Architecture dependence of thermal fluctuation effects on the order-disorder transition of block copolymer melts

Small-angle X-ray scattering has done to explore the difference in the strength of the thermal fluctuation effects between A-B diblock copolymer and (A/2)₂-B Y-shaped copolymer. SAXS profiles for both systems in their disordered states were analyzed with the Brazovskii-type non-mean field theory by Fredrickson and Helfand. The analyses yielded Ginzburg number characterizing the strength of thermal fluctuation effects. Ginzburg number of Y-shaped copolymer is larger than that of diblock copolymer, suggesting that the strength of the thermal fluctuation effects is affected by the architecture of copolymers.     

Temporal and Spatial Variations in N2O Emissions from a Chinese Cabbage Field as a Function of Type of Fertilizer and Application

We conducted a field experiment in an Andosol near Tsukuba (Japan) to study the effects of the type of nitrogen fertilizer on nitrous oxide (N₂O) emissions and on nitrogen uptake by Chinese cabbage (Brassica campestris L.). We used four treatments: fertilizer containing no nitrogen (CONT), broadcast application of urea (BR-U), band application of urea (B-U), and band application of controlled-release urea (B-CU). The application rate was 250 kg N ha⁻¹, a conventional rate in the region. We measured N₂O flux two or three times a week during the 82-day growth period, then divided the cumulative emissions into three stages: early (28 days), middle (27 days), and late (27 days). The temporal variation in N₂O emissions differed among the treatments. Broadcast urea application produced 70% of N₂O emissions during the early stage. N₂O emissions increased with increasing cabbage growth in the CONT treatment, indicating that plant growth accompanied by increasing root biomass could stimulate N₂O emissions from unfertilized soil. There were no differences in the patterns of temporal variation in N₂O flux between the two band applications (B-U and B-CU); N₂O emissions in the early and middle stages were 46 and 42%, respectively, for B-U, vs. 41 and 40% for B-CU. However, the overall N₂O emission was reduced by 40.5% in the B-CU treatment compared with the B-U treatment. N₂O emissions from the soils within fertilized bands were dramatically higher than those between the fertilized bands, and this trend continued until harvesting.     

Interlook cross-correlation function of speckle in SAR images of sea surface processed with partially overlapped subapertures

In the present paper, a general integral expression is derived and discussed for the cross-correlation function (CCF) of speckle patterns in synthetic aperture radar (SAR) images processed by using partially overlapped subapertures of arbitrary Doppler center frequencies (or equivalent azimuth times). It is shown that, under the white noise approximation for the backscattered field, the CCF of the interlook speckle intensity patterns is given by the squared modulus of the autocorrelation function of the amplitude weighting function of subapertures where the time lag is the center time difference. It is also shown that the CCF of the interlook speckle patterns is independent of the surface coherence time of sea surface. The integral expression for the intensity CCF is then evaluated for a rectangular weighting function, and comparison is made with Japanese Earth Resources Satellite-1 (JERS-1) L-band and RADARSAT-1 C-band SAR images of sea surface to test the theory. The CCFs computed from the JERS-1 SAR data show excellent agreement with the theory, and good agreement is obtained with the RADARSAT-1 data.     

Polycrystal isolation of InGaP/GaAs HBTs to reduce collectorcapacitance

InGaP/GaAs heterojunction bipolar transistors (HBTs) with polycrystalline GaAs buried under the base electrode have been fabricated using low-temperature gas-source molecular beam epitaxy on SiO₂-patterned substrates. A cutoff frequency of 120 GHz and a maximum oscillation frequency of 230 GHz were obtained for three parallel 0.7×8.5 μm HBTs. Compared to HBTs without the polycrystal, the collector capacitance was reduced by 28% and the maximum stable gain was improved by 1.2 dB due to complete carrier depletion in the polycrystal under the base electrode. These results show the high potential of the proposed HBTs for high-speed digital and broadband-amplifier applications     

Randomized prospective trial of gentian violet with dibutyryl cAMP and povidone-iodine with sugar as treatment for pressure sores infected with methicillin-resistant Staphylococcus aureus in elderly patients

A randomized prospective study was done to evaluate the two treatments for pressure sores infected with methicillin-resistant Staphylococcus aureus in elderly patients: Gentian violet plus dibutyryl cAMP (GVcAMP, n = 8) and povidone-iodine plus sugar (IS, n = 11). Age, underlying diseases, and nutritional status did not differ between the two groups. Specimens were obtained biweekly from the pressure sores and were cultured. The percentage of culture dishes with no methicillin-resistant S. aureus was 93% for the patients given GVcAMP, but only 74% for those given IS (p < 0.01). By the 14th week after the start of treatment, the mean area of the pressure sores in the GVcAMP group had decreased to 45% of the area at the start of treatment. In the IS group, the decrease was smaller to 56% of the area before treatment. No local or systemic adverse effects occurred in either group. GVcAMP is useful to treat pressure sores infected with methicillin-resistant S. aureus.     

