1,368 research outputs found

    Studies on the respiratory pigment of Urechis eggs

    Get PDF
    Experiments previously reported (1) have shown that the eggs of the Pacific marine worm, Urechis caupo, contain a reversible oxidation-reduction pigment. The pigment, called urechrome, is autoxidizable and changes color from red to yellow on oxidation. It is soluble in water (reduced form insoluble below pH 5) and in acidified methanol, but insoluble in ether, acetone, chloroform, and neutral alcohol. Evidence for participation of the pigment in cellular respiration has been previously given

    The Onset of Chaos in Pulsating Variable Stars

    Full text link
    Random changes in pulsation period occur in cool pulsating Mira variables, Type A, B, and C semiregular variables, RV Tauri variables, and in most classical Cepheids. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of the envelope convection in such stars. Such fluctuations are seemingly random over a few pulsation cycles of the stars, but are dominated by the regularity of the primary pulsation over the long term. The magnitude of stochasticity in pulsating stars appears to be linked directly to their dimensions, although not in simple fashion. It is relatively larger in M supergiants, for example, than in short-period Cepheids, but is common enough that it can be detected in visual observations for many types of pulsating stars. Although chaos was discovered in such stars 80 years ago, detection of its general presence in the group has only been possible in recent studies.Comment: To appear in the proceedings of the Odessa Variable Stars 2010 Conference (see http://uavso.org.ua/?page=vs2010&lang=en), edited by I. Andronov and V. Kovtyuk

    Stochastic Processes in Yellow and Red Pulsating Variables

    Full text link
    Random changes in pulsation period are well established in cool pulsating stars, in particular the red giant variables: Miras, semi-regulars of types A and B, and RV Tau variables. Such effects are also observed in a handful of Cepheids, the SX Phe variable XX Cyg, and, most recently, the red supergiant variable, BC Cyg, a type C semi-regular. The nature of such fluctuations is seemingly random over a few pulsation cycles of the stars, yet the regularity of the primary pulsation mechanism dominates over the long term. The degree of stochasticity is linked to the dimensions of the stars, the randomness parameter 'e' appearing to correlate closely with mean stellar radius through the period 'P', with an average value of e/P = 0.0136+-0.0005. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of envelope convection in such stars.Comment: Poster given at the "Stellar Pulsation: Challenges for Theory and Observation" conference in Santa Fe, New Mexico (2009

    Redefining Global Food Security: Do we really have a Global Food Crisis?

    Get PDF
    With the Climate change effects becoming more and more undoubted in the world populations, the reality of food production trends taking a negative curve is clear. This bring up the questions of whether the farmers will be able to produce food for the sustenance of the world population or not? The rate of developing food shortage coping mechanisms in this regard is slower that the ravaging negative climate change effects of drought and floods on farm performance. This commentary has the aim of requesting a fresh discussion around the fundamentals of what is food, what is a food security and what is nutritional security? It is possible that the humanity has a perception that needs refocusing. This is a perception that some people may choose out of non-food safety issues not to eat certain foods while other however healthily eat such food. It therefore becomes hard to technically accept that food is in short supply for those the opt not to eat that which is edible

    The H-alpha Variations of the Luminous Blue Variable P Cygni: Discrete Absorption Components and the Short S Doradus Phase

    Full text link
    P Cygni is a prototype of the Luminous Blue Variables (or S Doradus variables), and the star displays photometric and emission line variability on a timescale of years (known as the "short S Doradus phase" variations). Here we present new high resolution H-alpha spectroscopy of P Cyg that we combine with earlier spectra and concurrent V-band photometry to document the emission and continuum flux variations over a 24 y time span. We show that the emission and continuum fluxes vary in concert on timescales of 1.6 y and longer, but differ on shorter timescales. The H-alpha profile shape also varies on the photometric timescales, and we describe the observed co-variations of the emission peak and absorption trough properties. We argue that the episodes of photometric and emission brightening are caused by increases in the size of the emission region that are related to variations in wind mass loss rate and outflow speed. We find evidence of blueward accelerating, Discrete Absorption Components (DACs) in the absorption trough of the H-alpha profile, and these features have slower accelerations and longer durations than those observed in other lines. The DAC strengths also appear to vary on the photometric timescales, and we suggest that the propagation of the DAC-related wind structures is closely related to changes in the overall wind mass loss rate and velocity.Comment: 43 pages, 11 figures, 1 table, accepted to A

    Love, rights and solidarity: studying children's participation using Honneth's theory of recognition

    Get PDF
    Recent attempts to theorize children’s participation have drawn on a wide range of ideas, concepts and models from political and social theory. The aim of this article is to explore the specific usefulness of Honneth’s theory of a ‘struggle for recognition’ in thinking about this area of practice. The article identifies what is distinctive about Honneth’s theory of recognition, and how it differs from other theories of recognition. It then considers the relevance of Honneth’s conceptual framework to the social position of children, including those who may be involved in a variety of ‘participatory’ activities. It looks at how useful Honneth’s ideas are in direct engagement with young people’s praxis, drawing on ethnographic research with members of a children and young people’s forum. The article concludes by reflecting on the implications of this theoretical approach and the further questions which it opens up for theories of participation and of adult–child relations more generally

    SOME THOUGHTS ON FUTURE OF OTHER STATE FORESTS IN SRI LANKA

    Get PDF
    The agricultural frontier in the country has been expanding in recent years, primarilythrough the alienation and leasing out of large extents of forested state land to landlesspersons and also through encroachments. The remaining unutilized state lands also carryforests, and the demand for agricultural land in the future will have to be met by selectingfrom these areas, lands that are best suited for agricultural development.State land available for agriculture and other development purposes are currentlydesignated as Other State Forests (OSF). A part of the OSF is under the jurisdiction of theConservator of Forests and a part under the Divisional Secretaries. Much of this land inthe Wet Zone has either been distributed or encroached upon and hence the bulk of theOSF is to be found in the Dry and Intermediate Zones. The forest cover on these landshave been denuded because of widespread chena cultivation and therefore what remainstoday is sparse forest.As population increases, the demand for land from various users will increase and thisdemand will have to be met by the OSF. It is therefore very essential that all of the OSF inthe country are evaluated and divided into different land use categories. Initially, landssuitable for forestry should be separated and devoted exclusively to forestry development.The balance area will represent the lands available for other uses.The paper is in two parts. Part I will examine the need for catergorising OSF. Part II willpresents a methodology for categorising these lands based on 2 case studies undertaken inthe Anuradhapura and Ratnapura districts.

    Overview of feasibility study on conducting overflight measurements of shaped sonic boom signatures using RPV's

    Get PDF
    Before beginning this presentation, it is appropriate to acknowledge the sincere interest and financial support provided by the NASA LaRC under contract NAS9-17900. An outline of the material to be used in the present paper is given. It begins with a indication of the origin and objectives of the feasibility study. This is followed by a discussion of various simulation methods of establishing the persistence of shaped sonic boom signatures to large distances including the use of recoverable RPV/drones. The desirable features to be sought out in an RPV along with a rationale for the selection of a 'shaped' sonic boom signature will be addressed. Three candidate vehicles are examined as to their suitability with respect to a number of factors, in particular, modifiability. Area distributions and associated sonic boom signatures of the basic and modified Firebee vehicle will also be shown. An indication of the scope of the proposed wind tunnel and flight test programs will be presented including measurement technologies and predicted waveforms. Finally, some remarks will be made summarizing the study and highlighting the key findings
    corecore