Structural evolution during crystal nucleation in supercooled liquids with icosahedral short-range order

The structural evolution during crystal nucleation in supercooled Lennard–Jones liquids at a supercooling of 0.3T _m (T _m is the melting temperature) has been studied by molecular dynamic simulations. The icosahedral clusters are observed to compete with crystalline clusters in space, and rearrange before crystal nucleation. Both the stable face-centered-cubic and hexagonal-close-packed (hcp) structures and metastable body-centered-cubic (bcc) structures nucleate simultaneously, resulting in the formation of an incomplete bcc meso-layer in the nuclei. The nuclei form twinned crystal with five-fold axes through a successive twinning process bounded by planes with hcp atoms.     

Many-body potential for nitrogen in α-iron

N atom is one of the most frequent foreign interstitial atoms in α-iron along with C atoms. The Fe–C potential has been well-developed and can reproduce many significant interactions of C with point defects present in α-iron. However, there exists no satisfactory Fe–N potential to describe the interactions of N with point defects. Here, we develop a many-body potential for N in α-iron. The potential parameters are determined by fitting to ab initio data, which includes energetics, configurations, and relaxations of Fe atoms close to N atom. This potential successfully describes the interactions of Fe–N across a wide range of defect environments. The potential employs the embedded atom method form and hence is appropriate for large-scale molecular dynamics simulation.     

On the plasticity event in metallic glass

Based on a systematic molecular dynamics analysis, this study reveals that plastic deformation of metallic glass is not through a uniform configuration change but via many localized plasticity events. These events are manifested by the atomic clusters of high kinetic energy and high strain rate, emerging even in the elastic deformation regime. The life of such a plasticity event is on the order of 10^?12?s, during which the distribution of kinetic energy follows a power law. The study shows that yielding in metallic glass occurs at the sudden surge point of the number of plasticity events. In the steady plastic deformation regime, the continuous nucleation and annihilation of the plastic events lead to a steady flow stress and stabilized total potential energy.     

De/geneticizing Caste: Population Genetic Research in South Asia

Recent years have witnessed a number of population genetics studies aiming to explore the ‘genetic profile’ of the South Asian population and of the caste system. This paper examines four genetic studies and their mass media representations, and discusses interviews with leading historians and social scientists whose work has focused on issues of the caste system. Similar to earlier commentators—from colonial scholars and administrators to Hindu reformers and nationalists—who provided different explanations for the origin of the caste system, recent genetic studies have offered conflicting inferences on the nature of castes and tribes of the subcontinent. These studies, the way they were received on the subcontinent, and assayed by historians of caste, tell a story about agendas of geneticization competing with forces of resistance. On the one hand, they signal a new interest in the debate about the relationship between caste and ‘ethnicity’; on the other hand, they are used selectively by different social groups to strengthen their own political agendas, are denied cognitive validity by historians of caste, and never reach a consensus about the history of caste formation.     

The Religion of Genetics in Epistemology and Ethics

In the dialog between genetics and religion, the genetics of religion has received thoughtful attention from the possibility of free will to the evolution of human religious behavior. In this article, the author focuses on the reverse, the religion of genetics – specifically, two aspects of how religion shapes our understanding and use of genetics. If religion is (as often argued) whatever our ultimate concern or worldview is, it gives context and direction for the study and application of genetics. Some of the implications are traced through two examples of interaction with one religion, the varied Christian tradition.     

The Study of Socioethical Issues in Systems Biology

Systems biology is the rapidly growing and heavily funded successor science to genomics. Its mission is to integrate extensive bodies of molecular data into a detailed mathematical understanding of all life processes, with an ultimate view to their prediction and control. Despite its high profile and widespread practice, there has so far been almost no bioethical attention paid to systems biology and its potential social consequences. We outline some of systems biology's most important socioethical issues by contrasting the concept of systems as dynamic processes against the common static interpretation of genomes. New issues arise around systems biology's capacities for in silico testing, changing cultural understandings of life, synthetic biology, and commercialization. We advocate an interdisciplinary and interactive approach that integrates social and philosophical analysis and engages closely with the science. Overall, we argue that systems biology socioethics could stimulate new ways of thinking about socioethical studies of life sciences.     

