•Nb was deposited under oxygen enriched UHV conditions.•O-ion implantation and annealing allows to achieve a good quality Nb2O5 films on GaN.•Band gap of the Nb2O5 was determined to be ...4.7 eV.•Valence band offset of the Nb2O5/p-GaN interface amounts to 1.6 eV.
Non-stoichiometric niobium oxides were grown on p-GaN(0001) substrates using physical vapor deposition of Nb under ultrahigh vacuum (UHV) enriched with oxygen. The film consisted mainly of NbOx and Nb2O5 phases. NbO2 compound as well as trace amounts of NbO and Nb in metallic were also present in the film. Then, in order to eliminate non-insulating fractions, the method of oxygen-ion implantation followed by annealing was used. This resulted in a formation of insulator films composed almost only of Nb2O5 compound. The surface of the cleaned substrate and niobium oxides/GaN interfaces (prior and after an O-ion implantation) were characterized in situ by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The result allowed to determine band offsets at the Nb2O5/GaN interface.
The physical vapor deposition method is used to form layers of Al2O3 insulator on carbon enriched (0001)-oriented 6H-SiC substrate at room temperature. The substrate surface and the Al2O3/6H-SiC ...interface are characterized in situ by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The electron affinity (EA) of the pre-annealed up to 800 °C under ultrahigh vacuum 6H-SiC(0001) surface and the 7 nm thick Al2O3 layer deposited on the substrate amounts to 4.1 eV, and 1.9 eV respectively. The formation of the Al2O3 compound is confirmed by the appropriate binding energies of Al-2p and O-1s core level lines, which are 75.6 eV and 532.3 eV, respectively. The valence band offset (VBO) of the Al2O3/6H-SiC interface is found to be −3.2 eV and the conduction band offset is calculated to be 0.7 eV.
•The early stages of the Al2O3/6H-SiC(0001) interface formation at RT are investigated.•Al2O3 layers were deposited by physical vapor deposition.•After Al2O3 film deposition XPS does not show any evidence for an interfacial compounds formation at the phase boundary.•Bandgap of Al2O3 films does not depend on films thickness and is equal to 6.9 eV.•Energy band diagram in a function of Al2O3 thickness is presented.
Abstract Objective The aim of this study was to examine the survival of adult liver retransplant recipients depending on selected factors: time from the primary transplantation, cold ischemia time, ...indications for retransplantation, patient age and United Network for Organ Sharing (UNOS) status. Patients and Methods Between December 1989 and March 2011, we performed 43 orthotopic liver retransplantations (re-OLTs) among patients aged 20–62 years including 24 women and 19 men. The cold ischemia time was 250–820 minutes. UNOS status before re-OLT: UNOS 1 (n = 19; 44%) UNOS 2A (n = 15; 35%), and UNOS 2B (n = 4; 9%). The time from OLT to re-OLT was 1–2, 146 days. The indications for re-OLT were arterial thrombosis (n = 14; 33%), anastomotic biliary complication (n = 3; 7%), recurrence of the original disease (n = 9; 21%), hepatic vein thrombosis (n = 1; 2%), primary nonfunction (PNF) dysfunction (n = 2; 5% /6 14%), de novo hepatitis C cirrhosis (n = 2; 5%) and other etiologies (n = 6; 14%). Results The 6-year survival among the primary OLT group was 80% compared with 58% among the re-OLT group ( P = .0001). One-year survivals in the re-OLT group according to UNOS status 1, 2A, and 2B were 47%, 60%, and 75%, respectively ( P = .475). There was a low negative correlation between survival time and time between OLT and re-OLT. There was a low positive correlation between survival time and cold ischemia time. There was a low negative correlation between survival time and patient age. Conclusions There was a significant difference in survival between OLT and re-OLT. There was a correlation between survival time and time to re-OLTx; a shorter time corresponded to longer survival. There was a poor correlation between survival time and patient age. UNOS status before re-OLT and indication for re-OLTx influenced survival.
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•Alq3, Gaq3, Erq3 were deposited by PVD on graphene.•Graphene was formed in situ by annealing of 6H-SiC(0 0 0 1).•HOMO levels of Alq3, Gaq3, Erq3 were located at 1.55 eV, 1.75 eV, ...2.0 eV.•Schottky barriers between graphene and the molecules are 1.25 eV, 1.05 eV, 0.8 eV.•Tuning of bund structures can be done by changing the central atom M of the Mq3.
