Seasonal and Diel Patterns of Abundance and Productivity of Phototrophic Picoplankton in the Lower Chesapeake Bay

This study was performed to evaluate phototrophic pico-plankton (0.2 to 2.0 μm) dynamics within the lower Chesapeake Bay. A 15 month study of phototrophic picoplankton abundance and productivity was made from June 1988 to October 1989. Annual picoplankton abundance using epifluorescence microscopy ranged from 7.26 x 106 cells/1 in the winter to 9.28 x 108 cells/1 during late summer. In situ incubations of natural picoplankton populations over the 15 month study were used to test the applicability of the frequency of dividing cells technique in estimating phototrophic picoplankton growth rates. The regression equation o fμ = 2.37 x 10-3 (FDC) + 0.024 was developed to estimate phototrophic picoplankton growth rates in the lower Chesapeake Bay where productivity values were estimated using phototrophic picoplankton abundance and carbon content. Limitations and improvements in using the frequency of dividing cells technique were discussed. Productivity estimates using both frequency of dividing cells and sodium 14C-bicarbonate fractionation techniques identified phototrophic picoplankton contributing over 50% of total primary productivity during the summer season. Two high frequency diel studies measuring phototrophic picoplankton abundance and productivity in summer and winter seasons revealed physical factors in the water column partly determining phototrophic picoplankton distribution. Higher phototrophic picoplankton concentrations were associated with waters seasonally above the pycnocline. In summer, phototrophic picoplankton concentrations were highest during ebb tide when the dominant phototrophic picoplankton was phycocyanin enriched Synechococcus sp. In winter, phototrophic picoplankton concentrations were highest during flood tide when phycoerythrin enriched Synechococcus sp. dominated phototrophic picoplankton composition. Availability of phototrophic picoplankton carbon within the water column is discussed as to its influence to Bay trophodynamics

Seasonal Phytoplankton Development Within Three Rivers in the Lower Chesapeake Bay Region

The seasonal and inter-annual concentrations of phytoplankton were studied over a 50 month period in the lower James, York and Rappahannock Rivers (USA). Differences in the onset, duration and magnitude of major seasonal growth periods varied from year to year. There was a tendency for spring, summer and fall maxima, with a winter period of reduced abundance. An additional study of picoplankton over a 12 month period indicated greatest abundance during summer and fall, with least development in winter

PENSARE LA CONCILIAZIONE. IL CONCETTO DI CUORE IN PASCAL

La tesi di dottorato mira a mostrare il metodo e al tempo stesso il contenuto prezioso del cuore nella filosofia di Blaise Pascal. Il cuore suggerisce nella filosofia, nella lettura proposta, il tema della "conciliazione". Il tema del cuore infatti mostra non tanto o non solo una opposizione con la ragione, ma un accrescimento della ragione stessa, ovvero un recupero di quella dimensione patica che il razionalismo moderno tende a mettere da parte.This thesis aims to show the method and at the same time the precious content of the heart in the philosophy of Blaise Pascal. The heart proposes the theme of conciliation in philosophy. The theme of the heart in fact shows not an opposition with reason, but an increase in reason itself

Review of Diane Ravitch\u27s Book, The Life and Death of American Public Schools,”

“And who are you and why are you here?” asked a student my first day of my practicum at a public middle school in lower Manhattan. “I am here from NYU to help you with your reading,” I responded with a friendly smile. Looking back at this exchange, I realized that not only did I work hard to help and gain acceptance from the students, I was working just as hard to learn more about public school structures, specifically since I was in NY, the bureaucratic structure that is the NYC Board of Education. While I was working in the schools, I began to open my eyes wider and dig deeper to see what really was occurring in the schools. Diane Ravitch, a historian of education and also an NYU professor does the same in her book, “The Life and Death of American Public Schools.” I was lucky enough to hear her speak at the 2011 National Council for the Social Studies Conference in Washington D.C. Her speech discussed various educational reforms and displayed statistics reporting how schools are doing before and after the reforms. Ravitch concluded that the same reforms that were intended to make public education better are in fact making it worse

Stormwater Influence on Phytoplankton Composition and Dynamics in Lake Joyce, Virginia

A three year study of Lake Joyce, Virginia revealed relationships between the timing, duration, and amount of stormwater runoff and phytoplankton abundance and composition. Major phytoplankton taxa were identified and cyanophytes dominanted during periods of decreased rainwater input and increased lake water retention times. Increased freshwater input was associated with the growth of a diverse assemblage of both chlorophytes and diatoms. Phytoplankton dynamics as a result of significant rain events (i.e., hurricanes Floyd and Irene, 1999) were documented and specific taxa involved in nuisance algal blooms were identified

Environmental Factors Contributing to the Disaggregation of a Colonial Cyanoprokaryote and Its Influence on Picoplankton Abundance within Lake Joyce, Virginia

A colonial cyanoprokaryote, Aphanocapsa holsatica and autotrophic picoplankton abundance were monitored weekly over a two year period in Lake Joyce, Virginia. Significant differences were observed in both the cyanoprokaryote and picoplankton abundance over the study period and an inverse relationship was observed between these two plankton groups. Disaggregation of colonies was shown to contribute to picoplankton populations where water temperature and precipitation input apparently trigger colony dispersion. This relationship is suggested to occur in other aquatic habitats. Results of this work and its implications for ecosystem dynamics are discussed

Interstitial chemotherapy with biodegradable BCNU (Gliadel®) wafers in the treatment of malignant gliomas

Malignant gliomas represent the majority of primary brain tumors, and the prognosis of the patients afflicted with these tumors has been historically dismal, with almost uniform progressive neurologic impairment and rapid death. Even with multimodal treatment using surgery, focal radiation, and chemotherapy, no major strides were made until recently. The development of interstitial BCNU wafers (carmustine wafers, Gliadel®) has led to promising results in the treatment of a selected patients with malignant gliomas, as well as with other intracranial malignancies.BCNU is one of the first systemic chemotherapies which had obtained United States Food and Drug Administration (FDA) approval for the treatment of brain tumors. However, systemic use has been hampered by the modest prolongation of survival and by the prolonged myelosuppression and potentially fatal pulmonary toxicity. The development of interstitial therapies with BCNU represented a great step forward, allowing direct delivery to the tumor bed, with virtually no systemic toxicities. Clinical studies of BCNU wafers have showed good efficacy in both newly diagnosed and recurrent gliomas, as well as a possible therapeutic role in other primary or secondary intracranial malignancies. New studies are currently underway trying to improve the efficacy of the BCNU wafers (Gliadel®) by combining them with different systemic chemotherapies. An overview of the current knowledge ranging from the preclinical developments, to the efficacy and safety seen in the clinical trials and in clinical practice following the drug approval to the future avenues of research is therefore timely