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   

Strong hydrographic controls on spatial and seasonal variability of dissolved organic carbon in the Chukchi Sea   总被引：1，自引：0，他引：1  

Jeremy T. Mathis  Dennis A. Hansell  Nicholas R. Bates 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3245

A detailed analysis of dissolved organic carbon (DOC) distribution in the Western Arctic Ocean was performed during the spring and summer of 2002 and the summer of 2003. DOC concentrations were compared between the three cruises and with previously reported Arctic work. Concentrations of DOC were highest in the surface water where they also showed the highest degree of variability spatially, seasonally, and annually. Over the Canada Basin, DOC concentrations in the main water masses were: (1) surface layer (71±4 μM, ranging from 50 to 90 μM); (2) Bering Sea winter water (66±2 μM, ranging from 58 to 75 μM); (3) halocline layer (63±3 μM, ranging from 59 to 68 μM), (4) Atlantic layer (53±2 μM, ranging from 48 to 57 μM), and (5) deep Arctic layer (47±1 μM, ranging from 45 to 50 μM). In the upper 200 m, DOC concentrations were correlated with salinity, with higher DOC concentrations present in less-saline waters. This correlation indicates the strong influence that fluvial input from the Mackenzie and Yukon Rivers had on the DOC system in the upper layer of the Chukchi Sea and Bering Strait. Over the deep basin, there appeared to be a relationship between DOC in the upper 10 m and the degree of sea-ice melt water present. We found that sea-ice melt water dilutes the DOC signal in the surface waters, which is contrary to studies conducted in the central Arctic Ocean.  相似文献   

Relating the reproductive toxicity of five ingested metals in calanoid copepods with sulfur affinity   总被引：6，自引：0，他引：6  

Hook SE  Fisher NS 《Marine environmental research》2002,53(2):161-174

The sublethal toxicity of dietary Ag, Cd, Hg, Mn, and Zn to marine copepods, measured as depressed egg production, was evaluated as a function of ambient metal concentrations and metal concentrations in copepod tissues. All metals were toxic following 4-h feedings on metal-contaminated phytoplankton food, but there was a four order of magnitude difference between the inhibitory concentration in copepod tissues of the most toxic (2.4 nmol g(-1) dry wt. for Hg) and least toxic (13.4 micromol g(-1) dry wt. for Mn) metals. Metal concentrations in copepods that elicited a toxic response were about 3 times higher than background concentrations for Ag and 9 times higher for Hg, about 2 times higher for Cd, two orders of magnitude higher for Mn, and only 5% higher for Zn. Copepods exposed to lower concentrations of Zn for longer periods (1 week), resulting in tissue Zn concentrations similar to those in the short-term exposures, were not affected, suggesting that copepods were capable of adjusting to slowly increasing Zn by sequestration of this metal. Toxic metal concentrations in copepod tissues were directly proportional (r2 = 0.85) to the affinity of the metals for sulfur, as indicated by the solubility products of the metal sulfides. This relationship, together with protein analysis of eggs, published recently, suggests that metals affect egg production by binding to enzymes involved with vitellogenesis.  相似文献   

Multispecies analysis in Balsfjord, northern Norway: solution and sensitivity analysis of a simple ecosystem model     

Bax  Nicholas; Eliassen  Jens-Eric 《ICES Journal of Marine Science》1990,47(2):175-204

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Comparison of atmospheric forcing in four sub-arctic seas     

Muyin Wang  Nicholas A. Bond  James E. Overland 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2543

A comparative analysis was conducted on climate variability in four sub-arctic seas: the Sea of Okhotsk, the Bering Sea shelf, the Labrador Sea, and the Barents Sea. Based on data from the NCEP/NCAR reanalysis, the focus was on air–sea interactions, which influence ice cover, ocean currents, mixing, and stratification on sub-seasonal to decadal time scales. The seasonal cycles of the area-weighted averages of sea-level pressure (SLP), surface air temperature (SAT) and heat fluxes show remarkable similarity among the four sub-arctic seas. With respect to variation in climate, all four seas experience changes of comparable magnitude on interannual to interdecadal time scales, but with different timing. Since 2000 warm SAT anomalies were found during most of the year in three of the four sub-arctic seas, with the exception of the Sea of Okhotsk. A seesaw (out of phase) pattern in winter SAT anomalies between the Labrador and the Barents Sea in the Atlantic sector is observed during the past 50 years before 2000; a similar type of co-variability between the Sea of Okhotsk and the Bering Sea shelf in the Pacific is only evident since 1970s. Recent positive anomalies of net heat flux are more prominent in winter and spring in the Pacific sectors, and in summer in the Atlantic sectors. There is a reduced magnitude in wind mixing in the Sea of Okhotsk since 1980, in the Barents Sea since 2000, and in early spring/late winter in the Bering Sea shelf since 1995. Reduced sea-ice areas are seen over three out of four (except the Sea of Okhotsk) sub-arctic seas in recent decades, particularly after 2000 based on combined in situ and satellite observations (HadISST). This analysis provides context for the pan-regional synthesis of the linkages between climate and marine ecosystems.  相似文献   

Formation and occurrence of organic hydroperoxides in the troposphere: Laboratory and field observations     

C. Nicholas Hewitt  Gregory L. Kok 《Journal of Atmospheric Chemistry》1991,12(2):181-194

The formation and occurrence of hydroperoxides in the troposphere have been studied by laboratory experiments and by preliminary field measurements. Nine alkenes were reacted individually with ozone in a reaction chamber in the presence of excess water, and the amounts of hydrogen peroxide and of nine organic hydroperoxides produced in the gas and aerosol phases and deposited on the chamber walls determined by HPLC. The reactions of ethene, propene, 1-butene and isoprene gave hydroxymethyl hydroperoxide as the major product with no hydrogen peroxide observed. In the case of - and -pinene, 2-carene and limonene the major product was hydrogen peroxide. Cis-2-butene produced hydrogen peroxide and methyl hydroperoxide. Preliminary measurements of hydrogen peroxide and five organic hydroperoxides in ambient air were made at Niwot Ridge, Colorado from 24 July–4 August 1989. The gas-phase species were preconcentrated by cryotrapping with subsequent HPLC separation. The gas-phase concentrations of H₂O₂ ranged from 0.5–2 ppbv with the lowest concentrations being measured at night and the highest under conditions of strong photochemical activity. The maximum concentrations of hydroxymethyl hydroperoxide approximated those of H₂O₂. Methyl hydroperoxide concentrations ranged from <50 to 800 pptv and three other organic hydroperoxides were detected at concentrations below 200 pptv. High volume aerosol samples yielded H₂O₂ and methyl hydroperoxide concentrations <10 ng m^-3 while H₂O₂ and six organic species were detected in rainwater at concentrations in the range <0.01–50 M.  相似文献   

Corrigendum to “Sedimentology, stratigraphy, and glacier dynamics, western Scottish Highlands” [Quaternary Research 68 (2007) 79–95]     

Nicholas R. Golledge   《Quaternary Research》2007,68(3):456-457

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