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1.
In this paper, the authors deal with bifunctions defined on complete metric spaces and with values in locally convex spaces ordered by closed convex cones. The aim is to provide a vector version of Ekeland’s theorem related to equilibrium problems. To prove this principle, a weak notion of continuity of a vector-valued function is considered, and some of its properties are presented. Via the vector Ekeland’s principle, existence results for vector equilibria are proved in both compact and noncompact domains. 相似文献
2.
Summary Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde
128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity
surfaces ofF ionospheric region started by morning solar terminator. 相似文献
3.
4.
5.
We study the problem of directed polymers (DP) on a square lattice. The distribution of disorder is assumed to be independent but non-Gaussian. We show that for distributions with a power-law tailP() 1/||1+
, where>2, so that the mean and variance are well defined, the scaling exponentv of the DP model depends on in a continuous fashion. 相似文献
6.
Franco Piacenti Mario Bianchi Piero Frediani Ugo Matteoli 《Journal of organometallic chemistry》1975,87(3):C54-C55
Both normal and secondary alkylcobalt carbonyls are shown not to undergo isomerization under catalytic “oxo” conditions, and the relevance of this obervation for the mechanism of the “oxo” reaction is discussed. 相似文献
7.
8.
Costantini G Marini Bettolo Marconi U Kalibaeva G Ciccotti G 《The Journal of chemical physics》2005,122(16):164505
We study a two-dimensional gas of inelastic smooth hard dimers. Since the collisions between dimers are dissipative, being characterized by a coefficient of restitution alpha<1, and no external driving force is present, the energy of the system decreases in time and no stationary state is achieved. However, the resulting nonequilibrium state of the system displays several interesting properties in close analogy with systems of inelastic hard spheres, whose relaxational dynamics has been thoroughly explored. We generalize to inelastic systems a recently method introduced [G. Ciccotti and G. Kalibaeva, J. Stat. Phys. 115, 701 (2004)] to study the dynamics of rigid elastic bodies made up of different spheres held together by rigid bonds. Each dimer consists of two hard disks of diameter d, whose centers are separated by a fixed distance a. By describing the rigid bonds by means of holonomic constraints and deriving the appropriate collision rules between dimers, we reduce the dynamics to a set of equations which can be solved by means of event-driven simulation. After deriving the algorithm we study the decay of the total kinetic energy, and of the ratio between the rotational and the translational kinetic energy of inelastic dimers. We show numerically that the celebrated Haff's homogeneous cooling law t(-2), describing how the kinetic energy of an inelastic hard-sphere system with a constant coefficient of restitution decreases in time, holds even in the case of these nonspherical particles. We fully characterize this homogeneous decay process in terms of appropriate decay constants and confirm numerically the scaling behavior of the velocity distributions. 相似文献
9.
Andreas M. Küffner Miriam Linsenmeier Fulvio Grigolato Marc Prodan Remo Zuccarini Umberto Capasso Palmiero Lenka Faltova Paolo Arosio 《Chemical science》2021,12(12):4373
Biomolecular condensates are emerging as an efficient strategy developed by cells to control biochemical reactions in space and time by locally modifying composition and environment. Yet, local increase in protein concentration within these compartments could promote aberrant aggregation events, including the nucleation and growth of amyloid fibrils. Understanding protein stability within the crowded and heterogeneous environment of biological condensates is therefore crucial, not only when the aggregation-prone protein is the scaffold element of the condensates but also when proteins are recruited as client molecules within the compartments. Here, we investigate the partitioning and aggregation kinetics of the amyloidogenic peptide Abeta42 (Aβ-42), the peptide strongly associated with Alzheimer''s disease, recruited into condensates based on low complexity domains (LCDs) derived from the DEAD-box proteins Laf1, Dbp1 and Ddx4, which are associated with biological membraneless organelles. We show that interactions between Aβ-42 and the scaffold proteins promote sequestration and local increase of the peptide concentration within the condensates. Yet, heterotypic interactions within the condensates inhibit the formation of amyloid fibrils. These results demonstrate that biomolecular condensates could sequester aggregation-prone proteins and prevent aberrant aggregation events, despite the local increase in their concentration. Biomolecular condensates could therefore work not only as hot-spots of protein aggregation but also as protective reservoirs, since the heterogenous composition of the condensates could prevent the formation of ordered fibrillar aggregates.Biomolecular condensates sequester an aggregation-prone peptide and prevent its aggregation, showing that heterotypic interactions within the condensates can prevent the formation of amyloid fibrils, despite the local increase in concentration. 相似文献
10.
Scrimin P Tecilla P Tonellato U Veronese A Crisma M Formaggio F Toniolo C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(12):2753-2763
Three copies of peptide sequences from the peptaibol family, known to affect the permeability of the lipid bilayer of membranes, were connected to tris(2-aminoethyl)amine (TREN), a tripodal metal ion ligand, to prepare functional peptides capable of modifying the permeability of liposomal membranes. Some of the resulting tripodal polypeptide derivatives are very effective in promoting carboxyfluorescein (CF) leakage from CF-loaded unilamellar vesicles composed of a 70:30 phosphatidylcholine/cholesterol blend. The activity of these novel compounds was shown to be tunable upon metal ion coordination of the TREN subunit; the tripodal apopeptide was far more effective than its ZnII complex. Leakage experiments showed that a minimum number of five amino acids per peptide chain is required to form active systems. A mechanism is proposed in which the ZnII ion changes the conformation of the template from extended to globular and thus acts as an allosteric regulator of the activity of the systems. Molecular modeling studies indicate that when the three peptide chains are connected to the template in the extended conformation, the resulting tripodal polypeptide is able to span across the membrane, thus allowing the formation of permeable channels made of a cluster of molecules. The same change of conformation induces, to some extent, fusion of the membranes of different liposomes. 相似文献