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Pathak, Shiva,Regmi, Shobha,Gupta, Biki,Pham, Tung Thanh,Yong, Chul Soon,Kim, Jong Oh,Yook, Simmyung,Kim, Jae-Ryong,Park, Min Hui,Bae, Young Kyung,Jeong, Jee-Heon Federation of American Societies for Experimental 2017 The FASEB Journal Vol. No.
<P>An alternative route for pancreatic islet transplantation is the subcutaneous space; however, inadequate vascularization in the subcutaneous space limits the availability of oxygen and nutrients to the subcutaneously transplanted islets, which leads to the development of a necrotic core in the islets, thereby causing islet dysfunction. Thus, we aimed to prevent the early apoptosis of pancreatic islets after transplantation into subcutaneous space by preparing islet clusters of appropriate size. We prepared fully functional islet cell clusters (ICCs) by using the hanging-drop technique. We optimized the size of ICCs on the basis of viability and functionality after culture in an hypoxic environment. We transplanted ICCs into the subcutaneous space of diabetic mice and evaluated the viability of the islets at the transplantation site. In an hypoxic environment, ICCs exhibited improved viability and functionality compared with control islets. ICCs, upon transplantation into the hypoxic subcutaneous space of diabetic mice, showed better glycemic control compared with control islets. Live/dead imaging of the islets after retrieval fromthe transplanted area revealed significantly reduced apoptosis in ICCs. Transplantation of ICCsmay be an attractive strategy to prevent islet cell apoptosis that results from nonimmune-mediated physiologic stress at the transplantation site.-Pathak, S., Regmi, S., Gupta, B., Pham, T. T., Yong, C. S., Kim, J. O., Yook, S., Kim, J.-R., Park, M. H., Bae, Y. K., Jeong, J.-H. Engineeredislet cell clusters transplanted into subcutaneous space are superior to pancreatic islets in diabetes.</P>
Pathak, A.,Singh, P.,Dhama, P.,Dastidar, M.G.,Kim, D.J.,Heyes, G. Maney Publishing 2014 Canadian metallurgical quarterly Vol.53 No.1
The present study investigated the changes in nutrient profile of sewage sludge during bioleaching in a batch mode of operation. The study identified the optimum bioleaching period at which maximum solubilisation of metals is achieved while maintaining the fertilising property of the bioleached sludge. The bioleaching experiments were performed using anaerobically digested sewage sludge by employing indigenous iron and sulphur oxidising microorganisms. The results showed that bioleaching using sulphur oxidising microorganisms is comparatively advantageous due to the higher solubilisation of heavy metals. However, despite its high potential in solubilisation of heavy metals from the sludge, the bioleaching process resulted in the undesirable dissolution/loss of sludge bound nutrients (nitrogen and phosphorus), thus making the sludge less attractive for land application as a fertiliser. After 16 days of bioleaching about 45% of the nitrogen and 34% of the phosphorus were leached from the sludge using indigenous iron oxidising microorganisms, whereas about 78% of the nitrogen and 56% of the phosphorus were leached using indigenous sulphur oxidising microorganisms. The findings indicated that the fertilising property of the sewage sludge can be maintained by conducting the process for a shorter duration of time (up to 10 days). The optimum bioleaching period was 10 days where about 85%Cu, 71%Ni, 91%Zn and 61%Cr were solubilised from the sludge while the loss of nitrogen and phosphorus was only 56 and 51% respectively, by using sulphur oxidising microorganisms. The heavy metals remaining in the bioleached sludge were mostly in the residual fraction ensuring the safe disposal of bioleached sludge for land application as a fertiliser.
Fast Layout Generation of RF Embedded Passive Circuits Using Mathematical Programming
Pathak, M.,Sung Kyu Lim IEEE 2012 IEEE transactions on components, packaging, and ma Vol.2 No.1
<P>In this paper, we present a methodology for the automatic generation of layout for radio frequency (RF) designs using embedded passives. Our methodology is divided into three steps: 1) pre-layout optimization; 2) placement and routing; and 3) post-layout optimization. We show that our methodology generates layouts with small area and good performance response within a fraction of design time compared with fully manual design effort. We make use of circuit models to represent and optimize the physical layout of the resistance-inductance-capacitance (RLC) components as well as the entire RF circuit that uses them. We perform non-linear mathematical programming-based optimization at various stages of the methodology to achieve high quality layouts. Full wave electromagnetic simulations are kept completely out of the design loop, so our methodology significantly reduces design time. We have used our methodology to successfully generate layouts for large-scale filter circuits.</P>
Pathak, H.K.,Agarwal, R.P.,Cho, Y.J. Koninklijke Vlaamse Ingenieursvereniging ; Elsevie 2015 Journal of computational and applied mathematics Vol.283 No.-
In this paper, we consider some problems on coincidence point and fixed point theorems for multi-valued mappings. Applying the characterizations of P-functions, we establish some new existence theorems for coincidence point and fixed point distinct from Nadler's fixed point theorem, Berinde-Berinde's fixed point theorem, Mizoguchi-Takahashi's fixed point theorem and Du's fixed point theorem for nonlinear multi-valued contractive mappings in complete metric spaces. Our results compliment and extend the main results given by some authors in the literature. In the sequel, we consider a nonconvex integral inclusion and prove the Filippov type existence theorem by using an appropriate norm on the space of selection of a multi-function and a multi-valued contraction for set-valued mappings.
