A laser Doppler module easily integrated into a commercial ophthalmic microscope is proposed. Such setup adds flow measurement capability to standard visual inspection of the fundus. The proposed instrument may provide important clinical information such as the detection of vessel occlusion provided by surgical treatments (i.e. photocoagulation). The measuring system is based on a self-mixing laser diode Doppler flowmeter (SM-DF). Reduced costs, easy implementation and small size represent the main features of SM-DF. Moreover, this technique offers the advantage to have the excitation and measurement beams spatially overlapped, thus both overcoming the alignment difficulty of traditional laser Doppler flowmeter and, well fitting with to limited optical aperture of the pupil. Thanks to an on-board DSP-microcontroller, the optoelectronic module directly estimates the blood flow; USB connection and an ad-hoc developed user-friendly software interface allow displaying the result on a personal computer. Preliminary test demonstrates the applicability of the proposed measuring system.

Laser Doppler flowmetry (LDF) is now commonly used in clinical research to monitor microvascular blood flow. However, the dependence of the LDF signal on the microvascular architecture is still unknown. That is why we propose a new laser Doppler flowmeter for depth dependent monitoring of skin microvascular perfusion. This new laser Doppler flowmeter combines for the first time, in a device, several wavelengths and different spaced detection optical fibres. The calibration of the new apparatus is herein presented together with in vivo validation. Two in vivo validation tests are performed. In the first test, signals collected in the ventral side of the forearm are analyzed; in the second test, signals collected in the ventral side of the forearm are compared with signals collected in the hand palm. There are good indicators that show that different wavelengths and fibre distances probe different skin perfusion layers. However, multiple scattering may affect the results, namely the ones obtained with the larger fibre distance. To clearly understand the wavelength effect in LDF measurements, other tests have to be performed.

The effect of CO2 laser irradiation on pulpal microcirculation was studied in cat canines. The enamel surfaces of 4 teeth were exposed with energy densities of 304-1440J/cm2, using either a handpiece or a microslad, with a focal spot of 0.21mm and 0.33mm respectively. Pulpal blood flow (PBF) before and following lasing was recorded through the intact tooth surface by a laser Doppler flowmeter. CO2 laser irradiation caused an increase in PBF, which was immediate and transient. The PBF increase was higher in a large pulp than in a small pulp, and it was inversely related to the focal spot size. These findings confirm that the dental pulp is thermally affected by CO2 lasing of the tooth surface, however, without extensive pulp coagulation. It is concluded that the effects of laser irradiation on the pulpal microcirculation may be studied in situ by means of the presented methodology.

Objective: The objective of this study was to use non-invasive laser Doppler flowmeter to measure changes in blood flow in peripheral vessels in the legs before and after stress induced by leg elevation stress test and investigate correlations with the ankle-brachial pressure index (ABI).Methods: Subjects included 28 patients over 20 years of age (mean, 73 years) who reported chiefly of leg symptoms such as intermittent claudication, numbness, chills, or cramps had been examined at the study institution, and agreed to participate in the study. The ABI of both legs was measured, and patients were divided into two groups: low ABI (ABI ?0.9) and normal ABI (ABI ?0.9). Blood flow in the big toe was measured using a box-type laser Doppler flowmeter before, during, and after leg-elevation stress. Amplitude of the recorded waveform and changes in blood flow were compared.Results: Average ABI was 1.09 ± 0.10 in the normal ABI group (33 legs) and 0.68 ± 0.17 in the low ABI group (21 legs). Amplitude before and during stress was significantly smaller in the low ABI group than in the normal ABI group (p <0.01), and there was a significant correlation with ABI before and during stresses (r = 0.4606, r = 0.5048, respectively; p <0.05). Change in blood flow during stress was significantly lower in the low ABI group than in the normal ABI group (p <0.05). There was a significant correlation between change in blood flow during stress and ABI in both groups (r = 0.5073; p <0.05). There was also a significant correlation between change in blood flow and change in amplitude in both groups (r = 0.5477; p <0.05). Conclusion: Results of this study show, that comparing amplitude and change in blood flow before and after leg extension and elevation stress, there was a correlation between change in blood flow and amplitude, and ABI during stress. A box-type laser Doppler flowmeter may provide a means of screening for peripheral arterial disease.   

Recently, anti-inflammatory and tissue protective effects of statins have been shown independent from its anti-hyperlipidemic effect. It has been shown that one of the statins, rosuvastatin, may reduce ischemia/reperfusion (I/R)-induced tissue injury in the brain, intestines, and heart. We planned an experimental study to evaluate the effect of rosuvastatin on I/R injury encountered after the detorsion of the testicular torsion. Rats were divided into three groups. In group 1, testis basal blood flow (basal value) was measured with LASER Doppler flowmeter (LDF). Testis was relocated into the scrotum without torsion. Two and 3?h after the basal measurement, testis was brought out from the same incision, and the second (second value) and third (third value) testicular blood flow measurements...

Insulin is a potent vasoactive hormone which induces vasodilatation at physiological concentrations. Aerobic exercise is known to improve insulin vasodilatory activity in humans and experimental animals. Since both insulin and physical training is known to activate KATP and KCa2+ channels and increase nitric oxide (NO) synthesis, we hypothesized that insulin and exercise might use a common mechanism in mediating their vascular effect. The present study was carried out to investigate the role of NO, KATP and KCa2+ channels in enhancement of insulin-induced cutaneous vasorelaxation by exercise in rats. Male Wistar rats were submitted to exercise training for 8weeks on a treadmill. Cutaneous microvascular response to insulin was recorded from soles skin using a laser Doppler flowmeter. System...

Calibration of transit-time and Doppler ultrasonic flowmeters under two-component flow conditions has been conducted on 400 mm (16-in.) pipe. Testing covered total flows of 0.19 to 1.89 m{sup 3}/s (3000 to 30,000 gpm) and void fractions up to 40%. Both flowmeter types of accurately measured total volumetric flow over a portion of their ranges. Pipe average void fraction, based on a three-beam gamma densitometer, was used to determine water component flow under stratified flow conditions, with similar results. 2 refs.

The ultrasonic flowmeter for liquids has been in use in industry for over 30 years. In general these meters are available in two basic types - the Doppler type, and the Transit-Time (or Time-of-flight) type. There has been considerable development and advancement of this technology through the 1980`s and 1990`s due to the use of microelectronics, microprocessors and advanced software techniques. This advancement has allowed the ultrasonic flowmeter to be far more available for general use - in fact to be used as a {open_quotes}flowmeter{close_quotes}, not just as an ultrasonic flowmeter. All this because these advancements have produced lower costs, greater versatility, higher accuracy, and easier installation and maintenance. Both the Doppler type and the Transit Time type have benefited by these advances in technology. However the basic difference between the two types remains. That is that the Doppler type is primarily for {open_quotes}dirty{close_quotes} liquids: the fluid must contain reflectors or {open_quotes}scatterers{close_quotes} in the form of bubbles or solid particles. The Transit Time is for {open_quotes}clean{close_quotes} liquids: fluids that contain no second phase, although modem instruments can tolerate a much higher percentage of second phase than just 5 years ago. The Transit Time continues to provide the highest accuracy, greatest versatility and widest range of application.

On of the most important tools in production logging and well testing is the downhole flowmeter. Unfortunately, existing tools are inaccurate outside of an idealized single phase flow, regime. Spinner tools are inaccurate at extremely high or low, flow rates and when the flow rate is variable. Radioactive tracer tools have similar inaccuracies and are extremely sensitive to the flow regime. Both tools completely fail in the presence of multiphase flow, whether gas/ oil, gas/water or fluid/solid. Downhole flowmetering is important for locating producing zones and thief zones and monitoring production and injection rates. The effects of stimulation can also be determined. This goal of this project is the investigation of accurate downhole flowmetering techniques for all single phase flow regimes and multiphase flows. The measurement method investigated in this report is the use of ultrasound. There are two ways to use ultrasound for fluid velocity measurement. The first method, examined in Chapter 2, is the contrapropagation, or transit-time, method which compares travel times with and against fluid flow. Chapter 3 details the second method which measures the Doppler frequency shift of a reflected sound wave in the moving fluid. Both of these technologies need to be incorporated in order to build a true multiphase flowmeter. Chapter 4 describes the proposed downhole multiphase flowmeter. It has many advantages besides the ones previously mentioned and is in full in that chapter.

Combination of laser Doppler flowmetry and pulse oximetry methods allows for the direct assessment of oxygen supply to tissues at the microcirculatory level, namely, in that part of the vascular network where the transcapillary exchange takes place that is responsible for saturating tissues with oxygen. The microcirculation system comprises arterial and venous microvascular parts that differ in blood flow velocities. Frequency separation of the photodetector signal components related to different velocity ranges makes possible to distinguish the hemodynamic processes in these two parts of the microvascular system. Moreover, numerous studies of collective oscillatory processes in hemodynamics reveal that cardio-oscillations are more pronounced in arterioles, whereas venous hemodynamics is mostly influenced by the breath rhythm. Taking account of the above phenomena allows developing a signal-filtration system for separate characterization of blood-oxygenation states in arterial and venous blood flows. Light absorbance in the skin depends on both light wavelength and blood-oxygenation level. Processing the signals obtained with a two-channel dual-wavelength (630 and 1115 nm) laser Doppler flowmeter provides information about blood oxygenation levels at the entrance and exit of the microvascular system and allows assessing the specific levels of oxygenation levels at the entrance and exit of the microvascular system and allows assessing the specific levels of oxygen consumption in tissues. In particular, this approach allows revealing pathogenic processes resulting from hyper- and hypo-oxygenation in tissues. For instance, rapidly growing malignant tumors are characterized by intensive metabolism, rapid formation of capillaries, and active transcapillary oxygen exchange that results in higher level of oxygen diffusion into tissue, while the level of oxygen is lowered in the microvascular veins.

The effects of thermal stimulation, applied to the hindpaw via a hot bath set to either 40°C (non-noxious) or 49°C (noxious), upon ovarian blood flow were examined in nonpregnant anesthetized rats. Ovarian blood flow was measured using a laser Doppler flowmeter. Blood pressure was markedly increased following 49°C stimulation. Ovarian blood flow, however, showed no obvious change during stimulation, although a small increase was observed after stimulation. Ovarian blood flow and blood pressure responses to 49°C stimulation were abolished after hindlimb somatic nerves proximal to the stimuli were cut. Heat stimulation (49°C) resulted in remarkable increases in both ovarian blood flow and blood pressure in rats in which the sympathetic nerves supplying the ovary were cut but the hindlimb somatic nerves remained intact. The efferent activity of the ovarian plexus nerve was increased during stimulation at 49°C. Stimulation at 40°C had no effect upon ovarian blood flow, blood pressure or ovarian plexus nerve activity. Electrical stimulation of the distal part of the severed ovarian plexus nerve resulted in a decrease in both the diameter of ovarian arterioles, observed using a digital video microscope, and ovarian blood flow.The present results demonstrate that noxious heat, but not non-noxious warm, stimulation of the hindpaw skin in anesthetized rats influences ovarian blood flow in a manner that is attributed to reflex responses in ovarian sympathetic nerve activity and blood pressure.   

