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1.
BMC Public Health ; 24(1): 221, 2024 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-38238731

RESUMO

BACKGROUND: Inflammation exerts a critical role in the pathogenesis of infertility. The relationship between inflammatory parameters from peripheral blood and infertility remains unclear. Aim of this study was to investigate the association between inflammatory markers and infertility among women of reproductive age in the United States. METHODS: Women aged 20-45 were included from the National Health and Nutrition Examination Survey (NHANES) 2013-2020 for the present cross-sectional study. Data of reproductive status was collected from the Reproductive Health Questionnaire. Six inflammatory markers, systemic immune inflammation index (SII), lymphocyte count (LC), product of platelet and neutrophil count (PPN), platelet-lymphocyte ratio (PLR), neutrophil-lymphocyte ratio (NLR) and lymphocyte-monocyte ratio (LMR) were calculated from complete blood counts in mobile examination center. Survey-weighted multivariable logistic regression was employed to assess the association between inflammatory markers and infertility in four different models, then restricted cubic spline (RCS) plot was used to explore non-linearity association between inflammatory markers and infertility. Subgroup analyses were performed to further clarify effects of other covariates on association between inflammatory markers and infertility. RESULTS: A total of 3,105 women aged 20-45 was included in the final analysis, with 431 (13.88%) self-reported infertility. A negative association was found between log2-SII, log2-PLR and infertility, with an OR of 0.95 (95% CI: 0.78,1.15; p = 0.60), 0.80 (95% CI:0.60,1.05; p = 0.10), respectively. The results were similar in model 1, model 2, and model 3. Compared with the lowest quartile (Q1), the third quartile (Q3) of log2-SII was negatively correlation with infertility, with an OR (95% CI) of 0.56 (95% CI: 0.37,0.85; p = 0.01) in model 3. Similarly, the third quartile (Q3) of log2-PLR was negatively correlation with infertility, with an OR (95% CI) of 0.61 (95% CI: 0.43,0.88; p = 0.01) in model 3. No significant association was observed between log2-LC, log2-PPN, log2-NLR, log2-LMR and infertility in model 3. A similar U-shaped relationship between log2-SII and infertility was found (p for non-linear < 0.05). The results of subgroup analyses revealed that associations between the third quartile (Q3) of log2-SII, log2-PLR and infertility were nearly consistent. CONCLUSION: The findings showed that SII and PLR were negatively associated with infertility. Further studies are needed to explore their association better and the underlying mechanisms.


Assuntos
Infertilidade , Inflamação , Feminino , Humanos , Estudos Transversais , Infertilidade/epidemiologia , Inflamação/epidemiologia , Inquéritos Nutricionais , Estudos Retrospectivos , Adulto Jovem , Adulto , Pessoa de Meia-Idade
2.
Biom J ; 66(5): e202300075, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38953670

RESUMO

Closed testing has recently been shown to be optimal for simultaneous true discovery proportion control. It is, however, challenging to construct true discovery guarantee procedures in such a way that it focuses power on some feature sets chosen by users based on their specific interest or expertise. We propose a procedure that allows users to target power on prespecified feature sets, that is, "focus sets." Still, the method also allows inference for feature sets chosen post hoc, that is, "nonfocus sets," for which we deduce a true discovery lower confidence bound by interpolation. Our procedure is built from partial true discovery guarantee procedures combined with Holm's procedure and is a conservative shortcut to the closed testing procedure. A simulation study confirms that the statistical power of our method is relatively high for focus sets, at the cost of power for nonfocus sets, as desired. In addition, we investigate its power property for sets with specific structures, for example, trees and directed acyclic graphs. We also compare our method with AdaFilter in the context of replicability analysis. The application of our method is illustrated with a gene ontology analysis in gene expression data.


