27 research outputs found
Exact Solvability of Superintegrable Systems
It is shown that all four superintegrable quantum systems on the Euclidean
plane possess the same underlying hidden algebra . The gauge-rotated
Hamiltonians, as well as their integrals of motion, once rewritten in
appropriate coordinates, preserve a flag of polynomials. This flag corresponds
to highest-weight finite-dimensional representations of the -algebra,
realized by first order differential operators.Comment: 14 pages, AMS LaTe
An infinite family of solvable and integrable quantum systems on a plane
An infinite family of exactly-solvable and integrable potentials on a plane
is introduced. It is shown that all already known rational potentials with the
above properties allowing separation of variables in polar coordinates are
particular cases of this family. The underlying algebraic structure of the new
potentials is revealed as well as its hidden algebra. We conjecture that all
members of the family are also superintegrable and demonstrate this for the
first few cases. A quasi-exactly-solvable and integrable generalization of the
family is found.Comment: 30 pages, Introduction extended, description of known integrals
given, some statements clarified, one reference added, will be published in J
Phys A (FTC
Human mesenchymal stem cells response to multi-doped silicon-strontium calcium phosphate coatings
The search for apatitic calcium phosphate coatings to improve implants osteointegration is, nowadays, preferentially
focused in the obtaining of compositions closer to that of the inorganic phase of bone. Silicon and strontium are both
present in trace concentrations in natural bone and have been demonstrated, by separate, to significantly improve
osteoblastic response on calcium phosphate bioceramics. This work aims the controlled and simultaneous multidoping
of carbonated calcium phosphate coatings with both elements, Si and Sr, by pulsed laser deposition technique
and the biological response of human mesenchymal stem cells to them. A complete physicochemical characterization has
been also performed to analyze the coatings and significant positive effect was obtained at the osteogenic differentiation
of cells, confirming the enormous potential of this multi-doping coating approach.Technical staff of CACTI (University of Vigo) is gratefully acknowledged. This work was partially supported by the UE-POCTEP 0330IBEROMARE1P project, UE-INTERREG 2011-1/164MARMED and Ministerio de Ciencia e Innovacion (Project MAT2010-18281). M Lopez-Alvarez thanks funding support from FP7/REGPOT-2012-2013.1 (no 316265, BIOCAPS)
Energy Reflection Symmetry of Lie-Algebraic Problems: Where the Quasiclassical and Weak Coupling Expansions Meet
We construct a class of one-dimensional Lie-algebraic problems based on sl(2)
where the spectrum in the algebraic sector has a dynamical symmetry E -> - E.
All 2j+1 eigenfunctions in the algebraic sector are paired, and inside each
pair are related to each other by simple analytic continuation x -> ix, except
the zero mode appearing if j is integer. At j-> infinity the energy of the
highest level in the algebraic sector can be calculated by virtue of the
quasiclassical expansion, while the energy of the ground state can be
calculated as a weak coupling expansion. The both series coincide identically.Comment: Latex, 16 pages, 3 figures. Minor styllistic changes made, typos
corrected, a remark on the energy-reflection symmetry in the
quantum-algebraic Hamiltonians emerging in finite-difference problems added.
Final version, to be published in Physical Review
The Dusty Tori of Nearby QSOs as Constrained by High-Resolution Mid-IR Observations
We present mid-infrared (MIR; 7.5–13.5 μm) imaging and spectroscopy observations obtained with the CanariCam (CC) instrument on the 10.4-m Gran Telescopio CANARIAS for a sample of 20 nearby, MIR bright and X-ray luminous quasi-stellar objects (QSOs). We find that for the majority of QSOs the MIR emission is unresolved at angular scales ∼0.3 arcsec, corresponding to physical scales ≲ 600 pc. We find that the higher-spatial resolution CC spectra have similar shapes to those obtained with Spitzer/IRS, and hence we can assume that the spectra are not heavily contaminated by extended emission in the host galaxy. We thus take advantage of the higher signal-to-noise ratio Spitzer/IRS spectra, as a fair representation of the nuclear emission, to decompose it into a combination of active galactic nuclei (AGN), polycyclic aromatic hydrocarbon (PAH) and stellar components. In most cases, the AGN is the dominant component, with a median contribution of 85 per cent of the continuum light at MIR (5–15 μm) within the IRS slit. This IR AGN emission is well reproduced by clumpy torus models. We find evidence for significant differences in the parameters that describe the dusty tori of QSOs when compared with the same parameters of Seyfert 1 and 2 nuclei. In particular, we find a lower number of clouds (N0 ≲ 12), steeper radial distribution of clouds (q ∼ 1.5–3.0) and clouds that are less optically thick (τV ≲ 100) than in Seyfert 1, which could be attributed to dusty structures that have been partially evaporated and piled up by the higher radiation field in QSOs. We find that the combination of the angular width σtorus, viewing angle i, and number of clouds along the equatorial line, N0, produces large escape probabilities (Pesc \u3e 2 per cent) and low geometrical covering factors (f2 ≲ 0.6), as expected for AGN with broad lines in their optical spectra
