Artificial Mixes Research Articles

The Influence of Seawater on Fe(II)-Catalyzed Ferrihydrite Transformation and Its Subsequent Consequences for C Dynamics.

Short-range-ordered minerals like ferrihydrite often bind substantial organic carbon (OC), which can be altered if the minerals transform. Such mineral transformations can be catalyzed by aqueous Fe(II) (Fe(II)aq) in redox-dynamic environments like coastal wetlands, which are inundated with seawater during storm surges or tidal events associated with sea-level rise. Yet, it is unknown how seawater salinity will impact Fe(II)-catalyzed ferrihydrite transformation or the fate of bound OC. We reacted ferrihydrite with Fe(II)aq under anoxic conditions in the absence and presence of dissolved organic matter (DOM). We compared treatments with no salts (DI water), NaCl-KCl salts, and artificial seawater mixes (containing Ca and Mg ions) with or without SO42-/HCO3-. Both XRD and Mössbauer showed that NaCl-KCl favored lepidocrocite formation, whereas Ca2+/Mg2+/SO42-/HCO3- ions in seawater overrode the effects of NaCl-KCl and facilitated goethite formation. We found that the highly unsaturated and phenolic compounds (HuPh) of DOM selectively bound to Fe minerals, promoting nanogoethite formation in seawater treatments. Regardless of salt presence, only 5-9% of Fe-bound OC was released during ferrihydrite transformation, enriching HuPh relative to aliphatics in solution. This study offers new insights into the occurrence of (nano)goethite and the role of Fe minerals in OC protection in coastal wetlands.

An investigation into dynamic behaviour of reconstituted and undisturbed fine-grained soil during triaxial and simple shear

This study aims to evaluate the factors controlling the sensitivity of fine-grained soils to seismic stresses and revise the criteria previously proposed by the authors to diagnose liquefaction. To this end, dynamic tests have been performed on artificial mixes as well as natural soils from a wide area of an earthquake devastated city (Adapazari) using two types of dynamic testing. Studies have led to findings suggesting that the gray area between susceptible and non-susceptible soils proposed by several investigators in the past can now be dispensed with. Although physical properties of fine-grained soil supply sufficient information for diagnosis, the dynamic simple shear test is found to be a convenient and rapid way to confirm the judgement. However, it has been seen that dynamic testing alone may not be the last word in the determination of liquefaction, and physical properties should also be addressed. Anomalies observed in test results are also discussed. Conclusions show significant differences from existing proposed criteria in the literature.

A novel way to evaluate autoantibody interference in samples with mixed antinuclear antibody patterns in the HEp-2 cell based indirect immunofluorescence assay and comparison of conventional microscopic and computer-aided pattern recognition

BackgroundA major challenge of the HEp-2 cell-based indirect immunofluorescence (IIF) assays is the correct identification of the individual anti-nuclear antibodies (ANAs) if more than one is present in a sample. We created artificial mixes by pooling two different samples with a single autoantibody in different titers. Comparison of the expected and observed patterns and titers clarifies the interference between the two tested ANAs. MethodsSerum samples with a single homogeneous or speckled ANA pattern were serially diluted and mixed in 16 combinations, providing end-point titers of 1:5,120 to 1:80 for both patterns. These mixes were tested by a HEp-2 IIF assay and were evaluated by conventional evaluation, the EUROPattern (EPa) system and on-screen analysis. ResultsHomogeneous pattern can alter the identification of the speckled pattern much more than vice versa, but both has an interfering effect on the other. The effect of the interfering on the tested pattern was higher if the titer of the former one was higher. The pattern recognition efficacy of conventional and the on-screen evaluation was similar and superior compared to the EPa analysis. ConclusionsThe application of artificial mixed samples can help the evaluation of the efficacy of manual and computer-aided ANA HEp-2 pattern recognition.