Assuntos
Biometria , Biometria/métodos , Perfilação da Expressão Gênica/métodos , Ontologia Genética , Humanos
3.
BMC Med ; 21(1): 192, 2023 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-37226271

RESUMO

BACKGROUND: Both low-carbohydrate (LC) and calorie-restricted (CR) diets have been shown to have metabolic benefits. However, the two regimens have yet to be thoroughly compared. We conducted a 12-week randomized trial to compare the effects of these diets separately and in combination on both weight loss and metabolic risk factors in overweight/obese individuals. METHODS: A total of 302 participants were randomized to LC diet (n = 76), CR diet (n = 75), LC + CR diet (n = 76), or normal control (NC) diet (n = 75) using a computer-based random number generator. The primary outcome was the change in body mass index (BMI). The secondary outcomes included body weight, waist circumference, waist-to-hip ratio, body fat, and metabolic risk factors. All participants attended health education sessions during the trial. RESULTS: A total of 298 participants were analyzed. BMI change over 12 weeks was - 0.6 (95% CI, - 0.8 to - 0.3) kg/m2 in NC, - 1.3 (95% CI, - 1.5 to - 1.1) kg/m2 in CR, - 2.3 (95% CI, - 2.6 to - 2.1) kg/m2 in LC, and - 2.9 (95% CI, - 3.2 to - 2.6) kg/m2 in LC + CR. LC + CR diet was more effective than LC or CR diet alone at reducing BMI (P = 0.001 and P < 0.001, respectively). Furthermore, compared with the CR diet, the LC + CR diet and LC diet further reduced body weight, waist circumference, and body fat. Serum triglycerides were significantly reduced in the LC + CR diet group compared with the LC or CR diet alone. Plasma glucose, homeostasis model assessment of insulin resistance, and cholesterol concentrations (total, LDL, and HDL) did not change significantly between the groups during the 12-week intervention. CONCLUSIONS: The reduction of carbohydrate intake without restricting caloric intake is more potent to achieve weight loss over 12 weeks when compared to a calorie-restricted diet in overweight/obese adults. The combination of restricting carbohydrate and total calorie intake may augment the beneficial effects of reducing BMI, body weight, and metabolic risk factors among overweight/obese individuals. TRIAL REGISTRATION: The study was approved by the institutional review board of Zhujiang Hospital of Southern Medical University and registered at the China Clinical Trial Registration Center (registration number: ChiCTR1800015156).


Assuntos
Carboidratos da Dieta , Sobrepeso , Adulto , Humanos , Restrição Calórica , Obesidade , Dieta com Restrição de Carboidratos
4.
Biometrics ; 79(2): 1103-1113, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-35567306

RESUMO

The Globaltest is a powerful test for the global null hypothesis that there is no association between a group of features and a response of interest, which is popular in pathway testing in metabolomics. Evaluating multiple feature sets, however, requires multiple testing correction. In this paper, we propose a multiple testing method, based on closed testing, specifically designed for the Globaltest. The proposed method controls the familywise error rate simultaneously over all possible feature sets, and therefore allows post hoc inference, that is, the researcher may choose feature sets of interest after seeing the data without jeopardizing error control. To circumvent the exponential computation time of closed testing, we derive a novel shortcut that allows exact closed testing to be performed on the scale of metabolomics data. An R package ctgt is available on comprehensive R archive network for the implementation of the shortcut procedure, with applications on several real metabolomics data examples.


Assuntos
Metabolômica
5.
Molecules ; 28(6)2023 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-36985423

RESUMO

Non-magnetic metal nanoparticles have been previously applied for the growth of single-walled carbon nanotubes (SWNTs). However, the activation mechanisms of non-magnetic metal catalysts and chirality distribution of synthesized SWNTs remain unclear. In this work, the activation mechanisms of non-magnetic metal palladium (Pd) particles supported by the magnesia carrier and thermodynamic stabilities of nucleated SWNTs with different (n, m) are evaluated by theoretical simulations. The electronic metal-support interaction between Pd and magnesia upshifts the d-band center of Pd, which promotes the chemisorption and dissociation of carbon precursor molecules on the Pd surface, making the activation of magnesia-supported non-magnetic Pd catalysts for SWNT growth possible. To verify the theoretical results, a porous magnesia supported Pd catalyst is developed for the bulk synthesis of SWNTs by chemical vapor deposition. The chirality distribution of Pd-grown SWNTs is understood by operating both Pd-SWNT interfacial formation energy and SWNT growth kinetics. This work not only helps to gain new insights into the activation of catalysts for growing SWNTs, but also extends the use of non-magnetic metal catalysts for bulk synthesis of SWNTs.

