The JKR-type adhesive contact problems for transversely isotropic elastic solids

The JKR (Johnson, Kendall, and Roberts) and Boussinesq–Kendall models describe adhesive frictionless contact between two isotropic elastic spheres or between a flat end punch and an elastic isotropic half-space. Here adhesive contact is studied for transversely isotropic materials in the framework of the JKR theory. The theory is extended to much more general shapes of contacting axisymmetric solids, namely the distance between the solids is described by a monomial (power-law) function of an arbitrary degree d⩾1d⩾1. The classic JKR and Boussinesq–Kendall models can be considered as two particular cases of these problems, when the degree of the punch d is equal to two or it goes to infinity, respectively. It is shown that the formulae for extended JKR contact model for transversely isotropic materials have the same mathematical form as the corresponding formulae for isotropic materials; however the effective elastic contact moduli have different expression for different materials. The dimensionless relations between the actual force, displacements and contact radius are given in explicit form. Connections of the problems to nanoindentation of transversely isotropic materials are discussed

Caracterización química, perfil de ácidos grasos y actividad antioxidante del mesocarpio de la fruta Gustavia macarenensis y su aceite de la región amazónica de Ecuador como fuente no convencional de aceite vegetal

To our knowledge, this study is the first to report on the nutritional characterization, bioactive compounds and antioxidant activity of Amazonian G. macarenensis fruit. The fatty acid profile was determined using a high performance liquid chromatography analysis. The total phenolic content and antioxidant activity were determined using Folin Ciocalteu’s method and by radical scavenging activity, respectively. Moreover, a cluster analysis was carried out in order to classify the G. macarenensis fruit oil according to its fatty acid profile. Seven Fisher linear discriminant functions were obtained from the discriminant analysis. These models allow one to classify new fruits on the basis of their fatty acid profile. A high value for total lipids was obtained (53.57%). Its main components were palmitic and oleic acid. The TPC value (156.49 ± 2.62 mg GAE/Kg of oil) obtained from the G. macarenensis fruit pulp oil is higher than what was reported for some olive oil and Brazilian mango oil varieties.Hasta donde sabemos, este estudio sería el primero sobre la caracterización nutricional, los compuestos bioactivos y la actividad antioxidante de la fruta amazónica G. macarenensis. El perfil de ácidos grasos se determinó mediante análisis de cromatografía líquida de alta resolución. El contenido fenólico total y la actividad antioxidante se determinaron utilizando el método de Folin Ciocalteu y la medida de la actividad de eliminación de radicales, respectivamente. Además, se realizó un análisis de conglomerados para clasificar el aceite de fruta G. macarenensis según su perfil de ácidos grasos. Se obtuvieron siete funciones discriminantes lineales de Fisher a partir del análisis discriminante. Estos modelos permiten clasificar frutas nuevas en función de su perfil de ácidos grasos. Se obtuvo un alto valor para el total de lípidos (53.57%). Sus componentes principales son los ácidos palmítico y oleico. El valor TPC (156.49 ± 2.62 mg GAE/Kg de aceite) obtenido del aceite de pulpa de fruta de G. macarenensis es más alto que el que se reporta para algunas variedades de aceite de oliva y aceite de mango brasileño

The JKR-type adhesive contact problems for power-law shaped axisymmetric punches

The JKR (Johnson, Kendall, and Roberts) and Boussinesq–Kendall models describe adhesive frictionless contact between two isotropic elastic spheres, and between a flat-ended axisymmetric punch and an elastic half-space respectively. However, the shapes of contacting solids may be more general than spherical or flat ones. In addition, the derivation of the main formulae of these models is based on the assumption that the material points within the contact region can move along the punch surface without any friction. However, it is more natural to assume that a material point that came to contact with the punch sticks to its surface, i.e. to assume that the non-slipping boundary conditions are valid. It is shown that the frictionless JKR model may be generalized to arbitrary convex, blunt axisymmetric body, in particular to the case of the punch shape being described by monomial (power-law) punches of an arbitrary degree d≥1d≥1. The JKR and Boussinesq–Kendall models are particular cases of the problems for monomial punches, when the degree of the punch d is equal to two or it goes to infinity respectively. The generalized problems for monomial punches are studied under both frictionless and non-slipping (or no-slip) boundary conditions. It is shown that regardless of the boundary conditions, the solution to the problems is reduced to the same dimensionless relations among the actual force, displacements and contact radius. The explicit expressions are derived for the values of the pull-off force and for the corresponding critical contact radius. Connections of the results obtained for problems of nanoindentation in the case of the indenter shape near the tip has some deviation from its nominal shape and the shape function can be approximated by a monomial function of radius, are discussed

