Determination of surface properties and Gutmann’s Lewis acidity–basicity parameters of thiourea and melamine polymerized graphitic carbon nitride sheets by inverse gas chromatography

Sreekanth, T.V.M.,Basivi, Praveen Kumar,Nagajyothi, P.C.,Dillip, G.R.,Shim, J.,Ko, T.J.,Yoo, K. Elsevier 2018 Journal of chromatography Vol.1580 No.-

<P><B>Abstract</B></P> <P>Melamine and thiourea-derived graphitic carbon nitrides (M-GCN/T-GCN) were synthesized and characterized. The surface properties were investigated using inverse gas chromatography (IGC) and compared. Net retention volumes of M-GCN and T-GCN were measured with <I>n</I>-alkanes (C<SUB>5</SUB>–C<SUB>10</SUB>) and polar probes. The London dispersive surface free energies ( γ s d ), calculated using Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific components of the enthalpy and entropy of adsorption for the polar probes were obtained using the Schultz, Dong, and Sawyer–Brookman methods. The Gutmann’s Lewis acid–base parameters, <I>K<SUB>a</SUB> </I> and <I>K<SUB>b</SUB> </I>, were determined using the surface free energy ( Δ G a S ) via these methods. The surface character ‘<I>S’</I> values (<I>K<SUB>b</SUB> </I>/<I>K<SUB>a</SUB> </I>) of M-GCN and T-GCN using the respective methods are 4.04, 3.78, and 5.08 and 4.11, 5.27, and 2.86. Hence, the surfaces contain more basic than acidic sites and could interact strongly with acidic media. Thus, IGC elucidates the surface charges of the GCN matrix resulting from surface chemical modification.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Graphitic carbon nitride was synthesized using two precursors, melamine and thiourea. </LI> <LI> Physicochemical properties were confirmed by XRD, XPS and BET. </LI> <LI> Inverse gas chromatography was employed to understand surface free energy of GCN. </LI> <LI> The London dispersive parameters were determined by Schultz/Dorris–Gray methods. </LI> <LI> The Lewis acid–base parameters, showing the more basic character of GCN. </LI> </UL> </P>

A Donor–Acceptor–Donor Structured Organic Conductor with S···S Chalcogen Bonding

Bai, Monalisa,Thomas, Sajesh P.,Kottokkaran, Ranjith,Nayak, Susanta K.,Ramamurthy, Praveen C.,Guru Row, T. N. American Chemical Society 2014 Crystal Growth & Design Vol.14 No.2

<P>A novel thiophene derivative 7,9-di(thiophen-2-yl)-8<I>H</I>-cyclopenta[a]acenaphthylen-8-one (DTCPA) is shown to exhibit high electrical conductivity (1.97 × 10<SUP>–2</SUP> ± 0.0018 S/cm at RT) in the crystalline state. The material shows two orders of increase in conductivity from normal solid to single crystalline state. The crystal structure has S···S chalcogen bonding, C–H···O hydrogen bonding, and π···π stacking as the major intermolecular interactions. The nature and strength of the S···S interactions in this structure have been evaluated by theoretical charge density analysis, and its contribution to the crystal packing quantified by Hirshfeld surface analysis. Further, thermal and morphological characterizations have been carried out, and the second harmonic generation (SHG) efficiency has been measured using the Kurtz–Perry method.</P><P>A novel donor−acceptor−donor structured material with S···S chalcogen bonding is shown to exhibit high electrical conductivity in the crystalline state. Two different types of intermolecular S···S interactions present in the material are shown to be similar to type I and type II halogen bonds, in terms of charge density distribution.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cgdefu/2014/cgdefu.2014.14.issue-2/cg401069y/production/images/medium/cg-2013-01069y_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cg401069y'>ACS Electronic Supporting Info</A></P>

High Energy Swift Heavy Ion Irradiation and Annealing Effects on DC Electrical Characteristics of 200 GHz SiGe HBTs

Vinayakprasanna N. Hegde,K.C. Praveen,T.M. Pradeep,N. Pushpa,John D. Cressler,Ambuj Tripathi,K. Asokan,A.P. Gnana Prakash 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.5

