Hillslope Evolution by Bedrock Landslides     

AL Densmore  RS Anderson  BG McAdoo  MA Ellis 《Science (New York, N.Y.)》1997,275(5298):369-372

Bedrock landsliding is a dominant geomorphic process in a number of high-relief landscapes, yet is neglected in landscape evolution models. A physical model of sliding in beans is presented, in which incremental lowering of one wall simulates baselevel fall and generates slides. Frequent small slides produce irregular hillslopes, on which steep toes and head scarps persist until being cleared by infrequent large slides. These steep segments are observed on hillslopes in high-relief landscapes and have been interpreted as evidence for increases in tectonic or climatic process rates. In certain cases, they may instead reflect normal hillslope evolution by landsliding.  相似文献   

Bacteriophages with potential for inactivation of fish pathogenic bacteria: survival, host specificity and effect on bacterial community structure     

Pereira C  Silva YJ  Santos AL  Cunha A  Gomes NC  Almeida A 《Marine drugs》2011,9(11):2236-2255

Phage therapy may represent a viable alternative to antibiotics to inactivate fish pathogenic bacteria. Its use, however, requires the awareness of novel kinetics phenomena not applied to conventional drug treatments. The main objective of this work was to isolate bacteriophages with potential to inactivate fish pathogenic bacteria, without major effects on the structure of natural bacterial communities of aquaculture waters. The survival was determined in marine water, through quantification by the soft agar overlay technique. The host specificity was evaluated by cross infection. The ecological impact of phage addition on the structure of the bacterial community was evaluated by DGGE of PCR amplified 16S rRNA gene fragments. The survival period varied between 12 and 91 days, with a higher viability for Aeromonas salmonicida phages. The phages of Vibrio parahaemolyticus and of A. salmonicida infected bacteria of different families with a high efficacy of plating. The specific phages of pathogenic bacteria had no detectable impact on the structure of the bacterial community. In conclusion, V. parahaemolyticus and A. salmonicida phages show good survival time in marine water, have only a moderated impact on the overall bacterial community structure and the desired specificity for host pathogenic bacteria, being potential candidates for therapy of fish infectious diseases in marine aquaculture systems.  相似文献   

Selective extraction of humic acids from an anthropogenic Amazonian dark earth and from a chemically oxidized charcoal     

Joyce R. Araujo  Braulio S. Archanjo  Katia R. de Souza  Witold Kwapinski  Newton P. S. Falcão  Etelvino H. Novotny  Carlos A. Achete 《Biology and Fertility of Soils》2014,50(8):1223-1232

Spectroscopic techniques including X-ray photoelectron spectroscopy (XPS) can identify particular chemical groups of humic acids (HA) from “Terra Preta de Índios” (TPI) or Amazonian dark earth, the highly fertile anthropogenic soil found in the Amazonian region. The high fertility and resilience of these soils cannot be explained by their chemically inert pyrogenic C content alone, but the natural aging of this C generates reactive carboxyl functional groups attached directly to the recalcitrant polycondensed aromatic backbone. Through spectroscopic techniques used in this work, the HA fraction (the alkaline-soluble organic matter that precipitates at low pH) of the TPI soil was compared with humic and fulvic acids, obtained by oxidizing activated charcoal with sodium hypochlorite. The yields recovery of HA-like substances was 12 and 28 wt% by using 10 and 20 cmol L^?1 of oxidizing agent, respectively. X-ray photoelectron spectroscopy, energy dispersive X-ray, and solid-state ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopies were used to evaluate the elements and structures present in all samples. XPS C 1 s spectra of HA extracted from TPI soil and from prepared HA showed aromatic structures (C?=?C and π–π* shake-up satellite peak) bounded to carboxyl groups (COOH). The morphology and polycondensation level of aromatic C were evaluated by scanning electron microscopy (SEM). The similarities of the spectra indicated that the used method was efficient to obtain an organic amendment similar to TPI soil organic matter.  相似文献   

Mevalonate kinase activity during different stages of plant regeneration from nodular callus cultures in white pine (Pinus strobus)     

