A full-vectorial imaginary-distance beam propagation method based on a finite element scheme is newly formulated and is effectively applied to investigating the problem of leakage due to a finite ...number of arrays of air holes in photonic-crystal holey fibers (HFs). In order to treat arbitrarily shaped air holes and to avoid spurious solutions, a curvilinear edge/nodal hybrid element is introduced. Furthermore, in order to evaluate propagation characteristics of not only bound modes but leaky modes in HFs, an anisotropic perfectly matched layer is also employed as a boundary condition at computational window edges. It is confirmed from numerical results that the propagation loss increases rapidly with increasing wavelength, especially for HFs with one ring of smaller air holes, and that the propagation loss is drastically reduced by adding one more ring of air holes to the cladding region.
Single nucleotide polymorphisms (SNPs) have gained wide use in humans and model species and are becoming the marker of choice for applications in other species. Technology that was developed for work ...in model species may provide useful tools for SNP discovery and genotyping in non-model organisms. However, SNP discovery can be expensive, labour intensive, and introduce ascertainment bias. In addition, the most efficient approaches to SNP discovery will depend on the research questions that the markers are to resolve as well as the focal species. We discuss advantages and disadvantages of several past and recent technologies for SNP discovery and genotyping and summarize a variety of SNP discovery and genotyping studies in ecology and evolution.
A new structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed by using a full-vector finite element method with anisotropic perfectly matched layers. ...From the numerical results it is confirmed that the proposed fiber is low-loss SPSM-PCF within the wavelengths ranging from 1.48 to 1.6 μm, where only the slow-axis mode exists and the confinement loss is less than 0.1 dB/km.
Threshold carrier densities of GeSn quantum well (QW) lasers and the physical reason of low-temperature lasing of current GeSn laser are investigated through the comparison of threshold carrier ...densities of conventional III-V QW lasers. Electrons distributed over L-band is the main cause of decreased gain for GeSn QWs. To increase the gain (and improve the laser characteristics), a modulation-doped GeSn QW is proposed and the material gain is analyzed based on many-body theory for both qualitative and quantitative simulation. Significant gain increase can be expected for n-type modulation doping QWs. The doping condition for elevated temperature lasing is discussed and it was found that material gain curve similar to III-V QW is obtained for GeSn QW with n-type modulation doping of 6 × 10
cm
. It was also found that unlike III-V QW lasers, n-type modulation doping is more effective for high-speed operation in terms of differential gain than p-type modulation doping.
In order to control dispersion and dispersion slope of indexguiding photonic crystal fibers (PCFs), a new controlling technique of chromatic dispersion in PCF is reported. Moreover, our technique is ...applied to design PCF with both ultra-low dispersion and ultra-flattened dispersion in wide wavelength range. A full-vector finite element method with anisotropic perfectly matched layers is used to analyze the dispersion properties and the confinement losses in a PCF with finite number of air holes. It is shown from numerical results that it is possible to design a fourring PCF with flattened dispersion of 0 +/- 0.5 ps/(km.nm) from 1.19 m to 1.69 m wavelength range and a five-ring PCF with flattened dispersion of 0 +/- 0.4 ps/(km.nm) from 1.23 m to 1.72 m wavelength range.
Recent progress on numerical modeling methods for photonic crystal fibers (PCFs) such as the effective index approach, basis-function expansion approach, and numerical approach is described. An ...index-guiding PCF with an array of air holes surrounding the silica core region has special characteristics compared with conventional single-mode fibers (SMFs). Using a full modal vector model, the fundamental characteristics of PCFs such as cutoff wavelength, confinement loss, modal birefringence, and chromatic dispersion are numerically investigated.
Fishes of the order Cypriniformes are almost completely restricted to freshwater bodies and number > 3400 species placed in 5 families, each with poorly defined subfamilies and/or tribes. The present ...study represents the first attempt toward resolution of the higher-level relationships of the world's largest freshwater-fish clade based on whole mitochondrial (mt) genome sequences from 53 cypriniforms (including 46 newly determined sequences) plus 6 outgroups. Unambiguously aligned, concatenated mt genome sequences (14,563 bp) were divided into 5 partitions (first, second, and third codon positions of the protein-coding genes, rRNA genes, and tRNA genes), and partitioned Bayesian analyses were conducted, with protein-coding genes being treated in 3 different manners (all positions included; third codon positions converted into purine R and pyrimidine Y RY-coding; third codon positions excluded). The resultant phylogenies strongly supported monophyly of the Cypriniformes as well as that of the families Cyprinidae, Catostomidae, and a clade comprising Balitoridae + Cobitidae, with the 2 latter loach families being reciprocally paraphyletic. Although all of the data sets yielded nearly identical tree topologies with regard to the shallower relationships, deeper relationships among the 4 major clades (the above 3 major clades plus Gyrinocheilidae, represented by a single species Gyrinocheilus aymonieri in this study), were incongruent depending on the data sets. Treatment of the rapidly saturated third codon-position transitions appeared to be a source of such incongruities, and we advocate that RY-coding, which takes only transversions into account, effectively removes this likely "noise" from the data set and avoids the apparent lack of signal by retaining all available positions in the data set.
We propose and experimentally demonstrate a low-loss and low-crosstalk Mach-Zehnder mode/wavelength multi/demultiplexer for WDM/MDM transmission based on a Si-photonics platform. A broadband 3-dB ...mode divider, which is also newly devised here, makes it possible to compose a Mach-Zehnder filter for "mode" and "wavelength" simultaneously. Transmission characteristics of fabricated 3-dB mode dividers are in excellent agreement with theoretical results. Mach-Zehnder filters using the 3-dB mode divider with a free spectral range (FSR) of 20 and 1 nm are also fabricated and the modal crosstalk is less than -24 dB in the 40-nm wavelength range for the MZ filter with an FSR of 20 nm. The tuning of the peak wavelength position by the TiN heater is also demonstrated.
Here we review a role of a basal ganglia–brainstem (BG–BS) system throughout the mesopontine tegmentum in the control of various types of behavioral expression. First the basal ganglia–brainstem ...system may contribute to an automatic control of movements, such as rhythmic limb movements and adjustment of postural muscle tone during locomotion, which occurs in conjunction with voluntary control processes. Second, the basal ganglia–brainstem system can be involved in the regulation of awake–sleep states. We further propose the possibility that the basal ganglia–brainstem system is responsible for the integration of volitionally-guided and emotionally-triggered expression of motor behaviors. It can be proposed that dysfunction of the basal ganglia–brainstem system together with that of cortico-basal ganglia loop underlies the pathogenesis of behavioral disturbances expressed in basal ganglia dysfunction.
The organizing of magnetic skyrmions shows several forms similar to atomic arrays of solid states. Using Lorentz transmission electron microscopy, we report the first direct observation of a stable ...liquid-crystalline structure of skyrmions in chiral magnet Co8.5Zn7.5Mn4(110) thin film, caused by magnetic anisotropy and chiral surface twist. Elongated skyrmions are oriented and periodically arranged only in the ⟨110⟩ directions, whereas they exhibit short-range order along the ⟨001⟩ directions, indicating a smectic skyrmion state. In addition, skyrmions possess anisotropic interaction with an opposite sign depending on the crystal orientation, in contrast to existing isotropic interaction.
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