WorldWideScience
 
 
1

Evaluation of entrance surface air kerma from exposure index in computed radiography  

Science.gov (United States)

The aim of this study was to establish an indirect method to calculate the values of entrance surface air kerma in patients undergoing diagnostic examinations in X-ray systems with computed radiography based on the exposure index. The entrance surface air kerma values were compared with values obtained also indirectly based on measurements of X-ray tube output. The mean±standard deviation (1?) and third quartile for entrance surface air kerma calculated from the exposure index were 2.1±1.0 mGy and 3.0 mGy, respectively. For entrance surface air kerma based on measurements of the X-ray tube output, the mean±standard deviation (1?) and third quartile were respectively 3.1±1.9 mGy and 5.5 mGy. The observed values of entrance surface air kerma are smaller than the reference level adopted in Brazil (10 mGy). The results obtained with both methods were similar when taking into account the estimated uncertainties in the determination of air kerma values, although the reproducibility of the determinations based on the exposure index is better.

Costa, A. M.; Pelegrino, M. S.

2014-11-01

2

Image quality and volume computed tomography air kerma index (Cvol) evaluation in Recife  

International Nuclear Information System (INIS)

The Computed Tomography (CT) is an important diagnostic imaging method, widely used. However, in spite of all the advantages and technologic advances within the CT scanners, the tomographic procedures result in high absorbed doses to patients. The main objective of this work was to perform a dosimetric study of CT scanners located at Recife and to evaluate the image quality on CT examinations in these equipment. The volume CT air kerma index (CVOL) and air kerma length product (PKL,CT) were estimated. These values were calculated using normalized weighted air kerma indexes in CT standard dosimetry phantoms (nCW), supplied by ImPACT group for several CT scanners, and the scan parameters of routine head, routine chest and hi-resolution chest CT exams performed at 20 institutions. The irradiation parameters of 15 adult patients for each CT procedure were registered at six participating centres, at which the phantom from the American College of Radiology (ACR) CT accreditation protocol was used for the image quality measurements. For routine head exams, the CVOL values varied between 12 and 58 mGy (at the posterior fossa) and 15 to 58 mGy (at the cerebrum) and the PKL,CT, from 150 to 750 mGy·cm. The CVOL values for routine chest procedures varied from 3 to 26 mGy and the PKL,CT, between 120 and 460 mGy·cm. In relation to Hi-resolution chest exams, CVOL values were from 1.0 to 2.7 mGy and the PKL,CT values varied between 24 and 67 mGy·cm. The image quality evaluations results showed that almost all scanners presented at least one inadequacy. One of the equipment presented faults at 70% of the tests. With regard to the image noise, only two scanners presented acceptable results. From these results, it is possible to conclude that the volume CT air kerma index values are lower than the European reference levels. However, the image quality of these CT scanners does not attend the ACR requirements, suggesting the need to implement quality assurance programs at the evaluated institutions. (author)

3

Image quality and volume computed tomography air kerma index (C{sub vol}) evaluation in Recife; Avaliacao da qualidade de imagem e do indice volumetrico de Kerma ar em tomografia computadorizada (C{sub vol}) em Recife  

Energy Technology Data Exchange (ETDEWEB)

The Computed Tomography (CT) is an important diagnostic imaging method, widely used. However, in spite of all the advantages and technologic advances within the CT scanners, the tomographic procedures result in high absorbed doses to patients. The main objective of this work was to perform a dosimetric study of CT scanners located at Recife and to evaluate the image quality on CT examinations in these equipment. The volume CT air kerma index (C{sub VOL}) and air kerma length product (P{sub KL,CT}) were estimated. These values were calculated using normalized weighted air kerma indexes in CT standard dosimetry phantoms ({sub n}C{sub W}), supplied by ImPACT group for several CT scanners, and the scan parameters of routine head, routine chest and hi-resolution chest CT exams performed at 20 institutions. The irradiation parameters of 15 adult patients for each CT procedure were registered at six participating centres, at which the phantom from the American College of Radiology (ACR) CT accreditation protocol was used for the image quality measurements. For routine head exams, the C{sub VOL} values varied between 12 and 58 mGy (at the posterior fossa) and 15 to 58 mGy (at the cerebrum) and the P{sub KL,CT}, from 150 to 750 mGy{center_dot}cm. The C{sub VOL} values for routine chest procedures varied from 3 to 26 mGy and the P{sub KL,CT}, between 120 and 460 mGy{center_dot}cm. In relation to Hi-resolution chest exams, C{sub VOL} values were from 1.0 to 2.7 mGy and the P{sub KL,CT} values varied between 24 and 67 mGy{center_dot}cm. The image quality evaluations results showed that almost all scanners presented at least one inadequacy. One of the equipment presented faults at 70% of the tests. With regard to the image noise, only two scanners presented acceptable results. From these results, it is possible to conclude that the volume CT air kerma index values are lower than the European reference levels. However, the image quality of these CT scanners does not attend the ACR requirements, suggesting the need to implement quality assurance programs at the evaluated institutions. (author)

Andrade, Marcos Ely Almeida

2008-07-01

4

Air kerma rate constants for radionuclides  

International Nuclear Information System (INIS)

Conversion to SI units requires that the exposure rate constant which was usually quoted in R . h-1 . mCi-1 . cm2 be replaced by the air kerma rate constant with units m2 . Gy . Bq-1s-1. The conversion factor is derived and air kerma rate constants for 30 radionuclides used in nuclear medicine and brachytherapy are listed. A table for calculation of air kerma rates for other radionuclides is also given. To calculate absorbed dose to tissue, the air kerma rate has to be multiplied by approximately 1.1. A dose equivalent rate constant is thus listed which allows direct calculation of dose equivalent rate to soft tissue without resorting to exposure rate constants tabulated in the special units R . m2 . mCi-1h-1 which should no longer be used. (orig.)

5

Development of a phantom and a methodology for evaluation of depth kerma and kerma index for dental cone beam computed tomography  

International Nuclear Information System (INIS)

Basically, all modalities of diagnostic radiology require phantoms suitable for dosimetric evaluations. New technologies frequently arise unaccompanied of tools for dosimetric evaluations and quality control. In this study, a low-cost phantom and a consequent proposed methodology for dosimetric evaluations in cone beam computed tomography (CBCT) were presented. The developed phantom has typical dimensions of the human face, was built in polymethyl methacrylate and filled with water. Three devices with different technological concepts were evaluated and a proposed index, kerma index-height product (PKIH), was defined as an option to the use of air kerma-area product. The results of this study show relatively uniform kerma profiles for scanners with field of views (FOVs) of large diameters and non-uniform for FOVs of small diameters. With regard to the values obtained for the kerma indexes, much higher values were found for the equipment FOVs with small diameter compared with the values of the two other equipment that have larger diameters. The results indicate that (1) there is a need for special phantoms for use in CBCT, (2) the use of PKA in the evaluation of protocols on different equipment can lead to false interpretations and (3) the new index is a suitable alternative for the use of PKA in CBCT. (authors)

6

Determination of reference air kerma rate for BRIT sources  

International Nuclear Information System (INIS)

The Board of Radiation and Isotope Technology (BRIT) supplies 137Cs tube and 192Ir wire sources for brachytherapy applications. The source strength is quoted in mCi or MBq. This paper deals with the measurements carried out to correlate the quoted activity to reference air kerma rate, the internationally recommended unit for specification of brachytherapy sources

7

Air kerma rates measurement in an interventional cardiology suite  

International Nuclear Information System (INIS)

In Interventional Cardiology (IC), the assessment of the radiation that the physicians are exposed to is extremely important because the irradiation is not uniform and the received doses are substantially high. During the procedure, the radiation control is complex and there are several reasons for the high exposure levels. It is necessary to perform dosimetric assessments in different parts of the physicians' body and in different specific points of the examination room. By analyzing this information it is possible to determine the probable causes and to provide recommendations, aiming at optimizing the radiological protection. This work had the following objectives: to assess the exposition levels at representative points of critical anatomical regions of the physicians' body who perform IC examinations; to provide means to implement personal monitoring procedures; and to make them aware of the radiation risks. Measurements of air kerma rates were performed in 45 points around the examination table, along the room. Such measurements were made in the conditions frequently used in coronary angiography and coronary angioplasties procedures: adult patient phantom; RAO, LAO and AP incidences; fluoro and digital modes; 13cm and 17cm magnification modes; frequencies of 30f/s (fluoro) and 15 f/s (digital); typical field size used during examinations. Data were obtained at the lenses, chest, hands, gonads and knees levels. For AP incidence, the lowest contributions for scattidence, the lowest contributions for scattered radiation and a more homogeneous distribution of radiation were observed. The highest air kerma rates were obtained during digital acquisition mode and for LAO incidence on interventional radiologists, anaesthesists and nurses. The most critical anatomical regions were the knees and gonads. Air kerma rates of about 7,8mGy/h were registered in some places. At physicians' hands position, rates of about 5mGy/h were reached. In several points and levels measured (workload ? 6 examinations/day), this air kerma rates would produce a higher dose than the annual limits. This work shows the need to implement additional protection devices; to elaborate safety guidelines; to train staff on radiological protection, and to implement the use of additional dosemeters attached to critical points. (author)

8

Status of air kerma and absorbed dose standards in India  

International Nuclear Information System (INIS)

Full text: The Radiation Safety Systems Division of Bhabha Atomic Research Centre, India maintains Primary and Secondary Standards of various parameters of radiation measurements and provides calibration services to various users of radiation in the country. This is an apex laboratory in India and plays a pivotal role in ensuring accurate radiological measurements. The laboratory coordinates national intercomparisons of radiation measurements to maintain their uniformity and traceability and is linked through various programmes with the other International organizations such as Bureau Internationale des Poids et Mesures (BIPM) Paris, International Atomic Energy Agency (IAEA) Vienna, Asia Pacific Metrology Programme (APMP) Taiwan. It is the recognized Regional Secondary Standards Dosimetry Laboratory (SSDL) of IAEA/WHO (World Health Organisation). This paper brings out the status of various primary and secondary standards for radiological measurements maintained at BARC. 1. Primary Exposure/Air-kerma standard at Co-60 energy (therapy level): The primary standard for exposure/ air-kerma measurements maintained at BARC is a graphite cavity chamber of volume 4.362 cc with an internal diameter of 1.8 cm, internal height of 1.78 cm and wall thickness of 704.3mg/cm2. Correction factors for the difference between electron stopping powers, photon mass energy absorption coefficients of air and graphite wall, correction for recombination, radiation field non-uniformity, stem scatter and polarity effect are applied and the maximum overall uncertainty in the realisation of exposure/air-kerma is around ±1%. This standard has been intercompared with IAEA and BIPM through transfer standard and the agreement in the results are better than ±1%. An intercomparison under the APMP programme is to be held during May, 2002. 2. Primary Exposure/Air-kerma standard at protection and brachytherapy level: A set of three spherical graphite-walled cavity chambers of different air-volumes are maintained as primary standards for protection level and brachytherapy measurements of Ir-192, Cs-137 and Co-60 sources. These chambers are made of high purity reactor-grade graphite of density 1700 kg/m3. The three chambers have different wall thickness, the external diameters of all the chambers being equal. A reference standard in the form of a re-entrant chamber developed at BARC, calibrated against this primary standard was intercompared with a reference standard from M.D Anderson Centre, Houston, U.S.A and the results showed a good agreement. Recently one of the chambers was used for the Cs-137 intercomparison with IAEA and showed an agreement of better than ± 1%. 3. Primary Standard for X-rays - the free air chamber (FAC): This facility is utilized in conjunction with a Philips RT-250 X-ray machine for calibrating secondary standard dosemeters at different X-ray qualities in the 75 to 250 kV range. The total uncertainty in the realization of air kerma is around ±1% using the free air chamber. Accuracy of calibration of the secondary standards is estimated to be better than ±2%. The FAC has been intercompared via transferable transfer standards with FACs at BIPM (1971), BNM (France) RCL (Canada) and Kriss (Korea), which showed good agreement within ±1% after necessary correction for the spectral differences in X-ray beams. BARC is just now taking part in intercomparisons of X-ray air kerma calibration factors organised by Institute of Nuclear Energy Research (INER), Taiwan under Asia Pacific Metrology Programme. In addition to the above-mentioned primary standards, the SSDL is also maintaining the following secondary standards. For air kerma measurements at Co-60 gamma energy, ionisation chambers of Exradin A3, NE2571, NE2577 and Victoreen 415 types are calibrated and maintained. For Co-60 radiation dose to water measurements, NE 2571 and NE 2577 chambers calibrated at BIPM in terms of ND,W are maintained. For air kerma at medium energy x-rays, chambers of the type Exradin A2, NE 2571, NE2577, Victoreen 415 B, Victoreen 415, Exradin A3 and NE 2581 are

9

Comparison of air kerma measurements in mammography using thermoluminescent dosimeters  

International Nuclear Information System (INIS)

A co-ordinated research project, Image Quality and Patient Dose Optimization in Mammography in Eastern European Countries, was conducted by the IAEA, which aimed at defining a methodology for the implementation of a quality assurance programme in mammography and at exercising the assessment of image quality and patient doses in a sample of hospitals in eastern European countries.A comparison of dosimetry systems has been organized to ensure that dose measurements carried out within the framework of the project are comparable. Selected mammography units from the Czech Republic, Hungary, Poland, Romania, Slovakia and Spain participated in the exercise. The thermoluminescence method was selected for the comparison. The dosimeters were irradiated free in air to values of air kerma in the range of 5 mGy to 9 mGy and mailed to the participants for evaluation. Deviations of measured values from the true values of less than 10% were considered a measure of good dosimetry performance. The results of the comparison showed that about 70% of reported values of air kerma were outside the 10% acceptance limit. Two follow-up exercises were organized. The first follow-up resulted in only 20% of reported values exceeding the limit, and during the second follow-up all results were within the acceptance limit

10

Studies on the performance of diagnostic ionisation air Kerma meters in the United States  

International Nuclear Information System (INIS)

The dependence of response of air-kerma meters on air-kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed

11

Studies on the performance of diagnostic ionisation air kerma meters in the United States  

International Nuclear Information System (INIS)

The dependence of response of air kerma meters on air kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed. (author)

12

Estimation of the peak entrance surface air kerma for patients undergoing computed tomography-guided procedures  

International Nuclear Information System (INIS)

The purpose of this work was to develop a method for estimating the patient peak entrance surface air kerma from measurements using a pencil ionisation chamber on dosimetry phantoms exposed in a computed tomography (CT) scanner. The method described is especially relevant for CT fluoroscopy and CT perfusion procedures where the peak entrance surface air kerma is the risk-related quantity of primary concern. Pencil ionisation chamber measurements include scattered radiation, which is outside the primary radiation field, and that must be subtracted in order to derive the peak entrance surface air kerma. A Monte Carlo computer model has therefore been used to calculate correction factors, which may be applied to measurements of the CT dose index obtained using a pencil ionisation chamber in order to estimate the peak entrance surface air kerma. The calculations were made for beam widths of 5, 7, 10 and 20 mm, for seven positions of the phantom, and for the geometry of a GE HiSpeed CT/i scanner. The program was validated by comparing measurements and calculations of CTDI for various vertical positions of the phantom and by directly estimating the peak ESAK using the program. Both validations showed agreement within statistical uncertainties (standard deviation of 2.3% or less). For the GE machine, the correction factors vary by ?10% with slice width for a fixed phantom position, being largest for the 20 mm beam width, and at that beam width range from 0.87 when the phanbeam width range from 0.87 when the phantom surface is at the iso-centre to 1.23 when it is displaced vertically by 24 cm. (authors)

13

Computation of air kerma rate around an industrial radiography source  

International Nuclear Information System (INIS)

Use of Iridium-192 and Cobalt-60 sources in Industrial Radiography has recorded a steep rise in the last three decades in India. There are about 425 institutions in possession of 1100 radiography equipment's. Widespread use of these sources call for meticulous radiation safety programme in the use of these sources. A gamma radiography exposure device comprises of adequately shielded source holder assembly and accessories such as remote control cable and guide tube with suitable mechanism to facilitate radiation exposure in a safe manner for industrial radiography work. The source holder assembly is driven out of the shielded container through the guide tube by means of a suitable drive mechanism. Various built-in design safety features are incorporated in these devices to ensure safe operation and to avoid untoward incidents. In spite of effective regulatory control, accidents may take place. For example, an accident situation may arise due to decoupling of the source assembly which may lead to the source falling on the ground and consequent exposure of people around the source and also the personnel involved in source retrieval operations. A knowledge of the air kerma distribution around the source will be of use in estimating the doses to the concerned personnel. This paper discusses the air kerma distribution around and iridium-192 radiography source computed using Monte Carlo method

14

Air Kerma above environmental radiometric calibration facility for field equipment  

International Nuclear Information System (INIS)

The use of gamma ray spectrometers broadened the aims of gamma ray surveys, stead of measuring only the gross radiation, as was done with the GM tubes, it is now possible to be used for uranium exploration, geological mapping as an aid to the exploration of non radioactive ores like gold and tin, radiation background measurements to identify hot spots for radiation hazard evaluation and environmental monitoring of fallout from radiological and nuclear accidents. It became necessary to carefully and precisely calibrate the field equipment to be used to get all the information from such uses. There is an environmental radiometric calibration facility for field equipment, consisting of eight radioactive concrete sources, at the Institute of Radioprotection and Dosimetry - IRD (CNEN/Brazil). These sources are cylindrical with 3 m diameter, 0.5 m thick and weigh about 7.5 tons each. The amount and type of the radioactive material, 238 U and 232 Th and 40 K ores in secular radioactive equilibrium, added to the concrete to simulate rock outcrops, varies in order to obtain different gamma fields, varying in both energy and intensity. These different radiation fields were measured with a HPGe portable detector, specifically calibrated for spectrum stripping, and the air kerma energy distribution was determined for each concrete source and compared with the total air kerma calculated from the nuclide concentration and by others radiometric methocentration and by others radiometric methods. (author)

15

Air kerma based dosimetry calibration for the Leksell Gamma Knife.  

Science.gov (United States)

No accepted official protocol exists for the dosimetry of the Leksell Gamma Knife (GK) stereotactic radiosurgery device. Establishment of a dosimetry protocol has been complicated by the unique partial-hemisphere arrangement of 201 individual 60Co beams simultaneously focused on the treatment volume and by the rigid geometry of the GK unit itself. This article proposes an air kerma based dosimetry protocol using either an in-air or in-acrylic phantom measurement to determine the absorbed dose rate of fields of the 18 mm helmet of a GK unit. A small-volume air ionization chamber was used to make measurements at the physical isocenter of three GK units. The absorbed dose rate to water was determined using a modified version of the AAPM Task Group 21 protocol designed for use with 60Co-based teletherapy machines. This experimentally determined absorbed dose rate was compared to the treatment planning system (TPS) absorbed dose rate. The TPS used with the GK unit is Leksell GammaPlan. The TPS absorbed dose rate at the time of treatment is the absorbed dose rate determined by the physicist at the time of machine commissioning decay corrected to the treatment date. The TPS absorbed dose rate is defined as absorbed dose rate to water at the isocenter of a water phantom with a radius of 8 cm. Measurements were performed on model B and C Gamma Knife units. The absorbed dose rate to water for the 18 mm helmet determined using air-kerma based calculations is consistently between 1.5% and 2.9% higher than the absorbed dose rate provided by the TPS. These air kerma based measurements allow GK dosimetry to be performed with an established dosimetry protocol and without complications arising from the use of and possible variations in solid phantom material. Measurements were also made with the same ionization chamber in a spherical acrylic phantom for comparison. This methodology will allow further development of calibration methods appropriate for the smaller fields of GK units to be compared to a well established standard. PMID:19291973

Meltsner, Sheridan Griffin; DeWerd, Larry A

2009-02-01

16

Air kerma based dosimetry calibration for the Leksell Gamma Knife  

Energy Technology Data Exchange (ETDEWEB)

No accepted official protocol exists for the dosimetry of the Leksell Gamma Knife registered (GK) stereotactic radiosurgery device. Establishment of a dosimetry protocol has been complicated by the unique partial-hemisphere arrangement of 201 individual {sup 60}Co beams simultaneously focused on the treatment volume and by the rigid geometry of the GK unit itself. This article proposes an air kerma based dosimetry protocol using either an in-air or in-acrylic phantom measurement to determine the absorbed dose rate of fields of the 18 mm helmet of a GK unit. A small-volume air ionization chamber was used to make measurements at the physical isocenter of three GK units. The absorbed dose rate to water was determined using a modified version of the AAPM Task Group 21 protocol designed for use with {sup 60}Co-based teletherapy machines. This experimentally determined absorbed dose rate was compared to the treatment planning system (TPS) absorbed dose rate. The TPS used with the GK unit is Leksell GammaPlan. The TPS absorbed dose rate at the time of treatment is the absorbed dose rate determined by the physicist at the time of machine commissioning decay corrected to the treatment date. The TPS absorbed dose rate is defined as absorbed dose rate to water at the isocenter of a water phantom with a radius of 8 cm. Measurements were performed on model B and C Gamma Knife units. The absorbed dose rate to water for the 18 mm helmet determined using air-kerma based calculations is consistently between 1.5% and 2.9% higher than the absorbed dose rate provided by the TPS. These air kerma based measurements allow GK dosimetry to be performed with an established dosimetry protocol and without complications arising from the use of and possible variations in solid phantom material. Measurements were also made with the same ionization chamber in a spherical acrylic phantom for comparison. This methodology will allow further development of calibration methods appropriate for the smaller fields of GK units to be compared to a well established standard.

Meltsner, Sheridan Griffin; DeWerd, Larry A. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2009-02-15

17

Significant discrepancies in air kerma rates measured with free-air and cavity ionization chambers  

Science.gov (United States)

Air kerma rates were measured in the same narrow X-ray beams in the range 300-400 kV with a free-air ionization chamber and a graphite cavity ionization chamber. The graphite-to-air stopping-power ratios that are necessary to determine the air kerma rates according to the cavity theory were calculated by means of Monte Carlo methods based on measured energy distributions of the photon fluence and the ICRU 37 stopping-power values. As a result, it was found that the air kerma rates obtained with the cavity chamber were significantly higher, by up to about 2%. The discrepancies disappeared when different stopping-power values for graphite were used in the calculation of the graphite-to-air stopping-power ratios. The ICRU 37 values were calculated on the basis of a mean excitation energy in graphite of I=78 eV, in contrast to I=86 eV used for the calculation of those values solving the discrepancies obtained in the first approach. The results are of fundamental interest for primary standard dosimetry laboratories because all of them employ graphite cavity chambers to realize the unit of air kerma for 137Cs- and 60Co-?-radiation.

Büermann, L.; Hilgers, G.

2007-09-01

18

Determination of the reference air kerma rate for brachytherapy sources  

International Nuclear Information System (INIS)

The purpose of this paper is to report the results obtained determining the reference air kerma rate, Kr, for sources as Yb-169 and Cs-137 of low dose rates and Ir-192 sources of low and high dose rates, applying a standard formalism adopted by the 'Cominato per la Dosimetria in Radioterapia' (CDR) of the Associazione Italiana di Fisica Biomedica (AIFB). The formalism allows the evaluations of Kr by using ionization measurements in free air, carried out at 1 meter or at different distances from the source. As well known this kind of measurement needs the determination of several correction factors to be applied to the ion-chamber reading. The methods adopted to determine these corrections are examined in particular to determine: a) the collection efficiency at a low dose rate as well as other correction factors to obtain a standard measurement condition; b) the perturbation correction factors that take into account for the presence of scattered photons in the environment, the finite size of the ion-chamber and the presence of the air between the source and the detector. However, the method used to determine the calibration factor Nk (source) of the ion-chamber, implies an adequate choice of the number and qualities of the calibration beams. When an univocal dosimetric formalism was adopted in an Italian intercomparison of Ir-192 (wire sources) Kr determinations, the average deviation between the Kr values obtained by the centers was 0.994 with an extreme deviation of rs was 0.994 with an extreme deviation of no more than 2%. Once determined the Kr value for the brachytherapy source an indirect procedure to determine the Kr by using a well ionization chamber, calibrated at the hospital center, results the best suitable procedure for routine measurements required for brachytherapy quality assurance

19

Standardization of iridium-192 coiled source in terms of air kerma output  

International Nuclear Information System (INIS)

ICRU (1985) recommended that the output of gamma ray brachytherapy sources should be specified in terms of reference air kerma rate, defined as the kerma rate to air in air at a reference distance of 1 meter, perpendicular to the long axis of the source, corrected for air attenuation and scattering. As these measurements are difficult to carry out in the routine clinical use, it is the common practice to calibrate the re-entrant ionization chamber with respect to open air measurements and use the re-entrant chamber for routine measurements. This paper reports on the measurements carried out to correlate the nominal activity and air kerma rate of 192Ir wire sources supplied by the Board of Radiation and Isotope Technology, Department of Atomic Energy. (author). 3 refs, 1 tab

20

The IPEM code of practice for determination of the reference air kerma rate for HDR 192Ir brachytherapy sources based on the NPL air kerma standard  

Science.gov (United States)

This paper contains the recommendations of the high dose rate (HDR) brachytherapy working party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a Code of Practice (COP) for the UK for measuring the reference air kerma rate (RAKR) of HDR 192Ir brachytherapy sources. In 2004, the National Physical Laboratory (NPL) commissioned a primary standard for the realization of RAKR of HDR 192Ir brachytherapy sources. This has meant that it is now possible to calibrate ionization chambers directly traceable to an air kerma standard using an 192Ir source (Sander and Nutbrown 2006 NPL Report DQL-RD 004 (Teddington: NPL) http://publications.npl.co.uk). In order to use the source specification in terms of either RAKR, \\dot K_R (ICRU 1985 ICRU Report No 38 (Washington, DC: ICRU); ICRU 1997 ICRU Report No 58 (Bethesda, MD: ICRU)), or air kerma strength, SK (Nath et al 1995 Med. Phys. 22 209-34), it has been necessary to develop algorithms that can calculate the dose at any point around brachytherapy sources within the patient tissues. The AAPM TG-43 protocol (Nath et al 1995 Med. Phys. 22 209-34) and the 2004 update TG-43U1 (Rivard et al 2004 Med. Phys. 31 633-74) have been developed more fully than any other protocol and are widely used in commercial treatment planning systems. Since the TG-43 formalism uses the quantity air kerma strength, whereas this COP uses RAKR, a unit conversion from RAKR to air kerma strength was included in the appendix to this COP. It is recommended that the measured RAKR determined with a calibrated well chamber traceable to the NPL 192Ir primary standard is used in the treatment planning system. The measurement uncertainty in the source calibration based on the system described in this COP has been reduced considerably compared to other methods based on interpolation techniques.

Bidmead, A. M.; Sander, T.; Locks, S. M.; Lee, C. D.; Aird, E. G. A.; Nutbrown, R. F.; Flynn, A.

2010-06-01

 
 
 
 
21

X-rays spectrum and air Kerma during a mammography study  

International Nuclear Information System (INIS)

In this calculation series was modeled the source of electrons, the target and the filter. Using thermoluminescent dosemeters of ZrO2+PTFE the air Kerma was measured in five points located on a phantom made with acrylic and water when it was exposed to a X-rays beam produced by electrons of 24 KeV and 10 m A of current that produces a mammography. The air Kerma values at the entrance surface of the phantom were compared with values calculated by Monte Carlo methods. The air Kerma values measured indicate that approximately the five points receive the same air Kerma, what means that the beam is homogeneous, of the Monte Carlo calculations we find that the center receives a greater dose what implies that the beam is not uniform, the explanation of this fact is attributed to was used a simple model in the calculations, nevertheless, the air Kerma average measured at the entrance surface of the phantom was of 0.96 +- 0.03 m G, while the other obtained by the calculations was of 0.96 +- 0.06 mGy, to compare both do not exist significant differences. (author)

22

Second EUROMET comparison of air kerma rate and activity measurements of 192Ir brachytherapy wires  

International Nuclear Information System (INIS)

At the occasion of the EUROMET Workshop on Ionising Radiation and Radioactivity at the NPL, it was decided to carry out a second intercomparison on air kerma rate (AKR) and activity measurements on 192Ir brachytherapy sources in the frame of EUROMET project no. 219. The intercomparison has shown that both air kerma rate measurements and activity measurements of 192Ir brachytherapy wires are not trivial. One of the drawbacks is the appreciable inhomogeneity of the wires. Disregarding some outliers, the spread of the AKR measurements was below 1.5%, while the variation in the activity measurements was very large, due to reasons which are not completely understood. (orig.)

23

Air Kerma Rate estimation by means of in-situ gamma spectrometry: a Bayesian approach.  

Science.gov (United States)

Bayesian inference is used to determine the Air Kerma Rate based on in-situ gamma spectrum measurement performed with an NaI(Tl) scintillation detector. The procedure accounts for uncertainties in the measurement and in the mass energy transfer coefficients needed for the calculation. The WinBUGS program (Spiegelhalter et al., 1999) was used. The results show that the relative uncertainties in the Air Kerma estimate are of about 1%, and that the choice of unfolding procedure may lead to an estimate systematic error of 3%. PMID:19914079

Cabal, Gonzalo; Kluson, Jaroslav

2010-01-01

24

Air Kerma Rate estimation by means of in-situ gamma spectrometry: A Bayesian approach  

Energy Technology Data Exchange (ETDEWEB)

Bayesian inference is used to determine the Air Kerma Rate based on in-situ gamma spectrum measurement performed with an NaI(Tl) scintillation detector. The procedure accounts for uncertainties in the measurement and in the mass energy transfer coefficients needed for the calculation. The WinBUGS program () was used. The results show that the relative uncertainties in the Air Kerma estimate are of about 1%, and that the choice of unfolding procedure may lead to an estimate systematic error of 3%.

Cabal, Gonzalo [Department of Dosimetry and Applications of Ionizing Radiation, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 115 19 Prague 1 (Czech Republic); Department of Radiation Dosimetry, Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Na Truhlarce 39/64, 180 86 Prague 8 (Czech Republic)], E-mail: cabal@ujf.cas.cz; Kluson, Jaroslav [Department of Dosimetry and Applications of Ionizing Radiation, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 115 19 Prague 1 (Czech Republic)

2010-04-15

25

Spectrally average conversion coefficients for air kerma to ambient dose equivalent for clinical linear accelerator  

Energy Technology Data Exchange (ETDEWEB)

This work aims to calculate the conversion coefficients from air kerma to ambient dose equivalent, H*(10)/K{sub air} for photon beams produced by linear accelerators, such as the Clinac-4, Clinac-6, Clinac-18 and Clinac-2500, after transmission through primary barriers of radiotherapy treatment rooms. Concrete walls of thickness 1.0, 1.5 and 2.0 m were irradiated with 30 cmx30 cm primary beam spectra. The transmitted spectra were calculated to obtain the conversion coefficients for beams found in radiotherapy services. The calculations were done using the MCNP-4B Monte Carlo code. The results indicate the need to use a factor of about 1.20 to obtain the ambient dose equivalent for radiation surveys near primary barriers using instruments calibrated in air kerma.

Frota, Marco A. [Laboratorio de Radiobiologia e Radiometria, Departamento de Biologia Geral, Universidade Federal Fluminense, Outeiro de Sao Joao Batista, s/n, Caixa Postal 100.436-24001-970 Niteroi, RJ (Brazil)], E-mail: marcofrota@ufrj.br; Crispim, Verginia R.; Silva, Ademir X. [Programa de Engenharia Nuclear/COPPE, Universidade Federal do Rio de Janeiro, Ilha do Fundao, Caixa Postal 68509, 21945-970, Rio de Janeiro, RJ (Brazil); Kelecom, Alphonse [Laboratorio de Radiobiologia e Radiometria, Departamento de Biologia Geral, Universidade Federal Fluminense, Outeiro de Sao Joao Batista, s/n, Caixa Postal 100.436-24001-970 Niteroi, RJ (Brazil)

2009-01-15

26

Spectrally average conversion coefficients for air kerma to ambient dose equivalent for clinical linear accelerator  

International Nuclear Information System (INIS)

This work aims to calculate the conversion coefficients from air kerma to ambient dose equivalent, H*(10)/Kair for photon beams produced by linear accelerators, such as the Clinac-4, Clinac-6, Clinac-18 and Clinac-2500, after transmission through primary barriers of radiotherapy treatment rooms. Concrete walls of thickness 1.0, 1.5 and 2.0 m were irradiated with 30 cmx30 cm primary beam spectra. The transmitted spectra were calculated to obtain the conversion coefficients for beams found in radiotherapy services. The calculations were done using the MCNP-4B Monte Carlo code. The results indicate the need to use a factor of about 1.20 to obtain the ambient dose equivalent for radiation surveys near primary barriers using instruments calibrated in air kerma

27

Evaluating air kerma at a medical cyclotron after refined shielding design using the TLD approach  

International Nuclear Information System (INIS)

Cyclotrons are increasingly constructed at medical universities in Taiwan to produce nuclear medicine. However, their operation generates amounts of highly energetic photons from 18O(p, ?n)18F reactions. This reaction posed a health hazard to the public. Chung Shan University Hospital had to increase its 2-deoxy-2-[18F]-fluoro-D-glucose products in 2011 to 11.5 times that in 2004 and redesign the self-shielded (CTI) Radioisotope Delivery System (RDS)-111 to meet guild requirements regarding the production of positron emission tomography (PET). This study is the first to evaluate air kerma in a CTI RDS-111 cyclotron center with a thermoluminescent dosimeter (TLD). Air kerma of up to 17.0±2.8 mGy/mo indicated that heavy leakage of photons penetrated the PET/CT facility. The new L-shaped concrete shield and added d2 door can adequately protect the public. The minimum detectable limit of air kerma is discussed to demonstrate the reliability of the TLD approach. (author)

28

Comparison of air-kerma strength determinations for HDR 192Ir sources  

International Nuclear Information System (INIS)

Purpose: To perform a comparison of the interim air-kerma strength standard for high dose rate (HDR) 192Ir brachytherapy sources maintained by University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) with measurements of the various source models using modified techniques from the literature. The current interim standard was established by Goetsch et al. in 1991 and has remained unchanged to date. Methods: The improved, laser-aligned seven-distance apparatus of University of Wisconsin Medical Radiation Research Center (UWMRRC) was used to perform air-kerma strength measurements of five different HDR 192Ir source models. The results of these measurements were compared with those from well chambers traceable to the original standard. Alternative methodologies for interpolating the 192Ir air-kerma calibration coefficient from the NIST air-kerma standards at 137Cs and 250 kVp x rays (M250) were investigated and intercompared. As part of the interpolation method comparison, the Monte Carlo code EGSnrc was used to calculate updated values of Awall for the Exradin A3 chamber used for air-kerma strength measurements. The effects of air attenuation and scatter, room scatter, as well as the solution method were investigated in detail. Results: The average measurements when using the inverse NK interpolation method for the Classic Nucletron, Nucletron microSelectron, VariSource VS2000, GammaMedicroSelectron, VariSource VS2000, GammaMed Plus, and Flexisource were found to be 0.47%, -0.10%, -1.13%, -0.20%, and 0.89% different than the existing standard, respectively. A further investigation of the differences observed between the sources was performed using MCNP5 Monte Carlo simulations of each source model inside a full model of an HDR 1000 Plus well chamber. Conclusions: Although the differences between the source models were found to be statistically significant, the equally weighted average difference between the seven-distance measurements and the well chambers was 0.01%, confirming that it is not necessary to update the current standard maintained at the UWADCL.

29

Comparison of air-kerma strength determinations for HDR {sup 192}Ir sources  

Energy Technology Data Exchange (ETDEWEB)

Purpose: To perform a comparison of the interim air-kerma strength standard for high dose rate (HDR) {sup 192}Ir brachytherapy sources maintained by University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) with measurements of the various source models using modified techniques from the literature. The current interim standard was established by Goetsch et al. in 1991 and has remained unchanged to date. Methods: The improved, laser-aligned seven-distance apparatus of University of Wisconsin Medical Radiation Research Center (UWMRRC) was used to perform air-kerma strength measurements of five different HDR {sup 192}Ir source models. The results of these measurements were compared with those from well chambers traceable to the original standard. Alternative methodologies for interpolating the {sup 192}Ir air-kerma calibration coefficient from the NIST air-kerma standards at {sup 137}Cs and 250 kVp x rays (M250) were investigated and intercompared. As part of the interpolation method comparison, the Monte Carlo code EGSnrc was used to calculate updated values of A{sub wall} for the Exradin A3 chamber used for air-kerma strength measurements. The effects of air attenuation and scatter, room scatter, as well as the solution method were investigated in detail. Results: The average measurements when using the inverse N{sub K} interpolation method for the Classic Nucletron, Nucletron microSelectron, VariSource VS2000, GammaMed Plus, and Flexisource were found to be 0.47%, -0.10%, -1.13%, -0.20%, and 0.89% different than the existing standard, respectively. A further investigation of the differences observed between the sources was performed using MCNP5 Monte Carlo simulations of each source model inside a full model of an HDR 1000 Plus well chamber. Conclusions: Although the differences between the source models were found to be statistically significant, the equally weighted average difference between the seven-distance measurements and the well chambers was 0.01%, confirming that it is not necessary to update the current standard maintained at the UWADCL.

Rasmussen, Brian E.; Davis, Stephen D.; Schmidt, Cal R.; Micka, John A.; DeWerd, Larry A. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2011-12-15

30

Calculated neutron air kerma strength conversion factors for a generically encapsulated Cf-252 brachytherapy source  

CERN Document Server

The sup 2 sup 5 sup 2 Cf neutron air kerma strength conversion factor (S sub K sub N /m sub C sub f) is a parameter needed to convert the radionuclide mass (mu g) provided by Oak Ridge National Laboratory into neutron air kerma strength required by modern clinical brachytherapy dosimetry formalisms indicated by Task Group No. 43 of the American Association of Physicists in Medicine (AAPM). The impact of currently used or proposed encapsulating materials for sup 2 sup 5 sup 2 Cf brachytherapy sources (Pt/Ir-10%, 316L stainless steel, nitinol, and Zircaloy-2) on S sub K sub N /m sub C sub f was calculated and results were fit to linear equations. Only for substantial encapsulation thicknesses, did S sub K sub N /m sub C sub f decrease, while the impact of source encapsulation composition is increasingly negligible as Z increases. These findings are explained on the basis of the non-relativistic kinematics governing the majority of sup 2 sup 5 sup 2 Cf neutron interactions. Neutron kerma and energy spectra resul...

Rivard, M J; D'Errico, F; Tsai, J S; Ulin, K; Engler, M J

2002-01-01

31

Effects of aluminum-copper alloy filtration on photon spectra, air kerma rate and image contrast  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Este estudo avaliou a redução da taxa de kerma no ar, o espectro de energia dos raios X e alterações na qualidade da imagem radiográfica. Comparações com várias espessuras do filtro de liga de alumínio-cobre em três diferentes porcentagens foram feitas com o filtro de alumínio. Os experimentos foram [...] feitos utilizando-se um aparelho de raios X odontológico convencional, obtendo radiografias com auxílio de um fantoma de segmento de mandíbula e de uma escala de densidade confeccionada com alumínio laminado. Dependendo da espessura da filtração da liga de alumínio-cobre, o feixe de raios X pôde ser endurecido em relação ao filtro de alumínio. O uso do filtro de liga de alumínio-cobre resultou em 8,40% a 47,33% de redução da taxa média de kerma no ar e indicou contraste da imagem radiográfica sem alteração, quando comparado com a filtração de alumínio, mostrando que os filtros de liga de alumínio-cobre tornam-se alternativas aceitáveis em relação aos filtros de alumínio. Abstract in english This study evaluated the performance of aluminum-copper alloy filtration, without the original aluminum filter, for dental radiography in terms of x-ray energy spectrum, air kerma rate and image quality. Comparisons of various thicknesses of aluminum-copper alloy in three different percentages were [...] made with aluminum filtration. Tests were conducted on an intra-oral dental x-ray machine and were made on mandible phantom and on step-wedge. Depending on the thickness of aluminum-copper alloy filtration, the beam could be hardened and filtrated. The use of the aluminum-copper alloy filter resulted in reductions in air kerma rate from 8.40% to 47.33%, and indicated the same image contrast when compared to aluminum filtration. Aluminum-copper alloy filtration may be considered a good alternative to aluminum filtration.

Andréa, Gonçalves; João Manuel Domingos de Almeida, Rollo; Marcelo, Gonçalves; Francisco, Haiter Neto; Frab Norberto, Bóscolo.

2004-12-01

32

Sensitivity/uncertainty analysis for free-in-air tissue kerma due to initial radiation at Hiroshima and Nagasaki  

International Nuclear Information System (INIS)

Uncertainty estimates and cross correlations by range/survivor have been calculated for the Hiroshima and Nagasaki free-in-air (FIA) tissue kerma obtained from two-dimensional air/ground transport calculations. The uncertainties due to modeling parameter and basic nuclear transport data uncertainties were calculated for 700-, 1000-, and 1500-m ground ranges. Only the FIA tissue kerma due to initial radiation was treated in the analysis; the uncertainties associated with terrain and building shielding and phantom attenuation were not considered in this study. Uncertainties of --20% were obtained for the prompt neutron and secondary gamma kerma and 30% for the prompt gamma kerma at both cities. The uncertainties on the total prompt kerma at Hiroshima and Nagasaki are --18 and 15%, respectively. The estimated uncertainties vary only slightly by ground range and are fairly highly correlated. The total prompt kerma uncertainties are dominated by the secondary gamma uncertainties, which in turn are dominated by the modeling parameter uncertainties, particularly those associated with the weapon yield and radiation sources

33

Method for verifying the air kerma strength of I-125 plaques for the treatment of ocular melanoma.  

Science.gov (United States)

The purpose of this work was to develop a method for easily verifying that the activity or air kerma strength of pre-assembled eye plaques, used in the treatment of ocular melanomas, agrees with the activity or air kerma strength called for in the treatment plan. A Capintec CRC-7 Dose Calibrator with its standard vial/syringe sample holder was used to measure the activity of pre-assembled COMS and Eye Physics EP917 eye plaques using IsoAid Advantage I-125 seeds. Plaque activity measurements were made by placing the plaque face up in the center of a 5 cm tall Styrofoam insert in the source holder. Activity measurements were made with the source holder rotated to four angles (0°, 90°, 180°, and 270°). The average of these four values was converted to air kerma strength and divided by the assay air kerma strength, from the NIST traceable source calibration, and decayed to the plaque measurement date, to determine a plaque calibration factor. The average of the calibration factors for each plaque type was used to establish a calibration factor for each plaque type. Several partially loaded plaque configurations were included in this study and different methods were used to determine the effects of partial loading. This verification method is easy to implement with commonly available equipment and is effective in identifying possible errors. During this two-year study, the air kerma strength of 115 eye plaques was checked and 11 possible errors were identified. PMID:25207419

Zimmermann, L W; Wilkinson, D Allan

2014-01-01

34

SHORT COMMUNICATION: Re-evaluation of the BIPM international standard for air kerma in 60Co gamma radiation  

Science.gov (United States)

A re-evaluation of the BIPM standard for air kerma in 60Co radiation has been made. The changes to the air-kerma rate determination arise from four sources: (i) the results of Monte Carlo calculations of correction factors for the standard; (ii) a re-evaluation of the correction factor for saturation; (iii) a new evaluation of the air volume of the standard using an experimental chamber of variable volume; (iv) the adoption of a new reference beam at the BIPM. The combined effect of these changes is an increase in the BIPM determination of air-kerma rate by the factor 1.0054 and a reduction of the relative standard uncertainty of this determination to 1.5 parts in 103. A full uncertainty budget is presented. The new standard is effective from 1 November 2007.

Burns, David T.; Allisy, Penelope J.; Kessler, Cecilia

2007-12-01

35

Preliminary study on quality audit for air kerma strength determination of high dose rate brachytherapy sources  

International Nuclear Information System (INIS)

Brachytherapy is one of the modes of treatment of cancerous cells. High dose rate (HDR) brachytherapy using high activity 192Ir source has become very popular for all brachytherapy applications worldwide. The accurate dose delivery to the patient depends on many dosimetric parameters. Air Kerma Strength is one of the clinical parameters which is recommended by many international bodies to specify the brachytherapy source strength and used in the TG-43 dosimetry formalism. Our study concludes that TLD based Quality Audit method can be used for postal audit of HDR brachytherapy sources strength verification

36

Avaliação do kerma no ar na superfície de entrada e da qualidade da imagem em radiografias de tórax Evaluation of entrance surface air kerma rate and clinical images quality in chest radiography  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Avaliar os fatores de técnica utilizados durante exames de tórax póstero-anterior em pacientes-padrão e correlacioná-los aos valores de kerma no ar na superfície de entrada e à qualidade das imagens clínicas. MATERIAIS E MÉTODOS: O estudo foi realizado em três hospitais do Rio de Janeiro, num total de cinco salas de raios X, com dez pacientes por sala. As imagens foram avaliadas pelos radiologistas dos serviços segundo o protocolo europeu. O kerma no ar na superfície de entrada foi estimado a partir da curva de rendimento do equipamento de raios X, que foi obtida utilizando câmara de ionização acoplada a um eletrômetro. Análise de variância foi realizada para verificar se a diferença entre os valores de kerma no ar na superfície de entrada é significativa. RESULTADOS: Os valores de kerma no ar na superfície de entrada variaram entre 0,05 e 0,26 mGy, com média 60% inferior ao nível de referência publicado na Portaria 453. Das imagens avaliadas, 98% atenderam acima de 65% dos critérios de qualidade. CONCLUSÃO: Para um padrão de qualidade da imagem, aceitável para o diagnóstico, verificou-se ampla variação do kerma no ar na superfície de entrada para pacientes-padrão. Isto demonstra a falta de padronização dos fatores de técnica e a existência de um potencial de redução do valor do kerma no ar na superfície de entrada.OBJECTIVE: To evaluate technical factors involved in posteroanterior chest radiography in standard patients, and correlating them with entrance surface air kerma rate and with the clinical images quality. MATERIALS AND METHODS: The present study was developed at three hospitals in Rio de Janeiro, Brazil, involving a total of five x-ray rooms, with ten patients per room. The images were evaluated by the radiologists of the institutions, in accordance with the European protocol. The estimation of surface entrance air kerma rate was based on the x-ray equipment output curve obtained with an ionization chamber coupled with an electrometer. Variance analysis was performed to evaluate the significance of the difference between entrance surface air kerma rates. RESULTS: Entrance surface air kerma rates ranged between 0.05 and 0.26 mGy, with a mean value 60% lower than the reference level established by the Order (Portaria 453. Among the images evaluated, 98% fulfilled > 65% of the images quality criteria. CONCLUSION: For a standard image quality that is acceptable for diagnosis purposes, a significant variation was observed in the entrance surface air kerma rate for standard patients, demonstrating the lack of technical factors standardization and a potential for decreasing the entrance surface air kerma rate.

