Clinal differentiation and putative hybridization in a contact zone of Pinus ponderosa and P. arizonica (Pinaceae)

2001 ◽  
Vol 88 (6) ◽  
pp. 1052-1057 ◽  
Author(s):  
Bryan K. Epperson ◽  
Frank W. Telewski ◽  
Anne E. Plovanich-Jones ◽  
Jill E. Grimes
Keyword(s):  
Contact Zone ◽  
Pinus Ponderosa

Enlargement of canopy gaps associated with a fungal pathogen in Yosemite Valley, California

2000 ◽  
Vol 30 (10) ◽  
pp. 1501-1510 ◽  
Author(s):  
D M Rizzo ◽  
G W Slaughter ◽  
J R Parmeter, Jr.
Keyword(s):  
Contact Zone ◽  
Pinus Ponderosa ◽  
Tree Mortality ◽  
Host Density ◽  
Basal Area ◽  
Canopy Gaps ◽  
Heterobasidion Annosum ◽  
Conifer Forest ◽  
Yosemite Valley ◽  
Root Contact

The enlargement of 21 canopy gaps associated with the root pathogen Heterobasidion annosum (Fr.:Fr.) Bref. = Fomes annosus (Fr.) Karst.) in the mixed-conifer forest of Yosemite Valley was monitored between 1971 and 1998. Mean expanded gap area was 232 m2(range 38-802 m2) in 1971 and 1455 m2(range 150-4216 m2) in 1998. The pathogen is primarily spread among trees via root contacts; therefore, the spread and impact of H. annosum from the stump(s) where infection originated (gap makers) were characterized by describing the area of potential root contact as a variable-area plot. The potential root contact zone delineated the area that would be encompassed by mortality if all trees potentially in contact with the original gap makers had died. Of the 21 plots, the actual area of tree mortality exceeded the potential root contact zone in only two gaps. Enlargement rates around gap perimeters were uneven, ranging from 0 to 1.33 m/year. Incense-cedars (Calocedrus decurrens (Torr.) Florin) tended to die more slowly than ponderosa pines (Pinus ponderosa Dougl.), often 10-30 years after adjacent pines had died. Gap enlargement was not dependent on host density, basal area, or gap-maker diameter, and tended to stabilize over time, probably because of fungal competition in root wood and lack of sufficient suitable host material along gap margins.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

Stibnite vein from Dębowina near Bardo (polish Sudetes)

2013 ◽  
Vol 2 (1) ◽  
pp. 28-33
Author(s):  
Piotr Kotula
Keyword(s):  
Contact Zone

Abstract In the contact zone of the Bardo Structure and Kłodzko-Złoty Stok Intrusion and Kłodzko Metamorphic, metasomatic orebearing quartz-carbonate veins rich in Sb, Zn, Cu, Ag, Au, Pb are present. In 1771 the mine ,,Reiche Silber Gluck” within stibnite vein was founded in Dębowina near Bardo. Its entrance was discovered again in 2007. The stibnite vein is mainly build of stibnite and sphalerite and of quartz and dolomite rich in Mn. Stibnite crystallizes as columnar or forming radiate centres and aciculars. Its crystals reach size to 2 mm. Sphalerite appears as individual anhedral and polymineralic grained concentrations reaching size to 2,5 mm. Earlier pyrite and arsenopyrite crystallized - they occur locally in this deposit. There were found also in the deposit tetrahedrite rich in Ag, what wasn't reported earlier in studies from the mine in Dębowina.

Diachronic trends in the evolution of civilizations in the Nile valley

2018 ◽  
pp. 37-49
Author(s):  
Элеонора Кормышева ◽  
Eleonora Kormysheva
Keyword(s):  
Material Culture ◽  
Social History ◽  
Contact Zone ◽  
Scientific Discourse ◽  
Cultural Development ◽  
Nile Valley ◽  
Mediterranean World ◽  
The Mediterranean

The diachronic trends in socio-economic and cultural development of the societies in the Nile valley are revealed based on the materials from Giza necropolis (the 3rd millennium BC) and the settlement of Abu Erteila (1st century AD). The research made it possible to trace the typological similarities in the evolution of the studied societies in cultural and historical contexts. The main fields of the research were epigraphy, iconography, social history, and material culture. Many previously unknown monuments discovered by Russian archaeologists in Egypt and Sudan were introduced into scientific discourse. The basis was created for studying the Nile valley as a contact zone between the Mediterranean world and Africa.

Sign in / Sign up

Export Citation Format

Share Document