Changes in the fatty acid composition of the gill phospholipids in Gammarus duebeni with degree of gill contamination     

R.J. Morris  A.P.M. Lockwood  M.E. Dawson 《Marine pollution bulletin》1982,13(10):345-348

The fatty acid composition of the gill lipids from Gammarus duebeni have been compared in relation to the degree of contamination of the gills by lipophilic materials. The results indicate that at higher levels of gill contamination a greater proportion of polyunsaturated 20:5 fatty acid occurs in the gill phospholipids. We suggest this may be a response to a change in the physical state of the gill membranes resulting from the contamination.  相似文献   

« Surface-fed Dikes » — The origin of some unusual dikes along the Hilina fault zone,Kilauea volcano,Hawaii     

R. M. Easton  J. P. Lockwood 《Bulletin of Volcanology》1983,46(1):45-53

The origin of dike-like bodies along the Hilina fault scarp on the south flank of Kilauea Volcano. Hawaii has been the subject of recent controversy. Some geologists favour an origin by intrusion of magma from below, others favour « intrusion » of lava derived from above — lava derived from fluid surface flows which poured down open cracks. In order to distinguish between deep versus surface sources for the bodies, a suite of dike and other samples were analyzed for S, H₂O, and Cl. All surface flows are degassed, whereas known dikes are volatile-rich. Samples of the Hilina dikes, and dikes from the Ninole Formation, Mauna Loa are degassed, indicating that these dikes were surface-fed — formed by magma which had been de-volatized by surface transport. A model is presented whereby the Hilina dikes form in talus and lava cones that drape the Hilina fault scarp. Seismic activity during eruption may have played an important role in the formation of the Hilina dikes. Similar dikes in the Ninole Formation probably formed in a similar environment.  相似文献   

On the longitudinal extent of magnetopause reconnection pulses     

M. Lockwood  C. J. Davis 《Annales Geophysicae》1996,14(9):865-878

The open magnetosphere model of cusp ion injection, acceleration and precipitation is used to predict the dispersion characteristics for fully pulsed magnetic reconnection at a low-latitude magnetopause X-line. The resulting steps, as would be seen by a satellite moving meridionally and normal to the ionospheric projection of the X-line, are compared with those seen by satellites moving longitudinally, along the open/closed boundary. It is shown that two observed cases can be explained by similar magnetosheath and reconnection characteristics, and that the major differences between them are well explained by the different satellite paths through the events. Both cases were observed in association with poleward-moving transient events seen by ground-based radar, as also predicted by the theory. The results show that the reconnection is pulsed but strongly imply it cannot also be spatially patchy, in the sense of isolated X-lines which independently are intermittently active. Furthermore they show that the reconnection pulses responsible for the poleward-moving events and the cusp ion steps, must cover at least 3 h of magnetic local time, although propagation of the active reconnection region may mean that it does not extend this far at any one instant of time.  相似文献   

Correlated variations of planetary albedos and coincident solar-interplanetary variations     

Steven T. Suess  G. W. Lockwood 《Solar physics》1980,66(2):393-409

To locate two-dimensional positions of the solar decametric radio bursts a heliograph was developed on the basis of the UTR-2 radiotelescope (Khar'kov) operated in the range 10–26 MHz. The beamwidth of the heliograph rapid-scanning pencil-beam is 25 arc min at 25 MHz, and its field of view is about 3.5° (E-W) × 2.0° (N-S). The instrument yields rapidly forty records of the radio brightness of all (8 × 5) elementary parts (each 25 arc min in diameter) of the investigated sky area during every period of 1/4 s. Both coordinates of a burst center are measured with an accuracy 5 arc min. The bandwidth of the receiving system is 10 kHz. The heliograph operates in conjunction with a radiospectrograph connected to the output of a N-S arm of the UTR-2 array. The data observations with the UTR-2 correspond only to one linear polarized component.The ionospheric distortion of the test records of the radio source Cassiopeia-A that occurred sometimes is illustrated.First results of 25 MHz observations of the solar radio storm in August, 1976 with the heliograph are presented here. This storm is accompanied by the compact sunspot group travelling all over the optical disk. The type III and stria bursts were predominant during the storm. On the given day the scattering regions of their apparent centers were overlapped and the sizes of these regions were usually not more than 5 arc min. On some days there occurred additional burst sources displaced in position from the persistent storm region. It was found out that, as a rule, 25 MHz stria-bursts from the type IIIb chain coincided in position with the following type III burst at the same frequency. The difference of the daily averaged coordinates of both stria and type III bursts was considerably smaller than the mean diameter of their sources.The radial distance of the 25 MHz storm region from the solar center was calculated by using the three methods. The storm height was estimated as 1.8R from the rotation rate close to the central meridian of the storm center. Definite association of the spots with the storm near the limb allowed to determine the average value 2.1R for the height. The limb measurements give the mean height of 2.3R .The center-to-limb variation of the storm source height is a known fact in the meter-wavelength range. This is the evidence of the propagation effects in the solar corona being essential to interpret the results of the radio source location.  相似文献   

