Agronomic, economic and ecological aspects of the papaya (Carica papaya) production in Tabasco, Mexico

The cultivation of papaya is important in the tropic because it provides source of income to the farmer within a short time. Statistical data were obtained from farmers located in the Chontalpa, Rios and Centro-Sierra regions; the size of the survey was 67 farmers. The study shows the results of the farmers’ problem in a drastic reduction of their productivity because of the virosis and low prices in commercialization. The farmers were classified into three levels of technology, “low”, “middle” and “high”. The first one covers 88% of the farmers in seasonal conditions in contrast with the high technology that concentrates 4.5% in irrigation conditions. According to the technology used, the fertilizer shows more yields. Economically, the high technology had an internal tax return of 0.43 in comparison with the low technology of 0.25, which means that the investment is recovered with different yields. However, the use of high technology makes the system more competitive. Key words

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

Low-lying spectra in anharmonic three-body oscillators with a strong short-range repulsion

Three-body Schroedinger equation is studied in one dimension. Its two-body interactions are assumed composed of the long-range attraction (dominated by the L-th-power potential) in superposition with a short-range repulsion (dominated by the (-K)-th-power core) plus further subdominant power-law components if necessary. This unsolvable and non-separable generalization of Calogero model (which is a separable and solvable exception at L = K = 2) is presented in polar Jacobi coordinates. We derive a set of trigonometric identities for the potentials which generalizes the well known K=2 identity of Calogero to all integers. This enables us to write down the related partial differential Schroedinger equation in an amazingly compact form. As a consequence, we are able to show that all these models become separable and solvable in the limit of strong repulsion.Comment: 18 pages plus 6 pages of appendices with new auxiliary identitie

The Imaginary Part of Nucleon Self-energy in hot nuclear matter

A semiphenomenological approach to the nucleon self-energy in nuclear matter at finite temperatures is followed. It combines elements of Thermo Field Dynamics for the treatment of finite temperature with a model for the self-energy, which evaluates the second order diagrams taking the needed dynamics of the NN interaction from experiment. The approach proved to be accurate at zero temperature to reproduce Im(Sigma) and other properties of nucleons in matter. In the present case we apply it to determine Im(Sigma) at finite temperatures. An effective NN cross section is deduced which can be easily used in analyses of heavy ion reactions.Comment: 15 pages, 6 postscripts figures, to be published in Nucl. Phys.

Possible ring material around centaur (2060) Chiron

We propose that several short duration events observed in past stellar occultations by Chiron were produced by rings material. From a reanalysis of the stellar occultation data in the literature we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates l=(352+/-10) deg, b=(37+/-10) deg or l=(144+/-10) deg, b=(24+/-10) deg . The mean radius of the rings is (324 +/- 10) km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both imply lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23-m CAHA telescope and indeed its amplitude is smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at CASLEO 2.15-m telescope that is consistent with our predictions. Out of the two poles the l=(144+/-10) deg, b=(24+/-10) deg solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole, Chiron's long term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings as the tilt angle with respect to the Earth changes with time. Also, the variability of the water ice band in Chiron's spectra in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on the reasons why rings might be common in centaurs. We speculate on whether the known bimodal color distribution of centaurs could be due to presence of rings and lack of them

Episodic Vestibulocerebellar Ataxia Associated with a CACNA1G Missense Variant

Episodic vestibulocerebellar ataxias are rare diseases, frequently linked to mutations in different ion channels. Our objective in this work was to describe a kindred with episodic vestibular dysfunction and ataxia, associated with a novel CACNA1G variant. Two individuals from successive generations developed episodes of transient dizziness, gait unsteadiness, a sensation of fall triggered by head movements, headache, and cheek numbness. These were suppressed by carbamazepine (CBZ) administration in the proband, although acetazolamide and topiramate worsened instability, and amitriptyline and flunarizine did not prevent headache spells. On examination, the horizontal head impulse test (HIT) yielded saccadic responses bilaterally and was accompanied by cerebellar signs. Two additional family members were asymptomatic, with normal neurological examinations. Reduced vestibulo-ocular reflex gain values, overt and covert saccades were shown by video-assisted HIT in affected subjects. Hearing acuity was normal. Whole-exome sequencing demonstrated the heterozygous CACNA1G missense variant c.6958G>T (p.Gly2320Cys) in symptomatic individuals. It was absent in 1 unaffected member (not tested in the other asymptomatic individual) and should be considered likely pathogenic. CACNA1G encodes for the pore-forming, a1G subunit of the T-type voltage-gated calcium channel (VGCC), in which currents are transient owing to fast inactivation, and tiny, due to small conductance. Mutations in CACNA1G cause generalized absence epilepsy and adult-onset, dominantly inherited, spinocerebellar ataxia type 42. In this kindred, the aforementioned CACNA1G variant segregated with disease, which was consistent with episodic vestibulocerebellar ataxia. CBZ proved successful in bout prevention and provided symptomatic benefit in the proband, probably as a result of interaction of this drug with VGCC. Further studies are needed to fully determine the vestibular and neurological manifestations of this form of episodic vestibulocerebellar ataxia. This novel disease variant could be designated episodic vestibulocerebellar ataxia type 10. © 2021 The Author(s). Published by S. Karger AG, Basel

Factores determinantes para la implementación de prácticas de Responsabilidad Social empresarial en las PYMES del sector industrial del distrito de Tarapoto – 2014

The present study aims to explore the different factors that make up the Corporate Social responsibility in order to ascertain the degree of implementation of this management style between small and medium-sized enterprises (SMEs) in the industrial-manufacturero sector of the District of Tarapoto in the Peruvian region of San Martin. In this context of analysis, evaluated the five factors of CSR for SMEs proposed by Jenkins (2006): leadership of the owner/manager, style of management, organizational culture, promotion, and tools and methodologies of CSR management. To this end, a survey was applied to 95 industrial-manufacturero SMEs in Tarapoto district, found that of the five factors analyzed only one of them is practiced by more than half of those. While individual SMEs might have less margin of action compared to large firms which are traditionally the most important references in the field of CSR, taken together those are 14 times higher in number than these; Hence the importance of extending the practice of CSR to the whole of Peruvian companies, since this style of management in the long run is a factor for the improvement of their competitiveness, strengthening its business sustainability and also benefiting the whole of society.La presente investigación tiene como propósito explorar los diferentes factores que conforman la Responsabilidad Social Empresarial a fin de conocer el grado de implementación de este estilo de gestión entre las pequeñas y medianas empresas (PYMES) del sector industrial-manufacturero del distrito de Tarapoto, de la región peruana de San Martín. En ese marco de análisis, se evalúan los cinco factores de RSE para las PYMES propuestos por Jenkins (2006): liderazgo del propietario/gerente, estilo de gestión, cultura organizacional, promoción, y, herramientas y metodologías de gestión de la RSE. Para este fin, se aplicó una encuesta a 95 PYMES industrial-manufacturero del distrito de Tarapoto, encontrándose que de los cinco factores analizados solo uno de ellos es practicado por más de la mitad de aquellas. Si bien las PYMES a nivel individual podrían tener menos márgenes de acción en comparación a las grandes empresas que son tradicionalmente los referentes más importantes en materia de RSE, tomadas en conjunto aquellas son 14 veces más grandes en número que éstas; de ahí la importancia de extender la práctica de RSE al conjunto de las empresas peruanas, ya que este estilo de gestión a la larga se constituye en un factor para la mejora de su competitividad, afianzando su sostenibilidad empresarial y beneficiando además al conjunto de la sociedadTesi