342 research outputs found
Identification and tunable optical coherent control of transition-metal spins in silicon carbide
Color centers in wide-bandgap semiconductors are attractive systems for
quantum technologies since they can combine long-coherent electronic spin and
bright optical properties. Several suitable centers have been identified, most
famously the nitrogen-vacancy defect in diamond. However, integration in
communication technology is hindered by the fact that their optical transitions
lie outside telecom wavelength bands. Several transition-metal impurities in
silicon carbide do emit at and near telecom wavelengths, but knowledge about
their spin and optical properties is incomplete. We present all-optical
identification and coherent control of molybdenum-impurity spins in silicon
carbide with transitions at near-infrared wavelengths. Our results identify
spin for both the electronic ground and excited state, with highly
anisotropic spin properties that we apply for implementing optical control of
ground-state spin coherence. Our results show optical lifetimes of 60 ns
and inhomogeneous spin dephasing times of 0.3 s, establishing
relevance for quantum spin-photon interfacing.Comment: Updated version with minor correction, full Supplementary Information
include
Inter-site Coulomb interaction and Heisenberg exchange
Based on exact diagonalization results for small clusters we discuss the
effect of inter-site Coulomb repulsion in Mott-Hubbard or charge transfer
insulators. Whereas the exchange constant J for direct exchange is
substantially enhanced by inter-site Coulomb interaction, that for
superexchange is suppressed. The enhancement of J in the single-band models
holds up to the critical value for the charge density wave (CDW) instability,
thus opening the way for large values of J. Single-band Hubbard models with
sufficiently strong inter-site repulsion to be near a CDW instability thus may
provide `physical' realizations of t-J like models with the `unphysical'
parameter ratio J/t=1.Comment: Revtex file, 4 PRB pages, with 5 embedded ps-files. To appear in PRB,
rapid communications. Hardcopies of figures or the entire manuscript may also
be obtained by e-mail request to: [email protected]
Auger transition from orbitally degenerate systems: Effects of screening and multielectron excitations
We calculate Auger spectra given by the two-hole Green's function from
orbitally degenerate Hubbard-like models as a function of correlation strength
and band filling. The resulting spectra are qualitatively different from those
obtained from fully-filled singly degenerate models due to the presence of
screening dynamics and multielectron excitations. Application to a real system
shows remarkable agreement with experimental results leading to
reinterpretation of spectral features.Comment: To appear in Phy. Rev. Let
Divertor conditions relevant for fusion reactors achieved with linear plasma generator
Intense magnetized hydrogen and deuterium plasmas have been produced with electron densities up to 3.6¿×¿1020¿m-3 and electron temperatures up to 3.7¿eV with a linear plasma generator. Exposure of a W target has led to average heat and particle flux densities well in excess of 4¿MW m-2 and 1024¿m-2 s-1, respectively. We have shown that the plasma surface interactions are dominated by the incoming ions. The achieved conditions correspond very well to the projected conditions at the divertor strike zones of fusion reactors such as ITER. In addition, the machine has an unprecedented high gas efficiency
Incidence and impact of postoperative pancreatic fistula after minimally invasive and open distal pancreatectomy
BACKGROUND: Previous studies reported a higher rate of postoperative pancreatic fistula after minimally invasive distal pancreatectomy compared to open distal pancreatectomy. It is unknown whether the clinical impact of postoperative pancreatic fistula after minimally invasive distal pancreatectomy is comparable with that after open distal pancreatectomy. We aimed to compare not only the incidence of postoperative pancreatic fistula, but more importantly, also its clinical impact. METHODS: This is a post hoc analysis of a multicenter randomized trial investigating a possible beneficial impact of a fibrin patch on the rate of clinically relevant