Heavy ion induced K,L and M X-rays and their use in trace element analysis

Characteristic K, L and M X-ray and background production trends from high energy heavy ion bombardment were investigated on a series of target elements (14≤Z≤92) using 0.5 MeV/amu and 1 MeV/amu Nⁿ⁺, Oⁿ⁺, Cuⁿ⁺, Krⁿ⁺ and Xeⁿ⁺ beams. X-ray production for K and L shell X-rays roughly followed the same trends, i.e. increased yield with projectile size and energy and decreased yield with increasing X-ray energy. Broad simultaneous multielement coverage can be achieved using K, L and M Lines. Experimental detection limits of 0.8 to 10 ppm were obtained for elements between Mn and Se with K X-ray detection, between Sm and Pb using L X-ray detection, and for Th and U via M X-ray detection in biological samples with a 1MeV/amu Kr⁷⁺ beam of 70 nA for 1000 s. These detection limits are better for many elements than those obtained with a 1.65 MeV proton beam.     

Second-order perturbation treatment of dipole—dipole scattering

Using second-order perturbation theory the contribution of the dipole—dipole potential to elastic scattering is calculated in the limit where the energy defect is large making the first-order terms negligible. The results do not agree with the Keesom—Linder potential commonly used to interpret data in this region.     

Synthesis and characterisation of tungsten(VI) oxo-salicylate complexes for use in the chemical vapour deposition of self-cleaning films

Tungsten(VI) oxo-salicylate complexes were prepared in moderate yield (47 to 63%) by the reactions of WOCl4 and two equivalents of either 3-methylsalicylic acid (MesaliH2) or 3,5-di-isopropylsalicylic acid (di-i-PrsaliH2). Performing the reaction in refluxing toluene afforded the two analogous ditungsten complexes 1, [{WO(Mesali)(MesaliH)}2(mu-O)], and 2, [{WO(di-i-Prsali)(di-i-PrsaliH)}2(mu-O)], however in refluxing hexane the mononuclear tungsten complex , [WO(di-i-Prsali)(di-i-PrsaliH)Cl], was isolated. The single crystal X-ray study of revealed a pseudo-octahedral geometry around the tungsten centres. Aerosol assisted chemical vapour deposition of or afforded brown tungsten trioxide thin films. These films were converted to yellow fully oxidised WO3 on annealing in air at 550 degrees C for 30 minutes. The yellow WO3 films demonstrate preferred orientation on the substrate and show interesting functional properties-photo induced hydrophilicity and photocatalytic activity.     

Synthesis of 4'-methyl and 4'-cyano carbocyclic 2',3'-didehydro nucleoside analogues via 1,4-addition to substituted cyclopentenones

Carbocyclic 4'-methyl and 4'-cyano nucleoside analogues were synthesized using the Michael reaction to introduce the 4'-substituent and Pd-catalyzed allylic substitution to introduce the nucleoside base. Use of both the desired beta- and undesired alpha-1'-carbonate diastereomers in the Pd-catalyzed substitution was demonstrated in principle by epimerization of the alpha-diastereomer and kinetic diastereodifferentiation of a 1:1 alpha/beta mixture of 1'-carbonates.     

Gyrotron based on a superconducting magnet

The replacement of conventional pulsed magnetic field coils previously used to generate the intra-cavity B-field with an 11T superconducting magnet is reported. The resulting more stable mm-wave output pulse is shown and the refurbishment requirements of both the field emission, field-immersed, cold cathode and Marx bank spark gaps demonstrated. This system proved to be tunable, oscillating from 20GHz up to 110GHz, with peak power levels of 450kW and 300kW respectively. Other operating parameters were also examined including mm-wave pulse length as a function of anode-cathode position. The pulse length increased from 87±6ns to 310±10ns with a 2.5 cm horizontal transit of the cathode away from the anode. A similar effect was witnessed with the increase of the intra-cavity B-field from 1.00T to 5.00T resulting in the mm-wave pulse duration increasing from 250±40ns. Second harmonic operation of the cavity resulted in 0.5kW of radiation observed at 96GHz. The pulse-to-pulse mm-wave stability coupled with the mode selectivity of the ohmic-Q-dominated cavity resulted in the identification of several oscillating modes including the TE₁₂, cut-off frequency 21.1 GHz, the TE₀₂, cut-off frequency 29.1 GHz, the TE₃₅ at 74 GHz and the TE_14,2, at 88GHz.     

Top Down Tandem Mass Spectrometric Analysis of a Chemically Modified Rough-Type Lipopolysaccharide Vaccine Candidate

Recent advances in lipopolysaccharide (LPS) biology have led to its use in drug discovery pipelines, including vaccine and vaccine adjuvant discovery. Desirable characteristics for LPS vaccine candidates include both the ability to produce a specific antibody titer in patients and a minimal host inflammatory response directed by the innate immune system. However, in-depth chemical characterization of most LPS extracts has not been performed; hence, biological activities of these extracts are unpredictable. Additionally, the most widely adopted workflow for LPS structure elucidation includes nonspecific chemical decomposition steps before analyses, making structures inferred and not necessarily biologically relevant. In this work, several different mass spectrometry workflows that have not been previously explored were employed to show proof-of-principle for top down LPS primary structure elucidation, specifically for a rough-type mutant (J5) E. coli-derived LPS component of a vaccine candidate. First, ion mobility filtered precursor ions were subjected to collision induced dissociation (CID) to define differences in native J5 LPS v. chemically detoxified J5 LPS (dLPS). Next, ultra-high mass resolving power, accurate mass spectrometry was employed for unequivocal precursor and product ion empirical formulae generation. Finally, MS³ analyses in an ion trap instrument showed that previous knowledge about dissociation of LPS components can be used to reconstruct and sequence LPS in a top down fashion. A structural rationale is also explained for differential inflammatory dose-response curves, in vitro, when HEK-Blue hTLR4 cells were administered increasing concentrations of native J5 LPS v. dLPS, which will be useful in future drug discovery efforts.

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3He NMR study of (3)He@C(60)H(6) and (3)He@C(70)H(2)(-)(10)

The (3)He NMR of (3)He@C(60)H(6), (3)He@C(70)H(2), (3)He@C(70)H(4), (3)He@C(70)H(8), and (3)He@C(70)H(10) have been investigated. A new, unidentified C(60)H(6) isomer has been found by using (3)He NMR. (3)He@C(70)H(10) shows the most downfield-shifted (3)He NMR resonance among the neutral C(70) derivatives.