Biomedical radiation detecting probe Patent

Silicon radiation detecting probe design for in vivo biomedical us

In vitro osteoclast formation and resorption of silicon-substituted hydroxyapatite ceramics.

Materials that participate in bone remodeling at the implant/tissue interface represent a modern tissue engineering approach with the aim of balancing implant resorption and nascent tissue formation. Silicon-substituted hydroxyapatite (SiHA) ceramics are capable of stimulating new bone formation, but little is known about their interaction with osteoclasts (OC). The effects of soluble silicate and SiHA on OCs were investigated in this study. Soluble silicate below 500 μM did not stimulate cell metabolism at 4 days or alter resorption area at 7 days on calcium phosphate discs. On sintered ceramics, OC numbers were similar on HA, Si0.3 HA (0.5 wt % Si) and Si0.5 HA (1.2 wt % Si) after 21 days in vitro, but actin ring sealing zone morphology on SiHA resembled that commonly found on bone or on carbonate-substituted hydroxyapatite (CHA). Smaller and thicker actin rings on SiHA as compared to HA were probably the result of altered surface chemistry and solubility differences. The more stable sealing zones and increased lattice solubility likely contributed to increased individual pit volumes observed on Si0.5 HA. The delayed formation of OCs on Si0.5 HA (lower numbers at day 14) excludes earlier differentiation as a possible mechanism of increased individual OC pit volumes at later times (day 21). Materials characterization of Si containing biomaterials remains paramount as the Si type and amounts can subsequently impact downstream OC behaviour in a complex manner.Funded by - National Science Foundation Graduate Research Fellowship (RJF). Grant Number: DGE-1042796 - Cambridge International Scholarship from the Cambridge Overseas Trusts (RJF) - National Institute for Health Research (RAB)This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/jbm.a.3547

Synthesis, characterization and modelling of zinc and silicate co-substituted hydroxyapatite.

Experimental chemistry and atomic modelling studies were performed here to investigate a novel ionic co-substitution in hydroxyapatite (HA). Zinc, silicate co-substituted HA (ZnSiHA) remained phase pure after heating to 1100 °C with Zn and Si amounts of 0.6 wt% and 1.2 wt%, respectively. Unique lattice expansions in ZnSiHA, silicate Fourier transform infrared peaks and changes to the hydroxyl IR stretching region suggested Zn and silicate co-substitution in ZnSiHA. Zn and silicate insertion into HA was modelled using density functional theory (DFT). Different scenarios were considered where Zn substituted for different calcium sites or at a 2b site along the c-axis, which was suspected in singly substituted ZnHA. The most energetically favourable site in ZnSiHA was Zn positioned at a previously unreported interstitial site just off the c-axis near a silicate tetrahedron sitting on a phosphate site. A combination of experimental chemistry and DFT modelling provided insight into these complex co-substituted calcium phosphates that could find biomedical application as a synthetic bone mineral substitute.This work was supported by a NSFGRFP grant (DGE-1042796) (RJF) and a Cambridge International Scholarship (RJF). The modelling work was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council. HC would like to thank the UK Medical Research Council (Grant number U105960399) for their support.This is the final version of the article. It first appeared from Royal Society Publishing via http://dx.doi.org/10.1098/rsif.2015.019

Silica-magnesium-titanium Ziegler-Natta catalysts. Part 1: Structure of the pre-catalyst at a molecular level

In this paper, which is the first part of a more extended work, we elucidate the molecular level structure of a highly active SiO2-supported Ziegler-Natta precatalyst obtained by reacting a dehydroxylated silica and a solution of an organomagnesium compound with TiCl4. The synergetic combination of Ti K-edge and Ti L3-edge X-ray Absorption spectroscopy (XAS) and diffuse reflectance UV–Vis spectroscopies, complemented by Density Functional Theory (DFT) simulations, indicate that small TiCl3 clusters similar to β-TiCl3 coexist with isolated monomeric Ti(IV) species. Ti K-edge Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy allows the quantification of these two phases and demonstrates that the Ti(IV) sites are 6-fold coordinated (either by six chlorine ligands or by five chlorine and one oxygen ligands), but highly distorted, similar to what is modelled for TiCl4-capped MgCl2 nanoplatelets. Finally, IR spectroscopy suggests that the MgCl2 phase has a molecular character (Far-IR) and that the only accessible Mg2+ sites are uncoordinated cations acting as Lewis acid sites (IR of CO adsorbed at 100 K). Based on these experimental findings, we propose the co-existence in the precatalyst of small TiCl3 clusters and of mixed oxo-chloride magnesium-titanium structures deposited at the silica surface. The evolution of the precatalyst in the presence of the activator and of the monomer is discussed in the second part of this work

On the neural networks of empathy: A principal component analysis of an fMRI study

© 2008 Nomi et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Advancing the Compositional Analysis of Olefin Polymerization Catalysts with High-Throughput Fluorescence Microscopy

To optimize the performance of supported olefin polymerization catalysts, novel methodologies are required to evaluate the composition, structure, and morphology of both pristine and prepolymerized samples in a resource-efficient, high-throughput manner. Here, we report on a unique combination of laboratory-based confocal fluorescence microscopy and advanced image processing that allowed us to quantitatively assess support fragmentation in a large number of autofluorescent metallocene-based catalyst particles. Using this approach, significant inter- and intraparticle heterogeneities were detected and quantified in a representative number of prepolymerized catalyst particles (2D: ≥135, 3D: 40). The heterogeneity that was observed over several stages of slurry-phase ethylene polymerization (10 bar) is primarily attributed to the catalyst particles' diverse support structures and to the inhomogeneities in the metallocene distribution. From a mechanistic point of view, the 2D and 3D analyses revealed extensive contributions from a layer-by-layer fragmentation mechanism in synergy with a less pronounced sectioning mechanism. A significant number of catalyst particles were also found to display limited support fragmentation at the onset of the reaction (i.e., at lower polymer yields). This delay in activity or "dormancy" is believed to contribute to a broadening of the particle size distribution during the early stages of polymerization. 2D and 3D catalyst screening via confocal fluorescence microscopy represents an accessible and fast approach to characterize the structure of heterogeneous catalysts and assess the distribution of their fluorescent components and reaction products. The automation of both image segmentation and postprocessing with machine learning can yield a powerful diagnostic tool for future research as well as quality control on industrial catalysts

Numerical convergence of the block-maxima approach to the Generalized Extreme Value distribution

In this paper we perform an analytical and numerical study of Extreme Value distributions in discrete dynamical systems. In this setting, recent works have shown how to get a statistics of extremes in agreement with the classical Extreme Value Theory. We pursue these investigations by giving analytical expressions of Extreme Value distribution parameters for maps that have an absolutely continuous invariant measure. We compare these analytical results with numerical experiments in which we study the convergence to limiting distributions using the so called block-maxima approach, pointing out in which cases we obtain robust estimation of parameters. In regular maps for which mixing properties do not hold, we show that the fitting procedure to the classical Extreme Value Distribution fails, as expected. However, we obtain an empirical distribution that can be explained starting from a different observable function for which Nicolis et al. [2006] have found analytical results.Comment: 34 pages, 7 figures; Journal of Statistical Physics 201