Secondary data analysis investigating effects of marine omega-3 fatty acids on circulating levels of leptin and adiponectin in older adults.

BACKGROUND: Higher leptin and lower adiponectin levels have been linked to progressing systemic inflammation and diseases of aging. Among older adults with obesity and an inflammatory conditions, we quantified effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation on leptin, adiponectin, and the leptin-to-adiponectin ratio (LAR). We also examined associations among adipokine and cytokine levels. METHODS: Using a randomized, double-blind, placebo-controlled design, participants (mean age 61.3 ± 2.1) received 1.5 g EPA + 1.0 g DHA (n = 14) or mineral oil (n = 18) daily. Plasma adipokine and cytokine levels were quantified by electrochemiluminescence at all study intervals. RESULTS: While no between-group differences were detected, there was a reduction in the LAR (by 23%, p=.065) between weeks 4 and 8 among the EPA+DHA group. Adiponectin levels were negatively associated with IL-1ß levels at week 4 (p=.02) and TNF-α levels at week 8 (p=.03). CONCLUSION: Potential benefits of EPA+DHA supplementation among aging populations warrant further study.

The application of quantitative oil streaking to the HeartQuest left ventricular assist device.

Methods of flow visualization using oil streaking are established techniques for investigating surface shear and near wall flow patterns. Recent studies have used an array of oil dots on a surface which form streaks when exposed to shear forces. This method is generally qualitative, but it is possible to make quantitative measurements of the shear if the oil streaks have been calibrated. This paper presents the application of a quantitative oil streak method to the HeartQuest left ventricular assist device (LVAD). An array of dots was applied to the top housing of the pump, yielding quantitative values for the shear and qualitative patterns of the near wall flow in that region. The results were used to locate regions likely to promote thrombosis, such as stagnation points or recirculation regions. Regions of high shear, where hemolysis might occur, also can be identified with this method. In addition to being an important design technique, quantitative oil streaking assisted in the verification of computational fluid dynamics results within the HeartQuest LVAD.

Particle image velocimetry measurements of blood velocity in a continuous flow ventricular assist device.

The third prototype of a continuous flow ventricular assist device (CFVAD3) is being developed and tested for implantation in humans. The blood in the pump flows through a fully shrouded four-bladed impeller (supported by magnetic bearings) and through small clearance regions on either side of the impeller. Measurements of velocities using particle image velocimetry of a fluid with the same viscosity as blood have been made in one of these clearance regions. Particle image velocimetry is a technique that measures the instantaneous velocity field within an illuminated plane of the fluid field by scattering light from particles added to the fluid. These measurements have been used to improve understanding of the fluid dynamics within these critical regions, which are possible locations of both high shear and stagnation, both of which are to be avoided in a blood pump. Computational models of the pump exist and these models are currently being used to aid in the design of future prototypes. Among other things, these models are used to predict the potential for hemolysis and thrombosis. Measurements of steady flow at two operating speeds and flow rates are presented. The measurements are compared with the computed solutions to validate and refine, where necessary, the existing computational models.

Numerical studies of blood shear and washing in a continuous flow ventricular assist device.

The third prototype of a continuous flow ventricular assist device (CF3) is being developed and tested for implantation in humans. The blood in the pump flows through a fully shrouded four bladed impeller (supported by magnetic bearings) and through small clearance regions on either side of the impeller. Computational fluid dynamics (CFD) solutions for this flow have been obtained by using TascFlow, a software package available from AEA Technology, UK. These flow solutions have been used to estimate the shear stresses on the blood in the pump and, hence, to minimize hemolysis. In addition, the solutions are informative for achieving a design that will provide good washing of the blood to minimize the possibility of stagnation points that can lead to thrombosis. This study presents numerical studies of these phenomena in the CF3. The calculated shear rate results are compared with values published in the open literature. The comparisons indicate that hemolysis will not be a problem with CF3, which is in agreement with preliminary experimental measurements. Flow studies are being conducted to determine the optimal size of the clearance regions.

Numerical solution for blood flow in a centrifugal ventricular assist device.