A Novel Multi-Analytic Clinical Diagnostic Assay to Detect HLA Loss of Heterozygosity in Post-Hematopoietic Cell Transplant Relapse Patients

Genomic loss of heterozygosity in the HLA region (HLA LOH) can be an underlying driver of disease relapse in haploidentical and HLA mismatched hematopoietic cell transplantation (HCT) in which relapsing cells evade donor T-cell allorecognition by deleting non-shared HLA alleles through an acquired somatic uniparental disomy event. The presence of HLA LOH may indicate a loss of graft vs. leukemia effect, render treatments such as donor leukocyte infusion ineffective, and impact donor selection for subsequent allogeneic HCT. A major challenge in developing a clinical diagnostic assay to detect HLA LOH post-HCT is sensitive detection of a loss of genomic material against a background of multiple genomes. Cell enrichment may address this issue by isolating relapsed cells for downstream molecular analysis. However, detection of HLA LOH is most clinically useful early in relapse when the relapsed cells are likely in low abundance, the relapsed cells may not be a single clonal population, and the immunophenotypic aberrancies may be variable and/or unknown. To address these issues, we have developed a comprehensive multi-analytic approach to detect HLA LOH that includes sensitive flow cytometric enrichment of leukemic cells followed by genomic analysis. First, a "difference from normal” flow cytometry approach (ΔN:™), the approach used for determination of residual disease in Children's Oncology Group AML clinical trials, is utilized to characterize the aberrant cells for each patient and relapse episode to ensure specific enrichment of relapsed cells to high purity. Next, two complementary molecular assays are used, including detection of short tandem repeat (STR) loci throughout the HLA region and next-generation sequencing (NGS) of HLA loci to identify deleted HLA alleles. In combination, the two assays provide a sensitive and spatially resolved assessment of LOH across the entire HLA genomic region, enabling molecular characterization of LOH events ranging from an entire HLA haplotype, partial HLA haplotype, or a single HLA locus. The ability to detect a locus-specific HLA LOH event could be useful in mismatched unrelated HCT donor/recipient pairs which may differ at only one or two HLA loci. Validation of the flow cytometric methods and genomic assays were performed separately. DNA isolated from the flow sorting process was shown to be suitable for both genomic assays. The sensitivity of the molecular assays to detect HLA LOH was defined using artificial mixes of DNA from two individuals with allelic mismatching at various HLA loci. Cell lines with known HLA LOH were also used to confirm the performance of the molecular assays. As of this writing, 16 samples from post-HCT relapse patients were tested with this assay and HLA LOH was detected in 3 cases (19%), consistent with published reports on the frequency of HLA LOH detected in allogeneic HCT patients. Samples with a range of relapsed leukemic cells from <1% to 85% and cell sorting output from 800 to 250,000 cells all yielded valid results. Results were reported within an average of 7 days, allowing adequate time for integration into therapeutic decision making. Challenging and unusual patient samples such as those with extremely low blast counts will be presented. Initial results indicate this clinical diagnostic assay provides reliable and accurate detection of HLA LOH during relapse in post-HCT patients. Detection of HLA LOH using our multi-analytic diagnostic approach may also aid in optimizing therapeutic decisions to improve outcomes in allogeneic HCT patients.

Assessment of ITS1, ITS2, 5′-ETS, and trnL-F DNA Barcodes for Metabarcoding of Poaceae Pollen

Grass pollen is one of the major causes of allergy. Aerobiological monitoring is a necessary element of the complex of anti-allergic measures, but the similar pollen morphology of Poaceae species makes it challenging to discriminate species in airborne pollen mixes, which impairs the quality of aerobiological monitoring. One of the solutions to this problem is the metabarcoding approach employing DNA barcodes for taxonomical identification of species in a mix by high-throughput sequencing of the pollen DNA. A diverse set of 14 grass species of different genera were selected to create a local reference database of nuclear ITS1, ITS2, 5′-ETS, and plastome trnL-F DNA barcodes. Sequences for the database were Sanger sequenced from live field and herbarium specimens and collected from GenBank. New Poaceae-specific primers for 5′-ETS were designed and tested to obtain a 5′-ETS region less than 600 bp long, suitable for high-throughput sequencing. The DNA extraction method for single-species pollen samples and mixes was optimized to increase the yield for amplification and sequencing of pollen DNA. Barcode sequences were analyzed and compared by the barcoding gap and intra- and interspecific distances. Their capability to correctly identify grass pollen was tested on artificial pollen mixes of various complexity. Metabarcoding analysis of the artificial pollen mixes showed that nuclear DNA barcodes ITS1, ITS2, and 5′-ETS proved to be more efficient than the plastome barcode in both amplification from pollen DNA and identification of grass species. Although the metabarcoding results were qualitatively congruent with the actual composition of the pollen mixes in most cases, the quantitative results based on read-counts did not match the actual ratio of pollen grains in the mixes.

