The Effects of Micro-vessel Curvature Induced Elongational Flows on Platelet Adhesion

The emerging profile of blood flow and the cross-sectional distribution of blood cells have far reaching biological consequences in various diseases and vital internal processes, such as platelet adhesion. The effects of several essential blood flow parameters, such as red blood cell free layer width, wall shear rate, and hematocrit on platelet adhesion were previously explored to great lengths in straight geometries. In the current work, the effects of channel curvature on cellular blood flow are investigated by simulating the accurate cellular movement and interaction of red blood cells and platelets in a half-arc channel for multiple wall shear rate and hematocrit values. The results show significant differences in the emerging shear rate values and distributions between the inner and outer arc of the channel curve, while the cell distributions remain predominantly uninfluenced. The simulation predictions are also compared to experimental platelet adhesion in a similar curved geometry. The inner side of the arc shows elevated platelet adhesion intensity at high wall shear rate, which correlates with increased shear rate and shear rate gradient sites in the simulation. Furthermore, since the platelet availability for binding seems uninfluenced by the curvature, these effects might influence the binding mechanics rather than the probability. The presence of elongational flows is detected in the simulations and the link to increased platelet adhesion is discussed in the experimental results

Spontanous periodic breathing is associated with sympathetic hyperreactivity and baroreceptor dysfunction in hypertension

OBJECTIVES: Intermittent periods of hypoxemia such as during periodic breathing are associated with hypertension and increased sympathetic activity. In patients with sleep apnea syndrome, hypertension is common. Treating apnea improves hypertension and reduces sympathetic outflow. The aim of the present study was to investigate the phenomenon and mechanisms of spontaneous periodic breathing in patients with hypertension. METHOD: We examined 43 hypertensive patients with untreated hypertension without left-ventricular dysfunction, heart failure or sleep apnea syndrome. Muscle sympathetic nerve activity (MSA), heart rate (HR), blood pressure (BP) and respiration were continuously recorded at rest and during cold-pressor testing. Oxygen and a CO2-enriched gas were used to test central and peripheral chemoreceptors, respectively. Baroreceptor gain was measured using the alpha method. RESULTS: Seven out of 43 patients showed spontaneous periodic breathing while awake. No difference in MSA, HR and BP was seen between patients with and without periodic breathing at rest except the breathing pattern. However, the cold-pressor test caused a larger increase of MSA in patients with periodic breathing (203 +/- 62 vs. 62 +/- 8%, P < 0.0001 by ANOVA), as well as systolic (46 +/- 6 vs. 25 +/- 3 mmHg, P = 0.002) and diastolic BP (26 +/- 5 vs. 12 +/- 1 mmHg, P = 0.004, ANOVA). Baroreceptor gain was markedly higher in patients with periodic breathing. Chemoreceptor sensitivity was comparable. CONCLUSION: Spontaneous periodic breathing is relatively common in patients with hypertension and is associated with greatly enhanced responses to cold-pressor testing. We suggest increased baroreceptor gain and sympathetic outflow as a cause for the oscillatory respiration pattern via barorespiratory coupling

Of autoregressive continuous time model parameters estimation

This article revisits a sequential approach to the estimation of the parameter in a first-order autoregressive model (AR(1)) with continuous time. There is provided a numerical study to get a results of sequential estimations of the parameter in first-order autoregressive model with continuous time and is computed a stopping rule and the optimal time of observations. Also there is provided a comparing analysis of estimation results with using the sequential approach both the optimal time of observations

ICoNIK: Generating Respiratory-Resolved Abdominal MR Reconstructions Using Neural Implicit Representations in k-Space

Motion-resolved reconstruction for abdominal magnetic resonance imaging (MRI) remains a challenge due to the trade-off between residual motion blurring caused by discretized motion states and undersampling artefacts. In this work, we propose to generate blurring-free motion-resolved abdominal reconstructions by learning a neural implicit representation directly in k-space (NIK). Using measured sampling points and a data-derived respiratory navigator signal, we train a network to generate continuous signal values. To aid the regularization of sparsely sampled regions, we introduce an additional informed correction layer (ICo), which leverages information from neighboring regions to correct NIK's prediction. Our proposed generative reconstruction methods, NIK and ICoNIK, outperform standard motion-resolved reconstruction techniques and provide a promising solution to address motion artefacts in abdominal MRI

