148 research outputs found
Rotationally tunable polarization-insensitive single and multifocal metasurface
No full textMetasurfaces with superior capabilities to tailor wave fronts of light have become one of the most widely investigated optical elements. Incorporating tunable features into the metasurface design is required. In this study, we have proposed and designed highly efficient rotationally tunable metasurface lens structures inspired by Moire lenses operating at a 532 nm wavelength. The proposed structures consist of two cascaded all-dielectric metasurfaces, which have reverse phase profiles with respect to each other. The metasurfaces are designed with periodically arranged TiO2 nano-rods on a SiO2 substrate in a square lattice. We demonstrated that the focal length changes nonlinearly according to the mutual rotation of metasurfaces from 30 degrees to 150 degrees with a focusing efficiency as high as 55% and a wide focal length variation between 11.4 mu m and 4.2 mu m. Moreover, we have designed and proposed a tunable polarization-insensitive multifunctional focal system. Using the proposed multifunctional focal system, focal planes can be formed in consecutive planes and the number of focal planes can be made single or multiple.
Polarization-insensitive beam splitters using all-dielectric phase gradient metasurfaces at visible wavelengths
No full textBeam splitters play important roles in several optical applications, such as interferometers, spectroscopy, and optical communications. In this study, we propose and numerically examine polarization-insensitive beam splitters utilizing two-step phase gradient all-dielectric metasurfaces in the visible spectrum. The metasurface is made of periodically arranged binary unit cells, and phase difference between neighboring unit cells on the surface is 180 deg. The metasurface is shown to have a special phase gradient whose sign changes periodically. The angle of the split beams on both sides and the corresponding total transmission value at 532 nm wavelength are found to be +/- 46.8 degrees and 0.90, respectively. (c) 2018 Optical Society of America.
Multi-element ducts for ducted wind turbines: A numerical study
No full textMulti-element ducts are used to improve the aerodynamic performance of ducted wind turbines (DWTs). Steady-state, two-dimensional computational fluid dynamics (CFD) simulations are performed for a multi-element duct geometry consisting of a duct and a flap; the goal is to evaluate the effects on the aerodynamic performance of the radial gap length and the deflection angle of the flap. Solutions from inviscid and viscous flow calculations are compared. It is found that increasing the radial gap length results in an augmentation of the total thrust generated by the DWT, whereas a larger deflection angle has an opposite effect. Reasonable to good agreement is seen between the inviscid and viscous flow calculations, except for multi-element duct configurations characterized by large flap deflection angles. The viscous effects become stronger at large flap deflection angles, and the inviscid calculations are incapable of taking this phenomenon into account.</p
A decade of machine learning in protein corona research: Innovations and challenges
No full textNanomaterials, with their diverse biomedical applications spanning drug delivery to molecular imaging, undergo the adsorption of a protein corona (PC) layer upon exposure to biological environments. This dynamic layer, shaped by intricate interactions, significantly influences immune recognition, biodistribution, and nanoparticle toxicity. Traditional proteomic methods, such as liquid chromatography-tandem mass spectrometry, are effective but limited by low throughput, high costs, and the requirement for specialized expertise. The transition from unintentional PC analysis during polymer evaluations to a deliberate investigation of its role in drug targeting underscores the need for more efficient analytical approaches. The integration of machine learning (ML) into PC research has emerged as a promising solution. This computational methodology, which learns from datasets of characterized protein layers on specific nanoparticles, offers a more streamlined and resource-efficient alternative to traditional methods. Recent studies highlight ML’s ability to predict PC dynamics and biological effects, achieving notable accuracy in forecasting organ accumulation patterns. However, challenges remain, including the need for larger and more diverse datasets, significant computational demands, and the necessity for interdisciplinary collaboration between biologists, chemists, and data scientists. In addition, the development of standardized experimental protocols is crucial to ensure reproducibility and comparability across studies. Ethical considerations, such as potential job displacement in traditional fields, such as chemistry, also warrant careful attention as ML continues to evolve in this domain. In summary, while ML shows immense potential to revolutionize PC research, further refinement of methodologies and enhanced collaboration across disciplines are essential to fully realize its application in clinical nanomedicine
