Flow Amplitude Research Articles

Heat transfer characteristics of aluminum metal foam subjected to a pulsating/steady water flow: Experimental and numerical approach

The microminiaturization of electronic components has led to an increase in the heat dissipation rate (per unit area) of electronic chips. This paper presents the results of an experimental and numerical study of the use of aluminum foam as a heat sink for the Intel core i7 processor. The aluminum foam was subjected to a pulsating water flow with a frequency range between 0.04 and 0.1Hz, an amplitude range between 297 and 1353, and a heat flux range between 8.5 and 13.8W/cm2. The distributions of the cycle average local surface temperature over the heater representing the electronic surface and cycle average local Nusselt number were measured and compared with the numerical data obtained using the finite element method. The numerical results were in good agreement with the experimental data for different flow amplitudes and heat flux within a maximum relative error of 0.75% for the local temperature and 1.8% for the local Nusselt number. The pressure drop across the aluminum foam heat sink was measured and the effects of the dimensionless flow frequency and the flow amplitude on the heat transfer characteristics of the pulsating flow through the aluminum foam were analyzed. An empirical correlation of the average Nusselt number as a function of the dimensionless flow frequency and flow amplitude was developed. A comparison between the heat transfer characteristics of the steady and pulsating water flows was also conducted. The experimental results revealed that the cycle average local temperature decreases along with decreasing heat flux, increasing the pulsating flow frequency and amplitude. The local temperature distribution shows a convex profile due to the reversing flow and development of a boundary layer. Results also revealed a 14% increase in the average Nusselt number for pulsating flow when compared to the steady flow. Lastly, the thermal performance of the aluminum foam heat sink was evaluated. The experimental result revealed a 73% decrease in the uniformity index for pulsating flow when compared to the steady flow, indicating that the pulsating water flow leads to a more uniform temperature distribution. This finding is very important to the field of electronic cooling since the reliability of transistors and the operating speed are dependent upon temperature uniformity along the surface.

The meteorology of Gale Crater as determined from Rover Environmental Monitoring Station observations and numerical modeling. Part II: Interpretation

Numerical modeling results from the Mars Regional Atmospheric Modeling System are used to interpret the landed meteorological data from the Rover Environmental Monitoring Station onboard the Mars Science Laboratory rover Curiosity. In order to characterize seasonal changes throughout the Martian year, simulations are conducted at Ls 0, 90, 180 and 270. Two additional simulations at Ls 225 and 315 are explored to better understand the unique meteorological setting centered on Ls 270. The synergistic combination of model and observations reveals a complex meteorological environment within the crater. Seasonal planetary circulations, the thermal tide, slope flows along the topographic dichotomy, mesoscale waves, slope flows along the crater slopes and Mt. Sharp, and turbulent motions all interact in nonlinear ways to produce the observed weather. Ls 270 is shown to be an anomalous season when air within and outside the crater is well mixed by strong, flushing northerly flow and large amplitude, breaking mountain waves. At other seasons, the air in the crater is more isolated from the surrounding environment. The potential impact of the partially isolated crater air mass on the dust, water, noncondensable and methane cycles is also considered. In contrast to previous studies, the large amplitude diurnal pressure signal is attributed primarily to necessary hydrostatic adjustments associated with topography of different elevations, with contributions of less than 25% to the diurnal amplitude from the crater circulation itself. The crater circulation is shown to induce a suppressed boundary layer.

Stationary Zonal Flows during the Formation of the Edge Transport Barrier in the JET Tokamak.

High spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge Er. We observe fine-scale spatial structures in the edge Er well with a wave number krρi≈0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E×B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-mode transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.

