Energy Transfer Medium Research Articles

A new microwave-assisted synthetic approach to novel pyrimido[4,5-d]pyrimidines

An environmentally benign approach for the synthesis of novel 7-substituted 5-aryl-1H-pyrimido[4,5-d]pyrimidine-2,4-diones, using mineral supports for their catalytic role and as energy transfer media, is described. The methodology eliminates the usage of solvent during the reaction. The rate enhancement and high yield is attributed to the coupling of solvent-free conditions with microwaves. Further, the role of various supports is studied during the reaction and it is concluded that a MW-assisted basic alumina catalysed reaction is the best in terms of catalysis as well as reaction time and yield.Key words: microwave (MW) irradiation, SBT, pyrimido[4,5-d]pyrimidines, alumina, environmentally benign.

Solar wind-magnetosphere coupling functions on timescales of 1 day to 1 year

Abstract. There are no direct observational methods for determining the total rate at which energy is extracted from the solar wind by the magnetosphere. In the absence of such a direct measurement, alternative means of estimating the energy available to drive the magnetospheric system have been developed using different ionospheric and magnetospheric indices as proxies for energy consumption and dissipation and thus the input. The so-called coupling functions are constructed from the parameters of the interplanetary medium, as either theoretical or empirical estimates of energy transfer, and the effectiveness of these coupling functions has been evaluated in terms of their correlation with the chosen index. A number of coupling functions have been studied in the past with various criteria governing event selection and timescale. The present paper contains an exhaustive survey of the correlation between geomagnetic activity and the near-Earth solar wind and two of the planetary indices at a wide variety of timescales. Various combinations of interplanetary parameters are evaluated with careful allowance for the effects of data gaps in the interplanetary data. We show that the theoretical coupling, Pα, function first proposed by Vasyliunas et al. is superior at all timescales from 1-day to 1-year.

Laser Cleaning of Particles with the aid of Freezer/Chilling Plate

In steam laser cleaning, a thin water film layer, formed by the condensation of steam, on the substrate surface is used as an energy transfer medium to effectively remove particulate contaminants from the substrate surface. In this work, a new method is adopted for water film formation. Instead of steam condensation, the water film is now formed by condensation of ambient water vapour, a more uniform water film results and this new method would simplify the experimental setup of steam laser cleaning. Using this new method of water film formation and a pulsed 532 nm Nd:YAG laser (pulse width of ~70 ns at a pulse repetition rate of 5 kHz), the dependence of cleaning efficiency on processing parameters, such as laser fluence, pulse number/unit area, and temperature, are investigated and cleaning efficiency will be compared to that of dry and steam laser cleaning.

A Facile Synthesis for Novel Pyrimido[1,3,4]Triazepine

An efficient route to the synthesis of novel fused pyrimidotriazepine derivatives using inorganic solid supports under MWs is described herein. The methodology uses microwave as an alternative heating source, which eliminates the usage of solvent during the course of reaction. With this environmentally benign approach, the reaction time is brought down from hours to minutes along with the yield enhancement. In addition, the catalytic role of different inorganic supports is studied for this [2+5] condensation reaction and montmorillonite K-10 clay is found to be the best solid support in terms of catalyst as well as an energy transfer medium. Keywords: pyrimidotriazepine, thiosemicarbazone, thiobarbituric acid, microwave, solid support, montmorillonite k clay

Laser Cleaning of Particles from Silicon Wafers: Capabilities and Mechanisms

Introduction The preparation of surfaces free of particle contamination is one of the crucial prerequisites for a further increase in the integration density of ICs and for the progress in nanotechnology. Therefore the removal of sub-micron sized particles from silicon wafers is of great interest. For this purpose a variety of cleaning methods is currently under investigation. In semiconductor industry an ideal cleaning technique should be capable of removing particles with a diameter considerably below 100 nm, while a damage to the substrate has to be strictly avoided. Furthermore the process should be environmentally friendly and cost-effective. A promising approach which meets these requirements is called Laser Cleaning. So far two major approaches can be distinguished. The first one is called Dry Laser Cleaning (DLC), where the surface to be cleaned is simply irradiated by a short laser pulse [1,2,3]. In Steam Laser Cleaning (SLC) a thin layer of a liquid energy transfer medium is deposited on the surface prior to the laser pulse [1,2,4,5]. In this paper we will present a short overview of these techniques followed by some of our recent results. The emphasis lies on the underlying mechanisms and an industrial applicability of both cleaning methods.

