Cd3P2/Zn3P2 Core-Shell Nanocrystals: Synthesis and Optical Properties.

II-V semiconductor nanocrystals such as Cd3P2 and Zn3P2 have enormous potential as materials in next-generation optoelectronic devices requiring active optical properties across the visible and infrared range. To date, this potential has been unfulfilled due to their inherent instability with respect to air and moisture. Core-shell system Cd3P2/Zn3P2 is synthesized and studied from structural (morphology, crystallinity, shell diameter), chemical (composition of core, shell, and ligand sphere), and optical perspectives (absorbance, emission-steady state and time resolved, quantum yield, and air stability). The improvements achieved by coating with Zn3P2 are likely due to its identical crystal structure to Cd3P2 (tetragonal), highlighting the key role crystallographic concerns play in creating cutting edge core-shell NCs.

Effect of nanoparticles on spontaneous Ouzo emulsification.

Particles stabilize fluid interfaces. In particular, oil/water Pickering emulsions undergo limited coalescence, yielding droplets of smaller size as the amount of particles is increased. Herein, we studied the effect of hydrophobic nanoparticles (<10 nm, alkyl-coated) on submicronic droplets (ca 100 nm) formed in an Ouzo system. We investigated thoroughly the water/tetrahydrofuran (THF)/butylated hydroxytoluene (BHT) reference diagram, in the absence and in the presence of nanoparticles, using the Nanoparticle Tracking Analysis (NTA) technique. This allowed us to characterize the size distributions in a much finer way than what is usually obtained using conventional Dynamic Light Scattering (DLS). Both a Surfactant-Free Microemulsion (SFME, thermodynamically stable) and an Ouzo (metastable spontaneous emulsion) domains were identified and the transition from one to the other could be characterized by specific features of the droplet size distributions. We found that the presence of the nanoparticles limits coalescence in the metastable domain. We also show that the alkyl-coated nanoparticles are irreversibly attached to the liquid-liquid interface.

A science impact framework to measure impact beyond journal metrics.

Measuring the impact of public health science or research is important especially when it comes to health outcomes. Achieving the desired health outcomes take time and may be influenced by several contributors, making attribution of credit to any one entity or effort problematic. Here we offer a science impact framework (SIF) for tracing and linking public health science to events and/or actions with recognized impact beyond journal metrics. The SIF was modeled on the Institute of Medicine's (IOM) Degrees of Impact Thermometer, but differs in that SIF is not incremental, not chronological, and has expanded scope. The SIF recognizes five domains of influence: disseminating science, creating awareness, catalyzing action, effecting change and shaping the future (scope differs from IOM). For public health, the goal is to achieve one or more specific health outcomes. What is unique about this framework is that the focus is not just on the projected impact or outcome but rather the effects that are occurring in real time with the recognition that the measurement field is complex, and it takes time for the ultimate outcome to occur. The SIF is flexible and can be tailored to measure the impact of any scientific effort: from complex initiatives to individual publications. The SIF may be used to measure impact prospectively of an ongoing or new body of work (e.g., research, guidelines and recommendations, or technology) and retrospectively of completed and disseminated work, through linking of events using indicators that are known and have been used for measuring impact. Additionally, linking events offers an approach to both tell our story and also acknowledge other players in the chain of events. The value added by science can easily be relayed to the scientific community, policy makers and the public.

Sustainable quantum dot chemistry: effects of precursor, solvent, and surface chemistry on the synthesis of Zn3P2 nanocrystals.

The quest of exploring alternative materials for the replacement of toxic cadmium- and lead-based quantum dots (QDs) is necessary for envisaging a sustainable future but remains highly challenging. Tackling this issue, we present the synthesis of Zn3P2 nanocrystals (NCs) of unprecedented quality. New, reactive zinc precursors yield highly crystalline, colloidally stable particles, exhibiting oxide-free surfaces, size tunability and outstanding optical properties relative to previous reports of zinc phosphide QDs.

