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Background: Both amyloid (Aβ) load and APOE4 allele are associated with neurodegenerative changes in Alzheimer's disease (AD) prone regions and with risk for cognitive impairment.Objective: To evaluate the unique and independent contribution of APOE4 allele status (E4+∖E4-), Aβ status (Amy+∖Amy-), and combined APOE4 and Aβ status on regional cortical thickness (CoTh) and cognition among participants diagnosed as cognitively normal (CN, n = 251), early mild cognitive impairment (EMCI, n = 207), late mild cognitive impairment (LMCI, n = 196), and mild AD (n = 162) from the ADNI.Methods: A series of two-way ANCOVAs with post-hoc Tukey HSD tests, controlling independently for Aβ and APOE4 status and age were examined.Results: Among LMCI and AD participants, cortical thinning was widespread in association with Amy+ status, whereas in association with E4+ status only in the inferior temporal and medial orbito-frontal regions. Among CN and EMCI participants, E4+ status, but not Amy+ status, was independently associated with increased CoTh, especially in limbic regions [e.g., in the entorhinal cortex, CoTh was 0.123 mm greater (p = 0.002) among E4+ than E4-participants]. Among CN and EMCI, both E4+ and Amy+ status were independently associated with cognitive impairment, which was greatest among those with combined E4 + and Amy+ status.Conclusion: Decreased CoTh is independently associated with Amy+ status in many brain regions, but with E4+ status in very restricted number of brain regions. Among CN and EMCI participants, E4 + status is associated with increased CoTh, in medial and inferior temporal regions, although cognitive impairment at this state is independently associated with Amy+ and E4 + status. These findings imply a unique pathophysiological mechanism for E4 + status in AD and its progression. [ABSTRACT FROM AUTHOR]

Background: The rise in incidence of Alzheimer's disease (AD) has led to efforts to advance early detection of the disease during its preclinical stages. To achieve this, the field needs to develop more sensitive cognitive tests that relate to biological markers of disease pathology. Failure to recover from proactive interference (frPSI) is one such cognitive marker that is associated with volumetric reductions in the hippocampus, precuneus, and other AD-prone regions, and to amyloid load in the brain.Objective: The current study attempted to replicate and extend our previous findings that frPSI is a sensitive marker of early AD, and related to a unique pattern of volumetric loss in AD prone areas.Methods: Three different memory measures were examined relative to volumetric loss and cortical thickness among 45 participants with amnestic mild cognitive impairment.Results: frPSI was uniquely associated with reduced volumes in the hippocampus (r = 0.50) precuneus (r = 0.41), and other AD prone regions, replicating previous findings. Strong associations between frPSI and lower entorhinal cortex volumes and cortical thickness (r≥0.60) and precuneus (r = 0.50) were also observed.Conclusion: Unique and strong associations between volumetric reductions and frPSI as observed by Loewenstein and colleagues were replicated. Together with cortical thickness findings, these results indicate that frPSI is worthy of further study as a sensitive and early cognitive marker of AD. [ABSTRACT FROM AUTHOR]

It is well known that when particle size is reduced, surface effect becomes important. As a result, micro/nanoparticles tend to have well defined geometric shapes to reduce total surface energy, as opposed to the irregular shapes observed in most bulk materials. The surface of such micro/ nanostructures are smooth. Any deviation from a smooth surface implies an increased surface energy which is not energetically favorable. Here, we report an observation of spherical particles in an alloy of Al65Cu20Fe15 nominal composition prepared by arc melting. Such spherical particles stand out from those reported so far due to the decoration of concentric nanorings on the surface. Three models for the formation of these concentric ring patterns are suggested. The most prominent ones assume that the rings are frozen features of liquid motion which could open the door to investigate the kinetics of liquid motion on the micro/nanometer scale. [ABSTRACT FROM AUTHOR]

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A new M-Z interferometer all-optical switch (AOS) consisting of a single nonlinear fiber and a linear long-period fiber grating (LPFG) pair is investigated. The switching principle is based on shifting the transmission spectrum over half of the subspectrum width by the pump light. In this paper, two types of such devices are simulated. The first one concerns use of the usual silica fiber based on the Kerr effect, the switching power of which is 471 W, consisting of the experimental result3; the second one concerns the use of an erbium-doped fiber (EDF) based on the resonant nonlinearity, the switching power of which is reduced by less than 25 mW. The transmissions of the AOS in the EDF-LPFG pair for different parameters of LPFG are also discussed. [ABSTRACT FROM AUTHOR]

A dynamical addressing device for optical interconnection based on one-dimensional nonlinear photonic crystal made on the planar waveguide was designed and fabricated. The dynamical interconnection is performed by controlling the power density of the control light. In our device, when increasing the power density of the control light from 0 to 2.60 × 105 W/cm2, the angle of the signal beam can be changed by about 2°. This kind of devices is promising for use in all-optical interconnection, optical information processing and optical communication. [ABSTRACT FROM AUTHOR]

