Electrically Tunable Excitonic Light Emitting Diodes based on Monolayer WSe2 p-n Junctions

Light-emitting diodes are of importance for lighting, displays, optical interconnects, logic and sensors. Hence the development of new systems that allow improvements in their efficiency, spectral properties, compactness and integrability could have significant ramifications. Monolayer transition metal dichalcogenides have recently emerged as interesting candidates for optoelectronic applications due to their unique optical properties. Electroluminescence has already been observed from monolayer MoS2 devices. However, the electroluminescence efficiency was low and the linewidth broad due both to the poor optical quality of MoS2 and to ineffective contacts. Here, we report electroluminescence from lateral p-n junctions in monolayer WSe2 induced electrostatically using a thin boron nitride support as a dielectric layer with multiple metal gates beneath. This structure allows effective injection of electrons and holes, and combined with the high optical quality of WSe2 it yields bright electroluminescence with 1000 times smaller injection current and 10 times smaller linewidth than in MoS2. Furthermore, by increasing the injection bias we can tune the electroluminescence between regimes of impurity-bound, charged, and neutral excitons. This system has the required ingredients for new kinds of optoelectronic devices such as spin- and valley-polarized light-emitting diodes, on-chip lasers, and two-dimensional electro-optic modulators.Comment: 13 pages main text with 4 figures + 4 pages upplemental material

Electrical Tuning of Valley Magnetic Moment via Symmetry Control

Crystal symmetry governs the nature of electronic Bloch states. For example, in the presence of time reversal symmetry, the orbital magnetic moment and Berry curvature of the Bloch states must vanish unless inversion symmetry is broken. In certain 2D electron systems such as bilayer graphene, the intrinsic inversion symmetry can be broken simply by applying a perpendicular electric field. In principle, this offers the remarkable possibility of switching on/off and continuously tuning the magnetic moment and Berry curvature near the Dirac valleys by reversible electrical control. Here we demonstrate this principle for the first time using bilayer MoS2, which has the same symmetry as bilayer graphene but has a bandgap in the visible that allows direct optical probing of these Berry-phase related properties. We show that the optical circular dichroism, which reflects the orbital magnetic moment in the valleys, can be continuously tuned from -15% to 15% as a function of gate voltage in bilayer MoS2 field-effect transistors. In contrast, the dichroism is gate-independent in monolayer MoS2, which is structurally non-centrosymmetric. Our work demonstrates the ability to continuously vary orbital magnetic moments between positive and negative values via symmetry control. This represents a new approach to manipulating Berry-phase effects for applications in quantum electronics associated with 2D electronic materials.Comment: 13 pages main text + 4 pages supplementary material

COPD exacerbation: Lost in translation

The introduction and acceptance of a standard definition for exacerbations of COPD can be helpful in prompt diagnosis and management of these events. The latest GOLD executive committee recognised this necessity and it has now included a definition of exacerbation in the guidelines for COPD which is an important step forward in the management of the disease. This definition is pragmatic and compromises the different approaches for exacerbation. However, the inclusion of the "healthcare utilisation" approach (".. may warrant a change in regular medication") in the definition may introduce in the diagnosis of exacerbation factors related to the access to health care services which may not be related to the underlying pathophysiologal process which characterizes exacerbations. It should be also noted that the aetiology of COPD exacerbations has not yet been included in the current definition. In this respect, the definition does not acknowledge the fact that many patients with COPD may suffer from additional conditions (i.e. congestive cardiac failure or pulmonary embolism) that can masquerade as exacerbations but they should not be considered as causes of them. The authors therefore suggest that an inclusion of the etiologic factors of COPD exacerbations in the definition. Moreover, COPD exacerbations are characterized by increased airway and systemic inflammation and significant deterioration in lung fuction. These fundamental aspects should be accounted in diagnosis/definition of exacerbations. This could be done by the introduction of a "laboratory" marker in the diagnosis of these acute events. The authors acknowledge that the use of a test or a biomarker in the diagnosis of exacerbations meets certain difficulties related to performing lung function tests or to sampling during exacerbations. However, the introduction of a test that reflects airway or systemic inflammation in the diagnosis of exacerbations might be another step forward in the management of COPD

