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To cater to the heterogeneity in emerging applications, researchers have constantly been driven to invent novel dc–dc converter topologies. A review of prior art in dc–dc converter synthesis methods shows that many converter choices are available for a given input and output specification. This article quantifies the number of these choices using the flux balance equation (FBE). As the number of state variables that can be used to derive the FBE is limited, it is possible to find out the total number of possible FBEs available for a given voltage conversion ratio. Once the FBEs are known, synthesizing a converter is carried out as an inverse problem. Three different strategies to solve this inverse problem of converter synthesis and some critical synthesis results are summarized in this article. The dual synthesis of current-fed topologies with given current conversion ratios based on the charge balance equation (CBE) is also demonstrated. Four novel topologies were synthesized to illustrate the effectiveness of the CBE-based synthesis method. The mathematical formulation of the CBE-based inverse problem and the quantification of complexities in solving it are also reported.

Current-fed switched inverter (CFSI), a derivative of Z-source inverter, has the advantages of lower component count, single-stage conversion, high gain, and inherent shoot-through protection. But due to the limitation of modulation index, CFSI is forced to operate at higher dc-link voltage. As a result, voltage stress across the switches and capacitors increases. To mitigate this problem, a new pulsewidth modulation (PWM) technique is proposed. With the proposed scheme, CFSI can be operated at a lower dc-link voltage by increasing the modulation index. But operating at lower dc-link voltage increases peak-to-peak ripple in the inductor current and leads to condition of early discontinuous conduction mode. Therefore, this paper also implemented a variable duty cycle (VDC) scheme, which reduces the peak-to-peak ripple in the input inductor current and increases the continuous conduction mode (CCM) operating range of CFSI. The proposed PWM scheme along with VDC scheme is validated for CFSI, which helps to: 1) reduce the voltage stress form 280 to 180 V; 2) reduce the input current ripple from 53.33% to 15.15%; 3) enlarge CCM range from 56% to 82%; and 4) improve the efficiency by 3.5%.

This paper analyzes a coupled inductor based $LL$ – $LC$ network as a building block to achieve input or output current ripple cancellation in power converters. The proposed current ripple cancellation technique works on the principle of inductance matching. It also provides reduced current stress on the switching devices of the converter compared with the other current ripple cancellation networks discussed in the literature. The current ripple cancellation technique is verified in achieving input and output current ripple minimization in different converters. The effect of inductance mismatch, inductor and capacitor tolerances, and circuit parasitic is also studied. Some of the published research works are demonstrated to be a special case of the proposed idea. The effectiveness of the proposed method is validated by demonstrating the zero-ripple input current using a 31 V dc to 60 V dc, 240 W boost converter prototype and a 31 V dc to 115 V (rms) ac, 320 W current-fed-switched inverter prototype, and the zero-ripple output current using a 62 V to 42 V dc, 450 W buck converter prototype.

Vehicle collision on bridge piers is no more a rare possibility with crowded city roads, encroached spaces, and lack of recommended margins around piers. An attempt is made through this study to investigate the plasticity induced in a pier due to a colliding vehicle. Responses of several piers with varying geometries are studied by finite element analysis. The piers are subjected to collision loads, static as well as dynamic in nature. The study aims at identifying the areas of damage and roughly estimating the damage sustained by the pier under consideration. A range of results in the form of graphs have been presented. Subroutines capable of handling material nonlinear effects in the static as well as dynamic zones were developed using MATLAB. The programs were validated using ANSYS. Separate results are presented for static and dynamic analysis. The forces considered for static analysis are based on specifications of several countries, while the force-time histories adopted for transient elastoplastic response of the pier are adopted from simulated crash test results. An attempt is made to get a better insight into quantifying damage with plasticity as an indicator.

The copper salt of tenuazonic acid was studied by both positive and negative ion techniques. Fragmentation was elucidated with the aid of collision-induced dissociation/mass-analysed ion kinetic energy spectroscopy. During the course of the investigations, a homolog of tenuazonic acid was tentatively identified by using a combination of mass spectral techniques.

An esr spectrum was generated when a spin trap, t-nitroso butane (tNB), was added to potassium sorbate solution at pH of 6.4. This spectrum can be explained by the abstraction of allylic hydrogen by NO2, generated by the decomposition of tNB, followed by spin trapping of the radical product. With increasing concentration of NO2, which was accomplished by either the addition of sodium nitrite or by lowering the pH to cause rapid decomposition of tNB, a different esr spectrum was observed. This spectrum can be accounted for by a radical formed by addition of NO2to the 4,5 double bond of the sorbate and subsequent trapping by tNB.

