Low dark current high gain InAs quantum dot avalanche photodiodes monolithically grown on Si

Avalanche photodiodes (APDs) on Si operating at optical communication wavelength band are crucial for the Si-based transceiver application. In this paper, we report the first O-band InAs quantum dot (QD) waveguide APDs monolithically grown on Si with a low dark current of 0.1 nA at unit gain and a responsivity of 0.234 A/W at 1.310 μm at unit gain (−5 V). In the linear gain mode, the APDs have a maximum gain of 198 and show a clear eye diagram up to 8 Gbit/s. These QD-based APDs enjoy the benefit of sharing the same epitaxial layers and processing flow as QD lasers, which could potentially facilitate the integration with laser sources on a Si platform

Effect of Stagger Angle of Rotor Channels on the Wave Rotor

A wave rotor optimizes the use of energy resources by enhancing thermodynamic cycles, and further optimization of wave rotor geometry is emerging as an attractive research area. Among the geometric features, the stagger angle of channels lacks sufficient study in spite of its important effects. To address this question, this work developed and applied the velocity triangle models to modify the basic geometry of wave rotors for different stagger angles, and investigated the flow fields with two-dimensional numerical methods. Results showed that: (1) different stagger angles worked out similar unsteady pressure wave systems and kept nearly constant compression and expansion ratios of the wave rotor; (2) increased stagger angle made the inlet and outlet flows turn toward the axial direction, which was beneficial to compact and light-weighted integration of the wave rotor to a gas turbine; (3) increased stagger angle made the wave rotor consume more shaft power, but even the maximum shaft power was small. This work revealed a critical mechanism how the velocity variation across an unsteady pressure wave produced rim work in a staggered channel, and made a recommendation to comprehensive optimization of wave rotor geometry for better integration in a gas turbine and acceptable shaft power consumption

Effect of Stagger Angle of Rotor Channels on the Wave Rotor

A wave rotor optimizes the use of energy resources by enhancing thermodynamic cycles, and further optimization of wave rotor geometry is emerging as an attractive research area. Among the geometric features, the stagger angle of channels lacks sufficient study in spite of its important effects. To address this question, this work developed and applied the velocity triangle models to modify the basic geometry of wave rotors for different stagger angles, and investigated the flow fields with two-dimensional numerical methods. Results showed that: (1) different stagger angles worked out similar unsteady pressure wave systems and kept nearly constant compression and expansion ratios of the wave rotor; (2) increased stagger angle made the inlet and outlet flows turn toward the axial direction, which was beneficial to compact and light-weighted integration of the wave rotor to a gas turbine; (3) increased stagger angle made the wave rotor consume more shaft power, but even the maximum shaft power was small. This work revealed a critical mechanism how the velocity variation across an unsteady pressure wave produced rim work in a staggered channel, and made a recommendation to comprehensive optimization of wave rotor geometry for better integration in a gas turbine and acceptable shaft power consumption

Subwavelength Silicon Photonics

Subwavelength gratings refer to periodic structures that have a period less than half the wavelength of light in the material so that no Bragg diffraction mode is supported. Instead, the light will propagate as if it was in a homogeneous material with anisotropic refractive indices. Subwavelength gratings have attracted great interest recently, as they provide a useful degree of freedom for the crafting of the effective refractive index of the material in photonic devices. In this chapter, we will introduce some of the applications of subwavelength structures for silicon photonics devices. We start by introducing the background theory of subwavelength gratings and then discuss their applications for the engineering of waveguide grating couplers, suspended membrane devices for mid-infrared (mid-IR) wavelengths, and their use with numerical optimization techniques for optimizing photonic devices. We shall discuss the classic effective medium theory (EMT) for subwavelength gratings and show how EMT can reduce time-consuming three-dimensional (3D) numerical optimizations to an effective two-dimensional (2D) optimization problem

Paternity assignment in the polyploid Acipenser dabryanus based on a novel microsatellite marker system.

