Studio portraits of Rahel Bürger Apfel.

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Studio portrait of Samuel Isaac Bürger.

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The Genomes of Oryza sativa: A history of duplications

We report improved whole-genome shotgun sequences for the genomes of indica and japonica rice, both with multimegabase contiguity, or almost 1,000-fold improvement over the drafts of 2002. Tested against a nonredundant collection of 19,079 full-length cDNAs, 97.7% of the genes are aligned, without fragmentation, to the mapped superscaffolds of one or the other genome. We introduce a gene identification procedure for plants that does not rely on similarity to known genes to remove erroneous predictions resulting from transposable elements. Using the available EST data to adjust for residual errors in the predictions, the estimated gene count is at least 38,000 - 40,000. Only 2% - 3% of the genes are unique to any one subspecies, comparable to the amount of sequence that might still be missing. Despite this lack of variation in gene content, there is enormous variation in the intergenic regions. At least a quarter of the two sequences could not be aligned, and where they could be aligned, single nucleotide polymorphism ( SNP) rates varied from as little as 3.0 SNP/kb in the coding regions to 27.6 SNP/kb in the transposable elements. A more inclusive new approach for analyzing duplication history is introduced here. It reveals an ancient whole-genome duplication, a recent segmental duplication on Chromosomes 11 and 12, and massive ongoing individual gene duplications. We find 18 distinct pairs of duplicated segments that cover 65.7% of the genome; 17 of these pairs date back to a common time before the divergence of the grasses. More important, ongoing individual gene duplications provide a never-ending source of raw material for gene genesis and are major contributors to the differences between members of the grass family.

A base-emitter self-aligned multi-finger Si1-xGex/Si power heterojunction bipolar transistor

With a crystal orientation dependent on the etch rate of Si in KOH-based solution, a base-emitter self-aligned large-area multi-linger configuration power SiGe heterojunction bipolar transistor (HBT) device (with an emitter area of about 880 mu m(2)) is fabricated with 2 mu m double-mesa technology. The maximum dc current gain is 226.1. The collector-emitter junction breakdown voltage BVCEO is 10 V and the collector-base junction breakdown voltage BVCBO is 16 V with collector doping concentration of 1 x 10(17) cm(-3) and thickness of 400 nm. The device exhibited a maximum oscillation frequency f(max) of 35.5 GHz and a cut-off frequency f(T) of 24.9 GHz at a dc bias point of I-C = 70 mA and the voltage between collector and emitter is V-CE = 3 V. Load pull measurements in class-A operation of the SiGe HBT are performed at 1.9 GHz with input power ranging from 0 dBm to 21 dBm. A maximum output power of 29.9 dBm (about 977 mW) is obtained at an input power of 18.5 dBm with a gain of 11.47 dB. Compared to a non-self-aligned SiGe HBT with the same heterostructure and process, f(max) and f(T) are improved by about 83.9% and 38.3%, respectively.

Living Copolymerization of Ethylene with Norbornene Mediated by Heteroligated (Salicylaldiminato) (beta-enaminoketonato)Titanium Catalysts

Three heteroligated (salicylaldiminato)(beta-enaminoketonato)titanium complexes [3-Bu-t-2-OC6H3CH=N(C6F5)][(p-XC6H4)N=C(Bu-t)CHC(CF3)O]TiCl2 (3a: X = F, 3b: X = Cl, 3c: X = Br) were synthesized and investigated as the catalysts for ethylene polymerization and ethylene/norbornene copolymerization. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts exhibited high activities toward ethylene polymerization, similar to their parallel parent catalysts. Furthermore, they also displayed favorable ability to efficiently incorporate norbornene into the polymer chains and produce high molecular weight copolymers under the mild conditions, though the copolymerization of ethylene with norbornene leads to relatively lower activities. The sterically open structure of the beta-enaminoketonato ligand is responsible for the high norbornene incorporation. The norbornene concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer.