Contact probing of prestressed adhesive membranes of living cells

Atomic force microscopy (AFM) studies of living biological cells is one of main experimental tools that enable quantitative measurements of deformation of the cells and extraction of information about their structural and mechanical properties. However, proper modelling of AFM probing and related adhesive contact problems are of crucial importance for interpretation of experimental data. The Johnson–Kendall–Roberts (JKR) theory of adhesive contact has often been used as a basis for modelling of various phenomena including cell-cell interactions. However, strictly speaking the original JKR theory is valid only for contact of isotropic linearly elastic spheres, while the cell membranes are often prestressed. For the first time, effects caused by molecular adhesion for living cells are analytically studied taking into account the mechanical properties of cell membranes whose stiffness depends on the level of the tensile prestress. Another important question is how one can extract the work of adhesion between the probe and the cell. An extended version of the Borodich-Galanov method for non-direct extraction of elastic and adhesive properties of contacted materials is proposed to apply to experiments of cell probing. Evidently, the proposed models of adhesive contact for cells with prestressed membranes do not cover all types of biological cells because the structure and properties of the cells may vary considerably. However, the obtained results can be applied to many types of smooth cells and can be used to describe initial stages of contact and various other processes when effects of adhesion are of crucial importance. This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’

Caracterización fitoquímica y capacidad antioxidante de especies de Briofitas colectadas en el NOA

Las briofitas conforman un amplio grupo integrado por unas 22.000 especies deplantas pequeñas que crecen habitualmente en zonas húmedas sobre el suelo,troncos de árboles y rocas, son plantas embrionarias no vasculares que incluyenmusgos, hepáticas y antocerotes.No se han realizado muchos estudios de fitoquímica y bioactividades en briofitas, esto se debe a que son morfológicamente muy pequeñas y difíciles de recoger en grandes cantidades como muestra pura. Sin embargo, algunas de ellas han tenido tradicionalmente un uso medicinal.El objetivo de este trabajo es realizar una caracterización fitoquímica de extractos de 9 especies de briofitas colectadas en el Noroeste Argentino.Se prepararon extractos acuosos y etanólicos de las 9 especies a estudiar: Plagiochasma intermedium; Pleurochaete luteola; Marchantia papillata; Marchantiaplicata; Targionia hypophylla; Saitobryum lorentzii; Marchantia chenopoda; Anoectangium aestivum; Anoectangium euchloron. A estos extractos se les determinó el contenido de compuestos fenólicos utilizando el método colorimétrico de FolinCiocalteau, el contenido de flavonoides totales usando AlCl₃, y la capacidad antioxidante de los compuestos con el ensayo del radical catiónico ABTS.Los extractos etanólicos de Pleurochaete luteola, Marchantia papillata, Anoectangium aestivum y Anoectangium euchloron presentaron significativamente más compuestos fenólicos; además, Anoectangium aestivum, Anoectangium euchloron contenían más flavonoides que el resto de las especias estudiadas. Pleurochaete luteola y Anoectangium euchloron mostraron mayor capacidad antioxidante. En los extractos acuosos Plagiochasma intermedium y Marchantia papillata presentaron mayor contenido de compuestos fenólicos, pero en concentraciones menores a las de las muestras etanólicas. Anoectangium aestivum y Anoectangium euchloron tuvieron mayor contenido de flavonoides totales. Los extractos acuosos de Plagiochasma intermedium y Pleurochaete luteola resultaron muy buenos antioxidantes con potencia superior a los extractos etanólicos.Los resultados de este trabajo permitieron definir por primera vez que estas especies de briofitas contienen polifenoles y son potencialmente útiles como antioxidantes naturales.Fil: Jimenez, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina. Universidad Nacional de Tucumán. Instituto de Bioprospección y Fisiología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Bioprospección y Fisiología Vegetal; ArgentinaFil: Alvarez, M.. Universidad Nacional de Tucumán. Instituto de Bioprospección y Fisiología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Bioprospección y Fisiología Vegetal; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Suarez, Guillermo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Zampini, Iris Catiana. Universidad Nacional de Tucumán. Instituto de Bioprospección y Fisiología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Bioprospección y Fisiología Vegetal; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Isla, Maria Ines. Universidad Nacional de Tucumán. Instituto de Bioprospección y Fisiología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Bioprospección y Fisiología Vegetal; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaXIV Jornadas Internas de Comunicaciones en Investigación, Docencia y Extensión de la Facultad de Ciencias Naturales e IML, Universidad Nacional de TucumánSan Miguel de TucumánArgentinaUniversidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lill

