Notes: Two microemulsion systems, the ternary system H2O/AOT/isooctane and the binary system DDAB/toluene, were used to prepare metallic cobalt particles by borohydride reduction of a cobalt salt. The particles prepared in the AOT system were extremely small and superparamagnetic with magnetic moment per particle of 11.5μB, a blocking temperature of 2 K, and σs=146 emu/g at 1.7 K. The magnetic moment and σs combined imply a particle size of about 5.4 A(ring). However, the particles made in the DDAB system were relatively large, ∼10 nm. They were ferromagnetic at room temperature but with no coercivity.

Notes: We report studies of the magnetic critical behavior as a function of anisotropy strength in rare-earth-rich glasses. Anisotropy is induced in Gd-Co by alloying with Tb. The system studied is Gd65−xTbxCo35 and the random magnetic anisotropy (RMA) strength may be increased by increasing x. The x=0 alloy of this series has been shown to exhibit standard critical behavior expected for a second-order phase transition. With increasing x we find deviations from this behavior due to the presence of RMA. We present detailed results for the alloy with composition x=50 at. % and show that for large enough magnetic fields the system continues to show standard ferromagnetic scaling but for low enough fields the system crosses over to a behavior describable by nonlinear scaling similar to that found in spin-glass systems.

Notes: The magnetic state and anisotropy of amorphous rare-earth transition-metal systems with a microscopic random uniaxial anisotropy are discussed. Both sputtered Tb-Fe and rapidly quenched Gd65−xRxCo35 alloys (R is a rare earth) were studied. The low-temperature magnetic state of these alloys depends on the anisotropy, exchange, and applied field strength. For the case of weak anisotropy (alloys with small concentrations of anisotropic rare earth) the low-field results can be explained in terms of a correlated spin-glass state and the higher-field magnetization curves by a ferromagnet with wandering axis state. It is also shown that a weak anisotropy such as that found in Gd65−xErxCo35 (x〈8) can lead to double-transition behavior as a function of temperature. The microscopic anisotropy in Gd-Tb-Co, Gd-Er-Co, and Tb-Fe alloys leads to a large macroscopic anisotropy and hysteresis is observed in the torque at 2 K. The macroscopic anisotropy strength depends on the particular rare-earth component present in the alloy and shows a strong temperature dependence. None of the alloys of this work show a significant perpendicular anisotropy. In alloys where the macroscopic anisotropy is weak (Gd65Co35) a fixed in-plane anisotropy is found which is ascribed to anisotropic structural ordering in the plane of the sample. Finally, possible explanations for the movable macroscopic anisotropy found in some Tb-Fe alloys are discussed.

Notes: We have studied the critical behavior in amorphous Tb65Co35. Scaling analyses were done over a number of reduced temperature (t=||T−Tc||/Tc) ranges to ascertain that the critical regime had been reached. The magnetization follows linear (ferromagnetic) scaling at high fields (1–55 kOe) and nonlinear (spin-glass) scaling at low fields (〈1 kOe). The critical exponents for ferromagnetic scaling and for spin-glass scaling are not a function of reduced temperature range.

Notes: We have studied the effect of random magnetic anisotropy (RMA) on transition behavior in Gd-Co glasses. The large RMA induced by alloying with anisotropic rare-earth elements produces standard speromagnetic behavior which includes nonsaturation of magnetization at large enough concentrations at 4.2 K and high fields in all the alloys except the most concentrated Tb alloys. Although these latter alloys have the largest coercivity and the strongest RMA they appear to be closer to saturation at high fields than intermediate concentration Tb alloys. We discuss a mechanism by which this saturation may be produced by short-range correlations in the anisotropy axis.

Notes: Electron traps in undoped-GaAs epitaxial layers grown at low temperatures (〈300 °C) by molecular beam epitaxy were studied by the zero-bias thermally stimulated current technique. Four traps T1-4 were detected in as-grown samples. It was also found that all the traps detected can be annealed out except the T1 trap. However, the buffer layer, with or without annealing, was found to be an effective remedy for backgating in high electron mobility transistors, indicating that the T1 trap may have a much more significant role than the three shallower traps in the suppression of backgating. The T1 trap is believed to be the EL3 electron trap which is related to oxygen contamination.

