Effects of graphene oxide on aquatic macrophyte under the influence of humic substances.

The behavior of nanostructured graphene oxide (GO) in the environment is complex and must be completely understood to evaluate the risk involved. Studies show that humic acid (HA) can stabilize nanomaterials in water and change its behavior. The aquatic macrophyte duckweed (Lemna minor) is a good plant model for adverse effects evaluation of many test-materials due to its fast growth and small size. This study assessed the effect of GO, with and without HA, on the growth of L. minor on fronds number and biomass changes. The plants were exposed during 7 days to the nominal concentrations of GO equals to 0.0 (control), 0.1, 1.0, 10.0 and 100.0 mg L-1, in the absence or in the presence of 20 mg L-1 of HA. Tests were conducted in multiwell polystyreneplates where each well contained two fronds at the start of the experiment. The number of replicates for each test?concentration was 24 wells. The plants were exposed to a constant photoperiod (24:0, light:dark cycle) supplied by white fluorescent lamps (~700 lux) at the temperature of 20± 2 ºC. The fronds number was counted daily and the wet weight was assessed at the end of the experiment. The concentration that promoted 50% of inhibition in the growth rate in terms of fronds number (EC50-7d growth) and the concentration that promoted 50% of wet weight reduction (EC50-7d biomass) were calculated. The reduction of the growth rate by GO at the concentration of 100 mg L-1 was remarkable detected (P 100 mg L-1. This value attributes a practically non-toxicity for the test-material in terms of fronds production. On the other hand, the calculated EC50-7d biomass for the GO in the presence of HA or not was 2.8 and 2.4 mg L-1 respectively. These results indicate that the adverse effects of GO in L. minor are more pronounced on the biomass production since it was clearly observed that reductions in the fronds sizes were greater than in the fronds number. The EC50-7d biomass values assigns a moderate toxicity of GO to L. minor and these data may be useful for the establishment of maximum concentrations limits of this material in water bodies

Atividade inibitória de óleos fixos e essenciais no crescimento de isolados de Salmonella sp. e Salmonella typhimurium.

Neste trabalho foi avaliada a atividade antimicrobiana dos óleos essenciais de Cymbopogon wiinterianus, Pogostemon cablin, Ocimum basilicum, Ocimum gratissimum, Mentha arvensis, Eucalyptus spp., Ocimum basilicum var. Maria Bonita, Romarinus officinalis, Lippia sidoides, Cymbopogon citratus, Zingiber officinale, Azadirachta indica, Allium sativum contra Salmonella sp., e óleos de Pogostemon cablin, Ocimum basilicum var. Maria Bonita, Lippia sp., Lippia sidoides, Cymbopogon cytratus, Zingiber officinale e Ocimum gratissimum para Salmonella typhimurium

The Importance of Accounting for Landscape Position When Investigating Grasslands: A Multidisciplinary Characterisation of a California Coastal Grassland

Grasslands are one of the most common land-cover types, providing important ecosystem services globally, yet few studies have examined grassland critical-zone functioning throughout hillslopes. This study characterised a coastal grassland over a small hillslope at Point Reyes National Seashore, California, using multidisciplinary techniques, combining remotely-sensed, geophysical, plant, and soil measurements. Clustering techniques delineated the study area into four landscape zones, up-, mid-, and down-slope, and a bordering riparian ecotone, which had distinct environmental properties that varied spatially across the site, with depth, and time. Soil moisture increased with depth and down slope towards a bordering riparian zone, and co-varied with soil CO2 flux rates both spatially and temporally. This highlighted three distinct controls of soil moisture on soil respiration: CO2 fluxes were inhibited by high moisture content in the down-slope during the wet winter months, and converged across landscape positions in the dry summer months, while also displaying post-rain pulses. The normalised difference vegetation index (NDVI) ranged from 0.32 (September)–0.80 (April) and correlated positively with soil moisture and aboveground biomass, moving down slope. Yet, NDVI, aboveground biomass, and soil moisture were not correlated to soil organic carbon (SOC) content (0.4%–4.5%), which was highest in the mid-slope. The SOC content may instead be linked to shifts in dominant grassland species and their rhizosphere properties with landscape position. This multidisciplinary characterisation highlighted significant heterogeneity in grassland properties with landscape position, and demonstrated an approach that could be used to characterise other critical-zone environments on hillslopes

Association between soil organic carbon and calcium in acidic grassland soils from Point Reyes National Seashore, CA

Organo-mineral and organo-metal associations play an important role in the retention and accumulation of soil organic carbon (SOC). Recent studies have demonstrated a positive correlation between calcium (Ca) and SOC content in a range of soil types. However, most of these studies have focused on soils that contain calcium carbonate (pH > 6). To assess the importance of Ca-SOC associations in lower pH soils, we investigated their physical and chemical interaction in the grassland soils of Point Reyes National Seashore (CA, USA) at a range of spatial scales. Multivariate analyses of our bulk soil characterisation dataset showed a strong correlation between exchangeable Ca (Ca$_{Exch}$; 5–8.3 c.mol$_{c}$ kg$^{−1}$) and SOC (0.6–4%) content. Additionally, linear combination fitting (LCF) of bulk Ca K-edge X-ray absorption near-edge structure (XANES) spectra revealed that Ca was predominantly associated with organic carbon across all samples. Scanning transmission X-ray microscopy near-edge X-ray absorption fine structure spectroscopy (STXM C/Ca NEXAFS) showed that Ca had a strong spatial correlation with C at the microscale. The STXM C NEXAFS K-edge spectra indicated that SOC had a higher abundance of aromatic/olefinic and phenolic C functional groups when associated with Ca, relative to C associated with Fe. In regions of high Ca-C association, the STXM C NEXAFS spectra were similar to the spectrum from lignin, with moderate changes in peak intensities and positions that are consistent with oxidative C transformation. Through this association, Ca thus seems to be preferentially associated with plant-like organic matter that has undergone some oxidative transformation, at depth in acidic grassland soils of California. Our study highlights the importance of Ca-SOC complexation in acidic grassland soils and provides a conceptual model of its contribution to SOC preservation, a research area that has previously been unexplored

A multidisciplinary approach for the management of hypodontia: case report

Hypodontia is the congenital absence of one or more teeth and may affect permanent teeth. Several options are indicated to treat hypodontia, including the maintenance of primary teeth or space redistribution for restorative treatment with partial adhesive bridges, tooth transplantation, and implants. However, a multidisciplinary approach is the most important requirement for the ideal treatment of hypodontia. This paper describes a multidisciplinary treatment plan for congenitally missing permanent mandibular second premolars involving orthodontics, implantology and prosthodontic specialties