Stability Analysis of a Hybrid Cellular Automaton Model of Cell Colony Growth

Cell colonies of bacteria, tumour cells and fungi, under nutrient limited growth conditions, exhibit complex branched growth patterns. In order to investigate this phenomenon we present a simple hybrid cellular automaton model of cell colony growth. In the model the growth of the colony is limited by a nutrient that is consumed by the cells and which inhibits cell division if it falls below a certain threshold. Using this model we have investigated how the nutrient consumption rate of the cells affects the growth dynamics of the colony. We found that for low consumption rates the colony takes on a Eden-like morphology, while for higher consumption rates the morphology of the colony is branched with a fractal geometry. These findings are in agreement with previous results, but the simplicity of the model presented here allows for a linear stability analysis of the system. By observing that the local growth of the colony is proportional to the flux of the nutrient we derive an approximate dispersion relation for the growth of the colony interface. This dispersion relation shows that the stability of the growth depends on how far the nutrient penetrates into the colony. For low nutrient consumption rates the penetration distance is large, which stabilises the growth, while for high consumption rates the penetration distance is small, which leads to unstable branched growth. When the penetration distance vanishes the dispersion relation is reduced to the one describing Laplacian growth without ultra-violet regularisation. The dispersion relation was verified by measuring how the average branch width depends on the consumption rate of the cells and shows good agreement between theory and simulations.Comment: 8 pages, 6 figure

Continental Santa Anita, Tlajomulco de Zúñiga

En el reporte PAP se plasma todo el proceso que se planteó y llevo a cabo, para lograr la realización del proyecto PAP en la empresa huésped. Se manejó el proyecto con Project managment, para determinar todas las fases del proyecto, los alcances esperados con los entregables, los tiempos y finalmente obtener los resultados en los tiempos estimados. En este documento, se desglosa por capítulos, donde se toman en cuenta los tópicos principales para la explicación del desarrollo del proyecto, siempre mencionando los aspectos superficiales del proyecto a cumplir, cuidando la confidencialidad de la empresa huésped.ITESO, A.C

Deficit irrigation in Mediterranean environment. What lessons have we learnt from grapevine studies ?

Libro de Actas - X Simposium Hispano Português de Relaciones Hidricas, 2010Deficit irrigation techniques, implying that water is supplied at levels below full crop evapotranspiration throughout the growing season or in specific phenological stages, such as regulated deficit irrigation (RDI) or partial root drying (PRD), emerged as potential strategies to increase water savings with marginal decreases of yield and likely positive impact on fruit quality. Understanding the physiological and molecular bases for plant responses to mild to moderate water deficits is of utmost importance to modulate the appropriate balance between vegetative and reproductive development, to improve crop water-use efficiency and to control fruit quality. It is acknowledged that the timing and intensity of the response to soil and atmospheric water deficits, namely in what concerns stomatal control, depends greatly on the genotype. This has profound implications in irrigation management, in particular the timing and amount of irrigation to optimize source-sink relationships and achieve optimal fruit quality in each variety. Mild water deficits also exert direct and/or indirect (via the light environment in the cluster zone) effects on berry development and composition. A current research challenge is determining how the environment, in particular water deficits, regulates genes and proteins of the various metabolic pathways responsible for berry composition and therefore for wine qualit

Grapevine under deficit irrigation: hints from physiological and molecular data

Background - A large proportion of vineyards are located in regions with seasonal drought (e.g. Mediterraneantype climates) where soil and atmospheric water deficits, together with high temperatures, exert large constraints on yield and quality. The increasing demand for vineyard irrigation requires an improvement in the efficiency of water use. Deficit irrigation has emerged as a potential strategy to allow crops to withstand mild water stress with little or no decreases of yield, and potentially a positive impact on fruit quality. Understanding the physiological and molecular bases of grapevine responses to mild to moderate water deficits is fundamental to optimize deficit irrigation management and identify the most suitable varieties to those conditions. Scope - How the whole plant acclimatizes to water scarcity and how short- and long-distance chemical and hydraulic signals intervene are reviewed. Chemical compounds synthesized in drying roots are shown to act as long-distance signals inducing leaf stomatal closure and/or restricting leaf growth. This explains why some plants endure soil drying without significant changes in shoot water status. The control of plant water potential by stomatal aperture via feed-forward mechanisms is associated with ‘isohydric’ behaviour in contrast to ‘anysohydric’ behaviour in which lower plant water potentials are attained. This review discusses differences in this respect between grapevines varieties and experimental conditions. Mild water deficits also exert direct and/or indirect (via the light environment around grape clusters) effects on berry development and composition; a higher content of skin-based constituents (e.g. tannins and anthocyanins) has generally being reported. Regulation under water deficit of genes and proteins of the various metabolic pathways responsible for berry composition and therefore wine quality are reviewed

