Removal Of Surface Contaminants Research Articles

Successful analysis of gut contents in fungal-feeding oribatid mites by combining body-surface washing and PCR

The feeding habits of soil mesofauna have been a mystery for decades, and depending on the methods used, different degrees of feeding specialisation have been observed. A new way to study the almost unknown feeding habits of soil mesofauna e.g. oribatid mites is to use PCR-based techniques. When applying PCR on these small organisms, the low amount of ingested DNA can cause problems. Even more important is to certify that the amplified DNA does not originate from body-surface contamination. The aim of this study was to analyse if washing of the body surface combined with PCR can be a successful approach when identifying the food ingested by fungivorous mites. The method was developed in a laboratory system where we used the oribatid mite Archegozetes longisetosus as a model organism due to its relatively short life cycle and ease of laboratory culturing. The results demonstrated that surface contamination is a serious problem. Both washing and dissection was needed to remove surface contamination on such small organisms. To get a reliable result the samples also had to contain at least five pooled guts, but preferably ten. This is the first step towards a successful use of PCR-based methods to study natural feeding habits of species most likely contaminated on the body surface. When modified for field conditions, the results obtained by this method have a high potential to answer many questions about the animals feeding habits, and their functional role in the soil.

A novel surface cleaning method for chemical removal of fouling lead layer from chromium surfaces

Most products especially metallic surfaces require cleaning treatment to remove surface contaminations that remain after processing or usage. Lead fouling is a general problem which arises from lead fouling on the chromium surfaces of bores and other interior parts of systems which have interaction with metallic lead in high temperatures and pressures. In this study, a novel chemical solution was introduced as a cleaner reagent for removing metallic lead pollution, as a fouling metal, from chromium surfaces. The cleaner aqueous solution contains hydrogen peroxide (H 2O 2) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH 3COOH) as chelating agent of lead ions. The effect of some experimental parameters such as acetic acid concentration, hydrogen peroxide concentration and temperature of the cleaner solution during the operation on the efficiency of lead cleaning procedure was investigated. The results of scanning electron microscopy (SEM) showed that using this procedure, the lead pollution layer could be completely removed from real chromium surfaces without corrosion of the original surface. Finally, the optimum conditions for the complete and fast removing of lead pollution layer from chromium surfaces were proposed. The experimental results showed that at the optimum condition (acetic acid concentration 28% (V/V), hydrogen peroxide 8% (V/V) and temperature 35 °C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.

A Theoretical Investigation into the Effect of Laser Parameters on the Surface Cleaning of Ti-6Al-4V

Chemical cleaning has been used for several decades as a surface preparation technique for diffusion bonding. Here we present a theoretical investigation that examines the effect of changes in the process parameters when a laser is used as an alternative to chemical cleaning for surface contaminant removal. Here a theoretical model is described that includes laser beam attenuation in the plasma plume and its effect on evaporation of the material. Using the model, a comprehensive analysis of the effect of different fluences and other parameters for a KrF Excimer laser is presented. Calculations were carried out for a range of peak fluxes from below the ablation threshold to fluxes of the order of 9 x 1012 W/m2. The predicted effects on evaporation, melt depth and surface temperature are reported, illustrated by a number of surface topographic images from preliminary experiments. Finally, optimal parameters for cleaning according to the theoretical investigation are proposed.

Surface treatments toward obtaining clean GaN(0 0 0 1) from commercial hydride vapor phase epitaxy and metal-organic chemical vapor deposition substrates in ultrahigh vacuum

