Spectroscopic studies have been conducted for wurtzite ZnO/Mg
0.27Zn
0.73O multiple quantum wells. Internal electric fields at interfaces are found to have an influence on the photoluminescence (PL) ...properties for well width (
L
w) greater than
4.2
nm
. These experimentally observed features are characteristic of the quantum-confined Stark effects; the magnitude of the electric field due to spontaneous and piezoelectric polarizations and the depth of the triangle-shaped potential wells are the monotonically increasing functions of Mg concentration and the
L
w, respectively. Results of the time-resolved PL study are also presented.
High quality ZnO thin film was grown by Laser MBE. A pure ceramic ZnO target was ablated by the KrF laser pulses (248 nm, 10 Hz, 1 J/cm2) in an ultra high vacuum to deposit ZnO film on sapphire ...(0001) substrate. The lateral grain size was about 50 nm for the sample with thickness of 55 nm. At room temperature, the peak of the exciton absorption and the photoluminescence have the same energy. Under high density excitation (355 nm, 35 ps, 10 Hz), an exciton–exciton collision process was observed as P2 and P lines where 2S exciton and ionized exciton remain. From the edge of the sample, a very rapid increase of the P line was observed with the increase of the excitation power. A fine structure that comes from the cavity mode was also observed. These facts suggest that the lasing of the exciton was observed at room temperature.
Long-term cancer survivors risk development of second primary cancers (SPC). Vigilant follow-up may be required. We report outcomes of 92 patients who underwent chemoradiation for unresectable stage ...III non-small-cell lung cancer, with a median follow-up of 8.9 years. The incidence of SPC was 2.4 per 100 patient-years (95% confidence interval: 1.0-4.9).
Hexagonally shaped ZnO nanocrystal thin films were fabricated on sapphire(0001) substrates by laser molecular beam epitaxy. Nanocrystal structure was investigated by atomic force microscopy and ...transmission electron microscopy. Epitaxial growth of ZnO nanocrystal thin films on sapphire substrates was found to occur in a spiral and grain growth mode. The grain growth mode was interpreted by taking higher order epitaxial relationship of oxygen sublattice units between ZnO and sapphire into account. Nanocrystal size could be tuned from 50 to 200 nm controlling film thickness, growth conditions and stoichiometry of the target. The films having small nanocrystal size of about 50 nm showed excitonic stimulated emission having peak energy of 3.2 eV at room temperature with a very low threshold (24 kW cm
−2). Mode transition from excitonic stimulated emission to electron hole plasma appeared above another threshold (50 kW cm
−2). Well defined Fabry–Perot cavity mode was observed in the emission spectra measured from side edge of the film. It was concluded that the grain boundaries between nanocrystals serve not only as potential barriers confining excitons but also as cavity mirrors.
A reproducible real-time PCR method that targets the putative transcriptional regulator gene of Staphylococcus aureus was developed to quantify this microorganism in milk samples. On the basis of ...partial sequences of this gene determined from S. aureus strains, we designed the specific primers and probe for use in a quantitative PCR assay. These specificities were confirmed with 25 strains of S. aureus and 35 strains of other bacteria. A real-time PCR assay with serial 10-fold dilutions of purified DNA and pure culture was conducted. It was possible to construct standard curves with a high correlation coefficient (r2 = 0.99) in the range of 50 ng to 50 fg for purified DNA and 10(7) to 10(1) CFU/ml for a pure culture. The constructed standard curve for milk samples was similar to that for the pure culture, and the quantification of S. aureus in the range of 10(7) to 10(1) CFU/ml was possible. Moreover, to determine how our real-time PCR method would perform under actual analytical conditions, we quantified the DNA from S. aureus after two types of heat treatments were used for the pasteurization of milk. The amount of DNA found was affected after heat treatment at 63 degrees C for 30 min (low-temperature long-time method) but not at 72 degrees C for 15 s (high-temperature short-time method). The results indicate that the real-time PCR method developed in this study is effective for monitoring S. aureus contamination in milk because of its high specificity and sensitivity.
We report room-temperature measurements of optical gain and gain spectra of ultraviolet emission from ZnO thin film. An optical gain of 300 cm
−1 is measured at a fluence of 3.8 μJ/cm
2. The large ...gain is attributed to the modification of the spontaneous emission rate by the dielectric photonic structure of these films. The presence of excitonic gain is also observed in the room-temperature gain spectra.
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