Spectral analysis of the biharmonic operator subject to Neumann boundary conditions on dumbbell domains

We consider the biharmonic operator subject to homogeneous boundary conditions of Neumann type on a planar dumbbell domain which consists of two disjoint domains connected by a thin channel. We analyse the spectral behaviour of the operator, characterizing the limit of the eigenvalues and of the eigenprojections as the thickness of the channel goes to zero. In applications to linear elasticity, the fourth order operator under consideration is related to the deformation of a free elastic plate, a part of which shrinks to a segment. In contrast to what happens with the classical second order case, it turns out that the limiting equation is here distorted by a strange factor depending on a parameter which plays the role of the Poisson coefficient of the represented plate.Comment: To appear in "Integral Equations and Operator Theory

Dynamic Behavior of a Clamped-Clamped Bi-Stable Laminate for Energy Harvesting

Multi-stable laminates have many applications in morphing structures, energy harvesting devices, and metamaterials due to the specific characteristics attributed to the exhibited stable states. Changes between stable states allow for large deflections, on-demand variation of the stiffness of compliant structures embedded within these elements, and control of effective dynamic properties in periodic lattices. These changes in state can be accessed via a snap-through instability triggered by introducing a well-defined activation energy. The resulting oscillations could enable broadband energy harvesting via piezoelectric transduction and resistive circuits. In this paper, a clamped-clamped bi-stable laminate is studied to understand the behavior of the laminate at each stable state and determine energy harvesting capabilities. An FEA model is created to determine the frequency and shapes of resonant modes. Certain modal shapes have significant deformations near the clamp which are necessary for piezoelectric elements to generate a voltage. Small amplitude low frequency vibrations are used to excite the laminate at each stable state using a shaker. The laminate is then excited so that inter-well oscillations become present. The resonant characteristics of each stable state determined by the simulations are similar to the experimentally observed responses with some variation. The laminate shows inter-well dynamics at particular resonant frequencies and for a range of frequencies in which both sable states have similar modal characteristics. At higher excitations and a range of frequencies is observed causing chaotic and inter-well oscillations. This shows that the laminate exhibits vibrational dynamics which are capable of enabling broadband energy harvesting devices

Minkowski's Footprint revisited. Planetary Nebula formation from a single sudden event?

M1-92 can be considered an archetype of bipolar pre-planetary nebulae. It shows a clear axial symmetry, along with the kinematics and momentum excess characteristic of this class of envelopes around post-AGB stars. By taking advantage of the new extended configuration of the IRAM Plateau de Bure interferometer, we wanted to study the morphology and velocity field of the molecular gas better in this nebula, particularly in its central part. We performed sub-arcsecond resolution interferometric observations of the J=2-1 rotational line 13CO M1-92. We found that the equatorial component is a thin flat disk, which expands radially with a velocity proportional to the distance to the center. The kinetic age of this equatorial flow is very similar to that of the two lobes. The small widths and velocity dispersion in the gas forming the lobe walls confirm that the acceleration responsible for the nebular shape could not last more than 100-120 yr. The present kinematics of the molecular gas can be explained as the result of a single brief acceleration event, after which the nebula reached an expansion velocity field with axial symmetry. In view of the similarity to other objects, we speculate on the possibility that the whole nebula was formed as a result of a magneto-rotational explosion in a common-envelope system.Comment: 4 pages (2 figures

Morphological characterization of varieties of Chenopodium quinoa cultivated in the department of Boyacá, Colombia

In the department of Boyacá, seeds of Chenopodium quinoa Willd. are planted, which correspond to a mixture of varieties, producing different grain sizes and saponin concentrations, affecting the quality and yield of the derived products, and therefore their commercialization, whenever the buyer requires it for a certain purpose, sweet varieties for bakeries or with high contents of saponin for the detergent industry. The objective was to compare the morphological characters, to identify the six varieties, according to the constant and conspicuous characteristics, as well as physiological parameters in the reproductive and vegetative stages. Observations were made in the different stages of development; in seeds, germination tests were made, the diameter and weight were measured; In the seedling stage, the total height, hypocotyl length, cotyledon lamina length and changes in red pigmentation were determined, qualitatively evaluated by direct observation. In adult plants, reproductive and vegetative characters were reviewed. A taxonomic key was proposed for the identification of the varieties. Blanca Real recorded the highest germination percentage (98%). Amarilla Marangani presented the seeds with the greatest weight and diameter and the longest cotyledons. The height of the Black and Piartal seedlings was below the other varieties. Blanca de Jericó, Blanca Real and Piartal presented weak reddish colorations in the hypocotyl and cotyledons. The identification of each variety will result in better products for growers, marketers, and processors

