Impacts of mosquitofish,Gambusia affinis,on black mudfish,Neochanna diversus     

Nicholas Ling  Kate Willis 《新西兰海洋与淡水研究杂志》2013,47(6):1215-1223

The potential for western mosquitofish, Gambusia affinis, to negatively affect populations of black mudfish in New Zealand wetlands was investigated with annual fishing surveys of the Whangamarino wetland and by laboratory experiments evaluating competition and predation of mosquitofish on mudfish adults and larvae. Abundance of mudfish juveniles was reduced in the presence of mosquitofish at marginal wetland sites close to permanent water, but mosquitofish were not found at ephemeral adult mudfish habitats. In constructed wetland microcosms, mosquitofish reduced both growth and condition of post‐larval mudfish but did not attack or kill mudfish. In laboratory aquaria, mosquitofish rapidly consumed mudfish fry but survival time of the latter was significantly extended by an increase in density of submerged structures and by the presence of an alternative food source for mosquitofish. Because mosquitofish cannot survive in ephemeral wetlands that dry over summer, the impacts of mosquitofish on mudfish are likely to be minimal except in habitats where mosquitofish can survive year‐round owing to the presence of permanent standing water.  相似文献   

Modelling chemistry in the nocturnal boundary layer above tropical rainforest and a generalised effective nocturnal ozone deposition velocity for sub-ppbv NOx conditions     

Thomas A. M. Pugh  James Ryder  A. Robert MacKenzie  Sarah J. Moller  James D. Lee  Carole Helfter  Eiko Nemitz  Douglas Lowe  C. Nicholas Hewitt 《Journal of Atmospheric Chemistry》2010,65(2-3):89-110

Measurements of atmospheric composition have been made over a remote rainforest landscape. A box model has previously been demonstrated to model the observed daytime chemistry well. However the box model is unable to explain the nocturnal measurements of relatively high [NO] and [O₃], but relatively low observed [NO₂]. It is shown that a one-dimensional (1-D) column model with simple O₃-NO_x chemistry and a simple representation of vertical transport is able to explain the observed nocturnal concentrations and predict the likely vertical profiles of these species in the nocturnal boundary layer (NBL). Concentrations of tracers carried over from the end of the night can affect the atmospheric chemistry of the following day. To ascertain the anomaly introduced by using the box model to represent the NBL, vertically-averaged NBL concentrations at the end of the night are compared between the 1-D model and the box model. It is found that, under low to medium [NO_x] conditions (NO_x?<?1 ppbv), a simple parametrisation can be used to modify the box model deposition velocity of ozone, in order to achieve good agreement between the box and 1-D models for these end-of-night concentrations of NO_x and O₃. This parametrisation would could also be used in global climate-chemistry models with limited vertical resolution near the surface. Box-model results for the following day differ substantially if this effective nocturnal deposition velocity for ozone is implemented; for instance, there is a 9% increase in the following days peak ozone concentration. However under medium to high [NO_x] conditions (NO_x > 1 ppbv), the effect on the chemistry due to the vertical distribution of the species means no box model can adequately represent chemistry in the NBL without modifying reaction rate coefficients.  相似文献   

Landslides triggered by the 1949 Khait earthquake, Tajikistan, and associated loss of life   总被引：3，自引：0，他引：3  

Stephen G. Evans  Nicholas J. Roberts  Anatoli Ischuk  Keith B. Delaney  Galina S. Morozova  Olga Tutubalina 《Engineering Geology》2009,109(3-4):195-212

Earthquake-triggered landslides are a major geological hazard in Central Asia. In July 1949, the M7.4 Khait earthquake triggered many hundreds of landslides in a mountainous region near the southern limit of the Tien Shan Mountains, central Tajikistan. These landslides involved widespread rock-slope failure as well as large numbers of flowslides in loess that mantles the steep slopes of the region. In the Yasman valley hundreds of loess landslides coalesced to form a massive loess flow (est. vol. 245 Mm³) that travelled up to 20 km on a slope of only 2°. In an adjacent valley, the Khait landslide involved transformation of an earthquake-triggered rockslide into a very rapid flow by the entrainment of saturated loess into its movement. It travelled 7.41 km over a vertical distance of 1421 m with an estimated average velocity of ~30 m/s. We estimate its volume as 75 Mm³, an order of magnitude less that previously published estimates. The Khait landslide was simulated using DAN. The number of casualties due to earthquake-triggered landslides in the epicentral region was considerable. Approximately 4000 people were killed in the Yasman valley loess flow as 20 villages (kishlaks) were overwhelmed. In the Khait landslide alone we estimate ca. 800 people lost their lives when the villages of Khait and Khisorak were overrun by rapidly moving debris. Our data indicates that a total of approximately 7200 people were killed by earthquake-triggered landslides in the epicentral region of the Khait earthquake and that, in terms of loss of life, the 1949 Yasman valley loess flow was one of the most destructive landslides in recent history.  相似文献   

