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1

Maximum Tolerated Dose Studies  

Microsoft Academic Search

A three-stage maximum repeatable dose (MRD) protocol is described in which the MRD is established by dose incrementation, followed by administration of this dose for at least seven days, with the final stage being single dose administration of the doses anticipated for the one-month studies. The toxicokinetic measurements which are made in support of this protocol are illustrated with data

P. F. Carey; N. W. Spurling

1994-01-01

2

Maximum Power Point  

NSDL National Science Digital Library

Students learn how to find the maximum power point (MPP) of a photovoltaic (PV) panel in order to optimize its efficiency at creating solar power. They also learn about real-world applications and technologies that use this technique, as well as Ohm's law and the power equation, which govern a PV panel's ability to produce power.

Integrated Teaching And Learning Program

3

An appreciation of the maximum tolerated dose: an inadequately precise decision point in designing a carcinogenesis bioassay  

Microsoft Academic Search

Cancers arise in specific tissues. One difficulty with the present definitions of the Maximum Tolerated Dose (MTD), as they pertain to the rodent cancer bioassay, is that they base MTD on relatively crude parameters associated with the well-being of the entire animal rather than with the lack of specific tissue toxicity. Additional factors that could be included in the MTD

David B. Clayson; Frank Iverson; Rudolf Mueller

1991-01-01

4

Pointing at Maximum Power for PV  

NSDL National Science Digital Library

Student teams measure voltage and current in order to determine the power output of a photovoltaic (PV) panel. They vary the resistance in a simple circuit connected to the panel to demonstrate the effects on voltage, current, and power output. After collecting data, they calculate power for each resistance setting, creating a graph of current vs. voltage, and indentifying the maximum power point.

Integrated Teaching And Learning Program

5

Integrated photovoltaic maximum power point tracking converter  

Microsoft Academic Search

A low-power low-cost highly efficient maximum power point tracker (MPPT) to be integrated into a photovoltaic (PV) panel is proposed. This can result in a 25% energy enhancement compared to a standard photovoltaic panel, while performing functions like battery voltage regulation and matching of the PV array with the load. Instead of using an externally connected MPPT, it is proposed

Johan H. R. Enslin; Mario S. Wolf; D. B. Snyman; Wernher Swiegers

1997-01-01

6

A global maximum power point tracking DC-DC converter  

E-print Network

This thesis describes the design, and validation of a maximum power point tracking DC-DC converter capable of following the true global maximum power point in the presence of other local maximum. It does this without the ...

Duncan, Joseph, 1981-

2005-01-01

7

Pulmonary carcinogenicity of inhaled particles and the maximum tolerated dose.  

PubMed Central

Chronic inhalation bioassays in rodents are used to assess pulmonary carcinogenicity for purposes of hazard identification and potentially for risk characterization. The influence of high experimental doses on tumor development has been recognized for some time and has led to the concept of maximum tolerated dose (MTD) for dose selection, with the highest dose being at the MTD. Exposure at the MTD should ensure that the animals are sufficiently challenged while at the same time the animal's normal longevity is not altered from effects other than carcinogenicity. A characteristic of exposure-dose-response relationships for chronically inhaled particles is that lung tumors are significantly increased only at high exposure levels, and that lung tumors are seen in rats only but not in mice or hamsters. This lung tumor response in rats is thought to be secondary to persistent alveolar inflammation, indicating that the MTD may have been exceeded. Thus, mechanisms of toxicity and carcinogenicity may be dose dependent and may not operate at lower doses that humans normally experience. Despite awareness of this problem, carcinogenicity bioassays that evaluate particulate compounds in rodents have not always been designed with the MTD concept in mind. This is due to several problems associated with determining an appropriate MTD for particle inhalation studies. One requirement for the MTD is that some toxicity should be observed. However, it is difficult to define what degree of toxic response is indicative of the MTD. For particle inhalation studies, various noncancer end points in addition to mortality and body weight gain have been considered as indicators of the MTD, i.e., pulmonary inflammation, increased epithelial cell proliferation, increased lung weight, impairment of particle clearance function, and significant histopathological findings at the end of a subchronic study. However, there is no general agreement about quantification of these end points to define the MTD. To determine whether pulmonary responses are indicative of the MTD, we suggest defining an MTD based on results of a multidose subchronic and chronic inhalation study with a known human particulate carcinogen, e.g., asbestos or crystalline silica. Quantification of effects in such a study using the noncancer end points listed above would identify a dose level without significant signs of toxicity at the end of the subchronic study. If this dose level still results in significant lung tumor incidence at the end of the chronic study. We will have a sound basis for characterizing the MTD and justifying its use in future particle inhalation studies. Also, a better understanding of cellular and molecular mechanisms of particle-induced lung tumors is needed to support the MTD concept. PMID:9400749

Oberdörster, G

1997-01-01

8

Maximum tolerated dose: clinical endpoint for a bygone era?  

Microsoft Academic Search

The maximum tolerated dose (MTD) has been the classically recommended phase II dose for cytotoxic chemotherapy anticancer\\u000a agents. However, the development of molecular targeted therapies with highly specific mechanisms of action has raised questions\\u000a about the paradigm of dosing at the MTD. Inhibition of the molecular target may occur at dose levels substantially below those\\u000a producing dose limiting toxicities. The

Chris H. Takimoto

2009-01-01

9

MODIFIED ALSEP Maximum Antenna Pointing Error  

E-print Network

and high rates of 91 600 and 101 600 bps. The MSFN ground stations are considered to have either cooled angle and possible surface moon slopes could then cause a small amount of multipath signal cancellationĀ°, the third side lobe will reflect from the moon's surface also with a 35Ā° angle. The maximum loss from

Rathbun, Julie A.

10

A bayesian nonparametric approach to determining a maximum tolerated dose  

Microsoft Academic Search

This paper presents a Bayesian nonparametric approach to determining a maximum tolerated dose. Typically, this would be carried out in a phase 1 trial. We describe a design and analysis which makes use of the Polya tree prior distributions.

Pietro Muliere; Stephen Walker

1997-01-01

11

Preliminary estimates of the virtually safe dose for tumors obtained from the maximum tolerated dose  

Microsoft Academic Search

The purpose of this paper was to examine the correlation between the maximum tolerated dose (MTD) and the low-dose estimate of the virtually safe dose (VSD) for animal carcinogens. Chronic bioassay results from the National Cancer Institute\\/National Toxicology Program carcinogenesis screening program were used. Estimates of the VSD were obtained by linear low-dose extrapolation for which an adequate dose-response relationship

D GAYLOR

1989-01-01

12

Dynamic maximum power point tracker for photovoltaic applications  

Microsoft Academic Search

A dynamic process for reaching the maximum power point of a variable power source such as a solar cell is introduced. The process tracks maximum power nearly cycle-by-cycle during transients. Information from the natural switching ripple instead of external perturbation is used to support the maximizing process. The method is globally stable for DC-DC power converters, provided that a switching

Pallab Midya; Philip T. Krein; Robert J. Turnbull; Robert Reppa; Jonathan Kimball

1996-01-01

13

Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques  

Microsoft Academic Search

The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in

Trishan Esram; Patrick L. Chapman

2007-01-01

14

Maximum Power Point Estimation for Photovoltaic Systems Using Neural Networks  

Microsoft Academic Search

Solar panels are the power sources in photovoltaic applications which provide electrical power. Solar panel characteristics depend on environmental conditions (solar radiation level, temperature and etc.). In this paper, estimation of maximum power point of silicon solar panels is presented. We applied two different neural networks (back propagation and RBF) for the purpose of estimation in different environmental conditions. These

M. Taherbaneh; K. Faez

2007-01-01

15

Maximum power point tracking for low power photovoltaic solar panels  

Microsoft Academic Search

A maximum power point tracker unit is developed for the optimum coupling of photovoltaic panels (PVP) to the batteries and load through a controlled DC-DC power converter (chopper). The system consists of three main units: (i) the photovoltaic panels that convert solar power to electricity; (ii) a chopper which couples the power of PVP to the load or batteries at

Mehmet BODUR; Mummer ERMIS

1994-01-01

16

Maximum power point tracking control of direct methanol fuel cells  

NASA Astrophysics Data System (ADS)

The performance of a direct methanol fuel cell (DMFC) is closely related to its operating conditions, and there is a specific combination of operating conditions at which the DMFC produces maximum power. Working at the maximum power point (MPP) can lower the methanol crossover rate and ancillary power consumption, improving the global efficiency of the system. The fuzzy controller proposed in this paper provides a simple and robust way to keep the DMFC working at the MPP by adjusting the operating conditions followed by the variation of the driven load in real time. Simulation shows that the fuzzy control approach can yield satisfactory results.

Zhang, Mingbo; Yan, Ting; Gu, Jinguang

2014-02-01

17

A nomogram for calculating the maximum dose of local anaesthetic.  

PubMed

Toxic dose limits (mg.kg(-1)) for local anaesthetics based on body weight are well-established, but calculation of the maximum safe volume (ml) of a given agent and formulation is complex, and frequently results in errors. We therefore developed a nomogram to perform this calculation. We compared the performance of the nomogram with a spreadsheet and a general purpose calculator using simulated clinical data. Bland-Altman analysis showed close agreement between the nomogram and spreadsheet, with bias of -0.07 ml and limits of agreement of -0.38 to +0.24 ml (correlation coefficient r(2) = 0.9980; p < 0.001). The nomogram produced fewer and smaller errors compared with the calculator. Our nomogram calculates the maximum safe volume (ml) of local anaesthetic to a clinically acceptable degree of accuracy. It facilitates rapid cross-checking of dosage calculations performed by electronic or other means at negligible cost, and can potentially reduce the incidence of local anaesthetic toxicity. PMID:24820093

Williams, D J; Walker, J D

2014-08-01

18

Preliminary estimates of the virtually safe dose for tumors obtained from the maximum tolerated dose  

SciTech Connect

The purpose of this paper was to examine the correlation between the maximum tolerated dose (MTD) and the low-dose estimate of the virtually safe dose (VSD) for animal carcinogens. Chronic bioassay results from the National Cancer Institute/National Toxicology Program carcinogenesis screening program were used. Estimates of the VSD were obtained by linear low-dose extrapolation for which an adequate dose-response relationship existed at the same tumor site in the same sex for both rats and mice. Estimates of the VSD were compared with the MTD for 69 tumor sites from 38 chemicals for rats and mice. The MTDs ranged from high to low toxicity (1 ppb to 4.4% in the diet). The overall geometric mean of the ratio of the MTD to the VSD corresponding to a maximum estimated risk of 10(-6) was 3.8 x 10(5). Of the 138 cases, only 3 cases were more than a factor of 10 from the mean ratio. This suggested that a quick estimate of the VSD could be obtained by dividing the MTD, obtained from a subchronic study, by 400,000. Further, if the human exposure is less than 10(-7) X MTD, the estimated risk is likely to be negligible even if the chemical is a carcinogen. It may not be worthwhile to conduct a chronic bioassay for the purpose of demonstrating a negligible risk, if the chemical is likely to be carcinogenic, unless the human exposure is extremely low.

Gaylor, D.W.

1989-04-01

19

A maximum power point tracking algorithm for photovoltaic applications  

NASA Astrophysics Data System (ADS)

The voltage and current characteristic of a photovoltaic (PV) cell is highly nonlinear and operating a PV cell for maximum power transfer has been a challenge for a long time. Several techniques have been proposed to estimate and track the maximum power point (MPP) in order to improve the overall efficiency of a PV panel. A strategic use of the mean value theorem permits obtaining an analytical expression for a point that lies in a close neighborhood of the true MPP. But hitherto, an exact solution in closed form for the MPP is not published. This problem can be formulated analytically as a constrained optimization, which can be solved using the Lagrange method. This method results in a system of simultaneous nonlinear equations. Solving them directly is quite difficult. However, we can employ a recursive algorithm to yield a reasonably good solution. In graphical terms, suppose the voltage current characteristic and the constant power contours are plotted on the same voltage current plane, the point of tangency between the device characteristic and the constant power contours is the sought for MPP. It is subject to change with the incident irradiation and temperature and hence the algorithm that attempts to maintain the MPP should be adaptive in nature and is supposed to have fast convergence and the least misadjustment. There are two parts in its implementation. First, one needs to estimate the MPP. The second task is to have a DC-DC converter to match the given load to the MPP thus obtained. Availability of power electronics circuits made it possible to design efficient converters. In this paper although we do not show the results from a real circuit, we use MATLAB to obtain the MPP and a buck-boost converter to match the load. Under varying conditions of load resistance and irradiance we demonstrate MPP tracking in case of a commercially available solar panel MSX-60. The power electronics circuit is simulated by PSIM software.

Nelatury, Sudarshan R.; Gray, Robert

2013-05-01

20

Hardware Implementation of Maximum Power Point Tracking for Thermoelectric Generators  

NASA Astrophysics Data System (ADS)

This work describes the practical implementation of two maximum power point tracking (MPPT) algorithms, namely those of perturb and observe, and extremum seeking control. The proprietary dSPACE system is used to perform hardware in the loop (HIL) simulation whereby the two control algorithms are implemented using the MATLAB/Simulink (Mathworks, Natick, MA) software environment in order to control a synchronous buck-boost converter connected to two commercial thermoelectric modules. The process of performing HIL simulation using dSPACE is discussed, and a comparison between experimental and simulated results is highlighted. The experimental results demonstrate the validity of the two MPPT algorithms, and in conclusion the benefits and limitations of real-time implementation of MPPT controllers using dSPACE are discussed.

Maganga, Othman; Phillip, Navneesh; Burnham, Keith J.; Montecucco, Andrea; Siviter, Jonathan; Knox, Andrew; Simpson, Kevin

2014-06-01

21

Investigation of Maximum Power Point Tracking for Thermoelectric Generators  

NASA Astrophysics Data System (ADS)

In this paper, a thermoelectric generator (TEG) model is developed as a tool for investigating optimized maximum power point tracking (MPPT) algorithms for TEG systems within automotive exhaust heat energy recovery applications. The model comprises three main subsystems that make up the TEG system: the heat exchanger, thermoelectric material, and power conditioning unit (PCU). In this study, two MPPT algorithms known as the perturb and observe (P&O) algorithm and extremum seeking control (ESC) are investigated. A synchronous buck-boost converter is implemented as the preferred DC-DC converter topology, and together with the MPPT algorithm completes the PCU architecture. The process of developing the subsystems is discussed, and the advantage of using the MPPT controller is demonstrated. The simulation results demonstrate that the ESC algorithm implemented in combination with a synchronous buck-boost converter achieves favorable power outputs for TEG systems. The appropriateness is by virtue of greater responsiveness to changes in the system's thermal conditions and hence the electrical potential difference generated in comparison with the P&O algorithm. The MATLAB/Simulink environment is used for simulation of the TEG system and comparison of the investigated control strategies.

Phillip, Navneesh; Maganga, Othman; Burnham, Keith J.; Ellis, Mark A.; Robinson, Simon; Dunn, Julian; Rouaud, Cedric

2013-07-01

22

A new algorithm for rapid tracking of approximate maximum power point in photovoltaic systems  

Microsoft Academic Search

This paper presents a new algorithm for tracking maximum power point in photovoltaic systems. This is a fast tracking algorithm, where an initial approximation of maximum power point is (MPP) quickly achieved using a variable step-size. Subsequently, the exact maximum power point can be targeted using any conventional method like the hill-climbing or incremental conductance method. Thus, the drawback of

Sachin Jain; Vivek Agarwal

2004-01-01

23

The Expected Toxicity Rate at the Maximum Tolerated Dose in Bridging Studies in Alzheimer's Disease  

Microsoft Academic Search

A bridging study has been recommended to determine the maximum tolerated dose in Alzheimer's disease patients, because the maximum tolerated dose in the Alzheimer's disease patient population versus the normal population can vary greatly. Although bridging studies in Alzheimer's disease have often been conducted, it is surprising to note that very little is known about the statistical properties of the

Seung-Ho Kang; Chul Ahn

2005-01-01

24

Power and Sample Size Determination for a Stepwise Test Procedure for Finding the Maximum Safe Dose  

E-print Network

Power and Sample Size Determination for a Stepwise Test Procedure for Finding the Maximum Safe Dose This paper addresses the problem of power and sample size calculation for a stepwise multiple test procedure functions, respectively. The sample sizes necessary on the zero dose control and each of the positive doses

Tamhane, Ajit C.

25

New approach to photovoltaic arrays maximum power point tracking  

Microsoft Academic Search

The present trend for commercial telecommunication and scientific satellites is the utilization of standard platform, characterized by a high level of flexibility and reduced nonrecurring costs. One of the areas where flexibility is mandatory is the electrical primary power subsystem, due to the impact on solar array configuration and dimensions and on power conditioning unit. Use of the maximum power

Angelo Brambilla; Marcello Gambarara; Antonio Garutti; F. Ronchi

1999-01-01

26

Prediction-data-based maximum-power-point-tracking method for photovoltaic power generation systems  

Microsoft Academic Search

A new maximum-power-point-tracking (MPPT) method for a photovoltaic (PV) power generation system was studied which can efficiently generate PV power even under changing weather conditions. In order to research a method suitable for the actual photovoltaic power system, PV characteristics of the maximum power point were measured for more than six months using a PV curve tracer. The actual maximum

Nobuyoshi Mutoh; Takatoshi Matuo; Kazuhito Okada; Masahiro Sakai

2002-01-01

27

Dose Escalation Study for Defining the Maximum Tolerated Dose of Continuous Oral Trofosfamide in Pretreated Patients with Metastatic Lung Cancer  

Microsoft Academic Search

Background: Trofosfamide is increasingly used in the treatment of patients with several types of malignancies. However, the optimal dose of trofosfamide for patients with advanced cancer has not been systematically investigated yet. The aim of this study was to define the maximum tolerated dose (MTD) of continuous oral trofosfamide. Patients and Methods: 16 patients with advanced lung cancer (14 nonsmall

S.-E. Al-Batran; A. Atmaca; F. Bert; C. Frisch; A. Neumann; J. Orth; A. Knuth

2004-01-01

28

Topology Study of Photovoltaic Interface for Maximum Power Point Tracking  

Microsoft Academic Search

This paper looks at the performance of photovoltaic modules in nonideal conditions and proposes topologies to minimize the degradation of performance caused by these conditions. It is found that the peak power point of a module is significantly decreased due to only the slightest shading of the module, and that this effect is propagated through other nonshaded modules connected in

Weidong Xiao; Nathan Ozog; William G. Dunford

2007-01-01

29

An application of reinforced urn processes to determining maximum tolerated dose  

Microsoft Academic Search

Based on reinforced urn process introduced by Muliere et al. [2000. Urn schemes and reinforced random walks. Stochastic Process. Appl. 88(1), 59–78] we propose a Bayesian nonparametric approach to analyse a design determining the maximum tolerated dose (MTD) in Phase I clinical trials for new drug development when intrapatient dose escalation is allowed. A predictive distribution of MTD is obtained

Maura Mezzetti; Pietro Muliere; Paolo Bulla

2007-01-01

30

A Bayesian evaluation of enrolling additional patients at the maximum tolerated dose in Phase I trials  

Microsoft Academic Search

At the end of the dose escalation stage of Phase I trials, investigators occasionally enroll additional patients at the maximum tolerated dose (MTD) to further explore the tolerability of the regimen. There is no explicit statistical justification for doing so; neither are there any guidelines regarding the use of toxicity information from this additional cohort with respect to the modification

Mithat Gönen

2005-01-01

31

Regulatory Cancer Risk Assessment Based on a Quick Estimate of a Benchmark Dose Derived from the Maximum Tolerated Dose  

Microsoft Academic Search

The proposed U.S. Environmental Protection Agency carcinogen risk assessment guidelines employ a benchmark dose as a point of departure (POD) for low-dose risk assessment. If information on the carcinogenic mode of action for a chemical supports a nonlinear dose–response curve below the POD, a margin-of-exposure ratio between the POD and anticipated human exposure would be considered. The POD would be

David W. Gaylor; Lois Swirsky Gold

1998-01-01

32

Estimating the Maximum Effective Dose in a Quantitative Dose-Response Experiment1,2  

Microsoft Academic Search

A simulation study was conducted to compare several procedures for estimating the maxi- mum effective dose in a quantitative dose-response experiment. Using four equally spaced dose levels, data were generated from four different model types: the quadratic growth curve, the Mitcherlich growth curve, the linear-linear plateau spline model, and the quadratic-linear plateau spline model. Each model type was parameterized to

Marta D. Remmenga; George A. Milliken; Dal Kratzer; James R. Schwenke; Henry R. Rolka

33

Estimation of maximum tolerated dose for long-term bioassays from acute lethal dose and structure by QSAR  

Microsoft Academic Search

A quantitative structure-activity relationship (QSAR) model has been developed to estimate maximum tolerated doses (MTD) from structural features of chemicals and the corresponding oral acute lethal doses (LD50) as determined in male rats. The model is based on a set of 269 diverse chemicals which have been tested under the National Cancer Institute\\/National Toxicology Program (NCI\\/NTP) protocols. The rat oral

Viay K. Gombar; Kurt Enslein; Jeffrey B. Hart; Benjamin W. Blake; Harold H. Borgstedt

1991-01-01

34

Quick Estimate of the Regulatory Virtually Safe Dose Based on the Maximum Tolerated Dose for Rodent Bioassays  

Microsoft Academic Search

With a limited subset of National Cancer Institute\\/National Toxicology Program (NCI\\/NTP) bioassays, Gaylor (Regul. Toxicol. Pharmacol. 9, 101-108, 1989) showed that the regulatory virtually safe dose (VSD), corresponding to an estimated lifetime cancer risk of less than 10?6, could be estimated within a factor of 10 simply by dividing the maximum tolerated dose (MTD), estimated from the results of a

D. W. Gaylor; L. S. Gold

1995-01-01

35

Maximum-Power-Point Tracking Method of Photovoltaic Using Only Single Current Sensor  

E-print Network

Ā» Ā«Solar cell systemsĀ» Abstract This paper describes a novel strategy of maximum-power-point trackingMaximum-Power-Point Tracking Method of Photovoltaic Using Only Single Current Sensor Toshihiko-2188, Japan Phone: +81-258-47-9510, Fax: +81-258-47-9500 e-mail: tnoguchi@vos.nagaokaut.ac.jp URL: pelab

Fujimoto, Hiroshi

36

Bayesian designs of phase II oncology trials to select maximum effective dose assuming monotonic dose-response relationship  

PubMed Central

Background For many molecularly targeted agents, the probability of response may be assumed to either increase or increase and then plateau in the tested dose range. Therefore, identifying the maximum effective dose, defined as the lowest dose that achieves a pre-specified target response and beyond which improvement in the response is unlikely, becomes increasingly important. Recently, a class of Bayesian designs for single-arm phase II clinical trials based on hypothesis tests and nonlocal alternative prior densities has been proposed and shown to outperform common Bayesian designs based on posterior credible intervals and common frequentist designs. We extend this and related approaches to the design of phase II oncology trials, with the goal of identifying the maximum effective dose among a small number of pre-specified doses. Methods We propose two new Bayesian designs with continuous monitoring of response rates across doses to identify the maximum effective dose, assuming monotonicity of the response rate across doses. The first design is based on Bayesian hypothesis tests. To determine whether each dose level achieves a pre-specified target response rate and whether the response rates between doses are equal, multiple statistical hypotheses are defined using nonlocal alternative prior densities. The second design is based on Bayesian model averaging and also uses nonlocal alternative priors. We conduct simulation studies to evaluate the operating characteristics of the proposed designs, and compare them with three alternative designs. Results In terms of the likelihood of drawing a correct conclusion using similar between-design average sample sizes, the performance of our proposed design based on Bayesian hypothesis tests and nonlocal alternative priors is more robust than that of the other designs. Specifically, the proposed Bayesian hypothesis test-based design has the largest probability of being the best design among all designs under comparison and the smallest probability of being an inadequate design, under sensible definitions of the best design and an inadequate design, respectively. Conclusions The use of Bayesian hypothesis tests and nonlocal alternative priors under ordering constraints between dose groups results in a robust performance of the design, which is thus superior to other common designs. PMID:25074481

2014-01-01

37

A more efficient formulation for computation of the maximum loading points in electric power systems  

SciTech Connect

This paper presents a more efficient formulation for computation of the maximum loading points. A distinguishing feature of the new formulation is that it is of dimension (n + 1), instead of the existing formulation of dimension (2n + 1), for n-dimensional load flow equations. This feature makes computation of the maximum loading points very inexpensive in comparison with those required in the existing formulation. A theoretical basis for the new formulation is provided. The new problem formulation is derived by using a simple reparameterization scheme and exploiting the special properties of the power flow model. Moreover, the proposed test function is shown to be monotonic in the vicinity of a maximum loading point. Therefore, it allows one to monitor the approach to maximum loading points during the solution search process. Simulation results on a 234-bus system are presented.

Chiang, H.D. [Cornell Univ., Ithaca, NY (United States). School of Electrical Engineering; Jean-Jumeau, R. [Electricite d`Haita, Port-au-Prince (Haiti)

1995-05-01

38

Microcontroller Servomotor for Maximum Effective Power Point for Solar Cell System  

E-print Network

In this paper a Maximum Power point (MPP) tracking algorithm is developed using dual-axis servomotor feedback tracking control system. An efficient and accurate servomotor system is used to increase the system efficiency and reduces the solar cell...

Al-Khalidy, M.; Al-Rawi, O.; Noaman, N.

2010-01-01

39

Novel maximum-power-point-tracking controller for photovoltaic energy conversion system  

Microsoft Academic Search

A novel maximum-power-point-tracking (MPPT) controller for a photovoltaic (PV) energy conversion system is presented. Using the slope of power versus voltage of a PV array, the proposed MPPT controller allows the conversion system to track the maximum power point very rapidly. As opposed to conventional two-stage designs, a single-stage configuration is implemented, resulting in size and weight reduction and increased

Yeong-Chau Kuo; Tsorng-Juu Liang; Jiann-Fuh Chen

2001-01-01

40

Biological standardization and maximum tolerated dose estimation of an Alternaria alternata allergenic extract  

Microsoft Academic Search

Background: The manufacture of allergenic extracts from the mold Alternaria alternata is influenced by factors such as strain variability, allergenic origin, culturing conditions and extraction process, which affect the reproducibility of the preparations intended for diagnostic and therapeutic use. Objectives: To select the most adequate antigenic source of A. alternata extracts and determine its maximum tolerated dose (MTD) to be

M. T. Lizaso; A. Martķnez; J. A. Asturias; J. Algorta; B. Madariaga; N. Labarta; A. I. Tabar

41

The Maximum Number of Odd Integral Distances Between Points in the Plane  

Microsoft Academic Search

Four points in the plane with pairwise odd integral distances do not exist. The maximum number of odd distances betweenn points in the plane is proved to ben\\u000a 2\\/3+r(r-3)\\/6 for alln, wherer=1,2,3 andn?r (mod 3). This solves a recently stated problem of Erd?s.

L. Piepmeyer

1996-01-01

42

Maximum Throughput of IEEE 802.11 Access Points: Test Procedure and Measurements  

E-print Network

Maximum Throughput of IEEE 802.11 Access Points: Test Procedure and Measurements Enrico Pelletta 10th August 2004 #12;Abstract Performance measurements of IEEE 802.11 access points are becoming. Several different standards are currently part of the 802.11 family, but we restrict our investigation

Maguire Jr., Gerald Q.

43

Maximum tolerable dose (MTD): a new index for ultraviolet radiation toxicity in the lens  

Microsoft Academic Search

The maximum tolerable dose (MTD2.3:16) for avoidance of cataract on exposure to UVR-300 nm in the rat was currently estimated to 3.65 kJ\\/m2. For this, Sprague-Dawley rats were unilaterally exposed to UVR in the 300 nm wavelength region, generated with a high pressure mercury arc source. The intensity of forward light scattering was measured one week after exposure. MTD allows

Per G. Soederberg; Stefan Loefgren; Marcelo Ayala; M. Kakar

2001-01-01

44

High-dose ifosfamide/carboplatin/etoposide: maximum tolerable doses, toxicities, and hematopoietic recovery after autologous stem cell reinfusion.  

PubMed

We treated 115 patients in a phase I/II dose-escalation study of ifosfamide/carboplatin/etoposide (ICE) followed by autologous stem cell rescue. Patients treated had a variety of diagnoses, including breast cancer (high-risk stage II disease with eight or more positive nodes, stage III disease, and responsive metastatic disease), non-Hodgkin's lymphoma, Hodgkin's disease, acute leukemia in first remission, and various solid tumors that were responsive to induction therapy. Patients received autologous bone marrow stem cells or peripheral blood stem cells primed by one of several methods. The maximum tolerated dose of ICE was determined to be ifosfamide 20,100 mg/m2, carboplatin 1,800 mg/m2, and etoposide 3,000 mg/m2 when administered as a 6-day regimen. The dose-limiting toxicities included acute renal failure, severe central nervous system toxicity, and "leaky capillary syndrome" with hypoalbuminemia, profound fluid overload, and pulmonary insufficiency. Analysis of hematologic recovery based on stem cell source and influence of hematopoietic growth factor administration was undertaken. Hematopoietic growth factor use significantly reduced neutrophil engraftment time for patients receiving bone marrow stem cells, with evidence of earlier recovery times for patients receiving granulocyte colony-stimulating factor compared with granulocyte-macrophage colony-stimulating factor. Neutrophil recovery times varied based on the source of stem cells used, with the earliest engraftment times seen for patients receiving peripheral blood stem cells primed with cyclophosphamide and granulocyte colony-stimulating factor. Platelet recovery times were not statistically different for any of the subsets. In conclusion, the maximum tolerated dose of ICE has been defined, and the source of stem cells and the use of hematopoietic growth factors influence hematopoietic recovery. PMID:7527592

Fields, K K; Elfenbein, G J; Perkins, J B; Janssen, W E; Ballester, O F; Hiemenz, J W; Zorsky, P E; Kronish, L E; Foody, M C

1994-10-01

45

Wind speed sensorless maximum power point tracking control of variable speed wind energy conversion systems  

Microsoft Academic Search

A maximum power point tracking (MPPT) controller for variable speed wind energy conversion system (WECS) is proposed. The proposed method, without requiring the knowledge of wind speed, air density or turbine parameters, generates at its output the optimum speed command for speed control loop of rotor flux oriented vector controlled machine side converter control system using only the instantaneous active

J. S. Thongam; P. Bouchard; H. Ezzaidi; M. Ouhrouche

2009-01-01

46

Maximum Power Point Tracking Control for Photovoltaic System Using Adaptive Neuro-Fuzzy  

E-print Network

-fuzzy "ANFIS" control. The tracking algorithm integrated with a solar PV system has been simulated with boostMaximum Power Point Tracking Control for Photovoltaic System Using Adaptive Neuro- Fuzzy "ANFIS availability and vast potential, world has turned to solar photovoltaic energy to meet out its ever increasing

Paris-Sud XI, UniversitƩ de

47

Artificial Neural Network Maximum Power Point Tracker for Solar Electric Vehicle  

Microsoft Academic Search

This paper proposes an artificial neural network maximum power point tracker (MPPT) for solar electric vehicles. The MPPT is based on a highly efficient boost converter with insulated gate bipolar transistor (IGBT) power switch. The reference voltage for MPPT is obtained by artificial neural network (ANN) with gradient descent momentum algorithm. The tracking algorithm changes the duty-cycle of the converter

Theodore Amissah Ocran; Junyi Cao; Binggang Cao; Xinghua Sun

2005-01-01

48

A new maximum power point tracking method for photovoltaic arrays using golden section search algorithm  

Microsoft Academic Search

This paper introduces a new maximum power point tracking (MPPT) method with the golden section search (GSS) algorithm for photovoltaic (PV) systems. The basic principle and the implementation procedures of the GSS algorithm are elaborated in the paper; and the PV simulation model in Matlab\\/Simulink is also developed. Then the PV system with a boost chopper is modeled and simulated

Riming Shao; Liuchen Chang

2008-01-01

49

Review of the maximum power point tracking algorithms for stand-alone photovoltaic systems  

Microsoft Academic Search

A survey of the algorithms for seeking the maximum power point (MPP) is proposed. As has been shown, there are many ways of distinguishing and grouping methods that seek the MPP from a photovoltaic (PV) generator. However, in this article they are grouped as either direct or nondirect methods. The indirect methods (“quasi seeks”) have the particular feature that the

V. Salas; E. Olķas; A. Barrado; A. Lįzaro

2006-01-01

50

Performance of Photovoltaic Maximum Power Point Tracking Algorithms in the Presence of Noise  

E-print Network

Performance of Photovoltaic Maximum Power Point Tracking Algorithms in the Presence of Noise tracking (MPPT) algorithms for photovoltaic systems, including how noise affects both tracking speed-performance photovoltaic sys- tems. An intelligent controller adjusts the voltage, current, or impedance seen by a solar

Odam, Kofi

51

A Study of Maximum Power Point Tracking in Novel Small-Scale Photovoltaic LED Lighting Systems  

Microsoft Academic Search

While most of the current maximum power point tracking (MPPT) algorithms for large photovoltaic systems are complicated and inefficient, this paper proposes a novel method of MPPT specially used in small-scale photovoltaic LED lighting systems. The proposed algorithm is based on the improved research on the characteristics of the PV array in novel lighting systems. The proposed method in the

Xiaojin Wu; Zhiqiang Cheng; Xueye Wei

2009-01-01

52

Photovoltaic Maximum Power Point Prediction Using Robust Radial Basis Function Network  

NASA Astrophysics Data System (ADS)

By operating PV systems near the maximum power point (MPP), the output efficiency of PV panels can be increased. Traditionally, the k-means algorithm is one of the most popular methods to classify the input patterns of the radial basis function network (RBFN). Although the KMA has an ability to cluster the training patterns rapidly, it usually converges to a local minimum and can be oversensitive to randomly initial partitions. To solve these significant problems, a hybrid skill called Genetic k-Means Algorithm is proposed to improve the effectiveness of maximum power point track. By precisely clustering of the training patterns, the objective to accurately and rapidly approximate the MPP of PV system can be achieved with the least squares criterion in RBF network.

Liao, Chiung-Chou

2009-08-01

53

Efficiency improvement of the maximum power point tracking for PV systems using support vector machine technique  

NASA Astrophysics Data System (ADS)

The aim of this paper is to improve efficiency of maximum power point tracking (MPPT) for PV systems. The Support Vector Machine (SVM) was proposed to achieve the MPPT controller. The theoretical, the perturbation and observation (P&O), and incremental conductance (IC) algorithms were used to compare with proposed SVM algorithm. MATLAB models for PV module, theoretical, SVM, P&O, and IC algorithms are implemented. The improved MPPT uses the SVM method to predict the optimum voltage of the PV system in order to extract the maximum power point (MPP). The SVM technique used two inputs which are solar radiation and ambient temperature of the modeled PV module. The results show that the proposed SVM technique has less Root Mean Square Error (RMSE) and higher efficiency than P&O and IC methods.

Kareim, Ameer A.; Mansor, Muhamad Bin

2013-06-01

54

Achieving Maximum Power from Thermoelectric Generators with Maximum-Power-Point-Tracking Circuits Composed of a Boost-Cascaded-with-Buck Converter  

NASA Astrophysics Data System (ADS)

We propose a way of achieving maximum power and power-transfer efficiency from thermoelectric generators by optimized selection of maximum-power-point-tracking (MPPT) circuits composed of a boost-cascaded-with-buck converter. We investigated the effect of switch resistance on the MPPT performance of thermoelectric generators. The on-resistances of the switches affect the decrease in the conversion gain and reduce the maximum output power obtainable. Although the incremental values of the switch resistances are small, the resulting difference in the maximum duty ratio between the input and output powers is significant. For an MPPT controller composed of a boost converter with a practical nonideal switch, we need to monitor the output power instead of the input power to track the maximum power point of the thermoelectric generator. We provide a design strategy for MPPT controllers by considering the compromise in which a decrease in switch resistance causes an increase in the parasitic capacitance of the switch.

Park, Hyunbin; Sim, Minseob; Kim, Shiho

2015-01-01

55

Analysis of the flight dynamics of the Solar Maximum Mission (SMM) off-sun scientific pointing  

NASA Technical Reports Server (NTRS)

Algorithms are presented which were created and implemented by the Goddard Space Flight Center's (GSFC's) Solar Maximum Mission (SMM) attitude operations team to support large-angle spacecraft pointing at scientific objectives. The mission objective of the post-repair SMM satellite was to study solar phenomena. However, because the scientific instruments, such as the Coronagraph/Polarimeter (CP) and the Hard X-ray Burst Spectrometer (HXRBS), were able to view objects other than the Sun, attitude operations support for attitude pointing at large angles from the nominal solar-pointing attitudes was required. Subsequently, attitude support for SMM was provided for scientific objectives such as Comet Halley, Supernova 1987A, Cygnus X-1, and the Crab Nebula. In addition, the analysis was extended to include the reverse problem, computing the right ascension and declination of a body given the off-Sun angles. This analysis led to the computation of the orbits of seven new solar comets seen in the field-of-view (FOV) of the CP. The activities necessary to meet these large-angle attitude-pointing sequences, such as slew sequence planning, viewing-period prediction, and tracking-bias computation are described. Analysis is presented for the computation of maneuvers and pointing parameters relative to the SMM-unique, Sun-centered reference frame. Finally, science data and independent attitude solutions are used to evaluate the larg-angle pointing performance.

Pitone, D. S.; Klein, J. R.; Twambly, B. J.

1990-01-01

56

Analysis of the flight dynamics of the Solar Maximum Mission (SMM) off-sun scientific pointing  

NASA Technical Reports Server (NTRS)

Algorithms are presented which were created and implemented by the Goddard Space Flight Center's (GSFC's) Solar Maximum Mission (SMM) attitude operations team to support large-angle spacecraft pointing at scientific objectives. The mission objective of the post-repair SMM satellite was to study solar phenomena. However, because the scientific instruments, such as the Coronagraph/Polarimeter (CP) and the Hard X ray Burst Spectrometer (HXRBS), were able to view objects other than the Sun, attitude operations support for attitude pointing at large angles from the nominal solar-pointing attitudes was required. Subsequently, attitude support for SMM was provided for scientific objectives such as Comet Halley, Supernova 1987A, Cygnus X-1, and the Crab Nebula. In addition, the analysis was extended to include the reverse problem, computing the right ascension and declination of a body given the off-Sun angles. This analysis led to the computation of the orbits of seven new solar comets seen in the field-of-view (FOV) of the CP. The activities necessary to meet these large-angle attitude-pointing sequences, such as slew sequence planning, viewing-period prediction, and tracking-bias computation are described. Analysis is presented for the computation of maneuvers and pointing parameters relative to the SMM-unique, Sun-centered reference frame. Finally, science data and independent attitude solutions are used to evaluate the large-angle pointing performance.

Pitone, D. S.; Klein, J. R.

1989-01-01

57

Pilot Study of Low-Dose, Divided Maximum Tolerated Dose of CPT11 in 21 Consecutive Patients with Metastatic Colorectal or Gastric Cancer  

Microsoft Academic Search

Purpose We devised a new treatment regimen, delivering a frequent low dose of CPT-11, calculated by dividing the maximum tolerated dose (MTD) to reduce its toxicity without impairing its efficacy. Methods CPI-11, 25?mg\\/m 2, determined by dividing the MTD dose per month by 12, was given on days 1, 2, and 3 of every week, to 21 consecutive patients; 12

Yutaka Takahashi; Hidekazu Kitakata; Kaname Yamashita; Kazuo Yasumoto; Kazuhiko Omote; Toshinari Minamoto; Masayoshi Mai

2004-01-01

58

Comparison of the maximum tolerated dose (MTD) dermal response in three strains of mice following repeated exposure to acrylic acid  

Microsoft Academic Search

The dermal response of three strains of mice (ICR, C3H and B6C3F,) exposed to repeated doses of 0, l or 4% acrylic acid was examined over 13 wk. Microscopic and gross changes to the skin were classified as being indicative of exceeding the maximum tolerated dose (MTD), reaching the MTD, or tolerating the dose based on proposed MTD guidelines established

J. E. McLaughlin; J. Parno; F. M. Garner; J. J. Clary; W. C. Thomas; S. R. Murphy

1995-01-01

59

An overview of the report: Correlation between carcinogenic potency and the maximum tolerated dose: Implications for risk assessment  

Microsoft Academic Search

Current practice in carcinogen bioassay calls for exposure of experimental animals at doses up to and including the maximum tolerated dose (MTD). Such studies have been used to compute measures of carcinogenic potency such as the TD[sub 50] as well as unit risk factors such as q[sub 1] for predicting low-dose risks. Recent studies have indicated that these measures of

D. Krewski; D. W. Gaylor; A. P. Soms; M. Szyszkowicz

1993-01-01

60

A complementary review of maximum power point tracking methods for wind generators  

NASA Astrophysics Data System (ADS)

Maximum power point tracking (MPPT) is a very important necessity in a system of energy conversion from a renewable energy source. In this paper, is made an attempt to provide a brief review of 12 very recent publications, not analyzed in the last surveys appeared in 2010 and 2011, and to make a comparative analyze and a classification of all available MPPT algorithms, highlighting their strength and drawbacks. After addressing the reasons for use of MPPT techniques, various power optimization schemes are surveyed. The comparative analysis and a classification of the MPPT algorithms are useful for the designers of wind energy power systems.

Cr?ciunescu, Aurelian; Popescu, Claudia; Popescu, Mihai

2012-09-01

61

Magnification of starting torques of dc motors by maximum power point trackers in photovoltaic systems  

NASA Technical Reports Server (NTRS)

A calculation of the starting torque ratio of permanent magnet, series, and shunt-excited dc motors powered by solar cell arrays is presented for two cases, i.e., with and without a maximum-power-point tracker (MPPT). Defining motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 for the permanent magnet motor and a magnification of 7 for both the series and shunt motors are obtained. The study also shows that all motor types are less sensitive to solar insolation variation in systems including MPPTs as compared to systems without MPPTs.

Appelbaum, J.; Singer, S.

1989-01-01

62

IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 25, NO. 10, OCTOBER 2010 2531 Maximum Power Point Tracking for Photovoltaic  

E-print Network

manufacturing and efficiency as well as increasingly volatile fuel costs. Solar power is an at- tractive option a maximum power point track- ing algorithm that optimizes solar array performance and adapts to rapidly efficiencies exceeding 99% with transient rise-time to the maximum power point of less than 0.1 s. It is shown

Kulkarni, Sanjeev

63

Correlation of Point B and Lymph Node Dose in 3D-Planned High-Dose-Rate Cervical Cancer Brachytherapy  

SciTech Connect

Purpose: To compare high dose rate (HDR) point B to pelvic lymph node dose using three-dimensional-planned brachytherapy for cervical cancer. Methods and Materials: Patients with FIGO Stage IB-IIIB cervical cancer received 70 tandem HDR applications using CT-based treatment planning. The obturator, external, and internal iliac lymph nodes (LN) were contoured. Per fraction (PF) and combined fraction (CF) right (R), left (L), and bilateral (Bil) nodal doses were analyzed. Point B dose was compared with LN dose-volume histogram (DVH) parameters by paired t test and Pearson correlation coefficients. Results: Mean PF and CF doses to point B were R 1.40 Gy +- 0.14 (CF: 7 Gy), L 1.43 +- 0.15 (CF: 7.15 Gy), and Bil 1.41 +- 0.15 (CF: 7.05 Gy). The correlation coefficients between point B and the D100, D90, D50, D2cc, D1cc, and D0.1cc LN were all less than 0.7. Only the D2cc to the obturator and the D0.1cc to the external iliac nodes were not significantly different from the point B dose. Significant differences between R and L nodal DVHs were seen, likely related to tandem deviation from irregular tumor anatomy. Conclusions: With HDR brachytherapy for cervical cancer, per fraction nodal dose approximates a dose equivalent to teletherapy. Point B is a poor surrogate for dose to specific nodal groups. Three-dimensional defined nodal contours during brachytherapy provide a more accurate reflection of delivered dose and should be part of comprehensive planning of the total dose to the pelvic nodes, particularly when there is evidence of pathologic involvement.

Lee, Larissa J. [Harvard Radiation Oncology Program, Brigham and Women's Hospital, Boston, MA (United States); Sadow, Cheryl A. [Department of Radiology, Brigham and Women's Hospital, Boston, MA (United States); Russell, Anthony [Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States); Viswanathan, Akila N., E-mail: aviswanathan@lroc.harvard.ed [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)

2009-11-01

64

Maximum Tolerable Dose and Low-Dose Metronomic Chemotherapy Have Opposite Effects on the Mobilization and Viability of Circulating Endothelial Progenitor Cells1  

Microsoft Academic Search

There is growing evidence that vasculogenesis (progenitor cell-derived generation of new blood vessels) is required for the growth of some neoplastic diseases. Here we show that the administration of cyclophos- phamide (CTX) at the maximum tolerable dose with 21-day breaks or at more frequent low-dose (metronomic) schedules have opposite effects on the mobilization and viability of circulating endothelial progenitors (CEPs)

Francesco Bertolini; Saki Paul; Patrizia Mancuso; Silvia Monestiroli; Alberto Gobbi; Yuval Shaked; Robert S. Kerbel

2003-01-01

65

Solar Panel System for Street Light Using Maximum Power Point Tracking (MPPT) Technique  

NASA Astrophysics Data System (ADS)

Solar energy is one form of the renewable energy which is very abundant in regions close to the equator. One application of solar energy is for street light. This research focuses on using the maximum power point tracking technique (MPPT), particularly the perturb and observe (P&O) algorithm, to charge battery for street light system. The proposed charger circuit can achieve 20.73% higher power efficiency compared to that of non-MPPT charger. We also develop the LED driver circuit for the system which can achieve power efficiency up to 91.9% at a current of 1.06 A. The proposed street lightning system can be implemented with a relatively low cost for public areas.

Wiedjaja, A.; Harta, S.; Josses, L.; Winardi; Rinda, H.

2014-03-01

66

Maximum-likelihood estimation of a laser system pointing parameters by use of return photon counts.  

PubMed

A maximum-likelihood estimator used to determine boresight and jitter performance of a laser pointing system has been derived. The estimator is based on a Gaussian jitter model and uses a Gaussian far-field irradiance profile. The estimates are obtained using a set of return shots from the intended target. An experimental setup with a He-Ne laser and steering mirrors is used to study the performance of the proposed method. Both Monte Carlo simulations and experimental results demonstrate excellent performance of the estimator. Our study shows that boresight estimation is more challenging than jitter estimation when both quantities are estimated. Furthermore, their estimation performance improves with an increase in the number of shots. The experimental results are found to agree well with the simulation results. PMID:16623248

Borah, Deva K; Voelz, David; Basu, Santasri

2006-04-10

67

Some results regarding stability of photovoltaic maximum-power-point tracking dc-dc converters  

NASA Astrophysics Data System (ADS)

An analytical investigation of a class of photovoltaic (PV) maximum-power-point tracking dc-dc converters has yielded basic results relative to the stability of such devices. Necessary and sufficient conditions for stable operation are derived, and design tools are given. Specific results have been obtained for arbitrary PV arrays driving converters powering resistive loads and batteries. The analytical techniques are applicable to inverters, also. Portions of the theoretical results have been verified in operational devices: a 1500 watt unit has driven a 1-horsepower, 90-volt dc motor powering a water pump jack for over one year. Prior to modification shortly after initial installation, the unit exhibited instability at low levels of irradiance, as predicted by the theory. Two examples are provided.

Schaefer, John F.

68

MEASUREMENT OF MAXIMUM SKIN DOSE IN INTERVENTIONAL RADIOLOGY AND CARDIOLOGY AND CHALLENGES IN THE SET-UP OF EUROPEAN ALERT THRESHOLDS.  

PubMed

To help operators acknowledge patient dose during interventional procedures, EURADOS WG-12 focused on measuring patient skin dose using XR-RV3 gafchromic films, thermoluminescent detector (TLD) pellets or 2D TL foils and on investigating possible correlation to the on-line dose indicators such as fluoroscopy time, Kerma-area product (KAP) and cumulative air Kerma at reference point (CK). The study aims at defining non-centre-specific European alert thresholds for skin dose in three interventional procedures: chemoembolization of the liver (CE), neuroembolization (NE) and percutaneous coronary interventions (PCI). Skin dose values of >3 Gy (ICRP threshold for skin injuries) were indeed measured in these procedures confirming the need for dose indicators that correlate with maximum skin dose (MSD). However, although MSD showed fairly good correlation with KAP and CK, several limitations were identified challenging the set-up of non-centre-specific European alert thresholds. This paper presents preliminary results of this wide European measurement campaign and focuses on the main challenges in the definition of European alert thresholds. PMID:25316909

Farah, J; Trianni, A; Carinou, E; Ciraj-Bjelac, O; Clairand, I; Dabin, J; De Angelis, C; Domienik, J; Jarvinen, H; Kopec, R; Majer, M; Malchair, F; Negri, A; Novįk, L; Siiskonen, T; Vanhavere, F; Kneževi?, Z

2014-10-14

69

A Systemic Exposure-Based Alternative to the Maximum Tolerated Dose for Carcinogenicity Studies of Human Therapeutics  

Microsoft Academic Search

A systemic exposure-based alternative to the maximum tolerated dose (MTD) for high-dose selection in carcinogenicity studies for human therapeutics was accepted at the Second International Conference on Harmonization (ICH-2). The systemic exposure-based alternative to the MTD is suitable for nongenotoxic compounds with low rodent toxicity that are metabolized similarly in rodents and humans. This is the first product of an

Joseph F. Contrera; Abigail C. Jacobs; Hullahalli R. Prasanna; Mehul Mehta; Wendelyn J. Schmidt; Joseph De. George

1995-01-01

70

Experimental evaluation of actual delivered dose using mega-voltage cone-beam CT and direct point dose measurement  

SciTech Connect

Radiation therapy in patients is planned by using computed tomography (CT) images acquired before start of the treatment course. Here, tumor shrinkage or weight loss or both, which are common during the treatment course for patients with head-and-neck (H and N) cancer, causes unexpected differences from the plan, as well as dose uncertainty with the daily positional error of patients. For accurate clinical evaluation, it is essential to identify these anatomical changes and daily positional errors, as well as consequent dosimetric changes. To evaluate the actual delivered dose, the authors proposed direct dose measurement and dose calculation with mega-voltage cone-beam CT (MVCBCT). The purpose of the present study was to experimentally evaluate dose calculation by MVCBCT. Furthermore, actual delivered dose was evaluated directly with accurate phantom setup. Because MVCBCT has CT-number variation, even when the analyzed object has a uniform density, a specific and simple CT-number correction method was developed and applied for the H and N site of a RANDO phantom. Dose distributions were calculated with the corrected MVCBCT images of a cylindrical polymethyl methacrylate phantom. Treatment processes from planning to beam delivery were performed for the H and N site of the RANDO phantom. The image-guided radiation therapy procedure was utilized for the phantom setup to improve measurement reliability. The calculated dose in the RANDO phantom was compared to the measured dose obtained by metal-oxide-semiconductor field-effect transistor detectors. In the polymethyl methacrylate phantom, the calculated and measured doses agreed within about +3%. In the RANDO phantom, the dose difference was less than +5%. The calculated dose based on simulation-CT agreed with the measured dose within±3%, even in the region with a high dose gradient. The actual delivered dose was successfully determined by dose calculation with MVCBCT, and the point dose measurement with the image-guided radiation therapy procedure.

