Spin dynamics and spin freezing behavior in the two-dimensional antiferromagnet NiGa2_{2}S4_{4} revealed by Ga-NMR, NQR and μ\muSR measurements

We have performed $^{69,71}$Ga nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) and muon spin rotation/resonance on the quasi two-dimensional antiferromagnet (AFM) NiGa$_2$S$_4$, in order to investigate its spin dynamics and magnetic state at low temperatures. Although there exists only one crystallographic site for Ga in NiGa$_2$S$_4$, we found two distinct Ga signals by NMR and NQR. The origin of the two Ga signals is not fully understood, but possibly due to stacking faults along the c axis which induce additional broad Ga NMR and NQR signals with different local symmetries. We found the novel spin freezing occurring at $T_{\rm f}$, at which the specific heat shows a maximum, from a clear divergent behavior of the nuclear spin-lattice relaxation rate $1/T_{1}$ and nuclear spin-spin relaxation rate $1/T_{2}$ measured by Ga-NQR as well as the muon spin relaxation rate $\lambda$. The main sharp NQR peaks exhibit a stronger tendency of divergence, compared with the weak broader spectral peaks, indicating that the spin freezing is intrinsic in NiGa$_2$S$_4$. The behavior of these relaxation rates strongly suggests that the Ni spin fluctuations slow down towards $T_{\rm f}$, and the temperature range of the divergence is anomalously wider than that in a conventional magnetic ordering. A broad structureless spectrum and multi-component $T_1$ were observed below 2 K, indicating that a static magnetic state with incommensurate magnetic correlations or inhomogeneously distributed moments is realized at low temperatures. However, the wide temperature region between 2 K and $T_{\rm f}$, where the NQR signal was not observed, suggests that the Ni spins do not freeze immediately below $T_{\rm f}$, but keep fluctuating down to 2 K with the MHz frequency range.Comment: 14 pages, 14 figures. To appear in Phys. Rev.

Integrative Annotation of 21,037 Human Genes Validated by Full-Length cDNA Clones

The human genome sequence defines our inherent biological potential; the realization of the biology encoded therein requires knowledge of the function of each gene. Currently, our knowledge in this area is still limited. Several lines of investigation have been used to elucidate the structure and function of the genes in the human genome. Even so, gene prediction remains a difficult task, as the varieties of transcripts of a gene may vary to a great extent. We thus performed an exhaustive integrative characterization of 41,118 full-length cDNAs that capture the gene transcripts as complete functional cassettes, providing an unequivocal report of structural and functional diversity at the gene level. Our international collaboration has validated 21,037 human gene candidates by analysis of high-quality full-length cDNA clones through curation using unified criteria. This led to the identification of 5,155 new gene candidates. It also manifested the most reliable way to control the quality of the cDNA clones. We have developed a human gene database, called the H-Invitational Database (H-InvDB; http://www.h-invitational.jp/). It provides the following: integrative annotation of human genes, description of gene structures, details of novel alternative splicing isoforms, non-protein-coding RNAs, functional domains, subcellular localizations, metabolic pathways, predictions of protein three-dimensional structure, mapping of known single nucleotide polymorphisms (SNPs), identification of polymorphic microsatellite repeats within human genes, and comparative results with mouse full-length cDNAs. The H-InvDB analysis has shown that up to 4% of the human genome sequence (National Center for Biotechnology Information build 34 assembly) may contain misassembled or missing regions. We found that 6.5% of the human gene candidates (1,377 loci) did not have a good protein-coding open reading frame, of which 296 loci are strong candidates for non-protein-coding RNA genes. In addition, among 72,027 uniquely mapped SNPs and insertions/deletions localized within human genes, 13,215 nonsynonymous SNPs, 315 nonsense SNPs, and 452 indels occurred in coding regions. Together with 25 polymorphic microsatellite repeats present in coding regions, they may alter protein structure, causing phenotypic effects or resulting in disease. The H-InvDB platform represents a substantial contribution to resources needed for the exploration of human biology and pathology

Integrative annotation of 21,037 human genes validated by full-length cDNA clones.

