7,476 research outputs found
Natural handicaps in Dutch agricultural areas : assessment of less favoured areas based on biophysical criteria
In order to assess agricultural areas with natural handicaps, the European Commission proposed a set of biophysical criteria. In this report all criteria were applied to the Dutch agricultural areas. The application of the criteria showed that four criteria led to the delineation of areas with natural handicaps. The handicaps were soil drainage, texture, chemical properties and slope. The criteria for low temperature, heat stress, rooting depth and soil moisture balance were not applicable to the Dutch agricultural soils. All results were aggregated to LAU2 units (municipality). An area at the scale of LAU2 units was considered affected by significant natural handicaps if at least 66% of the Utilised Agricultural Areas met at least one of the biophysical criteria. In total 109 LAU2 units were considered a Less Favoured Are
Observation of electronic and atomic shell effects in gold nanowires
The formation of gold nanowires in vacuum at room temperature reveals a
periodic spectrum of exceptionally stable diameters. This is identified as
shell structure similar to that which was recently discovered for alkali metals
at low temperatures. The gold nanowires present two competing `magic' series of
stable diameters, one governed by electronic structure and the other by the
atomic packing.Comment: 4 pages, 4 figure
Spin Disorder and Magnetic Anisotropy in Fe3O4 Nanoparticles
We have studied the magnetic behavior of dextran-coated magnetite
(FeO) nanoparticles with median particle size \left=8 .
Magnetization curves and in-field M\"ossbauer spectroscopy measurements showed
that the magnetic moment of the particles was much smaller than the bulk
material. However, we found no evidence of magnetic irreversibility or
non-saturating behavior at high fields, usually associated to spin canting. The
values of magnetic anisotropy from different techniques indicate that
surface or shape contributions are negligible. It is proposed that these
particles have bulk-like ferrimagnetic structure with ordered A and B
sublattices, but nearly compensated magnetic moments. The dependence of the
blocking temperature with frequency and applied fields, ,
suggests that the observed non-monotonic behavior is governed by the strength
of interparticle interactions.Comment: 11 pages, 7 figures, 3 Table
Remote sensing and hydrologic models for performance assessment in Sirsa Irrigation Circle, India
Irrigation management / Irrigation systems / Irrigation canals / Performance evaluation / Remote sensing / GIS / Models / Irrigated farming / Hydrology / Satellite surveys / Irrigation scheduling / Evapotranspiration / India
Direct calorimetric measurements of isothermal entropy change on single crystal W-type hexaferrites at the spin reorientation transition
We report on the magnetic field induced isothermal entropy change, \Delta
s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are
performed by direct calorimetry. Single crystals of the composition
BaCoZnFeO, prepared by the flux method, are measured at
different fixed temperatures under an applied field perpendicular and parallel
to the c axis. At 296 K one deduces a value of K = 8.7 \times 10^{4} J
m for the first anisotropy constant, which is in good agreement with the
literature. The spin reorientation transition temperature is estimated to take
place between 200 and 220 K
Static interactions and stability of matter in Rindler space
Dynamical issues associated with quantum fields in Rindler space are
addressed in a study of the interaction between two sources at rest generated
by the exchange of scalar particles, photons and gravitons. These static
interaction energies in Rindler space are shown to be scale invariant, complex
quantities. The imaginary part will be seen to have its quantum mechanical
origin in the presence of an infinity of zero modes in uniformly accelerated
frames which in turn are related to the radiation observed in inertial frames.
The impact of a uniform acceleration on the stability of matter and the
properties of particles is discussed and estimates are presented of the
instability of hydrogen atoms when approaching the horizon.Comment: 28 pages, 4 figure
Fifty years of thoracic surgical research in South Africa
Aim. To investigate the scope and trends in clinical research inSouth African thoracic surgery between 1955 and 2006 and tomeasure its impact on clinical practice.Method. A systematic review of all SA thoracic surgicalpublications was performed.Results. There were 252 general thoracic publications and amarked decrease in publications was noted after the peakperiod of productivity of the 1980s. There was a shift towardthe private sector as an origin of articles and toward a local,non-indexed journal. Inflammatory lung disease was themost frequent topic of publication. Case series and casereports were the most frequent type of article.Conclusion. The vulnerability of a small specialty in adeveloping country is illustrated by the clear trends thatemerged. The study provides important indicators for futureresearch, highlights the need for a national database of clinicalexperience, and emphasises the importance of rekindlinginterest and a culture of research in thoracic surgery
Tachyonic preheating using 2PI-1/N dynamics and the classical approximation
We study the process of tachyonic preheating using approximative quantum
equations of motion derived from the 2PI effective action. The O(N) scalar
(Higgs) field is assumed to experience a fast quench which is represented by an
instantaneous flip of the sign of the mass parameter. The equations of motion
are solved numerically on the lattice, and the Hartree and 1/N-NLO
approximations are compared to the classical approximation. Classical dynamics
is expected to be valid, since the occupation numbers can rise to large values
during tachyonic preheating. We find that the classical approximation performs
excellently at short and intermediate times, even for couplings in the larger
region currently allowed for the SM Higgs. This is reassuring, since all
previous numerical studies of tachyonic preheating and baryogenesis during
tachyonic preheating have used classical dynamics. We also compare different
initializations for the classical simulations.Comment: 32 pages, 21 figures. Published version: Some details added, section
added, references added, conclusions unchange
Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3
SrRuO3 is an itinerant ferromagnet and in its thin film form when grown on
miscut SrTiO3 it has Tc of ~ 150 K and strong uniaxial anisotropy. We measured
both the Hall effect and the magnetoresistance (MR) of the films as a function
of the angle between the applied field and the normal to the films at
temperatures above Tc. We extracted the extraordinary Hall effect that is
proportional to the perpendicular component of the magnetization and thus the
MR for each angle of the applied field could be correlated with the magnitude
and orientation of the induced magnetization. We successfully fit the MR data
with a second order magnetization expansion, which indicates large anisotropic
MR in the paramagnetic state. The extremum values of resistivity are not
obtained for currents parallel or perpendicular to the magnetization, probably
due to the crystal symmetry.Comment: 3 pages, 3 figure
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