We studied processes of cleaning GaN(0 0 0 1) surfaces on four different types of wafers: two types were hydride vapor phase epitaxy (HVPE) free-standing substrates and two types were metal-organic chemical vapor deposition (MOCVD) films grown on these HVPE substrates and prepared by annealing and/or Ar ion sputtering in ultra high vacuum. We observed the surfaces through treatments using in situ low-energy electron diffraction (LEED), reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and Auger electron spectroscopy, and also using ex situ temperature programmed desorption, X-ray photoelectron spectroscopy, X-ray diffraction, and secondary ion mass spectrometry. For HVPE samples, we obtained relatively clean surfaces under optimized three-step annealing conditions (200 ° C for 12 h + 400 ° C for 1 h + 500 ° C for 5 min) without sputtering, after which the surface contamination of oxide and carbide was reduced to ∼ 20 % of that before annealing. Clear GaN(0 0 0 1) 1 × 1 patterns were obtained by LEED and RHEED. STM images showed flat terraces of ∼ 10 nm size and steps of ∼ 0.5 nm height. Upon annealing the HVPE-GaN samples at a much higher temperature ( > 550 ° C), three-dimensional (3D) islands with facets were formed and the surface stoichiometry was broken down with the desorption of nitrogen in the form of ammonia, since the samples include hydrogen as an impurity. Ar + sputtering was effective for removing surface contamination, however, postannealing could not recover the surface roughness but promoted the formation of 3D islands on the surface. For MOCVD/HVPE homoepitaxial samples, the surfaces are terminated by hydrogen and the as-introduced samples showed a clear 1 × 1 structure. Upon annealing at 500–600 ° C, the surface hydrogen was removed and a 3 × 3 reconstruction structure partially appeared, although a 1 × 1 structure was dominant. We summarize the structure differences among the samples under the same treatment and clarify the effect of crystal quality, such as dislocations, the concentration of hydrogen impurities, and the residual reactant molecules in GaN films, on the surface structure.

Rating the extent of surface scratches on photostimulable storage phosphor plates in a dental school environment

The aims of this study were (1) to subjectively quantify the degree of scratching and smudging that had taken place in the junior clinic in the 9 months following the implementation of digital radiology; (2) to compare the findings with a previously published report; and (3) to identify areas in the protocol and training that can be refined to minimize future scratching and smudging. Seven sets of blank clinical photostimulable storage phosphor (PSP) plates were scanned after exposing them at 65 kV and 7 mA for 0.80 s. Scanned plates were lightly wiped with a soft cloth and alcohol, repackaged in plastic sleeves, re-exposed and rescanned. The two sets of resulting images were subjectively rated independently by two investigators for artefacts and placed in five categories. Of all the images, approximately 75% were rated in the top 3 categories (most readable), leaving 17% and 8% in the poor and unsatisfactory categories, respectively. Mean rated values of the two image sets (before and after wiping) were not statistically different, but ratings slightly improved after cleaning the plates. Wiping all plates to remove surface contamination may not always be necessary or desirable. Systems that are designed to minimize handling of the plates may help minimize scratching of them.

A Theoretical Investigation into the Effect of Laser Parameters on the Surface Cleaning of Ti-6Al-4V

Chemical cleaning has been used for several decades as a surface preparation technique for diffusion bonding. Here we present a theoretical investigation that examines the effect of changes in the process parameters when a laser is used as an alternative to chemical cleaning for surface contaminant removal. Here a theoretical model is described that includes laser beam attenuation in the plasma plume and its effect on evaporation of the material. Using the model, a comprehensive analysis of the effect of different fluences and other parameters for a KrF Excimer laser is presented. Calculations were carried out for a range of peak fluxes from below the ablation threshold to fluxes of the order of 9 x 1012 W/m2. The predicted effects on evaporation, melt depth and surface temperature are reported, illustrated by a number of surface topographic images from preliminary experiments. Finally, optimal parameters for cleaning according to the theoretical investigation are proposed.

