Near-atomic-resolution structure of J-aggregated helical light-harvesting nanotubes.

Cryo-electron microscopy has delivered a resolution revolution for biological self-assemblies, yet only a handful of structures have been solved for synthetic supramolecular materials. Particularly for chromophore supramolecular aggregates, high-resolution structures are necessary for understanding and modulating the long-range excitonic coupling. Here, we present a 3.3 Å structure of prototypical biomimetic light-harvesting nanotubes derived from an amphiphilic cyanine dye (C8S3-Cl). Helical 3D reconstruction directly visualizes the chromophore packing that controls the excitonic properties. Our structure clearly shows a brick layer arrangement, revising the previously hypothesized herringbone arrangement. Furthermore, we identify a new non-biological supramolecular motif-interlocking sulfonates-that may be responsible for the slip-stacked packing and J-aggregate nature of the light-harvesting nanotubes. This work shows how independently obtained native-state structures complement photophysical measurements and will enable accurate understanding of (excitonic) structure-function properties, informing materials design for light-harvesting chromophore aggregates.

Efficient 2D to 0D Energy Transfer in HgTe Nanoplatelet-Quantum Dot Heterostructures through High-Speed Exciton Diffusion.

Large area absorbers with localized defect emission are of interest for energy concentration via the antenna effect. Transfer between 2D and 0D quantum-confined structures is advantageous as it affords maximal lateral area antennas with continuously tunable emission. We report the quantum efficiency of energy transfer in in situ grown HgTe nanoplatelet (NPL)/quantum dot (QD) heterostructures to be near unity (>85%), while energy transfer in separately synthesized and well separated solutions of HgTe NPLs to QDs only reaches 47 ± 11% at considerably higher QD concentrations. Using Kinetic Monte Carlo simulations, we estimate an exciton diffusion constant of 1-10 cm2/s in HgTe NPLs, the same magnitude as that of 2D semiconductors. We also simulate in-solution energy transfer between NPLs and QDs, recovering an R-4 dependence consistent with 2D-0D near-field energy transfer even in randomly distributed NPL/QD mixtures. This highlights the advantage of NPLs 2D morphology and the efficiency of NPL/QD heterostructures and mixtures for energy harvesting.

Exploring the design of superradiant J-aggregates from amphiphilic monomer units.

Excitonic chromophore aggregates have wide-ranging applicability in fields such as imaging and energy harvesting; however their rational design requires adapting principles of self-assembly to the requirements of excited state coupling. Using the well-studied amphiphilic cyanine dye C8S3 as a template-known to assemble into tubular excitonic aggregates-we synthesize several redshifted variants and study their self-assembly and photophysics. The new pentamethine dyes retain their tubular self-assembly and demonstrate nearly identical bathochromic shifts and lineshapes well into near-infrared wavelengths. However, detailed photophysical analysis finds that the new aggregates show a significant decline in superradiance. Additionally, cryo-TEM reveals that these aggregates readily form short bundles of nanotubes that have nearly half the radii of their trimethine comparators. We employ computational screening to gain intuition on how the structural components of these new aggregates affect their excitonic states, finding that the narrower tubes are able to assemble into a larger number of arrangements, resulting in more disordered aggregates (i.e. less superradiant) with highly similar degrees of redshift.

Point-of-Care Screening for a Current Hepatitis C Virus Infection: Influence on Uptake of a Concomitant Offer of HIV Screening.

Eliminating hepatitis C as a public health threat requires an improved understanding of how to increase testing uptake. We piloted point-of-care testing (POCT) for a current HCV infection in an inner-city Emergency Department (ED) and assessed the influence on uptake of offering concomitant screening for HIV. Over four months, all adults attending ED with minor injuries were first invited to complete an anonymous questionnaire then invited to test in alternating cycles offering HCV POCT or HCV+HIV POCT. Viral RNA was detected in finger-prick blood by GeneXpert. 814/859 (94.8%) questionnaires were returned and 324/814 (39.8%) tests were accepted, comprising 211 HCV tests and 113 HCV+HIV tests. Offering concomitant HIV screening reduced uptake after adjusting for age and previous HCV testing (odds ratio 0.51; 95% confidence interval [CI] 0.38-0.68; p < 0.001). HCV prevalence was 1/324 (0.31%; 95% CI 0.05-1.73); no participant tested positive for HIV. 167/297 (56.2%) POCT participants lived in the most deprived neighbourhoods in England. HCV RNA testing using finger-prick blood was technically feasible. Uptake was moderate and the offer of concomitant HIV screening showed a detrimental impact on acceptability in this low prevalence population. The findings should be confirmed in a variety of other community settings.

Adaptation of a behavioral parent-training curriculum for Hispanic caregivers: HOT DOCS Español.

This article presents the process utilized to adapt a behavioral parent-training curriculum for Hispanic caregivers from a program currently available in English. Throughout this process, a number of cultural and language elements were identified as needing to be modified to meet the needs of the Hispanic population served. Fidelity and fit were balanced to develop a curriculum acceptable to diverse Hispanic caregivers while also incorporating all the essential elements of a theory-based approach to training caregivers. The lessons learned from this adaptation may assist others in their attempts to meet the needs of Hispanic families.

Exposure to death is associated with positive attitudes and higher knowledge about end-of-life care in graduating medical students.

OBJECTIVE: To examine the relationship between exposure to death and attitudes and knowledge about end-of-life care in graduating medical students. PARTICIPANTS AND METHODS: Survey of students graduating from the University of Pittsburgh School of Medicine between 2001 and 2006. Students reported their personal experience with death and their exposure to death and dying patients during medical school. They rated their agreement, on a 4-point Likert scale, with 8 attitude items that were previously used in a national survey. Knowledge about end-of-life care was assessed with a 15-item test about pain and symptom management, ethics, treatment appropriateness, and hospice. RESULTS: Three hundred and eighty students completed the survey; the response rate was 47%. Seventy-six percent of students reported personal experience with death, and 73% reported caring for dying patients or witnessing a patient's death during their third-year clerkships. Students had positive attitudes about physicians' responsibility and ability to help dying patients and their families, but reported negative emotional reactions to end-of-life care. Students who reported personal or professional experience with death had more positive attitudes and higher knowledge scores than those who did not, p = 0.05. CONCLUSIONS: Educational initiatives should maximize the time medical students spend caring for dying patients. Teaching students end-of-life care during the course of their clinical clerkships is an effective way to improve attitudes about end-of-life care. Schools should focus on developing emotionally supportive settings in which to teach students about death and dying.