Search

A novel approach for image formation in optical coherence tomography (OCT) and microscopy is presented. The depth resolution of OCT, including recently developed nanosensitive OCT (nsOCT), is limited by the spectral bandwidth of the light source used for illumination. The proposed approach, synthetic OCT (synOCT), permits label‐free, depth‐resolved quantitative visualization of the subwavelength‐sized structures with nanosensitivity. Using synOCT it is possible to estimate the contribution of axial Fourier components of an object's structure in image formation at each small volume within the image. The size of such areas can be smaller than the resolution limit of the imaging system that provides potential for super‐resolution imaging. Visualization of the subwavelength periodic structures and quantitative visualization of the subwavelength internal structures of highly scattering biological samples, within voxels smaller than resolution limit of the imaging system, are demonstrated. In contrast to nsOCT, the trade‐off between spectral and spatial resolution is removed which results in dramatic improvement of both spectral and spatial resolution in synOCT relative to nsOCT. [ABSTRACT FROM AUTHOR]

Corneal cross‐linking (CXL) using ultraviolet‐A (UVA) irradiation with a riboflavin photosensitizer has grown from an interesting concept to a practical clinical treatment for corneal ectatic diseases globally, such as keratoconus. To characterize the corneal structural changes, existing methods such as X‐ray microscopy, transmission electron microscopy, histology and optical coherence tomography (OCT) have been used. However, these methods have various drawbacks such as invasive detection, the impossibility for in vivo measurement, or limited resolution and sensitivity to structural alterations. Here, we report the application of oversampling nanosensitive OCT for probing the corneal structural alterations. The results indicate that the spatial period increases slightly after 30 minutes riboflavin instillation but decreases significantly after 30 minutes UVA irradiation following the Dresden protocol. The proposed noninvasive method can be implemented using existing OCT systems, without any additional components, for detecting nanoscale changes with the potential to assist diagnostic assessment during CXL treatment, and possibly to be a real‐time monitoring tool in clinics. [ABSTRACT FROM AUTHOR]

For both fundamental study of biological processes and early diagnosis of diseases, information about nanoscale changes in tissue and cell structure is crucial. Nowadays, almost all currently known nanoscopy methods rely upon the contrast created by fluorescent stains attached to the object or molecule of interest. This causes limitations due to the impact of the label on the object and its environment, as well as its applicability in vivo, particularly in humans. In this paper, a new label‐free approach to visualize small structure with nano‐sensitivity to structural alterations is introduced. Numerically synthesized profiles of the axial spatial frequencies are used to probe the structure within areas whose size can be beyond the diffraction resolution limit. Thereafter, nanoscale structural alterations within such areas can be visualized and objects, including biological ones, can be investigated with sub‐wavelength resolution, in vivo, in their natural environment. Some preliminary results, including numerical simulations and experiments, which demonstrate the nano‐sensitivity and super‐resolution ability of our approach, are presented. [ABSTRACT FROM AUTHOR]

The possibility of practical realization of a two-stage chemical vapor deposition (CVD) process using as an example of nanocomposite coating 'molybdenum disulfide (filler)-silicon oxide (matrix)' is experimentally demonstrated for the first time. Deposition is performed in a two-zone vertical tubular quartz reactor. The formation of molybdenum disulfide nanoparticles by spray pyrolysis is carried out in the upper zone, and the lower zone is used for deposition of nanocomposite coatings by atmospheric pressure plasma-enhanced CVD. An aerosol of the ammonium thiomolybdate solution in dimethylformamide is used for the synthesis of molybdenum disulfide particles, and silicon dioxide coatings are deposited from tetraethoxysilane. The structure and the composition of nanocomposite coating deposited are studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, and Fourier transform infrared spectroscopy (FTIR) spectroscopy. [ABSTRACT FROM AUTHOR]

This paper describes the results of experimental evaluation of titanium dioxide thin films formed by CVD as active layers in semiconductor, resistive sensors for detection of ethanol vapors. TiO2 layers with a thickness of 90 nm are formed by CVD in the TTIP-O2-O3-Ar reaction system. Sensors manufactured with titania films formed under all the deposition conditions studied exhibit good electrical response to the ethanol vapors, with quick response-recovery characteristics in the temperature range 170-300 °C. Sensor performance is determined by the relative amount of anatase phase and grain size in the films. The response value (Rair/Rethanol) of the sample with the highest degree of crystallinity reached 37 at an operating temperature of 200 °C. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) provides fabrication of high purity conformal layers of titanium dioxide with different structure for various applications. In this work CVD of titania layers from titanium tetraisopropoxide (TTIP) and oxygen at 1 kPa and in the substrate temperature range Ts = 300-500 °C was studied. It was found that growth of TiO2 is a non-stationary process. Two periods of time characterized by different deposition rates were observed. Formation of amorphous TiO2 occurs at the initial period of the deposition process whereas polycrystalline titania with anatase crystal structure is deposited at the second period. Substrate temperature determines degree of crystallinity, texture, and microstructure of the deposited titania layers. [ABSTRACT FROM AUTHOR]

