Velocities V1 Research Articles

Impact of fractional magnetohydrodynamic and hall current on ree-eyring fluid flow by using radial basis function method

In the present work, an analysis has been arranged to study the Magnetohydrodynamic of Ree-Eyring fluid with the effect of Hall current between two parallel plates. Initially, both plates are at rest then suddenly plates are bought to steady velocities v0 and v1 at y=0 and y=d respectively. The governing problem is converted to the fractional partial differential equation and then numerically solved by using the radial basis functions collocation scheme. The Crank-Nicolson scheme is applied for the discretization of space derivatives. The numerical computation is performed for 0≤α≤1,0≤m≤1,0≤β≤1. The performance of the method is investigated with the help of tabulated results. The obtained results show the efficiency of the method for different parameters. The numerical results are compared for different fractional orders, and it is concluded that decreasing the fractional order increases the velocity which enhances the flow. Results are tabulated for different time levels, and it is concluded that method produces smooth solution for increasing values of T. Time fractional derivatives play a significant role in understanding non-Newtonian fluids and complex flow behaviors. They accurately model resistance forces in fluid flow, particularly in systems with non-standard behavior. This allows for a more detailed analysis of transient phenomena, providing valuable insights into fluid behavior over time. Ultimately, the use of time fractional derivatives enhances our capacity to describe and predict fluid flow in various practical applications such as physiology, biomedicine, and engineering.

How Laser Typesetting-Printing is Proofing that Light Photons Leading Edge Speeds have First Origin Dependant Velocities V2.3

Albert Einstein postulated a new science based on the assumption of the universal constancy of light-speed, wherein no variation of photon light speed can be rationalized from any form-variations of his special selected theoretic limited observations selections of trains and elevators! He called this new science: Special Relativity Theory, S.R.T

Optical analogue between relativistic Thomas effect in special relativity and phase response of the photonic integrated circuits-based all-pass filter

ABSTRACTWe report a link (or optical analogue) between the relativistic Thomas rotation angle effect found in the special theory of relativity (STR), and the phase response of an all-pass filter (APF), one of the building blocks of the rapidly evolving field of photonic integrated circuits. This link opens up the possibility of investigating STR phenomena in a ‘laboratory-on-a-chip’ setting. The Thomas effect is a spatial rotation of the reference frame due to Einstein’s velocity addition law of two successive velocities travelling in non-collinear directions. On the other hand, the APF is implemented with a microring resonator device with one waveguide bus. The analogue is established by associating two parameters. First, the transmission coupling coefficient τ of the APF is made to equal with the product of the two relativistic normalized velocities V1 and V2 (τ = V1V2), where the normalized velocities V1 = tanh [β1/2] and V2 = tanh [β2/2] with β1 (=tanh−1 (v1/c)) and β2 (=tanh−1 (v2/c)) being the rapidity values associated with the standard normalized speed. Second, the single-pass phase shift φ (or equivalently the phase detuning, Δφ or wavelength detuning, Δλ) parameter of the APF is related to the so-called generating angle θ of the two non-collinear relativistic velocities V1 and V2. We also introduce an additional photonic circuit to convert this phase-encoded Thomas angle into intensity for direct measurement. Lastly, other important and broader consequences of this link are briefly discussed.

Photometric and spectral observations of two W UMa stars with periods of one third of a day

Photometric and spectral observations of the W UMa binaries NSVS 254037 and V505 Lac with periods of around 8 hr are presented. The simultaneous light curve and radial velocity curve solutions revealed that their components are of G spectral type. The two targets undergo partial eclipses. They both have overcontact configurations of W subtype with fill‐out factor f ∼ 0.1. The derived parameters of NSVS 254037 are: mass ratio q = 2.42; orbital inclination i = 67.1°; temperatures T1 = 5800 K and T2 = 5585 K; masses M1 = 0.47 M⊙ and M2 = 1.15 M⊙; radii R1 = 0.72 R⊙ and R2 = 1.07 R⊙; luminosities L1 = 0.53 L⊙ and L2 = 1.0 L⊙; equatorial velocities V1 = 89 km−1 and V2 = 146 km−1; and distance d = 175 pc, almost the same as those of GAIA(DR2). The derived parameters of V505 Lac are: mass ratio q = 2.53; orbital inclination i = 57.30; temperatures T1 = 5,600 K and T2 = 5,166 K; masses M1 = 0.38 M⊙ and M2 = 0.97 M⊙; radii R1 = 0.69 R⊙ and R2 = 1.04 R⊙; luminosities L1 = 0.41 L⊙ and L2 = 0.68 L⊙; equatorial velocities V1 = 106 km−1 and V2 = 129 km−1; and distance d = 117 pc, smaller than those of GAIA by 19%. Thus, NSVS 254037 and V505 Lac turned out similar not only in periods and magnitudes but also in mass ratios, radii, and fill‐out factors.

