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1.
Proc Biol Sci ; 291(2027): 20240861, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39013425

RESUMO

Humans cooperate in groups in which mutual monitoring is common, and this provides the possibility of third-party arbitration. Third-party arbitration stabilizes reciprocity in at least two ways: first, when it is accurate, it reduces the frequency of misunderstandings resulting from perception errors, and second, even when it is inaccurate, it provides a public signal that allows pairs to align their expectations about how to behave after errors occur. Here, we describe experiments that test for these two effects. We find that in an iterated, sequential Prisoner's Dilemma game with errors, players with the highest average payoffs are those who make use of third-party arbitration and who also employ forgiving strategies. The combination of these two behaviours reduces the detrimental effects of errors on reciprocity, resulting in more cooperation.


Assuntos
Comportamento Cooperativo , Humanos , Dilema do Prisioneiro , Negociação , Percepção , Teoria dos Jogos , Perdão , Relações Interpessoais
2.
Radiat Oncol ; 19(1): 69, 2024 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-38822385

RESUMO

BACKGROUND: Multiple artificial intelligence (AI)-based autocontouring solutions have become available, each promising high accuracy and time savings compared with manual contouring. Before implementing AI-driven autocontouring into clinical practice, three commercially available CT-based solutions were evaluated. MATERIALS AND METHODS: The following solutions were evaluated in this work: MIM-ProtégéAI+ (MIM), Radformation-AutoContour (RAD), and Siemens-DirectORGANS (SIE). Sixteen organs were identified that could be contoured by all solutions. For each organ, ten patients that had manually generated contours approved by the treating physician (AP) were identified, totaling forty-seven different patients. CT scans in the supine position were acquired using a Siemens-SOMATOMgo 64-slice helical scanner and used to generate autocontours. Physician scoring of contour accuracy was performed by at least three physicians using a five-point Likert scale. Dice similarity coefficient (DSC), Hausdorff distance (HD) and mean distance to agreement (MDA) were calculated comparing AI contours to "ground truth" AP contours. RESULTS: The average physician score ranged from 1.00, indicating that all physicians reviewed the contour as clinically acceptable with no modifications necessary, to 3.70, indicating changes are required and that the time taken to modify the structures would likely take as long or longer than manually generating the contour. When averaged across all sixteen structures, the AP contours had a physician score of 2.02, MIM 2.07, RAD 1.96 and SIE 1.99. DSC ranged from 0.37 to 0.98, with 41/48 (85.4%) contours having an average DSC ≥ 0.7. Average HD ranged from 2.9 to 43.3 mm. Average MDA ranged from 0.6 to 26.1 mm. CONCLUSIONS: The results of our comparison demonstrate that each vendor's AI contouring solution exhibited capabilities similar to those of manual contouring. There were a small number of cases where unusual anatomy led to poor scores with one or more of the solutions. The consistency and comparable performance of all three vendors' solutions suggest that radiation oncology centers can confidently choose any of the evaluated solutions based on individual preferences, resource availability, and compatibility with their existing clinical workflows. Although AI-based contouring may result in high-quality contours for the majority of patients, a minority of patients require manual contouring and more in-depth physician review.


Assuntos
Inteligência Artificial , Planejamento da Radioterapia Assistida por Computador , Tomografia Computadorizada por Raios X , Humanos , Planejamento da Radioterapia Assistida por Computador/métodos , Órgãos em Risco/efeitos da radiação , Algoritmos , Processamento de Imagem Assistida por Computador/métodos
3.
Nat Commun ; 15(1): 4427, 2024 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-38789427

RESUMO

Atoms and their different arrangements into molecules are nature's building blocks. In a regime of strong coupling, matter hybridizes with light to modify physical and chemical properties, hence creating new building blocks that can be used for avant-garde technologies. However, this regime relies on the strong confinement of the optical field, which is technically challenging to achieve, especially at terahertz frequencies in the far-infrared region. Here we demonstrate several schemes of electromagnetic field confinement aimed at facilitating the collective coupling of a localized terahertz photonic mode to molecular vibrations. We observe an enhanced vacuum Rabi splitting of 200 GHz from a hybrid cavity architecture consisting of a plasmonic metasurface, coupled to glucose, and interfaced with a planar mirror. This enhanced light-matter interaction is found to emerge from the modified intracavity field of the cavity, leading to an enhanced zero-point electric field amplitude. Our study provides key insight into the design of polaritonic platforms with organic molecules to harvest the unique properties of hybrid light-matter states.

