Effect of Chain Stiffness on the Structure of Single-Chain Polymer Nanoparticles

Polymeric single-chain nanoparticles (SCNPs) are soft nano-objects synthesized by purely intramolecular cross-linking of single polymer chains. By means of computer simulations, we investigate the conformational properties of SCNPs as a function of the bending stiffness of their linear polymer precursors. We investigate a broad range of characteristic ratios from the fully flexible case to those typical of bulky synthetic polymers. Increasing stiffness hinders bonding of groups separated by short contour distances and increases looping over longer distances, leading to more compact nanoparticles with a structure of highly interconnected loops. This feature is reflected in a crossover in the scaling behaviour of several structural observables. The scaling exponents change from those characteristic for Gaussian chains or rings in $\theta$-solvents in the fully flexible limit, to values resembling fractal or `crumpled' globular behaviour for very stiff SCNPs. We characterize domains in the SCNPs. These are weakly deformable regions that can be seen as disordered analogues of domains in disordered proteins. Increasing stiffness leads to bigger and less deformable domains. Surprisingly, the scaling behaviour of the domains is in all cases similar to that of Gaussian chains or rings, irrespective of the stiffness and degree of cross-linking. It is the spatial arrangement of the domains which determines the global structure of the SCNP (sparse Gaussian-like object or crumpled globule). Since intramolecular stiffness can be varied through the specific chemistry of the precursor or by introducing bulky side groups in its backbone, our results propose a new strategy to tune the global structure of SCNPs.Comment: 20 pages, 17 figure

Paleoseismology of active faults based on multiscale seismic imaging

The study of active structures offshore requires very-high resolution seismic imaging in order to observe the most recent layers below sea floor. In the other hand, high penetration methods are necessary to observe deeper reflections for understanding the evolution of the structure throughout the time. The aim of our study is to establish the seismic potential of the offshore segment of the Carboneras Fault, Eastern Betics, based on multiscale seismic imaging. Three different scale methods have been acquired and are compared here: very-high-resolution sub-bottom profiler TOPAS, very-high-resolution single-channel seismic (Sparker) and high-resolution multi-channel seismic. From seismic profiles, faulted Quaternary layers suggest that the Carboneras Fault is active. Sediment coring and dating analysis are used to consider ages for key reflectors observed in TOPAS profiles, and a change in the vertical slip-rate through the Quaternary is inferred.Peer Reviewe

Simulation guided design of globular single-chain nanoparticles by tuning the solvent quality

The control of primary and further structures of individual folded/collapsed synthetic polymers has received significant attention in recent years. However, the synthesis of single-chain nanoparticles (SCNPs) showing a compact, globular conformation in solution has turned out so far to be highly elusive. By means of simulations, we propose two methods for obtaining globular SCNPs in solution. The first synthesis route is performed in the bad solvent, with the precursor anchored to a surface. In the second route we use a random copolymer precursor with unreactive solvophilic and reactive solvophobic units, which form a single core-shell structure. Both protocols prevent intermolecular cross-linking. After recovering good solvent conditions, the swollen nanoparticles maintain their globular character. The proposed methods are experimentally realizable and do not require specific sequence control of the precursors. Our results pave the way for the synthesis via solvent-assisted design of a new generation of globular soft nanoparticles mimicking global conformations of native proteins in solution.We acknowledge financial support from the Projects MAT2012-31088 (MINECO) and T-654-13 (GV).Peer Reviewe

Statistical analysis of the long-term influence of covid-19 on waste generation - a case study of Castellón in Spain

