Laser Doppler Velocimetry Method Research Articles

Mechanism of Anti-Salmonella Rabbit Immunoglobulin Adsorption on Polymer Particles.

The adsorption of anti-Salmonella rabbit immunoglobulin (IgaR) on negatively charged polymer particles leading to the formation of immunolatex was studied using various techniques comprising atomic force microscopy (AFM) and laser Doppler velocimetry (LDV). Initially, the basic physicochemical properties of IgaR molecules and the particles, inter alia their electrophoretic mobilities, the zeta potentials and hydrodynamic diameters, were determined under different ionic strengths and pHs. Applying AFM, single immunoglobulin molecules adsorbed on mica were also imaged, which allowed to determine their size. The adsorption of the IgaR molecules on the particles leading to changes in their electrophoretic mobility was monitored in situ using the LDV method. The obtained results were interpreted applying a general electrokinetic model which yielded quantitative information about the molecule coverage on the particles. The obtained immunolatex was thoroughly characterized with respect to its acid-base properties and its stability upon storage. Notably, the developed procedure demonstrated better efficiency compared to commercially applied methods, characterized by a higher immunoglobulin consumption.

Human Vimentin Layers on Solid Substrates: Adsorption Kinetics and Corona Formation Investigations.

Adsorption kinetics of human vimentin on negatively charged substrates (mica, silica, and polymer particles) was analyzed using atomic force microscopy (AFM), quartz microbalance (QCM), and the laser doppler velocimetry (LDV) method. AFM studies realized under diffusion conditions proved that the adsorbed protein layer mainly consisted of aggregates in the form of compact tetramers and hexamers of a size equal to 11–12 nm. These results were consistent with vimentin adsorption kinetics under flow conditions investigated by QCM. It was established that vimentin aggregates efficiently adsorbed on the negatively charged silica sensor at pH 3.5 and 7.4, forming compact layers with the coverage reaching 3.5 mg m–2. Additionally, the formation of the vimentin corona at polymer particles was examined using the LDV method and interpreted in terms of the electrokinetic model. This allowed us to determine the zeta potential of the corona as a function of pH and the electrokinetic charge of aggregates, which was equal to −0.7 e nm–2 at pH 7.4 in a 10 mM NaCl solution. The anomalous adsorption of aggregates exhibiting an average negative charge on the negatively charged substrates was interpreted as a result of a heterogeneous charge distribution. These investigations confirmed that it is feasible to deposit stable vimentin layers both at planar substrates and at carrier particles with well-controlled coverage and zeta potential. They can be used for investigations of vimentin interactions with various ligands including receptors of the innate immune system, immunoglobulins, bacterial virulence factors, and spike proteins of viruses.

The physicochemical properties of CTAB solutions in the presence of α-tocopherol

The electrolytic conductivity, electrophoretic mobility and zeta potential (LDV - laser Doppler velocimetry method) as well as the particles size distribution (DLS - dynamic light scattering method) were determined in the cetyltrimethylammonium bromide (CTAB) solutions (0.25–25.00mM) at different concentrations of α-tocopherol (0–11.6mM). The measurements were made at 25°C and 30°C. It was found that α-tocopherol (vitamin E) modifies the physicochemical properties of CTAB micellar solutions – the potential carrier of bioactive substances. The electrolytic conductivity of CTAB solutions was lowered by the addition of α-tocopherol. Particularly, the effect was observed in the concentration range 0.25–2.5mM, i.e. in the vicinity of CMC. The critical micelle concentration (CMC) of CTAB solutions determined from the conductivity data decreased with the increasing vitamin E content due to the mixed aggregates formation. At the same time the electrophoretic mobility and zeta potential increased as a result of higher degree of the mixed aggregates dissociation. This effect was observed for all surfactant concentrations at both temperatures. The hydrodynamic diameter of mixed CTAB/α-tocopherol particles increased from 7–8nm for the CTAB solutions to 50–60nm for those containing vitamin E. The information about the aggregates size and their electrokinetic properties can be useful in predicting the encapsulation of biomolecules in the surfactant micelles and their transport by different membranes.

Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser

We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO(2) laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

Power Augmentation of a HAWT by Mie-type Tip Vanes, considering Wind Tunnel Flow Visualisation, Blade-Aspect Ratios and Reynolds Number

Wind tunnel results are reported concerning the effects of blade aspect ratio and Reynolds number on the performance of a horizontal axis wind turbine (HAWT) with Mie-type1 tip attachments. The flow behaviour around the blade tips and the Mie-type tip vanes is presented. Detailed surface oil film visualization and velocity measurements around the blade tips, with and without Mie vanes, were obtained with the two-dimensional, Laser-Doppler Velocimetry method. Experiments were performed with rotors having blades with different aspect ratio and operating at different Reynolds numbers. The properties of the vortices generated by the Mie vanes and the blade tips were carefully studied. It was found that increased power augmentation by Mie vanes is achieved with blades having smaller aspect ratio and smaller Reynolds number.

The pattern of acropetal and basipetal cytoplasmic streaming velocities in Chara rhizoids and protonemata, and gravity effect on the pattern as measured by laser-Doppler-velocimetry.

The spatial pattern of acropetal and basipetal cytoplasmic streaming velocities has been studied by laser-Doppler-velocimetry (LDV) in the positively gravitropic (downward growing) rhizoids of Chara globularis Thuill. and for the first time in the negatively gravitropic (upward growing) protonemata. The LDV method proved to be precise and yielded reproducible results even when tiny differences in velocities were measured. In the apical parts of the streaming regions of both cell types, acropetal streaming was faster than basipetal streaming. Starting at the apical reversal point of streaming, the velocity increased basipetally with the distance from that point and became fairly constant close to the basal reversal point; subsequently, the velocity decreased slightly acropetally as the apical reversal point was again approached. There was no change in velocity at the basal reversal point. However, at the apical reversal point there was an abrupt decrease in velocity. The pattern of the ratio of acropetal to basipetal streaming velocity (VR) was a function of the relative distance of the site of measurement from the apical reversal point rather than a function of the absolute distance. Upon inversion of the rhizoids, the VR decreased on average by 3.8% (+/- 0.4%), indicating that the effect of gravity on the streaming velocity was merely physical and without a physiological amplification. Rhizoids that had developed on the slowly rotating horizontal axis of a clinostat, and had never experienced a constant gravity vector, were similar to normally grown rhizoids with respect to VR pattern. In protonemata, the VR pattern was not significantly different from that in rhizoids although the direction of growth was inverse. In rhizoids, oryzalin caused the polar organization of the cell to disappear and nullified the differences in streaming velocities, and cytochalasin D decreased the velocity of basipetal streaming slightly more than that of acropetal streaming. Cyclopiazonic acid, known as an inhibitor of the Ca2+-ATPase of the endoplasmic reticulum, also reduced the streaming velocities in rhizoids, but had slightly more effect on the acropetal stream. It is possible that the endogenous difference in streaming velocities in both rhizoids and protonemata is caused by differences in the cytoskeletal organization of the opposing streams and/or loading of inhibitors (like Ca2+) from the apical/subapical zone into the basipetally streaming endoplasm.

Mesure de vitesses acoustiques par anémométrie laser dans un tube de Rijke

We present some results of experimental investigations on thermoacoustic phenomemon, and more particularly on the Rijke's phenomenon. The goal is to give an experimental description of the instantaneous heat release between a hot grid and an acoustic wave leading to self excitation into a two open ended duct. As the unsteady thermal flux is directly related to the instantaneous velocity, measurements of the acoustic and mean velocities are made using the Laser Doppler Velocimetry method. This allows an evaluation of the unsteady heat released, and so of the amplitude of the thermoacoustic waves from theoretical models, which can then be compared to experimental results