Determination of the Reactivity of a Reactor Upon Insertion of Absorbing Rods

A method of measuring the subcriticality of a reactor, according to which the reactor is transferred from a critical into a subcritical state twice by moving control rods with different velocities V 1 and V 2, is substantiated. A correction to the indications of a reactivity meter for the spatial effect of reactivity is calculated according to detector signals which are recorded with each movement. The correction calculation does not require neutron-physical calculations. As an example this method is applied to water-moderated and -cooled reactors.

Stick-slip vs. smooth sliding in the multicontact interface

The stick-slip and smooth sliding regimes of motion for the multicontact frictional interface are studied within the earthquake-like model. It is shown that the stick-slip appears when two necessary conditions are fulfilled: first, the system must be soft enough for the elastic instability to emerge, and second, it must be ageing of the interface. The stick-slip exists only for an interval of sliding velocities v1 < vd < v2, where both boundary velocities v1,2 are determined by the ageing rate.

Effect of dissolved oxygen on swimming ability and physiological response to swimming fatigue of whiteleg shrimp (Litopenaeus vannamei)

The swimming endurance of whiteleg shrimp (Litopenaeus vannamei, 87.66 mm ± 0.25 mm, 7.73 g ± 0.06 g) was examined at various concentrations of dissolved oxygen (DO, 1.9, 3.8, 6.8 and 13.6 mg L−1) in a swimming channel against one of the five flow velocities (v 1, v 2, v 3, v 4 and v 5). Metabolite contents in the plasma, hepatopancreas and pleopods muscle of the shrimp were quantified before and after swimming fatigue. The results revealed that the swimming speed and DO concentration were significant factors that affected the swimming endurance of L. vannamei. The relationship between swimming endurance and swimming speed at various DO concentrations can be described by the power model (ν·t b = a). The relationship between DO concentration (mg L−1) and the swimming ability index (SAI), defined as SAI = ∫ 0 9000 vdt, can be described as SAI = 27.947 DO0.137(R 2 = 0.9312). The level of DO concentration directly affected the physiology of shrimp, and exposure to low concentrations of DO led to the increases in lactate and energetic substrate content in the shrimp. In responding to the low DO concentration at 1.9 mg L−1 and the swimming stress, L. vannamei exhibited a mix of aerobic and anaerobic metabolism to satisfy the energetic demand, mainly characterized by the utilization of total protein and glycogen and the production of lactate and glucose. Fatigue from swimming led to severe loss of plasma triglyceride at v 1, v 2, and v 3 with 1.9 mg L−1 DO, and at v 1 with 3.8, 6.8 and 13.6 mg L−1 DO, whereas the plasma glucose content increased significantly at v 3, v 4 and v 5 with 3.8 and 6.8 mg L−1 DO, and at v 5 with 13.6 mg L−1 DO. The plasma total protein and hepatopancreas glycogen were highly depleted in shrimp by swimming fatigue at various DO concentrations, whereas the plasma lactate accumulated at high levels after swimming fatigue at different velocities. These results were of particular value to understanding the locomotory ability of whiteleg shrimp and its physiological changes, further contributing to the improvement of capture and rearing technique.

