Showing papers by "University of Geneva published in 1985"

Ergodic theory of chaos and strange attractors

Abstract: Physical and numerical experiments show that deterministic noise, or chaos, is ubiquitous. While a good understanding of the onset of chaos has been achieved, using as a mathematical tool the geometric theory of differentiable dynamical systems, moderately excited chaotic systems require new tools, which are provided by the ergodic theory of dynamical systems. This theory has reached a stage where fruitful contact and exchange with physical experiments has become widespread. The present review is an account of the main mathematical ideas and their concrete implementation in analyzing experiments. The main subjects are the theory of dimensions (number of excited degrees of freedom), entropy (production of information), and characteristic exponents (describing sensitivity to initial conditions). The relations between these quantities, as well as their experimental determination, are discussed. The systematic investigation of these quantities provides us for the first time with a reasonable understanding of dynamical systems, excited well beyond the quasiperiodic regimes. This is another step towards understanding highly turbulent fluids.

Evoked mechanical responses of isolated cochlear outer hair cells

Abstract: Intracellular current administration evokes rapid, graded, and bidirectional mechanical responses of isolated outer hair cells from the mammalian inner ear. The cells become shorter in response to depolarizing and longer in response to hyperpolarizing currents in the synaptic end of the cell. The cells respond with either an increase or decrease in length to transcellular alternating current stimulation. The direction of the movement with transcellular stimuli appears to be frequency dependent. Iontophoretic application of acetylcholine to the synaptic end of the cell decreases its length. The microarchitecture of the organ of Corti permits length changes of outer hair cells in a manner that could significantly influence the mechanics of the cochlear partition and thereby contribute to the exquisite sensitivity of mammalian hearing.

Cachectin/tumor necrosis factor stimulates collagenase and prostaglandin E2 production by human synovial cells and dermal fibroblasts.

Abstract: Cachectin/TNF (tumor necrosis factor), an endotoxin-induced murine macrophage hormone implicated in the pathogenesis of cachexia and shock, has been found capable of stimulating collagenase and prostaglandin E2 (PGE2) production by isolated human synovial cells and dermal fibroblasts. This bioactivity associated with cachectin is comparable to that observed with the monokine interleukin 1 (IL-1), previously suggested as the major mediator of proteolysis. The ability of cachectin/TNF to stimulate collagenase and PGE2 production suggests that it may play a role in tissue destruction and remodelling, as these processes occur in inflammatory diseases.

Measurement of the Quadratic Magnetoelectric Effect on Single Crystalline BiFeO3

Abstract: By means of the quadratic magnetoelectric effect the components of the non-linear magnetoelectric susceptibility tensor βijk of the antiferromagnetic ferroelectric ferroelastic phase of BiFeO3 have been determined at 4 K: β_111 =5010^-19[sA^-1],β_113=8110^-19[sA^-1], β_311 =0310^-19[sA^-1],β_333=2110^-19[sA^-1]

Patient education as the basis for diabetes care in clinical practice and research

Abstract: Despite the obvious improvements made in the field of diabetes therapy during this century [1] the quality of diabetes care has, in general, remained poor. The widespread failure to acknowledge the impact of patient education appears to evolve as the primary reason for this unsatisfactory situation. Despite the firm and well founded recommendations put forward by some of the pioneers of modem diabetology, e.g. Drs. E.P.Joslin and R.D. Lawrence in the 1920s, it has taken almost 50 years for the beneficial effects of patient education to have finally and unequivocally been proven. The recently developed strategies for a global approach to diabetes therapy which combines biomedical, psychosocial and educational elements represents an exemplary therapeutic model for the care of many chronic diseases.

Computer animation

Abstract: Introduction The main goal of computer animation is to synthesize the desired motion effect which is a mixing of natural phenomena, perception and imagination. The animator designs the object's dynamic behavior with his mental representation of causality. He/she imagines how it moves, gets out of shape or reacts when it is pushed, pressed, pulled, or twisted. So, the animation system has to provide the user with motion control tools able to translate his/her wishes from his/her own language. Computer animation methods may also help to understand physical laws by adding motion control to data in order to show their evolution over time. Visualization has become an important way of validating new models created by scientists. When the model evolves over time, computer simulation is generally used to obtain the evolution of time, and computer animation is a natural way of visualizing the results obtained from the simulation.

Ca2+-dependent and Ca2+-independent phagocytosis in human neutrophils.

Abstract: The phagocytic function of neutrophils is a crucial element in host defence against invading microorganisms Two main specific receptor-mediated mechanisms operate in the phagocyte plasma membrane, one recognizing the C3b/bi fragment of complement and the other the Fc domain of immunoglobulin G (ref 1) There is evidence that phagocytosis mediated by these receptors differs in the number and nature of the intracellular signals generated However, the mechanisms by which receptor binding is transduced into a signal that generates the formation of the phagocyte pseudopod is not known, although extensive biochemical evidence has allowed the postulate that calcium ion gradients in the peripheral cytoplasm, by interacting with calcium-sensitive contractile proteins, initiate the process of engulfment Using the high-affinity fluorescent calcium indicator quin2 both to measure and to buffer intracellular calcium ([Ca2+]i), we show here that in human neutrophils two mechanisms of phagocytosis coexist: a [Ca2+]i-dependent and modulated phagocytosis, triggered by activation of the Fc receptor, and a [Ca2+]i-independent mechanism triggered by the activation of the C3b/bl receptors

Herbicide resistance and cross-resistance: changes at three distinct sites in the herbicide-binding protein.

