Detection of stellar light from quasar host galaxies at redshifts above 6.

The detection of starlight from the host galaxies of quasars during the reionization epoch (z > 6) has been elusive, even with deep Hubble Space Telescope observations1,2. The current highest redshift quasar host detected3, at z = 4.5, required the magnifying effect of a foreground lensing galaxy. Low-luminosity quasars4-6 from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP)7 mitigate the challenge of detecting their underlying, previously undetected host galaxies. Here we report rest-frame optical images and spectroscopy of two HSC-SSP quasars at z > 6 with the JWST. Using near-infrared camera imaging at 3.6 and 1.5 µm and subtracting the light from the unresolved quasars, we find that the host galaxies are massive (stellar masses of 13 × and 3.4 × 1010 M☉, respectively), compact and disc-like. Near-infrared spectroscopy at medium resolution shows stellar absorption lines in the more massive quasar, confirming the detection of the host. Velocity-broadened gas in the vicinity of these quasars enables measurements of their black hole masses (1.4 × 109 and 2.0 × 108 M☉, respectively). Their location in the black hole mass-stellar mass plane is consistent with the distribution at low redshift, suggesting that the relation between black holes and their host galaxies was already in place less than a billion years after the Big Bang.

Cu-Catalyzed Amination of Base-Sensitive Aryl Bromides and the Chemoselective N- and O-Arylation of Amino Alcohols.

We report a general and functional-group-tolerant method for the Cu-catalyzed amination of base-sensitive aryl bromides including substrates possessing acidic functional groups and small five-membered heteroarenes. The results presented herein substantially expand the scope of Cu-catalyzed C-N coupling reactions. The combination of L8, an anionic N1,N2-diarylbenzene-1,2-diamine ligand, along with the mild base NaOTMS leads to the formation of a stable yet reactive catalyst that resists deactivation from coordination to heterocycles or charged intermediates. This system enables the use of low catalyst and ligand loadings. Exploiting the differences in nucleophile deprotonation in C-O and C-N coupling reactions catalyzed by Cu·L8 we developed a method to chemoselectively N- and O-arylate a variety of amino alcohol substrates. Employing NaOt-Bu as the base resulted exclusively in C-O coupling when the amino alcohols featured primary alcohols and more hindered amines or aniline groups. Utilizing NaOTMS enabled the ability to override the steric-based selectivity of these reactions completely and exclusively promoted C-N coupling regardless of the structure of the amino alcohol. The ability to invert the observed chemoselectivity is distinct from previously described methods that require protecting group manipulations or rely entirely on steric effects to control reactivity. These results substantially improve the scope of Cu-catalyzed C-N coupling reactions using N1,N2-diarylbenzene-1,2-diamine ligands and introduce a new chemoselective method to arylate amino alcohols.

Two-Dimensional Polymers and Polymerizations.

Synthetic chemists have developed robust methods to synthesize discrete molecules, linear and branched polymers, and disordered cross-linked networks. However, two-dimensional polymers (2DPs) prepared from designed monomers have been long missing from these capabilities, both as objects of chemical synthesis and in nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization of covalently linked macromolecular sheets. Here we review 2DPs and 2D polymerization methods. Three predominant 2D polymerization strategies have emerged to date, which produce 2DPs either as monolayers or multilayer assemblies. We discuss the fundamental understanding and scope of each of these approaches, including: the bond-forming reactions used, the synthetic diversity of 2DPs prepared, their multilayer stacking behaviors, nanoscale and mesoscale structures, and macroscale morphologies. Additionally, we describe the analytical tools currently available to characterize 2DPs in their various isolated forms. Finally, we review emergent 2DP properties and the potential applications of planar macromolecules. Throughout, we highlight achievements in 2D polymerization and identify opportunities for continued study.

Room-Temperature Copper-Catalyzed Etherification of Aryl Bromides.

