A platform to synthesize a soluble poly(3,4‐ethylenedioxythiophene) analogue

Alkyl‐substituted polyhedral oligomeric silsesquioxane (POSS) cage is combined with 3,4‐ethylenedioxythiophene under the same roof. The corresponding monomer called EDOT‐POSS is used to get soluble poly(3,4‐ethylenedioxythiophene) (PEDOT‐POSS) analogue. Both chemically and electrochemically obtained polymers are soluble in common organic solvents like dichloromethane, chloroform, tetrahydrofuran, and so forth. The PEDOT‐POSS has somewhat higher band gap (1.71 eV at 618 nm) than its parent PEDOT (1.60 eV at 627 nm) and as expected the PEDOT‐POSS exhibits higher optical contrast (74% at 618 nm) and coloration efficiency (582 cm²/C for 100% switching), lower switching time (0.9 s), higher electrochemical stability (93% of its electroactivity retains after 5000 cycles under ambient conditions) when compared to the PEDOT. A number of advantages of the PEDOT‐POSS over the PEDOT can make it a promising material in the areas of electro‐optical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3935–3941     

Fluorescence spectroscopy combined with 5-aminolevulinic acid-induced protoporphyrin IX fluorescence in detecting oral premalignancy

BACKGROUND: Early detection of premalignant/malignant lesions in the oral cavity can certainly improve the patient's prognosis. This study presents fluorescence imaging with the topical application of 5-aminolevulinic as a way to improve detection of various oral tissue pathologies. This procedure depends mainly on comparing the intensity of red and green fluorescence emitted from tissues during examination. MATERIALS AND METHODS: Seventy-one patients who presented with clinically suspicious oral leukoplakia were recruited for this study. Each of the patients was required to have 5-aminolevulinic acid in the form of mouth rinse prior to fluorescence imaging. Following this a surgical biopsy was acquired from the exact examination site. The results of the fluorescence spectroscopy have been compared with histopathology. RESULTS: A Student's t-test was applied to test the viability of the ratio between red and green fluorescence. The red-to-green ratio was found to increase significantly when the lesion was identified as dysplastic or carcinoma in situ. By applying a threshold line to discriminate between normal and dysplastic lesions; a sensitivity of 83-90% and specificity of 79-89% were obtained. CONCLUSION: Fluorescence spectroscopy combined with 5-aminolevulinic acid-induced protoporphyrin IX was found as a valuable tool in the diagnosis of oral premalignancy. This technique offers the potential to be advantageous over other non-optical techniques in terms of providing real-time diagnosis, in situ monitoring, cost effectiveness and more tolerated by patient compared to surgical biopsy.     

A new MIP model for mine equipment scheduling by minimizing maintenance cost

Mining investment has been recognized as capital intensive due mainly to the cost of large equipment. Equipment capital costs for a given operation are usually within the order of hundreds of million dollars but may reach to billion dollars for large companies operating multiple mines. Such large investments require the optimum usage of equipment in a manner that the operating costs are minimized and the utilization of equipment is maximized through optimal scheduling. This optimum usage is required to ensure that the business remains sustainable and financially stable. Most mining operations utilize trucks to haul the mined material. Maintenance is one of the major operating cost items for these fleets as it can reach approximately one hundred million dollars yearly. There is no method or application in the literature that optimizes the utilization for truck fleet over the life of mine. A new approach based on mixed integer programming (MIP) techniques is used for annually scheduling a fixed fleet of mining trucks in a given operation, over a multi-year time horizon to minimize maintenance cost. The model uses the truck age (total hours of usage), maintenance cost and required operating hours to achieve annual production targets to produce an optimum truck schedule. While this paper focuses on scheduling trucks for mining operation, concept can be used in most businesses using equipment with significant maintenance costs. A case study for a large scale gold mine showed an annual discounted (10% rate) maintenance cost saving of over $2M and more than 16% ($21M) of overall maintenance cost reduction over 10 years of mine life, compared with the spreadsheet based approach used currently at the operation.     

A novel replacement policy for a linear deteriorating system using stochastic process with dependent components

In this study, a mechanical system with linear deterioration and preventive maintenance is considered. The state of the system over time is represented by a semicontinuous stochastic process with dependent components. The system cycles through on and off periods during its lifetime. The state of the system deteriorates linearly as a function of the usage time during on periods. When the system is offline, preventive maintenance is conducted, which improves the system state by a random amount. The system's on and off times and random improvement amounts are assumed to have general distributions. For such a system, our objective is to determine the expected value and variance for the number of preventive maintenance activities needed during the system lifetime and to propose a novel replacement policy for the system based on delay‐time modeling. Finally, the effectiveness of the obtained asymptotic results and the proposed replacement policy are tested through simulation.     