Initial Verification of an Application for the Calculation of Technological Parameters During Production of Trimix Mixture

Abstract The paper presents the results of an engineering thesis carried out at the Department of Underwater Works Technology of the Naval Academy in Gdynia. The subject of the thesis was to improve calculations during the production of a trimix mixture based on a previously produced nitrox mixture. This was done by developing a dedicated computer application. The article describes the reasons for using artificial breathing mixes, an application developed as part of the thesis and the method of its initial verification along with the directions for further research activities.

Taxonomic classification and abundance estimation using 16S and WGS—A comparison using controlled reference samples

The assessment of microbiome biodiversity is the most common application of metagenomics. While 16S sequencing remains standard procedure for taxonomic profiling of metagenomic data, a growing number of studies have clearly demonstrated biases associated with this method. By using Whole Genome Shotgun sequencing (WGS) metagenomics, most of the known restrictions associated with 16S data are alleviated. However, due to the computationally intensive data analyses and higher sequencing costs, WGS based metagenomics remains a less popular option. Selecting the experiment type that provides a comprehensive, yet manageable amount of information is a challenge encountered in many metagenomics studies. In this work, we created a series of artificial bacterial mixes, each with a different distribution of skin-associated microbial species. These mixes were used to estimate the resolution of two different metagenomic experiments - 16S and WGS - and to evaluate several different bioinformatics approaches for taxonomic read classification. In all test cases, WGS approaches provide much more accurate results, in terms of taxa prediction and abundance estimation, in comparison to those of 16S. Furthermore, we demonstrate that a 16S dataset, analysed using different state of the art techniques and reference databases, can produce widely different results. In light of the fact that most forensic metagenomic analysis are still performed using 16S data, our results are especially important.

Detection and Quantification of Spongospora subterranea Sporosori in Soil by Quantitative Real-Time PCR.

Powdery scab on potato tubers is caused by the obligate soilborne biotroph Spongospora subterranea and is known to cause substantial losses in potato production. The pathogen also infects roots of susceptible hosts, forming galls which can negatively affect root function. S. subterranea is also the vector of Potato mop-top virus, which causes a tuber necrosis disease that can, depending on temperature and cultivar, render potato tubers unmarketable. In this study, we adapted a published protocol to develop a sensitive and robust quantitative real-time PCR (qPCR) assay using specific primers and probes for detecting and quantifying S. subterranea sporosori in soil types that differ in physical properties, including organic matter content and soil pH. For the first time, an external control was utilized and applied directly to the soil prior to DNA extraction, which facilitated normalization of S. subterranea sporosori soil levels from sample to sample. The duplex qPCR protocol was demonstrated to be highly sensitive, capable of detecting and quantifying as few as 1 sporosorus/g of soil, with consistently high qPCR efficiency and the coefficient of determination (R2) values ranging from 94 to 99% and 0.98 to 0.99, respectively. The protocol was successfully implemented in enumerating S. subterranea sporosori in naturally infested field soil collected from several states and in artificial potting mixes with high organic matter content ranging from 64 to 71%. The qPCR method developed can be useful for potato growers to avoid agricultural soils highly infested with S. subterranea and in the development of risk assessment models in the future that incorporate cultivar susceptibility to powdery scab and soil infestation levels.

