20,154 research outputs found
Two-gap superconductivity in single crystal LuFeSi from penetration depth measurements
Single crystal of LuFeSi was studied with the tunnel-diode
resonator technique in Meissner and mixed states. Temperature dependence of the
superfluid density provides strong evidence for the two-gap superconductivity
with almost equal contributions from each gap of magnitudes
and . In the vortex state, pinning
strength shows unusually strong temperature dependence and is non-monotonic
with the magnetic field (peak effect). The irreversibility line is sharply
defined and is quite distant from the , which hints on to enhanced
vortex fluctuations in this two-gap system. Altogether our findings provide
strong electromagnetic - measurements support to the two-gap superconductivity
in LuFeSi previously suggested from specific heat measurements
Model Theory of Holomorphic Functions
This thesis is concerned with a conjecture of Zilber: that the complex field expanded with the exponential function should be `quasi-minimal'; that is, all its definable subsets should be countable or have countable complement. Our purpose is to study the geometry of this structure and other expansions by holomorphic functions of the complex field without having first to settle any number-theoretic problems, by treating all countable sets on an equal footing.
We present axioms, modelled on those for a Zariski geometry, defining a non-first-order class of ``quasi-Zariski'' structures endowed with a dimension theory and a topology in which all countable sets are of dimension zero. We derive a quantifier elimination theorem, implying that members of the class are quasi-minimal.
We look for analytic structures in this class. To an expansion of the complex field by entire holomorphic functions we associate a sheaf of analytic germs which is closed under application of the implicit function theorem. We prove that is also closed under partial differentiation and that it admits Weierstrass preparation. The sheaf defines a subclass of the analytic sets which we call -analytic. We develop analytic geometry for this class proving a Nullstellensatz and other classical properties. We isolate a condition on the asymptotes of the varieties of certain functions in . If this condition is satisfied then the -analytic sets induce a quasi-Zariski structure under countable union. In the motivating case of the complex exponential we prove a low-dimensional case of the condition, towards the original conjecture
Dietary supplementation of essential oils in dairy cows: evidence for stimulatory effects on nutrient absorption
Results of recent in vitro experiments suggest that essential oils (EO) may not only influence ruminal fermentation but also modulate the absorption of cations like Na+, Ca2+ and NH4+ across ruminal epithelia of cattle and sheep through direct interaction with epithelial transport proteins, such as those of the transient receptor potential family. The aim of the current study was to examine this hypothesis by testing the effect of a blend of essential oils (BEO) on cation status and feed efficiency in lactating dairy cows. In the experiment, 72 dairy cows in mid-to-end lactation were divided into two groups of 36 animals each and fed the same mixed ration with or without addition of BEO in a 2×2 cross-over design. Feed intake, milk yield and composition, plasma and urine samples were monitored. Feeding BEO elevated milk yield, milk fat and protein yield as well as feed efficiency, whereas urea levels in plasma and milk decreased. In addition, plasma calcium levels increased significantly upon BEO supplementation, supporting the hypothesis that enhanced cation absorption might contribute to the beneficial effects of these EO
Transverse momentum distributions and their forward- backward correlations in the percolating colour string approach
The forward-backward correlations in the distributions, which present a
clear signature of non-linear effects in particle production, are studied in
the model of percolating colour strings. Quantitative predictions are given for
these correlations at SPS, RHIC and LHC energies. Interaction of strings also
naturally explains the flattening of distributions and increase of
with energy and atomic number for nuclear collisionsComment: 6 pages in LaTex, 3 figures in Postscrip
Does geothermal exploitation trigger earthquakes in Tuscany?
For the past 25 years, power production has been accompanied by a small but steady increase in seismicity near geothermal wells. A new project seeks to explore why
An improved seismicity picture of the Southern Tyrrhenian area by the use of OBS and land-based networks: the TYDE experiment
The problem of large location uncertainties for seismicity occurring in the Southern Tyrrhenian
Sea have been partially exceeded during the implementation of the long-term scientific mission of
the TYrrhenian Deep sea Experiment (TYDE), which allowed the installation of 14 wide-band
Ocean Bottom Seismometers (OBS) and Hydrophones (OBH) in the period December 2000 – May
2001 on the sea-bottom floor around the Aeolian and Ustica Islands. Local events recorded at landstations
have been observed also on the seismograms of the Ocean Bottom Seismic Network
(OBSN). Moreover, some hundreds of low magnitude events, undetected from the land networks,
have been recorded.
We combined the readings of body wave arrival times from OBS-OBH with those from landstations
to localise seismic events. We focused our study on three clusters of events representative
of the seismic activity of the area: (i) “deep” events, (ii) Ustica (iii) NE-Sicily. The analysis of the
integrated data set of the seismicity off-shore and on-shore, obtained from the combined land-OBS
seismic network (Ustica sequence and Deep events), has improved locations in terms of RMS
residuals, azimuthal gap, epicentral and hypocentral errors. Moreover, further classes of events have
been analysed: the first one includes some local events that could be located only by integrating single trigger readings from the few available land-stations with the OBSN-data; the second one
comprises local events that have been detected only by the OBS-OBH stations. In particular, the last
cluster underlines the importance of an OBSN in the Tyrrhenian deep basin to reveal its unknown
intense micro-seismicity, permitting to better understand both the tectonic and geodynamic picture
of the area
Correlations between spectra with different symmetry: any chance to be observed?
A standard assumption in quantum chaology is the absence of correlation
between spectra pertaining to different symmetries. Doubts were raised about
this statement for several reasons, in particular, because in semiclassics
spectra of different symmetry are expressed in terms of the same set of
periodic orbits. We reexamine this question and find absence of correlation in
the universal regime. In the case of continuous symmetry the problem is reduced
to parametric correlation, and we expect correlations to be present up to a
certain time which is essentially classical but larger than the ballistic time
Enhanced quasiparticle heat conduction of the multigap superconductor Lu2Fe3Si5
The thermal transport measurements have been made on the Fe-based
superconductor Lu2Fe3Si5 (Tc ~ 6 K) down to a very low temperature Tc/120. The
field and temperature dependences of the thermal conductivity confirm the
multigap superconductivity with fully opened gaps on the whole Fermi surfaces.
In comparison to MgB2 as a typical example of the multigap superconductor in a
p-electron system, Lu2Fe3Si5 reveals a remarkably enhanced quasiparticle heat
conduction in the mixed state. The results can be interpreted as a consequence
of the electronic correlations derived from Fe 3d-electrons.Comment: 5 pages, 4 figure
Seismic array analysis of Tornillo-like signals recorded in Tuscany
With the scientific purpose to monitor the micro-seismicity in the Central Apennines, we recently
deployed in Eastern Tuscany (Casentino) a temporary 12 element seismic array, composed
exclusively of 3-component seismometers. During the one month of registration we recorded an
unexpected high rate of local micro-seismicity with up to 180 events per day
Mode-locking of incommensurate phase by quantum zero point energy in the Frenkel-Kontorova model
In this paper, it is shown that a configuration modulated system described by
the Frenkel-Kontorova model can be locked at an incommensurate phase when the
quantum zero point energy is taken into account. It is also found that the
specific heat for an incommensurate phase shows different parameter-dependence
in sliding phase and pinning phase. These findings provide a possible way for
experimentalists to verify the phase transition by breaking of analyticity.Comment: 6 pages in Europhys style, 3 eps figure
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