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Search Results: 1 - 10 of 7525 matches for " Esteban Castillo "
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On the dynamics of fluctuations in time crystals
Esteban Castillo,Benjamin Koch,Gonzalo Palma
Physics , 2014,
Abstract: We study the evolution of quantum fluctuations in systems known as time crystals, hypothetical systems for which the lowest energy state performs a periodic motion. We first discuss some general properties shared by time crystals, and deduce the effective field theory parametrizing the evolution of their fluctuations. We show that these fluctuations fall into categories analogous to acoustic and optical phonons, encountered in conventional crystals. The acoustic phonons correspond to gapless Goldstone boson modes parametrizing the broken time translation invariance of the crystal, whereas the optical phonons are identified with modes perpendicular to the broken symmetry of the system, which generically remain gapped. We study how these two modes decay and interact together, and discuss some observable features that could be tested in experimental realizations of time crystals.
On the integration of fields and quanta in time dependent backgrounds
Esteban Castillo,Benjamin Koch,Gonzalo Palma
Physics , 2013, DOI: 10.1007/JHEP05(2014)111
Abstract: Field theories with global continuous symmetries may admit configurations in which time translation invariance is broken by the movement of homogeneous background fields evolving along the flat directions implied by the symmetries. In this context, the field fluctuations along the broken symmetry are well parametrized by a Goldstone boson field that may non-trivially interact with other fields present in the theory. These interactions violate Lorentz invariance as a result of the broken time translation invariance of the background, producing a mixing between the field content and the particle spectrum of the theory. In this article we study the effects of such interactions on the low energy dynamics of the Goldstone boson quanta, paying special attention to the role of the particle spectrum of the theory. By studying the particular case of a canonical two-field model with a mexican-hat potential, we analyze the derivation of the low energy effective field theory for the Goldstone boson, and discuss in detail the distinction between integrating fields v/s integrating quanta, to finally conclude that they are equivalent. In addition, we discuss the implications of our analysis for the study of systems where time translation invariance is broken, such as cosmic inflation and time crystals.
In vitro antiviral activity of Chamaecrista nictitans (Fabaceae )against herpes simplex virus: Biological characterization of mechanisms of action
Herrero Uribe,Libia; Chaves Olarte,Esteban; Tamayo Castillo,Giselle;
Revista de Biología Tropical , 2004,
Abstract: we have previously identified a crude extract of the plant chamaecrista nictitans (fabaceae)with antiviral activity against herpes simplex virus.the main objectives of this research were to identify the step of the replication cycle of herpes simplex inhibited by the extract,and to attempt to characterize the chemical characteristics of this extract.the crude extract from chamaecrista nictitans (fabaceae)was extracted with a mixture of diclorometane/methanol,and further fractionated following a bioassay-guided protocol using a combination of preparative thin layer and column chromatography.toxicity and bioassay experiments were carried out in monolayers of vero cells.the antiviral activity of the extract was assessed by total inhibition of cytopathic effect after three-day incubation.the highest concentration of the extract which was not toxic to the cells was 200 m g/ml. western blot and immunofluorescence techniques were used to elucidate the antiviral mechanism of the extract by infecting vero cells with the virus at different times and monitoring the synthesis of viral proteins.a 60 kda protein was detected at 2 hr and 8 hr post-infection but no additional proteins were synthesized at later time intervals,and cytopathic effect was not observed after 24 hr.this result indicates that the extract acts at the intracellular level in order to inhibit late transcription.however,it does not inhibit transcription/translation of early viral proteins.these results were confirmed by immunofluorescence experiments.a strong fluorescent signal was observed in control cell monolayers at 24 hr post infection,accompanied with a clear cytopathic effect.in contrast,in the presence of acyclovir or the extract,cells showed very discrete immunofluorescence,characterized by a punctuated pattern, and no cytopathic effect was observed.neutralization assays were performed using pre-incubation of virus with either specific herpes simplex-1 antiserum,200 m g/ml of the extract or 20 m g /ml
Concordancia diagnóstica del puntaje de Gleason en biopsia por punción y prostatectomía radical y sus consecuencias clínicas
Arellano H,Leonardo; Castillo C,Octavio; Metrebián B,Esteban;
Revista médica de Chile , 2004, DOI: 10.4067/S0034-98872004000800009
