6,604 research outputs found
Spin-to-Orbital Angular Momentum Conversion and Spin-Polarization Filtering in Electron Beams
We propose the design of a space-variant Wien filter for electron beams that
induces a spin half-turn and converts the corresponding spin angular momentum
variation into orbital angular momentum of the beam itself by exploiting a
geometrical phase arising in the spin manipulation. When applied to a spatially
coherent input spin-polarized electron beam, such a device can generate an
electron vortex beam, carrying orbital angular momentum. When applied to an
unpolarized input beam, the proposed device, in combination with a suitable
diffraction element, can act as a very effective spin-polarization filter. The
same approach can also be applied to neutron or atom beams.Comment: 9 pages, 5 figure
Identification of Prunus domestica L. endocarps from a Phoenician-Punic context (5th - 2nd century BC) by image analysis.
Integrable mixing of A_{n-1} type vertex models
Given a family of monodromy matrices {T_u; u=0,1,...,K-1} corresponding to
integrable anisotropic vertex models of A_{(n_u)-1}-type, we build up a related
mixed vertex model by means of glueing the lattices on which they are defined,
in such a way that integrability property is preserved. Algebraically, the
glueing process is implemented through one dimensional representations of
rectangular matrix algebras A(R_p,R_q), namely, the `glueing matrices' zeta_u.
Here R_n indicates the Yang-Baxter operator associated to the standard Hopf
algebra deformation of the simple Lie algebra A_{n-1}. We show there exists a
pseudovacuum subspace with respect to which algebraic Bethe ansatz can be
applied. For each pseudovacuum vector we have a set of nested Bethe ansatz
equations identical to the ones corresponding to an A_{m-1} quasi-periodic
model, with m equal to the minimal range of involved glueing matrices.Comment: REVTeX 28 pages. Here we complete the proof of integrability for
mixed vertex models as defined in the first versio
Detecting and mapping the ‘ephemeral’: magnetometric survey of a Pastoral Neolithic settlement at Luxmanda, Tanzania
Common assumptions about the ephemeral archaeological signature of pastoralist settlements have limited the application of geophysical techniques in the investigation of past herding societies. Here, the authors present a geophysical survey of Luxmanda, Tanzania, the largest-known settlement documented for the Pastoral Neolithic era in eastern Africa (c. 5000–1200 BP). The results demonstrate the value and potential of fluxgate gradiometry for the identification of magnetic anomalies relating to archaeological features, at a category of site where evidence for habitation was long thought to be undetectable. The study provides comparative data to enable archaeologists to identify loci for future investigations of mobile populations in eastern Africa and elsewhere
Discovering Plum, Watermelon and Grape Cultivars Founded in a Middle Age Site of Sassari (Sardinia, Italy) through a Computer Image Analysis Approach
The discovery of several waterlogged plant remains in a Middle Ages context (1330–1360 AD) in Sassari (NS, Sardinia, Italy) enabled the characterisation of archaeological plum fruit stones and watermelon and grape seeds through computer image analysis. Digital seed/endocarp images were acquired by a flatbed scanner and processed and analysed by applying computerised image analysis techniques. The morphometric data were statistically elaborated using stepwise linear discriminant analysis (LDA), allowing comparisons among archaeological remains, wild populations and autochthonous cultivars. Archaeological samples of plum were compared with 21 autochthonous cultivars of Prunus domestica from Sardinia, while archaeological watermelon seeds were compared with 36 seed lots of Citrullus from Europe, Africa and Asia. Moreover, archaeological grape seeds were compared with 51 autochthonous traditional cultivars of Vitis vinifera subsp. vinifera from Sardinia, 16 cultivars from Tuscany, six cultivars from Liguria, and eight cultivars from Catalonia (Spain). Archaeological plum remains showed morphological affinity with five cultivars of Sardinia. Seed features of the archaeological watermelon remains demonstrated affiliation with a proper sweet dessert watermelon, Citrullus lanatus, and similarity with some Sardinian cultivars. Regarding the archaeological remains of grape, morphometric comparisons showed a high similarity with autochthonous cultivars from Catalonia and Liguria. This study provides new information about ancient fruit cultivated and consumed during the Middle Ages in Sardinia
Joint Elastic Side-Scattering Lidar and Raman Lidar Measurements of Aerosol Optical Properties in South East Colorado
We describe an experiment, located in south-east Colorado, USA, that measured
aerosol optical depth profiles using two Lidar techniques. Two independent
detectors measured scattered light from a vertical UV laser beam. One detector,
located at the laser site, measured light via the inelastic Raman
backscattering process. This is a common method used in atmospheric science for
measuring aerosol optical depth profiles. The other detector, located
approximately 40km distant, viewed the laser beam from the side. This detector
featured a 3.5m2 mirror and measured elastically scattered light in a bistatic
Lidar configuration following the method used at the Pierre Auger cosmic ray
observatory. The goal of this experiment was to assess and improve methods to
measure atmospheric clarity, specifically aerosol optical depth profiles, for
cosmic ray UV fluorescence detectors that use the atmosphere as a giant
calorimeter. The experiment collected data from September 2010 to July 2011
under varying conditions of aerosol loading. We describe the instruments and
techniques and compare the aerosol optical depth profiles measured by the Raman
and bistatic Lidar detectors.Comment: 34 pages, 16 figure
CLASH: New Multiple-Images Constraining the Inner Mass Profile of MACS J1206.2-0847
We present a strong-lensing analysis of the galaxy cluster MACS J1206.2-0847
(=0.44) using UV, Optical, and IR, HST/ACS/WFC3 data taken as part of the
CLASH multi-cycle treasury program, with VLT/VIMOS spectroscopy for some of the
multiply-lensed arcs. The CLASH observations, combined with our mass-model,
allow us to identify 47 new multiply-lensed images of 12 distant sources. These
images, along with the previously known arc, span the redshift range 1\la
z\la5.5, and thus enable us to derive a detailed mass distribution and to
accurately constrain, for the first time, the inner mass-profile of this
cluster. We find an inner profile slope of (in the range [1\arcsec, 53\arcsec], or 5\la r \la300 kpc), as
commonly found for relaxed and well-concentrated clusters. Using the many
systems uncovered here we derive credible critical curves and Einstein radii
for different source redshifts. For a source at , the critical
curve encloses a large area with an effective Einstein radius of
\theta_{E}=28\pm3\arcsec, and a projected mass of . From the current understanding of structure formation in
concordance cosmology, these values are relatively high for clusters at
, so that detailed studies of the inner mass distribution of clusters
such as MACS J1206.2-0847 can provide stringent tests of the CDM
paradigm.Comment: 7 pages, 1 table, 4 figures; submitted to ApJ Letters; V3: minor
correction
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