Fermi Surface and Anisotropic Spin-Orbit Coupling of Sb(111) studied by Angle-Resolved Photoemission Spectroscopy

High-resolution angle-resolved photoemission spectroscopy has been performed on Sb(111) to elucidate the origin of anomalous electronic properties in group-V semimetal surfaces. The surface was found to be metallic despite the semimetallic character of bulk. We clearly observed two surface-derived Fermi surfaces which are likely spin split, demonstrating that the spin-orbit interaction plays a dominant role in characterising the surface electronic states of group-V semimetals. Universality/disimilarity of the electronic structure in Bi and Sb is discussed in relation to the granular superconductivity, electron-phonon coupling, and surface charge/spin density wave.Comment: 4 pages, 3 figures. to be published in Phys. Rev. Let

Designing molecules to bypass the singlet-triplet bottleneck in the electroluminescence of organic light-emitting-diode materials

Electroluminescence in organic light emitting diode (OLED) materials occurs via the recombination of excitonic electrons-hole pairs Only the singlet excitons of commonly used OLED materials, e.g., Aluminum trihydroxyquinoline (AlQ$_3$), decay radiatively, limiting the external quantum efficiency to a maximum 25%. Thus 75% of the energy is lost due to the triplet bottleneck for radiative recombination. We consider molecules derived from AlQ$_3$ which bypass the triplet bottleneck by designing structures which contain strong spin-orbit coupling. As a first stage of this work, groundstate energies and vertical excitation energies of Al-arsenoquinolines and Al-boroarsenoquinolines are calculated. It is found that the substitution of N by As leads to very favourable results, while the boron substitution leads to no advantage.Comment: 4 pages, 4 figue

Evidence of local superconductivity in granular Bi nanowires fabricated by electrodeposition

An unusual enhancement of resistance (i.e., superresistivity) below a certain characteristic temperature Tsr was observed in granular Bi nanowires. This superresistive state was found to be dependent on the applied magnetic field (H) as well as the excitation current (I). The suppression of Tsr by magnetic field resembles that of a superconductor. The observed superresistivity appears to be related to the nucleation of local superconductivity inside the granular nanowire without long-range phase coherence. The phenomenon is reminiscent of the Bose-insulator observed previously in ultra thin two-dimensional (2D) superconducting films and 3D percolative superconducting films.Comment: 11 pages, 5 figures. submitted to PR

Magnetothermal Conductivity of Highly Oriented Pyrolytic Graphite in the Quantum Limit

We report on the magnetic field (0T$\le B \le 9$T) dependence of the longitudinal thermal conductivity $\kappa(T,B)$ of highly oriented pyrolytic graphite in the temperature range 5 K $\le T\le$ 20 K for fields parallel to the $c-$axis. We show that $\kappa(T,B)$ shows large oscillations in the high-field region (B > 2 T) where clear signs of the Quantum-Hall effect are observed in the Hall resistance. With the measured longitudinal electrical resistivity we show that the Wiedemann-Franz law is violated in the high-field regime.Comment: 4 Figures, to be published in Physical Review B (2003

Contribution to the understanding of tribological properties of graphite intercalation compounds with metal chloride

Intrinsic tribological properties of lamellar compounds are usually attributed to the presence of van der Waals gaps in their structure through which interlayer interactions are weak. The controlled variation of the distances and interactions between graphene layers by intercalation of electrophilic species in graphite is used in order to explore more deeply the friction reduction properties of low-dimensional compounds. Three graphite intercalation compounds with antimony pentachloride, iron trichloride and aluminium trichloride are studied. Their tribological properties are correlated to their structural parameters, and the interlayer interactions are deduced from ab initio bands structure calculations

Effect of contrast phase on quantitative analysis of skeletal muscle and adipose tissue by computed tomography

OBJECTIVES: Significant variability exists in the contrast phases applied during computed tomography (CT) studies when assessing morphometric measurements of muscle area (CT-assessed sarcopenia) and density (CT-assessed myosteatosis) and visceral adipose tissue area (CT-assessed visceral obesity). This study explored the impact of contrast phase timing on changes in morphometric measurements of body composition.METHODS: This single-center retrospective cohort study included 459 patients undergoing a multiphase CT scan. Morphometric measurements were obtained at the third lumbar vertebra level. Patients were classified as sarcopenic, myosteatotic, or visceral obese using predefined cutoff values. The intraclass correlation coefficient was used to assess correlations across different enhancement phases, and Cohen's κ measured the inter-enhancement agreement for sarcopenia, myosteatosis, and visceral obesity.RESULTS: Significant differences were observed in mean visceral adipose tissue area, muscle density, and muscle area (P &lt; 0.001). The intraclass correlation coefficient between unenhanced and arterial phases was 0.987 (95% confidence interval [CI], 0.759-0.996) for adipose tissue, 0.995 (95% CI, 0.989-0.997) for muscle area, and 0.850 (95% CI, 0.000-0.956) for muscle density. However, when morphometric measurements were categorized using predefined cutoffs, the κ agreement was considerably lower, particularly for CT-assessed myosteatosis, ranging from 0.635 (unenhanced to arterial) to 0.331 (unenhanced to late venous phase).CONCLUSIONS: Different CT contrast phases induce small but clinically significant alterations in the measurements of muscle area and density and visceral fat. Such minor changes can result in misclassification issues when fixed cutoff values are used to diagnose myosteatosis with CT. This underscores the importance of reporting absolute values and the specific contrast phase used in future studies.</p