We disclose the development of a Cu-catalyzed C-O coupling method utilizing a new N1,N2-diarylbenzene-1,2-diamine ligand, L8. Under optimized reaction conditions, structurally diverse aryl and heteroaryl bromides underwent efficient coupling with a variety of alcohols at room temperature using an L8-based catalyst. Notably, the L8-derived catalyst exhibited enhanced activity when compared to the L4-based system previously disclosed for C-N coupling, namely the ability to functionalize aryl bromides containing acidic functional groups. Mechanistic studies demonstrate that C-O coupling utilizing L8 ⋅ Cu involves rate-limiting alkoxide transmetallation, resulting in a mechanism of C-O bond formation that is distinct from previously described Pd-, Cu-, or Ni-based systems. This lower energy pathway leads to rapid C-O bond formation; a 7-fold increase relative to what is seen with other ligands. The results presented in this report overcome limitations in previously described C-O coupling methods and introduce a new ligand that we anticipate may be useful in other Cu-catalyzed C-heteroatom bond-forming reactions.

Room-Temperature Cu-Catalyzed Amination of Aryl Bromides Enabled by DFT-Guided Ligand Design.

Ullmann-type C-N coupling reactions represent an important alternative to well-established Pd-catalyzed approaches due to the differing reactivity and the lower cost of Cu. While the design of anionic Cu ligands, particularly those by Ma, has enabled the coupling of various classes of aryl halides and alkyl amines, most methods require conditions that can limit their utility on complex substrates. Herein, we disclose the development of anionic N1,N2-diarylbenzene-1,2-diamine ligands that promote the Cu-catalyzed amination of aryl bromides under mild conditions. Guided by DFT calculations, these ligands were designed to (1) increase the electron density on Cu, thereby increasing the rate of oxidative addition of aryl bromides, and (2) stabilize the active anionic CuI complex via a π-interaction. Under optimized conditions, structurally diverse aryl and heteroaryl bromides and a broad range of alkyl amine nucleophiles, including pharmaceuticals bearing multiple functional groups, were efficiently coupled at room temperature. Combined computational and experimental studies support a mechanism of C-N bond formation that follows a catalytic cycle akin to the well-explored Pd-catalyzed variants. Modification of the ligand structure to include a naphthyl residue resulted in a lower energy barrier to oxidative addition, providing a 30-fold rate increase relative to what is seen with other ligands. Collectively, these results establish a new class of anionic ligands for Cu-catalyzed C-N couplings, which we anticipate may be extended to other Cu-catalyzed C-heteroatom and C-C bond-forming reactions.

Electronic Spin Qubit Candidates Arrayed within Layered Two-Dimensional Polymers.

Molecular electronic spin qubits are promising candidates for quantum information science applications because they can be reliably produced and engineered via chemical design. Embedding electronic spin qubits within two-dimensional polymers (2DPs) offers the possibility to systematically engineer inter-qubit interactions while maintaining long coherence times, both of which are prerequisites to their technological utility. Here, we introduce electronic spin qubits into a diamagnetic 2DP by n-doping naphthalene diimide subunits with varying amounts of CoCp2 and analyze their spin densities by quantitative electronic paramagnetic resonance spectroscopy. Low spin densities (e.g., 6.0 × 1012 spins mm-3) enable lengthy spin-lattice (T1) and spin-spin relaxation (T2) times across a range of temperatures, ranging from T1 values of 164 ms at 10 K to 30.2 µs at 296 K and T2 values of 2.36 µs at 10 K to 0.49 µs at 296 K for the lowest spin density sample examined. Higher spin densities and temperatures were both found to diminish T1 times, which we attribute to detrimental cross-relaxation from spin-spin dipolar interactions and spin-phonon coupling, respectively. Higher spin densities decreased T2 times and modulated the T2 temperature dependence. We attribute these differences to the competition between hyperfine and dipolar interactions for electron spin decoherence, with the dominant interaction transitioning from the former to the latter as spin density and temperature increase. Overall, this investigation demonstrates that dispersing electronic spin qubits within layered 2DPs enables chemical control of their inter-qubit interactions and spin decoherence times.

Single-Crystalline Imine-Linked Two-Dimensional Covalent Organic Frameworks Separate Benzene and Cyclohexane Efficiently.

