An influence of static load on fatigue life of parts under combined stress

The paper deals with a special case of multiaxial fatigue in a plain stress possessing one component static and the other dynamic. Exponents of Haigs' limit curves were obtained experimentally both for tensile fatigue test and combined tensile/torgue tests. Errors of estimated fatigue lives are less than 20 %

Simulations of argon accident scenarios in the ATLAS experimental cavern: a safety analysis

Some characteristic accidents in the ATLAS experimental cavern (UX15) are simulated by means of STAR-CD, a code using the "Finite-Volume" method. These accidents involve different liquid argon leaks from the barrel cryostat of the detector, thus causing the dispersion of the argon into the Muon Chamber region and the evaporation of the liquid. The subsequent temperature gradients and distribution of argon concentrations, as well as their evolution in time are simulated and discussed, with the purpose of analysing the dangers related to asphyxiation and to contact with cryogenic fluids for the working personnel. A summary of the theory that stands behind the code is also given. In order to validate the models, an experimental test on a liquid argon spill performed earlier is simulated, showing that the program is able to output reliable results. At the end, some safety-related recommendations are listed

The Y-box factor ZONAB/DbpA associates with GEF-H1/Lfc and mediates Rho-stimulated transcription

Epithelial tight junctions recruit different types of signalling proteins that regulate cell proliferation and differentiation. Little is known about how such proteins interact functionally and biochemically with each other. Here, we focus on the Y-box transcription factor ZONAB (zonula occludens 1-associated nucleic-acid-binding protein)/DbpA (DNA-binding protein A) and the Rho GTPase activator guanine nucleotide exchange factor (GEF)-H1/Lbc's first cousin, which are two tight-junction-associated signalling proteins that regulate proliferation. Our data show that the two proteins interact and that ZONAB activity is Rho-dependent. Overexpression of GEF-H1 induces accumulation of ZONAB in the nucleus and activates transcription. Microtubule-affinity regulating kinase/partition-defective-1, another type of GEF-H1-associated signalling protein, remains in the cytoplasm and partially co-localizes with the exchange factor. GEF-H1 and ZONAB are required for expression of endogenous cyclin D1, a crucial RhoA signalling target gene, and GEF-H1-stimulated cyclin D1 promoter activity requires ZONAB. Our data thus indicate that GEF-H1 and ZONAB form a signalling module that mediates Rho-regulated cyclin D1 promoter activation and expression

Functional interaction between the ZO-1-interacting transcription factor ZONAB/DbpA and the RNA processing factor symplekin

Epithelial tight junctions participate in the regulation of gene expression by controlling the activity of transcription factors that can interact with junctional components. One such protein is the Y-box transcription factor ZONAB/DbpA that binds to ZO-1, a component of the junctional plaque. Symplekin, another nuclear protein that can associate with tight junctions, functions in the regulation of polyadenylation and thereby promotes gene expression. Here, we addressed the question of whether these two proteins interact and whether this is of functional relevance. We demonstrate that ZONAB/DbpA and symplekin form a complex in kidney and intestinal epithelial cells that can be immunoprecipitated and that exists in the nucleus. The interaction between ZONAB/DbpA and symplekin can be reconstituted with recombinant proteins. In reporter gene assays in which ZONAB/DbpA functions as a repressor, symplekin functionally interacts with ZONAB/DbpA, indicating that symplekin can also promote transcriptional repression. RNAi experiments indicate that symplekin depletion reduces the nuclear accumulation and the transcriptional activity of ZONAB/DbpA in colon adenocarcinoma cells, resulting in inhibition of proliferation and reduced expression of the ZONAB/DbpA-target gene cyclin D1. Our data thus indicate that symplekin and ZONAB/DbpA cooperate in the regulation of transcription, and that they promote epithelial proliferation and cyclin D1 expression

Pairing patterns and fitness in a free-ranging population of pinyon jays: What do they reveal about mate choice.

