342 research outputs found
Correction to: A T-junction device allowing for two simultaneous orthogonal views: application to bubble formation and break-up (Microfluidics and Nanofluidics, (2018), 22, 8, (85), 10.1007/s10404-018-2101-1)
No full textThe article ‘A T-junction device allowing for two simultaneous orthogonal views: application to bubble formation and break-up’, written by Davide Caprini, Giorgia Sinibaldi, Luca Marino, Carlo Massimo Casciola was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 30 July 2018 without open access
Costruzione di stati di ground su spaziotempi statici dotati di bordo di tipo tempo: libertà nascoste e divergenze infrarosse.
No full textIn this work we review the construction of ground states focusing on a real scalar field whose dynamics is ruled by the Klein-Gordon equation on a large class of static spacetimes with a time-like boundary. As in the analysis of the classical equations of motion, when enough isometries are present, via a mode expansion the construction of two-point correlation functions boils down to solving a second order, ordinary differential equation on an interval of the real line. Using the language of Sturm-Liouville theory, most compelling is the scenario when one endpoint of such interval is classified as a limit circle, as it often happens when one is working on globally hyperbolic spacetimes with a timelike boundary. In this case, beyond initial data, one needs to specify a boundary condition both to have a well-defined classical dynamics and to select a corresponding ground state. Here, we take into account boundary conditions of Robin type by using well-known results from Sturm-Liouville theory, but we go beyond the existing literature by exploring an unnoticed freedom that emerges from the intrinsic arbitrariness of secondary solutions at a limit circle endpoint. Accordingly, we show that infinitely many one-parameter families of sensible dynamics are admissible. In other words, we emphasize that physical constraints guaranteeing the construction of full-fledged ground states do not, in general, fix one such state unambiguously. In addition, we provide, in full detail, an example on (1+1)-half Minkowski spacetime to spell out the rationale in a specific scenario where analytic formulae can be obtained.\\
Then, on , we construct the two-point correlation functions for the ground and thermal states admitting generalized -boundary conditions. We follow the prescription we have developed for two different choices of secondary solutions. For each of them, we obtain a family of admissible boundary conditions parametrized by . We study how they affect the response of a static Unruh-DeWitt detector. The latter not only perceives variations of , but also distinguishes between the two families of secondary solutions in a qualitatively different, and rather bizarre, fashion. Our results highlight once more the existence of a freedom in choosing boundary conditions at a timelike boundary which is greater than expected and with a notable associated physical significance.\\
To conclude, we observe that, depending on the assigned boundary condition of Robin type, this procedure does not always lead to the existence of a suitable bi-distribution due to the presence of infrared divergences. As a concrete example we consider a Bertotti-Robinson spacetime in two different coordinate patches. In one case we show that infrared divergences do not occur only for Dirichlet boundary conditions as one might expect a priori, while, in the other case, we prove that they occur only when Neumann boundary conditions are imposed at the time-like boundary
TERNARY COMPLEXATION BETWEEN COPPER(II), D-ALANINE OR L-ALANINE AND A CHIRAL POLYMER OF (-)-TRANS-1,2-DIAMINOCYCLOHEXANE USED AS A CHROMATOGRAPHIC RESOLVING AGENT
No full textESR and titrimetric data are reported for the ternary interaction between Cu(II), a chiral polymer based upon (-)-trans-1,2-diaminocyclohexane, and L- or D-alanine in aqueous solution
Plant-Inspired Soft Bistable Structures Based on Hygroscopic Electrospun Nanofibers
No full textThe tissue composition and microstructures of plants have dynamic morphologies that change according to their environments. Recently, multifunctional responsive materials and smart structures also took inspiration from these plants' features. Dionaea muscipula leaves provide a remarkable example of an optimized structure that, owing to the synergistic integration of bistability, material, and geometrical properties, permits to overcome the performance limits of purely diffusive processes. In this paper, a hygroscopic bistable structure (HBS) inspired by the Venus flytrap leaves is presented, obtained by bonding prestretched poly(dimethylsiloxane) (PDMS) layers prior to depositing electrospun polyethylene oxide (PEO) nanofibers. A hygroresponsive bilayer (HBL) is also obtained by electrospinning of PEO on an unstretched PDMS layer. The hygroscopic material (Young's modulus and hygroscopic expansion) is mechanically characterized so as to predict the response time of a bending HBL in response to a step humidity variation. The HBS response time (≈1 s) is sensibly lower than the one of purely diffusive HBL (≈10 s) thanks to bistability. An illustrative implementation is also presented, exploiting an HBS to trigger the curvature of a PDMS optical focusing system. The developed plant-inspired soft bistable structure can also be used for sensing (e.g., humidity), energy harvesting, as well as advanced soft robotics applications
Misfolded proteins and neurodegeneration: role of non-native cytochrome c in cell death.
