590 research outputs found
Guidelines for reducing porpoise mortality in tuna purse seining
More than a decade has passed since the passage of the Marine Mammal Protection Act of 1972. During that time the U.S. tuna purse seine neet reduced its incidental porpoise mortality rate more than 10-fold. This was made possible through the development of gear and techniques aimed at reducing the frequency of many low probability events that contribute to the kill.
Porpoise are killed by becoming entangled or entrapped in folds and canopies of the net and suffocating. The configuration of the net, both before and during the backdown release procedure, is a major determinant of
the number of porpoise killed. Speedboats can be used to tow on the corkllne to prevent net collapse and also to
adjust the net configuration to reduce net canopies prior to backdown. Deepening a net can reduce the probability of porpoise being killed by prebackdown net collapse. The effects of environmental conditions and mechanical
failures on net configuration can result in high porpoise mortality unless mitigated by skilled vessel maneuvers or
prevented by the timely use of speedboats to adjust the net.
The backdown procedure is the only means to effectively release captured porpoise from a purse seine. It is
also the time during the set when most of the mortality occurs. The use of small mesh safety panels and aprons in
the backdown areas of nets reduces porpoise entanglement, and Increases the probability of an effective release.
The tie-down points on the net for preparing the backdown channel must be properly located in order to optimize porpoise release. A formula uses the stretched depth of the net to calculate one of these points, making it a simple matter to locate the other. Understanding the dynamics of the backdown procedure permits a thorough troubleshooting of performance, thus preventing the repetition of poorly executed backdowns and thereby reducing mortality.
Porpoise that cannot be released must be rescued by hand. A rescuer in a rigidly inflated raft can rescue porpoise
effectively at any time during a net set. Hand rescue can make the difference between above average kill and zero kill sets. In all circumstances, the skill and motivation of the captain and his crew are the final determinants in the prevention of incidental porpoise mortality in tuna seining. (PDF file contains 22 pages.
A Systematic Review of Strong Gravitational Lens Modeling Software
Despite expanding research activity in gravitational lens modeling, there is
no particular software which is considered a standard. Much of the
gravitational lens modeling software is written by individual investigators for
their own use. Some gravitational lens modeling software is freely available
for download but is widely variable with regard to ease of use and quality of
documentation. This review of 13 software packages was undertaken to provide a
single source of information. Gravitational lens models are classified as
parametric models or non-parametric models, and can be further divided into
research and educational software. Software used in research includes the
GRAVLENS package (with both gravlens and lensmodel), Lenstool, LensPerfect,
glafic, PixeLens, SimpLens, Lensview, and GRALE. In this review, GravLensHD,
G-Lens, Gravitational Lensing, lens and MOWGLI are categorized as educational
programs that are useful for demonstrating various aspects of lensing. Each of
the 13 software packages is reviewed with regard to software features
(installation, documentation, files provided, etc.) and lensing features (type
of model, input data, output data, etc.) as well as a brief review of studies
where they have been used. Recent studies have demonstrated the utility of
strong gravitational lensing data for mass mapping, and suggest increased use
of these techniques in the future. Coupled with the advent of greatly improved
imaging, new approaches to modeling of strong gravitational lens systems are
needed. This is the first systematic review of strong gravitational lens
modeling software, providing investigators with a starting point for future
software development to further advance gravitational lens modeling research
Effect of Hoop Stress on Ball Bearing Life Prediction