Composite Lipid Bilayers from Cell Membrane Extracts and Artificial Mixes as a Cell Culture Platform.

An artificial lipid bilayer is the closest possible model for the cell membrane. Despite that, current methods of lipid bilayer assembly and functionalization do not provide a satisfactory mimic of the cell-cell contact due to the inability to recreate an asymmetrical multicomponent system. In the current work, a method to produce an integrated solid-supported lipid bilayer combining natural extracts from cell membranes and artificially made lipid vesicles is proposed. This simple method allows delivery of transmembrane proteins and components of the extracellular matrix into the substrate. Biocompatibility of the composite natural/artificial lipid bilayers is evaluated by their interactions with the cardiomyocyte-like HL-1 cell line. Compared with fully artificial mixes, composite lipid bilayers allow cells to adhere and develop a morphologically more normal cytoskeleton.

Populating the Mix Space: Parametric Methods for Generating Multitrack Audio Mixtures

The creation of multitrack mixes by audio engineers is a time-consuming activity and creating high-quality mixes requires a great deal of knowledge and experience. Previous studies on the perception of music mixes have been limited by the relatively small number of human-made mixes analysed. This paper describes a novel “mix-space”, a parameter space which contains all possible mixes using a finite set of tools, as well as methods for the parametric generation of artificial mixes in this space. Mixes that use track gain, panning and equalisation are considered. This allows statistical methods to be used in the study of music mixing practice, such as Monte Carlo simulations or population-based optimisation methods. Two applications are described: an investigation into the robustness and accuracy of tempo-estimation algorithms and an experiment to estimate distributions of spectral centroid values within sets of mixes. The potential for further work is also described.

Bacterial contamination of in vitro plant cultures: confounding effects on somaclonal variation and detection of contamination in plant tissues

Bacterial contamination represents a serious problem for plant tissue culture research and applications. Bacterial interference with normal plant physiology and morphology can generate misleading conclusions if the presence of bacteria is ignored. Bacterial contaminants in in vitro plant culture are typically detected by direct observation; thus, it is assumed that cultures without visible symptoms are bacteria free. Here, we demonstrate that contaminating Bacillus DNA in plant DNA solutions from asymptomatic plants can interfere with the analysis of somaclonal variation in chrysanthemum. We studied somaclonal variation in chrysanthemum using short semi-specific PCR primers based on conserved motifs in NBS–LRR disease resistance genes and in mobile elements. Instead of true somaclonal variation we found three polymorphic bands derived from contaminant bacterial DNA in plant extracts. Although the detection of asymptomatic bacteria in in vitro plant cultures is a major issue, we found that it has not been adequately addressed to date, particularly for studies on somaclonal variation. We reviewed the most commonly cited contaminant bacteria in in vitro plant culture and designed specific 16S rRNA gene-based PCR primers for the main genera causing contamination (Bacillus, Pseudomonas, Staphylococcus, Lactobacillus, Erwinia/Enterobacter and Xanthomonas). Using a panel of pure bacterial DNAs, artificial mixes of bacterial/plant DNAs, and in vitro plant cultures with and without visible contamination we demonstrated that our primers are in most instances both reliable and sensitive, and appropriate for the identification and tracking of the most frequent bacterial contaminants in plant in vitro cultures. Implications of bacterial identification to molecular analysis of somaclonal variation and plant culture decontamination are discussed.

High-Sensitivity Hematopoietic Chimerism By qPCR For Relapse Prediction and Specific Identification Of HLA Loss Leukemic Variants

