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Background: Sellar and juxta-sellar lesions represent a surgical challenge due their deep and complex relationships to surrounding important neurovascular structures. The basal interhemispheric (BIH) approach, as a midline approach, has an advantage over the lateral approaches as it allows for the safe removal of these challenging tumors. Aim: To describe the technique of BIH approach in a prospective cohort of 17 patients with sellar and juxta-sellar lesions with different pathologies presented to Alexandria Main University and affiliated hospitals. As well as the clinical outcome and complications of this technique, these cases were followed up for a mean period of 20 weeks. Results: Gross total resection was achieved in 9 cases (52.9%), subtotal resection was achieved in 5 cases (29.5%), while partial resection was carried out in 3 cases (17.6%). Visual status improved following surgery in 10 patients (58.8%), remained stationary in 5 patients (29.4%) and worsened in 2 cases. Post-operative shunt was needed in three cases, and severe water and electrolyte disturbance was recorded in 3 cases and pan-hypopituitarism in a single case. A single mortality was recorded, but it was due to pulmonary embolism and was not related to the approach. Conclusion: BIH could be a panoramic safe approach that allows tumor removal from multiple corridors with identification of the regional anatomy of the tumor thus elaborating the surgical strategy for gross total tumor removal. [ABSTRACT FROM AUTHOR]

The classic cascaded boost–buck converter has inductors at the input and output ports of the converters, which makes it an ideal interface for bidirectional battery charging applications, where accurate current control and low ripple currents are required. This article proposes a split duty cycle coupled multiphase variant applied to the cascaded boost–buck converter and utilizes coupled inductor features to achieve very lower current ripples at the output, lower power losses, and reduction in magnetic component volume. Moreover, current sharing between each phase is inherently implemented, making it suitable for a high-conversion-ratio bidirectional operation in systematic energy storage applications, where the low-voltage port has very high current. This article covers a split duty cycle converter operation principle using coupled inductors between the input and the multiphase output. Magnetic component design and selection guidelines are presented. The proposed control method and the coupled inductor structure are validated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The high peak current withstand capability of thyristors makes them extremely suitable for pulsed power applications. Silicon carbide (SiC) thyristors provide significant efficiency advantages compared with their silicon counterparts due to their very fast switching transitions. This article presents the development and characteristics of 3 kV SiC thyristors. A novel current-source gate driver is proposed to enhance their switching speed and, hence, maximize their benefits in pulsed power applications. The proposed driver provides a very high gate current slew rate while limiting the peak of the current pulse. The higher gate current slew rate achieves faster and, thus, more efficient device switching transition. Gate driver circuit description, variant topologies, and experimental results for a 3 kV SiC thyristor for a pulsed power application are presented to verify the proposed concepts. [ABSTRACT FROM AUTHOR]

Microinverter-based photovoltaic (PV) systems now represent about 8% of the U.S. residential market, and offer many advantages including safety, performance, and simplified installation. The next-generation of PV microinverter will include more ancillary functions to support grid stability and reliability in more distributed generation smart-grid systems. A commercial ready PV microinverter not only focuses on efficiency and cost, but also on reliability, manufacturability, compliance of various grid-code, and electromagnetic interference regulations. This paper presents a detailed design and development process of a microinverter system from concept all the way to final commercial-ready prototype. Various design tradeoffs such as topology, control, filter solutions and power supplies, and mechanical packaging are provided. The required prototype testing and final system field tests are also presented. The presented design and test process intends to accelerate the future microinverter system design and development toward a commercial ready product. [ABSTRACT FROM PUBLISHER]

In this paper, a dc/dc power converter for distributed photovoltaic (PV) plant architectures is presented. The proposed converter has the advantages of simplicity, high efficiency, and low cost. High efficiency is achieved by having a portion of the input PV power directly fed forward to the output without being processed by the converter. The operation of this converter allows for a simplified maximum power point tracker design using fewer measurements. The stability analysis of the distributed PV system comprised of the proposed dc/dc converters confirms the stable operation even with a large number of deployed converters. The experimental results show a composite weighted efficiency of 98.22% with very high maximum power point tracking efficiency. [ABSTRACT FROM AUTHOR]