Angelo Bernardo Brasil de Souza

2009-10-01

37

Determination of air kerma to dose equivalent conversion factors for x-ray spectra  

International Nuclear Information System (INIS)

Full text: The pulse height spectra of x-radiation qualities N-15 to N-60 of the ISO narrow (N) spectrum series were measured using a planar high-purity Ge spectrometer and a specially designed lead collimator. The pulse height spectra were unfolded to fluence spectra using Monte Carlo generated data of the spectrometer response. In order to verify the measuring and unfolding method, air kerma rates Ka(N) for radiation qualities N-15 to N-60 were measured using a NE 2575 600 cc thin window ionization chamber and compared to those calculated from the fluence spectra. Differences in Ka(N) were less than 5 % between the two methods of determination. In addition, the first and second HVLs (half-value layers) were calculated from the fluence spectra and compared to measured values. The values agreed within ca. 2 %. For each radiation quality, the conversion coefficient hpK(10;N,0o) from air kerma Ka to personal dose equivalent at 10 mm depth Hp(10) at the angle of incidence ? = 0o was calculated from the fluence spectrum using tabulated monoenergetic conversion coefficients k?(E) and hpK(10;E,0o). The values of hpK(10;N,0o) were compared to the values presented in ISO 4037-3 and to other published values. The agreement with ISO 4037-3 was within ca. 7 %. (author)

38

Comparison of the standards for air kerma of the NIM and the BIPM for 60Co gamma radiation  

International Nuclear Information System (INIS)

A comparison of the standards for air kerma of the National Institute of Metrology of China and of the Bureau International des Poids et Mesures was carried out in 60Co gamma radiation at the BIPM in December 2001. The ratio of the NIM and the BIPM standards for air kerma is 0.9992, with a combined standard uncertainty of 0.0018. The degrees of equivalence between the NIM and the other participants in the ongoing key comparison BIPM.RI(I)-K1 have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. (authors)

39

Air Quality Index  

Science.gov (United States)

In this interactive activity adapted from Air Quality Index: A Guide to Air Quality and Your Health by the U.S. EPA, learn about common pollutants in the air we breathe, their health effects, and how their levels are reported.

WGBH Educational Foundation

2011-03-21

40

Air kerma transmission factors of scattered X-rays in the maze of a linac room for lead shield  

International Nuclear Information System (INIS)

Spectra of scattered X-rays in the maze of a Linac (X-ray energies of 4, 6, and 10 MV) room were estimated by means of the Monte Carlo simulation, and air kerma transmission factors of the X-rays scattered through a lead shield were evaluated based on those spectra. Spectra of scattered X-rays showed a maximum in the energy area below 200 keV. The higher the accelerated electron energy, also, the smaller the scattering angle that tended to spread to the higher energy area of the distribution of spectra. The air kerma transmission factor of 120 deg scattered X-rays of 4 MV X-rays obtained in this study was larger than the transmission factors of 124 deg scattered photons of 60Co gamma rays through a lead shield given in ICRP. The air kerma transmission factors of 120 deg scattered X-rays of 6 MV X-rays were smaller than the transmission factors of 90 deg scattered photons of 60Co gamma rays. The air kerma transmission factors of 120 deg scattered X-rays of 10 MV X-rays was slightly larger than transmission factors of 90 deg scattered photons of 60Co gamma rays. Therefore, in the case of a 4 MV X-ray Linac room, the calculation method given in the ''Manual of Practical Shield Calculation of Radiation Facilities (2000)'' causes underestimation of leakage doses. (authors)

 
 
 
 
41

Air kerma rate measurements of high dose rate (HDR) brachytherapy source in Gammamed plus HDR machine  

International Nuclear Information System (INIS)

High dose rate (HDR) machines with high intensity iridium-192 source are on the increase for brachytherapy in the recent past. The main advantage is, miniature size of the source which could give optimised radiation dose distributions by variable dwell time. For gamma irradiation of endovascular brachytherapy, these sources are being used with dosimetry made available using Monte Carlo calculations. The treatment times in various dwell positions of the active source relate primarily to the activity of the source and the dose planned to the volume of interest. The main quality assurance (QA) involves 1) standardization of source activity in terms of Air Kerma Rate (AKA) and 2) the spatial accuracy of the source

42

Air kerma standardization for diagnostic radiology in a secondary standard laboratory  

International Nuclear Information System (INIS)

The demand for calibration services and quality control in diagnostic radiology has grown in the country since the publication of the governmental regulation 453, issued by the Brazilian Ministry of Health in 1998. At that time, to produce results facing the new legislation, many laboratories used different standards and radiation qualities, some of which could be inadequate. The international standards neither supplied consistent radiation qualities and standardization for the different types of equipment available. This situation changed with the publication of the new edition of the IEC 61267 standard, published in 2005. The objective of this work was to implement the standardization of the air kerma for the unatenuated qualities (RQR) of IEC 61267 in the National Laboratory of Metrology of the Ionizing Radiations (LNMRI) of the Institute of Radiation Protection and Dosimetry (IRD). Technical procedures were developed together with uncertainty budget. Results of interlaboratory comparisons demonstrate that the quantity is standardized and internationally traceable. (author)

43

Air kerma standardization for diagnostic radiology in a secondary standard laboratory  

Energy Technology Data Exchange (ETDEWEB)

The demand for calibration services and quality control in diagnostic radiology has grown in the country since the publication of the governmental regulation 453, issued by the Brazilian Ministry of Health in 1998. At that time, to produce results facing the new legislation, many laboratories used different standards and radiation qualities, some of which could be inadequate. The international standards neither supplied consistent radiation qualities and standardization for the different types of equipment available. This situation changed with the publication of the new edition of the IEC 61267 standard, published in 2005. The objective of this work was to implement the standardization of the air kerma for the unatenuated qualities (RQR) of IEC 61267 in the National Laboratory of Metrology of the Ionizing Radiations (LNMRI) of the Institute of Radiation Protection and Dosimetry (IRD). Technical procedures were developed together with uncertainty budget. Results of interlaboratory comparisons demonstrate that the quantity is standardized and internationally traceable. (author)

Ramos, Manoel M.O.; Peixoto, J. Guilherme P. [Instituto de Radioprotecao e Dosimetria (IRD-CNEN/RJ), Rio de Janeiro, RJ (Brazil)], e-mail: mmoramos@ird.gov.br, e-mail: guilherm@ird.gov.br; Lopes, Ricardo T. [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)], e-mail: ricardo@lin.ufrj.br

2009-07-01

44

Sampling size in the verification of manufactured-supplied air kerma strengths  

International Nuclear Information System (INIS)

Quality control mandate that the air kerma strengths (SK) of permanent seeds be verified, this is usually done by statistics inferred from 10% of the seeds. The goal of this paper is to proposed a new sampling method in which the number of seeds to be measured will be set beforehand according to an a priori statistical level of uncertainty. The results are based on the assumption that the SK has a normal distribution. To demonstrate this, the SK of each of the seeds measured was corrected to ensure that the average SK of its sample remained the same. In this process 2030 results were collected and analyzed using a normal plot. In our opinion, the number of seeds sampled should be determined beforehand according to an a priori level of statistical uncertainty

45

Study and determination of the national dosimetric standards in terms of air kerma for X-rays radiation fields of low and medium-energies  

International Nuclear Information System (INIS)

Progress in radiation protection and radiotherapy, and the increased needs in terms of accuracy lead national metrology institutes to improve the standard. For ionizing radiation, the standard is defined by an absolute instrument used for air kerma rate measurement. The aim of the thesis is to establish standards, in terms of air kerma for X-rays beams of low and medium-energies. This work enables to complement the standard beam range of the Laboratoire National Henri Becquerel (LNHB). Two free-air chambers have been developed, WK06 for medium-energy and WK07 for low-energy. The air-kerma rate is corrected by several correction factors. Some are determined experimentally; and the others by using Monte Carlo simulations. The uncertainty budget of the air-kerma rate at one standard deviation has been established. These dosimetric standards were compared with those of counterparts' laboratories and are consistent in terms of degree of equivalence. (author)

46

Survivor dosimetry. Part B. DS02 free-in-air neutron and gamma tissue kerma relative to DS86  

International Nuclear Information System (INIS)

The major determinant of the radiation dose to a survivor at a given location with respect to the hypocenter of a bomb detonation is the radiation field in the open at that location. Therefore, a change in free-in-air (FIA) kerma at any given distance from the bomb has a proportional effect on the doses of all survivors at that distance, if the shielding is not changed. The fluence-to-kerma coefficients used in the DS02 studies are discussed in Chapter 12, Part A, where one can see that the differences between the newer DS02 and older DS86 kerma coefficients for soft tissues of the body are quite small at the neutron and gamma-ray energies that are most important in the radiation dosimetry for the survivors. Thus, the differences in DS02 and DS86 FIA tissue kermas from neutrons and photons are due essentially to differences in the DS02 and DS86 source term and transport calculations discussed in Chapters 2 and 3. (J.P.N.)

47

Comparison of the standards for air kerma of the VSL and the BIPM for 60Co gamma radiation  

International Nuclear Information System (INIS)

An indirect comparison of the standards for air kerma of the Dutch Metrology Institute (VSL), The Netherlands, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in September 2005. The comparison result, based on the calibration coefficients for three transfer standards and expressed as a ratio of the VSL and the BIPM standards for air kerma, is 0.9985 with a combined standard uncertainty of 2.2 * 10-3. The latest result agrees with the result of the previous comparison in 60Co ? rays, made in 1996 and updated for recent changes made to the standards to give a value of 0.9982(37). The degrees of equivalence between the VSL and the other participants in the key comparison BIPM.RI(I)-K1 have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. (authors)

48

SHORT COMMUNICATION: Re-evaluation of the BIPM international standards for air kerma in x-rays  

Science.gov (United States)

A re-evaluation of the BIPM standards for air kerma in low- and medium-energy x-rays has been made. The changes to the air-kerma rate determination arise from three sources: (i) the results of Monte Carlo calculations of diaphragm correction factors for the standards, (ii) a measurement of the effect of scatter from the diaphragm support and (iii) a re-evaluation of the electron-loss corrections for the medium-energy standard. Scatter from the diaphragm support explains a long-standing trend observed in the results of international comparisons for medium-energy x-rays. The new standards were implemented on 1 September 2009.

Burns, David T.; Kessler, Cecilia; Allisy, Penelope J.

2009-10-01

49

Comparison of the standards of air kerma of the LNE-LNHB and the BIPM for 60Co gamma radiation  

International Nuclear Information System (INIS)

A direct comparison of the standards for air kerma of the Laboratoire National de Metrologie et d'Essais - Laboratoire National Henri Becquerel (LNE-LNHB), France and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in December 2003. The results, expressed as ratios of the LNE-LNHB and the BIPM standards for air kerma, indicate a relative difference of 3.5 x 10-3 with a combined standard uncertainty of 2.7 x 10-3. The earlier direct comparison in 60Co ? rays, made in 1993, resulted in an agreement of the two standards within 2.5 x 10-3. (authors)

50

Traffic air quality index.  

Science.gov (United States)

Vehicle emissions are responsible for a considerable share of urban air pollution concentrations. The traffic air quality index (TAQI) is proposed as a useful tool for evaluating air quality near roadways. The TAQI associates air quality with the equivalent emission from traffic sources and with street structure (roadway structure) as anthropogenic factors. The paper presents a method of determining the TAQI and defines the degrees of harmfulness of emitted pollution. It proposes a classification specifying a potential threat to human health based on the TAQI value and shows an example of calculating the TAQI value for real urban streets. It also considers the role that car traffic plays in creating a local UHI. PMID:25461063

Bagie?ski, Zbigniew

2015-02-01

51

Comparison of the standards of air kerma of the LNMRI/IRD and the BIPM for 60Co ? rays  

International Nuclear Information System (INIS)

A third comparison of the standards for air kerma of Laboratorio Nacional de Metrologia das Radiacoes Ionizantes/Institute de Radioprotecao e Dosimetria (LNMRI/IRD), Rio de Janeiro, Brazil and of the Bureau International des Poids et Mesures (BIPM) has been carried out in 60Co radiation. The comparison result is 1.0007 and demonstrates that the LNMRI/IRD and BIPM standards agree closely, as was the case for the previous comparisons in 1986 and 1996. (authors)

52

Avaliação do kerma no ar na superfície de entrada e da qualidade da imagem em radiografias de tórax / Evaluation of entrance surface air kerma rate and clinical images quality in chest radiography  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Avaliar os fatores de técnica utilizados durante exames de tórax póstero-anterior em pacientes-padrão e correlacioná-los aos valores de kerma no ar na superfície de entrada e à qualidade das imagens clínicas. MATERIAIS E MÉTODOS: O estudo foi realizado em três hospitais do Rio de Janeiro, [...] num total de cinco salas de raios X, com dez pacientes por sala. As imagens foram avaliadas pelos radiologistas dos serviços segundo o protocolo europeu. O kerma no ar na superfície de entrada foi estimado a partir da curva de rendimento do equipamento de raios X, que foi obtida utilizando câmara de ionização acoplada a um eletrômetro. Análise de variância foi realizada para verificar se a diferença entre os valores de kerma no ar na superfície de entrada é significativa. RESULTADOS: Os valores de kerma no ar na superfície de entrada variaram entre 0,05 e 0,26 mGy, com média 60% inferior ao nível de referência publicado na Portaria 453. Das imagens avaliadas, 98% atenderam acima de 65% dos critérios de qualidade. CONCLUSÃO: Para um padrão de qualidade da imagem, aceitável para o diagnóstico, verificou-se ampla variação do kerma no ar na superfície de entrada para pacientes-padrão. Isto demonstra a falta de padronização dos fatores de técnica e a existência de um potencial de redução do valor do kerma no ar na superfície de entrada. Abstract in english OBJECTIVE: To evaluate technical factors involved in posteroanterior chest radiography in standard patients, and correlating them with entrance surface air kerma rate and with the clinical images quality. MATERIALS AND METHODS: The present study was developed at three hospitals in Rio de Janeiro, Br [...] azil, involving a total of five x-ray rooms, with ten patients per room. The images were evaluated by the radiologists of the institutions, in accordance with the European protocol. The estimation of surface entrance air kerma rate was based on the x-ray equipment output curve obtained with an ionization chamber coupled with an electrometer. Variance analysis was performed to evaluate the significance of the difference between entrance surface air kerma rates. RESULTS: Entrance surface air kerma rates ranged between 0.05 and 0.26 mGy, with a mean value 60% lower than the reference level established by the Order (Portaria) 453. Among the images evaluated, 98% fulfilled > 65% of the images quality criteria. CONCLUSION: For a standard image quality that is acceptable for diagnosis purposes, a significant variation was observed in the entrance surface air kerma rate for standard patients, demonstrating the lack of technical factors standardization and a potential for decreasing the entrance surface air kerma rate.

Angelo Bernardo Brasil de, Souza; Simone Kodlulovich, Dias; Fernando Mecca, Augusto; Winston Andrade, Marques.

2009-10-01

53

Uncertainty evaluation of the kerma in the air, related to the active volume in the ionization chamber of concentric cylinders, by Monte Carlo simulation  

International Nuclear Information System (INIS)

To implant the primary standard of the magnitude kerma in the air for X-ray between 10 - 50 keV, the National Metrology Laboratory of Ionizing Radiations (LNMRI) must evaluate all the uncertainties of measurement related with Victtoren chamber. So, it was evaluated the uncertainty of the kerma in the air consequent of the inaccuracy in the active volume of the chamber using the calculation of Monte Carlo as a tool through the Penelope software

54

Determination of conversion factors from air kerma to operational dose equivalent quantities for low-energy X-ray spectra  

International Nuclear Information System (INIS)

The conversion coefficients from air kerma to ICRU operational dose equivalent quantities for STUK's realisation of the X-radiation qualities N-15 to N-60 of the ISO narrow (N) spectrum series were determined by utilising X-ray spectrum measurements. The pulse-height spectra were measured using a planar high-purity germanium spectrometer and unfolded to fluence spectra using Monte Carlo generated data of the spectrometer response. To verify the measuring and unfolding method, the first and second half-value layers and the air kerma rate were calculated from the fluence spectra and compared with the values measured using an ionisation chamber. For each radiation quality, the spectrum was characterised by the parameters given in ISO 4037-1. The conversion coefficients from the air kerma to the ICRU operational quantities Hp(10), Hp(0.07), H'(0.07) and H*(10) were calculated using monoenergetic conversion coefficients at zero angle of incidence. The results are discussed with respect to ISO 4037-4, and compared with published results for low-energy X-ray spectra. (authors)

55

Direct calibration of a reference standard against the air kerma strength primary standard, at {sup 192}Ir HDR energy  

Energy Technology Data Exchange (ETDEWEB)

The primary standard of low air kerma rate sources or beams, maintained at the Radiological Standards Laboratory (RSL) of the Bhabha Atomic Research Centre (BARC), is a 60 cm{sup 3} spherical graphite ionization chamber. A {sup 192}Ir HDR source was standardized at the hospital site in units of air kerma strength (AKS) using this primary standard. A 400 cm{sup 3} bakelite chamber, functioning as a reference standard at the RSL for a long period, at low air kerma rates (compared to external beam dose rates), was calibrated against the primary standard. It was seen that the primary standard and the reference standard, both being of low Z, showed roughly the same scatter response and yielded the same calibration factor for the 400 cm{sup 3} reference chamber, with or without room scatter. However, any likelihood of change in the reference chamber calibration factor would necessitate the re-transport of the primary standard to the hospital site for re-calibration. Frequent transport of the primary standard can affect the long-term stability of the primary standard, due to its movement or other extraneous causes. The calibration of the reference standard against the primary standard at the RSL, for an industrial type {sup 192}Ir source maintained at the laboratory, showed excellent agreement with the hospital calibration, making it possible to check the reference chamber calibration at RSL itself. Further calibration procedures have been developed to offer traceable calibration of the hospital well ionization chambers. (author)

Govinda Rajan, K.N. [Radiological Physics and Advisory Division, BARC, Mumbai (India)]. E-mail: grajanmpss@vsnl.com; Palani Selvam, T.; Bhatt, B.C. [Radiological Physics and Advisory Division, BARC, Mumbai (India); Vijayam, M.; Patki, V.S.; Vinatha [Radiation Safety Systems Division, BARC, Mumbai (India); Pendse, A. M.; Kannan, V. [Hinduja Hospital and Research Centre, Mumbai (India)

2002-04-01

56

Direct calibration of a reference standard against the air kerma strength primary standard, at 192Ir HDR energy  

International Nuclear Information System (INIS)

The primary standard of low air kerma rate sources or beams, maintained at the Radiological Standards Laboratory (RSL) of the Bhabha Atomic Research Centre (BARC), is a 60 cm3 spherical graphite ionization chamber. A 192Ir HDR source was standardized at the hospital site in units of air kerma strength (AKS) using this primary standard. A 400 cm3 bakelite chamber, functioning as a reference standard at the RSL for a long period, at low air kerma rates (compared to external beam dose rates), was calibrated against the primary standard. It was seen that the primary standard and the reference standard, both being of low Z, showed roughly the same scatter response and yielded the same calibration factor for the 400 cm3 reference chamber, with or without room scatter. However, any likelihood of change in the reference chamber calibration factor would necessitate the re-transport of the primary standard to the hospital site for re-calibration. Frequent transport of the primary standard can affect the long-term stability of the primary standard, due to its movement or other extraneous causes. The calibration of the reference standard against the primary standard at the RSL, for an industrial type 192Ir source maintained at the laboratory, showed excellent agreement with the hospital calibration, making it possible to check the reference chamber calibration at RSL itself. Further calibration procedures have been developed alibration procedures have been developed to offer traceable calibration of the hospital well ionization chambers. (author)

57

NaI(Tl) scintillator detectors stripping procedure for air kerma measurements of diagnostic X-ray beams  

International Nuclear Information System (INIS)

Air kerma is an essential quantity for the calibration of national standards used in diagnostic radiology and the measurement of operating parameters used in radiation protection. Its measurement within the appropriate limits of accuracy, uncertainty and reproducibility is important for the characterization and control of the radiation field for the dosimetry of the patients submitted to diagnostic radiology and, also, for the assessment of the system which produces radiological images. Only the incident beam must be considered for the calculation of the air kerma. Therefore, for energy spectrum, counts apart the total energy deposition in the detector must be subtracted. It is necessary to establish a procedure to sort out the different contributions to the original spectrum and remove the counts representing scattered photons in the detector’s materials, partial energy deposition due to the interactions in the detector active volume and, also, the escape peaks contributions. The main goal of this work is to present spectrum stripping procedure, using the MCNP Monte Carlo computer code, for NaI(Tl) scintillation detectors to calculate the air kerma due to an X-ray beam usually used in medical radiology. The comparison between the spectrum before stripping procedure against the reference value showed a discrepancy of more than 63%, while the comparison with the same spectrum after the stripping procedure showed a discrepancy of less than 0.2%

58

Exposure and air-kerma standards for cobalt-60 gamma rays  

International Nuclear Information System (INIS)

The implementation of the measuring conditions for the determination of the quantities exposure and air-kerma for Cobalt-60 gamma rays have been done at the Laboratorio Nacional de Metrologia das Radiacoes Ionizantes (LNMRI). Several years of work have already been done, and the results so far indicate that both quantities can be measured accordingly with the recommendations of the International Organizations and with uncertainties comparable with the ones practiced in similar laboratories. The comparisons done with the data obtained at the Bureau International des Poids et Mesures with their standards and experimental conditions have shown an excellent agreement, which strongly indicates that the LNMRI standards have an appropriate design and characteristics to be standards of high quality and performance. The efforts made during the last years to accomplish this aim, have been successful. Hence, the LNMRI is now in position to measure those quantities and to proceed with the periodical international intercomparisons in order to maintain the traceability to the International Metrology Network. (author)

59

Air kerma standardization for diagnostic radiology, and requirements proposal for calibration laboratories  

International Nuclear Information System (INIS)

The demand for calibration services and quality control in diagnostic radiology has grown in the country since the publication of the governmental regulation 453, issued by the Ministry of Health in 1998. At that time, to produce results facing the new legislation, many laboratories used different standards and radiation qualities, some of which could be inadequate. The international standards neither supplied consistent radiation qualities and standardization for the different types of equipment available. This situation changed with the publication of the new edition of the IEC 61267 standard, published in 2005. A metrology network was created, but it is not yet accredited by the accreditation organism of the country, INMETRO. The objective of this work was to implement the standardization of the air kerma for the un attenuated qualities (RQR) of IEC 61267, and to develop a requirement proposal for instruments calibration laboratories. Results of interlaboratory comparisons demonstrate that the quantity is standardized and internationally traceable. A laboratory requirement proposal was finalized and it shall be submitted to INMETRO to be used as auxiliary normative document in laboratory accreditation. (author)

60

Air kerma standardization for diagnostic radiology, and requirements proposal for calibration laboratories; Padronizacao da grandeza Kerma no ar para radiodiagnostico e proposta de requisitos para laboratorios de calibracao  

Energy Technology Data Exchange (ETDEWEB)

The demand for calibration services and quality control in diagnostic radiology has grown in the country since the publication of the governmental regulation 453, issued by the Ministry of Health in 1998. At that time, to produce results facing the new legislation, many laboratories used different standards and radiation qualities, some of which could be inadequate. The international standards neither supplied consistent radiation qualities and standardization for the different types of equipment available. This situation changed with the publication of the new edition of the IEC 61267 standard, published in 2005. A metrology network was created, but it is not yet accredited by the accreditation organism of the country, INMETRO. The objective of this work was to implement the standardization of the air kerma for the un attenuated qualities (RQR) of IEC 61267, and to develop a requirement proposal for instruments calibration laboratories. Results of interlaboratory comparisons demonstrate that the quantity is standardized and internationally traceable. A laboratory requirement proposal was finalized and it shall be submitted to INMETRO to be used as auxiliary normative document in laboratory accreditation. (author)

Ramos, Manoel Mattos Oliveira

2009-07-01

 
 
 
 
61

Corrections to air kerma rate measurements from a 192Ir high dose rate brachytherapy source to free space conditions  

International Nuclear Information System (INIS)

The purpose of this experiment was to determine the combined air scatter and air absorption correction necessary to apply to measurements of the air kerma rate made at a distance of 1 metre from a 192Ir source free in air. This correction needs to be determined as the National Physical Laboratory (NPL) intends to set up a calibration service whereby secondary standard ionisation chambers can be calibrated against a primary standard in terms of air kerma rate at 1 metre in free space from a 192Ir source. Measurements were made with 2 types of chamber. Firstly measurements were made with a 100 cm3 spherical graphite transfer chamber and then measurements were repeated using a 1.79 cm3 cylindrical cavity chamber which is one of a set of 3 chambers which form the primary standard for 60Co and 137Cs maintained by the NPL. As both these chambers were originally intended for use with photons of higher energies the graphite caps of the chambers provide a sufficient build up region to develop charged particle equilibrium. The 192Ir source used is a pellet encapsulated in a stainless steel casing, with diameter 1.1 mm and length 5 mm. The source was exposed using a High Dose Rate (HDR) microSelectron brachytherapy unit manufactured by Nucletron. Results from measurements made using the transfer chamber gave an air attenuation correction to be applied to the measured charge at a source to chamber distansured charge at a source to chamber distance of 1 metre of (1.2 ± 0.3)%. Measurements made using the cylindrical cavity chamber could not be used to determine an estimate of the air attenuation correction for this set up. (author)

62

Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer  

International Nuclear Information System (INIS)

Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1–3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactoryed air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 ± 0.015 and 0.412 ± 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 ± 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation curve on the IMBL using a simple experimental method, namely, HVL measurements. The HVL measurements strongly supports the x-ray beam spectrum, which in turn has a profound effect on x-ray dosimetry.

63

Air kerma standard for calibration of well-type chambers in Brazil using 192Ir HDR sources and its traceability  

International Nuclear Information System (INIS)

In Brazil there are over 100 high dose rate (HDR) brachytherapy facilities using well-type chambers for the determination of the air kerma rate of 192Ir sources. This paper presents the methodology developed and extensively tested by the Laboratorio de Ciencias Radiologicas (LCR) and presently in use to calibrate those types of chambers. The system was initially used to calibrate six well-type chambers of brachytherapy services, and the maximum deviation of only 1.0% was observed between the calibration coefficients obtained and the ones in the calibration certificate provided by the UWADCL. In addition to its traceability to the Brazilian National Standards, the whole system was taken to University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) for a direct comparison and the same formalism to calculate the air kerma was used. The comparison results between the two laboratories show an agreement of 0.9% for the calibration coefficients. Three Brazilian well-type chambers were calibrated at the UWADCL, and by LCR, in Brazil, using the developed system and a clinical HDR machine. The results of the calibration of three well chambers have shown an agreement better than 1.0%. Uncertainty analyses involving the measurements made both at the UWADCL and LCR laboratories are discussed.

64

European inter-comparison of Monte Carlo codes users for the uncertainty calculation of the kerma in air beside a caesium-137 source  

International Nuclear Information System (INIS)

Within the frame of the CONRAD European project (Coordination Network for Radiation Dosimetry), and more precisely within a work group paying attention to uncertainty assessment in computational dosimetry and aiming at comparing different approaches, the authors report the simulation of an irradiator containing a caesium 137 source to calculate the kerma in air as well as its uncertainty due to different parameters. They present the problem geometry, recall the studied issues (kerma uncertainty, influence of capsule source, influence of the collimator, influence of the air volume surrounding the source). They indicate the codes which have been used (MNCP, Fluka, Penelope, etc.) and discuss the obtained results for the first issue

65

Comparison BIPM.RI(I)-K8 of high dose-rate Ir-192 brachytherapy standards for reference air kerma rate of the VSL and the BIPM  

DEFF Research Database (Denmark)

An indirect comparison of the standards for reference air kerma rate for 192Ir high dose rate brachytherapy sources of the Dutch Metrology Institute (VSL), The Netherlands, and of the Bureau International des Poids et Mesures (BIPM) was carried out at the VSL in November 2009. The comparison result, based on the calibration coefficients for a transfer standard and expressed as a ratio of the VSL and the BIPM standards for reference air kerma rate, is 0.9873 with a combined standard uncertainty of 0.0061.

Alvarez, J.T.; De Pooter, J.A.

2014-01-01

66

Conversion coefficients from air kerma to personal dose equivalent Hp(3) fir eye-lens dosimetry  

International Nuclear Information System (INIS)

This work has been performed within the frame of the European Union ORAMED project (Optimization of Radiation protection for Medical staff). The main goal of the project is to improve standards of protection for medical staff for procedure resulting in potentially high exposures and to develop methodologies for better assessing and for reducing exposures to medical staff. The Work Package WP2 is involved in the development of practical eye lens dosimetry in interventional radiology. This study is complementary of the part of the ENEA report concerning the calculations with the MCNP code of the conversion factors related to the operational quantity Hp(3). A set of energy and angular dependent conversion coefficients Hp(3)/Kair in the new proposed square cylindrical phantom of ICRU tissue, have been calculated with the Monte-Carlo code PENELOPE. The Hp(3) values have been determined in terms of absorbed dose, according to the definition of this quantity, and also with the kerma approximation as formerly reported in ICRU reports. At low photon energy, up to 1 MeV, the two sets of conversion coefficients are consistent. Nevertheless, the differences increase at higher energy. This is mainly due to the lack of electronic equilibrium, especially for small angle incidences. The values of the conversion coefficients obtained with the code MCNP published by ENEA, agree with the kerma approximation calculations with PENELOPE. They are coherent with previous calculations in phantoms different in shape. But above 1 MeV, differences between conversion coefficient values calculated with the absorbed dose and with kerma approximation are significantly increasing, especially at low incidence angles. At those energies the electron transport has to be simulated. (author)

67

Construction of a laboratory for the implantation of primary standardization of the magnitude kerma in the air for the X-ray beams used in mammography  

International Nuclear Information System (INIS)

Aiming to diminish the uncertainty in each phase of the metrological chain, and the uncertainty in dosimetry processed at the X-ray beam applied in the mammography, is necessary that the LNMRI/IRD to develop a reference primary standard for the absolute form to the magnitude kerma in the air

68

Calculation of the correction factors for the primary standard of kerma in the air at the LNMRI-IRD, Rio de Janeiro, Brazil  

International Nuclear Information System (INIS)

In order to determine the primary standardization in terms of kerma in the air, a graphite ionization chamber is used for calculation some correction factors. A program was elaborated, using the Monte Carlo Penelope for simulate the CC01-110 at the LNMRI/IRD, Rio de Janeiro, Brazil

69

Calculation of average conversion coefficients for air kerma to effective dose for diagnostic X-ray beams  

International Nuclear Information System (INIS)

This work aims to calculate the average conversion coefficients from air kerma to ambient dose equivalent, H*(10)/Kair, and effective dose, E/Kair, for 50 kVp, 100 kVp and 150 kVp X ray beams used for medical diagnostic, after transmission through barriers of lead. The X ray qualities used were those recommended by the Birch and Marshall for primary diagnostic X rays. Several lead layers were irradiated with 50cm X 50cm primary beam spectra. The transmitted spectra were calculated to obtain the conversion coefficients for beams found in radiodiagnostic services. The calculations were done using the MCNPX code and voxel model FAX. The values obtained were compared with data derived from the literature. In addition, conversion coefficients for X ray qualities after penetration of lead layers were studied to get data which might be of interest in shielding of diagnostic rooms. (author)

70

Measurement of conversion coefficients between free in air kerma and personal dose equivalent for diagnostic X-ray beams  

International Nuclear Information System (INIS)

Conversion coefficients between free in air kerma and personal dose equivalent were experimentally determined for the diagnostic X-ray qualities recommended by the International Electrotechnical Commission (IEC) for primary beams (RQR) and three RQA. Harshaw LiF-100H thermoluminescent dosemeters (TLD) were used for measurements after being calibrated against an ionization chamber traceable to the National Metrology Laboratory. A 300mmx300mmx150mm polymethilmethacrylate (PMMA) slab phantom was used for deep-dose measurements. The dosemeters were placed in the central axis of the X-ray beam at five different depths in the phantom (5, 10, 15, 25 and 35 mm) upstream the beam direction. The typical combined standard uncertainty of conversion coefficient value was 12%

71

From Reference Air Kerma Rate to Nominal Absorbed Dose Rate to Water: Paradigm Shift in Photon Brachytherapy  

International Nuclear Information System (INIS)

In brachytherapy (BT), photon radiation sources are presently calibrated in terms of the reference air kerma rate K? (or air kerma strength SK). By direct source calibration in terms of Dw,1, the nominal absorbed dose rate to water at the TG-43U1 reference position at 1 cm in water and with the ability to measure distributions of this quantity, the accuracy of clinical BT-dosimetry should increase due to decreased calibration uncertainties compared to present methods. Several Dw,1 primary standards are under development for high energy, high dose rate and low energy, low dose rate sources. To provide worldwide traceability and guidance for clinical medical physicists, an ISO standardization project, Clinical Dosimetry - Photon Radiation Sources Used in Brachytherapy, is considered, in continuation of ISO 21439 (2009) for beta sources. Clear terms and definitions are fundamental. Reclassification of BT-photon radiation qualities is also needed, introducing a range of medium energy photons with mean energies between 40 keV and 150 keV. Radionuclide BT-sources and electronic X ray BT-sources, BT-detectors and BT-phantoms should be characterized by sets of reference data, through which the clinical medical physicist could critically evaluate the data supplied by the manufacturer, prior to clinical application. Plastic scintillators have the potential for transfer standards of high accuracy and for verification measurements of Bcy and for verification measurements of BT-source output in phantoms. Based on and extending the AAPM TG-43U1 formalism, this planned ISO-standard will provide guidance for clinical BT-dosimetry in terms of absorbed dose to water and for estimating the uncertainties. (author)

72

Neutron fluence and kerma free in air in a fission beam  

International Nuclear Information System (INIS)

The reactor-neutron-therapy facility of the Munich research reactor provides an intense beam of fission radiation with nearly equal intensities of the neutron and photon component, both having complex spectral structure in the energy region from 0.01 MeV up to 10 MeV. We determined the physical properties of the beam behind a 2.5 cm lead filter (RENT I) and of the unfiltered beam (RENT II) at a separation distance of 545 cm. Total neutron fluence rates (I: 1.31.108 s-1cm-2, II: 2.28.108 s-1cm-2) and the fission neutron fluence rate (I: 1.3% 0.1.108 s-1cm-2, II: 2.3% 0.2.108 s-1cm-2) were measured by means of the Mn-bath technique and threshold activation detectors, respectively. For the determination of the Kerma rates two pairs of neutron sensitive (t) and insensitive (u) chambers were employed. By means of measurements in the beam without and with additional thin filters of polyethylene the wall effects could be determined separately for the neutron and photon radiation components. This procedure offered the possibility to determine the chamber parameters for any mixed radiation field if the neutron sensitivity ksub(t) could be calculated for the involved fields. The kerma rates at 12kW thermal converter power were found to be for RENT I: Ksub(n) = 21.5 cGy/min and Ksub(g) = 6.4 cGy/min and for RENT II: Ksub(n) = 36.4 cGy/min and Ksub(g) = 32 cGy/min

73

Distribution of kerma rate in the air inside of hemodynamic room for typical projections of interventionist cardiology procedures; Distribuicao da taxa de kerma no ar em uma sala de hemodinamica para projecoes tipicas de procedimentos de cardiologia intervencionista  

Energy Technology Data Exchange (ETDEWEB)

The evaluation of dose to physicians involved in Interventional Cardiology (IC) is an extreme important matter due to the high and non-uniform distribution of dose values. The radiation control during each procedure is complex and the reasons for the high exposures have many different causes. Many international recommendations have already been written aiming the radiation protection optimization in IC. In Brazil, there is not any special orientation for the protection of those occupational persons, nor a specific legislation. The purpose of this work is to evaluate the air kerma rate at critical anatomic regions of the occupationally exposed staff that carry out IC procedures, in representative incidences in order to give subsidies for individual monitoring procedures implementation and to give more information about their radiation protection. The air kerma rate has been measured in the often used condition in the two more common IC procedures namely angiography and coronary angioplasty, using an adult patient simulator irradiated under RAO, LAO and AP projections for fluoro and digital acquisition modes. The measurements have been made in 45 points around the examination table at 5 different representatives heights of: eyes lens, thorax, hands, gonads and knees. AP projection shows the smaller scattered radiation contributions and a more homogeneous exposure distribution. The digital acquisition mode gives air kerma rates about 4 times higher than fluoro mode for LAO projection in the position occupied by the interventionist doctor, the anesthetist and the nursing staff. The most critical anatomic regions are: knees and gonads (without protection). On the physician hands position, values as high as 5 mGy/h have been measured, which can overpass, depending on the number of procedures done, the individual occupational annual limit. Therefore, in IC it is necessary to implement additional protection tools, elaborate safety guides (based on international experiences and recommendations) and establish a permanent radiation protection training programs. (author)

Sanchez, Mirtha Elizabet Gamarra

2008-07-01

74

Uncertainty evaluation of the kerma in the air, related to the active volume in the ionization chamber of concentric cylinders, by Monte Carlo simulation; Avaliacao de incerteza no kerma no ar, em relacao ao volume ativo da camara de ionizacao de cilindros concentricos, por simulacao de Monte Carlo  

Energy Technology Data Exchange (ETDEWEB)

To implant the primary standard of the magnitude kerma in the air for X-ray between 10 - 50 keV, the National Metrology Laboratory of Ionizing Radiations (LNMRI) must evaluate all the uncertainties of measurement related with Victtoren chamber. So, it was evaluated the uncertainty of the kerma in the air consequent of the inaccuracy in the active volume of the chamber using the calculation of Monte Carlo as a tool through the Penelope software

Lo Bianco, A.S.; Oliveira, H.P.S.; Peixoto, J.G.P., E-mail: abianco@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

2009-07-01

75

Calculation of the uncertainty associated to the result of entrance surface air kerma for conventional radiology patients  

International Nuclear Information System (INIS)

Radiation doses from diagnostic radiology are the largest contribution to the collective dose and the use of guidance (reference levels) has proven to be a tool for optimization of protection. Recently, with the support of the International Atomic Energy Agency (IAEA), eight countries of the Latin-American region have been working together on a programme to test methodologies for determining preliminary values of guidance levels for X-ray chest, lumbar spine and breast examinations. The approach used was to obtain entrance surface air kerma from measurements of X-ray tube outputs, corrected for distance and backscatter and later for real exposure parameters used with patients. For quality control, some of these values for a reduced number of patients were compared with direct TLD measurements directly placed on the patient during exposure. Given the number of parameters involved in the two methods, relatively large differences are deemed to be found in the comparison. The only way of deciding if measurements and calculations are outliers, for example, due to a systematic error or a mistake, is to compare these differences with the combined uncertainty. The aim of this paper is to present (in a detailed way) the methodology used in the pilot program ARCAL LXXV, the analyses of data performed within the survey and the estimated uncertainty. The parameters analyzed were: precision of the readings, positioning of the detector, reproducibility of the mAs and kV, long term stability of the instrument, radiation quality, kerma rate, radiation incidence, field size and field homogeneity, calibration factor of the equipment, temperature and pressure measurement, X-ray tube output curve adjustment, backscatter factor and focus-patient distance. The combined standard uncertainty for Ke in chest radiography in adult patients of standard complexion, was 12%, and the expanded uncertainty (k=2) was 24%. (author)

76

Calculation of the humidity correction factor in air kerma strength measurement for 125I and 103Pd brachytherapy sources and its uncertainty by Monte Carlo method  

International Nuclear Information System (INIS)

Highlights: ? Humidity can affect the measurement of air kerma strength. ? Humidity correction factor “khumidity” values are calculated by using a Monte Carlo method. ? Humidity correction factors are calculated for 2% to 100% relative humidity. ? khumidity shows a minimum at 10% relative humidity and a maximum at 100%. ? The uncertainty in khumidity is calculated to be about 0.2% for 125I and 103Pd sources. - Abstract: Humidity is one of the sources of systematic error in the absolute measurement of air kerma strength of 125I and 103Pd low energy brachytherapy sources by using free air ionization chambers. In this paper, the humidity correction factor and its uncertainty for several environmental conditions have been calculated by applying an indigenous developed uncertainty analysis algorithm programmed in FORTRAN. The results of the analysis showed that the humidity could affect the corrected measured source strength value by about 0.2%

77

Attenuation factors in terms of air kerma to ambient dose equivalent and effective dose for diagnostic X rays rooms  

International Nuclear Information System (INIS)

In the present study, the attenuation of the quantities fluence and air kerma free-in-air by various layers of lead was compared with that of the quantities effective dose, E, and ambient dose equivalent, H*(d). This work aims to calculate the attenuation factors from 50 kV, 125 kV and 150 kV of X ray beams used for medical diagnostic, after transmission through barriers of lead. The X ray qualities used were those recommended by the Birch and Marshall for primary diagnostic X rays. Several lead layers were irradiated with a 50 cm x 50 cm field of primary X ray spectra. The transmitted spectra were calculated to obtain the attenuation factors for beams found in radiodiagnostic services. The calculations were done using the MCNPX Monte Carlo code and voxel model MAX. The values obtained were compared with data derived from the literature. In addition, attenuation factors for X ray qualities after penetration of lead layers were studied to get data which might be of interest in shielding of diagnostic rooms. (author)

78

Room scatter studies in the air kerma strength standardization of the Amersham CDCS-J-type {sup 137}Cs source: a Monte Carlo study  

Energy Technology Data Exchange (ETDEWEB)

Corrections for room scatter, [k{sub sc}(d, H)]{sub RM}, as a function of source-to-detector distance, d, and source-to-floor-height, H, and also departure from constant room scatter, k{sub sl}, have been computed for rooms of various sizes using Monte Carlo methods for air kerma strength standardization of the Amersham CDCS-J-type {sup 137}Cs brachytherapy source. These corrections will also be applicable to any type of {sup 137}Cs source that may be considered for standardization. It was found that, depending upon the relative position of the source with respect to the surrounding concrete scattering surfaces (side walls, floor and ceiling) and different set of d values, the assumption of constant room scatter overestimated the air kerma strength, S{sub k}, by between 0.2% and 0.6%. (author)

Palani Selvam, T.; Govinda Rajan, K.N.; Nagarajan, P.S.; Bhatt, B.C.; Sethulakshmi, P. [Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, CT and CRS Building, Mumbai (India)

2002-05-07

79

European comparison of Monte Carlo codes users on the uncertainty calculations of air kerma determined in front of a cesium-137 beam  

International Nuclear Information System (INIS)

Within the framework of the European project CONRAD (Coordinated Network for Radiation Dosimetry, contract FP6-12684) coordinated by EURADOS (European Radiation Dosimetry group), WP4 was devoted to numerical dosimetry under the title 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Within this activity, a working group sent a list of eight exercises, dealing with radiation transport of photons, neutrons, protons and electrons, to be solved by the international community. This paper presents exercise number 4, dealing with the calculation of air kerma for a 137Cs beam. This problem was aimed at estimating the components of the uncertainty on the air kerma which cannot be measured, namely those due to geometrical data such as the source location, the diameter of the collimator, the material density, etc. 12 institutes of 10 different countries took part in this work, showing the interest in this proposal. (authors)

80

Bilateral comparison COOMET.RI(I)-S2 of the air-kerma standards of the IAEA and the VNIIM, Russian Federation in medium energy x-rays  

Science.gov (United States)

A bilateral comparison has been made between the air-kerma standards of the IAEA and the VNIIM in the medium-energy x-ray range. The results show the standards to be in agreement at the level of the stated standard uncertainty for the comparison of 4.1 parts in 103. The comparison result, based on the calibration coefficients for a transfer chamber, is expressed as a ratio of the IAEA and the VNIIM standards for air kerma, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Czap, L.; Gomola, I.; Oborin, A. V.; Villevalde, A. Y.

