792 research outputs found

    Mass Energy and Flow in closed ecosystems

    Get PDF
    The general equations of biomass and energy transfer for an n-species, closed ecosystem are written. It is demonstrated how in "ecological time" the parameters describing the dynamics of biomass transfer are related to the parameters of energy transfer, such as respiration, fixation, and energy content. This relationship is determinate for the straight-chain ecosystem, and a simple example is worked out. The results show how the density dependent terms in population dynamics arise naturally, and how the stable system exhibits a hierarchy in energy per unit biomass. A procedure is proposed for extending the theory to include webbed systems, and the particular difficulties involved in the extension are brought before the scientific community for discussion

    The mechanical effects of water flow on fish eggs and larvae

    Get PDF
    The impact of mechanical stresses upon ichthyoplankton entrained in power plant cooling systems has long been considered negligible. Arguments and evidence exist, however, to show that such a supposition is not universally true, especially in nuclear power plants. The mechanisms of mechanical damage can be detailed in terms of pressure change, acceleration, and shear stress with in the fluid flow field. Laboratory efforts to quantify the effects of mechanical stress have been very sparse. A well-planned bioassay is urgently needed. (PDF has 11 pages.

    Some effects of tropical storm Agnes on water quality in the Patuxent River estuary

    Get PDF
    A post Agnes study emphasizing environmental factors...weekly sampling at eight stations from 28 June to August 30, 1972. Spatial and temporal changes in the distribution of many factors, e.g., salinity, dissolved oxygen (DO), seston, particulate carbon and nitrogen, inorganic and organic fractions of dissolved nitrogen and phosphorus, and chlorophyll a were studied and compared to earlier extensive records. Patterns shown by the present data were compared especially with a local heavy storm that occurred in the Patuxent drainage basin during July 1963. Some interesting correlations were observed in the data. (PDF has 39 pages.

    Scaling Behaviors of Weighted Food Webs as Energy Transportation Networks

    Full text link
    Food webs can be regarded as energy transporting networks in which the weight of each edge denotes the energy flux between two species. By investigating 21 empirical weighted food webs as energy flow networks, we found several ubiquitous scaling behaviors. Two random variables AiA_i and CiC_i defined for each vertex ii, representing the total flux (also called vertex intensity) and total indirect effect or energy store of ii, were found to follow power law distributions with the exponents α≈1.32\alpha\approx 1.32 and ÎČ≈1.33\beta\approx 1.33, respectively. Another scaling behavior is the power law relationship, Ci∌AiηC_i\sim A_i^\eta, where η≈1.02\eta\approx 1.02. This is known as the allometric scaling power law relationship because AiA_i can be treated as metabolism and CiC_i as the body mass of the sub-network rooted from the vertex ii, according to the algorithm presented in this paper. Finally, a simple relationship among these power law exponents, η=(α−1)/(ÎČ−1)\eta=(\alpha-1)/(\beta-1), was mathematically derived and tested by the empirical food webs

    Modeling the Chesapeake Bay and Tributaries: a synopsis

    Get PDF
    The last decade has seen the development and application of a spectrum of physical and numerical hydrographic models of the Chesapeake Bay and its tributaries. The success of the James River Hydraulic Model has initiated the construction of an estuarine hydraulic model of the entire Chesapeake System. Numerical analogues for hydrographic behavior and contaminant dispersion in one-, two-, and three dimensional model estuaries exist for various regions of the Bay. From an engineering viewpoint, one dimensional models are sufficiently advanced to be routinely employed in aiding management decisions. Bay investigators are playing leading roles in the development of two- and three-dimensional models of estuarine flows

    Some effects of Hurricane Agnes on water quality in the Patuxent River Estuary

    Get PDF
    A post-Agnes study that emphasized environmental factors was carried out on the Patuxent River estuary with weekly sampling at eight stations from 28 June t o 30 August 1972. Spatial and temporal changes in the distribution of many factors , e.g., salinity , dissolved oxygen, seston, particulate carbon and nitrogen, inorganic and organic fractions of dissolved nitrogen and phosphorus, and chlorophyll a were studied and compared t o extensive earlier records. Patterns shown by the present data were compared especially with a local heavy storm that occurred in the Patuxent drainage basin during July 1969. Estimates were made of the amounts of material contributed via upland drainage. A first approximation indicated that 14.8 x l0 (3) metric tons of seston were contributed t o the head of the estuary between 21 and 24 June. (PDF contains 46 pages

