Fine-structure excitation of CCS by He: Potential energy surface and scattering calculations

The fine structure excitation of the interstellar CCS radical induced by collisions with He is investigated. The first potential energy surface (PES) for the CCS-He van der Waals complex is presented. It was obtained from a highly correlated spin unrestricted coupled cluster approach with single double and perturbative triple excitations. The PES presents two shallow minima of 31.85 and 37.12 cm^-1 for the linear (He facing S) and the nearly T-shaped geometries, respectively. The dissociation energy of the complex was calculated and found to be D₀ = 14.183 cm^-1. Inelastic scattering calculations were performed using the close-coupling approach. Cross-sections for transitions between the 61 first fine structure levels of CCS were obtained for energy up to 600 cm^-1 and rate coefficients for the 5-50 K temperature range were derived. This set of collisional data can be used to model CCS emission spectra in dark molecular interstellar clouds and circumstellar envelopes and enable an accurate determination of CCS abundance in these astrophysical media.

Meteorites have inherited nucleosynthetic anomalies of potassium-40 produced in supernovae

Meteorites record processes that occurred before and during the formation of the Solar System in the form of nucleosynthetic anomalies: isotopic compositions that differ from the Solar System patterns. Nucleosynthetic anomalies are rarely seen in volatile elements such as potassium at bulk meteorite scale. We measured potassium isotope ratios in 32 meteorites and identified nucleosynthetic anomalies in the isotope potassium-40. The anomalies are larger and more variable in carbonaceous chondrite (CC) meteorites than in noncarbonaceous (NC) meteorites, indicating that CCs inherited more material produced in supernova nucleosynthesis. The potassium-40 anomaly of Earth is close to that of the NCs, implying that Earth's potassium was mostly delivered by NCs.

An isolated chemolithoautotrophic ecosystem deduced from environmental isotopes: Ayyalon cave (Israel)

The stable isotopes composition of chemolithoautotrophic cave ecosystems is known to differ from epigenic caves. Here we show that in addition, dead carbon (devoid of 14C), is utilized and transferred throughout this ecosystem, rendering it unsuitable for radiocarbon dating. The connectivity of the Ayyalon Cave ecosystem with the surface is studied, along with its sources of energy and carbon, as well as the interconnections between its constituents. We use isotopic evidence to show that its ancient resilient ecosystem is based on an underground food web depending on rich biomass production by chemolithoautotrophic nutrient supplies, detached from surface photosynthesis. Carbon isotopic values indicate that: (1) the microbial biota use bicarbonate from the groundwater (23.34 pMC [% of modern carbon]) rather than the atmospheric CO2 above the water (71.36 pMC); (2) the depleted 14C signal is transferred through the entire ecosystem, indicating that the ecosystem is well-adapted and based on the cave biofilm which is in turn based on groundwater-dissolved inorganic carbon. Incubation of Ayyalon biofilm with 14C-labelled bicarbonate indicates uptake of the radio-labeled bicarbonate by sulfur-oxidizing proteobacteria Beggiatoa, suggesting that these sulfur-oxidizing microorganisms use the water-dissolved inorganic carbon for chemolithoautotrophic carbon fixation. Organic matter in the cave is much lighter in its stable nitrogen and carbon isotopes compared with respective surface values, as expected in chemolithoautotrophic systems. This evidence may be applicative to subsurface voids of ancient Earth environments and extraterrestrial systems.

Glycine Peptide Chain Formation in the Gas Phase via Unimolecular Reactions

Peptide chain formation from amino acids such as glycine is a key step in the emergence of life. Unlike their synthesis by living systems, how peptide chains grow under abiotic conditions is an open question given the variety of organic compounds discovered in various astrophysical environments, comets and meteorites. We propose a new abiotic route in the presence of protonated molecular dimers of glycine in a cold gaseous atmosphere without further need for a solid catalytic substrate. The results provide evidence for the preferential formation of mixed protonated dimers of glycine consisting of a dipeptide and a glycine molecule instead of pure protonated glycine dimers. Additional measurements mimicking a cosmic-ray impact in terms of internal excitation show that a single gas-phase collision induces polymerization via dehydration in both the mixed and pure dimer ions. Peptide chain growth is thus demonstrated to occur via a unimolecular gas-phase reaction in an excited cluster ion.

Water Complex of Imidogen

Imidogen (NH) is the simplest nitrogen hydride that plays an important role in combustion and interstellar chemistry, and its combination with H₂O is the prototypical amidation reaction of O-H bonds involving a nitrene intermediate. Herein, we report the observation of the elusive water complex of NH, a prereaction complex associated with the amidation reaction in a solid N₂ matrix at 10 K. The hydrogen-bonded structure of NH···OH₂ (versus HN···HOH) is confirmed via IR spectroscopy with comprehensive isotope labeling (D, ¹⁸O, and ¹⁵N) and quantum chemical calculations at the UCCSD(T)/aug-cc-pVQZ level of theory. In line with the observed absorption at 350 nm, irradiation of the complex at 365 nm leads to O-H bond insertion, yielding hydroxylamine NH₂OH.

