Surface Reconstruction: Noble Metals

The paper reviews the most important achievements in the study of the surface-reconstruction phase transition on the low-index single crystals of Pt, Ir, and Au. A number of methods very sensitive to the surface layers are used to study the stable and metastable structures of the (100), (110), and (111) faces. Detailed consideration of the kinetics, critical parameters, activation energy, and geometrical models for 2D-surface phase transitions are presented. Main theoretical results based on the Ising 2D-model, calculations of the free energy with an embedded-atom method, and equilibrium Monte Carlo simulations are also given.В обзоре рассмотрены последние достижения в исследовании реконструкционных фазовых превращений в поверхностных слоях монокристаллов Pt, Ir и Au. Приведены результаты, полученные с помощью различных поверхностно-чувствительных экспериментальных методов. Наиболее подробно рассмотрены вопросы, относящиеся к кинетике, энергии активации, геометрическим моделям, критическим параметрам 2D-фазовых превращений. Представлены также результаты теоретических исследований, основанных на 2D-модели Изинга, методе внедренного атома и моделировании методом Монте-Карло.В обзорі розглянуто останні досягнення в дослідженні реконструкційніх фазових перетворень в поверхневих шарах монокристалів Pt, Ir та Au. Наведено результати, які отримані за допомогою різних повехнево-чутливих експериментальних методів. Найбільш детально розглянуто питання, що відносяться до кінетики, енергії активації, геометричних моделей, критичних параметрів 2D-фазових перетворень. Представлено також результати теоретичних досліджень, що базовані на 2D-моделі Ізінга, методі зануреного атому та моделюванні за методом Монте-Карло

Current limiting and negative differential resistance in indium oxide based ceramics

Indium oxide based ceramics with bismuth oxide addition were sintered in air in the temperature range 800-1300 ºC. Current-voltage characteristics of In2O3-Bi2O3 ceramics sintered at different temperatures are weakly nonlinear. After an additional heat treatment in air at about 200 ºC samples sintered at a temperature within the narrow range of about 1050-1100 ºC exhibit a current-limiting effect accompanied by low-frequency current oscillations. It is shown that the observed electrical properties are controlled by the grain-boundary barriers and the heat treatment in air at 200 ºC leads to the decrease in the barrier height. Electrical measurements, scanning electron microscopy and X-ray photoelectron spectroscopy results suggest that the current-limiting effect observed in In2O3-Bi2O3 may be explained in terms of a modified barrier model; the observed current-limiting effect is the result of an increase of barrier height with increasing electric field, due to additional oxygen absorption. It is found that In2O3-Bi2O3-Co3O4-Cr2O3 ceramic exhibits current-voltage characteristics with negative differential resistance due to Joule micro heating.This study was performed in part in the frames of the project SEP-2003-C02-42821, CONACYT, México. Funding from the Royal Society, United Kingdom (2007R1/R26999) is gratefully acknowledged

Prognosis of Elevated Serum Ferritin in Allogeneic-HCT

Introduction: Serum ferritin was demonstrated to be a useful tool to predict the risk in patients who undergo hematopoietic stem cell transplantation (HCT). Still it is not clear if its predictive value solely represents iron overload (IO) and published results are sometimes contradictory. So the objective of present study was to determine relationship between elevated pre-HCT serum ferritin levels, morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HCT) on one side, and its correlations with various risk indexes which were developed recently to predict outcomes after allo-HCT on the other side. Patients and Methods: In this retrospective study we have reviewed medical records of one hundred six consecutive patients (52 males and 54 females), with a median age of 32 years (range, 5 to 60), who underwent allo-HCT with unmanipulated grafts between Jan 2013 and Dec2014. We retrieved pre-allo-HCT serum ferritin levels and also calculated risk indexes before HCT. The incidence of complications and outcomes after allo-HCT was assessed. The median follow-up period was 12 (range, 4-27) months after allo-HCT. Results: We have determined a cuttoff ferritin level of 500 ng/mL for early complications and 737 for outcomes. We found increased incidence of number of febrile neutropenic episodes (P =0.02), number of bacterial infection episodes (P =0.009), pneumonias (P =0.039), slower period of neutrophil engraftment (P=0.032), demand for multiple red blood cell (RBC) transfusions (P =0.002) within 100 days post transplantation. A significant association was found between pre-transplant ferritin concentrations and different risk indexes; European Group for Blood and Marrow Transplantation (EBMT) risk score (P=0.001), Hematopoietic cell transplantation comorbidity index (HCT-CI) (P=0.003), Pre-transplant Assessment of Mortality (PAM) score (P=0.007) and disease risk (DR) (P =0.037). Conclusion: On the one hand we did confirmed that even moderate serum ferritin elevation is associated with increased incidence of infections, slower period to engraftment and increasing demand of RBC units transfusions, but strong correlation with pre-transplant indexes that take into account disease risk raises the question if IO is the only factor that adversely affect the outcome of HCT in patients with increased ferritin. This should be studied in prospective trials

Surface Reconstruction: Noble Metals

The paper reviews the most important achievements in the study of the surface-reconstruction phase transition on the low-index single crystals of Pt, Ir, and Au. A number of methods very sensitive to the surface layers are used to study the stable and metastable structures of the (100), (110), and (111) faces. Detailed consideration of the kinetics, critical parameters, activation energy, and geometrical models for 2D-surface phase transitions are presented. Main theoretical results based on the Ising 2D-model, calculations of the free energy with an embedded-atom method, and equilibrium Monte Carlo simulations are also given.В обзоре рассмотрены последние достижения в исследовании реконструкционных фазовых превращений в поверхностных слоях монокристаллов Pt, Ir и Au. Приведены результаты, полученные с помощью различных поверхностно-чувствительных экспериментальных методов. Наиболее подробно рассмотрены вопросы, относящиеся к кинетике, энергии активации, геометрическим моделям, критическим параметрам 2D-фазовых превращений. Представлены также результаты теоретических исследований, основанных на 2D-модели Изинга, методе внедренного атома и моделировании методом Монте-Карло.В обзорі розглянуто останні досягнення в дослідженні реконструкційніх фазових перетворень в поверхневих шарах монокристалів Pt, Ir та Au. Наведено результати, які отримані за допомогою різних повехнево-чутливих експериментальних методів. Найбільш детально розглянуто питання, що відносяться до кінетики, енергії активації, геометричних моделей, критичних параметрів 2D-фазових перетворень. Представлено також результати теоретичних досліджень, що базовані на 2D-моделі Ізінга, методі зануреного атому та моделюванні за методом Монте-Карло