1,088 research outputs found
Monitoring Fish Diversity in Massies Creek, Ohio
Streams are susceptible to numerous threats to their water quality and biodiversity. In our region of southwest Ohio a major driver of these impacts is associated with current and past agricultural practices. These changes include straightening, embanking, dredging, and removal of large rocks and woody debris, increased erosion, and non-point source pollution. These structural and chemical impacts are known to significantly affect biodiversity in these streams. This means a greater understanding of stream ecology is of utter importance to places such as Greene County, Ohio due to the prevalence of agricultural practices in the landscape. In 2010 a 2.2 mile stream restoration project was completed by Greene County on the north fork of Massieâs Creek. Biological surveys and stream monitoring began in 2011 and extended on a regular basis through Fall 2014. In our study, conducted in the fall of 2014, we expanded the scope to evaluate fish biodiversity at previously studied sites as well as four additional sites within the watershed. Our objective was to collect data in order to draw comparisons between 2014 and previous yearâs data including a study conducted in 1955 on Massieâs Creek.
We sampled in six different locations, once in all six sites and twice in two specific sites. We used a mix of restored, unrestored, and unaltered stretches of stream as our sample locations. To determine diversity we used two different diversity indices: Shannon (H) and Simpsonâs (D). Our Shannon value for the common unrestored site was 1.46 and our Simpsonâs value was 0.33. Our Shannon value for the common restored site was 1.22 and our Simpsonâs value was 0.36. Combining the data from the previous years with the 2014 data we found dominance to have decreased after restoration (which means there was more diversity)
The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118: A Violently Interacting Galaxy with Peculiar Kinematics
We present observations of the distribution and kinematics of neutral and
ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system.
Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk
of NGC 1144, but HI emission is detected over only 1/3 of this velocity range,
in an area that corresponds to the NW half of the disk. In the nuclear region
of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is
observed. Faint, narrow HI absorption lines are also detected against radio
sources in the SE part of the disk of NGC 1144, which includes regions of
massive star formation and a Seyfert nucleus. The peculiar HI distribution,
which is concentrated in the NW disk, seems to be the inverse of the molecular
distribution which is concentrated in the SE disk. Although this may partly be
the result of the destruction of HI clouds in the SE disk, there is
circumstantial evidence that the entire HI emission spectrum of NGC 1144 is
affected by a deep nuclear absorption line covering a range of 600 km/s, and is
likely blueshifted with respect to the nucleus. In this picture, a high
column-density HI stream is associated with the nuclear ionized gas velocity
discontinuity, and the absorption effectively masks any HI emission that would
be present in the SE disk of NGC 1144.Comment: manuscript, arp118.ps: 28 pages; 1 Table: arp118.tab1.ps; 16 Figures:
arp118.fig1-16.ps; Accepted to Ap
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Choice consequences: salinity preferences and hatchling survival in the mangrove rivulus (Kryptolebias marmoratus).
In heterogeneous environments, mobile species should occupy habitats in which their fitness is maximized. Mangrove rivulus fish inhabit mangrove ecosystems where salinities range from 0 to 65â
ppt, but are most often collected from areas with salinities of âŒ25â
ppt. We examined the salinity preference of mangrove rivulus in a lateral salinity gradient, in the absence of predators and competitors. Fish could swim freely for 8â
h throughout the gradient with chambers containing salinities ranging from 5 to 45â
ppt (or 25â
ppt throughout in the control). We defined preference as the salinity in which the fish spent most of their time, and also measured preference strength, latency to begin exploring the arena, and number of transitions between chambers. To determine whether these traits were repeatable, each fish experienced three trials. Mangrove rivulus spent a greater proportion of time in salinities lower (5-15â
ppt) than they occupy in the wild. Significant among-individual variation in the (multivariate) behavioral phenotype emerged when animals experienced the gradient, indicating strong potential for selection to drive behavioral evolution in areas with diverse salinity microhabitats. We also showed that mangrove rivulus had a significantly greater probability of laying eggs in low salinities compared with control or high salinities. Eggs laid in lower salinities also had higher hatching success compared with those laid in higher salinities. Thus, although mangrove rivulus can tolerate a wide range of salinities, they prefer low salinities. These results raise questions about factors that prevent mangrove rivulus from occupying lower salinities in the wild, whether higher salinities impose energetic costs, and whether fitness changes as a function of salinity
Choice consequences: salinity preferences and hatchling survival in the mangrove rivulus (Kryptolebias marmoratus).
In heterogeneous environments, mobile species should occupy habitats in which their fitness is maximized. Mangrove rivulus fish inhabit mangrove ecosystems where salinities range from 0 to 65â
ppt, but are most often collected from areas with salinities of âŒ25â
ppt. We examined the salinity preference of mangrove rivulus in a lateral salinity gradient, in the absence of predators and competitors. Fish could swim freely for 8â
h throughout the gradient with chambers containing salinities ranging from 5 to 45â
ppt (or 25â
ppt throughout in the control). We defined preference as the salinity in which the fish spent most of their time, and also measured preference strength, latency to begin exploring the arena, and number of transitions between chambers. To determine whether these traits were repeatable, each fish experienced three trials. Mangrove rivulus spent a greater proportion of time in salinities lower (5-15â
ppt) than they occupy in the wild. Significant among-individual variation in the (multivariate) behavioral phenotype emerged when animals experienced the gradient, indicating strong potential for selection to drive behavioral evolution in areas with diverse salinity microhabitats. We also showed that mangrove rivulus had a significantly greater probability of laying eggs in low salinities compared with control or high salinities. Eggs laid in lower salinities also had higher hatching success compared with those laid in higher salinities. Thus, although mangrove rivulus can tolerate a wide range of salinities, they prefer low salinities. These results raise questions about factors that prevent mangrove rivulus from occupying lower salinities in the wild, whether higher salinities impose energetic costs, and whether fitness changes as a function of salinity
Standing in a Garden of Forking Paths
According to the Path Principle, it is permissible to expand your set of beliefs iff (and because) the evidence you possess provides adequate support for such beliefs. If there is no path from here to there, you cannot add a belief to your belief set. If some thinker with the same type of evidential support has a path that they can take, so do you. The paths exist because of the evidence you possess and the support it provides. Evidential support grounds propositional justification.