A very small centrifugal pump, fully supported by magnetic bearings, is being developed for use as a ventricular assist device to be implanted in humans. In this paper, we apply computational fluid dynamics to model the blood flow to aid in the design of the ventricular assist device. The flow of blood through the pump has been modeled using computational fluid dynamics (CFD) software that is commercially available from AEA Technology, UK. The flow regions modeled in version 3 of the Continuous Flow Ventricular Assist Device (CF3) are the fully shrouded four bladed impeller and the two clearance regions around the impeller that are bounded by the pump hub and shroud. This paper describes the geometry and computational grids developed for the flow regions, and the equations of motion for the blood flow are developed. The overall numerically-evaluated flow rates and head rise have similar trends to the flow parameters experimentally measured, indicating that future pump designs can be effectively modeled numerically before being constructed and tested. Numerical solutions are presented and compared with experimentally-obtained overall pump performance results. These solutions are used to predict shear stress levels to be experienced by the blood flowing through the pump, and it is predicted that hemolysis will be insignificant. The solutions also indicate no regions of flow stagnation that can be a source of thrombosis in pumps. The calculations provide a viable design method to achieve improved efficiency in future versions of this pump.

Single-pulse, two-line temperature-measurement technique using KrF laser-induced O(2) fluorescence.

A new single-pulse, two-line laser-induced O(2) fluorescence (LIF) temperature-measurement technique was demonstrated. The fluorescence spectrum obtained with multichannel detection following simultaneous excitation of two coincident transitions in the 0-6 and the 2-7 bands of the B(3)Σ(-)(u)-X(3)Σ(-)(g) Schumann-Runge system was used to determine the gas temperature. The rms error of 100-pulse average LIF temperature measurements, referenced to their corresponding thermocouple measurements, was 1.3% over a temperature range of 1300-1800 K in atmospheric air. Photon shot noise was found to be the primary source of uncertainty for these measurements in a quiescent environment. Single-pulse temperature-measurement uncertainties (1 σ) ranged from approximately 13% at 1300 K to 7% at 1800 K.

Calibration source for OH laser-induced fluorescence-density measurements with thermally dissociated H2O in atmospheric air.

A calibration technique for OH laser-induced fluorescence (LIF) density measurements through the use of the thermal dissociation of ambient H(2)O in an atmospheric air furnace with a tunable KrF laser has been demonstrated. The stable and uniform concentration of OH produced in the furnace permits direct calibration of LIF signals without the uncertainties associated with reference flames. The presence of OH in atmospheric air that is heated to temperatures exceeding 1500 K is sufficient for LIF measurements with most OH LIF laser systems. The measured OH density is found to agree well with the computed OH chemical-equilibrium density over a temperature range of 1500-1850 K.

Surface temperature imaging below 300 K using La(2)O(2)S:Eu.

Surface temperature images obtained by the ratioing of visible (5)D(2) and (5)D(1), emissions from a La(2)O(2)S:Eu phosphor coating are demonstrated. The visible phosphor emissions permit imaging with standard CCD cameras. Temperature resolution to 1 K is achieved over a temperature range of 193-293 K.

Planar temperature measurement in compressible flows using laser-induced iodine fluorescence.

A laser-induced iodine fluorescence technique that is suitable for the planar measurement of temperature in cold nonreacting compressible air flows is investigated analytically and demonstrated in a known flow field. The technique is based on the temperature dependence of the broadband fluorescence from iodine excited by the 514-nm line of an argon-ion laser. Temperatures ranging from 165 to 245 K were measured in the calibration flow field. This technique makes complete, spatially resolved surveys of temperature practical in highly three-dimensional, low-temperature compressible flows.

Injectant mole-fraction imaging in compressible mixing flows using planar laser-induced iodine fluorescence.

A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions. The resulting images are, to our knowledge, the first quantitative planar measurements of mole-fraction distributions in a nonreacting compressible flow field and allow mixing to be studied directly.

Smith-Purcell radiation in the high conductivity and plasma frequency limits.

