Showing papers by "ETH Zurich published in 1978"
TL;DR: In this article, the shape selective catalysts with unique channel structures have been determined using model building, single crystal and powder X-ray data, and they have been shown to possess unusual catalytic properties and high thermal stability.
Abstract: ZEOLITE ZSM-5 (ref. 1) is a member of a new class of shape selective catalysts with unique channel structures which differ from the familiar large-pore faujasite and small-pore zeolites such as Linde Type A and erionite. They also possess unusual catalytic properties and have high thermal stability. We have determined their structure using model building, single crystal and powder X-ray data.
870 citations
TL;DR: In this paper, a quality test procedure for glass capillary columns is described that offers the following information: adsorption of hydroxyl function, adaption of aldehyde function, separation efficiency, acid-base behaviour and film thickness.
316 citations
TL;DR: In this paper, the surface-atom $4f$ level is shifted 0.40 eV to lower binding energy relative to the bulk value, and the surface density of states is narrowed by (7.6 \ifmmode\pm\else\textpm\fi{} 1.1)%.
Abstract: X-ray photoemission spectra of $4f$ and valence electrons in surface atoms of gold have been obtained. The surface-atom $4f$ level is shifted 0.40\ifmmode\pm\else\textpm\fi{}0.01 eV to lower binding energy relative to the bulk value. The surface density of states is narrowed by (7.6 \ifmmode\pm\else\textpm\fi{} 1.1)% and its center of gravity is shifted to lower binding energy by 0.51\ifmmode\pm\else\textpm\fi{}0.08 eV. A model is proposed to account for the core-level shift in terms of the modified surface density of states.
313 citations
TL;DR: In this paper, an injector without a septum is proposed for on-column injection of capillary columns, and some examples of applications are given. But the injector is not suitable for injection of volatile substances.
239 citations
TL;DR: In this article, the shape selective catalysts (ZSM-5 and ZSM-11) have been synthesized and the configuration of linked tetrahedra consisting of eight five-membered rings.
Abstract: ZSM-5 (refs 1, 2) is a member of a new class of shape selective catalysts which have unique channel structures with 10-membered ring openings. These catalysts have unusual properties. They can selectively convert methanol to high quality gasoline3–6 and are used in commercially significant processes, such as distillate dewaxing, ethylbenzene synthesis, xylene isomerisation and toluene disproportionation5,7 The framework of ZSM-5 (ref. 2) contains a novel configuration of linked tetrahedra consisting of eight five-membered rings. These configurational units may be linked through edges to form chains and the chains to form a three-dimensional framework which describes an intersecting channel system with openings intermediate between those in zeolite Linde type A and faujasite. We report here the synthesis and structure of another member of this family, ZSM-11.
234 citations
TL;DR: Correlations between parameters indicate that the adult height depends neither on theduration of growth, nor on the duration and height of the peak, and partial correlations given adult height reveal two compensating mechanisms between growth in the prepubertal and in the pubertal period.
Abstract: Height growth velocity curves between 4.5 and 17.75 years were estimated, using smoothing spline functions, for 112 boys and 110 girls from the Zurich Longitudinal Study (1955--1976). Parameters characterizing the growth process, such as peak height velocity and age at peak height velocity, were calculated directly from the estimated curves. The variability of parameters describing the adolescent growth spurt is large, both between and within sexes. Peak height, defined as increase of height velocity during the growth spurt, and age at peak height velocity both characterize the sex difference in growth in a highly significant manner. Peak height of at least 4 cm/year is found in 70% of the boys, but in only 11% of the girls. The age at peak height velocity averages 12.2 years in girls and 13.9 years in boys and has a wide range of 5.7 years and 3.8 years respectively. The sex difference in adult height of 12.6 cm is composed of the following 4 factors: +1.6 cm caused by more prepubertal growth in boys, +6.4 cm by the boys' delay in spurt, +6.0 cm by the more extensive spurt in boys and -1.4 cm by more post-spurt growth in girls. Correlations between parameters indicate that the adult height depends neither on the duration of growth, nor on the duration and height of the peak. Minimal pre-spurt height velocity and peak height velocity, but not peak height, are age- and height-dependent. Partial correlations given adult height reveal two compensating mechanisms between growth in the prepubertal and in the pubertal period. Small prepubertal height and low height velocity with respect to adult height are followed by a late adolescent spurt and vice versa. Small height at the onset of the spurt with respect to adult height is followed by a longer lasting, but not higher spurt and vice versa.
