The role of the stress proteins response in physiological adaptation of marine molluscs     

Brenda M. Sanders 《Marine environmental research》1988,24(1-4)

Organisms have evolved a highly conserved cellular response called the heat-shock or stress proteins response (SPR) that increases their tolerance to adverse environmental conditions. We have tested the hypothesis that the tissues of two molluscs, Mytilus edulis and Collisella pelta, respond to stressful situations by eliciting this response. We found that both heat-shock and Cd can induce the SPR in both species and are presently carrying out experiments to correlate the induction of stress proteins with an increased capacity to tolerate subsequent stressful conditions. These experiments should help us determine if the SPR plays an important role in the physiological adaptation of these species to their environment.  相似文献   

The 1970 Public Use Sample: A Geographical Context     

Ralph A. Sanders 《The Professional geographer》1975,27(3):347-350

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Cosmology with modified Newtonian dynamics (MOND)     

Sanders 《Monthly notices of the Royal Astronomical Society》1998,296(4):1009-1018

It is well known that the application of Newtonian dynamics to an expanding spherical region leads to the correct relativistic expression (the Friedmann equation) for the evolution of the cosmic scalefactor. Here, the cosmological implications of Milgrom's modified Newtonian dynamics (MOND) are considered by means of a similar procedure. Earlier work by Felten demonstrated that in a region dominated by modified dynamics the expansion cannot be uniform (separations cannot be expressed in terms of a scalefactor) and that any such region will eventually recollapse regardless of the initial expansion velocity and mean density. Here I show that, because of the acceleration threshold for the MOND phenomenology, a region dominated by MOND will have a finite size which, in the earlier Universe ( z >3), is smaller than the horizon scale. Therefore, uniform expansion and homogeneity on the horizon scale are consistent with MOND-dominated non-uniform expansion and the development of inhomogeneities on smaller scales. In the radiation-dominated era, the amplitude of MOND-induced inhomogeneities is much smaller than that implied by observations of the cosmic background radiation, and the thermal and dynamical history of the Universe is identical to that of the standard big bang model. In particular, the standard results for primordial nucleosynthesis are retained. When matter first dominates the energy density of the Universe, the cosmology diverges from that of the standard model. Objects of galaxy mass are the first virialized objects to form (by z =10), and larger structure develops rapidly. At present, the Universe would be inhomogeneous out to a substantial fraction of the Hubble radius.  相似文献   

Engineering a Remote Survey of Jet's Divertor Structure Under Conditions of Restricted Access Using Digital Photogrammetry     

B. Macklin  R. Brade  F. Hurd  S. F Mills  S. Sanders  R. Stokes  & J. Tait 《The Photogrammetric Record》1998,16(92):213-223

JET (Joint European Torus) Joint Undertaking is currently planning to install its new Gasbox Divertor remotely. In line with JET's policy and philosophy, it was decided to survey the divertor structure remotely to confirm its position, shape and integrity prior to installing the new tile configuration. A survey to metrology standards with sub-millimetre accuracy is required. While remote surveys have been carried out in the past, they have not been to this level of accuracy. Digital photogrammetry (the evolution of photogrammetry, using CCD cameras) in conjunction with “targetless” software was selected as being the most suitable technique. It was seen as the natural evolution of the survey techniques already developed for use at JET, as well as having the potential to assist in preparations for future remote handling operations. Photogrammetry requires a large number of retroreflective targets to ensure accurate results. Clearly it would not be practical to fit targets remotely to the divertor structure. However, a technique has been developed at JET which uses a combination of targeted and targetless photogrammetry. A number of frames fitted with targets will be remotely positioned on the divertor structure. When surveyed these targets allow accurate determination of camera positions. Specially developed software allows the selection of untargeted features of components in the digital pictures. Their co-ordinates can be determined by triangulation from the known camera positions. Trials have shown that accuracy of ±0.6 mm is achievable. This paper will describe the development of this concept, the design of the necessary equipment, the testing to prove the accuracy and feasibility and the trials carried out in JET's In-vessel Training Facility. These included remote handling of the six million pixel camera and other equipment, data handling and download via an ethernet link through the remote handling articulated boom, development of survey techniques, optimization of analysis techniques using coded targets for fast processing and finally the engineering assessment of the divertor structure based on survey results.  相似文献   

Phytoplankton population dynamics and productivity in a sewage-enriched tidal Creek in North Carolina     

James G. Sanders  Edward J. Kuenzler 《Estuaries and Coasts》1979,2(2):87-96

Calico Creek differs from neighboring estuaries in that it receives sewage effluent, and its waters therefore contain ample nutrients. High nutrient levels enable the phytoplankton population, which is probably light-limited, to reach densities of 10⁹ cells·1^?1 during the summer, 2 to 3 orders of magnitude higher than the surrounding, nutrient-limited populations. At cell densities greater than 10⁸ cells·1^?1 the number of dominant species is greatly reduced, and the level of diversity drops sharply. Calico Creek also differs by being very shallow; the population can be drastically affected by high runoff. The productivity of both the phytoplankton and the surroundingSpartina marsh is much higher than the neighboring unpolluted estuaries. Unlike the larger and more stable estuaries nearby, the dependence of the population on the effluent for nutrients, the possibility of toxic materials entering the creek with the effluent, and its small size make Calico Creek subject to sudden change.  相似文献   

Organic carbon accumulation in oligotrophic coastal lakes in southern Brazil during the last century     

Bueno  Carolina  Sanders  Christian J.  Niencheski  Felipe Hax  Andrade  Carlos  Burnett  William  Santos  Isaac R. 《Journal of Paleolimnology》2021,66(1):71-82

