Cleaning Step Research Articles

A Miniaturized DNA Amplifier: Its Application in Traditional Chinese Medicine

A Si-based miniaturized device for the polymerase chain reaction (PCR) has been developed. The device has Pt temperature sensors and heaters integrated on top of the reaction chamber for real-time accurate temperature sensing and control. Reaction temperature of the device is digitally controlled to achieve a temperature accuracy of +/-0.025 degrees C. The effects of PCR protocol optimization on the amplification performance of the surface-passivated chip reactor have been investigated in detail and quantitatively compared with that of the conventional thermal cycler. In this study, four traditional Chinese medicine genes including Fritillaria cirrhosa, Cartharmus tinctorius, Adenophora lobophilla, and Stephania tetrandra are used as model template. With appropriate chamber surface treatment (chlorotrimethylsilane/polyadenylic acid or SiO2 coatings), the device demonstrates amplification as efficient as that in the conventional thermal cycler at optimized MgCl2 concentration. The amplified DNA has concentration higher than 27 ng/microL, which is sufficient for subsequent on-chip analyses and detection. Experimental results reveal the importance of inclusion of BSA for an efficient amplification in the SiO2-passivated device and the excellent reusability of the device with a simple cleaning step.

Corrosion performance of environmentally acceptable alternatives to cadmium and chromium coatings: Chromium—Part II

Summary Corrosion data exist for a wide range of coating materials deposited by different techniques; however, as mentioned earlier, not all coating data can be compared directly because of variations in substrate material and surface preparation, the use sometimes of bond coatings and intermediate layers, the deposition parameters, coating thickness, coating porosity and surface finish, the use sometimes of posttreatmnts, the type of corrosion test performed, test conditions (e.g., solution concentration, temperature, pH, agitation), and interpretation and reporting of the results. With this caveat in mind much of the data presented in this paper has been collected together for convenience as Table X. To compare different coatings, as part of a selection process for a given application, the text (and original sources, if necessary) should be consulted for details of how the coatings were prepared and the tests performed to obtain the given data. In general it seems that there are a number of nickel and cobalt containing alloys, as well as a few inorganic (e.g., SiO2) and organic (e.g., DLC) coatings, that perform very well in terms of corrosion resistance. In the selection of substitutes for decorative and functional chromium coatings the following points should be taken into consideration. o 1. Besides corrosion resistance, other properties may be important and should be taken into account (e.g., hardness, wear resistance, appearance/color). 2. Electrolytic and electroless coating techniques are useful but usually require a postdeposition heat treatment to remove any occluded hydrogen: the heat treatment often modifies the properties of the coating and can affect substrate properties. 3. Coatings applied by “dry” techniques, such as PVD and HVOF thermal spraying avoid any problems with hydrogen embrittlement (unless the substrate pretreatment includes an acid cleaning or activation step). 4. Diffusion/cementation coating techniques can provide thick, adherent coatings on parts with simple geometries, but cannot be used for heatsensitive substrate materials (e.g., high strength steels). 5. Constituents of alloy coatings can be susceptible to preferential attack in aggressive environments, but this may be used to advantage for stripping coatings. 6. The salt fog test, although providing results in a short time period, cannot be related to in service use in most cases: a cyclic corrosion test is becoming more popular and field tests are the most informative if sufficient exposure time is available. Finally, there is no single substitute that meets all the desirable performance characteristics of chromium. Many original equipment manufacturers in the automotive, aerospace, appliance, furniture, plumbing, and architectural hardware industries, for example, have researched alternative coatings and have chosen their preferred solutions, such as electroless Ni-P, electroplated Sn-Ni alloys, and WC-Co coatings, for specific applications. Investigations continue, however, especially in the defense industrial base, where existing specifications or mission safety requirements make substitution more difficult, and because alternatives containing nickel may not be acceptable. The latter metal is included in the list of 17 high-priority chemicals for voluntary reduction published by the EPA.

