3,440 research outputs found
Geometric Algebras and Extensors
This is the first paper in a series (of four) designed to show how to use
geometric algebras of multivectors and extensors to a novel presentation of
some topics of differential geometry which are important for a deeper
understanding of geometrical theories of the gravitational field. In this first
paper we introduce the key algebraic tools for the development of our program,
namely the euclidean geometrical algebra of multivectors Cl(V,G_{E}) and the
theory of its deformations leading to metric geometric algebras Cl(V,G) and
some special types of extensors. Those tools permit obtaining, the remarkable
golden formula relating calculations in Cl(V,G) with easier ones in Cl(V,G_{E})
(e.g., a noticeable relation between the Hodge star operators associated to G
and G_{E}). Several useful examples are worked in details fo the purpose of
transmitting the "tricks of the trade".Comment: This paper (to appear in Int. J. Geom. Meth. Mod. Phys. 4 (6) 2007)
is an improved version of material appearing in math.DG/0501556,
math.DG/0501557, math.DG/050155
Approximate evolution for a system composed by two coupled Jaynes-Cummings Hamiltonians
In this work we construct an approximate time evolution operator for a system
composed by two coupled Jaynes-Cummings Hamiltonians. We express the full time
evolution operator as a product of exponentials and we analyze the validity of
our approximations contrasting our analytical results with those obtained by
purely numerical methods.Comment: 15 pages, 3 figures, 1 tabl
TYPOLOGY OF THE TRANSFORMATIONS OCCURRED IN THE PERI-URBAN SPACE OF HUERTA DE VALENCIA. EVIDENCE FROM NORTH ARCH OF VALENCIA (SPAIN)
[EN] This paper present the outputs obtained from the measurement and classification of the different types
of changes happened in the last 70 years on the Northern area of expansion of the city of Valencia. The
city has progressively been covering, with different rhythms and intensities, the space of La Huerta.
We can identify between 1944 and 2014 a group of transformations that occur repetitively, building a
change pattern identified as common on the city s expansion evolution. The methodology is based on
the analysis and measurement of changes occurred on land structure, land use, buildings occupation
and on the traditional structure of non-urban roads. The key sources to measure such changes have been
the use of the Cadastre of 1929 1944; 1972; and 1989; the orthophoto collections from the Valencian
Regional Library and the evolution of SIOSE mapping. The most outstanding results refer to the surprising
resilience of some elements from the structure of La Huerta de Valencia and the discovery and
identification of the main transformations patterns that could be generalized to the rest of La Huerta
de Valencia.Temes Cordovez, RR.; Moya Fuero, A. (2016). TYPOLOGY OF THE TRANSFORMATIONS OCCURRED
IN THE PERI-URBAN SPACE OF HUERTA DE VALENCIA.
EVIDENCE FROM NORTH ARCH OF VALENCIA (SPAIN). International Journal of Sustainable Development and Planning. 11(6):996-1003. doi:10.2495/SDP-V11-N6-996-1003S996100311
Giant and reversible extrinsic magnetocaloric effects in La0.7Ca0.3MnO3 films due to strain
Large thermal changes driven by a magnetic field have been proposed for
environmentally friendly energy efficient refrigeration, but only a few
materials which suffer hysteresis show these giant magnetocaloric effects. Here
we create giant and reversible extrinsic magnetocaloric effects in epitaxial
films of the ferromagnetic manganite La0.7Ca0.3MnO3 using strain mediated
feedback from BaTiO3 substrates near a first-order structural phase transition.