Dihydrocitrinone, 3,4-dihydro-6,8-dihydroxy-3,4,5-trimethyiisocoumarin-7-carboxylic acid, was isolated and identified as a urinary metabolite after oral administration of citrinin to rats. Male and female Osborne-Mendel rats received 30 mg citrinin/kg body weight by oral intubation. The metabolite dihydrocitrinone was present in urine collected at 0-2, 2-4, 4-6, 6-8, and 8-24 h after treatment. Only unchanged citrinin was found in blood collected 24 h after administration of the compound. The metabolite had a blue fluorescence and the same Rf on thin-layer chromatography, the same retention time on reverse-phase high-pressure liquid chromatography, and the same mass spectrum as an authentic sample of dihydrocitrinone.

The radicals produced by reactions of hydroxyl radicals with amino acids in aqueous solutions have been investigated. Hydroxyl radicals were formed by U.V.-photolysis of hydrogen peroxide and the short-lived amino acid radicals were spin-trapped by tert-nitrosobutane and identified by electron spin resonance spectroscopy. Nineteen amino acids were studied, and several radicals were identified which have not been observed previously by other methods. Only side-chain radicals were identified for alanine, threonine, aspartic acid, asparagine, lysine, phenylalanine, tyrosine, proline and hydroxyproline; whereas for glycine the C(2) carbon radical was spin-trapped. Both C(2) carbon radicals and side-chain radicals were assigned to valine, leucine, isoleucine, serine, glutamic acid, glutamine, arginine and methionine.

The gamma-radiolysis of de-aerated neutral aqueous solutions of uracil, thymine, cytosine and of the corresponding nucleosides and nucleotides and of calf-thymus DNA was investigated. For uracil and thymine, the U.V. photolysis of aqueous solutions containing H2O2 was also studied. The short-lived radicals were spin-trapped by tert-nitrosobutane and identified by electron-spin-resonance spectroscopy. For all compounds two or more radicals were observed, and these could be distinguished by following the thermal decay of the spin adducts. Radicals formed by the addition of H or OH at the C(5) or C(6) positions of the pyrimidine derivatives were observed in all cases. Sodium formate was used as a scavenger for H and OH to identify the radicals formed by eaq-. Spin-trapped radicals in gamma-irradiated aqueous solutions of polynucleotides exhibited broad e.s.r. lines. For DNA gel, additional narrow lines due to scission products were also found.

The post-irradiation growth of the spin-adduct nitroxide radical produced by the addition of the thymine-OD radical to t-nitrosobutane (tNB) in γ-irradiated, de-aerated D2O solutions was investigated by e.s.r. The thymine-OD radical was formed by the addition of an OD radical to the C(5) position of thymine. Growth reached a greater maximum value and was more rapid with increasing dose. At a fixed dose, growth was also greater and more rapid if oxygen was present after γ-radiolysis. The addition of a second radical to the spin-adduct nitroxide during radiolysis to give a diamagnetic intermediate, which can regenerate the spin-adduct radical during storage in air-free and in air-saturated solutions at room temperature, was inferred to be responsible for post-irradiation growth. U.V. photolysis at 260-280 nm of a solution containing the diamagnetic intermediate rapidly regenerates the spin-adduct nitroxide. The longer lifetime of the diamagnetic intermediate in oxygen-free solutions may be relevant to an understanding of the anoxic sensitization by nitroxides in cellular systems.

The reactions of hydroxyl radicals with 30 dipeptides and several larger peptides were studied in aqueous solutions. The OH radicals were generated by U.V. photolysis of H2O2. The short-lived peptide radicals were spin-trapped using t-nitrosobutane and identified by e.s.r. For dipeptides containing the amino terminal residues glycine, alanine and phenylalanine, abstraction of the hydrogen from the carbon adjacent to the peptide nitrogen was the major process leading to the spin-adducts. Such radicals will be referred to as backbone radicals. Dipeptides with a carbonyl terminal serine residue and also glycylglutamic acid form both backbone and side-chain radicals, with the latter being formed in larger quantities. For dipeptides, side-chain radicals were detected on either the carboxyl or amino terminal residues or both. The effect of pD on the e.s.r. spectrum of the spin-adducts of glycylglycine was studied and the pK of the carboxyl group of this radical was determined to be 2·5. For (Ala)3 and (Ala)n, with an average value of n = 1800, backbone and minor side-chain radicals were observed. For ribonucleases-S-peptide, containing 20 amino acid residues, both backbone and side-chain radicals were detected.