Stereolithography apparatus and digital light processing-based 3D bioprinting for tissue fabrication

Three-dimensional (3D) bioprinting has emerged as a class of promising techniques in biomedical research for a wide range of related applications. Specifically, stereolithography apparatus (SLA) and digital light processing (DLP)-based vat-polymerization techniques are highly effective methods of bioprinting, which can be used to produce high-resolution and architecturally sophisticated structures. Our review aims to provide an overview of SLA- and DLP-based 3D bioprinting strategies, starting from factors that affect these bioprinting processes. In addition, we summarize the advances in bioinks used in SLA and DLP, including naturally derived and synthetic bioinks. Finally, the biomedical applications of both SLA- and DLP-based bioprinting are discussed, primarily centered on regenerative medicine and tissue modeling engineering.

Observational and Energetic Properties of Astrophysical and Galactic Black Holes

The work reviews the investigation of electromagnetic, optical, and energetic properties of astrophysical and galactic black holes and surrounding matter. The astrophysical applications of the theoretical models of black hole environment to the description of various observed phenomena, such as cosmic rays of the ultra-high-energy, black hole shadow, gravitational lensing, quasinormal modes, jets showing relativistic effects such as the Doppler beaming, thermal radiation from the accretion discs, quasiperiodic oscillations are discussed. It has been demonstrated that the observational data strongly depends on the structure and evolution of the accretion disk surrounding the central black hole. It has been shown that the simulated images of supermassive black holes obtained are in agreement with the observational images obtained by event horizon telescope collaboration. High energetic activity from supermassive black holes due to the magnetic Penrose process discussed in the work is in agreement with the highly energetic cosmic rays observed. The astronomical observation of black holes provides rich fundamental physics laboratories for experimental tests and verification of various models of black hole accretion and different theories of gravity in the regime of strong gravity.

Spin-down by dynamo action in simulated radiative stellar layers

The evolution of a star is influenced by its internal rotation dynamics through transport and mixing mechanisms, which are poorly understood. Magnetic fields can play a role in transporting angular momentum and chemical elements, but the origin of magnetism in radiative stellar layers is unclear. Using global numerical simulations, we identify a subcritical transition from laminar flow to turbulence caused by the generation of a magnetic dynamo. Our results have many properties of the theoretically proposed Tayler-Spruit dynamo mechanism, which strongly enhances transport of angular momentum in radiative zones. The dynamo generates deep toroidal fields that are screened by the stellar outer layers. This mechanism could produce strong magnetic fields inside radiative stars without an observable field on their surface.

Monitoring the Light-induced Isomerisation of the Prototypical Polycyclic Aromatic Hydrocarbons C10 H8 + through Ion-Molecule Reactions

Structural rearrangements in ions are essential for understanding the composition and evolution of energetic and chemically active environments. This study explores the interconversion routes for simple polycyclic aromatic hydrocarbons, namely naphthalene and azulene radical cations (C₁₀ H₈ ⁺ ), by combining mass spectrometry and vacuum ultraviolet tunable synchrotron radiation through the chemical monitoring technique. Products of ion-molecule reactions are used to probe C₁₀ H₈ ⁺ structures that are formed as a function of their internal energies. Isomerisation from azulene radical cation towards naphthalene radical cation in a timescale faster than 80 μs was monitored, whereas no reverse isomerisation was observed in the same time window. When energising C₁₀ H₈ ⁺ with more than 6 eV, the reactivity of C₁₀ H₈ ⁺ unveils the formation of a new isomeric group with a contrasted reactivity compared with naphthalene and azulene cations. We tentatively assigned these structures to phenylvinylacetylene cations.

Reactions O(3P, 1D) + HCCCN(X1Σ+) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

Cyanoacetylene (HCCCN), the first member of the cyanopolyyne family (HC_nN, where n = 3, 5, 7, ...), is of particular interest in astrochemistry being ubiquitous in space (molecular clouds, solar-type protostars, protoplanetary disks, circumstellar envelopes, and external galaxies) and also relatively abundant. It is also abundant in the upper atmosphere of Titan and comets. Since oxygen is the third most abundant element in space, after hydrogen and helium, the reaction O + HCCCN can be of relevance in the chemistry of extraterrestrial environments. Despite that, scarce information exists not only on the reactions of oxygen atoms with cyanoacetylene but with nitriles in general. Here, we report on a combined experimental and theoretical investigation of the reactions of cyanoacetylene with both ground ³P and excited ¹D atomic oxygen and provide detailed information on the primary reaction products, their branching fractions (BFs), and the overall reaction mechanisms. More specifically, the reactions of O(³P, ¹D) with HCCCN(X¹Σ⁺) have been investigated under single-collision conditions by the crossed molecular beams scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy, E_c, of 31.1 kJ/mol. From product angular and time-of-flight distributions, we have identified the primary reaction products and determined their branching fractions (BFs). Theoretical calculations of the relevant triplet and singlet potential energy surfaces (PESs) were performed to assist the interpretation of the experimental results and clarify the reaction mechanism. Adiabatic statistical calculations of product BFs for the decomposition of the main triplet and singlet intermediates have also been carried out. Merging together the experimental and theoretical results, we conclude that the O(³P) reaction is characterized by a minor adiabatic channel leading to OCCCN (cyanoketyl) + H (experimental BF = 0.10 ± 0.05), while the dominant channel (BF = 0.90 ± 0.05) occurs via intersystem crossing to the underlying singlet PES and leads to formation of ¹HCCN (cyanomethylene) + CO. The O(¹D) reaction is characterized by the same two channels, with the relative CO/H yield being slightly larger. Considering the recorded reactive signal and the calculated entrance barrier, we estimate that the rate coefficient for reaction O(³P) + HC₃N at 300 K is in the 10^-12 cm³ molec^-1 s^-1 range. Our results are expected to be useful to improve astrochemical and photochemical models. In addition, they are also relevant in combustion chemistry, because the thermal decomposition of pyrrolic and pyridinic structures present in fuel-bound nitrogen generates many nitrogen-bearing compounds, including cyanoacetylene.