Radiation is calculated from currents produced by a nonrelativistic point charge that moves at a constant velocity above a conducting grating. Two different limits are considered. In the high conductivity limit, the surface charge is calculated from a nonretarded image charge, surface currents from the continuity equation, and the far field vector potential from the surface current. In the plasma frequency limit of the grating substrate a nonretarded electric potential is calculated from a two-region problem, bulk current from an interior potential, and the far field vector potential from the bulk current.

The nature of phonons and solitary waves in alpha-helical proteins.

A parametric study of the Davydov model of energy transduction in alpha-helical proteins is described. Previous investigations have shown that the Davydov model predicts that nonlinear interactions between phonons and amide-I excitations can stabilize the latter and produce a long-lived combined excitation (the so-called Davydov soliton), which propagates along the helix. The dynamics of this solitary wave are approximately those of solitons described using the nonlinear Schrödinger equation. The present study extends these previous investigations by analyzing the effect of helix length and nonlinear coupling efficiency on the phonon spectrum in short and medium length alpha-helical segments. The phonon energy accompanying amide-I excitation shows periodic variation in time with fluctuations that follow three different time scales. The phonon spectrum is highly dependent upon chain length but a majority of the energy remains localized in normal mode vibrations even in the long chain alpha-helices. Variation of the phonon-exciton coupling coefficient changes the amplitudes but not the frequencies of the phonon spectrum. The computed spectra contain frequencies ranging from 200 GHz to 6 THz, and as the chain length is increased, the long period oscillations increase in amplitude. The most important prediction of this study, however, is that the dynamics predicted by the numerical calculations have more in common with dynamics described by using the Frohlich polaron model than by using the Davydov soliton. Accordingly, the relevance of the Davydov soliton model was applied to energy transduction in alpha-helical proteins is questionable. We conclude that the Raman lines that have been assigned to solitons in E. coli are either associated with low frequency normal modes or are instrumental- or fluorescence-induced artifacts.

Temperature measurement in a compressible flow field using laser-induced iodine fluorescence.

The thermometric capability of a two-line fluorescence technique using iodine seed molecules in air is investigated analytically and verified experimentally in a known steady compressible flow field. Temperatures ranging from 165 to 295 K were measured in the flow field using two iodine transitions accessed with a 30-GHz dye-laser scan near 543 nm. The effect of pressure broadening on temperature measurement is evaluated.

Simultaneous multiple-point velocity measurements using laser-induced iodine fluorescence.

A technique is demonstrated for measuring velocity at multiple locations in a plane of a gaseous flowfield using Doppler-shifted absorption with fluorescence detection from iodine molecules, excited by a sheet of tunable single-axial-mode argon-ion laser radiation at 514.5 nm. Measurements were made simultaneously at 10,000 points in an iodine-seeded supersonic flowfield with a 100 x 100 element photodiode array camera and were found to agree well with a numerical solution for the velocity field. The accuracy with which a component of velocity can be measured is limited, in the current approach, by the iodine linewidth to about +/-5 m/sec.

Laser-induced fluorescence technique for velocity field measurements in subsonic gas flows.

A nonintrusive optical technique is reported for multiple-point velocity measurements in subsonic flows. The technique is based on the detection of fluorescence from a Doppler-shifted absorption line of seeded iodine molecules excited at a laser frequency fixed in the wing of the line. Counterpropagating laser sheets are used to illuminate the flow, in the present case a nitrogen round jet, thereby eliminating the need for an unshifted reference signal. The fluorescence is detected simultaneously at 10,000 points in a plane of the flow using a 100 x 100 element photodiode-array camera. The velocity at each point is computed from four successive camera frames, each recorded with a different beam direction. The measured mean velocities between 5 and 50 m/sec agree well with data from the literature.

High-resolution continuous-wave coherent anti-Stokes Raman spectroscopy in a supersonic jet.

We have obtained high-resolution cw coherent anti-Stokes Raman spectra of the nu(1) Q branch of methane in an underexpanded supersonic jet at temperatures as low as 31.5 K and pressures below 2 Torr.