Search Results - (Author, Cooperation:G. Valentin)

2013-09-27

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Cell Movement/*physiology ; Chemokine CXCL12/genetics/metabolism ; Chemotactic Factors/genetics/*metabolism ; Embryo, Nonmammalian ; Gene Expression Regulation, Developmental ; Receptors, CXCR/genetics/metabolism ; Zebrafish/genetics/*physiology ; Zebrafish Proteins/genetics/metabolism

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] SIR—Gene sequences encoded in the organellar genomes of many organisms are incompatible with function of the gene product. The 'errors' in the sequence are corrected after transcription of the gene by processes described by the term 'RNA editing'1. The persistence throughout evolution of ...

Electronic Resource

1617-4623

Group II intron ; Plant mitochondria ; Regulation of splicing ; RNA editing

Springer Online Journal Archives 1860-2000

Biology

Abstract The trans-splicing group II intron c/d in the Oenothera mitochondrial nad1 gene is modified by RNA editing in domain 6. This C-to-U conversion generates the typical domain 6 structure, which prompted us to speculate that this RNA editing event might be essential for splicing. To test this hypothesis, we investigated the influence of unedited and edited sequences of the Oenothera intron on splicing in vitro. The stem of domain 6 of intron nad1-c/d was transplanted into the autocatalytic yeast intron aI5c, yielding chimeras with the genomic C and the edited U, respectively, 5′ of the branchpoint A. When incubated under self-splicing conditions, only the edited chimera was released as a lariat, while the precursor with the genomically coded C remained inactive. Our results support the hypothesis that Oenothera group II intron nadl-c/d cannot be spliced from the primary transcript without previous editing in domain 6.

Electronic Resource

article

1996

Empirische Untersuchung ; Einstellung (Psy) ; Sozialisation ; Jugend ; Politik ; Wertorientierung ; Russland

Sociologiceskie issledovanija, (1996) H. 9, S. 95-100, 0132-1625

Russian

Literaturangaben 3, Tabellen 3

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

An instrumental system is described that combines an apparatus for pulsed laser deposition (PLD) with a vacuum "suitcase" for transport of air-sensitive compounds. Laser ablation, plume diagnostics, and thin-film deposition are readily accomplished through a flexible design. The PLD apparatus consists of two cubes coupled via a bellows assembly and whose distance is easily changed pneumatically. For both the PLD apparatus and the vacuum suitcase, compact-design considerations have been implemented. Consequently, the footprint of the PLD apparatus is relatively small, and the vacuum suitcase can be transported easily between sites. © 1999 American Institute of Physics.

Electronic Resource

1365-2958

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

We previously described the structures and functions of specific complexes between the bla promoter from Tn3(present in pBR322) and RNA polymerase (RNAP), showing that, at excess RNAP, complexes can form in which one or two RNAPs bind to the same promoter (1:1 and 2:1 complexes) (Duval-Valentin and Ehrlich, 1988). We report here that the 2:1 complex cannot be detected below 25° C; above that temperature, a 1:1 complex forms at a rate one order of magnitude faster than that of the 2:1 complex, and above 30° C, the amounts of both species become equal for RNAP/promoter ratio r30≤r≤70. The 2:1 complex decays back to a 1:1 complex losing the last RNAP at a rate about three times that of the 1:1 complex decay. Functional assays of the complexes formed at excess RNAP show that both 1:1 and 2:1 complexes are immediately and permanently inhibited, even when the promoters are pre-incubated with ribonucleotide selections potentially enabling entrance into abortive cycling or formation of a stressed complex. We conclude that the inhibition step probably takes place in the complex formation pathway between RPi and RPo, at a novel stable intermediate isomer, RPj, formed above 25° C. A possible mechanism of formation of the 2:1 complex is outlined. In vivo studies, in which r was modified by varying the bacterial growth rate, show a reduction of bla expression as r values are upshifted, specific to the bla promoter from Tn3.

Electronic Resource

0013-4686

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Physics

Electronic Resource

0013-4686

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Physics

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract A model of charge transport in fluidized bed electrodes, based on the model of Newman and Tobias, is proposed. It explains the dynamic behaviour of these particulate electrodes in terms of a.c. impedance thanks to a description based on a transmission line. In the case of gold beads in 1 M NaOH solutio, the impedance related to the mean contact between the particles, the interfacial impedance of the particle-solution and the solution resistivity can be obtained.

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract Impedance techniques are used to investigate the average dynamic behaviour of a fluidized bed of gold-coated beads in potassium ferri-ferrocyanide/NaOH solution. A transmission line is used as a model. The main features of the fluidized bed are correctly interpreted, especially the capacitive high frequency impedance related to the intermittent contacts between the particles. The use of a nonuniform transmission line is attempted in order to study the influence of a distance dependent charge transfer mechanism in the bulk of the fluidized bed.

Electronic Resource

1572-8838

ammonia ; cyclic voltammetry ; electrodeposition ; gas–liquid equilibria ; speciation diagrams ; zinc–nickel alloys

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract This paper describes the use of ammonia-containing baths for Zn–Ni alloy electrodeposition. Buffering properties of the ammonia/ammonium couple limit the local change in pH in the vicinity of the electrode surface caused by simultaneous hydrogen evolution. In addition, it is shown that the divalent zinc and nickel species exist in the form of Zn(NH3) 4 2+ and Ni(NH3) 6 2+ complexes over a large pH range. The electrochemistry of the deposition at pH 10 was investigated by galvanostatic experiments and cyclic voltammetry, and compared with deposition from ammonium chloride baths at pH 5. The Ni content in the alloys were found to be 40–60% higher from the ammonia-containing bath than from the acidic baths. Reduction of divalent ions and hydrogen evolution were shown to occur at potentials 250 mV more cathodic than with baths at pH 5; the deposition mechanism may be affected by complexation of the metal cations by ammonia.

