the power spectra of the electrical signal
reproduces very robustly the power law behaviour with the exponent 0.8,
experimentally measured in EEG spectra. The same value of the exponent is found
on small-world lattices and for leaky neurons, indicating that universality
holds for a wide class of brain models.Comment: 4 pages, 3 figure
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