Results for: “Science”
Phytochemicals are formed as a result of biochemical transformations in plants. They are present often in low or very low concentrations in a complex matrix. The analysis of individual natural products in complex crude extracts requires efficient separation methods prior to their detection. According to the type of study (quantification, standardization, fingerprinting, screening, etc.), very sensitive and selective methods may be needed.
Hyphenated techniques combining different separation and detection methods were first introduced by Tomas Hirschfeld about three decades ago
(Wilson and Brinkman, 2003). Hyphenated techniques allow a rapid structural determination of known plant constituents with a minute amount of plant material (Wolfender et al., 2000). With such a combined approach, the time-consuming isolation of common natural products is avoided and an efficient targeted isolation of compounds presenting interesting spectroscopic or biological features is performed. To discover new bioactive products, the dereliction of crude extracts performed prior to isolation work is of crucial importance in order to avoid the tedious isolation of known constituents. Hyphenated analytical methods have been fully integrated into the isolation process and are used for chemical screening of crude plant extracts.See All Chapters
|Peter H. Gleick||Island Press||ePub|
Average annual renewable freshwater resources are listed by country, updating Table 1 in the previous versions of The Worlds Water. Data from UN FAO AQUASTAT was updated to reflect the most recent data in that database. However, because these data are typically produced by modeling or estimation, rather than measurement, we use data from other sources where possible (even if older than data in AQUASTAT).
Data in this table typically comprise both renewable surface-water and groundwater supplies, including surface inflows from neighboring countries. The UN FAO refers to this as total natural renewable water resources. Flows to other countries are not subtracted from these numbers. All quantities are in cubic kilometers per year (km3/ yr). These data represent average freshwater resources in a countryactual annual renewable supply will vary from year to year.
These detailed country data should be viewed, and used, with caution. The data come from different sources and were estimated over different periods. Many countries do not directly measure or report internal water resources data, so some of these entries were produced using indirect methods.See All Chapters
|Dipak Chandra Ghosh, Nripesh Chandra Ghosh, and Prabir Kumar Haldar||Laxmi Publications|
· Take the LCM of the denominators of the reciprocals.
· Multiply each of the reciprocals in (i) by the LCM as obtained in
(ii) Inter-planar spacing
Lh d= M
+ 2 + 2 b c
where (h k l) are miller indices and a, b, c intercepts from axis x, y, z
· Write the numbers in first bracket n Bragg�s Law: 2d sin q = nl d = spacing between the consecutive Bragg planes of the crystal q = The glancing angle n = Order of reflection
Problem 1. Calculate �Atoms per unit cell, �co-ordination number� and �atomic radius� and atomic packing fraction for the case of simple cubic, face centered cubic and body centered cubic cells.
Solution. Atoms Per Unit Cell
(a) In the case of �simple cubic� (sc), each of the eight corner atoms in cubic cell contributes only
1 th of an atom to unit cell. So, there are in all 8 corner-atoms, their total contribution is equal to
´ 8th = 1
So, the number of atoms per unit cell for simple cubic cell is one 1.
(b) For the case of face centered cubic (fcc), there are six faces of a cube and each face-centered atom is shared by two unit cells. There are in addition eight corner-atoms.See All Chapters
|Elizabeth Emma Ferry||Indiana University Press||ePub|
I conclude with two images of Mexican minerals: one moving through space and the other through time.
In the spring of 1998, as we were preparing to return to the United States after twenty months of fieldwork, my husband and I gave a party at our house to say good-bye to our neighbors and friends. We rented chairs and a tent, hired a band, and engaged our neighbor and friend Paco to kill a pig and make carnitas. Our guests included our neighbors in the town of Santa Rosa de Lima, miners, and other cooperative members, faculty and students from the University of Guanajuato, and a regidor (alderman).