Assessment of copper contamination impact on inter-level dielectric reliability performed with time-dependent-dielectric-breakdown tests

Time-Dependent-Dielectric-Breakdown (TDDB) tests have been conducted on differently copper-contaminated Metal-Oxide-Silicon (MOS) capacitors in which the insulator was the same as the interconnects Inter-Level Dielectric (ILD). TDDB tests are particularly sensitive in addressing the properties of Cu-contaminated dielectric and they are suitable for the characterization of diffusion barrier layers for Cu based intconnects. The lifetime dependence of ILD on Cu contamination clearly shows that the lost of insulating performances can be a new degrading mechanism related to Cu-based interconnects. It is also shown that technological process steps could impact the reliability of Cu interconnects: without effective cleaning steps any effort made in providing strong diffusion barrier could vanish.

Lessons learned in preparing method 29 filters for compliance testing audits.

Companies conducting compliance testing are required to analyze audit samples at the time they collect and analyze the stack samples if audit samples are available. Eastern Research Group (ERG) provides technical support to the EPA's Emission Measurements Center's Stationary Source Audit Program (SSAP) for developing, preparing, and distributing performance evaluation samples and audit materials. These audit samples are requested via the regulatory Agency and include spiked audit materials for EPA Method 29-Metals Emissions from Stationary Sources, as well as other methods. To provide appropriate audit materials to federal, state, tribal, and local governments, as well as agencies performing environmental activities and conducting emission compliance tests, ERG has recently performed testing of blank filter materials and preparation of spiked filters for EPA Method 29. For sampling stationary sources using an EPA Method 29 sampling train, the use of filters without organic binders containing less than 1.3 microg/in.2 of each of the metals to be measured is required. Risk Assessment testing imposes even stricter requirements for clean filter background levels. Three vendor sources of quartz fiber filters were evaluated for background contamination to ensure that audit samples would be prepared using filters with the lowest metal background levels. A procedure was developed to test new filters, and a cleaning procedure was evaluated to see if a greater level of cleanliness could be achieved using an acid rinse with new filters. Background levels for filters supplied by different vendors and within lots of filters from the same vendor showed a wide variation, confirmed through contact with several analytical laboratories that frequently perform EPA Method 29 analyses. It has been necessary to repeat more than one compliance test because of suspect metals background contamination levels. An acid cleaning step produced improvement in contamination level, but the difference was not significant for most of the Method 29 target metals. As a result of our studies, we conclude: Filters for Method 29 testing should be purchased in lots as large as possible. Testing firms should pre-screen new boxes and/or new lots of filters used for Method 29 testing. Random analysis of three filters (top, middle, bottom of the box) from a new box of vendor filters before allowing them to be used in field tests is a prudent approach. A box of filters from a given vendor should be screened, and filters from this screened box should be used both for testing and as field blanks in each test scenario to provide the level of quality assurance required for stationary source testing.

Analysis of phenolic compounds in the evaluation of commercial quince jam authenticity.

The phenolic compounds present in 17 samples of Portuguese commercial and three homemade quince jams were analyzed by reversed-phase HPLC/DAD, to determine their authenticity. Two different extraction methods were needed for the complete definition of quince jams profiles, one of them including an Amberlite XAD-2 cleaning step. These analyses showed that all the samples presented a similar profile composed of at least eight identified phenolic compounds, several unidentified characteristic procyanidin polymers, and sodium benzoate as preservative of quince jams. Several samples also contained arbutin, suggesting that these quince jam samples were fraudulently adulterated with pear puree.

Real-time spectroscopic ellipsometry for III–V surface modifications Hydrogen passivation, oxidation and nitridation by plasma processing

Passivation of GaAs surfaces through an initial cleaning step by hydrogen plasmas followed by the formation of an oxide layer by UV-light-assisted oxygen plasma anodization or by the formation of a wide gap GaN layer by N 2 plasma nitridation is presented. The emphasis is on the chemical and microstructural modifications which surfaces undergo during the above passivation processes. In situ spectroscopic ellipsometry is used to monitor the surface in real-time. Specifically, the H 2 remote plasma is operated at 230°C to remove native oxide from GaAs and InP surfaces. Real-time ellipsometry well discriminates the cleaning end-point, the structural damage and the passivation of shallow defects operated by H-atoms, so explaining the observed change of the photoluminescence intensity as a function of hydrogen exposure. O 2 plasma anodization carried out at 130–250°C under UV-light irradiation of the sample is able to change the chemistry of the growing GaAs oxide layer, in that an As 2O 5-rich oxide with reduction of elemental arsenic is obtained. Segregation of As at the GaAs surface is also encountered during N 2 plasma nitridation of GaAs to form a GaN passivating layer. This problem is overcome by low-temperature (250–350°C) nitridation of GaAs with N 2–H 2 plasmas. An attempt is made to correlate the surface chemistry as determined by ellipsometry with the Fermi level unpinning as determined by X-ray photoelectron measurements.

