Pacific Islands: Next to slavery

Workers and crew on board vessels in the Pacific tuna fishery rarely enjoy the right to decent living and working conditions...

On the transition from finite-volume negatively buoyant releases to continuous fountains

An experimental investigation to identify the source conditions that distinguish finite-volume negatively buoyant fluid projectile behaviour from fountain behaviour in quiescent environments of uniform density is described. Finite-volume releases are governed by their source Froude number Fr D and the aspect ratio L/D of the release, where L denotes the length of the column of fluid dispensed vertically from the nozzle of diameter D. We establish the influence of L/D on the peak rise heights of a release formed by dispensing saline solution into fresh water for 0to the determination of Fr D, (L/D) f paired source conditions that give rise to solely Froude-number-dependent, i.e. fountain-like, behaviour. As such, we make the link between finite-volume releases and continuous fountains. The Fr D(L/D) f pairs led us directly to the classification of a Fr D, L/D space from which source conditions giving rise to either negatively buoyant projectiles or fountains may be readily identified. The variation of (L/D) f with Fr D corresponds closely to established fountain regimes of very weak, weak and forced fountains. Moreover, our results indicate that the formation or otherwise of a primary vortex, as fluid is ejected, has a profound influence on the length of the dispensed fluid column that is necessary to achieve rise heights equal to fountain rise heights. © 2012 Cambridge University Press.

Self-assembled multilayer graphene oxide membrane and carbon nanotubes synthesized using a rare form of natural graphite

The fabrication of flexible multilayer graphene oxide (GO) membrane and carbon nanotubes (CNTs) using a rare form of high-purity natural graphite, vein graphite, is reported for the first time. Graphite oxide is synthesized using vein graphite following Hummer's method. By facilitating functionalized graphene sheets in graphite oxide to self-assemble, a multilayer GO membrane is fabricated. Electric arc discharge is used to synthesis CNTs from vein graphite. Both multilayer GO membrane and CNTs are investigated using microscopy and spectroscopy experiments, i.e., scanning electron microscopy (SEM), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), core level photoelectron spectroscopy, and C K-edge X-ray absorption spectroscopy (NEXAFS), to characterize their structural and topographical properties. Characterization of vein graphite using different techniques reveals that it has a large number of crystallites, hence the large number of graphene sheets per crystallite, preferentially oriented along the (002) plane. NEXAFS and core level spectra confirm that vein graphite is highly crystalline and pure. Fourier transform infrared (FT-IR) and C 1s core level spectra show that oxygen functionalities (-C-OH, -CO,-C-O-C-) are introduced into the basal plane of graphite following chemical oxidation. Carbon nanotubes are produced from vein graphite through arc discharge without the use of any catalyst. HRTEM confirm that multiwalled carbon nanotube (MWNTs) are produced with the presence of some structure in the central pipe. A small percentage of single-walled nanotubes (SWNTs) are also produced simultaneously with MWNTs. Spectroscopic and microscopic data are further discussed here with a view to using vein graphite as the source material for the synthesis of carbon nanomaterials. © 2013 American Chemical Society.

One-pot synthesis and self-assembly of colloidal copper(I) sulfide nanocrystals

A simple one-pot method is developed to prepare size-and shape-controlled copper(I) sulfide (Cu2S) nanocrystals by thermolysis of a mixed solution of copper acetylacetonate, dodecanethiol and oleylamine at a relatively high temperature. The crystal structure, chemical composition and morphology of the as-obtained products are characterized by powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The morphology and size of the Cu2S nanocrystals can be easily controlled by adjusting the reaction parameters. The Cu2S nanocrystals evolve from spherical to disk-like with increasing reaction temperature. The spherical Cu2S nanocrystals have a high tendency to self-assemble into close-packed superlattice structures. The shape of the Cu2S nanodisks changes from cylinder to hexagonal prism with prolonged reaction time, accompanied by the diameter and thickness increasing. More interestingly, the nanodisks are inclined to self-assemble into face-to-face stacking chains with different lengths and orientations. This one-pot approach may extend to synthesis of other metal sulfide nanocrystals with different shapes and sizes.