6.
Int J Mol Sci ; 24(1)2022 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-36613506

RESUMO

Rickett's big-footed bat, Myotis pilosus, which belongs to the family Vespertilionida, is the only known piscivorous bat in East Asia. Accurate whole genome and transcriptome annotations are essential for the study of bat biological evolution. The lack of a whole genome for M. pilosus has limited our understanding of the molecular mechanisms underlying the species' evolution, echolocation, and immune response. In the present work, we sequenced the entire transcriptome using error-corrected PacBio single-molecule real-time (SMRT) data. Then, a total of 40 GB of subreads were generated, including 29,991 full-length non-chimeric (FLNC) sequences. After correction by Illumina short reads and de-redundancy, we obtained 26,717 error-corrected isoforms with an average length of 3018.91 bp and an N50 length of 3447 bp. A total of 1528 alternative splicing (AS) events were detected by transcriptome structural analysis. Furthermore, 1032 putative transcription factors (TFs) were identified, with additional identification of several long non-coding RNAs (lncRNAs) with high confidence. Moreover, several key genes, including PRL-2, DPP4, Glul, and ND1 were also identified as being associated with metabolism, immunity, nervous system processes, and auditory perception. A multitude of pattern recognition receptors was identified, including NLR, RLR, SRCR, the antiviral molecule IRF3, and the IFN receptor subunit IFNAR1. High-quality reference genomes at the transcriptome level may be used to quantify gene or transcript expression, evaluate alternative splicing levels, identify novel transcripts, and enhance genome annotation in bats.


Assuntos
Quirópteros , RNA Longo não Codificante , Animais , Transcriptoma , Quirópteros/genética , Perfilação da Expressão Gênica , Processamento Alternativo/genética , Isoformas de Proteínas/genética , RNA Longo não Codificante/genética
7.
Biom J ; 63(7): 1351-1365, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34046931

RESUMO

We construct confidence regions in high dimensions by inverting the globaltest statistics, and use them to choose the tuning parameter for penalized regression. The selected model corresponds to the point in the confidence region of the parameters that minimizes the penalty, making it the least complex model that still has acceptable fit according to the test that defines the confidence region. As the globaltest is particularly powerful in the presence of many weak predictors, it connects well to ridge regression, and we thus focus on ridge penalties in this paper. The confidence region method is quick to calculate, intuitive, and gives decent predictive potential. As a tuning parameter selection method it may even outperform classical methods such as cross-validation in terms of mean squared error of prediction, especially when the signal is weak. We illustrate the method for linear models in simulation study and for Cox models in real gene expression data of breast cancer samples.


Assuntos
Modelos Lineares , Simulação por Computador , Modelos de Riscos Proporcionais
8.
Biophys J ; 117(4): 631-645, 2019 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-31400914

RESUMO

Mitochondrial dysfunction has been implicated in many pathological conditions and diseases. The normal functioning of mitochondria relies on maintaining the inner mitochondrial membrane potential (also known as ΔΨm) that is essential for ATP synthesis, Ca2+ homeostasis, redox balance, and regulation of other key signaling pathways such as mitophagy and apoptosis. However, the detailed mechanisms by which ΔΨm regulates cellular function remain incompletely understood, partially because of the difficulty of manipulating ΔΨm with spatiotemporal resolution, reversibility, or cell type specificity. To address this need, we have developed a next generation optogenetic-based technique for controllable mitochondrial depolarization with light. We demonstrate successful targeting of the heterologous channelrhodopsin-2 fusion protein to the inner mitochondrial membrane and formation of functional cationic channels capable of light-induced selective ΔΨm depolarization and mitochondrial autophagy. Importantly, we for the first time, to our knowledge, show that optogenetic-mediated mitochondrial depolarization can be well controlled to differentially influence the fate of cells expressing mitochondrial channelrhodopsin-2; whereas sustained moderate light illumination induces substantial apoptotic cell death, transient mild light illumination elicits cytoprotection via mitochondrial preconditioning. Finally, we show that Parkin overexpression exacerbates, instead of ameliorating, mitochondrial depolarization-mediated cell death in HeLa cells. In summary, we provide evidence that the described mitochondrial-targeted optogenetics may have a broad application for studying the role of mitochondria in regulating cell function and fate decision.


