EXPERIMENTAL VERRUCOUS ENDOCARDITIS     

Mac Neal WJ  Blevins A  Slavkin AE  Scanlon H 《Science (New York, N.Y.)》1945,101(2625):415-416

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Oxygen Deficiency in Spartina alterniflora Roots: Metabolic Adaptation to Anoxia     

Mendelssohn IA  McKee KL  Patrick WH 《Science (New York, N.Y.)》1981,214(4519):439-441

The aerenchyma (air-space) tissue in the wetland macrophyte Spartina alterniflora conveys sufficient oxygen to roots for predominately aerobic respiration in moderately, but not highly, reduced substrates. Continuously flooded plants survive by respiring anaerobically, although growth is decreased. Two metabolic adaptations to flooding are displayed in this species, depending on the degree of soil reduction.  相似文献   

IN VITRO GROWTH AND MULTIPLICATION OF THE MALARIA PARASITE,PLASMODIUM KNOWLESI     

Ball EG  Anfinsen CB  Geiman QM  McKee RW  Ormsbee RA 《Science (New York, N.Y.)》1945,101(2630):542-544

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Imaging and manipulating molecules on a zeolite surface with an atomic force microscope     

Weisenhorn AL  Mac Dougall JE  Gould SA  Cox SD  Wise WS  Massie J  Maivald P  Elings VB  Stucky GD  Hansma PK 《Science (New York, N.Y.)》1990,247(4948):1330-1333

The adsorption of neutral molecules and ions on the surfaces of zeolites was observed in real time with an atomic force microscope (AFM). Direct imaging of the surface of the zeolite clinoptilolite was possible by using a diluted tert-butyl ammonium chloride solution as a medium. Images of the crystal in different liquids revealed that molecules could be bound to the surface in different ways; neutral molecules of tert-butanol formed an ordered array, whereas tert-butyl ammonium ions formed clusters. These absorbed molecules were not rearranged by the AFM tip when used in an imaging mode. However, when a sufficiently large force was applied, the tip of the AFM could rearrange the tert-butyl ammonium ions on the zeolite surface. This demonstration of molecular manipulation suggests new applications, including biosensors and lithography.  相似文献   

Assessment of the resistance of potato varieties to common scab     

R. K. McKee 《Potato Research》1958,1(1):65-80

Summary Field and glasshouse methods of assessing the resistance of potato varieties to common scab were investigated and procedures which were found to give satisfactory results are described in detail. Estimates of resistance for individual varieties in the two environments were closely correlated. Examination of a number of isolates ofStreptomyces scabies showed that these varied greatly in virulence but no evidence of physiological specialisation was found.

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Zusammenfassung Feld- und Gew?chshausmethoden zur Feststellung der Resistenz von Kartoffelsorten gegen Schorf wurden untersucht. Verfahren, die zufriedenstellende Resultate ergaben, sind in Einzelheiten beschrieben. Die Sch?tzungen der Resistenz bei den einzelnen Sorten in den beiden Umgebungen standen in enger Wechselbezichung zu einander. Die Prüfung einer Anzahl Absonderungen vonStreptomyces scabies ergab, dass diese in Virulenz stark variierten; aber es wurde kein Fall von physiologischer Spezialisierung gefunden.

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Résumé Des méthodes d'évaluation de la résistance à la gale commune de variétés de pommes de terre ont fait l'objet d'investigations en plein champ et en serre, alors que les modes opératoires donnant des résultats satisfaisants, ont été décrits en détail. Une corrélation étroite a été établie entre les estimations de la résistance pour chacune des variétés distinctes, placées dans les deux ambiances. L'examen de quelques cas isolés deStreptomyces scabies a démontré une grande variation dans la virulence sans qu'une preuve de spécialisation physiologique ne fút fournie.

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Received for publication Jan. 9, 1958.  相似文献   

Modified benzoxazinones in the system Oryza sativa-Echinochloa crus-galli: an approach to the development of biorational herbicide models     

Macías FA  Chinchilla N  Varela RM  Molinillo JM  Marín D  De Siqueira JM 《Journal of agricultural and food chemistry》2008,56(21):9941-9948

The utility of benzoxazinones and some of their synthetic derivatives in the search for new leads for herbicide model development has been explored. The work described focuses on obtaining derivatives that present selectivity in the system Oryza sativa- Echinochloa crus-galli. To achieve this goal the influence of lipophilicity in this system has been studied by preparing 14 ester derivatives at the N-4 position of D-DIBOA along with other compounds with different functionalization and chain lengths at position C-2. These compounds have been tested in the aforementioned system, and the dose-response profiles have been compared. The most active compound was 2-ethyl-4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one, which presented higher selectivity than the specific herbicide Cotanil-35. These results confirm the potential of D-DIBOA as a lead herbicide for the control of Echinochloa spp. in rice crops.  相似文献   

Phospholipid nonwoven electrospun membranes     

McKee MG  Layman JM  Cashion MP  Long TE 《Science (New York, N.Y.)》2006,311(5759):353-355