214 citations
TL;DR: In this article, a class of echo phenomena in coherent spectroscopy is described where defocusing and refocusing of coherence takes place at two different transition frequencies, and examples of heteronuclear transfer echoes and of multiple quantum transfer echoes in nuclear magnetic resonance are presented.
205 citations
TL;DR: A method is described that permits simultaneous determination of the net charge transfer associated with Ca2+ transport by the ruthenium-red-sensitive carrier and the ionized internal [Ca2+] in heart mitochondria and indicates that this carrier catalyses a charge-uncompensated flux of Ca2+.
Abstract: A method is described that permits simultaneous determination of the net charge transfer associated with Ca2+ transport by the ruthenium-red-sensitive carrier and the ionized internal [Ca2+] in heart mitochondria. The data indicate that this carrier catalyses a charge-uncompensated flux of Ca2+. Full charge compensation for Ca2+ influx is provided by the respiration-dependent efflux of H+. The net efflux of Ca2+ induced by Na+ is analysed in terms of two other carriers, a Na+-Ca2+ antiporter and a Na+-H+ antiporter. Evidence is presented that these two carriers are separate and that the Na+-H+ exchange is the more rapid. The fluxes of Ca2+, Na+ and H+ during the Na+-induced efflux of Ca2+ support a series of events in which the Na+-H+ exchange enables unidirectional Ca2+ fluxes via the uniport and antiport systems to be integrated into a cycle.
175 citations
TL;DR: In this article, two families of layer-structure halide perovskites with unbranched organic chains are considered: (C n H 2 n + 1 NH 3 ) 2 MX 4 and NH 3 ( CH 2 ) m NH 3 MX 4 with M = Cd, Cu, Fe, Mn or Pd, X = Br or Cl, n = 1, 2,..., 18, and m = 2, 3,..., 8.
162 citations
TL;DR: In this article, the chemistry of 33 basaltic rocks dredged from the West Mariana basin and from the Mariana trench during the R/V “Dmitry Mendeleev” 1976 cruise in the western Pacific is described.
160 citations
TL;DR: It is concluded that in Saccharomyces cerevisiae most if not all of the PP is located in the vacuoles, at least under the growth conditions used.
Abstract: Virtually all of the polyphosphate (PP) present in yeast protoplasts can be recovered in a crude particulate fraction if polybase-induced lysis is used for disrupting the protoplasts. This fraction contains most of the vacuoles, mitochondria and nuclei. Upon the purification of vacuoles the PP is enriched to the same extent as are the vacuolar markers. The amount of PP per vacuole is comparable to the amount of PP per protoplast. The possibility that PP is located in the cell wall is also considered. In the course of the incubation necessary for preparing protoplasts, 20% of the cellular PP is broken down. As this loss of PP occurs to the same extent in the absence of cell wall degrading enzymes, it is inferred that internal PP is metabolically degraded, no PP being located in the cell walls. It is concluded that in Saccharomyces cerevisiae most if not all of the PP is located in the vacuoles, at least under the growth conditions used.
TL;DR: In this article, the utility of multiple quantum transitions with regard to the elucidation of relaxation mechanisms in coupled spin systems is discussed with respect to the analysis of the information contained in the decay rates of the multiple quantum coherence in terms of the Redfield formalism.
Abstract: The utility of multiple quantum transitions is discussed with regard to the elucidation of relaxation mechanisms in coupled spin systems. The information contained in the decay rates of multiple quantum coherence is analysed in terms of the Redfield formalism, and experimental schemes suitable for their measurement are presented. As an illustration, external paramagnetic relaxation in a two-spin system is investigated, based on measured multiple and single quantum relaxation rates.
