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Background Bronchoscopic lung volume reduction using endobronchial valves (EBV) has been shown to be beneficial for severe emphysema patients. The most important predictor of treatment response is absence of collateral ventilation between the treatment target and ipsilateral lobe. However, there are still a substantial number of nonresponders and it would be useful to improve the pre-treatment identification of responders. Presumably, predictors of response will be multifactorial, and therefore our aim was to explore whether we can identify response groups using a cluster analysis. Methods At baseline and 1 year follow-up, pulmonary function, exercise capacity and quality of life were measured. A quantitative chest computed tomography scan analysis was performed at baseline and 2–6 months follow-up. The cluster analysis was performed using a hierarchical agglomerative method. Results In total, 428 patients (69% female, mean±sd age 61±8 years, forced expiratory volume in 1 s 27±8% predicted, residual volume 254±50% pred) were included in our analysis. Three clusters were generated: one nonresponder cluster and two responder clusters. Despite solid technical procedures, the nonresponder cluster had significantly less clinical response after treatment compared to the other clusters. The nonresponder cluster was characterised by significantly less emphysematous destruction, less air trapping and a higher perfusion of the target lobe, and a more homogeneous distribution of emphysema and perfusion between the target and ipsilateral lobe. Conclusions We found that target lobe characteristics are the discriminators between responders and nonresponders, which underlines the importance of visual and quantitative assessment of the potential treatment target lobe when selecting patients for EBV treatment.

Background: Atrial fibrillation (AF) is one of the most common arrhythmias encountered in patients with SARS-CoV-2 infection. There are racial disparities in the incidence of AF and COVID-19. Several studies have reported an association between AF and mortality. However, it remains to be determined if AF represents an independent risk factor for COVID-19-related mortality. Methods: A propensity score-matched (PSM) analysis was performed using data from the National Inpatient Sample to assess the risk of mortality among patients hospitalized with SARS-CoV-2 infection and incident AF from March 2020 through December 2020. Results: AF was less common among patients who tested positive for SARS-CoV-2 as compared to those who tested negative (6.8% vs 7.4%, p

Empagliflozin, a sodium-glucose transporter 2 inhibitor, has been shown to bind to late sodium channels in mice cardiomyocytes. We sought to investigate the electrocardiographic (ECG) features associated with empagliflozin use in patients with diabetes mellitus. We compared ECG features of 101 patients before and after initiation of empagliflozin and found that empagliflozin was associated with a significant increase in QRS duration among diabetes patients with heart failure.

Background: Dissolvable antibiotic-loaded calcium sulfate beads are used as an intraoperative adjunct during debridement with antibiotics and implant retention (DAIR) for periprosthetic joint infections (PJI) to reduce the historically higher failure rates than one- or two-stage exchange. This study evaluated clinical outcomes after DAIRs performed with and without these antibiotic beads. The primary outcome was post-DAIR failure secondary to recurrent PJI at 2 years. The secondary outcome was early failure secondary to recurrent PJI within 90 days. Material and methods: DAIRs performed for acute or acute hematogenous PJI at a single institution were retrospectively identified between 2013 and 2018. All DAIRs with adjunctive antibiotic beads (cases) were then exactly matched to a cohort of DAIRs without beads (controls) based on Charlson Comorbidity Index. The McNemar’s test and Wilcoxon signed-rank test were used to evaluate differences in outcomes and patient characteristics. Results: Twenty DAIR cases (with antibiotic beads) were matched with 20 DAIR controls. There was no difference in age, sex, body mass index, joint, erythrocyte sedimentation rate, C-reactive protein, microbiology profile, antibiotic-resistance profile, or intraoperative lavage adjuncts between groups. There were no statistically significant differences between cases and controls for either overall infection-related failure at 2 years (P = .21) or early infection-related failure at 90 days (P = 1.00). Conclusion: Adjunctive dissolvable antibiotic-loaded calcium sulfate beads did not reduce the incidence of recurrent PJIs at 2 years or 90 days postoperatively after DAIR. Given the added cost of these antibiotic dissolvable beads without clinical benefits, we cannot recommend their use as an adjunct treatment during DAIRs.

