Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 101
Filter
Add more filters

Country/Region as subject
Publication year range
1.
Cereb Cortex ; 34(2)2024 01 31.
Article in English | MEDLINE | ID: mdl-38282453

ABSTRACT

Using a syntactic priming task, we investigated the time course of syntactic encoding in Chinese sentence production and compared encoding patterns between younger and older adults. Participants alternately read sentence descriptions and overtly described pictures, while event-related potentials (ERPs) were recorded. We manipulated the abstract prime structure (active or passive) as well as the lexical overlap of the prime and the target (verb overlap or no overlap). The syntactic choice results replicated classical abstract priming and lexical boost effects in both younger and older adults. However, when production latency was taken into account, the speed benefit from syntactic repetition differed between the two age groups. Meanwhile, preferred priming facilitated production in both age groups, whereas nonpreferred priming inhibited production in the older group. For electroencephalography, an earlier effect of syntactic repetition and a later effect of lexical overlap showed a two-stage pattern of syntactic encoding. Older adults also showed a more delayed and interactive encoding pattern than younger adults, indicating a greater reliance on lexical information. These results are illustrative of the two-stage competition and residual activation models.


Subject(s)
Comprehension , Speech Perception , Humans , Aged , Comprehension/physiology , Speech Perception/physiology , Language , Evoked Potentials/physiology , China
2.
J Cogn Neurosci ; : 1-26, 2024 May 02.
Article in English | MEDLINE | ID: mdl-38695761

ABSTRACT

This present study identified an optimal model representing the relationship between orthography and phonology in Chinese handwritten production using dynamic causal modeling, and further explored how this model was modulated by word frequency and syllable frequency. Each model contained five volumes of interest in the left hemisphere (inferior frontal gyrus [IFG], middle frontal gyrus [MFG], angular gyrus [AG], supramarginal gyrus, and superior frontal gyrus), with the IFG as the driven input area. Results showed the superiority of a model in which both the MFG and the AG connected with the IFG, supporting the orthography autonomy hypothesis. Word frequency modulated the AG → superior frontal gyrus connection (information flow from the orthographic lexicon to the orthographic buffer), and syllable frequency affected the IFG → MFG connection (information transmission from the semantic system to the phonological lexicon). This study thus provides new insights into the connectivity architecture of neural substrates involved in writing.

3.
Environ Res ; 251(Pt 2): 118721, 2024 Jun 15.
Article in English | MEDLINE | ID: mdl-38490624

ABSTRACT

The gradual increase in cattle farming has led to a huge production of cattle manure (CM), but the conventional treatment methods are less efficient. In this study, the treatment method of anaerobic digestion (AD) of high-solids CM by combining nanobubble water (NBW) with different gases was proposed to present a new idea for the reduction, harmlessness, and resourcefulness of CM. It was found that the performance of the digester with added NBW was better than the control. Among them, the cumulative methane yield T-Air: 227.09 mL g-1 VSadded and T-CO2: 226.12 mL g-1 VSadded increased by 17.72 % and 17.22 %, respectively, compared with the control T: 192.90 mL g-1 VSadded under thermophilic conditions. Under mesophilic conditions, M-Air: 162.39 mL g-1 VSadded increased by 9.68 % compared with control M: 148.05 mL g-1 VSadded. Microbial communities analyzed at the genus level revealed that the relative abundance of bacteria favorable to hydrolysis and acid-producing processes, such as Defluviitalea, Haloplasma, and Bacillus, increased to varying degrees. Moreover, the relative abundance of archaea favorable for methanogenesis, such as Methanoculleus, Methanobrevibacter, and Methanosarcina, also increased to varying degrees. Therefore, the addition of NBW promoted the hydrolysis of high-solids CM, enhanced the stability of the reaction, improved the methanogenic performance, and increased the RA of favorable genera, which ultimately led to a better performance of the AD of high-solids CM.


