Co-axial acoustic-based optical coherence vibrometry probe for the quantification of resonance frequency modes in ocular tissue.

We present a co-axial acoustic-based optical coherence vibrometry probe (CoA-OCV) for vibro-acoustic resonance quantification in biological tissues. Sample vibrations were stimulated via a loudspeaker, and pre-compensation was used to calibrate the acoustic spectrum. Sample vibrations were measured via phase-sensitive swept-source optical coherence tomography (OCT). Resonance frequencies of corneal phantoms were measured at varying intraocular pressures (IOP), and dependencies on Young´s Modulus (E), phantom thickness and IOP were observed. Cycling IOP revealed hysteresis. For E = 0.3 MPa, resonance frequencies increased with IOP at a rate of 3.9, 3.7 and 3.5 Hz/mmHg for varied thicknesses and 1.7, 2.5 and 2.8 Hz/mmHg for E = 0.16 MPa. Resonance frequencies increased with thickness at a rate of 0.25 Hz/µm for E = 0.3 MPa, and 0.40 Hz/µm for E = 0.16 MPa. E showed the most predominant impact in the shift of the resonance frequencies. Full width at half maximum (FWHM) of the resonance modes increased with increasing thickness and decreased with increasing E. Only thickness and E contributed to the variance of FWHM. In rabbit corneas, resonance frequencies of 360-460 Hz were observed. The results of the current study demonstrate the feasibility of CoA-OCV for use in future OCT-V studies.

Erythrocyte interactions - Comparison of the aggregation power of polymer molecules used in medicine - Not only size does matter.

BACKGROUND: Different colloids are used as a part of solutions for fluid resuscitation and organ preservation: hydroxyethyl starches (HES), dextran (Dx), polyethylene glycols (PEG), polyvinyl pyrrolidone (PVP). Some of the problems associated with their application are addressed to alteration in erythrocyte (ERY) rheology. OBJECTIVE: We intended to estimate in vitro and compare the aggregation power (AP) of these molecules related to ERY interactions. METHODS: Washed human ERY are used during the study. The zeta sedimentation technique is used to quantify the cell aggregation. Zeta sedimentation ratio (ZSR) based indices (AI) are calculated. The hydrodynamic radius (Rh) of the polymer molecules is determined using viscometry. RESULTS: For all polymers tested a linear range in the relationship AI - concentration was found. The slope of the calculated line was interpreted as measure of the molecule's AP. The following ranking was obtained: PEG >PVP >DX >HES. Within the same chemical type of polymer, increasing Rh of the molecules leads to elevated AI. Comparison of the AP of molecules with similar Rh reveals a significant dependence on their chemical nature. CONCLUSIONS: Our results show that molecule's AP is significantly dependent on their chemical nature - i.e. not only molecular size does matter.

Atmospheric pressure PECVD nanoparticles: mechanism of nanoparticle self-organisation into micron sized fractal clusters on a solid surface.

This paper covers the results from a study of the formation mechanism of fractal clusters from nanoparticles synthesised in atmospheric pressure radio frequency discharge. Two-dimensional structures with random configuration and self-similarity properties are formed by nanoparticles on a solid substrate surface. The typical linear dimensions of such structures are in the micron range. On the basis of the previously demonstrated experimental results, a physico-mathematical model of the nanoparticle self-organisation was developed. The physical model includes the electrical charge effect of the deposit surface, the spatial distribution of the surface electrical potential and the topography rearrangement phenomenon under the arising electrostatic forces. The threshold character of the agglomeration process initiation was found. The dependence of the formed structure topography on the character of the electrical potential change was demonstrated. The requisite conditions for the classical fractal formation were revealed. The results from the computational simulation, which was conducted with the use of fractal analysis, indicate a high level of coincidence with the experimental results.

Formation of fractal structures from silicon dioxide nanoparticles synthesized by RF atmospheric pressure plasma enhanced chemical vapor deposition.

