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Background The severity and fatality of Coronavirus disease 2019 (COVID-19) infection are not the same in the infected population. The host immune response and Immune-stimulating factors appear to play a role in COVID-19 infection outcome. insulin-like growth factor-1 (IGF-1) affects the immune system by controlling the endocrine system. Recently, the effect of IGF-1 levels on COVID-19 prognosis has been considered. Objective To investigate the difference between circulating IGF-1 and inflammatory cytokines concentration among COVID-19 patients, infected patients admitted to the Intensive Care Unit (ICU) (n = 40; 35 ± 5 y) and patients with mild cases of COVID-19 (n = 40; 35 ± 5 y) were screened prior to participation in the study. There was no significant difference between the groups in terms of gender and preexisting inflammatory state. Collected samples were evaluated by ELISA for IGF-1 and IL-6. Results The study outcomes included a significant decrease in IGF-1 and an increase in IL-6 serum concentration, as an inflammatory marker, for infected patients admitted to the Intensive Care Unit (ICU) (P ≤ 0.001). Finally, there was a significant increase in the IGF-1 and a decrease in the IL-6 serum concentration of hospitalized patients. Discussion it appears that inflammatory cytokines (IL-6) serum concentration in the severe form of corona virus-based infections causes reduced defenses because of suppressed IGF-1. Conclusions Our findings show that lower IGF-1 concentrations are associated with a Severe form of COVID-19 disease. It seems, IGF-1 supplementation or anti-inflammatory treatment rescued the severe form of COVID-19 infection. Further studies are required to determine how to design COVID-19 therapeutic strategies targeting the IGF-1 pathway.

Background The severity and fatality of Coronavirus disease 2019 (COVID-19) infection are not the same in the infected population. The host immune response and Immune-stimulating factors appear to play a role in COVID-19 infection outcome. insulin-like growth factor-1 (IGF-1) affects the immune system by controlling the endocrine system. Recently, the effect of IGF-1 levels on COVID-19 prognosis has been considered. Objective To investigate the difference between circulating IGF-1 and inflammatory cytokines concentration among COVID-19 patients, infected patients admitted to the Intensive Care Unit (ICU) (n = 40; 35 ± 5 y) and patients with mild cases of COVID-19 (n = 40; 35 ± 5 y) were screened prior to participation in the study. There was no significant difference between the groups in terms of gender and preexisting inflammatory state. Collected samples were evaluated by ELISA for IGF-1 and IL-6. Results The study outcomes included a significant decrease in IGF-1 and an increase in IL-6 serum concentration, as an inflammatory marker, for infected patients admitted to the Intensive Care Unit (ICU) (P ≤ 0.001). Finally, there was a significant increase in the IGF-1 and a decrease in the IL-6 serum concentration of hospitalized patients. Discussion it appears that inflammatory cytokines (IL-6) serum concentration in the severe form of corona virus-based infections causes reduced defenses because of suppressed IGF-1. Conclusions Our findings show that lower IGF-1 concentrations are associated with a Severe form of COVID-19 disease. It seems, IGF-1 supplementation or anti-inflammatory treatment rescued the severe form of COVID-19 infection. Further studies are required to determine how to design COVID-19 therapeutic strategies targeting the IGF-1 pathway.

Objectives: This study aimed to evaluate the impact of a national media campaign to promote oral health and periodontal knowledge among adults after a three-month follow-up. Methods: We conducted a population-based study of adults aged 18 to 50 years using a stratified multi-stage sampling method in Tehran, Iran in 2011. The campaign included an animation clip about periodontal health and disease telecast on national TV for ten consecutive days. We used an instrument to assess the effect of the campaign at baseline, immediately after the campaign and after a three-month follow-up. A total of 543 participants responded at baseline and immediately after the intervention, and 294 were interviewed at the three-month follow-up assessment (response rate: 54.1%). We assessed each participant’s periodontal knowledge score, calculated as a sum of correct answers, and the change in their score following the campaign. We then used a five-item questionnaire to evaluate the participants’ opinion of the success of the campaign. We used descriptive statistics and generalised estimating equations (GEE) analysis to conduct the statistical analysis. Results: The mean score for knowledge improvement from baseline to immediate post-intervention evaluation was higher among those who saw the campaign (0.61) than among those who did not (0.29); the corresponding figures from immediate evaluation to three-month follow-up were −0.17 and 0.15, respectively. Adjusting for baseline values, the GEE analysis demonstrated that improvement in the mean score of post-campaign knowledge associated significantly with age, education and seeing the campaign. Significant interaction between the time since seeing the campaign and whether the participant saw it (p < 0.001) revealed that the mean difference in the knowledge score between the groups who did and did not see the campaign was 0.4 at the immediate evaluation and -0.04 at the three-month follow-up. The participants received the campai