High-voltage and high-current SiC bipolar diode modules are fabricated and characterized under static and dynamic conditions. The modules are built using 6 \times 6\ \mm^2 SiC chips that are fabricated on 3-in SiC substrates. Individual chips were also packaged in an ISOPLUS™ package and used to perform switching tests on the diodes. The modules have been fully characterized under static and dynamic conditions. These modules are targeted for high-voltage high-frequency applications as well as antiparallel diodes for 6.5-kV insulated gate bipolar transistors, insulated gate commutated thyristors, and injection enhanced insulated gate bipolar transistors. [ABSTRACT FROM AUTHOR]

The use of single-stage power-factor-corrected (SSPFC) three-level resonant ac/dc converters solves many problems that present SSPFC converters face today, namely, high component stresses, high circulating currents, and low efficiency. This makes single-stage three-level resonant ac/dc converters a good candidate for high-power applications. These converters provide the flexibility of simultaneously using two control variables. They can operate with a combined variable-frequency and asymmetrical pulsewidth modulation or with a combined variable-frequency phase-shift modulation. This provides good regulation of the output voltage, dc-bus voltage, and input current. The drawback of these methods is that the efficiency of the converter drops as the load is reduced because the converter starts to drift away from its resonance frequency, thus leading to more circulating currents and conduction losses. Therefore, a load-adaptive energy storage technique is proposed in this paper to guarantee the converter operation near its maximum efficiency point for a wide range of loading. This leads to almost constant converter efficiency from full load to 40% load. The use of interleaved converters is also proposed to extend the constant efficiency range of operation to lighter loads (15%–20% of full load). Analytical simulation and experimental results are presented to verify the proposed methods. [ABSTRACT FROM AUTHOR]

This paper presents a new single-stage power factor correction ac/dc converter based on a three-level half-bridge resonant converter topology. The proposed circuit integrates the operation of the boost power factor preregulator and the three-level resonant dc/dc converter. A variable-frequency asymmetrical pulsewidth modulation controller is proposed for this converter. This control technique is based on two integrated control loops: the output voltage is regulated by controlling the switching frequency of the resonant converter, whereas the dc-bus voltage and input current are regulated by means of duty cycle control of the boost part of the converter. This provides a regulated output voltage and a nearly constant dc-bus voltage regardless of the loading condition; this, in turn, allows using smaller switches and consequently having a lower on resistance helping to reduce conduction losses. Zero-voltage switching is also achieved for a wide range of loading and input voltage. The resulting circuit, therefore, has high conversion efficiency making it suitable for high-power wide-input-voltage-range applications. The effectiveness of this method is verified on a 2.3-kW 48-V converter with input voltage (90-265 Vrms). [ABSTRACT FROM AUTHOR]

This article presents a new three-level full bridge resonant single stage AC/DC converter. The converter is operated with a variable frequency pulse width modulation controller (PWM). A PWM is used to provide the required input current shaping as well as regulating the DC-bus voltage, whereas variable frequency control is used to tightly regulate the output voltage. Zero voltage switching (ZVS) is achieved for all switches. The proposed topology can operate with either continuous or discontinuous input current while maintaining high power factor. Owing to ZVS operation, reduced component stresses and low circulating currents the proposed converter has high conversion efficiency making it suitable for higher power operations compared to existing single stage AC/DC topologies as well as operating with universal input voltage. Operation, analysis and performance of the converter will be presented in this article. [ABSTRACT FROM AUTHOR]

In this paper, the performance of different three-level resonant converters is studied for single-stage power factor correction operation. These converters are suitable for power ranges higher than that in the currently available single-stage converters, due to their high efficiency and reduced component stresses. All the converters presented here are characterized by their ability to regulate the output voltage as well as the dc bus voltage. This leads to lower voltage stresses, wider input voltage range, higher output power applications, and improved efficiencies compared to existing single-stage topologies. Due to the availability of more degrees of freedom in the presented converters, two types of control strategies can be used for this purpose: variable frequency asymmetrical pulsewidth modulation control and variable frequency phase-shift modulation control. Three resonant converters will be studied in this paper and their performances as well as the applicability of the aforementioned control methods for each converter are compared. A 2.3-kW, 48-V converter with input voltage range of 90265 Vrms is used to study the performance of each case. [ABSTRACT FROM AUTHOR]

