Stabilization of chromium(VI) by hydroxysulfate green rust in chromium(VI)-contaminated soils

Chromium (Cr)-contaminated soils pose a great environmental risk, with high solubility and persistent leaching of Cr(VI). In this study, hydroxysulfate green rust (GR_SO4), with the general formula Fe(II)₄Fe(III)₂(OH)₁₂SO₄·8H₂O, was evaluated for its efficiency in Cr(VI) stabilization via Cr(VI) reduction to Cr(III) in four representative Cr(VI)-spiked soils. The initial concentrations of phosphate buffer-extractable Cr(VI) (Cr(VI)_b) in soils 1, 2, 3, and 4 were 382.4, 575.9, 551.3, and 483.7 mg kg^-1, respectively. Reduction of Cr(VI) to Cr(III) by structural Fe(II) (Fe(II)_s) in GR_SO4 in all studied soils was fast, wherein the application of GR_SO4 markedly decreased the amount of Cr(VI)_b at the Cr(VI)_b/Fe(II)_s stoichiometric mole ratio of 0.33. The kinetics of Cr(VI) reduction by GR_SO4 could not be determined as this reaction coincided with the release of Cr(VI) from soil during the experiment. The concentration of Cr(VI)_b decreased, as the Cr(VI)_b/Fe(II)_s ratio decreased from 0.46 to 0.20, generally to below 10 mg kg^-1. Back-transformation of the generated Cr(III) was examined in the presence of manganese oxide birnessite at the birnessite/initial Cr(III) mole ratio of 4.5. The results of batch tests showed that only 5.2% of the initial Cr(III) was converted to Cr(VI) after two months, while under field capacity moisture conditions, less than 0.05% of the initial Cr(III) was oxidized to Cr(VI) after six months. The results illustrated that remediation of Cr(VI)-contaminated soils would be fast, successful, and irreversible with an appropriate quantity of fresh GR_SO4.     

MONITORING THE PROGRESSION OF TARSAL OSSIFICATION WITH ULTRASONOGRAPHY AND RADIOGRAPHY IN THREE IMMATURE FOALS

Repeated ultrasonographic and radiographic examinations of both tarsi were performed on three immature foals at individually adjusted times to monitor the progression of ossification. The first examination was performed soon after birth, and all foals were found to have incomplete ossification of the tarsal bones. Two of the foals were monitored until ossification of the small tarsal bones was complete. The rate of ossification varied, and it seemed to be affected by the general health of the foal and by its weight-bearing. In two foals the pattern of ossification was markedly irregular and several ossifying foci were often found within the bones. Ultrasonography was found to be a practical method for monitoring the changes in the outline and echogenity of the bones in the distal tarsal area. Radiography confirmed the ultrasonographic findings and was necessary for evaluating the internal structure of the bones.     

Histomorphometrical and stereological study of the oesophagus in the adult male Persian squirrel (Sciurus anomalus)

The Persian squirrel (Sciurus anomalus) is habitat in the Middle East countries and feed on pine acorns and other seeds. The present study was carried out to investigate the histological and volumetric features of the oesophagus in Persian squirrels. Five adult male Persian squirrels were included in the study. The cervical, thoracic and abdominal oesophagus of all subjects were processed routinely and sectioned in a serial manner. Then, the total volume of the oesophagus and its different layers were estimated using Cavalieri's principle. Histological assessment revealed a non‐keratinized stratified squamous epithelium lining the mucosa. No glands were seen in the lamina propria and submucosa. Lamina muscularis was present as a distinct layer of smooth muscle cells separating the lamina propria from the tunica submucosa. The tunica muscularis consisted of two distinct layers of striated muscle fibres: inner circular and outer longitudinal that was intermingled with few scattered smooth muscle fibres especially in the abdominal region. The thoracic region contained more amount of the lamina muscularis and tunica muscularis in comparison to the cervical or abdominal regions. The obtained results revealed that the histological structure of the Persian squirrel oesophagus has differences and similarities with other rodents and even with other species of squirrel. These findings would be useful to improve the knowledge in the areas of histological structure of the rodent digestive system.     

Diagnosis of paratuberculosis in a dairy herd native to Brazil

Paratuberculosis (PTB) in Brazil has previously only been reported in imported animals and is officially considered as an exotic disease. A dairy herd, which had no imported animals, presented clinically suspect animals and was investigated for paratuberculosis using faecal culture, histopathology, indirect ELISA and the agar gel immunodiffusion test. Infection with Mycobacterium avium subsp. paratuberculosis (Map) was confirmed by culture of faeces from five cows with clinical symptoms of PTB and in 7/24 randomly selected asymptomatic cows from the same herd. Two cows with clinical symptoms were necropsied and their tissues were positive for Map by culture and histopathology. Twelve asymptomatic, randomly selected cows were positive on ELISA. The results confirmed the presence of PTB in this dairy herd and for the first time demonstrated the disease in a herd of native-bred cattle in Brazil.     