Notes: Background : It has been suggested that chronic, persistent, uncontrolled inflammations in the stomach could provide the basic step for the beginning of carcinogenesis. One of the potential clinical applications of rebamipide is the inhibition of the immunoinflammatory response in gastric mucosa imposed by Helicobacter pylori.Aim : To determine the implications of long-term rebamipide treatment in H. pylori infection, we studied the underlying moleculo-pathological changes in gastric lesions in mice infected with H. pylori (SS1 strain), following this treatment.Methods : C57BL/6 mice were sacrificed 24 and 50 weeks after H. pylori infection, respectively. Colonization rates of H. pylori, degree of gastric inflammation and other pathological changes including atrophic gastritis and metaplasia, serum levels of IL-1β, TNF-α, IFN-γ and IL-10, mRNA transcripts of various mouse cytokines and chemokines, and NF-κB binding activities, and finally the presence of gastric adenocarcinoma were compared between an H. pylori infected group (HP), and an H. pylori infected group administered with long-term rebamipide-containing pellet diets (HPR).Results : Serum levels of IL-1β, IFN-γ and TNF-α, the gastric mucosal expression of ICAM-1, HCAM and MMP, and transcriptional regulation of NF-κB-DNA binding were all significantly decreased in the HPR group compared with the HP group. An RNase protection assay showed, in the rebamipide administered group, significantly decreased mRNA levels of apoptosis-related genes such as caspase-8, FasL, Fas, TRAIL and various cytokines genes such as IFN-γ, RANTES, TNF-α, TNFR p75, IL-1β. In the experiment designed to provoke gastric cancer through MNU treatment with H. pylori infection, the incidence of gastric carcinoma was not different in either group. However, long-term administration of rebamipide showed the advantage of decreasing precancerous lesions like chronic atrophic gastritis and showed molecular evidence of attenuation of proliferation.Conclusion : The long-term administration of rebamipide should be considered in the treatment of H. pylori since it demonstrated molecular and biological advantages like a lessening of gastric inflammation and a possible chemopreventive effect.

Notes: Downregulation of TGF-β receptors is implicated in colon cancer development. Inactivation of either of the two transmembrane serine/threonine kinases, TGF-β1 types I/II receptors, is now implicated in carcinogenesis, especially gastrointestinal carcinogenesis.〈section xml:id="abs1-2"〉〈title type="main"〉Methods:We generated transgenic mice, called pS2–dnRII or ITF–dnRII, of which the dominant negative mutant of the TGF-β type II receptor was expressed under the control of tissue-specific promoters, the pS2 promoter for stomach and ITF for intestine. They were either infected with H.pylori (ATCC 43504 strain, CagA+ and VacA+) or administered with azoxymethane to determine the significance of loss of TGF-β signalling in gastrointestinal carcinogenesis.〈section xml:id="abs1-3"〉〈title type="main"〉Results:Gastric adenocarcinoma developed in pS2–dnRII mice, whereas only chronic active gastritis was noted in wild-type littermates after 36 weeks of H.pylori infection. Mice lacking in TGF-β signalling specifically in the stomach showed a significantly higher proliferation cell nuclear antigen-labelling index when infected with H.pylori than wild-type littermates (P 〈 0.01). Development of colonic aberrant crypt foci was provoked in mice by intraperitoneal injections of azoxymethane, and ITF–dnRII mice showed significantly higher incidences of ACF and colon cancers than wild-type littermates.〈section xml:id="abs1-4"〉〈title type="main"〉Conclusions:Maintaining normal TGF-β signalling in the gastrointestinal tract seems to be important either for preventing abnormal mucosal proliferation, or for suppressing or retarding carcinogenesis.