Pathak, Shiva,Regmi, Shobha,Gupta, Biki,Poudel, Bijay K.,Pham, Tung Thanh,Kim, Jae-Ryong,Park, Pil-Hoon,Yong, Chul Soon,Kim, Jong Oh,Bae, Young Kyung,Kim, Sang Kyoon,Jeong, Jee-Heon American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.39
<P>Hypoxic or near-anoxic conditions that occur in the core of transplanted islets induce necrosis and apoptosis during the early stages after transplantation, primarily due to loss of vascularization during the isolation process. Moreover, secretion of various cytokines from pancreatic islets is detrimental to the viability of islet cells in vitro. In this study, we aimed to protect pancreatic islet cells against apoptosis by establishing a method for in situ delivery of curcumin to the pancreatic islets. Self-assembled heterospheroids composed of pancreatic islet cells and curcumin-loaded polymeric micro spheres were prepared by the three-dimensional cell culture technique. Release of curcumin in the microenvironment of pancreatic islets promoted survival of the islets. In hypoxic culture conditions, which mimic the in vivo conditions after transplantation, viability of the islets was significantly improved, as indicated by a decreased expression of pro-apoptotic protein and an increased expression of anti-apoptotic protein. Additionally, oxidative stress-induced cell death was suppressed. Thus, unlike co-transplantation of pancreatic islets and free microspheres, which provided a wide distribution of microspheres throughout the transplanted area, the heterospheroid transplantation resulted in colocalization of pancreatic islet cells and microspheres, thereby exerting beneficial effects on the cells.</P>
Pathak Pankaj,Pandey Nidhi 한국자원공학회 2023 Geosystem engineering Vol.26 No.5
The present study is comprised of a hydrometallurgical process investigated for the recovery of critical metals viz. nickel (Ni) and cadmium (Cd) from spent Ni-Cd batteries with a focus on solvent extraction of Cd-ions. The leaching performed at 5 (w/v)% pulp density using 2.0 M H2SO4 with 7 (v/v)% H2O2 for 6 h duration at 90°C yielded the maximum leaching efficiency of >91% Ni and >99% Cd along with a significant quantity of Fe (>87%). Iron was subjected to hydrolytic precipitation to its complete removal (below 10 ppm in the solution) from the leach liquor at a pH of ~3.5. After that, the Ni-Cd-containing solution was contacted with di-(2-ethylhexyl) phosphoric acid (D2EHPA) to study the extraction behavior as a function of extractant concentration, equilibrium pH, and organic-to-aqueous (O:A) phase ratio. At an equilibrium pH of 3.3, a significant quantity of Ni (>18%) was co-extracted with ~73% Cd by contacting 20 (v/v)% D2EHPA, which was completely scrubbed by contacting 15 g/L CdSO4 solution at an O:A ratio of 2. The scrubbed organic containing 14.4 g/L Cd was then recovered by stripping with 1.5 M H2SO4 solution at an O: A ratio of 1, yielding >99% Cd into the aqueous phase. Further, Ni was recovered from the raffinate by adding soda ash at Na2CO3:Ni2+ ratio = 2.5, temperature = 50°C, and time = 1 h, which was analyzed to be NiCO3.2Ni(OH)2 with purity >99.9%. The experimental results showed the potential of hydrometallurgical tools for the recovery of critical metals from spent Ni-Cd batteries.
Pathak, Shiva,Regmi, Shobha,Nguyen, Tiep Tien,Gupta, Biki,Gautam, Milan,Yong, Chul Soon,Kim, Jong Oh,Son, Youlim,Kim, Jae-Ryong,Park, Min Hui,Bae, Young Kyung,Park, So Young,Jeong, Daewon,Yook, Simmyu Elsevier 2018 ACTA BIOMATERIALIA Vol.75 No.-
<P><B>Abstract</B></P> <P>Attenuation of senescence progression may be attractive way to preserve the functionality of pancreatic islets (PI) after transplantation. In this study, we developed a model for <I>in vitro</I> induction of premature senescence in rat PI and showed the effectiveness of quercetin (QU) to prevent the senescence. To provide targeted-delivery of QU to the PI after transplantation, we prepared the hybrid clusters (HC) of islet single cells (ISC) and QU-loaded polymeric microspheres (QU; ∼7.55 ng HC<SUP>−1</SUP>). Long-term culture of the HC revealed reduced levels of reactive oxygen species and decreased expression of senescence-associated beta galactosidase, Rb, p53, p16, and p21 compared to that of the control islets. Transplantation of HC into subcutaneous space of the immune-deficient mice produced better glycemic control compared to the control islets or the ICC-transplanted mice. SA-β-Gal staining of the <I>in vivo</I> transplanted HC sample showed lower intensity compared to that of the control islets or the islet cell clusters. Thus, <I>in situ</I> delivery of therapeutic agent may be a promising approach to improve therapeutic outcomes in cell therapy.</P> <P><B>Statement of Significance</B></P> <P>In this study, we aimed to improve outcomes in islet transplantation using <I>in situ</I> delivery of quercetin to pancreatic islets, using polymeric microspheres. We prepared prolonged release-type microspheres and constructed hybrid clusters of pancreatic islets and the microspheres using hanging drop method. The presence of quercetin in the cellular microenvironment attenuated the progression of senescence in the pancreatic islets in a long-term <I>in vitro</I> culture. Moreover, transplantation of the hybrid clusters in the diabetic mice produced better glycemic control compared to that of the control islets. In addition, quercetin delayed the progression of senescence in the pancreatic islets after <I>in vivo</I> transplantation. Thus, local delivery of antioxidants like quercetin may be an attractive way to improve outcomes in cell therapy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Quercetin prevents senescence of pancreatic islets <I>in vitro</I>. </LI> <LI> PLGA microspheres provide quercetin into the cellular microenvironment. </LI> <LI> Transplantation of the hybrid clusters produces better glycemic control. </LI> <LI> Hybrid clusters of cells and microspheres exhibit reduction of senescence. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>