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Open access

Zdeněk Vacek, Stanislav Vacek, Jiří Slanař, Lukáš Bílek, Daniel Bulušek, Igor Štefančík, Ivo Králíček and Karel Vančura

Abstract

In time of climate change, close-to-nature silviculture is growing in importance as a tool for future forest management. The paper study the tree layer and natural regeneration of monospecific Norway spruce (Picea abies [L.] Karst.), trough mixed spruce-beech to dominant European beech (Fagus sylvatica L.) forests in Jizerské hory Mts., the Czech Republic. In the locality, shelterwood and selection system have been applied since 2000. The research objectives were to evaluate production parameters, structural diversity, species richness, natural regeneration dynamics and radial growth of individual tree species in relation to climatic factors and air pollution. The stand volume on permanent research plots amounted to 441 – 731 m3 ha−1 in initial stage of transformation. Natural regeneration showed high expansion of beech and decrease of spruce compared to mature tree species composition. Radial growth of spruce was in significant negative correlation with SO2 and NOX concentrations compared to no effect on beech increment. Moreover, spruce was more sensitive to significant years with extreme low radial growth. Beech was more stable in radial growth. Spruce was more resistant to air pollution and climatic stress in mixed stands. Low temperature was limiting factor of radial growth together with climate extremes (such as strong frosts and more frequent droughts) and biotic factors (bark beetle, beech scale). Close-to-nature management supporting admixed tree species should lead in future to diversification of stand structure toward higher species, spatial and age structure to mitigate negative effect of climatic change.

Open access

Shan Xiong, Jinglai Li, Yanling Mu and Zhenqing Zhang

Abstract

Morroniside is one of the most important iridoid glycosides from Cornus officinalis Sieb. et Zucc. In the present study, the pharmacokinetics and bioavailability studies of morroniside were conducted on Sprague-Dawley (SD) rats. A rat in situ intestinal perfusion model was used to characterize the absorption of morroniside. Caco-2 cells were used to examine the transport mechanisms of morroniside. The pharmacokinetic study of morroniside exhibited linear dose-proportional pharmacokinetic characteristics and low bioavailability (4.3 %) in SD rats. Its average P eff value for transport across the small intestinal segments changed from (3.09 ± 2.03) × 10−6 to (4.53 ± 0.94) × 10−6 cm s−1. In Caco-2 cells, the P app values ranged from (1.61 ± 0.53) × 10−9 to (1.19 ± 0.22) × 10−7 cm s−1 for the apical to basolateral side and the P ratio values at three concentrations were all lower than 1.2. Morroniside showed poor absorption and it might not be a specific substrate of P-glycoprotein (P-gp).

Open access

Chuan-Yi Wei, Chun-Ru Liu, Chang-An Li, Gong-Ming Yin, Yu-Fen Zhang, Wen-Peng Li and Lu-Peng Yu

Abstract

Three quartz samples extracted from different origins were collected for ESR evaluation to appreciate the optical bleaching characteristics of the E1’ centre in a long time scale. After exposure of about 400 hours to artificial sunlight, the E1’ centre were bleached to a steady increasing level, about 2.5 times of its natural level, and the increase level also exhibit a small variability among different sample origins. The constant increasing level provide a significantly evidence for the potential use of the natural signal intensities of quartz E1’ centre in tracing sediment provenance. The results show that the signal intensity of E1’ centre increased within beginning 84 h and decreased after 202 h as previous researches have partly predicted. After long time exposed to sunlight, there is no correlation between irradiated samples’ dose rate and its E1’ centre ESR signal intensity. Thus, no new convenient indication shed light on the possible use of the E1’ centre for ESR sediment dating.

