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排序方式: 共有191条查询结果,搜索用时 15 毫秒
101.
Dong RY Geppi M Marini A Hamplova V Kaspar M Veracini CA Zhang J 《The journal of physical chemistry. B》2007,111(33):9787-9794
In this work, the liquid crystal (S)-2-methylbutyl-[4'-(4' '-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/*) was investigated by means of 13C NMR spectroscopy. This compound has a very peculiar mesomorphic behavior, showing the following phases: paraelectric SmA, ferroelectric SmC*, antiferroelectric SmC*A, re-entrant ferroelectric SmC*re, and ferroelectric hexatic Sm*HEX. The structural and orientational ordering properties of ZLL 7/* have been determined by exploiting the nuclear chemical shielding properties of 13C. To this aim, solid-state NMR techniques such as CP, SPINAL-64, and SUPER have been used in combination with DFT calculations. The agreement between experimental and in vacuo DFT shielding parameters appears to be satisfactory. The orientational order parameters obtained from the 13C shielding analysis have been discussed, taking into account different data analysis approaches and comparing them to those previously obtained from an independent 2H NMR study. 相似文献
102.
103.
104.
The long-chain branched thermoplastic tetrafluoroethylene–hexafluoropropylene–vinylidenefluoride terpolymers (LCB THV) investigated
in this paper are new polymers with a unique combination of properties like a high stability against aging or weathering and
a very good chemical resistance. But not much is known about the rheological behaviour of the LCB THV, yet. In this paper,
non-linear rheological properties like shear thinning and strain hardening are studied. Two different types of the THV with
different contents of comonomers and, therefore, different melting points are examined. The THV with the higher melting point
is insoluble. The other with the lower melting temperature is soluble and, therefore, was characterised by size exclusion
chromatography coupled with light scattering with respect to its molecular structure. The results of the rheological measurements
show a pronounced shear-thinning and strain-hardening behaviour for the long-chain branched materials. Both properties are
of great importance for processing operations governed by shear and elongational flows.
相似文献
Helmut MünstedtEmail: |
105.
Guido J. Reiss Anja Zimmer Kaspar Hegetschweiler 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):284-288
The structures of 3‐amino‐1,2R,4S,5‐tetraammoniopentane tetrachloride monohydrate, C5H21N54+·4Cl?·H2O, and 1,2R,3,4S,5‐pentaammoniopentane tetrachlorozincate trichloride monohydrate, (C5H22N5)[ZnCl4]Cl3·H2O, have been determined from single‐crystal X‐ray diffraction data. Both compounds show a complex network of N—H?O, O—H?Cl and N—H?Cl hydrogen bonds. There are a total of 14 H atoms of the tetra‐cation and 15 H atoms of the penta‐cation available for hydrogen bonding. However, due to the particular shape of the primary linear polyammonium cations, only a certain number of H atoms can be involved in hydrogen‐bond formation. It is further shown that hydrogen bonding has an influence on the conformation of such alkylammonium cations. 相似文献
106.
M. Rejmund K. H. Maier R. Broda B. Fornal M. Lach J. Wrzesiński J. Blomqvist A. Gadea J. Gerl M. Górska H. Grawe M. Kaspar H. Schaffner Ch. Schlegel R. Schubart H. J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2000,8(2):161-164
High-spin states in 202Pb and 203Pb have been investigated by in-beam γ-ray spectroscopy following the reaction 198Pt(9Be,xn). A search for magnetic rotational bands in these isotopes confirmed one of the two bands previously assigned to 202Pb and revealed a new band in this isotope. No evidence for magnetic rotation has been found in 203Pb.
Received: 24 July 2000 / Accepted: 28 September 2000 相似文献
107.
Track-terrain modelling and traversability prediction for tracked vehicles on soft terrain 总被引:4,自引:0,他引:4
Skid-steered tracked vehicles are the favoured platform for unmanned ground vehicles (UGVs) in poor terrain conditions. However, the concept of skid-steering relies largely on track slippage to allow the vehicle to conduct turning manoeuvres potentially leading to overly high slip and immobility. It is therefore important to predict such vulnerable vehicle states in order to prevent their occurrence and thus paving the way for improved autonomy of tracked vehicles. This paper presents an analytical approach to track-terrain modelling and a novel traversability prediction simulator for tracked vehicles conducting steady-state turning manoeuvres on soft terrain. Traversability is identified by predicting the resultant track forces acting on the track-terrain interface and the adopted models are modified to provide an analytical generalised solution. The validity of the simulator has been verified by comparison with available data in the literature and through an in-house experimental study. The developed simulator can be employed as a traversability predictor and also as a design tool to test the performance of tracked vehicles with different vehicle geometries operating on a wide range of soil properties. 相似文献
108.
