There is growing concern regarding the widespread use of antibiotics and their presence in the aqueous environment. Their removal in the water column is mediated by different types of degradation ...processes for which the mechanisms are still unclear. This research is focused on characterizing the photodegradation kinetics and pathways of two largely employed antibiotics families: sulfonamides (9 SDs) and fluoroquinolones (6 FQs). Degradation percentages and rates were measured in pure water exposed to simulated natural sunlight at a constant irradiance value (500 W m–2) during all the experiments, and the main photoproducts formed were characterized through accurate mass measurement using ultraperformance liquid chromatography–quadrupole-time-of-flight–mass spectrometry (UPLC-QToF-MS). Over 200 different phototransformation products were identified for SDs and FQs, 66% of them, to the best of our knowledge, have not been described before. Their sequential formation and disappearance over the course of the experiments reveals the existence of several pathways for the degradation of target antibiotics. Occurrence of new photoproducts derived from desulfonation and/or denitrification, as well as hydroxylation of photo-oxidized heterocyclic rings, have been identified during photodegradation of SDs, whereas a new pathway yielding oxidation of the benzene ring after the cleavage of the piperazine ring (e.g., CIP product with m/z 280) is described for FQs.
The study of visual illusions has proven to be a very useful approach in vision science. In this work we start by showing that, while convolutional neural networks (CNNs) trained for low-level visual ...tasks in natural images may be deceived by brightness and color illusions, some network illusions can be inconsistent with the perception of humans. Next, we analyze where these similarities and differences may come from. On one hand, the proposed linear eigenanalysis explains the overall similarities: in simple CNNs trained for tasks like denoising or deblurring, the linear version of the network has center-surround receptive fields, and global transfer functions are very similar to the human achromatic and chromatic contrast sensitivity functions in human-like opponent color spaces. These similarities are consistent with the long-standing hypothesis that considers low-level visual illusions as a by-product of the optimization to natural environments. Specifically, here human-like features emerge from error minimization. On the other hand, the observed differences must be due to the behavior of the human visual system not explained by the linear approximation. However, our study also shows that more ‘flexible’ network architectures, with more layers and a higher degree of nonlinearity, may actually have a worse capability of reproducing visual illusions. This implies, in line with other works in the vision science literature, a word of caution on using CNNs to study human vision: on top of the intrinsic limitations of the L + NL formulation of artificial networks to model vision, the nonlinear behavior of flexible architectures may easily be markedly different from that of the visual system.
The theory of open quantum systems (OQSs) is applied to partition the squared spin operator into fragment (local spin) and interfragment (spin-coupling) contributions in a molecular system. An atomic ...or fragment subsystem is described by a quantum mechanical mixed density operator composed of sectors, characterized by different integer number of electrons that appear with specific probabilities. The OQS fragment spin operators coincide with those defined by Clark and Davidson in their paper on local spins (
J. Chem. Phys.
, 2001,
115
, 7382) and are fully consistent with the theory of local operators by Stollhoff and Fulde (
J. Chem. Phys.
, 1980,
73
, 4548). OQSs provide a unique way to rationalize the non-zero values of local spins found in closed-shell molecules, a fact that has led to a large number of modified definitions being proposed, which we show suffer from inconsistencies. The OQS viewpoint makes it easy to build models for localized and itinerant spins. These models are used to classify possible local spin arrangements. The role of electron correlation is also studied through the analysis of the Hubbard Hamiltonian in small chains. Local spins result from a game played differently by localized and delocalized electrons. A number of examples exemplifying the ability of the OQS local spin perspective to uncover simple chemical patterns are examined.
The theory of open quantum systems (OQSs) is applied to partition the squared spin operator into fragment (local spin) and interfragment (spin-coupling) contributions in a molecular system.
Traditional ferroelectrics undergo thermally induced phase transitions whereby their structural symmetry increases. The associated higher-symmetry structure is dubbed paraelectric. Ferroelectric ...transition-metal dichalcogenide bilayers have been recently shown to become paraelectric, but not much has been said of the atomistic configuration of such a phase. As discovered through numerical calculations that include molecular dynamics here, their paraelectricity can only be ascribed to a time average of ferroelectric phases with opposing intrinsic polarizations, whose switching requires macroscopically large areas to slip in unison.