Two-dimensional (2D) covalent organic frameworks (COFs) are composed of structurally precise, permanently porous, layered macromolecular sheets, which are traditionally synthesized as polycrystalline solids with crystalline domain lengths smaller than 100 nm. Here, we polymerize imine-linked 2D COFs as suspensions of faceted single crystals in as little as 5 min at moderate temperature and ambient pressure. Single crystals of two imine-linked 2D COFs were prepared, consisting of a rhombic 2D COF (TAPPy-PDA) and a hexagonal 2D COF (TAPB-DMPDA). The sizes of TAPPy-PDA and TAPB-DMPDA crystals were tuned from 720 nm to 4 µm and 450 nm to 20 µm in width, respectively. High-resolution transmission electron microscopy revealed that the COF crystals consist of layered, 2D polymers comprising single-crystalline domains. Continuous rotation electron diffraction resolved the unit cell and crystal structure of both COFs, which are single-crystalline in the a-b plane but disordered in the stacking c dimension. Single crystals of both COFs were incorporated into gas chromatography separation columns and exhibited unusual selective retention of cyclohexane over benzene, with single-crystalline TAPPy-PDA significantly outperforming single-crystalline TAPB-DMPDA. Polycrystalline TAPPy-PDA exhibited no separation, while polycrystalline TAPB-DMPDA exhibited poor separation and the opposite order of elution, retaining benzene more than cyclohexane, indicating the importance of improved material quality for COFs to exhibit properties that derive from their precise, crystalline structures. This work represents the first example of synthesizing imine-linked 2D COF single crystals at ambient pressure and short reaction times and demonstrates the promise of high-quality COFs for molecular separations.

The role of hyperbaric oxygen for acute traumatic ischemias.

Acute traumatic ischemias are an array of disorders that range from crush injuries to compartment syndromes, from burns to frostbite and from threatened flaps to compromised reimplantations. Two unifying components common to these conditions are a history of trauma be it physical, thermal, or surgical coupled with ischemia to the traumatized tissues. Their pathophysiology resolves around the self-perpetuating cycle of edema and ischemia, and their severity represents a spectrum from mild, almost non-existent, to tissue death. Since ischemia is a fundamental component of the traumatic ischemias and hypoxia is a consequence of ischemia, hyperbaric oxygen is a logical intervention for those conditions where tissue survival, infection control and healing is at risk. Unfortunately, even with mechanisms of hyperbaric oxygen that strongly support its usefulness in traumatic ischemias coupled with supportive clinical data, clinicians are disinclined to utilize it for these conditions. This focuses on the orthopedic aspects of the traumatic ischemias, namely crush injury and compartment syndrome, and show how hyperbaric oxygen treatments can mitigate their severity.

Delayed recognition of Type II decompression sickness in a diver with chronic atrial fibrillation.

Introduction: This case report describes an initially overlooked Type II decompression sickness (DCS) occurrence that was confused with a cerebral vascular accident in a patient with chronic atrial fibrillation (AF). The purpose of this case report is to reinforce the maxim that DCS needs to be suspected anytime a scuba diver experiences signs or symptoms compatible with DCS after completing a scuba dive. Methods: A 71-year-old scuba diver with a history of AF and who was taking warfarin made four dives, all with maximum depths less than 60 fsw (20 msw) over a 10-hour interval. Shoulder pain developed before entering the water on the fourth dive and was worse after exiting from the fourth dive. Twenty minutes later the diver collapsed while standing and was unable to make a grip using his left hand. A literature review failed to locate any case reports of divers with AF presenting with strokelike symptoms only to find the cause was Type II DCS.. Findings: Initially the patient's findings were reviewed with a diving medicine team. The recommendation was for the patient to be managed for a stroke. The patient was transferred to a hospital for a computed tomography scan, but no recommendation was made for a hyperbaric oxygen recompression treatment. The scan showed no brain bleed or infarct. The attending neurologist (not diving medicine-trained) was concerned that the patient's findings were diving-related and arranged for transferring the patient to a hyperbaric medicine facility 25 hours later. With hyperbaric oxygen (HBO2) therapy the patient's symptoms remitted over several weeks. Conclusion: The presence of symptoms attributed to a stroke immediately after a scuba dive should not deter a trial of HBO2 therapy. The delay in starting HBO2 therapy is concerning and perhaps the reason recovery was delayed and the need for repetitive HBO2 therapies.

Postsynthetic Modification of a Covalent Organic Framework Achieved via Strain-Promoted Cycloaddition.