Mechanistical study on the formation of hydroxyacetone (CH3COCH2OH), methyl acetate (CH3COOCH3), and 3-hydroxypropanal (HCOCH2CH2OH) along with their enol tautomers (prop-1-ene-1,2-diol (CH3C(OH)CHOH), prop-2-ene-1,2-diol (CH2C(OH)CH2OH), 1-methoxyethen-1-ol (CH3OC(OH)CH2) and prop-1-ene-1,3-diol (HOCH2CHCHOH)) in interstellar ice analogs

We unravel, for the very first time, the formation pathways of hydroxyacetone (CH₃COCH₂OH), methyl acetate (CH₃COOCH₃), and 3-hydroxypropanal (HCOCH₂CH₂OH), as well as their enol tautomers within mixed ices of methanol (CH₃OH) and acetaldehyde (CH₃CHO) analogous to interstellar ices in the ISM exposed to ionizing radiation at ultralow temperatures of 5 K. Exploiting photoionization reflectron time-of-flight mass spectrometry (PI-ReToF-MS) and isotopically labeled ices, the reaction products were selectively photoionized allowing for isomer discrimination during the temperature-programmed desorption phase. Based on the distinct mass-to-charge ratios and ionization energies of the identified species, we reveal the formation pathways of hydroxyacetone (CH₃COCH₂OH), methyl acetate (CH₃COOCH₃), and 3-hydroxypropanal (HCOCH₂CH₂OH) via radical-radical recombination reactions and of their enol tautomers (prop-1-ene-1,2-diol (CH₃C(OH)CHOH), prop-2-ene-1,2-diol (CH₂C(OH)CH₂OH), 1-methoxyethen-1-ol (CH₃OC(OH)CH₂) and prop-1-ene-1,3-diol (HOCH₂CHCHOH)) via keto-enol tautomerization. To the best of our knowledge, 1-methoxyethen-1-ol (CH₃OC(OH)CH₂) and prop-1-ene-1,3-diol (HOCH₂CHCHOH) are experimentally identified for the first time. Our findings help to constrain the formation mechanism of hydroxyacetone and methyl acetate detected within star-forming regions and suggest that the hitherto astronomically unobserved isomer 3-hydroxypropanal and its enol tautomers represent promising candidates for future astronomical searches. These enol tautomers may contribute to the molecular synthesis of biologically relevant molecules in deep space due to their nucleophilic character and high reactivity.

Investigation of a light Dark Boson existence: The New JEDI project

Several experiments around the world are looking for a new particle, named Dark Boson, which may do the link between the Ordinary Matter (which forms basically stars, planets, interstellar gas...) and the Hidden Sectors of the Universe. This particle, if it exists, would act as the messenger of a new fundamental interaction of nature. In this paper, the underlying Dark Sectors theory will be introduced first. A non-exhaustive summary of experimental studies carried out to date and foreseen in the incoming years will be presented after,including the 8Be anomaly. The last section will provide a status of the New JEDI**** project which aims to investigate the existence or not of a Dark Boson in the MeV range.

Indirect measurement of the (n,γ)127Sb cross section

Sensitivity studies of the i process have identified the region around 135I as a bottleneck for the neutron capture flow. Nuclear properties such as the Maxwellian-averaged cross section (MACS) are key to constrain the uncertainties in the final abundance patterns. From the 124Sn(α, pγ)127Sb reaction we are able to indirectly measure the nuclear level density and γ-ray strength function for 127Sb using the Oslo method. From these two quantities we can calculate the MACS for the 126Sb(n, γ)127Sb reaction using the Hauser-Feshbach formalism, constrain its uncertainties and compare it to libraries such as JINA REACLIB, TENDL and BRUSLIB.

13C(α,n)16O: The Source of Neutrons for the s-process main component

The 13C(α, n)16O reaction operates in the He intershell of low-mass(M < 4 M⊙) AGB stars and it is the neutron source that allows the creation of the main component of the s-process elements. The reaction rate is then required to be well known in the energy range of astrophysical interest. Therefore, the 13C(α, n)16O reaction rate has been calculated in stellar like conditions using a nuclear-model based computer code TALYS. The results have been compared with available literature data and found to be in good agreement with experimental data and, evaluated data NACRE II as well.

