Automated microfluidic processing platform for multiplexed magnetic bead immunoassays

A microfluidic platform is presented which fully automates all incubation steps of a three-stage, multiplexed magnetic bead immunoassay, such as the Luminex^? xMAP technology. Magnetic actuation is used to transfer the microbeads between co-infused adjacent laminar flow streams to transport the beads into and out of incubation and wash solutions, with extended incubation channels to allow sufficient bead incubation times (1–30?min, commonly 5?min per stage) to enable high-sensitivity. The serial incubation steps of the immunoassay are completed in succession within the device with no operator interaction, and the continuous flow operation with magnetic bead transfer defines the incubation sequencing requiring no external fluidic controls beyond syringe pump infusion. The binding kinetics of the assay is empirically characterized to determine the required incubation times for specific assay sensitivities in the range 1?pg/ml to 100?ng/ml. By using a Luminex^? xMAP duplex assay, concurrent detection of IL-6 and TNF-α was demonstrated on-chip with a detection range 10?pg/ml to 1?ng/ml. This technology enables rapid automation of magnetic microbead assays, and has the potential to perform continuous concentration monitoring.     

Monitoring and control of biogas desulphurization using oxidation reduction potential under denitrifiying conditions

BACKGROUND: Hydrogen sulphide (H₂S) present in biogas can be oxidized to elemental sulphur (S₀) or sulphate (SO₄^2?) using nitrate and nitrite. Both nitrate and nitrite are normally available in most wastewater treatment plants and could be used to oxidize H₂S depending on the molar loading ratio of wastewater and biogas. A control approach is required in order to minimize the fluctuations in inlet and outlet H₂S concentrations in biogas, and the oxidation potential of the wastewater used. RESULTS: A control scheme has been developed for biogas desulphurization using oxidation reduction potential under industrial conditions. The redox potential was maintained at about + 50 to + 100 mV in the activated sludge plant to monitor the performance of the nitrification process. The redox potential in the bioscrubber was related to sulphide removal from biogas. More than 90% of the hydrogen sulphide was removed from the biogas. CONCLUSION: The oxidation reduction potential can be used as a key parameter for monitoring and controlling biogas cleaning. Fluctuations of the inlet H₂S concentration in biogas can be compensated by manipulating the flowrates of wastewater used in order to achieve consistent and desired H₂S concentrations in treated biogas. Copyright © 2011 Society of Chemical Industry     

Effect of synthesis parameters on the electrical conductivity of polypyrrole‐coated poly(ethylene terephthalate) fabrics

The effects of pyrrole, anthraquinone‐2‐sulphonic acid (AQSA) and iron(III) chloride (FeCl₃) concentrations, reaction time and temperature on the electrical conductivity of polypyrrole (PPy)—coated poly(ethylene terephthalate) (PET) fabrics were investigated. With an increase in both the AQSA and FeCl₃ concentrations, resistivity decreased to a point beyond which higher concentrations led to increased surface resistivity. Erosion of the polymer coating, in dynamic synthesis from continual abrasion, manifested as an exponential increase in the resistance of the coated textile substrate. This was not encountered in static synthesis conditions. Temperature affected the degree of surface and bulk polymerisation. The effect of polymerisation temperature on conductivity was negligible. Conductive polymer coating on textiles through chemical polymerisation enabled a smooth coherent film to encase individual fibres, which did not affect the tactile properties of the host substrate. The optimum FeCl₃/pyrrole and AQSA FeCl₃/pyrrole molar ratios were found to be 2.22 and 0.40 respectively. Copyright © 2003 Society of Chemical Industry     

Negative photoelectric effects in p — TlGaSe2

The report deals with the results obtained while studying the photoelectrical properties of p-TlGaSe₂ crystals at high injection levels. Two phenomena have been recorded and investigated, namely the negative photoconductivity and the negative remanent photoconductivity. The current-voltage, time, spectral, lux, and temperature dependences of the above phenomena have been studied and the mechanisms of these phenomena are suggested. The microprobe studies conducted, have allowed one to establish the presence of selenium inclusions in the form of 200 μm — long cylinders with butt-end diameters from 3 to 10 μm. The effect of these inclusions on the photoelectrical properties of TlGaSe₂ is shown.     

