Simplified Arrangements Research Articles

MRI-LINAC dosimetry approach by Monte Carlo codes coupling charged particle radiation transport with strong magnetic fields

This study investigates the dosimetric effects due to the strong magnetic fields in the MRI guided radiotherapy. FLUKA and PENELOPE Monte Carlo codes were used to study the deflection of the electron trajectories, while evaluating dosimetric effects, considering both simplified arrangements and complex realistic clinical applications setups. Simulation codes proved to be suitable, and comparisons with analytic approaches were satisfactory, thus remarking non-negligible dosimetry effects as a consequence of the presence of strong magnetic fields.

Spectral Analysis of Stationary Signals Based on Two Simplified Arrangements of Chirp Transform Spectrometer

The classical two-channel push-pull chirp transform spectrometer (CTS) has been widely applied in satellite-borne remote sensing systems for earth observation and deep space exploration. In this paper, we present two simplified structures with single M(l)-C(s) CTS arrangements for the spectral analysis of stationary signals. A simplified CTS system with a single M(l)-C(s) arrangement and a time delay line was firstly developed. Another simplified structure of CTS with a M(l)-C(s) arrangement and a frequency conversion channel was also developed for spectral analysis of stationary signals. Simulation and experiment results demonstrate that the two simplified arrangements can both realize spectrum measurement for the stationary signals and obtain the same frequency resolution, amplitude accuracy and system sensitivity as that of the classical two-channel push–pull CTS system. Compared to the classical CTS structure, the two simplified arrangements require fewer devices, save power consumption and have reduced mass. The matching problem between the two channels can be avoided in the two simplified arrangements. The simplified CTS arrangements may have potential application in the spectrum measurement of stationary signals in the field of aviation and spaceflight.

Dosimetric verification of dental stent efficacy in head and neck radiation therapy using modern radiation therapy techniques: quality of life and treatment compliance implications

During radiotherapy to the head and neck, metallic dental restorations produce secondary electrons that increase dose to nearby tissue causing painful ulcers that contribute to morbidity during treatment and lead to breaks in therapy. Various protective measures have been tested with simplified phantoms and beam arrangements. Our objective was to quantitatively assess electron scatter using an anatomical phantom and modern beam configurations. A tissue-equivalent phantom was created to simulate the oral cavity with gold crowns on opposing molars. Four-millimeter ethylene copolymer dosimetric dental stents were produced. The phantom was placed in a water bath to simulate soft tissue. Radiation was delivered in opposed lateral, nine-field intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) configurations. A GafChromic EBT3 film was used to simulate the mucosal surfaces of the tongue and the buccal mucosa. The film readings were then converted to isodose plots using DoseLab. With opposed beams, a 32 % reduction in maximum dose was measured in the occlusal plane with the use of stents. In the nine-field IMRT and VMAT plans, maximum dose to the adjacent film was reduced by approximately 40 % with the use of the dental stent. This approximately 40 % dose reduction implies that patients’ oral mucosae adjacent to dental fixtures could receive more than 100 Gy during a course of definitive radiotherapy to the head and neck without dental stents. In this era of increasing IMRT/VMAT utilization, our results emphasize the value of stent use to improve morbidity and reduce treatment breaks for patients undergoing head and neck radiotherapy.

A modelling investigation of solute transport in permeable porous media containing a discrete preferential flow feature

Preferential flow features (PFFs, e.g. fractures and faults) are common features in rocks that otherwise have significant matrix permeability. Despite this, few studies have explored the influence of a PFF on the distribution of solute plumes in permeable rock formations, and the current understanding of PFF effects on solute plumes is based almost entirely on low-permeability rock matrices. This research uses numerical modelling to examine solute plumes that pass through a PFF in permeable rock, to explore the PFF's influence on plume migration. The study adopts intentionally simplified arrangements involving steady-state solute plumes in idealised, moderate-to-high-permeability rock aquifers containing a single PFF. A range of matrix-PFF permeability ratios (4.9×10−6–2.5×10−2), typical of fractured sedimentary aquifers, is considered. The results indicate that for conditions representative of high-to-moderate-permeability sedimentary rock matrices containing a medium-sized fracture, the effect of the PFF on solute plume displacement and spreading can be considerable. For example, plumes are between 1.3 and 19 times wider than in associated porous media only scenarios, and medium-sized PFFs in moderately permeable matrices can reduce the maximum solute concentration by up to 104 times. Plume displacement and spreading is lower in aquifers of higher matrix-PFF permeability ratios, and where solute plumes are more dispersed at the point of intersection with the PFF. Asymmetry in the plume caused by the passage through the PFF is more pronounced for more dispersive plumes. The current study demonstrates that PFFs most likely govern solute plume characteristics in typical permeable matrices, given that a single PFF of aperture representing a medium-sized fracture (i.e. 5.0×10−4m) produces the equivalent spreading effects of 0.22–7.88m of plume movement through the permeable matrix.

