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Aquo-organic sol based F-doped SnO2 (Sn : F = 90 : 10) coatings on glass

100%

Biswas P. K. , Dua L. , Chaudhuri A. d. T.

Materials Science Poland

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2006

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tom Vol. 24, No. 2/1

367--374

EN

Aqueous precursor of F-doped SnO2 was prepared starting with hydrated Sn (IV) chloride, ammonium fluoride and water. Polyvinyl alcohol (Mol. Wt, 22000), a sol stabilizer was used for better adherence to glass substarte. Both the dipping and the spinning techniques were used to deposit layers of different thicknesses (200 to 650 š 10 nm). Air drying and subsequent curing at ~ 450°C in air yielded tetragonal cassiterite phase of SnO2 along with tetragonal Sn phase. Percentage of visible transmission of the spin coated samples was relatively high (~ 80 %). Incorporation of polyvinyl alcohol in the aqueous precursor minimized etching phenomenon by fluoride ion as revealed by the SEM pictures. Surface of the developed films seemed to be porous; the spin coated sample was relatively less porous. Refractive index (R.I.) of the dip coated samples was relatively smaller (range, 1.650 - 1.803) while the spin coated samples had the R. I. values in the range 1.670-1.823. Sheet resistance of the spin coated films was in the range, 3.3-1300 k? / while it was 1.4 - 2500 k? / in the case of dip coated samples.

2

Analysis and simulation of different types of power amplifiers used in electromagnetic levitation system

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Debnath S. , Biswas P. K. , Das U.

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tom Vol. 98, nr 2

220--227

EN

The objective of this paper is time and frequency response analysis of single quadrant and two-quadrant power amplifiers by using MATLAB SIMULINK, PSPICE and PSIM based software used in the electromagnetic levitation system. The power amplifier plays a key role in controlling the electromagnetic levitation system, controlling the current as well as the force between electromagnet and rail. Here the power amplifier is used to convert a fixed DC voltage to an adjustable DC output voltage. Different kinds of power amplifiers have been proposed for the electromagnetic levitation system. In this paper, only buck and asymmetrical converters are simulated in the simulation software. The exciting current of the electromagnet is controlled by the power amplifier, which controls the air gap and force between actuator and rail in a closed loop manner. PSPICE is an analog and digital circuit simulation software. PSIM is a general-purpose analog and digital electronic circuit simulator. It is also used for simulation and design software for power electronics, motor drives, and dynamic system simulation. SIMULINK is the graphic user interface software from MATLAB which helped us prepare the model of the various power systems, power electronics and control system.

3

Exogenous application of gibberellic acid mitigates drought-induced damage in spring wheat

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Moumita , Al Mahmud J. , Biswas P. K. , Nahar K. , Fujita M. , Hasanuzzaman M.

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nr 2

EN

Drought stress is a major problem in wheat production but it could be managed by using various exogenous protectants such as gibberellic acid (GA). Although GA is a plant growth hormone, it shows a potential to protect the plant in stress conditions. To investigate the possible role of GA in mitigating drought stress, we treated wheat (Triticum aestivum ‘BARI Gom-21’) seedlings with a GA spray under semihydroponic conditions. In the experiment, the combined effect of GA and drought stress (induced by 12% polyethylene glycol) was studied after 48 h and 72 h. In the absence of exogenous GA, drought-stressed wheat seedlings showed various physiological and biochemical changes in a time-dependent manner. Malondialdehyde (MDA), hydrogen peroxide (H2O2) and free proline (Pro) concentrations were increased, whereas catalase (CAT) and ascorbate peroxidase (APX) activities were reduced under drought stress. Gibberellic acid played a role in restoring the ascorbate (AsA) level, decreased the reduced/oxidized glutathione (GSH/GSSG) ratio and reduced monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) activities. Gibberellic acid significantly affected the glyoxalase system. Under drought stress, the methylglyoxal (MG) concentration was increased but GA application stimulated glyoxalase I (Gly I) and glyoxalase II (Gly II) activities to protect the wheat seedlings against stress. The study concluded that the severity of drought stress in wheat depends on the growth stage and it increases with an increase in the duration of stress, whereas exogenous GA helped the seedlings to survive by upregulating antioxidant defense mechanisms and the glyoxalase system.

PL

Stres spowodowany suszą jest głównym problemem w produkcji pszenicy, ale można mu zapo- biegać przy pomocy różnych egzogennych środków ochronnych, takich jak kwas giberelinowy (GA). Chociaż GA jest fitohormonem, wykazuje potencjalne działanie ochronne w stosunku do roślin rosnących w warunkach stresowych. W celu zbadania ewentualnego oddziaływania GA w łagodzeniu stresu suszy, sadzonki pszenicy (Triticum aestivum‘BARI Gom-21’) traktowaliśmy GA w formie oprysku w warunkach pół-hydroponicznych. W przeprowadzonym doświadczeniu badano łączny wpływ GA i stresu suszy (indukowanego przez 12% glikol polietylenowy) po 48 godzinach i 72 godzinach. W siewkach pszenicy poddanych działaniu suszy, pod nieobecność egzogennego GA, stwierdzono różnorodne zmiany fizjologiczne i biochemiczne, uzależnione od czasu ekspozycji. Pod wpływem suszy stężenia dialdehydu malonowego (MDA), nadtlenku wodoru (H2O2) oraz wolnej proliny (Pro) zwiększały się, podczas gdy aktywność katalazy (CAT) i peroksydazy askorbinianowej (APX) uległa zmniejszeniu. Kwas giberelinowy odgrywał rolę w przywracaniu prawidłowego poziomu askorbinianu (AsA), zmniejszał stosunek glutationu zredukowanego/utlenionego (GSH/GSSG) oraz obniżał aktywności reduktazy monodehydro- askorbinianowej (MDHAR) i reduktazy dehydroaskorbinianowej (DHAR). Kwas giberelinowy istotnie wpłynął na układ glioksalazy. Pod wpływem stresu suszy stężenie metyloglioksalu (MG) wzrosło, ale aplikacja GA stymulowała aktywność glioksalazy I (Gly I) i glioksalazy II (Gly II) chroniąc siewki pszenicy przed stresem. W badaniach wykazano, że natężenie stresu suszy u pszenicy zależy od etapu wzrostu i nasila się wraz z wydłużeniem czasu trwania stresu, podczas gdy egzogenny GA zwiększa możliwość przetrwania siewek poprzez wzmocnienie mechanizmów obrony antyoksydacyjnej i regulację systemu glioksalazy.