•Surface chemistry of the corrosion product layers on magnesium alloys.•Influence of the type of alloy on the carbonate surface enrichment.•Relation between surface composition and protection ...properties.
This paper studies the chemical composition of the corrosion product layers formed on magnesium alloys AZ31 and AZ61 following immersion in 0.6M NaCl, with a view to better understanding their protective action. Relative differences in the chemical nature of the layers were quantified by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDX) and low-angle X-ray diffraction (XRD). Corrosion behavior was investigated by Electrochemical Impedance Spectroscopy (EIS) and hydrogen evolution measurement. An inhibitive effect from the corrosion product layers was observed from EIS, principally in the case of AZ31, as confirmed by hydrogen evolution tests. A link was found between carbonate enrichment observed by XPS in the surface of the corrosion product layer, concomitant with the increase in the protective properties observed by EIS.
BACKGROUND AND AIMS: A glasshouse experiment was conceived to assess the role of a bacterial consortium (Pseudomonas composti SDT3, Aeromonasaquariorum SDT 13 and Bacillus sp. SDT14) isolated from ...the rizhosphere of S. densiflora on its growth and physiological tolerance to the physicochemical properties of marsh soils. METHODS: Two inoculation treatments (with and without inoculation) in combination with two soil types (from Piedras and Odiel marshes, SW Spain) were assigned for 50 days. Growth parameters, combined with measurements of gas exchange, efficiency of PSII biochemistry, photosynthetic pigments and leaf water content were measured. In addition, the accumulation of nutrients and trace elements were determined. RESULTS: The inoculation improved growth of S. densiflora through a beneficial effect on its photochemical apparatus due to its impact on chlorophyll concentration. This enhancement happened under both soil conditions and was mainly reflected in a greater length and diameter of roots. Also, inoculation favoured leaf water content through the decline in stomatal conductance and increment in root-to-shoot ratio. Moreover, this consortium was able to stimulate ion accumulation in roots and leaves. CONCLUSIONS: Selected rhizospheric bacteria appear to play a significant role in S. densiflora growth response and tolerance to the physicochemical properties of marshes soils.
There is an increasing interest to use halophytes for revegetation of salt affected ecosystems, as well as in understanding their mechanisms of salt tolerance. We hypothesized that bacteria from the ...phyllosphere of these plants might play a key role in its high tolerance to excessive salinity. Eight endophytic bacteria belonging to Bacillus and closely related genera were isolated from phyllosphere of the halophyte Arthrocnemum macrostachyum growing in salty agricultural soils. The presence of plant-growth promoting (PGP) properties, enzymatic activities and tolerance towards NaCl was determined. Effects of inoculation on seeds germination and adult plant growth under experimental NaCl treatments (0, 510 and 1030 mM NaCl) were studied. Inoculation with a consortium including the best performing bacteria improved considerably the kinetics of germination and the final germination percentage of A. macrostachyum seeds. At high NaCl concentrations (1030 mM), inoculation of plants mitigated the effects of high salinity on plant growth and physiological performance and, in addition, this consortium appears to have increased the potential of A. macrostachyum to accumulate Na
in its shoots, thus improving sodium phytoextraction capacity. Bacteria isolated from A. macrostachyum phyllosphere seem to play an important role in plant salt tolerance under stressing salt concentrations. The combined use of A. macrostachyum and its microbiome can be an adequate tool to enhance plant adaptation and sodium phytoextraction during restoration of salt degraded soils.
Arthrocnemum macrostachyum is a halophyte naturally growing in southwest coasts of Spain that can tolerate and accumulate heavy metals. A total of 48 bacteria (30 endophytes and 18 from the ...rhizosphere) were isolated from A. macrostachyum growing in the Odiel River marshes, an ecosystem with high levels of contamination. All the isolates exhibited plant-growth-promoting (PGP) properties and most of them were multiresistant to heavy metals. Although the presence of heavy metals reduced the capability of the isolates to exhibit PGP properties, several strains were able to maintain their properties or even enhance them in the presence of concrete metals. Two bacterial consortia with the best-performing endophytic or rhizospheric strains were selected for further experiments. Bacterial inoculation accelerated germination of A. macrostachyum seeds in both the absence and presence of heavy metals. These results suggest that inoculation of A. macrostachyum with the selected bacteria could ameliorate plant establishment and growth in contaminated marshes.
