Characterization of Regolith And Trace Economic Resources (CRATER): An Orbitrap-based laser desorption mass spectrometry instrument for in situ exploration of the Moon.

RATIONALE: Characterization of Regolith And Trace Economic Resources (CRATER), an Orbitrap™-based laser desorption mass spectrometry instrument designed to conduct high-precision, spatially resolved analyses of planetary materials, is capable of answering outstanding science questions about the Moon's formation and the subsequent processes that have modified its (sub)surface. METHODS: Here, we describe the baseline design of the CRATER flight model, which requires <20 000 cm3  volume, <10 kg mass, and <60 W peak power. The analytical capabilities and performance metrics of a prototype that meets the full functionality of the flight model are demonstrated. RESULTS: The instrument comprises a high-power, solid-state, pulsed ultraviolet (213 nm) laser source to ablate the surface of the lunar sample, a custom ion optical interface to accelerate and collimate the ions produced at the ablation site, and an Orbitrap mass analyzer capable of discriminating competing isobars via ultrahigh mass resolution and high mass accuracy. The CRATER instrument can measure elemental and isotopic abundances and characterize the organic content of lunar surface samples, as well as identify economically valuable resources for future exploration. CONCLUSION: An engineering test unit of the flight model is currently in development to serve as a pathfinder for near-term mission opportunities.

A prospective cohort study of renal function and bone turnover in adults with hepatitis B virus (HBV)-HIV co-infection with high prevalence of tenofovir-based antiretroviral therapy use.

OBJECTIVE: Tenofovir disoproxil fumarate (TDF) is a common component of antiretroviral therapy in hepatitis B virus (HBV)-HIV co-infected adults but few studies have evaluated worsening renal function and bone turnover, known effects of TDF. METHODS: Adults from eight North American sites were enrolled in this cohort study. Research assessments were conducted at entry and every 24 weeks for ≤192 weeks. Bone markers were tested at baseline, week 96 and week 192 from stored serum. We evaluated changes in markers of renal function and bone turnover over time and potential contributing factors. RESULTS: A total of 115 patients were prospectively followed; median age 49 years, 91% male and 52% non-Hispanic Black. Duration of HIV was 20.5 years. TDF use ranged from 80% to 92% throughout follow-up. Estimated glomerular filtration rate (eGFR) (ml/min/1.73m2 ) decreased from 87.1 to 79.9 over 192 weeks (p < 0.001); however, the prevalence of eGFR <60 ml/min/1.73m2 did not appear to differ over time (always <16%; p = 0.43). From baseline to week 192, procollagen type I N-terminal propeptide (P1NP) (146.7 to 130.5 ng/ml; p = 0.001), osteocalcin (14.4 to 10.2 ng/ml; p < 0.001) and C-terminal telopeptides of type I collagen (CTX-1) (373 to 273 pg/ml; p < 0.001) decreased. Younger age, male sex and overweight/obesity versus normal weight predicted a decrease in eGRF. Black race, healthy weight versus underweight, advanced fibrosis, undetectable HBV DNA, and lower parathyroid hormone level predicted worsening bone turnover. CONCLUSION: In this HBV-HIV cohort with high prevalence of TDF use, several biomarkers of renal function and bone turnover indicated worsening status over approximately 4 years, highlighting the importance of clinical awareness in co-infected adults.

Effect of Electronic Nicotine Delivery Systems on Cigarette Abstinence in Smokers With No Plans to Quit: Exploratory Analysis of a Randomized Placebo-Controlled Trial.

