Screening of Microorganisms Producing Esterase for the Production of $(R)-\beta-Acetylmercaptoisobutyric$ Acid from Methyl $(R,S)-\beta-Acetylmercaptoisobutyrate$

Gokul Boyapati,Lee Je-Hyuk,Song Ki-Bang,Panda T.,Rhee Sang-Ki,Kim Chul-Ho The Korean Society for Biotechnology and Bioengine 2000 Biotechnology and Bioprocess Engineering Vol.5 No.1

$(R)-\beta-acetylmercaptoisobutyric$ acid (RAM), a chiral compound, is an important intermediate for the chemical synthesis of various antihypertensive and congestive heart failure drugs. Microorganisms capable of converting $(R,S)-\beta-acetylmercaptoisobutyric$ acid ((R,S)-ester) to RAM were screened from soil microorganisms. A strain of Pseudomonas sp. 1001 screened from a soil sample was selected to be the best. Cells showed an activity of 540 U/mL from culture broth and the enzyme was thermostable up to $70^{\circ}C$. This strain could produce RAM asymmetrically from (R,S)-ester.

Formulation and development of nateglinide loaded sustained release ethyl cellulose microspheres by O/W solvent emulsification technique

Gokul Khairnar,Jitendra Naik,Vinod Mokale 한국약제학회 2014 Journal of Pharmaceutical Investigation Vol.44 No.6

The aim of this study was to investigate thecombined influence of 3 independent variables in thepreparation of sustained release Nateglinide (NTG)microspheres by O/W solvent emulsification method. A3-factor, 3-level Box–Behnken design was used to derivesecond order polynomial equation and construct contourplots to predict responses. The independent variablesselected were polymer concentration (A), surfactant concentration(B) and speed of the stirrer (C). Percentage drugloading (Y1) and Percentage drug release (Y2) were considereddependent variables. The prepared microsphereswere evaluated for percentage of yield, drug loading, drugrelease study in 6.8 phosphate buffer, Fourier transforminfrared (FT-IR), X-ray diffraction (XRD), scanning electronmicroscopy analysis. Contour plots were constructedto show the effects of of A, B, C on Y1 and Y2. The yieldof microspheres was found to be in the range of42.29–97.22 %. The drug loading was found to be in therange of 12.18 % (F9) to 24.55 % (F14). FT-IR analysisrevealed no drug excipient interference. The morphologyof evaluated microspheres were found to be spherical andsmooth in nature. In XRD analysis crystalline pattern ofpure NTG was changed to amorphous pattern when convertedto microspheres. Out of 17 batches, formulationbatches F1, F4, F12, F14, F17 had percentage drug loading52.75, 50.78, 43.88, 47.45, 44.78 % at 10 h respectivelywhich indicated excellent sustained drug release pattern. From this study it was concluded that NTG loaded ethylcellulose sustained release microspheres were developedusing 3-factor, 3-level Box–Behnken design.

THERMAL EFFECTS OF EYELID IN HUMAN EYE TEMPERATURE MODEL

Gokul, K.C.,Gurung, D.B.,Adhikary, P.R. The Korean Society for Computational and Applied M 2014 Journal of applied mathematics & informatics Vol.32 No.5

Presence of eyelid on anterior ocular surface and its thermal effects play significant role in maintaining eye temperature. In most of the literatures of thermal modeling in human eye, the eyelid is not considered as an eye component. In this paper, finite element model is developed to investigate the thermal effects of eyelid closure and opening in human eye. Based on different properties and parameter values reported in literatures, the bio-heat transfer process is simulated and compared with experimental results in steady and transient state cases. The sensitivity analysis using various ambient temperatures, evaporation rates, blood temperatures and lens thermal conductivities is carried out. The temperature values so obtained in open eye show a good agreement with past results. The closure of eyelid is found to increase/decrease the eye temperature significantly than its opening, when the parameter values are considered to be at extreme.

Design and Demonstration of Power Delivery Networks With Effective Resonance Suppression in Double-Sided 3-D Glass Interposer Packages

Kumar, Gokul,Sitaraman, Srikrishna,Jonghyun Cho,Sundaram, Venky,Joungho Kim,Tummala, Rao R. IEEE 2016 IEEE transactions on components, packaging, and ma Vol.6 No.1

