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Past and Present Management of Alfalfa Bees

Theresa L. Pitts-Singer

in Bee Pollination in Agricultural Ecosystems

There is a long history of the use of alfalfa by humans, including the intentional introduction of this forage crop from Eurasia to other continents. For producing alfalfa seeds, the management ... More

There is a long history of the use of alfalfa by humans, including the intentional introduction of this forage crop from Eurasia to other continents. For producing alfalfa seeds, the management systems for two bee pollinators have been developed. Use of managed alkali bees, Nomia melanderi, and alfalfa leafcutting bees, Megachile rotundata, has made alfalfa seed production a viable industry. The management systems for both bee species require care and commitment for combating parasites, pests, and diseases, and for meeting proper environmental conditions. Although the emphasis on the use of alkali bees has diminished, the use of the alfalfa leafcutting bees remains popular. Concerns and new ideas surrounding the current and future use of these bee species as commercial pollinators are discussed.Less

Structural Chemistry of Alkali and Alkaline-Earth Metals

Wai-Kee Li, Gong-Du Zhou, and Thomas Chung Wai Mak

in Advanced Structural Inorganic Chemistry

This chapter covers the structural chemistry of Groups 1 and 2 elements, except hydrogen. For Group 1 metals, special attention is paid to the oxides, lithium nitride, inorganic alkali metal ... More

This chapter covers the structural chemistry of Groups 1 and 2 elements, except hydrogen. For Group 1 metals, special attention is paid to the oxides, lithium nitride, inorganic alkali metal complexes, methyllithium compounds, π-complexes of lithium, sodium and potassium, alkalides and electrides, etc. For the Group 2 metals, the coverage includes their complexes, nitrides, low-valent oxides and nitrides, polymeric chains, Grignard reagents, metallocenes, etc. The chapter concludes with a section on the alkali and alkaline-earth metal complexes with inverse crown structures.Less

Other heteronuclear diatomic molecules: polar covalent bonds

Arne Haaland

in Molecules and Models: The molecular structures of main group element compounds

This chapter describes the structures of 25 heteronuclear, singly bonded diatomic molecules formed by combination of hydrogen, halogen, or alkali metal atoms (HX, HM, XX', or MM') in terms of their ... More

This chapter describes the structures of 25 heteronuclear, singly bonded diatomic molecules formed by combination of hydrogen, halogen, or alkali metal atoms (HX, HM, XX', or MM') in terms of their electric dipole moments, ionic characters, dissociation energies, and bond distances. The ionic characters of these compounds, as well as those of the alkali metal halides discussed in Chapter 5, increase with increasing difference between the electronegativity coefficients of the two bonded atoms:¦χA - χB¦. Similarly, the dissociation energies are found to increase and the bond distances to decrease with increasing electronegativity differences. A simple formula, the modified Schomaker-Stevenson (MSS) rule, allows the calculation of single bond distances between 17 elements (H and 16 elements in Groups 16-19) with an average error of 2 pm.Less

Experimental studies of momentum density in metals and alloys

N. Shiotani

in X-Ray Compton Scattering

This chapter provides a full review and evaluation of work on: alkali metals and their alloys; beryllium, aluminium and its alloys, silicon, 3d transition metals, their alloys and compounds, and ... More

This chapter provides a full review and evaluation of work on: alkali metals and their alloys; beryllium, aluminium and its alloys, silicon, 3d transition metals, their alloys and compounds, and doped fullerines. Particular attention is given to extent to which Compton data can be used to locate and reconstruct the Fermi surface, and determine the size of Fermi surface break in correlated electron systems. The results are compared to theoretical models and to analogous results from positron annihilation studies of angular correlation radiation.Less

Gaseous alkali metal halides: ionic bonds

Arne Haaland

in Molecules and Models: The molecular structures of main group element compounds

The evaporation of an alkali metal halide (MX) yields a mixture of monomers and smaller amounts of dimers, trimers, and tetramers. This chapter describes the monomers in terms of their electric ... More

The evaporation of an alkali metal halide (MX) yields a mixture of monomers and smaller amounts of dimers, trimers, and tetramers. This chapter describes the monomers in terms of their electric dipole moments, dissociation energies, and bond distances. The spherical ion model is used to construct potential energy curves and to calculate dissociation energies in reasonable agreement with their experimental counterparts from the experimental bond distances. Similar calculations on the dimers and on crystals with rock salt structure indicate that the M-X bond distances should be 5% and 15%, respectively, longer than in the monomers. The polarizable ion model leads to significantly better agreement between experimental and calculated electric dipole moments than the spherical ion model. Finally, the crystal structures of compounds containing a negatively charge alkali metal atom or even an isolated electron as cations are described.Less

TRANSPORT PROPERTIES OF DIFFERENT IONS

A.F. Borghesani

in Ions and electrons in liquid helium

This chapter describes the study of transport properties of several different positive ions in superfluid helium. In addition to alkali and alkaline-earth ions, the still unsolved problem of the ... More

This chapter describes the study of transport properties of several different positive ions in superfluid helium. In addition to alkali and alkaline-earth ions, the still unsolved problem of the so-called exotic ions is considered, which contain negative ions which are faster than the common electron bubbles, whose nature remains unknown. Several hypotheses have been made to explain their nature, among which the most intriguing is the electrino hypothesis, i.e., the possibility that the electron in the electron bubble may undergo fission.Less

Hypotheses and analogy

Peter R. Anstey

in John Locke and Natural Philosophy

This chapter argues that Locke believed hypotheses and analogical reasoning play a minor role in natural philosophical method and that this view is consistent with that of the proponents of the ... More

