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In this study, the mitochondrial genome (mitogenome) of Holothuria fuscocinerea was unraveled to be 15,890 bp in length, containing 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The PCGs were initiated by four initiation codons (ATG, TAC, ATC, and ATA). Only one PCG (nad6) and five tRNA genes (tRNASer(UCN), tRNAGln, tRNAAla, tRNAVal, and tRNAAsp) were encoded on the light chain, and the other genes were encoded on the heavy chain. A phylogenetic tree constructed with 16S rRNA sequences showed that H. fuscocinerea is most closely related to H. leucospilota.

Na+/H+ exchangers are the most common membrane proteins involved in the regulation of intracellular pH that concurrently transport Na+ into the cells and H+ out of the cells. In this study, the full-length cDNA of the Na+/H+ exchanger (NHE) from the Pacific white shrimp (Litopenaeus vannamei) was cloned. The LvNHE cDNA is 3167 bp long, contains a 5'-untranslated region (UTR) of 74 bp and a 3'-UTR of 456 bp and an open reading frame (ORF) of 2637 bp, coding for a protein of 878 amino acids with 11 putative transmembrane domains and a long cytoplasmic tail. LvNHE shows high sequence homology with mud crab NHE at the amino acid level. LvNHE mRNA was detected in the hepatopancreas, gill, eyestalk, skin, heart, intestine, muscle, brain and stomach, with the highest abundance in the intestine. In the shrimp intestinal fragment cultures exposed to gradually declining pH medium (from pH 8.0 to pH 6.4), the LvNHE mRNA expression was significantly stimulated, with the highest response when incubated in pH 7.0 medium for 6 h. To investigate the functional roles of LvNHE in pH regulation at the physiological and cellular levels, the LvNHE mRNA expression was silenced by siRNA knockdown. Upon low-pH challenge, the hemolymph pH was significantly reduced in the LvNHE mRNA knockdown shrimp. In addition, knockdown of LvNHE mRNA reduced the recovery capacity of intracellular pH in intestinal fragment cultures after acidification. Altogether, this study demonstrates the role of NHE in shrimp response to low pH stress and provides new insights into the acid/base homeostasis mechanisms of crustaceans.

Heat shock proteins (HSPs), a family of conserved proteins that are produced by cells in response to stresses, are known as molecular chaperones with a range of housekeeping and cellular protective functions. The 40 kD heat shock protein (HSP40) is a co-chaperone for HSP70 in the regulation of ATP hydrolysis. Unlike its well-documented cofactor HSP70, little is currently known regarding the biological functions of HSP40 in crustacean species such as penaeid shrimp. In the present study, the cDNA encoding HSP40 (Lv-HSP40) was identified from the Pacific white shrimp Litopenaeus vannamei, a highly significant commercial culture species. The structural organization indicates that Lv-HSP40 belongs to the type-I HSP40s. The muscle, gill, and hepatopancreas are the main sites of Lv-HSP40 transcript expression. Within these tissues, Lv-HSP40 mRNA were predominantly exhibited in the myocytes, epithelial cells and hepatopancreatic cells, respectively. Under acute thermal stress in the culture environment, Lv-HSP40 transcript levels are significantly induced in these three tissues, while low pH stress only upregulates Lv-HSP40 mRNA in the hepatopancreas and gill. During ontogenesis, Lv-HSP40 transcript levels are high at early embryonic stages and drop sharply at late embryonic and early larval stages. The ovary is another major organ of Lv-HSP40 mRNA expression in female shrimp, and Lv-HSP40 transcripts were mainly presented in the follicle cells but only weekly detected in the oocytes. Ovarian Lv-HSP40 mRNA levels increase continuously during gonadal development. Silencing of the Lv-HSP40 gene by RNA interference may effectively delay ovarian maturation after unilateral eyestalk ablation. The roles of Lv-HSP40 in ovarian development are speculated to be independent of its cofactor HSP70, and the vitellogenesis factor vitellogenin (Vg) and vitellogenin receptor (VgR). Our study, as a whole, provides new insights into the roles of HSP40 in multiple physiological processes in L. vannamei: (1) HSP40 is a responding factor during stressful conditions; and (2) HSP40 participates in embryonic and ovarian development.

