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Search Results: 1 - 10 of 312919 matches for " G. -H. Lamot "
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Classical Trajectories for two Ring-Shaped Potentials
M. Kibler,G. -H. Lamot,P. Winternitz
Physics , 1998,
Abstract: This paper deals with the classical trajectories for two super-integrable systems: a system known in quantum chemistry as the Hartmann system and a system of potential use in quantum chemistry and nuclear physics. Both systems correspond to ring-shaped potentials. They admit two maximally super-integrable systems as limiting cases, viz, the isotropic harmonic oscillator system and the Coulomb-Kepler system in three dimensions. The planarity of the trajectories is studied in a systematic way. In general, the trajectories are quasi-periodic rather than periodic. A constraint condition allows to pass from quasi-periodic motions to periodic ones. When written in a quantum mechanical context, this constraint condition leads to new accidental degeneracies for the two systems studied.
Off-shell effects in the electromagnetic production of strangeness
T. Mizutani,C. Fayard,G. -H. Lamot,B. Saghai
Physics , 1997, DOI: 10.1103/PhysRevC.58.75
Abstract: Previous approaches to the photo- and electro-production of strangeness off the proton, based upon effective hadronic Lagrangians, are extended here to incorporate the so called off-shell effects inherent to the fermions with spin >= 3/2. A formalism for intermediate-state, spin 3/2, nucleonic and hyperonic resonances is presented and applied to the processes $\gamma + p ---> K^{+} + \Lambda$, for $E_{\gamma}^{lab}$ <= 2.5 GeV, $e + p ---> e' + K^+ + \Lambda$, as well as the branching ratio for the crossed channel reaction $K^- + p ---> \gamma + \Lambda$, with stopped kaons. The sensitivity, from moderate to significant, of various observables to such effects are discussed.
Surco diagonal en el lóbulo de la oreja: signo de enfermedad arterial coronaria? Diagonal earlobe crease: a sign of coronary artery disease?
Sebastián B. Lamot,Gustavo G. Lonegro,Marcos Hernández,Juan M. Lamot
Medicina (Buenos Aires) , 2007,
Abstract: El surco diagonal es un signo encontrado en el lóbulo de la oreja, que estaría relacionado con la enfermedad arterial coronaria. Nuestro objetivo fue estudiar la utilidad del signo. Se examinaron 104 pacientes (entre 30 y 80 a os) clasificados por sexo y edad. Cuarenta y nueve tenían enfermedad arterial coronaria diagnosticada por coronariografía (obstrucción > del 70% en una de las grandes arterias) y/o gamagrafía de perfusión miocárdica con Talio 201 (defecto fijo). El grupo control estuvo compuesto por 55 pacientes (asintomáticos, con electrocardiograma normal). Los datos obtenidos fueron sensibilidad (61.2%), especificidad (78.2%), valor predictivo positivo de (71.4%) y valor predictivo negativo (69.3%.). Observamos una relación significativa entre la presencia de surco diagonal y enfermedad arterial coronaria. Consideramos que este signo podría resultar de utilidad en la práctica clínica, fundamentalmente para los pacientes entre 30 y 60 a os. The diagonal earlobe crease is a sign theorically related to coronary artery disease. The purpose of this study was to prove the usefulness of this sign. A total of 104 patients were examined (ages 30 to 80) grouped by age and sex. Forty nine of them were diagnosed of having coronary artery disease by coronary angiography (a 70% obstruction of one of the major arteries), and/or myocardial perfusion imaging with Thallium 201 (fixed defects). The control group included 55 patients (asymptomatic with normal electrocardiogram). Data here obtained included sensitivity (61.2%), specificity (78.2%), positive predictive value (71.4%) and negative predictive value (69.3%). We found a significant relation between the presence of the diagonal earlobe crease and coronary artery disease. We consider it a sign that could prove useful in clinical practice, mainly among patients aged between 30 and 60.
Surco diagonal en el lóbulo de la oreja: ?signo de enfermedad arterial coronaria?
Lamot,Sebastián B.; Lonegro,Gustavo G.; Hernández,Marcos; Lamot,Juan M.; Lapresa,Susana; Sobrino,Edgardo;
Medicina (Buenos Aires) , 2007,
Abstract: the diagonal earlobe crease is a sign theorically related to coronary artery disease. the purpose of this study was to prove the usefulness of this sign. a total of 104 patients were examined (ages 30 to 80) grouped by age and sex. forty nine of them were diagnosed of having coronary artery disease by coronary angiography (a 70% obstruction of one of the major arteries), and/or myocardial perfusion imaging with thallium 201 (fixed defects). the control group included 55 patients (asymptomatic with normal electrocardiogram). data here obtained included sensitivity (61.2%), specificity (78.2%), positive predictive value (71.4%) and negative predictive value (69.3%). we found a significant relation between the presence of the diagonal earlobe crease and coronary artery disease. we consider it a sign that could prove useful in clinical practice, mainly among patients aged between 30 and 60.
HESS Opinions "The art of hydrology"*
H. H. G. Savenije
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2009,
Abstract: Hydrological modelling is the same as developing and encoding a hydrological theory. A hydrological model is not a tool but a hypothesis. The whole discussion about the inadequacy of hydrological models we have witnessed of late, is related to the wrong concept of what a model is. Good models don't exist. Instead of looking for the "best" model, we should aim at developing better models. The process of modelling should be top-down, learning from the data while at the same time connection should be established with underlying physical theory (bottom-up). As a result of heterogeneity occurring at all scales in hydrology, there always remains a need for calibration of models. This implies that we need tailor-made and site-specific models. Only flexible models are fit for this modelling process, as opposed to most of the established software or "one-size-fits-all" models. The process of modelling requires imagination, inspiration, creativity, ingenuity, experience and skill. These are qualities that belong to the field of art. Hydrology is an art as much as it is science and engineering.