Invasive plant species that have the potential to alter fire regimes have significant impacts on native ecosystems. Concern that pine invasions in the Southern Hemisphere will increase fire activity ...and severity and subsequently promote further pine invasion prompted us to examine the potential for feedbacks between Pinus contorta invasions and fire in Patagonia and New Zealand. We determined how fuel loads and fire effects were altered by P. contorta invasion. We also examined post-fire plant communities across invasion gradients at a subset of sites to assess how invasion alters the post-fire vegetation trajectory. We found that fuel loads and soil heating during simulated fire increase with increasing P. contorta invasion age or density at all sites. However, P. contorta density did not always increase post-fire. In the largest fire, P. contorta density only increased significantly post-fire where the pre-fire P. contorta density was above an invasion threshold. Below this threshold, P. contorta did not dominate after fire and plant communities responded to fire in a similar manner as uninvaded communities. The positive feedback observed at high densities is caused by the accumulation of fuel that in turn results in greater soil heating during fires and high P. contorta density post-fire. Therefore, a positive feedback may form between P. contorta invasions and fire, but only above an invasion density threshold. These results suggest that management of pine invasions before they reach the invasion density threshold is important for reducing fire risk and preventing a transition to an alternate ecosystem state dominated by pines and novel understory plant communities.
In times when environmental concerns are on the rise and the search of ways to reduce waste generation and to create a circular economy is booming, Nature Based Solutions (NBSs) play a very important ...role. Vegetation Filters (VFs) are a type of Land Application System (LAS) in which wastewater is used to irrigate a forestry plantation to treat the water and produce biomass. VFs show multiple benefits that render this technology a suitable solution for wastewater treatment, especially for scattered populations or isolated buildings that lack of connection to sewer systems. This review aims to provide a comprehensive state of the art of VF implementation, highlighting the do's and don'ts for a successful performance focusing on those factors that are essential to water treatment. Results show that VFs have a great treatment capacity when all involving factors are considered, and their efficiency tends to increase with time, as the VF develops and “gets older”. Indeed, the presence of fine-textured soils, the selection of a proper vegetation species, the use of pre-treated wastewater and a water balance-based irrigation schedule alternating wetting and -drying cycles are all factors that help to achieve the best performance. However, it is necessary to design and follow a simple but rigorous operation and maintenance schedule to avoid system failure, which could lead to NO3–N leaching towards groundwater.
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•A review on Vegetation Filters (VFs) as wastewater treatment systems is carried out.•VFs represent a suitable alternative to conventional wastewater treatment plants.•To avoid N leaching towards the aquifer, a proper planning and management is needed.•Soil, vegetation, irrigation schedule and type of water are critical factors.•As time elapses, VF treatment efficiency tends to increase.
The prevailing magnetic spin coupling paradigm is based on a one-electron picture, and is therefore orbital dependent and unsatisfactory from a physical point of view. We examine it under a truly ...invariant real space perspective, focusing on the role of electron delocalization. We show that this view, compatible with orbital thinking, overcomes its limitations. By examining simple model systems we show that it is electron delocalization that drives any singlet-triplet gap, and that delocalization and ionic mixing are two sides of the same reality. It is in the end delocalization, fostered or hindered by the specific structure of a system, that lies behind its preferred magnetic coupling mode. In the case of superexchange-mediated coupling through atomic bridges, we also point out the non-essential role of the bridge's electrons in setting up singlet-triplet preferences. We show that the use of real space thinking allows for tuning singlet-triplet gaps using knobs that are not easily grasped from the orbital standpoint, opening new avenues in the design and control of molecular magnets.
The prevailing magnetic spin coupling paradigm is based on a one-electron picture, and is therefore orbital dependent and unsatisfactory from a physical point of view.
Although real space regions have been widely used in theoretical chemistry, not much effort has been devoted to treat them as open quantum systems. We embrace this task here, finding closed ...expressions for the density operator of a quantum subsystem in real space by tracing out the degrees of freedom in its complementary region. Our results are then linked to previous knowledge. For single-determinant descriptions it is shown that the entanglement orbitals coincide with Ponec’s domain natural orbitals. In general, the subsystem density operator is written as a direct sum of a fixed number of electron sectors, with weights that turn out to be equal to those found within the theory of electron distribution functions. As a computational application we show how to obtain the global first order density matrix of a subsystem and its eigensolution in a couple of toy systems. In the multideterminant wave function case, the domain natural orbitals defined through this open system approach do not coincide with those of Ponec and, contrary to the latter, have always strictly positive occupations.
Childhood rosacea and related disorders Noguera‐Morel, L.; Hernández‐Martín, A.; Torrelo, A.
Clinical and experimental dermatology,
April 2021, 2021-Apr, 2021-04-00, 20210401, Letnik:
46, Številka:
3
Journal Article
Recenzirano
Summary
Rosacea is a chronic inflammatory condition that affects the skin and the eyes. The pathogenesis of rosacea is complex and includes the interaction between genetic and environmental factors, ...dysregulation of the innate immune system, neurovascular modifications and the interaction with skin commensals. Clinical manifestations in children include the telangiectatic form, papulopustular rosacea, ocular rosacea, periorificial dermatitis, granulomatous rosacea and idiopathic facial aseptic granuloma. Management is aimed at identifying and avoiding triggers. Topical therapy is used for mild cases with topical antibiotics and anti‐inflammatory agents. Oral agents are indicated, in combination with topical therapy, for moderate to severe cases. Prolonged therapy may be required.
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