P-type GaAs/AlAs distributed Bragg mirrors have been grown using molecular beam epitaxy on (100) and (311)A GaAs substrates in a similar conditions. A comparison of I-V measurements shows that the resistance of the ungraded mirrors grown on the (311)A substrate is 35 times lower than those grown on the (100) substrate with similar structure. The effective barrier heights for both (311 )A and (1...

background: doppler indices of umbilical artery are used as indicator of fetal well being. objective: to compare doppler parameters of umbilical artery including pulsatility index (pi) and resistance index (ri) in patients with preeclampsia with those of normal pregnancies and to evaluate the diagnostic characteristics of these parameters in preeclampsia. materials and methods: in a case contro...

assessment and management of the environmental impacts of forest harvesting operations have become increasingly critical factors in practicing commercial forestry. this study investigated soil disturbance from a forest logging system operation on an 8-hectare mixed broadleaved stand in compartment no. 309 in gorazbon district in kheyrud educational and research forest. the objective of this stu...

OBJECTIVE To assess the reliability of the standing measurement of hand-to-foot bioimpedance compared with measurements made in the lying position. RESEARCH METHODS AND PROCEDURES In 205 volunteers 6 to 89 years of age, 111 males and 94 females from six ethnic groups, effects of posture, time, and age on hand-to-foot resistance were studied over a range of body size. The effect of time in a p...

BACKGROUND To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms. METHODS Children aged 2-10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, th...

Background: To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms. Methods: Children aged 2–10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, th...

Abstract: Ball mills are used in the last stage of ore processing for grinding raw materials. Forged 70Cr2 alloy steel and Austempered Ductile Iron (ADI) balls are materials from which grinding balls are made for Sarcheshmeh Copper Plant (SCP) ball mills. In the present study wear and impact properties of these two kinds of balls have been investigated. Some balls randomly were selected as ...