1,721,022 research outputs found
Oxygen isotopes of seawater and oxygen and nitrogen isotopes of dissolved nitrate measured in the Gulf of Maine in October, 2016
No full textThis dataset contains salinity and stable isotope measurements taken of water samples collected during an October 2016 research cruise in the Gulf of Maine aboard the NOAA ship Pisces. Water samples were collected at 44 different stations throughout the Gulf of Maine at various depths from the surface to the seafloor using a carousel sampler with 12 different Niskin bottles and attached to a SeaBIRD 911 CTD. Salinity was measured in situ using the SeaBird 911 CTD with auxiliary sensors. Water samples were collected from depth in Niskin bottles and transferred to triple rinsed Thermo Scientific Nalgene 4 Oz natural hdpe plastic wide mouth leakproof bottles. Parafilm was secured around the cap of each bottle to help prevent evaporation. Samples designated for δ18O(water) analyses were stored in containers in the wet lab of the boat. Samples designated for δ15N(NO3-) and δ18O(NO3-) analyses were immediately placed in a walk-in freezer set at − 8°C. Once back at port, samples were overnight shipped to the Stable Isotope Lab at Iowa State University. Frozen samples were shipped in coolers with additional ice added and, upon arrival, immediately placed back in a freezer. This dataset also contains two freshwater samples collected from the Kennebec River in November and December 2016. Samples were hand collected and stored in Thermo Scientific Nalgene 4 Oz natural hdpe plastic wide mouth leakproof bottles. Samples were shipped on dry ice to Iowa State University and processed in the same way as the other saltwater samples as detailed below. Once at Iowa State University, samples designated for δ18O(water) were stored in the temperature controlled laboratory and then analyzed using a Picarro L2130-I Isotopic Liquid Water Analyzer with attached autosampler. Three different isotopic reference standards, VSMOW, USGS 48, and USGS 47, were used. At least one reference standard sample was used per 5 samples. The average combined uncertainty (analytical and average correction factor) was ±0.20‰ (2σ). Samples designated for isotopic analyses (δ15N and δ18O) of dissolved NO3- were first unfrozen at Iowa State University and filtered using 0.2 μm pore filters (Sartorius Minisart high flow syringe sterile PES membrane). Subsequently, water samples were treated with sulfamic acid (ACS grade, 99.3-100.3%) to remove any NO2- following the procedures outlined in Granger and Sigman (2009; doi:10.1002/rcm.4307). Briefly, glassware was acid washed and baked at 500°C. 60 ml of sample were treated with 600 μL 0.4M sulfamic acid (made using 10% v/v HCl) to reduce the pH to between 1.6 and 1.8, which is necessary to reduce NO2- to N2 and therefore remove it from the sample. After the reaction was allowed to occur for at least 5 min, samples were neutralized by adding 2M NaOH to the sample to return the sample to a pH of 7 (±0.5). Approximately 310 μL of NaOH were added to each sample but the exact amount of NaOH varied by sample and was determined using a pH meter. Samples were then refrozen, put on dry ice and shipped overnight to the University of California Davis Stable Isotope Facility. Samples were analyzed for δ15N(NO3-) and δ18O(NO3-) using the bacterial denitrification assay method as outlined by Sigman et al., (2001; doi:10.1021/ac010088e) and Casciotti et al., (2002; doi:10.1021/ac020113w), respectively. Isotopes were measured using a Thermoscientific Delta V Plus isotope ratio mass spectrometer coupled to a ThermoFinnigan GasBench + PreCon trace gas concentration system. Seven different reference standards were used to correct samples and report values on the international scale, Air: USGS34 KNO3, USGS35 NaNO3, Acros KNO3, Fisher KNO3, Strem KNO3, New Acros KNO3, and IAEA-NO-3 KNO3 (not used on all samples). Average analytical uncertainty (2σ) was ±0.5‰ for δ15N(NO3-) and ±0.3‰ for δ18O(NO3-). In order to assess the extent to which nitrification is occurring in the Gulf of Maine, we used the following equation for Δ(15, 18), first proposed by Sigman et al., (2005; doi:10.1029/2005GB002458): Δ(15, 18) = (δ15N(NO3-) - δ15Nm)-(15ε/18ε)x(δ18O(NO3-)-δ18Om) δ15Nm and δ18Om are mean δ15N and δ18O of dissolved NO3- in deep source waters, respectively. In this case, we use average values for samples taken at and below 100 m, where δ15N(NO3-) and δ18O(NO3-) remain relatively constant with depth. 15ε/18ε is the ratio of isotope fractionation factors for nitrogen and oxygen, respectively, for assimilation, which is taken to be 1 here. The propagated ([a2+b2]1/2) uncertainty for Δ(15, 18), calculated using the uncertainty associated with δ15N(NO3-) and δ18O(NO3-), is ±0.6‰ (2σ)
Oxygen isotope and salinity measurements of coastal surface waters in the Gulf of Maine
No full textThese data include salinity and oxygen isotope measurements of water samples collected from coastal sites along the Gulf of Maine between 2003 and 2015. In particular, a suite of samples were collected along the coast of Maine, east of Penobscot Bay, on a monthly basis between April 2014 and March 2015. These data also include several freshwater samples collected from the Kennebec and Penobscot Rivers on a semi-monthly basis in 2014 and 2015.