Prediction of interference factor for homonuclear diatomic molecules: N2, O2
No full text33rd International Physics Congress of the Turkish-Physical-Society (TPS) -- SEP 06-10, 2017 -- Bodrum, TURKEYYoung type interference effect for quantum particles can be seen in the cross sections for electron impact ionization of diatomic molecules. Interference factor is determined for description of interference effects in the ionization cross sections. Although such structures are observed for small diatomic molecules, larger molecules are less discussed in the recent works. Interference effects are already observed in the ionization cross sections of H-2 and N-2 molecules by electron impact. Similar effects expected to be seen on cross sections of larger diatomic molecules. The aim of this work, is to further highlight the possibility of interference effects may be seen also in the ionization cross sections of larger diatomic molecules and also discuss the structure of interference factor. This study is a preliminary study for the experiments can be carried to investigate interference effects in the cross sections of larger homonuclear diatomic molecules.AKU-BAPK [15.HIZDES131, 16.KARIYER.163]Turkish Phys SocThis work was supported by AKU-BAPK through Grant 15.HIZDES131 and 16.KARIYER.163
Fluoxetine-induced toxicity results in human placental glutathione S-transferase- (GST-) dysfunction
No full textContext: The antidepressant drug fluoxetine (FLU) is considered in the group of selective serotonine re-uptake inhibitors. Its distribution in brain and binding to human brain glutathione S-transferase- (GST-) have been shown. FLU can cross blood brain barrier and placenta, accumulate in fetus and may cause congenital malformations. Objective: To elucidate the interaction of placental GST- with FLU. Materials and methods: First, concentration-dependent inhibition of human placental GST- was evaluated by using different FLU concentrations and then 0.3125, 0.625, 1.25, 2.5 and 5mM FLU concentrations were chosen and tested while keeping GSH concentration constant and 1-chloro-2,4-dinitrobenzene (CDNB) concentration varied and vice versa. The data were evaluated with different kinetic models and Statistica 9.00 for Windows. Results: The V-m, at variable [CDNB] (142 +/- 16U/mg protein) was 3 times higher than the V-m obtained at variable [GSH] (49 +/- 4U/mg protein). On the other hand, the K-m for CDNB was approximate to 10 times higher than the K-m for GSH (1.99 +/- 0.36mM versus 0.21 +/- 0.06mM). The IC50 value for FLU was 8.6mM. Both at constant [CDNB] and variable [GSH] and at constant [GSH] and variable [CDNB] the inhibition types were competitive with the K-i values of 5.62 +/- 4.37 and 8.09 +/- 1.27mM, respectively. Conclusion: Although the K-i values obtained for FLU in vitro are high, due to their uneven distribution, long elimination time and inhibitory behavior on detoxification systems, it may cause defects in adults but these effects may be much more severe in fetus and result in congenital malformations
Evaluation of the in vitro Inhibitory Impact of Hypericin on Placental Glutathione S-Transferase pi
No full textSt John's Wort (SJW) extracts are herbal products which are available without prescription in most countries and widely used in the treatment of mild to moderate depression. Since it is a herbal product and available without prescription, use of SJW is common among pregnant and/or lactating woman. The principal of the study was to clarify the effects of hypericin, one of the components of SJW, on glutathione S-transferase-pi (GST-pi) purified from human placenta. The K (m) values of GST-pi were 0.21 +/- A 0.03 mM for glutathione (GSH) and 2.29 +/- A 0.54 mM for 1-chloro-2,4-dinitrobenzene (CDNB). At fixed [GSH], the V (m) value calculated was about 3 times higher than the conditions in which [CDNB] was fixed; 201 +/- A 30 U/mg protein versus 74 +/- A 3 U/mg protein. At constant substrate concentrations (1 mM), an average IC (50) value of 0.70 +/- A 0.02 mu M was obtained. Hypericin inhibited GST-pi competitively with respect to both substrates. When GSH was the varied substrate a K (i) value of 0.31 +/- A 0.05 mu M was found; when CDNB was the varied substrate, a K (i) value of 0.85 +/- A 0.02 mu M was obtained. On the basis of these data considering transplacental transfer of hypericin and immature hepatic clearance of the baby, using this herbal product may cause abnormalites due to the inhibition of one of the most important placental detoxification enzymes, GST-pi
Response to Ni et al.: The possible use of hypericin to overcome drug resistance in cancer treatment
No full textThe inhibition characteristics of human placental glutathione S-transferase-π by tricyclic antidepressants: amitriptyline and clomipramine
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