Uniquely presented finitely generated commutative monoids

A finitely generated commutative monoid is uniquely presented if it has only a minimal presentation. We give necessary and sufficient conditions for finitely generated, combinatorially finite, cancellative, commutative monoids to be uniquely presented. We use the concept of gluing to construct commutative monoids with this property. Finally for some relevant families of numerical semigroups we describe the elements that are uniquely presented.Comment: 13 pages, typos corrected, references update

Selecting fast folding proteins by their rate of convergence

We propose a general method for predicting potentially good folders from a given number of amino acid sequences. Our approach is based on the calculation of the rate of convergence of each amino acid chain towards the native structure using only the very initial parts of the dynamical trajectories. It does not require any preliminary knowledge of the native state and can be applied to different kinds of models, including atomistic descriptions. We tested the method within both the lattice and off-lattice model frameworks and obtained several so far unknown good folders. The unbiased algorithm also allows to determine the optimal folding temperature and takes at least 3--4 orders of magnitude less time steps than those needed to compute folding times

Treating electrostatics with Wolf summation in combined quantum mechanical and molecular mechanical simulations

The Wolf summation approach [D. Wolf et al., J. Chem. Phys. 110, 8254 (1999)], in the damped shifted force (DSF) formalism [C. J. Fennell and J. D. Gezelter, J. Chem. Phys. 124, 234104 (2006)], is extended for treating electrostatics in combined quantum mechanical and molecular mechanical (QM/MM) molecular dynamics simulations. In this development, we split the QM/MM electrostatic potential energy function into the conventional Coulomb r −1 term and a term that contains the DSF contribution. The former is handled by the standard machinery of cutoff-based QM/MM simulations whereas the latter is incorporated into the QM/MM interaction Hamiltonian as a Fock matrix correction. We tested the resulting QM/MM-DSF method for two solution-phase reactions, i.e., the association of ammonium and chloride ions and a symmetric SN2 reaction in which a methyl group is exchanged between two chloride ions. The performance of the QM/MM-DSF method was assessed by comparing the potential of mean force (PMF) profiles with those from the QM/MM-Ewald and QM/MM-isotropic periodic sum (IPS) methods, both of which include long-range electrostatics explicitly. For ion association, the QM/MM-DSF method successfully eliminates the artificial free energy drift observed in the QM/MM-Cutoff simulations, in a remarkable agreement with the two long-range-containing methods. For the SN2 reaction, the free energy of activation obtained by the QM/MM-DSF method agrees well with both the QM/MM-Ewald and QM/MM-IPS results. The latter, however, requires a greater cutoff distance than QM/MM-DSF for a proper convergence of the PMF. Avoiding time-consuming lattice summation, the QM/MM-DSF method yields a 55% reduction in computational cost compared with the QM/MM-Ewald method. These results suggest that, in addition to QM/MM-IPS, the QM/MM-DSF method may serve as another efficient and accurate alternative to QM/MM-Ewald for treating electrostatics in condensed-phase simulations of chemical reactions

Assessing the accuracy of the isotropic periodic sum method through Madelung energy computation

We tested the isotropic periodic sum (IPS) method for computing Madelung energies of ionic crystals. The performance of the method, both in its nonpolar (IPSn) and polar (IPSp) forms, was compared with that of the zero-charge and Wolf potentials [D. Wolf, P. Keblinski, S. R. Phillpot, and J. Eggebrecht, J. Chem. Phys.110, 8254 (1999)]. The results show that the IPSn and IPSp methods converge the Madelung energy to its reference value with an average deviation of ∼10−4 and ∼10−7 energy units, respectively, for a cutoff range of 18–24a (a/2 being the nearest-neighbor ion separation). However, minor oscillations were detected for the IPS methods when deviations of the computed Madelung energies were plotted on a logarithmic scale as a function of the cutoff distance. To remove such oscillations, we introduced a modified IPSn potential in which both the local-region and long-range electrostatic terms are damped, in analogy to the Wolf potential. With the damped-IPSn potential, a smoother convergence was achieved. In addition, we observed a better agreement between the damped-IPSn and IPSp methods, which suggests that damping the IPSn potential is in effect similar to adding a screening potential in IPSp

Almost symmetric numerical semigroups with high type

We establish a one-to-one correspondence between numerical semigroups of genus g and almost symmetric numerical semigroups with Frobenius number F and type F − 2g , provided that F is greater than or equal to 4g − 1.The first author was partially supported by the Junta de Andalucía research group FQM-366, and by the project MTM2017-84890-P (MINECO/FEDER, UE). The second author was partially supported by the research groups FQM-024 (Junta de Extremadura/FEDER funds) and by the project MTM2015-65764-C3-1-P (MINECO/FEDER, UE) and by the project MTM2017-84890-P (MINECO/FEDER, UE)

Sistemas de ecuaciones lineales y la enseñanza de tensiones en el laboratorio de física en el bachillerato tecnológico

En el marco de un proyecto interinstitucional sobre docencia e investigación en matemática educativa, se indagó con estudiantes de tercer semestre en el laboratorio de física su comprensión de las tensiones en un cuerpo suspendido en equilibrio y de la resolución del sistema de ecuaciones que lo modela. Aunque los estudiantes comprendieron el fenómeno físico, no dieron sentido al modelo matemático. Los resultados obtenidos apuntan a la necesidad de investigar acerca de la forma en que la enseñanza pueda hacer efectiva para el estudiante la interrelación entre las distintas Unidades de Aprendizaje de las diferentes disciplinas, con miras al logro de los objetivos de los Programas de Estudios del bachillerato tecnológico