publication en ligne. Article dans revue scientifique avec comité de lecture. nationale.National audienceThe human genome sequence defines our inherent biological potential; the realization of the biology encoded therein requires knowledge of the function of each gene. Currently, our knowledge in this area is still limited. Several lines of investigation have been used to elucidate the structure and function of the genes in the human genome. Even so, gene prediction remains a difficult task, as the varieties of transcripts of a gene may vary to a great extent. We thus performed an exhaustive integrative characterization of 41,118 full-length cDNAs that capture the gene transcripts as complete functional cassettes, providing an unequivocal report of structural and functional diversity at the gene level. Our international collaboration has validated 21,037 human gene candidates by analysis of high-quality full-length cDNA clones through curation using unified criteria. This led to the identification of 5,155 new gene candidates. It also manifested the most reliable way to control the quality of the cDNA clones. We have developed a human gene database, called the H-Invitational Database (H-InvDB; http://www.h-invitational.jp/). It provides the following: integrative annotation of human genes, description of gene structures, details of novel alternative splicing isoforms, non-protein-coding RNAs, functional domains, subcellular localizations, metabolic pathways, predictions of protein three-dimensional structure, mapping of known single nucleotide polymorphisms (SNPs), identification of polymorphic microsatellite repeats within human genes, and comparative results with mouse full-length cDNAs. The H-InvDB analysis has shown that up to 4% of the human genome sequence (National Center for Biotechnology Information build 34 assembly) may contain misassembled or missing regions. We found that 6.5% of the human gene candidates (1,377 loci) did not have a good protein-coding open reading frame, of which 296 loci are strong candidates for non-protein-coding RNA genes. In addition, among 72,027 uniquely mapped SNPs and insertions/deletions localized within human genes, 13,215 nonsynonymous SNPs, 315 nonsense SNPs, and 452 indels occurred in coding regions. Together with 25 polymorphic microsatellite repeats present in coding regions, they may alter protein structure, causing phenotypic effects or resulting in disease. The H-InvDB platform represents a substantial contribution to resources needed for the exploration of human biology and pathology

Behavior of Spherical Ice Particle in Flowing Supercooled Water

Numerical calculation of behavior of a spherical ice particle (motion, melting and solidification) in flowing supercooled water inside a cooled circular tube was performed. By assuming that the single ice particle moved from its position on the upper or lower cooling surface in fully developed laminar flow, the variation of ice particle radius during the moving process could be calculated under various Reynolds numbers for water, initial ice particle radii and cooling conditions. For the particle motion in flowing water, the numerical results were in good agreement with the measurements obtained from visualization using paraffin particles (density : 926 kg/m^3). It was found that the initial ice particle radius, Reynolds number of water and the cooling wall temperature exerted pronounced effects on the ice particle radius at the tube exit ; however the inlet temperature of the flowing water had little effect on the radius at the tube exit.本研究は、流動過冷却水溶液を利用した管内製氷法の確立を最終目標として、その基礎的段階となる水平円管内を流動する過冷却液中を浮遊する単一氷粒子の運動並びに凝固、融解挙動の解明を目的として行ったものである。まず、管内流動水中の粒子運動について解析物理モデルを提案し、その解析モデルに基づき上述したBassetらによる粒子運動方程式を利用して粒子運動の計算を行い、パラフィン粒子を使用した水平円管内の粒子運動過程中の可視化実験結果と計算結果を比較することにより、このような粒子運動が連続相となる流動状態および粒子直径により如何に影響されるかについて検討する。そして、得られた粒子運動に関する計算結果に基づき、球状氷粒子の凝固あるいは融解挙動に及ぼす管内流動水のRe数、初期球状氷粒子径、管内流動水入り口温度および管内表面温度（冷却面温度）等の影響を定量的に把握し、最終的に管出口における球状氷粒子径に影響を及ぼすこれらの諸因子の効果を数値計算式に基づき検討するものである

