1
|
Retnakumari A, Setua S, Menon D, Ravindran P, Muhammed H, Pradeep T, Nair S, Koyakutty M. Molecular-receptor-specific, non-toxic, near-infrared-emitting Au cluster-protein nanoconjugates for targeted cancer imaging. NANOTECHNOLOGY 2010; 21:055103. [PMID: 20023317 DOI: 10.1088/0957-4484/21/5/055103] [Citation(s) in RCA: 220] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Molecular-receptor-targeted imaging of folate receptor positive oral carcinoma cells using folic-acid-conjugated fluorescent Au(25) nanoclusters (Au NCs) is reported. Highly fluorescent Au(25) clusters were synthesized by controlled reduction of Au(+) ions, stabilized in bovine serum albumin (BSA), using a green-chemical reducing agent, ascorbic acid (vitamin-C). For targeted-imaging-based detection of cancer cells, the clusters were conjugated with folic acid (FA) through amide linkage with the BSA shell. The bioconjugated clusters show excellent stability over a wide range of pH from 4 to 14 and fluorescence efficiency of approximately 5.7% at pH 7.4 in phosphate buffer saline (PBS), indicating effective protection of nanoclusters by serum albumin during the bioconjugation reaction and cell-cluster interaction. The nanoclusters were characterized for their physico-chemical properties, toxicity and cancer targeting efficacy in vitro. X-ray photoelectron spectroscopy (XPS) suggests binding energies correlating to metal Au 4f(7/2) approximately 83.97 eV and Au 4f(5/2) approximately 87.768 eV. Transmission electron microscopy and atomic force microscopy revealed the formation of individual nanoclusters of size approximately 1 nm and protein cluster aggregates of size approximately 8 nm. Photoluminescence studies show bright fluorescence with peak maximum at approximately 674 nm with the spectral profile covering the near-infrared (NIR) region, making it possible to image clusters at the 700-800 nm emission window where the tissue absorption of light is minimum. The cell viability and reactive oxygen toxicity studies indicate the non-toxic nature of the Au clusters up to relatively higher concentrations of 500 microg ml(-1). Receptor-targeted cancer detection using Au clusters is demonstrated on FR(+ve) oral squamous cell carcinoma (KB) and breast adenocarcinoma cell MCF-7, where the FA-conjugated Au(25) clusters were found internalized in significantly higher concentrations compared to the negative control cell lines. This study demonstrates the potential of using non-toxic fluorescent Au nanoclusters for the targeted imaging of cancer.
Collapse
|
|
15 |
220 |
2
|
Sathyendranath S, Gouveia AD, Shetye SR, Ravindran P, Platt T. Biological control of surface temperature in the Arabian Sea. Nature 1991. [DOI: 10.1038/349054a0] [Citation(s) in RCA: 160] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
|
34 |
160 |
3
|
van Vugt LK, Rühle S, Ravindran P, Gerritsen HC, Kuipers L, Vanmaekelbergh D. Exciton polaritons confined in a ZnO nanowire cavity. PHYSICAL REVIEW LETTERS 2006; 97:147401. [PMID: 17155289 DOI: 10.1103/physrevlett.97.147401] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Indexed: 05/12/2023]
Abstract
Semiconductor nanowires of high purity and crystallinity hold promise as building blocks for miniaturized optoelectrical devices. Using scanning-excitation single-wire emission spectroscopy, with either a laser or an electron beam as a spatially resolved excitation source, we observe standing-wave exciton polaritons in ZnO nanowires at room temperature. The Rabi splitting between the polariton branches is more than 100 meV. The dispersion curve of the modes in the nanowire is substantially modified due to light-matter interaction. This finding forms a key aspect in understanding subwavelength guiding in these nanowires.