The use of power ultrasound energy to support interface formation for structural adhesive bonding

A reliable performance is what the engineers need to take advantage of for the weight-saving potential of adhesive bonded structures. The present paper presents a new approach to ensure improved and quality assured adhesive bonds by using power ultrasound in combination with the adhesive application to support interface formation. In contrast to various known publications in this paper ultrasound is not used at low power-level as for inspection by nondestructive testing (NDT) but to influence interface cleaning and to improve contamination tolerance of the adhesive bonding process. Power ultrasound with an intensity of 10–100 W/cm 2 is used to transfer energy for a short time into the liquid adhesive. The general idea and various advantages for adhesive bonding by supplying energy for the developing adhesive/substrate interface are presented and discussed. Power ultrasound can be used: to remove surface contaminations, to obtain contamination tolerance for the bonding process, to improve substrate wetting, to mix adhesives, to outgas adhesives and the substrate surface or to establish chemical reactions at the interface. Results from adhesive bonded lap shear and roller peel tests with contaminated samples, rheological measurements and pictures from high speed videos demonstrate the effectiveness of the approach.

Transparent conducting ITAZO anode films grown by a composite target RF magnetron sputtering at room temperature for organic solar cells

The preparation and characteristics of AZO co-sputtered ITO (ITAZO) electrodes grown on glass and flexible substrates using a specially designed composite target in organic solar cells are described. It was found that both the electrical and optical properties of the ITAZO films were critically dependent on the Ar/O2 flow ratio and sputtering power. In addition, all ITAZO electrodes show the amorphous structure due to the low substrate temperature. Even though the ITAZO electrode was prepared at room temperature, we can obtain the ITAZO electrode with the sheet resistance of 23 Ω/square (on a glass substrate) and 26 Ω/square (on a flexible substrate) and the average optical transmittance of 87.5% (on a glass substrate) and 86.3% (on a flexible substrate) in the region between 450 and 800 nm wavelength. In addition, the Ar ion treatment of the polyethylene terephthalate (PET) substrate could remove surface contamination and increase the adherence of the ITAZO film with the PET substrate. Furthermore, organic solar cells prepared on the ITAZO electrode under optimized conditions show the typical current density–voltage characteristics with the conversion power efficiency of 3.2%. This indicates that the composite target sputtering technique is a promising sputtering process for transparent conducting electrodes for low-cost solar cell applications.

LCA of strippable coatings and of steam vacuum technology used for nuclear plants decontamination

The application of strippable coatings is an innovative technology for decontamination of nuclear plants and for any decontamination project aiming at removing surface contamination. An adhesive plastic coating is applied on the contaminated surface. The strippable coating is allowed to cure for up to 24 h, after which it can be easily peeled. The coating traps the contaminants in the polymer matrix. Strippable coatings are non-toxic and do not contain volatile compounds or heavy metals. Since the coating constitutes a solid waste, disposal is easier than treating contaminated liquid wastes, produced by the baseline technology: steam vacuum cleaning, based upon superheated pressurized water in order to remove contaminants from floors and walls. A life cycle assessment (LCA) has been carried out with the purpose of comparing the strippable coating with the steam vacuum technology. The functional unit of the study is represented by a surface of 1 m2 to be decontaminated. The results of LCA achieved using Sima Pro 5.0® software confirm the good environmental performances of strippable coatings. Taking into account both LCA and environmental costs for liquid wastes, the advantages of strippable coatings will be more and more evident.

Mechanism of gas absorption enhancement in presence of fine solid particles in mechanically agitated gas–liquid dispersion. Effect of molecular diffusivity

