Chimney Rock is a prominent geological rock formation in Morrill County in western Nebraska. Rising nearly 300 feet (91 m) above the surrounding North Platte River valley, the peak of Chimney Rock is 4,228 feet (1,289 m) above sea level. The formation served as a landmark along the Oregon Trail, the California Trail, and the Mormon Trail during the mid-19th century. The trails ran along the north side of the rock, which remains a visible landmark for modern travelers along U.S. Route 26 and Nebraska Highway 92. Chimney Rock National Historic Site was designated in 1956 and is an affiliated area of the National Park Service, operated by History Nebraska. Chimney Rock was added to the National Register of Historic Places on October 15, 1966. History Prior to exploration and settlement by European immigrants, the Native Americans of the area—mainly the Lakota Sioux—would refer to this formation by a term which meant "elk penis". The first non-natives to see the pillar were probably the Astorians of Robert Stuart in their eastward journey from the Pacific Ocean in 1813. Chimney Rock was recorded in many journals after the Stuart...

Chimney Rock is a prominent geological rock formation in Morrill County in western Nebraska. Rising nearly 300 feet (91 m) above the surrounding North Platte River valley, the peak of Chimney Rock is 4,228 feet (1,289 m) above sea level. The formation served as a landmark along the Oregon Trail, the California Trail, and the Mormon Trail during the mid-19th century. The trails ran along the north side of the rock, which remains a visible landmark for modern travelers along U.S. Route 26 and Nebraska Highway 92. Chimney Rock National Historic Site was designated in 1956 and is an affiliated area of the National Park Service, operated by History Nebraska. Chimney Rock was added to the National Register of Historic Places on October 15, 1966. History Prior to exploration and settlement by European immigrants, the Native Americans of the area—mainly the Lakota Sioux—would refer to this formation by a term which meant "elk penis". The first non-natives to see the pillar were probably the Astorians of Robert Stuart in their eastward journey from the Pacific Ocean in 1813. Chimney Rock was recorded in many journals after the Stuart...

Galaxy mergers can occur when two (or more) galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution. The merger rate also provides astronomers with clues about how galaxies bulked up over time. Description During the merger, stars and dark matter in each galaxy become affected by the approaching galaxy. Toward the late stages of the merger, the gravitational potential (i.e. the shape of the galaxy) begins changing so quickly that star orbits are greatly altered, and lose any trace of their prior orbit. This process is called “violent relaxation”. For example, when two disk galaxies collide they begin with their stars in an orderly rotation in the planes of the two separate disks. During...

Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane. Gram-negative bacteria are found in virtually all environments on Earth that support life. The gram-negative bacteria include the model organism Escherichia coli, as well as many pathogenic bacteria, such as Pseudomonas aeruginosa, Chlamydia trachomatis, and Yersinia pestis. They are a significant medical challenge as their outer membrane protects them from many antibiotics (including penicillin), detergents that would normally damage the inner cell membrane, and lysozyme, an antimicrobial enzyme produced by animals that forms part of the innate immune system. Additionally, the outer leaflet of this membrane comprises a complex lipopolysaccharide (LPS) whose lipid A component can cause a toxic reaction when bacteria are lysed by immune cells. This toxic reaction may lead to low blood pressure, respiratory failure,...