339 research outputs found
Quantum Interference of Coulomb Interaction and Disorder: Phase Shift of Friedel Oscillations and an Instability of the Fermi Sea
We investigate the influence of interference between Coulomb interaction and
impurity scattering on the static electronic response in
disordered metals to leading order in the effective Coulomb interaction. When
the transport relaxation time is much shorter than the
quasiparticle life time, we find a \mbox{sgn}(2p_F-q)/\sqrt{|2p_F-q|}
divergence of the polarization function at the Fermi surface (). It
causes a phase shift of the Friedel oscillations as well as an enhancement of
their amplitude. Our results are consistent with experiments and may be
relevant for understanding the stability of the amorphous state of certain
alloys against crystallization.Comment: 11 pages, 4 PostScript figures appended as a self-extracting tar
archive; includes output instruction
El prudencialismo táctico de Baltasar Gracián
Nos quejamos del poco valor humano y ético de muchos políticos de nuestro tiempo, pero no es difícil encontrar antecedentes del daño que puede hacer al bien común no comprender la misión de servicio a los demás que tienen tanto la vida política como cualquier puesto de dirección en las organizaciones humanas
La educación política en la antigüedad clásica griega
En la Antigüedad clásica la participación política era considerada de la máxima importancia y definitoria del hombre libre; ser hombre era ser ciudadano. Esto implicaba a su vez la necesidad e importancia determinante de una formación orientada en dos dimensiones: participación ciudadana responsable y preparación para gobernar competentemente. Los principales filósofos políticos de entonces han tratado profunda y muy acertadamente este asunto; tanto es así, que muchos especialistas contemporáneos afirman con pesimismo: «hoy día la única novedad son los clásicos», también porque abordaron temas de gran actualidad para hoy avant la lettre. Incluso un apretado resumen, como se ofrece en este artículo, acerca del modo que abordaron esta educación política los principales autores griegos de ese período, puede ayudar a exhumar interesantes ideas que son como un rico filón de inspiración para programas hodiernos de formación política inspirados en los clásicos.Political participation in the ancient Greek society was considered of the outmost importance, defining the free man: to be man was to be a citizen. This fact emphasized the need and importance of a formation oriented in two dimensions: responsible citizenship participation and preparation for government. The main Greek political philosophers dealt with these topics in depth and very rightly up to the extent that many contemporary specialists state with pessimism: «nowadays, the only novelty are the classics» also because they analyzed topics of outmost current importance. Even a short abstract – as the one in the present paper – about political education by the most important Greek authors in the classic period, may help to extract interesting ideas to inspire the modern programs of political formation based on the classical authors
El buen gobernante en la antigüedad clásica. Indagación de un enfoque sapiencial en Plutarco [Crónica]
Texto leído en la defensa de la tesis doctoral realizada en la Facultad Eclesiástica de Filosofía de la Universidad de Navarra, el día 11 de febrero de 2011. Dirigió la tesis el Prof. Rafael Alvira. El tribunal estuvo compuesto por los profesores: José Ángel García Cuadrado (presidente), Ángel Luis González,
Rafael Alvira, Kurt Spang, Javier Vergara (secretario)
78 Pseudomonas aeruginosa cupA encoded fimbria expression is regulated by a GGDEF and EAL domain dependent modulation of the intracellular level of cyclic diguanylate
Barriers and Facilitators of Safe Communication in Obstetrics: Results from Qualitative Interviews with Physicians, Midwives and Nurses.