TL;DR: From this it will now be possible without chemical modification of the protein, to compare in detail the solution conformations near the heme c in reduced and oxidized cytochrome c and thus hopefully to obtain additional insights into the mechanism of the biological redox reaction of this protein.
TL;DR: In this article, a review of the literature on pulse electrolysis is presented, where the theory of the method is reviewed and three independent parameters of pulse electrolyisation (pulse c.d., pulse length and cut-off time between two pulses) were varied within a wide range in the deposition of Cd (from an acid sulfate bath) and of Au (from a citric acid-cyanide bath with a Co additive).
TL;DR: In this paper, the authors discuss the usefulness of these reactions in the synthesis of carbonyl compounds and compare their usefulness with that of alternative recent methods, such as alkylation, silylation, sulfenylation, and oxygenation.
Abstract: Alkylhalogenidfreie Ether- oder THF-Losungen von Vinyllithiumverbindungen 2 – unterhalb von −110°C auch endstandige – sind durch Umsetzung von Vinylbromiden 1 mit 2 Molaquivv. tert-Butyllithium nach Gleichung (1) leicht zuganglich. Die Grenzen der Methode werden diskutiert. Iodierungen, Silylierungen, Sulfenylierungen und Oxygenierungen zu 4, 5, 6 bzw. 8 werden beschrieben (Tab. 1). Die Bedeutung dieser Reaktionen fur die Herstellung von Carbonylverbindungen wird mit der alternativer Verfahren verglichen. Beispiele fur die stereoselektive Synthese von Allylalkoholen 10, α,β-ungesattigten Carbonylverbindungen 11 und Olefinen 12 durch Carbonyladdition und Acylierung (Tab. 2) bzw. Alkylierung von 2 werden angegeben. Bei der Methylierung der Cycloalkenyllithiumverbindungen 2j–n mit Methyliodid ist es wichtig, das man THF als Losungsmittel verwendet und uberschussiges Alkylierungsmittel vermeidet, da sonst neben oder statt der gewunschten CC-Verknupfungsprodukte 13 Vinyliodide 4 entstehen (Tabellen 3 und 4).
Br/Li-Exchange in Vinyl Bromides with 2 Molequivalents of tert-Butyllithium. Reactions of Vinyllithium Compounds with Hetero and Carbon Electrophiles
Haloalkane-free solutions of vinyllithium compounds 2 – terminal ones at temperatures below −110°C — in THF or ether are generated from vinyl bromides 1 with two molequivalents of tert-butyllithium [eq. (1)]. The scope and limitations of the method are discussed. Iodinations, silylations, sulfenylations, and oxygenations leading to 4, 5, 6, and 8, respectively, are described (table 1). The usefulness of these reactions in the synthesis of carbonyl compounds is compared with that of alternative recent methods. Examples of the stereoselective preparation of allylic alcohols 10, α,β-unsaturated carbonyl compounds 11 and olefins 12 by addition of 2 to aldehydes and ketones and acylation (table 2) or alkylation are given. In the alkylations of cyclic representatives 2j–n with iodomethane, it was noticed that it is important to work in THF solvent and to avoid excess halide. Otherwise (table 3 and 4) vinyl iodides 4 can be the main products instead of the desired methylated compounds 13.
TL;DR: In this paper, the light damage of Fe doped KNbO3 is interpreted in terms of photoconductivity results, and the spatial frequency dependence of the light-induced index changes indicates, that diffusion processes of charge carriers are important for light damage if the fringe spacing α of the recorded hologram is smaller than 2 μm.
