ABSTRACT
Despite the ubiquity of thermal convection in nature and artificial systems, we still lack a unified formulation that integrates the system's geometry, fluid properties, and thermal forcing to characterize the transition from free to confined convective regimes. The latter is broadly relevant to understanding how convection transports energy and drives mixing across a wide range of environments, such as planetary atmospheres/oceans and hydrothermal flows through fractures, as well as engineering heatsinks and microfluidics for the control of mass and heat fluxes. Performing laboratory experiments in Hele-Shaw geometries, we find multiple transitions that are identified as remarkable shifts in flow structures and heat transport scaling, underpinning previous numerical studies. To unveil the mechanisms of the geometrically controlled transition, we focus on the smallest structure of convection, posing the following question: How free is a thermal plume in a closed system? We address this problem by proposing the degree of confinement [Formula: see text]-the ratio of the thermal plume's thickness in an unbounded domain to the lateral extent of the system-as a universal metric encapsulating all the physical parameters. Here, we characterize four convective regimes different in flow dimensionality and time dependency and demonstrate that the transitions across the regimes are well tied with [Formula: see text]. The introduced metric [Formula: see text] offers a unified characterization of convection in closed systems from the plume's standpoint.
ABSTRACT
The extent of littoral influence on lake gas dynamics remains debated in the aquatic science community due to the lack of direct quantification of lateral gas transport. The prevalent assumption of diffusive horizontal transport in gas budgets fails to explain anomalies observed in pelagic gas concentrations. Here, we demonstrate through high-frequency measurements in a eutrophic lake that daily convective horizontal circulation generates littoral-pelagic advective gas fluxes one order of magnitude larger than typical horizontal fluxes used in gas budgets. These lateral fluxes are sufficient to redistribute gases at the basin-scale and generate concentration anomalies reported in other lakes. Our observations also contrast the hypothesis of pure, nocturnal littoral-to-pelagic exchange by showing that convective circulation transports gases such as oxygen and methane toward both the pelagic and littoral zones during the daytime. This study challenges the traditional pelagic-centered models of aquatic systems by showing that convective circulation represents a fundamental lateral transport mechanism to be integrated into gas budgets.
ABSTRACT
BACKGROUND: There are few studies looking for collagen matrix defects in patients with inguinal bernia. AIM: To study the skin connective tissue in patients with and without inguinal bernia. PATIENTS AND METHODS: Skin from the surgical wound was obtained from 23 patients with and 23 patients without inguinal bernia. The samples were processed for conventional light microscopy. Collagen fibers were stained with Van Giesson and elastic fibers with Weigert stain. RESULTS: Patients without hernia had compact collagen tracts homogeneously distributed towards the deep dermis. In contrast, patients with hernia had zones in the dermis with thinner and disaggregated collagen tracts. Connective tissue had a lax aspect in these patients. Collagen fiber density was 52% lower in patients with hernia, compared to subjects without hernia. No differences in elastic fiber density or distribution was observed between groups. CONCLUSIONS: Patients with inguinal bernia have alterations in skin collagen fiber quality and density.
Subject(s)
Collagen/analysis , Elastic Tissue/chemistry , Hernia, Inguinal/pathology , Adolescent , Adult , Case-Control Studies , Collagen/ultrastructure , Female , Humans , Male , Middle AgedABSTRACT
En este trabajo el objetivo primordial de la investigacion consistia en disminuir la frecuencia de los casos de amibiasis a un grupo de escolares mediante la ensenanza de habitos higienicos, para ello se escogieron dos grupos de estudiantes de estratos socio-economicos y culturales similares y se dividieron en grupos iguales para conformar una muestra experimental; se les dio instruccion despues de un pre-test para calibrar los conocimientos que tenian acerca de la materia. A la muestra llamada control, solamente se aplico el pre-test. Inicialmente se les tomo a ambos grupos de escolares una muestra de materia fecal encontrandose un miltiparasitismo con predominio de amebas. A continuacion se les administro tratamiento especifico con metronidazol y mebendazol y simulataneamente se impartio instruccion al grupo experimental y luego se expusieron 90 dias para obtener una segunda muestra de materia fecal, ambos resultados mostraron una disminucion apreciable de parasitos tanto de helmintos como de amebas. Al comparar los resultados se encontro una diferencia entadisticamente significativa en ambos gurpos de estudiantes siendo mas amplia en el grupo experimental. Lo que nos demustra que la instruccion influyo significativamente en la diferencia estadistica observada, comprobandose de esta manera la hipostesis.