A Facile Synthesis of 2‐Aminobenzene‐1,3‐dicarbonitrile.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Fluorescence resonance energy transfer—a spectroscopic probe for organized surfactant media

Dyes commonly used as biological labels have been used to probe resonance energy transfer in organized media. In neat water, energy transfer between the dye pairs fluorescein (donor):Nile red (acceptor) and acridine orange (donor):Nile red (acceptor) has a very low probability of occurrence. This study shows that the rate constant of energy transfer increases by more than an order of magnitude in organized surfactant media, viz., micelles and reverse micelles of the surfactant Triton X-100. The reverse micelles provide a better medium for energy transfer than the micelles. The energy transfer studies also provide an idea about the location and proximity of donor and acceptor dyes within the various organized media. Assuming Poissonian statistics for dye distribution, the donor–acceptor distances within micelles and reverse micelles are determined from energy transfer parameters. Acridine orange has been found to function better as a donor than fluorescein. This may be due to steric and electrostatic factors.

Base Catalysed Pyrimidine Synthesis Using Microwave

An environmentally benign approach for the synthesis of 2-substituted-4,6-diaryl pyrimidines using inorganic solid supports for its catalytic role as well as an energy transfer medium is described. The methodology eliminates the usage of solvent during the reaction. The reaction time is brought down from hours to minutes along with yield enhancement. The rate enhancement and high yield is attributed to the coupling of solvent free conditions with microwaves. Further, the role of base is studied in the reaction and it is concluded that microwave assisted basic alumina catalysed reaction is the best in terms of catalysis as well as reaction time and yield.

Microwave‐Assisted Synthesis and Biological Activities of Some Bridgehead Nitrogen Heterocycles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Novel Approach to Furopyrimidinones Using Dry Media.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Novel Approach to Furopyrimidinones Using Dry Media

Abstract An environmentally benign approach to the synthesis of furopyrimidin-4(3H)-one under microwave irradiation (MWI) using an inorganic solid support for catalytic activity as well as an energy-transfer medium is described. The reaction time can be decreased from hours to minutes along with a yield enhancement. In addition, the differential activity of various solid supports was studied for a reaction which enables one to accomplish the one-pot synthesis of the required product via the 2-aminofuran-3-carbonitrile intermediate.

MICROWAVE ASSISTED SYNTHESIS OF NOVEL 1,2,4-TRIAZINES IN “DRY MEDIA”

An efficient facile and solventless synthesis of 1,2,4-triazines using microwave is described. A non conventional synthetic procedure has been developed where solid inorganic support is used as energy transfer medium under microwave irradiation (MWI) which devoids hazards of solution phase reactions. The reaction time has been brought down from hours to seconds with improved yield as compared to conventional heating.

A Facile Method for Nucleophilic Aromatic Substitution of Cyclic Amine

The expeditious solventless nucleophilic aromatic substitution using microwaves is described. A non-conventional synthetic procedure has been developed where basic alumina has been used as energy transfer medium under Microwave Irradiation (MW1). The results were compared with those obtained by the classical method. This rapid and environmentally benign method avoids the use of excess solvents and toxic bases usually employed in the process make this procedure very attractive for synthesis.

The energy supply to X-ray bright points

X-ray bright points (XBPs) are usually assumed to be isolated structures in the solar atmosphere that are powered exclusively by magnetic reconnection. We analyse a large XBP that does not satisfy this assumption. The XBP is observed to be connected to an active region approximately 280 000 km away by a magnetic loop. We find that the soft X-ray intensity and thermal energy of the XBP are very sensitive to the existence of the magnetic loop. Both the intensity and energy decrease significantly at the times when the loop disappears, indicating that the loop is a medium for energy transfer from the active region to the XBP. We deduce that the mechanism for the energy transfer is most likely to be Alfven or fast-mode magnetoacoustic waves created by photospheric motions in the active region. These waves can dissipate energy at the density gradient between the XBP and the loop via phase mixing or resonant absorption.

An Efficient Procedure for the Synthesis of Spiro (3H-Indole-3,4′ (1′H)pyrano[2,3-C]pyrrole]-5′-carbonitriles Using Solid Inorganic Supports and Microwave Activation

Microwave irradiation accelerates the Michael condensation of 3-dicyanomethylene-2H-indole-2-one with 2-pyrrolidone/ N-methy1-2-pyrrolidone (i) adsorbed on neutral alumina in “dry media” (ii) using absolute ethanol as energy transfer medium. 3-Dicyanoniethylene-2H-indol-2-one was synthesized under microwave irradiation using indole-2,3-dione and malononitrile. The results were compared with those obtained following the classical method. The advantages obtained by the use of microwave irradiation are demonstrated.

