Effect of in-flight particle behavior on the morphology of flame sprayed Er2O3 splats

The morphology and microstructure of splats impact the comprehensive capability of a new coating methodology called chelate flame spraying (CFS). This study addresses the quantitative characterization of the spread morphologies of flame sprayed Er₂O₃ splats directly deposited under different spray conditions on aluminum alloy substrates with a mirror finish. The influence of the in-flight particle temperature and velocity, carrier gas type, and carrier gas ratio on the solidification mechanism of molten droplets was investigated. Image analysis methods were employed to identify single splats from the morphology observed with field-emission scanning electron microscopy (FE-SEM). In addition, Er₂O₃ films were synthesized on an Al–Mg alloy (A5052) substrate using N₂ or O₂ as the carrier gas. When O₂ was used as the carrier gas, 109-μm-thick films were deposited on the A5052 substrate. The cross-sectional porosity of the films was 3.8%. In contrast, films with 101-μm thickness were synthesized on the A5052 substrate when N₂ was used as the carrier gas. The cross-sectional porosity of these films was 13.8%. The results showed that the carrier gas type (N₂) and carrier gas ratio had a significant effect on the flattening behavior of the molten droplets. A spraying method combined with multidimensional modes is proposed to control the morphology of the splats.     

Chemical sensor based on surface acoustic wave resonator using Langmuir-Blodgett film

A one-port surface acoustic wave (SAW) resonators incorporating Langmuir-Blodgett (LB) films has been investigated. SAW sensors are one potential applications of SAW devices. Most of the work reported on SAW sensor concerns delay lines. In this paper we characterize the mass loading effects of one-port resonators by depositing successive monolayers of LB films onto the surface. A 90 MHz SAW gas-phase sensor has been fabricated on an ST cut quartz substrate, and one-port resonator configurations have been used as the sensing element. Ultra thin monolayers of arachidic acid and arachidic acid ethyl ester have been deposited using the LB method. The resonant frequencies and the Q values have been measured as sensor response. Experimental results show that the Q values and the resonant frequencies of the one-port SAW resonator vary with film mass loading on the SAW device surface.     

A 20 MHz single-element ultrasonic probe using 0.91Pb(Zn(1/3 )Nb(2/3))O(3)-0.09PbTiO(3) single crystal

A 20 MHz single-element ultrasonic probe using 0.91Pb(Zn(1/3 )Nb(2/3))O(3)-0.09PbTiO(3) (PZN-PT 91/9) single crystal has been fabricated. The single crystal of PZN-PT 91/9 orientated to the (001) plane has longitudinal coupling factor of k(33)>90%, which is much larger than the k(33)=70 to 80% of conventional Pb(Zr(1-x),Ti(x))O(3) (PZT) based ceramics. A single crystal of PZN-PT 91/9 without inclusion or crack has been grown with dimensions of about 25x15x5 mm by the self-flux method. Because mechanical strength in the fabrication of disk transducers orientated to the (001) plane was sufficiently strong, under the same conditions as are applied to conventional PZT ceramics, a piston single-element probe with a diameter of 2.0 mm and a frequency of 20 MHz was successfully fabricated. The bandwidth of the PZN-PT 91/9 probe was 13-26 MHz, which was 4 MHz broader than that of the conventional PZT probe.     

Helicobacter pylori may cause "reflux" gastritis after gastrectomy

Patients with "reflux" gastritis after gastrectomy suffer from a variety of symptoms, and this type of gastritis may sometimes compromise the quality of life of these patients. Since Helicobacter pylori is considered to be one of the most important pathogenetic factors in gastritis, the association between H. pylori and reflux gastritis was investigated in this study. A total of 145 patients with gastrectomy were entered into the study. Five biopsy specimens from the gastric remnant were taken at upper gastrointestinal endoscopy. One specimen was examined pathohistologically, and the remaining four were examined for H. pylori infection. Fifty-two patients (36%) demonstrated H. pylori infection. The prevalence of H. pylori was significantly higher in patients who had a partial gastrectomy, and it was significantly lower in patients who had undergone gastrectomy more than 4 years previously. The histologic gastritis score in patients with H. pylori infection was significantly higher. Furthermore, H. pylori was eradicated in patients with some symptoms of gastritis and no bile reflux to the residual stomach at endoscopy; in these patients the symptoms were relieved and the histologic gastritis score decreased significantly. In conclusion, possible involvement of H. pylori is suspected in the pathogenesis of "nonreflux" gastritis after gastrectomy.     