<P>Ultrathin 3-D glass interposers with throughpackage vias at the same pitch as through-silicon vias (TSVs) have been proposed as a simpler and cheaper alternative to the direct 3-D stacking of logic and memory devices. Such 3-D interposers provide wide-I/O channels for high signal bandwidth (BW) between the logic device on one side of the interposer and memory stack on the other side, without the use of complex TSVs in the logic die. However, this configuration introduces power delivery design challenges due to resonance from: 1) the low-loss property of the glass substrate and 2) the parasitic inductance due to additional length from lateral power delivery path. This paper presents for the first time, the design and demonstration of power delivery networks (PDNs) in 30-μm thin, 3-D double-sided glass interposers, by suppressing the noise from mode resonances. The self-impedance of the 3-D glass interposer PDN was simulated using electromagnetic solvers, including printed-wiring-board and chip-level models. The 3-D PDN was compared with that of the 2-D glass packages having fully populated ball grid array connections. The resonance mechanism for each configuration was studied in detail, and the corresponding PDN loop inductances were evaluated. High impedance peaks in addition to the 2-D PDN were observed at high frequencies (near 7.3 GHz) in the 3-D interposer structure due to the increased inductances from lateral power delivery. This paper proposes and evaluates three important resonance suppression techniques based on: 1) 3-D interposer die configuration; 2) the selection and placement of decoupling capacitors; and 3) 3-D interposer package power and ground stack-up. Two-metal and four-metal layer test vehicles were fabricated on 30and 100-μm thick panel-based glass substrates, respectively, to validate the modeling and analysis of the proposed approach. The PDN test structures were characterized up to 20 GHz for plane resonances and network impedances, with good model-to-hardware correlation. The results in this paper suggest that the ultrathin 3-D interposer PDN structure can be effectively designed to meet the target impedance guidelines for high-BW applications, providing a compelling alternative to 3-D-IC stacking with the TSVs.</P>

Characterization of metallurgical and mechanical properties on the multi-pass welding of Inconel 625 and AISI 316L

K. Gokul Kumar,K. Devendranath Ramkumar,N. Arivazhagan 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3

This article investigated the weldability, metallurgical and mechanical properties of Inconel 625 and AISI 316L stainless steel weldmentsobtained by continuous current (CC) and pulsed current (PC) gas tungsten arc welding (GTAW) processes employing ERNiCr-3and ER2209 fillers. Microstructure studies showed the migrated grain boundaries at the weld zone of ERNiCr-3 weldments and multidirectionalgrain growth for ER2209 weldments. It was inferred from the tension tests that the fracture occurred at the parent metal ofAISI 316L in all the cases. Charpy V-notch impact tests accentuated that the CCGTA weldments employing ERNiCr-3 filler offeredbetter impact toughness of 77 J at room temperature. Further a detailed study has been carried out to analyze the structure - property relationshipsof these weldments using the combined techniques of scanning electron microscopy (SEM) and energy dispersive spectroscopy(EDS) analysis.

Synthesis of an antibiotic-preserving antimicrobial tetracycline-loaded gellan gum gel

Paramasivam Gokul,Dhamodharan Duraisami,Kishore Somasundaram Chandra,변헌수 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.9

Gels play a significant role in our daily lives as they provide stability and desired features to various items of regular use, such as cosmetics, pharmaceuticals, household items, and agricultural products. However, a microbial attack on gels commonly occurs during gel-based formulations. Antibiotic-loaded gels can reportedly be stored for a long time. In this study, we fabricated a tetracycline-loaded gellan gum (TC/GG) gel and assessed its long-term stability against microbial attack. Morphological analyses revealed a firm and smooth texture with multifold bumpy surfaces on the GG and TC/GG gels. Fourier transform infrared spectroscopic analysis showed that the gel was well hydrated and thus suitable for releasing antibiotics. The feasibility of inhibiting microorganisms was qualitatively examined using the disk diffusion method. Interestingly, the unloaded GG gel itself exhibited an antimicrobial effect, while the loaded TC/GG gel showed a better antibacterial effect on S. aureus than on E. coli. TC/GG can be used to store and protect gels from microbial attacks for a long duration. In addition, it is suitable for storing bioactive agents, which are used in the biomedical field.

Effect of modes of transportation on commuters' exposure to fine particulate matter (PM<SUB>2.5</SUB>) and nitrogen dioxide (NO₂) in Chennai, India

M. Gokul Raj,S. Karthikeyan 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.6

Daily commuting increases level of contaminants inhaled by urban community and it is influenced by mode and time of commuting. In this study, the commuters’ exposure to ambient particulate matter (PM2.5) and nitrogen dioxide (NO₂) was assessed during three modes of travel in six different road stretches of Chennai. The mean distance of road stretches was 25 km and the exposure to pollutants was assessed during peak hours and off-peak hours. The average travel duration was in the range of 39 to 91 min in motorbike, 83 to 140 min in car and 110 to 161 min in bus. Though there was variation on exposure to concentration in modes of transportation, the maximum exposure concentration of PM2.5 was observed as 709 μg/m³ in bus and the minimum exposure concentration was 29 μg/m³ in closed car. Similarly, the maximum exposure concentration of NO₂ was observed to be 312 μg/m³ in bus and the minimum exposure concentration was 21 μg/m³ in car. The concentration of elements in PM2.5 was in the order of Si > Na > Ca > Al ≥ K > S ≥ Cd, with Si and Cd concentration as 60% and < 1% of the PM2.5 concentration.

