Mixed Non-Uniform Width / Evanescent Mode Ceramic Resonator Waveguide Filter With Wide Spurious Free Bandwidth

This paper presents a method to improve the spurious performance of integrated ceramic waveguide filters. Nonuniform width ceramic waveguide resonator and evanescent mode ceramic resonators are employed together to the resonant frequencies of higher order modes. The proposed designs give 75% improvement in stop band response when compared to uniform width ceramic waveguide filter. Simulated results of two six pole chebyshev filters are presented here with improved stop band performance

Patient-Specific Pre-Treatment VMAT Plan Verification Using Gamma Passing Rates

Continuous gantry motion, continuous beam modulation, and variable dose rate are used in volumetric modulated arc therapy (VMAT) to obtain highly conformal radiation therapy dose distributions. Several errors during daily radiation therapy treatment can be sources of uncertainties in dose delivery. These errors include monitor unit calculation errors and other human mistakes. Due to the uncertainties in the excessively modulated VMAT plan, the intended dose distribution is not delivered perfectly, leading to a mismatch between the measured and planned dose distributions. This necessitates an extensive and effective quality assurance (QA) program for both machine and patient. In this study, VMAT QA plan verification of 62 head and neck (HN) and 19 prostate cases was done using Octavius 4D setup with its associating VeriSoft gamma analysis software. The plans showed a maximum 3D gamma passing rate with 4 mm/3 % gamma acceptance criteria, i.e., 99.7 % for the HN cancer cases and 99.5 % for the prostate cancer cases. Local gamma analysis was also performed for both regions. Furthermore, 2D and volumetric gamma analyses were also carried out. Gamma analysis with respect to different axis was also carried out. It was known that the transversal axis showed    the highest gamma passing rate in both HN and prostate cases, i.e., 99.17 % and 98.3 %, respectively. The transverse axis came to be a better fit for the planned dose distribution

Impedance Control Network Resonant dc-dc Converter for Wide-Range High-Efficiency Operation

This paper introduces a new resonant converter architecture that utilizes multiple inverters and a lossless impedance control network (ICN) to maintain zero voltage switching (ZVS) and near zero current switching (ZCS) across wide operating ranges. Hence, the ICN converter is able to operate at fixed frequency and maintain high efficiency across wide ranges in input and output voltages and output power. The ICN converter architecture enables increase in switching frequency (hence reducing size and mass) while achieving very high efficiency. Three prototype 200 W, 500 kHz ICN resonant converters, one with low-Q, one with medium-Q and one with high-Q resonant tanks, designed to operate over an input voltage range of 25 V to 40 V and an output voltage range of 250 V to 400 V are built and tested. The low-Q prototype ICN converter achieves a peak efficiency of 97.1%, maintains greater than 96.4% full power efficiency at 250 V output voltage across the nearly 2:1 input voltage range, and maintains full power efficiency above 95% across its full input and output voltage range. It also maintains efficiency above 94.6% over a 10:1 output power range across its full input and output voltage range owing to the use of burst-mode control.National Science Foundation (U.S.) (Award 1307699

Administration of an intravenous perfluorocarbon contrast agent improves echocardiographic determination of left ventricular volumes and ejection fraction: comparison with cine magnetic resonance imaging

AbstractObjectives. The purpose of this study was to determine whether contrast-enhanced transthoracic echocardiography improves the evaluation of left ventricular (LV) volumes and ejection fraction (EF).Background. Echocardiographic assessment of LV volumes and EF is widely used but may be inaccurate when the endocardium is not completely visualized. Recently the intravenous (IV) administration of perfluorocarbon microbubbles has been shown to enhance opacification of the LV cavity, but the utility of these agents to improve the echocardiographic assessment of LV systolic function is unknown.Methods. In 40 subjects (29 men and 11 women, aged 24 to 81 years) an assessment of LV volumes and EF was performed with a magnetic resonance imaging examination, followed immediately by a transthoracic echocardiogram before and after the intravenous administration of 2% dodecafluoropentane emulsion (EchoGen; Sonus Pharmaceuticals, Bothell, Washington).Results. Contrast enhanced the echocardiographic assessment of LV end diastolic volume (p < 0.02), end systolic volume (p < 0.01) and LVEF (p < 0.03). The percentage of subjects in whom the correct echocardiographic classification EF was normal, mild to moderately depressed or severely reduced improved significantly after contrast enhancement (from 71% before contrast to 94% after, p < 0.03). These findings were most striking in the subjects with two or more adjacent endocardial segments not visualized at baseline.Conclusions. Administration of an intravenous contrast agent improves the ability to accurately assess LV volumes and EF in humans. Contrast enhancement is most useful in subjects with two or more adjacent endocardial segments not seen at baseline

Prevalence of hepatitis B and C viral infections in Pakistan: Findings of a national survey appealing for effective prevention and control measures