Stellar initial mass function varies with metallicity and time

Most structural and evolutionary properties of galaxies strongly rely on the stellar initial mass function (IMF), namely the distribution of the stellar mass formed in each episode of star formation^1-4. The IMF shapes the stellar population in all stellar systems, and so has become one of the most fundamental concepts of modern astronomy. Both constant and variable IMFs across different environments have been claimed despite a large number of theoretical^5-7 and observational efforts^8-15. However, the measurement of the IMF in Galactic stellar populations has been limited by the relatively small number of photometrically observed stars, leading to high uncertainties^12-16. Here we report a star-counting result based on approximately 93,000 spectroscopically observed M-dwarf stars, an order of magnitude more than previous studies, in the 100-300 parsec solar neighbourhood. We find unambiguous evidence of a variable IMF that depends on both metallicity and stellar age. Specifically, the stellar population formed at early times contains fewer low-mass stars compared with the canonical IMF, independent of stellar metallicities. In more recent times, however, the proportion of low-mass stars increases with stellar metallicity. The variable abundance of low-mass stars in our Milky Way establishes a powerful benchmark for models of star formation and can heavily affect results in Galactic chemical-enrichment modelling, mass estimation of galaxies and planet-formation efficiency.

Magnetic and non-magnetic AGB mixing for s-processing

I outline a few features of recent models for the formation of the neutron source 13C(α,n)16O in low mass stars (1 ≲ M/M⊙ ≲ 3, LMS ) ascendingfor the second time the Red Giant Branch, generally called Asymptotic Giant Branch, or AGB stars. I also briefly outline the nucleosynthesis results obtained trough them. The mentioned models consider the physical structure below the frequent downward extensions of the convective envelope into the He-intershell (the so-called third dredge-up or TDU episodes). There, the conditions are such that the occurrence of further mixing is strongly facilitated, due to the minimal temperature gradient. A way to induce proton mixing from the envelope (certainly not the only one) arises whenever the ambient magnetic fields expected for LMS promote the buoyancy of strongly magnetized flux tubes. I review some characteristics of the ensuing mixing episodes, mentioning how different hydrodynamical processes might yield similar effects, thus encouraging stellar physicists to verify in more detail this possibility.

Decreasing ultrafast x-ray pulse durations with saturable absorption and resonant transitions

Saturable absorption is a nonlinear effect where a material's ability to absorb light is frustrated due to a high influx of photons and the creation of electron vacancies. Experimentally induced saturable absorption in copper revealed a reduction in the temporal duration of transmitted x-ray laser pulses, but a detailed account of changes in opacity and emergence of resonances is still missing. In this computational work, we employ nonlocal thermodynamic equilibrium plasma simulations to study the interaction of femtosecond x rays and copper. Following the onset of frustrated absorption, we find that a K-M resonant transition occurring at highly charged states turns copper opaque again. The changes in absorption generate a transient transparent window responsible for the shortened transmission signal. We also propose using fluorescence induced by the incident beam as an alternative source to achieve shorter x-ray pulses. Intense femtosecond x rays are valuable to probe the structure and dynamics of biological samples or to reach extreme states of matter. Shortened pulses could be relevant for emerging imaging techniques.

Neutron captures in stellar nucleosynthesis

Apart from cosmological hydrogen and helium, chemical elements in the Universe are produced in stars, during both quiescent and explosive phases. The Sun chemical distribution witnesses the pollution from already extinct stellar generations at different epochs before the Solar System formation. The two major nucleosynthesis processes responsible for the formation of elements heavier than iron are the slow neutron capture process (the s-process) and the rapid neutron capture process (the r-process). A third, less common, nucleosynthesis channel is related to the intermediate neutron capture process (the i-process), whose existence is not ascertained yet. Finally, a few proton-rich isotopes are created by the p-process. I will show their characteristics and the stellar sites where they are at work.

Factors affecting the independence and reliability of Science and how these are perceived

Science studies natural phenomena or uses laws, theories, models and mechanisms to explain them, which are revised when new evidence emerges. However, Science cannot give answer to all questions that may arise. The benefits of science are well known and there is no reason to expand on them. It is of interest though to examine the structure and factors that influence the scientific world and may hold it back from offering greater benefits to mankind. The current study is concerned with the question whether or not Science is independent and reliable. Social and political reasons can direct substantive research in specific areas, but they can also encourage the promotion of unfounded theories. External factors such as prejudice against new ideas and understanding of natural happenings can negatively affect the objectivity of Science. Such factors examined in this paper and influence Science are: Research funding, policy makers and industry; Journal editors; Dogma; Theories declared as Conspiracies; Mutual interests in Academia; Knowledge control, cover ups and war superiority. The above factors can be used negatively to restrain serious scientists from expressing educated opinions and publishing them in scientific journals. In this way healthy discussions between 'opposing parties' are restricted, with Science being the victim as no sound conclusions and consensus on important subjects are reached. To check how the above positions are perceived by the scientific community, a questionnaire was circulated among scientists in 11 countries. Analyzing the 106 responds that were anonymously received, indicated that the respondents were largely in line with the expressed positions of the present paper. It is proposed that the real answer to minimize the effect of the factors that influence Science negatively, is educating people's critical abilities and considering nothing for granted-especially under the influence of powerful Media-unless its validity is independently checked and verified.