Determination of organophosphate and carbamate pesticides based on enzyme inhibition using a pH-sensitive fluorescence probe

A flow injection system for the determination of organophosphate and carbamate pesticides is described. A sensitive fluorescence probe was synthesized and used as the pH indicator to detect the inhibition of the enzyme acetylcholinesterase (ACNE). The percentage inhibition of enzyme activity is correlated to the pesticide concentration. Several parameters influencing the performance of the system are discussed. The detection limits of 3.5, 50, 12 and 25 mug/l for carbofuran, carbaryl, paraoxon and dichlorvos, in pure water, respectively were achieved with an incubation time of 10 min. A complete cycle of analysis, including incubation time, took 14 min. The detection system has been applied to the determination of carbofuran in spiked vegetable juices (Chinese cabbage and cole), achieving recovery values between 93.2 and 107% for Chinese cabbage juice and 108 and 118% for cole juice at the different concentration levels assayed. (C) 2004 Elsevier B.V. All rights reserved.

Comparison of salt titration and potentiometric titration methods for the determination of zero point of charge

the salt ritration metod was evaluated as a method to determine zpc in comparison with the potentiometric titration method for 26 soil with variable charge clays,i.e.,Oxisols and Ultisols from Thailand and Andisols from Japan. In addition to the determination of ST-pH0 as the zero point of charge, a calculation procedure was adopted here in order to acquire more information from the titration curve . fuithermore, for the purpose of cross-checking of zpc determined by the pt method, the st procedure was successively applied to the samples analyzed by the pt method.

Photochemical synthesis and self-assembly of gold nanoparticles

Colloidal gold was prepared by UV light irradiation of the mixture of HAuCl4 aqueous solution and poly(vinyl pyrrolidone) (PVP) ethanol solution in the presence of silver ions. The resulting sheet-like nanoparticles were found to self-assemble into nanoflowers by a centrifuging process. The results of control experiments reflected that only suitable size sheet-like nanoparticles could assemble into the flower-like structures. The presence of Ag ions and PVP are essential for the formation process of nanoflowers.

Nafion-graphene nanocomposite film as enhanced sensing platform for ultrasensitive determination of cadmium

In this work, an ultrasensitive platform for the detection of cadmium (Cd2+) combining the nafion-graphene nanocomposite film with differential pulse anodic stripping voltammetry (DPASV) analysis was presented. It is found that this sensing platform exhibits enhanced response to the determination of the Cd2+ and has been used to determine the Cd2+ in real sample with good recovery.

PolydA and polyrA self-structured by a europium and amino acid complex

Different DNA selectivity was found for the newly synthesized europium-L-valine complex. Unexpected DNA and RNA selection results showed that europium-L-valine complex can cause single-stranded polydA and polyrA to self-structure. The sigmoidal melting curve profiles indicate the transition is cooperative, similar to the cooperative melting of a duplex DNA. This is different from another europium amino acid complex, europium-L-aspartic acid complex which can induce B-Z transition under the low salt condition. To our knowledge, there is no report to show that a metal-amino acid complex can cause the self-structuring of single-stranded DNA and RNA.

Determination of ranitidine in urine by capillary electrophoresis-electrochemiluminescent detection

The fast analysis of ranitidine is of clinical importance in understanding its efficiency and a patient's treatment history. In this paper, a novel determination method for ranitidine based on capillary electrophoresis-electrochemiluminescence detection is described. The conditions affecting separation and detection were investigated in detail. End-column detection of ranitidine in 5 mM Ru(bpy)(3)(2+) solution at applied voltage of 1.20 V was performed. Favorable ECL intensity with higher column efficiency was achieved by electrokinetic injection for 10 s at 10 kV. The R.S.D. values of ECL intensity and migration time were 6.38 and 1.84% for 10(-4) M and 6.01 and 0.60% for 10(-5) M, respectively. A detection limit of 7 x 10(-8) M (S/N = 3) was achieved. The proposed method was applied satisfactorily to the determination of ranitidine in urine in 6 min.

