Submikrobestimmung von Alkoxylgruppen mit Hilfe einer Mikrowaage

Ohne Zusammenfassung     

Die Konservierungsmittel Benzoes?ure (I), Dehydroessigs?ure (II), Salicyls?ure (III), Sorbins?ure (IV), Methyl- und Propyl-p-hydroxybenzoes?ureester (V bzw. VI)

Ohne Zusammenfassung     

Chemical synthesis of a pentaribonucleoside tetraphosphate constituting the 3'-acceptor stem sequence of E. coli tRNAIle using 2'-O-(3-methoxy-1,5-dicarbomethoxypentan-3-yl)-ribonucleoside building blocks. Application of a new achiral and acid-labile 2'-hydroxyl protecting group in tRNA synthesis

A synthesis of a pentaribonucleotide fragment constituting the residues 59-63 of 3'-terminus of E. coli tRNAIle, 5'-ApGpUpCpC-3', has been carried out using a new, easily accessible and achiral 2'-ketal protecting group. The new 2'-ketal group has an additional advantage in that it is easily functionalized to the diamide with aqueous ammonia in the penultimate step of deblocking of fully protected oligoribonucleotides. Such a functionalization of the 2'-ketal group at the penultimate step of deblocking of the fully protected tRNA molecule enhances its relative rate of removal under an acidic condition with a minimum of damage of the target tRNA molecule.     

Radiation transfer in an anisotropically scattering plane-parallel medium with space-dependent albedo ω(x)

A method of analysis is presented for solving radiation-transfer problems involving space-dependent albedo ω(x) for an absorbing, emitting and anisotropically scattering plane-parallel medium with reflecting boundaries. The albedo is represented in terms of Legendre polynomials in the form ω(x) = Σ^R_r=0D_rP_r(x/L), where x is the optical variable, L is the half optical-thickness of the slab, P_r(x/L) are the Legendre polynomials and D_r are known expansion coefficients. The effects of spatial variation of albedo on the reflectivity and transmissivity of a medium having a slab geometry are examined for the cases of both forward and backward anisotropic scattering over a wide range of system variables. The effects of ω(x) on the angular distribution of radiation are also shown for some representative cases.     

über die Darstellung von kondensierten Azolo-[1,2,4]-triazinen aus heterocyclischen Diazoverbindungen

Diazotized 3-amino-1,2,4-triazole reacted with 1,3-cyclohexanedione or its 5,5-dimethyl derivative to give the tricyclic 1,2,4-triazine derivatives1 a and1 b. With 1,3-indanedione the tetracyclic compound8 was obtained. Compound1 a or the diacetyl derivative4 a are transformed in an acid catalyzed reaction into the fully aromatic system6 a with simultaneous rearrangement. Chemical reductions of systems1, 10 and12 have been investigated and the compounds9, 11 and13 were isolated and identified. Diazotized 2-aminothiazole readily formed the coupling products with reactive methylene compounds, but only14 could be prepared pure by cyclodehydration.     

Integrals involving an exponential integral function and exponentials arising in the solution of radiation transfer

The solution of the equation of radiative transfer for a participating medium generally results in the evaluation of integrals involving a product of an exponential integral function or an exponential with a polynomial. Although expressions are available in the literature for the evaluation of such integrals, which appear to be structurally easy and simple to program, they are found to be not so accurate for certain parameters involved. To overcome such difficulties, alternative, computationally more accurate, analytic expressions are presented, and numerical techniques for their evaluation are discussed.     

Bleidner vapour phase extraction technique for the determination of organochlorine compounds in lake sediments

Summary The vapour phase extraction technique according to Bleidner has been applied to the trace analysis of organochlorine pesticides and PCB in water sediments. This method eliminates time consuming drying, extracting, and clean-up steps in comparison with the conventional (Soxhlet) methods. The method developed is sufficiently sensitive and shows satisfying recovery results — with the exception of -HCH. Low yields of the DDT family are not caused by artifacts but are rather due to irreversible adsorption to sediment and fast metabolizing power of this substrate.Dedicated to Prof. Dr. E. Lahmann, Institut für Wasser-, Boden-, und Lufthygiene, D-1000 Berlin 33, on the occasion of his 65th birthday