No full textSEPARATION OF DANSYLAMINO ACID ENANTIOMERS BY THIN-LAYER CHROMATOGRAPHY
No full textA simple thin-layer chromatographic method for the separation of D- and L-dansylamino acids using a new resolving agent is described. The enantiomeric resolution of racemates was accomplished on reversed-phase plates pre-treated with a poly-L-phenylalaninamide - copper(II) complex using water- acetonitrile mixtures as eluent under isocratic conditions. The polymeric ligand was easily prepared by reaction of the optically active amide with ethylene glycol diglycidyl ether at room temperature. The method is rapid and sensitive, and was successfully employed to resolve various dansylamino acids
CEC enantioseparations on chiral monolithic columns: A study of the stereoselective degradation of (R/S)-dichlorprop [2-(2,4-dichlorophenoxy)propionic acid] in soil
No full textFor the study of the stereoselective degradation of the herbicide 2-aryloxipropionic acid dichlorprop (DCPP) in soil, a porous monolithic chiral column (100 μm id) was prepared by in situ copolymerization of glycidyl methacrylate, methyl methacrylate and ethylene glycol dimethacrylate in the presence of formamide and 1-propanol as the porogen solvents. Subsequently, the epoxide groups at the surface of the monolith were reacted with (+)-1-(4-aminobutyl)-(5R,8S,10R)-terguride as the chiral selector. Optimum conditions for the herbicide resolution by CEC were found using mobile phases consisting of acetic acid/ triethylamine mixtures in ACN-methanol (9:1 v/v). Under these conditions fully separation of DCPP enantiomers in the presence of clofibric acid (internal standard) was achieved in about 5 min. Experiments on the incubation of rac-DCPP in soil at room temperature showed the herbicide undergone during 23 incubation days to a degradation to levels ≤20% of the initial concentration, with rates for (R)-DCPP slower than (S)-DCPP. More interesting results were observed when herbicide enantiomers were individually incubated. In both the experiments, the formation of the opposite isomer in the presence of the initial one, and reversed enantiomeric interconversion in the case of (S)-DCPP was observed. (R)-DCPP was found to be the most persistent isomer after incubation. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Experiments and DNS of a round jet with turbulent inlet
No full textExperimental and Direct Numerical Simulation data of a turbulent round jet fed by a turbulent pipe are compared in the near field. The Reynolds number achieved in both the experiment and the simulation, Re = 16000, allows a direct comparison of both the average and the fluctuating velocity statistics. In the experiments the jet is fed with olive oil droplets with a Stokes number St ' 1 whose dynamics is compared against the corresponding DNS simulation to asses the ability of particles to reproduce high order turbulence statistics and to asses the accumulation properties of inertial particles in the near field
"High-performance liquid chromatographic resolution of enantiomers on chiral epoxy polymer-coated silica gel"
No full textA chiral stationary phase for the separation of some D- and L-amino acid derivatives using a new resolving agent is described. The support was easily prepared by coating an epoxy polymer of L-valinamide on aminopropylsilaized macroporous silica
Boundary conditions and infrared divergences
No full textWe review the procedure to construct quasi-free ground states, for real scalar fields whose dynamics is dictated by the Klein-Gordon equation, on standard static Lorentzian manifolds with a time-like boundary. We observe that, depending on the assigned boundary condition of Robin type, this procedure does not always lead to the existence of a suitable bi-distribution ω2∈D′(M×M) due to the presence of infrared divergences. As a concrete example we consider a Bertotti-Robinson spacetime in two different coordinate patches. In one case we show that infrared divergences do not occur only for Dirichlet boundary conditions as one might expect a priori, while, in the other case, we prove that they occur only when Neumann boundary conditions are imposed at the time-like boundary
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