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Analytical formulations for the resonant frequency of a reentrant cavity for klystron are available in the literature only for such cavities having a single beam-tunnel. An improved analytical formulation has been proposed in this paper for the calculation of cavity gap-capacitance of reentrant cavities having single and multiple beam-tunnels and its effects on the resonant frequency are studied. The results obtained through analysis have been validated against those obtained from the 3D electromagnetic field simulations and measurements. The proposed analytical formulation provides good estimation of resonant frequency of cavity with single and multiple beam-tunnels. © 2021, DESIDOC.

In an effort to enhance the bandwidth of a multiple-beam klystron having rectangular double reentrant cavity with circular cylindrical ferrule, reduction of the unloaded quality factor of the cavity was proposed by placing circular cylindrical posts extending from one of the cavity side-walls to the opposite wall in an orientation perpendicular to the electric field. A typical cavity was analyzed using 3D electromagnetic field solver CST Studio and the post-loading was found to reduce the unloaded quality factor by around 90% compared to that for no-post-loading. The proposed method was found to be the only method other than the use of passive loss to achieve this order of reduction in the quality factor with a minor increase in the cavity transverse dimensions. Post made of highly resistive material was found to have pronounced effect in reducing the quality factor. The 3D electromagnetic analysis was validated against measurements on a typical S-band cavity.

A concise, protection-group free and sequential route has been developed for the synthesis of the nitroimidazole based FDA-approved multi-drug resistant anti-tuberculosis drug, Delamanid and anti-leishmanial lead candidate VL-2098. The synthesis required chiral epoxides (11 and 17) as key intermediates. The chiral epoxide 11 was synthesised by sequential reaction cascades viz., allylation, selective N-arylation, Mitsunobu etherification, Sharpless asymmetric dihydroxylation and epoxidation, which do not require any special/dry reaction conditions. The steps involved towards the synthesis of epoxide also worked nicely in gram scales. After the synthesis of epoxide 11, the synthesis of Delamanid was achieved by reaction with 2-bromo-4-nitroimidazole 12 with an overall yield of 27%. Similarly, anti-leishmanial lead candidate VL-2098 was also synthesized in an overall yield of 36%.

Closed-form formulation for the estimation of equivalent circuit capacitance and inductance of a rectangular double-reentrant klystron cavity with circular cylindrical ferrules was developed and us...

Equivalent circuit analysis of a rectangular double-reentrant cavity of klystron with circular cylindrical ferrule operating in the fundamental TM110 mode was developed for obtaining the lumped parameters such as capacitance and inductance by considering the cavity as a parallel resonant circuit. Resonant frequency and characteristic shunt impedance of the cavity were then obtained using these lumped parameters. Analysis was validated against 3-D electromagnetic simulations using CST Studio and measurements.

A simple method for estimation of the unloaded quality factor of single and double re-entrant cylindrical cavities was developed based on Wheeler�s incremental inductance rule. The proposed approach was benchmarked for a Ka-band re-entrant cavity against 3D electromagnetic simulation using CST Studio and also with measurements. The analysis is general and unlike the approach of Fujisawa, it could be extended to analyze the re-entrant cavity comprising dissimilar materials. The effect of surface roughness on the quality factor of the cavity also could be estimated using the present analysis. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.

Broadbanding of a rectangular reentrant cavity is proposed through reducing its unloaded quality factor by loading the cavity with periodic rectangular ridges placed on cavity transverse walls and orienting them perpendicular to the electric field. The effect of ridge loading on the cavity parameters, namely, resonant frequency, unloaded quality factor, and characteristics hunt impedance was investigated through 3-D electromagnetic simulations. Ridge loading of the cavity could facilitate around 70% reduction in the quality factor without any change in resonant frequency and negligible change in characteristic shunt impedance of that of a no-ridge-loaded cavity. The simulated resonant frequency and quality factor of typical S-band rectangular reentrant cavities were validated against measurements.

One-pot carbon-Ferrier rearrangement of glycals with unactivated aryl methyl ketones has been developed under mild Silyl triflate catalysis. Keto methyl group of various aryl methyl ketones without being converted into silyl enol ether could directly attack anomeric position of glycals to form keto functionalized C-glycosides in moderate to good yields with high α-selectivity. The versatility of this method has been extended to the synthesis of a small library of chromanone 3-C-glycosides.