In this paper, the nonlinear dynamics of a novel model based on optically pumped spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) with optical feedback is investigated numerically. Due to optical feedback being the external disturbance component, the complex nonlinear dynamical behaviors can be enhanced and the regions of different nonlinear dynamics in size can be extended with appropriate parameters of spin-VCSELs. According to the equations of the modified spin-flip model (SFM), the comparison of bifurcation diagrams is first presented for the clear presentation of different routes to chaos. Meanwhile, numerous bifurcation diagrams in color are illustrated to demonstrate the rich dynamical regimes intuitively, and the crucial effects of optical feedback strength, feedback delay, linewidth enhancement factor, and spin-flip relaxation rate on the region evolvement of complex dynamics of the proposed model are revealed to investigate the dependence of dynamical behaviors on external and internal parameters when the optical feedback scheme is introduced. These parameters play a remarkable role in enhancing the mechanism of complex dynamic oscillations. Furthermore, utilizing combination with time series, power spectra, and phase portraits, the various dynamical behaviors observed in the bifurcation diagram are simulated numerically. Correspondingly, the powerful measure 0–1 test is employed to distinguish between chaos and non-chaos.

This study investigated the influence of cerium nitrate in vanadate solutions on the properties of Ce–V conversion coatings on AZ31 magnesium alloys, and evaluated the self-healing behavior of the Ce–V conversion coating for AZ31 magnesium alloy. The results showed that the additions of cerium nitrate prevented pentavalent vanadium from reducing to tetravalent vanadium in the coatings during conversion reaction process. Adding appropriate cerium nitrate to vanadate solution led to a thicker coating with a more compact CeVO4 layer. The corrosion behavior of the Ce–V conversion coating was investigated by the electrochemical tests and the scratch immersion test in 3.5 wt.% NaCl solution. The self-healing ability of the coating was confirmed from all tests. The surface analysis revealed that the self-healing effect of the Ce–V conversion coating was only provided by the release and migration of vanadium compounds.

The relationship of creep rupture life and microstructural evolution under different high temperature oxidation conditions for Cr35Ni45 Nb alloy was studied by using SEM and quantitative electronic probe analysis. It was found that the microstructure gradually varied both in the edge and inside of the tube with increasing treatment time. The oxidation sequence showed that discontinuous oxidation films firstly developed at different places from the surface of the tube specimen,then they became continuous,and the carbide depleted zone developed as well during the high temperature oxidation process. As time went by,the oxidation films ruptured with temperature fluctuation,the characteristic of a higher oxygen partial pressure during the aging process resulted in the untimely recovery of the broken oxide films,and internal oxidation occurred at grain boundaries. Furthermore,creep rupture tests under different pretreating conditions of oxidation in air and argon gas atmosphere showed that the newly-built thin and continuous oxidation films improved the creep properties,while with increasing aging time,carbide depleted zone formation,oxidation film rupture and internal oxidation could decrease the creep properties of this alloy.

Measurement-device-independent quantum key distribution (MDI QKD) removes all detector side channels and enables secure QKD with an untrusted relay. It is suitable for building a star-type quantum access network, where the complicated and expensive measurement devices are placed in the central untrusted relay and each user requires only a low-cost transmitter, such as an integrated photonic chip. Here, we experimentally demonstrate a 1.25-GHz silicon photonic chip-based MDI QKD system using polarization encoding. The photonic chip transmitters integrate the necessary encoding components for a standard QKD source. We implement random modulations of polarization states and decoy intensities, and demonstrate a finite-key secret rate of 31 bit/s over 36-dB channel loss (or 180-km standard fiber). This key rate is higher than state-of-the-art MDI QKD experiments. The results show that silicon photonic chip-based MDI QKD, benefiting from miniaturization, low-cost manufacture, and compatibility with CMOS microelectronics, is a promising solution for future quantum secure networks.

Whole genome sequencing (WGS) has been widely used in traceability of food-borne outbreaks nowadays. Here, an interesting connection between Cronobacter sakazakii and food-borne acute gastroenteritis (AGE) was noticed. In October 2016, an AGE outbreak affecting 156 cases occurred in a local senior high school. Case-control study including 70 case-patients and 295 controls indicated a strong association between eating supper at school canteen of the outbreak onset and AGE, as revealed by the Odds Ratio (OR: 95.32). Six recovered Cronobacter strains were evaluated and compared using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and WGS. A phylogenetic tree of whole genomic single nucleotide polymorphisms (wgSNPs) were generated to traceback the potential contamination source in this outbreak. C. sakazakii isolates S2 from a patient’s rectal swab and S4 from leftover food sample shared identical PFGE pattern and sequence type (ST73), and clustered tightly together in the SNP phylogenetic tree. C. sakazakii isolates S5 and S6 from food delivery containers were both ST4 but with different PFGE patterns. Cronobacter isolates S1 and S3 from two patients’ rectal swab were sequenced to be C. malonaticus and shared another PFGE pattern (ST567). The interesting feature of this study was the implication of C. sakazakii as a causative agent in food-borne AGE occurring in healthy adults, although C. sakazakii is considered as an opportunistic pathogen and generally affects neonates, infants and immunocompromised adults.