Nonwoven fibrous membranes were formed from electrospinning lecithin solutions in a single processing step. As the concentration of lecithin increased, the micellar morphology evolved from spherical to cylindrical, and at higher concentrations the cylindrical micelles overlapped and entangled in a fashion similar to polymers in semi-dilute or concentrated solutions. At concentrations above the onset of entanglements of the wormlike micelles, electrospun fibers were fabricated with diameters on the order of 1 to 5 micrometers. The electrospun phospholipid fibers offer the potential for direct fabrication of biologically based, high-surface-area membranes without the use of multiple synthetic steps, complicated electrospinning designs, or postprocessing surface treatments.  相似文献   

Structure-activity relationship (SAR) studies of benzoxazinones, their degradation products, and analogues. Phytotoxicity on problematic weeds Avena fatua L. and Lolium rigidum Gaud     

Macías FA  Marín D  Oliveros-Bastidas A  Castellano D  Simonet AM  Molinillo JM 《Journal of agricultural and food chemistry》2006,54(4):1040-1048

Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass) are highly problematic weeds affecting a wide variety of cereal crops worldwide. The fact that both of these weeds have developed resistance to several herbicide groups made them optimal candidates as target organisms for ongoing research about the potential application of allelochemicals and analogue compounds as natural herbicide models. Benzoxazinones, a family of natural allelochemicals present in corn, wheat, and rye, including 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, together with some degradation products, found in crop soils as well as in other systems, and some synthetic analogues of them were tested on wild oat and rigid ryegrass seeds; the results were statistically treated, and some structure-activity relationships, useful in further development of natural herbicide models, were elucidated. The most active compounds were the synthetic benzoxazinone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazin-3-one, with highly significant inhibition on the development of both weeds. The ecological role of these compounds is discussed by considering both degradability and phytotoxicity. The bioactivity of aminophenoxazines has been correlated by their aqueous solubility-lipophilicity predicted by means of computational methods.  相似文献   

Modelling stemflow production by juvenile lodgepole pine (<Emphasis Type="Italic">Pinus contorta</Emphasis> var. <Emphasis Type="Italic">latifolia</Emphasis>) trees     

Adam J. McKee  Darryl E. Carlyle-Moses 《林业研究》2017,28(3):565-576

Stemflow is a focused point source input of precipitation and nutrients at the base of a tree or plant and can have a significant impact on site hydrology. To date, no known studies have modelled stemflow production for juvenile lodgepole pine (Pinus contorta var. latifolia). Meteorological conditions, tree characteristics, and stemflow were sampled for two juvenile lodgepole pine stands over the course of the 2009 growing season. Step-wise multiple regression was used to assess which meteorological and tree architecture variables influenced stemflow production for each research plot. Once predictor variables were identified, models were produced for each stand and a generic model was produced that applied to both plots. A model employing precipitation depth and crown projection area successfully explained 71.3% of the variation in stemflow production from sampled trees. Stemflow was found to represent 1.8% of the study period rainfall and, although not a large component of the plot-scale canopy water balance, it is an order of magnitude greater than the fractioning of stemflow from mature lodgepole and lodgepole pine dominated forest. Additionally, stemflow funnelling ratios were found to average 22.2 and 24.3 from the two sample plots over the study period with a single tree, single event maximum of 111.7 recorded for a tree with a 3.3 cm bole diameter and a rain depth of 17.4 mm.  相似文献   

人工油松林中跳虫群落恢复状况     

CHANG Liang  WANG Bai-Feng  LIU Xiang-Hui  Mac A. CALLAHAM Jr.  GE Feng 《土壤圈》2017,27(1):129-137

Large areas of forest plantations have been developed in China.It is important to evaluate the soil fauna in plantations and the conditions needed for their recovery in view of the large areas of plantations in China.Three Pinus tabulaeformis forests,a 26-year-old plantation (P26) and a 45-year-old plantation (P45),exposed to clear-cutting before plantation,and an 80-260-year-old natural forest (N260),were chosen to study the effects of different forest ages/types on Collembola community in the litter and soil layers during 2008 and 2009.Soil conditions in P26 and P45 were significantly deteriorated when compared to N260.A higher value of soil bulk density and lower values of soil organic matter,soil N,litter depth,soil pH,and soil water content were observed in P26 and P45.Totally,the same genera of Collembola tended to occur in the forests of all ages studied;however,the Collembola community structure was significantly impacted by the differences in forest age.Both in the litter and soil layers,the density and generic richness of the Collembola were the highest in N260 and the lowest in P26.Some collembolan groups were sensitive to soil conditions in particular forest ages.N260 was associated with relatively high abundance of Plutomurus collembolans and P45 with relatively high abundance of Pseudofolsomia collembolans.The canonical correspondence analysis showed that the community structure of Collembola was mainly affected by forest age in both litter and soil layer.The ordination analysis of non-metric multidimensional scaling also found that the Collembola community did not recover to the level of natural forests in 26-year regeneration after clear-cutting.Even in 45-year regeneration after clear-cutting,the Collembola community only showed a slight recovery to the level of natural forests.Our results clearly showed that both Collembola community and soil conditions did not recover in 26-and 45-year regeneration after clear-cutting in P.tabulaeformis plantations;however,they might have the potential to recover in the future because the same genera of Collembola were distributed in the plantations and natural forests.  相似文献