Grafting of branched polymers onto nano-sized silica surface: Postgrafting of polymers with pendant isocyanate groups of polymer chain grafted onto nano-sized silica surface

To control the surface wettability of nano-sized silica surface, the postgrafting of hydrophilic and hydrophobic polymers to grafted polymer chains on the surface was investigated. Polymers having blocked isocyanate groups were successfully grafted onto nano-sized silica surface by the graft copolymerization of methyl methacrylate (MMA) with 2-(O-[1′-methylpropylideneamino]caboxyamino)ethyl methacrylate (MOIB) initiated by azo groups previously introduced onto the surface. The blocked isocyanate groups of poly(MMA-co-MOIB)-grafted silica were stable in a desiccator, but isocyanate groups were readily regenerated by heating at 150 °C. The hydrophilic polymers, such as poly(ethylene glycol) (PEG) and poly(ethyleneimine) (PEI), were postgrafted onto the poly(MMA-co-MOIB)-grafted silica by the reaction of functional groups of PEG and PEI with pendant isocyanate groups of poly(MMA-co-MOI)-grafted silica to give branched polymer-grafted silica. The percentage of grafting increased with increasing molecular weight of PEG, but the number of postgrafted chain decreased, because of steric hindrance. The hydrophobic polymers, such as poly(dimethylsiloxane) were also postgrafted onto poly(MMA-co-MOI)-grafted silica. It was found that the grafting of hydrophobic polymer and the postgrafting of hydrophilic polymer branches readily controls the wettability of silica surface to water.     

Growth of High-Quality Pb((Zn1/3Nb2/3)0.91Ti0.09)O3 Single Crystals by Excess ZnO Addition

A high-quality single crystal of Pb((Zn_1/3Nb_2/3)_0.91Ti_0.09)O₃ (PZNT 91/9), 40 mm in diameter and 20 mm in length, was successfully grown using the solution Bridgman method with a slight excess amount of ZnO. High-quality wafers were sliced from the light-brown single crystal. No PbO inclusions or opaque areas were observed in the transparent wafers. An array probe for echocardiography was constructed with the single-crystal wafer, and its superior performance was demonstrated.     

Conception of Stretchable Resistive Memory Devices Based on Nanostructure‐Controlled Carbohydrate‐block‐Polyisoprene Block Copolymers

It is discovered that the memory‐type behaviors of novel carbohydrate‐block ‐polyisoprene (MH‐b ‐PI) block copolymers‐based devices, including write‐once‐read‐many‐times, Flash, and dynamic‐random‐access‐memory, can be easily controlled by the self‐assembly nanostructures (vertical cylinder, horizontal cylinder, and order‐packed sphere), in which the MH and PI blocks, respectively, provide the charge‐trapping and stretchable function. With increasing the flexible PI block length, the stretchability of the designed copolymers can be significantly improved up to 100% without forming cracks. Thus, intrinsically stretchable resistive memory devices (polydimethylsiloxane(PDMS)/carbon nanotubes(CNTs)/MH‐b ‐PI thin film/Al) using the MH‐b ‐PI thin film as an active layer is successfully fabricated and that using the MH‐b ‐PI_12.6k under 100% strain exhibits an excellent ON/OFF current ratio of over 10⁶ (reading at ?1 V) with stable V _set around ?2 V. Furthermore, the endurance characteristics can be maintained over 500 cycles upon 40% strain. This work establishes and represents a novel avenue for the design of green carbohydrate‐derived and stretchable memory materials.     

Novel hybrid block copolymer nanocarrier systems to load lipophilic drugs prepared by microphase inversion method

Nanoparticles based on block copolymers of oligosaccharides [β-cyclodextrin (βCyD) and maltoheptaose (Mal₇)] and poly(ε-caprolactone) (PCL) were prepared by microphase inversion method. Zeta-potential, particle size measurements and morphological analysis of drug-free and drug-loaded nanoparticles were performed by using, respectively, laser-doppler anemometry, dynamic and static light scattering and transmission electron microscopy. ρ-Ratio values were correlated with transmission electron microscopy observations. Both types of amphiphilic block copolymers, βCyD-b-PCL_5k and Mal₇-b-PCL_5k, self-assembled in water to form spherical vesicles, presented a hydrodynamic diameter of 72 and 34 nm, respectively. The incorporation of drugs into nanoparticles did not affect significantly the particle size for βCyD-b-PCL_5k-based nanoparticles with progesterone, unlike the other tested systems. On the other hand, all nanoparticles (with and without drug) were negatively charged. Both nanoparticulate systems showed high drug loading efficiency (higher than 95%), confirming their suitability as delivery system for lipophilic drugs.