Showing papers by "ETH Zurich published in 1972"
TL;DR: In this article, it is shown how the analytical relations can be satisfied in a stabilized manner in order to improve the numerical accuracy of the solution of the differential equations, which leads to a modified differential system which is often stable in the sense of Ljapunov.
1,429 citations
Journal Article•
314 citations
TL;DR: In this article, the problem of designing a stable recursive digital filter to have an arbitrarily prescribed frequency response may be considered as an approximation problem using the minimum p -error criterion, which is successfully solved using the Fletcher-Powell algorithm.
Abstract: The problem of designing a stable recursive digital filter to have an arbitrarily prescribed frequency response may be considered as an approximation problem. Using the minimum p - error criterion, a new problem of minimizing a function of n variables results, which is successfully solved using the Fletcher-Powell algorithm. An important theorem guaranteeing the existence of a stable optimum for a large class of synthesis problems is stated, and necessary modifications to the Fletcher-Powell algorithm to assure stability are considered. Finally a number of results of the application of this method are given.
265 citations
TL;DR: A comprehensive review of the subject of deviations from Matthiessens's Rule can be found in this article, including a historical survey and detailed critical evaluations of both theory and experimental data.
Abstract: We present a comprehensive review of the subject of Deviations from Matthiessens's Rule, including a historical survey and detailed critical evaluations of both theory and experimental data. We discuss deviations occurring: in substitutional alloys (both magnetic and non-magnetic); after quenching; after radiation damage; after plastic deformation; and in thin samples. The only topic omitted is that of anomalous negative deviations occurring at low temperatures (e.g. the Kondo effect).
246 citations
TL;DR: In this paper, the authors present numerical methods for the determination of the ultimate load of two-and three-dimensional structures assuming an ideal rigid-plastic behavior of the material.
226 citations
TL;DR: The most probable values of bond-lengths and bond-angles were assigned to the polymer models which also have ribose rings in the standard C3- endo conformation, whereas A-RNA is an eleven-fold helix whereas the A′-RNA helix is twelve-fold.
223 citations
TL;DR: In this article, from anisotropic response of the unit-cell dimensions, suggestions are made on the cation distribution on the (4f)- and (6h)-lattice sites.
170 citations
TL;DR: The carbohydrate composition of Saccharomyces cerevisiae cultivated aerobically in the chemostat at different growth rates was investigated and the specific activities of enzymes of the reserve carbohydrate pathways were compared.
Abstract: 1.
The carbohydrate composition of Saccharomyces cerevisiae cultivated aerobically in the chemostat at different growth rates was investigated. It was compared with the specific activities of enzymes of the reserve carbohydrate pathways. Under glucose limitation the synthesis of reserve carbohydrates increases strongly with increasing limitation of substrate supply, i.e., decreasing growth rate. Fermenting cells accumulate only glycogen, whereas more slowly growing organism with a purely oxidative metabolism contain trehalose and high amounts of glycogen.
2.
During the budding process the purely respirative cells degrade part of their reserves. In the presence of excess substrate the reserve carbohydrate content is low and remains unchanged during the cell cycle.
3.
The percentage of structural carbohydrates in the cells shows little changes during the budding cycle, being scarcely influence by the growth rate.
4.
At a growth rate of 0.077 h-1 the cells cultivated under glucose limitation contain even a higher amount of reserves than those grown under nitrogen limitation.
5.
The course of the specific activities of UDP-glucose pyrophosphorylase and glycogen phosphorylase as a function of the growth rate follows that of the reserve carbohydrates.
97 citations
TL;DR: In an investigation of the role of glucanases in modifying yeast cell walls at the location of new buds, vesicles derived from the endoplasmic reticulum, which are secreted locally into the cell wall of growing buds, and may be involved in the secretion of glucans, have been isolated.
Abstract: In an investigation of the role of glucanases in modifying yeast cell walls at the location of new buds, vesicles derived from the endoplasmic reticulum, which are secreted locally into the cell wall of growing buds, and may be involved in the secretion of glucanases, have been isolated.
86 citations
83 citations
TL;DR: In this article, a stabilization of the classical equations of two-body motion is offered, characterized by the use of the regularizing independent variable (eccentric anomaly) and by the addition of a control-term to the differential equations.
Abstract: A stabilization of the classical equations of two-body motion is offered. It is characterized by the use of the regularizing independent variable (eccentric anomaly) and by the addition of a control-term to the differential equations. This method is related to the KS-theory (Stiefel, 1970) which performed for the first time a stabilization of the Kepler motion. But in contrast to the KS-theory our method does not transform the coordinates of the particle. As far as the theory of stability and the numerical experiments are concerned we restrict ourselves to thepure Kepler motion. But, of course, the stabilizing devices will also improve the accuracy of the computation of perturbed orbits. We list, therefore, also the equations of the perturbed motion.
