TEM study of Mg-Zn precipitates in Mg-Zn-Y alloys

The precipitates in Mg-Zn-Y alloys in the as-cast state with nominal atomic composition of Mg₉₆Zn₁Y₃, Mg₉₆Zn₂Y₂ and Mg₉₇Zn₁Y₂ were studied by means of TEM as well as XRD techniques. The results show that there is a phase separation of Zn on the nanometer scale in these alloys. Two kinds of nano-sized precipitates were found, namely MgZn and MgZn₂. TEM observation shows that MgZn precipitates are distributed in both the Mg matrix and in Mg₂₄Y₅ grains, which is the typical precipitate in Mg-Zn-Y alloys. There is an inherent crystallographic relationship between MgZn and Mg₂₄Y₅ precipitates: // , // . The size of MgZn₂ precipitates is much smaller than that of MgZn precipitates. They are distributed only in Mg₂₄Y₅ grains, not in the Mg matrix. It is suggested that the nano-sized precipitates, MgZn and MgZn₂, can improve the mechanical properties of the Mg-Zn-Y alloys studied.     

Transmission electron microscopy study on the superstructure and the precipitation of γ′-Fe4N in initially homogeneous ɛ-iron nitride powders

Annealed and quenched ɛ-Fe_2-3N powders with an initially homogeneous composition of Fe₃N_1.0 were studied by transmission electron microscopy (TEM). TEM specimens were successfully prepared from the powder using a sandwiching technique. The superstructure in ɛ-powders was identified as ɛ′-Fe₃N type (space group P6₃22), and no other type of superstructure was observed. γ′-Fe₄N nitride precipitated from ɛ powders as individual grains during the annealing process, which is different from the typical fine lamellar structure observed in bulk iron-nitride samples. The observed orientation relationships between γ′ and ɛ grains are also different from that reported in the lamellar structure of bulk iron-nitride samples. This suggests that in the powder investigated by us there is no one specific orientation of the precipitated γ′ grains with respect to the parent ɛ grains.     

Electron beam-induced formation of nanosized α-Fe crystals

Focused electron beam induced chemical vapor deposition was performed in a scanning electron microscope with a field emission gun using a precursor of iron carbonyl. Due to the longer deposition time and higher gas pressure than those of our previous electron beam-induced deposition method, a new type of deposition occurred. A large amount of nanosized crystals were produced around the focused beam irradiation point on a carbon substrate at room temperature. The nanocrystals were systematically characterized using transmission electron microscopy with electron energy loss spectroscopy (EELS), and were identified to be single crystals of α-Fe.     

Simultaneous determination of intraparticle diffusivity and liquid film mass transfer coefficient from a single-component adsorption uptake curve

In general, the rate of adsorption involves both rates of liquid film mass transfer and intraparticle diffusion. Many researchers tried to minimize the effect of liquid film resistance when determining the effective intraparticle diffusivity. However, in some cases (for example, small adsorbent particle size), the liquid film resistance may not be easily eliminated in a fixed bed process. Therefore, this research proposed using the shallow bed technique to determine both intraparticle diffusivity (D(S)) and liquid film mass transfer coefficient (k(F)) simultaneously from a single-component adsorption uptake curve (AUC). The task was accomplished by the determination of the Biot number (Bi) from experimental adsorption uptake curve (EAUC). The Bi represents the ratio of the rate of transport across the liquid film to the rate of intraparticle mass transfer. The detailed calculation method is addressed in this paper. The method proposed in this research can be applied in the range of Bi between 0.5 and 200 where both liquid film resistance and intraparticle diffusion are significant.     

Coexistence of proguanylin (1-15) and somatostatin in the gastrointestinal tract

In order to identify proguanylin-secreting cells, we have raised an antiserum against the synthetic fragment of human proguanylin (1-15) and have examined the proguanylin-positive cells in the human and rat gastrointestinal tract by immunohistochemical methods. Numerous proguanylin (1-15)-immunoreactive cells were found in the gastrointestinal tract. They were either pyramidal or spindle shaped in the stomach. Spindle-shaped cells, frequently possessing long slender processes, were located at the base of the pyloric epithelium and did not extend to the lumen. In the duodenum and jejunum, these cells were mostly pyramidal in shape and often had a slender process towards the lumen. The immunostaining was completely blocked by the human proguanylin (1-15) fragment. Paneth and goblet cells were negative against this antiserum. The number of serotonin-positive cells was much larger than that of proguanylin-positive cells in all the segments tested. The number of proguanylin-positive cells decreased from the jejunum to the ileum and very few cells were observed in the colon. In contrast to serotonin-positive cells, most somatostatin-positive cells were also positive for proguanylin. Thus, proguanylin (1-15) or its related protein appears to coexist with somatostatin in intestinal endocrine D cells which may be a source of circulating proguanylin. Proguanylin, like somatostatin, may also regulate intestinal function as a local regulator.     