Flea parasites of small mammals in the Monte Desert biome in Argentina with new host and locality records

Fleas associated with small mammals from the Argentinean Monte Desert, were examined. The research was carried out in Ñacuñán Biosphere Reserve (34°02´S, 67°58´W), in the Chaqueña Biogeographic Subregion of the Neotropical Region. Mammal species trapped were as follows: Rodentia, Muridae, Sigmodontinae: Akodon molinae Contreras, 1968 (N = 44), Graomys griseoflavus (Waterhouse, 1837) (N = 15), Calomys musculinus (Thomas, 1913) (N = 12), and Eligmodontia typus F. Cuvier, 1837 (N = 7); Didelphiomorphia, Didelphidae, Mamorsinae: Thylamys pusillus (Desmarest, 1804) (N = 1). A total of 236 fleas were collected: Stephanocircidae, Craneopsyllinae: Craneopsylla minerva wolffhuegeli (Rothschild, 1909); Rhopalopsyllidae, Rhopalopsyllinae: Polygenis (Polygenis) bohlsi bohlsi (Wagner, 1901), Polygenis (Polygenis) platensis cisandinus (Jordan, 1939) and Polygenis (Neopolygenis) puelche Del Ponte, 1963; Rhopalopsyllidae, Parapsyllinae: Ectinorus (Ectinorus) barrerai Jordan, 1939. High values of total mean abundance (MA = 2.99) and total prevalence (P = 73.41%) were obtained. A. molinae (MA = 3.14; P = 93.18; flea specific richness S = 5; Shannon specific diversity index H = 1.25) and G. griseoflavus (MA = 6.40; P = 100%; S = 5; H = 0.76) showed the highest values of the infestation parameters. No fleas were collected from E. typus, possibly because of its habits. Fleas associated with T. pusillus are reported for the first time. Our collections extend the western limits of the distribution of both P. (N.) puelche and P. (P.) b. bohlsi. In addition, new host species are reported for every flea species and subspecies, and seven host-flea associations are mentioned for the first time.Fil: Lareschi, Marcela. Universidade Federal de Minas Gerais; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Ojeda, Ricardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Linardi, Pedro M.. Conselho Nacional de Desenvolvimiento Científico e Tecnológico; Brasi

Regalismo e Inquisición:: El proceso de expansión de las comisarías del Santo Oficio de México, 1709-1778

In the eighteenth century, a period when royal postures permeated Church-State relations, the Holy Office experienced a period of profound change, one that affected the nature of its competency, jurisdiction, and privileges. In Mexico, the policy of control and administrative efficiency was also manifest in the expansion of comisaria networks, which could even extend to (and embrace) pueblos de indios, which thereby lost their ethnic exclusivity. The operation of comisarias, on the other hand, favoured the emergence of new types of control, adapted to the immediate needs of respective jurisdictions. To understand the expansion of comisarias in Inquisitorial terms, sources were consulted from various archives, allowing a solid database to be established, indicating the breadth that comisarias acquired during this period.En el siglo XVIII, periodo en que las posturas regalistas van a permear las relaciones Iglesia-Estado, el Santo Oficio vivió un periodo de profundos cambios que afectaron la naturaleza de sus competencias, jurisdicción y privilegios. La política de control y de eficiencia administrativa en México también se manifestó en la expansión de la red de comisarías, que incluso alcanzaría a los pueblos de indios, perdiendo su antigua condición de exclusividad étnica. La funcionalidad y el mejor control de las distintas comisarías, por otra parte, también favorecieron la aparición de nuevos tipos de comisarios, adecuados a las necesidades inmediatas de las respectivas jurisdicciones. Para comprender la expansión de las comisarías en el distrito inquisitorial, a partir de fuentes de diversos archivos, fue necesario elaborar una sólida base de datos y conocer la amplitud que adquirieron en este periodo

Implementar la Metodología 5S, para mejorar la productividad en el Taller de Equipos de la Municipalidad Distrital de Curahuasi - Abancay - 2021

El presente trabajo de investigación se realizó con la finalidad de implementar la metodología de las 5S, en el taller de mantenimiento de equipos y maquinaria de la Municipalidad Distrital de Curahuasi – Abancay 2021. Usando una metodología básica aplicada de nivel descriptivo-explicativo de modelos preexperimental y cuasiexperimental, se tiene como objetivo incrementar la productividad en el taller de mantenimiento usando la metodología japonesa. Al realizar un diagnóstico inicial, se observó que existen demoras en las órdenes de trabajo (OT). Esto hace necesaria la implementación de la metodología de las 5S, la cual trata sobre la ingeniería de la eficacia y eficiencia, pensado en el ordenamiento del lugar de trabajo: clasificación de herramientas, limpieza del área de trabajo, estandarización de procesos de mantenimiento y el compromiso en la sostenibilidad mediante la disciplina y capacitación de los trabajadores. Se realizaron auditorías internas de carácter longitudinal en tiempos parciales de 15 días, para observar cómo evoluciona la implementación, notándose un incremento positivo en los porcentajes de cada una de las auditorías realizadas a la aplicación de la metodología 5S, logrando la clasificación de herramientas, ordenamiento de su gabinete, lugares más limpios, estandarización de los procesos y usos de herramientas y el compromiso de los colaboradores. A mediano plazo se logró reducir la respuesta a las solicitudes presentadas por los usuarios con respecto al requerimiento de los equipos y máquinas, optimizando la búsqueda de equipos y herramientas en el taller. Por consiguiente, se recomienda continuar con la metodología implementada en el taller de equipos para que los procesos de cada actividad sean óptimos y se logre incrementar la productividad