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Closed-form expressions for a rigid passive pile in a two-layered soil
No full textThis study analyses a single unrestrained rigid passive pile embedded in a soil profile consisting of an unstable layer overlying a stable one. The paper focuses on the evaluation of pile response when in the unstable layer the ultimate pressure, which is assumed to increase linearly with depth, is fully mobilised in the direction of the soil movement (i.e. flow mode). The portion of the pile below the sliding surface is analysed by an elastic−plastic model using the Winkler approach assuming the horizontal subgrade reaction and soil resistance as constant with depth. For a given depth of the sliding surface three distinct mechanisms of pile response are identified; the occurrence of a particular failure mode is controlled by the pile embedment in the stable layer and the distribution of horizontal soil resistance with depth. For each failure mechanism a set of analytical expressions is derived to calculate the pile head deflection, pile rotation, maximum bending moment and soil movement required to generate the flow mode. A numerical example is presented to illustrate the application of the proposed procedure
Elastic–Plastic Analysis of Rigid Passive Piles in Two-Layered Soils
Full text linkThe paper analyses the behavior of a rigid passive pile embedded in a soil profile consisting of a stable layer underlying an unstable layer subjected to a uniform soil displacement. Pile-soil interaction is considered by modeling the soil by a series of elastic-plastic springs along the pile shaft. The modulus of horizontal subgrade reaction is assumed to linearly increase with depth in the unstable layer and constant in the stable one. The ultimate soil resistance is assumed increasing with depth in both layers. The results of analysis are presented in dimensionless form in terms of shear force developed at the slip surface as a function of the pile embedment into the stable layer and the distribution of soil characteristics over depth. The method allows capturing pile response not only at the soil ultimate state but also at the intermediate states. Specifically, the governing equations for the elastic, elastic-plastic and plastic cases are discussed and, whenever possible, a set of closed-form expressions is provided to estimate the maximum bending moment along the shaft and the pile head deflection, so that for an assigned value of the required stabilizing force both ultimate and serviceability limit state of the pile can be checked. A numerical example is given to illustrate the application of the proposed procedure
Analytical solutions for piles subjected to a passive load
No full textThe paper analyses a single free-head flexible passive pile embedded in a soil profile consisting of an unstable layer overlying a stable one. The pile segment in the unstable layer is subjected to a linear distribution of the load, whereas the pile response is evaluated by assuming a uniform modulus of subgrade reaction in the stable layer. Closed-form expressions are derived for the pile head deflection and tabulated values are provided to evaluate the maximum bending moment as a function of dimensionless length of the pile segment in the unstable and stable layers. Analytical solutions for infinitely flexible and rigid piles have been obtained as special cases of the general solution. A novel rational rigidity criterion for passive piles is also proposed. A numerical example is finally presented to illustrate the application of the derived solution
Ultimate lateral resistance of passive piles in non cohesive soils
No full text In this paper, a single unrestrained passive pile in a two-layered cohesionless soil is analysed with the aim to evaluate its contribute in terms of resistance at the depth of an assigned sliding surface. The method assumes that the ultimate soil pressure is fully mobilised and increases linearly with depth. Six failure mechanisms are considered and dimensionless values of shear force and bending moment at sliding depth are derived in analytical and graphical form. The maximum shear force computed by the present theory reasonably agrees with data of model tests published in the literature, whereas the maximum bending moment is underestimated. This approach seems to be suitable to be implemented in traditional limit equilibrium methods when pile contribute is considered as an additional resistance. More sophisticated analyses based on an adequate soil constitutive model are requested when pile displacement must be predicted. </jats:p
Effects of diadenosine polyphosphates and fluid vesicles on rabbit sperm cells
No full textMembrane vesicles were isolated from rabbit seminal plasma. Electron microscopy analyses showed the presence of numerous small, round vesicles with a diameter of about 70 nm. Determination of enzyme activities was carried out by high performance liquid chromatography and showed that the vesicles can degrade the diadenosine polyphosphates (ApnA), Ap3A and Ap4A and ATP and ADP, but not AMP. Studies of the degradation of diadenosine compounds by the vesicles present in seminal fluid showed an increasing production of AMP as the by-product and a time-dependent generation of dephosphorylated products consistent with the presence of ecto-ATP diphosphophosphatase (ecto-apyrase). In the presence of rabbit spermatozoa, AMP did not accumulate because 5'nucleotidase and adenosine deaminase, present at the surface of sperm cells, transformed AMP into adenosine and inosine. The effects of seminal fluid vesicles and diadenosine compounds on the acquisition of fertilizing capacity by rabbit spermatozoa were evaluated by Pisum sativum agglutinin fluorescein isothiocyanate conjugated staining. The results obtained with uncapacitated spermatozoa showed that the capacitating effector BSA could be substituted efficiently by the addition of diadenosine compounds and vesicles previously incubated for 2 h to the capacitative medium. Under these experimental conditions, the spontaneous acrosome reaction rate was not increased. Capacitated rabbit spermatozoa did not undergo acrosome reaction when Lot-lysophosphatidylcholine was substituted by diadenosine compounds previously incubated with vesicles. In conclusion, this study has shown that rabbit seminal fluid vesicles can degrade diadenosine compounds to AMP and that the addition of the vesicles and diadenosine compounds to uncapacitated rabbit spermatozoa favours the acquisition of the fertilizing capacity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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