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61.
Carilli CL Lewis GF Djorgovski SG Mahabal A Cox P Bertoldi F Omont A 《Science (New York, N.Y.)》2003,300(5620):773-775
Images of the molecular CO 2-1 line emission and the radio continuum emission from the redshift 4.12 gravitationally lensed quasi-stellar object (QSO) PSS J2322+1944 reveal an Einstein ring with a diameter of 1.5". These observations are modeled as a star-forming disk surrounding the QSO nucleus with a radius of 2 kiloparsecs. The implied massive star formation rate is 900 solar masses per year. At this rate, a substantial fraction of the stars in a large elliptical galaxy could form on a dynamical time scale of 108 years. The observation of active star formation in the host galaxy of a high-redshift QSO supports the hypothesis of coeval formation of supermassive black holes and stars in spheroidal galaxies. 相似文献
62.
There is global recognition that sustainable land use requires monitoring that will detect change on a scale that protects the resource. That fundamental necessity is threatened where labor-intensive methods and high labor costs cause sampling deficiencies and increased Type-II error rates (false negatives). Ground-based imaging is a monitoring method that reduces monitoring labor costs. Nadir (vertical) images acquired with common digital cameras can be manually analyzed for cover using free software. We used an innovative field protocol to acquire standardized, freehand, nadir images (samples) of rangeland, then compared point intercept (PI) and image-analysis techniques. Between methods, precision (repeatability) across users was equivalent; cover measurements were often different, and the image-analysis technique took only a third as long to complete. Image analysis has several advantages over PI besides the reduced labor cost: Images are permanent resource records available for reanalysis if data are questioned, if software improves, or if management objectives change; and image analysis is less biased by moving vegetation, moving pointing devices, and bright vegetation color. 相似文献
63.
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65.
A soil-diagnostic key to manage saline and waterlogged catchments in the Mt Lofty Ranges, South Australia 总被引:1,自引:0,他引:1
Abstract. Dryland salinity in the Mt Lofty Ranges, South Australia has developed as a result of native vegetation being replaced with pastures that use less water. Groundwaters have risen and mobilized ions (sodium, chloride, sulphate and iron) stored within deeply weathered micaceous sandstones and schists. Salinity resulting from sodium chloride is common in agricultural catchments around Australia, but saline sulphidic soils (with sulphate and iron) have only been studied in South Australia. Salinity is also associated with waterlogging and secondary sodicity. The amelioration of dryland salinity and waterlogging involves management of whole catchments, not just the area that is currently saline. It is imperative that all processes operating in saline catchments and their interactions are clearly understood.
Salinity, waterlogging, sodicity, sulphidization and water erosion were studied in four saline sub-catchments in the Mt Lofty Ranges. Grey (bleached) and yellow mottles (iron depletions) or black and red stains (iron concentrations) develop under certain conditions of water saturation, salinization, sulphidization, sodification and water erosion in surface and subsurface horizons. The amounts of these diagnostic features were used to develop a farm planning key for managing saline catchments in the Mt Lofty Ranges. Using soil diagnostic features, soil-water processes in saline catchments are easily identified by farmers and land managers. Management options (e.g. fencing, tree planting and drainage) are then targeted to specific soils and can be easily incorporated by agricultural advisers into farm management plans. We recommend that soil diagnostic features which help predict the onset of land degradation be used in the production of land capability maps for farm planning purposes. 相似文献
Salinity, waterlogging, sodicity, sulphidization and water erosion were studied in four saline sub-catchments in the Mt Lofty Ranges. Grey (bleached) and yellow mottles (iron depletions) or black and red stains (iron concentrations) develop under certain conditions of water saturation, salinization, sulphidization, sodification and water erosion in surface and subsurface horizons. The amounts of these diagnostic features were used to develop a farm planning key for managing saline catchments in the Mt Lofty Ranges. Using soil diagnostic features, soil-water processes in saline catchments are easily identified by farmers and land managers. Management options (e.g. fencing, tree planting and drainage) are then targeted to specific soils and can be easily incorporated by agricultural advisers into farm management plans. We recommend that soil diagnostic features which help predict the onset of land degradation be used in the production of land capability maps for farm planning purposes. 相似文献
66.
The objective of this study was to investigate the effect of newly developed soya milk Tris (SMT)‐based phytoextender as an alternative to egg yolk Tris (EYT) extender used for cryopreservation of buffalo (Bubalus bubalis) spermatozoa on apoptosis. Fresh buffalo semen (control without dilution) was cryopreserved in conventional EYT (20% egg yolk v/v in Tris) and SMT (25% soya milk v/v in Tris) extender and used for the assessment of expression of apoptotic proteins. Proteins extracted from a total number of nine ejaculates from three individual buffalo bulls chosen at random were separated using SDS–PAGE followed by immunoblotting against caspase‐8, caspase‐9, caspase‐3, poly(ADP‐ribose)polymerase (PARP), cytochrome c and apoptosis inducing factor (AIF). In addition, fluorescence microscopy was used for the detection of mitochondrial membrane potential (JC‐1 assay) and apoptotic cells (annexin V‐FITC/PI assay). The results obtained clearly indicate the significant (p < 0.05) reduction in the expression of caspase‐3 (27 kDa), caspase‐8 (53 kDa), caspase‐9 (50 kDa) precursor and cytochrome c (17 kDa) in semen cryopreserved in SMT extender in comparison with EYT extender. A non‐significant (p > 0.05) reduction in expression of PARP‐DNA‐binding subunit (24 kDa) was observed in SMT extender. No expression of AIF was found in cryopreserved semen samples. A significant (p < 0.05) increase in the mean percentage of cells having high mitochondrial membrane potential and a non‐significant (p > 0.05) decrease in late apoptotic cells (AN+/PI+) was observed in SMT extender when compared to EYT extender. The results demonstrated that cryopreservation of buffalo semen in SMT‐based phytoextender can replace the traditional egg yolk extenders as it reduces the expression of apoptotic proteins maintaining high mitochondrial membrane potential and gives better protection to sperms in terms of its non‐animal origin. 相似文献
67.