Matsubara, Kana, E-mail: matsubara-kana@hs.tmu.ac.jp [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan); Kohno, Ryosuke [National Cancer Center Hospital East, Chiba (Japan); National Cancer Center Research Institute, Chiba (Japan); Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo [National Cancer Center Hospital East, Chiba (Japan); Saitoh, Hidetoshi [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan)

2013-07-01

71

A comparative study of maximum-power-point trackers for photovoltaic panels using switching-frequency modulation scheme  

Microsoft Academic Search

A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc\\/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of

K. K. Tse; Billy M. T. Ho; Henry Shu-Hung Chung; S. Y. Ron Hui

2004-01-01

72

Design and control of a three-phase grid-connected photovoltaic system with developed maximum power point tracking  

Microsoft Academic Search

In this paper an optimum design and control of three-phase grid-connected PV system has been proposed and analyzed. Also, a developed maximum power point tracking (MPPT) controller that uses the PV array differential power to voltage (dP\\/dV) as an index to provide the reference voltage of maximum power point (MPP) quickly and accurately is presented. The control scheme of a

Zhou Dejia; Zhao Zhengming; Mohamed Eltawil; Yuan Liqiang

2008-01-01

73

Application of Preclinical Data to Initiate the Modified Continual Reassessment Method for Maximum Tolerated Dose–Finding Trials  

Microsoft Academic Search

This study was conducted to evaluate whether the allometric approach can be used to predict maximum tolerated dose (MTD) in humans from animal data. Twenty-five anticancer drugs were taken from the literature and used in this analysis. The results of the study indicate that MTD can be predicted with reasonable accuracy using interspecies scaling. The predicted MTD can then be

Iftekhar Mahmood

2001-01-01

74

The Expected Toxicity Rate at the Maximum Tolerated Dose in the Standard Phase I Cancer Clinical Trial Design  

Microsoft Academic Search

A main purpose of Phase I cancer clinical trials is to identify the maximum tolerated dose (MTD) of a new agent for experimentation in Phase II and III studies. The continual reassessment method has been shown to be superior to the standard design. However, in practice, the standard design has still been widely used. Therefore, it is important to investigate

Seung-Ho Kang; Chul Ahn

2001-01-01

75

Dose dependent cataractogenesis and Maximum Tolerable Dose (MTD 2.3:16) for UVR 300 nm-induced cataract in C57BL\\/6J mice  

Microsoft Academic Search

The purpose of the present study was to investigate the in vivo dose response function for UVR 300nm-induced cataract in the C57BL\\/6J mouse lens and to establish a cataract threshold estimate expressed as Maximum Tolerable Dose (MTD2.3:16) for UVR 300 nm-induced cataract in the C57BL\\/6J mouse lens. Knowledge of the MTD2.3:16 in the C57BL\\/6J mouse will permit quantitative in vivo

Linda M. Meyer; Xiuqin Dong; Alfred Wegener; Per Söderberg

2008-01-01

76

Dose point kernel simulation for monoenergetic electrons and radionuclides using Monte Carlo techniques.  

PubMed

Monte Carlo (MC) simulation has been commonly used in the dose evaluation of radiation accidents and for medical purposes. The accuracy of simulated results is affected by the particle-tracking algorithm, cross-sectional database, random number generator and statistical error. The differences among MC simulation software packages must be validated. This study simulated the dose point kernel (DPK) and the cellular S-values of monoenergetic electrons ranging from 0.01 to 2 MeV and the radionuclides of (90)Y, (177)Lu and (103 m)Rh, using Fluktuierende Kaskade (FLUKA) and MC N-Particle Transport Code Version 5 (MCNP5). A 6-?m-radius cell model consisting of the cell surface, cytoplasm and cell nucleus was constructed for cellular S-value calculation. The mean absolute percentage errors (MAPEs) of the scaled DPKs, simulated using FLUKA and MCNP5, were 7.92, 9.64, 4.62, 3.71 and 3.84 % for 0.01, 0.1, 0.5, 1 and 2 MeV, respectively. For the three radionuclides, the MAPEs of the scaled DPKs were within 5 %. The maximum deviations of S(N?N), S(N?Cy) and S(N?CS) for the electron energy larger than 10 keV were 6.63, 6.77 and 5.24 %, respectively. The deviations for the self-absorbed S-values and cross-dose S-values of the three radionuclides were within 4 %. On the basis of the results of this study, it was concluded that the simulation results are consistent between FLUKA and MCNP5. However, there is a minor inconsistency for low energy range. The DPK and the cellular S-value should be used as the quality assurance tools before the MC simulation results are adopted as the gold standard. PMID:22923242

Wu, J; Liu, Y L; Chang, S J; Chao, M M; Tsai, S Y; Huang, D E

2012-11-01

77

Short-current pulse-based maximum-power-point tracking method for multiple photovoltaic-and-converter module system  

Microsoft Academic Search

This paper proposes a novel maximum-power-point tracking (MPPT) method with a simple algorithm for photovoltaic (PV) power generation systems. The method is based on use of a short-current pulse of the PV to determine an optimum operating current where the maximum output power can be obtained and completely differs from conventional hill-climbing-based methods. In the proposed system, the optimum operating

Toshihiko Noguchi; Shigenori Togashi; Ryo Nakamoto

2002-01-01

78

Sustained long-term hematologic efficacy of hydroxyurea at maximum tolerated dose in children with sickle cell disease  

Microsoft Academic Search

Hydroxyurea improves hematologic pa- rameters for children with sickle cell dis- ease (SCD), but its long-term efficacy at maximum tolerated dose (MTD) has not been determined. Between 1995 and 2002, hydroxyurea therapy was initiated for 122 pediatric patients with SCD including 106 with homozygous sickle cell anemia (HbSS), 7 with sickle hemoglobin C (HbSC), 7 with sickle\\/-thalassemia (HbS\\/ -thalassemia (6

Sherri A. Zimmerman; William H. Schultz; Jacqueline S. Davis; Chrisley V. Pickens; Nicole A. Mortier; Thad A. Howard; Russell E. Ware

2003-01-01

79

Maximum tolerable dose for avoidance of cataract induced by ultraviolet radiation-B for 18 to 60 week old rats  

Microsoft Academic Search

The purpose of the present study was to investigate the maximum tolerable dose for avoidance of UVR-B-induced cataract in rats in the age interval 18–60 weeks and establish the functional relationship between age and sensitivity to UVR-B. Four groups of 20 albino Sprague–Dawley rats each, aged 18, 26, 40 or 60 weeks, were included. Each age group was divided into

Xiuqin Dong; Stefan Löfgren; Marcelo Ayala; Per G. Söderberg

2005-01-01

80

An overview of the report: Correlation between carcinogenic potency and the maximum tolerated dose: Implications for risk assessment  

SciTech Connect

Current practice in carcinogen bioassay calls for exposure of experimental animals at doses up to and including the maximum tolerated dose (MTD). Such studies have been used to compute measures of carcinogenic potency such as the TD[sub 50] as well as unit risk factors such as q[sub 1] for predicting low-dose risks. Recent studies have indicated that these measures of carcinogenic potency are highly correlated with the MTD. Carcinogenic potency has also been shown to be correlated with indicators of mutagenicity and toxicity. Correlation of the MTDs for rats and mice implies a corresponding correlation in TD[sub 50] values for these two species. The implications of these results for cancer risk assessment are examined in light of the large variation in potency among chemicals known to induce tumors in rodents. 119 refs., 2 figs., 4 tabs.

Krewski, D. (Health and Welfare Canada, Ottawa, Ontario (Canada) Carleton Univ. Ottawa, Ontario (Canada)); Gaylor, D.W. (National Center for Toxicological Research, Jefferson, AR (United States)); Soms, A.P. (Univ. of Wisconsin, Madison, WI (United States)); Szyszkowicz, M. (Health and Welfare Canada, Ottawa, Ontario (Canada))

1993-08-01

81

Maximum tolerable dose of red pepper decreases fat intake independently of spicy sensation in the mouth  

Microsoft Academic Search

Dietary red pepper suppresses energy intake and modifies macronutrient intake. We have investigated whether a stimulus in the mouth and the sensation of spiciness are necessary for red pepper-induced changes in energy and macronutrient intake in human volunteers. In a preliminary test, sixteen Japanese male volunteers tasted samples of a soup with graded doses of red pepper in order to

Mayumi Yoshioka; Makoto Imanaga; Hiromi Ueyama; Miya Yamane; Yoshiko Kubo; André Boivin; Jonny St-Amand; Hiroaki Tanaka; Akira Kiyonaga

2004-01-01

82

Fuzzy-logic-based maximum power point tracking strategy for Pmsg variable-speed wind turbine generation systems  

Microsoft Academic Search

In order to achieve maximum power point tracking (MPPT) for wind power generation systems, the rotating speed of wind turbines should be adjusted in the real time according to wind speeds. However, fast wind speed variations and heavy inertia compromise the MPPT control of a wind turbine. In this paper, a fuzzy-logic based MPPT strategy is proposed for PMSG variable

Qingrong Zeng; Liuchen Chang; Riming Shao

2008-01-01

83

Combination of Fuzzy-Based Maximum Power Point Tracker and Sun Tracker for Deployable Solar Panels in Photovoltaic Systems  

Microsoft Academic Search

Solar panels are power sources in photovoltaic applications. Solar panels I-V curves depend on environmental conditions such as irradiance, temperature, load and degradation level. In this paper, design and implementation of simultaneous fuzzy-based maximum power point tracker (MPPT) and sun tracker are presented for deployable solar panels. A digital controller was implemented by an AVR microcontroller. Results showed that the

Mohsen Taherbaneh; Hasan Ghafori Frard; Amir Hossein Rezaie; Shahab Karbasian

2007-01-01

84

A Maximum Power Point Tracking Control Method of a Photovoltaic Power Generator with Consideration of Dynamic Characteristics of Solar Cells  

Microsoft Academic Search

This paper discusses a new control strategy for photovoltaic power generation systems with consideration of dynamic characteristics of the photovoltaic cells. The controller estimates internal currents of an equivalent circuit for the cells. This estimated, or the virtual current and the actual voltage of the cells are fed to a conventional Maximum-Power-Point-Tracking (MPPT) controller. Consequently, this MPPT controller still tracks

Takashi Watanabe; Toshiya Yoshida; Katsumi Ohniwa

2004-01-01

85

Evaluation of a photovoltaic energy mechatronics system with a built-in quadratic maximum power point tracking algorithm  

SciTech Connect

The historically high cost of crude oil price is stimulating research into solar (green) energy as an alternative energy source. In general, applications with large solar energy output require a maximum power point tracking (MPPT) algorithm to optimize the power generated by the photovoltaic effect. This work aims to provide a stand-alone solution for solar energy applications by integrating a DC/DC buck converter to a newly developed quadratic MPPT algorithm along with its appropriate software and hardware. The quadratic MPPT method utilizes three previously used duty cycles with their corresponding power outputs. It approaches the maximum value by using a second order polynomial formula, which converges faster than the existing MPPT algorithm. The hardware implementation takes advantage of the real-time controller system from National Instruments, USA. Experimental results have shown that the proposed solar mechatronics system can correctly and effectively track the maximum power point without any difficulties. (author)

Chao, R.M.; Ko, S.H.; Lin, I.H. [Department of Systems and Naval Mechatronics Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China); Pai, F.S. [Department of Electronic Engineering, National University of Tainan (China); Chang, C.C. [Department of Environment and Energy, National University of Tainan (China)

2009-12-15

86

One new quality of the maximum-likelihood estimation of laser pointing system by use of return photon counts  

NASA Astrophysics Data System (ADS)

In all laser pointing systems, boresight and jitter are two fundamental pointing errors arising from vibrations and atmospheric turbulence. The maximum-likelihood estimation1 advanced by Deva K.borah recently can simultaneously estimate jitter and boresight. Besides some traditional qualities just like high precision and speediness, the maximum-likelihood estimation has a new quality that the performance of this estimator is different when boresight and jitter errors are different. Furthermore, the Monte Carlo simulation results demonstrate that the maximum-likelihood estimation has a higher degree of precision when boresight is bigger than jitter. According to this, a careful analysis is made and some advice is given for the readers who wish to obtain high precise results.

Zhou, Lei; Tan, Yi; Ge, Ren

2010-11-01

87

Maximum tolerable dose for avoidance of cataract after repeated exposure to ultraviolet radiation in rats  

Microsoft Academic Search

The purpose of the present study was to determine the impact of inter-exposure interval between repeated equivalent exposures of ultraviolet radiation (UVR) on threshold accumulated dose for cataract development. Female Sprague–Dawley rats were randomly divided into 5 inter-exposure interval groups with 20 rats in each group. The inter-exposure intervals were 6h, 1, 3, 9 and 30days respectively. Each inter-exposure interval

Xiuqin Dong; Stefan Löfgren; Marcelo Ayala; Per G. Söderberg

2007-01-01

88

The Maximum or Minimum Number of Rational Points on Genus Three Curves over Finite Fields  

Microsoft Academic Search

We show that for all finite fields Fq, there exists a curve C over Fq of genus 3 such that the number of rational points on C is within 3 of the Serre–Weil upper or lower bound. For some q, we also obtain improvements on the upper bound for the number of rational points on a genus 3 curve over

Kristin Lauter; Jean-Pierre Serre

2002-01-01

89

A study to determine the safety profile and maximum tolerated dose of micafungin (FK463) in patients undergoing haematopoietic stem cell transplantation  

Microsoft Academic Search

This open-label, dose-escalation study assessed the maximum tolerated dose (MTD) of the new antifungal micafungin in patients undergoing haematopoietic stem cell transplantation (HSCT). Participants received 3, 4, 6 or 8 mg\\/kg\\/day micafungin intravenously from 7 days to a maximum of 28 days or until neutropaenia resolved. The MTD was defined as the highest dose not causing the same Grade 3

B Sirohi; R L Powles; R Chopra; N Russell; J L Byrne; H G Prentice; M Potter; S Koblinger

2006-01-01

90

Study of Different Implementation Approaches for a Maximum Power Point Florent Boico Brad Lehman  

E-print Network

(MPPT) for low power portable solar array applications. The discussion will compare different digital of solar panels has limited their use. As the efficiency is limited, harvesting the maximum amount of flexible and lightweight solar panel has unlocked many applications as they can deliver power where

Lehman, Brad

91

The maximum or minimum number of rational points on curves of genus three over finite fields  

Microsoft Academic Search

We show that for all finite fields F_q, there exists a curve C over F_q of genus 3 such that the number of rational points on C is within 3 of the Serre-Weil upper or lower bound. For some q, we also obtain improvements on the upper bound for the number of rational points on a genus 3 curve over

Kristin Lauter; Jean-Pierre Serre

2001-01-01

92

A novel maximum power point tracking technique for solar panels using a SEPIC or Cuk converter  

Microsoft Academic Search

A novel technique for efficiently extracting the maximum output power from a solar panel under varying meteorological conditions is presented. The methodology is based on connecting a pulse-width-modulated (PWM) DC\\/DC SEPIC or Cuk converter between a solar panel and a load or battery bus. The converter operates in discontinuous capacitor voltage mode whilst its input current is continuous. By modulating

Henry Shu-Hung Chung; K. K. Tse; S. Y. Ron Hui; C. M. Mok; M. T. Ho

2003-01-01

93

Maximum Principle of Optimal Control of the Primitive Equations of the Ocean with Two Point Boundary State Constraint  

SciTech Connect

We study in this article the Pontryagin's maximum principle for a class of control problems associated with the primitive equations (PEs) of the ocean with two point boundary state constraint. These optimal problems involve a two point boundary state constraint similar to that considered in Wang, Nonlinear Anal. 51, 509-536, 2002 for the three-dimensional Navier-Stokes (NS) equations. The main difference between this work and Wang, Nonlinear Anal. 51, 509-536, 2002 is that the nonlinearity in the PEs is stronger than in the three-dimensional NS systems.

Tachim Medjo, Theodore, E-mail: tachimt@fiu.ed [Florida International University, Department of Mathematics (United States)

2010-08-15

94

A Low-Cost Solar-Powered Light-Flasher with Built-in Maximum Power Point Tracking  

Microsoft Academic Search

This paper presents the development of a RISC- microcontroller based solar-powered light-flasher with built- in Maximum Power Point Tracking (MPPT) system. The unit captures solar energy by a solar array and delivers into battery through a boost converter. With the built-in MPPT, solar power can then be efficiently drawn from the solar array. In this research work, the MPPT based

Noppadol Khaehintung; Borpit Tuvirat; Krisada Pramotung; Phaophak Sirisuk

95

Theoretical and Experimental Analyses of Photovoltaic Systems with Voltage and Current-Based Maximum Power Point Tracking  

Microsoft Academic Search

Detailed theoretical and experimental analyses are presented for the comparison of two simple fast and reliable maximum power point tracking (MPPT) techniques for photovoltaic systems (PV): the voltage-based (VMPPT) and the current-based (CMPPT) approaches. A microprocessor-controlled tracker capable of online voltage and current measurements and programmed with both VMPPT and CMPPT algorithms is constructed. The load of the solar system

M. A. Masoum; H. Dehbonei; E. F. Fuchs

2002-01-01

96

TiO2 dye sensitized solar cell (DSSC): linear relationship of maximum power point and anthocyanin concentration  

Microsoft Academic Search

This study investigated the relationship of anthocyanin concentration from different organic fruit species and output voltage and current in a TiO2 dye-sensitized solar cell (DSSC) and hypothesized that fruits with greater anthocyanin concentration produce higher maximum power point (MPP) which would lead to higher current and voltage. Anthocyanin dye solution was made with crushing of a group of fresh fruits

Radin Ahmadian

2010-01-01

97

Efficient Energy Harvesting With Electromagnetic Energy Transducers Using Active Low-Voltage Rectification and Maximum Power Point Tracking  

Microsoft Academic Search

This paper reports on efficient interfacing of typical vibration-driven electromagnetic transducers for micro energy harvesting. For this reason, an adaptive charge pump for dynamic maximum power point tracking is compared with a novel active full-wave rectifier design. For efficient ultra-low voltage rectification, the introduced active diode design uses a common-gate stage in conjunction with supply-independent biasing. While this active rectifier

Dominic Maurath; Philipp F. Becker; Dirk Spreemann; Yiannos Manoli

2012-01-01

98

A Comparative Analysis of Low-Dose Metronomic Cyclophosphamide Reveals Absent or Low-Grade Toxicity on Tissues Highly Sensitive to the Toxic Effects of Maximum Tolerated Dose Regimens  

Microsoft Academic Search

The survival benefits of traditional maximum tolerated dose (MTD) cytotoxic therapy have been modest for the treatment of most types of metastatic malignancy and, moreover, often come with increased acute and chronic toxicity. Recent studies have demonstrated that the frequent administration of comparatively low doses of cytotoxic agents, with no extended breaks (low-dose metronomic (LDM) chemotherapy), may not only be

Urban Emmenegger; Shan Man; Yuval Shaked; Giulio Francia; John W. Wong; Daniel J. Hicklin; Robert S. Kerbel

2004-01-01

99

Suitability of point kernel dose calculation techniques in brachytherapy treatment planning  

PubMed Central

Brachytherapy treatment planning system (TPS) is necessary to estimate the dose to target volume and organ at risk (OAR). TPS is always recommended to account for the effect of tissue, applicator and shielding material heterogeneities exist in applicators. However, most brachytherapy TPS software packages estimate the absorbed dose at a point, taking care of only the contributions of individual sources and the source distribution, neglecting the dose perturbations arising from the applicator design and construction. There are some degrees of uncertainties in dose rate estimations under realistic clinical conditions. In this regard, an attempt is made to explore the suitability of point kernels for brachytherapy dose rate calculations and develop new interactive brachytherapy package, named as BrachyTPS, to suit the clinical conditions. BrachyTPS is an interactive point kernel code package developed to perform independent dose rate calculations by taking into account the effect of these heterogeneities, using two regions build up factors, proposed by Kalos. The primary aim of this study is to validate the developed point kernel code package integrated with treatment planning computational systems against the Monte Carlo (MC) results. In the present work, three brachytherapy applicators commonly used in the treatment of uterine cervical carcinoma, namely (i) Board of Radiation Isotope and Technology (BRIT) low dose rate (LDR) applicator and (ii) Fletcher Green type LDR applicator (iii) Fletcher Williamson high dose rate (HDR) applicator, are studied to test the accuracy of the software. Dose rates computed using the developed code are compared with the relevant results of the MC simulations. Further, attempts are also made to study the dose rate distribution around the commercially available shielded vaginal applicator set (Nucletron). The percentage deviations of BrachyTPS computed dose rate values from the MC results are observed to be within plus/minus 5.5% for BRIT LDR applicator, found to vary from 2.6 to 5.1% for Fletcher green type LDR applicator and are up to ?4.7% for Fletcher-Williamson HDR applicator. The isodose distribution plots also show good agreements with the results of previous literatures. The isodose distributions around the shielded vaginal cylinder computed using BrachyTPS code show better agreement (less than two per cent deviation) with MC results in the unshielded region compared to shielded region, where the deviations are observed up to five per cent. The present study implies that the accurate and fast validation of complicated treatment planning calculations is possible with the point kernel code package. PMID:20589118

Lakshminarayanan, Thilagam; Subbaiah, K. V.; Thayalan, K.; Kannan, S. E.

2010-01-01

100

Penetrative Rayleigh-Bénard convection in water near its maximum density point  

NASA Astrophysics Data System (ADS)

The presence of a density maximum in water near 4 °C significantly modifies the nature and onset conditions of convective flows due to imposed temperature differences. In the present study, vertical temperature gradients are imposed upon a horizontal, rectangular layer of water, with the top and bottom surfaces maintained above and below the maximum density temperature, respectively. In such an arrangement, convection beginning in the lower, unstable portion of the layer (as small as 1/3 of the layer height) may penetrate into the upper, stable region. The resulting convection patterns are visualized using schlieren or shadowgraph techniques along multiple visual axes. The measured onset conditions and observed patterns are discussed in the context of preceding predictions and experimental observations in similar penetrative systems. As expected from the non-Boussinesq nature of water in this temperature range, convection sets in at temperature differences below those predicted by linear stability theory when the unstable portion of the layer is sufficiently small. The conduction-convection transition is also hysteretic in nature. At onset, the convection pattern consists of parallel, transverse rolls due to the boundary conditions of the fluid chamber. When the unstable portion of the layer is significantly less than half of the fluid layer height, the convective motion is found to penetrate only partway into the upper stable region, within which weakly counter-rotating motions are driven. At higher Rayleigh numbers, the fluid undergoes secondary transitions to either hexagonal cellular or longitudinal roll states which are visualized for the first time. Pattern heights and wavenumbers were measured in some instances, establishing qualitative (in general) and quantitative (over some parameter ranges) agreement with linear theory.

Large, E.; Andereck, C. D.

2014-09-01

101

A constrained maximum likelihood approach to evaluate the impact of dose metric on cancer risk assessment: application to ?-chloroprene.  

PubMed

?-Chloroprene (2-chloro-1,3-butadiene, CD) is used in the manufacture of polychloroprene rubber. Chronic inhalation studies have demonstrated that CD is carcinogenic in B6C3F1 mice and Fischer 344 rats. However, epidemiological studies do not provide compelling evidence for an increased risk of mortality from total cancers of the lung. Differences between the responses observed in animals and humans may be related to differences in toxicokinetics, the metabolism and detoxification of potentially active metabolites, as well as species differences in sensitivity. The purpose of this study was to develop and apply a novel method that combines the results from available physiologically based kinetic (PBK) models for chloroprene with a statistical maximum likelihood approach to test commonality of low-dose risk across species. This method allows for the combined evaluation of human and animal cancer study results to evaluate the difference between predicted risks using both external and internal dose metrics. The method applied to mouse and human CD data supports the hypothesis that a PBK-based metric reconciles the differences in mouse and human low-dose risk estimates and further suggests that, after PBK metric exposure adjustment, humans are equally or less sensitive than mice to low levels of CD exposure. PMID:25010378

Allen, B C; Van Landingham, C; Yang, Y; Youk, A O; Marsh, G M; Esmen, N; Gentry, P R; Clewell, H J; Himmelstein, M W

2014-10-01

102

TiO2 dye sensitized solar cell (DSSC): linear relationship of maximum power point and anthocyanin concentration  

NASA Astrophysics Data System (ADS)

This study investigated the relationship of anthocyanin concentration from different organic fruit species and output voltage and current in a TiO2 dye-sensitized solar cell (DSSC) and hypothesized that fruits with greater anthocyanin concentration produce higher maximum power point (MPP) which would lead to higher current and voltage. Anthocyanin dye solution was made with crushing of a group of fresh fruits with different anthocyanin content in 2 mL of de-ionized water and filtration. Using these test fruit dyes, multiple DSSCs were assembled such that light enters through the TiO2 side of the cell. The full current-voltage (I-V) co-variations were measured using a 500 ? potentiometer as a variable load. Point-by point current and voltage data pairs were measured at various incremental resistance values. The maximum power point (MPP) generated by the solar cell was defined as a dependent variable and the anthocyanin concentration in the fruit used in the DSSC as the independent variable. A regression model was used to investigate the linear relationship between study variables. Regression analysis showed a significant linear relationship between MPP and anthocyanin concentration with a p-value of 0.007. Fruits like blueberry and black raspberry with the highest anthocyanin content generated higher MPP. In a DSSC, a linear model may predict MPP based on the anthocyanin concentration. This model is the first step to find organic anthocyanin sources in the nature with the highest dye concentration to generate energy.

Ahmadian, Radin

2010-09-01

103

A Maximum Power Point Tracking Control Method of a Photovoltaic Power Generator with Consideration of Dynamic Characteristics of Solar Cells  

NASA Astrophysics Data System (ADS)

This paper discusses a new control strategy for photovoltaic power generation systems with consideration of dynamic characteristics of the photovoltaic cells. The controller estimates internal currents of an equivalent circuit for the cells. This estimated, or the virtual current and the actual voltage of the cells are fed to a conventional Maximum-Power-Point-Tracking (MPPT) controller. Consequently, this MPPT controller still tracks the optimum point even though it is so designed that the seeking speed of the operating point is extremely high. This system may suit for applications, which are installed in rapidly changeable insolation and temperature-conditions e.g. automobiles, trains, and airplanes. The proposed method is verified by experiment with a combination of this estimating function and the modified Boehringer's MPPT algorithm.

Watanabe, Takashi; Yoshida, Toshiya; Ohniwa, Katsumi

104

Maximum likelihood approach for the adaptive optics point spread function reconstruction  

NASA Astrophysics Data System (ADS)

This paper is dedicated to a new PSF reconstruction method based on a maximum likelihood approach (ML) which uses as well the telemetry data of the AO system (see Exposito et al. (2013)1). This approach allows a joint-estimation of the covariance matrix of the mirror modes of the residual phase, the noise variance and the Fried parameter r0. In this method, an estimate of the covariance between the parallel residual phase and the orthogonal phase is required. We developed a recursive approach taking into account the temporal effect of the AO-loop, so that this covariance only depends on the r0, the wind speed and some of the parameters of the system (the gain of the loop, the interaction matrix and the command matrix). With this estimation, the high bandwidth hypothesis is no longer required to reconstruct the PSF with a good accuracy. We present the validation of the method and the results on numerical simulations (on a SCAO system) and show that our ML method allows an accurate estimation of the PSF in the case of a Shack-Hartmann (SH) wavefront sensor (WFS).

Exposito, J.; Gratadour, Damien; Rousset, Gérard; Clénet, Yann; Mugnier, Laurent; Gendron, Éric

2014-08-01

105

Evaluation of Cartesian coordinates and radiation doses in points determined with stereo x-ray techniques.  

PubMed

A Fortran computer program STEV (stereo evaluation) is described. The principles of the stereo techniques together with the calculation method of the stereo coordinates are given briefly. The determination of the rectangular coordinates from mean stereo coordinates is described. Radiation doses in anatomical points, during intracavitary and interstitial radiation therapy, are calculated, taking into account a statistical evaluation of the measurement errors. PMID:761457

Storchi, P R; van Kleffens, H J

1979-03-01

106

Assessment of maximum tolerated dose of a new herbal drug, Semelil (ANGIPARSTM) in patients with diabetic foot ulcer: A Phase I clinical trial  

Microsoft Academic Search

Background and the purpose of the study: In many cases of diabetic foot ulcer (DFU) management, wound healing is incomplete, and wound closure and epithelial junctional integrity are rarely achieved. Our aim was to evaluate the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of Semelil (ANGIPARSTM), a new herbal compound for wound treatment in a Phase I clinical trial.

Heshmat R; Mohammad K; Mohajeri Tehrani

107

A Solar-powered Battery Charger with Neural Network Maximum Power Point Tracking Implemented on a Low-Cost PIC-microcontroller  

Microsoft Academic Search

This paper presents the development of a maximum power point tracking algorithm using an artificial neural network for a solar power system. By applying a three layers neural network and some simple activation functions, the maximum power point of a solar array can be efficiently tracked. The tracking algorithm integrated with a solar-powered battery charging system has been successfully implemented

P. Petchjatuporn; W. Ngamkham; N. Khaehintung; P. Sirisuk; W. Kiranon

2005-01-01

108

Hybrid Energy Storage System Based on Compressed Air and Super-Capacitors with Maximum Efficiency Point Tracking (MEPT)  

NASA Astrophysics Data System (ADS)

This paper presents a hybrid energy storage system mainly based on Compressed Air, where the storage and withdrawal of energy are done within maximum efficiency conditions. As these maximum efficiency conditions impose the level of converted power, an intermittent time-modulated operation mode is applied to the thermodynamic converter to obtain a variable converted power. A smoothly variable output power is achieved with the help of a supercapacitive auxiliary storage device used as a filter. The paper describes the concept of the system, the power-electronic interfaces and especially the Maximum Efficiency Point Tracking (MEPT) algorithm and the strategy used to vary the output power. In addition, the paper introduces more efficient hybrid storage systems where the volumetric air machine is replaced by an oil-hydraulics and pneumatics converter, used under isothermal conditions. Practical results are also presented, recorded from a low-power air motor coupled to a small DC generator, as well as from a first prototype of the hydro-pneumatic system. Some economical considerations are also made, through a comparative cost evaluation of the presented hydro-pneumatic systems and a lead acid batteries system, in the context of a stand alone photovoltaic home application. This evaluation confirms the cost effectiveness of the presented hybrid storage systems.

Lemofouet, Sylvain; Rufer, Alfred

109

Phase-I\\/II study to evaluate dose limiting toxicity, maximum tolerated dose, and tolerability of bendamustine HCl in pre-treated patients with B-chronic lymphocytic leukaemia (Binet stages B and C) requiring therapy  

Microsoft Academic Search

Purpose: Bendamustine hydrochloride, an anti-neoplastic agent with unique mechanism of action, is known to cause impressive remissions\\u000a in relapsed nonHodgkin’s lymphoma and chronic lymphocytic leukaemia (CLL). Optimal bendamustine dosing for CLL patients had\\u000a not been finally established and a phase I\\/II study was conducted to determine the maximum tolerated dose (MTD) and dose limiting\\u000a toxicity (DLT) of bendamustine. Methods: The

T. Lissitchkov; G. Arnaudov; D. Peytchev; Kh. Merkle

2006-01-01

110

Silica nanoparticles administered at the maximum tolerated dose induce genotoxic effects through an inflammatory reaction while gold nanoparticles do not.  

PubMed

While the collection of genotoxicity data and insights into potential mechanisms of action for nano-sized particulate materials (NPs) are steadily increasing, there is great uncertainty whether current standard assays are suitable to appropriately characterize potential risks. We investigated the effects of NPs in an in vivo Comet/micronucleus (MN) combination assay and in an in vitro MN assay performed with human blood. We also incorporated additional endpoints into the in vivo study in an effort to delineate primary from secondary mechanisms. Amorphous silica NPs (15 and 55 nm) were chosen for their known reactivity, while gold nano/microparticles (2, 20, and 200 nm) were selected for their wide size range and lower reactivity. DNA damage in liver, lung and blood cells and micronuclei in circulating reticulocytes were measured after 3 consecutive intravenous injections to male Wistar rats at 48, 24 and 4h before sacrifice. Gold nano/microparticles were negative for MN induction in vitro and in vivo, and for the induction of DNA damage in all tissues. Silica particles, however, caused a small but reproducible increase in DNA damage and micronucleated reticulocytes when tested at their maximum tolerated dose (MTD). No genotoxic effects were observed at lower doses, and the in vitro MN assay was also negative. We hypothesize that silica NPs initiate secondary genotoxic effects through release of inflammatory cell-derived oxidants, similar to that described for crystalline silica (quartz). Such a mechanism is supported by the occurrence of increased neutrophilic infiltration, necrosis, and apoptotic cells in the liver, and induction of inflammatory markers TNF-? and IL-6 in plasma at the MTDs. These results were fairly consistent between silica NPs and the quartz control, thereby strengthening the argument that silica NPs may act in a similar, thresholded manner. The observed profile is supportive of a secondary genotoxicity mechanism that is driven by inflammation. PMID:22504169

Downs, Thomas R; Crosby, Meredith E; Hu, Ting; Kumar, Shyam; Sullivan, Ashley; Sarlo, Katherine; Reeder, Bob; Lynch, Matt; Wagner, Matthew; Mills, Tim; Pfuhler, Stefan

2012-06-14

111

Theoretical study of the maximum power point of n-type and p-type crystalline silicon space solar cells  

NASA Astrophysics Data System (ADS)

The performance of crystalline silicon n+/p/p+ and n+/n/p+ solar cells under AM0 spectrum, irradiated with 1 MeV electrons at fluences below 1017 cm-2 has been analyzed by means of computer simulation. The software used, fully developed by the authors, solves numerically in one dimension under steady-state conditions, the Poisson and continuity equations self-consistently. The influence of constructive characteristics and different levels of hazardous environmental work conditions on the maximum power point of over 150 devices has been investigated. The study has allowed the authors to propose a useful analytical model related to the constructive characteristics of the device such as polarity, base resistivity and total thickness, with the aim of examining the electrical performance of Si space solar cells. Results presented in this paper are important in order to contribute to the design of radiation-hardened devices.

Cappelletti, M. A.; Casas, G. A.; Cédola, A. P.; Blancį, E. L. Peltzer y.

2013-04-01

112

Hepatic intraarterial chemotherapy with gemcitabine in patients with unresectable cholangiocarcinomas and liver metastases of pancreatic cancer: a clinical study on maximum tolerable dose and treatment efficacy  

Microsoft Academic Search

Purpose  To define the maximum tolerated dose (MTD) of hepatic intraarterial chemotherapy with gemcitabine, administered with and without starch microspheres, in patients with inoperable intrahepatic cholangiocarcinomas and liver metastases of pancreatic carcinomas.Methods  Gemcitabine was administered on days 1 and 8 with intervals of 2 weeks between the cycles. In group A the initial gemcitabine dose of 1,000 mg\\/m2 (without microspheres) was increased in 200-mg\\/m2

Thomas J. Vogl; Wolfram Schwarz; Katrin Eichler; Kathrin Hochmuth; Renate Hammerstingl; Ursula Jacob; Albert Scheller; Stephan Zangos; Matthias Heller

2006-01-01

113

Temporal relationship of the induction of tolerance and physical dependence after continuous intoxication with maximum tolerable doses of ethanol in rats  

Microsoft Academic Search

Rats were treated by intragastric intubation of a 20% ethanol solution in doses of 9–15 g\\/kg in 3–5 fractions for 1–7 days. Both tolerance and physical dependence were demonstrated after this treatment with the maximum tolerable doses to only a few days. Tolerance was assessed by signs of severity of intoxication: coma, loss of righting reflex, ataxia-3, ataxia-2, ataxia-1, sedation,

Edward Majchrowicz; Walter A. Hunt

1976-01-01

114

Hepatic intraarterial chemotherapy with gemcitabine in patients with unresectable cholangiocarcinomas and liver metastases of pancreatic cancer: a clinical study on maximum tolerable dose and treatment eYcacy  

Microsoft Academic Search

Purpose To deWne the maximum tolerated dose (MTD) of hepatic intraarterial chemotherapy with gemcitabine, administered with and without starch microspheres, in patients with inoperable intrahepatic cholangiocarcinomas and liver metastases of pancre- atic carcinomas. Methods Gemcitabine was administered on days 1 and 8 with intervals of 2 weeks between the cycles. In group A the initial gemcitabine dose of 1,000 mg\\/m2

Thomas J. Vogl; Wolfram Schwarz; Katrin Eichler; Kathrin Hochmuth; Renate Hammerstingl; Ursula Jacob; Albert Scheller; Stephan Zangos; Matthias Heller

115

Maximum Tolerated Dose and Early Response — Results of a Phase I Trial of Paclitaxel and Cisplatin with Radiation Therapy in Carcinoma of the Cervix 1  

Microsoft Academic Search

AimsCisplatin-based chemotherapy with radiotherapy is currently the standard treatment for locally advanced carcinoma of the cervix. Recent studies have shown a better response with the addition of newer chemotherapeutic agents. The aim of this phase I study was to establish the maximum tolerated dose (MTD) of paclitaxel in combination with cisplatin as a radiosensitiser along with radiation therapy in the

E. Prasad; P. N. Viswanathan; V. F. Rangad; S. Pavamani; T. S. Ram

2009-01-01

116

Study of a thermoelectric system equipped with a maximum power point tracker for stand-alone electric generation.  

NASA Astrophysics Data System (ADS)

According to the International Energy Agency, 1.4 billion people are without electricity in the poorest countries and 2.5 billion people rely on biomass to meet their energy needs for cooking in developing countries. The use of cooking stoves equipped with small thermoelectric generator to provide electricity for basic needs (LED, cell phone and radio charging device) is probably a solution for houses far from the power grid. The cost of connecting every house with a landline is a lot higher than dropping thermoelectric generator in each house. Thermoelectric generators have very low efficiency but for isolated houses, they might become really competitive. Our laboratory works in collaboration with plane`te-bois (a non governmental organization) which has developed energy-efficient multifunction (cooking and hot water) stoves based on traditional stoves designs. A prototype of a thermoelectric generator (Bismuth Telluride) has been designed to convert a small part of the energy heating the sanitary water into electricity. This generator can produce up to 10 watts on an adapted load. Storing this energy in a battery is necessary as the cooking stove only works a few hours each day. As the working point of the stove varies a lot during the use it is also necessary to regulate the electrical power. An electric DC DC converter has been developed with a maximum power point tracker (MPPT) in order to have a good efficiency of the electronic part of the thermoelectric generator. The theoretical efficiency of the MMPT converter is discussed. First results obtained with a hot gas generator simulating the exhaust of the combustion chamber of a cooking stove are presented in the paper.

Favarel, C.; Champier, D.; Bédécarrats, J. P.; Kousksou, T.; Strub, F.

2012-06-01

117

Dose-volume histogram parameters of high-dose-rate brachytherapy for Stage I-II cervical cancer (?4cm) arising from a small-sized uterus treated with a point A dose-reduced plan.  

PubMed

We investigated the rectal dose-sparing effect and tumor control of a point A dose-reduced plan in patients with Stage I-II cervical cancer (?4 cm) arising from a small-sized uterus. Between October 2008 and August 2011, 19 patients with Stage I-II cervical cancer (?4 cm) were treated with external beam radiotherapy (EBRT) for the pelvis and CT-guided brachytherapy. Seven patients were treated with brachytherapy with standard loading of source-dwell positions and a fraction dose of 6 Gy at point A (conventional brachy-plan). The other 12 patients with a small uterus close to the rectum or small intestine were treated with brachytherapy with a point A dose-reduction to match D2cc of the rectum and <6 Gy as the dose constraint ('point A dose-reduced plan') instead of the 6-Gy plan at point A ('tentative 6-Gy plan'). The total doses from EBRT and brachytherapy were added up and normalized to a biological equivalent dose of 2 Gy per fraction (EQD2). The median doses to the high-risk clinical target volume (HR-CTV) D90 in the conventional brachy-plan, tentative 6-Gy plan and point A dose-reduced plan were 62 GyEQD2, 80 GyEQD2 and 64 GyEQD2, respectively. The median doses of rectal D2cc in the corresponding three plans were 42 GyEQD2, 62 GyEQD2 and 51 GyEQD2, respectively. With a median follow-up period of 35 months, three patients developed Grade-1 late rectal complications and no patients developed local recurrence. Our preliminary results suggested that CT-guided brachytherapy using an individualized point A dose-reduced plan might be useful for reducing late rectal complications while maintaining primary tumor control. PMID:24566721

Nakagawa, Akiko; Ohno, Tatsuya; Noda, Shin-ei; Kubo, Nobuteru; Kuwako, Keiko; Saitoh, Jun-Ichi; Nakano, Takashi

2014-07-01

118

Dose–volume histogram parameters of high-dose-rate brachytherapy for Stage I–II cervical cancer (?4cm) arising from a small-sized uterus treated with a point A dose-reduced plan  

PubMed Central

We investigated the rectal dose-sparing effect and tumor control of a point A dose-reduced plan in patients with Stage I–II cervical cancer (?4 cm) arising from a small-sized uterus. Between October 2008 and August 2011, 19 patients with Stage I–II cervical cancer (?4 cm) were treated with external beam radiotherapy (EBRT) for the pelvis and CT-guided brachytherapy. Seven patients were treated with brachytherapy with standard loading of source-dwell positions and a fraction dose of 6 Gy at point A (conventional brachy-plan). The other 12 patients with a small uterus close to the rectum or small intestine were treated with brachytherapy with a point A dose-reduction to match D2cc of the rectum and <6 Gy as the dose constraint (‘point A dose-reduced plan’) instead of the 6-Gy plan at point A (‘tentative 6-Gy plan’). The total doses from EBRT and brachytherapy were added up and normalized to a biological equivalent dose of 2 Gy per fraction (EQD2). The median doses to the high-risk clinical target volume (HR-CTV) D90 in the conventional brachy-plan, tentative 6-Gy plan and point A dose-reduced plan were 62 GyEQD2, 80 GyEQD2 and 64 GyEQD2, respectively. The median doses of rectal D2cc in the corresponding three plans were 42 GyEQD2, 62 GyEQD2 and 51 GyEQD2, respectively. With a median follow-up period of 35 months, three patients developed Grade-1 late rectal complications and no patients developed local recurrence. Our preliminary results suggested that CT-guided brachytherapy using an individualized point A dose-reduced plan might be useful for reducing late rectal complications while maintaining primary tumor control. PMID:24566721

Nakagawa, Akiko; Ohno, Tatsuya; Noda, Shin-ei; Kubo, Nobuteru; Kuwako, Keiko; Saitoh, Jun-ichi; Nakano, Takashi

2014-01-01

119

Study of positional dependence of dose to bladder, pelvic wall and rectal points in High-Dose-Rate Brachytherapy in cervical cancer patients  

PubMed Central

The objective of the study is to examine the variation in doses to, Bladder, pelvic wall and Rectal Points when a patient is simulated in Supine (S Position) and Lithotomy M shaped positions (LM Position), respectively as part of Intracavitary Brachytherapy in Cervical Cancer patients. Patients (n = 19) were simulated and orthogonal images were taken in S Position and LM Positions on a physical simulator. Digital orthogonal X-ray images were transferred to Brachyvision Treatment Planning System via Dicom to generate treatment plans. Radio opaque dye of 7 ml was injected into the Foley bulb for identification and digitization of International Commission on Radiological Units and Measurements (ICRU) Bladder point. Pelvic side wall points were marked in accordance with ICRU 38 recommendations. A Rectal tube containing dummy source marker wire was used to identify Rectal Point. Students’t-test was used to analyze the results. Doses in LM Position were lower and statistically significant when compared to S Position for ICRU Bladder Point, pelvic walls and Rectal Point. It was observed that movement of applicator could be the reason for the variations in doses between the two positions. Bladder, pelvic wall and rectal points systematically registered lower doses in LM Position as compared to S Position. PMID:24672152

Talluri, Anil Kumar; Alluri, Krishnam Raju; Gudipudi, Deleep Kumar; Ahamed, Shabbir; Sresty, Madhusudhana M.; Reddy, Aparna Yarrama

2013-01-01

120

Study of positional dependence of dose to bladder, pelvic wall and rectal points in High-Dose-Rate Brachytherapy in cervical cancer patients.  

PubMed

The objective of the study is to examine the variation in doses to, Bladder, pelvic wall and Rectal Points when a patient is simulated in Supine (S Position) and Lithotomy M shaped positions (LM Position), respectively as part of Intracavitary Brachytherapy in Cervical Cancer patients. Patients (n = 19) were simulated and orthogonal images were taken in S Position and LM Positions on a physical simulator. Digital orthogonal X-ray images were transferred to Brachyvision Treatment Planning System via Dicom to generate treatment plans. Radio opaque dye of 7 ml was injected into the Foley bulb for identification and digitization of International Commission on Radiological Units and Measurements (ICRU) Bladder point. Pelvic side wall points were marked in accordance with ICRU 38 recommendations. A Rectal tube containing dummy source marker wire was used to identify Rectal Point. Students't-test was used to analyze the results. Doses in LM Position were lower and statistically significant when compared to S Position for ICRU Bladder Point, pelvic walls and Rectal Point. It was observed that movement of applicator could be the reason for the variations in doses between the two positions. Bladder, pelvic wall and rectal points systematically registered lower doses in LM Position as compared to S Position. PMID:24672152

Talluri, Anil Kumar; Alluri, Krishnam Raju; Gudipudi, Deleep Kumar; Ahamed, Shabbir; Sresty, Madhusudhana M; Reddy, Aparna Yarrama

2013-10-01

121

A proposed adaptive step size perturbation and observation maximum power point tracking algorithm based on photovoltaic system modeling  

NASA Astrophysics Data System (ADS)

Solar energy becomes one of the major alternative renewable energy options for its huge abundance and accessibility. Due to the intermittent nature, the high demand of Maximum Power Point Tracking (MPPT) techniques exists when a Photovoltaic (PV) system is used to extract energy from the sunlight. This thesis proposed an advanced Perturbation and Observation (P&O) algorithm aiming for relatively practical circumstances. Firstly, a practical PV system model is studied with determining the series and shunt resistances which are neglected in some research. Moreover, in this proposed algorithm, the duty ratio of a boost DC-DC converter is the object of the perturbation deploying input impedance conversion to achieve working voltage adjustment. Based on the control strategy, the adaptive duty ratio step size P&O algorithm is proposed with major modifications made for sharp insolation change as well as low insolation scenarios. Matlab/Simulink simulation for PV model, boost converter control strategy and various MPPT process is conducted step by step. The proposed adaptive P&O algorithm is validated by the simulation results and detail analysis of sharp insolation changes, low insolation condition and continuous insolation variation.

Huang, Yu

122

Impact of the Point Spread Function on Maximum Standardized Uptake Value Measurements in Patients with Pulmonary Cancer  

PubMed Central

Maximum standardized uptake value (SUVmax) from fluorodeoxyglucose (FDG) positron emission tomography (PET) scans is a semi quantitative measure that is increasingly used in the clinical practice for diagnostic and therapeutic response assessment purposes. Technological advances such as the implementation of the point spread function (PSF) in the reconstruction algorithm have led to higher signal to noise ratio and increased spatial resolution. The impact on SUVmax measurements has not been studied in clinical setting. We studied the impact of PSF on SUVmax in 30 consecutive lung cancer patients. SUVmax values were measured on PET-computed tomography (CT) scans reconstructed iteratively with and without PSF (respectively high-definition [HD] and non-HD). HD SUVmax values were significantly higher than non-HD SUVmax. There was excellent correlation between HD and non-HD values. Details of reconstruction and PSF implementation in particular have important consequences on SUV values. Nuclear Medicine physicians and radiologists should be aware of the reconstruction parameters of PET-CT scans when they report or rely on SUV measurements. PMID:25191128

Gellee, S.; Page, J.; Sanghera, B.; Payoux, P.; Wagner, Thomas

2014-01-01

123

Three-dimensional dosimetric considerations from different point A definitions in cervical cancer low-dose-rate brachytherapy  

PubMed Central

Purpose To investigate the dosimetric difference due to the different point A definitions in cervical cancer low-dose-rate (LDR) intracavitary brachytherapy. Material and methods Twenty CT-based LDR brachytherapy plans of 11 cervical patients were retrospectively reviewed. Two plans with point As following the modified Manchester system which defines point A being 2 cm superior to the cervical os along the tandem and 2 cm lateral (Aos), and the American Brachytherapy Society (ABS) guideline definition in which the point A is 2 cm superior to the vaginal fornices instead of os (Aovoid) were generated. Using the same source strength, two plans prescribed the same dose to Aos and Aovoid. Dosimetric differences between plans including point A dose rate, treatment volume encompassed by the prescription isodose line (TV), and dose rate of 2 cc of the rectum and bladder to the prescription dose were measured. Results On average Aovoid was 8.9 mm superior to Aos along the tandem direction with a standard deviation of 5.4 mm. With the same source strength and arrangement, Aos dose rate was 19% higher than Aovoid dose rate. The average TV(Aovoid) was 118.0 cc, which was 30% more than the average TV(Aos) of 93.0 cc. D2cc/D(Aprescribe) increased from 51% to 60% for rectum, and increased from 89% and 106% for bladder, if the prescription point changed from Aos to Aovoid. Conclusions Different point A definitions lead to significant dose differences. Careful consideration should be given when changing practice from one point A definition to another, to ensure dosimetric and clinical equivalency from the previous clinical experiences. PMID:24474971

Chen, Ting; Kim, Leonard H.; Nelson, Carl; Gabel, Molly; Narra, Venkat; Haffty, Bruce; Yue, Ning J.

2013-01-01

124

Methodology used to compute maximum potential doses from ingestion of edible plants and wildlife found on the Hanford Site  

SciTech Connect

The purpose of this report is to summarize the assumptions, dose factors, consumption rates, and methodology used to evaluate potential radiation doses to persons who may eat contaminated wildlife or contaminated plants collected from the Hanford Site. This report includes a description of the number and variety of wildlife and edible plants on the Hanford Site, methods for estimation of the quantities of these items consumed and conversion of intake of radionuclides to radiation doses, and example calculations of radiation doses from consumption of plants and wildlife. Edible plants on the publicly accessible margins of the shoreline of the Hanford Site and Wildlife that move offsite are potential sources of contaminated food for the general public. Calculations of potential radiation doses from consumption of agricultural plants and farm animal products are made routinely and reported annually for those produced offsite, using information about concentrations of radionuclides, consumption rates, and factors for converting radionuclide intake into dose. Dose calculations for onsite plants and wildlife are made intermittently when appropriate samples become available for analysis or when special studies are conducted. Consumption rates are inferred from the normal intake rates of similar food types raised offsite and from the edible weight of the onsite product that is actually available for harvest. 19 refs., 4 tabs.

Soldat, J.K.; Price, K.R.; Rickard, W.H.