Positive and negative work during walking in children with cerebral palsy

Introduction:Walking velocity (WV) is known to influence different gait parameters [1,2]. Muscle length (ML) and especially lengthening velocity (MLV) increase with WV. Spasticity on the otherhand is associatedwith reducedMLandMLV [1]. Spasticmuscles show an increased coupling between EMG activity and MLV [3]. Therefore, we described the effect of walking speed on spastic hamstrings, with a focus on ML, MLV and EMG. Patients/materials and methods: 49 Children with CP (9.8±3 years)with aModified Ashworth Score≥1.5 for the hamstrings and 14 TD children (10.5±2.4 years) received a 3D lower limb gait analysis, including kinematics, kinetics (8 camera Vicon system), EMG of 8 muscles bilateral (Cometa, Wave EMG) and a clinical examination. They were instructed to walk at self-selected speed, faster and as fast as possible without running. To compare both groups, a linear regression model was created which resulted in two nondimensional gait velocities (v1, v2), used to compare a large set of parameters. Difference scores (DS) between both velocities were calculated. Statistical analysis was done using the Mann-Whitney U test. Results: During stance at both velocities, the CP group showed more knee flexion at IC (p<0.001) and duringmid stance (p<0.01), increasing with WV. The knee ROM during shock absorption was higher in the TD group. EMG activity in early stance phase was significantly higher in the CP group at v2 (p<0.05), corresponding to an increasing maximum hip moment (H1) in CP children, which was not seen in the TD group (DS: p=0.001). During swing, the maximum angular extension velocity was significantly higher in the TD group compared to the CP group at v1 and v2 (p<0.005), increasing with WV. Maximum MLV showed similar results, with a significant DS (p<0.005) indicating a higher increase in the TD group. No difference was seen in the maximum ML between both groups,while total range ofMLwas significantly higher in TD group at both speeds, with increasing length range at higher WV. EMG activity in swing showed significantly higher activity at v1 for the CP group, but not at v2. Discussion and conclusions: The effect of WV on knee kinematics at IC and mid stance are in accordance to Schwartz [2] and similar for TD and CP children. The increasing hamstrings activity in CP in early stance may be explained by the biomechanical demands (hip moment). In contrast with TD children who mainly use the gastrocnemius at late stance (push-off) to increase WV. In swing, TD children are capable of increasing their angular velocity and MLV more than children with CP. Van der Krogt [1] reported similar results. This confirms the fact that, although CP children are able to increase their MLV, they prefer to stay under their spastic threshold velocity during self-selectedWV. The TD group increases their EMG swing phase activity similar as CP children. This can be explained by a higher angular velocity due to the increased WV, demanding more eccentric contraction of the hamstrings to slow down knee extension motion. The difference in influence of WV on spastic hamstrings compared to TD children seems to be most pronounced on MLV, and less on EMG activity. Compared to the influence of WV on the spastic gastrocnemius, the latter showed an increase in EMG activity in swing, which was not seen in the TD group [4].

Interaction between walking speed and spasticity in children with spastic hamstrings

Introduction:Walking velocity (WV) is known to influence different gait parameters [1,2]. Muscle length (ML) and especially lengthening velocity (MLV) increase with WV. Spasticity on the otherhand is associatedwith reducedMLandMLV [1]. Spasticmuscles show an increased coupling between EMG activity and MLV [3]. Therefore, we described the effect of walking speed on spastic hamstrings, with a focus on ML, MLV and EMG. Patients/materials and methods: 49 Children with CP (9.8±3 years)with aModified Ashworth Score≥1.5 for the hamstrings and 14 TD children (10.5±2.4 years) received a 3D lower limb gait analysis, including kinematics, kinetics (8 camera Vicon system), EMG of 8 muscles bilateral (Cometa, Wave EMG) and a clinical examination. They were instructed to walk at self-selected speed, faster and as fast as possible without running. To compare both groups, a linear regression model was created which resulted in two nondimensional gait velocities (v1, v2), used to compare a large set of parameters. Difference scores (DS) between both velocities were calculated. Statistical analysis was done using the Mann-Whitney U test. Results: During stance at both velocities, the CP group showed more knee flexion at IC (p<0.001) and duringmid stance (p<0.01), increasing with WV. The knee ROM during shock absorption was higher in the TD group. EMG activity in early stance phase was significantly higher in the CP group at v2 (p<0.05), corresponding to an increasing maximum hip moment (H1) in CP children, which was not seen in the TD group (DS: p=0.001). During swing, the maximum angular extension velocity was significantly higher in the TD group compared to the CP group at v1 and v2 (p<0.005), increasing with WV. Maximum MLV showed similar results, with a significant DS (p<0.005) indicating a higher increase in the TD group. No difference was seen in the maximum ML between both groups,while total range ofMLwas significantly higher in TD group at both speeds, with increasing length range at higher WV. EMG activity in swing showed significantly higher activity at v1 for the CP group, but not at v2. Discussion and conclusions: The effect of WV on knee kinematics at IC and mid stance are in accordance to Schwartz [2] and similar for TD and CP children. The increasing hamstrings activity in CP in early stance may be explained by the biomechanical demands (hip moment). In contrast with TD children who mainly use the gastrocnemius at late stance (push-off) to increase WV. In swing, TD children are capable of increasing their angular velocity and MLV more than children with CP. Van der Krogt [1] reported similar results. This confirms the fact that, although CP children are able to increase their MLV, they prefer to stay under their spastic threshold velocity during self-selectedWV. The TD group increases their EMG swing phase activity similar as CP children. This can be explained by a higher angular velocity due to the increased WV, demanding more eccentric contraction of the hamstrings to slow down knee extension motion. The difference in influence of WV on spastic hamstrings compared to TD children seems to be most pronounced on MLV, and less on EMG activity. Compared to the influence of WV on the spastic gastrocnemius, the latter showed an increase in EMG activity in swing, which was not seen in the TD group [4].

