Ventilator support in the pretransplant period predisposes early graft failure after deceased donor liver transplantation.

Purpose: Deceased donor liver transplantation (DDLT) recipients in Korea are generally sicker due to an increasing organ shortage. In the present study, the risk factors for early 30-day liver graft failure after DDLT were identified. Methods: From August 2017 to February 2021, 265 adult DDLTs were performed. The characteristics of patients with and without 30-day graft failure were compared. Results: Liver graft failure occurred in 11 patients (17.7%) after DDLT. Baseline and perioperative characteristics of donors and recipients were not statistically significantly different between the 2 groups. The cumulative graft and overall survival rates at 6 months were 83.9% and 88.7%, respectively. Multivariate analysis showed ventilator support in the pretransplant period was a predisposing factor for 30-day graft failure after DDLT. Conclusion: Present study indicates that cautious decision is required when allocating DDLT in critically ill patients on mechanical ventilatory support.

Active doping of B in silicon nanostructures and development of a Si quantum dot solar cell.

Active doping of B was observed in nanometer silicon layers confined in SiO(2) layers by secondary ion mass spectrometry (SIMS) depth profiling analysis and confirmed by Hall effect measurements. The uniformly distributed boron atoms in the B-doped silicon layers of [SiO(2) (8 nm)/B-doped Si(10 nm)](5) films turned out to be segregated into the Si/SiO(2) interfaces and the Si bulk, forming a distinct bimodal distribution by annealing at high temperature. B atoms in the Si layers were found to preferentially substitute inactive three-fold Si atoms in the grain boundaries and then substitute the four-fold Si atoms to achieve electrically active doping. As a result, active doping of B is initiated at high doping concentrations above 1.1 × 10(20) atoms cm( - 3) and high active doping of 3 × 10(20) atoms cm( - 3) could be achieved. The active doping in ultra-thin Si layers was implemented for silicon quantum dots (QDs) to realize a Si QD solar cell. A high energy-conversion efficiency of 13.4% was realized from a p-type Si QD solar cell with B concentration of 4 × 10(20) atoms cm( - 3).

Size- and doping-dependent time-resolved photoluminescence of doped Si nanocrystals.

Time-resolved photoluminescence (PL) has been studied for B- and Sb-doped Si nanocrystals (NCs) fabricated by ion beam sputtering and annealing. For B-doped Si NCs, the PL intensity as well as the PL lifetime (τPL) increases as NC size (d) varies from 1.5 to 2.6 nm, similar to the case for undoped Si NCs, but with further increase of d, they decrease, possibly resulting from the increase of optically less active NCs with the increase of NCs containing more dopants. The PL intensity and τPL monotonically decrease with increasing doping concentration (nD), irrespective of doping element. Si NCs show smaller τPL in B doping than in Sb doping over the full range of nD. The sharp decrease in PL intensity, accompanied by the gradual decrease in τPL for the higher nD of Sb, may be attributed to Auger recombination due to the presence of Sb inside Si NCs. The higher PL quench rate by Sb compared to B could be attributed to better ionization of Sb dopants in Si NCs.

Nonvolatile floating-gate memories using Zr and ZrO2 nanodots.

Triple-layer structures of SiO2/Zr nanodots (NDs)/SiO2 for nonvolatile memories have been firstly fabricated at room temperature by using ion beam sputtering deposition (IBSD). High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy demonstrate that Zr NDs self-assembled between the SiO2 layers by IBSD are changed into ZrO2 NDs by annealing. The memory window that is estimated by capacitance-voltage curves increases up to a maximum value of 5.8 V with increasing Zr amount up to 6 monolayers for the annealed samples. The memory window and the charge-loss rate at the programmed state are smaller before annealing, which is explained with reference to double oxide barriers of SiO2 and ZrO2.

Plasmon-enhanced ultraviolet photoluminescence from hybrid structures of graphene/ZnO films.

We report substantially enhanced photoluminescence (PL) from hybrid structures of graphene/ZnO films at a band gap energy of ZnO (∼3.3 eV/376 nm). Despite the well-known constant optical conductivity of graphene in the visible-frequency regime, its abnormally strong absorption in the violet-frequency region has recently been reported. In this Letter, we demonstrate that the resonant excitation of graphene plasmon is responsible for such absorption and eventually contributes to enhanced photoemission from structures of graphene/ZnO films when the corrugation of the ZnO surface modulates photons emitted from ZnO to fulfill the dispersion relation of graphene plasmon. These arguments are strongly supported by PL enhancements depending on the spacer thickness, measurement temperature, and annealing temperature, and the micro-PL mapping images obtained from separate graphene layers on ZnO films.

Control of amorphous silica nanowire growth by oxygen content of Si-rich oxide.

Ni-coated Si-rich oxide (SRO, SiO(x)) on a p-type Si wafer has been annealed with Si powder to grow silica nanowires (NWs), which have a composition of stoichiometric SiO(2), irrespective of x. The diameters of the NWs are well controlled from 82 to 23 nm by increasing x from 0.4 to 1.2 and they have a uniform distribution at a fixed x. These results suggest that the oxygen content (x) plays a crucial role in determining the diameter of the NWs at the early stage of the NW formation. The growth behaviors of the NWs are explained well based on a modified vapor-liquid-solid mechanism.

Ge-nanodot multilayer nonvolatile memories.

1-5 period multilayers of Ge nanodots (NDs) for nonvolatile memories have been self-assembled by ion beam sputtering deposition of an ultra-small amount of Ge between SiO(2) layers at room temperature without post-annealing. High-resolution transmission electron microscopy demonstrates the existence of Ge ND layers well defined with respect to the SiO(2)/Si interface. The memory window that is estimated by capacitance-voltage hysteresis is proportional to the period, and finally reaches a plateau of about 11 V asymptotically over three periods. The program speed is enhanced over the full pulse-time range by increasing bias voltage or period. The charge-loss speed in the programmed state is slower in the samples with larger period. These memory properties are discussed based on possible physical mechanisms.