The dynamics and tuning of orchestral crotales

Crotales are center-weighted, tuned cymbals that are found in the percussion section of most orchestras. They are arranged like a keyboard in octave sets and are commercially available in two octaves, from C6 to C8. Little information about the physics of crotales has been reported in the literature, despite their having the interesting property of producing a particularly pleasing sound. In this study, the acoustic and vibrational properties of crotales from C6 to C8 are theoretically and experimentally investigated. Interferograms of typical vibrational modes are presented, and the frequencies of the acoustically important modes of crotales are identified and reported. The acoustic spectra of the crotales are compared to theoretical predictions for thin circular plates and annular plates clamped at the center. These models are found to be insufficient for predicting the normal modes of the crotales. An accurate model is developed using finite element analysis, and this model is used to investigate the effects of subtle changes in the magnitude and size of the center mass on the acoustic spectrum. This investigation serves as a basis for suggestions for improvement of the crotales by modifying the center mass. Finally, the physical parameters for a set of clamped annular plates are derived such that the set has similar acoustic properties to a set of crotales, but with more accurate tuning. The validity of these parameters is confirmed using finite element analysis

Analysis and use of VAS satellite data

A series of interrelated investigations has examined the analysis and use of VAS (VISSR Atmospheric Sounder) satellite data. A case study of VAS-derived mesoscale stability parameters suggested that they would have been a useful supplement to conventional data in the forecasting of thunderstorms on the day of interest. However, the meteorological significance of small or short lived stability features was uncertain. A second investigation examined the roles of first guess and VAS radiometric data in producing sounding retrievals. The radiance data often did not have a decisive influence on the final satellite soundings. Broad-scale patterns of the first guess, radiances, and retrievals frequently were similar, whereas small scale retrieval features, especially in the dew points, were often of uncertain origin

Analysis and use of VAS satellite data

Four interrelated investigations have examined the analysis and use of VAS satellite data. A case study of VAS-derived mesoscale stability parameters suggested that they would have been a useful supplement to conventional data in the forecasting of thunderstorms on the day of interest. A second investigation examined the roles of first guess and VAS radiometric data in producing sounding retrievals. Broad-scale patterns of the first guess, radiances, and retrievals frequently were similar, whereas small-scale retrieval features, especially in the dew points, were often of uncertain origin. Two research tasks considered 6.7 micron middle tropospheric water vapor imagery. The first utilized radiosonde data to examine causes for two areas of warm brightness temperature. Subsidence associated with a translating jet streak was important. The second task involving water vapor imagery investigated simulated imagery created from LAMPS output and a radiative transfer algorithm. Simulated image patterns were found to compare favorably with those actually observed by VAS. Furthermore, the mass/momentum fields from LAMPS were powerful tools for understanding causes for the image configurations

Diversity of Fe2+ entry and oxidation in ferritins

The essential metal iron presents two major problems for life: it is potentially highly toxic due to its redox activity, and its extremely low solubility in aqueous solution in the presence of O2 can make it hard to acquire and store safely. Ferritins are part of nature’s answer to these problems, as they store iron in a safe but accessible form in all types of cells. How they achieve this has been the subject of intense research for several decades. Here, we highlight recent progress in elucidating the routes by which Fe2+ ions access the catalytic ferroxidase centers, and the mechanisms by which Fe2+ is oxidized. Emerging from this is a picture of diversity, both in terms of Fe2+ entry pathways and the roles played by the structurally distinct diiron ferroxidase centers

Non-degenerate normal-mode doublets in vibrating flat circular plates

The vibrations of flat circular plates have been studied for hundreds of years, and they are well understood by the scientific community. Unfortunately, when vibrating circular plates are discussed in textbooks, the relationship between pairs of spatially orthogonal vibrational patterns that occur at each of the normal-mode frequencies is often ignored. Usually these orthogonal solutions are presented to the student as being degenerate in frequency; however, in practice the degeneracy of the doublet is often broken and the two spatially orthogonal solutions are separated in frequency. We show theoretically and experimentally that the degeneracy can be broken by a small asymmetry in the plate, and we derive a formula for predicting the magnitude of the frequency-splitting. We have used electronic speckle pattern interferometry to investigate the phenomena of doublet splitting and have confirmed the validity of the theory

Reaction and deactivation of HCl( v

Total decay rates for HCl(v = 2, 1) were measured in the range 294 - 439 K for Cl, 295 - 390 K for Br, and at 296 K for H. HCl(v = 2) was produced directly by pulsed laser excitation of the overtone. The fraction of HCl(v = 2) relaxed to HCl(v = 1) was determined. For HCl(v = 2) + Cl, relaxation gave entirely HCl(v = 1) within an experimental uncertainty of ± 10%, the total relaxation rate was large, k/v = 5 {Angstrom}{sup 2} , and rates varied only slightly with temperature. For Br + HCl(v = 2) reaction to HBr(v = 0) + Cl is exoergic by about kT. Relaxation to HCl(v = 1) is the dominant process. Reaction contributes roughly 17% and 34% to the loss of HCl(v = 2) at 295 and 390 K, respectively. In constrast to the result for Br and for O (reported previously) H + HCl(v = 2) gives 65% H{sub 2} + Cl and only 35% HCl(v = 1) +H. For HCl(v = 1) + H Cl, O the vibrational excitation energy is greater than the activation energy for reaction. The relaxation rates are between 1/2 and 1/3 of the A values for the measured thermal exchange rates Aexp(-{Delta}E{sub act}/RT). For HCl(v = 1) + Br, well below threshold, the rate is some 20 times less than for HCl(v = 1) + Cl. The rate for HCl(v = 2) + Br, just above reaction threshold is not dramatically larger. The ratios of vibrational relaxation rates for HCl(v = 2) vs HCl(v = 1) are 5.0 ± 1.3, 4.2 ± 0.4, and 5.0 ± 1.3 for O, Cl, and Br, respectively. Any first order linear perturbation treatment gives rates proportional to v; the data scale more closely as v{sup 2}