4.
Angew Chem Int Ed Engl ; 63(7): e202317565, 2024 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-38157448

RESUMO

We used in vitro selection to identify DNAzymes that acylate the exocyclic nucleobase amines of cytidine, guanosine, and adenosine in DNA oligonucleotides. The acyl donor was the 2,3,5,6-tetrafluorophenyl ester (TFPE) of a 5'-carboxyl oligonucleotide. Yields are as high as >95 % in 6 h. Several of the N-acylation DNAzymes are catalytically active with RNA rather than DNA oligonucleotide substrates, and eight of nine DNAzymes for modifying C are site-specific (>95 %) for one particular substrate nucleotide. These findings expand the catalytic ability of DNA to include site-specific N-acylation of oligonucleotide nucleobases. Future efforts will investigate the DNA and RNA substrate sequence generality of DNAzymes for oligonucleotide nucleobase N-acylation, toward a universal approach for site-specific oligonucleotide modification.


Assuntos
DNA Catalítico , DNA Catalítico/genética , Oligonucleotídeos , DNA , RNA , Catálise
5.
Opt Express ; 31(25): 42723-42729, 2023 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-38087639

RESUMO

Orthogonal optical coding is widely used in classical multi-user communication networks. Using the phase conjugation property of stimulated parametric down-conversion, we extend the current time-domain orthogonal optical coding scheme to the spatial domain to encode and decode image information. In this process, the idler beam inherits the complex conjugate of the field information encoded in the seed beam. An encoding phase mask introduced onto the input seed beam blurs the image transferred to the idler. The original image is restored by passing the coded transferred image through a corrective phase mask placed in the momentum space of the idler beam. We expect that this scheme can also inspire new techniques in secure image transmission, aberration cancellation, and frequency conversion imaging.

6.
Nano Lett ; 23(24): 11555-11561, 2023 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-38038228

RESUMO

Extensive research has focused on Mie modes in dielectric nanoresonators, enabling the creation of thin optical devices surpassing their bulk counterparts. This study investigates the interactions between two fundamental Mie modes, electric and magnetic dipoles, and the epsilon-near-zero (ENZ) mode. Analytical, simulation, and experimental analyses reveal that the presence of the ENZ substrate significantly modifies these modes despite a large size mismatch. Electric and magnetic dipole modes, both with ∼12 THz line widths, exhibit 21 and 26 THz anticrossings, respectively, when coupled to the ENZ mode, indicating strong coupling. We also demonstrate that this strongly coupled system yields notably large subpicosecond nonlinear responses. Our results establish a solid foundation for designing functional, nonlinear, dynamic dielectric metasurfaces with ENZ materials.

7.
Environ Sci Pollut Res Int ; 30(57): 120945-120962, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37947933

RESUMO

Ni/SBA-15 meso-structured catalysts modified with chromium and CeO2 (Ni-Cr-CeO2/SBA-15) were utilized to produce hydrogen from glycerol steam reforming (GSR). The catalysts were synthesized by a one-pot hydrothermal process and extensively characterized by analytical techniques such as N2 adsorption-desorption (BET), H2-temperature programmed reduction (H2-TPR), powder X-ray diffraction (PXRD), inductively coupled plasma-optical emission spectrometry (ICP-OES), and transmission electron microscopy (TEM). The low-angle XRD reflections affirmed that the catalysts were crystalline and possessed a 2D-ordered porosity. The BET results depicted that all the catalysts exhibited a good surface area ranging from 633 to 792m2/g, and the pore sizes were consistently in the mesoporous range (between 3 and 5 nm). TEM analysis of both calcined and spent catalysts revealed that the metal active sites were embedded in the hybrid CeO2-SiO2 support. Overall, the Ni-based catalysts exhibited higher glycerol conversion -12Ni-SBA-15-99.9%, 12Ni3CeO2-SBA-15-89.4%, and 8Ni4Cr3CeO2-SBA-15-99.7%. Monometallic 12Ni/SBA-15 performed exceptionally well, while 12Cr/SBA-15 performed poorly with the highest 71.48% CO selectivity. For short-term GSR reactions, CeO2 addition to 12Ni/SBA-15 did not have any effect, whereas Cr addition resulted in a 32% decrease in H2 selectivity. The long-term stability studies of 12Ni-SBA-15 showed H2 selectivity of ~ 64% and ~ 98% glycerol conversion. However, its activity was short-lived. After 20-30 h, the H2 selectivity and conversion dropped precipitously to 40%. The doping of mesoporous Ni/SBA-15 with Cr and CeO2 remarkably enhanced the long-term stability of the catalyst for 12Ni3CeO2-SBA-15, and 8Ni4Cr3CeO2-SBA-15 catalyst which showed ~ 58% H2 selectivity and ~ 100% conversion for the entire 60 h. Interestingly, Cr and CeO2 seem to improve the shelf-life of Ni-SBA-15 via different mechanistic pathways. CeO2 mitigated Ni poisoning through coke oxidation whereas Cr bolstered the catalyst stability via maintaining a well-defined pore size, structural rigidity, and integrity of the heterogeneous framework, thereby restricting structural collapse, and hence retard sintering of the Ni active sites during the long-term 60 h of continuous reaction. Hydrogen generation from renewable biomass like glycerol could potentially serve as a sustainable energy source and could substantially help reduce the carbon footprint of the environment.


