共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of Biomedical Engineering》1989,11(1):57-62
A reflectance fringe mode Laser Doppler microscope anemometer (LDMA) has been designed and tested. A novel beam splitter permits adjustment of the direction and separation of the two laser beams which form the fringe sensing volume, and furnishes the control needed to compensate for chromatic aberration and variation in optical quality. Tests conducted in a narrow 28:1 aspect rectangular flow channel filled with water showed close agreement between the predicted and measured velocity profiles. Velocity measurements, made alternately in the reflectance and transmittance modes using the same sensing volume in the channel, revealed deviations between the modes of less than 1.1% for water and 2.3% for whole blood. The deviation for the in vivo experiment was better than 2.8%. Velocity profiles were measured alternately in the same sensing volume, (dimensions were 10 × 12 μm) by reflectance and transmittance LDMA in 40 hamster cheek-pouch arterioles, ranging from 65 to 140 μm in diameter. These showed close agreement throughout the range of measured vessels. Reflectance LDMA makes non-invasive, high resolution velocity measurements in the range of 0.03 to 40 cm/s possible in small blood vessels near the surface of opaque organs and tissues. The accuracy and reproducibility of the readings were calculated to be better than 1.1%. Reflectance fringe mode LDMA greatly extends the applicability of LDMA because sites where transmittance LDMA can be applied are limited. 相似文献
2.
A digital image correlation (DIC) method was applied to characterize the mechanical behavior of Pseudomonas aeruginosa biofilms in response to wall shear stress using digital video micrographs taken from biofilm flow cells. The appearance of the biofilm in the transmitted light photomicrographs presented a natural texture which was highly conducive to random encoding for DIC. The displacement fields were calculated for two biofilm specimens. The DIC method concurred with previous analysis showing that biofilms exhibit viscoelastic behavior, but had the advantage over simple length measurements of longitudinal strain that it could precisely measure local strains in length (x) and width (y) within biofilm clusters with a 2 μm resolution as a function of time and wall shear stress. It was concluded that DIC was more accurate at measuring elastic moduli than simple length measurements, but that time-lapse 3D images would enable even more accurate estimates to be performed. 相似文献
3.
Sturgeon use benthic habitats in and adjacent to main channels where environmental conditions can include bedload sediment transport and high near‐bed flow velocities. Bed velocity measurements obtained with acoustic Doppler instruments provide a means to assess the concentration and velocity of sediment moving near the streambed, and are thus indicative of the bedload sediment transport rate, the near‐bed flow velocity, and the stability of the substrate. Acoustic assessments of benthic conditions in the Missouri River were conducted at scales ranging from the stream reach to individual bedforms. Reach‐scale results show that spatially‐averaged bed velocities in excess of 0.5 m s−1 frequently occur in the navigation channel. At the local scale, bed velocities are highest near bedform crests, and lowest in the troughs. Low‐velocity zones can persist in areas with extremely high mean bed velocities. Use of these low‐velocity zones may allow sturgeon to make use of portions of the channel where the average conditions near the bed are severe. To obtain bed velocity measurements of the highest possible quality, it is necessary to extract bottom‐track and GPS velocity information from the raw ADCP data files on a ping‐by‐ping basis. However, bed velocity measured from a point can also be estimated using a simplified method that is more easily implemented in the context of routine monitoring. The method requires only the transect distance and direction data displayed in standard ADCP data‐logging software. Bed velocity estimates obtained using this method are usually within 5–10% of estimates obtained from ping‐by‐ping processing. 相似文献
4.
《Biorheology》1996,33(6):463-470
We have applied our developed fiber-optic laser-Doppler anemometer microscope (FLDAM) for the study of the cerebral microcirculation in the rat. The red cell velocity in single pial microvessels was successfully measured through a closed cranial window for the vessel diameter range from 7.8 to 230 μm. The temporal resolution of the FLDAM was sufficiently high to detect the pulsation in the arterioles. Arterio-venous distributions of the temporal mean red cell velocity and wall shear rate are also described. 相似文献
5.