INTRODUCTION: The extent to which use of electronic nicotine delivery systems (ENDS) for smoking reduction leads to cigarette abstinence in smokers with no plans to quit smoking is unclear. This exploratory analysis examined the effects of ENDS delivering different amounts of nicotine on cigarette abstinence up to 24-week follow-up, in comparison to placebo or a behavioral substitute. METHODS: This four-arm parallel-group, randomized, placebo-controlled trial took place at two academic medical centers in the United States (Penn State Hershey and Virginia Commonwealth University). Participants were current adult smokers (N = 520) interested in reducing but not planning to quit. They received brief advice and were randomized to one of four 24-week conditions, receiving either an eGo-style ENDS paired with 0, 8, or 36 mg/ml nicotine liquid (double-blind) or a cigarette-shaped tube, as a cigarette substitute (CS). Self-reported daily cigarette consumption and exhaled carbon monoxide (CO) were measured at all study visits. Outcomes included intent-to-treat, self-reported 7-day cigarette abstinence, biochemically confirmed by exhaled CO at 24 weeks after randomization. RESULTS: At 24 weeks, significantly more participants in the 36 mg/ml condition (14/130, 10.8%) than in the 0 mg/ml condition (1/130, 0.8%) and the CS condition (4/130, 3.1%) were abstinent (relative risk = 14 [95% CI = 1.9-104.9] and 3.5 [95% CI = 1.2-10.4], respectively). The abstinence rate in the 8 mg/ml condition was 4.6% (6/130). CONCLUSIONS: When smokers seeking to reduce smoking tried ENDS, few quit smoking in the short term. However, if smokers continued to use an ENDS with cigarette-like nicotine delivery, a greater proportion completely switched to ENDS, as compared with placebo or a cigarette substitute. IMPLICATIONS: The extent to which use of electronic nicotine delivery systems (ENDS) for smoking reduction leads to cigarette abstinence in smokers with no plans to quit smoking was unclear. This randomized trial found that ENDS with nicotine delivery approaching that of a cigarette are more effective in helping ambivalent smokers to quit cigarette smoking.

A combined helium atom scattering and density-functional theory study of the Nb(100) surface oxide reconstruction: Phonon band structures and vibrational dynamics.

Helium atom scattering and density-functional theory (DFT) are used to characterize the phonon band structure of the (3 × 1)-O surface reconstruction of Nb(100). Innovative DFT calculations comparing surface phonons of bare Nb(100) to those of the oxide surface show increased resonances for the oxide, especially at higher energies. Calculated dispersion curves align well with experimental results and yield atomic displacements to characterize polarizations. Inelastic helium time-of-flight measurements show phonons with mixed longitudinal and shear-vertical displacements along both the ⟨1̄00⟩, Γ̄X̄ and ⟨11̄0⟩, Γ̄M̄ symmetry axes over the entire first surface Brillouin zone. Force constants calculated for bulk Nb, Nb(100), and the (3 × 1)-O Nb(100) reconstruction indicate much stronger responses from the oxide surface, particularly for the top few layers of niobium and oxygen atoms. Many of the strengthened bonds at the surface create the characteristic ladder structure, which passivates and stabilizes the surface. These results represent, to our knowledge, the first phonon dispersion data for the oxide surface and the first ab initio calculation of the oxide's surface phonons. This study supplies critical information for the further development of advanced materials for superconducting radiofrequency cavities.

Photoelectron spectroscopic study of dipole-bound and valence-bound nitromethane anions formed by Rydberg electron transfer.

Close-lying dipole-bound and valence-bound states in the nitromethane anion make this molecule an ideal system for studying the coupling between these two electronically different states. In this work, dipole-bound and valence-bound nitromethane anions were generated by Rydberg electron transfer and characterized by anion photoelectron spectroscopy. The presence of the dipole-bound state was demonstrated through its photoelectron spectral signature, i.e., a single narrow peak at very low electron binding energy, its strong Rydberg quantum number, n*, dependence, and its relatively large anisotropy parameter, ß. This work goes the furthest yet in supporting the doorway model of electron attachment to polar molecules.

Observation of the dipole- and quadrupole-bound anions of 1,4-dicyanocyclohexane.

Quadrupole-bound anions are negative ions in which their excess electrons are loosely bound by long-range electron-quadrupole attractions. Experimental evidence for quadrupole-bound anions has been scarce; until now, only trans-succinonitrile had been experimentally confirmed to form a quadrupole-bound anion. In this study, we present experimental evidence for a new quadrupole-bound anion. Our combined Rydberg electron transfer/anion photoelectron spectroscopy study demonstrates that the ee conformer of 1,4-dicyanocyclohexane (DCCH) supports a quadrupole-bound anion state, and that the cis-DCCH conformer forms a dipole-bound anion state. The electron binding energies of the quadrupole- and dipole-bound anions are measured as 18 and 115 meV, respectively, both of which are in excellent agreement with theoretical calculations by Sommerfeld.

The ground state, quadrupole-bound anion of succinonitrile revisited.