TL;DR: It is observed that synthetic peptides with the C-terminal amino-acid sequences 17–39 proposed for porcine1 (I) and human2 adrenocorticotrophic hormone (ACTH) (III) do not undergo deamidation in conditions where the natural hormones are completely deamidated, and this has prompted us to re-examine the amino- acid sequences of the two hormones.
Abstract: WE have observed that synthetic peptides with the C-terminal amino-acid sequences 17–39 proposed for porcine1 (I) and human2 adrenocorticotrophic hormone (ACTH) (III) do not undergo deamidation in conditions where the natural hormones are completely deamidated, and this has prompted us to re-examine the amino-acid sequences of the two hormones.
TL;DR: On the basis of the X-ray data for the reduced and the oxidized protein and the principal values of the electronic g-tensor, which had previously been measured by EPR in a frozen solution, the orientation relative to the heme group of the principal g-Tensor axes in the ferric protein was determined.
TL;DR: In this paper, the authors derived an energy level 1 scheme of the Sm monochalcogenides using a thermochemical process and concluded that the semiconductor- metal transformation is due to a pressure induced Sm 2+ → Sm 3+ transition and is intrinsic in nature.
TL;DR: In this article, the performance of a liquid-membrane electrode using a synthetic, neutral carrier in tris-(2-ethylhexyl)-phosphate as membrane component in a PVC matrix is described.
Abstract: The performance of a liquid-membrane electrode using a synthetic, neutral carrier in tris-(2-ethyl-hexyl)-phosphate as membrane component in a PVC matrix is described. Selectivities, working range and lifetime are discussed. The electrode makes possible the measurement of lithium ion activities in the range 1M to 10−5M. The selectivities of lithium over sodium, potassium, magnesium and calcium are 20, 140, 6,000, and 1,900 respectively.
TL;DR: It appears, however, that too little knowledge has as yet been accumulated on the correlations between non-bonded structural features and the 13C-NMR parameters for the method to be readily applicable to conformational studies in biopolymers.
TL;DR: The spin polarization of photoelectrons from (100) surfaces of pure and doped EuO monocrystals reveal a paramagnetic surface sheet existing at temperatures far below the Curie temperature of the bulk as mentioned in this paper.
Abstract: Measurements of the spin polarization of photoelectrons from (100) surfaces of "pure" and doped EuO monocrystals reveal a paramagnetic surface sheet existing at temperatures far below the Curie temperature of the bulk. The extra electrons that are introduced on doping produce an increase of the molecular field in the surface. ${\mathrm{Eu}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}\mathrm{O}$ crystals exhibit the highest degree of spin polarization (\ensuremath{\sim} 80%) observed in a photoemission experiment so far.
TL;DR: This communication describes the synthesis of a new derivative of c-AMP (“Sepharose-bound c-amp”) designed for use in affinity chromatography, and describes the isolation of proteins and of regulatory subunits from solutions containing inactive phosphokinases.
TL;DR: It is indicated by the observation that with groups of identically treated males the rate of recoverable sex-chromosome loss depended on the type of female used, and the mode of action of the maternal factors could not yet be determined.
Abstract: After X-irradiation of mature sperm of Drosophila melanogaster males carrying a genetically marked ring-X- and a genetically marked Y-chromosome, a high rate of sex-chromosome loss was observed. It is estimated that about three quarters of the losses resulted from damage induced in ring-X-chromosomes. The processes leading to chromosome loss were modified by maternal influences. This is indicated by the observation that with groups of identically treated males the rate of recoverable sex-chromosome loss depended on the type of female used. Owing to uncertainties with respect to the mechanism of radiation-induced chromosome loss, the mode of action of the maternal factors could not yet be determined.
TL;DR: In this paper, the authors unterstellt die Theorie von Linderberg & Michl, wonach bei Disulfiden with φ = ±90°, infolge der Entartung der Elektronenubergange niederer Energie und der irreduziblen Darstellung A bzw.
Abstract: Konformation und Konfiguration von cyclo-L-Cystin wurden mit spektroskopischen Methoden untersucht. Nach 1H- und 13C-NMR. besitzt die Molekel einen wannenformigen Diketopiperazin-Ring (CαH—NH-Diederwinkel ⋍ 40°) und eine chirale Ausbildung der Disulfidbrucke. In Molekelmodellen mit diesen Spezifikationen betragt der C-S-S-C-Diederwinkel φ ⋍ 90°. Im CD. war aber kein langwelliger Cotton-Effekt zu beobachten, welcher auf eine inharente optische Aktivitat des asymmetrischen Disulfid-Chromophors hinwiese. Dieses Verhalten stutzt die Theorie von Linderberg & Michl [3 b], wonach bei Disulfiden mit φ = ±90°, infolge der Entartung der beiden Elektronenubergange niederer Energie und der irreduziblen Darstellung A bzw. B, die sonst getrennten Absorptionsbanden bei 250 nm zusammenfallen und ihre entgegengesetzten Rotationasstarken sich aufheben.