Fractal structures were formed on silicon substrates from SiO2 nanoparticles homogeneously synthesized in low temperature atmospheric pressure plasma from tetraethoxysilane (TEOS). RF discharge (power absorbed was about 10 W) sustained between two parallel mesh electrodes was used to generate plasma. The average size of nanoparticles was in the range of 8-20 nm and was determined by process parameters. The obtained products were analyzed by SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy). Values of fractal dimension parameter of bidimensionals agglomerates formed on the substrate surface from nanoparticles were calculated with the use of Gwyddion and others. It was found that values of this parameter of the deposited structures varied in the range of 1.48-2 and were determined by combination of the process parameters. An empirical model explaining mechanism of the fractal structures formation and variation of the fractal dimension parameter with the process parameters was proposed.

A study of pyrolysis of polymethylsiloxanes by Fourier transform infrared.

This paper is dedicated to a comparative study of pyrolysis of decamethylcyclopentasiloxane and hexamethyldisiloxane, widely used as precursors for CVD of silicon dioxide films. The pyrolysis process was carried out in a hot-wall horizontal tube reactor made from quartz within the temperature range 25-1000 degrees C. FTIR spectroscopy has been used for the analysis of gaseous reaction products in the exhaust line of the reactor. It has been found that transformation of DMPSO was initiated by the open ring in the precursor molecules with its further transformation to linear biradicals followed by the chain's growth due to radical reactions. HMDSO transformation is connected with separation of silanon, silyl and methyl radicals with following multi-type interactions of siloxane radicals and formation of non-rigorously organized three-dimensional molecules.

Chemical vapor deposition of Ni-C films from bis-(ethylcyclopentadienyl) nickel.

Metal-organic chemical vapor deposition (MOCVD) is widely used for deposition of various nickel-containing coatings, such as catalytic nickel thin films and nanoparticles, nickel silicide alloys and magnetic carbon-nickel nanocomposite layers. Here we report preliminary results from an attempt to use bis-(ethylcyclopentadienyl) nickel [(EtCp)2Ni] as a precursor for MOCVD of Ni-C thin films in the (EtCp)2Ni-Ar and (EtCp)2Ni-H2-Ar reaction systems. Mechanism of precursor fragmentation was proposed on the basis of the results from a study of gaseous reaction products in the exhaust line of the reactor by means of mass-spectrometry. It was found that an introduction of hydrogen in the gas phase led to an increase in conversion rate of the precursor. Deposited films were analyzed by means of atomic force microscope (AFM), scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XFS). The effect of hydrogen on growth rate, composition, and morphology of the deposited Ni-C films were experimentally studied.

Chemical vapour deposition of nitrogen-doped titanium dioxide thin films.

Nitrogen-doped titanium dioxide is often considered as a promising nanomaterial for photocatalytic applications. Here we report the first results of a study of APCVD of N-doped TiO2 thin films prepared with the use of ammonia as a source of nitrogen and titanium tetraisopropoxide (TTIP) as a source of Ti and O atoms. The obtained films were analyzed with X-ray diffraction, infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, UV-Vis spectroscopy, and ellipsometry. It was found that the film growth rate in the TTIP-NH3-Ar reaction system varied insignificantly with substrate temperature in the range of 450,..., 750 degrees C and did not exceed 4.4 nm/min. Yellow and orange layers with nitrogen content of about 7.6% were formed at the deposition temperature higher than 600 degrees C. The results of the structure analysis of the deposited films showed that addition of ammonia led to stabilization of the amorphous phase in the films. The effect of ammonia on optical and photocatalytic properties was also considered.

Lisianthus Leaf Necrosis: A New Disease of Lisianthus Caused by Iris yellow spot virus.

