Uncertainty of measurement. Twenty years afterwards

The application of the concept "uncertainty" causes considerable difficulties. In this paper an analysis of the intrinsic contradictions of the concept itself and its relationship with the statements of metrology is given with the aim of establishing possible reasons for these difficulties. As a result of this analysis several examples are presented to demonstrate the conflicts of the concept and its several statements in the general fundamental notions of metrology.     

Arsenic speciation by capillary gas-liquid chromatography

Specific environmentally significant arsenic compounds are determined by capillary gas-liquid chromatography. Inorganic (arsenite, arsenate) and organic (monomethylarsonate, dimethylarsinate) arsenicals are measured as the corresponding methylthioglycolate derivatives, which are simultaneously separated on wide-bore borosilicate glass and fused-silica columns under conditions of temperature programming. Inorganic arsenate and arsenite cannot be differentiated by the derivatization technique. Flame-ionization and electron-capture detection are evaluated. A simple and rapid sample preparation procedure is used for water, urine, blood, and tissue.     

Internal molecular disorder in the nematic and smectic phases of thermotropic liquid crystals studied by NMR SPDE experiments

The recently developed NMR SPDE experiment is shown to provide a new and particularly convenient technique for probing the conformational dynamics of mesogens in thermotropic liquid crystals. Measurements have been made in the nematic and smectic phases of the 4,4′-di-n-alkoxyazoxybenzenes. It is shown for the first time that the internal disorder of the alkyl end chains is intimately related to the molecular organization of these mesophases.     

Extraction and micro-determination of manganese(II) with oxine and aliquat 336

A sensitive and selective method has been developed for the micro-determination of Mn(II) by the selective extraction of the yellow Mn(II)-8-hydroxyquinolinate complex with a liquid ion-exchanger, Aliquat 336, from basic medium. The molar absorptivity of the complex is 2.2 x 10(4)1.mole(-1).cm(-1) at 420 nm and the colour system obeys Beer's law in the range 0.1-3.5 ppm Mn(II) in the final solution. The composition and stability of the complex are discussed. Potential interferents have been examined and the method is applied to analysis of standard steel and bronze samples.     

An evaluation of acid digestion methods for amniotic fluid phospholipids

Five methods of acid digestion of amniotic fluid phospholipids for inorganic phosphate release were evaluated at a temperature of 225 °C and a heating time of 30 min. The methods used the following digestants: (A (perchloric acid), B (perchloric acid containing molybdate), C (sulfuric acid, 30% hydrogen peroxide, 5% urea), D (sulfuric-perchloric acids), and E (sulfuric-perchloric acids with vanadium pentoxide). After digestion and dilution with water, a hydrogen ion concentration of about 2.5 mol/ liter was obtained that permitted the use of stannous chloride-hydrazine sulfate as the reducing agent for phosphate color development. Recoveries of the different amniotic fluid phospholipids and aqueous phosphate standards were quantitative for all methods. A comparative study with amniotic fluids showed similar results for all methods. Since all methods were found to be equivalent under the specified conditions described, the choice was dependent upon the user's preference.     

Functional monomers and polymers. LXI. Photochemical reactions on the synthetic polymers containing thymine bases

Photodimerization of N-2-isobutyloxyethyl thymine (T-M), bis[2-(5-methyl-1-primidinyl)-ethyl] glutarate (T-T), poly(N-2-methacryloyloxyethyl thymine) (polyMAOT), and poly(N-2-acryloyloxyethyl thymine) (poly AOT) was studied in dimethylformamide solution. The rate of intramolecular photodimerization of polyMAOT and polyAOT was 5.7 and 7.2 times faster, respectively, than that of T-T. In T-M, however, intermolecular photodimerization did not occur under the reaction condition used. Quenching studies with isoprene suggest that the photodimerization of T-T occurs predominantly in an excited triplet state, whereas that of polyMAOT and polyAOT occur in singlet and triplet states. It was concluded that the photodimers of T-T, polyMAOT, and polyAOT are two syn-fused cyclobutane-type dimers (cis-syn and trans-syn). Quantum efficiencies of thymine base disappearance were determined by ultraviolet (UV) analysis to be 0.0012 for T-T, 0.0084 for polyMAOT, and 0.010 for polyAOT.     

The allyloxycarbonyl group for alcohol protection: quantitative removal or transformation into allyl protecting group via π-allyl complexes of palladium

In the presence of Pd catalysts and under mild, essentially nonbasic conditions, the allyloxycarbonyl derivatives of alcohols may be either converted into the corresponding allyl ethers or hydrogenolysed (Bu₃SnH) back to the starting alcohol.     

H-bonds of imidazole crystals. II. Determination of the magnitudes of the various anharmonic couplings of vs modes

In this article results given in a previous paper (part I), concerning the spectra of NH and ND species recorded with a polarization parallel to the c axis are analyzed, the necessary corrections on the raw data performed, v_s bands and their first moments are then compared with corresponding quantities predicted from a simple theory which describes quantitatively the anharmonic interactions of a single H-bond with a low frequency vibration of the same H-bond and with binary combinations of modes (Fermi resonances). This allows us to determine the magnitudes of the various anharmonic interactions involved. It appears that the low frequency vibration which modulates v_s is a bending mode of the H-bond (NH ↑ … N), a finding somewhat unexpected, as this low frequency vibration is usually thought to be the stretching vibration v_σ of the H-bond

     

The carbocyclic analog of cytidine,synthesis and antineoplastic activity

The carbocyclic analog (VI) of cytidine was prepared from the carbocyclic analog (I) of uridine. The intermediate stages were a tetrabenzoyl derivative of I, the tribenzoyl derivative of the uridine analog, and the tribenzoyl 4-chloropyrimidinone obtained from the latter derivative. The cytidine analog (VI) is active against KB cells in culture and against L1210 leukemia in mice. In the initial tests against L1210 leukemia, the highest dose (200 mg./kg./day, q.d. 1-9), of three active doses, increased lifespan by 82% and showed no evidence of toxicity.     

Dual-basis orthonormality-constrained variation method

The method of orthonormality-constrained variation is extended using a dual-basis set instead of a single orthonormal basis. The complete and the partial variation methods are discussed and applied to electronic systems. It is found that the present formulation leads to the most general equation in the coupling operator method.