E.coli 0157: H7 enterohemorrágico: un agente etiológico de diarrea y zoonosis en Colombia subestimado. Parte I

En los últimos años, la enfermedad diarreica aguda (EDA) se ha convertido en un serio problema de salud pública; la EDA tiene las características de una verdadera pandemia si tenemos en cuenta que ha afectado a múltiples países en Europa y América. A nivel mundial, la EDA es una de las causas más importantes de morbi-mortalidad sobre todo en lactantes, niños y ancianos. Se ha estimado que en Asia, Africa y Latinoamérica, en razón a los factores socioeconómicos y nutricionales, la probabilidad de que un niño muera por enfermedad diarreica antes de los 7 años pueda llegar al 50%. En los países desarrollados la mortalidad es mucho menor, pero todavía significativa. (Máttar 1998). Según la organización mundial de la salud (OMS), la EDA, afecta a 750 millones de niños anualmente, y en este período se calcula que unos 4.6 millones mueren debido a la deshidratación que producen estos procesos infecciosos. Datos del Instituto Nacional de Salud (INS) y del Ministerio de Salud de Colombia, muestran que en 1993 se presentaron 470.772 casos de EDA en una población de 4.224.121 niños menores de 5 años para los 33 departamentos del país, siendo así una de las patológias más comunes en la población infantil y en especial en los menores de 5 años (Máttar 1996). EDA es una de las principales causantes de muerte infantil en Colombia (Máttar 1996); es una entidad multifactorial en la que principalmente, el criterio diagnóstico ha sido clínico a través del tiempo, y donde, el diagnóstico etiológico preciso no es usualmente el empleado

La galectina-3, una nueva diana terapéutica para las alteraciones cardiovasculares asociadas al desarrollo de la estenosis aórtica severa

Aortic stenosis is one of the most common heart valve diseases, as well as one of the most common causes of heart failure in the elderly. Currently, there are no medical therapies to prevent or slow the progression of the disease. When symptoms develop alongside severe aortic stenosis, there is a poor prognosis unless aortic valve replacement is performed. Aortic stenosis is a heterogeneous disease with a complex pathophysiology involving structural and biological changes of the valve, as well as adaptive and maladaptive compensatory changes in the myocardium and vasculature in response to chronic pressure overload. Galectin-3 serves important functions in numerous biological activities including cell growth, apoptosis, differentiation, inflammation and fibrosis. With evidence emerging to support the function of Galectin-3, the current review aims to summarize the latest literature regarding the potential of Galectin-3 as therapeutic target in aortic valve and cardiovascular alterations associated with aortic stenosis.La estenosis aórtica severa degenerativa (EA) es una enfermedad muy prevalente, cuya incidencia se incrementará en los próximos años debido al envejecimiento de la población. Actualmente no existe ningún tratamiento farmacológico que retarde su progresión y, cuando aparecen los síntomas, la cirugía de recambio valvular es la única opción. La EA se caracteriza por la calcificación de la válvula aórtica y por la aparición de fibrosis miocárdica. Sin embargo, no se conocen los mecanismos fisiopatológicos de la EA necesarios para identificar y desarrollar nuevas estrategias terapéuticas adecuadas. La Galectina-3 (Gal-3) regula funciones biológicas como el crecimiento, la diferenciación, la apoptosis, la inflamación o la fibrosis. Esta revisión resume los principales trabajos que describen el potencial de la Gal-3 como diana terapéutica para las alteraciones cardíacas y valvulares asociadas con el desarrollo de EA

Desempeño productivo y conductas etológicas de gallinas ponedoras en tres tipos de manejo en condiciones de trópico cálido