Collapse
|
|
19 |
75 |
4
|
Arjunan V, Ravindran P, Rani T, Mohan S. FTIR, FT-Raman, FT-NMR, ab initio and DFT electronic structure investigation on 8-chloroquinoline and 8-nitroquinoline. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2010.12.032] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
|
14 |
61 |
5
|
Kishore MA, Ravindran P. Enhanced Photocatalytic Water Splitting in a C2N Monolayer by C-Site Isoelectronic Substitution. Chemphyschem 2017; 18:1526-1532. [DOI: 10.1002/cphc.201700165] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Indexed: 11/11/2022]
|
|
8 |
39 |
6
|
Arjunan V, Saravanan I, Ravindran P, Mohan S. Structural, vibrational and DFT studies on 2-chloro-1H-isoindole-1,3(2H)-dione and 2-methyl-1H-isoindole-1,3(2H)-dione. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009; 74:642-649. [PMID: 19660980 DOI: 10.1016/j.saa.2009.07.012] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 07/02/2009] [Accepted: 07/07/2009] [Indexed: 05/28/2023]
Abstract
The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-1H-isoindole-1,3(2H)-dione and 2-methyl-1H-isoindole-1,3(2H)-dione have been measured in the range of 4000-400 and 4000-100 cm(-1), respectively. Complete vibrational assignment and analysis of the fundamental modes of the compounds were performed using the observed FTIR and FT-Raman data. The geometry was optimised without any symmetry constraints using the DFT/B3LYP method with 6-31G(d,p) and 6-311++G(d,p) basis sets. The vibrational frequencies determined experimentally are compared with those obtained theoretically from DFT gradient calculations employing the B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p) methods for the optimised geometry of the compounds. The structural parameters and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The force fields obtained from DFT method were utilised and the potential energy distributions of all the fundamental vibrations of the compounds were calculated.
Collapse
|
|
16 |
39 |
7
|
|
|
44 |
37 |
8
|
Mohn CE, Allan NL, Freeman CL, Ravindran P, Stølen S. Order in the disordered state: local structural entities in the fast ion conductor Ba2In2O5. J SOLID STATE CHEM 2005. [DOI: 10.1016/j.jssc.2004.10.044] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
|
20 |
37 |
9
|
Ravindran P, Ansari N, Young CJ, Solomon MJ. Definitive surgical closure of enterocutaneous fistula: outcome and factors predictive of increased postoperative morbidity. Colorectal Dis 2014; 16:209-218. [PMID: 24521276 DOI: 10.1111/codi.12473] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 08/16/2013] [Indexed: 12/12/2022]
Abstract
AIM Enterocutaneous fistula (ECF) presents a complex management problem with significant mortality and morbidity. The aim of this study was to assess the outcome of patients undergoing surgical cure for ECF and to predict factors that might relate to increased postoperative morbidity. METHOD Medical records of all patients who underwent definitive surgery for cure of an ECF within our colorectal surgery unit between 2000 and 2010 were reviewed. RESULTS Forty-one patients (18 male) were identified, in whom 44 definitive procedures were performed. The median age was 54 (17-81) years. The median postoperative length of stay in hospital was 14 (2-213) days. Half (50%) of the ECFs occurred as a postoperative complication followed by spontaneous fistulation in Crohn's disease (36%). The interval to definitive surgery was influenced by the aetiology of the fistula. The median time to surgery after formation of postoperative fistula was 240 days (7.9 months). There was no 30-day postoperative mortality. There were two (4.5%) recurrences at 3 months. Thirty-eight (86%) patients suffered postoperative morbidity as defined by the Clavien-Dindo classification. High-grade morbidity occurred in 32% of patients. On univariate analysis, factors identified as being significantly associated with high-grade morbidity included a fistula output of > 500 ml/day (P = 0.004) in patients with postoperative ECF, malnutrition at presentation (P = 0.04) and a serum albumin value of < 30 g/l (P = 0.02) in patients with spontaneous ECF due to Crohn's disease. CONCLUSION The majority of persistent complex ECFs can be cured surgically with low mortality and recurrence in a multidisciplinary setting. Postoperative morbidity, however, remains a significant burden.
