Pulse Injection Method Research Articles

Scale-up of an electrochemical reactor for treatment of industrial wastewater with an electrochemically generated redox mediator

This paper presents the results of a study on the scale-up, from a batch to a continuous flow unit, of an electrochemical reactor applied for the treatment of textile wastewater. Decolourisation of the wastewater bearing a reactive dye Red Procion H-EXGL proceeded via indirect electro-oxidation, mediated by “active chlorine”. The kinetics of decolourisation in a single-cell reactor under different operating conditions were second order, with the highest apparent rate constant (k = 0.523 l mol−1 s−1) achieved at 40 °C. A low Hatta number (Ha = 0.03) indicated that the reaction occurred totally in the bulk solution, hence homogeneous reaction kinetics were used successively to scale-up a continuous flow electrochemical unit: a once-through filter-press reactor. Its hydrodynamic characteristics were defined by the residence time distribution (E(t)) function using a pulse injection method. The decolourisation efficiency experimentally determined in a continuous flow reactor was further compared with that predicted on the basis of the knowledge of the E(t) of the reactor and the homogeneous phase kinetic expression, obtained from the batch study and corrected for the geometric parameters of the reactors. A complete segregation of the fluid inside the flow reactor was assumed. For different applied flow rates, the experimentally defined conversion of the dye was close to the calculated value.

Use of stirred batch reactors for the assessment of adsorption constants in porous solid catalysts with simultaneous diffusion and reaction. Theoretical analysis

A simple, pseudo-equilibrium model was derived for a catalytic system with a first order chemical reaction and simultaneous diffusive and adsorptive processes, in order to assess the corresponding kinetics and Henry law's-type adsorption parameters. Solutions from this model were compared to exact solutions from a more detailed, general model. It was shown that under most of the experimental conditions used in stirred batch reactors and the usual model considerations, it is only possible to assess apparent adsorption parameters. Also, we observed that a stable relationship between the concentrations in the gas and solid phases is reached. The error produced in assuming that the apparent adsorption constant is the real one was calculated to be very important. The value of the apparent adsorption constant depends on various system properties and experimental conditions, such as the Thiele modulus, the amount of catalyst and the contact time. The ratio between the apparent and real adsorption constants was shown to be the transient effectiveness factor at any moment. This ratio reaches a maximum value for the pseudo-equilibrium state, that is always larger than the steady-state effectiveness factor, becoming closer as long as the system's adsorption capacity decreases. The analysis determines the operative conditions to reduce the parametric correlation. Also a criterion for the applicability of usual approximations in the assessment of kinetics and equilibrium adsorption parameters in porous solid catalysts by means of pulse injection methods is established.

Oxidation behavior of reduced (CeO 2) 1− x-(ZrO 2) x ( x = 0, 0.2, 0.5) catalysts

Oxidation properties of CeO 2-ZrO 2 catalysts were investigated as a function of oxidation temperature by a combination of TPR and O 2 pulse injection methods. Ce 3+ species formed from the CeO 2 phase in the CeO 2-ZrO 2(5/1) catalyst and CeO 2 were very sensitive to oxygen and the amount of oxygen stored was reproducible by the oxidation at temperatures as low as 373 K. However, Ce 3+ species formed in the solid solution of the CeO 2-ZrO 2(1/1) catalyst were relatively stable. The formation of solid solution facilitated the reducibility of Ce 4+ species at low temperature. It was speculated from the titration profile that there were a few steps to oxidize Ce 3+ species distributed from surface to bulk in the CeO 2-ZrO 2(1/1) catalyst.

Single Molecule Visualization of Coordination-Assembled Porphyrin Macrocycles Reinforced with Covalent Linkings

Coordination-assembled porphyrin macrocycles reinforced with covalent bondings were deposited on a metal surface by a pulse injection method, and their scanning tunneling microscopy (STM) images were recorded under ultrahigh vacuum conditions at liquid nitrogen temperature. The decamer ring consisting of 30 porphyrins gave clear circular STM images with hollow structure, whereas that without covalent linking did not give clear circular images, showing that covalent linking of the coordination pairs by ring-closing metathesis reaction was effective to reinforce the supramolecular structure on a metal surface. This strategy will be applicable to a variety of supramolecular assemblies.

Field Demonstration of DNAPL Dehalogenation Using Emulsified Zero-Valent Iron

This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nanoscale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, nonaqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (VOCs) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion.

