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1

Recent studies have reported potentially clinically meaningful dose differences when heterogeneity correction is used in breast balloon brachytherapy. In this study, we report on the relationship between heterogeneity-corrected and -uncorrected doses for 2 commonly used plan evaluation metrics: maximum point dose to skin surface and maximum point dose to ribs. Maximum point doses to skin surface and ribs were calculated using TG-43 and Varian Acuros for 20 patients treated with breast balloon brachytherapy. The results were plotted against each other and fit with a zero-intercept line. Max skin dose (Acuros) = max skin dose (TG-43) * 0.930 (R(2) = 0.995). The average magnitude of difference from this relationship was 1.1% (max 2.8%). Max rib dose (Acuros) = max rib dose (TG-43) * 0.955 (R(2) = 0.9995). The average magnitude of difference from this relationship was 0.7% (max 1.6%). Heterogeneity-corrected maximum point doses to the skin surface and ribs were proportional to TG-43-calculated doses. The average deviation from proportionality was 1%. The proportional relationship suggests that a different metric other than maximum point dose may be needed to obtain a clinical advantage from heterogeneity correction. Alternatively, if maximum point dose continues to be used in recommended limits while incorporating heterogeneity correction, institutions without this capability may be able to accurately estimate these doses by use of a scaling factor. PMID:23474368

Kim, Leonard; Narra, Venkat; Yue, Ning

2013-01-01

2

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 definition, or could be separately determined, are addressed. Many of these factors refer to toxic behavior in one or a few tissues and, if used in setting the MTD, may mask more relevant events occurring at higher dose levels in other tissues. Reducing the MTD to a level that fails to take into account pesticide or drug-related toxicity may lead to the loss of relevant information in the bioassay. It is concluded, therefore, that there are two possible approaches to a more appropriate use of the MTD. The highest dose of the test agent (MTD) may be chosen (i) to lie below the thresholds of carcinogenicity-related non-genotoxic toxicity or (ii) the present high level MTD may continue to be used and tumors that arise may be classified as being irrelvant to humans at some or all exposure levels. The latter approach is to be preferred. It has the potential to avoid missing high level effects of the test agent that may be relevant to the human population.91 references.

Clayson, D.B.; Iverson, F.; Mueller, R. (Toxicology Research Division, Health and Welfare Canada, Ottawa, Ontario (Canada))

1991-01-01

3

Analysis of Photovoltaic Maximum Power Point Trackers

NASA Astrophysics Data System (ADS)

The photovoltaic generator exhibits a non-linear i-v characteristic and its maximum power point (MPP) varies with solar insolation. An intermediate switch-mode dc-dc converter is required to extract maximum power from the photovoltaic array. In this paper buck, boost and buck-boost topologies are considered and a detailed mathematical analysis, both for continuous and discontinuous inductor current operation, is given for MPP operation. The conditions on the connected load values and duty ratio are derived for achieving the satisfactory maximum power point operation. Further, it is shown that certain load values, falling out of the optimal range, will drive the operating point away from the true maximum power point. Detailed comparison of various topologies for MPPT is given. Selection of the converter topology for a given loading is discussed. Detailed discussion on circuit-oriented model development is given and then MPPT effectiveness of various converter systems is verified through simulations. Proposed theory and analysis is validated through experimental investigations.

Veerachary, Mummadi

4

Pulmonary carcinogenicity of inhaled particles and the maximum tolerated dose.

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.

Oberdorster, G

1997-01-01

5

An integrated maximum power point tracker for photovoltaic panels

This paper proposes a maximum power point tracker (MPPT) for a photovoltaic panel, that is to be integrated with the panel during manufacturing. The MPPT is inexpensive, efficient and has few components that serve to increase the MPPT's mean time between failures (MTBF). The MPPT uses an inexpensive microcontroller to perform all of its functions. This includes maximum power point

Wernher Swiegers; Johan H. R. Enslin

1998-01-01

6

Development of an efficient photovoltaic maximum power point tracking controller

A high performance boost converter for maximum power point tracking (MPPT) of photovoltaic (PV) systems is presented. The proposed boost converter uses a new active snubber to minimize losses in the switching and improve efficiency of the converter. For tracking the maximum power point of a PV array, a closed loop fuzzy logic based MPPT controller has been developed. The

Subiyanto; Azah Mohamed; MA Hannan

2011-01-01

7

On the maximum area pentagon in a planar point set

A finite set of points in the plane is described as in convex position if it forms the set of vertices of a convex polygon. This work studies the ratio between the maximum area of convex pentagons with vertices in P and the area of the convex hull of P, where the planar point set P is in convex position.

Yatao Du; Ren Ding

2006-01-01

8

Comparative study of maximum power point tracking algorithms

Maximum power point trackers (MPPTs) play an important role in photovoltaic (PV) power systems because they maximize the power output from a PV system for a given set of conditions, and therefore maximize the array efficiency. Thus, an MPPT can minimize the overall system cost. MPPTs find and maintain operation at the maxi- mum power point, using an MPPTalgorithm. Many

D. P. Hohm; M. E. Ropp

2003-01-01

9

Maximum Power Point Tracking for Ocean Wave Energy Conversion

Many forms of renewable energy exist in the world's oceans, with ocean wave energy showing great potential. However, the ocean environment presents many challenges for cost-effective renewable energy conversion, including optimal control of a wave energy converter (WEC). This paper presents a maximum power point tracking (MPPT) algorithm for control of a point absorber WEC. The algorithm and testing hardware

Ean A. Amon; Ted K. A. Brekken; Alphonse A. Schacher

2012-01-01

10

Individual Module Maximum Power Point Tracking for Thermoelectric Generator Systems

NASA Astrophysics Data System (ADS)

In a thermoelectric generator (TEG) system the DC/DC converter is under the control of a maximum power point tracker which ensures that the TEG system outputs the maximum possible power to the load. However, if the conditions, e.g., temperature, health, etc., of the TEG modules are different, each TEG module will not produce its maximum power. If each TEG module is controlled individually, each TEG module can be operated at its maximum power point and the TEG system output power will therefore be higher. In this work a power converter based on noninverting buck-boost converters capable of handling four TEG modules is presented. It is shown that, when each module in the TEG system is operated under individual maximum power point tracking, the system output power for this specific application can be increased by up to 8.4% relative to the situation when the modules are connected in series and 16.7% relative to the situation when the modules are connected in parallel.

Vadstrup, Casper; Schaltz, Erik; Chen, Min

2013-07-01

11

Maximum power point tracker for photovoltaic power plants

The paper describes two different closed-loop control criteria for the maximum power point tracking of the voltage-current characteristic of a photovoltaic generator. The two criteria are discussed and compared, inter alia, with regard to the setting-up problems that they pose. Although a detailed analysis is not embarked upon, the paper also provides some quantitative information on the energy advantages obtained by using electronic maximum power point tracking systems, as compared with the situation in which the point of operation of the photovoltaic generator is not controlled at all. Lastly, the paper presents two high efficiency MPPT converters for experimental photovoltaic plants of the stand-alone and the grid-interconnected type.

Arcidiacono, V.; Corsi, S.; Lambri, L.

1982-09-01

12

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

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

13

Step-down maximum power point tracker for photovoltaic systems

A design of a simple, inexpensive, and efficient maximum power point tracker (MPPT) is presented. This design calls for a fixed voltage and a pilot cell to track the maximum power point voltage (V{sub mp}). The tracking is done by changing the duty cycle of a step-down chopper, which is controlled by a direct feedback analog circuit. The control voltage of the tracker is the open circuit voltage (V{sub oc}) of the pilot cell multiplied by a constant. This constant is preadjusted so that it tracks the V{sub mp} of the array in response to any changes due to temperatures or insolation. This MPPT can also function as a voltage regulator for battery charging.

Salameh, Z.M.; Dagher, F.; Lynch, W.A. (Univ. of Lowell, MA (United States))

1991-01-01

14

Maximum likelihood estimation for cytogenetic dose-response curves

In vitro dose-response curves are used to describe the relation between chromosome aberrations and radiation dose for human lymphocytes. The lymphocytes are exposed to low-LET radiation, and the resulting dicentric chromosome aberrations follow the Poisson distribution. The expected yield depends on both the magnitude and the temporal distribution of the dose. A general dose-response model that describes this relation has been presented by Kellerer and Rossi (1972, Current Topics on Radiation Research Quarterly 8, 85-158; 1978, Radiation Research 75, 471-488) using the theory of dual radiation action. Two special cases of practical interest are split-dose and continuous exposure experiments, and the resulting dose-time-response models are intrinsically nonlinear in the parameters. A general-purpose maximum likelihood estimation procedure is described, and estimation for the nonlinear models is illustrated with numerical examples from both experimental designs. Poisson regression analysis is used for estimation, hypothesis testing, and regression diagnostics. Results are discussed in the context of exposure assessment procedures for both acute and chronic human radiation exposure.

Frome, E.L.; DuFrain, R.J.

1986-03-01

15

Adaptive Maximum Power Point Tracking Algorithm for Photovoltaic Power Systems

NASA Astrophysics Data System (ADS)

This paper presents an adaptive maximum power point tracking (MPPT) algorithm. The aim is to dynamically adjust the step length for updating duty ratio (or operating voltage) so as to make full utilization of the output power of photovoltaic (PV) systems, even under the rapidly changing atmospheric conditions. To this end, the average slope in terms of voltage and power is exploited for reducing the harmful effect of noise and error (incurred in measurement or quantization) on the slope. Also, a statistical decision-making scheme is employed for reliably deciding the time instant at which atmospheric conditions actually change. Empirical study has adduced grounds for its dominance over existing references.

Ahn, Chang Wook; Choi, Ju Yeop; Lee, Dong-Ha; An, Jinung

16

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

17

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

18

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

2014-02-01

19

An approximate, maximum terminal velocity descent to a point

No closed form control solution exists for maximizing the terminal velocity of a hypersonic glider at an arbitrary point. As an alternative, this study uses neighboring extremal theory to provide a sampled data feedback law to guide the vehicle to a constrained ground range and altitude. The guidance algorithm is divided into two parts: 1) computation of a nominal, approximate, maximum terminal velocity trajectory to a constrained final altitude and computation of the resulting unconstrained groundrange, and 2) computation of the neighboring extremal control perturbation at the sample value of flight path angle to compensate for changes in the approximate physical model and enable the vehicle to reach the on-board computed groundrange. The trajectories are characterized by glide and dive flight to the target to minimize the time spent in the denser parts of the atmosphere. The proposed on-line scheme successfully brings the final altitude and range constraints together, as well as compensates for differences in flight model, atmosphere, and aerodynamics at the expense of guidance update computation time. Comparison with an independent, parameter optimization solution for the terminal velocity is excellent. 6 refs., 3 figs.

Eisler, G.R.; Hull, D.G.

1987-01-01

20

Computer program for the performance evaluation of maximum power point trackers.

National Technical Information Service (NTIS)

Maximum power point tracking is an important issue in photovoltaics. Therefore a Pascal computer program has been developed to facilitate performance measurements on maximum power point trackers (MPPT's) using an MS-DOS microcomputer with numeric coproces...

A. T. Veltman R. Kloeckner K. K. W. Geers J. Van Twisk

1991-01-01

21

Several statistical approaches were evaluated to identify an optimum method for determining a point of nonlinearity (PONL) in toxicokinetic data. (1) A second-order least squares regression model was fit iteratively starting with data from all doses. If the second order term was significant (?<0.05), the dataset was reevaluated with successive removal of the highest dose until the second-order term became non-significant. This dose, whose removal made the second order term non-significant, is an estimate of the PONL. (2) A least squares linear model was fit iteratively starting with data from all doses except the highest. The mean response for the omitted dose was compared to the 95% prediction interval. If the omitted dose falls outside the confidence interval it is an estimate of the PONL. (3) Slopes of least squares linear regression lines for sections of contiguous doses were compared. Nonlinearity was suggested when slopes of compared sections differed. A total of 33 dose-response datasets were evaluated. For these toxicokinetic data, the best statistical approach was the least squares regression analysis with a second-order term. Changing the ? level for the second-order term and weighting the second-order analysis by the inverse of feed consumption were also considered. This technique has been shown to give reproducible identification of nonlinearities in TK datasets. PMID:22487418

McFadden, Lisa G; Bartels, Michael J; Rick, David L; Price, Paul S; Fontaine, Donald D; Saghir, Shakil A

2012-07-01

22

Novel Maximum Power Point Tracking Controller for Wind Turbine Driven Permanent Magnet Generator

This paper presents Maximum Power Point Control for variable speed wind turbine driven permanent-magnet generator. The wind turbine generator is operated such that the rotor speed varies according to wind speed to adjust the duty cycle of power converter and maximizes Wind Energy Conversion System (WECS) efficiency. The maximum power point for each speed value is traced using Maximum Power

R. Bharanikumar; A. C. Yazhini; A. N. Kumar

2008-01-01

23

Implementation of a stand-alone photovoltaic pumping system with maximum power point tracking

Photovoltaic (PV) pumping systems using a maximum power point tracking (MPPT) technique aim to obtain the highest possible power to the pump under various insolation and temperature conditions, thus overcoming the mismatch between the photovoltaic panel and the pumping load. A simple method of tracking the maximum power points and forcing the system to operate close to these points is

Chen Kunlun; Zhao Zhengming; Yuan Liqiang

2001-01-01

24

Objective Computed tomography (CT)-based treatment planning for cervical cancer has allowed investigation into the volumetric radiation dose delivered to the rectum. The goal of intracavitary brachytherapy is to maximize the tumor dose while decreasing the dose to normal tissue like the rectum. We investigated the effects of tandem angle and maximum rectal distention on rectal dose delivered in HDR brachytherapy for locally advanced cervical cancer. Methods and Materials Between July 2007 and January 2010, 97 brachytherapy treatment planning CT scans from the first and last implant of 51 patients with locally advanced cervical cancer were reviewed. The rectum was manually contoured from the ischial tuberosity to the bottom of the sacroiliac joint. The maximum rectal distention was determined by measuring the largest anterior-posterior diameter of the rectum superior to the tandem ring and inferior to the end of the applicator. A volumetric measurement of the maximum and mean rectal dose, dose to 2cc (D2cc), dose to 1cc (D1cc) of the rectum was calculated. The tandem angle and the ICRU rectal point were recorded, and a dose volume histogram was referenced. Results The mean maximum rectal distention was 3.01cm. The mean D1cc, D2cc, mean rectal dose, maximum rectal dose, and ICRU rectal dose were 3.03 Gy, 2.78 Gy, 4.19 cGy, 1.40 cGy, and 2.99 Gy per treatment, respectively. In a multivariate analysis controlling for surface area, tandem angle, and body mass index (BMI), there was a significant increase in D2cc with increasing rectal distention (P=.016). There were no significant findings when observing the effects of tandem angle on D2cc. Conclusion Rectal distention significantly impacts D2cc delivered in HDR brachytherapy. In contrast, tandem angle does not. Concerted efforts to decrease rectal distention should be considered during treatment planning and delivery.

Lim, Jihoon; Durbin-Johnson, Blythe; Valicenti, Richard; Mathai, Matthew; Stern, Robin; Mayadev, Jyoti

2013-01-01

25

Implementation of a Solar Power Battery Energy Storage System with Maximum Power Point Tracking

This work implements a solar power battery energy storage system (BESS) with maximum power point tracking (MPPT) under substantial variation in temperature and intensity of illumination. A tracker is also designed based on the perturbation and observation method to track rapidly the maximum power point of the energy output of the solar cells. The power generation data are then transmitted

Yu-Lung Ke; Ying-Chun Chuang; Yuan-Kang Wu; Bo-Tsung Jou

2010-01-01

26

A boost-cascaded-with-buck converter based power conditioning system employing a seamless mode transfer maximum power point tracking controller is proposed to maximize energy production of a thermoelectric generator while balancing the vehicle battery charging, alternator output power, and vehicle load. When a maximum power point exceeds a load demand, the proposed controller switches to a power matching mode seamlessly by a

Rae-Young Kim; Jih-Sheng Lai

2007-01-01

27

A unity power factor, maximum power point tracking battery charger for low power wind turbines

This paper proposes a unique implementation of power factor correction (PFC) and maximum power point tracking (MPPT) for low power wind turbines. For a given wind condition, there is a unique electrical load which will harvest the maximum power from a wind turbine, the proposed control algorithm actively tracks this electrical loading condition for maximum power. An active 3-phase rectifier

Gustavo Gamboa; John Elmes; Christopher Hamilton; Jonathan Baker; Michael Pepper; Issa Batarseh

2010-01-01

28

Increasing maximum tumor dose to manage range uncertainties in IMPT treatment planning.

The accuracy of intensity modulated proton therapy (IMPT) is sensitive to range uncertainties. Geometric margins, as dosimetric surrogates, are ineffective and robust optimization strategies are needed. These, however, lead to increased normal tissue dose. We explore here how this dose increase can be reduced by increasing the maximum tumor dose instead. We focus on range uncertainties, modeled by scaling the stopping powers 5% up (undershoot) or down (overshoot) compared to the nominal scenario. Robust optimization optimizes for target dose conformity in the most likely scenario, not the worst, while constraining target coverage for the worst-case scenario. Non-robust plans are also generated. Different maximum target doses are applied (105% versus 120% versus 140%) to investigate the effect on normal tissue dose reduction. The method is tested on a homogeneous and a lung phantom and on a liver patient. Target D99 of the robust plans equals the prescription dose of 60 GyE for all scenarios, but decreases to 36 GyE for the non-robust plans. The mean normal tissue dose in a 2 cm ring around the target is 11% to 31% higher for the robust plans. This increase can be reduced to -8% and 3% (compared to the non-robust plan) by allowing a maximum tumor dose of 120% instead of 105%. Thus robustness leads to more normal tissue dose, but it can be compensated by allowing a higher maximum tumor dose. PMID:24077105

Petit, Steven; Seco, Joao; Kooy, Hanne

2013-10-21

29

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

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

30

New control method of maximum power point tracking for tidal energy generation system

This paper proposes new control method of maximum power point tracking for the tidal energy generation system using the duty ratio control of buck type DC-DC converter. An advantage of new MPPT(Maximum Power Point Tracking) control method presented in this paper is not necessary to use the tidal turbine characteristic at various tidal speed and measure the tidal speed or\\/and

Jae Sin Choi; Rag Gyo Jeong; Jae Hwa Shin; Cheon Kyu Kim; Young Seok Kim

2007-01-01

31

A new approach to achieve maximum power point tracking for PV system with a variable inductor

Maximum Power Transfer in solar photovoltaic applications is achieved by impedance matching with a dc-dc converter with maximum power point tracking by the incremental conductance method. Regulation and dynamic control is achieved by operating with continuous conduction. It can be shown that under stable operation, the required output inductor has an inductance versus current characteristic whereby the inductance falls off

Longlong Zhang; William Gerard Hurley; Werner Wolfle

2010-01-01

32

Simulation model of ANN based maximum power point tracking controller for solar PV system

In this paper the simulation model of an artificial neural network (ANN) based maximum power point tracking controller has been developed. The controller consists of an ANN tracker and the optimal control unit. The ANN tracker estimates the voltages and currents corresponding to a maximum power delivered by solar PV (photovoltaic) array for variable cell temperature and solar radiation. The

Anil K. Rai; N. D. Kaushika; Bhupal Singh; Niti Agarwal

2011-01-01

33

Comparison of maximum power point control methods for thermoelectric power generator

This paper describes the comparison of operating point control methods such as maximum power point tracking control (MPPT) and a constant voltage control applied to the thermoelectric devices. To experimentally evaluate the power control methods, a one-chip micro controller controlled DC-DC converter was inserted between the thermoelectric module and a load. The derived power from the module by constant voltage

H. Nagayoshi; T. Kajikawa; T. Sugiyama

2002-01-01

34

A novel maximum power point tracking algorithm for ocean wave energy devices

Many forms of renewable energy exist in the world's oceans, with ocean wave energy showing great potential. However, the ocean environment presents many challenges for cost-effective renewable energy conversion, including optimal control of a wave energy converter (WEC). This paper presents a novel maximum power point tracking (MPPT) algorithm for control of a point absorber WEC. The algorithm and control

Ean A. Amon; Alphonse A. Schacher; Ted K. A. Brekken

2009-01-01

35

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

36

Matlab/Simulink-Based Research on Maximum Power Point Tracking of Photovoltaic Generation

NASA Astrophysics Data System (ADS)

In order to improve the output efficiency of PV system, A novel variable step size perturbation and observation (P&O) method is proposed to track the maximum power point of PV system. Based on the mathematical model of PV system, this method tracks the maximum power point by regulating the output voltage after measuring the changes of output power. The simulation model of PV system is established, and the experiment is implemented. The experimental results show that the method can track the maximum power point fast and exactly, which shows that adaptive P&O has better steady-state and dynamic performance than the traditional P&O, and can improve the efficiency of photovoltaic power generation system effectively.

Qin, Lijun; Lu, Xiao

37

Control of a two-phase bi-directional interleaved converter for maximum power point tracking

The paper presents realization and control of a two-phase bi-directional interleaved converter for a photovoltaic (PV) system. Harmonic contents due to switching action in a dc-dc converter are reduced by the interleaving technique. A nonlinear function is used for predicting the maximum power point (MPP). A novel multi-loop control scheme is developed to achieve maximum PV power generation under all

Niphat Jantharamin; Li Zhang

2008-01-01

38

An EXCEL{reg_sign} spreadsheet has been developed that, when combined with the PC version of XOQDOQ, will generate estimates of maximum individual dose from routine atmospheric releases of radionuclides. The spreadsheet, MAXINE, utilizes a variety of atmospheric dispersion factors to calculate radiation dose as recommended by the US Nuclear Regulatory Commission in Regulatory Guide 1.109 [USNRC 1977a]. The methodology suggested herein includes use of both the MAXINE spreadsheet and the PC version of XOQDOQ.

Hamby, D.M.

1994-02-01

39

PV field distributed maximum power point tracking by means of an active bypass converter

An active bypass structure that was initially proposed as a solution to minimize the reduction in produced power caused by mismatch of photovoltaic modules is compared in terms of efficiency with single and distributed maximum power point solutions based in more conventional dc-dc structures. The analysis and simulations performed under simplified losses assumptions demonstrate that the bypass structure is very

R. Giral; C. E. Carrejo; M. Vermeersh; A. J. Saavedra-Montes; C. A. Ramos-Paja

2011-01-01

40

Sensorless Maximum Power Point Tracking of Wind by DFIG Using Rotor Position Phase Lock Loop (PLL)

This paper presents an invention, the rotor position phase lock loop (PLL), which enables maximum power point (MPPT) tracking of wind by doubly-fed induction generators without needing a tachometer, an absolute position encoder, or an anemometer. The rotor position PLL is parameter variation insensitive, requiring only an estimate of the magnetization inductance for it to operate. It is also insensitive

Baike Shen; Bakari Mwinyiwiwa; Yongzheng Zhang; Boon-Teck Ooi

2009-01-01

41

Maximum power point tracking: a cost saving necessity in solar energy systems

It is argued that a well-engineered renewable remote energy system utilizing the principal of maximum power point tracking (MPPT) can be cost effective, has a high reliability, and can improve the quality of life in remote areas. A highly efficient power electronic converter for converting the output voltage of a solar panel or wind generator to the required DC battery

J. H. R. Enslin

1990-01-01

42

Implementation of the RBF neural network on a SOPC for maximum power point tracking

In this paper, a radial basis function (RBF) neural network is implemented as a system on a programmable chip (SOPC) to carry out maximum power point tracking (MPPT) for photovoltaic (PV) control systems. The implementation of the SOPC can provide a traditional proportional integral derivative (PID) controller and some additional hardware like a pulse width modulation (PWM) generator by a

Bo Cao; Liuchen Chang; Howard Li

2008-01-01

43

This paper proposes a control strategy for variable speed wind energy conversion system (WECS), incorporating maximum power point tracking (MPPT) algorithm, using direct driven permanent magnet synchronous generator (PMSG). The generator is operated in the speed control mode below the base speed by controlling the terminal voltage using three phase front-end active-rectifier feeding power to the DC bus. The voltage

N. Srighakollapu; P. S. Sensarma

2008-01-01

44

Automatic maximum power point tracker for solar PV modules using dSPACE software

Maximization of power from a solar photovoltaic (SPV) module is of special interest as the efficiency of the SPV module is very low. The present work describes the maximum power point tracker (MPPT) for the SPV module connected at variable load conditions. A personal computer (PC) is used for control of the MPPT algorithm. The power tracker is developed and

S. Chatterji; Atif Iqbal

2010-01-01

45

Adaptive neuro-fuzzy inference system based maximum power point tracking of a solar PV module

This paper presents and analyses the operation of an Adaptive Neuro-Fuzzy Inference System (ANFIS) based maximum power point tracker (MPPT) for solar photovoltaic (SPV) energy generation system. The MPPT works on the principle of adjusting the voltage of the solar PV modules by changing the duty ratio of the boost converter. The duty ratio of boost converter is calculated for

A. Iqbal; H. Abu-Rub; S. M. Ahmed

2010-01-01

46

Modified hill-top algorithm based maximum power point tracking for solar PV module

This paper presents a maximum power point tracking (MPPT) controller employing a modified hill top algorithm implemented using embedded microcontroller for solar photovoltaic (PV) module. The proposed MPPT algorithm has high efficiency compared to conventional hill top algorithm in terms of transferring power from source to load. The designed controller regulates the output voltage through control of the DC-DC boost

S Rajasekar; Rajesh Gupta; Anurag Upadhyay; Puneet Agarwal; Sudhir Kumar; Y. Shasi Kumar

2012-01-01

47

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

48

Maximum power point tracker applied in batteries charging with PV panels

This work deals with the design and implementation prototype of a real time maximum power point tracker (MPPT) for photovoltaic panel (PV), aiming to improve energy transfer efficiency. This paper describes also the charging process of lead- acid batteries integrating the MPPT algorithm making an charging autonomous system that can be used to feed any autonomous application. The photovoltaic system

José António Barros Vieira; Alexandre Manuel Mota

2008-01-01

49

A new fuzzy control method based on PSO for Maximum Power Point Tracking of photovoltaic system

Maximum Power Point Tracking (MPPT) is the key technology in the solar energy photovoltaic system, which plays an important role in enhancing energy utilization effectively. Aiming at problems existing in traditional fuzzy tracking method, such as pre-confirmation of control parameters, weak self-study ability, and effective tracking cannot be organized under the circumstance that the environment condition is changed greatly, a

Qiang Fu; Nan Tong

2011-01-01

50

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

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. Olías; A. Barrado; A. Lázaro

2006-01-01

51

A novel ANFIS controller for maximum power point tracking in photovoltaic systems

This paper presents the design of a controller for maximum power point tracking (MPPT) of a photovoltaic system. The proposed controller relies upon an adaptive neuro-fuzzy inference system (ANFIS) which is designed as a combination of the concepts of Sugeno fuzzy model and neural network. The controller employs the ANFIS of five layers with nine fuzzy rules. Simulations with practical

Noppadol Khaehintung; Phaophak Sirisuk; Werasak Kurutach

2003-01-01

52

Realworld maximum power point tracking simulation of PV system based on Fuzzy Logic control

NASA Astrophysics Data System (ADS)

In the recent years, the solar energy becomes one of the most important alternative sources of electric energy, so it is important to improve the efficiency and reliability of the photovoltaic (PV) systems. Maximum power point tracking (MPPT) plays an important role in photovoltaic power systems because it maximize the power output from a PV system for a given set of conditions, and therefore maximize their array efficiency. This paper presents a maximum power point tracker (MPPT) using Fuzzy Logic theory for a PV system. The work is focused on the well known Perturb and Observe (P&O) algorithm and is compared to a designed fuzzy logic controller (FLC). The simulation work dealing with MPPT controller; a DC/DC ?uk converter feeding a load is achieved. The results showed that the proposed Fuzzy Logic MPPT in the PV system is valid.

Othman, Ahmed M.; El-arini, Mahdi M. M.; Ghitas, Ahmed; Fathy, Ahmed

2012-12-01

53

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

Maximum Power Point Tracking (MPPT) for on-body Context Systems

In this article we present the use of MPPT (maximum- power-point-tracking) for miniaturized on-body activity recognition systems. We evaluate different solar cells and apply MPPT to study the suitability for on-line activity systems. With a wrist worn solar cell, MPPT allows us to track power levels of 1.35 mW for indoors\\/wood-workshop lighting and 7.21 mW during dull outdoor lighting conditions.

Nagendra Bhargava Bharatula; Jamie A. Ward; Paul Lukowicz; Gerhard Tröster

2006-01-01

55

Development of a microcontroller-based, photovoltaic maximum power point tracking control system

Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system has been developed, consisting of a buck-type DC\\/DC converter, which is controlled by a microcontroller-based unit. The main difference between the method used in the

Eftichios Koutroulis; Kostas Kalaitzakis; Nicholas C. Voulgaris

2001-01-01

56

A boost-cascaded-with-buck converter-based power conditioning system employing a seamless mode transfer maximum power point tracking controller is proposed to maximize energy production of a thermoelectric generator while balancing a vehicle battery, alternator output power, and vehicle load. When a vehicle battery is fully charged, the proposed controller switches to a power matching mode seamlessly by a dual loop control system,

Rae-Young Kim; Jih-Sheng Lai

2008-01-01

57

TS Fuzzy Maximum Power Point Tracking Control of Solar Power Generation Systems

This paper presents maximum power point tracking (MPPT) control for stand-alone solar power generation systems via the Takagi-Sugeno (T-S) fuzzy-model-based approach. In detail, we consider a dc\\/dc buck converter to regulate the output power of the photovoltaic panel array. First, the system is represented by the T-S fuzzy model. Next, in order to reduce the number of measured signals, a

Chian-Song Chiu

2010-01-01

58

Maximum supercoolign in liquid /sup 3/He-/sup 4/He mixtures near the tricritical point

Measurements of supercooling in liquid /sup 3/He-/sup 4/He mixtures near the tricritical point are presented. The reduced temperature range 0.001 < epsilon identical to (1 - T/T/sub t/) < 0.01 was investigated for three different rates of cooling using a pressure-quench technique. For epsilon < 0.012, the maximum supercooling was found to be a function of the cooling rate. Comparisons with data in organic binary mixtures are given.

Sinha, D.N.; Hoffer, J.K.

1984-01-01

59

This paper describes a method of Maximum Power Point Tracking(MPPT) with MCU controlling system in grid-connected photovoltaic generation system, especially introduces the techniques and principles of DC-DC conversion. The MPPT is implemented with a Buck-Boost DC-DC converted circuit topology. The system is simple with good response speed, and the controlling method is flexible with software and hardware combined. And the

Weiping Luo; Gujing Han

2009-01-01

60

Tracking the global maximum power point of PV arrays under partial shading conditions

NASA Astrophysics Data System (ADS)

This thesis presents the theoretical and simulation studies of the global maximum power point tracking (MPPT) for photovoltaic systems under partial shading. The main goal is to track the maximum power point of the photovoltaic module so that the maximum possible power can be extracted from the photovoltaic panels. When several panels are connected in series with some of them shaded partially either due to clouds or shadows from neighboring buildings, several local maxima appear in the power vs. voltage curve. A power increment based MPPT algorithm is effective in identifying the global maximum from the several local maxima. Several existing MPPT algorithms are explored and the state-of-the-art power increment method is simulated and tested for various partial shading conditions. The current-voltage and power-voltage characteristics of the PV model are studied under different partial shading conditions, along with five different cases demonstrating how the MPPT algorithm performs when shading switches from one state to another. Each case is supplemented with simulation results. The method of tracking the Global MPP is based on controlling the DC-DC converter connected to the output of the PV array. A complete system simulation including the PV array, the direct current to direct current (DC-DC) converter and the MPPT is presented and tested using MATLAB software. The simulation results show that the MPPT algorithm works very well with the buck converter, while the boost converter needs further changes and implementation.

Fennich, Meryem

61

Use of iodine for water disinfection: iodine toxicity and maximum recommended dose.

Iodine is an effective, simple, and cost-efficient means of water disinfection for people who vacation, travel, or work in areas where municipal water treatment is not reliable. However, there is considerable controversy about the maximum safe iodine dose and duration of use when iodine is ingested in excess of the recommended daily dietary amount. The major health effect of concern with excess iodine ingestion is thyroid disorders, primarily hypothyroidism with or without iodine-induced goiter. A review of the human trials on the safety of iodine ingestion indicates that neither the maximum recommended dietary dose (2 mg/day) nor the maximum recommended duration of use (3 weeks) has a firm basis. Rather than a clear threshold response level or a linear and temporal dose-response relationship between iodine intake and thyroid function, there appears to be marked individual sensitivity, often resulting from unmasking of underlying thyroid disease. The use of iodine for water disinfection requires a risk-benefit decision based on iodine's benefit as a disinfectant and the changes it induces in thyroid physiology. By using appropriate disinfection techniques and monitoring thyroid function, most people can use iodine for water treatment over a prolonged period of time.

Backer, H; Hollowell, J

2000-01-01

62

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

63

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

64

Unbounded Binary Search for a Fast and Accurate Maximum Power Point Tracking

NASA Astrophysics Data System (ADS)

This paper presents a technique for maximum power point tracking (MPPT) of a concentrating photovoltaic system using cell level power optimization. Perturb and observe (P&O) has been a standard for an MPPT, but it introduces a tradeoff between the tacking speed and the accuracy of the maximum power delivered. The P&O algorithm is not suitable for a rapid environmental condition change by partial shading and self-shading due to its tracking time being linear to the length of the voltage range. Some of researches have been worked on fast tracking but they come with internal ad hoc parameters. In this paper, by using the proposed unbounded binary search algorithm for the MPPT, tracking time becomes a logarithmic function of the voltage search range without ad hoc parameters.