Abstract: Holographic measurements of optically induced refractive index changes (light damage) of Fe doped KNbO3 are interpreted in terms of photoconductivity results. In “undoped” KNbO3 the light damage is one order of magnitude smaller than in LiNbO3-The light induced index changes can be drastically reduced or enhanced by applying a relatively small de-field along the polar ±c axis. The space-charge field due to the “photovoltaic effect” is then increased or decreased by photoconductivity.The spatial frequency dependence of the light-induced index changes indicates, that diffusion processes of charge carriers are important for the light damage in KNbO3 if the fringe spacing α of the recorded hologram is smaller than 2 μm. For α = 0.35 μm this term is two orders of magnitude larger than the “photovoltaic effect” and the photoconductivity term.The dispersion of the absorption-and photoinduced current-density measurements yield basic information on the energy levels of the photorefractive centers controlling the i...
TL;DR: In this article, high resolution nuclear magnetic resonance was used to study the dynamic ensembles which constitute the conformations of globular proteins in solution, and the results showed that high resolution magnetic resonance can provide insight into the dynamics of the globular protein conformations.
TL;DR: In this paper, all available data of the vertical ozone distribution measured with chemical sondes have been assembled and combined with one year's results from the BUV satellite to obtain the best possible information on the VNO distribution averaged over longitude as a function of season (month by month).
Abstract: All available data of the vertical ozone distribution measured with chemical sondes have been assembled and combined with one year's results from the BUV satellite to obtain the best possible information on the vertical ozone distribution averaged over longitude as a function of season (month by month). For the southern hemisphere Umkehr data have been used as a guideline in the necessary smoothing procedure. Especially in the northern hemisphere considerable adaptation to the observed latitudinal mean of the total amount was needed because most sounding stations, are situated in upper air trough positions. The results are presented as vertical distributions, as meridional cross sections of partial pressure and of mixing ratio and as partial pressure isolines as a function of latitude and season at different levels. The interaction between photochemical processes and transport resonsible for the observed distribution is briefly discussed.
TL;DR: In this article, the potentialities and limitations of splitless injection are discussed, and the role of the solvent effect in on-column injection is emphasized, as well as some rules for the experimental realization.
Abstract: Splitless injection is based on the solvent effect as a mechanism condensing large vapour clouds down to infinitely shortened bands. The effect is controlled by the parameters column temperature, volatility and amount of solvent, and rate of injection. By properly selecting the variables the effect can easily be optimized for any combination of sample and column. It is the purpose of this paper to provide the mechanistic understanding as required for this optimization, as well as some rules for the experimental realization. Potentialities and limitations of splitless injection are discussed, and the role of the solvent effect in on-column injection is emphasized.
TL;DR: The use of NMR observations to describe the globular BPTI conformation in terms of a dynamic ensemble of rapidly interconverting molecular structures is reported here.
Abstract: BASIC PANCREATIC TRYPSIN INHIBITOR (BPTI) is a small globular protein of molecular weight 6,500 (refs 1–17). It consists of one polypeptide chain with 58 amino acid residues, including three disulphide bonds and four phenylalanines and four tyrosines as the only aromatics18. The crystal structure at 1.5 A resolution has been extensively refined19. In the 1H- and 13C-NMR (nuclear magnetic resonance) spectra, a large number of resolved resonance lines have been assigned to particular residues in the amino acid sequence6,8,10–16 and related to particular aspects of the molecular conformation1–17. Hence, NMR spectral similarities and differences between BPTI and related proteins can on the basis of these earlier studies be interpreted in terms of structural features in well defined locations of the protein molecule. We report here the use of NMR observations to describe the globular BPTI conformation in terms of a dynamic ensemble of rapidly interconverting molecular structures. BPTI was a suitable compound for this study as its globular form is outstandingly stable in aqueous solution (Table 1)1,9,20, leaving a large experimentally accessible range for studies of modified BPTI species with reduced stability. The chemically modified and homologous proteins used are characterised in the footnotes to Table 1.
TL;DR: Both the presence of sodium and of an electrical potential difference across the membrane have been found to be necessary in order to achieve optimald-glucose-protectable phlorizin binding to brush border membranes from rabbit small intestine.
