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Depressive disorders are heterogeneous diseases, and the complexity of symptoms has led to the formulation of several aethiopathological hypotheses. This heterogeneity may account for the following open issues about antidepressant therapy: (i) antidepressants show a time lag between pharmacological effects, within hours from acute drug administration, and therapeutic effects, within two-four weeks of subchronic treatment; (ii) this latency interval is critical for the patient because of the possible further mood worsening that may result in suicide attempts for the seemingly ineffective therapy and for the apparent adverse effects; (iii) and only 60–70 % of treated patients successfully respond to therapy. In this review, the complexity of the biological theories that try to explain the molecular mechanisms of these diseases is considered, encompassing (i) the classic “monoaminergic hypothesis” alongside the updated hypothesis according to which long-term therapeutical action of antidepressants is mediated by intracellular signal transduction pathways and (ii) the hypothalamic–pituitary-adrenal axis involvement. Although these models have guided research efforts in the field for decades, they have not generated a compelling and conclusive model either for depression pathophysiology or for antidepressant drugs’ action. So, other emerging theories are discussed: (iii) the alterations of neuroplasticity and neurotrophins in selective vulnerable cerebral areas; (iv) the involvement of inflammatory processes; (v) and the alterations in mitochondrial function and neuronal bioenergetics. The focus is put on the molecular and theoretical links between all these hypotheses, which are not mutually exclusive but otherwise tightly correlated, giving an integrated and comprehensive overview of the neurobiology of depressive disorders.

Radiative corrections in Lorentz violating (LV) models have already received a lot of attention in the literature in recent years, with many instances where a LV operator in one sector of the Standard Model Extension (SME) generates, via loop corrections, one of the LV coefficients in the photon sector, which is probably the most understood and well constrained part of the SME. In many of these works, however, the now standard notation of the SME is not used, which can obscure the comparison of different results, and their possible phenomenological relevance. In this work, we fill this gap, trying to build up a more general perspective on the topic, bringing many of the results to the SME conventional notation and commenting on their possible phenomenological relevance. We uncover one example where a result already presented in the literature can be used to place a stronger bound on the temporal component of the b μ coefficient of the fermion sector of the SME.

Most studies on buoyant microplastics in the marine environment rely on sea surface sampling. Consequently, microplastic amounts can be underestimated, as turbulence leads to vertical mixing. Models that correct for vertical mixing are based on limited data. In this study we report measurements of the depth profile of buoyant microplastics in the North Atlantic subtropical gyre, from 0 to 5 m depth. Microplastics were separated into size classes (0.5–1.5 and 1.5–5.0 mm) and types (‘fragments’ and ‘lines’) and associated with a sea state. Microplastic concentrations decreased exponentially with depth, with both sea state and particle properties affecting the steepness of the decrease. Concentrations approached zero within 5 m depth, indicating that most buoyant microplastics are present on or near the surface. Plastic rise velocities were also measured and were found to differ significantly for different sizes and shapes. Our results suggest that (1) surface samplers such as manta trawls underestimate total buoyant microplastic amounts by a factor of 1.04–30.0 and (2) estimations of depth-integrated buoyant plastic concentrations should be done across different particle sizes and types. Our findings can assist with improving buoyant ocean plastic vertical mixing models, mass balance exercises, impact assessments and mitigation strategies.

Attosecond-scale electron localization The primary event in photoexcitation — involved in processes such as photosynthesis and photoisomerization — is an electronic response that occurs on attosecond (1 as = 10 −18 s) timescales, a realm recently made accessible to spectroscopic investigation by the development of attosecond-scale light pulses. Sansone et al . report an experimental study in which electron localization in molecules is measured on attosecond timescales using pump–probe spectroscopy. H 2 and D 2 are dissociatively ionized by the sequence of an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends on the delay between the pump and probe pulses. This work demonstrates that combined experimental and computational efforts enable the use of attosecond pulses for the exploration of electron localization. Attosecond (10 −18 s) laser pulses make it possible to peer into the inner workings of atoms and molecules on the electronic timescale — phenomena in solids have already been investigated in this way. Here, an attosecond pump–probe experiment is reported that investigates the ionization and dissociation of hydrogen molecules, illustrating that attosecond techniques can also help explore the prompt charge redistribution and charge localization that accompany photoexcitation processes in molecular systems. For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10 −15 -s) timescale. However, studying the inner workings of atoms and molecules on the electronic timescale 1 , 2 , 3 , 4 has become possible only with the recent development of isolated attosecond (10 −18 -s) laser pulses 5 . Such pulses have been used to investigate atomic photoexcitation and photoionization 6 , 7 and electron dynamics in solids 8 , and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H 2 and D 2 was monitored on femtosecond timescales 9 and controlled using few-cycle near-infrared laser pulses 10 . Here we report a molecular attosecond pump–probe experiment based on that work: H 2 and D 2 are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends—with attosecond time resolution—on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump–probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born–Oppenheimer approximation.