Flow in no-sidewall fluidic gas flowmeter was investigated by LDV (laser Doppler velocity) measurement to visualize the flow. Flow vector and vorticity were calculated at 5 flow rates based on the ensemble-averaged mean velocities at 624 points in the gas meter, and the flow rate change of the flow pattern was investigated. The essential flow pattern of oscillatory flow was almost the same regardless of flow rate. Periodical vortex shedding was observed at Re{>=}285 in the wake behind the target, and no vortex development was observed at Re=171. The relationship between frequency dependency on flow rate and the flow rate change of the flow pattern was also investigated. The Strouhal number (St) was its maximum at approximately Re=300, and it was suggested that the vortex development in the wake behind the target causes increase of St in the low flow rate side. The change of St in the range between Re of 300 and 800 was successfully explained by velocity distribution variation in the nozzle. 10 refs., 15 figs., 1 tab.

Apelin is known to stimulate cholecystokinin (CCK) and inhibit insulin release, however the mechanisms on pancreatic secretion remain unclear. The present study aimed to determine the expression of apelin and apelin receptor in the pancreas by immunofluorescence studies and the effect of exogenous apelin on the secretion of pancreatic juice in anesthetized rats. Pancreatic-biliary juice (P-BJ) was collected from Wistar rats treated with apelin (10, 20 and 50 nmol/kg b.w., boluses given every 30 min intravenously or intraduodenaly). The same apelin doses were administered to rats subjected to intraduodenal tarazapide, capsaicin or vagotomy. Pancreatic blood flow was measured by a laser doppler flowmeter. Direct effects of apelin were tested on dispersed acinar cells. Apelin receptor was expressed on acinar cells, pancreatic duct and islets cells, whereas apelin in pancreatic acini, but not in the islets. Intravenous apelin decreased P-BJ volume, protein and trypsin outputs in a dose-dependent manner. In contrast, intraduodenal apelin stimulated P-BJ secretion. Pharmacological block of mucosal CCK(1) receptor by tarazepide, vagotomy and capsaicin pretreatment abolished the effects of intravenous and intraduodenal apelin on P-BJ volume, protein and tryspin outputs. Apelin decreased the pancreatic blood flow. Apelin at 10(-6) M increased the release of amylase from non-stimulated and CCK-8-stimulated acinar cells. In conclusion, apelin can affect the exocrine pancreas through a complex mechanism involving local blood flow regulation and is driven by vagal nerves. PMID:22460461

The involvement of nitric oxide (NO) in the lower lip vasodilatations mediated via parasympathetic and antidromic mechanisms was examined in ?-chloralose/urethane-anesthetized cats, with the two types of blood flow responses being recorded separately (by laser Doppler flowmeter) from the two sides of the lower lip. The central cut end of the lingual nerve (LN) or the peripheral cut end of the inferior alveolar nerve (IAN) was electrically stimulated to elicit parasympathetic or antidromic vasodilatation, respectively, in the lower lip. NG-nitro-L-arginine methyl ester (L-NAME), but not NG-nitro-D-arginine methyl ester (D-NAME) (each at 30 mg/kg), markedly reduced the increases in lip blood flow evoked by stimulation, the reduction being to a similar degree irrespective of whether LN or IAN was stimulated. Pretreatment with L-arginine did not prevent the L-NAME-induced attenuation of either type of vasodilatation. In conclusion, these results suggest that synthesized NO may have a common site of action in antidromic and parasympathetic vasodilator pathways to the cat lower lip.   

The aim of this study was to evaluate methodologic aspects of colonoscopic laser Doppler flowmetry. A Periflux PF1d flowmeter, set to 4 kHz/0.2 sec, with an endoscopic probe was used. In 20 patients, with a median age of 70 years and without colonic disease, flux was recorded at 10, 40, 30, 20 and again at 10 cm from the anal verge. A median of three repeated recordings were made at each level to calculate average flux and spatial variation. Median flux was 158 perfusion units, and the coefficient of variation of repeated recordings 0.14. There was no regional variation, and no increase in flux at 10 cm from the start until the end of the procedure. Pressure of the probe against the bowel wall and severe distention significantly reduced the flux. The interference of light from the endoscopic light source on the flux could not be predicted. It differed with different light sources, and also with the length of probe coming out of the colonoscope - that is, the distance from the light to the measurement point. To avoid the problem, the light source should be turned off while recording. 19 refs., 4 figs.

Ultrasonic flowmeters are one of the fastest-growing technologies within the general field of instruments for process monitoring, measurement and control. Today, acoustic/ultrasonic flowmeters utilize clamp-on and wetted transducers, single and multiple paths, paths on and off the diameter, passive and active principles, contrapropagating transmission, reflection (Doppler), tag correlation, vortex shedding, liquid level sensing of open channel flow or flow in partially-full conduits, and other interactions. Ultrasonic flowmeters are applicable to liquids, gases, and multiphase mixtures, but not without limits. However, no single technology, nor one type of interaction within a technology, can be best for all fluids, occasions and situations. Users who select a particular type of ultrasonic flowmeter over one based on a competing (nonultrasonic) technology often do so for one (or more) of the following reasons: ultrasonic equipment provides a useful measurement whether the fluid is single-phase or not single-phase; equipment is easy to use; flow regime can be laminar, transitional or turbulent; transducers are totally external (no penetration of the pressure boundary); transducers, if not clamp-on, are minimally invasive; no excess pressure drop; when certain conditions are met, accuracy can be better than 0.5%; fast (ms) response; reliable despite temperature extremes; reasonable purchase price, installation, operating and maintenance costs. Sometimes mass flowrate is obtainable. Energy flowrate might be achieved for natural gas and biogas in the near future. How did ultrasonic flowmeters advance in the past fifty years to support such claims? This paper tries to answer this question by looking at ultrasonic flowmeter inventions and publications since 1955, to see how four key problems were solved. PMID:16782156

Recently, the origins and pathways of cerebrovascular acetylcholine- and vasoactive intestinal polypeptide-containing nerves have been elucidated in detail in the rat: The sphenopalatine ganglion is the major source for postganglionic parasympathetic fibers to the vascular beds of the cerebral hemispheres. To clarify the functional role of the nerves on cerebral blood vessels in vivo, brain cortical microvascular blood flow was measured in rats during electrical stimulation of these particular postganglionic fibers. Animals were subjected to transection of the right nasociliary nerve 2 weeks before the flow measurements to eliminate activation of peptidergic sensory fibers. Relative change in microvascular blood flow was continuously recorded by a laser-Doppler flowmeter system under alpha-chloralose anesthesia. The postganglionic fibers were electrically stimulated just proximal to the ethmoidal foramen by a bipolar platinum electrode (5 V; 0.5 ms; 3, 10, 30, 60 Hz; as a continuous stimulation for 90 s). Stimulation at 10 Hz induced a marked increase of the cortical blood flow (CoBF) on the ipsilateral side, whereas no change was observed on the contralateral side. It reached a maximum mean value of 42.5% at 46 s, and then slightly declined during the remaining stimulation period. No significant changes were observed in the mean arterial blood pressure or blood gases during or after stimulation. Both atropine and scopolamine failed to alter this flow increase. Electrical stimulation of the postganglionic fibers at different frequencies revealed a maximal increase in the CoBF at 30 Hz in the control situation (47.2%), but at 10 Hz after scopolamine administration (51.6%).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2329125

An increase in cortical cerebral blood flow (CBF), independent of metabolic vasodilation, via the activation of cholinergic neurons originating in the nucleus basalis of Meynert (NBM) in the basal forebrain and projecting to the widespread cortices was recently demonstrated. In the present study, we aimed to clarify whether the increase in CBF following a stimulation of the NBM can improve delayed death of the cortical neurons following transient ischemia in rats. CBF was measured with a laser Doppler flowmeter, and the delayed neuronal death of the cerebral cortex produced by intermittent (every 5 s) occlusions of the unilateral common carotid artery for 60 min was measured histologically in the cortical hemisphere at 3 different coronal levels (6 ?m thickness). In control rats without occlusion there were 6,000–8,000 intact neurons and 9–19 damaged neurons in the cortical hemisphere at each coronal level. During the occlusions, CBF ipsilateral to the occluded artery decreased by 13–32% of the preocclusion level. Five days after the occlusions, the numbers of damaged neurons were increased to 75–181. Repetitive electrical stimulation was delivered to the NBM, ipsilateral to the occluded artery, starting 5 min before the occlusions and finishing around the end of them. The increase in CBF induced by NBM stimulation prevented the occlusion-induced decrease in CBF in all 3 of the cortices. The delayed death of the cortical neurons previously observed after the occlusions was scarcely observable in all the cortices when NBM was stimulated. The present results suggest that NBM-originating vasodilative activation can protect the ischemia-induced delayed death of cortical neurons by preventing a blood flow decrease in widespread cortices.   

Laurus novocanariensis is an endemic plant from the Madeira Island forest that derives a fatty oil, with a strong spicy odour, from its berries that has been used for centuries in traditional medicine to treat skin ailments. This work aimed to investigate the effect of the application of both the oil and its essential oil on normal skin, to assess their safety and potential benefits. Diffusion studies with Franz cells using human epidermal membranes were conducted. The steady-state fluxes of two model molecules through untreated skin were compared with those obtained after a 2-h pre-treatment with either the oil or the essential oil. Additionally, eleven volunteers participated in the in vivo study that was conducted on the forearm and involved daily application of the oil for 5 days. Measurements were performed every day in the treated site with bioengineering methods that measure erythema, irritation and loss of barrier function. Slightly higher steady-state fluxes were observed for both the lipophilic and the hydrophilic molecule when the epidermal membranes were pre-treated. Nevertheless, such differences had no statistical significance, which seems to confirm that neither the oil nor the essential oil impaired the epidermal barrier. Results collected with the Chromameter, the Laser Doppler Flowmeter and the visual scoring are in agreement with those established in the in vitro study. They indicate that the repeated application of the oil did not cause erythema, because the results observed in the first day of the study were maintained throughout the week. Application of the oil did not affect the skin barrier function, because the transepidermal water loss remained constant throughout the study. The stratum corneum hydration was slightly reduced on days 4 and 5. This work shows that both the oil and the essential oil were well tolerated by the skin and did not cause significant barrier impairment or irritation. PMID:22827296

A new method for estimating the measurement depth and volume in laser Doppler flowmetry (LDF) is presented. The method is based on Monte Carlo simulations of light propagation in tissue. The contribution from each individual Doppler shift is calculated and thereby multiple Doppler shifts are handled...

May 17, 1975 ... of the propagation path over the North Pole (i.e., there is little or no possi- ..... centroid and other calibration quantities, but also to measure and store ...... (laser ). APL doppler,. AMS secor raw APL doppler. ANNA 1 doppler .... function* S|ijj) is the inverse kernel derived by Molodensky, and the integrals are ...

We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO2 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.

Laser and Acoustic Doppler Techniques for the Measurement of Fluid Velocities .... tems,energy is transmitted to a moving scattercr (tracer) which then becomes a .... laser is abcut 10 cm @hich may be increased tc :O meters using an etalan) ...

Utilizing the large magnitudes of Doppler shifts obtainable from a CW gas laser, local velocity vectors are measured by using the visible light from the laser. This technique is applicable for the measurement of velocity of any moving surface.