Kim, Yong Sin; Winston, Roland

2011-12-01

65

Microbial fuel cell (MFC) technology offers a sustainable approach to harvest electricity from biodegradable materials. Energy production from MFCs has been demonstrated using external resistors or charge pumps, but such methods can only dissipate energy through heat or receive electrons passively from the MFC without any controllability. This study developed a new approach and system that can actively extract energy from MFC reactors at any operating point without using any resistors, especially at the peak power point to maximize energy production. Results show that power harvesting from a recirculating-flow MFC can be well maintained by the maximum power point circuit (MPPC) at its peak power point, while a charge pump was not able to change operating point due to current limitation. Within 18-h test, the energy gained from the MPPC was 76.8 J, 76 times higher than the charge pump (1.0 J) that was commonly used in MFC studies. Both conditions resulted in similar organic removal, but the Coulombic efficiency obtained from the MPPC was 21 times higher than that of the charge pump. Different numbers of capacitors could be used in the MPPC for various energy storage requirements and power supply, and the energy conversion efficiency of the MPPC was further characterized to identify key factors for system improvement. This active energy harvesting approach provides a new perspective for energy harvesting that can maximize MFC energy generation and system controllability. PMID:22486712

Wang, Heming; Park, Jae-Do; Ren, Zhiyong

2012-05-01

66

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

67

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

68

In radiosurgery narrow photon beams, the depth of maximum dose d(max), in the beam central axis increases as the size of the additional collimator increases. This behavior is the opposite of what is observed in radiotherapy conventional beams. To understand this effect, experimental depth dose curves of the additional collimators were obtained for a Siemens KD2 linear accelerator in 6 MV photon mode and the shift of d(max) varied from 11.0 +/- 0.6 mm for the 5 mm collimator to 14.5 +/- 0.6 mm for the 23 mm collimator. Monte Carlo simulations showed that the photons that had no interactions in the additional collimators, contributing more than 90% to the total dose in water, were responsible for the shift in d(max). Monte Carlo simulations also showed that electrons originated from these photons and contributing to the dose deposit in water in the beam central axis could be divided in two groups: those that deposit energy far away from their point of origin (the point of the first photon collision in water) and those that deposit energy locally (originated at more than one photon collision in water). Applying a simplified model based on the fact that the photons originating Compton electrons (at the first and subsequent collisions) have similar characteristics in air for all the additional collimators, it was shown that these electrons were also responsible for the shift of d(max) in the beam central axis. Finally, it was shown that the changes in the initial gradients of the depth dose curves of the additional collimators were mainly due to electrons originated from the first photon collision in water. PMID:14655937

Chaves, A; Lopes, M C; Alves, C C; Oliveira, C; Peralta, L; Rodrigues, P; Trindade, A

2003-11-01

69

A photovoltaic power generation system (PV system) is operated under various insolation conditions. Sometimes the PV system is operated under nonuniform insolation, which may generate several maximum output power points on the V-I curve of the PV array and raises serious problem on maximum power point tracking (MPPT) control of the system. In order to solve this problem, the authors

Kei Irisawa; Takeshi Saito; I. Takano; Y. Sawada

2000-01-01

70

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

NASA Astrophysics Data System (ADS)

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 estimation of toxicity for continuous response events with small sample experiments. Current safety standards for avoidance of cataract after exposure to UVR are based on a binary response event. It has however recently been shown that UVR-induced cataract is a continuous dose-dependent event. MTD provides a statistically well defined criterium of toxicity for continuous response events.

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

2001-06-01

71

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

72

A photovoltaic (PV) array shows relatively low output power density, and has a greatly drooping current-voltage (I-V) characteristic. Therefore, maximum power point tracking (MPPT) control is used to maximize the output power of the PV array. Many papers have been reported in relation to MPPT. However, the current-power (I-P) curve sometimes shows multilocal maximum points mode under nonuniform insolation conditions.

K. Kobayashi; I. Takano; Y. Sawada

2003-01-01

73

The research on the algorithm of maximum power point tracking in photo voltaic array of solar car

Combined with the practical working environment of the vehicle photovoltaic cell plate on the electric vehicle, according to the engineering mathematic model of photovoltaic cell, the output characteristics is nonlinear, and the maximum power is on one point. Adopting the improved conductance increment method, the maximum power tracking rate and accuracy are enhanced.

Xiujuan Ma; Yude Sun; Jiayu Wu; Shiqiang Liu

2009-01-01

74

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

NASA Astrophysics Data System (ADS)

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), are in the planning stages. Due to the flight durations, solar power systems have been utilized throughout the Long Duration Balloon (LDB) flight program to power the necessary electronic systems. Recently, Maximum Power Point Tracking (MPPT) charge controllers have become available off-the-shelf. These controllers along with high efficiency mono-crystalline solar cells have become reliable, low cost solutions even in the harsh environments they operate in. The LDB program at the Columbia Scientific Balloon Facility (CSBF) began supporting solar power systems with custom units fabricated by the Physical Science Laboratory (PSL) of New Mexico State University (NMSU). These charge controllers proved to be very reliable systems; however, they required intensive labor to build and were relatively expensive. As off-the-shelf MPPT charge controllers have become available, they have been integrated into the LDB flight support systems. Coupled with PSL developed interface electronics for monitoring and power switching, they have proven to be as reliable, less expensive, and more efficient. The addition of MPPT allows for the controller to operate the solar panel at it highest power production point. Newer, off-the-shelf controllers with smarter MPPT, are currently being tested. This paper describes the long and ultra-long balloon missions and the role that solar power plays in mission success. More importantly, it discusses the recent developments in off-the-shelf MPPT charge controllers configured for use in the harsh high altitude balloon environment.

Perez, Juan

75

NASA Astrophysics Data System (ADS)

An analog maximum power point tracking (MPPT) circuit for a thermoelectric generator (TEG) is proposed. We show that the peak point of the voltage conversion gain of a boost DC-DC converter with an input voltage source having an internal resistor is the maximum power point of the TEG. The key characteristic of the proposed MPPT controller is that the duty ratio of the input clock pulse to the boost DC-DC converter shifts toward the maximum power point of the TEG by seeking the peak gain point of the boost DC-DC converters. The proposed MPPT technique provides a simple and useful analog MPPT solution, without employing digital microcontroller units.

Park, Jungyong; Kim, Shiho

2012-06-01

76

Dose-response studies often form integral parts of pharmacological investigations of drug activity and efficacy and of toxicological investigations of drug and chemical safety. Standardized dose-response study protocols, statistical models, model fitting techniques, and computer programs are widely available for such applications. Many studies however, require nonstandard models and model fitting procedures to adequately describe the resulting data. Maximum likelihood analysis

P. I. Feder; C. T. Olson; D. W. Hobson; M. C. Matthews; R. L. Joiner

1991-01-01

77

A maximum-likelihood search for neutrino point sources with the AMANDA-II detector

NASA Astrophysics Data System (ADS)

Neutrino astronomy offers a new window to study the high energy universe. The AMANDA-II detector records neutrino-induced muon events in the ice sheet beneath the geographic South Pole, and has accumulated 3.8 years of livetime from 2000 - 2006. After reconstructing muon tracks and applying selection criteria, we arrive at a sample of 6595 events originating from the Northern Sky, predominantly atmospheric neutrinos with primary energy 100 GeV to 8 TeV. We search these events for evidence of astrophysical neutrino point sources using a maximum-likelihood method. No excess above the atmospheric neutrino background is found, and we set upper limits on neutrino fluxes. Finally, a well-known potential dark matter signature is emission of high energy neutrinos from annihilation of WIMPs gravitationally bound to the Sun. We search for high energy neutrinos from the Sun and find no excess. Our limits on WIMP-nucleon cross section set new constraints on MSSM parameter space.

Braun, James R.

78

NASA Technical Reports Server (NTRS)

Direct current (dc) motors are used in terrestrial photovoltaic (PV) systems such as in water-pumping systems for irrigation and water supply. Direct current motors may also be used for space applications. Simple and low weight systems including dc motors may be of special interest in space where the motors are directly coupled to the solar cell array (with no storage). The system will operate only during times when sufficient insolation is available. An important performance characteristic of electric motors is the starting to rated torque ratio. Different types of dc motors have different starting torque ratios. These ratios are dictated by the size of solar cell array, and the developed motor torque may not be sufficient to overcome the load starting torque. By including a maximum power point tracker (MPPT) in the PV system, the starting to rated torque ratio will increase, the amount of which depends on the motor type. The starting torque ratio is calculated for the permanent magnet, series and shunt excited dc motors when powered by solar cell arrays for two cases: with and without MPPT's. Defining a motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 was obtained for the permanent magnet motor and a magnification of 7 for both the series and shunt motors. The effect of the variation of solar insolation on the motor starting torque was covered. All motor types are less sensitive to insolation variation in systems including MPPT's as compared to systems with MPPT's. The analysis of this paper will assist the PV system designed to determine whether or not to include an MPPT in the system for a specific motor type.

Appelbaum, Joseph; Singer, S.

1989-01-01

79

NASA Astrophysics Data System (ADS)

A photovoltaic array shows relatively low output power density, and has a greatly drooping Current-Voltage (I-V) characteristic. Therefore, Maximum Power Point Tracking (MPPT) control is used to maximize the output power of the array. Many papers have been reported in relation to MPPT. However, the Current-Power (I-P) curve sometimes shows multi-local maximum points mode under non-uniform insolation conditions. The operating point of the PV system tends to converge to a local maximum output point which is not the real maximal output point on the I-P curve. Some papers have been also reported, trying to avoid this difficulty. However most of those control systems become rather complicated. Then, the two stage MPPT control method is proposed in this paper to realize a relatively simple control system which can track the real maximum power point even under non-uniform insolation conditions. The feasibility of this control concept is confirmed for steady insolation as well as for rapidly changing insolation by simulation study using software PSIM and LabVIEW. In addition, simulated experiment confirms fundament al operation of the two stage MPPT control.

Kobayashi, Kenji; Takano, Ichiro; Sawada, Yoshio

80

Although 131I-iodine (RAI) therapy is a mainstay in the treatment of metastatic thyroid cancer, there is controversy regarding the maximum activity that can safely be administered without dosi- metric determination of the maximum tolerable activity (MTA). At most institutions, a fixed empiric dosing strategy is often used, with administered activities ranging from 5.55 to 9.25 GBq (150-250 mCi). In our

R. Michael Tuttle; Rebecca Leboeuf; Richard J. Robbins; Rebecca Qualey; Keith Pentlow; Steven M. Larson; Chee Y. Chan

81

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

82

Primary barrier determinations for the shielding of medical radiation therapy facilities are generally made assuming normal beam incidence on the barrier, since this is geometrically the most unfavorable condition for that shielding barrier whenever the occupation line is allowed to run along the barrier. However, when the occupation line (for example, the wall of an adjacent building) runs perpendicular to the barrier (especially roof barrier), then two opposing factors come in to play: increasing obliquity angle with respect to the barrier increases the attenuation, while the distance to the calculation point decreases, hence, increasing the dose. As a result, there exists an angle (alpha(max)) for which the equivalent dose results in a maximum, constituting the most unfavorable geometric condition for that shielding barrier. Based on the usual NCRP Report No. 151 model, this article presents a simple formula for obtaining alpha(max), which is a function of the thickness of the barrier (t(E)) and the equilibrium tenth-value layer (TVL(e)) of the shielding material for the nominal energy of the beam. It can be seen that alpha(max) increases for increasing TVL(e) (hence, beam energy) and decreases for increasing t(E), with a range of variation that goes from 13 to 40 deg for concrete barriers thicknesses in the range of 50-300 cm and most commercially available teletherapy machines. This parameter has not been calculated in the existing literature for radiotherapy facilities design and has practical applications, as in calculating the required unoccupied roof shielding for the protection of a nearby building located in the plane of the primary beam rotation. PMID:18561656

Fondevila, Damián; Arbiser, Silvio; Sansogne, Rosana; Brunetto, Mónica; Dosoretz, Bernardo

2008-05-01

83

Primary barrier determinations for the shielding of medical radiation therapy facilities are generally made assuming normal beam incidence on the barrier, since this is geometrically the most unfavorable condition for that shielding barrier whenever the occupation line is allowed to run along the barrier. However, when the occupation line (for example, the wall of an adjacent building) runs perpendicular to the barrier (especially roof barrier), then two opposing factors come in to play: increasing obliquity angle with respect to the barrier increases the attenuation, while the distance to the calculation point decreases, hence, increasing the dose. As a result, there exists an angle ({alpha}{sub max}) for which the equivalent dose results in a maximum, constituting the most unfavorable geometric condition for that shielding barrier. Based on the usual NCRP Report No. 151 model, this article presents a simple formula for obtaining {alpha}{sub max}, which is a function of the thickness of the barrier (t{sub E}) and the equilibrium tenth-value layer (TVL{sub e}) of the shielding material for the nominal energy of the beam. It can be seen that {alpha}{sub max} increases for increasing TVL{sub e} (hence, beam energy) and decreases for increasing t{sub E}, with a range of variation that goes from 13 to 40 deg for concrete barriers thicknesses in the range of 50-300 cm and most commercially available teletherapy machines. This parameter has not been calculated in the existing literature for radiotherapy facilities design and has practical applications, as in calculating the required unoccupied roof shielding for the protection of a nearby building located in the plane of the primary beam rotation.

Fondevila, Damian; Arbiser, Silvio; Sansogne, Rosana; Brunetto, Monica; Dosoretz, Bernardo [Vidt Centro Medico, Vidt 1924, Buenos Aires (Argentina)

2008-05-15

84

In this paper a comparative study through experimental work between a new low-cost maximum power point tracker (MPPT) and the conventional configurations of the photovoltaic (PV) regulators under different atmospheric conditions is presented. The comparison is made by means of the energy production obtained by the PV generator of each system. From the results obtained it can be concluded that,

V. Salas; E. Olías; A. Lázaro; A. Barrado

2005-01-01

85

National Technical Information Service (NTIS)

It is common when optimizing a photovoltaic (PV) system to use a maximum power point tracker (MPPT) to increase the power output of the solar array. Currently, most military applications that utilize solar energy omit or use only a single MPPT per PV syst...

C. A. Stephenson

2012-01-01

86

This paper introduces a solar photovoltaic (PV) system suitable for undergraduate engineering education and training. The system consists of a buck converter using a simple maximum power point tracking (MPPT) method. Constant voltage control method is used for the approximate tracking and is implemented by analogue circuits. The circuit simplicity helps students to appreciate the benefit of MPPT in a

Dylan D. C. Lu; R. H. Chu; S. Sathiakumar; V. G. Agelidis

2007-01-01

87

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

88

The results of neutron-transport flux-density and dose rate calculations for implantable Californium-252 point and line sources in essentially infinite tissue-equivalent material are presented. The point-source flux densities were obtained from a discrete ordinates calculation, and the point dose rates were established by multiplying the flux densities by their appropriate kerma factors. Line-source dose rates were evaluated by integrating the point dose rates over the length of the line source. Dose-rate data are given within a 20 X 20-cm region from the source center for source lengths of 1.5, 2, and 3 cm. The dose rates established by these calculations showed good agreement with an independent Monte Carlo calculation. Detailed point-source flux-density data as a function of energy and position are also given. PMID:958169

Shapiro, A; Schwartz, B; Windham, J P; Kereiakes, J G

1976-01-01

89

A DSP-based single-stage maximum power point tracking PV inverter

This paper presents the design and implementation of a DSP-based single-stage photovoltaic (PV) inverter system which can extract maximum power from solar panel. A perturbation and observation (P&O) method is realized and cooperated with a digital unipolar voltage switching sinusoidal pulse width modulation. The studied single-stage topology provides the benefits of low cost, simple configuration and good overall efficiency compared

Wen Long Yu; Ting-Peng Lee; Guan-Hong Wu; Qing Su Chen; Huang-Jen Chiu; Yu-Kang Lo; F. Shih

2010-01-01

90

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&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&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&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. PMID:23266165

Matsubara, Kana; Kohno, Ryosuke; Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo; Saitoh, Hidetoshi

2013-01-01

91

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

92

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

93

A maximum power point tracker for photovoltaic arrays is presented. Components are optimized for weight\\/power-loss tradeoff in a solar-powered vehicle, resulting in over 97% efficiency. The control circuit uses a robust auto-oscillation method. Measurement and multiplication of array voltage and current is shown to be unnecessary, and the control is based only on output current measurement. Multiple local maxima arising

Charles R. Sullivan; Matthew J. Powers

1993-01-01

94

This paper presents the development of maximum power point tracking (MPPT) using a fuzzy logic controller (FLC). By applying the synthetic fuzzy inference algorithm, the relation between input and output of FLC can be effectively stored in a memory-limited lookup table (LUT). As a consequence, the controller can be efficiently implemented on a low-cost 16F872 RISC microcontroller. A practical system

N. Khaehintung; P. Sirisuk

2004-01-01

95

In the upcoming field of e-mobility roof-integrated photovoltaic systems are used to extend the cruising range of electric vehicles. Due to the roof's curvature the solar cells (SC) show different inclination angles to the sunlight, resulting in different maximum power points (MPP) and a lower harvested energy if all SCs are controlled by a centralized MPP-regulated DC\\/DC converter. A further

Reinhard Enne; Miodrag Nikolic; Horst Zimmermann

2012-01-01

96

In this study, optimum insulation position from maximum time lag and minimum decrement factor point of view has been investigated numerically. For this purpose, one-dimensional transient heat conduction equation was solved for a composite wall using Crank–Nicolson's scheme under periodic convection boundary conditions. Four-centimeter thick insulation was placed in different positions of 20-cm thick wall as a whole (1 piece,

H Asan

2000-01-01

97

In order to determine the components which give rise to the EPR spectrum around g = 2 we have applied Maximum Likelihood Common Factor Analysis (MLCFA) on the EPR spectra of enamel sample 1126 which has previously been analysed by continuous wave and pulsed EPR as well as EPR microscopy. MLCFA yielded agreeing results on three sets of X-band spectra

G. Vanhaelewyn; F. Callens; R. Grün

2000-01-01

98

Purpose This was a phase I trial to determine the maximum tolerated dose and toxicity of deforolimus (AP23573, MK-8669), an inhibitor of mammalian target of rapamycin (mTOR). The pharmacokinetics, pharmacodynamics, and antineoplastic effects were also studied. Experimental Design Deforolimus was administered intravenously over 30 min every 7 days according to a flat dosing schedule. Dose was escalated according to an accelerated titration design. Patients remained on study until disease progression as long as they tolerated the drug without significant toxicities. Results Forty-six patients were enrolled on the study. Common side effects included fatigue, anorexia, and mucositis. The maximum tolerated dose was 75 mg and mucositis was the dose-limiting toxicity. Similar to other mTOR inhibitors, deforolimus exhibited nonlinear pharmacokinetics and a prolonged half-life. Among 34 patients evaluable for response, 1 patient had a partial response, 21 patients had stable disease, and 12 had progressed. Percent change in tumor size was significantly associated with AUC (P = 0.015). A significant association was also detected for maximum change in cholesterol within the first two cycles of therapy and change in tumor size (r = ?0.38; P = 0.029). Conclusions Deforolimus was well tolerated on the schedule tested in this trial with toxicity and pharmacokinetic profiles that were similar to that of other mTOR inhibitors. Additional phase II studies are needed to determine if deforolimus is superior to other mTOR inhibitors in terms of efficacy. The change in serum cholesterol as a potential biomarker of activity should be studied further.

Hartford, Christine M.; Desai, Apurva A.; Janisch, Linda; Karrison, Theodore; Rivera, Victor M.; Berk, Lori; Loewy, John W.; Kindler, Hedy; Stadler, Walter M.; Knowles, Heather L.; Bedrosian, Camille; Ratain, Mark J.

2011-01-01

99

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

2010-08-01

100

NASA Astrophysics Data System (ADS)

A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This maximum age limit is a function of the saturation dose of the dosimeter material (silicate sediments) and the local ionizing radiation dose rate. The sources of ionizing radiation germane to optical dating are K, Rb, U, Th in the sediment/soil environment and cosmic rays. On Mars the near surface dose rate will be dominated by cosmic rays, however, at depth the decay of radioisotopes will be the principle contributor of ionizing radiation. In this work we present an evaluation of the maximum age limits for OSL dating on Mars as a function of depth. At this time we have considered only static burial. Our calculations are based on published models of and data for: (i) Mars surface cosmic dose rate and its attenuation by martian regolith, (ii) elemental analyses of Mars meteorites, (iii) an experimental evaluation of the saturation dose for the martian soil simulant JSC Mars-1. Our analysis confirms earlier inferences that optical dating should have a greater effective age range on Mars than on Earth. At depths easily accessible by penetrators or moles (1-3 m), maximum optical ages greater than 600 ka are possible. Geochronology on this scale would include at least two stadial/interstadial cycles within Mars' last "Glacial Epoch" (synchronized insolation variations between the poles). A wide range of landforms and surface processes associated with climate variability -- e.g. outwash and lacustrine deposition, large-scale eolian activation -- could potentially be optically dated. At greater depths, that could be reached by mobile drilling rigs or cryobots (10-30m), optical age maximums of 4.5 to greater than 35 Ma appear to be possible.

Franklund, R. T.; Lepper, K.

2004-12-01

101

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

102

Improved Estimates of External gamma Dose Rates in the Environs of Hinkley Point Power Station.

National Technical Information Service (NTIS)

The dominant source of external gamma dose rates at centers of population within a few kilometers of Hinkley Point Power Station is the routine discharge of 41-Ar from the 'A' station magnox reactors. Earlier estimates of the 41-Ar radiation dose rates we...

H. F. Macdonald I. M. G. Thompson P. M. Foster A. G. Robins

1988-01-01

103

According to the American Diabetes Association and the Adult Treatment Panel III, the starting point for treating metabolic syndrome (MS) is a change of lifestyle. In addition, action on the main symptoms of MS by means of dietary supplements, can be helpful in view of the chronic course of the disease. The term 'phytosterols' refers to sterols and stanols composed of lipophilic triterpenes, a family that is widely distributed in the plant kingdom and whose cholesterol-lowering properties have been amply demonstrated. In the light of the recent literature, the key points for maximum effectiveness and safety of sterols are the following. (A) Plant sterols should be taken with meals: clinical trials have shown that when plant sterols are consumed close to mealtimes, low-density lipoprotein cholesterol may decrease by 9.4%, while when they are taken between meals, the reduction is about 6%. (B) The optimal dosage is 2-2.5 g day(-1) in a single dose. More than 3 g day(-1) has not been found to have any additional beneficial effect and increases the risk of side effects. (C) The food matrix used to dissolve the phytosterols should contain a certain amount of fat. A milk-based matrix appears optimal from this point of view. © 2013 Society of Chemical Industry. PMID:23584958

Rondanelli, Mariangela; Monteferrario, Francesca; Faliva, Milena Anna; Perna, Simone; Antoniello, Neldo

2013-04-12

104

Accuracy of the point source approximation to high dose-rate Ir-192 sources.

The accuracy of the point source approximation used in dose calculations for an implant comprised of multiple high dose rate (HDR) Ir-192 source dwell positions is investigated. First, a single dwell position implant is modeled. The exposure rate about the source is calculated using both the point source approximation and the more rigorous line source formalism. A comparison of these calculated exposure rates is made. It is found that for each HDR Ir-192 source dwell position, the point source approximation results in a dose overestimation of 1% at a distance of 1 cm on the source transverse axis, while dose underestimations of more than 2% can be found at a distance of 1 cm on the source longitudinal axis. Even larger errors occur closer to the source. The results of this academic study are then extended to two clinical cases--an endobronchial treatment and a tandem and ovoids setup, both involving multiple source dwell positions. Since clinical HDR Ir-192 implants are comprised of many individual source dwell positions, there will be inaccuracy in the calculated overall dose distribution leading to dose delivery errors. For example, the dose delivered to a prescription point located 0.5 cm from an endobronchial applicator will be 3% lower than prescribed. Similar errors are produced in gynecologic implants. To decrease below 0.5% the dose delivery error resulting from the point source approximation, prescription points should be at a distance of at least 1 cm from any applicator. Since the dosimetry error is a direct result of the choice of model used to describe the source, the use of anisotropy factors accounting for the variation of photon fluence around the HDR Ir-192 source will not completely correct the calculation. PMID:7576091

Podgorsak, M B; DeWerd, L A; Paliwal, B R; Ho, A K; Sibata, C H

1995-01-01

105

National Technical Information Service (NTIS)

An examination was made of the characteristics of the solar daily variations recorded by east and west pointing directional telescopes at Mt. Chacaltaya (altitude = 5200 m, geomagnetic latitude = -4.8 degrees) during the years of maximum (1958) and minimu...

H. S. Ahluwalia V. I. Escobar M. Zubieta R. Anda M. Schreier

1965-01-01

106

Unlike the situation for ionic aqueous solutions, the relationship between the density maximum temperature Tmd and solute concentration for aqueous solutions of primary alcohols is known to be strongly non-linear. Using our recent theory for the existence of the maximum density in water in terms of quantum zero point energy effects, we explain why this is so. We also explain

F. A. Deeney; J. P. O’Leary; B. Cronin; D. M. O’Leary

2008-01-01

107

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

108

The dermal response of three strains of mice (ICR, C3H and B6C3F1) exposed to repeated doses of 0, 1 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 in US Environmental Protection Agency (EPA) Workshops on dermal carcinogenesis bioassays. A significant number of animals in all three strains with repeated exposure to 4% acrylic acid experienced skin irritation that was classified as having reached or exceeded the MTD compared with animals exposed to either 1% acrylic acid or the 0% acrylic acid acetone control. These results were observed within the first 3 wk of exposure, but there was some accommodation to irritation by 8 wk of exposure. Microscopic findings provided a more sensitive index for exceeding MTD than gross observations taken only at autopsy, but generally correlated well for MTD if gross observations were taken at regular intervals during treatment. That is, to set MTD, gross observations could be used if taken over the entire course of the exposure, but using microscopic findings was generally a more reliable or sensitive measure. EPA guidelines suggest that it is inappropriate to conduct a dermal bioassay at concentrations that exceed the MTD. Acrylic acid at 4% in acetone clearly exceeded the MTD based on microscopic or gross observation criteria. At 4%, strain differences were evident by gross observation only, with the ICR strain being less susceptible to irritation than C3H or B6C3F1 strains. These strain differences were not apparent with microscopic examination. Acrylic acid at 1% in acetone, although demonstrating signs of minimal irritation, was fairly well tolerated by all mice in all strains. Thus, acrylic acid at 1% in acetone, one-quarter of the concentration that was in clear excess of the MTD, would be the appropriate dose concentration for lifetime skin studies based on MTD criteria. PMID:7797178

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

1995-06-01

109

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

110

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

Several target configurations for the 41-MeV ( p/sup +/,Be) reaction have been evaluated for the characteristics of the radiation field produced; depth dose, dose rate per ..mu..A. From analysis, it is concluded that to achieve the desired 13.2-cm depth for 50% of maximum dose and acceptable dose rate at a target-to-skin distance (TSD) of 125--150 cm, the neutron spectra must be filtered to preferentially absorb the lower-energy neutrons. Further increases in depth of 50% of maximum dose and a significant reduction in beryllium heating problems result if a partial transmission target is used with the terminal 30% of proton energy being deposited in a copper target backing.

Smathers, J.B.; Graves, R.G.; Earls, L.; Otte, V.A.; Almond, P.R.

1982-11-01

112

Target point correction optimized based on the dose distribution of each fraction in daily IGRT

NASA Astrophysics Data System (ADS)

Purpose: To use daily re-calculated dose distributions for optimization of target point corrections (TPCs) in image guided radiation therapy (IGRT). This aims to adapt fractioned intensity modulated radiation therapy (IMRT) to changes in the dose distribution induced by anatomical changes. Methods: Daily control images from an in-room on-rail spiral CT-Scanner of three head-and-neck cancer patients were analyzed. The dose distribution was re-calculated on each control CT after an initial TPC, found by a rigid image registration method. The clinical target volumes (CTVs) were transformed from the planning CT to the rigidly aligned control CTs using a deformable image registration method. If at least 95% of each transformed CTV was covered by the initially planned D95 value, the TPC was considered acceptable. Otherwise the TPC was iteratively altered to maximize the dose coverage of the CTVs. Results: In 14 (out of 59) fractions the criterion was already fulfilled after the initial TPC. In 10 fractions the TPC can be optimized to fulfill the coverage criterion. In 31 fractions the coverage can be increased but the criterion is not fulfilled. In another 4 fractions the coverage cannot be increased by the TPC optimization. Conclusions: The dose coverage criterion allows selection of patients who would benefit from replanning. Using the criterion to include daily re-calculated dose distributions in the TPC reduces the replanning rate in the analysed three patients from 76% to 59% compared to the rigid image registration TPC.

Stoll, Markus; Giske, Kristina; Stoiber, Eva M.; Schwarz, Michael; Bendl, Rolf

2014-03-01

113

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

114

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

115

In the paper a linear system is considered. We are looking for inf {F(x):x?UCx=y0}, where Fis a convex functional and Uis a closed convex set. Sufficient conditions warrantying that the Maximum Principle of Pontryagin implies closedness of CXare given.

S. Rolewicz

1979-01-01

116

Simple analytical expressions for the dose of point photon sources in homogeneous media

NASA Astrophysics Data System (ADS)

The contributions to the dose of a point photon source in homogeneous media due to primary and first, second, ..., nth scattered photons are investigated. Assuming a simple statistical model, an analytical form comes out for each of these contributions. It includes a polynomial and a single exponential and depends on three parameters which have a physical meaning. The values of these parameters for different energies and for water, as a test case, are obtained from numerical fits to the results of a Monte Carlo simulation with the code PENELOPE. The average differences between the model and the Monte Carlo results, after the fitting process, are below 1%. Our model permits to obtain improved versions of the classical approach of Berger in a straightforward way. The expressions obtained also describe the dose build-up of the primary photons.

Sabariego, M. P.; Porras, I.; Lallena, A. M.

2008-11-01

117

Simple analytical expressions for the dose of point photon sources in homogeneous media.

The contributions to the dose of a point photon source in homogeneous media due to primary and first, second, ..., nth scattered photons are investigated. Assuming a simple statistical model, an analytical form comes out for each of these contributions. It includes a polynomial and a single exponential and depends on three parameters which have a physical meaning. The values of these parameters for different energies and for water, as a test case, are obtained from numerical fits to the results of a Monte Carlo simulation with the code PENELOPE. The average differences between the model and the Monte Carlo results, after the fitting process, are below 1%. Our model permits to obtain improved versions of the classical approach of Berger in a straightforward way. The expressions obtained also describe the dose build-up of the primary photons. PMID:18854613

Sabariego, M P; Porras, I; Lallena, A M

2008-11-01

118

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

119

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.

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

2013-01-01

120

NASA Astrophysics Data System (ADS)

We present the results of a search for cosmic-ray point sources at energies in excess of 4.0×1019 eV in the combined data sets recorded by the Akeno Giant Air Shower Array and High Resolution Fly's Eye stereo experiments. The analysis is based on a maximum likelihood ratio test using the probability density function for each event rather than requiring an a priori choice of a fixed angular bin size. No statistically significant clustering of events consistent with a point source is found.

Abbasi, R. U.; Abu-Zayyad, T.; Amann, J. F.; Archbold, G.; Atkins, R.; Bellido, J. A.; Belov, K.; Belz, J. W.; Ben-Zvi, S. Y.; Bergman, D. R.; Boyer, J. H.; Burt, G. W.; Cao, Z.; Clay, R. W.; Connolly, B. M.; Dawson, B. R.; Deng, W.; Farrar, G. R.; Fedorova, Y.; Findlay, J.; Finley, C. B.; Hanlon, W. F.; Hoffman, C. M.; Holzscheiter, M. H.; Hughes, G. A.; Hüntemeyer, P.; Jui, C. C. H.; Kim, K.; Kirn, M. A.; Knapp, B. C.; Loh, E. C.; Maestas, M. M.; Manago, N.; Mannel, E. J.; Marek, L. J.; Martens, K.; Matthews, J. A. J.; Matthews, J. N.; O'Neill, A.; Painter, C. A.; Perera, L.; Reil, K.; Riehle, R.; Roberts, M. D.; Sasaki, M.; Schnetzer, S. R.; Seman, M.; Simpson, K. M.; Sinnis, G.; Smith, J. D.; Snow, R.; Sokolsky, P.; Song, C.; Springer, R. W.; Stokes, B. T.; Thomas, J. R.; Thomas, S. B.; Thomson, G. B.; Tupa, D.; Westerhoff, S.; Wiencke, L. R.; Zech, A.

2005-04-01

121

NASA Astrophysics Data System (ADS)

The National Council on Radiation Protection and Measurements (NCRP) has issued a statement advising that it is considering lowering the maximum permissible dose for neutrons. This action would present substantive problems to radiation protection programs at DOE facilities where a potential for neutron exposure exists. In addition to altering administrative controls, a lowering of the maximum permissible dose for neutrons will require advances in personnel neutron dosimetry systems and neutron detection and measurement instrumentation. Improvement in the characterization of neutron fields and spectra at work locations will also be needed. DOE has initiated research and development programs in these areas. However, problems related to the control of personnel neutron exposure have yet to be resolved and investigators are encouraged to continue collaboration with both United States and international authorities.

Murphy, B. L.

