ABSTRACT
Thin films of the spin-crossover (SCO) molecule Fe{[Me2Pyrz]3BH}2 (Fe-pyrz) were sublimed on Si/SiO2 and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen)2(NCS)2, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (â¼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.
ABSTRACT
The interaction of hydrogen (H) and a ZnO(0001)-O surface has been investigated using a temperature programmed desorption (TPD) technique. When the surface is exposed to atomic hydrogen below 400 K, hydrogen is adsorbed on the surface. As the hydrogen exposure increases, bulk diffusion of hydrogen takes place. The existence of surface and bulk hydrogen has been confirmed using X-ray photoelectron spectroscopy (XPS). When the ZnO surface dosed with hydrogen is heated, surface hydrogen is desorbed at 432 K and bulk hydrogen is evolved at â¼539 K. Diffusion of hydrogen into the ZnO bulk is an activated process, and the activation energy is estimated to be 0.19 eV.
Subject(s)
Hydrogen/chemistry , Zinc Oxide/chemistry , Adsorption , Diffusion , Surface Properties , TemperatureABSTRACT
This paper describes a block-by-block basis image enhancement algorithm which uses the signal subspace method to enhance images corrupted by uncorrelated additive noise. The enhancement is performed by eliminating the noise components in the noise subspace and estimating the clean image from the remaining components in the signal subspace.
ABSTRACT
The purpose of this study was to determine the factors which were responsible for delaying early diagnosis and optimal management of rheumatoid arthritis (RA) in Korea. We interviewed 109 outpatients diagnosed as RA being treated by rheumatologists, and we eventually analyzed 98 patients' data. The median length of time from symptom onset to the first visit to a medical doctor, to diagnosis, and visiting a rheumatologist were 8 weeks, 23 weeks, and 42 months respectively. The subspecialist with whom the patients consulted with for the longest time before visiting a rheumatologist were an orthopaedic surgeon for 51 patients, a Chinese herbal doctor for 19 patients, and a pharmacist for 16 patients. For early diagnosis and optimal management of RA in Korea, we believe that it is necessary to reduce the use of unconventional medical services such as Chinese herbal medicine and nonprescribed medication, and to emphasize rheumatologic and rehabilitative care in the early stage.