Collapse
|
|
11 |
35 |
10
|
Ghosh CS, Ravindran P, Joshi M, Stearns SC. Reductions in hospital use from self management training for chronic asthmatics. Soc Sci Med 1998; 46:1087-93. [PMID: 9579760 DOI: 10.1016/s0277-9536(97)10047-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The purpose of this study was to assess the impact of asthma Self Management Training on the health status and resource use of patients with chronic asthma. The study consisted of a randomized control design of chronic asthmatic patients in a tertiary care center in India. The intervention group (153 patients) received four training sessions in addition to the regular care provided to the control group (150 patients). Health status and resource use were measured at baseline and over a one year follow-up period. The intervention group had significantly better health status (measured by breathing ability), fewer productive days lost, and lower resource use (hospitalizations and emergency room visits) than the control group. Total annual costs (direct and indirect) were also lower, though physician costs were not included in the assessment. Therefore, incorporation of asthma Self Management Training as part of clinical management of asthma can result in improvements in health status and reductions in hospital use.
Collapse
|
Clinical Trial |
27 |
35 |
11
|
Vajeeston P, Ravindran P, Kjekshus A, Fjellvåg H. Pressure-induced structural transitions in MgH2. PHYSICAL REVIEW LETTERS 2002; 89:175506. [PMID: 12398685 DOI: 10.1103/physrevlett.89.175506] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2002] [Indexed: 05/24/2023]
Abstract
The stability of MgH2 has been studied up to 20 GPa using density-functional total-energy calculations. At ambient pressure alpha-MgH2 takes a TiO2-rutile-type structure. alpha-MgH2 is predicted to transform into gamma-MgH2 at 0.39 GPa. The calculated structural data for alpha- and gamma-MgH2 are in very good agreement with experimental values. At equilibrium the energy difference between these modifications is very small, and as a result both phases coexist in a certain volume and pressure field. Above 3.84 GPa gamma-MgH2 transforms into beta-MgH2, consistent with experimental findings. Two further transformations have been identified at still higher pressure: (i) beta- to delta-MgH2 at 6.73 GPa and (ii) delta- to epsilon-MgH2 at 10.26 GPa.
Collapse
|
|
23 |
30 |
12
|
Iozzi MF, Vajeeston P, Vidya R, Ravindran P, Fjellvåg H. Structural and electronic properties of transparent conducting delafossite: a comparison between the AgBO2 and CuBO2 families (B = Al, Ga, In and Sc, Y). RSC Adv 2015. [DOI: 10.1039/c3ra47531j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Ag-based delafossite transparent conducting oxides are potential p-type materials for transparent electronics. However, they have attracted less attention due to their difficult synthetic chemistry and relatively low conductivity.
Collapse
|
|
10 |
25 |
13
|
Arjunan V, Raj A, Ravindran P, Mohan S. Structure-activity relations of 2-(methylthio)benzimidazole by FTIR, FT-Raman, NMR, DFT and conceptual DFT methods. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 118:951-965. [PMID: 24184580 DOI: 10.1016/j.saa.2013.09.100] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 09/11/2013] [Accepted: 09/26/2013] [Indexed: 06/02/2023]
Abstract
The vibrational fundamental modes of 2-(methylthio)benzimidazole (2MTBI) have been analysed by combining FTIR, FT-Raman and quantum chemical calculations. The structural parameters of the compound are determined from the optimised geometry by B3LYP with 6-31G(∗∗), 6-311++G(∗∗) and cc-pVTZ basis sets and giving energies, harmonic vibrational frequencies, depolarisation ratios, IR intensities and Raman activities. (1)H and (13)C NMR spectra have been analysed and (1)H and (13)C nuclear magnetic resonance chemical shifts are calculated using the gauge independent atomic orbital (GIAO) method. The structure-activity relationship of the compound is also investigated by conceptual DFT methods. The chemical reactivity and site selectivity of the molecule has been determined with the help of global and local reactivity descriptors.
