Synthesis of a novel constrained α-amino acid with quinoxaline side chain: 7-amino-6,7-dihydro-8H-cyclopenta[g]quinoxaline-7-carboxylic acid

A novel constrained 7-amino-6,7-dihydro-8H-cyclopenta[g]quinoxaline-7-carboxylic acid derivative was prepared starting from 4,5-dimethyl-o-phenylenediamine.     

Derivation of the probability distribution functions for succession quota random variables

The probability distribution functions (pdf's) of the sooner and later waiting time random variables (rv's) for the succession quota problem (k successes and r failures) are derived presently in the case of a binary sequence of order k. The probability generating functions (pgf's) of the above rv's are then obtained directly from their pdf's. In the case of independent Bernoulli trials, expressions for the pdf's in terms of binomial coefficients are also established.     

Relativistic corrections to the Lagrangian for interacting charged particles

We give the Lagrangian of a system of moving charged particles up to the fourth approximation in 1/c neglecting dipole radiation of the system. In this case the appearance of the electromagnetic waves (quadrupole radiation) by moving charges occurs in the fifth approximation in 1/c.     

Equilibrium results for the M/G/k group-arrival loss system

In this paper we consider a specific M/G/k group-arrival loss system, under statistical equilibrium and two cases of acceptance policy. In the first case the system works under the partial acceptance policy. Explicit results are obtained for the corresponding stationary distribution, which extend previous relevant results. In the second case, where the system works under the all-or-nothing acceptance policy, a sufficient condition is given for the stationary distribution to have a closed-product form. In both cases customers depart individually, while the joint service time distribution of the accepted members of a group may depend both on its initial and the accepted size plus an additional condition.     

Active control of liquid film flows: beyond reduced-order models

Nonlinear Dynamics - The ability to robustly and efficiently control the dynamics of nonlinear systems lies at the heart of many current technological challenges, ranging from drug delivery systems...     

Synthesis and biological evaluation of new benzo[f]furo[2,3‐h]‐and benzo[f]pyrano[2,3‐h]coumarin derivatives.

Furocoumarins 3,5 and pyranocoumarin 7 were synthesized from the reaction of furonaphthalenediones 2,4 and pyranonaphthalenedione 6 respectively with carbethoxymethylene(triphenyl)phosphorane in refluxing DCM for 3‐6 hours or under microwave irradiation in toluene for a few minutes. Compounds 3,5,7 and their precursors were tested as anti‐inflammatory/antioxidant agents. They were found to compete significantly high DMSO for OH radicals, to scavenge O₂^? and to inhibit lipoxygenase to a high extent.     

Studying pigments on painted plaster in Minoan,Roman and Early Byzantine Crete. A multi-analytical technique approach

Wall paintings spanning two millennia of Cretan painting history and technology were analysed in an effort to determine similarities and evolutions of painting materials and technology. A multi-technique approach was employed that combined the use of (a) laser-induced breakdown spectroscopy (LIBS) and Raman microspectroscopy, based on mobile instrumentation, appropriate for rapid, routine-level object characterization, and (b) non-destructive X-ray diffractometry (XRD), performed directly on the wall painting fragment, which provides detailed information on the minerals constituting the paint. Elemental analysis data obtained through LIBS were compared with molecular and crystal structure information from Raman spectroscopy and XRD. Cross-sections from selected samples were also investigated by means of optical microscopy and scanning electron microscopy coupled to micro-probe analysis and X-ray mapping that enabled identification of several mineral components of the paint confirming the results of the XRD analysis. In parallel, replica wall paintings, created with known pigments and binding media for reference purposes, were examined with optical microscopy and stain tested for organic materials. The overall study shows that the LIBS and Raman techniques offer key advantages, such as instrument mobility and speed of data collection and interpretation that are particularly important when dealing with on-site investigations. Thus, they are capable of providing important compositional information in an effective manner that enables quick surveying of wall paintings and permit targeted sample selection for further analysis by advanced laboratory techniques.     

Large area single-mode parity-time-symmetric laser amplifiers

By exploiting recent developments associated with parity-time (PT) symmetry in optics, we here propose a new avenue in realizing single-mode large area laser amplifiers. This can be accomplished by utilizing the abrupt symmetry breaking transition that allows the fundamental mode to experience gain while keeping all the higher order modes neutral. Such PT-symmetric structures can be realized by judiciously coupling two multimode waveguides, one exhibiting gain while the other exhibits an equal amount of loss. Pertinent examples are provided for both semiconductor and fiber laser amplifiers.     

The influence of electric fields and surface tension on Kelvin–Helmholtz instability in two-dimensional jets

We consider nonlinear aspects of the flow of an inviscid two-dimensional jet into a second immiscible fluid of different density and unbounded extent. Velocity jumps are supported at the interface, and the flow is susceptible to the Kelvin–Helmholtz instability. We investigate theoretically the effects of horizontal electric fields and surface tension on the nonlinear evolution of the jet. This is accomplished by developing a long-wave matched asymptotic analysis that incorporates the influence of the outer regions on the dynamics of the jet. The result is a coupled system of long-wave nonlinear, nonlocal evolution equations governing the interfacial amplitude and corresponding horizontal velocity, for symmetric interfacial deformations. The theory allows for amplitudes that scale with the undisturbed jet thickness and is therefore capable of predicting singular events such as jet pinching. In the absence of surface tension, a sufficiently strong electric field completely stabilizes (linearly) the Kelvin–Helmholtz instability at all wavelengths by the introduction of a dispersive regularization of a nonlocal origin. The dispersion relation has the same functional form as the destabilizing Kelvin–Helmholtz terms, but is of a different sign. If the electric field is weak or absent, then surface tension is included to regularize Kelvin–Helmholtz instability and to provide a well-posed nonlinear problem. We address the nonlinear problems numerically using spectral methods and establish two distinct dynamical behaviors. In cases where the linear theory predicts dispersive regularization (whether surface tension is present or not), then relatively large initial conditions induce a nonlinear flow that is oscillatory in time (in fact quasi-periodic) with a basic oscillation predicted well by linear theory and a second nonlinearly induced lower frequency that is responsible for quasi-periodic modulations of the spatio-temporal dynamics. If the parameters are chosen so that the linear theory predicts a band of long unstable waves (surface tension now ensures that short waves are dispersively regularized), then the flow generically evolves to a finite-time rupture singularity. This has been established numerically for rather general initial conditions.