1,721,056 research outputs found
Inequalities for overdamped fluctuating systems
No full textIn many ambits of the chemical sciences it happens to deal with complex systems udergoing thermal fluctuations in the overdamped regime of the motion (i.e., multidimensional diffusive processes). Although such stochastic dynamics are well specified in terms of the Fokker–Planck–Smoluchowski equation for the time-dependent probability density, the solution becomes rapidly unfeasible as the number of degrees of freedom increases beyond a few units. Here we present a strategy, based on inequalities for “completely monotone decreasing” functions viewed as convex functions of time, to by-pass such a difficulty and aimed to achieve only bounds (but with low computational effort) on some quantities that pertain the system’s dynamics. Namely, we derive (i) a lower bound for the maximum value of the probability density that develops from a given initial condition, and (ii) a lower bound on the correlation time for a generic self-correlation function. The former bound is quantified by means of simple operations on the initial condition, while the latter is gained by the knowledge of an initial “piece” of correlation function to be supplied, for instance, by molecular or Brownian dynamics simulations. Some practical applications are discussed
Recasting the mass-action rate equations of open chemical reaction networks into a universal quadratic format
No full textRecasting the rate equations of mass-action chemical kinetics into universal formats s a potentially useful strategy to rationalize typical features that are observed in the space of the species concentrations. For example, a remarkable feature is the appearance of the so-called slow manifolds (subregions of the concentration space where the trajectories bundle), whose detection can be exploited to simplify the description of the slow part of the kinetics via model reduction and to understand how the chemical network approaches the stationary state. Here we focus on generally open chemical reaction networks with continuous injection of species at constant rates, that is, the situation of idealized biochemical networks and microreactors under well-mixing conditions and externally controllable input of chemicals. We show that a unique format of pure quadratic ordinary differential equations can be achieved, regardless of the nonlinearity of the kinetic scheme, by means of a suitable change and extension of the set of dynamical variables. Then we outline some possible employments of such a format, with special emphasis on a low-computational-cost strategy to localize the slow manifolds which are indeed observed also for open systems
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Structural evolution of the Rieserferner pluton in the framework of the Oligo-Miocene tectonics of the Eastern Alps
No full textThe structural evolution of the Oligocene Rieserferner pluton (Eastern Alps), developed during pluton cooling and exhumation, includes localized deformation structures consisting of: (i) steeply dipping joints, leucocratic dykes and quartz-feldspar veins, and related ductile shear zones (formed at ∼600 °C); (ii) shallowly dipping joints with associated epidote and quartz veins, and related ductile shear zones (∼450 °C); (iii) steeply dipping mafic dykes and calcite + white mica-bearing brittle-ductile faults (∼300 °C); (iv) steeply dipping pseudotachylyte-bearing faults (< 250 °C); and (v) zeolite-bearing faults (< 200 °C). The structures (i-iii) and (iv-v) can be dated to the Oligocene and Early Miocene, respectively. The kinematic analysis suggests a change in local shortening direction from N290°to N350°, interpreted to reflect a change from transtension in the Early Oligocene, associated with a N060°-directed plate divergence, to transpression in the Miocene, associated with a (N)NW-directed plate convergence. This evolution reflects the sequence of transient and long-term geodynamic processes occurring in the Eastern Alps during the Tertiary, including slab break-off of the subducted European slab, the indentation of the Dolomites promontory against the Alpine stack of nappes, and the exhumation and lateral escape tectonics of the Alpine belt
Structural and metamorphic inheritance controls strain partitioning during orogenic shortening (Kalak Nappe Complex, Norwegian Caledonides)
No full textThe occurrence of pre-collisional structural and metamorphic fabrics may control the development of new structures during subsequent orogenic deformation. Structural, petrological and geochronological analyses have been performed on selected samples collected along a NW-SE cross section of the Kalak Nappe Complex (KNC) exposed on Kvaløya Island (Finnmark, Norway), in order to define pre-Caledonian or Caledonian affinity of deformation fabrics. Nappes within the KNC experienced different pre-collisional tectonometamorphic histories, resulting in contrasting pre-Caledonian fabrics, which in turn controlled orogen-scale strain partitioning and metamorphic re-equilibration during Caledonian shortening. Caledonian deformation during top-to-SE-directed thrusting occurred at 550–675 °C and 0.8–1.0 GPa in the presence of fluids. Suitably-oriented pre-collisional fabrics were firstly exploited as zones of localized shearing internal to the KNC and subjected to metamorphic re-equilibration during shortening. Fold geometry during Caledonian thrusting was also controlled by the orientation of pre-Caledonian fabrics. SE-verging asymmetric folds were developed after minor tilting of pre-Caledonian upright folds with orogen-parallel hinge in the hinterland consistently with top-to-SE shearing. Shear-parallel folds displaying orogen-perpendicular hinge lines resulted from top-to-SE general shearing of pre-collisional upright folds showing pre-collisional orogen-perpendicular hinge lines. Caledonian metamorphism appears to have been accompanied by infiltration of radiogenic 40Ar-rich fluids, which affected the Ar isotopic system in synkinematic micas
Investigating ankle dynamics during walking on a subject with bilateral ankle arthroplasty
Full text linkAnkle dynamics during walking was investigated on a subject with bilateral ankle arthroplasty via computing muscle power and work produced by each of the two legs during the double support phases, and by analyzing the angle-moment hysteresis characteristics at the ankle, to highlight the different energy production/absorption phases at the two ankles
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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