Independence of friction self-locking from kinematic singularity

Self-locking analysis in closed kinematic chains is sometimes likened to kinematic singularity. Here a novel approach to tackle self-locking analysis due to joints friction is exploited, that is completely different from the classical kinematic analysis based on the jacobian conditioning. It is shown that an inverse kinematic singularity always entails a self-locking phenomenon because of the general increasing of joints reactions and, then, friction forces; hence, a self-locking domain can be always identified including such a locus. On the other side, this paper is aimed at demonstrating that the aforementioned condition is not necessary: namely, self-locking may occurs also if the mechanism kinematics is well-conditioned. Then, the theoretical result is clarified performing the self-locking analysis on a simple crank-slider mechanism.     

Metal‐Chelated Polymer Nanodiscs for NMR Studies

Paramagnetic relaxation enhancement (PRE) is commonly used to speed up spin lattice relaxation time (T₁) for rapid data acquisition in NMR structural studies. Consequently, there is significant interest in novel paramagnetic labels for enhanced NMR studies on biomolecules. Herein, we report the synthesis and characterization of a modified poly(styrene‐co‐maleic acid) polymer which forms nanodiscs while showing the ability to chelate metal ions. Cu²⁺‐chelated nanodiscs are demonstrated to reduce the T₁ of protons for both polymer and lipid‐nanodisc components. The chelated nanodiscs also decrease the proton T₁ values for a water‐soluble DNA G‐quadruplex. These results suggest that polymer nanodiscs functionalized with paramagnetic tags can be used to speed‐up data acquisition from lipid bilayer samples and also to provide structural information from water‐soluble biomolecules.     

Boltzmann Games in Heterogeneous Consensus Dynamics

Journal of Statistical Physics - We consider a constrained hierarchical opinion dynamics in the case of leaders’ competition and with complete information among leaders. Each leaders’...     

Relaxivity of Gd-Based MRI Contrast Agents in Crosslinked Hyaluronic Acid as a Model for Tissues

The efficiency of MRI contrast agents depends on the relaxation rate enhancement that they can induce at imaging fields. It is well known that, at these fields, large relaxation rates are obtained by binding of gadolinium(III) ions to large molecules. By the same token, the interaction of the gadolinium(III) complexes with macromolecules that are found in biological tissues can be responsible for an increase of the relaxation rate with respect to the value observed in liquids. We investigate here the relaxation enhancement of gadoteridol (Gd-HP-DO3A) in crosslinked hyaluronic acid, taken as model tissue, using fast field-cycling relaxometry. The analysis of the relaxation profiles as a function of the magnetic fields indicates that a sizable increase in the relaxation rates is due to a modest interaction of the contrast agent with the hydrogel and to the slower mobility of the water molecules outside the first-coordination sphere of the gadolinium(III) ion.     

Correlating Oxygen Reduction Reaction Activity and Structural Rearrangements in MgO-Supported Platinum Nanoparticles

We develop a multi-scale approach towards the design of metallic nanoparticles with applications as catalysts in electrochemical reactions. The here discussed method exploits the relationship between nanoparticle architecture and electrochemical activity and is applied to study the catalytic properties of MgO(100)-supported Pt nanosystems undergoing solid-solid and solid-liquid transitions. We observe that a major increment in the activity is associated to the reconstruction of the interface layers, supporting the need for a full geometrical characterisation of such structures also when in-operando.     

Quantum calibration of measurement instrumentation

By quantum calibration we name an experimental procedure apt to completely characterize an unknown measurement apparatus by comparing it with a few other calibrated apparatuses. Here we show how to achieve the calibration of an arbitrary measuring apparatus, by using it in combination with a tomographer in a correlation setup with an input bipartite system. The method is robust to imperfections of the tomographer, and works for practically any input state of the bipartite system.     

On the nature and the order of the deconfining transition in QCD

The determination of the parameters of the deconfining transition in N _f = 2 QCD and its relevance to the understanding of the mechanism of color confinement are discussed.