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Effect of Preparation Routes on the Crystal Purity and Properties of BiFeO3 Nanoparticles
M. A. Matin,M. M. Rhaman,M. N. Hossain,F. A. Mozahid,M. A. Hakim,M. H. Rizvi,M. F. Islam 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.6
Sol–gel as a chemical solution deposition technique is compatible with functional device fabrication technology. Single-phase bismuth ferrite (BiFeO3) mutiferroic with its multi-functionality has extensively been studied for a variety of prospective novel device applications. However, the synthesis of BiFeO3 is confronted with a challenge to produce pure state without any secondary phase. Scarcity of unified process parameters impede justifi cation of best synthesis techniques. In this work, sol–gel methods with and without auto-combustion reactions were used to synthesize bismuth ferrite (BiFeO3) nanoparticles. Different techniques UV–Vis–NIR spectroscopy, XRD, EDS, and SEM were used to investigate the effect of preparation routes on the crystal purity and properties of prepared samples. Synthesized nanoparticles were calcined at temperature between 400 and 800 ◦ C and an optimal calcination temperature was found to be 600 ◦ C. Band-gap was determined by UV–Vis–NIR spectroscopy and found to vary from 1.93 to 2.07 eV. X-ray diff raction (XRD) has confi rmed single phase rhombohedral crystal structure with R3c symmetry. Avg crystallite size was found to be higher (40–68 nm) in auto-combustion reaction compared to that of 23–42 nm obtained in sol–gel method without auto-combustion reaction. The band-gap energy was found to reduce with decreasing crystallite size (above the critical size of 10 nm) following Brus’s eff ective mass model. Induced strain was found to exhibit an inverse relation with crystallite size and displayed substantial reduction in auto-combustion reaction route. The microstructural features were investigated by fi eld emission scanning electronic microscopy and avgparticle size was shown to vary from 107 to 197 nm depending on adopted synthesis route. A low reaction temperature (70 ◦ C–80 ◦ C) without auto-combustion and calcination temperature at 600◦ C were found to be optimal conditions for the preparation of low impurity un-doped bismuth ferrite nanaoparticles.
Cadmium stress in rice: toxic effects, tolerance mechanisms, and management: a critical review
Rizwan, M.,Ali, S.,Adrees, M.,Rizvi, H.,Zia-ur-Rehman, M.,Hannan, F.,Qayyum, M. F.,Hafeez, F.,Ok, Y. S. Springer Science + Business Media 2016 Environmental Science and Pollution Research Vol.23 No.18
<P>Cadmium (Cd) is one of the main pollutants in paddy fields, and its accumulation in rice (Oryza sativa L.) and subsequent transfer to food chain is a global environmental issue. This paper reviews the toxic effects, tolerance mechanisms, and management of Cd in a rice paddy. Cadmium toxicity decreases seed germination, growth, mineral nutrients, photosynthesis, and grain yield. It also causes oxidative stress and genotoxicity in rice. Plant response to Cd toxicity varies with cultivars, growth condition, and duration of Cd exposure. Under Cd stress, stimulation of antioxidant defense system, osmoregulation, ion homeostasis, and over production of signaling molecules are important tolerance mechanisms in rice. Several strategies have been proposed for the management of Cd-contaminated paddy soils. One such approach is the exogenous application of hormones, osmolytes, and signaling molecules. Moreover, Cd uptake and toxicity in rice can be decreased by proper application of essential nutrients such as nitrogen, zinc, iron, and selenium in Cd-contaminated soils. In addition, several inorganic (liming and silicon) and organic (compost and biochar) amendments have been applied in the soils to reduce Cd stress in rice. Selection of low Cd-accumulating rice cultivars, crop rotation, water management, and exogenous application of microbes could be a reasonable approach to alleviate Cd toxicity in rice. To draw a sound conclusion, long-term field trials are still required, including risks and benefit analysis for various management strategies.</P>
Lee, S.E.,Chang, H.J.,Rizvi, A.,Hadamitzky, M.,Kim, Y.J.,Conte, E.,Andreini, D.,Pontone, G.,Volpato, V.,Budoff, M.J.,Gottlieb, I.,Lee, B.K.,Chun, E.J.,Cademartiri, F.,Maffei, E.,Marques, H.,Leipsic, J C. V. Mosby Co 2016 American Heart Journal Vol.182 No.-
<P>Background The natural history of coronary artery disease (CAD) in patients with low-to-intermediate risk is not well characterized. Although earlier invasive serial studies have documented the progression of atherosclerotic burden, most were focused on high-risk patients only. The PARADIGM registry is a large, prospective, multinational dynamic observational registry of patients undergoing serial coronary computed tomographic angiography (CCTA). The primary aim of PARADIGM is to characterize the natural history of CAD in relation to clinical and laboratory data. Design The PARADIGM registry (ClinicalTrials. gov NCT02803411) comprises >= 2,000 consecutive patients across 9 cluster sites in 7 countries. PARADIGM sites were chosen on the basis of adequate CCTA volume, site CCTA proficiency, local demographic characteristics, and medical facilities to ensure a broad-based sample of patients. Patients referred for clinically indicated CCTA will be followed up and enrolled if they had a second CCTA scan. Patients will also be followed up beyond serial CCTA performance to identify adverse CAD events that include cardiac and noncardiac death, myocardial infarction, unstable angina, target vessel revascularization, and CAD-related hospitalization. Summary The results derived from the PARADIGM registry are anticipated to add incremental insight into the changes in CCTA findings in accordance with the progression or regression of CAD that confer prognostic value beyond demographic and clinical characteristics.</P>
A Simple Method on the Flow Dependent Background Errors in Hybrid 3dvar using Lorenz-95
Kwan-Young Chung,S.R.H. Rizvi,Dale M. Barker 한국기상학회 2007 한국기상학회 학술대회 논문집 Vol.2007 No.-
From the simple Lorenz-95 model study using small number of ensemble members (N=10), HYB(ENS) and HYB(FD) have the best performance with 0.3 and with 0.6-0.7 weighting factor (a) between the flow-dependent error covariance and the static error covariance, respectively. However as the number of ensemble members increases, HYB(ENS) shows the best results with a=0.1. Also, EnKF and HYB(ENS) have almost the same performance with larger ensemble members (N=20). Consequently, HYB(FD) shows that the errors are decreased by about 20 % compared to pure 3dvar on the simple model test.