Shear‐induced diffusion of red blood cells measured with dynamic light scattering‐optical coherence tomography
下载免费PDF全文
![点击此处可从《Journal of biophotonics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jianbo Tang Sefik Evren Erdener Baoqiang Li Buyin Fu Sava Sakadzic Stefan A. Carp Jonghwan Lee David A. Boas 《Journal of biophotonics》2018,11(2)
Quantitative measurements of intravascular microscopic dynamics, such as absolute blood flow velocity, shear stress and the diffusion coefficient of red blood cells (RBCs), are fundamental in understanding the blood flow behavior within the microcirculation, and for understanding why diffuse correlation spectroscopy (DCS) measurements of blood flow are dominantly sensitive to the diffusive motion of RBCs. Dynamic light scattering‐optical coherence tomography (DLS‐OCT) takes the advantages of using DLS to measure particle flow and diffusion within an OCT resolution‐constrained three‐dimensional volume, enabling the simultaneous measurements of absolute RBC velocity and diffusion coefficient with high spatial resolution. In this work, we applied DLS‐OCT to measure both RBC velocity and the shear‐induced diffusion coefficient within penetrating venules of the somatosensory cortex of anesthetized mice. Blood flow laminar profile measurements indicate a blunted laminar flow profile and the degree of blunting decreases with increasing vessel diameter. The measured shear‐induced diffusion coefficient was proportional to the flow shear rate with a magnitude of ~0.1 to 0.5 × 10?6 mm2. These results provide important experimental support for the recent theoretical explanation for why DCS is dominantly sensitive to RBC diffusive motion. 相似文献
6.
An enzymatic assay of D -3-hydroxybutyrate in which the hydroxybutyrate dehydrogenase reaction is coupled to the bacterial oxidoreductase—uciferase system is described. The bioluminescent assay is based on either, end-point, or on initial velocity measurements. This simple and rapid assay requires a single serum sample of 10 μl. Its linear range covers two orders of magnitude from 10?6 mol/I upwards. This assay is suitable for the routine determination of D -3-hydroxybutyrate in human blood with good accuracy. 相似文献
7.
The individual doublet microtubule (DMT) from Tetrahymena cilia had the appearance of a circular arc in solution and its contour length was around 5 to 6 μm as observed under a dark-field microscope. One end of the circular arc was exactly in focus on the slide under the microscope, whereas the other end was slightly out of focus, suggesting that the circular arc may be regarded as a part of a coiled helix. On measuring the contour length and the end-to-end distance of the arc in solution, we found that the Ca-induced transformation of the ciliary DMT took place at a Ca concentration of about 10?6m in the medium; that is, the radius of the arc was 3.4 ± 0.9 μm at 10?3m-Ca and 1.5 ± 0.1 μm at less than 10?6m-Ca. Change in the pH of the medium brought about no significant difference in the radius of the arc of the DMT. The individual DMT of a negatively stained sample appeared to have a configuration similar to that of the circular arc in solution, bending at right angles to the partition wall between the A and B-tubules. Based on the criterion that the A-tubule is wider than the B-tubule, we found that the A-tubule occurred on the outer side of the circular arc in 90 to 100% of the samples. 相似文献
8.
A compact high‐speed full‐field optical coherence microscope has been developed for high‐resolution in vivo imaging of biological tissues. The interferometer, in the Linnik configuration, has a size of 11 × 11 × 5 cm3 and a weight of 210 g. Full‐field illumination with low‐coherence light is achieved with a high‐brightness broadband light‐emitting diode. High‐speed full‐field detection is achieved by using part of the image sensor of a high‐dynamic range CMOS camera. En face tomographic images are acquired at a rate of 50 Hz, with an integration time of 0.9 ms. The image spatial resolution is 0.9 μm × 1.2 μm (axial × transverse), over a field of view of 245 × 245 μm2. Images of human skin, revealing in‐depth cellular‐level structures, were obtained in vivo and in real‐time without the need for stabilization of the subject. The system can image larger fields, up to 1 × 1 mm2, but at a reduced depth. 相似文献
9.