Assuntos
Nanopartículas Metálicas , Dióxido de Silício , Dióxido de Silício/química , Vapor , Glicerol/química , Níquel/química , Nanopartículas Metálicas/química , Hidrogênio/química
8.
Am J Orthod Dentofacial Orthop ; 164(6): 774-782, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37552148

RESUMO

INTRODUCTION: This study aimed to examine the stability of anterior open bite (AOB) treatment with clear aligners. METHODS: This retrospective cohort study included 52 adult AOB patients (aged >18 years; 15 males, 37 females) who underwent nonextraction clear aligner treatment and were at least 1 year posttreatment. Eleven cephalometric measurements were evaluated at pretreatment, end of active treatment, and at least 1-year posttreatment. Overbite change, the primary outcome variable, and other cephalometric changes during treatment and retention were calculated, and repeated measures analysis of variance were performed. Stepwise multiple regression was used to make a prediction equation for open bite relapse. RESULTS: The mean retention period was 2.1 ± 1.1 years. The mean change in overbite during treatment was 3.3 ± 1.5 mm; 6% of patients presented relapse at least 1 year after treatment completion. The mean change of overbite (0.2 ± 0.5 mm) during the retention period was not statistically significant (P = 0.59). None of the 11 cephalometric measurements showed significant change during the retention period. The prediction model showed that only the coefficient for a tongue posture issue at the initial examination was statistically significant. CONCLUSIONS: AOB was successfully corrected in all 52 patients using only clear aligners with no additional adjunctive aids such as microimplants. When retained with maxillary and mandibular fixed retainers and maxillary and mandibular vacuum-formed retainers, there was no significant change in cephalometric measurements during the short-term retention period.


Assuntos
Má Oclusão Classe II de Angle , Mordida Aberta , Aparelhos Ortodônticos Removíveis , Sobremordida , Masculino , Feminino , Humanos , Adulto , Estudos Retrospectivos , Mordida Aberta/terapia , Cefalometria , Recidiva
9.
Sci Rep ; 13(1): 10723, 2023 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-37400527

RESUMO

Organellar C-to-U RNA editing in plants occurs in complexes composed of various classes of nuclear-encoded proteins. DYW-deaminases are zinc metalloenzymes that catalyze hydrolytic deamination required for C-to-U modification editing. Solved crystal structures for DYW-deaminase domains display all structural features consistent with a canonical cytidine deamination mechanism. However, some recombinant DYW-deaminases from plants have been associated with ribonuclease activity in vitro. Direct ribonuclease activity by an editing factor is confounding since it is not required for deamination of cytosine, theoretically would be inimical for mRNA editing, and does not have a clear physiological function in vivo. His-tagged recombinant DYW1 from Arabidopsis thaliana (rAtDYW1) was expressed and purified using immobilized metal affinity chromatography (IMAC). Fluorescently labeled RNA oligonucleotides were incubated with recombinant AtDYW1 under different conditions. Percent relative cleavage of RNA probes was recorded at multiple time points from triplicate reactions. The effects of treatment with zinc chelators EDTA and 1, 10-phenanthroline were examined for rAtDYW1. Recombinant His-tagged RNA editing factors AtRIP2, ZmRIP9, AtRIP9, AtOZ1, AtCRR4, and AtORRM1 were expressed in E. coli and purified. Ribonuclease activity was assayed for rAtDYW1 in the presence of different editing factors. Lastly, the effects on nuclease activity in the presence of nucleotides and modified nucleosides were investigated. RNA cleavage observed in this study was linked to the recombinant editing factor rAtDYW1 in vitro. The cleavage reaction is sensitive to high concentrations of zinc chelators, indicating a role for zinc ions for activity. The addition of equal molar concentrations of recombinant RIP/MORF proteins reduced cleavage activity associated with rAtDYW1. However, addition of equal molar concentrations of purified recombinant editing complex proteins AtCRR4, AtORRM1, and AtOZ1 did not strongly inhibit ribonuclease activity on RNAs lacking an AtCRR4 cis-element. Though AtCRR4 inhibited AtDYW1 activity for oligonucleotides with a cognate cis-element. The observation that editing factors limit ribonuclease activity of rAtDYW1 in vitro, suggests that nuclease activities are limited to RNAs in absence of native editing complex partners. Purified rAtDYW1 was associated with the hydrolysis of RNA in vitro, and activity was specifically inhibited by RNA editing factors.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Ribonucleases , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Transporte/metabolismo , Quelantes/metabolismo , Plantas/metabolismo , Estrutura Terciária de Proteína , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Ribonucleases/metabolismo , RNA/metabolismo , Zinco/metabolismo
10.
ACS Appl Mater Interfaces ; 15(21): 26093-26103, 2023 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-37204834