This paper presents a new single-stage three-level resonant power factor correction ac-dc converter suitable for high power applications (in the order of multiple kilowatts) with a universal input voltage range (90-265 Vrms). The proposed topology integrates the boost input power factor preregulator with a half-bridge three-level resonant dc-dc converter. The converter operation is controlled by means of a combination of phase-shift and variable frequency control. The phase-shift between the switch gate pulses is used to provide the required input current shaping and to regulate the dc-bus voltage to a set reference value for all loading conditions, whereas, variable frequency control is used to tightly regulate the output voltage. An auxiliary circuit is used in order to balance the voltage across the two dc-bus capacitors. Zero voltage switching (ZVS) is also achieved for a wide range of loading and input voltage by having a lagging resonant current in addition to the flowing of the boost inductor current through the body diodes of the upper pair of switches in the free wheeling mode. The resulting circuit, therefore, has high conversion efficiency and lower component stresses making it suitable for high power, wide input voltage range applications. The effectiveness of the proposed converter is verified by analysis, simulation, and experimental results. [ABSTRACT FROM AUTHOR]

Purpose: To incorporate ciprofloxacin (CIP) into solid lipid nanoparticles (SLN) in order to enhance its biopharmaceutical properties and antibacterial activity. Methods: A sonication melt-emulsification method was employed for the preparation of CIP-loaded SLN. The composition of the SLN was varied in order to investigate factors such as lipid type and combination ratio, drug to lipid ratio, and surfactant ratio. The produced SLN formulations were evaluated for their particle size and shape, zeta potential, and entrapment efficiency. In addition, the effect of SLN formulation composition on its drug release profile and antimicrobial activity against Escherichia coli, Pseudomonas Aeruginosa, and Staphylococcus Aureus was also investigated. Results: The generated nanoparticles had particle size in the range of 165 to 320 nm. The zetapotential values were generally low within ± 5. All formulations exhibited entrapment efficiency between 50 and 90 %. CIP release exhibited a biphasic release profile with a low burst phase, followed by uniform controlled-release behavior of various rates. SLN-loaded CIP exhibited one-fold reduction in minimum inhibitory concentration (MIC) and caused significant inhibition of all the three bacterial strains tested, when compared with pure CIP. Conclusion: Loading of CIP into SLN significantly enhances its antimicrobial activity in vitro which can translate to significant enhancement of therapeutic outcomes by minimizing the dose-dependent adverse and side effects and/or enhancing the antimicrobial spectrum of activity. [ABSTRACT FROM AUTHOR]

This article presents novel transformerless single-stage buck-boost inverters with reactive power flow capability. The common-mode voltage of the proposed inverters is constant, which results in negligible leakage current. The output current of the proposed inverters is continuous that lowers the output harmonics and size of the output filtering capacitor. In the proposed inverters, only two switches receive high-frequency switching signals at a time, which reduces the power loss. The proposed topologies can achieve efficient power conversion with a wide input voltage range. A 120-Vrms/60-Hz output voltage, 74–200-V input voltage, and 500-W output power hardware prototype of the proposed inverter is built and tested with resistive, partially inductive, and partially capacitive loads. A peak efficiency of 97.3% is obtained. [ABSTRACT FROM AUTHOR]

This paper presents novel single-phase single-stage buck–boost inverters. The proposed inverters provide buck–boost operation for a wide variation of the input dc voltage. In addition, the proposed inverters are bidirectional and provide reactive power. Further, they require only one inductor. The proposed inverters also eliminate the common-mode leakage current by connecting the output neutral to the midpoint of input capacitors or directly to input voltage sources. Therefore, they are well suitable for photovoltaic applications. Although six switches are required, two switches are working at line frequency, resulting in negligible switching loss. Of the four remaining switches, only two are switching at high frequency at a time. The circuit operations are demonstrated through the analysis of the proposed inverters. A 120 Vrms/60 Hz/400 W hardware prototype was constructed and tested. The experimental results verified the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a novel control strategy to significantly reduce the high-frequency transformer loss in a modular solid-state transformer (SST) based converter system. The modular SST design is based on an ac–dc power-electronic building block comprised of an H-bridge at the ac input and a bidirectional soft-switching isolated dc–dc converter with a medium-voltage insulated high-frequency transformer. The ac terminals of input H-bridges are connected in series and directly coupled to the medium-voltage ac line, while the output dc terminals are all connected in parallel at a low voltage. The key innovation described in this paper, without sacrificing the output performance, is the control scheme that reduces core and winding losses associated with the dc–dc resonant stage by turning off the selected dc–dc converters in synchronism with the line voltage. The prototype for the test described in this paper is based on a modular SST where each module is rated at 50 kVA, with a 200 kHz transformer using 1.7 kV silicon carbide discrete mosfets, but the described control concepts are more broadly applicable to similar topologies. [ABSTRACT FROM AUTHOR]