Synthesis of o-phenylenediamine functionalized graphite

Here is reported the synthesis of o-phenylenediamine functionalized graphite (OPDFG) using the phosphorus trichloride surface modified graphite (PCl₃-SMG) and the o-phenylenediamine (OPD). PCl₃-SMG was obtained via chlorophosphorylation of graphite for the study. PCl₃-SMG and OPDFG were analyzed using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). UV-Vis analysis shows that OPDFG have higher absorbance than graphite and PCl₃-SMG. According to FTIR analysis, PCl₃-SMG has –PCl₂ functional groups, which shows that PCl₃ reacts with sp² C-H groups on graphite's edge planes during the formation of PCl₃-SMG. Synthesis of OPDFG can be explained by a replacement reaction of amine groups of OPD with –PCl₂ groups. XRD data show that after modification of graphite with PCl₃ and after amine treatment of PCl₃-SMG, crystallite sizes of PCl₃-SMG and OPDFG decrease. SEM analysis shows that both PCl₃-SMG and OPDFG have layered structures similar to graphite.     

Defects in TlGaSe2

Defects in TlGaSe₂ single crystals have been studied for the first time by the methods of X-ray microanalysis and transmission electron microscopy. A disturbance in the stoichiometry has been established in TlGaSe₂. The thallium and gallium deficiencies amount to 1.54 and 1.12 at.%, respectively, and the selenium excess is 2.7 at.%. An excessive concentration of cation vacancies leads to a helical twisting of dislocations. The dislocation density is 400 to 600 mm^?2.     

Effects of deposition strategies on thermo-mechanical characteristics of inconel 718 deposited region on AISI 1045 substrate with a cantilever structure by LENS process

The residual stress in the vicinity of the deposited region causes failure and excessive deformation of parts fabricated by a DED process. The deposition strategy remarkably affects characteristics of residual stress and deformation of the fabricated part for the case of depositing materials on a thin substrate with a cantilever structure. The goal of this paper is to investigate the effects of deposition strategies on thermo-mechanical characteristics of Inconel 718 deposited region on AISI 1045 substrate with a cantilever structure by a LENS process using finite element analyses. The influence of deposition strategies on temperature and residual stress distributions in the vicinity of the deposited region is examined to obtain appropriate deposition strategies. The effects of appropriate deposition strategies on the deflection and the distortion of the designed model are investigated. Finally, suitable deposition strategies are chosen from the viewpoints of characteristics of residual stress and deformation.

     

DETERMINATION OF CADMIUM,CHROMIUM, LEAD,AND MERCURY IN POLYETHYLENE AND POLYPROPYLENE AFTER XYLENE TREATMENT BY ENERGY DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY

A convenient organic solvent treatment method was developed for the determination of Cd, Cr, Hg, and Pb in polyethylene and polypropylene matrices by energy dispersive X-ray fluorescence spectrometry. The solvent treatment method had many advantages for the fast, simple, and accurate multi-element analysis of these materials. Calibration curves were prepared using organometallic compounds in xylene in the concentration range of 1–80 mg kg^?1. The prepared samples had a homogeneous elemental distribution and good durability. The trueness for the quantification of mentioned elements were checked by using a polyethylene certified reference material. The apparent recoveries of the elements with certified values were in the range of 0.81 (Hg) to 1.14 (Pb). The precision was normally better than 8% RSD, with the exception of Hg (10%). The method detection limits were found to be 12, 24, 12, and 12 mg kg^?1 for Cd, Cr, Hg, and Pb, respectively. Polyethylene and polypropylene samples were analyzed by both the XRF method and the reference technique for comparative purposes. Application of analysis of variance (ANOVA) showed no differences between the mean results. The proposed method could be also applied to several different xylene soluble plastics.     

A study of microwave transmission,reflection, absorption,and shielding effectiveness of conducting polypyrrole films

Microwave transmission, reflection, and absorption behavior and the shielding effectiveness of electrochemically synthesized polypyrrole films with dc conductivities ranging from 0.001 to 50 S/cm are presented. Results show that the electrical conductivity of the doped polypyrrole films has a significant effect on transmission, reflection, and absorption of microwaves. Heavily doped, conducting films were highly reflective, whereas lightly doped, semiconducting films had very high transmission. Intermediate conductivity polypyrrole samples were highly absorptive. The agreement between experimental data and theoretical modeling provided confidence to extend the modeling to include the effect of sample thickness on the transmission, reflection, and absorption properties of films with a wide range of conductivity values, hence, providing valuable information for the design of microwave devices and fundamental understanding of the material properties. A method of measuring the far-field sheilding effectiveness of polypyrrole films is also presented. Results of shielding experiments indicated the potential for such applications. © 1994 John Wiley & Sons, Inc.