The article covers the computational framework providing an insight on vapour phase coagulation of nanoparticles synthesized by atmospheric pressure PECVD in an RF capacitive discharge. The proposed model is based on the solution of motion equations for neutral and charged nanoparticles in the plasma downstream area featuring a nonuniform distribution of electric potential. Within the model particles collisions are accounted by an O'Rourke derived stochastic method, reduction of computational time is attained by division of the nanoparticle stack into parcels. We argue that nanoparticles are mainly synthesized in the plasma downstream area. Size distribution of the particles is governed by their uneven motion in the nonuniform electric field. We demonstrate that particles of tens of nanometer in diameter result from coagulation of neutral nanoparticles, whereas the larger nanoparticles result from coagulation of charged particles. The model shows that charged particles trapped in the potential well in the vicinity of the discharge electrode grow up to micron size. The proposed model is validated by the experimental results of silicon dioxide nanoparticles synthesis; it may be extended to a vast range of materials provided certain modifications of the particles motion equations are done. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Bioactive coatings on medical implants can be prepared from titanium dioxide due to its ability to induce the formation of hydroxylapatite (HA) from physiological solutions. In this study TiO2 layers were formed by chemical vapor deposition at different substrate temperatures in order to controllably change their structure from amorphous to consisting of preferentially oriented anatase crystallites. To evaluate the influence of phase composition and surface morphology of the deposited layers on their ability to form HA titania samples were immersed in Dulbecco's phosphate-buffered saline (DPBS). The obtained results showed that structure of TiO2 layers determines the structure of HA formed on their surface. Polycrystalline titania layers with random orientation of anatase crystallites are the most favorable for intensive nucleation and formation of continuous HA coatings in DPBS solution. The textured TiO2 layers with smooth surface enhanced formation of HA deposits which consisted of sparsely distributed large separate grains. On the basis of the experimental results it was proposed that formation of hydroxylapatite nuclei on the surface of titania layers occurs by a mechanism of epitaxial growth. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present an application of digital Fourier holography for selective imaging of scatterers with different sizes in turbid media such as biological tissues. A combination of Fourier holography and high-resolution digital recording, digital Fourier microscopy (DFM) permits crucial flexibility in applying filtering to highlight scatterers of interest in the tissue. The high-resolution digital hologram is a result of the collation of Fourier holographic frames to form a large-size composite hologram. It is expected that DFM has an improved signal-to-noise ratio as compared to conventional direct digital imaging, e.g., phase microscopy, as applied to imaging of small-size objects. The demonstration of the Fourier filtering capacity of DFM using a biological phantom represents the main focus of this article. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 14, 253–258, 2004; Published online inWiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20031 [ABSTRACT FROM AUTHOR]

Duodenase, a serine protease from bovine duodenum mucosa, was located in endoplasmic reticulum, the Golgi secretory granules of epithelial cells and ducts of Brunner's glands by the A-gold immunocytochemical method. Duodenase exhibits trypsin-like and chymotrypsin-like specificities with a preference for substrates having lysine at the P1 and proline at the P2 positions. The kinetic constants for the hydrolysis of 21 potential duodenase substrates are reported. The best substrates were found to be αN-tosyiglycylprolyllysine 4-nitroanilide (kcat/Km of 35 000 M-1 s-1), α-N-succinylthreonytprotyllysine 4nitroanilide (kcat/Km of 18 000 M-1 s-1) and α-N-serylprolyllysine 4-nitroanilide (kcat/Km of 2600 M-1 s-1), all of which contain the P1-P3 sequence of the enteropeptidase zymogen/activation site. On the basis of its catalytic properties and sites of localization, duodenase has been postulated to be an activator of the enteropeptidase precursor. A tetradecapeptide (LVTQEVSPKIVGGS) having the P9-P5'sequence of the cleavage site of zymogen activation of bovine proenteropeptidase was synthesized, and kinetic parameters of its hydrolysis by duodenase were determined (Km of 87 µM; kcat of 1.4 s-1; kcat/Km of 16 000 M-1 s-1). Crystals of duodenase frozen in a stream of liquid nitrogen diffracted synchrotron Xrays to 0.2-nm resolution. [ABSTRACT FROM AUTHOR]