Large Magnetoresistance Effects in LnLnCoAsO with a Ferromagnetic-Antiferromagnetic Transition

A large magnetoresistance (MR) effect was observed in the layered compounds NdCoAsO and SmCoAsO, in which ferromagnetically ordered itinerant-electrons of Co are sandwiched by localized 4$f$-electrons of $Ln^{3+}$, below ferromagnetic-antiferromagnetic transition (FAFT) temperature $T_\mathrm{N}$ as observed in other FAFT compounds. In SmCoAsO, the large MR effect is also observed up to the Curie temperature $T_\mathrm{C}$, and it is found to be originating in the presence of another antiferromagnetic phase in the low-magnetic field region of the ferromagnetic phase.Comment: 5 pages, 5 figure

Site-selective cobalt substitution in La-Co co-substituted magnetoplumbite-type ferrites: 59^{59}Co-NMR and DFT calculation study

The La-Co co-substituted magnetoplumbite-type (M-type) ferrites $A$Fe$_{12}$O$_{19}$ ($A$ = Ca, Sr and Ba, ion sizes Ca$^{2+}$ $<$ Sr$^{2+}$ $<$ Ba$^{2+}$) with Co compositions around 0.2 have been subjected to $^{59}$Co-NMR. The results show that Co occupies the 4f$_1$, 2a and 12k sites, and that the smaller the $A$ ion, the more Co tends to occupy the 4f$_1$ minority spin site, which is effective in enhancing both uniaxial anisotropy and magnetisation. First-principles total energy calculations based on density functional theory (DFT) of undoped $A$Fe$_{12}$O$_{19}$ and a supercell ($2 \times 2 \times 1$ of the unit cell) in which 1/96 of Fe$^{3+}$ is replaced by Co$^{2+}$ were performed to predict the stable structure and Co occupancy sites. The results show that regardless of $A$, Co is most stable when it occupies the 4f$_1$ site, followed by the 2a and 12k sites with energy differences on the order of 100 meV, and Co practically does not occupy the 2b and 4f$_2$ sites. As the $A$ ion becomes smaller, the energy difference when Co occupies each Fe site tends to increase, and the Co occupancy of the 4f$_1$ site also increases. The site selectivity of Co can be roughly explained as a result of the difference in uniaxial strain along the $c$-axis associated with the difference in $A$. However, the influence of the $A$ ion differs between the R and S blocks and the local strain also has a secondary effect on the Co distribution. Based on these results, the guidelines for improving the performance (anisotropy and magnetisation) of La-Co co-substituted M-type ferrite magnets with a limited amount of Co can be summarised as follows: It is effective to select as small $A$ ions as possible and to post-anneal at low temperature or cool slowly to concentrate Co at the 4f$_1$ site in tetrahedral coordination.Comment: 33 pages, 9 figure

Microbial Community Composition of Two Environmentally Conserved Estuaries in the Midorikawa River and Shirakawa River

To provide a general overview of the microbial communities in environmentally conserved estuaries, the top 5 cm of sediment was sampled from the sandy estuary of the Shirakawa River and from the muddy estuary of the Midorikawa River. Higher amounts of organic matter were detected in the Midorikawa estuary sample than in the Shirakawa estuary sample. Measurement of redox potential revealed that the Shirakawa estuary was aerobic and the Midorikawa estuary was much less aerobic. Clone analysis was performed by targeting partial 16S rRNA gene sequences and using extracted DNA from the samples as a template. Various bacteria were detected, among which Gammaproteobacteria was dominant at both estuaries. Unclassified clones were detected in the Gammaproteobacteria group, mainly among samples from the Midorikawa estuary. Other detected bacterial groups were Alphaproteobacteria, Deltaproteobacteria, Chloroflexi, Actinobacteria, and Bacteroidetes. All the Deltaproteobacteria clones were anaerobic sulfate-reducing bacteria. Those aerobic and anaerobic bacteria coexisted in the top 5 cm of the estuary sediments indicating the surface layer have active sulfur and carbon cycle. Abundance of aerobic Gammaproteobacteria may be an indicator for conserved estuaries

Pressure dependence of ferromagnetic phase boundary in BaVSe3 studied with high-pressure μ+SR

The magnetic nature of a quasi-one-dimensional compound, BaVSe3, has been investigated with positive muon spin rotation and relaxation (μ+SR) measurements at ambient and high pressures. At ambient pressure, the μ+SR spectrum recorded under zero external magnetic field exhibited a clear oscillation below the Curie temperature (TC∼41K) due to the formation of quasistatic ferromagnetic order. The oscillation consisted of two different muon spin precession signals, indicating the presence of two magnetically different muon sites in the lattice. However, the two precession frequencies, which correspond to the internal magnetic fields at the two muon sites, could not be adequately explained with relatively simple ferromagnetic structures using the muon sites predicted by density functional theory calculations. The detailed analysis of the internal magnetic field suggested that the V moments align ferromagnetically along the c axis but slightly canted toward the a axis by 28 that is coupled antiferromagnetically. The ordered V moment (MV) is estimated as (0.59, 0, 1.11) μB. As pressure increased from ambient pressure, TC was found to decrease slightly up to about 1.5 GPa, at which point TC started to increase rapidly with the further increase of the pressure. Based on a strong ferromagnetic interaction along the c axis, the high-pressure μ+SR result revealed that there are two magnetic interactions in the ab plane; one is an antiferromagnetic interaction that is enhanced with pressure, mainly at pressures below 1.5 GPa, while the other is a ferromagnetic interaction that becomes predominant at pressures above 1.5 GPa