1990-10-01

125

Maximum tolerated doses of methotrexate and 7-hydroxy-methotrexate in a model of acute toxicity in rats  

Microsoft Academic Search

Purpose: After more than 50?years of methotrexate (MTX) treatment of acute lymphoblastic leukaemia (ALL), it is currently believed\\u000a that as long as dose escalations are followed by adequate leucovorin rescue guided by monitoring MTX serum concentrations,\\u000a hydration and urinary alkalinization, high-dose MTX (HD-MTX) can be tolerated without life-threatening toxicity. However,\\u000a our recent experimental animal studies of the major metabolite of

Ole-Martin Fuskevåg; Christel Kristiansen; Sigurd Lindal; Jarle Aarbakke

2000-01-01

126

1023. Determination of the Maximum Tolerated Dose of the Replication-Competent Adenovirus Vector VRX-007 Following Intravenous Administration in Syrian Hamsters  

Microsoft Academic Search

We have developed the Syrian hamster as a permissive immunocompetent model to evaluate the safety and efficacy of replication-competent adenovirus (Ad) vectors for cancer gene therapy. One of our vectors is named VRX-007; VRX-007 overexpresses ADP, an Ad protein that mediates virus release and cell-to-cell spread. In order to determine the maximum tolerated dose (MTD) of VRX-007 in hamsters, we

Maria A. Thomas; Jacqueline F. Spencer; Jennifer M. Meyer; Marie C. LaRegina; Karoly Toth; Drew L. Lichtenstein; Ann E. Tollefson; Mohan Kuppuswamy; Baoling Ying; Louis A. Zumstein; William S. M. Wold

2005-01-01

127

Use of Lung Toxicity and Lung Particle Clearance to Estimate the Maximum Tolerated Dose (MTD) for a Fiber Glass Chronic Inhalation Study in the Rat  

Microsoft Academic Search

Short-term toxicity and lung clearance were assessed in rats exposed by inhalation to size-selected fibrous glass (FG) for 13 weeks. Results from this study and from a recent FG chronic inhalation study are presented here as guidelines for the selection of a maximum tolerated dose (MTD) for chronic inhalation studies of fibers. Fischer 344 rats were exposed using nose-only inhalation

T. W. Hesterberg; E. E. McConnell; W. C. Miiller; J. Chevalier; J. Everitt; P. Thevenaz; H. Fleissner; G. Oberdörster

1996-01-01

128

Phase I clinical trial to determine maximum tolerated dose of oral albendazole in patients with advanced cancer  

Microsoft Academic Search

Purpose  Albendazole is a potential anticancer agent that is currently under development for the treatment of cancer. We carried out\\u000a a dose-finding phase I study of oral albendazole in patients with advanced malignancies.\\u000a \\u000a \\u000a \\u000a Patients and methods  Thirty-six patients with refractory solid tumors were enrolled. Albendazole was given orally on a day 1–14 of a 3 weekly cycle,\\u000a starting at 400 mg BD with dose

Mohammad H. Pourgholami; Michael Szwajcer; Melvin Chin; Winston Liauw; Jonathan Seef; Peter Galettis; David L. Morris; Matthew Links

2010-01-01

129

RĆ©Ć©valuation of the Maximum Tolerated Dose of Continuous Venous Infusion of 5Fluorouracil with Pharmacokinetics  

Microsoft Academic Search

Fluorouracil (5-FU) was administered as a continuous ambulatory venous infusion to 25 patients in a Phase I trial. The principal dose limiting toxic effect observed was mucositis. Skin rash and diarrhea occurred less frequently. Hematological toxicity was modest, and no hepatic toxicity was seen. One partial remission of 138 days duration was seen in a patient with metastatic breast carcinoma

Darcy V. Spicer; Bach Ardalan; John R. Daniels; Howard Silberman; Kay Johnson

130

New Maximum Power Point Tracker Using Sliding-Mode Observer for Estimation of Solar Array Current in the Grid-Connected Photovoltaic System  

Microsoft Academic Search

A new maximum power point tracker (MPPT) for a grid-connected photovoltaic system without solar array current sensor is proposed. The solar array current information is obtained from the sliding-mode observer and fed into the MPPT to generate the reference voltage. The parameter values such as capacitances can be changed up to 50% from their nominal values, and the linear observer

Il-Song Kim; Myung-Bok Kim; Myung-Joong Youn

2006-01-01

131

Cascaded H-bridge multilevel converter for grid connected photovoltaic generators with independent maximum power point tracking of each solar array  

Microsoft Academic Search

This paper introduces a new control method and proportional PWM modulation of the cascaded H-bridge multilevel converter for grid-connected photovoltaic systems. This control makes each H-bridge module supply different power levels, allowing therefore for each module an independent maximum power point tracking of the corresponding photovoltaic array.

O. Alonso; P. Sanchis; E. Gubia; L. Marroyo

2003-01-01

132

Effect of maximum-tolerated doses and low-dose metronomic chemotherapy on serum vascular endothelial growth factor and thrombospondin-1 levels in patients with advanced nonsmall cell lung cancer  

Microsoft Academic Search

Background  Angiogenesis is regulated by a balance of both angiogenic inducers and inhibitors. This study was designed to evaluate the\\u000a effect of both maximum-tolerated doses (MTD) and low-dose metronomic chemotherapy (LDM) on serum vascular endothelial growth\\u000a factor (VEGF), thrombospondin-1 (TSP1) and VEGFR1 concentrations in patients with advanced nonsmall cell lung cancer.\\u000a \\u000a \\u000a \\u000a Patients and methods  Forty consecutive patients with advanced stage nonsmall cell

Faruk Tas; Derya Duranyildiz; Hilal O. Soydinc; Irfan Cicin; Meltem Selam; Kazim Uygun; Rian Disci; Vildan Yasasever; Erkan Topuz

2008-01-01

133

Safety and tolerability of metrifonate in patients with alzheimer's disease: Results of a maximum tolerated dose study  

Microsoft Academic Search

Metrifonate, a pro-drug that is transformed non-enzymatically into a potent inhibitor of acetylcholinesterase (AChE), has been used in the tropics for over 30 years for the treatment of schistosomiasis. A pilot study, and Phase I and Phase II studies of metrifonate in Alzheimer's disease (AD) patients conducted prior to the current study showed benign, dose-dependent adverse event profiles consisting primarily

Neal R Cutler; Stanford S Jhee; Pamela Cyrus; Florian Bieber; Paul TanPiengco; John J Sramek; Barbara Gulanski

1998-01-01

134

A Single-Stage Grid Connected Inverter Topology for Solar PV Systems With Maximum Power Point Tracking  

Microsoft Academic Search

This paper proposes a high performance, single-stage inverter topology for grid connected PV systems. The proposed configuration can not only boost the usually low photovoltaic (PV) array voltage, but can also convert the solar dc power into high quality ac power for feeding into the grid, while tracking the maximum power from the PV array. Total harmonic distortion of the

Sachin Jain; Vivek Agarwal

2007-01-01

135

Calculation of electron and isotopes dose point kernels with fluka Monte Carlo code for dosimetry in nuclear medicine therapy  

SciTech Connect

Purpose: The calculation of patient-specific dose distribution can be achieved by Monte Carlo simulations or by analytical methods. In this study, fluka Monte Carlo code has been considered for use in nuclear medicine dosimetry. Up to now, fluka has mainly been dedicated to other fields, namely high energy physics, radiation protection, and hadrontherapy. When first employing a Monte Carlo code for nuclear medicine dosimetry, its results concerning electron transport at energies typical of nuclear medicine applications need to be verified. This is commonly achieved by means of calculation of a representative parameter and comparison with reference data. Dose point kernel (DPK), quantifying the energy deposition all around a point isotropic source, is often the one. Methods: fluka DPKs have been calculated in both water and compact bone for monoenergetic electrons (10{sup -3} MeV) and for beta emitting isotopes commonly used for therapy ({sup 89}Sr, {sup 90}Y, {sup 131}I, {sup 153}Sm, {sup 177}Lu, {sup 186}Re, and {sup 188}Re). Point isotropic sources have been simulated at the center of a water (bone) sphere, and deposed energy has been tallied in concentric shells. fluka outcomes have been compared to penelope v.2008 results, calculated in this study as well. Moreover, in case of monoenergetic electrons in water, comparison with the data from the literature (etran, geant4, mcnpx) has been done. Maximum percentage differences within 0.8{center_dot}R{sub CSDA} and 0.9{center_dot}R{sub CSDA} for monoenergetic electrons (R{sub CSDA} being the continuous slowing down approximation range) and within 0.8{center_dot}X{sub 90} and 0.9{center_dot}X{sub 90} for isotopes (X{sub 90} being the radius of the sphere in which 90% of the emitted energy is absorbed) have been computed, together with the average percentage difference within 0.9{center_dot}R{sub CSDA} and 0.9{center_dot}X{sub 90} for electrons and isotopes, respectively. Results: Concerning monoenergetic electrons, within 0.8{center_dot}R{sub CSDA} (where 90%-97% of the particle energy is deposed), fluka and penelope agree mostly within 7%, except for 10 and 20 keV electrons (12% in water, 8.3% in bone). The discrepancies between fluka and the other codes are of the same order of magnitude than those observed when comparing the other codes among them, which can be referred to the different simulation algorithms. When considering the beta spectra, discrepancies notably reduce: within 0.9{center_dot}X{sub 90}, fluka and penelope differ for less than 1% in water and less than 2% in bone with any of the isotopes here considered. Complete data of fluka DPKs are given as Supplementary Material as a tool to perform dosimetry by analytical point kernel convolution. Conclusions: fluka provides reliable results when transporting electrons in the low energy range, proving to be an adequate tool for nuclear medicine dosimetry.

Botta, F.; Mairani, A.; Battistoni, G.; Cremonesi, M.; Di Dia, A.; Fasso, A.; Ferrari, A.; Ferrari, M.; Paganelli, G.; Pedroli, G.; Valente, M. [Medical Physics Department, European Institute of Oncology, Via Ripamonti 435, 20141 Milan (Italy); Istituto Nazionale di Fisica Nucleare (I.N.F.N.), Via Celoria 16, 20133 Milan (Italy); Medical Physics Department, European Institute of Oncology, Via Ripamonti 435, 20141 Milan (Italy); Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States); CERN, 1211 Geneva 23 (Switzerland); Medical Physics Department, European Institute of Oncology, Milan (Italy); Nuclear Medicine Department, European Institute of Oncology, Via Ripamonti 435, 2014 Milan (Italy); Medical Physics Department, European Institute of Oncology, Via Ripamonti 435, 20141 Milan (Italy); FaMAF, Universidad Nacional de Cordoba and CONICET, Cordoba, Argentina C.P. 5000 (Argentina)

2011-07-15

136

Calculation of electron and isotopes dose point kernels with fluka Monte Carlo code for dosimetry in nuclear medicine therapy  

SciTech Connect

The calculation of patient-specific dose distribution can be achieved by Monte Carlo simulations or by analytical methods. In this study, fluka Monte Carlo code has been considered for use in nuclear medicine dosimetry. Up to now, fluka has mainly been dedicated to other fields, namely high energy physics, radiation protection, and hadrontherapy. When first employing a Monte Carlo code for nuclear medicine dosimetry, its results concerning electron transport at energies typical of nuclear medicine applications need to be verified. This is commonly achieved by means of calculation of a representative parameter and comparison with reference data. Dose point kernel (DPK), quantifying the energy deposition all around a point isotropic source, is often the one.Methods: fluka DPKs have been calculated in both water and compact bone for monoenergetic electrons (10–3 MeV) and for beta emitting isotopes commonly used for therapy (89Sr, 90Y, 131I, 153Sm, 177Lu, 186Re, and 188Re). Point isotropic sources have been simulated at the center of a water (bone) sphere, and deposed energy has been tallied in concentric shells. fluka outcomes have been compared to penelope v.2008 results, calculated in this study as well. Moreover, in case of monoenergetic electrons in water, comparison with the data from the literature (etran, geant4, mcnpx) has been done. Maximum percentage differences within 0.8·RCSDA and 0.9·RCSDA for monoenergetic electrons (RCSDA being the continuous slowing down approximation range) and within 0.8·X90 and 0.9·X90 for isotopes (X90 being the radius of the sphere in which 90% of the emitted energy is absorbed) have been computed, together with the average percentage difference within 0.9·RCSDA and 0.9·X90 for electrons and isotopes, respectively.Results: Concerning monoenergetic electrons, within 0.8·RCSDA (where 90%–97% of the particle energy is deposed), fluka and penelope agree mostly within 7%, except for 10 and 20 keV electrons (12% in water, 8.3% in bone). The discrepancies between fluka and the other codes are of the same order of magnitude than those observed when comparing the other codes among them, which can be referred to the different simulation algorithms. When considering the beta spectra, discrepancies notably reduce: within 0.9·X90, fluka and penelope differ for less than 1% in water and less than 2% in bone with any of the isotopes here considered. Complete data of fluka DPKs are given as Supplementary Material as a tool to perform dosimetry by analytical point kernel convolution.Conclusions: fluka provides reliable results when transporting electrons in the low energy range, proving to be an adequate tool for nuclear medicine dosimetry.

Botta, F; Di Dia, A; Pedroli, G; Mairani, A; Battistoni, G; Fasso, A; Ferrari, A; Ferrari, M; Paganelli, G

2011-06-01

137

Half-dose Alteplase for Sub-massive Pulmonary Embolism Directed by Emergency Department Point-of-care Ultrasound  

PubMed Central

This report describes a patient with sub-massive pulmonary embolism (PE) who was successfully treated with half-dose thrombolytics guided by the use of point-of-care (POC) ultrasound. In this case, POC ultrasound was the only possible imaging since computed tomography was contraindicated. POC ultrasound demonstrated a deep vein thrombosis and evidence of cardiac strain. In situations or locations where definitive imaging is unobtainable, POC ultrasound can help diagnose submassive PE and direct the use of half-dose tissue plasminogen activator.

Amini, Richard; Panchal, Ashish R.; Bahner, David; Adhikari, Srikar

2015-01-01

138

A gradient Markov chain Monte Carlo algorithm for computing multivariate maximum likelihood estimates and posterior distributions: mixture dose-response assessment.  

PubMed

Multivariate probability distributions, such as may be used for mixture dose-response assessment, are typically highly parameterized and difficult to fit to available data. However, such distributions may be useful in analyzing the large electronic data sets becoming available, such as dose-response biomarker and genetic information. In this article, a new two-stage computational approach is introduced for estimating multivariate distributions and addressing parameter uncertainty. The proposed first stage comprises a?gradient Markov chain Monte Carlo?(GMCMC) technique to find Bayesian posterior mode estimates (PMEs) of parameters, equivalent to maximum likelihood estimates (MLEs) in the absence of subjective information. In the second stage, these estimates are used to initialize a Markov chain Monte Carlo (MCMC) simulation, replacing the conventional burn-in period to allow convergent simulation of the full joint Bayesian posterior distribution and the corresponding unconditional multivariate distribution (not conditional on uncertain parameter values). When the distribution of parameter uncertainty is such a Bayesian posterior, the unconditional distribution is termed?predictive. The method is demonstrated by finding conditional and unconditional versions of the recently proposed emergent dose-response function (DRF). Results are shown for the five-parameter common-mode and seven-parameter dissimilar-mode models, based on published data for eight benzene-toluene dose pairs. The common mode conditional DRF is obtained with a 21-fold reduction in data requirement versus MCMC. Example common-mode unconditional DRFs are then found using synthetic data, showing a 71% reduction in required data. The approach is further demonstrated for a PCB 126-PCB 153 mixture. Applicability is analyzed and discussed. Matlab(®) computer programs are provided. PMID:21906114

Li, Ruochen; Englehardt, James D; Li, Xiaoguang

2012-02-01

139

On dose distribution comparison  

NASA Astrophysics Data System (ADS)

In radiotherapy practice, one often needs to compare two dose distributions. Especially with the wide clinical implementation of intensity-modulated radiation therapy, software tools for quantitative dose (or fluence) distribution comparison are required for patient-specific quality assurance. Dose distribution comparison is not a trivial task since it has to be performed in both dose and spatial domains in order to be clinically relevant. Each of the existing comparison methods has its own strengths and weaknesses and there is room for improvement. In this work, we developed a general framework for comparing dose distributions. Using a new concept called maximum allowed dose difference (MADD), the comparison in both dose and spatial domains can be performed entirely in the dose domain. Formulae for calculating MADD values for various comparison methods, such as composite analysis and gamma index, have been derived. For convenience in clinical practice, a new measure called normalized dose difference (NDD) has also been proposed, which is the dose difference at a point scaled by the ratio of MADD to the predetermined dose acceptance tolerance. Unlike the simple dose difference test, NDD works in both low and high dose gradient regions because it considers both dose and spatial acceptance tolerances through MADD. The new method has been applied to a test case and a clinical example. It was found that the new method combines the merits of the existing methods (accurate, simple, clinically intuitive and insensitive to dose grid size) and can easily be implemented into any dose/intensity comparison tool.

Jiang, Steve B.; Sharp, Greg C.; Neicu, Toni; Berbeco, Ross I.; Flampouri, Stella; Bortfeld, Thomas

2006-02-01

140

Pharmacokinetic and Maximum Tolerated Dose Study of Micafungin in Combination with Fluconazole versus Fluconazole Alone for Prophylaxis of Fungal Infections in Adult Patients Undergoing a Bone Marrow or Peripheral Stem Cell Transplant  

Microsoft Academic Search

In this dose escalation study, 74 adult cancer patients undergoing bone marrow or peripheral blood stem cell transplantation received fluconazole (400 mg\\/day) and either normal saline (control) (12 subjects) or mica- fungin (12.5 to 200 mg\\/day) (62 subjects) for up to 4 weeks. The maximum tolerated dose (MTD) of micafungin was not reached, based on the development of Southwest Oncology

J. Hiemenz; P. Cagnoni; D. Simpson; S. Devine; N. Chao; J. Keirns; W. Lau; D. Facklam; D. Buell

2005-01-01

141

Predicting the maximum-tolerated dose of PNU-159548 (4-demethoxy-3?-deamino-3?-aziridinyl-4?-methylsulphonyl-daunorubicin) in humans using CFU-GM clonogenic assays and prospective validation  

Microsoft Academic Search

A haematotoxicity model was proposed by Parchment in 1998 to predict the maximum-tolerated dose (MTD) in humans of myelosuppressive antitumour agents by combining data from in vitro clonogenic assays on haematopoietic progenitors and in vivo systemic exposure data in animals. A prospective validation of this model in humans was performed with PNU-159548, a novel agent showing selective dose-limiting myelosuppression in

D Moneta; C Geroni; O Valota; P Grossi; M. J. A de Jonge; M Brughera; E Colajori; M Ghielmini; C Sessa

2003-01-01

142

Variability in reference point microindentation and recommendations for testing cortical bone: Maximum load, sample orientation, mode of use, sample preparation and measurement spacing.  

PubMed

Reference Point Indentation (RPI) is a novel microindentation tool that has emerging clinical potential for the assessment of fracture risk as well as use as a laboratory tool for straight-forward mechanical characterisation of bone. Despite increasing use of the tool, little research is available to advise the set-up of testing protocols or optimisation of testing parameters. Here we consider five such parameters: maximum load, sample orientation, mode of use, sample preparation and measurement spacing, to investigate how they affect the Indentation Distance Increase (IDI), the most published measurement parameter associated with the RPI device. The RPI tool was applied to bovine bone; indenting in the proximal midshaft of five femora and human bone; indenting five femoral heads and five femoral neck samples. Based on the findings of these studies we recommend the following as the best practice. (1) Repeat measurements should be utilised to reduce the coefficient of variation (e.g. 8-15 repeats to achieve a 5-10% error, however the 3-5 measurements used here gives a 15-20% error). (2) IDI is dependent on maximum load (r=0.45 on the periosteal surface and r=0.94 on the machined surface, p<0.05), mode of use (i.e. comparing the device held freehand compared to fixed in its stand, p=0.04) and surface preparation (p=0.004) so these should be kept consistent throughout testing. Though sample orientation appears to have minimal influence on IDI (p>0.05), care should also be taken in combining measurements from different orientations. (3) The coefficient of variation is higher (p=0.04) when holding the device freehand, so it should ideally be kept supported in its stand. (4) Removing the periosteum (p=0.04) and machining the surface of the bone (p=0.08) reduces the coefficient of variation, so should be performed where practical. (5) There is a hyperbolic relationship between thickness and IDI (p<0.001) with a sample thickness 10 fold greater than the maximum indentation depth recommended, to ensure a representative measurement. (6) Measurement spacing does not appear to influence the IDI (p>0.05), so it can be as low as 500µm. By following these recommendations, RPI users can minimise the potential confounding effects associated with the variables investigated here and reduce the coefficient of variation, hence achieving more consistent testing. This optimisation of the technique enhances both the clinical and laboratory potential of the tool. PMID:25455607

Jenkins, T; Coutts, L V; Dunlop, D G; Oreffo, R O C; Cooper, C; Harvey, N C; Thurner, P J

2015-02-01

143

Zero, minimum and maximum relative radial acceleration for planar formation flight dynamics near triangular libration points in the Earth-Moon system  

NASA Astrophysics Data System (ADS)

Assume a constellation of satellites is flying near a given nominal trajectory around L4 or L5 in the Earth-Moon system in such a way that there is some freedom in the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual distances between spacecraft. In this case, the existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. In the other case, the existence of regions of maximum relative radial acceleration with respect to the nominal trajectory will produce a larger expansion and contraction of the constellation. The goal of this paper is to study these regions in the scenario of the Circular Restricted Three Body Problem by means of a linearization of the equations of motion relative to the periodic orbits around L4 or L5. This study corresponds to a preliminar planar formation flight dynamics about triangular libration points in the Earth-Moon system. Additionally, the cost estimate to maintain the constellation in the regions of zero and minimum relative radial acceleration or keeping a rigid configuration is computed with the use of the residual acceleration concept. At the end, the results are compared with the dynamical behavior of the deviation of the constellation from a periodic orbit.

Salazar, F. J. T.; Masdemont, J. J.; Gómez, G.; Macau, E. E.; Winter, O. C.

2014-11-01

144

Etoposide (VP-16) and cisplatin at maximum tolerated dose in non-small cell lung carcinoma: a Cancer and Leukemia Group B study  

Microsoft Academic Search

A multi-institutional cooperative group trial was undertaken by the Cancer and Leukemia Group B (CALGB) to evaluate the efficacy of the combination of cisplatin and intravenous etoposide for the treatment of metastatic or recurrent non-small cell lung cancer (NSCLC). The doses used were those previously determined to be the maximally tolerated dose of this drug combination. Forty patients were entered

Joseph J. Muscato; Constance Cirrincione; Gerald Clamon; Michael C. Perry; George Omura; Irving Berkowitz; Thomas Reid; James E. Herndon; Mark R. Green

1995-01-01

145

Comparison between CT-based volumetric calculations and ICRU reference-point estimates of radiation doses delivered to bladder and rectum during intracavitary radiotherapy for cervical cancer  

Microsoft Academic Search

Purpose: To compare CT-based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the bladder and rectum in patients with carcinoma of the uterine cervix treated with definitive low-dose-rate intracavitary radiotherapy (ICRT). Methods and Materials: Between November 2001 and March 2003, 60 patients were prospectively enrolled in a pilot study of ICRT

Christopher E. Pelloski; Matthew B. S. Palmer; Gregory M. Chronowski; Anuja Jhingran; John Horton; Patricia J.. Eifel

2005-01-01

146

Inhibitory effects of fluorinated pyrimidines, 5¢-DFUR, UFT and T-506, in a model of hepatic metastasis of mouse colon 26 adenocarcinoma - assessment of inhibitory activity and adverse reactions at the maximum tolerated dose  

Microsoft Academic Search

The effects of fluorinated pyrimidines, 5¢-DFUR, UFT and T-506, on a mouse model of hepatic metastasis were assessed in regard to inhibitory activity and adverse reactions at the maximum tolerated dose. The model was prepared by injecting the mouse colonic cancer cell line, colon 26, into the portal vein of CDF1 mice. At the treatment regimens employed for 5¢-DFUR (1.0mmol\\/kg\\/day,

Kenji Tazawa; Takashi Sakamoto; Yoshito Kuroki; Iwao Yamashita; Masahiro Okamoto; Shinnya Katuyama; Masao Fujimaki

1997-01-01

147

ARMA-Based SEM When the Number of Time Points T Exceeds the Number of Cases N: Raw Data Maximum Likelihood.  

ERIC Educational Resources Information Center

Demonstrated, through simulation, that stationary autoregressive moving average (ARMA) models may be fitted readily when T>N, using normal theory raw maximum likelihood structural equation modeling. Also provides some illustrations based on real data. (SLD)

Hamaker, Ellen L.; Dolan, Conor V.; Molenaar, Peter C. M.

2003-01-01

148

Why are there no really big bony fishes? A point-of-view on maximum body size in teleosts and elasmobranchs  

Microsoft Academic Search

The most massive teleost, the ocean sunfish(Mola mola), is an order of magnitude smaller than the largest cartilaginous fish,the whale shark (Rhincodon typus), and issignificantly smaller than several other extantelasmobranch species. Possible reasons for this discrepancy in maximum size include:anatomical, physiological, ecological, and life-history\\/ontogenetic constraints. Weexamined life-history traits and growth ratesas the most likely constraints on maximum teleostsize. For pelagic

Jonathan A. Freedman; David L. G. Noakes

2002-01-01

149

Simulation of the Nonlinear Dose Dependence of Stabilized Point Defects This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

, the optical density at the F band peak goes like the square root of time of irradiation by deuterium UV light dependence of the concentration of point defects in alkali-halides as well as other crystals, as exhibited by the dependence of the thermoluminescence (TL), optical absorption and ESR on the dose of non-ionizing UV

Chen, Reuven

150

An Innovative Phase I Trial Design Allowing for the Identification of Multiple Potential Maximum Tolerated Doses with Combination Therapy of Targeted Agents  

Microsoft Academic Search

Treatment for cancer often involves combination therapies used both in medical practice and clinical trials. Korn and Simon listed three reasons for the utility of combinations: 1) biochemical synergism, 2) differential susceptibility of tumor cells to different agents, and 3) higher achievable dose intensity by exploiting non-overlapping toxicities to the host. Even if the toxicity profile of each agent of

Sarina A Piha-Paul

2010-01-01

151

The maximum tolerated dose and biologic effects of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) in combination with irinotecan for patients with refractory solid tumors  

PubMed Central

Purpose 3-AP is a ribonucleotide reductase inhibitor and has been postulated to act synergistically with other chemotherapeutic agents. This study was conducted to determine the toxicity and antitumor activity of 3-AP with irinotecan. Correlative studies included pharmacokinetics and the effects of ABCB1 and UGT1A1 polymorphisms. Methods The treatment plan consisted of irinotecan on day 1 with 3-AP on days 1-3 of a 21-day cycle. Starting dose was irinotecan 150 mg/m2 and 3-AP 85 mg/m2/d. Polymorphisms of ABCB1 were evaluated by pyrosequencing. Drug concentrations were determined by HPLC. Results Twenty-three patients were enrolled, 10 men and 13 women. Tumor types included 7 patients with pancreatic cancer, 4 with lung cancer, 2 with cholangiocarcinoma, 2 with mesothelioma, 2 with ovarian cancer, and 6 with other malignancies. Two patients experienced dose-limiting toxicity (DLT) at dose level 1, requiring amendment of the dose escalation scheme. Maximal tolerated dose (MTD) was determined to be 3-AP 60 mg/m2/d and irinotecan 200 mg/m2. DLTs consisted of hypoxia, leukopenia, fatigue, infection, thrombocytopenia, dehydration and ALT elevation. One partial response in a patient with refractory non-small cell lung cancer was seen. Genotyping suggests that patients with wild-type ABCB1 have a higher rate of grade 3 or 4 toxicity than those with ABCB1 mutations. Conclusions The MTD for this combination was 3-AP 60 mg/m2/d on days 1-3 and irinotecan 200 mg/m2 on day 1 every 21 days. Antitumor activity in a patient with refractory non-small cell lung cancer was noted at level 1. PMID:20127092

Choi, Brian S.; Alberti, Dona B.; Schelman, William R.; Kolesar, Jill M.; Thomas, James P.; Marnocha, Rebecca; Eickhoff, Jens C.; Ivy, S. Percy; Wilding, George; Holen, Kyle D.

2010-01-01

152

Novel applications using maximum-likelihood estimation in optical metrology and nuclear medical imaging: Point-diffraction interferometry and BazookaPET  

NASA Astrophysics Data System (ADS)

This dissertation aims to investigate two different applications in optics using maximum-likelihood (ML) estimation. The first application of ML estimation is used in optical metrology. For this application, an innovative iterative search method called the synthetic phase-shifting (SPS) algorithm is proposed. This search algorithm is used for estimation of a wavefront that is described by a finite set of Zernike Fringe (ZF) polynomials. In this work, we estimate the ZF coefficient, or parameter values of the wavefront using a single interferogram obtained from a point-diffraction interferometer (PDI). In order to find the estimates, we first calculate the squared-difference between the measured and simulated interferograms. Under certain assumptions, this squared-difference image can be treated as an interferogram showing the phase difference between the true wavefront deviation and simulated wavefront deviation. The wavefront deviation is defined as the difference between the reference and the test wavefronts. We calculate the phase difference using a traditional phase-shifting technique without physical phase-shifters. We present a detailed forward model for the PDI interferogram, including the effect of the nite size of a detector pixel. The algorithm was validated with computational studies and its performance and constraints are discussed. A prototype PDI was built and the algorithm was also experimentally validated. A large wavefront deviation was successfully estimated without using null optics or physical phase-shifters. The experimental result shows that the proposed algorithm has great potential to provide an accurate tool for non-null testing. The second application of ML estimation is used in nuclear medical imaging. A high-resolution positron tomography scanner called BazookaPET is proposed. We have designed and developed a novel proof-of-concept detector element for a PET system called BazookaPET. In order to complete the PET configuration, at least two detector elements are required to detect positron-electron annihilation events. Each detector element of the BazookaPET has two independent data-acquisition channels. One of the detector channels is a 4 x 4 silicon photomultiplier (SiPM) array referred to as the SiPM-side. The SiPM-side is directly coupled to an optical window of the scintillator with optical grease. The other channel is a CCD-based gamma camera with an imaging intensier called the Bazooka-side. Instead of coupling by direct contact like the SiPM-side, an F/1.4 lens pair is used for optical coupling. The scintillation light from the opposite optical window to the SiPM-side is imaged by the F/1.4 lens to the Bazooka-side. Using these two separate channels, we can potentially obtain high energy, temporal and spatial resolution data by associating the data outputs via several ML estimation steps. We present the concept of the system and the prototype detector element. In this work, we focus on characterizing individual detector channels, and initial experimental calibration results are shown along with preliminary performance-evaluation results. We also address the limitations and the challenges of associating the outputs of the two detector channels.

Park, Ryeojin

153

Metronomic chemotherapy: An attractive alternative to maximum tolerated dose therapy that can activate anti-tumor immunity and minimize therapeutic resistance.  

PubMed

The administration of chemotherapy at reduced doses given at regular, frequent time intervals, termed 'metronomic' chemotherapy, presents an alternative to standard maximal tolerated dose (MTD) chemotherapy. The primary target of metronomic chemotherapy was originally identified as endothelial cells supporting the tumor vasculature, and not the tumor cells themselves, consistent with the emerging concept of cancer as a systemic disease involving both tumor cells and their microenvironment. While anti-angiogenesis is an important mechanism of action of metronomic chemotherapy, other mechanisms, including activation of anti-tumor immunity and a decrease in acquired therapeutic resistance, have also been identified. Here we present evidence supporting a mechanistic explanation for the improved activity of cancer chemotherapy when administered on a metronomic, rather than an MTD schedule and discuss the implications of these findings for further translation into the clinic. PMID:25541061

Kareva, Irina; Waxman, David J; Lakka Klement, Giannoula

2015-03-28

154

Assessment of the health effects of chemicals in humans: I. QSAR estimation of the maximum recommended therapeutic dose (MRTD) and no effect level (NOEL) of organic chemicals based on clinical trial data.  

PubMed

The primary objective of this investigation was to develop a QSAR model to estimate the no effect level (NOEL) of chemicals in humans using data derived from pharmaceutical clinical trials and the MCASE software program. We believe that a NOEL model derived from human data provides a more specific estimate of the toxic dose threshold of chemicals in humans compared to current risk assessment models which extrapolate from animals to humans employing multiple uncertainty safety factors. A database of the maximum recommended therapeutic dose (MRTD) of marketed pharmaceuticals was compiled. Chemicals with low MRTDs were classified as high-toxicity compounds; chemicals with high MRTDs were classified as low-toxicity compounds. Two separate training data sets were constructed to identify specific structural alerts associated with high and low toxicity chemicals. A total of 134 decision alerts correlated with toxicity in humans were identified from 1309 training data set chemicals. An internal validation experiment showed that predictions for high- and low-toxicity chemicals were good (positive predictivity >92%) and differences between experimental and predicted MRTDs were small (0.27-0.70 log-fold). Furthermore, the model exhibited good coverage (89.9-93.6%) for three classes of chemicals (pharmaceuticals, direct food additives, and food contact substances). An additional investigation demonstrated that the maximum tolerated dose (MTD) of chemicals in rodents was poorly correlated with MRTD values in humans (R2 = 0.2005, n = 326). Finally, this report discusses experimental factors which influence the accuracy of test chemical predictions, potential applications of the model, and the advantages of this model over those that rely only on results of animal toxicology studies. PMID:16472220

Matthews, Edwin J; Kruhlak, Naomi L; Benz, R Daniel; Contrera, Joseph F

2004-01-01

155

Evaluation of Rectal Dose During High-Dose-Rate Intracavitary Brachytherapy for Cervical Carcinoma  

SciTech Connect

High-dose-rate intracavitary brachytherapy (HDR-ICBT) for carcinoma of the uterine cervix often results in high doses being delivered to surrounding organs at risk (OARs) such as the rectum and bladder. Therefore, it is important to accurately determine and closely monitor the dose delivered to these OARs. In this study, we measured the dose delivered to the rectum by intracavitary applications and compared this measured dose to the International Commission on Radiation Units and Measurements rectal reference point dose calculated by the treatment planning system (TPS). To measure the dose, we inserted a miniature (0.1 cm{sup 3}) ionization chamber into the rectum of 86 patients undergoing radiation therapy for cervical carcinoma. The response of the miniature chamber modified by 3 thin lead marker rings for identification purposes during imaging was also characterized. The difference between the TPS-calculated maximum dose and the measured dose was <5% in 52 patients, 5-10% in 26 patients, and 10-14% in 8 patients. The TPS-calculated maximum dose was typically higher than the measured dose. Our study indicates that it is possible to measure the rectal dose for cervical carcinoma patients undergoing HDR-ICBT. We also conclude that the dose delivered to the rectum can be reasonably predicted by the TPS-calculated dose.

Sha, Rajib Lochan [Department of Radiation Physics, Indo-American Cancer Institute and Research Centre, Hyderabad (India); Department of Physics, Osmania University, Hyderabad (India); Reddy, Palreddy Yadagiri [Department of Physics, Osmania University, Hyderabad (India); Rao, Ramakrishna [Department of Radiation Physics, MNJ Institute of Oncology and Regional Cancer Center, Hyderabad (India); Muralidhar, Kanaparthy R. [Department of Radiation Physics, Indo-American Cancer Institute and Research Centre, Hyderabad (India); Kudchadker, Rajat J., E-mail: rkudchad@mdanderson.org [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)

2011-01-01

156

Maximum Likelihood  

NSDL National Science Digital Library

This material introduces the basic theory of maximum likelihood estimation by discussing the likelihood function, the log likelihood function, and maximizing these functions using calculus. Several exercises ask students to derive certain estimators, while others have students compare the behavior of those estimators with other possibilities through the use of various JAVA applets. The applets use the same control features: the sliders set the parameter values, the Ā?Stop #Ā? drop down menu sets the number of samples taken, the Ā?Update #Ā? drop down menu sets how often the graph and tables update during the experiment, the single arrow takes one sample, the double arrow runs the full experiment, the square stops the experiment, and the back arrow resets the applet. This page is one lesson from the Virtual Laboratories in Statistics.

Siegrist, Kyle

157

MAXIMUM ADDITIONAL SCORE: 2 points Description  

E-print Network

) 3. PRESENTATION (SINGLE PERSON): MIN 10 MAX 12 SLIDES IN ENGLISH 4. PRESENTATION (TWO PERSONS): MIN 15 MAX 20 IN ENGLISH 5. First-Come-First-Serve procedure will be followed #12; Multi Challenge the Future of Multicore 5. IC Power Delivery-Voltage Regulation and Conversion, System

Silvano, Cristina

158

Recovery behavior of point defects after low-dose neutron irradiation at ˜423 K of sintered 6H-SiC by lattice parameter and macroscopic length measurements  

NASA Astrophysics Data System (ADS)

To evaluate neutron-irradiation-induced crystalline defects and its thermal stability, ?-SiC sintered bodies consisting of mainly 6H polytype were neutron irradiated using the Japan Materials Testing Reactor up to 1.9 × 1023 n/m2 (E > 0.1 MeV) at a low temperature of ˜423 K. Due to very low dose irradiation at low temperature, expected defects induced into crystalline lattice should only be simple point defects. Changes in the lattice parameters and macroscopic lengths resulting from post-irradiation isothermal annealing up to 6 h between room temperature and 1673 K were measured. Macroscopic volume swelling of ?-SiC specimens coincided well to those of unit cell volume changes, indicating the presence of only simple defects. The recovery behavior of the macroscopic length and lattice parameters showed almost the same tendencies, although residual changes in the c-axis length slightly exceeded that of the a-axis length at temperatures lower than 1273 K. Difference in these axes lengths diminished at temperatures above 1273 K. Calculation of activation energies, obtained from precise length measurement using a dilatometer during each isothermal annealing step, revealed that length recovery behavior between 473 and 1573 K could almost be completely explained by a first-order reaction, and three stages with activation energies of 0.14, 0.26, and 1.13 eV. Changes in activation energy were related to the behavior of lattice parameter changes. The results indicated the presence of several kinds of point defects, some of which induced anisotropic lattice expansion.

Yano, Toyohiko; Futamura, Yusuke; Yamazaki, Saishun; Sawabe, Takashi; Yoshida, Katsumi

2013-11-01

159

Benchmark Dose Modeling  

EPA Science Inventory

Finite doses are employed in experimental toxicology studies. Under the traditional methodology, the point of departure (POD) value for low dose extrapolation is identified as one of these doses. Dose spacing necessarily precludes a more accurate description of the POD value. ...

160

Variability of Marker-Based Rectal Dose Evaluation in HDR Cervical Brachytherapy  

SciTech Connect

In film-based intracavitary brachytherapy for cervical cancer, position of the rectal markers may not accurately represent the anterior rectal wall. This study was aimed at analyzing the variability of rectal dose estimation as a result of interfractional variation of marker placement. A cohort of five patients treated with multiple-fraction tandem and ovoid high-dose-rate (HDR) brachytherapy was studied. The cervical os point and the orientation of the applicators were matched among all fractional plans for each patient. Rectal points obtained from all fractions were then input into each clinical treated plan. New fractional rectal doses were obtained and a new cumulative rectal dose for each patient was calculated. The maximum interfractional variation of distances between rectal dose points and the closest source positions was 1.1 cm. The corresponding maximum variability of fractional rectal dose was 65.5%. The percentage difference in cumulative rectal dose estimation for each patient was 5.4%, 19.6%, 34.6%, 23.4%, and 13.9%, respectively. In conclusion, care should be taken when using rectal markers as reference points for estimating rectal dose in HDR cervical brachytherapy. The best estimate of true rectal dose for each fraction should be determined by the most anterior point among all fractions.

Wang Zhou, E-mail: Zhou.Wang@RoswellPark.or [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY (United States); Jaggernauth, Wainwright; Malhotra, Harish K.; Podgorsak, Matthew B. [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY (United States)

2010-01-01

161

In Vivo Dosimetry of High-Dose-Rate Interstitial Brachytherapy in the Pelvic Region: Use of a Radiophotoluminescence Glass Dosimeter for Measurement of 1004 Points in 66 Patients With Pelvic Malignancy  

SciTech Connect

Purpose: To perform the largest in vivo dosimetry study for interstitial brachytherapy yet to be undertaken using a new radiophotoluminescence glass dosimeter (RPLGD) in patients with pelvic malignancy and to study the limits of contemporary planning software based on the results. Patients and Methods: Sixty-six patients with pelvic malignancy were treated with high-dose-rate interstitial brachytherapy, including prostate (n = 26), gynecological (n = 35), and miscellaneous (n = 5). Doses for a total of 1004 points were measured by RPLGDs and calculated with planning software in the following locations: rectum (n = 549), urethra (n = 415), vagina (n = 25), and perineum (n = 15). Compatibility (measured dose/calculated dose) was analyzed according to dosimeter location. Results: The compatibility for all dosimeters was 0.98 {+-} 0.23, stratified by location: rectum, 0.99 {+-} 0.20; urethra, 0.96 {+-} 0.26; vagina, 0.91 {+-} 0.08; and perineum, 1.25 {+-} 0.32. Conclusions: Deviations between measured and calculated doses for the rectum and urethra were greater than 20%, which is attributable to the independent movements of these organs and the applicators. Missing corrections for inhomogeneity are responsible for the 9% negative shift near the vaginal cylinder (specific gravity = 1.24), whereas neglect of transit dose contributes to the 25% positive shift in the perineal dose. Dose deviation of >20% for nontarget organs should be taken into account in the planning process. Further development of planning software and a real-time dosimetry system are necessary to use the current findings and to achieve adaptive dose delivery.

Nose, Takayuki [Department of Radiation Oncology, Cancer Institute Hospital of the Japanese Foundation for Cancer Research, Tokyo (Japan); Department of Physics, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo (Japan)], E-mail: takayuki.nose@jfcr.or.jp; Koizumi, Masahiko [Department of Radiation Oncology, Osaka Medical Center, Osaka (Japan); Yoshida, Ken [Department of Radiology, Osaka National Hospital, Osaka (Japan); Nishiyama, Kinji; Sasaki, Junichi; Ohnishi, Takeshi [Department of Radiation Oncology, Osaka Medical Center, Osaka (Japan); Kozuka, Takuyo; Gomi, Kotaro; Oguchi, Masahiko [Department of Radiation Oncology, Cancer Institute Hospital of the Japanese Foundation for Cancer Research, Tokyo (Japan); Sumida, Iori [Department of Radiation Oncology, Cancer Institute Hospital of the Japanese Foundation for Cancer Research, Tokyo (Japan); Department of Physics, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo (Japan); Takahashi, Yutaka; Ito, Akira [Department of Physics, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo (Japan); Yamashita, Takashi [Department of Radiation Oncology, Cancer Institute Hospital of the Japanese Foundation for Cancer Research, Tokyo (Japan); Department of Physics, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo (Japan)

2008-02-01

162

Fictitious Hyperglycemia: Point-of-Care Glucose Measurement Is Inaccurate During High-Dose Vitamin C Infusion for Burn Shock Resuscitation.  

PubMed

The use of high-dose vitamin C (hdVC, 66?mg/kg/hour × 18 hours) infusion is a useful adjunct to reducing fluid requirements during resuscitation of burn shock. Routine point-of-care glucose (POCG) analysis has been inaccurately high in observed patients undergoing hdVC. Inaccurate POCG could potentially lead to iatrogenic hypoglycemia if the fictitious hyperglycemia is treated with insulin. This study is a retrospective analysis of plasma glucose measurements from a central laboratory (LG) compared with POCG during and 24 hours after hdVC infusion. Records of adult patients receiving hdVC infusions during burn resuscitation over 1 year were reviewed. Charts selected for analysis included those with glucose measurements using POCG and LG that were taken simultaneously, during hdVC infusion, and 24 hours after completion. All specimens were drawn from arterial lines. POCG was measured with Accu-Chek Inform (Roche, Indianapolis, IN) and LG was measured by Siemens Dimension Vista 500 (Siemens, Deerfield, IL) using biochromic analysis. Nonparametric statistical analysis was performed using Wilcoxon's matched pairs test and Spearman correlation with significance at P < .05. Of 18 adult patients undergoing burn resuscitation with hdVC infusion, 5 were chosen for analysis (%TBSA 40?±?15; age 51?±?18). All data were pooled with 11 comparisons both during and after hdVC. The mean POCG (225?±?71) was significantly higher than mean LG (138?±?41) on hdVC (P = .002). There was no difference between POCG (138?±?30) and LG (128?±?23) after hdVC was finished (P = .09). There was a negative correlation between POCG and LG on hdVC (-0.64, P = .04) and a positive correlation off hdVC (0.89, P = .0005). POCG analysis during hdVC infusion is significantly higher than laboratory glucose measurements. Once the hdVC infusion is complete, POCG and laboratory glucose measurements are not statistically different. Treating erroneously high glucose based on POC testing is potentially dangerous and could lead to hypoglycemia and seizures. PMID:25162951

Kahn, Steven A; Lentz, Christopher W

2014-08-26

163

MAMMARY GLAND DEVELOPMENT AS A SENSITIVE END-POINT FOLLOWING ACUTE PERNATAL EXPOSURE TO A LOW DOSE ATRAZINE METABOLITE MIXTURE IN FEMALE LONG EVANS RATS  

EPA Science Inventory

In order to characterize the potential developmental effects of atrazine (ATR) metabolites at low doses, an environmentally-based mixture (EBM) of ATR and its metabolites hydroxyatrazine, diaminochlorotriazine, deethylatrazine, and deisopropylatrazine was formulated based on surv...

164

The effect of dose heterogeneity on radiation risk in medical imaging.  

PubMed

The current estimations of risk associated with medical imaging procedures rely on assessing the organ dose via direct measurements or simulation. The dose to each organ is assumed to be homogeneous. To take into account the differences in radiation sensitivities, the mean organ doses are weighted by a corresponding tissue-weighting coefficients provided by ICRP to calculate the effective dose, which has been used as a surrogate of radiation risk. However, those coefficients were derived under the assumption of a homogeneous dose distribution within each organ. That assumption is significantly violated in most medical-imaging procedures. In helical chest CT, for example, superficial organs (e.g. breasts) demonstrate a heterogeneous dose distribution, whereas organs on the peripheries of the irradiation field (e.g. liver) might possess a discontinuous dose profile. Projection radiography and mammography involve an even higher level of organ dose heterogeneity spanning up to two orders of magnitude. As such, mean dose or point measured dose values do not reflect the maximum energy deposited per unit volume of the organ. In this paper, the magnitude of the dose heterogeneity in both CT and projection X-ray imaging was reported, using Monte Carlo methods. The lung dose demonstrated factors of 1.7 and 2.2 difference between the mean and maximum dose for chest CT and radiography, respectively. The corresponding values for the liver were 1.9 and 3.5. For mammography and breast tomosynthesis, the difference between mean glandular dose and maximum glandular dose was 3.1. Risk models based on the mean dose were found to provide a reasonable reflection of cancer risk. However, for leukaemia, they were found to significantly under-represent the risk when the organ dose distribution is heterogeneous. A systematic study is needed to develop a risk model for heterogeneous dose distributions. PMID:23118440

Samei, Ehsan; Li, Xiang; Chen, Baiyu; Reiman, Robert

2013-06-01

165

SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: Measurement of radiation dose at the north interaction point of BEPC II  

NASA Astrophysics Data System (ADS)

The technique details for measuring radiation dose are expounded. The results of gamma and neutron radiation levels are presented and the corresponding radiation shielding is discussed based on the simplified estimation. In addition, the photon radiation level move as background for future experiments is measured by a NaI(Tl) detector.

Mo, Xiao-Hu; Zhang, Jian-Yong; Zhang, Tian-Bao; Zhang, Qing-Jiang; Achasov, Mikhail; Fu, Cheng-Dong; Muchnoi, Nikolay; Qin, Qing; Qu, Hua-Min; Wang, Yi-Fang; Wu, Jing-Min; Xu, Jin-Qiang; Yu, Bo-Xiang

2009-10-01

166

Neural network modelling of dose distribution and dose uniformity in the Tunisian Gamma Irradiator.  

PubMed

In this paper an approach to model dose distributions, isodose curves and dose uniformity in the Tunisian Gamma Irradiation Facility using artificial neural networks (ANNs) are described. For this purpose, measurements were carried out at different points in the irradiation cell using polymethyl methacrylate dosemeters. The calculated and experimental results are compared and good agreement is observed showing that ANNs can be used as an efficient tool for modelling dose distribution in the gamma irradiation facility. Monte Carlo (MC) photon-transport simulation techniques have been used to evaluate the spatial dose distribution for extensive benchmarking. ANN approach appears to be a significant advance over the time-consuming MC or the less accurate regression methods for dose mapping. As a second application, a detailed dose mapping using two different product densities was carried out. The minimum and maximum dose locations and dose uniformity as a function of the irradiated volume for each product density were determined. Good agreement between ANN modelling and experimental results was achieved. PMID:23633649

Manai, K; Trabelsi, A

2013-11-01

167

Last Glacial Maximum  

NSDL National Science Digital Library

Short lecture on CLIMAP project (see PowerPoint) 20 minutes Powerpoint (PowerPoint 444kB Nov7 10) Group activity - Reading for CLIMAP study assumptions, 20 minutes to read, 20 minutes for discussion Student Handout (Microsoft Word 50kB Nov7 10) Students break into groups (4 per group is good division of work) with 2 students per paper. Split the assumptions between students. Each group skims the CLIMAP papers for the assumptions (modern and/or LGM) used in the CLIMAP model-based reconstruction of the LGM. In the groups, students compare the assumptions between papers. Resources: CLIMAP (1976), The surface of the ice-age earth, Science, 191(4232), 1131-1137 and CLIMAP (1984), The last interglacial ocean, Quaternary Research, 21(2), 123. Class Discussion - Summarize assumptions used in CLIMAP studies. Group activity Exploring CLIMAP LGM Reconstructions, 40 minutes for model data, 20 minutes for discussion (Could be modified with as a "jigsaw" activity with a larger class). Learn more about the jigsaw teaching method. Students work on this activity in pairs; one person will create LGM maps, the other modern. Students should sit together with their computer monitors close together to compare. The students will use the IRI/LDEO Climate Data Library to access the CLIMAP reconstruction and produce maps using the tools available on this web site. In a web browser, go to http://iridl.ldeo.columbia.edu/SOURCES/.CLIMAP/ This is the main page for the CLIMAP Model output for the LGM 18,000 BP. In the middle of the page is the label "Datasets and variables" with two data sets below http://iridl.ldeo.columbia.edu/SOURCES/.CLIMAP/.LGM/ and http://iridl.ldeo.columbia.edu/SOURCES/.CLIMAP/.MOD/. Each student clicks on the link they are assigned to. There are several data sets listed for each period and the students will examine each data set and compare the LGM and Modern. As a class, go through each data set allowing pairs to compare the maps then summarize the results as a class. The worksheet has a table for the students and the PowerPoint has table for summarizing. Class Discussion - Summarize differences between modern and LGM in the CLIMAP model output. Discuss how the assumptions of the CLIMAP model studies may have influenced the results. Extra activities The students can explore the data further using the data selection and filters in the IRI/LDEO Climate Data Library. For the two SST data sets, click on "Data Selection" and narrow the data to the just the tropics (23.5ŗ N-S). Click on "Filters" then select XY next to "Average over." The next window gives you the average over the tropics close to the top of the page. In the next class, the students repeat the Readings exercise by reading the COHMAP and MARGO papers to see how the scientific knowledge has progressed since the original CLIMAP studies. COHMAP Members, (1988), Climatic Changes of the Last 18,000 Years: Observations and Model Simulations, Science, 241(4869), 1043-1052. MARGO (2009), Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum, Nature Geoscience, 2(2), 127-132.