Collapse
|
|
11 |
22 |
14
|
Su C, Melby T, DeMasi R, Ravindran P, Heilek-Snyder G. Genotypic changes in human immunodeficiency virus type 1 envelope glycoproteins on treatment with the fusion inhibitor enfuvirtide and their influence on changes in drug susceptibility in vitro. J Clin Virol 2006; 36:249-57. [PMID: 16765082 DOI: 10.1016/j.jcv.2006.03.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Revised: 02/28/2006] [Accepted: 03/08/2006] [Indexed: 11/21/2022]
Abstract
BACKGROUND Previous studies have established the importance of substitutions at amino acids 36-45 of HIV-1 gp41 in the development of viral resistance to the peptide fusion inhibitor enfuvirtide. However, the influence of other loci in the HIV-1 envelope is not well established. OBJECTIVE To identify positions showing genotypic changes that are associated with particularly high levels of changes in enfuvirtide susceptibility. STUDY DESIGN We examined full-length baseline and on treatment sequences of gp120 and gp41 for isolates from 369 patients in Phase III studies of enfuvirtide, including 281 patients receiving ENF+OB and 88 patients receiving OB alone. Individual changes in gp41 and gp120 were evaluated for correlations with on treatment phenotype changes by analysis of variance (ANOVA). This modeling was done with (two-way) and without (one-way) ANOVA adjusting for the effects of any changes in gp41 amino acids 36-45 modeled as a single variable (ANY(36-45)). Positions displaying significance levels of p<0.05 by either one- or two-way ANOVA were then studied by multi-way ANOVA (stepwise regression). RESULTS In addition to changes at gp41 amino acids 36-45, changes at three positions in the HR2 domain (126, 129 and 133) occurred significantly more often in patients undergoing virologic failure on enfuvirtide. However, ANY(36-45) alone accounted for slightly more than 90% of the variation in phenotype explained by the ANOVA models. Relative to ANY(36-45) alone, significant increases in the geometric mean of the fold-change in inhibitory concentration (19.6-236.3-fold higher) were observed for amino acid changes at positions gp41: 18, 42,126, 247, 256 and 312; gp120: 330, 389 and 424 and significant reductions (18.8-29.7-fold lower) for gp41: 3, 46, 165, 232 and 324. CONCLUSIONS This study represents a statistical approach to highlight positions in HIV envelope that undergo mutations in the presence of enfuvirtide. Several of the identified positions have been implicated in the viral fusion process by other studies. The specific impact of positions 330. Three hundred and eighty-nine and 424 on viral fusion kinetics remains to be studied further by site-directed mutagenesis experiments.
Collapse
|
Journal Article |
19 |
21 |
15
|
Stølen S, Mohn CE, Ravindran P, Allan NL. Topography of the Potential Energy Hypersurface and Criteria for Fast-Ion Conduction in Perovskite-Related A2B2O5 Oxides. J Phys Chem B 2005; 109:12362-5. [PMID: 16852527 DOI: 10.1021/jp050697g] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We discuss the importance of the topography of the potential energy hypersurface for the ionic conductivity of perovskite-related A(2)B(2)O(5) oxides. A correlation between the energetic preference of the cations for different coordination geometries and the ionic conductivity is proposed based on a first principles periodic density functional theory study of selected possible structures for Ba(2)In(2)O(5), Sr(2)Fe(2)O(5), Sr(2)Mn(2)O(5), and La(2)Ni(2)O(5). There are a large number of low-energy local minima on the potential energy hypersurfaces of the two first compounds due to an energetic preference for BO(4) tetrahedra. Tetrahedral environments are energetically unfavorable for Mn(III) in Sr(2)Mn(2)O(5) and for Ni(II) in La(2)Ni(2)O(5), and the number of low-energy configurations is relatively low in these two cases. Consistent with our findings, in contrast to Sr(2)Fe(2)O(5) and Ba(2)In(2)O(5), Sr(2)Mn(2)O(5) and La(2)Ni(2)O(5) do not exhibit transitions to disordered phases on heating, and there appear to be no reports of enhanced ionic conductivity for these compounds. Thus we suggest that the possibility of many different oxygen orderings associated with a variety of low-energy connectivity schemes within tetrahedral layers such as in the brownmillerite-based structures of Sr(2)Fe(2)O(5) and Ba(2)In(2)O(5) is a prerequisite for high ionic conductivity in perovskite-related A(2)B(2)O(5) oxides.