Coherent beam combination of four holmium amplifiers with phase control via a direct digital synthesizer chip.

We present the coherent beam combination of four 2100 nm holmium amplifiers with their phase controlled through acousto-optic modulators driven by the RF output of direct digital synthesizer chips. Phase alignment was achieved through the use of a field programmable gate array based stochastic parallel gradient descent algorithm.

A Library of Selenourea Precursors to PbSe Nanocrystals with Size Distributions near the Homogeneous Limit.

We report a tunable library of N,N,N'-trisubstituted selenourea precursors and their reaction with lead oleate at 60-150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields. Single exponential conversion kinetics can be tailored over 4 orders of magnitude by adjusting the selenourea structure. The wide range of conversion reactivity allows the extent of nucleation ([nanocrystal] = 4.6-56.7 µM) and the size following complete precursor conversion (d = 1.7-6.6 nm) to be controlled. Narrow size distributions (σ = 0.5-2%) are obtained whose spectral line widths are dominated (73-83%) by the intrinsic single particle spectral broadening, as observed using spectral hole burning measurements. The intrinsic broadening decreases with increasing size (fwhm = 320-65 meV, d = 1.6-4.4 nm) that derives from exciton fine structure and exciton-phonon coupling rather than broadening caused by the size distribution.

CO2 laser-fabricated cladding light strippers for high-power fiber lasers and amplifiers.

We present and characterize a simple CO2 laser processing technique for the fabrication of compact all-glass optical fiber cladding light strippers. We investigate the cladding light loss as a function of radiation angle of incidence and demonstrate devices in a 400 µm diameter fiber with cladding losses of greater than 20 dB for a 7 cm device length. The core losses are also measured giving a loss of <0.008±0.006 dB/cm. Finally we demonstrate the successful cladding light stripping of a 300 W laser diode with minimal heating of the fiber coating and packaging adhesives.

High precision 9.6 µm CO(2) laser end-face processing of optical fibres.

Reproducible, precise cleaving of optical fibres is of great importance to the fibre laser and telecommunications industries. We present a novel approach to the end-face processing of optical fibres using a 9.6 µm CO2 laser to produce flat, smooth and symmetric fibre end-face profiles with no rounding or melting at the edges of the fibre. As a demonstration, precision cleaving of a 400 µm diameter optical fibre is reported. For this fibre a topographical profile height of <400 nm (0.06°) and a reproducibility better than 200 nm (0.03°) was achieved. To the best of our knowledge this is the first demonstration of a CO2 process that has generated a fibre end-face topography substantially smaller than a typical mechanical cleave. Highlighting the flexibility of this system, we have also demonstrated the generation of near arbitrary fiber end-face profiles such as discrete phase steps and non-spherical surface profiles.

Participation and contribution in crowdsourced surveys.

This paper identifies trends within and relationships between the amount of participation and the quality of contributions in three crowdsourced surveys. Participants were asked to perform a collective problem solving task that lacked any explicit incentive: they were instructed not only to respond to survey questions but also to pose new questions that they thought might-if responded to by others-predict an outcome variable of interest to them. While the three surveys had very different outcome variables, target audiences, methods of advertisement, and lengths of deployment, we found very similar patterns of collective behavior. In particular, we found that: the rate at which participants submitted new survey questions followed a heavy-tailed distribution; the distribution in the types of questions posed was similar; and many users posed non-obvious yet predictive questions. By analyzing responses to questions that contained a built-in range of valid response we found that less than 0.2% of responses lay outside of those ranges, indicating that most participants tend to respond honestly to surveys of this form, even without explicit incentives for honesty. While we did not find a significant relationship between the quantity of participation and the quality of contribution for both response submissions and question submissions, we did find several other more nuanced participant behavior patterns, which did correlate with contribution in one of the three surveys. We conclude that there exists an optimal time for users to pose questions early on in their participation, but only after they have submitted a few responses to other questions. This suggests that future crowdsourced surveys may attract more predictive questions by prompting users to pose new questions at specific times during their participation and limiting question submission at non-optimal times.

