Quantification of neurons in Alzheimer and control brains with ex vivo high resolution magic angle spinning proton magnetic resonance spectroscopy and stereology

Samples from human brains were examined with both stereologic methods for neuronal counting and high resolution magic angle spinning (HRMAS) proton magnetic resonance spectroscopy (1HMRS) for quantification of cellular metabolites. A statistically significant linear correlation between neuronal density and the concentration of N-acetylaspartate (NAA) in the superior temporal sulcus (STS) area was observed. Although NAA has been widely utilized as a neuronal marker in in vivo MRS, an emerging sub-discipline of diagnostic neuroradiology, the experimental proof of the unilateral relationship between NAA and neurons has yet to be confirmed. The observed correlation provides experimental evidence that NAA concentration is proportional to the neuronal density. Metabolite ratios measured from the STS area were compared to those from frontal association cortex for their sensitivities in differentiating Alzheimer disease brains from control brains.     

Power-law scaling for macroscopic entropy and microscopic complexity: evidence from human movement and posture

We investigated the relationship between macroscopic entropy and microscopic complexity of the dynamics of body rocking and sitting still across adults with stereotyped movement disorder and mental retardation (profound and severe) against controls matched for age, height, and weight. This analysis was performed through the examination of center of pressure (COP) motion on the mediolateral (side-to-side) and anteroposterior (fore-aft) dimensions and the entropy of the relative phase between the two dimensions of motion. Intentional body rocking and stereotypical body rocking possessed similar slopes for their respective frequency spectra, but differences were revealed during maintenance of sitting postures. The dynamics of sitting in the control group produced lower spectral slopes and higher complexity (approximate entropy). In the controls, the higher complexity found on each dimension of motion was related to a weaker coupling between dimensions. Information entropy of the relative phase between the two dimensions of COP motion and irregularity (complexity) of their respective motions fitted a power-law function, revealing a relationship between macroscopic entropy and microscopic complexity across both groups and behaviors. This power-law relation affords the postulation that the organization of movement and posture dynamics occurs as a fractal process.     

Entropy compensation in human motor adaptation

This experiment examined the changes in entropy of the coordination of isometric force output under different levels of task demands and feedback from the environment. The goal of the study was to examine the hypothesis that human motor adaptation can be characterized as a process of entropy conservation that is reflected in the compensation of entropy between the task, organism (motor output), and environment. Healthy young individuals produced two-finger force output to a total constant level under different task (error tolerance) and environmental (feedback frequency) conditions. Information entropy of the coordination dynamics (relative phase) of the motor output was made conditional on the idealized situation of human movement, for which the goal is always achieved. Conditional entropy of the motor output decreased as the error tolerance and feedback frequency were decreased. Thus, as the likelihood of meeting the task demands is decreased (increased task entropy) and/or the amount of information from the environment is reduced (increased environmental entropy), the subjects employed fewer coordination patterns in the force output to achieve the goal.     

Developments in WTDM technology for high-capacity optical studio networks

This paper reviews results achieved in high-capacity optical networking for television studios under RACE projects 1036 and 2001. A network based on wavelength- and time-division multiplexing (WTDM) has been demonstrated, which, using 16 wavelengths, provides a total capacity of 39.8 Gbit s^-1. We summarize previously reported results obtained in the system test-bed, which demonstrate the distribution of uncompressed digital video signals ranging from PAL at 142 Mbit s^-1 to HDTV at 1.15 Gbit s^-1. The process of further developing this technology for a pilot installation has established that it will be applicable not only to central routeing within a television studio but also to resilient network provision and the interconnection of remote sites. We review how network resilience is achieved by multiple interconnected star architectures and outline how recent results with integrated star couplers suggest that these designs can be delivered at low cost. We report new experiments demonstrating an optically amplified network over a commercially installed 36-km link, thus confirming the feasibility of a long-reach routeing system. We also report results illustrating how lithium niobate devices can perform optical switching on the wavelength multiplex and thus offer potential advantages in system transparency and throughput. Our conclusion is that we have confirmed the feasibility of the WTDM concept and demonstrated its potential for wider application.GEC-Marconi Defence SystemsThomson-CSFNorthern Telecom Europe     

