Study of brainstem auditory evoked potentials in early (grade I) essential hypertensive patients

Background: Essential hypertension is one of the most common world’s health diseases. It   frequently affects central nervous system (CNS) by producing micro-infarctions which results into altered evoked potentials. Previous studies have shown correlation between hypertension and brain stem auditory evoked potentials. But very scarce data is available on all the parameters of BAEP and essential hypertension especially “amplitude ratio” which distinguishes between central and peripheral impairment. This study was undertaken to evaluate the brain stem auditory evoked potentials (BAEPs) as early marker of cognitive damage in essential hypertension.Methods: BAEPs were recorded in 50 hypertensive subjects and in 50 normotensive controls. Absolute peak latencies, interpeak latencies of different waves and amplitude ratio were compared in both the groups by using unpaired student’s T test.Results: Significant changes in absolute latencies of wave I and V, Interpeak latency I-III, III-V and I-V and amplitude ratio V/I was observed in hypertensive group as compared to control group.Conclusions: Findings of the current study suggests that hypertension does affect the neuronal excitation in the auditory pathways, thereby suggesting that BAEP may provide the early evidence for the presence of CNS dysfunction in the patients of essential hypertension

Diffeomorphic Metric Mapping and Probabilistic Atlas Generation of Hybrid Diffusion Imaging based on BFOR Signal Basis

We propose a large deformation diffeomorphic metric mapping algorithm to align multiple b-value diffusion weighted imaging (mDWI) data, specifically acquired via hybrid diffusion imaging (HYDI), denoted as LDDMM-HYDI. We then propose a Bayesian model for estimating the white matter atlas from HYDIs. We adopt the work given in Hosseinbor et al. (2012) and represent the q-space diffusion signal with the Bessel Fourier orientation reconstruction (BFOR) signal basis. The BFOR framework provides the representation of mDWI in the q-space and thus reduces memory requirement. In addition, since the BFOR signal basis is orthonormal, the L2 norm that quantifies the differences in the q-space signals of any two mDWI datasets can be easily computed as the sum of the squared differences in the BFOR expansion coefficients. In this work, we show that the reorientation of the $q$-space signal due to spatial transformation can be easily defined on the BFOR signal basis. We incorporate the BFOR signal basis into the LDDMM framework and derive the gradient descent algorithm for LDDMM-HYDI with explicit orientation optimization. Additionally, we extend the previous Bayesian atlas estimation framework for scalar-valued images to HYDIs and derive the expectation-maximization algorithm for solving the HYDI atlas estimation problem. Using real HYDI datasets, we show the Bayesian model generates the white matter atlas with anatomical details. Moreover, we show that it is important to consider the variation of mDWI reorientation due to a small change in diffeomorphic transformation in the LDDMM-HYDI optimization and to incorporate the full information of HYDI for aligning mDWI

Tension-compression asymmetry and shear strength of titanium alloys

The relation between the tension-compression asymmetry (TCA) and shear strength in a wide variety of Ti alloys was examined. For this purpose, uniaxial tensile and compression, and double shear strength tests were performed on 13 Ti alloys, which have different microstructural phases (α, α+β, and β) and underwent different thermo-mechanical histories. Results show that the tensile-to-compressive yield strength and shear-to-tensile strength ratios of the alloys vary widely (between 0.79 to 1.24 and 0.52 to 0.86, respectively). A linear dependence between shear yield strength and tensile or compressive yield strength (whichever is lower) of all the alloys is found. While the ultimate shear and tensile strengths also show a linear dependence, data obtained on the fully β alloys are distinct. Finite element analyses employing the Drucker-Prager (DP) yield condition (to account for pressure-dependence on yield), Ludwick's strain hardening model, and Rice-Tracey failure criterion were performed to gain insights into the experimental trends. Results show that TCA decreases the shear yield stress while the shear strength is sensitive to the rate of hardening. A good correlation between the experimental and simulated shear-to-tensile yield strength ratios was observed. Based on a large, simulated dataset (generated using different combinations of material parameters), an empirical relation between shear strength, TCA, and tensile strengths was identified.Agency for Science, Technology and Research (A*STAR)This work was supported by the funding from A∗STAR, Singapore via the Structural Metals and Alloys Programme (No. A18B1b0061)

Patient Complications after Interscalene Block: A Retrospective Comparison of Liposomal Bupivacaine to Nonliposomal Bupivacaine

Background. The purpose of this study was to investigate if the addition of liposome bupivacaine (LB) to an interscalene block (ISB) had an effect on the number of patients with surgical- or block-related complications. Methods. This was a single-center retrospective chart view performed by identifying patients who received an ISB from January 1, 2014, through April 26, 2018, at the University of Minnesota. 1,518 patients were identified who received an ISB (LB = 784, nonliposomal bupivacaine = 734). Patients were divided into two groups those who did receive liposome bupivacaine in their ISB and those who did not receive liposome bupivacaine in their ISB. Medical records were individually reviewed for surgical procedure, block medications, complications related to the block or surgical procedure, phone calls to the healthcare system for issues related to opioids or pain within 3 and within 30 days, readmissions within 30 days, and emergency room visits for complications within 3 and 30 days. Results. There was no significant difference in the number of patients with surgical or anesthetic complications. Only phone calls for pain within 3 days were significantly different. The LB group had 3.2% of patients call compared to 5.6% in the nonliposomal bupivacaine group (aOR = 1.71 (95% CI: 1.04–2.87), p=0.036). We found no significant difference in any of the other secondary outcomes. Conclusions. The use of LB in an ISB demonstrated no significant difference compared to nonliposomal bupivacaine in numbers of complications, emergency room visits, and readmissions