1981-09-01

122

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

123

Maximum contact and fillet stresses in normal and high contact ratio spur gears are evaluated based on load sharing ratio using finite element method through single- and multi-point loaded models as well as multi-pair contact model. The multi-pair contact model has been justified as an appropriate one for the present analysis as this model exclusively considers the influence of the

Rama Thirumurugan; G. Muthuveerappan

2011-01-01

124

This study presents a new method of image signal-to-noise ratio (SNR) enhancement by utilizing a newly developed 2D two-point maximum entropy regularization method (TPMEM). When utilized as an image filter, it is shown that 2D TPMEM offers unsurpassed flexibility in its ability to balance the complementary requirements of image smoothness and fidelity. The technique is evaluated for use in the

A. Jirasek; Q. Matthews; M. Hilts; G. Schulze; M. W. Blades; R. F. B. Turner

2006-01-01

125

A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This

R. T. Franklund; K. Lepper

2004-01-01

126

This paper reports that it is important in the design of future fusion reactors and associated facilities that incorporate passive safety to take account of the possible environmental impact of accidental tritium release. Reliable information on dose consequences can be obtained by evaluating urine samples from persons exposed to tritium. Translating the results of the environmental HT experiment performed in

M. Taeschner; C. Bunnenberg; W. Gulden

1991-01-01

127

As part of the assessment of the potential radiological consequences of the proposed Waste Isolation Pilot Plant (WIPP), this report evaluates the post-closure radiation dose commitments associated with a possible breach event which involves dissolution of the repository by groundwaters and subsequent transport of the nuclear waste through an aquifer to a well assumed to exist at a point 3 miles downstream from the repository. The concentrations of uranium and plutonium isotopes at the well are based on the nuclear waste inventory presently proposed for WIPP and basic assumptions concerning the transport of waste as well as treatment to reduce the salinity of the water. The concentrations of U-233, Pu-239, and Pu-240, all radionuclides originally emplaced as waste in the repository, would exceed current EPA drinking water limits. The concentrations of U-234, U-235, and U-236, all decay products of plutonium isotopes originally emplaced as waste, would be well below current EPA drinking water limits. The 50-year dose commitments from one year of drinking treated water contaminated with U-233 or Pu-239 and Pu-240 were found to be comparable to a one-year dose from natural background. The 50-year dose commitments from one year of drinking milk would be no more than about 1/5 the dose obtained from ingestion of treated water. These doses are considered upper bounds because of several very conservative assumptions which are discussed in the report.

Spiegler, P.

1981-09-01

128

The larvae of calliphorid flies are used to debride wounds of patients with severe tissue destruction, often concurrently with antimicrobials. The current study evaluates the effects of ceftazidime, tobramycin, amikacin, gentamicin, polymyxin B, doxycycline, paromomycin, amphotericin B, sodium stibogluconate, and miltefosine at 1, 10, and 100 x the Maximum Clinical Concentration (mg/kg/d) in raw liver assays. Effects on larvae were small and depended on dose and antimicrobial formulation, with hours in assay (24 or 48 h) having a significant effect on larval survival. Sodium stibgluconate had the strongest effect on maggot survival (80.0% at 48 h). These results suggest that the antimicrobials tested here may be used simultaneously with maggot debridement therapy, and may actually increase the effectiveness of maggot debridement therapy in certain applications where >1 x Maximum Clinical Concentration is indicated, such as topical creams for cutaneous leishmaniasis. PMID:23025196

Peck, George W; Kirkup, Benjamin C

2012-09-01

129

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

130

The melting point of ice I(h), as well as the temperature of maximum density (TMD) in the liquid phase, has been computed using the path integral Monte Carlo method. Two new models are introduced, TIP4PQ_D2O and TIP4PQ_T2O, which are specifically designed to study D(2)O and T(2)O respectively. We have also used these models to study the "competing quantum effects" proposal of Habershon, Markland and Manolopoulos; the TIP4PQ/2005, TIP4PQ/2005 (D(2)O) and TIP4PQ/2005 (T(2)O) models are able to study the isotopic substitution of hydrogen for deuterium or tritium whilst constraining the geometry, while the TIP4PQ_D2O and TIP4PQ_T2O models, where the O-H bond lengths are progressively shortened, permit the study of the influence of geometry (and thus dipole moment) on the isotopic effects. For TIP4PQ_D2O-TIP4PQ/2005 we found a melting point shift of 4.9 K (experimentally the value is 3.68 K) and a TMD shift of 6 K (experimentally 7.2 K). For TIP4PQ_T2O-TIP4PQ/2005 we found a melting point shift of 5.2 K (experimentally the value is 4.49 K) and a TMD shift of 7 K (experimentally 9.4 K). PMID:23042133

McBride, Carl; Aragones, Juan L; Noya, Eva G; Vega, Carlos

2012-11-21

131

NASA Astrophysics Data System (ADS)

The Tsubasa satellite developed by the Japan Aerospace Exploration Agency was launched in Feb 2002 into Geo-stationary Transfer Orbit GTO Perigee 500km Apogee 36000km and had been operated well until Sep 2003 The objective of this satellite was to verify the function of commercial parts and new technologies of bus-system components in space Thus the on-board experiments were conducted in the more severe radiation environment of GTO rather than in Geo-stationary Earth Orbit GEO or Low Earth Orbit LEO The Space Environment Data Acquisition equipment SEDA on board the Tsubasa satellite had the Single-event Upset Monitor SUM and the DOSimeter DOS to evaluate influences on electronic devices caused by radiation environment that was also measured by the particle detectors of the SEDA the Standard DOse Monitor SDOM for measurements of light particles and the Heavy Ion Telescope HIT for measurements of heavy ions The SUM monitored single-event upsets and single-event latch-ups occurred in the test sample of two 64-Mbit DRAMs The DOS measured accumulated radiation dose at fifty-six locations in the body of the Tsubasa satellite Using the data obtained by these instruments single-event and total-dose effects in GTO during solar-activity maximum period especially their rapid changes due to solar flares and CMEs in the region from L 1 1 through L 11 is discussed in this paper

Koshiishi, H.; Kimoto, Y.; Matsumoto, H.; Goka, T.

132

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

133

A tipping point in drug dosing in late-life schizophrenia.

Minimally effective doses of antipsychotics are likely influenced by several clinical and demographic characteristics of patients, with age being one of the most important elements. In light of age-related physiologic changes as well as interindividual differences in pharmacokinetic and pharmacodynamic systems, individualized dosing with regard to age will be critically important for safer drug treatment for older patients with schizophrenia. In the present review, we propose the following cautious psychopharmacologic interventions for this population: 1) simple regimen (avoid polypharmacy), 2) be aware of the presence of patients who are very sensitive to drugs, 3) gradual dose titration, and 4) timely and thorough assessments of therapeutic and side effects. The age-related antipsychotic sensitivity highlights the importance of finding the lowest possible effective dose of antipsychotic drugs as patients with schizophrenia age to maximize therapeutic effects and minimize side effects. PMID:21327902

Tsuboi, Takashi; Suzuki, Takefumi; Uchida, Hiroyuki

2011-06-01

134

Purpose The goal of this study was to develop a novel multi-point plastic scintillation detector (mPSD) capable of measuring the dose accurately at multiple positions simultaneously using a single optical transmission line. Methods A 2-point mPSD used a band-pass approach that included splitters, color filters, and an EMCCD camera. The 3-point mPSD was based on a new full-spectrum approach, in which a spectrograph was coupled to a CCD camera. Irradiations of the mPSDs and of an ion chamber were performed with a 6-MV photon beam at various depths and lateral positions in a water tank. Results For the 2-point mPSD, the average relative differences between mPSD and ion chamber measurements for the depth-dose were 2.4±1.6% and 1.3±0.8% for BCF-60 and BCF-12, respectively. For the 3-point mPSD, the average relative differences over all conditions were 2.3±1.1%, 1.6±0.4%, and 0.32±0.19% for BCF-60, BCF-12, and BCF-10, respectively. Conclusions This study demonstrates the practical feasibility of mPSDs. This type of detector could be very useful for pre-treatment quality assurance applications as well as an accurate tool for real-time in vivo dosimetry.

Therriault-Proulx, Francois; Archambault, Louis; Beaulieu, Luc; Beddar, Sam

2013-01-01

135

NASA Astrophysics Data System (ADS)

Based on the past studies regarding the insolation fluctuation, the smoothing effect of insolation among different locations would not be enough for the longer cycle than a few ten minutes. This study evaluated the maximum fluctuation width (MFW) within at most 120 min of ensemble average insolation of 40 points, its clearness index, and ensemble average insolation excluding sun-position dependent component. As the results, when the weather condition became worse after the noon in almost all area, the ensemble average insolation significantly reduced, resulting in MFW of 540W/m2 within 120 min. As other example, when the weather recovered during the morning in many areas, MFW was also large. By using the data observed for 6 months, this study calculated the cumulative frequency distribution of MFW of ensemble average insolation, its clearness index, and ensemble average insolation excluding sun-position dependent component. As the results, the absolute value of MFW of ensemble average insolation calculated with 120 min width window ranges mainly between 200-300W/m2. The absolute value of MWF of insolation excluding sun-position dependent component evaluated with 120 min width window is smaller than 200W/m2 in most days, and is not so different from MWF evaluated with 60 min width window. Finally, this study discussed the practical usability of insolation forecast.

Kumazawa, Shinsuke; Kato, Takeyoshi; Honda, Nobuyuki; Koaizawa, Masakazu; Nishino, Shinichi; Suzuoki, Yasuo

136

Regulatory and homeland security agencies undertake safety and risk assessments to assess the potential hazards of radiation, chemical, biological, and pharmaceutical agents. By law, these assessments must be science-based to ensure public safety and environmental quality. These agencies use dose-response modeling and benchmark dose methods to identify points of departure across single end points elicited by the agent. Regulatory agencies

Lyle D. Burgoon; Timothy R. Zacharewski

2008-01-01

137

Generating Arbitrary Chemical Patterns for Multi-Point Dosing of Single Cells

Living cells reside within anisotropic microenvironments that orchestrate a broad range of polarized responses through physical and chemical cues. To unravel how localized chemical signals influence complex behaviors, tools must be developed for establishing patterns of chemical gradients that vary over subcellular dimensions. Here, we present a strategy for addressing this critical need in which an arbitrary number of chemically distinct, subcellular dosing streams are created in real time within a microfluidic environment. In this approach, cells are cultured on a thin polymer membrane that serves as a barrier between the cell-culture environment and a reagent chamber containing multiple reagent species flowing in parallel under low Reynolds number conditions. Focal ablation of the membrane creates pores that allow solution to flow from desired regions within this reagent pattern into the cell-culture chamber, resulting in narrow, chemically distinct dosing streams. Unlike previous dosing strategies, this system provides the capacity to tailor arbitrary patterns of reagents on-the-fly to suit the geometry and orientation of specific cells.

Hoppe, Todd J.; Moorjani, Samira G.; Shear, Jason B.

2013-01-01

138

In this article, the effectiveness of a multi-targeted chemo-switch (C-S) schedule that combines metronomic chemotherapy (MET) after treatment with the maximum tolerated dose (MTD) is reported. This schedule was tested with gemcitabine in two distinct human pancreatic adenocarcinoma orthotopic models and with cyclophosphamide in an orthotopic ovarian cancer model. In both models, the C-S schedule had the most favourable effect, achieving at least 80% tumour growth inhibition without increased toxicity. Moreover, in the pancreatic cancer model, although peritoneal metastases were observed in control and MTD groups, no dissemination was observed in the MET and C-S groups. C-S treatment caused a decrease in angiogenesis, and its effect on tumour growth was similar to that produced by the MTD followed by anti-angiogenic DC101 treatment. C-S treatment combined an increase in thrombospondin-1 expression with a decrease in the number of CD133+ cancer cells and triple-positive CD133+/CD44+/CD24+ cancer stem cells (CSCs). These findings confirm that the C-S schedule is a challenging clinical strategy with demonstrable inhibitory effects on tumour dissemination, angiogenesis and CSCs. PMID:23649709

Vives, Marta; Ginestà, Mireia M; Gracova, Kristina; Graupera, Mariona; Casanovas, Oriol; Capellà, Gabriel; Serrano, Teresa; Laquente, Berta; Viñals, Francesc

2013-11-15

139

The objective of this work was to investigate and quantify the effect of sharp edges of the phantom on the point dose measurement during patient-specific dosimetry with Rapid Arc (RA). Ten patients with carcinoma of prostate were randomly selected for this dosimetric study. Rapid Arc plans were generated with 6 MV X-rays in the Eclipse (v 8.6.14) with single arc (clockwise). Dosimetry verification plans were generated for two phantoms (cylindrical and rectangular). The cylindrical phantom was solid water (diameter 34 cm) and the rectangular phantom was a water phantom (25 cm × 25 cm × 10 cm). These phantoms were pre-scanned in computed tomography (CT) machine with cylindrical ionization chamber (FC65) in place. The plans were delivered with Novalis Tx linear accelerator with 6 MV X-rays for both the phantoms separately. The measured dose was compared with the planned dose for both the phantoms. Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively. No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The sharp edges of the phantom do not perturb the patient specific Rapid Arc dosimetry significantly.

Kinhikar, R. A.; Pandey, V. P.; Jose, Rojas K.; Mahantshetty, U.; Dhote, D. S.; Deshpande, D. D.; Shrivastava, S. K.

2013-01-01

140

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

141

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

142

The author calculated the daily dose of Benzalkonium Chloride (BAC) in eye drops used in glaucoma treatment from the patients point of view, which means the real amount of BAC applied in the conjunctival sac. The information about BAC concentration in 1 milliliter (mL) do not offer sufficient picture about real circumstances, because the size of the drop, especially after the introducing of the use of generic products in clinical practice in specific anti-glaucomatic drugs, differs significantly. The daily dose of BAC may have substantial significance in the patients treatment tolerance. The overview of BAC daily dose in single therapeutic groups and drugs follows: betablockers: Timo-COMOD 0, Arutimol 2.6, Vistagan 2.8, Timolol-POS 3.0, Arteoptic 3.7, Betoptic S 4.8, Timoptol MSD 6.3, Betoptic 10.0; alpha-mimetics: Alphagan 3.5, Luxfen 3.5, Aruclonin 7.1; derivates of prostaglandine, prostamides: Taflotan 0, Monopost 0, Lumigan 1.4, Unilat 3.1, Travatan 3.9, Latanoprost Apotex 4.3, Rescula 5.8, Latanoprost POS 5.9, Xalatan 6.0, Latanoprost Ratiopharm 6.0, Latanoprost Actavis 6.0, Latanoprost Arrow 6.0, Arulatan 5.4, Latalux 6.0, Glaucotens 6.0, Xaloptic 6.0, Solusin 6.1; carboanhydrase inhibitors: Batidor 3.8, Azopt 4.8, Trusopt 5.4, Oftidor 8.1; fixed combinations: Ganfort 1.4, Dorzolamid/timolol TEVA 2.8, Combigan 3.2, Duotrav 4.3, Cosopt 5.6, Xalacom 6.0, Glaucotima 6.0, Latanoprost/timolol Apotex 6.3, Azarga 6.4, Dorzogen Combi 6.5, and Dozotima 8.8 µl. Key words: glaucoma, antiglaucomatic treatment, preservatives, Benzalconium Chloride, BAC, daily dose of BAC. PMID:25032794

Výborný, P; Si?áková, S; Veselá Flórová, Z

2014-01-01

143

NASA Astrophysics Data System (ADS)

Hot particle' skin dosimetry calculations are commonly performed using homogeneous dose-point kernels (DPK) in conjunction with scaling and backscatter models to account for non-homogeneous geometries. A new scaling model for determining the actual DPK for beta-particles transmitted by a high- Z source material has been developed. The model is based on a determination of the amount of mono-energetic electron absorption that occurs in a given source thickness through the use of EGSnrc (Electron Gamma Shower) Monte Carlo simulations. Integration over a particular beta spectrum provides the betaparticle DPK following self-absorption as a function of source thickness and radial depth in water, thereby accounting for spectral hardening that may occur in higher-Z materials. Beta spectra of varying spectral shapes and endpoint energies were used to test our model for select source materials with 7.42 < Z ? 94. A new volumetric backscatter model has also been developed. This model corrects for beta-particle backscattering that occurs both in the source medium and in the atmosphere surrounding the source. Hot particle backscatter factors are constructed iteratively through selective integration of point-source backscatter factors over a given source geometry. Selection criteria are based on individual source-point positions within the source and determine which, if any, backscatter factors are used. The new scaling model and backscatter model were implemented into the DPK-based code VARSKIN 4 for extensive dose testing and verification. Verification results were compared to equivalent Monte Carlo simulations. The results demonstrate that significant improvements can be made to DPK-based models when dealing with high-Z volumetric sources in non-homogeneous geometries.

Mangini, Colby D.

144

This research paper aims to employ a new permanent magnet reluctance generator in a variable speed wind energy conversion system (WECS) of a grid-tied distributed generation application. The grid integration of WECS is achieved through cascaded dc-dc converters ensuring maximum power extraction from the wind energy while maintaining a constant output voltage at the grid side. The surplus power is

Kazmi Syed Muhammad Raza; Hiroki Goto; Hai-Jiao Guo; Osamu Ichinokura

2007-01-01

145

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

146

OBJECTIVE The purpose of this article is to estimate the absorbed radiation dose in radiosensitive organs during coronary MDCT angiography using 320-MDCT and to determine the effects of tube voltage variation and heart rate (HR) control on absorbed radiation dose. MATERIALS AND METHODS Semiconductor field effect transistor detectors were used to measure absorbed radiation doses for the thyroid, midbreast, breast, and midlung in an anthropomorphic phantom at 100, 120, and 135 kVp at two different HRs of 60 and 75 beats per minute (bpm) with a scan field of view of 320 mm, 400 mA, 320 × 0.5 mm detectors, and 160 mm collimator width (160 mm range). The paired Student’s t test was used for data evaluation. RESULTS At 60 bpm, absorbed radiation doses for 100, 120, and 135 kVp were 13.41 ± 3.59, 21.7 ± 4.12, and 29.28 ± 5.17 mGy, respectively, for midbreast; 11.76 ± 0.58, 18.86 ± 1.06, and 24.82 ± 1.45 mGy, respectively, for breast; 12.19 ± 2.59, 19.09 ± 3.12, and 26.48 ± 5.0 mGy, respectively, for lung; and 0.37 ± 0.14, 0.69 ± 0.14, and 0.92 ± 0.2 mGy, respectively, for thyroid. Corresponding absorbed radiation doses for 75 bpm were 38.34 ± 2.02, 59.72 ± 3.13, and 77.8 ± 3.67 mGy for midbreast; 26.2 ± 1.74, 44 ± 1.11, and 52.84 ± 4.07 mGy for breast; 38.02 ± 1.58, 58.89 ± 1.68, and 78 ± 2.93 mGy for lung; and 0.79 ± 0.233, 1.04 ± 0.18, and 2.24 ± 0.52 mGy for thyroid. Absorbed radiation dose changes were significant for all organs for both tube voltage reductions as well as for HR control from 75 to 60 bpm at all tube voltage settings (p < 0.05). The absorbed radiation doses for the calcium score protocol were 11.2 ± 1.4 mGy for midbreast, 9.12 ± 0.48 mGy for breast, 10.36 ± 1.3 mGy for lung, and 0.4 ± 0.05 mGy for thyroid. CONCLUSION CT angiography with 320-MDCT scanners results in absorbed radiation doses in radiosensitive organs that compare favorably to those previously reported. Significant dose reductions can be achieved by tube voltage reductions and HR control.

Nikolic, Boris; Khosa, Faisal; Lin, Pei-Jan Paul; Khan, Atif N.; Sarwar, Sheryar; Yam, Chun-Shan; Court, Laurence E.; Raptopoulos, Vassilios; Clouse, Melvin E.

2012-01-01

147

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 into the trial, 37 of whom were eligible for evaluation. Cisplatin (35 mg/M2/day for 3 days) and etoposide (200 mg/M2/day for 3 days) were administered every 28 days for a planned 6 cycles of therapy. Sixteen of 37 evaluable patients (43%) responded to therapy. Myelosuppression was the dominant toxicity, with 89% of the patients experiencing grade 4 neutropenia, and nearly half grade 3 or 4 thrombocytopenia. Median survival was 8.5 months, with 30% of the patients alive at 1 year and 10% alive at 2 years. Malaise, fatigue, and peripheral neuropathy were the other major toxicities. The combination of etoposide at the dose of 200 mg/M2/day for 3 days and cisplatin at 35 mg/M2/day for 3 days is a highly potent combination against metastatic non-small cell carcinoma. PMID:8719068

Muscato, J J; Cirrincione, C; Clamon, G; Perry, M C; Omura, G; Berkowitz, I; Reid, T; Herndon, J E; Green, M R

1995-12-01

148

National Technical Information Service (NTIS)

A relatively simple proof of the maximum principle is presented. The main objective was to obtain a proof, similar to that due to Halkin, but replacing the use of Brouwer's fixed point theorem by an easily proven contraction mapping theorem. The first use...

G. F. Bryant D. Q. Mayne

1973-01-01

149

We will present single event effects and dose rate test results for the Honeywell Radiation Hardened 32-Bit Processor Central Processing Unit, Floating Point Processor and Cache Memory. These three chip types comprise the processor core for a 32-bit radiation-hardened, fault-tolerant processor

Gary R. Brown; Lee F. Hoffmann; Scott C. Leavy; Jeffrey A. Mogensen; Julie Brichacek

1997-01-01

150

Acute cytotoxic exposure causes decreases in bone marrow progenitors that precedes the neutrophil nadir. Experiments in animal models reveal a relationship between the reduction in granulocyte-macrophage progenitors (CFU-GM) and the decrease in absolute neutrophil count [Toxicol. Pathol. 21 (1993) 241]. Recently, the prevalidation of a model for predicting acute neutropenia by the CFU-GM assay has been reported [Toxicol. In Vitro 15 (2001) 729]. The model was based on prediction of human MTD by adjusting the animal-derived MTD for the differential sensitivity between CFU-GM from animal species and humans. In this study, this model has been applied on a new antitumoral drug, Yondelis (Ecteinascidin; ET-743). Preclinical studies showed that hematotoxicity was the main side effect in mice, being the MTD of 600 microg/m2 [Drugs Future 21 (1996) 1155]. The sensitivity of myeloid progenitors was higher in mice than in humans, with IC90 values of 0.69+/-0.22 nM and 1.31+/-0.21 nM for murine and human CFU-GMs respectively. This study predicts a human MTD of 1145 microg/m2. The reported human MTD of ET-743 given as a 24-h continuous infusion every 3 weeks is 1800 microg/m2 [J. Clin. Oncol. 19 (2001) 1256]. Since our predicted MTD is within fourfold of the actual MTD (the interspecies variation in tolerated dose due to differences in clearance rates, metabolism pathways and infusion rate) the result confirms the profit of the prediction model. PMID:14599461

Gómez, Susana G; Bueren, Juan A; Faircloth, Glynn; Albella, Beatriz

2003-01-01

151

Modeling the radio-induced effects in biological medium still requires accurate physics models to describe the interactions induced by all the charged particles present in the irradiated medium in detail. These interactions include inelastic as well as elastic processes. To check the accuracy of the very low energy models recently implemented into the GEANT4 toolkit for modeling the electron slowing-down in liquid water, the simulation of electron dose point kernels remains the preferential test. In this context, we here report normalized radial dose profiles, for mono-energetic point sources, computed in liquid water by using the very low energy "GEANT4-DNA" physics processes available in the GEANT4 toolkit. In the present study, we report an extensive intra-comparison of profiles obtained by a large selection of existing and well-documented Monte-Carlo codes, namely, EGSnrc, PENELOPE, CPA100, FLUKA and MCNPX. PMID:23478094

Champion, C; Incerti, S; Perrot, Y; Delorme, R; Bordage, M C; Bardiès, M; Mascialino, B; Tran, H N; Ivanchenko, V; Bernal, M; Francis, Z; Groetz, J-E; Fromm, M; Campos, L

2014-01-01

152

Deconvolution of planar scintigrams by maximum entropy.

Planar scintigrams are deconvolved with a point spread function using the maximum entropy method with the aim of improving image quality. The technique requires the specification of several parameters. These are related to the level of noise present in the data and our a priori knowledge of the object imaged. The performance of the technique is tested for a wide range of these parameters using images of a Williams phantom in scattering material and a figure of merit, derived from the detectability of the smallest cold spot, is calculated. For close to optimal values of the parameters a factor of two improvement in the figure is found. A processed bone image shows improved contrast and resolution. Maximum entropy processing could be used to increase image quality or allow comparable image quality with reduced imaging time or patient dose. PMID:7708837

Simpson, D E; Fleming, J S; Aldous, A J; Daniell, G J

1995-01-01

153

Purpose: GATE is a Monte Carlo simulation toolkit based on the Geant4 package, widely used for many medical physics applications, including SPECT and PET image simulation and more recently CT image simulation and patient dosimetry. The purpose of the current study was to calculate dose point kernels (DPKs) using GATE, compare them against reference data, and finally produce a complete dataset of the total DPKs for the most commonly used radionuclides in nuclear medicine. Methods: Patient-specific absorbed dose calculations can be carried out using Monte Carlo simulations. The latest version of GATE extends its applications to Radiotherapy and Dosimetry. Comparison of the proposed method for the generation of DPKs was performed for (a) monoenergetic electron sources, with energies ranging from 10 keV to 10 MeV, (b) beta emitting isotopes, e.g., {sup 177}Lu, {sup 90}Y, and {sup 32}P, and (c) gamma emitting isotopes, e.g., {sup 111}In, {sup 131}I, {sup 125}I, and {sup 99m}Tc. Point isotropic sources were simulated at the center of a sphere phantom, and the absorbed dose was stored in concentric spherical shells around the source. Evaluation was performed with already published studies for different Monte Carlo codes namely MCNP, EGS, FLUKA, ETRAN, GEPTS, and PENELOPE. A complete dataset of total DPKs was generated for water (equivalent to soft tissue), bone, and lung. This dataset takes into account all the major components of radiation interactions for the selected isotopes, including the absorbed dose from emitted electrons, photons, and all secondary particles generated from the electromagnetic interactions. Results: GATE comparison provided reliable results in all cases (monoenergetic electrons, beta emitting isotopes, and photon emitting isotopes). The observed differences between GATE and other codes are less than 10% and comparable to the discrepancies observed among other packages. The produced DPKs are in very good agreement with the already published data, which allowed us to produce a unique DPKs dataset using GATE. The dataset contains the total DPKs for {sup 67}Ga, {sup 68}Ga, {sup 90}Y, {sup 99m}Tc, {sup 111}In, {sup 123}I, {sup 124}I, {sup 125}I, {sup 131}I, {sup 153}Sm, {sup 177}Lu {sup 186}Re, and {sup 188}Re generated in water, bone, and lung. Conclusions: In this study, the authors have checked GATE's reliability for absorbed dose calculation when transporting different kind of particles, which indicates its robustness for dosimetry applications. A novel dataset of DPKs is provided, which can be applied in patient-specific dosimetry using analytical point kernel convolution algorithms.

Papadimitroulas, Panagiotis; Loudos, George; Nikiforidis, George C.; Kagadis, George C. [Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04 (Greece) and Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens (Greece); Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens (Greece); Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04 (Greece)

2012-08-15

154

A ring-shaped Fricke device was developed to measure the absolute dose on the transverse bisector of a 192Ir high dose rate (HDR) source at 1 cm from its center in water, D(r0, theta0). It consists of a polymethylmethacrylate (PMMA) rod (axial axis) with a cylindrical cavity at its center to insert the 192Ir 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(r0, theta0). Irradiations were performed with a Nucletron microselectron HDR unit loaded with an 192Ir 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 192Ir 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(r0, theta0) by 2.0%. Applying the corresponding correction factor, the D(r0, theta0) 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(r0, theta0) and audit HDR source calibrations. PMID:19175095

Austerlitz, C; Mota, H C; Sempau, J; Benhabib, S M; Campos, D; Allison, R; DeAlmeida, C E; Zhu, D; Sibata, C H

2008-12-01

155

Point kernels describe the energy deposited at a certain distance from an isotropic point source and are useful for nuclear medicine dosimetry. They can be used for absorbed-dose calculations for sources of various shapes and are also a useful tool when comparing different Monte Carlo (MC) codes. The aim of this study was to compare point kernels calculated by using the mixed MC code, PENELOPE (v. 2006), with point kernels calculated by using the condensed-history MC codes, ETRAN, GEANT4 (v. 8.2), and MCNPX (v. 2.5.0). Point kernels for electrons with initial energies of 10, 100, 500, and 1 MeV were simulated with PENELOPE. Spherical shells were placed around an isotropic point source at distances from 0 to 1.2 times the continuous-slowing-down-approximation range (R(CSDA)). Detailed (event-by-event) simulations were performed for electrons with initial energies of less than 1 MeV. For 1-MeV electrons, multiple scattering was included for energy losses less than 10 keV. Energy losses greater than 10 keV were simulated in a detailed way. The point kernels generated were used to calculate cellular S-values for monoenergetic electron sources. The point kernels obtained by using PENELOPE and ETRAN were also used to calculate cellular S-values for the high-energy beta-emitter, 90Y, the medium-energy beta-emitter, 177Lu, and the low-energy electron emitter, 103mRh. These S-values were also compared with the Medical Internal Radiation Dose (MIRD) cellular S-values. The greatest differences between the point kernels (mean difference calculated for distances, <0.9 r/R(CSDA)), using PENELOPE and those from ETRAN, GEANT4, and MCNPX, were 3.6%, 6.2%, and 14%, respectively. The greatest difference between the cellular S-values for monoenergetic electrons was 1.4%, 2.5%, and 6.9% for ETRAN, GEANT4, and MCNPX, respectively, compared to PENELOPE, if omitting the S-values when the activity was distributed on the cell surface for 10-keV electrons. The largest difference between the cellular S-values for the radionuclides, between PENELOPE and ETRAN, was seen for 177Lu (1.2%). There were large differences between the MIRD cellular S-values and those obtained from PENELOPE: up to 420% for monoenergetic electrons and <22% for the radionuclides, with the largest difference for 103mRh. In conclusion, differences were found between the point kernels generated by different MC codes, but these differences decreased when cellular S-values were calculated, and decreased even further when the energy spectra of the radionuclides were taken into consideration. PMID:19694581

Uusijärvi, Helena; Chouin, Nicolas; Bernhardt, Peter; Ferrer, Ludovic; Bardiès, Manuel; Forssell-Aronsson, Eva

2009-08-01

156

In a previous study of prevalidation, a standard operating procedure (SOP) for two independent in vitro tests (human and mouse) had been developed, to evaluate the potential hematotoxicity of xenobiotics from their direct and the adverse effects on granulocyte-macrophages (CFU-GM). A predictive model to calculate the human maximum tolerated dose (MTD) was set up, by adjusting a mouse-derived MTD for the differential interspecies sensitivity. In this paper, we describe an international blind trial designed to apply this model to the clinical neutropenia, by testing 20 drugs, including 14 antineoplastics (Cytosar-U, 5-Fluorouracil, Myleran, Thioguanine, Fludarabine, Bleomycin, Methotrexate, Gemcitabine, Carmustine, Etoposide, Teniposide, Cytoxan, Taxol, Adriamycin); two antivirals (Retrovir, Zovirax,); three drugs for other therapeutic indications (Cyclosporin, Thorazine, Indocin); and one pesticide (Lindane). The results confirmed that the SOP developed generates reproducible IC90 values with both human and murine GM-CFU. For 10 drugs (Adriamycin, Bleomycin, Etoposide, Fludarabine, 5-Fluorouracil, Myleran, Taxol, Teniposide, Thioguanine, and Thorazine), IC90 values were found within the range of the actual drug doses tested (defined as the actual IC90). For the other 10 drugs (Carmustine, Cyclosporin, Cytosar-U, Cytoxan, Gemcitabine, Indocin, Lindane, Methotrexate, Retrovir, and Zovirax) extrapolation on the regression curve out of the range of the actual doses tested was required to derive IC90 values (extrapolated IC90). The model correctly predicted the human MTD for 10 drugs out of 10 that had "actual IC90 values" and 7 drugs out of 10 for those having only an extrapolated IC90. Two of the incorrect predictions (Gemcitabine and Zovirax) were within 6-fold of the correct MTD, instead of the 4-fold range required by the model, whereas the prediction with Cytosar-U was approximately 10-fold in error. A possible explanation for the failure in the prediction of these three drugs, which are pyrimidine analogs, is discussed. We concluded that our model correctly predicted the human MTD for 20 drugs out of 23, since the other three drugs (Topotecan, PZA, and Flavopiridol) were tested in the prevalidation study. The high percentage of predicitivity (87%), as well as the reproducibility of the SOP testing, confirm that the model can be considered scientifically validated in this study, suggesting promising applications to other areas of research in developing validated hematotoxicological in vitro methods. PMID:12883091

Pessina, A; Albella, B; Bayo, M; Bueren, J; Brantom, P; Casati, S; Croera, C; Gagliardi, G; Foti, P; Parchment, R; Parent-Massin, D; Schoeters, G; Sibiril, Y; Van Den Heuvel, R; Gribaldo, L

2003-10-01

157

Polo-like kinases (Plks) play an important role in cell cycle checkpoint controls and are over-expressed in acute myeloid leukaemia (AML). BI 2536, a novel Plk inhibitor, induces mitotic arrest and apoptosis. In this phase I/II trial of BI 2536 in 68 elderly patients with relapsed/refractory AML, three schedules were investigated (day 1, days 1-3, and days 1 + 8). Maximum tolerated dose was 350 and 200 mg in the day 1 and days 1 + 8 schedules, respectively. The day 1-3 schedule appeared equivalent to the day 1 schedule and was discontinued early. BI 2536 exhibited multi-compartmental pharmacokinetic behaviour. The majority of patients showed an increase of bone marrow cells in G2/M with a characteristic pattern of mitotic catastrophe. The overall response rate in the day 1 and day 1 + 8 schedules was 9% (5/54) with 2 complete and 3 partial responses. The majority of drug-related adverse events grade ?3 were haematological. Taken together, Plk inhibition induced cell cycle arrest in AML blasts in vivo and BI 2536 monotherapy showed modest clinical activity in this poor prognosis patient group. PMID:24033250

Müller-Tidow, Carsten; Bug, Gesine; Lübbert, Michael; Krämer, Alwin; Krauter, Jürgen; Valent, Peter; Nachbaur, David; Berdel, Wolfgang E; Ottmann, Oliver G; Fritsch, Holger; Munzert, Gerd; Garin-Chesa, Pilar; Fleischer, Frank; Taube, Tillmann; Döhner, Hartmut

2013-10-01

158

The purpose of this study was to analyze the dosimetric outcome of 3D image-guided high-dose-rate (HDR) brachytherapy planning for cervical cancer treatment and compare dose coverage of high-risk clinical target volume (HRCTV) to traditional Point A dose. Thirty-two patients with stage IA2-IIIB cervical cancer were treated using computed tomography/magnetic resonance imaging-based image-guided HDR brachytherapy (IGBT). Brachytherapy dose prescription was 5.0-6.0 Gy per fraction for a total 5 fractions. The HRCTV and organs at risk (OARs) were delineated following the GYN GEC/ESTRO guidelines. Total doses for HRCTV, OARs, Point A, and Point T from external beam radiotherapy and brachytherapy were summated and normalized to a biologically equivalent dose of 2 Gy per fraction (EQD2). The total planned D90 for HRCTV was 80-85 Gy, whereas the dose to 2 mL of bladder, rectum, and sigmoid was limited to 85 Gy, 75 Gy, and 75 Gy, respectively. The mean D90 and its standard deviation for HRCTV was 83.2 {+-} 4.3 Gy. This is significantly higher (p < 0.0001) than the mean value of the dose to Point A (78.6 {+-} 4.4 Gy). The dose levels of the OARs were within acceptable limits for most patients. The mean dose to 2 mL of bladder was 78.0 {+-} 6.2 Gy, whereas the mean dose to rectum and sigmoid were 57.2 {+-} 4.4 Gy and 66.9 {+-} 6.1 Gy, respectively. Image-based 3D brachytherapy provides adequate dose coverage to HRCTV, with acceptable dose to OARs in most patients. Dose to Point A was found to be significantly lower than the D90 for HRCTV calculated using the image-based technique. Paradigm shift from 2D point dose dosimetry to IGBT in HDR cervical cancer treatment needs advanced concept of evaluation in dosimetry with clinical outcome data about whether this approach improves local control and/or decreases toxicities.

