A family of complex potentials with real spectrum

We consider a two-parameter non hermitean quantum-mechanical hamiltonian that is invariant under the combined effects of parity and time reversal transformation. Numerical investigation shows that for some values of the potential parameters the hamiltonian operator supports real eigenvalues and localized eigenfunctions. In contrast with other PT symmetric models, which require special integration paths in the complex plane, our model is integrable along a line parallel to the real axis.Comment: Six figures and four table

Harmonic oscillator well with a screened Coulombic core is quasi-exactly solvable

In the quantization scheme which weakens the hermiticity of a Hamiltonian to its mere PT invariance the superposition V(x) = x^2+ Ze^2/x of the harmonic and Coulomb potentials is defined at the purely imaginary effective charges (Ze^2=if) and regularized by a purely imaginary shift of x. This model is quasi-exactly solvable: We show that at each excited, (N+1)-st harmonic-oscillator energy E=2N+3 there exists not only the well known harmonic oscillator bound state (at the vanishing charge f=0) but also a normalizable (N+1)-plet of the further elementary Sturmian eigenstates \psi_n(x) at eigencharges f=f_n > 0, n = 0, 1, ..., N. Beyond the first few smallest multiplicities N we recommend their perturbative construction.Comment: 13 pages, Latex file, to appear in J. Phys. A: Math. Ge

Desempenho estudantil acadêmico na parte inicial da carreira de Doutor em Medicina da Universidade da República

Adriana Fernández-Álvarez: Departamento de Educación Médica, Facultad de Medicina, Universidad de la República. Coordinación del Ciclo Básico Clínico Comunitario, Unidad de Coordinación Curricular, Facultad de Medicina, Universidad de la República, Uruguay.-- Julio C. Siciliano: Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Uruguay. Coordinación del Ciclo Básico Clínico Comunitario, Unidad de Coordinación Curricular, Facultad de Medicina, Universidad de la República, Uruguay.-- Contacto: Adriana Fernández-Álvarez. E-mail: [email protected] este trabajo se presentan los resultados de una indagación de carácter diagnóstico acerca del desempeño académico de los estudiantes de Medicina en los cursos y exámenes correspondientes al ciclo Básico Clínico Comunitario (semestres 2 al 6 de la carrera) en el lapso 2009 a 2016. Los datos correspondientes a inscripciones, aprobaciones y no aprobaciones de cursos y exámenes se obtuvieron y sistematizaron a partir de fuentes secundarias oficiales de origen institucional. Se realizó un análisis cuantitativo ex-post en un estudio de tipo descriptivo que incluyó análisis estadístico inferencial en uno de sus ítems. El análisis evidenció que: I) en la evaluación de los exámenes predomina como resultado la no aprobación sin embargo en la evaluación de cursos predomina la aprobación; II) recursar tras renunciar a cursos aprobados no mejora el desempeño estudiantil en los cursos; III) el desempeño en cursos y exámenes de una cohorte es superior en los estudiantes que aprueban el examen final de BCC1 en el primer o segundo período que en quienes no lo hacen (test χ2; p < 0,001). Además, existió asociación positiva entre aprobar BCC1 en el primer o segundo período y la aprobación de mayor cantidad de cursos (V de Cramer 0,508; p < 0,001) y exámenes (V de Cramer según períodos 0,813 y 0,727; p < 0,001) en el tramo de carrera considerado. Estos datos constituyen un insumo para la evaluación de la implementación del plan de estudios y de la necesidad eventual de realizar ajustes a la normativa vigente.This paper presents the results of aresearch that deals with the academic performance of medical students in the courses and exams corresponding to semesters from 2 to 6 of medical school, which includes basic, clinical and community studies. Data about enrollment, approval and non-approval of courses and exams, between 2009 and 2016, were obtained and systematized from official sec-ondary sources of institutional origin. A quantitative ex-post analysis was performed in a descriptive study that included inferential statistical analysis in one of its items. Results showed:I) non-approval condition predominates in the exams califications, however, approval condition predominates at the courses evaluations; II) recoursing after renouncing to a previously approved course does not improve performance; III)performance in courses and exams of a cohort is better in those students who ap-proved the final exam of BCC1 immediately after course than in those that did not (test χ; p < 0,001). In addition, it was detected a positive association between approving BCC1 immediately after course and the approval of a greater number of courses (Cramer ́s V 0.508, p < 0.001) and exams (Cramer ́s V according to periods 0.813 and 0.727, p < 0.001) in the considered lapse at medical school. These data will be useful for the evaluation of the curriculum structure implementation and for an eventual adjustment of the current regulations.Este artigo apresenta os resultados de um inquérito de diagnóstico sobre o desempenho acadêmico dos estudantes de medicina nos cursos e exames correspondentes ao ciclo clínico comunitário bási-co (semestres 2 a 6 do curso) no período de 2009 a 2016. Os dados para inscrição, aprovação e não aprovação de cursos e exames foram obtidos e sistematizados a partir de fontes secundárias oficiais de origem institucional. Uma análise quantitativa ex-post foi realizada em um estudo descritivo que incluía análise estatística inferencial em um de seus itens. A análise mostrou que: I) na avaliação dos exames, a não aprovação predomina como resultado, no entanto, na avaliação dos cursos, a aprovação predomina; II) voltar a cursar cursos já aprovados não melhora o desempenho dos alunos nos cursos; III) o desempenho em cursos e exames de uma coorte é maior nos alunos que passam o exame BCC1 final no primeiro ou segundo período do que naqueles que não (teste χ2; p <0,001). Além disso, houve associação positiva entre a aprovação de BCC1 no primeiro ou segundo período e a aprovação de mais cursos (Cramer V 0.508; p <0.001) e exames (Cramer V de acordo com os períodos 0.813 e 0.727; p <0.001) no trecho considerado. Esses dados constituem um insumo para a avaliação da implementa-ção do currículo e a eventual necessidade de fazer ajustes aos regulamentos vigentes