Kristine DeLong

168

Duality in a maximum generalized entropy model  

NASA Astrophysics Data System (ADS)

This paper discusses a possible generalization for the maximum entropy principle. A class of generalized entropy is introduced by that of generator functions, in which the maximum generalized distribution model is explicitly derived including q-Gaussian distributions, Wigner semicircle distributions and Pareto distributions. We define a totally geodesic subspace in the total space of all probability density functions in a framework of information geometry. The model of maximum generalized entropy distributions is shown to be totally geodesic. The duality of the model and the estimation in the maximum generalized principle is elucidated to give intrinsic understandings from the point of information geometry.

Eguchi, Shinto; Komori, Osamu; Ohara, Atsumi

2015-01-01

169

Determination of absorbed dose in water at the reference point D(r{sub 0},{theta}{sub 0}) for an {sup 192}Ir HDR brachytherapy source using a Fricke system  

SciTech Connect

A ring-shaped Fricke device was developed to measure the absolute dose on the transverse bisector of a {sup 192}Ir high dose rate (HDR) source at 1 cm from its center in water, D(r{sub 0},{theta}{sub 0}). It consists of a polymethylmethacrylate (PMMA) rod (axial axis) with a cylindrical cavity at its center to insert the {sup 192}Ir radioactive source. A ring cavity around the source with 1.5 mm thickness and 5 mm height is centered at 1 cm from the central axis of the source. This ring cavity is etched in a disk shaped base with 2.65 cm diameter and 0.90 cm thickness. The cavity has a wall around it 0.25 cm thick. This ring is filled with Fricke solution, sealed, and the whole assembly is immersed in water during irradiations. The device takes advantage of the cylindrical geometry to measure D(r{sub 0},{theta}{sub 0}). Irradiations were performed with a Nucletron microselectron HDR unit loaded with an {sup 192}Ir Alpha Omega radioactive source. A Spectronic 1001 spectrophotometer was used to measure the optical absorbance using a 1 mL quartz cuvette with 1.00 cm light pathlength. The PENELOPE Monte Carlo code (MC) was utilized to simulate the Fricke device and the {sup 192}Ir Alpha Omega source in detail to calculate the perturbation introduced by the PMMA material. A NIST traceable calibrated well type ionization chamber was used to determine the air-kerma strength, and a published dose-rate constant was used to determine the dose rate at the reference point. The time to deliver 30.00 Gy to the reference point was calculated. This absorbed dose was then compared to the absorbed dose measured by the Fricke solution. Based on MC simulation, the PMMA of the Fricke device increases the D(r{sub 0},{theta}{sub 0}) by 2.0%. Applying the corresponding correction factor, the D(r{sub 0},{theta}{sub 0}) value assessed with the Fricke device agrees within 2.0% with the expected value with a total combined uncertainty of 3.43%(k=1). The Fricke device provides a promising method towards calibration of brachytherapy radiation sources in terms of D(r{sub 0},{theta}{sub 0}) and audit HDR source calibrations.

Austerlitz, C.; Mota, H. C.; Sempau, J.; Benhabib, S. M.; Campos, D.; Allison, R.; Almeida, C. E. de; Zhu, D.; Sibata, C. H. [Department of Radiation Oncology, East Carolina University, Greenville, North Carolina 27834 (United States); Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, 08028 Barcelona (Spain); Department of Radiation Oncology, East Carolina University, Greenville, North Carolina 27834 (United States); Laboratorio de Cie circumflex ncias Radiologicas, Universidade do Estado do Rio de Janeiro, 20550 Rio de Janeiro (Brazil); Department of Radiation Oncology, East Carolina University, Greenville, North Carolina 27834 (United States)

2008-12-15

170

Total Maximum Daily Load Program  

NSDL National Science Digital Library

The Environmental Protection Agency (EPA) provides this informative resource on Total Maximum Daily Loads (TMDL). A term used to discuss water quality, TMDL refers to "a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards." The TMDL Program Website offers background information on TMDLs (including FAQs), a National Overview of Impaired Waters in the US, and two standard presentations on TMDLs (HTML and Power Point). The heart of the site, however, is the interactive map of the US, which allows users access to each state's TMDL Program. Within each state, watershed names and maps, as well as source information (Water body, Parameter of Concern, Priority for TMDL Development), are provided.

171

Point Estimation  

NSDL National Science Digital Library

Created by Kyle Siegrist of the University of Alabama-Huntsville, this is an online, interactive lesson on point estimation. The author provides examples, exercises, and applets about the topic. More specifically, they concern estimators, method of moments, maximum likelihood, Bayes' estimators, best unbiased estimators, and sufficient, complete and ancillary statistics. Additionally, the author provides links to external resources for students looking to engage in a more in-depth study of the topic. This is simply one lesson in a series of seventeen. They are easily accessible as the author has created the site in an online textbook format.

Siegrist, Kyle

2009-02-23

172

NOTE: A model to calculate the induced dose rate around an 18 MV ELEKTA linear accelerator  

NASA Astrophysics Data System (ADS)

The dose rate due to activity induced by (?, n) reactions around an ELEKTA Precise accelerator running at 18 MV is reported. A model to calculate the induced dose rate for a variety of working practices has been derived and compared to the measured values. From this model, the dose received by the staff using the machine can be estimated. From measured dose rates at the face of the linear accelerator for a 10 × 10 cm2 jaw setting at 18 MV an activation coefficient per MU was derived for each of the major activation products. The relative dose rates at points around the linac head, for different energy and jaw settings, were measured. Dose rates adjacent to the patient support system and portal imager were also measured. A model to calculate the dose rate at these points was derived, and compared to those measured over a typical working week. The model was then used to estimate the maximum dose to therapists for the current working schedule on this machine. Calculated dose rates at the linac face agreed to within +/-12% of those measured over a week, with a typical dose rate of 4.5 ?Sv h-1 2 min after the beam has stopped. The estimated maximum annual whole body dose for a treatment therapist, with the machine treating at only 18 MV, for 60000 MUs per week was 2.5 mSv. This compares well with value of 2.9 mSv published for a Clinac 21EX. A model has been derived to calculate the dose from the four dominant activation products of an ELEKTA Precise 18 MV linear accelerator. This model is a useful tool to calculate the induced dose rate around the treatment head. The model can be used to estimate the dose to the staff for typical working patterns.

Perrin, Bruce; Walker, Anne; Mackay, Ranald

2003-03-01

173

Localized maximum entropy shape modelling.  

PubMed

A core part of many medical image segmentation techniques is the point distribution model, i.e., the landmark-based statistical shape model which describes the type of shapes under consideration. To build a proper model, that is flexible and generalizes well, one typically needs a large amount of landmarked training data, which can be hard to obtain. This problem becomes worse with increasing shape complexity and dimensionality. This work presents a novel methodology applicable to principal component-based shape model building and similar techniques. The main idea of the method is to make regular PCA shape modelling more flexible by using merely covariances between neighboring landmarks. The remaining unknown second order moments are determined using the maximum entropy principle based on which the full covariance matrix--as employed in the PCA--is determined using matrix completion. The method presented can be applied in a variety of situations and in conjunction with other technique facilitating model building. The experiments on point distributions demonstrate that improved shape models can be obtained using this localized maximum entropy modelling. PMID:17633734

Loog, Marco

2007-01-01

174

Organ and effective dose reduction in adult chest CT using abdominal lead shielding  

PubMed Central

Objectives The purpose of this study was to evaluate and compare organ and effective dose savings that could be achieved using conventional lead aprons and a new, custom-designed shield as out-of-plane shielding devices during chest CT scans. Methods Thermoluminescent dosimeters were used to measure doses throughout the abdomen and pelvis during CT scans of the chest of a RANDO phantom. Dose measurements were made with no shielding, with lead aprons and with the new shield around the abdomen and pelvis in order to quantify the achievable organ and effective dose reductions. Results Average dose savings in the 10 phantom sections ranged from 5% to 78% with the highest point dose saving of 93% being found in the mid-pelvis. When shielding was used, the maximum measured organ dose reduction was a 72% dose saving to the testes. Significant dose savings were found throughout the abdomen and pelvis, which contributed to an effective dose saving of 4% that was achieved over and above the dose savings obtained through conventional optimisation strategies. This could yield significant population dose savings and reductions in collective radiation risk. Conclusion In this study significant organ and effective dose reductions have been achieved through the use of abdominal shielding during chest CT examinations and it is therefore recommended that out-of-plane patient shielding devices should be used for all chest CT scans and potentially for every CT scan, irrespective of body part. PMID:22011831

Iball, G R; Brettle, D S

2011-01-01

175

Dose measurement for medical staff with glass dosemeters and thermoluminescence dosemeters during 125I brachytherapy for prostate cancer.  

PubMed

Photoluminescence glass dosemeters (PLDs) and thermoluminescence dosemeters (TLDs) are commonly used as a personal monitoring dosemeter. PLDs and TLDs were used for surface dose monitoring of medical staff involved in (125)I brachytherapy for prostate cancer because these dosemeters have a wide dose-response linearity and high sensitivity for low photon energy. Surface doses measured with PLDs agreed with those with TLDs within ?20 % except for a few cases. Surface doses at a surgeon's left hand and arm were higher than those at the other measuring points. A surgeon received a maximum dose of 650 ?Gy at the back of left hand. Surface doses to an assistant were <100 ?Gy. Surface doses to a nurse, a radiologist, an anaesthesiologist and a radiological technologist were <10 ?Gy. The occupational exposure to a surgeon could be reduced by the adjustment of fluoroscopic parameters and the use of lead gloves. PMID:21212076

Fujii, K; Ko, S; Nako, Y; Tonari, A; Nishizawa, K; Akahane, K; Takayama, M

2011-03-01

176

Patient-specific quantification of respiratory motion-induced dose uncertainty for step-and-shoot IMRT of lung cancer  

PubMed Central

Purpose: The objective of this study was to quantify respiratory motion-induced dose uncertainty at the planning stage for step-and-shoot intensity-modulated radiation therapy (IMRT) using an analytical technique. Methods: Ten patients with stage II/III lung cancer who had undergone a planning four-dimensional (4D) computed tomographic scan and step-and-shoot IMRT planning were selected with a mix of motion and tumor size for this retrospective study. A step-and-shoot IMRT plan was generated for each patient. The maximum and minimum doses with respiratory motion were calculated for each plan, and the mean deviation from the 4D dose was calculated, taking delivery time, fractionation, and patient breathing cycle into consideration. Results: For all patients evaluated in this study, the mean deviation from the 4D dose in the planning target volume (PTV) was <2.5%, with a standard deviation <1.2%, and maximum point dose variation from the 4D dose was <6.2% in the PTV assuming delivery dose rate of 200 MU/min and patient breathing cycle of 8 s. The motion-induced dose uncertainty is a function of motion, fractionation, MU (plan modulation), dose rate, and patient breathing cycle. Conclusions: Respiratory motion-induced dose uncertainty varies from patient to patient. Therefore, it is important to evaluate the dose uncertainty on a patient-specific basis, which could be useful for plan evaluation and treatment strategy determination for selected patients. PMID:24320498

Li, Heng; Park, Peter; Liu, Wei; Matney, Jason; Liao, Zhongxing; Balter, Peter; Li, Yupeng; Zhang, Xiaodong; Li, Xiaoqiang; Zhu, X. Ronald

2013-01-01

177

Patient-specific quantification of respiratory motion-induced dose uncertainty for step-and-shoot IMRT of lung cancer  

SciTech Connect

Purpose: The objective of this study was to quantify respiratory motion-induced dose uncertainty at the planning stage for step-and-shoot intensity-modulated radiation therapy (IMRT) using an analytical technique.Methods: Ten patients with stage II/III lung cancer who had undergone a planning four-dimensional (4D) computed tomographic scan and step-and-shoot IMRT planning were selected with a mix of motion and tumor size for this retrospective study. A step-and-shoot IMRT plan was generated for each patient. The maximum and minimum doses with respiratory motion were calculated for each plan, and the mean deviation from the 4D dose was calculated, taking delivery time, fractionation, and patient breathing cycle into consideration.Results: For all patients evaluated in this study, the mean deviation from the 4D dose in the planning target volume (PTV) was <2.5%, with a standard deviation <1.2%, and maximum point dose variation from the 4D dose was <6.2% in the PTV assuming delivery dose rate of 200 MU/min and patient breathing cycle of 8 s. The motion-induced dose uncertainty is a function of motion, fractionation, MU (plan modulation), dose rate, and patient breathing cycle.Conclusions: Respiratory motion-induced dose uncertainty varies from patient to patient. Therefore, it is important to evaluate the dose uncertainty on a patient-specific basis, which could be useful for plan evaluation and treatment strategy determination for selected patients.

Li, Heng; Park, Peter; Liu, Wei; Matney, Jason; Balter, Peter; Zhang, Xiaodong; Li, Xiaoqiang; Zhu, X. Ronald [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)] [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Liao, Zhongxing [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)] [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Li, Yupeng [Applied Research, Varian Medical Systems, Palo Alto, California 94304 (United States)] [Applied Research, Varian Medical Systems, Palo Alto, California 94304 (United States)

2013-12-15

178

MAXIMUM MULTIPLE ATTENUATION  

Microsoft Academic Search

Recently Common Depth Point Stacking has become the general rule for seismic evaluation. Stack shooting is carried out to enhance the' primary event as well as to attenuate the multiple. Actual multiple attenuation can only take place providing the multiple event is stacked out of phase. Such out of stacking can only take place providing there is an increase of

W. HRYHOR

179

Benefits of the maximum tolerated dose (MTD) and maximum tolerated concentration (MTC) concept in aquatic toxicology  

Microsoft Academic Search

There is increasing recognition of the need to identify specific sublethal effects of chemicals, such as reproductive toxicity, and specific modes of actions of the chemicals, such as interference with the endocrine system. To achieve these aims requires criteria which provide a basis to interpret study findings so as to separate these specific toxicities and modes of action from not

Thomas H. Hutchinson; Christian Bögi; Matthew J. Winter; J. Willie Owens

2009-01-01

180

Spline-based procedures for dose-finding studies with active control  

PubMed Central

In a dose-finding study with an active control, several doses of a new drug are compared with an established drug (the so-called active control). One goal of such studies is to characterize the dose–response relationship and to find the smallest target dose concentration d*, which leads to the same efficacy as the active control. For this purpose, the intersection point of the mean dose–response function with the expected efficacy of the active control has to be estimated. The focus of this paper is a cubic spline-based method for deriving an estimator of the target dose without assuming a specific dose–response function. Furthermore, the construction of a spline-based bootstrap CI is described. Estimator and CI are compared with other flexible and parametric methods such as linear spline interpolation as well as maximum likelihood regression in simulation studies motivated by a real clinical trial. Also, design considerations for the cubic spline approach with focus on bias minimization are presented. Although the spline-based point estimator can be biased, designs can be chosen to minimize and reasonably limit the maximum absolute bias. Furthermore, the coverage probability of the cubic spline approach is satisfactory, especially for bias minimal designs. © 2014 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. PMID:25319931

Helms, Hans-Joachim; Benda, Norbert; Zinserling, Jörg; Kneib, Thomas; Friede, Tim

2015-01-01

181

Spline-based procedures for dose-finding studies with active control.  

PubMed

In a dose-finding study with an active control, several doses of a new drug are compared with an established drug (the so-called active control). One goal of such studies is to characterize the dose-response relationship and to find the smallest target dose concentration d(*) , which leads to the same efficacy as the active control. For this purpose, the intersection point of the mean dose-response function with the expected efficacy of the active control has to be estimated. The focus of this paper is a cubic spline-based method for deriving an estimator of the target dose without assuming a specific dose-response function. Furthermore, the construction of a spline-based bootstrap CI is described. Estimator and CI are compared with other flexible and parametric methods such as linear spline interpolation as well as maximum likelihood regression in simulation studies motivated by a real clinical trial. Also, design considerations for the cubic spline approach with focus on bias minimization are presented. Although the spline-based point estimator can be biased, designs can be chosen to minimize and reasonably limit the maximum absolute bias. Furthermore, the coverage probability of the cubic spline approach is satisfactory, especially for bias minimal designs. © 2014 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. PMID:25319931

Helms, Hans-Joachim; Benda, Norbert; Zinserling, Jörg; Kneib, Thomas; Friede, Tim

2015-01-30

182

Maximum gravitational recoil.  

PubMed

Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of approximately 4000 km s-1 for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger. PMID:17677894

Campanelli, Manuela; Lousto, Carlos O; Zlochower, Yosef; Merritt, David

2007-06-01

183

NAIRAS aircraft radiation model development, dose climatology, and initial validation  

NASA Astrophysics Data System (ADS)

The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) is a real-time, global, physics-based model used to assess radiation exposure to commercial aircrews and passengers. The model is a free-running physics-based model in the sense that there are no adjustment factors applied to nudge the model into agreement with measurements. The model predicts dosimetric quantities in the atmosphere from both galactic cosmic rays (GCR) and solar energetic particles, including the response of the geomagnetic field to interplanetary dynamical processes and its subsequent influence on atmospheric dose. The focus of this paper is on atmospheric GCR exposure during geomagnetically quiet conditions, with three main objectives. First, provide detailed descriptions of the NAIRAS GCR transport and dosimetry methodologies. Second, present a climatology of effective dose and ambient dose equivalent rates at typical commercial airline altitudes representative of solar cycle maximum and solar cycle minimum conditions and spanning the full range of geomagnetic cutoff rigidities. Third, conduct an initial validation of the NAIRAS model by comparing predictions of ambient dose equivalent rates with tabulated reference measurement data and recent aircraft radiation measurements taken in 2008 during the minimum between solar cycle 23 and solar cycle 24. By applying the criterion of the International Commission on Radiation Units and Measurements (ICRU) on acceptable levels of aircraft radiation dose uncertainty for ambient dose equivalent greater than or equal to an annual dose of 1 mSv, the NAIRAS model is within 25% of the measured data, which fall within the ICRU acceptable uncertainty limit of 30%. The NAIRAS model predictions of ambient dose equivalent rate are generally within 50% of the measured data for any single-point comparison. The largest differences occur at low latitudes and high cutoffs, where the radiation dose level is low. Nevertheless, analysis suggests that these single-point differences will be within 30% when a new deterministic pion-initiated electromagnetic cascade code is integrated into NAIRAS, an effort which is currently underway.

Mertens, Christopher J.; Meier, Matthias M.; Brown, Steven; Norman, Ryan B.; Xu, Xiaojing

2013-10-01

184

Determination of transit dose profile for a {sup 192}Ir HDR source  

SciTech Connect

Purpose: Several studies have reported methodologies to calculate and correct the transit dose component of the moving radiation source for high dose rate (HDR) brachytherapy planning systems. However, most of these works employ the average source speed, which varies significantly with the measurement technique used, and does not represent a realistic speed profile, therefore, providing an inaccurate dose determination. In this work, the authors quantified the transit dose component of a HDR unit based on the measurement of the instantaneous source speed to produce more accurate dose values. Methods: The Nucletron microSelectron-HDR Ir-192 source was characterized considering the Task Group 43 (TG-43U1) specifications. The transit dose component was considered through the calculation of the dose distribution using a Monte Carlo particle transport code, MCNP5, for each source position and correcting it by the source speed. The instantaneous source speed measurements were performed in a previous work using two optical fibers connected to a photomultiplier and an oscilloscope. Calculated doses were validated by comparing relative dose profiles with those obtained experimentally using radiochromic films. Results: TG-43U1 source parameters were calculated to validate the Monte Carlo simulations. These agreed with the literature, with differences below 1% for the majority of the points. Calculated dose profiles without transit dose were also validated by comparison with ONCENTRA{sup Registered-Sign} Brachy v. 3.3 dose values, yielding differences within 1.5%. Dose profiles obtained with MCNP5 corrected using the instantaneous source speed profile showed differences near dwell positions of up to 800% in comparison to values corrected using the average source speed, but they are in good agreement with the experimental data, showing a maximum discrepancy of approximately 3% of the maximum dose. Near a dwell position the transit dose is about 22% of the dwell dose delivered by the source dwelling 1 s and reached 104.0 cGy per irradiation in a hypothetical clinical case studied in this work. Conclusions: The present work demonstrated that the transit dose correction based on average source speed fails to accurately correct the dose, indicating that the correct speed profile should be considered. The impact on total dose due to the transit dose correction near the dwell positions is significant and should be considered more carefully in treatments with high dose rate, several catheters, multiple dwell positions, small dwell times, and several fractions.

Fonseca, G. P. [Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP, Sao Paulo 05508-000, Brazil and Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands); Rubo, R. A.; Santos, G. R. dos [Hospital das Clinicas da Universidade de Sao Paulo - HC/FMUSP, Sao Paulo 05403-900 (Brazil); Minamisawa, R. A. [Laboratory for Micro- and Nanotechnology Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Antunes, P. C. G.; Yoriyaz, H. [Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP, Sao Paulo 05508-000 (Brazil)

2013-05-15

185

Can we improve the dose distribution for single or multi-lumen breast balloons used for Accelerated Partial Breast Irradiation?  

PubMed Central

Purpose The aim of the study was to verify dose distribution parameters for multi-lumen, and artificially created single-lumen balloon applicator used for the same patient with two optimization algorithms: inverse planning simulated annealing (IPSA) and dose point optimization with distance option. Material and methods Group of 24 patients with multi-lumen balloon applied were investigated. Each patient received 10 fractions of 3.4 Gy (2 fractions daily). For every patient, four treatment plans were prepared. Firstly, for five-lumen balloon optimized with IPSA algorithm and optimization parameters adjusted for each case. Secondly, for the same applicator optimized with dose point optimization and distant option. Two other plans were prepared for single-lumen applicator, created by removing four peripheral lumens, optimized with both algorithms. Results The highest D95 parameter was obtained for plans optimized with IPSA algorithm, mean value 99.3 percent of prescribed dose, and it was significantly higher than plans optimized with dose point algorithm (mean = 83.50%, p < 0.0001), IPSA single-lumen balloon plan (mean = 83.50%, p = 0.0037) and optimized to dose point single-lumen balloon (mean = 85.51%, p < 0.0001). There were no statistically significant differences concerning maximum doses distributed to skin surface for neither application nor optimization method. Volumes receiving 200% of prescribed dose in PTV were higher for multi-lumen balloon dose point optimized plans (mean = 8.78%), than for other plans (IPSA multi-lumen balloon plan: mean = 7.37%, p < 0.0001, single-lumen IPSA: mean = 7.20%, p < 0.0001, single-lumen dose point: mean = 7.19%, p < 0.0001). Conclusions Basing on performed survey, better dose distribution parameters are obtained for patients with multi-lumen balloon applied and optimized using IPSA algorithm with individualized optimization parameters. PMID:24143147

Biel?da, Grzegorz; ?aski, Piotr; Kycler, Witold

2013-01-01

186

Development, validation and transfer of a near infrared method to determine in-line the end point of a fluidised drying process for commercial production batches of an approved oral solid dose pharmaceutical product.  

PubMed

Pharmaceutical companies are progressively adopting and introducing the principles of Quality by Design with the main purpose of assurance and built-in quality throughout the whole manufacturing process. Within this framework, a Partial Least Square (PLS) model, based on Near Infrared (NIR) spectra and humidity determinations, was built in order to determine in-line the drying end point of a fluidized bed process. The in-process method was successfully validated following the principles described within The International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use - ICH Q2 (r1) - Validation of Analytical Procedures: Text and Methodology. However, in some aspects, the cited guidelines were not appropriate to in-process methods developed and validated exclusively with in-line samples and implemented in dynamic systems, such as drying processes. In this work, a customized interpretation of guidelines has been adopted which provided the framework of evidence to support a validated application. The application has been submitted to the United States Food and Drug Administration (FDA) and The European Medicines Agency (EMA) during applications for grant of licences. Representatives from these Regulatory Authorities have specifically reviewed this novel application during on-site inspections, and have subsequently approved both the product and this application. Currently, the NIR method is implemented as a primary in-line method to control the drying end point in real-time (to below a control limit of not greater than 1.2% w/w) for commercial production batches of an approved, solid, oral-dose medicine. The implementation of this in-process method allows real-time control with benefits including a reduction in operation time and labour; sample handling and waste generation; and a reduced risk to product quality in further unit operations due to improved consistency of intermediate output at this stage. To date, this has achieved approximately 10% savings in energy efficiency and operational time for this part of the manufacturing process. PMID:20801599

Peinado, Antonio; Hammond, Jonathan; Scott, Andrew

2011-01-01

187

Impact of the number of control points has on isodose distributions in a dynamic multileaf collimator intensity-modulated radiation therapy delivery  

SciTech Connect

Intensity-modulated radiation therapy (IMRT) is a powerful technique in planning the delivery of dose. The most common IMRT delivery requires the use of moving multileaf collimators (MLCs) to deliver the requested fluence pattern. A dynamic delivery IMRT field file will contain several control points that are defined MLC shapes at a marked fraction of the delivered monitor units. The size of this file and the fidelity of the deliverable fluence are proportional to the number of control points defined. This study investigates the effect of reducing the number of control points has on the resultant dose distribution quality in complex IMRT in efforts to reduce transfer times, loading times, check sum times and file storage. Analysis was performed with 6 head and neck patients on an Eclipse version 8.5 treatment planning system (Varian, Palo Alto, CA). To ensure the quality of all treatments, Eclipse defines a minimum of 64 and a maximum of 320 control points per subfield (Eclipse Algorithms Reference guide). All 6 patients' plans were calculated with fixed 64, 166, and 320 control points using the sliding window technique. In addition, each plan was calculated in variable mode (Normal mode) in which the planning system determined the required number of control points. Each of the 4 plans for each patient was renormalized to provide the same mean planning target volume (PTV) 70 dose. Dose values for critical and target structures were examined for each patient. When examining the minimum, maximum, and mean doses to all target structures, it was noted that the greatest reduction in target dose coverage caused by reduced number of control points was 0.5%, which occurred for the minimum dose to the PTV56 structure in one plan.' Dose analysis for critical structures showed no clinically significant increase in dose when compared with the 320 control point plan.

Goraj, Andrew [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY (United States); Boer, Steven F. de, E-mail: steven.deboer@roswellpark.org [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY (United States); Department of Physiology and Biophysics, State University of New York at Buffalo, NY (United States)

2012-01-01

188

DALI: Defining Antibiotic Levels in Intensive care unit patients: a multi-centre point of prevalence study to determine whether contemporary antibiotic dosing for critically ill patients is therapeutic  

PubMed Central

Background The clinical effects of varying pharmacokinetic exposures of antibiotics (antibacterials and antifungals) on outcome in infected critically ill patients are poorly described. A large-scale multi-centre study (DALI Study) is currently underway describing the clinical outcomes of patients achieving pre-defined antibiotic exposures. This report describes the protocol. Methods DALI will recruit over 500 patients administered a wide range of either beta-lactam or glycopeptide antibiotics or triazole or echinocandin antifungals in a pharmacokinetic point-prevalence study. It is anticipated that over 60 European intensive care units (ICUs) will participate. The primary aim will be to determine whether contemporary antibiotic dosing for critically ill patients achieves plasma concentrations associated with maximal activity. Secondary aims will compare antibiotic pharmacokinetic exposures with patient outcome and will describe the population pharmacokinetics of the antibiotics included. Various subgroup analyses will be conducted to determine patient groups that may be at risk of very low or very high concentrations of antibiotics. Discussion The DALI study should inform clinicians of the potential clinical advantages of achieving certain antibiotic pharmacokinetic exposures in infected critically ill patients. PMID:22768873

2012-01-01

189

Factors Associated With Chest Wall Toxicity After Accelerated Partial Breast Irradiation Using High-Dose-Rate Brachytherapy  

SciTech Connect

Purpose: The purpose of this analysis was to evaluate dose-volume relationships associated with a higher probability for developing chest wall toxicity (pain) after accelerated partial breast irradiation (APBI) by using both single-lumen and multilumen brachytherapy. Methods and Materials: Rib dose data were available for 89 patients treated with APBI and were correlated with the development of chest wall/rib pain at any point after treatment. Ribs were contoured on computed tomography planning scans, and rib dose-volume histograms (DVH) along with histograms for other structures were constructed. Rib DVH data for all patients were sampled at all volumes {>=}0.008 cubic centimeter (cc) (for maximum dose related to pain) and at volumes of 0.5, 1, 2, and 3 cc for analysis. Rib pain was evaluated at each follow-up visit. Patient responses were marked as yes or no. No attempt was made to grade responses. Eighty-nine responses were available for this analysis. Results: Nineteen patients (21.3%) complained of transient chest wall/rib pain at any point in follow-up. Analysis showed a direct correlation between total dose received and volume of rib irradiated with the probability of developing rib/chest wall pain at any point after follow-up. The median maximum dose at volumes {>=}0.008 cc of rib in patients who experienced chest wall pain was 132% of the prescribed dose versus 95% of the prescribed dose in those patients who did not experience pain (p = 0.0035). Conclusions: Although the incidence of chest wall/rib pain is quite low with APBI brachytherapy, attempts should be made to keep the volume of rib irradiated at a minimum and the maximum dose received by the chest wall as low as reasonably achievable.

Brown, Sheree, E-mail: shereedst32@hotmail.com [Department of Radiation Oncology, WellStar Kennestone Hospital, Marietta, Georgia (United States); Vicini, Frank [Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan (United States); Vanapalli, Jyotsna R.; Whitaker, Thomas J.; Pope, D. Keith [Department of Radiation Oncology, WellStar Kennestone Hospital, Marietta, Georgia (United States); Lyden, Maureen [BioStat International, Inc., Tampa, Florida (United States); Bruggeman, Lisa; Haile, Kenneth L.; McLaughlin, Mark P. [Department of Radiation Oncology, WellStar Kennestone Hospital, Marietta, Georgia (United States)

2012-07-01

190

Maximum Likelihood Estimation (MLE) of students' understanding of vector subtraction  

E-print Network

Maximum Likelihood Estimation (MLE) of students' understanding of vector subtraction Tianren Wang- dimensional vector subtraction tasks. We use Maximum Likelihood Estimation (MLE) analysis to analyze students (both pointing to the right or opposed), and operation (left-right subtraction or right-left subtraction

Zollman, Dean

191

The Sherpa Maximum Likelihood Estimator  

NASA Astrophysics Data System (ADS)

A primary goal for the second release of the Chandra Source Catalog (CSC) is to include X-ray sources with as few as 5 photon counts detected in stacked observations of the same field, while maintaining acceptable detection efficiency and false source rates. Aggressive source detection methods will result in detection of many false positive source candidates. Candidate detections will then be sent to a new tool, the Maximum Likelihood Estimator (MLE), to evaluate the likelihood that a detection is a real source. MLE uses the Sherpa modeling and fitting engine to fit a model of a background and source to multiple overlapping candidate source regions. A background model is calculated by simultaneously fitting the observed photon flux in multiple background regions. This model is used to determine the quality of the fit statistic for a background-only hypothesis in the potential source region. The statistic for a background-plus-source hypothesis is calculated by adding a Gaussian source model convolved with the appropriate Chandra point spread function (PSF) and simultaneously fitting the observed photon flux in each observation in the stack. Since a candidate source may be located anywhere in the field of view of each stacked observation, a different PSF must be used for each observation because of the strong spatial dependence of the Chandra PSF. The likelihood of a valid source being detected is a function of the two statistics (for background alone, and for background-plus-source). The MLE tool is an extensible Python module with potential for use by the general Chandra user.

Nguyen, D.; Doe, S.; Evans, I.; Hain, R.; Primini, F.

2011-07-01

192

RESEARCH Open Access Therapeutic efficacy of fixed dose artesunate-  

E-print Network

blister). There were five age-weight dosing categories and the maximum MQ dose was capped at 1,500 mg because of its poor tolerability [5]. When dosed by age rather than weight, a substantial minorityRESEARCH Open Access Therapeutic efficacy of fixed dose artesunate- mefloquine for the treatment

Paris-Sud XI, UniversitƩ de

193

Radiological Dose Assessment 8 2007 Site environmental report8-  

E-print Network

Radiological Dose Assessment 8 2007 Site environmental report8- DRAFT Brookhaven National that the overall radiological dose impact to members of the public, workers, visitors, and the environment is "As radiological dose to the public is calculated at the site boundary as the "maximum" dose that could be received

194

Dose error from deviation of dwell time and source position for high dose-rate 192Ir in remote afterloading system  

PubMed Central

The influence of deviations in dwell times and source positions for 192Ir HDR-RALS was investigated. The potential dose errors for various kinds of brachytherapy procedures were evaluated. The deviations of dwell time ?T of a 192Ir HDR source for the various dwell times were measured with a well-type ionization chamber. The deviations of source position ?P were measured with two methods. One is to measure actual source position using a check ruler device. The other is to analyze peak distances from radiographic film irradiated with 20 mm gap between the dwell positions. The composite dose errors were calculated using Gaussian distribution with ?T and ?P as 1? of the measurements. Dose errors depend on dwell time and distance from the point of interest to the dwell position. To evaluate the dose error in clinical practice, dwell times and point of interest distances were obtained from actual treatment plans involving cylinder, tandem-ovoid, tandem-ovoid with interstitial needles, multiple interstitial needles, and surface-mold applicators. The ?T and ?P were 32 ms (maximum for various dwell times) and 0.12 mm (ruler), 0.11 mm (radiographic film). The multiple interstitial needles represent the highest dose error of 2%, while the others represent less than approximately 1%. Potential dose error due to dwell time and source position deviation can depend on kinds of brachytherapy techniques. In all cases, the multiple interstitial needles is most susceptible. PMID:24566719

Okamoto, Hiroyuki; Aikawa, Ako; Wakita, Akihisa; Yoshio, Kotaro; Murakami, Naoya; Nakamura, Satoshi; Hamada, Minoru; Abe, Yoshihisa; Itami, Jun

2014-01-01

195

Secondary Neutron Doses for Several Beam Configurations for Proton Therapy  

SciTech Connect

Purpose: To compare possible neutron doses produced in scanning and scattering modes, with the latter assessed using a newly built passive-scattering proton beam line. Methods and Materials: A 40 x 30.5 x 30-cm water phantom was irradiated with 230-MeV proton beams using a gantry angle of 270{sup o}, a 10-cm-diameter snout, and a brass aperture with a diameter of 7 cm and a thickness of 6.5 cm. The secondary neutron doses during irradiation were measured at various points using CR-39 detectors, and these measurements were cross-checked using a neutron survey meter with a 22-cm range and a 5-cm spread-out Bragg peak. Results: The maximum doses due to secondary neutrons produced by a scattering beam-delivery system were on the order of 0.152 mSv/Gy and 1.17 mSv/Gy at 50 cm from the beam isocenter in the longitudinal (0{sup o}) and perpendicular (90{sup o}) directions, respectively. The neutron dose equivalent to the proton absorbed dose, measured from 10 cm to 100 cm from the isocenter, ranged from 0.071 mSv/Gy to 1.96 mSv/Gy in the direction of the beam line (i.e., {phi} = 0 deg.). The largest neutron dose, of 3.88 mSv/Gy, was observed at 135{sup o} and 25 cm from the isocenter. Conclusions: Although the secondary neutron doses in proton therapy were higher when a scattering mode rather than a scanning mode was used, they did not exceed the scattered photon dose in typical photon treatments.

Shin, Dongho; Yoon, Myonggeun; Kwak, Jungwon; Shin, Jungwook [Proton Therapy Center, National Cancer Center, Goyang (Korea, Republic of); Lee, Se Byeong [Proton Therapy Center, National Cancer Center, Goyang (Korea, Republic of)], E-mail: sblee@ncc.re.kr; Park, Sung Yong [Proton Therapy Center, National Cancer Center, Goyang (Korea, Republic of); Park, Soah [Department of Radiation Oncology, Kangnam Sacred Heart Hospital, Seoul (Korea, Republic of); Kim, Dae Yong; Cho, Kwan Ho [Proton Therapy Center, National Cancer Center, Goyang (Korea, Republic of)

2009-05-01

196

PRECEDENTS FOR AUTHORIZATION OF CONTENTS USING DOSE RATE MEASUREMENTS  

SciTech Connect

For the transportation of Radioactive Material (RAM) packages, the requirements for the maximum allowed dose rate at the package surface and in its vicinity are given in Title 10 of the Code of Federal Regulations, Section 71.47. The regulations are based on the acceptable dose rates to which the public, workers, and the environment may be exposed. As such, the regulations specify dose rates, rather than quantity of radioactive isotopes and require monitoring to confirm the requirements are met. 10CFR71.47 requires that each package of radioactive materials offered for transportation must be designed and prepared for shipment so that under conditions normally incident to transportation the radiation level does not exceed 2 mSv/h (200 mrem/h) at any point on the external Surface of the package, and the transport index does not exceed 10. Before shipment, the dose rate of the package is determined by measurement, ensuring that it conforms to the regulatory limits, regardless of any analyses. This is the requirement for all certified packagings. This paper discusses the requirements for establishing the dose rates when shipping RAM packages and the precedents for meeting these requirements by measurement.

Abramczyk, G.; Bellamy, S.; Nathan, S.; Loftin, B.

2012-06-05

197

CT based three dimensional dose-volume evaluations for high-dose rate intracavitary brachytherapy for cervical cancer  

PubMed Central

Background In this study, high risk clinical target volumes (HR-CTVs) according to GEC-ESTRO guideline were contoured retrospectively based on CT images taken at the time of high-dose rate intracavitary brachytherapy (HDR-ICBT) and correlation between clinical outcome and dose of HR-CTV were analyzed. Methods Our study population consists of 51 patients with cervical cancer (Stages IB-IVA) treated with 50 Gy external beam radiotherapy (EBRT) using central shield combined with 2–5 times of 6 Gy HDR-ICBT with or without weekly cisplatin. Dose calculation was based on Manchester system and prescribed dose of 6 Gy were delivered for point A. CT images taken at the time of each HDR-ICBT were reviewed and HR-CTVs were contoured. Doses were converted to the equivalent dose in 2 Gy (EQD2) by applying the linear quadratic model (?/??=?10 Gy). Results Three-year overall survival, Progression-free survival, and local control rate was 82.4%, 85.3% and 91.7%, respectively. Median cumulative dose of HR-CTV D90 was 65.0 Gy (52.7-101.7 Gy). Median length from tandem to the most lateral edge of HR-CTV at the first ICBT was 29.2 mm (range, 18.0-51.9 mm). On univariate analysis, both LCR and PFS was significantly favorable in those patients D90 for HR-CTV was 60 Gy or greater (p?=?0.001 and 0.03, respectively). PFS was significantly favorable in those patients maximum length from tandem to edge of HR-CTV at first ICBT was shorter than 3.5 cm (p?=?0.042). Conclusion Volume-dose showed a relationship to the clinical outcome in CT based brachytherapy for cervical carcinoma. PMID:24938757

2014-01-01

198

18 CFR 157.211 - Delivery points.  

Code of Federal Regulations, 2013 CFR

...end-user, the location of the delivery point, and the...showing the location of the proposed...through the proposed delivery tap upon the certificate... (2) The location and maximum quantities...delivered at such delivery point;...

2013-04-01

199

18 CFR 157.211 - Delivery points.  

Code of Federal Regulations, 2014 CFR

...end-user, the location of the delivery point, and the...showing the location of the proposed...through the proposed delivery tap upon the certificate... (2) The location and maximum quantities...delivered at such delivery point;...

2014-04-01

200

Dose perturbation caused by high-density inhomogeneities in small beams in stereotactic radiosurgery  

NASA Astrophysics Data System (ADS)

The influence of high-density tissue heterogeneities in small-diameter beams used in stereotactic radiosurgery has been investigated. Dose perturbation immediately behind aluminium sheets, used to simulate a high-density tissue inhomogeneity such as bone, was studied in a solid water phantom. Dose reduction factors (DRFs), which are the ratios of the dose in the presence of the inhomogeneity to dose in a uniform density solid water phantom, were measured with a diamond detector for three thicknesses of aluminium. DRFs exhibit dependence on both the inhomogeneity thickness and the beam diameter. The DRF decreases with inhomogeneity thickness. The DRF initially decreases with increase in the beam diameter from 12.5 to 25 mm. For fields greater than 25 mm, the DRFs are nearly constant. The commonly used algorithms such as the TAR ratio method underestimate the magnitude of the measured effect. A good agreement between these measurements and Monte Carlo calculations is obtained. The influence of the high-density inhomogeneity on the tissue maximum ratio (TMR) was also measured with the inhomogeneity at a fixed depth from the entrance surface. The TMR is reduced for all detector-inhomogeneity distances investigated. The dose build-up phenomenon observed in the presence of low-density air inhomogeneity is absent in the presence of a high-density inhomogeneity. The beam width (defined by 50% dose points) immediately beyond the inhomogeneity is unaffected by the high-density inhomogeneity. However, the 90%-10% and 80%-20% dose penumbra widths and the dose outside the beam edge (beyond the 50% dose point) are reduced. This reduction in dose outside the beam edge is caused by the reduced range of the secondary radiation (photons and electrons) in the high-density medium.

Rustgi, Surendra N.; Rustgi, Atul K.; Jiang, Steve B.; Ayyangar, Komanduri M.

1998-12-01

201

Preliminary liver dose estimation in the new facility for biomedical applications at the RA-3 reactor.  

PubMed

As a part of the project concerning the irradiation of a section of the human liver left lobe, a preliminary estimation of the expected dose was performed. To obtain proper input values for the calculation, neutron flux and gamma dose rate characterization were carried out using adequate portions of cow or pig liver covered with demineralized water simulating the preservation solution. Irradiations were done inside a container specially designed to fulfill temperature preservation of the organ and a reproducible irradiation position (which will be of importance for future planification purposes). Implantable rhodium based self-powered neutron detectors were developed to obtain neutron flux profiles both external and internal. Implantation of SPND was done along the central longitudinal axis of the samples, where lowest flux is expected. Gamma dose rate was obtained using a neutron shielded graphite ionization chamber moved along external surfaces of the samples. The internal neutron profile resulted uniform enough to allow for a single and static irradiation of the liver. For dose estimation, irradiation condition was set in order to obtain a maximum of 15 Gy-eq in healthy tissue. Additionally, literature reported boron concentrations of 47 ppm in tumor and 8 ppm in healthy tissue and a more conservative relationship (30/10 ppm) were used. To make a conservative estimation of the dose the following considerations were done: i). Minimum measured neutron flux inside the sample (approximately 5 x 10(9) n cm-2 s-1) was considered to calculate dose in tumor. (ii). Maximum measured neutron flux (considering both internal as external profiles) was used to calculate dose in healthy tissue (approximately 8.7 x 10(9) n cm-2 s-1). (iii). Maximum measured gamma dose rate (approximately 13.5 Gy h-1) was considered for both tumor and healthy tissue. Tumor tissue dose was approximately 69 Gy-eq for 47 ppm of (10)B and approximately 42 Gy-eq for 30 ppm, for a maximum dose of 15 Gy-eq in healthy tissue. As can be seen from these results, even for the most conservative case, minimum tumor dose will be acceptable from the treatment point of view, which shows that the irradiation conditions at this facility have quite good characteristics for the proposed irradiation. PMID:19394239

Gadan, M; Crawley, V; Thorp, S; Miller, M

2009-07-01

202

The 1980 solar maximum mission event listing  

NASA Technical Reports Server (NTRS)

Information is contained on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1980 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Hard X-Ray Imaging Spectrometer, (4) Flat Crystal Spectrometer, (5) Bent Crystal Spectrometer, (6) Ultraviolet Spectrometer and Polarimeter, and (7) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from Sun center are also included.

Speich, D. M.; Nelson, J. J.; Licata, J. P.; Tolbert, A. K.

1991-01-01

203

The 1988 Solar Maximum Mission event list  

NASA Technical Reports Server (NTRS)

Information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1988 pointed observations is presented. Data from the following SMM experiments are included: (1) gamma ray spectrometer; (2) hard x ray burst spectrometer; (3) flat crystal spectrometers; (4) bent crystal spectrometer; (5) ultraviolet spectrometer polarimeter; and (6) coronagraph/polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts, or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observation. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included.

Dennis, B. R.; Licata, J. P.; Tolbert, A. K.

1992-01-01

204

The 1989 Solar Maximum Mission event list  

NASA Technical Reports Server (NTRS)

This document contains information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1989 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Flat Crystal Spectrometer, (4) Bent Crystal Spectrometer, (5) Ultraviolet Spectrometer Polarimeter, and (6) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Satellite (GOES) X-ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included.

Dennis, B. R.; Licata, J. P.; Tolbert, A. K.

1992-01-01

205

Dose gradient impact on equivalent dose at 2 Gy for high dose rate interstitial brachytherapy  

PubMed Central

Purpose To evaluate a new calculation model estimating the equivalent dose at 2 Gy (EQD2) taking into account dose gradient in high dose rate interstitial brachytherapy (HDRIB). Material and methods Forty dose-volume histograms (DVHs) of breast (20 pts) and prostate (20 pts) cancer dose distributions were reviewed. Physical prescribed doses (PPD) were 34 Gy (10f/5d) and 18 Gy (6f/2d) for breast (partial irradiation protocol) and prostate (boost after external irradiation) treatment, respectively. For each DVH, clinical target volume (CTV), V100, V150, V200, D90 and D100 were determined. Based on DVH segmentation, elementary doses (d) delivered to elementary volumes were determined, then multiplied by C (% of CTV receiving d). According to the linear quadratic model, EQD2 was calculated for different ?/? ratios. Results For breast implant, median EQD2 (?/? = 4) was 42 Gy and 76 Gy (66-85) without and with dose gradient consideration, respectively. For prostate implant, median EQD2 (?/? = 1.5) was 39 Gy and 98 Gy (90-103) whether dose gradient was not or was taken into account, respectively. Conclusions This study pointed out that for brachytherapy, EQD2 calculation must take into account the dose gradient. Because this model is a mathematical one, it has to be cautiously applied. Nevertheless, it appears as a useful tool for EQD2 comparison between the same PPD delivered through EBRT or brachytherapy regarding trial result interpretation. PMID:23346135

Hannoun-Levi, Jean-Michel; Chand-Fouche, Marie-Eve; Dejean, Catherine

2012-01-01

206

Bayesian estimation of dose thresholds  

NASA Technical Reports Server (NTRS)

An example is described of Bayesian estimation of radiation absorbed dose thresholds (subsequently simply referred to as dose thresholds) using a specific parametric model applied to a data set on mice exposed to 60Co gamma rays and fission neutrons. A Weibull based relative risk model with a dose threshold parameter was used to analyse, as an example, lung cancer mortality and determine the posterior density for the threshold dose after single exposures to 60Co gamma rays or fission neutrons from the JANUS reactor at Argonne National Laboratory. The data consisted of survival, censoring times and cause of death information for male B6CF1 unexposed and exposed mice. The 60Co gamma whole-body doses for the two exposed groups were 0.86 and 1.37 Gy. The neutron whole-body doses were 0.19 and 0.38 Gy. Marginal posterior densities for the dose thresholds for neutron and gamma radiation were calculated with numerical integration and found to have quite different shapes. The density of the threshold for 60Co is unimodal with a mode at about 0.50 Gy. The threshold density for fission neutrons declines monotonically from a maximum value at zero with increasing doses. The posterior densities for all other parameters were similar for the two radiation types.

Groer, P. G.; Carnes, B. A.

2003-01-01

207

Continuity of the Maximum-Entropy Inference  

NASA Astrophysics Data System (ADS)

We study the inverse problem of inferring the state of a finite-level quantum system from expected values of a fixed set of observables, by maximizing a continuous ranking function. We have proved earlier that the maximum-entropy inference can be a discontinuous map from the convex set of expected values to the convex set of states because the image contains states of reduced support, while this map restricts to a smooth parametrization of a Gibbsian family of fully supported states. Here we prove for arbitrary ranking functions that the inference is continuous up to boundary points. This follows from a continuity condition in terms of the openness of the restricted linear map from states to their expected values. The openness condition shows also that ranking functions with a discontinuous inference are typical. Moreover it shows that the inference is continuous in the restriction to any polytope which implies that a discontinuity belongs to the quantum domain of non-commutative observables and that a geodesic closure of a Gibbsian family equals the set of maximum-entropy states. We discuss eight descriptions of the set of maximum-entropy states with proofs of accuracy and an analysis of deviations.

Stephan, Weis

2014-09-01

208

Continuity of the Maximum-Entropy Inference  

E-print Network

We study the inverse problem of inferring the state of a finite-level quantum system from expected values of a fixed set of observables, by maximizing a continuous ranking function. We have proved earlier that the maximum-entropy inference can be a discontinuous map from the convex set of expected values to the convex set of states because the image contains states of reduced support, while this map restricts to a smooth parametrization of a Gibbsian family of fully supported states. Here we prove for arbitrary ranking functions that the inference is continuous up to boundary points. This follows from a continuity condition in terms of the openness of the restricted linear map from states to their expected values. The openness condition shows also that ranking functions with a discontinuous inference are typical. Moreover it shows that the inference is continuous in the restriction to any polytope which implies that a discontinuity belongs to the quantum domain of non-commutative observables and that a geodesic closure of a Gibbsian family equals the set of maximum-entropy states. We discuss eight descriptions of the set of maximum-entropy states with proofs of accuracy and an analysis of deviations.

Stephan Weis

2014-04-21

209

Maximum likelihood decoding of Reed Solomon Codes  

SciTech Connect

We present a randomized algorithm which takes as input n distinct points ((x{sub i}, y{sub i})){sup n}{sub i=1} from F x F (where F is a field) and integer parameters t and d and returns a list of all univariate polynomials f over F in the variable x of degree at most d which agree with the given set of points in at least t places (i.e., y{sub i} = f (x{sub i}) for at least t values of i), provided t = {Omega}({radical}nd). The running time is bounded by a polynomial in n. This immediately provides a maximum likelihood decoding algorithm for Reed Solomon Codes, which works in a setting with a larger number of errors than any previously known algorithm. To the best of our knowledge, this is the first efficient (i.e., polynomial time bounded) algorithm which provides some maximum likelihood decoding for any efficient (i.e., constant or even polynomial rate) code.

Sudan, M. [IBM Thomas J. Watson Research Center, Yorktown Heights, NY (United States)

1996-12-31

210

The myth of mean dose as a surrogate for radiation risk?  

NASA Astrophysics Data System (ADS)

The current estimations of risk associated with medical imaging procedures rely on assessing the organ dose via direct measurements or simulation. Each organ dose is assumed to be homogeneous, a representative sample or mean of which is weighted by a corresponding tissue weighting factor provided by ICRP publication 103. The weighted values are summed to provide Effective Dose (ED), the most-widely accepted surrogate for population radiation risk. For individual risk estimation, one may employ Effective Risk (ER), which further incorporates gender- and age-specific risk factors. However, both the tissue-weighting factors (as used by ED) and the risk factors (as used by ER) were derived (mostly from the atomic bomb survivor data) under the assumption of a homogeneous dose distribution within each organ. That assumption is significantly violated in most medical imaging procedures. In chest CT, for example, superficial organs (eg, breasts) demonstrate a heterogeneous distribution while organs on the peripheries of the irradiation field (eg, liver) possess a nearly discontinuous dose profile. Projection radiography and mammography involve an even wider range of organ dose heterogeneity spanning up to two orders of magnitude. As such, mean dose or point measured dose values do not reflect the maximum energy deposited per unit volume of the organ, and therefore, effective dose or effective risk, as commonly computed, can misrepresent irradiation risk. In this paper, we report the magnitude of the dose heterogeneity in both CT and projection x-ray imaging, provide an assessment of its impact on irradiation risk, and explore an alternative model-based approach for risk estimation for imaging techniques involving heterogeneous organ dose distributions.