Function-related replacement of bacterial siderophore pathways

© The Author(s) 2018. Bacterial genomes are rife with orphan biosynthetic gene clusters (BGCs) associated with secondary metabolism of unrealized natural product molecules. Often up to a tenth of the genome is predicted to code for the biosynthesis of diverse metabolites with mostly unknown structures and functions. This phenomenal diversity of BGCs coupled with their high rates of horizontal transfer raise questions about whether they are really active and beneficial, whether they are neutral and confer no advantage, or whether they are carried in genomes because they are parasitic or addictive. We previously reported that Salinispora bacteria broadly use the desferrioxamine family of siderophores for iron acquisition. Herein we describe a new and unrelated group of peptidic siderophores called salinichelins from a restricted number of Salinispora strains in which the desferrioxamine biosynthesis genes have been lost. We have reconstructed the evolutionary history of these two different siderophore families and show that the acquisition and retention of the new salinichelin siderophores co-occurs with the loss of the more ancient desferrioxamine pathway. This identical event occurred at least three times independently during the evolution of the genus. We surmise that certain BGCs may be extraneous because of their functional redundancy and demonstrate that the relative evolutionary pace of natural pathway replacement shows high selective pressure against retention of functionally superfluous gene clusters

Cloning, sequencing and analysis of the enterocin biosynthesis gene cluster from the marine isolate ‘Streptomyces maritimus’: evidence for the derailment of an aromatic polyketide synthase

AbstractBackground: Polycyclic aromatic polyketides, such as the tetracyclines and anthracyclines, are synthesized by bacterial aromatic polyketide synthases (PKSs). Such PKSs contain a single set of iteratively used individual proteins for the construction of a highly labile poly-β-carbonyl intermediate that is cyclized by associated enzymes to the core aromatic polyketide. A unique polyketide biosynthetic pathway recently identified in the marine strain ‘Streptomyces maritimus’ deviates from the normal aromatic PKS model in the generation of a diverse series of chiral, non-aromatic polyketides.Results: A 21.3 kb gene cluster encoding the biosynthesis of the enterocin and wailupemycin family of polyketides from ‘S. maritimus’ has been cloned and sequenced. The biosynthesis of these structurally diverse polyketides is encoded on a 20 open reading frames gene set containing a centrally located aromatic PKS. The architecture of this novel type II gene set differs from all other aromatic PKS clusters by the absence of cyclase and aromatase encoding genes and the presence of genes encoding the biosynthesis and attachment of the unique benzoyl-CoA starter unit. In addition to the previously reported heterologous expression of the gene set, in vitro and in vivo expression studies with the cytochrome P-450 EncR and the ketoreductase EncD, respectively, support the involvement of the cloned genes in enterocin biosynthesis.Conclusions: The enterocin biosynthesis gene cluster represents the most versatile type II PKS system investigated to date. A large series of divergent metabolites are naturally generated from the single biochemical pathway, which has several metabolic options for creating structural diversity. The absence of cyclase and aromatase gene products and the involvement of an oxygenase-catalyzed Favorskii-like rearrangement provide insight into the observed spontaneity of this pathway. This system provides the foundation for engineering hybrid expression sets in the generation of structurally novel compounds for use in drug discovery

A photo- and electrochemically-active porphyrin–fullerene dyad electropolymer

A hole- and electron-conducting polymer has been prepared by electropolymerization of aporphyrin–fullerene monomer. The porphyrin units are linked by aminophenyl groups to form a linear chain in which the porphyrin is an integral part of the polymer backbone. The absorption spectrum of a film formed on indium-tin-oxide-coated glass resembles that of a model porphyrin–fullerene dyad, but with significant peak broadening. The film demonstrates a first oxidation potential of 0.75 V vs. SCE, corresponding to oxidation of the porphyrin polymer, and a first reduction potential of -0.63 V vs. SCE, corresponding to fullerene reduction. Time-resolved fluorescence studies show that the porphyrin first excited singlet state is strongly quenched by photoinduced electron transfer to fullerene. Transient absorption investigations reveal that excitation generates mobile charge carriers that recombine by both geminate and nongeminate pathways over a large range of time scales. Similar studies on a related polymer that lacks the fullerene component show complex, laser-intensity-dependent photoinduced electron transfer behavior. The properties of the porphyrin–fullerene electropolymer suggest that it maybe useful in organic photovoltaic applications, wherein light absorption leads to charge separationwithin picoseconds in a “molecular heterojunction” with no requirement for exciton migration.Fil: Gervaldo, Miguel Andres. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; ArgentinaFil: Liddell, Paul A.. Arizona State University; Estados UnidosFil: Kodis, Gerdenis. Arizona State University; Estados UnidosFil: Brennan, Bradley J.. Arizona State University; Estados UnidosFil: Johnson, Christopher R.. Arizona State University; Estados UnidosFil: Bridgewater, James W.. Arizona State University; Estados UnidosFil: Moore, Ana L.. Arizona State University; Estados UnidosFil: Moore, Thomas A.. Arizona State University; Estados UnidosFil: Gust, Devens. Arizona State University; Estados Unido