Role of flexibility in the water repellency of water strider legs: Theory and experiment

2012 ◽  
Vol 85 (2) ◽  
Author(s):  
Xiang-Ying Ji ◽  
Jia-Wen Wang ◽  
Xi-Qiao Feng
Keyword(s):  
Water Repellency ◽  
Water Strider ◽  
Theory And Experiment

The role of tree stem proximity in the spatial variability of soil water repellency in a eucalypt plantation in coastal Portugal

Soil Research ◽  
2005 ◽  
Vol 43 (3) ◽  
pp. 251 ◽  
Author(s):  
J. J. Keizer ◽  
A. J. D. Ferreira ◽  
C. O. A. Coelho ◽  
S. H. Doerr ◽  
M. C. Malvar ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Repellency ◽  
Soil Water Repellency ◽  
Individual Measurement ◽  
Hydrophobic Compounds ◽  
Ethanol Droplet ◽  
Central Portugal ◽  
Living Organisms ◽  
Tree Stem

Certain organic compounds derived from living organisms or their decaying parts are generally accepted to induce soil water repellency. Water repellency may therefore be expected to increase with proximity to organisms releasing hydrophobic compounds. This hypothesis is tested here for Eucalyptus globulus trees, since eucalypt species are frequently associated with elevated repellency levels. In a young, first-rotation plantation on coastal dune sands in central Portugal, repeat measurements of water repellency using the ‘Molarity of an Ethanol Droplet’ (MED) test were carried out in situ between April 2001 and May 2002. On 25 dates, repellency was measured at initially 2 and later 3 distances on 2 sides of 8–11 randomly selected trees. On 15 occasions, additional repellency measurements were performed within small grids aside 3 of the selected trees. The postulated decrease in topsoil water repellency with increased distance from eucalypt tree stems was found to apply on several individual measurement dates, as well as, more unexpectedly since repellency usually is a transient phenomenon, for the study period as a whole. The results confirm the general association of eucalypt trees with water repellency, and indicate that tree stem proximity is an important but not sufficient factor to explain repellency distribution in topsoil.

Poincare's Silence and Einstein's Relativity: The Role of Theory and Experiment in Poincaré's Physics

1970 ◽  
Vol 5 (1) ◽  
pp. 73-84 ◽  
Author(s):  
Stanley Goldberg
Keyword(s):  
Special Theory ◽  
Theoretical Physics ◽  
Theory Of Relativity ◽  
Special Theory Of Relativity ◽  
Henri Poincaré ◽  
Home Town ◽  
Académie Des Sciences ◽  
The Subject ◽  
Theory And Experiment

It is a matter of record that Henri Poincaré never responded publicly to Einstein's Special Theory of Relativity (RT). Since almost no private papers of Poincaré are available, his attitude toward Einstein's work and his silence on that score become somewhat of a mystery. It is almost certain that Poincaré knew of Einstein's work in RT. First, he was fluent in German, having learned it as a young man when the Germans occupied his home town of Nancy in 1870. Second, he often reported to the members of the Académie des Sciences on current work in electrodynamics in Germany. It is highly improbable that he would have missed the abstract of Einstein's first paper on RT or the subsequent articles by Einstein on the subject, especially those which were translated into French, since they were in areas directly related to his own interests in theoretical physics.

Extraction of compounds associated with water repellency in sandy soils of different origin

Soil Research ◽  
2005 ◽  
Vol 43 (3) ◽  
pp. 225 ◽  
Author(s):  
S. H. Doerr ◽  
C. T. Llewellyn ◽  
P. Douglas ◽  
C. P. Morley ◽  
K. A. Mainwaring ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Sandy Soils ◽  
Water Repellency ◽  
Organic Carbon Content ◽  
Soil Water Repellency ◽  
Diverse Range ◽  
Additional Information ◽  
The Uk

After an initial evaluation of several solvents, the efficiency of Soxhlet extractions with isopropanol/ammonia (s.g. 0.88) (70 : 30 v : v; 24 h) in extracting compounds associated with water repellency in sandy soils was examined using a range of repellent and wettable control soils (n = 15 and 4) from Australia, Greece, Portugal, The Netherlands, and the UK. Extraction efficiency and the role of the extracts in causing soil water repellency was examined by determining extract mass, sample organic carbon content and water repellency (after drying at 20°C and 105°C) pre- and post-extraction, and amounts of aliphatic C–H removed using DRIFT, and by assessing the ability of extracts to cause repellency in acid-washed sand (AWS). Key findings are: (i) none of organic carbon content, amount of aliphatic C–H, or amount of material extracted give any significant correlation with repellency for this diverse range of soils; (ii) sample drying at 105°C is not necessarily useful before extraction, but may provide additional information on extraction effectiveness when used after extraction; (iii) the extraction removed repellency completely from 13 of the 15 repellent samples; (iv) extracts from all repellent and wettable control soils were capable of inducing repellency in AWS. The findings suggest that compounds responsible for repellency represent only a fraction of the extract composition and that their presence does not necessarily always cause repellency.

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