Subject(s)
Manure , Methane , Manure/microbiology , Animals , Cattle , Anaerobiosis , Methane/metabolism , Methane/analysis , Water/chemistry , Bioreactors , Bacteria/metabolism
4.
Psychol Res ; 88(2): 652-669, 2024 Mar.
Article in English | MEDLINE | ID: mdl-37561202

ABSTRACT

This study used an image-description paradigm with concurrent eye movement recordings to investigate differences of grammatical advance planning between young and older speakers in spoken sentence production. Participants were asked to produce sentences with simple or complex initial phrase structures (IPS) in Experiment 1 while producing individual words in Experiment 2. Young and older speakers showed comparable speaking latencies in sentence production task, whereas older speakers showed longer latencies than young speakers in word production task. Eye movement data showed that compared with young speakers, older speakers had higher fixation percentage on object 1, lower percentage of gaze shift from object 1 to 2, and lower fixation percentage on object 2 in simple IPS sentences, while they showed similar fixation percentage on object 1, similar percentage of gaze shift from object 1 to 2, and lower fixation percentage on object 2 in complex IPS sentences, indicating a decline of grammatical encoding scope presenting on eye movement patterns. Meanwhile, speech analysis showed that older speakers presented longer utterance duration, slower speech rate, and longer and more frequently occurred pauses in articulation, indicating a decline of speech articulation in older speakers. Thus, our study suggests that older speakers experience an ageing effect in the sentences with complex initial phrases due to limited cognitive resources.


Subject(s)
Eye Movements , Language , Humans , Aged , Speech , Aging
5.
Int J Mol Sci ; 25(7)2024 Apr 07.
Article in English | MEDLINE | ID: mdl-38612904

ABSTRACT

Cardiovascular diseases (CVDs) pose a significant global health threat due to their complex pathogenesis and high incidence, imposing a substantial burden on global healthcare systems. Integrins, a group of heterodimers consisting of α and ß subunits that are located on the cell membrane, have emerged as key players in mediating the occurrence and progression of CVDs by regulating the physiological activities of endothelial cells, vascular smooth muscle cells, platelets, fibroblasts, cardiomyocytes, and various immune cells. The crucial role of integrins in the progression of CVDs has valuable implications for targeted therapies. In this context, the development and application of various integrin antibodies and antagonists have been explored for antiplatelet therapy and anti-inflammatory-mediated tissue damage. Additionally, the rise of nanomedicine has enhanced the specificity and bioavailability of precision therapy targeting integrins. Nevertheless, the complexity of the pathogenesis of CVDs presents tremendous challenges for monoclonal targeted treatment. This paper reviews the mechanisms of integrins in the development of atherosclerosis, cardiac fibrosis, hypertension, and arrhythmias, which may pave the way for future innovations in the diagnosis and treatment of CVDs.


Subject(s)
Cardiovascular Diseases , Hypertension , Humans , Integrins , Endothelial Cells , Cell Membrane
6.
Water Sci Technol ; 90(1): 287-302, 2024 Jul.
Article in English | MEDLINE | ID: mdl-39007320

ABSTRACT

Extracellular polymeric substances (EPS) are a critical influencing factor in sludge dewatering. Disrupting such EPS contributes to the release of bound water in sludge, enhancing the sludge dewatering performance. In This study, quaternized straw fibers that are destructive to the EPS structure and components in active sludge were prepared useing heterogeneous free radical graft polymerization. Straw fibers, dimethyl diallyl ammonium chloride (DMDAAC), ammonium persulfate (APS), and acrylamide (AM) were taken as the substrate, grafting monomer, catalyst, and cross-linking agent, respectively.The optimal processing conditions determined for the DMDAAC-based quaternization and graft modification of straw fibers were as follows: reaction temperature of 60 °C, reaction time of 5 h, 0.100 g of catalyst APS dosage per gram of straw, and 3.000 ml of DMDAAC dosage per gram of straw. The optimal processing conditions yielded 1.335 g of modified straw fibers per gram of straw, 33.67% grafting rate, and 31.70% substitution of the quaternary ammonium groups. The capillary suction time (CST) was conditioned from 243.3 ± 22.6 s in the original sludge to 134.5 ± 34.45 s. The specific resistance to filtration (SRF) was reduced from 8.82 ± 0.51 × 1012 m/kg in the original sludge to 4.59 ± 0.23 × 1012 m/kg.