IV consenso mexicano sobre Helicobacter pylori
Desde el último consenso mexicano para el diagnóstico y tratamiento de la infección por Helicobacter pylori (H. pylori) en el 2007, han existido avances importantes al respecto. Por tal motivo, la Asociación Mexicana de Gastroenterología convocó a 20 expertos para la realización del «IV consenso mexicano sobre H. pylori». Durante febrero y junio del 2017 se organizaron 4 mesas de trabajo, una revisión de la literatura y 3 rondas de votaciones donde se establecieron 32 enunciados para discusión y consenso. Dentro de las recomendaciones se destaca el reconocer a México como un país con riesgo de cáncer gástrico bajo a intermedio a pesar de la alta prevalencia de infección por H. pylori. Se corrobora que enfermedad ulcerosa péptica, presencia de lesiones premalignas, antecedentes de cáncer gástrico y linfoma asociado a la mucosa deben considerarse indicaciones claras para erradicación. La relación del H. pylori con los síntomas dispépticos sigue siendo controversial. La triple terapia de erradicación con amoxicilina, claritromicina y un inhibidor de la bomba de protones ya no debe ser considerada la primera línea de tratamiento. En su lugar, se proponen 2 opciones: la terapia cuádruple con bismuto (inhibidor de la bomba de protones, subcitrato de bismuto, tetraciclina y metronidazol) y la terapia cuádruple sin bismuto (inhibidor de la bomba de protones, amoxicilina, claritromicina y metronidazol). Se establece la necesidad de la realización de sensibilidad antimicrobiana ante la falla a 2 tratamientos de erradicación. Finalmente, se proponen campañas de educación respecto al diagnóstico y tratamiento del H. pylori para médicos de primer contacto y población general.
Abstract
Important advances have been made since the last Mexican consensus on the diagnosis and treatment of Helicobacter pylori (H. pylori) infection was published in 2007. Therefore, the Asociación Mexicana de Gastroenterología summoned 20 experts to produce ‘‘The Fourth Mexican Consensus on Helicobacter pylori’’. From February to June 2017, 4 working groups were organized, a literature review was performed, and 3 voting rounds were carried out, resulting in the formulation of 32 statements for discussion and consensus. From the ensuing recommendations, it was striking that Mexico is a country with an intermediate-to-low risk for gastric cancer, despite having a high prevalence of H. pylori infection. It was also corroborated that peptic ulcer disease, premalignant lesions, and histories of gastric cancer and mucosaassociated lymphoid tissue lymphoma should be considered clear indications for eradication.
The relation of H. pylori to dyspeptic symptoms continues to be controversial. Eradication triple therapy with amoxicillin, clarithromycin, and a proton pump inhibitor should no longer be considered first-line treatment, with the following 2 options proposed to take its place:
quadruple therapy with bismuth (proton pump inhibitor, bismuth subcitrate, tetracycline, and metronidazole) and quadruple therapy without bismuth (proton pump inhibitor, amoxicillin, clarithromycin, and metronidazole). The need for antimicrobial sensitivity testing when 2 eradication treatments have failed was also established. Finally, the promotion of educational campaigns on the diagnosis and treatment of H. pylori for both primary care physicians and the general population were proposed
Cooperativity and flexibility in enzyme evolution
Enzymes are flexible catalysts, and there has been substantial
discussion about the extent to which this flexibility contributes
to their catalytic efficiency. What has been significantly less
discussed is the extent to which this flexibility contributes to
their evolvability. Despite this, recent years have seen an
increasing number of both experimental and computational
studies that demonstrate that cooperativity and flexibility play
significant roles in enzyme innovation. This review covers key
developments in the field that emphasize the importance of
enzyme dynamics not just to the evolution of new enzyme
function(s), but also as a property that can be harnessed in the
design of new artificial enzymes.The European Research Council has provided financial support under the
European Community’s Seventh Framework Program (FP7/2007-2013)/ERC
Grant Agreement No. 306474. This work was also funded by the Feder
Funds, Grants from the Spanish Ministry of Economy and Competitiveness
(BIO2015-66426-R and CSD2009-00088) and the Human Frontier Science
Program (RGP0041/2017). A.P. is a Wenner-Gren Foundations Postdoctoral
Fellow and S. C. L. K. is a Wallenberg Academy Fellow
The Mexican consensus on non-cardiac chest pain
Introduction: Non-cardiac chest pain is defined as a clinical syndrome characterized by ret-rosternal pain similar to that of angina pectoris, but of non-cardiac origin and produced byesophageal, musculoskeletal, pulmonary, or psychiatric diseases.
