ASDTIC: A feedback control innovation

The ASDTIC (Analog Signal to Discrete Time Interval Converter) control subsystem provides precise output control of high performance aerospace power supplies. The key to ASDTIC operation is that it stably controls output by sensing output energy change as well as output magnitude. The ASDTIC control subsystem and control module were developed to improve power supply performance during static and dynamic input voltage and output load variations, to reduce output voltage or current regulation due to component variations or aging, to maintain a stable feedback control with variations in the loop gain or loop time constants, and to standardize the feedback control subsystem for power conditioning equipment

Reliability approach to rotating-component design

A probabilistic methodology for designing rotating mechanical components using reliability to relate stress to strength is explained. The experimental test machines and data obtained for steel to verify this methodology are described. A sample mechanical rotating component design problem is solved by comparing a deterministic design method with the new design-by reliability approach. The new method shows that a smaller size and weight can be obtained for specified rotating shaft life and reliability, and uses the statistical distortion-energy theory with statistical fatigue diagrams for optimum shaft design. Statistical methods are presented for (1) determining strength distributions for steel experimentally, (2) determining a failure theory for stress variations in a rotating shaft subjected to reversed bending and steady torque, and (3) relating strength to stress by reliability

Design features and results from fatigue reliability research machines

Design and performance tests for reversed bending with steady torque fatigue test machine using notched steel specimen

Toward a computational history of science: The dynamics of socio-epistemic networks and the renaissance of general relativity

The exploding amount of available historical data provides intriguing possibilities as well as major challenges to historians of science. In the last years, several quantitative methods have been developed in order to analyze historical data. At the same time, new analytical frameworks need to be developed to bring together quantitative methods with the more traditional historians’ toolkit. The present paper has a twofold aim. The first one is to briefly review major quantitative approaches that have been developed in the history of science in two areas: data modeling and network analysis. The second part of the contribution focuses on applications of social network analysis to the evolution of knowledge systems. We propose a methodological and conceptual framework aiming at uncovering the dynamical transformations of intra- and inter-connections within and between different layers of the scientific enterprise. We define knowledge networks as being composed of three different layers: the social network, the semiotic network, and the semantic network. The first is defined as the collection of relations involving individuals and institutions. The semiotic network is defined as the collection of the material or formal representations of knowledge. The semantic network is the collection of knowledge elements and their relations. We call socio-epistemic networks the interlinked set of these three levels. As an illustration of this methodology results drawn from our own work on social and conceptual changes in the history of general relativity in the 20th century will be presented

The dynamics of collaboration networks and the history of general relativity, 1925–1970

This paper presents a novel methodology for defining and analyzing the dynamics of the collaboration networks of scientists working on general relativity from the mid-1920s–1970. During these four and a half decades the status of the theory underwent a radical transformation: from a marginal theory before the mid-1950s to a pillar of modern physics. To investigate this passage—known as the renaissance of general relativity—we used a definition of collaboration networks broader than the co-authorship relations retrievable from online datasets. We constructed a multilayer network, in which each layer represents a different kind of collaboration. After having analyzed the evolution over time of specific parameters of the co-authorship network, we investigated the effects of adding one type of collaboration edge at a time, in a cumulative fashion, on the values of these parameters and on the topology of the collaboration network through time, including rapid shifts in the dynamic evolution of the largest component. This analysis provides robust quantitative evidence that a shift in the structure of the relativity collaboration network occurred between the late 1950s and the early 1960s, when a giant component started forming. We interpret this shift as the central social dynamic of the renaissance process and then identify its central actors. Our analysis disproves common explanations of the renaissance process. It shows that this phenomenon was not a consequence of astrophysical discoveries in the 1960s, nor was it a simple by-product of socio-economic transformations in the physics landscape after World War II