Background: Periprosthetic femur fracture following total knee arthroplasty (TKA) is a devastating complication. Although trauma-related periprosthetic femur fractures have been well studied, early atraumatic insufficiency periprosthetic fractures (IPFs) are gaining attention. We present the largest IPF series to date to better understand and prevent this complication. Methods: A retrospective study of all patients who underwent a revision surgery for periprosthetic fracture within 6 months of primary TKA between 2007 and 2020 was performed. Patient demographics, preoperative radiographs, implant details, and fracture radiographs were reviewed. Alignment measurements and fracture characteristics were assessed. Results: Sixteen patients met criteria (rate 0.05%), and 11 had posterior-stabilized TKAs. The mean age was 79 years, mean body mass index was 31 kg/m2, and 94% (15/16) were female. Seven (47%) patients had a confirmed history of osteoporosis. IPF occurred on average 4 weeks (range, 4 days-13 weeks) after the index TKA. Overall, 12 of 16 (73%) had preoperative valgus deformities, and 11 patients (10 valgus, 1 varus) had preoperative deformities >10 degrees. A characteristic radiographic appearance of femoral condylar impaction and collapse was noted in 12 of 16 cases (75%); 11 of these 12 fractures (92%) involved the unloaded compartment based on preoperative varus/valgus deformity. Conclusions: Patients who developed IPFs were most commonly elderly, obese women with osteoporosis and severe preoperative valgus deformities. The apparent mechanism of failure was overloading of previously unloaded osteopenic femoral condyle. In high-risk patients, the use of a cruciate-retaining femoral component or a femoral stem for a posterior-stabilized femur may be considered to help avoid this catastrophic complication.

Abstract The traditionally held assumption that photo-dependent processes are the predominant source of H2O2 in natural waters has been recently questioned by an increrasing body of evidence showing the ubiquitiousness of H2O2 in dark water bodies and in groundwater. In this study, we conducted field measurement of H2O2 in an intra-meander hyporheic zone and in surface water at East River, CO. On-site detection using a sensitive chemiluminescence method suggests H2O2 concentrations in groundwater ranging from 6 nM (at the most reduced region) to ~ 80 nM (in a locally oxygen-rich area) along the intra-meander transect with a maxima of 186 nM detected in the surface water in an early afternoon, lagging the maximum solar irradiance by ∼ 1.5 h. Our results suggest that the dark profile of H2O2 in the hyporheic zone is closely correlated to local redox gradients, indicating that interactions between various redox sensitive elements could play an essential role. Due to its transient nature, the widespread presence of H2O2 in the hyporheic zone indicates the existence of a sustained balance between H2O2 production and consumption, which potentially involves a relatively rapid succession of various biogeochemically important processes (such as organic matter turnover, metal cycling and contaminant mobilization). More importantly, this study confirmed the occurrence of reactive oxygen species at a subsurface redox transition zone and further support our understanding of redox boundaries on reactive oxygen species generation and as key locations of biogeochemical activity.

Background Multiple studies have shown that patients with severe emphysema can significantly benefit from bronchoscopic lung volume reduction endobronchial valve (EBV) treatment up to 1 year after treatment. However, hardly any data exist on longer term follow-up, especially on quality of life. Our aim was to investigate long-term follow-up after EBV treatment up to 3 years including quality of life in a real-life routine clinical setting. Methods We retrospectively included patients who underwent EBV treatment in our hospital in the Netherlands at least 3 years prior. Patients were invited for annual visits to our hospital, and spirometry, body plethysmography, 6-min walk distance (6MWD) test and St George's Respiratory Questionnaire (SGRQ) were performed during these visits. Results At 1-, 2- and 3-year follow-up, data were available from 189, 146 and 112 patients, respectively. Forced expiratory volume in 1 s, residual volume and SGRQ total score significantly improved up to 3 years after treatment compared with baseline, and 6MWD up to 2 years after treatment. In general, the magnitude of improvements gradually decreased over time. Conclusions Our results show that patients can benefit at least up to 3 years after EBV treatment. For the first time we found that patients can also benefit in terms of quality of life in the long term, which is an important outcome for this group of patients with end-stage COPD.

