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  • Author: S. Sina x
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Simulation of the thermo-optic coupling effect in mid-infrared second harmonic generation of ZnGeP2 crystal

Abstract

The thermo-optic coupling process of second harmonic generation was numerically simulated in ZnGeP2 crystals pumped by a pulsed CO2 laser at the wavelength of 9.6 μm, under the strong and weak cooling conditions. The conversion efficiencies, temperature distributions were calculated during the evolution of the thermo-optic coupling. The results showed that the thermooptic coupling was weak in the strong cooling condition, which nearly did not disturb the conversion processes and temperature distribution, while in the weak cooling case, the temperature distribution showed a great influence on the conversion efficiency and light intensity. Finally, it was found that compensation of the phase mismatch induced by the thermal effect can well recover the conversion efficiency.

Open access
Cubic Graphs with Total Domatic Number at Least Two

Abstract

Let G be a graph with no isolated vertex. A total dominating set of G is a set S of vertices of G such that every vertex is adjacent to at least one vertex in S. The total domatic number of a graph is the maximum number of total dominating sets which partition the vertex set of G. In this paper we provide a criterion under which a cubic graph has total domatic number at least two.

Open access
Genetic conservation in Parkia biglobosa (Fabaceae: Mimosoideae) - what do we know?

Abstract

The medicinal and food tree species Parkia biglobosa (Fabaceae: Mimosoideae) is widespread in the Sudanian savannahs of sub-Saharan Africa, where it has a strong socio-cultural and economic importance. Populations of this species are highly threatened in large parts of its range due to overexploitation and environmental degradation. In the light of climatic changes, safeguarding the genetic diversity of the species is crucial to foster adaptation and to support its long-term survival. Genetic insight is also relevant to guide sustainable harvesting. This paper has the objective to review information on the species’ geographic distribution, reproductive biology, genetic characteristics and existing conservation practices, and to identify knowledge gaps to orientate future conservation and research focus. The literature review revealed that the species is mainly outcrossed and is pollinated by a diversity of vectors, including bats that allow long-pollen dispersal. When bats are absent, pollination is mainly carried out by honey bees and stingless bees and in such case pollen-mediated gene flow is relatively restricted. Data of a large-scale genetic study based on allozyme markers showing a moderate genetic differentiation among populations were reanalyzed using an inverse distance weighted interpolation function. Three distinctive regions of diversity based on allelic richness and expected heterozygosity were identified. Finally, we discuss future challenges for genetic conservation by emphasizing the need to use both neutral and adaptive markers in future research.

Open access