Den starken, negativen Cotton-Effekt bei 228 nm (CD., in Athanol) ordnen wir dem n,π*Ubergang der Peptid-Carbonylgruppe zu. Vorzeichen und Rotationsstarke (R = −45,4×10−40 erg · cm3) dieser Bande deuten wir als starke Indizien fur das Vorliegen des cyclo-L-Cystins als P-helikales Diastereomeres.
01 Jan 1972
TL;DR: Answers to the following questions were expected from fine structure analyses of imaginal disks: how many cell layers and cell types constitute a disk?
Abstract: Answers to the following questions were expected from fine structure analyses of imaginal disks:
1)
How are disks organized at the cellular level? Specifically, how many cell layers and cell types constitute a disk?
2)
Is the determined state, for whose exploration imaginal disks appear so suited, expressed morphologically? Are the cells of a wing disk, e.g., distinguishable from those of an eye disk at the fine structural level? Or are cells of known lineage within a disk distinguishable from their neighbors? And finally, is transdetermination expressed at the morphological level?
3)
How do the cells of imaginal disks, derivatives of the larval hypodermis, respond to the humoral control that is known to govern the larval molts?
4)
How do the internally located disks form the exterior adult appendages during morphogenesis?
5)
Is there a morphological parallel to the cell-cell communication that might convey positional information when the adult pattern of surface specializations is laid down?
6)
Does selective cell death occur during disk morphogenesis?
TL;DR: In this article, a theoretical method of predicting the pressure drop and hold up in stratified and wavy two-phase flow is presented, based on the flow model of Lockhart and Martinelli.
TL;DR: Adult acquired lactase deficiency is accompanied by the lack of small‐intestinal phlorizin‐hydrolase activity, an enzyme which had not been previously investigated in man, and observations point to related biological regulation mechanism(s) for the two enzymes.
Abstract: Adult acquired lactase deficiency is accompanied by the lack of small-intestinal phlorizin-hydrolase activity, an enzyme which had not been previously investigated in man. The two activities correlate closely in the human biopsy specimens examined. These observations, together with others previously made on the rat lactase-phlorizin-hydrolase complex, point to related biological regulation mechanism(s) for the two enzymes (or active sites).
Phlorizin-hydrolase activity in the human small intestine is due to more than one catalytic site. Lactase itself is responsible for only one quarter of the total phlorizin-hydrolase activity.
TL;DR: In this paper, several methods for the extraction of lipids from Candida yeast grown on n-alkanes were compared and evaluated and special attention was paid to the completeness of extraction and to protect the unsaturated fractions from oxydation.
Abstract: 1.
Several methods for the extraction of lipids from Candida yeast grown on n-alkanes were compared and evaluated. Special attention was paid to the completeness of extraction and to protect the unsaturated fractions from oxydation.
2.
Significant alteration of the fatty acid composition during batch growth on hexadecane was observed. These changes make it necessary to harvest cells in a well defined state of the growing cell population.
3.
If alkanes of chain length from C12 to C17 served as sole source of carbon fatty acids with corresponding chain length predominated. Even numbered alkane chains led to fatty acid profiles containing about 95% even numbered acids. Using odd numbered alkanes as substrates, the cells contained about 50% odd numbered fatty acids.
4.
Cells grown on glucose and acetate media were also examined. Inhibition of de novo synthesis of fatty acids is stronger when the chain length of alkane substrates increases.
TL;DR: The observation by nuclear magnetic resonance (NMR) spectroscopy of high spin iron (II)(Fe2+,S=2) in chemically modified horse cytochrome c (CM-Cyt c), where the methionyl residues had been carboxymethylated with 2-bromoacetate in the presence of KCN is reported.
TL;DR: Differential ground state capture cross sections have been measured at 0° and Tp = 600 MeV for the reactions d (p, π + ) t, 3 He (p, π+ ) 4 He and 4 He ( p, ρ + ) 5 He as discussed by the authors.
TL;DR: In this paper, the influence of mass transport on electrocrystallization is discussed in terms of the influence on the surface properties of the materials at the limiting diffusion current, and it is shown that it is possible to prevent this phenomenon by adding a suitable levelling agent to the solution.