THE SPECTRAL AMPLITUDE OF STELLAR CONVECTION AND ITS SCALING IN THE HIGH-RAYLEIGH-NUMBER REGIME

ABSTRACT Convection plays a central role in the dynamics of any stellar interior, and yet its operation remains largely hidden from direct observation. As a result, much of our understanding concerning stellar convection necessarily derives from theoretical and computational models. The Sun is, however, exceptional in that regard. The wealth of observational data afforded by its proximity provides a unique test bed for comparing convection models against observations. When such comparisons are carried out, surprising inconsistencies between those models and observations become apparent. Both photospheric and helioseismic measurements suggest that convection simulations may overestimate convective flow speeds on large spatial scales. Moreover, many solar convection simulations have difficulty reproducing the observed solar differential rotation owing to this apparent overestimation. We present a series of three-dimensional stellar convection simulations designed to examine how the amplitude and spectral distribution of convective flows are established within a star’s interior. While these simulations are nonmagnetic and nonrotating in nature, they demonstrate two robust phenomena. When run with sufficiently high Rayleigh number, the integrated kinetic energy of the convection becomes effectively independent of thermal diffusion, but the spectral distribution of that kinetic energy remains sensitive to both of these quantities. A simulation that has converged to a diffusion-independent value of kinetic energy will divide that energy between spatial scales such that low-wavenumber power is overestimated and high-wavenumber power is underestimated relative to a comparable system possessing higher Rayleigh number. We discuss the implications of these results in light of the current inconsistencies between models and observations.

A method to detect and characterize sub‐daily flow fluctuations

AbstractHydro peaking causes an important environmental impact on running water ecosystems. Many affected rivers have a poor ecological status. In rivers affected by hydro peaking, the flow conditions are highly complex and difficult to grasp. To develop a general framework for detecting and characterizing sub‐daily flow fluctuations, we analysed more than 500 Austrian hydrographs, covering the whole range from unimpacted to heavily impacted rivers. Different fluctuation types could be identified according to the potential source: e.g. sub‐daily flow fluctuations caused by hydro peaking, rainfall or snow and glacier melt. Additionally, the term ‘hydro fibrillation’ was established, to indicate frequently occurring artificial fluctuations with comparably low intensities. An automatic procedure was used to detect frequency and intensity of each flow fluctuation. Using variables based on duration curves of flow fluctuation rates (ramping rates), amplitudes, flow ratios, durations and daily numbers of fluctuations, a predictive model (linear discriminant analysis) was fitted to classify hydrographs into predominant fluctuation regimes. This is the basis for a detailed investigation of present sub‐daily flow regimes and to analyse the differences between the regimes. Based on the results, we finally propose a general framework that enables a standardized assessment of flow fluctuations regarding event intensities and/or event timing. The proposed framework offers a standardized selection of particular flow fluctuations referring to increase and decrease events separately. The selection of specific flow fluctuations can be defined with respect to several research questions (e.g. ecologically relevant fluctuations), which offers a wide range of applications. Copyright © 2015 John Wiley & Sons, Ltd.

Fabrication of a polyvinylidene difluoride fiber with a metal core and its application as directional air flow sensor

We fabricated a sensitive air flow detector that mimic the sensing mechanism found at the tail of some insects. [see Y. Yang, A. Klein, H. Bleckmann and C. Liu, Appl. Phys. Lett. 99(2) (2011); J. J. Heys, T. Gedeon, B. C. Knott and Y. Kim, J. Biomech. 41(5), 977 (2008); J. Tao and X. Yu, Smart Mat. Struct. 21(11) (2012)]. Our bionic airflow sensor uses a polyvinylidene difluoride (PVDF) microfiber with a molybdenum core which we produced with the hot extrusion tensile method. The surface of the fiber is partially coated with conductive silver adhesive that serve as surface electrodes. A third electrode, the metal core is used to polarize polyvinylidene difluoride (PVDF) under the surface electrodes. The cantilever beam structure of the prepared symmetric electrodes of metal core piezoelectric fiber (SMPF) is used as the artificial hair airflow sensor. The surface electrodes are used to measure output voltage. Our theoretical and experimental results show that the SMPF responds fast to air flow changes, the output charge has an exponential correlation with airflow velocity and a cosine relation with the direction of airflow. Our bionic airflow sensor with directional sensing ability can also measure air flow amplitude. [see H. Droogendijk, R. G. P. Sanders and G. J. M. Krijnen, New J. Phys. 15 (2013)]. By using two surface electrodes, our sensing circuit further improves sensitivity.