The self-mixing interference effect in a laser-diode (LD)-pumped microchip solid-state polarization vector laser has been examined in the laser Doppler velocimetry (LDV) scheme. Distinct enhancement of the LDV signal in the laser output power spectrum, which corresponds to the self-mixing intensity modulation, has been observed as compared with a linearly polarized laser subjected to a common moving target.

We investigate sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of systems and an adiabatic ramping of the laser parameters allows to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25(3)microK and 47(5)microK in high-density samples of the two isotopes 39K and 41K, respectively. Our findings will find application to other atomic systems.

In recent advanced lasers, 2 micron solid-state lasers such as Tm:YAG and Ho:YAG lasers are very attractive for laser radar remote sensing technologies because of eye safety, realizations of all solid-state laser pumped by diode laser and smaller dimension, tunability of lasing wavelength, possibility of coherent detection, etc. Featuring these advantages, 2 micron lasers have been candidated as laser transmitters for use in water vapor Differential Absorption Lidar (DIAL), laser altimeter, Doppler wind sensor, Mie lidar, etc. Characterization of a tunable Cr, Tm, Ho:YAG laser and its applications to spectroscopy concerning absorption and reflectance are reported.

A brief description is given of the different methods for the measurement of wind velocities. One of these methods, the ultrasonic method, was selected to measure wind velocity for purposes of wind turbulence studies. Other methods examined are the mechanical methods, cup and propellor, the hot wire method and the SODAR (SOund Detection And Ranging) Doppler and laser doppler methods. 8 refs.

The first experimental observations of sub-Doppler linewidths in a cell made using tunable far-infrared radiation are reported. A double-resonance scheme has been used, combining CO2-laser infrared radiation with tunable far-infrared radiation to observe a sub-Doppler line shape in an excited vibrational state of CH3OH.

A high-penetration swept-source optical coherence tomography (HP-SS-OCT) system based on a 1-?m short cavity laser is developed. Doppler OCT processing is applied, along with a custom-made numerical phase stabilization algorithm; this process does not require additional calibration hardware. Thus, our phase stabilization method is simple and can be employed in a variety of SS-OCT systems. The bidirectional blood flow and vasculature in the deep choroid was successfully imaged via two Doppler modes that use different time intervals for Doppler processing. En face projection image of squared power of Doppler shift is compared to ICGA, and the utility of our method is verified. PMID:22330511

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume B 'Linear Polyatomic Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

Barnes, N. P.; Walsh, B. M.; and Reichle, D. J., Jr." Solid State Laser Ultraviolet. Source. Presented ..... Errors in Doppler. Global ..... Magnetostrictive. Actuator Using ...... Ismail, S.; Browell, E. V.; and Fen'are, R. A.: LASE Measurements of Water ...

This document is part of Part 2 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

... of the scanner portion of the laser Doppler system for detecting and monitoring aircraft trailing ... The scanner system is capable of being scanned in elevation and range, ... When this operating mode is selected, the conditions above persist ...

This document is part of Part 3 of Subvolume D `Asymmetric Top Molecules' of Volume 29 `Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II `Molecules and Radicals'.

This document is part of Part 2 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Part 2 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Part 2 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Part 3 of Subvolume D `Asymmetric Top Molecules' of Volume 29 `Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II `Molecules and Radicals'.

Laser Doppler flowmetry is a method for continuous quantification of microvascular perfusion. During the measurements, low energy helium-neon laser light is applied to the tissue. Doppler shifted light reflected out of the tissue is then analyzed, and the shift of frequency quantitated. The output signal is proportional to the flux of blood cells in the measuring tissue of some few mm{sup 3}. Laser Doppler flowmetry can easily be applied for measurements on skin and surgically exposed surfaces. Measurements can also be obtained through an endoscope. Measuring probes of diameter 0.5 mm can be introduced into tissues to quantitate microvascular perfusion within tissues. The article reviews the theory of laser Doppler flowmetry measurements, presents methodological aspects, and gives examples of clinical application. 20 refs., 4 figs.

This document is part of Subvolume C 'Symmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume C 'Symmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Part 2 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume C 'Symmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Part 1 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Part 1 of Subvolume D 'Asymmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

This document is part of Subvolume C 'Symmetric Top Molecules' of Volume 29 'Molecular Constants Mostly from Microwave, Molecular Beam, and Sub-Doppler Laser Spectroscopy' of Landolt-Börnstein - Group II 'Molecules and Radicals'.

Introduction.? Erectile dysfunction is a common side effect following radical prostatectomy mainly due to damage of the pelvic autonomic nerve fibers (cavernous nerves). Intraoperative electrical stimulation of the cavernous nerves while measuring changes in penile girth has previously been shown to provide the surgeon with feedback of nerve integrity. Aim.? To test the feasibility of recording changes in glans penis blood flow by Laser Doppler flowmetry from cavernous nerve stimulation. Methods.? Fifteen patients with localized prostate cancer undergoing radical prostatectomy had electrical stimulation of the proximal and distal parts of the neurovascular bundles after prostate removal. The stimulation consisted of 30-40?seconds biphasic constant current (10-30?mA) with 0.5?millisecond pulse duration. Main Outcome Measures.? Stimulus induced changes in penile blood flow was recorded from a Laser Doppler probe attached to the glans penis. Changes in penile girth were simultaneously recorded from a mercury-in rubber strain gauge. Erectile function was evaluated three months after surgery. Results.? Ten patients had stimulus induced increase in Laser Doppler flow unilaterally (N?=?7) or bilaterally (N?=?3). Out of 10 patients, 6 reported some preserved erectile function postoperatively at 3?months follow-up (indicating 6 true and 4 false positives). Three patients had no Doppler response from stimulation and had no postoperative erectile function postoperatively (indicating three true negatives). Two patients were excluded from the study due to bad signal quality in the Laser Doppler signal. In the majority of patients, stimulation produced increase in penile girth sensed by the strain gauge. Conclusion.? This preliminary report provides evidence that Laser Doppler Flowmetry is able to detect increased penile blood flow from intraoperative electrical stimulation of the neurovascular bundles. However, further improvement in the recording technique is required. Laser Doppler Flowmetry may also be feasible to confirm autonomic nerve sparing in women undergoing pelvic surgery. Axelson HW, Johansson E, and Bill-Axelson A. Intraoperative cavernous nerve stimulation and Laser-Doppler flowmetry during radical prostatectomy. J Sex Med **;**:**-** PMID:22909402

A system for analyzing the fill characteristics of a container. A container having a filling material therein is positioned adjacent a sound generator. Sound waves from the generator are applied to the container, causing it to vibrate. A vibration detector is used to determine the amount of container vibration. A preferred vibration detector involves a laser vibrometer which applies a reference laser beam to the vibrating container. The reference beam is reflected off of the container to generate a reflected laser beam. The reflected beam experiences a Doppler frequency shift compared with the reference beam which is caused by container vibration. The Doppler shift of the reflected beam is then compared with standardized Doppler shift data from a control container. Repeated Doppler shift measurements may also be undertaken which are converted into a vibration profile that is compared with a standardized vibration profile from a control container.

Optical methods have been widely used in basic neuroscience research to study the cerebral blood flow dynamics in order to overcome the low spatial resolution associated with magnetic resonance imaging and positron emission tomography. Although laser Doppler imaging and laser speckle imaging can map out en face cortical hemodynamics and columns, depth resolution is not available. Two-photon microscopy has been used for mapping cortical activity. However, flow measurement requires fluorescent dye injection, which can be problematic. The noninvasive and high resolution tomographic capabilities of optical coherence tomography make it a promising technique for mapping depth resolved cortical blood flow. Here, we present a functional Doppler optical coherence tomography (OCT) imaging modality for quantitative evaluation of cortical blood flow in a mouse model. Fast, repeated, Doppler OCT scans across a vessel of interest were performed to record flow dynamic information with a high temporal resolution of the cardiac cycles. Spectral Doppler analysis of continuous Doppler images demonstrates how the velocity components and longitudinally projected flow-volume-rate change over time, thereby providing complementary temporal flow information to the spatially distributed flow information of Doppler OCT. The proposed functional Doppler OCT imaging modality can be used to diagnose vessel stenosis/blockage or monitor blood flow changes due to pharmacological agents/neuronal activities. Non-invasive in-vivo mice experiments were performed to verify the capabilities of function Doppler OCT.

Doppler particle sizing by self-mixing laser was demonstrated by using a laser-diode-pumped thin-slice Nd:GdVO4 laser with extreme optical sensitivity. A substantial improvement of optical frequency shifters led to quick and accurate sizing of Brownian particles with concentration as low as 50 parts per billion (ppb) for 262-nm polystyren latex spheres in water. A successful real-time measurement of sub-nanometer vibrations was also demonstrated with the present self-mixing laser.   

This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Environments; Determining {lambda}{sub o}; resonant refraction effects; fringe shift interpretation; shot-to-shot consistency; laser ablation in vacuum and low pressure, inert, background gas; theoretically modeling plume expansion in vacuum and low pressure, inert, background gas; and laser ablation in higher pressure, inert, background gas.

A type of spectroscopy using the Zeeman shift has been developed by using a dispersive-like signal obtained from the subtraction of two different circularly polarized Doppler-free saturated absorption signals in the presence of a small magnetic field along the propagation direction of the probe laser. The signal is very useful for stabilizing the frequency of a diode laser.

Dual-comb spectroscopy is extended to the visible spectral range with a set-up based on two frequency-doubled femtosecond ytterbium-doped fiber lasers. The dense rovibronic spectrum of iodine around 19240 cm-1 is recorded within 12 ms at Doppler-limited resolution with a simple scheme that only uses free-running femtosecond lasers.

An important aspect of any process control system that requires fluid flow measurement is properly selecting and applying the flow sensor or flowmeter. A bewildering array of terms, factors and concepts that must be considered to ensure optimum design can make this a complex and sometimes confusing process. To select a proper meter for a specific application, a complete understanding of the process operating conditions and equipment performance requirements is necessary. Once these parameters are specified, actual flowmeter selection is greatly simplified. Selection parameters include accuracy, rangeability, and additional characteristics. Commonly used flowmeters include differential pressure devices, variable area meters, vortex shedding flowmeters, displacement meters, magnetic flowmeters, coriolis mass meters, thermal flowmeters, and ultrasonic flowmeters.

In this paper we will describe the ground based Doppler lidar system which is mounted in a modified delivery van to allow field deployment and operations. The system includes an aerosol double edge receiver optimized for aerosol backscatter Doppler measurements at 1064 nm and a molecular double edge receiver which operates at 355 nm. The lidar system will be described including details of the injection seeded diode pumped laser transmitter and the piezoelectrically tunable high spectral resolution Fabry Perot etalon which is used to measure the Doppler shift. Examples of tropospheric wind profiles obtained with the system will also be presented to demonstrate its capabilities.

The standard Doppler-free technique of collinear laser spectroscopy has been successfully applied to radioisotopes from the ion-guide isotope separator (IGISOL) at the University of Jyvaeskylae. The laser resonance fluorescence signals for the {sup 140,142,144}Ba radioisotopes show that the ion beam energy spread is less than 6 eV, allowing the laser technique to have both high resolution and a sensitivity comparable with the best obtained at conventional facilities. (orig.). 8 refs.