Subject(s)
Sewage , Sewage/chemistry , Waste Disposal, Fluid/methods , Quaternary Ammonium Compounds/chemistry , Allyl Compounds/chemistry
7.
Opt Express ; 31(2): 853-863, 2023 Jan 16.
Article in English | MEDLINE | ID: mdl-36785133

ABSTRACT

To reveal the effect of the incident polarization on the spin splitting of the photonic spin Hall effect (that is, the spatial and angular in-plane and out-of-plane spin splitting), we systematically study the phenomena and characteristics of these four spin splitting generated when the beam with arbitrary linear polarization is reflected from the non-absorbing medium interface and the absorbing medium interface. Several features of the relationship between the incident polarization and the four kinds of spin splitting are found. In addition, It is also found that the in-plane angular and spatial shifts are significantly enhanced near the critical angle, even reaching their theoretical upper limit. However, the out-of-plane shifts are not enhanced. The research in this paper will contribute to a deeper understanding of PSHE. These findings can also provide new ideas and methods for precision metrology, photonic manipulation, and photonic device fabrication.

8.
Int J Mol Sci ; 24(7)2023 Mar 24.
Article in English | MEDLINE | ID: mdl-37047140

ABSTRACT

Integrins are a group of heterodimers consisting of α and ß subunits that mediate a variety of physiological activities of immune cells, including cell migration, adhesion, proliferation, survival, and immunotolerance. Multiple types of integrins act differently on the same immune cells, while the same integrin may exert various effects on different immune cells. In the development of cancer, integrins are involved in the regulation of cancer cell proliferation, invasion, migration, and angiogenesis; conversely, integrins promote immune cell aggregation to mediate the elimination of tumors. The important roles of integrins in cancer progression have provided valuable clues for the diagnosis and targeted treatment of cancer. Furthermore, many integrin inhibitors have been investigated in clinical trials to explore effective regimens and reduce side effects. Due to the complexity of the mechanism of integrin-mediated cancer progression, challenges remain in the research and development of cancer immunotherapies (CITs). This review enumerates the effects of integrins on four types of immune cells and the potential mechanisms involved in the progression of cancer, which will provide ideas for more optimal CIT in the future.


Subject(s)
Disease Progression , Immune System , Immunotherapy , Integrins , Neoplasms , Animals , Humans , B-Lymphocytes/immunology , Dendritic Cells/immunology , Integrins/antagonists & inhibitors , Integrins/metabolism , Killer Cells, Natural/immunology , Macrophages/immunology , Neoplasms/immunology , Neoplasms/metabolism , Neoplasms/pathology , Neoplasms/therapy , Neutrophils/immunology , T-Lymphocytes/immunology , Immune System/cytology , Immune System/immunology
9.
J Cogn Neurosci ; 34(6): 951-966, 2022 05 02.
Article in English | MEDLINE | ID: mdl-35303083

ABSTRACT

How quickly are different kinds of conceptual knowledge activated in action picture naming? Using a masked priming paradigm, we manipulated the prime category type (artificial vs. natural), prime action type (precision, power, vs. neutral grip), and target action type (precision vs. power grip) in action picture naming, while electrophysiological signals were measured concurrently. Naming latencies showed an inhibition effect in the congruent action type condition compared with the neutral condition. ERP results showed that artificial and natural category primes induced smaller waveforms in precision or power action primes than neutral primes in the time window of 100-200 msec. Time-frequency results consistently presented a power desynchronization of the mu rhythm in the time window of 0-210 msec with precision action type artificial objects compared with neutral primes, which localized at the supplementary motor, precentral and postcentral areas in the left hemisphere. These findings suggest an inhibitory effect of affordances arising at conceptual preparation in action picture naming and provide evidence for embodied cognition.


