Excitonic Effects and Optical Spectra of Single-Walled Carbon Nanotubes

Many-electron effects often dramatically modify the properties of reduced dimensional systems. We report calculations, based on an many-electron Green's function approach, of electron-hole interaction effects on the optical spectra of small-diameter single-walled carbon nanotubes. Excitonic effects qualitatively alter the optical spectra of both semiconducting and metallic tubes. Excitons are bound by ~ 1 eV in the semiconducting (8,0) tube and by ~ 100 meV in the metallic (3,3) tube. These large many-electron effects explain the discrepancies between previous theories and experiments.Comment: 6 pages, 3 figures, 2 table

Ultrafast Optical Spectroscopy of Micelle-Suspended Single-Walled Carbon Nanotubes

We present results of wavelength-dependent ultrafast pump-probe experiments on micelle-suspended single-walled carbon nanotubes. The linear absorption and photoluminescence spectra of the samples show a number of chirality-dependent peaks, and consequently, the pump-probe results sensitively depend on the wavelength. In the wavelength range corresponding to the second van Hove singularities (VHSs), we observe sub-picosecond decays, as has been seen in previous pump-probe studies. We ascribe these ultrafast decays to intraband carrier relaxation. On the other hand, in the wavelength range corresponding to the first VHSs, we observe two distinct regimes in ultrafast carrier relaxation: fast (0.3-1.2 ps) and slow (5-20 ps). The slow component, which has not been observed previously, is resonantly enhanced whenever the pump photon energy resonates with an interband absorption peak, and we attribute it to radiative carrier recombination. Finally, the slow component is dependent on the pH of the solution, which suggests an important role played by H$^+$ ions surrounding the nanotubes.Comment: 6 pages, 8 figures, changed title, revised, to be published in Applied Physics

Nonsteroidal Antiinflammatory Drug Use and Association With Incident Hypertension in Ankylosing Spondylitis.

ObjectiveNonsteroidal antiinflammatory drugs (NSAIDs) increase blood pressure and potentially cardiovascular burden, which may limit their use in ankylosing spondylitis (AS). Our objective was to determine the association of NSAID use with incident hypertension in a longitudinal AS cohort.MethodsAdults with AS were enrolled in a prospective cohort study of patient outcomes and examined every 4-6 months. Hypertension was defined by patient-reported hypertension; antihypertensive medication use; or, on 2 consecutive visits, systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg. Continuous NSAID use was dichotomized based on the validated NSAID index. We assessed the association of NSAID use as a time-varying exposure with the incidence of hypertension using Cox proportional hazards models.ResultsOf the 1,282 patients in the cohort, 628 patients without baseline hypertension had at least 1 year of follow-up and were included in the analysis. Of these, 72% were male, the mean age at baseline was 39 ± 13 years, and 200 patients used NSAIDs continuously. On follow-up, 129 developed incident hypertension. After controlling for other variables, continuous NSAID use was associated with a hazard ratio of 1.12 for incident hypertension (95% confidence interval 1.04-1.20), compared to noncontinuous or no use. The association did not differ in subgroups defined by age, body mass index, biologic use, or disease activity.ConclusionIn our prospective, longitudinal AS cohort, continuous NSAID use was associated with a 12% increased risk for the development of incident hypertension, as compared to noncontinuous or no NSAID use

Evaluation of harmful algal bloom outreach activities

This is the final version of the article. Available from MDPI via the link in this record.With an apparent increase of harmful algal blooms (HABs) worldwide, healthcare providers, public health personnel and coastal managers are struggling to provide scientifically-based appropriately-targeted HAB outreach and education. Since 1998, the Florida Poison Information Center-Miami, with its 24 hour/365 day/year free Aquatic Toxins Hotline (1-888-232-8635) available in several languages, has received over 25,000 HAB-related calls. As part of HAB surveillance, all possible cases of HAB-related illness among callers are reported to the Florida Health Department. This pilot study evaluated an automated call processing menu system that allows callers to access bilingual HAB information, and to speak directly with a trained Poison Information Specialist. The majority (68%) of callers reported satisfaction with the information, and many provided specific suggestions for improvement. This pilot study, the first known evaluation of use and satisfaction with HAB educational outreach materials, demonstrated that the automated system provided useful HAB-related information for the majority of callers, and decreased the routine informational call workload for the Poison Information Specialists, allowing them to focus on callers needing immediate assistance and their healthcare providers. These results will lead to improvement of this valuable HAB outreach, education and surveillance tool. Formal evaluation is recommended for future HAB outreach and educational materials.The funding for this study was provided by the Florida Department of Health and the Centers for Disease Control and Prevention (CDC) and Florida Harmful Algal Bloom Taskforce, as well as the National Science Foundation and National Institute of Environmental Health Sciences Oceans and Human Health Center at the University of Miami Rosenstiel School (NSF 0CE0432368; NIEHS 1 P50 ES12736), the former National Institute of Environmental Health Sciences Marine and Freshwater Biomedical Sciences Center at the University of Miami Rosenstiel School (NIEHS P30ES05705), and the National Institute of Environmental Health Sciences Red Tide POI (P01 ES 10594)

