DNA Repair in fish from polluted estuaries     

Noel G. Espina  Peddrick Weis   《Marine environmental research》1995,39(1-4)

A cancer-resistant fish, the mummichog Fundulus heteroclitus, was assayed for its ability to repair damage to its genome caused by an alkylating agent. Although DNA may be alkylated at several sites, the persistence of O⁶-alkylguanine has been correlated with carcinogenesis. O⁶-alkylguanine, if not repaired before the next round of replication, can lead to base transition mutations. The DNA repair protein, O⁶-alkylguanine transferase (O⁶-AGT), removes alkyl groups from the O⁶ position of guanine.Populations from polluted and relatively pristine estuaries were compared. O⁶-AGT activity was assayed by incubating extracts of liver from feral fish with previously methylated calf thymus DNA. After incubation, the DNA was depurinated by acid hydrolysis and the O⁶-methylguanine (O⁶-MeG) was separated and quantified by HPLC. Activity was measured by the reduction of O⁶-MeG in the incubated sample as compared to controls.Both populations demonstrated O⁶-AGT activity in their livers. Both had activity levels which were not as high as those seen in mammals. The reference population had O⁶-AGT levels inversely correlated with size, which is expected since younger fish have more DNA synthesis in their livers. The polluted population did not have a significant correlation with size, and generally exhibited less activity than the reference population. The lower O⁶-AGT activity in the polluted population suggests an environmental impact, and does not answer the question as to why this species is cancer resistant.  相似文献   

Remarkable Link between Projected Uncertainties of Arctic Sea-Ice Decline and Winter Eurasian Climate   总被引：1，自引：0，他引：1  

Hoffman H.N.CHEUNG  Noel KEENLYSIDE  Nour-Eddine OMRANI  Wen ZHOU 《大气科学进展》2018,35(1):38-51

We identify that the projected uncertainty of the pan-Arctic sea-ice concentration(SIC) is strongly coupled with the Eurasian circulation in the boreal winter(December–March; DJFM), based on a singular value decomposition(SVD) analysis of the forced response of 11 CMIP5 models. In the models showing a stronger sea-ice decline, the Polar cell becomes weaker and there is an anomalous increase in the sea level pressure(SLP) along 60°N, including the Urals–Siberia region and the Iceland low region. There is an accompanying weakening of both the midlatitude westerly winds and the Ferrell cell,where the SVD signals are also related to anomalous sea surface temperature warming in the midlatitude North Atlantic.In the Mediterranean region, the anomalous circulation response shows a decreasing SLP and increasing precipitation. The anomalous SLP responses over the Euro-Atlantic region project on to the negative North Atlantic Oscillation–like pattern.Altogether, pan-Arctic SIC decline could strongly impact the winter Eurasian climate, but we should be cautious about the causality of their linkage.  相似文献   

Numerical experiments on the long-term morphodynamics of the Colorado River Delta     

Yovani Montaño  Noel Carbajal 《Ocean Dynamics》2008,58(1):19-29

The interaction among tidal currents, sediment transport, and long-term changes of the sea bottom in the Colorado River Delta have been investigated applying a two dimensional nonlinear hydrodynamic-numerical finite differences model. The system was forced by the dominant M ₂ tidal component at the open boundary. We carried out calculations to study the morphodynamics of the actual bathymetry caused by the bedload sediment transport. To investigate the origin of actual morphological features, we performed experiments using a smoothed bathymetry, in which the islands Montague, Gore, and Pelícano were eliminated. Under the imposed tidal hydrodynamics, the results indicate that the bedload transport contributes significantly in the genesis of sandbanks and in the formation and maintaining of the Montague and Gore Islands.  相似文献   

Adapting science to a warming world     

Corrine Noel Knapp  Sarah F. Trainor 《Global Environmental Change》2013,23(5):1296-1306

Climate change is complicating the variables that Alaskans consider when planning for the future. Communities, agencies and other entities have begun to grapple with both the information that they need to adapt to a changing climate and how the processes and practices of science should change to make science more useful. We reviewed sixty-three documents that expressed practical research needs related to climate change in Alaska. Documents nearly unanimously expressed that science, as it is currently practiced, is inadequate to meet the challenges of climate change. They call for processes that are more transparent, collaborative, and accessible. They recommend changed practices including maintaining accessible data-sharing archives, building networks for knowledge sharing, and creating place-based long-term partnerships with communities. They advocate integrating local knowledge, but infrequently address the complexities of how this is best accomplished. They also suggest the need for improved training in interdisciplinary research and changes in the incentive structure of research institutions. This review complements the climate-change literature by providing concrete suggestions about how to increase the utility of science from a region that is experiencing some of the most dramatic climatic change on the planet.  相似文献   

