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.     

Numerical approach for solving linear Fredholm integro-differential equation with piecewise intervals by Bernoulli polynomials

In this paper a numerical method is given for the solution of linear Fredholm integro-differential equation (FIDE) with piecewise intervals under the mixed conditions using the Bernoulli polynomials. The aim of this article is to present an efficient numerical procedure for solving linear FIDE with piecewise intervals. This method transforms linear FIDE with piecewise intervals and the given conditions into matrix equation which corresponds to a system of linear algebraic equation. Finally, some experiments and their numerical solutions are given. The results reveal that this method is reliable and efficient.     

Effect of Annealing on the Surface Morphology and Current–Voltage Characterization of a CZO Structure Prepared by RF Magnetron Sputtering

Semiconductors - In this study, we investigated the Cu-doped ZnO (CZO) structure. This structure was deposited on the Si and glass substrates using the RF magnetron sputtering technique....     

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.     

Thickness-Dependent Permanent Magnet Properties of Zr $$_{2}$$ Co $$_{11}$$ Thin Films Grown on Si with Pt Underlayer

Metallurgical and Materials Transactions A - Zr-Co is one of the essential magnetic materials due to its interesting magnetic and structural properties. In this work, we studied the magnetic and...     

The long‐term effects of arteriovenous fistula creation on the development of pulmonary hypertension in hemodialysis patients

The aim of this prospective study was to evaluate long‐term effects of arteriovenous fistula (AVF) on the development of pulmonary arterial hypertension (PAH) and the relationship between blood flow rate of AVF and pulmonary artery pressure (PAP) in the patients with end‐stage renal disease (ESRD). This prospective study was performed in 20 patients with ESRD. Before an AVF was surgically created for hemodialysis, the patients were evaluated by echocardiography. Then, an AVF was surgically created in all patients. After mean 23.50 ± 2.25 months, the second evaluation was performed by echocardiography. Also, the blood flow rate of AVF was measured at the second echocardiographic evaluation. Pulmonary arterial hypertension was defined as a systolic PAP above 35 mmHg at rest. Mean age of 20 patients with ESRD was 55.05 ± 13.64 years; 11 of 20 patients were males. Pulmonary arterial hypertension was detected in 6 (30%) patients before AVF creation and in 4 (20%) patients after AVF creation. Systolic PAP value was meaningfully lower after AVF creation than before AVF creation (29.95 ± 10.26 mmHg vs. 35.35 ± 7.86 mmHg, respectively, P: 0.047). However, there was no significant difference between 2 time periods in terms of presence of PAH (P>0.05). Pulmonary artery pressure did not correlate with blood flow rate of AVF and duration after AVF creation (P>0.05). In hemodialysis patients, a surgically created AVF has no significant effect on the development of PAH within a long‐term period. Similarly, blood flow rate of AVF also did not affect remarkably systolic PAP within the long‐term period.     

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.     

Efficient power analysis for an irreversible Carnot heat engine

In this paper, the finite‐time thermodynamic optimization is carried out based on the efficient power criterion for an irreversible Carnot heat engine. The obtained results are compared with those obtained by using the maximum power (MP) and maximum power density (MPD) criteria. The optimal design parameters have been derived analytically, and the effect of the irreversibilities on the general and optimal performances is investigated. Maximizing the efficient power gives a compromise between power and efficiency. The results showed that the design parameter at the maximum efficient power (MEP) condition leads to more efficient engines than at the MP conditions and that the MEP criterion may have a significant power advantage with respect to the MPD criterion. Copyright © 2007 John Wiley & Sons, Ltd.