Self-assembly and induced circular dichroism in dendritic supramolecules with cholesteric pendant groups.

We report on the solid-state structural features of self-assembled chiral supramolecules based on ionic complexation of chiral cholesteric pendant groups with achiral dendritic macromolecules and show that their optical activity exhibits a systematic change in the ultraviolet/visible light (UV-vis) absorption and enhancement in the circular dichroism (CD) signal, indicating the occurrence of supramolecular chirality, also referred to as induced circular dichroism (ICD). We construct a homologous series of complexes by varying systematically from 1 to 3 the generation of dendritic units contained in dendrons, dendrimers, and dendronized polymers. The structural properties of the complexes are investigated by means of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM).

What differs in visual recognition of handwritten vs. printed letters? An fMRI study.

In models of letter recognition, handwritten letters are considered as a particular font exemplar, not qualitatively different in their processing from printed letters. Yet, some data suggest that recognizing handwritten letters might rely on distinct processes, possibly related to motor knowledge. We applied functional magnetic resonance imaging to compare the neural correlates of perceiving handwritten letters vs.

Temporal integration of vowel periodicity in the auditory cortex.

Cortical sensitivity to the periodicity of speech sounds has been evidenced by larger, more anterior responses to periodic than to aperiodic vowels in several non-invasive studies of the human brain. The current study investigated the temporal integration underlying the cortical sensitivity to speech periodicity by studying the increase in periodicity-specific cortical activation with growing stimulus duration. Periodicity-specific activation was estimated from magnetoencephalography as the differences between the N1m responses elicited by periodic and aperiodic vowel stimuli.

Observing touch activates human primary somatosensory cortex.

We used magnetoencephalography to show that the human primary somatosensory (SI) cortex is activated by mere observation of touch. Somatosensory evoked fields were measured from adult human subjects in two conditions. First, the experimenter touched the subject's right hand with her index finger (Experienced touch).

Multivariate multi-way analysis of multi-source data.

Motivation: Analysis of variance (ANOVA)-type methods are the default tool for the analysis of data with multiple covariates. These tools have been generalized to the multivariate analysis of high-throughput biological datasets, where the main challenge is the problem of small sample size and high dimensionality. However, the existing multi-way analysis methods are not designed for the currently increasingly important experiments where data is obtained from multiple sources.

Tunability of the optical absorption in small silver cluster-polymer hybrid systems.

We have calculated the absorption characteristics of different hybrid systems consisting of Ag, Ag(2), or Ag(3) atomic clusters and poly(methacrylic acid) using the time-dependent density-functional theory. The polymer is found to have an extensive structural-dependency on the spectral patterns of the hybrid systems relative to the bare clusters. The absorption spectrum can be "tuned" to the visible range for hybrid systems with an odd number of electrons per silver cluster, whereas for hybrid systems comprising an even number of electrons per silver cluster, the leading absorption edge can be shifted up to approximately 4.

Conversion of carbonyl compounds to alkynes: general overview and recent developments.

The preparation of alkynes from carbonyl compounds via a one-carbon homologation has become a very useful pathway for the synthesis of acetylenic compounds, both internal and terminal. This tutorial review provides an overview of the different methods available for this transformation, including their scope and limitations, recent developments and applications in total syntheses.

Semantic categorization precedes affective evaluation of visual scenes.

We compared the primacy of affective versus semantic categorization by using forced-choice saccadic and manual response tasks. Participants viewed paired emotional and neutral scenes involving humans or animals flashed rapidly in extrafoveal vision. Participants were instructed to categorize the targets by saccading toward the location occupied by a predefined target scene.

The relationship between peripheral and early cortical activation induced by transcranial magnetic stimulation.

The purpose of this study was to assess the relationship between peripheral muscle responses (motor evoked potentials, MEP) evoked by transcranial magnetic stimulation (TMS) and the early components of the TMS-evoked EEG response, both of which reflect cortical excitability. Left primary motor cortex of five healthy volunteers was stimulated with 100% of the motor threshold. The relationship between MEP amplitudes and the peak-to-peak amplitudes of the N15-P30 complex of the evoked EEG signal was determined at the single-trial level.

Local non-linear interactions in the visual cortex may reflect global decorrelation.

The classical receptive field in the primary visual cortex have been successfully explained by sparse activation of relatively independent units, whose tuning properties reflect the statistical dependencies in the natural environment. Robust surround modulation, emerging from stimulation beyond the classical receptive field, has been associated with increase of lifetime sparseness in the V1, but the system-wide modulation of response strength have currently no theoretical explanation. We measured fMRI responses from human visual cortex and quantified the contextual modulation with a decorrelation coefficient (d), derived from a subtractive normalization model.

Conformational ensembles of flexible beta-turn mimetics in DMSO-d6.

Beta-turns play an important role in peptide and protein chemistry, biophysics, and bioinformatics. The aim of this research was to study short linear peptides that have a high propensity to form beta-turn structures in solution. In particular, we examined conformational ensembles of beta-turn forming peptides with a general sequence CBz-L-Ala-L-Xaa-Gly-L-Ala-OtBu.

The brain in time: insights from neuromagnetic recordings.

The millisecond time resolution of magnetoencephalography (MEG) is instrumental for investigating the brain basis of sensory processing, motor planning, cognition, and social interaction. We review the basic principles, recent progress, and future potential of MEG in noninvasive tracking of human brain activity. Cortical activation sequences from tens to hundreds of milliseconds can be followed during, e.

Model-based method for transcription factor target identification with limited data.

We present a computational method for identifying potential targets of a transcription factor (TF) using wild-type gene expression time series data. For each putative target gene we fit a simple differential equation model of transcriptional regulation, and the model likelihood serves as a score to rank targets. The expression profile of the TF is modeled as a sample from a Gaussian process prior distribution that is integrated out using a nonparametric Bayesian procedure.

Linear and nonlinear projective nonnegative matrix factorization.

A variant of nonnegative matrix factorization (NMF) which was proposed earlier is analyzed here. It is called projective nonnegative matrix factorization (PNMF). The new method approximately factorizes a projection matrix, minimizing the reconstruction error, into a positive low-rank matrix and its transpose.

Aberrant temporal and spatial brain activity during rest in patients with chronic pain.

In the absence of external stimuli, human hemodynamic brain activity displays slow intrinsic variations. To find out whether such fluctuations would be altered by persistent pain, we asked 10 patients with unrelenting chronic pain of different etiologies and 10 sex- and age-matched control subjects to rest with eyes open during 3-T functional MRI. Independent component analysis was used to identify functionally coupled brain networks.

Gaze-Direction-Based MEG Averaging During Audiovisual Speech Perception.

To take a step towards real-life-like experimental setups, we simultaneously recorded magnetoencephalographic (MEG) signals and subject's gaze direction during audiovisual speech perception. The stimuli were utterances of /apa/ dubbed onto two side-by-side female faces articulating /apa/ (congruent) and /aka/ (incongruent) in synchrony, repeated once every 3 s. Subjects (N = 10) were free to decide which face they viewed, and responses were averaged to two categories according to the gaze direction.

Sensitivity of the human auditory cortex to acoustic degradation of speech and non-speech sounds.

Background: Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform.

Short and straightforward synthesis of (-)-1-deoxygalactonojirimycin.

The mildness and low basicity of vinylzinc species functioning as a nucleophile in addition to alpha-chiral aldehydes is characterized by lack of epimerization of the vulnerable stereogenic center. This is demonstrated by a highly diastereoselective synthesis of 1-deoxygalactonojirimycin in eight steps from commercial starting materials with overall yield of 35%.