A fossil species of the enigmatic early polypod fern genus Cystodium (Cystodiaceae) in Cretaceous amber from Myanmar

The monospecific fern genus Cystodium (Cystodiaceae;Polypodiales) occurs exclusively in the tropical forests of the Malay Archipelago, the Admiralty Islands, the Louisiade Archipelago, and the Solomon Islands. Divergence time estimates suggest that the genus originated in the Mesozoic;however, fossil evidence to validate this suggestion has been lacking. Amber from Myanmar (Burmese amber) is an important source of new information on the diversity of vascular cryptogams in the Cretaceous. This paper describes the fossil taxon Cystodium sorbifolioides nov. sp. based on a fragment of a fertile leaf preserved in Burmese amber that represents the first fossil evidence of the family Cystodiaceae. Cystodium sorbifolioides is used to obtain a minimum age estimate for the Cystodiaceae and the closely related, monogeneric Lonchitidaceae and Lindsaeaceae. The fossil strengthens the hypothesis that the forest ecosystems of Malesia and Melanesia represent refugia for many tropical plant lineages that originated in the Cretaceous

Deficit irrigation in Mediterranean vineyards - a tool to increase water use efficiency and to control grapevine and berry growth

IHC - IS Viti&Climate: Effect of Climate Change on Production and Quality of Grapevines and their Products, 28 th, 2012Water is increasingly scarce in Mediterranean Europe and irrigated agriculture is one of the largest and most inefficient users of this natural resource. Ecological topics such as the “water foot print” have become more relevant for the academy, consumers, governments and food industry. The wine sector needs solutions to improve its economical and environmental sustainability. Agronomical solutions, such as deficit irrigation (water supply below full crop evapotranspiration) have emerged as a tool for more efficient water use in irrigated viticulture and with likely positive effects on berry quality. Improving our understanding on the physiological and molecular basis of grapevine responses to water stress is an important task for research on irrigated viticulture. Better knowledge of the different genotypic responses (e.g., leaf gas exchange) to water stress can help to optimize crop/soil management and improve yield as well as berry quality traits under unfavourable climate conditions. Mild water deficits have direct and/or indirect (via the light environment in the cluster zone) effects on berry growth and composition. Another important challenge is to determine how soil water deficit regulate genes and proteins of the various metabolic pathways influencing berry composition and consequently wine quality

Quantum Noise and Polarization Fluctuations in Vertical Cavity Surface Emitting Lasers

We investigate the polarization fluctuations caused by quantum noise in quantum well vertical cavity surface emitting lasers (VCSELs). Langevin equations are derived on the basis of a generalized rate equation model in which the influence of competing gain-loss and frequency anisotropies is included. This reveals how the anisotropies and the quantum well confinement effects shape the correlations and the magnitude of fluctuations in ellipticity and in polarization direction. According to our results all parameters used in the rate equations may be obtained experimentally from precise time resolved measurements of the intensity and polarization fluctuations in the emitted laser light. To clarify the effects of anisotropies and of quantum well confinement on the laser process in VCSELs we therefore propose time resolved measurements of the polarization fluctuations in the laser light. In particular, such measurements allow to distinguish the effects of frequency anisotropy and of gain-loss anisotropy and would provide data on the spin relaxation rate in the quantum well structure during cw operation as well as representing a new way of experimentally determinig the linewidth enhancement factor alpha.Comment: 16 pages and 3 Figures, RevTex, to be published in Phys. Rev.