Recovery of datable charcoal beneath young lavas: Lessons from Hawaii     

J. P. Lockwood  P. W. Lipman 《Bulletin of Volcanology》1980,43(3):609-615

Field studies in Hawaii aimed at providing a radiocarbon-based chronology of prehistoric eruptive activity have led to a good understanding of the processes that govern the formation and preservation of charcoal beneath basaltic lava flows. Charcoal formation is a rate-dependent process controlled primarily by temperature and duration of heating, as well as by moisture content, density, and size of original woody material. Charcoal will form wherever wood buried by lava is raised to sufficiently high temperatures, but owing to the availability of oxygen it is commonly burned to ash soon after formation. Wherever oxygen circulation is sufficiently restricted, however, charcoal will be preserved, but where atmospheric oxygen circulates freely, charcoal will only be preserved at lower temperature, below that required for charcoal ignition or catalytic oxidation. These factors cause carbonized wood, especially that derived from living roots, to be commonly preserved beneath all parts of pahoehoe flows (where oxygen circulation is restricted), but only under margins of aa. Pratical guidelines are given for the recovery of datable charcoal beneath pahoehoe and aa. Although based on Hawaiian basaltic flows, the guidelines should be applicable to other areas.  相似文献   

Assessment of Managed Aquifer Recharge Site Suitability Using a GIS and Modeling          下载免费PDF全文

Tess A. Russo  Andrew T. Fisher  Brian S. Lockwood 《Ground water》2015,53(3):389-400

We completed a two‐step regional analysis of a coastal groundwater basin to (1) assess regional suitability for managed aquifer recharge (MAR), and (2) quantify the relative impact of MAR activities on groundwater levels and sea water intrusion. The first step comprised an analysis of surface and subsurface hydrologic properties and conditions, using a geographic information system (GIS). Surface and subsurface data coverages were compiled, georeferenced, reclassified, and integrated (including novel approaches for combining related datasets) to derive a spatial distribution of MAR suitability values. In the second step, results from the GIS analysis were used with a regional groundwater model to assess the hydrologic impact of potential MAR placement and operating scenarios. For the region evaluated in this study, the Pajaro Valley Groundwater Basin, California, GIS results suggest that about 7% (15 km²) of the basin may be highly suitable for MAR. Modeling suggests that simulated MAR projects placed near the coast help to reduce sea water intrusion more rapidly, but these projects also result in increased groundwater flows to the ocean. In contrast, projects placed farther inland result in more long‐term reduction in sea water intrusion and less groundwater flowing to the ocean. This work shows how combined GIS analysis and modeling can assist with regional water supply planning, including evaluation of options for enhancing groundwater resources.  相似文献   

Spatial and temporal infiltration dynamics during managed aquifer recharge     

Racz AJ  Fisher AT  Schmidt CM  Lockwood BS  Los Huertos M 《Ground water》2012,50(4):562-570

