• 제목/요약/키워드: DHAR

검색결과 83건 처리시간 0.043초

FIXED POINT THEOREMS IN QUASI-METRIC SPACES

  • Abdelkarim Kari;Mohamed Rossafi;Jung Rye Lee
    • Nonlinear Functional Analysis and Applications
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    • 제28권2호
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    • pp.311-335
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    • 2023
  • Fixed point theory is the center of focus for many mathematicians from last few decades. A lot of generalizations of the Banach contraction principle have been established. In this paper, we introduce the concepts of 𝜃-contraction and 𝜃-𝜑-contraction in quasi-metric spaces to study the existence of the fixed point for them.

FIXED POINT THEOREMS IN CONTROLLED RECTANGULAR METRIC SPACES

  • Mohamed Rossafi;Abdelkarim Kari
    • 한국수학교육학회지시리즈B:순수및응용수학
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    • 제30권2호
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    • pp.169-190
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    • 2023
  • In this paper, we introduce an extension of rectangular metric spaces called controlled rectangular metric spaces, by changing the rectangular inequality in the definition of a metric space. We also establish some fixed point theorems for self-mappings defined on such spaces. Our main results extends and improves many results existing in the literature. Moreover, an illustrative example is presented to support the obtained results.

Nitric oxide modulates antioxidant defense and the methylglyoxal detoxification system and reduces salinity-induced damage of wheat seedlings

  • Hasanuzzaman, Mirza;Hossain, Mohammad Anwar;Fujita, Masayuki
    • Plant Biotechnology Reports
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    • 제5권4호
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    • pp.353-365
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    • 2011
  • The present study investigates the possible regulatory role of exogenous nitric oxide (NO) in antioxidant defense and methylglyoxal (MG) detoxification systems of wheat seedlings exposed to salt stress (150 and 300 mM NaCl, 4 days). Seedlings were pre-treated for 24 h with 1 mM sodium nitroprusside, a NO donor, and then subjected to salt stress. The ascorbate (AsA) content decreased significantly with increased salt stress. The amount of reduced glutathione (GSH) and glutathione disulfide (GSSG) and the GSH/GSSG ratio increased with an increase in the level of salt stress. The glutathione S-transferase (GST) activity increased significantly with severe salt stress (300 mM). The ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT) and glutathione peroxidase (GPX) activities did not show significant changes in response to salt stress. The glutathione reductase (GR), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon the imposition of salt stress, especially at 300 mM NaCl, with a concomitant increase in the $H_2O_2$ and lipid peroxidation levels. Exogenous NO pretreatment of the seedlings had little influence on the nonenzymatic and enzymatic components compared to the seedlings of the untreated control. Further investigation revealed that NO pre-treatment had a synergistic effect; that is, the pre-treatment increased the AsA and GSH content and the GSH/GSSG ratio, as well as the activities of MDHAR, DHAR, GR, GST, GPX, Gly I, and Gly II in most of the seedlings subjected to salt stress. These results suggest that the exogenous application of NO rendered the plants more tolerant to salinity-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.

THE EFFECT OF BLOCK RED-BLACK ORDERING ON BLOCK ILU PRECONDITIONER FOR SPARSE MATRICES

  • GUESSOUS N.;SOUHAR O.
    • Journal of applied mathematics & informatics
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    • 제17권1_2_3호
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    • pp.283-296
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    • 2005
  • It is well known that the ordering of the unknowns can have a significant effect on the convergence of a preconditioned iterative method and on its implementation on a parallel computer. To do so, we introduce a block red-black coloring to increase the degree of parallelism in the application of the block ILU preconditioner for solving sparse matrices, arising from convection-diffusion equations discretized using the finite difference scheme (five-point operator). We study the preconditioned PGMRES iterative method for solving these linear systems.

THE ROLE OF INSTANT NUTRIENT REPLENISHMENT ON PLANKTON SPECIES IN A CLOSED SYSTEM

  • Dhar, J.;Sharma, A.K.
    • Journal of applied mathematics & informatics
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    • 제32권5_6호
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    • pp.555-566
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    • 2014
  • In this paper, we formulate two chemostat type models of phytoplankton and zooplankton population dynamics with instant nutrient recycling to study the role of viral infection on phytoplankton. The infection is transmitted only among phytoplankton population and it makes them more vulnerable to predation by zooplankton. It is observe that the chemostat system is very stable in the absence of viral infection but the presence of viral infection make the chemostat system sensitive with respect to the grazing rate of infected-phytoplankton by zooplankton. Further, if the grazing rate is less than certain threshold the system remain stable and exhibits Hopf-bifurcation after crossing it.

Cadmium-Induced Phytotoxicity in Tomato Seedlings Due to the Accumulation of H2O2 That Results from the Reduced Activities of H2O2 Detoxifying Enzymes

  • Cho, Un-Haing
    • The Korean Journal of Ecology
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    • 제27권2호
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    • pp.107-114
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    • 2004
  • Tomato (Lycopersicon esculentum) seedlings exposed to various concentrations of $CdC1_2$ (0∼100 $\mu$M) in the nutrient solution for up to 9 days were analyzed with the seedling growth, $H_2O_2$ production, glutathione levels and activity changes of enzymes related to $H_2O_2$ removal. The growth of seedlings was inhibited with over 50 $\mu$M Cd, whereas the levels of $H_2O_2$ and glutathione were enhanced with Cd exposure level and time. Meanwhile, Cd exposure increased the activities of catalase (CAT) and glutathione reductase (GR) but decreased the activities of dehydroascorbate acid reductase (DHAR) and ascorbate peroxidase (APX) in both leaves and roots. These results suggest that the altered activities of antioxidant enzymes particularly involved in the $H_2O_2$ removal and the subsequent $H_2O$$_2$ accumulation could induce the Cd-induced phytotoxicity.

FIXED POINT THEOREMS FOR (𝜙, F)-CONTRACTION IN GENERALIZED ASYMMETRIC METRIC SPACES

  • Rossafi, Mohamed;Kari, Abdelkarim;Lee, Jung Rye
    • 한국수학교육학회지시리즈B:순수및응용수학
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    • 제29권4호
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    • pp.369-399
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    • 2022
  • In the last few decades, a lot of generalizations of the Banach contraction principle have been introduced. In this paper, we present the notion of (𝜙, F)-contraction in generalized asymmetric metric spaces and we investigate the existence of fixed points of such mappings. We also provide some illustrative examples to show that our results improve many existing results.