ram ram - Academia.edu (original) (raw)
Papers by ram ram
Applied Optics, 1996
The emission spectrum of the A 1 P-X 1 S 1 system of AlH, excited in a hollow-cathode discharge l... more The emission spectrum of the A 1 P-X 1 S 1 system of AlH, excited in a hollow-cathode discharge lamp, has been observed at high resolution with a Fourier-transform spectrometer. The rotational lines in the 0-0 and the 1-1 bands have been measured with a precision of 60.001 cm 21 . The present measurements provide a considerable improvement over the previous data of Zeeman and Ritter 3Can. J. Phys. 32, 555 1195424. The present data, combined with the previous high-resolution measurements of the 1-0 vibration-rotation band by White et al. 3J. Chem. Phys. 99, 8371 1199324 and the J 5 1-0 pure rotational line of Goto and Saito 3Astrophys. J. 452, L147 1199524 have been used to determine improved molecular constants for the A 1 P state. r
Journal of Molecular Spectroscopy, 2009
Emission spectra of WO have been observed in the 4000–35 000 cm−1 region using a Fourier transfor... more Emission spectra of WO have been observed in the 4000–35 000 cm−1 region using a Fourier transform spectrometer. Molecules were produced by exciting a mixture of WCl6 vapor and He in a microwave discharge lamp. A 3Σ− state has been assigned as the ground state of WO based on a rotational analysis of the observed bands and ab initio calculations. After rotational analysis, a majority of strong bands have been classified into three groups. Most of the transitions belonging to the first group have an Ω = 0+ state as the lower state while the bands in the second group have an Ω′′ = 1 state as the lower state. These two lower states have been assigned as X0+ and X1 spin components of the X3Σ− ground state of WO. The third group consists of additional bands interconnected by common vibrational levels involving some very low-lying states. The spectroscopic properties of the low-lying electronic states have been predicted from ab initio calculations. The details of the rotational analysis are presented and an attempt has been made to explain the experimental observations in the light of the ab initio results.
Smart Materials & Structures, 2007
In this paper, an analysis of a Gunn loaded stacked annular ring microstrip antenna is presented ... more In this paper, an analysis of a Gunn loaded stacked annular ring microstrip antenna is presented using a circuit concept. Consequently, various parameters such as input impedance, voltage standing wave ratio, return loss, band width, radiation pattern, and beam width of the antenna are evaluated as a function of bias voltage for different threshold values. It is found that the operating frequency of the Gunn loaded stacked patch is controllable with the bias voltage. The band width of the Gunn loaded stacked patch is improved to 11.61% as compared to the 9.16% band width of the stacked patch in addition to there being better matching and wider tunability. The radiated power and beam width of the stacked patch are also enhanced by loading a Gunn diode with it.
Microwave and Optical Technology Letters, 2008
A broad band U-slot microstrip patch antenna on a single layer foam substrate is investigated usi... more A broad band U-slot microstrip patch antenna on a single layer foam substrate is investigated using equivalent circuit concept. A parametric study has been carried out to investigate the effects caused by arm length, base length, and slot width of the U-slot. The effects of substrate height and feed position are also analyzed to obtain the optimum values for broadband operation. Broadband (bandwidth 33.52%) enhancement of the antenna is achieved by inserting U-slot into the patch. A comparison between theoretical and simulated results is also presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1069–1073, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23274
Microwave and Optical Technology Letters, 2008
A broadband microstrip patch antenna with U-shaped parasitic elements is proposed and analyzed us... more A broadband microstrip patch antenna with U-shaped parasitic elements is proposed and analyzed using equivalent circuit theory concept. The effects of gap between the main patch and the U-shaped parasitic elements, substrate thickness, and the feed point location are analyzed to obtain the optimum conditions for broadband operation of the antenna. The antenna shows an operational frequency band from 4.88 to 6.44 GHz with 28.36% bandwidth at center frequency 5.5 GHz. The radiation patterns of the proposed antenna are similar to that of a rectangular patch. The antenna shows 3-dB beam width of 98.6° at lower resonance frequency whereas it is 77.6° at higher resonance frequency. The theoretical results are in good agreement with experimental results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2059–2063, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23573
Progress in Electromagnetics Research Letters, 2008
AbstractA broadband stacked U-slot microstrip patch antenna is presented using circuit theory co... more AbstractA broadband stacked U-slot microstrip patch antenna is presented using circuit theory concept. The antenna shows two resonance frequencies that are very closely spaced to give broadband characteristics. The frequency band of 186MHz (36.4% impedance ...