2014-01-01

 
 
 
 
81

Calculations of air-kerma strength, dose rate constant and radial dose function for Cathetron 60Co brachytherapy source using EGS-4 and MCNP Monte Carlo codes  

International Nuclear Information System (INIS)

The present study is aimed at computing air-kerma strength Sk' dose rate constant L, and radial dose function g(r) in compliance with AAPM TG43 formalism for Cathetron 60Co brachytherapy source and discussing significance of secondary electron transport where electronic equilibrium did not exit. The Monte Carlo-based EGS4 and MCNP (version 3.1) codes were used for this purpose

82

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the NIST, USA and the BIPM in mammography x-rays  

International Nuclear Information System (INIS)

A first key comparison has been made between the air-kerma standards of the NIST and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.2 parts in 103. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. (authors)

83

Monte Carlo aided room scatter studies in the primary air kerma strength standardization of a remote afterloading {sup 192}Ir HDR source  

Energy Technology Data Exchange (ETDEWEB)

Corrections for room scatter, [k{sub sc}(d, H)]{sub RM}, were derived using Monte Carlo methods for rooms of various sizes, including the brachytherapy treatment room, in which primary air kerma strength standardization of a remote afterloading microSelectron {sup 192}Ir HDR source was carried out, using a 60 cm{sup 3} spherical graphite ion chamber. It was observed that for a given source-to-floor height, H, the air kerma rate due to room scatter was found to be decreasing with increase in source-to-detector distance, d, whereas it is assumed to be constant in the experimental determination (multiple-distance method) of the air kerma strength (AKS). Irrespective of the room size considered in the present study and when H=100 cm, the assumption of 'constant room scatter' for d=50, 75 and 100 cm resulted in overestimation of the AKS by about 1%. However, when d was in the range 13-25 cm, it was only 0.20%. The room scatter correction for the shadow cone method was also computed and the result showed that no additional correction was required on account of forward scatter from the cone. Further, at larger d (50-100 cm), the number of low-energy photons (40-200 keV) relative to the total number of photons was found to be very significant, which may be useful to revisit the Spencer-Attix cavity theory. (author)

Palani Selvam, T.; Govinda Rajan, K.N.; Nagarajan, P.S.; Sethulakshmi, P.; Bhatt, B.C. [Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, CT and CRS Building, Anushaktinagar, Mumbai (India)

2001-09-01

84

A study of the relationship between peak skin dose and cumulative air kerma in interventional neuroradiology and cardiology  

International Nuclear Information System (INIS)

A study of peak skin doses (PSDs) during neuroradiology and cardiology interventional procedures has been carried out using Gafchromic XR-RV2 film. Use of mosaics made from squares held in cling film has allowed doses to the head to be mapped successfully. The displayed cumulative air kerma (CAK) has been calibrated in terms of cumulative entrance surface dose (CESD) and results indicate that this can provide a reliable indicator of the PSD in neuroradiology. Results linking PSD to CESD for interventional cardiology were variable, but CAK is still considered to provide the best option for use as an indicator of potential radiation-induced effects. A CESD exceeding 3 Gy is considered a suitable action level for triggering follow-up of patients in neuroradiology and cardiology for possible skin effects. Application of dose action levels defined in this way would affect 8% of neurological embolisation procedures and 5% of cardiology ablation and multiple stent procedures at the hospitals where the investigations were carried out. A close relationship was observed between CESD and dose-area product (DAP) for particular types of procedure, and DAPs of 200-300 Gy cm2 could be used as trigger levels where CAK readings were not available. The DAP value would depend on the mean field size and would need to be determined for each application.

85

A PROPOSED UNIFORM AIR POLLUTION INDEX  

Science.gov (United States)

A uniform air pollution index for the U.S. is proposed. The index was developed from ten criteria identified in a survey of all the air pollution indices currently in use in the U.S. and Canada. The proposed index, named the Pollutant Standards Index (PSI), was designed to overco...

86

Coomet Project 445: Comparison of National Measurement Standards of Air Kerma for Cs-137 Gamma Radiation at Protection Level  

International Nuclear Information System (INIS)

A COOMET supplementary comparison of the national measurement standards of air kerma for Cs-137 gamma radiation at protection level (?10 mGy/h) was carried out between May 2011 and February 2013. Participants were VNIIM (Russia), BelGIM (Belarus), CPHR (Cuba), GEOSTM (Georgia), INSM (Moldova), NSC-'IM' (Ukraine), SMU (Slovakia), PTB (Germany), BIM (Bulgaria), VMT/FTMC (Lithuania) and the International Atomic Energy Agency (IAEA). The PTB acted as the pilot laboratory. The comparison reference value (CRV) was obtained as the mean of the results obtained by PTB and VNIIM, both of which had previously taken part in the key comparison BIPM-RI (I)-K5. Results will be published in Appendix B of the BIPM key comparison database (KCDB) using the identifier COOMET.RI(I)-S1 as soon as the Draft B report is accepted. The comparison was organized within an extended COOMET project (identified as Project 445/DE/08), the aim of which was not only to compare national standards but also for educational purposes. Some of the participants had taken part in such a comparison for the first time and, therefore, an introductory seminar was held at PTB in May 2011. The seminar was open for participation also to those countries of the COOMET region which did not participate in the comparison and to nonMRA signatories and countries without an approved quality management system in order to acquire measurement routine and theoretical as well as organizational knowledge for future comparisons. The main goal of this seminar was to prepare the participants for the procedure of having entries accepted for the CMC list in the metrological area of Ionising Radiation, Section I, x and gamma rays

87

Comparison of the air kerma standards of the IAEA and the BIPM in mammography x-rays  

Science.gov (United States)

The Dosimetry Laboratory of the International Atomic Energy Agency (IAEA), Seibersdorf, Austria, calibrates reference standards in mammography x-ray beams for IAEA/WHO SSDL Network members (more than 80 laboratories worldwide). As a signatory of the Mutual Recognition Arrangement (CIPM MRA), the IAEA laboratory maintains a Quality Management System (QMS) complying with ISO 17025 and requires updated 'supporting evidence' for its dosimetry calibration and measurement capabilities (CMC), first published in Appendix C of the CIPM MRA key comparison database in 2007. For this purpose, an indirect comparison has been made between the air kerma standards of the IAEA and the Bureau International des Poids et Mesures (BIPM) in the mammography x-ray range from 25 kV to 35 kV, using as transfer instruments two thin-window parallel-plate ionization chambers belonging to the IAEA. The IAEA and BIPM standards for mammography x-rays are shown to be in agreement within the standard uncertainty of the comparison of 5.5 parts in 103. This agreement can be used to support the calibration and measurements capabilities of the IAEA listed in Appendix C of the key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Burns, D. T.; Czap, L.; Csete, I.; Gomola, I.

2013-01-01

88

Intercomparison of the air kerma and absorbed dose to water therapy calibrations provided by NRPA and CPRH SSDLs  

International Nuclear Information System (INIS)

The primary goal of any calibration laboratory is to routinely provide calibration services of the highest accuracy. To this end, the laboratory should be equipped with measuring standards of the highest metrological quality traceable to the international measuring system, should establish the appropriate calibration conditions and implement good measuring and working practices. In the case of the Secondary Standard Dosimetry Laboratory (SSDL) members of the IAEA/WHO Network of SSDLs, a great deal of the service quality relies on the appropriate laboratory design and implementation of the recommended calibration practices. Different approaches have been used by SSDLs to guarantee the traceability of the reference standard to the international measurement system. These include calibration of their standards at the IAEA Dosimetry Laboratory, direct calibration at a primary standards laboratory or at a national calibration laboratory. The stability of reference and working standards is usually checked by means of radioactive check source measurements. The most comprehensive way that a laboratory could test its overall measurement competence is by taking part in comparisons with other laboratories of the same or higher metrological level. Regular efforts have been done at the regional scale by organizing such intercomparison exercises where the evaluation of the accuracy of secondary standards or the validation of new calibration methods has been the main objectives. Perhmethods has been the main objectives. Perhaps, the most important contribution to the assessment of SSDLs quality has been the periodical external measurement audit provided by the IAEA during the last years. Mos of these efforts have, however, only been focused on in-air and recently in-water calibration at the 60Co radiation quality. An intercomparison of the therapy calibration services available at the SSDLs of the Norwegian Radiation Protection Authority (NRPA) and of the Center for Radiation Protection and Hygiene (CPHR) was organized in February 2000. The comparison comprised the calibration of a field class ionization chamber in terms of air kerma at low and medium-energy kilo voltage X-ray qualities and 60Co as well as the calibration in terms of absorbed dose to water (at 60Co radiation quality). The intercomparison represents for the CPHR the validation of the newly implemented calibration service at X-ray qualities. The NRPA SSDL has in recent years participated in EUROMET and IAEA dosimetry intercomparisons with satisfactory results. Experiences derived from the present comparison are discussed and summarized in this report. Recommendations to the SSDL members of the IAEA/WHO Network in order to encourage regional cooperation by organizing similar intercomparison exercises as well as the possibility for the IAEA to extend the present audit services, to cover certain X-ray beam qualities, are also commented

89

Air kerma national standard of Russian Federation for x-ray and gamma radiation. Activity SSDL/VNIIM in medical radiation dosimetry field  

International Nuclear Information System (INIS)

Primary standard of unities air kerma and air kerma rate X-ray and gamma radiation, placed at VNIIM, consists of: plate-parallel free-air ionization chamber IK 10-60 for low-energy X-ray in the generating potential range from 10 to 50 kV; plate-parallel free-air ionization chamber IK 50-400 for medium-energy X-ray in the generating potential range from 50 to 300 kV; cavity cylindrical graphite chambers C1 and C30 with volumes 1 cm3 and 30 cm3 for reproduction and transmission the dimensions gamma radiation unities using Cs-137 and Co-60 sources. The next irradiation facilities are used at VNIIM: in low-energy X-ray range: a constant-potential high-voltage generator and a tungsten-anode Xray tube with inherent filtration of around 1 mm Be; in medium-energy X-ray range: set on the basis of an industrial X-ray apparatus Isovolt-400 and a tungsten-anode X-ray tube with inherent filtration of around 3,5 mm Al; in gamma radiations field: units with a radioactive sources Cs-137 with activity 140 and 1200 GBq and Co-60 with activity 120 GBq and irradiation set with a source from Co-60 (activity 3200 GBq). The last one belongs to Central Research Institute for Radiology and Roentgenology (CNIRRI). For measuring currents and charges of standard chambers we use electrometers such as Keithley of model 6517A and B7-45 manufactured by 'Belvar' (Republic Belarus). The reference radiation qualities L, N, H series according to ISO 4037 and the radiation qualities RQR, RQA and RQF according to IEC 61267 for calibration and verification of the therapeutic, diagnostic measurement means are realized in the low-energy and medium-energy X-ray standards. The VNIIM air kerma primary standard of has been participated in the international comparisons: key comparison BIPM.R1(I)-K1 for gamma radiation of Co-60 in 1997; supplementary comparisons BIPM.R1(I)-S10 for gamma radiation of Cs-137 in 1997; key comparison BIPM.R1(I)-K2 for low-energy X-ray range in 1998; key comparison BIPM.R1(I)-K3 for medium-energy X-ray range in 1998. The results of comparisons are presented in the table 1. Dimensions of unities of air kerma and air kerma rate are transmitted from primary standard to secondary standards with expanded uncertainty from 1,3 to 2,5 % (k=2), which are including and at laboratory SSDL/VNIIM and base dosimetry laboratory CNIRRI. The comparisons of secondary standards with the primary standard VNIIM are performed one time in 5 years. The laboratory SSDL/VNIIM is the component of state primary standards laboratory in the field of measurement ionizing radiations VNIIM. SSDL/VNIIM has the secondary standard - universal dosimeter UNIDOS with ionization chambers of volume from 0,6 cm3 to 10 liters, radioactive sources from Fe-55, Cd-109, Am-241, Cs-137 and Co-60 with activity from 0,03 to 140 GBq. The primary standard equipment and facility on the basis industrial X-ray apparatus YRD-1 with a tungsten-anode X-ray tube and inherent filtration of around 3 mm Al (at generating potential from 50 to 250 kV) are used for calibration dosimetric devices in the field X-ray. There is termoluminescence dosimetric system such as KDT-02M with TL detectors from LiF for spending audit measurements by method 'dose-post'. Laboratory SSDL/VNIIM and base dosimetric laboratory CNIRRI are carried out calibrations and verifications of air kerma and air kerma rate reference standards and working measurement means for X-ray and gamma therapy and diagnostics, belonging to the oncology and diagnostic centers, clinics and hospitals. The laboratory CNIRRI fulfils the verification of measurement means and supervision of the application in the medical radiology, but the regional departments of radial diagnostics put into practice monitoring of doses, obtained by patients and staff at fulfilling of diagnostic and medical procedures. The diagnostic and clinical dosimeters are calibrated directly under the primary standard of air kerma and air kerma rate for achievement the highest accuracy. At 2000-2001 this calibrations were carried out for the Belarusian Research Institute of Oncol

90

European comparison of Monte Carlo codes users on the uncertainty calculations of air kerma determined in front of a cesium-137 beam; Intercomparaison europeenne d'utilisateurs de codes Monte Carlo pour le calcul d'incertitudes sur le kerma dans l'air determine dans un faisceau de cesium-137  

Energy Technology Data Exchange (ETDEWEB)

Within the framework of the European project CONRAD (Coordinated Network for Radiation Dosimetry, contract FP6-12684) coordinated by EURADOS (European Radiation Dosimetry group), WP4 was devoted to numerical dosimetry under the title 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Within this activity, a working group sent a list of eight exercises, dealing with radiation transport of photons, neutrons, protons and electrons, to be solved by the international community. This paper presents exercise number 4, dealing with the calculation of air kerma for a {sup 137}Cs beam. This problem was aimed at estimating the components of the uncertainty on the air kerma which cannot be measured, namely those due to geometrical data such as the source location, the diameter of the collimator, the material density, etc. 12 institutes of 10 different countries took part in this work, showing the interest in this proposal. (authors)

De carlan, L.; Bordy, J.M.; Gouriou, J. [CEA Saclay, LIST, Laboratoire National Henri Becquerel, Laboratoire de Metrologie de la Dose, 91191 Gif-Sur-Yvette Cedex (France)

2011-07-15

91

Comparison of the air kerma standards of the NIST and the BIPM in the low-energy X-ray range  

International Nuclear Information System (INIS)

A direct comparison has been made between the air-kerma standards of the NIST and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement to around 0.5 % at reference beam qualities up to 50 kV and at 100 kV. Agreement at the 80 kV quality is less satisfactory, which may be attributed to an incorrect value for the electron-loss correction for the NIST standard at this quality. (authors)

92

Calculation of the correction factors for the primary standard of kerma in the air at the LNMRI-IRD, Rio de Janeiro, Brazil; Calculo de fatores de correcao para o padrao primario em kerma no ar do LNMRI-IRD, Rio de Janeiro, Brasil  

Energy Technology Data Exchange (ETDEWEB)

In order to determine the primary standardization in terms of kerma in the air, a graphite ionization chamber is used for calculation some correction factors. A program was elaborated, using the Monte Carlo Penelope for simulate the CC01-110 at the LNMRI/IRD, Rio de Janeiro, Brazil

Silva, Cosme Norival Mello da, E-mail: cosme@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

2009-07-01

93

Construction of a laboratory for the implantation of primary standardization of the magnitude kerma in the air for the X-ray beams used in mammography; Construcao de um laboratorio para a implantacao da padronizacao primaria da grandeza kerma no ar para os feixes de raios X empregados em mamografia  

Energy Technology Data Exchange (ETDEWEB)

Aiming to diminish the uncertainty in each phase of the metrological chain, and the uncertainty in dosimetry processed at the X-ray beam applied in the mammography, is necessary that the LNMRI/IRD to develop a reference primary standard for the absolute form to the magnitude kerma in the air

Cardozo, W.L.; Magalhes, L.A.A.M.F.; Peixoto, J.G.P., E-mail: wagnerlc@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

2009-07-01

94

Calculation of conversion factor of Kerma in the air for ambient dose equivalent in radiotherapy; Calculo dos fatores de conversao de Kerma no ar para equivalente de dose ambiental em radioterapia  

Energy Technology Data Exchange (ETDEWEB)

This work aims to estimate the average conversion factor of Kerma in air to H {sup *} (10) using photon beams coming from clinic linear accelerators, transmitted through concrete walls of a radiotherapic treatment room. The transmitted photon spectra by both 1 meter and 2 meters concrete walls, in an area of 40 x 40 cm{sup 2}, were calculated when the primary beam impart in an angle of 0 deg. The (secondary) photon beams transmitted respectively by 0,5 meter, 1,0 meter, 1,0 meter and 2,0 meter concrete walls, after they scattered by an angle of 90 deg in a cylindric phantom inside the room, were also determined. Generally, 50 millions of histories were computed for each simulation made for the primary beam. For the 90 deg spread, the number of histories was 100 millions. The computational code used on this work was the MCNP4B. The most common clinic accelerators used on radiotheraphic treatments were used on this work CLINAC-4, CLINAC-6, CLINAC-18 and CLINAC-2500. From the spectra analysis obtained in this work, it was possible to dispose the conversion factor for realistic beams found in radiotherapeutic establishment. (author)

Lima, Marco Antonio Frota

2000-03-01

95

Determination of air kerma rate at IEN/CNEN, due to cyclotron RDS-111 and the radioactive waste deposit  

International Nuclear Information System (INIS)

The Instituto de Engenharia Nuclear - IEN - (Institute of Nuclear Engineering) is a branch of CNEN (Comissao Nacional de Energia Nuclear), the national regulatory authority, established in 1962 with the commitment to carry out research aiming the nuclear technological development in Brazil. In 1995, PERES, S.S., carried out measurements, using thermoluminescent dosemeter of CaSO4: Dy and LiF: Mg, Ti; and a Saphymo SRAT SPP2-NF scintillation detector, for the evaluation of the effect on environment of the activities developed in the IEN. Since that time, the Institute Radioactive Waste Deposit stores a greater amount of radioactive waste, accumulated during the operational life of IEN, and also a new cyclotron particle accelerator has been installed, the RDS-111, in operation since 2003, which is currently used for the production 18F - fluorodeoxyglucose, FDG, a radiopharmaceutical of great use in Positron Emission of Tomography (PET). In this work, measurements of ambient kerma have been carried out, using thermoluminescent dosemeter of LiF:Mg, Cu, P, TLD - 100 H, manufactured by Harshaw, and the same scintillation detector used by PERES, with the intention of verify the contribution of these two radioactive installations in the values of the ambient kerma of the IEN. The results have shown good conformity among the data obtained with the TLD and scintillation detectors. Moreover, the variation of ambient kerma of IEN presently found to the measured value bEN presently found to the measured value by PERES in 1995 was not significant. (author)

96

Use of a new breast phantom for dosimetric determination of incident air kerma and mean glandular dose in digital mammography system  

International Nuclear Information System (INIS)

Mammography aims to achieve a high image quality associated with a dose in the patient as low as feasible. Values of average glandular dose, DG, can be obtained by means of two dosimetric methods: one based on the measurement of incident air kerma, Ki, associated with tables of conversion factors that depend on the half value layer, the thickness and the glandular composition of the breast. And the one that makes the measure directly to thermoluminescent dosimeters, TLDs, placed in a new dosimetric phantom. Thus, this study aims to determine the incident air kerma (Ki) and average glandular dose (DG) applied on patients in a digital mammography system (DR) using the phantom dosimetric developed. Another objective is to compare the results with the values of DG determined from Ki and also with the values of Ki and DG indicated in the examination of each patient by the digital mammography unit. The result of the average values measured in 77 patients with compressed breast thickness within the range of 5.5 cm and 6.5 cm, shows that the Ki values ranged around 7.9% between the methods of action. The result of the values of DG ranged around 14.7% between the two methods of action. It is observed that the estimate of DG by the software is higher than the values measured with the dosimetric phantom. (author)

97

Comparisons of the standards for air kerma of the PTB and the BIPM for 60Co and 137Cs gamma radiation  

International Nuclear Information System (INIS)

Direct comparisons of the standards for air kerma of the Physikalisch-Technische Bundesanstalt (PTB, Germany) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the 60Co and 137 Cs radiation beams of the BIPM in 2000. The results, expressed as ratios of the PTB and the BIPM standards for air kerma, indicate a relative difference in 60Co of 9.9 x 10-3 with a combined standard uncertainty of 1.8 x 10-3, and in 137Cs of 6.4 x 10-3 with a combined standard uncertainty of 2.8 x 10-3. The earlier comparisons in 60Co ? rays made in 1971 (direct) and 1989 (indirect) resulted in an agreement of the two standards within 2 x 10-3. The differences obtained now are due to the application of new correction factors for wall effects and point source non-uniformity of the beam, kwall and kpn, for the PTB standards, which were calculated using Monte Carlo methods. (authors)

98

Intercomparison of absorbed dose to water and air-kerma based dosimetry protocols for photon and electron beams  

International Nuclear Information System (INIS)

Full text: During the last three decades the International Atomic Energy Agency (IAEA), the American Association of Physicists in Medicine (AAPM) and organizations from various countries have published Codes of Practice (CoP) and dosimetry protocols for the calibration of high-energy photon and electron beams. They are based on the air-kerma or exposure calibration factor of an ionization chamber in a 60Co gamma ray beam and formalism for the determination of absorbed dose to water in reference conditions. In recent years, the IAEA (IAEA TRS-398) and the AAPM (AAPM TG-51) have published new external beam dosimetry protocols that are based on the use of an ionization chamber calibrated in terms of absorbed dose to water in a standards laboratory's reference quality beam. These two new protocols follow those by the German Standard DIN, the British IPSM and the IAEA CoP for plane-parallel chambers, which have discussed and implemented the procedures for the determination of absorbed dose-to-water based on standards of absorbed dose-to-water. Since the publication of these protocols and CoPs, many comparisons, theoretical as well as experimental, between them have been published in the literature providing valuable information about the sources of similarities and discrepancies that exist among them. For example, the differences in the basic data for photon and electron beams included in the various IAEA CoPs are very small for the second edition of TRS-277 for photons, TRS-381 for electrons and TRS-398. In these cases the data changes posed by the adoption of TRS-398 are within about ±0.3% for the most commonly used energies. When implementing TRS-398 in these cases, the main difference will arise from the transition from Kair to Dw standards. For example, experimental comparison of absorbed doses between TRS-398 and TRS-277 for photons show an average difference of about 0.3% for most commonly used energies with a maximum difference of about 1% at a TPR20,10 value of 0.80; for electrons a maximum difference of about 1% is observed between TRS-398 and TRS-381 and about 1.8% between TRS-398 and TRS277 for energies ranging from 6-18 MeV. The comparison of TRS-398 with TG-51 reveals that photon beam dosimetry agrees within about ±0.3% for most commonly used energies. For electron beam dosimetry, comparison of TRS-398 with TG-51 reveals agreement within about ±0.4% for cylindrical chambers for energies above 10 MeV approximately; however, for plane-parallel chambers, differences of almost up to 2% is observed between the two protocols. On the other hand, the agreement for these chambers when cross-calibration procedures are used is excellent. This talk will provide a comprehensive review of intercomparisons of all these protocols. The reasons for the discrepancies between theory and experiments will be discussed terms of the combined effect of small data differences and the influence of ND,w/NK for the various chamber types. (author)

99

Comparison of the air kerma standards for 137Cs and 60Co gamma-ray beams between the IAEA and the NIST  

International Nuclear Information System (INIS)

A comparison of the air kerma standards for 137Cs and 60Co gamma ray beams was performed between the NIST and the IAEA. Two reference class ionization chambers owned by the IAEA were used as part of this comparison and were calibrated at each facility. The calibration coefficients, NK, were determined for both chambers and in both gamma-ray beams. The measurements were performed at the IAEA and NIST facilities starting in the fall of 2009 and were completed in 2010. The comparison ratio of the calibration coefficients for each chamber, NK, IAEA / NK, NIST, between the IAEA and NIST were 0.999 and 0.997 for the 137Cs and 60Co gamma ray beams respectively. The relative standard uncertainty for each of these ratios is 0.5 %. (authors)

100

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the VSL, Netherlands and the BIPM in low-energy x-rays  

International Nuclear Information System (INIS)

A key comparison has been made between the air-kerma standards of the VSL, Netherlands and the BIPM in the low-energy X-ray range. The results for the direct comparison show the standards to be in general agreement for the 10 kV, 30 kV and 25 kV radiation qualities at the level of the expanded uncertainty for the comparison of 6.6 parts in 103. For the 50 kV qualities, differences approaching twice the expanded uncertainty are observed. The results for an indirect comparison made at the same time are not consistent with the direct results, in the worst case (10 kV) differing by 4 parts in 102. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. (authors)

 
 
 
 
101

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the BEV, Austria and the BIPM in medium-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the BEV, Austria and the BIPM in the medium-energy x ray range. The results show the standards to be in general agreement at the level of the expanded uncertainty (k = 2) of the comparison of 6.4 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Burns, D. T.; Kessler, C.; Steurer, A.; Tiefenboeck, W.; Bauer, M.

2015-01-01

102

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the BEV, Austria and the BIPM in mammography x-rays  

Science.gov (United States)

A first key comparison has been made between the air-kerma standards of the BEV and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.4 parts in 103. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Burns, D. T.; Steurer, A.; Tiefenboeck, W.; Bauer, M.

2015-01-01

103

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the BEV, Austria and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the BEV and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the combined standard uncertainty of 4.7 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Burns, D. T.; Kessler; Steurer, A.; Tiefenboeck, W.; Bauer, M.

2015-01-01

104

The IPEMB code of practice for electron dosimetry for radiotherapy beams of initial energy from 2 to 50 MeV based on an air kerma calibration  

Science.gov (United States)

This report contains the recommendations of the Electron Dosimetry Working Party of the UK Institution of Physics and Engineering in Medicine and Biology (IPEMB). The recommendations consist of a code of practice for electron dosimetry for radiotherapy beams of initial energy from 2 to 50 MeV. The code is based on the 2 MV (or ) air kerma calibration of the NE 2561/2611 chamber, which is used as the transfer instrument between national standards laboratory and hospitals in the UK. The code utilizes an approach. Designated chambers are the NE 2571 (graphite-walled Farmer chamber), to be calibrated against the transfer instrument in a megavoltage photon beam, and three parallel-plate chambers, to be calibrated against the NE 2571 in a higher-energy electron beam. The practical code is supplemented by comprehensive discussion of the theoretical background and the sources and values of included data.

Thwaites, D. I.; Burns, D. T.; Klevenhagen, S. C.; Nahum, A. E.; Pitchford, W. G.

1996-12-01

105

Summary of the B.I.P.M..R.I.(1)-K1 comparison for air kerma in 60Co gamma radiation  

International Nuclear Information System (INIS)

International comparisons of air kerma have been made at the Bureau International des Poids et Mesures (B.I.P.M.) since 1975. Twenty-one national metrology institutes have taken part, some of which have repeated the comparison over the years. The key comparison reference value (K.C.R.V.) is unity, each comparison result being the ratio of the national metrology institute (N.M.I.) evaluation to that of the B.I.P.M. standard. The degrees of equivalence between each N.M.I. and the K.C.R.V., and between each pair of N.M.I.s., are given in the form of a matrix, using the most recent published result of the past ten years for each of fifteen N.M.I.s.. A graphical presentation is also given. (authors)

106

Ionization chambers for measuring air kerma integrated over beam area. Deviations in calibration values using simplified calibration methods  

Science.gov (United States)

Calibrations of kerma-area product meters (KAP meters) are often performed using simplified methods. The accuracy thus obtained can be insufficient, especially when the KAP meters are used for optimizing radiological procedures. The deviations between the best available calibration factor (k) and the simplified calibration factor were measured at different clinical x-ray installations. Depending on the type of x-ray installation and calibration method, the quotient ranged from 0.83 to 1.19, reflecting the error made in practice using these methods. A simple alternative calibration method based on comparison with a KAP meter calibrated by the best available method is described. Depending on tube potential and the stability of the electrometers, the uncertainty in the calibration factor derived with this method was between 3.8% and 5.6% (at 95% confidence level).

Larsson, J. P.; Persliden, J.; Alm Carlsson, G.

1998-03-01

107

Ionization chambers for measuring air kerma integrated over beam area. Deviations in calibration values using simplified calibration methods  

International Nuclear Information System (INIS)

Calibrations of kerma-area product meters (KAP meters) are often performed using simplified methods. The accuracy thus obtained can be insufficient, especially when the KAP meters are used for optimizing radiological procedures. The deviations between the best available calibration factor (k) and the simplified calibration factor (ks) were measured at different clinical x-ray installations. Depending on the type of x-ray installation and calibration method, the quotient ks/k ranged from 0.83 to 1.19, reflecting the error made in practice using these methods. A simple alternative calibration method based on comparison with a KAP meter calibrated by the best available method is described. Depending on tube potential and the stability of the electrometers, the uncertainty in the calibration factor derived with this method was between 3.8% and 5.6% (at 95% confidence level). (author)

108

Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer  

Energy Technology Data Exchange (ETDEWEB)

Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 {+-} 0.015 and 0.412 {+-} 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 {+-} 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation curve on the IMBL using a simple experimental method, namely, HVL measurements. The HVL measurements strongly supports the x-ray beam spectrum, which in turn has a profound effect on x-ray dosimetry.

Crosbie, Jeffrey C.; Rogers, Peter A. W. [Department of Obstetrics and Gynaecology, University of Melbourne, The Royal Women' s Hospital, Parkville, Victoria 3052 (Australia); Stevenson, Andrew W. [CSIRO Materials Science and Engineering, Clayton, Victoria 3169 (Australia); Hall, Christopher J. [Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168 (Australia); Lye, Jessica E. [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia); Nordstroem, Terese [KTH Royal Institute of Technology, Stockholm SE-100 44 (Sweden); Midgley, Stewart M. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Lewis, Robert A. [Department of Medical Imaging and Radiation Sciences, Monash University, Clayton, Victoria 3800 (Australia)

2013-06-15

109

Control letters and uncertainties of the kerma patterns in air, dose absorbed in water and dose absorbed in air of the LSCD  

International Nuclear Information System (INIS)

With the purpose of characterizing the component of uncertainty of long term of the patron ionization chambers of the LSCD, for the magnitudes: speed of kerma in air ??·, dose speed absorbed in water D?·, and speed absorbed dose in air D?·, it use the technique of letters of control l-MR/S. This statistical technique it estimates the component of uncertainty of short term by means of the deviation standard inside groups ?? and that of long term by means of the standard deviation among groups ??, being this it finishes an estimator of the stability of the patterns.The letters of control l-MR/S it construct for: i) ??·, in radiation field of 60Co for patterns: primary CC01 series 131, secondary NE 2611 series 176, secondary PTW TN30031 series 578 and Third PTW W30001 series 365. ii) D?),en radiation field of 60Co for patterns: primary CC01 series 131, Secondary PTW TN30031 series 578 and tertiary PTW W30001 series 365. iii) I-MR/S with extrapolation chamber PTW primary pattern, measurement realizes in secondary patron fields of 90Sr-90Y. The expanded uncertainty U it is calculated of agreement with the Guide of the ISO/BIPM being observed the following thing: a. In some the cases ??, is the component of the U that more contributed to this. Therefore, it is necessary to settle down technical of sampling in those mensurations that allow to reduce the value of ??. For example with sizes of subgroup ?? 30 data, or with a number of subgroups ??. That which is achieved automating the mensuration processes. b.The component of the temperature is also one of those that but they contribute to the U, of there the necessity of: to recover the tracking for this magnitude of it influences and to increase the precision in the determinations of the temperature to diminish their influence in the U. c. The percentage difference of the magnitudes dosemeters carried out by it patterns are consistent with U certain. However, it is necessary to diminish the uncertainty in the physical factors different to ?? and ?? for the one case of the primary patterns; because these they should be those of smaller value of U. d. In the case of the secondary patterns and tertiary for the realization of the??· is necessary to determine the corrections explicitly for recombination and polarization; and to analyze their contribution in the U. e. It is necessary to recover the tracking for the mensurations of the humidity. f. It is recommended to continue the control mensurations for each pattern, taking its the least a measure every fifteen days, that it corresponds at two measured for month and 24 at the year. g. The operation of the air conditioned perturb the measurement for such as it recommends not to use it, and alone to leave in balance the chamber with the air of the engine room. (Author)

110

Radiological investigations at the “Taiga” nuclear explosion site, part II: man-made ?-ray emitting radionuclides in the ground and the resultant kerma rate in air  

International Nuclear Information System (INIS)

Samples of soil and epigeic lichens were collected from the “Taiga” peaceful nuclear explosion site (61.30°N 56.60°E, the Perm region, Russia) in 2009 and analyzed using high resolution ?-ray spectrometry. For soil samples obtained at six different plots, two products of fission (137Cs and 155Eu), five products of neutron activation (60Co, 94Nb, 152Eu, 154Eu, 207Bi) and 241Am have been identified and quantified. The maximal activity concentrations of 60Co, 137Cs, and 241Am for the soils samples were measured as 1650, 7100, and 6800 Bq kg?1 (d.w.), respectively. The deposit of 137Cs for the top 20 cm of soil on the tested plots at the “Taiga” site ranged from 30 to 1020 kBq m?2; the maximal value greatly (by almost 3 orders of magnitude) exceeded the regional background (from global fallout) level of 1.4 kBq m?2. 137Cs contributes approximately 57% of the total ground inventory of the man-made ?-ray emitters for the six plots tested at the “Taiga” site. The other major radionuclides –241Am and 60Co, constitute around 40%. Such radionuclides as 60Co, 137Cs, 241Am, and 207Bi have also been determined for the epigeic lichens (genera Cladonia) that colonized certain areas at the ground lip produced by the “Taiuced by the “Taiga” explosion. Maximal activity concentrations (up to 80 Bq kg?1 for 60Co, 580 Bq kg?1 for 137Cs, 200 Bq kg?1 for 241Am, and 5 Bq kg?1 for 207Bi; all are given in terms of d.w.) have been detected for the lower dead section of the organisms. The air kerma rates associated with the anthropogenic sources of gamma radiation have been calculated using the data obtained from the laboratory analysis. For the six plots tested, the kerma rates ranged from 50 to 1200 nGy h?1; on average, 51% of the dose can be attributed to 137Cs and 45% to 60Co. These estimates agree reasonably well with the results of the in situ measurements made during our field survey of the “Taiga” site in August 2009. - Highlights: ? Soil and lichen samples from the “Taiga” nuclear explosion site were analyzed. ? 60Co, 94Nb, 137Cs, 152Eu, 154Eu, 155Eu, 207Bi and 241Am have been quantified in soil. ? 137Cs contributed approximately 57% of total ground inventory of the radionuclides. ? In 2009, 137Cs inventory for the six sampling plots ranged from 30 to 1020 kBq m?2. ? Air kerma rates, calculated from soil activities, ranged from 50 to 1200 nGy h?1.

111

Estudo comparativo da qualidade da imagem e do kerma, de entrada e de saída, em simulador de tórax utilizando sistemas analógico e digitalizado CR de aquisição de imagens Comparative study of image quality and entrance and exit air kerma measurements on chest phantom utilizing analog and CR digital imaging systems  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: O processo de migração de sistemas analógicos para digitalizados, para aplicações diagnósticas, requer cuidados específicos, a fim de manter a qualidade das imagens e minimizar a dose no paciente. Este trabalho tem como objetivo analisar e comparar a qualidade da imagem e o kerma num simulador não antropomórfico de tórax gerados por sistemas analógicos e digitalizados CR. MATERIAIS E MÉTODOS: Foram analisados a qualidade da imagem e o kerma, de entrada e saída, no simulador para dois equipamentos de raios X diferentes (Siemens e Emic, com diferentes sistemas de retificação de onda (12 pulsos e alta frequência. Ambos os sistemas (analógico e digitalizado estavam sendo utilizados no mesmo local. Foram geradas imagens em filme e em image plates. RESULTADOS: Foi observado aumento na tensão e/ou na carga transportada pelo tubo de raios X quando houve a migração para o sistema CR, para manutenção das características diagnósticas da imagem. Isto resultou em aumento de kerma coletado. CONCLUSÃO: As maiores diferenças determinadas (aumento de dose e redução da qualidade da imagem foram observadas no equipamento com retificação de onda de 12 pulsos e transdutor de imagem CR (image plates.OBJECTIVE: The process of migration from analog to digital imaging system requires specific attention to preserve images quality and minimizing the dose to the patients. The present study was aimed at analyzing and comparing images quality and entrance and exist air kerma measurements in a non-anthropomorphic chest phantom with analog and CR digital imaging systems. MATERIALS AND METHODS: Two different X-ray units (Siemens and Emic with different wave rectification systems (12-pulse and high-frequency were utilized in a single institution along the process of migration from analog to CR digital imaging system. Images were acquired on films and image plates. RESULTS: An increase on the X-ray tube peak voltage and/or load was observed in the migration from analog to CR digital system to preserve the diagnostic quality of the image. As a result, an increase in the air kerma rate was observed. CONCLUSION: The greatest differences (increase in dose and decrease in image quality were observed with the 12-pulse wave rectification system with the CR image transducer (imaging plates.

Renata Matos da Luz

2010-02-01

112

Estudo comparativo da qualidade da imagem e do kerma, de entrada e de saída, em simulador de tórax utilizando sistemas analógico e digitalizado CR de aquisição de imagens / Comparative study of image quality and entrance and exit air kerma measurements on chest phantom utilizing analog and CR digital imaging systems  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: O processo de migração de sistemas analógicos para digitalizados, para aplicações diagnósticas, requer cuidados específicos, a fim de manter a qualidade das imagens e minimizar a dose no paciente. Este trabalho tem como objetivo analisar e comparar a qualidade da imagem e o kerma num simul [...] ador não antropomórfico de tórax gerados por sistemas analógicos e digitalizados CR. MATERIAIS E MÉTODOS: Foram analisados a qualidade da imagem e o kerma, de entrada e saída, no simulador para dois equipamentos de raios X diferentes (Siemens e Emic), com diferentes sistemas de retificação de onda (12 pulsos e alta frequência). Ambos os sistemas (analógico e digitalizado) estavam sendo utilizados no mesmo local. Foram geradas imagens em filme e em image plates. RESULTADOS: Foi observado aumento na tensão e/ou na carga transportada pelo tubo de raios X quando houve a migração para o sistema CR, para manutenção das características diagnósticas da imagem. Isto resultou em aumento de kerma coletado. CONCLUSÃO: As maiores diferenças determinadas (aumento de dose e redução da qualidade da imagem) foram observadas no equipamento com retificação de onda de 12 pulsos e transdutor de imagem CR (image plates). Abstract in english OBJECTIVE: The process of migration from analog to digital imaging system requires specific attention to preserve images quality and minimizing the dose to the patients. The present study was aimed at analyzing and comparing images quality and entrance and exist air kerma measurements in a non-anthr [...] opomorphic chest phantom with analog and CR digital imaging systems. MATERIALS AND METHODS: Two different X-ray units (Siemens and Emic) with different wave rectification systems (12-pulse and high-frequency) were utilized in a single institution along the process of migration from analog to CR digital imaging system. Images were acquired on films and image plates. RESULTS: An increase on the X-ray tube peak voltage and/or load was observed in the migration from analog to CR digital system to preserve the diagnostic quality of the image. As a result, an increase in the air kerma rate was observed. CONCLUSION: The greatest differences (increase in dose and decrease in image quality) were observed with the 12-pulse wave rectification system with the CR image transducer (imaging plates).

Renata Matos da, Luz; Gabriela, Hoff.

2010-02-01

113

Comparison between absorbed dose to water standards established by water calorimetry at the LNE-LNHB and by application of international air-kerma based protocols for kilovoltage medium energy x-rays  

International Nuclear Information System (INIS)

Nowadays, the absorbed dose to water for kilovoltage x-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water has just been established for these beams at the LNE-LNHB, using water calorimetry, at a depth of 2 cm in water in accordance with protocols. The aim of this study is to compare these new standards in terms of absorbed dose to water, to the dose values calculated from the application of four international protocols based on air-kerma standards (IAEA TRS-277, AAPM TG-61, IPEMB and NCS-10). The acceleration potentials of the six beams studied are between 80 and 300 kV with half-value layers between 3.01 mm of aluminum and 3.40 mm of copper. A difference between the two methods smaller than 2.1% was reported. The standard uncertainty of water calorimetry being below 0.8%, and the one associated with the values from protocols being around 2.5%, the results are in good agreement. The calibration coefficients of some ionization chambers in terms of absorbed dose to water, established by application of calorimetry and air-kerma based dosimetry protocols, were also compared. The best agreement with the calibration coefficients established by water calorimetry was found for those established with the AAPM TG-61 protocol. (paper)

114

Radiological investigations at the "Taiga" nuclear explosion site, part II: man-made ?-ray emitting radionuclides in the ground and the resultant kerma rate in air.  