Abstract A physically plausible lower bound on the spatially varying geostrophic mesoscale eddy energy dissipation time‐scale within the ocean, related to the geographical energy transfer rate out of the geostrophic mesoscales, is provided by means of a simple and computational inexpensive inverse calculation. Data diagnosed from a high resolution global configuration ocean simulation is supplied to a parameterized model of the geostrophic mesoscale eddy energy, from which the dissipation time‐scale results as a solution to an optimization calculation. We find that the dissipation time‐scale is shortest in the Southern Ocean, in the Western Boundary Currents, and on the western boundaries, consistent with the expectation that these regions are notable sites of baroclinic activity with processes leading to energy transfer out of the geostrophic mesoscales. Although our solution should be interpreted as a lower bound given the assumptions going into the calculation, it serves as an important physically consistent base line reference for further investigations into ocean energetics, as well as for an intended inference calculation that is more complete but also much more complex.

Abstract We present evidence that in ~ 1650 BCE (~ 3600 years ago), a cosmic airburst destroyed Tall el-Hammam, a Middle-Bronze-Age city in the southern Jordan Valley northeast of the Dead Sea. The proposed airburst was larger than the 1908 explosion over Tunguska, Russia, where a ~ 50-m-wide bolide detonated with ~ 1000× more energy than the Hiroshima atomic bomb. A city-wide ~ 1.5-m-thick carbon-and-ash-rich destruction layer contains peak concentrations of shocked quartz (~ 5–10 GPa); melted pottery and mudbricks; diamond-like carbon; soot; Fe- and Si-rich spherules; CaCO3 spherules from melted plaster; and melted platinum, iridium, nickel, gold, silver, zircon, chromite, and quartz. Heating experiments indicate temperatures exceeded 2000 °C. Amid city-side devastation, the airburst demolished 12+ m of the 4-to-5-story palace complex and the massive 4-m-thick mudbrick rampart, while causing extreme disarticulation and skeletal fragmentation in nearby humans. An airburst-related influx of salt (~ 4 wt.%) produced hypersalinity, inhibited agriculture, and caused a ~ 300–600-year-long abandonment of ~ 120 regional settlements within a > 25-km radius. Tall el-Hammam may be the second oldest city/town destroyed by a cosmic airburst/impact, after Abu Hureyra, Syria, and possibly the earliest site with an oral tradition that was written down (Genesis). Tunguska-scale airbursts can devastate entire cities/regions and thus, pose a severe modern-day hazard.

Permanent magnets constructed from metal ions and organic linkers using molecular design principles could bring transformative advances in areas such as energy conversion, transportation, and information storage. This comment highlights the recent discovery of a metal–organic magnet ordering at 242 °C, and discusses future research directions and possible applications involving such materials.

During the 1960s, small quantities of radioactive materials were co-disposed with chemical waste at the Little Forest Legacy Site (LFLS, Sydney, Australia). The microbial function and population dynamics in a waste trench during a rainfall event have been previously investigated revealing a broad abundance of candidate and potentially undescribed taxa in this iron-rich, radionuclide-contaminated environment. Applying genome-based metagenomic methods, we recovered 37 refined archaeal MAGs, mainly from undescribed DPANN Archaea lineages without standing in nomenclature and ‘Candidatus Methanoperedenaceae’ (ANME-2D). Within the undescribed DPANN, the newly proposed orders ‘Ca. Gugararchaeales’, ‘Ca. Burarchaeales’ and ‘Ca. Anstonellales’, constitute distinct lineages with a more comprehensive central metabolism and anabolic capabilities within the ‘Ca. Micrarchaeota’ phylum compared to most other DPANN. The analysis of new and extant ‘Ca. Methanoperedens spp.’ MAGs suggests metal ions as the ancestral electron acceptors during the anaerobic oxidation of methane while the respiration of nitrate/nitrite via molybdopterin oxidoreductases would have been a secondary acquisition. The presence of genes for the biosynthesis of polyhydroxyalkanoates in most ‘Ca. Methanoperedens’ also appears to be a widespread characteristic of the genus for carbon accumulation. This work expands our knowledge about the roles of the Archaea at the LFLS, especially, DPANN Archaea and ‘Ca. Methanoperedens’, while exploring their diversity, uniqueness, potential role in elemental cycling, and evolutionary history.

