Diameter-dependent conductance of InAs nanowires

Electrical conductance through InAs nanowires is relevant for electronic applications as well as for fundamental quantum experiments. Here we employ nominally undoped, slightly tapered InAs nanowires to study the diameter dependence of their conductance. Contacting multiple sections of each wire, we can study the diameter dependence within individual wires without the need to compare different nanowire batches. At room temperature we find a diameter-independent conductivity for diameters larger than 40 nm, indicative of three-dimensional diffusive transport. For smaller diameters, the resistance increases considerably, in coincidence with a strong suppression of the mobility. From an analysis of the effective charge carrier density, we find indications for a surface accumulation layer.Comment: 9 pages, 5 figure

Evaluation of a Subject specific dual-transmit approach for improving B1 field homogeneity in cardiovascular magnetic resonance at 3T

BACKGROUND: Radiofrequency (RF) shading artifacts degrade image quality while performing cardiovascular magnetic resonance (CMR) at higher field strengths. In this article, we sought to evaluate the effect of local RF (B(1) field) shimming by using a dual-source–transmit RF system for cardiac cine imaging and to systematically evaluate the effect of subject body type on the B(1) field with and without local RF shimming. METHODS: We obtained cardiac images from 37 subjects (including 11 patients) by using dual-transmit 3T CMR. B(1) maps with and without subject-specific local RF shimming (exploiting the independent control of transmit amplitude and phase of the 2 RF transmitters) were obtained. Metrics quantifying B(1) field homogeneity were calculated and compared with subject body habitus. RESULTS: Local RF shimming across the region encompassed by the heart increased the mean flip angle (μ) in that area (88.5 ± 15.2% vs. 81.2 ± 13.3%; P = 0.0014), reduced the B(1) field variation by 42.2 ± 13%, and significantly improved the percentage of voxels closer to μ (39% and 82% more voxels were closer to ± 10% and ± 5% of μ, respectively) when compared with no RF shimming. B(1) homogeneity was independent of subject body type (body surface area [BSA], body mass index [BMI] or anterior-posterior/right-left patient width ratio [AP/RL]). Subject specific RF (B(1)) shimming with a dual-transmit system improved local RF homogeneity across all body types. CONCLUSION: With or without RF shimming, cardiac B1 field homogeneity does not depend on body type, as characterized by BMI, BSA, and AP/RL. For all body types studied, cardiac B(1) field homogeneity was significantly improved by performing local RF shimming with 2 independent RF-transmit channels. This finding indicates the need for subject-specific RF shimming

Risk-Assessment of Esophageal Surgery:Diagnosis and Treatment of Celiac Trunk Stenosis

Anastomotic leakage of the gastric conduit following surgical treatment of esophageal cancer is a life-threatening complication. An important risk factor associated with anastomotic leakage is calcification of the supplying arteries of the gastric conduit. The patency of calcified splanchnic arteries cannot be assessed on routine computed tomography (CT) scans for esophageal cancer and, as such, in selected patients with known or assumed mesenteric artery disease, additional CT angiography of the abdominal arteries with 1mm slices is strongly encouraged. If the mesenteric perfusion is compromised in patients with resectable esophageal cancer, angioplasty procedures with stenting of the mesenteric arteries could be performed to prevent possible ischemia of the gastric conduit

Probing Charging and Localization in the Quantum Hall Regime by Graphene pnp Junctions

Using high quality graphene pnp junctions, we observe prominent conductance fluctuations on transitions between quantum Hall (QH) plateaus as the top gate voltage Vtg is varied. In the Vtg-B plane, the fluctuations form crisscrossing lines that are parallel to those of the adjacent plateaus, with different temperature dependences for the conductance peaks and valleys. These fluctuations arise from Coulomb-induced charging of electron- or hole-doped localized states when the device bulk is delocalized, underscoring the importance of electronic interactions in graphene in the QH regime

Spin splitting and even-odd effects in carbon nanotubes

The level spectrum of a single-walled carbon nanotube rope, studied by transport spectroscopy, shows Zeeman splitting in a magnetic field parallel to the tube axis. The pattern of splittings implies that the spin of the ground state alternates by 1/2 as consecutive electrons are added. Other aspects of the Coulomb blockade characteristics, including the current-voltage traces and peak heights, also show corresponding even-odd effects.Comment: Preprint, pdf format only, 4 pages including figure

Long-Term Survival Associated with Direct Oral Feeding Following Minimally Invasive Esophagectomy:Results from a Randomized Controlled Trial (NUTRIENT II)

Advancements in perioperative care have improved postoperative morbidity and recovery after esophagectomy. The direct start of oral intake can also enhance short-term outcomes following minimally invasive Ivor Lewis esophagectomy (MIE-IL). Subsequently, short-term outcomes may affect long-term survival. This planned sub-study of the NUTRIENT II trial, a multicenter randomized controlled trial, investigated the long-term survival of direct versus delayed oral feeding following MIE-IL. The outcomes included 3- and 5-year overall survival (OS) and disease-free survival (DFS), and the influence of complications and caloric intake on OS. After excluding cases of 90-day mortality, 145 participants were analyzed. Of these, 63 patients (43.4%) received direct oral feeding. At 3 years, OS was significantly better in the direct oral feeding group (p = 0.027), but not at 5 years (p = 0.115). Moreover, 5-year DFS was significantly better in the direct oral feeding group (p = 0.047) and a trend towards improved DFS was shown at 3 years (p = 0.079). Postoperative complications and caloric intake on day 5 did not impact OS. The results of this study show a tendency of improved 3-year OS and 5-year DFS, suggesting a potential long-term survival benefit in patients receiving direct oral feeding after esophagectomy. However, the findings should be further explored in larger future trials.</p