Natural groundwater recharge is inherently difficult to quantify and predict, largely because it comprises a series of processes that are spatially distributed and temporally variable. Infiltration ponds used for managed aquifer recharge (MAR) provide an opportunity to quantify recharge processes across multiple scales under semi-controlled conditions. We instrumented a 3-ha MAR infiltration pond to measure and compare infiltration patterns determined using whole-pond and point-specific methods. Whole-pond infiltration was determined by closing a transient water budget (accounting for inputs, outputs, and changes in storage), whereas point-specific infiltration rates were determined using heat as a tracer and time series analysis at eight locations in the base of the pond. Whole-pond infiltration, normalized for wetted area, rose rapidly to more than 1.0 m/d at the start of MAR operations (increasing as pond stage rose), was sustained at high rates for the next 40 d, and then decreased to less than 0.1 m/d by the end of the recharge season. Point-specific infiltration rates indicated high spatial and temporal variability, with the mean of measured values generally being lower than rates indicated by whole-pond calculations. Colocated measurements of head gradients within saturated soils below the pond were combined with infiltration rates to calculate soil hydraulic conductivity. Observations indicate a brief period of increasing saturated hydraulic conductivity, followed by a decrease of one to two orders of magnitude during the next 50 to 75 d. Locations indicating the most rapid infiltration shifted laterally during MAR operation, and we suggest that infiltration may function as a "variable source area" processes, conceptually similar to catchment runoff.  相似文献   

极区电离层对IMF B_z 4次快速转向的响应——EISCAT/ESR雷达观测          下载免费PDF全文

蔡红涛  马淑英  I.W. McCrea  J. A. Davis  M. Lockwood  S.E. Milan 《地球物理学报》2009,52(7):1685-1692

利用EISCAT VHF和EISCAT Svalbard（ESR）雷达观测数据,对2003年2月12日IMF B_z分量4次快速方向转换期间,极区电离层,尤其是极尖/极隙区的响应特征进行了分析研究.随着IMF B_z方向的多次快速变化,地面雷达观测到极尖/极隙区所在位置随着开放-闭合磁力线边界在纬度方向上来回移动.在此期间,极区电离层等离子体水平对流多次反向,表现出与IMF B_z分量强的负相关性.进一步分析表明：极区磁层-电离层系统在日侧对IMF极性变化的平均响应时间约为3 min.  相似文献   

A Prominent Apparition of Neptune's South Polar Feature     

Kathy RagesHeidi B. Hammel  G.W. Lockwood 《Icarus》2002,159(1):262-265

During the last week of June 2001, a bright apparition of Neptune's South Polar Feature (SPF) at 70°S was observed to develop and decay in less than 30 hours, displaying contrast of ∼2.5 at 619 nm. Assuming that the same SPF was observed on two consecutive rotations of Neptune, the feature moved eastward at 3.2±1.8° hr⁻¹ (130±80 m s⁻¹). The SPF made no obvious appearances during eight other Hubble Space Telescope (HST) observations of Neptune between July 2000 and June 2001, although there was a faint feature at 70°S in one image in October 2000. A prominent SPF was present in near-IR Keck Telescope images in August 2000. Bright SPFs are seen on ∼10% of the HST images of Neptune obtained since 1994, and a fainter SPF is visible on another ∼10%. An SPF bright enough to be visible at HST resolution was present around half the time during the last week of Voyager's approach to Neptune in August 1989, with one prominent brightening, suggesting that the SPF is less visible now than in 1989.  相似文献   

Solar Proton Rigidity Spectra From 1 to 10 gv of Selected Flare Events Since 1960     

Lockwood  J.A.  Debrunner  H.  Flueckiger  E.O.  Ryan  J.M. 《Solar physics》2002,208(1):113-140

We have deduced the power-law rigidity spectra, J(P)=AP ^–, and the spectral evolution of the solar flare events that occurred in the present solar activity cycle on 6 November 1997, 14 July 2000, and 15 and 18 April 2001. The implications of these results for the acceleration of high-energy protons are discussed. The analysis is based on the ratios of the Mt. Washington to the Durham neutron monitor count-rate increases during the solar flare events. These two neutron monitors are located at different elevations (828 and 1030 g cm^–2, respectively) but at approximately the same geographical latitude and longitude. The proton spectra from 1 to 10 GV determined from the ratios of the count rate increases of the two neutron monitors are found to agree with those deduced from the global neutron monitor network or selected neutron monitors in 10 solar flare events from 1960 to 1990 for which comparative results are available. Thus the ratio method is quick, easy and reliable for deducing the spectral shape of solar flare protons at neutron monitor rigidities and for obtaining the spectral evolution as a function of time.  相似文献