Using a combination of Rydberg electron transfer and negative ion photoelectron spectroscopy, we revisited an earlier study which, based on several separate pieces of evidence, had concluded that trans- and gauche-succinonitrile can form quadrupole bound anions (QBAs) and dipole bound anions (DBAs), respectively. In the present work, succinonitrile anions were formed by Rydberg electron transfer and interrogated by negative ion photoelectron spectroscopy. The resulting anion photoelectron spectra exhibited distinctive spectral features for both QBA and DBA species in the same spectrum, thereby providing direct spectroscopic confirmation of previous indirect conclusions. Just as importantly, this work also introduces the integrated combination of Rydberg electron transfer and anion photoelectron spectroscopy as a powerful, tandem technique for studying diffuse excess electron states.

Separation of Isotopes in Space and Time by Gas-Surface Atomic Diffraction.

The separation of isotopes in space and time by gas-surface atomic diffraction is presented as a new means for isotopic enrichment. A supersonic beam of natural abundance neon is scattered from a periodic surface of methyl-terminated silicon, with the ^{20}Ne and ^{22}Ne isotopes scattering into unique diffraction channels. Under the experimental conditions presented in this Letter, a single pass yields an enrichment factor 3.50±0.30 for the less abundant isotope, ^{22}Ne, with extension to multiple passes easily envisioned. The velocity distribution of the incident beam is demonstrated to be the determining factor in the degree of separation between the isotopes' diffraction peaks. In cases where there is incomplete angular separation, the difference in arrival times of the two isotopes at a given scattered angle can be exploited to achieve complete temporal separation of the isotopes. This study explores the novel application of supersonic molecular beam studies as a viable candidate for separation of isotopes without the need for ionization or laser excitation.

Electrophilicity of oxalic acid monomer is enhanced in the dimer by intermolecular proton transfer.

We have analyzed the effect of excess electron attachment on the network of hydrogen bonds in the oxalic acid dimer (OA)2. The most stable anionic structures may be viewed as complexes of a neutral hydrogenated moiety HOA˙ coordinated to an anionic deprotonated moiety (OA-H)-. HOA˙ acts as a double proton donor and (OA-H)- as a double proton acceptor. Thus the excess electron attachment drives intermolecular proton transfer. We have identified several cyclic hydrogen bonded structures of (OA)2-. Their stability has been analyzed in terms of the stability of the involved conformers, the energetic penalty for deformation of these conformers to the geometry of the dimer, and the two-body interaction energy between the deformed HOA˙ and (OA-H)-. There are at least seven isomers of (OA)2- with stabilization energies in the range of 1.26-1.39 eV. These energies are dominated by attractive two-body interaction energies. The anions are vertically bound electronically by 3.0-3.4 eV and adiabatically bound by at least 1.6 eV. The computational predictions are consistent with the anion photoelectron spectrum of (OA)2-. The spectrum consists of a broad feature, with an onset of 2.5 eV and spanning to 4.3 eV. The electron vertical detachment energy (VDE) is assigned to be 3.3 eV.

The onset of electron-induced proton-transfer in hydrated azabenzene cluster anions.

The prospect that protons from water may be transferred to N-heterocyclic molecules due to the presence of an excess electron is studied in hydrated azabenzene cluster anions using anion photoelectron spectroscopy and computational chemistry. In the case of s-triazine (C3H3N3), which has a positive adiabatic electron affinity, proton transfer is not energetically favored nor observed experimentally. Heterocyclic rings with only 1 or 2 nitrogen atoms have negative electron affinities, but the addition of solvating water molecules can yield stable negative ions. In the case of the diazines (C4H4N2: pyrazine, pyrimidine, and pyridazine) the addition of one water molecule is enough to stabilize the negative ion, with the majority of the excess electron density in a π* orbital of the heterocycle but not significantly extended over the hydrogen bonded water network. Pyridine (C5H5N), with the most negative electron affinity, requires three water molecules to stabilize its negative ion. Although our computations suggest proton transfer to be energetically viable in all five N-heterocyclic systems studied here when three or more water molecules are present, proton transfer is not observed experimentally in the triazine nor in the diazine series. In pyridine, however, proton transfer competes energetically with hydrogen bonding (solvation), when three water molecules are present, i.e., both motifs are observed. Pyridine clusters containing four or more water molecules almost exclusively exhibit proton transfer along with solvated [C(6-x)H(6-x+1)N(x)·OH](-) ions.