This experiment was conducted to evaluate the effect of feeding regimens for the breeder broiler hen on the performance of broiler chickens. Breeder broiler hens (196 hens and 28 roosters; age between 31 and 38 wk) were randomly assigned to 7 dietary treatments that differ in the proportion of daily allowance served at different times with 1 (100% at 0400 h), 2 (50% at 0400 and 1600, or 75% and 25% at 0400 and 1600, respectively), 3 (33% at 0400, 1200 and 1600, or 50% at 0400 and 25% at 1200 and 1600), and 4 (33% at 0400, 22% at 0800, 1200 and 1600, or 55% at 0400 and 17% at 0800, 1200 and 1600) meals in every 24-h cycle. There were 4 replicates per treatment, each consisted of 7 hens and 1 rooster received experimental diets for 8 wk continuously. The growth performance, feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the broiler chicken were evaluated for 42 d. Dietary regimens (frequency and timetable) for breeder broiler hens affected (P < 0.001) the feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the offspring (d 0–42). Overall feed conversion, protein conversion and energy conversion in broiler chickens from breeder hens received daily allowances in 3 or 4 meals were improved compared to those from breeder hens received 100% dietary allowance as a single meal. It is concluded that providing the daily diet allowance of breeder broiler hens in 3 or 4 meals is likely to improve growth performance in their offspring.

This experiment was conducted to evaluate the effect of feeding regimens for the breeder broiler hen on the performance of broiler chickens. Breeder broiler hens (196 hens and 28 roosters; age between 31 and 38 wk) were randomly assigned to 7 dietary treatments that differ in the proportion of daily allowance served at different times with 1 (100% at 0400 h), 2 (50% at 0400 and 1600, or 75% and 25% at 0400 and 1600, respectively), 3 (33% at 0400, 1200 and 1600, or 50% at 0400 and 25% at 1200 and 1600), and 4 (33% at 0400, 22% at 0800, 1200 and 1600, or 55% at 0400 and 17% at 0800, 1200 and 1600) meals in every 24-h cycle. There were 4 replicates per treatment, each consisted of 7 hens and 1 rooster received experimental diets for 8 wk continuously. The growth performance, feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the broiler chicken were evaluated for 42 d. Dietary regimens (frequency and timetable) for breeder broiler hens affected (P < 0.001) the feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the offspring (d 0–42). Overall feed conversion, protein conversion and energy conversion in broiler chickens from breeder hens received daily allowances in 3 or 4 meals were improved compared to those from breeder hens received 100% dietary allowance as a single meal. It is concluded that providing the daily diet allowance of breeder broiler hens in 3 or 4 meals is likely to improve growth performance in their offspring.

Objectives: This study aimed to evaluate the impact of a national media campaign to promote oral health and periodontal knowledge among adults after a three-month follow-up. Methods: We conducted a population-based study of adults aged 18 to 50 years using a stratified multi-stage sampling method in Tehran, Iran in 2011. The campaign included an animation clip about periodontal health and disease telecast on national TV for ten consecutive days. We used an instrument to assess the effect of the campaign at baseline, immediately after the campaign and after a three-month follow-up. A total of 543 participants responded at baseline and immediately after the intervention, and 294 were interviewed at the three-month follow-up assessment (response rate: 54.1%). We assessed each participant’s periodontal knowledge score, calculated as a sum of correct answers, and the change in their score following the campaign. We then used a five-item questionnaire to evaluate the participants’ opinion of the success of the campaign. We used descriptive statistics and generalised estimating equations (GEE) analysis to conduct the statistical analysis. Results: The mean score for knowledge improvement from baseline to immediate post-intervention evaluation was higher among those who saw the campaign (0.61) than among those who did not (0.29); the corresponding figures from immediate evaluation to three-month follow-up were −0.17 and 0.15, respectively. Adjusting for baseline values, the GEE analysis demonstrated that improvement in the mean score of post-campaign knowledge associated significantly with age, education and seeing the campaign. Significant interaction between the time since seeing the campaign and whether the participant saw it (p < 0.001) revealed that the mean difference in the knowledge score between the groups who did and did not see the campaign was 0.4 at the immediate evaluation and -0.04 at the three-month follow-up. The participants received the campai