Molecular characterization of Xenopus embryo heparan sulfate. Differential structural requirements for the specific binding to basic fibroblast growth factor and follistatin

Enzymatic elimination of heparan sulfate (HS) causes abnormal mesodermal and neural formation in Xenopus embryos, and HS plays an indispensable role in establishing the embryogenesis and tissue morphogenesis during early Xenopus development (Furuya, S., Sera, M., Tohno-oka, R., Sugahara, K., Shiokawa, K., and Hirabayashi, Y. (1995) Dev. Growth Differ. 37, 337-346). In this study, HS was purified from Xenopus embryos to investigate its disaccharide composition and binding ability to basic fibroblast growth factor (bFGF) and follistatin (FS), the latter being provided in two isoforms with core sequences of 315 and 288 amino acids (designated FS-315 and FS-288) originating from alternative mRNA splicing. Disaccharide composition analysis of the purified Xenopus HS showed the preponderance of a disulfated disaccharide unit with uronic acid 2-O-sulfate and glucosamine 2-N-sulfate, which has been implicated in the interactions with bFGF. Specific binding of the HS to bFGF and FS-288, the COOH-terminal truncated form, was observed in the filter binding assay, whereas HS did not bind to FS-315, indicating that the acidic Glu-rich domain of FS-315 precluded the binding. The binding of the HS to bFGF or FS-288 was markedly inhibited by heparin (HP) and various HS preparations, but not by chondroitin sulfate, supporting the binding specificity of HS. The binding specificity was further investigated using FS-288 and bovine intestinal [3H]HS. Competitive inhibition assays of the HS binding to FS-288 using size-defined HP oligosaccharides revealed that the minimum size required for significant inhibition was a dodecasaccharide, which is larger than the pentasaccharide required for bFGF binding. The binding affinity of FS to HS increased in the presence of activin, a growth/differentiation factor, which could be inactivated by direct binding to FS. These results, taken together, indicate that the structural requirement for binding of HS to bFGF and FS is different. HS may undergo dynamic changes in its structure during early Xenopus embryogenesis in response to the temporal and spatial expression of various growth/differentiation factors.     

Radiation therapy with neoadjuvant hormonal therapy for prostate cancer confined to pelvis

Neoadjuvant endocrine treatment prior to radical prostatectomy for prostate cancer confined to pelvis has of some value to prevent progression although there are many controversies. In order to improve the prognosis of locally advanced prostate cancer (stage B2 and C), definitive radiotherapy with neoadjuvant endocrine therapy has been investigated. Endocrine therapy reduces the volume of prostate, thus reduces the amount of side effect via reducing the area of irradiated normal tissue. Effect of radiation and that of endocrine therapy to induce apoptosis might be synergistic. The result is favorable although the follow-up period is too short. Further studies are needed to make conclusion.     

Surgical management of late esophageal perforation

A simple and rapid high-performance capillary electrophoresis (HPCE) method for the determination of 2-mercaptopyridine-1-oxide (pyrithione) was developed. After addition of ethylenediaminetetraacetic acid (EDTA), pyrithione was determined in the form of the free anion using 50 mM borate (pH 9.2) as background electrolyte and was detected at 244 nm with a limit of detection (LOD) of 0.636 ppm (S/N = 3). The method was used to check the purity of pyrithione preparations and for the determination of pyrithione in shampoo.     

Thieno[2,3-d]pyrimidine-3-acetic acids. A new class of nonpeptide endothelin receptor antagonists

On the basis of structural information for the cyclic hexapeptide endothelin (ET) receptor antagonist, TAK-044, a series of thieno[2,3-d]pyrimidine-2,4-dione derivatives bearing a carboxyl group and aromatic rings that were important for receptor binding were designed, synthesized, and evaluated for ET receptor binding affinities and inhibitory activities against ET-induced vasoconstriction. Optimization of each substituent in the thieno[2,3-d]pyrimidine ring led to the discovery of a novel and potent nonpeptide ET receptor antagonist, 6-(4-methoxymethoxyphenyl)-5-methylsulfonylaminomethyl-1-(2- methylthiobenzyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]p yrimidine-3- acetic acid (32 g), which binded to human ETA and ETB receptor subtypes with affinities (IC50) of 7.6 and 100 nM, respectively. Compound 32 g effectively antagonized ET-induced vasoconstriction and the inhibitory effect mediated by the ETB receptor was more potent than that of bosentan, while the inhibitory effect mediated by the ETA receptor was slightly less potent than that of bosentan.