Coupling of HPLC and NMR 1—analysis of flowing liquid chromatographic fractions by proton magnetic resonance

A procedure is described which allows the recording of ¹H NMR spectra from high performance liquid chromatography (HPLC) fractions flowing through the magnetic field with a velocity of either 0.05 or 0.25 cm/s. The NMR spectra are obtained by the pulse Fourier transform technique; the beginning and the termination of the pulse sequence is timed according either to the chromatogram from a UV detector or to the free induction decay of the appropriate HPLC fraction. The linewidth of the signals in the NMR spectra is between 1.5 and 2.0 Hz.     

A criterion for tangential flatness

We prove that a local homomorphism induces a flat homomorphism of the graduations with respect to the maximal ideals iff it is flat itself and the tangent cone of the fiber is just the fiber of the tangent cone mapping. More explicit, the statement we want to prove here is as follows.     

Semi-regular plane polygons of integral type

A polygon is called semi-regular if its interior angles are equal to one another. The paper deals mainly with semi-regular polygons whose sides have integral lengths.     

Groups with strongly self-centralizing 3-centralizers

LetG be a finite group with a subgroupM which is the centralizer inG of each of its nonidentity elements and let 3 divide the order ofM. Such groups are classified under the assumption that eitherq=[N _G (M):M]=2^s;s≧0 ands ≠ 3 orq<8. This paper was written while the author was visiting the Department of Mathematics, University of Illinois, Urbana, Illinois 61801.     

Semi-empirical molecular orbital calculations for pyridinealdoximes and acetamidopyridines

Tautomerism of pyridinealdoximes and acetamidopyridines is discussed with regard to their electronic absorption spectra. The spectra of both neutral and ionic forms of the molecules are interpreted by means of the Pariser—Parr—Pople type of calculation in a satisfactory way.The stability of 2- and 4-pyridinealdoxime tautomers is investigated using the CNDO/2 method. The lactim are more stable than the lactam forms of the molecules. The molecules having the substituent group of the syn-configuration are more stable than the molecules with other configurations of the substituent.     

Permutation groups generated by cycles of fixed length

Combinatorial conditions on a set of cycles of fixed degree inS _n are studied, so that they generateA _n orS _n . It is shown thatA _n orS _n is so generated if and only if a graph associated with the set of cycles is connected, provided two of the cycles satisfy certain, not too restrictive, criteria. As a corollary, the minimum number of cycles of degreem ≧ 2 that generateA _n or S_n is determined.     

The sign of the electric field gradient at the nuclear site of Zn in Zn metal

By use of low temperature nuclear quadrupole orientation the quadrupole coupling constant of^69mZn in a Zn single crystal has been determined asv _Q=eQV _zz/h=–28(3) MHz.A positive sign forV _zzat the nuclear site of Zn in Zn is deduced. The half-life of^69mZn has been remeasured asT _1/2=13.756 (18)h.     

Ratio of the electric quadrupole moments of122,124Sb

Low temperature nuclear orientation experiments have been performed with^122,124Sb in Sb and Zn single crystals. The ratio of the quadrupole moments of¹²⁴Sb and¹²²Sb is derived from the data asQ ¹²⁴/Q ¹²²= +2.17 (11). The sign of the effective electric field gradient at the nuclear site of Sb was found to be negative for host Sb and positive for host Zn.