Two-dimensional covalent organic frameworks (2D COFs) are layered, structurally regular, and permanently porous macromolecules. When reactive groups are embedded into a COF structure, subsequent chemical reactions can be performed following polymerization. As such, a postsynthetic modification (PSM) strategy provides diverse materials from a single set of COF monomers and polymerization protocols. Here, we report the synthesis of an asymmetric dibenzocyclooctyne-containing imine-linked 2D COF, which readily undergoes strain-promoted azide-alkyne cycloaddition (SPAAC) reactions without catalyst under mild and dilute conditions. This approach was used to quantitatively decorate the COF lattice with alkyl chains and amines, all without the need for exogenous species. Functionalization may result in spontaneous delamination of bulk COF materials into solution-stable sheets, demonstrating the utility of this technique. As such, this platform is useful for postsynthetic functionalization with sensitive chemical functionalities that are not amenable to direct polymerization or existing PSM strategies.

Lithium-Conducting Self-Assembled Organic Nanotubes.

Supramolecular polymers are compelling platforms for the design of stimuli-responsive materials with emergent functions. Here, we report the assembly of an amphiphilic nanotube for Li-ion conduction that exhibits high ionic conductivity, mechanical integrity, electrochemical stability, and solution processability. Imine condensation of a pyridine-containing diamine with a triethylene glycol functionalized isophthalaldehyde yields pore-functionalized macrocycles. Atomic force microscopy, scanning electron microscopy, and in solvo X-ray diffraction reveal that macrocycle protonation during their mild synthesis drives assembly into high-aspect ratio (>103) nanotubes with three interior triethylene glycol groups. Electrochemical impedance spectroscopy demonstrates that lithiated nanotubes are efficient Li+ conductors, with an activation energy of 0.42 eV and a peak room temperature conductivity of 3.91 ± 0.38 × 10-5 S cm-1. 7Li NMR and Raman spectroscopy show that lithiation occurs exclusively within the nanotube interior and implicates the glycol groups in facilitating efficient Li+ transduction. Linear sweep voltammetry and galvanostatic lithium plating-stripping tests reveal that this nanotube-based electrolyte is stable over a wide potential range and supports long-term cyclability. These findings demonstrate how the coupling of synthetic design and supramolecular structural control can yield high-performance ionic transporters that are amenable to device-relevant fabrication, as well as the technological potential of chemically designed self-assembled nanotubes.

Diverse Proton-Conducting Nanotubes via a Tandem Macrocyclization and Assembly Strategy.

Macrocycles that assemble into nanotubes exhibit emergent properties stemming from their low dimensionality, structural regularity, and distinct interior environments. We report a versatile strategy to synthesize diverse nanotube structures in a single, efficient reaction by using a conserved building block bearing a pyridine ring. Imine condensation of a 2,4,6-triphenylpyridine-based diamine with various aromatic dialdehydes yields chemically distinct pentagonal [5 + 5], hexagonal [3 + 3], and diamond-shaped [2 + 2] macrocycles depending on the substitution pattern of the aromatic dialdehyde monomer. Atomic force microscopy and in solvo X-ray diffraction demonstrate that protonation of the macrocycles under the mild conditions used for their synthesis drives assembly into high-aspect ratio nanotubes. Each of the pyridine-containing nanotube assemblies exhibited measurable proton conductivity by electrochemical impedance spectroscopy, with values as high as 10-3 S m-1 (90% R.H., 25 °C) that we attribute to differences in their internal pore sizes. This synthetic strategy represents a general method to access robust nanotube assemblies from a universal pyridine-containing monomer, which will enable systematic investigations of their emergent properties.

Trends in the thermal stability of two-dimensional covalent organic frameworks.

Two-dimensional covalent organic frameworks (2D COFs) are synthetically diverse, layered macromolecules. Their covalent lattices are thought to confer high thermal stability, which is typically evaluated with thermogravimetric analysis (TGA). However, TGA measures the temperature at which volatile degradation products are formed and is insensitive to changes of the periodic structure of the COF. Here, we study the thermal stability of ten 2D COFs using a combination of variable-temperature X-ray diffraction, TGA, diffuse reflectance infrared spectroscopy, and density functional theory calculations. We find that 2D COFs undergo a general two-step thermal degradation process. At the first degradation temperature, 2D COFs lose their crystallinity without chemical degradation. Then, at higher temperatures, they chemically degrade into volatile byproducts. Several trends emerge from this exploration of 2D COF stability. Boronate ester-linked COFs are generally more thermally stable than comparable imine-linked COFs. Smaller crystalline lattices are more robust to thermal degradation than chemically similar larger lattices. Finally, pore-functionalized COFs degrade at significantly lower temperatures than their unfunctionalized analogues. These trends offer design criteria for thermally resilient 2D COF materials. These findings will inform and encourage a broader exploration of mechanical deformation in 2D networks, providing a necessary step towards their practical use.