Open access

Oluwatoyin T. Fatunsin, Oluwasegun T. Adetunde and Kehinde O. Olayinka

Abstract

Cancer is on the increase globally. Cancer could be associated with hazards from anthropogenic activities. This study attempted to determine the site-specific potential human risks from polycyclic aromatic hydrocarbons (PAHs) in sites of different socio-economic human activities from soils across Lagos metropolis in Nigeria by including a geographic information system (GIS) approach. A Human Simulation Test method was used to determine bio-accessibility for 16 priority PAHs. This was then spatially modelled using a GIS. The spatial vulnerability index for cancer developed show some variation within the study area from 0.2 – 0.0002 all falling below the normal exposure risk level of 1.0. The vulnerability to cancer based on different anthropogenic activities assessed were within the acceptable risk levels. However, it is important to reduce human exposure to even low concentrations of bio-accessible PAHs due to their tendency to bio-accumulate in plants, humans and other organisms.

Open access

Giacomo Sardo, Charles Odilichukwu R. Okpala, Cristiano Bombardi, Sergio Vitale and Elena Fabbri

Abstract

In this current study, the retinal cell morphology of two dolphin species, Tursiops truncatus and Stenella coeruleoalba was compared, and supplemented with a miniature review of how it relates to surrounding environment. Retinal cell morphology involved sectioning and retino-separation of eyes, morphometric analysis of retinal cell layers and its corresponding neurons, followed by stratigraphy of both retina and area/density of ganglion neuron cell bodies. A qualification criteria was developed to describe both thickness and visibility. To relate with surrounding environment of studied species, we searched relevant synthesized literature combining such key words as ‘dolphin’, ‘Tursiops truncatus’, ‘Stenella coeruleoalba’, ‘eye’, ‘vision’, ‘ecology’ and ‘environment’. Retinal cell morphology comparisons showed that the thickness of outer nuclear layer had upper (37.8 – 38.5 μm) whereas outer plexiform layer had lower (7.8 – 8.7 μm) range values, with some differences between individual retinal layers (p<0.05) but specific to some cases. Area of ganglion cell layer of multipolar neurons of retina of both studied species could surpass the 800 μm2 mark, which suggests the presence of ‘giant’ size cell types. Plausibly, the retino-morphological comparisons of studied dolphin species depict the context of micro-view, and able to relate with a macro-view with respect to its surrounding environment.

Open access

M. Irshad Ahamed and K. Sathish Kumar

Abstract

In this communication, we report on Cu2SnS3 quantum dots synthesized by the solvothermal process using different solvents. The optical properties of the quantum dots are analyzed by UV-Vis-NIR and photoluminescence spectroscopy. The results suggest that Cu2SnS3 material has tunable energy bandgap and appropriate wavelength for fabrication of light emitting diodes and laser diodes as sources for fiber optic communication. They exhibit wide absorption in the near infrared range. Further morphological studies with the use of atomic force microscope confirm the surface topography and the existence of quantum dots. The observed characteristics prove the efficiency of Cu2SnS3 quantum dots for O-band wavelength detection used in fiber optic communication and solar cell applications.

Open access

M. Suresh, S. Asath Bahadur and S. Athimoolam

Abstract

In the present work, a new organic second order NLO material: L-isoleucinium p-toluenesulfonate monohydrate (LIPT) is synthesized and reported for the first time. The LIPT is crystallized in a non-centrosymmetric monoclinic space group P21. Structural and hydrogen bond nature of the compound is analyzed using single crystal X-ray diffraction studies. The crystal exhibits very good optical properties such as wide optical transparency in the region of 210 nm to 1100 nm and the ultraviolet wavelength emission (λ = 283 nm). The second harmonic generation efficiency is found to be 1.7 times the standard KDP. Good thermal, mechanical properties and low dielectric constant at high frequency range show that the material may be a potential candidate for optoelectronic applications.

Open access

Tibor Vajsz, László Számel and Árpád Handler

Abstract

Synchronous reluctance motor drives are one of the most attractive alternatives of permanent magnet synchronous motor drives and induction motor drives in the field of conventional industrial and household applications. This tendency is expected to be continued in the case of motion control applications as well. This article investigates two torque-control algorithms that are possible candidates for motion control synchronous reluctance motor applications. The examined torque-control algorithms are direct torque control (DTC) and hysteresis current vector control (HCVC).