Synthesis and characterization of the titanium complexes bearing two regioisomeric trifluoromethyl-containing enaminoketonato ligands and their behavior in ethylene polymerization

A series of new titanium complexes bearing two regioisomeric trifluoromethyl-containing enaminoketonato ligands (3a-h and 6a-h), [PhN=CRCHC(CF3)O](2)TiCl2 (3a, R = Me; 3b, R = n-C5H11; 3c, R = i-Pr; 3d, R = Cy; 3e, R = t-Bu; 3f, R = CH=CHPh; 3g, R = Et; 3h, R = n-C11H23) and [PhN=C(CF3)CHC(R)O](2)TiCl2 (6a, R = Ph; 6b, R = n-C5H11; 6c, R = i-Pr; 6d, R = Cy; 6e, R = t-Bu; 6f, R = CH=CHPh; 6g, R = CHPh2; 6h, R = CF3) have been synthesized and characterized. X-ray crystal structures analyses suggest that complexes 3c-e and 6c-d all adopt a distorted octahedral geometry around the titanium center. Complexes 3c, 3d and 6c display a cis-configuration of the two chlorine atoms around the titanium center, while complex 6d shows a trans-configuration of the two chlorine atoms. Especially, the configurational isomers (cis and trans) of complex 3e were identified both in solution and in the solid state by NMR and X-ray analyses. With modified methylaluminoxane as a cocatalyst, all the complexes are active towards ethylene polymerization, and produce high molecular weight polymers.

Fe(acac)_3-Al(i-Bu)_3对马来酸酐与茴香脑共聚的催化性能

研究了Fe(acac) 3 Al(i Bu) 3 (acac =乙酰丙酮 )催化体系对马来酸酐 (MA)与茴香脑 (ANE)共聚反应的催化性能 .动力学研究结果表明 ,MA与ANE共聚对单体的浓度呈一级反应 ,其表观活化能为 31 0kJ/mol.用IR和13 CNMR研究了共聚物的结构 ,结果表明聚合物是交替的 ,其中酸酐的含量为 4 5 6 % .用GPC测定了聚合物的分子量及其分布 ,结果表明分子量的分布较窄 ,PDI =1 19～ 1 4 2 .用DTA研究了聚合物的热力学性质 ,其分解温度为 5 0 1 1℃.

Fe(2-EHA)(3)/Al(i-Bu)(3)/hydrogen phosphite catalyst for preparing syndiotactic 1,2-polybutadiene

Polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene with art iron(III) catalyst system has been investigated. Activity of the catalyst was affected by the type of cocatalyst alkylaluminum and the phosphorus compound as an electron donor, molar ratio of catalyst components, and their aging sequence and aging time of the catalyst. The microstructure and configuration of the polymer was decided by the catalyst components, the higher [Al]/[Fe] molar ratio tending to yield syndiotactic 1,2-polybutadiene, while the higher [P]/[Fe] molar ratio favors the formation of amorphous 1,2-polybutadiene.

Synthesis, structure and characterization of a novel asymmetrical half-sandwich binuclear iron carborane complex [eta(5)-C5H3 (t-Bu)(2)](2)Fe-2 (CO)(3)Se2C2B10H10

Halfsandwich iron dicarbonyl complex [eta(5)-C5H3(t-Bu)(2)]Fe(CO)(2)Cl(1) reacts with 1, 2-dilithium diseleno carborane Li(2)Se(2)C(2)B(10)H10 (2) to give a binuclear iron carborane complex [eta(5)-C5H3(t-Bu)(2)](2)Fe-2(CO)(3) Se2C2B10H10(3). The X-ray diffraction analysis of complex 3 reveals that one of the iron atoms is chiral.

1,1 '-di(tert-butyl)metallocenium cations. The x-ray crystal structures of [M((C5H4Bu)-Bu-t)(2)]PF6 (M = Fe, Co) and [Co((C5H4Bu)-Bu-t)(2)](2)CoCl4

The hexafluorophosphate salts [Fe((C5H4Bu)-Bu-t)(2)]PF6 (1) and [Co((C5H4Bu)-Bu-t)(2)]PF6 (2) crystallize in isotypic structures with centrosymmetric cations which have a staggered (transoid) conformation of the exactly parallel ring Ligands (conformational angle tau = 180 degrees). The tetrachlorocobaltate salt, [CO((C5H4Bu)-Bu-t)(2)](2)CoCl4 (3), contains one almost eclipsed (tau = 140.4 degrees) and one almost staggered (tau = 101.4 degrees) cobaltocenium cation; in both cases, the cyclopentadienyl ring planes are slightly inclined (by alpha = 5.4 degrees and 4.1 degrees, respectively) to give more room to the tert-butyl substituents which are bent away from the metal in all three complexes 1 - 3.