Optimizing Differentiated HIV Treatment Models in Urban Zimbabwe: Assessing Patient Preferences Using a Discrete Choice Experiment.

Differentiated service delivery holds great promise for streamlining the delivery of health services for HIV. This study used a discrete choice experiment to assess preferences for differentiated HIV treatment delivery model characteristics among 500 virally suppressed adults on antiretroviral therapy in Harare, Zimbabwe. Treatment model characteristics included location, consultation type, healthcare worker cadre, operation times, visit frequency and duration, and cost. A mixed effects logit model was used for parameter estimates to identify potential preference heterogeneity among participants, and interaction effects were estimated for sex and age as potential sources of divergence in preferences. Results indicated that participants preferred health facility-based services, less frequent visits, individual consultations, shorter waiting times, lower cost and, delivered by respectful and understanding healthcare workers. Some preference heterogeneity was found, particularly for location of service delivery and group vs. individual models; however, this was not fully explained by sex and age characteristics of participants. In urban areas, facility-based models, such as the Fast Track model requiring less frequent clinic visits, are likely to better align with patient preferences than some of the other community-based or group models that have been implemented. As Zimbabwe scales up differentiated treatment models for stable patients, a clear understanding of patient preferences can help in designing services that will ensure optimal utilization and improve the efficiency of service delivery.

RESUMEN: La entrega de servicios diferenciados representa una gran promesa para optimizar la prestación de servicios sanitarios para el VIH. Este estudio utilizó un experimento de elecciones discretas para evaluar las preferencias en cuanto a las características de los modelos diferenciados de prestación de tratamiento para el VIH entre 500 adultos con supresión viral bajo tratamiento antirretroviral en Harare, Zimbabue. Las características de los modelos de tratamientos incluyeron el lugar, el tipo de consulta, la estructura en la que estaba inserto el trabajador sanitario, los tiempos operativos, la frecuencia y duración de las visitas y los costos. Se utilizó un modelo de probabilidad de efectos mixtos para las estimaciones de los parámetros para identificar una posible heterogeneidad en las preferencias entre los participantes, y se estimaron los efectos de las interacciones por el sexo y la edad como fuentes potenciales de diferencia en las preferencias. Los resultados indicaron que los participantes preferían servicios basados en centros de salud, visitas menos frecuentes, consultas individuales, tiempos de espera más cortos y menores costos, proporcionados por trabajadores sanitarios respetuosos y comprensivos. Se hallaron algunas heterogeneidades en las preferencias, particularmente para el lugar de la prestación del servicio y para los modelos grupales frente a individuales; sin embargo, esto no se explicó totalmente por las características de sexo y edad de los participantes. En áreas urbanas, los modelos basados en los centros, como el modelo de atención rápida (Fast Track), que requieren visitas menos frecuentes a la clínica, probablemente concuerden mejor con las preferencias de los pacientes que los otros modelos grupales o comunitarios que se han propuesto. A medida que en Zimbabue se amplíen los modelos de tratamiento diferenciado para los pacientes estables, un claro conocimiento de las preferencias de los pacientes puede ayudar a diseñar servicios que garantizarán una utilización óptima y mejorarán la eficiencia de la prestación de servicios.

Nucleation-Elongation Dynamics of Two-Dimensional Covalent Organic Frameworks.