postoperative pancreatic fistula (International Study Group for Pancreatic Surgery grade B/C) after distal pancreatectomy. Primary outcomes of the current analysis are the incidence and clinical impact of postoperative pancreatic fistula after both minimally invasive distal pancreatectomy and open distal pancreatectomy. RESULTS: From October 2010 to August 2017, 252 patients undergoing distal pancreatectomy were randomized, and data of 247 patients were available for analysis: 87 minimally invasive distal pancreatectomy and 160 open distal pancreatectomies. The postoperative pancreatic fistula rate after minimally invasive distal pancreatectomy was significantly higher than that after open distal pancreatectomy (28.7% vs 16.9%, P = .029). More patients were discharged with an abdominal surgical drain after minimally invasive distal pancreatectomy compared to open distal pancreatectomy (30/87, 34.5% vs 26/160, 16.5%, P = .001). In patients with postoperative pancreatic fistula, additional percutaneous catheter drainage procedures were performed less often (52% vs 84.6%, P = .012), with fewer drainage procedures (median [range], 2 [1-4] vs 2, [1-7], P = .014) after minimally invasive distal pancreatectomy. CONCLUSION: In this post hoc analysis, the postoperative pancreatic fistula rate after minimally invasive distal pancreatectomy was higher than that after open distal pancreatectomy, whereas the clinical impact was less
The Effect of Chemical Information on the Spatial Distribution of Fruit Flies: II Parameterization, Calibration, and Sensitivity
In a companion paper (Lof et al., in Bull. Math. Biol., 2008), we describe a spatio-temporal model for insect behavior. This model includes chemical information for finding resources and conspecifics. As a model species, we used Drosophila melanogaster, because its behavior is documented comparatively well
Impact of shifting from laparoscopic to robotic surgery during 600 minimally invasive pancreatic and liver resections
Background: Many centers worldwide are shifting from laparoscopic to robotic minimally invasive hepato-pancreato-biliary resections (MIS-HPB) but large single center series assessing this process are lacking. We hypothesized that the introduction of robot-assisted surgery was safe and feasible in a high-volume center. Methods: Single center, post-hoc assessment of prospectively collected data including all consecutive MIS-HPB resections (January 2010–February 2022). As of December 2018, all MIS pancreatoduodenectomy and liver resections were robot-assisted. All surgeons had participated in dedicated training programs for laparoscopic and robotic MIS-HPB. Primary outcomes were in-hospital/30-day mortality and Clavien-Dindo ≥ 3 complications. Results: Among 1875 pancreatic and liver resections, 600 (32%) were MIS-HPB resections. The overall rate of conversion was 4.3%, Clavien-Dindo ≥ 3 complications 25.7%, and in-hospital/30-day mortality 1.8% (n = 11). When comparing the period before and after the introduction of robotic MIS-HPB (Dec 2018), the overall use of MIS-HPB increased from 25.3 to 43.8% (P < 0.001) and blood loss decreased from 250 ml [IQR 100–500] to 150 ml [IQR 50–300] (P < 0.001). The 291 MIS pancreatic resections included 163 MIS pancreatoduodenectomies (52 laparoscopic, 111 robotic) with 4.3% conversion rate. The implementation of robotic pancreatoduodenectomy was associated with reduced operation time (450 vs 361 min; P < 0.001), reduced blood loss (350 vs 200 ml; P < 0.001), and a decreased rate of delayed gastric emptying (28.8% vs 9.9%; P = 0.009). The 309 MIS liver resections included 198 laparoscopic and 111 robotic procedures with a 3.6% conversion rate. The implementation of robotic liver resection was associated with less overall complications (24.7% vs 10.8%; P = 0.003) and shorter hospital stay (4 vs 3 days; P < 0.001). Conclusion: The introduction of robotic surgery was associated with greater implementation of MIS-HPB in up to nearly half of all pancreatic and liver resections. Although mortality and major morbidity were not affected, robotic surgery was associated with improvements in some selected outcomes. Ultimately, randomized studies and high-quality registries should determine its added value. Graphical Abstract: [Figure not available: see fulltext.].</p
- …