Las dos caras del reflejo venoarteriolar: vasoconstricción y vasodilatación cutánea al bajar y subir el brazo

The veno-arteriolar reflex (VAR) is triggered by an increase in the transmural venous pressure on placing a part of the body in the same direction as the gravitational acceleration below the heart. To assess the VAR in healthy subjects on raising a part of the body above the level of the heart. VAR was studied in 16 healthy subjects (20-65 years old) by means of changes in the blood flow in the skin detected using a digital infrared photoplethysmograph attached to the fingertip under the following conditions: right arm at the height of the heart, right arm below the heart and right arm below the level of the heart. The variables measured were: amplitude of the blood flow in the skin with the arm raised to the height of the heart (baseline amplitude), percentage decrease of the blood flow in the skin with the arm below the heart and percentage increase in blood flow with the arm above the heart. The percentage of vasoconstriction with the right arm below the heart was 35%, and that of vasodilation, 50%. Evaluation of the VAR with the arm below the heart causes vasoconstriction, and elevation of the arm causes an important degree of vasodilation. Vasoconstriction and vasodilation are maintained while the limb is kept above or below the heart. This is an economical and potentially very useful way of studying the innervation of the microcirculation in a number of different peripheral neuropathies of thin and mixed fibres.

Oscillatory Darcy Flow in Porous Media

We investigate the flow in a porous medium subjected to an oscillatory (sinusoidal) pressure gradient. Direct numerical simulation (DNS) has been performed to benchmark the analytical solutions of the unsteady Darcy equation with two different expressions of the time scale: one given by a consistent volume averaging of the Navier–Stokes equation with a steady-state closure for the flow-resistance term, another given by volume averaging of the kinetic energy equation with a closure for the dissipation rate. For small and medium frequencies, the analytical solutions with the time scale obtained by the energy approach compare well with the DNS results in terms of amplitude and phase lag. For large dimensionless frequencies (\(\omega \tau \gtrsim 10\)), we observe a slightly smaller damping of the amplitude than predicted by the unsteady Darcy equation with the low-frequency time scale. This can be explained by a change in the velocity fields towards a potential flow solution. Note that at those high frequencies, the flow amplitudes remain below 1 % of those of the steady-state flows. Our DNSs, however, indicate that the time scale predicted by the steady-state closure for the flow-resistance term is too small. In general, this study supports the use of the unsteady form of Darcy’s equation with constant coefficients to solve time-periodic Darcy flow, provided the proper time scale has been found.

Rheological evidence for the existence of subphases in the liquid crystalline 4-n-alkoxybenzoic acids

ABSTRACTThe rheological behaviour of the homologous series, the alkyloxybenzoic acids, has been studied at steady flow and small amplitude oscillatory shear. The temperature dependencies of the viscosity were compared with differential scanning calorimetry data in order to estimate pretransitional phenomena in mesophases. The values of the viscosity and flow activation energy (E) can be indicative of the mesophase state. 4-n-pentyloxybenzoic acid yields a classic nematic (N) phase while the next homologues show a cybotactic nematic phase having a higher E value. The N phase is a Newtonian fluid of lower viscosity than that of the isotropic phase. The cybotactic nematic phase by its rheological properties takes an intermediate position between the N phase and a smectic C (SmC) phase. The SmC phase is a viscoelastic and viscoplastic medium. The SmC phase of 4-n-octyloxy-, 4-n-nonyloxy-, 4-n-decyloxy- and 4-n-dodecyloxybenzoic acid can exist in high- and low-ordered states. The more ordered smectic phase is characterised by higher stiffness, viscosity and yield stress than those of the less ordered. The SmC phase of 4-n-hexadecyloxybenzoic acid is characterised by the only state with unstable value of apparent viscosity. The phase state and the transition temperature can be dependent on the thermal history of the sample and a mechanical shear.

Impact of Water-Depletion Layer on Transport in Hydrophobic Nanochannels.