Science.gov (United States)

Samples of soil and epigeic lichens were collected from the "Taiga" peaceful nuclear explosion site (61.30°N 56.60°E, the Perm region, Russia) in 2009 and analyzed using high resolution ?-ray spectrometry. For soil samples obtained at six different plots, two products of fission ((137)Cs and (155)Eu), five products of neutron activation ((60)Co, (94)Nb, (152)Eu, (154)Eu, (207)Bi) and (241)Am have been identified and quantified. The maximal activity concentrations of (60)Co, (137)Cs, and (241)Am for the soils samples were measured as 1650, 7100, and 6800 Bq kg(-1) (d.w.), respectively. The deposit of (137)Cs for the top 20 cm of soil on the tested plots at the "Taiga" site ranged from 30 to 1020 kBq m(-2); the maximal value greatly (by almost 3 orders of magnitude) exceeded the regional background (from global fallout) level of 1.4 kBq m(-2). (137)Cs contributes approximately 57% of the total ground inventory of the man-made ?-ray emitters for the six plots tested at the "Taiga" site. The other major radionuclides -(241)Am and (60)Co, constitute around 40%. Such radionuclides as (60)Co, (137)Cs, (241)Am, and (207)Bi have also been determined for the epigeic lichens (genera Cladonia) that colonized certain areas at the ground lip produced by the "Taiga" explosion. Maximal activity concentrations (up to 80 Bq kg(-1) for (60)Co, 580 Bq kg(-1) for (137)Cs, 200 Bq kg(-1) for (241)Am, and 5 Bq kg(-1) for (207)Bi; all are given in terms of d.w.) have been detected for the lower dead section of the organisms. The air kerma rates associated with the anthropogenic sources of gamma radiation have been calculated using the data obtained from the laboratory analysis. For the six plots tested, the kerma rates ranged from 50 to 1200 nGy h(-1); on average, 51% of the dose can be attributed to (137)Cs and 45% to (60)Co. These estimates agree reasonably well with the results of the in situ measurements made during our field survey of the "Taiga" site in August 2009. PMID:22541991

Ramzaev, V; Repin, V; Medvedev, A; Khramtsov, E; Timofeeva, M; Yakovlev, V

2012-07-01

115

Implementation of the method air-kerma product area in KAP camera calibration with reference qualities of X-ray series at the SSDL RQR of Mexico  

International Nuclear Information System (INIS)

The X-Ray machines, at a reference laboratory for the instrument calibration in diagnostic radiology, should compliance with the ISO requirements. Sometimes there is not available as much laboratories as needed in Latin American countries. So this project shows the KAP ionization chamber implementation method using the TRS-457 radiation quality from the IAEA at the SSDL of Mexico. The KAP instruments calibration method consists in doing a substitution comparison using a standard reference with traceability to a primary laboratory and a transmission-monitoring chamber that measures the number of photons of the X-ray primary beam. A KAP chamber calibration requires a special array that consists in collocating the chamber in two different positions of its calibration process. Then, with air kerma-area product coefficient together with a corrected electrometer measure at referential conditions, the patient dosimetry magnitudes are calculated. The dosimetry necessity at hospitals always will be in function of possessing a highly reliable calibration coefficient chamber for making these measures. That dosimetry results will help in reducing the total or partial irradiation emitted to the human body of the patient. This is how stochastic risks will be lessened due to diagnostic studies. The purpose of this project is to have a synergy with calibration for making known that the SSDL of Mexico has the technical capacity to act as a link between primary standard dosimetry laboratories and the ionizing radiation equipment users who require that their KAP chamber have traceability from the primary standard to the user. (author)

116

APMP/TCRI key comparison report of measurement of air kerma for medium-energy x-rays (APMP.RI(I)-K3)  

Energy Technology Data Exchange (ETDEWEB)

The APMP/TCRI Dosimetry Working Group performed the APMP.RI(I)-K3 key comparison of measurement of air kerma for medium-energy x-rays (100 kV to 250 kV) between 2000 and 2003. In total, 11 institutes took part in the comparison, among which 8 were APMP member laboratories. Two commercial cavity ionization chambers were used as transfer instruments and circulated among the participants. All the participants established the 100 kV, 135 kV, 180 kV and 250 kV x-ray beam qualities equivalent to those of the BIPM. The results showed that the maximum difference between the participants and the BIPM in the medium-energy x-ray range, evaluated using the comparison data of the linking laboratories ARPANSA and PTB, is less than 1.4%. The degrees of equivalence between the participants are presented and this comparison confirms the calibration capabilities of the participating laboratories. (authors)

Lee, J.H.; Hwang, W.S. [Institute of Nuclear Energy Research, Longtan, Taiwan (China); Kotler, L.H.; Webb, D.V. [Australian Radiation Protection and Nuclear Safety Agency, Yallambie (Australia); Buermann, L. [Physikalisch Technische Bundesanstalt, Braunschweig (Germany); Burns, D.T. [Bureau International de Poids et Mesures, 92 - Sevres (France); Takeyeddin, M. [Atomic Energy Commission, Damascus (Syrian Arab Republic); Shaha, V.V. [Bhabha Atomic Research Centre, Mumbai (India); Srimanoroth, S. [Department of Medical Sciences, Nonthaburi (Thailand); Meghzifene, A. [International Atomic Energy Agency, Vienna (Austria); Hah, S.H.; Chun, K.J. [Korea Research Institute of Standards and Science, Yusong (Korea, Republic of); Kadni, T.B. [Malaysian Nuclear Agency, Kajang (Malaysia); Takata, N. [National Metrology Institute of Japan, Tsukuba (Japan); Msimang, Z. [National Metrology Institute of South Africa, Pretoria (South Africa)

2008-10-15

117

Monte Carlo aided room scatter corrections in the air-kerma strength standardization of {sup 169}Yb and {sup 60}Co brachytherapy sources  

Energy Technology Data Exchange (ETDEWEB)

For accurate evaluation of air-kerma strength, S{sub k}, of {sup 169}Yb and {sup 60}Co brachytherapy sources, the present study reports Monte Carlo (MC) based corrections for (1) room scatter, and (2) departure from constant room scatter for rooms of various sizes. Correction for exponential attenuation of effective primary in air is also reported for the above sources. Values of S{sub k} per contained mCi, S{sub k}/A{sub c}, predicted by MC calculations for {sup 169}Yb source (model X1267) with and without Ti K x-rays are 1.302 {+-} 0.03% (this value is in excellent agreement with the published value reported by Piermattei et al) and 1.260 {+-} 0.03% cGy cm{sup 2} h{sup -1} mCi{sup -1} respectively, and in the case of Cathetron {sup 60}Co source the value of S{sub k}/A{sub c} is 11.015 {+-} 0.01% cGy cm{sup 2} h{sup -1} mCi{sup -1}. It is observed that depending upon the position of the source with respect to the surrounding concrete scattering surfaces and set of d values, the assumption of constant room scatter has resulted in overestimation of S{sub k} that varied between 0.30% and 1.5% for the {sup 169}Yb source and only between 0.10% and 0.20% for the {sup 60}Co source. (note)

Selvam, T Palani; Rajan, K N Govinda; Sethulakshmi, P; Bhatt, B C [Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 094 (India)

2003-06-07

118

Comparison of the air-kerma standards of the PTB and the BIPM in the low-energy X-ray range  

International Nuclear Information System (INIS)

A direct comparison has been made between the air-kerma standards of the Physikalisch-Technische Bundesanstalt (PTB), Germany, and the Bureau International des Poids et Mesures (BIPM) in the x-ray range from 10 kV to 50 kV. Additional measurements were made at 80 kV and 100 kV to provide information on the electron-loss correction for the BIPM standard at these qualities. The comparison took place at the BIPM in March 1999 using the reference conditions recommended by the CCRI. There is general agreement at the level of one standard uncertainty, although there is a significant trend in the results between 30 kV and 50 kVa. This is in part due to the treatment of fluorescence radiation. The effect of fluorescence for the BIPM standard has been calculated using the Monte Carlo code EGSnrc and the fluorescence correction calculated in this way and the effect of including these new values in the present comparison are given. It should be noted, however, that these new correction factors for the BIPM standard have not yet been adopted. The result at 10 kV is significantly different from the others. This is not uncommon and raises a number of possibilities, for example the large corrections for air attenuation and guard wire attenuation, or unexplained aperture effects that have arisen in certain comparisons. In this respect, it is possible that the uncertainties for the 10 kV quality are underestimated. The measurements at 80 kV and 100 kV were made principally to test the correction factors for the BIPM standard, making use of the fact that the large electrode separation of the PTB PK100 chamber results in very little electron loss. (authors)

119

Nuclear heating constant KERMA library  

International Nuclear Information System (INIS)

Based on evaluated nuclear data file JENDL-3, published in April 1990, we produced a nuclear group constant KERMA library for fusion nuclear group constant set FUSION-J3 instead of the KERMA library for GICX40. Neutron KERMA factors were calculated directly by considering the kinematics in collisions, called 'Direct Method'. In this method, uncertainties in calculated KERMA factors are expected to be reduced since subtraction between great numbers is not necessary as in the energy balance method. Gamma ray KERMA factors were calculated by the energy balance method. In case of gamma ray, there is no problem in calculating gamma ray KERMA by the energy balance method since gamma ray heating means energy deposition of kinetic energy in gamma ray. Produced KERMA library is applicable to fusion neutronics calculations. It is expected that highly accurate results will be obtained in nuclear heating calculations for fusion reactor designs. (author)

120

Control letters and uncertainties of the kerma patterns in air, dose absorbed in water and dose absorbed in air of the LSCD; Cartas de control e incertidumbres de los patrones de kerma en aire, dosis absorbida en agua y dosis absorbida en aire del LSCD  

Energy Technology Data Exchange (ETDEWEB)

With the purpose of characterizing the component of uncertainty of long term of the patron ionization chambers of the LSCD, for the magnitudes: speed of kerma in air {kappa}{sub {alpha}}{sub {center_dot}}, dose speed absorbed in water D{alpha}{sub {center_dot}}, and speed absorbed dose in air D{alpha}{sub {center_dot}}, it use the technique of letters of control l-MR/S. This statistical technique it estimates the component of uncertainty of short term by means of the deviation standard inside groups {sigma}{sub {omega}} and that of long term by means of the standard deviation among groups {sigma}{sub {beta}}, being this it finishes an estimator of the stability of the patterns.The letters of control l-MR/S it construct for: i) {kappa}{sub {alpha}}{sub {center_dot}}, in radiation field of {sup 60}Co for patterns: primary CC01 series 131, secondary NE 2611 series 176, secondary PTW TN30031 series 578 and Third PTW W30001 series 365. ii) D{alpha}),en radiation field of {sup 60}Co for patterns: primary CC01 series 131, Secondary PTW TN30031 series 578 and tertiary PTW W30001 series 365. iii) I-MR/S with extrapolation chamber PTW primary pattern, measurement realizes in secondary patron fields of {sup 90}Sr-{sup 90}Y. The expanded uncertainty U it is calculated of agreement with the Guide of the ISO/BIPM being observed the following thing: a. In some the cases {sigma}{sub {beta}}, is the component of the U that more contributed to this. Therefore, it is necessary to settle down technical of sampling in those mensurations that allow to reduce the value of {sigma}{sub {beta}}. For example with sizes of subgroup {eta}{sub {approx}} 30 data, or with a number of subgroups {kappa}{sub {>=}}. That which is achieved automating the mensuration processes. b.The component of the temperature is also one of those that but they contribute to the U, of there the necessity of: to recover the tracking for this magnitude of it influences and to increase the precision in the determinations of the temperature to diminish their influence in the U. c. The percentage difference of the magnitudes dosemeters carried out by it patterns are consistent with U certain. However, it is necessary to diminish the uncertainty in the physical factors different to {kappa}{sub {tau}} and {sigma}{sub {beta}} for the one case of the primary patterns; because these they should be those of smaller value of U. d. In the case of the secondary patterns and tertiary for the realization of the{kappa}{sub {alpha}}{sub {center_dot}} is necessary to determine the corrections explicitly for recombination and polarization; and to analyze their contribution in the U. e. It is necessary to recover the tracking for the mensurations of the humidity. f. It is recommended to continue the control mensurations for each pattern, taking it{sup s} the least a measure every fifteen days, that it corresponds at two measured for month and 24 at the year. g. The operation of the air conditioned perturb the measurement for such as it recommends not to use it, and alone to leave in balance the chamber with the air of the engine room. (Author)

Alvarez R, M.T.; Tovar M, V.M.; Cejudo A, J. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

2005-12-15

 
 
 
 
121

Ferramenta computacional para avaliação de kerma no ar em aplicações de radioproteção em áreas de internação de pacientes: proposição de um método simples para avaliação experimental / Computational toolkit for evaluating air kerma with the purpose of radiation protection of hospital inpatients: proposal of a simple experimental evaluation method  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Apresentar uma ferramenta de análise de dados que pode ser utilizada para proteção de pacientes e trabalhadores em áreas de uso de equipamentos móveis. MATERIAIS E MÉTODOS: Foi desenvolvida uma ferramenta, em planilha ativa Excel®, que utiliza medidas de exposição para gerar um banco de da [...] dos de fatores de forma e calcular o kerma no ar ao entorno de um leito. O banco de dados inicial foi coletado com três equipamentos móveis. Um espalhador não antropomórfico foi utilizado, sendo realizadas medidas de exposição em uma malha de (4,2 × 4,2) m², ao passo de 0,3 m. RESULTADOS: A ferramenta calcula o kerma no ar (associado à exposição de pacientes expostos e ao equivalente de dose ambiente) à radiação secundária. Para distâncias inferiores a 60,0 cm, valores acima do limite máximo de equivalente de dose ambiente definido para área livre (0,5 mSv/ano) foram verificados. Os dados coletados a 2,1 m foram sempre inferiores a 12% do referido limite. CONCLUSÃO: A ferramenta é capaz de auxiliar na proteção radiológica de pacientes e trabalhadores, quando associada à coleta de dados adequada, pois possibilita a determinação de áreas livres ao entorno de leitos em áreas onde equipamentos móveis geradores de radiação X são utilizados. Abstract in english OBJECTIVE: To present a data analysis toolkit that may be utilized with the purpose of radiation protection of hospital inpatients and workers in areas where mobile apparatuses are used. MATERIALS AND METHODS: An Excel® ActiveSheet was utilized to develop a computational toolkit with exposure measur [...] ements to generate a database of shape factors and to calculate the air kerma around hospital beds. The initial database included data collected with three mobile apparatuses. A non-anthropomorphic phantom was utilized and exposure measurements were performed on a (4.2 × 4.2) m² mesh-grid at 0.3 m steps. RESULTS: The toolkit calculates the air kerma (associated with patients' radiation exposure and with ambient equivalent dose) under secondary radiation. For distances lower than 60.0 cm, values above the maximum ambient equivalent dose threshold defined for radiation free areas (0.5 mSv/year) were verified. Data collected at 2.1 m have always presented values lower than 12% of that threshold. CONCLUSION: The toolkit can aid in the radiological protection of patients and workers, provided it is combined with appropriate data collection, since it allows the determination of radiation free areas around beds in rooms where mobile X-ray apparatuses are utilized.

Gabriela, Hoff; José Rodrigo Mendes, Andrade; Andréia Caroline Fischer da Silveira, Fischer; Alexandre, Bacelar.

2012-04-01

122

Air Quality Index (AQI) -- A Guide to Air Quality and Your Health  

Science.gov (United States)

Local Air Quality Conditions Zip Code: State : National Summary Air Quality Index (AQI) - A Guide to Air Quality and Your Health You will need Adobe Reader ... AirNow PDF page to learn more. Publications Air Quality Index - A Guide to Air Quality and Your ...

123

Key comparison B.I.P.M..R.I.(1)-K3 of the air-kerma standards of the N.I.M. and the B.I.P.M. in medium-energy x-rays  

International Nuclear Information System (INIS)

A key comparison has been made between the air-kerma standards of the N.I.M. and the B.I.P.M. in the medium-energy x-ray range. The results show the standards to be in general agreement at the level of twice the stated relative standard uncertainty of 3.1 X 10-3, although there is evidence of a trend in the results at different radiation qualities. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the B.I.P.M. key comparison database. (authors)

124

Implementation of the method air-kerma product area in KAP camera calibration with reference qualities of X-ray series at the SSDL RQR of Mexico; Implementacion del metodo producto kerma en aire-area en la calibracion de camaras KAP con calidades de referencia de rayos X de la serie RQR en el LSCD de Mexico  

Energy Technology Data Exchange (ETDEWEB)

The X-Ray machines, at a reference laboratory for the instrument calibration in diagnostic radiology, should compliance with the ISO requirements. Sometimes there is not available as much laboratories as needed in Latin American countries. So this project shows the KAP ionization chamber implementation method using the TRS-457 radiation quality from the IAEA at the SSDL of Mexico. The KAP instruments calibration method consists in doing a substitution comparison using a standard reference with traceability to a primary laboratory and a transmission-monitoring chamber that measures the number of photons of the X-ray primary beam. A KAP chamber calibration requires a special array that consists in collocating the chamber in two different positions of its calibration process. Then, with air kerma-area product coefficient together with a corrected electrometer measure at referential conditions, the patient dosimetry magnitudes are calculated. The dosimetry necessity at hospitals always will be in function of possessing a highly reliable calibration coefficient chamber for making these measures. That dosimetry results will help in reducing the total or partial irradiation emitted to the human body of the patient. This is how stochastic risks will be lessened due to diagnostic studies. The purpose of this project is to have a synergy with calibration for making known that the SSDL of Mexico has the technical capacity to act as a link between primary standard dosimetry laboratories and the ionizing radiation equipment users who require that their KAP chamber have traceability from the primary standard to the user. (author)

Cejudo, Jesus; Tovar, Victor M., E-mail: jesus.cejudo@ini.gob.mx, E-mail: victor.tovar@inin.gob.mx [lnstituto Nacional de lnvestigaciones Nucleares (DMRI/LSDC/lNlN), Ocoyoacac (Mexico). Centro Nuclear Dr. Nabor Carrillo Flores. Laboratorio Secundario de Calibracion Dosimetrica

2013-10-01

125

Measurement of conversion coefficients between air Kerma and personal dose equivalent and backscatter factors for diagnostic X-ray beams; Determinacao experimental dos coeficientes de conversao de Kerma no ar para o equivalente de dose pessoal, Hp(d), e fatores de retroespalhamento em feixes de raios-x diagnostico  

Energy Technology Data Exchange (ETDEWEB)

Two sets of quantities are import in radiological protection: the protection and operational quantities. Both sets can be related to basic physical quantities such as kerma through conversion coefficients. For diagnostic x-ray beams the conversion coefficients and backscatter factors have not been determined yet, those parameters are need for calibrating dosimeters that will be used to determine the personal dose equivalent or the entrance skin dose. Conversion coefficients between air kerma and personal dose equivalent and backscatter factors were experimentally determined for the diagnostic x-ray qualities RQR and RQA recommended by the International Electrotechnical Commission (IEC). The air kerma in the phantom and the mean energy of the spectrum were measured for such purpose. Harshaw LiF-100H thermoluminescent dosemeters (TLD) were used for measurements after being calibrated against an 180 cm{sup 3} Radcal Corporation ionization chamber traceable to a reference laboratory. A 300 mm x 300 mm x 150 mm polymethylmethacrylate (PMMA) slab phantom was used for deep-dose measurements. Tl dosemeters were placed in the central axis of the x-ray beam at 5, 10, 15, 25 and 35 mm depth in the phantom upstream the beam direction Another required parameter for determining the conversion coefficients from was the mean energy of the x-ray spectrum. The spectroscopy of x-ray beams was done with a CdTe semiconductor detector that was calibrated with {sup 133} Ba, {sup 241} Am and {sup 57} Co radiation sources. Measurements of the x-ray spectra were carried out for all RQR and RQA IEC qualities. Corrections due to the detector intrinsic efficiency, total energy absorption, escape fraction of the characteristic x-rays, Compton effect and attenuation in the detector were done aiming an the accurate determination of the mean energy. Measured x-ray spectra were corrected with the stripping method by using these response functions. The typical combined standard uncertainties of conversion coefficients and backscatter factors were 12% and 6% respectively. (author)

Rosado, Paulo Henrique Goncalves

2008-07-01

126

Kinematic kerma factors  

International Nuclear Information System (INIS)

The HEATR module of NJOY computes heat production by energy-balance (usually); that is, it assumes that the energy available for charged-particle emission and nuclear recoil can be obtained from the available energy (E + Q) minus the energy carried away by neutrons (E/sub n/) and the energy carried away by photons (anti E/sub ?/). If there are errors in either anti E/sub n/ or anti E /sub ?/, the local heating will be incorrect. In a large enough system, this heating error will be exactly compensated for by photon energy deposition, and the correct result for total heating will be obtained. However, in very small systems where most of the photons escape, the local heating can have very large errors resulting from a lack of energy conservation in the nuclear data evaluation. Accurate values for this local heating can be computed for some reactions by kinematics (radiative capture, elastic and inelastic neutron scattering). Reactions that emit charged particles are more difficult because the ENDF/B files do not contain the required particle spectra or angular distributions. Nevertheless, it is possible to establish an upper limit for the kinematic kerma factor by assuming that such reactions emit no photons. The HEATR module has been modified to add kinematic kerma factors computed in this way to the NJOY calculational path. This means that they are available for either multigroup or Monte Carlo processing

127

Report on EUROMET.RI(I)-K1 and EUROMET.RI(I)-K4 (EUROMET project no. 813): Comparison of air kerma and absorbed dose to water measurements of {sup 60}Co radiation beams for radiotherapy  

Energy Technology Data Exchange (ETDEWEB)

The results of an unprecedented international effort involving 26 countries are reported. The EUROMET.RI(I)-K1 and EUROMET.RI(I)-K4 key comparisons were conducted with the goal of supporting the relevant calibration and measurement capabilities (CMC) planned for publication by the participant laboratories. The measured quantities were the air kerma (K{sub air}) and the absorbed dose to water (Dw) in {sup 60}Co radiotherapy beams. The comparison was conducted by the pilot laboratory MKEH (Hungary), in a star-shaped arrangement from January 2005 to December 2008. The calibration coefficients of four transfer ionization chambers were measured using two electrometers. The largest deviation between any two calibration coefficients for the four chambers in terms of air kerma and absorbed dose to water was 2.7% and 3.3% respectively. An analysis of the participant uncertainty budgets enabled the calculation of degrees of equivalence (DoE), in terms of the deviations of the results and their associated uncertainties. As a result of this EUROMET project 813 comparison, the BIPM key comparison database (KCDB) will include eleven new Kair and fourteen new D{sub w} DoE values of European secondary standard dosimetry laboratories (SSDLs), and the KCDB will be updated with the new DoE values of the other participant laboratories. The pair-wise degrees of equivalence of participants were also calculated. In addition to assessing calibration techniques and uncertainty calculations of the participants, these comparisons enabled the experimental determinations of N{sub Dw}/N{sub Kair} ratios in the {sup 60}Co gamma radiation beam for the four radiotherapy transfer chambers. (authors)

Csete, I. [National Office of Measures (OMH) - pilot laboratory and corresponding author (Hungary); Leiton, A.G. [Research Centre for Energy, Environment and Technology (CMRI-CIEMAT) (Spain); Sochor, V. [Czech Metrology Institute (CMI) (Czech Republic); Lapenas, A. [Latvian National Metrology Center (LNMC-RMTC) (Latvia); Grindborg, J.E. [Swedish Radiation Protection Authority (SSI) (Sweden); Jokelainen, I. [Radiation and Nuclear Safety Authority (STUK) (Finland); Bjerke, H. [Norwegian Radiation Protection Authority (NRPA) (Norway); Dobrovodsky, J. [Slovak Institute of Metrology (SMU) (Slovakia); Megzifene, A. [International Atomic Energy Agency, IAEA, Vienna (Austria); Hourdakis, C.J. [Hellenic Atomic Energy Committee (HAEC-HIRCL) (Greece); Ivanov, R. [National Centre of Metrology (NCM) (Bulgaria); Vekic, B. [Rudjer Boskovic Institute (IRB) (Croatia); Kokocinski, J. [Central Office of Measures (GUM) (Poland); Cardoso, J. [Institute for Nuclear Technology (ITN-LMRIR) (Portugal); Buermann, L. [Physikalisch Technische Bundesanstalt (PTB) (Germany); Tiefenboeck, W. [Bundesamt fur Eich und Vermesungswesen (BEV) (Austria); Stucki, G. [17 Bundesamt fur Metrologie (METAS) (Switzerland); Van Dijk, E. [NMi Van Swinden Laboratorium (NMi) (Netherlands); Toni, M.P. [ENEA-CR Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti (ENEA) (Italy); Minniti, R. [20 National Institute of Standards and Technology (NIST) (United States); McCaffrey, J.P. [National Research Council Canada (NRC) (Canada); Silva, C.N.M. [National Metrology Laboratory of Ionizing Radiation (LNMRI-IRD) (Brazil); Kharitonov, I. [D I Mendeleyev Institute for Metrology (VNIIM) (RU); Webb, D. [Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) (Australia); Saravi, M. [National Atomic Energy Commission (CNEA-CAE) (Argentina); Delaunay, F. [Laboratoire National Henri Becquerel (LNE-LNHB) (France)

2010-06-15

128

A new method for calculation of an air quality index  

Energy Technology Data Exchange (ETDEWEB)

Air quality measurement programs in Finnish towns have expanded during the last few years. As a result of this it is more and more difficult to make use of all the measured concentration data. Citizens of Finnish towns are nowadays taking more of an interest in the air quality of their surroundings. The need to describe air quality in a simplified form has increased. Air quality indices permit the presentation of air quality data in such a way that prevailing conditions are more easily understandable than when using concentration data as such. Using an air quality index always means that some of the information about concentrations of contaminants in the air will be lost. How much information is possible to extract from a single index number depends on the calculation method. A new method for the calculation of an air quality index has been developed. This index always indicates the overstepping of an air quality guideline level. The calculation of this air quality index is performed using the concentrations of all the contaminants measured. The index gives information both about the prevailing air quality and also the short-term trend. It can also warn about the expected exceeding of guidelines due to one or several contaminants. The new index is especially suitable for the real-time monitoring and notification of air quality values. The behaviour of the index was studied using material from a measurement period in the spring of 1994 in Kaepylae, Helsinki. Material from a pre-operational period in the town of Oulu was also available. (author)

Ilvessalo, P. [Finnish Meteorological Inst., Helsinki (Finland). Air Quality Dept.

1995-12-31

129

The influence of micro location on the air freezing index  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper are exposed research results of air freezing index values occurring in area of Bosnia and Herzegovina. Theoretic probabilities of air freezing index occurrence are calculated, based on data of 26 meteorological stations, in order to determine its return periods of appearing (the probability of air freezing index appearance average once in period considered. To this purpose five the most frequent in praxis theoretic distribution functions are used: GAUSS, GALTON, LOG-PEARSON, PEARSON and GUMBEL. As the most appropriate function for all meteorogic stations the LOG-PEARSON was selected because it on the best way approximates values of calculated air freezing index. Regarding to influence of micro location on the value of air freezing index some independent parameters of location which are measurable (variables and have supposed influence, are took in analysis. To this purpose the mathematic model of multi variant regression analysis was used and the regression equation of the associated influence of independent parameters was determined. Using this discovered equation designers of road pavement can for each micro-location cutted by the road line, calculate the air freezing index and check the pavement structure on the harmful freezing effects.

Mazi? Branko

2004-01-01

130

The air pollution index system in Hong Kong  

Energy Technology Data Exchange (ETDEWEB)

The Hong Kong Environmental Protection Department (EPD) is currently operating an air quality monitoring network in the territory. There are nine monitoring stations, each with air quality monitoring equipment, meteorological instruments and a data logger. Five minute averaged data are transmitted through telephone lines to the central computer at the EPD Air Laboratory and are also stored in the data logger on site, as backup. At present, the EPD releases its air quality measurements to the public via monthly and special press releases, and annual reports. However, as public awareness of air pollution problems has increased, there has been an urgent need for timely and simpler information about air pollution levels. The development and operation of an Air Pollution Index (API) system has addressed that need. This presentation discusses the API computation, the information and advice released to the general public and how they can access the API information. Some API results are also presented. (author)

Lee, F.Y.P.; Gervat, G.P. [Hong Kong Government, Wanchai (Hong Kong). Environmental Protection Dept.

1995-12-31

131

Air Kerma Calibration Factors and kch Values for PTW Soft X-ray, NACP and Roos Ionization Chambers at Very Low X-ray Energies (0.035 mm - 1.0 mm Al HVL)  

International Nuclear Information System (INIS)

Several national and international protocols have been established for the dosimetry of x-ray beams used in radiotherapy. For the very low energy x-rays (0.035mm-1.0 mm Al HVL) only two codes are available: the UK IPEMB Code of Practice and the German standard, DIN 6809 Part 4. The measurement of very low energy x-ray beams is normally performed with parallel plate ionization chambers calibrated at a standards laboratory and characterized by an air kerma calibration factor Nk. According to the IPEMB Code of Practice the absorbed dose in the user's beam should be determined by taking measurements with the parallel plate chamber positioned such that its entrance window is at the surface of a full-scatter water equivalent phantom. The absorbed dose to water can then be determined using an equation which includes a factor, kch, which accounts for the change in response of the ionization chamber between the calibration in air and measurement at the surface of the phantom. Nk and kch values for the PTW soft X-ray, NACP and Roos ionization chambers are reported. It was found that kch values varied from about 1.01 to 1.08 depending on the chamber, beam quality and phantom material. It is recommended that the IPEMB Code of Practice should be revised to incorporate these values

132

Remarks on KERMA Factors in ACE files  

Science.gov (United States)

Some neutron KERMA factors in ACE files are negative and extremely large if nuclear data libraries do not keep energy-balance. The status of neutron KERMA factors in the official ACE file of ENDF/B-VII.1 is examined. As a result, it is found out that neutron KERMA factors of nuclei more than 200 in ENDF/B-VII.1 have some problems. Effects of the inadequate KERMA factor are also investigated, which are large for neutron heat while those are small for total (neutron + gamma) heat. Users who use only neutron KERMA factors should check if the factors are adequate or not before they use the factors.

Konno, C.; Ochiai, K.; Takakura, K.; Sato, S.

2014-04-01

133

Hold your breath: A new index of air pollution  

International Nuclear Information System (INIS)

Environmental quality and climate change have been discussed prominently as urgent problems that – due to air pollution – produce severe consequences affecting the everyday life of millions of people. Using a Multiple Indicators Multiple Causes (MIMIC) model, we calculate a new index of air pollution and provide a ranking for 122 countries for every fifth year between 1985 and 2005. The empirical analysis supports the Environmental Kuznets Curve (EKC) hypothesis and shows a significant influence of determinants such as energy efficiency, industrial production, the electricity produced from coal sources, and demographic transition on air pollution. According to the index, Norway, Switzerland, Japan, Luxembourg, and Iceland are among the top 5 countries in terms of air quality performance. Eritrea, Mozambique, Tajikistan, the Democratic Republic of Congo, and Ethiopia performed worst in 2005. - Highlights: ? We calculate a new index of air pollution and provide a ranking for 122 countries. ? The empirical analysis supports the EKC hypothesis. ? Country ranking of this air pollution index is comparable across the period 1985 to 2005. ? Definition of the underlying variables does not change and the methodology is consistent

134

The use of air quality index (AQI) in environmental management  

International Nuclear Information System (INIS)

The air quality index (AQI) is considered a global air quality index in a particular moment or day and in a specific monitoring station. The AQI is to be interpreted as a guiding air quality index for the general public. Specialists should take into account other factors when studying the pollution levels. The behaviour of air pollution is studied by using the AQI in two monitoring points in Regla, where the main pollutants are measured: SO2, NO2 and total suspended particulates. It was founded that particulates and NO2 are the pollutants that contribute most to the air quality deterioration, which occurs with greater frequency-days in the categories Poor and Bad, and show an increase in the categories Terrible and Critical. The necessary recommendations for the reduction of air pollution are given. The use of this AQI for assessing air pollution in settlements is recommended as a good tool for environmental information and management. A visual scale is proposed to improve and facilitate the public's understanding

135

Hold Your Breath. A New Index of Air Quality  

International Nuclear Information System (INIS)

Environmental quality and climate change have long attracted attention in policy debates. Recently, air quality has emerged on the policy agenda. We calculate a new index of air quality using CO2 and SO2 emissions per capita as indicators and provide a ranking for 122 countries from 1985 to 2005.The empirical analysis supports the EKC hypothesis (Environmental Kuznets Curve) and shows a significant influence of determinants such as energy efficiency, industrial production, electricity produced from coal sources, and urbanization on air quality. According to our index, Luxemburg, Norway, Iceland, Switzerland, and Japan are among the top 5 countries in terms of air quality performance. The Democratic Republic of Congo, Eritrea, Ethiopia, Togo, and Nepal performed worst in 2005.

136

Hold Your Breath. A New Index of Air Quality  

Energy Technology Data Exchange (ETDEWEB)

Environmental quality and climate change have long attracted attention in policy debates. Recently, air quality has emerged on the policy agenda. We calculate a new index of air quality using CO2 and SO2 emissions per capita as indicators and provide a ranking for 122 countries from 1985 to 2005.The empirical analysis supports the EKC hypothesis (Environmental Kuznets Curve) and shows a significant influence of determinants such as energy efficiency, industrial production, electricity produced from coal sources, and urbanization on air quality. According to our index, Luxemburg, Norway, Iceland, Switzerland, and Japan are among the top 5 countries in terms of air quality performance. The Democratic Republic of Congo, Eritrea, Ethiopia, Togo, and Nepal performed worst in 2005.

Buehn, A. [Utrecht School of Economics, Utrecht University, Utrecht (Netherlands); Reza Farzanega, M. [Dresden University of Technology and ZEW Mannheim, Mannheim (Germany)

2011-12-15

137

Air quality health index variation across British Columbia  

Energy Technology Data Exchange (ETDEWEB)

The new Air Quality Health Index (AQHI) is a tool aiming to present the health risks related to air pollution in Canada. This index can be used by individuals to help them reduce their health risk resulting from poor air quality. An assessment of the short term health risk induced by poor air quality is provided to Canadians through the AQHI. The AQHI is based on three factors: ambient concentrations of nitrogen dioxide, fine particulate matter and ozone, the local air quality information being presented on an hourly and daily basis and being calculated each hour for several locations across Canada. Pulmonary disorders and impacts on cardiac function are the more significant short term health risks. Longer term exposure to poor air quality is associated with increased rates of allergies and asthma, low birth weight, atherosclerosis, poorer lung development in children, lung cancer and ear infections. Information on the AQHI and on the variation across British Columbia of the health risk associated with this index are presented in this document. 19 refs., 5 tabs., 5 figs.

Hasselback, P. [Interior Health Authority, Kelowna, BC (Canada); Taylor, E. [British Columbia Ministry of Health Living and Sport, Vancouver, BC (Canada)

2010-09-15

138

40 CFR Appendix G to Part 58 - Uniform Air Quality Index (AQI) and Daily Reporting  

Science.gov (United States)

... Uniform Air Quality Index (AQI) and Daily Reporting G Appendix G to Part 58 Protection of Environment ENVIRONMENTAL...CONTINUED) AMBIENT AIR QUALITY SURVEILLANCE Pt. 58, App. G Appendix G to Part 58—Uniform Air Quality Index...

2010-07-01

139

Calculation of neutron kerma in tissues  

Energy Technology Data Exchange (ETDEWEB)

Neutron kerma of normal and tumor tissues has been calculated using the tissues elemental concentration. A program developed in Math cad contains the kerma factors of C, H, O, N, Na, Mg, P, S, Cl, K, etc. that are in normal and tumor human tissues. Having the elemental composition of any human tissue the neutron kerma can be calculated. The program was tested using the elemental composition of tumor tissues such as sarcoma, melanoma, carcinoma and adenoid cystic, also neutron kerma for adipose and muscle tissue for normal adult was calculated. The results are in agreement with those published in literature. The neutron kerma for water was also calculated because in some dosimetric calculations water is used to describe normal and tumor tissues. From this comparison was found that at larger energies kerma factors are approximately the same, but energies less than 100 eV the differences are large. (Author)

Vega C, H.R.; Manzanares A, E. [Unidades Academicas de Estudios Nucleares, Ing. Electrica y Matematicas, Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)]. E-mail: rvega@cantera.reduaz.mx

2004-07-01

140

Neutron KERMA factors of Human Tissues  

Directory of Open Access Journals (Sweden)

Full Text Available A program to calculate the neutron KERMA in human tissues has been developed. The program was developed in Mathcad and contains the neutron kerma factors of those elements that are present in different human tissues. Having the elemental composition of any human tissue the neutron kerma can be easily calculated. The program was tested using the elemental composition of tumor tissues such as sarcoma, melanoma, carcinoma and adenoid cystic. Neutron kerma for adipose and muscle tissue for normal adult was calculated. The results are in agreement with those published in literature. The neutron kerma for water was also calculated because in some dosimetric calculations water is used to describe normal and tumor tissues. From this comparison was found that at larger energies kerma factors are approximately the same, but energies less than 100 eV the differences are large.

Martin-Martin, A.

2007-07-01

 
 
 
 
141

Interpretation of air quality data using an air quality index for the city of Kanpur, India  

Energy Technology Data Exchange (ETDEWEB)

Essential features of an Air Quality Index (AQI) are described and results of ambient air quality measurements for the city of Kanpur, one of the most heavily polluted cities in India, are discussed. The air quality data is interpreted using an air quality index developed at the Indian Institute of Technology in Kanpur, India. Results show that air quality worsens in winter months and also during the early summer months of March, April and May. These early summer months are characterized by dusty winds resulting in high concentrations of suspended particulates. Air quality generally improves in the monsoon and post-monsoon periods. Suspended particulate matter was the responsible pollutant over 95 per cent of the time, with nitrogen oxide also becoming a significant pollutant on several occasions. 13 refs., 5 tabs., 6 figs.

Sharma, M.; Maheshwari, M. [Indian Institute of Technology, Dept. of Civil Engineering, Kanpur (India); Pandey, R.; Shukla, B. P.; Gupta, N. K. [Central Pollution Control Board, Parivesh Bhawan, East Arjun Nagar, Delhi (India); Johri, S. [Degree College, Dept. of Chemistry, Kanpur (India)

2003-11-01

142

Development of fuzzy air quality index using soft computing approach.  

Science.gov (United States)

Proper assessment of air quality status in an atmosphere based on limited observations is an essential task for meeting the goals of environmental management. A number of classification methods are available for estimating the changing status of air quality. However, a discrepancy frequently arises from the quality criteria of air employed and vagueness or fuzziness embedded in the decision making output values. Owing to inherent imprecision, difficulties always exist in some conventional methodologies like air quality index when describing integrated air quality conditions with respect to various pollutants parameters and time of exposure. In recent years, the fuzzy logic-based methods have demonstrated to be appropriated to address uncertainty and subjectivity in environmental issues. In the present study, a methodology based on fuzzy inference systems (FIS) to assess air quality is proposed. This paper presents a comparative study to assess status of air quality using fuzzy logic technique and that of conventional technique. The findings clearly indicate that the FIS may successfully harmonize inherent discrepancies and interpret complex conditions. PMID:22083398

Mandal, T; Gorai, A K; Pathak, G

2012-10-01

143

KERMA received in neck by woman subject to mammography survey  

International Nuclear Information System (INIS)

This paper provides information about the Air KERMA received in the neck by women subjected to mammography surveys. In this investigation we demonstrated that the protection given in mammography units is insufficient because the neck protector is only made up of plastic, in consequence the neck receives unnecessary doses. We used for the radiological survey an Electrometer RADCAL, model: 9060, serial 99-1724 and an Ionization Chamber 180 cc. RADCAL, model: 10X5-60, serial: 18304.We carried out 15 Quality Control inspections in different mammography units used for screening breast cancer from different manufacturers and these QC inspections included radiological surveys. These inspections were made in a two year period. The ionization chamber was placed around the thyroid protector (left, front and right) and the Air KERMA was measured under clinical condition. We found inadequate protection in the thyroid protector. The Air KERMA around the thyroid protector was between 40 and 80 mGy/min. This investigation demonstrates that is impossible to postpone the need to demand mammography manufacturer to modify and reinforce the thyroid protector, and we urge all International Radiological Protection Association to take steps to insure the well being of our patients and to pursuit manufacturers to meet security standards required in order to reduce the exposure of the patient's neck. (author)

144

Comparison of conversion coefficients for equivalent dose in terms of air kerma using a sitting and standing female adult voxel simulators exposure to photons in antero-posterior irradiation geometry  

Science.gov (United States)

Due to the difficulty in implementing invasive techniques for calculations of dose for some exposure scenarios, computational simulators have been created to represent as realistically as possible the structures of the human body and through radiation transport simulations to obtain conversion coefficients (CCs) to estimate dose. In most published papers simulators are implemented in the standing posture and this may not describe a real scenario of exposure. In this work we developed exposure scenarios in the Visual Monte Carlo (VMC) code using a female simulator in standing and sitting postures. The simulator was irradiated in the antero-posterior (AP) geometry by a plane source of monoenergetic photons with energy from 10 keV to 2 MeV. The conversion coefficients for equivalent dose in terms of air kerma (HT/Kair) were calculated for both scenarios and compared. The results show that the percentage difference of CCs for the organs of the head and thorax was not significant (less than 5%) since the anatomic position of the organs is the same in both postures. The percentage difference is more significant to the ovaries (71% for photon energy of 20 keV), to the bladder (39% at 60 keV) and to the uterus (37% at 100 keV) due to different processes of radiation interactions in the legs of the simulator when its posture is changed. For organs and tissues that are distributed throughout the entire body, such as bone (21% at 100 keV) and muscle (30% at 80 keV) the percentage difference of CCs reflects a reduction of interaction of photons with the legs of the simulator. Therefore, the calculation of conversion coefficients using simulators in the sitting posture is relevant for a more accurate dose estimation in real exposures to radiation.

Cavalcante, F. R.; Galeano, D. C.; Carvalho Júnior, A. B.; Hunt, J.

2014-02-01

145

Comparison of conversion coefficients for equivalent dose in terms of air kerma for photons using a male adult voxel simulator in sitting and standing posture with geometry of irradiation antero-posterior  

Science.gov (United States)

The dose conversion coefficient (DCC) is important to quantify and assess effective doses associated with medical, professional and public exposures. The calculation of DCCs using anthropomorphic simulators and radiation transport codes is justified since in-vivo measurement of effective dose is extremely difficult and not practical for occupational dosimetry. DCCs have been published by the ICRP using simulators in a standing posture, which is not always applicable to all exposure scenarios, providing an inaccurate dose estimation. The aim of this work was to calculate DCCs for equivalent dose in terms of air kerma (H/Kair) using the Visual Monte Carlo (VMC) code and the VOXTISS8 adult male voxel simulator in sitting and standing postures. In both postures, the simulator was irradiated by a plane source of monoenergetic photons in antero-posterior (AP) geometry. The photon energy ranged from 15 keV to 2 MeV. The DCCs for both postures were compared and the DCCs for the standing simulator were higher. For certain organs, the difference of DCCs were more significant, as in gonads (48% higher), bladder (16% higher) and colon (11% higher). As these organs are positioned in the abdominal region, the posture of the anthropomorphic simulator modifies the form in which the radiation is transported and how the energy is deposited. It was also noted that the average percentage difference of conversion coefficients was 33% for the bone marrow, 11% for the skin, 13% for the bone surface and 31% for the muscle. For other organs, the percentage difference of the DCCs for both postures was not relevant (less than 5%) due to no anatomical changes in the organs of the head, chest and upper abdomen. We can conclude that is important to obtain DCCs using different postures from those present in the scientific literature.

Galeano, D. C.; Cavalcante, F. R.; Carvalho, A. B.; Hunt, J.

2014-02-01

146

Seasonal ARIMA for Forecasting Air Pollution Index: A Case Study  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Both developed and developing countries are the major reason that affects the world environment quality. In that case, without limit or warning, this pollution may affect human health, agricultural, forest species and ecosystems. Therefore, the aim of this study was to determine the monthly and seasonal variations of Air Pollution Index (API at all monitoring stations in Johor. Approach: In this study, time series models will be discussed to analyze future air quality and used in modeling and forecasting monthly future air quality in Malaysia. A Box-Jenkins ARIMA approach was applied in order to analyze the API values in Johor. Results: In all this three stations, high values recorded at sekolah menengah pasir gudang dua (CA0001. This situation indicates that the most polluted area in Johor located in Pasir Gudang. This condition appears to be the reason that Pasir Gudang is the most developed area especially in industrial activities. Conclusion: Time series model used in forecasting is an important tool in monitoring and controlling the air quality condition. It is useful to take quick action before the situations worsen in the long run. In that case, better model performance is crucial to achieve good air quality forecasting. Moreover, the pollutants must in consideration in analysis air pollution data.

Muhammad H. Lee

2012-01-01

147

Determination of backscatter factors for diagnostic x-ray beams by experimental and Monte Carlo Methods and determination of air kerma to dose equivalent conversion factors for the calibration of personal monitors  

International Nuclear Information System (INIS)

Backscatter measurements are essential for the determination of the Dose Equivalent quantity H(0.07) in phantoms or H'(0.07) in ICRU sphere, both for area monitoring and individual monitoring purposes. Backscatter factor data for the diagnostic x-ray beams are sparsely Some of the published data are entirely from calculations for idealised irradiation conditions available. A Siemens Polymat 501 diagnostic x-ray machine was used for the investigations. Variations in kV, mA and time of exposure of the machine are microprocessor-controlled, giving a highly stable output. A light beam diaphragm was attached to the x-ray tube and the total inherent filtration was estimated as 2.9 mm Al. The spectra in terms of exposure per keV interval as well as Photon fluence per keV interval of the three collimated reference beams of 40 kV, 60 kV, 81 kV were determined by attenuation analysis method, using a free air chamber and pure aluminium and copper attenuators. A 3 c.c. spherical Shonka C-552 chamber and a 0.2 c.c. Nuclear Enterprises type 2577 graphite walled chamber which were calibrated against low kV primary standard free air chamber were used to determine back scatter factors for PMMA and water phantom respectively. The measuring set-up consisted of locally designed Varactor input operational amplifier in conjunction with a Philips digital voltmeter and 1 nano Farad reference capacitance. Back scatter factors were determined using 30 cm x 30 cm x 15 cm PMMA phantom and a 30 ccm x 30 cm x 15 cm PMMA phantom and a 30 cm x 30 cm x 25.6 cm reference water phantom and conversion coefficients in terms of H(0.07)/Air kerma were determined, which can be used to calibrate personal monitors. The Monte Carlo Code for Neutrons and Photons (MCNP) was also used to find out the Back scatter factors and back scattered spectra for the PMMA and water phantom. The paper gives the details of the experiment and results and comparisons with published data. Typical Results: The ratio of measured to Monte Carlo determined backscatter values were with ±3% at the three beams used. The Monte Carlo values showed an agreement of better than ±6% with Physikalische Technische Bundesanstat (PTB) Monte Carlo values of nearest narrow spectra. (author)

148

Air kerma calibration factors and chamber correction values for PTW soft x-ray, NACP and Roos ionization chambers at very low x-ray energies  

International Nuclear Information System (INIS)

This paper evaluates the characteristics of ionization chambers for the measurement of absorbed dose to water using very low-energy x-rays. The values of the chamber correction factor, kch, used in the IPEMB 1996 code of practice for the UK secondary standard ionization chambers (PTW type M23342 and PTW type M23344), the Roos (PTW type 34001) and NACP electron chambers are derived. The responses in air of the small and large soft x-ray chambers (PTW type M23342 and PTW type M23344) and the NACP and Roos electron ionization chambers were compared. Besides the soft x-ray chambers, the NACP and Roos chambers can be used for very low-energy x-ray dosimetry provided that they are used in the restricted energy range for which their response does not change by more than 5%. The chamber correction factor was found by comparing the absorbed dose to water determined using the dosimetry protocol recommended for low-energy x-rays with that for very low-energy x-rays. The overlap energy range was extended using data from Grosswendt and Knight. Chamber correction factors given in this paper are chamber dependent, varying from 1.037 to 1.066 for a PTW type M23344 chamber, which is very different from a value of unity given in the IPEMB code. However, the values of kch determined in this paper agree with those given in the DIN standard within experimental uncertainty. The authors recommend that the very low-energy section of the IPEMB code is amended to include n of the IPEMB code is amended to include the most up-to-date values of kch. (author)

149

SELFAS2 : radio emission from cosmic ray air showers. Effect of realistic air refractive index  

CERN Document Server

Using the simulation code SELFAS2, we present predictions of the radio signal emitted by extensive air showers (EAS) during their development in the atmosphere. The radio emission in the MHz range coming from air showers is the superposition of two mechanisms: the variation of the transverse current due to the systematic opposite drift of electrons and positrons in the Earth's magnetic field and the variation of the charge excess due to the electrons in excess in the shower front. In this paper, we stress particularly the effect of the realistic air refractive index on the radio signal predicted by SELFAS2.

Marin, Vincent

2012-01-01

150

Comparison of conversion coefficients for equivalent dose in terms of air kerma for photons using a male adult voxel simulator in sitting and standing posture with geometry of irradiation antero-posterior  

International Nuclear Information System (INIS)

The dose conversion coefficient (DCC) is important to quantify and assess effective doses associated with medical, professional and public exposures. The calculation of DCCs using anthropomorphic simulators and radiation transport codes is justified since in-vivo measurement of effective dose is extremely difficult and not practical for occupational dosimetry. DCCs have been published by the ICRP using simulators in a standing posture, which is not always applicable to all exposure scenarios, providing an inaccurate dose estimation. The aim of this work was to calculate DCCs for equivalent dose in terms of air kerma (H/Kair) using the Visual Monte Carlo (VMC) code and the VOXTISS8 adult male voxel simulator in sitting and standing postures. In both postures, the simulator was irradiated by a plane source of monoenergetic photons in antero-posterior (AP) geometry. The photon energy ranged from 15 keV to 2 MeV. The DCCs for both postures were compared and the DCCs for the standing simulator were higher. For certain organs, the difference of DCCs were more significant, as in gonads (48% higher), bladder (16% higher) and colon (11% higher). As these organs are positioned in the abdominal region, the posture of the anthropomorphic simulator modifies the form in which the radiation is transported and how the energy is deposited. It was also noted that the average percentage difference of conversion coefficients was 33% for the bone marrow, 11% for the skin, 13% for the bone surface and 31% for the muscle. For other organs, the percentage difference of the DCCs for both postures was not relevant (less than 5%) due to no anatomical changes in the organs of the head, chest and upper abdomen. We can conclude that is important to obtain DCCs using different postures from those present in the scientific literature. - Highlights: • Scenarios of external photon exposures were performed in VMC code. • The VOXTISS8 simulator was irradiated in standing and sitting postures. • The irradiation geometry used was the antero-posterior (AP). • The DCCs for standing and sitting postures were compared. • Significant differences between the DCCs in both postures were observed

151

Índice integrado de calidad del aire para ciudades colombianas / Integrated air quality index for Colombian cities  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish En este trabajo se propone un índice que integra información sobre los dos contaminantes criterio de mayor incidencia sobre la salud humana en las ciudades colombianas, ozono (O3) y material particulado con diámetro menor a 10?m (PM10), utilizando lógica difusa. El índice se calcula para las normas [...] de calidad del aire que rigen actualmente en Colombia, aunque su adaptación a otras reglamentaciones es sencilla. Abstract in english In this work an integrated index is proposed using fuzzy logic which incorporates information on the two criteria pollutants of highest incidence on human health in Colombian cities, ozone (O3) and particulate matter with diameter less than 10?m (PM10). The index is calculated for current Colombian [...] air quality standards, although its adaptation to others is straightforward.