Abstract: background: the gleason histological score is an independent prognostic factor in prostate cancer that helps in therapeutic decisions. aim: to analyze the concordance between the gleason score of needle prostatic biopsy and the score from the study of the surgical piece obtained during radical prostatectomy. material and methods: retrospective analysis of 212 cases of prostate cancer, diagnosed between february 1993 and march 2003. all had the gleason histological scores from needle prostatic biopsies and in the surgical piece obtained during radical prostatectomy. all pathological studies were done by the same observer. results: there was an exact concordance of gleason scores between needle biopsy and the surgical piece in 49% of cases and a concordance of ± 1 unit in 89%. the concordance improved in the second half of the study period. no cases with a gleason score of less than 5 were detected since 1999 in the surgical piece. conclusions: the concordance of gleason score of needle prostatic biopsies and surgical pieces is good. this concordance increases with the experience of the pathologist (rev méd chile 2004; 132: 971-8)
In vitro antiviral activity of Chamaecrista nictitans (Fabaceae )against herpes simplex virus: Biological characterization of mechanisms of action
Libia Herrero Uribe,Esteban Chaves Olarte,Giselle Tamayo Castillo
Revista de Biología Tropical , 2004,
Abstract: We have previously identified a crude extract of the plant Chamaecrista nictitans (Fabaceae)with antiviral activity against herpes simplex virus.The main objectives of this research were to identify the step of the replication cycle of herpes simplex inhibited by the extract,and to attempt to characterize the chemical characteristics of this extract.The crude extract from Chamaecrista nictitans (Fabaceae)was extracted with a mixture of diclorometane/methanol,and further fractionated following a bioassay-guided protocol using a combination of preparative thin layer and column chromatography.Toxicity and bioassay experiments were carried out in monolayers of Vero cells.The antiviral activity of the extract was assessed by total inhibition of cytopathic effect after three-day incubation.The highest concentration of the extract which was not toxic to the cells was 200 mu g/ml. Western blot and immunofluorescence techniques were used to elucidate the antiviral mechanism of the extract by infecting Vero cells with the virus at different times and monitoring the synthesis of viral proteins.A 60 kDa protein was detected at 2 hr and 8 hr post-infection but no additional proteins were synthesized at later time intervals,and cytopathic effect was not observed after 24 hr.This result indicates that the extract acts at the intracellular level in order to inhibit late transcription.However,it does not inhibit transcription/translation of early viral proteins.These results were confirmed by immunofluorescence experiments.A strong fluorescent signal was observed in control cell monolayers at 24 hr post infection,accompanied with a clear cytopathic effect.In contrast,in the presence of acyclovir or the extract,cells showed very discrete immunofluorescence,characterized by a punctuated pattern, and no cytopathic effect was observed.Neutralization assays were performed using pre-incubation of virus with either specific herpes simplex-1 antiserum,200 mu g/ml of the extract or 20 mu g /ml of acyclovir.After 1 hr incubation,cells were infected and monitored for cytopathic effect.Only the virus treated with acyclovir showed viral activity,while no cytopathic effect was induced by samples of virus incubated with the extract.It is concluded that the extract inhibits both the attachment of the virus to the cell and the secondary transcription of the virus within the cells.Chemical characterization of the extract showed the presence of tannins.Rev.Biol.Trop.52(3):807-816. Epub 2004 Dic 15. Previamente se había identificado un extracto crudo a partir de Chamaecrista nictitans (Faba
Concordancia diagnóstica del puntaje de Gleason en biopsia por punción y prostatectomía radical y sus consecuencias clínicas Concordance of Gleason histological scoring for prostatic cancer in needle biopsies and the surgical piece obtained during radical prostatectomy
Leonardo Arellano H,Octavio Castillo C,Esteban Metrebián B
Revista médica de Chile , 2004,
Abstract: Background: The Gleason histological score is an independent prognostic factor in prostate cancer that helps in therapeutic decisions. Aim: To analyze the concordance between the Gleason score of needle prostatic biopsy and the score from the study of the surgical piece obtained during radical prostatectomy. Material and methods: Retrospective analysis of 212 cases of prostate cancer, diagnosed between February 1993 and March 2003. All had the Gleason histological scores from needle prostatic biopsies and in the surgical piece obtained during radical prostatectomy. All pathological studies were done by the same observer. Results: There was an exact concordance of Gleason scores between needle biopsy and the surgical piece in 49% of cases and a concordance of ± 1 unit in 89%. The concordance improved in the second half of the study period. No cases with a Gleason score of less than 5 were detected since 1999 in the surgical piece. Conclusions: The concordance of Gleason score of needle prostatic biopsies and surgical pieces is good. This concordance increases with the experience of the pathologist (Rev Méd Chile 2004; 132: 971-8)
Análisis de las Visiones del Turismo en México
Alexandre Panosso Netto,Esteban Arias Casta?eda,Marcelino Castillo Nechar
Revista Turismo em Análise , 2012,
