oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Feeding Currents Generated by Upside Down Jellyfish  [PDF]
Terry Rodriguez,Christina Hamlet,Megan Gyoerkoe,Laura Miller
Physics , 2010,
Abstract: We present fluid dynamics videos of the pulsing dynamics and the resulting fluid flow generated by the upside down jellyfish, Cassiopea spp. Medusae of this genus are unusual in that they typically rest upside down on the ocean floor and pulse their bells to generate feeding currents, only swimming when significantly disturbed. The pulsing kinematics and fluid flow around these upside down jellyfish is investigated using a combination of videography, flow visualization, and numerical simulation. Significant mixing occurs around and directly above the oral arms and secondary mouths. Numerical simulations using the immersed boundary method with a porous layer representing the oral arms agree with the experimental results. The simulations also suggest that the presence of porous oral arms induce net horizontal flow towards the bell. Coherent vortex rings are not seen in the wake above the jellyfish, but starting and stopping vortices are observed before breaking up as they pass through the elaborate oral arms (if extended).
Investigation of the Biochemical and Histological Changes Induced by Zearalenone Mycotoxin on Liver in Male Mice and the Protective Role of Crude Venom Extracted from Jellyfish Cassiopea Andromeda  [PDF]
Madeha Al-Seeni, Nagwa El-Sawi, Soad Shaker, Asma Al-Amoudi
Food and Nutrition Sciences (FNS) , 2011, DOI: 10.4236/fns.2011.24045
Abstract: Zearalenone (ZEN) is a non steroidal estrogenic mycotoxin produced by Fusarium species of fungi which contaminate human foods and animal feeds worldwide. In this study hepatotoxicity of ZEN was evaluated in mice by oral adminis-tration of single and repeated doses of ZEN mycotoxin (2.7 mg/kg b.w.). The protective effect of crude venom extracted from jellyfish Cassiopea andromeda was also assessed. Mice were divided into four groups (N = 10). G1: receiving the toxin once and sacrificed 48 h later, G2: toxin administered twice for one week, G3: toxin administered twice a week for two weeks, G4: pretreated orally by a single dose of crude venom (1.78 mg/20g) 24 hours prior to administration of ZEN twice a week for two weeks. Each treated group had its corresponding control which received 1% DMSO sa-line.ZEN treatment significantly increased alanine aminotransferase (ALT), aspartateaminotrnsferase (AST) and alka-line phosphatase (ALP) activities after 48 hours and two weeks, while ALT was also significantly increased after one week. Tumor necrosis factoralpha (TNF-α) level was undetected in treated and control groups except the group treated with ZEN for one week. Alphafetoprotein (AFP) level was increased significantly only after two weeks. The activity of antioxidants was significantly increased in all groups. ZEN was also found to modify the serum proteins especially gamma-globulin which showed a significant decrease after 48 h and two weeks. Improvement in liver func-tion occurred in the group pretreated with the crude venom, and AFP and antioxidants returned to normal level, while TNF-α level was also undetected. Gamma globulin was significantly increased. The recovery observed in the group which was pretreated with crude venom may related to bradykinin content of this venom which exhibits a hepatoprotective effect. Histological changes in mouse liver coincided with biochemical changes. In conclusion, this study revealed that ZEN induced liver function and structural changes promising an approach for using a crude venom of jellyfish to enhance liver function.
3D simulations of self-propelled, reconstructed jellyfish using vortex methods  [PDF]
J. T. Rasmussen,D. Rosinelli,F. Storti,P. Koumoutsakos,J. H. Walther
Physics , 2009,
Abstract: We present simulations of the vortex dynamics associated with the self-propelled motion of jellyfish. The geometry is obtained from image segmentation of video recordings from live jellyfish. The numerical simulations are performed using three-dimensional viscous, vortex particle methods with Brinkman penalization to impose the kinematics of the jellyfish motion. We study two types of strokes recorded in the experiment1. The first type (stroke A) produces two vortex rings during the stroke: one outside the bell during the power stroke and one inside the bell during the recovery stroke. The second type (stroke B) produces three vortex rings: one ring during the power stroke and two vortex rings during the recovery stroke. Both strokes propel the jellyfish, with stroke B producing the highest velocity. The speed of the jellyfish scales with the square root of the Reynolds number. The simulations are visualized in a fluid dynamics video.