Mauricio, Jaramillo; Daniel Enrique, González; María Eugenia, Núñez; Gloria, Portilla.

2009-06-01

152

Air  

Science.gov (United States)

... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it ... may be affected by high levels of ozone. Air Quality Index (AQI) How do you know if ...

153

A tandem calibration method for kerma-area product meters  

International Nuclear Information System (INIS)

Full text: The kerma-area product (KAP) of an X ray beam is the surface integral of air kerma over a plane perpendicular to the beam. The quantity is commonly used in diagnostic radiology to evaluate radiation exposure to patients. It can be measured, closely according to definition, using a KAP meter with a transmission ionization chamber. To achieve adequate accuracy in measurements, appropriate calibration of the KAP meter is needed. An uncertainty of lower than 7% (with a coverage factor k = 2) is pursued in air kerma measurements in diagnostic X ray beams. The same level of accuracy can be seen as a challenging goal also for KAP measurements. According to international standard IEC 60580 a combined standard uncertainty of 25% (k 2) should not be exceeded in KAP measurements. The aim of this study was to investigate whether better accuracy can be achieved by improving the calibration procedures for KAP meters. The KAP meter should indicate the kerma-area product of the X ray beam delivered through the chamber to the patient. It is also generally recommended that calibration of a KAP meter of an X ray equipment (field KAP meter) should be performed using the actual X ray stand and irradiation geometry, mainly because of the characteristics of extra focal and stray radiation specific to the X ray equipment. A portable KAP meter can also be calibrated in a calibration laboratory but the effects of extra focal and stray radiation should be tested separately with the Xion should be tested separately with the X ray equipment in which the KAP meter is used. In calibrations on user's site the KAP reference value is usually determined by approximating the surface integral by the product of the X ray field area and the air kerma measured in the centre of the field. This beam area method works well in uniform, sharp-edged X ray fields. Non-uniformities and irregularities of the field may cause distorted dependence on field size to the determined calibration coefficients. Another important source of uncertainty is the measurement of field size. The accuracy of calibration can be improved by measuring the reference KAP value as an integral according the definition. Larsson, et al. have used TLDs to measure this surface integral. In this work a tandem calibration method was introduced in which the reference KAP value is measured using a KAP meter. In this approach the reference KAP chamber is placed in the X ray beam simultaneously with the field KAP chamber, using a distance of 30 cm between the chambers. The reference KAP meter has to be calibrated for the incident beam. In tandem method the measurement distance is not critical and field area measurements are not needed. As the reference KAP value is based on the measurement of the surface integral, the nonuniformities of the X ray field are inherently included. Because of remarkable dependence of the response on energy, the main uncertainties arise from the interpolation of the calibration coefficient of the reference KAP meter between X ray beam qualities. For tandem method, preliminary results indicate that uncertainty of 5% or lower could be achieved in the calibration of a field KAP meter. However, to achieve this level of accuracy, a comprehensive calibration of the reference KAP meter is required. Independent of calibration methods, the aim of 7% uncertainty in patient measurements is possible to achieve only in limited conditions of use and (or) by instruments of improved quality. This work has a contribution to the IAEA Coordinated Research Project for Testing of the Implementation of the IAEA Code of Practice on Dosimetry in X ray Diagnostic Radiology. (author)

154

Tolerance Levels of Roadside Trees to Air Pollutants Based on Relative Growth Rate and Air Pollution Tolerance Index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Motor vehicles release carbon monoxide, nitrogen dioxide, sulphur dioxide, and particulate matters to the air as pollutants. Vegetation can absorb these pollutants through gas exchange processes. The objective of this study was to examine the combination of the relative growth rate (RGR) and physiological responses in determining tolerance levels of plant species to air pollutants. Physiological responses were calculated as air pollution tolerance index (APTI). Eight roadside tree species wer...

SULISTIJORINI; ZAINAL ALIM MAS’UD; NIZAR NASRULLAH; AHMAD BEY; SOEKISMAN TJITROSEMITO

2008-01-01

155

ZZ KERMAL, Neutron and Gamma Kerma Library from ENDL and EGDL  

International Nuclear Information System (INIS)

Description of program or function: 1 - Calculated Neutron Kerma Factors: - Format: TART Monte Carlo neutron transport code; - Number of groups: 175 neutron energy groups; - Nuclides: tissue, bone, muscle, standard man, plastic,nylon-6.6/6, Lucite, liquid muscle equivalent, water, acetylene, dry air, water-saturated air, carbon dioxide, Ethylene, Te gas with methane. - Origin: LLNL Evaluated Nuclear Data Library (ENDL). 2 - Calculated Photon kerma Factors: - Format: TART Monte Carlo neutron transport code; - Number of groups: 191 energy groups; - Nuclides: tissue, bone, muscle, standard man, plastic,nylon-6.6/6, Lucite, liquid muscle equivalent, water, acetylene, dry air, water-saturated air, carbon dioxide, Ethylene, Te gas with methane. - Origin: LLNL Evaluated Gamma-Ray Data Library (ENDL). These libraries contain neutron and gamma ray Kerma factors. KENDL, the neutron Kerma factors have been calculated from the LLNL Evaluated Nuclear Data Library (ENDL) data file. The results are for the 175 neutron energy groups used by the TART Monte Carlo neutron transport code for isotopes and elemental mixtures. They are tabulated for 15 composite materials and for the isotopes or elements in the ENDL file from Z=1 to Z=29. The incident neutron energies range from 1.882 x 1.0 E-5 to 20 MeV for the composite materials and from 1.307 x 1.0 E-9 to 20 MeV for the isotopes and elements. KEGDL, the gamma-ray KERMA factors calculated from the LLNL Evaluated Gamors calculated from the LLNL Evaluated Gamma-Ray Data Library (EGDL) file, are tabulated for the elements from Z=1 to Z=30 and for 15 composite materials. The KERMA factors are presented for 191 energy groups over the incident photon energy range from 100 eV to 100 MeV. The following composite materials are tabulated: tissue, bone, muscle, standard man, plastic, nylon-6.6/6, Lucite, liquid muscle equivalent, water, acetylene, dry air, water-saturated air, carbon dioxide, gas Te with methane

156

Tsp and Pm10 Measurement and Description of Air Quality Index (Aqi) in the Ambient Air in Shariati Hospital District  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Apparently, breathing clean air is of significant importance to human beings and thus attention to what enters our body through inhalation is on the increase. Tehran’s air pollution has received considerable media coverage in recent years: Since particulate matter (TSP and PM10) is one of the important pollutants in this city, an attempt was made to study TSP and PM10 concentrations and to make a qualitative assessment of air using the Air Quality Index (AQI), with TSP and PM10 sampling bot...

Mesbah, A. S.; Shariat, M.; Naddafi, K.; Kermani, M.

2004-01-01

157

Survivor dosimetry. Part A. Fluence-to-kerma conversion coefficients  

International Nuclear Information System (INIS)

An important step in the dosimetry evaluation is to relate the radiation passing through a unit volume of a material of interest (fluence) to the energy release (kerma) in the material, which determines the absorbed dose. The fluence-to-kerma conversion coefficients or 'kerma coefficients' used in the Dosimetry System 1986 (DS86) are taken from Kerr (1982). These kerma coefficients are based on body tissue compositions for Reference Man from the International Commission on Radiological Protection (1975) and Kerr (1982), the mass energy-absorption coefficients for photons from Hubbell (1982), and the elemental kerma coefficients for neutrons from Caswell et al. (1980). Hence, the kerma coefficients used in DS86 are approximately 20 years old. In order to provide an updated set of kerma coefficients for use in the Dosimetry System 2002 (DS02), a new evaluation has been completed. This new evaluation considered recently suggested changes in the composition of soft tissues of the body in ICRU Report 44 (International Commission on Radiation Units and Measurements 1989), the mass energy-absorption coefficients for photons by Hubbell and Seltzer (1996), and the elemental kerma coefficients for neutrons in ICRU Report 63 (International Commission on Radiation Units and Measurements 2000). The new DS02 kerma coefficients for soft tissue are presented as both point-wise data for use in Monte Carlo radiation transport calculations and multigroup data for use in discrete ordinates radiation transport calculations. (author)

158

AIR QUALITY MONITORING WITH THE LICHEN BIODIVERSITY INDEX (LBI IN THE DISTRICT OF FAENZA (ITALY  

Directory of Open Access Journals (Sweden)

Full Text Available The Lichen Biodiversity Index (LBI is a method for monitoring air pollution. This method employs lichens living on lime trees because they are sensitive to NOx and SOx, and it considers the variations in their communities. This study was performed in 16 stations located in the suburbs of Faenza city town and the result shows a more than acceptable air quality although in some stations the air was affected by the polluting effects of the vehicle traffic.

Manuela Cioffi

2009-07-01

159

Tsp and Pm10 Measurement and Description of Air Quality Index (Aqi in the Ambient Air in Shariati Hospital District  

Directory of Open Access Journals (Sweden)

Full Text Available Apparently, breathing clean air is of significant importance to human beings and thus attention to what enters our body through inhalation is on the increase. Tehran’s air pollution has received considerable media coverage in recent years: Since particulate matter (TSP and PM10 is one of the important pollutants in this city, an attempt was made to study TSP and PM10 concentrations and to make a qualitative assessment of air using the Air Quality Index (AQI, with TSP and PM10 sampling both daily and on a monthly basis. Shariati Hospital district was selected as study area from 22 December 2001 to 20 April 2002. To determine the amount of TSP and PM10 according to EPA and WHO standards, 61 samples were taken for TSP and 61 samples for PM10 with High Volume Sampler. The results indicated that: •As for TSP and PM10, the period extending from 20 February to 20 March (Esfand was the most heavily polluted one in this study. The cleanest spell was observed from 21 March to 20 April (Farvardin. •Saturdays and Mondays were the most polluted days of the week for TSP and PM10 and Fridays were the cleanest. •As for TSP, In 51 percent of the samples the Air Quality Index (AQI was below 100 (AQI100. •In the case of PM10, in 75.5 percent of samples the Air Quality Index (AQI was below 100 (AQI100.

A.S Mesbah

2004-06-01

160

Preparation and determination of kerma for Iridium 192 sources of low dose rate for brachytherapy  

International Nuclear Information System (INIS)

The practice of Brachytherapy with Iridium-192 sources of low dose rate (0.4 - 0.8 Gy/h) is a technique used in the treatment of diverse illnesses. in this work the preparation, quality control and calibration are presented in terms of kerma in air of Iridium-192 using as target these recycled Iridium-Platinum wires. The targets were obtained as decayed sources of different radio therapeutical centers in the country and they were characterized by Scanning electron microscopy in order to determine their chemical composition. Subsequently it was developed an experimental design to establish the effect of neutron flux, geometrical array and irradiation time over the activity and percentage of the sources homogeneity. The homogeneity was determined by auto radiography and by Gamma spectroscopy. Once the optimal irradiation conditions were established, it is determined the apparent activity and kerma in air using a well type ionization chamber with traceability to a primary laboratory. Iridium-192 sources were obtained with an average homogeneity 96 %, apparent activity 282.129 ± 0.531 M Bq and kerma in air 0.03200 ± 0.00006 m Gy m/h A. (Author)

 
 
 
 
161

Energy absorption coefficients and photon kerma for LiF  

International Nuclear Information System (INIS)

Accurate knowledge of energy absorption coefficients is needed to calculate the absorbed dose in any material. The photon kerma for LiF relative to air and soft tissue is computed using energy absorption coefficient values for Li, F, air, and tissue. Values of energy absorption coefficients for air are already available in J. H. Hubbell's (Photon Cross-Sections, Attenuation Coefficients and Energy Absorption Coefficients from 10 KeV to 100 GeV. National Standard Reference Data System-National Bureau of Standards Report No. 29, Washington, D. C., 1969) tables. Those for tissue are obtained by adding the weighted average of the energy absorption coefficients to the different elements constituting the tissue. For fluorine, they are computed from the values given by F. H. Attix and W. C. Roesche (Eds, Radiation Dosimetry, Vol. I, Fundamentals. Academic Press, New York/London, 1968) for CaF2 and Ca. The values for lithium have been computed taking into consideration the photoelectric effect, Compton process, and pair production. Corrections for radiative energy losses, fluorescence yields, screening of electrons, etc., are appropriately applied. The energy absorption coefficients due to photoeffect, Compton scattering, and pair production are added to get the total. The energy absorption cross-section data for photon energies from 0.01 to 10 MeV are tabulated for each interaction

162

Conversion factors neutron fluene - neutron kerma in silicon  

International Nuclear Information System (INIS)

For measuring and calculating the radiation resistance of electronic components, the availability of conversion factors neutron fluence - neutron kerma is needed. Silicon is chosen as representative material for advanced electronic components production. So, in this paper, the conversion factors neutron fluence - neutron kerma in silicon are calculated, starting by data concerning the breaks of interaction of neutrons with silicon. (author)

163

Precision interferometric measurements of refractive index of polymers in air and liquid  

Science.gov (United States)

We have developed a procedure for precise measurement of the group refractive index for materials in air and liquid environments, using a low coherence interferometer. For example, in manufacturing of soft contact lenses, the lenses are always kept hydrated in a saline solution. Knowing accurate refractive index of the lens is important to metrology and quality control purposes. The small refractive index difference between the liquid and the lens makes such tasks especially challenging. The developed procedure allows us to obtain measurement repeatability for group refractive index less than 1 x 10-3 for materials with thicknesses on the order of 100 microns, when measured in liquid. The measurement repeatability further improves for measurements in air, or for thicker materials.

Marcus, Michael A.; Hadcock, Kyle J.; Gibson, Donald S.; Herbrand, Matthew E.; Ignatovich, Filipp V.

2013-09-01

164

An international calibration of Kerma - Area Product meters for patient dose optimisation study  

International Nuclear Information System (INIS)

The results of international calibration of Kerma Area Product (KAP) meters for European SENTINEL survey on patient dose optimisation of cardiac and interventional radiology practice are presented. Twelve countries were involved in the study. An investigation was conduced on 25 KAP meters fitted to under-couch X-ray tubes; 13 KAP meters were installed on cardiac units and the remaining 12 on interventional ones. The simplified calibration method has been applied, consisting of KAP estimation by multiplying the air kerma at the centre of the X-ray field by the irradiated area. The obtained values of calibration factors range from 0.4 to 0.9 and from 0.4 to 0.8 for KAP meters installed on cardiac and interventional units, respectively. They account also for table and mattress attenuation. For air kerma assessment, measurements with thermoluminescent dosemeters have been applied and when possible compared against an additional reference dosemeter. As the result of the investigation, the importance of calibration of KAP meters in clinical conditions that include mattress and table attenuation has been recognised. (authors)

165

Estimation of Air Temperature Using Temperature-Vegetation Index (TVX Method  

Directory of Open Access Journals (Sweden)

Full Text Available The determination of air temperature is important in the energy balance calculation, hydrology and meteorological studies. In this regard, the limited number of meteorological stations is one of the serious problems for air temperature determination on a large spatial scale. The remote sensing technique by covering large areas and using updated satellite images might be appropriate for estimation of this parameter. In this research, the negative correlation between land surface temperature and vegetation index (NDVI has been used for air temperature estimation through TVX method in which the inference of air temperature is based on the hypothesis that the temperature of the dense vegetation canopy is close to air temperature. For investigation the performance of TVX method, images of MODIS sensor have been applied for the Sefidrod River basin in the years 1381- 1382-1384. The spilt window technique which was developed by Price has been used for land surface temperature calculation. The mean difference between observed and estimated land surface temperature using Price algorithm was about 6.2Co. This error can affect the air temperature values. Because of using NDVI index in TVX method, this method has the sensitivity to the vegetation density, though in the parts with sparse vegetation, the value of error increases. 4 percent variation of air temperature against the 0.05 increasing of maximum NDVI indicates the high performance of TVX method for air temperature estimation in large areas.

L. Parviz

2011-07-01

166

Active suppression of air refractive index fluctuation using a Fabry-Perot cavity and a piezoelectric volume actuator  

Energy Technology Data Exchange (ETDEWEB)

Air refractive index fluctuation ({Delta}n{sub air}) is one of the largest uncertainty sources in precision interferometry systems that require a resolution of nanometer order or less. We introduce a method for the active suppression of {Delta}n{sub air} inside a normal air-environment chamber using a Fabry-Perot cavity and a piezoelectric volume actuator. The temporal air refractive index (n{sub air}) at a local point is maintained constant with an expanded uncertainty of {approx}4.2x10{sup -9} (k=2), a sufficiently low uncertainty for precise measurements unaffected by {Delta}n{sub air} to be made inside a chamber.

Banh, Tuan Quoc; Ohkubo, Yuria; Murai, Yoshinosuke; Aketagawa, Masato

2011-01-01

167

Arima and integrated arfima models for forecasting air pollution index in Shah Alam, Selangor  

International Nuclear Information System (INIS)

Air pollution is one of the major issues that has been affecting human health, agricultural crops, forest species and ecosystems. Since 1980, Malaysia has had a series of haze episodes and the worst ever was reported in 1997. As a result, the government has established the Malaysia Air Quality Guidelines, the Air Pollution Index (API) and Haze Action Plan, to improve the air quality. The API was introduced as an index system for classifying and reporting the ambient air quality in Malaysia. The API for a given period is calculated based on the sub-index value (sub-API) for all the five air pollutants, namely sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO) and particulate matter below 10 micron size (PM10). The forecast of air pollution can be used for air pollution assessment and management. It can serve as information and warning to the public in cases of high air pollution levels and for policy management of many different chemical compounds. Hence, the objective of this project is to fit and illustrate the use of time series models in forecasting the API in Shah Alam, Selangor. The data used in this study consists of 70 monthly observations of API (from March 1998 to December 2003) published in the Annual Reports of the Department of Environment, Selangor. The time series models that were being considered were the Integrated Autoregressive Moving Average (ARIMA) and the Integrated Long Memoerage (ARIMA) and the Integrated Long Memory Model (ARFIMA) models. The lowest MAE, RMSE and MAPE values were used as the model selection criteria. Between these two models considered, the integrated ARFIMA model appears to be the better model as it has the lowest MAPE value. However, the actual value of May 2003 falls outside the 95% forecast interval, probably due to emissions from mobile sources (i.e., motor vehicles), industrial emissions, burning of solid wastes and forest fires. (author)

168

Conversion factors neutron fluene - neutron kerma in silicon  

Energy Technology Data Exchange (ETDEWEB)

For measuring and calculating the radiation resistance of electronic components, the availability of conversion factors neutron fluence - neutron kerma is needed. Silicon is chosen as representative material for advanced electronic components production. So, in this paper, the conversion factors neutron fluence - neutron kerma in silicon are calculated, starting by data concerning the breaks of interaction of neutrons with silicon. (author). 6 refs.; 2 figs.; 1 table.

Kaljevic, J.; Orlic, M.

1984-01-01

169

Trends of air pollution in Denmark - Normalised by a simple weather index model  

International Nuclear Information System (INIS)

This report is a part of the Traffic Pool projects on 'Traffic and Environments', 1995-99, financed by the Danish Ministry of Transport. The Traffic Pool projects included five different projects on 'Surveillance of the Air Quality', 'Atmospheric Modelling', 'Atmospheric Chemistry Modelling', 'Smog and ozone' and 'Greenhouse effects and Climate', [Rasmussen, 2000]. This work is a part of the project on 'Surveillance of the Air Quality' with the main objectives to make trend analysis of levels of air pollution from traffic in Denmark. Other participants were from the Road Directory mainly focusing on measurement of traffic and trend analysis of the air quality utilising a nordic model for the air pollution in street canyons called BLB (Beregningsmodel for Luftkvalitet i Byluftgader) [Vejdirektoratet 2000], National Environmental Research Institute (HERI) mainly focusing on. measurements of air pollution and trend analysis with the Operational Street Pollution Model (OSPM) [DMU 2000], and the Copenhagen Environmental Protection Agency mainly focusing on measurements. In this study a more simple statistical model has been developed for trend analysis of the air quality. The model is filtering out the influence of the variations from year to year in the meteorological conditions on the air pollution levels. The weather factors found most important are wind speed, wind direction and mixing height. Measurements of CO, NO and NO2 from three streets in Copenhagen h2 from three streets in Copenhagen have been used, these streets are Jagtvej, Bredgade and H. C. Andersen's Boulevard (HCAB). The years 1994-1996 were used for evaluation of the method and annual indexes of air pollution index dependent only on meteorological parameters, called WEATHIX, were calculated for the years 1990-1997 and used for normalisation of the observed air pollution trends. Meteorological data were taken from either the background stations at the H.C. Oersted - building situated close to one of the street stations or the synoptic station at Kastrup Airport just outside Copenhagen. The mixing height was calculated using a bulk Richardson method on vertical profiles provided by the Numerical Weather Prediction model DMI-HIRLAM (Danish Meteorological Institute - High Resolution Limited Area Model). The model in general gives a good explanation of variations from year to year in the air quality. (au)

170

Tolerance Levels of Roadside Trees to Air Pollutants Based on Relative Growth Rate and Air Pollution Tolerance Index  

Directory of Open Access Journals (Sweden)

Full Text Available Motor vehicles release carbon monoxide, nitrogen dioxide, sulphur dioxide, and particulate matters to the air as pollutants. Vegetation can absorb these pollutants through gas exchange processes. The objective of this study was to examine the combination of the relative growth rate (RGR and physiological responses in determining tolerance levels of plant species to air pollutants. Physiological responses were calculated as air pollution tolerance index (APTI. Eight roadside tree species were placed at polluted (Jagorawi highway and unpolluted (Sindangbarang field area. Growth and physiological parameters of the trees were recorded, including plant height, leaf area, total ascorbate, total chlorophyll, leaf-extract pH, and relative water content. Scoring criteria for the combination of RGR and APTI method was given based on means of the two areas based on two-sample t test. Based on the total score of RGR and APTI, Lagerstroemia speciosa was categorized as a tolerant species; and Pterocarpus indicus, Delonix regia, Swietenia macrophylla were categorized as moderately tolerant species. Gmelina arborea, Cinnamomum burmanii, and Mimusops elengi were categorized as intermediate tolerant species. Lagerstroemia speciosa could be potentially used as roadside tree. The combination of RGR and APTI value was better to determinate tolerance level of plant to air pollutant than merely APTI method.

SULISTIJORINI

2008-09-01

171

Air trapping on computed tomography images of healthy individuals: effects of respiration and body mass index  

International Nuclear Information System (INIS)

Aim: To evaluate the relationships of changes in the lung area during respiration and of individual body mass index (BMI) to air trapping on expiratory computed tomography (CT) in young non-smoking adults of either gender. Methods: The volunteers were 10 women and 10 men (mean age 25.7 years) who were healthy lifelong non-smokers. We obtained both end-inspiratory and end-expiratory CT images at three levels: the upper, middle and lower lung. The ratio of cross-sectional lung area upon expiration to cross-sectional lung area upon inspiration (lung area ratio) was determined for each lung at each of the three levels. In cases showing air trapping, we calculated the percentage of area of air in relation to the total lung area in each section. BMI was calculated for each participant. Results: Air trapping was present in dependent areas of the lungs of 6 women and 5 men. The mean percentage of area of air trapped was statistically greater for men (9.8 ± 9.2%) than for women (4.9 ± 5.2%). The mean lung area ratio was 0.52 ± 0 14 among volunteers with air trapping (66 sections) and 0.69 ± 0.12 among those without air trapping (54 sections) (p < 0.001). At each lung level, the mean lung area ratio was greater in individuals with air trapping than in those without. Mean BMI was also greater in these people (p = 0.009). Conclusion: Change in the respiratory lung area and BMI contribute to development of air trapping

172

Measurement and calculation of fluence, spectra and tissue kerma at large distances from a fission source  

International Nuclear Information System (INIS)

An experimental program is underway at the Army Pulse Radiation Division reactor (APRDR) at Aberdeen Proving Ground, Maryland, to provide benchmark quality radiation transport data characterizing an air-over-ground environment. The data are used to evaluate analytical radiation transport models and provide validation for techniques used to measure radiation protection or shielding of various materiel. The APRDR is a bare critical assembly fueled with uranium ten weight percent molybdenum alloy. For this application the reactor is operated outdoors 14M above ground. Todate measurements have been made by both US and German scientists of neutron and gamma fluence, spectra, and kerma at ranges from 1 to 400 meters from the reactor

173

Comparison of the Revised Air Quality Index with the PSI and AQI indices  

Energy Technology Data Exchange (ETDEWEB)

Air pollution indices are commonly used to indicate the level of severity of air pollution to the public. The Pollution Standards Index (PSI) was initially established in response to a dramatic increase in the number of people suffering respiratory irritation due to the deteriorating air quality. The PSI was subsequently revised and implemented by the USEPA in 1999, and became known as the Air Quality Index (AQI) that includes data relating to particle suspension, PM{sub 2.5}, and a selective options of either 8-hour or 1-hour ozone concentration during increased O{sub 3} periods. Yet, the costs of launching a network of PM{sub 2.5} monitoring stations are prohibitively high for many countries to implement the AQI from the PSI system in the foreseeable future. Therefore, the purpose of this research is to discuss the optimal method of assessing air quality using the latest developed Revised AQI (RAQI), a system that serves as an alternative to the PSI and AQI systems. The feasibility, effectiveness, and the differences between RAQI, AQI, and PSI in their applications to several air pollution conditions are also studied in this research. The results show that southern Taiwan's suspended particulates have significantly greater impact on PM{sub 2.5}/PM{sub 10} ratios than in central and northern metropolitan areas, and that the ratios are higher in Taiwan as a whole compared to many other countries. We also found that the RAQI shows more significant results compared to the PSI and AQI as it has a wider coverage of the range of pollutant concentration levels. (author)

Cheng, Wan-Li; Chen, Yu-Song; Chang, Shiang-Hung [Dept of Environmental Science and Engineering, Tunghai University, Taichung 407 (China); Zhang, Junfeng [Division of Environmental and Occupational Health, University of Medicine and Dentistry of New Jersey, NJ 08854 (United States); Lyons, T.J. [Environmental Science, Murdoch University, Murdoch, WA 6150 (Australia); Pai, Joy-Lynn [Sunway Environmental Technology Co., Ltd., Taipei 104 (China)

2007-09-01

174

Differential displacement kerma cross sections for neutron interactions in Si and GaAs  

Science.gov (United States)

The cross-section processing code NJOY has been modified to calculate flux-averaged partially integrated differential displacement kerma cross sections or displacement kerma matrix elements for neutron interactions. These, along with total displacement kerma cross sections, have been calculated using ENDF/B-V and ENDL-84 data files for Si, Ga, and As. These displacement kerma matrices for Si and GaAs allow calculations of the distribution of displacement energy between displacement cascades. The tabulation of kerma cross sections for Si constitutes a complete revision of the data used in current standard practices. Another contribution is the tabulated kerma cross sections for GaAs.

Ougouag, A. M.; Williams, J. G.; Danjaji, M. B.; Yang, S.-Y.; Meason, J. L.

1990-12-01

175

Preparation and determination of kerma for Iridium 192 sources of low dose rate for brachytherapy; Preparacion y determinacion del kerma de fuentes de iridio-192 de baja tasa de dosis para braquiterapia  

Energy Technology Data Exchange (ETDEWEB)

The practice of Brachytherapy with Iridium-192 sources of low dose rate (0.4 - 0.8 Gy/h) is a technique used in the treatment of diverse illnesses. in this work the preparation, quality control and calibration are presented in terms of kerma in air of Iridium-192 using as target these recycled Iridium-Platinum wires. The targets were obtained as decayed sources of different radio therapeutical centers in the country and they were characterized by Scanning electron microscopy in order to determine their chemical composition. Subsequently it was developed an experimental design to establish the effect of neutron flux, geometrical array and irradiation time over the activity and percentage of the sources homogeneity. The homogeneity was determined by auto radiography and by Gamma spectroscopy. Once the optimal irradiation conditions were established, it is determined the apparent activity and kerma in air using a well type ionization chamber with traceability to a primary laboratory. Iridium-192 sources were obtained with an average homogeneity 96 %, apparent activity 282.129 {+-} 0.531 M Bq and kerma in air 0.03200 {+-} 0.00006 m Gy m/h A. (Author)

Tendilla, J.I.; Tovar M, V.; Mitsoura, E.; Aguilar H, F.; Alanis M, J. [Instituto Nacional de Investigaciones Nucleares, C.P. 52045-1, Salazar, Esrado de Mexico, D.F. (Mexico)

2000-07-01

176

MACK, Fluence to Kerma Generator from ENDF/B  

International Nuclear Information System (INIS)

1 - Nature of physical problem solved: The principal purpose of the program is in calculating pointwise neutron energy release parameters (fluence-to-kerma factors) at an arbitrary energy mesh from nuclear data in ENDF/B format (2). The kerma factors are of prime importance for calculating heating and dose rates in any nuclear system. The program processes all reactions significant to energy deposition. In addition, the program calculates energy group kerma factors and group cross sections by reactions (group constants not transfer matrices) averaged over an arbitrary input weighting function or any of the 'built-in' functions. When resonance data is available, the code calculates the contribution from the resolved and unresolved resonance parameters. The pointwise cross sections, pointwise kerma factors, energy group cross sections and energy group kerma factors can be printed, punched, and/or saved on tape for all reactions and the sum as selected by input. The pointwise kerma factors can be saved for later use (3) to generate group kerma factors for a different energy group structure or possibly for inclusion in the ENDF/B evaluation for the nuclide with the appropriate MT numbers in the 300's series (2). 2 - Method of solution: The expressions for the energy release per reaction are obtained from a solution of the kinematics of nuclear reactions. The anisotropy of elastic and inelastic scattering is considered. The contribution to energy deposition from radioactivution to energy deposition from radioactive decay of the residual nucleus can be added by reaction and is calculated using Fermi theory in the case of beta decay. In the resolved resonance region, MACK accepts either single or multi level Breit-Wigner parameters. Doppler broadening is performed at an arbitrary input temperature. The unresolved resonance treatment includes some shielding effects through a 1/sigma t weighting. The energy group kerma factors and cross sections are calculated by averaging the pointwise data over either a user supplied input spectrum or 'built-in' weighting functions. The program calculates the contribution to the energy release from all reactions and the accuracy of the kerma factor calculation is set only by the availability of the required nuclear data. 3 - Restrictions on the complexity of the problem: Because of the variable dimensioning technique used in the program, the principal restriction on the size of the problem is the availability of sufficient core storage. Problems with up to about 1500 energy points can be run in less than 65 k words of core storage. Core storage requirements are not affected by the number of reactions processed for the nuclides or the number of nuclides in the run. The code recognizes almost all of the multiplicity of data formats allowed by ENDF

177

HIgh energy neutron and proton kerma factors for different elements  

International Nuclear Information System (INIS)

A generalisation of the kerma concept for uncharged particles, extending it to all ionising radiations, is proposed. In accordance with the new concept, the kerma factor of ionising particles, k, is considered as a sum of the nuclear, kn, and electromagnetic, ke, components, where ke for charged particles is equal to L?/?. The values of the nuclear component of kerma factor, kn, for neutrons and protons with energies 20-1000 MEV have been calculated for 25 elements from hydrogen to lead as well as for the ICRU muscle tissue. The cascade-exciton model of nuclear interactions was used in the calculations. The presented results of test calculations of the secondary charged particle spectra from reactions of nucleons with different nuclei demonstrate good agreement with experiment. The calculated data also agree well with the experimental values of high energy neutron kerma in light nuclei. The results obtained will remedy a shortage of information on high energy nucleon kerma and will find an application in different fields of radiation protection. (author)

178

HIgh energy neutron and proton kerma factors for different elements  

Energy Technology Data Exchange (ETDEWEB)

A generalisation of the kerma concept for uncharged particles, extending it to all ionising radiations, is proposed. In accordance with the new concept, the kerma factor of ionising particles, k, is considered as a sum of the nuclear, k{sub n}, and electromagnetic, k{sub e}, components, where k{sub e} for charged particles is equal to L{sub {infinity}}/{rho}. The values of the nuclear component of kerma factor, k{sub n}, for neutrons and protons with energies 20-1000 MEV have been calculated for 25 elements from hydrogen to lead as well as for the ICRU muscle tissue. The cascade-exciton model of nuclear interactions was used in the calculations. The presented results of test calculations of the secondary charged particle spectra from reactions of nucleons with different nuclei demonstrate good agreement with experiment. The calculated data also agree well with the experimental values of high energy neutron kerma in light nuclei. The results obtained will remedy a shortage of information on high energy nucleon kerma and will find an application in different fields of radiation protection. (author).

Savitskaya, E.N.; Sannikov, A.V. [Institut Fiziki Vysokikh Ehnergij, Protvino (Russian Federation)

1995-12-31

179

A proper method of kerma-length product measurement during QC procedures in panoramic radiography  

International Nuclear Information System (INIS)

As a relevant dose descriptor in panoramic radiography, product of kerma and length PKL is used. The introduction of PKL was recommended by NRPB. Anyway, NRPB termed this quantity dose-width product (DWP), the name product of kerma and length comes from a new dosimetry formalism being developed by IAEA and ICRU. The product of kerma and length in panoramic radiography is an integral of kerma profile created at a front side of the secondary collimator along a line perpendicular to the collimator. The PKL should be measured at a place of maximum intensity of the beam with respect to vertical direction. The signal is integrated over the whole exposure cycle as well. Currently, no dose descriptor in panoramic radiography is measured in the Czech Republic during the QC measurements. Therefore the measurement of PKL should be included in QC procedures as well. A pilot study using three different methods of PKL measurement is being done in the Czech Republic since 2005. The measurements are performed by an X ray film attached to the front side of a secondary collimator, by a column of thermoluminescent detectors (TLDs) and pencil ionization chamber placed perpendicular to the secondary collimator. The results obtained through the mentioned methods agree within 10% generally. The film based method has a significant disadvantage. Air kerma in a profile maximum reaches values up to 30 mGy. Standard X ray films have no dosim30 mGy. Standard X ray films have no dosimetric properties for such a high dose, because the response lies in a region of plateau at a characteristic curve of the film. Therefore, a primary collimator has to be covered by a shielding material. It increases energy dependence of the detection system naturally. An advantage of the film based method is knowledge of a complete kerma distribution within an X ray field. This information is used for proper positioning of a CT pencil ionization chamber or a stack of TLDs within an X ray beam. In the study, monochromatic films Foma Medix XBU (18x24 cm) and a attenuating filter with thickness of 1 mm Cu were used. For film scanning, a laser scanner Lumisys LS50 was used, with scanning resolution 0,2 mm. Before each measurement, the scanner was calibrated by a PTW calibration film in a range of optical densities 0.08/3.4. The simplest and the fastest method is the pencil ionization chamber method. Pencil ionization chambers designed for CT dosimetry were used in the study, especially a type 10X5-3CT with an electrometer Radcal 9015 and a type CT 77336 with an electrometer PTW Nomex 7723. Dependent on a way of calibration of a relevant chamber and an electrometer, a quantity indicated by the electrometer is either integral of kerma profile along a chamber length (Nomex system), which is the required PKL, or just air kerma (Radcal system). In the latter case, indicated air kerma is multiplied by a chamber effective length. Calibration factor of the chambers was verified for beam qualities relevant to panoramic radiography, which are different from those in CT. For a beam quality 50 kV, total filtration 1 mm Al and effective energy Eef 22,7 keV, there was only a 5% difference in calibration factor according to CT energy range. For the TLD measurements, a column of 30 sintered pellets of LiF:Mg, Ti was used. Total length of the TLD column is 27 mm, which is a sufficient length to cover a useful part of the kerma profile. A manual TLD reader Harshaw 4500 was used for the readout of detectors. For routine measurements of several exposure settings at a given X ray unit, TLDs are not appropriate because of time consuming preparation and readout of the dosemeters. The TLD and X ray film systems were calibrated using a reference X ray machine Planmeca Intra in a national reference laboratory for X ray dosimetry. Beam quality for calibration was 70 kV, total filtration 2,2 mm Al, Eef 31 keV. It seems to be most user-friendly and appropriate to measure PKL by means of pencil ionization chamber, for which the calibration factor will be verified for beam qualities relevant to panoramic r

180

Air quality index around National Thermal Power Corporation, Unchahar, Rae Bareli  

Energy Technology Data Exchange (ETDEWEB)

The AQI (air quality index) has been determined at four different sites located in four respective directions around NTPC (National Thermal Power Corporation), Unchahar, India and in control site. SPM, SO{sub 2} and NOx are the three parameters considered during the study. The results show the fluctuation in the AQI values during the year due to meteorological conditions prevailing in the region. On the basis of AQI Arkha and Khojanpur are categorized as polluted sites whereas Gangehra and Kandrawan are categorized as moderately polluted and fairly clean sites, respectively. 8 refs., 2 figs., 6 tabs.

Kumar, A.; Kazmi, S. [Feroze Gandhi College, Rae Bareli (India). Environment Research Centre

2005-07-01

 
 
 
 
181

Comparison of TLD air kerma measurements in mammography  

International Nuclear Information System (INIS)

The mammography examination is usually targeted at asymptomatic women so the narrow balance between benefit and undesirable effects is important. During the past few decades there have been significant advances in the equipment used for mammography. Even when the latest equipment and imaging systems are used, there is considerable variation from centre-to-centre in the choice of imaging parameters and techniques. There may be quite large differences in image quality and breast dose among the centres. A Co-ordinated Research Programme on 'Image quality and patient dose optimization in mammography in Eastern European Countries' was conducted by the IAEA, aiming at defining a methodology for the implementation of a quality assurance (QA) programme in mammography and at exercising the assessment of image quality and patient doses in a sample of hospitals in East European countries. Selected mammography clinics from Czech Republic, Hungary, Poland, Romania and Slovakia participate in the project. The teams consisted of experienced clinicians and physicists. They were supported by a group of experts (clinicians and medical physicists) from France, Italy and Spain. As an outcome of the project, improvements in these indicators (image quality and patient dose) after the implementation of the QA programme are expected. A comparison of dosimetry systems has been organized to assure that dosimetry measurements done in the frame of the project are comparable and traceable to the international measurement system. All five East European countries plus Spain took part in the exercise. The thermoluminescent (TL) method was selected for the comparison

182

Active suppression of air refractive index fluctuation using a Fabry-Perot cavity and a piezoelectric volume actuator  

International Nuclear Information System (INIS)

Air refractive index fluctuation (?nair) is one of the largest uncertainty sources in precision interferometry systems that require a resolution of nanometer order or less. We introduce a method for the active suppression of ?nair inside a normal air-environment chamber using a Fabry-Perot cavity and a piezoelectric volume actuator. The temporal air refractive index (nair) at a local point is maintained constant with an expanded uncertainty of ?4.2x10-9 (k=2), a sufficiently low uncertainty for precise measurements unaffected by ?nair to be made inside a chamber.

183

Spatial and seasonal variations of the air pollution index and a driving factors analysis in china.  

Science.gov (United States)

In this study, the daily air pollution index (API) of 110 cities based on ground monitoring was conducted on the 2011 data set from the Ministry of Environmental Protection of China. The pollutant concentrations, seasonal variations, and spatial autocorrelations were evaluated. The results show that the major principal pollutants in China are inhalable particles. In addition, the total number of clean days (API ? 50) is apparently smaller in the northern cities than in the southern cities as a result of fuel utilization and large-scale organized central heating. Seasonally, air pollution is most severe in winter and is caused by low-frequency rainfall, strong northwest winds, dry climate, and high energy consumption; this is followed by spring, which is a season of frequent sandstorms. According to spatial autocorrelation analysis, clusters with high API value agglomeration (High-High clusters) are mainly concentrated in the middle and northern parts of China, whereas clusters with low API agglomeration (Low-Low clusters) are principally concentrated in the southern parts of China due to a favorable climate and abundant rainfall. Meteorological data, including wind speed and temperature, have great impacts on API. The air quality effects of industrial structure, energy use, urban greening, and traffic congestion were also analyzed. With the ecological function of purifying the air, industries that use natural resources and urban greening could help to reduce API, whereas secondary industry and gas use, which have a positive coefficient, increase the API value. The risk of exposure to poor air quality is largest in the winter, smallest in the summer, and remains relatively unchanged in the spring and autumn. PMID:25602202

Jiang, Hong-Yue; Li, Hai-Rong; Yang, Lin-Sheng; Li, Yong-Hua; Wang, Wu-Yi; Yan, Ya-Chen

2014-11-01

184

Investigation of Humidity Effect on the Air Refractive Index using an Optical Fiber Design  

Directory of Open Access Journals (Sweden)

Full Text Available In this study operation of an optical design based on the intensity modulation for the refractive index change has been described. The reported instrument measures the transmitted output power depending up on the medium refractive index in the light path of a fiber-to-fiber design. A liquid cell is located between the fibers in the light path and power variations for different cold and hot water levels in the cell are measured. By using a reference humidity meter the calibration curve representing the relative humidity (%RH as a function of the transmitted output power is obtained. For the hot water with the final temperature of T = 32.7C the output power range of 255.0 -313.0 nW is measured for a relative humidity change of 32.76 -41.26%. A power variation of 58 nW is noted for the 8.5% RH variation which shows the high sensitivity for the reported sensor. For the light transmitted in dry air path the output power is 516.7 nW while for the water path such power is 784.6 nW. Thus, the reported device can check the presence of the water vapor, water, or any other transparent liquid in the gap between the two axially aligned fibers. Performance of the new system is satisfactory as a refractive index monitoring mean and for the water/water vapor sensing.

H. Golnabi

2011-01-01

185

The Aggregate Risk Index: An intuitive tool providing the health risks of air pollution to health care community and public  

Science.gov (United States)

In the framework of the European project PASODOBLE (FP7), we set up downstream information services by combining environmental and health data with a view to support the health care community and to improve vulnerable people welfare. Indeed there is a profound relationship between human health, well-being and air pollution levels. The main objectives are to establish correlations between air quality, exposure of populations and their reactivity, to develop and validate air quality indexes and to construct a prediction model of this sanitary index. This index will be implemented on 3 European sites: Greece (Athens and Thessaloniki), the Netherlands and "Provence Alpes Côte d'Azur" (South East of France). The selected region and cities are among the most affected by the atmospheric pollution in Europe and leads to serious sanitary concerns. The service aims to provide up-to-date, detailed information on air quality discomfort. The Aggregate Risk Index is based on the Cairncross's concept, obtained from the Relative Risk associated with short-term exposure to common air pollutants and takes into account the possible effects of a mixture of pollutants. This communication tool, easy to use and intuitive, about the levels of air pollution and the associated health risks, will be used to communicate information to the general population, authorities and to the health care community and will provide advanced warning of potentially health-damaging air pollution events.

Sicard, Pierre; Talbot, Charles; Lesne, Olivia; Mangin, Antoine; Alexandre, Nicolas; Collomp, Rémy

2012-01-01

186

Displacement Kerma Cross Sections for Neutron Interactions in Molybdenum  

Energy Technology Data Exchange (ETDEWEB)

Modifications to the displacement kerma cross section methods employed in the NJOY99 nuclear data processing code are described. Calculations were performed with the modified code for molybdenum using ENDF-6 neutron interaction data. Results are presented for a range of plausible Ed values.

A. M. Ougouag; C. A. Wemple; C. D. Van Siclen

2004-04-01

187

Evaluation of air pollution tolerance index of selected plant species along roadsides in Thiruvananthapuram, Kerala.  