Morphologies of Ly-emitting galaxies     

Nicholas Bond   《New Astronomy Reviews》2009,53(3):42

Lyman alpha emitters (LAEs) are high-redshift galaxies that are believed to be actively star-forming and low in mass. Although such a population of galaxies would not be expected to lie on the Hubble Sequence, there is much we can learn from their morphological properties, including the size and distribution of their star-forming regions, the spatial correlation between emission in different bandpasses, and the possible presence of a merger/interaction with one or more neighboring galaxies. Early morphological studies suggest that most LAEs are small in size (1 kpc) and concentrated, but some (20–45%) are seen to display clumpy/irregular morphologies extending over larger radii. Constructing a more detailed picture will require a standard set of depth-independent morphological diagnostics for high-redshift galaxies. These diagnostics can then be measured differentially with redshift, shedding light on the evolution of the galaxy formation process with time.  相似文献   

Kilometric type III burst enhancements associated with interplanetary shocks     

Nicholas Dunckel 《Solar physics》1976,46(2):461-464

Type III bursts have been observed in the 30–100 kHz range which show localized enhancements in their spectra. The enhancements exhibited by a series of type III bursts extending over a period of several hours show a consistent decrease in frequency. The rate of this decrease is consistent with the movement of an interplanetary shock. The passage of such a shock by the Earth is suggested by the occurrence of sudden commencements at approximately the expected time.  相似文献   

Development and application of data collection forms for post-earthquake surveys of structural damage and human casualties     

Choudhury  G. Sayeed  Jones  Nicholas P. 《Natural Hazards》1996,13(1):17-38

To reduce loss of life and injury resulting from earthquakes, the relationship between earthquake-induced building failure and injury severity and distribution needs to be clarified. For this purpose, a series of data collection forms were developed to collect pertinent data for post-event analysis and to provide a basis for structural triage in the field shortly following an earthquake for search and rescue purposes. A companion paper described the identification of variables affecting the outcome of an occupant of a damaged building and the classification of these variables into three levels of priority for data collection. This paper continues the development by describing the design of the data collection forms and the application of the forms to damaged buildings from past earthquakes. These forms represent a significant departure from existing forms in that they consider both casualties and building damage jointly, and in a consistent format.  相似文献   

Time for a change?     

Nicholas C. Pepin 《Area》1997,29(1):59-71

Summary This paper analyses the geographical variation in changes in lighting conditions at opposite ends of the working day which would arise from the proposal to align UK clocks with those in Europe. Strong spatial contrasts are illustrated, the pattern of benefit and disadvantage depending on the threshold times used to define darkness. In most areas disadvantage outweighs benefit. In addition, comparisons are made with mainland Europe.  相似文献   

Scenarios of Future Climate Change: Effects on Frost Occurrence and Severity in the Maritime Uplands of Northern England     

Nicholas C. Pepin 《Geografiska Annaler: Series A, Physical Geography》1997,79(1-2):121-137

Changes in annual frost frequency and annual frost accumulation associated with a variety of temperature change scenarios are mapped for northern England. Estimates of future changes are obtained through application of analytical theory to convert predictions of mean daily minimum temperatures and their inter-diurnal variability to accumulated frost degrees and frost frequency. The baseline climate is provided by regression analysis of surface data involving up to ten terrain variables. Future scenarios include warm and cold analogues, maritime and continental airflow scenarios, arbitrary warming and two general circulation model (GCM) simulations: UKHI (United Kingdom Meteorological Office High Resolution GCM Equilibrium Experiment) and GISS (Goddard Institute for Space Studies). Considerable contrasts emerge between scenarios, with substantial reductions in frost frequency and accumulation in the two GCM 2 *CO₂ simulations. This is to be expected in a maritime area where small changes in temperature have a large influence on parameters involving threshold temperatures. Increases in frost occur under the continental airflow scenario. Changes in frost do not necessarily complement those in accumulated warmth, and therefore indices combining possible changes in warmth and frost are helpful.  相似文献   

多元PCR在黑鲍(Haliotis rubra)微卫星遗传研究中的应用   总被引：2，自引：1，他引：2  

黎中宝  Appleyard Sharon A  Elliott Nicholas G 《海洋与湖沼》2005,36(4):319-325

根据D03等11个微卫星引物单位点PCR扩增时优化的扩增条件(退火温度、MgCl2等)和11个微卫星引物所带有的荧光颜色、等位基因大小变异范围及反应的灵敏度，可将11个微卫星引物分成A组(D03、G04、B04和H08)、B组(A09、H11、A08和G01)和C组(CmrHrl．24、CmrHr2．30和CmrHr2．23)进行多元PCR扩增，结果显示各组内位点之间的分离清晰，这表明多元PCR可以大大提高微卫星检测仪器的使用效率和提高实验效果，在微卫星研究中是一种快速便捷的方法。  相似文献   

Efficient higher-order finite-difference schemes for parabolic models     

Nicholas Dodd   《Coastal Engineering》1996,28(1-4)

Implicit finite-difference schemes for use in parabolic equation models are developed. Like the familiar Crank-Nicolson scheme, which has hitherto been used almost exclusively for the solution of these equations, these schemes are unconditionally stable and use a computational molecule of only six points on two “time” levels. However, they are accurate to a higher order than the Crank-Nicolson scheme, thus allowing the solution grid to be coarser and the solution time to be (approximately) halved. Examples of computations on constant depth are shown, in which significant reductions in time and grid-point density are achieved, for two different parabolic models. The schemes are then extended to refraction and diffraction, and are shown to have a similar effect in this more general case too. It is recommended that finite-difference schemes based on these higher-order (or Hermitian) methods replace the more commonly used Crank-Nicolson scheme in all physical domain parabolic equation models, but especially in minimax (wide-angle) equation models.  相似文献