Production of axion-like particles from photon conversions in large-scale solar magnetic fields

The Sun is a well-studied astrophysical source of axion-like particles (ALPs), produced mainly through the Primakoff process. Moreover, in the Sun there exist large-scale magnetic fields that catalyze an additional ALP production via a coherent conversion of thermal photons. We study this contribution to the solar ALP emissivity, typically neglected in previous investigations. Furthermore, we discuss additional bounds on the ALP-photon coupling from energy-loss arguments, and the detection perspectives of this new ALP flux at future helioscope and dark matter experiments.Comment: v2: 15 pages, 7 pdf figures. Figures improved, typos removed. Matches the version published on PR

Interpreting the Terahertz Spectrum of Complex Materials: The Unique Contribution of the Bayesian Analysis

In the last few decades, experimental studies of the terahertz spectrum of density fluctuations have considerably improved our knowledge of the mesoscopic dynamics of disordered materials, which also have imposed new demands on the data modelling and interpretation. Indeed, lineshape analyses are no longer limited to the phenomenological observation of inelastic features, as in the pioneering stage of Neutron or X-ray spectroscopy, rather aiming at the extraction from their shape of physically relevant quantities, as sound velocity and damping, relaxation times, or other transport coefficients. In this effort, researchers need to face both inherent and practical obstacles, respectively stemming from the highly damped nature of terahertz modes and the limited energy resolution, accessible kinematic region and statistical accuracy of the typical experimental outcome. To properly address these challenges, a global reconsideration of the lineshape modelling and the enforcement of evidence-based probabilistic inference is becoming crucial. Particularly compelling is the possibility of implementing Bayesian inference methods, which we illustrated here through an in-depth discussion of some results recently obtained in the analysis of Neutron and X-ray scattering results

Nipple Reconstruction Using the “Arrow Flap” Technique: Outcomes and Patients Satisfaction

Introduction: Skin-sparing mastectomy (SSM) entails complete removal of the breast tissue and the nipple and areola complex (NAC) with preservation of as much of the overlying skin as possible. The preservation of the natural skin envelope during SSM improves the aesthetic outcome of immediate breast reconstruction, but the lack of NAC determines that the reconstructed breast remains anatomically incomplete with not always satisfactory final results. For this purpose, the aim of the present study was to investigate and evaluate the impact of nipple reconstruction after skin sparing and skin reducing mastectomy on the patients' perception and intimate life. Materials and method: This was a comparative single-center prospective study that involved 42 patients underwent NAC reconstruction after SSM. A pre- and postoperative quality-of-life and psychological questionnaires Breast-Q questionnaire (Breast Conserving therapy module) were given to all the patients before the surgery and 6 months after. The statistical analysis with chi-square test was performed. Results: After 6 months a prevalence of patients reported to be very satisfied in regard to shape, appearance, naturalness, projection, position and symmetry. The study shows an overall improvement in all the psychological items analyzed with statistically significant difference regarding: "patient's satisfaction," "self-confidence," "appearance of the breast." Conclusion: The authors believe that the NAC reconstruction has useful functional and aesthetic results particularly appreciated by patients who feel demoralized after breast demolition surgery

Ice phonon spectra and Bayes inference: a gateway to a new understanding of terahertz sound propagation in water

Understanding how molecules engage in collective motions in a liquid where a network of bonds exists has both fundamental and applied relevance. On the one hand, it can elucidate the ``ordering" role of long-range correlations in an otherwise strongly dissipative system; on the other hand, it can inspire new avenues to control such order to implement sound manipulation. Water represents an ideal investigation case to unfold these general aspects and, across the decades, it has been the focus of thorough scrutiny. Despite this investigative effort, the spectrum of terahertz density fluctuations of water largely remains a puzzle for Condensed Matter physicists. To unravel it, we compare previous scattering measurements of water spectra with new ones on ice. Thanks to the unique asset of Bayesian inference, we draw a more detailed portrayal of the phonon response of ice. The comparison with the one of liquid water challenges the current understanding of density fluctuations in water, or more in general, of any networked liquid.Comment: 30 pages, 9 figure