Recent experiments showed that by fabricating nanofluidic channels with hydrophobic materials, the measured amplitudes of both electroosmotic flow (EOF) and ionic current deviated significantly from the conventional electrokinetic modeling indication. Among these unexpected observations, the complicated dependence of EOF on the surface charge concentration of the channel wall remains most confusing. In this work we give a complete and unified picture for the phenomena by outlining the competing two mechanisms in the water-depletion layer around the channel wall: the decreasing trend of fluidic flow due to the redistribution of net charges, and the increasing trend because of the reduced solution viscosity there. Our quantitative evaluation illustrates that the alternate dominating by the two mechanisms leads to the observed transport behaviors. Furthermore, by considering the decreasing of ionic mobility in the depletion layer, our calculations show quantitative agreement with the latest experiments using BN nanotube channels.

Experimental Assessment and Future Applications of the Shikani Tracheostomy Speaking Valve.

Tracheostomy speaking valve use may increase airflow resistance and work of breathing. It remains unclear which valve offers the best performance characteristics. We compared the performance characteristics of the Shikani speaking valve (SSV; unidirectional-flow ball valve) with those of the Passy-Muir valve (PMV; bias-closed flapper valve). Airflow resistance was measured for both the SSV and the PMV at 8 flow amplitudes and in 3 orientations (-15°, 0°, +20°) in the bias-open and bias-closed configurations. Significantly lower airflow resistance was observed for the SSV (bias open) compared with the PMV at -15° (p < .001), 0° (p < .001), and +20° (p = .006) from the horizon. No significant difference was observed between the PMV and the SSV (bias-closed) configuration at any of the tested angles. A nonsignificant trend toward decreased airflow resistance was observed between the SSV bias-open and bias-closed configurations at each of the angles tested. The SSV demonstrated lower airflow resistance compared with the PMV across 8 flow amplitudes in the bias-open configuration at -15°, 0°, and +20° from the horizon. Further investigation is needed to determine the clinical impact of these findings on patient comfort, work of breathing, phonation, and airway protection during swallowing.

A novel isothermal microcalorimetry tool to assess drug effects on Ancylostoma ceylanicum and Necator americanus.

Soil-transmitted helminths, which affect the poorest communities, worldwide cause a range of symptoms and morbidity, yet few treatment options are available and drug resistance is a concern. To improve and accelerate anthelminthic drug discovery, novel drug screening tools such as isothermal microcalorimetry (IMC) have been tested with great potential. In this study, we used a novel microcalorimeter, the calScreener™, to study the viability on the hookworms Necator americanus and Ancylostoma ceylanicum as well as the whipworm Trichuris muris. Significant heat flow signals could be obtained with already one adult worm per channel for all three species. High-amplitude oscillations were observed for the hookworms; however, adult T. muris showed a twofold heat flow decrease during the first 24 h. Antinematodal effects of ivermectin and levamisole at 1, 10, and 100 μg/ml were evaluated on adult N. americanus and A. ceylanicum. Levamisole-treated hookworms showed a decline in heat flow and oscillation amplitude in a dose-response manner. Heat flow for ivermectin-treated hookworms increased proportionally with increased concentrations of ivermectin, though the wavelet analysis showed an opposite trend as observed by flatter wavelets. In conclusion, the calScreener™ is an excellent tool to study drug effects on intestinal hookworms at the adult worm stage as it offers a lower detection limit than other IMC devices and the possibility to monitor worm viability online.