Improvement of drought tolerance in Tobacco (Nicotiana rustica L.) plants by Silicon

Ameliorative effect of silicon (Si) (2 mM as sodium silicate (Na₂SiO₃)) was studied in tobacco (Nicotiana rustica L.) plants grown under control at 100% field capacity (FC), mild drought (60% FC), and severe drought (30% FC) conditions. Si-treated plants had higher biomass of particularly above-ground parts both under drought and control conditions. Plants with Si supply had significantly higher net assimilation rates but lower transpiration rates. Silicon supply enhanced osmotic potentials only in the leaves, but not in the roots. A considerable rise in the concentrations of soluble sugars was observed particularly in the leaves under both drought and Si treatments. Soluble proteins, free α-amino acids, and proline concentrations increased in Si-treated plants under all watering treatments. Si enhanced the activity of antioxidative enzymes and decreased hydrogen peroxide (H₂O₂) concentrations. Results indicate that Si supplementation alleviates drought stress via improvement of water relation parameters, enhancement of photosynthesis, and elevation of antioxidant defenses.     

High selfing rate inferred for white fonio [<Emphasis Type="Italic">Digitaria exilis</Emphasis> (Kippist.) Stapf] reproductive system opens up opportunities for breeding programs

In a context of the global major changes, it is mandatory to enlarge the range of crops supporting food security and pay great attention to neglected and underutilized species. However, basic knowledge of the biology of many neglected and underutilized species is still lacking to increase their yields. In this study, the mating system of white fonio [Digitaria exilis (Kippist.) Stapf], a West African minor and promising cereal, is assessed. Progenies arrays from both homozygous and heterozygous mothers were genotyped with microsatellites markers. The rate of genotyping errors in the experiments was assessed and a likelihood framework was used to determine the probability of different mating systems: outcrossing, self-fertilization and apomixis. The results suggested that white fonio has a highly selfing reproductive system with a possible outcrossing rate of 1.7%. Understanding the reproduction system of white fonio opens up opportunities for more effective breeding programs and a wider use of this cereal for food security improvement.     

Evaluating the potential of sentinel-2, landsat-8, and irs satellite images in tree species classification of hyrcanian forest of iran using random forest

ABSTRACT

Spatially explicit information on tree species composition of any forest provides valuable information to forest managers as well as to nature conservationists. In this study, the potential of three spaceborne sensors: (1) Landsat-8, (2) Sentinel-2, and (3) IRS-Pansharpened were compared by applying Random Forest (RF) classification algorithms to classify the three most common tree species: Pinus taeda, Alnus spp., and Populus spp., in Hyrcanian forest of Iran. Three RF models with optimized parameters of mtry and ntree were used for the classification of trees species. Based on our Overall Accuracy (OA) and Kappa Coefficient (KC) analysis, IRS-Pansharpened data showed the highest accuracy (OA = 84.9% and KC = 79.7%), followed by Landsat-8 (OA = 78.2% and KC = 70.6%), and Sentinel-2 (OA = 77% and KC = 70%). According to the Mean Decrease in Accuracy (MDA) criterion delivered as an output of RF, the near-IR spectral band was found on the top rank (high variable importance) as compared to all other spectral bands for tree species classification. The findings of this study can be used by the researcher, forest managers, economists and policy and decision makers in the context of sustainable forest management of Hyrcanian forest resources.     

Trace and major element contents,microbial communities,and enzymatic activities of urban soils of Marrakech city along an anthropization gradient

Journal of Soils and Sediments - Due to their close proximity with the population, urban soils are extensively affected by human activities that release considerable technogenic inputs resulting in...     

Natural regeneration of oriental beech(Fagus orientalis Lipsky)trees in canopy gaps and under closed canopy in a forest in northern Iran

For developing nature-based silvicultural practices in a beech forest to promote, abundance, height,vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies.A systematic 50×50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies.Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps.Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy.Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps.Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured.The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration.The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.     

Electrospun curcumin loaded poly(lactic acid) nanofiber mat on the flexible crosslinked PVA/PEG membrane film: Characterization and <Emphasis Type="Italic">in vitro</Emphasis> release kinetic study

Herein, a biodegradable and biocompatible composite comprising of support membrane based on crosslinked PVA/PEG film and curcumin loaded electrospun poly(lactic acid) (PLA) nanofiber mat is introduced. The membrane film was prepared from PVA/PEG blend followed by crosslinking with an optimum amount of citric acid, 15 wt.%. After then, PLA solutions with different curcumin content, 0-11 wt.%, were electrospinned on the prepared membrane substrate. The prepared film showed high water absorption, water vapor transmission rate and superior mechanical properties with improved elastic modulus, tensile strength and with an elongation of around 320 % with respect to the non-crosslinked one. Also, the scanning electron microscopy was revealed uniformly dispersed pores throughout the membrane film with a nearly narrow in size distribution centered at 36 μm. As well, a nanostructure porous morphology was found for the electrospun fibrous curcumin loaded PLA from the scanning electron microscopy micrographs and the average fiber diameter was decreased with curcumin content. In vitro drug release from the prepared flexible composite into the vertical diffusion cell was recorded by the measuring curcuminoids content using high performance liquid chromatography and drug release kinetic evaluations were revealed that the release pattern of all prepared samples, containing different content of curcumin, well fitted to the Higuchi’s model signifying diffusion-controlled release mechanism. As well, the determined release rate at the second release stages, i.e. steady state flux (J), was varied from 0.31 to 43.53 μg·cm^-2·h^-1 with increasing drug content from 1 to 11 wt.%. Regarding this results, this flexible composite by providing the moist environment along with miraculous healing properties of curcumin, can be potential candidate for transdermal drug delivery.