9,453 research outputs found
Common cellular events occur during wound healing and organ regeneration in the sea cucumber Holothuria glaberrima
<p>Abstract</p> <p>Background</p> <p>All animals possess some type of tissue repair mechanism. In some species, the capacity to repair tissues is limited to the healing of wounds. Other species, such as echinoderms, posses a striking repair capability that can include the replacement of entire organs. It has been reported that some mechanisms, namely extracellular matrix remodeling, appear to occur in most repair processes. However, it remains unclear to what extent the process of organ regeneration, particularly in animals where loss and regeneration of complex structures is a programmed natural event, is similar to wound healing. We have now used the sea cucumber <it>Holothuria glaberrima </it>to address this question.</p> <p>Results</p> <p>Animals were lesioned by making a 3–5 mm transverse incision between one of the longitudinal muscle pairs along the bodywall. Lesioned tissues included muscle, nerve, water canal and dermis. Animals were allowed to heal for up to four weeks (2, 6, 12, 20, and 28 days post-injury) before sacrificed. Tissues were sectioned in a cryostat and changes in cellular and tissue elements during repair were evaluated using classical dyes, immmuohistochemistry and phalloidin labeling. In addition, the temporal and spatial distribution of cell proliferation in the animals was assayed using BrdU incorporation. We found that cellular events associated with wound healing in <it>H. glaberrima </it>correspond to those previously shown to occur during intestinal regeneration. These include: (1) an increase in the number of spherule-containing cells, (2) remodeling of the extracellular matrix, (3) formation of spindle-like structures that signal dedifferentiation of muscle cells in the area flanking the lesion site and (4) intense cellular division occurring mainly in the coelomic epithelium after the first week of regeneration.</p> <p>Conclusion</p> <p>Our data indicate that <it>H. glaberrima </it>employs analogous cellular mechanisms during wound healing and organ regeneration. Thus, it is possible that regenerative limitations in some organisms are due either to the absence of particular mechanisms associated with repair or the inability of activating the repair process in some tissues or stages.</p
A probabilistic patient scheduling model for reducing the number of no-shows
No-shows in medical centres cause under-utilisation of resources and increase waiting times in specialty health care services. Although this problem has been addressed in literature, behavioural issues associated with the patient's socio-demographic characteristics and diagnosis have not been widely studied. In this article, we propose a model that includes such behavioural issues in order to reduce impact of no-shows in medical services. The objective is maximising the health centre's expected revenue by using show-up probabilities estimated for each combination of patient and appointment slot. Additionally, the model considers the requirements imposed by both the health centre's management and the health authorities. An extension of the model allows overbooking in some appointment slots. Experimental results show that the proposed model can reduce the waiting list length by 13%, and to attain an increase of about 5% in revenue, when comparing to a model that assigns patients to the first available slot
Transcultural study of perceived competence in physical education and leisure time
El objetivo fue analizar la influencia de la competencia percibida en el
sexo, el patrón de actividad físico-deportiva y las etapas de cambio en la práctica
de actividad físico-deportiva de tiempo libre. La muestra fue de 2168 estudiantes
del primer curso de Enseñanza Secundaria Obligatoria, de Costa Rica (423),
México (408) y España (1337). Se realizaron análisis de Chi-cuadrado (x2), tstudent,
ANOVA y modelo lineal univariante. Los alumnos con mayor índice de
práctica y en etapas activas presentaron una mayor competencia percibida,
siendo superior también en los chicos que en las chicas. Por los resultados de
esta investigación, hay pocas posibilidades de que la mayoría de los escolares
lleguen a ser físicamente activos. Por tanto, en los tres países existe un nivel
bajo de actividad físico-deportiva que podría mejorar a través de diseños
metodológicos en la Educación Física escolar orientados a la mejora de
competenciaThe objective was to analyze the influence of perceived competence on gender,
the pattern of physical-sport activity and the stages of change in the practice of
physical activity in leisure. The sample was of 2168 students of the first course
of Compulsory Secondary Education, of Costa Rica (423), Mexico (408) and
Spain (1337). Chi-square (x2), t-student, ANOVA and univariate linear model
analyzes were performed. The students with the highest index of practice and in
active stages presented a greater perceived competence, also being superior in
the boys than in the girls. From the results of this research, it is very probably
that most schoolchildren will not become physically active. Therefore, in the
three countries there is a low level of physical-sport activity that could be
improved through methodological designs in Physical Education aimed at
improving perceived competenc
Evolución de la ley (AG/CU) en monedas árabes durante los siglos VIII al X D.C mediante SEM-EDX y TXRF