Subject(s)
Evoked Potentials , Inhibition, Psychological , Cognition , Humans , Motor Activity , Reaction Time/physiology
10.
J Cogn Neurosci ; 34(12): 2320-2340, 2022 11 01.
Article in English | MEDLINE | ID: mdl-36069653

ABSTRACT

Writing is an important way to communicate in everyday life because it can convey information over time and space, but its neural substrates remain poorly known. Although the neural basis of written language production has been investigated in alphabetic scripts, it has rarely been examined in nonalphabetic languages such as Chinese. The present functional magnetic resonance imaging study explored the neural substrates of handwritten word production in Chinese and identified the brain regions sensitive to the psycholinguistic factors of word frequency and syllable frequency. To capture this, we contrasted neural activation in "writing" with "speaking plus drawing" and "watching plus drawing." Word frequency (high, low) and syllable frequency (high, low) of the picture names were manipulated. Contrasts between the tasks showed that writing Chinese characters was mainly associated with brain activation in the left frontal and parietal cortex, whereas orthographic processing and the motor procedures necessary for handwritten production were also related to activation in the right frontal and parietal cortex as well as right putamen/thalamus. These results demonstrate that writing Chinese characters requires activation in bilateral cortical regions and the right putamen/thalamus. Our results also revealed no brain activation associated with the main effects of word frequency and syllable frequency as well as their interaction, which implies that word frequency and syllable frequency may not affect the writing of Chinese characters on a neural level.


Subject(s)
Brain Mapping , Language , Humans , Reading , Magnetic Resonance Imaging/methods , China
11.
Psychol Res ; 86(6): 1918-1929, 2022 Sep.
Article in English | MEDLINE | ID: mdl-34757437

ABSTRACT

This study aimed to examine the locus of age of acquisition (AoA) and word frequency (WF) effects in Chinese spoken picture naming, using a picture-word interference task. We conducted four experiments manipulating the properties of picture names (AoA in Experiments 1 and 2, while controlling WF; and WF in Experiments 3 and 4, while controlling AoA), and the relations between distractors and targets (semantic or phonological relatedness). Both Experiments 1 and 2 demonstrated AoA effects in picture naming; pictures of early acquired concepts were named faster than those acquired later. There was an interaction between AoA and semantic relatedness, but not between AoA and phonological relatedness, suggesting localisation of AoA effects at the stage of lexical access in picture naming. Experiments 3 and 4 demonstrated WF effects: pictures of high-frequency concepts were named faster than those of low-frequency concepts. WF interacted with both phonological and semantic relatedness, suggesting localisation of WF effects at multiple levels of picture naming, including lexical access and phonological encoding. Our findings show that AoA and WF effects exist in Chinese spoken word production and may arise at related processes of lexical selection.


Subject(s)
Names , Semantics , China , Humans , Reaction Time
12.
Proc Natl Acad Sci U S A ; 115(22): E5174-E5182, 2018 05 29.
Article in English | MEDLINE | ID: mdl-29760100

ABSTRACT

In the primary visual cortex (V1) of many mammalian species, neurons are spatially organized according to their preferred orientation into a highly ordered map. However, whether and how the various presynaptic inputs to V1 neurons are organized relative to the neuronal orientation map remain unclear. To address this issue, we constructed genetically encoded calcium indicators targeting axon boutons in two colors and used them to map the organization of axon boutons of V1 intrinsic and V2-V1 feedback projections in tree shrews. Both connections are spatially organized into maps according to the preferred orientations of axon boutons. Dual-color calcium imaging showed that V1 intrinsic inputs are precisely aligned to the orientation map of V1 cell bodies, while the V2-V1 feedback projections are aligned to the V1 map with less accuracy. Nonselective integration of intrinsic presynaptic inputs around the dendritic tree is sufficient to reproduce cell body orientation preference. These results indicate that a precisely aligned map of intrinsic inputs could reinforce the neuronal map in V1, a principle that may be prevalent for brain areas with function maps.


Subject(s)
Presynaptic Terminals/physiology , Visual Cortex/physiology , Visual Pathways/physiology , Animals , Axons/physiology , Calcium/metabolism , Feedback, Physiological/physiology , Mice , Molecular Imaging , Visual Cortex/diagnostic imaging , Visual Pathways/diagnostic imaging
13.
J Phycol ; 55(5): 1059-1070, 2019 10.
Article in English | MEDLINE | ID: mdl-31206671