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•48 bacteria isolated from A. macrostachyum with plant-growth promoting properties•Most of the isolates were multi-resistant to heavy metals.•Several strains maintained their PGP properties in the presence of concrete metals.•Endophytic and rhizospheric bacterial consortia selected for further experiments•Inoculation accelerated seeds germination in the absence and presence of heavy metals
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•S. maritima rhizosphere bacteria from the polluted Tinto River estuary is analysed.•PGP properties are studied in the absence and the presence of copper.•Four strains with salt and ...heavy metal resistance and PGP properties are selected.•The selected strains are tested in M. sativa seedlings, enhancing root elongation.•The inoculation of S. maritima may be determinant for restoration programs.
Spartina maritima is a native endangered heavy metal rhizoaccumulator cordgrass naturally growing in southwest coasts of Spain, where is used as a biotool to rehabilitate degraded salt marshes. Fifteen bacterial strains were isolated from the rhizosphere of S. maritima growing in the estuary of the Tinto River, one of the most polluted areas in the world. A high proportion of bacteria were resistant towards several heavy metals. They also exhibited multiple plant growth promoting (PGP) properties, in the absence and the presence of Cu. Bacillus methylotrophicus SMT38, Bacillusaryabhattai SMT48, B. aryabhattai SMT50 and Bacilluslicheniformis SMT51 were selected as the best performing strains. In a gnobiotic assay, inoculation of Medicago sativa seeds with the selected isolates induced higher root elongation. The inoculation of S. maritima with these indigenous metal-resistant PGP rhizobacteria could be an efficient method to increase plant adaptation and growth in contaminated estuaries during restoration programs.
•Anomalous HE observed for AZ31 and AZ91 Mg alloys.•Passivity exhibited by Mg17Al12 with anomalous HE originating at anodic regions.•Mg17Al12 phase exhibited lower HE rates than AZ Mg alloys during ...polarization.•Results consistent with anomalous HE originating at actively dissolving Mg sites.•Greater amounts of Mg17Al12 decrease dissolution rates of Mg matrix.
The role of the Mg17Al12 second phase on the anomalous HE and anodic dissolution of AZ31 and AZ91 Mg alloys was investigated. A passive-like behavior was exhibited by the Mg17Al12 phase with strong anomalous HE originating from local anodic regions where the passive film had broken down. The Mg17Al12 exhibited lower HE rates than the AZ Mg alloys during anodic polarization. Surface characterization confirmed that dissolution of Mg17Al12 in the AZ91 alloy only occurred above the Eb for the Mg17Al12. Under anodic polarization, greater amounts of Mg17Al12 are beneficial for AZ Mg alloys durability, decreasing the Mg matrix dissolution rates.
Pollution of coasts by toxic metals and metalloids is a worldwide problem for which phytoremediation using halophytes and associated microbiomes is becoming relevant. Metal(loid) excess is a ...constraint for plant establishment and development, and plant growth promoting rhizobacteria (PGPR) mitigate plant stress under these conditions. However, mechanisms underlying this effect remain elusive. The effect of toxic metal(loid)s on activity and gene expression of ROS-scavenging enzymes in roots of the halophyte Spartina densiflora grown on real polluted sediments in a greenhouse experiment was investigated. Sediments of the metal-polluted joint estuary of Tinto and Odiel rivers and control, unpollutred samples from the Piedras estuary were collected and submitted to ICP-OES. Seeds of S. densiflora were collected from the polluted Odiel marshes and grown in polluted and unpolluted sediments. Rhizophere biofilm-forming bacteria were selected based on metal tolerance and inoculated to S. densiflora and grown for 4 months. Fresh or frozen harvested plants were used for enzyme assays and gene expression studies, respectively. Metal excess induced SOD (five-fold increase), whereas CAT and ascorbate peroxidase displayed minor induction (twofold). A twofold increase of TBARs indicated membrane damage. Our results showed that metal-resistant PGPR (P. agglomerans RSO6 and RSO7 and B. aryabhattai RSO25) contributed to alleviate metal stress, as deduced from lower levels of all antioxidant enzymes to levels below those of non-exposed plants. The oxidative stress index (OSI) decreased between 50 and 75% upon inoculation. The results also evidenced the important role of PAL, involved in secondary metabolism and/or lignin synthesis, as a pathway for metal stress management in this halophyte upon inoculation with appropriate PGPR, since the different inoculation treatments enhanced PAL expression between 3.75- and five-fold. Our data confirm, at the molecular level, the role of PGPR in alleviating metal stress in S. densiflora and evidence the difficulty of working with halophytes for which little genetic information is available.
