Showing papers by "Mark D. Johnson published in 2023"

Navigating the 16-dimensional Hilbert space of a high-spin donor qudit with electric and magnetic fields

Abstract: Efficient scaling and flexible control are key aspects of useful quantum computing hardware. Spins in semiconductors combine quantum information processing with electrons, holes or nuclei, control with electric or magnetic fields, and scalable coupling via exchange or dipole interaction. However, accessing large Hilbert space dimensions has remained challenging, due to the short-distance nature of the interactions. Here, we present an atom-based semiconductor platform where a 16-dimensional Hilbert space is built by the combined electron-nuclear states of a single antimony donor in silicon. We demonstrate the ability to navigate this large Hilbert space using both electric and magnetic fields, with gate fidelity exceeding 99.8% on the nuclear spin, and unveil fine details of the system Hamiltonian and its susceptibility to control and noise fields. These results establish high-spin donors as a rich platform for practical quantum information and to explore quantum foundations.

Systematic reviews and consensus definitions for the Standardised Endpoints in Perioperative Medicine (StEP) initiative: mortality, morbidity, and organ failure.

Abstract: BackgroundMortality, morbidity, and organ failure are important and common serious harms after surgery. However, there are many candidate measures to describe these outcome domains. Definitions of these measures are highly variable, and validity is often unclear. As part of the International Standardised Endpoints in Perioperative Medicine (StEP) initiative, this study aimed to derive a set of standardised and valid measures of mortality, morbidity, and organ failure for use in perioperative clinical trials.MethodsThree domains of endpoints (mortality, morbidity, and organ failure) were explored through systematic literature review and a three-stage Delphi consensus process using methods consistently applied across the StEP initiative. Reliability, feasibility, and patient-centredness were assessed in round 3 of the consensus process.ResultsA high level of consensus was achieved for two mortality time points, 30-day and 1-yr mortality, and these two measures are recommended. No organ failure endpoints achieved threshold criteria for consensus recommendation. The Clavien–Dindo classification of complications achieved threshold criteria for consensus in round 2 of the Delphi process but did not achieve the threshold criteria in round 3 where it scored equivalently to the Post Operative Morbidity Survey. Clavien–Dindo therefore received conditional endorsement as the most widely used measure. No composite measures of organ failure achieved an acceptable level of consensus.ConclusionsBoth 30-day and 1-yr mortality measures are recommended. No measure is recommended for organ failure. One measure (Clavien–Dindo) is conditionally endorsed for postoperative morbidity, but our findings suggest that no single endpoint offers a reliable and valid measure to describe perioperative morbidity that is not dependent on the quality of deli-vered care. Further refinement of current measures, or development of novel measures, of postoperative morbidity might improve consensus in this area.

The effects of aneurysmal subarachnoid hemorrhage on cerebral vessel diameter and flow velocity.

Abstract: Background Transcranial Doppler flow velocity is used to monitor for cerebral vasospasm following aneurysmal subarachnoid hemorrhage. Generally, blood flow velocities appear inversely related to the square of vessel diameter representing local fluid dynamics. However, studies of flow velocity-diameter relationships are few, and may identify vessels for which diameter changes are better correlated with Doppler velocity. We therefore studied a large retrospective cohort with concurrent transcranial Doppler velocities and angiographic vessel diameters. Methods This is a single-site, retrospective, cohort study of adult patients with aneurysmal subarachnoid hemorrhage, approved by the UT Southwestern Medical Center Institutional Review Board. Study inclusion required transcranial Doppler measurements within 1.1, R2>0.9). Furthermore, velocity and diameter changed (P<0.033) consistent with the signature time course of cerebral vasospasm. Conclusions These results suggest that middle cerebral artery velocity-diameter relationships are most influenced by local fluid dynamics, which supports these vessels as preferred endpoints in Doppler detection of cerebral vasospasm. Other vessels showed less influence of local fluid dynamics, pointing to greater role of factors outside the local vessel segment in determining flow velocity.

Non-English primary language and disparities in stroke outcomes after mechanical thrombectomy: a single institution study

Abstract: Delays in acute treatment of ischemic stroke have been associated with worse outcomes. While having a non-English primary language has not been shown to delay receiving thrombolytic therapy, we assessed whether non-English primary language was associated with worse functional outcomes in patients receiving mechanical thrombectomy (MT).This is a retrospective study of our MT database from two comprehensive stroke centers from January 2016 to May 2021. Primary endpoint was discharge modified Rankin Scale (mRS) 0-2. Differences between English primary language (EPL) and non-English primary language (nEPL) groups were evaluated using an analysis of variance (ANOVA), Kruskal-Wallis and chi square test. Multivariable logistic regression was used to evaluate EPL vs. nEPL patients using data driven models determined by stepwise selection approach.We identified 276 patients receiving MT with 83% EPL and 17% nEPL patients. nEPL patients had higher mean hemoglobin A1c, were less likely to have insurance, and more likely to have symptomatic intracranial hemorrhage compared to EPL patients (Table). We observed a longer median ED arrival to groin puncture time in the nEPL group. No differences were observed in discharge or mRS 0-2 in the univariate or multivariable logistic regression.Despite finding longer ED length of stay among nEPL patients, there was no difference between nEPL and EPL in good functional outcome rates in patients treated with MT.

Fitness Training-Associated Vertebral Artery Dissection

Abstract: Introduction Cervical-artery dissections (CADs) include both the internal carotid arteries (ICA) and vertebral arteries (VA). VAdissections are less common than ICA dissections (1). The etiology could be spontaneous (more common) or traumatic (including trivial day-to-day activities) (1). Traumatic vertebral artery (VA) dissection can occur secondary to excessive cervical rotation, distraction, or flexion-extension injuries during high-intensity interval training (HIIT).HIIT includesmultiplemodalities as for example CrossFit and BodyPump. BodyPump is a high-intensity, lowweight, high-repetition group exercise program. The goal of this article is to report the first case, to our knowledge, of a VA dissection associated to BodyPump training and to draw the attention of the readers to alterations in the intensity, technique, and form of the exercise program that may lead to a higher risk for developing CAD.