ABSTRACT

This study aimed to address the importance of glutamine synthetase II (GSII) during nitrogen assimilation in macroalga Gracilariopsis lemaneiformis. The cDNA full-length sequence of the three glGSII genes was revealed to have the 5' m7 G cap, 5'-untranslated region, open reading frame (ORF), 3'-untranslated region, and a 3' poly (A) tail. The three glGSIIs were classified into plastid glGS2 and cytosolic glGS1-1 and glGS1-2, having conserved GSII domains but different cDNA sequences. The complicated 5' end flanking region indicates complex function of glGS genes. glGS1 genes were significantly up-regulated under the different NH4+ : NO3- ratio (i.e., 40:10, 25:25, 10:40, and 0:50) except glGS2 which dramatically up-regulated under the low NH4+ : NO3- ratio (i.e., 10:40 and 0:50) during different cultivation times. These different expression patterns perhaps are due to the different biological roles of GS1 and GS2 in the gene family. Furthermore, hypothetical working model of nitrogen assimilation pathway exhibiting the role of glGS1 and glGS2 is proposed. Finally, glGS2 was expressed in Escherichia coli BL21 (DE3), and the optimal conditions for culture (15°C, overnight), purification (500 mM imidazole washing), and activity (pH 7.4, 37°C) were established. This study lays a very important foundation for exploring the role of GS in nitrogen assimilation in algae and plants.


Subject(s)
Rhodophyta , Seaweed , Glutamate-Ammonia Ligase , Nitrogen , RNA, Messenger
14.
Water Sci Technol ; 79(10): 1878-1886, 2019 May.
Article in English | MEDLINE | ID: mdl-31294704

ABSTRACT

In this study, an ordered mesoporous silica modified with lanthanum oxide was synthesized using diatomite as silica source and applied for adsorption of phosphate from aqueous solution. By taking cost-effectiveness for practical application into consideration, the adsorbent with a theoretical La/SiO2 molar ratio of 0.2 (La0.2M41) possessed a promising performance. In the batch adsorption tests, the adsorbents with La2O3 loading possessed markedly enhanced adsorption capacities. Phosphate uptake by La0.2M41 was pH-dependent with the highest sorption capacities observed over a pH range of 3.0-6.0. Coexistent anions displayed an adverse effect on phosphate adsorption following the order of CO3 2-  > F-  > NO3 - > Cl- > SO4 2-. In the kinetic study, phosphate adsorption onto La0.2M41 followed the pseudo-second-order equation better than the pseudo-first-order, suggesting chemisorption. The Langmuir isothermal model well described the adsorption isotherm data, showing a maximum adsorption capacity for phosphate of up to 263.16 mg/g at 298 K. In a real treated wastewater effluent with phosphate concentration of 2.5 mg P/L, La0.2M41 efficiently reduced the phosphate concentration to 28 µg P/L.


Subject(s)
Diatomaceous Earth/chemistry , Phosphates , Silicon Dioxide , Lanthanum , Oxides
15.
Extremophiles ; 22(5): 739-749, 2018 Sep.
Article in English | MEDLINE | ID: mdl-29936543

ABSTRACT

A novel gene (ANK58566) encoding a cold-active α-amylase was cloned from marine bacterium Bacillus sp. dsh19-1 (CCTCC AB 2015426), and the protein was expressed in Escherichia coli. The gene had a length of 1302 bp and encoded an α-amylase of 433 amino acids with an estimated molecular mass of 50.1 kDa. The recombinant α-amylase (AmyD-1) showed maximum activity at 20 °C and pH 6.0, and retained about 35.7% of activity at 4 °C. The AmyD-1 activity was stimulated by Ca2+ and Na+. However, the chelating agent, EDTA, inactivated the enzyme. Moreover, AmyD-1 displayed extreme salt tolerance, with the highest activity in the presence of 2.0 M NaCl and 60.5% of activity in 5.0 M NaCl. The Km, Vmax and kcat of AmyD-1 in 2.0 M NaCl were 2.8 mg ml-1, 21.8 mg ml-1 min-1 and 933.5 s-1, respectively, at 20 °C and pH 6.0 with soluble starch as substrate. MALDI-TOF MS (Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry) revealed that the end products of starch hydrolysis by AmyD-1 were glucose, maltose, maltotriose, maltotetraose, and malt oligosaccharides. Thus, AmyD-1 is one of the very few α-amylases that can tolerate low temperatures and high salt concentrations, which makes it to be a potential candidate for research in basic and applied microbiology.