Comparative analytical quantitation of clenbuterol in biological matrices using GC-MS and EIA.

A simple and sensitive procedure utilizing GC-MS for the identification and quantitation of clenbuterol in biofluids and tissues is described. This improved method utilizes trimethylboroxine for the derivatization of clenbuterol, requires only 1 mL/g of biological sample, and most importantly does not require an extra cleaning step for urine specimens prior to extraction. Linear quantitative response curves have been generated for derivatized clenbuterol over a concentration range of 5-200 ng/mL. The extraction efficiency at four representative points of the standard curve exceeded 90% in both specimen types (plasma and urine). Linear regression analyses of the standard curve in both specimen types exhibited correlation coefficients ranging from 0.997 to 1.000. The Limit of detection (LOD) and Limit of quantitation (LOQ) values for plasma specimens were determined to be 0.5 and 1.5 ng/mL respectively. For urine specimens, LOD and LOQ values were 0.2 and 0.7 ng/microL respectively. Percentage recoveries ranged from 91 to 95% for urine and 89 to 101% for plasma. Precision and accuracy (within-run and between-run) studies reflected a high level of reliability and reproducibility of the method. In addition to its reliability, sensitivity and simplicity, this modified procedure is more efficient and cost effective, requiring less time, only 1 mL of sample, and minimal amounts of extraction solvents. The applicability of the method for the detection and quantitation of clenbuterol in biological tissues of rats treated with the drug was demonstrated successfully. For comparative analysis of clenbuterol in plasma and liver samples, both GC-MS and enzyme immunoassay (EIA) methods are found to be suitable. Due to potential antibody-cross reactivity with EIA, the GC-MS method is the method of choice for most samples because of its specificity. However, the EIA method is considered the method of choice for analysis of clenbuterol found in concentrations below the limits of quantitation by GC-MS due to its sensitivity.

High-quality GaAs on Si substrate by the epitaxial lift-off technique using SeS2

In this letter, we demonstrate the realization of strong bonding between GaAs epilayers on Si substrates by using selenium sulphide (SeS2) compound. After bonding, the sample has been transplanted to Si substrate using the epitaxial lift-off process. Such a transplanted film was found to be very smooth and adhered well to Si. The resulting chemical bond was covalent in nature, robust, and withstood clean room processing steps. The film bonded in this manner exhibited very good photoluminescence and high crystal quality by double crystal x-ray diffraction. The double crystal x-ray diffraction had a low full width at half maximum of 44 arcsec, and the strain was absent in these types of heterostructures. The interfacial chemical reaction and bonding were studied by depth profile x-ray photoelectron spectroscopy. It was concluded that Ga–Se and Si–S phases such as Ga2Se3 and SiS2 were responsible for the strong bonding between GaAs and Si.

The development of a draft protocol for the sampling and analysis of particulate and organic contaminants in the gas from small biomass gasifiers