Abstract: Plants and algae resistant to the commonly used s-triazine herbicides display a wide spectrum of cross-resistance to other herbicides that act in a similar manner Analysis of uniparental mutants of the green alga Chlamydomonas reinhardi showed that three different amino acid residues in the 32-kilodalton thylakoid membrane protein can be independently altered to produce three different patterns of resistance to s-triazine and urea-type herbicides These results clarify the molecular basis for herbicide resistance and cross-resistance Two of the mutations do not alter normal electron transport and thus may have applications of agronomic interest

A trans-acting class II regulatory gene unlinked to the MHC controls expression of HLA class II genes

Abstract: Class II (or Ia) antigens are highly polymorphic surface molecules which are essential for the cellular interactions involved in the immune response In man, these antigens are encoded by a complex multigene family which is located in the major histocompatibility complex (MHC) and which comprises up to 12 distinct alpha- and beta-chain genes, coding for the HLA-DR, -DQ and -DP antigens One form of congenital severe combined immunodeficiency (SCID) in man, which is generally lethal, is characterized by an absence of HLA-DR histocompatibility antigens on peripheral blood lymphocytes (HLA class II-deficient SCID) In these patients, as reported here, we have observed an absence of messenger RNA for the alpha- and beta-chains of HLA-DR, -DQ and -DP, indicating a global defect in the expression of all class II genes Moreover, the lack of expression of HLA class II mRNAs could not be corrected by gamma-interferon, an inducer of class II gene expression in normal cells Family studies have established that the genetic defect does not segregate with the MHC We conclude, therefore, that the expression of the entire family of class II genes is normally controlled by a trans-acting class II regulatory gene which is unlinked to the MHC and which is affected in the patients This gene controls a function or a product necessary for the action of gamma-interferon on class II genes

The insulin factory: a tour of the plant surroundings and a visit to the assembly line. The Minkowski lecture 1973 revisited.

Abstract: Le point sur les recents resultats du point de vue morphologique sur la biosynthese, la maturation et la degradation de l'insuline et sur l'organisation des cellules endocrines au sein des ilots de Langerhans

Polymorphic Transformation of Some Drugs Under Compression

Abstract: The existence of various crystalline forms in drugs is a phenomenon frequently encountered (about 40% of the USP XX tablet monographs with dissolution tests are concerned with such compounds). Some studies concerning trituration or grinding of polymorphs have been published; surprisingly little information is available on the transformation under compression, although of great relevance. In this work, thirty-two drugs known to exist as polymorphs were submitted to a trituration test for possible transitions. Out of the eleven transforming substances (approximately 34%), three model drugs, namely caffeine, sulfabenzamide and maprotiline hydrochloride were chosen for tabletting tests. Differential scanning calorimetry and hot stage microscopy were used to investigate polymorphic changes on the upper and lower surfaces, middle region and side of the compacts. The relationships between the extent of transformation and the compression pressure, and the energy of compression were examined, as well as th...

Human endothelial cell cultures: phenotypic modulation by leukocyte interleukins.

Abstract: We report here that soluble factors from activated mononuclear leukocytes have a dramatic effect on cultured endothelial cells. While human umbilical vein endothelial cells grown under standard conditions show a polygonal, epithelial-like morphology, cells exposed to culture media conditioned by lectin-activated human mononuclear leukocytes become extremely elongated and/or send out numerous cytoplasmic processes, assuming a dendritic configuration. This effect cannot be mimicked by exogenous cyclic AMP, is reversible upon interruption of the treatment, and appears specific for endothelial cells, since it has not been observed so far with other cell types. The shape changes are accompanied by a reorganization of the endothelial cell cytoskeleton: actin microfilament bundles tend to be disposed in parallel arrays, while intermediate filaments and microtubules penetrate up to the extremity of the cytoplasmic processes. Colchicine prevents endothelial cell elongation but only slightly impairs the formation of lateral cell processes ("dendritic configuration"). Purified interleukins were tested for their ability to induce these changes of cell shape. Escherichia coli-recombinant human interleukin 2 had no effect, and gamma-interferon only a slight effect on endothelial cell morphology. Interleukin 1 induced moderate cell elongation, while combined treatment with both interleukin 1 and gamma-interferon resulted in shape changes indistinguishable from those elicited by supernatants of activated mononuclear leukocytes. The possible relevance of the observed endothelial cell changes to the reported angiogenic activity of mononuclear cell products is discussed.

