1,299 research outputs found
Crisis, learning and policy change in the European Union
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.What is the causal relationship between crisis, learning and change? How does causality works in the current responses to the sovereign debt crisis provided by the European Union? We question the conventional identification of the cause-and-effect relationship provided by theories of crisis management, integration and policy learning. Drawing on models of contingent learning developed within psychology and behavioural and evolutionary economics, we theorise that surprise produces behavioural change via a fast-paced associative cue-outcome mechanism and that policy learning follows change. We then run our exercise in causal identification through a plausibility probe. We show that our argument passes the plausibility probe. Our conclusions on cognition and situational effects on learning suggest a new research agenda, more sensitive to how individuals behave in the real world and more robust in its micro-foundations
Non-collinear long-range magnetic ordering in HgCr2S4
The low-temperature magnetic structure of \HG has been studied by
high-resolution powder neutron diffraction. Long-range incommensurate magnetic
order sets in at T22K with propagation vector
\textbf{k}=(0,0,0.18). On cooling below T, the propagation vector
increases and saturates at the commensurate value \textbf{k}=(0,0,0.25). The
magnetic structure below T consists of ferromagnetic layers in the
\textit{ab}-plane stacked in a spiral arrangement along the \textit{c}-axis.
Symmetry analysis using corepresentations theory reveals a point group symmetry
in the ordered magnetic phase of 422 (D), which is incompatible with
macroscopic ferroelectricity. This finding indicates that the spontaneous
electric polarization observed experimentally cannot be coupled to the magnetic
order parameter
Measuring design diversity: A new application of Ostrom's rule types
We draw on the Institutional Grammar Tool's rule types to empiricallyanalyze the design of four major procedural regulatoryinstruments in the 27 member states of the European Union andthe UK. They are: consultation, regulatory impact assessment,freedom of information, and the Ombudsman. By adopting theInstitutional Grammar Tool as conceptual lens we end up witha single measurement template applicable to a variety of actionsituations. We derive measures that are conceptually robust andsuitable for comparative analysis. With original data gathered onthe official legal base in the 28 cases, we carry out principal componentsanalysis. We identify design patterns across countriesand instruments; the specialization of each instrument in termsof rule type; and the components that best explain cross-countryvariation. In the conclusions we argue that to reframe the designfeatures of the four instruments in conceptual, theoreticalcategories is not simply a taxonomical exercise but it extends tothe territory of comparative policy analysis, practice and reform
Electric field control of magnetic properties and electron transport in BaTiO3-based multiferroic heterostructures
In this paper, we report on a purely electric mechanism for achieving the electric control of the interfacial spin polarization and magnetoresistance in multiferroic tunneling junctions. We investigate micrometric devices based on the Co/Fe/BaTiO3/La0.7Sr0.3MnO3 heterostructure, where Co/Fe and La0.7Sr0.3MnO3 are the magnetic electrodes and BaTiO3 acts both as a ferroelectric element and tunneling barrier. We show that, at 20 K, devices with a 2 nm thick BaTiO3 barrier present both tunneling electroresistance (TER = 12   ±   0.1%) and tunneling magnetoresistance (TMR). The latter depends on the direction of the BaTiO3 polarization, displaying a sizable change of the TMR from  -0.32   ±   0.05% for the polarization pointing towards Fe, to  -0.12   ±   0.05% for the opposite direction. This is consistent with the on-off switching of the Fe magnetization at the Fe/BaTiO3 interface, driven by the BaTiO3 polarization, we have previously demonstrated in x-ray magnetic circular dichroism experiments
High Performances Corrugated Feed Horns for Space Applications at Millimetre Wavelengths
We report on the design, fabrication and testing of a set of high performance
corrugated feed horns at 30 GHz, 70 GHz and 100 GHz, built as advanced
prototypes for the Low Frequency Instrument (LFI) of the ESA Planck mission.
