Tungsten(VI) oxide supported rhodium nanoparticles: Highly active catalysts in hydrogen generation from ammonia borane

Herein, we report the use of tungsten(VI) oxide (WO₃) as support for Rh⁰ nanoparticles. The resulting Rh⁰/WO₃ nanoparticles are highly active and stable catalysts in H₂ generation from the hydrolysis of ammonia borane (AB). We present the results of our investigation on the particle size distribution, catalytic activity and stability of Rh⁰/WO₃ catalysts with 0.5%, 1.0%, 2.0% wt. Rh loadings in the hydrolysis reaction. The results reveal that Rh⁰/WO₃ (0.5% wt. Rh) is very promising catalyst providing a turnover frequency of 749 min^?1 in releasing 3.0 equivalent H₂ per mole of AB from the hydrolysis at 25.0 °C. The high catalytic activity of Rh⁰/WO₃ catalyst is attributed to the reducible nature of support. The report covers the results of kinetics study as well as comparative investigation of activity, recyclability, and reusability of colloidal(0) nanoparticles and Rh⁰/WO₃ (0.5 % wt. Rh) catalyst in the hydrolysis reaction.     

Threshold value of glucose screening tests in pregnancy: could it be standardized for every population?

We aimed to determine a threshold value that perfectly demarcates women at high risk for gestational diabetes mellitus (GDM) in the Turkish population. One thousand gravid women of 24 to 32 weeks of gestation were given 50 g, 1-hour glucose screening tests. A 100 g, 3-hour glucose tolerance test (GTT) was performed on all patients whose screening test plasma glucose value was 130 mg/dL or greater. The sensitivity and specificity of each screening test value was found, and the GDM rate of each value was calculated. Three-hundred-and-five patients were identified for GTT and 66 were shown to have GDM with two or more abnormal values in GTT. The incidence of GDM was found to be 6.6%. The maximum specificity and sensitivity were met at 140 mg/dL. However, this value underestimated 12% of patients with GDM, and the lowest value for a positive GTT appeared to be 134 mg/dL. We recommend a 135 mg/dL threshold for GTT since this threshold accurately diagnoses almost all women with GDM while eliminating unnecessary GTT.     

An experimental investigation on the low velocity impact response of composite plates repaired by VARIM and hand lay-up processes

This paper presents results of an experimental investigation on the impact response of repaired and unrepaired glass/epoxy composite plates. Repaired samples were prepared by two different manufacturing methods; vacuum assisted resin infusion process and hand lay-up technique. In order to compare impact response of the repaired and unrepaired samples a number of single impact tests were performed under various impact energies. Damage process of the samples is analyzed from cross-examining load–deflection curves and damaged specimens. From the visual inspection, for the impacted side of the samples, it is noted that the main damage modes for repaired samples are matrix and fiber cracks around point of impact and delaminations while severe matrix cracks expanded through fiber directions are the dominant damage mode for unrepaired samples. At the back surfaces, delaminations and fiber–matrix debonding oriented in the fiber directions are observed for unrepaired samples. However, for repaired samples the fiber fractures through repair line as well as the delaminations become dominant modes. For a reasoning justification in discussing impact test results, interlaminar fracture toughness (Mode I and Mode II) and flexural tests for repaired and non-repaired samples were also conducted.     

Moisture Dependent Physical Properties of Dry Sweet Corn Kernels

Physical properties of sweet corn kernels have been evaluated as a function of kernel moisture content, varying from 9.12 to 17.06% (db). In the moisture range, kernel length, width, thickness, and geometric mean diameter increased linearly from 9.87 to11.09 mm, 7.41 to 9.25 mm, 3.25 to 4.37 mm, and 6.18 to 7.62 mm, respectively, with increase in moisture content from 9.12–17.06%. The sphericity index, kernel volume, kernel surface area, and thousand seed weight increased linearly from 62.6 to 68.8, 93.8 to 194.3 mm³, 120.1 to 182.9 mm², and 220 to 268 gr, respectively. Apparent density and bulk density decreased linearly from 1.315 to 1.232 g/cm³ and 0.765 to 0.698 g/cm³, respectively, while bulk porosity increased from 41.8 to 43.3%. The highest static coefficient of friction was found on the plywood surface. The static coefficient of friction increased from 0.680 to 0.891, 0.605 to 0.741, and 0.530 to 0.644 for plywood, galvanized iron, and aluminum surfaces, respectively. The angle of repose increased linearly from 30.2 to 35.2° with the increase of moisture content.     