IntroductionAllogeneic Hematopoietic Stem Cell Transplantation (HSCT) is the best curative option for many patients with hematologic malignancies. Still, disease relapse remains a major clinical issue, and therapeutic options available to date are largely unsatisfactory. Thus interest has risen in how to anticipate the detection of residual malignant cells by more sensitive techniques, such as those based on quantitative PCR (qPCR), to prompt preemptive treatments. Adding further complexity to the issue of leukemia recurrence, our group described in the context of HSCT from partially incompatible donors novel variants of post-transplantation leukemia relapse, characterized by genomic loss of the mismatched HLA (Vago et al, N Engl J Med, 2009). These leukemia variants are not detected by routine diagnostic assays and are expected to be resistant to donor lymphocyte infusions, warranting the development of novel specific diagnostic assays and therapeutic algorithms. MethodsHere we prospectively validated a commercial hematopoietic chimerism assay based on qPCR detection of 34 insertion/deletion (indel) polymorphisms mapping on 19 different chromosomes, all outside the HLA complex (AlleleSEQR® Chimerism Assay, Celera Genomics). The assay was tested on 403 bone marrow samples harvested from 115 transplanted patients during 18 months of follow-up. Results obtained from qPCR-based chimersim were compared with standard Short Tandem Repeat (STR) chimerism analysis performed in parallel on the same samples. To discriminate between “classical” and “HLA loss” relapses, we developed chimerism assays targeted to specific HLA-A allele groups, based on the same qPCR technology of the commercial “outside HLA” assay and targeted to display its same sensitivity. ResultsqPCR chimerism displayed high informativity, providing at least a patient-specific indel marker in all the patients analyzed and at least two markers in 109/115 patients (94.7%). When two polymorphic indel markers were analyzed in parallel on the same sample concordance was extremely high (r2=0.97). As expected, qPCR chimerism demonstrated a higher sensitivity in detection of residual host cells as compared to STR: 131/403 samples exhibit a host chimerism above 0.5% (32.5%) and 91/403 above 1% (22.6%), whereas 79/395 (20%) were positive in STR. qPCR chimerism could predict impending relapse with a sensitivity of 37.5% and a specificity of 72.5% for a 0.5% host threshold, and with a sensitivity of 29.2% and a specificity of 83.5% for a 1% host threshold, comparing favourably in terms of sensitivity with STR (sensitivity 20.8%, specificity 84.8%). We designed and validated 5 qPCR reactions able to specifically detect 9 different HLA-A allele groups, displaying a combined frequency of 81% in Caucasians, and providing an informative patient-specific HLA-A allele as chimerism marker to more than 50% of the patients transplanted from mismatched related donors in our centre. Technical validation of the newly developed reactions with artificial mixes of HLA-typed DNA demonstrated for each reaction the sensitivity to detect at least 0.2% target cells and efficiency above 80%. Clinical utility was tested on 80 bone marrow samples harvested from transplanted patients, using the new “inside HLA” reactions in combination with the commercial “outside HLA” assay: combination of the results obtained from the two assays allowed us to unequivocally discriminate HLA loss relapses (n=5) from classical relapses (n=15). ConclusionHematopoietic chimerism detection by qPCR appears promising, displaying a higher sensitivity and a superimposable specificity as compared to techniques currently in use, and allowing by the novel assay we developed the simultaneous detection of leukemic variants characterized by genomic HLA loss. Disclosures:Bonini:MolMed SpA: Consultancy. Bost:Celera Genomics: Former Employee, Former Employee Other; KimerDx: Employment. Fleischhauer:Celera Genomics: Research Funding.

Interfacial Transition Zone (ITZ) Analysis in Hydraulic Lime Restoration Mortars for Grouting of Historical Masonries

In this study, binder-aggregate interfacial transition zone (ITZ) of some hydraulic lime based mortars is analyzed in order to determine the way in which their morphological and compositional structure is related to strength and durability development. To achieve this determination, using a lime mortar as a starting point, several hydraulic mixes were prepared with metakaolin (MK), sepiolite, and Portland cement additions. Lime mortar ITZ was compared with hydraulic mortars, obtained both from a natural hydraulic lime (NHL) and from the mentioned artificial hydraulic lime mixes. Scanning electron microscopy (SEM) and energy dispersion X-ray analysis (EDX) microanalysis techniques in combination with stress tests were carried out. Results showed the most radical behavior with the MK addition to mortar rather than with the Portland cement addition, even at 1:1 ratio. Continual transition zones together with higher strengths correspond to mortars with smaller aluminate phases and hydrogarnets. Thus, a small contribution of the latter to binder-aggregate bonding and mechanical resistance can be considered. Finally, sepiolite addition does not affect mechanical behavior under these work conditions.