The electromagnetic designs include linear (100 GHz) and dual shaped (30 and 70
GHz) profiles. Fabrication has been achieved by direct machining at 30 GHz, and
by electro-formation at higher frequencies. The measured performances on side
lobes and return loss meet the stringent Planck requirements over the large
(20%) instrument bandwidth. Moreover, the advantage in terms of main lobe shape
and side lobes levels of the dual profiled designs has been demonstrated.Comment: 16 pages, 7 figures, accepted for publication in Experimental
Astronom
Glauber slow dynamics of the magnetization in a molecular Ising chain
The slow dynamics (10^-6 s - 10^4 s) of the magnetization in the paramagnetic
phase, predicted by Glauber for 1d Ising ferromagnets, has been observed with
ac susceptibility and SQUID magnetometry measurements in a molecular chain
comprising alternating Co{2+} spins and organic radical spins strongly
antiferromagnetically coupled. An Arrhenius behavior with activation energy
Delta=152 K has been observed for ten decades of relaxation time and found to
be consistent with the Glauber model. We have extended this model to take into
account the ferrimagnetic nature of the chain as well as its helicoidal
structure.Comment: 4 pages, 4 figures (low resolution), 16 references. Submitted to
Physical Review Letter
Temperature and field dependence of the phase separation, structure, and magnetic ordering in LaCaMnO, (, 0.50, and 0.53)
Neutron powder diffraction measurements, combined with magnetization and
resistivity data, have been carried out in the doped perovskite
LaCaMnO (, 0.50, and 0.53) to elucidate the structural,
magnetic, and electronic properties of the system around the composition
corresponding to an equal number of Mn3+ and Mn4+. At room temperature all
three samples are paramagnetic and single phase, with crystallographic symmetry
Pnma. The samples then all become ferromagnetic (FM) at K. At
K, however, a second distinct crystallographic phase (denoted A-II)
begins to form. Initially the intrinsic widths of the peaks are quite large,
but they narrow as the temperature decreases and the phase fraction increases,
indicating microscopic coexistence. The fraction of the sample that exhibits
the A-II phase increases with decreasing temperature and also increases with
increasing Ca doping, but the transition never goes to completion to the lowest
temperatures measured (5 K) and the two phases therefore coexist in this
temperature-composition regime. Phase A-II orders antiferromagnetically (AFM)
below a N\'{e}el temperature K, with the CE-type magnetic
structure. Resistivity measurements show that this phase is a conductor, while
the CE phase is insulating. Application of magnetic fields up to 9 T
progressively inhibits the formation of the A-II phase, but this suppression is
path dependent, being much stronger for example if the sample is field-cooled
compared to zero-field cooling and then applying the field. The H-T phase
diagram obtained from the diffraction measurements is in good agreement with
the results of magnetization and resistivity.Comment: 12 pages, 3 tables, 11 figure
Cooling rate dependence of the antiferromagnetic domain structure of a single crystalline charge ordered manganite
The low temperature phase of single crystals of NdCaMnO
and GdCaMnO manganites is investigated by squid
magnetometry. NdCaMnO undergoes a charge-ordering
transition at =245K, and a long range CE-type antiferromagnetic state
is established at =145K. The dc-magnetization shows a cooling rate
dependence below , associated with a weak spontaneous moment. The
associated excess magnetization is related to uncompensated spins in the
CE-type antiferromagnetic structure, and to the presence in this state of
fully orbital ordered regions separated by orbital domain walls. The observed
cooling rate dependence is interpreted to be a consequence of the rearrangement
of the orbital domain state induced by the large structural changes occurring
upon cooling.Comment: REVTeX4; 7 pages, 4 figures. Revised 2001/12/0
Physiological and sensorial aspects of peach fruits cv. Chimarrita depending on the season and management of green pruning.
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Crystal and magnetic structure of the LaCaMnO compound
We studied the crystal and magnetic structure of the
LaCaMnO compound for and . At T=300 K both
samples are paramagnetic with crystallographic symmetry . At low
temperatures they undergo a monoclinic distortion from orthorhombic -type
structure with to a monoclinic
structure with (,
) and space group below . The
onset of the structural transformation coincides with the development of the
-type long range antiferromagnetic order with propagation vector . The monoclinic unit cell allowed us to determine the
direction of the Mn magnetic moment with respect to the crystallographic axes:
it is perpendicular to the propagation vector, . The amplitude of the ordered magnetic moment at K
is found to be and for and 0.85,
respectively.Comment: In press (Phys. Rev B 01 Feb 2002
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