Effect of Co Doping on the Structure and Magnetic Properties of TmMn1-xCoxO3

We report the structure and magnetic properties of Co-doped TmMnO3 polycrystals for Co doping levels of 0 ≤ x ≤ 0.9. TmMnO3 (x = 0) prepared at ambient pressure was hexagonal. Hexagonal and orthorhombic phases coexisted in TmMn1−xCoxO3 for 0 ≤ x < 0.5. We obtained almost single-phase orthorhombic samples with 0.5 ≤ x ≤ 0.9 using complex polymerization. Ferromagnetic orthorhombic TmMn1−xCoxO3 formed upon Co doping. The ionic states of Tm, Mn, and Co were determined through magnetization measurements. The rapid decrease in magnetization for 0.5 ≤ x ≤ 0.7 below about 25 K was explained using a model consisting of a combination of ferromagnetic Mn–Co and paramagnetic Tm sublattices

希土類酸化物RMnO3における元素置換効果と化学圧力効果

ABO3型ペロブスカイトRMnO3（R:希土類元素）は同時に複数の秩序状態を持つマルチフェロイック物質として広く研究されている。本論文では、直方晶GdMnO3（空間群Pnma）と六方晶TmMnO3(P63cm)について、元素置換効果と化学圧力効果について調べた。GdMnO3のX線回折測定結果は、TN以下でAタイプの反強磁性であることを示しているが、Mnスピンは完全には反平行でなく、わずかにチルトしていることが知られている。これはキャント磁性あるいは弱強磁性と呼ばれている。この系のMnをCoで置換したGdMn1-xCoxO3の結晶構造は、0≦x≦1で直方晶系である。x=0.3,0.5,0.7では、転移温度Tcにおいて磁場中冷却(FC)磁化MFCは、温度低下とともにMnとCoモーメントのキャントの結果として急激に増加する。特に、x=0.3のMFCは約40Kで最大値を示し、温度の低下とともに急激に減少し、20K以下では負の磁化を示した。他方、重希土類酸化物TmMnO3は、反強磁性転移温度TNが41K, 強誘電転移温度TCが86Kである。この構造を持つRMnO3の結晶構造は、高圧合成により直方晶に変化することが知られているが、Coで置換したTmMn1-xCoxO3においてもその構造はxに依存して六方晶から直方晶系へ変化し、0.5≦xでは、直方晶単相(Pnma)を得た。TmMn1-xCoxO3のMFCは、温度の減少とともに、約60Kで強磁性的に増加し、0.6≦x≦0.7でも負の磁化を示す。しかし、x=0.8のMFCはもはや温度低下とともに強磁性的な増加を示さない。これらの温度低下に伴うTcでの強磁性的な磁化の増大は、Co置換による混合原子価状態の結果として理解できる。また負の磁化、すなわちスピン反転は、MnとCoモーメントに対するGdあるいはTmスピンの反強磁性的カップリングによって説明できる。我々はまた、GdやTm を非磁性希土類元素La、Y、Luで置換したGd1-yRyMn1-xCoxO3とTm1-yRyMn1-xCoxO3の物性についても調べた。Gd3+、Tm3+、La3+、Y3+、Lu3+のイオン半径の違いから、我々は、TmまたはGdを非磁性希土類元素で置換することによる単位格子体積(V)の変化による圧力効果を期待できる。Tm1-y(Y,Lu)yMn0.5Co0.5O3の調査から、いくつかの顕著な構造の詳細が得られた。Tm1-yLuyMn0.5Co0.5O3とTm1-yYyMn0.5Co0.5O3のVは、それぞれyの増加とともに減少と増加した。直方晶歪みを特徴づけるパラメータ(a-c)/aは、Tmイオンを置換するために、Luドープでは連続的に増加し、Yドープでは減少する。直方晶Tm1-y(Y,Lu)yMn0.5Co0.5O3におけるTmのYまたはLuによる置換は、系統的な単位格子体積の変化を誘起する。これは化学圧力効果である。磁化測定から、我々はMFCと単位胞体積の増加が転移温度TCにおける増加に寄与すると結論する。直方晶Gd1-yRyMn0.7Co0.3O3(R=非磁性希土類元素) のy=0.1,0.3,0.5についても、化学圧力効果の研究を行った。Gd1-yRyMn1-xCoxO3におけるGdのLa,Y,Lu置換は、単位胞体積の系統的な変化を誘起する。我々の結果は、化合物の希土類元素の平均イオン半径の増加あるいは減少が、磁気転移温度TCに影響することを示す。非磁性元素による置換で生じたGdの割合の減少は、スピン反転効果を弱める。The ABO3 type perovskite RMnO3 (R: rare-earth element) has investigated extensively as the multiferroic materials which possess two or more types of orders simultaneously. In this thesis, we investigated the effect of element substitution and chemical pressure in orthorhombic GdMnO3 (space group Pnma) and hexagonal TmMnO3 (P63cm). The X-ray diffraction measurement results of GdMnO3 shows A-type antiferromagnetism is below TN, but it is known that Mn spins are not perfectly antiparallel, but exist with a slight tilt. This is called cant magnetism or weak ferromagnetism. The crystal structure of GdMn1-xCoxO3 is orthorhombic for 0≤x≤1.0. For x=0.3, 0.5, and 