Electron Paramagnetic Resonance Spectra of PrIons Doped in Sr2SnO4and Ba2SnO4

The isotropic electron paramagnetic resonance (EPR) spectra of powders with Pr⁴⁺doped inM₂SnO₄(M=Sr, Ba) with K₂NiF₄-type structure were measured at 4.2 K. A very large hyperfine interaction with the¹⁴¹Pr nucleus was observed. The results were analyzed based on the weak field approximation, andgvalues and hyperfine coupling constantsAwere obtained. The measuredgvalues are much smaller than ∣−10/7∣, showing that the crystal field effect on the behavior of a 4felectron is large. The value of ∣g∣ decreases from 0.646 (Pr⁴⁺/Ba₂SnO₄) to 0.615 (Pr⁴⁺/Sr₂SnO₄), which is caused by the increase of the crystal field due to the shrinking of the lattice. In contrast, the hyperfine coupling constants are almost constant:A=0.0605 cm⁻¹.     

Investigatins of the extraction of adenosine phosphates with N,N′-dioctadecyl-1,4-diazabicyclo[2.2.2.]octane and N,N,N′,N′-tetramethyl-N,N′-dioctadecyldiammonium alkanes

The extraction of adenosine phosphates with hydrophobic cyclic diammonium or alkyl diammonium salts is described. The selectivity of these compounds is governed by two factors, the length of the spacer arm between the two ammonium nitrogens and the pH of the system. The cyclic compound exhibits less selectivity than the similar noncyclic alkyl compounds. It is shown that several of the compounds are fairly selective for adenosine 5′-triphosphate (ATP). The best of these, N,N,N′-tetramethyl-N,N′-dioctadecyldiammoniumethane, is tested for assay of ATP in spiked urines.     

Asymptotic behavior of the stationary distributions in the GI/PH/c queue with heterogeneous servers

Summary This paper deals with the stablec-server queue with renewal input. The service time distributions may be different for the various servers. They are however all probability distributions of phase type. It is shown that the stationary distribution of the queue length at arrivals has an exact geometric tail of rate , 0<<1. It is further shown that the stationary waiting time distribution at arrivals has an exact exponential tail of decay parameter >0. The quantities and may be evaluated together by an elementary algorithm. For both distributions, the multiplicative constants which arise in the asymptotic forms may be fully characterized. These constants are however difficult to compute in general.This research was supported by the National Science Foundation under Grant Nr. ENG-7908351 and by the Air Force Office of Scientific Research under Grant Nr. AFOSR-77-3236.     

An interesting inclusion phenomenon with (S)-1-(hydroxydiphenylmethyl)-5-azoniaspiro[4.4]nonane bromide and (S)-1-(hydroxydiphenylmethyl)-5-azoniaspiro[4.5]decane bromide and optical resolution of binaphthyl and biphenanthyl diols by inclusion crystallization with these optically active ammonium salts

Recrystallization of the spiro-pyrrolidinium salts (S)-1-(hydroxydiphenyl methyl)-5-azoniaspiro[4.4]nonane bromide or (S)-1-(hydroxydiphenylmethyl)-5-azoniaspiro[4.5] decane bromide from chloroform afforded a crystalline spiro-pyrrolidinium salt including two molecules of chloroform which was determined by 'H nmr elemental analysis, and X-ray analysis. Racemic 2.2-dihydroxy-1, 1-binaphthyl and 10, 10-dihydroxy-9,9-biphenanthryl have been resolved effectively by inclusion crystallization using these chiral ammonium salts.     

State of Fe3+ ion and Fe3+ −F− interaction in calcium fluorosilicate glasses

The state of Fe³⁺ ions and Fe³⁺ ?F^? interaction in calcium fluorosilicate glasses xCaF₂·(1- x)CaO·SiO₂) (0 ≤ x ≤ 0.3) containing a small amount of iron were investigated by ESR spectroscopy. Two resonances observed near g = 2.0 and g = 4.3 were assigned to dipole-dipole interacted Fe³⁺ ions and Fe³⁺ ions in a rhombic crystal field, respectively. The fraction of Fe³⁺ ions in a rhombic crystal field decreased and that of dipole-dipole interacted Fe³⁺ ions increased with increasing Fe₂O₃ content. It was found that the quantity of dipole-dipole interacted Fe³⁺ ions depends on the negative partial charge of fluorine ions and shows a maximum at 10 mol% CaF₂ (x = 0.2). The maximum is attributed to the largest difference between absolute values of the ionic potentials of ferric and fluorine ions which is caused by the smallest negative partial charge of flourine at 10 mol% CaF₂.     

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)-alkenyl)iodonium tetrafluoroborates with tetrabutyl-ammonium halides: retention of configuration

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)alkenyl)-phenyliodonium tetrafluoroborates 1 with tetrabutylammonium halides (Cl, Br, and I) proceed with exclusive retention of configuration at room temperature and afford (Z)-β-(phenylsulfonyl)vinyl halides 2 in high yields.     

INTERACTION OF 9-AMINOACRIDINE WITH 7-METHYLGUANOSINE AND 1,N6-ETHENOADENOSINE MONOPHOSPHATE

Abstract—Fluorescence properties of 9-aminoacridine in aqueous solutions of 7-methylguanosine (7MeG) and 1, N ⁶-ethenoadenosine monophosphate (εAMP) have been examined. It was found that fluorescence of the dye was quenched by 7MeG and εAMP as well as by unmodified nucleotides such as GMP and AMP. Quantitative analysis of the results shows that both dynamic and static quenching processes are responsible for the quenching of fluorescence.     

Pyrimidines. LII Synthesis of pyrido[2,3-d]pyrimidine-2,4-diones and pyrido[2,3-d:6,5-d']dipyrimidine-2,4,6,8-tetrones

Reactivities of 5-dimethylaminomethylene-6-imino-1,3-dimethyluracil hydrochloride ( 1 ) toward a variety of active methylene compounds 2 and 5 were investigated. Treatment of 1 with active methylene compounds such as malononitrile and ethyl cyanoacetate in the presence of triethylamine gave pyrido[2,3-d]pyrimidine-2,4-dione derivatives 3. Reaction of 1 with barbituric acids resulted in the formation of pyrido[2,3-d:6,5-d′]di-pyrimidine-2,4,6,8-tetrone derivatives 6.