A statistical study of variation in the catch of plankton nets

Staternent of the Problern.----In a previous communication, Winsor and Walford (1936) analyzed the results of repeated vertical hauls of different types of plankton nets, making use of data available in the literature. They concluded that the observed results could be accounted for reasonably well on the assumptions that (a) the organisms were randomly distributed in the medium and (b) that the volume of medium effectively sampled varied from haul to haul. From this result it follows that as the total catch is increased (as by increasing the net size) the reliability of a population estimate is ultimately limited by variation in volume sampled; and that where such conditions hold, it is useless to attempt greater accuracy by increasing either the total catch or the fraction counted much beyond the point where 100 organisms of the kind in question are counted

Linking the 8.2 ka Event and its Freshwater Forcing in the Labrador Sea

The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in (delta)18O of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we demonstrate that approx. 3 C of near-surface ocean cooling masked an 1.0 % decrease in western Labrador Sea (delta)18O of seawater concurrent with Lake Agassiz drainage. Comparison with North Atlantic (delta)18O of seawater records shows that the freshwater discharge was transported to regions of deep-water formation where it could perturb AMOC and force the 8.2 ka event

Evidence for the Gompertz Curve in the Income Distribution of Brazil 1978-2005

This work presents an empirical study of the evolution of the personal income distribution in Brazil. Yearly samples available from 1978 to 2005 were studied and evidence was found that the complementary cumulative distribution of personal income for 99% of the economically less favorable population is well represented by a Gompertz curve of the form $G(x)=\exp [\exp (A-Bx)]$, where $x$ is the normalized individual income. The complementary cumulative distribution of the remaining 1% richest part of the population is well represented by a Pareto power law distribution $P(x)= \beta x^{-\alpha}$. This result means that similarly to other countries, Brazil's income distribution is characterized by a well defined two class system. The parameters $A$, $B$, $\alpha$, $\beta$ were determined by a mixture of boundary conditions, normalization and fitting methods for every year in the time span of this study. Since the Gompertz curve is characteristic of growth models, its presence here suggests that these patterns in income distribution could be a consequence of the growth dynamics of the underlying economic system. In addition, we found out that the percentage share of both the Gompertzian and Paretian components relative to the total income shows an approximate cycling pattern with periods of about 4 years and whose maximum and minimum peaks in each component alternate at about every 2 years. This finding suggests that the growth dynamics of Brazil's economic system might possibly follow a Goodwin-type class model dynamics based on the application of the Lotka-Volterra equation to economic growth and cycle.Comment: 22 pages, 15 figures, 4 tables. LaTeX. Accepted for publication in "The European Physical Journal B

Pressure Induced Topological Phase Transitions in Membranes

Some highly unusual features of a lipid-water liquid crystal are revealed by high pressure x-ray diffraction, light scattering and dilatometric studies of the lamellar (bilayer $L_{\alpha}$) to nonlamellar inverse hexagonal ($H_{II}$) phase transition. (i) The size of the unit cell of the $H_{II}$ phase increases with increasing pressure. (ii) The transition volume, $\Delta V_{bh}$, decreases and appears to vanish as the pressure is increased. (iii) The intensity of scattered light increases as $\Delta V_{bh}$ decreases. Data are presented which suggest that this increase is due to the formation of an intermediate cubic phase, as predicted by recent theoretical suggestions of the underlying universal phase sequence.Comment: 12 pages, typed using REVTEX 2.

Expanding Efficiency: Women\u27s Communication in Engineering

As engineering fields strive to be more inclusive of women, focusing on perceptions of women\u27s work is vital to understanding how women can succeed and the limitations they may face. One area in need of more attention is the connection between communication and women\u27s experiences in engineering. This article examines the gendered nature of writing labor in engineering, focusing on case studies of three women who were able to use writing effectively, yet how communication emerged as a gendered form of labor subject to gendered perceptions. While these women\u27s communication skills led to professional success, their association with writing echoes a historical division, where writing is viewed as less valuable than technical knowledge. This division has the potential to disadvantage women who are asked to take on more writing-related tasks. In addition, their writing and communication are subject to gendered perceptions of being ‘chatty’ or blunt rather than effective or efficient. Articulating these perceptions and attitudes can lead to a breakdown of the binary between writing and technical labor as well as appropriately valuing the contributions women make in engineering through writing

Comparative genomics of isolates of a pseudomonas aeruginosa epidemic strain associated with chronic lung infections of cystic fibrosis patients

Pseudomonas aeruginosa is the main cause of fatal chronic lung infections among individuals suffering from cystic fibrosis (CF). During the past 15 years, particularly aggressive strains transmitted among CF patients have been identified, initially in Europe and more recently in Canada. The aim of this study was to generate high-quality genome sequences for 7 isolates of the Liverpool epidemic strain (LES) from the United Kingdom and Canada representing different virulence characteristics in order to: (1) associate comparative genomics results with virulence factor variability and (2) identify genomic and/or phenotypic divergence between the two geographical locations. We performed phenotypic characterization of pyoverdine, pyocyanin, motility, biofilm formation, and proteolytic activity. We also assessed the degree of virulence using the Dictyostelium discoideum amoeba model. Comparative genomics analysis revealed at least one large deletion (40-50 kb) in 6 out of the 7 isolates compared to the reference genome of LESB58. These deletions correspond to prophages, which are known to increase the competitiveness of LESB58 in chronic lung infection. We also identified 308 non-synonymous polymorphisms, of which 28 were associated with virulence determinants and 52 with regulatory proteins. At the phenotypic level, isolates showed extensive variability in production of pyocyanin, pyoverdine, proteases and biofilm as well as in swimming motility, while being predominantly avirulent in the amoeba model. Isolates from the two continents were phylogenetically and phenotypically undistinguishable. Most regulatory mutations were isolate-specific and 29% of them were predicted to have high functional impact. Therefore, polymorphism in regulatory genes is likely to be an important basis for phenotypic diversity among LES isolates, which in turn might contribute to this strain's adaptability to varying conditions in the CF lung

Magnetic confinement of an electric arc in transverse supersonic flow

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77344/1/AIAA-2803-657.pd

Adaptive remodeling of the bacterial proteome by specific ribosomal modification regulates Pseudomonas infection and niche colonisation

Post-transcriptional control of protein abundance is a highly important, underexplored regulatory process by which organisms respond to their environments. Here we describe an important and previously unidentified regulatory pathway involving the ribosomal modification protein RimK, its regulator proteins RimA and RimB, and the widespread bacterial second messenger cyclic-di-GMP (cdG). Disruption of rimK affects motility and surface attachment in pathogenic and commensal Pseudomonas species, with rimK deletion significantly compromising rhizosphere colonisation by the commensal soil bacterium P. fluorescens, and plant infection by the pathogens P. syringae and P. aeruginosa. RimK functions as an ATP-dependent glutamyl ligase, adding glutamate residues to the C-terminus of ribosomal protein RpsF and inducing specific effects on both ribosome protein complement and function. Deletion of rimK in P. fluorescens leads to markedly reduced levels of multiple ribosomal proteins, and also of the key translational regulator Hfq. In turn, reduced Hfq levels induce specific downstream proteomic changes, with significant increases in multiple ABC transporters, stress response proteins and non-ribosomal peptide synthetases seen for both ΔrimK and Δhfq mutants. The activity of RimK is itself controlled by interactions with RimA, RimB and cdG. We propose that control of RimK activity represents a novel regulatory mechanism that dynamically influences interactions between bacteria and their hosts; translating environmental pressures into dynamic ribosomal changes, and consequently to an adaptive remodeling of the bacterial proteome