New strategy for the identification of amino acids by TLE and TLC using basic or buffered mobile phases

Summary Direct, simple and reliable means for characterization of the common amino acids, using mixtures of structural analogues of amino acids and combinations of low-voltage electrophoresis (1.04 mol dm^–3 formic acid) and chromatography (tert-butanol/methanol/pyridine/formic acid/water, 33:43:9.6:0.4:20, v/v, methanol/pyridine/formic acid/water, 70:9.6:0.4:20, v/v, or tertpentanol/methylethylketone/pyridine/water, 37.5:37.5:5:20, v/v) on amorphous cellulose thin-layer are given. The efficiency of the procedures is evaluated in various examples.Abbreviations used: TLC = thin-layer chromatography, TLE = thin-layer electrophoresis, TLP = thin-layer plate; other abbreviations: see Table I and end of text.for structural analogues of amino acids and glucosamine, see Table I.     

Low temperature specific heat of Ni-Co and Ni-Fe alloys

Values of the low temperature specific heat of f.c.c. Ni-Co and Ni-Fe alloys have been determined in the 1.2–8 K range with a relative accuracy of 10^-3 and analysed to separate the electron, phonon, magnon and hyperfine terms. Results are in good agreement with former data^5–7 and with theory: Gomes' model⁴ of a d-d tight-binding scattering in the dilute case, Hasegawa's^12,13 CPA calculations are both consistent with experiments.     

Definitive evidence for a proximal effect of pyridine in the NaOCl/Mn(porphyrin)x / pyridine catalytic oxygenation system

Using pyridine-attached manganese porphyrins, it has been possible to obtain definitive evidence that pyridine behaves as a proximal ligand in the NaOCl/Mn(porphyrin)X catalytic oxygenation system.     

The role of soft gluons in lepton pair production

We derive expressions for the exponentiation of soft gluon effects in lepton pair production and discuss their phenomenological implications for the rapidity and Q² dependence of the so-called $\text{“K-}\text{factor}\text{”}$. Predictions are given for scaling violations to be seen in the determination of the pion structure function.     

Formation of arynezirconocenes from substituted diaryl bis (t-butylcyclopentadienyl) zirconium: application to the synthesis of new functionalized ortho-dichalcogenobenzene compounds

The para-substituted diphenylzirconocenes [(t-BuCp)₂Zr(p-C₆H₄R)₂; R = Br, NMe₂] (A) were easily obtained from the reaction of the appropriate organolithium reagent with bis(t-butylcyclopentadienyl)zirconium dichloride. Elimination of bromobenzene or N,N-dimethylaminobenzene from A by slight heating led to arynezirconocenes into which were inserted two equivalents of elementary chalcogens. As a result dichalcogenated zirconacycles [(t-BuCp)₂ZrY₂C₆H₃R; Y = S, Se] (B) were obtained. Complexes B constitute useful potential synthons in organic synthesis and a large family of new functionalized dichalcogenated benzenic compounds was prepared by reacting electrophiles. The structure of complexes B as well as related benzenic derivatives has been confirmed by microanalysis, ¹H NMR and mass spectrometry.     

Intensities and air broadening coefficients of O3 in the 5- and 3-μm regions

Absolute intensities, self-broadening, and nitrogen and oxygen broadening of O₃ were measured on 22 lines in two different spectral regions: 5 μm corresponding to ν₁ + ν₃ band and 3 μm to ν₁ + ν₂ + ν₃. The results are reported along with their accuracies and compared with theoretical studies.     

L'oxyde double TeVO4 II. Structure cristalline de TeVO4-β-relations structurales

β-TeVO₄ crystallizes in the monoclinic system with the space group $\text{P2}{}_1\text{c}$ and the parameters: a = 4.379 Å, b = 13.502 Å, c = 5.446 Å, and β = 91.72°. Vanadium occupies the center of a square pyramid of oxygens, an extra oxygen is at VO = 2.77 Å. These distorted octahedra share corners forming puckered sheets parallel to (010). The sheets are held together by [Te₂O₆]^4? groups in which tellurium is one-side coordinated by four oxygen atoms.     

Relationship between vitamin D status and skin phototype in general adult population

A link between bone mineral density and skin color has been reported recently, and pigmentation has been shown to affect cutaneous vitamin D production. In the present study, we investigated the relationship between phototype, global self-assessed sun exposure, geographical location and vitamin D serum levels in 1191 French adults. When the factors were analyzed separately, individuals with lower phototypes as well as those with lower sun exposure showed significantly lower levels of vitamin D than those with darker phototypes or those with higher sun exposure. However, when factors were analyzed as a whole, the vitamin D status was no longer linked with the phototype, but with sun exposure and geographical location. Since phototypes and global self-assessments of sun exposure were positively linked, our data suggest that lower vitamin D levels in fair-skinned individuals are due to their sun exposure behavior.     

Synthèse de systèmes comportant deux cycles thiophéniques orthocondensés à un hétérocycle à sept chainons

The reduction of the carbonyl group of bithienyls carrying on each thiophene ring a formyl group bonded to the carbon atom next to the intercyclic bond leads to the expected primary di-alcohols. These dialcohols can give the corresponding bis-halogeno-methylated bithienyls. The dehydration of the alcohols and the action of sodium sulfide or amines upon the obtained halides leads respectively to the dihydrodithieno[c,e] oxepines, thiepines and azepines. The tetramethyl derivatives of the previous oxepines have been obtained from diacetylbithienyls.