It is of great importance to identify quantitative trait loci (QTL) controlling fiber quality traits and yield components for future marker-assisted selection (MAS) and candidate gene function identifications. In this study, two kinds of traits in 231 F6:8 recombinant inbred lines (RILs), derived from an intraspecific cross between Xinluzao24, a cultivar with elite fiber quality, and Lumianyan28, a cultivar with wide adaptability and high yield potential, were measured in nine environments. This RIL population was genotyped by 122 SSR and 4729 SNP markers, which were also used to construct the genetic map. The map covered 2477.99 cM of hirsutum genome, with an average marker interval of 0.51 cM between adjacent markers. As a result, a total of 134 QTLs for fiber quality traits and 122 QTLs for yield components were detected, with 2.18–24.45 and 1.68–28.27% proportions of the phenotypic variance explained by each QTL, respectively. Among these QTLs, 57 were detected in at least two environments, named stable QTLs. A total of 209 and 139 quantitative trait nucleotides (QTNs) were associated with fiber quality traits and yield components by four multilocus genome-wide association studies methods, respectively. Among these QTNs, 74 were detected by at least two algorithms or in two environments. The candidate genes harbored by 57 stable QTLs were compared with the ones associated with QTN, and 35 common candidate genes were found. Among these common candidate genes, four were possibly “pleiotropic.” This study provided important information for MAS and candidate gene functional studies.

Using a classical political economy approach we find aggregate regularities in the patterns of technical change followed by high income and developing countries (mostly from Latin America and Sub Saharan Africa) respectively. Such regularities allow us to propose an alternative definition of de-industrialization and study the issue of “premature de-industrialization” from a political economy perspective. In the (capital productivity, labor productivity) plane, a characteristic trajectory of high-income countries typically fluctuates in the quadrant where labor productivity growth rates are positive while capital productivity growth rates are negative (the industrialization quadrant). De-industrializing countries, on the other hand, have transitioned from the quadrant with positive labor productivity growth rates and negative capital productivity growth rates to the opposite quadrant (with negative labor productivity and positive capital productivity growth) and remained in this quadrant during the 1980s and 1990s. Both groups of countries, high income and de-industrializing seem to follow a cyclical pattern, revealing that the rate of industrialization is constantly fluctuating with varying labor and capital productivity growth rates. JEL codes: B12, O33, O47

Soil salinization erodes the farmlands and poses a serious threat to human life, reuse of the saline-alkali lands as cultivated resources becomes increasingly prominent. Pacific white shrimp (Litopenaeus vannamei) is an important farmed aquatic species for the development and utilization of the saline-alkali areas. However, little is known about the adaptation mechanism of this species in terms of high-pH stress. In the present study, a transcriptome analysis on the gill tissues of L. vannamei in response to high-pH stress (pH 9.3 ± 0.1) was conducted. After analyzing, the cyclic nucleotide gated channel-Ca2+ (CNGC-Ca2+) and patched 1 (Ptc1) were detected as the majority annotated components in the cAMP signaling pathway (KO04024), indicating that the CNGC-Ca2+ and Ptc1 might be the candidate components for transducing and maintaining the high-pH stress signals, respectively. The immunoglobulin superfamily (IgSF), heat shock protein (HSP), glutathione s-transferase (GST), prophenoloxidase/phenoloxidase (proPO/PO), superoxide dismutase (SOD), anti-lipopolysaccharide factor (ALF) and lipoprotein were discovered as the major transcribed immune factors in response to high-pH stress. To further detect hub regulation-genes, protein-protein interaction (PPI) networks were constructed; the genes/proteins "Polymerase (RNA) II (DNA directed) polypeptide A" (POLR2A), "Histone acetyltransferase p300" (EP300) and "Heat shock 70kDa protein 8" (HSPA8) were suggested as the top three hub regulation-genes in response to acute high-pH stress; the genes/proteins "Heat shock 70kDa protein 4" (HSPA4), "FBJ murine osteosarcoma viral oncogene homolog" (FOS) and "Nucleoporin 54kDa" (NUP54) were proposed as the top three hub regulation-genes involved in adapting endurance high-pH stress; the protein-interactions of "EP300-HSPA8" and "HSPA4-NUP54" were detected as the most important biological interactions in response to the high-pH stress; and the HSP70 family genes might play essential roles in the adaptation of the high-pH stress environment in L. vannamei. These findings provide the first insight into the molecular and immune basis of L. vannamei in terms of high-pH environments, and the construction of a PPI network might improve our understanding in revealing the hub regulation-genes in response to abiotic stress in shrimp species and might be beneficial for further studies.