Abstract: Both the presence of sodium and of an electrical potential difference across the membrane have been found to be necessary in order to achieve optimald-glucose-protectable phlorizin binding to brush border membranes from rabbit small intestine. The effect of
$$\Delta \tilde \mu _{Na} $$
on phlorizin binding shows a close similarity to that ond-glucose transport, confirming that phlorizin is indeed bound to thed-glucose transporting protein. Possible modulations of binding by a transmembrane potential are discussed on the basis of some models.
TL;DR: In this paper, the reactions of SnCl2 with the complexes cis-PtCl2P2, P=trialkyl and triaryl phosphines and phosphites, in CDCl3 and CD2Cl2 have been studied using 31P and 195Pt NMR methods.
Abstract: The reactions of SnCl2 with the complexes cis-PtCl2P2, P=trialkyl and triaryl phosphines and phosphites, in CDCl3 and CD2Cl2 have been studied using 31P and 195Pt NMR. methods. For equimolar amounts of Sn and Pt, products of the type PtCl(SnCl3)P2 are formed with the complex geometry depending on the nature of P. For PPEt3 and P(OPh)3, further addition of SnCl2 produces trans-Pt(SnCl3)2 complexes. The syntheses of trans-PtCl(SnCl3) (PEt3)2 and trans-Pt(SnCl3)2 (OPh3)2 are described.
TL;DR: In this paper, the authors analyzed the x-ray photoemission spectra of the entire lanthanide series and concluded that the $4f$ electron remains strictly localized in all compounds.
Abstract: All the Ce pnictides crys allize in the NaCl structure with lattice constant increasing systematically from CeN to CeBi. Since Ce has the largest $4f$-orbital radius in the entire lanthanide series, it is quite interesting to follow the evolution of his level as the distance between the Ce atoms is varied. The core levels and the valence-band region of CeN, CeP, CeAs, and CeSb have been studied by high-resolution x-ray photoemission spectroscopy. The $4d$ and $3d$ core-level spectra of Ce show clearly that the $4f$ state remains strictly localized in all compounds. In CeN a superposition of lines corresponding to two valences is found which reveals the intermediate valence character of this compound. In the valence-band spectrum, the $4f$ level is found to be pinned at the Fermi level and superimposed on the $5d$ states. The extended valence states originating from the anion $p$ states are located at higher binding energies. In the compounds of heavier rare-earth elements the $4f$ state moves away from the Fermi level and gradually overlaps in energy with $p$ states, so that the probability for interatomic Auger processes in the photoemission final state increases rapidly. The natural width of the $4f$ peak is already 0.8 eV in CeP, and becomes so large in CeAs and CeSb that this line can no longer be unambiguously identified in the other valence-band structure. Finally, it can be concluded from the similarity of the $4d$ spectrum of metallic Ce and CeN that the $4f$ electron remains localized in the $\ensuremath{\alpha}$ phase of this metal.
TL;DR: In this paper, the effect of specific solvation, apparently characteristic of diazonium ions, by various solvents (fluorinated alcohols, methanol, water, dimethyl sulfoxide, pyridine, and hexamethylphosphoric triamide) on the mechanism was investigated.
Abstract: On heating, aromatic diazonium salts eliminate nitrogen by two fundamentally different mechanistic pathways, i.e. heterolysis and homolysis. Among these pathways a series of variants are known, giving rise to a whole variety of mechanisms. This article considers the effect of specific solvation, apparently characteristic of diazonium ions, by various solvents (fluorinated alcohols, methanol, water, dimethyl sulfoxide, pyridine, and hexamethylphosphoric triamide) on the mechanism. Apart from the donor properties of the solvent, the oxidation potential and the presence of additives play a major role in determining what reaction type will predominate.
TL;DR: A partial amino acid sequence of the N-terminal region of the isomaltase subunit includes an extremely hydrophobic sequence, which agrees with and supports the conclusion reached that additional events to be postulated in the biosynthesis and/or the insertion process of SI.