Journal of Paleolimnology - We report organic carbon (OC) accumulation rates in three freshwater ecosystems in southern Brazil, along the largest shallow coastal lagoon ecosystem in the world, the...  相似文献   

The weak shock in the core of the Perseus cluster     

J. Graham  A. C. Fabian  J. S. Sanders 《Monthly notices of the Royal Astronomical Society》2008,386(1):278-288

The dissipation of energy from sound waves and weak shocks is one of the most promising mechanisms for coupling active galactic nucleus (AGN) activity to the surrounding intracluster medium, and so offsetting cooling in cluster cores. We present a detailed analysis of the weak shock found in deep Chandra observations of the Perseus cluster core. A comparison of the spectra either side of the shock front shows that they are very similar. By performing a deprojection analysis of a sector containing the shock, we produce temperature and density profiles across the shock front. These show no evidence for a temperature jump coincident with the density jump. To understand this result, we model the shock formation using 1D hydrodynamic simulations including models with thermal conduction and  γ < 5/3  gas. These models do not agree well with the data, suggesting that further physics is needed to explain the shock structure. We suggest that an interaction between the shock and the Hα filaments could have a significant effect on cooling the post-shock gas.
We also calculate the thermal energy liberated by the weak shock. The total energy in the shocked region is about 3.5 times the work needed to inflate the bubbles adiabatically, and the power of the shock is around  6 × 10⁴⁴ erg s⁻¹  per bubble, just over  10⁴⁵ erg s⁻¹  in total.  相似文献   

System versus component response of a two-span reinforced concrete bridge system     

Nathan Johnson  M. Saiid Saiidi  David Sanders 《Bulletin of Earthquake Engineering》2009,7(2):503-517

A large-scale 20.5 m long asymmetric two-span reinforced concrete bridge was tested to failure using the shake table system at the University of Nevada Reno. Upon completion of testing, in depth analytical modeling was conducted to evaluate the accuracy of conventional methods in reproducing the bridge model response and to develop a model for further study. Utilizing the experimentally verified computer model, the system effect was investigated, comparing the system and response of individual bents as well as the response of several other bridge models. In comparing computational model of the shake table specimen and models of the individual bents with tributary mass, it was shown that for all of the columns in this study, there was generally not an increase in hysteretic energy or large displacement cycles from system response at given displacement demand. The response of the bents for each high amplitude test motion was also compared. It was shown that there were significant differences in the bent demands for a given excitation due to system effects. In addition to the shake table model, four bridge systems with a constant total lateral stiffness were used in a parametric study to determine the system effect. The symmetric and uniform versions of the bridge specimen were shown to be comparable in nonlinear performance to the bridge specimen for the same high amplitude demand. The failure progression of the bridge model and the analytical comparisons suggested that the reserve capacity from varied column heights could provide a beneficial substructure redundancy.  相似文献   

ParBreZo: A parallel,unstructured grid,Godunov-type,shallow-water code for high-resolution flood inundation modeling at the regional scale     

Brett F. Sanders  Jochen E. Schubert  Russell L. Detwiler 《Advances in water resources》2010

Topographic data are increasingly available at high resolutions (<10 m) over large spatial extents to support detailed flood inundation modeling and loss estimation analyses required for flood risk management. This paper describes ParBreZo, the parallel implementation of a two-dimensional, Godunov-type, shallow-water code, to address the computational demand of high-resolution flood modeling at the regional scale (10²–10⁴ km²). A systematic approach to unstructured grid partitioning (domain decomposition) is presented, and the Single Process Multiple Data (SPMD) paradigm of distributed-memory parallelism is implemented so the code can be executed on computer clusters with distributed memory, shared memory, or some combination of the two (now common with multi-core architectures). In a fully-wetted, load-balanced test problem, the code scales very well with a parallel efficiency of close to 100% on up to 512 processes (maximum tested). A weighted grid partitioning is used to partially address the load balancing challenge posed by partially wetted domains germane to flooding applications, where the flood extent varies over time, while the partitioning remains static. An urban dam-break flood test problem shows that weighted partitions achieve a parallel efficiency exceeding 70% using up to 48 processes. This corresponds to a 97% reduction in execution time so results are obtained in a matter of minutes, which is attractive for routine engineering analyses. A hurricane storm surge test problem shows that a 10 m resolution, 12 h inundation forecast for a 40 km length of coastline can be completed in under 2 h using 512 processors. Hence, if coupled to a hurricane forecast system capable of resolving storm surge, inundation forecasts could be made at 10 m resolution with at least a 10 h lead time.  相似文献   

Non-thermal X-rays, a high-abundance ridge and fossil bubbles in the core of the Perseus cluster of galaxies     

J. S. Sanders  A. C. Fabian  R. J. H. Dunn 《Monthly notices of the Royal Astronomical Society》2005,360(1):133-140

Using a deep Chandra observation of the Perseus cluster of galaxies, we find a high-abundance shell 250 arcsec (93 kpc) from the central nucleus. This ridge lies at the edge of the Perseus radio mini-halo. In addition we identify two Hα filaments pointing towards this shell. We hypothesize that this ridge is the edge of a fossil radio bubble, formed by entrained enriched material lifted from the core of the cluster. There is a temperature jump outside the shell, but the pressure is continuous indicating a cold front. A non-thermal component is mapped over the core of the cluster with a morphology similar to the mini-halo. Its total luminosity is  4.8 × 10⁴³ erg s⁻¹  , extending in radius to ∼75 kpc. Assuming the non-thermal emission to be the result of inverse Compton scattering of the cosmic microwave background and infrared emission from NGC 1275, we map the magnetic field over the core of the cluster.  相似文献