Relatively Moving Systems in “True Transformations Relativity”

In this paper the physical systems consisting of relatively moving subsystems are considered in the true transformations relativity. It is found in a manifestly covariant way that there is a second-order electric field outside stationary current-carrying conductor. It is also found that there are opposite charges on opposite sides of a square loop with current and these charges are invariant charges.     

Separation of structurally related peptides by open-tubular capillary electrochromatography using (metallo)porphyrins as the adsorbed stationary phase

Several (metallo)porphyrins, particularly the porphyrin derivative tetraphenylporphyrin, and complexes of porphyrin derivatives with metal ions (Zn2+, Cu2+, Ni2+, Co2+, Co3+) have been employed as the stationary phase physically adsorbed onto the inner fused-silica capillary surface for open-tubular capillary electrochromatography, and applied for the separation of structurally related peptides. Four octapeptides, derivatives of the B23-B30 fragment of the B-chain of human insulin with minor changes in their sequences (presence of lysine or ornithine in position B-29, presence or absence of phenylacetyl protecting group on the amino group of lysine/ornithine or N-terminal amino group of glycine), were studied as model analytes. Separations were performed both in alkaline (pH 9.0) and in acidic (pH 2.25) background electrolytes, and the changes in the migration/retention behaviour of the model set of peptides were investigated with respect to the porphyrin periphery/central metal atom and the charge of the octapeptides modified. The key moment of successful separation of these peptides seems to be the accessibility of functional groups of the peptides to the interaction with the modifiers tested herein.     

Heats of atomization of conjugated hydrocarbons by a new semiempirical method

Heats of atomization of a range of conjugated hydrocarbons are calculated by a semiempirical method which combines characteristic features of the MO and the VB theory. The -ground state of each hydrocarbon is represented as a linear combination of Kekulé structures where, unlike the VB theory, each Kekulé structure is a determinant containing bond Orbitals. In this approach only the Hückel parameter has to be adjusted. Experimental heats of atomization are by this method reproduced approximately equally well as by the more sophisticated SCF-MO approach. The use of this method is however much simpler since it amounts to a single diagonalization of a matrix of the order equal to the number of Kekulé structures only.     

Vibrational isotope effect of linear and planar molecules: Deuterated bromoethenes

Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites are considered. Stretching (bending, out-of-plane) frequencies _k and normal modes _k of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies _i and the corresponding normal modes _i of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes | _i of the normal modes _i at those sites that are affected by isotopic substitution. The rule which interlaces frequencies _k of molecule A with frequencies _i of molecule B is derived. Given two isotopic molecules A and B that differ by a single isotopic substitution at site , the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site in terms of stretching (bending, out-of-plane) frequencies of molecules A and B . As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is =2.74 cm^–1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is 1=2.84 cm^–1, c=2.96 cm^–1 and t=2.72 cm^–1.     

Macrocyclic vs acyclic derivatives of chiral bis(oxazolines); ligand distortion and enantioselectivity of Pd(II) complexes in catalytic allylic alkylation

Pd(II) complexes of acyclic (1,2;4,5) and macrocyclic (3,6-10) derivatives of 1,5-bis(oxazolines), are tested in the enantioselective allylic alkylation of racemic 1,3-diphenyl-3-acetoxyprop-2-ene (14) by dimethylmalonate anion to allyl malonate derivative 15. Conformation in solution of representative allyl Pd(II) complexes 12 and 13 is studied by 2D NMR and CD spectroscopy. 2D NMR data reveal loss of C₂ symmetry of the ligands in Pd(II)allyl-bis(oxazoline) complexes. CD spectra indicate distortion of the bidentate ligand in the complex and a conformationally forced larger twist between two chromophores in the macrocyclic complex. Only moderate variation of enantioselectivity with the length and ring size of the ligand is observed, and a rationale offered.     

A unique catalyst effects the rapid room-temperature cross-coupling of organozinc reagents with carboxylic acid fluorides, chlorides, anhydrides, and thioesters

We have identified a catalyst capable of effecting the rapid, room-temperature cross-coupling between acid fluorides and diorganozinc reagents. The use of acid fluorides as electrophilic partners allows this reaction to tolerate epimerizable functionality as well as beta leaving groups. The same catalyst is also capable of cross-coupling acid chlorides, acyl cyanides, anhydrides, thioesters, and pyridyl esters. Noteworthy is the ability of the reaction to successfully transfer both groups from the organometalic fragment.     

Evaluation of novel sample identification approach based on chromatographic fingerprint set correlation homogeneity analysis

Instead of usual rationale for chromatographic fingerprint based sample identification which relies upon visual inspection or principal component analysis of raw or aligned chromatograms novel nonparametric statistical measure of fingerprint set homogeneity is proposed. Randomization test is applied for significance analysis of fingerprint set homogeneity while average maximum crosscorrelation is used as a merit function. Chromatogram sets generated by random selection from standard and unknown sample chromatogram collections are compared with respect to merit function values with set of chromatograms that represents standard and/or unknown sample. In that instance fingerprint homogeneity significance is represented by the fraction of random chromatogram sets that have higher merit values than the standard and/or unknown sample sets. A set of peptide maps corresponding to different haemoglobin variants has been selected for evaluation of proposed test. This approach is compared to chromatogram alignment based on correlation optimized warping coupled with principal component or cluster analysis. Proposed method is simple i.e. straightforward sample identification procedure which reliability has been evaluated here. Impact of this approach on peptide mapping validation and system suitability analysis is discussed.     

Fullerene Graphs with Exponentially Many Perfect Matchings

We show that for all sufficiently large even p there is a fullerene graph on p vertices that has exponentially many perfect matchings in terms of the number of vertices. Further, we show that all fullerenes with full icosahedral symmetry group have exponentially many perfect matchings and indicate how such results could be extended to the fullerenes with lower symmetry.     

Analysis of ozone monitoring data

The concentration data obtained by monitoring pollutants do not follow a symmetric or even regular, for example log-normal, distribution so that statistical methods which are insensitive to the type of distribution are required. Such a robust statistical method has been applied for the analysis of data obtained by monitoring ozone in different environments. Since ozone is formed at ground level through photochemical reactions, its volume fractions follow a typical diurnal behaviour with a maximum at about noon and a minimum during the night. A convenient way of representing ozone monitoring data is described. The distribution is represented by percentiles, and for each hour of a day averaged over the whole period. Five most characteric percentiles are represented by so-called boxes and whiskers.     

Hydrovinylsilanes in sequential reactions: A route to graft copolymers [1]

The radical copolymerization of styrene or methyl methacrylate and diphenylvinylsilane 1 led to Si–H functionalized polyolefins 5–7 and 8–10 , respectively. The efficiency of incorporation of 1 was low. In addition, the molecular weights were inversely proportional to the concentration of 1 , indicating that, while the silane behaves as a monomer (Si–CH=CH₂), its primary role was as a chain termination and a chain transfer (Si–H) agent. The copolymers contained about 1 mol% Si–H groups: the methacrylate derivatives also contained Si-vinyl groups. The residual Si–H groups in the copolymers remained chemically active. It was thus possible to graft vinylsilicones onto 9 using transition metal catalyzed hydrosilation to give 11 , or vinylanthracene onto 9 using radically induced hydrosilation to give 12. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:241–251, 1998