One of the major challenges in the machining process is measuring the temperature accurately which has a considerable importance in calibrating finite element models and investigating thermodynamic of machining process. In the present paper, one of the effective methods for measuring temperature in the machining processes - i.e. infrared imaging - is used and effective parameters which increase measurement accuracy are investigated. One of the most effective parameter in the temperature measurement accuracy of infrared imaging is extracting and calibrating the emissivity coefficient for different temperature ranges. The obtained results show that the lack of precision calibration of the emissivity for different temperature ranges may cause high error in the measurement results. To measure temperature, several experiments are performed for turning a thin walled workpiece which is made of aluminium alloy Al-7075 and the effects of the machining parameters and tool material - polycrystalline diamond (PCD) and cemented carbide - are studied. Based on the achieved results, it can be concluded that the generated temperature in the cutting area can be decreased significantly by using PCD tools and selecting appropriate machining parameters.

This experiment was conducted to evaluate the effect of feeding regimens for the breeder broiler hen on the performance of broiler chickens. Breeder broiler hens (196 hens and 28 roosters; age between 31 and 38 wk) were randomly assigned to 7 dietary treatments that differ in the proportion of daily allowance served at different times with 1 (100% at 0400 h), 2 (50% at 0400 and 1600, or 75% and 25% at 0400 and 1600, respectively), 3 (33% at 0400, 1200 and 1600, or 50% at 0400 and 25% at 1200 and 1600), and 4 (33% at 0400, 22% at 0800, 1200 and 1600, or 55% at 0400 and 17% at 0800, 1200 and 1600) meals in every 24-h cycle. There were 4 replicates per treatment, each consisted of 7 hens and 1 rooster received experimental diets for 8 wk continuously. The growth performance, feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the broiler chicken were evaluated for 42 d. Dietary regimens (frequency and timetable) for breeder broiler hens affected (P < 0.001) the feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the offspring (d 0–42). Overall feed conversion, protein conversion and energy conversion in broiler chickens from breeder hens received daily allowances in 3 or 4 meals were improved compared to those from breeder hens received 100% dietary allowance as a single meal. It is concluded that providing the daily diet allowance of breeder broiler hens in 3 or 4 meals is likely to improve growth performance in their offspring.

This experiment was conducted to evaluate the effect of feeding regimens for the breeder broiler hen on the performance of broiler chickens. Breeder broiler hens (196 hens and 28 roosters; age between 31 and 38 wk) were randomly assigned to 7 dietary treatments that differ in the proportion of daily allowance served at different times with 1 (100% at 0400 h), 2 (50% at 0400 and 1600, or 75% and 25% at 0400 and 1600, respectively), 3 (33% at 0400, 1200 and 1600, or 50% at 0400 and 25% at 1200 and 1600), and 4 (33% at 0400, 22% at 0800, 1200 and 1600, or 55% at 0400 and 17% at 0800, 1200 and 1600) meals in every 24-h cycle. There were 4 replicates per treatment, each consisted of 7 hens and 1 rooster received experimental diets for 8 wk continuously. The growth performance, feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the broiler chicken were evaluated for 42 d. Dietary regimens (frequency and timetable) for breeder broiler hens affected (P < 0.001) the feed intake, feed conversion ratio, protein intake, protein conversion ratio, energy intake, and energy conversion ratio in the offspring (d 0–42). Overall feed conversion, protein conversion and energy conversion in broiler chickens from breeder hens received daily allowances in 3 or 4 meals were improved compared to those from breeder hens received 100% dietary allowance as a single meal. It is concluded that providing the daily diet allowance of breeder broiler hens in 3 or 4 meals is likely to improve growth performance in their offspring.