Chemiluminescence determination of trace ascorbic acid with chromium (VI)-H2O2-luminol system

A new chemiluminescence(CL) system for the determination of ascorbic acid has been established. By the fast reduction reaction between chromium(VI) and ascorbic acid, chromium(M was generated to react with luminol and hydrogen peroxide in alkaline aqueous solution and hydrogen peroxide to produce CL. The CL emission intensity was correlated with ascorbic acid concentration in the range 8.0 x 10(-9) to 1.6 x 10(-4) mol/L, and the detection limit was 8.0 x 10(-9) mol/L ascorbic acid. The relative standard deviation (n = 11) for 1.0 x 10(-6) mol/L ascorbic acid is 0.9%. The method has been applied to the determination of ascorbic acid in vitamin C tablets with satisfactory results.

Determination of 14 rare earth impurities in Y2O3 by petroleum sulfoxide extraction chromatography

Petroleum sulfoxide-NH4SCN extraction chromatography was developed for the separation of Y from other rare earth elements. Some chromatographic parameters were chosen and separation factors between Y and other rare earth elements were determined. A column of resin coated with petroleum sulfoxide was used. The Y in the sample was eluted with NH4SCN, then titrated with EDTA. The recovery was 67%-120% and relative standard deviation +/-4.0%-19.4%. This method can be applied to the determination of trace amounts of rare earth impurities in Y2O3 with a purity of 99.999 9%-99. 999 99%.

Determination of rare-earth impurities in ultra-highly pure Er2O3 and Ho2O3 by [HEH(HEP)] extraction chromatography-atomic emission spectrometry

This article applied [HEH(HEP)] (2-ethyhexyldrogen-2-ethylhexyl phosphonate)extraction chromatography to separate 14 rare earth impurities from ultra-highly pure Er2O3 and Ho2O3, and then the impurities were determined by atomic emission spectrometry. The average percentage recovery for each element is in the range of 70%similar to 140%. The relative standard deviations of the determination are +/-3.3%similar to 2.2%. This method can be applied to the determination of the trace amounts of rare eath impurities in Er2O3 and Ho2O3 with a purity of 99.999 9%-99.999 99%.

Study on the self-packing of SnO2 nanoparticles at the air-hydrosol interface and its composite LB films with arachidic acid

SnO2 nanoparticles were found to self-pack at the air-hydrosol interface and form a nanoparticulate film. The self-packed films were observed under a Brewster angle microscope, and investigated by recording the time evolution of surface pressure and pi-A isotherms. The results show that SnO2 nanoparticles take 3 h to form a complete film at the air-hydrosol interface. Composite monolayers of SnO2 and arachidic acid were obtained by spreading arachidic acid onto a fresh hydrosol surface. Composite Y-type LB films were transferred from the air-hydrosol interface onto substrates, and characterized by FTIR, UV-vis, X-ray diffraction spectroscopy and TEM techniques. The results show that the composite films have good structure, with SnO2 nanoparticles uniformly and compactly distributed in the arachidate matrix. (C) 1998 Elsevier Science S.A. All rights reserved.

Electrochemical study of interactions between DNA and viologen-thiol self-assembled monolayers

We investigated the binding characteristics of double-stranded DNA to self-assembled monolayers (SAMs) containing viologen groups formed on the surface of gold electrodes via Au-S bonds. The positive charged and hydrophobic surfaces of the viologen SAMs modified gold electrodes are suitable to bind strongly dth DNA, whose interactions to solution DNA and adsorbed DNA both lead to positive shifts (22.5 mV and 65 mV, respectively) in the first redox potential ci viologen centers, indicating that the main interaction is from a hydrophobic interaction. Meanwhile, the binding of DNA strongly affects the kinetics of electron transfer of the viologen group so that the separation of anodic and cathodic peak potentials becomes larger and the heterogeneous electron transfer constant becomes smaller.