[EN] Existing research recognizes the COVID-19 impact on waste generation. However, the preliminary studies were made at an early pandemic stage, focused on the household waste fraction, and employed descriptive statistics that lacked statistical support. This study tries to fill this gap by providing a reliable statistical analysis setting inferential confidence in the waste generation differences found in Castellón. Repeated measures ANOVA were carried out for all the waste fractions collected and recorded in the city landfill database from 2017 to 2020. Additionally, Bonferroni¿s multiple comparison test (p < 0.05) was used to assure confidence level correction and identify which pairs of years¿ differences appeared. The longitudinal study identified trends for each waste fraction before the pandemic and showed how they changed with the advent of the crisis. Compared to 2019, waste collection in 2020 significantly grew for glass and packaging; remained unchanged for beaches, paper and cardboard, and dropped substantially for households, streets, markets, bulky waste, hospitals, and recycling centres. Total waste showed no differences between 2017 and 2019 but dropped significantly in 2020. These findings may help us better understand the long-term implications of COVID-19 and improve municipal solid waste management in a similar crisis.Artacho Ramírez, MÁ.; Moreno-Solaz, H.; Lo-Iacono-Ferreira, VG.; Cloquell Ballester, VA. (2022). Statistical analysis of the long-term influence of covid-19 on waste generation - a case study of Castellón in Spain. International Journal of Environmental research and Public Health (Online). 19(10):1-17. https://doi.org/10.3390/ijerph19106071117191

Circuit-specific dendritic development in the piriform cortex

Dendritic geometry is largely determined during postnatal development and has a substantial impact on neural function. In sensory processing, postnatal development of the dendritic tree is affected by two dominant circuit motifs, ascending sensory feedforward inputs and descending and local recurrent connections. Two subtypes of layer 2 neurons in the three-layered anterior piriform cortex, layer 2a and layer 2b neurons, display a clear vertical segregation of these two circuit motifs. Here, we combined electrophysiology, detailed morphometry and Ca(2+) imaging-both of neuronal networks as well as of subcellular structures-in acute mouse brain slices and modeling. This allowed us to compare the functional implications of distinct circuit-specific postnatal dendritic growth patterns in these two neuronal subtypes. We observed that determination of branching complexity, dendritic length increases and pruning occurred in distinct growth phases. Layer 2a and layer 2b neurons displayed growth phase specific developmental differences between their apical and basal dendritic trees. This was reflected by compartment-specific differences in Ca(2+) signaling. The morphological and functional developmental pattern differences between layer 2a and layer 2b neurons dendrites provide further evidence that they constitute two functionally distinct streams of olfactory information processing

Advantages of orthogonal folding of single polymer chains to soft nanoparticles

We investigate, by means of computer simulations, the formation of soft nanoparticles by irreversible intramolecular cross-linking of homofunctional polymer precursors in good solvent. Simulations reveal that the early and intermediate stages of the cross-linking process are dominated by bonding at short contour distances. Because of the initial self-avoiding character of the precursor, bonding at long contour distances, which is the efficient mechanism for global compactation, is a rare event that essentially occurs in the late stage of cross-linking. Thus, irreversible cross-linking of precursors with identical molecular weight and linker fraction produces both compact and sparse objects. This is confirmed by a detailed analysis of the size and shape distribution of the fully cross-linked nanoparticles. We also investigate intramolecular cross-linking of heterofunctional polymers with two species of orthogonal linkers, bonding between distinct species being forbidden. It is found that simultaneous cross-linking of both species and sequential cross-linking (activation of one species after full cross-linking of the other) lead to the same structural properties for the resulting nanoparticles. The heterofunctional nanoparticles are on average smaller and more spherical than the homofunctional counterparts, though still a significant fraction of sparse objects is found. The simulation results are compared with results from SEC/MALLS and SAXS experiments in real polymeric nanoparticles. © 2013 American Chemical Society.We acknowledge financial support from Projects No. MAT2012-31088 (Spanish Government) and No. IT654-13 (Basque Government). A.S.-S. expresses thanks for the Ph.D. grant support of the Basque Government (Spain).Peer Reviewe

Effect of Quark Scatter on Baryogenesis by Electroweak Strings

The amount of baryon asymmetry generated by the electroweak strings at a rough estimate is smaller than that generated by the bubble expansion since the collapsing strings cannot cover the whole volume of the universe. However, the interaction cross section of the strings with particles can be larger than the geometrical area of the order of the string thickness. The scattering cross section of quarks from the electroweak strings is calculated using Dirac equation in the string background. It it proportional to the reverse of the momentum perpendicular to the string axis. Thus the effective interaction area can be enhanced at least ten times so that the suppression compared to the first order phase transition scenario might be also improved.Comment: 12 pages (LaTeX), no figure, Astroparticle Physics (1996