The hydrogen-bond collective dynamics in liquid methanol

The relatively simple molecular structure of hydrogen-bonded (HB) systems is often belied by their exceptionally complex thermodynamic and microscopic behaviour. For this reason, after a thorough experimental, computational and theoretical scrutiny, the dynamics of molecules in HB systems still eludes a comprehensive understanding. Aiming at shedding some insight into this topic, we jointly used neutron Brillouin scattering and molecular dynamics simulations to probe the dynamics of a prototypical hydrogen-bonded alcohol, liquid methanol. The comparison with the most thoroughly investigated HB system, liquid water, pinpoints common behaviours of their THz microscopic dynamics, thereby providing additional information on the role of HB dynamics in these two systems. This study demonstrates that the dynamic behaviour of methanol is much richer than what so far known, and prompts us to establish striking analogies with the features of liquid and supercooled water. In particular, based on the strong differences between the structural properties of the two systems, our results suggest that the assignment of some dynamical properties to the tetrahedral character of water structure should be questioned. We finally highlight the similarities between the characteristic decay times of the time correlation function, as obtained from our data and the mean lifetime of hydrogen bond known in literature

Switching off hydrogen-bond-driven excitation modes in liquid methanol

Abstract Hydrogen bonding plays an essential role on intermolecular forces, and consequently on the thermodynamics of materials defined by this elusive bonding character. It determines the property of a vital liquid as water as well as many processes crucial for life. The longstanding controversy on the nature of the hydrogen bond (HB) can be settled by looking at the effect of a vanishing HB interaction on the microscopic properties of a given hydrogen-bonded fluid. This task suits the capabilities of computer simulations techniques, which allow to easily switch off HB interactions. We then use molecular dynamics to study the microscopic properties of methanol, a prototypical HB liquid. Fundamental aspects of the dynamics of methanol at room temperature were contextualised only very recently and its rich dynamics was found to have striking analogies with that of water. The lower temperature (200 K) considered in the present study led us to observe that the molecular centre-of-mass dynamics is dominated by four modes. Most importantly, the computational ability to switch on and off hydrogen bonds permitted us to identify which, among these modes, have a pure HB-origin. This clarifies the role of hydrogen bonds in liquid dynamics, disclosing new research opportunities and unexplored interpretation schemes

The damping of terahertz acoustic modes in aqueous nanoparticle suspensions

In this work, we investigate the possibility of controlling the acoustic damping in a liquid when nanoparticles are suspended in it. To shed light on this topic, we performed Inelastic X-Ray Scattering (IXS) measurements of the terahertz collective dynamics of aqueous suspensions of nanospheres of various materials, size, and relative concentration, either charged or neutral. A Bayesian analysis of measured spectra indicates that the damping of the two acoustic modes of water increases upon nanoparticle immersion. This effect seems particularly pronounced for the longitudinal acoustic mode, which, whenever visible at all, rapidly damps off when increasing the exchanged wavevector. Results also indicate that the observed effect strongly depends on the material the immersed nanoparticles are made of

The Effect of Embedded Nanoparticles on the Phonon Spectrum of Ice: An Inelastic X-ray Scattering Study

As a contribution to the ongoing effort toward high-frequency sound manipulation in composite materials, we use Inelastic X-ray Scattering to probe the phonon spectrum of ice, either in a pure form or with a sparse amount of nanoparticles embedded in it. The study aims at elucidating the ability of nanocolloids to condition the collective atomic vibrations of the surrounding environment. We observe that a nanoparticle concentration of about 1 % in volume is sufficient to visibly affect the phonon spectrum of the icy substrate, mainly canceling its optical modes and adding nanoparticle phonon excitations to it. We highlight this phenomenon thanks to the lineshape modeling based on a Bayesian inference, which enables us to capture the finest detail of the scattering signal. The results of this study can empower new routes toward the shaping of sound propagation in materials through the control of their structural heterogeneity

Facilitating co-production in public services: management implications from a systematic literature review

Drawing on the results of a systematic literature review of empirical studies, this paper sheds light on six broad factors that facilitate the initiation and implementation of co-production in public services. The factors are classified into two overarching categories: organizational factors, including organizational arrangements, professional roles, and managerial tools; and procedural factors, including participant recruitment, participant preparation, and process design. For each set of factors, the paper provides a series of management implications. It concludes with additional observations for practice. Unfortunately, ‘one-size-fits-all’ does not apply to co-production. Policy-makers and public managers need use their knowledge, skills, and judgment to design, activate, and implement co-production activities. The paper presents three organizational factors (organizational arrangements, professional roles, and managerial tools) and three procedural factors (participant recruitment, participant preparation, and process design) that facilitate the initiation and implementation of co-production. Moreover, for each set of factors, the paper provides an important series of management implications that offer guidance to those who are using, or who wish to use, co-production in their organizations. Thus, this paper provides evidence-driven advice that can assist public managers and policy makers looking for ways to improve co-production in public services