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Simple Experiment (simple + experiment)
Selected AbstractsCross-correlated and conventional dipolar carbon-13 relaxation in methylene groups in small, symmetric moleculesCONCEPTS IN MAGNETIC RESONANCE, Issue 2 2007Leila Ghalebani Abstract A theory for dipolar cross-correlated relaxation processes in AMX or AX2 spin system, with special reference to 13C-methylene groups, is reviewed briefly. Simple experiments and protocols for measuring the transfer rates between the carbon-13 Zeeman order and the three-spin order, and for their analogues in the transverse plane, are discussed using a concentrated solution of the disaccharide trehalose as a model system. Experimental data sets consisting of conventional carbon-13 relaxation parameters (T1, T2, and NOE), along with the cross-correlated relaxation rates, are also presented for some small, rigid, polycyclic molecules. These data are interpreted using spectral density functions appropriate to spherical or symmetric tops reorienting according to small-step rotational diffusion model. The analysis results in a consistent picture of the auto- and cross-correlated spin relaxation processes. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 100,115, 2007. [source] Recombinant DRB sequences produced by mismatch repair of heteroduplexes during cloning in Escherichia coliINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 6 2002M. Longeri Summary Recombinant chimeric sequences originating from a mixture of the sequences of two different alleles are frequently found after amplification and cloning in Escherichia coli of exon 2 of the major histocompatibility complex (MHC) DRB genes. Several authors have suggested that the recombinant molecules result from in vitro recombination during PCR; nevertheless, a clear experimental demonstration of this hypothesis is lacking. In order to understand the mechanism producing the chimeric sequences, we set up a simple experiment based on the different restriction patterns of parental and recombinant sequences. Our data demonstrate that in the analysed case most of the recombinant variants were not produced by in vitro recombination during PCR, but were the result of the mismatch repair of heteroduplex molecules during cloning in E. coli. The high mutation rate in the ,-helix region of DRB expressed genes, both after cloning in E. coli and after the germ-line differentiation process in vertebrates, suggests that the observed mutations are the result of similar gene conversion processes, probably favoured by chi-dependent microrecombination events. [source] When does a reproducing female viper (Vipera aspis) ,decide' on her litter size?JOURNAL OF ZOOLOGY, Issue 2 2003Olivier Lourdais Abstract Some organisms rely on stored energy to fuel reproductive expenditure (capital breeders) whereas others use energy gained during the reproductive bout itself (income breeders). Most species occupy intermediate positions on this continuum, but few experimental data are available on the timescale over which food intake can affect fecundity. Mark,recapture studies of free-ranging female aspic vipers Vipera aspis have suggested that reproductive output relies not only on the energy in fat bodies accumulated in previous years, but also on food intake immediately before ovulation. A simple experiment was conducted to test this hypothesis, maintaining female snakes in captivity throughout the vitellogenic period and controlling their food intake. The energy input of a female strongly influenced the amount of mass that she gained and the number of ova that she ovulated. Multiple regression showed that litter size in these snakes was affected both by maternal body condition in early spring (an indicator of foraging success over previous years) and by food intake in the spring before ovulation. Our experimental data thus reinforce the results of descriptive studies on free-ranging snakes, and emphasize the flexibility of energy allocation patterns among vipers. Reproducing female vipers may combine energy from ,capital' and ,income' to maximize their litter sizes in the face of fluctuating levels of prey abundance. [source] Intrinsic lifetime of polyethylene pipelinesPOLYMER ENGINEERING & SCIENCE, Issue 4 2007Norman Brown An equation was developed for calculating the time to failure by slow crack growth (SCG) failure in any polyethylene structure. The equation requires the following experimental inputs: (1) the resistance to SCG as measured by the PENT test (ASTM F1473), (2) the stress intensity of the defect from which failure originates, and (3) the temperature. A simple experiment for determining the stress intensity is presented. The equation was applied to SCG failures that are associated with the inherent random defects that occur in the wall of all pipes. The size of the inherent random defect that exists in commercial gas pipes was found to be 0.14 mm. POLYM. ENG. SCI., 47:477,480, 2007. © 2007 Society of Plastics Engineers. [source] Development of pictograms for dynamic traffic control systems in South KoreaJOURNAL OF ADVANCED TRANSPORTATION, Issue 1 2008Jaisung Choi This study developed a set of pictograms for lane control systems, to provide additional information to drivers on weather and traffic incidents. The results suggest that in the design of traffic signs, it is important to consider local context and not simply adopt standards and practices that are developed elsewhere. The differences in the social and cultural environments may affect the ease of reading and comprehension by local drivers. However, the study also showed that not all locally developed signs were rated higher for their ease of reading than others, Since some design characteristics are more salient, whereas others tend to be more dependent on the local context, it is important to conduct simple experiments and exploratory research to find the optimal designs to be used. [source] Mass Balances in Porous Foods ImpregnationJOURNAL OF FOOD SCIENCE, Issue 9 2001V. Roa ABSTRACT: A simple model based on mass balance equations is proposed for prediction of the final mass and composition of products subjected to vacuum impregnation. It was applied to some tropical fruits in a fruit-sucrose solution system. The phenomenon can be described in terms of volumetric fraction of impregnating solution as the basic modeling parameter, instead of effective porosity. To use the equations of the model, only routine laboratory equipment and simple experiments are required. Prediction of the final weight of impregnated fruit was accomplished with an average absolute error of 2 to 3%, while in final composition of the fruit (total solids), it was 5.7 %. [source] Causes and consequences of aggregation by neonatal tiger snakes (Notechis scutatus, Elapidae)AUSTRAL ECOLOGY, Issue 2 2009FABIEN AUBRET Abstract Although snakes traditionally have been regarded as asocial animals, recent studies have revealed complex interactions among neonatal snakes and their mothers. We noticed frequent aggregation by captive neonatal Australian elapids (tiger snakes, Notechis scutatus), and conducted simple experiments to clarify the proximate causation of, and potential consequences of, aggregative behaviour. Litters of neonates exhibited statistically significant aggregation (clustering) in empty containers, especially if the test area was subjected to rapid cooling. Aggregation was most pronounced inside shelter-sites, and familiar shelters (i.e. containing scent cues from the litter) attracted snakes more than did novel (unscented) shelters. Snakes in larger aggregations cooled more slowly (reflecting their higher combined mass and thus, thermal inertia) and higher body temperatures facilitated neonatal locomotor performance, retreat-site location and anti-predator tactics. Plausibly, aggregation in neonatal tiger snakes (and other reptiles) functions to retard cooling rates, with the result that the young snakes are better able to evade or repel attacks by predators. [source] | |||||||||||||