Samei, Ehsan; Li, Xiang; Chen, Baiyu; Reiman, Robert

2010-04-01

211

Evaluation of brachytherapy lung implant dose distributions from photon-emitting sources due to tissue heterogeneities  

SciTech Connect

Purpose: Photon-emitting brachytherapy sources are used for permanent implantation to treat lung cancer. However, the current brachytherapy dose calculation formalism assumes a homogeneous water medium without considering the influence of radiation scatter or tissue heterogeneities. The purpose of this study was to determine the dosimetric effects of tissue heterogeneities for permanent lung brachytherapy. Methods: The MCNP5 v1.40 radiation transport code was used for Monte Carlo (MC) simulations. Point sources with energies of 0.02, 0.03, 0.05, 0.1, 0.2, and 0.4 MeV were simulated to cover the range of pertinent brachytherapy energies and to glean dosimetric trends independent of specific radionuclide emissions. Source positions from postimplant CT scans of five patient implants were used for source coordinates, with dose normalized to 200 Gy at the center of each implant. With the presence of fibrosis (around the implant), cortical bone, lung, and healthy tissues, dose distributions and {sub PTV}DVH were calculated using the MCNP *FMESH4 tally and the NIST mass-energy absorption coefficients. This process was repeated upon replacing all tissues with water. For all photon energies, 10{sup 9} histories were simulated to achieve statistical errors (k = 1) typically of 1%. Results: The mean PTV doses calculated using tissue heterogeneities for all five patients changed (compared to dose to water) by only a few percent over the examined photon energy range, as did PTV dose at the implant center. The {sub PTV}V{sub 100} values were 81.2%, 90.0% (as normalized), 94.3%, 93.9%, 92.7%, and 92.2% for 0.02, 0.03, 0.05, 0.1, 0.2, and 0.4 MeV source photons, respectively. Relative to water, the maximum bone doses were higher by factors of 3.7, 5.1, 5.2, 2.4, 1.2, and 1.0 The maximum lung doses were about 0.98, 0.94, 0.91, 0.94, 0.97, and 0.99. Relative to water, the maximum healthy tissue doses at the mediastinal position were higher by factors of 9.8, 2.2, 1.3, 1.1, 1.1, and 1.1. However, the maximum doses to these healthy tissues were only 3.1, 7.2, 11.3, 10.9, 9.0, and 8.1 Gy while maximum bone doses were 66, 177, 236, 106, 49, and 39 Gy, respectively. Similarly, maximum lung doses were 55, 66, 73, 74, 73, and 73 Gy, respectively. Conclusions: The current brachytherapy dose calculation formalism overestimates PTV dose and significantly underestimates doses to bone and healthy tissue. Further investigation using specific brachytherapy source models and patient-based CT datasets as MC input may indicate whether the observed trends can be generalized for low-energy lung brachytherapy dosimetry.

Yang Yun; Rivard, Mark J. [Tufts University School of Medicine, Boston, Massachusetts 02111 (United States)

2011-11-15

212

Graphs with maximum connectivity index  

Microsoft Academic Search

Let G be a graph and dv the degree (=number of first neighbors) of its vertex v. The connectivity index of G is ?=?(dudv)?1\\/2, with the summation ranging over all pairs of adjacent vertices of G. In a previous paper (Comput. Chem. 23 (1999) 469), by applying a heuristic combinatorial optimization algorithm, the structure of chemical trees possessing extremal (maximum

Gilles Caporossi; Ivan Gutman; Pierre Hansen; Ljiljana Pavlovic

2003-01-01

213

Common Sense and Maximum Entropy  

Microsoft Academic Search

This paper concerns the question of how to draw inferences common sensically from uncertain knowledge. Since the early work of Shore and Johnson, [10], Paris and Vencovsk a, [6], and Csiszár, [1], it has been known that the Maximum Entropy Inference Process is the only inference process which obeys certain common sense principles of uncertain reasoning. In this paper we

Jeff Paris

2000-01-01

214

Maximum throughput of clandestine relay  

Microsoft Academic Search

The maximum throughput of relaying information flows while concealing their presence is studied. The concealment is achieved by embedding transmissions of information flows into truly independent transmission schedules that resemble the normal transmission behaviors without any flow. Such embedding may reduce the throughput for delay-sensitive flows, and the paper provides a quantitative characterization of the level of reduction. Under a

Ting He; Lang Tong; Ananthram Swami

2009-01-01

215

Local hardness equalization and the principle of maximum hardness.  

PubMed

The chemical potential, hardness, and hyperhardnesses equalization principles are used to show that the leading term associated with charge transfer in the total interaction energy among the fragments in which a molecule is divided is directly proportional to minus the hardness of the molecule in its ground state, as established by the principle of maximum hardness. The additional terms in the interaction energy, associated with the changes in the external potential of the fragments, provide explanation for deviations between the point of maximum hardness and the point of minimum energy. It is also found that the dual descriptor plays a very important role in hardness equalization. PMID:23758354

Gįzquez, José L; Vela, Alberto; Chattaraj, Pratim K

2013-06-01

216

Low-dose metronomic chemotherapy: a systematic literature analysis.  

PubMed

Low-dose metronomic (LDM) chemotherapy, the frequent and continuous use of low doses of conventional chemotherapeutics, is an emerging alternative to conventional chemotherapy. While promising tumour control rates and excellent safety profiles have been observed, there are no definitive phase III trial results. Furthermore, the selection of patients, drug dosages and dosing intervals is empirical. To systematically review the current state of knowledge regarding LDM chemotherapy, we searched the MEDLINE, EMBASE, CENTRAL and PubMed databases for fully published LDM chemotherapy trials. We calculated the relative dose-intensity (RDI, mg/m(2)/week) of each LDM regimen as compared to conventional maximum tolerated dose (MTD) dosages and the 'dosing-density' (DD, % of days with chemotherapy administration per cycle). Meta-regression was performed to examine factors associated with disease control rate (DCR; complete response (CR)+partial response (PR)+stable disease (SD)). Eighty studies involving mainly pretreated patients with advanced/metastatic breast (26.25%) and prostate (11.25%) cancers were retrieved. The most commonly used drug was cyclophosphamide (43%). LDM chemotherapy was frequently combined with other therapies (64.5%). Response rate (RR) and progression-free survival (PFS) were the most frequent primary end-points (24% and 19%). Mean RR was 26.03% (95% confidence interval (CI): 21.4-30.7), median PFS was 4.6months (interquartile range (IQR): 2.9-7.0) and mean DCR was 56.3% (95% CI: 50.9-61.6). RDI, DD and metronomic drug used were not associated with DCR. Grade 3/4 adverse events were rare (anaemia 7.78%, fatigue 13.4%). Thus, LDM therapy appears to be clinically beneficial and safe in a broad range of tumors. However, meta-regression analysis did not identify predictive factors of response. PMID:23880474

Lien, K; Georgsdottir, S; Sivanathan, L; Chan, K; Emmenegger, U

2013-11-01

217

A {gamma} dose distribution evaluation technique using the k-d tree for nearest neighbor searching  

SciTech Connect

Purpose: The authors propose an algorithm based on the k-d tree for nearest neighbor searching to improve the {gamma} calculation time for 2D and 3D dose distributions. Methods: The {gamma} calculation method has been widely used for comparisons of dose distributions in clinical treatment plans and quality assurances. By specifying the acceptable dose and distance-to-agreement criteria, the method provides quantitative measurement of the agreement between the reference and evaluation dose distributions. The {gamma} value indicates the acceptability. In regions where {gamma}{<=}1, the predefined criterion is satisfied and thus the agreement is acceptable; otherwise, the agreement fails. Although the concept of the method is not complicated and a quick naieve implementation is straightforward, an efficient and robust implementation is not trivial. Recent algorithms based on exhaustive searching within a maximum radius, the geometric Euclidean distance, and the table lookup method have been proposed to improve the computational time for multidimensional dose distributions. Motivated by the fact that the least searching time for finding a nearest neighbor can be an O(log N) operation with a k-d tree, where N is the total number of the dose points, the authors propose an algorithm based on the k-d tree for the {gamma} evaluation in this work. Results: In the experiment, the authors found that the average k-d tree construction time per reference point is O(log N), while the nearest neighbor searching time per evaluation point is proportional to O(N{sup 1/k}), where k is between 2 and 3 for two-dimensional and three-dimensional dose distributions, respectively. Conclusions: Comparing with other algorithms such as exhaustive search and sorted list O(N), the k-d tree algorithm for {gamma} evaluation is much more efficient.

Yuan Jiankui; Chen Weimin [ICT Radiotherapy, Livingston, New Jersey 07039 (United States) and Northeast Radiation Oncology Center, Dunmore, Pennsylvania 18509 (United States); ICT Radiotherapy, Livingston, New Jersey 07039 (United States)

2010-09-15

218

Use of new radiochromic devices for peripheral dose measurement: potential in-vivo dosimetry application  

PubMed Central

The authors have studied the feasibility of using three new high-sensitivity radiochromic devices in measuring the doses to peripheral points outside the primary megavoltage photon beams. The three devices were GAFCHROMIC® EBT film, prototype Low Dose (LD) Film, and prototype LD Card. The authors performed point dosimetry using these three devices in water-equivalent solid phantoms at x = 3,5,8,10, and 15 cm from the edge of 6 MV and 15 MV photon beams of 10x10 cm2, and at depths of 0, 0.5 cm, and depth of maximum dose. A full sheet of EBT film was exposed with 5000 MU. The prototype LD film pieces were 1.5x2 cm2 in size. Some LD films were provided in the form of a card in 1.8x5 cm2 holding an active film in 1.8x2 cm2. These are referred to as “LD dosimeter cards”. The small LD films and cards were exposed with 500 MU. For each scanned film, a 6 mm circular area centered at the measurement point was sampled and the mean pixel value was obtained. The calibration curves were established from the calibration data for each combination of film/cards and densitometer/scanner. The doses at the peripheral points determined from the films were compared with those obtained using ion chamber at respective locations in a water phantom and general agreements were found. It is feasible to accurately measure peripheral doses of megavoltage photon beams using the new high-sensitivity radiochromic devices. This near real-time and inexpensive method can be applied in a clinical setting for dose measurements to critical organs and sensitive patient implant devices. PMID:21610987

Chiu-Tsao, S-T; Chan, MF

2009-01-01

219

Development, validation and transfer of a Near Infrared method to determine in-line the end point of a fluidised drying process for commercial production batches of an approved oral solid dose pharmaceutical product  

Microsoft Academic Search

Pharmaceutical companies are progressively adopting and introducing the principles of Quality by Design with the main purpose of assurance and built-in quality throughout the whole manufacturing process. Within this framework, a Partial Least Square (PLS) model, based on Near Infrared (NIR) spectra and humidity determinations, was built in order to determine in-line the drying end point of a fluidised bed

Antonio Peinado; Jonathan Hammond; Andrew Scott

2011-01-01

220

A Prospective Clinical Trial of Bladder Filling and 3D-Dosimetry in High-Dose-Rate Vaginal-Cuff Brachytherapy  

PubMed Central

Purpose To investigate the impact of bladder filling state on dosimetry and determine the best bladder dosimetric parameter in vaginal-cuff brachytherapy. Materials and Methods Twenty women received vaginal cylinder high-dose-rate (HDR) brachytherapy with each fraction followed by a planning CT scan on a prospective clinical trial. The bladder was full for fraction 2 and empty for fraction 3. Dose volume histogram (DVH) and dose surface histogram (DSH) values were generated for the bladder, rectum, and urethra. The midline maximum bladder point (MBP) and the midline maximum rectal point (MRP) were recorded. Paired t-tests, Pearson correlations, and regression analyses were performed. Results The volume and surface area of bladder irradiated were significantly smaller when the bladder was empty than when full. Of several DVH and DSH parameters evaluated, the bladder D2cc, V50, V70 and SA50 significantly predicted the difference in empty versus full filling states. The V70 and D2cc were significantly correlated with the MBP. Bladder filling did not alter the volume or surface area of rectum irradiated. However, an empty bladder did result in the nearest point of bowel being significantly closer to the vaginal cylinder than when the bladder was full. Conclusions In order to minimize radiation dose to the bladder, patients receiving vaginal-cuff HDR brachytherapy should be treated with an empty bladder if feasible. The MBP correlates well with the volumetric assessments of bladder dose and provides a non-invasive method for reporting maximum bladder point dose using 3D imaging. The MBP can therefore be used as a surrogate for complex dosimetry in the clinic. PMID:18395360

Stewart, Alexandra J.; Cormack, Robert A.; Lee, Hang; Xiong, Li; Hansen, Jorgen L.; O’Farrell, Desmond A.; Viswanathan, Akila N.

2010-01-01

221

The accuracy of dose calculations by anisotropic analytical algorithms for stereotactic radiotherapy in nasopharyngeal carcinoma  

NASA Astrophysics Data System (ADS)

Nasopharyngeal tumors are commonly treated with intensity-modulated radiotherapy techniques. For photon dose calculations, problems related to loss of lateral electronic equilibrium exist when small fields are used. The anisotropic analytical algorithm (AAA) implemented in Varian Eclipse was developed to replace the pencil beam convolution (PBC) algorithm for more accurate dose prediction in an inhomogeneous medium. The purpose of this study was to investigate the accuracy of the AAA for predicting interface doses for intensity-modulated stereotactic radiotherapy boost of nasopharyngeal tumors. The central axis depth dose data and dose profiles of phantoms with rectangular air cavities for small fields were measured using a 6 MV beam. In addition, the air-tissue interface doses from six different intensity-modulated stereotactic radiotherapy plans were measured in an anthropomorphic phantom. The nasopharyngeal region of the phantom was especially modified to simulate the air cavities of a typical patient. The measured data were compared to the data calculated by both the AAA and the PBC algorithm. When using single small fields in rectangular air cavity phantoms, both AAA and PBC overestimated the central axis dose at and beyond the first few millimeters of the air-water interface. Although the AAA performs better than the PBC algorithm, its calculated interface dose could still be more than three times that of the measured dose when a 2 × 2 cm2 field was used. Testing of the algorithms using the anthropomorphic phantom showed that the maximum overestimation by the PBC algorithm was 20.7%, while that by the AAA was 8.3%. When multiple fields were used in a patient geometry, the dose prediction errors of the AAA would be substantially reduced compared with those from a single field. However, overestimation of more than 3% could still be found at some points at the air-tissue interface.

Kan, M. W. K.; Cheung, J. Y. C.; Leung, L. H. T.; Lau, B. M. F.; Yu, P. K. N.

2011-01-01

222

Maximum Neighborhood Margin Discriminant Projection for Classification  

PubMed Central

We develop a novel maximum neighborhood margin discriminant projection (MNMDP) technique for dimensionality reduction of high-dimensional data. It utilizes both the local information and class information to model the intraclass and interclass neighborhood scatters. By maximizing the margin between intraclass and interclass neighborhoods of all points, MNMDP cannot only detect the true intrinsic manifold structure of the data but also strengthen the pattern discrimination among different classes. To verify the classification performance of the proposed MNMDP, it is applied to the PolyU HRF and FKP databases, the AR face database, and the UCI Musk database, in comparison with the competing methods such as PCA and LDA. The experimental results demonstrate the effectiveness of our MNMDP in pattern classification. PMID:24701144

Zhan, Yongzhao; Shen, Xiangjun; Du, Lan

2014-01-01

223

[Consideration of the newly standardized interventional reference point].  

PubMed

The interventional reference point is standardized by the International Electrotechnical Commission (IEC), and is adapted to adult cardiovascular studies. We examined the precision of the indicated incident dose at the interventional reference point. As a fundamental examination, we compared entrance phantom dose and incident dose at the interventional reference point. We also compared the entrance skin dose of patients with incident dose at the interventional reference point and evaluated the possibility of clinical application. Results showed that the incident dose at the interventional reference point indicated an underestimation of 0.77 times to an overestimation of 2.2 times when representing entrance surface dose. In clinical application, the incident dose at the interventional reference point calculated from the dose area product tended to overestimate by about 1.17 times the entrance skin dose measured by thermoluminescence dosimeter (TLD). Furthermore, the evaluation varied according to the angles of the C-arm of the x-ray system. A interventional reference point is a useful standard for simple, real-time dose measurement by the indirect method. It is important to understand the characteristics of the indicated incident dose at the interventional reference point in clinical use. PMID:15159671

Sakamoto, Hajime; Aikawa, Yoshihito; Ikegawa, Hiroaki; Sano, Yoshitomo; Araki, Tsutomu

2004-04-01

224

HADOC: a computer code for calculation of external and inhalation doses from acute radionuclide releases  

SciTech Connect

The computer code HADOC (Hanford Acute Dose Calculations) is described and instructions for its use are presented. The code calculates external dose from air submersion and inhalation doses following acute radionuclide releases. Atmospheric dispersion is calculated using the Hanford model with options to determine maximum conditions. Building wake effects and terrain variation may also be considered. Doses are calculated using dose conversion factor supplied in a data library. Doses are reported for one and fifty year dose commitment periods for the maximum individual and the regional population (within 50 miles). The fractional contribution to dose by radionuclide and exposure mode are also printed if requested.

Strenge, D.L.; Peloquin, R.A.

1981-04-01

225

Maximum life spur gear design  

NASA Technical Reports Server (NTRS)

Optimization procedures allow one to design a spur gear reduction for maximum life and other end use criteria. A modified feasible directions search algorithm permits a wide variety of inequality constraints and exact design requirements to be met with low sensitivity to initial guess values. The optimization algorithm is described, and the models for gear life and performance are presented. The algorithm is compact and has been programmed for execution on a desk top computer. Two examples are presented to illustrate the method and its application.

Savage, M.; Mackulin, B. J.; Coe, H. H.; Coy, J. J.

1991-01-01

226

A fast maximum power extraction algorithm for wind energy systems  

Microsoft Academic Search

With the advancements in the variable speed direct drive design and control of wind energy systems, the efficiency and energy capture of these systems is also increasing. As such, many maximum power point tracking methods have been developed and implemented. These MPPT algorithms can be broadly categorized into three types: Tip-Speed control, Power- Signal feedback, and Hill climb search based.

Shravana Musunuri; H. L. Ginn III

2011-01-01

227

Comprehensive review of wind energy maximum power extraction algorithms  

Microsoft Academic Search

With the advancements in the variable speed direct drive design and control of wind energy systems, the efficiency and energy capture of these systems is also increasing. As such, many maximum power point tracking methods have been developed and implemented. These MPPT algorithms can be broadly categorized into three types: Tip-Speed control, Power- Signal feedback, and Hill climb search based.

Shravana Musunuri; H. L. Ginn III

2011-01-01

228

Dew Point  

NSDL National Science Digital Library

Determine the dew point temperature for your classroom through a hands-on experiment. Use humidity and temperature probes to investigate the temperature at which it would rain in your classroom! Learn about water density and the conditions necessary to produce fog or rain.

2012-07-19

229

Dose and Dose Risk Caused by Natural Phenomena - Proposed Powder Metallurgy Core Manufacturing Facility  

SciTech Connect

The offsite radiological effects from high velocity straight winds, tornadoes, and earthquakes have been estimated for a proposed facility for manufacturing enriched uranium fuel cores by powder metallurgy. Projected doses range up to 30 mrem/event to the maximum offsite individual for high winds and up to 85 mrem/event for very severe earthquakes. Even under conservative assumptions on meteorological conditions, the maximum offsite dose would be about 20 per cent of the DOE limit for accidents involving enriched uranium storage facilities. The total dose risk is low and is dominated by the risk from earthquakes. This report discusses this test.

Holmes, W.G.

2001-08-16

230

Fast range-corrected proton dose approximation method using prior dose distribution  

NASA Astrophysics Data System (ADS)

For robust plan optimization and evaluation purposes, one needs a computationally efficient way to calculate dose distributions and dose-volume histograms (DVHs) under various changes in the variables associated with beam delivery and images. In this study, we report an approximate method for rapid calculation of dose when setup errors and anatomical changes occur during proton therapy. This fast dose approximation method calculates new dose distributions under various circumstances based on the prior knowledge of dose distribution from a reference setting. In order to validate the method, we calculated and compared the dose distributions from our approximation method to the dose distributions calculated from a clinically commissioned treatment planning system which was used as the ground truth. The overall accuracy of the proposed method was tested against varying degrees of setup error and anatomical deformation for selected patient cases. The setup error was simulated by rigid shifts of the patient; while the anatomical deformation was introduced using weekly acquired repeat CT data sets. We evaluated the agreement between the dose approximation method and full dose recalculation using a 3D gamma index and the root-mean-square (RMS) and maximum deviation of the cumulative dose volume histograms (cDVHs). The average passing rate of 3D gamma analysis under 3% dose and 3 mm distance-to-agreement criteria were 96% and 89% for setup errors and severe anatomy changes, respectively. The average of RMS and maximum deviation of the cDVHs under the setup error was 0.5% and 1.5%, respectively for all structures considered. Similarly, the average of RMS and maximum deviations under the weekly anatomical change were 0.6% and 2.7%, respectively. Our results show that the fast dose approximation method was able to account for the density variation of the patient due to the setup and anatomical changes with acceptable accuracy while significantly improving the computation time.

Park, Peter C.; Cheung, Joey; Zhu, X. Ronald; Sahoo, Narayan; Court, Laurence; Dong, Lei

2012-06-01

231

Fast range-corrected proton dose approximation method using prior dose distribution.  

PubMed

For robust plan optimization and evaluation purposes, one needs a computationally efficient way to calculate dose distributions and dose-volume histograms (DVHs) under various changes in the variables associated with beam delivery and images. In this study, we report an approximate method for rapid calculation of dose when setup errors and anatomical changes occur during proton therapy. This fast dose approximation method calculates new dose distributions under various circumstances based on the prior knowledge of dose distribution from a reference setting. In order to validate the method, we calculated and compared the dose distributions from our approximation method to the dose distributions calculated from a clinically commissioned treatment planning system which was used as the ground truth. The overall accuracy of the proposed method was tested against varying degrees of setup error and anatomical deformation for selected patient cases. The setup error was simulated by rigid shifts of the patient; while the anatomical deformation was introduced using weekly acquired repeat CT data sets. We evaluated the agreement between the dose approximation method and full dose recalculation using a 3D gamma index and the root-mean-square (RMS) and maximum deviation of the cumulative dose volume histograms (cDVHs). The average passing rate of 3D gamma analysis under 3% dose and 3 mm distance-to-agreement criteria were 96% and 89% for setup errors and severe anatomy changes, respectively. The average of RMS and maximum deviation of the cDVHs under the setup error was 0.5% and 1.5%, respectively for all structures considered. Similarly, the average of RMS and maximum deviations under the weekly anatomical change were 0.6% and 2.7%, respectively. Our results show that the fast dose approximation method was able to account for the density variation of the patient due to the setup and anatomical changes with acceptable accuracy while significantly improving the computation time. PMID:22588165

Park, Peter C; Cheung, Joey; Zhu, X Ronald; Sahoo, Narayan; Court, Laurence; Dong, Lei

2012-06-01

232

Can digoxin dose requirements be predicted?  

PubMed Central

A search for patient variables relevant to digoxin dose requirements was made in fourty-three patients with a wide range of renal and hepatic function. The daily dose of digoxin to achieve a mean serum concentration of 1.5 ng/ml, the standardized dose, was calculated for each patient. The standardized dose correlated significantly with the following variables, in descending order of correlation coefficient; creatinine clearance, serum creatinine concentration, body weight and serum albumin concentration. An equation containing the two independent variables, creatinine clearance and serum albumin concentration, had a significantly stronger correlation with standardized dose than creatinine clearance alone. Attempts were made in each patient to predict the standardized dose using both empirical prescribing methods and the published nomograms. Although a maximum of 70% of the variance of the standardized dose was explained, this corresponded approximately to one patient in three having a predicted dose outside the 95% confidnece limits for the standardized dose. There remain important sources of individual variation in digoxin dose requirements yet to be identified. Future application of empirical prescribing methods, such as multiple linear regression and Bayes' theorem, to prescription for large, defined patient groups may improve dose prediction for individual patients. PMID:973957

Dobbs, S M; Mawer, G E; Rodgers, M; Woodcock, B G; Lucas, S B

1976-01-01

233

A Comprehensive Analysis of Cardiac Dose in Balloon-Based High-Dose-Rate Brachytherapy for Left-Sided Breast Cancer  

SciTech Connect

Purpose: To investigate radiation dose to the heart in 60 patients with left-sided breast cancer who were treated with balloon-based high-dose-rate brachytherapy using MammoSite or Contura applicators. Methods and Materials: We studied 60 consecutive women with breast cancer who were treated with 34 Gy in 10 twice-daily fractions using MammoSite (n = 37) or Contura (n = 23) applicators. The whole heart and the left and right ventricles were retrospectively delineated, and dose-volume histograms were analyzed. Multiple dosimetrics were reported, such as mean dose (D{sub mean}); relative volume receiving 1.7, 5, 10, and 20 Gy (V1.7, V5, V10, and V20, respectively); dose to 1 cc (D{sub 1cc}); and maximum point dose (D{sub max}). Biologic metrics, biologically effective dose and generalized equivalent uniform dose were computed. The impact of lumpectomy cavity location on cardiac dose was investigated. Results: The average {+-} standard deviation of D{sub mean} was 2.45 {+-} 0.94 Gy (range, 0.56-4.68) and 3.29 {+-} 1.28 Gy (range, 0.77-6.35) for the heart and the ventricles, respectively. The average whole heart V5 and V10 values were 10.2% and 1.3%, respectively, and the heart D{sub max} was >20 Gy in 7 of 60 (11.7%) patients and >25 Gy in 3 of 60 (5%) patients. No cardiac tissue received {>=}30 Gy. The V1.7, V5, V10, V20, and D{sub mean} values were all higher for the ventricles than for the whole heart. For balloons located in the upper inner quadrant of the breast, the average whole heart D{sub mean} was highest. The D{sub mean}, biologically effective dose, and generalized equivalent uniform dose values for heart and ventricles decreased with increasing minimal distance from the surface of the balloon. Conclusions: On the basis of these comprehensive cardiac dosimetric data, we recommend that cardiac dose be routinely reported and kept as low as possible in balloon-based high-dose-rate brachytherapy treatment planning for patients with left-sided breast cancer so the correlation with future cardiac toxicity data can be investigated.

Valakh, Vladimir, E-mail: vladimir@valakh.com [Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, PA (United States); Kim, Yongbok; Werts, E. Day; Trombetta, Mark G. [Department of Radiation Oncology, Allegheny General Hospital, Pittsburgh, PA (United States); Drexel University College of Medicine, Allegheny Campus, Pittsburgh, PA (United States)

2012-04-01

234

Pregnancy under high-dose buprenorphine  

Microsoft Academic Search

ObjectiveThis study was first conducted to compare the consequences of the use of methadone and high-dose buprenorphine in pregnancy in France and secondly to describe the heterogeneity of women under high-dose buprenorphine. This paper focuses on the second point only.

Laurence Simmat-Durand; Claude Lejeune; Laurent Gourarier

2009-01-01

235

Graphing Points  

NSDL National Science Digital Library

Let's learn how to use the lines on graphs (the x & y axis) to plot information. Choose any of the activities below to test your knowledge of identifying the coordinates correctly. Meteoroid Coordinates Soccer Coordinates Donut Coordinates Graphing Points Save the Zogs!-Using Linear Equations Using your coordinate plane knowledge and linear equations help to rescue the Zogs! Can you find the axis for these problems too? What have you noticed about linear equations? What do the lines in linear equations look ...

Izzy

2012-02-07

236

2011 Radioactive Materials Usage Survey for Unmonitored Point Sources  

SciTech Connect

This report provides the results of the 2011 Radioactive Materials Usage Survey for Unmonitored Point Sources (RMUS), which was updated by the Environmental Protection (ENV) Division's Environmental Stewardship (ES) at Los Alamos National Laboratory (LANL). ES classifies LANL emission sources into one of four Tiers, based on the potential effective dose equivalent (PEDE) calculated for each point source. Detailed descriptions of these tiers are provided in Section 3. The usage survey is conducted annually; in odd-numbered years the survey addresses all monitored and unmonitored point sources and in even-numbered years it addresses all Tier III and various selected other sources. This graded approach was designed to ensure that the appropriate emphasis is placed on point sources that have higher potential emissions to the environment. For calendar year (CY) 2011, ES has divided the usage survey into two distinct reports, one covering the monitored point sources (to be completed later this year) and this report covering all unmonitored point sources. This usage survey includes the following release points: (1) all unmonitored sources identified in the 2010 usage survey, (2) any new release points identified through the new project review (NPR) process, and (3) other release points as designated by the Rad-NESHAP Team Leader. Data for all unmonitored point sources at LANL is stored in the survey files at ES. LANL uses this survey data to help demonstrate compliance with Clean Air Act radioactive air emissions regulations (40 CFR 61, Subpart H). The remainder of this introduction provides a brief description of the information contained in each section. Section 2 of this report describes the methods that were employed for gathering usage survey data and for calculating usage, emissions, and dose for these point sources. It also references the appropriate ES procedures for further information. Section 3 describes the RMUS and explains how the survey results are organized. The RMUS Interview Form with the attached RMUS Process Form(s) provides the radioactive materials survey data by technical area (TA) and building number. The survey data for each release point includes information such as: exhaust stack identification number, room number, radioactive material source type (i.e., potential source or future potential source of air emissions), radionuclide, usage (in curies) and usage basis, physical state (gas, liquid, particulate, solid, or custom), release fraction (from Appendix D to 40 CFR 61, Subpart H), and process descriptions. In addition, the interview form also calculates emissions (in curies), lists mrem/Ci factors, calculates PEDEs, and states the location of the critical receptor for that release point. [The critical receptor is the maximum exposed off-site member of the public, specific to each individual facility.] Each of these data fields is described in this section. The Tier classification of release points, which was first introduced with the 1999 usage survey, is also described in detail in this section. Section 4 includes a brief discussion of the dose estimate methodology, and includes a discussion of several release points of particular interest in the CY 2011 usage survey report. It also includes a table of the calculated PEDEs for each release point at its critical receptor. Section 5 describes ES's approach to Quality Assurance (QA) for the usage survey. Satisfactory completion of the survey requires that team members responsible for Rad-NESHAP (National Emissions Standard for Hazardous Air Pollutants) compliance accurately collect and process several types of information, including radioactive materials usage data, process information, and supporting information. They must also perform and document the QA reviews outlined in Section 5.2.6 (Process Verification and Peer Review) of ES-RN, 'Quality Assurance Project Plan for the Rad-NESHAP Compliance Project' to verify that all information is complete and correct.

Sturgeon, Richard W. [Los Alamos National Laboratory

2012-06-27

237

Dose evaluation for skin and organ in hepatocellular carcinoma during angiographic procedure  

PubMed Central

Purpose The purpose of this study is to evaluate the radiation dose in patients undergoing liver angiographic procedure and verify the usefulness of different dose measurements to prevent deterministic effects. Gafchromic film, MicroMOSFET data and DIAMENTOR device of the X-ray system were used to characterize the examined interventional radiology (IR) procedure. Materials and methods A liver embolization procedure, the SIRT (Selective Internal Radiation Therapy), was investigated. The exposure parameters from the DIAMENTOR as well as patient and geometrical data were registered. Entrance skin dose map obtained using Gafchromic film (ESDGAF) in a standard phantom as well as in 12 patients were used to calculate the maximum skin dose (MSDGAF). MicroMOSFETs were used to assess ESD in relevant points/areas. Moreover, the maximum value of five MicroMOSFETs array, due to the extension of treated area and to the relative distance of 2–3 cm of two adjacent MicroMOSFETs, was useful to predict the MSD without interfering with the clinical practice. PCXMC vers.1.5 was used to calculate effective dose (E) and equivalent dose (H). Results The mean dose-area product (DAPDIAMENTOR) for SIRT procedures was 166 Gycm2, although a wide range was observed. The mean MSDGAF for SIRT procedures was 1090 mGy, although a wide range was experienced. A correlation was found between the MSDGAF measured on a patient and the DAPDIAMENTOR value for liver embolizations. MOSFET and Gafchromic data were in agreement within 5% in homogeneous area and within 20% in high dose gradient regions. The mean equivalent dose in critical organs was 89.8 mSv for kidneys, 22.9 mSv for pancreas, 20.2 mSv for small intestine and 21.0 mSv for spleen. Whereas the mean E was 3.7 mSv (range: 0.5-13.7). Conclusions Gafchromic films result useful to study patient exposure and determine localization and amplitude of high dose skin areas to better predict the skin injuries. Then, DAPDIAMENTOR or MOSFET data could offer real-time methods, as on-line dose alert, to avoid any side effects during liver embolization with prolonged duration. PMID:24423052

2013-01-01

238

Multiple Early Eocene Thermal Maximums  

NASA Astrophysics Data System (ADS)

Periodic dissolution horizons signifying abrupt shoaling of the lysocline and CCD are characteristic features of deep-sea sections and often attributed to Milankovitch forcing via their diagnostic frequencies. Prominent dissolution horizons also correspond to abrupt climate events, such as the Paleocene-Eocene thermal maximum (PETM), as a result of input of significant CH4 - CO2 into the ocean-atmosphere system. The question arises whether other significant dissolution horizons identified in sediments of late Paleocene and early Eocene age similar to the recently identified ELMO (Lourens et al., 2004) were formed as a result of greenhouse gas input, or whether they were related to cumulative effects of periodic changes in ocean chemistry and circulation. Here we report the discovery of a 3rd thermal maximum in early Eocene (about 52 Ma) sediments recovered from the South Atlantic during ODP Leg 208. The prominent clay layer was named the "X" event and was identified within planktonic foraminifer zone P7 and calcareous nannofossil zone CP10 at four Walvis Ridge Transect sites with a water depth range of 2000 m (Sites 1262 to 1267). Benthics assemblages are composed of small individuals, have low diversity and high dominance. Dominant taxa are Nuttallides truempyi and various abyssaminids, resembling the post PETM extinction assemblages. High-resolution bulk carbonate \\delta13C measurements of one of the more shallow Sites 1265 reveal a rapid about 0.6 per mill drop in \\delta13C and \\delta18O followed by an exponential recovery to pre-excursion \\delta13C values well known for the PETM and also observed for the ELMO. The planktonic foraminiferal \\delta13C records of Morozovella subbotina and Acaranina soldadoensis in the deepest Site 1262 show a 0.8 to 0.9 per mill drop, whereas the \\delta13C drop of benthic foraminifera Nuttallides truempyi is slightly larger (about 1 per mill). We are evaluating mechanisms for the widespread change in deep-water chemistry, its connection to the surface-water response, and the relationship of the event, as well as the PETM and ELMO, with current astronomical solutions (Laskar et al., 2004; Varadi et al., 2003). References 1. Lourens, L.J., Sluijs, A., Kroon, D., Zachos, J.C., Thomas, E., Roehl, U., and the ODP Leg 208 Shipboard Scientific Party, 2004. An early Eocene transient warming (~53 Ma): Implications for astronomically-paced early Eocene hyperthermal events.- Abstract, 8th International Conference on Paleoceanography (ICP), 5-10 September 2004, Biarritz, France. 2. F. Varadi, B. Bunnegar, M. Ghil, Astrophysical J. 592, 620-630 (2003). 3. J. Laskar et al., Astronomy and Astrophysics (2004).

Roehl, U.; Zachos, J. C.; Thomas, E.; Kelly, D. C.; Donner, B.; Westerhold, T.

2004-12-01

239

Dynamically accumulated dose and 4D accumulated dose for moving tumors  

SciTech Connect

Purpose: The purpose of this work was to investigate the relationship between dynamically accumulated dose (dynamic dose) and 4D accumulated dose (4D dose) for irradiation of moving tumors, and to quantify the dose uncertainty induced by tumor motion. Methods: The authors established that regardless of treatment modality and delivery properties, the dynamic dose will converge to the 4D dose, instead of the 3D static dose, after multiple deliveries. The bounds of dynamic dose, or the maximum estimation error using 4D or static dose, were established for the 4D and static doses, respectively. Numerical simulations were performed (1) to prove the principle that for each phase, after multiple deliveries, the average number of deliveries for any given time converges to the total number of fractions (K) over the number of phases (N); (2) to investigate the dose difference between the 4D and dynamic doses as a function of the number of deliveries for deliveries of a 'pulsed beam'; and (3) to investigate the dose difference between 4D dose and dynamic doses as a function of delivery time for deliveries of a 'continuous beam.' A Poisson model was developed to estimate the mean dose error as a function of number of deliveries or delivered time for both pulsed beam and continuous beam. Results: The numerical simulations confirmed that the number of deliveries for each phase converges to K/N, assuming a random starting phase. Simulations for the pulsed beam and continuous beam also suggested that the dose error is a strong function of the number of deliveries and/or total deliver time and could be a function of the breathing cycle, depending on the mode of delivery. The Poisson model agrees well with the simulation. Conclusions: Dynamically accumulated dose will converge to the 4D accumulated dose after multiple deliveries, regardless of treatment modality. Bounds of the dynamic dose could be determined using quantities derived from 4D doses, and the mean dose difference between the dynamic dose and 4D dose as a function of number of deliveries and/or total deliver time was also established.

Li Heng; Li Yupeng; Zhang Xiaodong; Li Xiaoqiang; Liu Wei; Gillin, Michael T.; Zhu, X. Ronald [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)

2012-12-15

240

Dynamically accumulated dose and 4D accumulated dose for moving tumors  

PubMed Central

Purpose: The purpose of this work was to investigate the relationship between dynamically accumulated dose (dynamic dose) and 4D accumulated dose (4D dose) for irradiation of moving tumors, and to quantify the dose uncertainty induced by tumor motion. Methods: The authors established that regardless of treatment modality and delivery properties, the dynamic dose will converge to the 4D dose, instead of the 3D static dose, after multiple deliveries. The bounds of dynamic dose, or the maximum estimation error using 4D or static dose, were established for the 4D and static doses, respectively. Numerical simulations were performed (1) to prove the principle that for each phase, after multiple deliveries, the average number of deliveries for any given time converges to the total number of fractions (K) over the number of phases (N); (2) to investigate the dose difference between the 4D and dynamic doses as a function of the number of deliveries for deliveries of a “pulsed beam”; and (3) to investigate the dose difference between 4D dose and dynamic doses as a function of delivery time for deliveries of a “continuous beam.” A Poisson model was developed to estimate the mean dose error as a function of number of deliveries or delivered time for both pulsed beam and continuous beam. Results: The numerical simulations confirmed that the number of deliveries for each phase converges to K/N, assuming a random starting phase. Simulations for the pulsed beam and continuous beam also suggested that the dose error is a strong function of the number of deliveries and/or total deliver time and could be a function of the breathing cycle, depending on the mode of delivery. The Poisson model agrees well with the simulation. Conclusions: Dynamically accumulated dose will converge to the 4D accumulated dose after multiple deliveries, regardless of treatment modality. Bounds of the dynamic dose could be determined using quantities derived from 4D doses, and the mean dose difference between the dynamic dose and 4D dose as a function of number of deliveries and/or total deliver time was also established. PMID:23231285

Li, Heng; Li, Yupeng; Zhang, Xiaodong; Li, Xiaoqiang; Liu, Wei; Gillin, Michael T.; Zhu, X. Ronald

2012-01-01

241

The maximum drag reduction asymptote  

NASA Astrophysics Data System (ADS)

Addition of a small amount of long chain polymers to a Newtonian solvent can lead to a dramatic drag reduction in turbulent flows. This effect has been extensively studied since its discovery in the late 1940's. The drag reduction at first is proportional to the polymer concentration (Weisenberg number) but then saturates to the maximum drag reduction (MDR) asymptote. It is commonly believed that drag reduction results from an adjustment of the turbulent flow structure due to the action of the polymers. We here present experimental results of turbulent pipe flows using dilute polyacrylamid solutions at relatively large Weisenberg numbers (˜10). Our results show that for relatively low polymer concentrations transition to turbulence is postponed to higher Reynolds numbers. However when the Weisenberg number is increased further we find that the subcritical transition to turbulence, typical for Newtonian pipe flow disappears. Instead a supercritical instability is found at much lower Reynolds numbers which gives rise to a disordered flow. The observed drag of this disordered flow is identical to the well known MDR asymptote.

Hof, Björn; Samanta, Devranjan; Wagner, Christian

2011-11-01

242

Technical basis for dose reconstruction  

SciTech Connect

The purpose of this paper is to consider two general topics: technical considerations of why dose-reconstruction studies should or should not be performed and methods of dose reconstruction. The first topic is of general and growing interest as the number of dose-reconstruction studies increases, and one asks the question whether it is necessary to perform a dose reconstruction for virtually every site at which, for example, the Department of Energy (DOE) has operated a nuclear-related facility. And there is the broader question of how one might logically draw the line at performing or not performing dose-reconstruction (radiological and chemical) studies for virtually every industrial complex in the entire country. The second question is also of general interest. There is no single correct way to perform a dose-reconstruction study, and it is important not to follow blindly a single method to the point that cheaper, faster, more accurate, and more transparent methods might not be developed and applied.

Anspaugh, L.R.

1996-01-31

243

Failure-probability driven dose painting  

PubMed Central

Purpose: To demonstrate a data-driven dose-painting strategy based on the spatial distribution of recurrences in previously treated patients. The result is a quantitative way to define a dose prescription function, optimizing the predicted local control at constant treatment intensity. A dose planning study using the optimized dose prescription in 20 patients is performed. Methods: Patients treated at our center have five tumor subvolumes from the center of the tumor (PET positive volume) and out delineated. The spatial distribution of 48 failures in patients with complete clinical response after (chemo)radiation is used to derive a model for tumor control probability (TCP). The total TCP is fixed to the clinically observed 70% actuarial TCP at five years. Additionally, the authors match the distribution of failures between the five subvolumes to the observed distribution. The steepness of the dose–response is extracted from the literature and the authors assume 30% and 20% risk of subclinical involvement in the elective volumes. The result is a five-compartment dose response model matching the observed distribution of failures. The model is used to optimize the distribution of dose in individual patients, while keeping the treatment intensity constant and the maximum prescribed dose below 85 Gy. Results: The vast majority of failures occur centrally despite the small volumes of the central regions. Thus, optimizing the dose prescription yields higher doses to the central target volumes and lower doses to the elective volumes. The dose planning study shows that the modified prescription is clinically feasible. The optimized TCP is 89% (range: 82%–91%) as compared to the observed TCP of 70%. Conclusions: The observed distribution of locoregional failures was used to derive an objective, data-driven dose prescription function. The optimized dose is predicted to result in a substantial increase in local control without increasing the predicted risk of toxicity. PMID:23927314

Vogelius, Ivan R.; Håkansson, Katrin; Due, Anne K.; Aznar, Marianne C.; Berthelsen, Anne K.; Kristensen, Claus A.; Rasmussen, Jacob; Specht, Lena; Bentzen, Sųren M.

2013-01-01

244

Radiation Dose Chart  

NSDL National Science Digital Library

This is an illustration of the ionizing radiation dose a person can absorb from various sources. It provides a visual comparison of doses ranging from 0.1 microsieverts (from eating a banana) to a fatal dose of 8 sieverts.

Munroe, Randall

245

Maximum entropy principal for transportation  

SciTech Connect

In this work we deal with modeling of the transportation phenomenon for use in the transportation planning process and policy-impact studies. The model developed is based on the dependence concept, i.e., the notion that the probability of a trip starting at origin i is dependent on the probability of a trip ending at destination j given that the factors (such as travel time, cost, etc.) which affect travel between origin i and destination j assume some specific values. The derivation of the solution of the model employs the maximum entropy principle combining a priori multinomial distribution with a trip utility concept. This model is utilized to forecast trip distributions under a variety of policy changes and scenarios. The dependence coefficients are obtained from a regression equation where the functional form is derived based on conditional probability and perception of factors from experimental psychology. The dependence coefficients encode all the information that was previously encoded in the form of constraints. In addition, the dependence coefficients encode information that cannot be expressed in the form of constraints for practical reasons, namely, computational tractability. The equivalence between the standard formulation (i.e., objective function with constraints) and the dependence formulation (i.e., without constraints) is demonstrated. The parameters of the dependence-based trip-distribution model are estimated, and the model is also validated using commercial air travel data in the U.S. In addition, policy impact analyses (such as allowance of supersonic flights inside the U.S. and user surcharge at noise-impacted airports) on air travel are performed.

Bilich, F. [University of Brasilia (Brazil); Da Silva, R. [National Research Council (Brazil)

2008-11-06

246

Safety and pharmacokinetics of multiple doses of aclidinium bromide administered twice daily in healthy volunteers.  

PubMed

Chronic obstructive pulmonary disease (COPD) is characterized by progressive airway obstruction and increased cholinergic tone. The global initiative for chronic obstructive lung disease (GOLD) guidelines recommend long-acting anticholinergics for COPD maintenance treatment. Aclidinium bromide is a novel, long-acting muscarinic antagonist developed for the treatment of COPD. A phase I, randomized, single-blind, multiple-dose clinical trial was conducted to assess the safety and pharmacokinetics (PK) of multiple doses of twice-daily (BID) aclidinium in healthy subjects. Thirty healthy male and female subjects received aclidinium 200 ?g, 400 ?g, 800 ?g, or placebo twice daily for 7 days. Subjects were randomized to 1 of 3 cohorts and 10 subjects in each cohort were randomized (8:2) to either aclidinium or placebo groups. Safety was assessed via adverse events (AEs), laboratory evaluations, vital signs, and ECGs. Plasma samples were obtained at multiple time points throughout the study and analyzed for aclidinium and its inactive acid and alcohol metabolites using a fully validated method of liquid chromatography coupled with tandem mass spectrometry. A total of 9 treatment-emergent AEs were reported (1, placebo; 3, aclidinium 400 ?g; 5, aclidinium 800 ?g), all of which were mild in severity. No serious AEs were reported. There were no clinically meaningful changes in laboratory parameters or vital signs. PK parameters on Day 7 following BID dosing of aclidinium showed that steady state was achieved for aclidinium and its metabolites. On Days 1 and 7, maximum plasma concentrations (Cmax) of aclidinium were generally observed at the first PK time point (5 min postdose) and rapidly declined, with plasma concentrations generally less than 10% of Cmax by 6 h postdose in all aclidinium groups. Mean effective t(½) after the evening dose on Day 7 ranged from 4.6 to 7.0 h for aclidinium 400 ?g and 800 ?g, similar to the terminal t(½) observed on Day 1 (4.5-5.9 h). Exposure for aclidinium and both metabolites increased with increasing dose, with the increase in exposure being less than dose proportional between the 400 ?g and 800 ?g doses. Overall, all doses of aclidinium were safe and well tolerated throughout the study. Pharmacokinetic steady state was reached for aclidinium and both metabolites within the 7-day treatment period for all doses tested. Aclidinium bromide exhibited time-independent PK following dosing to steady state, indicating that similar concentration versus time profiles will occur after repeated administration at the same dose and frequency. PMID:22366196

Lasseter, K; Dilzer, S; Jansat, J M; Garcia Gil, E; Caracta, C F; Ortiz, S

2012-04-01

247

Carcinoma of the cervix: analysis of bladder and rectal radiation dose and complications.  

PubMed

From April 1969 through December 1980, 527 patients with epidermoid carcinoma of the cervix received radical radiation therapy at North Carolina Memorial Hospital (NCMH). The treatment was designed to deliver a combined dose (external beam plus intracavitary) of 7000-8000 cGy to Point A and 5000-6500 cGy to the pelvic lymph nodes depending upon the stage of the disease. The maximum dose to the bladder and to the rectum were calculated from the orthogonal intracavitary placement films with contrast material in these organs. Thirty-three cases of cystitis and fifty-eight cases of proctitis were recorded. The mean bladder dose for the group of patients with cystitis was higher, 6661 +/- 1309 cGy, than that for the patients without cystitis, 6298 +/- 1305 cGy, p = .19. The risk of cystitis increased as a function of bladder dose ranging from 3% for patients receiving less than or equal to 5000 cGy to the bladder to 12% for patients receiving greater than or equal to 8001 cGy to the bladder. A similar correlation was also found for rectal dose and proctitis. The mean rectal dose for the group of patients with proctitis was higher, 6907 +/- 981 cGy, than that for the patients without proctitis, 6381 +/- 1290 cGy, p = .003. The risk of proctitis increased as a function of rectal dose ranging from 2% for patients receiving less than or equal to 5000 cGy to the rectum to 18% for patients receiving greater than or equal to 8001 cGy to the rectum. A study of the severity of the cystitis as a function of bladder dose revealed a relationship between bladder dose and the severity of the complication (Grade I cystitis = 6600 +/- 1318 cGy vs Grade III cystitis = 6856 +/- 853 cGy). A dose-response relationship was found between the rectal dose and the severity of the complication (Grade I proctitis = 6810 +/- 906 cGy vs Grade III proctitis = 6997 +/- 1137 cGy). This relationship was statistically significant, p = .003. While there was no difference in the frequency of cystitis as a function of dose to the whole pelvis, the risk of proctitis did increase with increasing doses of external beam to the whole pelvis. It ranged from 3% for patients who received 2000 cGy or less to the whole pelvis to 14% for patients who received greater than 4000 cGy to the whole pelvis, p = .02. PMID:2912959

Montana, G S; Fowler, W C

1989-01-01

248

Adaptive Urn Designs for Estimating Several Percentiles of a DoseResponse Curve  

E-print Network

), the median lethal dose (denoted LD50) (e.g., Dixon and Mood, 1948), the maximum tolerated dose in phase IAdaptive Urn Designs for Estimating Several Percentiles of a DoseĀ­Response Curve Raymond Mugno 1.S.A. \\Lambda eĀ­mail:mugno@ams.sunysb.edu Summary. Dose response experiments are crucial in biomedical studies

New York at Stoney Brook, State University of

249

Radiological Dose Assessment 8 2003 SITE ENVIRONMENTAL REPORT8-1  

E-print Network

Radiological Dose Assessment 8 2003 SITE ENVIRONMENTAL REPORT8-1 Brookhaven National Laboratory routinely assesses its operations to ensure that any potential radiological dose to the public, BNL workers radiological dose to the public is calculated as the maximum dose to a hypothetical Maximally Exposed

Homes, Christopher C.

250

CORA: Emission Line Fitting with Maximum Likelihood  

NASA Astrophysics Data System (ADS)

The advent of pipeline-processed data both from space- and ground-based observatories often disposes of the need of full-fledged data reduction software with its associated steep learning curve. In many cases, a simple tool doing just one task, and doing it right, is all one wishes. In this spirit we introduce CORA, a line fitting tool based on the maximum likelihood technique, which has been developed for the analysis of emission line spectra with low count numbers and has successfully been used in several publications. CORA uses a rigorous application of Poisson statistics. From the assumption of Poissonian noise we derive the probability for a model of the emission line spectrum to represent the measured spectrum. The likelihood function is used as a criterion for optimizing the parameters of the theoretical spectrum and a fixed point equation is derived allowing an efficient way to obtain line fluxes. As an example we demonstrate the functionality of the program with an X-ray spectrum of Capella obtained with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra observatory and choose the analysis of the Ne IX triplet around 13.5 Å.