Progress in Electromagnetics Research B, 2008
AbstractAnalysis of a frequency agile broadband E-shaped patch antenna (ESPA) symmetrically load... more AbstractAnalysis of a frequency agile broadband E-shaped patch antenna (ESPA) symmetrically loaded with tunnel diodes is presented in this paper. The notch parameters such as notch-length, notch-width and position are optimized to achieve the optimum broadband ...
Progress in Electromagnetics Research B, 2008
A theoretical analysis of a gap-coupled stacked annular ring microstrip antenna with superstrate ... more A theoretical analysis of a gap-coupled stacked annular ring microstrip antenna with superstrate is performed in order to obtain wider bandwidth operation. The effects of air gap, superstrate thickness and feeding point location on the antenna performance are analyzed in TM 11 mode using equivalent circuit concept. It is noted that the proposed antenna is very sensitive to the feeding point location in TM 11 mode while annular ring microstrip patch antenna is independent of feed point in that mode. The optimized proposed antenna shows an impedance bandwidth of 13.96% whereas the antenna without air-gap has 8.75% bandwidth and without superstrate it has bandwidth of 10.89%. The theoretical results are compared with simulated and experimental results.
Tetrahedron, 2008
Chlorine substituent-promoted Diels-Alder reaction of 2-aryl-3-chlorofurans with dimethyl acetyle... more Chlorine substituent-promoted Diels-Alder reaction of 2-aryl-3-chlorofurans with dimethyl acetylenedicarboxylate at 100 C afforded highly substituted m-chlorophenolic biaryls in 59-78% yields.
Tetrahedron Letters, 1995
Phenacyl esters gave the deprotected carboxylic acids, alongwith PhCO2H, PhCHO and CO2 on heating... more Phenacyl esters gave the deprotected carboxylic acids, alongwith PhCO2H, PhCHO and CO2 on heating with CuCl2 or CuSO4 in aqueous DMF (50% v/v) at reflux with continuous bubbling of O2.Graphic
Journal of Chemical Research-s, 2000
Synthetic Communications, 2008
Unexpected Aromatization of 2-Acetoxy-3, 3-dichloro-4-(a-chloroalkyl)tetrahydrofurans to 3-Alkyl-... more Unexpected Aromatization of 2-Acetoxy-3, 3-dichloro-4-(a-chloroalkyl)tetrahydrofurans to 3-Alkyl-4-chlorofurans with NaI/DMF ... Ram N. Ram and I. Charles Department of Chemistry, Indian Institute of Technology, New Delhi, India ... Abstract: An unexpected ...
Journal of Chemical Research-s, 2006
Abstract: Aniline and unhindered alkyl-substituted anilines undergo solvolysis in dioxane and DME... more Abstract: Aniline and unhindered alkyl-substituted anilines undergo solvolysis in dioxane and DME saturated with dry hydrogen chloride on diazotisation with isoamyl nitrite to give 2-(2-chloroethoxy) ethyl aryl ethers and 2-methoxyethyl aryl ethers respectively in 36-47% ...
Tetrahedron Letters, 2007
CuCl/bpy-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates in r... more CuCl/bpy-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates in refluxing benzene gave benzannulated chloroarenes and benzannulated symmetrical biaryls along with reductive dehalogenation products. The unusual decarboxylative benzannulation and biaryl formation might be explained by a further intramolecular radical addition on the benzene ring of the eight-membered lactone intermediate, initially formed through 8-endo-trig halogen atom transfer radical cyclization, followed by decarboxylation, radical dimerization and dehydrochlorination reactions.
Synthetic Communications, 1993
Abstract Oximes, O-benzoyloximes and sodium salt of aldoximes and ketoximes were deoximated to th... more Abstract Oximes, O-benzoyloximes and sodium salt of aldoximes and ketoximes were deoximated to their parent carbonyl compounds with copper (II) chloride dihydrate in acetonitrile as well as water. This method works well with both aldoximes and ketoximes ...