Flow electrification characteristics of oil-pressboard insulation under ac superimposed on DC electric field

Converter transformer plays an important role in the HVDC transmission system. The valve side insulation in converter transformer withstands AC superimposed DC electric field during operation. In order to investigate the flow electrification characteristics of oil-paper insulation under the AC superimposed DC electric field, an oil-paper tube model with concentric cylindrical electrode geometry was built in laboratory. Experiment study on flow electrification under DC electric field was carried using the closed oil circulating system, and the influence rule and mechanism of amplitude of AC superimposed DC electric field, the DC component ratio and oil flow velocity on the flow electrification was analyzed. The experiment results demonstrated that influences of oil flow velocity and amplitude of applied voltage on streaming currents were related to temperature. At low temperature the streaming currents increased linearly with flow velocity and amplitude of applied voltage. Increase the DC component ratio enhanced the streaming currents. At high temperature the streaming currents increased exponentially with flow velocity and showed peak effect with amplitude of applied voltage. The peak point voltage decreased with the DC component ratio. The theoretical analysis based on the experiment results demonstrated that ions generation speed at the oil-paper interface depended on the dissipation speed of positive and negative ions. Saturation of negative ions migration current in the paper and leakage current at the outer electrode lead to peak effect of streaming currents. Changing of temperature can influence the flow electrification characteristics by affecting the ions migration speed and the electric field distribution in the insulation.

Choroidal blood flow and thickness measurements

SummaryMost of the ocular blood supply goes into the choroidal circulation. Intensive research has been directed towards choroidal structure and function in health and disease. Indeed, choroidal blood flow and its regulation has been found to be altered in several ocular diseases, such as age‐related macular degeneration. Several techniques for the assessment of choroidal blood flow have been developed including laser Doppler flowmetry, laser speckle flowgraphy, laser interferometric measurement of fundus pulsation amplitude or pneumotonometric measurement of pulsatile ocular blood flow. All these techniques have significant limitations and currently no gold standard method for the assessment of choroidal blood flow exists.With the introduction of enhanced depth imaging optical coherence tomography (OCT) systems, it is now possible to image choroidal thickness in vivo. Alterations in choroidal thickness have been observed in several ocular diseases. The correlation between functional and structural choroidal parameters is, however, weak. Further research is required to better understand the results obtained in patients with ocular pathologies and to investigate whether choroidal thickness is a good biomarker for choroidal disease.

Sex-dependent alterations in resting-state cerebral blood flow, amplitude of low-frequency fluctuations and their coupling relationship in schizophrenia.

We aimed to investigate sex-dependent alterations in resting-state relative cerebral blood flow, amplitude of low-frequency fluctuations and relative cerebral blood flow-amplitude of low-frequency fluctuations coupling in patients with schizophrenia. Resting-state functional magnetic resonance imaging and three-dimensional pseudo-continuous arterial spin labeling imaging were performed to obtain resting-state amplitude of low-frequency fluctuations and relative cerebral blood flow in 95 schizophrenia patients and 99 healthy controls. Sex differences in relative cerebral blood flow and amplitude of low-frequency fluctuations were compared in both groups. Diagnostic group differences in relative cerebral blood flow, amplitude of low-frequency fluctuations and relative cerebral blood flow-amplitude of low-frequency fluctuations coupling were compared in male and female subjects, respectively. In both healthy controls and schizophrenia patients, the males had higher relative cerebral blood flow in anterior brain regions and lower relative cerebral blood flow in posterior brain regions than did the females. Compared with multiple regions exhibiting sex differences in relative cerebral blood flow, only the left middle frontal gyrus had a significant sex difference in amplitude of low-frequency fluctuations. In the females, schizophrenia patients exhibited increased relative cerebral blood flow and amplitude of low-frequency fluctuations in the basal ganglia, thalamus and hippocampus and reduced relative cerebral blood flow and amplitude of low-frequency fluctuations in the frontal, parietal and occipital regions compared with those of healthy controls. However, there were fewer brain regions with diagnostic group differences in the males than in the females. Brain regions with diagnostic group differences in relative cerebral blood flow and amplitude of low-frequency fluctuations only partially overlapped. Only the female patients exhibited increased relative cerebral blood flow-amplitude of low-frequency fluctuations couplings compared with those of healthy females. The alterations in the relative cerebral blood flow and amplitude of low-frequency fluctuations in schizophrenia are sex-specific, which should be considered in future neuroimaging studies. The relative cerebral blood flow and amplitude of low-frequency fluctuations have different sensitivity in detecting changes in neuronal activity in schizophrenia and can provide complementary information.