Science.gov (United States)

To develop the usefulness of plants as bioindicators requires an appropriate selection of plant species which entail an utmost importance for a particular situation. In the present study a periodic evaluation of air pollution tolerance index [APTI] of selected tree species such as Polyalthia longifolia, (Sonner) Thw., Alstonia scholaris, R. Br., Mangifera indica, L., and shrubs Clerodendron infortunatum, L., Eupatorium odoratum, L., and Hyptis suaveolens, (L.) Poit., growing adjacent to the National Highway-47 passing through Thiruvananthapuram District which lies on the south-west coast of India, was carried out with a view to find out the air pollution tolerance as well as sensitivity of the plant species during different seasons. Among the trees in the roadside areas studied, Polyalthia longifolia, (Sonner) Thw., expressed highest APTI values and proved to be a tolerant variety and the others as sensitive species to air pollutants. In the case of shrubs, Clerodendron infortunatum, L., exhibited highest APTI values (7.34) and found to be more tolerant compared to the other two shrub species studied. PMID:21047015

Jyothi, S Jissy; Jaya, D S

2010-05-01

188

X ray beam quality specification for kerma area product meters  

International Nuclear Information System (INIS)

Full text: The kerma area product (KAP) in a diagnostic X ray beam is usually measured with a plane parallel transmission ionization chamber. The response of KAP chambers depend significantly on the energy distribution of radiation, and KAP meters are commonly calibrated with a discrete set of radiation qualities. Appropriate specification of radiation quality is needed to allow interpolation between the measured calibration coefficients. This is especially evident when calibration coefficients for laboratory radiation qualities are converted to clinical qualities. Radiation quality of an X ray beam can be specified explicitly by the tube voltage and total filtration, together with anode angle and material. The half value layer (HVL) of the X ray beam is a generally used beam quality specifier and depends on all these parameters. When a high quality cavity ionization chamber is used properly, the response of the chamber depends on energy rather smoothly and the HVL can be used to specify radiation quality and to interpolate the calibration coefficients between radiation qualities. This is not the case with KAP chambers, however. The energy dependence of the response is affected by the materials and design of the KAP chamber. IEC standard for KAP meters sets a requirement of maximum overall uncertainty of 25% (2 SD) for the accuracy of KAP measurement, including the maximum deviation of ±8% arising from X ray tube voltage variation, in the range of 50 kV to 150 kV wittion, in the range of 50 kV to 150 kV with a 2,5 mm aluminium filtration. No requirements for the response are stated in the standard for other filtrations. ICRU recommendations for diagnostic dosimetry state a maximum overall uncertainty of 7% (2 SD) for KAP measurements. This also emphasizes the need for accurate beam quality specification. In this work the energy dependence of KAP ionization chambers was investigated using a tungsten anode X ray tube (anode angle 20 deg.) with a set of standard and clinical radiation qualities. Tube voltages of 40 kV-150 kV and filtrations from 1,3 mm to 5 mm Al, and 4 mm Al with 0,1 mm and 0,2 mm Cu were used. The HVL values ranged from 1 mm to 9 mm Al. A diaphragm providing a strictly defined radiation field was designed and the KAP measurements were performed at 5 cm distance from the diaphragm. The reference value for the kerma area product was determined as the product of air kerma measured in the field centre and the area of the field at the same distance. For a KAP meter the calibration coefficient was determined as a quotient of the reference value by the measured KAP value. Calibration coefficients were expressed relative to different beam quality specifiers: HVL, tube voltage and filtration. For any individual KAP meter the variation of calibration coefficients was in the range of 20%-30% for the used beam qualities, yet the behaviour of the response relative to radiation quality was clearly different for KAP chambers of different design. For constant HVL values the variation of calibration coefficients ranged up to 10% among typical clinical radiation qualities used in this study, and thus the HVL alone cannot specify the radiation quality adequately. At least two beam quality specifiers need to be known to describe the response of a KAP meter. For a KAP meter, it is not possible to interpolate calibration coefficients between different X ray qualities relative to the HVL alone. Adequate and convenient specifiers in practice are the tube voltage and total filtration or, if one of these parameters is not known, the HVL instead of that. To allow the interpolations, measured calibration coefficients should cover the range of all clinically used radiation qualities. This work is part of the IAEA coordinated research project for testing the implementation of the IAEA Code of Practice on Dosimetry in X ray Diagnostic Radiology. (author)

189

Calibration of Kerma Area Product Meters with a Patient Dose Calibrator  

International Nuclear Information System (INIS)

Kerma area product (KAP) meters used in X ray imaging for monitoring patient exposure were calibrated using different reference meters. Typically, the reference KAP value is the product of the air kerma and the X ray field size. In the tandem method, the reference value is measured with another KAP meter; in this study, a large KAP meter of novel type, the patient dose calibrator (PDC), was used for this purpose. The properties of the PDC meter were studied and the use of the meter as a reference meter was reviewed throughout the whole train of events from calibration in a secondary standard dosimetry laboratory to using the meter in clinical situations. Compared to conventional KAP meters, the advantages of the PDC are the lower energy dependence of response and the possibility to use larger field sizes. In laboratory measurements, the properties of the PDC meter were proved suitable to be used as a reference meter. The uncertainty related to the differences in X ray tube output used in calibration at the laboratory and in measurements at the clinic is highlighted. The calibration coefficients for field KAP meters calibrated by the PDC meter and by other meters were congruent on the average within 4%. Clinical measurements emphasized the need for in situ calibration of clinical KAP meters. Particularly in the under-couch situation, the calibration should be performed with the couch in the beam. (author)

190

The ambient air quality accounts for the Nova Scotia Genuine Progress Index  

International Nuclear Information System (INIS)

The Nova Scotia Genuine Progress Index (GPI) is a measure of sustainable development which provides a complete and accurate picture of our well-being as a society. The GPI assigns explicit values to environmental quality, population health, livelihood security, equity, free time, and educational attainment. The Nova Scotia GPI includes 22 social, economic and environmental components, including ambient air quality. This report investigates Nova Scotia's ambient air concentrations and emissions of carbon monoxide (CO), total particulate matter (PM), sulphur dioxide (SO2), nitrogen oxides (NOx), and volatile organic compounds (VOC). The costs of damages caused by the these key air pollutants are also examined. Exposure to these pollutants results in negative impacts on human health, damage to materials, agricultural crops and changes in forest productivity. From 1979 to 1996, national ambient concentrations of each of these pollutants decreased significantly. However, the national average concentration of ground-level ozone increased by 34 per cent during the same time period. In Nova Scotia, concentrations of CO, PM and SO2 have declined dramatically since 1979, but the trends for NO2 and ground-level ozone do not show significant declines. On a per capita basis, SOx emissions from electric power generation in the province are more than 8 times the Canadian average. The province also had higher per capita emissions of CO, PM, SOx and VOper capita emissions of CO, PM, SOx and VOCs than all reporting OECD countries. Electric power generation is the greatest source of fuel combustion emissions in the province, followed by industrial and transportation sources. This report also described some individual actions that can be taken to reduce air pollutant emissions. 174 refs., 37 tabs., 60 figs

191

Radioactive Aerosols as an Index of Air Pollution in the City of Thessaloniki, Greece  

International Nuclear Information System (INIS)

This study summarizes results of an investigation done in order to find out how the radioactive aerosols of 7Be could serve as indicators of air pollution conditions. Beryllium-7 is a cosmic-ray produced radionuclide with an important fraction of its production to take place in the upper troposphere. Once it is formed is rapidly associated with submicron aerosol particles and participates in the formation and growth of the accumulation mode aerosols, which is a major reservoir of pollutants in the atmosphere. In order to define any influence of AMAD of 7Be aerosols by air pollution conditions, the aerodynamic size distribution of 7Be aerosols was determined by collecting samples at different locations in the suburban area of the city of Thessaloniki, including rural areas, industrial areas, high elevations, marine environment and the airport area. The aerodynamic size distribution of 7Be aerosols in different locations was obtained by using Andersen 1-ACFM cascade impactors and the Activity Median Aerodynamic Diameter (AMAD) was determined. Some dependency of the AMADs on height has been observed, while in near marine environment the 7Be activity size distribution was dominant in the upper size range of aerosol particles. Low AMADs as low as 0.62 to 0.74 ?m of 7Be aerosols have been observed at locations characterized with relative low pollution, while it is concluded that in the activity size distribucluded that in the activity size distribution of ambient aerosols, 7Be changes to larger particle sizes in the presence of pollutants, since low AMADs of 7Be aerosols have been observed at low polluted locations. Preliminary data of simultaneous measurements of 214Pb and 212Pb with gaseous air pollutants CO, NO, NOX, SO2 and total suspended particulate matter (TSP) show that radon decay products near the ground could be a useful index of air pollution potential conditions and transport processes in the boundary layer.

192

Development of a calibration methodology and tests of kerma area product meters; Desenvolvimento de uma metodologia de calibracao e testes de medidores de produto Kerma-Area  

Energy Technology Data Exchange (ETDEWEB)

The quantity kerma area product (PKA) is important to establish reference levels in diagnostic radiology exams. This quantity can be obtained using a PKA meter. The use of such meters is essential to evaluate the radiation dose in radiological procedures and is a good indicator to make sure that the dose limit to the patient's skin doesn't exceed. Sometimes, these meters come fixed to X radiation equipment, which makes its calibration difficult. In this work, it was developed a methodology for calibration of PKA meters. The instrument used for this purpose was the Patient Dose Calibrator (PDC). It was developed to be used as a reference to check the calibration of PKA and air kerma meters that are used for dosimetry in patients and to verify the consistency and behavior of systems of automatic exposure control. Because it is a new equipment, which, in Brazil, is not yet used as reference equipment for calibration, it was also performed the quality control of this equipment with characterization tests, the calibration and an evaluation of the energy dependence. After the tests, it was proved that the PDC can be used as a reference instrument and that the calibration must be performed in situ, so that the characteristics of each X-ray equipment, where the PKA meters are used, are considered. The calibration was then performed with portable PKA meters and in an interventional radiology equipment that has a PKA meter fixed. The results were good and it was proved the need for calibration of these meters and the importance of in situ calibration with a reference meter. (author)

Costa, Nathalia Almeida

2013-07-01

193

Use of a sensory irritation potential index to characterize improvement of indoor air quality in French schools by ventilation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

After several cases of health problems in French schools, a methodology for health risk assessment related to indoor air quality (IAQ) was required. Based on measured concentrations in schools where acute symptoms possibly due to exposure to airborne sensory irritants were reported, an index quantifying the sensory irritation potential was built and used. This paper focuses on one classroom where the index was successively applied without any ventilation system, after the implementation of pa...

Mandin, Corinne; Meininghaus, Roman; Cicolella, Andre?

2003-01-01

194

A conformal index determination to evaluate the prostate interstitial implants quality with high dose rate (HDR)  

International Nuclear Information System (INIS)

For interstitial application of high dose rate (HDR) afterloading brachytherapy, generally a single stepping iridium-192 source is used, making possible optimization of the dose distribution by optimization of the relative time (dwell time) that the source remains at a certain position (dwell position). We analyzed the effects of geometric-volume optimization by three normalize methods in 22 prostate volume implants. In all patients the reference dose is specified at 85% of the mean central dose (as is done in the Paris System for dose specification. We compared the uniformity index, the irradiated volume, the total reference air kerma and a conformal index K that we introduce. It is clear from the table presented that the best optimization method is to normalize by a reference point and geometrical-volume optimization. The results show that the conformal index K presented is a useful and practical index to improve the quality of treatment of interstitial brachytherapy implants. (author)

195

Multiple pulse train interference-based measurement of refractive index of air using a femtosecond optical frequency comb  

Science.gov (United States)

We report a novel measurement method, referred to as the multiple pulse train interference (MPTI)-based method, to measure the refractive index of air using a femtosecond optical frequency comb. The temperature change around the region of interest is recorded based on the interference of multiple pulse trains, and this change is reflected as the distance between MPTI fringes via the use of the conventional Fourier transformation method. The proposed method is demonstrated using a sealed 600-mm cell containing a given volume of water. The results of this preliminary experiment reveal the potential of the MPTI method towards obtaining a high-accuracy evaluation of the refractive index of air.

Wei, Dong; Takamasu, Kiyoshi; Matsumoto, Hirokazu

2012-11-01

196

Assessment of air pollution tolerance index of some trees in Moradabad city, India.  

Science.gov (United States)

To see the relative tolerance of the plant species, ten different plant species i.e. Ficus rumphii, Pongamia pinnata, Alstonia scholaris, Holoptelea integrifolia, Saraca indica, Pithecolobium dulcis, Cassia simea, Bauhinia variegata, Azadirachta indica and Grewelia robusta was taken from residential (SI), industrial (SII) and commercial (SIII) area of the city as this florais very much common to the Brass city and is planted on the roadside. The quality of air with respect to SPM, SO2 and NO2 has been also assessed on respective sites to see its effect on biochemical parameters of the leaves i.e. pH, total water content, chlorophyll and ascorbic acid and evaluate the (air pollution tolerance index (APTI) of various plants. It was concluded that Pongamia pinnata 15.8, Pithecolobium dulcis 34.8, Holoptelea integrifolia 55.8 and Saraca indica 52.0 have very high APTI value over control so these are considered as high tolerant tree species, Ficus rumphii 35.7, Azadirachta indica 30.5 and Grewelia robusta 34.3 have slightlymoreAPTI value over control so these are considered as moderately tolerant tree species and Alstonia scholaris 21.5, Cassia simea 6.09 and Bauhinia variegata 18.22 have lessAPTI value than control, so these are sensitive species respectively. One way ANOVA finds the obtained values to be highly significant (p < 0.001) at the industrial site. Thus present findings show that Brass and allied industries are the prominent sources responsible for the elevated level of air pollutants at the industrial site. PMID:20120494

Tripathi, Anamika; Tiwari, P B; Mahima; Singh, Dharmveer

2009-07-01

197

Review of Kerma-Area Product and total energy incident on patients in radiography, mammography and CT.  

Science.gov (United States)

This study estimated the energy incident on patients in radiography, mammography and CT using data related to X-ray beam quantity and quality. The total X-ray beam quantity is the average Air Kerma multiplied by the X-ray beam area and expressed as the Kerma-Area Product (Gy cm(-2)). The X-ray beam quality primarily depends on the target material (and anode angle), X-ray voltage (and ripple) as well as X-ray beam filtration. For any X-ray spectra, dividing total energy (fluence × mean energy) by the X-ray beam Kerma-Area Product yields the energy per Kerma-Area Product value (?/KAP). Published data on X-ray spectra characteristics and energy fluence per Air Kerma conversion factors were used to determine ?/KAP factors. In radiography, ?/KAP increased from 6 mJ Gy(-1) cm(-2) at the lowest X-ray tube voltage (50 kV) to 25 mJ Gy(-1) cm(-2) at the highest X-ray tube voltage (140 kV). ?/KAP values ranged between 1 and 5 mJ Gy(-1) cm(-2) in mammography and between 24 and 42 mJ Gy(-1) cm(-2) in CT. Changes in waveform ripple resulted in variations in ?/KAP of up to 15 %, similar to the effect of changes resulting in the choice of anode angle. For monoenergetic X-ray photons, there was a sigmoidal-type increase in ?/KAP from 2 mJ Gy(-1) cm(-2) at 20 keV to 42 mJ Gy(-1) cm(-2) at 80 keV. However, between 80 and 150 keV, the ?/KAP shows variations with changing photon energy of area of radiological imaging can be estimated from the total X-ray beam intensity (KAP) when X-ray beam quality is taken into account. Energy incident on the patient can be used to estimate the energy absorbed by the patient and the corresponding patient effective dose. PMID:24821931

Yao, Hai; Huda, Walter; Mah, Eugene; He, Wenjun

2015-02-01

198

Partial Kerma Factors for Neutron Scattering from ^16O^  

Science.gov (United States)

Success for the use of neutron for radiation therapy and other applications in radiological physics depends on the understanding of the interaction of neutron with elements in the tissue. Study of the mechanisms of energy deposition by neutron interaction with matter is very important to improve the understanding of the neutron dosimetry. Cross section data are the basic inputs for many types of calculations in radiation physics. One important quantity in some radiological applications of neutron is the kerma (kinetic energy released in material.) Differential elastic and inelastic neutron scattering from some elements of biological interests are available at energies 18 -- 26 MeV. Optical Model Potentials based on these measured cross sections may be used to calculate various quantities of interest for the neutron dosimetry at higher energies where cross section data may not be available. Kerma values for elastic and inelastic scattering of neutron from ^16O are obtained from differential cross sections.

Islam, Mohammed

2011-10-01

199

[Evaluation of calibration error for applying exposure index].  

Science.gov (United States)

Exposure indicators of digital radiography systems have been termed by manufacturers individually. The International Electrotechnical Commission (IEC) provided a concept of exposure index (EI) that unified the exposure indicators in order to recognize the deviations from the intended exposure. Although the IEC determined the calibration conditions between the exposure indicator and the air kerma at the detector surface, the tolerance was described was limited concerning the beam conditions. The purpose of this study is to evaluate the calibration error regarding the geometry and the added filtrations. The relative errors of calibrations based on the IEC condition were derived using the value of exposure indicators at EI value of 200, 500 and 1000 for field size of 10×10 cm, 20×20 cm, 30×30 cm and 43×43 cm, and source-image receptor distance (SID) of 100 cm, 120 cm, 150 cm and 200 cm. The beam qualities using added filtrations of 0.5 mm Cu+2 mm Al, 0.6 mm Cu and 21 mm Al were adjusted to RQA 5. The air kerma at the detector surface over the clinical use ranged from 0.18 to 26.3 µGy. Consequently, the relative errors for the calibrations were less than 6% at a field size of more than 10 × 10 cm and at SID of more than 100 cm with all added filtrations. PMID:22104235

Ariga, Eiji

2011-01-01

200

Evaluation of calibration error for applying exposure index  

International Nuclear Information System (INIS)

Exposure indicators of digital radiography systems have been termed by manufacturers individually. The International Electrotechnical Commission (IEC) provided a concept of exposure index (EI) that unified the exposure indicators in order to recognize the deviations from the intended exposure. Although the IEC determined the calibration conditions between the exposure indicator and the air kerma at the detector surface, the tolerance was described was limited concerning the beam conditions. The purpose of this study is to evaluate the calibration error regarding the geometry and the added filtrations. The relative errors of calibrations based on the IEC condition were derived using the value of exposure indicators at EI value of 200, 500 and 1000 for field size of 10 x 10 cm, 20 x 20 cm, 30 x 30 cm and 43 x 43 cm, and source-image receptor distance (SID) of 100 cm, 120 cm, 150 cm and 200 cm. The beam qualities using added filtrations of 0.5 mm Cu +2 mm Al, 0.6 mm Cu and 21 mm Al were adjusted to RQA 5. The air kerma at the detector surface over the clinical use ranged from 0.18 to 26.3 ?Gy. Consequently, the relative errors for the calibrations were less than 6% at a field size of more than 10 x 10 cm and at SID of more than 100 cm with all added filtrations. (author)

 
 
 
 
201

Kerma factors for tissue compositions, compounds and mixtures  

International Nuclear Information System (INIS)

Tables of calculated kerma factors for neutrons, being prepared for an ICRU report on Neutron Dosimetry for Biology and Medicine, are discussed. The philosophy and limitations of the calculations, some of the problems encountered, and new experimental and theoretical information needed to improve the knowledge of energy transfer to matter are covered. The tables cover the energy range from thermal to 30 MeV and will appear in the ICRU report

202

Absorbed dose evaluation by SISCODES code, kerma and fluence deviations  

Energy Technology Data Exchange (ETDEWEB)

Radiotherapy is a common treatment of cancer. Radiotherapy exposes the patient to a radiation field, producing ionization, and absorbed dose. A precise dose calculation and the ability to execute the irradiation on the patient are necessary in order to avoid serious injuries on the surrounding health tissue, thus, the maximum acceptable absorbed dose error from the prescribed and applied is about 5%. The doses on radiotherapy are usually calculated by superimposition experimental dose profile, namely PDP, which is experimentally measured in a water simulator. Moreover, the radiation interaction with human body tissues depends on the chemical composition and the tissue density, which means the anthropomorphism and anthropometric of the human being. This paper evaluates the deviation of calculated value of kerma, induced by human body heterogeneities. To do this job two thorax voxel models created on SISCODES (one filled with various tissues other filled with water) were applied. The result of simulations permits two different comparisons. One is the ratio between tissues kermas and water kerma. Another is the ratio between human phantom fluence, where exists radiation scatter and reflection, and water phantom fluence. The reconstructed pictures of studied regions showing the calculated ratios, and graphs of the ratios versus energy of each tissue are shown. The dose ratio deviations obtained are, in some situations, larger than the acceptable 5% point out serious miscalculation of doses for some spatial regions on the human body. (author)

Trindade, Bruno M.; Campos, Tarcisio P.R. de [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Programa de Pos-Graduacao em Ciencias e Tecnicas Nucleares]. E-mail: bmtrindade@yahoo.com; campos@nuclear.ufmg.br

2007-07-01

203

The spatial-time distribution of vertical gradient of refraction index of air in territory of Mongolia  

International Nuclear Information System (INIS)

The results of calculation of the vertical gradient of refraction index of air in 2-300 m and 2-900 m layer of troposphere by 3 year (1987-1989) data of 8 meteorological stations in the Mongolia is been showed. Year course and integral distribution of gn of this stations are discriminated

204

Response surface models for CFD predictions of air diffusion performance index in a displacement ventilated office  

Energy Technology Data Exchange (ETDEWEB)

Based on the Response Surface Methodology (RSM), the development of first- and second-order models for predicting the Air Diffusion Performance Index (ADPI) in a displacement-ventilated office is presented. By adopting the technique of Computational Fluid Dynamics (CFD), the new ADPI models developed are used to investigate the effect of simultaneous variation of three design variables in a displacement ventilation case, i.e. location of the displacement diffuser (L{sub dd}), supply temperature (T) and exhaust position (L{sub ex}) on the comfort parameter ADPI. The RSM analyses are carried out with the aid of a statistical software package MINITAB. In the current study, the separate effect of individual design variable as well as the second-order interactions between these variables, are investigated. Based on the variance analyses of both the first- and second-order RSM models, the most influential design variable is the supply temperature. In addition, it is found that the interactions of supply temperature with other design variables are insignificant, as deduced from the second-order RSM model. The optimised ADPI value is subsequently obtained from the model equations. (author)

Ng, K.C. [Department of Research and Applications, O.Y.L. R and D Center, Lot 4739, Jalan BRP 8/2, Taman Bukit Rahman Putra, 47000, Sungai Buloh, Selangor Darul Ehsan (Malaysia); Kadirgama, K. [Department of Mechanical Engineering, Universiti Tenaga Nasional, Km. 7, Jalan Kajang-Puchong, 43009 Kajang, Selangor Darul Ehsan (Malaysia); Ng, E.Y.K. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

2008-07-01

205

Solar radiation estimation using sunshine hour and air pollution index in China  

International Nuclear Information System (INIS)

Highlights: • Aerosol can affect coefficients of A–P equation to estimate solar radiation. • Logarithmic model performed best, according to MBE, MABE, MPE, MAPE, RMSE and NSE. • Parameters of A–P model can be adjusted by API, geographical position and altitude. • A general equation to estimate solar radiation was established in China. - Abstract: Angström–Prescott (A–P) equation is the most widely used empirical relationship to estimate global solar radiation from sunshine hours. A new approach based on Air Pollution Index (API) data is introduced to adjust the coefficients of A–P equation in this study. Based on daily solar radiation, sunshine hours and API data at nine meteorological stations from 2001 to 2011 in China, linear, exponential and logarithmic models are developed and validated. When evaluated by performance indicators of mean bias error, mean absolute bias error, mean percentage error, mean absolute percentage error, root mean square error, and Nash–Sutcliffe Equation, it is demonstrated that logarithmic model performed better than the other models. Then empirical coefficients for three models are given for each station and the variations of these coefficients are affected by API, geographical position, and altitude. This indicates that aerosol can play an important role in estimation solar radiation from sunshine hours, especially in those highly polluted regions. Finally, a countrywide general equation is established based on the sunshine hour data, API and geographical parameters, which can be used to estimate the daily solar radiation in areas where the radiation data is not available

206

Development of a health-based air quality index for Canada : public opinion research 2004-05 : final report  

International Nuclear Information System (INIS)

Canadians rely on an air quality indexes (AQIs) to inform them about air pollution conditions in their communities. However, there is no AQI common to all of Canada, and there is a lack of consistency in the way in which air quality is calculated and reported, as well as in the use of health-based messages. This paper reported findings of a public opinion research survey conducted to gauge Canadians' awareness, perceptions and behavioural responses to air quality, air pollution and AQIs. The aim of the study was to guide the development of health messages to more effectively communicate the AQI to Canadians with respect to the health risks associated with poor air quality. Telephone surveys were conducted immediately following a poor air quality episode to measure the public's awareness and response to these events, as well as residents' general awareness and use of AQIs. A separate research project was then conducted which consisted of in-depth qualitative interviews with 28 individuals recruited from the general population. A comprehensive national telephone survey was then conducted following the summer 2004 'smog season', which focused on the public's awareness of air pollution and AQIs. Results from the first 2 phases of the research were then presented at a workshop comprised of health and environmental communities specializing in air issues in Canada. Focus groups were then held to test public reaction to new AQI communications concepts derived from the researcications concepts derived from the research. Results indicated that Canadians widely identify air pollution as a significant environmental problem. However, the information from AQIs had a limited impact in terms of prompting actions to reduce personal exposure. A new type of national AQI for Canada was developed that conveyed information on air quality conditions and their significance. Key features include a 0 to 10 point unbounded scale showing current air quality conditions; a forecast of future conditions; standardized information covering health risks; targeted information for groups most at risk; and recommended activities

207

Development of a calibration methodology and tests of kerma area product meters  

International Nuclear Information System (INIS)

The quantity kerma area product (PKA) is important to establish reference levels in diagnostic radiology exams. This quantity can be obtained using a PKA meter. The use of such meters is essential to evaluate the radiation dose in radiological procedures and is a good indicator to make sure that the dose limit to the patient's skin doesn't exceed. Sometimes, these meters come fixed to X radiation equipment, which makes its calibration difficult. In this work, it was developed a methodology for calibration of PKA meters. The instrument used for this purpose was the Patient Dose Calibrator (PDC). It was developed to be used as a reference to check the calibration of PKA and air kerma meters that are used for dosimetry in patients and to verify the consistency and behavior of systems of automatic exposure control. Because it is a new equipment, which, in Brazil, is not yet used as reference equipment for calibration, it was also performed the quality control of this equipment with characterization tests, the calibration and an evaluation of the energy dependence. After the tests, it was proved that the PDC can be used as a reference instrument and that the calibration must be performed in situ, so that the characteristics of each X-ray equipment, where the PKA meters are used, are considered. The calibration was then performed with portable PKA meters and in an interventional radiology equipment that has a PKA meter fixed. The results were good and it was proved the need for calibration of these meters and the importance of in situ calibration with a reference meter. (author)

208

Analysis of the Tandem Calibration Method for Kerma Area Product Meters Via Monte Carlo Simulations  

International Nuclear Information System (INIS)

The IAEA recommends that uncertainties of dosimetric measurements in diagnostic radiology for risk assessment and quality assurance should be less than 7% on the confidence level of 95%. This accuracy is difficult to achieve with kerma area product (KAP) meters currently used in clinics. The reasons range from the high energy dependence of KAP meters to the wide variety of configurations in which KAP meters are used and calibrated. The tandem calibration method introduced by Poeyry, Komppa and Kosunen in 2005 has the potential to make the calibration procedure simpler and more accurate compared to the traditional beam-area method. In this method, two positions of the reference KAP meter are of interest: (a) a position close to the field KAP meter and (b) a position 20 cm above the couch. In the close position, the distance between the two KAP meters should be at least 30 cm to reduce the effect of back scatter. For the other position, which is recommended for the beam-area calibration method, the distance of 70 cm between the KAP meters was used in this study. The aim of this work was to complement existing experimental data comparing the two configurations with Monte Carlo (MC) simulations. In a geometry consisting of a simplified model of the VacuTec 70157 type KAP meter, the MCNP code was used to simulate the kerma area product, PKA, for the two (close and distant) reference planes. It was found that PKA values for the tube voltage of 40 kV web> values for the tube voltage of 40 kV were about 2.5% lower for the distant plane than for the close one. For higher tube voltages, the difference was smaller. The difference was mainly caused by attenuation of the X ray beam in air. Since the problem with high uncertainties in PKA measurements is also caused by the current design of X ray machines, possible solutions are discussed. (author)

209

Retrospective assessment of exposure to traffic air pollution using the ExTra index in the VESTA French epidemiological study.  

Science.gov (United States)

This study applies a traffic exhaust air dispersion model (the ExTra index) to 403 children enrolled in a French multicentric case-control study, the VESTA study (Five [V] Epidemiological Studies on Transport and Asthma). The ExTra index (previously validated by our team) was used to assess lifelong average traffic-related air pollutant (TAP) concentrations (nitrogen oxides) children in the study were exposed to in front of their living places. ExTra index took into account traffic density, topographical parameters (building height, road and pavement width), weather conditions (wind direction and strength) and background pollution levels. Topographical and traffic data were collected, using a specific questionnaire for each home, school or nursery address, attended by children. The assessment of time-weighted NOx levels in front of the children's living places highlighted significant disparities: mean ExTra index values and share attributable to proximity traffic were, respectively, 70+/-42 and 14+/-22 microg/m3 NOx equivalent NO2 for the 403 children in our study. Not only would this diversity not have been revealed using urban background pollution data provided by air quality networks, it would have resulted in 40% of the children being misclassified with regard to their TAP exposure by underestimating it in half of the cases and overestimating it in the other half. Such errors of classification, which are highly prejudicial in epidemiology, argue strongly for the use of an index such as the ExTra, which enables TAP exposure to be reconstructed within the framework of retrospective or prospective epidemiological studies. PMID:15942641

Reungoat, Patrice; Chiron, Mireille; Gauvin, Stéphanie; Zmirou-Navier, Denis; Momas, Isabelle

2005-11-01

210

Kerma-factors in neutron interactions with lithium hydride  

International Nuclear Information System (INIS)

Models to calculate heat generation in a substance have been developed for all kinds of neutron reactions in any energy range. The calculational model for kerma-factors is based on a precise solution of kinematic equations. The calculated kerma-factors for 6Li, 7Li, 1H (in terms of eVxb/atom) and for LiH with natural Li (in Wxs/cmxneutr) in the energy range from 10-4 to 107 eV are presented. In neutron interactions with 6Li the major contributions to heat generation were assumed to be from the 6Li(n,t)He reaction; with 7Li - from the reactions of elastic scattering, inelastic scattering on the level E=0.478 MeV, (n,n't) and (n,?); with hydrogen the main contribution is made from the reactions of elastic scattering and capture. Data of the ENDF/B-4 library and latest experimental results were used in the calculations. It is pointed out that the accuracy of the calculations depends only on the availability and accuracy of corresponding nuclear data

211

Methods for calculating probability distributions of radio-wave attenuation on ground paths due to anomalies of the air refractive index  

Science.gov (United States)

The paper analyzes and compares existing methods for calculating radio-wave attenuation statistics at frequencies above 10 GHz associated with anomalies of the air refractive index. An algorithm is proposed for calculating the sum distributions.

Pozhidaev, V. N.; Sviatogor, V. V.

1992-07-01

212

DISDOS, Kerma in Model Man from External Gamma Source  

International Nuclear Information System (INIS)

1 - Description of problem or function: The absorbed dose (actually Kerma) is calculated for simplified human phantoms (elliptical cylinders) irradiated by external photon sources. The phantoms are divided into three parts: head, trunk, and legs. Three source distributions are considered: collimated beam, point source, and isotropic irradiation; other sources may be considered since the codes are segmented. 2 - Method of solution: Monte Carlo calculations provide estimates of the dose and the standard deviation in each zone. The source energy spectrum may be discrete, uniformly distributed in an energy range, or given by a piece-wise continuous function. 3 - Restrictions on the complexity of the problem: Pair production is accounted for in the field of the nuclei only. Electron binding corrections to Compton scattering are omitted. The body has 22 organs

213

40 CFR Appendix G to Part 58 - Uniform Air Quality Index (AQI) and Daily Reporting  

Science.gov (United States)

...concentration data from population-oriented State/Local Air Monitoring Station (SLAMS) or parts of the...non-approved measurements to approved methods by statistical linear regression is referenced in section 13 below. 11. Do I...

2010-07-01

214

A radiation exposure index for CT.  

Science.gov (United States)

The purpose of this study is to define an Exposure Index for CT (EI(CT)) and to estimate the magnitude of the EI(CT) for common clinical CT examinations. For a single-axial rotation of a CT X-ray tube that includes only rays that pass through the patient, the CT Exposure Index (EI(CT)) is defined as the average Air Kerma that would be incident on an extended 360° detector array completely surrounding the patient. For an axial scan of a uniform cylindrical phantom, EI(CT) can be approximated as T × [(CTDI(air))/4] × [?°/360°] where T is the fractional transmission through the cylinder, CTDI(air) is the CT Dosimetry Index-determined 'free in air' at isocentre, and ?/2 is the fan beam angle that will completely irradiate a cylindrical phantom at isocentre. The value of CTDI(air) can be estimated from the weighted CTDI (CTDI(w)) for a given CT examination, and the angle ? depends on the irradiation geometry that can be obtained from the cylinder diameter (r) and the focus to isocentre distance (R). At a voltage of 120 kV, transmission through an adult head was ?2.6%, through an adult abdomen?0.4% and through a 5-y-old paediatric abdomen ?3%. Average ratios of CTDI(air)/CTDI(w) were 1.42 ± 0.12 in 16-cm dosimetry phantom and 2.82 ± 0.37 in 32-cm phantom. Values of ? ranged from 30.1° (R = 61 cm and r=8 cm) to 85.3° (R = 55 cm and r=20 cm). For an adult head CT examination, EI(CT) was estimated to be?70 µGy at a CTDI(vol) of 75 mGy (16 cm), and for an adult abdominal CT examination, EI(CT) was estimated to be?11 µGy at a CTDI(vol) of 25 mGy (32 cm). For an abdomen CT examination in a 5-y-old child, EI(CT) was estimated to be ?21 µGy at a CTDI(vol) of 20 mGy (16 cm). The EI(CT) is introduced that provides a quantitative measure of the amount of the radiation used to generate images in any CT examination and is analogous to the average image receptor Exposure Index recently proposed for use in projection imaging. The EI(CT) metric provides operators with an objective index of the amount of the radiation used to create CT images and can be used to control quantum mottle in CT. PMID:23690648

Huda, Walter

2013-12-01

215

Radio Emission from Cosmic Ray Air Showers based on Shower Simulations: On the Importance of a Realistic Atmospheric Index of Refraction  

CERN Document Server

We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from three-dimensional Monte Carlo simulations of air showers in a realistic geo-magnetic field. We discuss the importance of a correct treatment of the index of refraction in air, given by the law of Gladstone and Dale, which affects the pulses enormously for certain configurations, compared to a simplified treatment using a constant index. We also provide some information about the numerical procedures referred to as EVA 1.0.

Werner, Klaus; Scholten, Olaf

2012-01-01

216

Air Pollution Tolerance Index (APTI) of some tree species growing near rail roads of Madurai, Tamil Nadu (India).  

Science.gov (United States)

Biological monitoring and assessment studies due to urban--rail road pollutants were carried out using Air Pollution Tolerance Index (APTI) of plants. Four plant (leaf) parameters--namely ascorbic acid, total chlorophyll, relative water content and leaf extract pH were combined together in a formulation signifying the APTI of plants. APTI was calculated for five different species such as Azadirachta indica, Delonix regia, Ficus religiosa, Pongamia pinnata and Polyalthia longifolia growing in two different areas, i.e. control area and along the railway track of Madurai, Tamil Nadu (India). The control site was selected in the college campus. None of the four plant parameters indicated a consistent response to pollutants. In the present study, Delonix regia and Pongamia pinnata lost the tolerance towards air pollutants and became more sensitive, but Azadirachta indica, Ficus religiosa, and Polyalthia longifolia indicated high APTI values over control area and hence considered as tolerant species. The APTI of plants showed a marked gradation as the pollutant load decreased from rail road to control area. The APTI can be used as a good indicator of impact of the air pollution on plants. PMID:22312796

Thambavani, D Sarala; Kamala, C

2010-10-01

217

Monte Carlo evaluation of kerma in an HDR brachytherapy bunker  

International Nuclear Information System (INIS)

In recent years, the use of high dose rate (HDR) after-loader machines has greatly increased due to the shift from traditional Cs-137/Ir-192 low dose rate (LDR) to HDR brachytherapy. The method used to calculate the required concrete and, where appropriate, lead shielding in the door is based on analytical methods provided by documents published by the ICRP, the IAEA and the NCRP. The purpose of this study is to perform a more realistic kerma evaluation at the entrance maze door of an HDR bunker using the Monte Carlo code GEANT4. The Monte Carlo results were validated experimentally. The spectrum at the maze entrance door, obtained with Monte Carlo, has an average energy of about 110 keV, maintaining a similar value along the length of the maze. The comparison of results from the aforementioned values with the Monte Carlo ones shows that results obtained using the albedo coefficient from the ICRP document more closely match those given by the Monte Carlo method, although the maximum value given by MC calculations is 30% greater. (note)

218

Humidity dependence in kerma area product meter used in diagnostic X ray examinations  

International Nuclear Information System (INIS)

The air-kerma area product, PKA, is a dosimetric quantity that can be directly related to the patient dose and used for risk assessment associated with different x-ray examinations. PKA has the unit Gym2 and can be directly measured by use of a Kerma Area Product (KAP) meter placed in the radiation beam. PKA is the recommended quantity for use in the establishment of diagnostic reference levels (DRLs) for conventional x-ray examinations and is also a good indicator for when threshold doses for deterministic effects are reached in interventional x-ray procedures. Most modern x-ray equipment provides the operator with the total PKA from the examination or procedure. This PKA is either obtained from PKA measurements from a built-in KAP meter or calculated from exposure parameters. To get a reliable estimate of DRLs and the patient dose, it is essential that the PKA measurement is correct. Thus all environmental influences on the KAP meter should be taken into account. These influences can either be corrected for or included in the measurement uncertainty. These have to be considered both in the calibration of the KAP-meters, in the use of the KAP meters and in the determination of DRLs. A KAP meter is an electrometer and a plane parallel ion chamber with an active area of typical 15 cm X 15 cm. The KAP meter usually consist of three plastic plates (PMMA) which is coated with a conductates (PMMA) which is coated with a conducting layer made of indium oxide doped with tin (In2O3:Sn). This coating is used due to its transparency to light. The air layers between the plates (sensitive volume) are open to the air. Thus the readings from the KAP meter have to be corrected for air pressure and temperature as for other ion chambers. It has been assumed that the humidity dependence of the KAP meter is so small that no correction has been necessary. This work will show that KAP meter with PMMA plastic plates coated with In2O3:Sn shows a humidity dependence so large that corrections should be considered. The measurements were performed by carefully controlling the humidity in the laboratory. Between each measurement the humidity was changed with steps of 5 to 10 %RH in the range 20-60 %RH. The measurements were performed two days after the humidity change, so the humidity inside the chamber could stabilise. The setup was as for a substitution calibration with the KAP meter 100 cm from the x- ray source and exposed to a beam limited by a aperture of 5 cm X 5 cm at 95 cm as described in TRS-457. A Capintec PR-30 was used as a monitor chamber. This chamber is made of C-552 and has small humidity dependence. Two KAP-chambers were tested. Both chambers showed the same humidity dependence. The humidity dependence for the chambers was (0.24 ± 0.10) % pr. %RH (k=2). The transmission factor of the chambers showed no humidity dependence. One of the chambers were tested at five different qualities from 40 kV to 150 kV (RQR2, RQR5, RQR8, RQR9, RQR 10). The humidity dependence was the same for all qualities. In an environment with no humidity control the humidity can typically vary from 20 %RH to 80 %RH. According to the results this can lead to about 14 % change in the KAP reading. This is a larger effect than recommended for KAP meters, ± 3.0 %, in the IEC 60580 standard. The observed humidity dependence means that great care have to be take when calibrating and using KAP meter for dose measurements. The humidity effect is not fully understood but it seems that the conducting layer on the PMMA is the origin of the effect

219

Kermas for various substances averaged over the energy spectra of fast neutron therapy beams: A study in uncertainties  

International Nuclear Information System (INIS)

Kermas for various substances averaged over the energy spectra of fast neutron therapy beams, as well as ratios of average kermas relative to muscle, were calculated in an attempt to estimate the uncertainties introduced in these quantities by the poor knowledge of the elemental kerma functions, actual neutron energy spectra, and composition of tissues and other materials. Average kermas have uncertainties of the order of 7%--25%, while for ratios of average kermas the uncertainties are of the order of 2%--5% for materials of clinical interest. It is concluded that the ratio of average kerma of muscle to A-150 tissue-equivalent plastic should be 0.93 +- 0.03 for the new p+Be clinical neutron beams

220

Fundamental relationships between linear energy transfer, absorbed dose, kerma, and exposure. Application to changes of mediums; Relations fondamentales entre transfert lineique d'energie dose absorbee, kerma et exposition application aux changements de milieux  

Energy Technology Data Exchange (ETDEWEB)

After briefly defining the quantities used in dosimetry and presenting them with a view to their simple adaptation to health physics problems, the authors establish simple mathematical relationships to express the absorbed dose, kerma and exposure in the case of electrons and photons, and also relationships between these various quantities considered in air. They then proceed to study the variations in these quantities at the interface between the air and the soft tissues of the organism and in depth in the tissues. They give the numerical values of the discontinuities liable to appear at the interface and the values obtained, relative to air, after electronic equilibrium is established in depth in the tissues. An example of application to dosimetry is also given in the case of an aluminium-walled ionization chamber. To conclude, the conditions to be fulfilled in order to make a direct measurement of the absorbed dose in the tissues are presented and discussed. (authors) [French] Apres un bref rappel des definitions des grandeurs utilisees en dosimetrie et leur presentation en vue d'une adaptation simple aux problemes de radioprotection, les auteurs etablissent des relations mathematiques simples pour exprimer, dans le cas des electrons et des photons, la dose absorbee, le kerma et l'exposition ainsi que des relations entre ces diverses grandeurs considerees dans l'air. Les auteurs etudient ensuite les variations de ces grandeurs a l'interface de separation air-tissus mous de l'organisme et en profondeur dans les tissus. Ils donnent les valeurs numeriques des discontinuites susceptibles d'apparaitre a l'interface et les valeurs obtenues, relativement a l'air, apres etablissement de l'equilibre electronique en profondeur dans les tissus. Un exemple d'application a la dosimetrie est egalement donne dans le cas d'une chambre d'ionisation a paroi d'aluminium. En conclusion, les conditions a remplir en vue d'une mesure directe de la dose absorbee dans les tissus sont presentees et discutees. (auteurs)

Joffre, H.; Pages, L. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-07-01

 
 
 
 
221

Determination of mass attenuation coefficients, effective atomic and electron numbers, mean free paths and kermas for PbO, barite and some boron ores  

International Nuclear Information System (INIS)

The total mass attenuation coefficients, ?m, for PbO, barite, colemanite, tincal and ulexite were determined at 80.1, 302.9, 356.0, 661.7 and 1250.0 keV photon energies by using NaI (Tl) scintillation detector. Effective atomic number, Zeff, effective electron number, Neff, total atomic cross-section, ?t, total electronic cross-section, ?e, mean free path, mfp, and kerma relative to air were determined experimentally and theoretically. The theoretical mass attenuation coefficients were estimated using mixture rule. The calculated values were compared with the experimental values for all samples.

222

Determination of mass attenuation coefficients, effective atomic and electron numbers, mean free paths and kermas for PbO, barite and some boron ores  

Science.gov (United States)

The total mass attenuation coefficients, ? m, for PbO, barite, colemanite, tincal and ulexite were determined at 80.1, 302.9, 356.0, 661.7 and 1250.0 keV photon energies by using NaI (Tl) scintillation detector. Effective atomic number, Z eff, effective electron number, N eff, total atomic cross-section, ? t, total electronic cross-section, ? e, mean free path, mfp, and kerma relative to air were determined experimentally and theoretically. The theoretical mass attenuation coefficients were estimated using mixture rule. The calculated values were compared with the experimental values for all samples.

Un, A.; Sahin, Y.

2011-07-01

223

Status of Obesity in Terms of Body Mass Index among Indian Air Force Personnel  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: This paper investigates the prevalence of obesity (BMI >30 kg/m2 among five geographical groups of Indian Air Force personnel of different age. Purpose of study: To observe the status of obesity among IAF and see whether there is age-wise and regional difference in obesity among the different geographical groups. Results: Gradual increase in mean BMI is seen as age of the population increases. There is an overall marked increase in BMI level among all the three age groups for all the other four zones. F-ratio test of normal range BMI does show significant difference among the zones. There is a statistically significant difference in normal BMI (18.5–24.9 wt/ht2 among all the age groups (F-ratio=11.561, p < 0.05. BMI correlated positively with age in the 20-25 age groups (r = 0.119, p= 0.000 and 26-30 age groups (r = 0.075, p= 0.009 respectively, but BMI did not show any statistically significant correlation with age in the 31-35 age group. Observations: A marked increase in overweight and pre-obese prevalence is seen both age and region wise in the IAF personnel if the Asian BMI cut off levels are applied

L. Robert Varte

2011-10-01

224

Calculated photon KERMA factors based on the LLNL EGDL [Evaluated Gamma-Ray Data Library] data file  

International Nuclear Information System (INIS)

Photon (Gamma-Ray) KERMA factors calculated from the LLNL EGDL (Evaluated Gamma-Ray Data Library) file are tabulated for the elements from Z=1 to Z=30 and for 15 composite materials. The KERMA factors are presented for 191 energy groups over the incident photon energy range from 100 eV to 100 MeV. 3 refs

225

Wind erosion risk in the southwest of Buenos Aires Province, Argentina, and its relationship to the productivity index  

Science.gov (United States)

Wind erosion risk (WER) for soils of each municipality in the southwest (SW) of Buenos Aires Province (10,491,172 ha) was determined using the wind erosion equation (WEQ) model. WER results from multiplying the soil erodibility index (" I") of the soil by the climatic factor ( C). WER (Mg ha -1 year -1) of each municipality was: Bahía Blanca: 22.4, Coronel Dorrego: 18.6, Coronel Pringles: 4.5, Coronel Rosales: 48.2, Coronel Suárez: 4.5, Guaminí: 3.0, Patagones: 104.6, Puan: 12.2, Saavedra: 3.0, Tornquist: 6.8, and Villarino: 31.7. The maximum weighted average of " I" (Mg ha -1 year -1) corresponded to Coronel Rosales (87.6), Patagones (87.2), Villarino (85.7), Puan (67.9); Guaminí (59.6), Coronel Dorrego (53.1), and Bahía Blanca (39.3); the remaining municipalities ranged between 34.9 and 32.1 Mg ha -1 year -1. The highest C (%) corresponded to Patagones (120), Bahía Blanca (57), Coronel Rosales (55), Villarino (37), Coronel Dorrego (35), Tornquist (21), and Puan (18); for the remaining municipalities it was 14%. The productivity index (PI) is known to establish a numerical value of the productive capacity of lands. The relationship between WER and PI, weighted averages, in all the studied municipalities was fitted by means of a linear model, WER (Mg ha -1 year -1) = 95.23 - 2.09 * PI (%) ( R2 = 66%), and a second-order polynomial model, WER (Mg ha -1 year -1) = 139.41 - 5.86 * PI (%) + 0.07 * PI 2 (%) ( R2 = 74%). No statistically significant relationship was found between WER and PI for each municipality.

