On the Long Time Behavior of Infinitely Extended Systems of Particles Interacting via Kac Potentials

We analyze the long time behavior of an infinitely extended system of particles in one dimension, evolving according to the Newton laws and interacting via a non-negative superstable Kac potential (x)=(x), (0, 1]. We first prove that the velocity of a particle grows at most linearly in time, with rate of order . We next study the motion of a fast particle interacting with a background of slow particles, and we prove that its velocity remains almost unchanged for a very long time (at least proportional to ^–1 times the velocity itself). Finally we shortly discuss the so called Vlasov limit, when time and space are scaled by a factor .     

Further relaxation kinetic investigations of iron(III) chelation. Data for diglycolic,tartaric, and citric acids

The kinetics of the reactions of iron(III) with diglycolic, tartaric, and citric acids have been studied in aqueous acid solutions by the temperature-jump method at 25.0°C and at ionic strengths 1.0 (for tartaric and citric acids) and 0.50 mol/dm³ (for diglycolic acid). The experimental data indicate that iron(III) monochelate formation occurs by the same reaction mechanism for all three ligands examined and that only pathways involving the FeOH²⁺ ion contribute to the chelation process. The reacting species for citric acid is the undissociated ligand. For tartaric and diglycolic acids both the neutral ligands and the corresponding monoanions react significantly under the experimental conditions used. Kinetic evidence for the contribution of intermediate steps to the limiting rate in the overall chelate-formation process has been obtained and discussed.     

High-performance liquid chromatography/electrospray ionization ion-trap tandem mass spectrometric analysis and quantification of phosphatidylcholine molecular species in the serum of cystic fibrosis subjects supplemented with docosahexaenoic acid

Since phosphatidylcholine (PC) is the most abundant phospholipid (PL) class in human serum, its concentration represents an important marker for the evaluation of lipid absorption and metabolism. High-performance liquid chromatography coupled on-line with electrospray ionization ion-trap tandem mass spectrometry (HPLC/ESI-MS/MS) was successfully applied to the quantitative analysis of PC molecular species from serum of cystic fibrosis (CF) subjects before and after supplementation with docosahexaenoic acid (DHA). Seven molecular species of PC (containing C16:0/C20:4, C16:0/C22:6, C18:0/C20:4, C18:0/C22:6, C16:0/C18:1, C16:0/C18:2 and C18:0/C18:2, respectively) were quantified using MS in the negative scan mode with 1,2-diundecanoyl-sn-glycero-phosphocholine as the internal standard. The molecular species containing DHA, C16:0/C22:6 and C18:0/C22:6, increased from 41.3 +/- 31.7 and 33.1 +/- 18.2 to 85.4 +/- 20.4 and 52.1 +/- 20.7 microg/mL serum, respectively, after a 3-month supplementation. Interestingly, the species containing arachidonic acid (C18:0/C20:4 and C16:0/C20:4) decreased from 115 +/- 55 and 139 +/- 57 to 58.1 +/- 22.5 and 70.5 +/- 28.1, respectively. HPLC/ESI-MS/MS allowed the direct analysis of the lipid extract without previous purification of PLs, thus it is a useful analytical support in CF research in order to understand the extent of lipid dysfunctions typical of CF or other diseases. The present method might also be used for quantitative analysis of each serum phospholipid class molecular species. However, the instrument response was found to be very dependent on the phospholipid class considered, and thus the use of appropriate standards for each class of PLs is recommended.     

On the Motion of a Charged Particle Interacting with an Infinitely Extended System

 We study the time evolution of a charged particle moving in a medium under the action of a constant electric field E. In the framework of fully Hamiltonian models, we discuss conditions on the particle/medium interaction which are necessary for the particle to reach a finite limit velocity. We first consider the case when the charged particle is confined in an unbounded tube of ℝ³. The electric field E is directed along the symmetry axis of the tube and the particle also interacts with an infinitely many particle system. The background system initial conditions are chosen in a set which is typical for any reasonable thermodynamic (equilibrium or non-equilibrium) state. We prove that, for large E and bounded interactions between the charged particle and the background, the velocity v(t) of the charged particle does not reach a finite limit velocity, but it increases to infinite as: |v(t)−Et|≤C ₀ (1+t), where C ₀ is a constant independent of E. As a corollary we obtain that, if the initial conditions of the background system are distributed according to any Gibbs state, then the average velocity of the charged particle diverges as time goes to infinite. This result is obtained for E large enough in comparison with the mean energy of the Gibbs state. We next study the one-dimensional case, in which the estimates can be improved. We finally discuss, at an heuristic level, the existence of a finite limit velocity for unbounded interactions, and give some suggestions about the case of small electric fields. Received: 7 March 2002 / Accepted: 23 September 2002 Published online: 8 January 2003 RID="*" ID="*" Work partially supported by the GNFM-INDAM and the Italian Ministry of the University. Communicated by J.L. Lebowitz     

Electron-mediated entanglement in semiconductor phonon systems

Phonons in condensed matter systems are usually treated as a decohering thermal bath. We study the entanglement between the phononic modes which is created by the interaction with a fermionic system (electrons) whose degrees of freedom are traced out as a thermal bath. The resulting picture thus reverses the usual scheme and aims at highlighting the possibility of exploiting bosonic degrees of freedom in condensed matter systems for new quantum computing protocols.     