Patient safety is an important objective in health care. Preventable adverse events (pAEs) as the counterpart to patient safety are harmful incidents that fell behind health care standards and have led to temporary or permanent harm or death. As safe communication and mutual understanding are of crucial importance for providing a high quality of care under everyday conditions, we aimed to identify barriers and facilitators that impact safe communication in obstetrics from the subjective perspective of health care workers. A qualitative study with 20 semi-structured interviews at two university hospitals in Germany was conducted to explore everyday perceptions from a subjective perspective (subjective theories). Physicians, midwives, and nurses in a wide span of professional experience and positions were enrolled. We identified a structural area of conflict at the professional interface between midwives and physicians. Mandatory interprofessional meetings, acceptance of subjective mistakes, mutual understanding, and debriefings of conflict situations are reported to improve collaboration. Additionally, emergency trainings, trainings in precise communication, and handovers are proposed to reduce risks for pAEs. Furthermore, the participants reported time-constraints and understaffing as a huge burden that hinders safe communication. Concluding, safety culture and organizational management are closely entwined and strategies should address various levels of which communication trainings are promising
Adaptive Optics Imaging of a Massive Galaxy Associated with a Metal-rich Absorber
The damped and sub-damped Lyman-alpha absorption line systems in quasar
spectra are believed to be produced by intervening galaxies. However, the
connection of quasar absorbers to galaxies is not well-understood, since
attempts to image the absorbing galaxies have often failed. While most DLAs
appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs,
has been discovered in recent studies. Here we report high-resolution K-band
imaging with the Keck Laser Guide Star Adaptive Optics (LGSAO) system of the
field of quasar SDSSJ1323-0021 in search of the galaxy producing the z = 0.72
sub-DLA absorber. With a metallicity of 2-4 times the solar level, this
absorber is of the most metal-rich systems found to date. Our data show a large
bright galaxy with an angular separation of only 1.25" from the quasar,
well-resolved from the quasar at the high resolution of our data. The galaxy
has a magnitude of K = 17.6-17.9, which corresponds to a luminosity of ~ 3-6
L*. Morphologically, the galaxy is fit with a model with an effective radius,
enclosing half the total light, of R_e = 4 kpc and a bulge-to-total ratio of
0.4-1.0, indicating a substantial bulge stellar population. Based on the
mass-metallicity relation of nearby galaxies, the absorber galaxy appears to
have a stellar mass > 10^{11} M_sun. Given the small impact parameter, this
massive galaxy appears to be responsible for the metal-rich sub-DLA. The
absorber galaxy is consistent with the metallicity-luminosity relation observed
for nearby galaxies, but is near the upper end of metallicity. Our study marks
the first application of LGSAO for study of structure of galaxies producing
distant quasar absorbers. Finally, this study offers the first example of a
massive galaxy with a substantial bulge producing a metal-rich absorber.Comment: 17 pages, 4 figures, 1 table; Accepted for publication in The
Astronomical Journa
Nonequilibrium coupled Brownian phase oscillators
A model of globally coupled phase oscillators under equilibrium (driven by
Gaussian white noise) and nonequilibrium (driven by symmetric dichotomic
fluctuations) is studied. For the equilibrium system, the mean-field state
equation takes a simple form and the stability of its solution is examined in
the full space of order parameters. For the nonequilbrium system, various
asymptotic regimes are obtained in a closed analytical form. In a general case,
the corresponding master equations are solved numerically. Moreover, the
Monte-Carlo simulations of the coupled set of Langevin equations of motion is
performed. The phase diagram of the nonequilibrium system is presented. For the
long time limit, we have found four regimes. Three of them can be obtained from
the mean-field theory. One of them, the oscillating regime, cannot be predicted
by the mean-field method and has been detected in the Monte-Carlo numerical
experiments.Comment: 9 pages 8 figure
Mesoscopic Aharonov-Bohm oscillations in metallic rings
We study the amplitude of mesoscopic Aharonov-Bohm oscillations in
quasi-one-dimensional (Q1D) diffusive rings. We consider first the
low-temperature limit of a fully coherent sample. The variance of oscillation
harmonics is calculated as a function of the length of the leads attaching the
ring to reservoirs. We further analyze the regime of relatively high
temperatures, when the dephasing due to electron-electron interaction
suppresses substantially the oscillations. We show that the dephasing length
L_phi^AB governing the damping factor exp(-2pi R /L_phi^AB) of the oscillations
is parametrically different from the common dephasing length for the Q1D
geometry. This is due to the fact that the dephasing is governed by energy
transfers determined by the ring circumference 2pi R, making L_phi^AB
R-dependent.Comment: 16 pages, 4 figures, to appear in proceedings of NATO/Euresco
Conference "Fundamental Problems of Mesoscopic Physics: Interactions and
Decoherence", Granada (Spain), September 200
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