Low energy static Yang-Mills configurations

Non-singular static solutions for the SU(2) Yang-Mills field equations in the presence of external sources are presented. These solutions possess energies less than those of the magnetic dipole solutions, and can in fact have vanishingly small energies.     

“Fluorescent electron emission” — A prediction for resonant photoemission spectra

We have studied the effects of electronic relaxation in resonant photoemission spectra using a model of discrete plasmon-type relaxation with finite plasmon lifetime. In addition to the usual satellite peak with fixed binding energy, we predict the existence of a “fluorescent electron emission” peak at fixed electron kinetic energy.     

Strengths and Weaknesses of Molecular Simulations of Electrosprayed Droplets

The origin and the magnitude of the charge in a macroion are critical questions in mass spectrometry analysis coupled to electrospray and other ionization techniques that transfer analytes from the bulk solution into the gaseous phase via droplets. In many circumstances, it is the later stages of the existence of a macroion in the containing solvent drop before the detection that determines the final charge state. Experimental characterization of small (with linear dimensions of several nanometers) and short-lived droplets is quite challenging. Molecular simulations in principle may provide insight exactly in this challenging for experiments regime. We discuss the strengths and weaknesses of the molecular modeling of electrosprayed droplets using molecular dynamics. We illustrate the limitations of the molecular modeling in the analysis of large macroions and specifically proteins away from their native states.

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Recent advances in N-heterocycles synthesis through catalytic C−H functionalization of azobenzenes

Azobenzenes are well known as crucial structural motifs used in material sciences, nonlinear optical devices, and pharmaceuticals. They also represent an important class of organic intermediates for the transformation of azo and azoxy groups into various useful molecules. Azo groups have a dual character, both electronically increasing the reactivity of the aryl ring and controlling the site-selectivity of the reaction, which significantly increases their utility in organic synthesis. As a complement to previous protocols, the strategy of transition-metal-catalyzed C–H activation of azobenzenes using various coupling partners, such as alkenes, alkynes, aldehydes, diazo esters, organic azides, and sulfoxonium ylides, has recently emerged as a powerful tool to create the corresponding heterocycles. Thus, this review focuses on the recent progress on the direct synthesis of N-heterocycles via C(sp²)–H functionalization of azobenzenes using transition-metal catalysis. This review includes most of the reported methods until the beginning of 2018.     

On the structure of pseudo-holomorphic discs with totally real boundary conditions

In this paper, we study the structure ofJ-holomorphic discs in relation to the Fredholm theory of pseudo-holomorphic discs with totally real boundary conditions in almost complex manifolds (M, J). We prove that anyJ-holomorphic disc with totally real boundary condition that is injective in the interior except at a discrete set of points, which we call a “normalized disc,” must either have some boundary point that is regular and has multiplicity one, or satisfy that its image forms a smooth immersed compact surface (without boundary) with a finite number of self-intersections and a finite number of branch points. In the course of proving this theorem, we also prove several theorems on the local structure of boundary points ofJ-holomorphic discs, and as an application we give a complete treatment of the transverslity result for Floer’s pseudo-holomorphic trajectories for Lagrangian intersections in symplectic geometry. This paper is supported in part by NSF Grant DMS 9215011.     

Dehn filling, reducible 3-manifolds, and Klein bottles

Let be a compact, connected, orientable, irreducible 3-manifold whose boundary is a torus. We announce that if two Dehn fillings create reducible manifold and manifold containing Klein bottle, then the maximal distance is three.

     

The injected carbon impurities in intermixed GaAs/AlAs multiple quantum wells during thermal treatment

Photoluminescence (PL) measurements were performed in order to investigate the carbon impurity effects on the intermixing behavior of GaAs/AlAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The GaAs/AlAs MQWs were annealed with a carbon source in a furnace annealing system. The PL spectra show that the magnitude of the intermixing of Al and Ga induced by thermal annealing in GaAs/AlAs MQWs increases with depth. The nonuniformity of the intermixing as a function of the depth originated from the carbon impurities which were injected during thermal treatment.     

Properties of self-assembled InAs quantum dots grown by various growth techniques

The properties of self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy on GaAs substrates were investigated. The surface properties of samples were monitored by reflection high-energy electron diffraction to determine growth. Photoluminescence (PL) and transmission electron microscope (TEM) were then used to observe optical properties and the shapes of the InAs-QDs. Attempts were made to grow InAs-QDs using a variety of growth techniques, including insertion of the InGaAs strained-reducing layer (SRL) and the interruption of In flux during QD growth. The emission wavelength of InAs-QDs embedded in a pure GaAs matrix without interruption of In flux was about 1.21 μm and the aspect ratio was about 0.21. By the insertion InGaAs SRL and interruption of In flux, the emission wavelength of InAs-QDs was red shifted to 1.37 μm and the aspect ratio was 0.37. From the PL and TEM analysis, the properties of QDs were improved, particularly when interruption techniques were used.