Ocean plastic can persist in sea surface waters, eventually accumulating in remote areas of the world’s oceans. Here we characterise and quantify a major ocean plastic accumulation zone formed in subtropical waters between California and Hawaii: The Great Pacific Garbage Patch (GPGP). Our model, calibrated with data from multi-vessel and aircraft surveys, predicted at least 79 (45–129) thousand tonnes of ocean plastic are floating inside an area of 1.6 million km 2 ; a figure four to sixteen times higher than previously reported. We explain this difference through the use of more robust methods to quantify larger debris. Over three-quarters of the GPGP mass was carried by debris larger than 5 cm and at least 46% was comprised of fishing nets. Microplastics accounted for 8% of the total mass but 94% of the estimated 1.8 (1.1–3.6) trillion pieces floating in the area. Plastic collected during our study has specific characteristics such as small surface-to-volume ratio, indicating that only certain types of debris have the capacity to persist and accumulate at the surface of the GPGP. Finally, our results suggest that ocean plastic pollution within the GPGP is increasing exponentially and at a faster rate than in surrounding waters.

There is strong evidence that neonates imitate previously unseen behaviours. These behaviours are predominantly used in social interactions, demonstrating neonates' ability and motivation to engage with others. Research on neonatal imitation can provide a wealth of information about the early mirror neuron system (MNS), namely its functional characteristics, its plasticity from birth and its relation to skills later in development. Although numerous studies document the existence of neonatal imitation in the laboratory, little is known about its natural occurrence during parent–infant interactions and its plasticity as a consequence of experience. We review these critical aspects of imitation, which we argue are necessary for understanding the early action–perception system. We address common criticisms and misunderstandings about neonatal imitation and discuss methodological differences among studies. Recent work reveals that individual differences in neonatal imitation positively correlate with later social, cognitive and motor development. We propose that such variation in neonatal imitation could reflect important individual differences of the MNS. Although postnatal experience is not necessary for imitation, we present evidence that neonatal imitation is influenced by experience in the first week of life.

The applications of isolated attosecond pulses reported to date, which have demonstrated the great potential of attosecond technology in the investigation of ultrafast electronic processes, have been limited by the low photon flux of the available attosecond sources. We report on the generation of isolated sub-160-as pulses (at a photon energy of ∼30 eV) with a pulse energy, on target, of a few nanojoules. The efficient generation of isolated attosecond pulses in noble gases is produced by 5-fs driving pulses with controlled electric field and peak intensity beyond the gas saturation intensity. The availability of attosecond sources with high peak intensities has potential in opening new avenues for attosecond-pump/attosecond-probe studies of electronic processes in atomic and molecular physics, with interesting prospects in the field of coherent control of electronic motion in complex systems in the attosecond temporal regime. Researchers report the generation of isolated sub-160-attosecond pulses that have photon energies of 30 eV, resulting in an on-target pulse energy of a few nanojoules. The availability of attosecond sources with high peak intensities may open new avenues for attosecond pump/probe studies of electronic processes in atomic and molecular physics.

On November 1st, 2023, the Lucy spacecraft encountered the main-belt asteroid Dinkinesh, revealing the first confirmed contact binary moon, (152830) Dinkinesh I Selam. Here, we show that Selam likely formed through a series of low-velocity collisions of similarly sized moonlets that once orbited the primary. To gain insight into the processes that shape satellites in small binary systems, we simulate plausible formation scenarios for Selam. The mergers that form each lobe are consistent with collisions that occur beyond four primary radii at impact velocities between 1 and 1.5 times their mutual escape velocity and impact angles between 5 and 15 ∘ . Similar collisions could also explain the oblate shape of asteroid Dimorphos, the secondary in the Didymos system and the target of NASA’s Double Asteroid Redirection Test (DART), though further data from ESA’s Hera mission will provide additional insights. These results indicate that binary asteroid systems can undergo multiple moon-forming events and exhibit a wider diversity of satellite shapes than currently observed. Space missions imaging small asteroid moons revealed the variety in shapes. Here, the authors show that repeated low-speed collisions can explain the shape of Selam, which is the smaller component in Dinkinesh-Selam binary asteroid system.