The effect of fine particle addition in physical gas desorption and absorption with fast reaction (sulphite oxidation in the presence of a cobalt catalyst) has been studied in a stirred cell with a flat gas–liquid interface and mechanically agitated gas–liquid bubble dispersion in a wide range of stirring speeds. Activated carbon and TiO 2 were used at low loadings ( 0.5 – 1 kg m - 3 ) . The desorption was used to avoid supersaturation effect which was observed during oxygen and hydrogen absorption into liquid saturated with nitrogen. Using two gases with sufficiently different diffusivity (O 2, H 2), the effect of molecular diffusivity on the mass transfer coefficient was estimated in the form k L ∼ D n , with the exponent n indicating the surface mobility accompanying the effect of the particles. The value n = 2 / 3 indicates a fully rigid and the value 1 / 2 a fully mobile mass transfer interface. Chemisorption experiments confirmed that the particles do not affect mass transfer area of the agitated dispersion. After addition of particles, k L for physical desorption from bubbles in dispersion was increased by 10–30% in water and by 20–60% in sulphate solution with decreasing agitation rate. In the stirred cell, the increases were much higher reaching 200% and 230% for water and sulphate solution, respectively. The exponent n exhibited a significant decrease in the presence of particles ranging from 10% (for dispersion in water) to 33% (for stirred cell in sulphate solution). The decrease in n encountered in dispersion indicated the transition from a partially mobile to a fully mobile surface. The reduction of k L was interpreted through the physicochemical effect of surfactants removal from the gas–liquid interface by activated carbon particles. The results have confirmed that the mechanism of mass transfer enhancement in the presence of fine particles, based on the removal of surface contaminants from the liquid by adsorption onto the hydrophobic surface of the particles, as suggested by Kaya and Schumpe [2005. Surfactant adsorption rather than “shuttle effect”? Chemical Engineering Science 60, 6504–6510] for stirred cell, is valid also for the enhancement of absorption rate from bubbles in mechanically agitated dispersion.

High resolution micromill sampling for analysis of fish otoliths by ICP-MS: Effects of sampling and specimen preparation on trace element fingerprints

Otoliths are calcified structures in the head of fish that record environmental information about fish’s life history. Gathering the elemental information from the core of an otolith corresponding to the juvenile period of fish’s life is critical to discriminate the adult fish to their natal habitats reliably. A high resolution micromill has been used to isolate the otolith core from a whole otolith for elemental analysis. The effects of micromilling procedures (e.g., sectioning, embedding and drilling) on contamination to otolith trace element levels were examined using paired blackfin tuna ( Thunnus atlanticus) otoliths. Otoliths were decontaminated by dilute hydrogen peroxide and nitric acid throughout to remove surface contamination. A preconcentration procedure was used to determine the trace elements from the small core material by ICP-MS. It was found that micromilling procedures introduce significant contamination to otoliths, especially for Al, Cu, Pb and Zn. The sectioning procedure caused significant contamination for Co and Cu, while the embedding procedure resulted in contamination for nearly all trace elements (Al, Cd, Co, Cu, Ga, Mn, Ni, Pb, V and Zn). The combined sectioning, embedding and drilling procedure also resulted in contamination for most trace elements. Despite the contamination across all procedural steps, the decontamination procedure effectively removed the surface contamination with the exception of Pb and Zn. Bias (e.g., residual contamination) on Pb was small in comparison to overall concentration of Pb expected to occur in fish otoliths, therefore, its effect may be minor in discriminating individuals. Bias on Zn was larger that could limit its application in discriminating individuals.

Scanning the laser beam for ultrafast pulse laser cleaning of paint

Powerful ultrafast femtosecond laser pulses have the unique ability to ablate material with minimal collateral damage. This ability offers the potential for new applications of ultrafast lasers for removing surface contamination and unwanted surface layers in the conservation of artworks and heritage objects. In this paper we concentrate on the problem of precise and fast scanning of the laser spot over the treated surface for cleaning relatively large surface areas. Preliminary results are presented for the removal of intrusive paint layers, using a 12-ps laser with 1.5 MHz repetition rate, and 0.5 ps laser with 10 kHz repetition rate.

A method for removing surface contamination on ultra-pure copper spectrometer components

Spectrometers for the lowest-level radiometric measurements require materials of extreme radiopurity. Measurements of rare nuclear decays, e.g., neutrinoless double-beta decay, can require construction and shielding materials with bulk radiopurity reaching one micro-Becquerel per kilogram or less. When such extreme material purity is achieved, surface contamination, particularly solid daughters in the natural radon decay chains, can become the limiting background. High-purity copper is an important material for ultra-low-background spectrometers and thus is the focus of this work. A method for removing surface contamination at very low levels without attacking the bulk material is described. An assay method using a low-background proportional counter made of the material under examination is employed, and the preliminary result of achievable surface contamination levels is presented.

