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

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