Silenzi, Juan C.; Echeverría, Nora E.; Vallejos, Adrián G.; Bouza, Mariana E.; De Lucia, Martín P.

2012-01-01

226

Spatial variation of dose and kerma in a composite slab - an interface study  

International Nuclear Information System (INIS)

This work investigates the spatial variation of kerma and dose, when 60Co, 4 MV and 6 MV conical photon beams are incident on composite slab in contact geometry. Discontinuities in both kerma and dose profiles have been observed at the interfaces. The influence of Bone+Marrow (BM) on dose and secondary-electron fluence, in the Fat-BM interface, have mainly been discussed in this work. It is seen that at the Fat-BM interface, the dose has been enhanced by about 3 %, at 0.25 mm in the backward direction, for all photon beams considered in the calculations. (author)

227

Axial kerma and dose equivalent for neutrons in the ICRU-sphere  

International Nuclear Information System (INIS)

This report is compiled and published as a supplement to GSF-report S-880, 1982, 'Discrete Ordinates and SAM-CE Monte-Carlo calculations in the ICRU-sphere'. It contains the complete data set of calculated axial kerma and kerma equivalents in the ICRU-sphere for external irradiation with a parallel homogeneous beam of neutrons. The calculations have been performed by means of the Ssub(N)-transport programme DOT-2, distributed by RSIC-ORNL, Oak Ridge. The results were verified by those of Monte-Carlo calculations for several incident energies, demonstrating perfect agreement. (orig./HP)

228

Energy absorption buildup factors, exposure buildup factors and Kerma for optically stimulated luminescence materials and their tissue equivalence for radiation dosimetry  

Science.gov (United States)

Optically stimulated luminescence (OSL) materials are sensitive dosimetric materials used for precise and accurate dose measurement for low-energy ionizing radiation. Low dose measurement capability with improved sensitivity makes these dosimeters very useful for diagnostic imaging, personnel monitoring and environmental radiation dosimetry. Gamma ray energy absorption buildup factors and exposure build factors were computed for OSL materials using the five-parameter Geometric Progression (G-P) fitting method in the energy range 0.015-15 MeV for penetration depths up to 40 mean free path. The computed energy absorption buildup factor and exposure buildup factor values were studied as a function of penetration depth and incident photon energy. Effective atomic numbers and Kerma relative to air of the selected OSL materials and tissue equivalence were computed and compared with that of water, PMMA and ICRU standard tissues. The buildup factors and kerma relative to air were found dependent upon effective atomic numbers. Buildup factors determined in the present work should be useful in radiation dosimetry, medical diagnostics and therapy, space dosimetry, accident dosimetry and personnel monitoring.

Singh, Vishwanath P.; Badiger, N. M.

2014-11-01

229

Use of Segregation Indices, Townsend Index, and Air Toxics Data to Assess Lifetime Cancer Risk Disparities in Metropolitan Charleston, South Carolina, USA  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Studies have demonstrated a relationship between segregation and level of education, occupational opportunities, and risk behaviors, yet a paucity of research has elucidated the association between racial residential segregation, socioeconomic deprivation, and lifetime cancer risk. Objectives: We examined estimated lifetime cancer risk from air toxics by racial composition, segregation, and deprivation in census tracts in Metropolitan Charleston. Methods: Segregation indices were used to measure the distribution of groups of people from different races within neighborhoods. The Townsend Index was used to measure economic deprivation in the study area. Poisson multivariate regressions were applied to assess the association of lifetime cancer risk with segregation indices and Townsend Index along with several sociodemographic measures. Results: Lifetime cancer risk from all pollution sources was 28 persons/million for half of the census tracts in Metropolitan Charleston. Isolation Index and Townsend Index both showed significant correlation with lifetime cancer risk from different sources. This significance still holds after adjusting for other sociodemographic measures in a Poisson regression, and these two indices have stronger effect on lifetime cancer risk compared to the effects of sociodemographic measures. Conclusions: We found that material deprivation, measured by the Townsend Index and segregation measured by the Isolation index, introduced high impact on lifetime cancer risk by air toxics at the census tract level.

LaShanta J. Rice

2014-05-01

230

Measurement of air-refractive-index fluctuation from laser frequency shift with uncertainty of order 10?9  

International Nuclear Information System (INIS)

In the previous work (Ishige et al 2009 Meas. Sci. Technol. 20 084019), we presented a method of measuring the relative air-refractive-index fluctuation (?nair) from the laser frequency shift with the measurement uncertainty of order 10?8 using a phase modulation homodyne interferometer (Basile et al 1991 Metrologia 28 455), which was supported by an ultralow thermal expansion material (ULTEM) and an external cavity laser diode (ECLD). In this paper, an improvement in the uncertainty of the ?nair measurement is presented. The improvement method is based on a Fabry–Perot cavity constructed on the ULTEM, which has a thermal expansion coefficient of 2 × 10?8 K?1 and an ECLD. The Pound–Drever–Hall method (Drever et al 1983 Appl. Phys. B 31 97) is also used to control the ECLD frequency to track the resonance of the cavity. ?nair can be derived from the ECLD frequency shift. The estimated measurement uncertainty of ?nair for a short time (?150 s) in the experiment is of order 2.5 × 10?9 or less

231

Review of the research and application of KERMA factor and DPA cross section  

International Nuclear Information System (INIS)

The data for recoil atom spectra, KERMA factor and displacement cross sections from neutron-induced reactions are calling increasing interest for applications to the study of radiation damage, calculation of heat generation in reactor, neutron therapy and biological research. PKA spectra sub-working group was recently established in Japanese Nuclear Data Committee as a part of developing JENDL Special Purpose Data Files. Current status of the data and various features of application of the KERMA-related problems were reviewed and discussed at the first meeting of the sub-working group. Present report is a compilation of the items presented at the meeting, covering a brief review of the existing research and the data, method of calculation, the KERMA factor data in neutron therapy, the deduction of KERMA factor of C-12 from neutron reaction measurement and analysis, the data base for radiation damage, the damage simulation calculation, and the method of storaging the evaluated data in ENDF/B-VI format. (author)

232

ZZ DLC-10B AVKER, Neutron Kerma Response Function Data Library  

International Nuclear Information System (INIS)

1 - Nature of physical problem solved: Number of groups: Kerma factors at 816 energy points within the energy range 0.023 eV to 19.2 MeV or as kerma factors for a specified group structure. Nuclides: H, Li-6, Li-7, Be, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Fe, and Nb. Origin: O5R and ENDF/B libraries except for P and F. Weighting spectrum: Flat or 1/E. The original library was compiled for use in computing energy release in tissue and heating in various materials. The elements compiled for the first library are H, 6-Li, 7-Li, Be, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Fe, and Nb. The cross sections used were based on the O5R and ENDF/B libraries except for P, which the authors of ref. 1 compiled, and F which came from GAM-2. 2 - Method of solution: The quantity kerma (kinetic energy release in material) is evaluated by an integration over energy of the product of the kerma factor and flux density at any spatial position

233

Spatial and temporal analysis of Air Pollution Index and its timescale-dependent relationship with meteorological factors in Guangzhou, China, 2001-2011.  

Science.gov (United States)

There is an increasing interest in spatial and temporal variation of air pollution and its association with weather conditions. We presented the spatial and temporal variation of Air Pollution Index (API) and examined the associations between API and meteorological factors during 2001-2011 in Guangzhou, China. A Seasonal-Trend Decomposition Procedure Based on Loess (STL) was used to decompose API. Wavelet analyses were performed to examine the relationships between API and several meteorological factors. Air quality has improved since 2005. APIs were highly correlated among five monitoring stations, and there were substantial temporal variations. Timescale-dependent relationships were found between API and a variety of meteorological factors. Temperature, relative humidity, precipitation and wind speed were negatively correlated with API, while diurnal temperature range and atmospheric pressure were positively correlated with API in the annual cycle. Our findings should be taken into account when determining air quality forecasts and pollution control measures. PMID:24732883

Li, Li; Qian, Jun; Ou, Chun-Quan; Zhou, Ying-Xue; Guo, Cui; Guo, Yuming

2014-07-01

234

Performance of GEANT4 in dosimetry applications: Calculation of X-ray spectra and kerma-to-dose equivalent conversion coefficients  

International Nuclear Information System (INIS)

In order to validate the Geant4 toolkit for dosimetry applications, simulations were performed to calculate conversion coefficients h(10, ?) from air kerma free-in-air to personal dose equivalent Hp(10, ?). The simulations consisted of two parts: the production of X-rays with radiation qualities of narrow and wide spectra, and the interaction of radiation with ICRU tissue-equivalent and ISO water slab phantoms. The half-value layers of the X-ray spectra obtained by simulation were compared with experimental results. Mean energy, spectral resolution, half-value layers and conversion coefficients were compared with ISO reference values. The good agreement between results from simulation and reference data shows that the Geant4 is suitable for dosimetry applications which involve photons with energies in the range of ten to a few hundreds of keV

235

Elucidating inequality in Nubia: An examination of entheseal changes at Kerma (Sudan).  

Science.gov (United States)

Located 10 km south of the Third Cataract of the Nile River, the ancient city of Kerma was once capital to the second largest state in Africa. The Eastern Cemetery at Kerma (?4 km east of city center) encompasses 80+ hectares and was used over a period of 1,500 years (3,200-1,500 BC). Excavated in the early 20th century by George Reisner, the cemetery contained an estimated 20,000-40,000 individuals. Reisner classified these burials into multiple categories, including chiefs and human sacrifices, based on burial position and grave goods. This study investigates the skeletal embodiment of social inequality by examining variation in entheseal severity between the Kerma burial classifications. Seventeen entheses were examined using the Hawkey and Merbs (1995) scoring method (n?=?205 individuals); age, sex, and body size variables were considered by employing Mann-Whitney U tests and partial Spearman's correlations. This analysis suggests that significant differences in entheseal changes existed between select burial types. Specifically, "corridor sacrifices" had significantly higher rates of entheseal changes while "chiefs" and "subsidiary burials" had similar entheseal changes; furthermore, within these burial categories, males had higher entheseal scores despite body size controls. The elevated entheseal changes in the sacrificial burials may be due to an intensive agro-pastoral lifestyle or other demanding forms of manual labor. In conclusion, the disparity of entheseal markers between burial subgroups at Kerma might reflect a degree of social inequality within this state level society. This bioarchaeological research informs our understanding of socially-defined categories of persons as well as everyday life in Ancient Kerma. Am J Phys Anthropol, 2014. © 2014 Wiley Periodicals, Inc. PMID:25327628

Schrader, Sarah A

2014-10-18

236

Measured neutron carbon kerma factors from 14.1 MeV to 18 MeV  

International Nuclear Information System (INIS)

For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in the hydrogen abundance in these materials, the principal uncertainty is due to the kerma factors of carbon and oxygen. We have measured carbon kerma factor values of 0.183 +- 0.015 10-8 cGy cm2 and 0.210 +- 0.16 10-8 cGy cm2 at 14.1-MeV and 15-MeV neutron energy, respectively. A preliminary value of 0.297 +- 0.03 10-8 cGy cm2 has been determined at 17.9 MeV. A recent microscopic cross section measurement of the (n,n'3?) reaction in carbon at 14.1-MeV energy gives a kerma factor of 0.184 +- 0.019 108 cGy cm2 in agreement with the present result. 9 refs., 4 figs., 2 tabs

237

Measured neutron carbon kerma factors from 14.1 MeV to 18 MeV  

International Nuclear Information System (INIS)

For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in the hydrogen abundance in these materials, the principal uncertainty is due to the kerma factors of carbon and oxygen. We have measured carbon kerma factor values of 0.183+-0.015 10-8 cGy cm2 and 0.210+-0.016 10-8cGy cm2 at 14.1-MeV and 15-MeV neutron energy, respectively. A preliminary value of 0.297+-0.03 10-8cGy cm2 has been determined at 17.9 MeV. A recent microscopic cross section measurement of the (n,n'3?) reaction in carbon at 14.1-MeV energy gives a kerma factor of 0.184+-0.019 10-8cGy cm2 in agreement with the present result

238

Measurement of the tissue to A-150 tissue equivalent plastic kerma ratio at two p(66)Be neutron therapy facilities.  

Science.gov (United States)

The ICRU tissue to A-150 tissue equivalent plastic kerma ratio is needed for neutron therapy dosimetry. The current ICRU protocol for neutron dosimetry recommends using a common conversion factor of 0.95 at all high-energy neutron therapy facilities. In an effort to determine facility specific ICRU tissue to A-150 plastic kerma ratios, an experimental approach was pursued. Four low pressure proportional counters that differed in wall materials (i.e. A-150, carbon, zirconium and zirconium-oxide) were used as dosimeters and integral kerma ratios were determined directly in the clinical beam. Measurements were performed at two p(66)Be facilities: iThemba LABS near Cape Town and Fermilab near Chicago. At the iThemba facility the clinical neutron beam is routinely filtered by a flattening and hardening filter combination. The influence of beam filtration on the kerma ratio was evaluated. Using two recent gas-to-wall dose conversion factor (r(m,g) value) evaluations a mean ICRU tissue to A-150 plastic kerma ratio of 0.93 +/- 0.05 was determined for the clinical beam at iThemba LABS. The respective value for the Fermilab beam is 0.95 +/- 0.05. The experimentally determined ICRU tissue to A-150 plastic kerma ratios for the two clinical beams are in agreement with theoretical evaluations. Beam filtration reduces the kerma ratio by 3 +/- 2%. PMID:12812451

Langen, K M; Binnss, P J; Schreuder, A N; Lennox, A J; Deluca, P M

2003-05-21

239

The EVA code; macroscopic modeling of radio emission from air showers based on full MC simulations including a realistic index of refraction  

Science.gov (United States)

A comprehensive overview of the newly developed EVA-code is given. To take into account Cherenkov effects and include realistic showers in combination with shower-to-shower fluctuations we have developed the EVA code (Electric fields, using a Variable index of refraction in Air shower simulations code). The EVA-code is based on histograms obtained from a full Monte-Carlo CONEX simulation to calculate radio emission from cosmic-ray-induced air showers. The EVA-code makes use of the finite dimensions of the particle distributions to overcome the divergences in the fields due to Cherenkov effects without making any approximations.

de Vries, Krijn D.; Scholten, Olaf; Werner, Klaus

2013-05-01

240

Using daily air temperature thresholds to evaluate snow melting occurrence and amount on Alpine glaciers by T-index models: the case study of the Forni Glacier (Italy)  

Science.gov (United States)

Glacier melt conditions (i.e., null surface temperature and positive energy budget) can be assessed by analyzing data acquired by a supraglacial automatic weather station (AWS), such as the station installed on the surface of Forni Glacier (Italian Alps). When an AWS is not present, the assessment of actual melt conditions and the evaluation of the melt amount is more difficult and simple methods based on T-index (or degree days) models are generally applied. These models require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 0 °C. In this paper, we applied both energy budget and T-index approaches with the aim of solving this issue. We start by distinguishing between the occurrence of snowmelt and the reduction in snow depth due to actual ablation (from snow depth data recorded by a sonic ranger). Then we find the daily average temperature thresholds (by analyzing temperature data acquired by an AWS on Forni Glacier) which, on the one hand, best capture the occurrence of significant snowmelt conditions and, on the other, make it possible, using the T-index, to quantify the actual snow ablation amount. Finally we investigated the applicability of the mean tropospheric lapse rate to reproduce air temperature conditions at the glacier surface starting from data acquired by weather stations located outside the glacier area. We found that the mean tropospheric lapse rate allows for a good and reliable reconstruction of glacier air temperatures and that the choice of an appropriate temperature threshold in T-index models is a very important issue. From our study, the application of the +0.5 °C temperature threshold allows for a consistent quantification of snow ablation while, instead, for detecting the beginning of the snow melting processes a suitable threshold has proven to be at least -4.6 °C.

Senese, A.; Maugeri, M.; Vuillermoz, E.; Smiraglia, C.; Diolaiuti, G.

2014-10-01

 
 
 
 
241

Studies on mass attenuation coefficient, mass energy absorption coefficient and kerma of some vitamins  

International Nuclear Information System (INIS)

Highlights: ? Kerma is essential for nuclear medicine, diagnostics and radiation dosimeter. ? The values of ?m and ?e/? depends on the photon energy and chemical content of vitamins. ? New experiments should be performed to study physical parameters of biomolecules. -- Abstract: The mass attenuation coefficients for some vitamins (retinol, beta-carotene, thiamine, riboflavin, niacinamide, pantothenic acid, pyridoxine, biotin, folic acid, cyanocobalamin, ascorbic acid, cholecalciferol, alpha-tocopherol, ketamine, hesperidin) were determined experimentally and theoretically at 356.61, 661.66, 1250 and 1408.01 keV photon energies by using a NaI(Tl) scintillation detector. Also, the mass energy absorption coefficients and kerma have been calculated. The calculated values were compared with the semi-empirical values for vitamins.

242

A simple device for the measurement of kerma based on commercial PIN photo diodes  

Science.gov (United States)

The development of a dose reader for the measurement of the radiation dose from neutron and ionizing radiation is presented. The dose reader (kerma meter) is using as active element commercial PIN diodes with long base, which can provide a maximal dependence of the lifetime of minority carriers from the absorbed dose. We consider a simple theory of PIN diodes for the role of the kerma meter and discuss the idea for optimization of the calibration procedure. The characteristics of the dosimeter were measured for a few types of commercial diodes. The device can be useful for many practical tasks of control for radiation environments in the environment, nuclear physics and for industrial application.

Kushpil, V.; Kushpil, S.; Huna, Z.

2012-04-01

243

Calculated neutron KERMA factors based on the LLNL ENDL data file. Volume 27  

International Nuclear Information System (INIS)

Neutron KERMA factors calculated from the LLNL ENDL data file are tabulated for 15 composite materials and for the isotopes or elements in the ENDL file from Z = 1 to Z = 29. The incident neutron energies range from 1.882 x 10-5 to 20. MeV for the composite materials and from 1.30 x 10-9 to 20. MeV for the isotopes and elements

244

Studies on effective atomic number, electron density and kerma for some fatty acids and carbohydrates  

DEFF Research Database (Denmark)

The effective atomic number, Z(eff), the effective electron density, N-el, and kerma have been calculated for some fatty acids and carbohydrates for photon interaction in the extended energy range from 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. The significant variation of Z(eff) and N-el is due to the variations in the dominance of different interaction processes in different energy regions. The maximum values of Z(eff) and N-el are found in the low-energy range, where photoelectric absorption is the main interaction process. The minimum values of Z(eff) and N-el are found at intermediate energies, typically 0.05 MeV kerma than fatty acids in the low-energy region, where photoelectric absorption dominates. In contrast, fatty acids have a larger kerma than carbohydrates in the MeV range, where Compton scattering is the main interaction process.

Manohara, S.R.; Hanagodimath, S.M.

2008-01-01

245

Determination of mass attenuation coefficients, effective atomic and electron numbers, mean free paths and kermas for PbO, barite and some boron ores  

Energy Technology Data Exchange (ETDEWEB)

The total mass attenuation coefficients, {mu}{sub m}, for PbO, barite, colemanite, tincal and ulexite were determined at 80.1, 302.9, 356.0, 661.7 and 1250.0 keV photon energies by using NaI (Tl) scintillation detector. Effective atomic number, Z{sub eff}, effective electron number, N{sub eff}, total atomic cross-section, {sigma}{sub t}, total electronic cross-section, {sigma}{sub e}, mean free path, mfp, and kerma relative to air were determined experimentally and theoretically. The theoretical mass attenuation coefficients were estimated using mixture rule. The calculated values were compared with the experimental values for all samples.

Un, A., E-mail: ademun25@yahoo.com [Agri Ibrahim Cecen University, Faculty of Arts and Sciences, Department of Physics, 04100 Agri (Turkey); Sahin, Y. [Atatuerk University, Faculty of Sciences, Department of Physics, 25240 Erzurum (Turkey)

2011-07-01

246

A new multipollutant, no-threshold air quality health index based on short-term associations observed in daily time-series analyses.  

Science.gov (United States)

Air quality indices currently in use have been criticized because they do not capture additive effects of multiple pollutants, or reflect the apparent no-threshold concentration-response relationship between air pollution and health. We propose a new air quality health index (AQHI), constructed as the sum of excess mortality risk associated with individual pollutants from a time-series analysis of air pollution and mortality in Canadian cities, adjusted to a 0-10 scale, and calculated hourly on the basis of trailing 3-hr average pollutant concentrations. Extensive sensitivity analyses were conducted using alternative combinations of pollutants from single and multipollutant models. All formulations considered produced frequency distributions of the daily maximum AQHI that were right-skewed, with modal values of 3 or 4, and less than 10% of values at 7 or above on the 10-point scale. In the absence of a gold standard and given the uncertainty in how to best reflect the mix of pollutants, we recommend a formulation based on associations of nitrogen dioxide, ozone, and particulate matter of median aerodynamic diameter less than 2.5 microm with mortality from single-pollutant models. Further sensitivity analyses revealed good agreement of this formulation with others based on alternative sources of coefficients drawn from published studies of mortality and morbidity. These analyses provide evidence that the AQHI represents a valid approach to formulating an index with the objective of allowing people to judge the relative probability of experiencing adverse health effects from day to day. Together with health messages and a graphic display, the AQHI scale appears promising as an air quality risk communication tool. PMID:18376646

Stieb, David M; Burnett, Richard T; Smith-Doiron, Marc; Brion, Orly; Shin, Hwashin Hyun; Economou, Vanita

2008-03-01

247

Measurement of air-refractive-index fluctuation from frequency change using a phase modulation homodyne interferometer and an external cavity laser diode  

International Nuclear Information System (INIS)

We present a method for air-refractive-index (nair) fluctuation measurement using a laser interferometer. The method is based on a combination of a phase modulation homodyne interferometer (PMHI), an external cavity laser diode (ECLD) and an ultralow thermal expansion material (ULTEM). The PMHI utilizes a Michelson interferometer which is constructed on the ULTEM plate under the condition of an air temperature fluctuation of less than 10 mK, so that the optical path change or the air-refractive-index fluctuation (?nair) caused by the thermal disturbance can be neglected. Meanwhile, the ECLD is controlled by adjusting its frequency to track some of the dark fringes of the interferometer, so that ?nair can be derived from the ECLD frequency change. The uncertainty of the ?nair measurement in the experiment is of 10?8 order. However, it will be possible to decrease the uncertainty to 10?9 or less if the signal-to-noise ratio (SNR) of the control system is improved

248

National air toxics information clearinghouse: Bibliography of selected reports and federal register notices related to air toxics. Index, 1992. Final report  

International Nuclear Information System (INIS)

The purpose of the bibliography is to provide State and local agencies with citations to report and Federal Register notices useful to them in developing and operating air toxics control programs. The reports selected for this bibliography were published by the following agencies: U.S. EPA, NAS, NCI, NIEHS, NTP, NIOSH, ATSDR, CPSC, and WHO, including the International Agency for Research on Cancer. Relevant reports published by various State and local agencies are also included in this edition. The edition of the bibliography updates the cumulative bibliography previously published by the National Air Toxics Information Clearinghouse, Bibliography of Selected Reports and Federal Register Notices Related to Air Toxics, July 1991. The citations selected for this year were compiled from sources available through January 31, 1992

249

Exposure and air-kerma standards for cobalt-60 gamma rays  

International Nuclear Information System (INIS)

This paper deals with the measurements made with the cavity chamber standards of LNMRI performed under the actual experimental conditions at the LNMRI and some measurements done under the Bureau International des Poids et Mesures (BIPM) irradiation and measurement conditions. For the correction factors needed to derive the absolute value of exposure the numerical values have been obtained both at the BIPM and LNMRI. Finally it is presented the results of a comparison made between the LNMRI chambers with the BIPM standard as well as with the values obtained from previous comparisons involving the standards of several national laboratories with the BIPM standard. (author)

250

Doses monitoring in radiology: calibration of air kerma-area product (PKA) meters  

International Nuclear Information System (INIS)

Materials and methods: different qualities of both incident and transmitted beams were utilized in conditions similar to a clinical setting, analyzing the influence from the reference dosimeter, from the distance between meters, from the filtration and from the average beam energy. Calibrations were performed directly against a standard 30 cm3 cylindrical chamber or a parallel-plate monitor chamber, and indirectly against the PDC meter. Results: the lowest energy dependence was observed for transmitted beams. The cross calibration between the Diamentor E2 and the PDC meters, and the PDC presented the greatest propagation of uncertainties. Conclusion: the calibration coefficient of the PDC meter showed to be more stable with voltage, while the Diamentor E2 calibration coefficient was more variable. On the other hand, the PDC meter presented greater uncertainty in readings (5.0%) than with the use of the monitor chamber (3.5%) as a reference. (author)

251

An EGSnrc investigation of cavity theory for ion chambers measuring air kerma  

International Nuclear Information System (INIS)

The EGSnrc system is used to compare the response of an aluminum-walled thimble chamber to that of a graphite-walled thimble chamber for a 60Co beam. When compared to previous experimental results, the EGSnrc values of the ratios of chamber response differ by as much as 0.7% from the experiment. However, it is shown that this difference can be more than accounted for by switching from using the graphite mean excitation energy of 78 eV used in dosimetry protocols to the value of 86.8 eV suggested by more recent stopping-power experiments. This suggests that the uncertainty analysis of Monte Carlo results must be done more carefully, by taking into account uncertainties in the underlying basic data such as the electron and photon cross sections. In comparison to Spencer-Attix cavity theory for a thick-walled ion chamber, the Monte Carlo calculated values of the chamber response differ from the expected ones by 0.15% and 0.01% for the graphite and aluminum chambers, respectively, which are comparable to previously reported values for the Spencer-Attix correction factors. EGSnrc is also used to investigate the effect on the chamber response of thin dag layers on the inside of the aluminum wall. There is good agreement between the calculated and measured changes in chamber response versus the thickness of the dag. The results are compared to the predictions of the Almond-Svensson extension of cavity theory and show that the theory does not correctly predict the the theory does not correctly predict the chamber response in the presence of thin dag layers. This finding is in agreement with previously reported experimental results. It is demonstrated that the values of ?, the fraction of ionizations in the gas arising from electrons generated in the dag layer, used in the theory, are not the source of the disagreement

252

Air  

International Nuclear Information System (INIS)

In recent years several regulations and standards for air quality and limits for air pollution were issued or are in preparation by the European Union, which have severe influence on the environmental monitoring and legislation in Austria. This chapter of the environmental control report of Austria gives an overview about the legal situation of air pollution control in the European Union and in specific the legal situation in Austria. It gives a comprehensive inventory of air pollution measurements for the whole area of Austria of total suspended particulates, ozone, volatile organic compounds, nitrogen oxides, sulfur dioxide, carbon monoxide, heavy metals, benzene, dioxin, polycyclic aromatic hydrocarbons and eutrophication. For each of these pollutants the measured emission values throughout Austria are given in tables and geographical charts, the environmental impact is discussed, statistical data and time series of the emission sources are given and legal regulations and measures for an effective environmental pollution control are discussed. In particular the impact of fossil-fuel power plants on the air pollution is analyzed. (a.n.)

253

Scattering study at free air ionization chamber diaphragm  

International Nuclear Information System (INIS)

The maim of this work consisted in the assessment of the correction factor for air kerma, due to scattered radiation in the diaphragm of the free-air ionization chamber model 481. LNMRl measurements were made to acquire x-ray spectra corresponding to the Qualities RQR-M, described in IEC 61627 standards (2005). These spectra were used as input data in the MC simulations. The operational range of energy spectra provide up to 35 keV. This energy range is typically used in diagnostic radiology, although there is not primary standard for air kerma. The determination of this factor is a fundamental process in the primary standardization of the air kerma. These factors were obtained by computer simulation using the Penelope code. The results are kRQR-M1=0,9946, kRQR-M2=0,9932, kRQR-M3=0,9978 and kRQR-M4=0,9885; with uncertainties of 0,007 and coverage factor equal to 2. lt can be concluded that, with respect to the diaphragm, the chamber can be used in the primary standard of air kerma. (author)

254

Doses monitoring in radiology: calibration of air kerma-area product (PKA) meters / Monitoração de doses em radiologia: a calibração de medidores do produto kerma-área (PKA)  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Objective The authors have sought to study the calibration of a clinical PKA meter (Diamentor E2) and a calibrator for clinical meters (PDC) in the Laboratory of Ionizing Radiation Metrology at Instituto de Energia e Ambiente - Universidade de São Paulo. Materials and Methods Different qualities [...] of both incident and transmitted beams were utilized in conditions similar to a clinical setting, analyzing the influence from the reference dosimeter, from the distance between meters, from the filtration and from the average beam energy. Calibrations were performed directly against a standard 30 cm3 cylindrical chamber or a parallel-plate monitor chamber, and indirectly against the PDC meter. Results The lowest energy dependence was observed for transmitted beams. The cross calibration between the Diamentor E2 and the PDC meters, and the PDC presented the greatest propagation of uncertainties. Conclusion The calibration coefficient of the PDC meter showed to be more stable with voltage, while the Diamentor E2 calibration coefficient was more variable. On the other hand, the PDC meter presented greater uncertainty in readings (5.0%) than with the use of the monitor chamber (3.5%) as a reference.

Ricardo Andrade, Terini; Maria Carolina de Santana, Campelo; Jose Neres de, Almeida Jr.; Silvio Bruni, Herdade; Marco Aurelio Guedes, Pereira.

2013-12-01

255

KAOS-V code: An evaluation tool for neutron kerma factors and other nuclear responses  

International Nuclear Information System (INIS)

The accurate evaluation of neutron fluence-to-kerma factors from microscopic nuclear data is the subject of this report. The algorithms developed for this purpose combine in a consistent manner the two basic methods for computing kerma factors, namely kinematics and direct energy balance. These algorithms are implemented in the code KAOS-V which was used as the main evaluation tool to construct the response function library KAOS/LIB-V. KAOS-V uses data from the evaluated nuclear data files ENDF/B/V. Auxiliary nuclear data bases, e.g., the Japanese evaluated nuclear data library JENDL-2 can be used as a source of isotopic cross sections when these data are not provided in ENDF/B-V files for a natural element. These are needed mainly to estimate average quantities such as effective Q-values for the natural element. The code has the ability to compare the different results which aids in the choice of a consistent set of algorithms to evaluate kerma factors. Data in ENDF/B-IV and ENDF/B-V format can be processed. For resonance treatment, the code has the ability to access NJOY and NPTXS interface files in formatted or binary forms. No input instructions are necessary to run the code interactively. The user can simply respond to the interactive messages sent by the code if an INPUT file is absent. An INPUT file is automatically generated following an interactive run, and can be edited and used to rerun or produce different results. Grouped and point output data can be produced along with graphic representation. These features are instrumental in detecting and understanding energy balance deficiencies and other problems in the nuclear data files. 60 refs., 4 figs

256

Absorbed Dose and Collision Kerma Relationship for High-Energy Photons  

Science.gov (United States)

Historically, exposure has been used as an important quantity to specify X- or (gamma)- ray beams. For any photon beam the energy fluence is proportional to the exposure. Exposure can be calculated and/or measured if the spectrum of the beam is known and charged particle equilibrium (CPE) exists. For low energy photons (up to approximately 1 MeV), due to the existence of CPE, absorbed dose (D) is equal to the collision kerma (K(,c)). For megavoltage photons this equality is lost due to CPE failure, which also restricts the measurement of exposure. It is possible, though, to find a relationship between the absorbed dose and collision kerma when transient charged particle equilibrium (TCPE) exists. This basic idea was originally proposed by Roesch in 1958 and its refinement has been discussed by Attix in 1979 and 1983. The modified Roesch's formula which enables us to measure exposure even for high-energy photons is given by D = (beta) K(,c) (TURNEQ) K(,c) (1 + (mu)' ) where (mu)' is the effective linear attenuation coefficient and is the mean distance the secondary electrons carry kinetic energy in the direction of the photon beam while depositing it as absorbed dose. The symbol (beta) is the quotient of the absorbed dose and the collision kerma. The importance of Roesch's formula has been recognized and used implicitly in the recent dosimetry protocol of the AAPM (Task Group 21). However, the value used in the protocol is based on theoretical calculations which do not include photon scattering. As a result of the present effort the parameters (mu)' and have been determined experimentally, for the first time. The dependence of (beta) on several factors has been studied and (beta) has been obtained including the effects of scattering. Calculations were also performed for several photon energies and materials, using the Roesch method, which does not include photon scattering effects. Comparisons of measured and calculated values of show reasonable agreement.

Sibata, Claudio Hissao

257

The variability in kerma output and radiation quality of medical diagnostic x-ray units  

International Nuclear Information System (INIS)

The use of diagnostic x-ray tubes results in an increased roughness of the anode surface. This effect of tube ageing increases the inherent filtration of the x-ray tube, hereby reducing kerma output and changing radiation quality. To study this effect, used rotating anodes were collected; the surface profiles and surface roughness of 8 focal tracks were determined. The surface profiles were then used to calculate x-ray spectra using a computer code. The results indicate that an increased roughness induces an additional filtration in the tungsten anode. The roughest surface (Ra=5.22 ?m) yields a mean additional absorber thickness in direction of the x-ray beam of about 18 ?m with a corresponding loss in kerma output of about 30 % at 70 kV. The effects on mean photon energy and HVL are rather small but highest around 70 kV and lowest at 140 kV. This is due to the K-edge in the attenuation coefficients of tungsten at 69.5 keV. To study the influence of tube ageing on beam quality with clinical x-ray units, kerma measurements were made for 19 samples as to determine attenuation curves. A fit method for the determination of total filtration including the effects of anode surface deterioration was devised. The thicknesses of the tungsten layers obtained using this method vary from 2.43 ?m to 11.89 ?m with an associated surface roughness Ra from 1.5 to 4.5 ?m corresponding very well to the thicknesses of the additional absorbing layers determined for rough anodes. A detrs determined for rough anodes. A determination of additional filtration in terms of an equivalent aluminium filter gave thicknesses from 0.34 to 1.72 mm aluminium. The results showed that the effects of tube ageing on the x-rays could be described by an additional filtration of aluminium. (author)

258

Determination of the kerma factors for 14-MeV neutrons in TEP, C, Mg, and Fe  

International Nuclear Information System (INIS)

Kerma factors, defined as kerma per unit neutron fluence, for 14 MeV D-T neutrons in tissue equivalent plastic, C, Mg and Fe were determined in this work. Rossi-type TEP, C, Mg and Fe walled proportional counters filled with propane-based tissue-equivalent gas and Ar gas at low pressure were employed to measure the energy deposition in the counters. Based upon the concept of Crossers, Insiders, Starters and Stoppers (CISS) developed by Caswell, a theoretical model was used for the analysis of energy deposition in spherical detectors. Because of the detailed analyses the uncertainties in the kerma factors as obtained in this work are evaluated to be between 8 to 11% which are significantly lower than those reported previously for experimental measurements

259

Local control related to Kerma rate in T2/T3 breast cancers treated by external irradiation and brachytherapy  

International Nuclear Information System (INIS)

Introduction: This study was conducted to determine the impact of the brachytherapy parameters on local control in patients treated with irradiation alone for breast cancer. Material and Methods: From 1985 to 1991, 241 patients with T2 (187pts) T3 (54 pts) N0 (196 pts) N1 (45 pts) M0 breast cancer have been treated with the combination of external irradiation and brachytherapy boost without surgery. Doses delivered to the whole breast and the regional nodes were 54 Gy and 50 Gy respectively (1.8 or 2 Gy/fraction, 5 fr/wk). Twenty Gy were then boosted to the primary tumor, according to the tumor shrinkage, by Ir 192 implants. Plastic tubes and rigid needles were used in 85 % and 15 % of the cases respectively. The brachytherapy boost was delivered at 85% of the basal dose rate (Reference dose rate) according to the Paris system. In some instances, dose distribution heterogeneities were observed leading to the choice of another reference isodose. Results: Median follow-up for the entire population was 75 months (9-122). Local control at 6 years follow-up for T2 and T3 was 76% (+/- 6%). Age, SBR grading and steroid receptors were found to be significantly correlated to local control. The role of the brachytherapy boost was analysed. Reference dose rate was not found to have any impact on local control, (? 0.6 vs > 0.6 Gy/h). This result was perhaps linked to the particular choice of the reference isodose. To avoid this bias we have evaluated the impact of the Kerma ratve evaluated the impact of the Kerma rate (Activity x Time x total length) on local control. Median kerma rate was 8600 ?Gy h-1 cm-1 m2 (2200-16600). Local control rate for T2 at 6 years was 77% +/- 8% (Kerma >8600) and 73 %+/- 10% (Kerma ? 8600). For T3 local control rate was 82% +/-12% (Kerma >8600) and 37 % +/- 34 % (p<0.0002). Conclusion: This study demonstrated that the impact of brachytherapy on local control was better evaluated by the Kerma rate than by the reference dose rate. Whereas the basal dose rate cannot be changed after the application, it may be possible to adapt the kerma parameters (activity, length, treatment duration) in order to achieve a more efficient treatment

260

W/sub n/ and neutron kerma for methane-based tissue-equivalent gas  

International Nuclear Information System (INIS)

The principal dosimeter used to determine the absorbed dose of neutrons employed in radiobiology and radiotherapy is the homogeneous tissue-equivalent (TE) ionization chamber. A methane-based TE gas mixture is most commonly used in the chamber cavity. This instrument is used to measure the charge liberated in the gas by the secondary charged particles set in motion by the neutrons. Conversion of this charge to absorbed dose requires knowledge of W/sub n/, the mean energy expended to form an ion pair in the gas by the initial spectra of secondary particles produced by the neutrons. The computation of W/sub n/ requires that secondary charged particle spectra calculated from neutron interaction cross sections and energetics be employed for each neutron energy used, as is done in this report. The computation of W/sub n/ also requires that experimental data on W for each type of secondary charged particle be available. Revision puts them in sufficient agreement with the other data that they are here given equal weight in the evaluations of W. Further, this report discusses the relative kermas contributed by the various types of charged particles. By combining computed charged particle spectra with the evaluations of W, the number of ion pairs produced in the gas by each type of charged particle is derived, from which W/sub n/ is computed as the quotient of the total kerma by the total number of ion pairs

 
 
 
 
261

Geomagnetic activity related NOx enhancements and polar surface air temperature variability in a chemistry climate model: modulation of the NAM index  

Directory of Open Access Journals (Sweden)

Full Text Available The atmospheric chemistry general circulation model ECHAM5/MESSy is used to simulate polar surface air temperature effects of geomagnetic activity variations. A transient model simulation was performed for the years 1960–2004 and is shown to develop polar surface air temperature patterns that depend on geomagnetic activity strength, similar to previous studies. In order to eliminate influencing factors such as sea surface temperatures (SST or UV variations, two nine-year long simulations were carried out, with strong and weak geomagnetic activity, respectively, while all other boundary conditions were held to year 2000 levels. Statistically significant temperature effects that were observed in previous reanalysis and model results are also obtained from this set of simulations, suggesting that such patterns are indeed related to geomagnetic activity. In the model, strong geomagnetic activity and the associated NOx enhancements lead to polar stratospheric ozone loss. Compared with the simulation with weak geomagnetic activity, the ozone loss causes a decrease in ozone radiative cooling and thus a temperature increase in the polar winter mesosphere. Similar to previous studies, a cooling is found below the stratopause, which other authors have attributed to a decrease in the mean meridional circulation. In the polar stratosphere this leads to a more stable vortex. A strong (weak Northern Hemisphere vortex is known to be associated with a positive (negative Northern Annular Mode (NAM index; our simulations exhibit a positive NAM index for strong geomagnetic activity, and a negative NAM for weak geomagnetic activity. Such NAM anomalies have been shown to propagate to the surface, and this is also seen in the model simulations. NAM anomalies are known to lead to specific surface temperature anomalies: a positive NAM is associated with warmer than average northern Eurasia and colder than average eastern North Atlantic. This is also the case in our simulation. Our simulations suggest a link between geomagnetic activity, ozone loss, stratospheric cooling, the NAM, and surface temperature variability.

P. Jöckel

2010-12-01

262

High NDVI and Potential Canopy Photosynthesis of South American Subtropical Forests despite Seasonal Changes in Leaf Area Index and Air Temperature  

Directory of Open Access Journals (Sweden)

Full Text Available The canopy photosynthesis and carbon balance of the subtropical forests are not well studied compared to temperate and tropical forest ecosystems. The main objective of this study was to assess the seasonal dynamics of Normalized Difference Vegetation Index (NDVI and potential canopy photosynthesis in relation to seasonal changes in leaf area index (LAI, chlorophyll concentration, and air temperatures of NE Argentina subtropical forests throughout the year. We included in the analysis several tree plantations (Pinus, Eucalyptus and Araucaria species that are known to have high productivity. Field studies in native forests and tree plantations were conducted; stem growth rates, LAI and leaf chlorophyll concentration were measured. MODIS satellite-derived LAI (1 km SIN Grid and NDVI (250m SIN Grid from February 2000 to 2012 were used as a proxy of seasonal dynamics of potential photosynthetic activity at the stand level. The remote sensing LAI of the subtropical forests decreased every year from 6 to 5 during the cold season, similar to field LAI measurements, when temperatures were 10 °C lower than during the summer. The yearly maximum NDVI values were observed during a few months in autumn and spring (March through May and November, respectively because high and low air temperatures may have a small detrimental effect on photosynthetic activity during both the warm and the cold seasons. Leaf chlorophyll concentration was higher during the cold season than the warm season which may have a compensatory effect on the seasonal variation of the NDVI values. The NDVI of the subtropical forest stands remained high and fairly constant throughout the year (the intra-annual coefficient of variation was 1.9%, and were comparable to the values of high-yield tree plantations. These results suggest that the humid subtropical forests in NE Argentina potentially could maintain high canopy photosynthetic activity throughout the year and thus this ecosystem may be a large carbon sink.

Piedad M. Cristiano

2014-02-01

263

Air Pollution Quality Index (AQI and Density of PM1, PM2.5 and PM10 in the Air of Qom  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives: Air pollution has broad social, economical, political and technical aspects. one of the major issues in this regard is taking measures to prevent its increase. Since suspended particles are among the standard pollutants, the present study was carried out with the aim of measuring the amounts of these particles.Methods: In the present study, the suspended particles ( PM1, PM2.5 and PM10 were measured at two sites in Qom city. For each of them, 60 samples were selected with the Enviro Check during five consecutive months during summer (2 months and fall.Results: During sampling, PM10 in the period between October 22'th to November 22nd 2007 had the maximum amount with the mean of 117µg/m3 and in the period between September 22'th to October 22nd 2007 it had the minimum amount with the mean of 83µg/m3. PM2.5 in the period between November 22nd to December 22nd 2007 with the mean of 33µg/m3 had the maximum amount and in the period between July 22nd to October 22nd 2007 it had the minimum amount with the mean of 8µg/m3. Conclusion: Based on the findings of this study, the densities of suspended particles PM1, PM2.5 and PM10 were below the standard levels on most occasions. The amounts of AQI for them were normal and acceptable.

Safdari M

2011-06-01

264

A Distributed Air Index Based on Maximum Boundary Rectangle over Grid-Cells for Wireless Non-Flat Spatial Data Broadcast  

Directory of Open Access Journals (Sweden)

Full Text Available In the pervasive computing environment using smart devices equipped with various sensors, a wireless data broadcasting system for spatial data items is a natural way to efficiently provide a location dependent information service, regardless of the number of clients. A non-flat wireless broadcast system can support the clients in accessing quickly their preferred data items by disseminating the preferred data items more frequently than regular data on the wireless channel. To efficiently support the processing of spatial window queries in a non-flat wireless data broadcasting system, we propose a distributed air index based on a maximum boundary rectangle (MaxBR over grid-cells (abbreviated DAIM, which uses MaxBRs for filtering out hot data items on the wireless channel. Unlike the existing index that repeats regular data items in close proximity to hot items at same frequency as hot data items in a broadcast cycle, DAIM makes it possible to repeat only hot data items in a cycle and reduces the length of the broadcast cycle. Consequently, DAIM helps the clients access the desired items quickly, improves the access time, and reduces energy consumption. In addition, a MaxBR helps the clients decide whether they have to access regular data items or not. Simulation studies show the proposed DAIM outperforms existing schemes with respect to the access time and energy consumption.

Seokjin Im

2014-06-01

265

A Hybrid Method to Improve Forecasting Accuracy - An Introduction of a Day of the Week Index for Air Cargo Weight Data  

Directory of Open Access Journals (Sweden)

Full Text Available Air cargo loading weight forecasting is an important factor for managers in the aviation industry because revenue is dependent on the amount of weight loaded. In this paper, we propose a new method to improve forecasting accuracy and confirm them by the numerical example. Focusing that the equation of exponential smoothing method(ESM is equivalent to (1,1 order ARMA model equation, a new method of estimation of smoothing constant in exponential smoothing method is proposed before by us which satisfies minimum variance of forecasting error. Generally, smoothing constant is selected arbitrarily. But in this paper, we utilize above stated theoretical solution. Firstly, we make estimation of ARMA model parameter and then estimate smoothing constants. Thus theoretical solution is derived in a simple way and it may be utilized in various fields. Combining the trend removing method with this method, we aim to improve forecasting accuracy. Furthermore, “a day of the week index” is newly introduced for the daily air cargo weight data and we have obtained good result. The effectiveness of this method should be examined in various cases.