A finite-element analysis (FEA) of a generic, dimensionally normalized inner race of an angular-contact ball bearing was performed under varying conditions of speed and the press (or interference) fit of the inner-race bore on a journal. The FEA results at the ball-race contact were used to derive an equation from which was obtained the radius of an equivalent cylindrical bearing race with the same or similar hoop stress. The radius of the equivalent cylinder was used to obtain a generalized closed-form approximation of the hoop stresses at the ball-inner-race contact in an angular-contact ball bearing. A life analysis was performed on both a 45- and a 120-mm-bore, angular-contact ball bearing. The predicted lives with and without hoop stress were compared with experimental endurance results obtained at 12000 and 25000 rpm with the 120-mm-bore ball bearing. A life factor equation based on hoop stress is presented
Alteration of Neutrophil Function in BCG-Treated and Non-Treated Swine after Exposure to Salmonella typhimurium
Salmonella typhimurium infection in swine causes an enterocolitis followed by a persistent carrier state, but little is known about the mechanisms that allow this organism to colonize and persist in host tissues. Neutrophils provide a first line of defense against invading pathogens such as Salmonella typhimurium. The purpose of this study was to evaluate porcine neutrophil function after in vivo exposure to Salmonella and to determine if the immunomodulator, bacillus Calmette Guerin (BCG), exerts any effect on neutrophil function or on the colonization and persistence of S. typhimurium in the pig. Compared to negative controls, neutrophils from pigs exposed to S. typhimurium exhibited significantly decreased iodination, cytochrome-C reduction, antibody-dependent cell-mediated cytotoxicity, random migration, and chemotaxis (Pâ¤0.05). Neutrophil bactericidal activity against S. typhimurium was significantly enhanced. Most of the significant differences were noted in the first two days after exposure to Salmonella. Often the functional alterations were biphasic, peaking again 7â10 days after exposure. BCG alone significantly depressed random migration and cytochrome-C reduction in unstimulated neutrophils. The clinical course, colonization pattern, and persistence of Salmonella were similar between pigs receiving BCG and untreated pigs. These data suggest that S. typhimurium infection causes a depression in oxidative metabolism and motility, yet an increase in overall bactericidal activity against S. typhimurium in circulating porcine neutrophils. It also appears that BCG treatment, as reported here, does not enhance resistance of pigs to S. typhimurium colonization or reduce the number of persistent organisms in the porcine ileum
Host-specific cues cause differential attractiveness of Kenyan men to the African malaria vector Anopheles gambiae
BACKGROUND: Many studies have suggested that variability in the attractiveness of humans to host-seeking mosquitoes is caused by differences in the make-up of body emanations, and olfactory signals in particular. Most investigations have either been laboratory-based, utilising odour obtained from sections of the body, or have been done in the field with sampling methods that do not discriminate between visual, physical and chemical cues of the host. Accordingly, evidence for differential attractiveness based on body emanations remains sparse in spite of the far-reaching epidemiological implications of this phenomenon. METHODS: A new three-port olfactometer that accommodates complete human beings as sources of host-seeking stimuli was used to study behavioural responses of Anopheles gambiae Giles sensu stricto (hereafter An. gambiae) under semi-field conditions in western Kenya. Differential attractiveness of nine male Kenyans was assessed by simultaneously exposing the mosquitoes to (a mixture of) total body emanations of 3 people occupying separate tents. Controls (empty tents) were included and the effect of residual odours following tent occupation was also examined. RESULTS: Trap catches increased significantly (P < 0.001) when a tent was occupied. Based on 'competition' experiments, the nine persons were classified into least, medium and most attractive groups. There was no significant interaction between person and trap (P = 0.302) or person and test period (P = 0.223). Presence (P < 0.001) or absence (P = 0.949) of significant differences in the number of mosquitoes caught per trap when tents were simultaneously occupied by one person in each or left empty, respectively, demonstrated that residual odours following tent occupation did not affect behavioural responses of the mosquitoes. CONCLUSION: We provide evidence that in the vicinity of humans, when exposed to a blend of physical and olfactory signals from more than one host, An. gambiae can effectively and consistently express host-selection behaviour that results in non-random biting