Electronic Resource

1572-8927

Osmotic coefficient ; freezing point method ; ion association ; tris-propylenediaminocobalt(III) chloride, bromide and nitrate ; tris-trimethylenediaminocobalt(III) chloride and bromide

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract The osmotic coefficients of dilute aqueous solutions of [Co(pn)3]X3 [pn=1,2-diaminopropane and X=Cl−, Br− and (NO3)−] and [Co(tn)3]X3 (tn=1,3-diaminopropane and X=Cl− and Br−) have been measured from 0.00 to 0.02 mol-kg−1 at 0°C by the freezing point method. The results have been compared with those obtained from the numerical integration of the Poisson-Boltzmann equation.

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1572-932X

Primary: 54B15, 54C10, 54E50, 54F45 ; Secondary: 54C60, 54C65 ; Countable-dimensional space ; open mapping ; perfect mapping ; set-valued mapping ; selection ; t(U)-approximate section

Springer Online Journal Archives 1860-2000

Mathematics

Abstract Every open continuous mappingf from a metric space (X, d) onto a countable-dimensional metric spaceY admits a special type of factorization (Y×[0, 1] throughout), provided all fibers off are dense in itself and complete with respect tod. On this basis, an upper semi-continuous Cantor bouquet of disjoint usco selections for a class of 1.s.c. mappings between metrizable spaces is constructed.

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1572-932X

set-valued mapping ; continuous ; d-continuous ; proximal-continuous ; strongly lower semi-factorizable ; selection ; P λ-embedding ; relative covering dimension

Springer Online Journal Archives 1860-2000

Mathematics

Abstract The paper is devoted to selection theorems for ‘continuous’ set-valued mappings which are not necessarily convex-valued on finite-dimensional subsets of the domain. As a result, we get natural generalizations of the famous Kuratowski–Dugundji extension theorem. The technique, developed in the paper, applies to l.s.c. mappings with paracompact, or similar, domain as well. Also, it leads us to a new construction of set-valued continuous selections that involves dimension-type arguments.

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract The present paper deals with a theoretical investigation of a potential step at a channel electrode. The study consists in the numerical solution of the partial differential equations relevant to the transient mass balance in the vicinity of the electrode, taking into account the convective term. Although such an equation has been investigated previously for both heat and mass transfer, we present the results obtained with the help of two packages relying upon either the numerical method of lines (DSS/2) or a derived Gear technique (LSODA). Results of the simulation — concentration profile and wall concentration gradient — are reported and a comparison with previous results is carried out. Both packages used yield very similar current variations which are observed to be in a good agreement with experimental data.

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract This paper deals with the experimental determination of the mass transfer rates between the liquid of an agitated vessel and a spherical particle immersed in a reactor. The spatial distribution of the mass transfer coefficients is obtained using an electrochemical method and the influence of the most pertinent hydrodynamic parameters (impeller speed and fluid residence time inside the vessel) is deduced from experimental results. The study considers the two limiting cases of mechanical agitation alone and agitation induced by the liquid jets generated by the feed nozzles. It is shown that knowledge of the specific power dissipated per unit mass of fluid can be useful for the theoretical prediction of the mass transfer rates.

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract The electrochemical reduction ofN-nitroso-2-methylindoline toN-amino-2-methylindoline is studied experimentally using a batch stirred-tank electrochemical reactor. The influence of important parameters such as temperature, specific electrode area, hydrodynamics of the electrolyte, and initial reactant concentration are examined to quantify their effect on the overall process selectivity. It is shown that the product yield is very sensitive to these parameters due to the complex chemical reaction sequence coupled with the desired heterogeneous electrochemical reaction.

Electronic Resource

1572-932X

Primary: 54C60, 54C65, 54D05 ; secondary: 54F45, 54C20, 54D35 ; Set-valued mapping ; selection ; lower semi-continuous (l.s.c.) mapping ; quasi-lower semi-continuous (q.l.s.c.) mapping ; equi-LC n ,C n

Springer Online Journal Archives 1860-2000

Mathematics

Abstract Every quasi-lower semi-continuous (q.l.s.c.) mapping admits a lower semi-continuous (l.s.c.) selection preserving all important (from the selection point of view) properties of the former mapping. Special-type extensions of l.s.c. mappings are established on this base.

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract Electrochemical processes involving gas production are of great technical importance but the mechanisms involved in the growth of electrogenerated bubbles and transport processes involving gas near an electrode still remain obscure. This paper describes an original technique, based on the inhibition of the fluorescence of an appropriate substance by dissolved oxygen, for the measurement of the local concentration of dissolved oxygen near an electrode. The possibilities offered by this technique and typical results are presented and discussed.

Electronic Resource

1572-8838

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electrical Engineering, Measurement and Control Technology

Abstract This paper presents a mathematical model of a batch stirred-tank electrochemical reactor where a required cathodic reduction reaction is coupled with a complex reaction sequence between the reactant and the key product. The set of coupled, non-linear differential equations is solved numerically and simple dimensionless quantities characterizing the cell performance and selectivity are derived. The experimental results presented in Part I of this paper are found to be in excellent agreement with the model. In the particular case where the homogeneous chemical reactions may be neglected in the cathodic diffusion boundary layer, a simplified analytical expression of the process selectivity is proposed. This quantifies the effects of the operating conditions by means of a single dimensionless criterion.

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