Thermal analysis of Ni(II) N-methylimidazole compounds

In this study the thermal decomposition of compounds with the formula Ni(NMIz)_nX₂ (NMIz=N-methylimidazole,n= 6, 4, 2 or 1 andX= Cl, Br or I) has been investigated with the aid of differential scanning calorimetry (DSC), thermogravimetry (TG), evolved gas analysis (EGA) and X-ray powder diffraction in the temperature region 20–500°. The reaction steps were obtained with TG. The intermediate products of the reactions were also confirmed by high-temperature Guinier-de Wolff X-ray photographs.The decomposition enthalpies were calculated from differential scanning calorimetry analysis. The enthalpies were compared with the data from a previous study of the imidazole compounds in order to get more information about the hydrogen bonding in the imidazole compounds. The hydrogen-bonding is stronger for smaller anions and decreases the decomposition enthalpy for imidazole compounds. The decomposition enthalpy ofN-methylimidazole compounds is hardly influenced by the anion size.

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Zusammenfassung In diesen Untersuchungen wird über die thermische Zersetzung von Verbindungen der Formel Ni(NMIz)_nX₂ (NMIz=N-methylimidazol,n=6, 4, 2 oder 1 undX=Cl, Br oder I) mit Hilfe der Differential-Scanning-Kalorimetrie (DSC), der Thermogravimetrie (TG), der Analyse der entwickelten Gase (EGA) und der Röntgenpulverdiffraktion im Temperaturbereich von 20 bis 500° berichtet. Die Reaktionsstufen wurden durch TG erhalten. Die Zwischenprodukte der Reaktionen wurden durch Guinier-de Wolff-sche Hochtemperatur-Röntgenaufnahmen bestätigt.Die Zersetzungsenthalpien wurden aus den Ergebnissen der Differential-Scanning-Kalorimetrie berechnet. Die Enthalpien wurden mit den Angaben aus einer vorangegangenen Untersuchung der Imidazolverbindungen verglichen, um mehr Informationen über die Wasserstoffbindungen in den Imidazolverbindungen zu erhalten. Die Wasserstoffbindung ist für kleinere Anionen stärker und setzt die Zersetzungsenthalpie der Imidazolverbindungen herab. Die Zersetzungsenthalpie derN-Methylimidazolverbindungen wird durch die Grösse des Anions kaum beeinflusst.

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Résumé La décomposition thermique des composés de formule Ni(NMIz)nX₂ (NMIz=N-méthyl-imidazole,n= 6, 4, 2 ou 1 etX= Cl, Br ou I) a été étudiée par analyse calorimétrique différentielle (DSC), thermogravimétrie (TG), analyse des gaz émis (AGE) et diffraction sur poudre des rayons X dans l'intervalle des températures comprises entre 20 et 500°.Les étapes réactionnelles ont été suivies par TG. Les phases intermédiaires formées ont été déterminées par rayons X à hautes températures d'après la méthode de Guinier-de Wolff.Les enthalpies de décomposition ont été calculées à partir des courbes DSC. On a comparé les valeurs ainsi trouvées à celles d'une étude préalable des composés de l'imidazole, afin d'obtenir plus d'informations sur les liaisons d'hydrogène dans les composés de l'imidazole. Les liaisons d'hydrogène sont plus fortes si les anions sont petits et diminuent l'enthalpie de décomposition des composés de l'imidazole. L'enthalpie de décomposition des composés duN-méthyl-imidazole n'est presque pas influencée par la taille de l'anion.

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Ni(NMIz)_nX₂ (NMIz=N-, =6,4,2 1, X=l, r I) , (), 20–500°. . , - -. . . . N- .

     

The transverse energy distribution in hadron-lead collisions

The transverse energy cross-sectiondσ/dE _T has been measured in the pseudorapidity region 0.6<η<2.4 for hadron-lead collisions at 200 GeV/c incident hadron momentum. TheE _T distribution extends to 40 GeV, which is twice the kinematic limit forp-p collisions at the same incident beam momentum. The distribution ofE _T is found to shift towards low pseudorapidities with increasing total transverse energy.     

Starting SCF calculations by superposition of atomic densities

We describe the procedure to start an SCF calculation of the general type from a sum of atomic electron densities, as implemented in GAMESS-UK. Although the procedure is well known for closed-shell calculations and was already suggested when the Direct SCF procedure was proposed, the general procedure is less obvious. For instance, there is no need to converge the corresponding closed-shell Hartree-Fock calculation when dealing with an open-shell species. We describe the various choices and illustrate them with test calculations, showing that the procedure is easier, and on average better, than starting from a converged minimal basis calculation and much better than using a bare nucleus Hamiltonian.     

The Dual of the martingale Hardy space ℋΦ with general Young function Φwith general Young function Φ

[10], ¹ . [4] K _q-, , 1p2 _pp K _q, q=p/p–1)(q=+, p=1 K = ). — p ⊃<<. , , , — , K . , ( ) , q .     