RESUMO

Direct electrification of oxygen-associated reactions contributes to large-scale electrical storage and the launch of the green hydrogen economy. The design of the involved catalysts can mitigate the electrical energy losses and improve the control of the reaction products. We evaluate the effect of the interface composition of electrocatalysts on the efficiency and productivity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), both mechanistically and at device levels. The ORR and OER were benchmarked on mesoporous nickel(II) oxide and nickel cobaltite (NiO and NiCo2O4, respectively) obtained by a facile template-free hydrothermal synthesis. Physicochemical characterization showed that both NiO and NiCo2O4 are mesoporous and have a cubic crystal structure with abundant surface hydroxyl species. NiCo2O4 showed higher electrocatalytic activity in OER and selectivity to water as the terminal product of ORR. On the contrary, ORR over NiO yielded hydroxyl radicals as products of a Fenton-like reaction of H2O2. The product selectivity in ORR was used to construct two electrolyzers for electrified purification of oxygen and generation of hydroxyl radicals.

11.
Australas Psychiatry ; 31(4): 435-440, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37102589

RESUMO

OBJECTIVES: To understand: a) whether adults receiving public mental health care were aware they were officially referred to as 'consumers' and, b) their views and preferences on the terms used to refer to them. METHODS: Single-page, anonymous survey conducted across two community mental health services in Northern New South Wales (NNSW). Ethics approval obtained from the local research office. RESULTS: 108 people completed the survey with a response rate of approximately 22%. The vast majority (77%) of respondents were not aware that they were officially referred to as 'consumers'. 32% of respondents disliked the term 'consumer' and 11% found it offensive. Half preferred the term 'patient', particularly when consulting a psychiatrist (55%). A small minority (5-7%) preferred the term 'consumer' for any care interaction. CONCLUSION: Most respondents in this survey wished to be referred to as a 'patient' and a large proportion disliked being referred to as a 'consumer' or found it offensive. Further surveys should include broader sociodemographic and diagnostic/treatment variables. Official terms used to refer to people receiving public mental health care should be person-centred and evidence based.


Assuntos
Serviços Comunitários de Saúde Mental , Saúde Mental , Adulto , Humanos , Austrália , New South Wales
12.
Opt Lett ; 48(8): 2194-2197, 2023 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-37058675

RESUMO

There are various performance advantages when using temporal phase-based data encoding and coherent detection with a local oscillator (LO) in free-space optical (FSO) links. However, atmospheric turbulence can cause power coupling from the Gaussian mode of the data beam to higher-order modes, resulting in significantly degraded mixing efficiency between the data beam and a Gaussian LO. Photorefractive crystal-based self-pumped phase conjugation has been previously demonstrated to "automatically" mitigate turbulence with limited-rate free-space-coupled data modulation (e.g., <1 Mbit/s). Here, we demonstrate automatic turbulence mitigation in a 2-Gbit/s quadrature-phase-shift-keying (QPSK) coherent FSO link using degenerate four-wave-mixing (DFWM)-based phase conjugation and fiber-coupled data modulation. Specifically, we counter-propagate a Gaussian probe from the receiver (Rx) to the transmitter (Tx) through turbulence. At the Tx, we generate a Gaussian beam carrying QPSK data by a fiber-coupled phase modulator. Subsequently, we create a phase conjugate data beam through a photorefractive crystal-based DFWM involving the Gaussian data beam, the turbulence-distorted probe, and a spatially filtered Gaussian copy of the probe beam. Finally, the phase conjugate beam is transmitted back to the Rx for turbulence mitigation. Compared to a coherent FSO link without mitigation, our approach shows up to ∼14-dB higher LO-data mixing efficiency and achieves error vector magnitude (EVM) performance of <16% under various turbulence realizations.

