The influence of dietary iron on zinc in rat

Cortical bone remodeling rates for rib samples from three archaeological populations and a modern autopsy sample were determined using an algorithm developed by Frost (Frost [1987a] Calcif. Tissue Res. 3:211-237). When plotted against the relative antiquities for population samples, histomorphometric variables; i.e., activation frequency (mu rc), net bone formation (netVf,r,t), and mean annual bone formation rate (Vf,r,t), exhibit a concordant trend of increased cortical bone remodeling activity levels over time. Two intensive foraging populations, Windover and Gibson, are similar for all bone remodeling parameters and have the lowest remodeling activity levels among the samples. The more recent Ledders sample, which is reported to practice agricultural subsistence, is consistently intermediate between these and a modern autopsy sample. Although there appear to be differences in bone formation rates among the populations it is concluded that these differences cannot be attributed to differences in bone remodeling rates among the populations, but rather are reflecting different effective ages of adult compacta for their ribs. These findings suggest that the earlier populations, particularly Windsor and Gibson, appear to have reached skeletal maturity at an older age than observed for modern.     

Stochastic two-sided U-type assembly line balancing: a genetic algorithm approach

In this paper, a novel stochastic two-sided U-type assembly line balancing (STUALB) procedure, an algorithm based on the genetic algorithm and a heuristic priority rule-based procedure to solve STUALB problem are proposed. With this new proposed assembly line design, all advantages of both two-sided assembly lines and U-type assembly lines are combined. Due to the variability of the real-life conditions, stochastic task times are also considered in the study. The proposed approach aims to minimise the number of positions (i.e. the U-type assembly line length) as the primary objective and to minimise the number of stations (i.e. the number of operators) as a secondary objective for a given cycle time. An example problem is solved to illustrate the proposed approach. In order to evaluate the efficiency of the proposed algorithm, test problems taken from the literature are used. The experimental results show that the proposed approach performs well.     

Series resistance determination of Au/Polypyrrole/p-Si/Al structure by current–voltage measurements at low temperatures

The current–voltage (I–V) characteristics of Polypyrrole(PPy)/p-Si/Al structure have been investigated as a function of temperature. A modified Norde function combined with conventional forward I–V method has been used to extract the junction parameters including the ideality factor, barrier height and series resistance. Norde function has been compared with the Cheung functions and it has been seen that there is a good agreement with both method for the barrier height values. However, the values of series resistance have very different especially towards to the lower temperatures. This is attributed to non-ideal I–V characteristics of the Au/PPy/p-Si/Al structure and non-pure Thermionic emission theory due to the low temperature effects.     

A study of the rectifying behaviour of aniline green-based Schottky diode

An Al/aniline green (AG)/Ga₂Te₃ device was fabricated and the current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of the device have been investigated at room temperature. The values of the ideality factor, series resistance and barrier height obtained from Cheung and Norde methods were compared, and it was seen that there was an agreement with each other. It was seen that the forward bias current-voltage characteristics at sufficiently large voltages has shown the effect of the series resistance. In addition, it was seen from the C-f characteristics that the values of capacitance have been decreased towards to the high frequencies. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the Ga₂Te₃ that can follow the ac signal.     

Determination of susceptibility to intergranular corrosion and electrochemical reactivation behaviour of AISI 316L type stainless steel

In this study, double loop electrochemical potentiokinetic reactivation (DLEPR) test was applied to determine the degree of sensitization in 316L type stainless steel, where obtained results were correlated with revealed microstructures after oxalic acid test and weight loss measurements of Streicher and Huey acid tests. Best agreement was provided with test parameters which are 1 M H₂SO₄ and 0.005 M KSCN at 0.833 mV/s scan rate at 30 °C. Specimens were classified structurally as absence of chromium carbides - step, no single grain completely surrounded by carbides - dual and one or more grain completely surrounded by carbides - ditch, in the as-etched structure, if the I_r:I_a (×100) ratios were obtained to be between 0 and 0.2, 0.2 and 5.0 and 5.0 and higher, respectively. It was also found that at high KSCN concentrations, reactivation current profile skewed to higher potentials where this was attributed the formation of metastable pits, during the anodic scan of the test procedure.     

The analysis of the current–voltage characteristics of the high barrier Au/Anthracene/n-Si MIS devices at low temperatures

The Au/Anthracene/n-Si/Al MIS device was fabricated on the basis of anthracene film covalently bonded to a Si substrate. The MIS device showed Schottky behavior with barrier heights of 0.85 eV and ideality factors of 1.88 at 300 K. The barrier height of the Au/n-Si has increased after deposition of the anthracene layer onto Si. Temperature dependent current–voltage (I–V) measurements were performed on the Au/Anthracene/n-Si/Al MIS diodes in the range 140–300 K. From the temperature dependence of forward bias I–V, the barrier height was observed to increase with temperature. However, the ideality factor decreased with increasing temperature. The values of activation energy (E_a) and Richardson constant (A*) were determined as 0.24 eV and 7.57 × 10⁻⁶ A cm⁻² K⁻² from the slope and the intercept at ordinate of the linear region of Richardson plot, respectively. The increase of the series resistance R_s with the fall of temperature was attributed to lack of free carrier concentration at low temperatures.     