Imaging or Imagining? A Neuroethics Challenge Informed by Genetics

From a twenty-first century partnership between bioethics and neuroscience, the modern field of neuroethics is emerging, and technologies enabling functional neuroimaging with unprecedented sensitivity have brought new ethical, social and legal issues to the forefront. Some issues, akin to those surrounding modern genetics, raise critical questions regarding prediction of disease, privacy and identity. However, with new and still-evolving insights into our neurobiology and previously unquantifiable features of profoundly personal behaviors such as social attitude, value and moral agency, the difficulty of carefully and properly interpreting the relationship between brain findings and our own self-concept is unprecedented. Therefore, while the ethics of genetics provides a legitimate starting point—even a backbone—for tackling ethical issues in neuroimaging, they do not suffice. Drawing on recent neuroimaging findings and their plausible real-world applications, we argue that interpretation of neuroimaging data is a key epistemological and ethical challenge. This challenge is two-fold. First, at the scientific level, the sheer complexity of neuroscience research poses challenges for integration of knowledge and meaningful interpretation of data. Second, at the social and cultural level, we find that interpretations of imaging studies are bound by cultural and anthropological frameworks. In particular, the introduction of concepts of self and personhood in neuroimaging illustrates the interaction of interpretation levels and is a major reason why ethical reflection on genetics will only partially help settle neuroethical issues. Indeed, ethical interpretation of such findings will necessitate not only traditional bioethical input but also a wider perspective on the construction of scientific knowledge.     

人格研究中的行为遗传学取向的发展

人格的行为遗传学研究,是以研究遗传和环境的差异来解释人格的个体差异的程度为目的,为探讨遗传和环境在个体发展中的作用提供了新的研究途径。该文以天性和教养为突破口,紧紧围绕行为遗传学在人格研究领域的发展脉络:遗传力、环境、特定基因的研究,进一步探讨在个体人格发展过程中遗传和环境的交互作用的关系。     

SPIRIT, METHOD, AND CONTENT IN SCIENCE AND RELIGION: THE THEOLOGICAL PERSPECTIVE OF A GENETICIST

Abstract. There are three ways in which bridges may be built between science and theology: spirituality, methodology, and content. Spirituality is the power which drives each to address reality and the expectations with which each approaches the pursuit of truth. The methodology of science is summarized in terms of three activities: taxonomy; the hypothetico-deductive cycle; derivative technology. The content of science, especially with respect to the phenomena of givenness, connectedness and openness in the life sciences, is correlated with theological constructs. Attention is drawn to the role of the double helix in biology and a possible parallel is proposed to the function of the icon in religion and theology.     

Quasi-dynamic choice models: Melioration and ratio invariance

There is continuing controversy about the behavioral process or processes that underlie the major regularities of free-operant choice such as molar matching and systematic deviations therefrom. A recent interchange between Vaughan and Silberberg and Ziriax concerned the relative merits of melioration, and a computer simulation of molecular maximizing. There are difficulties in evaluating theories expressed as computer programs because many arbitrary decisions must often be made in order to get the programs to operate. I therefore propose an alternative form of model that I term quasi-dynamic as a useful intermediate form of theory appropriate to our current state of knowledge about free-operant choice. Quasi-dynamic models resemble the game-theoretic analyses now commonplace in biology in that they can predict stable and unstable equilibria but not dynamic properties such as learning curves. It is possible to interpret melioration as a quasi-dynamic model. An alternative quasi-dynamic model for probabilistic choice, ratio invariance, has been proposed by Horner and Staddon. The present paper compares the predictions of melioration and ratio invariance for five experimental situations: concurrent variable-interval variable-interval schedules, concurrent variable-interval variable-ratio schedules, the two-armed bandit (concurrent random-ratio schedules), and two types of frequency-dependent schedule. Neither approach easily explains all the data, but ratio invariance seems to provide a better picture of pigeons' response to probabilistic choice procedures. Ratio invariance is also more adaptive (less susceptible to “traps”) and closer to the original expression of the law of effect than pure hill-climbing processes such as momentary maximizing and melioration, although such processes may come in to play on more complex procedures that provide opportunities for temporal discrimination.