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Jain R  Kabir K  Gilroy JB  Mitchell KA  Wong KC  Hicks RG 《Nature》2007,445(7125):291-294
For over two decades there have been intense efforts aimed at the development of alternatives to conventional magnets, particularly materials comprised in part or wholly of molecular components. Such alternatives offer the prospect of realizing magnets fabricated through controlled, low-temperature, solution-based chemistry, as opposed to high-temperature metallurgical routes, and also the possibility of tuning magnetic properties through synthesis. However, examples of magnetically ordered molecular materials at or near room temperature are extremely rare, and the properties of these materials are often capricious and difficult to reproduce. Here we present a versatile solution-based route to a new class of metal-organic materials exhibiting magnetic order well above room temperature. Reactions of the metal (M) precursor complex bis(1,5-cyclooctadiene)nickel with three different organics A-TCNE (tetracyanoethylene), TCNQ (7,7,8,8-tetracyanoquinodimethane) or DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone)--proceed via electron transfer from nickel to A and lead to materials containing Ni(II) ions and reduced forms of A in a 2:1 Ni:A ratio--that is, opposite to that of conventional (low Curie temperature) MA(2)-type magnets. These materials also contain oxygen-based species within their architectures. Magnetic characterization of the three compounds reveals spontaneous field-dependent magnetization and hysteresis at room temperature, with ordering temperatures well above ambient. The unusual stoichiometry and striking magnetic properties highlight these three compounds as members of a class of stable magnets that are at the interface between conventional inorganic magnets and genuine molecule-based magnets.  相似文献   
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在利用构件进行软件开发时,用户的需求通常是模糊和不确定的.提出了基于非线性模糊质量功能展开(NF-QFD)的构件选择模型.该模型在考虑构件之间高内聚、低耦合的同时还兼顾用户需求最大化,通过该模型可以解决软件系统开发时构件选择的优化问题,为设计人员提供更多的决策支持.  相似文献   
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The molecular pathogenesis of renal cell carcinoma (RCC) is poorly understood. Whole-genome and exome sequencing followed by innovative tumorgraft analyses (to accurately determine mutant allele ratios) identified several putative two-hit tumor suppressor genes, including BAP1. The BAP1 protein, a nuclear deubiquitinase, is inactivated in 15% of clear cell RCCs. BAP1 cofractionates with and binds to HCF-1 in tumorgrafts. Mutations disrupting the HCF-1 binding motif impair BAP1-mediated suppression of cell proliferation but not deubiquitination of monoubiquitinated histone 2A lysine 119 (H2AK119ub1). BAP1 loss sensitizes RCC cells in vitro to genotoxic stress. Notably, mutations in BAP1 and PBRM1 anticorrelate in tumors (P = 3 × 10(-5)), and combined loss of BAP1 and PBRM1 in a few RCCs was associated with rhabdoid features (q = 0.0007). BAP1 and PBRM1 regulate seemingly different gene expression programs, and BAP1 loss was associated with high tumor grade (q = 0.0005). Our results establish the foundation for an integrated pathological and molecular genetic classification of RCC, paving the way for subtype-specific treatments exploiting genetic vulnerabilities.  相似文献   
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Assembly of microarrays for genome-wide measurement of DNA copy number.   总被引:20,自引:0,他引:20  
We have assembled arrays of approximately 2,400 BAC clones for measurement of DNA copy number across the human genome. The arrays provide precise measurement (s.d. of log2 ratios=0.05-0.10) in cell lines and clinical material, so that we can reliably detect and quantify high-level amplifications and single-copy alterations in diploid, polyploid and heterogeneous backgrounds.  相似文献   
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Zusammenfassung Hydroxylamin, welches spezifisch mit Cytosin reagiert, stört die Struktur der verschiedenen Chromosomen in Pollenmutterzellen der Tomate unterschiedlich stark. Das Chromosomenpaar Nr. 2 wird wesentlich weniger stark geschädigt als die übrigen. Die Bedeutung dieses Befundes wird kurz angedeutet.  相似文献   
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