8,662 research outputs found
Transport anisotropy in biaxially strained La(2/3)Ca(1/3)MnO(3) thin films
Due to the complex interplay of magnetic, structural, electronic, and orbital
degrees of freedom, biaxial strain is known to play an essential role in the
doped manganites. For coherently strained La(2/3)Ca(1/3)MnO(3) thin films grown
on SrTiO(3) substrates, we measured the magnetotransport properties both
parallel and perpendicular to the substrate and found an anomaly of the
electrical transport properties. Whereas metallic behavior is found within the
plane of biaxial strain, for transport perpendicular to this plane an
insulating behavior and non-linear current-voltage characteristics (IVCs) are
observed. The most natural explanation of this anisotropy is a strain induced
transition from an orbitally disordered ferromagnetic state to an orbitally
ordered state associated with antiferromagnetic stacking of ferromagnetic
manganese oxide planes.Comment: 5 pages, 4 figure
meV resolution in laser-assisted energy-filtered transmission electron microscopy
The electronic, optical, and magnetic properties of quantum solids are
determined by their low-energy (< 100 meV) many-body excitations. Dynamical
characterization and manipulation of such excitations relies on tools that
combine nm-spatial, fs-temporal, and meV-spectral resolution. Currently,
phonons and collective plasmon resonances can be imaged in nanostructures with
sub-nm and 10s meV space/energy resolution using state-of-the-art
energy-filtered transmission electron microscopy (TEM), but only under static
conditions, while fs-resolved measurements are common but lack spatial or
energy resolution. Here, we demonstrate a new method of spectrally resolved
photon-induced near-field electron microscopy (SRPINEM) that allows us to
obtain nm-fs-resolved maps of nanoparticle plasmons with an energy resolution
determined by the laser linewidth (20 meV in this work), and not limited by
electron beam and spectrometer energy spreading. This technique can be extended
to any optically-accessible low-energy mode, thus pushing TEM to a previously
inaccessible spectral domain with an unprecedented combination of space, energy
and temporal resolution.Comment: 19 pages, 7 figure
Torsion pendulum facility for direct force measurements of LISA GRS related disturbances
A four mass torsion pendulum facility for testing of the LISA GRS is under
development in Trento. With a LISA-like test mass suspended off-axis with
respect to the pendulum fiber, the facility allows for a direct measurement of
surface force disturbances arising in the GRS. We present here results with a
prototype pendulum integrated with very large-gap sensors, which allows an
estimate of the intrinsic pendulum noise floor in the absence of sensor related
force noise. The apparatus has shown a torque noise near to its mechanical
thermal noise limit, and would allow to place upper limits on GRS related
disturbances with a best sensitivity of 300 fN/Hz^(1/2) at 1mHz, a factor 50
from the LISA goal. Also, we discuss the characterization of the gravity
gradient noise, one environmental noise source that could limit the apparatus
performances, and report on the status of development of the facility.Comment: Submitted to Proceedings of the 6th International LISA Symposium, AIP
Conference Proceedings 200
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Past performance and entry in procurement: An experimental investigation
There is widespread concern that incentive mechanisms based on past performance may hinder entry in procurement markets. We report results from a laboratory experiment as- sessing this concern. Within a simple dynamic procurement game where suppliers com- pete on price and quality we study how an incentive mechanism based on past per- formance affects outcomes and entry rates. Results indicate that some past-performance based mechanisms indeed hinder entry, but when appropriately designed may significantly increase both entry and quality provision without increasing costs to the procurer
Thermal gradient-induced forces on geodetic reference masses for LISA
The low frequency sensitivity of space-borne gravitational wave observatories
will depend critically on the geodetic purity of the trajectories of orbiting
test masses. Fluctuations in the temperature difference across the enclosure
surrounding the free-falling test mass can produce noisy forces through several
processes, including the radiometric effect, radiation pressure, and
outgassing. We present here a detailed experimental investigation of thermal
gradient-induced forces for the LISA gravitational wave mission and the LISA
Pathfinder, employing high resolution torsion pendulum measurements of the
torque on a LISA-like test mass suspended inside a prototype of the LISA
gravitational reference sensor that will surround the test mass in orbit. The
measurement campaign, accompanied by numerical simulations of the radiometric
and radiation pressure effects, allows a more accurate and representative
characterization of thermal-gradient forces in the specific geometry and
environment relevant to LISA free-fall. The pressure dependence of the measured
torques allows clear identification of the radiometric effect, in quantitative
agreement with the model developed. In the limit of zero gas pressure, the
measurements are most likely dominated by outgassing, but at a low level that
does not threaten the LISA sensitivity goals.Comment: 21 pages, 16 figures, submitted to Physical Review
Interleukin-18 mediates cardiac dysfunction induced by western diet independent of obesity and hyperglycemia in the mouse
Obesity and diabetes are independent risk factors for heart failure and are associated with the consumption of diet rich in saturated fat and sugar, Western diet (WD), known to induce cardiac dysfunction in the mouse through incompletely characterized inflammatory mechanisms. We hypothesized that the detrimental cardiac effects of WD are mediated by interleukin-18 (IL-18), pro-inflammatory cytokine linked to cardiac dysfunction. C57BL/6J wild-type male mice and IL-18 knockout male mice were fed high-saturated fat and high-sugar diet for 8 weeks. We measured food intake, body weight and fasting glycemia. We assessed left ventricular (LV) systolic and diastolic function by Doppler echocardiography and cardiac catheterization. In wild-type mice, WD induced a significant increase in isovolumetric relaxation time, myocardial performance index and left ventricular end-diastolic pressure, reflecting an impairment in diastolic function, paired with a mild reduction in LV ejection fraction. IL-18 KO mice had higher food intake and greater increase in body weight without significant differences in hyperglycemia. Despite displaying greater obesity, IL-18 knockout mice fed with WD for 8 weeks had preserved cardiac diastolic function and higher left ventricular ejection fraction. IL-18 mediates diet-induced cardiac dysfunction, independent of food intake and obesity, thus highlighting a disconnect between the metabolic and cardiac effects of IL-18
Microscopic cluster model for the description of (18O,16O) two-neutron transfer reactions
Excitation energy spectra and absolute cross-section angular distributions were measured for the 13C(18O,16O)15C two-neutron transfer reaction at 84 MeV incident energy. Exact finite-range coupled reaction channel calculations are used to analyse the data considering both the direct two-neutron transfer and the two-step sequential mechanism. For the direct calculations, two approaches are discussed: The extreme cluster and the newly introduced microscopic cluster. The latter makes use of spectroscopic amplitudes in the centre-of-mass reference frame, derived from shell-model calculations. The results describe well the experimental cross sections
Microscopic cluster model for the description of new experimental results on the C 13 (O 18, O 16) C 15 two-neutron transfer at 84 MeV incident energy
The C13(O18,O16)C15 reaction is studied at 84 MeV incident energy. Excitation energy spectra and absolute cross-section angular distributions for the strongest transitions are measured with good energy and angular resolutions. Strong selectivity for two-neutron configurations in the states of the residual nucleus is found. The measured cross-section angular distributions are analyzed by exact finite-range coupled reaction channel calculations. The two-particle wave functions are extracted using the extreme cluster and the independent coordinate scheme with shell-model derived coupling strengths. A new approach also is introduced, the microscopic cluster, in which the spectroscopic amplitudes in the center-of-mass reference frame are derived from shell-model calculations using the Moshinsky transformation brackets. This new model is able to describe well the experimental cross section and to highlight cluster configurations in the involved wave functions
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