Acipenser dabryanus is listed as a Critical Endangered species in the IUCN Red List and the first class protected animals in China. Fortunately, A. dabryanus specimens are being successfully bred in captivity for conservation. However, for effective ex situ conservation, we should be aware of the genetic diversity and the degree of relatedness of the individuals selected for breeding. In this study, we aimed at the development of novel and reliable microsatellites used for the genetic study of A. dabryanus. A total of 14,321 simple sequence repeats (SSRs) were detected by transcriptome sequencing and screening. We selected 20 novel and polymorphic microsatellites (non-dinucleotide) with good repeatability from the 100 tested loci for a subsequent genetic and paternity study. A set of captive broodstock (F1 stock, n = 43) and their offspring (F2 stock, n = 96) were used to examine the efficiency of the 20 SSRs for assigning parentage to offspring, with an allocation success of 91.7%. We also found that only a few families predominantly contributed to the progeny produced by the 43 breeders. In addition, mitochondrial DNA data showed that the captive broodstock (F1 individuals) had an excellent probability of the same lineage, implying that a high level of inbreeding may have occurred in these individuals. Our research provides useful information on genetic diversity and reproductive pattern of A. dabryanus, and the 20 SSRs developed in this study can be applied to the future breeding program to avoid inbreeding for this stock or other related species of Acipenseriformes

Transcriptome sequencing of the spleen of the Yangtze sturgeon (Acipenser dabryanus) under Edwardsiella tarda and poly(I:C) treatments

Acipenser dabryanus is an ancient living fossil and a flagship species of the Yangtze River. However, A. dabryanus was listed as a critically endangered species due to the dramatic decrease in its population, and disease outbreaks occurring during captive breeding have hindered the protection of this species. Here, we investigated the effect of the pathogenic bacterium Edwardsiella tarda and poly(I:C) on A. dabryanus at the histopathological and transcriptomic levels. After 48 h of infection with E. tarda, A. dabryanus exhibited marked pathological changes in the intestine and liver. We then conducted full-length transcriptome sequencing of the spleen by SMRT sequencing technology. Using the full-length transcriptome data as a reference, transcriptomic results obtained through Illumina sequencing technology revealed that a total of 894 and 963 unigenes were differentially expressed between the PBS and bacterial infection groups and between the PBS and poly(I:C) challenge groups, respectively. E3 ubiquitin ligases family members, T-cell receptor and clusters of differentiation were significantly upregulated by bacteria or poly(I:C) treatment, while the complement was significantly downregulated, suggesting that they might participate in multiple immune pathways in the response to pathogen invasion. Pathogen infection also induced changes in some key rate-limiting enzymes involved in energy metabolism. Our study can provide important information on the molecular mechanisms underlying the immune response of fish to pathogenic microbial infections and help explore the antibacterial and antiviral immunity of A. dabryanus

Parsimonious clinical prediction model for the diagnosis of complicated appendicitis

Objective: To develop a logistic regression model that combines clinical and radiological parameters for prediction of complicated appendicitis. Methods: 248 patients with histologically proven uncomplicated (n = 214) and complicated (n = 34) acute appendicitis were analyzed retrospectively. All patients had undergone a presurgical abdominal and/or pelvic computed tomography (CT) scan, assessed by two radiologists. A model using univariate and multivariate logistic regression analyses was developed, and the strength of association between independent predictors and complicated acute appendicitis was evaluated by adjusted odds radio. Clinical parameters were gender, age, anorexia, vomiting, duration of symptoms, right lower abdominal quadrant (RLQ) tenderness, rebound tenderness, body temperature, white blood cell (WBC) count, and neutrophil ratio. Radiological parameters were appendix diameter, appendicolith, caecal wall thickening, mesenteric lymphadenopathy, extraluminal air, abscess, fat stranding, and periappendicular fluid. Results: Four features (body temperature＞37.2 °C, vomiting, appendicolith, and periappendiceal fluid) were included in the logistic regression model, and yielded an area under the curve (AUC) of 0.87 (95% confidence interval (CI), 0.80–0.93), sensitive of 88%, and specificity of 74%. Conclusion: The logistic regression model makes an accurate and simple prediction of complicated appendicitis possible

