Poly[di-mu-aqua-bis(mu-2-amino-4-nitrobenzoato)dicaesium]

In the structure of title compound [Cs2(C7H5N2O4)2(H2O)2]n the asymmetric unit comprises two independent and different Cs centres, one nine-coordinate, the other seven coordinate, with both having irregular stereochemistry. The CsO9 coordination comprises oxygen donors from three bridging water molecules, one of which is doubly bridging, three from carboxylate groups, and three from nitro groups, of which two are bidentate chelate bridging. The CsO6N coordination comprises the two bridging water molecules, one amine N donor, one carboxyl O donor and four O donors from nitro groups (two from the chelate bridges). The extension of the dimeric unit gives a two-dimensional polymeric structure which is stabilized by both intra- and intermolecular amine N-H...O and water O-H...O hydrogen bonds to carboxyl O acceptors, as well as inter-ring pi-pi interactions [minimum ring centroid separation, 3.4172(15)A].

Raman spectroscopic study of the magnesium carbonate mineral– hydromagnesite Mg5[(CO3)4(OH)2]•4H2O

Magnesium minerals are important for the understanding of the concept of geosequestration. One method of studying the hydrated hydroxy magnesium carbonate minerals is through vibrational spectroscopy. A combination of Raman and infrared spectroscopy has been used to study the mineral hydromagnesite. An intense band is observed at 1121 cm-1 attributed CO32- ν1 symmetric stretching mode. A series of infrared bands at 1387, 1413, 1474 cm-1 are assigned to the CO32- ν3 antisymmetric stretching modes. The CO32- ν3 antisymmetric stretching vibrations are extremely weak in the Raman spectrum and are observed at 1404, 1451, 1490 and 1520 cm-1. A series of Raman bands at 708, 716, 728, 758 cm-1 are assigned to the CO32- ν2 in-plane bending mode. The Raman spectrum in the OH stretching region is characterised by bands at 3416, 3516 and 3447 cm-1. In the infrared spectrum a broad band is found at 2940 cm-1 assigned to water stretching vibrations. Infrared bands at 3430, 3446, 3511, 2648 and 3685 cm-1 are attributed to MgOH stretching modes.

[P,P-Di-tert-butyl-N-trimethylsilyl- P-(trimethylsilylamino)phosphineimidato-N,N]bis(pyridine-N)- lithium(I)

In the title compound, [Li(C14H36N2PSi2)(C5H5N)2], the bulky chelating monoanionic P,P-di-tert-butyl-N-trimethylsilyl-P-(trimethylsilylamino)phosphine imidate ligand and two pyridine ligands bind to Li in a pseudo-tetrahedral arrangement with twofold symmetry. The Li-N [phosphine]distance is 2.048 (5) Å, while the LiP distance is 2.520 (6) Å

Platinum/graphene nanosheet/SiC contacts and their application for hydrogen gas sensing

Pt/graphene nanosheet/SiC based devices are fabricated and characterized and their performances toward hydrogen gas are investigated. The graphene nanosheets are synthesized via the reduction of spray-coated graphite oxide deposited onto SiC substrates. Raman and X-ray photoelectron spectroscopies indicate incomplete reduction of the graphite oxide, resulting in partially oxidized graphene nanosheet layers of less than 10 nm thickness. The effects of interfaces on the nonlinear behavior of the Pt/graphene and graphene/SiC junctions are investigated. Current-voltage measurements of the sensors toward 1% hydrogen in synthetic air gas mixture at various temperatures ranging up to 100. ° C are performed. From the dynamic response, a voltage shift of ∼100 mV is recorded for 1% hydrogen at a constant current bias of 1 mA at 100. °C. © 2010 American Chemical Society.

Reverse biased Pt/nanostructured MoO3/SiC Schottky diode based hydrogen gas sensors

Pt/nanostructured molybdenum oxide (MoO3) /SiC Schottky diode based gas sensors were fabricated for hydrogen (H2) gas sensing. Due to the enhanced performance, which is ascribed to the application of MoO3 nanostructures, these devices were used in reversed bias. MoO3 characterization by scanning electron microscopy showed morphology of randomly orientated nanoplatelets with thicknesses between 50 and 500 nm. An α-Β mixed phase crystallographic structure of MoO3 was characterized by x-ray diffraction. At 180 °C, 1.343 V voltage shift in the reverse I-V curve and a Pt/ MoO3 barrier height change of 20 meV were obtained after exposure to 1% H2 gas in synthetic air. © 2009 American Institute of Physics.

A hydrogen gas sensor based on Pt/nanostructured WO3/SiC Schottky diode

Pt/nanostructured WO3/SiC Schottky diodes were fabricated and applied for hydrogen gas sensing applications. The nanostructured WO3 films were synthesized from tungsten coated SiC substrates via an acid-etching method using a 1.5 M HNO3 solution for 1 hr, 2 hrs and 3 hrs duration. Scanning electron microscopy of the developed films revealed platelet crystals with thicknesses in the order of 20-60 nm and lengths between 100-700 nm. X-ray diffraction analysis revealed that the rate of oxidation of tungsten increases as the duration of acid-etching increases. The devices were tested towards hydrogen gas balanced in air at different temperatures from 25°C to 200°C. At 200°C, voltage shifts of 0.45 V, 0.93 V and 2.37 V were recorded for devices acid-etched for 1 hr, 2 hrs and 3 hrs duration, respectively upon exposure to 1% hydrogen, under a constant forward bias current of 500 µA.