AB0690 Antiphospholipid antibodies and spondyloarthritis. Truth or myth? Our results in a third level hospital

[EN] The importance of antiphospholipid antibodies and their clinical involvement in thrombotic phenomena, isolated or associated with certain autoimmune diseases such as systemic lupus erythematosus, is known. However, in spondyloarthritis (SpA) there is little published data about it.S

Quasi-exactly solvable quartic potentials with centrifugal and Coulombic terms

PT symmetric complex potential V(r) = - r^4 + i a r^3 + b r^2 + i c r + i d/r + e/r^2 is studied. Arbitrarily large multiplets of its closed bound-state solutions with real energies are shown obtainable quasi-exactly (i.e., with a certain relationship between their charges and energies) from a single underlying finite-dimensional secular equation.Comment: 13 pages, 1 figure, submitted to J. Phys. A: Math. Ge

Phenological Characterization and Production of Biomass from 12 Varieties of Sugar to Feed Cattle

Context: One of the main limiting factors of cattle production in Cuba is linked to low availability of quality pasture in sufficient amounts, during the dry season. Sugar cane has anatomical and physiological features that offer advantages as food and energetic supplement to ruminants. Objective: To characterize 12 varieties of sugar cane for cattle nutrition. Methods: Phenological evaluations were made and biomass production was determined in a study conducted at the Territorial Station of Sugar Cane Research (ETICA), mid-east Camagüey, in dry lands. A randomized block experimental design was made, consisting of 12 treatments (varieties) and three replications. The phenological composition of the stump (stem, top, and whole) was determined at 14 months in all the varieties. Agronomic variables plant height, stem diameter, number of stems m-2, active leaves, and production of green biomass by fractions and as a whole, were determined as well. Results: The study demonstrated the existence of no significant differences in the phenological composition among the varieties. Concerning variables crop yield and green biomass production, varieties C92-325, C86-12, C99-374, C90-530, and C97-366 showed the greatest potential. Conclusions: Its use is recommended in the major cattle raising areas in the province and the country with similar edaphoclimatic conditions to the experimental area

PT-symetrically regularized Eckart,Poeschl-Teller and Hulthen potentials

Version 1: The well known Eckart's singular s-wave potential is PT-symmetrically regularized and continued to the whole real line. The new model remains exactly solvable and its bound states remain proportional to Jacobi polynomials. Its real and discrete spectrum exhibits several unusual features. Version 2: Parity times time-reversal symmetry of complex Hamiltonians with real spectra is usually interpreted as a weaker mathematical substitute for Hermiticity. Perhaps an equally important role is played by the related strengthened analyticity assumptions. In a constructive illustration we complexify a few potentials solvable only in s-wave. Then we continue their domain from semi-axis to the whole axis and get the new exactly solvable models. Their energies come out real as expected. The new one-dimensional spectra themselves differ quite significantly from their s-wave predecessors.Comment: Original 10-page letter ``PT-symmetrized exact solution of the singular Eckart oscillator" is extended to a full pape