Principal component analysis of the main factors of line intensity enhancements observed in oscillating direct current plasma

Enhancement of emission line intensities by induced oscillations of direct current (DC) arc plasma with continuous aerosol sample supply was investigated using multivariate statistics. Principal component analysis (PCA) was employed to evaluate enhancements of 34 atomic spectral lines belonging to 33 elements and 35 ionic spectral lines belonging to 23 elements. Correlation and classification of the elements were done not only by a single property such as the first ionization energy, but also by considering other relevant parameters. Special attention was paid to the influence of the oxide bond strength in an attempt to clarify/predict the enhancement effect. Energies of vaporization, atomization, and excitation were also considered in the analysis. In the case of atomic lines, the best correlation between the enhancements and first ionization energies was obtained as a negative correlation, with weak consistency in grouping of elements in score plots. Conversely, in the case of ionic lines, the best correlation of the enhancements with the sum of the first ionization energies and oxide bond energies was obtained as a positive correlation, with four distinctive groups of elements. The role of the gas-phase atom-oxide bond energy in the entire enhancement effect is underlined.     

One-pot synthesis of polyrotaxanes via acyclic diene metathesis polymerization of supramolecular monomers

A one-pot synthesis of polyrotaxanes has been developed. The method employs a supramolecular monomer comprising a polymerizable ammonium salt and crown ether, in combination with dynamic ADMet polymerization. Ultimately, highly efficient complexation, polymerization, and end-capping were accomplished in a single operation to yield polyrotaxanes with M(w) up to 19.3 kDa and >80% of the repeat units being complexed.     

Comparative analysis of65Zn and40K in human urine by Library Least Squares and window methods using a personal computer

The Library Least Squares method was adapted for use on a standard personal computer. It was found to be considerably more sensitive than the window method in the accurate assessment of⁶⁵Zn and⁴⁰K simultaneously presented in human urine samples.U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area is an equal opportunitylaffirmative action employer and all agency services are available without discrimination.Mention of a trademark or proprietary product does not contitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Time-varying many-server finite-queues in tandem: Comparing blocking mechanisms via fluid models

This paper focuses on the mechanism of Blocking Before Service (BBS), in time-varying many-server queues in tandem. BBS arises in telecommunication networks, production lines and healthcare systems. We model a stochastic tandem network under BBS and develop its corresponding fluid limit, which includes reflection due to jobs lost. Comparing our fluid model against simulation shows that the model is accurate and effective. This gives rise to design/operational insights regarding network throughput, under both BBS and BAS (Blocking After Service).     

QED limits for many-server systems under a priority policy

A multi-class many-server priority system operating in the quality-and-efficiency-driven regime is considered. Both arrival processes and service times are general. The many-server heavy-traffic diffusion asymptotic is characterized in terms of the corresponding limiting infinite-server process.     

Evolution of Oxygen–Metal Electron Transfer and Metal Electronic States During Manganese Oxide Catalyzed Water Oxidation Revealed with In Situ Soft X‐Ray Spectroscopy

Manganese oxide (MnO_x) electrocatalysts are examined herein by in situ soft X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS) during the oxidation of water buffered by borate (pH 9.2) at potentials from 0.75 to 2.25 V vs. the reversible hydrogen electrode. Correlation of L‐edge XAS data with previous mechanistic studies indicates Mn^IV is the highest oxidation state involved in the catalytic mechanism. MnO_x is transformed into birnessite at 1.45 V and does not undergo further structural phase changes. At potentials beyond this transformation, RIXS spectra show progressive enhancement of charge transfer transitions from oxygen to manganese. Theoretical analysis of these data indicates increased hybridization of the Mn?O orbitals and withdrawal of electron density from the O ligand shell. In situ XAS experiments at the O K‐edge provide complementary evidence for such a transition. This step is crucial for the formation of O₂ from water.     

Mechanism of sorption of pertechnetate onto ordered mesoporous carbon

Ordered mesoporous carbon (OMC) was used as an adsorbent for the removal of pertechnetate (TcO₄ ^?) anion. The maximum uptake (93 %) of TcO₄ ^? was obtained after 60 min of contact. The adsorption of TcO₄ ^? is almost pH-independent in very wide pH region (from 4.0 to 10.0). Maximum K _d of 6.6 × 10³ cm³ g^?1 was found at pH 2.0. TcO₄ ^? interacts with carboxylic functional groups present at the surface of the OMC by displacing the OH^? ions with TcO₄ ^? via ion exchange mechanism.     

Flood search under the California Split rule

We consider flood search on a line and show that no algorithm can achieve an average-case competitive ratio of less than 4 when compared to the optimal off-line algorithm. We also demonstrate that the optimal scanning sequences are described by simple recursive relationships that yield surprisingly complex behavior related to Hamiltonian chaos.