Effect of surface roughness on the bandwidth of a high frequency multiple beam klystron (MBK) cavity circuit is investigated. Surface roughness reduces the surface conductivity of the base material which in turn reduces the unloaded quality factor of the cavity and increases the bandwidth of the cavity. First, effective conductivity is calculated analytically for a given surface roughness, and then it is related to the quality factor and 3dB bandwidth of the cavity. Analytical results are compared with those obtained from 3D simulations.

Novel polar functionalities containing 6-nitro-2,3-dihydroimidazooxazole (NHIO) analogues were synthesized to produce a compound with enhanced solubility. Polar functionalities including sulfonyl, uridyl, and thiouridyl-bearing NHIO analogues were synthesized and evaluated against Mycobacterium tuberculosis (MTB) H37Rv. The aqueous solubility of compounds with MIC values ≤0.5 μg/mL were tested, and six compounds showed enhanced aqueous solubility. The best six compounds were further tested against resistant (Rif(R) and MDR) and dormant strains of MTB and tested for cytotoxicity in HepG2 cell line. Based on its overall in vitro characteristics and solubility profile, compound 6d was further shown to possess high microsomal stability, solubility under all tested biological conditions (PBS, SGF and SIF), and favorable oral in vivo pharmacokinetics and in vivo efficacy.

A phase sensitive detector employed in microwave/mm wave radiometric systems measures an output as a pure dc, proportional to the difference between the phase of the input modulated signal and a reference signal. This difference signal takes the form of a square wave, one level corresponding to a constant blackbody temperature and the other to the incoming radiation, cancelling the inherent noise of the receiver, thereby achieving a high degree of stability of the radiometer. A phase sensitive (or a synchronous) detector was designed and fabricated to be used in the microwave receiver. The phase sensitive detector was fabricated for a minimum reference signal of 3 V square wave and a minimum signal input of 75 mV with an integration time of 6 s.

An efficient asymmetric synthesis of 5-hexadecanolide from a chiral epoxide is described. Both the enantiomeric forms of the chiral epoxide are easily available from mannitol and ascorbic acid. The key step in the synthesis is the formation of δ-lactone from δ-hydroxy acetal using m-CPBA and BF 3 ·OEt 2 .

N-Bromosuccinimide in chloroform in the presence of a catalytic amount of AIBN is found to cleave O-benzylidene sugar into bromobenzoate in efficient manner. THP-ethers were cleaved into bromides and bromo-esters in high yield.

In the presence of a catalytic amount of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetrahydropyranyl ethers are readily hydrolysed to their corresponding alcohols in wet acetonitrile under mild conditions.

Reaction of a variety of epoxides with DMSO-Oxalyl chloride in the presence of a catalytic amount of methanol and a base was studied. Disubstituted epoxides gave α-chloroketones in high yields. Aliphatic terminal epoxide underwent opening reaction to provide α-chloroketone as a major product. Trisubstututed epoxides provided α-chloroketones as major products through the formation of more stable carbocation. In case of a homoallylic alcohol, enedione was obtained. The efficiency of the method was shown by applying it to the enantioselective synthesis of (3S)-2,3-oxidosqualene.

This paper describes the overall design of a Ku-band 19 beam klystron amplifier. The device is designed to operate near to 2.5 KV with the total beam current of 0.5A equally distributed among its various beamlets. Two new schemes of magnetic focusing arrangement have been analyzed and experimented A block window design has been incorporated for the RF input and output. First, in-house developed codes and 1D code AJ Disk is used for initial design, later commercially available 3D simulation codes like CST-studio and Ansoft HFSS have been used for final optimization of the design.

This paper describes the design and experimentation of electrostatic focusing of electron beam using a demountable vacuum measurement setup. Initially a focusing setup is designed for focusing a single on-axis low perveance beam. The design was carried out using an in house developed 2.5D finite difference electron optics code PIERCE and CST Particle Studio. This focusing scheme is being extended for multiple beams of same perveance for a compact klystron device.

This paper describes a simple, fast and accurate method for the design of coupler for helix TWTs, using a simulation approach. It shows that a coupler can be analysed and optimized without modelling of a matching attenuator or user generated perfect matched boundary at the sever end. The proposed method not only considerably reduces the computational time but also provides exact results for the coupler performance.

Epoxides on treatment with DMSO, oxalyl chloride, and 10 mole % of methanol in the presence of triethylamine at −60° C are converted to α-chloro ketones in high yield.