Subject(s)
Bacillus/enzymology , Cold Temperature , Enzyme Activation/drug effects , alpha-Amylases , Calcium Chelating Agents/pharmacology , Cloning, Molecular/methods , Edetic Acid/pharmacology , Enzyme Stability/drug effects , Escherichia coli/enzymology , Gene Expression , Hydrogen-Ion Concentration , Hydrolysis , Microbiological Techniques/methods , Protein Engineering/methods , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , alpha-Amylases/chemistry , alpha-Amylases/genetics , alpha-Amylases/metabolism
16.
Water Sci Technol ; 2017(3): 802-811, 2018 Jul.
Article in English | MEDLINE | ID: mdl-30016298

ABSTRACT

Bioleaching, the addition of bacteria to geological materials, has been applied to sludge to remove metals and improve upon sludge dewaterability. This paper investigates the effect of using different quantities of inoculum (bacteria) during bioleaching on sludge dewaterability. The analysis was based on bioleaching experiments conducted in a 20 L bio-reactor using different quantities of inoculum (20%, 10%, 5%, 2%, 0%). Changes in pH, oxidation reduction potential (ORP), capillary suction time (CST), specific resistance to filtration (SRF) and extracellular polymeric substances (EPS) were determined to gauge sludge dewatering. Results indicate that sludge dewaterability during the 2%, 10%, and 20% inoculum experiments declined through time. Decreased dewaterability is attributed to increases in the quantity of proteins and polysaccharides in slime EPS. Dewaterability improved during the 5% inoculum experiment, and reached a maximum when pH was 2.3. During this latter experiment, CST and SRF were reduced by 74% and 62%, respectively, in comparison to control conditions, while total EPS content decreased by 71%. The decrease in total EPS was primarily due to a decrease in proteins associated with tightly bound EPS (TB-EPS). Thus, changes in the amount of proteins in TB-EPS and sludge pH played a crucial role in sludge dewaterability.


Subject(s)
Sewage/microbiology , Waste Disposal, Fluid/methods , Water/chemistry , Bacteria , Filtration , Hydrogen-Ion Concentration , Metals , Polymers/chemistry , Polysaccharides , Proteins , Water Pollutants, Chemical
17.
Exp Cell Res ; 345(2): 218-29, 2016 07 15.
Article in English | MEDLINE | ID: mdl-27237096

ABSTRACT

This study investigated the pro-proliferative effect of hyaluronic acid (HA) on human amniotic mesenchymal stem cells (hAMSCs) and the underlying mechanisms. Treatment with HA increased cell population growth in a dose- and time-dependent manner. Analyses by flow cytometry and immunocytochemistry revealed that HA did not change the cytophenotypes of hAMSCs. Additionally, the osteogenic, chondrogenic, and adipogenic differentiation capabilities of these hAMSCs were retained after HA treatment. Moreover, HA increased the mRNA expressions of wnt1, wnt3a, wnt8a, cyclin D1, Ki-67, and ß-catenin as well as the protein level of ß-catenin and cyclin D1 in hAMSCs; and the nuclear localization of ß-catenin was also enhanced. Furthermore, the pro-proliferative effect of HA and up-regulated expression of Wnt/ß-catenin pathway-associated proteins - wnt3a, ß-catenin and cyclin D1 in hAMSCs were significantly inhibited upon pre-treatment with Wnt-C59, an inhibitor of the Wnt/ß-catenin pathway. These results suggest that HA may positively regulate hAMSCs proliferation through regulation of the Wnt/ß-catenin signaling pathway.