In this paper, the optimal jamming of wireless localization systems is investigated. Two optimal power allocation schemes are proposed for jammer nodes in the presence of total and peak power constraints. In the first scheme, power is allocated to jammer nodes in order to maximize the average Cramér-Rao lower bound (CRLB) of target nodes, whereas in the second scheme, the power allocation is performed for the aim of maximizing the minimum CRLB of target nodes. Both the schemes are formulated as linear programs, and a closed-form solution is obtained for the first scheme. For the second scheme, under certain conditions, the property of full total power utilization is specified, and a closed-form solution is obtained when the total power is lower than a specific threshold. In addition, it is shown that non-zero power is allocated to at most NT jammer nodes according to the second scheme in the absence of peak power constraints, where NT is the number of target nodes. In the presence of parameter uncertainty, robust versions of the power allocation schemes are proposed. Simulation results are presented to investigate the performance of the proposed schemes and to illustrate the theoretical results., QC 20161031

The geometrical parameters of 639 discontinuities that surveyed in powerhouse cavern of Rodbar Lorestan pumped storage power plant project have been investigated by scanline and areal sampling methods. As regards the processing and correction of bias types, one bedding and three joint sets are existed in the site. The tectonic activities and direction of principal stresses have caused for each of trace length and spacing characteristics, the probability distribution function of joint sets differ to each other as regards their genetic types. The calculated mean trace length by scanline and areal method are very close together for one joint set and for another one the difference is 28%. The actual intensity differences between circular and rectangle sampling windows for joint sets J1 and J2 are 7% and 38%, respectively. Meanwhile, the calculation of volumetric intensity by various methods shows the estimation of this characteristic is very difficult in the field.

Graphite oxide (GO) in liquid acetonitrile undergoes a transition from an ordered phase around ambient temperature to a gel-like disordered phase at temperatures below 260 K, as demonstrated by in situ X-ray diffraction. The stacking order of GO layers is restored below the freezing point of acetonitrile (199 K). The reversible swelling transition between a stacked crystalline phase and an amorphous delaminated state observed upon cooling provides an unusual example of increased structural disorder at lower temperatures. The formation of the gel-like phase is attributed to the thermo-responsive conformational change of individual GO flakes induced by stronger solvation. Scanning force microscopy demonstrates that GO flakes deposited onto a solid substrate from acetonitrile dispersions at a temperature below 260 K exhibit corrugations and wrinkling which are not observed for the flakes deposited at ambient temperature. The thermo-responsive transition between the delaminated and stacked phases reported here can be used for sonication-free dispersion of graphene oxide, micro-container applications, or the preparation of new composite materials.

In this paper, the problem of conguration selection i.e. sensor/actuator placement for piecewise ane (PWA) systems subject to both sensor and actuator faults is considered. A method is proposed that provides a tool for the design phase to decide about the optimal placement of sensor/actuators where the recongurability of the system subject to sensor and actuator faults is also taken into account. Using a lattice of possible congurations (sensor/actuator placements), the recongurability of the system subject to faults for each conguration is evaluated and based on that one can draw conclusions about the recongurability of the system and the optimal conguration in the architecture design phase. A recongurable control must ensure stability of the recongured system and, if possible, a graceful degradation in the performance. Therefore, in the proposed recongurability analysis, we consider both stabilizability and performance of the system. The efficiency of the proposed method is demonstrated on several numerical examples

The non-protein amino acid ornithine (Orn) plays essential roles in regulation of the urea cycle and polyamines biosynthesis in tobacco. Herein, we show that d-enantiomer of Orn, can actively participate in metabolites production in tobacco cells, functioning a positive role in plant cells metabolism, as opposed to the common l-enantiomer. Using a comprehensive amino acids and amines profiling method by liquid chromatography–electrospray ionization triple quadruple mass spectrometry (LC–ESI-QqQ-MS) in combination with chiral LC–ESI-MS, it was shown that d-Orn has a potential advantage in promoting selective and large accumulation of l-arginine (l-Arg) in tobacco cells. Exogenous d-Orn resulted in a selective up-regulation of l-Arg by 80-fold, while l-Orn slightly increased the levels of all amino acids. Changes of all the urea cycle related intermediates, e.g. citrulline, Arg and Orn were also shown to be critical following change of Orn's stereochemistry. GC/MS profiling of the metabolites revealed that high nicotine production was the dominant change driven by l-Orn treatments. From these observations, d-Orn was shown to be a selective regulator of l-Arg biosynthesis and the urea cycle. We propose that d-Orn has a potential function in the tobacco cells which through some previously unidentified mechanism result in l-Arg accumulation.