APPLICATION OF LASER DOPPLER VELOCIMETRY TO LUNG TRANSPLANTATION

The relationship between healing of a bronchial anastomosis and regional blood flow was studied in adult mongrel dogs after allotransplantation of the left lung. Animals were divided into the following three groups according to the immunosuppressive regimen. Group A: no immunosuppressive treatment (n = 7); Group B: azathioprine (5 mg/kg/day) and prednisolone (2 mg/kg/day) (n = 4); Group C: cyclosporine (20 mg/kg/day) (n = 4). The mucosal blood flow was examined serially after transplantation with laser Doppler velocimetry (LDV) at the tracheal bifurcation of the recipient (1st LDV) and at the bifurcation of the upper lobe bronchus of the transplanted lung (2nd LDV). The LDV values were expressed as a ratio to the preoperative values at the same site. Healing of the bronchial anastomosis was also assessed macroscopically with a fiberoptic bronchoscope and microscopically. The 2nd LDV value of the animals in group A at 13 days after transplantation remained low (32.9 +/- 27.6%). The 2nd LDV value in group B, although not significantly different from group A, had recovered to the preoperative level by that time (93.7 +/- 23.4%). By contrast, the 2nd LDV value in group C remained significantly higher than that in group A (119.9 +/- 23.0%, P less than 0.05). The 1st and 2nd LDV values were reduced in animals having infection at the bronchial anastomosis, even those in groups B and C. Bronchial mucosal blood flow appeared to be affected by infection and rejection of the transplanted lung, and to correlate closely with the healing of the bronchial anastomosis. This LDV method is useful to evaluate bronchial mucosal blood flow in experimental, and possibly in clinical, fields.

Quantitative Assessment of Alcohol-Provoked Flushing

Objective measurements of temperature and blood flow changes by telethermometry and laser Doppler velocimetry (LDV), respectively, were performed continuously in normal subjects after they ingested 0.4 g/kg of ethanol in a volume of 300 mL. Cutaneous temperatures were interpreted by the change in malar thermal circulation index (delta MTCI) method. Both the delta MTCI method and LDV output correlated significantly with the presence of flushing. The delta MTCI method also correlated significantly with LDV output, indicating that the intensity of the flushing reaction can be assessed by both methods. The sensitivity, specificity, and predictive value of a positive result were greater with the LDV method. The time to maximum delta MTCI correlated quite closely with the time to maximum LDV output. The results indicate that both LDV and delta MTCI methods are valid, noninvasive assays for flushing reactions.

The Effects of Antipsoriatic Treatment on Cutaneous Blood Flow in Psoriasis Measured by 133Xe Washout Method and Laser Doppler Velocimetry

In 8 patients with psoriasis vulgaris, the cutaneous blood flow (CBF) was measured simultaneously in both involved and uninvolved psoriatic skin before (i.e., on the first day of hospitalization) and on the 3rd, 7th, 14th, and 28th days of treatment with tar. The 133Xe washout method was used after epicutaneous labeling and compared to the laser Doppler velocimetry (LDV) technique. Control experiments were performed in 10 normal individuals. Before treatment the mean CBF in involved psoriatic skin was 62.6 +/- 18.7 SD ml X (100 g X min)-1, which is significantly higher than CBF of uninvolved skin in psoriatic patients, 9.5 +/- 4.0 SD ml X (100 g X min)-1, (p less than 0.01) and is 13.6 times higher than CBF in the normal individuals (p less than 0.01). Fifty hours following onset of treatment (i.e., after only 2 applications of tar), mean CBF of the involved psoriatic skin had decreased significantly to 35.0 +/- 13.9 SD ml X (100 g X min)-1, (p less than 0.01), which was not statistically different from the CBF on the 7th day. During the following weeks, the CBF in involved psoriatic skin decreased at a more moderate rate than that observed during the first week and was 15.0 +/- 6.1 SD ml X (100 g X min)-1 on the 28th day. This value is not significantly different from the CBF of uninvolved skin in these patients. At the end of treatment, the CBF of the uninvolved skin had decreased significantly (p less than 0.05) in all the patients to values similar to those observed in the skin of normal individuals. A parallel decline was observed in a clinical psoriatic score index; however, it is not known whether the observed decrease in CBF was preceded or succeeded by the clinical improvement. A comparison of the 133Xe measurements and LDV measurements in the normal individuals by linear regression analysis yielded a correlation coefficient of -0.24 (N = 20, p greater than 0.05). In the skin of psoriatic patients the correlation coefficient was 0.01, (N = 47, p greater than 0.05) for unaffected skin, and 0.61 (N = 47, p less than 0.001) in the involved psoriatic skin sites. The LDV measurements did not reflect changes in the uninvolved skin in psoriatic patients during treatment and resulted in a remarkably high C.V. in the bilateral measurements of skin in normal individuals (43.8%) compared to the C.V. of 133Xe flow measurements (14.8%). It is concluded that while the LDV method gives a rough estimate of blood flow in cutaneous tissue with a high capillary perfusion rate, inaccurate measurements are made in skin areas with normal to twice the normal CBF range.