Microtesla MRI of the human brain combined with MEG

One of the challenges in functional brain imaging is integration of complementary imaging modalities, such as magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive superconducting quantum interference devices (SQUIDs) to directly measure magnetic fields of neuronal currents, cannot be combined with conventional high-field MRI in a single instrument. Indirect matching of MEG and MRI data leads to significant co-registration errors. A recently proposed imaging method--SQUID-based microtesla MRI--can be naturally combined with MEG in the same system to directly provide structural maps for MEG-localized sources. It enables easy and accurate integration of MEG and MRI/fMRI, because microtesla MR images can be precisely matched to structural images provided by high-field MRI and other techniques. Here we report the first images of the human brain by microtesla MRI, together with auditory MEG (functional) data, recorded using the same seven-channel SQUID system during the same imaging session. The images were acquired at 46 microT measurement field with pre-polarization at 30 mT. We also estimated transverse relaxation times for different tissues at microtesla fields. Our results demonstrate feasibility and potential of human brain imaging by microtesla MRI. They also show that two new types of imaging equipment--low-cost systems for anatomical MRI of the human brain at microtesla fields, and more advanced instruments for combined functional (MEG) and structural (microtesla MRI) brain imaging--are practical.     

Structural investigation of an amorphous Si24Nb76 alloy produced by mechanical alloying using reverse Monte Carlo simulations

The atomic structure of an amorphous Si₂₄Nb₇₆ alloy produced by mechanical alloying was investigated by using one X-ray total structure factor S(K) as input data for reverse Monte Carlo (RMC) simulations. The partial S_Si–Si(K), S_Si–Nb(K), S_Nb–Nb(K) structure factors and G_Si–Si(r), G_Si–Nb(r), G_Nb–Nb(r) pair probability functions were obtained from the RMC simulations. The structural parameters (interatomic distances and co-ordination numbers) for the first neighbors were extracted and compared with those found in the Nb₃Si compound. It was observed some resemblance between these phases.     

Computing Integrated Information (Φ) in Discrete Dynamical Systems with Multi-Valued Elements

Integrated information theory (IIT) provides a mathematical framework to characterize the cause-effect structure of a physical system and its amount of integrated information (Φ). An accompanying Python software package (“PyPhi”) was recently introduced to implement this framework for the causal analysis of discrete dynamical systems of binary elements. Here, we present an update to PyPhi that extends its applicability to systems constituted of discrete, but multi-valued elements. This allows us to analyze and compare general causal properties of random networks made up of binary, ternary, quaternary, and mixed nodes. Moreover, we apply the developed tools for causal analysis to a simple non-binary regulatory network model (p53-Mdm2) and discuss commonly used binarization methods in light of their capacity to preserve the causal structure of the original system with multi-valued elements.     

Experimental Investigation of the Mechanical Behavior and Permeability of 3D Printed Sandstone Analogues Under Triaxial Conditions

Transport in Porous Media - Consolidated drained triaxial tests arise as one of the most exhaustive methods to quantify the strength, volumetric behavior and failure process of rocks. Understanding...     

Application of thermal analysis to the rhenium recovery process from copper and molybdenum sulphides minerals

Journal of Thermal Analysis and Calorimetry - Rhenium production from copper and molybdenum sulphides involves the use of a pyrometallurgical process. In traditional pyrometallurgy processes, gases...     

1-[Ferrocenyl(hydroxy)methyl]-1,7-dicarba<Emphasis Type="Italic">-closo</Emphasis>-dodecaborane: Synthesis and X-ray crystal structure

The synthesis and molecular structure of the novel 1-[ferrocenyl(hydroxy)methyl]-1,7-dicarba-closo-dodecaborane (1) is described. Compound 1 was synthesized from reaction of m-carborane and ferrocene carboxaldehyde using n-butyllithium (n-BuLi) or tetrabutylammonium fluoride (TBAF) in THF in 45% and 36% yield, respectively. Compound 1 consists of a ferrocene molecule tethered to m-carborane through a methylhydroxy bridge. The crystal structure of 1 was determined by single crystal X-ray diffraction analysis. Crystal data: 1 [Fe(C₅H₅)(C₅H₄-CH₂O-1,7-C₂B₁₀H₁₂)], formula weight = 359.17, crystallized in orthorhombic system, space group Pna2 ₁ with a=19.698(4) ?, b=10.709(2) ?, c=8.520(2) ?, and V=1797.3(7) ?³ and Z=4. Refined to R ₁=0.043 for 4124 observed reflections with I/σ>2σ(I). The compound was crystallized as racemic twins in a ratio of 73(2)/27(2). The unsubstituted Cp ring was disordered and modeled as two conformations in a 53(3)/47(3) ratio. Intermolecular hydrogen bonding was observed from the hydrogen of the meta-carbon on the carborane cluster towards the hydroxyl oxygen.     

Magnetic microsphere-based methods to study the interaction of teicoplanin with peptides and bacteria

Teicoplanin (teic) from Actinoplanes teichomyceticus is a glycopeptide antibiotic used to treat many Gram-positive bacterial infections. Glycopeptide antibiotics inhibit bacterial growth by binding to carboxy-terminal d-Ala-d-Ala intermediates in the peptidoglycan of the cell wall of Gram-positive bacteria. In this paper we report the derivatization of magnetic microspheres with teic (teic-microspheres). Fluorescence-based techniques have been developed to analyze the binding properties of the microspheres to two d-Ala-d-Ala terminus peptides. The dissociation constant for the binding of carboxyfluorescein-labeled d-Ala-d-Ala-d-Ala to teic on microspheres was established via fluorimetry and flow cytometry and was determined to be 0.5 × 10⁻⁶ and 3.0 × 10⁻⁶ mol L⁻¹, respectively. The feasibility of utilizing microparticles with fluorescence methods to detect low levels (the limit of bacterial detection was determined to be 30 colon-forming units; cfu) of Gram-positive bacteria has been demonstrated. A simple microfluidic experiment is reported to demonstrate the possibility of developing microsphere-based affinity assays to study peptide–antibiotic interaction.     

Chemometric experimental design based optimization techniques in capillary electrophoresis: a critical review of modern applications

A critical review of recent developments in the use of chemometric experimental design based optimization techniques in capillary electrophoresis applications is presented. Current advances have led to enhanced separation capabilities of a wide range of analytes in such areas as biological, environmental, food technology, pharmaceutical, and medical analysis. Significant developments in design, detection methodology and applications from the last 5 years (2002–2007) are reported. Furthermore, future perspectives in the use of chemometric methodology in capillary electrophoresis are considered.