266 research outputs found
Variations in Chlorophyll and Carotenoid Pigmentation Among Prochloron (Prochlorophyta) Symbionts in Diverse Marine Ascidians
High-performance liquid chromatography (HPLC) was used to separate and quantify chlorophylls a and b as well as major carotenoid pigments present in freeze-dried preparations of diverse Prochloron- didemnid associations and in Prochloron cells separated from host colonies. Both chlorophyll a and b were consistently observed in each association. Chlorophyll a : b ratios ranged from 4.14 to 19.71. Ratio differences reflected species differences among didemnid hosts, which proved consistent over time and space. Generally good agreement was found between ratios determined in isolated cell preparations and in symbiotic colonies (in hospite). These values are 1.5 to 5-fold higher than ratios determined in a variety of eukaryotic green plants. The carotenoids in Prochloron are quantitatively and qualitatively similar to those found in various freshwater and marine cyanophytes from high-light environments. However, Prochloron differs from most cyanophytes in the absence of myxoxanthophyll and related glycosidic carotenoids. The consistent presence of chlorophyll b and individuality in carotenoid pigmentation render Prochloron biochemically distinct from cyanophytes, despite the fact that cells of both prokaryotic groups are often found in light-saturated environments
The Impact of Counterstereotypic Training and Related Correction Processes on the Application of Stereotypes
Small grid embeddings of 3-polytopes
We introduce an algorithm that embeds a given 3-connected planar graph as a
convex 3-polytope with integer coordinates. The size of the coordinates is
bounded by . If the graph contains a triangle we can
bound the integer coordinates by . If the graph contains a
quadrilateral we can bound the integer coordinates by . The
crucial part of the algorithm is to find a convex plane embedding whose edges
can be weighted such that the sum of the weighted edges, seen as vectors,
cancel at every point. It is well known that this can be guaranteed for the
interior vertices by applying a technique of Tutte. We show how to extend
Tutte's ideas to construct a plane embedding where the weighted vector sums
cancel also on the vertices of the boundary face
Svestka's Research: Then and Now
Zdenek Svestka's research work influenced many fields of solar physics,
especially in the area of flare research. In this article I take five of the
areas that particularly interested him and assess them in a "then and now"
style. His insights in each case were quite sound, although of course in the
modern era we have learned things that he could not readily have envisioned.
His own views about his research life have been published recently in this
journal, to which he contributed so much, and his memoir contains much
additional scientific and personal information (Svestka, 2010).Comment: Invited review for "Solar and Stellar Flares," a conference in honour
of Prof. Zden\v{e}k \v{S}vestka, Prague, June 23-27, 2014. This is a
contribution to a Topical Issue in Solar Physics, based on the presentations
at this meeting (Editors Lyndsay Fletcher and Petr Heinzel
Attitudes toward westbound refugees in the East German press
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67107/2/10.1177_002200277001400303.pd
Health inequalities, fundamental causes and power:Towards the practice of good theory
Reducing health inequalities remains a challenge for policy makers across the world. Beginning from Lewin’s famous dictum that “there is nothing as practical as a good theory”, this paper begins from an appreciative discussion of ‘fundamental cause theory’, emphasizing the elegance of its theoretical encapsulation of the challenge, the relevance of its critical focus for action, and its potential to support the practical mobilisation of knowledge in generating change. Moreover, it is argued that recent developments in the theory, provide an opportunity for further theoretical development focused more clearly on the concept of power (Dickie et al. 2015). A critical focus on power as the essential element in maintaining, increasing or reducing social and economic inequalities – including health inequalities – can both enhance the coherence of the theory, and also enhance the capacity to challenge the roots of health inequalities at different levels and scales. This paper provides an initial contribution by proposing a framework to help to identify the most important sources, forms and positions of power, as well as the social spaces in which they operate. Subsequent work could usefully test, elaborate and adapt this framework, or indeed ultimately replace it with something better, to help focus actions to reduce inequalities
Microflares and the Statistics of X-ray Flares
This review surveys the statistics of solar X-ray flares, emphasising the new
views that RHESSI has given us of the weaker events (the microflares). The new
data reveal that these microflares strongly resemble more energetic events in
most respects; they occur solely within active regions and exhibit
high-temperature/nonthermal emissions in approximately the same proportion as
major events. We discuss the distributions of flare parameters (e.g., peak
flux) and how these parameters correlate, for instance via the Neupert effect.
We also highlight the systematic biases involved in intercomparing data
representing many decades of event magnitude. The intermittency of the
flare/microflare occurrence, both in space and in time, argues that these
discrete events do not explain general coronal heating, either in active
regions or in the quiet Sun.Comment: To be published in Space Science Reviews (2011
GJ 367b: a dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star
Stars and planetary system
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