Search results for "force"
showing 10 items of 3423 documents
Probing the role of water in protein conformation and function
2004
Life began in a bath of water and has never escaped it. Cellular function has forced the evolution of many mechanisms ensuring that cellular water concentration has never changed significantly. To free oneself of any conceptual distinction among all small molecules, solutes and solvents, means that experiments to probe water's specific role in molecular function can be designed like any classical chemical reaction. Such an ‘osmotic stress’ strategy will be described in general and for an enzyme, hexokinase. Water behaves like a reactant that competes with glucose in binding to hexokinase, and modulates its conformational change and activity. This ‘osmotic stress’ strategy, now applied to ma…
Fibre Bundle for Spin and Charge in General Relativity
2000
The Lorentzian and spin structures of general relativity are shown to allow a natural extension, by means of which the set of possible electromagnetic bundles is linked to the topology and geometry of the underlying causal structure. Further, both the Dirac operator and the electromagnetic potential are obtainable from a single linear connection 1-form.
Implant-supported fixed prostheses in a Patient with Osteogenesis Imperfecta : a 4-year follow-up
2017
Osteogenesis Imperfecta (OI) is a rare autosomal dominant connective tissue disorder in wich, the bone quality and density is affected. OI includes some metabolic disorders and have a wide range of clinical presentations. In Osteogenesis Imperfecta bone has a very low density and it is a disorder currently treated with bisphosphonates. Quality and quantity of bone is important for establishment of osseointegration in dental implants. There are few reported cases in the literature. This is a case report of a 61 year-old man with grade IV OI, rehabilitated with implant-supported fixed prostheses in the posterior right and left mandible, whithout bone grafts. At the 4-year follow-up, clinical …
Elementary Newtonian Mechanics
2010
This chapter deals with the kinematics and the dynamics of a finite number of mass points that are subject to internal, and possibly external, forces, but whose motions are not further constrained by additional conditions on the coordinates. Constraints such as requiring some mass points to follow given curves in space, to keep their relative distance fixed, or the like, are introduced in Chap. 2. Unconstrained mechanical systems can be studied directly by means of Newton’s equations and do not require the introduction of new, generalized coordinates that incorporate the constraints and are dynamically independent. This is what is meant by “elementary” in the heading of this chapter — thoug…
Italian marine reserve effectiveness: does enforcement matter?
2008
Marine protected areas (MPAs) have become popular tools worldwide for ecosystem conservation and fishery management. Fish assemblages can benefit from protection provided by MPAs, especially those that include fully no-take reserves. Fish response to protection can thus be used to evaluate the effectiveness of marine reserves. Most target fish are high-level predators and their overfishing may affect entire communities through trophic cascades. In the Mediterranean rocky sublittoral, marine reserves may allow fish predators of sea urchins to recover and thus whole communities to be restored from coralline barrens to macroalgae. Such direct and indirect reserve effects, however, are likely t…
Learning About Forces Using Multiple Representations
2017
We present two research-based interventions to measure upper secondary student learning of forces using multiple representations (MRs). The first intervention is the Representational Variant of the Force Concept Inventory (R-FCI) – a multiple-choice test for evaluating students’ representational consistency in answering triplets of isomorphic items in the context of forces. The second intervention is an interaction diagram (ID) – a visual representation that helps students to identify forces resulting from interactions between two objects. Students’ representational consistency on the R-FCI pre-test correlated with their normalised learning gain on the Force Concept Inventory (FCI) suggesti…
Stress-Strain Law for Confined Concrete with Hardening or Softening Behavior
2013
This paper provides a new general stress-strain law for concrete confined by steel, fiber reinforced polymer (FRP), or fiber reinforced cementitious matrix (FRCM), obtained by a suitable modification of the well-known Sargin’s curve for steel confined concrete. The proposed law is able to reproduce stress-strain curve of any shape, having both hardening or softening behavior, by using a single closed-form simple algebraic expression with constant coefficients. The coefficients are defined on the basis of the stress and the tangent modulus of the confined concrete in three characteristic points of the curve, thus being related to physical meaningful parameters. It will be shown that if the v…
Diritti, sicurezza, solidarietà e responsabilità nella protezione della persona migrante
2018
1. Uno sguardo d’insieme. 2. Dopo Lisbona: le competenze dell’UE e la Carta dei diritti dinanzi alle crisi migratorie e all’onda lunga del populismo. 3. Protezione della persona migrante, Costituzione e decretazione di urgenza. 4. Solidarietà e diritti nella prospettiva costituzionale: uguaglianza, bisogni primari e contenuto essenziale
Long-range cohesive interactions of non-local continuum faced by fractional calculus
2008
Abstract A non-local continuum model including long-range forces between non-adjacent volume elements has been studied in this paper. The proposed continuum model has been obtained as limit case of two fully equivalent mechanical models: (i) A volume element model including contact forces between adjacent volumes as well as long-range interactions, distance decaying, between non-adjacent elements. (ii) A discrete point-spring model with local springs between adjacent points and non-local springs with distance-decaying stiffness connecting non-adjacent points. Under the assumption of fractional distance-decaying interactions between non-adjacent elements a fractional differential equation in…
Using the Theory of Regular Functions to Formally Prove the ε-Optimality of Discretized Pursuit Learning Algorithms
2014
Learning Automata LA can be reckoned to be the founding algorithms on which the field of Reinforcement Learning has been built. Among the families of LA, Estimator Algorithms EAs are certainly the fastest, and of these, the family of Pursuit Algorithms PAs are the pioneering work. It has recently been reported that the previous proofs for e-optimality for all the reported algorithms in the family of PAs have been flawed. We applaud the researchers who discovered this flaw, and who further proceeded to rectify the proof for the Continuous Pursuit Algorithm CPA. The latter proof, though requires the learning parameter to be continuously changing, is, to the best of our knowledge, the current …