548 research outputs found
The Inextricable Link Between Food and Linguistic Diversity: Wild Food Plants among Diverse Minorities in Northeast Georgia, Caucasus
The Inextricable Link Between Food and Linguistic Diversity: Wild Food Plants Among Diverse Minorities in Northeast Georgia, Caucasus. Divergences in the categorization and use of wild food plants among ethnic and linguistic groups living within the same environment are prototypical for the dual nature of biocultural diversity, which is generally richer on ecological and cultural edges. We interviewed 136 people from seven ethnolinguistic groups living in Georgia documenting the use of wild food plants. The results show the inextricable link between food and linguistic diversity; moreover, we observed a greater number of commonly used plants among Christian communities, as Muslim communities shared just one taxon widely used in all regions. Comparison with other Georgian regions and selected ethnic groups living in Azerbaijan showed lower use of wild food plants. Future investigations in the region should widen the ethnolinguistic research to include other aspects of ethnobiology and to dedicate more in-depth studies to understanding the underlying reasons for homogenization and plant-use erosion
Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}
The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature
superconducting energy gap \Delta_0 was studied for a series of
Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on
\Delta_0 was found to scale with the one on the superconducting transition
temperature. These experimental results are in quantitative agreement with
predictions from a polaronic model for cuprate high-temperature superconductors
and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure
The polarizability model for ferroelectricity in perovskite oxides
This article reviews the polarizability model and its applications to
ferroelectric perovskite oxides. The motivation for the introduction of the
model is discussed and nonlinear oxygen ion polarizability effects and their
lattice dynamical implementation outlined. While a large part of this work is
dedicated to results obtained within the self-consistent-phonon approximation
(SPA), also nonlinear solutions of the model are handled which are of interest
to the physics of relaxor ferroelectrics, domain wall motions, incommensurate
phase transitions. The main emphasis is to compare the results of the model
with experimental data and to predict novel phenomena.Comment: 55 pages, 35 figure
Millimeter Wavelength Brightness Fluctuations of the Atmosphere Above the South Pole
We report measurements of the millimeter wavelength brightness fluctuations
produced by the atmosphere above the South Pole made with the Arcminute
Cosmology Bolometer Array Receiver (ACBAR). The data span the 2002 Austral
winter during which ACBAR was mounted on the Viper telescope at the South Pole.
We recover the atmospheric signal in the presence of instrument noise by
calculating the correlation between signals from distinct elements of the ACBAR
bolometer array. With this method, it is possible to measure atmospheric
brightness fluctuations with high SNR even under the most stable atmospheric
conditions. The observed atmospheric signal is characterized by the parameters
of the Komolgorov-Taylor (KT) model, which are the amplitude and power law
exponent describing the atmospheric power spectrum, and the two components of
the wind angular velocity at the time of the observation. The KT model is
typically a good description of the observed fluctuations, and fits to the data
produce values of the Komolgorov exponent that are consistent with theoretical
expectations. By combining the wind angular velocity results with measurements
of the wind linear velocity, we find that the altitude of the observed
atmospheric fluctuations is consistent with the distribution of water vapor
determined from radiosonde data. For data corresponding to frequency passbands
centered on 150, 219, and 274 GHz, we obtain median fluctuation power
amplitudes of [10, 38, 74] mK^{2} rad^{-5/3} in Rayleigh-Jeans temperature
units. Comparing with previous work, we find that these median amplitudes are
approximately an order of magnitude smaller than those found at the South Pole
during the Austral summer and at least 30 times lower than found at the ALMA
site in the Atacama desert.Comment: 13 pages, 15 figures, submitted to ApJ, vertical margins fixe
In Situ Characterisation of Permanent Magnetic Quadrupoles for focussing proton beams
High intensity laser driven proton beams are at present receiving much
attention. The reasons for this are many but high on the list is the potential
to produce compact accelerators. However two of the limitations of this
technology is that unlike conventional nuclear RF accelerators lasers produce
diverging beams with an exponential energy distribution. A number of different
approaches have been attempted to monochromise these beams but it has become
obvious that magnetic spectrometer technology developed over many years by
nuclear physicists to transport and focus proton beams could play an important
role for this purpose. This paper deals with the design and characterisation of
a magnetic quadrupole system which will attempt to focus and transport
laser-accelerated proton beams.Comment: 20 pages, 42 figure
Charge-density-wave instability in the Holstein model with quartic anharmonic phonons
The molecular-crystal model, that describes a one-dimensional electron gas
interacting with quartic anharmonic lattice vibrations, offers great potentials
in the mapping of a relatively wide range of low-dimensional fermion systems
coupled to optical phonons onto quantum liquids with retarded interactions.