Although it is not as common for people to bring gifts to a party (such as a bottle of wine or flowers) as it is in some U.S. contexts, one cooperative member, who worked in the automotive department, brought me a small rock wrapped in tissue paper. It was a specimen of native silver growing out of a base of black acanthite (silver sulfide). The silver looked like the slightly curved bristles on a toothbrush. The specimen came from the El Cubo mine, he told me, and he wanted to give it to me to remind me of my friends in Guanajuato. I was delighted to receive this gift and carried it back to the United States with pride.See All Chapters
|Jarrad, F., Editor||CAB International|
Agent-based Bayesian Spread
Model Applied to Red Imported
Fire Ants in Brisbane
Jonathan M. Keith* and Daniel Spring
Monash University, Clayton, Australia
Red imported fire ants were first detected in
Brisbane in February 2001. Since then, the
National Red Imported Fire Ant Eradication
Program has been collecting data on the locations of detected nests and keeping a record of the areas searched and treated with baits. The result is an exceptionally large and detailed record of both the spread of the ant and the effects of human intervention on the invasion. In recent work, these data have been used to reconstruct the history of the invasion in terms of the trajectories of nest abundance and geographic range. A novel feature of the method is that it explicitly models individual nests and can thus reconstruct the invasion to a high level of spatial and temporal detail.
Some important lessons have been learned from this reconstruction. One is that an invasion can continue to expand its geographic range despite a drop in the number of invaders. Another is that immature nests – those not yet able to found new nests and generally too small to be detected – outnumbered mature nests at every stage of the invasion. Both of these lessons highlight the importance of sophisticated models to assist in monitoring an invasion and managing an eradication programme.See All Chapters
|Ace Academics||Ace Academics||ePub|
|Steven K. Madsen||Utah State University Press||ePub|
Terby Barnes found this important manuscript in the Rodgers Family Papers on a research trip in 1984 to Washington, D.C. She subsequently transcribed the document and shared it with me. (A typescript of her transcription can be found in the holdings of the Utah State Historical Society, Salt Lake City.) In 2007 I visited the Manuscript Division of the Library of Congress and made my own copy and transcription of the file, published here.
Dimmock wrote the 23–page manuscript on legal-sized paper, possibly supplied from the law firm in Maryland where he worked. In April 1860, Macomb “ran over to ‘Balt[imore]’ and …transacted my business with Mr. Dimmock.” Macomb possibly obtained the document from him at that time. More likely, he picked up the 1860 manuscript map drawn by both men, now located in the Cartographic Division of the National Archives in Washington, D.C.
Why Macomb failed to enter Dimmock’s topographical data in his report of the San Juan Exploring Expedition is open to speculation. One reason might be that Dimmock later joined the Confederacy in the Civil War which Macomb would have considered treasonous.See All Chapters
|Darin A. Croft||Indiana University Press||ePub|
Location Coastal Buenos Aires province, central Argentina.
Geology Loess-derived paleosols of the upper Chapadmalal Formation.
Geologic Age Pliocene, about 4.5–3.3 million years (based on radiometric dating and paleomagnetic correlation).
Mammal Age Chapadmalalan.
Mammals Identified About 65 species (the presence of some species is uncertain) (appendix 16).
THE CHAPADMALAL SEA CLIFFS NEAR THE CITY OF MAR DEL PLATA, like the outcrops of Catamarca, preserve a rich fossil record of late Cenozoic mammals. Most of the fossils from this site are Pliocene in age and therefore younger than those of Catamarca, between about 4.5 and 3.3 million years old. Fossils of these species are generally found in layers of fine aeolian sediments known as loess that are typical of late Cenozoic sites in central Argentina, including Arroyo Chasicó (chapter 13). Ancient burrows can still be found in these loess-derived rocks, some of which include remains of their presumed inhabitants. Ancient tuco-tucos (ctenomyids) such as Actenomys priscus and small notoungulates of the genus Paedotherium (section 16.5) were among the more common burrowers at Chapadmalal, and several other types of small rodents either lived in these burrows opportunistically or constructed their own.See All Chapters
|Rehana Khan||Laxmi Publications|
The term mutation refers both to the change in the genetic material and to the process by which the change occurs.
Mutation is the ultimate source of all genetic variation, it provides the raw material for evolution. Spontaneous mutations are those that occur without a known cause.
This class of mutation may result from errors in DNA replication or they may actually be caused by mutagenic agents present in environment. Spontaneous mutation occurs infrequently, although the observed frequencies vary from gene to gene and from organism to organism.