Ness, Jan-Uwe; Wichmann, Rainer

2011-12-01

251

CORA - emission line fitting with Maximum Likelihood  

NASA Astrophysics Data System (ADS)

The advent of pipeline-processed data both from space- and ground-based observatories often disposes of the need of full-fledged data reduction software with its associated steep learning curve. In many cases, a simple tool doing just one task, and doing it right, is all one wishes. In this spirit we introduce CORA, a line fitting tool based on the maximum likelihood technique, which has been developed for the analysis of emission line spectra with low count numbers and has successfully been used in several publications. CORA uses a rigorous application of Poisson statistics. From the assumption of Poissonian noise we derive the probability for a model of the emission line spectrum to represent the measured spectrum. The likelihood function is used as a criterion for optimizing the parameters of the theoretical spectrum and a fixed point equation is derived allowing an efficient way to obtain line fluxes. As an example we demonstrate the functionality of the program with an X-ray spectrum of Capella obtained with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra observatory and choose the analysis of the Ne IX triplet around 13.5 Å.

Ness, J.-U.; Wichmann, R.

2002-07-01

252

HYDROMETEOROLOGICAL REPORT NO. 39 PROBABLE MAXIMUM PRECIPITATION"  

E-print Network

HYDROMETEOROLOGICAL REPORT NO. 39 PROBABLE MAXIMUM PRECIPITATION" IN THE HAWAllAN ISLANDS LOAN COPY (Nos. 6-22 Numbered Retroactively) *No: 1. Maximum possible precipitation over the Ompompanoos~c Basin above Union Villag~, Vt. 1943. *No. 2. Maximum possible precipitation over'the Ohio River-Basin above

253

Parameterized Algorithms for Directed Maximum Leaf Problems  

E-print Network

Parameterized Algorithms for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 spanning tree, then D contains one with at least (n/2) 1/5 - 1 leaves. 1 Introduction The Maximum Leaf a digraph D, the Directed Maximum Leaf OutĀ­Branching problem is the problem of finding an outĀ­branching in D

Krivelevich, Michael

254

Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose  

NASA Technical Reports Server (NTRS)

While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.

Welton, Andrew; Lee, Kerry

2010-01-01

255

Measurement verification of dose distributions in pulsed-dose rate brachytherapy in breast cancer  

PubMed Central

Aim The aim of the study was to verify the dose distribution optimisation method in pulsed brachytherapy. Background The pulsed-dose rate brachytherapy is a very important method of breast tumour treatment using a standard brachytheraphy equipment. The appropriate dose distribution round an implant is an important issue in treatment planning. Advanced computer systems of treatment planning are equipped with algorithms optimising dose distribution. Materials and methods The wax-paraffin phantom was constructed and seven applicators were placed within it. Two treatment plans (non-optimised, optimised) were prepared. The reference points were located at a distance of 5 mm from the applicators’ axis. Thermoluminescent detectors were placed in the phantom at suitable 35 chosen reference points. Results The dosimetry verification was carried out in 35 reference points for the plans before and after optimisation. Percentage difference for the plan without optimisation ranged from ?8.5% to 1.4% and after optimisation from ?8.3% to 0.01%. In 16 reference points, the calculated percentage difference was negative (from ?8.5% to 1.3% for the plan without optimisation and from ?8.3% to 0.8% for the optimised plan). In the remaining 19 points percentage difference was from 9.1% to 1.4% for the plan without optimisation and from 7.5% to 0.01% for the optimised plan. No statistically significant differences were found between calculated doses and doses measured at reference points in both dose distribution non-optimised treatment plans and optimised treatment plans. Conclusions No statistically significant differences were found in dose values at reference points between doses calculated by the treatment planning system and those measured by TLDs. This proves the consistency between the measurements and the calculations. PMID:24416545

Mantaj, Patrycja; Zwierzchowski, Grzegorz

2013-01-01

256

Dose escalation improves therapeutic outcome: post hoc analysis of data from a 12-week, multicentre, double-blind, parallel-group trial of trospium chloride in patients with urinary urge incontinence  

PubMed Central

Background Flexible dosing of anticholinergics used for overactive bladder (OAB) treatment is a useful strategy in clinical practice for achieving a maximum effective and maximum tolerated level of therapeutic benefit. In this post hoc analysis we evaluated the efficacy and tolerability of trospium chloride treatment for urinary urge incontinence (UUI) with focus on flexible dosing. Methods The data came from a 12-week, randomised, double-blind, phase IIIb study in which 1658 patients with urinary frequency plus urge incontinence received trospium chloride 15 mg TID (n = 828) or 2.5 mg oxybutynin hydrochloride TID (n = 830). After four weeks, daily doses were doubled and not readjusted in 29.2% (242/828) of patients in the trospium group, and in 23.3% (193/830) in the oxybuytnin group, until the end of treatment. We assessed the absolute reduction in weekly UUI episodes and the change in intensity of dry mouth, recorded in patients' micturition diaries. Adverse events were also evaluated. Statistics were descriptive. Results Dose escalation of either trospium or oxybutynin increased reduction in UUI episodes in the population studied. At study end, there were no relevant differences between the "dose adjustment" subgroups and the respective "no dose adjustment" subgroups (trospium: P = 0.249; oxybutynin: P = 0.349). After dose escalation, worsening of dry mouth was higher in both dose adjusted subgroups compared to the respective "no dose adjustment" subgroups (P < 0.001). Worsening of dry mouth was lower in the trospium groups than in the oxybutynin groups (P < 0.001). Adverse events were increased in the dose adjusted subgroups. Conclusions Flexible dosing of trospium was proven to be as effective, but better tolerated as the officially approved adjusted dose of oxybutynin. Trial registration (parent study) The study was registered with the German Federal Institute for Drugs and Medical Devices (BfArM, Berlin, Germany), registration number 4022383, as required at the time point of planning this study. PMID:20840754

2010-01-01

257

High dose rate endobronchial brachytherapy using a new applicator  

Microsoft Academic Search

Background and purpose: To obtain adequate spatial dose distribution for endobronchial brachytherapy, we applied reference dose points according to the bronchial diameter. For this purpose, we devised a new applicator of which the source transfer tube is contained in the center of the lumen for high dose rate (HDR) brachytherapy.Materials and methods: Thirty-nine patients with endobronchial cancer underwent endobronchial brachytherapy

Yoshihito Nomoto; Kazufusa Shouji; Shun Toyota; Masahiro Sasaoka; Shuuichi Murashima; Maki Ooi; Kan Takeda; Tsuyoshi Nakagawa

1997-01-01

258

A Comparative Performance Analysis and Optimization of the Irreversible Atkinson Cycle Under Maximum Power Density and Maximum Power Conditions  

NASA Astrophysics Data System (ADS)

This article reports the thermodynamic optimization based on the maximum power (MP) and maximum power density (MPD) criteria for an irreversible Atkinson heat-engine model which includes internal irreversibility resulting from the adiabatic processes. The power density, power output, and thermal efficiency are obtained by introducing the isentropic temperature ratio of the compression process, cycle temperature ratio, and the compression and expansion efficiencies. Optimal performance and design parameters of the Atkinson cycle are obtained analytically for the MP conditions and numerically for the MPD conditions. The results at MPD conditions are compared with those results obtained by using the MP and maximum thermal efficiency criteria. The effects of the cycle temperature ratio and irreversibilities on the general and optimal performances are investigated. It is shown that for the Atkinson cycle, a design based on the MPD conditions is more advantageous from the point of view of engine sizes and thermal efficiency.

Ust, Yasin

2009-06-01

259

Georgia fishery study: implications for dose calculations. Revision 1  

SciTech Connect

Fish consumption will contribute a major portion of the estimated individual and population doses from L-Reactor liquid releases and Cs-137 remobilization in Steel Creek. It is therefore important that the values for fish consumption used in dose calculations be as realistic as possible. Since publication of the L-Reactor Environmental Information Document (EID), data have become available on sport fishing in the Savannah River. These data provide SRP with a site-specific sport fish harvest and consumption values for use in dose calculations. The Georgia fishery data support the total population fish consumption and calculated dose reported in the EID. The data indicate, however, that both the EID average and maximum individual fish consumption have been underestimated, although each to a different degree. The average fish consumption value used in the EID is approximately 3% below the lower limit of the fish consumption range calculated using the Georgia data. Maximum fish consumption in the EID has been underestimated by approximately 60%, and doses to the maximum individual should also be recalculated. Future dose calculations should utilize an average adult fish consumption value of 11.3 kg/yr, and a maximum adult fish consumption value of 34 kg/yr. Consumption values for the teen and child age groups should be increased proportionally: (1) teen average = 8.5; maximum = 25.9 kg/yr; and (2) child average = 3.6; maximum = 11.2 kg/yr. 8 refs.

Turcotte, M.D.S.

1983-08-05

260

APPLICATION AND USE OF DOSE ESTIMATING EXPOSURE MODEL (DEEM) FOR ROUTE TO ROUTE DOSE COMPARISONS AFTER EXPOSURE TO TRICHLOROETHYLENE (TCE)  

EPA Science Inventory

Route-to-route extrapolations are a crucial step in many risk assessments. Often the doses which result In toxicological end points in one route must be compared with doses resulting from typical environmental exposures by another route. In this case we used EPA's Dose Estimati...

261

APPLICATION AND USE OF DOSE ESTIMATING EXPOSURE MODEL (DEEM) FOR DOSE COMPARISONS AFTER EXPOSURE TO TRICHLOROETHYLENE (TCE)  

EPA Science Inventory

Route-to-route extrapolations are a crucial step in many risk assessments. Often the doses which result In toxicological end points in one route must be compared with doses resulting from typical environmental exposures by another route. In this case we used EPA's Dose Estimati...

262

Applicationsfor2014 5 points 4 points 3 points 2 points 1 point  

E-print Network

(Individual) State Open (Senior State Representation) Coach Career Management Program Australian School Boys/Girls Footballers' Association (A or W League) Member of Australian Team open or underage (all sports) Member of Australian underage team for a particular sport #12;MUSIC Applicationsfor2014 5 points 4 points 3 points 2

New South Wales, University of

263

Retrospective Cohort Study of Bronchial Doses and Radiation-Induced Atelectasis After Stereotactic Body Radiation Therapy of Lung Tumors Located Close to the Bronchial Tree  

SciTech Connect

Purpose: To evaluate the dose–response relationship between radiation-induced atelectasis after stereotactic body radiation therapy (SBRT) and bronchial dose. Methods and Materials: Seventy-four patients treated with SBRT for tumors close to main, lobar, or segmental bronchi were selected. The association between incidence of atelectasis and bronchial dose parameters (maximum point-dose and minimum dose to the high-dose bronchial volume [ranging from 0.1 cm{sup 3} up to 2.0 cm{sup 3}]) was statistically evaluated with survival analysis models. Results: Prescribed doses varied between 4 and 20 Gy per fraction in 2-5 fractions. Eighteen patients (24.3%) developed atelectasis considered to be radiation-induced. Statistical analysis showed a significant correlation between the incidence of radiation-induced atelectasis and minimum dose to the high-dose bronchial volumes, of which 0.1 cm{sup 3} (D{sub 0.1cm3}) was used for further analysis. The median value of D{sub 0.1cm3} (?/? = 3 Gy) was EQD{sub 2,LQ} = 147 Gy{sub 3} (range, 20-293 Gy{sub 3}). For patients who developed atelectasis the median value was EQD{sub 2,LQ} = 210 Gy{sub 3}, and for patients who did not develop atelectasis, EQD{sub 2,LQ} = 105 Gy{sub 3}. Median time from treatment to development of atelectasis was 8.0 months (range, 1.1-30.1 months). Conclusion: In this retrospective study a significant dose–response relationship between the incidence of atelectasis and the dose to the high-dose volume of the bronchi is shown.

Karlsson, Kristin, E-mail: kristin.karlsson@karolinska.se [Department of Medical Physics, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Nyman, Jan [Department of Oncology, Sahlgrenska University Hospital, Gothenburg (Sweden); Baumann, Pia; Wersäll, Peter [Department of Oncology, Radiumhemmet, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Drugge, Ninni [Department of Radiation Physics, Sahlgrenska University Hospital, Gothenburg (Sweden); Gagliardi, Giovanna [Department of Medical Physics, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Johansson, Karl-Axel [Department of Radiation Physics, Sahlgrenska University Hospital, Gothenburg (Sweden); Persson, Jan-Olov [Statistical Research Group, Mathematical Statistics, Stockholm University, Stockholm (Sweden); Rutkowska, Eva [Physics Department, Clatterbridge Cancer Centre, Wirral (United Kingdom); Tullgren, Owe [Department of Oncology, Radiumhemmet, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Lax, Ingmar [Department of Medical Physics, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden)

2013-11-01

264

Peripheral doses from pediatric IMRT  

SciTech Connect

Peripheral dose (PD) data exist for conventional fields ({>=}10 cm) and intensity-modulated radiotherapy (IMRT) delivery to standard adult-sized phantoms. Pediatric peripheral dose reports are limited to conventional therapy and are model based. Our goal was to ascertain whether data acquired from full phantom studies and/or pediatric models, with IMRT treatment times, could predict Organ at Risk (OAR) dose for pediatric IMRT. As monitor units (MUs) are greater for IMRT, it is expected IMRT PD will be higher; potentially compounded by decreased patient size (absorption). Baseline slab phantom peripheral dose measurements were conducted for very small field sizes (from 2 to 10 cm). Data were collected at distances ranging from 5 to 72 cm away from the field edges. Collimation was either with the collimating jaws or the multileaf collimator (MLC) oriented either perpendicular or along the peripheral dose measurement plane. For the clinical tests, five patients with intracranial or base of skull lesions were chosen. IMRT and conventional three-dimensional (3D) plans for the same patient/target/dose (180 cGy), were optimized without limitation to the number of fields or wedge use. Six MV, 120-leaf MLC Varian axial beams were used. A phantom mimicking a 3-year-old was configured per Center for Disease Control data. Micro (0.125 cc) and cylindrical (0.6 cc) ionization chambers were appropriated for the thyroid, breast, ovaries, and testes. The PD was recorded by electrometers set to the 10{sup -10} scale. Each system set was uniquely calibrated. For the slab phantom studies, close peripheral points were found to have a higher dose for low energy and larger field size and when MLC was not deployed. For points more distant from the field edge, the PD was higher for high-energy beams. MLC orientation was found to be inconsequential for the small fields tested. The thyroid dose was lower for IMRT delivery than that predicted for conventional (ratio of IMRT/cnventional ranged from 0.47-0.94) doses {approx}[0.4-1.8 cGy]/[0.9-2.9 cGy]/fraction, respectively. Prior phantom reports are for fields 10 cm or greater, while pediatric central nervous system fields range from 4 to 7 cm, and effectively much smaller for IMRT (2-6 cm). Peripheral dose in close proximity (<10 cm from the field edge) is dominated by internal scatter; therefore, field-size differences overwhelm phantom size affects and increased MU. Distant peripheral dose, dominated by head leakage, was higher than predicted, even when accounting for MUs ({approx}factor of 3) likely due to the pediatric phantom size. The ratio of the testes dose ranged from 3.3-5.3 for IMRT/conventional. PD to OAR for pediatric IMRT cannot be predicted from large-field full phantom studies. For regional OAR, doses are likely lower than predicted by existing ''large field'' data, while the distant PD is higher.

Klein, Eric E.; Maserang, Beth; Wood, Roy; Mansur, David [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110 (United States)

2006-07-15

265

Understanding and using fluoroscopic dose display information.  

PubMed

Fluoroscopically guided procedures are an area of radiology in which radiation exposure to the patient is highly operator dependent. Modern fluoroscopy machines display a variety of information, including technique factors, field of view, operating geometry, exposure mode, fluoroscopic time, air kerma at the reference point (RAK), and air kerma area-product. However, the presentation of this information is highly vendor specific, and many users are unaware of how to interpret this information and use it to perform a study with the minimum necessary dose. A conceptual framework for understanding the radiation dose readout during a procedure is to compare it to the dashboard of an automobile, where the rate at which radiation is being applied (the RAK rate [mGy/min]) is the dose "speed" and the cumulative amount of radiation applied (cumulative RAK [mGy]) is the dose "odometer." This analogy can be used as a starting point to improve knowledge of these parameters, including how RAK is measured, how RAK correlates with skin dose, and how parameters are displayed differently during fluoroscopy and fluorography. Awareness of these factors is critical to understanding how dose parameters translate to patient risk and the consequences of high-dose studies. With this increased awareness, physicians performing fluoroscopically guided procedures can understand how to use built-in features of the fluoroscopic equipment (pulse rate, beam filtration, and automatic exposure control) and fluoroscopic techniques (procedure planning, patient positioning, proper collimation, and magnification) to reduce patient radiation dose, thereby improving patient safety. PMID:25442356

Weinberg, Brent D; Guild, Jeffrey B; Arbique, Gary M; Chason, David P; Anderson, Jon A

2015-01-01

266

Maximum Power Transfer Tracking for a Photovoltaic-Supercapacitor Energy System  

E-print Network

Maximum Power Transfer Tracking for a Photovoltaic-Supercapacitor Energy System Younghyun Kim optimization from an energy generation source (e.g., a solar cell array) to an energy storage element (e.g., a supercapacitor bank). Previous maximum power point tracking (MPPT) methods do not consider the fact

Pedram, Massoud

267

Robust maximum torque per amp (MTPA) control of PM-assisted synchronous reluctance motor  

Microsoft Academic Search

In this paper, a practical maximum torque per ampere control scheme along with a simple parameter estimator for PMa-SynRM is introduced. In this method, MTPA condition is achieved by calculation of the output torque and perturbing one variable while seeking the maximum output torque at the particular operating point. The maximization of the electromagnetic torque might be sensitive to the

Peyman Niazi; Hamid A. Toliyat

2006-01-01

268

A maximum likelihood estimation technique for spatial-temporal modal analysis  

Microsoft Academic Search

The authors use the data collected by a linear, multisensor array to identify the wavenumber, damping factor, frequency and amplitude of individual point sources in the far field. The algorithm is based on the principle of maximum likelihood. The solution to this optimization problem yields the maximum likelihood estimates of the spatial-temporal parameters for each source in a far field

Michael P. Clark; Louis L. Scharf

1991-01-01

269

A novel method to estimate the maximum power for a photovoltaic inverter system  

Microsoft Academic Search

This paper describes a novel method to approximate the maximum power for a photovoltaic inverter system for solar distributed generation. It is designed for power systems applications and utilities. The proposed method takes in consideration the interaction between solar panels, photovoltaic inverter, maximum power point tracking (MPPT) control, solar panel DC side dynamic model and the effective intensity of light

E. I. rtiz-Rivera; Fang Peng

2004-01-01

270

THE LIMIT DISTRIBUTION OF THE MAXIMUM INCREMENT OF A HEAVY-TAILED RANDOM WALK  

Microsoft Academic Search

In this paper we deal with the asymptotic distribution of the maximum increment of a random walk with heavy-tailed step sizes in the sense that their distribution is regularly varying. This problem is motivated by a long-standing problem on change point detection for epidemic alternatives. It turns out that the limit distribution of the maximum increment of the random walk

THOMAS MIKOSCH; ALFREDAS RA’

271

Treatment Planning Methods in High Dose Rate Interstitial Brachytherapy of Carcinoma Cervix: A Dosimetric and Radiobiological Analysis  

PubMed Central

Treatment planning is a trial and error process that determines optimal dwell times, dose distribution, and loading pattern for high dose rate brachytherapy. Planning systems offer a number of dose calculation methods to either normalize or optimize the radiation dose. Each method has its own characteristics for achieving therapeutic dose to mitigate cancer growth without harming contiguous normal tissues. Our aim is to propose the best suited method for planning interstitial brachytherapy. 40 cervical cancer patients were randomly selected and 5 planning methods were iterated. Graphical optimization was compared with implant geometry and dose point normalization/optimization techniques using dosimetrical and radiobiological plan quality indices retrospectively. Mean tumor control probability was similar in all the methods with no statistical significance. Mean normal tissue complication probability for bladder and rectum is 0.3252 and 0.3126 (P = 0.0001), respectively, in graphical optimized plans compared to other methods. There was no significant correlation found between Conformity Index and tumor control probability when the plans were ranked according to Pearson product moment method (r = ?0.120). Graphical optimization can result in maximum sparing of normal tissues. PMID:24587919

Anbumani, Surega; Anchineyan, Pichandi; Narayanasamy, ArunaiNambiraj; Palled, Siddanna R.; Sathisan, Sajitha; Jayaraman, Punitha; Selvi, Muthu; Bilimagga, Ramesh S.

2014-01-01

272

Signal analysis using the maximum entropy method  

NASA Astrophysics Data System (ADS)

The analysis of discrete series is explained using the maximum entropy method in order to solve data processing problems in the aeroelastic study of wind turbines. Discrete Fourier spectrum and maximum entropy spectrum are compared. This method searches for an autoregressive model for a series containing a maximum of information about entropy. The autoregressive model is outlined and the notions 'information' and 'entropy' in signal analysis are defined. Energy and phase spectrum construction, starting from an autoregressive model, is described, with examples. The maximum entropy method is valuable where Fourier transformation techniques hardly work or fail.

Kuik, W.

1981-03-01

273

Determining the effects of microsphere and surrounding material composition on {sup 90}Y dose kernels using egsnrc and mcnp5  

SciTech Connect

Purpose: Recent advances in the imaging of {sup 90}Y using positron emission tomography (PET) and improved uncertainty in the branching ratio for the internal pair production component of {sup 90}Y decay allow for a more accurate determination of the activity distribution of {sup 90}Y microspheres within a patient. This improved activity distribution can be convolved with the dose kernel of {sup 90}Y to calculate the dose distribution within a patient. This work investigates the effects of microsphere and surrounding material composition on {sup 90}Y dose kernels using egsnrc and mcnp5 and compares the results of these two transport codes. Methods: Monte Carlo simulations were performed with egsnrc and mcnp5 to calculate the dose rate at multiple radial distances around various {sup 90}Y sources. Point source simulations were completed with mcnp5 to determine the optimal electron transport settings for this work. After determining the optimal settings, point source simulations were completed using egsnrc (user code edknrc) and mcnp5 in water and liver [as defined by the International Commission on Radiation Units and Measurements (ICRU) Report 44]. The results were compared to ICRU Report 72 reference data. Point source simulations were also completed in water with a density of 1.06 g{center_dot}cm{sup -3} to evaluate the effect of the density of the surrounding material. Glass and resin microsphere simulations were performed with average and maximum diameter and density values (based on values given in the literature) in water and in liver. The results were compared to point source simulation results using the same transport code and in the same surrounding material. All simulations had statistical uncertainties less than 1%. Results: The optimal transport settings in mcnp5 for this work included using the energy-and step-specific algorithm (DBCN 17J 2) and ESTEP set to 10. These settings were used for all subsequent simulations with mcnp5. The point source simulations in water for both egsnrc and mcnp5 were found to agree within 2% of the ICRU 72 reference data over the investigated range. Point source simulations in liver had large differences relative to ICRU 72, approaching -60% near the maximum range of {sup 90}Y. These differences are mostly attributed to the difference in density between water (1.0 g{center_dot}cm{sup -3}) and liver (1.06 g{center_dot}cm{sup -3}). Glass and resin microsphere simulations showed a slight decrease in the dose rate near the maximum range of {sup 90}Y relative to the point source simulations. The largest relative differences were approximately -4.2% and -2.8% for the glass and resin microspheres, respectively. Agreement between the egsnrc and mcnp5 simulations results was generally good. Conclusions: The presence of the microsphere material causes slight differences in the {sup 90}Y dose kernel compared to those calculated with point sources. Large differences were seen between simulations in water and those in liver. For the most accurate calculation of the dose distribution, the density of the patient's liver should be accounted for in the calculation of the dose kernel. Lastly, due to the need to determine the optimal transport settings with mcnp5, electron transport with this code should be used with caution.

Paxton, Adam B.; Davis, Stephen D.; DeWerd, Larry A. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 and McGill University Health Centre, Department of Medical Physics, Montreal, Quebec H3G 1A4 (Canada); Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)

2012-03-15

274

Calculation of three-dimensional photon primary absorbed dose using forward and backward spread dose-distribution functions  

Microsoft Academic Search

This paper describes a method of calculating three-dimensional (3-D) photon primary absorbed dose in a homogeneous or heterogeneous medium. The method is based on a technique of convolving a pair of forward and backward spread dose-distribution functions with the primary water collision kerma distribution. Both spread dose-distribution functions can be constructed by analyzing the zero-area tissue-maximum ratio, the primary absorbed

Akira Iwasaki

1990-01-01

275

"Hedgehog Point" feature point matching based on point structure information  

NASA Astrophysics Data System (ADS)

Based on points structure information, this paper presents a new method called "hedgehog point" matching, a fast algorithm for point pattern matching is proposed to effectively solve the problems of optimal matches between two point pattern under geometrical transformation and correctly identify the missing or spurious points of patterns. Theorems and algorithms are developed to determine the matching pairs support of each point pair and its transformation parameters (scaling S and rotation ?) on a two-parameter space (S, ?). Experiments are conducted both on real and synthetic data. The experimental results show that the proposed matching algorithm can handle translation, rotation, and scaling differences under noisy or distorted condition.

Xu, Yi-dan; Zhu, Xian-wei; Yu, Qi-feng

2009-07-01

276

49 CFR 107.329 - Maximum penalties.  

Code of Federal Regulations, 2012 CFR

...the maximum civil penalty is $110,000 if the violation results in death, serious illness...minimum $495 civil penalty applies to a violation...the maximum civil penalty is $110,000 if the violation results in death, serious...

2012-10-01

277

49 CFR 107.329 - Maximum penalties.  

Code of Federal Regulations, 2010 CFR

...the maximum civil penalty is $110,000 if the violation results in death, serious illness...minimum $495 civil penalty applies to a violation...the maximum civil penalty is $110,000 if the violation results in death, serious...

2010-10-01

278

49 CFR 107.329 - Maximum penalties.  

Code of Federal Regulations, 2011 CFR

...the maximum civil penalty is $110,000 if the violation results in death, serious illness...minimum $495 civil penalty applies to a violation...the maximum civil penalty is $110,000 if the violation results in death, serious...

2011-10-01

279

49 CFR 107.329 - Maximum penalties.  

Code of Federal Regulations, 2013 CFR

...the maximum civil penalty is $175,000 if the violation results in death, serious illness...no minimum civil penalty, except for a minimum...the maximum civil penalty is $175,000 if the violation results in death, serious...

2013-10-01

280

49 CFR 107.329 - Maximum penalties.  

Code of Federal Regulations, 2014 CFR

...the maximum civil penalty is $175,000 if the violation results in death, serious illness...no minimum civil penalty, except for a minimum...the maximum civil penalty is $175,000 if the violation results in death, serious...

2014-10-01

281

Maximum likelihood training of probabilistic neural networks  

Microsoft Academic Search

A maximum likelihood method is presented for training probabilistic neural networks (PNN's) using a Gaussian kernel, or Parzen window. The proposed training algorithm enables general nonlinear discrimination and is a generalization of Fisher's method for linear discrimination. Important features of maximum likelihood training for PNN's are: 1) it economizes the well known Parzen window estimator while preserving feedforward NN architecture,

Roy L. Streit; Tod E. Luginbuhl

1994-01-01

282

DISCRETE MAXIMUM ENTROPY ESTIMATORS FOR SPATIAL INTERPOLATION  

Microsoft Academic Search

This study applies the maximum entropy principle to develop estimators for spatial interpolation. Rather than continuous probability distributions commonly applied in the literature, this study tries to develop the estimators based on discrete probabilities. The maximum entropy estimators established include those random fields assuming second-order stationary and intrinsic hypothesis. For further comparison, this study also investigates both the random fields

Yuh-Ming Lee

283

Estimating landscape carrying capacity through maximum clique analysis.  

PubMed

Habitat suitability (HS) maps are widely used tools in wildlife science and establish a link between wildlife populations and landscape pattern. Although HS maps spatially depict the distribution of optimal resources for a species, they do not reveal the population size a landscape is capable of supporting--information that is often crucial for decision makers and managers. We used a new approach, "maximum clique analysis," to demonstrate how HS maps for territorial species can be used to estimate the carrying capacity, N(k), of a given landscape. We estimated the N(k) of Ovenbirds (Seiurus aurocapillus) and bobcats (Lynx rufus) in an 1153-km2 study area in Vermont, USA. These two species were selected to highlight different approaches in building an HS map as well as computational challenges that can arise in a maximum clique analysis. We derived 30-m2 HS maps for each species via occupancy modeling (Ovenbird) and by resource utilization modeling (bobcats). For each species, we then identified all pixel locations on the map (points) that had sufficient resources in the surrounding area to maintain a home range (termed a "pseudo-home range"). These locations were converted to a mathematical graph, where any two points were linked if two pseudo-home ranges could exist on the landscape without violating territory boundaries. We used the program Cliquer to find the maximum clique of each graph. The resulting estimates of N(k) = 236 Ovenbirds and N(k) = 42 female bobcats were sensitive to different assumptions and model inputs. Estimates of N(k) via alternative, ad hoc methods were 1.4 to > 30 times greater than the maximum clique estimate, suggesting that the alternative results may be upwardly biased. The maximum clique analysis was computationally intensive but could handle problems with < 1500 total pseudo-home ranges (points). Given present computational constraints, it is best suited for species that occur in clustered distributions (where the problem can be broken into several, smaller problems), or for species with large home ranges relative to grid scale where resampling the points to a coarser resolution can reduce the problem to manageable proportions. PMID:23387124

Donovan, Therese M; Warrington, Gregory S; Schwenk, W Scott; Dinitz, Jeffrey H

2012-12-01

284

Absorbed doses from temporomandibular joint radiography  

SciTech Connect

Thermoluminescent dosimeters were used in a tissue-equivalent phantom to measure doses of radiation absorbed by various structures in the head when the temporomandibular joint was examined by four different radiographic techniques--the transcranial, transorbital, and sigmoid notch (Parma) projections and the lateral tomograph. The highest doses of radiation occurred at the point of entry for the x-ray beam, ranging from 112 mrad for the transorbital view to 990 mrad for the sigmoid notch view. Only the transorbital projection a radiation dose to the lens of the eye. Of the four techniques evaluated, the lateral tomograph produced the highest doses to the pituitary gland and the bone marrow, while the sigmoid notch radiograph produced the highest doses to the parotid gland.

Brooks, S.L.; Lanzetta, M.L.

1985-06-01

285

Magnetic field generated resistivity maximum in graphite  

NASA Technical Reports Server (NTRS)

In zero magnetic field, B, the electrical resistivity, rho(O,T) of highly oriented pyrolytic (polycrystalline) graphite drops smoothly with decreasing T, becoming constant below 4 K. However, in a fixed applied magnetic field B, the resistivity rho(B,T) goes through a maximum as a function of T, with larger maximum for larger B. The temperature of the maximum increases with B, but saturates to a constant value near 25 K (exact T depends on sample) at high B. In single crystal graphite a maximum in rho(B,T) as a function of T is also present, but has the effects of Landau level quantization superimposed. Several possible explanations for the rho(B,T) maximum are proposed, but a complete explanation awaits detailed calculations involving the energy band structure of graphite, and the particular scattering mechanisms involved.

Wollam, J. A.; Kreps, L. W.; Rojeski, M.; Vold, T.; Devaty, R.

1976-01-01

286

Multiple-dose, linear, dose-proportional pharmacokinetics of retigabine in healthy volunteers.  

PubMed

Retigabine, a first-in-class selective M-current potassium channel opener, is a novel antiepileptic compound currently in clinical development. The purpose of this randomized placebo-controlled study was to assess retigabine oral safety and pharmacokinetics in healthy male volunteers (N = 45). Subjects received one dose on day 1 and doses every 12 hours for the next 14 days. Fixed doses were given to the first four groups (200, 400, 500, and 600 mg per day). Titrated doses were given to group 5 in 100 mg increases every 4 days, achieving 700 mg per day on day 15. Serial blood samples were collected on days 1 and 15. Pharmacokinetic parameters were compared between days and among dose groups. After administration of a single dose, retigabine was rapidly absorbed, with maximum concentrations of 387 ng/ml (normalized to a 100 mg dose) occurring within 1.5 hours. Retigabine was eliminated with a mean terminal half-life of 8.0 hours and an apparent oral clearance of 0.70 L/h/kg in white subjects. In black subjects, retigabine clearance and volume of distribution were 25% and 30% lower, respectively, after normalizing by body weight, leading to higher exposure in this population. Retigabine's pharmocokinetics was linearly dose proportional. Steady-state pharmacokinetics was in agreement with single-dose pharmacokinetics, and the accumulation ratio was about 1.5. Retigabine and AWD21-360 trough evening concentrations were significantly lower (about 30% to 35%) than morning values. The titration regimen allowed for higher doses to be tolerated compared to the fixed-dose regimen. In conclusion, the pharmacokinetics of retigabine is linearly dose proportional for daily doses of 100 to 700 mg and is not modified on multiple administrations. PMID:11831540

Ferron, Geraldine M; Paul, Jeffrey; Fruncillo, Richard; Richards, Lyette; Knebel, Norbert; Getsy, John; Troy, Steven

2002-02-01

287

MPI Point-to-Point Communication  

NSDL National Science Digital Library

This module details and differentiates the various types of point-to-point communication available in MPI. Point-to-point communication involves transmission of a message between a pair of processes, as opposed to collective communication, which involves a group of processes.

288

Triadic conceptual structure of the maximum entropy approach to evolution.  

PubMed

Many problems in evolutionary theory are cast in dyadic terms, such as the polar oppositions of organism and environment. We argue that a triadic conceptual structure offers an alternative perspective under which the information generating role of evolution as a physical process can be analyzed, and propose a new diagrammatic approach. Peirce's natural philosophy was deeply influenced by his reception of both Darwin's theory and thermodynamics. Thus, we elaborate on a new synthesis which puts together his theory of signs and modern Maximum Entropy approaches to evolution in a process discourse. Following recent contributions to the naturalization of Peircean semiosis, pointing towards 'physiosemiosis' or 'pansemiosis', we show that triadic structures involve the conjunction of three different kinds of causality, efficient, formal and final. In this, we accommodate the state-centered thermodynamic framework to a process approach. We apply this on Ulanowicz's analysis of autocatalytic cycles as primordial patterns of life. This paves the way for a semiotic view of thermodynamics which is built on the idea that Peircean interpretants are systems of physical inference devices evolving under natural selection. In this view, the principles of Maximum Entropy, Maximum Power, and Maximum Entropy Production work together to drive the emergence of information carrying structures, which at the same time maximize information capacity as well as the gradients of energy flows, such that ultimately, contrary to Schrödinger's seminal contribution, the evolutionary process is seen to be a physical expression of the Second Law. PMID:21055440

Herrmann-Pillath, Carsten; Salthe, Stanley N

2011-03-01

289

Pharmacokinetics of BILR 355 after Multiple Oral Doses Coadministered with a Low Dose of Ritonavir ?  

PubMed Central

The pharmacokinetics and safety of BILR 355 following oral repeated dosing coadministered with low doses of ritonavir (RTV) were investigated in 12 cohorts of healthy male volunteers with a ratio of 6 to 2 for BILR 355 versus the placebo. BILR 355 was given once a day (QD) coadministered with 100 mg RTV (BILR 355/r) at 5 to 50 mg in a polyethylene glycol solution or at 50 to 250 mg as tablets. BILR 355 tablets were also dosed at 150 mg twice a day (BID) coadministered with 100 mg RTV QD or BID. Following oral dosing, BILR 355 was rapidly absorbed, with the mean time to maximum concentration of drug in serum reached within 1.3 to 5 h and a mean half-life of 16 to 20 h. BILR 355 exhibited an approximately linear pharmacokinetics for doses of 5 to 50 mg when given as a solution; in contrast, when given as tablets, BILR 355 displayed a dose-proportional pharmacokinetics, with a dose range of 50 to 100 mg; from 100 to 150 mg, a slightly downward nonlinear pharmacokinetics occurred. The exposure to BILR 355 was maximized at 150 mg and higher due to a saturated dissolution/absorption process. After oral dosing of BILR 355/r, 150/100 mg BID, the values for the maximum concentration of drug in plasma at steady state, the area under the concentration-time curve from 0 to the dose interval at steady state, and the minimum concentration of drug in serum at steady state were 1,500 ng/ml, 12,500 h·ng/ml, and 570 ng/ml, respectively, providing sufficient suppressive concentration toward human immunodeficiency virus type 1. Based on pharmacokinetic modeling along with the in vitro virologic data, several BILR 355 doses were selected for phase II trials using Monte Carlo simulations. Throughout the study, BILR 355 was safe and well tolerated. PMID:18955519

Huang, Fenglei; Drda, Kristin; MacGregor, Thomas R.; Scherer, Joseph; Rowland, Lois; Nguyen, Thuy; Ballow, Charles; Castles, Mark; Robinson, Patrick

2009-01-01

290

A note on the classical weak and strong maximum principles for linear parabolic partial differential inequalities  

NASA Astrophysics Data System (ADS)

In this note, we highlight a difference in the conditions of the classical weak maximum principle and the classical strong maximum principle for linear parabolic partial differential inequalities. We demonstrate, by the careful construction of a specific function, that the condition in the classical strong maximum principle on the coefficient of the zeroth-order term in the linear parabolic partial differential inequality cannot be relaxed to the corresponding condition in the classical weak maximum principle. In addition, we demonstrate that results (often referred to as boundary point lemmas) which conclude positivity of the outward directional derivatives of nontrivial solutions to linear parabolic partial differential inequalities at certain points on the boundary where a maxima is obtained cannot be obtained under the same zeroth-order coefficient conditions as in the classical strong maximum principle.

Needham, David John; Meyer, John Christopher

2015-01-01

291

A simple method of independent treatment time verification in gamma knife radiosurgery using integral dose  

SciTech Connect

The purpose of this study is to develop a simple independent dose calculation method to verify treatment plans for Leksell Gamma Knife radiosurgery. Our approach uses the total integral dose within the skull as an end point for comparison. The total integral dose is computed using a spreadsheet and is compared to that obtained from Leksell GammaPlan registered . It is calculated as the sum of the integral doses of 201 beams, each passing through a cylindrical volume. The average length of the cylinders is estimated from the Skull-Scaler measurement data taken before treatment. Correction factors are applied to the length of the cylinder depending on the location of a shot in the skull. The radius of the cylinder corresponds to the collimator aperture of the helmet, with a correction factor for the beam penumbra and scattering. We have tested our simple spreadsheet program using treatment plans of 40 patients treated with Gamma Knife registered in our center. These patients differ in geometry, size, lesion locations, collimator helmet, and treatment complexities. Results show that differences between our calculations and treatment planning results are typically within {+-}3%, with a maximum difference of {+-}3.8%. We demonstrate that our spreadsheet program is a convenient and effective independent method to verify treatment planning irradiation times prior to implementation of Gamma Knife radiosurgery.

Jin Jianyue; Drzymala, Robert; Li Zuofeng [Department of Radiation Oncology, Siteman Cancer Center, Washington University Medical Center, St. Louis, Missouri 63110 (United States)

2004-12-01

292

Estimating the seasonal maximum light use efficiency  

NASA Astrophysics Data System (ADS)

Light use efficiency (LUE) is a key parameter in estimating gross primary production (GPP) based on global Earth-observation satellite data and model calculations. In current LUE-based GPP estimation models, the maximum LUE is treated as a constant for each biome type. However, the maximum LUE varies seasonally. In this study, seasonal maximum LUE values were estimated from the maximum incident LUE versus the incident photosynthetically active radiation (PAR) and the fraction of absorbed PAR. First, an algorithm to estimate maximum incident LUE was developed to estimate GPP capacity using a light response curve. One of the parameters required for the light response curve was estimated from the linear relationship of the chlorophyll index and the GPP capacity at a high PAR level of 2000 (µmolm-2s-1), and was referred to as" the maximum GPP capacity at 2000". The relationship was determined for six plant functional types: needleleaf deciduous trees, broadleaf deciduous trees, needleleaf evergreen trees, broadleaf evergreen trees, C3 grass, and crops. The maximum LUE values estimated in this study displayed seasonal variation, especially those for deciduous broadleaf forest, but also those for evergreen needleleaf forest.

Muramatsu, Kanako; Furumi, Shinobu; Soyama, Noriko; Daigo, Motomasa

2014-11-01

293

Bladder and rectum dose estimations on digitized radiographs for vaginal brachytherapy after hysterectomy.  

PubMed

The purpose of this study was to evaluate the feasibility of assessing bladder and rectal point doses, using orthogonal radiographs without treatment planning, for vaginal cylinder applicator (VC), high-dose-rate (HDR) vaginal cuff brachytherapy (BT) after hysterectomy. Thirty-three VC HDR BT treatment plans from 31 postop- erative endometrial cancer patients were retrospectively analyzed. Single-channel VC with four differing diameters - 2.0 cm, 2.3 cm, 2.6 cm, and 3.0 cm - were analyzed. Dose-distance modeling was performed to estimate bladder and rectal point doses by measuring distances on each orthogonal radiograph without treat- ment planning. The estimated doses were then compared with doses calculated on treatment planning system (TPS). Their percent (%) dose differences were recorded. Analysis was performed for each VC size, ICRU bladder and rectal points, and the closest rectal point. The estimated doses obtained from dose-distance modeling displayed on average less than 2.5% difference when compared with TPS doses at ICRU bladder and rectal points for each VC size. Dose percent differences between estimated values and TPS values were on average 1.9% and 2.5% for ICRU blad- der and rectal point, respectively, regardless of VC sizes. Dose-distance modeling for closest rectal point presented on average 5.4% dose difference when compared with TPS values of all VC sizes. It was feasible to estimate rectal and bladder point doses by measuring distances on orthogonal radiographs without treatment plan- ning. Percent dose differences were 2.5% less for both ICRU bladder and rectal points, regardless of VC sizes. The use of closest rectal point is not recommended for estimating rectal dose.  PMID:25493529

Zhang, Winson; Bhatia, Sundershan K; Sun, Wenqing; Modrick, Joseph M; Kim, Yusung

2014-01-01

294

ALL-PATHWAYS DOSE ANALYSIS FOR THE PORTSMOUTH ON-SITE WASTE DISPOSAL FACILITY  

SciTech Connect

A Portsmouth On-Site Waste Disposal Facility (OSWDF) All-Pathways analysis has been conducted that considers the radiological impacts to a resident farmer. It is assumed that the resident farmer utilizes a farm pond contaminated by the OSWDF to irrigate a garden and pasture and water livestock from which food for the resident farmer is obtained, and that the farmer utilizes groundwater from the Berea sandstone aquifer for domestic purposes (i.e. drinking water and showering). As described by FBP 2014b the Hydrologic Evaluation of Landfill Performance (HELP) model (Schroeder et al. 1994) and the Surface Transport Over Multiple Phases (STOMP) model (White and Oostrom 2000, 2006) were used to model the flow and transport from the OSWDF to the Points of Assessment (POAs) associated with the 680-ft elevation sandstone layer (680 SSL) and the Berea sandstone aquifer. From this modeling the activity concentrations radionuclides were projected over time at the POAs. The activity concentrations were utilized as input to a GoldSimTM (GTG 2010) dose model, described herein, in order to project the dose to a resident farmer over time. A base case and five sensitivity cases were analyzed. The sensitivity cases included an evaluation of the impacts of using a conservative inventory, an uncased well to the Berea sandstone aquifer, a low waste zone uranium distribution coefficient (Kd), different transfer factors, and reference person exposure parameters (i.e. at 95 percentile). The maximum base case dose within the 1,000 year assessment period was projected to be 1.5E-14 mrem/yr, and the maximum base case dose at any time less than 10,000 years was projected to be 0.002 mrem/yr. The maximum projected dose of any sensitivity case was approximately 2.6 mrem/yr associated with the use of an uncased well to the Berea sandstone aquifer. This sensitivity case is considered very unlikely because it assumes leakage from the location of greatest concentration in the 680 SSL in to the Berea sandstone aquiver over time and does not conform to standard private water well construction practices. The bottom-line is that all predicted doses from the base case and five sensitivity cases fall well below the DOE all-pathways 25 mrem/yr Performance Objective.

Smith, F.; Phifer, M.

2014-04-10

295

Variations in skin dose using 6MV or 18MV x-ray beams  

Microsoft Academic Search

This research aimed to quantitatively evaluate the differences in percentage dose of maximum for 6MV and 18MV x-ray beams\\u000a within the first 1cm of interactions. Thus provide quantitative information regarding the basal, dermal and subcutaneous dose\\u000a differences achievable with these two types of high-energy x-ray beams. Percentage dose of maximum build up curves are measured\\u000a for most clinical field sizes

P. K. N. Yu; T. Cheung; M. J. Butson

2003-01-01

296

14 CFR 65.47 - Maximum hours.  

Code of Federal Regulations, 2011 CFR

...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...

2011-01-01

297

14 CFR 65.47 - Maximum hours.  

Code of Federal Regulations, 2014 CFR

...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...

2014-01-01

298

14 CFR 65.47 - Maximum hours.  

Code of Federal Regulations, 2012 CFR

...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...

2012-01-01

299

14 CFR 65.47 - Maximum hours.  

Code of Federal Regulations, 2013 CFR

...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...

2013-01-01

300

14 CFR 65.47 - Maximum hours.  

Code of Federal Regulations, 2010 CFR

...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...

2010-01-01

301

Raman self-focusing at maximum coherence  

NASA Astrophysics Data System (ADS)

We demonstrate a type of Raman self-focusing and -defocusing that is inherent in operation at maximum coherence. In this regime the two-photon detuning from the Raman resonance controls the refractive index of the medium.

Walker, D. R.; Yavuz, D. D.; Shverdin, M. Y.; Yin, G. Y.; Sokolov, A. V.; Harris, S. E.

2002-12-01

302

Monte Carlo comparison of superficial dose between flattening filter free and flattened beams.  

PubMed

This study investigates the superficial dose from FFF beams in comparison with the conventional flattened ones using a Monte Carlo (MC) method. Published phase-space files which incorporated real geometry of a TrueBeam accelerator were used for the dose calculation in phantom and clinical cases. The photon fluence on the central axis is 3 times that of a flattened beam for a 6 MV FFF beam and 5 times for a 10 MV beam. The mean energy across the field in air at the phantom surface is 0.92-0.95 MeV for the 6 MV FFF beam and 1.18-1.30 MeV for the corresponding flattened beam. At 10 MV, the values are 1.52-1.72 and 2.15-2.87 MeV for the FFF and flattened beams, respectively. The phantom dose at the depth of 1 mm in the 6 MV FFF beam is 6% ± 2.5% (of the maximum dose) higher compared to the flattened beam for a 25 × 25 cm(2) field and 14.6% ± 1.9% for the 2 × 2 cm(2) field. For the 10 MV beam, the corresponding differences are 3.4% ± 1.5% and 10.7% ± 0.6%. The skin dose difference at selected points on the patient's surface between the plans using FFF and flattened beams in the head-and-neck case was 6.5% ± 2.3% (1SD), and for the breast case it was 6.4% ± 2.3%. The Monte Carlo simulations showed that due to the lower mean energy in the FFF beam, the clinical superficial dose is higher without the flattening filter compared to the flattened beam. PMID:24662096

Javedan, Khosrow; Feygelman, Vladimir; Zhang, Ray R; Moros, Eduardo G; Correa, Candace R; Trotti, Andy; Li, Weiqi; Zhang, Geoffrey G

2014-06-01

303

Maximum, Minimum, and Current Temperature Protocol  

NSDL National Science Digital Library

The purpose of this activity is to measure air (and optionally soil) temperature within one hour of solar noon and the maximum and minimum air temperatures for the previous 24 hours. Intended outcomes are that students will learn to read minimum, maximum, and current temperatures using a U-shaped thermometer, understand diurnal and annual temperature variations, and recognize factors that influence atmospheric temperatures. Supporting background materials for both student and teacher are included.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

304

The use of spatial dose gradients and probability density function to evaluate the effect of internal organ motion for prostate IMRT treatment planning  

NASA Astrophysics Data System (ADS)

The aim of this study is to investigate the effects of internal organ motion on IMRT treatment planning of prostate patients using a spatial dose gradient and probability density function. Spatial dose distributions were generated from a Pinnacle3 planning system using a co-planar, five-field intensity modulated radiation therapy (IMRT) technique. Five plans were created for each patient using equally spaced beams but shifting the angular displacement of the beam by 15° increments. Dose profiles taken through the isocentre in anterior-posterior (A-P), right-left (R-L) and superior-inferior (S-I) directions for IMRT plans were analysed by exporting RTOG file data from Pinnacle. The convolution of the 'static' dose distribution D0(x, y, z) and probability density function (PDF), denoted as P(x, y, z), was used to analyse the combined effect of repositioning error and internal organ motion. Organ motion leads to an enlarged beam penumbra. The amount of percentage mean dose deviation (PMDD) depends on the dose gradient and organ motion probability density function. Organ motion dose sensitivity was defined by the rate of change in PMDD with standard deviation of motion PDF and was found to increase with the maximum dose gradient in anterior, posterior, left and right directions. Due to common inferior and superior field borders of the field segments, the sharpest dose gradient will occur in the inferior or both superior and inferior penumbrae. Thus, prostate motion in the S-I direction produces the highest dose difference. The PMDD is within 2.5% when standard deviation is less than 5 mm, but the PMDD is over 2.5% in the inferior direction when standard deviation is higher than 5 mm in the inferior direction. Verification of prostate organ motion in the inferior directions is essential. The margin of the planning target volume (PTV) significantly impacts on the confidence of tumour control probability (TCP) and level of normal tissue complication probability (NTCP). Smaller margins help to reduce the dose to normal tissues, but may compromise the dose coverage of the PTV. Lower rectal NTCP can be achieved by either a smaller margin or a steeper dose gradient between PTV and rectum. With the same DVH control points, the rectum has lower complication in the seven-beam technique used in this study because of the steeper dose gradient between the target volume and rectum. The relationship between dose gradient and rectal complication can be used to evaluate IMRT treatment planning. The dose gradient analysis is a powerful tool to improve IMRT treatment plans and can be used for QA checking of treatment plans for prostate patients.

Jiang, Runqing; Barnett, Rob B.; Chow, James C. L.; Chen, Jeff Z. Y.

2007-03-01

305

LOGIT: a program for dose-response analysis.  

PubMed

We describe a FORTRAN computer program for fitting the logistic distribution function: (formula: see text) Where x represents dose or time, to dose-response data. The program determines both weighted least squares and maximum likelihood estimates for the parameters alpha and beta. It also calculates the standard errors of alpha and beta under both estimation methods, as well as the median lethal dose (LD50) and its standard error. Dose--response curves found by both fitting methods can be plotted as well as the 95% confidence bands for these lines. PMID:467012

Koshiver, J; Moore, D

1979-07-01

306

Structural and electrical properties of high dose nitrogen implanted tantalum  

NASA Astrophysics Data System (ADS)

High purity tantalum foils were implanted with 20 keV molecular nitrogen ions at dose levels varying from 5 × 1016 to 1 × 1018 N2+ cm-2. The Fourier Transform Infrared (FTIR) spectra of the implanted layers show the formation of tantalum nitrides of different structures depending on the total ion dose. The X-Ray Diffraction (XRD) studies show the formation of Ta2N and TaN0.8 at all doses and TaN at higher doses (5 × 1017 to 1 × 1018 N+2 cm-2). The FTIR, XRD and electrical studies show sputter limited maximum nitride concentrations.

