Speciation analysis of arsenic in groundwater from Inner Mongolia with an emphasis on acid-leachable particulate arsenic

Arsenic in drinking water affects millions of people around the world. While soluble arsenic is commonly measured, the amount of particulate arsenic in drinking water has often been overlooked. We report here determination of the acid-leachable particulate arsenic and soluble arsenicals in well water from an arsenic-poisoning endemic area in Inner Mongolia, China. Water samples (583) were collected from 120 wells in Ba Men, Inner Mongolia, where well water was the primary drinking water source. Two methods were demonstrated for the determination of soluble arsenic species (primarily inorganic arsenate and arsenite) and total particulate arsenic. The first method used solid phase extraction cartridges and membrane filters to separate arsenic species on-site, followed by analysis of the individual arsenic species eluted from the cartridges and filters. The other method uses liquid chromatography separation with hydride generation atomic fluorescence detection to determine soluble arsenic species. Analysis of acidified water samples using inductively coupled plasma mass spectrometry provided the total arsenic concentration. Arsenic concentrations in water samples from the 120 wells ranged from <1 to ∼1000 μg L⁻¹. On average, particulate arsenic accounted for 39 ± 38% (median 36%) of the total arsenic. In some wells, particulate arsenic was six times higher than the soluble arsenic concentration. Particulate arsenic can be effectively removed using membrane filtration. The information on particulate and soluble arsenic in water is useful for optimizing treatment options and for understanding the geochemical behavior of arsenic in groundwater.     

Determination of the collisionally activated dissociation of a substituted indole by orthogonal acceleration quadrupole time-of-flight mass spectrometry

The use of orthogonal acceleration quadrupole time-of-flight (Q-TOF) mass spectrometry to determine the collisionally activated dissociation (CAD) of a test compound 1-(3-[5-[1,2,4-triazol-4-yl]-1H-indol-3-yl]propyl)-4-(2-[3-fluorophenyl]ethyl)piperazine is described. At unit-mass resolution the identity of many ions is ambiguous because of the complexity of the resulting product ion spectrum. Using the high resolution capabilities of the Q-TOF instrument, exact masses for each fragment were determined. These data were used to infer molecular formulas for each fragment through software interpretation and, by further applying chemical intuition, the majority of ions were fully assigned. Additionally, by utilizing in-source fragmentation at high cone voltage, analyses of second-generation products allowed derivation of a consistent sequential fragmentation pathway. This study clearly demonstrates the power of Q-TOF mass spectrometry to elucidate complex product ion spectra.     

The adamantane-derived bananins are potent inhibitors of the helicase activities and replication of SARS coronavirus

Bananins are a class of antiviral compounds with a unique structural signature incorporating a trioxa-adamantane moiety covalently bound to a pyridoxal derivative. Six members of this class of compounds: bananin, iodobananin, vanillinbananin, ansabananin, eubananin, and adeninobananin were synthesized and tested as inhibitors of the SARS Coronavirus (SCV) helicase. Bananin, iodobananin, vanillinbananin, and eubananin were effective inhibitors of the ATPase activity of the SCV helicase with IC50 values in the range 0.5-3 microM. A similar trend, though at slightly higher inhibitor concentrations, was observed for inhibition of the helicase activities, using a FRET-based fluorescent assay. In a cell culture system of SCV, bananin exhibited an EC50 of less than 10 microM and a CC50 of over 300 microM. Kinetics of inhibition are consistent with bananin inhibiting an intracellular process or processes involved in SCV replication.     

Multiple-spot optical tweezers created with microlens arrays fabricated by proton beam writing

We report two different applications for using arrays of microlenses on glass substrate to facilitate multiple-spot optical trapping of colloidal microbeads. The array of microlenses was made of SU8 or PMMA resist and created by a combination of Proton-Beam writing followed by thermal reflow processes. Firstly, similar to previous reports [8, 9, 10 ], the lenses were utilized as an optical element in generating multiple laser spot arrays that were subsequently focused down to impose a microbead array. In addition, we demonstrated the feasibility of a novel approach of integrating the microlens array into a sample chamber to provide localized optical trapping. PACS 07.60.Pb; 41.75.Ak; 42.15.Eq; 42.65.Jx; 42.79.Bh     