The non-protein amino acid ornithine (Orn) plays essential roles in regulation of the urea cycle and polyamines biosynthesis in tobacco. Herein, we show that d-enantiomer of Orn, can actively participate in metabolites production in tobacco cells, functioning a positive role in plant cells metabolism, as opposed to the common l-enantiomer. Using a comprehensive amino acids and amines profiling method by liquid chromatography–electrospray ionization triple quadruple mass spectrometry (LC–ESI-QqQ-MS) in combination with chiral LC–ESI-MS, it was shown that d-Orn has a potential advantage in promoting selective and large accumulation of l-arginine (l-Arg) in tobacco cells. Exogenous d-Orn resulted in a selective up-regulation of l-Arg by 80-fold, while l-Orn slightly increased the levels of all amino acids. Changes of all the urea cycle related intermediates, e.g. citrulline, Arg and Orn were also shown to be critical following change of Orn's stereochemistry. GC/MS profiling of the metabolites revealed that high nicotine production was the dominant change driven by l-Orn treatments. From these observations, d-Orn was shown to be a selective regulator of l-Arg biosynthesis and the urea cycle. We propose that d-Orn has a potential function in the tobacco cells which through some previously unidentified mechanism result in l-Arg accumulation.

The Thirteenth East Asia-Pacific Conference on Structural Engineering and Construction (EASEC-13), September 11-13, 2013, Sapporo, Japan.

We have investigated optical properties of Ga0.64In0.36N0.006As0.994/GaAs single quantum-well structures using photoluminescence technique. We have found that nitrogen creates potential fluctuations in the InGaNAs structures, so it is the cause of trap centres in these structures and leads to localized excitons recombination dynamics. The near-band edge PL at 2 K exhibited a blueshift with an increase in excitation intensity of a sample but there is not such a shift in the PL peak position energy of same sample at 150 K. It has been found that PL spectra have a large full width at half maximum (FWHM) value at 2 K. These results are discussed in terms of carrier localization. Additionally, our results suggest decreasing PL integrated intensity in this structure, possibly due to non-radiative recombination. It has been shown that thermal annealing reduces the local strain created by nitrogen. By annealing process, a blue shifted emission can be observed., QC 20100525

We report the results from detailed optical spectroscopy from MOCVD grown GaN/AlGaN multiple quantum wells (MQWs), as opposed to most previous studies where MBE was employed by means of photoluminescence (PL) technique. In this paper we will present theoretical and experimental results demonstrating how polarization induced electric fields and bound interface charges in GaN/AlGaN MQWs affect the emission peak energy, PL line shape, as well as the emission line width. Theoretically estimated fields in this work are consistent with experimental data. Transition energy of the heavy hole and electron ground state Ee-hh in GaN/AlGaN MQWs were calculated and it is found that it stays in good agreement with the experimental data.

Due to many important applications, the group III-nitride semiconductors have recently attracted remarkable attention among the semiconductor researchers and engineers. In this paper, we report on the impact of the extrinsic and temporal carriers on the screening of the polarization internal fields. The optical efficiency of GaN/AlGaN multiple quantum well (MQW) nanostructures were studied by means of photoluminescence (PL) and time-resolved PL measurements. Extrinsic carriers come from Si doping in the barriers while temporal carriers originate when the samples are excited by the laser beam. The emission peaks of MQWs in PL spectra of the undoped and low-doped samples show a shift towards higher energy levels as excitation intensity increases, while the other samples do not exhibit such a phenomenon due to the dominance of the extrinsic carriers. The transient data confirm the results of the PL measurements.

We report the results from detailed optical spectroscopy from MOCVD grown GaN/AlGaN multiple quantum wells (MQWs), as opposed to most previous studies where MBE was employed by means of photoluminescence (PL) technique. In this paper we will present theoretical and experimental results demonstrating how polarization induced electric fields and bound interface charges in GaN/AlGaN MQWs affect the emission peak energy, PL line shape, as well as the emission line width. Theoretically estimated fields in this work are consistent with experimental data. Transition energy of the heavy hole and electron ground state Ee-hh in GaN/AlGaN MQWs were calculated and it is found that it stays in good agreement with the experimental data.