Flue-cured tobacco (Nicotiana tabacum L.) is a high value-per-acre crop that is intensively managed to optimise the yield of high-quality cured leaf. A 15-day study assessed the potential of hyperspectral reflectance data for detecting Phytophthora nicotianae (black shank) incidence in flue-cured tobacco. Hyperspectral reflectance data were taken from a commercial flue-cured tobacco field with a progressing black shank infestation. The effort encompassed two key objectives. First, develop hyperspectral indices and/or machine learning classification models capable of detecting Phytophthora nicotianae (black shank) incidence in flue-cured tobacco. Second, evaluate the model’s ability to separate pre-symptomatic plants from healthy plants. Two hyperspectral indices were developed to detect black shank incidence based on differences in the spectral profiles of asymptomatic flue-cured tobacco plants compared to those with black shank symptoms. While one of the indices is a broad-band index and the other uses narrow wavelength values, the statistical difference between the two indices was not significant and both provided an accurate classification of symptomatic plants. Further analysis of the indices showed significant differences between the index values of healthy and symptomatic plants (α = 0.05). In addition, the indices were able to detect black shank symptoms pre-symptomatically (α = 0.09). Subspace linear discriminant analysis, a machine learning classification, was also used for prediction of black shank incidence with up to 85.7 % classification accuracy. The implications of using either spectral indices or machine learning for classification for future black shank research are discussed.

Introduction Bronchoscopic lung volume reduction with endobronchial valves is an important treatment option in selected patients with severe emphysema and absence of collateral ventilation in the treatment target lobe. The Chartis system provides an important physiological assessment of the presence or absence of collateral ventilation. We aimed to evaluate a new feature and determine whether low flow during a Chartis measurement is predictive for the absence of collateral ventilation, and whether this allows for a procedure to be shortened by earlier terminating the Chartis measurement. This is measured with the “volume trend for the previous 20 s” (VT20). Methods We retrospectively evaluated 249 Chartis assessments of patients scheduled for bronchoscopic lung volume reduction procedures. The VT20 was calculated, and several thresholds were compared between patients with collateral ventilation (CV positive) and without collateral ventilation (CV negative). Results 100% of the CV negative patients reached a threshold of VT20 ≤6 mL, whereas all CV positive patients reached a VT20 ≥7 mL. The median “time saved” between VT20=6 mL and end of assessment was 60 s (range 5–354 s). Conclusion The threshold of VT20 ≤6 mL is a reliable method to exclude the presence of collateral ventilation when air flow rates are low and can therefore reduce bronchoscopic lung volume procedure times.

Abstract Background Cardiovascular events have been reported in the setting of coronavirus disease‐19 (COVID‐19). It has been hypothesized that systemic inflammation may aggravate arrhythmias or trigger new‐onset conduction abnormalities. However, the specific type and distribution of electrocardiographic disturbances in COVID‐19 as well as their influence on mortality remain to be fully characterized. Methods Electrocardiograms (ECGs) were obtained from 186 COVID‐19‐positive patients at a large tertiary care hospital in Northern Nevada. The following arrhythmias were identified by cardiologists: sinus bradycardia, sinus tachycardia, atrial fibrillation (A‐Fib), atrial flutter, multifocal atrial tachycardia (MAT), premature atrial contraction (PAC), premature ventricular contraction (PVC), atrioventricular block (AVB), and right bundle branch block (RBBB). The mean PR interval, QRS duration, and corrected QT interval were documented. Fisher's exact test was used to compare the ECG features of patients who died during the hospitalization with those who survived. The influence of ECG features on mortality was assessed with multivariable logistic regression analysis. Results A‐Fib, atrial flutter, and ST‐segment depression were predictive of mortality. In addition, the mean ventricular rate was higher among patients who died as compared to those who survived. The use of therapeutic anticoagulation was associated with reduced odds of death; however, this association did not reach statistical significance. Conclusion The underlying pathogenesis of COVID‐19‐associated arrhythmias remains to be established, but we postulate that systemic inflammation and/or hypoxia may induce potentially lethal conduction abnormalities in affected individuals. Longitudinal studies are warranted to evaluate the risk factors, pathogenesis, and management of COVID‐19‐associated cardiac arrhythmias.