Kim, Hayeon [Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA (United States); Beriwal, Sushil, E-mail: beriwals@upmc.ed [Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA (United States); Houser, Chris; Huq, M. Saiful [Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA (United States)

2011-07-01

159

The purpose of this study was to analyze the dosimetric outcome of 3D image-guided high-dose-rate (HDR) brachytherapy planning for cervical cancer treatment and compare dose coverage of high-risk clinical target volume (HRCTV) to traditional Point A dose. Thirty-two patients with stage IA2-IIIB cervical cancer were treated using computed tomography/magnetic resonance imaging-based image-guided HDR brachytherapy (IGBT). Brachytherapy dose prescription was 5.0-6.0 Gy per fraction for a total 5 fractions. The HRCTV and organs at risk (OARs) were delineated following the GYN GEC/ESTRO guidelines. Total doses for HRCTV, OARs, Point A, and Point T from external beam radiotherapy and brachytherapy were summated and normalized to a biologically equivalent dose of 2 Gy per fraction (EQD2). The total planned D90 for HRCTV was 80-85 Gy, whereas the dose to 2 mL of bladder, rectum, and sigmoid was limited to 85 Gy, 75 Gy, and 75 Gy, respectively. The mean D90 and its standard deviation for HRCTV was 83.2 ± 4.3 Gy. This is significantly higher (p < 0.0001) than the mean value of the dose to Point A (78.6 ± 4.4 Gy). The dose levels of the OARs were within acceptable limits for most patients. The mean dose to 2 mL of bladder was 78.0 ± 6.2 Gy, whereas the mean dose to rectum and sigmoid were 57.2 ± 4.4 Gy and 66.9 ± 6.1 Gy, respectively. Image-based 3D brachytherapy provides adequate dose coverage to HRCTV, with acceptable dose to OARs in most patients. Dose to Point A was found to be significantly lower than the D90 for HRCTV calculated using the image-based technique. Paradigm shift from 2D point dose dosimetry to IGBT in HDR cervical cancer treatment needs advanced concept of evaluation in dosimetry with clinical outcome data about whether this approach improves local control and/or decreases toxicities. PMID:20488690

Kim, Hayeon; Beriwal, Sushil; Houser, Chris; Huq, M Saiful

2011-01-01

160

Maximum a Posteriori Filtering and Smoothing Algorithms.

National Technical Information Service (NTIS)

The paper presents the approximate solution of the non-linear two-point boundary value problem for maximum a posteriori estimation. Filtering, fixed point smoothing, fixed interval smoothing, and fixed lag smoothing algorithms are obtained by the discrete...

A. P. Sage

1969-01-01

161

NASA Astrophysics Data System (ADS)

Monte Carlo calculations using the codes PENELOPE and GEANT4 have been performed to characterize the dosimetric properties of monoenergetic photon point sources in water. The dose rate in water has been calculated for energies of interest in brachytherapy, ranging between 10 keV and 2 MeV. A comparison of the results obtained using the two codes with the available data calculated with other Monte Carlo codes is carried out. A ?2-like statistical test is proposed for these comparisons. PENELOPE and GEANT4 show a reasonable agreement for all energies analyzed and distances to the source larger than 1 cm. Significant differences are found at distances from the source up to 1 cm. A similar situation occurs between PENELOPE and EGS4.

Almansa, Julio F.; Guerrero, Rafael; Al-Dweri, Feras M. O.; Anguiano, Marta; Lallena, Antonio M.

2007-05-01

162

Did you mean: "Comparison of fixed-dose combinations of telmisartan/hydrochlorothiazide 40/12.5 mg and 80/12.5 mg and a fixed-dose combination of Leisuretowne/hydrochlorothiazide 50/12.5 mg in mild to moderate essential hypertension: pooled analysis of two multicenter prospective randomized open-label blinded-end point (PROBE) trials." ?

163

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

164

Purpose: To perform an intracavitary radiotherapy (ICR) plan comparison between the conventional point A plan (conventional plan) and computed tomography (CT)-guided clinical target volume-based plan (CTV plan) by analysis of the quantitative dose-volume parameters and irradiated volumes of organs at risk in patients with cervical cancer. Methods and Materials: Thirty plans for {sup 192}Ir high-dose-rate ICR after 30-40-Gy external beam radiotherapy were investigated. CT images were acquired at the first ICR session with artifact-free applicators in place. The gross tumor volume, clinical target volume (CTV), point A, and International Commission on Radiation Units and Measurements Report 38 rectal and bladder points were defined on reconstructed CT images. A fractional 100% dose was prescribed to point A in the conventional plan and to the outermost point to cover all CTVs in the CTV plan. The reference volume receiving 100% of the prescribed dose (V{sub ref}), and the dose-volume parameters of the coverage index, conformal index, and external volume index were calculated from the dose-volume histogram. The bladder, rectal point doses, and percentage of volumes receiving 50%, 80%, and 100% of the prescribed dose were also analyzed. Results: Conventional plans were performed, and patients were categorized on the basis of whether the 100% isodose line of point A prescription dose fully encompassed the CTV (Group 1, n = 20) or not (Group 2, n = 10). The mean gross tumor volume (11.6 cm{sup 3}) and CTV (24.9 cm{sup 3}) of Group 1 were smaller than the corresponding values (23.7 and 44.7 cm{sup 3}, respectively) for Group 2 (p = 0.003). The mean V{sub ref} for all patients was 129.6 cm{sup 3} for the conventional plan and 97.0 cm{sup 3} for the CTV plan (p = 0.003). The mean V{sub ref} in Group 1 decreased markedly with the CTV plan (p < 0.001). For the conventional and CTV plans in all patients, the mean coverage index, conformal index, and external volume index were 0.98 and 1.0, 0.23 and 0.34, and 3.86 and 2.15, respectively. Statistical analysis showed that the conformal index and external volume index improved significantly with the CTV plan, and this improvement was more marked in Group 1. The mean values of the bladder and rectal point doses and volume fractions receiving 50%, 80%, and 100% of the reference dose did not differ between plans for all patients. The reduction in the mean rectal and bladder point doses and irradiated volumes for the CTV plan was statistically significant in Group 1. Conclusion: Computed tomography-guided CTV planning of ICR is superior to conventional point A planning in terms of conformity of target coverage and avoidance of overdosed normal tissue volume. To ascertain the potential benefit of treatment outcome, ICR with image-guided three-dimensional plans will be pursued and correlated with the dose-volume parameters.

Shin, Kyung Hwan [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Kim, Tae Hyun [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of)]. E-mail: k2onco@ncc.re.kr; Cho, Jung Keun [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Kim, Joo-Young [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Park, Sung Yong [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Park, Sang-Yoon [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Kim, Dae Yong [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Chie, Eui Kyu [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Pyo, Hong Ryull [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of); Cho, Kwan Ho [Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi (Korea, Republic of)

2006-01-01

165

This paper presents maximum score type estimators for linear, binomial, tobit and truncated regression models. These estimators estimate the normalized vector of slopes and do not provide the estimator of intercept, although it may appear in the model. Strong consistency is proved. In addition, in the case of truncated and tobit regression models, maximum score estimators allow restriction of the

Marcin Owczarczuk

2009-01-01

166

Maximum thrust mode evaluation

NASA Technical Reports Server (NTRS)

Measured reductions in acceleration times which resulted from the application of the F-15 performance seeking control (PSC) maximum thrust mode during the dual-engine test phase is presented as a function of power setting and flight condition. Data were collected at altitudes of 30,000 and 45,000 feet at military and maximum afterburning power settings. The time savings for the supersonic acceleration is less than at subsonic Mach numbers because of the increased modeling and control complexity. In addition, the propulsion system was designed to be optimized at the mid supersonic Mach number range. Recall that even though the engine is at maximum afterburner, PSC does not trim the afterburner for the maximum thrust mode. Subsonically at military power, time to accelerate from Mach 0.6 to 0.95 was cut by between 6 and 8 percent with a single engine application of PSC, and over 14 percent when both engines were optimized. At maximum afterburner, the level of thrust increases were similar in magnitude to the military power results, but because of higher thrust levels at maximum afterburner and higher aircraft drag at supersonic Mach numbers the percentage thrust increase and time to accelerate was less than for the supersonic accelerations. Savings in time to accelerate supersonically at maximum afterburner ranged from 4 to 7 percent. In general, the maximum thrust mode has performed well, demonstrating significant thrust increases at military and maximum afterburner power. Increases of up to 15 percent at typical combat-type flight conditions were identified. Thrust increases of this magnitude could be useful in a combat situation.

Orme, John S.; Nobbs, Steven G.

1995-01-01

167

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...

168

Maximum likelihood estimation in statistics leads to the problem of\\u000amaximizing a product of powers of polynomials. We study the algebraic degree of\\u000athe critical equations of this optimization problem. This degree is related to\\u000athe number of bounded regions in the corresponding arrangement of\\u000ahypersurfaces, and to the Euler characteristic of the complexified complement.\\u000aUnder suitable hypotheses, the maximum

Serkan Hosten; Amit Khetan; Bernd Sturmfels

2006-01-01

169

This paper presents the concept, principles, and analysis of maximum ratio transmission for wireless communications, where multiple antennas are used for both transmission and reception. The principles and analysis are applicable to general cases, including maximum-ratio combining. Simulation results agree with the analysis. The analysis shows that the average overall signal-to-mise ratio (SNR) is proportional to the cross correlation between

Titus K. Y. Lo

1999-01-01

170

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. ...

171

Purpose: To evaluate the feasibility of dose escalation in a multi-institutional study in prostate cancer patients.Methods and Materials: Between October 1995 and October 1998, 164 patients with localized adenocarcinoma of the prostate were treated with 3-dimensional conformal radiotherapy at one of five French institutions. The dose of radiation was escalated from 66 to 80 Gy (ICRU point). The maximum dose

Pierre Bey; Christian Carrie; Véronique Beckendorf; Chantal Ginestet; Pierre Aletti; Georges Madelis; Elisabeth Luporsi; Pascal Pommier; Didier Cowen; Laurence Gonzague-Casabianca; Michèle Simonian-Sauve; Philippe Maingon; Suzanne Naudy; Jean-Léon Lagrange; Serge Marcie

2000-01-01

172

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

173

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

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

174

Background Therapy with intravenous unfractionated heparin improves clinical outcome in patients with active thromboembolic disease, but achieving and maintaining a therapeutic level of anticoagulation remains a major challenge for clinicians. Methods A total of 113 patients requiring heparin for at least 48 hours were randomly assigned at 7 medical centers to either weight-adjusted or non-weight-adjusted dose titration. They were separately

Richard C. Becker; Steven P. Ball; Paul Eisenberg; Steven Borzak; A. Christian Held; Frederick Spencer; Stephen J. Voyce; Robert Jesse; Robert Hendel; Yunsheng Ma; Thomas Hurley; James Hebert

1999-01-01

175

Maximum oxygen uptake utilising different treadmill protocols.

The study compared five treadmill protocols (four utilising a motorised, and one a non-motorised, treadmill) on maximum oxygen uptake. The five male and five female subjects, all actively engaged in training, were assigned the tests in random order. Statistical analysis revealed no significant differences between the five protocols for maximal oxygen uptake, maximum ventilation, maximum heart rate and blood lactate inflection point, relative to maximal oxygen uptake. Significant differences were observed between the 3' protocol with incline increments of 1.5% and all other protocols on time to exhaustion (p = less than 0.01) and maximum blood lactate levels (HLA, p = less than 0.05). The results indicate that the protocols used in this study did not significantly influence the maximum oxygen uptake attained. Images p74-a p74-b p74-c

Davies, B.; Daggett, A.; Jakeman, P.; Mulhall, J.

1984-01-01

176

Introduction to maximum entropy

The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. We review the need for such methods in data analysis and show, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. We conclude with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab.

Sivia, D.S.

1988-01-01

177

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

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

178

Maximum Entropy Estimation for Survey sampling

Calibration methods have been widely studied in survey sampling over the last decades. Viewing calibration as an inverse problem, we extend the calibration technique by using a maximum entropy method. Finding the optimal weights is achieved by considering random weights and looking for a discrete distribution which maximizes an entropy under the calibration constraint. This method points a new frame

Fabrice Gamboa; Jean-Michel Loubes; Paul Rochet

2009-01-01

179

The purpose of this study is a retrospective estimation of the influence of dose and dose rate of the red bone marrow chronic radiation exposure in combination with various modifying factors (gender, age, comorbidity) on the frequency of deviations from normal values of the results of peripheral blood investigation in humans exposed on the Techa River. The results of investigation show that humans chronically exposed to radiation can develop marked changes in the cellular composition of peripheral blood characterized by a tendency to cytopenia (signs of the decompensation of hemopoiesis). The tendency to cytopenia can be identified earlier in the lymphoid germ, and later in platelet and erythroid lines. A high lability of granulocytes under the influence of various, often infectious, factors is the cause of the lack of statistically significant differences in terms of frequency of neutropenia. Several non-radiation factors (gender, age, health status) in combination with radiation exposure could have a modifying influence on hematopoiesis, which contributed to the disruption of adaptation processes and the development of conditions characterized by a tendency to cytopenias in exposed individuals. The red bone marrow dose rate reduction resulted in a gradual decrease in the frequency of erythrocytopenia, thrombocytopenia, neutropenia and lymphocytopenia in the group of exposed population. Increased frequencies of erythrocytosis, thrombocytosis, lymphocytosis, monocytosis and neutrophilia were observed when the median dose rate was reduced to the level of 0.024 Gy/year (in the year 1956), which could be regarded as activation of regenerative processes in hematopoiesis. PMID:22690575

Akleev, A V; Dimov, G P; Varfolomeeva, T A

2012-01-01

180

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

181

Estimating Maximum Discharge of Geothermal Wells

We cannot tell how 'good' a well is unless we can estimate the maximum flow possible under such ideal conditions as complete permeability a t the production horizon and boiling point throughout the depth of the reservoir. Calculated Lip pressures for vertical wide-open discharge under these conditions are surprisingly independent of the kind of fluid tapped by the well, whether dry saturated steam or saturated hot water. The status of an actual well can be established by comparing the measured Lip pressure with the calculated theoretical maximum. Discharges are simply determined from the values of Lip pressure and supply fluid enthalpy.

James, Russell

1980-12-16

182

Purpose: This article presents a general procedural framework to assess the point-by-point precision in mapped dose associated with the intrinsic uncertainty of a deformable image registration (DIR) for any arbitrary patient. Methods: Dose uncertainty is obtained via a three-step process. In the first step, for each voxel in an imaging pair, a cluster of points is obtained by an iterative DIR procedure. In the second step, the dispersion of the points due to the imprecision of the DIR method is used to compute the spatial uncertainty. Two different ways to quantify the spatial uncertainty are presented in this work. Method A consists of a one-dimensional analysis of the modules of the position vectors, whereas method B performs a more detailed 3D analysis of the coordinates of the points. In the third step, the resulting spatial uncertainty estimates are used in combination with the mapped dose distribution to compute the point-by-point dose standard deviation. The process is demonstrated to estimate the dose uncertainty induced by mapping a 62.6 Gy dose delivered on maximum exhale to maximum inhale of a ten-phase four-dimensional lung CT. Results: For the demonstration lung image pair, the standard deviation of inconsistency vectors is found to be up to 9.2 mm with a mean {sigma} of 1.3 mm. This uncertainty results in a maximum estimated dose uncertainty of 29.65 Gy if method A is used and 21.81 Gy for method B. The calculated volume with dose uncertainty above 10.00 Gy is 602 cm{sup 3} for method A and 1422 cm{sup 3} for method B. Conclusions: This procedure represents a useful tool to evaluate the precision of a mapped dose distribution due to the intrinsic DIR uncertainty in a patient. The procedure is flexible, allowing incorporation of alternative intrinsic error models.

Salguero, Francisco J.; Saleh-Sayah, Nahla K.; Yan Chenyu; Siebers, Jeffrey V. [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia, 23298 (United States)

2011-01-15

183

Changes in context and perception of maximum reaching height.

Successfully performing a given behavior requires flexibility in both perception and behavior. In particular, doing so requires perceiving whether that behavior is possible across the variety of contexts in which it might be performed. Three experiments investigated how (changes in) context (ie point of observation and intended reaching task) influenced perception of maximum reaching height. The results of experiment 1 showed that perceived maximum reaching height more closely reflected actual reaching ability when perceivers occupied a point of observation that was compatible with that required for the reaching task. The results of experiments 2 and 3 showed that practice perceiving maximum reaching height from a given point of observation improved perception of maximum reaching height from a different point of observation, regardless of whether such practice occurred at a compatible or incompatible point of observation. In general, such findings show bounded flexibility in perception of affordances and are thus consistent with a description of perceptual systems as smart perceptual devices. PMID:24919349

Wagman, Jeffrey B; Day, Brian M

2014-01-01

184

BSP\\/CGM Algorithms for Maximum Subsequence and Maximum Subarray

\\u000a The maximum subsequence problem finds the contiguous subsequence of n real numbers with the highest sum. This problem appears in the analysis of DNA or protein sequences. It can be solved sequentially\\u000a in O(n) time. In the 2-D version, given an n × n array A, the maximum subarray of A is the contiguous subarray that has the maximum sum.

Carlos E. R. Alves; Edson Cáceres; Siang W. Song

2004-01-01

185

The maximum bias of robust covariances

This paper deals with the maximum asymptotic bias of two classes of robust estimates of the dispersion matrix V of a p-dimensional random vector x, under a contamination model of the form , where P is the distribution of x,P0 is a spherical distribution, and ?(x0) is a point mass at x0. Estimators VQ,? of the first class minimize the

Yohai J. Victor; Maronna A. Ricardo

1990-01-01

186

Background. From the beginning of the dialysis era, the issue of optimal dialysis dose and frequency has been a central topic in the delivery of dialysis treatment. Methods. We undertook a discussion to achieve a consensus on key points relating to dialysis dose and frequency, focusing on the relationships with clinical and patient outcomes. Results. Traditionally, dialysis adequacy has been

Francesco Locatelli; Umberto Buoncristiani; Bernard Canaud; Hans Kohler; Thierry Petitclerc; Pietro Zucchelli; Ospedale A. Manzoni; CHU Montpellier; Schwerpunkt Nephrologie

2004-01-01

187

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

188

A Maximum Likelihood Stereo Algorithm

A stereo algorithm is presented that optimizes a maximum likelihood cost function. The maximum likelihood cost function assumes that corresponding features in the left and right images are normally distributed about a common true value and consists of a weighted squared error term if two features are matched or a (fixed) cost if a feature is determined to be occluded.

Ingemar J. Cox; Sunita L. Hingorani; Satish B. Rao; Bruce M. Maggs

1996-01-01

189

Bayesian Point Cloud Reconstruction

In this paper, we propose a novel surface reconstruction technique based on Bayesian statistics: The measure- ment process as well as prior assumptions on the measured objects are modeled as probability distributions and Bayes' rule is used to infer a reconstruction of maximum probability. The key idea of this paper is to define both measurements and reconstructions as point clouds

Philipp Jenke; Michael Wand; Martin Bokeloh; Andreas Schilling; Wolfgang Straßer

2006-01-01

190

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.

2012-01-01

191

AMSR-E Arctic Sea Ice: September 2010 to March 2011: Scientists tracking the annual maximum extent of Arctic sea ice said that 2011 was among the lowest ice extents measured since satellites began ...

192

Power controller design for maximum power tracking in solar installations

A state space approach to the design of a maximum power point (MPP) tracking system for photovoltaic energy conversion is presented. The problem of optimal-power control of a nonlinear time-varying system is reduced to an ordinary problem of dynamic system stability in state space by applying MPP conditions in controller design. The resulting tracking system searches for the reference point

Eugene V. Solodovnik; Shengyi Liu; Roger A. Dougal

2004-01-01

193

Methods for utilizing maximum power from a solar array

NASA Technical Reports Server (NTRS)

A preliminary study of maximum power utilization methods was performed for an outer planet spacecraft using an ion thruster propulsion system and a solar array as the primary energy source. The problems which arise from operating the array at or near the maximum power point of its 1-V characteristic are discussed. Two closed loop system configurations which use extremum regulators to track the array's maximum power point are presented. Three open loop systems are presented that either: (1) measure the maximum power of each array section and compute the total array power, (2) utilize a reference array to predict the characteristics of the solar array, or (3) utilize impedance measurements to predict the maximum power utilization. The advantages and disadvantages of each system are discussed and recommendations for further development are made.

Decker, D. K.

1972-01-01

194

Abstract Background. With the increasing use of cone beam computed tomography (CBCT) for patient position verification and radiotherapy treatment adaptation, there is an increasing need to develop techniques that can take into account concomitant dose using a personalized approach. Material and methods. A total of 20 patients (10 pelvis and 10 head and neck) who had undergone radiation therapy using intensity modulated radiation therapy (IMRT) were selected and the dose from kV CBCT was retrospectively calculated using a treatment planning system previously commissioned for this purpose. The imaging dose was added to the CT images used for treatment planning and the difference in its addition prior to and after the planning was assessed. Results. The additional isocenter dose as a result of daily CBCT is in the order of 3-4 cGy for 35-fraction head and neck and 23-47 cGy for 25-fraction pelvis cases using the standard head and neck and pelvis image acquisition protocols. The pelvic dose is especially dependent on patient size and body mass index (BMI), being higher for patients with lower BMI. Due to the low energy of the kV CBCT beam, the maximum energy deposition is at or near the surface with the highest dose being on the patient's left side for the head and neck (? 7 cGy) and on the posterior for the pelvic cases (? 80 cGy). Addition of imaging dose prior to plan optimization resulted in an average reduction of 4% in the plan monitor units and 5% in the number of control points. Conclusion. Dose from daily kV CBCT has been added to patient treatment plans using previously commissioned kV CBCT beams in a treatment planning system. Addition of imaging dose can be included in IMRT treatment plan optimization and would facilitate customization of imaging protocol based on patient anatomy and location of isocenter. PMID:24438661

Alaei, Parham; Spezi, Emiliano; Reynolds, Margaret

2014-06-01

195

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

196

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

197

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

198

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

199

Feature extraction by structured stepwise nonparametric maximum margin criterion

In this paper, a new feature extraction method named structured stepwise nonparametric maximum margin criterion (SSNMMC) is proposed. Previous nonparametric discriminant analysis methods only use the point-to-point distance to measure class difference. In the proposed method, point-to-line distance with nearest neighbor line (NNL) theory is adopted and more intrinsic structure information of training samples is preserved in the feature space.

Yu-Jie Zheng; Xiaojun Wu; Dongjun Yu; Jingyu Yang; Wei-dong Wang; Yong-Zhi Li

2006-01-01

200

A formalism for independent checking of Gamma Knife dose calculations.

For stereotactic radiosurgery using the Leksell Gamma Knife system, it is important to perform a pre-treatment verification of the maximum dose calculated with the Leksell GammaPlan (DLGP) stereotactic radiosurgery system. This verification can be incorporated as part of a routine quality assurance (QA) procedure to minimize the chance of a hazardous overdose. To implement this procedure, a formalism has been developed to calculate the dose DCAL(X,Y,Z,dav,t) using the following parameters: average target depth (dav), coordinates (X,Y,Z) of the maximum dose location or any other dose point(s) to be verified, 3-dimensional (3-dim) beam profiles or off-centerratios (OCR) of the four helmets, helmet size i, output factor Oi, plug factor Pi, each shot j coordinates (x,y,z)i,j, and shot treatment time (ti,j). The average depth of the target dav was obtained either from MRI/CT images or ruler measurements of the Gamma Knife Bubble Head Frame. DCAL and DLGP were then compared to evaluate the accuracy of this independent calculation. The proposed calculation for an independent check of DLGP has been demonstrated to be accurate and reliable, and thus serves as a QA tool for Gamma Knife stereotactic radiosurgery. PMID:11585215

Tsai, J S; Engler, M J; Rivard, M J; Mahajan, A; Borden, J A; Zheng, Z

2001-09-01

201

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

202

Gaussian Prior for Smoothing Maximum Entropy Models.

National Technical Information Service (NTIS)

In certain contexts, maximum entropy (ME) modeling can be viewed as maximum likelihood training for exponential models, and like other maximum likelihood methods is prone to overfitting of training data. Several smoothing methods for maximum entropy model...

S. F. Chen R. Rosenfeld

1999-01-01

203

Maximum Acceptable Weight of Lift

This paper discusses the maximum amount of weight that an individual can be expected to lift comfortably and without strain. Recommendations based on empirical estimates, biomechanical techniques, and psychophysical methods are reviewed, including those of the International Labour Office, the Swiss Accident Insurance Institute, the Danish National Association for Infantile Paralysis, and the U. S. Air Force. The approach used

S. H. Snook; C. H. Irvine

1967-01-01

204

Graphs with maximum connectivity index

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

205

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

206

NASA Astrophysics Data System (ADS)

A climate tipping point, at least as I have used the phrase, refers to a situation in which a changing climate forcing has reached a point such that little additional forcing (or global temperature change) is needed to cause large, relatively rapid, climate change. Present examples include potential loss of all Arctic sea ice and instability of the West Antarctic and Greenland ice sheets. Tipping points are characterized by ready feedbacks that amplify the effect of forcings. The notion that these may be runaway feedbacks is a misconception. However, present "unrealized" global warming, due to the climate system's thermal inertia, exacerbates the difficulty of avoiding global warming tipping points. I argue that prompt efforts to slow CO2 emissions and absolutely reduce non-CO2 forcings are both essential if we are to avoid tipping points that would be disastrous for humanity and creation, the planet as civilization knows it.

Hansen, J.

2007-12-01

207

Solar maximum: Solar array degradation

NASA Technical Reports Server (NTRS)

The 5-year in-orbit power degradation of the silicon solar array aboard the Solar Maximum Satellite was evaluated. This was the first spacecraft to use Teflon R FEP as a coverglass adhesive, thus avoiding the necessity of an ultraviolet filter. The peak power tracking mode of the power regulator unit was employed to ensure consistent maximum power comparisons. Telemetry was normalized to account for the effects of illumination intensity, charged particle irradiation dosage, and solar array temperature. Reference conditions of 1.0 solar constant at air mass zero and 301 K (28 C) were used as a basis for normalization. Beginning-of-life array power was 2230 watts. Currently, the array output is 1830 watts. This corresponds to a 16 percent loss in array performance over 5 years. Comparison of Solar Maximum Telemetry and predicted power levels indicate that array output is 2 percent less than predictions based on an annual 1.0 MeV equivalent election fluence of 2.34 x ten to the 13th power square centimeters space environment.

Miller, T.

1985-01-01

208

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

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

209

Purpose: To investigate experimentally the impact of different head-and-neck intensity-modulated radiation therapy (IMRT) planning techniques on doses to the skin and shallow targets. Methods and Materials: A semicylindrical phantom was constructed with micro-MOSFET dosimeters (Thomson-Nielson, Ottawa, Ontario, Canada) at 0-, 3-, 6-, 9-, and 12-mm depths. The planning target volume (PTV) was pulled back 0, 3, or 5 mm from the body contour. The IMRT plans were created to maximize PTV coverage, with one of the following strategies: (a) aim for a maximum 110% hotspot, with 115% allowed; (b) aims for a maximum 105% hotspot; (c) aims for a maximum 105% hotspot and 50% of skin to get a maximum 70% of the prescribed dose; and (d) aim for 99% of the PTV volume to receive 90-93% of prescribed dose, with a maximum 105% hotspot, and with the dose to the skin structure minimized. Doses delivered using a linear accelerator were measured. Setup uncertainty was simulated by intentionally shifting the phantom in a range of {+-}8 mm, and calculating the delivered dose for a range of systematic and random uncertainties. Results: From lowest to highest skin dose, the planning strategies were in the order of c, d, b, and a, but c showed a tendency to underdose tissues at depth. Delivered doses varied by 10-20%, depending on planning strategy. For typical setup uncertainties, cumulative dose reduction to a point 6 mm deep was <4%. Conclusions: It is useful to use skin as a sensitive structure, but a minimum dose constraint must be used for the PTV if unwanted reductions in dose to nodes near the body surface are to be avoided. Setup uncertainties are unlikely to give excessive reductions in cumulative dose.

Court, Laurence E. [Department of Radiation Oncology, Dana-Farber and Brigham and Women's Cancer Center, Boston, MA (United States)], E-mail: lcourt@lroc.harvard.edu; Tishler, Roy B. [Department of Radiation Oncology, Dana-Farber and Brigham and Women's Cancer Center, Boston, MA (United States)

2007-10-01

210

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, M. J.; Coe, H. H.; Coy, J. J.

1991-01-01

211

Maximum Flux Transition Paths of Conformational Change.

Given two metastable states A and B of a biomolecular system, the problem is to calculate the likely paths of the transition from A to B. Such a calculation is more informative and more manageable if done for a reduced set of collective variables chosen so that paths cluster in collective variable space. The computational task becomes that of computing the "center" of such a cluster. A good way to define the center employs the concept of a committor, whose value at a point in collective variable space is the probability that a trajectory at that point will reach B before A. The committor "foliates" the transition region into a set of isocommittors. The maximum flux transition path is defined as a path that crosses each isocommittor at a point which (locally) has the highest crossing rate of distinct reactive trajectories. This path is based on the same principle as the minimum resistance path of Berkowitz et al (1983), but it has two advantages: (i) the path is invariant with respect to a change of coordinates in collective variable space and (ii) the differential equations that define the path are simpler. It is argued that such a path is nearer to an ideal path than others that have been proposed with the possible exception of the finite-temperature string method path. To make the calculation tractable, three approximations are introduced, yielding a path that is the solution of a nonsingular two-point boundary-value problem. For such a problem, one can construct a simple and robust algorithm. One such algorithm and its performance is discussed. PMID:20890401

Zhao, Ruijun; Shen, Juanfang; Skeel, Robert D

2010-08-10

212

This paper outlines a theoretical approach to the problem of estimating and choosing dose-volume constraints. Following this approach, a method of choosing dose-volume constraints based on biological criteria is proposed. This method is called "reverse normal tissue complication probability (NTCP) mapping into dose-volume space" and may be used as a general guidance to the problem of dose-volume constraint estimation. Dose-volume histograms (DVHs) are randomly simulated, and those resulting in clinically acceptable levels of complication, such as NTCP of 5 +/- 0.5%, are selected and averaged producing a mean DVH that is proven to result in the same level of NTCP. The points from the averaged DVH are proposed to serve as physical dose-volume constraints. The population-based critical volume and Lyman NTCP models with parameter sets taken from literature sources were used for the NTCP estimation. The impact of the prescribed value of the maximum dose to the organ, D(max), on the averaged DVH and the dose-volume constraint points is investigated. Constraint points for 16 organs are calculated. The impact of the number of constraints to be fulfilled based on the likelihood that a DVH satisfying them will result in an acceptable NTCP is also investigated. It is theoretically proven that the radiation treatment optimization based on physical objective functions can sufficiently well restrict the dose to the organs at risk, resulting in sufficiently low NTCP values through the employment of several appropriate dose-volume constraints. At the same time, the pure physical approach to optimization is self-restrictive due to the preassignment of acceptable NTCP levels thus excluding possible better solutions to the problem. PMID:17022241

Schinkel, Colleen; Stavrev, Pavel; Stavreva, Nadia; Fallone, B Gino

2006-09-01

213

Genetic algorithm for maximum entropy image restoration

NASA Astrophysics Data System (ADS)

Linear image restoration techniques induce erroneous detail around sharp intensity changes. Thus, considerable work has centered on nonlinear methods, which incorporate constraints to reduce the artifacts generated in the restoration. In our paper, we examine the applicability of genetic algorithms to solving optimization problems posed by nonlinear image recovery techniques, particularly by maximum entropy restoration. Each point in the solution space is a feasible image, with the pixels as decision variables. Search is multiobjective: the entropy of the estimate must be maximized, subject to constraints dependent on the observed data and image degradation model. We use Pareto techniques to achieve this combined requirement, and problem-oriented knowledge to direct the search. Typical issues for genetic algorithms are addressed: chromosomal representation, genetic operators, selection scheme, and initialization.