HESS Opinions "Topography driven conceptual modelling (FLEX-Topo)"
H. H. G. Savenije
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2010,
Abstract: Heterogeneity and complexity of hydrological processes offer substantial challenges to the hydrological modeller. Some hydrologists try to tackle this problem by introducing more and more detail in their models, or by setting-up more and more complicated models starting from basic principles at the smallest possible level. As we know, this reductionist approach leads to ever higher levels of equifinality and predictive uncertainty. On the other hand, simple, lumped and parsimonious models may be too simple to be realistic or representative of the dominant hydrological processes. In this commentary, a new approach is proposed that tries to find the middle way between complex distributed and simple lumped modelling approaches. Here we try to find the right level of simplification while avoiding over-simplification. Paraphrasing Einstein, the maxim is: make a model as simple as possible, but not simpler than that. The approach presented is process based, but not physically based in the traditional sense. Instead, it is based on a conceptual representation of the dominant physical processes in certain key elements of the landscape. The essence of the approach is that the model structure is made dependent on a limited number of landscape classes in which the topography is the main driver, but which can include geological, geomorphological or land-use classification. These classes are then represented by lumped conceptual models that act in parallel. The advantage of this approach over a fully distributed conceptualisation is that it retains maximum simplicity while taking into account observable landscape characteristics.
Determination of evaporation from a catchment water balance at a monthly time scale
H. H. G. Savenije
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 1997,
Abstract: A method is presented to determine total evaporation from the earth's surface at a spatial scale that is adequate for linkage with climate models. The method is based on the water balance of catchments, combined with a calibrated autoregressive rainfall-runoff model. The time scale used is in the order of decades (10 days) to months. The rainfall-runoff model makes a distinction between immediate processes (interception and short term storage) and the remaining longer-term processes. Besides the calibrated rainfall-runoff model and the time series of observed rainfall and runoff, the method requires a relation between transpiration and soil moisture storage. The method is applied to data of the Bani catchment in Mali, a sub-catchment of the Niger river basin.
HESS Opinions "Topography driven conceptual modelling (FLEX-Topo)"
H. H. G. Savenije
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-4635-2010
Abstract: Heterogeneity and complexity of hydrological processes offer substantial challenges to the hydrological modeller. Some hydrologists try to tackle this problem by introducing more and more detail in their models, or by setting-up more and more complicated models starting from basic principles at the smallest possible level. As we know, this reductionist approach leads to ever higher levels of equifinality and predictive uncertainty. On the other hand, simple, lumped and parsimonious models may be too simple to be realistic or representative of the dominant hydrological processes. In this commentary, a new model approach is proposed that tries to find the middle way between complex distributed and simple lumped modelling approaches. Here we try to find the right level of simplification while avoiding over-simplification. Paraphrasing Einstein, the maxim is: make a model as simple as possible, but not simpler than that. The approach presented is process based, but not physically based in the traditional sense. Instead, it is based on a conceptual representation of the dominant physical processes in certain key elements of the landscape. The essence of the approach is that the model structure is made dependent on a limited number of landscape classes in which the topography is the main driver, but which can include geological, geomorphological or land-use classification. These classes are then represented by lumped conceptual models that act in parallel. The advantage of this approach over a fully distributed conceptualisation is that it retains maximum simplicity while taking into account observable landscape characteristics.
HESS Opinions "The art of hydrology"*
H. H. G. Savenije
Hydrology and Earth System Sciences Discussions , 2008,
Abstract: Hydrological modelling is the same as developing and encoding a hydrological theory. A hydrological model is not a tool but a theory. The whole discussion about the inadequacy of hydrological models we have witnessed of late, is related to the wrong concept of what a model is. Good models don't exist. Instead, hydrological research should focus on improving models and enhancing understanding. The process of modelling should be top-down, learning from the data. There is always a need for calibration, which implies that we need tailor-made and site-specific models. Only flexible models are fit for this modelling process, as opposed to most of the "established" models, "one-size-fits-all" models or "models of everywhere". The process of modelling requires imagination, inspiration, creativity, ingenuity, experience and skill. These are qualities that belong to the field of art. Hydrology is an art as much as it is science and engineering.
A New Parallel Algorithm for Simulation of Spin-Glass Systems on Scales of Space-Time Periods of an External Field  [PDF]
A. S. Gevorkyan, H. G. Abajyan, H. S. Sukiasyan
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.26059
Abstract: We study the statistical properties of an ensemble of disordered 1D spatial spin-chains (SSCs) of certain length in the external field. On nodes of spin-chain lattice the recurrent equations and corresponding inequal-ity conditions are obtained for calculation of local minimum of a classical Hamiltonian. Using these equa-tions for simulation of a model of 1D spin-glass an original high-performance parallel algorithm is developed. Distributions of different parameters of unperturbed spin-glass are calculated. It is analytically proved and shown by numerical calculations that the distribution of the spin-spin interaction constant in the Heisenberg nearest-neighboring Hamiltonian model as opposed to the widely used Gauss-Edwards-Anderson distribu-tion satisfies the Lévy alpha-stable distribution law which does not have variance. We have studied critical properties of spin-glass depending on the external field amplitude and have shown that even at weak external fields in the system strong frustrations arise. It is shown that frustrations have a fractal character, they are self-similar and do not disappear at decreasing of calculations area scale. After averaging over the fractal structures the mean values of polarizations of the spin-glass on the scales of external field's space-time peri-ods are obtained. Similarly, Edwards-Anderson’s ordering parameter depending on the external field ampli-tude is calculated. It is shown that the mean values of polarizations and the ordering parameter depending on the external field demonstrate phase transitions of first-order.
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