Random changes in the heifer rumen in bacterial community structure,physico-chemical and fermentation parameters, and in vitro fiber degradation

The variability over time of several main ruminal characteristics was studied in heifers over 15 consecutive weeks. Three heifers were assigned to a low-fiber diet (27% NDF) and three to a high-fiber diet (44% NDF). The physico-chemical (pH and redox potential) and fermentation(volatile fatty acids and ammonia contents) parameters were determined on 1 day per week for 15 consecutive weeks. On the same days the bacterial community structure was studied using a molecular fingerprint technique and the ruminal fiber degradation was studied by in vitro incubation of a withdrawn ruminal content sample. Numerous random changes were observed from week to week for all physico-chemical and fermentative parameters and in vitro fiber degradation. The redox potential was the only parameter to show a significant interaction between diet and week. Except for the ammonia content, the amplitudes of fluctuations observed were higher for the low-fiber diet. The bacterial community structure did not differ between diets or weeks. The in vitro fiber degradation was similar for both diets, with numerous random changes throughout the study. The findings of this study indicated that most of the parameters of the ruminal ecosystem had time-related changes with random fluctuations around a mean value which reflect an unstable equilibrium. This conclusion was valid for both low- and high-fiber diets

Reverberation limits the release from informational masking obtained in the harmonic and binaural domains

A difference in fundamental frequency (ΔF0) and a difference in spatial location (ΔSL) are two cues known to provide masking releases when multiple speakers talk at once in a room. Situations were examined in which reverberation should have no effect on the mechanisms underlying the release from energetic masking produced by these two cues. Speech reception thresholds using both unpredictable target sentences and the coordinate response measure followed a similar pattern. Both ΔF0s and ΔSLs provided masking releases in the presence of non-speech maskers (matched in excitation pattern and temporal envelope to speech maskers) which, as intended, were robust to reverberation. Larger masking releases were obtained for speech maskers, but critically, they were affected by reverberation. The results suggest that reverberation either limits the amount of informational masking there is to begin with, or affects its release by ΔF0s or ΔSLs

Boosting transducer matrix sensitivity for 3D large field ultrasound localization microscopy using a multi-lens diffracting layer: a simulation study

Mapping blood microflows of the whole brain is crucial for early diagnosis of cerebral diseases. Ultrasound localization microscopy (ULM) was recently applied to map and quantify blood microflows in 2D in the brain of adult patients down to the micron scale. Whole brain 3D clinical ULM remains challenging due to the transcranial energy loss which significantly reduces the imaging sensitivity. Large aperture probes with a large surface can increase both resolution and sensitivity. However, a large active surface implies thousands of acoustic elements, with limited clinical translation. In this study, we investigate via simulations a new high-sensitive 3D imaging approach based on large diverging elements, combined with an adapted beamforming with corrected delay laws, to increase sensitivity. First, pressure fields from single elements with different sizes and shapes were simulated. High directivity was measured for curved element while maintaining high transmit pressure. Matrix arrays of 256 elements with a dimension of 10x10 cm with small ( $\lambda$ /2), large (4 $\lambda$ ), and curved elements (4 $\lambda$ ) were compared through point spread functions analysis. A large synthetic microvessel phantom filled with 100 microbubbles per frame was imaged using the matrix arrays in a transcranial configuration. 93% of the bubbles were detected with the proposed approach demonstrating that the multi-lens diffracting layer has a strong potential to enable 3D ULM over a large field of view through the bones

Other-regarding preferences and giving decision in a risky environment: experimental evidence

We investigate whether and how an individual giving decision is affected in risky environments in which the recipient’s wealth is random. We demonstrate that, under risk neutrality, the donation of dictators with a purely ex post view of fairness should, in general, be affected by the riskiness of the recipient’s payoff, while dictators with a purely ex ante view should not be. Furthermore, we observe that some influential inequality aversion preferences functions yield opposite predictions when we consider ex post view of fairness. Hence, we report on dictator games laboratory experiments in which the recipient’s wealth is exposed to an actuarially neutral and additive background risk. Our experimental data show no statistically significant impact of the recipient’s risk exposure on dictators’ giving decisions. This result appears robust to both the experimental design (within subjects or between subjects) and the origin of the recipient’s risk exposure (chosen by the recipient or imposed on the recipient). Although we cannot sharply validate or invalidate alternative fairness theories, the whole pattern of our experimental data can be simply explained by assuming ex ante view of fairness and risk neutrality

0059 : Non invasive ultrasonic chordal cutting

ObjectiveChordal cutting targeting leaflet tethering has been described to improve the efficiency of annuloplasty during ischemic mitral regurgitation surgery. Histotripsy is an ultrasound based technique for tissue fragmentation through the cavitation generated by a very intense ultrasonic pulse. In this study we investigate the feasibility of using histotripsy for chordal cutting to avoid cardiopulmonary bypass and invasive surgery in infarcted heart.MethodsExperiments were performed in vitro in explanted sheep heart (N=10) and in vivo in sheep beating heart (N=5, 40+/-4kg). In vitro, the mitral valve basal chordae was removed, fixed on a holder in a water tank. The ultrasound pulses were emitted from the therapeutic device (1- MHz focused transducer, pulses of 8μs duration, peak negative pressure of 17 MPa, repetition frequency of 100Hz) placed at a distance of 64mm. In vivo, we performed sternotomy and the device was applied on the thorax cavity which was filled out with water. We analysed MV coaptation and chordae by real time 3D echocardiography. The animals were sacrificed at the end of the procedure, for postmortem anatomical exploration of the heart.ResultsIn vitro, all the basal chordae were completely cut. The mean procedure time was 5.5 (+/-1.7) minutes. The diameter of the chordae was the main criteria affecting the duration of procedure. In the sheep, central basal chordae of anterior leaflet were completely cut. The mean procedure time was 22 (+/-9) minutes. By echography, the sectioned chordae was visible and no mitral valve prolapse was found. All the postmortem anatomical exploration of hearts confirmed the section of the basal chordea. No additional lesions were objectified.ConclusionsNoninvasive ultrasound histotripsy succeed to cut mitral valve basal chordae in vitro and in vivo in beating heart. If positive, this will open the door of completely noninvasive technique for MV repair especially in case of ischemic or functional MR