Toma, Cristian E.; Datcu, Mihai P.

1994-06-01

214

Maximum neighborhood margin discriminant projection for classification.

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

Gou, Jianping; Zhan, Yongzhao; Wan, Min; Shen, Xiangjun; Chen, Jinfu; Du, Lan

2014-01-01

215

Maximum Neighborhood Margin Discriminant Projection for Classification

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.

Zhan, Yongzhao; Shen, Xiangjun; Du, Lan

2014-01-01

216

RV strings of maximum curvature

To design an effective interceptor for a string of reentry vehicles (RV's) released by a post-boost vehicle (PBV), it is necessary to have information about possible geometries of the string when it reaches a given altitude above the target. The geometry of the string, assumed for simplicity to contain three RV's, is determined by the motion of the PBV which is controlled by varying its thrust direction. Of interest in this study is maximizing the curvature of the string, which is represented by the distance of RV{sub 2} from the line joining RV{sub 1} and RV{sub 3} when RV{sub 1} reaches the intercept attitude, subject to the constraints that all three RV's must land within 3000 ft distance of the target. The maximum curvature problem is formulated as a parameter optimization problem and solved by a nonlinear programming code known as GRG2. The thrust angles are assumed to be piecewise linear, and a total of 21 parameters is used. The maximum curvature is shown to be approximately 2900 ft. 4 refs., 8 figs.

Hull, D.G. (Texas Univ., Austin, TX (United States)); Zazworsky, R.M. (Sandia National Labs., Albuquerque, NM (United States))

1991-01-01

217

Linear time maximum margin clustering.

Maximum margin clustering (MMC) is a newly proposed clustering method which has shown promising performance in recent studies. It extends the computational techniques of support vector machine (SVM) to the unsupervised scenario. Traditionally, MMC is formulated as a nonconvex integer programming problem which makes it difficult to solve. Several methods have been proposed in the literature to solve the MMC problem based on either semidefinite programming (SDP) or alternating optimization. However, these methods are still time demanding when handling large scale data sets, which limits its application in real-world problems. In this paper, we propose a cutting plane maximum margin clustering (CPMMC) algorithm. It first decomposes the nonconvex MMC problem into a series of convex subproblems by making use of the constrained concave-convex procedure (CCCP), then for each subproblem, our algorithm adopts the cutting plane algorithm to solve it. Moreover, we show that the CPMMC algorithm takes O(sn) time to converge with guaranteed accuracy, where n is the number of samples in the data set and s is the sparsity of the data set, i.e., the average number of nonzero features of the data samples. We also derive the multiclass version of our CPMMC algorithm. Experimental evaluations on several real-world data sets show that CPMMC performs better than existing MMC methods, both in efficiency and accuracy. PMID:20083456

Wang, Fei; Zhao, Bin; Zhang, Changshui

2010-02-01

218

The contribution from transit dose for (192)Ir HDR brachytherapy treatments.

Brachytherapy treatment planning systems that use model-based dose calculation algorithms employ a more accurate approach that replaces the TG43-U1 water dose formalism and adopt the TG-186 recommendations regarding composition and geometry of patients and other relevant effects. However, no recommendations were provided on the transit dose due to the source traveling inside the patient. This study describes a methodology to calculate the transit dose using information from the treatment planning system (TPS) and considering the source's instantaneous and average speed for two prostate and two gynecological cases. The trajectory of the (192)Ir HDR source was defined by importing applicator contour points and dwell positions from the TPS. The transit dose distribution was calculated using the maximum speed, the average speed and uniform accelerations obtained from the literature to obtain an approximate continuous source distribution simulated with a Monte Carlo code. The transit component can be negligible or significant depending on the speed profile adopted, which is not clearly reported in the literature. The significance of the transit dose can also be due to the treatment modality; in our study interstitial treatments exhibited the largest effects. Considering the worst case scenario the transit dose can reach 3% of the prescribed dose in a gynecological case with four catheters and up to 11.1% when comparing the average prostate dose for a case with 16 catheters. The transit dose component increases by increasing the number of catheters used for HDR brachytherapy, reducing the total dwell time per catheter or increasing the number of dwell positions with low dwell times. This contribution may become significant (>5%) if it is not corrected appropriately. The transit dose cannot be completely compensated using simple dwell time corrections since it may have a non-uniform distribution. An accurate measurement of the source acceleration and maximum speed should be incorporated in clinical practice or provided by the manufacturer to determine the transit dose component with high accuracy. PMID:24625517

Fonseca, G P; Landry, G; Reniers, B; Hoffmann, A; Rubo, R A; Antunes, P C G; Yoriyaz, H; Verhaegen, F

2014-04-01

219

The contribution from transit dose for 192Ir HDR brachytherapy treatments

NASA Astrophysics Data System (ADS)

Brachytherapy treatment planning systems that use model-based dose calculation algorithms employ a more accurate approach that replaces the TG43-U1 water dose formalism and adopt the TG-186 recommendations regarding composition and geometry of patients and other relevant effects. However, no recommendations were provided on the transit dose due to the source traveling inside the patient. This study describes a methodology to calculate the transit dose using information from the treatment planning system (TPS) and considering the source's instantaneous and average speed for two prostate and two gynecological cases. The trajectory of the 192Ir HDR source was defined by importing applicator contour points and dwell positions from the TPS. The transit dose distribution was calculated using the maximum speed, the average speed and uniform accelerations obtained from the literature to obtain an approximate continuous source distribution simulated with a Monte Carlo code. The transit component can be negligible or significant depending on the speed profile adopted, which is not clearly reported in the literature. The significance of the transit dose can also be due to the treatment modality; in our study interstitial treatments exhibited the largest effects. Considering the worst case scenario the transit dose can reach 3% of the prescribed dose in a gynecological case with four catheters and up to 11.1% when comparing the average prostate dose for a case with 16 catheters. The transit dose component increases by increasing the number of catheters used for HDR brachytherapy, reducing the total dwell time per catheter or increasing the number of dwell positions with low dwell times. This contribution may become significant (>5%) if it is not corrected appropriately. The transit dose cannot be completely compensated using simple dwell time corrections since it may have a non-uniform distribution. An accurate measurement of the source acceleration and maximum speed should be incorporated in clinical practice or provided by the manufacturer to determine the transit dose component with high accuracy.

Fonseca, G. P.; Landry, G.; Reniers, B.; Hoffmann, A.; Rubo, R. A.; Antunes, P. C. G.; Yoriyaz, H.; Verhaegen, F.

2014-04-01

220

From 1983 to 1992, 248 patients with carcinoma of the uterine cervix were treated with intracavitary radiation therapy using the 60Co remotely controlled high dose rate afterloading system apace (RALS). Five-year survival rates were 92,8 +/- 7 % for Stage I, 72.4 +/- 5% for Stage II and 52.1 +/- 4% for Stage III. The relations among the sequelae in surrounding organs, local control rates and the calculated dose in the rectum, sigmoid colon, bladder and small intestine were evaluated using X-ray CT images. The patients were treated with intracavitary radiation of 6 Gy/fraction at point A. A total of 5 fractions were delivered once a week. The dose calculation was performed by, and dose distribution shown on, a system developed in our hospital with a personal computer. The average values of maximum dose at certain points of the walls of the rectum and sigmoid colon were similar to point A dose. The incidence of late sequelae increased significantly in the group receiving a maximum dose to the rectum and sigmoid colon higher than 8 space Gy/fraction. This report describes the program for automatic optimization of dose distribution by modifying the hot spot (higher than 8 space Gy/fraction) and the cold spot (lower than 6 space Gy/ fraction). PMID:8692655

Satoh, S; Sakata, S

1996-04-01

221

Cost Based Filtering vs. Upper Bounds for Maximum Clique

In this paper we consider a branch-and-bound algorithm for the maximum clique problem. We introduce cost based filtering techniques for the so-called candidate set (i.e. a set of nodes that can possibly extend the clique in the current choice point). Doing this, we can reduce the number of choice points visited by a typical factor of 10 - 50. Additionally,

Torsten Fahle

2002-01-01

222

Monte Carlo-based revised values of dose rate constants at discrete photon energies

Absorbed dose rate to water at 0.2 cm and 1 cm due to a point isotropic photon source as a function of photon energy is calculated using the EDKnrc user-code of the EGSnrc Monte Carlo system. This code system utilized widely used XCOM photon cross-section dataset for the calculation of absorbed dose to water. Using the above dose rates, dose rate constants are calculated. Air-kerma strength Sk needed for deriving dose rate constant is based on the mass-energy absorption coefficient compilations of Hubbell and Seltzer published in the year 1995. A comparison of absorbed dose rates in water at the above distances to the published values reflects the differences in photon cross-section dataset in the low-energy region (difference is up to 2% in dose rate values at 1 cm in the energy range 30–50 keV and up to 4% at 0.2 cm at 30 keV). A maximum difference of about 8% is observed in the dose rate value at 0.2 cm at 1.75 MeV when compared to the published value. Sk calculations based on the compilation of Hubbell and Seltzer show a difference of up to 2.5% in the low-energy region (20–50 keV) when compared to the published values. The deviations observed in the values of dose rate and Sk affect the values of dose rate constants up to 3%.

Selvam, T. Palani; Shrivastava, Vandana; Chourasiya, Ghanashyam; Babu, D. Appala Raju

2014-01-01

223

Calculation of organ doses from breast cancer radiotherapy: a Monte Carlo study.

The current study aimed to: a) utilize Monte Carlo simulation methods for the assessment of radiation doses imparted to all organs at risk to develop secondary radiation induced cancer, for patients undergoing radiotherapy for breast cancer; and b) evaluate the effect of breast size on dose to organs outside the irradiation field. A simulated linear accelerator model was generated. The in-field accuracy of the simulated photon beam properties was verified against percentage depth dose (PDD) and dose profile measurements on an actual water phantom. Off-axis dose calculations were verified with thermoluminescent dosimetry (TLD) measurements on a humanoid physical phantom. An anthropomorphic mathematical phantom was used to simulate breast cancer radiotherapy with medial and lateral fields. The effect of breast size on the calculated organ dose was investigated. Local differences between measured and calculated PDDs and dose profiles did not exceed 2% for the points at depths beyond the depth of maximum dose and the plateau region of the profile, respectively. For the penumbral regions of the dose profiles, the distance to agreement (DTA) did not exceed 2 mm. The mean difference between calculated out-of-field doses and TLD measurements was 11.4% ± 5.9%. The calculated doses to peripheral organs ranged from 2.32 cGy up to 161.41 cGy depending on breast size and thus the field dimensions applied, as well as the proximity of the organs to the primary beam. An increase to the therapeutic field area by 50% to account for the large breast led to a mean organ dose elevation by up to 85.2% for lateral exposure. The contralateral breast dose ranged between 1.4% and 1.6% of the prescribed dose to the tumor. Breast size affects dose deposition substantially. PMID:23318389

Berris, Theocharis; Mazonakis, Michael; Stratakis, John; Tzedakis, Antonios; Fasoulaki, Anastasia; Damilakis, John

2013-01-01

224

NSDL National Science Digital Library

In this activity best suited as a demonstration, learners observe that when a piece of iron gets too hot, it loses its ability to be magnetized. The temperature at which this occurs is known as the Curie Point. This simple set-up involving a lantern battery and Tinkertoysâ¢ demonstrates this phenomenon. Adult supervision required, as the wire will get hot in this activity.

Exploratorium, The

2012-01-30

225

Attitude sensor alignment calibration for the solar maximum mission

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

Daniel S. Pitone; Malcolm D. Shuster

1990-01-01

226

FORECASTING MAXIMUM TEMPERATURES VIA FUZZY NEAREST NEIGHBOUR MODEL OVER DELHI

This paper introduces nearest neighbour based fuzzy model (NNFM) based on membership values for forecasting the daily maximum temperature at Delhi . Fuzzy mem- bership values has been used to make single point forecasts into the future on the basis of past nearest neighbours. Compared with other statistical method and artiflcial neural network (ANN) technique, this approach has the advantages

A. K MITRA; SANKAR NATH

227

Comprehensive review of wind energy maximum power extraction algorithms

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

NASA Astrophysics Data System (ADS)

Variations in skin dose caused by a silicon-based burn dressing used in radiotherapy during treatment have been investigated. Measurement of these variations in skin dose has been achieved using thermoluminescent dosimeters (TLDs) and Gafchromic film. For a 6 MV x-ray beam results have shown that an approximately 0.4 mm thick silicon mesh dressing increases the average surface dose by approximately 12.5% to 14% of the maximum and average dose at 1 mm depth and by 4% to 6% of the maximum for field sizes ranging from 5 cm × 5 cm up to 40 cm × 40 cm at 100 cm source to surface distance (SSD). The radiation effective thickness of the silicon dressing was calculated to be 0.5 mm +/- 0.05 mm water equivalent. TLDs of various thicknesses provide point-dose assessment and Gafchromic film can provide a detailed two-dimensional dose map with a high spatial resolution. Results have shown that a large variation in skin dose is delivered under the dressing depending on the amount of material directly above it as defined by the silicon mesh outline.

Butson, Martin J.; Cheung, Tsang; Yu, Peter K. N.; Metcalfe, Peter

2002-06-01

229

A randomized, double-blind, placebo-controlled, 3-period crossover study was conducted in 54 healthy adults to assess the effect of ceftaroline fosamil on the corrected QT (QTc) interval. The QT interval, corrected for heart rate using an individual correction formula (QTcIb), was determined predose and at 1, 1.25, 1.5, 2, 4, 8, 12, and 24.5 h after intravenous dosing with a supratherapeutic dose (1,500 mg) of ceftaroline fosamil, 400 mg moxifloxacin (positive control), and placebo. The pharmacokinetic profile of ceftaroline was also evaluated. At each time point following ceftaroline fosamil administration, the upper limit of the 90% confidence interval (CI) for the placebo-corrected change from predose baseline in QTcIb (??QTcIb) was below 10 ms (maximum, 3.4 ms at 1.5 h after dosing), indicating an absence of clinically meaningful QTc increase. The lower limit of the 90% CI of ??QTcIb for moxifloxacin versus placebo was greater than 5 ms at 5 time points (maximum, 12.8 ms at 1 h after dosing), demonstrating assay sensitivity. There was no apparent correlation between ceftaroline plasma concentrations and ??QTcIb. The supratherapeutic dose of ceftaroline fosamil (1,500 mg) resulted in substantially greater systemic exposure to ceftaroline than previously observed with standard therapeutic doses. Ceftaroline fosamil was well tolerated after a single 1,500-mg intravenous dose, and no clinically meaningful abnormalities in laboratory values or vital signs were observed.

Rekeda, Ludmyla; Rank, Douglas; Llorens, Lily

2013-01-01

230

National Technical Information Service (NTIS)

The methods are discussed of measuring dose rate or dose using a scintillation counter. A plastic scintillator based on polystyrene with PBD and POPOP activators and coated with ZnS(Ag) was chosen for the projected monitor. The scintillators were cylindri...

O. Novakova J. Ryba V. Slezak B. Svobodova L. Viererbl

1984-01-01

231

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

232

Absorbed dose calculations provide a scientific basis for evaluating the biological effects associated with administered radiopharmaceuticals. In cancer therapy, radiation dosimetry also supports treatment planning, dose-response analyses, predictions of therapy effectiveness, and completeness of patient medical records. In this study, we evaluated the organ radiation absorbed doses resulting from intravenously administered 111In- and 90Y-Ibritumomab Tiuxetan (Zevalin). Methods: Ten patients (six male, four female) with non-Hodgkin’s lymphoma, cared for at three different medical centers, were administered tracer 111In-Ibritumomab Tiuxetan and were assessed using planar scintillation camera imaging at five time points, blood clearance measurements, and CT-organ volumetrics, to determine patient-specific organ biokinetics and dosimetry. Explicit attenuation correction based on transmission scan or transmission measurements provided the fraction of 111In administered activity in seven major organs, the whole body, and remainder tissues over time through complete decay. Activity-time curves were constructed, and radiation doses were calculated using MIRD methods and implementing software (OLINDA-EXM). Results: Mean radiation absorbed doses in 10 cancer patients for 111In- and for 90-Y-Ibritumomab Tiuxetan are reported for 24 organs and the whole body. Biological uptake and retention data are given for seven major source organs, remainder tissues, and the whole body. Median absorbed dose values calculated by this method were compared to previously published dosimetry for Zevalin and the product package insert. Conclusions: Careful dosimetry techniques provide useful information on absorbed dose from administered radiopharmaceuticals in patients. The importance of patient-specific dosimetry emerges in high-dose radioimmunotherapy when the objective of treatment planning is to achieve disease cures safely by limiting radiation doses to any critical normal organ to a maximum tolerable value.

Fisher, Darrell R.; Shen, Sui; Meredith, Ruby F.

2009-04-16

233

Maximum Entropy Principle for Transportation

NASA Astrophysics Data System (ADS)

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.; Dasilva, R.

2008-11-01

234

Maximum entropy principal for transportation

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

235

Dose Calculations for [131I] Meta-Iodobenzylguanidine-Induced Bystander Effects

Targeted radiotherapy is a potentially useful treatment for some cancers and may be potentiated by bystander effects. However, without estimation of absorbed dose, it is difficult to compare the effects with conventional external radiation treatment. Methods: Using the Vynckier – Wambersie dose point kernel, a model for dose rate evaluation was created allowing for calculation of absorbed dose values to two cell lines transfected with the noradrenaline transporter (NAT) gene and treated with [131I]MIBG. Results: The mean doses required to decrease surviving fractions of UVW/NAT and EJ138/NAT cells, which received medium from [131I]MIBG-treated cells, to 25 – 30% were 1.6 and 1.7 Gy respectively. The maximum mean dose rates achieved during [131I]MIBG treatment were 0.09 – 0.75 Gy/h for UVW/NAT and 0.07 – 0.78 Gy/h for EJ138/NAT. These were significantly lower than the external beam gamma radiation dose rate of 15 Gy/h. In the case of control lines which were incapable of [131I]MIBG uptake the mean absorbed doses following radiopharmaceutical were 0.03 – 0.23 Gy for UVW and 0.03 – 0.32 Gy for EJ138. Conclusion: [131I]MIBG treatment for ICCM production elicited a bystander dose-response profile similar to that generated by external beam gamma irradiation but with significantly greater cell death.

Gow, M. D.; Seymour, C. B.; Boyd, M.; Mairs, R. J.; Prestiwch, W. V.; Mothersill, C. E.

2014-01-01

236

Estimation Of Organ Doses From Solar Particle Events For Future Space Exploration Missions

NASA Technical Reports Server (NTRS)

Radiation protection practices define the effective dose as a weighted sum of equivalent dose over major organ sites for radiation cancer risks. Since a crew personnel dosimeter does not make direct measurement of the effective dose, it has been estimated with skin-dose measurements and radiation transport codes for ISS and STS missions. If sufficient protection is not provided near solar maximum, the radiation risk can be significant due to exposure to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR) on future exploratory-class and long-duration missions. For accurate estimates of overall fatal cancer risks from SPEs, the specific doses at various blood forming organs (BFOs) were considered, because proton fluences and doses vary considerably across marrow regions. Previous estimates of BFO doses from SPEs have used an average body-shielding distribution for the bone marrow based on the computerized anatomical man model (CAM). With the development of an 82-point body-shielding distribution at BFOs, the mean and variance of SPE doses in the major active marrow regions (head and neck, chest, abdomen, pelvis and thighs) will be presented. Consideration of the detailed distribution of bone marrow sites is one of many requirements to improve the estimation of effective doses for radiation cancer risks.

Kim, Myung-Hee; Cucinotta, Francis A.

2006-01-01

237

Investigation of 1-cm dose equivalent for photons behind shielding materials

The ambient dose equivalent at 1-cm depth, assumed equivalent to the 1-cm dose equivalent in practical dose estimations behind shielding slabs of water, concrete, iron or lead for normally incident photons having various energies was calculated by using conversion factors for a slab phantom. It was compared with the 1-cm depth dose calculated with the Monte Carlo code EGS4. It was concluded from this comparison that the ambient dose equivalent calculated by using the conversion factors for the ICRU sphere could be used for the evaluation of the 1-cm dose equivalent for the sphere phantom within 20% errors. Average and practical conversion factors are defined as the conversion factors from exposure to ambient dose equivalent in a finite slab or an infinite one, respectively. They were calculated with EGS4 and the discrete ordinates code PALLAS. The exposure calculated with simple estimation procedures such as point kernel methods can be easily converted to ambient dose equivalent by using these conversion factors. The maximum value between 1 and 30 mfp can be adopted as the conversion factor which depends only on material and incident photon energy. This gives the ambient dose equivalent on the safe side. 13 refs., 7 figs., 2 tabs.

Hirayama, Hideo (National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)); Tanaka, Shun-ichi (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan))

1991-03-01

238

Residents of the Techa riverside villages chronically exposed to ionizing radiation (the average dose rate in 1951-1956 was 0.047 Gy/year, the maximum reached 2.44 Gy/year) developed marked changes in the cellular composition of peripheral blood. The maximum reduction of peripheral blood counts occurred in the years 1951-1953, after which the beginning of the restoration of cellularity to the control level was observed. The dose rate at this point (1956) was about 0.02 Gy/year. The factors of radiation and non-radiation nature (gender, the age at the onset of exposure, health related disorders) in different combinations affect the number of peripheral blood cells. The influence of dose rate of a chronic radiation exposure on a platelet count takes precedence over other factors. The factors of gender and dose rate determine the number of erythrocytes in exposed persons. The changes accompanying the health status and dose rate significantly affect the number of neutrophils. The influence of comorbidity, age and dose rate on the number of monocytes was noted. A lymphocyte count was mainly determined by the age at the onset of exposure and concomitant diseases. A joint influence of chronic radiation exposure and concomitant diseases increases a mutual action on erythro- and thrombocytopoiesis. The decrease of the dose rate was followed by a gradual predominance of the somatic disease influence on leukocyte (neutrophils, lymphocytes and monocytes) counts. PMID:22690574

Akleev, A V; Dimov, G P; Varfolomeeva, T A

2012-01-01

239

Maximum Parsimony on Phylogenetic networks

Background Phylogenetic networks are generalizations of phylogenetic trees, that are used to model evolutionary events in various contexts. Several different methods and criteria have been introduced for reconstructing phylogenetic trees. Maximum Parsimony is a character-based approach that infers a phylogenetic tree by minimizing the total number of evolutionary steps required to explain a given set of data assigned on the leaves. Exact solutions for optimizing parsimony scores on phylogenetic trees have been introduced in the past. Results In this paper, we define the parsimony score on networks as the sum of the substitution costs along all the edges of the network; and show that certain well-known algorithms that calculate the optimum parsimony score on trees, such as Sankoff and Fitch algorithms extend naturally for networks, barring conflicting assignments at the reticulate vertices. We provide heuristics for finding the optimum parsimony scores on networks. Our algorithms can be applied for any cost matrix that may contain unequal substitution costs of transforming between different characters along different edges of the network. We analyzed this for experimental data on 10 leaves or fewer with at most 2 reticulations and found that for almost all networks, the bounds returned by the heuristics matched with the exhaustively determined optimum parsimony scores. Conclusion The parsimony score we define here does not directly reflect the cost of the best tree in the network that displays the evolution of the character. However, when searching for the most parsimonious network that describes a collection of characters, it becomes necessary to add additional cost considerations to prefer simpler structures, such as trees over networks. The parsimony score on a network that we describe here takes into account the substitution costs along the additional edges incident on each reticulate vertex, in addition to the substitution costs along the other edges which are common to all the branching patterns introduced by the reticulate vertices. Thus the score contains an in-built cost for the number of reticulate vertices in the network, and would provide a criterion that is comparable among all networks. Although the problem of finding the parsimony score on the network is believed to be computationally hard to solve, heuristics such as the ones described here would be beneficial in our efforts to find a most parsimonious network.

2012-01-01

240

Secondary Neutron Doses for Several Beam Configurations for Proton Therapy

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

241

PRECEDENTS FOR AUTHORIZATION OF CONTENTS USING DOSE RATE MEASUREMENTS

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

242

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

243

Mammography segmentation with maximum likelihood active contours.

We present a computer-aided approach to segmenting suspicious lesions in digital mammograms, based on a novel maximum likelihood active contour model using level sets (MLACMLS). The algorithm estimates the segmentation contour that best separates the lesion from the background using the Gamma distribution to model the intensity of both regions (foreground and background). The Gamma distribution parameters are estimated by the algorithm. We evaluate the performance of MLACMLS on real mammographic images. Our results are compared to those of two leading related methods: The adaptive level set-based segmentation method (ALSSM) and the spiculation segmentation using level sets (SSLS) approach, and show higher segmentation accuracy (MLACMLS: 86.85% vs. ALSSM: 74.32% and SSLS: 57.11%). Moreover, our results are qualitatively compared with those of the Active Contour Without Edge (ACWOE) and show a better performance. Further, the suitability of using ML as the objective function as opposed to the KL divergence and to the energy functional of the ACWOE is also demonstrated. Our algorithm is also shown to be robust to the selection of a required single seed point. PMID:22831774

Rahmati, Peyman; Adler, Andy; Hamarneh, Ghassan

2012-08-01

244

Mammographic image restoration using maximum entropy deconvolution

NASA Astrophysics Data System (ADS)

An image restoration approach based on a Bayesian maximum entropy method (MEM) has been applied to a radiological image deconvolution problem, that of reduction of geometric blurring in magnification mammography. The aim of the work is to demonstrate an improvement in image spatial resolution in realistic noisy radiological images with no associated penalty in terms of reduction in the signal-to-noise ratio perceived by the observer. Images of the TORMAM mammographic image quality phantom were recorded using the standard magnification settings of 1.8 magnification/fine focus and also at 1.8 magnification/broad focus and 3.0 magnification/fine focus; the latter two arrangements would normally give rise to unacceptable geometric blurring. Measured point-spread functions were used in conjunction with the MEM image processing to de-blur these images. The results are presented as comparative images of phantom test features and as observer scores for the raw and processed images. Visualization of high resolution features and the total image scores for the test phantom were improved by the application of the MEM processing. It is argued that this successful demonstration of image de-blurring in noisy radiological images offers the possibility of weakening the link between focal spot size and geometric blurring in radiology, thus opening up new approaches to system optimization.

Jannetta, A.; Jackson, J. C.; Kotre, C. J.; Birch, I. P.; Robson, K. J.; Padgett, R.

2004-11-01

245

Mammographic image restoration using maximum entropy deconvolution.

An image restoration approach based on a Bayesian maximum entropy method (MEM) has been applied to a radiological image deconvolution problem, that of reduction of geometric blurring in magnification mammography. The aim of the work is to demonstrate an improvement in image spatial resolution in realistic noisy radiological images with no associated penalty in terms of reduction in the signal-to-noise ratio perceived by the observer. Images of the TORMAM mammographic image quality phantom were recorded using the standard magnification settings of 1.8 magnification/fine focus and also at 1.8 magnification/broad focus and 3.0 magnification/fine focus; the latter two arrangements would normally give rise to unacceptable geometric blurring. Measured point-spread functions were used in conjunction with the MEM image processing to de-blur these images. The results are presented as comparative images of phantom test features and as observer scores for the raw and processed images. Visualization of high resolution features and the total image scores for the test phantom were improved by the application of the MEM processing. It is argued that this successful demonstration of image de-blurring in noisy radiological images offers the possibility of weakening the link between focal spot size and geometric blurring in radiology, thus opening up new approaches to system optimization. PMID:15584533

Jannetta, A; Jackson, J C; Kotre, C J; Birch, I P; Robson, K J; Padgett, R

2004-11-01

246

Tracked Vehicle Acceleration: Maximum and Minimum Speeds.

National Technical Information Service (NTIS)

This document describes procedures for conducting acceleration and maximum and minimum speed tests of tracked vehicles. Acceleration and maximum speed are basic measures of vehicle power; they define the ability of a vehicle to execute a change in locatio...

1987-01-01

247

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.

2014-01-01

248

The Relaxed Online Maximum Margin Algorithm

We describe a new incremental algorithm for training linear threshold functions: the Relaxed Online Maximum Margin Algorithm, or ROMMA. ROMMA can be viewed as an approximation to the algorithm that repeatedly chooses the hyperplane that classifies previously seen examples correctly with the maximum margin. It is known that such a maximum-margin hypothesis can be computed by minimizing the length of

Yi Li; Philip M. Long

2002-01-01

249

[Consideration of the newly standardized interventional reference point].

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

250

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

251

Intensity-modulated radiation therapy (IMRT) is one of the most complex applications of radiotherapy that requires patient-specific quality assurance (QA). Here, we describe a novel method of 3-dimensional (3D) dose-verification using 12 acrylic slabs in a 3D phantom (30 x 30 x 12 cm{sup 3}) with extended dose rate (EDR2) films, which is both faster than conventionally used methods, and clinically useful. With custom-written software modules written in Microsoft Excel Visual Basic Application, the measured and planned dose distributions for the axial, coronal, and sagittal planes were superimposed by matching their origins, and the point doses were compared at all matched positions. Then, an optimization algorithm was used to correct the detected setup errors. The results show that this optimization method significantly reduces the average maximum dose difference by 7.73% and the number of points showing dose differences of more than 5% by 8.82% relative to the dose differences without an optimization. Our results indicate that the dose difference was significantly decreased with optimization and this optimization method is statistically reliable and effective. The results of 3D optimization are discussed in terms of various patient-specific QA data obtained from statistical analyses.

Shin, Dongho; Yoon, Myonggeun [Research Institute and Hospital, National Cancer Center, Ilsandong-gu, Goyang (Korea, Republic of); Park, Sung Yong [Research Institute and Hospital, National Cancer Center, Ilsandong-gu, Goyang (Korea, Republic of)], E-mail: cool_park@ncc.re.kr; Park, Dong Hyun; Lee, Se Byeong; Kim, Dae Yong; Cho, Kwan Ho [Research Institute and Hospital, National Cancer Center, Ilsandong-gu, Goyang (Korea, Republic of)

2007-01-01

252

Optimized Dose Distribution of Gammamed Plus Vaginal Cylinders

Endometrial carcinoma is the most common malignancy arising in the female genital tract. Intracavitary vaginal cuff irradiation may be given alone or with external beam irradiation in patients determined to be at risk for locoregional recurrence. Vaginal cylinders are often used to deliver a brachytherapy dose to the vaginal apex and upper vagina or the entire vaginal surface in the management of postoperative endometrial cancer or cervical cancer. The dose distributions of HDR vaginal cylinders must be evaluated carefully, so that clinical experiences with LDR techniques can be used in guiding optimal use of HDR techniques. The aim of this study was to optimize dose distribution for Gammamed plus vaginal cylinders. Placement of dose optimization points was evaluated for its effect on optimized dose distributions. Two different dose optimization point models were used in this study, namely non-apex (dose optimization points only on periphery of cylinder) and apex (dose optimization points on periphery and along the curvature including the apex points). Thirteen dwell positions were used for the HDR dosimetry to obtain a 6-cm active length. Thus 13 optimization points were available at the periphery of the cylinder. The coordinates of the points along the curvature depended on the cylinder diameters and were chosen for each cylinder so that four points were distributed evenly in the curvature portion of the cylinder. Diameter of vaginal cylinders varied from 2.0 to 4.0 cm. Iterative optimization routine was utilized for all optimizations. The effects of various optimization routines (iterative, geometric, equal times) was studied for the 3.0-cm diameter vaginal cylinder. The effect of source travel step size on the optimized dose distributions for vaginal cylinders was also evaluated. All optimizations in this study were carried for dose of 6 Gy at dose optimization points. For both non-apex and apex models of vaginal cylinders, doses for apex point and three dome points were higher for the apex model compared with the non-apex model. Mean doses to the optimization points for both the cylinder models and all the cylinder diameters were 6 Gy, matching with the prescription dose of 6 Gy. Iterative optimization routine resulted in the highest dose to apex point and dome points. The mean dose for optimization point was 6.01 Gy for iterative optimization and was much higher than 5.74 Gy for geometric and equal times routines. Step size of 1 cm gave the highest dose to the apex point. This step size was superior in terms of mean dose to optimization points. Selection of dose optimization points for the derivation of optimized dose distributions for vaginal cylinders affects the dose distributions.

Supe, Sanjay S. [Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore, Karnataka (India)], E-mail: sanjayssupe@gmail.com; Bijina, T.K.; Varatharaj, C.; Shwetha, B.; Arunkumar, T.; Sathiyan, S.; Ganesh, K.M.; Ravikumar, M. [Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore, Karnataka (India)

2009-04-01

253

Propane spectral resolution enhancement by the maximum entropy method

NASA Astrophysics Data System (ADS)

The Burg algorithm for maximum entropy power spectral density estimation is applied to a time series of data obtained from a Michelson interferometer and compared with a standard FFT estimate for resolution capability. The propane transmittance spectrum was estimated by use of the FFT with a 2 to the 18th data sample interferogram, giving a maximum unapodized resolution of 0.06/cm. This estimate was then interpolated by zero filling an additional 2 to the 18th points, and the final resolution was taken to be 0.06/cm. Comparison of the maximum entropy method (MEM) estimate with the FFT was made over a 45/cm region of the spectrum for several increasing record lengths of interferogram data beginning at 2 to the 10th. It is found that over this region the MEM estimate with 2 to the 16th data samples is in close agreement with the FFT estimate using 2 to the 18th samples.