One of the many definitions of "cloud" is that of an infrastructure-as-a-service (IaaS) system, in which IT infrastructure is deployed in a provider's data center as virtual machines. With IaaS ...clouds' growing popularity, tools and technologies are emerging that can transform an organization's existing infrastructure into a private or hybrid cloud. OpenNebula is an open source, virtual infrastructure manager that deploys virtualized services on both a local pool of resources and external IaaS clouds. Haizea, a resource lease manager, can act as a scheduling back end for OpenNebula, providing features not found in other cloud software or virtualization-based data center management software.
Although a large amount of acoustic indicators have already been proposed in the literature to evaluate the hypokinetic dysarthria of people with Parkinson's Disease, the goal of this work is to ...identify and interpret new reliable and complementary articulatory biomarkers that could be applied to predict/evaluate Parkinson's Disease from a diadochokinetic test, contributing to the possibility of a further multidimensional analysis of the speech of parkinsonian patients. The new biomarkers proposed are based on the kinetic behaviour of the envelope trace, which is directly linked with the articulatory dysfunctions introduced by the disease since the early stages. The interest of these new articulatory indicators stands on their easiness of identification and interpretation, and their potential to be translated into computer based automatic methods to screen the disease from the speech. Throughout this paper, the accuracy provided by these acoustic kinetic biomarkers is compared with the one obtained with a baseline system based on speaker identification techniques. Results show accuracies around 85% that are in line with those obtained with the complex state of the art speaker recognition techniques, but with an easier physical interpretation, which open the possibility to be transferred to a clinical setting.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Calcium signalling is fundamental to the function of the nervous system, in association with changes in ionic gradients across the membrane. Although restoring ionic gradients is energetically ...costly, a rise in intracellular Ca2+ acts through multiple pathways to increase ATP synthesis, matching energy supply to demand. Increasing cytosolic Ca2+ stimulates metabolite transfer across the inner mitochondrial membrane through activation of Ca2+‐regulated mitochondrial carriers, whereas an increase in matrix Ca2+ stimulates the citric acid cycle and ATP synthase. The aspartate–glutamate exchanger Aralar/AGC1 (Slc25a12), a component of the malate–aspartate shuttle (MAS), is stimulated by modest increases in cytosolic Ca2+ and upregulates respiration in cortical neurons by enhancing pyruvate supply into mitochondria. Failure to increase respiration in response to small (carbachol) and moderate (K+‐depolarization) workloads and blunted stimulation of respiration in response to high workloads (veratridine) in Aralar/AGC1 knockout neurons reflect impaired MAS activity and limited mitochondrial pyruvate supply. In response to large workloads (veratridine), acute stimulation of respiration occurs in the absence of MAS through Ca2+ influx through the mitochondrial calcium uniporter (MCU) and a rise in matrix Ca2+. Although the physiological importance of the MCU complex in work‐induced stimulation of respiration of CNS neurons is not yet clarified, abnormal mitochondrial Ca2+ signalling causes pathology. Indeed, loss of function mutations in MICU1, a regulator of MCU complex, are associated with neuromuscular disease. In patient‐derived MICU1 deficient fibroblasts, resting matrix Ca2+ is increased and mitochondria fragmented. Thus, the fine tuning of Ca2+ signals plays a key role in shaping mitochondrial bioenergetics.
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