The hydrogen bond strength of the phenol-phenolate anionic complex: a computational and photoelectron spectroscopic study.

The phenol-phenolate anionic complex was studied in vacuo by negative ion photoelectron spectroscopy using 193 nm photons and by density functional theory (DFT) computations at the ωB97XD/6-311+G(2d,p) level. We characterize the phenol-phenolate anionic complex as a proton-coupled phenolate pair, i.e., as a low-barrier hydrogen bond system. Since the phenol-phenolate anionic complex was studied in the gas phase, its measured hydrogen bond strength is its maximal ionic hydrogen bond strength. The D(PhO(-)···HOPh) interaction energy (26-30 kcal mol(-1)), i.e., the hydrogen bond strength in the PhO(-)···HOPh complex, is quite substantial. Block-localized wavefunction (BLW) computations reveal that hydrogen bonded phenol rings exhibit increased ring π-electron delocalization energies compared to the free phenol monomer. This additional stabilization may explain the stronger than expected proton donating ability of phenol.

Parent Anions of Iron, Manganese, and Nickel Tetraphenyl Porphyrins: Photoelectron Spectroscopy and Computations.

The singly charged, parent anions of three transition metal, tetraphenyl porphyrins, M(TPP) [Fe(TPP), Mn(TPP), and Ni(TPP)], were studied by negative ion photoelectron spectroscopy. The observed (vertical) transitions from the ground state anions of these porphyrins to the various electronic states of their neutral counterparts were modeled by density functional theory computations. Our experimental and theoretical results were in good agreement.

Carbon dioxide is tightly bound in the [Co(Pyridine)(CO2)](-) anionic complex.

The [Co(Pyridine)(CO2)](-) anionic complex was studied through the combination of photoelectron spectroscopy and density functional theory calculations. This complex was envisioned as a primitive model system for studying CO2 binding to negatively charged sites in metal organic frameworks. The vertical detachment energy (VDE) measured via the photoelectron spectrum is 2.7 eV. Our calculations imply a structure for [Co(Pyridine)(CO2)](-) in which a central cobalt atom is bound to pyridine and CO2 moieties on either sides. This structure was validated by acceptable agreement between the calculated and measured VDE values. Based on our calculations, we found CO2 to be bound within the anionic complex by 1.4 eV.

CO2 binding in the (quinoline-CO2)(-) anionic complex.

We have studied the (quinoline-CO2)(-) anionic complex by a combination of mass spectrometry, anion photoelectron spectroscopy, and density functional theory calculations. The (quinoline-CO2)(-) anionic complex has much in common with previously studied (N-heterocycle-CO2)(-) anionic complexes both in terms of geometric structure and covalent bonding character. Unlike the previously studied N-heterocycles, however, quinoline has a positive electron affinity, and this provided a pathway for determining the binding energy of CO2 in the (quinoline-CO2)(-) anionic complex. From the theoretical calculations, we found CO2 to be bound within the (quinoline-CO2)(-) anionic complex by 0.6 eV. We also showed that the excess electron is delocalized over the entire molecular framework. It is likely that the CO2 binding energies and excess electron delocalization profiles of the previously studied (N-heterocycle-CO2)(-) anionic complexes are quite similar to that of the (quinoline-CO2)(-) anionic complex. This class of complexes may have a role to play in CO2 activation and/or sequestration.

Strong, low-barrier hydrogen bonds may be available to enzymes.

The debate over the possible role of strong, low-barrier hydrogen bonds in stabilizing reaction intermediates at enzyme active sites has taken place in the absence of an awareness of the upper limits to the strengths of low-barrier hydrogen bonds involving amino acid side chains. Hydrogen bonds exhibit their maximal strengths in isolation, i.e., in the gas phase. In this work, we measured the ionic hydrogen bond strengths of three enzymatically relevant model systems in the gas phase using anion photoelectron spectroscopy; we calibrated these against the hydrogen bond strength of HF2(-), measured using the same technique, and we compared our results with other gas-phase experimental data. The model systems studied here, the formate-formic acid, acetate-acetic acid, and imidazolide-imidazole anionic complexes, all exhibit very strong hydrogen bonds, whose strengths compare favorably with that of the hydrogen bifluoride anion, the strongest known hydrogen bond. The hydrogen bond strengths of these gas-phase complexes are stronger than those typically estimated as being required to stabilize enzymatic intermediates. If there were to be enzyme active site environments that can facilitate the retention of a significant fraction of the strengths of these isolated (gas-phase), hydrogen bonded couples, then low-barrier hydrogen bonding interactions might well play important roles in enzymatic catalysis.

