In adult readers, letters, and words are rapidly identified within visual networks to allow for efficient reading abilities. Neuroimaging studies of orthography have mostly used words and letter strings that recruit many hierarchical levels in reading. Understanding how single letters are processed could provide further insight into orthographic processing. The present study investigated orthographic processing using single letters and pseudoletters when adults were encouraged to pay attention to or away from orthographic features. We measured evoked potentials (EPs) to single letters and pseudoletters from adults while they performed an orthographic-discrimination task (letters vs. pseudoletters), a color-discrimination task (red vs. blue), and a target-detection task (respond to #1 and #2). Larger and later peaking N1 responses (~170 ms) and larger P2 responses (~250 ms) occurred to pseudoletters as compared to letters. This reflected greater visual processing for pseudoletters. Dipole analyses localized this effect to bilateral fusiform and inferior temporal cortices. Moreover, this letter-pseudoletter difference was not modulated by task and thus indicates that directing attention to or away from orthographic features did not affect early visual processing of single letters or pseudoletters within extrastriate regions. Paying attention to orthography or color as compared to disregarding the stimuli (target-detection task) elicited selection negativities at about 175 ms, which were followed by a classical N2-P3 complex. This indicated that the tasks sufficiently drew participant's attention to and away from the stimuli. Together these findings revealed that visual processing of single letters and pseudoletters, in adults, appeared to be sensory-contingent and independent of paying attention to stimulus features (e.g., orthography or color).

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The DNA-anti-DNA antibody immune complexes were isolated from plasma of systemic lupus erythematosus (SLE) patients and DNA fragments separated from immune complexes were subjected to molecular cloning. The resulting recombinant DNA clones showed a molecular size of 37-79 base pairs, a high guanine and cytosine content, high frequencies of CpG dinucleotides, and palindromic sequences, and also clusters of G + C- and A + T-rich segments. These clones hybridized randomly to total human DNA. The reactivity of dsDNA antibodies, both monoclonal and polyclonal, from SLE was examined with a cloned SLE antigen DNA. A competitive inhibition assay showed that human monoclonal antibodies had at least one magnitude higher affinity to the cloned DNA than to the native DNA fragments. In order to characterize the factors that were recognized by antibodies, human G + C-rich and also A + T-rich 100 bp DNA fragments were cloned, and their base sequences determined. The antibody showed a higher affinity to the G + C-rich DNA fragment (71% G + C) than to the A + T-rich DNA fragment (46% G + C). When cytosines in CpG doublets in G + C-rich fragments were methylated (mCpG), the reactivity increased up to 100-fold. The native anti-DNA antibodies from SLE patients also showed preferential binding to G + C-rich fragments. These observations suggested that human anti-dsDNA antibodies may recognize some unique structures around the G + C regions or G + C clusters of DNA.

The effect of local curvature of a sample surface on capillary and interface tension adhesion forces of the water meniscus formed between the AFM tip and sample in air is demonstrated both theoretically and experimentally. We propose an analytical solution for capillary and tension adhesive force derived from approximation of the thermodynamic equilibrium of a symmetric water meniscus formed at the tip−sample contact region. It is shown that the sample local curvature strongly affects the water meniscus geometry and the adhesion force. Compared to the force computed for a flat sample surface, the theoretical model predicts a larger/smaller adhesive force for a concave/convex local curvature. Our theoretical predictions were confirmed by experiment. Atomic force spectroscopy measurements were performed for a silicon nitride cantilever and a standard sample of platinum-covered quartz patterned with 1.5 × 1.5 μm square, 20 nm deep pits. Maps of sample surface topography and adhesive force showed a much larger force at the bottom of the pit edge, where the local curvature was concave. This was contrasted with a much smaller force observed at the top of the pit edge, where the local curvature was convex.