Heteroduplex analysis of tra delta f' plasmids and the mechanism of their formation

Four tra delta FargG+ plasmids, derived from matings between Hfr AB312 and a recA recipient, have been shown to have deletions of at least 50% of the F genome, including the region in which the tra genes map. The mutant plasmids do contain the F genes required for plasmid maintenance. Correlations can be made between, on the one hand, the F genes present on the tradelta F' plasmids and the F genes transferred early by an Hfr donor, and, on the other hand, the F genes deleted from the tradelta F' plasmids and the F genes transferred late by an Hfr donor. A biased representation of proximally and distally transferred chromosomal markers among the tradelta F' elements was also demonstrated. Taken Taken together, the asymmetrical representation of Hfr genes and the cis dominance of the Tra phenotype of these mutants can best be explained by the hypothesis that the tradelta F' plasmids are formed by repliconation of the transferred exogenote in a recA recipient

Kinetics governing phase separation of nanostructured Sn_xGe_(1–x) alloys

We have studied the dynamic phenomenon of Sn_xGe_(1–x)/Ge phase separation during deposition by molecular beam epitaxy on Ge(001) substrates. Phase separation leads to the formation of direct band gap semiconductor nanowire arrays embedded in Ge oriented along the [001] growth direction. The effect of strain and composition on the periodicity were decoupled by growth on Ge(001) and partially relaxed Si_yGe_(1–y)/Ge(001) virtual substrates. The experimental results are compared with three linear instability models of strained film growth and find good agreement with only one of the models for phase separation during dynamic growth

Clinical outcome of instrumented fusion for the treatment of failed back surgery syndrome: a case series of 100 patients

Scientific Assessment and Innovation in Neurosurgical Treatment Strategie

Musical events and perceptual ecologies

This paper, followed by two responses, discusses the application of ecological theory to an understanding of a number of issues in the aesthetics of music. It argues for an understanding of music as based in event perception, with an expanded conception of the sources that are specified by those events. Building on the theory of affordances, it considers the limitations of an information theoretic conception of musical complexity, discusses the importance of perceptual learning (understood as shaping by a structured environment) in understanding the affordances of music for different listeners, and raises the challenging problem of the terms in which musical materials might be appropriately described. The apparent tension between ecological and aesthetic positions—in which adaptation and accommodation seem to be at odds with a modernist aesthetic perspective which prioritizes the unsettling and defamiliarizing function of art—is confronted, before the paper concludes with some observations about different disciplinary perspectives on aesthetics, and matters of specificity and generality

Elatinaceae are Sister to Malpighiaceae; Peridiscaceae Belong to Saxifragales

Phylogenetic data from plastid (ndhF and rbcL) and nuclear (PHYC) genes indicate that, within the order Malpighiales, Elatinaceae are strongly supported as sister to Malpighiaceae. There are several putative morphological synapomorphies for this clade; most notably, they both have a base chromosome number of X = 6 (or some multiple of three or six), opposite or whorled leaves with stipules, unicellular hairs (also uniseriate in some Elatinaceae), multicellular glands on the leaves, and resin (Elatinacae) or latex (Malpighiaceae). Further study is needed to determine if these features are synapomorphic within the order. Malpighiaceae have previously been inferred as sister to Peridiscaceae based on rbcL sequence data, but the rbcL sequence of Whittonia is a chimera of two sequences, neither of which appears to be Whittonia. Our data from plastid (atpB, rbcL) and nuclear (18S rDNA) genes instead place Peridiscaeace as a member of the Saxifragales.Organismic and Evolutionary Biolog

Temporal changes in key maternal and fetal factors affecting birth outcomes: A 32-year population-based study in an industrial city

<p>Abstract</p> <p>Background</p> <p>The link between maternal factors and birth outcomes is well established. Substantial changes in society and medical care over time have influenced women's reproductive choices and health, subsequently affecting birth outcomes. The objective of this study was to describe temporal changes in key maternal and fetal factors affecting birth outcomes in Newcastle upon Tyne over three decades, 1961–1992.</p> <p>Methods</p> <p>For these descriptive analyses we used data from a population-based birth record database constructed for the historical cohort <b>Pa</b>rticulate <b>M</b>atter and <b>P</b>erinatal <b>E</b>vents <b>R</b>esearch (PAMPER) study. The PAMPER database was created using details from paper-based hospital delivery and neonatal records for all births during 1961–1992 to mothers resident in Newcastle (out of a total of 109,086 singleton births, 97,809 hospital births with relevant information). In addition to hospital records, we used other sources for data collection on births not included in the delivery and neonatal records, for death and stillbirth registrations and for validation.</p> <p>Results</p> <p>The average family size decreased mainly due to a decline in the proportion of families with 3 or more children. The distribution of mean maternal ages in all and in primiparous women was lowest in the mid 1970s, corresponding to a peak in the proportion of teenage mothers. The proportion of older mothers declined until the late 1970s (from 16.5% to 3.4%) followed by a steady increase. Mean birthweight in all and term babies gradually increased from the mid 1970s. The increase in the percentage of preterm birth paralleled a two-fold increase in the percentage of caesarean section among preterm births during the last two decades. The gap between the most affluent and the most deprived groups of the population widened over the three decades.</p> <p>Conclusion</p> <p>Key maternal and fetal factors affecting birth outcomes, such as maternal age, parity, socioeconomic status, birthweight and gestational age, changed substantially during the 32-year period, from 1961 to 1992. The availability of accurate gestational age is extremely important for correct interpretation of trends in birthweight.</p