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Search Results: 1 - 10 of 464486 matches for " Milena; Camacho A "
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Ventilación de alta frecuencia oscilatoria en pacientes pediátricos
Donoso F,Alejandro; Cruces R,Pablo; León B,José; Ramírez A,Milena; Camacho A,Jorge;
Revista chilena de enfermedades respiratorias , 2006, DOI: 10.4067/S0717-73482006000100004
Abstract: introduction: high-frequency oscillatory ventilation (hfov) uses small tidal volumes, often smaller than the anatomic dead space, with high respiratory rates (> 1 hz). this therapeutic option has become more popular in our country in the last years. study objectives: to review the clinical experience with hfov in our pediatric intensive care unit and to describe the patient's characteristics, hfov strategies and outcome. patients: a prospective study included patients less than 16 years old with acute respiratory distress syndrome (ards) refractary to conventional mechanical ventilation (cmv). we compare two periods (1999-2001 and 2002-2004). measurements and results: forty-nine patients underwent onto 51 episodes of hfo ventilation, 80% presented with primary ards. previous conventional ventilation was 47 hours long. the median value of the oxygenation index (oi) at the beginning of hfov was 24. mean airway pressure was initially set at 9 cmh2o above the value in conventional ventilation. all the patients presented a decrease of their oi and ventilation was improved during the first 48 hours of therapy. median duration on hfov was 102 hours. the most frequent side effect was transient hypotension (25%). in the second period we observed a decrease in hemodynamic complications and also an increase in hfo duration. the mortality rate was 33% (22% due to pulmonary cause). conclusion: hfov is an effective therapy for pediatric respiratory failure refractory to conventional mechanical ventilation
The role of the quantum properties of gravitational radiation in the dete ction of gravitational waves
A. Camacho
Physics , 1998, DOI: 10.1142/S0217751X99001007
Abstract: The role that the quantum properties of a gravitational wave could play in the detection of gravitational radiation is analyzed. It is not only corroborated that in the current laser-interferometric detectors the resolution of the experimental apparatus could lie very far from the corresponding quantum threshold (thus the backreaction effect of the measuring device upon the gravitational wave is negligible), but it is also suggested that the consideration of the quantum properties of the wave could entail the definition of dispersion of the measurement outputs. This dispersion would be a function not only of the sensitivity of the measuring device, but also of the interaction time (between measuring device and gravitational radiation) and of the arm length of the corresponding laser- interferometer. It would have a minimum limit, and the introduction of the current experimental parameters insinuates that the dispersion of the existing proposals could lie very far from this minimum, which means that they would show a very large dispersion.
Decoherence and time emergence
A. Camacho
Physics , 1998,
Abstract: In this work the possible role that Decoherence Model could play in the emergence of the classical concept of time is analyzed. We take the case of a Mixmaster universe with small anisotropy and construct its Halliwell propagator. Afterwards we introduce in our system terms that comprise the effects of Decoherence Model. This is done by means of the so called Restricted Path Integral Formalism. We obtain Halliwell's modified propagator and find that a gauge invariant physical time emerges as consequence of this process.
Gravitomagnetism in Metric Theories: Analysis of Earth Satellites Results, and its Coupling with Spin
A. Camacho
Physics , 2002, DOI: 10.1023/A:1020078802195
Abstract: Employing the PPN formalism the gravitomagnetic field in different metric theories is considered in the analysis of the LAGEOS results. It will be shown that there are several models that predict exactly the same effect that general relativity comprises. In other words, these Earth satellites results can be taken as experimental evidence that the orbital angular momentum of a body does indeed generate space--time geometry, notwithstanding they do not endow general relativity with an outstanding status among metric theories. Additionally the coupling spin--gravitomagnetic field is analyzed with the introduction of the Rabi transitions that this field produces on a quantum system with spin 1/2. Afterwards, a continuous measurement of the energy of this system is introduced, and the consequences upon the corresponding probabilities of the involved gravitomagnetic field will be obtained. Finally, it will be proved that these proposals allows us, not only to confront against future experiments the usual assumption of the coupling spin--gravotimagnetism, but also to measure some PPN parameters and to obtain functional dependences among them.