DoE-Driven Development of an Organocatalytic Enantioselective Addition of Acetaldehyde to Nitrostyrenes in Water**

The development of an enantioselective enamine-catalysed addition of masked acetaldehyde to nitroalkenes via a rational approach helped to move away from the use of chloroform. The presented research allows the use of water as a reaction medium, therefore improving the industrial relevance of a protocol to access very important pharmaceutical intermediates. Critical to the success is the use of chemometrics-assisted ‘Design of Experiments’ (DoE) optimisation during the development of the presented new synthetic approach, which allows to investigate the chemical space in a rational way.     

Enhancing Auxiliary-Mediated Native Chemical Ligation at Challenging Junctions with Pyridine Scaffolds

To expand the scope of native chemical ligation (NCL) beyond reactions at cysteine, ligation auxiliaries are appended to the peptide N-terminus. After the introduction of a pyridine-containing auxiliary, which provided access to challenging junctions (proline or β-branched amino acids), we herein probe the role of the pyridine-ring nitrogen. We observed side reactions leading to preliminary auxiliary loss. We describe a new easy to attach β-mercapto-β-(4-methoxy-2-pyridinyl)-ethyl (MMPyE) auxiliary, which 1) has increased stability; 2) enables NCL at sterically encumbered junctions (e. g., Leu-Val); and 3) allows removal under mildly basic (pH 8.5) conditions was introduced. The synthesis of a 120 aa long peptide containing eight MUC5AC tandem repeats via ligation of two 60mers demonstrates the usefulness. Making use of hitherto unexplored NCL to tyrosine, the MMPyE auxiliary provided access to a head-to-tail-cyclized 21-mer peptide and a His₆-tagged hexaphosphorylated peptide comprising 6 heptapeptide repeats of the RNA polymerase II C-terminal domain.     

Enumerating the Walecki‐Type Hamiltonian Cycle Systems

Let be the complete graph on v vertices. A Hamiltonian cycle system of odd order v (briefly ) is a set of Hamiltonian cycles of whose edges partition the edge set of . By means of a slight modification of the famous of Walecki, we obtain 2ⁿ pairwise distinct and we enumerate them up to isomorphism proving that this is equivalent to count the number of binary bracelets of length n, i.e. the orbits of , the dihedral group of order 2n, acting on binary n‐tuples.     

Uniqueness of Tangent Cones for Two‐Dimensional Almost‐Minimizing Currents

We consider two‐dimensional integer rectifiable currents that are almost area minimizing and show that their tangent cones are everywhere unique. Our argument unifies a few uniqueness theorems of the same flavor, which are all obtained by a suitable modification of White's original theorem for area‐minimizing currents in the euclidean space. This note is also the first step in a regularity program for semicalibrated two‐dimensional currents and spherical cross sections of three‐dimensional area‐minimizing cones.© 2017 Wiley Periodicals, Inc.     

In Silico and In Vitro Analysis of Major Cannabis-Derived Compounds as Fatty Acid Amide Hydrolase Inhibitors

Accumulated evidence suggests that enhancing the endocannabinoid (eCB) tone, in particular of anandamide (N-arachidonoylethanolamine, AEA), has therapeutic potential in many human diseases. Fatty acid amide hydrolase (FAAH) is a membrane-bound enzyme principally responsible for the degradation of AEA, and thus it represents a relevant target to increase signaling thereof. In recent years, different synthetic and natural compounds have been developed and tested on rat FAAH, but little is known of their effect on the human enzyme. Here, we sought to investigate six major cannabis-derived compounds to compare their action on rat and human FAAHs. To this aim, we combined an in silico analysis of their binding mode and affinity, with in vitro assays of their effect on enzyme activity. This integrated approach allowed to disclose differences in efficacy towards rat and human FAAHs, and to highlight the role of key residues involved in the inhibition of both enzymes. This study suggests that the therapeutic efficacy of compounds targeted towards FAAH should be always tested in vitro on both rat and human enzymes.