Spontaneous mutations arise without exposure to external agents. This class of mutations may result from errors in DNA replication. A few of the more prevalent mechanisms are described in the following paragraphs.
Generally replication errors occur when the base of a template nucleotide takes on a rare tautomeric form. Tautomerism is the relationship between two structural isomers that are in chemical equilibrium and readily change into each other. Bases typically exist in the keto form. However, they can at times take either an enol form. These tautomeric shifts change the hydrogen bonding characteristics of the bases, allowing purine for purine or pyrimidine for pyrimidine substitutions that can eventually lead to a stable alteration of the nucleotide sequence. Such substitutions are known as transition mutations and are relatively common, although most of them are repaired by various proofreading functions. In transversion mutations, a purine is substituted for a pyrimidine or a pyrimidine for a purine. These mutations are rarer due to the steric problem of pairing purines with purines and pyrimidines with pyrimidines.See All Chapters
|Dian Olson Belanger||University Press of Colorado||ePub|
The Seabees go now and build camps, the stargazers come later.
—Seabee, Deep Freeze I, 19551
When Captain George Dufek reported for command of the U.S. Naval Support Force, Antarctica (Task Force 43), on 16 August 1954, charged to ensure all logistical support for the International Geophysical Year, he knew the Navy had “exactly two years and ten months to lay out the red carpet for the scientists.” The scientific community might continue its Antarctic IGY planning right to the eve of departure, but Dufek could lose no time in marshaling the necessary personnel, ships, aircraft, land transport, equipment, materials, and supplies. To have seven stations built and fully functioning by 1 July 1957, the first expedition would have to be en route by early November 1955. This would allow one season to establish the first two bases, at McMurdo Sound and Little America. From these footholds there would be but one more short austral summer to build the two incomparably more difficult inland stations, as well as the three widely scattered coastal latecomers, even as the scientists were arriving. The northern summer and fall would be frantic.2See All Chapters
|Rachel C. Benton||Indiana University Press||ePub|
7.1. Map showing the distribution of the White River Group and correlative strata across the northern Great Plains. B = Badlands National Park, South Dakota; D = Douglas, Wyoming; F = Flagstaff Rim, southwest of Casper, Wyoming; L = Little Badlands of southwest North Dakota; P = Pawnee Buttes of northwest Colorado; R = Reva Gap, east of Buffalo, South Dakota; S = Scotts Bluff National Monument, Nebraska; T = Toadstool Geologic Park, north of Crawford, Nebraska.
The Eocene and Oligocene epochs are specific intervals of time recognized across the globe, but in order to understand their significance, it is important to understand how they are identified. The geologic history of our planet is stored within the archives of various types of rock bodies and strata, and the plant and animal remains preserved within them. Early scientists were aware that changes in plant and animal life had occurred, that the types of plants and animals preserved in a type of rock varied even if the rock type was the same, and that the existence of fossil remains in rock layers high on the tops of mountains suggested that the landscape had not always been as it appeared. Other than methods that allowed early geologists to establish the relative ages of various rock bodies, such as superposition, which states that in a sequence of horizontal strata the oldest layers of rock are on the bottom, these early scientists had no way to quantify the ages of strata and their associated fossils, when deposition started, how long it lasted, or when it stopped. Relative ages could be established across broad regions by tracing laterally continuous rock units or occurrences of particular fossils that allowed these early scientists to construct a relative geologic order of important paleontological and geological events, such as the appearance and extinction of the dinosaurs, but absolute ages for these events were unavailable. This changed with the development of radiometric dating of geologic materials and the discovery of magnetic signatures preserved in rock. The combination of radiometric dating plus paleomagnetism in sedimentary rock strata around the globe has allowed the establishment of a chronologic framework within which the patterns of evolution and geologic events portrayed in the geologic column can be placed.See All Chapters
|K.V.S.G. Murali Krishna||Laxmi Publications|
Thermodynamics and Air Pollution
THERMODYNAMICS AND AIR
Thermodynamics is the science of energy transfer and its effect on the physical properties of substances. The applications of the laws of thermodynamics are found in almost all fields of air pollution, from formation to control. The principles of thermodynamics, as such, are the basics in the fields of energy technologies notably in steam and nuclear power plants, internal combustion engines, gas turbines, air-conditioning, refrigeration, gas dynamics, jet propulsion, compressors, chemical process plants and direct energy conversion devices.