Ultrahigh vacuum deposition of CdSe nanocrystals on surfaces by pulse injection

The fabrication of thin films of colloidal semiconductor nanocrystals is attracting muchattention due to their exceptional optoelectronic properties. This requires the developmentof new methods for depositing nanocrystals under well-controlled conditions. Here, wereport the use of the pulse injection method to deposit CdSe nanocrystals under ultrahighvacuum (UHV) on clean and well-ordered surfaces. The deposition of nanocrystals has beentested by x-ray photoelectron spectroscopy (XPS) and near edge x-ray absorption finestructure spectroscopy. Special attention has been paid to the preparation of verypure solutions of CdSe nanocrystals using cadmium stearate, trioctylphosphineoxide (TOPO) and the TOP/Se adduct for the nanocrystals synthesis followed bydissolution in pentane. It has been found that CdSe nanocrystals adsorb with similarsticking coefficients on graphite, hydrogenated silicon (100) and hydrogenateddiamond (100) surfaces. Furthermore, the XPS analysis has revealed that thesurface of the CdSe nanocrystal is Cd rich, which has important consequencesfor the optical and chemical properties. This ability to deposit semiconductornanocrystals under UHV conditions on clean and well-ordered surfaces opens up newperspectives for studying in a reliable manner all their chemical, electronic and opticalproperties.

Chiral separation of ketoprofen racemate by using chirex® 3005 and kromasil® CHI-II chiral column

Ketoprofen is a non-steroid anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory and antipyretic properties, of which pharmacological activity has been contributed mainly by the S-ketoprofen enantiomer. To gain highly purified S-ketoprofen enantiomer from ketoprofen racemate, suitable stationary phase was investigated by comparing R-type naphthylglycine and 3,5-dinitrobenzoic acid of Chirex® 3005 and O,O′-bis(4-tertbutyl-benzoyl)-N and N′-diallyl-L-tartardiamide of Kromasil® CHI-II. S-ketoprofen enantiomer was successfully isolated by using the Kromasil column as well as the mobile phase of hexane/tert-butyl methyl ether/acetic acid (v/v)= 60/40/0.1. Equilibrium constants of R-and S-ketoprofen were obtained by pulsed injection method (PIM) at various concentrations of ketoprofen racemate and loading sample amounts, which serve the basic information on overloading sample volume and amounts. A volume of 100 ml containing 3.0 mg of ketoprofen racemate to Kromasil column (250 mm×4.6 mm) resulted in 85% recovery of injected sample under an high concentration (30 mg/ml) feed condition.

Pulse Injection of Conducting Polymers onto H-terminated Si(100) Surfaces

We demonstrated fixing of conducting polymers onto hydrogen-terminated Si(100) surfaces via a pulse valve. The pulse-injected molecules were multiwalled carbon-nanotube, π-conjugated poly(3-hexlthiophene-2,5-diyl), poly(N-tert-butoxycarbonyl diphenylamine-4,4'-diyl), and poly((3-hexylthiophene-2,5-diyl)-co-(diphenyldisulfide-4,4'-diyl)). Each sample was dispersed or dissolved in a certain solvent before pulse injection. In all cases, the isolated molecules were observed by scanning tunneling microscopy. The results indicate that the pulse injection method can be used for fixing and isolating various conducting polymers. [DOI: 10.1380/ejssnt.2004.28]

High-resolution scanning tunneling microscopy imaging of Escherichia coli lysine transfer ribonucleic acid

We have obtained high-resolution scanning tunneling microscopy (STM) images of Escherichia coli lysine transfer ribonucleic acid (tRNA) adsorbed onto Cu(111) substrates using a pulse injection method. One of the two arms of the L-shaped structure of the observed tRNA is longer than the other. Because hydrogen bonds that maintain the unique three-dimensional structure of tRNAs exist in the hinge region and in one arm of L-shaped structures that include the anticodon stem, we concluded that the longer arm in the L-shaped structure includes the anticodon stem, and the shorter arm includes the acceptor stem. This work supports the view that STM is a powerful tool for obtaining high-resolution images of biomolecules that are too difficult to crystallize.

Visualization of detailed structures within DNA

Here we report ultrahigh-resolution scanning tunneling microscopy images of detailed structures within DNA composed of a well-defined base sequence, deposited on substrates using a pulsed injection method. Poly(G–C)–poly(G–C) and poly(A–T)–poly(A–T) have been differentiated by comparing their secondary (helical) structures. We have visualized the structure of poly(A–T)–poly(A–T) with a resolution high enough to recognize individual nucleotides. By comparing the size of individual nucleotides (the primary structure) of poly(A–T)–poly(A–T), sequencing of individual nucleotides can be achieved successfully. These results validate the Watson and Crick DNA model at the single molecule level 50 years after its discovery.