Behaviour of ultrasonic velocities and elastic constants in Ag-Zn alloys

The ultrasonic properties of the hexagonal closed packed structured Ag-Zn alloys have been studied at room temperature for their characterization. For the investigations of ultrasonic properties, I have also computed second order elastic constants using Lennard–Jones Potential. The velocities V1 and V2 have minima and maxima respectively with 45 0 with unique axis of the crystal, while V3 increases with the angle from unique axis. The inconsistent behaviour of angle dependent velocities is associated to the action of second order elastic constants. Debye average sound velocities of these alloys are increasing with the angle and has maximum at 550 with unique axis at room temperature. Hence when a sound wave travels at 55 0 with unique axis of these alloys, then the average sound velocity is found to be maximum. Ag0.2Zn0.8 alloy is more suitable for industrial and other uses, as it having highest elastic constants and lowest attenuation in comparison to other Ag-Zn samples. The mechanical and ultrasonic properties of these alloys will not be better than pure Ag and Zn due to their low SOEC and high ultrasonic attenuation. Achieved results have been discussed and compared with available experimental and theoretical results.

Acoustic wave propagation in Ni3 R (R = Mo, Nb, Ta) compounds

The ultrasonic properties of the hexagonal closed packed structured Ni3Mo, Ni3Nb and Ni3Ta compounds were studied at room temperature for their characterization. For the investigations of ultrasonic properties, the second-order elastic constants using Lennard–Jones potential were computed. The velocities V 1 and V 2 have minima and maxima respectively at 45° with the unique axis of the crystal, while V 3 increases with respect to angle with the unique axis of the crystal. The inconsistent behaviour of angle-dependent velocities is associated with the action of second-order elastic constants. Debye average sound velocities of these compounds increase with the angle and has maximum at 55° with the unique axis at room temperature. Hence, when a sound wave travels at 55° with the unique axis of these materials, the average sound velocity is found to be maximum. The results achieved are discussed and compared with the available experimental and theoretical results.

INELASTIC COLLISION OF KINKS AND ANTIKINKS IN THE ϕ6 SYSTEM

In this paper, we study the kink–antikink interaction in the ϕ6 system. This system has soliton-like solutions which fall into two categories with opposite topological charges. We consider the interaction of a kink solution with an antikink at different incident energies (velocities) and observe the outcome. In general, the collision is inelastic. There are two critical velocities v1 and v2 in the system, between which there are enormous number of narrow scattering windows. We study the fractal-like structure of the windows. Below v1 the pair are absorbed into each other. Above v1 the pair get separated after the inelastic interaction. Finally, we obtain the internal modes of the kink in this system and address its relevance to the interaction behavior.

Stationary Distribution of Random Motion with Delay in Reflecting Boundaries

In this paper we study a continuous time random walk in the line with two boundaries [a,b], a < b. The particle can move in any of two directions with different velocities v1 and v2. We consider a special type of boundary which can trap the particle for a random time. We found closed-form expressions for the stationary distribution of the position of the particle not only for the alternating Markov process but also for a broad class of semi-Markov processes.