Corrosion and wear behaviors of boronized AISI 316L stainless steel

In this study, the effects of a boronizing treatment on the corrosion and wear behaviors of AISI 316L austenitic stainless steel (AISI 316L) were examined. The corrosion behavior of the boronized samples was studied via electrochemical methods in a simulation body fluid (SBF) and the wear behavior was examined using the ball-on-disk wear method. It was observed that the boride layer that formed on the AISI 316L surface had a flat and smooth morphology. Furthermore, X-ray diffraction analyses show that the boride layer contained FeB, Fe₂B, CrB, Cr₂B, NiB, and Ni₂B phases. Boride layer thickness increased with an increasing boronizing temperature and time. The boronizing treatment also increased the surface hardness of the AISI 316L. Although there was no positive effect of the coating on the corrosion resistance in the SBF medium. Furthermore, a decrease in the friction coefficient was recorded for the boronized AISI 316L. As the boronizing temperature increased, the wear rate decreased in both dry and wet mediums. As a result, the boronizing treatment contributed positively to the wear resistance by increasing the surface hardness and by decreasing the friction coefficient of the AISI 316L.     

Errors of estimation due to mineralization and sampling density in massive copper deposits

ABSTRACT

This study is aimed to determine the effects of spatial variation of the grade, and sampling density, on the errors of estimations of the geological and recoverable reserve for typical massive copper deposits.

A spectrum of copper deposits which have log-normal distributions was numerically modelled on a rectangular grid using the simulation method of turning bands. Spherical variograms with six different random to structured variance ratios were used. The mean block grades were estimated for four different sampling densities by employing the kriging method. The two-dimensional dynamic programming algorithm was utilized for determining the ultimate pit limits. The estimation errors were calculated by deducing the actual values from the estimated values.

The magnitude and patterns of errors due to a broad spectrum of sampling density and nugget effect values have thus been determined. It has been found that the percent estimation error for the recoverable net value is much higher than the percent estimation error for the geological reserves, and therefore deserves more attention.     

Field correlation for flat-topped beam in non-Kolmogorov turbulent medium

Absolute field correlation of flat-topped beam in non-Kolmogorov turbulent medium is examined at the receiver plane. The power law exponent increase affects absolute field correlation inversely. It is found that the absolute field correlation decreases when the propagation distance, deviation from the receiver axis, diagonal transverse distance from the receiver point and turbulence strength increase. Beam flatness order increase yields smaller absolute field correlation. For the employed parameters, the flat-topped beam attains higher absolute field correlation when the wavelength and the source size increase.     

RELATIONSHIP BETWEEN ORGANIC MATTER,SULPHUR AND PHOSPHATE CONTENTS IN UPPER CRETACEOUS MARINE CARBONATES (KARABOGAZ FORMATION,SE TURKEY): IMPLICATIONS FOR EARLY OIL GENERATION

In this paper, we discuss the relationship between the organic matter, sulphur and phosphate contents of Upper Cretaceous marine carbonates (Karabogaz Formation) in the Adiyaman Petroleum Province of SE Turkey. The results of organic geochemical analyses of core samples obtained from the Karabogaz Formation suggest that phosphate deposition occurred in settings where the water column was oxic to sub-oxic. However, the preservation of organic matter was favoured in anoxic environments. Moreover, the presence of sulphur (especially sulphur incorporated into kerogen) in organic matter-rich layers led to early oil generation. The results of stepwise py-gc analyses are consistent with a model in which, with increasing maturity, S-S and C-S bonds are the first to be eliminated from the macromolecular kerogen structure. Study of the maturity evolution of S-rich kerogen by laboratory pyrolysis implies that marginally mature and/or mature kerogen in the Karabogaz Formation, which may be classified as classic “Type II” kerogen, was most probably Type II/S at lower maturity stages. This enabled oil generation to occur at relatively shallow burial depths and relatively early stages of maturation. It is reasonable to conclude that Type II/S kerogen, overlooked in previous studies, was abundant in TOC-rich intervals in the Karabogaz Formation. Early generation (and expulsion) from Type II/S kerogen may have sourced the sulphur-rich oils in the Adiyaman area oilfields.