Search results for " Optics"
showing 10 items of 5880 documents
Deep learning approach for the segmentation of aneurysmal ascending aorta.
2020
Diagnosis of ascending thoracic aortic aneurysm (ATAA) is based on the measurement of the maximum aortic diameter, but size is not a good predictor of the risk of adverse events. There is growing interest in the development of novel image-derived risk strategies to improve patient risk management towards a highly individualized level. In this study, the feasibility and efficacy of deep learning for the automatic segmentation of ATAAs was investigated using UNet, ENet, and ERFNet techniques. Specifically, CT angiography done on 72 patients with ATAAs and different valve morphology (i.e., tricuspid aortic valve, TAV, and bicuspid aortic valve, BAV) were semi-automatically segmented with Mimic…
Comparison of two different devices to assess intraocular lenses
2016
[EN] In this paper, we have compared the performance of two commercial systems, Kaleo-I and IOLA Plus, in the characterization of monofocal intraocular lenses (IOLs) according to the International Standard requirements (ISO 11979-2). The dioptric power (DP) and the Modulation Transfer Function (MTF) at 100.1p/mm and 3.0 mm aperture have been measured with both instruments in twenty commercial monofocal HEMA IOLs and their agreement was assessed by Bland Altman analysis. Compared with the designed power, IOLA Plus gave lower values in 85% of measures: Kaleo I errors are dependent on the power of the lens: measurements were higher than the designed power in the low-medium power range and lowe…
Lensless object scanning holography for two-dimensional mirror-like and diffuse reflective objects
2013
Recently proposed lensless object scanning holography (LOSH) [Opt. Express 20, 9382 (2012)] is a fully lensless method capable of improving the image quality in digital Fourier holography applied to one-dimensional (1D) reflective objects and it involves a very simplified experimental setup. LOSH is based on the recording and digital postprocessing of a set of digital lensless Fourier transform holograms, which finally results in a synthetic image with improved resolution, field-of-view (FOV), signal-to-noise ratio (SNR), and depth of field. In this paper, LOSH is extended to the cases of two-dimensional (2D) mirror-like and 1D diffuse-based objects. For 2D mirror-like objects, the experime…
Theoretical electronic spectra of 2-aminopurine in vapor and in water
2006
The accurate quantum chemical CASSCF and CASPT2 methods combined with a Monte Carlo procedure to mimic solvation effects have been used in the calculation of the spectroscopic properties of two tautomers of 2-aminopurine (2AP). Absorption and emission spectra have been simulated both in vacuum and in aqueous environment. State and transition energies and properties have been obtained with high accuracy, leading to the assignment of the most important spectroscopic features. The lowest-lying 1 (,*) ( 1 La) state has been determined as responsible for the first band in the absorption spectrum and also for the strong fluorescence observed for the system in water. The combined approach used in …
Enthalpic and entropic contributions of water molecules to the functional T → R transition of human hemoglobin in solution
1992
Generalized solvent-mediated forces contribute to free energy at the functional T → R transition of human hemoglobin A (HbA). Their contribution is here sorted out quantitatively in both its enthalpic and entropic parts, along with the average number of water molecules involved. The latter (about 75 waters in average) must be considered together with HbA as one statistically defined functional unit for oxygen transport. Their configurations are expected to undergo frequent structural rearrangements. Lifetimes of statistically relevant configurations do not need to (although, of course, they may) exceed by more than a factor 5 the normal H-bond lifetimes of the pure solvent. Compared to the …
Sequestration of alkyltin(IV) cations by complexation with amino-polycarboxylic chelating agents
2013
Abstract The binding capacity of four amino-polycarboxylic ligands (APCs) [nitrilotriacetate (NTA), ethylenediamine- N , N , N′ , N′ -tetraacetate (EDTA), (S,S)-ethylenediamine- N , N ′-disuccinic acid (S,S-EDDS) and diethylenetriamine- N , N , N′ , N″ , N″ -pentaacetate (DTPA)] towards mono-, di- and tri-alkyltin(IV) cations [(CH 3 )Sn 3 + , (CH 3 ) 2 Sn 2 + , (C 2 H 5 ) 2 Sn 2 + , (CH 3 ) 3 Sn + or (C 2 H 5 ) 3 Sn + ] was studied, in aqueous solutions, by ISE-H + potentiometry, at I = 0.1 mol L − 1 (NaCl) and at T = 298.15 K. In all the systems R x Sn (4 − x)+ − APC (R = CH 3 or C 2 H 5 ) a strong 1:1 species is formed together with protonated, hydroxo and dinuclear complexes. The valu…
Gold based plasmonic stripes co-integrated with low loss Si3N4 platform in aqueous environment
2018
We demonstrate a butt-coupled interface between LPCVD Si 3 N 4 and gold based plasmonic waveguides in aqueous environment, exhibiting 2.3dB coupling loss and 75μm propagation length at 1550nm, towards future employment in biosensing applications.
Interaction of quinine with negatively charged lipid vesicles studied by fluorescence spectroscopy Influence of the pH
1997
Abstract The interaction of quinine with dimyristoylphosphatidic acid (DMPA) and dimyristoylphosphatidyl glycerol (DMPG) small unilamellar vesicles in the gel phase was studied by steady-state fluorescence spectroscopy at pHs 7, 6, 5 and 4 and 20°C. In aqueous solution, with excitation at 335 nm, the emission fluorescence spectrum of quinine varied with pH reflecting the occurrence of different charged species of the drug. In all cases, the emission maximum centered at 383 or 443 nm shifted to lower wavelength in the presence of vesicles. This indicates that the membrane-bound state quinine is in an environment of low polarity. Drug monocationic species were deeply buried in DMPG relative t…
Physical origin of Na+/Cl− selectivity of tight junctions between epithelial cells. Nonlocal electrostatic approach
2020
Abstract Tight junctions (TJs) of epithelial cells play a key role in regulation of the ion exchange between NaCl solutions separated by the layer of these cells. Their functioning is based on a strong difference in the permeabilities of these channels for Na+ and Cl− ion migrational fluxes owing to specific properties of the protein network inside TJs. It has been assumed in this study that this phenomenon originates from combination of two effects related to this specific TJ protein (claudin) which segments are partially located inside the TJ space. First, their ionogenic groups create a negative charge distributed inside TJs, thus inducing a difference between the Na+ and Cl− concentrati…
A simple model for barrier frequencies for enzymatic reactions.
2010
We present a simple model to rationalize the effects of environment on the reaction barrier frequencies derived from free energy profiles. These frequencies are relevant in deviations of a rate constant from its transition state theory value and in determining which environmental dynamics participate in the reaction. In particular, this simple model can be used to understand the changes in the reaction barrier frequencies of an enzymatic catalyzed reaction and the corresponding uncatalyzed process in aqueous solution, a change which has implications for dynamical environmental effects on the enzymatic reaction. Two possible cases are analyzed, in which the polarity (charge separation/locali…