This paper presented experimental views of nano- and microaerosol distribution and deposition in turbulent tran-bend flows. These views included the particle flow measurement and particle depositions through individual bends, bifurcation bends, and those behind bends. Selected experiments were summarized and compared according to the gas flow, the bend geometry, and the particle flow properties. Based on recent studies, the influencing factors of environmental humidity, particle and surface properties, nanoparticle formation, coagulation, or evolution phenomena were discussed, and then research suggestions were given for future research and applications. It is specially mentioned that the new particle formation and nanoparticle growth affect its deposition under environmental contaminant conditions; nanoscale particle dynamics and transport have a growing trend on attracting the research and industry attentions.

Soot generally refers to carbonaceous particles formed during incomplete combustion of hydrocarbon fuels. A typical simulation of soot formation and evolution contains two parts: gas chemical kinetics, which models the chemical reaction from hydrocarbon fuels to soot precursors, that is, polycyclic aromatic hydrocarbons or PAHs, and soot dynamics, which models the soot formation from PAHs and evolution due to gas-soot and soot-soot interactions. In this study, two detailed gas kinetic mechanisms (ABF and KM2) have been compared during the simulation (using the solver Chemkin II) of ethylene combustion in counterflow diffusion flames. Subsequently, the operator splitting Monte Carlo method is used to simulate the soot dynamics. Both the simulated data from the two mechanisms for gas and soot particles are compared with experimental data available in the literature. It is found that both mechanisms predict similar profiles for the gas temperature and velocity, agreeing well with measurements. However, KM2 mechanism provides much closer prediction compared to measurements for soot gas precursors. Furthermore, KM2 also shows much better predictions for soot number density and volume fraction than ABF. The effect of nozzle exit velocity on soot dynamics has also been investigated. Higher nozzle exit velocity renders shorter residence time for soot particles, which reduces the soot number density and volume fraction accordingly.

Vitellogenesis is the process of yolk formation via accumulating vitellin (Vn) with nutrients in the oocytes. Expression of vitellogenin (Vg), the precursor of Vn, is one of the indicators for the start of vitellogenesis. In Pacific white shrimp (Litopenaeus vannamei), the type-II vitellogenesis-inhibiting hormone (VIH-2) effectively suppresses hepatopancreatic Vg mRNA expression. In this study, we demonstrate the increasing transcript levels of hepatopancreatic Vg during L. vannamei ovarian development, suggesting that the hepatopancreas-derived Vg/Vn may also contribute to vitellogenesis in this species. Using a combination of in vivo injections and in vitro primary cell cultures, we provide evidences that the inhibition of VIH-2 on hepatopancreatic Vg gene expression is mediated through a functional coupling of the GC/cGMP pathway with different MAPK-dependent cascades in female shrimp. In VIH-2 signaling, the NO-independent GC/cGMP/PKG cascades were upstream of the MAPKs. Activations of the MAPK signal by VIH-2 include the phosphorylation of JNK and the mRNA/protein expression of P38MAPK. Additionally, the cAMP/PKA pathway is another positive intracellular signal for hepatopancreatic Vg mRNA expression but is independent of its VIH-2 regulation. Our findings establish a model for the signal transduction mechanism of Vg regulation by VIH and shed light on the biological functions and signaling of the CHH family in crustaceans.

The identification problem of multivariable controlled autoregressive systems with measurement noise in the form of the moving average process is considered in this paper. The key is to filter the input–output data using the data filtering technique and to decompose the identification model into two subidentification models. By using the negative gradient search, an adaptive data filtering-based gradient iterative (F-GI) algorithm and an F-GI with finite measurement data are proposed for identifying the parameters of multivariable controlled autoregressive moving average systems. In the numerical example, we illustrate the effectiveness of the proposed identification methods.

