Magnetism and local distortions near carbon impurity in γ\gamma-iron

Local perturbations of crystal and magnetic structure of $\gamma$-iron near carbon interstitial impurity is investigated by {\it ab initio} electronic structure calculations. It is shown that the carbon impurity creates locally a region of ferromagnetic ordering with substantial tetragonal distortions. Exchange integrals and solution enthalpy are calculated, the latter being in a very good agreement with experimental data. Effect of the local distortions on the carbon-carbon interactions in $\gamma$-iron is discussed.Comment: 4 pages 3 figures. Final version, accepted to Phys.Rev. Let

Depinning transition for a screw dislocation in a model solid solution

On the basis of the classical dislocation theory, the Solid Solution Hardening (SSH) is commonly ascribed to the pinning of the edge dislocations. At the atomic level, the theoretical study of the dislocation cores contrasts with such a prediction. Using the static molecular simulations with some interatomic effective potentials, we demonstrate numerically that the critical resolved shear stress associated to a screw dislocation in a random Ni(Al) single crystal has same order as the edge one. Such a result is imposed by the details of the dislocation stacking fault and the core dissociation into Shockley partials. The SSH statistical theory is employed to tentatively predict analytically the data acquired through our atomistic simulations at different Al concentration

Systematic pathway generation and sorting in martensitic transformations: Titanium alpha to omega

Structural phase transitions are governed by the underlying atomic transformation mechanism; martensitic transformations can be separated into strain and shuffle components. A systematic pathway generation and sorting algorithm is presented and applied to the problem of the titanium alpha to omega transformation under pressure. In this algorithm, all pathways are constructed within a few geometric limits, and efficiently sorted by their energy barriers. The geometry and symmetry details of the seven lowest energy barrier pathways are given. The lack of a single simple geometric criterion for determining the lowest energy pathway shows the necessity of atomistic studies for pathway determination.Comment: 11 pages, 2 figure

Functional ectodomain of the hemagglutinin-neuraminidase protein is expressed in transgenic tobacco cells as a candidate vaccine against Newcastle disease virus.

Recently, the use of plants for the production of recombinant proteins has been well demonstrated with promising outcomes. In this study, an efficient Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) cells system expressing the ectodomain of hemagglutinin-neuraminidase (eHN) protein from Newcastle disease virus (NDV) strain AF2240 was established. Transgenic tobacco BY-2 cell cultures expressing the immunogenic eHN protein were generated and the translation efficiency of eHN protein was enhanced using the 5′-untranslated region of Nicotiana tabacum alcohol dehydrogenase gene (NtADH 5′-UTR) under the control of strong cauliflower mosaic virus (CaMV 35S) promoter. Transgenic lines verified by real-time PCR showed high level of eHN mRNA transcripts and immunoblotting confirmed the presence of 66 kD eHN protein. The eHN protein was stably produced in an average of 0.2–0.4 % total soluble protein. Green fluorescent protein-tagged eHN protein was expressed and localized at the cytosol of BY-2 cell. All mice receiving purified eHN protein from transgenic tobacco BY-2 cells produced specific anti-NDV antibodies. We concluded that plant made eHN elicit immune response and can serve as candidate vaccine against NDV

Subtypes of children with attention disabilities.

Subtypes of children with attentional problems were investigated using cluster analysis. Subjects were 9-year-old-elementary school children (N = 443). The test battery administered to these children comprised a comprehensive set of common attention tests, covering different aspects of attentional functioning, and a test of reading comprehension. Cluster analysis of these data yielded eight stable and reproducible clus¬ters. The test profiles of two subgroups were indicative of distinct attentional problems. One group ap¬peared deficient in speed of processing, the other in attentional control. A third subgroup showed a reading deficit. Two additional clusters had very poor and excellent performance on the whole battery, respec¬tively. Finally, three clusters were found with minor variations approximating average performance. The internal validity, that is, the adequacy and stability of the cluster solution, appeared to be reasonably good, as indicated by a variety of measures. The long-term stability over an 18-month period was also checked and found to be satisfactory

Endocytosis as a biological response in receptor pharmacology: evaluation by fluorescence microscopy

The activation of G-protein coupled receptors by agonist compounds results in diverse biological responses in cells, such as the endocytosis process consisting in the translocation of receptors from the plasma membrane to the cytoplasm within internalizing vesicles or endosomes. In order to functionally evaluate endocytosis events resulted from pharmacological responses, we have developed an image analysis method -the Q-Endosomes algorithm- that specifically discriminates the fluorescent signal originated at endosomes from that one observed at the plasma membrane in images obtained from living cells by fluorescence microscopy. Mu opioid (MOP) receptor tagged at the carboxy-terminus with yellow fluorescent protein (YFP) and permanently expressed in HEK293 cells was used as experimental model to validate this methodology. Time-course experiments performed with several agonists resulted in different sigmoid curves depending on the drug used to initiate MOP receptor endocytosis. Thus, endocytosis resulting from the simultaneous activation of co-expressed MOP and serotonin 5-HT2C receptors by morphine plus serotonin was significantly different, in kinetics as well as in maximal response parameters, from the one caused by DAMGO, sufentanyl or methadone. Therefore, this analytical tool permits the pharmacological characterization of receptor endocytosis in living cells with functional and temporal resolution

Hydrogen Interaction with Dislocations in Si

An H plasma has a remarkable effect on dislocation mobility in silicon, reducing its activation energy to 1.2 eV. Applying density functional theory to the interactions of H and H? With the core of the 90 degrees partial dislocation in Si, we have identified a path for motion involving kink formation and migration at hydrogenated core bonds which conforms exactly to the experimentally measured activation energ

Executive functioning in children with an autism spectrum disorder: Can we differentiate

The aim of this study was to investigate whether children with high-functioning autism (HFA), Asperger's syndrome (AS), and pervasive developmental disorder not otherwise specified (PDDNOS) can be differentiated from each other and from normal controls on their neurocognitive executive functioning (EF) profile. Children with HFA and AS showed the most EF deficits. The EF profile of the PDDNOS group was more disturbed that the normal control group, but was less disturbed than the profile of the HFA and AS groups. Little difference was found between the three PDD subtypes with respect to EF. This study supports the view that executive dysfunctioning plays an important role in autism. The usefulness of a distinction between different PDD subtypes was not demonstrated. © 2006 Springer Science+Business Media, Inc