A compensation method of frequency-dependent attenuation for pulsed Doppler systems by adapting the transmitting waveform

Pulsed Doppler systems require a high signal-to-noise ratio (SNR) to differentiate the low amplitude of the blood flow echoes from the floor noise. Conventional quadrature demodulation (QDM) assumes that the central frequency of the emitted pulse is the same as the received echoes and uses this frequency as demodulation frequency. Nevertheless, the central frequency of the received echoes is actually downshifted due to the frequency-dependent attenuation (FRDA). This downshifting produces loss of SNR due to discarding energy of the down-mixed signal. In this study, by estimating the spectrum of a Gaussian modulated pulse, the downshift caused by the FRDA was obtained to create a new compensated pulse with the aim of forcing the echo central frequency to match with the demodulation frequency. The method was evaluated by using Field II simulation. Considering an attenuation of 0.5 dB/MHz/cm, a 5 MHz transducer and a relative bandwidth of approximately 50%, at a depth of 16 cm, compensated pulses reduced the frequency shift from 1.11 to 0.32 MHz and the SNR degradation from 9.25 to 0.41 dB. [This study was supported by the MEXT-Support Program for the Strategic Research Foundation at Private Universities, 2013–2017].

Solar-Cycle Variation of Subsurface Meridional Flow Derived with Ring-Diagram Analysis

We study the solar-cycle variation of the meridional flow in the near-surface layers of the solar convection zone from the surface to a depth of 16 Mm. We have analyzed Global Oscillation Network Group (GONG) Dopplergrams with a ring-diagram analysis covering about 13 years (July 2001 – October 2014), from the maximum of Cycle 23 through the rising phase of Cycle 24, and Helioseismic and Magnetic Imager (HMI) Dopplergrams covering more than four years (May 2010 – January 2015). GONG and HMI lead to similar meridional flows during common epochs and latitudes. The meridional flow averaged over a Carrington rotation is poleward up to about $70^{\circ}$ in both hemispheres at all depths after correcting for systematic effects. The flow amplitude peaks at about $40^{\circ}$ latitude with an amplitude of about 16 to $20~\mbox{m}\,\mbox{s}^{-1}$ depending on depth. The meridional flow varies with the solar cycle; the flow amplitudes are larger during cycle minimum than during maximum at low- and mid-latitudes. The flows are mainly faster or more-poleward-than-average on the equatorward side of the mean latitude of activity and slower or less-poleward-than-average on its poleward side. The residual meridional flow converges near the mean latitude of activity. A comparison with the corresponding zonal flow derived from GONG and HMI data shows that the bands of more-poleward-than-average meridional flow coincide with the bands of faster-than-average zonal flow and that the bands of less-poleward-than-average meridional flow coincide with the bands of slower-than-average zonal flow. This implies that the residual flows are cyclonic. The bands of fast meridional flow appear at mid-latitudes about three years before magnetic activity of Cycle 24 is present in synoptic maps.

Can biofeedback training of psychophysiological responses enhance athletes’ sport performance? A practitioner’s perspective

Background: In recent years, biofeedback has become increasingly popular for its proven success in peak performance training – the psychophysiological preparation of athletes for high-stakes sport competitions, such as the Olympic games. The aim of this research was to test whether an 8-week period of exposure to biofeedback training could improve the psychophysiological control over competitive anxiety and enhance athletic performance in participating subjects. Methods: Participants of this study were highly competent athletes, each training in different sport disciplines. The experimental group consisted of 18 athletes (4 women, 14 men), whereas the Control group had 21 athletes (4 women, 17 men). All athletes were between 16 and 34 years old. The biofeedback device, Nexus 10, was used to detect and measure the psychophysiological responses of athletes. Athletes from both groups (control and experimental) were subjected to stress tests at the beginning of the study and once again at its conclusion. In between, the experimental group received training in biofeedback techniques. We then calculated the overall percentage of athletes in the experimental group compared with those in the control group who were able to control respiration, skin conductance, heart rate, blood flow amplitude, heart rate variability, and heart respiration coherence. One year following completion of the initial study, we questioned athletes from the experimental group, to determine whether they continued to use these skills and if they could detect any subsequent enhancement in their athletic performance. Results: We demonstrated that a greater number of participants in the experimental group were able to successfully control their psychophysiological parameters, in comparison to their peers in the control group. Significant results (p < 0.05) were noted in regulation of GSR following short stress test conditions (p = 0.037), in regulation of HR after exposure to STROOP stressor (p = 0.037), in regulation of GSR following the Math and GSR stressors (p = 0.033, p = 0.409) and in achieving HR – breathing coherence following the math stressor (p = 0.042). Conclusion: One year following completion of the training program, all participants from the experimental group indicated that they were still using the biofeedback – psycho-regulation skills. Furthermore, these participants uniformly reported believing that these skills had enhanced their athletic performance and general well-being.

