526 research outputs found
Laser geodynamic satellite (LAGEOS II)
The Laser Geodynamic Satellite 2 (LAGEOS 2) is nearly identical to the LAGEOS 1 satellite, which was launched by NASA in 1976. However, LAGEOS 2 is completely passive, and is equipped with fused silian corner reflectors for ranging with ground-based lasers. The addition of LAGEOS 2 will provide the GSFC laser network with significantly increased satellite tracking opportunities, because LAGEOS 1 is at a 110-degree inclination and LAGEOS 2 will be at a 52-degree inclination. The flight profile is given, and information is presented in tabular form on the following topics: Deep Space Network support, frequency assignments, telemetry, tracking, and tracking support responsibility
Intermittency and non-Gaussian fluctuations of the global energy transfer in fully developed turbulence
We address the experimentally observed non-Gaussian fluctuations for the
energy injected into a closed turbulent flow at fixed Reynolds number. We
propose that the power fluctuations mirror the internal kinetic energy
fluctuations. Using a stochastic cascade model, we construct the excess kinetic
energy as the sum over the energy transfers at different levels of the cascade.
We find an asymmetric distribution that strongly resembles the experimental
data. The asymmetry is an explicit consequence of intermittency and the global
measure is dominated by small scale events correlated over the entire system.
Our calculation is consistent with the statistical analogy recently made
between a confined turbulent flow and a critical system of finite size.Comment: To appear in Physical Review Letter
SMA applications in an innovative multishot deployment mechanism
An innovative Deployment and Retraction hinge Mechanism (DARM) in the frame of a technological program is examined. The mechanism includes two restraint/release devices, which enable it to be stable in its stowed or deployed position while sustaining all associated loads, and to carry its payload by remote command. The main characteristics of the DARM are as follows: deployment and retraction movements are spring actuated; the available amount of functional sequences is almost unlimited; and no use of electrical motors is made. These features were accomplished by: the application of a special kinematic scheme to the mechanical connection between the spring motor and the swivel head arm; and the use of shape memory alloys (SMA) actuators for both release and spring recharge functions. DARM is thus a mechanism which can find many applications in the general space scenario of in-orbit maintenance and servicing. In such a frame, the DARM typical concept, which has a design close to very simple one-shot deployment mechanisms, has a good chance to replace existing analog machines. Potential items that could be moved by DARM are: booms for satellite instruments; antenna reflector tips; entire antenna reflectors; and solar panels
Up and Down Quark Masses and Corrections to Dashen's Theorem from Lattice QCD and Quenched QED
In a previous letter (arXiv:1306.2287) we determined the isospin mass
splittings of the baryon octet from a lattice calculation based on quenched QED
and QCD simulations with 5 lattice spacings down to
, lattice sizes up to and average up-down
quark masses all the way down to their physical value. Using the same data we
determine here the corrections to Dashen's theorem and the individual up and
down quark masses. For the parameter which quantifies violations to Dashens's
theorem, we obtain , where the first error is
statistical, the second is systematic, and the third is an estimate of the QED
quenching error. For the light quark masses we obtain,
and in the
scheme at and the isospin breaking ratios
, and
. Our results exclude the solution to the strong
CP problem by more than standard deviations
Precision computation of the kaon bag parameter
Indirect CP violation in K \rightarrow {\pi}{\pi} decays plays a central role
in constraining the flavor structure of the Standard Model (SM) and in the
search for new physics. For many years the leading uncertainty in the SM
prediction of this phenomenon was the one associated with the nonperturbative
strong interaction dynamics in this process. Here we present a fully controlled
lattice QCD calculation of these effects, which are described by the neutral
kaon mixing parameter B_K . We use a two step HEX smeared clover-improved
Wilson action, with four lattice spacings from a\approx0.054 fm to
a\approx0.093 fm and pion masses at and even below the physical value.
Nonperturbative renormalization is performed in the RI-MOM scheme, where we
find that operator mixing induced by chiral symmetry breaking is very small.
