985 research outputs found
Solar electric propulsion system tests
Design and performance of solar-powered electric propulsion system for interplanetary space exploratio
Intercalation and dynamics of hydrated Fe2+ in the vermiculites from Santa Olalla and Ojén
Although the intercalation of Fe3+ into layered phyllosicilicates-especially into smectites-attracted much attention in the past two decades, the information about Fe2+ loaded phyllosilicates is sparse. Here we present an investigation of the Fe2+ exchanged vermiculites from Santa Olalla and Ojén (Andalusia, Spain) by means of Mössbauer spectroscopy. The room temperature Mössbauer spectra are very similar to those of the starting compounds (Na forms) except for a decrease of the contribution of structural Fe3+ and a concomitant increase of the contribution of Fe2+ sites, indicating an internal redox process. The extent of this redox reaction is different for the two vermiculites. Thus, the intercalated Fe2+ acts as an electron mediator from the external medium to the structural Fe3+ ions. A new component attributable to intercalated Fe2+ is practically invisible in the room temperature Mössbauer spectra, but increases strongly and continuously during cooling to 4.2 K, where it is the dominant feature of the Mössbauer patterns. At 4.2 K, its quadruple splitting amounts to 3.31 mm/s, which is in excellent agreement with the quadrupole slitting of Fe2+ coordinated to six water molecules in a highly symmetric octahedral arrangement. The strong decrease of the Mössbauer-Lamb factor of this component with increasing temperature indicates a weak bonding of the Fe 2+ in the interlayer space
Opioid-induced hyperalgesia after rapid titration with intravenous morphine: Switching and re-titration to intravenous methadone
Rapid titration with intravenous morphine (IV-MO) provides fast and efficient pain relief in cancer patients with severe-excruciating pain. However, some patients, after an initially favourable response, can develop an hyperexcitated state unrelieved or worsened by further dose increments
Ultra-compact modulators based on novel CMOS-compatible plasmonic materials
We propose several planar layouts of ultra-compact plasmonic waveguide
modulators that utilize alternative CMOS-compatible materials. The modulation
is efficiently achieved by tuning the carrier concentration in a transparent
conducting oxide layer, thereby tuning the waveguide either in plasmonic
resonance or off-resonance. Resonance significantly increases the absorption
coefficient of the plasmonic waveguide, which enables larger modulation depth.
We show that an extinction ratio of 86 dB/um can be achieved, allowing for a
3-dB modulation depth in less than one micron at the telecommunication
wavelength. Our multilayer structures can potentially be integrated with
existing plasmonic and photonic waveguides as well as novel semiconductor-based
hybrid photonic/electronic circuits
CMOS compatible integrated all-optical radio frequency spectrum analyzer
We report an integrated all-optical radio frequency spectrum analyzer based on a ~4cm long doped silica glass waveguide, with a bandwidth greater than 2.5 THz. We use this device to characterize the intensity power spectrum of ultrahighrepetition rate mode-locked lasers at repetition rates up to 400 GHz, and observe dynamic noise related behavior not observable with other technique
How does the geodesic rule really work for global symmetry breaking first order phase transitions?
The chain of events usually understood to lead to the formation of
topological defects during phase transitions is known as the Kibble mechanism.
A central component of the mechanism is the so-called ``geodesic rule''.
Although in the Abelian Higgs model the validity of the geodesic rule has been
questioned recently, it is known to be valid on energetic grounds for a global
U(1) symmetry breaking transition. However, even for these globally symmetric
models no dynamical analisys of the rule has been carried to this date, and
some points as to how events proceed still remain obscure. This paper tries to
clarify the dynamics of the geodesic rule in the context of a global U(1)
model. With an appropriate ansatz for the field modulus we find a family of
analytical expressions, phase walls, that accounts for both geodesic and
nongeodesic configurations. We then show how the latter ones are unstable and
decay into the former by nucleating pairs of defects. Finnally, we try to give
a physical perspective of how the geodesic rule might really work in these
transitions.Comment: 10 pages, 9 multiple figre
Self-locked optical parametric oscillation in a CMOS compatible microring resonator: a route to robust optical frequency comb generation on a chip
We report a novel geometry for OPOs based on nonlinear microcavity resonators. This approach relies on a self-locked scheme that enables OPO emission without the need for thermal locking of the pump laser to the microcavity resonance. By exploiting a CMOS-compatible microring resonator, we achieve oscillation featured by a complete absence of “shutting down”, i.e. the self-terminating behavior that is a very common and detrimental occurrence in externally pumped OPOs. Further, our scheme consistently produces very wide bandwidth (>300nm, limited by our experimental set-up) combs that oscillate at a spacing equal to the FSR of the micro cavity resonance
Behaviour of the neutrophil to lymphocyte ratio in young subjects with acute myocardial infarction
In the last years the neutrophil to lymphocyte ratio (NLR) has been examined in cardiovascular disorders and in particular in coronary artery disease and acute myocardial infarction (AMI). Now we examined this parameter in subjects with juvenile myocardial infarction at the initial stage and after 3 and 12 months. We enrolled 123 young subjects (112 men and 11 women, mean age 39.4\ub15.8 yrs) with AMI. The time interval between the AMI onset and the investigation was 13\ub17 days. The mean value of NLR observed in young AMI subjects was significantly increased compared to normal controls (N = 1.817\ub10.711; young AMI subjects = 2.376\ub10.873, p < 0.0001). NLR does not discriminate STEMI (2.427\ub10.878) and non STEMI (2.392\ub10.868) or diabetics (2.604\ub11.000) and non diabetics (2.324\ub10.853), but it differentiates smokers (2.276\ub10.853) and non smokers (2.837\ub11.072). NLR at the initial stage is not correlated with the number of cardiovascular risk factors or with the extent of the coronary disease. In this study we found a significant decrease of neutrophil count at 3 and 12 months later AMI without any significant variation of lymphocyte and consequently we observed a decrease in NLR at these two intervals of time in comparison with the initial stage. Despite some limitations present in this study, it is interesting to underline that also in juvenile myocardial infarction this low-cost haematological marker may be considered together with other inflammatory indicators
Un metodo per riconoscere faglie attive sepolte mediante misure areali di radon dal suolo
Lo studio riassume i risultati di una campagna
di misure geochimiche e strutturali
condotte nel 2004 (Neri et al., 2011) e
riguarda la misurazione delle emissioni
di gas radon e thoron dal suolo effettuate lungo
il fianco orientale dell’Etna, in una zona caratterizzata
dalla presenza di numerose faglie attive.
Le elaborazioni statistiche effettuate hanno
permesso di riconoscere soglie di anomalia
dei dati geochimici, nonché la produzione di
mappe di distribuzione che hanno evidenziato
una significativa correlazione spaziale tra le
anomalie riscontrate e i principali lineamenti
tettonici. Entrambe le anomalie di radon e
thoron si trovavano in aree interessate da sismicità
relativamente profonda, in particolare
in corrispondenza delle zone di intersezione tra
faglie differentemente orientate. Questo studio
conferma che la mappatura della distribuzione
di gas radon e thoron dal suolo può rivelare la
presenza di faglie nascoste da coperture recenti,
o faglie che non sono chiaramente visibili
in superficie
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