A laser Doppler Velocimetry (LDV) technique has been developed to simultaneously measure the gas and particulate phase velocities in a high-speed jet plume in a 2D bubbling fluidized bed. The laser, optics, and signal processing filters were configured to eliminate problematic laser-beam intensity fluctuations, which can contaminate Doppler signals in optically dense flows. In order to avoid damaging the optical access windows, the high-speed gas jet was seeded with small ice crystals. LDV bursts from the bed particles and gas tracer ice crystals were simultaneously recorded. The Doppler signals from the tracer crystals and bed particles were differentiated based on their burst intensity and coincidence to yield the particulate and gas phase velocities at a given location within the jet pl...

Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit population-wide sub-Doppler cooling due to their near degeneracy of excited and ground state Lande g factors. We discuss here an additional, unusual intra-MOT sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser intensity and magnetic quadrupole gradient increase beyond critical values. Specifically, anisotropically sub-Doppler-cooled cores appear, and their orientation with respect to the quadrupole axis flips at a critical ratio of the MOT laser intensity along the quadrupole axis versus that in the plane of symmetry. This phenomenon can be traced to a loss of the velocity-selective resonance at zero velocity in the cooling force along directions in which the atomic polarization is oriented by the quadrupole field. We present data characterizing this anisotropic laser cooling phenomenon and discuss a qualitative model for its origin based on the extraordinarily large Dy magnetic moment and Dy's near degen...

Avoiding laser frequency drifts is a key issue in many atomic physics experiments. Several techniques have been developed to lock the laser frequency using sub-Doppler dispersive atomic lineshapes as error signals in a feedback loop. We propose here a two-beam technique that uses nonlinear properties of an atomic vapor around sharp resonances to produce sub-Doppler dispersivelike lineshapes that can be used as error signals. Our simple and robust technique has the advantage of not needing either modulation or magnetic fields. PMID:22858948

The Goldstone Solar System Radar (GSSR) has collected a self-consistent set of delay-Doppler near-nadir radar echo data from Mars since 1988. Prior to the Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) global topography for Mars, these radar data provided local elevation information, along with radar scattering information with global coverage. Two kinds of GSSR Mars delay-Doppler data exist: low 5 km x 150 km resolution and, more recently, high (5 to 10 km) spatial resolution. Radar data, and non-imaging delay-Doppler data in particular, requires significant data processing to extract elevation, reflectivity and roughness of the reflecting surface. Interpretation of these parameters, while limited by the complexities of electromagnetic scattering, provide information directly relevant to geophysical and geomorphic analyses of Mars. In this presentation we want to demonstrate how to compare GSSR delay-Doppler data to other Mars datasets, including some idiosyncracies of the radar data. Additional information is included in the original extended abstract.

Using a low power, rapid (nsec) pulse-modulated quantum cascade (QC) laser, collective coherent effects in the 5 ?m spectrum of nitric oxide have been demonstrated by the observation of sub-Doppler hyperfine splitting and also Autler-Townes splitting of Doppler broadened lines. For nitrous oxide, experiments and model calculations have demonstrated that two main effects occur with pulse-modulated (chirped) quantum cascade lasers: free induction decay signals, and signals induced by rapid passage during the laser chirp. In the open shell molecule, NO, in which both ?-doubling splitting and hyperfine structure occur, laser field-induced coupling between the hyperfine levels of the two ?-doublet components can induce a large ac Stark effect. This may be observed as sub-Doppler structure, field-induced splittings, or Autler-Townes splitting of a Doppler broadened line. These represent an extension of the types of behaviour observed in the closed shell molecule nitrous oxide, using the same apparatus, when probed with an 8 ?m QC laser. PMID:22583242

Skin blood flow responses in the human forearm, assessed by three commonly used technologies-single-point laser-Doppler flowmetry, integrated laser-Doppler flowmetry, and laser-Doppler imaging-were compared in eight subjects during normothermic baseline, acute skin-surface cooling, and whole body heat stress (? internal temperature=1.0±0.2 degrees C; Pstressed, subjects were exposed to 30-mmHg lower-body negative pressure (LBNP). Skin blood flow was normalized to the maximum value obtained at each site during local heating to 42 degrees C for at least 30 min. Furthermore, comparisons of forearm blood flow (FBF) measures obtained using venous occlusion plethysmography and Doppler ultrasound were made during the aforementioned perturbations. Relative to normothermic baseline, skin blood flow decreased during normothermia+LBNP (Pskin-surface cooling (Pskin blood flow relative to control heat stress (Pskin blood flow was similar between the three measurement devices (main effect of device: P>0.05 for all conditions). Similarly, no differences were identified across all perturbations between FBF measures using plethysmography and Doppler ultrasound (P>0.05 for all perturbations). These data indicate that when normalized to maximum, assessment of skin blood flow in response to vasoconstrictor and dilator perturbations are similar regardless of methodology. Likewise, FBF responses to these perturbations are similar between two commonly used methodologies of limb blood flow assessment. PMID:20634360

Purpose There is a long-standing interest in the study of retinal blood flow in humans. In the recent years techniques have been established to measure retinal perfusion based on optical coherence tomography (OCT). In the present study we used a technique called dual-beam bidirectional Doppler Fourier-domain optical coherence tomography (FD-OCT) to characterize the effects of 100% oxygen breathing on retinal blood flow. These data were compared to data obtained with a laser Doppler velocimeter (LDV). Methods 10 healthy subjects were studied on 2 study days. On one study day the effect of 100% oxygen breathing on retinal blood velocities was studied using dual-beam bidirectional Doppler FD-OCT. On the second study day the effect of 100% oxygen breathing on retinal blood velocities was assessed by laser Doppler velocimetry (LDV). Retinal vessel diameters were measured on both study days using a commercially available Dynamic Vessel Analyzer. Retinal blood flow was calculated based on retinal vessel diameters and red blood cell velocity. Results As expected, breathing of pure oxygen induced a pronounced reduction in retinal vessel diameters, retinal blood velocities and retinal blood flow on both study days (p<0.001). Blood velocity data correlated well between the two methods applied under both baseline as well as under hyperoxic conditions (r?=?0.98 and r?=?0.75, respectively). Data as obtained with OCT were, however, slightly higher. Conclusion A good correlation was found between red blood cell velocity as measured with dual-beam bidirectional Doppler FD-OCT and red blood cell velocity assessed by the laser Doppler method. Dual-beam bidirectional Doppler FD-OCT is a promising approach for studying retinal blood velocities in vivo. PMID:19797199

Magnesium atoms are cooled in a magneto-optical trap(MOT) using the 3s{sup 21}S{sub 0} {yields} 3s3p{sup 1}P{sub 1} resonance transition. Magnesium is a simple atom which offers a unique possibility for comparison to the Doppler theory of laser cooling. We measure trap parameters as a function of laser-intensity, -detuning and magnetic field gradient. We find the main features well accounted for by Doppler theory, but temperature measurements gave significant higher values than predicted by the Doppler theory. We also observe radiation pressure effects within the MOT that limit the maximum achievable density. Comparing our results to predictions by models in the literature shows a good agreement. Recently we have improved our set-up and now trap about 150 x 10{sup 6} atoms.

Because flow is one of the most common process variables measured, numerous types of flowmeters based on a variety of measurement principles are available. Although these numerous flowmeter types allow one to measure almost any flow, the wide variety also makes selecting an appropriate flowmeter a complex and potentially difficult task. This paper reviews the definition and importance of basic hydraulic principles and the design parameters critical to an accurate flow measurement, the principles used in flow monitoring and their advantages and disadvantages, and a method for selecting an appropriate flowmeter. 6 refs.

A new development in the field of ultrasonic liquid flowmeasurements has been achieved with the multichannel liquid ultrasonic flowmeter; the first for use in maintenance-free custody transfer applications. Although ultrasonic flowmeters are used for applications in the oil industry for many years, this new development will have a big impact on custody transfer flow measurement. Not only because of the compactness, but also because of the low investment and operating cost of this flowmeter. This paper describes the system and the method of operation as well as practical experiences and achieved test results of this flowmeter. (author)

The new hydrocyclone system has been completed and is in operation. The design of this system was described in the second quarterly report. The system has performed even beyond our expectations. Parameters that can be varied on this system include flow rate, inlet area, hydrocyclone chamber length, vortex finder diameter and length, underflow diameter and cone angle (from 20/sup 0/ to 120/sup 0/ in 20/sup 0/ increments). This hydrocyclone is much more flexible than the original system; however, both systems are being utilized in this research. Modifications and improvements to the new system that have already been incorporated include the purchase and installation of a doppler flowmeter with digital display. This meter is especially nice in that the sensors are clamped to the outside of the pipe and consequently, do not disturb the flow. The system with digital readout was purchased for $2600. The system has also been modified so that the hydrocyclone now effectively discharges to the atmosphere. Data using the spheres in the new system has been taken to further investigate the effect of cone angle. Studies presently underway address the affects of variable hydrocyclone length (cylindrical portion) on the efficiency of the system.

The interactions between ultrahigh intense laser and overdense plasmas were investigated by the use of a 1-1/2 dimensional electromagnetic relativistic particle-in-cell code, EMPAC. When the effective electron plasma frequency is reduced below the laser frequency by increasing the inertial electron mass due to the relativistic effect, the ultrahigh intense short pulse laser can penetrate the overdense plasma, but is completely reflected after propagating to a certain extent, except for a portion of the absorbed laser. The pulse length of the reflected laser is expanded more than that of the incident laser by a modulation due to the anomalous penetration, and the pulse expansion factor can be predicted by the schematic model. The frequency of the reflected laser can be calculated by the Doppler shift formula coupled with a relativistic dispersion relation, and is good agreement with the simulation result. The anomalously penetrating pulse shows soliton-like behaviors in the plasma after the incident laser has vanished.   

An experimental and theoretical investigation of the flow at the outlet of a Francis turbine runner is carried out in order to elucidate the causes of a sudden drop in the draft tube pressure recovery coefficient at a discharge near the best efficiency operating point. Laser Doppler anemometry veloc...

The tissue microcirculation, as measured by laser Doppler flowmetry (LDF), comprises both capillary, arterial and venous blood flow. With the classical LDF approach, it has been impossible to differentiate between different vascular compartments. We suggest an alternative LDF algorithm that estimate...

peer-reviewed , This paper reviews the development and use of laser Doppler perfusion monitors and imagers. Despite their great success and almost universal applicability in microcirculation research, they have had great difficulty in converting to widespread clinical application. The enormous interest...

The evolution of the velocity components of the wake behind a cylinder has been investigated in the range 40 < Re < 300 using a moving fringe Laser Doppler anemometer. The order parameter (amplitude of the perpendicular velocity fluctuations) obeys Landau's law. We confirm the existence of several m...

A compact cw Tm,Ho:YLF laser with single-mode tunability over +/- 4 GHz has been ... testbed 2-pm Doppler lidar, It is pumped by nominal 1-W diode array at 792 nm, which is located remotely and coupled into the LO unit via optical fiber.

