Long-range ferromagnetic correlations between Anderson impurities in a semiconductor host

We study the two-impurity Anderson model for a semiconductor host using the quantum Monte Carlo technique. We find that the impurity spins exhibit ferromagnetic correlations with a range which can be much more enhanced than in a half-filled metallic band. In particular, the range is longest when the Fermi level is located above the top of the valence band and decreases as the impurity bound state becomes occupied. Comparisons with the photoemission and optical absorption experiments suggest that this model captures the basic electronic structure of Ga_{1-x}Mn_xAs, the prototypical dilute magnetic semiconductor (DMS). These numerical results might also be useful for synthesizing DMS or dilute-oxide ferromagnets with higher Curie temperatures.Comment: 4 pages, 4 figure

Fusarium phytotoxin trichothecenes have an elicitor-like activity in Arabidopsis thaliana, but the activity differed significantly among their molecular species

金沢大学学際科学実験センター遺伝子研究施設Phytopathogenic fungi such as Fusarium spp. synthesize trichothecene family phytotoxins. Although the type B trichothecene, deoxynivalenol (DON), is thought to be a virulence factor allowing infection of plants by their trichothecene-producing Fusarium spp., little is known about effects of trichothecenes on the defense response in host plants. Therefore, in this article, we investigated these effects of various trichothecenes in Fusarium-susceptible Arabidopsis thaliana. Necrotic lesions were observed in Arabidopsis leaves infiltrated by 1 μM type A trichothecenes such as T-2 toxin. Trichothecene-induced lesions exhibited dead cells, callose deposition, generation of hydrogen peroxide, and accumulation of salicylic acids. Moreover, infiltration by trichothecenes caused rapid and prolonged activation of two mitogen-activated protein kinases and induced expression of both PR-1 and PDF1.2 genes. Thus, type A trichothecenes trigger the cell death by activation of an elicitor-like signaling pathway in Arabidopsis. Although DON did not have such an activity even at 10 μM, translational inhibition by DON was observed at concentrations above 5 μM. These results suggested that DON is capable of inhibiting translation in Arabidopsis cells without induction of the elicitor-like signaling pathway. © 2006 The American Phytopathological Society.

The MKK2 Pathway Mediates Cold and Salt Stress Signaling in Arabidopsis

AbstractThe Arabidopsis mitogen-activated protein kinase (MAPK) kinase 2 (MKK2) and the downstream MAPKs MPK4 and MPK6 were isolated by functional complementation of osmosensitive yeast mutants. In Arabidopsis protoplasts, MKK2 was specifically activated by cold and salt stress and by the stress-induced MAPK kinase kinase MEKK1. Yeast two-hybrid, in vitro, and in vivo protein kinase assays revealed that MKK2 directly targets MPK4 and MPK6. Accordingly, plants overexpressing MKK2 exhibited constitutive MPK4 and MPK6 activity, constitutively upregulated expression of stress-induced marker genes, and increased freezing and salt tolerance. In contrast, mkk2 null plants were impaired in MPK4 and MPK6 activation and were hypersensitive to salt and cold stress. Full genome transcriptome analysis of MKK2-overexpressing plants demonstrated altered expression of 152 genes involved in transcriptional regulation, signal transduction, cellular defense, and stress metabolism. These data identify a MAP kinase signaling cascade mediating cold and salt stress tolerance in plants

Relationship between petal abscission and programmed cell death in Prunus yedoensis and Delphinium belladonna

Depending on the species, the end of flower life span is characterized by petal wilting or by abscission of petals that are still fully turgid. Wilting at the end of petal life is due to programmed cell death (PCD). It is not known whether the abscission of turgid petals is preceded by PCD. We studied some parameters that indicate PCD: chromatin condensation, a decrease in nuclear diameter, DNA fragmentation, and DNA content per nucleus, using Prunus yedoensis and Delphiniumbelladonna which both show abscission of turgid petals at the end of floral life. No DNA degradation, no chromatin condensation, and no change in nuclear volume was observed in P. yedoensis petals, prior to abscission. In abscising D.belladonna petals, in contrast, considerable DNA degradation was found, chromatin was condensed and the nuclear volume considerably reduced. Following abscission, the nuclear area in both species drastically increased, and the chromatin became unevenly distributed. Similar chromatin changes were observed after dehydration (24 h at 60°C) of petals severed at the time of flower opening, and in dehydrated petals of Ipomoea nil and Petunia hybrida, severed at the time of flower opening. In these flowers the petal life span is terminated by wilting rather than abscission. It is concluded that the abscission of turgid petals in D. belladonna was preceded by a number of PCD indicators, whereas no such evidence for PCD was found at the time of P. yedoensis petal abscission. Dehydration of the petal cells, after abscission, was associated with a remarkable nuclear morphology which was also found in younger petals subjected to dehydration. This nuclear morphology has apparently not been described previously, for any organism

