The magnetic reorientation transition in thin ferromagnetic films treated by many-body Green's function theory

This contribution describes the reorientation of the magnetization of thin ferromagnetic Heisenberg films as function of the temperature and/or an external field. Working in a rotating frame allows an exact treatment of the single-ion anisotropy when going to higher-order Green's functions. Terms due to the exchange interaction are treated by a generalized Tyablikov (RPA) decoupling.Comment: 9 pages, 2 figure

Stacking-fault energies in simple metals: applications to BCC metals

Presents a general method for calculating the stacking-fault energy in simple metals, and applies this to the (112) faults in body-centered cubic (BCC) metals. The method contains no approximations for a given wavenumber characteristic (or equivalently the pair potential). The results show that metastable faults do indeed exist in the simple BCC metals (Li, Na, K, Rb, Cs, Ca, Sr, Ba), but the currently available potentials do not yield sufficiently accurate stacking-fault energies because they do not predict BCC as the lowest energy phase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49179/2/jfv11i12p2497.pd

Coincidence site lattice twist boundary energies for metals with long-ranged potentials

The author has calculated the coincidence site lattice Sigma twist boundary energies for copper and aluminium. The boundaries were on (100) planes and he considered Sigma values of 5, 13, 17, 25, 29 and 37. The method employed was a wavenumber space summation which includes all effects due to the long-ranged potentials. The trend was for the twist boundary energy, gamma , to be proportional to Sigma independent of the metal and the potential used.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49180/2/jfv12i6pL79.pd

Suppression of properties associated with malignancy in murine melanoma-melanocyte hybrid cells.

Murine and human melanoma cells differ relatively reliably from non-tumorigenic melanocytes in certain biological properties. When cultured at low pH, melanocytes tend to be pigmented and melanoma cells unpigmented. The growth of virtually all metastatic melanoma cells is inhibited by phorbol esters such as TPA (12-O-tetradecanoyl phorbol-13-acetate), which stimulate melanocyte growth. Melanocytes fail to grow in suspension culture or produce tumours when implanted in animals, while many melanoma lines can do both. Here we studied which of these properties were dominant in hybrid cells formed by fusion of drug-resistant murine B16-F10RR melanoma cells to melanocytes of the albino and brown lines, melan-c and melan-b. The albino melanocytes are unpigmented but well-differentiated, the brown melanocytes produce pale brown pigment and the melanoma cells are unpigmented under the conditions used. All hybrid colonies observed produced black pigment, except some melan-b/melanoma hybrids when growing sparsely with TPA. Thus pigmentation was generally dominant. 14/15 hybrid lines showed stimulation of proliferation by TPA, as do melanocytes. Most hybrid lines showed no or reduced capacity for growth in suspension, though some grew better in suspension when TPA was present. There was marked suppression of the tumorigenicity of the parental melanoma cells in 4/8 hybrids examined, and tumorigenicity was reduced in the others, despite considerable chromosome loss by the passage level tested. Thus most properties of the non-tumorigenic pigment cells were dominant, as often observed for other cell lineages, and providing further evidence for gene loss in the genesis of malignant melanoma

On the emergent Semantic Web and overlooked issues

The emergent Semantic Web, despite being in its infancy, has already received a lotof attention from academia and industry. This resulted in an abundance of prototype systems and discussion most of which are centred around the underlying infrastructure. However, when we critically review the work done to date we realise that there is little discussion with respect to the vision of the Semantic Web. In particular, there is an observed dearth of discussion on how to deliver knowledge sharing in an environment such as the Semantic Web in effective and efficient manners. There are a lot of overlooked issues, associated with agents and trust to hidden assumptions made with respect to knowledge representation and robust reasoning in a distributed environment. These issues could potentially hinder further development if not considered at the early stages of designing Semantic Web systems. In this perspectives paper, we aim to help engineers and practitioners of the Semantic Web by raising awareness of these issues

Stimulating Multiple-Demand Cortex Enhances Vocabulary Learning

It is well established that networks within multiple-demand cortex (MDC) become active when diverse skills and behaviors are being learnt. However, their causal role in learning remains to be established. In the present study, we first performed functional magnetic resonance imaging on healthy female and male human participants to confirm that MDC was most active in the initial stages of learning a novel vocabulary, consisting of pronounceable nonwords (pseudowords), each associated with a picture of a real object. We then examined, in healthy female and male human participants, whether repetitive transcranial magnetic stimulation of a frontal midline node of the cingulo-opercular MDC affected learning rates specifically during the initial stages of learning. We report that stimulation of this node, but not a control brain region, substantially improved both accuracy and response times during the earliest stage of learning pseudoword– object associations. This stimulation had no effect on the processing of established vocabulary, tested by the accuracy and response times when participants decided whether a real word was accurately paired with a picture of an object. These results provide evidence that noninvasive stimulation to MDC nodes can enhance learning rates, thereby demonstrating their causal role in the learning process. We propose that this causal role makes MDC candidate target for exper- imental therapeutics; for example, in stroke patients with aphasia attempting to reacquire a vocabulary

HI Narrow Self-Absorption in Dark Clouds: Correlations with Molecular Gas and Implications for Cloud Evolution and Star Formation

We present the results of a comparative study of HI narrow self-absorption (HINSA), OH, 13CO, and C18O in five dark clouds. The HINSA follows the distribution of the emission of the carbon monoxide isotopologues, and has a characteristic size close to that of 13CO. This confirms that the HINSA is produced by cold HI which is well mixed with molecular gas in well-shielded regions. The ratio of the atomic hydrogen density to total proton density for these sources is 5 to 27 x 10^{-4}. Using cloud temperatures and the density of HI, we set an upper limit to the cosmic ray ionization rate of 10^{-16} s^{-1}. Comparison of observed and modeled fractional HI abundances indicates ages for these clouds to be 10^{6.5} to 10^{7} yr. The low values of the HI density we have determined make it certain that the time scale for evolution from an atomic to an almost entirely molecular phase, must be a minimum of several million years. This clearly sets a lower limit to the overall time scale for star formation and the lifetime of molecular clouds

Packing polymorphism of dapivirine and its impact on the performance of a dapivirine-releasing silicone elastomer vaginal ring

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