Subject(s)
Amnion/cytology , Hyaluronic Acid/pharmacology , Mesenchymal Stem Cells/cytology , Mesenchymal Stem Cells/metabolism , Wnt Signaling Pathway/drug effects , Benzeneacetamides/pharmacology , Cell Differentiation/drug effects , Cell Lineage/drug effects , Cell Proliferation/drug effects , Cell Shape/drug effects , Cyclin D1/metabolism , Female , Fluorescent Antibody Technique , Gene Expression Regulation/drug effects , Humans , Mesenchymal Stem Cells/drug effects , Osteogenesis/drug effects , Phenotype , Pregnancy , Proto-Oncogene Proteins c-myc/metabolism , Pyridines/pharmacology , Wnt Signaling Pathway/genetics , beta Catenin/metabolism
18.
Appl Opt ; 55(34): 9668-9674, 2016 Dec 01.
Article in English | MEDLINE | ID: mdl-27958455

ABSTRACT

We comprehensively investigate the energy band diagrams, carrier distribution, spontaneous emission rate rsp, and the internal quantum efficiency ηIQE in the lattice-matched GeSn/SiGeSn double heterostructure light-emitting diode (LED) wrapped in a Si3N4 liner stressor. The large tensile strain introduced into the device by the expansion of the Si3N4 liner is characterized by numerical simulation. A lower Sn composition required for the indirect to direct bandgap transition and a higher ratio of the electron occupation probability in the Γ conduction valley are achieved in the tensile strained GeSn/SiGeSn LED in comparison with the relaxed device. Analytical calculation shows that the tensile strained LED wrapped in the Si3N4 liner stressor exhibits the improved rsp and ηIQE compared to the relaxed device. rsp and ηIQE also can be enhanced by increasing Sn composition, carrier injection density, and n-type doping concentration in the GeSn active layer.

19.
Opt Express ; 23(2): 739-46, 2015 Jan 26.
Article in English | MEDLINE | ID: mdl-25835833

ABSTRACT

In this paper, we design a biaxial tensile strained GeSn photodetector with fin structure wrapped in Si(3)N(4) liner stressor. A large biaxial tensile strain is induced in GeSn fins by the expansion of Si(3)N(4) liner stressor. The distribution of tensile strain in GeSn fins was calculated by a finite element simulation. It is observed that magnitude of the strain increases with the reduction of fin thickness T(fin). Under the biaxial tensile strain, the direct band gap E(G,Γ) of GeSn fin photodetector is significantly reduced by lowering Γ conduction valley in energy and lifting of degeneracy of valence bands. As the 30 nm Si(3)N(4) liner stressor expanses by 1%, a E(G,Γ) reduction of ~0.14 eV is achieved in Ge(0.92)Sn(0.08) fins with a T(fin) of 100 nm. The cut-off wavelengths of strained Ge(0.96)Sn(0.04), Ge(0.92)Sn(0.08) and Ge(0.90)Sn(0.10) fin photodetectors with a T(fin) of 100 nm are extended to 2.4, 3.3, and 4 µm, respectively. GeSn fin photodetector integrated with Si(3)N(4) liner stressor provides an effective technique for extending the absorption edge of GeSn with Sn composition less than 10% to mid-infrared wavelength.

20.
Opt Express ; 23(6): 7924-32, 2015 Mar 23.
Article in English | MEDLINE | ID: mdl-25837129

ABSTRACT

We theoretically investigate a tensile strained GeSn waveguide integrated with Si3N4 liner stressor for the applications in mid-infrared (MIR) detector and modulator. A substantial tensile strain is induced in a 1 × 1 µm² GeSn waveguide by the expansion of 500 nm Si3N4 liner stressor and the contour plots of strain are simulated by the finite element simulation. Under the tensile strain, the direct bandgap E(G,Γ) of GeSn is significantly reduced by lowering the Γ conduction valley in energy and lifting of degeneracy of valence bands. Absorption coefficients of tensile strained GeSn waveguides with different Sn compositions are calculated. As the Si3N4 liner stressor expands by 1%, the cut-off wavelengths of tensile strained Ge(0.97)Sn(0.03), Ge(0.95)Sn(0.05), and Ge(0.90)Sn(0.10) waveguide photodetectors are extended to 2.32, 2.69, and 4.06 µm, respectively. Tensile strained Ge(0.90)Sn(0.10) waveguide electro-absorption modulator based on Franz-Keldysh (FK) effect is demonstrated in theory. External electric field dependence of cut-off wavelength and propagation loss of tensile strained Ge(0.90)Sn(0.10) waveguide is observed, due to the FK effect.

SELECTION OF CITATIONS
SEARCH DETAIL