Crowdsourcing novel childhood predictors of adult obesity.

Effective and simple screening tools are needed to detect behaviors that are established early in life and have a significant influence on weight gain later in life. Crowdsourcing could be a novel and potentially useful tool to assess childhood predictors of adult obesity. This exploratory study examined whether crowdsourcing could generate well-documented predictors in obesity research and, moreover, whether new directions for future research could be uncovered. Participants were recruited through social media to a question-generation website, on which they answered questions and were able to pose new questions that they thought could predict obesity. During the two weeks of data collection, 532 participants (62% female; age  =  26.5±6.7; BMI  =  29.0±7.0) registered on the website and suggested a total of 56 unique questions. Nineteen of these questions correlated with body mass index (BMI) and covered several themes identified by prior research, such as parenting styles and healthy lifestyle. More importantly, participants were able to identify potential determinants that were related to a lower BMI, but have not been the subject of extensive research, such as parents packing their children's lunch to school or talking to them about nutrition. The findings indicate that crowdsourcing can reproduce already existing hypotheses and also generate ideas that are less well documented. The crowdsourced predictors discovered in this study emphasize the importance of family interventions to fight obesity. The questions generated by participants also suggest new ways to express known predictors.

Probability of a shockable presenting rhythm as a function of EMS response time.

INTRODUCTION: Survival from cardiac arrest is associated with having a shockable presenting rhythm (VF/pulseless VT) upon EMS arrival. A concern is that several studies have reported a decline in the incidence of VF/PVT over the past few decades. One plausible explanation is that contemporary cardiovascular therapies, such as increased use of statin and beta blocker drugs, may shorten the duration of VF/PVT after arrest. As a result, EMS response time would become an increasingly important factor in the likelihood of a shockable presenting rhythm, and consequently, cardiac arrest survival. OBJECTIVE: To develop a model describing the likelihood of shockable presenting rhythm as a function of EMS response time. METHODS: We conducted a retrospective observational study of cardiac arrest using the North Carolina Prehospital Care Reporting System (PreMIS). Inclusionary criteria consisted of adult patients suffering nontraumatic cardiac arrests witnessed by a layperson between January 1 and June 30, 2012. Patients defibrillated prior to EMS arrival were excluded. Chi-square and t-tests were used to analyze the relationship between shockable presenting rhythm and patient age, gender, and race; response time measured as elapsed minutes between 9-1-1 call receipt and scene arrival; and bystander CPR. Logistic regression was used to calculate the adjusted odds ratio (OR) of shockable presenting rhythm as a function of response time while controlling for statistically significant covariates. RESULTS: A total of 599 patients met inclusion criteria. Overall, VF/PVT was observed in 159 patients (26.5%). VF/PVT was less likely with increasing EMS response time (OR 0.92, 95% CI = 0.87-0.97, p < 0.01) and age (OR 0.98, 95% CI = 0.97-0.99, p < 0.01), while males (OR 1.98, 95% CI = 1.29-3.03, p < 0.01) and Caucasians (OR 1.86, 95% CI = 1.17-2.95, p < 0.01) were more likely to have shockable presenting rhythm. Bystander CPR was not associated with shockable presenting rhythm, although EMS response time was longer among patients with bystander CPR compared to those without (9.83 vs. 8.83 minutes, p < 0.01). CONCLUSIONS: We found that for every one minute of added ambulance response time, the odds of shockable presenting rhythm declined by 8%. This information could prove useful for EMS managers tasked with developing EMS system response strategies for cardiac arrest management.

Evaluating the use of an online gaming community in a pediatric hemodialysis center.

Children that suffer from chronic illnesses are at risk of developing behavioral disorders stemming from a lack of self esteem,frequent removal from their peer support networks, and feeling a sense of injustice with regards to their medical condition and the health of their peers.Furthermore, the process of hemodialysis can be a socially isolating experience by way of being tied to a machine that restricts freedom of movement and social activity amongst concomitant users.