Search

Motor weakness is an important sequela after traumatic brain injury (TBI). Although the majority of cases of TBI are classified as mild TBI, little is known about motor weakness in mild TBI. In this study, we attempted to investigate injury of the corticospinal tract (CST), an important neural tract for motor function, in patients with mild TBI, using diffusion tensor tractography (DTT). There were 53 patients with mild TBI and 36 control subjects who were recruited. The patients were assigned to two groups according to the presence of abnormality of the right (dominant) hand function in terms of fine motor activity and grip strength: group A-abnormal hand function, group B-normal hand function. The left CST was reconstructed, and DTT parameters (fractional anisotropy [FA] and fiber number) and configuration were estimated. There were 35 (66%) patients who had an abnormal function of the right hand. The values of FA and fiber number of patient group A were significantly lower than those of patient group B and the control group ( p < 0.001). On configurational analysis of DTT for the left CST in patient group A, 80% showed partial tearing at the subcortical white matter and 20% showed narrowing. We found that in terms of DTT parameters and configuration, a significant portion of patients with mild TBI showed injury of the CST. These results suggest that DTT could provide useful information in detecting injury of the CST, and evaluation of the CST using DTT would be necessary for patients who complain of hand weakness after mild TBI. [ABSTRACT FROM AUTHOR]

Inthis study, a new ReaxFF reactive force field has been developed todescribe reactions in Ti/O/Cl/H materials. This force field was appliedto etching simulations for titanium metal and titanium dioxide withchlorine and hydrogen chloride gases. The ReaxFF force field parametersare fitted against a quantum mechanical (QM) training set containingstructures and energies related to bond dissociations, angle and dihedraldistortions, and reactions between titanium and chlorine gases aswell as heats of formation of TiClxcrystals.These newly developed Ti–Cl force field parameters were combinedwith a recently developed Ti–O–H force field. ReaxFFaccurately reproduces the QM training set for structures and energeticsof small clusters and TiClxcrystals.In the etching simulations, titanium and titanium dioxide slab modelswith chlorine and hydrogen chloride gases were used in molecular dynamicssimulations. The etching ratio between HCl and Cl2arecompared to experimental results, and satisfactory results are obtained,indicating that this ReaxFF extension provides a useful tool for studyingthe atomistic-scale details of the etching process. [ABSTRACT FROM AUTHOR]

A newReaxFF reactive force field has been developed to describereactions in the Ti–O–H system. The ReaxFF force fieldparameters have been fitted to a quantum mechanical (QM) trainingset containing structures and energies related to bond dissociationenergies, angle and dihedral distortions, and reactions between waterand titanium dioxide, as well as experimental crystal structures,heats of formation, and bulk modulus data. Model configurations forthe training set were based on DFT calculations on molecular clustersand periodic systems (both bulk crystals and surfaces). ReaxFF reproducesaccurately the QM training set for structures and energetics of smallclusters. ReaxFF also describes the relative energetics for rutile,brookite, and anatase. The results of ReaxFF match reasonably wellwith those of QM for water binding energies, surface energies, andH2O dissociation energy barriers. To validate this ReaxFFdescription, we have compared its performance against DFT/MD simulationsfor 1 and 3 monolayers of water interacting with a rutile (110) surface.We found agreement within a 10% error between the DFT/MD and ReaxFFwater dissociation levels for both coverages. [ABSTRACT FROM AUTHOR]

Abstract: The mouse prostate gland develops by branching morphogenesis from the urogenital epithelium and mesenchyme. Androgens and developmental factors, including FGF10 and SHH, promote prostate growth (Berman, D.M., Desai, N., Wang, X., Karhadkar, S.S., Reynon, M., Abate-Shen, C., Beachy, P.A., Shen, M.M., 2004. Roles for Hedgehog signaling in androgen production and prostate ductal morphogenesis. Dev. Biol. 267, 387–398; Donjacour, A.A., Thomson, A.A., Cunha, G.R., 2003. FGF-10 plays an essential role in the growth of the fetal prostate. Dev. Biol. 261, 39–54), while BMP4 signaling from the mesenchyme has been shown to suppresses prostate branching (Lamm, M.L., Podlasek, C.A., Barnett, D.H., Lee, J., Clemens, J.Q., Hebner, C.M., Bushman, W., 2001. Mesenchymal factor bone morphogenetic protein 4 restricts ductal budding and branching morphogenesis in the developing prostate. Dev. Biol. 232, 301–314). Here, we show that Bone Morphogenetic Protein 7 (BMP7) restricts branching of the prostate epithelium. BMP7 is expressed in the periurethral urogenital mesenchyme prior to formation of the prostate buds and, subsequently, in the prostate epithelium. We show that BMP7 lacZ/lacZ null prostates show a two-fold increase in prostate branching, while recombinant BMP7 inhibits prostate morphogenesis in organ culture in a concentration-dependent manner. We further explore the mechanisms by which the developmental signals may be interpreted in the urogenital epithelium to regulate branching morphogenesis. We show that Notch1 activity is associated with the formation of the prostate buds, and that Notch1 signaling is derepressed in BMP7 null urogenital epithelium. Based on our studies, we propose a model that BMP7 inhibits branching morphogenesis in the prostate and limits the number of domains with high Notch1/Hes1 activity. [Copyright &y& Elsevier]

• ReaxFF force field parameters are newly developed for Ni-Cr-Fe-H-O system. • The driving forces for atomistic SCC initiation were calculated. • The classic slip-dissolution model for SCC initiation is extended. Targeting atomistic initiation of stress corrosion cracking (SCC) of Alloy 690, reactive molecular dynamics simulations of SCC of polycrystalline Ni 60 Cr 30 Fe 10 alloys under water with dissolved oxygen at 900 K were performed employing newly developed reactive force field (ReaxFF) of Ni-Cr-Fe-H-O system. Observed atomistic mechanochemical mechanism involve dissolution-precipitation and diffusion-oxidation behaviors for corrosion, and cleavage-slipping-twinning behaviors for cracking initiation with its driving forces including loacl shear stress/strain and oxidation-enhanced atomistic stress. Roles of cold work, tensile strain and grain boundary (GB) structures in impacting these mechanochemical behaviors were explored based on calculated surface and GB energy, GB diffusivity and atomistic stress/strain. [ABSTRACT FROM AUTHOR]

Quantifying the irreversible chemical and structural changes of Si during cycling remains challenging. In this study, a continuous reactive molecular dynamics delithiation algorithm, with well-controlled potential gradient and delithiation rate, was developed and used to investigate the "natural" delithiation responses of an aluminum-oxide coated silicon thin-film. Fast delithiation led to the formation of dense Si network near the surface and nanoporosity inside the a-LixSi, resulting in 141% volume dilation and significant amount of Li trapped inside (a-Li1.2Si) at the end of delithiation process. In contrast, slow delithiation allowed the a-LixSi to shrink by near-equilibrium condition, demonstrating no permanent inner pore with nearly Li-free structure (a-Li0.2Si) and minimal volume dilation (44%). However, even without trapped Li, the delithiated a-LixSi still exhibited higher volume (lower density) than the equilibrium structure with the same Li concentration, despite delithiation rate. The origin of this excess volume is the loss of directly bonded Si–Si pairs, which made the subsequent relithiation faster. On the basis of the atomistic modeling and the quantified degradation mechanism, battery operating guidelines, including the delithiation rate and the depth of charge to avoid trapped Li and coating delamination, were suggested to improve the durability Si electrodes. [ABSTRACT FROM AUTHOR]