Mark Bartholomä Dr. Sergej Gisbrecht Dipl.‐Chem. Stefan Stucky Dr. Christian Neis Dr. Bernd Morgenstern Dr. Kaspar Hegetschweiler Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(11):3326-3340
The hexadentate ligand all‐cis‐N1,N2‐bis(2,4,6‐trihydroxy‐3,5‐diaminocyclohexyl)ethane‐1,2‐diamine (Le) was synthesized in five steps with an overall yield of 39 % by using [Ni(taci)2]SO4?4 H2O as starting material (taci=1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol). Crystal structures of [Na0.5(H6Le)](BiCl6)2Cl0.5?4 H2O ( 1 ), [Ni(Le)]‐ Cl2?5 H2O ( 2 ), [Cu(Le)](ClO4)2?H2O ( 3 ), [Zn(Le)]CO3?7 H2O ( 4 ), [Co(Le)](ClO4)3 ( 5 c ), and [Ga(H?2Le)]‐ NO3?2 H2O ( 6 ) are reported. The Na complex 1 exhibited a chain structure with the Na+ cations bonded to three hydroxy groups of one taci subunit of the fully protonated H6(Le)6+ ligand. In 2 , 3 , 4 , and 5 c , a mononuclear hexaamine coordination was found. In the Ga complex 6 , a mononuclear hexadentate coordination was also observed, but the metal binding occurred through four amino groups and two alkoxo groups of the doubly deprotonated H?2(Le)2?. The steric strain within the molecular framework of various M(Le) isomers was analyzed by means of molecular mechanics calculations. The formation of complexes of Le with MnII, CuII, ZnII, and CdII was investigated in aqueous solution by using potentiometric and spectrophotometric titration experiments. Extended equilibrium systems comprising a large number of species were observed, such as [M(Le)]2+, protonated complexes [MHz(Le)]2+z and oligonuclear aggregates. The pKa values of H6(Le)6+ (25 °C, μ=0.10 m ) were found to be 2.99, 5.63, 6.72, 7.38, 8.37, and 9.07, and the determined formation constants (log β) of [M(Le)]2+ were 6.13(3) (MnII), 20.11(2) (CuII), 13.60(2) (ZnII), and 10.43(2) (CdII). The redox potentials (vs. NHE) of the [M(Le)]3+/2+ couples were elucidated for Co (?0.38 V) and Ni (+0.90 V) by cyclic voltammetry. 相似文献
109.
Kaspar D. Ko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(12):1037-23482
We present a graphical user interface, based on the modified long-wavelength approximation, to compute the optical properties of single metal nanoparticles of ellipsoidal geometry (spheres, rods, and disks). The user-friendly interface allows one to readily gauge the accuracy of results obtained using the modified long-wavelength approximation. For spherical particles, up to 10-nm diameter, we confirm that our approach yields an exact correspondence with Mie theory, and gives an approximation error of less than 15% for gold (silver) particles with diameters approaching 40 nm (26 nm). Results are shown to be sensitive to the source data for the optical constants for a given material. The modular nature of the simulation platform provides a quick and intuitive guide for optical characterization experiments. 相似文献
110.
Leitch JJ Collins J Friedrich AK Stimming U Dutcher JR Lipkowski J 《Langmuir : the ACS journal of surfaces and colloids》2012,28(5):2455-2464
Quantitative subtractively normalized interfacial Fourier transform infrared reflection spectroscopy (SNIFTIRS) was used to determine the conformation and orientation of sodium dodecyl sulfate (SDS) molecules adsorbed at the single crystal Au(111) surface. The SDS molecules form a hemimicellar/hemicylindrical (phase I) structure for the range of potentials between -200 ≤ E < 450 mV and condensed (phase II) film for electrode potentials ≥500 mV vs Ag/AgCl. The SNIFTIRS measurements indicate that the alkyl chains within the two adsorbed states of SDS film are in the liquid-crystalline state rather than the gel state. However, the sulfate headgroup is in an oriented state in phase I and is disordered in phase II. The newly acquired SNIFTIR spectroscopy measurements were coupled with previous electrochemical, atomic force microscopy, and neutron reflectivity data to improve the current existing models of the SDS film adsorbed on the Au(111) surface. The IR data support the existence of a hemicylindrical film for SDS molecules adsorbed at the Au(111) surface in phase I and suggest that the structure of the condensed film in phase II can be more accurately modeled by a disordered bilayer. 相似文献