Assuntos
Apoptose , Channelrhodopsins/metabolismo , Potencial da Membrana Mitocondrial , Optogenética/métodos , Células Cultivadas , Channelrhodopsins/genética , Células HeLa , Humanos , Mitocôndrias/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo
9.
Analyst ; 144(12): 3800-3806, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31116196

RESUMO

In typical photoelectrochemical (PEC) biosensing assays, electrodes are generally modified with photoactive probes and/or target recognition probes, which makes the processes complicated, time-consuming, and difficult to achieve excellent reproducibility. Hence, to overcome such shortcomings, we propose here an immobilization-free and label-free PEC aptasensor using solution-phase methylene blue (MB) as the PEC signal probe. Based on the unique T-Hg2+-T base pairs, and the diffusivity difference between free MB molecules and the MB/G-quadruplex composite towards the ITO electrode surface with negative charge, the "signal-off" approach for Hg2+ detection is developed. In the presence of target Hg2+, via the T-Hg2+-T bond formation, the two sticky ends of the hairpin DNA probe form a rigid duplex stem, which triggers the exonuclease III-facilitated target cycling amplification, and the formation of multiple G-quadruplexes. Upon the intercalation of MB in G-quadruplexes, significantly decreased photocurrent is obtained owing to the increased electrostatic repulsion between the MB/G-quadruplex composite and the ITO electrode. Therefore, highly sensitive and ultrasensitive Hg2+ determination is achieved, with a low detection limit of 1.2 pM, well below the maximum allowable Hg2+ level in drinking water defined by the WHO, China's Ministry of Health, and the US EPA. Due to the avoidance of sophisticated electrode modification and recognition probe immobilization processes, as well as an expensive labeling procedure, the PEC aptasensor proposed here demonstrates the advantages of simplicity, good reproducibility, rapidness and low cost.


Assuntos
Aptâmeros de Nucleotídeos/química , Técnicas Biossensoriais/métodos , Sondas de DNA/química , Exodesoxirribonucleases/química , Mercúrio/análise , Azul de Metileno/química , Aptâmeros de Nucleotídeos/genética , Pareamento de Bases , DNA/química , DNA/genética , Sondas de DNA/genética , Água Potável/análise , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Quadruplex G , Substâncias Intercalantes/química , Substâncias Intercalantes/efeitos da radiação , Sequências Repetidas Invertidas , Lagos/análise , Limite de Detecção , Mercúrio/química , Azul de Metileno/efeitos da radiação , Técnicas de Amplificação de Ácido Nucleico/métodos , Reprodutibilidade dos Testes , Timina/química , Compostos de Estanho/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
10.
Mol Med ; 24(1): 43, 2018 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-30134927