Excimer Laser Induced Removal of Particles from Hydrophilic Silicon Surfaces

A pulsed KrF excimer laser was used to remove several types of submicron-sized particles from silicon surfaces. Polystyrene latex particles, 0.1 μm and larger, were removed from silicon surfaces by dry laser cleaning (no water layer condensed on the surface) but SiO2 particles could not be so removed. However, during steam laser cleaning, in which a thin film of water is deposited on the surface as both an energy transfer medium and an adhesion force reduction agent, these 0.1–0.2 μm SiO2 particles were almost entirely removed. Calculations of the various forces contributing to adhesion indicate that hydrogen bonds are the major contributor to the adhesion of inorganic particles to substrate surfaces. Photoacoustic detection, using piezoelectric transducers, monitored the surface vibrations induced by the laser pulses.

Synthesis and antimicrobial evaluation of some new fluorinated spiro[[1,5] -benzothiazepin-2,3′[3′ H]-indol]-2′(1′ H)-ones

A series of fluorinated spiro[1,5-benzothiazepin-2,3′[3′ H]-indol]-2′(1′ H)-ones have been prepared by the reaction of 2-aminobenzene-thiols with 1,3-dihydro-3-[2-phenyl/(4-fluorophenyl)-2-oxoethylidene)-indol-2(1 H)-ones ( I) under microwave irradiation in open vessels using ethylene glycol as energy transfer medium and thermally in absolute ethanol saturated with hydrogen chloride gas. The comparative studies indicated that the microwave assisted organic synthesis has advantages of significantly reduced reaction time, improved yields and cleaner reactions as compared to the conventional method. All synthesized compounds have been characterized by analytical and spectral data and were screened for their antifungal activity against Alternaria alternata and Fusarium oxysporium and antitubercular activity against Mycobacterium tuberculosis IVb (R = F, X = F) and IVe (R = F, X = CH 3) have shown above 90% inhibition in reducing fungal growth of A. alternata while IVa (R = H, X — F) has shown 98% antitubercular activity on primary screening.

IMPROVED ONE-POT SYNTHESIS OF 3-SPIRO INDOLINES UNDER MICROWAVE IRRADIATION

The potential of the domestic microwave oven has been utilized to accelerate the one-pot synthesis of spiro[indole-thiazolidine]diones and spiro[indole-benzothiazine]diones by condensation of substituted indole-2.3-diones (1) and appropriate anilines (2) with mercaptopropionic acid (4a/b) and o-mercaptobenzoic acid (5) in open borosilicate vessels, using ethanol as energy transfer medium. The reaction rate was 400–500 times faster than the reaction rate in the conventional way. Excellent isolated yields with easier workup than classical heating were the main advantages observed.

Synthesis of fluorinated ethyl 4-aryl-6-methyl-1,2,3,4-tetrahydropyrimidin-2-one/thione-5-carboxylates under microwave irradiation

Microwaves have been found to greatly accelerate the Biginelli synthesis of fluorine containing ethyl 4-aryl-6-methyl-1,2,3,4-tetrahydropyrimidin-2-one/thione-5-carboxylates in unsealed vessels using ethanol as energy transfer medium. Results were compared with those obtained following the classical method. The advantages obtained by the use of microwave irradiation were demonstrated. All synthesized compounds have been characterized on the basis of elemental analyses, IR, 1H NMR and 19F NMR spectral studies.

MICROWAVE INDUCED SYNTHESIS OF 2-SUBSTITUTEDPHENYL-3-(3-ALKYL/ARYL-5,6-DIHYDRO-S-TRIAZOLO) [2,4-B] [1,3,4] THIADIAZO 6-YL INDOLES AND 2-PHENYL-3 [2, SUBSTITUTED BENZOTHIAZOLE] DERIVATIVES AND THEIR FUNGICIDAL ACTIVITY

The title compounds were synthesised by condensation of 3-alykl/aryl-4-amino-5-mercaptotriazole (II) and 5-substituted 2-aminothiophenols (IV) with appropriate 2-phenyl-1H-indole-3-carboxaldehyde (I) under microwave irradiation in the presence of piperidine/p-toluenesulphonic acid using ethanol/DMF as energy transfer media. The considerable increase in reaction rate with improved yield has been observed, using microwave as compared to classical method.