63/65^{63/65}Cu- and 35/37^{35/37}Cl-NMR Studies of Triplet Localization in the Quantum Spin System NH4_4CuCl3_3

$^{63/65}$Cu- and $^{35/37}$Cl-NMR experiments were performed to investigate triplet localization in the $S=1/2$ dimer compound NH$_4$CuCl$_3$, which shows magnetization plateaus at one-quarter and three-quarters of the saturation magnetization. In $^{63/65}$Cu-NMR experiments, signal from only the singlet Cu site was observed, because that from the triplet Cu site was invisible due to the strong spin fluctuation of onsite 3$d$-spins. We found that the temperature dependence of the shift of $^{63/65}$Cu-NMR spectra at the singlet Cu site deviated from that of macroscopic magnetization below T=6 K. This deviation is interpreted as the triplet localization in this system. From the $^{35/37}$Cl-NMR experiments at the 1/4-plateau phase, we found the two different temperature dependences of Cl-shift, namely the temperature dependence of one deviates below T=6 K from that of the macroscopic magnetization as observed in the $^{63/65}$Cu-NMR experiments, whereas the other corresponds well with that of the macroscopic magnetization in the entire experimental temperature region. We interpreted these dependences as reflecting the transferred hyperfine field at the Cl site located at a singlet site and at a triplet site, respectively. This result also indicates that the triplets are localized at low temperatures. $^{63/65}$Cu-NMR experiments performed at high magnetic fields between the one-quarter and three-quarters magnetization plateaus have revealed that the two differently oriented dimers in the unit cell are equally occupied by triplets, the fact of which limits the theoretical model on the periodic structure of the localized triplets.Comment: 19 pages, 9 figures, submitted to PRB (in press

Synthesis of zinc oxide/silica composite nanoparticles by flame spray pyrolysis

Zinc oxide (ZnO)/silica (SiO2) composite nanoparticles were made by flame spray pyrolysis. The effects of the Zn/Si ratio on particle properties were examined and compared with those of the pure ZnO and SiO2 particles made at the same conditions. Polyhedral aggregates of nano-sized primary particles were obtained in all experiments. The mixed-oxide primary particle size was smaller than that of pure oxides. The primary particles consisted of ZnO nano-crystals and amorphous SiO2, as seen by high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) analysis using the fundamental parameter approach. The XRD size of ZnO was controlled from 1.2 to 11.3 nm by the initial precursor composition and it was consistent with HR-TEM. The composite particles exhibited an excellent thermal stability and little crystalline growth of ZnO (e.g., from 1.9 to 2.2 nm) was observed even after calcination at 600°

Single molecule and single quantum dot photodynamics by polarization-rotating modulation microscopy

We present our recent study of polarization modulating fluorescence imaging microscopy on single CdSe colloidal quantum dots (QDs) and quantum rods (QRs) adsorbed on silica glass substrates at room temperatures. Simple optical setup is introduced to provide detection of emission profiles projected on to the sample plane as well as detection of rotating excitation polarization effect. While most studies so far in structural changes in biological or amorphous systems rely on extrinsic fluorophores with linear transition dipoles, those with twofold degenerate dipoles are noteworthy due to the intrinsic advantage for 3D orientation information. Performance of modulations is also evaluated in combination with tetramethylrodamine moieties as typical linear emitters. CdSe QDs with aspect ratio of 1.3 actually reveal plane-polarized emission at room temperature and, based on maximum-likelihood analysis, are exceptionally highly oriented on silica glass substrates

Fabrication of Unglazed Ceramic Tile Using Dense Structured Sago Waste and Clay Composite

In Indonesia, the sago processing industry generates every year huge amount of sago waste, and converting this waste into a useful material is possible. In the present study, physical properties of dense structured sago waste and clay composite were investigated in order to study the feasibility of reuse this sample as raw material in the producing of ceramics. Firstly, the chemical composition of ash (obtained from the sago waste) and clay was characterized. The prepared sample was sintered at the temperature range from 800 to 1,200 °C using electric furnace. The density, linear shrinkage and water absorption of the sintered sample were determined by using the Archimedes' method. The experimental result indicated that the density of the sintered sample increased with increasing sintering temperature up to 1100 °C and then slightly decreased afterward. The water absorption of the products decreased with an increase in sintering temperature. In the sintered sample at 1,100 °C, the water absorption decreased rapidly and water adsorption of less than 1%was achieved. This water absorption was less than 5% which was needed for unglazed floor tile. The result of water adsorption suggest that it is possible to use this sample as a raw material for producing the ceramic floor tile

Relationships between a roller and a dynamic pressure distribution in circular hydraulic jumps

We investigated numerically the relation between a roller and the pressure distribution to clarify the dynamics of the roller in circular hydraulic jumps. We found that a roller which characterizes a type II jump is associated with two high pressure regions after the jump, while a type I jump (without the roller) is associated with only one high pressure region. Our numerical results show that building up an appropriate pressure field is essential for a roller.Comment: 10 pages, 7 PS files. To appear in PR

Distribusi Vertikal Dan Horizontal Asplenium Nidus L. Di Taman Nasional Gunung Halimun, Jawa Barat [Vertical and Horizontal Distributions of Asplenium Nidus L. in Gunung Halimun National Park, West Java]

The study was carried out on August 2000 to July 2001, in 1-ha permanent plot, near Cikaniki Research Station, in Halimun Mountain National Park, West Java.The results shows that, from 1 ha (100 sub plots, each 10x10 m size) studied there were 388 individual numbers of Asplenium nidus L. with some variation on rosette leaves size. The individual numbers of A. nidus were greater at host plant stem with diameter class distribution between 1.3-9.9 cm (45,6%), and than percentages value were decreased in the larger of host plant stem diameter class. Also the individual numbers of A. nidus were greater at under 5 m height position above ground, that is 252 (65,1%).There were no correlation between host plant height (tree trunk height) and A. nidus height position above ground.However there were little linear correlation between rosette leaves size with stem diameter of host plant(Y=1.5586x+317.37 and R =0.0211), and little linear correlation between rosette leaves size with host plant height(Y=2.8241x+304.63, and R =0.0226), but there were no significant increased for both. It was assumed the effects of microclimate(temperature, humidity, light, and rainfall) to distribution of A. nidus as well as horizontal or vertical distribution

Long-term Outcome of Low-concentration Hexyl-5-aminolaevulinate Daylight Photodynamic Therapy for Treatment of Actinic Keratoses

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