The incidence of bar-like kinematic flows in CALIFA galaxies

We carry out a direct search for bar-like non-circular flows in intermediate-inclination, gas-rich disk galaxies with a range of morphological types and photometric bar classifications from the first data release (DR1) of the CALIFA survey. We use the DiskFit algorithm to apply rotation only and bisymmetric flow models to H$\alpha$ velocity fields for 49/100 CALIFA DR1 systems that meet our selection criteria. We find satisfactory fits for a final sample of 37 systems. DiskFit is sensitive to the radial or tangential components of a bar-like flow with amplitudes greater than $15\,$km$\,$s$^{-1}$ across at least two independent radial bins in the fit, or ~2.25 kpc at the characteristic final sample distance of ~75 Mpc. The velocity fields of 25/37 $(67.6^{+6.6}_{-8.5}\%)$ galaxies are best characterized by pure rotation, although only 17/25 $(68.0^{+7.7}_{-10.4}\%)$ of them have sufficient H$\alpha$ emission near the galaxy centre to afford a search for non-circular flows. We detect non-circular flows in the remaining 12/37 $(32.4^{+8.5}_{-6.6}\%)$ galaxies. We conclude that the non-circular flows detected in 11/12 $(91.7^{+2.8}_{-14.9}\%)$ systems stem from bars. Galaxies with intermediate (AB) bars are largely undetected, and our detection thresholds therefore represent upper limits to the amplitude of the non-circular flows therein. We find 2/23 $(8.7^{+9.6}_{-2.9}\%)$ galaxies that show non-circular motions consistent with a bar-like flow, yet no photometric bar is evident. This suggests that in ~10% of galaxies either the existence of a bar may be missed completely in photometry or other processes may drive bar-like flows and thus secular galaxy evolution.

Testing the dynamic coupling of the core‐mantle and inner core boundaries

AbstractThe proposal that the seismically observed hemispherical asymmetry of Earth's inner core is controlled by the heat flux structure imposed on the outer core by the lower mantle is tested with numerical dynamo models driven by mixed thermochemical convection. We find that models driven by a single core‐mantle boundary (CMB) spherical harmonic of degree and mode 2, the dominant mode in lower mantle seismic shear velocity tomography, produce a similar structure at the inner core boundary (ICB) shifted 30∘ westward. The sensitivity of the ICB to the CMB is further tested by increasing the CMB heterogeneity amplitude. In addition, two seismic tomographic models are tested: first with CMB resolution up to degree and order 4, and second with resolution up to degree and order 8. We find time‐averaged ICB heat flux in these cases to be similar at large scale, with small‐scale differences due to higher CMB harmonics (above degree 4). The tomographic models produce “Earth‐like” magnetic fields, while similar models with twice the CMB heat flow amplitudes produce less Earth‐like fields, implying that increasing CMB heterogeneity forces the model out of an Earth‐like regime. The dynamic ICB heat fluxes are compared to the proposed translation mode of the inner core to test whether the CMB controls inner core growth and structure. This test indicates that, although CMB tomography is unlikely to be driving inner core translation, the ICB heat flux response is weak enough to not interfere with the most unstable translation mode, if it is occurring.