A retrospective study of risk factors, causative micro-organisms and healthcare resources consumption associated with prosthetic joint infections (PJI) using the Clinical Practice Research Datalink (CPRD) Aurum database

BACKGROUND

Prosthetic joint infection (PJI) is a serious complication after joint replacement surgery and it is associated with risk of mortality and morbidity along with high direct costs.

METHODS

The Clinical Practice Research Datalink (CPRD) data were utilized to quantify PJI incidence after hip or knee replacement up to 5 years after implant and a variety of risk factors related to patient characteristics, medical and treatment history along with characteristics of the original surgery were analyzed through Cox proportional hazard.

RESULTS

221,826 patients (individual joints 283,789) met all the inclusion and exclusion criteria of the study; during the study follow-up period (5 years), 707 and 695 PJIs were diagnosed in hip and knee, respectively. Patients undergoing joint replacement surgery during an unscheduled hospitalization had greater risk of PJI than patients whose surgery was elective; similarly, the risk of developing PJI after a secondary hip or knee replacement was about 4 times greater than after primary arthroplasty when adjusted for all other variables considered. A previous diagnosis of PJI, even in a different joint, increased the risk of a further PJI. Distribution of average LoS per each hospitalization caused by PJI exhibited a right skewed profile with median duration [IQR] duration of 16 days [8-32] and 13 days [7.25-32] for hip and knee, respectively. PJIs causative micro-organisms were dependent on the time between initial surgery and infection offset; early PJI were more likely to be multispecies than later (years after surgery); the identification of Gram- pathogens decreased with increasing post-surgery follow-up.

CONCLUSIONS

This study offers a contemporary assessment of the budgetary and capacity (number and duration of hospitalizations along with the number of Accident and Emergency (A&E) visits) posed by PJIs in UK for the national healthcare system (NHS). The results to provide risk management and planning tools to health providers and policy makers in order to fully assess technologies aimed at controlling and preventing PJI. The findings add to the existing evidence-based knowledge surrounding the epidemiology and burden of PJI by quantifying patterns of PJI in patients with a relatively broad set of prevalent comorbidities.

A physics-based neural network reconstruction of the dense matter equation of state from neutron star observables

We introduce a novel technique that utilizes a physics-driven deep learning method to reconstruct the dense matter equation of state from neutron star observables, particularly the masses and radii. The proposed framework involves two neural networks: one to optimize the EoS using Automatic Differentiation in the unsupervised learning scheme; and a pre-trained network to solve the Tolman–Oppenheimer–Volkoff (TOV) equations. The gradient-based optimization process incorporates a Bayesian picture into the proposed framework. The reconstructed EoS is proven to be consistent with the results from conventional methods. Furthermore, the resulting tidal deformation is in agreement with the limits obtained from the gravitational wave event, GW170817.

Big Bang nucleosynthesis as a probe of new physics

The Big Bang Nucleosynthesis (BBN) model is a cornerstone for the understanding of the evolution of the early universe, making seminal predictions that are in outstanding agreement with the present observation of light element abundances in the universe. Perhaps, the only remaining issue to be solved by theory is the so-called “lithium abundance problem". Dedicated experimental efforts to measure the relevant nuclear cross sections used as input of the model have lead to an increased level of accuracy in the prediction of the light element primordial abundances. The rise of indirect experimental techniques during the preceding few decades has permitted the access of reaction information beyond the limitations of direct measurements. New theoreticaldevelopments have also opened a fertile ground for tests of physics beyond the standard model of atomic,nuclear, statistics, and particle physics. We review the latest contributions of our group for possible solutions of the lithium problem.

A naturalist perspective of microbiology: Examples from methanogenic archaea

Storytelling has been the primary means of knowledge transfer over human history. The effectiveness and reach of stories are improved when the message is appropriate for the target audience. Oftentimes, the stories that are most well received and recounted are those that have a clear purpose and that are told from a variety of perspectives that touch on the varied interests of the target audience. Whether scientists realize or not, they are accustomed to telling stories of their own scientific discoveries through the preparation of manuscripts, presentations, and lectures. Perhaps less frequently, scientists prepare review articles or book chapters that summarize a body of knowledge on a given subject matter, meant to be more holistic recounts of a body of literature. Yet, by necessity, such summaries are often still narrow in their scope and are told from the perspective of a particular discipline. In other words, interdisciplinary reviews or book chapters tend to be the rarity rather than the norm. Here, we advocate for and highlight the benefits of interdisciplinary perspectives on microbiological subjects.