Collapse
|
|
20 |
20 |
16
|
Vajeeston P, Ravindran P, Fjellvåg H. Structural phase stability studies on MBeH3 (M = Li, Na, K, Rb, Cs) from density functional calculations. Inorg Chem 2008; 47:508-14. [PMID: 18088114 DOI: 10.1021/ic7015897] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Density functional theory calculations within the generalized-gradient approximation are used to establish the ground-state structure, equilibrium structural parameters, and electronic structure for MBeH(3) phases. From the 24 structural arrangements used as inputs for structural optimization calculations, the ground-state crystal structures of MBeH(3) phases have been predicted. At ambient conditions, LiBeH(3) and NaBeH(3) crystallize with perovskite-related orthorhombic and cubic structures, respectively. The remaining phases KBeH(3), RbBeH(3), and CsBeH(3) crystalize in a monoclinic structure. In the predicted phases one can store up to 15.93 wt % of hydrogen. The formation energy for the MBeH(3) phases have been investigated along different reaction pathways. The electronic structures reveal that all these phases are insulators with estimated band gaps varying between 1.79 and 3.44 eV.
Collapse
|
|
17 |
19 |
17
|
Vajeeston P, Ravindran P, Fjellvåg H. Phonon, IR, and Raman Spectra, NMR Parameters, and Elastic Constant Calculations for AlH3 Polymorphs. J Phys Chem A 2011; 115:10708-19. [DOI: 10.1021/jp2011342] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
|
14 |
19 |
18
|
Ravindran P, Subramoniam G, Asokamani R. Ground-state properties and relative stability between the L12 and DOa phases of Ni3Al by Nb substitution. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:1129-1137. [PMID: 9983569 DOI: 10.1103/physrevb.53.1129] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
|
29 |
17 |
19
|
Ravindran P, Asokamani R. Electronic structure, phase stability, equation of state, and pressure-dependent superconducting properties of Zr3Al. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:668-678. [PMID: 9975728 DOI: 10.1103/physrevb.50.668] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
|
31 |
16 |
20
|
Ravindran P, Sankaralingam S, Asokamani R. Electronic structure and phase-stability studies on superconducting YNi2B2C, YRh3B, and nonsuperconducting YNi4B. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:12921-12930. [PMID: 9980463 DOI: 10.1103/physrevb.52.12921] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
|
30 |
15 |
21
|
Roy DC, Ravindran P, Padmanabhan R. Bronchobiliary fistula secondary to amebic liver abscess. Chest 1972; 62:523-4. [PMID: 5078017 DOI: 10.1378/chest.62.4.523] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
|
Case Reports |
53 |
15 |
22
|
Arjunan V, Mohan S, Ravindran P, Mythili CV. Vibrational spectroscopic investigations, ab initio and DFT studies on 7-bromo-5-chloro-8-hydroxyquinoline. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009; 72:783-788. [PMID: 19112045 DOI: 10.1016/j.saa.2008.11.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 11/10/2008] [Accepted: 11/15/2008] [Indexed: 05/27/2023]
Abstract
The Fourier transform infrared (FTIR) and FT-Raman spectra of 7-bromo-5-chloro-8-hydroxyquinoline (BCHQ) have been measured in the range 4000-400 and 4000-100cm(-1), respectively. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FTIR and FT-Raman data. The geometry was optimised without any symmetry constrains using the DFT/B3LYP and HF methods with 6-31G** basis set. The vibrational frequencies which were determined experimentally are compared with those obtained theoretically from ab initio HF and density functional theory (DFT) gradient calculations employing the HF/6-31G** and B3LYP/6-31G** methods for the optimised geometry of the compound. The structural parameters and normal modes of vibration obtained from HF and DFT methods are in good agreement with the experimental data. Normal coordinate analysis was also carried out with ab initio force fields utilising Wilson's FG matrix method.