In vivo study of rat cortical hemodynamics using a stereotaxic‐apparatus‐compatible photoacoustic microscope
下载免费PDF全文
![点击此处可从《Journal of biophotonics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Brain imaging is an important technique in cognitive neuroscience. In this article, we designed a stereotaxic‐apparatus‐compatible photoacoustic microscope for the studies of rat cortical hemodynamics. Compared with existing optical resolution photoacoustic microscopy (ORPAM) systems, the probe owns feature of fast, light and miniature. In this microscope, we integrated a miniaturized ultrasound transducer with a center frequency of 10 MHz to detect photoacoustic signals and a 2‐dimensional (2D) microelectromechanical system (MEMS) scanner to achieve raster scanning of the optical focus. Based on phantom evaluation, this imaging probe has a high lateral resolution of 3.8 μm and an effective imaging domain of 2 × 2 mm2. Different from conventional ORPAMs, combining with standard stereotaxic apparatus enables broad studies of rodent brains without any motion artifact. To show its capability, we successfully captured red blood cell flow in the capillary, monitored the vascular changes during bleeding and blood infusion and visualized cortical hemodynamics induced by middle cerebral artery occlusion. 相似文献
10.
《Journal of Biomedical Engineering》1984,6(2):134-140
Several non-invasive methods are in use for recording mechanocardiograms. In this paper a new laser technique will be presented to measure heart motion, chest wall displacement and other displacement curves of cardiovascular structures. Principles of the laser displacement technique are described. The measurement range within which displacement is sensed, is 32 mm with a detector to object distance of 25 cm and a resolution of 8 μm (digital output) or 16 μm (analogue output). The specific surface of which motion is sensed is 1 mm2. The sensitivity of the system is 156 mV/mm at a frequency bandwidth of 0–2 kHz. Assessment of the laser displacement technique was carried out during 6 dog experiments on the closed chest, on the exposed heart, on blood vessels and also on the chest wall of 5 normal subjects. Displacement of the chest wall at the apical site ranges between 0.3–0.8 mm and of the exposed heart between 3–10 mm. 相似文献
11.
Characterization of benthic microhabitat: An experimental system for aquatic insects 总被引:1,自引:1,他引:0
An experimental system used to determine microhabitat current velocity and microhabitat selection by aquatic insects is described. The experimental system includes a microvelocity probe and a hydraulically calibrated artificial substrate. A thermistor velocity probe detects flow velocities to 0.5 m s–1 near the surface of substrates at locations inhabited by aquatic insects. The artificial substrate was designed to provide two major habitat types, highly turbulent vortex areas and regions with unidirectional, near laminar flow. Substrate calibration and microhabitat characteristics of the substrates are demonstrated. Experimental studies of Simulium sp. location on substrates indicated that while simuliid larvae are characteristic of lotic, erosional habitats, actual microhabitats selected are governed by substantially lower flow velocity. 相似文献
12.
《Animal reproduction science》1997,49(1):37-43
Cryopreserved semen has been utilised in the artificial insemination of livestock species for over 40 years, even though the detrimental effects of cryopreservation on sperm function and fertility are well documented. In the present study, computer-automated sperm-head morphometry was used to determine if goat sperm-head morphometry was affected by freezing and thawing. A microscope slide was prepared from single semen samples, collected by artificial vagina, from 10 sexually active Saanen bucks. The remainder of each sample was frozen in a tris-citrate-yolk extender. After thawing, semen smears were prepared on microscope slides. All slides were stained in haematoxylin and mean sperm-head measurements of length, width, width/length, area and perimeter were determined for each slide by computer aided sperm morphometry analysis. The effects of sperm freezing on sperm-head dimensions within and among all bucks were determined. No significant (P > 0.10) freezing effect was found between fresh semen and postthaw samples for length (7.00 μm vs 7.13 μm), width (3.77 μm vs 3.87 μm), width/length (0.54 μm vs 0.54 μm), area (19.67 μm2 vs 20.57 μm2) and perimeter (18.62 μm vs 18.83 μm) when analysed across all bucks. Significant differences (P < 0.05) were however found within three bucks for area, perimeter, length and width, with the percentage increase in measurements being significantly greater than in the remaining bucks. The variability of the morphometric dimensions were not affected by freezing. The results indicate that semen freezing did not affect the overall dimensions of sperm heads across the entire population of bucks sampled. However, since sperm-head dimensions from three bucks were affected, changes in sperm-head morphometry may be indicative of spermatozoa of the semen from individuals to successfully freeze. Because the overall mean sperm-head dimensions acquired from frozen/thawed semen were not different from those of fresh semen, previously reported measurements of goat sperm heads are probably reflective of fresh semen. More importantly, retrospective studies of sperm-head morphometry and fertility may now be performed utilising extensive breeding records from frozen semen. 相似文献
13.