Novel low-cost approach for removal of surface contamination before texturization of commercial monocrystalline silicon solar cells

This paper reports a novel approach on the surface treatment of monocrystalline silicon solar cells using an inorganic chemical, sodium hypochlorite (NaOCl) that has some remarkable properties. The treatment of contaminated crystalline silicon wafer with hot NaOCl helps the removal of organic contaminants due to its oxidizing properties. The objective of this paper is to establish the effectiveness of this treatment using hot NaOCl solution before the saw damage removal step of the conventional NaOH texturing approach. A comparative study of surface morphology and FTIR analyses of textured monocrystalline silicon surfaces with and without NaOCl pre-treatment is also reported. The process could result in a significant low cost approach viable for cleaning silicon wafers on a mass production scale.

Spatial distribution of major and trace elements in bladder and kidney stones

The spatial distribution of major and trace elements has been studied in a range of human kidney and bladder stones with well documented histories to understand their initiation and formation. The stones were cut in half using a clean diamond saw and further cleaned, to remove surface contamination, in an ultrasonic bath. The cut surfaces were analyzed using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). The spatial distribution of Li, B, Mg, Al, P, Ca, Cr, Mn, Zn, Rb, Sr, Ba and Pb has been determined across the width of each stone.

Effect of various chemical decontamination treatments on natural microflora and sensory characteristics of poultry

Regulation (EC) No. 853/2004 of the European Parliament and of the Council provides a legal basis permitting the use of antimicrobial treatments to remove surface contamination from poultry. This paper reports the results of research into the effects on natural microflora, pH, and sensorial characteristics achieved by dipping chicken legs (15 min, 18 ± 1 °C) into solutions (wt/vol) of 12% trisodium phosphate (TSP), 1200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), 220 ppm peroxyacids (Inspexx 100™; PA), and water. Samples were collected immediately after evisceration, subjected to the treatments listed or left untreated (control) and tested after 0, 1, 3 and 5 days of storage (3 °C ± 1 °C). For most microbial groups similar counts were observed on water-dipped and on untreated legs. All the chemical compounds were effective in reducing microbial populations throughout storage, with TSP, ASC and CA showing the strongest antimicrobial activity. The average reductions (mean ±standard deviation) relative to untreated samples caused by chemical treatments when considering simultaneously all storage days ranged (log 10 cfu/g skin) from 0.53 ± 0.83 (PA) to 1.98 ± 0.62 (TSP) for mesophilic aerobic counts, from 0.11 ± 0.89 (PA) to 1.27 ± 1.02 (CA) (psychrotrophs), from 1.34 ± 1.40 (PA) to 2.15 ± 1.20 (CA) ( Enterobacteriaceae), from 1.18 ± 1.24 (PA) to 1.98 ± 1.16 (CA) (coliforms), from 0.66 ± 0.99 (PA) to 1.86 ± 1.80 (TSP) ( Micrococcaceae), from 0.54 ± 0.74 (TSP) to 2.17 ± 1.37 (CA) (enterococci), from 0.72 ± 0.66 (TSP) to 2.08 ± 1.60 (CA) ( Brochothrix thermosphacta), from 0.78 ± 1.02 (PA) to 1.99 ± 0.96 (TSP) (pseudomonads), from 0.21 ± 0.61 (PA) to 1.23 ± 0.60 (TSP) (lactic acid bacteria), and from 1.14 ± 0.89 (PA) to 1.45 ± 0.61 (ASC) (moulds and yeasts). The microbial reductions throughout storage increased, decreased, or did not vary, in accordance with microbial group and chemical involved. Similar pH values were observed for untreated samples and for those dipped in PA and water on all sampling days. ASC-treated samples showed a lower pH than controls to day 1. TSP-treated legs exhibited the highest pH values and CA-treated ones the lowest, throughout storage. Hedonic evaluation (nine-point structured scale, untrained panellists) showed similar colour, smell and overall acceptability scores for dipped and untreated samples on day 0 and day 1. From day 3 sensorial attributes scored lower for untreated, PA- and water-dipped legs, as compared to legs treated with TSP, ASC and CA. Only for these three groups of samples were average scores higher than 6 (shelf-life limit value) observed by the end of storage. Results from the present study suggest that the treatments tested improve the microbial quality of chicken without adverse sensorial effects.