13.
Rev Sci Instrum ; 94(2): 023902, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36859015

RESUMO

A recently presented chemical vapor deposition (CVD) method involves using plasma electrons as reducing agents for deposition of metals. The plasma electrons are attracted to the substrate surface by a positive substrate bias. Here, we present how a standard quartz crystal microbalance (QCM) system can be modified to allow applying a DC bias to the QCM sensor to attract plasma electrons to it and thereby also enable in situ growth monitoring during the electron-assisted CVD method. We show initial results from mass gain evolution over time during deposition of iron films using the biased QCM and how the biased QCM can be used for process development and provide insight into the surface chemistry by time-resolving the CVD method. Post-deposition analyses of the QCM crystals by cross-section electron microscopy and high-resolution x-ray photoelectron spectroscopy show that the QCM crystals are coated by an iron-containing film and thus function as substrates in the CVD process. A comparison of the areal mass density given by the QCM crystal and the areal mass density from elastic recoil detection analysis and Rutherford backscattering spectrometry was done to verify the function of the QCM setup. Time-resolved CVD experiments show that this biased QCM method holds great promise as one of the tools for understanding the surface chemistry of the newly developed CVD method.

14.
Toxicol Rep ; 10: 357-366, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36923444

RESUMO

Mucopolysaccharidosis Type IIIB (MPS IIIB) is an ultrarare, fatal pediatric disease with no approved therapy. It is caused by mutations in the gene encoding for lysosomal enzyme alpha-N-acetylglucosaminidase (NAGLU). Tralesinidase alfa (TA) is a fusion protein comprised of recombinant NAGLU and a modified human insulin-like growth factor 2 that is being developed as an enzyme replacement therapy for MPS IIIB. Since MPS IIIB is a pediatric disease the safety/toxicity, pharmacokinetics and biodistribution of TA were evaluated in juvenile non-human primates that were administered up to 5 weekly intracerebroventricular (ICV) or single intravenous (IV) infusions of TA. TA administered by ICV slow-, ICV isovolumetric bolus- or IV-infusion was well-tolerated, and no effects were observed on clinical observations, electrocardiographic or ophthalmologic parameters, or respiratory rates. The drug-related changes observed were limited to increased cell infiltrates in the CSF and along the ICV catheter track after ICV administration. These findings were not associated with functional changes and are associated with the use of ICV catheters. The CSF PK profiles were consistent across all conditions tested and TA distributed widely in the CNS after ICV administration. Anti-drug antibodies were observed but did not appear to significantly affect the exposure to TA. Correlations between TA concentrations in plasma and brain regions in direct contact with the cisterna magna suggest glymphatic drainage may be responsible for clearance of TA from the CNS. The data support the administration of TA by isovolumetric bolus ICV infusion to pediatric patients with MPS IIIB.

15.
PNAS Nexus ; 2(3): pgad054, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36970180

RESUMO

Differences in social norms are a key source of behavioral variation among human populations. It is widely assumed that a vast range of behaviors, even deleterious ones, can persist as long as they are locally common because deviants suffer coordination failures and social sanctions. Previous models have confirmed this intuition, showing that different populations may exhibit different norms even if they face similar environmental pressures or are linked by migration. Crucially, these studies have modeled norms as having a few discrete variants. Many norms, however, have a continuous range of variants. Here we present a mathematical model of the evolutionary dynamics of continuously varying norms and show that when the social payoffs of the behavioral options vary continuously the pressure to do what others do does not result in multiple stable equilibria. Instead, factors such as environmental pressure, individual preferences, moral beliefs, and cognitive attractors determine the outcome even if their effects are weak, and absent such factors populations linked by migration converge to the same norm. The results suggest that the content of norms across human societies is less arbitrary or historically constrained than previously assumed. Instead, there is greater scope for norms to evolve towards optimal individual or group-level solutions. Our findings also suggest that cooperative norms such as those that increase contributions to public goods might require evolved moral preferences, and not just social sanctions on deviants, to be stable.

