A new PVC-activated charcoal fiber coated on silver wire; application in determination of n-alkanes in the headspace of soil samples by SPME-GC.
(57/1192)
In this study, a new solid phase microextraction (SPME) fiber based on activated charcoal and polyvinyl chloride (PVC) coated on silver wire is presented. This fiber is very mechanically and thermally stable. Unlike commercial fiber, which is coated on fused silica, this fiber has a metallic base to which the coating adheres very strongly. On the other hand, producing this fiber is very fast, and can be completed in less than 30 min. This compares favorably with the time to make a fiber based on fused silica, which may last several days, due to many steps, such as conditioning in HCl, drying, deactivation, impregnation with a binder and coating. Also, this fiber is stable up to 250 degrees C. It has been successfully used for the analysis of n-alkanes in the gaseous phase and headspace of soil samples after optimization of the experimental parameters by capillary gas chromatography. The relatively high capacity of the sorbent allows 20-30% of the analytes to be transferred to a separative system during first extraction. (+info)
Structure and innervation of extraocular muscles of Carassius.
(58/1192)
The extraocular muscles of the carp Carassius contain two types of muscle fibre. Large white fibres have ribbon-shaped peripheral myofibrils and triads located at the Z line. Small red fibres, rich in mitochondria, have polygonal-shaped myofibrils and triads at the A-I junction. Silver- and cholinesterase-stained preparations show that the large fibres are innervated by axons which spiral around them and exhibit intense cholinesterase activity over long distances. Axons supplying small muscle fibres run across bundles of fibres, making one contact with each fibre. By electron microscopy the nerve endings on each fibre type appear identical, both having a smooth post-junctional muscle membrane. The differences in structure and innervation pattern of the two fibre types are discussed in relation to their possible functional roles. (+info)
Array-based electrical detection of DNA with nanoparticle probes.
(59/1192)
A DNA array detection method is reported in which the binding of oligonucleotides functionalized with gold nanoparticles leads to conductivity changes associated with target-probe binding events. The binding events localize gold nanoparticles in an electrode gap; silver deposition facilitated by these nanoparticles bridges the gap and leads to readily measurable conductivity changes. An unusual salt concentration-dependent hybridization behavior associated with these nanoparticle probes was exploited to achieve selectivity without a thermal-stringency wash. Using this method, we have detected target DNA at concentrations as low as 500 femtomolar with a point mutation selectivity factor of approximately 100,000:1. (+info)
Effects of Sn, Ga, and In additives on properties of Ag-Pd-Au-Cu alloy for ultra-low fusing ceramics.
(60/1192)
Nine 35% Ag-30% Pd-20% Au-15% Cu alloys containing 2, 4 and 6 mass% of Sn, Ga or In as an additive metal were experimentally prepared to investigate the effects of different additives and their content on the physical and mechanical properties as well as the bond with a ultra-low fusing ceramic. Both the different additives and their content or either of these two factors significantly influenced most of the evaluated properties except for the area fraction of the retained ceramic. Based on the evaluated properties three experimental alloys (2% Sn-added alloy, 4% Ga-added alloy and 2% In-added alloy) can be recommended as a suitable alloy for ceramic-metal restorations using ultra-low fusing ceramics. (+info)
Using multimodal ligands to influence network topology in silver(I) coordination polymers.
(61/1192)
A range of Ag(I) one- and two-dimensional coordination frameworks has been prepared and structurally characterized by using the multimodal ligand 3,6-di-pyrazin-2-yl-(1,2,4,5)-tetrazine, which offers both monodentate and chelating binding sites. It is demonstrated that multimodal ligands can be used to prepare coordination frameworks with novel and unusual topologies and to influence the precise geometrical arrangement of both ligands and metal centers within such supramolecular arrays. (+info)
Inhibition of the plastidial phosphatidylcholine synthesis by silver, copper, lead and mercury induced by formation of mercaptides with the lyso-PC acyltransferase.
(62/1192)
Plastids greatly rely on the import of extraplastidial precursors for the synthesis of their own lipids, and several studies have shown that a lyso-PC acyltransferase located in the envelope may be involved in the import process. Because the presence of heavy metals in soil or in nutrient solutions induces changes in the lipid composition of plastid membranes (and therefore greatly reduces the photosynthetic capability of plants), we analysed the effect of several metal salts on plastidial lyso-PC acyltransferase activity. Among the 12 heavy metals studied, silver, copper, mercury and lead inhibited this activity. Metal bound to the enzyme was not - or only very slightly - released from the protein except when thiol-reducing agents (and not imidazole) were added. The results strongly suggest that the inhibitory effect is due to a formation of mercaptide between metal and cysteine(s). The relationship between the inhibition of the plastidial lyso-PC acyltransferase activity and the in vivo effects of metal salts on the plastid membranes is discussed. (+info)
Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier.
(63/1192)
A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated. (+info)
Rapid diagnosis of M. tuberculosis using a piezoelectric immunosensor.
(64/1192)
A piezoelectric immunosensor was developed for detecting Mycobacteria Tuberculosis (M. TB). Protein A was modified onto a silver-coated piezoelectric quartz-crystal sensor. Antibodies could be bond onto the crystal surface in an ordered orientation through protein A. An impendence analyzer was employed to record the admittance-frequency curve. The experimental results showed a successful and less-rigid bonding of protein A and antibodies. Compared with other traditional detection methods of TB, the method suggested in this paper was sensitive, selective and effective. The nonspecific response was limited by using control antibody-rabbit anti-honey bee venom (anti-HBV). A glycine-HCI buffer solution (pH = 2.4) was used to release antibodies from a crystal coated with protein A, and 0.5 mg/mL anti-TB was used to remove TB from a crystal that was bonded by an antibody. Good reusability was exhibited. Spike samples of sputum and saliva from normal people with and without adding M. tuberculosis were diagnosed using the proposed method. Good results were obtained. (+info)