Little rock Anderson, Karen
2010., 20131110, 2013, 2010, 2010-01-01, Letnik:
66
eBook
The desegregation crisis in Little Rock is a landmark of American history: on September 4, 1957, after the Supreme Court struck down racial segregation in public schools, Arkansas Governor Orval ...Faubus called up the National Guard to surround Little Rock Central High School, preventing black students from going in. On September 25, 1957, nine black students, escorted by federal troops, gained entrance. With grace and depth, Little Rock provides fresh perspectives on the individuals, especially the activists and policymakers, involved in these dramatic events. Looking at a wide variety of evidence and sources, Karen Anderson examines American racial politics in relation to changes in youth culture, sexuality, gender relations, and economics, and she locates the conflicts of Little Rock within the larger political and historical context.
A Social History of Early Rock 'n' Roll in Germany explores the people and spaces of St. Pauli's rock'n'roll scene in the 1960s. Starting in 1960, young British rockers were hired to entertain ...tourists in Hamburg's red-light district around the Reeperbahn in the area of St. Pauli. German youths quickly joined in to experience the forbidden thrill of rock'n'roll, and used African American sounds to distance themselves from the old Nazi generation. In 1962 the Star Club opened and drew international attention for hosting some of the Beatles' most influential performances. In this book, Julia Sneeringer weaves together this story of youth culture with histories of sex and gender, popular culture, media, and subculture. By exploring the history of one locale in depth, Sneeringer offers a welcome contribution to the scholarly literature on space, place, sound and the city, and pays overdue attention to the impact that Hamburg had upon music and style. She is also careful to place performers such as The Beatles back into the social, spatial, and musical contexts that shaped them and their generation. This book reveals that transnational encounters between musicians, fans, entrepreneurs and businessmen in St. Pauli produced a musical style that provided emotional and physical liberation and challenged powerful forces of conservatism and conformity with effects that transformed the world for decades to come.
Bob Beatty dives deep into the motivations and musicalbackground of Duane Allman to tell the story of what made At Fillmore Eastnot just a smash hit, but one of the most important live rock albums ...inhistory.
When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence ...during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress
σ
cc
, crack initiation stress
σ
ci
, crack damage stress
σ
cd
, and uniaxial compressive strength
σ
ucs
; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress
σ
cd
, its threshold, and a possible relationship between
σ
cd
and the uniaxial compressive strength. The
σ
cd
of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of
σ
cd
/σ
ucs
for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in
σ
cd
/σ
ucs
between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average
σ
cd
/σ
ucs
resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of
σ
cd
/σ
ucs
for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on
σ
cd
/σ
ucs
. The ratio
σ
cd
/
σ
ucs
could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.
Randall Stephens traces rock's inspiration to the Pentecostal churches where Elvis, Little Richard, and others worshipped. Faith, which served as a vehicle for whites' fears, led them to condemn the ...godless music of blacks and hippies. But in a reversal of strategy, evangelicals later embraced Christian rock as a way to project Jesus's message.
Rock and rock-like materials such as concrete, soil, and underground backfilling materials are considered to be geomaterials. Geomaterials are essential for life due to human construct extraction, ...mining, storage, and transport areas in the Earth’s crust for raw material. Drilling and excavations of underground openings in the Earth’s crust are requirements for the exploitation and utilization of mineral resources, energy resources, and underground spaces. The deepest drilling depth has exceeded 12 km, and the deepest underground excavation now operates mines with depths exceeding 4 to 5 km. Drilling, excavation, and rock support processes largely rely on the physical and mechanical properties of geomaterials. Rock excavations are faced with some instability phenomena, such as caving, rock bursts, slabbing, large deformation, and zonal disintegration, posing a serious threat to the safety of mining and tunneling operations. Rock drilling also encounters many challenges deep underground. Deformation, fracture, failure, and fragmentation are the different stages of geomaterials, the monitoring and control of which are essential for ensuring drilling and excavation safety. Therefore, understanding the response processes of geomaterials during drilling and excavation activities depends on the precise characterizations of geomaterials.