Yadav, A. D.; Dubey, S. K.; Gupta, G. K.; Rao, T. K. Gundu

307

Genetic algorithm dose minimization for an operational layout.  

SciTech Connect

In an effort to reduce the dose to operating technicians performing fixed-time procedures on encapsulated source material, a program has been developed to optimize the layout of workstations within a facility by use of a genetic algorithm. Taking into account the sources present at each station and the time required to complete each procedure, the program utilizes a point kernel dose calculation tool for dose estimates. The genetic algorithm driver employs the dose calculation code as a cost function to determine the optimal spatial arrangement of workstations to minimize the total worker dose.

McLawhorn, S. L. (Steve L.); Kornreich, D. E. (Drew E.); Dudziak, Donald J.

2002-01-01

308

The 1984 - 1987 Solar Maximum Mission event list  

NASA Technical Reports Server (NTRS)

Information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1984-1987 pointed observations is presented. Data from the following SMM experiments are included: (1) gamma ray spectrometer; (2) hard x-ray burst spectrometer; (3) flat crystal spectrometer; (4) bent crystal spectrometer; (5) ultraviolet spectrometer polarimeter; and (6) coronograph/polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included.

Dennis, B. R.; Licata, J. P.; Nelson, J. J.; Tolbert, A. K.

1992-01-01

309

Neutron dose equivalent meter  

DOEpatents

A neutron dose equivalent detector for measuring neutron dose capable of accurately responding to neutron energies according to published fluence to dose curves. The neutron dose equivalent meter has an inner sphere of polyethylene, with a middle shell overlying the inner sphere, the middle shell comprising RTV.RTM. silicone (organosiloxane) loaded with boron. An outer shell overlies the middle shell and comprises polyethylene loaded with tungsten. The neutron dose equivalent meter defines a channel through the outer shell, the middle shell, and the inner sphere for accepting a neutron counter tube. The outer shell is loaded with tungsten to provide neutron generation, increasing the neutron dose equivalent meter's response sensitivity above 8 MeV.

Olsher, Richard H. (Los Alamos, NM); Hsu, Hsiao-Hua (Los Alamos, NM); Casson, William H. (Los Alamos, NM); Vasilik, Dennis G. (Los Alamos, NM); Kleck, Jeffrey H. (Menlo Park, CA); Beverding, Anthony (Foster City, CA)

1996-01-01

310

Variations in skin dose using 6MV or 18MV x-ray beams.  

PubMed

This research aimed to quantitatively evaluate the differences in percentage dose of maximum for 6MV and 18MV x-ray beams within the first 1 cm of interactions. Thus provide quantitative information regarding the basal, dermal and subcutaneous dose differences achievable with these two types of high-energy x-ray beams. Percentage dose of maximum build up curves are measured for most clinical field sizes using 6MV and 18MV x-ray beams. Calculations are performed to produce quantitative results highlighting the percentage dose of maximum differences delivered to various depths within the skin and subcutaneous tissue region by these two beams. Results have shown that basal cell layer doses are not significantly different for 6MV and 18MV x-ray beams. At depths beyond the surface and basal cell layer there is a measurable and significant difference in delivered dose. This variation increases to 20% of maximum and 22% of maximum at 1 mm and 1 cm depths respectively. The percentage variations are larger for smaller field sizes where the photon in phantom component of the delivered dose is the most significant contributor to dose. By producing graphs or tables of % dose differences in the build up region we can provide quantitative information to the oncologist for consideration (if skin and subcutaneous tissue doses are of importance) during the beam energy selection process for treatment. PMID:12956189

Yu, P K N; Cheung, T; Butson, M J

2003-06-01

311

Effect of jaw size in megavoltage CT on image quality and dose  

SciTech Connect

Purpose: Recently, the jaw size for the TomoTherapy Hi-Art II{sup Registered-Sign} (TomoTherapy Inc., Madison, WI) was reduced from 4 mm (J4) to 1 mm (J1) to improve the longitudinal (IEC-Y) resolution in megavoltage computed tomography (MVCT) images. This study evaluated the effect of jaw size on the image quality and dose, as well as the dose delivered to the lens of the eye, which is a highly radiosensitive tissue. Methods: MVCT image quality (image noise, uniformity, contrast linearity, high-contrast resolution, and full width at half-maximum) and multiple scan average dose (MSAD) were measured at different jaw sizes. A head phantom and photoluminescence glass dosimeters (PLDs) were used to measure the exposed lens dose (cGy). Different MVCT scan modes (pitch = 1, 2, and 3) and scan lengths (108 mm, 156 mm, and 204 mm) were applied in the MSAD and PLDs measurements. Results: The change in jaw size from J4 to J1 produced no change or only a slight improvement in image noise, uniformity, contrast linearity, and high-contrast resolution. However, the full-width at half-maximum reduced from approximately 7.2 at J4 to 4.5 mm at J1, which represents an enhancement in the longitudinal resolution. The MSAD at the center point changed from approximately 0.69-2.32 cGy (peripheral: 0.83-2.49 cGy) at J4 to 0.85-2.81 cGy (peripheral: 1.05-2.86 cGy) at J1. The measured lens dose increased from 0.92-3.36 cGy at J4 to 1.06-3.91 cGy at J1. Conclusions: The change in jaw size improved longitudinal resolution. The MVCT imaging dose of approximately 3.86 cGy, 1.92 cGy, and 1.22 cGy was delivered at a pitch of 1, 2, and 3, respectively, per fraction in the head and neck treatment plans. Therefore, allowance for an approximately 15% increase in lens dose over that with J4 should be provided with J1.

Jung, Jae Hong; Cho, Kwang Hwan; Kim, Yong Ho; Moon, Seong Kwon; Min, Chul Kee; Kim, Woo Chul; Kim, Eun Seog; Chang, Ah Ram; Kim, Tae Ho; Yoon, Jai-Woong; Suh, Tae-Suk; Huh, Hyun Do [Department of Radiation Oncology, College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon 1174, Korea and Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea Seoul 137-701 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon 1174 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Soonchunhyang University Cheonan Hospital, Cheonan 23-20 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Soonchunhyang University Seoul Hospital, Seoul 657 (Korea, Republic of); Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 505 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Inha University of Korea, Incheon 7-206 (Korea, Republic of)

2012-08-15

312

24 CFR 941.306 - Maximum project cost.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...

2011-04-01

313

24 CFR 941.306 - Maximum project cost.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...

2012-04-01

314

24 CFR 941.306 - Maximum project cost.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...

2013-04-01

315

40 CFR 141.13 - Maximum contaminant levels for turbidity.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Maximum contaminant levels for turbidity. 141.13 Section 141.13...DRINKING WATER REGULATIONS Maximum Contaminant Levels § 141.13 Maximum contaminant levels for turbidity. The maximum...

2010-07-01

316

40 CFR 141.65 - Maximum residual disinfectant levels.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Maximum residual disinfectant levels. 141.65 Section 141...Contaminant Levels and Maximum Residual Disinfectant Levels § 141.65 Maximum residual disinfectant levels. (a) Maximum residual...

2010-07-01

317

ATS 351, Spring 2010 Weather Radar -55 points  

E-print Network

ATS 351, Spring 2010 Lab #9 Weather Radar - 55 points 1. (5 points) If a radar has a maximum) Explain the presence of a bright band. 3. (5 points) What are the differences between the Clear Air Mode Collins during a 5-hour period. This heavy rainfall caused the Spring Creek to spill over its banks, which

Rutledge, Steven

318

Maximum permissible voltage of YBCO coated conductors  

NASA Astrophysics Data System (ADS)

Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (Ic) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the Ic degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.

Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z.; Hong, Z.; Wang, D.; Zhou, H.; Shen, X.; Shen, C.

2014-06-01

319

Cell development obeys maximum Fisher information  

E-print Network

Eukaryotic cell development has been optimized by natural selection to obey maximal intracellular flux of messenger proteins. This, in turn, implies maximum Fisher information on angular position about a target nuclear pore complex (NPR). The cell is simply modeled as spherical, with cell membrane (CM) diameter 10 micron and concentric nuclear membrane (NM) diameter 6 micron. The NM contains about 3000 nuclear pore complexes (NPCs). Development requires messenger ligands to travel from the CM-NPC-DNA target binding sites. Ligands acquire negative charge by phosphorylation, passing through the cytoplasm over Newtonian trajectories toward positively charged NPCs (utilizing positive nuclear localization sequences). The CM-NPC channel obeys maximized mean protein flux F and Fisher information I at the NPC, with first-order delta I = 0 and approximate 2nd-order delta I = 0 stability to environmental perturbations. Many of its predictions are confirmed, including the dominance of protein pathways of from 1-4 proteins, a 4nm size for the EGFR protein and the approximate flux value F =10^16 proteins/m2-s. After entering the nucleus, each protein ultimately delivers its ligand information to a DNA target site with maximum probability, i.e. maximum Kullback-Liebler entropy HKL. In a smoothness limit HKL approaches IDNA/2, so that the total CM-NPC-DNA channel obeys maximum Fisher I. Thus maximum information approaches non-equilibrium, one condition for life.

B. R. Frieden; R. A. Gatenby

2014-04-29

320

Maximum magnitude earthquakes induced by fluid injection  

NASA Astrophysics Data System (ADS)

of numerous case histories of earthquake sequences induced by fluid injection at depth reveals that the maximum magnitude appears to be limited according to the total volume of fluid injected. Similarly, the maximum seismic moment seems to have an upper bound proportional to the total volume of injected fluid. Activities involving fluid injection include (1) hydraulic fracturing of shale formations or coal seams to extract gas and oil, (2) disposal of wastewater from these gas and oil activities by injection into deep aquifers, and (3) the development of enhanced geothermal systems by injecting water into hot, low-permeability rock. Of these three operations, wastewater disposal is observed to be associated with the largest earthquakes, with maximum magnitudes sometimes exceeding 5. To estimate the maximum earthquake that could be induced by a given fluid injection project, the rock mass is assumed to be fully saturated, brittle, to respond to injection with a sequence of earthquakes localized to the region weakened by the pore pressure increase of the injection operation and to have a Gutenberg-Richter magnitude distribution with a b value of 1. If these assumptions correctly describe the circumstances of the largest earthquake, then the maximum seismic moment is limited to the volume of injected liquid times the modulus of rigidity. Observations from the available case histories of earthquakes induced by fluid injection are consistent with this bound on seismic moment. In view of the uncertainties in this analysis, however, this should not be regarded as an absolute physical limit.

McGarr, A.

2014-02-01

321

Melting point, boiling point, and symmetry.  

PubMed

The relationship between the melting point of a compound and its chemical structure remains poorly understood. The melting point of a compound can be related to certain of its other physical chemical properties. The boiling point of a compound can be determined from additive constitutive properties, but the melting point can be estimated only with the aid of nonadditive constitutive parameters. The melting point of some non-hydrogen-bonding, rigid compounds can be estimated by the equation MP = 0.772 * BP + 110.8 * SIGMAL + 11.56 * ORTHO + 31.9 * EXPAN - 240.7 where MP is the melting point of the compound in Kelvin, BP is the boiling point, SIGMAL is the logarithm of the symmetry number, EXPAN is the cube of the eccentricity of the compound, and ORTHO indicates the number of groups that are ortho to another group. PMID:2235894

Abramowitz, R; Yalkowsky, S H

1990-09-01

322

The pharmacokinetics, CNS pharmacodynamics and adverse event profile of brivaracetam after single increasing oral doses in healthy males  

PubMed Central

What is already known about this subject Brivaracetam is a new chemical entity structurally related to levetiracetam, displaying a markedly higher affinity for the binding site believed to be primarily involved in the antiepileptic effect of levetiracetam. Studies to evaluate the pharmacological profile of brivaracetam demonstrate an approximately 10-fold higher potency than levetiracetam as well as a higher efficacy in models of epilepsy. If translated into therapeutic effects in humans, this would mean a greater decrease in seizure frequency and a higher number of responders and seizure-free patients in refractory epileptic patients as seen with levetiracetam. What this study adds This article reports the results of the first in human study with brivaracetam. Its pharmacokinetics and adverse events profile after single administration are evaluated, together with the effect of food on the former. Aims The objective of the study was to evaluate the pharmacokinetics (and how they are affected by food), CNS pharmacodynamics and the adverse event profile of brivaracetam after single increasing doses. Methods Healthy males (n = 27, divided into three alternating panels of nine subjects) received two different single oral doses of brivaracetam (10–1400 mg) and one dose of placebo during three periods of a randomized, double-blind, placebo-controlled study. The effect of food on its pharmacokinetics was assessed using a standard two-way crossover design in a further eight subjects who received two single oral doses of brivaracetam (150 mg) in the fasting state and after a high fat meal. Results Adverse events, none of which were serious, were mostly CNS-related and included somnolence, dizziness, and decreased attention, alertness, and motor control. Their incidence, severity and duration were dose-related. The maximum tolerated dose was established to be 1000 mg. Severe somnolence lasting 1 day occurred in one subject following 1400 mg. Brivaracetam was rapidly absorbed under fasting conditions, with a median tmax of approximately 1 h. Cmax was dose-proportional from 10 to 1400 mg, whereas AUC deviated from dose linearity above 600 mg. A high-fat meal had no effect on AUC (point estimate 0.99, 90%CI: 0.92–1.07) but delayed tmax (3 h) and decreased Cmax (point estimate 0.72, 90%CI: 0.66–0.79). Conclusions Brivaracetam was well tolerated after increasing single doses that represent up to several times the expected therapeutic dose. Brivaracetam was found to have desirable pharmacokinetic properties. The most common adverse events were somnolence and dizziness. PMID:17223857

Sargentini-Maier, Maria Laura; Rolan, Paul; Connell, John; Tytgat, Dominique; Jacobs, Tom; Pigeolet, Etienne; Riethuisen, Jean-Michel; Stockis, Armel

2007-01-01

323

Maximum Aerodynamic Force on an Ascending Space Vehicle  

NASA Astrophysics Data System (ADS)

The March 2010 issue of The Physics Teacher includes a great article by Metz and Stinner on the kinematics and dynamics of a space shuttle launch. Within those pages is a brief mention of an event known in the language of the National Aeronautics and Space Administration (NASA) as "maximum dynamic pressure" (called simply "Max.AirPressure" in the article), where the combined effect of air density and the shuttles speed produce the greatest aerodynamic stress on the vehicle as it ascends through the atmosphere toward orbit. Official commentary during a launch2 refers to this point in the ascent with language such as "space shuttle main engines throttling back as vehicle enters area of maximum dynamic pressure" and occurs in a range between 45 and 60 s after launch. (In dealing with this stress, the space shuttles main engines reduce their thrust at approximately 45 s to reduce acceleration, and return to normal levels again some 15 s later as maximum dynamic pressure is traversed.) This paper presents an analysis, accessible to introductory-level students, that predicts the time of Max. AirPressure for a given ascending spacecraft.

Backman, Philip

2012-03-01

324

EXTENSIVE DISEASE SMALL CELL LUNG CANCER DOSE-RESPONSE RELATIONSHIPS: IMPLICATIONS FOR RESISTANCE MECHANISMS  

PubMed Central

Background Some studies (but not others) suggested high doses are beneficial in small cell lung cancer (SCLC). We hypothesized dose-response curve (DRC) shape reflects resistance mechanisms. Methods We reviewed published SCLC clinical trialss and converted response rates into estimated mean tumor cell kill, assuming killing is proportional to reduction in tumor volume. Mean % cell survival was plotted vs planned dose-intensity. Nonlinear and linear meta-regression analyses (weighted according to the number of patients in each study) were used to assess DRC characteristics. Results Although associations between dose and cell survival were not statistically significant, DRCs sloped downward for 5 of 7 agents across all doses and for all 7 when lowest doses were excluded. Maximum mean cell kill across all drugs and doses was approximately 90%, suggesting there may be a maximum achievable tumor cell kill irrespective of number of agents or drug doses. Conclusions Downward DRC slopes suggest that maintaining relatively high doses may possibly maximize palliation, although the associations between dose and slope did not achieve statistical significance, and slopes for most drugs tended to be shallow. DRC flattening at higher doses would preclude cure, and would suggest that “saturable passive resistance” (deficiency of factors required for cell killing) limits maximum achievable cell kill. An example of factors that could flatten the dose-response curve at higher doses and lead to saturable passive resistance would be presence of quiescent, non-cycling cells. PMID:20881640

Stewart, David J.; Johnson, Constance; Lopez, Adriana; Glisson, Bonnie; Rhee, Jay M.; Bekele, B. Nebiyou

2010-01-01

325

Dose tracking and dose auditing in a comprehensive computed tomography dose-reduction program.  

PubMed

Implementation of a comprehensive computed tomography (CT) radiation dose-reduction program is a complex undertaking, requiring an assessment of baseline doses, an understanding of dose-saving techniques, and an ongoing appraisal of results. We describe the role of dose tracking in planning and executing a dose-reduction program and discuss the use of the American College of Radiology CT Dose Index Registry at our institution. We review the basics of dose-related CT scan parameters, the components of the dose report, and the dose-reduction techniques, showing how an understanding of each technique is important in effective auditing of "outlier" doses identified by dose tracking. PMID:25129210

Duong, Phuong-Anh; Little, Brent P

2014-08-01

326

Evaluation of performance of photovoltaic system with maximum power point (MPP)  

Microsoft Academic Search

Performance of the photovoltaic system is highly influenced by the weather, especially the irradiation and the temperature. To simplify the design of solar generator power, a mathematical model and its validity of the solar cell are required. In this work, the value of the parameters in the mathematical model is obtained by the measurement of the I–V curve of the

Harsono Hadi; Shinobu Tokuda; Slamet Rahardjo

2003-01-01

327

Low-Power Maximum Power Point Tracker with Digital Control for Thermophotovoltaic Generators  

E-print Network

This paper describes the design, optimization, and evaluation of the power electronics circuitry for a low-power portable thermophotovotaic (TPV) generator system. TPV system is based on a silicon micro-reactor design and ...

Pilawa, Robert

328

THE MINIMUM AND MAXIMUM NUMBER OF RATIONAL POINTS ON JACOBIAN SURFACES OVER FINITE FIELDS  

E-print Network

numbers, the arithmetic- geometric mean states that n c1 . . . cn 1 n (c1 + Ā· Ā· Ā· + cn) with equality the arithmetic-geometric mean, Serre [10] proved that g i=1 xi gm,(2) and so Proposition 1 implies that #A). Thus Tk 1.(3) On the other hand, using the arithmetic-geometric mean, we obtain T 1/(g k) k 1 g k {i1

Paris-Sud XI, UniversitƩ de

329

Long Duration Balloon Maximum Power Point Tracking (MPPT) solar power system development  

Microsoft Academic Search

High altitude scientific balloons have been used for many years to provide scientists with access to near space at a fraction of the cost of satellite based or sounding rocket experiments. In recent years, these balloons have been successfully used for long duration missions of up to 40 days. Longer missions, with durations of up to 100 days (Ultra Long),

Juan Perez

2008-01-01

330

A Fuzzy-Based Maximum Power Point Tracker for Body Mounted Solar Panels in LEO Satellites  

Microsoft Academic Search

Solar panels are the power subsystem components which provide satellite electrical power. Solar panels characteristics depend on environmental conditions (insolation level, temperature and etc.). In this paper, design and simulation of fuzzy-based MPPT for the body mounted solar panel in a LEO satellite are presented. To show how good the proposed technique is; we applied it into a real system.

M. Taherbaneh; M. B. Menhaj

2007-01-01

331

A new maximum power point tracker of photovoltaic arrays using fuzzy controller  

Microsoft Academic Search

Studies on photovoltaic systems are increasing because of a large, secure, essentially exhaustible and broadly available resource as a future energy supply. However, the output power induced in the photovoltaic modules is influenced by an intensity of solar cell radiation, temperature of the solar cells and so on. Therefore, to maximize the efficiency of the renewable energy system, it is

Chung-Yuen Won; Duk-Heon Kim; Sei-Chan Kim; Won-Sam Kim; Hack-Sung Kim

1994-01-01

332

Maximum spin of black holes driving jets  

NASA Astrophysics Data System (ADS)

Unbound outflows in the form of highly collimated jets and broad winds appear to be a ubiquitous feature of accreting black hole systems. The most powerful jets are thought to derive a significant fraction, if not the majority, of their power from the rotational energy of the black hole. Whatever the precise mechanism that causes them, these jets must, therefore, exert a braking torque on the black hole. Consequently, we expect jet production to play a significant role in limiting the maximum spin attainable by accreting black holes. We calculate the spin-up function - the rate of change of black hole spin normalized to the black hole mass and accretion rate - for an accreting black hole, accounting for this braking torque. We assume that the accretion flow on to a Kerr black hole is advection-dominated (ADAF) and construct easy-to-use analytic fits to describe the global structure of such flows based on the numerical solutions of Popham & Gammie. We find that the predicted black hole spin-up function depends only on the black hole spin and dimensionless parameters describing the accretion flow. Using recent relativistic magnetohydrodynamical (MHD) numerical simulation results to calibrate the efficiency of angular momentum transfer in the flow, we find that an ADAF flow will spin a black hole up (or down) to an equilibrium value of about 96 per cent of the maximal spin value in the absence of jets. Combining our ADAF system with a simple model for jet power, we demonstrate that an equilibrium is reached at approximately 93 per cent of the maximal spin value, as found in the numerical simulation studies of the spin-up of accreting black holes, at which point the spin-up of the hole by accreted material is balanced by the braking torque arising from jet production. The existence of equilibrium spin means that optically dim active galactic nuclei (AGNs) that have grown via accretion from an advection-dominated flow will not be maximally rotating. It also offers a possible explanation for the tight correlation observed by Allen et al. between the Bondi accretion rate and jet power in nine, nearby, X-ray luminous giant elliptical galaxies. We suggest that the black holes in these galaxies must all be rotating close to their equilibrium value. Our model also yields a relationship between jet efficiency and black hole spin that is in surprisingly good agreement with that seen in the simulation studies, indicating that our simple model is a useful and convenient description of ADAF inflow - jet outflow about a spinning black hole for incorporation in semi-analytic modelling as well as cosmological numerical simulation studies focusing on the formation and evolution of galaxies, groups and clusters of galaxies.

Benson, Andrew J.; Babul, Arif

2009-08-01

333

Environmental monitoring and dose assessment following the December 1991 K-reactor aqueous tritium release.  

PubMed

Between 22 December and 25 December 1991, approximately 570 L of tritiated water was released from the K Reactor at the Savannah River Site. Analyses of river flow rates and measured tritium concentrations showed that approximately 210 TBq of tritium had been released from the reactor and was being transported down the Savannah River. Elevated tritium concentrations in the Savannah River were first detected on 26 December 1991. The maximum measured tritium concentration at Highway 301 (a major sampling point 37 km downstream of the Savannah River Site) was 2.5 Bq mL-1. A hypothetical maximum individual located at Highway 301 would have received a drinking water dose of approximately 0.35 microSv, less than 1% of the Environmental Protection Agency's 40 microSv y-1 drinking water standard. Concentrations at the intake canals to two water treatment facilities, approximately 160 km downstream, began to rise above normal on 28 December. The population dose to users of the downstream domestic water supplies and consumers of Savannah River biota was estimated to be 4.7 x 10(-3) person-Sv. PMID:8505227

Hamby, D M; Addis, R P; Beals, D M; Boni, A L; Cadieux, J R; Carlton, W H; Dunn, D L; Hall, G; Hayes, D W; Heffner, J D

1993-07-01

334

Decay heat and gamma dose-rate prediction capability in spent LWR fuel  

SciTech Connect

The ORIGEN2 code was established as a valid means to predict decay heat from LWR spent fuel assemblies for decay times up to 10,000 year. Calculational uncertainties ranged from 8.6% to a maximum of 16% at 2.5 years and 300 years cooling time, respectively. The calculational uncertainties at 2.5 years cooling time are supported by experiment. Major sources of uncertainty at the 2.5 year cooling time were identifed as irradiation history (5.7%) and nuclear data together with calculational methods (6.3%). The QAD shielding code was established as a valid means to predict interior and exterior gamma dose rates of spent LWR fuel assemblies. A calculational/measurement comparison was done on two assemblies with different irradiation histories and supports a 35% calculational uncertainty at the 1.8 and 3.0 year decay times studied. Uncertainties at longer times are expected to increase, but not significantly, due to an increased contribution from the actinides whose inventories are assigned a higher uncertainty. The uncertainty in decay heat rises to a maximum of 16% due to actinide uncertainties. A previous study was made of the neutron emission rate from a typical Turkey Point Unit 3, Region 4 spent fuel assembly at 5 years decay time. A conservative estimate of the neutron dose rate at the assembly surface was less than 0.5 rem/hr.

Neely, G J; Schmittroth, F

1982-08-01

335

Cancer chemoprevention by dietary chlorophylls: a 12,000-animal dose-dose matrix biomarker and tumor study.  

PubMed

Recent pilot studies found natural chlorophyll (Chl) to inhibit carcinogen uptake and tumorigenesis in rodent and fish models, and to alter uptake and biodistribution of trace (14)C-aflatoxin B1 in human volunteers. The present study extends these promising findings, using a dose-dose matrix design to examine Chl-mediated effects on dibenzo(def,p)chrysene (DBC)-induced DNA adduct formation, tumor incidence, tumor multiplicity, and changes in gene regulation in the trout. The dose-dose matrix design employed an initial 12,360 rainbow trout, which were treated with 0-4000ppm dietary Chl along with 0-225ppm DBC for up to 4weeks. Dietary DBC was found to induce dose-responsive changes in gene expression that were abolished by Chl co-treatment, whereas Chl alone had no effect on the same genes. Chl co-treatment provided a dose-responsive reduction in total DBC-DNA adducts without altering relative adduct intensities along the chromatographic profile. In animals receiving DBC alone, liver tumor incidence (as logit) and tumor multiplicity were linear in DBC dose (as log) up to their maximum-effect dose, and declined thereafter. Chl co-treatment substantially inhibited incidence and multiplicity at DBC doses up to their maximum-effect dose. These results show that Chl concentrations encountered in Chl-rich green vegetables can provide substantial cancer chemoprotection, and suggest that they do so by reducing carcinogen bioavailability. However, at DBC doses above the optima, Chl co-treatments failed to inhibit tumor incidence and significantly enhanced multiplicity. This finding questions the human relevance of chemoprevention studies carried out at high carcinogen doses that are not proven to lie within a linear, or at least monotonic, endpoint dose-response range. PMID:22079312

McQuistan, Tammie J; Simonich, Michael T; Pratt, M Margaret; Pereira, Cliff B; Hendricks, Jerry D; Dashwood, Roderick H; Williams, David E; Bailey, George S

2012-02-01

336

Dose-Limiting Toxicity After Hypofractionated Dose-Escalated Radiotherapy in Non–Small-Cell Lung Cancer  

PubMed Central

Purpose Local failure rates after radiation therapy (RT) for locally advanced non–small-cell lung cancer (NSCLC) remain high. Consequently, RT dose intensification strategies continue to be explored, including hypofractionation, which allows for RT acceleration that could potentially improve outcomes. The maximum-tolerated dose (MTD) with dose-escalated hypofractionation has not been adequately defined. Patients and Methods Seventy-nine patients with NSCLC were enrolled on a prospective single-institution phase I trial of dose-escalated hypofractionated RT without concurrent chemotherapy. Escalation of dose per fraction was performed according to patients' stratified risk for radiation pneumonitis with total RT doses ranging from 57 to 85.5 Gy in 25 daily fractions over 5 weeks using intensity-modulated radiotherapy. The MTD was defined as the maximum dose with ? 20% risk of severe toxicity. Results No grade 3 pneumonitis was observed and an MTD for acute toxicity was not identified during patient accrual. However, with a longer follow-up period, grade 4 to 5 toxicity occurred in six patients and was correlated with total dose (P = .004). An MTD was identified at 63.25 Gy in 25 fractions. Late grade 4 to 5 toxicities were attributable to damage to central and perihilar structures and correlated with dose to the proximal bronchial tree. Conclusion Although this dose-escalation model limited the rates of clinically significant pneumonitis, dose-limiting toxicity occurred and was dominated by late radiation toxicity involving central and perihilar structures. The identified dose-response for damage to the proximal bronchial tree warrants caution in future dose-intensification protocols, especially when using hypofractionation. PMID:24145340

Cannon, Donald M.; Mehta, Minesh P.; Adkison, Jarrod B.; Khuntia, Deepak; Traynor, Anne M.; Tomé, Wolfgang A.; Chappell, Richard J.; Tolakanahalli, Ranjini; Mohindra, Pranshu; Bentzen, Sųren M.; Cannon, George M.

2013-01-01

337

Maximum predictive power and the superposition principle  

NASA Technical Reports Server (NTRS)

In quantum physics the direct observables are probabilities of events. We ask how observed probabilities must be combined to achieve what we call maximum predictive power. According to this concept the accuracy of a prediction must only depend on the number of runs whose data serve as input for the prediction. We transform each probability to an associated variable whose uncertainty interval depends only on the amount of data and strictly decreases with it. We find that for a probability which is a function of two other probabilities maximum predictive power is achieved when linearly summing their associated variables and transforming back to a probability. This recovers the quantum mechanical superposition principle.

Summhammer, Johann

1994-01-01

338

Radiation Dose Estimates from  

E-print Network

Summary: Radiation Dose Estimates from Hanford Radioactive Material Releases to the Air and the Columbia River April 21,1994 TheTechnid Steering Panel of the Hanford - Environmental Dose Reconstruction than 40years, the U.S. Government made plutonium for nuclear weapons at the Hanford

339

Critical metal blistering doses  

Microsoft Academic Search

Critical He ion bombardment doses associated with blistering of Nb and stainless steel were measured. It was found that the critical doses for these materials are close together and in the range 1 to 4 x 10Ā¹ā· ion\\/cmĀ². (JRD)

B. A. Kalin; N. M. Kirilin; A. A. Pisarev; D. M. Skorov; V. G. Tel'kovskii; S. K. Fedyaev; G. N. Shishkin

1975-01-01

340

BENCHMARK DOSE SOFTWARE (BMDS)  

EPA Science Inventory

EPA has announced the latest update to the Benchmark Dose Software (BMDS) tool which is used to facilitate the application of benchmark dose (BMD) methods to EPA hazardous pollutant risk assessments. This latest version (1.4.1b) contains seventeen (17) different models that ar...

341

Accuracy and optimal timing of activity measurements in estimating the absorbed dose of radioiodine in the treatment of Graves' disease  

NASA Astrophysics Data System (ADS)

Calculation of the therapeutic activity of radioiodine 131I for individualized dosimetry in the treatment of Graves' disease requires an accurate estimate of the thyroid absorbed radiation dose based on a tracer activity administration of 131I. Common approaches (Marinelli-Quimby formula, MIRD algorithm) use, respectively, the effective half-life of radioiodine in the thyroid and the time-integrated activity. Many physicians perform one, two, or at most three tracer dose activity measurements at various times and calculate the required therapeutic activity by ad hoc methods. In this paper, we study the accuracy of estimates of four 'target variables': time-integrated activity coefficient, time of maximum activity, maximum activity, and effective half-life in the gland. Clinical data from 41 patients who underwent 131I therapy for Graves' disease at the University Hospital in Pisa, Italy, are used for analysis. The radioiodine kinetics are described using a nonlinear mixed-effects model. The distributions of the target variables in the patient population are characterized. Using minimum root mean squared error as the criterion, optimal 1-, 2-, and 3-point sampling schedules are determined for estimation of the target variables, and probabilistic bounds are given for the errors under the optimal times. An algorithm is developed for computing the optimal 1-, 2-, and 3-point sampling schedules for the target variables. This algorithm is implemented in a freely available software tool. Taking into consideration 131I effective half-life in the thyroid and measurement noise, the optimal 1-point time for time-integrated activity coefficient is a measurement 1 week following the tracer dose. Additional measurements give only a slight improvement in accuracy.

Merrill, S.; Horowitz, J.; Traino, A. C.; Chipkin, S. R.; Hollot, C. V.; Chait, Y.

2011-02-01

342

A chronic oral reference dose for hexavalent chromium-induced intestinal cancer.  

PubMed

High concentrations of hexavalent chromium [Cr(VI)] in drinking water induce villous cytotoxicity and compensatory crypt hyperplasia in the small intestines of mice (but not rats). Lifetime exposure to such cytotoxic concentrations increases intestinal neoplasms in mice, suggesting that the mode of action for Cr(VI)-induced intestinal tumors involves chronic wounding and compensatory cell proliferation of the intestine. Therefore, we developed a chronic oral reference dose (RfD) designed to be protective of intestinal damage and thus intestinal cancer. A physiologically based pharmacokinetic model for chromium in mice was used to estimate the amount of Cr(VI) entering each intestinal tissue section (duodenum, jejunum and ileum) from the lumen per day (normalized to intestinal tissue weight). These internal dose metrics, together with corresponding incidences for diffuse hyperplasia, were used to derive points of departure using benchmark dose modeling and constrained nonlinear regression. Both modeling techniques resulted in similar points of departure, which were subsequently converted to human equivalent doses using a human physiologically based pharmacokinetic model. Applying appropriate uncertainty factors, an RfD of 0.006 mg kg(-1) day(-1) was derived for diffuse hyperplasia-an effect that precedes tumor formation. This RfD is protective of both noncancer and cancer effects in the small intestine and corresponds to a safe drinking water equivalent level of 210 µg l(-1). This concentration is higher than the current federal maximum contaminant level for total Cr (100 µg l(-1)) and well above levels of Cr(VI) in US drinking water supplies (typically ? 5 µg l(-1)). PMID:23943231

Thompson, Chad M; Kirman, Christopher R; Proctor, Deborah M; Haws, Laurie C; Suh, Mina; Hays, Sean M; Hixon, J Gregory; Harris, Mark A

2014-05-01

343

A chronic oral reference dose for hexavalent chromium-induced intestinal cancer†  

PubMed Central

High concentrations of hexavalent chromium [Cr(VI)] in drinking water induce villous cytotoxicity and compensatory crypt hyperplasia in the small intestines of mice (but not rats). Lifetime exposure to such cytotoxic concentrations increases intestinal neoplasms in mice, suggesting that the mode of action for Cr(VI)-induced intestinal tumors involves chronic wounding and compensatory cell proliferation of the intestine. Therefore, we developed a chronic oral reference dose (RfD) designed to be protective of intestinal damage and thus intestinal cancer. A physiologically based pharmacokinetic model for chromium in mice was used to estimate the amount of Cr(VI) entering each intestinal tissue section (duodenum, jejunum and ileum) from the lumen per day (normalized to intestinal tissue weight). These internal dose metrics, together with corresponding incidences for diffuse hyperplasia, were used to derive points of departure using benchmark dose modeling and constrained nonlinear regression. Both modeling techniques resulted in similar points of departure, which were subsequently converted to human equivalent doses using a human physiologically based pharmacokinetic model. Applying appropriate uncertainty factors, an RfD of 0.006?mg?kg–1?day–1 was derived for diffuse hyperplasia—an effect that precedes tumor formation. This RfD is protective of both noncancer and cancer effects in the small intestine and corresponds to a safe drinking water equivalent level of 210 µg l–1. This concentration is higher than the current federal maximum contaminant level for total Cr (100 µg l–1) and well above levels of Cr(VI) in US drinking water supplies (typically???5 µg l–1). © 2013 The Authors. Journal of Applied Toxicology published by John Wiley & Sons, Ltd. PMID:23943231

Thompson, Chad M; Kirman, Christopher R; Proctor, Deborah M; Haws, Laurie C; Suh, Mina; Hays, Sean M; Hixon, J Gregory; Harris, Mark A

2014-01-01

344

A Dose–Response Study for I-125 Prostate Implants  

Microsoft Academic Search

Purpose: No dose–response study has ever been performed for I-125 prostate implants using modern techniques of implant evaluation and modern treatment outcome end points. The amount of activity per volume implanted was increased over time based on review of postimplant dosimetry. This resulted in different delivered dose levels. This study explores the relationship between dose, biochemical failure, and biopsy results.Materials

Richard G Stock; Nelson N Stone; Andrea Tabert; Christopher Iannuzzi; J. Keith DeWyngaert

1998-01-01

345

Dose finding with continuous outcome in phase I oncology trials.  

PubMed

The goal of a phase I clinical trial in oncology is to find a dose with acceptable dose-limiting toxicity rate. Often, when a cytostatic drug is investigated or when the maximum tolerated dose is defined using a toxicity score, the main endpoint in a phase I trial is continuous. We propose a new method to use in a dose-finding trial with continuous endpoints. The new method selects the right dose on par with other methods and provides more flexibility in assigning patients to doses in the course of the trial when the rate of accrual is fast relative to the follow-up time. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25408518

Wang, Yunfei; Ivanova, Anastasia

2014-11-19

346

Sotalol, hypokalaemia, syncope, and torsade de pointes  

Microsoft Academic Search

Thirteen patients developed syncope and a prolonged QTc interval while taking therapeutic doses of sotalol. Polymorphous ventricular tachycardia was observed in 12 patients, and criteria typical of torsade de pointes were present in 10. In 12 patients sotalol had been given with hydrochlorothiazide in a combined preparation, Sotazide, but with inadequate or no potassium supplementation. Serum potassium concentrations were reduced

J K McKibbin; W A Pocock; J B Barlow; R N Millar; I W Obel

1984-01-01

347

BENCHMARK DOSE TECHNICAL GUIDANCE DOCUMENT (EXTERNAL REVIEW DRAFT)  

EPA Science Inventory

The purpose of this document is to provide guidance for the Agency on the application of the benchmark dose approach in determining the point of departure (POD) for health effects data, whether a linear or nonlinear low dose extrapolation is used. The guidance includes discussion...

348

Pharmacokinetics and Tolerability of a Higher Rifampin Dose versus the Standard Dose in Pulmonary Tuberculosis Patients?  

PubMed Central

Rifampin is a key drug for tuberculosis (TB) treatment. The available data suggest that the currently applied 10-mg/kg of body weight dose of rifampin may be too low and that increasing the dose may shorten the treatment duration. A double-blind randomized phase II clinical trial was performed to investigate the effect of a higher dose of rifampin in terms of pharmacokinetics and tolerability. Fifty newly diagnosed adult Indonesian TB patients were randomized to receive a standard (450-mg, i.e., 10-mg/kg in Indonesian patients) or higher (600-mg) dose of rifampin in addition to other TB drugs. A full pharmacokinetic curve for rifampin, pyrazinamide, and ethambutol was recorded after 6 weeks of daily TB treatment. Tolerability was assessed during the 6-month treatment period. The geometric means of exposure to rifampin (area under the concentration-time curve from 0 to 24 h [AUC0-24]) were increased by 65% (P < 0.001) in the higher-dose group (79.7 mg·h/liter) compared to the standard-dose group (48.5 mg·h/liter). Maximum rifampin concentrations (Cmax) were 15.6 mg/liter versus 10.5 mg/liter (49% increase; P < 0.001). The percentage of patients for whom the rifampin Cmax was ?8 mg/liter was 96% versus 79% (P = 0.094). The pharmacokinetics of pyrazinamide and ethambutol were similar in both groups. Mild (grade 1 or 2) hepatotoxicity was more common in the higher-dose group (46 versus 20%; P = 0.054), but no patient developed severe hepatotoxicity. Increasing the rifampin dose was associated with a more than dose-proportional increase in the mean AUC0-24 and Cmax of rifampin without affecting the incidence of serious adverse effects. Follow-up studies are warranted to assess whether high-dose rifampin may enable shortening of TB treatment. PMID:17452486

Ruslami, Rovina; Nijland, Hanneke M. J.; Alisjahbana, Bachti; Parwati, Ida; van Crevel, Reinout; Aarnoutse, Rob E.

2007-01-01

349

High-dose combination cyclophosphamide, cisplatin, and melphalan with autologous bone marrow support  

Microsoft Academic Search

A total of 23 patients were treated at five dose escalations with high-dose combination cyclophosphamide, cisplatin, and melphalan with autologous bone marrow support. The maximum tolerated doses of cyclophosphamide, cisplatin, and melphalan were 5,625, 180, and 80 mg\\/m2, respectively. The dose-limiting toxicity was cardiac toxicity. Objective tumor regression occurred in 14 of 18 evaluable cases, with a median duration of

William P. Peters; Ann Stuart; Mary Klotman; Colleen Gilbert; Roy B. Jones; Elizabeth J. Shpall; Jon Gockerman; Robert C. Bast; Joseph O. Moore

1989-01-01

350

Maximum entropy image restoration in astronomy  

Microsoft Academic Search

The theoretical basis and applications of the Maximum Entropy Method of inference for obtaining the most probable nonnegative image consistent with astronomical data are detailed. The generalized image restoration problem is reviewed, noting the effects of atmospheric blurring and the practice of representing images as a Fourier series. The problem is encountered in both single aperture and synthesis observations, and

Ramesh Narayan; Rajaram Nityananda

1986-01-01

351

Menu Plans: Maximum Nutrition for Minimum Cost.  

ERIC Educational Resources Information Center

Suggests that menu planning is the key to getting maximum nutrition in day care meals and snacks for minimum cost. Explores United States Department of Agriculture food pyramid guidelines for children and tips for planning menus and grocery shopping. Includes suggested meal patterns and portion sizes. (HTH)

Texas Child Care, 1995

1995-01-01

352

: runout specimen max : maximum fatigue stress  

E-print Network

: runout specimen max : maximum fatigue stress fe,i : elastic limit strength of each specimen 750 uniaxial tensile fatigue stress. Interests in tensile fatigue strength and behaviour come from the fact.g. cantilever of bridge deck slab). Tensile Fatigue behaviour of UHPFRC Doctoral student: Tohru Makita

353

Maximum rotation frequency of strange stars  

SciTech Connect

Using the MIT bag model of strange-quark matter, we calculate the maximum angular frequency of the uniform rotation of strange stars. After studying a broad range of the MIT bag-model parameters, we obtain an upper bound of 12.3 kHz.

Zdunik, J.L.; Haensel, P. (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, PL-00-716 Warsaw (Poland))

1990-07-15

354

Maximum Galactic Disks vs. Hot Dark Halos  

E-print Network

A series of arguments is presented for heavy galaxy disks not only in the optical regions, but also in the dark matter dominated regions of spirals. We are testing this possibility with extreme maximum disk N-body models without any conventional spheroidal dark halo.

Daniel Pfenniger

2000-09-04

355

Weak Scale From the Maximum Entropy Principle  

E-print Network

The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\

Yuta Hamada; Hikaru Kawai; Kiyoharu Kawana

2014-09-23

356

Comparing maximum pressures in internal combustion engines  

NASA Technical Reports Server (NTRS)

Thin metal diaphragms form a satisfactory means for comparing maximum pressures in internal combustion engines. The diaphragm is clamped between two metal washers in a spark plug shell and its thickness is chosen such that, when subjected to explosion pressure, the exposed portion will be sheared from the rim in a short time.

Sparrow, Stanwood W; Lee, Stephen M

1922-01-01

357

Maximum entropy analysis of hydraulic pipe networks  

NASA Astrophysics Data System (ADS)

A Maximum Entropy (MaxEnt) method is developed to infer mean external and internal flow rates and mean pressure gradients (potential differences) in hydraulic pipe networks, without or with sufficient constraints to render the system deterministic. The proposed method substantially extends existing methods for the analysis of flow networks (e.g. Hardy-Cross), applicable only to deterministic networks.

Waldrip, Steven H.; Niven, Robert K.; Abel, Markus; Schlegel, Michael

2014-12-01

358

Network Flow Maximum Flow and Minimum Cut  

E-print Network

3/3/2011 1 1 Chapter 7 Network Flow 2 Maximum Flow and Minimum Cut Max flow and min cut. Two very duality. Nontrivial applications / reductions. Data mining. Open-pit mining. Project selection. Airline-camera scene reconstruction. Many many more ... 3 Flow network. Abstraction for material flowing through

Srinivasan, Padmini

359

Correction of CT artifacts and its influence on Monte Carlo dose calculations  

SciTech Connect

Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact-known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact-corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact-corrected geometry for photon and electron beams. The maximum errors in 6 MV photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact-corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five 18 MV photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact-corrected geometry. This was found to be mostly due to miss-assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts.

Bazalova, Magdalena; Beaulieu, Luc; Palefsky, Steven; Verhaegen, Frank [Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G1A4 (Canada); Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec City, Quebec, G1K7P4 (Canada) and Department de Radio-Oncologie, Hotel Dieu de Quebec, Centre Hospitalier Universitaire de Quebec, Quebec City, Quebec, G1R2J6 (Canada); Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G1A4 (Canada)

2007-06-15

360

Know your dose: RADDOSE  

PubMed Central

The program RADDOSE is widely used to compute the dose absorbed by a macromolecular crystal during an X-ray diffraction experiment. A number of factors affect the absorbed dose, including the incident X-ray flux density, the photon energy and the composition of the macromolecule and of the buffer in the crystal. An experimental dose limit for macromolecular crystallography (MX) of 30?MGy at 100?K has been reported, beyond which the biological information obtained may be compromised. Thus, for the planning of an optimized diffraction experiment the estimation of dose has become an additional tool. A number of approximations were made in the original version of RADDOSE. Recently, the code has been modified in order to take into account fluorescent X-­ray escape from the crystal (version 2) and the inclusion of incoherent (Compton) scattering into the dose calculation is now reported (version 3). The Compton cross-section, although negligible at the energies currently commonly used in MX, should be considered in dose calculations for incident energies above 20?keV. Calculations using version 3 of RADDOSE reinforce previous studies that predict a reduction in the absorbed dose when data are collected at higher energies compared with data collected at 12.4?keV. Hence, a longer irradiation lifetime for the sample can be achieved at these higher energies but this is at the cost of lower diffraction intensities. The parameter ‘diffraction-dose efficiency’, which is the diffracted intensity per absorbed dose, is revisited in an attempt to investigate the benefits and pitfalls of data collection using higher and lower energy radiation, particularly for thin crystals. PMID:20382991

Paithankar, Karthik S.; Garman, Elspeth F.

2010-01-01

361

Theoretical Analysis of Maximum Flow Declination Rate versus Maximum Area Declination Rate in Phonation  

ERIC Educational Resources Information Center

Purpose: Maximum flow declination rate (MFDR) in the glottis is known to correlate strongly with vocal intensity in voicing. This declination, or negative slope on the glottal airflow waveform, is in part attributable to the maximum area declination rate (MADR) and in part to the overall inertia of the air column of the vocal tract (lungs to…

Titze, Ingo R.

2006-01-01

362

Point-to-Point Tunneling Protocol (PPTP)  

Microsoft Academic Search

This document specifies a protocol which allows the Point to Point Protocol (PPP) to be tunneled through an IP network. PPTP does not specify any changes to the PPP protocol but rather describes a new vehicle for carrying PPP. A client-server architecture is defined in order to decouple functions which exist in current Network Access Servers (NAS) and support Virtual

W. Verthein; J. Taarud; G. Zorn

1996-01-01

363

Point Counter Point UAR Codons for Glutamine  

E-print Network

Point Counter Point UAR Codons for Glutamine P.J. Keeling and W.F. Doolittle (1996) reported that UAR (TAR) codons incorporate glutamine in Hexamiti- dae. They state that ``the particular variation became the sole chain termination codon and UAA and UAG were removed from the terminator sites

Keeling, Patrick

364

Magnetization structure of a Bloch point singularity  

NASA Astrophysics Data System (ADS)

Switching of magnetic vortex cores involves a topological transition characterized by the presence of a magnetization singularity, a point where the magnetization vanishes (Bloch point). We analytically derive the shape of the Bloch point that is an extremum of the free energy with exchange, dipolar and Landau terms. From a one parameter family of solutions, two types of singularities are distinguished, a radial one (hedgehog) corresponding to a local energy maximum, and a twisted one corresponding to a local energy minimum. Micromagnetic simulations show that the hedgehog magnetization naturally evolves to a twisted one if the size of the ferromagnet is much larger than the exchange length.

Elķas, R. G.; Verga, A.

2011-07-01

365

Computed tomography dose optimization.  

PubMed

Use of computed tomography (CT) as a medical diagnostic imaging tool has increased in recent decades because of its technical advances in data acquisition speed and image reconstruction technology. The increased reliance on CT was accompanied by increased patient exposure to ionizing radiation, however, and concerns among radiologic professionals and the public regarding CT dose resulted in increasing attention to dose reduction. Research and education efforts have addressed many of these concerns, and radiologic technologists play a critical role in optimizing image quality and radiation dose in CT for individual patients and for the industry in general. PMID:25002653

Seeram, Euclid

2014-01-01

366

Cervix cancer brachytherapy: high dose rate.  

PubMed

Cervical cancer, although less common in industrialized countries, is the fourth most common cancer affecting women worldwide and the fourth leading cause of cancer death. In developing countries, these cancers are often discovered at a later stage in the form of locally advanced tumour with a poor prognosis. Depending on the stage of the disease, treatment is mainly based on a chemoradiotherapy followed by uterovaginal brachytherapy ending by a potential remaining tumour surgery or in principle for some teams. The role of irradiation is crucial to ensure a better local control. It has been shown that the more the delivered dose is important, the better the local results are. In order to preserve the maximum of organs at risk and to allow this dose escalation, brachytherapy (intracavitary and/or interstitial) has been progressively introduced. Its evolution and its progressive improvement have led to the development of high dose rate brachytherapy, the advantages of which are especially based on the possibility of outpatient treatment while maintaining the effectiveness of other brachytherapy forms (i.e., low dose rate or pulsed dose rate). Numerous innovations have also been completed in the field of imaging, leading to a progress in treatment planning systems by switching from two-dimensional form to a three-dimensional one. Image-guided brachytherapy allows more precise target volume delineation as well as an optimized dosimetry permitting a better coverage of target volumes. PMID:25151650

Miglierini, P; Malhaire, J-P; Goasduff, G; Miranda, O; Pradier, O

2014-10-01

367

Impact of Surface Curvature on Dose Delivery in Intraoperative High-Dose-Rate Brachytherapy  

SciTech Connect

In intraoperative high-dose-rate (IOHDR) brachytherapy, a 2-dimensional (2D) geometry is typically used for treatment planning. The assumption of planar geometry may cause serious errors in dose delivery for target surfaces that are, in reality, curved. A study to evaluate the magnitude of these errors in clinical practice was undertaken. Cylindrical phantoms with 6 radii (range: 1.35-12.5 cm) were used to simulate curved treatment geometries. Treatment plans were developed for various planar geometries and were delivered to the cylindrical phantoms using catheters inserted into Freiburg applicators of varying dimension. Dose distributions were measured using radiographic film. In comparison to the treatment plan (for a planar geometry), the doses delivered to prescription points were higher on the concave side of the geometry, up to 15% for the phantom with the smallest radius. On the convex side of the applicator, delivered doses were up to 10% lower for small treated areas ({<=} 5 catheters) but, interestingly, the dose error was negligible for large treated areas (>5 catheters). Our measurements have shown inaccuracy in dose delivery when the original planar treatment plan is delivered with a curved applicator. Dose delivery errors arising from the use of planar treatment plans with curved applicators may be significant.

