Evolution of Seismic Site Classification According to the Criteria in Chilean Design Codes

Design codes establish seismic site classifications to determine the seismic demand of a structure according to the response of the soil foundation under the action of earthquake ground motions; the site classification can even condition the feasibility of a project. The occurrence of great earthquakes in Chile has tested its design codes, generating much information and experience regarding the seismic design of structures that have allowed researchers to identify variations in seismic demands according to the kind of ground foundation and to propose seismic site classification methods in Chilean regulations since the 1930s; countries in the vanguard of seismic design, such as the USA, Japan, and New Zealand, proposed methods even earlier. In this document, the evolution of methodologies for seismic site classification according to the criteria in Chilean codes is analysed from their implementation in the 1930s to the most recently proposed design code NCh 433, 2018–2021. Although the distinctive features of each country shape the criteria in their design codes, clear knowledge of the evolution of established criteria from their origins is considered an important tool that contributes to the better understanding, interpretation and application of the seismic site classification methodologies contained in a design code with better criteria. Likewise, the review indicates a distinct need to conduct a continuous evaluation of the classification criteria supported by records of new earthquakes, as well as by physical and numerical models that allow incorporating variables which condition the response of the terrain such as topography, lateral heterogeneities, and basic effects.

Nanoscale Sub-Compartmentalization of the Dendritic Spine Compartment

Compartmentalization of the membrane is essential for cells to perform highly specific tasks and spatially constrained biochemical functions in topographically defined areas. These membrane lateral heterogeneities range from nanoscopic dimensions, often involving only a few molecular constituents, to micron-sized mesoscopic domains resulting from the coalescence of nanodomains. Short-lived domains lasting for a few milliseconds coexist with more stable platforms lasting from minutes to days. This panoply of lateral domains subserves the great variety of demands of cell physiology, particularly high for those implicated in signaling. The dendritic spine, a subcellular structure of neurons at the receiving (postsynaptic) end of central nervous system excitatory synapses, exploits this compartmentalization principle. In its most frequent adult morphology, the mushroom-shaped spine harbors neurotransmitter receptors, enzymes, and scaffolding proteins tightly packed in a volume of a few femtoliters. In addition to constituting a mesoscopic lateral heterogeneity of the dendritic arborization, the dendritic spine postsynaptic membrane is further compartmentalized into spatially delimited nanodomains that execute separate functions in the synapse. This review discusses the functional relevance of compartmentalization and nanodomain organization in synaptic transmission and plasticity and exemplifies the importance of this parcelization in various neurotransmitter signaling systems operating at dendritic spines, using two fast ligand-gated ionotropic receptors, the nicotinic acetylcholine receptor and the glutamatergic receptor, and a second-messenger G-protein coupled receptor, the cannabinoid receptor, as paradigmatic examples.

MODERN ALGORITHMS AND SOFTWARE FOR INTERPRETATION OF RESISTIVITY LOGGING DATA

The electrodynamics of geological media investigates the interrelations of resistivity logging signals and properties of fluid-containing rocks and creates innovative well logging technologies. Its development is inextricably linked with modern techniques for mathematical modeling and quantitative interpretation of high-precision data. In order to increase the information content of galvanic and electromagnetic logging, we have developed algorithms and software for numerical simulation and inversion of field data. In our study of the Cretaceous and Jurassic deposits of West Siberia, a quantitative interpretation of high-frequency electromagnetic and lateral logging signals was carried out. To create geoelectric models, we interpreted the field resistivity logging data by an unconventional quantitative technique based on their joint numerical inversion and estimations of the vertical resistivity of permeable deposits. Another line of our research was aimed at a scientific substantiation of a new technology for mapping and spatial tracking of lateral heterogeneities and oil-promising zones in the Bazhenov Formation. The aim was achieved by using the TEM sounding data on a spatially distributed system of directional and horizontal wells.