The jellyfish fishery in Mexico  [PDF]
Juana López-Martínez, Javier álvarez-Tello
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.46A009
Abstract: Jellyfish has been captured in Asia for 1700 years, and it has been considered a delicacy. Since the 70s important jellyfish fisheries have developed in several parts of the world, with catches increasing exponentially, reaching 500,000 tons per year in the mid-nineties. In Mexico, only the cannonball jellyfish Stomolophus meleagris is captured commercially. Most of the capture of this jellyfish species is obtained within the Gulf of California, specifically in the state of Sonora. The total reported capture in 2010 was 16,581 metric t and 14,220 in 2011. With these capture volumes jellyfish was ranked as the third most important fishing resource in the state of Sonora. The fishing season in Sonora is from April to May; a total of 4 or 5 weeks, and the catch per unit effort is around 3 tons by trip. Currently, there are nine jellyfish marketing companies, with about 20 processing plants distributed along the coast of Sonora, primarily in Guaymas, Kino Bay, and Puerto Penasco. Although the process is simple, the large amounts of jellyfish required and the need to optimize production costs make jellyfish processing an intense activity that employs hundreds of people during the fishing season, becoming an alternative employment for the people who depend on the fishing industry.
Reynolds number limits for jet propulsion: A numerical study of simplified jellyfish  [PDF]
Gregory Herschlag,Laura A. Miller
Physics , 2010,
Abstract: The Scallop Theorem states that reciprocal methods of locomotion, such as jet propulsion or paddling, will not work in Stokes flow (Reynolds number = 0). In nature the effective limit of jet propulsion is still in the range where inertial forces are significant. It appears that almost all animals that use jet propulsion swim at Reynolds numbers (Re) of about 5 or more. Juvenile squid and octopods hatch from the egg already swimming in this inertial regime. The limitations of jet propulsion at intermediate Re is explored here using the immersed boundary method to solve the two-dimensional Navier Stokes equations coupled to the motion of a simplified jellyfish. The contraction and expansion kinematics are prescribed, but the forward and backward swimming motions of the idealized jellyfish are emergent properties determined by the resulting fluid dynamics. Simulations are performed for both an oblate bell shape using a paddling mode of swimming and a prolate bell shape using jet propulsion. Average forward velocities and work put into the system are calculated for Reynolds numbers between 1 and 320. The results show that forward velocities rapidly decay with decreasing Re for all bell shapes when Re < 10. Similarly, the work required to generate the pulsing motion increases significantly for Re < 10. When compared actual organisms, the swimming velocities and vortex separation patterns for the model prolate agree with those observed in Nemopsis bachei. The forward swimming velocities of the model oblate jellyfish after two pulse cycles are comparable to those reported for Aurelia aurita, but discrepancies are observed in the vortex dynamics between when the 2D model oblate jellyfish and the organism.
Jellyfish: Networking Data Centers Randomly  [PDF]
Ankit Singla,Chi-Yao Hong,Lucian Popa,P. Brighten Godfrey
Computer Science , 2011,
Abstract: Industry experience indicates that the ability to incrementally expand data centers is essential. However, existing high-bandwidth network designs have rigid structure that interferes with incremental expansion. We present Jellyfish, a high-capacity network interconnect, which, by adopting a random graph topology, yields itself naturally to incremental expansion. Somewhat surprisingly, Jellyfish is more cost-efficient than a fat-tree: A Jellyfish interconnect built using the same equipment as a fat-tree, supports as many as 25% more servers at full capacity at the scale of a few thousand nodes, and this advantage improves with scale. Jellyfish also allows great flexibility in building networks with different degrees of oversubscription. However, Jellyfish's unstructured design brings new challenges in routing, physical layout, and wiring. We describe and evaluate approaches that resolve these challenges effectively, indicating that Jellyfish could be deployed in today's data centers.