Assessment of natural resources of thermal aquifers — formulation, test data, results

A method is worked out for the assessment of natural (dynamic) resources Qd of relatively small thermal deposits representing drainage zone of a hydrothermal system. The hydrogeological conditions in such a system are schematized by a vertical circular aquifer with impermeable lateral boundary and permeable upper and lower boundaries with surface Fd (fig. 1). The lower surface of the area is influenced by uniformly distributed constant recharge Qd coming from the depth. Qd is drained over the upper surface by natural springs and/or by existing flowing wells. Some part of recharge Qd stay hidden because of its distribution as a small quantities in different parts of the aquifer and/or because of the leakage trough the materials of the river terrace, where the drainage zone normally is located. Because of this hidden part of the natural resource the total quantity of Qd remains unknown. For determining its value a pumping test is carried out with two constant discharges Q1 and Q2. The pumping well or wells has to be located approximately in the middle of the aquifer. Each one of the two discharges must be greater than the total recharge Qd. Under such condition the velocity of drawdoun of piezometric level in one observation well becomes constant after some time elapsed from the start of the pumping. The values of these constant velocities v1 and v2 are functions of the pumping rate. The value of Qd is determined according to formulas (8) and (9). In the paper are given some complimentary explanations for application of the methodology including an example of determining the natural resources of one thermal deposit.

118 CRYOPRESERVATION OF CONVENTIONAL AND SEX-SORTED BULL SPERM USING A DIRECTIONAL FREEZING METHOD

The objective of this study was to find an optimal parameter (liquid-ice interface velocity; velocity) of the directional freezing method (Arav et al. 2002 Reprod. Nutr. Dev. 42, 583–586) for conventionally processed bull sperm stored in 0.5-mL straws. We also evaluated sex-sorted bull sperm frozen using this method. Experiment 1: Each single ejaculate from two Holstein bulls was split and processed in egg yolk citrate extender (2 steps, 6% glycerol final; EYC) or egg yolk Tris extender (1 step, 7% glycerol final; EYT1). After cooling and loading in 0.5-mL plastic straws, each batch of semen was frozen using a directional 0.5-mL straw freezer (MTG 550; IMT, Ltd., Ness-Ziona, Israel) in 6 different velocities (v2.0, v2.2, v2.4, v2.6, v2.8, v3.0; mm s-1). Ice seeding time was 45 s. Static freezing in liquid nitrogen vapor was used as the control. Sperm parameters were measured using computer-assisted semen analysis (CASA) at 0, 1, and 2 h after thawing. The thawed samples were also evaluated for sperm viability and acrosomal integrity by triple staining. The experiment was repeated 3 times. Data were analyzed by ANOVA. No significant differences in general and progressive motility were observed in each extender regardless of the freezing method. However, sperm viability and acrosomal integrity of sperm frozen in EYC were highest at v3.0 (73.2% and 84.7%, respectively) and were generally higher after MTG freezing (63.4 to 73.2% and 80.6 to 84.7%, respectively) than in the control (52.6% and 73.1%, respectively; P &amp;lt; 0.05 or 0.01) except for v2.4 (54.5% and 70.8%). Sperm viability (74.6 to 77.9% vs. 63.2%) and acrosomal integrity (84.8 to 88.9% vs. 79.3%) in EYT after MTG freezing were also higher than in the control (P &amp;lt; 0.01). Experiment 2: Two single ejaculates from a Holstein bull were flow cytometrically sex-sorted (Schenk et al. 1999 Theriogenology 52, 1375–1391) for X sperm. Each ejaculate was assigned to processing in EYC or egg yolk Tris extender (2 steps, 6% glycerol final; EYT2). Processed sperm was frozen using MTG 550 (velocity set at v3.0) or in liquid nitrogen vapor as control and analyzed as in Experiment 1. In the control, general (40.2% vs. 21.1%; P &amp;lt; 0.01) and progressive (16.3% vs. 4.3%; P &amp;lt; 0.05) motility in EYC were higher than in EYT2, respectively, at 0 h. In MTG freezing, motility (at 0 h, 42.0% vs. 28.3%; P &amp;lt; 0.05), viability (60.5% vs. 40.8%; P &amp;lt; 0.01), and acrosomal integrity (86.9% vs. 71.0%; P &amp;lt; 0.05) in EYC were higher than in EYT2, respectively. But in experiment 2, there were no differences in motility, progressive motility, viability, and acrosomal integrity between MTG freezing and control. The above results suggest that MTG freezing improves membrane and acrosomal quality of bull sperm frozen in 0.5-mL straws. Faster interface velocity (3.0 mm s-1) seems optimal for the given condition. Egg yolk citrate extender seems to be beneficial for MTG freezing of sex-sorted bull sperm, but further studies using ejaculates from different bulls are required to confirm the apparent benefit.