Efficient delivery of Cre-recombinase to neurons in vivo and stable transduction of neurons using adeno-associated and lentiviral vectors

Background

As development proceeds the human embryo attains an ever more complex three dimensional (3D) structure. Analyzing the gene expression patterns that underlie these changes and interpreting their significance depends on identifying the anatomical structures to which they map and following these patterns in developing 3D structures over time. The difficulty of this task greatly increases as more gene expression patterns are added, particularly in organs with complex 3D structures such as the brain. Optical Projection Tomography (OPT) is a new technology which has been developed for rapidly generating digital 3D models of intact specimens. We have assessed the resolution of unstained neuronal structures within a Carnegie Stage (CS)17 OPT model and tested its use as a framework onto which anatomical structures can be defined and gene expression data mapped.

Results

Resolution of the OPT models was assessed by comparison of digital sections with physical sections stained, either with haematoxylin and eosin (H&E) or by immunocytochemistry for GAP43 or PAX6, to identify specific anatomical features. Despite the 3D models being of unstained tissue, peripheral nervous system structures from the trigeminal ganglion (~300 μm by ~150 μm) to the rootlets of cranial nerve XII (~20 μm in diameter) were clearly identifiable, as were structures in the developing neural tube such as the zona limitans intrathalamica (core is ~30 μm thick). Fourteen anatomical domains have been identified and visualised within the CS17 model. Two 3D gene expression domains, known to be defined by Pax6 expression in the mouse, were clearly visible when PAX6 data from 2D sections were mapped to the CS17 model. The feasibility of applying the OPT technology to all stages from CS12 to CS23, which encompasses the major period of organogenesis for the human developing central nervous system, was successfully demonstrated.

Conclusion

In the CS17 model considerable detail is visible within the developing nervous system at a minimum resolution of ~20 μm and 3D anatomical and gene expression domains can be defined and visualised successfully. The OPT models and accompanying technologies for manipulating them provide a powerful approach to visualising and analysing gene expression and morphology during early human brain development.     

Unintegrated parton distributions and inclusive jet productionat HERA

We describe how unintegrated parton distributions can be calculated from conventional integrated distributions. We extend and improve the last-step evolution approach, and explain why doubly unintegrated parton distributions are necessary. We generalise k _t-factorisation to (z,k _t)-factorisation. We apply the formalism to inclusive jet production in deep-inelastic scattering, mainly at leading order, but we also study the extension to next-to-leading order. We compare the predictions with recent HERA data.Received: 19 June 2003, Published online: 19 September 2003     

The thermal accommodation of helium and argon on a tungsten wire,deduced from the heat lost by the wire

Experimental data are presented on the heat imparted by a polycrystalline tungsten wire of preferred orientation (such that the [110] direction was approximately parallel to the wire axis) to helium and argon at pressures of order 10^?3 torr. Values of the accommodation coefficient (α) are deduced, the temperature of the gases being 300°K and that of the tungsten ranging from 1073 to 1785°K. Over this temperature range the values of α for helium and argon are 0.018 and 0.25 respectively, being virtually independent of the temperature difference between the gases and the tungsten.     

A study of the level properties of 57Co from the (τ, d) reaction on 56Fe

The ⁵⁶Fe(τ, d)⁵⁷Co reaction has been studied at E_τ = 18 MeV using the Tandem Van de Graaff accelerator and the multichannel magnetic spectrograph of the Nuclear Physics Laboratory, Oxford, Angular distributions have been measured for most of the levels up to E_x ≈ 7.8 MeV and are analysed in terms of the DWBA theory of direct reactions. The l_p values and the transition strengths compared with available theories.     

Configurational analysis of rotational states in the SD shell

It is shown that the shell-model states belonging to a given rotational band in ²³Na and ²⁴Mg have very similar subshell occupancies, different bands being characterised by different occupancies. On the one hand this establishes a connection, somewhat different from that provided by the SU (3) scheme, between the spherical shell model and the idea of an intrinsic state, and on the other hand helps discriminate between possible candidates for membership of a band and imposes limits on the lengths of the bands.     

Wasserdampf-Sorption in Jutefasern

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