For the water samples with sample IDs starting with DSW, JSW, NSW, or OSW: The water samples were collected by hand from shore or boat using French square glass bottles with phenolic polycone lined caps. Salinity was measured using a Oakton SALT 6+ handheld salinity meter. Oxygen isotopes were measured using a Picarro L2130-i Isotopic Liquid Water Analyzer with an attached autosampler. Water samples with sample IDs starting with ASW were collected from shore. Samples with sample IDs starting with DMC 2010 were collected at the flowing seawater laboratory at the Darling Marine Center. Samples with sample IDs starting with Summer 2011 were collected from a boat. For these last 3 sample types (ASW, DMC 2010, Summer 2011): Salinity was measured with YSI Professional Plus salinity meter and oxygen isotopes were measured using a Picarro L1102-i Isotopic Liquid Water Analyzer with an attached autosampler. Data from Owen et al., 2008 and Wanamaker et al. (2006, 2007) was collected from the flowing seawater laboratory at the Darling marine center. Salinity was measured using a YSI model 85 oxygen, conductivity, salinity, and temperature system and oxygen isotopes were measured using a dual-inlet VG/Micromass SIRA (CO2–H2O equilibration method at 30 °C for 12 h)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
A Late Holocene Reconstruction of Ocean Climate Variability in the Gulf of Maine, USA, Based on Calibrated Isotope Records and Growth Histories from the Long-lived Ocean Quahog (Arctica islandica L.)
Full text linkUnderstanding regional patterns of interannual to decadal-scale climate variability over the past 1000 years is critical for evaluating recently observed trends in atmosphere/ocean conditions, particularly in highly-productive ecosystems such as the Gulf of Maine (GOM) that are sensitive to minor changes in climate and/or changes in slope water input. To develop quantitative relationships between bivalve shell chemistry (d18Oc) and growing conditions, aquaculture-based experiments were developed using Mytilus edulis collected in the GOM and Greenland. These experiments yielded a highly accurate and precise paleothermometer [e.g., T °C = 16.28 (± 0.10) - 4.57 (± 0.15) {d18Oc VPBD – d18Ow VSMOW} + 0.06 (± 0.06) {d18Oc VPBD – d 18Ow VSMOW}2; r2 = 0.99; N= 323; p \u3c 0.0001] for M. edulis, and the techniques were applied to the long-lived bivalve species Arctica islandica. To examine ocean variability in the Western GOM during the last millennium, a 142-year-old living A. islandica and three fossil A. islandica shells (corrected 14CAMS = 1030 ± 78 AD; 1320 ± 45 AD; 1357 ± 40 AD) were collected for d18O and growth increment analysis. The standardized annual growth index (SGI) of the modern shell is significantly correlated with continuous GOM plankton recorder data (1961 – 2003; Calanus finmarchicus; r2 = 0.55; p \u3c 0.0001), and SGIs during the late Holocene contain significant periods of 2-6 years, suggesting that slope water variability coupled with North Atlantic Oscillation (NAO) dynamics is primarily responsible for productivity variability. Mean shell-derived isotopic changes were + 0.47 ‰ from 1000 AD to present, and likely reflect a 2 °C cooling caused by an increase in Labrador Current (LC) transport of ~ 0.7 Sv (1 Sv = 106 m3 s-1) and a corresponding decrease in Gulf Stream influence on GOM water temperatures during the past millennium. This hypothesis is consistent with modern observational relationships among the LC, GOM water temperatures, NAO, and Atlantic Multi-Decadal Oscillation (AMO). These results corroborate recent evidence of a large-scale cooling of slope waters and/or dynamical oceanographic changes outside the GOM during the Holocene, and suggest that a direct link exists between the GOM and Northwestern Atlantic
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