Bonavito, N. L.; Stewart, K. P.; Hurley, E. J.; Yeh, K. C.; Inguva, R.

1990-05-01

254

This is a study using LiF:Mg;Ti thermoluminescent dosimeter (TLD) rods in phantoms to investigate the effect of lack of backscatter on exit dose. Comparing the measured dose with anticipated dose calculated using tissue maximum ratio (TMR) or percentage depth dose (PDD) gives rise to a correction factor. This correction factor may be applied to in-vivo dosimetry results to derive true dose to a point within the patient. Measurements in a specially designed humanoid breast phantom as well as patients undergoing radiotherapy treatment were also been done. TLDs with reproducibility of within +/- 3% (1 SD) are irradiated in a series of measurements for 6 and 10 MV photon beams from a medical linear accelerator. The measured exit doses for the different phantom thickness for 6 MV beams are found to be lowered by 10.9 to 14.0% compared to the dose derived from theoretical estimation (normalized dose at dmax). The same measurements for 10 MV beams are lowered by 9.0 to 13.5%. The variations of measured exit dose for different field sizes are found to be within 2.5%. The exit doses with added backscatter material from 2 mm up to 15 cm, shows gradual increase and the saturated values agreed within 1.5% with the expected results for both beams. The measured exit doses in humanoid breast phantom as well as in the clinical trial on patients undergoing radiotherapy also agreed with the predicted results based on phantom measurements. The authors' viewpoint is that this technique provides sufficient information to design exit surface bolus to restore build down effect in cases where part of the exit surface is being considered as a target volume. It indicates that the technique could be translated for in vivo dose measurements, which may be a conspicuous step of quality assurance in clinical practice. PMID:12416587

Banjade, D P; Shrestha, S L; Shukri, A; Tajuddin, A A; Bhat, M

2002-09-01

255

An evaluation of maximum likelihood reconstruction for SPECT

A reconstruction method for SPECT (single photon emission computerized tomography) that uses the maximum likelihood (ML) criterion and an iterative expectation-maximization (EM) algorithm solution is examined. The method is based on a model that incorporates the physical effects of photon statistics, nonuniform photon attenuation, and a camera-dependent point-spread response function. Reconstructions from simulation experiments are presented which illustrate the ability

E. S. Chornoboy; C. J. Chen; M. I. Miller; T. R. Miller; D. L. Snyder

1990-01-01

256

Background:High incidences of cardiovascularevents coincide with a surge in blood pressure (BP) that occurs in the early morning hours at the time of arousal. Thus, control of BP at this time of day, using oral fixed-dose combinations (FDCs) as required, is important in reducing cardiovascular risk in hypertensive patients.

Yves Lacourcière; Joel M. Neutel; Helmut Schumacher

2005-01-01

257

An empirical model for independent dose verification of the Gamma Knife treatment planning.

A formalism for an independent dose verification of the Gamma Knife treatment planning is developed. It is based on the approximation that isodose distribution for a single shot is in the shape of an ellipsoid in three-dimensional space. The dose profiles for a phantom along each of the three major axes are fitted to a function which contains the terms that represent the contributions from a point source, an extrafocal scattering, and a flat background. The fitting parameters are extracted for all four helmet collimators, at various shot locations, and with different skull shapes. The 33 parameters of a patient's skull shape obtained from the Skull Scaling Instrument measurements are modeled for individual patients. The relative doses for a treatment volume in the form of 31 x 31 x 31 matrix of points are extracted from the treatment planning system, the Leksell Gamma-Plan (LGP). Our model evaluates the relative doses using the same input parameters as in the LGP, which are skull measurement data, shot location, weight, gamma-angle of the head frame, and helmet collimator size. For 29 single-shot cases, the discrepancy of dose at the focus point between the calculation and the LGP is found to be within -1% to 2%. For multi-shot cases, the value and the coordinate of the maximum dose point from the calculation agree within +/-7% and +/-3 mm with the LGP results. In general, the calculated doses agree with the LGP calculations within +/-10% for the off-center locations. Results of calculation with this method for the dimension and location of the 50% isodose line are in good agreement with results from Leksell GammaPlan. Therefore, this method can be served as a useful tool for secondary quality assurance of Gamma Knife treatment plans. PMID:12349920

Phaisangittisakul, Nakorn; Ma, Lijun

2002-09-01

258

On March 1, 1954, radioactive fallout from the nuclear test at Bikini Atoll code-named BRAVO was deposited on Utirik Atoll which lies about 187 km (300 miles) east of Bikini Atoll. The residents of Utirik were evacuated three days after the fallout started and returned to their atoll in May 1954. In this report we provide a final dose assessment for current conditions at the atoll based on extensive data generated from samples collected in 1993 and 1994. The estimated population average maximum annual effective dose using a diet including imported foods is 0.037 mSv y{sup -1} (3.7 mrem y{sup -1}). The 95% confidence limits are within a factor of three of their population average value. The population average integrated effective dose over 30-, 50-, and 70-y is 0.84 mSv (84, mrem), 1.2 mSv (120 mrem), and 1.4 mSv (140 mrem), respectively. The 95% confidence limits on the population-average value post 1998, i.e., the 30-, 50-, and 70-y integral doses, are within a factor of two of the mean value and are independent of time, t, for t > 5 y. Cesium-137 ({sup 137}Cs) is the radionuclide that contributes most of this dose, mostly through the terrestrial food chain and secondarily from external gamma exposure. The dose from weapons-related radionuclides is very low and of no consequence to the health of the population. The annual background doses in the U. S. and Europe are 3.0 mSv (300 mrem), and 2.4 mSv (240 mrem), respectively. The annual background dose in the Marshall Islands is estimated to be 1.4 mSv (140 mrem). The total estimated combined Marshall Islands background dose plus the weapons-related dose is about 1.5 mSv y{sup -1} (150 mrem y{sup -1}) which can be directly compared to the annual background effective dose of 3.0 mSv y{sup -1} (300 mrem y{sup -1}) for the U. S. and 2.4 mSv y{sup -1} (240 mrem y{sup -1}) for Europe. Moreover, the doses listed in this report are based only on the radiological decay of {sup 137}Cs (30.1 y half-life) and other radionuclides. However, we continually see {sup 137}Cs in the groundwater at all contaminated atolls; the turnover time of the groundwater is about 5 y. The {sup 137}Cs can only get to the groundwater by leaching through the soil column when a portion of the soluble fraction of {sup 137}Cs inventory in the soil is transported to the groundwater when rainfall is heavy enough to cause recharge of the aquifer. This process is causing a loss of {sup 137}Cs out of the root zone of the plants that provides an environmental loss constant ({lambda}{sub env}) in addition to radiological decay {lambda}{sub rad}. Consequently, there is an effective rate of loss, {lambda}{sub eff} = {lambda}{sub rad} + {lambda}{sub env} that is the sum of the radiological and environmental-loss decay constants. We have had, and continue to have, a vigorous program to determine the rate of the environmental loss process. What we do know at this time is that the loss of {sup 137}Cs over time is greater than the estimate based on radiological decay only, and that the actual dose received by the Utirik people over 30-, 50-, or 70-y will be less than those presented in this report.

Robison, W.L.; Conrado, C.L.; Bogen, K.T

1999-10-06

259

Dose enhancement by various nanoparticles in prostate brachytherapy.

The aim of this Monte Carlo study is to calculate dose enhancement in tumours by various nanoparticles in prostate brachytherapy using (125)I interstitial implants. ProstaSeed (125)I brachytherapy source was simulated using MCNPX Monte Carlo code. Dose rate constant, radial dose function and anisotropy function values were calculated and compared with previously published data. Dose enhancement factors (DEFs) were calculated for Fe2O3, Ag, Gd, Pt and Au nanoparticles with concentrations of 7, 18 and 30 mg/ml. Our source simulation was validated by comparing our results with previously published data. Maximum DEF values on the central transverse line, within the tumour, for Fe2O3, Ag, Gd, Pt and Au nanoparticles with 30 mg/ml concentration were 1.27, 1.15, 1.14, 1.32, 1.79, respectively. No general trend in DEF with increasing atomic number, or concentration of nanoparticles was observed. However, DEF was the highest for 30 mg/ml concentration of Au. The 50 % isodose line tightened toward the central point of the spherical tumour and the central 100 % isodose line expanded outward. The presence of nanoparticles in a prostate tumour increases the dose inside tumour and decreases the dose outside it, thus the treatment time and source activity can be decreased due to dose enhancement in the tumour. While more preclinical studies on other aspects are necessary, using nanoparticles can be proposed as a useful tool in prostate brachytherapy. Au nanoparticles with higher concentrations can be more useful for this purpose when compared to other nanoparticles. PMID:24307601

Ghorbani, Mahdi; Bakhshabadi, Mahdi; Golshan, Alireza; Knaup, Courtney

2013-12-01

260

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

261

The objective of this study was to determine the toxicities and maximum tolerated dose (MTD) of a dose-dense schedule with a fixed dose of cisplatin and escalating doses of paclitaxel in patients with metastatic or irresectable squamous cell-, adeno-, or undifferentiated carcinoma of the oesophagus. Patients received paclitaxel over 3 h followed by a 3-h infusion of a fixed dose

M. B Polee; J Verweij; P. D Siersema; H. W Tilanus; T. A. W Splinter; G Stoter; A Van der Gaast

2002-01-01

262

Maximum Urban Heat Island Intensity in Seoul.

NASA Astrophysics Data System (ADS)

The maximum urban heat island (UHI) intensity in Seoul, Korea, is investigated using data measured at two meteorological observatories (an urban site and a rural site) during the period of 1973-96. The average maximum UHI is weakest in summer and is strong in autumn and winter. Similar to previous studies for other cities, the maximum UHI intensity is more frequently observed in the nighttime than in the daytime, decreases with increasing wind speed, and is pronounced for clear skies. A multiple linear regression analysis is performed to relate the maximum UHI to meteorological elements. Four predictors considered in this study are the maximum UHI intensity for the previous day, wind speed, cloudiness, and relative humidity. The previous-day maximum UHI intensity is positively correlated with the maximum UHI, and the wind speed, cloudiness, and relative humidity are negatively correlated with the maximum UHI intensity. Among the four predictors, the previous-day maximum UHI intensity is the most important. The relative importance among the predictors varies depending on time of day and season. A three-layer back-propagation neural network model with the four predictors as input units is constructed to predict the maximum UHI intensity in Seoul, and its performance is compared with that of a multiple linear regression model. For all test datasets, the neural network model improves upon the regression model in predicting the maximum UHI intensity. The improvement of the neural network model upon the regression model is 6.3% for the unstratified test data, is higher in the daytime (6.1%) than in the nighttime (3.3%), and ranges from 0.8% in spring to 6.5% in winter.

Kim, Yeon-Hee; Baik, Jong-Jin

2002-06-01

263

Dose profile measurement of a four-dimensional CT (4D-CT) including scattered radiation

NASA Astrophysics Data System (ADS)

We have developed a four-dimensional CT (4D CT) using continuous rotation of cone-beam x-ray. The maximum nominal beam width of the 4D CT is 128 mm at the center of rotation in the longitudinal direction. In order to obtain appropriate estimations of exposure dose, detailed single-slice dose profi les perpendicular to the rotation axis including scattered radiation were measured in PMMA cylindrical phantoms, which were cylindrical lucite phantoms of 160 mm and 320 mm diameter and 900 mm length. Dose profi les were measured with a pin photodiode detector at the center and a peripheral point of 10 mm depth. A pin silicon photodiode sensor with 3 × 3 × 3 mm sensitive region was used as an x-ray detector, which was scanned along longitudinal direction in the phantom for beam widths of 20, 42, 74, 106 and 138 mm. The dose profi les had long tails caused by scattered radiation more than 200 mm out of the beam width edge. The exposure dose covered 95 % was distributed along about 360 mm length at the center and about 310 mm at the periphery, which was independent of the beam width. Before the advent of multi-detector CT, CTDI100 was used to approximate integral dose for clinical scan conditions. However, for 4D CT employing a variable beam width, the standard CTDI was not a good estimation. This work was carried out to establish a method of the dose measurements including scattered radiation for cone-beam CT such as 4D CT. In order to perform the dose assessment including scattered radiation, dose measured length should be recommended to measure integral dose over beam widths plus at least 230 mm, which covered 95 % total exposure dose.

Endo, Masahiro; Mori, Schin'ichiro; Tsunoo, Takanori; Nishizawa, Kanae; Aoyama, Takahiko

2004-05-01

264

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

2010-03-01

265

On the maximum mass of neutron stars

Upper limits to the maximum mass of neutron stars with locally isotropic pressure are derived within the framework of general relativity and discussed. The equations of stellar structure for stars with locally anisotropic pressure are derived from the field equations of general relativity, and upper limits to the maximum mass for such stars as derived and discussed. The equations of

D. R. Mikkelsen

1975-01-01

266

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

267

49 CFR 107.329 - Maximum penalties.

Code of Federal Regulations, 2010 CFR

...the maximum civil penalty is $100,000 if the violation results in death, serious illness...minimum $450 civil penalty applies to a violation...the maximum civil penalty is $100,000 if the violation results in death, serious...

2009-10-01

268

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

269

Radiochemical spectral analysis by maximum likelihood

The radiochemical spectral analysis problem is expressed mathematically. ; Maximum likelihood estimates are derived for the two situations of standard ; spectra well-known and standard spectra imprecise. The maximum likelihood method ; is applied to backward-scattered alpha particle analysis of lunar soil samples ; from the Surveyor V moonlander. The standard spectra are assumed known. (JSR)

W. L. Nicholson; D. L. Jr. Stevens

1975-01-01

270

Maximum Likelihood Estimation in Generalized Rasch Models

We review various models and techniques that have been proposed for item analysis according to the ideas of Rasch. A general model is proposed that unifies them, and maximum likelihood procedures are discussed for this general model. We show that unconditional maximum likelihood estimation in the functional Rasch model, as proposed by Wright and Haberman, is an important special case.

Jan De Leeuw; Norman Verhelst

1986-01-01

271

Maximum Entropy Pole-Zero Estimation.

National Technical Information Service (NTIS)

Maximum Entropy has been suggested by numerous authors as a good objective measure for optimally modeling the power spectrum of a wide-sense stationary random process. This documents describes a new Maximum Entropy pole-zero spectrum estimation method. Th...

B. R. Musicus A. M. Kabel

1985-01-01

272

Motion from point matches: Multiplicity of solutions

In this paper, we study the multiplicity of solutions of the motion problem. Given n point matches between two frames, how many solutions are there to the motion problem? We show that the maximum number of solutions is 10 when 5 point matches are available. This settles a question that has been around in the computer vision community for a

Olivier D. Faugeras; Stephen J. Maybank

1990-01-01

273

Motion from point matches: multiplicity of solutions

In this article, we study the multiplicity of solutions of the motion problem. Given n point matches between two frames, how many solutions are there to the motion problem ? we show that the maximum number of solutions is 10 when five point matches are available. This settles a question which has been around in the Computer Vision community for

Olivier D. Faugeras; Stephen J. Maybank

1988-01-01

274

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

275

Targeted Maximum Likelihood Estimation of the Parameter of a Marginal Structural Model

Targeted maximum likelihood estimation is a versatile tool for estimating parameters in semiparametric and nonparametric models. We work through an example applying targeted maximum likelihood methodology to estimate the parameter of a marginal structural model. In the case we consider, we show how this can be easily done by clever use of standard statistical software. We point out differences between

Michael Rosenblum; Mark J. van der Laan

2010-01-01

276

A maximum likelihood estimation technique for spatial-temporal modal analysis

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

277

Analytical representation for Varian EDW factors at off-center points

The purpose of this study is to describe and evaluate a new analytical model for Varian enhanced dynamic wedge factors at off-center points. The new model was verified by comparing measured and calculated wedge factors for the standard set of wedge angles (i.e., 15 deg., 30 deg., 45 deg. and 60 deg.), different symmetric and asymmetric fields, and two different photon energies. The maximum difference between calculated and measured wedge factors is less than 2%. The average absolute difference is within 1%. The obtained results indicate that the suggested model can be useful for independent dose calculation with enhanced dynamic wedges.

Kuperman, Vadim Y. [James A. Haley Veterans Hospital, Tampa, Florida 33612 (United States)

2005-05-01

278

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.

279

Triadic conceptual structure of the maximum entropy approach to evolution.

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

280

Instrument air dew point requirements -- 108-P, L, K

The 108 Building dew point analyzers measure dew point at atmospheric pressure. Existing 108 Roundsheets state the maximum dew point temperature shall be less than -50 F. After repeatedly failing to maintain a -50 F dew point temperature Reactor Engineering researched the basis for the existing limit. This report documents the results of the study and provides technical justification for

1994-01-01

281

Validation of maximum-likelihood analysis of electron microscopic autoradiographs

The authors have recently reported a new method based on the maximum-likelihood method of statistics for estimating the concentrations of radioactive tracers in subcellular structures in electron microscopic (EM) autoradiographs. The maximum-likelihood algorithm (MLA) appears to be superior to other widely used methods. It is derived from a Poisson statistical model describing the radioactive decay process and is therefore suitable for the low decay rates observed in EM autoradiography. In contrast to other analytical methods which use transition-probability estimates based on pooled data from many micrographs, the MLA applies the function describing the spread of grains around point sources of radioactivity to each grain and uses the information inherent in the unique configuration of subcellular structures surrounding each grain. Earlier evaluations of the MLA were based on a Gaussian approximation of the function describing the spread of grains around point sources of radioactivity. New validation results based on measurement simulations employing a more completely modeled point-spread function show that the MLA provides significantly improved estimates of tracer distributions compared to the conventional mask-overlay method.

Miller, M.I.; Roysam, B.; Saffitz, J.E.; Larson, K.B.; Thomas, L.J. Jr.

1986-03-01

282

Laplacian eigenvalues and the maximum cut problem

We introduce and study an eigenvalue upper bound?(G) on the maximum cut mc (G) of a weighted graph. The function?(G) has several interesting properties that resemble the behaviour of mc (G). The following results are presented.

Charles Delorme; Svatopluk Poljak

1993-01-01

283

Density estimation by maximum quantum entropy.

National Technical Information Service (NTIS)

A new Bayesian method for non-parametric density estimation is proposed, based on a mathematical analogy to quantum statistical physics. The mathematical procedure is related to maximum entropy methods for inverse problems and image reconstruction. The in...

R. N. Silver T. Wallstrom H. F. Martz

1993-01-01

284

Entropy Maximum Principle and Instantaneous Failure Statistics.

National Technical Information Service (NTIS)

A Shannon entropy for instantaneous failure statistics is defined in terms of an integral over the full epoch of possible failure times. An entropy maximum principle subject only to the normalization of the probability density integral and the existence o...

S. Teitler, A. K. Rajagopal, K. L. Ngai

1984-01-01

285

5 CFR 534.203 - Maximum stipends.

Code of Federal Regulations, 2010 CFR

...L-2 Second year college undergraduate ...L-3 Third year college undergraduate ...L-4 Fourth year college undergraduate ...1 The maximum money amount in...agency may pay a student-employee a...Office of Personnel Management has...

2010-01-01

286

5 CFR 534.203 - Maximum stipends.

Code of Federal Regulations, 2010 CFR

...L-2 Second year college undergraduate ...L-3 Third year college undergraduate ...L-4 Fourth year college undergraduate ...1 The maximum money amount in...agency may pay a student-employee a...Office of Personnel Management has...

2009-01-01

287

A dual method for maximum entropy restoration

NASA Technical Reports Server (NTRS)

A simple iterative dual algorithm for maximum entropy image restoration is presented. The dual algorithm involves fewer parameters than conventional minimization in the image space. Minicomputer test results for Fourier synthesis with inadequate phantom data are given.

Smith, C. B.

1979-01-01

288

Dopamine: biphasic dose responses.

The present article indicates that dopamine and/or its agonists induce biphasic dose-response relationships for numerous endpoints. These include locomotion, pain sensitivity, blood pressure, prolactin secretion, oxytocin release, heart rate, memory, and neuronal adenylate cyclase activity. Biphasic responses were reported predominantly with male Sprague-Dawley rats, but also with mice, dogs, monkeys, and humans. Regardless of the model or endpoint the maximum changes from the control were always modest being within the 10 to 80% range. The range of stimulatory responses was quite variable, extending from slightly greater than a factor of 10 for the endpoints such as memory, pain-vocalization, and diastolic blood pressure to the 10(6) range for prolactin release and the 10(8) range for oxytocin release. Mechanistic studies suggested that the stimulatory and inhibitory effects of dopamine are mediated by different receptors or receptor subtypes having opposite actions and different ligand affinities. PMID:11504182

Calabrese, E J

2001-07-01

289

Monte Carlo-based revised values of dose rate constants at discrete photon energies.

Absorbed dose rate to water at 0.2 cm and 1 cm due to a point isotropic photon source as a function of photon energy is calculated using the EDKnrc user-code of the EGSnrc Monte Carlo system. This code system utilized widely used XCOM photon cross-section dataset for the calculation of absorbed dose to water. Using the above dose rates, dose rate constants are calculated. Air-kerma strength Sk needed for deriving dose rate constant is based on the mass-energy absorption coefficient compilations of Hubbell and Seltzer published in the year 1995. A comparison of absorbed dose rates in water at the above distances to the published values reflects the differences in photon cross-section dataset in the low-energy region (difference is up to 2% in dose rate values at 1 cm in the energy range 30-50 keV and up to 4% at 0.2 cm at 30 keV). A maximum difference of about 8% is observed in the dose rate value at 0.2 cm at 1.75 MeV when compared to the published value. Sk calculations based on the compilation of Hubbell and Seltzer show a difference of up to 2.5% in the low-energy region (20-50 keV) when compared to the published values. The deviations observed in the values of dose rate and Sk affect the values of dose rate constants up to 3%. PMID:24600166

Selvam, T Palani; Shrivastava, Vandana; Chourasiya, Ghanashyam; Babu, D Appala Raju

2014-01-01

290

Maximum forces and deflections from orthodontic appliances.

The maximum bending moment of an orthodontic wire is an important parameter in the design and use of an orthodontic appliance. It is the wire property that determines how much force an appliance can deliver. A bending test which allows direct measurement of the maximum bending moment was developed. Data produced from this test are independent of wire length and configuration. The maximum bending moment, percent recovery, and maximum springback were determined for round and rectangular cross sections of stainless steel, nickel-titanium, and beta-titanium wires. The data suggest the need for more specifically defining maximum moment and maximum springback. Three maximum bending moments are described: Me, My, and Mult. My and Mult are clinically the most significant. Appliances that are required to have no permanent deformation must operate below My. Appliances that exhibit marked permanent deformation may be used in some applications and, if so, higher bending moments can be produced. In order of magnitude, the maximum bending moment at yield is largest in stainless steel, beta-titanium, and nickel-titanium for a given cross section. Nickel-titanium and beta-titanium have significantly larger springback than stainless steel determined at the moment at yield. Nickel-titanium did not follow the theoretical ratio between ultimate bending moment and the bending moment at yield, exhibiting a very large ratio. The study supports the hypothesis that most orthodontic appliances are activated in a range where both plastic and elastic behavior occurs; therefore, the use of yield strengths for calculation of force magnitude can lead to a significant error in predicting the forces delivered. PMID:6576645

Burstone, C J; Goldberg, A J

1983-08-01

291

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

292

MAXIMUM NORM ANALYSIS OF OVERLAPPING NONMATCHING GRID DISCRETIZATIONS OF ELLIPTIC EQUATIONS

In this paper, we provide a maximum norm analysis of a finite difference scheme defined on overlapping nonmatching grids for second order elliptic equations. We consider a domain which is the union of p overlapping subdomains where each subdomain has its own independently generated grid. The grid points on the subdomain boundaries need not match the grid points from adjacent

XIAO-CHUAN CAI; TAREK P. MATHEW; MARCUS V. SARKIS

1998-01-01

293

We present in this paper a comprehensive analysis of the mutual information based feature selection algorithms. We point out the limitations of some recent work in this area then propose an improvement to overcome the weak points. The experiment results confirm that we achieve a better feature sets compared with the two recent developed algorithms, which are Maximum Relevance and

La The Vinh; Nguyen Duc Thang; Young-Koo Lee

2010-01-01

294

Dose rate effects on total dose damage

Total ionizing dose tests have been performed on MOS n-channel and p-channel devices at various dose rates. These tests were made at two test temperatures, 23 C and 125 C, and at two widely differing dose rates. The threshold shifts at the various dose rates and temperatures are compared. The total threshold shifts are separated into the contributions from interface

Joseph L. Azarewicz

1986-01-01

295

Low-dosage Maximum-A-Posteriori Focusing and Stigmation.

Radiation damage is often an issue during high-resolution imaging, making low-dose focusing and stigmation essential, in particular when no part of the sample can be "sacrificed" for this. An example is serial block-face electron microscopy, where the imaging resolution must be kept optimal during automated acquisition that can last months. Here, we present an algorithm, which we call "Maximum-A-Posteriori Focusing and Stigmation (MAPFoSt)," that was designed to make optimal use of the available signal. We show that MAPFoSt outperforms the built-in focusing algorithm of a commercial scanning electron microscope even at a tenfold reduced total dose. MAPFoSt estimates multiple aberration modes (focus and the two astigmatism coefficients) using just two test images taken at different focus settings. Using an incident electron dose density of 2,500 electrons/pixel and a signal-to-noise ratio of about one, all three coefficients could be estimated to within <7% of the depth of focus, using 19 detected secondary electrons per pixel. A generalization to higher-order aberrations and to other forms of imaging in both two and three dimensions appears possible. PMID:23380003

Binding, Jonas; Mikula, Shawn; Denk, Winfried

2013-02-01

296

NASA Technical Reports Server (NTRS)

The overall objective of this study was to apply and evaluate several of the currently available classification schemes for crop identification. The approaches examined were: (1) a per point Gaussian maximum likelihood classifier, (2) a per point sum of normal densities classifier, (3) a per point linear classifier, (4) a per point Gaussian maximum likelihood decision tree classifier, and (5) a texture sensitive per field Gaussian maximum likelihood classifier. Three agricultural data sets were used in the study: areas from Fayette County, Illinois, and Pottawattamie and Shelby Counties in Iowa. The segments were located in two distinct regions of the Corn Belt to sample variability in soils, climate, and agricultural practices.

Scholz, D.; Fuhs, N.; Hixson, M.

1979-01-01

297

NASA Astrophysics Data System (ADS)

Optimizing targeted radionuclide therapy requires patient-specific estimation of organ doses. The organ doses are estimated from quantitative nuclear medicine imaging studies, many of which involve planar whole body scans. We have previously developed the quantitative planar (QPlanar) processing method and demonstrated its ability to provide more accurate activity estimates than conventional geometric-mean-based planar (CPlanar) processing methods using physical phantom and simulation studies. The QPlanar method uses the maximum likelihood-expectation maximization algorithm, 3D organ volume of interests (VOIs), and rigorous models of physical image degrading factors to estimate organ activities. However, the QPlanar method requires alignment between the 3D organ VOIs and the 2D planar projections and assumes uniform activity distribution in each VOI. This makes application to patients challenging. As a result, in this paper we propose an extended QPlanar (EQPlanar) method that provides independent-organ rigid registration and includes multiple background regions. We have validated this method using both Monte Carlo simulation and patient data. In the simulation study, we evaluated the precision and accuracy of the method in comparison to the original QPlanar method. For the patient studies, we compared organ activity estimates at 24 h after injection with those from conventional geometric mean-based planar quantification using a 24 h post-injection quantitative SPECT reconstruction as the gold standard. We also compared the goodness of fit of the measured and estimated projections obtained from the EQPlanar method to those from the original method at four other time points where gold standard data were not available. In the simulation study, more accurate activity estimates were provided by the EQPlanar method for all the organs at all the time points compared with the QPlanar method. Based on the patient data, we concluded that the EQPlanar method provided a substantial increase in accuracy of organ activity estimates from 24 h planar images compared to the CPlanar using 24 h SPECT as the golden standard. For other time points, where no golden standard is available, better agreement between estimated and measured projections was observed by using the EQPlanar method compared to the QPlanar method. This phenomenon is consistent with the improvement in goodness of fit seen in both simulation data and 24 h patient data. Therefore, this indicates the improved reliability of organ activity estimates obtained though the EQPlanar method.

Song, N.; He, B.; Wahl, R. L.; Frey, E. C.

2011-09-01

298

Maximum magnitudes in aftershock sequences in Taiwan

NASA Astrophysics Data System (ADS)

In this work, Båth's Law, the b-value in Gutenberg–Richter Law (G–R Law) in the form of the 1/? relationship, and both the a- and b-values in the G–R Law were introduced in order to estimate maximum aftershock magnitudes of earthquake sequences in the Taiwan region. The averaged difference of magnitude between the mainshock and the maximum aftershock is 1.20, and is consistent with Båth's Law, however, with a large uncertainty. The large uncertainty implies that the difference may result from a variable controlled by other factors, such as the aftershocks number of an earthquake sequence and magnitude threshold for mainshock. With 1/?, since 86% of the earthquake sequences with a M ? 6.0 mainshock follow this relationship, the upper bound of the maximum magnitude can be estimated for an earthquake sequence with a large mainshock. The a- and b-values in the G–R Law was also considered by evaluating maximum aftershock magnitudes. As there are low residuals between the model and the observations, the results suggest that the G–R Law is a good index for maximum aftershock magnitude determinations. In order to evaluate the temporal decays of maximum aftershock magnitudes, modified Omori's Law was introduced. Using the approaches mentioned above, the maximum magnitudes and the temporal evolution of an earthquake sequence could be modeled. Among them, the model of the G–R Law has the best fit with observations for most of earthquake sequences. It shows its feasibility. The results of this work may benefit seismic hazards mitigation in the form of rapid re-evaluations for short-term seismic hazards immediately following devastating earthquakes.

Chan, Chung-Han; Wu, Yih-Min

2013-09-01

299

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

300

Acute effects of high-dose methylprednisolone on diaphragm muscle function.

The time- and dose-dependent effects of acute high-dose corticosteroids on the diaphragm muscle are poorly defined. This study aimed to examine in rabbits the temporal relationships and dose-response effects of acute high-dose methylprednisolone succinate on diaphragmatic contractile and structural properties. Animals were assigned to groups receiving: (1) 80 mg/kg/day methylprednisolone (MP80) intramuscularly for 1, 2, and 3 days; (2) 10 mg/kg/day methylprednisolone (MP10, pulse-dose) for 3 days; or (3) saline (placebo) for 3 days; and (4) a control group. Diaphragmatic in vitro force-frequency and force-velocity relationships, myosin heavy chain (MyHC) isoform protein and mRNA, insulin-like growth factor-1 (IGF-1), muscle atrophy F-box (MAF-box) mRNA, and volume density of abnormal myofibrils were measured at each time-point. MP80 did not affect animal nutritional state or fiber cross-sectional area as assessed in separate pair-fed groups receiving methylprednisolone or saline for 3 days. Compared with control values, MP80 decreased diaphragmatic maximum tetanic tension (Po) by 19%, 24%, and 34% after 1, 2, and 3 days (P < 0.05), respectively, whereas MP10 decreased Po modestly (12%; P > 0.05). Vmax and MyHC protein proportions were unchanged in both the MP80 and MP10 groups. Maximum power output decreased after 2 and 3 days of MP80. Suppression of IGF-1 and overexpression of MAF-box mRNA occurred in both MP groups. Significant myofibrillar disarray was also observed in both MP groups. The decline in Po was significantly associated with the increased volume density of abnormal myofibrils. Thus, very high-dose methylprednisolone (MP80) can produce rapid reductions in diaphragmatic function, whereas pulse-dose methylprednisolone (MP10) produces only modest functional loss. PMID:18671291

Sassoon, Catherine S H; Zhu, Ercheng; Pham, H Tony; Nelson, Renee S; Fang, Liwei; Baker, Michael J; Caiozzo, Vincent J

2008-09-01

301

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

302

Docetaxel, a novel anticancer agent, was given to 26 patients by short i.v. infusion (1–2 h) at various dose levels (70–115 mg\\/m2, the maximum tolerated dose) during 2 phase I studies. Two population analyses, one using NONMEM (nonlinear mixed-effect modeling) and the other using NPML (nonparametric maximum-likelihood), were performed sequentially to determine the structural model; estimate the mean population parameters,

M. C. Launay-Iliadis; R. Bruno; V. Cosson; J. C. Vergniol; D. Oulid-Aissa; M. Marty; M. Clavel; M. Aapro; N. Bail; A. Iliadis

1995-01-01

303

National Technical Information Service (NTIS)

Direct current (dc) motors are used in terrestrial photovoltaic (PV) systems such as in water-pumping systems for irrigation and water supply. Direct current motors may also be used for space applications. Simple and low weight systems including dc motors...

J. Appelbaum S. Singer

1989-01-01

304

Equipment for testing of maximum power point trackers under variable, programmable conditions.

National Technical Information Service (NTIS)

MPPT performance measurement equipment is presented which allows test and comparison of MPPT's under equivalent, predefined conditions. The equipment consists of a hardware simulator of predefined insolation and temperature patterns, of the particular sol...