The reactions of hydrated electrons (eaq-) with amino acids were investigated by the spin-trapping method and by electron spin resonance. Tertiary nitrosobutane was used as a spin-trap to stabilize the short-lived radicals. Hydrated electrons were produced by γ-radiolysis of de-aerated aqueous solutions of amino acids in the presence of sodium formate or tertiary butanol to scavenge OH. Radicals produced by reductive deamination of 19 amino acids were identified. Radicals formed by scission of the CH3-S- and -S-CH2- bonds of methionine as well as by deamination were observed. In the case of phenylalanine the radical formed by electron addition followed by proton transfer was identified. The reaction of proline and of hydroxyproline with eaq- resulted in the opening of the cyclic structure.

The "modified" steady-state analysis of the current-source inverter (CSI) drive given in this paper includes the effects of the following factors neglected in the ``conventional'' analysis given in present literature: 1) the variation of the ac back electromotive force (EMF) of the induction motor (load) during commutation, and 2) the phase shift of the fundamental component of the line current due to the finite commutation interval. It is shown that the effective leakage inductance of the motor during commutation is lower than the value obtained by the low-frequency blocked rotor test. A procedure for measuring the effective leakage inductance is given. At high stator frequencies the inverter operation is influenced by the conduction of series diodes outside their usual 120° period. A method of calculating the ``critical'' frequency where this effect begins to occur is given.

In clinical practice, broad ligament (BL) tumors are seldom encountered. Paraganglioma of the BL is exceedingly rare entity. Here we present an unusual case of broad ligament paraganglioma, presenting as a cystic mass, in a 50-year-old postmenopausal female. A high degree of suspicion along with detailed immunohistopathological work-up is needed for arriving at an accurate diagnosis.

Background. Xanthogranulomatous inflammation is an uncommon affection of the female genital tract. The youngest case reported of xanthogranulomatous salpingooophoritis in literature was by Shilpa et al. in 2013 in an eighteen-year-old female. Case Report. We report a case of 2-year-old female child with right-sided xanthogranulomatous salpingooophoritis presented as mass in abdomen. This is a case report of the youngest documented case of xanthogranulomatous salpingooophoritis in literature. As per abdominal examination, there was generalized distention of abdomen and a mass was palpable which was arising out of pelvis more on the right side. The ultrasonography (USG) abdomen and pelvis revealed a thick-walled mass measuring 9.2 cm × 6.0 cm × 7.6 cm in pelvis. We did right salpingooophorectomy of the patient. On histopathology, the diagnosis of xanthogranulomatous salpingooophoritis was confirmed. Conclusion. Clinical presentation, radiological appearance, and gross features of xanthogranulomatous lesions of ovary can mimic neoplastic lesions and lead to misdiagnosis. Though, it is very rare in pediatric age group, xanthogranulomatous salpingooophoritis as one of the differential diagnoses should be kept in mind while dealing with tuboovarian masses in this age group.

The paper discusses the operating principles and control characteristics of a dynamic voltage restorer (DVR). It is assumed that the source voltages contain interharmonic components in addition to fundamental components. The main aim of the DVR is to produce a set of clean balanced sinusoidal voltages across the load terminals irrespective of unbalance, distortion and voltage sag/swell in the supply voltage. An algorithm has been discussed for extracting fundamental phasor sequence components from the samples of three-phase voltages or current waveforms having integer harmonics and interharmonics. The DVR operation based on extracted components is demonstrated. The switching signal is generated using a deadbeat controller. It has been shown that the DVR is able to compensate these interharmonic components such that the load voltages are perfectly regulated. The DVR operation under deep voltage sag is also discussed. The proposed DVR operation is verified through the computer simulation studies using the MATLAB software package.

The paper discusses the operating principles and control characteristics of a dynamic voltage restorer (DVR). It is assumed that the source voltages contain interharmonic components in addition to fundamental components. The main aim of the DVR is to produce a set of clean balanced sinusoidal voltages across the load terminals irrespective of unbalance, distortion and voltage sag/swell in the supply voltage. An algorithm has been discussed for extracting fundamental phasor sequence components from the samples of three-phase voltages or current waveforms having integer harmonics and interharmonics. The DVR operation based on extracted components is demonstrated. The switching signal is generated using a deadbeat controller. It has been shown that the DVR is able to compensate these interharmonic components such that the load voltages are perfectly regulated. The DVR operation under deep voltage sag is also discussed. The proposed DVR operation is verified through the computer simulation studies using the MATLAB software package.

Presents remarks from several physicians on dealing with a fellow surgeon who had unprotected sex with several men and women. Risk posed by the surgeon to patients according to Doctor Angelika Schmiedel; Issues facing the surgeon according to Michael Wilks; Suggestion on discussing health concerns according to Henrietta Hughes.