Showing 1741 - 1750 of 2039 Items
Statement gathered at Motahkomikuk-Indian Township, Maine, November 12, 2014
Date: 2014-11-12
Creator: Karen Sabattis
Anonymous
Stephanie Bailey
Jeanie Grant
Molly Socoby
Selina Mitchell-Lola
Katherine Newell
Access: Open access
Statement gathered at Indian Island, Maine, November 17, 2014
Date: 2014-11-17
Creator: Barbara Kates
Stephanie Bailey
Maria Girouard
Arla Patch
Wenona Lola
Esther Attean
Access: Open access
New insights on obtaining phytoplankton concentration and composition from in situ multispectral Chlorophyll fluorescence
Date: 2010-01-01
Creator: Christopher W. Proctor
Collin S. Roesler
Access: Open access
- A three-channel excitation (435 nm, 470 nm, and 532 nm) Chlorophyll fluorometer (695 nm emission) was calibrated and characterized to improve uncertainty in estimated in situ Chlorophyll concentrations. Protocols for reducing sensor-related uncertainties as well as environmental-related uncertainties were developed. Sensor calibrations were performed with thirteen monospecific cultures in the laboratory, grown under limiting and saturating irradiance, and sampled at different growth phases. Resulting uncertainties in the calibration slope induced by natural variations in the in vivo fluorescence per extracted Chlorophyll yield were quantified. Signal variations associated with the sensors (i.e., dark current configurations, drift, and stability) and the environment (i.e., temperature dependent dark currents and contamination by colored dissolved organic matter [CDOM] fluorescence) yielded errors in estimating in situ Chlorophyll concentration exceeding 100%. Calibration protocols and concurrent observations of in situ temperature and CDOM fluorescence eliminate these uncertainties. Depending upon excitation channel, biomass calibration slopes varied between 6-and 10-fold between species and as a function of growth irradiance or growth phase. The largest source of slope variability was due to variations in accessory pigmentation, and thus the variance could be reduced among pigment-based taxonomic lines. Fluorescence ratios were statistically distinct among the pigment-based taxonomic groups, providing not only a means for approximating bulk taxonomic composition, but also for selecting the appropriate calibration slope to statistically improve the accuracy of in situ Chlorophyll concentration estimates. Application to 5 months of deployment in China Lake, Maine, USA reduced the error in estimating extracted Chlorophyll concentration from > 30% to < 6%. © 2010, by the American Society of Limnology and Oceanography, Inc.
Identification, physiological actions, and distribution of TPSGFLGMRamide: A novel tachykinin-related peptide from the midgut and stomatogastric nervous system of Cancer crabs
Date: 2007-06-01
Creator: Elizabeth A. Stemmler
Braulio Peguero
Emily A. Bruns
Patsy S. Dickinson
Andrew E., Christie
Access: Open access
- In most invertebrates, multiple species-specific isoforms of tachykinin-related peptide (TRP) are common. In contrast, only a single conserved TRP isoform, APSGFLGMRamide, has been documented in decapod crustaceans, leading to the hypothesis that it is the sole TRP present in this arthropod order. Previous studies of crustacean TRPs have focused on neuronal tissue, but the recent demonstration of TRPs in midgut epithelial cells in Cancer species led us to question whether other TRPs are present in the gut, as is the case in insects. Using direct tissue matrix assisted laser desorption/ionization Fourier transform mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation, we found that at least one additional TRP is present in Cancer irroratus, Cancer borealis, Cancer magister, and Cancer productus. The novel TRP isoform, TPSGFLGMRamide, was present not only in the midgut, but also in the stomatogastric nervous system (STNS). In addition, we identified an unprocessed TRP precursor APSGFLGMRG, which was detected in midgut tissues only. TRP immunohistochemistry, in combination with preadsorption studies, suggests that APSGFLGMRamide and TPSGFLGMRamide are co-localized in the stomatogastric ganglion (STG), which is contained within the STNS. Exogenous application of TPSGFLGMRamide to the STG elicited a pyloric motor pattern that was identical to that elicited by APSGFLGMRamide, whereas APSGFLGMRG did not alter the pyloric motor pattern. © 2007 The Authors.
On Kindleberger and Hegemony: From Berlin to M.I.T. and Back
Date: 2013-09-29
Creator: Stephen Meardon
Access: Open access
- The most notable idea of Charles P. Kindleberger’s later career is the value of a single country acting as stabilizer of an international economy prone to instability. It runs through his widely read books, The World in Depression, 1929-1939 (1973), Manias, Crises, and Panics (1978), A Financial History of Western Europe (1984), and kindred works. “Hegemonic stability,” the idea is called in the literature it inspired. This essay traces Kindleberger’s attachment to the idea back to his tenure as chief of the State Department’s Division of German and Austrian Economic Affairs from 1945 to 1947 and adviser to the European Recovery Program from 1947 to 1948. In both capacities Kindleberger observed and participated indirectly in the 1948 monetary reform in Western Germany. In the 1990s, during his octogenary decade, he revisited the German monetary reform with a fellow participant, economist, and longtime friend, F. Taylor Ostrander. Their collaborative essay marked Kindleberger’s effort to reclaim hegemonic stability theory from the scholars who developed it following his works of the 1970s and 1980s.
