780 research outputs found
Property Taxation of Multifamily Housing: An Empirical Analysis of Vertical and Horizontal Equity and Assessment Methods
This study used the hedonic price technique to focus on a housing characteristic that has been studied infrequently: whether a home is site-built or manufactured. Two hedonic price regression models were used to determine the predictive power of construction type on home price. The ?rst, which controlled for factors found to relate to home prices in previous research, showed a signi?cant difference between the prices of the two types of homes. The second, which also included other variables through a stepwise regression, found that the type of construction had more predictive power than any other explanatory variable in the model.
Landau Zener method to study quantum phase interference of Fe8 molecular nanomagnets
We present details about an experimental method based on the Landau Zener
model which allows to measure very small tunnel splittings in
molecular clusters Fe8. The measurements are performed with an array of
micro-SQUIDs. The observed oscillations of Delta as a function of the magnetic
field applied along the hard anisotropy axis are explained in terms of
topological quantum interference of two tunnel paths of opposite windings.
Transitions between M = -S and (S - n), with n even or odd, revealed a parity
(symmetry) effect which is analogous to the suppression of tunneling predicted
for half integer spins. This observation is the first direct evidence of the
topological part of the quantum spin phase (Berry phase) in a magnetic system.
The influence of intermolecular dipole interactions on the measured tunnel
splittings are shown.Comment: 6 pages, 14 figures, conference proceedings of MMM 1999, San Jose,
15-18 Nov., session number CD-0
The effects of nuclear spins on the quantum relaxation of the magnetization for the molecular nanomagnet Fe_8
The strong influence of nuclear spins on resonant quantum tunneling in the
molecular cluster Fe_8 is demonstrated for the first time by comparing the
relaxation rate of the standard Fe_8 sample with two isotopic modified samples:
(i) 56_Fe is replaced by 57_Fe, and (ii) a fraction of 1_H is replaced by 2_H.
By using a recently developed "hole digging" method, we measured an intrinsic
broadening which is driven by the hyperfine fields. Our measurements are in
good agreement with numerical hyperfine calculations. For T > 1.5 K, the
influence of nuclear spins on the relaxation rate is less important, suggesting
that spin-phonon coupling dominates the relaxation rate at higher temperature.Comment: 4 pages, 5 figure
Journalists in the UK
Based on one of the most comprehensive surveys of UK journalists ever carried out, this report describes journalists’ personal characteristics, employment conditions, and working routines. It also analyses journalists’ opinions on: ethics, influences on their work, the trustworthiness of institutions such as parliament and the police, their role in society, and changes in journalism over time. The report includes findings on UK journalism’s: lack of ethnic diversity and of women in senior positions; modest pay, especially for young journalists; and changing employment patterns and working routines in the digital age. It also reveals how journalists, while believing their profession is changing significantly, remain committed to traditional journalistic values; that although they adhere closely to professional codes and standards, UK journalists push ethical boundaries more than some of their international colleagues; and that rather than living up to the stereotype of the cynical hack, journalists in the UK are relatively trusting
Microwave photon detectors based on semiconducting double quantum dots
Detectors of microwave photons find applications in different fields ranging from security to cosmology. Due to the intrinsic difficulties related to the detection of vanishingly small energy quanta ¯hω, significant portions of the microwave electromagnetic spectrum are still uncovered by suitable techniques. No prevailing technology has clearly emerged yet, although different solutions have been tested in different contexts. Here, we focus on semiconductor quantum dots, which feature wide tunability by external gate voltages and scalability for large architectures. We discuss possible pathways for the development of microwave photon detectors based on photon-assisted tunneling in semiconducting double quantum dot circuits. In particular, we consider implementations based on either broadband transmission lines or resonant cavities, and we discuss how developments in charge sensing techniques and hybrid architectures may be beneficial for the development of efficient photon detectors in the microwave range
Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet
W-band ({\nu} ca. 94 GHz) electron paramagnetic resonance (EPR) spectroscopy
was used for a single-crystal study of a star-shaped Fe3Cr single-molecule
magnet (SMM) with crystallographically imposed trigonal symmetry. The high
resolution and sensitivity accessible with W-band EPR allowed us to determine
accurately the axial zero-field splitting terms for the ground (S =6) and first
two excited states (S =5 and S =4). Furthermore, spectra recorded by applying
the magnetic field perpendicular to the trigonal axis showed a pi/6 angular
modulation. This behavior is a signature of the presence of trigonal transverse
magnetic anisotropy terms whose values had not been spectroscopically
determined in any SMM prior to this work. Such in-plane anisotropy could only
be justified by dropping the so-called 'giant spin approach' and by considering
a complete multispin approach. From a detailed analysis of experimental data
with the two models, it emerged that the observed trigonal anisotropy directly
reflects the structural features of the cluster, i.e., the relative orientation
of single-ion anisotropy tensors and the angular modulation of single-ion
anisotropy components in the hard plane of the cluster. Finally, since
high-order transverse anisotropy is pivotal in determining the spin dynamics in
the quantum tunneling regime, we have compared the angular dependence of the
tunnel splitting predicted by the two models upon application of a transverse
field (Berry-phase interference).Comment: 13 pages, 9 figure
Food Price Volatility over the Last Decade in Niger and Malawi: Extent, Sources and Impact on Child Malnutrition
Recently, considerable attention has rightly been paid to the nutritional impact of the sharp
hikes in international food prices which took place in 2007-8 and, again, in 2010-11. While sacrosanct,
this growing focus has somewhat obscured the effect of other factors which do affect malnutrition in
the Sub-Saharan Africa context, i.e. the long term impact of agricultural policies, huge and persistent
seasonal variation in domestic food prices, and the impact of famines which still regularly stalk the
continent. This paper focuses on the relative weight of these factors in explaining child malnutrition
(proxied by the number of child admissions to feeding centers) in Malawi and Niger, two prototypical
countries in the region. The analysis shows that the drivers of domestic food staple prices and of the
ensuing child malnutrition have to be found not only – or not primarily – in the changes of
international food prices but mainly in the impact of agricultural policies on food production, the
persistence of a strong food price seasonality, and recurrent and often poorly attended famines.
Indeed, even during years of declines in international food prices, these factors often exert a huge
upward pressures on domestic food prices and child malnutrition
Macroscopic Quantum Tunneling in Small Antiferromagnetic Particles: Effects of a Strong Magnetic Field
We consider an effect of a strong magnetic field on the ground state and
macroscopic coherent tunneling in small antiferromagnetic particles with
uniaxial and biaxial single-ion anisotropy. We find several tunneling regimes
that depend on the direction of the magnetic field with respect to the
anisotropy axes. For the case of a purely uniaxial symmetry and the field
directed along the easy axis, an exact instanton solution with two different
scales in imaginary time is constructed. For a rhombic anisotropy the effect of
the field strongly depends on its orientation: with the field increasing, the
tunneling rate increases or decreases for the field parallel to the easy or
medium axis, respectively. The analytical results are complemented by numerical
simulations.Comment: 11 pages, 6 figure
Franck-Condon Blockade in a Single-Molecule Transistor
We investigate vibron-assisted electron transport in single-molecule
transistors containing an individual Fe4 Single-Molecule Magnet. We observe a
strong suppression of the tunneling current at low bias in combination with
vibron-assisted excitations. The observed features are explained by a strong
electron-vibron coupling in the framework of the Franck-Condon model supported
by density-functional theory
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