RESUMO

BACKGROUND: Type 2 diabetes mellitus (T2DM) is characterized by pancreatic ß-cell failure, which arises from metabolic stress and results in ß cell dedifferentiation, leading to ß-cell death. Pathological activation of the renin-angiotensin system (RAS) contributes to increase cell stress, while RAS intervention reduces the onset of T2DM in high-risk populations and promotes insulin secretion in rodents. In this study, we investigated whether and how RAS induces ß-cell dedifferentiation and the mechanism underlying this process. METHODS: In vitro, with the methods of quantitative real-time reverse transcriptase-PCR (qRT-PCR) and western blotting, we examined the change of cell identity-related gene expression, progenitor like gene expression, cellular function, and nuclear factor kappa b (NF-κb) signaling activity in ß cell lines after exposure to angiotensin II (AngII) and disruption of RAS. In vivo, parallel studies were performed using db/db mice. Related protein expression was detected by Immunofluorescence analysis. RESULT: Activation of RAS induced dedifferentiation and impaired insulin secretion, eventually leading to ß-cell failure. Mechanistically, Angll induced ß-cell dedifferentiation via NF-κb signaling, while treatment with lrbesartan and sc-514 reversed the progenitor state of ß cells. CONCLUSION: The present study found that RAS might induce ß-cell dedifferentiation via angiotensin II receptor type 1 activation, which was promoted by NF-κb signaling. Therefore, blocking RAS or NF-kb signaling efficiently reversed the dedifferentiated status of ß cells, suggesting a potential therapy for patients with type 2 diabetes.


Assuntos
Angiotensina II/farmacologia , Desdiferenciação Celular/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , NF-kappa B/antagonistas & inibidores , Animais , Linhagem Celular Tumoral , Diabetes Mellitus Tipo 2/metabolismo , Expressão Gênica/efeitos dos fármacos , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Masculino , Camundongos Endogâmicos C57BL , NF-kappa B/metabolismo , Ratos , Sistema Renina-Angiotensina , Transdução de Sinais/efeitos dos fármacos
11.
Anal Chem ; 90(15): 9591-9597, 2018 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-29991254

RESUMO

In conventional photoelectrochemical (PEC) analysis, photoactive materials are usually immobilized on electrode surfaces, and such immobilization procedures are tedious and time-consuming, and it is also difficult to prepare electrodes with good reproducibility. To circumvent such limitations, we propose here a truly immobilization-free diffusivity-mediated PEC bionsensing strategy for microRNA assay, using methylene blue (MB) in solution as the photoactive probe, and nonmodified indium tin oxide (ITO) glass as the working electrode. The hybridization between the target microRNA and the MB-labeled single-stranded DNA probe (MB-DNA) triggers the digestion of MB-DNA by T7 exonuclease (T7 Exo), thus to generate MB-labeled mononucleotide, and then the released target microRNA initiates the subsequent cycling processes and generates a large amount of MB-labeled mononucleotides. Due to the diffusivity difference between MB-DNAs and MB-labeled mononucleotides, significantly increased photocurrent signal is observed for MB-labeled mononucleotides as compared to that of MB-DNAs. Therefore, via this "signal-on" mode and the T7 Exo facilitated signal amplification, a facile and highly sensitive immobilization-free PEC microRNA assay is readily realized, with a detection limit down to 27 aM. Moreover, this strategy exhibits excellent specificity and is successfully applied in detecting microRNA spiked in serum samples. Since all the reactions take place in homogeneous solutions and no electrode modification is needed, this PEC biosensing strategy exhibits the advantages of simplicity, rapidness, and good reproducibility. More significantly, it provides a novel concept to design truly immobilization-free PEC biosensing systems, and shows potential to be applied in bioanalysis and biochemical research.


Assuntos
Técnicas Biossensoriais/métodos , DNA de Cadeia Simples/química , Técnicas Eletroquímicas/métodos , Azul de Metileno/química , MicroRNAs/sangue , Técnicas Biossensoriais/instrumentação , Sondas de DNA/química , Difusão , Técnicas Eletroquímicas/instrumentação , Eletrodos , Desenho de Equipamento , Humanos , MicroRNAs/análise , Reprodutibilidade dos Testes , Compostos de Estanho/química
12.
Opt Express ; 25(13): 14089-14097, 2017 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-28788994

RESUMO

Terahertz sensing of highly absorptive aqueous solutions remains challenging due to strong absorption of water in the terahertz regime. Here, we experimentally demonstrate a cost-effective metamaterial-based sensor integrated with terahertz time-domain spectroscopy for highly absorptive water-methanol mixture sensing. This metamaterial has simple asymmetric wire structures that support multiple resonances including a fundamental Fano resonance and higher order dipolar resonance in the terahertz regime. Both the resonance modes have strong intensity in the transmission spectra which we exploit for detection of the highly absorptive water-methanol mixtures. The experimentally characterized sensitivities of the Fano and dipole resonances for the water-methanol mixtures are found to be 160 and 305 GHz/RIU, respectively. This method provides a robust route for metamaterial-assisted terahertz sensing of highly absorptive chemical and biochemical materials with multiple resonances and high accuracy.