Hot Restartable Electronic Ballast for HID Lamps Based on Immittance Conversion Theory.

Novel electric ballast for HID lamps which can not only supply the stable discharge current but also generate high voltage for initiate its restarting instantaneously is presented. On the restarting process of the HID lamps, the discharging starts at a glow-discharge and changes to stable arc-discharge. However, it is necessary to inject adequate voltage onto the HID lamp depending upon the previous discharging condition. The immittance-conversion elements, which are composed of a coaxial cables, are applied in order to realize above mentioned requirements. Furthermore, multi pulse injection method is presented for quick restarting of the HID lamps. The effectiveness of the proposed circuit is verified through the experimental results on the experimental setup for 75W HID lamp.

Plasma enhanced atomic layer deposition of SrTiO3 thin films with Sr(tmhd)2 and Ti(i-OPr)4

SrTiO 3 (STO) thin films were deposited in the deposition temperature range of 250–350 °C by plasma enhanced atomic layer deposition (PEALD) with Sr(tmhd)2 (tmhd=tetramethyl heptanedionate) and Ti(i-OPr)4 (i-OPr=iso-propoxide) as a precursor. Two precursors were dissolved in tetrahydrofuran, delivered into the vaporizer separately by a newly developed pulse injection method, and the vapor mixture was introduced into the reactor. An argon purge was inserted after the precursor injection and afterward, plasma was generated with the oxygen introduction. Deposition rate was saturated at 0.3–0.4 Å/cycle. Despite the poor volatility of Sr(tmhd)2, SrTiO3 thin films were reproducibly deposited and using plasma activated O2 gas as an oxidant, films could be deposited at low temperature with carbon residue of STO thin films minimized. Step coverage of both SrO and SrTiO3 were above 90% due to the self-limiting growth behavior of atomic layer deposition process.

Single and competitive isotherms of phenol ando-cresol by pulsed-input method

There is a considerable industrial interest in both the scale-up and optimization of chromatographic operations used in the purification of fine chemicals and biomolecules. One of the major factors affecting the adsorption operation is the adsorption isotherm. Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to measure the adsorption isotherm of phenol ando-cresol. From the experimental results, the retention times were decreased with increasing sample sizes, and the front of the peak was very stiff, so Langmuir adsorption isotherm was applied. Also Early-eluting component, phenol, in a mixture of the two components elutes faster than that in a pure component. Pulsed-injection method (PIM) was used to determine the two parameters of the Langmuir isotherm. The resulting parameters, a and b, were used to calculate the elution profiles of phenol ando-cresol in pure and mixed state. The agreement between the experimental data and calculated elution profiles was fairly good in a mixture as well as a pure component.

Base Sequence Dependence of Deoxyribonucleic Acid Studied by Scanning Tunneling Microscopy

In order to identify high-order structures and pitch length of deoxyribonucleic acid (DNA), poly(dA-dT)·poly(dA-dT) and poly(dG-dC)·poly(dG-dC) were adsorbed on Cu(111) substrates by the pulse injection method and were observed by ultra high vacuum (UHV) scanning tunneling microscopy (STM). In large-scale STM images, the high-order structure of poly(dG-dC)·poly(dG-dC) has a higher divergence and shorter dimension compared with those of poly(dA-dT)·poly(dA-dT). High-resolution STM images revealed that the pitch lengths of poly(dA-dT)·poly(dA-dT) and poly(dG-dC)·poly(dG-dC) adsorbed onto the surface were longer than those possessed in the aqueous solution.

Does the Macrostructure of Deoxyribonucleic Acid Molecules Adsorbed on Substrates by the Pulse Injection Method Reflect That in Solution?

In order to investigate whether the concentration-dependent macrostructure of Deoxyribonucleic acid (DNA) molecules can be retained after pulse injection, as compared to that originally present in the aqueous solution, we performed scanning tunneling microscopy (STM) imaging of plasmid DNA pulse-injected from an aqueous solution containing different DNA concentrations. The observed STM images revealed the presence of a relaxed circular macrostructure at low concentrations (1.2 µg/ml of DNA and 0.3 mM of Na+) whereas an entangled circular macrostructure was observed at high concentration (60 µg/ml of DNA and 15 mM of Na+). We conclude that plasmid DNA molecules retain the macrostructures possessed in the aqueous solution even after pulse injection onto a solid surface under vacuum environment.

