1,721,058 research outputs found
Conformation of actinomycin-D
No full textNUCLEAR magnetic resonance (NMR) spectroscopy has recently been found useful for investigating the conformations of polypeptides like gramicidin S1,2, valinomicin3 and so on. We now report preliminary conclusions on the conformation of the two peptide lactone rings of actinomycin D4 on the basis of NMR results and theoretical conformational analysis. Fig. 1 depicts the NMR spectra of actinomycin D obtained in different experimental conditions. The assignment has been made on the basis of chemical shift values, and the characteristics of the signals in double and triple resonance experiments. By examining the results obtained, some interesting features can be derived. © 1970 Nature Publishing Group
Report on the first maga circe conference on metabolic systems analysis
No full text[No abstract available
N.m.r. studies of butadiene - styrene copolymers
No full textThe microstructures of block or random samples of butadiene-styrene copolymer [9003-55-8] were detd. in terms of triads of monomeric sequences from their 13C [14762-74-4] NMR spectra. The obsd. bands. were assigned on the basis of correlation with homopolymers and on the basis of the frequencies for the single triads, calcd. by additivity rules
13C n.m.r. spectra of styrene-butadiene copolymers on solid samples
No full textThe carbon-13 [14762-74-4] NMR spectra of solid samples and solns. of block and random butadiene-styrene copolymer [9003-55-8] samples were given and discussed
Sequence distributions in ethylene-vinyl acetate copolymers. I. 13C Nuclear Magnetic Resonance studies
No full textThe sequence distribution of ethylene-vinyl acetate copolymers has been studied using 13C nmr spectroscopy.
Signal attributions were obtained both by following the rules of Grant and Paul as well as by comparison of
spectra of samples of varying composition. Quantitative analysis at low vinyl acetate content are reported. Zerothorder
Markoffian distribution of the monomer units in the copolymer chain was verified. In addition, a 13C spectrum of
solid polymer was obtained
13C n.m.r. studies of butadiene-styrene copolymers. A revised assignment
No full textOff-resonance 13C NMR data on butadiene-styrene copolymer [9003-55-8] are consistent with the assignment of J. R. Ebdon and T. N. Huckerby (1976) for atactic polystyrene
Effectiveness of different distributions of viscous damping coefficients for the seismic retrofit of regular and irregular RC frames
No full textThe main purpose of this research has been to investigate the effectiveness of different vertical distributions of the damping coefficients of nonlinear viscous dampers for the seismic retrofit of existing multi-storey reinforced concrete frames. In particular, different simple distributions were compared with other procedures proposed in literature, including two energy methods and a repetitive simplified sequential search algorithm. The effectiveness of the different distributions was then examined by performing time-history analyses and considering a nonlinear behaviour for both the viscous dampers and the structural members. The structures being considered are five RC frames with a different number of storeys and both regular and irregular configurations in elevation. The results of the nonlinear dynamic analyses were examined in terms of maximum and residual interstorey drifts, peak floor accelerations and maximum damper forces. The energy methods, in particular, provided good results in terms of reduction in cost, efficiency of the distribution and simplicity of application, compared to other effective, but more complex methods
Influence of vertical distribution of damper properties for seismic upgrading of regular and irregular RC frames
No full textThe main purpose of this research is to investigate the effects of different vertical distributions of the properties of nonlinear fluid-viscous dampers for the retrofit of existing multi-storey reinforced concrete frames. In particular, the different distributions are defined on the basis of the same value of the supplemental damping ratio. Since the viscous dampers are used for the retrofit of existing buildings, they are dimensioned assuming that the structure can exceed the elastic limit, with the only condition to satisfy the prefixed performance limit. In the design phase the different vertical distributions of damper properties are compared in terms of the total sum of the damping coefficients. The effectiveness of the different distributions is then examined by performing time-history analysis of several case studies considering a nonlinear behaviour both for the viscous dampers and for the structural members. The results of the nonlinear dynamic analyses are examined in terms of interstorey drifts and dampers forces. The considered case studies are five RC frames characterized by different number of storeys (3, 6 and 9 storeys) and also by different properties in terms of regularity in elevation. In this way it is also possible to investigate the effect of the vertical distribution of the damper properties for regular and irregular frames
13C n.m.r. spectra of polybutadienes:2
No full textThe exptl. chem. shifts shown in the carbon-13 [14762-74-4] NMR spectra of polybutadiene [9003-17-2] samples contg. 85% 1,2-units and 15% cis-1,4-units and contg. 94% 1,2- and 6% trans-1,4-units were consistent with those calcd. using additivity rules
Metabolomics and medical practice
No full textHigh resolution NMR spectroscopy, currently known as " metabolomics", is a technology enabling the rapid, noninvasive and low cost determination of low molecular weigh metabolites (e.g. aminoacids) in biological fluids such as plasma, urine, saliva, cerebrospinal fluid and others. According to Nicholson "Metabolomics is the quantitative measurement of the dynamic multiparametric metabolic response of living systems to pathophysiological stimuli or genetic modification". Over the past 10 years this technology made it possible to discover of a number of lesser-known organ-specific metabolites that has been demonstrated to be reliable indicators of both organ function and viability. Consequently metabolomics has been used, with interesting results, for the functional evaluation of many organs (kidney, liver, heart), drug toxicity and post-transplant monitoring. The international literature demonstrates a growing interest for this technology and its capabilities
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