Carbon monoxide gas produced by a giant impact in the inner region of a young system.

Models of terrestrial planet formation predict that the final stages of planetary assembly-lasting tens of millions of years beyond the dispersal of young protoplanetary disks-are dominated by planetary collisions. It is through these giant impacts that planets like the young Earth grow to their final mass and achieve long-term stable orbital configurations1. A key prediction is that these impacts produce debris. So far, the most compelling observational evidence for post-impact debris comes from the planetary system around the nearby 23-million-year-old A-type star HD 172555. This system shows large amounts of fine dust with an unusually steep size distribution and atypical dust composition, previously attributed to either a hypervelocity impact2,3 or a massive asteroid belt4. Here we report the spectrally resolved detection of a carbon monoxide gas ring co-orbiting with dusty debris around HD 172555 between about six and nine astronomical units-a region analogous to the outer terrestrial planet region of our Solar System. Taken together, the dust and carbon monoxide detections favour a giant impact between large, volatile-rich bodies. This suggests that planetary-scale collisions, analogous to the Moon-forming impact, can release large amounts of gas as well as debris, and that this gas is observable, providing a window into the composition of young planets.

Atmospheric characterization of terrestrial exoplanets in the mid-infrared: biosignatures, habitability, and diversity.

Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper, submitted to ESA in response to the Voyage 2050 Call, we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the mid-infrared wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large mid-infrared exoplanet mission within the scope of the "Voyage 2050" long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large mid-infrared exoplanet imaging mission will be needed to help answer one of humankind's most fundamental questions: "How unique is our Earth?"

Visualizing Cholesterol in the Brain by On-Tissue Derivatization and Quantitative Mass Spectrometry Imaging.

Despite being a critical molecule in the brain, mass spectrometry imaging (MSI) of cholesterol has been under-reported compared to other lipids due to the difficulty in ionizing the sterol molecule. In the present work, we have employed an on-tissue enzyme-assisted derivatization strategy to improve detection of cholesterol in brain tissue sections. We report distribution and levels of cholesterol across specific structures of the mouse brain, in a model of Niemann-Pick type C1 disease, and during brain development. MSI revealed that in the adult mouse, cholesterol is the highest in the pons and medulla and how its distribution changes during development. Cholesterol was significantly reduced in the corpus callosum and other brain regions in the Npc1 null mouse, confirming hypomyelination at the molecular level. Our study demonstrates the potential of MSI to the study of sterols in neuroscience.

Severe length-dependent peripheral polyneuropathy in a patient with subacute combined spinal cord degeneration secondary to recreational nitrous oxide abuse: A case report and literature review.

Nitrous oxide abuse can have detrimental effects on the central and peripheral nervous systems. This case study report aims to demonstrate a combination of severe generalized sensorimotor polyneuropathy and cervical myelopathy related to vitamin B12 deficiency following nitrous oxide abuse. We present a clinical case study and literature review examining primary research-published between 2012 and 2022-reporting nitrous oxide abuse affecting the spinal cord (myelopathy) and peripheral nerves (polyneuropathy); 35 articles were included in the review with a total of 96 patients, where the mean "patients" age was 23.9 years and were in a 2:1 male/female ratio. Of the 96 cases, within the review, 56% of patients were diagnosed with polyneuropathy, most commonly impacting the nerves of the lower limb (62%), while 70% of patients were diagnosed with myelopathy, most commonly impacting the cervical region (78%) on the spinal cord. In our clinical case study, a 28-year-old male underwent a multitude of diagnostic investigations for bilateral "foot drop" and sense of lower limb stiffness as ongoing complications of a vitamin B12 deficiency secondary to recreational nitrous oxide abuse. Both the literature review and our case report emphasize the dangers of recreational nitrous oxide inhalation, colloquially termed "nanging" and the risks it presents to both the central and peripheral nervous systems, which is erroneously considered by many recreational drug users to be less harmful than other illicit substances.

Relationship between molecular properties and degradation mechanisms of organic solar cells based on bis-adducts of phenyl-C61 butyric acid methyl ester.