Spectroscopic and Photometric Observations of the Short-Period RS CVn-Type Star UV Piscium

High-resolution spectroscopic observations around the Hα line and BVRI photometry from 1993 to 2003 of the eclipsing short-period RS CVn star BH Vir are presented. The simultaneous solution of our radial velocity curves and light curves yielded the following values for global parameters of the components: M1 = 1.173 ± 0.006 M� ; M2 = 1.046 ± 0.005 M� ; R1 = 1.22 ± 0.05 R� ; R2 = 1.11 ± 0.04 R� ;i = 87.5 ◦ ± 0.8 ◦ . The measured rotational broadening of the spectral lines corresponds to equatorial velocities V1 = 79.8 km s −1 and V2 = 68.4 km s −1 . Our data reveal considerable Hα emission excess of the two stellar components. We modelled the photometric data to find the size and location of the starspots for each year. The established decreasing trend of the spot latitudes may indicate a latitudinal cycle of at least a decade.

On advection and diffusion in the mesosphere and lower thermosphere: The role of rotational fluxes

A formalism to describe the advective and diffusive eddy transport in terms of the mean tracer is presented. It is based on Eulerian averaging, the flux‐gradient relation, and the decomposition of the eddy flux of a tracer into advective, diffusive, and rotational components. The rotational (nondivergent) flux arises because the conservation equation for the mean tracer contains only a divergence of the eddy flux of the tracer. To provide a closure, a modification to the flux separation technique based on the eddy variance equation is introduced. The “eddy‐induced” advective velocity is represented as the sum of two velocities v1 and v2. Velocity v1 is similar to that in the Transformed Eulerian Mean (TEM) formulation but is generalized to account for both horizontal and vertical eddy fluxes and mean gradients. The velocity v2 depends on the flux of eddy variance of the tracer. The diffusion coefficient is represented as a sum of K1, which may serve as a diagnostic of an irreversible mixing, and K2, which describes up‐ or down‐gradient eddy fluxes of the tracer due to local transformations of the eddy variance. Both v2 and K2 arise from taking account of the rotational fluxes. The scheme is applied to output from a global circulation model of the middle atmosphere. It is shown that in the meridional plane the correction v2 to the TEM velocity is small in the mesosphere and lower thermosphere. For the diffusion coefficient, however, the correction K2 must be accounted for above approximately 110 km.