Homogeneous two-dimensional (2D) polymerization is a poorly understood process in which topologically planar monomers react to form planar macromolecules, often termed 2D covalent organic frameworks (COFs). While these COFs have traditionally been limited to weakly crystalline aggregated powders, they were recently grown as micron-sized single crystals by temporally resolving the growth and nucleation processes. Here, we present a quantitative analysis of the nucleation and growth rates of 2D COFs via kinetic Monte Carlo (KMC) simulations using COF-5 as an example, which show that nucleation and growth have second-order and first-order dependences on monomer concentration, respectively. The computational results were confirmed experimentally by systematic measurements of COF nucleation and growth rates performed via in situ X-ray scattering, which validated the respective monomer concentration dependencies of the nucleation and elongation processes. A major consequence is that there exists a threshold monomer concentration below which growth dominates over nucleation. Our computational and experimental findings rationalize recent empirical observations that, in the formation of 2D COF single crystals, growth dominates over nucleation when monomers are added slowly, so as to limit their concentrations. This mechanistic understanding of the nucleation and growth processes will inform the rational control of polymerization in two dimensions and ultimately enable access to high-quality samples of designed two-dimensional polymers.

New Mechanistic Insights into the Formation of Imine-Linked Two-Dimensional Covalent Organic Frameworks.

A more robust mechanistic understanding of imine-linked two-dimensional covalent organic frameworks (2D COFs) is needed to improve their crystalline domain sizes and to control their morphology, both of which are necessary to fully realize their application potential. Here, we present evidence that 2D imine-linked COFs rapidly polymerize as crystalline sheets that subsequently reorganize to form stacked structures. Primarily, this study focuses on the first few minutes of 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde polymerization, which yields an imine-linked 2D COF. In situ X-ray diffraction and thorough characterization of solids obtained using gentler isolation and activation methods than have typically been used in the literature indicate that periodic imine-linked 2D structures form within 60 s, which then form more ordered stacked structures over the course of several hours. This stacking process imparts improved stability toward the isolation process relative to that of the early stage materials, which likely obfuscated previous mechanistic conclusions regarding 2D polymerization that were based on products isolated using harsh activation methods. This revised mechanistic picture has useful implications; the 2D COF layers isolated at very short reaction times are easily exfoliated, as observed in this work using high-resolution transmission electron microscopy and atomic force microscopy. These results suggest improved control of imine-linked 2D COF formation can be obtained through manipulation of the polymerization conditions and interlayer interactions. Qualitatively similar results were obtained for analogous materials obtained from 2,5-di(alkoxy)terephthaldehyde derivatives, except for the COF with the longest alkoxy chains examined (OC12H25), which, although shown by in situ X-ray diffraction to be highly crystalline in the reaction mixture, is much less crystalline when isolated than the other COFs examined, likely due to the more severe steric impact of the dodecyloxy functionality on the stacking process.

Menstrual health management and schooling experience amongst female learners in Gauteng, South Africa: a mixed method study.

BACKGROUND: There has been increased attention to the menstrual health management (MHM) needs of girls and young women in Eastern and Southern Africa, relating to dignity, and to the potential link between the lack of access to sanitary products and school absenteeism. In the South Africa, there is inadequate evidence to guide appropriate national responses. This study explored the extent of access to modern sanitary products amongst female high school learners and the range of needs and challenges that they face in managing their menses in school settings in Gauteng, South Africa. METHODS: We collected mixed method data from 10 schools in Sedibeng district between June and August 2018. The qualitative component consisted of in-depth interviews with female learners (n = 30), educators (n = 8) and mothers of female learners (n = 9) and focus group discussions (FGDs) with male learners (n = 7) and female learners (n = 10). Five hundred and five female learners were recruited into the quantitative component consisting of a self-administered survey focussing on factors associated with access to sanitary products. RESULTS: The median age of survey participants was 17 years (interquartile range 16-18 years) and average age at menarche was 13.36 years. One in seven female learners reported not having enough sanitary products for every period in the last 3 months and this was reflected across the school quintiles. There was a complex interaction between menstrual-related challenges (physical discomfort, teasing, and feeling distracted in class) experienced by female learners, often amplified or compounded by factors in the school environment (unhygienic sanitation facilities and inadequate rest areas), and schooling participation and attendance. Girls who did not have enough products for every period in the last 3 months more likely reported missing school than those who reported sufficient products (46.27% vs 22.49% respectively, p < 0.001). However, there was no statistically significant difference between the groups in number of days missed. CONCLUSIONS: Provision of sanitary products is important but only one component of a comprehensive MHM response. Ongoing attention over the link between product access and absenteeism risks overlooking complex systemic and structural factors which can negatively impact the sexual and reproductive health of learners in the school context, and more broadly.

Toxic inoculation associated with a presumptive stingray injury.