カーネーション ノ カブツキバナ ト キリバナ ニ オケル カイカ ナラビニ ヒンシツ ホジ キカン ノ サイ ト トウ ガンユヨウリョウ ノ カンケイ

カーネーション`ノラ\u27の株つき花と切り花を用いて,花の品質保持期間の差異と糖含有量との関係を調査した。その結果,株つき花の品質保持期間は21日,花径の最大値は73mmに達したのに対して,切り花では8日で64mmであった。株つき花の新鮮重は8日目まで直線的に増加し,その後の21日目までほぼ一定の値を示したのに対して,切り花では2日目から6日目までほぼ一定した値を示した後,低下した。切り花の花弁のフルクトース,グルコース含有量は4日目までは株つき花とほぼ同程度の含有量であったが,8日目以後スクロースを除いて低下したのに対して,株つき花では8日目から21日目にかけてほぼ一定の値を示し,切り花よりも高い値で推移した。葉身部と茎の糖含量では株つき花と切り花の間には著しい差が認められなかったが,株つき花では花の品質保持期間終了後にスクロースとフルクトース含有量が増加した。以上の結果,カーネーションの株つき花と切り花の品質保持期間の差は,主として糖の供給量の違いによるものと推測された。We compared the longevity and content of soluble carbohydrates in cut flower with intact flower of carnation \u27Nora\u27. The longevity of cut flower and intact flower was 8 and 21 days, and flower diameter at full bloom was 7.3cm and 6.4cm, respectively. Fresh weight in flower organ of the cut flower increased to 6 days and then decreased, on the other hand, that of the intact flower increased linearly during first 8 days and was constant thereafter to 21 days. Fructose and glucose contents in petals of the cut flower increased slowly in the first 6 days and then decreased to 14 days linearly, but those of the intact flower increased rapidly to 8 days and kept those high levels to 21 days. Sucrose content in leaves of the intact flower decreased to 14 days, and then increased in 21 days significantly, however that of the cut flower decreased to the end of the experiment (14 days). Sucrose and glucose contents in stem of the cut flower and intact flower decreased to 8 days and 14 days, respectively, and then increased in 14 days and 21 days, respectively. These results suggest that difference in longevity and diameter of flower between cut and intact flower are attributed to sugars supplied from the plant

Mitogen-Activated Protein Kinase Regulated by the CLAVATA Receptors Contributes to Shoot Apical Meristem Homeostasis

In Arabidopsis, the CLAVATA (CLV) pathway operates in the regulation of the size of the stem cell population in the shoot apical meristem (SAM). CLV3 functions as a small peptide ligand to negatively regulate the expression of the WUSCHEL (WUS) transcription factor through three major receptor kinase complexes of CLV1, CLV2-SUPPRESSOR OF LLP1-2 (SOL2)/CORYNE (CRN) and recently identified RECEPTOR-LIKE PROTEIN KINASE 2 (RPK2)/TOADSTOOL 2 (TOAD2). Aiming to understand the precise molecular details of CLV3 signaling, we investigated the contribution of phospho-signaling, potentially regulated by these kinase complexes, to the CLV pathway. We detected CLV3-triggered CLV1 phosphorylation, which is also conditioned by the rest of the CLV receptors, presumably by their direct association. Our comprehensive analysis of the activities of the respective CLV receptors on mitogen-activated protein kinases (MAPKs) suggested that the precise balanced regulation of MAPK activity by the CLV receptors is likely to be key for SAM homeostasis

Recent Results from LHD Experiment with Emphasis on Relation to Theory from Experimentalist’s View

he Large Helical Device (LHD) has been extending an operational regime of net-current free plasmas towardsthe fusion relevant condition with taking advantage of a net current-free heliotron concept and employing a superconducting coil system. Heating capability has exceeded 10 MW and the central ion and electron temperatureshave reached 7 and 10 keV, respectively. The maximum value of β and pulse length have been extended to 3.2% and 150 s, respectively. Many encouraging physical findings have been obtained. Topics from recent experiments, which should be emphasized from the aspect of theoretical approaches, are reviewed. Those are (1) Prominent features in the inward shifted configuration, i.e., mitigation of an ideal interchange mode in the configuration with magnetic hill, and confinement improvement due to suppression of both anomalous and neoclassical transport, (2) Demonstration ofbifurcation of radial electric field and associated formation of an internal transport barrier, and (3) Dynamics of magnetic islands and clarification of the role of separatrix