Environmental stability remains a major challenge for the commercialisation of organic solar cells and degradation pathways remain poorly understood. Designing materials for improved device stability requires an understanding of the relationship between the properties of the donor or acceptor molecule and different degradation mechanisms. Here we study the correlations between various molecular parameters of the fullerene derivative bis-PCBM and the degradation rate of polymer:bis-PCBM organic solar cells, based on the same carbazole-alt-benzothiadiazole polymer, in aerobic and anaerobic conditions. We compare eight high purity bis-PCBM isomers with different electronic, chemical and packing properties along with PCBM and the mixture of bis isomers. In the case of aerobic photodegradation, we find that device degradation rate is positively correlated to the LUMO energy of the bis-PCBM isomer and to the degree of crystallinity of the isomer, while the correlation of degradation with driving force for epoxide formation is unclear. These results support the idea that in these samples, aerobic photodegradation proceeds via superoxide formation by the photogenerated polaron on the fullerene, followed by further chemical reaction. In the absence of air, photodegradation rate is correlated with molecular structure, supporting the mechanism of microstructural degradation via fullerene dimerization. The approach and findings presented here show how control of specific molecular parameters through chemical design can serve as a strategy to enhance stability of organic solar cells.

Mid-infrared images of beta Pictoris and the possible role of planetesimal collisions in the central disk.

When viewed in optical starlight scattered by dust, the nearly edge-on debris disk surrounding the A5V star beta Pictoris (distance 19.3 pc; ref. 1) extends farther than 1,450 au from the star. Its large-scale complexity has been well characterized, but the detailed structure of the disk's central approximately 200-au region has remained elusive. This region is of special interest, because planets may have formed there during the star's 10-20-million-year lifetime, perhaps resulting in both the observed tilt of 4.6 degrees relative to the large-scale main disk and the partial clearing of the innermost dust. A peculiarity of the central disk (also possibly related to the presence of planets) is the asymmetry in the brightness of the 'wings', in which the southwestern wing is brighter and more extended at 12 microm than the northeastern wing. Here we present thermal infrared images of the central disk that imply that the brightness asymmetry results from the presence of a bright clump composed of particles that may differ in size from dust elsewhere in the disk. We suggest that this clump results from the collisional grinding of resonantly trapped planetesimals or the cataclysmic break-up of a planetesimal.

Accurate mass measurement by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. II. Measurement of negative radical ions using porphyrin and fullerene standard reference materials.

A method for the accurate mass measurement of negative radical ions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is described. This is an extension to our previously described method for the accurate mass measurement of positive radical ions (Griffiths NW, Wyatt MF, Kean SD, Graham AE, Stein BK, Brenton AG. Rapid Commun. Mass Spectrom. 2010; 24: 1629). The porphyrin standard reference materials (SRMs) developed for positive mode measurements cannot be observed in negative ion mode, so fullerene and fluorinated porphyrin compounds were identified as effective SRMs. The method is of immediate practical use for the accurate mass measurement of functionalised fullerenes, for which negative ion MALDI-TOFMS is the principal mass spectrometry characterisation technique. This was demonstrated by the accurate mass measurement of six functionalised C(60) compounds.

Accurate mass measurement by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. I. Measurement of positive radical ions using porphyrin standard reference materials.

A method for the accurate mass measurement of positive radical ions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is described. Initial use of a conjugated oligomeric calibration material was rejected in favour of a series of meso-tetraalkyl/tetraalkylaryl-functionalised porphyrins, from which the two calibrants required for a particular accurate mass measurement were chosen. While all measurements of monoisotopic species were within +/-5 ppm, and the method was rigorously validated using chemometrics, mean values of five measurements were used for extra confidence in the generation of potential elemental formulae. Potential difficulties encountered when measuring compounds containing multi-isotopic elements are discussed, where the monoisotopic peak is no longer the lowest mass peak, and a simple mass-correction solution can be applied. The method requires no significant expertise to implement, but care and attention is required to obtain valid measurements. The method is operationally simple and will prove useful to the analytical chemistry community.

Investigation of solvent-free MALDI-TOFMS sample preparation methods for the analysis of organometallic and coordination compounds.