Abstract: ResumenEste artículo tiene como finalidad el ejercicio crítico reflexivo de la importancia de la construcción del conocimiento del turismo desde la perspectiva científica. Se revisarán algunas polémicas y planteamientos de autores que lo abordan desde la perspectiva más convencional positivista que descartan su posibilidad como disciplina o ciencia, y existen otras que lo hacen desde una postura antipositivista, donde revaloran la noción de disciplina y ciencia. La visión antipositivista rebasa la parte formal positivista la cual le da posibilidad para calificarlo como ciencia, que bajo la dimensión hermenéutica, fenomenológica, dialéctica o crítica, la revaloración de conocimiento científico del turismo permite reconocer que existen comunidades, temáticas, procedimientos de cómo investigar y que también se observan intervenciones en la realidad.Palabras clave: turismo; antipositivista; ciencia; crítica; epistemología del turismo. ResumoO artigo tem por objetivo o exercício crítico reflexivo da importancia da constru o do conhecimento em turismo a partir da perspectiva científica. S o revisadas algumas polêmicas e propostas de autores que abordam o turismo do ponto de vista positivista mais convencional, que descartam sua possibilidade como disciplina ou ciência, e aqueles que o abordam a partir de uma postura antipositivista, na qual revalorizam a no o de disciplina e ciência. A vis o antipositivista ultrapassa a parte formal positivista, a qual oferece a possibilidade de qualificar o turismo como ciência, que sob as dimens es hermenêutica, fenomenológica, dialética ou crítica, a revaloriza o do conhecimento científico do turismo permite reconhecer que existem comunidades, temas e procedimentos de como investigar, que também permitem observar as interven es na realidade.Palavras chave: turismo; antipositivista; ciência; crítica; epistemologia do turismo. The article has as objective the critical reflexive exercise on the importance of knowledge construction in tourism from a scientific perspective. Some polemics and proposals from authors who approach tourism from a more conventional point of view discarding its possibility as discipline and science are reviewed along with the view of those who approach tourism from a more anti-positivist position, in which they revalue the notion of tourism as science. An anti-positivist view surpasses the positivist formal part, which offers the possibility of quali
Gravitational Fragmentation in Galaxy Mergers: A Stability Criteria
Andres Escala,Fernando Becerra,Luciano del Valle,Esteban Castillo
Physics , 2012, DOI: 10.1088/0004-637X/763/1/39
Abstract: We study the gravitational stability of gaseous streams in the complex environment of a galaxy merger, because mergers are known to be places of ongoing massive cluster formation and bursts of star formation. We find an analytic stability parameter for case of gaseous streams orbiting around the merger remnant. We test our stability criteria using hydrodynamical simulations of galaxy mergers, obtaining satisfactory results. We find that our criteria successfully predicts the streams that will be gravitationally unstable to fragment into clumps.
MPPT for Photovoltaic Modules via Newton-Like Extremum Seeking Control
Héctor Zazo,Esteban del Castillo,Jean Fran?ois Reynaud,Ramon Leyva
Energies , 2012, DOI: 10.3390/en5082652
Abstract: The paper adapts the Newton-like Extremum-Seeking Control technique to extract the maximum power from photovoltaic panels. This technique uses the gradient and Hessian of the panel characteristic in order to approximate the operating point to its optimum. The paper describes in detail the gradient and Hessian estimations carried out by means of sinusoidal dithering signals. Furthermore, we compare the proposed technique with the common Extremum Seeking Control that only uses the gradient. The comparison is done by means of PSIM simulations and it shows the different transient behaviors and the faster response of the Newton-like Extremum-Seeking Control solution.
Effect of Vermicompost and Compost on Lettuce Production
Hernández,Adriana; Castillo,Hugo; Ojeda,Dámaris; Arras,Ana; López,Julio; Sánchez,Esteban;
Chilean journal of agricultural research , 2010, DOI: 10.4067/S0718-58392010000400008
Abstract: a greenhouse study was conducted to evaluate the effect on total growth and leaf nutritional content in lettuce (lactuca sativa l.) in the agrotechnology sciences department of the universidad autonoma de chihuahua, mexico in 2007. three types of fertilization treatments were analyzed: two organic and one conventional or inorganic. both vermicompost and compost were produced from cattle manure in a 25-wk process. the study included 12 experimental units made up of lettuce plantlets var. great lakes. a linear model was fitted for statistical analysis using a completely randomized experimental design. anova was performed and means were compared by orthogonal contrasts. results showed differences in weight and leaf content for the n and k variables, and the highest mean values for these variables were in the urea treatment. leaf content of ca, mg, and mn showed higher values in organic fertilization treatments. the vermicompost treatment showed a higher contribution of mg, fe, zn, and cu, and lower na in lettuce leaf content when compared to compost usage.
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