The Scattered Disk as the source of the Jupiter Family comets

The short period Jupiter family comets (JFCs) are thought to originate in the Kuiper Belt; specifically, a dynamical subclass of the Kuiper Belt known as the `scattered disk' is argued to be the dominant source of JFCs. However, the best estimates from observational surveys indicate that this source may fall short by more than two orders of magnitude the estimates obtained from theoretical models of the dynamical evolution of Kuiper belt objects into JFCs. We re-examine the scattered disk as a source of the JFCs and make a rigorous estimate of the discrepancy. We find that the uncertainties in the dynamical models combined with a change in the size distribution function of the scattered disk at faint magnitudes (small sizes) beyond the current observational limit offer a possible but problematic resolution to the discrepancy. We discuss several other possibilities: that the present population of JFCs is a large fluctuation above their long term average, that larger scattered disk objects tidally break-up into multiple fragments during close planetary encounters as their orbits evolve from the trans-Neptune zone to near Jupiter, or that there are alternative source populations that contribute significantly to the JFCs. Well-characterized observational investigations of the Centaurs, objects that are transitioning between the trans-Neptune Kuiper belt region and the inner solar system, can test the predictions of the non-steady state and the tidal break-up hypotheses. The classical and resonant classes of the Kuiper belt are worth re-consideration as significant additional or alternate sources of the JFCs.Comment: 33 pages, 6 figures. Revised Content. To be published in The Astrophysical Journa

A simple breathing circuit allowing precise control of inspiratory gases for experimental respiratory manipulations

BACKGROUND: Respiratory manipulations modulating blood flow and oxygenation levels have become an important component of modern functional MRI applications. Manipulations often consist of temporarily switching inspired fractions of CO(2) and O(2); and have typically been performed using simple oxygen masks intended for applications in respiratory therapy. However, precise control of inspired gas composition is difficult using this type of mask due to entrainment of room air and resultant dilution of inspired gases. We aimed at developing a gas delivery apparatus allowing improved control over the fractional concentration of inspired gases, to be used in brain fMRI studies. FINDINGS: The breathing circuit we have conceived allowed well controlled step changes in FiO(2) and FiCO(2), at moderate flow rates achievable on standard clinical flow regulators. In a two run test inside the scanner we demonstrate that tightly controlled simple gas switching manipulations can afford good intra-subject reproducibility of induced hyperoxia/hypercapnia responses. Although our approach requires a non-vented mask fitting closely to the subject’s face, the circuit ensures a continuous supply of breathable air even if the supply of medical gases is interrupted, and is easily removable in case of an emergency. The apparatus we propose is also compact and MRI compatible, allowing subject placement in confined spaces such as an MRI scanner for brain examinations. CONCLUSIONS: We have reported a new approach for the controlled administration of medical gases, and describe an implementation of the breathing circuit that is MRI compatible and uses commercially available parts. The resultant apparatus allows simple, safe and precise manipulations of FiO(2) and FiCO(2)

Innovative airplane ground handling system for green operations

The aim of this work is to develop a new concept of taxiing, in order to reduce the pollution in terms of noise and gas emission and to introduce a higher level of safety during ground operations. In the area close to the airport gates, the airplane ground handlings are currently performed through the airplane engines, which have the task of providing the trust necessary to move the airplane to the runway. Pollutant emissions and the noise level near the gates, however, could be drastically reduced by introducing an innovative autonomous tractor called CHAT (Clean Hydrogen Autonomous Tractor), developed from the standard pushback tractor. The ground operations could be basically modified by extending the time in which the airplane engines are idle and the airplane is towed by the tractors powered by renewable energy

Innovative airplane ground handling system for green operations

The aim of this work is to develop a new concept of taxiing, in order to reduce the pollution in terms of noise and gas emission and to introduce a higher level of safety during ground operations. In the area close to the airport gates, the airplane ground handlings are currently performed through the airplane engines, which have the task of providing the trust necessary to move the airplane to the runway. Pollutant emissions and the noise level near the gates, however, could be drastically reduced by introducing an innovative autonomous tractor called CHAT (Clean Hydrogen Autonomous Tractor), developed from the standard pushback tractor. The ground operations could be basically modified by extending the time in which the airplane engines are idle and the airplane is towed by the tractors powered by renewable energy

W+W−W^+W^- production at hadron colliders in NNLO QCD

Charged gauge boson pair production at the Large Hadron Collider allows detailed probes of the fundamental structure of electroweak interactions. We present precise theoretical predictions for on-shell $W^+W^-$ production that include, for the first time, QCD effects up to next-to-next-to-leading order in perturbation theory. As compared to next-to-leading order, the inclusive $W^+W^-$ cross section is enhanced by 9% at 7 TeV and 12% at 14 TeV. The residual perturbative uncertainty is at the 3% level. The severe contamination of the $W^+W^-$ cross section due to top-quark resonances is discussed in detail. Comparing different definitions of top-free $W^+W^-$ production in the four and five flavour number schemes, we demonstrate that top-quark resonances can be separated from the inclusive $W^+W^-$ cross section without significant loss of theoretical precision.Comment: 7 pages, 3 figure