An investigation of various solvent-free matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) sample preparation methods for the characterization of organometallic and coordination compounds is described. Such methods are desirable for insoluble materials, compounds that are only soluble in disadvantageous solvents, or complexes that dissociate in solution, all of which present a major "difficulty" to most mass spectrometry techniques. First-row transition metal acetylacetonate complexes, which have been characterized previously by solution preparation MALDI-TOFMS, were used to evaluate the various solvent-free procedures. These procedures comprise two distinct steps: the first being the efficient "solids mixing" (the mixing of sample and matrix), and the second being the effective transfer of the sample/matrix mixture to the MALDI target plate. This investigation shows that vortex mixing is the most efficient first step and that smearing using a microspatula is the most effective second step. In addition, the second step is shown to be much more critical than the first step in obtaining high-quality data. Case studies of truly insoluble materials highlight the importance of these techniques for the wider chemistry community.

Toward Improved Environmental Stability of Polymer:Fullerene and Polymer:Nonfullerene Organic Solar Cells: A Common Energetic Origin of Light- and Oxygen-Induced Degradation.

With the emergence of nonfullerene electron acceptors resulting in further breakthroughs in the performance of organic solar cells, there is now an urgent need to understand their degradation mechanisms in order to improve their intrinsic stability through better material design. In this study, we present quantitative evidence for a common root cause of light-induced degradation of polymer:nonfullerene and polymer:fullerene organic solar cells in air, namely, a fast photo-oxidation process of the photoactive materials mediated by the formation of superoxide radical ions, whose yield is found to be strongly controlled by the lowest unoccupied molecular orbital (LUMO) levels of the electron acceptors used. Our results elucidate the general relevance of this degradation mechanism to both polymer:fullerene and polymer:nonfullerene blends and highlight the necessity of designing electron acceptor materials with sufficient electron affinities to overcome this challenge, thereby paving the way toward achieving long-term solar cell stability with minimal device encapsulation.

A planetesimal orbiting within the debris disc around a white dwarf star.

Many white dwarf stars show signs of having accreted smaller bodies, implying that they may host planetary systems. A small number of these systems contain gaseous debris discs, visible through emission lines. We report a stable 123.4-minute periodic variation in the strength and shape of the Ca ii emission line profiles originating from the debris disc around the white dwarf SDSS J122859.93+104032.9. We interpret this short-period signal as the signature of a solid-body planetesimal held together by its internal strength.

Strategies for the analysis of poly(methacrylic acid) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

We evaluated several aqueous-based sample preparation protocols for the analysis of poly(methacrylic acid) (PMAA) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The sample contained a pentaerythritol tetra(3-mercaptopropionate) end-group, and was characterized in positive and negative ion modes using 2,5-dihydroxybenzoic acid (DHB) and 2,4,6-trihydroxyacetophenone (THAP) matrices. The major series observed were the [M + Na](+) species, in positive ion mode, and the [M - H](-) species, in negative ion mode. The performance of DHB and THAP matrices was comparable in positive ion mode, but THAP outperformed DHB in negative ion mode. The use of ion-exchange beads (IXB) benefited the analysis, while the addition of sodium acetate (NaOAc) or trifluoroacetic acid (TFA) proved disadvantageous in positive ion mode.

The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc.

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

An Efficient, "Burn in" Free Organic Solar Cell Employing a Nonfullerene Electron Acceptor.

A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'″-di(2-octyldodecyl)-2,2';5',2″;5″,2'″-quaterthiophen-5,5'″-diyl)] (PffBT4T-2OD) as a donor polymer blended with either the nonfullerene acceptor EH-IDTBR or the fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC71 BM) as electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9.5 ± 0.2%. The devices exhibit a high open circuit voltage of 1.08 ± 0.01 V, attributed to the high lowest unoccupied molecular orbital (LUMO) level of EH-IDTBR. Photoluminescence quenching and transient absorption data are employed to elucidate the ultrafast kinetics and efficiencies of charge separation in both blends, with PffBT4T-2OD exciton diffusion kinetics within polymer domains, and geminate recombination losses following exciton separation being identified as key factors determining the efficiency of photocurrent generation. Remarkably, while encapsulated PffBT4T-2OD:PC71 BM solar cells show significant efficiency loss under simulated solar irradiation ("burn in" degradation) due to the trap-assisted recombination through increased photoinduced trap states, PffBT4T-2OD:EH-IDTBR solar cell shows negligible burn in efficiency loss. Furthermore, PffBT4T-2OD:EH-IDTBR solar cells are found to be substantially more stable under 85 °C thermal stress than PffBT4T-2OD:PC71 BM devices.