Journal of Chemical Research-s, 2000
Various dicarboxylic acids have been converted selectively into monomethyl esters in which the no... more Various dicarboxylic acids have been converted selectively into monomethyl esters in which the nonconjugated carboxyl group is selectively esterified in the presence of an aromatic or conjugated carboxyl group at room temperature (~ 25-27°C) in methanol using a catalytic amount of thionyl chloride.
Chemical Communications, 1999
A simple method for the synthesis of 3-substituted and 2,3-disubstituted 4-chlorofurans is descri... more A simple method for the synthesis of 3-substituted and 2,3-disubstituted 4-chlorofurans is described which involves CuCl/bipy-catalysed regioselective cyclisation of 1-acetoxy-2,2,2-trichloroethyl allyl ethers followed successively by dechloroacetoxylation with Zn dust and tandem dehydrohalogenation-aromatisation with Bu t OK/18-crown-6.
Tetrahedron, 1997
Unhindered aliphatic nonconjugated carboxylic acids were esterified selectively in the presence o... more Unhindered aliphatic nonconjugated carboxylic acids were esterified selectively in the presence of aromatic or conjugated acids on heating in the corresponding alcoholic solutions at reflux for 3–13hr with 10 mol% of NiCl2.6H2O catalyst.Graphic
Synthetic Communications, 2001
Diaryl ketones condense with p-toluenesulfonamide in refluxing 1,2-dichloroethane in the presence... more Diaryl ketones condense with p-toluenesulfonamide in refluxing 1,2-dichloroethane in the presence of TiCl4/ Ti(O-iPr)4 or TiCl4/Et3N to give N-sulfonylimines in generally good yields. ... N-sulfonylimines are useful precursors for the preparation of important synthetic intermediates such as ...
Journal of Organic Chemistry, 2008
Reaction of several trichloromethyl carbinols with 2 equiv of CuCl/bpy in refluxing DCE for 3 h a... more Reaction of several trichloromethyl carbinols with 2 equiv of CuCl/bpy in refluxing DCE for 3 h afforded chloromethyl ketones in excellent yield by 1,2-H shift in the copper-chlorocarbenoid intermediate.
Applied Optics, 1996
The emission spectrum of the A 1 P-X 1 S 1 system of AlH, excited in a hollow-cathode discharge l... more The emission spectrum of the A 1 P-X 1 S 1 system of AlH, excited in a hollow-cathode discharge lamp, has been observed at high resolution with a Fourier-transform spectrometer. The rotational lines in the 0-0 and the 1-1 bands have been measured with a precision of 60.001 cm 21 . The present measurements provide a considerable improvement over the previous data of Zeeman and Ritter 3Can. J. Phys. 32, 555 1195424. The present data, combined with the previous high-resolution measurements of the 1-0 vibration-rotation band by White et al. 3J. Chem. Phys. 99, 8371 1199324 and the J 5 1-0 pure rotational line of Goto and Saito 3Astrophys. J. 452, L147 1199524 have been used to determine improved molecular constants for the A 1 P state. r
Journal of Molecular Spectroscopy, 2009
Emission spectra of WO have been observed in the 4000–35 000 cm−1 region using a Fourier transfor... more Emission spectra of WO have been observed in the 4000–35 000 cm−1 region using a Fourier transform spectrometer. Molecules were produced by exciting a mixture of WCl6 vapor and He in a microwave discharge lamp. A 3Σ− state has been assigned as the ground state of WO based on a rotational analysis of the observed bands and ab initio calculations. After rotational analysis, a majority of strong bands have been classified into three groups. Most of the transitions belonging to the first group have an Ω = 0+ state as the lower state while the bands in the second group have an Ω′′ = 1 state as the lower state. These two lower states have been assigned as X0+ and X1 spin components of the X3Σ− ground state of WO. The third group consists of additional bands interconnected by common vibrational levels involving some very low-lying states. The spectroscopic properties of the low-lying electronic states have been predicted from ab initio calculations. The details of the rotational analysis are presented and an attempt has been made to explain the experimental observations in the light of the ab initio results.