Enthalpic and Entropic Contributions to Interleaflet Coupling Drive Domain Registration and Anti-registration in Biological Membrane

Biological membrane is a complex self-assembly of lipids, sterols and proteins organized as a fluid bilayer of two closely stacked lipid leaflets. Differential molecular interactions among its diverse constituents give rise to heterogeneities in the membrane lateral organization. Under certain conditions, heterogeneities in the two leaflets can be spatially synchronised and exist as registered domains across the bilayer. Several contrasting theories behind mechanisms that induce registration of nanoscale domains have been suggested[1–3]. Following a recent study[4] showing the effect of position of lipid tail unsaturation on domain registration behavior, we decided to develop an analytical theory to elucidate the driving forces that create and maintain domain registry across leaflets. Towards this, we formulated a Hamiltonian for a stacked lattice system where site variables encapsulate the lipid molecular properties including the position of unsaturation and various other interactions that could drive phase separation and interleaflet coupling. We solve the Hamiltonian using Monte Carlo simulations and create a complete phase diagram that reports the presence or absence of registered domains as a function of various Hamiltonian parameters. We find that the interleaflet coupling should be described as a competing enthalpic contribution due to interaction of lipid tail termini, primarily due to saturated-saturated interactions, and an interleaflet entropic contribution from overlap of unsaturated tail termini. We find that higher position of unsaturation provides weaker interleaflet coupling. We also find points in our parameter space that allow thermodynamically stable nanodomains in our bilayer model, which we have verified by carrying out extended Monte Carlo simulations. These persistent non-coalescing registered nanodomains close to the lower end of the accepted nanodomain size range also point towards a possible “nanoscale” emulsion description of lateral heterogeneities in biological membrane leaflets.

Imaging azimuthal anisotropy in the alpine crust from ambient noise beamforming.

<p>Noise cross-correlations provide a good azimuthal coverage, limited only by the distribution of noise sources and the layout of the stations used. It is therefore a promising method to constrain azimuthal anisotropy. As noise cross-correlations consist mainly of surface waves, they are especially sensitive to the crust and provide good depth constraints, as opposed to SKS-splitting data that are more sensitive to the upper mantle. We use the AlpArray network as well as stations from permanent networks all across Europe to perform time-domain beamforming on noise cross-correlations. The extent and density of the AlpArray network allows us to obtain reliable measurements all across the Alps. We divide the area in smaller zones using all stations outside the zone as sources and all stations inside as a sub-array for beamforming. This allows us to estimate the quality of our measurements in a region where strong lateral heterogeneities make measurements challenging, by estimating the magnitude of bias due to heterogeneities using the cos(theta) amplitude and evaluating uncertainties with bootstrap. This way, we measure Rayleigh wave azimuthal anisotropy in several period bands between 15 s and 60 s period. Inversion of dispersion curves in specific areas allows us to constrain the depth of the observed anisotropy. The results are broadly similar to results from SKS-splitting as they are generally parallel to the mountain belt. However, we observe lower anisotropy at short periods (40 seconds and less) in the Alps themselves than in surrounding regions. We also observe several structures in the crust that are not observed with SKS-splitting data. The most striking is a strong and spatially coherent NE-oriented anisotropy to the NW of the Alps that is possibly related to Variscan inheritance (at 40 seconds and less, in the upper and lower crust).  In the Northern Apennines, we observe anisotropy perpendicular to the belt at 30 s period (middle crust) that correlates well with an area of strong radial anisotropy recently observed by Alder et al (in review) at 30 km depth. </p>

Understanding the Functional Properties of Lipid Heterogeneity in Pulmonary Surfactant Monolayers at the Atomistic Level

Pulmonary surfactant is a complex mixture of lipids and proteins lining the interior of the alveoli, and constitutes the first barrier to both oxygen and pathogens as they progress toward blood circulation. Despite decades of study, the behavior of the pulmonary surfactant is poorly understood on the molecular scale, which hinders the development of effective surfactant replacement therapies, useful in the treatment of several lung-related diseases. In this work, we combined all-atom molecular dynamics simulations, Langmuir trough measurements, and AFM imaging to study synthetic four-component lipid monolayers designed to model protein-free pulmonary surfactant. We characterized the structural and dynamic properties of the monolayers with a special focus on lateral heterogeneity. Remarkably, simulations reproduce almost quantitatively the experimental data on pressure–area isotherms and the presence of lateral heterogeneities highlighted by AFM. Quite surprisingly, the pressure–area isotherms do not show a plateau region, despite the presence of liquid-condensed nanometer–sized domains at surface pressures larger than 20 mN/m. In the simulations, the domains were small and transient, but they did not coalesce to yield a separate phase. The liquid–condensed domains were only slightly enriched in DPPC and cholesterol, and their chemical composition remained very similar to the overall composition of the monolayer membrane. Instead, they differed from liquid-expanded regions in terms of membrane thickness (in agreement with AFM data), diffusion rates, acyl chain packing, and orientation. We hypothesize that such lateral heterogeneities are crucial for lung surfactant function, as they allow both efficient packing, to achieve low surface tension, and sufficient fluidity, critical for rapid adsorption to the air–liquid interface during the breathing cycle.