Following a non-perturbative approach involving non-Gaussian partial functional
integrations of lattice degrees of freedom, the exact expression of the
phonon-mediated two-electron action for this model is derived. With the help of
Hubbard-Stratonovich transformation the charge-density-wave instability is
examined in the sequel, with particular emphasis on the effect of the quartic
anharmonic phonons on the charge-density-wave transition temperature.Comment: 12 pages, 3 figure
Medicinal plants used to treat the most frequent diseases encountered in Ambalabe rural community, Eastern Madagascar
Far-infrared spectroscopy of a lensed starburst: a blind redshift from Herschel
We report the redshift of HATLAS J132427.0+284452 (hereafter HATLAS J132427),
a gravitationally lensed starburst galaxy, the first determined 'blind' by the
Herschel Space Observatory. This is achieved via the detection of [C II]
consistent with z = 1.68 in a far-infrared spectrum taken with the SPIRE
Fourier Transform Spectrometer. We demonstrate that the [C II] redshift is
secure via detections of CO J = 2 - 1 and 3 - 2 using the Combined Array for
Research in Millimeter-wave Astronomy and the Institut de Radioastronomie
Millimetrique's Plateau de Bure Interferometer. The intrinsic properties appear
typical of high-redshift starbursts despite the high lensing-amplified fluxes,
proving the ability of the FTS to probe this population with the aid of
lensing. The blind detection of [C II] demonstrates the potential of the SAFARI
imaging spectrometer, proposed for the much more sensitive SPICA mission, to
determine redshifts of multiple dusty galaxies simultaneously without the
benefit of lensing.Comment: 6 pages, 5 figures, accepted for publication in MNRAS as a Lette
Fluctuating Cu-O-Cu Bond model of high temperature superconductivity in cuprates
Twenty years of extensive research has yet to produce a general consensus on
the origin of high temperature superconductivity (HTS). However, several
generic characteristics of the cuprate superconductors have emerged as the
essential ingredients of and/or constraints on any viable microscopic model of
HTS. Besides a Tc of order 100K, the most prominent on the list include a
d-wave superconducting gap with Fermi liquid nodal excitations, a d-wave
pseudogap with the characteristic temperature scale T*, an anomalous
doping-dependent oxygen isotope shift, nanometer-scale gap inhomogeneity, etc..
The key role of planar oxygen vibrations implied by the isotope shift and other
evidence, in the context of CuO2 plane symmetry and charge constraints from the
strong intra-3d Coulomb repulsion U, enforces an anharmonic mechanism in which
the oxygen vibrational amplitude modulates the strength of the in-plane Cu-Cu
bond. We show, within a Fermi liquid framework, that this mechanism can lead to
strong d-wave pairing and to a natural explanation of the salient features of
HTS
Analogies of structural instabilities in EuTiO3 and SrTiO3
Specific heat measurements and theoretical calculations reveal an intimate
analogy between EuTiO3 and SrTiO3. For EuTiO3 a hitherto unknown specific heat
anomaly is discovered at TA=282(1)K which is analogous to the well known
specific heat anomaly of SrTiO3 at TA=105K caused by an antiferrodistortive
transition. Since the zone center soft phonon mode observed in both systems can
be modeled with the same parameters we ascribe the new 282(1)K instability of
EuTiO3 to an antiferrodistortive phase transition. The higher transition
temperature of EuTiO3 as compared to SrTiO3 results from spin phonon coupling.Comment: PRB to be published, 12 pages, 3 Figure
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