The total ionizing dose (TID) and non ionizing energy loss (NIEL) effects of 100 MeV phosphorous (P7þ)and 80 MeV nitrogen (N6þ) ions on 200 GHz silicon-germanium heterojunction bipolar transistors (SiGeHBTs) were examined in the total dose range from 1 to 100 Mrad(Si). The in-situ IeV characteristics likeGummel characteristics, excess base current (DIB), net oxide trapped charge (NOX), current gain (hFE),avalanche multiplication (M 1), neutral base recombination (NBR) and output characteristics (IC-VCE)were analysed before and after irradiation. The significant degradation in device parameters wasobserved after 100 MeV P7þ and 80 MeV N6þ ion irradiation. The 100 MeV P7þ ions create more damagein the SiGe HBT structure and in turn degrade the electrical characteristics of SiGe HBTs more whencompared to 80 MeV N6þ. The SiGe HBTs irradiated up to 100 Mrad of total dose were annealed from50 C to 400 C in different steps for 30 min duration in order to study the recovery of electrical characteristics. The recovery factors (RFs) are employed to analyse the contribution of room temperature andisochronal annealing in total recovery.

Enhanced Antibiotic Production by Streptomyces sindenensis Using Artificial Neural Networks Coupled with Genetic Algorithm and Nelder-Mead Downhill Simplex

( Tripathi C. K. M. ),( Mahvish Khan ),( Vandana Praveen ),( Saif Khan ),( Akanksha Srivastava ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.7

Antibiotic production with Streptomyces sindenensis MTCC 8122 was optimized under submerged fermentation conditions by artificial neural network (ANN) coupled with genetic algorithm (GA) and Nelder-Mead downhill simplex (NMDS). Feed forward back-propagation ANN was trained to establish the mathematical relationship among the medium components and length of incubation period for achieving maximum antibiotic yield. The optimization strategy involved growing the culture with varying concentrations of various medium components for different incubation periods. Under non-optimized condition, antibiotic production was found to be 95 μg/ml, which nearly doubled (176 μg/ml) with the ANN-GA optimization. ANN-NMDS optimization was found to be more efficacious, and maximum antibiotic production (197 μg/ml) was obtained by cultivating the cells with (g/l) fructose 2.7602, MgSO4 1.2369, (NH4)2PO4 0.2742, DL-threonine 3.069%, and soyabean meal 1.952%, for 9.8531 days of incubation, which was roughly 12% higher than the yield obtained by ANN coupled with GA under the same conditions.

An analysis of 175 MeV Nickel ion irradiation and annealing effects on silicon NPN rf power transistors

N. Pushpa,K.C. Praveen,A.P. Gnana Prakash,S.K. Gupta,D. Revannasiddaiah 한국물리학회 2013 Current Applied Physics Vol.13 No.1

In this study NPN rf power transistors were irradiated by 175 MeV Ni13þ ions in the dose range of 100 krad to 100 Mrad. Their characteristics such as excess base current (DIB ¼ IBpost IBpre), dc current gain (hFE), transconductance (gm) and collector-saturation current (ICSat) were studied before and after irradiation. The damage factor (K) for hFE was calculated using MessengereSpratt relation. The base current (IB) was found to increase significantly after irradiation and in turn decreases the hFE. The gm and collector current (IC) in the saturation region (ICSat) were found to decrease with increase in radiation dose. The results obtained here were also compared with that obtained by 140 MeV Si10þ ions, 100 MeV F8þ ions, 95 MeV O7þ ions and 50 MeV Li3þ ions irradiation studies in the same dose ranges to understand the LET effects. The recovery in the IeV characteristics of irradiated NPN transistors were studied by isothermal and isochronal annealing methods.

Perioperative Anesthesia Lean Implementation Is Associated With Increased Operative Efficiency in Posterior Cervical Surgeries at a HighVolume Spine Center

Simon G. Ammanuel,Andrew K. Chan,Anthony M. DiGiorgio,Mohanad Alazzeh,Kelechi Nwachuku,Leslie C. Robinson,Errol Lobo,Praveen V. Mummaneni 대한척추신경외과학회 2020 Neurospine Vol.17 No.2