Implementation of a single-phase matrix converter induction motor drive

This paper presents an implementation of a single-phase matrix converter for a variable speed single-phase induction motor. The paper analyzes the characteristics of a single-phase ac–ac converter drive with particular emphasis on the harmonic content, input voltage utilization and variable speed performance of the motor. Both square and sinusoidal wave modulation signals in PWM generation have been used to demonstrate the effect of the modulating signal on the input voltage utilization and output harmonic content. Simulation and experimental results for an R–L and induction motor loads are presented. Promising results illustrate that a good performance of a single-phase induction motor fed by a matrix converter is achievable.     

Temperature-dependent <Emphasis Type="Italic">C-V</Emphasis> characteristics of Au/ZnO/n-Si device obtained by atomic layer deposition technique

Since the importance of Schottkky devices, Au/ZnO/n-Si device were obtained, and the capacitance–voltage (C-V) and conductance-voltage (G-V) characteristics of Au/ZnO/n-Si device were studied using admittance spectroscopy at changing temperature from 160 to 340 K with 20 K intervals and ?1 to +2 V bias voltage range. The interface thin film ZnO layer was deposited on the n-type Si wafer by atomic layer deposition technique (ALD) in order to obtain homogenous interface layer. The layer thickness of ZnO was taken as 10 nm by the resulting ZnO film growth rate at about 1.45 Å per cycle. This thin film layer was characterized with XRD and AFM analyses. It can be seen from the C-V curves of the device that the capacitance values increased in depletion region with increasing temperature and exhibited peaks towards to forward biases after 240 K temperature. The changing of capacitance values confirmed re-ordering and re-structuring of charges in the interface of the device with changing temperature. The G-V curves of the device also increased with increasing temperature and towards to forward bias voltages due to increasing free charges in the interface. The series resistance (\({R}_{s}\)) of the device was taken into account to understand its effect on main electrical parameters, and it could be seen from these results that the \({R}_{s}\) strongly depends on the device temperature. The impedance (Z) values decreased with changing from ?1 to +2 V bias voltages and increasing temperature. The barrier height which was obtained from the C ^?2 -V plots increased a slope of 0.00108 eV/K with a decrease in temperature from 160 to 340 K. It can be concluded that the Au/ZnO/n-Si device may be used and improved for next technological applications such as capacitor and memristor.     

Thermoelectric and Magnetic Properties of Pt-Substituted $${BaFe_{4-{x}}Pt_{{x}}Sb_{12}}$$ Compounds

\({BaFe_{4-{x}}Pt_{{x}}Sb_{12}}\) (x = 0, 0.1, 0.2) compounds were prepared by melting and annealing, followed by a spark plasma sintering method. Low-temperature thermoelectric and magnetic properties were investigated based on Seebeck coefficient, electrical and thermal conductivity and magnetization measurements. The structural properties of \({BaFe_{4-{x}}Pt_{{x}}Sb_{12}}\) (x = 0, 0.1, 0.2) compounds were ascertained by powder x-ray diffraction analysis, confirming that all samples have a main phase of a skutterudite structure with the space group Im\({\mathrm {\bar{3}}}\). The lattice parameters obtained, 9.202(5), 9.199(5) and 9.202(1) Å for x = 0, 0.1 and 0.2, respectively, were found consistent with literature. The Seebeck coefficient sign shows that holes are dominant carriers in all compounds. The local maximum Seebeck coefficient was observed around 50 K which may be a trace of paramagnon-drag effect of charge carriers. Thermal conductivity and electrical resistivity measurements were carried out between 4.2 and 300 K. Temperature dependence of electrical resistivity reflects that all samples show semi-metallic behavior in our temperature range of 4.2–300 K. Samples for x = 0.1 and x = 0.2 show Kondo-like behavior. In magnetization measurement, we observe that there are two successive magnetic transitions in Pt-substituted compounds; however, there is only one (transition from a paramagnetic state to long-range magnetic ordering) in Pt-free compounds. In Pt-substituted compounds, the first transition appears at \( T _{ {\rm c}}\) = 48 K. In addition, the second transition is observed at \( T _{ {\rm irr}}\) = 30 K where an intermediate state is observed before the magnetic ordering transforms to an irreversible ferromagnetic state. We concluded that Pt substitution on the Fe side effectual on the thermoelectric and magnetic properties of \({BaFe_{4-{x}}Pt_{{x}}Sb_{12}}\) (x = 0, 0.1, 0.2) compounds.