Integrated biochemical, transcriptomic and metabolomic analyses provide insight into heat stress response in Yangtze sturgeon (Acipenser dabryanus)

Temperature fluctuations caused by climate change and global warming pose a great threat to various species. Most fish are particularly vulnerable to elevated temperatures. Understanding the mechanism of high-temperature tolerance in fish can be beneficial for proposing effective strategies to help fish cope with global warming. In this study, we systematically studied the effects of high temperature on Acipenser dabryanus, an ancient living fossil and flagship species of the Yangtze River, at the histological, biochemical, transcriptomic and metabolomic levels. Intestinal and liver tissues from the control groups (18 °C) and acute heat stress groups (30 °C) of A. dabryanus were sampled for histological observation and liver tissues were assessed for transcriptomic and metabolomic profiling. Histopathological analysis showed that the intestine and liver tissues were damaged after heat stress. The plasma cortisol content and the levels of oxidative stress markers (catalase/glutathione reductase) and two aminotransferases (aspartate aminotransferase/alanine aminotransferase) increased significantly in response to acute heat stress. Transcriptomic and metabolomic methods showed 6707 upregulated and 4189 downregulated genes and 64 upregulated and 78 downregulated metabolites in the heat stress group. Heat shock protein (HSP) genes showed striking changes in expression under heat stress, with 21 genes belonging to the HSP30, HSP40, HSP60, HSP70 and HSP90 families significantly upregulated by short-term heat stress. The majority of genes associated with ubiquitin and various immune-related pathways were also markedly upregulated in the heat stress group. In addition, the combined analysis of metabolites and gene profiles suggested an enhancement of amino acid metabolism and glycometabolism and the suppression of fatty acid metabolism during heat stress, which could be a potential energy conservation strategy for A. dabryanus. To the best of our knowledge, the present study represents the first attempt to reveal the mechanisms of heat stress responses in A. dabryanus, which can provide insights into improved cultivation of fish in response to global warming

Gonadal transcriptome sequencing of the critically endangered Acipenser dabryanus to discover candidate sex-related genes

Background Acipenser dabryanus, an endemic Chinese species, has been listed as a first-class protected animal in China. Sturgeons are among the oldest and most primitive group of existing fish in the world and occupy a special place in the evolutionary history of fish. Thus, a study of the reproduction and sex differentiation of sturgeon will be of great value for fish as well as the whole vertebrate group. Methods In this study, we conducted comparative analysis of the testes and ovaries transcriptomes of A. dabryanus to screen for sex-differentiation and sexual development-related genes. Results The transcriptome sequencing of six cDNA libraries generated 265 million clean reads, encompassing 79 Gb of sequences. The N50 and mean length of the identified 91,375 unigenes were 1,718 and 989 bp, respectively. A total of 6,306, 9,961, 13,170, 15,484, and 23,588 unigenes were annotated in the clusters of orthologous groups, gene ontology categories, Kyoto Encyclopedia of Genes and Genomes Pathway, euKaryotic orthologous groups, and NCBI non-redundant protein databases, respectively. A total of 5,396 differentially expressed genes were found between the two sexes, with 1,938 predicted to be up-regulated in ovaries and 3,458 in testes. A total of 73 candidate genes known to be involved in sex differentiation and sexual development were searched in the transcriptome of A. dabryanus of which 52 showed significant similarity. We highlighted six genes that are differentially expressed between the two sexes and may play important roles in sex differentiation and gonad maintenance. In addition, 24,271 simple sequence repeats (SSRs) and 550,519 single-nucleotide polymorphisms (SNPs) were detected. Discussion This work represents the first transcriptome study comparing the ovary and testis in A. dabryanus. The putative differentially expressed genes between the gonads provide an important source of information for further study of the sex-differentiation related genes and the sex-differentiation mechanism in sturgeons. The SSRs or SNPs identified in this study will be helpful in the discovery of sex-related markers in A. dabryanus