Bifurcation and generalized mixed loading conditions in geomaterials     

François Nicot  Noel Challamel  Jean Lerbet  Florent Prunier  Félix Darve 《国际地质力学数值与分析法杂志》2011,35(13):1409-1431

The concept of bifurcation has been widely discussed, based, for example, on homogeneous tests in soil mechanics. Essentially two‐dimensional (axisymmetric) conditions have been considered. This paper aims at deriving a bifurcation criterion in geomechanics, independently of the problem's dimension. This criterion is related to the vanishing of the determinant of the symmetric part of the material's (or the discrete system's) constitutive (or stiffness) matrix. The derivation is essentially based on the notion of loading parameters (controlling the loading). Basically, a bifurcation occurs when the existence of a unique solution to the quasistatic problem, involving a given set of loading parameters, is lost. Interestingly, the criterion is shown to be independent of the choice of loading parameters. As a possible extension, the context of structure mechanics is considered, and the close connection between both soil and structure analysis is discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Analysis of an Ensemble of High-Resolution WRF Simulations for the Rapid Intensification of Super Typhoon Rammasun(2014)     

Xun LI  Noel E. DAVIDSON  Yihong DUAN  Kevin J. TORY  Zhian SUN  Qinbo CAI 《大气科学进展》2020,37(2):187-210

Diagnostics are presented from an ensemble of high-resolution forecasts that differed markedly in their predictions of the rapid intensification(RI)of Typhoon Rammasun.We show that the basic difference stems from subtle differences in initializations of(a)500-850-h Pa environmental winds,and(b)midlevel moisture and ventilation.We then describe how these differences impact on the evolving convective organization,storm structure,and the timing of RI.As expected,ascent,diabatic heating and the secondary circulation near the inner-core are much stronger in the member that best forecasts the RI.The evolution of vortex cloudiness from this member is similar to the actual imagery,with the development of an inner cloud band wrapping inwards to form the eyewall.We present evidence that this structure,and hence the enhanced diabatic heating,is related to the tilt and associated dynamics of the developing inner-core in shear.For the most accurate ensemble member:(a)inhibition of ascent and a reduction in convection over the up-shear sector allow moistening of the boundary-layer air,which is transported to the down-shear sector to feed a developing convective asymmetry;(b)with minimal ventilation,undiluted clouds and moisture from the down-shear left quadrant are then wrapped inwards to the up-shear left quadrant to form the eyewall cloud;and(c)this process seems related to a critical down-shear tilt of the vortex from midlevels,and the vertical phase-locking of the circulation over up-shear quadrants.For the member that forecasts a much-delayed RI,these processes are inhibited by stronger vertical wind shear,initially resulting in poor vertical coherence of the circulation,lesser moisture and larger ventilation.Our analysis suggests that ensemble prediction is needed to account for the sensitivity of forecasts to a relatively narrow range of environmental wind shear,moisture and vortex inner-structure.  相似文献   

The writing class     

Noel Castree 《Geoforum》2002,33(1):iii

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Archaeomagnetic evidence for the age and duration of firing of mediaeval hearths from Coffee Yard, York     

Meng Zhaoqin  Mark Noel 《Geophysical Journal International》1989,97(2):357-359

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A method for correcting geographically separated remanence directions for the purpose of archaeomagnetic dating     

M. Noel  C. M. Batt 《Geophysical Journal International》1990,102(3):753-756

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The potential for photosynthesis in hydrothermal vents: a new avenue for life in the Universe?     

Noel Perez  Rolando Cardenas  Osmel Martin  Leiva-Mora Michel 《Astrophysics and Space Science》2013,346(2):327-331

We perform a quantitative assessment for the potential for photosynthesis in hydrothermal vents in the deep ocean. The photosynthetically active radiation in this case is from geothermal origin: the infrared thermal radiation emitted by hot water, at temperatures ranging from 473 up to 673 K. We find that at these temperatures the photosynthetic potential is rather low in these ecosystems for most known species. However, species which a very high efficiency in the use of light and which could use infrared photons till 1300 nm, could achieve good rates of photosynthesis in hydrothermal vents. These organisms might also thrive in deep hydrothermal vents in other planetary bodies, such as one of the more astrobiologically promising Jupiter satellites: Europa.  相似文献