The objective of this study was to evaluate the effect of management systems (T1:cage, T2:litter floor and T3:free range) on productive performance and behavior of laying hens of a commercial line in a hot tropical environment conditions, 220 laying hens of Lohmann Brown line with 56 weeks of age were randomly assigned to three treatments. Physiological, anatomical, behavioral and productive variables were studied. Caged birds had a higher incidence of ridges, chin, legs and plumage with undesirable characteristics, indicator for the housing problems, like increased mortality (P=0.002). The highest eggs production (79.9%) was observed in litter floor management, with no effect (P>0.05) of management systems on egg weight and morbidity. Birds kept in cage spent more time (P<0.05) feed intake. Hens managed in grazing and spent more time on floor (P<0.05) stretching activities, and “bath” with sand or floor material. It is concluded that the handling of hens in litter floor promoted a better productive performance and facilitated the expression of own behavior of these birds, while handling cages negatively affected bird performance, appearance and welfare.El objetivo del estudio fue evaluar el efecto del tipo de manejo (T1:jaula; T2:piso y T3:pastoreo) sobre variables de tipo etológico, fisiológico y de desempeño productivo en gallinas de postura en condiciones de trópico, para lo cual, 220 aves de la línea Lohmann Brown con 56 semanas de edad fueron asignadas aleatoriamente a los tres tratamientos (tipo de manejo), para evaluar variables fisiológicas, anatómicas, productivas y etológicas. Las aves enjauladas presentaron mayor frecuencia (%) de crestas, barbilla, plumaje y patas con características no deseables, indicadoras de problemas durante el alojamiento, al igual que mayor mortalidad (P=0,002). Las gallinas manejadas en piso presentaron el mayor porcentaje de postura (79,9%); el tipo de manejo no afectó (P>0,05) ni el peso del huevo ni la morbilidad. Las aves en jaula dedicaron más tiempo (P<0.05) al consumo de alimento. Las gallinas en pastoreo y las manejadas en piso dedicaron más tiempo (P<0,05) a actividades de estiramiento, y “baños” con arena o material del piso. Se concluye que el manejo de gallinas en piso promovió un mejor desempeño productivo y facilitó la expresión de conductas propias de estas aves, mientras que el manejo en jaulas afectó negativamente el desempeño de las aves, la apariencia y el bienestar de las mismas

Actividad antimicrobiana de bacterias endófitas aisladas de orégano serrano (Lippia origanoides) contra Burkholderia glumae y Colletotrichum gloeosporioides

The objective of this study was to determinate endophytic diversity associated to Lippia origanoides from Sabana subregion in the Department of Sucre, Colombia and evaluate their antimicrobial activity against Colletotrichum gloeosporioides and Burkholderia glumae. Tissue surface disinfection technique was used and isolation was performed on R2A agar culture medium. Population density (CFU / g tissue) was estimated by direct counting of colonies on plate. Statistics significances between population density in relation to tissues and site, was made by multivariate analysis and multiple range test (Tukey). Endophytic bacteria that showed inhibition of pathogenic microorganisms were subjected to an extraction of secondary metabolites. The antimicrobial, antifungal and secondary metabolites test were carried out by testing confrontation and qualitative estimation. The results show that there is a population density of endophytic bacteria associated with oregano plants and abundance is related to tissues. None of the morphotypes showed antimicrobial activity for B. glumae. One morphotypes had antifungal activity against C. gloeosporioides and metabolites extraction was performed for antifungal activity from cell suspensions.El objetivo de éste estudio fue determinar la diversidad de bacterias endófitas asociadas a la especie vegetal Lippia origanoides de la subregión sabanas en el Departamento de Sucre, Colombia y evaluar su actividad antimicrobiana contra Colletotrichum gloeosporioides y Burkholderia glumae. Se utilizó la técnica de desinfección superficial de tejidos y el aislamiento se realizó en medio de cultivo agar R2A. La densidad poblacional (UFC/g de tejido) se estimó por conteo directo de colonias en placa. Las significancias estadísticas entre densidad poblacional, con relación a tejidos y sitio, se realizó mediante análisis multifactorial y prueba múltiple de rango (Tukey). Las bacterias endófitas que presentaron inhibición contra los microorganismos patógenos fueron sometidas a un proceso de extracción de metabolitos secundarios. La prueba antimicrobiana, antifúngica y de metabolitos secundarios se llevaron a cabo mediante ensayos de confrontación y estimación cualitativa. Los resultados muestran que existe una densidad poblacional de bacterias endófitas asociadas a plantas de orégano serrano y la abundancia está relacionada con el tejido. Ninguno de los morfotipos presentó actividad antimicrobiana para B. glumae. Uno de los morfotipos tuvo actividad antifúngica frente a C. gloeosporioides y se le realizó extracción de metabolitos para determinar la actividad antifúngica a partir de suspensiones celulares

Analysis of streamflow variability and trends in the Meta River, Colombia

The aim of this research is the detection and analysis of existing trends in the Meta River, Colombia, based on the streamflow records from seven gauging stations in its main course, for the period between June 1983 to July 2019. The Meta River is one of the principal branches of the Orinoco River, and it has a high environmental and economic value for this South American country. The methods employed for the trend detection and quantification were the Mann–Kendall (MK) test, the modified MK (MMK) test, and the Sen’s slope (SS) estimator. Statistically significant trends (at a 95% level of confidence) were detected in more than 30% of the 105 evaluated datasets. The results from the MK test indicate the presence of statistically significant downward trends in the upstream stations and upward trends in the downstream stations, with the latter presenting steep positive slopes. The findings of this study are valuable assets for water resources management and sustainable planning in the Meta River Basin