Swell–consolidation characteristics of artificial sand clay mixes

Many remedial measures have been devised to lessen the damage caused by expansive soils. Physical alteration, chemical stabilization, innovative foundation techniques like belled piers, drilled piers, under-reamed piles and granular pile anchors are some of these remedial measures. Mixing a non swelling material such as gravel or sand to expansive soil is one of the methods of physical alteration. This paper presents experimental data on artificially prepared sand-clay mixes. Swell and consolidation characteristics of these artificially prepared sand-clay mixes were studied in one dimensional consolidometer. Fine sand content and fines content in the expansive soil were arbitrarily varied in the investigation. The fines content was varied as 425–300 μm and 150–75 μm, separated from the same expansive soil based on the grain size. Swell potential and swelling pressure decreased with increasing fine sand content but increased with increasing fines content. Coefficient of compressibility, coefficient of volume compressibility and compression index of the samples decreased initially up to a sand content of 15% and thereafter increased at higher sand contents.

Frequency Dependence of Permittivity of Free and Bound Water in Soils for Different Textures

In microwave methods of the soil moisture remote sensing it is necessary to have models for determining the complex dielectric permeability (CDP) dependence on moisture, frequency, mineralogy and particle-size distribution. The soil permeability measurement shows that the basic contribution to the CDP is introduced by free and bound water, and permeability of soil water depends on a soil type. To establish the influence of particle-size distribution of soil particles on CDP of the bound and free soil water we carried out the measurements of the frequency and moisture dependencies of refraction index of artificial sandy-clay mixes having different mineral structure and particle-size distribution. The carried out research at the frequencies from 30MHz up to 4 GHz has shown that the refraction index of free soil water depends on the quartz granules sizes, as well as on the clay fraction relative content. The characteristic feature of the free soil water is the increase of refraction index at frequency reduction. This dependence is the stronger the more clay the sample has. The similar properties are also observed in the bound water.

Quantitative Single-letter Sequencing: a method for simultaneously monitoring numerous known allelic variants in single DNA samples

BackgroundPathogens such as fungi, bacteria and especially viruses, are highly variable even within an individual host, intensifying the difficulty of distinguishing and accurately quantifying numerous allelic variants co-existing in a single nucleic acid sample. The majority of currently available techniques are based on real-time PCR or primer extension and often require multiplexing adjustments that impose a practical limitation of the number of alleles that can be monitored simultaneously at a single locus.ResultsHere, we describe a novel method that allows the simultaneous quantification of numerous allelic variants in a single reaction tube and without multiplexing. Quantitative Single-letter Sequencing (QSS) begins with a single PCR amplification step using a pair of primers flanking the polymorphic region of interest. Next, PCR products are submitted to single-letter sequencing with a fluorescently-labelled primer located upstream of the polymorphic region. The resulting monochromatic electropherogram shows numerous specific diagnostic peaks, attributable to specific variants, signifying their presence/absence in the DNA sample. Moreover, peak fluorescence can be quantified and used to estimate the frequency of the corresponding variant in the DNA population.Using engineered allelic markers in the genome of Cauliflower mosaic virus, we reliably monitored six different viral genotypes in DNA extracted from infected plants. Evaluation of the intrinsic variance of this method, as applied to both artificial plasmid DNA mixes and viral genome populations, demonstrates that QSS is a robust and reliable method of detection and quantification for variants with a relative frequency of between 0.05 and 1.ConclusionThis simple method is easily transferable to many other biological systems and questions, including those involving high throughput analysis, and can be performed in any laboratory since it does not require specialized equipment.