Now that additional treatment options for severe chronic obstructive pulmonary disease (COPD) have emerged in recent years, patients with severe COPD should not be left in the rather hopeless situation of “there is nothing to improve” any more. Inertia or fatalism is a disservice to our patients. Ranging from advanced care planning to quite intense and demanding therapies such as multidisciplinary pulmonary rehabilitation, (endoscopic) lung volume reduction, chronic noninvasive ventilation and lung transplantation, caregivers should try to provide a personalised treatment for every severe COPD patient. In this review, we aim to describe the multidimensional approach to these patients at our centre along the lines of treatable traits leading to specific additional treatment modalities on top of standard care.

Magnesium and its alloys are ideal candidates for bioabsorbable implants. However, they can dissolve too rapidly in the human body for most applications. In this research, high purified magnesium (HP-Mg) was coated with stearic acid (SA) to slow the corrosion rate of magnesium in simulated body fluid at 37 ± 1 °C. HP-Mg was anodized (AC and DC voltages) to form an oxide/hydroxide layer, and then it was immersed in a SA solution. The SA coated layer surface, anodized layer, and the thickness of the oxide/hydroxide layer were investigated with Scanning Electron Microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were used to estimate the corrosion rate of HP-Mg specimens. The results confirm that the hydrophobic coating can decrease the corrosion rate of HP-Mg by more than 1000x. The protectiveness of coated layer for anodized specimens with AC voltage continue for 2 and 3 weeks. For the HP-Mg coated anodized with DC voltage, the coated layer could improve the corrosion resistance for only a few days. Keywords: Magnesium, Biomaterials, Hydrophobic layer, Stearic acid, Simulated body fluid, Electrochemical impedance spectroscopy

Background: In North Carolina, the Strengthen Opioid Misuse Prevention Act of 2017 (STOP Act) went into effect on January 1, 2018, intending to increase oversight over opioid prescriptions. This study compares postoperative narcotic prescription practices following operative fixation of ankle fractures before and after the STOP Act. Methods: This study was a retrospective review of patients 18 years and older who underwent operative fixation of ankle fractures between January 1 and June 30, 2017 (before STOP Act), and between January 1 and June 30, 2018 (after STOP Act). Variables of interest included demographics, amount of opioids prescribed postoperatively, number of prescription refills, and number of pain-related calls or visits to the emergency department (ED) or clinic after surgery. This study assessed 71 patients in the Pre group and 47 patients in the Post group. Results: There was a statistically significant decrease in the average number of postoperative narcotic pills prescribed after the STOP Act (52.7 vs 76.2, P < .001). There was also a statistically significant decrease in the average number of prescription refills (0.6 vs 1.0, P = .037). There were no significant changes in pain-related clinic calls (35.2% Pre vs 34.0% Post, P = .896), pain-related clinic visits ahead of schedule (4.2% Pre vs 6.4% Post, P = .681), or pain-related ED visits (2.8% Pre vs 10.6% Post, P = .113). Conclusion: In the postoperative period after operative fixation of ankle fractures, the volume of narcotic prescriptions decreased after the new legislation, without an associated strain on medical resources. Level of Evidence: Level III, therapeutic, comparative study.

While flow-electrode capacitive deionization (FCDI) operated in short-circuited closed cycle (SCC) mode appears to hold promise for removal of salt from brackish source waters, there has been limited investigation on the removal of other water constituents such as nitrate, fluoride or bromide in combination with salt removal. Of particular concern is the effectiveness of FCDI when ions, such as nitrate, are recognized to non-electrostatically adsorb strongly to activated carbon particles thereby potentially rendering it difficult to regenerate these particles. In this study, SCC FCDI was used to desalt source waters containing nitrate at different concentrations. Results indicate that nitrate can be removed from source waters using FCDI to concentrations