In order to get the lowest switching power in the ring-resonator-coupled M-Z interferometer switching devices, the loss in the ring resonator has to approach zero. However, in practice, the loss in the ring and coupler cannot be neglected, as it might make the switch unworkable. Therefore, we suggest inserting a gain-controllable optical amplifier into the ring to compensate for the losses and enhance the ring finesse to reduce the switching power. By adjusting the gain, a tradeoff between the switching power and the switching time can be obtained. [ABSTRACT FROM AUTHOR]

Planar optical waveguides consisting of layers from different materials created at elevated temperatures usually exhibit substantial stresses. These stresses are caused by thermal-induced strains that originate from the bonding of the layers in addition to intrinsic strains. For the first time, the analytical form of thermal stress formula is derived for the waveguide glass layer of the silicon-based silica waveguide in bilayer structures by the thin-film approximation and under the strain compatibility and the force equilibrium conditions. These conditions address the composite nature of the waveguide glass layer containing the waveguide core layer and the cladding layers within the optical planar waveguide. The developed formula reveals that temperature parameter, material parameters, and structural parameters affect the distribution of the thermal stress. By applying the formula, we demonstrate that it is possible to achieve the thermal stress-free, and, hence, the stress-induced birefringence-free waveguide devices by proper waveguide designs. [ABSTRACT FROM PUBLISHER]

Studies the crystal structure of a homologous compound series, Ga[sub 2]O[sub 3](ZnO). Structural requirements; Solid-state reactions; Possible space groups selected from extinction rules; Results of high-resolution lattice imaging and high spatial resolution energy-dispersive X-ray spectroscopy.

Using a planar optical waveguide electro-optic modulator and simple double beam interfering device, the experimental study of optical bistability and multistability is successfully performed. The waveguide modulator is made by depositing aluminium as electrodes on the Ti-diffused LiNbO planar optical waveguide which is fabricated by ourselves. Laser beam is coupled directly into the end of optical waveguide modulator and out of the BiGeO prism. Optical rotation arising from BiGeO crystal is overcome in experiment. In addition to analyzing and discussing optical bistability, the multistabilitical hysteresis curves of different shapes obtained in experiments are particularly investigated. [ABSTRACT FROM AUTHOR]

We investigate the performance of S-band amplification for Tm3+-doped fluoride fiber pumped at 787 nm with cooperative lasing at 1.8 mum through numerical analysis based on a theoretical model. The simulated results show that the signal gain at 1470 nm in a 3-m-long Tm3+-doped fluoride fiber with the pumping of 0.5-W 787-nm laser diode can be enhanced by 15.66 dB when 1.8-mum laser oscillates. [ABSTRACT FROM PUBLISHER]

The chiral photonic crystal (PC) with layered structure is investigated by using the finite-difference time-domain method. The bandgap separation for right-hand/left-hand circularly polarized light in chiral PC is demonstrated by comparing to the achiral case. The effect of layer number and the optical nonlinearity on bandgap structure is analyzed. Optical switching with the help of the change in bandgap structure is discussed. A novel scheme of an all-optical switch based on sideband improved by apodization is proposed [ABSTRACT FROM PUBLISHER]

Reports on the production of nanocrystalline composites by annealing of copper-mold cast zirconium-nickel-copper-aluminum bulk amorphous alloys. Tensile strength of the nanostructured alloys; Microstructure of the amorphous alloys; Role of medium range order domains.

Studies singlet excited-state absorption properties and optical limiting behaviors of organochromium and organomolybdenum fullerene (C[sub 60]) derivatives using a double frequency ns/ps Nd:YAG pulse laser system at wavelength of 532 nm and pulse width 21 ps. Optical limiting properties; Effect of structural moieties on photophysical properties.

Examines the nonlinear absorption in cadmium texaphyrin solution using 8 nanosecond and 23 picosecond laser pulses. Occurrence of reverse saturable absorption in the nanosecond case; Presentation of six-level model for nonlinear absorption effects; Determination of cadmium texaphyrin parameters.

An icosahedral quasicrystalline phase was found in a Hf[sub 65]Al[sub 7.5]Ni[sub 10]Cu[sub 12.5]Pd[sub 5] metallic glass annealed in the supercooled liquid region. Upon annealing at high temperature, the quasicrystalline phase was found to decompose to regular crystalline phases, indicating that it is a metastable phase. The present alloy was compared with the previously reported Zr- and Ti-based alloys with the formation of icosahedral quasicrystalline phases. Hf, Zr, and Ti belong to the same 4A column in the element periodical table. Based on the above comparison, conditions in terms of atomic radius and alloy composition which favor the formation of icosahedral quasicrystalline phase in 4A element based alloys, were suggested. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]