Development of Antibiotic-Protected Antimicrobial Tetracycline-Loaded GU (Guar Gum) Gel for Long-Term Storage

Paramasivam Gokul,Dhamodharan Duraisami,변헌수 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.3

Gels are widely used in our everyday lives, spanning personal care, cosmetics, oral care, food and beverages, household products, medical supplies, electronics, and arts and crafts. Their adaptable characteristics contribute to improved product performance, user satisfaction, and overall convenience. However, generation of microbial invasion is a common obstacle observed on gels and its formulations. Antibiotic loaded on gels is a better alternative to chemical-based preservative for long-term storage of gels. In this research, the gel was fabricated with two diff erent components with guar gum (GU) and tetracycline (TC) and its antimicrobial ability was tested over a period of time. We conducted morphological analyses that revealed a solid and rough surface on both GU and reduced sign of microbial attack on TC/GU-based gels. Identifi cation of functional groups is observed using Fourier transform infrared (FTIR) spectroscopy that confi rms the gel is well hydrated and make it suitable to deliver antimicrobial agents. Antimicrobial ability performed by antibiotics was tested using disc diff usion method. The unloaded GU gel does not exhibit an observed antimicrobial property, whereas GU/TC gel reveals a better antibacterial effi ciency on S. aureus compared to E. coli . Our fi ndings suggest that GU/TC gel can eff ectively safeguard gels from microbial attacks during long-term storage. Furthermore, this GU/TC gel can be used as a drug transport system for bioactive agents in biomedical applications.

Pile-up and sink-in nanoindentation behaviors in AlCoCrFeNi multi-phase high entropy alloy

Muthupandi, Gokul,Lim, Ka Ram,Na, Young-Sang,Park, Jieun,Lee, Dongyun,Kim, Hanjong,Park, Seonghun,Choi, Yoon Suk Elsevier 2017 Materials science & engineering. properties, micro Vol.696 No.-

<P><B>Abstract</B></P> <P>Microstructures and nanoindentation behaviors were studied on annealed AlCoCrFeNi high entropy alloy. Both pile-up and sink-in characteristics were found in the grain boundary and grain regions, respectively. The multiple phases present in the AlCoCrFeNi high entropy alloy are the reasons behind the different nanoindentation behaviors, which were identified using electron microscopy. The identified phases showed the grain boundary segregation to have A1 lattice, <I>viz.</I>, FCC structure while the grain was distributed with A2 and B2 lattices, <I>viz.</I>, BCC and ordered BCC structures, forming the matrix with nano-precipitates of the other. The reason for the pile-up and sink-in is attributed to the dislocation activity in the individual crystal structure: large dislocation activities were found under the pile-up and little dislocation activities under the sink-in, only limited to the indenter tip. Results from a finite element analysis under an isotropic elasto-plastic condition by varying the hardness-to-modulus ratio show that high hardness-to-modulus ratio results in pile-up and the lower ratio results in sink-in. This was associated with the susceptibility to plasticity and the elastic recovery for individual phases of the AlCoCrFeNi high entropy alloy.</P>

Development of Superhydrophobic Microfibers for Bandage Coatings

T.S. Gokul Raja,K. Jeyasubramanian,M. Indhumathy 한국섬유공학회 2018 Fibers and polymers Vol.19 No.6

In this research work, a fabricated composite fiber is proposed to protect wound surfaces from infectious organisms present in water. The composite fiber comprising PMMA, ZnO, and zinc stearate was developed using an electrospinning technique. The fiber surface was scientifically studied using scanning electron microscope, Energy dispersive analysis of X-rays, powder X-ray diffraction analysis and Fourier transform Infra-Red analysis. The pores present in between perpendicularly aligned fibers serves as an excellent medium for vapor transport to a wound surface. The maximum water contact angle of the developed fiber surface was approximately 151 degrees. A commercial cotton bandage after coated with this composite layer behaves as a perfect barrier to the entry of infectious water towards the wound. The pores in the fiber surface support rich supply of environmental oxygen and transport of exudate vapor from the wound. This fiber when coated over a cotton bandage cloth on one side served as an excellent wound protecting bandage against the penetration of external microbial water and also it admits the air, water vapor etc., towards the interior. Water penetration ability of hydrophilic cotton bandage and the water arresting ability of superhydrophobic fiber coated bandage were evaluated using a facile technique. Furthermore, antimicrobial activity of test samples was evaluated against gram positive and gram negative microorganism. Also, a bacterial infiltration test supports the blocking capability of superhydrophobic fiber to water-borne bacteria. The results obtained through this experiment may be used in future as wound healing bandages in an efficient manner.