Investigation into accurate mass capability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, with respect to radical ion species.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been shown to be an effective technique for the characterization of organometallic, coordination, and highly conjugated compounds. The preferred matrix is 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), with radical ions observed. However, MALDI-TOFMS is generally not favored for accurate mass measurement. A specific method had to be developed for such compounds to assure the quality of our accurate mass results. Therefore, in this preliminary study, two methods of data acquisition, and both even-electron (EE+) ion and odd-electron (OE+.) radical ion mass calibration standards, have been investigated to establish the basic measurement technique. The benefit of this technique is demonstrated for a copper compound for which ions were observed by MALDI, but not by electrospray (ESI) or liquid secondary ion mass spectrometry (LSIMS); a mean mass accuracy error of -1.2 ppm was obtained.

MALDI-TOFMS analysis of coordination and organometallic complexes: a nic(h)e area to work in.

A mini-review of the characterisation of metal-containing compounds by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is presented. Organometallic and coordination compounds have many varied applications, most notably in industrial catalytic processes and also in the electronics and healthcare sectors. In general, the compounds discussed, be they small or large molecules, have a high percentage metal content, rather than simply containing 'a metal atom'. A brief history of the field is given, but the main scope over the last 5 years is covered in some detail. How MALDI-TOFMS compliments electrospray for metal-containing compounds is highlighted. Perspectives on recent advances, such as solvent-free and air/moisture-sensitive sample preparation, and potential future challenges and developments, such as nanomaterials and metallodrug/metallometabolite imaging, are given.

Analysis of various organic and organometallic compounds using nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS).

Nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS) has been developed recently as a matrix-free/surface-assisted alternative to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The NALDI surface of silicon nanowires is already very effective for the analysis of small to medium sized, polar organic molecules in positive ion mode. The current study examined this technology for the analysis of several nonpolar organic, organometallic, and ionic compounds in positive ion mode, as well as a fluorinated compound and various acids in negative ion mode. NALDI data are compared and contrasted with MALDI data for the same compounds, and the higher sensitivity of NALDI is highlighted by the successful characterization of two porphyrins for a sample amount of 10 amol per spot.

Analysis of transition-metal acetylacetonate complexes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Transition-metal acetylacetonate complexes of the form Metal(acac)(2), where Metal = Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), and Metal(acac)(3), where Metal = V(III), Cr(III), Mn(III), Fe(III), and Co(III), were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The data was acquired using the aprotic, electron transfer matrix, 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), and the observation of positive radical ions is shown clearly to depend on the metal element and the oxidation state it occupies. The ionization energy of DCTB was calculated to be 8.08 eV by density functional theory methods, which is notably lower than the experimental value, but within the range of other computational values. This value is very close to those of the analytes, so the existing electron transfer mechanism which is based on the ionization energies of the matrix and analyte, cannot be used predictively. Similarly, the data neither proves nor disproves the validity of the existing electron transfer ionization mechanism, with respect to metal coordination complexes without strong chromophores. In this case, periodic trends may be more useful in explaining the observed species and the prediction of species from sets of similar complexes. The addition of a sodium salt benefits the MALDI-TOFMS characterization of certain compounds studied, but the benefit of the addition of ammonium or silver salts is negligible.

Characterisation of organometallic and coordination compounds by solvent-free matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry.

Insoluble or low solubility organometallic and coordination compounds have been characterised by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, with solvent-free sample preparation being the key step toward successful analysis.

Design of polymeric stabilizers for size-controlled synthesis of monodisperse gold nanoparticles in water.

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (approximately 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.