[en] A phase-field model for predicting the coherent microstructure evolution in constrained thin films is developed. It employs an analytical elastic solution derived for a constrained film with arbitrary eigenstrain distributions. The domain structure evolution during a cubic->tetragonal proper ferroelectric phase transition is studied. It is shown that the model is able to simultaneously predict the effects of substrate constraint and temperature on the volume fractions of domain variants, domain-wall orientations, domain shapes, and their temporal evolution. [copyright] 2001 American Institute of Physics

[en] We report for the first time coherent ultraviolet radiation at 284 nm by intracavity sum-frequency generation of a 607 nm Pr:YLF laser and a 532 nm frequency doubling Nd:YVO₄ laser. The ultraviolet laser is obtained by using double resonator, type-I critical phase matching CsLiB₆O₁₀ (CLBO) crystal sum-frequency mixing. With a total pump power of 18.8 W (3.1 W pump power for the 607 nm Pr:YLF laser and 15.7 W pump power for the 532 nm Nd:YVO₄ frequency doubling laser), a TEM₀₀ mode ultraviolet laser beam at 284 nm of 242 mW is obtained. The power stability is better than 3.4% and laser beam quality M2 factors are 1.13 and 1.22 in the horizontal and vertical dimensions respectively. (letter)

[en] We report for the first time (to our knowledge) a quasi-three-level Nd:Sr₃Ga₂Ge₄O₁₄ (Nd:SGG) laser emitting at 902 nm. An end-pumped Nd:SGG crystal yielded 718 mW of continuous-wave (CW) output power for 17.9 W of incident pump power. Intracavity second-harmonic generation (SHG) in CW mode has also been demonstrated with a power of 116 mW at 451 nm by using a LiB₃O₅ (LBO) nonlinear crystal. The blue beam quality factor M² was less than 1.27. The green power stability was less 5.3% in 4 hour

[en] The ultraviolet photolysis of CH₂I₂ was studied in water and salt water solutions using photochemistry and picosecond time-resolved resonance Raman spectroscopy. Photolysis in both types of environments produces mainly CH₂(OH)₂ and HI products. However, photolysis of CH₂I₂ in salt water leads to the formation of different products/intermediates (CH₂ICl and Cl₂^-) not observed in the absence of salt in aqueous solutions. The amount of CH₂(OH)₂ and HI products appears to decrease after photolysis of CH₂I₂ in salt water compared to pure water. We briefly discuss possible implications of these results for photolysis of CH₂I₂ and other polyhalomethanes in sea water and other salt aqueous environments compared to nonsalt water solvated environments

[en] We report an experimental observation of H⁺ and I^- being formed following ultraviolet photolysis of CH₂I₂ in liquid water. The concentration of H⁺ and I^- are about the same and suggest a reaction that produces a HI leaving group. A preliminary ab initio investigation is reported for the O-H insertion reactions of the isodiiodomethane (CH₂I-I) carbenoid species with H₂O and 2H₂O and these are compared to the related reactions for the dichlorocarbene (:CCl₂) species. The CH₂I-I carbenoid reacts with water via an O-H insertion/HI elimination reaction mechanism. These reactions produce a HI leaving group whereas the dichlorocarbene O-H insertion reaction has no need for a leaving group. The differing structures and properties of the CH₂I-I and the :CCl₂ species can account for the differences in their O-H insertion reactions. The CH₂I-I species O-H insertion/HI elimination reactions can be catalyzed by a second water molecule when two water molecules are available and this occurs in a way similar to that previously observed for the reaction of :CCl₂ with two water molecules. These results suggest that isopolyhalomethane molecules (like CH₂I-I and others) are noticeably reactive towards O-H bonds like those found in water and can likely account for the strong acid formation observed experimentally after ultraviolet photolysis of polyhalomethanes in water. Possible implications for the photochemistry of polyhalomethanes in the atmosphere and oceans are briefly discussed