Thermal conductivity of tin-doped bismuth between 50 mK and 7K

The authors report on the thermal conductivity of tin-doped bismuth between 50 mK and 27K. A quantitative interpretation of the data is presented. At the lowest temperatures the electronic thermal conductivity dominates, but above 0.1K lattice waves carry most of the heat. Below 1K phonons are scattered mostly by crystal boundaries, while near the dielectric maximum point defects are important. Their scattering rate is directly proportional to the atomic concentration of the tin impurity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48999/2/jcv18i15p3001.pd

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

Association of iliofemoral calcium score and major vascular complications within the first year after lower limb endovascular revascularization

BACKGROUND: The accumulation of calcium load in peripheral lower extremity arteries has been associated with increased severity of peripheral arterial disease (PAD) and mortality. While calcium scores are commonly calculated from non-contrast computed tomography (CT) scans, patients with PAD often undergo contrast-enhanced CT scans. This study aims to explore the association between a length-adjusted calcium score (LACS) of the iliofemoral arteries, determined through pre-intervention contrast-enhanced CT, and major adverse events in patients with chronic limb-threatening ischemia (CLTI).METHODS: A cohort of CLTI patients subjected to endovascular revascularization between 2005 and 2017 at a tertiary referral center were categorized into two groups. The complication group experienced one of the composite outcomes (reintervention, above-the-ankle amputation, and/or all-cause mortality within one year of the primary endovascular procedure), while control patients did not encounter this composite endpoint. Patients from the complication group were matched one-to-one with controls based on sex and Fontaine classification. LACS was calculated (Ca volume[mm3]/length[cm]) at three arterial segments; 1. the common iliac artery (CIA), 2. the external iliac artery and common femoral artery (EIA+CFA), and 3. the superficial femoral artery plus the popliteal artery (SFA+PA). Binary logistic regression analysis was conducted to investigate the association between LACS in the different arterial segments and the occurrence of the composite binary outcome (complication and control) and LACS of the different segments, adjusting influences of age, sex, BMI &gt;25, Fontaine classification, diabetes mellitus type 1 &amp; 2, chronic kidney disease stage, and hemodialysis treatment.RESULTS: Sixty-four CLTI patients were included in this study (complication group [n=32], and control group [n=32]). A significant difference (higher LACS was found for the complication group in the CIA, the SFA+PA, as well as the total trajectory. CLTI patients with high LACS in the SFA+PA or the total trajectory were more likely to suffer adverse events (SFA+PA: OR: 1.010, 95% CI: 1.000-1.020, p=0.04; Total LACS: OR: 1.008, 95% CI: 1.000-1.017, p=0.05).CONCLUSIONS: Patients with a high calcium load in the ilio-femoral arteries are at increased risk of major adverse events during one year after endovascular revascularization. The calcium score, derived from contrast-enhanced CT scans, holds potential utility in decision making for CLTI patients.</p

Diameter-dependent thermopower of Bi nanowires

We present a study of electronic transport in individual Bi nanowires of large diameter relative to the Fermi wavelength. Measurements of the resistance and thermopower of intrinsic and Sn-doped Bi wires with various wire diameters, ranging from 150-480 nm, have been carried out over a wide range of temperatures (4-300 K) and magnetic fields (0-14 T). We find that the thermopower of intrinsic Bi wires in this diameter range is positive (type-p) below about 150 K, displaying a peak at around 40 K. In comparison, intrinsic bulk Bi is type-n. Magneto-thermopower effects due to the decrease of surface scattering when the cyclotron diameter is less than the wire diameter are demonstrated. The measurements are interpreted in terms of a model of diffusive thermopower, where the mobility limitations posed by hole-boundary scattering are much less severe than those due to electron-hole scattering.Comment: 32 pages, 12 figures. Previous version replaced to improve readabilit