This paper describes an experimental study of flow characteristics of isothermal axisymmetric suddenly expanding swirling flow with bluff body using a backward-scatter two-component laser-Doppler velocimeter. Axial and tangential velocity components including time-mean and rms fluctuating values are determined. Some quantitative information, such as the boundary and strength of the reverse-flow zone, are provided.   

In this paper, we present the latest results on the measurement of the Boltzmann constant kB , by laser spectroscopy of ammonia at 10 ?m. The Doppler absorption profile of a ro-vibrational line of an NH3 gas sample at thermal and pressure equilibrium is measured as accurately as possible. The absorp...

We use an extended laser Doppler technique to track optically the velocity of individual particles in a high Reynolds number turbulent flow. The particle sizes are of the order of the Kolmogorov scale and the time resolution, 30 microseconds, resolves the fastest scales of the fluid motion. Particle...

Flow past an inclined flat plate at an angle of attack of 30° and a Reynolds number of 30 000 is investigated experimentally. The velocity field in the wake is measured with a laser doppler anemometer (LDA) in the region from one plate breadth downstream to three and a half-plate breadths downstream...

We demonstrate sub-nanosecond range and unambiguous sub-50-Hz Doppler resolved laser radar (LADAR) measurements using spectral holographic processing in rare-earth ion doped crystals. The demonstration utilizes pseudo-random-noise 2 giga-sample-per-second baseband waveforms modulated onto an optical carrier.

In this study, we present preliminary experimental results for the evaluation and identification of constitutive equations for viscoelastic polymer melts using flow field measurements such as Laser-Doppler velocimetry and flow-induced birefringence. We focus on the influence of temperature and flow ...

The theory of Doppler-free magnetic optical activity associated with a single absorption line is presented. The transmission of tunable laser light, linearly polarized, through a dilute gaseous medium along a steady magnetic field is studied in the presence of a second counterpropagating saturating ...

The aim of this study was to establish the degree to which a standardized test based on laser Doppler blood flow measurement is dependent on the particular equipment set-up being used. For this purpose, we examined finger skin blood flow with laser Doppler instruments in 20 healthy subjects. In laser Doppler perfusion monitoring (LDPM), we used a custom-made probe with two detecting fibers placed 0.25 and 1.2 mm from the illuminating fiber, respectively, and two laser Doppler perfusion imagers (LDPI) with a wavelength of 632.8 nm and 780 nm, respectively. Warming of the hand was achieved with a Peltier element, and reflex vasoconstriction was induced by immersing the other hand for 3 min into a water bath kept at 15 degrees C. As a measure for the change in skin blood flow, a vasoconstriction index (VAC: cooling/before cooling) was calculated and used for the comparison of the different devices. VAC values gathered around 0.6 for all devices. However, LDPI with a wavelength of 632.8 nm showed a slightly higher VAC index, and the difference was significant. We conclude that using a standardized test is the most appropriate for monitoring changes in blood flow rather than recording and comparing discrete values in intermittent recordings. Although a difference was noted when comparing the devices, different fiber separations and wavelengths seem then to be of little consequence. PMID:16403539

An interferometric method for parallel optical spectroscopy in the kilohertz range is reported, as well as its experimental validation in the context of high speed laser Doppler imaging in vivo. The interferometric approach enables imaging in the low light conditions of a 2 kHz frame rate recording ...

Two experiments carried out on rat skin flaps are described, where microvascular flow has been measured noninvasively by a laser Doppler velocimeter. Using this technique it is possible to define the limits of an axial pattern flap in terms of microvascular flow; this was found to increase when the ...

Laser Doppler Vibrometers (LDV) are optical instruments for accurately measuring velocity and displacement of vibrating structures completely without contact.A rugged optic head (roughly the same size as a video camera) mounts to a tripod and can be easily pointed at a vibrating object.

10.6 pm pulsed Doppler lidar in providing flow visualization in a stable planetary ... scanner, a data system to record, analyze and display the laser sensed wind field data ..... tion of its kind for terrain induced drainage flows. This case is ... (of thh pa~e). 21. NO. OF PAGES. 22. PRICE. Unclassified. Unclassified. A0 2. F~~ = le ...

Discusses design and principle of operation of the laser Doppler anemometer developed by the Central Mining Institute in Poland for use in underground coal mines with dust sources. The prototype consists of two cylindrical flameproof enclosures - one for the laser transmitter, the other for the detector. Both enclosures are attached to the rigid body containing all the necessary optical elements. The laser transmitter itself is a conventional construction used in various types of laser equipment developed in Poland for the coal industry. Frequency range is 1 kHz to 6 MHz.

We demonstrate that a Doppler broadened two-level medium can be made transparent to a laser pulse by an appropriate adiabatic variation of the laser field amplitude and its nominal detuning. This new technique of adiabatic self-induced transparency (ASIT) is compared with the well known self-induced transparency (SIT) phenomenon, showing that the adiabatic method is much more robust to variations of the system parameters. We also discuss a possible experimental implementation of ASIT using 87-Rb atoms.

This study is carried out system error evaluation of an incoherent wind Doppler LIDAR system that uses an iodine filter. Sharp slopes of an iodine filter provide better wind-measuring sensitivity than a Fabry–Perot etalon. The magnitude and sign of the Doppler shift are obtained from the ratio of the intensities of two signals arising from two slopes of an iodine absorption line. Systematic errors of wind measurement are caused mainly by the fluctuations of laser frequency and iodine absorption linewidth. The standard deviation of the zero Doppler shift is experimentally evaluated to be 1.8 MHz, which corresponds to the uncertainty in line-of-sight wind velocity of 0.5 m/s. This result shows a good agreement with the result of an experiment of the tuning stability of laser frequency with respect to the absorption line slope. Moreover, comparison of wind profiles is made between the Doppler LIDAR and concurrent radiosonde measurements. The measured horizontal wind speeds are from 8 to 21 m/s in the altitude range from 8 to 25 km, indicating a reasonable agreement between the two instruments. Experimentally, the total optical efficiency of this Doppler LIDAR system is estimated to be 4.0%, which is close to the value expected from the evaluation of each component of the instrument.   

This report gives a detailed description of the operation of the Laser Doppler Velocimeter (LDV) system maintained by DIAL at MSU. LDV is used for the measurement of flow velocities and turbulence levels in various fluid flow settings. Ills report details the operation and maintenance of the LDV system and provides a first-time user with pertinent information regarding the system`s setup for a particular application. Particular attention has been given to the use of the Doppler signal analyzer (DSA) and the burst spectrum analyzer (BSA) signal processors and data analysis.

...Directives; General Electric Company Turbofan Engines...applies to certain General Electric Company (GE) CF6-80C2...flowmeter to the Integrated Drive Generator (IDG) fuel...applies to all General Electric Company (GE) CF6-80C2...flowmeter to the Integrated Drive Generator (IDG)...

The Space Physics Research Laboratory at the University of Michigan has been operating a direct detection, high resolution Doppler Lidar (HRDL) to measure winds in the boundary layer, free troposphere and lower stratosphere. A direct detection Doppler lidar measures the Doppler shift of the aerosol or Rayleigh backscattered signal, from which the wind velocity vector can be retrieved (Benedetti-Michelangeli et al, 1972, 1974; Chanin et al., 1989; Abreu et al., 1992). The system components are shown. The transmitting system is a Continuum NY-60 Nd:YAG laser frequency doubled to a wavelength of 532 nm. The laser is injection seeded for single line mode operation yielding a linewidth of 0.0045 cm(exp -1) (135 MHz) with excellent shot-to-shot frequency stability. The laser produces 60 mJ pulses and operates at a 50 Hz repetition rate for an effective output power of 3.0 W. A description of the University of Michigan's Doppler lidar is given with examples of wind profiles for the boundary layer, free troposphere, and for the lower stratosphere. The system provides a reliable method of remotely measuring the wind. The wind error is smallest in regions of high aerosols. The system also produces aerosol extinction profiles versus altitude which can be determined by the shape of the spectra. The system has been installed in a trailor so that measurements can be made for field campaigns. Winds and aerosol data are available immediately at the site for use in forecasting.

Objective: We compared the inter-day reproducibility of post-occlusive reactive hyperemia (PORH) assessed by single-point laser Doppler flowmetry (LDF) and laser speckle contrast analysis (LSCI), and the reproducibility of local thermal hyperemia (LTH) assessed by LDF, laser Doppler imaging (LDI) and LSCI. We also tested whether skin blood flow assessment by LDF and by LSCI are correlated. Methods: Skin blood flow was evaluated during PORH and LTH using LDF, LDI (for LTH only) and LSCI on the forearms of healthy volunteers, at a 7day interval. Data are expressed as cutaneous vascular conductance (CVC), as a function of baseline and scaled to the thermal plateau. Reproducibility is expressed as within subject coefficients of variation (CV, in %) and intra-class correlation coefficients (ICC...

We demonstrate two ways of obtaining sub-natural linewidth for probe absorption through room-temperature Rb vapor. Both techniques use a control laser that drives the transition from a different ground state. The coherent drive splits the excited state into two dressed states (Autler-Townes doublet), which have asymmetric linewidths when the control laser is detuned from resonance. In the first technique, the laser has a large detuning of 1.18 GHz to reduce the linewidth to 5.1 MHz from the Doppler width of 560 MHz. In the second technique, we use a counter-propagating pump beam to eliminate the first-order Doppler effect. The unperturbed probe linewidth is about 13 MHz, which is reduced below 3 MHz (0.5 \\Gamma) at a detuning of 11.5 MHz.

Adequate skin perfusion is one of the most important prerequisites for healing of trophic lesions and amputation wounds in patients with peripheral arterial disease. The discrepancies possible between macro- and microcirculations stress the necessity of new methods for assessment of terminal vascular beds. With laser-Doppler flowmetry, in addition to determination of transcutaneous oxygen partial pressure and capillary microscopy, a noninvasive method is provided for clinical evaluation of the cutaneous microcirculation. Even though the description of the method and the initial investigative results have been available for more than ten years, the diagnostic usefulness of the procedure remains to be clearly established. This may be primarily due to the fact that current examination methods such as Xenon-133-clearance, photoplethysmography and skin temperature measurements are not relevant reference standards and that there is a paucity of fundamental work with respect to reproducibility and validity of laser-Doppler flowmetry as well as, to some degree, because of discrepancies generated by varying examination techniques, differing sites of examination, non-standardized examination parameters and accordingly non-comparable study results from different working groups. Part of the difficulty is also attributable to the structural complexity, physiologic fluctuations of erythrocyte flow velocity and the morphologic differences with respect to the site of examination. The measurement principle is based on registration of refraction, reflection and partial absorption of the emitted 2 mW He-Ne laser signal (wave length 632.8 nm) in the tissue being examined. An output signal, in volts, is created which is proportional to the product of the number of moving cells and their mean velocity. The housing of the laser-Doppler probe is fitted with a heating element. Accordingly, thermostatic measurements can be carried out with a temperature between 28 and 44 degrees C. The depth of penetration of the laser-Doppler signal is about 0.7 to 1 mm such that a tissue hemisphere of approximately 1 mm can be examined. The relative portion of the signal derived from the arterioles, capillaries, arteriovenules and arteriovenous anastomoses as well as the venules cannot be differentiated. While in-vitro experiments with flow models have shown a linear correlation between erythrocyte flow and laser-Doppler signals, in-vivo measurements are encumbered by skin pigmentation, thickness of the epidermis, capillary morphology and capillary number, hemoglobin content and angle of incidence of the laser-Doppler signal.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3061920

A laser fluorescence anemometer which comprises a three-component laser Doppler velocimeter system with a fourth channel to measure fluorescent dye concentration has been installed in the NASA Langley 16- by 24-in water tunnel. The system includes custom designed optics, data acquisition, and traverse control instruments and a custom software package. Feasibility studies demonstrated how water tunnels can be used in conjunction with advanced optical techniques to provide nonintrusive detailed flow field measurements of complex fluid flows with a minimum of expense. The measurements show that the laser fluorescence anemometer can provide new insight into the structure, entrainment, control and of mixing vortical and shear layer flows.