A number of companies have developed, and are developing, power generation technology based on the gasification of biomass. These technologies have three process steps: the gasification reactor, cleaning of the producer gas, and an engine generator set. The producer gas from all gasification reactors contains particulates and organic contaminants (tars) which, if not removed, would damage the engine or incur an unacceptable level of maintenance. The efficiency of the gas cleaning step is therefore fundamental to the successful operation of this technology. A number of different sampling and analysis methods have been used by manufacturers and other workers in this field to determine the level of particulates and organic contaminants in the gas exiting the gas cleaning system. This diversity of methods makes the comparison of operating data from different sources very difficult. This represents a significant barrier to the further development and commercialisation of the technology. The members of the Gasification Task of the IEA Bioenergy Agreement, the US DoE and DGXVII of the European Commission have been aware of this barrier for some time. To address it they called a joint meeting in Brussels, Spring 1998, where it was decided to develop two sampling and analysis protocols that could be used as reference methods for further work. One protocol would be used for small scale, fixed bed, engine based systems and the other for larger utility scale plant. The meeting delegated the preparation of the protocols to two working groups, one for each scale of operation. The goal is for these groups to progress the two protocols within a short time to a status that is sufficiently developed to enable work to start on the preparation of US and EU standards. This report details the initial discussions and conclusions reached by the working group for the small scale protocol. In principle, the group decided that a method similar to that used for sampling PAHs in stack gas would be appropriate. The main elements of the system would be an isokinetic probe for sample extraction, a heated filter for particulate collection, a water condenser and a series of impingers, containing cooled solvent to collect the organic contaminants. The group felt that the method should include both gravimetric and chromatographic determinations of the concentration of organic contaminants. Dichloromethane was selected by the group as the solvent that would be used for all aspects of the method. However, at this stage, there remains some uncertainty over this selection. To resolve this and other uncertainties a programme of work is described that will progress the protocol to a stage where procedures could be started to adopt it as a European and US standard. The report is structured in three sections. Section 1, the Working Group Report, documents the discussions of the working group and wider meeting. Section 2 is a draft protocol. The protocol is necessarily in a preliminary form at present but will be updated successively as a result of further work and consultations. Section 3 contains calculations for typical equipment items and procedures.

The electronic passivation properties of Si nanoislands on GaAs(110) step defects induced by cleaving

Scanning tunneling microscopy and spectroscopy (STS) have been used to investigate submonolayer Si depositions on clean cleaved GaAs(110). These studies focus on the effect of cleaving-induced step defects on GaAs(110), the resultant Si overlayer formation, and the electrical properties of the substrate/overlayer system formed at 280 °C. STS measurements at a clean step edge on GaAs(110) show that the Fermi level shifts towards midgap for both n and p type, while measurements performed on Si nanoislands at step edges show that the Fermi level reverts back towards its “ideal” position. Results indicate the passivation properties of Si on GaAs(110) when deposited under these conditions. Implications for use in laser facets are discussed.

Precise Th/U-dating of small and heavily coated samples of deep sea corals

Marine carbonate skeletons like deep-sea corals are frequently coated with iron and manganese oxides/hydroxides which adsorb additional thorium and uranium out of the sea water. A new cleaning procedure has been developed to reduce this contamination. In this further cleaning step a solution of Na 2EDTA (Na 2H 2T B) and ascorbic acid is used which composition is optimised especially for samples of 20 mg of weight. It was first tested on aliquots of a reef-building coral which had been artificially contaminated with powdered ferromanganese nodule. Applied on heavily contaminated deep-sea corals (scleractinia), it reduced excess 230Th by another order of magnitude in addition to usual cleaning procedures. The measurement of at least three fractions of different contamination, together with an additional standard correction for contaminated carbonates results in Th/U-ages corrected for the authigenic component. A good agreement between Th/U- and 14C-ages can be achieved even for extremely coated corals.

Electroless Gold Plating of 316 L Stainless Steel Beads

This paper describes an electroless gold plating process for particulate 316L stainless steel. The process is based on a mildly acidic gold sodium thiosulfate/ascorbic acid plating solution and is performed under an inert environment at room temperature. The process affords a gold deposition efficiency of ∼50% as inferred from a modified tin chloride based spectrophotometric assay for gold ion concentration. Successful gold deposition depended on the removal of the thin, passivating surface oxide layer on the stainless steel; this was accomplished by an initial cleaning step with 2 M HCl. In situ cyclic voltammetry experiments on a stainless steel electrode and atomic force microscopy scans on small coupons were used to further characterize the oxide removal and gold deposition reactions. © 1999 The Electrochemical Society. All rights reserved. ©2001 American Geophysical Union

Optimization of commercial zirconic acid based pretreatment on hot-dip galvanized and Galfan coated steel

