Extremal problems for certain analytic (Nevanlinna) functions

We obtain sharp bounds on some basic functionals defined on the sets of all analytic functions having the representations \(f\left( z \right) \equiv \int\limits_{ - 1}^1 {\frac{{d\mu \left( t \right)}}{{z - t}}} \) and \(\varphi \left( z \right) \equiv \int\limits_{ - 1}^1 {\frac{{z\mu \left( t \right)}}{{1 - tz}}} \) ; respectively. Here μ is a probability measure.     

Real-time volumetric growth rate measurements and feedback control of three-dimensional laser chemical vapor deposition

Received: 4 June 1997/Accepted: 12 June 1997     

Buffer-gas cooling of NH via the beam loaded buffer-gas method

NH radicals from a molecular beam are cooled using a novel beam-loaded buffer gas method. The radicals are produced in a glow discharge beam source and injected into cryogenic helium gas. Up to 10¹² molecules in their ground electronic, vibrational, and rotational state are detected in the buffer gas and translational temperatures under 6 K are achieved. The cooling method presented is general and can be applied to any molecules in a molecular beam.Received: 20 July 2004, Published online: 26 October 2004PACS: 33.80.Ps Optical cooling of molecules; trapping - 34.50.Ez Rotational and vibrational energy transfer - 39.10. + j Atomic and molecular beam sources and techniquesB. Friedrich: Present address: Department of Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.     

Bridged ring systems—VIII A novel ring expansion reaction

Acid treatment of 2-(β-Benzoylethyl)-cyclopentanone (III) leads directly to a phenylcycloheptene carboxylic acid (VII) and the related lactone (XI), via a bicyclic intermediate.     

Biomolecules-carbon nanotubes doped conducting polymer nanocomposites and their sensor application

A simple method for preparing bio-functionalized soluble single-walled carbon nanotubes (SWNTs) is described. Different proteins such as bovine serum albumin (BSA), cytochrome c and horseradish peroxidase (HRP) were used to solubilize low functionality SWNTs in water aided by sonication. The unbound proteins were removed by column chromatography and the SWNT-protein conjugate was used as the sole anionic dopant in electropolymerization of polypyrrole from polymerization solution at pH above the isoelectric point of the protein to provide a negative charge. The morphology of the polypyrrole with SWNT-protein dopant was found to be three-dimensional and fibrous with wide open interlocking pores in contrast to smooth and cauliflower-like for chloride doped polypyrrole. Enhanced sensor performance was demonstrated for hydrogen peroxide detection on polypyrrole/SWCNT-HRP nanocomposites modified electrode. Such nanocomposites can be potentially applied for other biosensor and bio-fuel cell applications.     

Headspace single-drop microextration for the detection of organotin compounds

The performance of single-drop microextraction (SDME), coupled with gas chromatography/mass spectrometry, was assessed for the determination of tributyltin compounds in water and solid samples. Experimental parameters impacting the performance of SDME, such as microextraction solvent and sampling and stirring time, were investigated. Analytical results obtained by SDME were compared with those generated by conventional solid phase microextraction (SPME) and liquid-liquid extraction (LLE) for the determination of TBT in PACS-2 sediment certified reference material (CRM).     

Bioconjugation of ultrabright semiconducting polymer dots for specific cellular targeting

Semiconducting polymer dots (Pdots) represent a new class of ultrabright fluorescent probes for biological imaging. They exhibit several important characteristics for experimentally demanding in vitro and in vivo fluorescence studies, such as their high brightness, fast emission rate, excellent photostability, nonblinking, and nontoxic feature. However, controlling the surface chemistry and bioconjugation of Pdots has been a challenging problem that prevented their widespread applications in biological studies. Here, we report a facile yet powerful conjugation method that overcomes this challenge. Our strategy for Pdot functionalization is based on entrapping heterogeneous polymer chains into a single dot, driven by hydrophobic interactions during nanoparticle formation. A small amount of amphiphilic polymer bearing functional groups is co-condensed with the majority of semiconducting polymers to modify and functionalize the nanoparticle surface for subsequent covalent conjugation to biomolecules, such as streptavidin and immunoglobulin G (IgG). The Pdot bioconjugates can effectively and specifically label cellular targets, such as cell surface marker in human breast cancer cells, without any detectable nonspecific binding. Single-particle imaging, cellular imaging, and flow cytometry experiments indicate a much higher fluorescence brightness of Pdots compared to those of Alexa dye and quantum dot probes. The successful bioconjugation of these ultrabright nanoparticles presents a novel opportunity to apply versatile semiconducting polymers to various fluorescence measurements in modern biology and biomedicine.     

Interaction of surfactants with hydrophobic surfaces in nanopores

Surfactant-induced wetting of hydrophobic nanopores is investigated. SDS micelles interact with the C18 layer on the nanopore walls with their hydrophobic tails, creating a charged wall lining with their head groups and inducing a breakthrough of the aqueous solution to wet the pores. The surface coverage of the surfactant molecules is evaluated electrophoretically. A surprising discovery is that pore wetting is achieved with 0.73 μmol/m(2) coverage of SDS surfactant, corresponding to only 18% of a monolayer on the walls of the nanopores. Clearly, the surfactant molecules cannot organize as a compact uninterrupted monolayer. Instead, formation of hemimicelles is thermodynamically favored. Modeling shows that, to be consistent with the experimental observations, the aggregation number of hemimicelles is lower than 25 and the size of hemimicelle is limited to a maximum radius of 11.7 ?. The hydrophobic tails of SDS thus penetrate into and intercalate with the C18 layer. The insight gained in the C18-surfactant interactions is essential in the surfactant-induced solubilization of hydrophobic nanoporous particles. The results have bearing on the understanding of the nature of hydrophobic interactions.