578 research outputs found
Direct and indirect measurements of the magnetic and magnetocaloric properties of Ni0.895Cr0.105MnGe1.05 melt-spun ribbons in high magnetic fields
We report the magnetic and magnetocaloric properties of rapidly solidified Ni0.895Cr0.105MnGe1.05 melt-spun ribbons studied by both direct (adiabatic temperature change) and indirect (isothermal magnetic entropy change) methods in intermediate and high magnetic fields up to 10 T. The maximum values of the adiabatic temperature changes (ÎTad) and magnetic entropy changes (ÎSM) were found to be âŒ2.6 K (”oH = 10 T) and 4.4 J kgâ1 Kâ1 (”oÎH = 5 T), respectively, near the Curie temperature (TC). The ÎTad curves and magnetization isotherms were found to be completely reversible, which indicates the high degree of reversibility of the MCEs in this system. A large temperature span (of about 61 K) and a non-saturating behavior of ÎTad were observed at magnetic fields up to 10 T. The adiabatic temperature change was found to be a linear function of (”oH)2/3 near TC, in accordance with the Landau theory of phase transitions
High-magnetic field characterization of magnetocaloric effect in FeZrB(Cu) amorphous ribbons
"The magnetic and magnetocaloric properties of a series of Fe-rich FeZrB(Cu) amorphous ribbons were investigated under magnetic field values up to mu H-0 of 8 T. A correlation between the saturation magnetization and the maximum magnetic entropy change vertical bar Delta S-M(peak)vertical bar is clearly evidenced. Although these metallic glasses show relatively low vertical bar Delta S-M(peak)vertical bar values (from 3.6 to 4.4 J kg(-1) K-1 for mu(0)Delta H - 8 T), the Delta S-M(T) curve broadens upon the increase in mu(0)Delta H, giving rise to a large refrigerant capacity RC (above 900 J kg(-1) for mu(0)Delta H-8 T). Using the universal curve method for rescaling the Delta S-M(T, mu(0)Delta H) curves, we found a collapse of the curves around the Curie temperature. However, in the low-temperature range the curves do not match into a single one due to the existence of magnetic frustration.
The effect of cooling rate on magnetothermal properties of Fe49Rh51
We have investigated the effects of quenching rate on the thermal dependence of the magnetic entropy change ÎSM(T) and the magnetic field induced hysteresis loss through the antiferromagnetic (AFM)âŻââŻferromagnetic (FM) transformation in bulk Fe49Rh51. Two nearly identical square-prism-shaped samples were subjected to two different temperature cooling regimes; one was rapidly quenched (FQ) in iced-water and another slow cooled (SC) to room temperature at a cooling rate of 2âŻK/min. The temperature of the AFMâŻââŻFM transition is similar for both samples, but the FQ sample shows much sharper temperature- and magnetic field-induced magnetization change; in addition, the total magnetization change is 14% larger. In FQ material, the magnetocaloric effect, i.e., ÎSM(T) quickly approaches saturation above 1âŻT and shows a large peak value at 2âŻT (13.9 versus 8.9âŻJkgâ1âŻKâ1 in SC material), but a larger average hysteresis loss \u3cHL\u3eFWHM in the temperature range coinciding with of the full-width at half-maximum of the ÎSM(T) curve
Operations of and Future Plans for the Pierre Auger Observatory
Technical reports on operations and features of the Pierre Auger Observatory,
including ongoing and planned enhancements and the status of the future
northern hemisphere portion of the Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200
Historical Isolation versus Recent Long-Distance Connections between Europe and Africa in Bifid Toadflaxes (Linaria sect. Versicolores)
Background: Due to its complex, dynamic and well-known paleogeography, the Mediterranean region provides an ideal framework to study the colonization history of plant lineages. The genus Linaria has its diversity centre in the Mediterranean region, both in Europe and Africa. The last land connection between both continental plates occurred during the Messinian Salinity Crisis, in the late Miocene (5.96 to 5.33 Ma). Methodology/Principal Findings: We analyzed the colonization history of Linaria sect. Versicolores (bifid toadflaxes), which includes c. 22 species distributed across the Mediterranean, including Europe and Africa. Two cpDNA regions (rpl32-trnL UAG and trnK-matK) were sequenced from 66 samples of Linaria. We conducted phylogenetic, dating, biogeographic and phylogeographic analyses to reconstruct colonization patterns in space and time. Four major clades were found: two of them exclusively contain Iberian samples, while the other two include northern African samples together with some European samples. The bifid toadflaxes have been split in African and European clades since the late Miocene, and most lineage and speciation differentiation occurred during the Pliocene and Quaternary. We have strongly inferred four events of post-Messinian colonization following long-distance dispersal from northern Africa to the Iberian Peninsula, Sicily and Greece. Conclusions/Significance: The current distribution of Linaria sect. Versicolores lineages is explained by both ancien
Calibration of the Logarithmic-Periodic Dipole Antenna (LPDA) Radio Stations at the Pierre Auger Observatory using an Octocopter
An in-situ calibration of a logarithmic periodic dipole antenna with a
frequency coverage of 30 MHz to 80 MHz is performed. Such antennas are part of
a radio station system used for detection of cosmic ray induced air showers at
the Engineering Radio Array of the Pierre Auger Observatory, the so-called
Auger Engineering Radio Array (AERA). The directional and frequency
characteristics of the broadband antenna are investigated using a remotely
piloted aircraft (RPA) carrying a small transmitting antenna. The antenna
sensitivity is described by the vector effective length relating the measured
voltage with the electric-field components perpendicular to the incoming signal
direction. The horizontal and meridional components are determined with an
overall uncertainty of 7.4^{+0.9}_{-0.3} % and 10.3^{+2.8}_{-1.7} %
respectively. The measurement is used to correct a simulated response of the
frequency and directional response of the antenna. In addition, the influence
of the ground conductivity and permittivity on the antenna response is
simulated. Both have a negligible influence given the ground conditions
measured at the detector site. The overall uncertainties of the vector
effective length components result in an uncertainty of 8.8^{+2.1}_{-1.3} % in
the square root of the energy fluence for incoming signal directions with
zenith angles smaller than 60{\deg}.Comment: Published version. Updated online abstract only. Manuscript is
unchanged with respect to v2. 39 pages, 15 figures, 2 table
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand events above 10^18 eV observed by the fluorescence detector of the
Pierre Auger Observatory in coincidence with at least one surface detector
station are selected for the analysis. The average shower maximum was found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
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