The Highest Resolution Mass Map of Galaxy Cluster Substructure To Date Without Assuming Light Traces Mass: LensPerfect Analysis of Abell 1689
We present a strong lensing mass model of Abell 1689 which resolves
substructures ~25 kpc across (including about ten individual galaxy subhalos)
within the central ~400 kpc diameter. We achieve this resolution by perfectly
reproducing the observed (strongly lensed) input positions of 168 multiple
images of 55 knots residing within 135 images of 42 galaxies. Our model makes
no assumptions about light tracing mass, yet we reproduce the brightest visible
structures with some slight deviations. A1689 remains one of the strongest
known lenses on the sky, with an Einstein radius of RE = 47.0" +/- 1.2" (143
+3/-4 kpc) for a lensed source at zs = 2. We find a single NFW or Sersic prole
yields a good fit simultaneously (with only slight tension) to both our strong
lensing (SL) mass model and published weak lensing (WL) measurements at larger
radius (out to the virial radius). According to this NFW fit, A1689 has a mass
of Mvir = 2.0 +0.5/-0.3 x 10^15 Msun / h70 (M200 = 1.8 +0.4/-0.3 x 10^15 Msun /
h70) within the virial radius rvir = 3.0 +/- 0.2 Mpc / h70 (r200 = 2.4
+0.1/-0.2 Mpc / h70), and a central concentration cvir = 11.5 +1.5/-1.4 (c200 =
9.2 +/- 1.2). Our SL model prefers slightly higher concentrations than previous
SL models, bringing our SL+WL constraints in line with other recent
derivations. Our results support those of previous studies which find A1689 has
either an anomalously large concentration or significant extra mass along the
line of sight (perhaps in part due to triaxiality). If clusters are generally
found to have higher concentrations than realized in simulations, this could
indicate they formed earlier, perhaps as a result of early dark energy.Comment: 27 pages, 17 figures, submitted to ApJ. See
http://www.its.caltech.edu/~coe/LPA1689/ for complete set of color multiple
images (observed and delensed) and more. Comments welcome at
http://scirate.com/who.php?id=1005.xxxx&what=comments (insert arXiv number at
xxxx; free & easy registration
Integrated stratigraphy of the Kimmeridge Clay Formation (Upper Jurassic) based on exposures and boreholes in south Dorset, UK
For the purposes of a high-resolution multi-disciplinary study of the Upper Jurassic Kimmeridge Clay Formation, two boreholes were drilled at Swanworth Quarry and one at Metherhills, south Dorset, UK. Together, the cores represent the first complete section through the entire formation close to the type section. We present graphic logs that record the stratigraphy of the cores, and outline the complementary geophysical and analytical data sets (gamma ray, magnetic susceptibility, total organic carbon, carbonate, [delta]13Corg). Of particular note are the new borehole data from the lowermost part of the formation which does not crop out in the type area. Detailed logs are available for download from the Kimmeridge Drilling Project web-site at http://kimmeridge.earth.ox.ac.uk/. Of further interest is a mid-eudoxus Zone positive shift in the [delta]13Corg record, a feature that is also registered in Tethyan carbonate successions, suggesting that it is a regional event and may therefore be useful for correlation. The lithostratigraphy of the cores has been precisely correlated with the nearby cliff section, which has also been examined and re-described. Magnetic-susceptibility and spectral gamma-ray measurements were made at a regular spacing through the succession, and facilitate core-to-exposure correlation. The strata of the exposure and core have been subdivided into four main mudrock lithological types: (a) medium-darkâdark-grey marl; (b) medium-darkâdark greyâgreenish black shale; (c) dark-greyâolive-black laminated shale; (d) greyish-blackâbrownish-black mudstone. The sections also contain subordinate amounts of siltstone, limestone and dolostone. Comparison of the type section with the cores reveals slight lithological variation and notable thickness differences between the coeval strata. The proximity of the boreholes and different parts of the type section to the PurbeckâIsle of Wight Disturbance is proposed as a likely control on the thickness changes
Ante-Autobiography and the Archive of Childhood
This essay examines the concept of childrenâs autobiography via several autobiographical extracts
written by the author as a child. Although only a small proportion of people will compose and
publish a full-length autobiography, almost everyone will, inadvertently, produce an archive of
the self, made from public records and private documents. Here, such works are seen as providing