En este trabajo se presenta el estudio analítico, mediante fluorescencia de ra
yos X por reflexión total (TXRF) y microscopía electrónica de barrido con aná
lisis de energía dispersiva de rayos X (SEM-EDX). de un amplio grupo de mo
nedas islámicas (532 piezas), con el fin de establecer una correlación entre la ley
de la moneda islámica en España y los acontecimientos históricos más relevan
tes tícurridos durante los siglos VIII al X d.C. Los resultados analíticos obteni
dos han permitido establecer el proceso de devaluación en la riqueza de la alea-
ción Ag/Cu. en este período. Las tendencias observadas se correlacionan con el
déficit de plata sufrido por el estado Omeya de Córdoba. Por otro lado, la com
binación de las técnicas de TXRF y SEM-EDX ha permitido caracterizar de forma
concluyente la tecnología de la producción, así como la evolución histórica su
frida por este tipo de materiales
Statistical Complexity and Nontrivial Collective Behavior in Electroencephalografic Signals
We calculate a measure of statistical complexity from the global dynamics of
electroencephalographic (EEG) signals from healthy subjects and epileptic
patients, and are able to stablish a criterion to characterize the collective
behavior in both groups of individuals. It is found that the collective
dynamics of EEG signals possess relative higher values of complexity for
healthy subjects in comparison to that for epileptic patients. To interpret
these results, we propose a model of a network of coupled chaotic maps where we
calculate the complexity as a function of a parameter and relate this measure
with the emergence of nontrivial collective behavior in the system. Our results
show that the presence of nontrivial collective behavior is associated to high
values of complexity; thus suggesting that similar dynamical collective process
may take place in the human brain. Our findings also suggest that epilepsy is a
degenerative illness related to the loss of complexity in the brain.Comment: 13 pages, 3 figure
Numerical prediction of saturation in dual scale fibrous reinforcements during Liquid Composite Molding
This paper presents a fractional flow model based on two-phase flow, resin and air, through a porous
medium to simulate numerically Liquid Composites Molding (LCM) processes. It allows predicting the
formation, transport and compression of voids in the modeling of LCM. The equations are derived by
combining Darcy’s law and mass conservation for each phase (resin/air). In the model, the relative permeability
and capillary pressure depend on saturation. The resin is incompressible and the air slightly
compressible. Introducing some simplifications, the fractional flow model consists of a saturation equation
coupled with a pressure/velocity equation including the effects of air solubility and compressibility.
The introduction of air compressibility in the pressure equation allows for the numerical prediction of the
experimental behavior at low constant resin injection flow rate. A good agreement was obtained between
the numerical prediction of saturation in a glass fiber reinforcement and the experimental observations
during the filling of a test mold by Resin Transfer Molding (RTM).
2015 Elsevier Ltd. All rights reserved.The authors acknowledge financial support of the Spanish Government (Project DPI2013-44903-R-AR).Gascón Martínez, ML.; García Manrique, JA.; Lebel, F.; Ruiz, E.; Trochu, F. (2015). Numerical prediction of saturation in dual scale fibrous reinforcements during Liquid Composite Molding. Composites Part A: Applied Science and Manufacturing. 77:275-284. https://doi.org/10.1016/j.compositesa.2015.05.019S2752847
Quo vadis high-resolution continuum source atomic/molecular absorption spectrometry?
After more than a decade since its commercial introduction, high-resolution continuum source atomic/molecular absorption spectrometry may be facing a mid-life crisis. Certainly, it is no longer a novel technique full of unknown potential, so it would already be time to establish the fields for which it is most suitable. This is, however, not so simple for a number of reasons. In the first place, more than a technique what we are discussing herein is a type of instrumentation with the potential to use two different techniques (atomic or molecular absorption), making it somewhat unique. Furthermore, the two techniques have not been explored equally, and more research on the mechanisms of formation of diatomic molecules is clearly needed. In the second place, new possibilities have recently appeared in the literature that need to be weighed as well. And there is the still unfulfilled, but nowadays more technically feasible than ever, promise to significantly increase the multi-elemental capabilities. This review critically examines the main research areas currently explored (namely, (i) direct analysis of solids and complex liquid materials, and (ii) determination of non-metals at trace levels via monitoring of molecular species) as well as the new venues (specifically, (i) isotopic analysis via monitoring of molecular species, and (ii) selective detection, quantification and sizing of nanoparticles) while also considering new instrumental developments, in an attempt to properly place high-resolution continuum source atomic/molecular absorption spectrometry in the field of trace element and isotopic analysis
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