Unusual viral symptoms were seen on lisianthus (Eustoma russellianum) grown in the Besor area in Israel. Symptoms included necrotic spots and rings on leaves and systemic necrosis. Preliminary analyses suggested that the disease was caused by a tospovirus. Virus particles typical of a tospovirus were observed with electron microscopy in samples taken only from symptomatic leaves. Double-antibody sandwich enzyme-linked immunosorbent assay tests of leaf sap, extracted from lisianthus and mechanically inoculated indicator plants, gave a strong positive reaction to Iris yellow spot virus (IYSV). Polyclonal antibodies prepared against IYSV enabled specific detection of the virus in crude sap from infected plants. Western blot analysis showed that IYSV was serologically distinct from Tomato spotted wilt virus (TSWV). Primers specific to the nucleocapsid gene of IYSV were used in a reverse transcription-polymerase chain reaction assay (RT-PCR) to verify the presence of IYSV. RT-PCR gave an expected PCR product of approximately 850 bp. The sequence of the cloned nucleocapsid gene confirmed the identity of IYSV, thus confirming IYSV infection of lisianthus. This is the first report of IYSV infection in dicotyledons.

[Fungal aspartic proteinase from Trichoderma viride. Specificity during oligopeptide hydrolysis]. / Gribnaia aspartatnaia proteinaza iz Trichoderma viride. Spetsifichnost' pri gidrolize oligopeptidov.

We isolated, purified, and characterized an aspartic protease from fungus Trichoderma viride. The pH-dependence of the enzyme functioning was determined, and its specificity in the limited proteolysis of insulin and melittin was compared to the specificities of pepsin A and gastricsin. The kinetics of melittin hydrolysis by these enzymes was studied by mass spectrometry.

Subcellular localization, substrate specificity and crystallization of duodenase, a potential activator of enteropeptidase.

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 alpha-N-tosylglycylprolyllysine 4-nitroanilide (k[cat]/Km of 35000 M[-1] s[-1]), alpha-N-succinylthreonylprolyllysine 4-nitroanilide (k[cat]/Km of 18000 M[-1] s[-1]) and alpha-N-serylprolyllysine 4-nitroanilide (k[cat]/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 microM; k[cat] of 1.4 s[-1]; k[cat]/Km of 16000 M[-1] s[-1]). Crystals of duodenase frozen in a stream of liquid nitrogen diffracted synchrotron X-rays to 0.2-nm resolution.

Accumulation of amino acids and glucose in isolated epitheliocytes from the small intestine of chickens depending on both breed and sex.

In an experiment with chickens breed differences were established in accumulation of 14C-lysine, methionine and glycine, as well as intra-line differences in glycine accumulation in intestinal epitheliocytes from Plymouth Rock chickens. Differences were found in both methionine and glycine accumulation, between B line and four-line hybrids as well. Methionine accumulation in epitheliocytes from the small intestine of male chickens was higher than in female chickens from A line, higher than accumulation of tryptophane in both A and C lines and accumulation of glucose in D line. In male chickens of four-line hybrid, glycine accumulation was higher than in females.

Effects of increased supply of essential amino acids on the metabolism of the isolated perfused guinea-pig mammary gland.

The effects of high rates of infusion of essential amino acids on amino acid uptake by the isolated perfused guinea-pig mammary gland were studied. Infusion of methionine, tyrosine, phenylalanine, histidine and tryptophan (designated group 1) resulted in significant increases in the uptakes of tyrosine, phenylalanine and histidine. Methionine, tryptophan and other essential amino acids were not significantly affected. Infusion of threonine, valine, isoleucine, leucine, lysine and arginine (designated group 2) resulted in significant increases in uptake of all these amino acids. Group 1 amino acid uptake was not significantly affected. Infusion of all the essential amino acids (i.e. groups 1 and 2 together) resulted in significant increases in all their uptakes. Using as index 'the predicted rate of protein synthesis', infusion of group 1 and 2 together led to an apparent 27% increase in protein synthesis. The above results are discussed in relation to the control of milk protein synthesis by limiting essential amino acids.

Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland.

When individual essential amino acids were omitted for periods of 40--100 min from the infusate substrate solution in isolated perfused guinea-pig mammary gland experiments, uptake of methionine, tyrosine, phenylalanine, histidine and tryptophan (group 1) was significantly depressed by a mean of 49.8%, whereas the remaining essential amino acids (group 2) showed no significant decrease in uptake. During depletion periods oxidation of [14C]amino acids was increased. The possible significance of the differences in absorption between the 2 groups of amino acids is discussed.