Using fully nonperturbative continuum running, we obtain our main result
B_K^{RI}(3.5GeV)=0.531(6)_{stat}(2)_{sys}. A perturbative 2-loop conversion
yields B_K^{MSbar-NDR}(2GeV)=0.564(6)_{stat}(3)_{sys}(6)_{PT}, which is in good
agreement with current results from fits to experimental data.Comment: 10 pages, 7 figures. v2: Added one reference and one figure, replaced
2 figures for better readability and updated ensembles, conclusions
unchanged. Final, published versio
The true size of the ECB: new insights from National Central Bank balance sheets
The balance sheet of the European Central Bank (ECB) represents a very small fraction (onetenth) of the reported balance sheet of the Euro Area system as a whole. This paper presents evidence that the effective size of the ECB’s balance sheet is massively higher than this, and indeed is significantly higher even than the reported balance sheet of the Eurosystem as a whole. We point to strong evidence that most NCBs (especially those of the larger countries) effectively act on autopilot, as branches of a near‐monolithic institution which we term the “Mega‐ECB”. The lending behaviour of the “Mega‐ECB” appears to have been driven primarily by the borrowing needs of the distressed countries of the EU’s southern periphery
Isospin splittings in the light-baryon octet from lattice QCD and QED
While electromagnetic and up-down quark mass difference effects on octet
baryon masses are very small, they have important consequences. The stability
of the hydrogen atom against beta decay is a prominent example. Here we include
these effects by adding them to valence quarks in a lattice QCD calculation
based on simulations with 5 lattice spacings down to 0.054 fm,
lattice sizes up to 6 fm and average up-down quark masses all the way down to
their physical value. This allows us to gain control over all systematic
errors, except for the one associated with neglecting electromagnetism in the
sea. We compute the octet baryon isomultiplet mass splittings, as well as the
individual contributions from electromagnetism and the up-down quark mass
difference. Our results for the total splittings are in good agreement with
experiment.Comment: 5 pages, 3 figures. Version accepted for publication by Phys. Rev.
Let
New Antenna Deployment, Pointing and Supporting Mechanism
On ITALSAT Flight 2, the Italian telecommunications satellite, the two L-Ka antennas (Tx and Rx) use two large deployable reflectors (2000-mm diameter), whose deployment and fine pointing functions are accomplished by means of an innovative mechanism concept. The Antenna Deployment & Pointing Mechanism and Supporting Structure (ADPMSS) is based on a new configuration solution, where the reflector and mechanisms are conceived as an integrated, self-contained assembly. This approach is different from the traditional configuration solution. Typically, a rigid arm is used to deploy and then support the reflector in the operating position, and an Antenna Pointing Mechanism (APM) is normally interposed between the reflector and the arm for steering operation. The main characteristics of the ADPMSS are: combined implementation of deployment, pointing, and reflector support; optimum integration of active components and interface matching with the satellite platform; structural link distribution to avoid hyperstatic connections; very light weight and; high performance in terms of deployment torque margin and pointing range/accuracy. After having successfully been subjected to all component-level qualification and system-level acceptance tests, two flight ADPMSS mechanisms (one for each antenna) are now integrated on ITALSAT F2 and are ready for launch. This paper deals with the design concept, development, and testing program performed to qualify the ADPMSS mechanism
Electromagnetic corrections to light hadron masses
At the precision reached in current lattice QCD calculations, electromagnetic
effects are becoming numerically relevant. We will present preliminary results
for electromagnetic corrections to light hadron masses, based on simulations in
which a degree of freedom is superimposed on QCD
configurations from the BMW collaboration.Comment: 7 pages, 2 figures, The XXVIII International Symposium on Lattice
Field Theory, June 14-19,2010, Villasimius, Sardinia Ital
VARIAZIONE DELLA CARICA VIRALE HCV DURANTE IL TRATTAMENTO FARMACOLOGICO CON BOCEPREVIR. STUDIO CONDOTTO PRESSO L’U.O.C. MALATTIE INFETTIVE DEL P.O. SANT’ANTONIO ABATE DI TRAPANI
Definiamo l’Epatite C come una patologia cronico-degenerativa a carico del fegato con esordio prevalentemente asintomatico, solo pochi pazienti infatti sono consapevoli di essere infetti per il manifestarsi di un episodio acuto (tra l’altro non molto frequente) caratterizzato dalla comparsa di ittero, dolore al fianco destro, sensazione di malessere e stanchezza e, segno predominante, un notevole aumento delle Transaminasi. I sintomi si possono presentare dopo due o tre mesi dall’infezione in corrispondenza del picco delle Transaminasi e della comparsa dell’HCV RNA in circolo. L’agente eziologico responsabile è un virus a singolo filamento di RNA e che presenta 6 diversi genotipi denominato HCV,trasmesso principalmente per contatto diretto attraverso il sangue infetto. Se il precedente approccio terapeutico prevedeva la somministrazione di agenti stimolanti il Sistema Immunitario quali il PEG- Interferone alfa associato alla Ribavirina, nuove frontiere terapeutiche hanno previsto l’introduzione di 2 farmaci che hanno un’azione diretta nei confronti dell’HCV; Boceprevir e Telaprevir. Questi “Agenti Antivirali Diretti” (DAA), inibendo la proteasi NS3/4A del virus, bloccano il ciclo replicativo virale
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