Decoherence-induced violations of Einstein equivalence principle
A. Camacho
Physics , 2001, DOI: 10.1142/S0218271801001542
Abstract: In this essay it will be shown that Decoherence Model and Einstein Equivalence Principle are conceptually incompatible. In other words, assuming only the validity of the Weak Equivalence Principle the present work concludes that we face two possibilities: (i) if Decoherence Model provides a correct description of nature at quantum level, then there are systems which violate Local Position Invariance, or, (ii) if all the postulates behind Einstein Equivalence Principle are valid, even on quantum realm, then Decoherence Model breaks down in curved spacetimes. Finally, the present results are confronted against Schiff's conjecture.
Aharonov-Bohm Effect and Coordinate Transformations
A. Camacho
Physics , 1999, DOI: 10.1142/S0217732399001541
Abstract: Resorting to a Gedankenexperiment which is very similar to the famous Aharonov-Bohm proposal it will be shown that, in the case of a Minkowskian spacetime, we may use a nonrelativistic quantum particle and a noninertial coordinate system and obtain geometric information of regions that are, to this particle, forbidden. This shows that the outcome of a nonrelativistic quantum process is determined not only by the features of geometry at those points at which the process takes place, but also by geometric parameters of regions in which the quantum system can not enter. From this fact we could claim that geometry at the quantum level plays a non-local role. Indeed, the measurement outputs of some nonrelativistic quantum experiments are determined not only by the geometry of the region in which the experiment takes place, but also by the geometric properties of spacetime volumes which are, in some way, forbidden in the experiment.
Measurement-induced interference in an inhomogeneous gravitational field
A. Camacho
Physics , 1999, DOI: 10.1016/S0375-9601(99)00565-4
Abstract: A very interesting quantum mechanical effect is the emergence of gravity-induced interference, which has already been detected. This effect also shows us that gravity is at the quantum level not a purely geometric effect, the mass of the employed particles appears explicitly in the interference expression. In this work we will generalize some previous results. It will be shown that the introduction of a second order approximation in the propagator of a particle, immersed in the Earth's gravitational field, and whose coordinates are being continuously monitored, allows us to include, in the corresponding complex oscillator, a frequency which now depends on the geometry of the source of the gravitational field, a fact that is absent in the case of a homogeneous field. Using this propagator we will analyze the interference pattern of two particle beams whose coordinates are being continuously monitored. We will compare our results againt the case of a homogeneous field, and also against the measurement ouputs of the Colella, Overhauser, and Werner experiment, and find that the difference in the dependence upon the geometry of the source of the gravitational field could render detectable differences in their respective measurement outputs.
Revista Psicogente , 2009,
Abstract: This research determined the level of influence that assertive style of communication of teachers in the school learning. We used an experimental design; the sample included twelve teachers for the experimental group, and other twelve for the control group of the Empresarial de los Andes School (Department of Huila). The results show that school’s a stage of social life where the educational processes of the teachers have a deep character communicative and the institution have not recognized the importance of communication in processes like the personality, socialization and learning development. Similarly, was established that both, teachers and students, use alternate indirect ways of communication, which does not allow a proper process of personal interaction. It was shown, that with appropriate intervention, the communication channels are optimized, improving the academic performance of students.
Continuous quantum measurements of a particle in a Paul trap
A. Camacho,A. Camacho-Galvan
Physics , 1998, DOI: 10.1016/S0375-9601(98)00586-6
Abstract: We calculate the propagator of a particle caught in a Paul trap and subject to the continuous quantum measurement of its position. The probabilities of the measurement outputs, the possible trajectories of the particle, are also found. This enables us to propose a series of experiments that would allow to confront the predictions of one of the models that describe the interaction between a measured quantum system and measuring device, namely the so called Restricted Path-Integral Formalism, with the experiment.
Time emergence by self-measurement in a quantum anisotropic universe
A. Camacho,A. Camacho-Galvan
Physics , 1999,
Abstract: We begin this work calculating Halliwell's propagator in the case of a Mixmaster universe with small anisotropy. Afterwards in the context of the Decoherence Model we introduce in our system terms that comprise the self-measurement of the universe of this model by higher multipoles of matter. Analyzing self-measurement with the Restricted Path Integral Formalism we obtain Halliwell's modified propagator and find that a gauge invariant physical time emerges as consequence of this process. The conditions leading to Wheeler-DeWitt dynamics are also obtained. The comparison of our results with those of the isotropic case will enable us to conclude that the number of conditions to be satisfied in order to have Halliwell's regime is in the anisotropic situation bigger than in an isotropic universe. We obtain also in terms of the parameters of the measurement process an expression for the threshold in time beyond which the scale factors of this model are meaningless.
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