Resonant X-ray photoelectron spectroscopy: identification of atomic contributions to valence states.

Valence electronic structure is crucial for understanding and predicting reactivity. Valence non-resonant X-ray photoelectron spectroscopy (NRXPS) provides a direct method for probing the overall valence electronic structure. However, it is often difficult to separate the varying contributions to NRXPS; for example, contributions of solutes in solvents or functional groups in complex molecules. In this work we show that valence resonant X-ray photoelectron spectroscopy (RXPS) is a vital tool for obtaining atomic contributions to valence states. We combine RXPS with NRXPS and density functional theory calculations to demonstrate the validity of using RXPS to identify atomic contributions for a range of solutes (both neutral and ionic) and solvents (both molecular solvents and ionic liquids). Furthermore, the one-electron picture of RXPS holds for all of the closed shell molecules/ions studied, although the situation for an open-shell metal complex is more complicated. The factors needed to obtain a strong RXPS signal are investigated in order to predict the types of systems RXPS will work best for; a balance of element electronegativity and bonding type is found to be important. Additionally, the dependence of RXPS spectra on both varying solvation environment and varying local-covalent bonding is probed. We find that RXPS is a promising fingerprint method for identifying species in solution, due to the spectral shape having a strong dependence on local-covalency but a weak dependence on the solvation environment.

A one-pot-one-reactant synthesis of platinum compounds at the nanoscale.

The preparation of inorganic nanomaterials with a desired structure and specific properties requires the ability to strictly control their size, shape and composition. A series of chemical reactions with platinum compounds carried out within the 1.5 nm wide channel of single-walled carbon nanotubes (SWNTs) have demonstrated the ability of SWNTs to act as both a very effective reaction vessel and a template for the formation of nanocrystals of platinum di-iodide and platinum di-sulphide, materials that are difficult to synthesise in the form of nanoparticles by traditional synthetic methods. The stepwise synthesis inside nanotubes has enabled the formation of Pt compounds to be monitored at each step of the reaction by aberration-corrected high resolution transmission electron microscopy (AC-HRTEM), verifying the atomic structures of the products, and by an innovative combination of fluorescence-detected X-ray absorption spectroscopy (FD-XAS) and Raman spectroscopy, monitoring the oxidation states of the platinum guest-compounds within the nanotube and the vibrational properties of the host-SWNT, respectively. This coupling of complementary spectroscopies reveals that electron transfer between the guest-compound and the host-SWNT can occur in either direction depending on the composition and structure of the guest. A new approach for nanoscale synthesis in nanotubes developed in this study utilises the versatile coordination chemistry of Pt which has enabled the insertion of the required chemical elements (e.g. metal and halogens or chalcogens) into the nanoreactor in the correct proportions for the controlled formation of PtI2 and PtS2 with the correct stoichiometry.

Serum prolactin and LH responses to photoperiod in bull calves.

Two bull calves were subjected to changes in daily illumination over a 12-week interval, with ambient temperature maintained at 22 C. When photoperiod was shortened from 16 to 8 h, serum prolactin decreased from a maximum of 57 mg/ml to a minimum of 8 ng/ml. Conversely, with another 4 bulls, increasing the photoperiod from 8 to 16 h of light caused serum prolactin concentrations to increase from 25 to 100 ng/ml. The increase in serum prolactin in response to increasing photoperiod was delayed approximately 7 weeks, whereas the response to decreasing photoperiod was delayed only about 1 week. Changes in photoperiod had no effect on serum LH concentrations. We conclude that changes in photoperiod account, at least partially, for the seasonal changes in serum prolactin previously noted in cattle.

Obese hypoventilation syndrome of early childhood requiring ventilatory support.

In December 1986 a 30-month-old female child with morbid obesity and respiratory failure was admitted to the Izaak Walton Killam Hospital for Children in Halifax. The etiology of the obesity was found to be dietary in origin after ruling out genetic, neurological and metabolic causes. This patient exhibited somnolence and cyanosis in association with hypercapnia and right ventricular overload. Her respiratory failure in the presence of a normal upper airway required ventilatory support, first with nasal endotracheal intubation, and then, tracheotomy. Weight reduction normalized her capillary blood gases and her somnolence disappeared. Subglottic stenosis hampered removal of the tracheotomy tube until 9 months after admission. The pathogenesis and management of obese hypoventilation syndrome are reviewed by the authors.

Serum growth hormone concentrations after growth hormone or thyrotropin releasing hormone in cows.

A single subcutaneous injection of 10, 50, or 100 mg bovine growth hormone into lactating Holstein cows increased concentrations of growth hormone, insulin, and glucose in serum above preinjection baselines for at least 16 h. Growth hormone concentrations in serum after injection of growth hormone or thyrotropin-releasing hormone were greater in cows during early (2 to 4 mo) as compared with cows during late (8 to 12 mo) lactation. Stage of lactation did not affect rate of metabolic clearance of growth hormone in eight cows, but larger cows cleared growth hormone more rapidly than smaller cows. Data of these experiments may help to explain how injections of growth hormone every 3 days stimulate milk yields.

Plasma concentration of flumazenil following intranasal administration in children.

PURPOSE: A pharmacokinetic study in children to determine plasma flumazenil concentrations after the intranasal administration of 40 microg x kg(-1). METHODS: Following institutional approval and informed written consent, 11 ASA physical status I-II patients, aged two to six years, undergoing general anesthesia for dental surgery were recruited. After induction, 40 microg x kg(-1) flumazenil Anexate, Roche, 0.1 mg x mL(-1) (0.4 mL x kg(-1))) were administered via a syringe as drops, prior to nasal intubation. Venous plasma samples were drawn prior to administration of flumazenil (t = 0), and then at 2, 4, 6, 8, 10, 15, 20, 30, 40, 60, and 120 min thereafter. The plasma samples were immediately processed by the on-site laboratory and then stored at -70 degrees C, before batch analysis via high performance liquid chromatography assay. Pharmacokinetic data calculations were performed using WinNonLin software (Scientific Consulting Inc.). RESULTS: Eleven patients were studied, but data for one patient were discarded due to insufficient sampling. The median age was 4.3 yr (range 3 to 6), with a median weight of 18.9 kg (range 14.9 to 22.2). There were seven boys and three girls. Mean Cmax was 67.8 ng x mL(-1) (SD 41.9), with Tmax at two minutes. The calculated half-life was 122 min (SD 99). CONCLUSION: The mean plasma concentrations of flumazenil attained were similar to those reported after intravenous administration, and may be sufficient to antagonize the side-effects of benzodiazepines. This route of administration may be useful when the intravenous route is not readily available.