Genetic Diversity and Phylogenetic Analysis of Zygophyllum loczyi in Northwest China's Deserts Based on the Resequencing of the Genome.

In order to study the genetics of local adaptation in all main deserts of northwest China, whole genomes of 169 individuals were resequenced, which covers 20 populations of Zygophyllum loczyi (Zygophyllales: Zygophylaceae). We describe more than 15 million single nucleotide polymorphisms and numerous InDels. The expected heterozygosity and PIC values associated with local adaptation varied significantly across biogeographic regions. Variation in environmental factors contributes largely to the population genetic structure of Z. loczyi. Bayesian analysis performed with STRUCTURE defined four genetic clusters, while the results of principle component analysis were similar. Our results shows that the Qaidam Desert group appears to be diverging into two branches characterized by significant geographic separation and gene flow with two neighboring deserts. Geological data assume that it is possible that the Taklamakan Desert was the original distribution site, and Z. loczyi could have migrated later on and expanded within other desert areas. The above findings provide insights into the processes involved in biogeography, phylogeny, and differentiation within the northwest deserts of China.

Compact hybrid plasmonic slot waveguide sensor with a giant enhancement factor for surface-enhanced Raman scattering application.

In this paper, a surface-enhanced Raman scattering (SERS) sensor with a giant field enhancement factor based on the coupling of surface plasmon polaritons (SPPs) is designed and studied theoretically. The proposed sensor adopts a metal-dielectric layered hybrid slot waveguide structure, combining thin metal (gold) layers and silicon nitride strip waveguides. Unlike other similar sensors, the silicon nitride waveguide structure does not serve as an excitation signal channel, conventionally loaded with the guided modes, but as an auxiliary layer, making it easier to concentrate the light field in the slot. Therefore, the sensor has a higher enhancement factor compared to the pure metal or dielectric slot structure. The results exhibit that we can obtain a maximum enhancement factor exceeding 10^6 under the compact configuration of 510 × 300 × 225nm^3 at the wavelength of 785 nm. By analyzing the dependence of the sensor performance on the structural parameters, we show that the structure of such sensor can directly be applied to SERS spectroscopic analysis as well as integrated with micro-and nano-photonic platform to perform on-chip detection system.

Threshold conditions of electric field enhancement and energy confinement in the low-index core of nanoscale waveguides.

Threshold conditions to realize electric field enhancement and energy confinement in the low-refractive-index core of nanoscale waveguides are studied by solving the field function. When the incident lightwave meets the relation of special thresholds, we observe the enhanced electric field and a concentrated light energy in the core. The electric field enhancement and the confined light power are highly dependent on the light wavelength. When the core width is 30 nm, for a wavelength of 1.55 µm, we achieve a power confinement factor above 40%. As the basis for a growing number of potential applications, the threshold conditions discovered in this work will find significant applications in many fields, such as optical sensors and optical communication components.

[Nonlalocalized interference in multiple-beam interferometer].

The authors studied the nonlocalized interference in multiple-beam interferometer. The light intensity distribution function was obtained. The result shows that the function in the circle center has the same form with localized interference. Numerical simulation method was used to analyse the light intensity distribution function. As the reflection coefficient increases, the stripe becomes sharp, Resolution ratio was improved, while the noise occured around the lower interference index. The noise becomes obviously as the reflection coefficient increases. While changing the receiving screen distance, the simulation result shows that linear relationship exists between inteference index and cosine value of interference stripe dip angle. The mirror spacing can be obtained through the straight line slope. With changing the mirror spacing, the numerical simulation result shows that linear relationship exists between interference index and stripe radii square. The straight slope shows a linear relationship with the mirror spacing.