Smart Materials & Structures, 2007
In this paper, an analysis of a Gunn loaded stacked annular ring microstrip antenna is presented ... more In this paper, an analysis of a Gunn loaded stacked annular ring microstrip antenna is presented using a circuit concept. Consequently, various parameters such as input impedance, voltage standing wave ratio, return loss, band width, radiation pattern, and beam width of the antenna are evaluated as a function of bias voltage for different threshold values. It is found that the operating frequency of the Gunn loaded stacked patch is controllable with the bias voltage. The band width of the Gunn loaded stacked patch is improved to 11.61% as compared to the 9.16% band width of the stacked patch in addition to there being better matching and wider tunability. The radiated power and beam width of the stacked patch are also enhanced by loading a Gunn diode with it.
Microwave and Optical Technology Letters, 2008
A broad band U-slot microstrip patch antenna on a single layer foam substrate is investigated usi... more A broad band U-slot microstrip patch antenna on a single layer foam substrate is investigated using equivalent circuit concept. A parametric study has been carried out to investigate the effects caused by arm length, base length, and slot width of the U-slot. The effects of substrate height and feed position are also analyzed to obtain the optimum values for broadband operation. Broadband (bandwidth 33.52%) enhancement of the antenna is achieved by inserting U-slot into the patch. A comparison between theoretical and simulated results is also presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1069–1073, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23274
Microwave and Optical Technology Letters, 2008
A broadband microstrip patch antenna with U-shaped parasitic elements is proposed and analyzed us... more A broadband microstrip patch antenna with U-shaped parasitic elements is proposed and analyzed using equivalent circuit theory concept. The effects of gap between the main patch and the U-shaped parasitic elements, substrate thickness, and the feed point location are analyzed to obtain the optimum conditions for broadband operation of the antenna. The antenna shows an operational frequency band from 4.88 to 6.44 GHz with 28.36% bandwidth at center frequency 5.5 GHz. The radiation patterns of the proposed antenna are similar to that of a rectangular patch. The antenna shows 3-dB beam width of 98.6° at lower resonance frequency whereas it is 77.6° at higher resonance frequency. The theoretical results are in good agreement with experimental results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2059–2063, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23573
Progress in Electromagnetics Research Letters, 2008
AbstractA broadband stacked U-slot microstrip patch antenna is presented using circuit theory co... more AbstractA broadband stacked U-slot microstrip patch antenna is presented using circuit theory concept. The antenna shows two resonance frequencies that are very closely spaced to give broadband characteristics. The frequency band of 186MHz (36.4% impedance ...
Progress in Electromagnetics Research B, 2008
AbstractAnalysis of a frequency agile broadband E-shaped patch antenna (ESPA) symmetrically load... more AbstractAnalysis of a frequency agile broadband E-shaped patch antenna (ESPA) symmetrically loaded with tunnel diodes is presented in this paper. The notch parameters such as notch-length, notch-width and position are optimized to achieve the optimum broadband ...
Progress in Electromagnetics Research B, 2008
A theoretical analysis of a gap-coupled stacked annular ring microstrip antenna with superstrate ... more A theoretical analysis of a gap-coupled stacked annular ring microstrip antenna with superstrate is performed in order to obtain wider bandwidth operation. The effects of air gap, superstrate thickness and feeding point location on the antenna performance are analyzed in TM 11 mode using equivalent circuit concept. It is noted that the proposed antenna is very sensitive to the feeding point location in TM 11 mode while annular ring microstrip patch antenna is independent of feed point in that mode. The optimized proposed antenna shows an impedance bandwidth of 13.96% whereas the antenna without air-gap has 8.75% bandwidth and without superstrate it has bandwidth of 10.89%. The theoretical results are compared with simulated and experimental results.
Tetrahedron, 2008
Chlorine substituent-promoted Diels-Alder reaction of 2-aryl-3-chlorofurans with dimethyl acetyle... more Chlorine substituent-promoted Diels-Alder reaction of 2-aryl-3-chlorofurans with dimethyl acetylenedicarboxylate at 100 C afforded highly substituted m-chlorophenolic biaryls in 59-78% yields.
