Hall plateaus at magic angles in bismuth beyond the quantum limit

We present a study of the angular dependence of the resistivity tensor up to 35 T in elemental bismuth complemented by torque magnetometry measurements in a similar configuration. For at least two particular field orientations a few degrees off the trigonal axis, the Hall resistivity was found to become field-independent within experimental resolution in a finite field window corresponding to a field which is roughly three times the frequency of quantum oscillations. The Hall plateaus rapidly vanish as the field is tilted off theses magic angles. We identify two distinct particularities of these specific orientations, which may play a role in the emergence of the Hall plateaus.Comment: 5 pages, 5 figure

An electronic instability in bismuth far beyond the quantum limit

We present a transport study of semi-metallic bismuth in presence of a magnetic field applied along the trigonal axis extended to 55 T for electric conductivity and to 45 T for thermoelectric response. The results uncover a new field scale at about 40 T in addition to the previously detected ones. Large anomalies in all transport properties point to an intriguing electronic instability deep in the ultraquantum regime. Unexpectedly, both the sheer magnitude of conductivity and its metallic temperature dependence are enhanced by this instability.Comment: 5 pages, 4 figure

The Impact of Lower Extremity Skeletal Muscle Atrophy and Myosteatosis on Revascularization Outcomes in Patients with Peripheral Arterial Disease

Background: This study investigated whether lower extremity muscle atrophy and myosteatosis in patients with peripheral arterial disease (PAD) are correlated to postoperative outcomes, such as reintervention or amputation-free survival. Methods: In this single-center retrospective cohort study of 462 patients treated for peripheral arterial disease scheduled for intervention, muscle mass and the presence of fattening of the lower extremity muscles were measured semiautomatically in a single computed tomography slice of the treated leg. Binary logistic regression models and Cox proportional hazards models were used to determine the effect of muscle atrophy and myosteatosis on reintervention and amputation. Results: Muscle atrophy and myosteatosis increased in PAD patients with Fontaine class IV compared with Fontaine class IIa. In PAD patients with muscle atrophy or myosteatosis, no association was found with the reintervention rate or reintervention-free survival, but an association was found with amputation-free survival, even after adjustment for patient-related, disease-severity, and comorbidities-related factors. Conclusion: Muscle atrophy and mysosteatosis increased in PAD patients with increasing disease severity. Lower extremity muscle atrophy and myosteatosis are associated with amputation rate and amputation-free survival in PAD patients. No association with reintervention rate or reintervention-free survival was found. Muscle atrophy and myosteatosis may serve as additional risk factors in decision making in the often frail vascular patient

Validation of a Length-Adjusted Abdominal Arterial Calcium Score Method for Contrast-Enhanced CT Scans

BACKGROUND: The Agatston score on noncontrast computed tomography (CT) scans is the gold standard for calcium load determination. However, contrast-enhanced CT is commonly used for patients with atherosclerotic cardiovascular diseases (ASCVDs), such as peripheral arterial occlusive disease (PAOD) and abdominal aortic aneurysm (AAA). Currently, there is no validated method to determine calcium load in the aorta and peripheral arteries with a contrast-enhanced CT. This study validated a length-adjusted calcium score (LACS) method for contrast-enhanced CT scans.METHOD: The LACS (calcium volume in mm 3/arterial length in cm) in the abdominal aorta was calculated using four-phase liver CT scans of 30 patients treated between 2017 and 2021 at the University Medical Center Groningen (UMCG) with no aortic disease. Noncontrast CT scans were segmented with a 130 Hounsfield units (HU) threshold, and a patient-specific threshold was used for contrast-enhanced CTs. The LACS was calculated and compared from both segmentations. Secondly, the interobserver variability and the influence of slice thickness (0.75 mm vs. 2.0 mm) was determined. RESULTS: There was a high correlation between the LACS from contrast-enhanced CT scans and the LACS of noncontrast CTs ( R 2 = 0.98). A correction factor of 1.9 was established to convert the LACS derived from contrast-enhanced CT to noncontrast CT scans. LACS interobserver agreement on contrast-enhanced CT was excellent (1.0, 95% confidence interval = 1.0-1.0). The 0.75 mm CT threshold was 541 (459-625) HU compared with 500 (419-568) HU on 2 mm CTs ( p = 0.15). LACS calculated with both thresholds was not significantly different ( p = 0.63). CONCLUSION: The LACS seems to be a robust method for scoring calcium load on contrast-enhanced CT scans in arterial segments with various lengths.</p

Thermoelectric power of polycrystalline bismuth : phonon drag size effect

Doctorat en sciences appliquées -- UCL, 196

Phonon-drag low temperature thermoelectric refrigeration

Recent low temperature thermoelectric data on group V semimetals show that pure bismuth is one of the best candidates for low temperature thermoelectric refrigeration. Though the figure of merit is still more than one order of magnitude too small for practical applications, it is suggested that further investigations into the physics of the transport properties of this material might improve the situation.Anglai