This paper concerns physicochemical properties of three interfaces composed of organic layers of Alq3, Gaq3 or Erq3 vapor deposited on graphene/6H-SiC(0 0 0 1) surfaces. A graphene termination of 6H-SiC(0 0 0 1), about one monolayer thick, was produced in situ by thermal annealing of the substrate. The formation of the final interfaces and their characterization were also performed in situ under ultrahigh vacuum conditions. X-ray/UV photoelectron spectroscopies (XPS/UPS) were employed in this study. XPS results showed that the organic layers did not react chemically with the graphene/6H-SiC(0 0 0 1) surfaces at room temperature. In turn, UPS measurements showed that the adsorption of organic layers decreased the position of the vacuum level of the initial surface and one covered with the organic layers which initiated the surface dipoles. The vacuum level was lowered by 0.15 eV, 0.4 eV, and 0.9 eV for Alq3, Gaq3, Erq3 layers, respectively. The positions of highest occupied molecular orbitals (HOMOs) were also found. They were located at 1.55 eV, 1.75 eV, and 2.0 eV below the Fermi level, respectively, for Alq3, Gaq3, and Erq3 layers. The band energy diagrams for the three interfaces were constructed.
In this paper the behaviour of the Mn/GaN system under the influence of annealing is presented. The interface is formed by Mn vapour deposition onto the GaN crystal, (0001)-oriented, non-doped under ...ultrahigh vacuum. Physicochemical properties and structural changes of the interface induced by annealing are investigated in situ by employing X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction (LEED). The impact of annealing on the subsurface layer morphology is observed. Annealing effects, which have been confirmed by XPS and UPS, demonstrate Ga diffusion into the Mn film and Mn dissolution in the bulk GaN. LEED patterns confirm MnGa alloy formation, which in the plane parallel to the substrate surface is arranged in a square lattice with lattice constant equal to about 3.9 Å, and exists in epitaxial configuration relative to the substrate. Incorporation of Mn atoms into the GaN lattice results in the creation of (Mn,Ga)N-like alloy.
•Mn/GaN system was formed at room temperature by Mn vapour deposition onto non-doped GaN(0001) surface under ultrahigh vacuum.•Annealing of Mn/GaN system resulted in Ga diffusion into the Mn film and Mn dissolution in the bulk GaN.•LEED patterns confirm MnGa alloy formation with (111) orientation. The square lattice constant is equal to circa 3.9 Å.•Incorporation of Mn atoms into the GaN matrix leads to the (Mn,Ga)N-like alloy formation.
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•Native oxide-covered n- and p-type GaN(0001) samples are used in this study.•Combining Kelvin probe, SPV and X-ray photoemission measurements are made.•Fermi level pinning is 2.7 eV ...and 1.75 eV above the VBM for n- and p-type GaN.•SPV is ~0.5 V in magnitude and is directed oppositely between n- and p-type GaN.•Ga3d peak is located at 20.8 eV and 18.9 eV depending on dopant type.
Band bending and Fermi level pinning at GaN(0001) surfaces have proved controversial despite their fundamental importance. By combining Kelvin probe, surface photovoltage and X-ray photoemission measurements, we clarify how the Fermi level pinning affects the band bending for n- and p-type GaN(0001). The presence of two different mid-gap pinning levels is confirmed on native oxide-covered samples, and they lie at remarkably similar energies to those previously found for atomically clean GaN(0001). The population of these bistable pinning levels and their influence on the band bending both depend on the bulk doping and level of illumination by above-gap photons.
Abstract Introduction Early hepatic artery thrombosis remains one of the major causes of graft failure and mortality in liver transplant recipients. It is the most frequent severe vascular ...complication after orthotopic liver transplantation (OLT) accounting for >50% of all arterial complications. Most patients need to be considered for urgent liver retransplantation. Materials and Methods Among 911 OLTs in 862 from 1989 to 2011, we observed 23 cases (2.6%) of acute early hepatic artery thrombosis. Seventeen patients were qualified immediately for liver retransplantation, and 6 underwent endovascular therapies, including intra-arterial heparin infusion or percutaneous transluminal angioplasty with stent placement. Results Among patients who were assigned to early liver retransplantation, 11/17 survived with 3 succumbling due to postoperative complications, including 1 portal vein thrombosis, and 3 succumbling on the waiting list. All patients who underwent endovascular therapy survived with an excellent result obtained in 1 who underwent treatment <24 hours after arterial thrombosis. In 2 patients we achieved a satisfactory result not requiring retransplantation, but 3 patients assigned to endovascular treatment >24 hours after arterial thrombosis needed to be reassigned to liver retransplantation because of poor results of endovascular treatment. Conclusions Endovascular treatment efforts should be made to rescue liver grafts through urgent revascularization depending on the patient's condition and the interventional expertise at the transplant center, reserving the option of retransplantation for graft failure or severe dysfunction.