Due to many important applications, the group III-nitride semiconductors have recently attracted remarkable attention among the semiconductor researchers and engineers. In this paper, we report on the impact of the extrinsic and temporal carriers on the screening of the polarization internal fields. The optical efficiency of GaN/AlGaN multiple quantum well (MQW) nanostructures were studied by means of photoluminescence (PL) and time-resolved PL measurements. Extrinsic carriers come from Si doping in the barriers while temporal carriers originate when the samples are excited by the laser beam. The emission peaks of MQWs in PL spectra of the undoped and low-doped samples show a shift towards higher energy levels as excitation intensity increases, while the other samples do not exhibit such a phenomenon due to the dominance of the extrinsic carriers. The transient data confirm the results of the PL measurements.

We have investigated optical properties of Ga0.64In0.36N0.006As0.994/GaAs single quantum-well structures using photoluminescence technique. We have found that nitrogen creates potential fluctuations in the InGaNAs structures, so it is the cause of trap centres in these structures and leads to localized excitons recombination dynamics. The near-band edge PL at 2 K exhibited a blueshift with an increase in excitation intensity of a sample but there is not such a shift in the PL peak position energy of same sample at 150 K. It has been found that PL spectra have a large full width at half maximum (FWHM) value at 2 K. These results are discussed in terms of carrier localization. Additionally, our results suggest decreasing PL integrated intensity in this structure, possibly due to non-radiative recombination. It has been shown that thermal annealing reduces the local strain created by nitrogen. By annealing process, a blue shifted emission can be observed.

Continuous wave photoluminescence (cw PL) spectroscopy has been used to study the optical properties of a set of InGaNAs epilayers and single quantum wells with nitrogen concentration less than a few per cent at different temperatures and different excitation powers. We found that nitrogen has a critical role on the emission light of InGaNAs nanostructures and the recombination mechanism. The incorporation of a few per cent of nitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gap reduction has been investigated both experimentally and theoretically by using a band anticrossing model. We have found that localization of excitons that have been caused by incorporation of a few per cent of nitrogen in these structures is the main explanation of such anomalous behavior observed in the low-temperature photoluminescence spectra of these nanostructures. The localization energies of carriers have been evaluated by studying the variation of the quantum well (QW) emission versus temperature, and it was found that the localization energy increases with increasing nitrogen composition. Our data also show that, with increasing excitation intensity, the PL peak position moves to higher energies (blue shift) due to the filling of localized states and capture centers for excitons by photo-generated carriers., QC 20100525

Continuous wave photoluminescence (cw PL) spectroscopy has been used to study the optical properties of a set of InGaNAs epilayers and single quantum wells with nitrogen concentration less than a few per cent at different temperatures and different excitation powers. We found that nitrogen has a critical role on the emission light of InGaNAs nanostructures and the recombination mechanism. The incorporation of a few per cent of nitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gap reduction has been investigated both experimentally and theoretically by using a band anticrossing model. We have found that localization of excitons that have been caused by incorporation of a few per cent of nitrogen in these structures is the main explanation of such anomalous behavior observed in the low-temperature photoluminescence spectra of these nanostructures. The localization energies of carriers have been evaluated by studying the variation of the quantum well (QW) emission versus temperature, and it was found that the localization energy increases with increasing nitrogen composition. Our data also show that, with increasing excitation intensity, the PL peak position moves to higher energies (blue shift) due to the filling of localized states and capture centers for excitons by photo-generated carriers. © IOP Publishing Ltd.

Due to many important applications, the group III-Nitride semiconductors have recently attracted remarkable attention among semiconductor researchers and engineers. In this paper, we report on the impact of extrinsic and temporal carriers on the screening of polarization internal fields. The optical efficiency of GaN/AlGaN multiple quantum well (MQW) nanostructures were studied by means of photoluminescence (PL) and time-resolved PL measurements. Extrinsic carriers come from Si doping in the barriers, while temporal carriers originate when the samples are excited by laser beam. The emission peaks of MQWs in PL spectra of the undoped and low-doped samples show a shift towards higher energy levels as excitation intensity increases, while the other samples do not exhibit such a phenomenon due to the dominance of the extrinsic carriers. The transient data confirm the results of the PL measurements.

Masoudi, S., Gholami, M. A., Iariche, J. M., & Vafadar, A. (2017). Infrared temperature measurement and increasing infrared measurement accuracy in the context of machining process. Advances in Production Engineering & Management, 12(4), 353-362. Available here.