C-N bond formation via ligand-induced nucleophilicity at a coordinated triamidoamine ligand

Reaction of (N(3)N)ZrX complexes (X = amido, Cl(-), CH(3)(-)) with carbodiimide substrates results in insertion into an Zr-N bond of the triamidoamine ligand rather than the Zr-X bond as has been observed for related (N(3)N)ZrX complexes (X = PR(2)(-), AsR(2)(-)).     

Size-selective concentration and label-free characterization of protein aggregates using a Raman active nanofluidic device

Trace detection and physicochemical characterization of protein aggregates have a large impact in understanding and diagnosing many diseases, such as ageing-related neurodegeneration and systemic amyloidosis, for which the formation of protein aggregates is one of the pathological hallmarks. Here we demonstrate an innovative label-free method for detecting and characterizing small amounts of early stage protein aggregates using a Raman active nanofluidic device. Sub-micrometre channels formed by a novel elastomeric collapse technique enable the separation and concentration of matured protein aggregates from small protein molecules. The Raman enhancement by gold nanoparticle clusters fixed below a micro/nanofluidic junction allows characterization of intrinsic properties of protein aggregates at concentration levels (～fM) much lower than can be done with traditional analytical tools. With our device we show for the first time the concentration dependence of protein aggregation over these low concentration ranges. We expect that our method could facilitate definitive diagnosis and possible therapeutics of diseases at early stages.     

Synchrotron fourier transform infrared microspectroscopy: A new tool to monitor the fate of organic contaminants in plants

FTIR microspectroscopy, with synchrotron radiation as a source, was used for the first time to study changes in plant structure induced by organic contaminants. Sunflower (Helianthus annuus L.) plants were grown hydroponically in the presence of benzotriazole. Changes in the plant structure due to uptake, incorporation, and/or transformation of benzotriazole were observed. False color intensity maps of benzotriazole treated secondary root sections showed changes in plant structure, as well as the presence of aromatic CH peaks due to incorporation of benzotriazole within the plant. The presence of the characteristic benzotriazole CH out-of-plane bending mode suggests that the contaminant aromatic ring remains intact upon the uptake by the plant. Simultaneously, the changes in the lignin structure suggest that the plant suffered damage by the uptake of the benzotriazole. Spectral variations between the untreated and benzotriazole treated sunflowers were uncovered using principal components analysis (PCA). PCA also revealed clustering according to the different benzotriazole treatments.     

Thermal treatment of moolooite

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. Moolooite as the natural copper(II) oxalate mineral is a classic example. High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition takes place at 260°C. Evolved gas mass spectrometry shows the gas lost at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper(II) oxalate as compared to the synthetic compound which is the dihydrate. The high resolution thermogravimetry was complimented with hot stage Raman spectroscopy. The temperature at which no intensity remains in the bands assigned to the oxalate vibrations is the upper limit of the stability of the moolooite. This revised version was published online in August 2006 with corrections to the Cover Date.     

A new quasi-optical filter: the reflective polarizing interferometer

Conclusions A new type of optical filter element has been described and tested, offering an alternative frequency response to that of a Fabry-Perot or Michelson interferometer. It is quite compact, mechanically stable, and suitable for cryogenic operation. Use of this device is planned as a sideband filter in a 15 element imaging array receiver for 90–115 GHz.     

On anti-stokes luminescence from Rhodamine 6G in ethanol solutions

Anti-Stokes luminescence form Rhodamine 6G ethanol solutions excited by a He-Ne laser is observed to be strongly temperature dependent. A theoretical model is proposed for the absorption line shape on the long wavelength side of the pure electronic transition which fits the absorption and luminescence data. Vavilov's law is found to hold even when the absorption coefficient is 10^-6 times the peak absorption coefficient for the Rhodamine 6G dye solution. Another luminescence peak at 6650 Å is observed which is attributed to impurity fluorescence. It could not be related to photochemical products.     

ESCA study of fractional monolayer quantities of chemisorbed gases on tungsten

X-ray photoelectron spectroscopy (ESCA) has been used in a study of CO and O₂ chemisorbed on a polycrystalline tungsten sample. Working under ultra-high vacuum conditions, the surface was cleaned and then covered with known monolayer and fractional monolayer quantities of adsorbed CO and O₂. The O(ls) and C(ls) spectral features were detected, and the influence of an adsorbed layer on the tungsten spectral features was determined. A chemical shift of 3.4 eV in the O(ls) line from chemisorbed CO is related to the different modes of bonding of CO to tungsten. A model calculation of the photoelectron yields expected from an adsorbed monolayer is in good agreement with the experimental results.     

Comparison of high-performance liquid chromatography electrochemical detectors for the determination of aporphines,catecholamines and melatonin

A Bioanalytical Systems detector showed a greater sensitivity for low-level determinations of apomorphine, norepinephrine, epinephrine, dopamine, and melatonin compared to a Brinkmann Instruments system. Modifications of the Bioanalytical Systems flow cell, which have been developed in our laboratories, increase the sensitivity toward certain catecholic compounds, generally decrease baseline noise, and allow for serial coupling of detectors.²     

Heat transfer to magnetohydrodynamic flow in a flat duct

Zusammenfassung Die Untersuchung befasst sich mit der Wärmeübertragung von den Wänden eines flachwandigen Kanals auf eine elektrisch leitende Flüssigkeit bei erzwungener Laminarströmung und in Gegenwart eines quergerichteten Magnetfeldes. Betrachtet wird der Fall konstanter Wandtemperatur mit variierender innerer Wärmeentwicklung durch viskose und elektrische Energiedissipation. Die massgebende Differentialgleichung wird durch eine Differenzengleichung ersetzt und mit der elektronischen Rechenmaschine gelöst. Als Resultat wird die Nusseltzahl angegeben, für die Prandtlzahl 1, die Hartmannzahlen 0, 4, 10 und die Graetzzahlen von 10 bis 10 000, wobei die Kennzahlen für Zähigkeit und elektrische Feldstärke als Parameter auftreten.