The new method presented here reports on combining the advantages of diffraction and spectroscopy techniques by a sophisticated computer software: the Difference Electron Nanoscope (DEN). On the ...example of synthetic fayalite α‐Fe2SiO4 the possibilities of the DEN are outlined, especially the derivation and display of the fundamental physical property here concerned, the electric field gradient EFG on the Fe bearing M1 site. It is shown within the difference electron densities of the crystal lattice and in connection with surrounding structural units, the distorted oxygen ion octahedra. By using low‐temperature Mössbauer data published elsewhere, the angles between the EFG and the internal magnetic field at the Fe nucleus, H(0), can be taken to fully describe the magnetic ordering of synthetic fayalite in the antiferromagnetic state, with an accuracy normally provided by neutron diffraction. Even small details of the magnetic coupling involved can be detected on the DEN images.
M1 position of synthetic fayalite at 0.5,0.5,0.5 with a blue wire frame model representing the electric field gradient, surrounding difference electron densities (light brown) from synchrotron diffraction data and direction of the internal magnetic field H(0) at 50K (red arrow) from Mössbauer spectroscopy
Non-doped GaN(0001) crystals are used as substrates in this study, on which Mn films are vapour deposited in situ under ultrahigh vacuum (UHV). The early stages of the Mn/GaN(0001) interface ...formation at room temperature are determined by means of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction (LEED). The electron affinity for the already cleaned GaN(0001)-(1 × 1) surface, achieved by thermal cleaning, is 3.5 eV. The binding energy (BE) of the Ga-3d core level line shifts from 20.3 eV to 19.8 eV and the Mn-3p state from 47.6 eV to 47.2 eV upon stepwise Mn deposition due to charge transfer, e.g. Schottky barrier (SB) formation. The splitting of the Mn-2p doublet amounts to 11.2 eV and the Mn-2p3/2 peak has a BE of 638.7 eV, these values corresponding to metallic manganese. The work function of the Mn films with the thickness of 1 nm is 3.4 eV and slightly decreases to 3.2 eV with further overlayer thickness. The SB height of the interface is determined to be 1.2 eV. The Mn films show no LEED patterns. The XPS results, generally, show the absence of any interfacial compound formation.
•The early stages of the Mn/GaN(0001) interface formation at RT are investigated.•Electron affinity for the already cleaned GaN(0001)-(1 × 1) surface is 3.5 eV.•After Mn films deposition XPS results do not show any evidence for an interfacial compound formation.•The WF of Mn films equals 3.2 eV.•The Schottky barrier height of the interface is found to be 1.2 eV.
The preliminary outcomes of patients with acute liver failure treated with the Prometheus Fractionated Plasma Separation and Absorption (FPSA) system are presented herein.
The procedures were ...performed in 13 patients (4, intoxication by Amanita phalloides; 4, unknown reason; 3, acetaminophen intoxication; 1, Wilson disease, and 1, liver insufficiency after hemihepatectomy owing to metastases of colon adenocarcinoma). The patients were qualified for the procedure according to the King’s College Hospital criteria. The patients’ general status was assessed on basic of GCS, UNOS, and the 4-grade encephalopathy classifications. The procedures were performed with the Prometheus 4008H Fresenius Medical Care unit.
The 29 procedures were of mean duration 6.5 hours. There were statistically significant reductions in total bilirubin, ammonia, and aminotransferase levels. In addition, the procedures corrected water, mineral, and carbohydrate disorders. One patient did not require liver transplantation. Seven patients received liver transplants: three patients with positive outcomes; two died due to septicemia within 30 days perioperatively, one died at 6 months after OLT owing to respiratory failure; and one, owing to hemorrhagic diathesis. Four patients did not receive a liver transplant because of lack of a organ, no consent for the surgery, or neoplastic disease with metastases.
The Prometheus FPSA-System was an effective detoxication method for patients with acute liver failure. The system was useful as a symptomatic treatment before liver transplantation allowing a longer wait for a graft.
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