Liquid Crystal-Based Geometric Phase-Enhanced Platform for Polarization and Wavefront Analysis Techniques with the Short-TeraHertz FEL Oscillator TerRa@BriXSinO

In this work, we propose to design a liquid crystal–based modular and extendable platform of cutting-edge optical technologies for studying materials based on the analysis of polarization and wavefront of light in the wavelength range of 10–50 μm, which is considered to work even in the longer wavelengths range. This platform will be driven by the future THz-FEL source TerRa@BriXSinO that produces high power radiation in THz-range from 6 THz up to 30 THz (Mid-/Far-IR). The lack of optical infrastructures in this range has been tackled by fabricating liquid crystal–based geometric phase components that have been specifically designed for this purpose. This is in order to optimally exploit all the source’s potential for maximum accuracy and efficiency in determining polarization- and wavefront-sensitive properties of materials. We present an overview of a few experiments for characterizing bulk inhomogeneities, dielectric anisotropy, surface roughness, cracks, impact damages, and stress and strain effects with special emphasis on non-destructive tests on composite structures. The tools for wavefront shaping developed within our platform will be exploited to add a further degree of freedom, i.e., orbital angular momentum, to nonlinear optics techniques, such as Terahertz Hyper-Raman spectroscopy, for investigating chiral agents’ properties.

Is there a link between the length of the solar cycle and Earth’s temperature?

The Sun provides most of external energy to Earth’s system and thus has the potential of influencing it. Various studies reported a correlation between the solar cycle length and the northern hemisphere temperatures on Earth. Here, we reassess the cycle length record by incorporating the newly revised and updated sunspot number series as well as plage area composite, before comparing it to Earth temperature records. We find that cycle length series constructed from sunspot and plage data exhibit the same behaviour, both showing a downward trend after 1940. Our results suggest that the agreement between solar cycle lengths and temperatures found earlier is an artefact of (1) some arbitrary choices made by those studies when constructing the cycle length series as well as (2) a rather short time interval, to which the analyses were restricted. When considering the entire period of reliable sunspot and temperature data, these records diverge before about 1870 and after 1960. We also find a poor agreement between Earth temperatures and cycle length when using plage areas instead of sunspot data to derive cycle lengths. Our result of the divergence between cycle length series and Earth’s temperature after 1960 implies that the cycle length cannot be used to support a solar origin for the warming on Earth over the last 5 decades.

EmulART: Emulating radiative transfer—a pilot study on autoencoder-based dimensionality reduction for radiative transfer models

Dust is a major component of the interstellar medium. Through scattering, absorption and thermal re-emission, it can profoundly alter astrophysical observations. Models for dust composition and distribution are necessary to better understand and curb their impact on observations. A new approach for serial and computationally inexpensive production of such models is here presented. Traditionally these models are studied with the help of radiative transfer modelling, a critical tool to understand the impact of dust attenuation and reddening on the observed properties of galaxies and active galactic nuclei. Such simulations present, however, an approximately linear computational cost increase with the desired information resolution. Our new efficient model generator proposes a denoising variational autoencoder (or alternatively PCA), for spectral compression, combined with an approximate Bayesian method for spatial inference, to emulate high information radiative transfer models from low information models. For a simple spherical dust shell model with anisotropic illumination, our proposed approach successfully emulates the reference simulation starting from less than 1% of the information. Our emulations of the model at different viewing angles present median residuals below 15% across the spectral dimension and below 48% across spatial and spectral dimensions. EmulART infers estimates for $$\sim $$ ∼ 85% of information missing from the input, all within a total running time of around 20 minutes, estimated to be 6$$\times $$ × faster than the present target high information resolution simulations, and up to 50$$\times $$ × faster when applied to more complicated simulations.

Evidence of structural discontinuities in the inner core of red-giant stars

Red giants are stars in the late stages of stellar evolution. Because they have exhausted the supply of hydrogen in their core, they burn the hydrogen in the surrounding shell . Once the helium in the core starts fusing, the star enters the clump phase, which is identified as a striking feature in the color-magnitude diagram. Since clump stars share similar observational properties, they are heavily used in astrophysical studies, as probes of distance, extinction through the galaxy, galaxy density, and stellar chemical evolution. In this work, we perform the detailed observational characterization of the deepest layers of clump stars using asteroseismic data from Kepler. We find evidence for large core structural discontinuities in about 6.7% of the stars in our sample, implying that the region of mixing beyond the convective core boundary has a radiative thermal stratification. These stars are otherwise similar to the remaining stars in our sample, which may indicate that the building of the discontinuities is an intermittent phenomenon.

Microwave imaging of quasi-periodic pulsations at flare current sheet

Quasi-periodic pulsations (QPPs) are frequently detected in solar and stellar flares, but the underlying physical mechanisms are still to be ascertained. Here, we show microwave QPPs during a solar flare originating from quasi-periodic magnetic reconnection at the flare current sheet. They appear as two vertically detached but closely related sources with the brighter ones located at flare loops and the weaker ones along the stretched current sheet. Although the brightness temperatures of the two microwave sources differ greatly, they vary in phase with periods of about 10-20 s and 30-60 s. The gyrosynchrotron-dominated microwave spectra also present a quasi-periodic soft-hard-soft evolution. These results suggest that relevant high-energy electrons are accelerated by quasi-periodic reconnection, likely arising from the modulation of magnetic islands within the current sheet as validated by a 2.5-dimensional magnetohydrodynamic simulation.