Parkinson's disease is the second most common neurodegenerative disease. While age is the most significant risk factor, the exact cause of this disease and the most effective approaches to mitigation remain unclear. It has long been proposed that dopamine may play a role in the pathology of Parkinson's disease in view of its ability to generate both protein-modifying quinones such as aminochrome and reactive oxygen species, especially in the presence of pathological iron accumulation in the primary site of neuron loss. Given the clinically measured acidosis of post-mortem Parkinson's disease brain tissue, the interaction between dopamine and iron was investigated over a pH range of 7.4 to 6.5 with emphasis on the accumulation of toxic quinones and generation of reactive oxygen species. Our results show that the presence of iron accelerates the formation of aminochrome with ferrous iron (Fe[II]) being more efficient in this regard than ferric iron (Fe[III]). Our results further suggest that a reduced aminochrome rearrangement rate coupled with an enhanced turnover rate of Fe[II] as a result of brain tissue acidosis could result in aminochrome accumulation within cells. Additionally, under these conditions, the enhanced redox cycling of iron in the presence of dopamine aggravates oxidative stress as a result of the production of damaging reactive species, including hydroxyl radicals.

Over the past decade, arthroscopic microfracture has become increasingly popular to treat full-thickness (Outerbridge grade IV) chondral defects of the hip. This procedure borrows marrow stimulation treatment principles and techniques from knee arthroscopy, with similar mixed clinical outcomes that may be more favorable in the short term (

Microfracture of hip chondral lesions has been performed for more than a decade with modified treatment principles and techniques from knee arthroscopy. This note and accompanying video review the pertinent techniques, pearls, and pitfalls of the microfracture procedure in the treatment of hip chondral lesions. After debridement of damaged chondral tissue, the size of the lesion is approximated to determine the number of microfracture holes to create. The working portal may be adjusted based on the site of the lesion. Microfracture picks of different angles are used to ensure perpendicular advancement to a depth of 3 to 4 mm in the subchondral bone. The holes are placed at a gap of approximately 3 to 4 mm. The debris is washed out to obtain open holes connecting the marrow with the articular surface. The microfracture procedure should be performed near the end of the overall procedure to secure the bleeding bone marrow within the joint and prevent washout.

The reaction between Fe(II) and H2O2 to yield hydroxyl radicals (HO•), the Fenton reaction, is of interest due to its role in trace metal and natural organic matter biogeochemistry, its utility in water treatment and its role in oxidative cell degradation and associated human disease. There is significant dispute over whether HO•, the most reactive of the so-called reactive oxygen species, is formed in this reaction, particularly under circumneutral conditions relevant to natural systems. In this work we have studied the oxidation kinetics of Fe(II) complexed by L = citrate, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) and also measured HO• production using phthalhydrazide as a probe compound at pH 8.2. It is shown that HO• is the sole product of the Fe(II)L-H2O2 reaction for L = EDTA and DTPA, with kinetic modelling of the full reaction pathway utilized to confirm this finding. Quantitative HO• production also appears likely for L = citrate, although uncertainties with the speciation of Fe(II)-citrate complexes as well as difficulties in modelling the oxidation kinetics of these complexes has prevented a definitive conclusion. In the absence of ligands at circumneutral pH, inorganic Fe(II) reacts with H2O2 to yield a species other than HO•, contrary to the well-established production of HO• from inorganic Fe(II) at low pH. Our results suggest that at high pH Fe(II) must be complexed for HO• production to occur.

Materials that simultaneously exhibit permanent porosity and high-temperature magnetic order could lead to advances in fundamental physics and numerous emerging technologies. Herein, we show that the archetypal molecule-based magnet and magnonic material V(TCNE)2 (TCNE = tetracyanoethylene) can be desolvated to generate a room-temperature microporous magnet. The solution-phase reaction of V(CO)6 with TCNE yields V(TCNE)2·0.95CH2Cl2, for which a characteristic temperature of T* = 646 K is estimated from a Bloch fit to variable-temperature magnetization data. Removal of the solvent under reduced pressure affords the activated compound V(TCNE)2, which exhibits a T* value of 590 K and permanent microporosity (Langmuir surface area of 850 m2/g). The porous structure of V(TCNE)2 is accessible to the small gas molecules H2, N2, O2, CO2, ethane, and ethylene. While V(TCNE)2 exhibits thermally activated electron transfer with O2, all the other studied gases engage in physisorption. The T* value of V(TCNE)2 is slightly modulated upon adsorption of H2 (T* = 583 K) or CO2 (T* = 596 K), while it decreases more significantly upon ethylene insertion (T* = 459 K). These results provide an initial demonstration of microporosity in a room-temperature magnet and highlight the possibility of further incorporation of small-molecule guests, potentially even molecular qubits, toward future applications.