Deposition of conductive TiN shells on SiO<Subscript>2</Subscript> nanoparticles with a fluidized bed ALD reactor

Conductive TiN shells have been deposited on SiO₂ nanoparticles (10–20 nm primary particle size) with fluidized bed atomic layer deposition using TDMAT and NH₃ as precursors. Analysis of the powders confirms that shell growth saturates at approximately 0.4 nm/cycle at TDMAT doses of >1.2 mmol/g of powder. TEM and XPS analysis showed that all particles were coated with homogeneous shells containing titanium. Due to the large specific surface area of the nanoparticles, the TiN shells rapidly oxidize upon exposure to air. Electrical measurements show that the partially oxidized shells are conducting, with apparent resistivity of approximately ~11 kΩ cm. The resistivity of the powders is strongly influenced by the NH₃ dose, with a smaller dose giving an order-of-magnitude higher resistivity.     

Determination of chlormequat in pears by liquid chromotagraphy/mass spectrometry

A straightforward and reliable method was developed for the determination of chlormequat in pears by liquid chromatography/mass spectrometry (LC/MS). Water and methanol were compared as extraction solvents. Because no significant differences in extraction efficiency or repeatability were found, water was chosen as the extraction solvent. The extracts were analyzed without cleanup by either an ion-trap liquid chromatograph/mass spectrometer in the single MS mode or a triple-quadrupole instrument in the MS/MS mode, using electrospray ionization. Both instruments were equally suitable for quantitation and confirmation of identity. Recoveries were 76-103%, and reproducibility was < or = 12%. The lowest detection limit (0.007 mg/kg) was obtained with the triple-quadrupole instrument in the MS/MS mode.     

Determination of polar organophosphorus pesticides in aqueous samples by direct injection using liquid chromatography-tandem mass spectrometry

It was demonstrated that four out of six of the very polar organophosphorus pesticides (OPs), i.e. acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion, could not be extracted from water using commonly available SPE cartridges. In addition, GC analysis on all six compounds was found to be troublesome due to their polar and thermolabile character. This initiated the development of an alternative highly sensitive and selective method for the determination of the above mentioned very polar OPs in water, based on LC-MS. Large volume (1 ml) water samples were directly injected onto an RP18 HPLC column with a polar endcapping. The latter was essential for obtaining retention and maintaining column performance under 100% aqueous conditions during the sampling. The compounds were ionized using atmospheric pressure chemical ionization and detected on a tandem mass spectrometer operated in multiple reaction-monitoring mode. The detection limits were in the range of 0.01-0.03 microg/l. Compared to conventional GC methods, the developed LC-MS procedure is very straightforward, fast and more reliable. This application demonstrates the applicability of LC-MS for analysis of polar OPs in surface, ground and drinking water, as a more favourable alternative to GC.     

Method for HVPE growth of thick crack-free GaN layers

Twenty-five micrometer thick GaN was grown with hydride vapor phase epitaxy (HVPE) on metal-organic chemical vapor deposition (MOCVD) grown templates on sapphire substrates with the gallium treatment step (GTS) technique with varying buffer layer thickness. The samples are studied with atomic force microscopy (AFM), etching and scanning electron microscopy (SEM), photo-luminescence (PL), X-ray diffraction (XRD) and optical microscopy. The results show that the thickness of the buffer layer is not important for the layer quality once the growth in MOCVD starts to make the transition from 3D growth to 2D growth and HVPE continues in the same growth mode. We show that the MOCVD templates with GTS technique make excellent templates for HVPE growth, allowing growth of GaN without cracks in either sapphire or GaN.     

Simultaneous quantification of cyclophosphamide, 4-hydroxycyclophosphamide, N,N',N"-triethylenethiophosphoramide (thiotepa) and N,N',N"-triethylenephosphoramide (tepa) in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry

The alkylating agents cyclophosphamide (CP) and N, N', N"-triethylenethiophosphoramide (thiotepa) are often co-administered in high-dose chemotherapy regimens. Since these regimens can be complicated by the occurrence of severe and sometimes life-threatening toxicities, pharmacokinetically guided administration of these compounds, to reduce variability in exposure, may lead to improved tolerability. For rapid dose adaptations during a chemotherapy course, we have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), for the routine quantification of CP, thiotepa and their respective active metabolites 4-hydroxycyclophosphamide (4OHCP) and N, N', N"-triethylenephosphoramide (tepa) in plasma. Because of the instability of 4OHCP in plasma, the compound is derivatized with semicarbazide (SCZ) immediately after sample collection and quantified as 4OHCP-SCZ. Sample pretreatment consisted of protein precipitation with a mixture of methanol and acetronitrile using 100 microl of plasma. Chromatographic separation was performed on an Zorbax Extend C18 column (150 x 2.1 mm i.d., particle size 5 microm), with a quick gradient using 1 mM ammonia solution and acetonitrile, at a flow-rate of 0.4 ml min(-1). The analytical run time was 10 min. The triple quadrupole mass spectrometer was operating in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges 200-40,000 ng ml(-1) for CP, 50-5000 ng ml(-1) for 4OHCP-SCZ and 5-2500 ng ml(-1) for thiotepa and tepa, using 100 microl of human plasma. These dynamic concentration ranges proved to be relevant in daily practice. Hexamethylphosphoramide was used as an internal standard. The coefficients of variation were <12% for both intra-day and inter-day precisions for each compound. Mean accuracies were also between the designated limits (+/- 15%). This robust and rapid LC/MS/MS assay is now successfully applied for routine therapeutic drug monitoring of CP, thiotepa and their metabolites in our hospital.