High-Resolution Laboratory Measurements and Identification of Fe IX Lines near 171 Å

A multitude of weaker Fe IX lines have been predicted in the vicinity of the strong 171 Å line that dominates the spectra of many astrophysical and laboratory sources. Some of these weaker lines have only recently been identified in the laboratory, albeit some only tentatively. Here, we present measurements on the Livermore EBIT-I electron beam ion trap that span the region from 170.0 to 173.6 Å, which surrounds the 171 Å line. The measurements stepped through electron beam energy to determine the charge state of iron associated with each observed feature. Moreover, we have minimized the presence of oxygen in the trap, because oxygen lines obscured possible Fe IX lines in past measurements and prevented their identification. Our measurement confirms formerly tentative identifications and adds several new assignments.

Direct retrieval of Zernike-based pupil functions using integrated diffractive deep neural networks

Retrieving the pupil phase of a beam path is a central problem for optical systems across scales, from telescopes, where the phase information allows for aberration correction, to the imaging of near-transparent biological samples in phase contrast microscopy. Current phase retrieval schemes rely on complex digital algorithms that process data acquired from precise wavefront sensors, reconstructing the optical phase information at great expense of computational resources. Here, we present a compact optical-electronic module based on multi-layered diffractive neural networks printed on imaging sensors, capable of directly retrieving Zernike-based pupil phase distributions from an incident point spread function. We demonstrate this concept numerically and experimentally, showing the direct pupil phase retrieval of superpositions of the first 14 Zernike polynomials. The integrability of the diffractive elements with CMOS sensors shows the potential for the direct extraction of the pupil phase information from a detector module without additional digital post-processing.

Measurement of the Central Galactic Black Hole by Extremely Large Mass-Ratio Inspirals

In the galaxy, extremely large mass-ratio inspirals (X-MRIs) composed of brown dwarfs and the massive black hole at the galactic center are expected to be promising gravitational wave sources for space-borne detectors. In this work, we simulate the gravitational wave signals from twenty X-MRI systems by an axisymmetric Konoplya–Rezzolla–Zhidenko metric with varied parameters. We find that the mass, spin, and deviation parameters of the Kerr black hole can be determined accurately (∼10−5−10−6) with only one X-MRI event with a high signal-to-noise ratio. The measurement of the above parameters could be improved with more X-MRI observations.

Intersystem crossing in the entrance channel of the reaction of O(3P) with pyridine

Two quantum effects can enable reactions to take place at energies below the barrier separating reactants from products: tunnelling and intersystem crossing between coupled potential energy surfaces. Here we show that intersystem crossing in the region between the pre-reactive complex and the reaction barrier can control the rate of bimolecular reactions for weakly coupled potential energy surfaces, even in the absence of heavy atoms. For O(3P) plus pyridine, a reaction relevant to combustion, astrochemistry and biochemistry, crossed-beam experiments indicate that the dominant products are pyrrole and CO, obtained through a spin-forbidden ring-contraction mechanism. The experimental findings are interpreted-by high-level quantum-chemical calculations and statistical non-adiabatic computations of branching fractions-in terms of an efficient intersystem crossing occurring before the high entrance barrier for O-atom addition to the N-atom lone pair. At low to moderate temperatures, the computed reaction rates prove to be dominated by intersystem crossing.

A long-duration gamma-ray burst with a peculiar origin

It is generally believed that long-duration gamma-ray bursts (GRBs) are associated with massive star core collapse¹, whereas short-duration GRBs are associated with mergers of compact star binaries². However, growing observations^3-6 have suggested that oddball GRBs do exist, and several criteria (prompt emission properties, supernova/kilonova associations and host galaxy properties) rather than burst duration only are needed to classify GRBs physically⁷. A previously reported long-duration burst, GRB 060614 (ref. ³), could be viewed as a short GRB with extended emission if it were observed at a larger distance⁸ and was associated with a kilonova-like feature⁹. As a result, it belongs to the type I (compact star merger) GRB category and is probably of binary neutron star (NS) merger origin. Here we report a peculiar long-duration burst, GRB 211211A, whose prompt emission properties in many aspects differ from all known type I GRBs, yet its multiband observations suggest a non-massive-star origin. In particular, substantial excess emission in both optical and near-infrared wavelengths has been discovered (see also ref. ¹⁰), which resembles kilonova emission, as observed in some type I GRBs. These observations point towards a new progenitor type of GRBs. A scenario invoking a white dwarf (WD)-NS merger with a post-merger magnetar engine provides a self-consistent interpretation for all the observations, including prompt gamma rays, early X-ray afterglow, as well as the engine-fed^11,12 kilonova emission.

A kilonova following a long-duration gamma-ray burst at 350 Mpc

Gamma-ray bursts (GRBs) are divided into two populations^1,2; long GRBs that derive from the core collapse of massive stars (for example, ref. ³) and short GRBs that form in the merger of two compact objects^4,5. Although it is common to divide the two populations at a gamma-ray duration of 2 s, classification based on duration does not always map to the progenitor. Notably, GRBs with short (≲2 s) spikes of prompt gamma-ray emission followed by prolonged, spectrally softer extended emission (EE-SGRBs) have been suggested to arise from compact object mergers^6-8. Compact object mergers are of great astrophysical importance as the only confirmed site of rapid neutron capture (r-process) nucleosynthesis, observed in the form of so-called kilonovae^9-14. Here we report the discovery of a possible kilonova associated with the nearby (350 Mpc), minute-duration GRB 211211A. The kilonova implies that the progenitor is a compact object merger, suggesting that GRBs with long, complex light curves can be spawned from merger events. The kilonova of GRB 211211A has a similar luminosity, duration and colour to that which accompanied the gravitational wave (GW)-detected binary neutron star (BNS) merger GW170817 (ref. ⁴). Further searches for GW signals coincident with long GRBs are a promising route for future multi-messenger astronomy.