Magnetic Control of Valley Pseudospin in Monolayer WSe2

Local energy extrema of the bands in momentum space, or valleys, can endow electrons in solids with pseudo-spin in addition to real spin. In transition metal dichalcogenides this valley pseudo-spin, like real spin, is associated with a magnetic moment which underlies the valley-dependent circular dichroism that allows optical generation of valley polarization, intervalley quantum coherence, and the valley Hall effect. However, magnetic manipulation of valley pseudospin via this magnetic moment, analogous to what is possible with real spin, has not been shown before. Here we report observation of the valley Zeeman splitting and magnetic tuning of polarization and coherence of the excitonic valley pseudospin, by performing polarization-resolved magneto-photoluminescence on monolayer WSe2. Our measurements reveal both the atomic orbital and lattice contributions to the valley orbital magnetic moment; demonstrate the deviation of the band edges in the valleys from an exact massive Dirac fermion model; and reveal a striking difference between the magnetic responses of neutral and charged valley excitons which is explained by renormalization of the excitonic spectrum due to strong exchange interactions

Effect of exacerbations on health status in subjects with chronic obstructive pulmonary disease

<p>Abstract</p> <p>Background</p> <p>Acute exacerbations may cause deteriorations in the health status of subjects with chronic obstructive pulmonary disease (COPD). The present study prospectively evaluated the effects of such exacerbations on the health status and pulmonary function of subjects with COPD over a 6-month period, and examined whether those subjects showed a steeper decline in their health status versus those subjects without exacerbations.</p> <p>Methods</p> <p>A total of 156 subjects with COPD (mean age 71.4 ± 6.3 years) were included in the analysis. At baseline and after 6 months, their pulmonary function and health status were evaluated using the Chronic Respiratory Disease Questionnaire (CRQ) and the St. George's Respiratory Questionnaire (SGRQ). An acute exacerbation was defined as a worsening of respiratory symptoms requiring the administration of systemic corticosteroids or antibiotics, or both.</p> <p>Results</p> <p>Forty-eight subjects experienced one or more exacerbations during the 6-month study period, and showed a statistically and clinically significant decline in Symptom scores on the SGRQ, whereas subjects without exacerbations did not show a clinically significant decline. Logistic multiple regression analyses confirmed that the exacerbations significantly influenced the Fatigue and Mastery domains of the CRQ, and the Symptoms in the SGRQ. Twelve subjects with frequent exacerbations demonstrated a more apparent decline in health status.</p> <p>Conclusion</p> <p>Although pulmonary function did not significantly decline during the 6-month period, acute exacerbations were responsible for a decline in health status. To minimize deteriorations in health status, one must prevent recurrent acute exacerbations and reduce the exacerbation frequencies in COPD subjects.</p

Perceived intensity of somatosensory cortical electrical stimulation

Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood. Based on prior work in cortical stimulation, we hypothesized that perceived intensity of electrical stimulation may be explained by the population response of the neurons affected by the stimulus train. To explore this hypothesis, we modeled perceived intensity of a stimulation pulse train with a leaky neural integrator. We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex. We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train

Why less may be more: a mixed methods study of the work and relatedness of 'weak ties' in supporting long-term condition self-management

Background: The distribution of the roles and responsibilities of long-term condition management (LTCM) outside of formal health services implicates a wide set of relationships and activities of involvement. Yet, compared to studies of professional implementation, patient systems of implementation remain under-investigated. The aim of this paper is to explore the work, meaning and function attributed to ‘weaker’ ties relative to other more bonding relationships in order to identify the place of these within a context of systems of support for long-term conditions. Methods: This is a mixed methods survey with nested qualitative study. A total of 300 people from deprived areas in the North West of England with chronic illnesses took part in a survey conducted in 2010 to 2011. A concentric circles diagram was used as a research tool with which participants identified 2,544 network members who contributed to illness management. Notions of ‘work’ were used to describe activities associated with chronic illness and to identify how weaker ties are included and perceived to be involved through social network members (SNM) contributions. Results: The results provide an articulation of how SNMs are substantially involved in weak tie illness management. Weaker ties constituted 16.1% of network membership involved in illness work. The amount of work undertaken was similar but less than that of stronger ties. Weaker ties appeared more durable and less liable to loss over time than stronger ties. The qualitative accounts suggested that weak ties enabled the moral positioning of the self-managing ‘self’ and acted on the basis of a strong sense of reciprocity. Conclusions: Weak ties act as an acceptable bridge between a sense of personal agency and control and the need for external support because it is possible to construct a sense of moral acceptability through reciprocal exchange. Access to weak tie resources needs to be taken into account when considering the ways in which systems of health implementation for chronic illness are designed and delivered

Smoking status and anti-inflammatory macrophages in bronchoalveolar lavage and induced sputum in COPD