0.7, at the ordering temperature TC, the field-cooled (FC) magnetization MFC rapidly increase which results from cating of the Mn and Co moments with decreasing temperature. Especially, MFC for x= 0.3 showed maximum values at 40K, decreased rapidly with decreasing temperature and showed a negative magnetization blow 20K. On the other hand, the heavy rare earth oxide TmMnO3 is that an antiferromagnetic transition temperature TN is 41K, and ferroelectric transition temperature TC is 86K. It is known that the crystal structure of RMnO3 having this structure changes to the orthorhombic (Pnma) by performing high-pressure synthesis, but even in TmMn1-xCoxO3 with substitution by Co the structure changes from hexagonal to an orthorhombic, and we can obtain an orthorhombic single phase (Pnma) at 0.5≤x. MFC of TmMn1-xCoxO3 was increase in ferromagnetically at about 60K with decreasing temperature, and also showed negative magnetization in 0.6≦x≦0.7. but MFC for x=0.8 no longer showed a ferromagnetic increase with decreasing temperature. The increase in ferromagnetic magnetization with decreasing temperature at TC can be understood as a result of the mixed-valence state due to Co substitution. The negative magnetization observed in both samples, so-called the spin reversal, can be explained by the antiferromagnetic coupling of the Gd or Tm spin to the Mn and Co moments. We also investigated Gd1-yRyMn1-xCoxO3 and Tm1-yRyMn0.5Co0.5O3 (R: nonmagnetic rare-earth element) with substitution by nonmagnetic rare- earth elements La, Y, Lu. We can expect the chemical pressure effect due to the unit-cell volume (V) change by substituting Tm or Gd with nonmagnetic rare-earth elements. From Tm1-y(Y, Lu)yMn0.5Co0.5O3 observation we can obtained some remarkable structural details: owing to the ion radii, V of Tm1-yLuyMn0.5Co0.5O3 and Tm1-yYyMn0.5Co0.5O3 decreases and increases with increasing y, respectively; the parameter (a−c)/a, which is characterizes the orthorhombic distortion, continuously increases on Lu doping and decreases on Y-doping due to the substitution of Tm ions. Substitution of Tm with Y or Lu in orthorhombic Tm1-y(Lu, Y)yMn1-xCoxO3induces a systematic unit-cell volume change. This is the chemical pressure effect. From the magnetization measurement, we conclude that an increase of MFC and the unit-cell volume is responsible for the increase in transition temperature TC. We also studied the effects of chemical pressure with orthorhombic Gd1-yRyMn1-xCoxO3 (y = 0.1, 0.3, and 0.5). The substitution of Gd with La, Y, or Lu in Gd1-yRyMn1-xCoxO3 induced a systematic change in the unit-cell volume. Our results reveal that increasing or decreasing the average ionic radius of the rare-earth element in the compound affects the magnetic ordering temperature TC. The reduction in the proportion of Gd owing to substitution by nonmagnetic elements weakens the spin reversal effect.室蘭工業大学 (Muroran Institute of Technology)博士（工学

