Abnormal integrity of association fiber tracts in amnestic mild cognitive impairment.

The association fiber tracts integrity of the inter-hemispheric and within-hemispheric communication was poor understood in amnestic type mild cognitive impairment (aMCI) patients by diffusion tensor imaging (DTI). A region of interest-based DTI approach was applied to explore fiber tract differences between 22 aMCI patients and 22 well-matched normal aging. Correlations were also sought between fractional anisotropy (FA) values and the cognitive performance scores in the aMCI patients. Extensive impairment of association fiber tracts integrity was observed in aMCI patients, including bilateral inferior fronto-occipital fascicles, the genu of corpus callosum, bilateral cingulate bundles and bilateral superior longitudinal fascicles II (SLE II) subcomponent. In addition, the FA value of right SLE II was significantly negatively correlated to the performance of Trail Making Test A and B, whilst the values of right posterior cingulate bundle was significantly positive correlation with MMSE score. As aMCI is a putative prodromal syndrome to Alzheimer's disease (AD), this study suggested that investigation of association fiber tracts between remote cortexes may yield important new data to predict whether a patient will eventually develop AD.

Multivariate Statistical Analysis Applied to an IL6 Signal Transduction Model in Hepatocytes

This paper introduces the application of linear multivariate statistical techniques, including partial least squares (PLS), canonical correlation analysis (CCA) and reduced rank regression (RRR), into the area of Systems Biology. This new approach aims to extract the important proteins embedded in complex signal transduction pathway models.The analysis is performed on a model of intracellular signalling along the janus-associated kinases/signal transducers and transcription factors (JAK/STAT) and mitogen activated protein kinases (MAPK) signal transduction pathways in interleukin-6 (IL6) stimulated hepatocytes, which produce signal transducer and activator of transcription factor 3 (STAT3).A region of redundancy within the MAPK pathway that does not affect the STAT3 transcription was identified using CCA. This is the core finding of this analysis and cannot be obtained by inspecting the model by eye. In addition, RRR was found to isolate terms that do not significantly contribute to changes in protein concentrations, while the application of PLS does not provide such a detailed picture by virtue of its construction.This analysis has a similar objective to conventional model reduction techniques with the advantage of maintaining the meaning of the states prior to and after the reduction process. A significant model reduction is performed, with a marginal loss in accuracy, offering a more concise model while maintaining the main influencing factors on the STAT3 transcription.The findings offer a deeper understanding of the reaction terms involved, confirm the relevance of several proteins to the production of Acute Phase Proteins and complement existing findings regarding cross-talk between the two signalling pathways.

Characterisation of microwave phase conjugate signal generation using nonlinearly loaded wire frequency selective surface (FSS)

Both experimental and theoretical information regarding the scattering and phase conjugate mixing properties of a 2D double-periodic array of wires loaded with nonlinear/linear lumped elements have been provided. An experimental means for assessing the phase conjugate energy production capability for the array is given. These investigations enable identification of the fundamental operational characteristics and underlying mechanisms associated with the production of phase conjugate energy by this type of artificial electromagnetic media. Means for enhancing the phase conjugate energy production capability of the structure by using additional linear lumped loads is examined theoretically and limits on the production of phase conjugate energy established. Theoretical far-field prediction of the behaviour of the structure indicates that retro-directive reflector action as well as negative refraction should be possible.

Physical modelling of millimetre wave signal reflection from forward biased PIN diodes

This paper examines the DC power requirements of PIN diodes which, with suitable applied DC bias, have the potential to reflect or to permit transmission of millimetre wave energy through them by the process of inducing a semiconductor plasma layer in the i-region. The study is conducted using device level simulation of SOI and bulk PIN diodes and reflection modelling based on the Drude conduction model. We examined five diode lengths (60–140 µm) and seven diode thicknesses (4–100 µm). Simulation output for the diodes of varying thicknesses was subsequently used in reflection modelling to assess their performance for 100 GHz operation. It is shown that substantially high DC input power is required in order to induce near total reflection in SOI PIN diodes at 100 GHz. Thinner devices consume less DC power, but reflect less incident radiation for given input power. SOI diodes are shown to have improved carrier confinement compared with bulk diodes.

Signal residuals and hermit crab displays: flaunt it if you have it!

In animal contests selection should favour information gathering regarding the likely costs and benefits of continued conflict, and displays may provide a means for contestants to gain information about the fighting ability or aggressive intent of competitors. However, there is debate over the reliability of such displays and low levels of deception may occur within otherwise honest signalling systems. Hermit crabs use displays involving the chelipeds during agonistic encounters. We examined how variation in chelae size in relation to body size, a determinant of fighting ability, affects their use in displays and the process and outcome of contests over gastropod shells. In accordance with deceptive use of an otherwise honest signal, we found that contestants with large chelipeds for their body size spent more time performing the cheliped presentation display. Moreover, cheliped residuals and displays influenced the escalation level of encounters. There was a positive association between cheliped displays and the occurrence of 'grappling', but a negative association between displays and the occurrence of shell fights, suggesting that displays may signal aggressive intent and a reluctance to back off or accept the more passive defender role in a fight. Furthermore, the smaller of the two contestants in shell fights had larger cheliped residuals compared to those smaller contestants not involved in shell fights, which is consistent with disrupted opponent assessment. This study adds to mounting evidence that when acting as a signaller, individuals for whom the display exaggerates competitive ability attempt to manipulate opponents, using the display more often. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.