<p>Abstract</p> <p>Background</p> <p>Macrophages have been implicated in the pathogenesis of COPD. M1 and M2 macrophages constitute subpopulations displaying pro- and anti-inflammatory properties. We hypothesized that smoking cessation affects macrophage heterogeneity in the lung of patients with COPD. Our aim was to study macrophage heterogeneity using the M2-marker CD163 and selected pro- and anti-inflammatory mediators in bronchoalveolar lavage (BAL) fluid and induced sputum from current smokers and ex-smokers with COPD.</p> <p>Methods</p> <p>114 COPD patients (72 current smokers; 42 ex-smokers, median smoking cessation 3.5 years) were studied cross-sectionally and underwent sputum induction (M/F 99/15, age 62 ± 8 [mean ± SD] years, 42 (31-55) [median (range)] packyears, post-bronchodilator FEV₁63 ± 9% predicted, no steroids past 6 months). BAL was collected from 71 patients. CD163⁺macrophages were quantified in BAL and sputum cytospins. Pro- and anti-inflammatory mediators were measured in BAL and sputum supernatants.</p> <p>Results</p> <p>Ex-smokers with COPD had a higher percentage, but lower number of CD163⁺macrophages in BAL than current smokers (83.5% and 68.0%, p = 0.04; 5.6 and 20.1 ×10⁴/ml, p = 0.001 respectively). The percentage CD163⁺M2 macrophages was higher in BAL compared to sputum (74.0% and 30.3%, p < 0.001). BAL M-CSF levels were higher in smokers than ex-smokers (571 pg/ml and 150 pg/ml, p = 0.001) and correlated with the number of CD163⁺BAL macrophages (Rs = 0.38, p = 0.003). No significant differences were found between smokers and ex-smokers in the levels of pro-inflammatory (IL-6 and IL-8), and anti-inflammatory (elafin, and Secretory Leukocyte Protease Inhibitor [SLPI]) mediators in BAL and sputum.</p> <p>Conclusions</p> <p>Our data suggest that smoking cessation partially changes the macrophage polarization <it>in vivo </it>in the periphery of the lung towards an anti-inflammatory phenotype, which is not accompanied by a decrease in inflammatory parameters.</p

Nanotechnology in Head and Neck Cancer: The Race Is On

Rapid advances in the ability to produce nanoparticles of uniform size, shape, and composition have started a revolution in the sciences. Nano-sized structures herald innovative technology with a wide range of potential therapeutic and diagnostic applications. More than 1000 nanostructures have been reported, many with potential medical applications, such as metallic-, dielectric-, magnetic-, liposomal-, and carbon-based structures. Of these, noble metallic nanoparticles are generating significant interest because of their multifunctional capacity for novel methods of laboratory-based diagnostics, in vivo clinical diagnostic imaging, and therapeutic treatments. This review focuses on recent advances in the applications of nanotechnology in head and neck cancer, with special emphasis on the particularly promising plasmonic gold nanotechnology

A community based participatory approach to improving health in a Hispanic population

ABSTRACT: BACKGROUND: The Charlotte-Mecklenburg region has one of the fastest growing Hispanic communities in the country. This population has experienced disparities in health outcomes and diminished ability to access healthcare services. This city is home to an established practice-based research network (PBRN) that includes community representatives, health services researchers, and primary care providers. The aims of this project are: to use key principles of community-based participatory research (CBPR) within a practice-based research network (PBRN) to identify a single disease or condition that negatively affects the Charlotte Hispanic community; to develop a community-based intervention that positively impacts the chosen condition and improves overall community health; and to disseminate findings to all stakeholders. METHODS/DESIGN: This project is designed as CBPR. The CBPR process creates new social networks and connections between participants that can potentially alter patterns of healthcare utilization and other health-related behaviors. The first step is the development of equitable partnerships between community representatives, providers, and researchers. This process is central to the CBPR process and will occur at three levels -- community members trained as researchers and outreach workers, a community advisory board (CAB), and a community forum. Qualitative data on health issues facing the community -- and possible solutions -- will be collected at all three levels through focus groups, key informant interviews and surveys. The CAB will meet monthly to guide the project and oversee data collection, data analysis, participant recruitment, implementation of the community forum, and intervention deployment. The selection of the health condition and framework for the intervention will occur at the level of a community-wide forum. Outcomes of the study will be measured using indicators developed by the participants as well as geospatial modeling.On completion, this study will: determine the feasibility of the CBPR process to design interventions; demonstrate the feasibility of geographic models to monitor CBPR-derived interventions; and further establish mechanisms for implementation of the CBPR framework within a PBRN