[en] A combined experimental and theoretical study of the ultraviolet photolysis of CH₂I₂ in water is reported. Ultraviolet photolysis of low concentrations of CH₂I₂ in water was experimentally observed to lead to almost complete conversion into CH₂(OH)₂ and 2HI products. Picosecond time-resolved resonance Raman spectroscopy experiments in mixed water/acetonitrile solvents (25%-75% water) showed that appreciable amounts of isodiiodomethane (CH₂I-I) were formed within several picoseconds and the decay of the CH₂I-I species became substantially shorter with increasing water concentration, suggesting that CH₂I-I may be reacting with water. Ab initio calculations demonstrate the CH₂I-I species is able to react readily with water via a water-catalyzed O-H-insertion and HI-elimination reaction followed by its CH₂I(OH) product undergoing a further water-catalyzed HI-elimination reaction to make a H₂C=O product. These HI-elimination reactions produce the two HI leaving groups observed experimentally and the H₂C=O product further reacts with water to produce the other final CH₂(OH)₂ product observed in the photochemistry experiments. These results suggest that CH₂I-I is the species that reacts with water to produce the CH₂(OH)₂ and 2HI products seen in the photochemistry experiments. The present study demonstrates that ultraviolet photolysis of CH₂I₂ at low concentration leads to efficient dehalogenation and release of multiple strong acid (HI) leaving groups. Some possible ramifications for the decomposition of polyhalomethanes and halomethanols in aqueous environments as well as the photochemistry of polyhalomethanes in the natural environment are briefly discussed

[en] A multi-channel readout electronics system for GEM and MICROMEGAS has been developed. It consists of a front-end ASIC, a multi-channel ADC and a FPGA to sample the signal waveforms in real time. The gain of the front-end ASIC can be programmable from 1 mV/fC to 19 mV/fC and the output pulse width can be adjusted from 200 ns to 800 ns. The ENC is measured to be below 2000 e for C_in < 20 pF and below 5000 e for C_in < 60 pF. Detailed circuit performance and test results with detectors will be described in this paper.

[en] Since pigs are important in the zoonotic transmission of schistosomiasis japonica in China, a veterinary vaccine might contribute to the control of the disease in humans. Pigs were immunized with three doses each of 10 000 cercariae of Schistosoma japonicum attenuated with ultraviolet light (400 μWatt.min/cm²). The experiment was performed with portable irradiation equipment in a rural area of the Hubei Province (P.R. China). A challenge infection of 1000 untreated cercariae was given 2.5 or 6 months after the last immunization, and age-matched naive pigs were challenged as a control. Immunized pigs developed about 90% resistance against the challenge. The liver egg load of these animals was reduced by over 90%. Less than 0.01% of the immunizing cercariae developed to adult parasites and the vaccination had no apparent adverse influence on the pig's health. (Author)

[en] We report a coherent blue-green radiation at 497 nm by self-sum-frequency generation of the 936 and 1060 nm laser-lines of the Nd:YCa₄O(BO₃)₃ (Nd:YCOB) crystal. With a diode pump power of 14.3 W, the maximum blue-green output power of 75 mW is obtained. The beam quality M² value is 1.22 in both horizontal and vertical dimensions. The output power stability over 30 min is better than 4.1%. To the best of our knowledge, this is first work on self-sum-frequency generation of a diode pumped Nd:YCOB laser at 497 nm

[en] The purpose of this study is to synthesize and characterize fluorescent polymers, rhodamine B-ethylenediamine-hyaluronan acid (RhB-EA-HA). RhB-EA-HA was successfully synthesized by ester ammonolysis reaction and amidation reaction. Moreover, the structural properties of RhB-EA-HA were characterized by ¹H-NMR spectra, UV-vis spectrometry and Fourier transform infrared spectroscopy (FT-IR). RhB-EA-HA can be grafted on the surface of silica nanomaterials, which may be potential biological functional materials for drug delivery system. (paper)