The mitochondrial genome of Holothuria leucospilota was 15,906 bp in length, containing 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes. There were four initiation codons (ATG, ATT, ATC, and ATA) for the PCGs, and the termination codon of most PCGs was TAA, except for nad4 (TAG) and nad6 (TAG). Only one PCG (nad6) and five tRNA genes (tRNASer(UCN), tRNAGln, tRNAAla, RNAVal, and tRNAAsp) were encoded on the light chain; the other genes were encoded on the heavy chain. H. leucospilota was most closely related to Holothuria scabra in a phylogenetic tree.

The aim of this work was to make biodegradable plastics from renewable resources. Paper-based biodegradable plastics were produced via a sol-gel process by using zinc chloride solution. The optimum conditions were a zinc chloride concentration of 65%, reaction temperature of 70 °C, reaction time of 5 s, aging time of 3 h, and glycerol concentration of 10%. Fourier transform infrared spectroscopy (FT-IR) and wide-angle X-ray diffraction (XRD) revealed that no chemical reaction occurred and the crystal form of the cellulose remained cellulose I, but the degree of crystallinity decreased. Compared to other biodegradable plastics, these paper-based biodegradable plastics had better mechanical properties and greater biodegradability.

ABSTRACT The dynamics and significance of aerosol transmission of respiratory viruses are still controversial, for the major reasons that virus aerosols are inefficiently collected by commonly used air samplers and that the collected viruses are inactivated by the collection method. Without knowledge of virus viability, infection risk analyses lack accuracy. This pilot study was performed to (i) determine whether infectious (viable) respiratory viruses in aerosols could be collected from air in a real world environment by the viable virus aerosol sampler (VIVAS), (ii) compare and contrast the efficacy of the standard bioaerosol sampler, the BioSampler, with that of the VIVAS for the collection of airborne viruses in a real world environment, and (iii) gain insights for the use of the VIVAS for respiratory virus sampling. The VIVAS operates via a water vapor condensation process to enlarge aerosolized virus particles to facilitate their capture. A variety of viable human respiratory viruses, including influenza A H1N1 and H3N2 viruses and influenza B viruses, were collected by the VIVAS located at least 2 m from seated patients, during a late-onset 2016 influenza virus outbreak. Whereas the BioSampler when operated following our optimized parameters also collected virus aerosols, it was nevertheless overall less successful based on a lower frequency of virus isolation in most cases. This side-by-side comparison highlights some limitations of past studies based on impingement-based sampling, which may have generated false-negative results due to either poor collection efficiency and/or virus inactivation due to the collection process. IMPORTANCE The significance of virus aerosols in the natural transmission of respiratory diseases has been a contentious issue, primarily because it is difficult to collect or sample virus aerosols using currently available air sampling devices. We tested a new air sampler based on water vapor condensation for efficient sampling of viable airborne respiratory viruses in a student health care center as a model of a real world environment. The new sampler outperformed the industry standard device (the SKC BioSampler) in the collection of natural virus aerosols and in maintaining virus viability. These results using the VIVAS indicate that respiratory virus aerosols are more prevalent and potentially pose a greater inhalation biohazard than previously thought. The VIVAS thus appears to be a useful apparatus for microbiology air quality tests related to the detection of viable airborne viruses.

The Pacific white shrimp (Litopenaeus vannamei) is an important cultured crustacean species worldwide. However, little is known about the molecular mechanism of this species involved in the response to cold stress. In this study, four separate RNA-Seq libraries of L. vannamei were generated from 13°C stress and control temperature. Total 29,662 of Unigenes and overall of 19,619 annotated genes were obtained. Three comparisons were carried out among the four libraries, in which 72 of the top 20% of differentially-expressed genes were obtained, 15 GO and 5 KEGG temperature-sensitive pathways were fished out. Catalytic activity (GO: 0003824) and Metabolic pathways (ko01100) were the most annotated GO and KEGG pathways in response to cold stress, respectively. In addition, Calcium, MAPK cascade, Transcription factor and Serine/threonine-protein kinase signal pathway were picked out and clustered. Serine/threonine-protein kinase signal pathway might play more important roles in cold adaptation, while other three signal pathway were not widely transcribed. Our results had summarized the differentially-expressed genes and suggested the major important signaling pathways and related genes. These findings provide the first profile insight into the molecular basis of L. vannamei response to cold stress.

Electroencephalogram (EEG) plays an important role in identifying brain activity and behavior. However, the recorded electrical activity always be contaminated with artifacts and then affect the analysis of EEG signal. Hence, it is essential to develop methods to effectively detect and extract the clean EEG data during encephalogram recordings. Several methods have been proposed to remove artifacts, but the research on artifact removal continues to be an open problem. This paper tends to review the current artifact removal of various contaminations. We first discuss the characteristics of EEG data and the types of different artifacts. Then, a general overview of the state-of-the-art methods and their detail analysis are presented. Lastly, a comparative analysis is provided for choosing a suitable methods according to particular application.