Prevalence and risk factors for atopic disease in a population of preschool children in Rome: Challenges to early intervention

Background: Allergic diseases are complex identities determined by an interplay of genetic and environmental factors, resulting in the clinical manifestation of the disease. So far in Italy, updated data about the prevalence and risk factors of respiratory and allergic diseases in preschool children are not available. Methods: Children aged 3-5 years, attending four different nursery schools in an urban district of the city of Rome. A standardized questionnaire developed under the SIDRIA-2 protocol was administered to the parents of the children for the assessment of the potential risk factors and the outcomes. Results: A total of 494 children were enrolled in the study; 289 of them (60.3%) performed a skin prick test (SPT). In the 12 months preceding the interviews, 15% of children experienced at least one episode of wheezing, 5.5% of allergic rhinitis, 11% of children had a doctor diagnosis of asthma, 12% of children who underwent the SPT were positive to at least one of the tested allergens, being diagnosed as atopic. The univariate analysis for the health outcomes of the study shows that asthma was positively associated with daycare attendance, mother's history of atopy, siblings' history of atopy, recurrent siblings' bronchitis, and dermatitis. Atopy was positively associated with mother's history of atopy and dermatitis, whereas there is a borderline protective association with recurrent siblings' bronchitis. Conclusions: This study represents a first comprehensive epidemiological evaluation of prevalence of respiratory and allergic diseases in children aged 3-5 years in the city of Rome and an updating of the evolution of allergic diseases

Cholesterol depletion inhibits synaptic transmission and synaptic plasticity in rat hippocampus.

Several neurodegenerative disorders are associated with impaired cholesterol homeostasis in the nervous system where cholesterol is known to play a role in modulating synaptic activity and stabilizing membrane microdomains. In the present report, we investigated the effects of methyl-beta-cyclodextrin-induced cholesterol depletion on synaptic transmission and on the expression of 1) paired-pulse facilitation (PPF); 2) paired-pulse inhibition (PPI) and 3) long-term potentiation (LTP) in the CA1 hippocampal region. Results demonstrated that cyclodextrin strongly reduced synaptic transmission and blocked the expression of LTP, but did not affect PPF and PPI. The role of glutamatergic and GABAergic receptors in these cholesterol depletion-mediated effects was evaluated pharmacologically. Data indicate that, in cholesterol depleted neurons, modulation of synaptic transmission and synaptic plasticity phenomena are sustained by AMPA-, kainate-and NMDA-receptors but not by GABA-receptors. The involvement of AMPA-and kainate-receptors was confirmed by fluorimetric analysis of intracellular calcium concentrations in hippocampal cell cultures. These data suggest that modulation of receptor activity by manipulation of membrane lipids is a possible therapeutic strategy in neurodegenerative disease

Navigation Facility for High Accuracy Offline Trajectory and Attitude Estimation in Airborne Applications

The paper focuses on a navigation facility, relying on commercial-off-the-shelf (COTS) technology, developed to generate high-accuracy attitude and trajectory measurements in postprocessing. Target performance is cm-level positioning with tenth of degree attitude accuracy. The facility is based on the concept of GPS-aided inertial navigation but comprises carrier-phase differential GPS (CDGPS) processing and attitude estimation based on multiantenna GPS configurations. Expected applications of the system include: (a) performance assessment of integrated navigation systems, developed for general aviation aircraft and medium size unmanned aircraft systems (UAS); (b) generation of reference measurements to evaluate the flight performance of airborne sensors (e.g., radar or laser); and (c) generation of reference trajectory and attitude for improving imaging quality of airborne remote sensing data. The paper describes system architecture, selected algorithms for data processing and integration, and theoretical performance evaluation. Experimental results are also presented confirming the effectiveness of the implemented approach

A fast vertical trajectory prediction method for air traffic management, and relevant ATM system

The invention concerns a method and system for the prediction of aircrafts vertical trajectory, in particular for Air Traffic Management, comprising the following flight calculation modules: Take-off; Climb; Cruise; Descent; and Landing, corresponding to the relevant flight phases, wherein: the calculation of the predicted aircraft trajectory is effected by using a set of TEM equations comprising, as output variables, the vertical rate of climb or descent, the true air speed, the energy share factor, the thrust and the drag, the mass of the aircraft modeled as point-mass, and comprising, as inpu variables, the Mach number depending on true air speed and temperature and altitude, the gravity acceleration, and the fuel flow, and the flight path angle; the calculation of the predicted aircraft trajectory for Cruise phase, wherein only the mass is varying, is performed by using the following analytical solution to said set of TEM equations