13.
Biochem Eng J ; 124: 122-129, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28736500

RESUMO

Chinese hamster ovary (CHO) cells have been widely used to express heterologous genes and produce therapeutic proteins in biopharmaceutical industry. Different CHO host cells have distinct cell growth rates and protein expression characteristics. In this study, the expression of about 1,307 host proteins in three sublines, i.e. CHO K1, CHO S and CHO/dihydrofolate reductase (dhfr)- , were investigated and compared using proteomic analysis. The proteins involved in cell growth, glycolysis, tricarboxylic acid cycle, transcription, translation and glycosylation were quantitated using Liquid chromatography tandem-mass spectrometry (LC-MS/MS). The key host cell proteins that regulate the kinetics of cell growth and the magnitude of protein expression levels were identified. Furthermore, several rational cell engineering strategies on how to combine the desired features of fast cell growth and efficient production of therapeutic proteins into one new super CHO host cell have been proposed.

14.
Small ; 12(19): 2610-5, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-27007192

RESUMO

Metamaterials, offering unprecedented functionalities to manipulate electromagnetic waves, have become a research hotspot in recent years. Through the incorporation of active media, the exotic electromagnetic behavior of metamaterials can be dramatically empowered by dynamic control. Many ferroelectric materials such as BaSrTiO3 (abbreviated as BST), exhibiting strong response to external electric field, hold great promise in both microwave and terahertz tunable devices. A new active Ba0.6 Sr0.4 TiO3 -silicon hybrid metamaterial device, namely, a SRR (square split-ring resonator)-BaSrTiO3 thin film-silicon three-layer structure is fabricated and intensively studied. The active Ba0.6 Sr0.4 TiO3 thin film hybrid metamaterial, with nanoscale thickness, delivers a transmission contrast up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate. This work has significantly increased the low modulation rate of ferroelectric based devices in terahertz range, a major problem in this field remaining unresolved for many years. The proposed BST metamaterial is promising in developing high-performance real world photonic devices for terahertz technology.

15.
Small ; 12(19): 2609, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-27167323

RESUMO

A giant terahertz modulation based on a Ba0.6 Sr0.4 TiO3 -silicon hybrid metamaterial is reported by L. Wu, W. Zhang, and co-workers on page 2610. The proposed nanoscale Ba0.6 Sr0.4 TiO3 (BST) hybrid metamaterial, delivering a transmission contrast of up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate, is promising in developing high-performance real world photonic devices for terahertz technology.

16.
Opt Lett ; 41(19): 4562-4565, 2016 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-27749881

RESUMO

Recently reported active metamaterial analogues of electromagnetically induced transparency (EIT) are promising in developing novel optical components, such as active slow light devices. However, most of the previous works have focused on manipulating the EIT resonance strength at a fixed characteristic frequency and, therefore, realized on-to-off switching responses. To further extend the functionalities of the EIT effect, here we present a frequency tunable EIT analogue in the terahertz regime by integrating photoactive silicon into the metamaterial unit cell. A tuning range from 0.82 to 0.74 THz for the EIT resonance frequency is experimentally observed by optical pump-terahertz probe measurements, allowing a frequency tunable group delay of the terahertz pulses. This straightforward approach delivers frequency agility of the EIT resonance and may enable novel ultrafast tunable devices for integrated plasmonic circuits.