A. T. Veltman R. Kloeckner K. K. W. Geers J. Van Twisk

1991-01-01

305

Modeling of Wind Turbine Driving Permanent Magnet Generator with Maximum Power Point Tracking System

This paper elaborates on the analysis and simulation of 15 kW Wind Turbine Generator (WTG) driving low speed Permanent Magnet Synchronous Generator (PMSG) using PSIM computer simulation program. The system consists of wind turbine, permanent magnet generator, three-phase diode rectifier, boost converter, and voltage source inverter models. In the WTG model, the best performance coefficient has been determined according to

Ali M. Eltamaly

2007-01-01

306

Maximum power point tracking using GA-optimized artificial neural network for Solar PV system

Solar energy is a green energy which is not only perennial but also accessible to every strata of the world. An easy way to convert solar energy into electric energy is to use Solar Photovoltaic (SPV) system. Solar panel is a power source having nonlinear internal resistance. As the intensity of light falling on the panel varies, its voltage as

R. Ramaprabha; V. Gothandaraman; K. Kanimozhi; R. Divya; B. L. Mathur

2011-01-01

307

In the present study, a number of brachytherapy sources and activation media were simulated using MCNPX code and the results were analyzed based on the dose enhancement factor values. Furthermore, two new brachytherapy sources (¹³¹Cs and a hypothetical ¹??Tm) were evaluated for their application in photon activation therapy (PAT). ¹²?I, ¹?³Pd, ¹³¹Cs and hypothetical ¹??Tm brachytherapy sources were simulated in water and their dose rate constant and the radial dose functions were compared with previously published data. The sources were then simulated in a soft tissue phantom which was composed of Ag, I, Pt or Au as activation media uniformly distributed in the tumour volume. These simulations were performed using the MCNPX code, and dose enhancement factor (DEF) was obtained for 7, 18 and 30 mg/ml concentrations of the activation media. Each source, activation medium and concentration was evaluated separately in a separate simulation. The calculated dose rate constant and radial dose functions were in agreement with the published data for the aforementioned sources. The maximum DEF was found to be 5.58 for a combination of the ¹??Tm source with 30 mg/ml concentration of I. The DEFs for ¹³¹Cs and ¹??Tm sources for all the four activation media were higher than those for other sources and activation media. From this point of view, these two sources can be more useful in photon activation therapy with photon emitter sources. Furthermore, ¹³¹Cs and ¹??Tm brachytherapy sources can be proposed as new options for use in the field of PAT. PMID:23934379

Bakhshabadi, Mahdi; Ghorbani, Mahdi; Meigooni, Ali Soleimani

2013-09-01

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

A Maximum Likelihood Approach to Estimating Correlation Functions

NASA Astrophysics Data System (ADS)

We define a maximum likelihood (ML for short) estimator for the correlation function, ?, that uses the same pair counting observables (D, R, DD, DR, RR) as the standard Landy & Szalay (LS for short) estimator. The ML estimator outperforms the LS estimator in that it results in smaller measurement errors at any fixed random point density. Put another way, the ML estimator can reach the same precision as the LS estimator with a significantly smaller random point catalog. Moreover, these gains are achieved without significantly increasing the computational requirements for estimating ?. We quantify the relative improvement of the ML estimator over the LS estimator and discuss the regimes under which these improvements are most significant. We present a short guide on how to implement the ML estimator and emphasize that the code alterations required to switch from an LS to an ML estimator are minimal.

Jones Baxter, Eric; Rozo, Eduardo

2013-12-01

310

Estimation of Maximum Earthquakes in Northeast India

NASA Astrophysics Data System (ADS)

We attempt to estimate possible maximum earthquakes in the northeast Indian region for four seismic source zones, namely EHZ, MBZ, EBZ, and SHZ, which encapsulates the various seismogenic structures of the region and also for combined source zones taken as a single seismic source regime. The latter case exhibits a high maximum earthquake estimate of MW 9.4 (±0.85) through Bayesian interpretation of frequency magnitude distribution with Gamma function implicating a moderate deviation from the standard Gutenberg Richter model at the higher magnitudes. However, tapering Gutenberg Richter models with corner magnitudes at MW 8.01, 8.7 and 9.1, respectively indicated maximum values corresponding to MW 8.4, 9.0, and 9.3. The former approach was applied to each of the source zones wherein the data are presented in parts according to the data completeness, thereof. EHZ, MBZ, EBZ and SHZ are seen with maximum earthquakes of MW 8.35 (±0.59), 8.79 (±0.31), 8.20 (±0.50), and 8.73 (±0.70), respectively. The maximum possible earthquakes estimated for each individual zone are seen to be lower than that estimated for the single regime. However, the pertaining return periods estimated for the combined zone are far less than those estimated for the demarcated ones.

Thingbaijam, K. K. S.; Nath, S. K.

2008-05-01

311

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

312

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

313

Gigantic Maximum of Nanoscale Noncontact Friction

NASA Astrophysics Data System (ADS)

We report measurements of noncontact friction between surfaces of NbSe2 and SrTiO3 and a sharp Pt-Ir tip that is oscillated laterally by a quartz tuning fork cantilever. At 4.2 K, the friction coefficients on both the metallic and insulating materials show a giant maximum at the tip-surface distance of several nanometers. The maximum is strongly correlated with an increase in the spring constant of the cantilever. These features can be understood phenomenologically by a distance-dependent relaxation mechanism with distributed time scales.

Saitoh, Kohta; Hayashi, Kenichi; Shibayama, Yoshiyuki; Shirahama, Keiya

2010-12-01

314

Density estimation by maximum quantum entropy

A new Bayesian method for non-parametric density estimation is proposed, based on a mathematical analogy to quantum statistical physics. The mathematical procedure is related to maximum entropy methods for inverse problems and image reconstruction. The information divergence enforces global smoothing toward default models, convexity, positivity, extensivity and normalization. The novel feature is the replacement of classical entropy by quantum entropy, so that local smoothing is enforced by constraints on differential operators. The linear response of the estimate is proportional to the covariance. The hyperparameters are estimated by type-II maximum likelihood (evidence). The method is demonstrated on textbook data sets.

Silver, R.N.; Wallstrom, T.; Martz, H.F.

1993-11-01

315

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

316

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.1 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

317

24 CFR 941.306 - Maximum project cost.

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 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...

2010-04-01

318

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

319

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

320

40 CFR 94.107 - Determination of maximum test speed.

Code of Federal Regulations, 2010 CFR

...false Determination of maximum test speed. 94.107 Section 94.107 Protection...107 Determination of maximum test speed. (a) Overview. This section specifies how to determine maximum test speed from a lug curve. This maximum...

2009-07-01

321

40 CFR 94.107 - Determination of maximum test speed.

Code of Federal Regulations, 2013 CFR

...false Determination of maximum test speed. 94.107 Section 94.107 Protection...107 Determination of maximum test speed. (a) Overview. This section specifies how to determine maximum test speed from a lug curve. This maximum...

2013-07-01

322

40 CFR 94.107 - Determination of maximum test speed.

Code of Federal Regulations, 2010 CFR

...false Determination of maximum test speed. 94.107 Section 94.107 Protection...107 Determination of maximum test speed. (a) Overview. This section specifies how to determine maximum test speed from a lug curve. This maximum...

2010-07-01

323

40 CFR 141.13 - Maximum contaminant levels for turbidity.

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Maximum contaminant levels for turbidity. 141.13 Section 141.13...DRINKING WATER REGULATIONS Maximum Contaminant Levels Â§ 141.13 Maximum contaminant levels for turbidity. The maximum...

2013-07-01

324

40 CFR 141.65 - Maximum residual disinfectant levels.

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Maximum residual disinfectant levels. 141.65 Section 141.65 Protection...Drinking Water Regulations: Maximum Contaminant Levels and Maximum Residual Disinfectant Levels Â§ 141.65 Maximum residual...

2013-07-01

325

This work is the development of a MOSFET based surface in vivo dosimetry system for total body irradiation patients treated with bilateral extended SSD beams using PMMA missing tissue compensators adjacent to the patient. An empirical formula to calculate midplane dose from MOSFET measured entrance and exit doses has been derived. The dependency of surface dose on the air-gap between the spoiler and the surface was investigated by suspending a spoiler above a water phantom, and taking percentage depth dose measurements (PDD). Exit and entrances doses were measured with MOSFETs in conjunction with midplane doses measured with an ion chamber. The entrance and exit doses were combined using an exponential attenuation formula to give an estimate of midplane dose and were compared to the midplane ion chamber measurement for a range of phantom thicknesses. Having a maximum PDD at the surface simplifies the prediction of midplane dose, which is achieved by ensuring that the air gap between the compensator and the surface is less than 10 cm. The comparison of estimated midplane dose and measured midplane dose showed no dependence on phantom thickness and an average correction factor of 0.88 was found. If the missing tissue compensators are kept within 10 cm of the patient then MOSFET measurements of entrance and exit dose can predict the midplane dose for the patient. PMID:22298238

Satory, P R

2012-03-01

326

Maximum Fillet Stresses in Breech Ring.

National Technical Information Service (NTIS)

The effect of fillet geometry and wall thickness on maximum fillet stresses was investigated in the 105mm M137 Howitzer breech ring. The NASTRAN finite element analysis of three fillet geometries and two wall thicknesses shows that an elliptical fillet is...

Y. F. Cheng

1972-01-01

327

Maximum versus meaningful discrimination in scale response

This paper argues for the use of the number of response categories that are meaningful to respondents as a criterion in designing attribute rating scales in marketing in contrast to a focus in past research on using scales to maximize the discrimination elicited from respondents. Whereas scales eliciting a maximum level of discrimination may be more reliable than scales eliciting

Madhubalan Viswanathan; Seymour Sudman; Michael Johnson

2004-01-01

328

Maximum Sunspot Numbers and Active Days

NASA Astrophysics Data System (ADS)

Parameters associated with solar minimum have been studied to relate them to solar activity at solar maximum so that one could possibly predict behaviors of an upcoming solar cycle. The number of active days has been known as a reliable indicator of solar activity around solar minimum. Active days are days with sunspots reported on the solar disk. In this work, we have explored the relationship between the sunspot numbers at solar maximum and the characteristics of the monthly number of active days. Specifically, we have statistically examined how the maximum monthly sunspot number of a given solar cycle is correlated with the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days for the corresponding solar cycle. We have calculated the linear correlation coefficient r and the Spearman rank-order correlation coefficient rs for data sets prepared under various conditions. Even though marginal correlations are found, they turn out to be insufficiently significant (r ~ 0.3). Nonetheless, we have confirmed that the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days is less steep when solar cycles belonging to the "Modern Maximum" are considered compared with rests of solar cycles. We conclude, therefore, that the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days is indeed dependent on the solar activity at its maxima, but that this simple relationship should be insufficient as a valid method to predict the following solar activity amplitude.

Chang, Heon-Young

2013-09-01

329

Maximum output of an OTEC power plant

This paper theoretically investigates the effects of the temperature and flowrate of cold seawater on the net output of an OTEC plant. Parameters of pipe length, pipe diameter, seawater depth, and the flowrate of seawater are considered. It shows that a maximum output of the net work exists at a certain flowrate of cooling seawater. The output work is higher

Rong-Hua Yeh; Tar-Zen Su; Min-Shong Yang

2005-01-01

330

Heliospheric Magnetic Field Structure At Solar Maximum

The evolution of the heliospheric magnetic field (HMF) from the relative simplicity at solar minimum has been charted by the Ulysses spacecraft through the ascending phase of the solar cycle through the recent maximum activity epoch. The changes that occurred in solar and coronal magnetic fields from 1997 to 2001 are reflected in a com- plex way in the evolution

A. Balogh; E. J. Smith; R. J. Forsyth; G. H. Jones; D. J. McComas

2002-01-01

331

Mammographic image restoration using maximum entropy deconvolution

An image restoration approach based on a Bayesian maximum entropy method (MEM) has been applied to a radiological image deconvolution problem, that of reduction of geometric blurring in magnification mammography. The aim of the work is to demonstrate an improvement in image spatial resolution in realistic noisy radiological images with no associated penalty in terms of reduction in the signal-to-noise

A. Jannetta; J. C. Jackson; C. J. Kotre; I. P. Birch; K. J. Robson; R. Padgett

2004-01-01

332

Predicting maximum lake depth from surrounding topography.

Information about lake morphometry (e.g., depth, volume, size, etc.) aids understanding of the physical and ecological dynamics of lakes, yet is often not readily available. The data needed to calculate measures of lake morphometry, particularly lake depth, are usually collected on a lake-by-lake basis and are difficult to obtain across broad regions. To span the gap between studies of individual lakes where detailed data exist and regional studies where access to useful data on lake depth is unavailable, we developed a method to predict maximum lake depth from the slope of the topography surrounding a lake. We use the National Elevation Dataset and the National Hydrography Dataset - Plus to estimate the percent slope of surrounding lakes and use this information to predict maximum lake depth. We also use field measured maximum lake depths from the US EPA's National Lakes Assessment to empirically adjust and cross-validate our predictions. We were able to predict maximum depth for ?28,000 lakes in the Northeastern United States with an average cross-validated RMSE of 5.95 m and 5.09 m and average correlation of 0.82 and 0.69 for Hydrological Unit Code Regions 01 and 02, respectively. The depth predictions and the scripts are openly available as supplements to this manuscript. PMID:21984945

Hollister, Jeffrey W; Milstead, W Bryan; Urrutia, M Andrea

2011-01-01

333

Multiple target tracking using maximum likelihood principle

Proposes a method (tracking algorithm (TAL)) based on the maximum likelihood (ML) principle for multiple target tracking in near-field using outputs from a large uniform linear array of passive sensors. The targets are assumed to be narrowband signals and modeled as sample functions of a Gaussian stochastic process. The phase delays of these signals are expressed as functions of both

A. Satish; Rangasami L. Kashyap

1995-01-01

334

Entropy Maximum Principle and Relaxation Phenomena.

National Technical Information Service (NTIS)

A Shannon (epoch) entropy is defined in terms of an integral over the full temporal epoch of relaxation. A maximum entropy principle yields a linear exponential as a fundamental form for relaxation to equilibrium. It is observed that the time scale of mea...

A. K. Rajagopal, S. Teitler, K. L. Ngai

1984-01-01

335

Maximum entropy image restoration in astronomy

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

336

A ship moving steadily forward in shallow water of constant depth h is usually subject to downward forces and hence squat, which is a potentially dangerous sinkage or increase in draft. Sinkage increases with ship speed, until it reaches a maximum at just below the critical speed p gh. Here we use both a linear transcritical shallow-water equation and a

T. P. Gourlay; E. O. Tuck

337

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

338

Maximum Residue Limits (MRLs) are standards that represent the maximum residue concentration expected to be found if a veterinary drug is administered according to good practice in the use of veterinary drugs (GVP). MRLs are established only where the exposure to residues in food resulting from particular use patterns of the veterinary drug pass a public health risk assessment. The current model diet as used by major regulators overstates mean consumption of food for populations when compared to results from food surveys of actual consumption. Exposure to residues is overestimated when calculating long-term (chronic) exposure using the model diet leading to the risk to consumers being overstated. Additionally the model diet underestimates the size of large portions eaten by the group of consumers that eat large quantities of a particular food in a single meal potentially leading to understating of risks associated with exposure to residues of drugs that produce an adverse effect after a single exposure. A revision of dietary consumption figures is proposed that will better match the consumption figures used in point-estimates of dietary exposure to the timeframe for consumption that is relevant to the reference dose. PMID:22203043

MacLachlan, Dugald J; Mueller, Utz

2012-02-01

339

Climate Change Impacts on Probable Maximum Precipitation

NASA Astrophysics Data System (ADS)

The estimation of the potential impacts of anthropogenic forcing of the climate system on extreme weather events relies heavily on the direct output of global and regional climate models, combined perhaps with extreme value statistical techniques. In this study, we use these tools along with physical and theoretical considerations to examine the potential impacts on Probable Maximum Precipitation estimates. Probable Maximum Precipitation (PMP) is the theoretically greatest depth of precipitation for a given duration that is physically possible over a particular drainage basin at a particular time of year. PMP values are used in the design of long-lived structures with lifetimes of many decades, such as dams. Climate change is an unavoidable consideration on those time scales. Many studies have documented an upward temporal trend in the frequency and intensity of extreme precipitation events. As the globe warms in response to increasing greenhouse gas concentrations, there is the potential for further changes in precipitation extremes. There are reasons why warming could lead to increased PMP values. One, the Clausius-Clapeyron relationship indicates that the saturation water vapor pressure increases with temperature; thus, precipitation-producing systems could have more "fuel" to precipitate. Two, warming may lead to an increase in the length of the convective season, when most of the extreme precipitation events occur. The methodology for estimation of PMP values has changed little over the last 30-40 years. The basic approach is to consider the factors that contribute to heavy precipitation and then consider the potential precipitation rates if all of those factors were simultaneously maximized. Convergence and vertical motion is one factor. Past work has assumed that there no empirical or satisfactory theoretical basis for assigning maximum values to this factor. The approach has been to use observed rainfall in notable storms as an indirect measure of maximum convergence and vertical motion. Notable storms are chosen to indicate the likely occurrence of near-maximum values. A second central factor is moisture availability. Observational data are used to determine maximum levels of moisture availability. Where topographic effects are important, wind maximization is a third factor. We are examining these factors in present-day and future simulations from global and regional climate models. Initial results strongly indicate the possibility for large future increases in maximum moisture, by about the same amount as increases in mean moisture content. This would lead directly to substantial increases in PMP values. Given the potential catastrophic consequences of dam failure, these findings should be considered carefully in future design activities.

Kunkel, K.; Easterling, D. R.

2011-12-01

340

A mathematical absorption model (e.g. transit compartment model) is useful to describe complex absorption process. However, in such a model, an assumption has to be made to introduce multiple doses that a prior dose has been absorbed nearly completely when the next dose is administered. This is because the drug input cannot be determined from drug depot compartment through integration of the differential equation system and has to be analytically calculated. We propose a method of dose superimposition to introduce multiple doses; thereby eliminating the assumption. The code for implementing the dose superimposition in WinNonlin and NONMEM was provided. For implementation in NONMEM, we discussed a special case (SC) and a general case (GC). In a SC, dose superimposition was implemented solely using NM-TRAN abbreviated code and the maximum number of the doses that can be administered for any subject must be pre-defined. In a GC, a user-supplied function (FUNCA) in FORTRAN code was defined to perform dose superimposition to remove the restriction that the maximum number of doses must be pre-defined. PMID:22555854

Shen, Jun; Boeckmann, Alison; Vick, Andrew

2012-06-01

341

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

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.

2013-01-01

342

Maximum Frequency of Beams Including Shear Effects.

National Technical Information Service (NTIS)

The study considers the effect of shear deformation on the optimal design, with respect to the fundamental frequency of transverse vibration of a linear, elastic beam with a point mass attached. Since the system is conservative, Rayleigh's quotient furnis...

J. J. Walters, R. M. Brach

1970-01-01

343

Technical basis for dose reconstruction

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

344

Influence of maximum bite force on jaw movement during gummy jelly mastication.

It is known that maximum bite force has various influences on chewing function; however, there have not been studies in which the relationships between maximum bite force and masticatory jaw movement have been clarified. The aim of this study was to investigate the effect of maximum bite force on masticatory jaw movement in subjects with normal occlusion. Thirty young adults (22 men and 8 women; mean age, 22.6 years) with good occlusion were divided into two groups based on whether they had a relatively high or low maximum bite force according to the median. The maximum bite force was determined according to the Dental Prescale System using pressure-sensitive sheets. Jaw movement during mastication of hard gummy jelly (each 5.5 g) on the preferred chewing side was recorded using a six degrees of freedom jaw movement recording system. The motion of the lower incisal point of the mandible was computed, and the mean values of 10 cycles (cycles 2-11) were calculated. A masticatory performance test was conducted using gummy jelly. Subjects with a lower maximum bite force showed increased maximum lateral amplitude, closing distance, width and closing angle; wider masticatory jaw movement; and significantly lower masticatory performance. However, no differences in the maximum vertical or maximum anteroposterior amplitudes were observed between the groups. Although other factors, such as individual morphology, may influence masticatory jaw movement, our results suggest that subjects with a lower maximum bite force show increased lateral jaw motion during mastication. PMID:24612273

Kuninori, T; Tomonari, H; Uehara, S; Kitashima, F; Yagi, T; Miyawaki, S

2014-05-01

345

Planning Consequences of the Maximum dB(A) CONCEPT—A Perspective

NASA Astrophysics Data System (ADS)

The maximum noise concept based on the noisiest event represents a new principle to control the effects of an environmental pollutant in the urban area. The report describes these newly developed dose descriptors for the relation between exposure and effects and presents examples for practical actions to control noise exposure.

RYLANDER, R.; BJÖRKMAN, M.

2002-02-01

346

Advanced point cloud processing

The high pulse frequencies of today's airborne, mobile and terrestrial laser scanners enable the acquisition of point clouds with densities from some 20-50 points\\/m2 for airborne scanners to several thousands points\\/m2 for mobile and terrestrial scanners. For the (semi-)automated extraction of geo-information from point clouds these high point densities are very beneficial. The large number of points on the surfaces

GEORGE VOSSELMAN

347

Batch maximum likelihood (ML) and maximum a posteriori (MAP) estimation with process noise is now more than thirty-five years old, and its use in multiple target tracking has long been considered to be too computationally intensive for real-time applications. While this may still be true for general usage, it is ideally suited for special needs such as bias estimation, track

Aubrey B. Poore; Benjamin J. Slocumb; Brian J. Suchomel; Fritz H. Obermeyer; Shawn M. Herman; Sabino M. Gadaleta

2004-01-01

348

Batch maximum likelihood (ML) and maximum a posteriori (MAP) estimation with process noise is now more than thirty-five years old, and its use in multiple target tracking has long been considered to be too computationally intensive for real-time applications. While this may still be true for general usage, it is ideally suited for special needs such as bias estimation, track

Aubrey B. Poore; Benjamin J. Slocumb; Brian J. Suchomel; Fritz H. Obermeyer; Shawn M. Herman; Sabino M. Gadaleta

2003-01-01

349

National Technical Information Service (NTIS)

Batch maximum likelihood (ML) and maximum a posteriori (MAP) estimation with process noise is now more than thirty-five years old, and its use in multiple target tracking has long been considered to be too computationally intensive for real-time applicati...

A. B. Poore B. J. Slocumb B. J. Suchomel F. H. Obermeyer S. M. Herman

2003-01-01

350

Failure-probability driven dose painting

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.

Vogelius, Ivan R.; Håkansson, Katrin; Due, Anne K.; Aznar, Marianne C.; Kristensen, Claus A.; Rasmussen, Jacob; Specht, Lena [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark)] [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark); Berthelsen, Anne K. [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark)] [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark); Bentzen, Søren M. [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Departments of Human Oncology and Medical Physics, University of Wisconsin, Madison, Wisconsin 53792 (United States)] [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Departments of Human Oncology and Medical Physics, University of Wisconsin, Madison, Wisconsin 53792 (United States)

2013-08-15

351

Finding maximum colorful subtrees in practice.

In metabolomics and other fields dealing with small compounds, mass spectrometry is applied as a sensitive high-throughput technique. Recently, fragmentation trees have been proposed to automatically analyze the fragmentation mass spectra recorded by such instruments. Computationally, this leads to the problem of finding a maximum weight subtree in an edge-weighted and vertex-colored graph, such that every color appears, at most once in the solution. We introduce new heuristics and an exact algorithm for this Maximum Colorful Subtree problem and evaluate them against existing algorithms on real-world and artificial datasets. Our tree completion heuristic consistently scores better than other heuristics, while the integer programming-based algorithm produces optimal trees with modest running times. Our fast and accurate heuristic can help determine molecular formulas based on fragmentation trees. On the other hand, optimal trees from the integer linear program are useful if structure is relevant, for example for tree alignments. PMID:23509858

Rauf, Imran; Rasche, Florian; Nicolas, François; Böcker, Sebastian

2013-04-01

352

Maximum Noise Levels in City Traffic

NASA Astrophysics Data System (ADS)

Manual and automatic noise measurements were made along 13 streets in Gothenburg, Sweden to explore sources of maximum noise levels. Noise from different types of vehicles driven in a realistic way in inner city traffic was measured. In summary, the results show that the most important vehicle component as regards the maximum noise level in inner city traffic was a medium-weight truck (delivery truck). Among the higher noise levels measured (>80 dB(A)), this type of vehicle is dominant. This is supported by tests that demonstrated that the noise level of a light truck, driven in a realistic way, exceeds that of cars and is on the same level as heavy trucks. Measures can be taken against the noisiest vehicle types specifically, and the noise load can be limited by introducing noise bans for particular streets in which vehicles that emit greater than a certain noise level would not be allowed use of the street.

Björkman, M.; Rylander, R.

1997-08-01

353

Radiation Doses in Perspective

... Health Effects Ionizing & Non-Ionizing Radiation Understanding Radiation: Radiation Doses in Perspective Health Effects Main Page Exposure ... Sources Doses from Common Radiation Sources Average U.S. Radiation Doses and Sources All of us are exposed ...

354

Maximum drag reduction simulation using rodlike polymers

NASA Astrophysics Data System (ADS)

Simulations of maximum drag reduction (MDR) in channel flow using constitutive equations for suspensions of noninteracting rods predict a few-fold larger turbulent kinetic energy than in experiments using rodlike polymers. These differences are attributed to the neglect of interactions between polymers in the simulations. Despite these inconsistencies the simulations correctly reproduce the essential features of MDR, with universal profiles of the mean flow and the shear stress budgets that do not depend on the polymer concentration.

Gillissen, J. J. J.

2012-10-01

355

Maximum likelihood drift estimation for multiscale diffusions

We study the problem of parameter estimation using maximum likelihood for fast\\/slow systems of stochastic differential equations. Our aim is to shed light on the problem of model\\/data mismatch at small scales. We consider two classes of fast\\/slow problems for which a closed coarse-grained equation for the slow variables can be rigorously derived, which we refer to as averaging and

A. Papavasiliou; G. A. Pavliotis; A. M. Stuart

2009-01-01

356

Maximum Likelihood Drift Estimation for Multiscale Diffusions

We study the problem of parameter estimation using maximum likelihood for fast\\/slow systems of stochastic differential equations. Our aim is to shed light on the problem of model\\/data mismatch at small scales. We consider two classes of fast\\/slow problems for which a closed coarse-grained equation for the slow variables can be rigorously derived, which we refer to as averaging and

A. Papavasiliou; G. A. Pavliotis; A. M. Stuart

2008-01-01

357

Maximum entropy and Bayesian methods. Proceedings.

NASA Astrophysics Data System (ADS)

This volume contains a selection of papers presented at the Tenth Annual Workshop on Maximum Entropy and Bayesian Methods. The thirty-six papers included cover a wide range of applications in areas such as economics and econometrics, astronomy and astrophysics, general physics, complex systems, image reconstruction, and probability and mathematics. Together they give an excellent state-of-the-art overview of fundamental methods of data analysis.

Grandy, W. T., Jr.; Schick, L. H.

358

Critical thermal maximum of seven estuarine fishes

Critical thermal maximum (CTM) and loss of righting response (LRR) were determined in seven estuarine fishes. The critical thermal maxima (CTM) ranged from 39.5°C to 44.5°C for fishes acclimated to 28°C. Lates calcarifer and Liza dussumeri had the highest CTM (44.5°C) and Siganus javus had the lowest CTM (39.5°C). The rate of change of CTM due to thermal acclimation was

S. Rajaguru

2002-01-01

359

Maximum entropy production - Full steam ahead

NASA Astrophysics Data System (ADS)

The application of a principle of Maximum Entropy Production (MEP, or less ambiguously MaxEP) to planetary climate is discussed. This idea suggests that if sufficiently free of dynamical constraints, the atmospheric and oceanic heat flows across a planet may conspire to maximize the generation of mechanical work, or entropy. Thermodynamic and information-theoretic aspects of this idea are discussed. These issues are also discussed in the context of dust devils, convective vortices found in strongly-heated desert areas.

Lorenz, Ralph D.

2012-05-01

360

Maximum Mass of a Neutron Star

On the basis of Einstein's theory of relativity, the principle of causality, and Le Chatelier's principle, it is here established that the maximum mass of the equilibrium configuration of a neutron star cannot be larger than 3.2M[m?]. The extremal principle given here applies as well when the equation of state of matter is unknown in a limited range of densities.

Clifford E. Rhoades; Remo Ruffini

1974-01-01

361

Maximum Correntropy Criterion for Robust Face Recognition

In this paper, we present a sparse correntropy framework for computing robust sparse representations of face images for recognition. Compared with the state-of-the-art l 1 norm-based sparse representation classifier (SRC), which assumes that noise also has a sparse representation, our sparse algorithm is developed based on the maximum correntropy criterion, which is much more insensitive to outliers. In order to

Ran He; Wei-Shi Zheng; Bao-Gang Hu

2011-01-01

362

Identifying Semantic Roles Using Maximum Entropy Models

\\u000a In this paper, a supervised learning method of semantic role labeling is presented. It is based on maximum entropy conditional probability models. This method acquires the linguistic knowledge from an annotated corpus and this knowledge is represented in the form of\\u000a features. Several types of features have been analyzed for a few words selected from sections of the Wall Street

Paloma Moreda; Manuel Fernández; Manuel Palomar; Armando Suárez

2004-01-01

363

The maximum rate of mammal evolution.

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

364

"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

365

Maximum Solutions of Normalized Ricci Flow on 4-Manifolds

NASA Astrophysics Data System (ADS)

We consider the maximum solution g( t), t ? [0, + ?), to the normalized Ricci flow. Among other things, we prove that, if ( M, ?) is a smooth compact symplectic 4-manifold such that {b_2^+(M) > 1} and let g( t), t ? [0, ?), be a solution to (1.3) on M whose Ricci curvature satisfies that |Ric( g( t))| ? 3 and additionally ?( M) = 3? ( M) > 0, then there exists an {min mathbb{N}} , and a sequence of points { x j, k ? M}, j = 1, . . . , m, satisfying that, by passing to a subsequence, {{(M, g(tk+t), x_{1,k},ldots, x_{m,k})stackrel{d_{GH}}longrightarrow ({\\coprod limitsm_{j=1}} N_j , g_{infty}, x_{1,infty}, ldots, x_{m,infty}),}} t ? [0, ?), in the m-pointed Gromov-Hausdorff sense for any sequence t k ? ?, where ( N j , g ?), j = 1, . . . , m, are complete complex hyperbolic orbifolds of complex dimension 2 with at most finitely many isolated orbifold points. Moreover, the convergence is C ? in the non-singular part of {\\coprod _1^m Nj} and {text{Vol}_{g0}(M)=sum_{j=1}mtext{Vol}_{g_{infty}}(Nj)} , where ?( M) (resp. ?( M)) is the Euler characteristic (resp. signature) of M.

Fang, Fuquan; Zhang, Yuguang; Zhang, Zhenlei

2008-10-01

366

A novel dose uncertainty model and its application for dose verification

Based on statistical approach, a novel dose uncertainty model was introduced considering both nonspatial and spatial dose deviations. Non-space-oriented uncertainty is mainly caused by dosimetric uncertainties, and space-oriented dose uncertainty is the uncertainty caused by all spatial displacements. Assuming these two parts are independent, dose difference between measurement and calculation is a linear combination of nonspatial and spatial dose uncertainties. Two assumptions were made: (1) the relative standard deviation of nonspatial dose uncertainty is inversely proportional to the dose standard deviation {sigma}, and (2) the spatial dose uncertainty is proportional to the gradient of dose. The total dose uncertainty is a quadratic sum of the nonspatial and spatial uncertainties. The uncertainty model provides the tolerance dose bound for comparison between calculation and measurement. In the statistical uncertainty model based on a Gaussian distribution, a confidence level of 3{sigma} theoretically confines 99.74% of measurements within the bound. By setting the confidence limit, the tolerance bound for dose comparison can be made analogous to that of existing dose comparison methods (e.g., a composite distribution analysis, a {gamma} test, a {chi} evaluation, and a normalized agreement test method). However, the model considers the inherent dose uncertainty characteristics of the test points by taking into account the space-specific history of dose accumulation, while the previous methods apply a single tolerance criterion to the points, although dose uncertainty at each point is significantly different from others. Three types of one-dimensional test dose distributions (a single large field, a composite flat field made by two identical beams, and three-beam intensity-modulated fields) were made to verify the robustness of the model. For each test distribution, the dose bound predicted by the uncertainty model was compared with simulated measurements. The simulated measurements were within the tolerance bound as expected by a statistical prediction of the model. Using the dose uncertainty distributions, an uncertainty length (uncertainty area and uncertainty volume for two-dimensional and three-dimensional, respectively) histogram (a plot of the dose uncertainty of 1{sigma} received by a length of field) was made. The histogram provides additional information on superiority of a treatment plan in terms of uncertainty. In summary, the uncertainty model provides the dose comparison tool as well as the evaluation tool of a treatment planning system.

Jin Hosang; Chung Heetaek; Liu Chihray; Palta, Jatinder; Suh, Tae-Suk; Kim, Siyong [Department of Nuclear and Radiological Engineering, University of Florida, Gainesville, Florida 32610 (United States); Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610 (United States); Department of Biomedical Engineering, Catholic Medical University (Korea, Republic of); Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610 (United States)

2005-06-15

367

A novel dose uncertainty model and its application for dose verification.