Tang W  Newton RJ 《Tree physiology》2006,26(2):195-200

Mevalonate kinase (MK) catalyzes a step in the isoprenoid biosynthetic pathway, which leads to a huge number of compounds that play important roles in plant growth and development. Here, we report on changes in MK activity in white pine (Pinus strobus L.) during plant regeneration by adventitious shoot organogenesis from cotyledons of mature embryos, including nodular callus induction, shoot formation and rooting. Nodular calli were induced from Pinus strobus (PS) embryos by culture in nodular callus induction medium in a 0-, 8- or 16-h photoperiod. Mevalonate kinase activity peaked in nodular calli after three weeks of culture on nodular callus induction medium in a 16-h photoperiod, whereas frequency of nodular callus formation peaked after 4 weeks of culture on nodular callus induction medium in darkness. During adventitious shoot formation, MK activity peaked in shoots derived from dark-grown nodular calli after 3 weeks on bud formation medium, and frequency of shoot formation was highest in dark-grown nodular calli cultured on bud formation medium for 4 weeks. During rooting, MK activity peaked 2 weeks after transfer of adventitious shoots to rooting medium and rooting frequency was highest in adventitious shoots after 3 weeks on rooting medium. Although during nodular callus induction in darkness MK activity was inversely related to frequency of nodular callus formation, MK activity was highly correlated with frequency of shoot formation and with rooting frequency. The observed increase in MK activity preceding rooting suggests that MK could serve as a marker for rooting of white pine shoots in vitro.  相似文献   

Gonioscopy in the dog: inter‐examiner variability and the search for a grading scheme          下载免费PDF全文

J. A. C. Oliver  B. C. Cottrell  J. R. Newton  C. S. Mellersh 《The Journal of small animal practice》2017,58(11):652-658

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Assessment of horse owners’ ability to recognise equine laminitis: A cross‐sectional study of 93 veterinary diagnosed cases in Great Britain          下载免费PDF全文

D. Pollard  C. E. Wylie  K. L. P. Verheyen  J. R. Newton 《Equine veterinary journal》2017,49(6):759-766

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Bilateral renal and ureteral calculi in a 10-year-old gelding.     

S A Newton  M T Cheeseman  G B Edwards 《The Veterinary record》1999,144(14):383-385

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Effect of partial replacement of alfalfa hay with Moringa species leaves on milk yield and composition of Najdi ewes     

Elfadıl E. Babiker  Fahad AL Juhaimi  Kashif Ghafoor  H. E. Mohamed  Khalid A. Abdoun 《Tropical animal health and production》2016,48(7):1427-1433

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Invasive silver carp may compete with unionid mussels for algae: First experimental evidence     

Elizabeth P. Tristano  Alison A. Coulter  Teresa J. Newton  James E. Garvey 《水产资源保护:海洋与淡水生态系统》2019,29(10):1749-1757

A CASE ASSESSMENT OF THE MECHANISMS INVOLVED IN HUMAN‐INDUCED LAND DEGRADATION IN NORTHEASTERN KUWAIT     

J. M. AL‐Awadhi 《Land Degradation \u0026amp; Development》2013,24(1):2-11

Soil degradation and vegetation deterioration in contrasting areas (open desert versus protected desert) in the northeastern part of Kuwait were investigated, using field measurements, and laboratory methodologies. The average infiltration rate of compacted soils studied was found to be 52 per cent lower than that of the undisturbed soils we investigated. The bulk density of the compacted soils was 19 per cent higher than that of the non‐compacted soils. The average topsoil resistance of severely compacted soils was 13 per cent greater than that of undisturbed soils and is mainly due to overgrazing, and off‐road vehicle use. We found that the overall vegetation cover status of open areas investigated was approximately 70 per cent less than for the protected areas studied. As a consequence of soil compaction and vegetation deterioration, sand deflation processes, and sand movement prevail in open areas. The total average percentages of course grain sizes in unprotected soils and heavily disturbed soils by vehicles (off‐road) are 51 and 103 per cent greater, respectively. The annual rate of sand transport during the last 20 years, from the prevailing wind direction (NW) in the area has increased by 81 per cent. The delicate balance between soil and natural vegetation cover is easily disturbed by off‐road vehicle use associated with overgrazing and recreation activity. A restoration plan is needed in order to reduce land degradation and to allow natural vegetation recovery. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献