A prevalence survey on hepatitis B and C infections was carried out to obtain national estimates and assess epidemiological dynamics and underlying risk factors. Overall prevalence of hepatitis B surface antigen (HBsAg) and anti-hepatitis C virus (HCV) of 2.5% and 4.8%, respectively, reflected a combined infection rate of 7.6% in the general population, consistent with an ongoing high burden of chronic liver disease (CLD). There was significant association of these viral infections with a range of risk factors led by reuse of syringes. These findings validate currently implemented strategies by the national programme for the control of hepatitis viral infections, including universal vaccination of newborns and high-risk groups, support of auto-disable syringes, promotion of infection control and patient safety, public health education, and management of needy CLD patients as a poverty-reduction health intervention

Design and evaluation of a reconfigurable stacked active bridge dc/dc converter for efficient wide load-range operation

This paper presents the design and implementation of a large-step-down soft-switched dc-dc converter based on the active bridge technique which overcomes some of the limitations of the conventional Dual Active Bridge (DAB) converter. The topology comprises a double stacked-bridge inverter coupled to a reconfigurable rectifier through a special three-winding leakage transformer. This particular combination of stages enable the converter to run in an additional low-power mode that greatly increases light-load efficiency by reducing core loss and extending the zero-voltage switching (ZVS) range. The converter is implemented with a single compact magnetic component, providing power combining, voltage transformation, isolation, and energy transfer inductance. A 175 kHz, 300 W, 380 V to 12 V GaN-based prototype converter achieves 95.9% efficiency at full load, a peak efficiency of 97.0%, an efficiency above 92.7% down to 10% load and an efficiency above 79.8% down to 3.3% load.National Science Foundation (U.S.) (Award Number 1307699)MIT Skoltech Initiativ

Comparative Study of the Dynamics of Cosmic Rays for the Pakistan and China Atmospheric Regions

This paper presents an analysis of cosmic ray intensity in Pakistan air space using spatial interpolation, comparing it with Chinese cosmic ray records from 1984 to 1993. The Exploratory Data Analytic (EDA) approach was applied to compare the cosmic ray fluctuations in both countries. The time series plot of the monthly cosmic rays showed relatively flatter counts in Pakistan than in China. The cosmic ray data for the years 1984 to 1993 fell within Solar Cycle 22, which lasted from 1986 to 1996, with its maximum phase in 1989 to 1991. The cosmic radiation varies between the atmospheric regions of Pakistan and China due to modulations in intensity that are accessible accordingly. It can be explained by purely astrophysical phenomena: (1) the source of emission of cosmic radiation may be different, (2) the rate at which emanation takes place depends on bursts of deep space dynamical objects from their sources that may be affected by solar wind and other solar radiations. Therefore, modulations in intensity are not only due to different geophysical locations. This study will help government organizations to predict and forecast cosmic rays values

Impedance Control Network Resonant Step-Down DC-DC Converter Architecture

In this paper, we introduce a step-down resonant dc-dc converter architecture based on the newly-proposed concept of an Impedance Control Network (ICN). The ICN architecture is designed to provide zero-voltage and near-zero-current switching of the power devices, and the proposed approach further uses inverter stacking techniques to reduce the voltages of individual devices. The proposed architecture is suitable for large-step-down, wide-input-range applications such as dc-dc converters for dc distribution in data centers. We demonstrate a first-generation prototype ICN resonant dc-dc converter that can deliver 330 W from a wide input voltage range of 260 V – 410 V to an output voltage of 12 V.MIT Skoltech InitiativeMIT Energy InitiativeNational Science Foundation (U.S.) (Award 1307699)Texas Instruments Incorporated (Graduate Women's Fellowship for Leadership in Microelectronics

‘That’s My Stuff’: Pasifika Literature and Pasifika Identity

Pasifika literature is an expanding, dynamic field which, like other Pasifika creative productions, is often seen as representative of exciting new directions, and reflective of a nascent generation of young Pasifika who are firmly established in New Zealand. This thesis considers the relationship between Pasifika literature and Pasifika identity, tracing some ways that Pasifika literature articulates, references, and mediates Pasifika identity through the creative work of two prominent New Zealand-born Pacific scholar-poets: Karlo Mila (Tongan, Palangi, Samoan) and Selina Tusitala Marsh (Samoan, Tuvaluan, French, English). Both these women are highly acclaimed, award winning poets and academics who are well respected in their respective Pacific communities. Reading their creative works firstly as examples of a mixed-race Pasifika literature and then as Pasifika feminist texts offers compelling insights into their worlds as young ‘brown’ women in New Zealand. Their work makes a significant contribution to Pacific literature and New Zealand literature, and offers many points of entry for exploring what it might mean to be a Pasifika person in Aotearoa today. This work is furthered in a final chapter, which gestures towards a new generation of Pasifika writers. By referencing some of the new writing being produced by young Pasifika, in particular the work of Grace Taylor and Courtney Sina Meredith, I illustrate how Mila and Marsh’s writing has opened up necessary creative spaces for Pasifika voices to be heard and their senses of identity to be affirmed. Ultimately, the connections between Pasifika literature and Pasifika identities that have been explored in this thesis continue to be strengthened and developed by a new generation of young Pasifika writers, who continue to affirm identities that are fluid, open, and progressive