Gigaelectronvolt emission from a compact binary merger

An energetic γ-ray burst (GRB), GRB 211211A, was observed on 11 December 20211,2. Despite its long duration, typically associated with bursts produced by the collapse of massive stars, the observation of an optical-infrared kilonova points to a compact binary merger origin3. Here we report observations of a significant (more than five sigma) transient-like emission in the high-energy γ-rays of GRB 211211A (more than 0.1 gigaelectronvolts) starting 103 seconds after the burst. After an initial phase with a roughly constant flux (about 5 × 10-10 erg per second per square centimetre) lasting about 2 × 104 seconds, the flux started decreasing and soon went undetected. Our detailed modelling of public and dedicated multi-wavelength observations demonstrates that gigaelectronvolt emission from GRB 211211A is in excess with respect to the flux predicted by the state-of-the-art afterglow model at such late time. We explore the possibility that the gigaelectronvolt excess is inverse Compton emission owing to the interaction of a late-time, low-power jet with an external source of photons, and find that kilonova emission can provide the seed photons. Our results open perspectives for observing binary neutron star mergers.

Unraveling sulfur chemistry in interstellar carbon oxide ices

Formyl radical (HCO•) and hydroxycarbonyl radical (HOCO•) are versatile building blocks in the formation of biorelevant complex organic molecules (COMs) in interstellar medium. Understanding the chemical pathways for the formation of HCO• and HOCO• starting with primordial substances (e.g., CO and CO2) is of vital importance in building the complex network of prebiotic chemistry. Here, we report the efficient formation of HCO• and HOCO• in the photochemistry of hydroxidooxidosulfur radical (HOSO•)–a key intermediate in SO2 photochemistry–in interstellar analogous ices of CO and CO2 at 16 K through hydrogen atom transfer (HAT) reactions. Specifically, 266 nm laser photolysis of HOSO• embedded in solid CO ice yields the elusive hydrogen‑bonded complexes HCO•···SO2 and HOCO•···SO, and the latter undergoes subsequent HAT to furnish CO2···HOS• under the irradiation conditions. Similar photo-induced HAT of HOSO• in solid CO2 ice leads to the formation of HOCO•···SO2. The HAT reactions of HOSO• in astronomical CO and CO2 ices by forming reactive acyl radicals may contribute to understanding the interplay between the sulfur and carbon ice-grain chemistry in cold molecular clouds and also in the planetary atmospheric chemistry.

Interstellar Benzene Formation Mechanisms via Acetylene Cyclotrimerization Catalyzed by Fe+ Attached to Water Ice Clusters: Quantum Chemistry Calculation Study

Benzene is the simplest building block of polycyclic aromatic hydrocarbons and has previously been found in the interstellar medium. Several barrierless reaction mechanisms for interstellar benzene formation that may operate under low-temperature and low-pressure conditions in the gas phase have been proposed. In this work, we studied different mechanisms for interstellar benzene formation based on acetylene cyclotrimerization catalyzed by Fe⁺ bound to solid water clusters through quantum chemistry calculations. We found that benzene is formed via a single-step process with one transition state from the three acetylene molecules on the Fe⁺(H₂O)_n (n = 1, 8, 10, 12 and 18) cluster surface. Moreover, the obtained mechanisms differed from those of single-atom catalysis, in which benzene is sequentially formed via multiple steps.

A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars

The fine structure constant α sets the strength of the electromagnetic force. The Standard Model of particle physics provides no explanation for its value, which could potentially vary. The wavelengths of stellar absorption lines depend on α but are subject to systematic effects owing to astrophysical processes in stellar atmospheres. We measured precise line wavelengths from observations of 17 stars, selected to have almost identical atmospheric properties to those of the Sun (solar twins), which reduces those systematic effects. We found that α varies by ≲ 50 parts per billion within 50 parsecs from Earth. Combining the results from all 17 stars provides an empirical local reference for stellar measurements of α, with an ensemble precision of 12 parts per billion.

The discovery and scientific potential of fast radio bursts

Fast radio bursts (FRBs) are millisecond-time-scale bursts of coherent radio emission that are luminous enough to be detectable at cosmological distances. In this Review, I describe the discovery of FRBs, subsequent advances in understanding them, and future prospects. Thousands of potentially observable FRBs reach Earth every day, which likely originate from highly magnetic and/or rapidly rotating neutron stars in the distant Universe. Some FRBs repeat, with this subclass often occurring in highly magnetic environments. Two repeating FRBs exhibit cyclic activity windows, consistent with an orbital period. One nearby FRB was emitted by a Galactic magnetar during an x-ray outburst. The host galaxies of some FRBs have been located, providing information about the host environments and the total baryonic content of the Universe.