We describe the design and realization of a scheme for uv laser spectroscopy of singly-ionized iron (Fe II) with very high resolution. A buffer-gas cooled laser ablation source is used to provide a plasma close to room temperature with a high density of Fe II. We combine this with a scheme for pulsed-laser saturation spectroscopy to yield sub-Doppler resolution. In a demonstration experiment, we have examined an Fe II transition near 260 nm, attaining a linewidth of about 250 MHz. The method is well-suited to measuring transition frequencies and hyperfine structure. It could also be used to measure small isotope shifts in isotope-enriched samples.

Atmospheric pressure CO2 plasma was generated by a laser driven plasma wind tunnel. At an ambient pressure of 0.38 MPa, a stable plasma was maintained by a laser power of 1000 W for more than 20 min. The translational temperature was measured using laser absorption spectroscopy with the atomic oxygen line at 777.19 nm. The measured absorption profiles were analyzed by a Voigt function considering Doppler, Stark, and pressure-broadening effects. Under the assumption of thermochemical equilibrium, all broadening effects were consistent with each other. The measured temperature ranged from 8500 K to 8900 K.

This letter presents the principles and techniques of active optical clock, a special laser combining the laser physics of one-atom laser, bad-cavity gas laser, super-cavity stabilized laser and optical atomic clock. As an example, a compact version of active optical clock based on thermal Strontium atomic beam shows a quantum-limited linewidth of 0.51 Hz, which is insensitive to laser cavity-length noise, and may surpass the recorded narrowest 6.7 Hz of Hg ion optical clock and 27Hz of very recent optical lattice clock. The estimated 0.1Hz one-second instability and 0.27Hz uncertainty are limited only by the relativistic Doppler effect may be improved to 10mHz by using cold atoms.

Progress made in developing tunable semiconductor lasers for application to air pollution monitoring is summarized. The researchers report achieving tunability in the near- and mid-infrared with Doppler-limited spectral resolution using pressure-tuned GaAs and PbSSe diodes at 77/sup 0/K. A stable and compact pressure tuning system was developed and used in the experiments that were conducted. Detailed accounts are provided on: (1) pressure-tuning of semiconductor lasers; (2) laser diode fabrication and performance; and (3) external cavity control of diode lasers. The researchers found that operation of a GaAs diode laser in an external cavity with a grating can provide significant improvement over other common laser cavity configurations. With improvements which appear possible in the tuning range and in diode output power, the device could prove particularly useful for multichannel optical communications, absorption, and/or Raman spectroscopy or other experiments.

We investigated the influence of inducible nitric oxide synthase (iNOS) on acute ischemic injury and chronic angiogenesis. In a hindlimb ischemia model, NO produced by endothelial NO synthase (eNOS) reduces ischemic injury and promotes angiogenesis. However, the effect of the large amounts of NO generated by induced iNOS is unclear. Experimental groups of mice were as follows: (1) wild-type group (Wild), (2) iNOS-knockout group (iNOS-KO), and (3) aminoguanidine-treated wild-type group (Wild + AG), which received aminoguanidine from day 0 to day 3 after ischemia. Acute ischemic injury was evaluated by measuring the plasma CK value and ischemic score. Chronic angiogenesis was evaluated by microangiography and with a non-contact type Doppler blood flowmeter on day 3. Compared with the Wild group (251 ± 34.7 IU/l), the CK value was significantly elevated in the iNOS-KO (497 ± 126.7 IU/l) and Wild + AG (587.2 ± 128.7 IU/l) groups. The ischemic score was significantly increased in the iNOS-KO (92%) and Wild ± AG (66.6%) groups compared with the Wild group (23%). Blood flow was significantly increased in the iNOS-KO group (58.7 ± 15.3%) compared with the Wild (38.1 ± 15.9%) and Wild ± AG (43.5 ± 9.8%) groups in the chronic stage. Microangiography revealed a significantly increased number of blood vessels in the iNOS-KO (0.29 ± 0.02) group compared with the Wild (0.12 ± 0.01) and Wild + AG (0.15 ± 0.02) groups. Our findings indicate that NO generated by iNOS has a biphasic action, reducing acute ischemic injury and inhibiting angiogenesis in the chronic stage.   

LISA relies on several techniques to reduce the initial laser frequency noise in order to achieve an interferometric length measurement with an accuracy of {approx}10pmsq rootHz. LISA will use ultra-stable reference cavities as a first step to reduce the laser frequency noise. In a second step the frequency will be stabilized to the LISA arms which provide a better reference in the frequency band of interest. We present experimental results demonstrating Arm locking with LISA-like light travel times and Doppler shifts. We also integrated this system with a LISA-like pre-stabilization system using our ultra-stable cavities. The addition of realistic Doppler shifts led to further refinements of the arm locking controllers compared to the controller architecture discussed in the past. A first experimental result of the new controller is also presented.

Laser Doppler Anemometers have long been the device-of-choice for air velocity measurements due to their avoidance of turbulence induced by insertion-method air velocity measurement devices. At first glance, the use of a Laser Doppler Anemometer (LDA) for calibrating air velocity meters appears to be a relatively simple and straightforward process. As is typical in most metrological applications the process becomes much more complex when attempting to use the apparatus to make high-performance, metrology measurements. This paper focuses on the considerations for calibration of a LDA beginning with a discussion why an LDA needs to be calibrated. Other areas of discussion include alignment of the optics, dealing with imperfections in the alignment process, establishing the traceability of measurements from the apparatus and design and development of and experiences with using a calibration apparatus.

High resolution (Doppler-limited) near-infrared spectra of several hydrocarbons and other light molecules of atmospheric significance were surveyed and catalogued using a unique difference-frequency laser spectrometer. Such spectra can be applied to the detection, identification, and quantitative monitoring of molecular air contaminants using lasers or other high-resolution spectroscopic instruments. Presented here are the complete Doppler-limited spectra of the complex and rich C-H stretching bands of formaldehyde (H2CO), ethylene (C2H4), ethane (C2H6), and allene (C3H4). Precise frequencies and intensities of the spectral lines also are listed in an atlas for each molecule along with assignments, made by several collaborators, for most of the observed transitions.

The bioactivity of a novel topical glucocorticosteroid, mometasone furoate 0.1% fatty cream was compared with betamethasone dipropionate 0.05% cream and betametasone valerate 0.1% cream. An ultraviolet light (UV-B)-induced inflammation assay in humans was used, and the combined effect of a single, open application of the corticosteroids was evaluated. Reduction of UV-B induced inflammation was monitored by laser Doppler blood flowmetry, clinical skin scoring and skin reflectance spectrophotometry. Skin scoring and reflectance spectrophotometry were found unsuitable because one of the cream vehicles contained titanium dioxide which shielded skin erythema. Laser Doppler blood flowmetry showed that mometasone furoate 0.1% fatty cream was more than twofold better in reducing UV-B-induced inflammation than betamethasone dipropionate 0.05% cream and betametasone valerate 0.1% cream, and that the effect was sustained for at least 24 h after a single application. PMID:8274288

Synchronized oscillation of smooth muscle cells tension in arterioles is the main control system of microvascular skin blood flow. An important autogenic vasomotion activity is recognized in 0.1Hz oscillations through power spectrum analysis of laser Doppler flowmetry. Severe dysautonomia in diabetic neuropathy is correlated with loss of 0.1Hz vasomotor activity, hence with impaired blood microcirculation. FREMS is a novel transcutaneous electrotherapy characterized by sequences of electrical stimuli of high voltage and low pulse duration which vary both in frequency and duration. We have evaluated the changes in laser Doppler flow in the volar part of the forearm before, during and after FREMS. Normal controls (n=10, 6 females, age range 21-39 years) demonstrated significant 0.1Hz vasomot...

A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at about 1.5 micrometers - beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceler...

We report on a precision measurement of the 2 {sup 3}{ital S}--3 {sup 3}{ital P} transition in {sup 4}He. Doppler-free spectra of the transition were observed by exciting metastable helium atoms, produced by a chopped rf discharge, using 389-nm radiation generated by a frequency-doubled Ti-doped sapphire laser. A frequency measurement of the Doppler-free lines was made by interferrometric comparison of the Ti-doped sapphire frequency with that of an iodine-stabilized He-Ne laser using a 1-m evacuated Fabry-Perot etalon. The measurement uncertainty was 2 parts in 10{sup 9} (3 standard deviations), which gives an improvement of a factor of 60 in the term value of the 3 {sup 3}{ital P} level with respect to earlier measurements. This result makes it possible to determine the one electron Lamb-shift correction to the 3 {sup 3}{ital P} state with an accuracy of 0.8%.

Among the topics discussed are improved aluminum coatings for UV optical components, thick optical films for the conduction of optical and IR radiation, glancing incidence optics for high-power lasers, the optical quality of pulsed aerodynamic laser windows, optical tooling for Antares, modeling the CF4 laser, optical fiber probes, ultraviolet phase conjugation and its implications, laser-induced bioluminescence, the use of a free-expansion jet in ultrahigh-resolution Raman spectroscopy, and sub-Doppler optoacoustic spectroscopy. Also considered are new liquid scintillators for fiber optic applications, the frequency response of the thermal lens, meteorological lidar developments, the design and performance of a new emission-line coronagraph, Smartt interferometers, multigigahertz beam diagnostics for laser fusion, and the surface characterization of metal optics.

The measurement accuracy of a Doppler lidar and other laser spectra research is very sensitive to the frequency drift of the laser transmitter. Because currently used frequency locking methods usually involve complicated optics and are sensitive to the working conditions, we present a simple and robust locking method—locking the laser to iodine absorption lines with a software-based PID controller. The locking strategy was successfully applied to three kinds of cw single-frequency Nd: YAG lasers with different tuning actuators. The disadvantage of a slow tuning response is eliminated by using a parameter-adjustable PID algorithm. The frequency stability is better than 200 kHz for 3 h which, to our knowledge is one of the best long-period locking result achieved for this kind of laser.

Registration, also known as pose estimation and position registration, is an essential part of the accurate quantitative analysis of velocity data obtained with a scanning laser Doppler vibrometer (SLDV). This paper presents a hybrid method of registration using a general linear laser model. The general linear laser model uses sets of slopes and intercepts rather than nonlinear functions of mirror angles to describe the spatial path of the laser beam. This simplifies registration mathematics and also allows the hybrid registration algorithm to be applied to any type of SLDV using any length unit system. The hybrid registration algorithm is comparable in accuracy to existing methods, but eliminates the need for laser rangefinders and the generation of high quality starting points in optimiz...