Aim: To present a consensus review based on evidence regarding the definition, epidemiology,pathophysiology, and diagnosis of non-cardiac chest pain, as well as the therapeutic options forthose patients.
Methods Three general coordinators carried out a literature review of all articles published inEnglish and Spanish on the theme and formulated 38 initial statements, dividing them into 3 maincategories: 1) definitions, epidemiology, and pathophysiology, 2) diagnosis, and 3) treatment.The statements underwent 3 rounds of voting, utilizing the Delphi system. The final statementswere those that reached > 75% agreement, and they were rated utilizing the GRADE system.
Results and conclusions The final consensus included 29 statements. All patients presentingwith chest pain should initially be evaluated by a cardiologist. The most common cause of non-cardiac chest pain is gastroesophageal reflux disease. If there are no alarm symptoms, the initialapproach should be a therapeutic trial with a proton pump inhibitor for 2-4 weeks. If dysphagiaor alarm symptoms are present, endoscopy is recommended. High-resolution manometry isthe best method for ruling out spastic motor disorders and achalasia and pH monitoring aidsin demonstrating abnormal esophageal acid exposure. Treatment should be directed at thepathophysiologic mechanism. It can include proton pump inhibitors, neuromodulators and/orsmooth muscle relaxants, psychologic intervention and/or cognitive therapy, and occasionallysurgery or endoscopic therapy
Consenso mexicano sobre dolor torácico no cardiaco
Introducción: Dolor torácico no cardíaco (DTNC) se define como un síndrome clínico caracte-rizado por dolor retroesternal semejante a la angina de pecho, pero de origen no cardiaco ygenerado por enfermedades esofágicas, osteomusculares, pulmonares o psiquiátricas.Objetivo: Presentar una revisión consensuada basada en evidencias sobre definición, epidemio-logía, fisiopatología, diagnóstico y opciones terapéuticas para pacientes con DTNC.Métodos: Tres coordinadores generales realizaron una revisión bibliográfica de todas las publi-caciones en inglés y espa˜nol sobre el tema y elaboraron 38 enunciados iniciales divididosen tres categorías principales: 1) definiciones, epidemiología y fisiopatología; 2) diagnóstico,y 3) tratamiento. Los enunciados fueron votados (3 rondas) utilizando el sistema Delphi, y losque alcanzaron un acuerdo > 75% fueron considerados y calificados de acuerdo con el sistemaGRADE.
Resultados y conclusiones: El consenso final incluyó 29 enunciados Todo paciente que debutacon dolor torácico debe ser inicialmente evaluado por un cardiólogo. La causa más común deDTNC es la enfermedad por reflujo gastroesofágico (ERGE). Como abordaje inicial, si no existensíntomas de alarma, se puede dar una prueba terapéutica con inhibidor de bomba de pro-tones (IBP) por 2-4 semanas. Si hay disfagia o síntomas de alarma, se recomienda hacer unaendoscopia. La manometría de alta resolución es el mejor método para descartar trastornosmotores espásticos y acalasia. La pHmetría ayuda a demostrar exposición esofágica anormal alácido. El tratamiento debe ser dirigido al mecanismo fisiopatológico, y puede incluir IBP, neu-romoduladores y/o relajantes de músculo liso, intervención psicológica y/o terapia cognitiva,y ocasionalmente cirugía o terapia endoscópica.
ABSTRACT
Introduction: Non-cardiac chest pain is defined as a clinical syndrome characterized by retros-ternal pain similar to that of angina pectoris, but of non-cardiac origin and produced byesophageal, musculoskeletal, pulmonary, or psychiatric diseases.Aim: To present a consensus review based on evidence regarding the definition, epidemiology,pathophysiology, and diagnosis of non-cardiac chest pain, as well as the therapeutic options forthose patients.
Methods: Three general coordinators carried out a literature review of all articles published inEnglish and Spanish on the theme and formulated 38 initial statements, dividing them into 3 maincategories: (i) definitions, epidemiology, and pathophysiology; (ii) diagnosis, and (iii) treatment.The statements underwent 3 rounds of voting, utilizing the Delphi system. The final statementswere those that reached > 75% agreement, and they were rated utilizing the GRADE system.Results and conclusions: The final consensus included 29 statements. All patients presentingwith chest pain should initially be evaluated by a cardiologist. The most common cause ofnon-cardiac chest pain is gastroesophageal reflux disease. If there are no alarm symptoms, the initial approach should be a therapeutic trial with a proton pump inhibitor for 2-4 weeks. Ifdysphagia or alarm symptoms are present, endoscopy is recommended. High-resolution mano-metry is the best method for ruling out spastic motor disorders and achalasia and pH monitoringaids in demonstrating abnormal esophageal acid exposure. Treatment should be directed at thepathophysiologic mechanism. It can include proton pump inhibitors, neuromodulators and/orsmooth muscle relaxants, psychologic intervention and/or cognitive therapy, and occasionallysurgery or endoscopic therapy