Metal-Containing Polymers Synthesized via Acyclic Diene Metathesis (ADMET) Polymerization Using Electrochemically Reduced Tungsten-Based Catalyst: Polycarbogermanes

Various germanium-containing dienes, bis(4-pentenyl)diethylgermanium (1), bis(4-pentenyl)dimethylgermanium (2) and bis(3-butenyl)diethylgermanium (3), were synthesized and polymerized using an electrochemically reduced tungsten-based catalyst system via acyclic diene metathesis (ADMET) polymerization. All polymer structures were characterized by ¹H- and ¹³C-NMR spectroscopy. These results indicate the retention of the double bonds in the polymer structure with high trans content (57–70%) as expected from a step condensation reaction. These polymers have low molecular weight (M _W) that range from 7400 to 19,100. The thermal stability of polymers was evaluated by thermogravimetric analysis. The glass transition temperatures of the polymer of monomer 1, 2 and 3 were −24, −9 and −47°C, respectively. Synthesis, characterization and the general limitations of ADMET polymers obtained by this catalyst are discussed. An erratum to this article can be found at     

Mineralogy-induced radiological aspects with characterization of commercial granites exploited in Turkey

This study deals with natural radioactivity levels of the ten most important commercial granites from various districts currently being exploited as dimension stone in Turkey. Determining the level of radioactivity is important for human health, particularly for indoor use of granites. This study shows that the relationship between the natural radioactivity and the radiogenic mineralogical contents of the granites exploited for commercial utilization in Turkey is variable. The natural radioactivity levels (i.e., activity concentrations of radionuclides ²²⁶Ra, ²³²Th, and ⁴⁰K) of granite samples were determined by high-resolution gamma-ray spectrometry. Using these activities, radiological hazard dose rates (absorbed and annual effective) and gamma-activity indexes were calculated using standard equations accepted by public health bodies, taking relevant international reports and guidelines into account. Three of the granites exploited in the Black Sea, Aegean, and Central Anatolia regions were found to be high in radium-equivalent activities and annual effective doses due to minerals bearing the radionuclides, including zircon, apatite, allanite, xenotime, uranothorite, K-feldspars, and biotite. Of those, uranothorite contains large amounts of radionuclides and is present in samples of granites collected from the Black Sea and Aegean regions. Radioactivity measurements using high-resolution gamma-ray spectroscopy serve as a rapid screening tool to evaluate natural radioactivity, whereas detailed petrographic, mineralogical, and elemental investigations can reveal the source of radioactive emissions in granites.     

Electrodeposition of poly(4‐methyl carbazole‐3‐carboxylic acid) on steel surfaces and corrosion protection of steel

The electropolymerization of 4‐methyl carbazole‐3‐carboxylic acid was successfully performed on a stainless steel (316L) surface with lithium perchlorate/acetonitrile as the supporting electrolyte. The corrosion resistance of the new coating, poly(4‐methyl carbazole‐3‐carboxylic acid) (PCz), was investigated. To this end, potentiodynamic polarization curves, open circuit potentials, and electrochemical impedance spectroscopy were used to evaluate the capacity of the PCz coating to protect the steel surface. The corrosion tests indicated that PCz exhibited effective anodic protection in a corrosive test solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A simulation-based comparison of two goods-to-person order picking systems in an online retail setting

Design and analysis of order picking systems continues to be an active topic of interest both in academia and practice, especially in light of the significant increase in online retail sales. In this paper, we examine two types of well-known, goods-to-person order picking systems, namely, a miniload system and a Kiva system. Using a simulation model, we compare the performance of the two systems on the basis of expected throughput and expected container retrieval times to process the same set of customer orders. We also discuss some of the advantages and limitations of the two systems.     

Expected move request waiting times in single-device, polling-based material handling systems

We present an analytical approach to approximate the expected waiting times of move requests (customers) served by a single handling device (server) that operates according to the First-Encountered-First-Served (FEFS) rule, which is a common rule employed for polling-based material handling systems. Under the FEFS rule, the device inspects each station according to a prespecified polling sequence and serves the first move request it encounters. Polling resumes as soon as the device completes serving a move request. The expected waiting times are important for estimating the expected Work-In-Process (WIP) levels at individual stations and to gauge the overall performance of the system. Moreover, the polling sequence itself can affect the expected waiting times. If the device meets the throughput requirement under more than one polling sequence, the results we present can also be used to evaluate alternative polling sequences. In fact, using the analytical results and a numerical example, we show that alternative polling sequences, even if they impose the same “workload factor” on the device, can lead to significantly different expected WIP levels     

Voltammetric behavior of nicotine at pencil graphite electrode and its enhancement determination in the presence of anionic surfactant

The electrochemical oxidation of nicotine was studied in aqueous as well as micellar media at a pencil graphite electrode using cyclic, differential pulse and square-wave voltammetric techniques. The compound was oxidized irreversibly at low positive potentials in one (in acidic and neutral media) or two (in alkaline media) oxidation steps. The response was evaluated with respect to pH, scan rate, addition of surfactant and other variables. For analytical purposes, very resolved voltammetric peaks at +0.84 V (versus Ag/AgCl) were obtained in phosphate buffer at pH 7.0 containing 2 mM sodium dodecylsulfate using square-wave mode. The process could be used to determine nicotine concentrations in the range of 7.6–107.5 μM with a detection limit of 2.0 μM (0.33 mg L⁻¹). The proposed method was applied to the determination of nicotine in different brands of commercial cigarettes.     

Effect of rock properties on the Los Angeles abrasion and impact test characteristics of the aggregates

Aggregate is the most fundamental and widely used component of construction. It is used as an unbound material which constitutes about 100% of the volume of base courses, 95 to 93% of the volume of asphalt and about 85 to 75% of the volume of Portland cement concrete. Aggregate is exposed to a number of physical and chemically degrading forces during processing, transporting, and construction. As the main load carrying component of unbound and bituminous and Portland cement concretes, the aggregate must be clean, hard, sound, durable, resistant to abrasion, uniform in quality and free of any detrimental quantities of soft, friable, thin, elongated or laminated pieces, disintegrated material, alkali or other deleterious substance. For assesing the abrasion resistance of aggregates, the most common method is the Los Angeles abrasion and impact test (LAAI) which determines the relative competence or resistance to abrasion of the aggregates.In this study, four limestones, four travertines, three crystalline marbles and one andesite were tested to evaluate the correlations between the LAAI values and the physical properties covering bulk density, Schmidt hardness, shore hardness, P-wave velocity and mechanical properties such as uniaxial compressive strength, point load index, and indirect tensile strength of rocks. Since these properties are of great importance as a source of aggregates, tests on the rock can give an indication of the strength of the aggregates.The above rock properties were determined through standard testing methods in order to investigate the correlation between LAAI and each rock property by using regression analysis. A simple equation predicting the LAAI value based on each rock property was suggested. From the statistical tests, rock properties were found to be significant in estimating the LAAI values of rocks.     

A dynamic neural network model for accelerating preliminary parameterization of 3D triangular mesh surfaces

Neural Computing and Applications - This study proposes an effective and fast preliminary mapping algorithm for 3D triangular mesh surfaces. The proposed method exploits barycentric mapping theory...