Today energy conservation is the main consideration in an effective project management. Sun is the basic source of energy (sufficient for 10 billion years) and any reduction in the amounts of incoming solar energy would be detrimental to life on earth. Air pollution control devices could result in an overall gain of energy and in the short-term evaluation, the control mechanism that provides the most effective emission reduction at a minimum expenditure of energy is usually used. A thorough study of the role of thermodynamics reveals that the techniques to improve energy conservation can also be the techniques to control air pollution. The study of thermodynamics is useful not only in controlling the emissions of pollutants in the plant but also in reducing the concentrations of pollutants after their discharge into the atmosphere from chimneys. The thermodynamics of formation of CO, SOx and NOx and combustion are described in detail in this chapter.See All Chapters
The last period of the Mesozoic era (denoted with a K in geological abbreviations), lasted for about 80 million years and was named after a special rock, “chalk” (from the German word Kreide), that formed in large amounts at this time. Although the specific Cretaceous “writing chalk” formed from the remains of masses of chrysophyte algae familiar across northwestern Europe is not found in the Carpathian Basin, formations of other Cretaceous-aged deposits are nevertheless common.
This originally bi-, or tripartite (recently declared officially bipartite) period is usually divided into 12 stages by geologists. Most stages—just like those of the Jurassic—were named after (usually French) villages. The Cretaceous, following the relatively calm Jurassic, was one of Earth history’s most eventful periods from a tectonic point of view. Because of this activity, the Cretaceous layers in the Carpathian Basin are very diverse, and include rocks of continental and marine (both nearshore and offshore) origin.See All Chapters
|Nicole Klein||Indiana University Press||ePub|
EVA MARIA GRIEBELER AND JAN WERNER
Because sauropod dinosaurs are extinct, it might seem impossible to fully reconstruct their life cycles. Nevertheless, information on reproduction, reproductive behavior, growth in body size, and sexual maturity can be indirectly derived from the fossil record. In addition, we can also use living, phylogenetically related taxa as models for these extinct animals in order to support and expand our knowledge on sauropod life cycles. Predictions from life history theory on the relationship between reproductive traits and body size as well as the analyses of life cycle characteristics of extant reptiles, birds, and mammals are also appropriate. In the present chapter, we utilize this complex approach for the reconstruction of sauropod life cycles. We summarize the information on eggs, clutches, nests, hatching, adolescence, and growth in body size that has been derived from the fossil record. In addition, we try to fill the gaps in our knowledge concerning the reproductive behavior, the total reproductive output of animals, and the mortality during the life cycle using information from extant phylogenetic brackets or predictions of life history theory. Finally, we discuss hypotheses explaining gigantism of sauropods based on their life cycles.See All Chapters
|Elof Axel Carlson||Indiana University Press||ePub|
Semen has long been recognized as necessary for producing offspring. It is liquid, somewhat viscous, and usually clear or slightly cloudy in appearance; certainly the unaided eye can see no visible body within it. The Greeks, especially through Hippocrates and later Galen, embraced a theory of vital fluids, which they called humors. Blood was considered the major constituent of life, at least among vertebrates. It was considered the progenitor of semen in the male body, and believed to be the hereditary material that allowed a species to generate offspring in its likeness.
Semen was endowed with a capacity to impose form on the pliable material supplied by females. That material was also thought to be blood: sometimes it was associated with menstrual blood, and sometimes it was thought to be another type of semen. Female semen was not clarified, like male semen, but still bloodlike and clotted—a type of miniscule clay ready to be molded into shape by the empowering effect of male semen. For more than two thousand years, arguments were made about the relative roles that males and females play in forming a new individual through their fluids, which were commingled after copulation. There were inside–outside theories in which the male supplied the outer components of the new baby. There were theories in which the female role was passive, being shaped exclusively by the male, forcing some observable phenomena, such as the equal contributions made to the skin color of the offspring of a black person and a white person, to be swept under a mental rug.See All Chapters