Abstract The influence of a commercial zirconic acid based pretreatment has been investigated on hot-dip galvanized and Galfan coated steel. The studied pretreatment system includes two alkaline cleaning steps, an alkaline oxidation and a zirconic acid based after rinse. The optimum conditions for the after rinse were tested by varying the rinse parameters such as treatment time, temperature, solution concentration and pre- and postdrying of panels. The pretreated panels were characterized by using electron spectroscopy for chemical analysis (ESCA), glow discharge optical emission spectroscopy (GD-OES) and contact angle measurements. Pretreated panels were also clear coated and corrosion resistance of the coated panels was tested. The results show that, for the two lowest solution concentrations, time and temperature are the most important treatment parameters. They affect the amount of zirconium adsorbed in the conversion coating, but are less important for the highest solution concentration. The highest level of zirconium on the samples is obtained with the intermediate concentration, in combination with the longest treatment time and highest temperature. According to peak positions in the ESCA spectra, the Zr adsorbed is mainly in the form of ZrO2. GD-OES depth profiles show that the zirconic acid based pretreatment has reacted to different depths in the studied zinc coated steel strip materials. The trend in the corrosion resistance is similar for both substrates. According to contact angle measurements the initial pretreated surface is wetting and hydrophilic in nature. The pretreated surface was also found to age rapidly.

Applications of total reflection X-ray fluorescence to analysis of VLSI micro contamination

This paper demonstrates the microcontamination analysis on wafers after they have been through the conventional ULSI processing steps, by using the vapor phase decomposition/total reflection X-ray fluorescence (VPD/TXRF) technique. It was found that the wafer location in the holding cassette during the chemical cleaning step affected the cleanness of the wafer, and the class 1 environment was not enough to keep the wafer to a contamination level below 5/spl times/10/sup 9/ atoms/cm/sup 2/ for three days storing. The breakdown characteristic of a gate oxide was shown to be closely related with the cleanness of the surface of the oxide.

A Multidimensional Code for Isothermal Magnetohydrodynamic Flows in Astrophysics

We present a multidimensional numerical code to solve isothermal magnetohydrodynamic (IMHD) equations for use in modeling astrophysical flows. First we have built a one-dimensional code which is based on an explicit finite-difference method on an Eulerian grid, called the total variation diminishing (TVD) scheme. The TVD scheme is a second-order-accurate extension of the Roe-type upwind scheme. Recipes for building the one-dimensional IMHD code, including the normalized right and left eigenvectors of the IMHD Jacobian matrix, are presented. Then we have extended the one-dimensional code to a multidimensional IMHD code through a Strang-type dimensional splitting. In the multidimensional code, an explicit cleaning step has been included to eliminate nonzero ∇B at every time step.

Nanofiltration of caustic and acidic cleaning solutions with high COD part 2. Recycling of HNO 3

Nanofiltration is suitable not only for the recovery of alkaline cleaning solutions (as described in Part 1 of this work), but also, in principal, for the recycling of acidic cleaning agents. In the present study the nanofiltration of two spent HNO 3 solutions, coming from the dairy industry, was investigated. One solution had a rather high COD of 18.5 kg/m 3, while the other had 1.8 kg/m 3. The highly contaminated acidic solution had been used before an alkaline cleaning and it was shown that the nitric acid could not be recycled for economic reasons. During the cleaning procedure a large portion of mineral compounds was dissolved, which led to a higher osmotic pressure of the spent solution. Besides having a low flux, the permeate quality (COD = 4.45 kg/m 3) was also not satisfactory. In the case of the second polluted acid, which was applied (as in the most cases) after an alkaline cleaning step, a high retention (COD) of approx. 93% was achieved. The COD in the permeate totalled 0.45 kg/m 3. The average flux was found to be 1.210 −5 m 3/m 2/s. The cross-flow velocity had no influence on the performance of the nanofiltration, whereas the flux climbed linearly with increasing pressure.