The principle is mistaken. There are permissible steps you may take that others may not even if you have the very same evidence. There are permissible steps that you cannot take that others can even if your beliefs receive the same type of evidential support. Because we have to assume almost nothing about the nature of evidential support to establish these results, we should reject evidentialism
Metacognition as Evidence for Evidentialism
Metacognition is the monitoring and controlling of cognitive processes. I examine the role of metacognition in âordinary retrieval casesâ, cases in which it is intuitive that via recollection the subject has a justiïŹed belief. Drawing on psychological research on metacognition, I argue that evidentialism has a unique, accurate prediction in each ordinary retrieval case: the subject has evidence for the proposition she justiïŹedly believes. But, I argue, process reliabilism has no unique, accurate predictions in these cases. I conclude that ordinary retrieval cases better support evidentialism than process reliabilism. This conclusion challenges several common assumptions. One is that non-evidentialism alone allows for a naturalized epistemology, i.e., an epistemology that is fully in accordance with scientiïŹc research and methodology. Another is that process reliabilism fares much better than evidentialism in the epistemology of memory
Theoretical studies of the historical development of the accounting discipline: a review and evidence
Many existing studies of the development of accounting thought have either been atheoretical or have adopted Kuhn's model of scientific growth. The limitations of this 35-year-old model are discussed. Four different general neo-Kuhnian models of scholarly knowledge development are reviewed and compared with reference to an analytical matrix. The models are found to be mutually consistent, with each focusing on a different aspect of development. A composite model is proposed. Based on a hand-crafted database, author co-citation analysis is used to map empirically the entire literature structure of the accounting discipline during two consecutive time periods, 1972â81 and 1982â90. The changing structure of the accounting literature is interpreted using the proposed composite model of scholarly knowledge development
The DLV System for Knowledge Representation and Reasoning
This paper presents the DLV system, which is widely considered the
state-of-the-art implementation of disjunctive logic programming, and addresses
several aspects. As for problem solving, we provide a formal definition of its
kernel language, function-free disjunctive logic programs (also known as
disjunctive datalog), extended by weak constraints, which are a powerful tool
to express optimization problems. We then illustrate the usage of DLV as a tool
for knowledge representation and reasoning, describing a new declarative
programming methodology which allows one to encode complex problems (up to
-complete problems) in a declarative fashion. On the foundational
side, we provide a detailed analysis of the computational complexity of the
language of DLV, and by deriving new complexity results we chart a complete
picture of the complexity of this language and important fragments thereof.
Furthermore, we illustrate the general architecture of the DLV system which
has been influenced by these results. As for applications, we overview
application front-ends which have been developed on top of DLV to solve
specific knowledge representation tasks, and we briefly describe the main
international projects investigating the potential of the system for industrial
exploitation. Finally, we report about thorough experimentation and
benchmarking, which has been carried out to assess the efficiency of the
system. The experimental results confirm the solidity of DLV and highlight its
potential for emerging application areas like knowledge management and
information integration.Comment: 56 pages, 9 figures, 6 table
The Vela Cloud: A Giant HI Anomaly in the NGC 3256 Group
We present Australia Telescope Compact Array (ATCA) observations of a
galaxy-sized intergalactic HI cloud (the Vela Cloud) in the NGC 3256 galaxy
group. The group contains the prominent merging galaxy NGC 3256, which is
surrounded by a number of HI fragments, the tidally disturbed galaxy NGC 3263,
and several other peculiar galaxies. The Vela Cloud, with an HI mass of 3-5 *
10**9 solar masses, resides southeast of NGC 3256 and west of NGC 3263, within
an area of 9' x 16' (100 kpc x 175 kpc for an adopted distance of 38 Mpc). In
our ATCA data the Vela Cloud appears as 3 diffuse components and contains 4
density enhancements. The Vela Cloud's properties, together with its group
environment, suggest that it has a tidal origin. Each density enhancement
contains ~10**8 solar masses of HI gas which is sufficient material for the
formation of globular cluster progenitors. However, if we represent the
enhancements as Bonnor-Ebert spheres, then the pressure of the surrounding HI
would need to increase by at least a factor of 6 in order to cause the collapse
of an enhancement. Thus we do not expect them to form massive bound stellar
systems like super star clusters or tidal dwarf galaxies. Since the HI density
enhancements have some properties in common with High Velocity Clouds, we
explore whether they may evolve to be identified with these starless clouds
instead.Comment: 47 pages, 13 figures (incl. a & b), accepted by AJ, changes are minor
additions, rearranging, and clarifications esp. in sections 6 &
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