Our findings should inspire the discovery of giant magnetocaloric effects in a
wide range of magnetic materials, and the parallel development of
nanostructured bulk samples for practical applications.Comment: 32 pages, 1 Table, 5 figures, supplementary informatio
Engineering physiological environments to advance kidney organoid models from human pluripotent stem cells
During embryogenesis, the mammalian kidney arises because of reciprocal interactions between the ureteric bud (UB) and the metanephric mesenchyme (MM), driving UB branching and nephron induction. These morphogenetic processes involve a series of cellular rearrangements that are tightly controlled by gene regulatory networks and signaling cascades. Here, we discuss how kidney developmental studies have informed the definition of procedures to obtain kidney organoids from human pluripotent stem cells (hPSCs). Moreover, bioengineering techniques have emerged as potential solutions to externally impose controlled microenvironments for organoid generation from hPSCs. Next, we summarize some of these advances with major focus On recent works merging hPSC-derived kidney organoids (hPSC-kidney organoids) with organ-on-chip to develop robust models for drug discovery and disease modeling applications. We foresee that, in the near future, coupling of different organoid models through bioengineering approaches will help advancing to recreate organ-to-organ crosstalk to increase our understanding on kidney disease progression in the human context and search for new therapeutics
Orbital M1 versus E2 strength in deformed nuclei: A new energy weighted sum rule
Within the unified model of Bohr and Mottelson we derive the following linear
energy weighted sum rule for low energy orbital 1 excitations in even-even
deformed nuclei S_{\rm LE}^{\rm lew} (M_1^{\rm orb}) \cong (6/5) \epsilon
(B(E2; 0^+_1 \rightarrow 2_1^+ K=0)/Z e^2^2) \mu^2_N with B(E2) the E2
strength for the transition from the ground state to the first excited state in
the ground state rotational band, the charge r.m.s. radius squared and
the binding energy per nucleon in the nuclear ground state. It is
shown that this energy weighted sum rule is in good agreement with available
experimental data. The sum rule is derived using a simple ansatz for the
intrinsic ground state wave function that predicts also high energy 1
strength at 2 carrying 50\% of the total moment of the
orbital M1 operator.Comment: REVTEX (3.0), 9 pages, RU924
The CoRoT Evolution and Seismic Tools Activity: Goals and Tasks
The forthcoming data expected from space missions such as CoRoT require the
capacity of the available tools to provide accurate models whose numerical
precision is well above the expected observational errors. In order to secure
that these tools meet the specifications, a team has been established to test
and, when necessary, to improve the codes available in the community. The CoRoT
evolution and seismic tool activity (ESTA) has been set up with this mission.
Several groups have been involved. The present paper describes the motivation
and the organisation of this activity, providing the context and the basis for
the presentation of the results that have been achieved so far. This is not a
finished task as future even better data will continue to demand more precise
and complete tools for asteroseismology.Comment: 11 pages, 3 figures, accepted for publication in Astrophysics and
Space Science, 'CoRoT ESTA' special volum
Circularly polarized laser emission induced in isotropic and achiral dye systems
The production of efficient, tunable, and switchable circularly polarized laser emission would have far reaching implications in optical communications or biophotonics. In this work, it is demonstrated the direct generation of circularly polarized (CP) laser emission in achiral and isotropic dye laser systems without the use of extracavity polarizing elements, and without resorting to chiral dyes, chiral liquid crystal matrices, or interferometric methods. The origin of this ellipticity arises from the dynamic birefringence induced by the strong and polarized laser pumping and the subsequent orientation anisotropy of the excited molecular dipoles. A complete polarimetric characterization of the polarization state of conventional dye laser oscillators as a function of different experimental parameters is performed and it is shown that the generated light always possesses a certain level of circularity that changes in a distinctive way with pump energy and polarization. These results demonstrate that it is possible to generate and modulate CP laser light from efficient and photostable conventional laser dyes.Peer Reviewe
A Mall Intercept Survey on Religion and Worldview in the Cape Flats of Cape Town, South Africa
This study analyzes worldviews and religious beliefs and practices in the Cape Flats area of Cape Town, South Africa, using a mall intercept survey of n=513 visitors to five shopping centers. Variables considered included demographic characteristics, measures of religiosity and religious pluralism, participation in religious activities, and supernaturalism (both related and unrelated to a traditional Christian-Abrahamic worldview). The majority (69.4%) of respondents identifies as Christian, though denominational affiliation is very diverse. The other two prevalent religious affiliations are the African Traditional Religion (16.4%) and Islam (11.7%). Only 1.6% of the respondents self-identified as non-religious, a smaller percentage than has been found in research on Cape Town as a whole or South Africa nationally. The degree of self-reported religiosity, participation in religious activities, and belief in supernatural phenomena are all high. Associations between demographic characteristics and religion and worldview variables are analyzed in detail
Synthesis and tomographic characterization of the displaced Fock state of light
Displaced Fock states of the electromagnetic field have been synthesized by
overlapping the pulsed optical single-photon Fock state |1> with coherent
states on a high-reflection beamsplitter and completely characterized by means
of quantum homodyne tomography. The reconstruction reveals highly non-classical
properties of displaced Fock states, such as negativity of the Wigner function
and photon number oscillations. This is the first time complete tomographic
reconstruction has been performed on a highly non-classical optical state
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