Collapse
|
|
16 |
15 |
23
|
Varunaa R, Ravindran P. Potential hydrogen storage materials from metal decorated 2D-C 2N: an ab initio study. Phys Chem Chem Phys 2019; 21:25311-25322. [PMID: 31701096 DOI: 10.1039/c9cp05105h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two dimensional nitrogenated holey graphene (2D-C2N) is often considered as an ideal material for hydrogen storage applications owing to its lower mass density and high surface-to-volume ratio. As the interaction between H2 and pristine 2D-C2N is very weak with an adsorption energy of only 0.10 eV per H2, it is important to improve it through appropriate materials design. Using density functional theory calculations, we investigated the hydrogen storage properties of metal (M = Mg, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, and Zn) decorated 2D-C2N. From this study, we found that M binding energy on 2D-C2N is greater than the cohesive energy of the respective bulk metals, indicating that the metal is strongly bonded with the 2D-C2N, which rules out the metal clustering issue. In particular, 2D-C2N with Mg decoration leads to 6.79 wt% hydrogen storage capacity with a desirable adsorption energy which is above the Department of Energy's target. The electronic structure analyses show that the Mg decoration leads to a semiconductor-to-metallic transition in 2D-C2N. Our chemical bonding analyses through partial density of states, charge density, electron localization function, charge transfer, and Bader effective charge confirm the presence of an iono-covalent character for Mg decorated 2D-C2N. This indicates that the H2 molecules are adsorbed by a polarization mechanism. Overall, our results suggest that Mg decorated 2D-C2N is a promising candidate for potential hydrogen storage applications.
Collapse
|
Journal Article |
6 |
14 |
24
|
Arjunan V, Saravanan I, Ravindran P, Mohan S. Ab initio, density functional theory and structural studies of 4-amino-2-methylquinoline. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009; 74:375-384. [PMID: 19581121 DOI: 10.1016/j.saa.2009.06.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2008] [Revised: 05/25/2009] [Accepted: 06/08/2009] [Indexed: 05/28/2023]
Abstract
The Fourier transform infrared (FTIR) and FT-Raman spectra of 4-amino-2-methylquinoline (AMQ) have been recorded in the range 4000-400 and 4000-100 cm(-1), respectively. The experimental vibrational frequency was compared with the wavenumbers obtained theoretically by ab initio HF and DFT-B3LYP gradient calculations employing the standard 6-31 G** and high level 6-311 ++G** basis sets for optimised geometry of the compound. The complete vibrational assignment and analysis of the fundamental modes of the compounds were carried out using the experimental FTIR and FT-Raman data, and quantum mechanical studies. The geometry and normal modes of vibration obtained from the HF and DFT methods are in good agreement with the experimental data. The potential energy distribution of the fundamental modes was calculated with ab initio force fields utilising Wilson's FG matrix method. The NH-pi interactions and the influence of amino and methyl groups on the skeletal modes are investigated.
Collapse
|
|
16 |
14 |
25
|
Abstract
We describe a case of catamenial hemothorax and hemopneumothorax occurring on both sides simultaneously; the patient responded remarkably with danazol therapy. To our knowledge, this is previously unreported in the literature.
Collapse
|
Case Reports |
32 |
13 |