Photoelectron spectroscopic and computational study of hydrated pyrimidine anions.

The stabilization of the pyrimidine anion by the addition of water molecules is studied experimentally using photoelectron spectroscopy of mass-selected hydrated pyrimidine clusters and computationally using quantum-mechanical electronic structure theory. Although the pyrimidine molecular anion is not observed experimentally, the addition of a single water molecule is sufficient to impart a positive electron affinity. The sequential hydration data have been used to extrapolate to -0.22 eV for the electron affinity of neutral pyrimidine, which agrees very well with previous observations. These results for pyrimidine are consistent with previous studies of the hydrated cluster anions of uridine, cytidine, thymine, adenine, uracil, and naphthalene. This commonality suggests a universal effect of sequential hydration on the electron affinity of similar molecules.

Communication: Remarkable electrophilicity of the oxalic acid monomer: an anion photoelectron spectroscopy and theoretical study.

Our experimental and computational results demonstrate an unusual electrophilicity of oxalic acid, the simplest dicarboxylic acid. The monomer is characterized by an adiabatic electron affinity and electron vertical detachment energy of 0.72 and 1.08 eV (±0.05 eV), respectively. The electrophilicity results primarily from the bonding carbon-carbon interaction in the singly occupied molecular orbital of the anion, but it is further enhanced by intramolecular hydrogen bonds. The well-resolved structure in the photoelectron spectrum is reproduced theoretically, based on Franck-Condon factors for the vibronic anion → neutral transitions.

Enhancing patient outcomes: the role of clinical utility in guiding healthcare providers in curating radiology AI applications.

With advancements in artificial intelligence (AI) dominating the headlines, diagnostic imaging radiology is no exception to the accelerating role that AI is playing in today's technology landscape. The number of AI-driven radiology diagnostic imaging applications (digital diagnostics) that are both commercially available and in-development is rapidly expanding as are the potential benefits these tools can deliver for patients and providers alike. Healthcare providers seeking to harness the potential benefits of digital diagnostics may consider evaluating these tools and their corresponding use cases in a systematic and structured manner to ensure optimal capital deployment, resource utilization, and, ultimately, patient outcomes-or clinical utility. We propose several guiding themes when using clinical utility to curate digital diagnostics.

Increase in Charge and Density Improves the Strength and Toughness of Mussel Foot Protein 5 Inspired Protein Materials.

Mussel foot protein 5 (fp5) found in the adhesive byssal plaque of Mediterranean mussel Mytilus galloprovincialis exhibits exceptional underwater adhesion to diverse surfaces to the extent that adhesion strength typically exceeds the cohesive strength of the plaque. While sequence effects such as presence of charged residues, metal ion coordination, and high catechol content have been identified to govern fp5's interaction with surfaces, molecular contributors to its cohesive strength remain to be fully understood. Addressing this issue is critical for designing mussel-inspired sequences for new adhesives and biomaterials enabled by synthetic biology. Here we carry out all-atom molecular dynamics simulations on hydrated model fp5 biopolymer melts to understand how sequence features such as tyrosine and charge content affect packing density and inter-residue and ionic interaction strengths and consequently influence the cohesive strength and toughness. Systematic serine (S) substitutions for lysine (K), arginine (R) and tyrosine (Y) residues reveal that Y to S substitution surprisingly results in improvement of cohesive strength due to densification of the material by removal of steric hindrances, whereas the removal of charge in K and R to S substitutions has a detrimental impact on strength and toughness as it reduces cohesive interactions facilitated by electrostatic interactions. Additionally, melts formed from split fp5 sequences with only C or N terminal halves show distinct mechanical responses that further illustrate the role of charge. Our findings provide new insights for designing materials that could potentially surpass the performance of existing biomolecular and bioinspired adhesives, specifically by tailoring sequences for balancing charge and excluded volume effects.