IFE Plant Technology Overview and contribution to HiPER proposal

HiPER is the European Project for Laser Fusion that has been able to join 26 institutions and signed under formal government agreement by 6 countries inside the ESFRI Program of the European Union (EU). The project is already extended by EU for two years more (until 2013) after its first preparatory phase from 2008. A large work has been developed in different areas to arrive to a design of repetitive operation of Laser Fusion Reactor, and decisions are envisioned in the next phase of Technology Development or Risk Reduction for Engineering or Power Plant facilities (or both). Chamber design has been very much completed for Engineering phase and starting of preliminary options for Reactor Power Plant have been established and review here

Unmasking a new prognostic marker and therapeutic target from the GDNF-RET/PIT1/p14ARF/p53 pathway in acromegaly

Most of acromegaly is caused by a sporadic somatotropinoma and a couple of novel gene mutations responsible for somatotropinoma have recently been reported. To determine the cause of sporadic somatotropinoma in Japanese patients, we analyzed 61 consecutive Japanese patients with somatotropinoma without apparent family history. Comprehensive genetic analysis revealed that 31 patients harbored guanine nucleotide-binding protein, alpha stimulating (GNAS) mutations (50.8%) and three patients harbored aryl hydrocarbon receptor interacting protein (AIP) mutations (4.9%). No patients had G protein-coupled receptor 101 (GPR101) mutations. The patients in this cohort study were categorized into three groups of AIP, GNAS, and others and compared the clinical characteristics. The AIP group exhibited significantly younger age at diagnosis, larger tumor, and higher nadir GH during oral glucose tolerance test. In all patients with AIP mutation, macro- and invasive tumor was detected and repetitive surgery or postoperative medical therapy was needed. One case showed a refractory response to postoperative somatostatin analogue (SSA) but after the addition of cabergoline as combined therapy, serum IGF-I levels were controlled. The other case showed a modest response to SSA and the switching to cabergoline monotherapy was also effective. These data suggest that although resistance to SSA has been reported in patients with AIP mutations, the response to dopamine agonist (DA) may be retained. In conclusion, the cause of sporadic somatotropinoma in Japanese patients was comparable with the previous reports in Caucasians, patients with AIP mutations showed unique clinical characteristics, and DA may be a therapeutic option for patients with AIP mutations

RET signalling provides tumorigenic mechanism and tissue specificity for AIP-related somatotrophinomas

International audienceIt is unclear how loss-of-function germline mutations in the widely-expressed co-chaperone AIP , result in young-onset growth hormone secreting pituitary tumours. The RET receptor, uniquely co-expressed in somatotrophs with PIT1, induces apoptosis when unliganded, while RET supports cell survival when it is bound to its ligand. We demonstrate that at the plasma membrane, AIP is required to form a complex with monomeric-intracellular-RET, caspase-3 and PKCδ resulting in PIT1/CDKN2A-ARF/p53-apoptosis pathway activation. AIP-deficiency blocks RET/caspase-3/PKCδ activation preventing PIT1 accumulation and apoptosis. The presence or lack of the inhibitory effect on RET-induced apoptosis separated pathogenic AIP variants from non-pathogenic ones. We used virogenomics in neonatal rats to demonstrate the effect of mutant AIP protein on the RET apoptotic pathway in vivo. In adult male rats altered AIP induces elevated IGF-1 and gigantism, with pituitary hyperplasia through blocking the RET-apoptotic pathway. In females, pituitary hyperplasia is induced but IGF-1 rise and gigantism are blunted by puberty. Somatotroph adenomas from pituitary-specific Aip -knockout mice overexpress the RET-ligand GDNF, therefore, upregulating the survival pathway. Somatotroph adenomas from patients with or without AIP mutation abundantly express GDNF, but AIP -mutated tissues have less CDKN2A-ARF expression. Our findings explain the tissue-specific mechanism of AIP-induced somatotrophinomas and provide a previously unknown tumorigenic mechanism, opening treatment avenues for AIP -related tumours

The effects of pre-harvest and post-harvest factors on the nutritional quality of strawberry fruits: A review

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