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Raktim Bhattacharya,Sulagna Saha,Olga Kostina,Lyudmila Muravnik,Adinpunya Mitra 한국현미경학회 2020 Applied microscopy Vol.50 No.1
Sample preparation including dehydration and drying of samples is the most intricate part of scanning electron microscopy. Most current sample preparation protocols use critical-point drying with liquid carbon dioxide. Very few studies have reported samples that were dried using chemical reagents. In this study, we used hexamethyldisilazane, a chemical drying reagent, to prepare plant samples. As glandular trichomes are among the most fragile and sensitive surface structures found on plants, we used Millingtonia hortensis leaf samples as our study materials because they contain abundant glandular trichomes. The results obtained using this new method are identical to those produced via critical-point drying.
Biswas, Raktim,Ahn, Jin Chul,Moon, Jeong Hwan,Kim, Jungbin,Choi, Young-Hoon,Park, So Young,Chung, Phil-Sang Elsevier 2018 Biochimica et biophysica acta, General subjects Vol.1862 No.8
<P><B>Abstract</B></P> <P>The overall goal is to study the effect of low-level laser therapy (LLLT) on membrane distribution of major water channel protein aquaporin 5 (AQP5) in salivary gland during hyperglycemia. Par C10 cells treated with high glucose (50 mM) showed a reduced membrane distribution of AQP5. The functional expression of AQP5 was downregulated due to intracellular Ca<SUP>2+</SUP> overload and ER stress. This reduction in AQP5 expression impairs water permeability and therefore results in hypo-salivation. A reduced salivary flow was also observed in streptozotocin (STZ)-induced diabetic mice model and the expression of AQP5 and phospho-AQP5 was downregulated. Low-level laser treatment with 850 nm (30 mW, 10 min = 18 J/cm<SUP>2</SUP>) reduced ER stress and recovered AQP5 membrane distribution via serine phosphorylation in the cells. In the STZ-induced diabetic mouse, LLLT with 850 nm (60 J/cm<SUP>2</SUP>) increased salivary flow and upregulated of AQP5 and p-AQP5. ER stress was also reduced via downregulation of caspase 12 and CHOP. In silico analysis confirmed that the serine 156 is one of the most favorable phosphorylation sites of AQP5 and may contribute to the stability of the protein. Therefore, this study suggests high glucose inhibits phosphorylation-dependent AQP5 membrane distribution. High glucose induces intracellular Ca<SUP>2+</SUP> overload and ER stress that disrupt AQP5 functional expression. Low-level laser therapy with 850 nm improves salivary function by increasing AQP5 membrane distribution in hyperglycemia-induced hyposalivation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High glucose induces intracellular Ca<SUP>2+</SUP> overload and ER stress. </LI> <LI> This inhibits phosphorylation-dependent AQP5 translocation to the cellular membrane. </LI> <LI> Reduced AQP5 expression impairs water permeability that results in hypo-salivation. </LI> <LI> LLLT is effective to reduce high glucose induced ER stress. </LI> <LI> LLLT preserves AQP5 membrane abundance necessary for water permeability in salivary glands. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Experimental choices for the determination of carbonyl compounds in air
Pal, Raktim,Kim, Ki-Hyun WILEY-VCH Verlag 2007 Journal of Separation Science Vol.30 No.16
<P>The analysis of carbonyls in ambient air has received a great deal of scientific attention with the advancement of analytical techniques and increased demand for the build-up of its data base. In this review article, we have attempted to provide some insight into the relative performance of different instrumental approaches available for the analysis of ambient carbonyls with a major emphasis on high performance liquid chromatographic and gas chromatographic methods. Reported in several international standard procedures, derivatization of carbonyls with 2,4-dinitrophenylhydrazine (2,4-DNPH) with either an impinger or cartridges is the most commonly used method of HPLC detection. In this respect, a number of alternative hydrazine reagents have also been discussed for use with HPLC. In contrast, GC methods based on the combined application of adsorptive enrichment on solid sorbents and thermal desorption are examined with regard to their suitability for carbonyl analysis in air. Particular emphasis has been directed towards the advantages and drawbacks of these different instrumental techniques for ambient carbonyls. Based on this comparative approach, we discuss the suitability for each method for carbonyl analysis.</P>
Optimal Controller Switching for Resource-constrained Dynamical Systems
이국태,Raktim Bhattacharya 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.3
In this paper, we present the resource-optimal controller switching synthesis for dynamical systems subject to resource constraints. Particularly, for systems having limited computational power (CPU) and onboard energy (battery), it is crucial to keep resource usage as low as possible. Although restrictions on resource utilization may save a CPU time and battery life, it degrades system performance. This paper provides three distinct algorithms that synthesize a controller switching policy for the purpose of resource savings, while not debasing system performance significantly. To measure system performance, we adopted the Waserstein distance that quantifies uncertainty in a probability density function level. The cost function to minimize is then defined based on this Wasserstein metric with a resource utilization penalty. As an example, quadrotor dynamics with two controllers, high performing / high resource consuming and moderate performing / resource saving controllers, is presented. The efficiency and usefulness of the proposed methods are validated in this example.