On the Spatial Distribution of Temporal Complexity in Resting State and Task Functional MRI

Measuring the temporal complexity of functional MRI (fMRI) time series is one approach to assess how brain activity changes over time. In fact, hemodynamic response of the brain is known to exhibit critical behaviour at the edge between order and disorder. In this study, we aimed to revisit the spatial distribution of temporal complexity in resting state and task fMRI of 100 unrelated subjects from the Human Connectome Project (HCP). First, we compared two common choices of complexity measures, i.e., Hurst exponent and multiscale entropy, and observed a high spatial similarity between them. Second, we considered four tasks in the HCP dataset (Language, Motor, Social, and Working Memory) and found high task-specific complexity, even when the task design was regressed out. For the significance thresholding of brain complexity maps, we used a statistical framework based on graph signal processing that incorporates the structural connectome to develop the null distributions of fMRI complexity. The results suggest that the frontoparietal, dorsal attention, visual, and default mode networks represent stronger complex behaviour than the rest of the brain, irrespective of the task engagement. In sum, the findings support the hypothesis of fMRI temporal complexity as a marker of cognition.     

Exploring AuRh Nanoalloys: A Computational Perspective on the Formation and Physical Properties

We studied the formation of AuRh nanoalloys (between 20–150 atoms) in the gas phase by means of Molecular Dynamics (MD) calculations, exploring three possible formation processes: one-by-one growth, coalescence, and nanodroplets annealing. As a general trend, we recover a predominance of Rh@Au core-shell ordering over other chemical configurations. We identify new structural motifs with enhanced thermal stabilities. The physical features of those selected systems were studied at the Density Functional Theory (DFT) level, revealing profound correlations between the nanoalloys morphology and properties. Surprisingly, the arrangement of the inner Rh core seems to play a dominant role on nanoclusters’ physical features like the HOMO-LUMO gap and magnetic moment. Strong charge separations are recovered within the nanoalloys suggesting the existence of charge-transfer transitions.     

Combining different theoretical perspectives for analyzing students’ difficulties in vector spaces theory

This paper originates from our doctorate research project, in which we investigated graduate and undergraduate students’ errors and difficulties in vector space theory (VST). After a brief account of the whole study, we will focus on the analyses carried out through the lenses of two different theoretical frameworks: Fischbein’s Theory of Tacit Models and Sfard’s process/object duality theory. We also propose a retrospective reflection concerning the reasons why we chose to carry out our analysis according to more than one theoretical framework and why we chose those specific theoretical frameworks as well. Hence this contribution has a double focus: on the one hand it reports on the results drawn from our study on students’ difficulties in VST; on the other hand it presents a personal retrospective reflection on the use of theoretical frames within that study.     

Diterpenes based on the dolabellane skeleton from dictyota dichotoma

From a variety of Dictyota dichotoma we have isolated, in addition to previously reported dolabellane (6-8) and perhydroazulene diterpenes (9,10), four new diterpenoids (2-5). Their structure have been elucidated by spectral analysis and chemical degradation. All the new dolabellane derivatives possess antimicrobial activity against gram-positive and gram-negative organisms.     

In situ study of the thermoresponsive behavior of micropatterned hydrogel films by imaging ellipsometry

A patterned hydrogel was immobilized on a polymer substrate by low-pressure argon plasma treatment using a masking technique. The polymer sample showed a thermoresponsive aggregation behavior in the region of 35-37 degrees C. The micropatterned, thermoresponsive hydrogel film has been characterized with imaging ellipsometry. The characterization was carried out on the dry film as well as on a swollen sample in water. The thermoresponsive behavior was studied in deionized water by temperature-dependent measurements in a solid-liquid cell. Through imaging ellipsometry, it was possible to distinguish the different regions of interest on a micrometer scale and to follow the swelling of the hydrogel part as a function of the temperature. It was possible to visualize the swelling as 3D profiles of Delta at various temperatures. Long-term changes of the sample could also be detected, which cannot be picked up by conventional ellipsometry.     

Optical parametric generation of nearly transform-limited mid-infrared pulses in dispersion-engineered nonlinear waveguides

Optical parametric generation in dispersion-engineered waveguides fabricated by proton exchange in periodically poled lithium niobate is numerically investigated as a means for producing widely tunable mid-infrared ultrashort pulses starting from low energy pump pulses at a 1.55 mum wavelength and with 100 fs duration, which are typical parameters of amplified Er-fiber oscillators. Numerical evidence is given about the generation of sub-100 fs nearly transform-limited pulses in the 2.4-4.4 mum spectral range.     

Two Polymorphs of 1-(2-Methyl-3-oxoisoindolin-5-yl)urea

Abstract  

4-Ureidophthalimide or ureido isoindolin-1-one based ligands were shown by NMR spectroscopy and theoretical studies to bind the CG base pairs in the major groove. To examine this hydrogen-bonded complex, we cocrystallized 5-fluorocytosine, 9-methylguanine and 1-(2-methyl-3-oxoisoindolin-5-yl)urea. Two polymorphs of the latter compound were obtained during the cocrystallization attempts. Both crystallized in monoclinic space groups: form Ia in P2₁/c with cell parameters of a = 11.382(2), b = 6.042(1), c = 14.102(2) ? and β = 96.51(1)°, and form Ib in P2₁/n with cell parameters of a = 7.092(1), b = 11.643(2), c = 11.580(2) ? and β = 93.48(1)°. An identical molecular conformation of the two polymorphs is observed. Both polymorphs have an R ₂²(8) N–H···O interaction linking the urea fragments of two molecules to a centrosymmetric dimer. Nevertheless, the crystal packing for both forms is completely different. In Ia, two dimers are connected by two R ₂¹(6) N–H···O bonds simultaneously to a shifted ribbon motif, whereas in Ib the two R ₂¹(6) interactions link two molecules from two different dimers.