Study on the Carry Capacity of Edible Jellyfish Fishery in Liaodong Bay Study on the Carry Capacity of Edible Jellyfish Fishery in Liaodong Bay  [PDF]
YOU Kui,BIAN Yongning,MA Caihua,CHI Xupeng,LIU Zhiqiang,ZHANG Yuyu
- , 2016,
Abstract: Jellyfish fishing is a special type of fishery that mainly exists in some countries of East and Southeast Asia. China has the largest jellyfish fishery yield in the world with an annual harvest of around 300 thousand tons. Liaodong Bay is the most important jellyfish fishery ground in China. However, due to the high benefits of jellyfish fishery, which leads to illegal and out-of-season jellyfish fishing occurring each year in Liaodong Bay. Illegal jellyfish fishery in Liaodong Bay is a typical example of the tragedy of the commons. The key problem is that fishermen seek to an illegally initiate jellyfish fishing as early as possible. In this paper, basing on the data of edible jellyfish's biology and ecology, we mainly analyzed the history of jellyfish fishery in China, especially in Liaodong bay, and then we calculated the carry capacity of edible jellyfish in Liaodong Bay which is about 300 thousand tons one year. This number is equal to the recent annual yield of edible jellyfish in China. Furthermore, basing on the carry capacity and reasonable quotas price analysis, we set up a Jellyfish fishing quotas and deficit quotas buyback system which could be a suitable and effective solution for jellyfish fishery management and development in Liaodong Bay at the underlying roots. Although China is the first country with edible jellyfish aquaculture, the annual yield of jellyfish aquaculture is only one fifth of jellyfish fishing. So, there is a very bright developing prospect about edible jellyfish aquaculture in China
RR Lyrae Pulsation Theory  [PDF]
Marcella Marconi
Physics , 2009, DOI: 10.1063/1.3246450
Abstract: RR Lyrae stars play an important role as distance indicators and stellar population tracers. In this context the construction of accurate pulsation models is crucial to understand the observed properties and to constrain the intrinsic stellar parameters of these pulsators. The physical mechanism driving pulsation in RR Lyrae stars has been known since the middle of the 20th century and many efforts have been performed during the last few decades in the construction of more and more refined pulsation models. In particular, nonlinear pulsation models including a nonlocal time-dependent treatment of convection, such as the ones originally developed in Los Alamos in the seventies, allow us to reproduce all the relevant observables of radial pulsation and to establish accurate relations and methods to constrain the intrinsic stellar properties and the distance of these variables. The most recent results on RR Lyrae pulsation obtained through these kinds of models will be presented and a few still debated problems will be discussed.
Jellyfish Stings and Their Management: A Review  [PDF]
Luca Cegolon,William C. Heymann,John H. Lange,Giuseppe Mastrangelo
Marine Drugs , 2013, DOI: 10.3390/md11020523
Abstract: Jellyfish (cnidarians) have a worldwide distribution. Despite most being harmless, some species may cause local and also systemic reactions. Treatment of jellyfish envenomation is directed at: alleviating the local effects of venom, preventing further nematocyst discharges and controlling systemic reactions, including shock. In severe cases, the most important step is stabilizing and maintaining vital functions. With some differences between species, there seems to be evidence and consensus on oral/topical analgesics, hot water and ice packs as effective painkillers and on 30 s application of domestic vinegar (4%–6% acetic acid) to prevent further discharge of unfired nematocysts remaining on the skin. Conversely, alcohol, methylated spirits and fresh water should be carefully avoided, since they could massively discharge nematocysts; pressure immobilization bandaging should also be avoided, as laboratory studies show that it stimulates additional venom discharge from nematocysts. Most treatment approaches are presently founded on relatively weak evidence; therefore, further research (especially randomized clinical trials) is strongly recommended. Dissemination of appropriate treatment modalities should be deployed to better inform and educate those at risk. Adequate signage should be placed at beaches to notify tourists of the jellyfish risk. Swimmers in risky areas should wear protective equipment.
Jellyfish Modulate Bacterial Dynamic and Community Structure  [PDF]
Tinkara Tinta, Tja?a Kogov?ek, Alenka Malej, Valentina Turk
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039274
Abstract: Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom - forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish - enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to ‘jellyfish - associated’ and ‘free - living’ bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in bacterial population dynamics and nutrient pathways following jellyfish blooms which have important implications for ecology of coastal waters.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.