Based on statistical approach, a novel dose uncertainty model was introduced considering both nonspatial and spatial dose deviations. Non-space-oriented uncertainty is mainly caused by dosimetric uncertainties, and space-oriented dose uncertainty is the uncertainty caused by all spatial displacements. Assuming these two parts are independent, dose difference between measurement and calculation is a linear combination of nonspatial and spatial dose uncertainties. Two assumptions were made: (1) the relative standard deviation of nonspatial dose uncertainty is inversely proportional to the dose standard deviation sigma, and (2) the spatial dose uncertainty is proportional to the gradient of dose. The total dose uncertainty is a quadratic sum of the nonspatial and spatial uncertainties. The uncertainty model provides the tolerance dose bound for comparison between calculation and measurement. In the statistical uncertainty model based on a Gaussian distribution, a confidence level of 3sigma theoretically confines 99.74% of measurements within the bound. By setting the confidence limit, the tolerance bound for dose comparison can be made analogous to that of existing dose comparison methods (e.g., a composite distribution analysis, a gamma test, a chi evaluation, and a normalized agreement test method). However, the model considers the inherent dose uncertainty characteristics of the test points by taking into account the space-specific history of dose accumulation, while the previous methods apply a single tolerance criterion to the points, although dose uncertainty at each point is significantly different from others. Three types of one-dimensional test dose distributions (a single large field, a composite flat field made by two identical beams, and three-beam intensity-modulated fields) were made to verify the robustness of the model. For each test distribution, the dose bound predicted by the uncertainty model was compared with simulated measurements. The simulated measurements were within the tolerance bound as expected by a statistical prediction of the model. Using the dose uncertainty distributions, an uncertainty length (uncertainty area and uncertainty volume for two-dimensional and three-dimensional, respectively) histogram (a plot of the dose uncertainty of 1sigma received by a length of field) was made. The histogram provides additional information on superiority of a treatment plan in terms of uncertainty. In summary, the uncertainty model provides the dose comparison tool as well as the evaluation tool of a treatment planning system. PMID:16013732

Jin, Hosang; Chung, Heetaek; Liu, Chihray; Palta, Jatinder; Suh, Tae-Suk; Kim, Siyong

2005-06-01

368

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

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.

Mantaj, Patrycja; Zwierzchowski, Grzegorz

2013-01-01

369

The impact of dose calculation algorithms on partial and whole breast radiation treatment plans

Background This paper compares the calculated dose to target and normal tissues when using pencil beam (PBC), superposition/convolution (AAA) and Monte Carlo (MC) algorithms for whole breast (WBI) and accelerated partial breast irradiation (APBI) treatment plans. Methods Plans for 10 patients who met all dosimetry constraints on a prospective APBI protocol when using PBC calculations were recomputed with AAA and MC, keeping the monitor units and beam angles fixed. Similar calculations were performed for WBI plans on the same patients. Doses to target and normal tissue volumes were tested for significance using the paired Student's t-test. Results For WBI plans the average dose to target volumes when using PBC calculations was not significantly different than AAA calculations, the average PBC dose to the ipsilateral breast was 10.5% higher than the AAA calculations and the average MC dose to the ipsilateral breast was 11.8% lower than the PBC calculations. For ABPI plans there were no differences in dose to the planning target volume, ipsilateral breast, heart, ipsilateral lung, or contra-lateral lung. Although not significant, the maximum PBC dose to the contra-lateral breast was 1.9% higher than AAA and the PBC dose to the clinical target volume was 2.1% higher than AAA. When WBI technique is switched to APBI, there was significant reduction in dose to the ipsilateral breast when using PBC, a significant reduction in dose to the ipsilateral lung when using AAA, and a significant reduction in dose to the ipsilateral breast and lung and contra-lateral lung when using MC. Conclusions There is very good agreement between PBC, AAA and MC for all target and most normal tissues when treating with APBI and WBI and most of the differences in doses to target and normal tissues are not clinically significant. However, a commonly used dosimetry constraint, as recommended by the ASTRO consensus document for APBI, that no point in the contra-lateral breast volume should receive >3% of the prescribed dose needs to be relaxed to >5%.

2010-01-01

370

The MILDOS Computer Code estimates impacts from radioactive emissions from uranium milling facilities. These impacts are presented as dose commitments to individuals and the regional population within an 80 km radius of the facility. Only airborne releases of radioactive materials are considered: releases to surface water and to groundwater are not addressed in MILDOS. This code is multi-purposed and can be used to evaluate population doses for NEPA assessments, maximum individual doses for predictive 40 CFR 190 compliance evaluations, or maximum offsite air concentrations for predictive evaluations of 10 CFR 20 compliance. Emissions of radioactive materials from fixed point source locations and from area sources are modeled using a sector-averaged Gaussian plume dispersion model, which utilizes user-provided wind frequency data. Mechanisms such as deposition of particulates, resuspension. radioactive decay and ingrowth of daughter radionuclides are included in the transport model. Annual average air concentrations are computed, from which subsequent impacts to humans through various pathways are computed. Ground surface concentrations are estimated from deposition buildup and ingrowth of radioactive daughters. The surface concentrations are modified by radioactive decay, weathering and other environmental processes. The MILDOS Computer Code allows the user to vary the emission sources as a step function of time by adjustinq the emission rates. which includes shutting them off completely. Thus the results of a computer run can be made to reflect changing processes throughout the facility's operational lifetime. The pathways considered for individual dose commitments and for population impacts are: • Inhalation • External exposure from ground concentrations • External exposure from cloud immersion • Ingestioo of vegetables • Ingestion of meat • Ingestion of milk • Dose commitments are calculated using dose conversion factors, which are ultimately based on recommendations of the International Commission on Radiological Protection (ICRP). These factors are fixed internally in the code, and are not part of the input option. Dose commitments which are available from the code are as follows: • Individual dose commitments for use in predictive 40 CFR 190 compliance evaluations (Radon and short-lived daughters are excluded) • Total individual dose commitments (impacts from all available radionuclides are considered) • Annual population dose commitments (regional, extraregional, total and cummulative). This model is primarily designed for uranium mill facilities, and should not be used for operations with different radionuclides or processes.

Strange, D. L.; Bander, T. J.

1981-04-01

371

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

372

Life-stage-dependent toxicity and dose-dependent toxicokinetics (TK) were evaluated in Sprague Dawley rats following dietary exposure to 2,4-dichlorophenoxyacetic acid (2,4-D). 2,4-D renal clearance is impacted by dose-dependent saturation of the renal organic anion transporter; thus, this study focused on identifying inflection points of onset of dietary nonlinear TK to inform dose selection decisions for toxicity studies. Male and female rats were fed 2,4-D-fortified diets at doses to 1600 ppm for 4-weeks premating, <2 weeks during mating, and to test day (TD) 71 to parental (P1) males and to P1 females through gestation/lactation to TD 96. F1 offspring were exposed via milk with continuing diet exposure until postnatal day (PND) 35. As assessed by plasma area under the curve for the time-course plasma concentration, nonlinear TK was observed ? 1200 ppm (63 mg/kg/day) for P1 males and between 200 and 400 ppm (14-27 mg/kg/day) for P1 females. Dam milk and pup plasma levels were higher on lactation day (LD) 14 than LD 4. Relative to P1 adults, 2,4-D levels were higher in dams during late gestation/lactation and postweaning pups (PND 21-35) and coincided with elevated intake of diet/kg body weight. Using conventional maximum tolerated dose (MTD) criteria based on body weight changes for dose selection would have resulted in excessive top doses approximately 2-fold higher than those identified incorporating critical TK data. These data indicate that demonstration of nonlinear TK, if present at dose levels substantially above real-world human exposures, is a key dose selection consideration for improving the human relevance of toxicity studies compared with studies employing conventional MTD dose selection strategies. PMID:24105888

Saghir, Shakil A; Marty, Mary S; Zablotny, Carol L; Passage, Julie K; Perala, Adam W; Neal, Barbara H; Hammond, Larry; Bus, James S

2013-12-01

373

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

374

Analysis of multiple-dose bioequivalence studies

In multiple-dose bioequivalence studies, it is possible at steady state to take repeated measurements of pharmacokinetic variables, such as area under the curve (AUC) and the maximum concentration (CMAX) of the blood concentration-time profile, within each period of a crossover design. We develop a bivariate random effects model for such a situation in a 2 × 2 crossover design using

Vernon M. Chinchilli; James D Esinhart; William H. Barr

1994-01-01

375

Maximum Entropy Coordinates for Arbitrary Polytopes

Barycentric coordinates can be used to express any point inside a triangle as a unique convex com- bination of the triangle's vertices, and they provide a convenient way to linearly interpolate data that is given at the vertices of a triangle. In recent years, the ideas of barycentric coordinates and barycentric interpolation have been extended to arbitrary polygons in the

K. Hormann; N. Sukumar

2008-01-01

376

Targeted maximum likelihood based causal inference: Part I.

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

377

Estimating maximum performance: effects of intraindividual variation.

Researchers often estimate the performance capabilities of animals using a small number of trials per individual. This procedure inevitably underestimates maximum performance, but few studies have examined the magnitude of this effect. In this study we explored the effects of intraindividual variation and individual sample size on the estimation of locomotor performance parameters. We measured sprint speed of the lizard Sceloporus occidentalis at two temperatures (20 degrees C and 35 degrees C), obtaining 20 measurements per individual. Speed did not vary temporally, indicating no training or fatigue effects. About 50% of the overall variation in speed at each temperature was due to intraindividual variation. While speed was repeatable, repeatability decreased slightly with increasing separation between trials. Speeds at 20 degrees C and 35 degrees C were positively correlated, indicating repeatability across temperatures as well. We performed statistical sampling experiments in which we randomly drew a subset of each individual's full set of 20 trials. As expected, the sample's maximum speed increased with the number of trials per individual; for example, five trials yielded an estimate averaging 89% of the true maximum. The number of trials also influenced the sample correlation between mean speeds at 20 degrees C and 35 degrees C; for example, five trials yielded a correlation coefficient averaging 90% of the true correlation. Therefore, intraindividual variation caused underestimation of maximal speed and the correlation between speeds across temperatures. These biases declined as the number of trials per individual increased, and depended on the magnitude of intraindividual variation, as illustrated by running sampling experiments that used modified data sets. PMID:18375858

Adolph, Stephen C; Pickering, Trevor

2008-04-01

378

Dynamical maximum entropy approach to flocking

NASA Astrophysics Data System (ADS)

We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.

Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M.

2014-04-01

379

The 2009 Perseid Maximum - Photographic Results

NASA Astrophysics Data System (ADS)

An astronomical camp was organized by Comet and Meteors Workshop during the 2009 Perseids maximum. 69 meteors were photographed during four consecutive nights. We found that photographic Perseid radiant was very compact and located at alpha=48.7 deg, delta=58.6 deg. Our main goal was the determination of the radiant from single station photographic observations, however we also calculated two double station trajectories using additional data which were send to us by casual photographic observer from other parts of Poland. Dozens of radio reflections were observed with simple radio receiver, some of them were identified with photographic images.

Zolcadek, P.; Wisniewski, M.; Polakowski, K.; Wala, E.; Walczak, K.; Poleski, R.

2010-01-01

380

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

381

Maximum aposteriori joint source/channel coding

NASA Technical Reports Server (NTRS)

A maximum aposteriori probability (MAP) approach to joint source/channel coder design is presented in this paper. This method attempts to explore a technique for designing joint source/channel codes, rather than ways of distributing bits between source coders and channel coders. For a nonideal source coder, MAP arguments are used to design a decoder which takes advantage of redundancy in the source coder output to perform error correction. Once the decoder is obtained, it is analyzed with the purpose of obtaining 'desirable properties' of the channel input sequence for improving overall system performance. Finally, an encoder design which incorporates these properties is proposed.

Sayood, Khalid; Gibson, Jerry D.

1991-01-01

382

The sun and heliosphere at solar maximum

NASA Technical Reports Server (NTRS)

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'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.

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.

2003-01-01

383

Dynamical maximum entropy approach to flocking.

We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter. PMID:24827278

Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M

2014-04-01

384

36.8 33.8 43.9 32.7 16.1 23.6 23.8 25.5 0 5 10 15 20 25 30 35 40 45 50 Bx in Degassed Buffer Flash-frozen Bx Pre-Dose Deep Pre-Dose Shallow Post-Dose Shallow Validation and Fitness Testing of a Quantitative Immunoassay for HIF1? in Biopsy Specimens

385

NASA Astrophysics Data System (ADS)

Through analyzing the dynamics characteristic of maximum neural network with an added vertex, we find that the solution quality is mainly determined by the added vertex weights. In order to increase maximum neural network ability, a stochastic nonlinear self-feedback and flexible annealing strategy are embedded in maximum neural network, which makes the network more powerful to escape local minima and be independent of the initial values. Simultaneously, we present that solving ability of maximum neural network is dependence on problem. We introduce a new parameter into our network to improve the solving ability. The simulation in k random graph and some DIMACS clique instances in the second DIMACS challenge shows that our improved network is superior to other algorithms in light of the solution quality and CPU time.

Yang, Gang; Tang, Zheng; Dai, Hongwei

386

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.

2010-01-01

387

Energy and maximum norm estimates for nonlinear conservation laws

NASA Technical Reports Server (NTRS)

We have devised a technique that makes it possible to obtain energy estimates for initial-boundary value problems for nonlinear conservation laws. The two major tools to achieve the energy estimates are a certain splitting of the flux vector derivative f(u)(sub x), and a structural hypothesis, referred to as a cone condition, on the flux vector f(u). These hypotheses are fulfilled for many equations that occur in practice, such as the Euler equations of gas dynamics. It should be noted that the energy estimates are obtained without any assumptions on the gradient of the solution u. The results extend to weak solutions that are obtained as point wise limits of vanishing viscosity solutions. As a byproduct we obtain explicit expressions for the entropy function and the entropy flux of symmetrizable systems of conservation laws. Under certain circumstances the proposed technique can be applied repeatedly so as to yield estimates in the maximum norm.

Olsson, Pelle; Oliger, Joseph

1994-01-01

388

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

389

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...

390

391

Probably maximum flood of the Sava River

NASA Astrophysics Data System (ADS)

The Nuclear Power Plant Krško (NEK) situated on the left bank of the Save River close to the border of Croatia. Probably Maximum Flood, on the location of the NEK could result in combination of probably maximum precipitation, sequential storm before PMP or snowmelt on the Sava River watershed. Mediterranean climate characterises very high precipitation and temporary high snow pack. The HBV-96 model as Integrated Hydrological Modelling System (IHMS) used for modelling. Model was calibrated and verification for daily time step at first for time period 1190-2006. Calibration and verification for hourly time step was done for period 1998-1999. The stream routing parameters were calibrated for flood event in years 1998 and 2007 and than verification for flood event in 1990. Discharge routing data analysis shown that possible inundation of Ljubljana and Savinja valley was not properly estimated. The flood areas are protected with levees and water does not spread over flooded areas in events used for calibration. Inundated areas in Ljubljana valley and Savinja valley are protected by levees and model could not simulate properly inundation of PMF. We recalibrate parameters controlled inundation on those areas for the worst scenario. Calculated PMF values drop down tramendosly after recalibration.

Brilly, Mitja; Vidmar, Andrej; Raj, Mojca Å.

2010-05-01

392

Maximum Correntropy Criterion for Robust Face Recognition.

In this paper, we present a sparse correntropy framework for computing robust sparse representations of face images for recognition. Compared with the state-of-the-art $l^1$-norm based sparse representation classifier (SRC), which assumes that noise also has a sparse representation, our sparse algorithm is developed based on the maximum correntropy criterion, which is much more insensitive to outliers. In order to develop a more tractable and practical approach, we in particular impose non-negativity constraint on the variables in the maximum correntropy criterion, and develop a half-quadratic optimization technique to approximately maximize the objective function in an alternating way, so that the complex optimization problem is reduced to learning a sparse representation through a weighted linear least squares problem with non-negativity constraint at each iteration. Our extensive experiments demonstrate that the proposed method is more robust and efficient in dealing with the occlusion and corruption problems in face recognition, as compared to the related state-of-the-art methods. In particular, it shows that the proposed method can improve both recognition accuracy and receiver operator characteristic (ROC) curves, while the computational cost is much lower than the SRC algorithms. PMID:21135440

He, Ran; Zheng, Wei-Shi; Hu, Bao-Gang

2010-11-30

393

We sought to create a population pharmacokinetic model for total mycophenolic acid (MPA), to study the effects of different covariates on MPA pharmacokinetics, to create a limited sampling schedule (LSS) to characterize MPA exposure (i.e., area under the curve or AUC) with maximum a posteriori Bayesian estimation, and to simulate an optimized dosing scheme for allogeneic hematopoietic cell transplantation (HCT) recipients. 4,496 MPA concentration-time points from 408 HCT recipients were analyzed retrospectively using a nonlinear mixed effects modeling approach. MPA pharmacokinetics was characterized with a two-compartment model with first-order elimination and a time-lagged first-order absorption process. Concomitant cyclosporine and serum albumin were significant covariates. The median MPA clearance and volume of the central compartment were 24.2 L/hr and 36.4 L, respectively, for a 70 kg patient receiving tacrolimus with a serum albumin of 3.4 g/dL. Dosing simulations indicated that higher oral MMF doses are needed with concomitant cyclosporine, which increases MPA clearance by 33.8%. The optimal LSS was immediately before and at 0.25, 1.25, 2, and 4hr after oral MMF administration. MPA AUC in an individual HCT recipient can be accurately estimated using a five-sample LSS and maximum a posteriori Bayesian estimation.

Li, H; Mager, D E; Sandmaier, B M; Maloney, D G; Bemer, M J; McCune, J S

2012-01-01

394

We sought to create a population pharmacokinetic model for total mycophenolic acid (MPA), to study the effects of different covariates on MPA pharmacokinetics, to create a limited sampling schedule (LSS) to characterize MPA exposure (i.e., area under the curve or AUC) with maximum a posteriori Bayesian estimation, and to simulate an optimized dosing scheme for allogeneic hematopoietic cell transplantation (HCT) recipients. Four thousand four hundred ninety-six MPA concentration-time points from 408 HCT recipients were analyzed retrospectively using a nonlinear mixed effects modeling approach. MPA pharmacokinetics was characterized with a two-compartment model with first-order elimination and a time-lagged first-order absorption process. Concomitant cyclosporine and serum albumin were significant covariates. The median MPA clearance (CL) and volume of the central compartment were 24.2?L/hour and 36.4?L, respectively, for a 70?kg patient receiving tacrolimus with a serum albumin of 3.4?g/dL. Dosing simulations indicated that higher oral MMF doses are needed with concomitant cyclosporine, which increases MPA CL by 33.8%. The optimal LSS was immediately before and at 0.25?hours, 1.25?hours, 2?hours, and 4?hours after oral mycophenolate mofetil administration. MPA AUC in an individual HCT recipient can be accurately estimated using a five-sample LSS and maximum a posteriori Bayesian estimation. PMID:23382105

Li, H; Mager, D E; Sandmaier, B M; Maloney, D G; Bemer, M J; McCune, J S

2013-04-01

395

Georgia fishery study: implications for dose calculations. Revision 1

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

396

Sulfonylureas are often titrated to maximum doses despite evidence that their efficacy plateaus above half-maximum doses.\\u000a The aim of this study was to determine the impact of doubling the dose of glyburide and glipizide to high doses on hemoglobin\\u000a A1c (HbA1c) in Veterans Affairs patients with type 2 diabetes. A retrospective review of 131 patient cases with prescriptions\\u000a for high-dose

Kathryn M. HurrenEmily; Emily P. Bartley; Jessica L. O’Neill; David L. Ronis

397

Peripheral doses from pediatric IMRT

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

398

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

399

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

400

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

401

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

402

33 CFR 183.35 - Maximum weight capacity: Outboard boats.

Code of Federal Regulations, 2010 CFR

...false Maximum weight capacity: Outboard boats. 183.35 Section 183.35 Navigation...SECURITY (CONTINUED) BOATING SAFETY BOATS AND ASSOCIATED EQUIPMENT Safe Loading...35 Maximum weight capacity: Outboard boats. (a) The maximum weight capacity...

2010-07-01

403

49 CFR 230.24 - Maximum allowable stress.

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....

2011-10-01

404

49 CFR 230.24 - Maximum allowable stress.

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....

2012-10-01

405

40 CFR 141.13 - Maximum contaminant levels for turbidity.

Code of Federal Regulations, 2010 CFR

... false Maximum contaminant levels for turbidity. 141.13 Section 141.13 Protection...141.13 Maximum contaminant levels for turbidity. The maximum contaminant levels for turbidity are applicable to both community...

2010-07-01

406

49 CFR 230.24 - Maximum allowable stress.

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress Â§ 230.24 Maximum allowable stress. (a) Maximum allowable stress value....

2010-10-01

407

49 CFR 230.24 - Maximum allowable stress.

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress Â§ 230.24 Maximum allowable stress. (a) Maximum allowable stress value....

2013-10-01

408

49 CFR 230.24 - Maximum allowable stress.

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress Â§ 230.24 Maximum allowable stress. (a) Maximum allowable stress value....

2009-10-01

409

REMARKS ON THE MAXIMUM ENTROPY METHOD APPLIED TO FINITE TEMPERATURE LATTICE QCD.

We make remarks on the Maximum Entropy Method (MEM) for studies of the spectral function of hadronic correlators in finite temperature lattice QCD. We discuss the virtues and subtlety of MEM in the cases that one does not have enough number of data points such as at finite temperature. Taking these points into account, we suggest several tests which one should examine to keep the reliability for the results, and also apply them using mock and lattice QCD data.

UMEDA, T.; MATSUFURU, H.

2005-07-25

410

Hydraulic Limits on Maximum Plant Transpiration

NASA Astrophysics Data System (ADS)

Photosynthesis occurs at the expense of water losses through transpiration. As a consequence of this basic carbon-water interaction at the leaf level, plant growth and ecosystem carbon exchanges are tightly coupled to transpiration. In this contribution, the hydraulic constraints that limit transpiration rates under well-watered conditions are examined across plant functional types and climates. The potential water flow through plants is proportional to both xylem hydraulic conductivity (which depends on plant carbon economy) and the difference in water potential between the soil and the atmosphere (the driving force that pulls water from the soil). Differently from previous works, we study how this potential flux changes with the amplitude of the driving force (i.e., we focus on xylem properties and not on stomatal regulation). Xylem hydraulic conductivity decreases as the driving force increases due to cavitation of the tissues. As a result of this negative feedback, more negative leaf (and xylem) water potentials would provide a stronger driving force for water transport, while at the same time limiting xylem hydraulic conductivity due to cavitation. Here, the leaf water potential value that allows an optimum balance between driving force and xylem conductivity is quantified, thus defining the maximum transpiration rate that can be sustained by the soil-to-leaf hydraulic system. To apply the proposed framework at the global scale, a novel database of xylem conductivity and cavitation vulnerability across plant types and biomes is developed. Conductivity and water potential at 50% cavitation are shown to be complementary (in particular between angiosperms and conifers), suggesting a tradeoff between transport efficiency and hydraulic safety. Plants from warmer and drier biomes tend to achieve larger maximum transpiration than plants growing in environments with lower atmospheric water demand. The predicted maximum transpiration and the corresponding leaf water potential compare well with measured peak transpiration and minimum water potentials across plant types and biomes, suggesting that plant water transport system and stomatal regulation co-evolved to meet peak atmospheric demands, thus sustaining carbon uptake while avoiding tissue damage even in such harsh conditions.

Manzoni, S.; Vico, G.; Katul, G. G.; Palmroth, S.; Jackson, R. B.; Porporato, A. M.

2011-12-01

411

The rubber industry has been using curemeters for 30 years; however, the maximum cure rate (CRMAX) at the inflection point on the cure curve was not easily measured to a high level of precision. Now a digitized cure curve can be analyzed with computer software programs to produce a maximum cure rate determination to a high degree of precision.The use

J. S. Dick; H. Pawlowski

1996-01-01

412

Dose-response curves and competing risks.

Points of the underlying dose-response curve of a lethal response or group of lethal responses induced by varying doses of a toxicant in a homogeneous population can be estimated from knowledge of the time of occurrence for all responses if the response(s) of interest is (are) statistically independent from the other competing responses (risks). In the case of statistical dependence, only tight upper and lower bounds can be established within which the points of the dose-response curve have to lie. These bounds for the response(s) of interest are far apart if the frequency of occurrence of the competing response(s) is large. In such situations, the shape of the underlying dose-response curve is only suggested by the imaginary band connecting the estimated bounds. The estimation procedures for both cases are illustrated with data from an experiment in which beagles received injections of 239Pu.

Groer, P G

1978-01-01

413

Detection of point sources with spark chamber gamma-ray telescopes

NASA Astrophysics Data System (ADS)

The sensitivity of cross correlation and maximum likelihood, two methods under consideration by the EGRET team for detecting point sources, is analyzed numerically. Cross correlation is found to be 9 +/- 2 percent more sensitive than maximum likelihood.

Mattox, J. R.

1991-04-01

414

Detection of point sources with spark chamber gamma-ray telescopes

NASA Technical Reports Server (NTRS)

The sensitivity of cross correlation and maximum likelihood, two methods under consideration by the EGRET team for detecting point sources, is analyzed numerically. Cross correlation is found to be 9 +/- 2 percent more sensitive than maximum likelihood.

Mattox, J. R.

1991-01-01

415

The Maximum Age of Trapezium Systems

NASA Astrophysics Data System (ADS)

We sought to determine the maximum age of Trapezium systems by studying possible trapezium systems that were selected independently of their occurrence in H II regions. We started with the unpublished catalog by Allen, Tapia, & Parrao of all the known visual systems having three or more stars in which the maximum separation is less than 3.0 times the minimum separation. Their catalog has 968 such systems whose most frequent primary type is F, which does not describe young systems. With a CCD on the Kitt Peak 0.9 m telescope we obtained UBV frames for 265 systems accessible with our equipment on Kitt Peak. The frames were used to obtain UBV photometry for about 1500 stars with an accuracy of +/-0.04 mag between V=7 and 14 mag. Also these frames were used to obtain astrometry with an accuracy of +/-0.015d in position angle and +/-0.01" in separation. For the brightest star in each system we obtained a spectral type to determine the distance and reddening to the system. The measures were used to determine physical membership from stars that (1) fit a single color-magnitude diagram, (2) fit a common color-color diagram, and (3) show no astrometric motion compared to visual measures made (mostly) a century ago. Combining the results with spectroscopic data for 20 additional Allen et al. systems by Abt, we found that 126 systems had only optical companions to the primaries, 116 systems contained only a single physical pair, 13 were hierarchical systems with 3-6 members and having separation ratios of more than a factor of 10, two were small clusters, and only 28 fitted the criteria of Trapezium systems. However, as shown by Ambartsumian, about 9% of the hierarchical systems should appear to be Trapezium systems in projection. Those, like other hierarchical systems, have a broad distribution of primary spectral types. We isolated 14 systems that seem to be true Trapezium systems. They have primary types of B3 or earlier, indicating a maximum age of about 5×107 yr. This upper limit is consistent with the estimate made by Allen & Poveda for an age of several million years for these dynamically unstable systems. These Trapezia are also large with a median radius of 0.2 pc and a maximum radius of 2.6 pc. We asked why the sample of 285 possible Trapezium systems yielded only 14 true ones, despite the attempt made by Allen et al. to eliminate optical companions with a ``1% filter,'' i.e., demanding that each companion have less than a 1% chance of being a field star of that magnitude within a circle of its radius from the primary. The explanation seems to be that the double star catalogs are based mostly on BD magnitudes that, fainter than V=12 mag, are systematically too faint by 1 mag.

Abt, Helmut A.; Corbally, Christopher J.

2000-10-01

416

Maximum power flux of auroral kilometric radiation

NASA Astrophysics Data System (ADS)

Distant observations of intense auroral kilometric radiation (AKR) are discussed in light of the increased maximum AKR power flux registered by the 3D radio-mapping instrument on ISEE 3. Only AKR events that contain the highest frequency signals are selected, and during spacecraft rotation the spacecraft antenna gain is employed to increase the dynamic range of the instrument. The technique is found to result in the screening of false signals created by instrument overloading as well as the detection of genuine second-harmonic AKR signals while the spacecraft was 17 R(E) from earth. A very strong power flux of fundamental AKR is also reported, exceeding 3 x 10 to the -13th W/sq m/Hz at 360 kHz. The most intense source-region values detected by Isis I and Viking measurements are compared to the strong signal, and the signal is concluded to be the combined signal of a number of sources.

Benson, Robert F.; Fainberg, Joseph

1991-08-01

417

Approximate maximum likelihood decoding of block codes

NASA Technical Reports Server (NTRS)

Approximate maximum likelihood decoding algorithms, based upon selecting a small set of candidate code words with the aid of the estimated probability of error of each received symbol, can give performance close to optimum with a reasonable amount of computation. By combining the best features of various algorithms and taking care to perform each step as efficiently as possible, a decoding scheme was developed which can decode codes which have better performance than those presently in use and yet not require an unreasonable amount of computation. The discussion of the details and tradeoffs of presently known efficient optimum and near optimum decoding algorithms leads, naturally, to the one which embodies the best features of all of them.

Greenberger, H. J.

1979-01-01

418

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

419

Intrinsic point cloud simplification

Modelling and visualisation methods working directly with point-sampled geometry have developed into attractive alternatives to more traditional mesh-based surface processing. In this paper, we consider a vital step in any point-based surface processing pipeline, point cloud simplification. Building upon the intrinsic point cloud simplification idea put forward in (14), we obtain a simplification algorithm allowing for intuitive density control and

Carsten Moenning; Neil A. Dodgson

2004-01-01

420

Environmental gamma dose rates and influencing factors in buildings

Environmental gamma radiation measured in buildings in Dhaka shows a cosinusoidal variation of indoor dose rate with time mainly due to seasonally varied ventilation and air exchange rates of the houses. In connection, the nature and characteristics of the buildings were also discussed. As expected, a maximum dose rate was found in winter and a minimum in summer. The variations

M. Idrish Miah

2004-01-01

421

Maximum magnitude in the Lower Rhine Graben

NASA Astrophysics Data System (ADS)

Estimating Mmax, the assumed magnitude of the largest future earthquakes expected on a fault or in an area, involves large uncertainties. No theoretical basis exists to infer Mmax because even where we know the long-term rate of motion across a plate boundary fault, or the deformation rate across an intraplate zone, neither predict how strain will be released. As a result, quite different estimates can be made based on the assumptions used. All one can say with certainty is that Mmax is at least as large as the largest earthquake in the available record. However, because catalogs are often short relative to the average recurrence time of large earthquakes, larger earthquakes than anticipated often occur. Estimating Mmax is especially challenging within plates, where deformation rates are poorly constrained, large earthquakes are rarer and variable in space and time, and often occur on previously unrecognized faults. We explore this issue for the Lower Rhine Graben seismic zone where the largest known earthquake, the 1756 Düren earthquake, has magnitude 5.7 and should occur on average about every 400 years. However, paleoseismic studies suggest that earthquakes with magnitudes up to 6.7 occurred during the Late Pleistocene and Holocene. What to assume for Mmax is crucial for critical facilities like nuclear power plants that should be designed to withstand the maximum shaking in 10,000 years. Using the observed earthquake frequency-magnitude data, we generate synthetic earthquake histories, and sample them over shorter intervals corresponding to the real catalog's completeness. The maximum magnitudes appearing most often in the simulations tend to be those of earthquakes with mean recurrence time equal to the catalog length. Because catalogs are often short relative to the average recurrence time of large earthquakes, we expect larger earthquakes than observed to date to occur. In a next step, we will compute hazard maps for different return periods based on the synthetic catalogs, in order to determine the influence of underestimating Mmax.

Vanneste, Kris; Merino, Miguel; Stein, Seth; Vleminckx, Bart; Brooks, Eddie; Camelbeeck, Thierry

2014-05-01

422

External gamma dose responses from residual radioactive materials in soil

External gamma dose responses from radioactive soils have previously been calculated as air-absorbed doses in a point receptor above the ground. Such responses, however, are not accurate measures for estimating the effective dose equivalent (H{sub E}) for assessing radiological risks to humans, as defined by the International Commission on Radiological Protection (ICRP). The ambient dose equivalent H*(10), as defined by

S. Y. Chen; Y. C. Yuan

1989-01-01

423

Point Cloud Collision Detection

In the past few years, many efficient rendering and surface reconstruction algorithms for point clouds have been de- veloped. However, collision detection of point clouds has not been considered until now, although this is a prerequisite to use them for interactive or animated 3D graphics. We present a novel approach for time-critical collision detection of point clouds. Based solely on

Jan Klein; Gabriel Zachmann

2004-01-01

424

Fast Forward Maximum entropy reconstruction of sparsely sampled data.

We present an analytical algorithm using fast Fourier transformations (FTs) for deriving the gradient needed as part of the iterative reconstruction of sparsely sampled datasets using the forward maximum entropy reconstruction (FM) procedure by Hyberts and Wagner [J. Am. Chem. Soc. 129 (2007) 5108]. The major drawback of the original algorithm is that it required one FT and one evaluation of the entropy per missing datapoint to establish the gradient. In the present study, we demonstrate that the entire gradient may be obtained using only two FT's and one evaluation of the entropy derivative, thus achieving impressive time savings compared to the original procedure. An example: A 2D dataset with sparse sampling of the indirect dimension, with sampling of only 75 out of 512 complex points (15% sampling) would lack (512-75)×2=874 points per ?(2) slice. The original FM algorithm would require 874 FT's and entropy function evaluations to setup the gradient, while the present algorithm is ?450 times faster in this case, since it requires only two FT's. This allows reduction of the computational time from several hours to less than a minute. Even more impressive time savings may be achieved with 2D reconstructions of 3D datasets, where the original algorithm required days of CPU time on high-performance computing clusters only require few minutes of calculation on regular laptop computers with the new algorithm. PMID:22975245

Balsgart, Nicholas M; Vosegaard, Thomas

2012-10-01

425