Theory of oscillation type viscometers III: A thin disk

The small amplitude oscillation of a thin disk of finite radius suspended in an infinite fluid is considered with a view toward its use as a viscometer. The fluid motion is analyzed under the assumption that the boundary layer thickness of the fluid is small compared with the radius of the disk but large compared with the thickness of the disk. Formulas are obtained relating the frequency and decrement of oscillation to the density and viscosity of the fluid.

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Zusammenfassung Es wird untersucht, inwieweit eine dünne aufgehängte Scheibe endlicher Abmessung, wenn sie mit kleiner Amplitude schwingt, sich zur Messung der Zähigkeit verwenden lässt. Die Bewegung der Flüssigkeit wird unter der Voraussetzung analysiert, dass die Grenzschichtdicke klein ist im Vergleich zum Radius der Scheibe, aber gross verglichen mit der Scheibendicke. Die Formeln zeigen die Abhängigkeit der Frequenz und des logarithmischen Dekrements der Schwingung von der Dichte und der Zähigkeit der Flüssigkeit.

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This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under contract No. AF 18 (600) 1548. Reproduction in whole or in part is permitted for any purpose of the United States Government. Part of the work was done while one of the authors (G. F. N.) was being supported by a grant from the Alfred P. Sloan Foundation.     

Theory of oscillation type viscometers V: Disk oscillating between fixed plates

A disk oscillating between two fixed plates is considered as an instrument for absolute measurements of viscosity. The existing theories relating the viscosity to the decrement of oscillation are improved by calculating the effects of the edge. This is done by assuming that the separation between the plates is small compared with both the radius of the disk and the boundary layer thickness. A comparison is made with the experimental data ofKestin andPilarczyk for which the present theory is estimated to be correct to 0·1%.

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Zusammenfassung Es wird untersucht, ob eine zwischen zwei feststehenden Platten schwingende Scheibe als Gerät für die Absolutmessung der Zähigkeit von Flüssigkeiten benutzt werden kann. Die dafür bestehenden Theorien, bei denen die Viskosität aus dem logarithmischen Dekrement der Schwingung berechnet wird, sind hier durch die Berücksichtigung der Randeffekte erweitert worden, unter der Voraussetzung, dass der Abstand zwischen den beiden feststehenden Platten klein ist im Verhältnis zum Radius der Scheibe und zur Grenzschichtdicke. Die Theorie stimmt mit den vonKestin undPilarczyk experimentell gefundenen Werten auf 0,1% genau überein.

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This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under contract No. AF 18 (600) 1548. Reproduction in whole or in part is permitted for any purpose of the United States Govermnent. Part of the work was done while the author was being supported by a grant from the Alfred P. Sloan Foundation.     

Renaissance of Topotactic Ion-Exchange for Functional Solids with Close Packed Structures

Recently, many new, complex, functional oxides have been discovered with the surprising use of topotactic ion-exchange reactions on close-packed structures, such as found for wurtzite, rutile, perovskite, and other structure types. Despite a lack of apparent cation-diffusion pathways in these structure types, synthetic low-temperature transformations are possible with the interdiffusion and exchange of functional cations possessing ns² stereoactive lone pairs (e. g., Sn(II)) or unpaired nd^x electrons (e. g., Co(II)), targeting new and favorable modulations of their electronic, magnetic, or catalytic properties. This enables a synergistic blending of new functionality to an underlying three-dimensional connectivity, i. e., [-M−O-M-O-]_n, that is maintained during the transformation. In many cases, this tactic represents the only known pathway to prepare thermodynamically unstable solids that otherwise would commonly decompose by phase segregation, such as that recently applied to the discovery of many new small bandgap semiconductors.     

