11,548 research outputs found
Optical-lattice-assisted magnetic phase transition in a spin-orbit-coupled Bose-Einstein condensate
We investigate the effect of a periodic potential generated by a
one-dimensional optical lattice on the magnetic properties of an
spin-orbit-coupled Bose gas. By increasing the lattice strength one can achieve
a magnetic phase transition between a polarized and an unpolarized Bloch wave
phase, characterized by a significant enhancement of the contrast of the
density fringes. If the wave vector of the periodic potential is chosen close
to the roton momentum, the transition could take place at very small lattice
intensities, revealing the strong enhancement of the response of the system to
a weak density perturbation. By solving the Gross-Pitaevskii equation in the
presence of a three-dimensional trapping potential, we shed light on the
possibility of observing the magnetic phase transition in currently available
experimental conditions.Comment: 10 pages, 6 figures. Revised version, published in PR
Micro-displacement sensors based on plastic photonic bandgap Bragg fibers
We demonstrate an amplitude-based micro-displacement sensor that uses a
plastic photonic bandgap Bragg fiber with one end coated with a silver layer.
The reflection intensity of the Bragg fiber is characterized in response to
different displacements (or bending curvatures). We note that the Bragg
reflector of the fiber acts as an efficient mode stripper for the wavelengths
near the edge of the fiber bandgap, which makes the sensor extremely sensitive
to bending or displacements at these wavelengths. Besides, by comparison of the
Bragg fiber sensor to a sensor based on a regular multimode fiber with similar
outer diameter and length, we find that the Bragg fiber sensor is more
sensitive to bending due to presence of mode stripper in the form of the
multilayer reflector. Experimental results show that the minimum detection
limit of the Bragg fiber sensor can be smaller than 5 um for displacement
sensing
Generation of finite wave trains in excitable media
Spatiotemporal control of excitable media is of paramount importance in the
development of new applications, ranging from biology to physics. To this end
we identify and describe a qualitative property of excitable media that enables
us to generate a sequence of traveling pulses of any desired length, using a
one-time initial stimulus. The wave trains are produced by a transient
pacemaker generated by a one-time suitably tailored spatially localized finite
amplitude stimulus, and belong to a family of fast pulse trains. A second
family, of slow pulse trains, is also present. The latter are created through a
clumping instability of a traveling wave state (in an excitable regime) and are
inaccessible to single localized stimuli of the type we use. The results
indicate that the presence of a large multiplicity of stable, accessible,
multi-pulse states is a general property of simple models of excitable media.Comment: 6 pages, 6 figure
Mechanisms of Surviving Burial: Dune Grass Interspecific Differences Drive Resource Allocation After Sand Deposition
Sand dunes are important geomorphic formations of coastal ecosystems that are critical in protecting human populations that live in coastal areas. Dune formation is driven by ecomorphodynamic interactions between vegetation and sediment deposition. While there has been extensive research on responses of dune grasses to sand burial, there is a knowledge gap in understanding mechanisms of acclimation between similar, coexistent, dune-building grasses such as Ammophila breviligulata (C3), Spartina patens (C4), and Uniola paniculata (C4). Our goal was to determine how physiological mechanisms of acclimation to sand burial vary between species. We hypothesize that (1) in the presence of burial, resource allocation will be predicated on photosynthetic pathway and that we will be able to characterize the C3 species as a root allocator and the C4 species as leaf allocators. We also hypothesize that (2) despite similarities between these species in habitat, growth form, and life history, leaf, root, and whole plant traits will vary between species when burial is not present. Furthermore, when burial is present, the existing variability in physiological strategy will drive species-specific mechanisms of survival. In a greenhouse experiment, we exposed three dune grass species to different burial treatments: 0 cm (control) and a one-time 25-cm burial to mimic sediment deposition during a storm. At the conclusion of our study, we collected a suite of physiological and morphological functional traits. Results showed that Ammophila decreased allocation to aboveground biomass to maintain root biomass, preserving photosynthesis by allocating nitrogen (N) into light-exposed leaves. Conversely, Uniola and Spartina decreased allocation to belowground production to increase elongation and maintain aboveground biomass. Interestingly, we found that species were functionally distinct when burial was absent; however, all species became more similar when treated with burial. In the presence of burial, species utilized functional traits of rapid growth strategy, although mechanisms of change were interspecifically variable
