On applicability of PCA,voxel-wise variance normalization and dimensionality assumptions for sliding temporal window sICA in resting-state fMRI

Subject-level resting-state fMRI (RS-fMRI) spatial independent component analysis (sICA) may provide new ways to analyze the data when performed in the sliding time window. However, whether principal component analysis (PCA) and voxel-wise variance normalization (VN) are applicable pre-processing procedures in the sliding-window context, as they are for regular sICA, has not been addressed so far. Also model order selection requires further studies concerning sliding-window sICA. In this paper we have addressed these concerns. First, we compared PCA-retained subspaces concerning overlapping parts of consecutive temporal windows to answer whether in-window PCA and VN can confound comparisons between sICA analyses in consecutive windows. Second, we compared the PCA subspaces between windowed and full data to assess expected comparability between windowed and full-data sICA results. Third, temporal evolution of dimensionality estimates in RS-fMRI data sets was monitored to identify potential challenges in model order selection in a sliding-window sICA context. Our results illustrate that in-window VN can be safely used, in-window PCA is applicable with most window widths and that comparisons between windowed and full data should not be performed from a subspace similarity point of view. In addition, our studies on dimensionality estimates demonstrated that there are sustained, periodic and very case-specific changes in signal-to-noise ratio within RS-fMRI data sets. Consequently, dimensionality estimation is needed for well-founded model order determination in the sliding-window case. The observed periodic changes correspond to a frequency band of ≤ 0.1 Hz, which is commonly associated with brain activity in RS-fMRI and become on average most pronounced at window widths of 80 and 60 time points (144 and 108 s, respectively). Wider windows provided only slightly better comparability between consecutive windows, and 60 time point or shorter windows also provided the best comparability with full-data results. Further studies are needed to determine the cause for dimensionality variations.     

Flexible active matrix addressed displays manufactured by printing and coating techniques

A flexible electrochromic active matrix addressed display, including 8 × 8 pixels, is demonstrated by using solution processing based on standard printing and coating manufacturing techniques. Each organic electrochromic display (OECD) pixel and its corresponding organic electrochemical transistor (OECT) are located on different sides of the flexible PET substrate. Electronic vias generated through the plastic substrate connects each OECD pixel with one addressing OECT. When comparing this display with actively addressed OECDs with all its components located on the same side, the present approach based on this electronic via substrate provides an enhanced pixel resolution and a relatively more simplified manufacturing process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Renormalization of Cellular Automata and Self-Similarity

We study self-similarity in one-dimensional probabilistic cellular automata (PCA) using the renormalization technique. We introduce a general framework for algebraic construction of renormalization groups (RG) on cellular automata and apply it to exhaustively search the rule space for automata displaying dynamic criticality.     

Weak coupling of a Reynolds model and a Stokes model for hydrodynamic lubrication

The Reynolds model is a reduced Stokes model, valid for narrow lubrication regions. In order to be able to handle locally non‐narrow regions such as pits or grooves, often displaying rapid geometrical variations, there is a need to be able to transit to the more accurate Stokes model. A fundamental problem is how to couple the two models in a numerical simulation, preferably allowing for different meshes in the different domains. In this paper, we present a weak coupling method for Reynolds and Stokes models for lubrication computations, including the possibility of cavitation in the different regions. The paper concludes with a numerical example. Copyright © 2010 John Wiley & Sons, Ltd.     

Enantioselective Syntheses of the Methylene- and Fluoromethylene-Phosphonate Analogues of 3-Phospho-D-Glyceric Acid

Abstract

The racemic methylene analogue of 3-phospho-D-glyceric acid^1–4 has been shown to be a viable substrate for the combined action of 3-phosphoglycerate kinase, PGK, and glyceraldehyde 3-phosphate dehydrogenase, GPD. We have shown that replacement of CH₂ by CHF or CF₂ in a variety of nucleotide analogues^4,5 can lead to improved Performance as enzyme substrates or inhibitors. We have therefore undertaken enantiospecific syntheses of the methylene- and fluoro-methylene-analogues of 3-phospho-D-glyceric acid to investigate their interaction with PGK and GPD and explore whether the fluorine atom in the latter can mimic an oxygen lone-pair in binding to enzymes.     

Fiber crystal growth from the melt for non-linear optical applications

During several years, we have been involved in the growth and characterization of non-linear optical crystals by the two most common techniques for growing single-crystal fibers from the melt: laser-heated pedestal growth and micro-pulling down. Their specific features are presented in this study and their versatility is demonstrated through two typical examples of incongruently melting materials: K₃Li_2?xNb_5+xO_15+2x (solid solution of the ternary system K₂O–Li₂O–Nb₂O₅) and Ca₅(BO₃)₃F which can only be grown from a flux.     

Synthesis of Non-glucosamino Glucan Oligosaccharides Related to Heparin and Heparan Sulphate

Abstract

A series of three oligosaccharides, α-d-Glc-(1→4)-β-d-GlcA-1ωe, β-d-GlcA-(1→4)-α-d-Glc-(1→4)-β-d-GlcA-lωe and α-d-Glc-(1→4)-β-d-GlcA-(1→4)-α-d-Glc-(1→4)-β-d-GlcA-1ωe was prepared by a short synthetic route, using maltose and glucuronic acid derivatives as starting materials. The oligosaccharides contain glucose residues instead of glucosamines, and have a less complicated structure than the corresponding unsulphated structures found in native heparin and heparan sulphate. This simplification in structure has diminished the number of synthetic steps and raised the total yield compared to the preparation of the corresponding heparin/heparan sulphate structures which have been found to bind acidic and basic FGF.     

Synthesis of the Methyl, 1-Octyl,and D-Trifluoro-Acetamidophentlethyl α-Glycosides of 3,6-Di-O-(α-D-Galactopyranosyl)-D-Glucopyranose and an Acyclic Analogue Thereof

Abstract

The title trisaccharides were synthesized from a common trisaccharide thioglycoside derivative, which was, in turn, prepared from monosaccharide thioglycoside precursors. An acyclic analogue, methyl 3-O-(α-D-galacto-pyranosyl)-6-O-[(2′-hydroxyethyl)oxymethyl]-α-D-glucopyranoside, which carries a 2′-hydroxyethyloxymethyl group in place of the 6-O-galactosyl residue, was also synthesized.