Electrospun PGA/gelatin nanofibrous scaffolds and their potential application in vascular tissue engineering

Hadi Hajiali1, Shapour Shahgasempour1, M Reza Naimi-Jamal2, Habibullah Peirovi11Nanomedicine and Tissue Engineering Research Center, Shahid Beheshti University of Medical Sciences; 2Department of Chemistry, Iran University of Science and Technology, Tehran, IranBackground and methods: In this study, gelatin was blended with polyglycolic acid (PGA) at different ratios (0, 10, 30, and 50 wt%) and electrospun. The morphology and structure of the scaffolds were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The mechanical properties were also measured by the tensile test. Furthermore, for biocompatibility assessment, human umbilical vein endothelial cells and human umbilical artery smooth muscle cells were cultured on these scaffolds, and cell attachment and viability were evaluated.Results: PGA with 10 wt% gelatin enhanced the endothelial cells whilst PGA with 30 wt% gelatin increased smooth muscle cell adhesion, penetration, and viability compared with the other scaffold blends. Additionally, with the increase in gelatin content, the mechanical properties of the scaffolds were improved due to interaction between PGA and gelatin, as revealed by Fourier transform infrared spectroscopy and differential scanning calorimetry.Conclusion: Incorporation of gelatin improves the biological and mechanical properties of PGA, making promising scaffolds for vascular tissue engineering.Keywords: polyglycolic acid, gelatin, nanofiber, vascular tissue engineering, biocompatible scaffold&nbsp

Bathymetric modelin from satellite imagery via Single Band Algorithm (SBA) and Principal Components Analysis (PCA) in southern Caspian Sea

Remotely sensed imagery is proving to be a useful tool to estimate water depths in coastal zones. Bathymetric algorithms attempt to isolate water attenuation and hence depth from other factors by using different combinations of spectral bands. In this research, images of absolute bathymetry using two different but related methods in a region in the southern Caspian Sea coasts has been produced. The first method used a Single Band Algorithm (SBA) and assumed a constant water attenuation coefficient throughout the blue band. The second method used Principal Components Analysis (PCA) to adjust for varying water attenuation coefficients without additional ground truth data. PCA method (r=-0.672394) appears to match our control points slightly better than single band algorithm (r=-0.645404). It is clear that both methods can be used as rough estimates of bathymetry for many coastal zone studies in the southern Caspian Sea such as near shore fisheries, coastal erosion, water quality, recreation siting and so forth. The presented methodology can be considered as the first step toward mapping bathymetry in the southern Caspian Sea. Further research must investigate the determination of the nonlinear optimization techniques as well as the assessment of these models’ performance in the study area

Influence of vertical distribution of phytoplankton on remote sensing signal of Case II waters : southern Caspian Sea case study

Reliable monitoring of coastal waters is not possible without using remote sensing data. On the other hand, it is quite difficult to develop remote sensing algorithms that allow one to retrieve water characteristics (like chlorophyll-a concentration) in optically complex coastal and inland waters (called also Case II waters) as the concentrations of optically active substances (phytoplankton, suspended matter, and colored dissolved organic matter) vary independently from each other and the range of variability is often high. Another problem related to developing remote sensing algorithms for retrieving concentrations of optically active substances in such complex waters is vertical distribution of these substances. For example, phytoplankton distribution in the water column is often characterized with maxima just below the surface mixed layer, and some phytoplankton species even have the capability to migrate in the water column and tend to form layers at depths optimal for their growth. Twenty-three field campaigns were performed during the spring-summer period in the coastal waters of the southern Caspian Sea where vertical distribution of phytoplankton was measured by means of chlorophyll-a fluorometer. There results showed that there is usually a chlorophyll-a maximum between 10 and 20 m where the concentration is about one order of magnitude higher than in the top mixed layer. The Hydrolight 5.0 radiative transfer model used to estimate if the vertical distribution of biomass have detectable impact on remote sensing signal in these waters. For that purpose, several stations with distinctly different chlorophyll-a profiles were selected and two simulations for each of those measuring stations was carried out. First the Hydrolight was run with the actual chlorophyll-a vertical distribution profile and second a constant chlorophyll-a value (taken as an average of measured chlorophyll-a in the surface layer) was used in the model simulation. The modelling results show that the “deep” chlorophyll maximum has negligible effect on the remote sensing reflectance spectra. Consequently, there is no need to take into account the vertical distribution of phytoplankton while developing remote sensing algorithms for the Caspian Sea coastal water

Effets du pâturage sur le couvert végétal et la qualité des sols dans les parcours des zones arides

Rangelands constitute a significant component of the production systems. Their use raises several questions regarding their durability. Indeed, the stocking density impacts their ecological functioning. This paper reviews the impacts of grazing on vegetation cover and soil quality of rangelands in arid and semi-arid regions. The impacts of grazing on vegetation cover, surface soil characteristics and hydrodynamic properties of soils depend on the one hand, on ecosystem characteristics (soil, vegetation, climate), and on the other hand on grazing intensity and frequency. In particular grazing reduces soil vegetation cover and impacts its structure, composition and extent. With time, the quality of vegetation cover regresses and its fodder productivity decreases. In humid pastoral ecosystems, grazing packs soil surface because of the high stocking density. This soil packing associated with a reduction of vegetation cover implies a reduction of soil infiltration capacity and an increase of runoff and erosion. On the other hand, in arid regions, the effects of grazing on soil characteristics are variable. Some studies showed that the soil is packed when the stocking density is high. Others pointed out that animal trampling does not impact soil packing. Observed differences are mainly due to soil type, moisture and the nature of grazing. Limited or moderate grazing, characterized by appropriate movement of animals makes allow for sustainable use of rangelands. Keywords: Rangelands, Grazing, Vegetation cover; Soil characteristics; Hydrological behavior of soilsLes parcours constituent une composante importante des systèmes de production. Leur utilisation pose plusieurs questions concernant leur durabilité. En effet, la charge animale impacte leur fonctionnement écologique. Ce papier synthétise les impacts du pâturage sur le couvert végétal et le sol des parcours dans les zones arides et semi-arides. Les impacts du pâturage sur le couvert végétal, les caractéristiques de l'état de surface et les propriétés hydrodynamiques du sol dépendent d'une part, des caractéristiques de l’écosystème (sol, végétation, climat), et d'autre part de l'intensité et la fréquence du pâturage. Le pâturage réduit en particulier la couverture végétale du sol et impact sa structure, sa composition et son étendue. Avec le temps, la qualité du couvert végétal régresse et sa productivité fourragère diminue. Dans les écosystèmes pastoraux humides, le pâturage tasse la surface du sol à cause de la charge animale élevée. Ce tassement associé à une réduction du couvert végétal se traduit par une diminution de la capacité d'infiltration du sol et une augmentation du ruissellement et de l’érosion. Par contre, dans les zones arides, les effets du pâturage sur les caractéristiques du sol sont variables. Des études ont montré que le sol est tassé quand la charge animale est élevée. D'autres ont signalé que le piétinement animal n'a pas d'effet de tassement sur le sol. Les différences constatées sont dues au type de sol, à l'humidité et à la nature du pâturage. Le pâturage léger ou modéré, caractérisé par une circulation adéquate des animaux permet d’utiliser durablement les parcours Mots clefs: Parcours, Pâturage, Couvert végétal, Caractéristiques des sols, Comportement hydrologique des sol