The prevalence of polycystic ovary syndrome in reproductive-aged women of different ethnicity: a systematic review and meta-analysis
The prevalence of PCOS was investigated in many studies in different continents. However, there is no established prevalence of PCOS for distinct ethnic groups. In the current analysis, we conducted searches in PubMed, The Cochrane Library, EMBASE, CINAHL up to Jan. 2017 to identify studies reporting prevalence of PCOS in the general female population. Forty-two studies were identified, with 13 eligible for evidence synthesis. The prevalence among different ethnicity was estimated using random effect modelling. Our results suggested the lowest prevalence in Chinese women(2003 Rotterdam criterion: 5.6% 95% interval: 4.4–7.3%), and then in an ascending order for Caucasians (1990 NIH criterion: 5.5% 95% interval: 4.8–6.3%), Middle Eastern (1990 NIH 6.1% 95% interval: 5.3–7.1%; 2003 Rotterdam 16.0% 95% interval: 13.8–18.6%; 2006 AES 12.6% 95% interval: 11.3–14.2%), and Black women (1990 NIH: 6.1% 95% interval: 5.3–7.1%).There is variation in prevalence of PCOS under different diagnostic criteria and across ethnic groups. This emphasises the need for ethnicity-specific guidelines for PCOS to prevent under- or over-diagnosis of the condition given that under-diagnosis may lead to rapid conversion of metabolic disorders for patients whereas over-diagnosis may exert negative psychological effects on patients which worsens the major symptoms of PCOS
Protein slot blotting : an easy, rapid and reliable technique to identify the expression of a protein in transgenic plants
Hyperhoneycomb boron nitride with anisotropic mechanical, electronic and optical properties
Boron nitride structures have excellent thermal and chemical stabilities.
Based on state-of-art theoretical calculations, we propose a wide gap
semiconducting BN crystal with a three-dimensional hyperhoneycomb structure
(Hp-BN), which is both mechanically and thermodynamically stable. Our
calculated results show that Hp-BN has a higher bulk modulus and a smaller
energy gap as compared to c-BN. Moreover, due to the unique bonding structure,
Hp-BN exhibits anisotropic electronic and optical properties. It has great
adsorption in the ultraviolet region, but it is highly transparent in the
visible and infrared region, suggesting that the Hp-BN crystal could have
potential applications in electronic and optical devices
¿Es Deng Xizi el Primer Representante del Movimiento Intelectual Denominado Escuela de los Nombres?
La publicación de los códigos penales en el estado de Zheng de la época de las Primaveras y Otoños de China, concretamente en el año 536 a. C., marcó el comienzo del movimiento intelectual denominado Mingjia, que los historiógrafos de la dinastÃa Han equipararon en importancia con la de otras escuelas de pensamiento de la misma época tales como el Confucianismo y el TaoÃsmo. Sus miembros eran destacados activistas polÃticos y sociales y al mismo tiempo se dedicaban al estudio de los nombres conceptuales. Estos dos tipos de actividades no eran incompatibles, sino mutuamente complementarias para estos filósofos elocuentes, quienes contribuyeron especialmente al estudio de Xingming y a las teorÃas lógicas de la antigua China.La publicació dels codis penals en l'estat de Zheng de l'època de les Primaveres i Tardors de Xina, concretament l'any 536 a. C., va marcar el començament del moviment intel·lectual denominat Mingjia, que els historiògrafs de la dinastia Han van equiparar en importà ncia amb la d'altres escoles de pensament de la mateixa època tals com el Confucianisme i el Taoisme. Els seus membres eren destacats activistes polÃtics i socials i al mateix temps es dedicaven a l'estudi dels noms conceptuals. Aquests dos tipus d'activitats no eren incompatibles, sinó mútuament complementà ries per a aquests filòsofs eloqüents, els qui van contribuir especialment a l'estudi de Xingming i a les teories lògiques de l'antiga Xina
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