Cold hardiness and water content during deacclimation of grapevine bud and cane tissue

1988 Summer.Covers not scanned.Includes bibliographical references.Computer assisted thermal analysis was used to measure deep supercooling in dormant bud and cane tissue of Vitis vinifera L. cv. 'Merlot' during a five week deacclimation time period. The temperature of the Low Temperature Exotherm (LTE), an indicator of hardiness, of both cane (internode) and primary bud tissue responded to weekly increases in air temperatures with bud tissue responding faster than cane tissue. Bud tissue from pruned and unpruned canes retained the capacity to supercool until early bud swell 18 April 1987, when the mean LTE temperature of -9.8°C became obscured by High Temperature Exotherms (HTEs) occurring between -5 and -8°C. Cane tissue had lower LTEs than bud tissue on each date and at each position. Cane positions nearest the trunk, whether canes were pruned or unpruned, were found to be slightly hardier than those more distally oriented, which was not observed with buds. Pruning treatments did not influence the loss of hardiness in either bud or cane tissue. Water content of canes was more affected by all three factors (date, position, and pruning) than was hardiness. Bud water content was only affected by date, and was lower than cane water content for every date and each position throughout the study. Canes increased in water content with each more distal position. Pruning slowed the rate of cane hydration during the week it was most rapid, especially at the most distal position. Observations during the most pertinent three weeks of this study indicate that cane tissue hydrates rapidly but dehardens only slowly, while buds deharden more quickly yet have only a small increase in bulk water content. The main effect of pruning was on cane water content

High speed hydrogen/graphite interaction

Various aspects of a research program on high speed hydrogen/graphite interaction are presented. Major areas discussed are: (1) theoretical predictions of hydrogen/graphite erosion rates; (2) high temperature, nonequilibrium hydrogen flow in a nozzle; and (3) molecular beam studies of hydrogen/graphite erosion

Graduate Education in Airport Administration: Preparing Airport Managers for the 21st Century

Growing numbers of students pursuing management careers in aviation are seeking graduate degrees to prepare for the complex and evolving challenges in the aviation industry. This study questioned members of the American Association of Airport Executives (AAAE) about their profession and the appropriateness of current education opportunities in aviation administration. The purpose of this study was to identify the knowledge and skills that the next generation of airport administrators will need to effectively contend with the new industrial environment

High resolution study of associated C IV absorption systems in NGC 5548

We present the results of a careful analysis of associated absorption systems toward NGC 5548. Most of the well resolved narrow components in the associated system, defined by the Lyman alpha, C IV and N V profiles, show velocity separation similar (to within 10~\kms) to the C IV doublet splitting. We estimate the chance probability of occurrence of such pairs with velocity separation equal to C IV doublet splitting to be $6\times10^{-3}$. Thus it is more likely that most of the narrow components are line-locked with C IV doublet splitting. This will mean that the radiative acceleration plays an important role in the kinematics of the absorbing clouds. We build grids of photoionization models and estimate the radiative acceleration due to all possible bound-bound transitions. We show that the clouds producing absorption have densities less than $10^9 cm^{-3}$, and are in the outer regions of the broad emission line region (BLR). We note that the clouds which are line-locked cannot produce appreciable optical depths of O VII and O VIII, and hence cannot be responsible for the observed ionized edges, in the soft X-ray. We discuss the implications of the presence of optically thin clouds in the outer regions of the BLR to the models of broad emission lines.Comment: 21 pages, latex (aasms4 style), incluedes 4 ps figures. To appear in Astrophysical Journa

Dipolar ordering in Fe8?

We show that the low-temperature physics of molecular nanomagnets, contrary to the prevailing one-molecule picture, must be determined by the long-range magnetic ordering due to many-body dipolar interactions. The calculations here performed, using Ewald's summation, suggest a ferromagnetic ground state with a Curie temperature of about 130 mK. The energy of this state is quite close to those of an antiferromagnetic state and to a glass of frozen spin chains. The latter may be realized at finite temperature due to its high entropy.Comment: 7 pages, no figures, submitted to EP

Bias in meta-analyses using Hedges’ d

The type of metric and weighting method used in meta-analysis can create bias and alter coverage of confidence intervals when the estimated effect size and its weight are correlated. Here, we investigate bias associated with the common metric, Hedges’ d, under conditions common in ecological meta-analyses. We simulated data from experiments, computed effect sizes and their variances, and performed meta-analyses applying three weighting schemes (inverse variance, sample size, and unweighted) for varying levels of effect size, within-study replication, number of studies in the meta-analysis, and among-study variance. Unweighted analyses, and those using weights based on sample size, were close to unbiased and yielded coverages close to the nominal level of 0.95. In contrast, the inverse-variance weighting scheme led to bias and low coverage, especially for meta-analyses based on studies with low replication. This bias arose because of a correlation between the estimated effect and its weight when using the inverse-variance method. In many cases, the sample size weighting scheme was most efficient, and, when not, the differences in efficiency among the three methods were relatively minor. Thus, if using Hedges’ d, we recom

Top-down pulses reduce prey population sizes and persistence

Resource pulses are well documented and have important consequences for population dynamics relative to continuous inputs. However, pulses of top-down factors (e.g. predation) are less explored and appreciated in the ecological literature. Here, we use a simple differential equation population model to show how pulsed removals of individuals from a population alter population size relative to continuous dynamics. Pulsed removals result in lower equilibrium population sizes relative to continuous removals, and the differences are greatest at low population growth rates, high removal rates, and with large, infrequent pulses. Furthermore, the timing of the removal pulses (either stochastic or cyclic) affects population size. For example, cyclic removals are less likely than stochastic removals to result in population eradication, but when eradication occurs, the time until eradication is shorter for cyclic than with stochastic removals.Open Access Support Fun