Rapid Pulse Injection of Indocyanine Green Angiography for Evaluation of Choroidal Venous Circulation

Purpose: To investigate the influence of the injection duration on the early phase of indocyanine green fundus angiography, we performed indocyanine green fundus angiography using a rapid pulse injection method, and compared early-phase findings with those obtained using a previous injection method. Methods: Rabbit eyes were used. Normal eyes (10), eyes with chorioretinal atrophy (5), and eyes with occlusion of vortex veins (5) were examined. Results: In normal eyes, rapid pulse injection resulted in visualization of some small bright fluorescent boluses from 6 to 12 seconds after injection, whereas with the previous method they were unclear. In eyes with occlusion of vortex veins, rapid pulse injection resulted in visualization of delayed hyperfluorescence of choroidal veins against the background, and the region of delayed venous filling could easily be determined. In eyes with chorioretinal atrophy, only the rapid pulse injection clearly revealed delayed filling of choroidal veins. Conclusions: The rapid pulse injection method enabled detection of lesions which were not clearly visible using the previous injection method, and is useful for study of choroidal circulation.

Visualization of DNA by Scanning Probe Microscopy.

Using the pulse injection method, single-stranded DNA and double-stranded plasmid DNA have been deposited on well-defined Cu (111) surfaces under ultra-high vacuum (UHV) condition to obtain high resolution scanning tunneling microscopy (STM) images. These particular UHV-STM images have revealed that DNA molecules are adsorbed directly onto a clean Cu (111) surface, and exhibited the detailed structures of DNA which have not been resolved earlier. The single-stranded DNA oligomers have exhibited the images of individual internal base molecules and helix structures made of complementary base sequence. For the double-stranded plasmid DNA, the images has visualized Watson-Crick double-helix structures.

Ferroelectric Properties of La-doped Bi4Ti3O12 Thin Films deposited directly on Si by pulse-injection MOCVD

Abstract(Bi,La)4Ti3O12(BLT) thin films were prepared on Si(100) substrates by the pulse injection metalorganic chemical vapor deposition (MOCVD) process, in which Ti and La precursors were injected with periodic pauses while Bi precursor was supplied continuously. In case of the pulse injection method, the film composition was relatively uniform and the Bi content at the interface was relatively uniform and the Bi content at the interface was increased. The BLT films, which were deposited by the pulse injection MOCVD, showed better crystallinity and thinner ionterfacial amorphous layer than the continuous BLT films. The continuous BLT films, although measured at 1 MHz showed similar C-V characteristics to those measured at low frequency region, and their flatband voltages also shifted severely to the negative voltage direction. On the other hand, the pulse BLT films exhibited clockwise ferroelectric hysteresis in the C-V curves. The memory window and the leakage current density were about 2V and 1.46×10−7 A/cm2 at 9V (180 kV/cm), respectively.

High-resolution scanning tunneling microscopy imaging of DNA molecules on Cu(111) surfaces

Using the pulse injection method, single-stranded DNA and double-stranded plasmid DNA have been deposited on well-defined Cu(111) surfaces under ultrahigh vacuum (UHV) conditions to obtain high-resolution scanning tunneling microscope (STM) images. These particular UHV-STM images have revealed that DNA molecules are adsorbed directly onto a clean Cu(111) surface and exhibited the detailed structures of DNA, which has not been resolved previously. The single-stranded DNA oligomers have exhibited the images of individual internal base molecules and the helix structures made of complementary base sequences. For the double-stranded plasmid DNA, the images have shown the Watson–Crick double-helix structure.

Relationship between oxidation states of copper supported on alumina and activities for catalytic combustion of NH3

The relationship between the oxidation state of Cu supported on an alumina catalyst (Cu/Al2O3) and the activity for combustion of NH3 was investigated. Combustion of NH3 on the catalyst treated in hydrogen at 800°C occurred at lower temperature than on the catalyst treated in air. It was also much better than Pt and Rh catalysts for the conversion of NH3 to N2. Characteristics of the catalyst were investigated by XRD, XPS, and the N2O pulse injection method to understand the reason of its high catalytic activity. The reason of the high activity of the catalyst treated in hydrogen at the high temperature was attributed to the lower oxidation state of Cu in the catalyst.