Parkinson's disease (PD) is characterized by age-dependent neurodegeneration and the accumulation of toxic phosphorylated [alpha]-synuclein (pS129-[alpha]-syn). The mechanisms underlying these crucial pathological changes remain unclear. Mutations in parkin RBR E3 ubiquitin protein ligase (PARK2), the gene encoding parkin that is phosphorylated by PTEN-induced putative kinase 1 (PINK1) to participate in mitophagy, cause early onset PD. However, current parkin-KO mouse and pig models do not exhibit neurodegeneration. In the current study, we utilized CRISPR/Cas9 technology to establish parkin-deficient monkey models at different ages. We found that parkin deficiency leads to substantia nigra neurodegeneration in adult monkey brains and that parkin phosphorylation decreases with aging, primarily due to increased insolubility of parkin. Phosphorylated parkin is important for neuroprotection and the reduction of pS129-[alpha]-syn. Consistently, overexpression of WT parkin, but not a mutant form that cannot be phosphorylated by PINK1, reduced the accumulation of pS129-[alpha]-syn. These findings identify parkin phosphorylation as a key factor in PD pathogenesis and suggest it as a promising target for therapeutic interventions., Introduction Parkinson's disease (PD) is a prevalent neurodegenerative disease that affects 1%-2% of individuals over the age of 65 years (1). Although the majority of PD cases are sporadic with [...]

Evidence from previous studies suggests that the male reproductive system can be disrupted by fetal or neonatal exposure to diethylstilbestrol (DES). However, the molecular basis for this effect remains unclear. To evaluate the effects of DES on mouse spermatocytes and to explore its potential mechanism of action, the levels of DNA methyltransferases (DNMTs) and DNA methylation induced by DES were detected. The results showed that low doses of DES inhibited cell proliferation and cell cycle progression and induced apoptosis in GC-2 cells, an immortalized mouse pachytene spermatocyte-derived cell line, which reproduces primary cells responses to E2. Furthermore, global DNA methylation levels were increased and the expression levels of DNMTs were altered in DES-treated GC-2 cells. A total of 141 differentially methylated DNA sites were detected by microarray analysis. Rxra, an important component of the retinoic acid signaling pathway, and mybph, a RhoA pathway-related protein, were found to be hypermethylated, and Prkcd, an apoptosis-related protein, was hypomethylated. These results showed that low-dose DES was toxic to spermatocytes and that DNMT expression and DNA methylation were altered in DES-exposed cells. Taken together, these data demonstrate that DNA methylation likely plays an important role in mediating DES-induced spermatocyte toxicity in vitro.

Infrared absorption spectroscopy remains a challenge due to the weak light-matter interaction between micron-wavelengthed infrared light and nano-sized molecules. A highly doped semiconductor supports intrinsic plasmon modes at infrared frequencies, and is compatible with the current epitaxial growth processing, which makes it promising for various applications. Here, we propose an all-semiconductor plasmonic resonator to enhance the infrared absorption of the adsorbed molecules. An optical model is employed to investigate the effect of structural parameters on the spectral features of the resonator and the enhanced infrared absorption characteristics are further discussed. When a molecular layer is deposited upon the resonator, the weak molecular absorption signal can be significantly enhanced. A high enhancement factor of 470 can be achieved once the resonance wavelength of the resonator is overlapped with the desired vibrational mode of the molecules. Our study offers a promising approach to engineering semiconductor optics devices for mid-infrared sensing applications.

A graphene-based long-period fiber grating (LPFG) surface plasmon resonance (SPR) sensor is proposed. A monolayer of graphene is coated onto the Ag film surface of the LPFG SPR sensor, which increases the intensity of the evanescent field on the surface of the fiber and thereby enhances the interaction between the SPR wave and molecules. Such features significantly improve the sensitivity of the sensor. The experimental results demonstrate that the sensitivity of the graphene-based LPFG SPR sensor can reach 0.344 nm%−1 for methane, which is improved 2.96 and 1.31 times with respect to the traditional LPFG sensor and Ag-coated LPFG SPR sensor, respectively. Meanwhile, the graphene-based LPFG SPR sensor exhibits excellent response characteristics and repeatability. Such a SPR sensing scheme offers a promising platform to achieve high sensitivity for gas-sensing applications.