Influence of Certain Factors on Supercooling Phenomenon of Still Water

Supercooling characteristics in quiescent bulk water enclosed in a circular tube were investigated on a basic level through numerous experiments. In the experiments, three kinds of water with different specific resistances were used as the test samples and their freezing temperatures were measured. The critical degree of supercooling depended on the property of the heat transfer surface and the cooling rate, and it became larger for a smoother surface and a higher cooling rate. It was found that the specific resistance of the water had little effect on the critical degree of supercooling . However, the insoluble particles included in the water greatly affected the ice nucleation in the supercooled water and the size effect of the insoluble particles was found to become important in the range of 0.1-1.0 μm in particle radius. For particle radii larger than this range, the critical degree of supercooling was independent of the size, while below this range it sharply increased with a decrease in the particle size.本研究は、流動過冷却水を利用したスラリー状の連続製氷技術の確立を最終目標とし、その基本的モデルとなる容器内に充墳した比較的容積の大きな水の静止状態における過冷却現象の解明を対象として取り上げ、その過冷却現象の基本的特徴を探るものである。第一に核生成の要因が、不均質核生成に強く依存する条件のもとでの水の限界過冷却度が、その容積、冷却速度、冷却面の材質および表面性状等に如何に影響されるかを明らかにした上で、試料水内に含まれる異質浮遊粒子および水の比抵抗値に影響を及ぼすようなイオン系溶解分子等の不純物質が、水の過冷却度に及ぼす影響を実験的に検討するものである。なお、得られた水の過冷却現象に関する情報は、流動過冷却水による連続製氷技術の基礎資料となりうるものであり、新しい氷蓄熱システムの構築に役立つものと思われる

Effects of Some Factors on Critical Condition of Ice Formation for Flowing Supercooled Water and Water Solution inside Cooled Circular Tube

Supercooling characteristics of water and water solution in a forced flow were investigated both experimentally and analytically. The critical conditions of ice nucleation in a cooled circular tube were examined for five sets of tube dimensions under various Reynolds numbers. It was found that the critical degree of supercooling based on the inner wall temperature was independent of Reynolds number in a laminar flow region. However, in a turbulent flow region, it decreased with increasing Reynolds number. An ice nucleation model for the flowing supercooled liquid was developed to predict the critical conditions of ice formation, in which the effects of the flow and temperature conditions, tube dimensions and solute mass fraction were taken into consideration. Nondimensional correlation equations for the critical condition of ice formation were derived in laminar and turbulent flow regions as a function of some nondimensional parameters obtained by analyzing the ice nucleation model.近年、製氷方法の多様性、輸送性の良さ、融解時の高い負荷追従性の観点から、スラリー状氷に対する関心が増大している。スラリー状氷の有効な形成方法の一つとして、前報において報告した水あるいは水溶液の過冷却状態を利用する方法は、製氷装置も比較的簡単で、将来有望なスラリー状氷の製造方法となる可能性を秘めているが、流動状態にある水あるいは水溶液の過冷却現象に関して、その過冷却安定性および管内での過冷却状態の解消に伴う管内凍結発生条件に影響を及ぼす諸因子の影響について検討するものである

Influence of Certain Factors on Supercooling Phenomenon of Still Water

Supercooling characteristics in quiescent bulk water enclosed in a circular tube were investigated on a basic level through numerous experiments. In the experiments, three kinds of water with different specific resistances were used as the test samples and their freezing temperatures were measured. The critical degree of supercooling depended on the property of the heat transfer surface and the cooling rate, and it became larger for a smoother surface and a higher cooling rate. It was found that the specific resistance of the water had little effect on the critical degree of supercooling . However, the insoluble particles included in the water greatly affected the ice nucleation in the supercooled water and the size effect of the insoluble particles was found to become important in the range of 0.1-1.0 μm in particle radius. For particle radii larger than this range, the critical degree of supercooling was independent of the size, while below this range it sharply increased with a decrease in the particle size.本研究は、流動過冷却水を利用したスラリー状の連続製氷技術の確立を最終目標とし、その基本的モデルとなる容器内に充墳した比較的容積の大きな水の静止状態における過冷却現象の解明を対象として取り上げ、その過冷却現象の基本的特徴を探るものである。第一に核生成の要因が、不均質核生成に強く依存する条件のもとでの水の限界過冷却度が、その容積、冷却速度、冷却面の材質および表面性状等に如何に影響されるかを明らかにした上で、試料水内に含まれる異質浮遊粒子および水の比抵抗値に影響を及ぼすようなイオン系溶解分子等の不純物質が、水の過冷却度に及ぼす影響を実験的に検討するものである。なお、得られた水の過冷却現象に関する情報は、流動過冷却水による連続製氷技術の基礎資料となりうるものであり、新しい氷蓄熱システムの構築に役立つものと思われる