A Liposomal Formulation to Exploit the Bioactive Potential of an Extract from Graciano Grape Pomace

Antioxidant compounds with health benefits can be found in food processing residues, such as grape pomace. In this study, antioxidants were identified and quantified in an extract obtained from Graciano red grape pomace via a green process. The antioxidant activity of the extract was assessed by the DPPH and FRAP tests, and the phenolic content by the Folin–Ciocalteu test. Furthermore, nanotechnologies were employed to produce a safe and effective formulation that would exploit the antioxidant potential of the extract for skin applications. Anthocyanins, flavan-3-ols and flavanols were the main constituents of the grape pomace extract. Phospholipid vesicles, namely liposomes, were prepared and characterized. Cryo-TEM images showed that the extract-loaded liposomes were predominantly spherical/elongated, small, unilamellar vesicles. Light scattering results revealed that the liposomes were small (~100 nm), homogeneously dispersed, and stable during storage. The non-toxicity of the liposomal formulation was demonstrated in vitro in skin cells, suggesting its possible safe use. These findings indicate that an extract with antioxidant properties can be obtained from food processing residues, and a liposomal formulation can be developed to exploit its bioactive value, resulting in a promising healthy product

CLASSIFICAÇÃO INTERNACIONAL DE FUNCIONALIDADE, INCAPACIDADE E SAÚDE (CIF): AMPLIANDO O OLHAR SOBRE A CRIANÇA COM DEFICIÊNCIA MOTORA

A Classificação Internacional de Funcionalidade, Incapacidade e Saúde (CIF), criada pela Organização Mundial de Saúde (OMS) em 2001, é um sistema de classificação em saúde direcionado para a funcionalidade e fatores contextuais. A CIF compreende 5 domínios: função e estrutura do corpo, atividade, participação, fatores ambientais, e pessoais e pode ser utilizada em todos os níveis de atenção à saúde. Através dessa classificação, os profissionais de saúde conseguem ampliar o olhar durante a avaliação, desenvolver objetivos viáveis e realistas para a intervenção, além de identificar o momento correto para a alta terapêutica. O crescente número de crianças com deficiência motora no Brasil tem impulsionado os profissionais a utilizarem a CIF para avaliar aspectos específicos do desenvolvimento em crianças. A participação em atividades de lazer em casa, escola e comunidade contribui para o desenvolvimento, funcionalidade e qualidade de vida dessa população com deficiência motora. O uso da CIF na avaliação e reabilitação de crianças com deficiência motora deve ser visto como uma estratégia de mudança no modelo tradicional de reabilitação, ampliando o olhar sobre a criança e identificando aspectos relacionados à funcionalidade e ao contexto, os quais podem ser influenciadores diretos no processo de reabilitação. Palavras-chave: CIF. Criança com deficiência. Participação social. Reabilitação

A cross-sectional study to assess the level of satisfaction with virtual education in Peruvian medical students

"Objectives: Education has totally changed in the context of the pandemic. Therefore, the objective of the present study was to evaluate the factors associated with the level of satisfaction with virtual education in Peruvian medical students during COVID-19. Methods: Analytical and cross-sectional study, based on an online survey of students nationwide. We use previously validated instruments to measure the level of satisfaction and stress (EPP-10-c) of students with virtual education. For the associated factors, adjusted prevalence ratios (PR) were estimated using Poisson regression. Results: Of the 1,878 students surveyed, the median age was 21 years, 57.8% (1,086) were women, 34.8% (654) had a high level of satisfaction with virtual education and 10.7% (202) presented high levels of stress. The factors associated with a low level of satisfaction were attending the fifth year of study, the partial and non-virtual adaptation of the university to virtual education, and a high level of stress. On the other hand, the factors associated with a high level of satisfaction were the education platform used and the study method used. Conclusion: Seven out of 10 students presented a low level of satisfaction with virtual education, 1 out of 10 presented a high level of stress. The factors associated with the low level of satisfaction were attending the fifth year of study, the non-virtual and partial adaptation of the university to virtual education, and the high level of stress.