Effect of Soil Type on the Establishment of Grape Phylloxera Colonies in the Pacific Northwest

Soils from the Pacific Northwest were investigated to determine if soil type affects the establishment of new phylloxera populations. Soils included those of the Abegg, Helvetia, and Jory series in Oregon, the Burke series in Washington, and two artificial soils, a soilless mix and a Jory/sand mix. <i>Vitis vinifera</i> cv. Pinot noir vines in each soil were infested with phylloxera eggs originating from the Willamette Valley in western Oregon and the Yakima Valley in eastern Washington. After three months, phylloxera numbers were collected through investigation of soil core samples. Soils from all six soil types supported phylloxera establishment, regardless of population origin. Overall, soil from the Burke series had the lowest percentage of establishment and significantly lower population means. All Oregon soil types and the artificial mixes consistently supported higher population numbers of phylloxera. Based on establishment and proliferation of population numbers in the Burke series soil, we conclude that some soils may provide an environment that suppresses the growth of phylloxera populations. However, none of the soils tested in this study prevented grape phylloxera establishment.

Ageing of chromium(III)-bearing slag and its relation to the atmospheric oxidation of solid chromium(III)-oxide in the presence of calcium oxide

Slag arising in ferrochromium and stainless steel production is known to contain residual levels of trivalent chromium. As the chromium is normally bound in the slag matrix in various silicate or spinel phases, and hence not easily mobilised, utilisation or controlled disposal of such slag is generally considered unproblematic. Experimental test work with a number of slag materials indicates, however, that very gradual oxidation of trivalent to hexavalent chromium does occur when the slag is exposed to atmospheric oxygen, rendering a quantifiable but small portion of chromium in this much more mobile and toxic form. Mechanisms and rates of the oxidation reaction were investigated in a number of long-term studies using both original slag materials and artificial mixes of chromium and calcium oxides. Powders of these materials, some of them rolled into balls, were left to age under different conditions for periods of up to 12 months. In the slag samples, which contained between 1 and 3 wt.% chromium, 1000–10 000 μg Cr(VI) were found per gram of chromium within 6–9 months of exposure to an ambient atmosphere. The rate of the oxidation reaction decreased exponentially, and the reaction could generally be said to have ceased within 12 months. In mixtures of calcium and chromium oxides the oxidation reaction is presumed to occur at the boundaries between chromium oxide and calcium oxide phases through diffusion of oxygen along the grain boundaries and of Cr 3+ across the boundaries, resulting in the formation of calcium chromate. In the slags, where calcium and chromium oxide can form a solid solution, the oxidation is likely to occur at the exposed surface of grains containing this solution.

Determining Air Entry Value in Peat Substrates

Insufficient aeration in artificial mixes used for nursery and greenhouse production is commonly reported to be a problem. To diagnose aeration problems, gas relative diffusivity estimates can be used. These estimates can be obtained indirectly from measurements of air entry value, saturated hydraulic conductivity and the water desorption curve. In here, a rapid tension chamber method for measuring air entry is proposed. To verify applicability of the method, different potted substrates were inserted into a tension chamber apparatus and water was extracted from the saturated substrate by establishing a contact with an unsaturated body located outside the chamber. The potential within the chamber was monitored over a 5‐min period and the point of air entry was calculated thereafter. Statistically equal estimates of air entry were obtained with this technique compared with values derived from the tension table, for a wide range of air entry values in peat‐based substrates.

Determining Air Entry Value in Peat Substrates

Insufficient aeration in artificial mixes used for nursery and greenhouse production is commonly reported to be a problem. To diagnose aeration problems, gas relative diffusivity estimates can be used. These estimates can be obtained indirectly from measurements of air entry value, saturated hydraulic conductivity and the water desorption curve. In here, a rapid tension chamber method for measuring air entry is proposed. To verify applicability of the method, different potted substrates were inserted into a tension chamber apparatus and water was extracted from the saturated substrate by establishing a contact with an unsaturated body located outside the chamber. The potential within the chamber was monitored over a 5-min period and the point of air entry was calculated thereafter. Statistically equal estimates of air entry were obtained with this technique compared with values derived from the tension table, for a wide range of air entry values in peat-based substrates.