Electronegativity, described by Linus Pauling described as “The power of an atom in a molecule to attract electrons to itself” (Pauling in The nature of the chemical bond, 3rd edn, Cornell University Press, Ithaca, p 88, 1960), is used to predict bond polarity. There are dozens of methods for empirically quantifying electronegativity including: the original thermochemical technique (Pauling in J Am Chem Soc 54:3570–3582, 1932), numerical averaging of the ionisation potential and electron affinity (Mulliken in J Chem Phys 2:782–784, 1934), (...) effective nuclear charge and covalent radius analysis (Sanderson in J Chem Phys 23:2467, 1955) and the averaged successive ionisation energies of an element’s valence electrons (Martynov and Batsanov in Zhurnal Neorganicheskoi Khimii 5:3171–3175, 1980), etc. Indeed, there are such strong correlations between numerous atomic parameters—physical and chemical—that the term “electronegativity” integrates them into a single dimensionless number between 0.78 and 4.00 that can be used to predict/describe/model much of an element’s physical character and chemical behaviour. The design of the common and popular medium form of the periodic table is in large part determined by four quantum numbers and four associated rules. However, adding electronegativity completes the construction so that it displays the multi-parameter periodic law operating in two dimensions, down the groups and across the periods, with minimal ambiguity. (shrink)
Psychologists recognize the need to know and adhere to the ethics code in the country or countries in which they work. However, most countries do not have ethics codes that govern the work of psychologists. Thus, psychologists working in countries that do not have an ethics code face a dilemma: They need to behave ethically yet do not know the guidelines or standards that govern these behaviors. This article highlights some cross-national conditions about which psychologists should be aware when working (...) cross-nationally, especially in countries that may lack an ethics code. These include knowledge of the host country's prevailing moral values, its laws and administrative policies, and ethics codes as well as policies approved by international agencies and associations. Eight guidelines are provided for psychologists working in host countries that lack ethics codes. (shrink)
This paper addresses what some view as a progressive and decades-long devaluing of the liberal arts in our educational institutions and society at large. It draws attention to symptoms of this trend and possible contributing factors, identifies benefits commonly attributed to the liberal arts, and then shows how insights from recent research on neuroplasticity provide good reason to believe that a traditional liberal education has positive effects on a person's brain. The paper supports the thesis that well-designed liberal arts courses (...) can literally transform students' minds and lives as a result of unique and synergistic brain processes activated and strengthened by the leaming experiences such courses provide. It finishes with recommendations to help reinvigorate and promote the value of liberal education. (shrink)
In the light of contemporary allelopathic research, the intuitively based statements of the early botanists stand up surprisingly well. The walnut tree is now understood to affect the growth of neighboring plants via juglone leached from the leaves, roots, and fruits.118 The replant or soil sickness problem of peach orchards has been related to the toxigenic breakdown of amygdalin, a constituent of peach roots.119 The declining yield of many crop species grown under continuous monoculture has been linked to the accumulation (...) of allelopathic substances in the soil, especially through the mediation of microorganisms.120 Numerous plants cited by de Candolle as being injurious, such as Erigeron,121 thistle (Cirsium),122 flax (Linum),123 and various crucifers (such as Brassica nigra),124 have been found to posses marked allelopathic activity. Over fifty years before the discovery of rhizobia, de Candolle considered the excretory material of legumes to be beneficial to cereals.125Modern reviews of allelopathy commonly credit de Candolle with an insight that was not equaled by the technology of his era.126 In fairness to his detractors, his toxin theory of plant interactions was largely the by-product of an outdated and misconstrued notion of plant nutrition. His critics and most earlier botanists had similarly erred in seeking a single factor responsible for plant growth, much as had the alchemists sought the legendary philosopher's stone. Taking all this into account and considering the forceful personality of Liebig, one can readily appreciate how, 130 years ago, Liebig's theories preempted and stifled those of de Candolle.Today, with modern techniques of plant physiology and soil biochemistry, allelopathy has been shown to be a real but subtle factor in the dynamics of natural and agricultural plant communities. It is unfortunate that the single-mindedness characteristic of previous centuries still persists. The dichotomy between allelopathy and competition is exacerbated by the inherited bias toward the nutritional model of plant interaction fostered by Liebig, and is accentuated in the fact that in modern nutritional studies it is still basically unnecessary to consider plant-plant chemical interactions and their concomitant effects, whereas in allelopathic investigations the converse is regarded as axiomatic.In summary, de Candolle should not be seen as “a prophet crying in the wilderness,” as Fisher would have it.127 The bases of de Candolle's concept of allelopathy were the dubious experiments of Macaire and his own obsolete theory of plant nutrition. Despite this, modern experimental work indicates that allelopathy is important in many plant interactions. De Candolle seems to have been right, at least in part—but for the wrong reasons. (shrink)
Soil is fragile and nonrenewable but the most basic of natural resources. It has a capacity to tolerate continuous use but only with proper management. Improper soil management and indiscriminate use of chemicals have contributed to some severe global environmental issues, e.g., volatilization losses and contamination of natural waters by sediments and agricultural fertilizers and pesticides. The increasing substitution of energy for labor and other cultural inputs in agriculture is another issue. Fertilizers and chemicals account for about 25% of the (...) production energy investment in agriculture. An additional 60% is accounted for by machinery, gasoline, electricity, and power-related inputs. Fertilizer additions to cropland are not utilized fully and significant amounts, depending on conditions, are either lost in surface runoff or leached into the ground water. The annual discharge of dissolved solids from agricultural lands to the waterways in the USA is substantial. The increasing use of herbicides in agriculture is a threat to the quality of surface and ground water, although this threat is dependent upon both the chemistry of the compound and the ecosystem in which it is used. Especially within the Third World, development of an environmental ethic and environmental laws have not kept pace with the increase in pesticide use. Above all is the severe and global problem of soil degradation currently occurring at the rate of five to seven million hectares per year. The policy and moral aspects of these issues are discussed. (shrink)
Raney Pd and Rh fine particles were prepared from decagonal Al75Pd25 and Al9Rh2 with an Al9Co2-type structure, respectively, by leaching with NaOH aqueous solution. The atomic pair distribution functions (PDFs) for the Raney Pd and Rh fine particles indicate structural features similar to an fcc structure, suggesting atomic rearrangement toward the closest packing of constituents during the leaching process. Transmission electron micrographs indicate that Raney Pd and Rh are aggregates of fcc-structured nano-crystallites with a diameter of 5?6?nm.