Spectroscopic monitoring of the jet in the symbiotic star MWC 560

We present the results of an intensive monitoring program of the jet absorptions in the symbiotic system MWC 560, obtained with the FEROS echelle spectrograph at the ESO 1.5 m Telescope. MWC 560 is a unique jet source because the line of sight lies practically parallel to the jet axis so that the outflowing gas is seen as absorption in the continuum of the accreting object, in the emission line spectrum of the accretion disk and temporary also in the spectrum of the red giant companion. Highly variable, blue-shifted jet absorption components, due to H i ,H ei ,N ai ,C aii and Fe ii are observed, which are detached from the undisplaced, narrow emission line components. The allowed emission lines from neutral and singly ionized heavy elements vary simultaneously with the strongly variable continuum emission. Therefore they can be attributed to the irradiated (chromospheric) layers of the neutral part of the accretion disk. The fluxes of forbidden emission lines are practically constant because they originate in a much larger volume. The structure and variability of the jet absorptions indicate the presence of three distinct outflow regions along the jet axis: i. An initial acceleration region above the disk with low velocities <600 km s 1 which covers only partly the central continuum source; ii. A highly variable outflow region covering the continuum source and up to about half of the line emission from the disk. This region shows repeatedly high velocity components1800 2500 km s 1 which are decelerated to <1500 km s 1 within one to a few days. The appearance of high velocity components is anti-correlated and therefore closely related to the low velocity absorptions of region i. The life time of the high velocity components suggests that region ii extends to about one to a few AU from the jet source; iii. A steady flow at an intermediate velocity of900 1300 km s 1 at a distance of the order 10 AU from the jet source. This component covers the hot continuum source and the entire narrow line region of the accretion disk. At the beginning of our campaign region iii covers also the extended red giant companion with two absorption components at 1250 km s 1 and 1140 km s 1 ,w hich can be considered as terminal velocities v1 of the jet outflow. The components disappear during the following several weeks as expected for the end of an occultation phase of the red giant by the collimated jet occuring probably regularly once per binary orbit. Several fast moving (1300 1700 km s 1 ), narrow absorptions are present in the Ca ii resonance lines. The high speed, low column density, and the long life time (months) suggest that these are radiative bow shocks in the jet cocoon generated by the collision of the transient high velocity components with slower moving jet material. A geometric model for the jet outflow in MWC 560 is presented. System parameters are derived based on our spectroscopic data and previous studies. Beside other parameters a binary separation of the order 4 AU, a jet inclination of <16, a mass accretion rate of 5 10 7 M yr 1 and a jet outflow rate larger than 7 10 9 M yr 1 are derived.

Elastic wave velocities of granite at experimental simulated partial melting conditions

Laboratory investigations of ultrasonic wave velocities in granite samples from the Saxonian Erzgebirge were carried out under simulated in situ conditions. Using a gas pressure vessel with internal heating a method was developed to measure elastic wave velocities vp and v2 up to 1,000°C. In the case of a sample from the Kirchberg massiv (Erzgebirge) the velocity decrease with increasing temperature becomes extreme nonlinear at temperatures higher than 700°C. The influence on shear wave velocity is larger than on compressional wave velocity. Thermal cracking as a result of differential thermal expansion of the constituent minerals, the α-β transition of quartz and melting are discussed as possible reasons for this phenomenon. Thin sections of the sample after being subjected to temperatures of 750°C and 800°C and a pressure of 500 MPa show melt margins at grain boundaries. This fact and the temperature dependence of Poisson's ratio at 500 MPa support the conclusion that the velocity drop at temperatures above 700°C is mainly caused by partial melting.

Pressure gradients across bileaflet aortic valves by direct measurement and echocardiography

Pressure gradients calculated from echo-cardiography after aortic valve replacement are commonly much higher than would be expected from in vitro measurements. The mean, peak-to-peak, and maximal gradients across bileaflet aortic prostheses (St. Jude Medical) were measured invasively in 52 patients at high and low heart rate, cardiac index, and stroke volume. One week after operation the gradients were calculated from a standard transthoracic echocardiogram (delta p = 4v2(2)). In a second study 3 to 12 months later, gradients were calculated using the standard, simplified Bernoulli equation, and with the equation considering subvalvular flow velocities (delta p = 4(v2(2-)v1(2)). Invasive and echocardiographic measurements were matched and compared. Invasively measured mean gradients for 21 to 29-mm valves ranged from 7.4 +/- 4.9 to 4.3 +/- 1.6 mm Hg at systolic flow rates from 11.3 +/- 0.7 to 16.2 +/- 1.8 L.min-1.m-2. Mean echocardiographic gradients were 15.1 +/- 4.5 to 7.5 +/- 2.2 mm Hg (p < 0.001) with the standard method, and 10.5 +/- 1.9 to 5.6 +/- 1.5 mm Hg when considering the subvalvular flow velocity (p < 0.001). Mean gradients across bileaflet prostheses are generally low, even in small valves and with high systolic flow. The correlation of the invasive in vivo with in vitro gradients is good. Standard echocardiography overestimates gradients across bileaflet heart valves and high gradients are not due to valve dysfunction. Gradients obtained by echocardiography considering the subvalvular flow velocity correlate better to invasively measured and in vitro gradients.