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Mary E. Neubert DAVID G. ABDALLAH Jr Sandra S. Keast Julie M. Kim Soonnam Lee Ryan M. Stayshich Margaret E. Walsh Rolfe G. Petschek Shin-Tson Wu 《Liquid crystals》2003,30(6):711-731
New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1-4; and X = C n H 2n + 1 , F, CF 3 or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF 3 when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices.
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
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Plastic microchannels (4.5 cm long) fabricated from an etched glass master were tested for high-resolution single-stranded DNA analysis. Using replaceable denaturing linear polyacrylamide as sieving matrix, one-color separation of a fragment sizing standard with single-base resolution (R > 0.5) was achieved up to 275 bases. Two-color sizing analysis of four loci short tandem repeat (STR) allelic ladder (CSF1PO, TPOX, TH01, vWA) with single-base resolution (R = 0.62) on TH01 alleles 9.3 (198 bp) and 10 (199 bp) was demonstrated. An average standard deviation of +/- 0.06 bp and +/-0.11 bp in sizing 32 alleles of the CTTv ladder was attained between runs and between channels, respectively. Four-color sequencing separation of a terminator sequencing standard showed a base-calling accuracy of 99.1% out to 320 bases in 13 min. 相似文献
5.
Rolfe Tomlinson 《The Journal of the Operational Research Society》1980,31(6):467-476
This paper is concerned with the need for more interdisciplinary, systems oriented, research directed towards major problems encountered by decision makers in industry and government; a need which is more difficult to meet in the face of traditional methods of organising knowledge and research. It emphasises the need to acknowledge the true complexity of the problems and the interactive nature of any effective research procedure. As an illustration, both of the need and the problems involved in meeting it, the development of a new program of research into problems of Management and Technology at the International Institute of Applied Systems Analysis, which is supported by seventeen nations of all political complexions, is analysed. The implication is that we can do something about the future, but we must be prepared to do. 相似文献
6.
Adams RD Captain B Herber RH Johansson M Nowik I Smith JL Smith MD 《Inorganic chemistry》2005,44(18):6346-6358
The reaction of Re2(CO)8[mu-eta2-C(H)=C(H)Bu(n)](mu-H) with Ph3SnH at 68 degrees C yielded the new compound Re2(CO)8(mu-SnPh2)2 (10) which contains two SnPh2 ligands bridging two Re(CO)(4) groups, joined by an unusually long Re-Re bond. Fenske-Hall molecular orbital calculations indicate that the bonding in the Re2Sn2 cluster is dominated by strong Re-Sn interactions and that the Re-Re interactions are weak. The 119Sn M?ssbauer spectrum of 10 exhibits a doublet with an isomer shift (IS) of 1.674(12) mm s(-1) and a quadrupole splitting (QS) of 2.080(12) mm s(-1) at 90 K,characteristic of Sn(IV) in a SnA2B2 environment. The IS is temperature dependent, -1.99(14) x 10(-4) mm s(-1) K(-1); the QS is temperature independent. The temperature-dependent properties are consistent with the known Gol'danskii-Kariagin effect. The germanium compound Re2(CO)8(mu-GePh2)2 (11) was obtained from the reaction of Re2(CO)8[mu-eta2-C(H)=C(H)Bu(n)](mu-H) with Ph3GeH. Compound 11 has a structure similar to that of 10. The reaction of 10 with Pd(PBu(t)3)2 at 25 degrees C yielded the bis-Pd(PBu(t)3) adduct, Re2(CO)8(mu-SnPh2)2[Pd(PBu(t)3)]2 (12); it has two Pd(PBu(t)3) groups bridging two of the four Re-Sn bonds in 10. Fenske-Hall molecular orbital calculations show that the Pd(PBu(t)3) groups form three-center two-electron bonds with the neighboring rhenium and tin atoms. The mono- and bis-Pt(PBu(t)3) adducts, Re2(CO)8(mu-SnPh2(2)[Pt(PBu(t)3)] (13) and Re2(CO)8(mu-SnPh2)2[Pt(PBu(t)3)]2 (14), were formed when 10 was treated with Pt(PBu(t)3)2. A mono adduct of 11, Re2(CO)8(mu-GePh2)2[Pt(PBu(t)3)] (15), was obtained similarly from the reaction of 11 with Pt(PBu(t)3)2. 相似文献
7.
Herber U Pechmann T Weberndörfer B Ilg K Werner H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(1):309-319
A series of dinuclear chelate complexes of the general composition [Rh2(kappa2-L)2(mu-CR2)2(mu-SbiPr3)] (R = Ph, p-Tol; L = CF3CO2-, acac-, acac-f3-) and [Rh2Cl(kappa2-L)(mu-CR2)2(mu-SbiPr3)] (R = Ph, p-Tol; L = acac-, acac-f3-) has been prepared by replacement of the chloro ligands in the precursors [Rh2Cl2(mu-CR2)2(mu-SbiPr3)] by anionic chelates. The lability of the SbiPr3 bridge in the rhodium dimers is illustrated by the reactions of [Rh2(kappa2-acac)2(mu-CR2)2(mu-SbiPr3)] (7, 8) with Lewis bases such as CO, CNtBu, and SbEt3 which lead to the formation of the substitution products [Rh2(kappa2-acac)2(mu-CR2)2(mu-L')] (13-16) in excellent yields. Treatment of 7 and 8 with sterically demanding tertiary phosphanes PR3 (R3 = iPr3, iPr2Ph, iPrPh2, Ph3) affords the mixed-valence Rh0-RhII complexes [(kappa2-acac)2Rh(mu-CPh2)2Rh(PR3)] (21-24) and [(kappa2-acac)2Rh(mu-C(p-Tol)2]2Rh(PiPr3)] (25) for which there is no precedence. The terminal PiPr3 ligand of 21 is easily displaced by alkynes, CNtBu, and CO to give, by preserving the [(kappa2-acac)2Rh(mu-CPh2)2Rh] molecular core, the related dinuclear compounds 26-31 in which the coordination number of the Rh0 center is 3, 4, or 5. The molecular structures of [Rh2Cl(kappa2-acac)(mu-CPh2)2(mu-SbiPr3)] (5), [Rh2(kappa2-acac)2(mu-CPh2)2(mu-CO)] (13), [(kappa2-acac)2Rh(mu-CPh2)2Rh(PiPr3)] (21), and [(kappa2-acac)2Rh(mu-CPh2)2Rh(CNtBu)2] (30) have been determined crystallographically. 相似文献
8.
Kirumakki S Samarajeewa S Harwell R Mukherjee A Herber RH Clearfield A 《Chemical communications (Cambridge, England)》2008,(43):5556-5558
We have designed a new family of layered Sn(iv)phosphonate (SnPP) materials which are very efficient catalysts in the BV oxidation of aromatic aldehydes without any solvent and using aqueous H(2)O(2) (30%) as the oxidant. 相似文献
9.
Prof. Dr. Sjoerd Harder Dominik Naglav Dr. Christian Ruspic Prof. Dr. Claudia Wickleder Dr. Matthias Adlung Dr. Wilfried Hermes Dr. Matthias Eul Prof. Dr. Rainer Pöttgen Dr. Daniel B. Rego Prof. Dr. Frederic Poineau Prof. Dr. Kenneth R. Czerwinski Prof. Dr. Rolfe H. Herber Prof. Dr. Israel Nowik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(37):12173-12173
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