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Asthana, Amit,Asthana, Yamini,Sung, In-Kyung,Kim, Dong-Pyo Royal Society of Chemistry 2006 Lab on a chip Vol.6 No.9
<P>In this report we have described fabrication of preceramic polymer-derived transparent, solvent-resistant, thermally stable and bio-compatible microchannels and substrates using soft-lithography methods such as micromolding in capillary (MIMIC) and micromolding. The micromolding technique was preferred in the current work to fabricate channels by thermal and photo crosslinking of a commercially available poly(vinyl silazane) (VL 20, KION Corporation, USA). Both thermal and photo cured preceramic polymer channels were found to possess unique glass-like characteristics, such as transparency and chemical inertness. However, their surfaces were identified to be hydrophobic with a contact angle of 101°. To have an insight on the nature of the surface groups present on the surface of the cured preceramic polymer, ATR-IR was carried out. The hydrophobic nature of the cured polymer was best utilized for direct patterning of protein by nonspecific binding.</P> <P>Graphic Abstract</P><P>For the first time, this paper describes the fabrication of preceramic polymer-based transparent, solvent-resistant, thermally stable and bio-compatible microchannels and substrates by using soft-lithography techniques. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b603763c'> </P>
Asthana Rajiv,Singh Mrityunjay,Sobczak Natalia The Korean Ceramic Society 2005 한국세라믹학회지 Vol.42 No.11
The infiltration of ceramics by liquid metals to fabricate ceramic-metal composites is discussed. In particular, the complexity of infiltrating ceramics by liquid metals at high temperatures due to interfacial reactions, metal oxidation, pore modulation and closure, and transient capillary forces has been highlighted. The role of these factors is discussed in the context of reactive infiltration with examples from ceramic/metal composites of practical interest. In addition to flow through porous ceramics, reactive penetration of dense ceramics via chemical dissolution and reaction is also discussed.
Asthana, Yamini,Hong, Lan-Young,Kim, Dong-Pyo,Lee, Taek Seung,Sung, Yun-Mo TaylorFrancis 2007 Molecular Crystals and Liquid Crystals Vol.463 No.1
<P> Formation of coatings with combined properties of being superhydrophilic/superhydrophobic are of immense applications in the field of optics. In our present work, we have developed a transparent, organic/inorganic hybrid coating by mixing appropriate ratios of organic silanol coupling agents and monoacrylates to impart strong adhesion to the substrate, and inorganic components comprising of a hybrid mixture of silica-titania, and certain vinyl components as well as hydrophilic surfactants for improved antifogging behavior. Polycarbonate lens or glass slides, as substrates were dip coated into the hybrid precursor solution at a suitable withdrawal rate of 5 cm/min to form uniform and crack free film of thickness 458 nm. The sequential process of drying of the coated films involved thermal curing at varied temperature and time in the presence of an appropriate thermal initiator, dicumyl peroxide. The surface chemistry and thermal behavior along with the superhydrophilicty and fogging behavior of the coated substrates were assessed by respective ATR-IR, 29Si NMR, TGA/DSC analysis and AFM measurements. The remarkabale observation was that the composite of organic-inorganic mixture exhibited desired properties of being superhydrophilic as well as antifogging on the substrate by curing at appropriate temperature of 50°C for 24 hr and 120°C for 8 hr, respectively.</P>
Facile single step fabrication of microchannels with varying size
Asthana, Amit,Kim, Kyeong-Ohn,Perumal, Jayakumar,Kim, Dong-Myung,Kim, Dong-Pyo Royal Society of Chemistry 2009 Lab on a chip Vol.9 No.8
<P>In this report, we present a non-lithographic embedded template method for rapid and cost-effective fabrication of a monolithic microfluidic device with channels of various sizes. The procedure presented here enables the preparation of microchannels with varying dimensions in a single device without using any sophisticated micromachining instrumentation. In addition, this non-lithographic technique has also been used to fabricate a multilayer–multilevel biopolymer microdevice in a single step. To demonstrate the versatility of the presented method, we have fabricated microfluidic devices with four different materials under different curing/cross linking conditions. We have also demonstrated the application of the fabricated device to generate structured copper alginate microbeads, <I>in vitro</I> protein synthesis in three phase flow, and alternate plugs with liquid spacers.</P> <P>Graphic Abstract</P><P>We present a non-lithographic method for rapid and cost-effective fabrication of a monolithic microfluidic device with varying channel sizes. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b818987k'> </P>