Pairing in 141 pairs of Pinyon Jays (Gymnorhinus cyanocephalus ) was assortative for age, but was random for bill length and body weight. Assortative pairing for age may be favored because similar-aged partners produced slightly more young than dissimilar-aged ones and their young survived longer than young from dissimilar-aged pairs. Large jays appear to have the highest genetic quality because they lived longer and body size was heritable. Genetic quality of a mate, however, may be negated if phenotypic properties of partners are not compatible

Electromiograph Study of Patients Treated with Overdentures Retined with Implants

INTRODUCTION: Long Term edentulous patients present severe bone loss in their alveolar ridges, as a consequence there is serious compromise in esthetics and function. A therapeutic alternative which we can offer to these patients is an overdenture retined with dental implants, in order to improve retention and stability. AIM OF THE WORK: The aim of the study was to determine by electromiography whether the muscular groups involved in masticatory function present any special activity in patients treated with overdentures retined with dental implants. MATERIAL AND METHODS: We selected ten complete edentulous patients with inferior overdentures retined with two implants and a bar.Myotronics K6-I with eight channels, and registration of anterior and posterior temporalis muscle maseter and dygastric muscles. We performed recordings in rest positions and maximum force bite. RESULTS AND CONCLUSION: The results obtained indicate an increase in activity in the rest position of the posterior temporalis group

The polarized expression of Na+,K+-ATPase in epithelia depends on the association between beta-subunits located in neighboring cells

The polarized distribution of Na+,K+-ATPase plays a paramount physiological role, because either directly or through coupling with co- and countertransporters, it is responsible for the net movement of, for example, glucose, amino acids, Ca2+, K+, Cl-, and CO3H- across the whole epithelium. We report here that the beta-subunit is a key factor in the polarized distribution of this enzyme. 1) Madin-Darby canine kidney (MDCK) cells (epithelial from dog kidney) express the Na+,K+-ATPase over the lateral side, but not on the basal and apical domains, as if the contact with a neighboring cell were crucial for the specific membrane location of this enzyme. 2) MDCK cells cocultured with other epithelial types (derived from human, cat, dog, pig, monkey, rabbit, mouse, hamster, and rat) express the enzyme in all (100%) homotypic MDCK/MDCK borders but rarely in heterotypic ones. 3) Although MDCK cells never express Na+,K+-ATPase at contacts with Chinese hamster ovary (CHO) cells, they do when CHO cells are transfected with beta(1)-subunit from the dog kidney (CHO-beta). 4) This may be attributed to the adhesive property of the beta(1)-subunit, because an aggregation assay using CHO (mock-transfected) and CHO-beta cells shows that the expression of dog beta(1)-subunit in the plasma membrane does increase adhesiveness. 5) This adhesiveness does not involve adherens or tight junctions. 6) Transfection of beta(1)-subunit forces CHO-beta cells to coexpress endogenous a-subunit. Together, our results indicate that MDCK cells express Na+,K+-ATPase at a given border provided the contacting cell expresses the dog P,-subunit. The cell-cell interaction thus established would suffice to account for the polarized expression and positioning of Na+,K+-ATPase in epithelial cells

Global cell-by-cell evaluation of endothelial viability after two methods of graft preparation in Descemet membrane endothelial keratoplasty

PURPOSE: To describe a novel method of global cell viability assessment for Descemet membrane endothelial keratoplasty (DMEK) and the comparison of two contemporary methods of donor tissue preparation. METHODS: DMEK transplants were prepared using two different methods: liquid bubble separation and manual peeling (n=8 each group). Samples were incubated with Hoechst, calcein-AM and ethidium homodimer prior to mounting on a curved imaging chamber. Z-stacked fluorescence microscopy images were combined to produce an in-focus global image capable of resolving all cell nuclei. Image processing software was used to define a calcein-positive live cell area, count all cell nuclei within this area and subtract ethidium-positive dead cells to derive the total viable endothelial cell count. Corrected global cell density was calculated by dividing the number of viable cells by the graft area, which had been corrected for imaging a curved surface. RESULTS: Corrected global cell density was lower than the central endothelial cell density in both groups: 85.5% of the pre-preparation central endothelial cell density in the peel group and 75.8% in the bubble group. Corrected global cell density was significantly lower in the liquid bubble separation group than in the peel group (p=0.04). CONCLUSIONS: Eye bank estimations of central endothelial cell density overestimate true cell density after graft preparation in DMEK. A peel method is less damaging and more consistent than a liquid bubble method. Cell loss correlated strongly with the degree of stromal hydration prior to bubble separation in the liquid bubble group

Organ culture storage of pre-prepared corneal donor material for Descemet's membrane endothelial keratoplasty