Parrin AP Netherton SE Bross LS McFadden CS Blackstone NW 《The Biological bulletin》2010,219(2):112-121
Cilia-based transport systems characterize sponges and placozoans. Cilia are employed in cnidarian gastrovascular systems as well, but typically function in concert with muscular contractions. Previous reports suggest that anthozoans may be an exception to this pattern, utilizing only cilia in their gastrovascular systems. With an inverted microscope and digital image analysis, we used stoloniferan octocoral colonies growing on microscope cover glass to quantitatively describe the movement of fluids in this system for the first time. Flow in stolons (diameter ≈300 μm) is simultaneously bidirectional, with average velocities of 100-200 μm/s in each direction. Velocities are maximal immediately adjacent to the stolon wall and decrease to a minimum in the center of the stolon. Flow velocity is unaffected by stolonal contractions, suggesting that muscular peristalsis is not a factor in propelling the flow. Stolon intersections (diameter ≈500 μm) occur below polyps and serve as traffic roundabouts with unidirectional, circular flow. Such cilia-driven transport may be the plesiomorphic state for the gastrovascular system of cnidarians. 相似文献
14.
Mohesh Moothanchery Kapil Dev Ghayathri Balasundaram Renzhe Bi Malini Olivo 《Journal of biophotonics》2020,13(2)
Photoacoustic microscopy (PAM) can be classified as optical resolution (OR)‐PAM and acoustic resolution (AR)‐PAM depending on the type of resolution achieved. Using microelectromechanical systems (MEMS) scanner, high‐speed OR‐PAM system was developed earlier. Depth of imaging limits the use of OR‐PAM technology for many preclinical and clinical imaging applications. Here, we demonstrate the use of a high‐speed MEMS scanner for AR‐PAM imaging. Lateral resolution of 84 μm and an axial resolution of 27 μm with ~2.7 mm imaging depth was achieved using a 50 MHz transducer‐based AR‐PAM system. Use of a higher frequency transducer at 75 MHz has further improved the resolution characteristics of the system with a reduction in imaging depth and a lateral resolution of 53 μm and an axial resolution of 18 μm with ~1.8 mm imaging depth was achieved. Using the two‐axis MEMS scanner a 2 × 2 .5 mm2 area was imaged in 3 seconds. The capability of achieving acoustic resolution images using the MEMS scanner makes it beneficial for the development of high‐speed miniaturized systems for deeper tissue imaging. 相似文献
15.
16.
Amino acid effector binding to rabbit muscle pyruvate kinase 总被引:1,自引:0,他引:1
l-Phenylalanine, an allosteric inhibitor of rabbit muscle pyruvate kinase, is shown to bind to the tetrameric enzyme in a ratio of 4 moles effector per mole of tetramer. This binding is slightly cooperative in the absence of divalent cation activators, but the cooperativity is strongly increased when measured in the presence of 2.5 mm Mg2+ or Mn2+. The effector affinity is somewhat decreased under these conditions. l-Alanine was known to antagonize all measured phenylalanine effects and is shown here to also bind to 4 sites on the protein. The binding is noncooperative and little affected by the presence of the divalent activating cations. Competition experiments with phenylalanine and alanine suggest competition for the same site. Substrate kinetic measurements at P-enolpyruvate and Mg2+ concentrations under 100 μm show considerable inhibition of the enzyme at phenylalanine concentrations around 100 μm, near the serum levels of the free amino acid. The approach to the phenylalanine-inhibited velocity occurs with half-times less than 1 sec. 相似文献
17.