Retinoic acid expands the evolutionarily reduced dentition of zebrafish
Date: 2012-12-01
Creator: Pawat Seritrakul
Eric Samarut
Tenzing T.S. Lama
Yann Gibert
Vincent, Laudet
William R. Jackman
Access: Open access
- Zebrafish lost anterior teeth during evolution but retain a posterior pharyngeal dentition that requires retinoic acid (RA) cell-cell signaling for its development. The purposes of this study were to test the sufficiency of RA to induce tooth development and to assess its role in evolution. We found that exposure of embryos to exogenous RA induces a dramatic anterior expansion of the number of pharyngeal teeth that later form and shifts anteriorly the expression patterns of genes normally expressed in the posterior tooth-forming region, such as pitx2 and dlx2b. After RA exposure, we also observed a correlation between cartilage malformations and ectopic tooth induction, as well as abnormal cranial neural crest marker gene expression. Additionally, we observed that the RA-induced zebrafish anterior teeth resemble in pattern and number the dentition of fish species that retain anterior pharyngeal teeth such as medaka but that medaka do not express the aldh1a2 RA-synthesizing enzyme in tooth-forming regions. We conclude that RA is sufficient to induce anterior ectopic tooth development in zebrafish where teeth were lost in evolution, potentially by altering neural crest cell development, and that changes in the location of RA synthesis correlate with evolutionary changes in vertebrate dentitions. © FASEB.
Social Media as Technologies of Accountability: Explaining Resistance to Implementation Within Organizations
Creator: Jeffrey Treem
Access: Open access
The Effects of Exchange Rates on Employment in Canada
Date: 2013-06-05
Creator: Yao Tang
Haifang Huang
Ke Pang
Access: Open access
- Under the flexible exchange rate regime, the Canadian economy is constantly affected by fluctuations in exchange rates. This paper focuses on employment in Canada. We find that appreciations of the Canadian dollar have significant effects on employment in manufacturing industries; such effects are mostly associated with the export-weighted exchange rate and not the import-weighted exchange rate. The export-weighted exchange rate elasticity of employment is -0.52. However, we also find that exchange rate fluctuations have little impact on Canada’s nonmanufacturing employment. Because the manufacturing sector accounts for only about 10% of the employment in Canada, the overall employment effect of exchange rates is small. In addition, we assess the potential employment impact of a boom in the global commodity market, which often leads to appreciations of the Canadian dollar. We find that a 12.21% increase in commodity prices (one standard deviation in the 1994-2007 data) reduces Canada’s manufacturing employment by 0.98%, less than 0.1% of the total industrial employment.
Emergence of dispersive shocks and rarefaction waves in power-law contact models
Date: 2017-06-16
Creator: H. Yasuda
C. Chong
J. Yang
P. G. Kevrekidis
Access: Open access
- In the present work, motivated by generalized forms of the Hertzian dynamics associated with granular crystals, we consider the possibility of such models to give rise to both dispersive shock and rarefaction waves. Depending on the value p of the nonlinearity exponent, we find that both of these possibilities are realizable. We use a quasicontinuum approximation of a generalized inviscid Burgers model in order to predict the solution profile up to times near the formation of the dispersive shock, as well as to estimate when it will occur. Beyond that time threshold, oscillations associated with the highly dispersive nature of the underlying model emerge, which cannot be captured by the quasicontinuum approximation. Our analytical characterization of the above features is complemented by systematic numerical computations.
Microblogging Practices of Virtual Organizations: Commonalities and Contrasts
Creator: Jing Wang
Access: Open access
- Microblogging is becoming increasingly pervasive in computer-supported collaboration, attracting various types of users. Organizations, as one type, are willing to leverage this social media service for their operation, but lack guidance of how to effectively manage their organizational microblogs. However, research on microblogging practices at organizational level, especially in virtual organizations, is very limited. To enhance the understanding of how virtual organizations use microblogs in similar and different ways, we investigate microblogging practices of two virtual organizations by examining the content characteristics of their Twitter posts. We identify eleven categories of microblog themes of three dimensions, consisting of both common and different categories between the two organizations. We further enumerate their potential impacts on organizational context, discuss differences between the two organizations, and compare these organizational practices with personal ones.