In deep underground coal mining, engineering activities are performed within anisotropic in-situ stress fields due to engineering disturbances and tectonic stress. Many such activities involve the ...development of excavations in soft rock and anisotropic coal. Accordingly, studying the mechanical properties of soft rocks is important for the stability of deep underground excavations. In this study, the deformation, strength, and failure characteristics of soft sandstone and raw coal under two different true triaxial loading paths were investigated using a self-developed true triaxial test apparatus. The results indicated that the inelastic strain in the pre-peak stage of sandstone and coal gradually increased with increasing intermediate principal stress. Also, the strength-drop in the post-peak stage increased. The crack initiation stress, crack damage stress, and peak strength of sandstone and coal first increased and then decreased with increasing intermediate principal stress for a given σ3. Moreover, with increasing intermediate principal stress, the failure mode of sandstone and coal changed from shear to tensile shear, and from brittle to semi-brittle. The linear Mogi criteria as found to characterize the true triaxial strength of coal well, while the modified Lade criteria was more applicable to soft sandstone. Owning to the symmetry assumption, the linear Mogi criteria predicted low strength when the intermediate principal stress coefficient exceeded to 0.5. In addition, the peak strength curve of rock on the π plane and the influence of weak structures on the failure mode of anisotropic coal was discussed. Weak structures have an important influence on the failure mode of coal, which depends on the strength difference between the structural plane and the coal rock mass. The strength envelope on the π plane had a significant stress Lode angle effect, which gradually decreased as the mean stress increased.
•Influence of the intermediate principal stress on deformation, strength, and failure mode of sandstone and coal.•Different Mogi-type strength criteria were discussed and compared.•The interval effect of intermediate principal stress on coal rock strength was discussed.•The envelope of true triaxial strength of rocks on the π plane was discussed.•The influence of weak structures on the failure mode of coal was discussed.
Cubic specimens of granite, marble, and sandstone, with side lengths of 50 mm, were prepared in the laboratory. True triaxial compression tests were conducted on each rock type with minor principal ...stress (σ3) magnitudes of 10, 20, 30, 50, and 100 MPa and the intermediate principal stress (σ2) varying from σ2 = σ3 to σ2 = σ1 (where σ1 represents the major principal stress). The experimental results demonstrated that the failure strength, fracture dip angle, non-linear behavior and failure mode of these rocks under true triaxial conditions were affected by both σ2 and σ3, as well as by the rock lithology. When σ3 was kept constant and σ2 increased, failure strength showed an initial increase followed by a decrease, whereas the fracture dip angle increased monotonically. The non-linear behavior before the peak strength point of granite became more apparent by the increase of σ3, whereas σ2 had an opposite effect on the non-linear behavior of granite under high σ3 (e.g. 100 MPa). The non-linear behavior before the peak strength point was always found in marble and sandstone for all of the stress state conditions. Analyses of fracture dip angle and failure mode showed that when σ3 = 10, 20, and 30 MPa and σ2/σ3 ≥ 5, 7.5, and 10, respectively, the failure mode of granite changed from shear to slabbing, whereas marble and sandstone always fractured in the shear direction. This study confirms that rocks may experience slabbing failure under true triaxial stress, and slabbing failure mode is likely to be induced in high-strength and brittle rocks under low σ3 with the stress ratio of σ2/σ3 exceeding a particular threshold value.
Petrology on Mars McSween, Harry Y
The American mineralogist,
11/2015, Letnik:
100, Številka:
11-12
Journal Article
Recenzirano
Odprti dostop
Petrologic investigations of martian rocks have been accomplished by mineralogical, geochemical, and textural analyses from Mars rovers (with geologic context provided by orbiters), and by laboratory ...analyses of martian meteorites. Igneous rocks are primarily lavas and volcaniclastic rocks of basaltic composition, and ultramafic cumulates; alkaline rocks are common in ancient terranes and tholeiitic rocks occur in younger terranes, suggesting global magmatic evolution. Relatively uncommon feldspathic rocks represent the ultimate fractionation products, and granitic rocks are unknown. Sedimentary rocks are of both clastic (mudstone, sandstone, conglomerate, all containing significant igneous detritus) and chemical (evaporitic sulfate and less common carbonate) origin. High-silica sediments formed by hydrothermal activity. Sediments on Mars formed from different protoliths and were weathered under different environmental conditions from terrestrial sediments. Metamorphic rocks have only been inferred from orbital remote-sensing measurements. Metabasalt and serpentinite have mineral assemblages consistent with those predicted from low-pressure phase equilibria and likely formed in geothermal systems. Shock effects are common in martian meteorites, and impact breccias are probably widespread in the planet's crustal rocks. The martian rock cycle during early periods was similar in many respects to that of Earth. However, without plate tectonics Mars did not experience the thermal metamorphism and flux melting associated with subduction, nor deposition in subsided basins and rapid erosion resulting from tectonic uplift. The rock cycle during more recent time has been truncated by desiccation of the planet's surface and a lower geothermal gradient in its interior. The petrology of Mars is intriguingly different from Earth, but the tried-and-true methods of petrography and geochemistry are clearly translatable to another world.