In the presence of a catalytic amount of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetrahydropyranyl ethers are readily hydrolysed to their corresponding alcohols in wet acetonitrile under mild conditions.

An efficient asymmetric synthesis of 5-hexadecanolide from a chiral epoxide is described. Both the enantiomeric forms of the chiral epoxide are easily available from mannitol and ascorbic acid. The key step in the synthesis is the formation of δ-lactone from δ-hydroxy acetal using m-CPBA and BF 3 ·OEt 2 .

The level of stereocontrol obtained in the reduction of the free radical derived from the intramolecular addition of an acyl radical to an α-branched vinylogous carbonate is dependent upon the ring-size of the cyclic ether.

(+)-Boronolide, a polyacetoxy natural product having four contiguous asymmetric centers has been synthesized from d -mannitol.

An approach to modeling a resonant meanderline attenuator of helical slow-wave structure for a travelingwave tube is presented that uses eigen-mode solver in HFSS. The dispersion, interaction impedance and attenuation characteristics of the structure in the presence of the resonant attenuator were predicted using the model and were validated against experimental results, published elsewhere.

This paper describes the design of an electron gun and focusing system for a multi-beam klystron amplifier. The electron gun is designed for a beam voltage of 2.5 kV and a current of 700 mA, which is equally distributed among the 19 beamlets. An electrostatic and a magnetostatic focusing system have been investigated using 2.5D and 3D simulation codes.

In several human cancers, increased production of the tryptophan metabolite kynurenine by the enzymes indoleamine 2,3-dioxygenase (IDO1) and tryptophan 2,3-dioxygenase (TDO) creates a tolerogenic environment that promotes tumor driven immune suppression. One or both of these enzymes is up-regulated in a number of immune cells and in approximately 50% of human tumors (Pilotte et al., 2012). We have designed and synthesized novel inhibitors of IDO1 and dual inhibitors of IDO1 and TDO (PCT/US14/24920) that inhibit IDO1 in vitro and drop kynurenine production in established human cellular models of IDO1 (IFNγ treated HeLa cells) and/or TDO (A172 glioblastoma cells) and enhance T cell proliferation in a mixed culture assay. Further, these molecules cause a steep and durable reduction in plasma kynurenine in LPS treated c57/Bl6 mice, demonstrating inverse correlation between drug and kynurenine levels. In order to evaluate their therapeutic potential we monitored tumor penetration by the compounds and concomitant tumor kynurenine reduction in Balb/c mice implanted with the murine colon carcinoma CT-26 cell line. Several compounds drastically reduced tumor kynurenine levels compared to vehicle treated animals. One such compound, Compound 1, was further evaluated for its ability to reduce tumor burden both as monotherapy and in combination with doxorubicin. Currently we have nominated candidate compounds which are either IDO1 specific or IDO1/TDO dual inhibitors for regulatory toxicology. Citation Format: Monali Banerjee, Sandip Middya, Ritesh Shrivastava, Sushil Raina, Dharmendra Yadav, Satveer Singh, Anindita Manna, Debjani Chakraborty, Arjun Surya. Novel inhibitors of human IDO1 and TDO. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A59.

This paper describes a novel approach to model and analyze a helix to coaxial transition using three-dimensional electromagnetic computer code, the High Frequency Structure Simulator (HFSS) based on the Finite Element Method (FEM). For a K-Ka band helix TWT, RF Coaxial Coupler consisting of a helix to coaxial transition and a RF coaxial window is designed. The novelty of this simulation approach is that the RF matching to helix slow wave structure at the other end was provide by lossy resistive thin films being placed them on either side of three dielectric support rods. For a broadband K-Ka band helix TWT where the optimum VSWR expected for a transition is high, the used approach is promising of giving more realistic estimate of the performance of a transition compared to the method in which at both ends of helix a identical transition is modelled. The simulation approach for the coupler of an X-Ku band production tube compares well with measured results.

(+)-Boronolide, a polyacetoxy natural product having four contiguous asymmetric centers has been synthesized from d -mannitol.

The level of stereocontrol obtained in the reduction of the free radical derived from the intramolecular addition of an acyl radical to an α-branched vinylogous carbonate is dependent upon the ring-size of the cyclic ether.

Epoxides on treatment with DMSO, oxalyl chloride, and 10 mole % of methanol in the presence of triethylamine at −60° C are converted to α-chloro ketones in high yield.