TL;DR: In this article, the authors used a single integral constitutive equation to describe the stress growth after sudden imposition of a constant shear rate flow and stress relaxation after cessation of steady shear flow.
Abstract: Shear creep and constrained elastic recovery experiments on a well characterized low-density polyethylene melt are reported. The temperature dependence of the shear strain and the primary normal stress difference is discussed in detail. Comparison is made with predictions of a strain-dependent single integral constitutive equation, which has already been successfully used for the same polymer melt to describe the stress growth after sudden imposition of a constant shear rate flow and stress relaxation after cessation of steady shear flow. It should be emphasized that this constitutive equation contains no adjustable parameters. The linear-viscoelastic part of the memory function is related to the linear-viscoelastic relaxation spectrum, while the nonlinear, strain-dependent part was determined from rapid-strain experiments. In the case of a prescribed shear stress history the resulting integral equation cannot be solved by closed integration but has to be inverted by numerical methods. Agreement between theoretical predictions and experimental data is rather encouraging for shear strain and primary normal stress difference during creep and retardation tests. Within experimental error, the strain and shear rate dependence of the recoverable portion of the total strain can be correctly predicted.
TL;DR: Measurements of the initial rate of valinomycin-dependent K+ uptake have shown that nearly 4 K+ are taken up as 2 electrons are transferred from cytochrome c to oxygen, proving directly that a charge separation of nearly 4 occurs across the inner mitochondrial membrane each time 2 electron are transferred to oxygen.
Abstract: The operation of cytochrome c oxidase with ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine as substrate in antimycin-A-inhibited rat liver mitochondria is coupled to proton ejection Measurements of the initial rate of valinomycin-dependent K+ uptake have shown that nearly 4 K+ are taken up as 2 electrons are transferred from cytochrome c to oxygen This proves directly that a charge separation of nearly 4 occurs across the inner mitochondrial membrane each time 2 electrons are transferred to oxygen Measurements of the initial rate of proton movement after addition of the reductant show that about 16 protons are released by the mitochondria as 2 electrons are transferred from cytochrome c to oxygen The data support the suggestion of a proton pump coupled to the operation of cytochrome c oxidase [Wikstrom, M F K (1977) Nature (Lond) 266, 271--273]
TL;DR: In this paper, the thermal expansion, magnetization, magnetostriction, and ac electrical resistance of the compound ErRh/sub 4/B/sub4/ have been measured at low temperatures and the qualitative behavior of the upper critical field as a function of temperature has been determined from the experiments.
Abstract: The thermal expansion, magnetization, magnetostriction, and ac electrical resistance of the compound ErRh/sub 4/B/sub 4/ have been measured at low temperatures. The influence of magnetic fields on the superconducting and magnetic properties of this compound is emphasized, and the qualitative behavior of the upper critical field as a function of temperature has been determined from the experiments.
TL;DR: Comparison with the corresponding data on horse heart cytochrome c showed that the locations of high spin density on the heme c periphery as well as the in-plane principal axes x and y of the electronic g-tensor are rotated by approximately 90° in ferricy tochrome c-551 relative to horse ferricies c.
TL;DR: In this paper, a working rule for establishing the optimal chromatographic conditions for handling large sample volumes while ensuring full separation efficiency yet avoiding harm to the column is presented for on-column injection.
Abstract: During one year continuous use of on-column injection, the typical advantages described in our first report have fully been confirmed. In addition the analysis of large sample volumes has proved promising. Only minor modifications have been applied to the on-column injector device. Broad evidence has been gathered showing that full separation efficiency of the capillary columns after on-column injection is attained only when cold trapping or the solvent effect, as band shortening mechanisms, are working- While, under the conditions of on-column injection, cold trapping is less efficient than with other injection techniques, the opposite holds true for the solvent effect. Compared with splitless injection, the danger of excessive solvent condensation on the column is increased. A working rule is presented for establishing the optimal chromatographic conditions for handling large sample volumes while ensuring full separation efficiency yet avoiding harm to the column.