Determination of trace amount of iron cations using electrochemical methods at N, S doped GQD modified electrode.

In this work, nitrogen and sulfur co-doped graphene quantum dot-modified glassy carbon electrodes (N, S-GQD/GCE) were used for the recognition of iron cations in aqueous solutions. The dissolved cations are detected based on the faradaic reduction or oxidation current of Fe(III) and Fe(II) obtained at the N, S-GQD/GCE surface. Cyclic voltammetry (CV), square wave voltammetry (SWV), and hydrodynamic amperometry are used as suitable electrochemical techniques for studying electrochemical behavior and determination of Fe cations. Based on the obtained results, it is concluded that the presence of free electrons in the structure of N, S-GQD could facilitate electron transfer reaction between Fe(III) and electrode surface which with increased surface area results in increased sensitivity and lower limit of detection. By performing suitable experiments, the best condition for preparing the modified electrode and determining Fe(III) was selected. Under optimized conditions, the amperometric response is linear from 1 to 100 nM of Fe(III) with a detection limit of 0.23 nM. The validity of the method and applicability of the sensor is successfully tested by the determination of Fe(III) in drug and water real samples. This sensor opened a new platform based on doped nanoparticles for highly sensitive and selective detection of analytes.

Studying the influence of mass media and environmental factors on influenza virus transmission in the US Midwest.

OBJECTIVES: Disease burden and high financial cost of seasonal influenza emphasize the importance of studying the epidemics transmission dynamics. Our aim in this article is to extend the Susceptible Exposed Infectious Recovered (SEIR) model, a well-studied classical compartmental epidemic model, by incorporating socio-environmental factors. Particularly, the potential influence of mass media function and absolute humidity are examined on the model simultaneously. STUDY DESIGN: The proposed model is fitted to Center for Disease Control and Prevention (CDC) influenza data of region five of the US for four outbreak seasons. Then, a full-performance comparison between the conventional and extended model is carried out. METHODS: Implementing the mass media and climate factors into the classical epidemic models, e.g., Susceptible Infectious Recovered (SIR) and SEIR, is a promising and ongoing research field in the public health area. In this article, we particularly address the potential effect of mass media and absolute humidity to modify the SEIR model. RESULTS: Computational simulations are carried out for both standard and extended models for four influenza seasons in CDC region five of the US. Moreover, the accuracy assessment is performed based on the following criteria: i) the root mean square error (RMSE); ii) the Akaike information criterion (AIC); iii) the outbreak peak time; and iv) the number of infected individuals at the peak time. Based on these criteria, the proposed model provided a better fit than a null model with smaller RMSE and AIC values for the last three study seasons. Specifically, RMSE values declined from 20 to 11.08 and from 26.87 to 19.15 for seasons 2010/11 and 2011/12, respectively; also, lower AIC values for these seasons indicate that the modified SEIR (referred to M-SEIR) model is a better-fitting model. CONCLUSIONS: Parameter estimation techniques are important tools to determine the key parameters of the epidemic models. Based on our results, introducing the mass media and climate factors into the classic models will improve the model precision.

Rate constants and branching ratios for the dissociative recombination of C3D(+)7 and C4D(+)9.

Product branching ratios and thermal rate coefficients for the dissociative recombination of C3D(+)7 and C4D(+)9 have been measured in the ion storage ring CRYRING. The results for C3D(+)7 are believed to be slightly more accurate than those obtained earlier for C3H(+)7. Only the C-C bond breaking channels could be measured for C4D(+)9 and were found to be in excellent agreement with earlier data.

First observation of four-body breakup in electron recombination: C2D+5.

We report the first observation of four-body breakup in electron dissociative recombination of a molecular ion: C2D+5. In an ion storage ring experiment, the branching ratio for the process C2D+5 + e(-)-->C2D2 + D + D + D was determined to be 13%. This means that three covalent chemical bonds are broken as a result of the action of a single electron. This is the first time a four-body breakup of chemical bonds has been observed in a low-energy binary reaction.

An enhanced cosmic-ray flux towards zeta Persei inferred from a laboratory study of the H3+-e- recombination rate.

The H3+ molecular ion plays a fundamental role in interstellar chemistry, as it initiates a network of chemical reactions that produce many molecules. In dense interstellar clouds, the H3+ abundance is understood using a simple chemical model, from which observations of H3+ yield valuable estimates of cloud path length, density and temperature. But observations of diffuse clouds have suggested that H3+ is considerably more abundant than expected from the chemical models. Models of diffuse clouds have, however, been hampered by the uncertain values of three key parameters: the rate of H3+ destruction by electrons (e-), the electron fraction, and the cosmic-ray ionization rate. Here we report a direct experimental measurement of the H3+ destruction rate under nearly interstellar conditions. We also report the observation of H3+ in a diffuse cloud (towards Persei) where the electron fraction is already known. From these, we find that the cosmic-ray ionization rate along this line of sight is 40 times faster than previously assumed. If such a high cosmic-ray flux is ubiquitous in diffuse clouds, the discrepancy between chemical models and the previous observations of H3+ can be resolved.