In the present study a cytological, histological and morphometrical comparison between the ovaries of the llama, the cow and the sheep is presented, at two phases of the ovarian cycle. There were found differences in the amount of primordial and primary follicles, the size of secondary follicles and follicular cells, and type and distribution of the connective tissue inside the stroma of the ovary. It would be necessary to study the fine structure of the ovary and the so-called "embryological remnants", for its permanent appearance in most (50%) of the ovaries. 相似文献
68.
B. S. Cox C. S. Guy W. A. Fredenberg L. R. Rosenthal 《Fisheries Management and Ecology》2013,20(5):390-400
Management agencies in several western states of the United States are implementing suppression programmes to control non‐native lake trout, Salvelinus namaycush (Walbaum), for the conservation of native species. This study was implemented to ascertain the population demographics of an expanding lake trout population and use those data to construct an age‐structured model to inform suppression efforts. Population projection matrices were used to model population growth and identify age or stage classes with the greatest influence on population growth. The size and age structure of lake trout sampled was skewed towards juveniles, indicating strong recruitment and a growing population. Matrix‐model simulations corroborated the observed size and age structure, as the lake trout population was predicted to grow exponentially (λ = 1.35, 95% CL: 1.25–1.43) with no suppression efforts. Elasticity analysis of matrix models indicated the relative contribution of survival rates to population growth among immature age classes was equal from age 0 to age at first maturity, but immature survival rates contributed more than adult survival and fertility rates. These results emphasise the importance of targeting juvenile lake trout for suppression efforts during exponential growth in recently established populations. 相似文献
69.
V. Phogat A. K. Yadav R. S. Malik Sanjay Kumar Jim Cox 《Paddy and Water Environment》2010,8(4):333-346
The HYDRUS-ID model was experimentally tested for water balance and salt build up in soil under rice crop irrigated with different
salinity water (ECiw) of 0.4, 2, 4, 6, 8 and 10 dS m−1 in micro-lysimeters filled with sandy loam soil. Differences of means between measured (M) and HYDRUS-1D predicted (P) values of bottom flux (Q
o) and leachate EC as tested by paired t test were not found significant at P = 0.05 and a close agreement between RMSE values showed the applicability of the HYDRUS-1D to simulate percolation and salt
concentration in the micro-lysimeters under rice crop. Potential ET values of rice as obtained from CROPWAT matched well with
model predicted and measured one at all ECiw treatments. The model predicted root water uptake varied from 66.1 to 652.7 mm
and the maximum daily salt concentration in the root zone was 0.46, 2.3, 4.5, 6.7, 8.4 and 10.2 me cm−3 in 0.4, 2, 4, 6, 8 and 10 dS m−1 ECiw treatments, respectively. The grain production per unit evapotranspiration (
\textWP\textET\texta {\text{WP}}_{{{\text{ET}}_{\text{a}} }} ) value of 2.56 in ECiw of 0.4 dS m−1 treatment declined to 1.31 with ECiw of 2 dS m−1. The
\textWP\textET\texta {\text{WP}}_{{{\text{ET}}_{\text{a}} }} reduced to one-fifth when percolation was included in the productivity determination. Similarly, the water productivity in
respect of total dry matter production (TDM) was also reduced in different treatments. Therefore, the model predicted values
of water balance can be effectively utilized to calculate the water productivity of rice crop. 相似文献
70.
Judith A. Hudson DVM PhD Susan T. Finn-Bodner DVM MS Joan R. Coates DVM Donald C. Sorjonen DVM MS Stephen T. Simpson DVM MS James C. Wright DVM PhD Jan E. Steiss DVM PhD Nancy R. Cox DVM PhD Dana M. Vaughn DVM PhD Starr C. Miller BS Scott A. Brown DVM PhD Phillip D. Garrett DVM MS 《Veterinary radiology & ultrasound》1995,36(6):542-547
Doppler ultrasonography of the spinal cord was performed in 34 normal, anesthetized dogs following hemilaminectomy. This study was part of an investigation to evaluate the efficacy of a 21-aminosteroid compound and high dose methylprednisolone for the treatment of spinal cord trauma. Grey-scale images of the canine spinal cord were similar to those described for the spinal cord of people. Doppler waveforms of intraparenchymal spinal arteries exhibited high end diastolic blood flow velocities, indicating low resistance to flow. Doppler values (mean ± SD) for arteries immediately ventrolateral to the central canal were: Peak Systolic Velocity = 5.78 ± 2.5 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Systolic/Diastolic ratio = 169 ± 0.19, Pulsatility Index = 0.53 ± 0.09, and Resistance Index = 0.4 ± 0.06. 相似文献