Laser removal of loose uranium compound contamination from metal surfaces

Pulsed laser removal of surface contamination of uranyl nitrate and uranium dioxide from stainless steel has been studied. Most of the loosely bound contamination has been removed at fluence levels below 0.5 J cm −2, leaving about 5% fixed contamination for uranyl nitrate and 15% for uranium dioxide. Both alpha and beta activities are then sufficiently low that contaminated objects can be taken out of a restricted radiation area for re-use. The ratio of beta to alpha activity is found to be a function of particle size and changes during laser removal. In a separate experiment using technetium-99m, the collection of removed radioactivity in the filter was studied and an inventory made of removed and collected contamination.

Automated ion imaging with the NanoSIMS ion microprobe

Automated ion imaging systems developed for Cameca IMS3f and IMS6f ion microprobes are very useful for the analysis of large numbers of presolar dust grains, in particular with respect to the identification of rare types of presolar grains. The application of these systems is restricted to the study of micrometer-sized grains, thereby by-passing the major fraction of presolar grains which are sub-micrometer in size. The new generation Cameca NanoSIMS 50 ion microprobe combines high spatial resolution, high sensitivity, and simultaneous detection of up to 6 isotopes which makes the NanoSIMS an unprecedented tool for the analysis of presolar materials. Here, we report on the development of a fully automated ion imaging system for the NanoSIMS at MPI for Chemistry in order to extend its analytical capabilities further. The ion imaging consists of five steps: (i) Removal of surface contamination on the area of interest. (ii) Secondary ion image acquisition of up to 5 isotopes in multi-detection. (iii) Automated particle recognition in a pre-selected image. (iv) Automated measurement of all recognised particles with appropriate raster sizes and measurement times. (v) Stage movement to new area and repetition of steps (ii)–(iv).

Analysis of endogenous cortisol concentrations in the hair of rhesus macaques

Short-term changes in activity of the hypothalamic–pituitary–adrenocortical (HPA) system are routinely assessed by measuring glucocorticoid or metabolite concentrations in plasma, saliva, urine, or feces. However, there are no current methods for determining long-term (i.e., weeks or months) activity of this system. Herein, we describe the development and validation of a simple procedure for measuring cortisol concentrations in the hair of rhesus macaques. This procedure involves two brief isopropanol washes of the hair strands to remove surface contaminants, subsequent powdering of the washed and dried hair, a 24-h methanol extraction followed by evaporation of the solvent and reconstitution of the extract in assay buffer, and finally analysis of the extracted cortisol by a sensitive and specific enzyme immunoassay. Our results confirm the specificity of the procedure for cortisol, show that proximal and distal segments of hair do not differ in their cortisol concentration, and demonstrate that a significant and prolonged stressful experience produces a significant increase in hair cortisol. This new procedure should be valuable for assessing baseline HPA activity in nonhuman primates (and, with appropriate validation, in other species as well) over relatively long periods of time, and also for monitoring chronic stress that might be associated with various experimental manipulations.

Surface softening and hardening of WC-Co using pulsed laser irradiation

The surface of cobalt-containing tungsten-carbide was treated using a pulsed Nd: YAG laser beam under atmospheric conditions in order to control its surface hardness by means of surface diffusion or concentration of cobalt. Elemental analyses of the treated surfaces revealed a laser fluence of 0.25 J/cm 2 to be the most suitable condition for the concentration of cobalt and the removal of surface contaminants, such as hydrocarbons and oxygen gas, without damaging the surface. At this laser fluence, the concentration of cobalt was reduced close to the center of irradiation but increased in the area surrounding the irradiation center. This concentration of cobalt resulted in a softening of the WC-Co surface by over 10% compared to the non-treated surface, as measured by a Knoop hardness tester under a load of 9.8 × 10 − 2 N.