Rajiv Asthana,Mrityunjay Singh,Natalia Sobczak 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.11
The infiltration of ceramics by liquid metals to fabricate ceramic-metal composites is discussed. In particular, the complexity of infiltrating ceramics by liquid metals at high temperatures due to interfacial reactions, metal oxidation, pore modulation and closure, and transient capillary forces has been highlighted. The role of these factors is discussed in the context of reactive infiltration with examples from ceramic/metal composites of practical interest. In addition to flow through porous ceramics, reactive penetration of dense ceramics via chemical dissolution and reaction is also discussed
Nidhi Asthana,Haewon Byeon 한국정보통신학회JICCE 2024 Journal of information and communication convergen Vol.22 No.1
User preferences and ratings may be anticipated by recommendation systems, which are widely used in social networking, online shopping, healthcare, and even energy efficiency. Constructing trustworthy recommender systems for various applications, requires the analysis and mining of vast quantities of user data, including demographics. This study focuses on holding elections with vague voter and candidate preferences. Collaborative user ratings are used by filtering algorithms to provide suggestions. To avoid information overload, consumers are directed towards items that they are more likely to prefer based on the profile data used by recommender systems. Better interactions between governments, residents, and businesses may result from studies on recommender systems that facilitate the use of e-government services. To broaden people’s access to the democratic process, the concept of “e-democracy” applies new media technologies. This study provides a framework for an electronic voting advisory system that uses machine learning.
Nandi, Moujhuri,Mandal, Abhijit,Asthana, Anupam Kumar Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.9
Background: A retrospective analysis of all cancer patients attending the radiotherapy outpatient department (OPD) of a single unit during the period of January 2005 till December 2006 was conducted to know the geographical distribution and incidence of the most common cancers, their stage of presentation, treatment compliance among the patients and follow-up. Materials and Methods: A total of 4,484 patients were registered in the Institute of Medical Sciences, Banaras Hindu University during the period of January 2005-December 2006; of which 1,975 registered in an individual unit were included for the retrospective analysis. Results: Most of the patients hailed from the various districts of UP and Bihar. Females outnumbered males with a ratio of 1.33:1. Females mostly belonged to the age group of 40-59 years; whilst males were a decade older. Major cancer sites in females were cervix and breast followed by head and neck. Leading cancer sites in males were head and neck, brain, bone, soft tissue and lung. Most of the cases presented in advanced stage of disease (74%). Squamous cell carcinoma was the most common histopathology (56%). A significant proportion of patients defaulted after undergoing preliminary investigations (16%). Only 53.9% of females and 58.5% of males took treatment out of which 68% and 63% completed the prescribed treatment. Compliance with follow-up was poor. Conclusions: The outcome of this study will significantly help us to define region specific strategies needed for cancer management in eastern Uttar Pradesh.
T. Karthik,Saket Asthana 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
A novel multifunctional behavior was observed by site specific cation substitution in NBT ceramicsprepared by conventional solid state reaction technique. X-ray diffraction studies revealed veryweak orthorhombic phase co-existence in co-substituted NBT system along with the primary R3cphase. Raman spectroscopy of NBT-GM ceramics reveals a substantial change in all phonon modesin terms of suppression and frequency shift, indicates that the substitution affects the nature ofcation displacement, octahedral tilt and further the Bi-O, Ti-O hybridization. Reduced polarizationvalue in NBT-GM ceramics with non-saturated hysteresis loops evidences the suppression offerroelectricity. Temperature dependent magnetization measurements from R.T to 2.5K in NBTGMceramics show the occurrence of spin-paramagnetic behavior. Susceptibility plots show someevidence for weak AFM interaction between Mn4+ ions at low temperatures below 30K. UV-Visspectroscopy measurements reveal the indirect transition allowed band gap nature for both NBTand NBT-GM ceramics with a slight increase in band gap value for NBT-GM ceramics. Photoluminescencemeasurements show a strong blue emission at 390nm (3.18 eV) in Gd-Mn substitutedNBT system, which corresponds to the radiative transition from 4T1g ! 4A2g energy levels ofMn4+-ions.