Oh, Moonseong [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY (United States)], E-mail: Moonseong.Oh@Mercy.net; Wang Zhou; Malhotra, Harish K.; Jaggernauth, Wainwright; Podgorsak, Matthew B. [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, NY (United States)

2009-04-01

368

On the definition of absorbed dose  

NASA Astrophysics Data System (ADS)

Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before.

Grusell, Erik

2015-02-01

369

Modelling lateral beam quality variations in pencil kernel based photon dose calculations  

NASA Astrophysics Data System (ADS)

Standard treatment machines for external radiotherapy are designed to yield flat dose distributions at a representative treatment depth. The common method to reach this goal is to use a flattening filter to decrease the fluence in the centre of the beam. A side effect of this filtering is that the average energy of the beam is generally lower at a distance from the central axis, a phenomenon commonly referred to as off-axis softening. The off-axis softening results in a relative change in beam quality that is almost independent of machine brand and model. Central axis dose calculations using pencil beam kernels show no drastic loss in accuracy when the off-axis beam quality variations are neglected. However, for dose calculated at off-axis positions the effect should be considered, otherwise errors of several per cent can be introduced. This work proposes a method to explicitly include the effect of off-axis softening in pencil kernel based photon dose calculations for arbitrary positions in a radiation field. Variations of pencil kernel values are modelled through a generic relation between half value layer (HVL) thickness and off-axis position for standard treatment machines. The pencil kernel integration for dose calculation is performed through sampling of energy fluence and beam quality in sectors of concentric circles around the calculation point. The method is fully based on generic data and therefore does not require any specific measurements for characterization of the off-axis softening effect, provided that the machine performance is in agreement with the assumed HVL variations. The model is verified versus profile measurements at different depths and through a model self-consistency check, using the dose calculation model to estimate HVL values at off-axis positions. A comparison between calculated and measured profiles at different depths showed a maximum relative error of 4% without explicit modelling of off-axis softening. The maximum relative error was reduced to 1% when the off-axis softening was accounted for in the calculations.

Nyholm, T.; Olofsson, J.; Ahnesjö, A.; Karlsson, M.

2006-08-01

370

Bladder and rectal dose of gynecologic high-dose-rate implants: comparison of orthogonal radiographic measurements with in vivo and CT-assisted measurements.  

PubMed

Bladder and rectal doses were retrospectively reviewed in 281 patients who underwent implantation of 575 gynecologic iridium-192 high-dose-rate devices. Dose measurements obtained with orthogonal radiography, in vivo thermoluminescent dosimetry, and computed tomography (CT)-assisted planning were compared. Measurements of bladder dose derived from radiographs revealed a significant difference between bladder neck dose and bladder base dose (P less than .0001). In 17% of cases, the dose to the bladder base was at least double the dose to the bladder neck. The mean dose to the rectum calculated from radiographs was 85.9% (cervix) and 90.2% (vaginal vault) of the prescribed fraction dose. The correlation coefficient factor between doses determined with orthogonal radiographs and doses determined with in vivo measurements was .9694. The dose to the bladder neck and to four rectal points determined with corresponding CT images revealed a deviation of 4% and 7%, respectively. However, calculations at the rectal wall cephalic to the specified rectal points showed higher doses to the rectum, with a ratio of 1-1.6. CT-assisted calculations at the bladder base also revealed doses that were higher than those obtained with radiographs alone by a ratio of 1.4-2.2. CT-assisted dosimetry is the method of choice. PMID:1947116

Stuecklschweiger, G F; Arian-Schad, K S; Poier, E; Poschauko, J; Hackl, A

1991-12-01

371

A real time dose monitoring and dose reconstruction tool for patient specific VMAT QA and delivery  

SciTech Connect

Purpose: To develop a real time dose monitoring and dose reconstruction tool to identify and quantify sources of errors during patient specific volumetric modulated arc therapy (VMAT) delivery and quality assurance. Methods: The authors develop a VMAT delivery monitor tool called linac data monitor that connects to the linac in clinical mode and records, displays, and compares real time machine parameters with the planned parameters. A new measure, called integral error, keeps a running total of leaf overshoot and undershoot errors in each leaf pair, multiplied by leaf width, and the amount of time during which the error exists in monitor unit delivery. Another tool reconstructs Pinnacle{sup 3} Trade-Mark-Sign format delivered plan based on the saved machine logfile and recalculates actual delivered dose in patient anatomy. Delivery characteristics of various standard fractionation and stereotactic body radiation therapy (SBRT) VMAT plans delivered on Elekta Axesse and Synergy linacs were quantified. Results: The MLC and gantry errors for all the treatment sites were 0.00 {+-} 0.59 mm and 0.05 {+-} 0.31 Degree-Sign , indicating a good MLC gain calibration. Standard fractionation plans had a larger gantry error than SBRT plans due to frequent dose rate changes. On average, the MLC errors were negligible but larger errors of up to 6 mm and 2.5 Degree-Sign were seen when dose rate varied frequently. Large gantry errors occurred during the acceleration and deceleration process, and correlated well with MLC errors (r= 0.858, p= 0.0004). PTV mean, minimum, and maximum dose discrepancies were 0.87 {+-} 0.21%, 0.99 {+-} 0.59%, and 1.18 {+-} 0.52%, respectively. The organs at risk (OAR) doses were within 2.5%, except some OARs that showed up to 5.6% discrepancy in maximum dose. Real time displayed normalized total positive integral error (normalized to the total monitor units) correlated linearly with MLC (r= 0.9279, p < 0.001) and gantry errors (r= 0.742, p= 0.005). There is a strong correlation between total integral error and PTV mean (r= 0.683, p= 0.015), minimum (r= 0.6147, p= 0.033), and maximum dose (r= 0.6038, p= 0.0376). Conclusions: Errors may exist during complex VMAT planning and delivery. Linac data monitor is capable of detecting and quantifying mechanical and dosimetric errors at various stages of planning and delivery.

Tyagi, Neelam; Yang Kai; Gersten, David; Yan Di [Department of Radiation Oncology, William Beaumont Hospital, 3601 West Thirteen Mile Road, Royal Oak, Michigan 48073 (United States)

2012-12-15

372

SPS antenna pointing control  

NASA Technical Reports Server (NTRS)

The pointing control of a microwave antenna of the Satellite Power System was investigated emphasizing: (1) the SPS antenna pointing error sensing method; (2) a rigid body pointing control design; and (3) approaches for modeling the flexible body characteristics of the solar collector. Accuracy requirements for the antenna pointing control consist of a mechanical pointing control accuracy of three arc-minutes and an electronic phased array pointing accuracy of three arc-seconds. Results based on the factors considered in current analysis, show that the three arc-minute overall pointing control accuracy can be achieved in practice.

Hung, J. C.

1980-01-01

373

Calculate Your Radiation Dose  

MedlinePLUS

... Ionizing & Non-Ionizing Radiation Understanding Radiation: Calculate Your Radiation Dose Health Effects Main Page Exposure Pathways Calculate ... of the US do you live in? Internal radiation (in your body): From food and water, (e. ...

374

Calculate Your Radiation Dose  

NSDL National Science Digital Library

This calculator by the Environmental Protection Agency allows you to estimate your annual radiation dose. The calculator is easy to use and the bottom of the page includes links to more information about radiation dosage.

2011-05-12

375

Pareto versus lognormal: A maximum entropy test  

NASA Astrophysics Data System (ADS)

It is commonly found that distributions that seem to be lognormal over a broad range change to a power-law (Pareto) distribution for the last few percentiles. The distributions of many physical, natural, and social events (earthquake size, species abundance, income and wealth, as well as file, city, and firm sizes) display this structure. We present a test for the occurrence of power-law tails in statistical distributions based on maximum entropy. This methodology allows one to identify the true data-generating processes even in the case when it is neither lognormal nor Pareto. The maximum entropy approach is then compared with other widely used methods and applied to different levels of aggregation of complex systems. Our results provide support for the theory that distributions with lognormal body and Pareto tail can be generated as mixtures of lognormally distributed units.

Bee, Marco; Riccaboni, Massimo; Schiavo, Stefano

2011-08-01

376

On optimizing maximum-power heat engines  

NASA Astrophysics Data System (ADS)

For a general class of heat engines operating at maximum power, in which the generic sources of irreversibility are finite-rate heat transfer and friction only, a study is made of (1) the time-dependent driving functions that maximize power when heat input and heat rejection are constrained to be nonisothermal, as is the case in many conventional heat engines, and (2) the specific impact of friction on the nature of the engine cycle that maximizes power, and on the engine's power-efficiency characteristics. The extent to which maximum power is affected by the constraints on the driving function is evaluated, as well as the time divisions on the different branches of the optimal cycle. The fundamental differences in engine performance that arise from frictional losses being internally dissipative, as opposed to externally dissipative, are derived, and illustrative examples are presented.

Gordon, J. M.; Huleihil, Mahmoud

1991-01-01

377

MAXIMUM LIKELIHOOD ESTIMATION FOR SOCIAL NETWORK DYNAMICS  

PubMed Central

A model for network panel data is discussed, based on the assumption that the observed data are discrete observations of a continuous-time Markov process on the space of all directed graphs on a given node set, in which changes in tie variables are independent conditional on the current graph. The model for tie changes is parametric and designed for applications to social network analysis, where the network dynamics can be interpreted as being generated by choices made by the social actors represented by the nodes of the graph. An algorithm for calculating the Maximum Likelihood estimator is presented, based on data augmentation and stochastic approximation. An application to an evolving friendship network is given and a small simulation study is presented which suggests that for small data sets the Maximum Likelihood estimator is more efficient than the earlier proposed Method of Moments estimator. PMID:25419259

Snijders, Tom A.B.; Koskinen, Johan; Schweinberger, Michael

2014-01-01

378

Zipf's law, power laws and maximum entropy  

NASA Astrophysics Data System (ADS)

Zipf's law, and power laws in general, have attracted and continue to attract considerable attention in a wide variety of disciplines—from astronomy to demographics to software structure to economics to linguistics to zoology, and even warfare. A recent model of random group formation (RGF) attempts a general explanation of such phenomena based on Jaynes' notion of maximum entropy applied to a particular choice of cost function. In the present paper I argue that the specific cost function used in the RGF model is in fact unnecessarily complicated, and that power laws can be obtained in a much simpler way by applying maximum entropy ideas directly to the Shannon entropy subject only to a single constraint: that the average of the logarithm of the observable quantity is specified.

Visser, Matt

2013-04-01

379

Study of maximum power tracking techniques and control of DC\\/DC converters for photovoltaic power system  

Microsoft Academic Search

As the electric power supplied by solar arrays depends on the insolation, temperature and array voltage, it is necessary to control the operating points to draw the maximum power of the solar array. The object of this paper is to investigate the maximum power tracking algorithms which were often used to compare the tracking efficiencies for the system operating under

Chihchiang Hua; Chihming Shen

1998-01-01

380

Maximum likelihood estimation of population parameters  

Microsoft Academic Search

One of the most important parameters in population genetics is [theta] = 4N[sub e][mu] where N[sub e] is the effective population size and [mu] is the rate of mutation per gene per generation. The authors study two related problems, using the maximum likelihood method and the theory of coalescence. One problem is the potential improvement of accuracy in estimating the

Y. X. Fu; W. H. Li

1993-01-01

381

The Maximum Size of Dynamic Data Structures  

E-print Network

_->l. MAXIMUM SIZE OF DYNAMIC DATA STRUCTURES 811 intervals [ti, ti+l], with endpoints ti=i/n, for O Size2 _- a2 (2.3) dynamic queries over time. Let us denote the data structure size at time by Size(t). If we think of the items as horizontal intervals, then Size(t) is just the number of intervals "cut" by the vertical line...

Kenyon-Mathieu, Claire M.; Vitter, Jeffrey Scott

1991-10-01

382

The Maximum Principle for Holomorphic Operator Functions  

Microsoft Academic Search

We show that if an operator-valued analytic function f of a complex variable attains its maximum modulus at z\\u000a 0, then the coefficients of the nonconstant terms in the power series expansion about z\\u000a 0 cannot be invertible, provided a complex uniform convexity condition holds. One application is that the norm of the resolvent\\u000a of an operator on a complex

Andrzej Daniluk

2011-01-01

383

Dialogue act recognition using maximum entropy  

Microsoft Academic Search

A dialogue-based interface for information systems is considered a potentially very useful approach to infor- mation access. A key step in computer processing of natural-language dialogues is dialogue-act (DA) recogni- tion. In this paper, we apply a feature-based classification approach for DA recognition, by using the maximum entropy (ME) method to build a classifier for labeling utterances with DA tags.

Kwok Cheung Lan; Kei Shiu Ho; Robert Wing Pong Luk; Hong Va Leong

2008-01-01

384

Therapeutic Experience of Maximum Feasible Participation  

E-print Network

Therapeutic Experience of Maximum Feasible Participation George Pierre Castile In 1965 a number of scholars looked about them at the state of Native Americans, among them was Henry Dobyns, whose contribution to the collec tion, "The American... Indian Today," was titled "Therapeutic Experience of Re sponsible Democracy" (Dobyns 1968). This phrase was taken from a statement by John Collier, Commissioner of Indian affairs from 1933-45. Collier had de clared "The experience of responsible...

Castile, George Pierre

2006-03-01

385

"SPURS" in the North Atlantic Salinity Maximum  

NASA Astrophysics Data System (ADS)

The North Atlantic Salinity Maximum is the world's saltiest open ocean salinity maximum and was the focus of the recent Salinity Processes Upper-ocean Regional Study (SPURS) program. SPURS was a joint venture between US, French, Irish, and Spanish investigators. Three US and two EU cruises were involved from August, 1012 - October, 2013 as well as surface moorings, glider, drifter and float deployments. Shipboard operations included underway meteorological and oceanic data, hydrographic surveys and turbulence profiling. The goal is to improve our understanding of how the salinity maximum is maintained and how it may be changing. It is formed by an excess of evaporation over precipitation and the wind-driven convergence of the subtropical gyre. Such salty areas are getting saltier with global warming (a record high SSS was observed in SPURS) and it is imperative to determine the relative roles of surface water fluxes and oceanic processes in such trends. The combination of accurate surface flux estimates with new assessments of vertical and horizontal mixing in the ocean will help elucidate the utility of ocean salinity in quantifying the changing global water cycle.

Schmitt, Raymond

2014-05-01

386

The maximum rate of mammal evolution.  

PubMed

How fast can a mammal evolve from the size of a mouse to the size of an elephant? Achieving such a large transformation calls for major biological reorganization. Thus, the speed at which this occurs has important implications for extensive faunal changes, including adaptive radiations and recovery from mass extinctions. To quantify the pace of large-scale evolution we developed a metric, clade maximum rate, which represents the maximum evolutionary rate of a trait within a clade. We applied this metric to body mass evolution in mammals over the last 70 million years, during which multiple large evolutionary transitions occurred in oceans and on continents and islands. Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. When differences in generation time are considered, we find an exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous-Paleogene (K-Pg) extinction event. Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases. Our findings allow more rigorous comparisons of microevolutionary and macroevolutionary patterns and processes. PMID:22308461

Evans, Alistair R; Jones, David; Boyer, Alison G; Brown, James H; Costa, Daniel P; Ernest, S K Morgan; Fitzgerald, Erich M G; Fortelius, Mikael; Gittleman, John L; Hamilton, Marcus J; Harding, Larisa E; Lintulaakso, Kari; Lyons, S Kathleen; Okie, Jordan G; Saarinen, Juha J; Sibly, Richard M; Smith, Felisa A; Stephens, Patrick R; Theodor, Jessica M; Uhen, Mark D

2012-03-13

387

Effets pathogčnes d'un faible débit de dose : la relation « dose effet »  

NASA Astrophysics Data System (ADS)

There is no evidence of pathogenic effects in human groups exposed to less than 100 mSv at low dose-rate. The attributed effects are therefore the result of extrapolations from higher doses. The validity of such extrapolations is discussed from the point of view of epidemiology as well as cellular and molecular biology. The Chernobyl accident resulted in large excess of thyroid cancers in children; it also raised the point that some actual sanitary effects among distressed populations might be a direct consequence of low doses. Studies under the control of UN have not confirmed this point identifying no dose-effect relationship and " severe socio-economic and psychological pressures… poverty, poor diet and living conditions, and lifestyle factors" as the main cause for depressed health. Some hypothesis are considered for explaining the dose-dependence and high prevalence of non-cancer causes of death among human groups exposed to more than 300 mSv. To cite this article: R. Masse, C. R. Physique 3 (2002) 1049-1058.

Masse, Roland

2002-10-01

388

Targeted maximum likelihood based causal inference: Part I.  

PubMed

Given causal graph assumptions, intervention-specific counterfactual distributions of the data can be defined by the so called G-computation formula, which is obtained by carrying out these interventions on the likelihood of the data factorized according to the causal graph. The obtained G-computation formula represents the counterfactual distribution the data would have had if this intervention would have been enforced on the system generating the data. A causal effect of interest can now be defined as some difference between these counterfactual distributions indexed by different interventions. For example, the interventions can represent static treatment regimens or individualized treatment rules that assign treatment in response to time-dependent covariates, and the causal effects could be defined in terms of features of the mean of the treatment-regimen specific counterfactual outcome of interest as a function of the corresponding treatment regimens. Such features could be defined nonparametrically in terms of so called (nonparametric) marginal structural models for static or individualized treatment rules, whose parameters can be thought of as (smooth) summary measures of differences between the treatment regimen specific counterfactual distributions. In this article, we develop a particular targeted maximum likelihood estimator of causal effects of multiple time point interventions. This involves the use of loss-based super-learning to obtain an initial estimate of the unknown factors of the G-computation formula, and subsequently, applying a target-parameter specific optimal fluctuation function (least favorable parametric submodel) to each estimated factor, estimating the fluctuation parameter(s) with maximum likelihood estimation, and iterating this updating step of the initial factor till convergence. This iterative targeted maximum likelihood updating step makes the resulting estimator of the causal effect double robust in the sense that it is consistent if either the initial estimator is consistent, or the estimator of the optimal fluctuation function is consistent. The optimal fluctuation function is correctly specified if the conditional distributions of the nodes in the causal graph one intervenes upon are correctly specified. The latter conditional distributions often comprise the so called treatment and censoring mechanism. Selection among different targeted maximum likelihood estimators (e.g., indexed by different initial estimators) can be based on loss-based cross-validation such as likelihood based cross-validation or cross-validation based on another appropriate loss function for the distribution of the data. Some specific loss functions are mentioned in this article. Subsequently, a variety of interesting observations about this targeted maximum likelihood estimation procedure are made. This article provides the basis for the subsequent companion Part II-article in which concrete demonstrations for the implementation of the targeted MLE in complex causal effect estimation problems are provided. PMID:21969992

van der Laan, Mark J

2010-01-01

389

Optimization and it's influence on value of doses in HDR and PDR brachytherapy.  

PubMed

The aim of this work is to examine the influence of the dose optimization procedure on the value of radiation doses in organs of risk and to compare value of doses measured in healthy tissues according to chosen different PDR brachytherapy (PDRBT) and HDR brachytherapy (HDRBT) fractionation schedule. Fifty one patients treated with PDRBT were qualified for calculations. This group included patients with head and neck cancer, brain tumor, breast cancer, sarcoma, penile cancer and rectal cancer. The doses were calculated in chosen critical points in surrounded healthy tissues. For all treatment plans the doses were compared with the use of the BED (Biologically Equivalent Dose) formula and PDR along with HDR values were calculated. Differences among total doses in PDRBT and different schemas of HDRBT in critical points before and after dose point and volume optimization, were analyzed. The same dependences were examined also for BEDs. One ascertained that in biologic equivalent (to PDR) HDRBT the increase of fraction dose from 4 Gy to 10 Gy caused the necessity of decrease of total dose in treatment area (p<0,001). The use of HDR instead of PDR essentially lowered physical and biological doses in examined organs of risk. In many examined critical points in organs of risk where biological equivalence dose in the treatment area was the same, one ascertained the decrease of total physical HDR dose according to the growth of the fraction dose. Similar dependences appeared also for biologically equivalent doses. The optimization process in PDRBT improved the dose homogeneity in the treatment area, but simultaneously induced unprofitable (essential statistically) increase of dose in some healthy organs of risk, what makes an increase risk for radiation-induced complications. The use of biologically equivalent HDRBT instead of PDRBT makes for the decrease of physical doses in the treatment area and the decrease of physical and biologically equivalent doses in healthy organs of risk. PMID:20429630

Skowronek, J; Zwierzchowski, G; Piotrowski, T; Milecki, P

2010-01-01

390

The estimation of galactic cosmic ray penetration and dose rates  

NASA Technical Reports Server (NTRS)

This study is concerned with approximation methods that can be readily applied to estimate the absorbed dose rate from cosmic rays in rads - tissue or rems inside simple geometries of aluminum. The present work is limited to finding the dose rate at the center of spherical shells or behind plane slabs. The dose rate is calculated at tissue-point detectors or for thin layers of tissue. This study considers cosmic-rays dose rates for both free-space and earth-orbiting missions.

Burrell, M. O.; Wright, J. J.

1972-01-01

391

Lithium dose prediction based on 24 hours single dose levels: a prospective evaluation  

Microsoft Academic Search

The authors present the results of the utilization of a pharmacokinetic prediction test for lithium posology. Based on a single point (plasma lithium determination 24h after a single dose) such a test aims to adapt the posology as soon as the second day of treatment rather than after one week as clinicians must wait for a steady state to be

N. Gervasoni; M.-P. Zona-Favre; Ch. Osiek; L. Roth; G. Bondolfi; G. Bertschy

2003-01-01

392

EPROM erasure in transient and total dose gamma environments  

NASA Astrophysics Data System (ADS)

Four versions of 32Kbit EPROMs from three manufacturers were exposed to transient gamma and total dose radiation environments. At a maximum tested transient level of 3.9 x 10 to the 9th rad(Si)/sec, the devices were found to be resistant to erasure. Failures from the total dose exposures occurred at different levels for the four device types. The most susceptible part type failed between 3200 and 4500 rad(Si). The most resistant type failed between 9500 and 11000 rad(Si). These variations in total dose failure threshold are attributed to the floating gate oxide thickness differences between the four versions of this EPROM.

Linderman, P. B.; Okuma, J.

1982-12-01

393

Attitude sensor alignment calibration for the solar maximum mission  

NASA Technical Reports Server (NTRS)

An earlier heuristic study of the fine attitude sensors for the Solar Maximum Mission (SMM) revealed a temperature dependence of the alignment about the yaw axis of the pair of fixed-head star trackers relative to the fine pointing Sun sensor. Here, new sensor alignment algorithms which better quantify the dependence of the alignments on the temperature are developed and applied to the SMM data. Comparison with the results from the previous study reveals the limitations of the heuristic approach. In addition, some of the basic assumptions made in the prelaunch analysis of the alignments of the SMM are examined. The results of this work have important consequences for future missions with stringent attitude requirements and where misalignment variations due to variations in the temperature will be significant.

Pitone, Daniel S.; Shuster, Malcolm D.

1990-01-01

394

30 CFR 57.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2012-07-01

395

30 CFR 57.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2011-07-01

396

30 CFR 56.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2012-07-01

397

30 CFR 57.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2013-07-01

398

30 CFR 57.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2014 CFR

... 2014-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2014-07-01

399

30 CFR 56.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2013-07-01

400

30 CFR 56.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2011-07-01

401

30 CFR 56.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2010-07-01

402

30 CFR 57.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2010-07-01

403

30 CFR 56.19062 - Maximum acceleration and deceleration.  

Code of Federal Regulations, 2014 CFR

... 2014-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...

2014-07-01

404

40 CFR 35.2205 - Maximum allowable project cost.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...

2012-07-01

405

40 CFR 35.2205 - Maximum allowable project cost.  

Code of Federal Regulations, 2014 CFR

...2014-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...

2014-07-01

406

40 CFR 35.2205 - Maximum allowable project cost.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...

2013-07-01

407

40 CFR 35.2205 - Maximum allowable project cost.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...

2010-07-01

408

40 CFR 35.2205 - Maximum allowable project cost.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...

2011-07-01

409

16 CFR 1505.7 - Maximum acceptable surface temperatures.  

Code of Federal Regulations, 2014 CFR

... false Maximum acceptable surface temperatures. 1505.7 Section 1505.7 Commercial...1505.7 Maximum acceptable surface temperatures. The maximum acceptable surface temperatures for electrically operated toys...

2014-01-01

410

16 CFR 1505.7 - Maximum acceptable surface temperatures.  

Code of Federal Regulations, 2011 CFR

... false Maximum acceptable surface temperatures. 1505.7 Section 1505.7 Commercial...1505.7 Maximum acceptable surface temperatures. The maximum acceptable surface temperatures for electrically operated toys...

2011-01-01

411

16 CFR 1505.7 - Maximum acceptable surface temperatures.  

Code of Federal Regulations, 2012 CFR

... false Maximum acceptable surface temperatures. 1505.7 Section 1505.7 Commercial...1505.7 Maximum acceptable surface temperatures. The maximum acceptable surface temperatures for electrically operated toys...

2012-01-01

412

16 CFR 1505.7 - Maximum acceptable surface temperatures.  

Code of Federal Regulations, 2010 CFR

... false Maximum acceptable surface temperatures. 1505.7 Section 1505.7 Commercial...1505.7 Maximum acceptable surface temperatures. The maximum acceptable surface temperatures for electrically operated toys...

2010-01-01

413

16 CFR 1505.7 - Maximum acceptable surface temperatures.  

Code of Federal Regulations, 2013 CFR

... false Maximum acceptable surface temperatures. 1505.7 Section 1505.7 Commercial...1505.7 Maximum acceptable surface temperatures. The maximum acceptable surface temperatures for electrically operated toys...

2013-01-01

414

33 CFR 183.35 - Maximum weight capacity: Outboard boats.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Maximum weight capacity: Outboard boats. 183.35 ...EQUIPMENT Safe Loading § 183.35 Maximum weight capacity: Outboard boats. (a) The maximum weight capacity marked on a boat that is...

2011-07-01

415

33 CFR 183.35 - Maximum weight capacity: Outboard boats.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Maximum weight capacity: Outboard boats. 183.35 ...EQUIPMENT Safe Loading § 183.35 Maximum weight capacity: Outboard boats. (a) The maximum weight capacity marked on a boat that is...

2010-07-01

416

A practical method for determining organ dose during CT examination.  

PubMed

A practical method, based on depth dose, for determining organ dose during computed tomography (CT) examination is presented. For 4-slice spiral CT scans, performed at radii of 0, 37.5, 75.0, 112.5, and 150.0 mm, measurement of depth dose has been made using thermoluminescent dosimeters (TLDs) inserted into a modified International Electrotechnical Commission (IEC) standard dosimetry phantom and also additional TLDs placed on the surface of the phantom. A regression equation-linking dose with distance from the center of the phantom has been formulated, from which dose to a point of interest relative to the surface dose can also be calculated. The approximation reflects the attenuation properties of X-rays in the phantom. Using the equation, an estimate of organ dose can be ascertained for CT examination, assuming water equivalence of human tissue and a known organ position and volume. Using the 4-slice spiral scanner, relative doses to a patients' lung have been calculated, the location and size of the lung in vivo being found from the CT scan image, and the lung being divided into 38 segments to calculate the relative dose. Results from our test case show the dose to the lung to have been 69+/-13% of surface dose. PMID:16979343

Cheung, Tsang; Cheng, Qijun; Feng, Dinghua

2007-02-01

417

Depth dose dependence of the mouse bone using kilovoltage photon beams: A Monte Carlo study for small-animal irradiation  

NASA Astrophysics Data System (ADS)

This study investigated the dose enhancement due to the presence of mouse bone irradiated by the kilovoltage (kV) photon beams. Dosimetry of the bone associated with soft and lung tissue was determined by Monte Carlo simulations using the EGSnrc-based code in millimeter scale. Two inhomogeneous phantoms with 2 mm of bone layer sandwiched by: (1) water and lung (bone-lung phantom); and (2) water (bone-water phantom), were used. Relative depth doses along the central beam axes in the phantoms and dose enhancement ratios (bone dose in the above inhomogeneous phantoms to the dose at the same point in the water phantom) were determined using the 100 and 225 kVp photon beams. For the 100 kVp photon beams, the depth dose gradient in the bone was significantly larger compared to that in a water phantom without the bone. This is due to the beam hardening effect that some low-energy photons were filtered out in the deeper depth, resulting in less photoelectric interactions and hence energy depositions in the bone. Moreover, dose differences between the top and downstream (bottom) bone edges at depths of 1-5 mm were 168-192% and 149-166% for the bone-lung and bone-water phantom, respectively. These differences were larger than 21-27% (bone-lung) and 12-23% (bone-water) for the 225 kVp photon beams. The maximum dose enhancement ratio in the bone for the bone-lung and bone-water phantoms in various depths was about 5.7 using the 100 kVp photon beams. This ratio was larger than two times of that (2.4) for the 225 kVp photon beams. It is concluded that, apart from the basic beam characteristics such as attenuation and penumbra, which are related to the photon beam energy in the mouse irradiation, the bone dose is another important factor to consider when selecting the beam energy in the small-animal treatment planning, provided that the bone dose enhancement is a concern in the preclinical model.

Chow, James C. L.

2010-05-01

418

New Observations of Subarcsecond Photospheric Bright Points  

NASA Technical Reports Server (NTRS)

We have used an interference filter centered at 4305 A within the bandhead of the CH radical (the 'G band') and real-time image selection at the Swedish Vacuum Solar Telescope on La Palma to produce very high contrast images of subarcsecond photospheric bright points at all locations on the solar disk. During the 6 day period of 1993 September 15-20 we observed active region NOAA 7581 from its appearance on the East limb to a near-disk-center position on September 20. A total of 1804 bright points were selected for analysis from the disk center image using feature extraction image processing techniques. The measured Full Width at Half Maximum (FWHM) distribution of the bright points in the image is lognormal with a modal value of 220 km (0 sec .30) and an average value of 250 km (0 sec .35). The smallest measured bright point diameter is 120 km (0 sec .17) and the largest is 600 km (O sec .69). Approximately 60% of the measured bright points are circular (eccentricity approx. 1.0), the average eccentricity is 1.5, and the maximum eccentricity corresponding to filigree in the image is 6.5. The peak contrast of the measured bright points is normally distributed. The contrast distribution variance is much greater than the measurement accuracy, indicating a large spread in intrinsic bright-point contrast. When referenced to an averaged 'quiet-Sun' area in the image, the modal contrast is 29% and the maximum value is 75%; when referenced to an average intergranular lane brightness in the image, the distribution has a modal value of 61% and a maximum of 119%. The bin-averaged contrast of G-band bright points is constant across the entire measured size range. The measured area of the bright points, corrected for pixelation and selection effects, covers about 1.8% of the total image area. Large pores and micropores occupy an additional 2% of the image area, implying a total area fraction of magnetic proxy features in the image of 3.8%. We discuss the implications of this area fraction measurement in the context of previously published measurements which show that typical active region plage has a magnetic filling factor on the order of 10% or greater. The results suggest that in the active region analyzed here, less than 50% of the small-scale magnetic flux tubes are demarcated by visible proxies such as bright points or pores.

Berger, T. E.; Schrijver, C. J.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Scharmer, G.

1995-01-01

419

Motion as a perturbation: Measurement-guided dose estimates to moving patient voxels during modulated arc deliveries  

SciTech Connect

Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90 Degree-Sign (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT MLC sequences. For all phantoms and plans, time-resolved (10 Hz) ion chamber dose was collected. In addition, coronal (XY) films were exposed in the cube phantom to a VMAT beam with two different starting phases, and compared to the reconstructed motion-perturbed dose planes. Results: For the X or Y motions with the moving strip and geometrical phantoms, the maximum difference between perturbation-reconstructed and ion chamber doses did not exceed 1.9%, and the average for any motion pattern/starting phase did not exceed 1.3%. For the VMAT plans on the cubic and thoracic phantoms, one point exhibited a 3.5% error, while the remaining five were all within 1.1%. Across all the measurements (N = 22), the average disagreement was 0.5 {+-} 1.3% (1 SD). The films exhibited {gamma}(3%/3 mm) passing rates {>=}90%. Conclusions: The dose to an arbitrary moving voxel in a patient can be estimated with acceptable accuracy for a VMAT delivery, by performing a single QA measurement with a cylindrical phantom and applying two consecutive perturbations to the TPS-calculated patient dose. The first one accounts for the differences between the planned and delivered static doses, while the second one corrects for the motion.

Feygelman, Vladimir; Zhang, Geoffrey; Hunt, Dylan; Opp, Daniel [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Wolf, Theresa K. [Live Oak Technologies LLC, Kirkwood, Missouri 63122 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)

2013-02-15

420

Investigation of bladder dose and volume factors influencing late urinary toxicity after external beam radiotherapy for prostate cancer  

PubMed Central

Background We sought to identify the bladder dose-volume factors associated with an increased risk of late urinary toxicity among prostate cancer patients treated with radiotherapy. Materials and methods This retrospective analysis included data from 128 prostate cancer patients treated on protocol with 2Gy/fraction to 46Gy followed by a boost to 78Gy. The end-point for this analysis was grade 1 or greater late genitourinary (GU) toxicity occurring within 2 years of treatment. The Lyman-Kutcher-Burman, mean dose, threshold dose, and hottest volume models were fitted to the toxicity data using the maximum likelihood method. Results Model fits based on dose volume histograms tended to fit the toxicity data better than models based on dose wall histograms. The hottest volume (hot-spot) model was found to be the best-fitting model investigated. The best fit was for the hottest 2.9% of bladder (95% C.I. 1.1% to 6.8%). This model has an area under the receiver operating characteristic curve of 0.74. The hot-spot model separated the patients into clinically meaningful subgroups with about 25% of the patients who received < 78Gy to the hottest 2.9% of bladder experienced GU toxicity at 8 years compared to about 50% when the dose was ? 78Gy (p = 0.002). Conclusion This provides the first evidence supporting that bladder “hot-spots” are related to GU toxicity within 2 years after external beam radiotherapy for prostate cancer. Confirming data are needed from other investigators. Particular attention should be given to hot spots higher than 78Gy in bladder in radiation treatment planning. PMID:17241755

Cheung, Rex; Tucker, Susan L.; Dong, Lei; Crevoisier, Renaud de; Lee, Andrew K.; Frank, Steven; Kudchadker, Rajat J.; Thames, Howard; Mohan, Radhe; Kuban, Deborah

2007-01-01

421

Forward Intensity-Modulated Radiotherapy Planning in Breast Cancer to Improve Dose Homogeneity: Feasibility of Class Solutions  

SciTech Connect

Purpose: To explore forward planning methods for breast cancer treatment to obtain homogeneous dose distributions (using International Commission on Radiation Units and Measurements criteria) within normal tissue constraints and to determine the feasibility of class solutions. Methods and Materials: Treatment plans were optimized in a stepwise procedure for 60 patients referred for postlumpectomy irradiation using strict dose constraints: planning target volume (PTV){sub 95%} of >99%; V{sub 107%} of <1.8 cc; heart V{sub 5Gy} of <10% and V{sub 10Gy} of <5%; and mean lung dose of <7 Gy. Treatment planning started with classic tangential beams. Optimization was done by adding a maximum of four segments before adding beams, in a second step. A breath-hold technique was used for heart sparing if necessary. Results: Dose constraints were met for all 60 patients. The classic tangential beam setup was not sufficient for any of the patients; in one-third of patients, additional segments were required (<3), and in two-thirds of patients, additional beams (<2) were required. Logistic regression analyses revealed central breast diameter (CD) and central lung distance as independent predictors for transition from additional segments to additional beams, with a CD cut-off point at 23.6 cm. Conclusions: Treatment plans fulfilling strict dose homogeneity criteria and normal tissue constraints could be obtained for all patients by stepwise dose intensity modification using limited numbers of segments and additional beams. In patients with a CD of >23.6 cm, additional beams were always required.

Peulen, Heike, E-mail: h.peulen@nki.nl [Department of Radiation Oncology, MAASTRO Clinic, Maastricht (Netherlands); Hanbeukers, Bianca; Boersma, Liesbeth; Baardwijk, Angela van; Ende, Piet van den; Houben, Ruud; Jager, Jos; Murrer, Lars; Borger, Jacques [Department of Radiation Oncology, MAASTRO Clinic, Maastricht (Netherlands)

2012-01-01

422

Mapping dose distributions.  

PubMed

Clinical dose calculations are often performed by scaling distances from a dose distribution measured in one medium to calculate the dose in another. These perturbation calculations have the mathematical form of a mapping. In this paper we identify five conditions required for particle transport to reduce to this form and develop a new mapping for electrons which approximately satisfies these conditions. This continuous scattering mapping is based on two parameters, the scattering power of the medium which determines the shape of the scaling paths, and the stopping power of the medium which determines where the energy is deposited along these paths. Pencil beam dose distributions are calculated with EGS4 in one medium and mapped to other media. The resultant distributions are compared with EGS4 calculations done directly in the second medium. The accuracy of the mapping algorithm is shown to be superior to both linear density scaling and the MDAH electron pencil beam algorithm [Kenneth R. Hogstrom, Michael D. Mills, and Peter R. Almond, "Electron beam dose calculations," Phys. Med. Biol. 26, 445-459 (1981)] for pencil beams in homogeneous media and inhomogeneous phantoms (both slab and nonslab geometries) for a variety of materials of clinical interest. PMID:9800702

Beckett, C; Dickof, P

1998-10-01

423

The sun and heliosphere at solar maximum.  

PubMed

Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes. PMID:14615526

Smith, E J; Marsden, R G; Balogh, A; Gloeckler, G; Geiss, J; McComas, D J; McKibben, R B; MacDowall, R J; Lanzerotti, L J; Krupp, N; Krueger, H; Landgraf, M

2003-11-14

424

On the maximum drawdown during speculative bubbles  

NASA Astrophysics Data System (ADS)

A taxonomy of large financial crashes proposed in the literature locates the burst of speculative bubbles due to endogenous causes in the framework of extreme stock market crashes, defined as falls of market prices that are outlier with respect to the bulk of drawdown price movement distribution. This paper goes on deeper in the analysis providing a further characterization of the rising part of such selected bubbles through the examination of drawdown and maximum drawdown movement of indices prices. The analysis of drawdown duration is also performed and it is the core of the risk measure estimated here.

Rotundo, Giulia; Navarra, Mauro

2007-08-01

425

Design of toroidal transformers for maximum efficiency  

NASA Technical Reports Server (NTRS)

The design of the most efficient toroidal transformer that can be built given the frequency, volt-ampere rating, magnetic flux density, window fill factor, and materials is described. With the above all held constant and only the dimensions of the magnetic core varied, the most efficient design occurs when the copper losses equal 60 percent of the iron losses. When this criterion is followed, efficiency is only slightly dependent on design frequency and fill factor. The ratios of inside diameter to outside diameter and height to build of the magnetic core that result in transformers of maximum efficiency are computed.

Dayton, J. A., Jr.

1972-01-01

426

Maximum a posteriori decoder for digital communications  

NASA Technical Reports Server (NTRS)

A system and method for decoding by identification of the most likely phase coded signal corresponding to received data. The present invention has particular application to communication with signals that experience spurious random phase perturbations. The generalized estimator-correlator uses a maximum a posteriori (MAP) estimator to generate phase estimates for correlation with incoming data samples and for correlation with mean phases indicative of unique hypothesized signals. The result is a MAP likelihood statistic for each hypothesized transmission, wherein the highest value statistic identifies the transmitted signal.

Altes, Richard A. (Inventor)

1997-01-01

427

Maximum profit performance of an absorption refrigerator  

SciTech Connect

The operation of an absorption refrigerator is viewed as a production process with exergy as its output. The relations between the optimal profit and COP (coefficient of performance), and the COP bound at the maximum profit of the refrigerator are derived based on a general heat transfer law. The results provide a theoretical basis for developing and utilizing a variety of absorption refrigerators. The focus of this paper is to search the compromise optimization between economics (profit) and the utilization factor (COP) for finite-time endoreversible thermodynamic cycles.

Chen, L.; Sun, F. [Naval Academy of Engineering, Wuhan (China)] [Naval Academy of Engineering, Wuhan (China); Wu, C. [Naval Academy, Annapolis, MD (United States). Mechanical Engineering Dept.] [Naval Academy, Annapolis, MD (United States). Mechanical Engineering Dept.

1996-12-01

428

Developed Algorithm of Maximum Power Tracking for Stand-Alone Photovoltaic System  

Microsoft Academic Search

The rapid increase in the cost of conventional energy sources leads to the use of nonconventional energy sources. The photovoltaic (PV) is one nonconventional source that is safe, reliable, and environmentally healthy. However, the PV system is expensive and needs a large area to operate. To solve these disadvantages, it is necessary to operate at the maximum power point (MPP)

ABD EL-SHAFY A. NAFEH; FATEN H. FAHMY; OSAMA A. MAHGOUB; ESSAM M. ABOU EL-ZAHAB

1998-01-01

429

Delivery verification and dose reconstruction in tomotherapy  

NASA Astrophysics Data System (ADS)

It has long been a desire in photon-beam radiation therapy to make use of the significant fraction of the beam exiting the patient to infer how much of the beam energy was actually deposited in the patient. With a linear accelerator and corresponding exit detector mounted on the same ring gantry, tomotherapy provides a unique opportunity to accomplish this. Dose reconstruction describes the process in which the full three-dimensional dose actually deposited in a patient is computed. Dose reconstruction requires two inputs: an image of the patient at the time of treatment and the actual energy fluence delivered. Dose is reconstructed by computing the dose in the CT with the verified energy fluence using any model-based algorithm such as convolution/superposition or Monte Carlo. In tomotherapy, the CT at the time of treatment is obtained by megavoltage CT, the merits of which have been studied and proven. The actual energy fluence delivered to the patient is computed in a process called delivery verification. Methods for delivery verification and dose reconstruction in tomotherapy were investigated in this work. It is shown that delivery verification can be realized by a linear model of the tornotherapy system. However, due to the measurements required with this initial approach, clinical implementation would be difficult. Therefore, a clinically viable method for delivery verification was established, the details of which are discussed. With the verified energy fluence from delivery verification, an assessment of the accuracy and usefulness of dose reconstruction is performed. The latter two topics are presented in the context of a generalized dose comparison tool developed for intensity modulated radiation therapy. Finally, the importance of having a CT from the time of treatment for reconstructing the dose is shown. This is currently a point of contention in modern clinical radiotherapy and it is proven that using the incorrect CT for dose reconstruction can lead to misleading conclusions regarding a treatment. With the correct CT, dose reconstruction may allow for adaptive radiotherapy, in which errors in previous fraction(s) are remedied in subsequent fraction(s), and improved outcomes.

Kapatoes, Jeffrey Michael

2000-11-01

430

Comparison of 2D and 3D Imaging and Treatment Planning for Postoperative Vaginal Apex High-Dose Rate Brachytherapy for Endometrial Cancer  

SciTech Connect

Purpose: To evaluate bladder and rectal doses using two-dimensional (2D) and 3D treatment planning for vaginal cuff high-dose rate (HDR) in endometrial cancer. Methods and Materials: Ninety-one consecutive patients treated between 2000 and 2007 were evaluated. Seventy-one and 20 patients underwent 2D and 3D planning, respectively. Each patient received six fractions prescribed at 0.5 cm to the superior 3 cm of the vagina. International Commission on Radiation Units and Measurements (ICRU) doses were calculated for 2D patients. Maximum and 2-cc doses were calculated for 3D patients. Organ doses were normalized to prescription dose. Results: Bladder maximum doses were 178% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were no different than ICRU doses (p = 0.22). Two-cubic centimeter doses were 59% of maximum doses (p < 0.0001). Rectal maximum doses were 137% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 87% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 64% of maximum doses (p < 0.0001). Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final bladder dose to within 10% for 44%, 59%, 83%, 82%, and 89% of patients by using the ICRU dose, and for 45%, 55%, 80%, 85%, and 85% of patients by using the maximum dose, and for 37%, 68%, 79%, 79%, and 84% of patients by using the 2-cc dose. Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final rectal dose to within 10% for 100%, 100%, 100%, 100%, and 100% of patients by using the ICRU dose, and for 60%, 65%, 70%, 75%, and 75% of patients by using the maximum dose, and for 68%, 95%, 84%, 84%, and 84% of patients by using the 2-cc dose. Conclusions: Doses to organs at risk vary depending on the calculation method. In some cases, final dose accuracy appears to plateau after the third fraction, indicating that simulation and planning may not be necessary in all fractions. A clinically relevant level of accuracy should be determined and further research conducted to address this issue.

Russo, James K. [Department of Radiation Oncology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina (United States); Armeson, Kent E. [Division of Biostatistics and Epidemiology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina (United States); Richardson, Susan, E-mail: srichardson@radonc.wustl.edu [Department of Radiation Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri (United States)

2012-05-01

431

Biologically effective uniform dose (D) for specification, report and comparison of dose response relations and treatment plans  

NASA Astrophysics Data System (ADS)

Developments in radiation therapy planning have improved the information about the three-dimensional dose distribution in the patient. Isodose graphs, dose volume histograms and most recently radiobiological models can be used to evaluate the dose distribution delivered to the irradiated organs and volumes of interest. The concept of a biologically effective uniform dose (D) assumes that any two dose distributions are equivalent if they cause the same probability for tumour control or normal tissue complication. In the present paper the D concept both for tumours and normal tissues is presented, making use of the fact that probabilities averaged over both dose distribution and organ radiosensitivity are more relevant to the clinical outcome than the expected number of surviving clonogens or functional subunits. D can be calculated in complex target volumes or organs at risk either from the 3D dose matrix or from the corresponding dose volume histograms of the dose plan. The value of the D concept is demonstrated by applying it to two treatment plans of a cervix cancer. Comparison is made of the D concept with the effective dose (Deff) and equivalent uniform dose (EUD) that have been suggested in the past. The value of the concept for complex targets and fractionation schedules is also pointed out.

Mavroidis, Panayiotis; Lind, Bengt K.; Brahme, Anders

2001-10-01

432

Points, Lines, and Planes  

NSDL National Science Digital Library

This lesson will define the important basics of Geometry: Points, Lines, and Planes Let's take notes on our first lesson! Click on the link below to get started: Points, Lines, and Planes Now, here is an activity to check your understanding: Points, Lines and Planes Activity OK! Now, here is a quiz to really see if you got it: Points, Lines, and Planes Quiz! Good Job! Now, your homework can be found on your Canvas account or my website calendar on ...

Neubert, Mrs.

2011-08-18

433

CRYSTALLOGRAPHIC POINT AND SPACE  

E-print Network

CRYSTALLOGRAPHIC POINT AND SPACE GROUPS Andy Elvin June 10, 2013 #12;Contents Point and Space no reflection axes #12;Cube and Octahedron are dual Symmetries under Oh #12;Space Groups Subgroups of E(3) Point Group + Translation { R | 0 }{ E | t }a = { R | t }a = Ra + t 230 Space Groups 73 symmorphic space

California at Santa Cruz, University of

434

Point processes, spatialtemporal  

E-print Network

Ā­time or spatio-temporal point process) is a random collection of points, where each point rep- resents the time and location of an event. Examples of events include incidence of disease, sightings or births of a species County, CA, recorded by the Los Angeles County Department of Public Works (times of the events not shown

Schoenberg, Frederic Paik (Rick)

435

Fluence-to-dose confusion regarding external stochastic dose determination within the DOE complex.  

SciTech Connect

The Department of Energy's (DOE) occupational radiation protection dose limits are specified in 10 CFR 835 (hereafter referred to as 'regulation'). Ambiguity in the regulation regarding designation of dose and fluence-to-dose conversion factors leads to confusion and disagreement regarding the appropriate choice of conversion factors. Three primary dose quantities of relevance are absorbed dose, D, quality factor, Q, and the product of those, called dose equivalent, H. The modifier Q is intended to express the long-term fatal cancer causing potential of different radiation types and generally increases with energy for neutrons. For photons, Q is close to unity regardless of energy. In principle, H could be estimated by incorporating a phantom and relevant Q values in a radiation-transport model. In practice, this would entail too much model complexity and computer time. The evaluator of H instead relies on pre-calculated energy-dependent fluence-to-dose conversion factors. Three primary sets of fluence-to-dose conversion factors are commonly used to determine stochastic dose for neutrons and photons: (1) ANSI/ANS-6.1.1-1977 that incorporates the NCRP-38 data for neutrons and sets based on Claiborne and Wells for photons, (2) ANSI/ANS -6.1.1-1991 that are based on and nearly identical to the neutron and photon sets in ICRP -51, and (3) neutron and photon sets in ICRP-74. The first set is maximum H values in a 30-cm diameter cylinder phantom for neutrons and in a 30-cm thick slab phantom for photons. The second set is effective dose equivalent, HE, derived from an anthropomorphic phantom by summing the products of tissue dose equivalents, HT, and tissue weighting factors, w{sub T}. The third set is effective dose, E, also derived from an anthropomorphic phantom by summing the products of H{sub T} and w{sub T}. E is functionally identical to H{sub E} except H{sub T} is the product of D and the radiation weighting factor, w{sub R}, which is similar in meaning to Q.

Shores, E. F. (Erik F.); Brown, T. H. (Thomas H.)

2002-01-01

436

Maximum likelihood estimation of population parameters  

SciTech Connect

One of the most important parameters in population genetics is [theta] = 4N[sub e][mu] where N[sub e] is the effective population size and [mu] is the rate of mutation per gene per generation. The authors study two related problems, using the maximum likelihood method and the theory of coalescence. One problem is the potential improvement of accuracy in estimating the parameter [theta] over existing methods and the other is the estimation of parameter [lambda] which is the ratio of two [theta]'s. The minimum variances serve as the lower bounds of the variances of all possible estimates of [theta] in practice. The authors then show that Watterson's estimate of [theta] based on the number of segregating sites is asymptotically an optimal estimate of [theta]. However, for a finite sample of sequences, substantial improvement over Watterson's estimate is possible when [theta] is large. The maximum likelihood estimate of [lambda] = [theta][sub 1]/[theta][sub 2] is obtained and the properties of the estimate are discussed. 9 refs., 3 figs., 3 tabs.

Fu, Y.X.; Li, W.H. (Univ. of Texas, Houston, TX (United States))

1993-08-01

437

Maximum likelihood estimation of population parameters.  

PubMed

One of the most important parameters in population genetics is theta = 4Ne mu where Ne is the effective population size and mu is the rate of mutation per gene per generation. We study two related problems, using the maximum likelihood method and the theory of coalescence. One problem is the potential improvement of accuracy in estimating the parameter theta over existing methods and the other is the estimation of parameter lambda which is the ratio of two theta's. The minimum variances of estimates of the parameter theta are derived under two idealized situations. These minimum variances serve as the lower bounds of the variances of all possible estimates of theta in practice. We then show that Watterson's estimate of theta based on the number of segregating sites is asymptotically an optimal estimate of theta. However, for a finite sample of sequences, substantial improvement over Watterson's estimate is possible when theta is large. The maximum likelihood estimate of lambda = theta 1/theta 2 is obtained and the properties of the estimate are discussed. PMID:8375660

Fu, Y X; Li, W H

1993-08-01