Extensive experimental investigations of a variety of fluidic flowmeters based on the Coanda principle were conducted in order to find a design suitable for use as a compact residential gas meter. As a result of these investigations a fundamentally different type of fluidic oscillator was invented, which has been named the Trapped Vortex Pair (TVP) flowmeter. The TVP fluidic flowmeter operates over the range of 1.75 cfh to 146 cfh with a pressure drop of 0.59 inches of water and a linearity of plus or minus 3.0%. A much wider range of operation from 0.5 to 200 cfh can be achieved if the pressure-drop constraint is relaxed.

The performance analysis of natural gas flowmeters Turbine and Ultra-sonic Type installed in a same stream connected to a flow computers for 18 months it allowed to identify errors between Ultra-sonic flowmeter and Turbine flowmeter. All measurements of the measured volumes during test period were stored in flow computers and they were tabulated for analysis and study. The measured values were compared making possible analysis of measurement errors between the two instruments. All maintenance events of the measurement system in subject were registered, allowing analysis of all fails occurred during the test period. (author)

We report laser Doppler ophthalmoscopic fundus imaging in the rat eye with near-IR heterodyne holography. Sequential sampling of the beat of the reflected radiation against a frequency-shifted optical local oscillator is made onto an array detector. Wide-field maps of fluctuation spectra in the 10 Hz to 25 kHz band exhibit angiographic contrasts in the retinal vascular tree without requirement of an exogenous marker.

This paper presents results from an experimental study of the atomisation of semi-industrial-scale sprays of heavy fuel oil. The sprays were characterised at a thermal input ranging from 0.75 to 2.0 MW. Measurements of drop size and velocity were performed with a Phase-Doppler Particle Analyser (PDPA) for inlet spray conditions corresponding to combustion studies at MIT and IFRF. Laser-sheet visualisation was used for a qualitative characterisation of the spray structure. (author)

The flow field inside an annular seal with a 0.00127 m clearance was measured using a 3-D laser Doppler anemometer system. Through the use of this system, the mean velocity vector and the entire Reynolds stress tensor distributions were measured for the entire length of the seal (0.0373 m). The seal was operated at a Reynolds number of 27,000 and a Taylor number of 6,600.

A photon correlation method is introduced for measuring components of the shear rate tensor in a turbulent soap film. This new scheme, which is also applicable to three-dimensional flows, is shown to give the same results as Laser Doppler velocimetry, but with less statistical noise. The technique yields the mean shear rate s, its standard deviation, and a simple mathematical transform of the probability density function P(s) of the shear rate itself.

We report on the observation of enhanced four-wave mixing via crossover resonance in a Doppler broadened cesium vapor. Using a single laser frequency, a resonant parametric process in a double-$\\Lambda$ level configuration is directly excited for a specific velocity class. We investigate this process in different saturation regimes and demonstrate the possibility of generating intensity correlation and anti-correlation between the probe and conjugate beams. A simple theoretical model is developed that accounts qualitatively well to the observed results.

Several technologies are available for interferometrically measuring laser wavelength to the precision of a Doppler width. These include instruments based on Fabry-Perot etalons, Fizeau wedges, Michelson interferometers, and other novel schemes. The current state of the art of these instruments is reviewed. Two new pulsed wavemeter designs are presented, the solid Fizeau wedge and the index mismatched interferometer. These instruments exhibit accuracies in the 10/sup 6/ range, and are very compact and inexpensive to fabricate. 28 refs., 10 figs.

The behavior of air in a model of a mixed-flow bowl pump has been investigated using a laser-Doppler anemometer. Velocity measurements were obtained at a number of sections within, upstream and downstream of the rotor. All three components of velocity were determined, and related to the rotating frame of reference using a computerised data acquisition method. The results provide useful data relevant to some complex problems of incompressible flow in turbomachines, including annular casing boundary layer growth.

In this letter, Doppler spread estimation in different Doppler spectra is investigated and some efficient methods are proposed to calculate the maximum Doppler frequency from autocorrelation function easily.   

Conversion of partial- to full-thickness injuries, even after the burning has stopped, remains a significant clinical problem. We developed a rat model with a wide range of burn depths to study this phenomenon by microvascular assessment. Fifty-four male Sprague-Dawley rats weighing 460 g on average were studied. Real-time tissue monitoring of pH, paCO2, and paO2 was achieved by placement of a continuous blood gas monitor transducer in the aorta. Ten, 2-cm x 2-cm burns were created on each animal with milled aluminum templates (100 degrees C) with varying contact times. Conversion of burn depth in these wounds was documented by serial laser Doppler imager scanning over a 5-hour period. Animals received Ringer's lactate resuscitation at 0, 2, 4, 6, and 8 ml/kg/%burn. Serial laser Doppler scanning directly demonstrated progressive loss of perfusion to partial-thickness burns dependent upon the amount of fluid resuscitation. Conversion of partial- to full-thickness burns in this rat model (documented by laser Doppler microvascular assessment) was dependent upon how the animals were resuscitated. PMID:11761393

A 32×32 pixel array has been fabricated in a 0.35-?m complementary metal-oxide semiconductor process with the aim of producing two-dimensional laser Doppler blood-flow images. In the design, each pixel contains five basic elements: a photodiode, a front-end consisting of a current to voltage converter, voltage amplifier, antialiasing filter, and buffer. The analog design is optimized for the detection of laser Doppler blood-flow signals and thus offers advantages over conventional sensors. The analog outputs are passed through an on-chip multiplexer and digitized by an external analog-to-digital converter. The sensor has been fully characterized electrically and optically using modulated electrical and optical signals. A calibration process for fixed pattern noise reduces the standard deviation of the ac gain by a factor of 2. The imaging response is tested by imaging a vibrating test structure and a rotating diffuser. Blood-flow measurements on a finger before and after occlusion demonstrate that the sensor array is capable of detecting blood-flow signals from tissue. The knowledge gained from the characterization of the design can be used to develop a fully integrated laser Doppler blood-flow sensors with a higher number of pixels.

The collisional dependence of saturated polarization spectroscopy with a picosecond laser is investigated by probing hydroxyl in a flow cell. While nanosecond lasers have been used often for nonlinear diagnostic measurements of flame composition, picosecond lasers provide a potentially superior source for such techniques. Compared to a nanosecond laser, picosecond lasers produce significantly greater peak power for the same pulse energy, and this could improve the signal strength of multi-photon techniques such as degenerate four-wave mixing (DFWM) and polarization spectroscopy (PS). It has been suggested that the signal produced by such lasers would be less dependent on the collisional environment because the behavior of the molecular system probed by short-pulse lasers is governed more by the spectral width of the laser and the Doppler effect. To investigate the collisional dependence of the polarization spectroscopy signal generated with a picosecond laser, the authors probe the A{sup 2}{Sigma}{sup +}-X{sup 2}{Pi} (0,0) band of OH in a flow cell. In this well-controlled environment, the authors monitor the change in signal strength as they vary the buffer gas pressure by a factor of 50. Hydroxyl (OH) is created by photolysis of hydrogen peroxide using a Nd:YAG laser.

Absolute wave numbers with a typical uncertainty of 1 MHz (95% confidence) were measured for 102 hyperfine-structure components of {sup 127}I{sub 2}. The data cover the range 560-656 nm, with no gaps over 50 cm{sup -1}. The spectra were observed using Doppler-free frequency modulation spectroscopy with tunable cw laser. The laser was locked to selected iodine components and its wave number measured with a high precision Fabry-Perot wavemeter. Accuracy is confirmed by good agreement of 9 of the lines with previous results from other laboratories. These measurements provide a well-distributed set of precise reference lines for this spectral region.

It is noted that the application of advanced optical data links permits both a reduction of antenna diameters and position determination error by orders of magnitude. For a typical mission to Jupiter, three different optical technologies are examined, which use CO2, Nd:YAG, and semiconductor diode lasers. The first two systems make it possible to realize coherent optical transponders which are required for a two-way Doppler measurement with the optical carrier. Direct detection with pulse position modulation is assumed for the semiconductor laser system.

We present the fundamentals of an instantaneous, unseeded and nonintrusive measurement technique for flows, which is based on light diffraction by electrostrictive laser-induced gratings (LIG). We show that the peaks in the power spectrum are situated closely to the frequencies that contain the direct information on flow velocity and temperature. We compare the results of the LIG measurements using a heterodyne detection scheme with those provided by the Laser Doppler Anemometry (LDA). Furthermore, we measured simultaneously flow velocity and temperature in a submerged air jet behind a slot nozzle. (author)

With the HIRAB (High Resolution Atomic Beam) building, the photodetachment experiments at LAMPF was able to continue. The 1988 runs provided data to complement that of 1986 on effects of electric fields on photodetachment cross section of H{sup -} and interaction of thin foils with relativistic H{sup -} ions. The first multiphoton detachment of H{sup -} was observed. In each of these experiments, a high-powered laser beam was allowed to intersect the relativistic ion beam; the photon energy in the barycentric system is Doppler shifted, and the laser may thus effectively be tuned (through up to a decade) by changing the angle of intersection of the 2 beams.

We have detected and analyzed narrow, high contrast coherent population trapping resonances, which appear in transmission of the probe monochromatic light beam under action of the counterpropagating two-frequency laser radiation, on example of the nonclosed three level ?-system formed by spectral components of the Doppler broadened D2 line of cesium atoms (in the cell with the rarefied Cs vapor). These nontrivial resonances are determined directly by the trapped atomic population on the definite lower level of the ?-system and may be used in atomic frequency standards, sensitive magnetometers and in ultrahigh resolution laser spectroscopy of atoms and molecules.

An experiment in which visible wavelength lasers traversed a well-documented two dimensional jet was conducted. Temperature perturbations varied from 0.25 to 1.80 K and velocity fluctuations ranged from 9.2 to 30.8 m/sec. Measured central spot intensities were as low as 18% of the undisturbed beam, depending on jet Mach number, beam position theory and experiment was two percent in terms of far field intensity. To supplement the flow field information, a laser Doppler velocimeter was developed to measure both mean and fluctuating velocities and a photo correlator was used as a signal processor.

Elastic and anelastic properties of polycryatalline ?-Mn at low temperature have been studied using electromagnetic acoustic resonance (EMAR) and resonance ultrasound spectroscopy coupled with a laser Doppler interferometer (RUS/Laser). ?-Mn showed low Poisson’s ratio both in the paramagnetic state at 290 K and in the anti-ferromagnetic state at 4 K. The acoustic Debye temperature was 479 K, showing good consistency with the previous work. Around the magnetic transition temperature (TN=98 K), remarkable changes in Poisson’s ratio and internal friction are identified, indicating strong magnetic acoustic interaction at the transition temperature.   