Method for separating single-wall carbon nanotubes and compositions thereof

The invention relates to a process for sorting and separating a mixture of (n, m) type single-wall carbon nanotubes according to (n, m) type. A mixture of (n, m) type single-wall carbon nanotubes is suspended such that the single-wall carbon nanotubes are individually dispersed. The nanotube suspension can be done in a surfactant-water solution and the surfactant surrounding the nanotubes keeps the nanotube isolated and from aggregating with other nanotubes. The nanotube suspension is acidified to protonate a fraction of the nanotubes. An electric field is applied and the protonated nanotubes migrate in the electric fields at different rates dependent on their (n, m) type. Fractions of nanotubes are collected at different fractionation times. The process of protonation, applying an electric field, and fractionation is repeated at increasingly higher pH to separated the (n, m) nanotube mixture into individual (n, m) nanotube fractions. The separation enables new electronic devices requiring selected (n, m) nanotube types

Double differentiation in a cross-national comparison of populist political movements and online media uses in the United States and the Netherlands

In a context of highly visible and politically influential populist movements, this study considers the online self-representation of the Tea Party Patriots (TPP) in the United States and the Party for Freedom (PVV) in the Netherlands. A multi-methodological approach was adopted to compare the discursive manifestation of key populism concepts: leadership characteristics, adversary definition and mobilizing information. Analyses reconstruct and account for similarities and differences in discursive framing strategies of 'double differentiation' through which both movements attempt inclusion in and exclusion from the political establishment, and, in doing so, mobilize communities of support. Altogether, this study advances the understanding of what constitutes 'unmediated' content that is presented through user-generated media production, and how self-determined media spaces have facilitated shifts in populist media legitimation and political representation in two politically unique countries

Pushing for answers: is myosin V directly involved in moving mitochondria?

In budding yeast, the actin-based class V myosin motors, Myo2 and Myo4, transport virtually all organelles from mother to bud during cell division. Until recently, it appeared that mitochondria may be an exception, with studies showing that the Arp2/3 complex is required for their movement. However, several recent studies have proposed that Myo2 has a direct involvement in mitochondria inheritance. In this issue, Altmann et al. (Altmann, K., M. Frank, D. Neumann, S. Jakobs, and B. Westermann. 2008. J. Cell Biol. 181:119–130) provide the strongest support yet that Myo2 and its associated light chain Mlc1 function directly and significantly in both mitochondria–actin interactions and in the movement of mitochondria from mother to bud. The conflicting functions of Arp 2/3 and Myo2 may be reconciled by the existence of multiple pathways involved in mitochondrial transport

Confidentiality, anonymity and amnesty for midwives in distress seeking online support – Ethical?

BACKGROUND: Midwife health is intrinsically linked to the quality of safe patient care. To ensure safe patient care, there is a need to deliver emotional support to midwives. One option that midwives may turn to may be a confidential online intervention, instead of localised, face-to-face support. RESEARCH DESIGN: Following the Realist And MEta-narrative Evidence Syntheses: Evolving Standards publication standards, this realist synthesis approach explores the ethical considerations in permitting confidentiality, anonymity and amnesty in online interventions to support midwives in work-related psychological distress. An iterative search methodology was used to select nine papers for review. To assimilate information, papers were examined for ideas relating to ethical dimensions of online interventions to support midwives in work-related psychological distress. This review takes a narrative approach. FINDINGS: Online interventions can support the development of insight, help seeking and open discussion. Additionally, Internet support groups can become morally persuasive in nature. Anonymity and confidentiality are both effective and therapeutic features of online interventions when used in collaboration with effective online moderation. Yet, ethical dilemmas remain where users cannot be identified. DISCUSSION: Confidentiality and anonymity remain key components of successful online interventions. However, sanctioning the corollary component of amnesty may provoke moral discomfort for those seeking immediate accountability. For others, amnesty is seen as essential for open disclosure and help seeking. Ultimately, the needs of midwives must be balanced with the requirement to protect the public and the professional reputation of midwifery. CONCLUSION: In supporting midwives online, the principles of anonymity, confidentiality and amnesty may evoke some resistance on ethical grounds. However, without offering identity protection, it may not be possible to create effective online support services for midwives. The authors of this article argue that the principles of confidentiality, anonymity and amnesty should be upheld in the pursuit of the greatest benefit for the greatest number of people