Rapid and highly automated determination of adenine and pyridine nucleotides in extracts of Saccharomyces cerevisiae using a micro robotic sample preparation-HPLC system

An ion-pair reversed-phase chromatography method was adapted for the simultaneous separation and quantification of adenine and pyridine nucleotide concentrations in cell extracts of Saccharomyces cerevisiae. Microbial extracts including metabolites, macromolecular constituents and inorganic compounds were loaded onto a ODS pre-column in the presence of triethylamine phosphate (TEA-P i ) resulting in a selective binding of the nucleotides and removing of interfering compounds. After washing the enrichment cartridge with 30 mM TEA-P i buffer, adenine and pyridine nucleotides were eluted with a gradient of Mg(II), the competing hetaeron. This combined cleaning and concentration step leads to remarkable improvement of the detection limit for all nucleotides of interest and column lifetimes. The clean up and separation procedures were performed automatically with a micro robotic-system and a control software package written in PASCAL. The paper reports about the application of the proposed method to separation of adenine and pyridine nucleotides in cells extracts of S. cerevisiae grown anaerobically in a continuous culture ( D=0.1 h −1). Rapidity of analysis, high sensitivity as well as reproducibility of the system and the accurate evaluation of the adenine and pyridine nucleotide concentrations make this method particularly useful for routine analysis.

Influence of ramp shape and morphology on the properties of YBa 2Cu 3O 7− δ-ramp-type junctions

The correlation between the shape and the morphology of ramps prepared by ion-beam etching of YBa 2Cu 3O 7− δ thin films, and the properties of ramp-type junctions were investigated in detail. We examined the influence of different fabrication parameters on the YBa 2Cu 3O 7− δ ramps by atomic force microscopy. Ramp-type junctions were fabricated using PrBa 2Cu 2.9Ga 0.1O 7− δ as barrier material. We observed a strong influence of the shape of the ramp on the homogeneity and, thus, on the transport properties of the junctions. Furthermore, we observed that the roughness of the ramps is strongly influenced by the voltage of the ion-beam during etching. Best results are achieved when an additional wet cleaning step by bromine solution in ethanol is introduced prior to the deposition of the barrier and the top electrode. As a result from our optimization, the on-chip spread of the junction critical current was reduced to 11%.

Laser cleaning of ablation debris from CO 2-laser-etched vias in polyimide

CO 2-laser-drilled vias in polyimide-based flex circuits generate substantial surface debris, requiring new approaches to reduce or eliminate the debris and therefore do away with wet chemical or plasma cleaning steps. A dry laser cleaning process based on a wavelength-tunable CO 2 laser is shown for the first time to effectively remove the ablation debris. Other techniques based on gas flow, pressure control, or ultraviolet lasers, were found ineffective due to the presence of both massive (>10 μm) fibrous debris and submicron (<500 nm) soot. The debris-removal process is driven by disparate mechanisms. The soot is ejected in only ∼5 laser pulses by rapid thermal expansion of the laser-heated polyimide substrate. The removal of fibrous debris develops over many more pulses and involves Fresnel diffraction, surface-rippling phenomena, and multipulse ablation of the debris fragments. The fastest debris cleaning time of 2.5 s per via was provided by the 9R12 laser line at 20 Hz and 0.6 J/cm 2 fluence.

A Previous Study of Phenolic Profiles of Quince, Pear, and Apple Purees by HPLC Diode Array Detection for the Evaluation of Quince Puree Genuineness

An HPLC/DAD methodology for separating 13 phenolic compounds is described. This methodology is applied to the definition of qualitative and quantitative profiles of quince, pear, and apple purees and a blending of these purees. Two different extraction methods were needed for the complete definition of their profiles, one of them including an Amberlite XAD-2 cleaning step. The analysis of phenolics of each fruit puree profile and that of a blending seems to indicate that this methodology can be applied to the detection of apple and/or pear fraudulently added to quince puree. The presence of apple can be detected by phloretin 2‘-xylosylglucoside and phloretin 2‘-glucoside, while that of pear is detected by arbutin. In addition, 3-O-caffeoylquinic acid is present at a considerable relative amount (∼23.4%) in quince puree, while the sample of pear puree contains only 8.2%; this compound is absent in apple puree. Keywords: HPLC; phenolics; quince; purees; adulteration