Purpose To evaluate the effect of media composition and storage method on pre-prepared Descemet's membrane endothelial keratoplasty (DMEK) grafts. Methods 50 corneas were used. Endothelial wound healing and proliferation in different media were assessed using a standard injury model. DMEK grafts were stored using three methods: peeling with free scroll storage; partial peeling with storage on the stroma and fluid bubble separation with storage on the stroma. Endothelial cell (EC) phenotype and the extent of endothelial overgrowth were examined. Global cell viability was assessed for storage methods that maintained a normal cell phenotype. Results 1 mm wounds healed within 4 days. Enhanced media did not increase EC proliferation but may have increased EC migration into the wounded area. Grafts that had been trephined showed evidence of EC overgrowth, whereas preservation of a physical barrier in the bubble group prevented this. In grafts stored in enhanced media or reapposed to the stroma after trephination, endothelial migration occurred sooner and cells underwent endothelial-mesenchymal transformation. Ongoing cell loss, with new patterns of cell death, was observed after returning grafts to storage. Grafts stored as free scrolls retained more viable ECs than grafts prepared with the fluid bubble method (74.2± 3% vs 60.3±6%, p=0.04 (n=8). Conclusion Free scroll storage is superior to liquid bubble and partial peeling techniques. Free scrolls only showed overgrowth of ECs after 4 days in organ culture, indicating a viable time window for the clinical use of pre-prepared DMEK donor material using this method. Methods for tissue preparation and storage media developed for whole corneas should not be used in pre-prepared DMEK grafts without prior evaluation

The Villalcampo Shear Zone (Zamora, Spain), geometry, kinematics and the physical conditions of the strain

[Resumen] En este trabajo se presenta una cartografía detallada de un sistema de cizalla que incluye la zona de cizalla de Villalcampo propiamente dicha y las bandas asociadas. Este sistema tiene carácter regional, afecta a granitos intruidos después de la segunda fase hercínica y a sus encajantes metamórficos en un área de al menos 150 Km2. El estudio geométrico y cinemático de las bandas, la distribución de las rocas de falla, así como el estudio microestructural han permitido interpretar todo el sistema como una cizalla subvenical dextra de carácter dúctil-frágil, que termina hacia el NW en un abanico extensional y que se prolonga hacia el SE en otra amplia área interpretada como un duplex extensional. El valor de la cizalla 'Y es de 1,55 y el desplazamiento mínimo calculado es de 3,7 Km. Todas las bandas de cizalla que incluye el sistema de Villalcampo y las venas o filones asociados pueden relacionarse con un único campo de esfuerzos en el que la trayectoria del esfuerzo principal al, subhorizontal y de dirección aproximadamente N-S sufre una desviación en la zona terminal de la banda en sentido diferente según el labio de que se trate, tal como propone Anderson (1951). Para caracterizar el régimen y los mecanismos de la deformación se ha realizado un análisis microestructural detallado de las rocas de falla y un estudio petrográfico y de la petrofábrica de las milonitas. Se concluye que los yacimientos de oro de Pino están controlados estructuralmente por este sistema de cizalla ya que aparecen en venas extensionales ocupadas por milonitas brechificadas; las condiciones de la deformación de carácter alternativamente dúctil-frágil habrtan permitido la migración de fluidos mineralizadores y el sellado de las fracturas en ciclos repetidos. Se propone como hipótesis que los yacimientos de estaño y wolframio que aparecen en la región de Villaseco-Almaraz de Duero puedan estar controlados también por el duplex extensional de este sistema de cizalla.[Abstract] The present work reports" on a detailed mapping of the Villalcampo shear system, including the Villalcampo shear itself together with related shears and veins. This regional shear system affects granites intruded after the second hercynian deformation phase and their metamorphic host rocks over an area of about 150 Km2. A st~ctural study of the shear bands, encompassing geometric and kinematic criteria and also the distribution of fault rocks, has allowed the authors to interpret the whole of the system as a ductile-fragile subvenical dextral shear spaying to the NW in an extensional fan that is prolonged to the SE over a broad area interpreted as an extensional duplex. The value of the shear strain, 'Y = 1.55, and the minimum displacement, s = 3.700 m, is calculated. The distribution of shear bands and veins is coherent with the notion of a single stress field where the principal stress, o"¡, is subhorizontal and has a N-S trajectory that deviates to the tips of the main shear, as proposed by Anderson (1951). With a view to gaining insight into the shearing regimen and the physical conditions of the deformation, a microestructural exploration of the fault rocks was carried out together with a petrographical and petrofabric study of the mylonites. It is concluded that the Pino ore veins -with Au mineralization- are structurally controlled by this shear system because they are related to the extensional veins infilled by brecchiated mylonites. Additionally, it is proposed that the deformation conditions would have alternated between brittle and ductile; this would have permited the migration and sealing of microfractures by mineralizing fluids during repeated cycles. As an hypothesis, it is proposed that the Sn and W ores situated in -the Villaseco -Almaraz area are possibly related to the extensional duplex