A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 .mu.m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of .mu.L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

Prototype Fast Breeder Reactor (PFBR) is a 500MWe, sodium cooled, pool type, mixed oxide (MOX) fueled reactor. Sodium flow measurement in various loops of the reactor is of prime importance from the operational and safety aspects. To measure the flow of electrically conducting liquid sodium in secondary circuits, permanent magnet flowmeters (PMFMs) made up of ALNICO-5 are used in Fast Breeder Test Reactor (FBTR), PFBR and existing sodium loops in Indira Gandhi Centre for Atomic Research (IGCAR). PMFM made up of ALNICO-5 are bulky and heavy, hence to reduce size of flowmeter a PMFM made up of Samarium Cobalt (SmCo) is designed and calibrated in existing sodium loop. Calibration of flowmeter requires dedicated sodium rig with pipe sizes of same dimension as flowmeter pipe, which needs modifi...

Mass flowmeters have been used to improve crude oil measurement at individual wells throughout the Little Knife field. This type of meter uses the principle of the Coriolis effect to measure the mass flow rate of fluid. Mass measurement eliminates problems encountered by conventional volumetric flowmeters because of the presence of free gas in the liquid phase. After 5 years of operation, mass flowmeters have proved to be a significant improvement over conventional flowmeters. Excellent agreement has been consistently achieved between the sum of the measurement from the allocation meters and the custody transfer meters, which receive the commingled oil. In addition to the performance improvement, significant capital and operating cost savings were realized compared with a more conventional oilfield approach.

quires a short engine having a minimum over-all wall thickness, free of external flanges and ... the requirement for a vacuum furnace for the brazing cycles. Another disadvantage is that .... Flows were measured on rotary-vane-type flowmeters ...

The ,probe rake assembly was designed to with'_tand turbine engi_'.e exhaust ...... The _;ample transport lines were heated with steam tracing mid insulated ...... E-15). The flow wag regulated with a flowmeter located down,stream of the cells.

In this work, a laser torsional vibrameter was used to measure the torsion vibration of a rotating shaft system under electrical network impact. Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) are non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. Furthermore, a highly complex shafting system is analyzed by a modified Riccati torsional transfer matrix. The system is modeled as a chain consisting of an elastic spring with concentrated mass points, and the multi-segments lumped mass model is established for this shafting system. By the modified Riccati torsional transfer matrix method, an accumulated calculation is effectively eliminated to obtain the natural frequencies. The electrical network impacts can activize the torsional vibration of shaft system, and the activized torsion vibration frequencies contained the natural frequencies of shaft system. The torsional vibrations of the shaft system were measured under electrical network impacts in laser Doppler torsional vibrometer. By comparisons, the natural frequencies by measurement were consistent with the values by calculation. The results verify the instrument is robust, user friendly and can be calibrated in situ. The laser torsional vibrometer represents a significant step forward in rotating machinery diagnostics.

Background: Patients with orthostatic hypotension have pathologic hemodynamics related to changes in body posture. A new cephalic laser blood flowmeter that can be worn on the tragus to investigate the hemodynamics upon rising from a sitting or squatting posture was developed. Methods and Results: The relationship between cephalic hemodynamics and cerebral ischemic symptoms in 63 subjects in a sitting, squatting, and standing positions using the new device was evaluated. Transient decrease in blood pressure within 15 s after rising to an erect position possibly causes dizziness, syncope, and fall. Subjects exhibiting dizziness upon standing showed a significant decrease in the cephalic blood flow (CBF) and indirect beat-to-beat systolic blood pressure, as monitored by the Finometer, and a significant correlation was observed between the drop ratio (drop value on rising/mean value in the squatting position) of CBF and that of systolic blood pressure. Conclusions: This new wearable CBF-meter is potentially useful for estimating cephalic hemodynamics and objectively diagnosing cerebral ischemic symptoms of subjects in a standing posture. (Circ J 2009; 73: 1950-1955)   

Air-water swirling flows in a one-fifth model of a steam separator in a boiling water nuclear reactor are measured to obtain a database for modeling and verification of numerical methods for predicting swirling flows in the separator. Flow patterns, liquid film thicknesses, separated flow rates and the ratio Ws* of the separated flow to the total liquid flow are measured using a high-speed camera, a laser focus displacement meter and flowmeters. Main conclusions obtained are as follows: (1) liquid transfer from droplets to liquid film is caused not only by droplet deposition but also by the collection of droplets on the vanes of the swirler, (2) Ws* increases with the gas volume flux JG and does not depend on the liquid volume flux JL so much because a large centrifugal force caused by the swirler makes most of droplets in the gas core deposit on the liquid film before the separation and (3) a local peak appears in the axial distribution of film thickness, the position of which corresponds to the location where the droplet deposition caused by the centrifugal force has completed.   

Microprocessor based flowmeter technologies for liquids, such as Coriolis mass meters, and Ultrasonic flowmeters hold great promise. These technologies offer many advantages, such as no rotating parts, self-diagnostic checks, which can help anticipate and warn of impending failures before they have a major impact on the measurement. These meters are substantially different though than other primary devices due to their heavy reliance on the accompanying secondary electronics. One method to prove that they are accurate would be proving the flowmeter, using a pipe prover or small volume prover (SVP), but these proving methods are designed to count 'real time' pulses from a turbine or PD meter between a known volume, they are not designed to count 'time delayed' 'manufactured pulses' from a microprocessor. There are limitations of the manufactured pulse train and it affects the ability of the flowmeter to be proved using current proving technology. The author of this paper, a chairman of an American Petroleum Institute working group, investigated how the 'microprocessor generated pulses' produced by these types of flowmeters, interacted with the existing measurement technologies in use today. Several microprocessor based flowmeter technologies have been tested, including; Ultrasonic, Coriolis, and Helical Turbine with pulse multiplying preamplifier. Wherever possible, flowmeters of various sizes, and from several vendors have been tested. A significant amount of data has been collected which sheds light into why these types of flowmeters are sometimes difficult to prove. This paper describes the API testing program, and the methodology behind it. It presents results and findings, and offers specific recommendations that may eventually be incorporated into API documents and/or standards in the future. (author)

The conventional laser-two-focus (L2F) method, also known as laser transit anemometry (LTA), measures two components of the flow vector in the plane normal to the optical axis by measuring the time-of-flight of particles crossing the two laser beams in the probe volume. Recently a new three component system was developed, named 3C, Doppler L2F, which operates with the same confocal optical set-up as the two component L2F system, thus enabling three component measurements even under the extremely difficult conditions of limited optical accessibility as they appear for example in centrifugal compressors. The new hybrid system combines the principle of the L2F technique with the basic idea of the doppler global velocimetry (DGV). The two velocity components in the plane perpendicular to the optical axis are measured by the L2F time-of-flight technique, the third velocity component in the direction of the optical axis is determined by analyzing the Doppler frequency shift of the scattered light. The system was developed with respect to an application in a transonic centrifugal compressor and designed in the shape of an optical probe. The set-up and all important components of the 3C, Doppler L2F system are described here in detail, as well as the principle of operation and calibration of the system. Tests on a free jet demonstrate the measurement accuracy of the hybrid technique. Its successful application to a transonic centrifugal compressor was the first time that three component velocity data could be collected from a high loaded, high speed centrifugal impeller. The data are presented and discussed. (orig.)

Light has been used to non-invasively alter the excitability of both neural and cardiac tissue. Recently, pulsed laser light has been shown to be capable of eliciting action potentials in peripheral nerves and in cultured cardiomyocytes. Here, for the first time, we demonstrate optical pacing of an intact heart in vivo. Pulsed 1.875-µm infrared laser light was used to lock the heart rate to the pulse frequency of the laser. A laser Doppler velocimetry signal was used to verify the pacing. At low radiant exposures, embryonic quail hearts were reliably paced in vivo without detectable damage to the tissue, indicating that optical pacing has great potential as a tool with which to study embryonic cardiac dynamics and development. In particular, optical pacing can be used to control the heart rate, thereby altering stresses and mechanically transduced signalling.

The effect of a continuous-wave (cw) laser based anemometer's probe volume on the measurement of wind turbulence is studied in this paper. Wind speed time series acquired by both a remote sensing cw laser anemometer, whose line-of-sight was aligned with the wind direction, and by a reference sensor (sonic anemometer) located in the same direction, were used. The spectral transfer function, which describes the attenuation of the power spectral density of the wind speed turbulence, was calculated and found to be in good agreement with the theoretical exponential function, which is based on the properties of the probe volume of a focused Gaussian laser beam. Parameters such as fluctuations of the wind direction, as well as the overestimation of the laser Doppler spectrum threshold, were found to affect the calculation of the spectral transfer function by introducing high frequency noise. PMID:22462910

We present a scheme for stabilizing multiple lasers at wavelengths between 795 and 866 nm to the same atomic reference line. A reference laser at 852 nm is stabilized to the Cs D2 line using a Doppler-free frequency modulation technique. Through transfer cavities, four lasers are stabilized to the relevant atomic transitions in 40Ca+. The rms linewidth of a transfer-locked laser is measured to be 123 kHz with respect to an independent atomic reference, the Rb D1 line. This stability is confirmed by the comparison of an excitation spectrum of a single 40Ca+ ion to an eight-level Bloch equation model. The measured Allan variance of 10^(-22) at 10 s demonstrates a high degree of stability for time scales up to 100 s.

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generates mid-IR at 3 ?m with a power of ?2.5 ?W and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm-1) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm-1 (3.0345 ?m) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm·m was estimated.   

A large ac Stark effect has been observed when nitric oxide, at low pressure in a long optical path (100 m) Herriot cell, is subjected to infrared radiation from a rapidly swept, continuous wave infrared quantum cascade laser. As the frequency sweep rate of the laser is increased, an emission signal induced by rapid passage occurs after the laser frequency has passed through the resonance of 1-0 R(11.5)(3/2 /)molecular absorption line. At very high sweep rates a laser field-induced splitting of the absorptive part of the signal is observed, due to the ac Stark effect. This splitting is related to the Autler-Townes mixing of the e, f lambda doublet components of the 1-0 R(11.5)(3/2) transition, which lie under the Doppler broadened envelope. PMID:22583241

The level population of a beam of relativistic positive ions with Z greater than or equal to 2 having a single bound electron may be inverted by the application of a ''..pi.. pulse'' of laser radiation tuned to the Doppler shifted 1s-2p transition. When the laser beam and ion beam move in opposite directions the required laser frequency is reduced by a factor 2..gamma... Subsequently applied short wavelength resonant radiation moving in the same direction as the ion beam (with an inverted population) will be amplified via stimulated emission, the wavelength in the lab frame now being shorter than the original laser wavelength by a factor (2..gamma..)/sup 2/. 7 refs.

Tunable, high precision gamma-ray sources are under development to enable nuclear photonics, an emerging field of research. This paper focuses on the technological and theoretical challenges related to precision Compton scattering gamma-ray sources. In this scheme, incident laser photons are scattered and Doppler upshifted by a high brightness electron beam to generate tunable and highly collimated gamma-ray pulses. The electron and laser beam parameters can be optimized to achieve the spectral brightness and narrow bandwidth required by nuclear photonics applications. A description of the design of the next generation precision gamma-ray source currently under construction at Lawrence Livermore National Laboratory is presented, along with the underlying motivations. Within this context, high-gradient X-band technology, used in conjunction with fiber-based photocathode drive laser and diode pumped solid-state interaction laser technologies, will be shown to offer optimal performance for high gamma-ray spectral flux, narrow bandwidth applications.