Bayesian models for the determination of resonant frequencies in a DI diesel engine

A time series method for the determination of combustion chamber resonant frequencies is outlined. This technique employs the use of Markov-chain Monte Carlo (MCMC) to infer parameters in a chosen model of the data. The development of the model is included and the resonant frequency is characterised as a function of time. Potential applications for cycle-by-cycle analysis are discussed and the bulk temperature of the gas and the trapped mass in the combustion chamber are evaluated as a function of time from resonant frequency information.

Hydrogen gas sensing properties of Pt/Ta2O5 Schottky diodes based on Si and SiC substrates

In this paper, we fabricated Pt/tantalum oxide (Ta2O5) Schottky diodes for hydrogen sensing applications. Thin (4 nm) layer of Ta2O5 was deposited on silicon (Si) and silicon carbide (SiC) substrates by radio frequency (RF) sputtering technique. We compared the performance of these sensors at different elevated temperatures of 100 ∘C and 150 ∘C. At these temperatures, the sensor based on SiC exhibited a larger sensitivity while the sensor based on Si exhibited a faster response toward hydrogen gas. We discussed herein, the responses exhibited by the Pt/Ta2O5 based Schottky diodes demonstrated a promising potential for hydrogen sensing applications.

Hydrogen gas sensing performance of a Pt/graphene/SiC device

In this work, we present the development of a Pt/graphene/SiC device for hydrogen gas sensing. A single layer of graphene was deposited on 6H-SiC via chemical vapor deposition. The presence of graphene C-C bonds was observed via X-ray photoelectron spectroscopy analysis. Current-voltage characteristics of the device were measured at the presence of hydrogen at different temperatures, from 25°C to 170°C. The dynamic response of the device was recorded towards hydrogen gas at an optimum temperature of 130°C. A voltage shift of 191 mV was recorded towards 1% hydrogen at −1 mA constant current.

Effect of magnesium depletion and potassium and chlorothiazide on intracellular pH in the rat, studied by 31P NMR

1. Both dietary magnesium depletion and potassium depletion (confirmed by tissue analysis) were induced in rats which were then compared with rats treated with chlorothiazide (250 mg/kg diet) and rats on a control synthetic diet. 2. Brain and muscle intracellular pH was measured by using a surface coil and [31P]-NMR to measure the chemical shift of inorganic phosphate. pH was also measured in isolated perfused hearts from control and magnesium-deficient rats. Intracellular magnesium status was assessed by measuring the chemical shift of β-ATP in brain. 3. There was no evidence for magnesium deficiency in the chlorothiazide-treated rats on tissue analysis or on chemical shift of β-ATP in brain. Both magnesium and potassium deficiency, but not chlorothiazide treatment, were associated with an extracellular alkalosis. 4. Magnesium deficiency led to an intracellular alkalosis in brain, muscle and heart. Chlorothiazide treatment led to an alkalosis in brain. Potassium deficiency was associated with a normal intracellular pH in brain and muscle. 5. Magnesium depletion and chlorothiazide treatment produce intracellular alkalosis by unknown mechanism(s).

Problems in the assessment of magnesium depletion in the rat by in vivo 31P NMR

Prior in vitro studies, utilizing 31Pn uclear magnetic resonance (31PN MR) to measure the chemical shift (CT) of 0-ATP and lengthening of the phosphocreatine spin-spin (7"') relaxation time, suggested an assessment of their efficacy in measuring magnesium depletion in vivo. Dietary magnesium depletion (Me$) produced markedly lower magnesium in plasma (0.44 vs 1. I3 mmol/liter) and bone (1 30 vs 190 pmol/g) but much smaller changes in muscle (41 vs 45 pmol/g, P < 0.01), heart (42.5 vs 44.6 prnol/g), and brain (30 vs 32 pmollg). NMR experiments in anesthetized rats in a Bruker 7-T vertical bore magnet showed that in M e $ rats there was a significant change in brain j3-ATP shift (16.15 vs 16.03 ppm, P < 0.05). These chemical shifts gave a calculated free [Mg"] of 0.71 mM (control) and 0.48 mM (MgZ+$). In muscle the change in j3-ATP shift was not significant (Me$ 15.99 ppm, controls 15.96 ppm), corresponding to a calculated free M P of 0.83 and 0.95 mM, respectively. Phosphccreatine Tz (Carr-Purcell, spin-echo pulse sequence) was no different with M e $ in muscle in vivo (surface coil) (M$+$ 136, control 142 ms) or in isolated perfused hearts (Helmholtz coil) (control 83, M e $ 92 ms). 3'P NMR is severely limited in its ability to detect dietary magnesium depletion in vivo. Measurement of j3-ATP shift in brain may allow studies of the effects of interaction in group studies but does not allow prediction of an individual magnesium status.