Fabrication of magnetic nanodot array using electrochemical deposition processes

We investigated fabrication processes of magnetic nanodot arrays for the ultra-high density magnetic recording media by using an electrodeposition. A CoZrNb underlayer was sputter-deposited on a glass disk substrate as a soft magnetic underlayer (SUL). Nano-patterns were formed on the substrate by UV-nanoimprint lithography (UV-NIL) and CoPt was electrodeposited into the nano-patterns. For obtaining uniform CoPt nanodot arrays with high perpendicular coercivities, we applied thin Cu intermediate layer on CoZrNb SUL and minimized its thickness. As a result, we obtained CoPt nanodot arrays with 150-nm diameter, 300-nm pitches, and 20-nm heights, which have uniform structures, on the substrates with the construction of Cu (1-2 nm)/CoZrNb (100 nm)/Cr (5 nm)/glass disk. The perpendicular coercivity of the CoPt nanodot arrays was as high as 5.4 kOe. From these results, we showed that the Cu intermediate layer with even 1-2 nm thick considerably improved the deposition condition on the substrates with CoZrNb SUL to successfully fabricate CoPt nanodot arrays with the diameter and pitches of 80 nm and 160 nm with sufficient uniformity.     

Precision control of radical polymerization via transition metal catalysis: from dormant species to designed catalysts for precision functional polymers

In the past decade, living radical polymerization has provided one of the most versatile methods to precisely construct designed polymer architectures with complexity and polar functionality. This process takes advantage of carbon-radical intermediates, which tolerate a variety of functional groups in monomers and reaction media. "Transition metal-catalyzed living radical polymerization", one of these living systems, has widely been employed for precision polymer synthesis. Not only can this process produce well-defined functional polymers, but it can also generate hybrids or conjugates with other (often biological) materials. Metal-catalyzed systems retain the advantages of conventional radical polymerization but distinguish themselves through a catalytic reversible halogen exchange equilibrium: the growing radical exists alongside a dormant speciesa covalent precursor capped with a terminal halogen from an initiator. The catalyst dictates the selectivity, exchange rate, and control over the polymerization. This Account provides an updated overview of our group's efforts in transition metal-catalyzed living radical polymerization with specific emphasis on the design of metal catalysts and the resulting precision polymer syntheses. With increasing use of the living processes as convenient tools for materials synthesis, researchers are currently seeking more active and versatile metal catalysts that are tolerant to functional groups. Such catalysts would enable a wider range of applications and target products, would have low metal content, could be readily removed from products, and would allow recycling. Since we first developed the "transition metal-catalyzed living radical polymerization" with RuCl 2(PPh 3) 3, FeCl 2(PPh 3) 2, and NiBr 2(PPh 3) 2, we have strived to systematically design metal catalysts to meet these new demands. For example, we have enhanced catalytic activity and control through several modifications: electron-donating or resonance-enhancing groups, moderate bulkiness, heterochelation via a ligand, and halogen-donor additives. For some catalysts, the use of amphiphilic and polymeric ligands allow efficient recovery of catalysts and convenient use in aqueous media. We have also used ligand design (phosphines) and other methods to improve the thermal stability of iron- and nickel-based catalysts and their tolerance to functional groups.     

Revealing the formation mechanism of granules by drying simulation of slurry droplet

The formation mechanism of granules in spray drying process was investigated by DEM-CIP method simulation coupled with a new binder segregation model. To confirm the validity of proposed binder segregation model, experiment on drying of aqueous slurry containing fine particles and binder was performed. The experimental concentration distribution of binder in a dried powder bed agreed well with the simulated one and this result shows that the proposed segregation model is valid to represent segregation phenomenon in the dried granule. Spherical hollow granules were formed with increasing of binder concentration, and the granules were depressed in higher concentration of binder. When the binder concentration in the surface region of a slurry droplet increased during drying, a crust of granule was formed because particle migration was hindered by high fluid viscosity. For the rigid crust layer, granules were hollow. When the crust layer was formed early in drying and its thickness was thin, granule surface partially collapsed inward, whereas the granule resulted in depression granules.