A study on the accuracy of surface charge measurement

The measurement of accumulated surface charge for thick specimens requires multipoint probe outputs to establish the inverse calculation for the determination of an unknown charge distribution. Until now, studies on the various errors associated with the measurement have been conducted only for simplified arrangements mainly in axisymmetric geometry where the charged surface is parallel to the ground. We have numerically analyzed a model measurement set-up more comparable to practical conditions by a highly efficient surface charge method. We have studied the effect of probe position, the induction from charge existing not directly beneath the (probe) sensor and the difference in matrix components computed by two numerical methods. In particular, we have studied the accuracy of the reconstructed charge distributions by numerical simulations of the inverse calculation. It has been shown that the assumed measurement errors make much larger differences in the reconstructed charge distributions, although the influence depends considerably on the assumed charge distribution. Reducing the condition number of the matrix improves the accuracy of the inverse calculation for uniform and linearly changing charge distributions.

SOURCES REQUIRED TO MAKE A CRITICAL EDITION OF AN AMERICAN MUSICAL: A REPORT OF WORK UNDERWAY BY AMERICAN SCHOLARS AND THE EDITORIAL BOARD OF A NEW KURT WEILL EDITION

To date, no one has published the full score of an American Broadway musical and offered it for sale.1 Traditionally, publishers have printed only popular, simplified arrangements of songs in sheet music format and/or a piano-vocal score which might, or might not, have been approved by the composer before publication. A handful of American scholars are now committed to preserving the most important of these works in schol arly editions, for collectively they represent one of America's unique and ubiquitous contributions to 20th-century music. For the most part, my comments pertain to those musical theater works created for the com mercial, Broadway theater between 1935 and 1970, but certain aspects will be relevant to works dating backward to those of Victor Herbert and forward to the present day. Because time is limited, I will exclude from the discussion all issues not directly related to source studies and editor ial decisions, such as copyright obstacles, questions relating to selection criteria, and the justifications for undertaking such editions in the first place. Two efforts to grapple with the editorial problems inherent in this venture are now in the formative stages. The American Musicological Society is considering including a number of ?Broadway musicals? in its projected ?Music in the United States? (MUSA) series. The steering committee for the series has thus far made only an informal analysis of

An Experimental Assessment of the Influence of Downstream Conditions on the Performance of a Transonic Turbine Nozzle of High Turning

The present work was conducted to extend information derived in a previous study where it was found that the performance of a transonic turbine nozzle of high turning angle was significantly affected by the design and operation of the downstream rotor and the detailed characteristics of the nozzle flow field. Measurements obtained in an operating stage environment were compared with information from simplified test arrangements. In particular, it was possible to make direct comparisons of static pressure distributions at the vane root as affected by downstream conditions. Detailed exit flow surveys indicated areas susceptible to the influence of rotor presence. Probe interaction effects also were assessed in a special series of tests conducted over a representative range of Mach numbers. Finally, experiments were performed with a perforated plate simulating rotor presence, in an attempt to determine the limitations of such simplified test arrangements in the generation of pertinent data. The results shed further light on a complex subject, and have been aimed at practical validation of test arrangements and techniques.

Rearrangement of integrated viral DNA sequences in mouse cells transformed by simian virus 40.

The organization of viral DNA sequences in several cell lines derived from a primary colony of simian virus 40 (SV40)-transformed mouse cells was analyzed to examine the origin of the various distinctive patterns of SV40 sequence arrangement present in transformed cells. This analysis revealed a complex arrangement of viral sequences in the uncloned transformed cells but simplified arrangements in cloned derivatives of the primary transformant. The cell lines studied had certain SV40 sequence arrangements in common, but the cloned lines had lost some parental arrangements and acquired new arrangements. These results indicate that the arrangement of viral sequences in some SV40-transformed cells is not fixed but that alterations occur after integration, creating a heterogeneous population of transformants. In the process, expression of viral genes may be altered. Possible causes for and implications of this genetic instability are discussed.

A Penetrating Gaze at One Open Phase: Analyzing the Polyphase Induction Motor Dilemma

Portions of the material proposed for a chapter in a new IEEE Standard (#399-the ``Brown Book'') being prepared by the Power System Analysis Subcommittee of the I & CPS Committee are presented. In order to establish a library of approved analytical methods, the material provides a review of the more important basic electrical circuit analysis techniques used for determining the voltage and current relationships which describe various power system network events and operating conditions. Certain simplified circuit arrangements are examined. They illustrate the power and merit of the analytical methods that evolve, as well as the errors that can occur because of improper regard for the restraints that apply. Using the analytical methods, the classical problem of a three-phase induction motor operating with one phase of the supply line open-circuited is studied in considerable detail. Finally, important observations and conclusions are presented regarding the motor protection requirements.

Fan Performance Testing Using Inlet Measuring Methods

To contend with installation variants the fan must be tested in a system that resembles its site installation. Four simplified system arrangements are covered with two inlet test methods—ducted inlet and free inlet—by adding ducts to the free discharge. With free inlet tests a plenum chamber is attached to the fan inlet in order to obtain the required measurements; investigations to provide information concerning the optimum configuration of this test method are described. Determination of static pressure, selection of inlet devices for flow measurement; simulation of inlet and outlet ducts and the method of loading are also discussed.

Fan Performance Testing Using Inlet Measuring Methods

To contend with installation variants the fan must be tested in a system that resembles its site installation. Four simplified system arrangements are covered with two inlet test methods—ducted inlet and free inlet—by adding ducts to the free discharge. With free inlet tests a plenum chamber is attached to the fan inlet in order to obtain the required measurements; investigations to provide information concerning the optimum configuration of this test method are described. Determination of static pressure, selection of inlet devices for flow measurement; simulation of inlet and outlet ducts and the method of loading are also discussed.