The linear structural relation for several sets of data

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The ecology of colonial radiolarians : their colony morphology, trophic interactions and associations, behavior, distribution, and the photosynthesis of their symbionts

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1979Colonial radiolarians (Spumellaria) are among the most common and abundant large zooplankton, but they have been little studied by modern biologists. Colonies were found on 98% of epipelagic diving stations in the period from 1977 to 1979. Measured abundances ranged from .04 to 540 colonies per m3. Colony morphology of common genera and species is described and three new shell-less species which reach a length in excess of 1 m are discussed in detail. Some simple behavioral responses are documented, including control of colony buoyancy and position of algae in the colonies. Radiolarians feed on a wide variety of planktonic organisms including tintinnids, copepods, appendicularians, mollusc larvae and hydromedusae. They are hosts to parasitic hyperiid amphipods, particularly those of the genus Hyperietta. Radiolarians are prey of the amphipod Oxycephaius ciausi, an unidentified turbellarian and possibly the Harpacticoid copepods Miracia efferata and Sapphirina sp. Colonial radiolarians are also hosts to symbiotic dinoflagellates. Experiments were done at sea on the net incorporation of CO2 by these algae using 14C labelled NaHC03. Data from these experiments were related to content of carbon and chlorophyll as a function of colony size (cell number). Carbon content of colonies related well with colony size. Mean values were 50, 85, 100 and 200 ng C per radiolarian cell for coiiozoum inerme, C. iongiforme, Acrosphaera spinosa and coiiozoum radiosum respectively. Chlorophyll content varied widely between colonies and chlorophyll per radiolarian cell decreased with increasing colony size in Acrosphaera spinosa. Net carbon incorporation increased with colony size at given light intensities as did phutosynthetic assimilation (mmoles CO2.mg Chl a -l.hr -1) in A. spinosa. In experiments on the effect of light intensity on photosynthesis, there was no evidence for photoinhibition at high intensities in Acrosphaera spinosa. Replicate pieces of the large colonies of C. longiforme were incubated together, each colony at a different light intensity. Representative pieces were measured and used for chlorophyll carbon and nitrogen analysis and counted for abundance of radiolarian and algal cells and tintinnid prey. Incorporation per unit length varied little within colonies Photosynthetic assimilation followed no predictable pattern as a function of light intensity. However, it related directly to abundance of tintinnid prey remains. This effect apparently overrides that of light intensity. Total photosynthesis incorporation was only 0.1 to 0.8% of the total colony carbon per hour. The contribution of colonial radiolarians to total productivity of the regions studied was insignificant. However, the radiolarians' productivity is available to a unique portion of the planktonic food web. Because of their size and abundance radiolarians are important as substrates in their environment.This research was supported in part by the Woods Hole Oceanographic Institution Education Program and the National Science Foundation, Oceanographic Section, Grant Nos. OCE75-2l7l5 and OCE77-225ll

Tracking interacting dust: comparison of tracking and state estimation techniques for dusty plasmas

When tracking a target particle that is interacting with nearest neighbors in a known way, positional data of the neighbors can be used to improve the state estimate. Effects of the accuracy of such positional data on the target track accuracy are investigated in this paper, in the context of dusty plasmas. In kinematic simulations, notable improvement in the target track accuracy was found when including all nearest neighbors in the state estimation filter and tracking algorithm, whereas the track accuracy was not significantly improved by higher-accuracy measurement techniques. The state estimation algorithm, involving an extended Kalman filter, was shown to either remove or significantly reduce errors due to "pixel locking". It is concluded that the significant extra complexity and computational expense to achieve these relatively small improvements are likely to be unwarranted for many situations. For the purposes of determining the precise particle locations, it is concluded that the simplified state estimation algorithm can be a viable alternative to using more computationally-intensive measurement techniques.Comment: 11 pages, 6 figures, Conference paper: Signal and Data Processing of Small Targets 2010 (SPIE

Tensor damping in metallic magnetic multilayers

The mechanism of spin-pumping, described by Tserkovnyak et al., is formally analyzed in the general case of a magnetic multilayer consisting of two or more metallic ferromagnetic (FM) films separated by normal metal (NM) layers. It is shown that the spin-pumping-induced dynamic coupling between FM layers modifies the linearized Gilbert equations in a way that replaces the scalar Gilbert damping constant with a nonlocal matrix of Cartesian damping tensors. The latter are shown to be methodically calculable from a matrix algebra solution of the Valet-Fert transport equations. As an example, explicit analytical results are obtained for a 5-layer (spin-valve) of form NM/FM/NM'/FM/NM. Comparisons with earlier well known results of Tserkovnyak et al. for the related 3-layer FM/NM/FM indicate that the latter inadvertently hid the tensor character of the damping, and instead singled out the diagonal element of the local damping tensor along the axis normal to the plane of the two magnetization vectors. For spin-valve devices of technological interest, the influence of the tensor components of the damping on thermal noise or spin-torque critical currents are strongly weighted by the relative magnitude of the elements of the nonlocal, anisotropic stiffness-field tensor-matrix, and for in-plane magnetized spin-valves are generally more sensitive to the in-plane element of the damping tensor.Comment: 16 pages (manuscript form). 2 embedded figures. Likely to be submitted for publication. Version 2 has a revised Introduction section more suitable for pulication, and additional relevant references (Ref. 5. and particularly Ref. 6, along with an acknowledgment). Eqs. 9, 21, and 22 were slightly modified for improved clarity and/or consistanc

Ideal gas behavior of a strongly-coupled complex (dusty) plasma

In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly-coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.Comment: 5 pages, 5 figures, 5 authors, published versio

A practical action perspective and understanding on becoming a networked learning educator

In the paper we examine one of the enduring issues in networked learning of the reticence of academics to work with and/or run networked learning courses mediated by technology. The paper is based on an analysis of the situated practice of members of an academic department and the work done in becoming a networked learning educator. It builds on the recent interest in practice based studies (PBS) that has led to an increase in looking at learning and knowing through the doing of practice. Following Schatzki, (2001) we see practice as an embodied and materially mediated activity around practical understanding. The research approach we have chosen to look at this is that associated with ethnomethodology; which has a long-standing interest in the understanding of practical action. In the paper we offer an account of the social fact of the competent university teacher as constructed in what Garfinkel (1967) refers to as ‘common understanding’ exhibited in the methods used and descriptions of practice-in-action of members of the department. We go on to examine an account of designing an online module and the practice-in-action exhibited by Emma in becoming a networked learning educator. We conclude with the suggestion that the pattern and rhythm of said module could be used as a starting point for a pedagogical framework that can accommodate and/or exhibit the practical understanding of pedagogy for members of the department