4D ultrafast ultrasound flow imaging: in vivo quantification of arterial volumetric flow rate in a single heartbeat

ABSTRACT: We present herein 4D ultrafast ultrasound flow imaging, a novel ultrasound-based volumetric imaging technique for the quantitative mapping of blood flow. Complete volumetric blood flow distribution imaging was achieved through 2D tilted plane-wave insonification, 2D multi-angle cross-beam beamforming, and 3D vector Doppler velocity components estimation by least-squares fitting. 4D ultrafast ultrasound flow imaging was performed in large volumetric fields of view at very high volume rate (>4000 volumes s(-1)) using a 1024-channel 4D ultrafast ultrasound scanner and a 2D matrix-array transducer. The precision of the technique was evaluated in vitro by using 3D velocity vector maps to estimate volumetric flow rates in a vessel phantom. Volumetric Flow rate errors of less than 5% were found when volumetric flow rates and peak velocities were respectively less than 360 ml min(-1) and 100 cm s(-1). The average volumetric flow rate error increased to 18.3% when volumetric flow rates and peak velocities were up to 490 ml min(-1) and 1.3 m s(-1), respectively. The in vivo feasibility of the technique was shown in the carotid arteries of two healthy volunteers. The 3D blood flow velocity distribution was assessed during one cardiac cycle in a full volume and it was used to quantify volumetric flow rates (375 +/- 57 ml min(-1) and 275 +/- 43 ml min(-1)). Finally, the formation of 3D vortices at the carotid artery bifurcation was imaged at high volume rates

When Should I Use my Active Workstation? The impact of Physical Demand and Task Difficulty on IT Users’ Perception and Performance

The seated position in our daily computer interactions has been identified as a major threat for health. Active workstations have been proposed as a healthy solution to these problems. However, research findings on the effects of such workstations on users’ productivity is not conclusive. We argue that physical demand and task difficulty play a role in influencing IT users’ performance and perceptions when using active workstations. An experiment manipulating task difficulty, direct and indirect physical demands was performed. Results suggest that task difficulty moderates the relationships between physical demand (direct and indirect) and users’ perceptions and performance. Findings will help organizations and employees determine if it is appropriate for them to use active workstations

Entrainment, Diffusion and Effective Compressibility in a Self-Similar Turbulent Jet

An experimental Lagrangian study based on particle tracking velocimetry has been completed in an incompressible turbulent round water jet freely spreading into water. The jet is seeded with tracers only through the nozzle: inhomogeneous seeding called nozzle seeding. The Lagrangian flow tagged by these tracers therefore does not contain any contribution from particles entrained into the jet from the quiescent surrounding fluid. The mean velocity field of the nozzle seeded flow, ⟨Uφ⟩, is found to be essentially indistinguishable from the global mean velocity field of the jet, ⟨U⟩, for the axial velocity while significant deviations are found for the radial velocity. This results in an effective compressibility of the nozzle seeded flow for which ∇⋅⟨Uφ⟩≠0 even though the global background flow is fully incompressible. By using mass conservation and self-similarity, we quantitatively explain the modified radial velocity profile and analytically express the missing contribution associated to entrained fluid particles. By considering a classical advection-diffusion description, we explicitly connect turbulent diffusion of mass (through the turbulent diffusivity KT) and momentum (through the turbulent viscosity νT) to entrainment. This results in new practical relations to experimentally determine the non-uniform spatial profiles of KT and νT (and hence of the turbulent Prandtl number σT=νT/KT) from simple measurements of the mean tracer concentration and axial velocity profiles. Overall, the proposed approach based on nozzle seeded flow gives new experimental and theoretical elements for a better comprehension of turbulent diffusion and entrainment in turbulent jets

Imaging the dynamics of cardiac fiber orientation in vivo using 3D Ultrasound Backscatter Tensor Imaging

The assessment of myocardial fiber disarray is of major interest for the study of the progression of myocardial disease. However, time-resolved imaging of the myocardial structure remains unavailable in clinical practice. In this study, we introduce 3D Backscatter Tensor Imaging (3D-BTI), an entirely novel ultrasound-based imaging technique that can map the myocardial fibers orientation and its dynamics with a temporal resolution of 10 ms during a single cardiac cycle, non-invasively and in vivo in entire volumes. 3D-BTI is based on ultrafast volumetric ultrasound acquisitions, which are used to quantify the spatial coherence of backscattered echoes at each point of the volume. The capability of 3D-BTI to map the fibers orientation was evaluated in vitro in 5 myocardial samples. The helicoidal transmural variation of fiber angles was in good agreement with the one obtained by histological analysis. 3D-BTI was then performed to map the fiber orientation dynamics in vivo in the beating heart of an open-chest sheep at a volume rate of 90 volumes/s. Finally, the clinical feasibility of 3D-BTI was shown on a healthy volunteer. These initial results indicate that 3D-BTI could become a fully non-invasive technique to assess myocardial disarray at the bedside of patients