Cryogenic OrbiSIMS Localizes Semi-Volatile Molecules in Biological Tissues

OrbiSIMS is a recently developed instrument for label-free imaging of chemicals with micron spatial resolution and high mass resolution. We report a cryogenic workflow for OrbiSIMS (Cryo-OrbiSIMS) that improves chemical detection of lipids and other biomolecules in tissues. Cryo-OrbiSIMS boosts ionization yield and decreases ion-beam induced fragmentation, greatly improving the detection of biomolecules such as triacylglycerides. It also increases chemical coverage to include molecules with intermediate or high vapor pressures, such as free fatty acids and semi-volatile organic compounds (SVOCs). We find that Cryo-OrbiSIMS reveals the hitherto unknown localization patterns of SVOCs with high spatial and chemical resolution in diverse plant, animal, and human tissues. We also show that Cryo-OrbiSIMS can be combined with genetic analysis to identify enzymes regulating SVOC metabolism. Cryo-OrbiSIMS is applicable to high resolution imaging of a wide variety of non-volatile and semi-volatile molecules across many areas of biomedicine.     

Enhanced wet adhesion and shear of elastomeric micro-fiber arrays with mushroom tip geometry and a photopolymerized p(DMA-co-MEA) tip coating

Using principles inspired by the study of naturally occurring sticky systems such as the micro- and nanoscale fibers on the toes of geckos and the adhesive proteins secreted by marine animals such as mussels, this study describes the development and evaluation of a novel patterned and coated elastomeric microfibrillar material for enhanced repeatable adhesion and shear in wet environments. A multistep fabrication process consisting of optical lithography, micromolding, polymer synthesis, dipping, stamping, and photopolymerization is described to produce uniform arrays of polyurethane elastomeric microfibers with mushroom-shaped tips coated with a thin layer of lightly cross-linked p(DMA-co-MEA), an intrinsically adhesive synthetic polymer. Adhesion and shear force characterization of these arrays in contact with a glass hemisphere is demonstrated, and significant pull-off force, overall work of adhesion, and shear force enhancements in submerged aqueous environments are shown when compared to both unpatterned and uncoated samples, as well as previously evaluated patterned and coated arrays with differing geometry. Such materials may have potential value as repeatable adhesives for wet environments, such as for medical devices.     

Hydrogen oxidation and production using nickel-based molecular catalysts with positioned proton relays

Highly efficient electrocatalysts for both hydrogen evolution and hydrogen oxidation have been designed, synthesized, and characterized. The catalysts in their resting states are air-stable, mononuclear nickel(II) complexes containing cyclic diphosphine ligands with nitrogen bases incorporated into the ligand backbone. X-ray diffraction studies have established that the cation of [Ni(P(Ph)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2), 6a, (where P(Ph)(2)N(Ph)(2) is 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyclooctane) is a trigonal bipyramid with bonds to four phosphorus atoms of the two bidentate diphosphine ligands and the nitrogen atom of an acetonitrile molecule. Two of the six-membered rings formed by the diphosphine ligands and Ni have boat conformations with an average Ni- - -N distance to the two pendant bases of 3.4 A. The cation of [Ni(P(Cy)(2)N(Bz)(2))(2)](BF(4))(2), 6b, (where Cy = cyclohexyl and Bz = benzyl) is a distorted square planar complex. For 6b, all four six-membered rings formed upon coordination of the diphosphine ligands to the metal are in the boat form. In this case, the average Ni- - -N distance to the pendant base is 3.3 A. Complex 6a is an electrocatalyst for hydrogen production in acidic acetonitrile solutions, and compound 6b is an electrocatalyst for hydrogen oxidation in basic acetonitrile solutions. It is demonstrated that the high catalytic rates observed with these complexes are a result of the positioning of the nitrogen base so that it plays an important role in the formation and cleavage of the H-H bond.