Objective: Lean management strategies aim to increase efficiency by eliminating waste or by improving processes to optimize value. The operating room (OR) is an arena where these strategies can be implemented. We assessed changes in OR efficiency after the application of lean methodology on perioperative anesthesia associated with posterior cervical spine surgeries. Methods: We utilized pre- and post-lean study design to identify inefficiencies during the perioperative anesthesia process and implemented strategies to improve the process. Patient characteristics were recorded to assess for differences between the 2 groups (group 1, prelean; group 2, post-lean). In the pre-lean period, key steps in the perioperative anesthesia process were identified that were amenable to lean implementation. The time required for each identified key step was recorded by an independent study coordinator. The times for each step were then compared between the groups utilizing univariate analyses. Results: After lean implementation, there was a significant decrease in overall perioperative anesthesia process time (88.4 ± 4.7 minutes vs. 76.2 ± 3.2 minutes, p = 0.04). This was driven by significant decreases in the steps: transport and setup (10.4 ± 0.8 minutes vs. 8.0 ± 0.7 minutes, p = 0.03) and positioning (20.8 ± 2.1 minutes vs. 15.7 ± 1.3 minutes, p = 0.046). Of note, the total time spent in the OR was lower for group 2 (270.1 ± 14.6 minutes vs. 252.8 ± 14.1 minutes) but the result was not statistically significant, even when adjusting for number of operated levels. Conclusion: Lean methodology may be successfully applied to posterior cervical spine surgery whereby improvements in the perioperative anesthetic process are associated with significantly increased OR efficiency.

Cold-Adapted and Rhizosphere-Competent Strain of Rahnella sp. with Broad-Spectrum Plant Growth-Promotion Potential

( Pratibha Vyas ),( Robin Joshi ),( K. C. Sharma ),( Praveen Rahi ),( Ashu Gulati ),( Arvind Gulati ) 한국미생물 · 생명공학회 2010 Journal of microbiology and biotechnology Vol.20 No.12

A phosphate-solubilizing bacterial strain isolated from Hippophae rhamnoides rhizosphere was identified as Rahnellu sp. based on its phenotypic features and 165 rRNA gene sequence. The bacterial strain showed the growth characteristics of a cold-adapted psychrotroph, with the multiple plant growth-promoting traits of inorganic and organic phosphate solubilization, 1-aminocyclopropane-1-carboxylate-deaminase activity, ammonia generation, and siderophore production. The strain also produced indole-3-acetic acid, indole-3-acetaldehyde, indole-3-acetamide, indole-3-acetonitrile, indole-3-lactic acid, and indole-3-pyruvic acid in tryptophan-supplemented nutrient broth. Gluconic, citric and isocitric acids were the major organic acids detected during tricalcium phosphate solubilization. A rifampicin-resistant mutant of the strain exhibited high rhizosphere competence without disturbance to the resident microbial populations in pea rhizosphere. Seed bacterization with a charcoal-based inoculum significantly increased growth in barley, chickpea, pea, and maize under the controlled environment. Microplot testing of the inoculum at two different locations in pea also showed significant increase in growth and yield. The attributes of cold-tolerance, high rhizosphere competence, and broad-spectrum plant growth-promoting activity exhibited the potential of Rahnella sp. BIHB 783 for increasing agriculture productivity.

Lightweight Polyaniline-Cobalt Coated Fly Ash Cenosphere Composite Film for Electromagnetic Interference Shielding

Pritom J Bora,K. J. Vinoy,Praveen C Ramamurthy,Kishore,Giridhar Madras 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.5

Thermal power plant’s solid environmental waste fly ashcenosphere (FAC) is cobalt coated chemically and functionalizedby in situ synthesis of polyaniline (PANI) under nitrogenatmosphere at −30 ± 2 °C and characterized by various techniques. The electromagnetic interference shielding effectiveness (EMISE) of free standing PANI/Co-FAC (PCC) films prepared bysolution casting indicates an appreciable shielding. The mosteffective average EMI SE of ~ 30 dB was obtained for 89 ± 3 μmthicker flexible film over the frequency range of 12.4-18 GHz(Ku-band). Mechanistically, EMI shielding due to absorption wasfound to be dominant. The obtained shielding effectiveness dueto absorbance (SEA) of PCC film is nearly two times higher thanPC film. The microwave conductivity (σ) of PCC film (157-184Sm−1) is much higher than PC film (118-142 Sm−1). Moreover, thehigh EM attenuation constant (α) value of PCC film indicatesexcellent suitability of EMI shielding due to absorption.