    Ghost Images: Representations of Second-Generation Memory in Contemporary Children's Literature

    Get PDF
    Ghost Images: Representations of Second-Generation Memory in Contemporary Children's Literature, studies how texts produced for and about children represent the child's unique capacity to remember events that preceded her/his birth in order to address questions of how traumatic historical events should be remembered and mourned. Drawing on such theorists and critics as Augustine, Maurice Halbwachs, Henri Bergson, Walter Benjamin, Paul Ricoeur, and Marianne Hirsch, I argue that second-generation memory may be defined, first, by its position at the critical intersection between collective and individually-experienced memory, and second, by its reliance upon the mimetic faculty. Insofar as such an order of memory depends heavily on intergenerational relationships between witnesses and their children, and insofar as it depends upon a capacity for mimetic thought and action (which, according to Benjamin, is most dramatically evidenced in the figure of the child) I elaborate of this definition and its implications by performing close readings of recently published texts produced for and/or about children, such as Helen Epstein's Children of the Holocaust, Zlata Filipovic's Zlata's Diary, Marsha Forchuk Skrypuch's The Hunger, Judy Blume's Starring Sally J. Freedman as Herself, and M. Night Shyamalan's feature film, The Sixth Sense. In my analyses of these respective texts, I elaborate on how second-generation memory is shaped by the political discourses of diasporic and national communities, the relationship between the intergenerational and intertextuality, and dominant cultural notions of childhood. Moreover, I consider how the proliferation of texts such as these during the last quarter of the twentieth century may be indicative of a general cultural inclination to memorialize - often without romanticizing - past traumatic events, an inclination that has been largely influenced by the development of the new media, multicultural discourse, and the effects of globalization

    Narrative, Nonfiction, and the Nuclear Other: Western Representations of Chernobyl in the Works of Adam Higginbotham, Serhii Plokhy, and Kate Brown

    Get PDF
    The essay intends to demonstrate how three recent works of non-fiction authored by Western journalists and scholars—Adam Higginbotham’s Midnight in Chernobyl (2019), Plokhy’s Chernobyl: The History of a Nuclear Catastrophe (2018), and Kate Brown’s Manual For Survival: A Chernobyl Guide to the Future (2019)—resist “great man” modes of historiography in order to expose the underlying structural causes and consequences of the Chernobyl disaster. Insofar as they do so, these texts also posit Chernobyl as an event—a literal and figurative historical flashpoint—that was at once an effect of the Cold War and a cause of its conclusion. And yet, although the three studies uphold the central thesis that the massive and unwieldy “Soviet system itself” was largely responsible for the Chernobyl event and in turn the unravelling of the Cold War, they nevertheless arrive at this conclusion through discrete narratives and notably different methodologies. Journalist Higginbotham’s largely omniscient and chronological account of the catastrophe focuses primarily on the consequences of post-1970’s era Soviet “gigantomania” and the subsequent influences of Western “hard” and “soft” diplomacy in mitigating the disaster; Ukrainian-American scholar Plokhy’s history of the event, explicitly framed by the perspective of a [post-] Soviet emigrĂ©, calls attention to how “eco-nationalist” movements that emerged within the post-Chernobyl Soviet Union contributed to its implosion; and environmental historian Kate Brown’s own narrative places into relief her immediate position as an American scholar-traveler in order to expose the relationship between a socio-geographically localized event and Cold War-era nuclear policies that at once were contained by and transgressed geo-political borders. Read together, these three Western works of non-fiction offer a prismatic image of Chernobyl’s spatio-temporal role in the proceedings of and ultimate conclusion to the Cold War. Moreover, and just as crucially, these texts also progressively unsettle overdetermined, triumphalist Western narratives of the Cold War that dwell exclusively on the failures of Soviet nuclear ventures and thus posit the USSR as the West’s “nuclear Other.”Peer reviewe

    A survey for the use of remote sensing in the Chesapeake Bay region

    Get PDF
    Environmental problem areas concerning the Chesapeake Bay region are reviewed along with ongoing remote sensing programs pertaining to these problems, and recommendations are presented to help fill lacunae in present research and to utilize the remote sensing capabilities of NASA to their fullest. A list of interested organizations and individuals is presented for each category. The development of technologies to monitor dissolved nutrients in bay waters, the initiation of a census of the disappearing rooted acquatic plants in the littoral zones, and the mapping of natural building constraints in the growth regions of the states of Maryland and Virginia are among the recommendations presented
    • 

    corecore