Universal factorial Schur P,QP,Q-functions and their duals

We define universal factorial Schur $P,Q$-functions and their duals, which specialize to generalized (co)-homology "Schubert basis" for loop spaces of the classical groups. We also investigate some of their properties.Comment: 10 pages, old paper written in 2012.1

Effects of Chemical Pressure on Rare-Earth Oxide GdNIn0.7Co0.3O3 with Nonmagnetic Element Substitution

We studied the effects of chemical pressure on Gd1-yRyMn0.7Co0.3O3 (R = nonmagnetic rare-earth element) with y = 0.1, 0.3, and 0.5. The substitution of Gd with La, Y, or Lu in orthorhombic Gd1-yRyMn1-xCoxO3 induced a systematic change in the unit-cell volume. Our results reveal that increasing or decreasing the average ionic radius of the rare-earth element in the compound affects the magnetic ordering temperature T-C. The reduction in the proportion of Gd owing to substitution by nonmagnetic elements weakens the spin reversal effect

Trends and associated factors of HIV, HCV and syphilis infection among different drug users in the China-Vietnam border area: an 11-year cross-sectional study (2010-2020)

BACKGROUND: Data on recent human immunodeficiency virus (HIV), hepatitis C virus (HCV) and syphilis prevalence among drug users in the Southwest China are sparse despite the high burden of drug use. This study aims at assessing the prevalence trends and related factors of HIV, HCV and syphilis infection among different drug users in the China-Vietnam border area. METHODS: A continuous cross-sectional survey was conducted among drug users from 2010 to 2020 in the China-Vietnam border area. Chi-square trend tests were used to assess the trend of HIV, HCV and syphilis prevalence and the proportion for drug type used by drug users. Multivariate logistic regression was used to identify associated factors of HIV, HCV and syphilis infection in different drug users. RESULTS: In this study, a total of 28,951 drug users were included, of which 27,893 (96.45%) male, 15,660 (54.09%) aged 13-34 years, 24,543 (84.77%) heroin-only users, 2062 (7.12%) synthetic drug-only (SD-only) users and 2346 (8.10%) poly-drug users. From 2010 to 2020, the proportion of heroin-only users decreased from 87.79% to 75.46%, whereas SD-only users and poly-drug users increased from 5.16% to 16.03%, and from 7.05% to 8.52%, respectively. The prevalence of HIV, HCV, and syphilis during the study period declined from 12.76%, 60.37% and 5.72% to 4.35%, 53.29% and 4.53%, respectively, among heroin-only users and declined from 18.30%, 66.67% and 15.69% to 6.95%, 27.81% and 5.35%, respectively, among poly-drug users; however, the prevalence of HIV and HCV among SD-only users increased from 0.89% and 8.93% to 2.84% and 18.75%, respectively. Having ever injected drugs and needle sharing were common associated factors for both HIV and HCV infection among poly-drug users and heroin-only users. Aged ≥ 35 years old was an associated factor for HIV, HCV and syphilis infection among the SD-only users. Female drug users were at high risk of contracting syphilis among three different drug users. CONCLUSIONS: The prevalence of HIV, HCV and syphilis among heroin-only users and poly-drug users decreased during the study period. However, the prevalence of HIV and HCV among SD-only users increased. Comprehensive intervention strategies, particularly focusing on the SD-only users are needed in order to bring down the disease burden in this population in the China-Vietnam border areas

A Built-In Mechanism to Mitigate the Spread of Insect-Resistance and Herbicide-Tolerance Transgenes into Weedy Rice Populations