Distal unfolding of ferricytochrome C induced by the F82K mutation

It is well known that axial coordination of heme iron in mitochondrial cytochrome c has redox-dependent stability. The Met80 heme iron axial ligand in the ferric form of the protein is relatively labile and can be easily replaced by alternative amino acid side chains under non-native conditions induced by alkaline pH, high temperature, or denaturing agents. Here, we showed a redox-dependent destabilization induced in human cytochrome c by substituting Phe82\u2014conserved amino acid and a key actor in cytochrome c intermolecular interactions\u2014with a Lys residue. Introducing a positive charge at position 82 did not significantly affect the structure of ferrous cytochrome c but caused localized unfolding of the distal site in the ferric state. As revealed by1 H NMR fingerprint, the ferric form of the F82K variant had axial coordination resembling the renowned alkaline species, where the detachment of the native Met80 ligand favored the formation of multiple conformations involving distal Lys residues binding to iron, but with more limited overall structural destabilization

Surprising Complexity of the [Gd(AAZTA)(H2O)2]- Chelate Revealed by NMR in the Frequency and Time Domains

Typically, Ln(III) complexes are isostructural along the series, which enables studying one particular metal chelate to derive the structural features of the others. This is not the case for [Ln(AAZTA)(H2O)x]- (x = 1, 2) systems, where structural variations along the series cause changes in the hydration number of the different metal complexes, and in particular the loss of one of the two metal-coordinated water molecules between Ho and Er. Herein, we present a 1H field-cycling relaxometry and 17O NMR study that enables accessing the different exchange dynamics processes involving the two water molecules bound to the metal center in the [Gd(AAZTA)(H2O)2]- complex. The resulting picture shows one Gd-bound water molecule with an exchange rate ∼6 times faster than that of the other, due to a longer metal-water distance, in accordance with density functional theory (DFT) calculations. The substitution of the more labile water molecule with a fluoride anion in a diamagnetic-isostructural analogue of the Gd-complex, [Y(AAZTA)(H2O)2]-, allows us to follow the chemical exchange process by high-resolution NMR and to describe its thermodynamic behavior. Taken together, the variety of tools offered by NMR (including high-resolution 1H, 19F NMR as a function of temperature, 1H longitudinal relaxation rates vs B0, and 17O transverse relaxation rates vs T) provides a complete description of the structure and exchange dynamics of these Ln-complexes along the series

Lichens as bioindicators of atmospheric heavy metal deposition in Valencia, Spain

The lichens due to their symbiotic nature have unique characteristics that confer them a key role as bioindicators of the environmental contamination. Many investigations have been done using epiphytic lichens as bioindicators, but only a few of these studies have used epilithiccrustose lichens. Three different epilithic-crustose lichens species: Candelariella sp., Lecanora sp. and Caloplaca sp. were studied as bioindicators of V, Cr,Mn, Co, Ni, Cu, Zn, As, Rb, Sr,Mo, Cd, Sb, Ba, Pb, Bi and U trace elements. Inductively Coupled Plasma Mass Spectrometry routine procedure is used to determining these element concentrations. Two sites were selected for lichens sampling according to environmental contamination. The lichens were collected on the facade of the Santos Juanes church in an urban area of Valencia; and on the rural area of Albarracin. The main aim of this work is showing the efficacy of the epilithic-crustose lichens as bioindicators of the air pollution. This study shows that the city of Valencia, compared with the rural area has high levels of Cu and Pb as detected using lichens as bioindicators. Therefore on the basis of these results, it can be hypothesized that Candelariella sp., Lecanora sp. and Caloplaca sp. are good accumulators of air borne heavy metals.This work has financial support of the Spanish Ministerio de Ciencia e Innovacion with a Ph.D. scholarship for Pilar Bosch Roig (BES-2006-12110) and with a three months stay scholarship to do this research in the Opificio delle Pietre Dure in Florence, Italy with Doctor Carlo Lalli. The authors wish to thank to the priest of the Santos Juanes Church of Valencia; the Direccion General de Patrimonio; to Prof. Pilar Roig Picazo and Prof. Ignacio Bosch Reig; the Instituto Universitario de Restauracion del Patrimonio from the Universitat Politecnica de Valencia; to the Ministero per I Beni Culturali; Italy.Bosch Roig, MDP.; Barca, D.; Crisci, G.; Lalli Galliano, C. (2013). 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