17.
Opt Express ; 23(22): 29222-30, 2015 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-26561192

RESUMO

The realization of high refractive index is of significant interest in optical imaging with enhanced resolution. Strongly coupled subwavelength resonators were proposed and demonstrated at both optical and terahertz frequencies to enhance the refractive index due to large induced dipole moment in meta-atoms. Here, we report an alternative design for flexible free-standing terahertz metasurface in the strong coupling regime where we experimentally achieve a peak refractive index value of 14.36. We also investigate the impact of the nearest neighbor coupling in the form of frequency tuning and enhancement of the peak refractive index. We provide an analytical circuit model to explain the impact of geometrical parameters and coupling on the effective refractive index of the metasurface. The proposed meta-atom structure enables tailoring of the peak refractive index based on nearest neighbor coupling and this property offers tremendous design flexibility for transformation optics and other index-gradient devices at terahertz frequencies.

18.
Opt Express ; 23(21): 27152-8, 2015 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-26480376

RESUMO

Metasurfaces provide great flexibility in tailoring light beams and reveal unprecedented prospects on novel functional components. However, techniques to dynamically control and manipulate the properties of metasurfaces are lagging behind. Here, for the first time to our knowledge, we present an active wave deflector made from a metasurface with phase discontinuities. The active metasurface is capable of delivering efficient real-time control and amplitude manipulation of broadband anomalous diffraction in the terahertz regime. The device consists of complementary C-shape split-ring resonator elements fabricated on a doped semiconductor substrate. Due to the Schottky diode effect formed by the hybrid metal-semiconductor, the real-time conductivity of the doped semiconductor substrate is modified by applying an external voltage bias, thereby effectively manipulating the intensity of the anomalous deflected terahertz wave. A modulation depth of up to 46% was achieved, while the characteristics of broadband frequency responses and constant deflected angles were well maintained during the modulation process. The modulation speed of diffraction amplitude reaches several kilohertz, limited by the capacitance and resistance of the depletion region. The scheme proposed here opens up a novel approach to develop tunable metasurfaces.

19.
Phys Rev Lett ; 113(9): 093901, 2014 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-25215984

RESUMO

By utilizing the vector nature of light as well as the inherent anisotropy of artificial meta-atoms, we investigate parity time symmetry breaking in polarization space using a metasurface with anisotropic absorption, whose building blocks consist of two orthogonally orientated meta-atoms with the same resonant frequency but different loss coefficients. By varying their coupling strength, we directly observe a phase transition in the eigenpolarization states of the system, across which the long axis of the eigenpolarization ellipses experience a sudden rotation of 45°. Despite the lack of rotational symmetry of the metasurface, precisely at the phase transition, known as the exceptional point, the eigenmodes coalesce into a single circularly polarized state. The PT symmetric metasurfaces are experimentally implemented at terahertz frequencies.

20.
Bioorg Med Chem Lett ; 24(14): 3018-22, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-24881565

RESUMO

Phenethylaminoheterocycles have been prepared and assayed for inhibition of the Kv1.5 potassium ion channel as a potential approach to the treatment of atrial fibrillation. A diverse set of heterocycles were identified as potent Kv1.5 inhibitors and were advanced to pharmacodynamic evaluation based on selectivity and pharmacokinetic profile. Heterocycle optimization and template modification lead to the identification of compound 24 which demonstrated increased atrial effective refractory period in the rabbit pharmacodynamic model with mild effects on blood pressure and heart rate.


Assuntos
Carbamatos/farmacologia , Desenho de Fármacos , Indazóis/farmacologia , Canal de Potássio Kv1.5/antagonistas & inibidores , Bloqueadores dos Canais de Potássio/farmacologia , Animais , Carbamatos/síntese química , Carbamatos/química , Relação Dose-Resposta a Droga , Átrios do Coração/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Humanos , Indazóis/síntese química , Indazóis/química , Modelos Moleculares , Estrutura Molecular , Bloqueadores dos Canais de Potássio/síntese química , Bloqueadores dos Canais de Potássio/química , Coelhos , Ratos , Relação Estrutura-Atividade
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