Oxygen is a critical gas in numerous industries and is produced globally on a gigatonne scale, primarily through energy-intensive cryogenic distillation of air. The realization of large-scale adsorption-based air separations could enable a significant reduction in associated worldwide energy consumption and would constitute an important component of broader efforts to combat climate change. Certain small-scale air separations are carried out using N2-selective adsorbents, although the low capacities, poor selectivities, and high regeneration energies associated with these materials limit the extent of their usage. In contrast, the realization of O2-selective adsorbents may facilitate more widespread adoption of adsorptive air separations, which could enable the decentralization of O2 production and utilization and advance new uses for O2. Here, we present a detailed evaluation of the potential of metal-organic frameworks (MOFs) to serve as O2-selective adsorbents for air separations. Drawing insights from biological and molecular systems that selectively bind O2, we survey the field of O2-selective MOFs, highlighting progress and identifying promising areas for future exploration. As a guide for further research, the importance of moving beyond the traditional evaluation of O2 adsorption enthalpy, ΔH, is emphasized, and the free energy of O2 adsorption, ΔG, is discussed as the key metric for understanding and predicting MOF performance under practical conditions. Based on a proof-of-concept assessment of O2 binding carried out for eight different MOFs using experimentally derived capacities and thermodynamic parameters, we identify two existing materials and one proposed framework with nearly optimal ΔG values for operation under user-defined conditions. While enhancements are still needed in other material properties, the insights from the assessments herein serve as a guide for future materials design and evaluation. Computational approaches based on density functional theory with periodic boundary conditions are also discussed as complementary to experimental efforts, and new predictions enable identification of additional promising MOF systems for investigation.

ABSTRACT Host-specific serovars of Salmonella enterica often have large-scale chromosomal rearrangements that occur by recombination between rrn operons. Two hypotheses have been proposed to explain these rearrangements: (i) replichore imbalance from horizontal gene transfer drives the rearrangements to restore balance, or (ii) the rearrangements are a consequence of the host-specific lifestyle. Although recent evidence has refuted the replichore balance hypothesis, there has been no direct evidence for the lifestyle hypothesis. To test this hypothesis, we determined the rrn arrangement type for 20 Salmonella enterica serovar Typhi strains obtained from human carriers at periodic intervals over multiple years. These strains were also phage typed and analyzed for rearrangements that occurred over long-term storage versus routine culturing. Strains isolated from the same carrier at different time points often exhibited different arrangement types. Furthermore, colonies isolated directly from the Dorset egg slants used to store the strains also had different arrangement types. In contrast, colonies that were repeatedly cultured always had the same arrangement type. Estimated replichore balance of isolated strains did not improve over time, and some of the rearrangements resulted in decreased replicore balance. Our results support the hypothesis that the restricted lifestyle of host-specific Salmonella is responsible for the frequent chromosomal rearrangements in these serovars. IMPORTANCE Although it was previously thought that bacterial chromosomes were stable, comparative genomics has demonstrated that bacterial chromosomes are dynamic, undergoing rearrangements that change the order and expression of genes. While most Salmonella strains have a conserved chromosomal arrangement type, rearrangements are very common in host-specific Salmonella strains. This study suggests that chromosome rearrangements in the host-specific Salmonella enterica serovar Typhi, the causal agent of typhoid fever, occur within the human host over time. The results also indicate that rearrangements can occur during long-term maintenance on laboratory medium. Although these genetic changes do not limit survival under slow-growth conditions, they may limit the survival of Salmonella Typhi in other environments, as predicted for the role of pseudogenes and genome reduction in niche-restricted bacteria.