16.
Opt Express ; 31(2): 1501-1515, 2023 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-36785184

RESUMO

High-speed spatial light modulators (SLM) are crucial components for free-space communication and structured illumination imaging. Current approaches for dynamical spatial mode generation, such as liquid crystal SLMs or digital micromirror devices, are limited to a maximum pattern refresh rate of 10 kHz and have a low damage threshold. We demonstrate that arbitrary spatial profiles in a laser pulse can be generated by mapping the temporal radio-frequency (RF) waveform sent to an acousto-optic modulator (AOM) onto the optical field. We find that the fidelity of the SLM performance can be improved through numerical optimization of the RF waveform to overcome the nonlinear effect of AOM. An AOM can thus be used as a 1-dimensional SLM, a technique we call acousto-optic spatial light modulator (AO-SLM), which has 50 µm pixel pitch, over 1 MHz update rate, and high damage threshold. We simulate the application of AO-SLM to single-pixel imaging, which can reconstruct a 32×32 pixel complex object at a rate of 11.6 kHz with 98% fidelity.

17.
Opt Lett ; 48(3): 783-786, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36723588

RESUMO

Bianisotropic media can be used to engineer absorbance, scattering, polarization, and dispersion of electromagnetic waves. However, the demonstration of a tunable light-induced bianisotropy at optical frequencies is still lacking. Here, we propose an experimentally feasible concept for a light-induced tunable bianisotropic response in a homogeneous sphere made of an epsilon-near-zero (ENZ) material. By exploiting the large linear absorption and the large possible intensity-dependent changes in the permittivity of ENZ materials, the direction-dependent scattering and absorption cross sections could be obtained. Our findings pave the way for further studies and applications in the optical regime requiring full dynamic control of the bianisotropic behavior.

18.
ACS Photonics ; 10(1): 162-169, 2023 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-36691428

RESUMO

Epsilon-near-zero (ENZ) polaritons in a thin transparent conducting-oxide film exhibit a significant electric field enhancement and localization within the film at frequencies close to their plasma frequency, but do not propagate. Meanwhile, plasmon polariton modes in thin metallic films can propagate for several microns, but are more loosely confined in the metal. Here, we propose a strongly coupled bilayered structure of a thin gold film on a thin indium tin oxide (ITO) film that supports hybrid polariton modes. We experimentally characterize the dispersion of these modes and show that they have propagation lengths of 4-8 µm while retaining mode confinement greater than that of the polariton in gold films by nearly an order of magnitude. We study the tunability of this coupling strength by varying the thickness of the ITO film and show that ultrastrong coupling is possible at certain thicknesses. The unusual linear and nonlinear optical properties of ITO at ENZ frequencies make these bifilms useful for the active tuning of strong coupling, ultrafast switching, and enhanced nonlinear interactions at near-infrared frequencies.

19.
Nanomaterials (Basel) ; 14(1)2023 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-38202492

RESUMO

Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin-orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, it is known that the excitons formed from electrons in the lower-energy conduction bands are dark in nature, whereas low-energy emissions in the photoluminescence spectrum have been linked to the brightening of these transitions, either via defect scattering or via phonon scattering with first-order phonon replicas. Through temperature and incident-power-dependent studies of WS2 grown by CVD or exfoliated from high-purity bulk crystal on different substrates, we demonstrate that the strong exciton-phonon coupling yields brightening of dark transitions up to sixth-order phonon replicas. We discuss the critical role of defects in the brightening pathways of dark excitons and their phonon replicas, and we elucidate that these emissions are intrinsic to the material and independent of substrate, encapsulation, growth method, and transfer approach.

20.
J Opt Soc Am A Opt Image Sci Vis ; 39(12): C161-C166, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36520767

RESUMO

Optical communications, remote sensing, particle trapping, and high-resolution imaging are a few research areas that benefit from new techniques to generate structured light. We present a method of generating polarization-structured laser beams that contain both full and partial polarization states. We demonstrate this method by generating an optical beam that contains every state of partial and full polarization. We refer to this beam as a volumetrically full Poincaré beam to distinguish it from full Poincaré beams, which contain all states of full polarization only. In contrast to methods relying upon spatial coherence to generate polarization-structured beams with partial polarization, our method creates well-collimated beams by relying upon temporal coherence.

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