7,108 research outputs found
Solar wind data from the MIT plasma experiments on Pioneer 6 and Pioneer 7
Hourly averages are presented of solar wind proton parameters obtained from experiments on the Pioneer 6 and Pioneer 7 spacecraft during the period December 16, 1965 to August 1971. The number of data points available on a given day depends upon the spacecraft-earth distance, the telemetry bit rate, and the ground tracking time allotted to each spacecraft. Thus, the data obtained earlier in the life of each spacecraft are more complete. The solar wind parameters are given in the form of plots and listings. Trajectory information is also given along with a detailed description of the analysis procedures used to extract plasma parameters from the measured data
Failure mechanisms and surface roughness statistics of fractured Fontainebleau sandstone
In an effort to investigate the link between failure mechanisms and the
geometry of fractures of compacted grains materials, a detailed statistical
analysis of the surfaces of fractured Fontainebleau sandstones has been
achieved. The roughness of samples of different widths W is shown to be self
affine with an exponent zeta=0.46 +- 0.05 over a range of length scales ranging
from the grain size d up to an upper cut-off length \xi = 0.15 W. This low zeta
value is in agreement with measurements on other sandstones and on sintered
materials. The probability distributions P(delta z,delta h) of the variations
of height over different distances delta z > d can be collapsed onto a single
Gaussian distribution with a suitable normalisation and do not display
multifractal features. The roughness amplitude, as characterized by the
height-height correlation over fixed distances delta z, does not depend on the
sample width, implying that no anomalous scaling of the type reported for other
materials is present. It is suggested, in agreement with recent theoretical
work, to explain these results by the occurence of brittle fracture (instead of
damage failure in materials displaying a higher value of zeta = 0.8).Comment: 7 page
Interaction of the solar wind with Venus
Two topics related to the interaction of the solar wind with Venus are considered. First, a short review of the experimental evidence with particular attention to plasma measurements carried out on Mariner-5 and Mariner-10 is given. Secondly, the results of some recent theoretical work on the interaction of the solar wind with the ionosphere of Venus are summarized
HAR Inference: Recommendations for Practice
The classic papers by Newey and West (1987) and Andrews (1991) spurred a large body of work on how to improve heteroscedasticity- and autocorrelation-robust (HAR) inference in time series regression. This literature finds that using a larger-than-usual truncation parameter to estimate the long-run variance, combined with Kiefer-Vogelsang (2002, 2005) fixed-b critical values, can substantially reduce size distortions, at only a modest cost in (size-adjusted) power. Empirical practice, however, has not kept up. This article therefore draws on the post-Newey West/Andrews literature to make concrete recommendations for HAR inference. We derive truncation parameter rules that choose a point on the size-power tradeoff to minimize a loss function. If Newey-West tests are used, we recommend the truncation parameter rule S = 1.3T 1/2 and (nonstandard) fixed-b critical values. For tests of a single restriction, we find advantages to using the equal-weighted cosine (EWC) test, where the long run variance is estimated by projections onto Type II cosines, using ν = 0.4T 2/3 cosine terms; for this test, fixed-b critical values are, conveniently, tν or F. We assess these rules using first an ARMA/GARCH Monte Carlo design, then a dynamic factor model design estimated using a 207 quarterly U.S. macroeconomic time series
Charting self-esteem during marital dissolution.