This chapter argues that Locke believed hypotheses and analogical reasoning play a minor role in natural philosophical method and that this view is consistent with that of the proponents of the Experimental Philosophy. This is illustrated by his discussions of the acid and alkali theory of matter and by his correspondence with Thomas Molyneux.Less

Environmental Justice: The Mercury Connection

Jerome Nriagu, Niladri Basu, and Simone Charles

in Mercury in the Environment: Pattern and Process

For many communities, exposure to mercury through fish consumption is an exemplary case of environmental injustice. Groups that rely on fishing for food, cultural identity, spiritual wellbeing, or ... More

For many communities, exposure to mercury through fish consumption is an exemplary case of environmental injustice. Groups that rely on fishing for food, cultural identity, spiritual wellbeing, or economic prosperity are more vulnerable to mercury pollution. The vulnerability is heightened because sources and hotspots of mercury are found disproportionately in areas near communities of color, low-income and immigrant communities, and indigenous peoples. This chapter reviews cases where mercury has impacted the health, culture, and identity of local communities. Such communities are victims of environmental injustice because they have derived little or no benefit from the products and services of mercury-releasing industries, but they now bear the burden of the wastes left behind. Existing strategies for reducing mercury exposure are not always effective in communities at risk. Fish advisories that warn of health risks from eating contaminated fish themselves perpetuate environmental injustice. The shift in policy from risk reduction to risk avoidance places these communities in a lose-lose situation: either eat fish and suffer the health effects from contaminants or do not eat fish and suffer the health and cultural effects of losing a critical diet food. By allowing significant mercury contamination to remain in place while advising the population at risk to change their lifestyle, regulators are indirectly perpetuating discrimination against communities that attach different normative values to fish.Less

Mojave Desert Scrub Vegetation

Todd Keeler-Wolf

in Terrestrial Vegetation of California, 3rd Edition

Mojave Desert scrub vegetation includes all the shrub and woodland vegetation of the Mojave Desert Region below the cool desert zone. This chapter reviews the classification of Mojave Desert scrub ... More

Mojave Desert scrub vegetation includes all the shrub and woodland vegetation of the Mojave Desert Region below the cool desert zone. This chapter reviews the classification of Mojave Desert scrub vegetation, identifying environmental relationships among and between these types. These vegetation types include alkali sink vegetation, mesquite vegetation, desert riparian vegetation, saltbrush scrub, alkaline marshes, sand dunes, bajadas, hills, and washes.Less

Colorado Desert Vegetation

Allan A. Schoenherr and Jack H. Burk

in Terrestrial Vegetation of California, 3rd Edition

The Colorado Desert of California represents the northwesternmost portion of the Sonoran Desert, which extends into Arizona, Baja California, and Sonora. This chapter describes the types of ... More

The Colorado Desert of California represents the northwesternmost portion of the Sonoran Desert, which extends into Arizona, Baja California, and Sonora. This chapter describes the types of vegetation and distribution of dominant plants in the Colorado Desert, presenting vegetation types based on dominant species and on assemblages of species with similar strategies for coping with specific microclimates and soil types. The plant community types of the Colorado Desert include the creosote bush scrub, cactus scrub, saltbush scrub, alkali sink, microphyll woodland, palm oasis, and psammophytic scrub.Less

Alkali atoms and laser cooling

Massimo Inguscio and Leonardo Fallani

in Atomic Physics: Precise Measurements and Ultracold Matter

This chapter starts with the spectrum of alkali atoms, which have a very similar electronic structure to hydrogen. It describes the hyperfine structure of alkali atoms in the context of the ... More

This chapter starts with the spectrum of alkali atoms, which have a very similar electronic structure to hydrogen. It describes the hyperfine structure of alkali atoms in the context of the development of microwave atomic clocks that currently provide the definition of the SI second. The simple and accessible electronic transitions of alkali atoms were used for the first demonstration of laser cooling, the revolutionary approach to atomic physics developed in the '80s, which the chapter discusses with a review of its most important configurations (optical molasses, magneto-optical traps, sub-Doppler cooling). The application of laser cooling to the development of very precise atomic clocks and to the field of atom interferometry is also covered.Less

The Nobel Laureate

in Science and Conscience: The Life of James Franck

In 1926, James Franck went to Stockholm to receive the 1925 Nobel Prize in physics, which he shared with Gustav Hertz for their experiments supporting Neil Bohr's theory of the atom. He then began to ... More

In 1926, James Franck went to Stockholm to receive the 1925 Nobel Prize in physics, which he shared with Gustav Hertz for their experiments supporting Neil Bohr's theory of the atom. He then began to investigate absorption spectra of alkali halides with Heinrich Kuhn and Günter Rollefson. Franck, Born, and Pohl founded a regional branch of the German Physical Society, the Gauverein Niedersachsen der Deutschen Physikalischen Gesellschaft and they spoke about their research on adsorption catalysis in its semi-annual conventions.Less

Experimental Survey I: The Periodic Table

Kamran Behnia

in Fundamentals of Thermoelectricity

This chapter is devoted to a survey of elemental solids. It begins by comparing the Seebeck coefficient of a metal (cooper), a semi-metal (bismuth) and a semiconductor (silicon). Monovalent metallic ... More

This chapter is devoted to a survey of elemental solids. It begins by comparing the Seebeck coefficient of a metal (cooper), a semi-metal (bismuth) and a semiconductor (silicon). Monovalent metallic (i.e. alkali and noble) are expected to be most akin to a free electron gas. However, this is not the case. Giant enhancement of thermoelectric response by adding a small amount of magnetic impurities is a known signature of Kondo effect. The puzzle of positive Seebeck coefficient of noble metals and the proposed solutions to this puzzle are reviewed. The chapter ends by a discussion of thermoelectric data obtained on elements of column-V (such as bismuth) and column IV (such as silicon).Less