access to writing both about and by children. The essay explores the ethics and poetics of
childrenâs writing via the key debates in life writing; in particular, the dynamic relationship
between adults and children, both as distinct stages of life and dual parts of one autobiographical
identity. The term âante-autobiographyâ is coined to refer to these texts which come before or
instead of a full-length narrative. They are not read as less than or inadequate versions of
autobiography, but rather as transgressive and challenging to chronological notions of the genre
Food Stamp Participation and Reasons for Nonparticipation: 1986
The decision of eligible households to participate in the food stamp program is analyzed utilizing the 1986 Panel Study of Income Dynamics. Less than one-half of the sample of eligible households receive food stamps in 1986. The results of a multinomial logit model suggest that participation is related negatively to the age and educational level of the household head and positively to the benefit level. Participation is lower for single men and households residing in the West and higher for people with disabilities and households receiving some form of public transfer income. Problems regarding information about food stamps and personal attitudes toward food stamp use have the greatest impact on the decision to participate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44658/1/10834_2004_Article_418066.pd
Linking Wheels for use in quantum information processing
Heterometallic Cr7Ni-containing wheels have been identified as potential qubits for use in quantum information processing. The work described in this thesis details attempts to form a variety of multi-qubit systems for the purposes of better understanding the interactions occurring between the wheels and also forming potential 2-qubit quantum gates using redox/photo-active links. Mono-substituted wheels of type [Pr2NH2][Cr7MF8(O2CCMe3)15(L)], where L is acarboxylate with a pendant coordinating group, have been synthesised for use as bulky ligands in coordination chemistry with metal complexes. Various carboxylates have been substituted into the wheels and the products reacted with first row transition metal complexes in order to extend the series of linked-wheel systems. Many of these novel complexes have been characterised by X-ray crystallography, and in certain cases EPR studies have been undertaken to probe the strength of interactions occurring via different bridging units. The first well-established substituted wheel, [Pr2NH2][Cr7NiF8(O2CCMe3)15(O2CPy)] (Py= pyridine), has also been used in reactions with second and third row transition metal centres to show its ability to act as a ligand under more harsh conditions. In addition, the disubstituted product [Pr2NH2][Cr7NiF8(O2CCMe3)14(O2CPy)2] has been reacted with a copper complex in order to form a polymeric structure. Purple wheels of type [Cr7NiF3(O2CCMe3)15(EtGu)(H2O)] have been linked through a variety of extended organic molecules containing a minimum of two pendent pyridyl groups. Use of a ligand containing four pyridyl groups, 2,2´:4,4´´:4´,4´´´-quaterpyridyl(qpy) produced a three-wheel-containing system, creating an interesting modification of the wheel backbone not seen before. A series of transition metal complexes, containing qpy and its extended derivative bbpe, has been synthesised in order to form linked-wheel systems. While none of these systems has to date yielded a crystal structure, a significant amount of evidence has been collected to confirm successful formation of the desired products. UV-vis spectroscopic and electrochemical measurements show that these compounds are photo and/or redox-active,and preliminary luminescence studies indicate that the presence of the wheels quenches the emission from metal-to-ligand charge-transfer excited states. A series of mixed-wheel systems has been synthesised by reacting four different monosubstituted green wheels with four purple wheels (Cr7M, where M = Ni, Co, Mn or Zn). A total of fourteen novel systems has been formed, with two of the attempted reactions failing to occur. EPR studies on Cr7Ni-Cr7Ni linked systems show that the strongest interaction occurs when using isonicotinate as a link, with 4-pyridazinecarboxylate giving the weakest coupling. Studies have also been undertaken on Cr7Ni-Cr7Mn and Cr7Ni-Cr7Zn systems, with the former showing interactions and the latter showing none. Initial work to link wheels together indirectly via their templates was ultimately unsuccessful, but a variety of potential linker molecules were synthesised and are described.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
- âŚ