ObjectiveThe purpose of this study was to chart changes in self-esteem before and after marital dissolution to identify the factors that shape individuals' self-esteem during this life transition.MethodWe analyzed 10 annual waves of self-esteem data from 291 divorcees from a nationally representative panel study of the Netherlands (N ~ 13,000). We charted the course of self-esteem before and after marital dissolution and tested a broad set of moderator variables that may shape individuals' self-esteem trajectories.ResultsThe average divorcee experienced significant decrease in self-esteem preceding marital dissolution and remained stable afterward. There were substantial individual differences in self-esteem trajectories, both before and after marital separation. Divorcees who experienced financial hardship, were affiliated with a church or religion, or scored low in Conscientiousness showed the most pronounced decrease in self-esteem during the years approaching marital dissolution.ConclusionThis study highlights the importance of assessing people multiple times before and after marital dissolution to dissect how people approach and respond to this life event. Results are consistent with perspectives that view divorce as an opportunity to abate the strains of an unhappy marriage
An interpretative phenomenological analysis of men’s and women’s coping strategy selection during early IVF treatment
Objectives: To describe the coping strategies that men and women adopted during the early stages of in vitro fertilisation treatment, and explore why and how they selected those strategies. Background: Previous research has identified coping strategies used during fertility treatment and the impact of those strategies on adjustment, but not how and why individuals choose the strategies they did, which is important for understanding coping strategy use as a self-regulatory process. Methods: Three heterosexual couples took part in two or three individual semi-structured interviews over six months, producing fourteen accounts, which were analysed using interpretative phenomenological analysis. Results: The emergent themes were: not dwelling on emotional issues; getting on with treatment; and keeping busy with other things. Participants selected coping strategies in a conscious, deliberate way, by making comparisons with other patients and by drawing on their broader, customary ways of coping. The strategies participants adopted made sense in the context of their long-term goals as well as their short-term treatment objectives. Conclusion: This research shows that for these participants, shorter-term behavioural strategies were informed by longer-term goals, which is consistent with a self-regulatory approach to understanding how people cope with the stress of treatment for infertility.N/
Goitre and Iodine Deficiency in Europe
The prevalence of endemic iodine-deficiency goitre in Europe has been reduced in many areas by the introduction of iodination programmes. Recent reports, however, show that goitre remains a significant problem and that its prevalence has not decreased in a number of European countries. Hetzel1 has pointed out that the high global prevalence of iodine-deficiency disorders could be eradicated within 5-10 years by introduction of an iodised salt programme. The current World Health Organisation recommendations for iodine intake are between 150 and 300 μg/da
Host-symbiont stability and fast evolutionary rates in an ant-bacterium association : cospeciation of Camponotus species and their endosymbionts, Candidatus Blochmannia
Author Posting. © Society of Systematic Biologists, 2004. This article is posted here by permission of Taylor and Francis for personal use, not for redistribution. The definitive version was published in Systematic Biology 53 (2004): 95-110, doi:10.1080/10635150490264842.Bacterial endosymbionts are widespread across several insect orders and are involved in interactions ranging from obligate mutualism to reproductive parasitism. Candidatus Blochmannia gen. nov. (Blochmannia) is an obligate bacterial associate of Camponotus and related ant genera (Hymenoptera: Formicidae). The occurrence of Blochmannia in all Camponotus species sampled from field populations and its maternal transmission to host offspring suggest that this bacterium is engaged in a long-term, stable association with its ant hosts. However, evidence for cospeciation in this system is equivocal because previous phylogenetic studies were based on limited gene sampling, lacked statistical analysis of congruence, and have even suggested host switching. We compared phylogenies of host genes (the nuclear EF-1alphaF2 and mitochondrial COI/II) and Blochmannia genes (16S ribosomal DNA [rDNA], groEL, gidA, and rpsB), totaling more than 7 kilobases for each of 16 Camponotus species. Each data set was analyzed using maximum likelihood and Bayesian phylogenetic reconstruction methods. We found minimal conflict among host and symbiont phylogenies, and the few areas of discordance occurred at deep nodes that were poorly supported by individual data sets. Concatenated protein-coding genes produced a very well-resolved tree that, based on the Shimodaira-Hasegawa test, did not conflict with any host or symbiont data set. Correlated rates of synonymous substitution (dS) along corresponding branches of host and symbiont phylogenies further supported the hypothesis of cospeciation. These findings indicate that Blochmannia-Camponotus symbiosis has been evolutionarily stable throughout tens of millions of years. Based on inferred divergence times among the ant hosts, we estimated rates of sequence evolution of Blochmannia to be sim0.0024 substitutions per site per million years (s/s/MY) for the 16S rDNA gene and sim0.1094 s/s/MY at synonymous positions of the genes sampled. These rates are several-fold higher than those for related bacteria Buchnera aphidicola and Escherichia coli. Phylogenetic congruence among Blochmannia genes indicates genome stability that typifies primary endosymbionts of insects.Funding
for this research was provided by the NIH (R01 GM62626-01), the
NSF (DEB 0089455 and associated REU supplement award), the NASA
Astrobiology Institute (NCC2-1054), and the Josephine Bay Paul and
C. Michael Paul Foundation
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