Bonding study of TiC and TiN. I. High-precision x-ray-diffraction determination of the valence-electron density distribution, Debye-Waller temperature factors, and atomic static displacements in TiC 0.94 and TiN 0.99

Abstract: Single-crystal, high-precision, high-resolution x-ray-diffraction measurements of the substoichiometric refractory compounds TiC and TiN have been performed with AgK\ensuremath{\alpha} radiation. Severe anisotropic general extinction affects the intense low-order reflections. Inhomogeneity in the mosaic spread and domain size produces small but significant differences between reflection and antireflection for the same plane of diffraction. These effects have been modeled and refined together with a scale factor, isotropic thermal parameters, a population parameter of the nonmetal site, the amplitude of metal-atom static displacements around nonmetal vacancies, and an atomic model which includes occupancy factors of the separate orbital contributions of the valence electrons combined with \ensuremath{\kappa} expansion-contraction parameters. At convergence, the ``agreement indices'' (or ``reliability factors'') were R=0.0025 for ${\mathrm{TiC}}_{0.94}$ and R=0.0023 for ${\mathrm{TiN}}_{0.99}$. The refined population parameters indicate a chemical composition of ${\mathrm{TiC}}_{0.939(9)}$ and ${\mathrm{TiN}}_{0.99(2)}$. The mean-square amplitudes of thermal vibrations, 〈${u}^{2}$${〉}_{\mathrm{Ti}}$=0.002 38(2) A${\mathrm{\r{}}}^{2}$, 〈${u}^{2}$${〉}_{\mathrm{C}}$=0.003 35(8) A${\mathrm{\r{}}}^{2}$, 〈${u}^{2}$${〉}_{\mathrm{Ti}}$=0.002 94(1) A${\mathrm{\r{}}}^{2}$, and 〈${u}^{2}$${〉}_{\mathrm{N}}$=0.003 08(12) A${\mathrm{\r{}}}^{2}$ are consistent with the respective atomic masses. 36% of the metal atoms in ${\mathrm{TiC}}_{0.94}$ are involved in a relaxation around the nonmetal vacancies, being displaced from their sublattice sites by 0.097(2) \AA{} along [100]. No evidence for static displacements was found in ${\mathrm{TiN}}_{0.99}$. The valence-electron density distribution can be described satisfactorily in terms of deformed atoms. No buildup of charge density occurs between atomic sites. Our analysis, similar to a Mulliken partitioning, shows first that ionicity is important, with a charge transfer from the metal to the nonmetal of [2.1(4)]e in the carbide and [1.9(4)]e in the nitride, and secondly that the charge asphericity around the metal atoms is larger in the former than in the latter, while no departure from spherical symmetry is observed around the nonmetal atoms. The titanium 3d electrons can be split into a spherical shell that contains [1.27(6)]e plus an excess of [0.24(5)]e shared by two orbitals of ${e}_{g}$ symmetry in the carbide and conversely into a spherical shell that contains [0.88(11)]e plus an excess of [0.12(9)]e shared by three orbitals of ${t}_{2g}$ symmetry in the nitride. This suggests that the metal-to-metal bonding is similar in TiC and in TiN while the metal-to-nonmetal bonding is greater in TiC than in TiN.

Triangulation With Expanded Range Of Depth

Abstract: In conventional triangulation systems for 3-D sensing there is a trade-off between range of depth and resolution. We propose a triangulation system with a large depth of field (1 m or more) and, at the same time, high resolution (20µm or better). The system is based essentially on a tele-axicon in the illumination device and on the use of the Scheimpflug condition in the observation device. A suitable scanning-by-deflection geometry is described.

The pH of human crevicular fluid measured by a new microanalytical technique

Abstract: In physiological and pathological conditions, the pH of the crevicular fluid may play a significant role on the structure and function of the gingival crevice In the present investigation the pH of human crevicular fluid was determined by a new microanalytical technique The fluid was collected in 32 sites (19 patients) with capillary tubes The tip of a double barreled, neutral carrier based microelectrode, highly selective for H+ ions was introduced directly into the capillary tubes containing either the samples or the reference solutions In each sampling site, the GI and the crevicular fluid volume were recorded and correlated with the pH As the inflammation increased, an elevation of pH from 690 to as much as 866 was observed These values have been measured at 20°C in absence of CO2 Whether this increase is due to the bacterial flora or to any metabolic activity in the crevice area is not clear at the moment

Nonsense mutations in the Chlamydomonas chloroplast gene that codes for the large subunit of ribulosebisphosphate carboxylase/oxygenase.

Abstract: The Chlamydomonas reinhardtii chloroplast mutants 18-5B and 18-7G lack both the chloroplast-encoded large subunit and nuclear-encoded small subunit of the chloroplast enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39). A chloroplast intergenic-suppression model has been postulated to account for the genetic instability of 18-5B revertants. Here, we have determined the molecular basis of the 18-5B and 18-7G mutants. They contain nonsense mutations close to the 3′ and 5′ ends of their large-subunit genes, respectively. Pulse-chase experiments revealed that the 18-5B mutant produces a truncated large subunit that is unstable. In connection with previous experiments, this work identifies nonsense suppression in the chloroplast. Small subunits are also synthesized but then degraded in the mutants. Thus, the coordinated absence of subunits is achieved through degradation of the small subunit in the specific absence of the large subunit.