BACKGROUND: The major challenge of cultivating genetically modified (GM) rice (Oryza sativa) at the commercial scale is to prevent the spread of transgenes from GM cultivated rice to its coexisting weedy rice (O. sativa f. spontanea). The strategic development of GM rice with a built-in control mechanism can mitigate transgene spread in weedy rice populations. METHODOLOGY/PRINCIPAL FINDINGS: An RNAi cassette suppressing the expression of the bentazon detoxifying enzyme CYP81A6 was constructed into the T-DNA which contained two tightly linked transgenes expressing the Bt insecticidal protein Cry1Ab and the glyphosate tolerant 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), respectively. GM rice plants developed from this T-DNA were resistant to lepidopteran pests and tolerant to glyphosate, but sensitive to bentazon. The application of bentazon of 2000 mg/L at the rate of 40 mL/m(2), which is approximately the recommended dose for the field application to control common rice weeds, killed all F(2) plants containing the transgenes generated from the Crop-weed hybrids between a GM rice line (CGH-13) and two weedy rice strains (PI-63 and PI-1401). CONCLUSIONS/SIGNIFICANCE: Weedy rice plants containing transgenes from GM rice through gene flow can be selectively killed by the spray of bentazon when a non-GM rice variety is cultivated alternately in a few-year interval. The built-in control mechanism in combination of cropping management is likely to mitigate the spread of transgenes into weedy rice populations

Joint analysis of three genome-wide association studies of esophageal squamous cell carcinoma in Chinese populations

We conducted a joint (pooled) analysis of three genome-wide association studies (GWAS) 1-3 of esophageal squamous cell carcinoma (ESCC) in ethnic Chinese (5,337 ESCC cases and 5,787 controls) with 9,654 ESCC cases and 10,058 controls for follow-up. In a logistic regression model adjusted for age, sex, study, and two eigenvectors, two new loci achieved genome-wide significance, marked by rs7447927 at 5q31.2 (per-allele odds ratio (OR) = 0.85, 95% CI 0.82-0.88; P=7.72x10−20) and rs1642764 at 17p13.1 (per-allele OR= 0.88, 95% CI 0.85-0.91; P=3.10x10−13). rs7447927 is a synonymous single nucleotide polymorphism (SNP) in TMEM173 and rs1642764 is an intronic SNP in ATP1B2, near TP53. Furthermore, a locus in the HLA class II region at 6p21.32 (rs35597309) achieved genome-wide significance in the two populations at highest risk for ESSC (OR=1.33, 95% CI 1.22-1.46; P=1.99x10−10). Our joint analysis identified new ESCC susceptibility loci overall as well as a new locus unique to the ESCC high risk Taihang Mountain region

Anionic Amino-Cope Rearrangement Studies and Development of Designer Sulfur-Rich Materials using Sulfur, Sulfur Monochloride and Dithiophosphoric Acids

This dissertation is divided into six chapters, containing both works related to the explorations of new anionic amino-Cope cascade reaction as well as development and characterizations of new sulfur-rich materials. Chapter 1 presents diverse results of the anionic amino-Cope cascades when strategically employing γ-substituted dienolates nucleophile. In Chapter 2, efforts to challenge anionic amino-Cope reactions with steric effect are reported, resulting in the formation of conjugate di- and trienamides with selective configuration of double bond geometry. Chapter 3 highlights the first comprehensive study of the sulfur-rich polymer material prepared through inverse vulcanization, which undeniably assigns the major microstructure of the polymer through degradation studies, collaborative computational calculations, and solid state NMR analysis. Chapter 4 describes the structural characterization of deuterated poly(S-r-DIB) material. Chapter 5 focuses on the design and synthesis of olefinic monomers for polymerization with S2Cl2, as well as the structural characterization of the polymer through degradation studies. Chapter 6 presents a new polymer functionalization method using dithiophosphoric acid, which resulted in an improving thermomechanical, optical properties and flame retardancy.Release after 12/08/202