Comment on "Slave-boson mean field versus quantum Monte Carlo results for the Hubbard model"
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As the millennium approaches nurses are challenged to reflect on the evolving role of technology on the profession. A preview of the technologies coming to the clinical arena in the not-so-distant future is provided. Eight guidelines for wise technology integration are offered to assist providers in appropriately using technology while preserving humanity in an increasingly high-technology world.
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A large number of molecular, cellular, and epidemiologic factors have been implicated in the regulation of bone development. A major unsolved problem is how to integrate these disparate findings into a concept that explains the development of bone as an organ. Often events on the organ level are simply presented as the cumulative effect of all factors that individually are known to influence bone development. In such a cumulative model it must be assumed that each bone cell carries the construction plan of the entire skeletal anatomy in its genes. This scenario is implausible, because it would require an astronomical amount of positional information. We therefore propose a functional model of bone development, which is based on Frost's mechanostat theory. In this model the genome only provides positional information for the basic outline of the skeleton as a cartilaginous template. Thereafter, bone cell action is coordinated by the mechanical requirements of the bone. When mechanical challenges exceed an acceptable level (the mechanostat set point), bone tissue is added at the location where it is mechanically necessary. The main mechanical challenges during growth result from increases in bone length and in muscle force. Hormones, nutrition, and environmental factors exert an effect on bone either directly by modifying the mechanostat system or indirectly by influencing longitudinal bone growth or muscle force. Predictions based on this model are in accordance with observations on prenatal, early postnatal, and pubertal bone development. We propose that future studies on bone development should address topics that can be derived from the mechanostat model.
Female sex determination in the germ line of Drosophila melanogaster is regulated by genes functioning in the soma as well as genes that function within the germ line. Genes known or suspected to be involved in germ-line sex determination in Drosophila melanogaster have been examined to determine if they are required upstream or downstream of Sex-lethal+, a known germ-line sex determination gene. Seven genes required for female-specific splicing of germ-line Sex-lethal+ pre-mRNA are identified. These results together with information about the tissues in which these genes function and whether they control sex determination and viability or just sex determination in the germ line have been used to deduce the genetic hierarchy regulating female germ-line sex determination. This hierarchy includes the somatic sex determination genes transformer+, transformer-2+ and doublesex+ (and by inference Sex-lethal+), which control a somatic signal required for female germ-line sex determination, and the germ-line ovarian tumor genes fused+, ovarian tumor+, ovo+, sans fille+, and Sex-lethal+, which are involved in either the reception or interpretation of this somatic sex determination signal. The fused+, ovarian tumor+, ovo+ and sans fille+ genes function upstream of Sex-lethal+ in the germ line.
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Common morality theory must confront apparent counterexamples from the history of morality, such as the widespread acceptance of slavery in prior eras, that suggest core norms have changed over time. A recent defense of common morality theory addresses this problem by drawing a distinction between the content of the norms of the common morality and the range of individuals to whom these norms apply. This distinction is successful in reconciling common morality theory with practices such as slavery, but only at the cost of underscoring the limits of common morality theory, in particular its inability to resolve disputes about the moral status of entities. Given that many controversies in bioethics center on the disputed status of various entities, such as embryos and nonhuman animals, this is an important limitation. Nonetheless, common morality theory still can be a useful resource in diminishing moral conflict on issues that do not involve disputes over moral status.