Potential of extravasated platelet aggregation as a surrogate marker for overall survival in patients with advanced gastric cancer treated with preoperative docetaxel, cisplatin and S-1: a retrospective observational study

Background: The theory of extravasated platelet aggregation in cancer lesions was recently introduced. We investigated the association of platelet aggregation in gastric cancer stroma with clinicopathological features, chemotherapeutic response, pathological response, and survival. Methods: The study comprised 78 patients with advanced gastric cancer who had undergone gastrectomy with or without combination of docetaxel, cisplatin and S-1 (DCS) as preoperative chemotherapy between 2005 and 2014. The patients were divided into two groups: patients who had received preoperative DCS therapy forming the p-DCS group and patients who had not received preoperative DCS therapy forming the control group. The 39 patients in the control group had received gastrectomy and postoperative chemotherapy of S-1 alone. Platelet aggregation in biopsy specimens before preoperative DCS therapy in the p-DCS group and at the time of diagnosis in the control group were evaluated using CD42b immunohistochemical staining. Results: Twenty-four patients in the p-DCS group and 19 in the control group were found to have platelet aggregation in their cancer stroma. Patients with histologically confirmed platelet aggregation had significantly higher rates of chemoresistance (58.3%) than those without platelet aggregation (20.0%) (P = 0.019). According to multivariate analysis, CD42b expression (odds ratio: 5.102, 95% confidence interval: 1.039-25.00, P = 0.045) was correlated with chemoresistance. CD42b expression and histological non-responder status were both significantly correlated with poor overall survival (OS) (P = 0.012, P = 0.016); however, RECIST was not correlated with OS. In the control group, CD42b expression was also significantly correlated with poor overall survival (OS) (P = 0.033). In the p-DCS group, according to multivariate analysis, male sex (hazard ratio: 0.281, 95% confidence interval: 0.093-0.846, P = 0.024) was correlated with good prognosis and CD42b expression (hazard ratio: 4.406, 95% confidence interval: 1.325-14.65, P = 0.016) with poor prognosis. Conclusions: This study suggests that platelets in gastric cancer stroma may create a favorable microenvironment for chemoresistance. CD42b immunohistochemical staining of biopsy specimens is a promising candidate for being a prognostic marker in patients with gastric cancer. © 2017 The Author(s)

Background Factors Affecting Visual Acuity at Initial Visit in Eyes with Central Retinal Vein Occlusion : Multicenter Study in Japan

Purpose: To determine the baseline characteristics of patients with central retinal vein occlusion (CRVO) that were significantly associated with the best-corrected visual acuity (BCVA) at the initial examination. Methods: This was a retrospective multicenter study using the medical records registered in 17 ophthalmological institutions in Japan. Patients with untreated CRVO (≥20-years-of-age) who were initially examined between January 2013 and December 2017 were studied. The patients’ baseline factors that were significantly associated with the BCVA at the initial examination were determined by univariate and multivariate linear regression analyses. Results: Data from 517 eyes of 517 patients were analyzed. Univariate analyses showed that an older age (r = 0.194, p < 0.001) and the right eye (r = −0.103, p < 0.019) were significantly associated with poorer BCVA at the initial visit. Multivariate analyses also showed that an older age (β = 0.191, p < 0.001) and the right eye (β = −0.089, p = 0.041) were significantly associated with poorer BCVA at the initial visit. Conclusions: The results indicate that an older age, a known strong factor, and the right eye were significantly associated with poorer BCVA at the initial visit to the hospital. These results suggest that functional and/or anatomical differences between the right and left eyes may be involved in these results

Magnetic resonance imaging study of hippocampal volume in chronic, combat-related posttraumatic stress disorder

This study used quantitative volumetric magnetic resonance imaging techniques to explore the neuroanatomic correlates of chronic, combat-related posttraumatic stress disorder (PTSD) in seven Vietnam veterans with PTSD compared with seven nonPTSD combat veterans and eight normal nonveterans. Both left and right hippocampi were significantly smaller in the PTSD subjects compared to the Combat Control and Normal subjects, even after adjusting for age, whole brain volume, and lifetime alcohol consumption. There were no statistically significant group differences in intracranial cavity, whole brain, ventricles, ventricle:brain ratio, or amygdala. Subarachnoidal cerebrospinal fluid was increased in both veteran groups. Our finding of decreased hippocampal volume in PTSD subjects is consistent with results of other investigations which utilized only trauma-unexposed control groups. Hippocampal volume was directly correlated with combat exposure, which suggests that traumatic stress may damage the hippocampus. Alternatively, smaller hippocampi volume may be a pre-existing risk factor for combat exposure and/or the development of PTSD upon combat exposure