INTRODUCTION: Stingray spine injuries are among the most common marine animal injuries in humans. While most resolve with immersion in warm water, a few become infected and require antibiotics. We present a case report of a presumptive stingray injury that evolved to a major slough and which required prolonged healing in a patient with diabetes mellitus. Our literature review was unable to find a similarly reported case. MATERIALS: A co-author was asked to evaluate and manage an ominous-appearing wound on the right foot of a diabetic. The problem developed after the individual had been wading in shallow ocean beach water. The patient's diabetic sensory neuropathy obscured the immediate association of the problem with a stingray injury, but this became the presumptive diagnosis when pain developed and necessitated that he seek medical care. FINDINGS/CLINICAL COURSE: After an initial urgent care visit, increasing pain and worsening appearance of the patient's foot necessitated a visit to our emergency department. The patient was admitted the next day due to symptoms of systemic sepsis. On the fourth hospital day, a large bulla on the lateral side of the right foot was excised. This unroofed a full-thickness slough to the periosteum level of the underlying bones. Not until the 16th hospital day had enough improvement occurred to discharge the patient. Over the next 16 weeks, the wound improved, developed a vascular base and epithelialized. CONCLUSION: With a dearth of literature about stingray injuries in patients with diabetes mellitus reported, our case is unique: The patient's wound course more closely resembled a toxic inoculation than the typical puncture wound-cellulitis presentations associated with stingray injuries.

HIV testing preferences among pregnant women attending antenatal care and their male partners: a discrete choice experiment in Uganda.

HIV testing rates remain stubbornly low among men - a crucial target population for reaching the ambitious global and regional goals of the HIV programme. In an era of declining donor funding, identifying cost-effective strategies to increase testing rates amongst men remains paramount. Antenatal care is an effective entry-point for the delivery of HIV testing services for women, and partner testing presents an important opportunity to reach their male partners. We present the results of a discrete choice experiment in Uganda, examining preferences among 824 pregnant women and 896 male partners regarding service delivery characteristics of HIV testing. Both men and women preferred nurse administered testing to self-testing (OR = 0.835; p < 0.001), oral testing over a finger-prick test (OR = 1.176; p < 0.001) and testing with a partner over testing alone (OR = 1.230; p < 0.001). Men had a preference for testing at home compared to testing at a clinic (OR = 1.099; p = 0.024), but women were indifferent regarding the testing location. The cost of testing had the biggest effect on preferences. Free testing was preferred over a cost of US$2.90 (OR = 0.781; p < 0.001) or US$2.00 (OR = 0.670; p < 0.001). Offering an incentive of US$3.40 increased men's preferences compared to a free test (OR = 1.168; p < 0.001), although this did not affect women's preferences. Partner testing linked to antenatal care is a potential strategy to increase testing coverage among men, particularly given the preference for partner testing - provided costs to clients remain low. Future cost-effectiveness evaluations should investigate the economic impact of reaching men using these strategies.

Cooperative Self-Assembly of Pyridine-2,6-Diimine-Linked Macrocycles into Mechanically Robust Nanotubes.

Nanotubes assembled from macrocyclic precursors offer a unique combination of low dimensionality, structural rigidity, and distinct interior and exterior microenvironments. Usually the weak stacking energies of macrocycles limit the length and mechanical strength of the resultant nanotubes. Imine-linked macrocycles were recently found to assemble into high-aspect ratio (>103 ), lyotropic nanotubes in the presence of excess acid. Yet these harsh conditions are incompatible with many functional groups and processing methods, and lower acid loadings instead catalyze macrocycle degradation. Here we report pyridine-2,6-diimine-linked macrocycles that assemble into high-aspect ratio nanotubes in the presence of less than 1 equiv of CF3 CO2 H per macrocycle. Analysis by gel permeation chromatography and fluorescence spectroscopy revealed a cooperative self-assembly mechanism. The low acid concentrations needed to induce assembly enabled nanofibers to be obtained by touch-spinning, which exhibit higher Young's moduli (1.33 GPa) than many synthetic polymers and biological filaments. These findings represent a breakthrough in the design of inverse chromonic liquid crystals, as assembly under such mild conditions will enable the design of structurally diverse and mechanically robust nanotubes from synthetically accessible macrocycles.