Shared genetic variance between obesity and white matter integrity in Mexican Americans.

peer reviewedObesity is a chronic metabolic disorder that may also lead to reduced white matter integrity, potentially due to shared genetic risk factors. Genetic correlation analyses were conducted in a large cohort of Mexican American families in San Antonio (N = 761, 58% females, ages 18-81 years; 41.3 +/- 14.5) from the Genetics of Brain Structure and Function Study. Shared genetic variance was calculated between measures of adiposity [(body mass index (BMI; kg/m(2)) and waist circumference (WC; in)] and whole-brain and regional measurements of cerebral white matter integrity (fractional anisotropy). Whole-brain average and regional fractional anisotropy values for 10 major white matter tracts were calculated from high angular resolution diffusion tensor imaging data (DTI; 1.7 x 1.7 x 3 mm; 55 directions). Additive genetic factors explained intersubject variance in BMI (heritability, h (2) = 0.58), WC (h (2) = 0.57), and FA (h (2) = 0.49). FA shared significant portions of genetic variance with BMI in the genu (rhoG = -0.25), body (rhoG = -0.30), and splenium (rhoG = -0.26) of the corpus callosum, internal capsule (rhoG = -0.29), and thalamic radiation (rhoG = -0.31) (all p's = 0.043). The strongest evidence of shared variance was between BMI/WC and FA in the superior fronto-occipital fasciculus (rhoG = -0.39, p = 0.020; rhoG = -0.39, p = 0.030), which highlights region-specific variation in neural correlates of obesity. This may suggest that increase in obesity and reduced white matter integrity share common genetic risk factors

Utilizing a handheld electrode array for localized muscle impedance measurements

Introduction: Electrical impedance myography (EIM) is a non-invasive technique used for assessment of muscle health in which a high-frequency, low-amplitude electric current is applied to the skin overlying a muscle, and the resulting surface voltage is measured. We have previously used adhesive electrodes, application of which is inconvenient. We present data using a handheld electrode array (HEA) that we devised to expedite the EIM procedure in a clinical setting. Methods: Thirty-four healthy volunteers and 24 radiculopathy subjects underwent EIM testing using the HEA and adhesive electrodes. Results: The HEA was shown to have good test-retest reproducibility, with intraclass correlation coefficients as high as 0.99. HEA data correlated strongly with data from adhesive electrodes, ρ = 0.85 in healthy volunteers (p < 0.001) and ρ = 0.75 in radiculopathy subjects (p < 0.001). Discussion: These data support the potential use of a handheld array for performing rapid localized surface impedance measurements

Two-neutron knockout as a probe of the composition of states in 22^{22}Mg, 23^{23}Al, and 24^{24}Si

Simpson and Tostevin proposed that the width and shape of exclusive parallel momentum distributions of the A-2 residue in direct two-nucleon knockout reactions carry a measurable sensitivity to the nucleon single-particle configurations and their couplings within the wave functions of exotic nuclei. We report here on the first benchmarks and use of this new spectroscopic tool. Exclusive parallel momentum distributions for states in the neutron-deficient nuclei $^{22}$Mg, $^{23}$Al, and $^{24}$Si populated in such direct two-neutron removal reactions were extracted and compared to predictions combining eikonal reaction theory and shell-model calculations. For the well-known $^{22}$Mg and $^{23}$Al nuclei, measurements and calculations were found to agree, supporting the dependence of the parallel momentum distribution width on the angular momentum composition of the shell-model two-neutron amplitudes. In $^{24}$Si, a level at 3439(9) keV, of relevance for the important $^{23}$Al(p,$\gamma$)$^{24}$Si astrophysical reaction rate, was confirmed to be the $2^+_2$ state, while the $4^+_1$ state, expected to be strongly populated in two-neutron knockout, was not observed. This puzzle is resolved by theoretical considerations of the Thomas-Ehrman shift, which also suggest that a previously reported 3471-keV state in $^{24}$Si is in fact the ($0^+_2$) level with one of the largest experimental mirror-energy shifts ever observed.Comment: Accepted for publication in Phys. Rev. C as a Rapid Communicatio