Search results for "Length"
showing 10 items of 2188 documents
Crystal structure of N,N,N′,N′,N′′,N′′-hexamethylguanidinium cyanate 1.5-hydrate
2015
The title hydrated salt, C7H18N3+·OCN−.1.5H2O, was synthesized starting fromN,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water molecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6):0.148 (6). The C—N bond lengths in both guanidinium ions range from 1.329 (2) to 1.358 (10) Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H...N hydrogen bonds between the crystal water molecules and the cyanate ions and strong O—H...O hyd…
Crystal structure of bis-(2-methyl-1H-imidazole-κN (3))(meso-tetra-p-tol-ylporphyrinato-κ(4) N)iron(III) perchlorate tetra-hydro-furan sesquisolvate.
2016
The crystal structure of the six-coordinate, highly ruffled, ferric porphyrinate bis(2-methylimidazole)[meso-tetrakis(p-tolyl)porphyrinato]iron(III) perchlorate is reported.
Crystal structure of N′′-benzyl-N′′-[3-(benzyldimethylazaniumyl)propyl]-N,N,N′,N′-tetramethylguanidinium bis(tetraphenylborate)
2015
In the crystal structure of the title salt, C24H38N42+·2C24H20B−, the C—N bond lengths in the central CN3unit of the guanidinium ion are 1.3364 (13), 1.3407 (13) and 1.3539 (13) Å, indicating partial double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3plane. The bonds between the N atoms and the terminal methyl groups of the guanidinium moiety and the four C—N bonds to the central N atom of the (benzyldimethylazaniumyl)propyl group have single-bond character. In the crystal, C—H...π interactions between the guanidinium H atoms and the phenyl C atoms of the tetraphenylborate ions …
Tetrakis(dimethoxyboryl)methane
2016
The title compound, tetrakis(dimethoxyboryl)methane (systematic name: octamethyl methanetetrayltetraboronate), C9H24B4O8or C[B(OMe)2]4, is a useful synthetic intermediate. Crystals of this compound at 102 K conform to the orthorhombic space groupPbcn. The molecules, which reside on sites of crystallographic twofold symmetry, have idealized -4 point symmetry like most other CX4molecules in which eachXgroup bears two non-H substituents at the 1-position. The central C atom has a slightly distorted tetrahedral coordination geometry, with C—B bond lengths of 1.5876 (16) and 1.5905 (16) Å. One of the methoxy groups is disordered over two sets of sites; the major component has an occupancy factor…
On the intrinsic population of the lowest triplet state of uracil
2007
Abstract From CASPT2//CASSCF quantum-chemical computations it is determined that the lowest triplet state of uracil can be efficiently populated from the initially activated singlet manifold through respective singlet–triplet crossings of the singlet state with the low-lying 3nπ∗ state at 4.6 eV and with the lowest 3ππ∗ state at 4.2 eV located along the minimum energy path of the low-lying 1ππ∗ state. Large spin–orbit coupling elements predict, in particular for the former case, efficient intersystem crossing processes. The wavelength dependence measured for the triplet quantum yield can be explained by the location of the singlet–triplet crossing regions.
Structure and properties ofn-alkyldimethylsilyl bonded silica reversed-phase packings
1978
Summary The effects of the modifier functionality and the chain length ofn-alkylchlorosilanes on the surface structure of packings and on their retention behaviour in reversed-phase chromatography were investigated. Comparative retention studies on three silica packings that had been treated to maximum conversion withn-octyltrichlorosilane (I),n-octylmethyldichlorosilane (II) andn-octyldimethylmonochlorosilane (III) showed that the most pronounced reversed-phase character is obtained by using III as the modifying reagent. A series ofn-alkyldimethylsilyl bonded silica packings were prepared with widely differingn-alkyl chain lengths. Although the packings are very hydrophobic, the maximum su…
An existence and uniqueness principle for a nonlinear version of the Lebowitz-Rubinow model with infinite maximum cycle length
2017
The present article deals with existence and uniqueness results for a nonlinear evolution initial-boundary value problem, which originates in an age-structured cell population model introduced by Lebowitz and Rubinow (1974) describing the growth of a cell population. Cells of this population are distinguished by age a and cycle length l. In our framework, daughter and mother cells are related by a general reproduction rule that covers all known biological ones. In this paper, the cycle length l is allowed to be infinite. This hypothesis introduces some mathematical difficulties. We consider both local and nonlocal boundary conditions.
Evidence from mtDNA RFLP analysis for the introduction of Fundulus heteroclitus to southwestern Spain
1996
Restriction analysis of mitochondrial DNA confirmed the taxonomic status of a southwestern Iberian Peninsula population of Fundulus heteroclitus and its probable origin in North America.
A Cross-sectional Growth Study of Forearm Length and Tibial Length in an Indigenous Andean Population of 6 to 19 Years of Age.
1997
Patterns of growth in forearm length and tibial length were studied in 149 school-children of Aymara ancestry (73 boys and 76 girls), aged 6 to 19 years. The investigation was based on a cross-sectional survey performed in 1987 in the rural community of Putre (3, 530 m), northern Chile. The results show that there is little sexual dimorphism over the age period of 6 to 13 years, while sex differences are more pronounced between the ages of 14 and 17 years, both for forearm length and tibial length, with boys having higher means. Correspondingly, the maximum values achieved for both measurements are greater in boys than in girls. The growth spurt begins about two years earlier in girls than …
The Born–Oppenheimer equilibrium bond distance of GeO from millimetre- and submillimetre-wave spectra and quantum-chemical calculations
2014
The millimetre- and submillimetre-wave spectra of the five common isotopologues of (GeO)-O-16 in their electronic and vibrational ground state have been recorded in the spectral region 115-732GHz; for (GeO)-Ge-74-O-16, the rotational spectrum in the v = 1 state has been detected as well. Exploiting the high precision of the measurements, the Born-Oppenheimer breakdown parameter Delta(Ge)(01) could be determined from a Dunham analysis of the spectral data, whereas Delta(O)(01) was obtained from quantum-chemical calculations, because of the lack of high-precision measurements for the (GeO)-O-18 isotopologues. From the rotational equilibrium constant, the Born-Oppenheimer equilibrium distance …