Pattern formation of a diffusive predator-prey model with herd behavior and nonlocal prey competition

In this paper, we study the influence of the nonlocal interspecific competition of the prey population on the dynamics of the diffusive predator-prey model with prey social behavior. Using the linear stability analysis, the conditions for the positive constant steady state at which undergoes Hopf bifurcation, T-H bifurcation (Turing-Hopf bifurcation) are investigated. The Turing patterns occur in the presence of the nonlocal competition and cannot be found in the original system. For determining the dynamical behavior near T-H bifurcation point, the normal form of the T-H bifurcation has been used. Some graphical representations are provided to illustrate the theoretical results.     

An experimental work on optical component based on D-fiber/slab evanescent coupling structure

Fiber/slab coupler structure has been exploited as a passive in-line optical fiber component for functions of filtering, intensity modulating and switching by many researchers. In this work a device based on the elliptic core D-fiber and polymer slab waveguide is proposed and its fabrication is experimentally investigated. The device is constructed by placing the polymer slab on the top of the flat side of the D-fiber, and then they are tested for transmission characteristics and polarization preserving properties for various configurations. The geometrical uniformity of the device is examined under Scanning Electron Microscope for the purpose of device performance evaluation. Potential usage of this device as an all-optical switch is also discussed at the end.     

Amperometric titration of cobalt and nickel with sodium diethyldithiocarbamate at zero applied voltage using rotating wire-platinum electrode

Analytical and Bioanalytical Chemistry -     

Radiative lifetimes in MoI using a novel atomic beam source

Radiative lifetimes of the 4d⁵ (a⁶S)5pz ⁷P^o levels and the 4d⁵ (a⁶S)5pz⁵P^o levels in MoI are reported as follows: $\text{τ(}\text{z}{}^7\text{P}{}_4{}^{\mathrm{<mtext>O</mtext>}}\text{) = 15.9}\text{ns}$, $\text{τ(}\text{z}{}^7\text{P}{}_3{}^{\mathrm{<mtext>O</mtext>}}\text{) = 17.0}\text{ns}$, $\text{τ(}\text{z}{}^7\text{P}{}_2{}^{\mathrm{<mtext>O</mtext>}}\text{) = 17.1}\text{ns}$, $\text{τ(}\text{z}{}^5\text{P}{}_3{}^{\mathrm{<mtext>O</mtext>}}\text{) = 22.3}\text{ns}$, $\text{τ(}\text{z}{}^5\text{P}{}_2{}^{\mathrm{<mtext>O</mtext>}}\text{) = 22.1}\text{ns}$, and $\text{τ(}\text{z}{}^5\text{P}{}_1{}^{\mathrm{<mtext>O</mtext>}}\text{) = 21.7}\text{ns}$ (±5%). The lifetimes are measured using time resolved laser induced fluorescence and a novel atomic beam source. This novel hollow cathode effusive beam source produces an intense beam of ground state Mo atoms and metastable Mo atoms. Our measurements on the z ⁷P^O levels are in agreement with earlier lifetime measurements. Our measurements on the z ⁵P^O levels are the first direct radiative lifetime measurements of these levels; the z ⁵P^O measurements are of particular interest because the a⁵S → z⁵P^O multiplet is used to determine the solar abundance of Mo.     

One- and two-electron reduction of chromium(VI) by polyaminocarboxylatocobaltate(II) complexes and the formation of chromium(V) and chromium(IV)

The kinetics of the oxidation of Co^IILⁿ complexes {where L = ethylenediaminetetraacetate (EDTA), diethylenetriaminepentaacetate (DTPA), or N-(2-hydroxyethyl)ethylenediaminetriacetate (HEDTA)} by Cr^VI were studied under pseudo-first-order conditions with [Co^IILⁿ] ? [Cr^VI]. The kinetics showed first-order dependence on [Cr^VI]. The rate constant, k _obs, decreases with increasing concentration of [Cr^VI]. At constant [H⁺], ionic strength, and temperature, the rate law is described by Eq. (i)

$$ - {\text{d}}\left[ {{\text{Cr}}^{\text{VI}} } \right] / {\text{dt}} = \left\{ {{\text{k}}_{ 2} \left[ {{\text{Co}}^{\text{II}} {\text{L}}^{\text{n}} } \right]{\text{ + k}}_{ 3} \left[ {{\text{Co}}^{\text{II}} {\text{L}}^{\text{n}} } \right]^{ 2} } \right\}\left[ {{\text{HCrO}}_{4}^{ - } } \right] $$

(i)

Both k ₂ and k ₃ showed acid-dependent and acid-independent pathways. The direct conversion Co^IILⁿ to Co^IIIL^m is ruled out by spectrophotometric and ESR spectroscopic measurements that showed the formation of initial reaction intermediate(s). The rate law is consistent with one-electron and concurrent two-electron transfers leading to the formation of Cr^V and Cr^IV, respectively. An inner-sphere process, at least for the first term, leading to the formation of a relatively stable Cr^V species is almost certain. The kinetic term showing second-order dependence on [Co^IILⁿ], most likely, involves concurrent two-electron transfer leading to the formation of Cr^IV. The type of rate law and the proposed mechanism, reported here, depart from the well-established rate laws observed and mechanisms proposed for the oxidation of one-electron reductants by Cr^VI.