Optimum PCF tapers for blue-enhanced supercontinuum sources

Tapering of photonic crystal fibers has proven to be an effective way of blueshifting the dispersive wavelength edge of a supercontinuum spectrum down in the deep-blue. In this article we will review the state-of-the-art in fiber tapers, and discuss the underlying mechanisms of supercontinuum generation in tapers. We show, by introducing the concept of a group-acceleration mismatch, that for a given taper length, the downtapering section should be as long as possible to enhance the amount of blueshifted light. We also discuss the noise properties of supercontinuum generation in uniform and tapered fibers, and we demonstrate that the intensity noise at the spectral edges of the generated supercontinuum is at a constant level independent on the pump power in both tapered and uniform fibers.     

Substituent Effects on the Bands Near 1600 cm−1 in The Ir Spectra of Azobenzene and Some Substituted Azobenzenes

Abstract

The mean positions and apparent extinction coefficients of the ring stretching bands near 1600 cm^?1 in the IR spectra of trans azobenzene and some substituted trans azobenzenes are reported. These results are discussed in relation to values reported for substituted benzenes.     

Controlled aspiration and positioning of biological cells in a micropipette

Manipulating single cells with a micropipette is the oldest, yet still a widely used technique. This paper discusses the aspiration of a single cell into a micropipette and positioning the cell accurately to a target position inside the micropipette. Due to the small volume of a single cell (picoliter) and nonlinear dynamics involved, these tasks have high skill requirements and are labor intensive in manual operation that is solely based on trial and error and has high failure rates. We present automated techniques in this paper for achieving these tasks via computer vision microscopy and closed-loop motion control. Computer vision algorithms were developed to detect and track a single cell outside and inside a micropipette for automated single-cell aspiration. A closed-loop robust controller integrating the dynamics of cell motion was designed to accurately and efficiently position the cell to a target position inside the micropipette. The system achieved high success rates of 98% for cell detection and 97% for cell tracking (n = 100). The automated system also demonstrated its capability of aspirating a single cell into a micropipette within 2 s (versus 10 s by highly skilled operators) and accurately positioning the cell inside the micropipette within 8 s (versus 25 s by highly skilled operators).     

Synthesis of tetrahydro-β-carbolines via isomerization of N-allyltryptamines: a metal-catalyzed variation on the Pictet-Spengler theme

An efficient and broadly applicable alternative to the classical Pictet-Spengler synthesis of tetrahydro-β-carbolines is presented. The method relies on metal-catalyzed isomerization of allylic amines to form reactive iminium intermediates which can be trapped by a tethered indole nucleophile.     

Measurement of atmospheric neutrino flux consistent with tau neutrino appearance

A search for the appearance of tau neutrinos from nu(mu) <--> nu(tau) oscillations in the atmospheric neutrinos has been performed using 1489.2 days of atmospheric neutrino data from the Super-Kamiokande-I experiment. A best fit tau neutrino appearance signal of 138+/-48(stat)-32(+15)(syst) events is obtained with an expectation of 78+/-26(syst). The hypothesis of no tau neutrino appearance is disfavored by 2.4 sigma.     

The unexpected formation of a lithium-enolate from bis2-[(dimethylamino)methyl]phenyl copper lithium. X-ray structure of Li4[OC(CH2)C6H4CH2NMe2-2]4

Attempted crystallization of the bis(aryl)lithium cuprate, Cu₂Li₂(C₆H₄CH₂-NMe₂-2)₄, from diethyl ether/pentane afforded in according to an X-ray diffraction analysis appeared to be the lithium enolate, Li₄[OC(=CH₂)C₆H₄CH₂NMe₂-2]₄. This consists of a central Li₄O₄ cube with intramolecular LiN coordination of the CH₂NMe₂ substituent. This enolate, which has also been prepared via an independent route, is the first example of a structurally characterized lithium enolate and contains Li centres that are intramolecularly coordinated.     

Infrared spectra of the polymorphs of naphthazarin: Microscopy and low temperature studies

The infrared microscope spectra of theA,B, andC polymorphs of naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) can be distinguished clearly. When naphthazarin is dispersed in KBr, such a distinction can only be made when experimental precautions are taken during the preparation of the pellet. Low temperature infrared studies indicate that a phase transition takes place in naphthazarin around 110 K.