Tetrahedron Letters, 1995
Phenacyl esters gave the deprotected carboxylic acids, alongwith PhCO2H, PhCHO and CO2 on heating... more Phenacyl esters gave the deprotected carboxylic acids, alongwith PhCO2H, PhCHO and CO2 on heating with CuCl2 or CuSO4 in aqueous DMF (50% v/v) at reflux with continuous bubbling of O2.Graphic
Journal of Chemical Research-s, 2000
Synthetic Communications, 2008
Unexpected Aromatization of 2-Acetoxy-3, 3-dichloro-4-(a-chloroalkyl)tetrahydrofurans to 3-Alkyl-... more Unexpected Aromatization of 2-Acetoxy-3, 3-dichloro-4-(a-chloroalkyl)tetrahydrofurans to 3-Alkyl-4-chlorofurans with NaI/DMF ... Ram N. Ram and I. Charles Department of Chemistry, Indian Institute of Technology, New Delhi, India ... Abstract: An unexpected ...
Journal of Chemical Research-s, 2006
Abstract: Aniline and unhindered alkyl-substituted anilines undergo solvolysis in dioxane and DME... more Abstract: Aniline and unhindered alkyl-substituted anilines undergo solvolysis in dioxane and DME saturated with dry hydrogen chloride on diazotisation with isoamyl nitrite to give 2-(2-chloroethoxy) ethyl aryl ethers and 2-methoxyethyl aryl ethers respectively in 36-47% ...
Tetrahedron Letters, 2007
CuCl/bpy-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates in r... more CuCl/bpy-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates in refluxing benzene gave benzannulated chloroarenes and benzannulated symmetrical biaryls along with reductive dehalogenation products. The unusual decarboxylative benzannulation and biaryl formation might be explained by a further intramolecular radical addition on the benzene ring of the eight-membered lactone intermediate, initially formed through 8-endo-trig halogen atom transfer radical cyclization, followed by decarboxylation, radical dimerization and dehydrochlorination reactions.
Synthetic Communications, 1993
Abstract Oximes, O-benzoyloximes and sodium salt of aldoximes and ketoximes were deoximated to th... more Abstract Oximes, O-benzoyloximes and sodium salt of aldoximes and ketoximes were deoximated to their parent carbonyl compounds with copper (II) chloride dihydrate in acetonitrile as well as water. This method works well with both aldoximes and ketoximes ...
Journal of Chemical Research-s, 2000
Various dicarboxylic acids have been converted selectively into monomethyl esters in which the no... more Various dicarboxylic acids have been converted selectively into monomethyl esters in which the nonconjugated carboxyl group is selectively esterified in the presence of an aromatic or conjugated carboxyl group at room temperature (~ 25-27°C) in methanol using a catalytic amount of thionyl chloride.
Chemical Communications, 1999
A simple method for the synthesis of 3-substituted and 2,3-disubstituted 4-chlorofurans is descri... more A simple method for the synthesis of 3-substituted and 2,3-disubstituted 4-chlorofurans is described which involves CuCl/bipy-catalysed regioselective cyclisation of 1-acetoxy-2,2,2-trichloroethyl allyl ethers followed successively by dechloroacetoxylation with Zn dust and tandem dehydrohalogenation-aromatisation with Bu t OK/18-crown-6.
Tetrahedron, 1997
Unhindered aliphatic nonconjugated carboxylic acids were esterified selectively in the presence o... more Unhindered aliphatic nonconjugated carboxylic acids were esterified selectively in the presence of aromatic or conjugated acids on heating in the corresponding alcoholic solutions at reflux for 3–13hr with 10 mol% of NiCl2.6H2O catalyst.Graphic
Synthetic Communications, 2001
Diaryl ketones condense with p-toluenesulfonamide in refluxing 1,2-dichloroethane in the presence... more Diaryl ketones condense with p-toluenesulfonamide in refluxing 1,2-dichloroethane in the presence of TiCl4/ Ti(O-iPr)4 or TiCl4/Et3N to give N-sulfonylimines in generally good yields. ... N-sulfonylimines are useful precursors for the preparation of important synthetic intermediates such as ...
Journal of Organic Chemistry, 2008
Reaction of several trichloromethyl carbinols with 2 equiv of CuCl/bpy in refluxing DCE for 3 h a... more Reaction of several trichloromethyl carbinols with 2 equiv of CuCl/bpy in refluxing DCE for 3 h afforded chloromethyl ketones in excellent yield by 1,2-H shift in the copper-chlorocarbenoid intermediate.