D. Varentsov A. Bogdanov V.S. Demidov A.A. Golubev A. Kantsyrev P.M. Lang D.N. Nikolaev N. Markov F. Natale L. Shestov P. Simoniello G.N. Smirnov M. Durante 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2013,29(2):208-213
High-energy proton microscopy provides unique capabilities in penetrating radiography including the combination of high spatial resolution and field-of-view, dynamic range of density for measurements, and reconstructing density variations to less than 1% inside volumes and in situ environments. We have recently proposed to exploit this novel proton radiography technique for image-guided stereotactic particle radiosurgery. Results of a first test for imaging biological and tissue-equivalent targets with high-energy (800 MeV) proton microscopy are presented here. Although we used a proton microscope setup at ITEP (Moscow, Russia) optimized for fast dynamic experiments in material research, we could reach a spatial resolution of 150 μm with approximately 1010 protons per image. The potential of obtaining high-resolution online imaging of the target using a therapeutic proton beam in the GeV energy region suggests that high-energy proton microscopy may be used for image-guided proton radiosurgery. 相似文献
18.
Vasileios Diamantis Ioannis Papaspyrou Parasxos Melidis Alexander Aivasidis 《Bioprocess and biosystems engineering》2010,33(2):293-298
Aerated channel reactors with a uniform field of aeration may display flow stratification and short-circuit phenomena in wastewater
treatment systems. In this study, we present data suggesting that flow stratification is closely related to the aeration rate
and the arrangement of aerators. A full-scale oxidation ditch, with a total volume of 6,500 m3 and a membrane-diffused aerated zone of 60 × 7 × 5 m (length–width–depth), was selected for water velocity measurements.
Two profiles of the oxidation ditch were studied in detail: the first one was at the end of the aerated zone and the second
one at the end of the anoxic zone. The results of this work demonstrate that the horizontal water velocity at the end of the
aerated zone displayed significant stratification, with maximum velocity near the water surface (0.5–0.7 m/s) and almost zero
velocity at a depth of 2.5 m. At the end of the anoxic zone, water velocity was uniform and equal to 0.27–0.31 m/s. Increasing
the aeration rate from 1,800 to 4,300 m3/h, almost 90% of the water flow was found to discharge through the upper-half of the channel reactor profile. Different options
to mitigate flow stratification of the oxidation ditch are discussed in this paper. 相似文献
19.
A simple, accurate, and precise bioanalytical method was developed and validated for the determination of pharmacokinetic parameters of sodium copper chlorophyllin, a USFDA approved food additive and colorant in rat plasma. The column used was Luna® C18 250×4.6 mm, 100 Å, having particle size 4.5 μm, and the mobile phase used was methanol (MeOH), and 10 mM ammonium acetate buffer in the ratio of 90 : 10, the flow rate was 1 ml/min, and the injection volume of 20 μL. The retention time of sodium copper chlorophyllin was obtained at 9 min. The method was found to be linear at the range of 0.50–8.00 μg mL?1. 相似文献
20.
R E Daigle C W Miller M B Histand F D McLeod D E Hokanson 《Journal of applied physiology》1975,38(6):1153-1160
The measurement of blood velocity fields, volume flow, and arterial wall motion in the descending thoracic aorta provides essential hemodynamic information for both research and clinical diagnosis. The close proximity of the esophagus to the aorta in the dog makes it possible to obtain such data nonsurgically using an ultrasonic esophageal probe; however, the accuracy of such a probe is limited if the angle between the sound beam and the flow axis, known as the Doppler angle, is not precisely known. By use of a pulsed Doppler velocity meter (PUDVM) and a triangulation procedure, accurate empirical measurement of the Doppler angle has been obtained, allowing quantification of blood velocity scans across the aorta. Volume flow is obtained by integration of blood velocity profiles and arterial wall motion is measured with an ultrasonic echo tracking device. Accuracy of the probe was substantiated by comparison with ultrasonic and electromagnetic implanted flow cuff measurements. Use of the probe in measurement of blood velocity, volume flow and arterial wall motion at various locations along the 8- and 10-cm length of the descending thoracic aorta in adult beagle dogs is detailed. The simplicity, accuracy, and nontraumatic aspect of the technique should allow increasing use of such a probe in numerous research and clinical applications. 相似文献