Tatsuhiro Kuroda

2012-11-01

266

Tissue kerma vs distance relationships for initial nuclear radiation from the atomic devices detonated over Hiroshima and Nagasaki  

International Nuclear Information System (INIS)

Initial nuclear radiation is comprised of prompt neutrons and prompt primary gammas from an exploding nuclear device, prompt secondary gammas produced by neutron interactions in the environment, and delayed neutrons and delayed fission-product gammas from the fireball formed after the nuclear device explodes. These various components must all be considered in establishing tissue kerma vs distance relationships which describe the decrease of initial nuclear radiation with distance in Hiroshima and in Nagasaki. The tissue kerma at ground evel from delayed fission-product gammas and delayed neutrons was investigated using the NUIDEA code developed by Science Applications, Inc. This code incorporates very detailed models which can take into account such features as the rise of the fireball, the rapid radioactive decay of fission products in it, and the perturbation of the atmosphere by the explosion. Tissue kerma vs distance relationships obtained by summing results of these current state-of-the-art calculations will be discussed. Our results clearly show that the prompt secondary gammas and delayed fission-product gammas are the dominant components of total tissue kerma from initial nuclear radiation in the cases of the atomic (or pure-fission) devices detonated over Hiroshima and Nagasaki

267

Effect of the new ASTM E 722-93 (Si) Kerma displacement data on reactor neutron dosimetry  

International Nuclear Information System (INIS)

Studies on hardening performed with PROSPERO and CALIBAN reactors require dosimetry in order to measure the 1 MeV (Si) equivalent neutron fluence, either with activation detectors, or with PIN (Si) diodes. Taking into account the latest ASTM E 722-93 (Si) Kerma displacement data enhances the accuracy and consistency of the results. (orig.)

268

Air pollution reduction with respect to the conversion of biomass into electricity and heat. Emission and cost indexes  

International Nuclear Information System (INIS)

Although biomass conversion is considered to be a CO2-free method of producing electricity and heat other emissions have to be taken into account: SO2, NOx, HCl, HF, Hg, Cd, dusts, etc. The aim of the study on the title subject is to support the Dutch Ministry of Housing, Planning and Environment (VROM) in the determination of feasible emission standards for bioconversion installations. The Centre for Energy conservation and clean technology (CE) compiled information on the costs for flue gas purification for different degrees of purification. Because of the fact that the composition of flue gases strongly depends on the biomass flow and the applied conversion technique, both biomass flows and conversion techniques must be distinguished. The following biomass conversion techniques were studied: large-scale combustion of wood wastes and sludges, large-scale gasification of wood wastes, cocombustion of wood wastes and sludges, small-scale combustion of wood wastes and chicken manure, small-scale gasification of wood wastes, and fermentation of wastes from vegetables, fruits and gardens. For each combination it is determined what the emissions are in case of a minimal flue gas purification, what the emissions are and how much additional costs are involved in case the regulations in the BLA (decree on air pollution of waste incineration) are taken into account, and what the emissions are and how much additional costs are involved for a number of levels in between the two for a number of levels in between the two fore-mentioned cases. refs

269

Geomagnetic activity related NOx enhancements and polar surface air temperature variability in a chemistry climate model: modulation of the NAM index  

Directory of Open Access Journals (Sweden)

Full Text Available The atmospheric chemistry general circulation model ECHAM5/MESSy is used to simulate polar surface air temperature effects of geomagnetic activity variations. A transient model simulation was performed for the years 1960–2004 and is shown to develop polar surface air temperature patterns that depend on geomagnetic activity strength, similar to previous studies. In order to eliminate influencing factors such as sea surface temperatures (SST or UV variations, two nine-year long simulations were carried out, with strong and weak geomagnetic activity, respectively, while all other boundary conditions were held to year 2000 levels. Statistically significant temperature effects that were observed in previous reanalysis and model results are also obtained from this set of simulations, suggesting that such patterns are indeed related to geomagnetic activity. In the model, strong geomagnetic activity and the associated NOx (= NO + NO2 enhancements lead to polar stratospheric ozone loss. Compared with the simulation with weak geomagnetic activity, the ozone loss causes a decrease in ozone radiative cooling and thus a temperature increase in the polar winter mesosphere. Similar to previous studies, a cooling is found below the stratopause, which other authors have attributed to a decrease in the mean meridional circulation. In the polar stratosphere this leads to a more stable vortex. A strong (weak Northern Hemisphere vortex is known to be associated with a positive (negative Northern Annular Mode (NAM index; our simulations exhibit a positive NAM index for strong geomagnetic activity, and a negative NAM for weak geomagnetic activity. Such NAM anomalies have been shown to propagate to the surface, and this is also seen in the model simulations. NAM anomalies are known to lead to specific surface temperature anomalies: a positive NAM is associated with warmer than average northern Eurasia and colder than average eastern North Atlantic. This is also the case in our simulation. Our simulations suggest a link between geomagnetic activity, ozone loss, stratospheric cooling, the NAM, and surface temperature variability. Further work is required to identify the precise cause and effect of the coupling between these regions.

P. Jöckel

2011-05-01

270

Paediatric entrance doses from exposure index in computed radiography  

International Nuclear Information System (INIS)

Over the last two years we have evaluated paediatric patient doses in projection radiography derived from exposure level (EL) in computed radiography (CR) in a large university hospital. Entrance surface air kerma (ESAK) for 3501 paediatric examinations was calculated from the EL, which is a dose index parameter related to the light emitted by the phosphor-stimulable plate, archived in the Digital Imaging and Communications in Medicine (DICOM) header of the images and automatically transferred to a database using custom-built dedicated software. Typical mean thicknesses for several age bands of paediatric patients was estimated to calculate ESAK from the EL values, using results of experimental measurements with phantoms for the typical x-ray beam qualities used in paediatric examinations. Mean/median ESAK values (in ?Gy) for the age bands of <1 year, 1-5 years, 6-10 years and 11-15 years have been obtained for chest without a bucky: 51/41, 57/34, 91/54 and 122/109; chest with a bucky (for only the last three age bands): 114/87, 129/105 and 219/170; abdomen: 119/91, 291/225, 756/600 and 1960/1508 and pelvis: 65/48, 455/314, 943/707 and 2261/1595. Sample sizes of clinical images used for the (indirect) measurements were 1724 for chest without a bucky, 799 for chest with a bucky, 337 for abdomen and 641 for pelvis. The methodology we describe could be applicable to other centres using CR as an imaging modality for paediatrics. Presently, this method is the only practicresently, this method is the only practical approach to automatically extract parameters contained in the DICOM header, for the calculation of patient dose values for the CR modality

271

Patient Specific Kerma Area Product as an Exposure Estimator in Computed Tomography: The Concept and Typical Values  

International Nuclear Information System (INIS)

Monitoring of exposure levels in computed tomography is important from the radiation safety point of view. In this paper, the concept suggested by Huda of using the patient specific kerma area product as an exposure estimator is extended by providing both a rigorous definition of this quantity and a method for its evaluation. The method was demonstrated on an axial scan of the standard CT dosimetry head phantom taken with a Siemens Somatom Open CT scanner. The resulting patient specific kerma area product was 0.25 Gy cm2 for the X ray tube voltage of 120 kV, tube current of 100 mA, scanning time of 1 s, and beam width at the isocentre of 1.2 cm. To implement this method, the CT scanner must be equipped with a KAP meter, and the calculation procedure must be added to the scanner's software. Alternatively, the patient specific kerma area product can be calculated by the CT scanner without using a KAP meter. In this case, however, the extra safety feature provided by the direct monitoring of the X ray beam by the KAP meter is lost. (author)

272

W/sub n/ and neutron kerma for methane-based tissue-equilvalent gas  

International Nuclear Information System (INIS)

Homogeneous tissue-equivalent ionization chambers containing a methane-based gas mixture are widely used to determine the absorbed dose of neutrons employed in radiobiology and radiotherapy. Conversion of the measured ionization charge to the absorbed dose requires knowledge of W/sub n, the mean energy expended to form an ion pair in the gas by the initial spectra of secondary charged particles produced by the neutrons. This report discusses the computed charged particle spectra in the gas and the relative kermas contributed by the various types of charged particles. These spectra are combined with an evaluation of the available experimental data on W for the secondary particles to compute W/sub n/ as a function of neutron energy. Over the energy range of 0.1 to 20 MeV, W/sub n/ was found to vary from 32.8 to 31.0 eV, respectively, including sharp changes in W/sub n/ due to large resonances in the energy transferred to carbon and oxygen. It is recommended that the data presented be used to evaluate W/sub n/ for each neutron spectrum for which accurate dosimetry is required. A single value of 31.9 +- 0.9 eV is recommended for less demanding applications or when neutron spectra are poorly known

273

NOTE: Monte Carlo evaluation of kerma in an HDR brachytherapy bunker  

Science.gov (United States)

In recent years, the use of high dose rate (HDR) after-loader machines has greatly increased due to the shift from traditional Cs-137/Ir-192 low dose rate (LDR) to HDR brachytherapy. The method used to calculate the required concrete and, where appropriate, lead shielding in the door is based on analytical methods provided by documents published by the ICRP, the IAEA and the NCRP. The purpose of this study is to perform a more realistic kerma evaluation at the entrance maze door of an HDR bunker using the Monte Carlo code GEANT4. The Monte Carlo results were validated experimentally. The spectrum at the maze entrance door, obtained with Monte Carlo, has an average energy of about 110 keV, maintaining a similar value along the length of the maze. The comparison of results from the aforementioned values with the Monte Carlo ones shows that results obtained using the albedo coefficient from the ICRP document more closely match those given by the Monte Carlo method, although the maximum value given by MC calculations is 30% greater.

Pérez-Calatayud, J.; Granero, D.; Ballester, F.; Casal, E.; Crispin, V.; Puchades, V.; León, A.; Verdú, G.

2004-12-01

274

ZZ KAOS/LIB-V, Kerma Factors, Nuclear Response Function Library for Fission, Fusion  

International Nuclear Information System (INIS)

Description of program or function: Format: FIDO; Number of groups: 174 neutron groups; Nuclides: H, He, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, W, Pb, Bi, Th, Pa, U, Np, Pu, Am. Origin: ENDF/B-V, JENDL-2; Weighting spectrum: VITAMIN-E weighting function. The library includes neutron kerma factors, gas production, tritium breeding cross sections, and all important reaction cross sections for a large number of materials of interest in fission and fusion systems. The library was generated with the KAOS-V code (PSR-306) employing basic nuclear data from ENDF/B-V. Auxiliary nuclear data bases, such as the Japanese library JENDL-2, were used as a source of isotopic cross sections when these data are not provided in ENDF/B-V files for a natural element. KAOS/LIB-V employs the VITAMIN-E weighting function and energy group structure of 174 neutron groups. The library is designed for fusion and fission applications

275

Scattering study at free air ionization chamber diaphragm; Estudo do espalhamento no diafragma da camara de ionizacao de ar livre  

Energy Technology Data Exchange (ETDEWEB)

The maim of this work consisted in the assessment of the correction factor for air kerma, due to scattered radiation in the diaphragm of the free-air ionization chamber model 481. LNMRl measurements were made to acquire x-ray spectra corresponding to the Qualities RQR-M, described in IEC 61627 standards (2005). These spectra were used as input data in the MC simulations. The operational range of energy spectra provide up to 35 keV. This energy range is typically used in diagnostic radiology, although there is not primary standard for air kerma. The determination of this factor is a fundamental process in the primary standardization of the air kerma. These factors were obtained by computer simulation using the Penelope code. The results are k{sub RQR-M1}=0,9946, k{sub RQR} {sub -M2}=0,9932, k{sub RQR-M3}=0,9978 and k{sub RQR-M4}=0,9885; with uncertainties of 0,007 and coverage factor equal to 2. lt can be concluded that, with respect to the diaphragm, the chamber can be used in the primary standard of air kerma. (author)

Santos, Alexandre Lo Bianco dos

2011-07-01

276

Calibration methodology application of kerma area product meters in situ: Preliminary results  

Science.gov (United States)

The kerma-area product (KAP) is a useful quantity to establish the reference levels of conventional X-ray examinations. It can be obtained by measurements carried out with a KAP meter on a plane parallel transmission ionization chamber mounted on the X-ray system. A KAP meter can be calibrated in laboratory or in situ, where it is used. It is important to use one reference KAP meter in order to obtain reliable quantity of doses on the patient. The Patient Dose Calibrator (PDC) is a new equipment from Radcal that measures KAP. It was manufactured following the IEC 60580 recommendations, an international standard for KAP meters. This study had the aim to calibrate KAP meters using the PDC in situ. Previous studies and the quality control program of the PDC have shown that it has good function in characterization tests of dosimeters with ionization chamber and it also has low energy dependence. Three types of KAP meters were calibrated in four different diagnostic X-ray equipments. The voltages used in the two first calibrations were 50 kV, 70 kV, 100 kV and 120 kV. The other two used 50 kV, 70 kV and 90 kV. This was related to the equipments limitations. The field sizes used for the calibration were 10 cm, 20 cm and 30 cm. The calibrations were done in three different cities with the purpose to analyze the reproducibility of the PDC. The results gave the calibration coefficient for each KAP meter and showed that the PDC can be used as a reference instrument to calibrate clinical KAP meters.

Costa, N. A.; Potiens, M. P. A.

2014-11-01

277

PTRAC file utilization for calculation of free-air ionization chamber correction factors by MCNPX  

International Nuclear Information System (INIS)

A free-air ionization chamber is used as a standard of photon air-kerma. Several correction factors are applied to the air-kerma value. Correction factors for electron loss: k(loss) and for additional ionization current caused by photon scatter: k(sc), photon fluorescence: k(fl), photon transmission through diaphragm edge k(dtr), and photon scatter from the surface of the diaphragm aperture k(dsc) were determined by the MCNPX code utilizing information stored in Particle Track (PTRAC) output files. Individual steps of the procedure are described and the calculated values of the correction factors are presented. The values are in agreement with the correction factors published in the literature for similar free-air chambers and low-energy photons. (authors)

278

Experimental double-differential cross sections and derived kerma factors for oxygen at incident neutron energies from reaction thresholds to 65 MeV  

International Nuclear Information System (INIS)

The double-differential cross sections (energy spectra) for the (n, px), (n, dx), (n, tx) and (n, ?x) reactions on oxygen have been measured for nine incident neutron energies in the range 25 to 65 MeV at lab angles between 20 deg. and 160 deg. in steps of 10 deg. From these measurements, the energy differential cross sections have been determined and consequently the partial and total kerma factors. Based on the obtained experimental partial kerma factors in the incident neutron energy range 25-65 MeV, a procedure is proposed for the extrapolation of these values to the reaction threshold energy of each measured reaction channel. Results of the experimental double-differential, energy differential and total cross sections are presented. The deduced partial and total kerma factors of the present work are compared with results of previous measurements and theoretical predictions. (author)

279

Validity of constant room scatter assumption in the air kerma strength standardization of a remote afterloading 192Ir HDR source  

International Nuclear Information System (INIS)

The objective of the present study is to examine the validity of the constant room scatter assumption for rooms of various sizes (including the room size where the standardization of a 192Ir HDR source was carried out) for a remote afterloading micro selectron 192Ir HDR source. The well-established Monte Carlo simulation code MCNP (Version 3.1, 1980) was used in the study

280

Experimental arrangement and data acquisition system at LNMRI for exposure and air-kerma measurement of cobalt-60 gamma rays  

International Nuclear Information System (INIS)

A graphite cavity ionization chamber made by the Osterreichisches Forschunggszentrum, Seiberdorf has been installed as a primary standard for 60Co radiation at the Laboratorio Nacional de Metrologia das Radiacoes Ionizantes (LNMRI). The paper describes several aspects of the experimental arrangement the radiation source and all modifications made in the beam collimating system in order to improve its flatness; the additional shutter built to avoid output changes due to the cobalt pellets movement inside the capsule; the special insulated room constructed inside of one of the existing facilities to minimize the temperature gradient inside the room and the chamber positioning system using a position transducer. In addition, description of the automated data acquisition system, the mathematical formalism for the calculation of the quantities of interest and the statistical treatment are given. The results of an intercomparison made with the Bureau International des Poids et Mesures (BIPM) has shown an agreement better than 0.1%. Furthermore, comparisons made with several secondary standards under the same experimental conditions has also shown an excellent agreement. (author). 6 refs., 3 figs., 2 tabs

 
 
 
 
281

Geomagnetic activity related NOx enhancements and polar surface air temperature variability in a chemistry climate model: modulation of the NAM index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The atmospheric chemistry general circulation model ECHAM5/MESSy is used to simulate polar surface air temperature effects of geomagnetic activity variations. A transient model simulation was performed for the years 1960–2004 and is shown to develop polar surface air temperature patterns that depend on geomagnetic activity strength, similar to previous studies. In order to eliminate influencing factors such as sea surface temperatures (SST) or UV variations, two nine-year ...

Baumgaertner, A. J. G.; Seppa?la?, A.; Jo?ckel, P.; Clilverd, M. A.

2011-01-01

282

Index transforms  

CERN Document Server

This book deals with the theory and some applications of integral transforms that involve integration with respect to an index or parameter of a special function of hypergeometric type as the kernel (index transforms). The basic index transforms are considered, such as the Kontorovich-Lebedev transform, the Mehler-Fock transform, the Olevskii Transform and the Lebedev-Skalskaya transforms. The L p theory of index transforms is discussed, and new index transforms and convolution constructions are demonstrated. For the first time, the essentially multidimensional Kontorovich-Lebedev transform is

Iakubovich, Semen B

1996-01-01

283

Characterization of a free-air ionization chamber in direct X-ray beams as used in mammography  

International Nuclear Information System (INIS)

At this work stability and characterization tests were undertaken on a Victoreen free-air ionization chamber, model 481. The tests were realized using direct X-ray beams as a contribution for its establishment as a primary standard system of the quantity air kerma. The characterization tests were: saturation curve, ion collection efficiency, polarity effect, response linearity with the air kerma rate and response linearity with the chamber volume variation. The ion collection efficiency allowed the determination of the ion recombination factor. Most of the test results showed agreement with the limits established by international standards. Furthermore, the air attenuation factors for the mammography beams with aluminum and molybdenum filters were obtained. The factors for photon transmission and scattering at the diaphragm edges were also determined for mammography beams with aluminum filter and for the standard beam with molybdenum filter. (author)

284

Evaluation of Kerma rate in the skin entrance in interventional procedures guided by fluoroscopy; Avaliacao da taxa de Kerma na entrada da pele em procedimentos intervencionistas guiados por fluorosocopia  

Energy Technology Data Exchange (ETDEWEB)

Interventional therapeutic procedures guided by fluoroscopy are responsible for delayed exposure to radiation of professionals and patients. The technology employed on generation of the pulsed fluoroscopy can be an important tool of protection used for reducing the exposure time. It generates constant width and varied frequency pulse or width pulse or varied frequency for a constant frequency. The typical doses into the skin and its relationship with the quality of the images in the various technical and operational conditions should be known by the professionals so that they can optimize them. Generated radiation doses were evaluated using the Toshiba Infinitix equipment used in invasive cardiology procedures and electrophysiological studies through the Kerma rate at the entrance of the patient's skin measured throughout the year of 2004. With these information shall be set out the criteria for the decision of the technical-operational conditions that allow minimizing of dose.

Medeiros, Regina Bitelli; Alves, Fatima Faloppa Rodrigues; Ruberti Filha, Eny M. [Universidade Federal de Sao Paulo (UNIFESP), SP (Brazil)

2005-07-01

285

Got Dirty Air?  

Science.gov (United States)

Students are introduced to the concepts of air pollution and technologies that have been developed by engineers to reduce air pollution. Students develop an understanding of visible air pollutants with an incomplete combustion demonstration, a "smog in a jar" demonstration, construction of simple particulate matter collectors and by exploring engineering roles related to air pollution. Next, students develop awareness and understanding of the daily air quality and trends in air quality using the Air Quality Index (AQI) listed in the newspaper. Finally, students build and observe a variety of simple models in order to develop an understanding of how engineers use these technologies to clean up and prevent air pollution.

Integrated Teaching and Learning Program,

286

Effects of radiation quality on the calibration of kerma-area product meters in x-ray beams  

Science.gov (United States)

The calibration coefficients of kerma-area product meters significantly depend on the energy spectrum of the x-ray beam. This effect was examined by measuring the calibration coefficients for several radiation qualities in the range generally used in diagnostic x-ray imaging. The intention was to determine the calibration coefficients for other radiation qualities by interpolation between the measured values, relative to one or more suitable parameters. The x-ray tube voltage, total filtration and half-value thickness were examined as possible specifiers of the energy distribution. No single parameter provided an interpolation of calibration coefficients with the accuracy recommended by the ICRU and IAEA, except for a narrow range of radiation qualities. At least two of the parameters are needed to reliably specify the radiation quality for the interpolation of calibration coefficients.

Toroi, P.; Komppa, T.; Kosunen, A.; Tapiovaara, M.

2008-09-01

287

Calculation of the backscattering in water and compared to the values in air; Calculo del factor de retrodispersion en agua y comparativa con los valores en aire  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this paper is to calculate values of BSF in water and comparison with data on air 11SF found in the literature. For this simulations have been performed by the Monte Carlo method for calculating values ??kerma water in the presence of a manikin of this material and in the absence thereof. The simulations were performed for monoenergetic beams in order to facilitate the calculation of the BSF for any spectral distribution of those found in the field of radiology.

Minano Herrero, J. A.; Sarasa Rubio, A.; Roldan Arjona, J. M.

2011-07-01

288

Power and polarization beam-splitters, mirrors, and integrated interferometers based on air-hole photonic crystals and lateral large index-contrast waveguides.  

Science.gov (United States)

Air hole 2D photonic crystals (PhC) and air slots have been used in association with semiconductor ridge waveguides to produce highly compact beam-splitters (less than 10 microm x10 microm) for power or polarization separators and mirrors. An efficiency of 99 % (in both 2D and 3D formulations) has been obtained for the power beam-splitter using finite-difference time-domain (FDTD) simulations - and around 95 % has been measured experimentally for structures realized in silicon-on-insulator (SOI) waveguides. In the polarization splitter, an extinction ratio as large as 11 dB was also reached experimentally. Examples of combinations of these elements in the form of interferometers are also presented. PMID:19516730

Pottier, Pierre; Mastroiacovo, Sara; De La Rue, Richard M

2006-06-12

289

Guidebook/index  

Energy Technology Data Exchange (ETDEWEB)

The Guidebook/Index introduces information dealing with the general rationale for energy conservation and deals with some of the definitions and concepts common to each of the subjects covered in the series of 10 booklets. The master index for the series is presented. Subjects covered are saving money in heating, cooling, and lighting; in process design and heat recovery; through production optimization; through combustion control; through steam and compressed air management; in transportation and delivery; through efficient people moving; in office practices; and through employee motivation and participation.

1977-01-01

290

A Hybrid Method to Improve Forecasting Accuracy - An Introduction of a Day of the Week Index for Air Cargo Weight Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Air cargo loading weight forecasting is an important factor for managers in the aviation industry because revenue is dependent on the amount of weight loaded. In this paper, we propose a new method to improve forecasting accuracy and confirm them by the numerical example. Focusing that the equation of exponential smoothing method(ESM) is equivalent to (1,1) order ARMA model equation, a new method of estimation of smoothing constant in exponential smoothing method is proposed before by us whic...

Tatsuhiro Kuroda; Keiko Nagata; Kazuhiro Takeyasu

2012-01-01

291

Characterization of the new free-air primary standard for low-energy X-rays at CMI  

Science.gov (United States)

In 2011 a decision was made by Czech Metrology Institute to build a free-air ionization chamber (FAC) intended to be used as a primary standard of air kerma rate for low-energy X-rays (photon energy below 50 keV, including mammography X-ray qualities) in order to replace the currently used secondary ionization chamber and to decrease the uncertainty of air kerma reference value. In the period 2011-2012, the FAC has been designed, manufactured and put into operation. Its performance was tested using a calibrated secondary chamber and then by an informal comparison with a national primary standard of BEV (Austria). Physical characteristics of the FAC are described and individual correction factors are discussed focusing on computational methods utilized in their estimation. Summary of the correction factors with the uncertainty budget is presented.

Šolc, Jaroslav; Sochor, Vladimír

2014-11-01

292

Intelligent indexing  

International Nuclear Information System (INIS)

In this paper we discuss the relevance of artificial intelligence to the automatic indexing of natural language text. We describe the use of domain-specific semantically-based thesauruses and address the problem of creating adequate knowledge bases for intelligent indexing systems. We also discuss the relevance of the Hilbert space ?2 to the compact representation of documents and to the definition of the similarity of natural language texts. (author). 17 refs., 2 figs

293

Doses monitoring in radiology: calibration of air kerma-area product (P{sub KA}) meters; Monitoracao de doses em radiologia: a calibracao de medidores do produto kerma-area (P{sub KA})  

Energy Technology Data Exchange (ETDEWEB)

Materials and methods: different qualities of both incident and transmitted beams were utilized in conditions similar to a clinical setting, analyzing the influence from the reference dosimeter, from the distance between meters, from the filtration and from the average beam energy. Calibrations were performed directly against a standard 30 cm{sup 3} cylindrical chamber or a parallel-plate monitor chamber, and indirectly against the PDC meter. Results: the lowest energy dependence was observed for transmitted beams. The cross calibration between the Diamentor E2 and the PDC meters, and the PDC presented the greatest propagation of uncertainties. Conclusion: the calibration coefficient of the PDC meter showed to be more stable with voltage, while the Diamentor E2 calibration coefficient was more variable. On the other hand, the PDC meter presented greater uncertainty in readings (5.0%) than with the use of the monitor chamber (3.5%) as a reference. (author)

Terini, Ricardo Andrade; Campelo, Maria Carolina de Santana; Almeida Junior, Jose Neres de, E-mail: rterini@pucsp.br [Pontificia Universidade Catolica de Sao Paulo (PUC-SP), SP (Brazil); Herdade, Silvio Bruni; Pereira, Marco Aurelio Guedes [Universidade de Sao Paulo (IEE/USP), SP (Brazil). Instituto de Energia e Ambiente

2013-11-15

294

Cross sections and partial kerma factors for elastic and inelastic neutron scattering from nitrogen, oxygen and calcium at En = 21.6 MeV.  

Science.gov (United States)

The Studsvik high-resolution, low-background time-of-flight facility has been used to measure differential neutron scattering cross sections for nitrogen, oxygen and calcium at a neutron energy of 21.6 MeV. Angular distributions in the range 10 degrees-160 degrees have been measured for both elastic and inelastic scattering from some low-lying levels in the three nuclei. Angle-integrated cross sections have been determined by fitting Legendre polynomial expansions to the differential data. Partial kerma factors for elastic and inelastic scattering have been deduced from these fits. Analyses in terms of the spherical optical model and the distorted-wave Born approximation have provided information on potential parameters and deformations, which have been used to calculate cross sections and partial kerma factors. Comparisons have been made with other recent data sets and model predictions, as well as with the evaluated neutron data file ENDF/B-V. PMID:2236207

Olsson, N; Ramström, E; Trostell, B

1990-09-01

295

Calculation and evaluation of cross-sections and kerma factors for neutrons up to 100 MeV on {sup 16}O and {sup 14}N  

Energy Technology Data Exchange (ETDEWEB)

We present evaluations of the interaction of neutrons with energies between 20 and 100 MeV with oxygen and nitrogen nuclei, which follows on from our previous work on carbon. Our aim is to accurately represent integrated cross sections, inclusive emission spectra, and kerma factors, in a data library which can be used in radiation transport calculations. We apply the FKK-GNASH nuclear model code, which includes Hauser-Feshbach, preequilibrium, and direct reaction mechanisms, and use experimental measurements to optimize the calculations. We determine total, elastic, and nonelastic cross sections, angle-energy correlated emission spectra for light ejectiles with A {<=} 4 and gamma-rays, and average energy depositions. Our results for charged-particle emission spectra agree well with the measurements of Subramanian et al. We compare kerma factors derived from our evaluated cross sections with experimental data, providing an integral benchmarking of our work. (author). 52 refs.

Chadwick, M.B. [California Univ., Livermor, CA (United States). Lawrence Livermore National Lab.; Young, P.G.

1997-03-01

296

Jung Index  

Science.gov (United States)

Compiled by Matthew Clapp of the University of Georgia, the Jung Index is a collection of more than 300 online resources about and related to the life and work of Carl Jung, the Swiss psychologist and psychiatrist who founded analytic psychology. Resources are indexed into ten major topic areas and include sections such as Research Resources, Jungian Psychology, and Psychoanalysis, among others. A What's New? section, a What's Cool? section, and the JungNet Newsletter keep frequent visitors up to date on the latest and greatest resources in analytic psychology. In addition, the site provides a glossary of Jungian terms, a gallery of Jungian images, and a moderated forum for Jungian discussion.

1999-01-01

297

GCUBE Indexing  

Directory of Open Access Journals (Sweden)

Full Text Available Spatial Online Analytical Processing System involves the non-categorical attribute information alsowhereas standard online analytical processing system deals with only categorical attributes. Providingspatial information to the data warehouse (DW; twomajor challenges faced are; 1.Defining andAggregation of Spatial or Continues values and 2.Representation, indexing, updating and efficient queryprocessing. In this paper, we present GCUBE (Geographical Cube storage and indexing procedure toaggregate the spatial information/Continuous values. We employed the proposed approach storing andindexing using synthetic and real data sets and evaluated its build, update and Query time. It is observedthat the proposed procedure offers significant performance advantage.

M.Laxmaiah

2013-07-01

298

The Influence of the Air Density on the Special Properties of X Ray Radiation Qualities with Mean Energies from 6 KeV to 90 KeV  

International Nuclear Information System (INIS)

The use of X ray facilities for precise irradiations requires exact knowledge of the radiation field. The effect of different ambient conditions on the radiation field is investigated. To correct the effect which different air densities exert on the characteristic spectrum properties of the radiation, such as the conventional true value of the air kerma, conversion coefficients from air kerma to personal (or ambient) dose equivalent, the mean energy or the half-value layer, calculations were performed for a large number of different spectrum properties for all radiation qualities defined in the ISO 4037-1 standard and in the German standard DIN 6818-1 at a high voltage of up to 120 kV. The calculations were checked by comparing some of the data with experimental results. (author)

299

Variacion temporal de índices de precipitaciones extremas en el centro de la provincia de Buenos Aires / Temporal variation of extreme precipitations indexes in the centre of Buenos Aires province  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish El objetivo de esta investigación consiste en estudiar la evolución temporal de precipitaciones diarias para detectar la presencia de tendencias y la frecuencia de eventos extremos. Las series de precipitaciones observadas corresponden a cuatro estaciones meteorológicas ubicadas en el centro de la P [...] rovincia de Buenos Aires, Argentina. Los cambios en las precipitaciones extremas a nivel diario se evalúan con los índices propuestos por la World Meteorological Organization-Commission for Climatology (WMO-CCL) y el World Climate Research Programme (WCRP) - Climate Variability and Predictability. Para estudiar los posibles cambios en la relación período de retorno - precipitaciones máximas se aplicaron a las series dos funciones de densidad de probabilidades, la Generalizada de Valores Extremos y la Gamma de dos parámetros. Los resultados estimados con las dos funciones de densidad de probabilidades de la precipitación máxima, generalmente muestran un incremento de la precipitación asociado a la misma probabilidad de ocurrencia en el período 1971-1999 respecto a 1951-1970. Los eventos de precipitación que produjeron crecidas, ocurridos en Olavarría y Azul desde la década del 80 son una clara indicación del interés del estudio de este tema tanto por sus implicancias sociales asociadas con las inundaciones, como por la necesidad de actualizar las estimaciones de los parámetros de diseño de obras hidráulicas. Los valores de los índices estimados indican la existencia de una tendencia positiva en la precipitación en la mayoría de las estaciones meteorológicas y una mayor frecuencia de ocurrencia de valores extremos para el periodo 1971-1999 en relación al periodo 1951-1970. Abstract in english The objective of this research is to study the temporal evolution of daily precipitation in order to detect the presence of trends and to estimate the frequency of extreme events. The observed precipitation series correspond to four meteorological stations located in the center of the Province of Bu [...] enos Aires, Argentina. Changes in daily extreme precipitation were assessed through the indices proposed by the World Meteorological Organization-Commission for Climatology (WMO-CCL) and the World Climate Research Program (WCRP) -Climate Variability and Predictability. In order to analyze possible changes in the return period - maximum precipitation relationship, two probability density functions were applied to the series, the Generalized Extreme Values and the two parameters Gamma. The obtained results show, in general, a higher probability of occurrence of greater precipitations over the period 1971-1999 respect of period 1951-1970. The rainfall events that caused floods in Olavarría and Azul since the '80s clearly show the interest of studying this subject, not only because of its social implications associated to floods, but the demand of developing techniques to update the estimation of design parameters of hydraulic works. The estimated indices suggest a positive trend in the precipitation at most of the analyzed meteorological stations and a higher frequency of occurrence of extreme values over the period 1971-1999 compared to the period 1951-1970.

Mónica, Gelmi; Rafael, Seoane.

2013-06-01

300

Characterization of a free-air ionization chamber in direct X-ray beams as used in mammography; Caracterizacao de uma camara de ionizacao de ar-livre em feixes diretos de raios X utilizados em mamografia  

Energy Technology Data Exchange (ETDEWEB)

At this work stability and characterization tests were undertaken on a Victoreen free-air ionization chamber, model 481. The tests were realized using direct X-ray beams as a contribution for its establishment as a primary standard system of the quantity air kerma. The characterization tests were: saturation curve, ion collection efficiency, polarity effect, response linearity with the air kerma rate and response linearity with the chamber volume variation. The ion collection efficiency allowed the determination of the ion recombination factor. Most of the test results showed agreement with the limits established by international standards. Furthermore, the air attenuation factors for the mammography beams with aluminum and molybdenum filters were obtained. The factors for photon transmission and scattering at the diaphragm edges were also determined for mammography beams with aluminum filter and for the standard beam with molybdenum filter. (author)

Lima, Mateus Hilario de

2014-08-01

 
 
 
 
301

Energy buildup factor for ICRU 33 sphere surrounded by an air layer  

International Nuclear Information System (INIS)

The buildup factor due to the air surrounding an ICRU 33 sphere is a desirable quantity in the assessment of the air kerma rate for external exposure to gamma emitters distributed on the ground. A Monte Carlo algorithm has been developed to perform the photon transport calculation within the air layer around the sphere. The energy buildup factor due to the air layer has been calculated for an extended radioactive source - the contaminated ground. The transport of photons within the air layer surrounding a sphere -ICRU 33 phantom - is done by calculating separately the energies deposited by photons into the sphere when this one is in vacuum and when it is surrounded by the air, respectively. The results are given for an air layer of 100 m thickness and photon energy between 0.01 and 3.0 MeV. (Author) 1 Fig., 1 Tab., 9 Refs

302

Evaluated cross-section libraries and kerma factors for neutrons up to 100 MeV on {sup 12}C  

Energy Technology Data Exchange (ETDEWEB)

A program is being carried out at Lawrence Livermore National Laboratory to develop high-energy evaluated nuclear data libraries for use in Monte Carlo simulations of cancer radiation therapy. In this report we describe evaluated cross sections and kerma factors for neutrons with incident energies up to 100 MeV on {sup 12}C. The aim of this effort is to incorporate advanced nuclear physics modeling methods, with new experimental measurements, to generate cross section libraries needed for an accurate simulation of dose deposition in fast neutron therapy. The evaluated libraries are based mainly on nuclear model calculations, benchmarked to experimental measurements where they exist. We use the GNASH code system, which includes Hauser-Feshbach, preequilibrium, and direct reaction mechanisms. The libraries tabulate elastic and nonelastic cross sections, angle-energy correlated production spectra for light ejectiles with A{le}and kinetic energies given to light ejectiles and heavy recoil fragments. The major steps involved in this effort are: (1) development and validation of nuclear models for incident energies up to 100 MeV; (2) collation of experimental measurements, including new results from Louvain-la-Nueve and Los Alamos; (3) extension of the Livermore ENDL formats for representing high-energy data; (4) calculation and evaluation of nuclear data; and (5) validation of the libraries. We describe the evaluations in detail, with particular emphasis on our new high-energy modeling developments. Our evaluations agree well with experimental measurements of integrated and differential cross sections. We compare our results with the recent ENDF/B-VI evaluation which extends up to 32 MeV.

Chadwick, M.B.; Blann, M.; Cox, L. [Lawrence Livermore National Lab., CA (United States); Young, P.G. [Los Alamos National Lab., NM (United States); Meigooni, A. [Kentucky Univ., Lexington, KY (United States). Dept. of Radiation Medicine

1995-04-11

303

Photon and neutron fluence-to-kerma conversion factors for ICRP-1975 reference man using improved elemental compositions for bone and marrow of the skeleton  

International Nuclear Information System (INIS)

A twelve-element approximation of the total-body, soft-tissue and skeletal components of ICRP-1975 Reference Man is used to investigate particle fluence-to-kerma conversion factors for photons with energies between 1 keV and 20 MeV and neutrons with energies between 0.0253 eV and 20 MeV. Several recent ICRP revisions to the elemental composition of Reference Man, which have not been included in other kerma-factor calculations, are taken into account. This work suggests some additional revisions to the major-element content (i.e., H, C, N, and O) and to the mineral and trace-element content (i.e., Na, Mg, P, S, Cl, K, Ca, and Fe) of various total-body, soft-tissue, and skeletal components of Reference Man. The revisions to the bone and red marrow of the skeleton offer significant new refinements in red-bone-marrow dosimetry

304

Determination of the kerma factors in tissue-equivalent plastic, C, Mg, and Fe for 14.7-MeV neutrons.  

Science.gov (United States)

Microdosimetric measurements were made with tissue-equivalent plastic (TEP), C-, Mg-, and Fe-walled proportional counters filled with propane-based tissue equivalent (TE) gas and Ar gas and irradiated with 14.7-MeV neutrons. A theoretical model was used for the analysis of energy deposition in spherical detectors. An effective average mass stopping-power ratio and a W correction were calculated to convert the gas ionization to the kerma in the wall material. The neutron fluence at the position of microdosimetric measurements was determined with an associated particle chamber mounted with surface barrier detectors. The experimental measurements along with the calculated correction factors yielded kerma factors of 0.660 X 10(-8) cGy cm2 for TEP, 0.219 X 10(-8) cGy cm2 for C, 0.122 X 10(-8) cGy cm2 for Mg, and 0.479 X 10(-9) cGy cm2 for Fe. The estimated uncertainties are 8.0% for TEP, 10.5% for C, and 9.3% for Mg and Fe. PMID:3696064

Wuu, C S; Milavickas, L R

1987-01-01

305

Evaluation of cross sections and calculation of kerma factors for neutrons up to 80 MeV on {sup 12}C  

Energy Technology Data Exchange (ETDEWEB)

We have evaluated the cross sections for neutrons with incident energies from 20 to 80 MeV on {sup 12}C for the JENDL high-energy file. The total cross sections were determined by a generalized least-squares method with available experimental data. The cross sections of elastic and inelastic scattering to the first 2{sup +} were evaluated with the theoretical calculations. The optical potentials necessary for these calculations were derived using a microscopic approach by Jeukenne-Lejeune-Mahaux. For the evaluation of double differential emission cross sections (DDXs), we have developed a code system SCINFUL/DDX in which total 35 reactions including the 3-body simultaneous breakup process (n+{sup 12}C {yields} n+{alpha}+{sup 8}Be) can be taken into consideration in terms of a Monte Carlo method, and have calculated the DDXs of all light-emissions (A{<=}4) and heavier reaction products. The results for protons, deuterons, and alphas showed overall good agreement with experimental data. The code is also applicable for calculations of total and partial kerma factors. Total kerma factors calculated for energies from 20 to 80 MeV were compared with the measurements and the other latest evaluations from the viewpoints of medical application and nuclear heating estimation. (author)

Harada, M.; Watanabe, Y. [Kyushu Univ., Fukuoka (Japan); Chiba, S.; Fukahori, T.

1997-03-01

306

Determination of the air attenuation and electronic loss for the free air concentric cylinders ionization chamber  

International Nuclear Information System (INIS)

Along the latest years, the LNMRI has been proceeding a continuous research work with a concentric cylinders type free air ionizing chamber (VICTOREEN, model 481), aiming to establish it as a new national standard, and, as a consequence, replace the worldwide accepted secondary standard, calibrated by PTB. Taking into account that the absolute determination of kerma in air with a free air ionizing chamber implies the acquirement of a number of correction factors. The main objective of the present work comprises the determination of the two factors, specifically, electronic loss (ke) and air attenuation (ka). The correction factors were obtained through mammography qualities reference spectrum, using Monte Carlo simulation method. The Penelope code was used in the simulation procedures. Simulations took place in two stages, the acquirement of specters related to the qualities of interest (mammography) with the x ray tube (Pantak, model HF160 e Panalytical, model XRF window), and the free-air ionization chamber. The data were compared to those related to the BIPM chamber, to electronic loss were not detected. The comparison between air attenuation factors was obtained data bellow 0.13%. (author)

307

Are exposure index values consistent in clinical practice? A multi-manufacturer investigation  

International Nuclear Information System (INIS)

The advent of digital radiography poses the risk of unnoticed increases in patient dose. Manufacturers have responded to this by offering an exposure index (EI) value to the clinician. Whilst the EI value is a measure of the air kerma at the detector surface, it has been recommended by international agencies as a method of monitoring radiation dose to the patient. Recent studies by the group have shown that EI values are being used in clinical practice to monitor radiation dose and assess image quality. This study aims to compare the clinical consistency of the EI value in computed radiography (CR) and direct digital radiography (DR) systems. An anthropomorphic phantom was used to simulate four common radiographic examinations: skull, pelvis, chest and hand. These examinations were chosen as they provide contrasting exposure parameters, image detail and radiation dose measurements. Four manufacturers were used for comparison: Agfa Gaevert CR, Carestream CR, Philips Digital Diagnost DR and Siemens DR. For each examination, the phantom was placed in the optimal position and exposure parameters were chosen in accordance with European guidelines and clinical practice. Multiple exposures were taken and the EI recorded. All exposure parameters and clinical conditions remained constant throughout. For both DR systems, the EI values remained consistent throughout. No significant change was noted in any examination. In both CR systems, there were noteworthy fluctuations in the there were noteworthy fluctuations in the EI values for all examinations. The largest for the Agfa system was a variation of 1.88-2.21 for the skull examination. This represents to the clinician a doubling of detector dose, despite all exposure parameters remaining constant. In the Kodak system, the largest fluctuation was seen for the chest examination where the EI ranged from 2560 to 2660, representing approximately an increase of 30% in radiation dose, despite consistent parameters. The fluctuations seen with the CR systems are most likely due to image processing delay, replacing of the imaging plate and calibration factors. Fluctuations in EI values may result in confusion to the clinician and unnecessary repeat examinations. The reliability of EI values as a feedback mechanism for CR is also questionable. (authors)

308

Estimating the Mean Annual Surface Air Temperature at Armagh Observatory, Northern Ireland, and the Global Land-Ocean Temperature Index for Sunspot Cycle 24, the Current Ongoing Sunspot Cycle  

Science.gov (United States)

As noted by Gray et al., Sir William Herschel was the first to suggest a possible close connection between the Sun and the Earth’s climate. The Sun, being the source of energy that impacts and drives the Earth’s climate system, displays a variety of changes over both short and long term time scales, the most obvious examples being the somewhat regular waxing and waning of sunspots with time (i.e., the sunspot cycle (SC)), first described by Samuel Heinrich Schwabe, a German apothecary and amateur astronomer who observed the Sun from Dessau, Germany, and the now well established variation of the Sun’s irradiance over the SC. Other factors related to the SC have been linked to changes in climate as well. Some of these other factors include the role of cosmic rays and the solar wind (i.e., the geomagnetic cycle) on climate, as well as the apparent close association between trends in global and northern hemispheric temperature and the length of the SC, although some investigators have described the inferred association between climate and, in particular, SC length as now being weak. More recently, Solheim et al. have reported on the relation between SC length and the average temperature in the same and immediately following SC for a number of meteorological stations in Norway and in the North Atlantic region. They noted that while they found no significant trend (correlation) between SC length and the average temperature when measured for the same cycle, in contrast, they found a significant negative trend when SC length was compared with the following cycle’s average temperature. From this observation, they suggested that average northern hemispheric temperature during the present ongoing SC (SC24) will be lower by about 0.9 °C than was seen in SC23 (spanning 1996–2007, based on yearly averages of sunspot number (SSN), and onset for SC24 occurring in 2008). The purpose of this Technical Publication (TP) is to examine the annual variations of the Armagh surface air temperature (ASAT) and the Global Land-Ocean Temperature Index (GLOTI) in relation to SSN and the SC in order to determine their likely values during SC24. Hence, it may provide insight as to whether solar forcing of global temperature is now lessening as a contributor to global warming, thereby indicating a possible cooling in the near term immediate future that potentially could ameliorate the effect of increased anthropogenic warming.

Wilson, Robert M.

2013-01-01

309

Spatial variability of air dry bulb temperature and black globe humidity index in a broiler house during the heating phase / Variabilidade espacial de variáveis ambientais em um galpão avícola durante a fase de aquecimento  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A temperatura de bulbo seco do ar (t bs) bem como o índice de temperatura do globo negro e umidade (ITGU) exercem grande influência no desenvolvimento de frangos de corte durante a fase de aquecimento. Sendo assim, o objetivo deste trabalho foi analisar a estrutura e a magnitude da variabilidade esp [...] acial da t bs e ITGU, utilizando ferramentas da geoestatística por meio de análise de semivariograma e, ainda, a produção de mapas de isolinhas por meio de interpolação por krigagem. O experimento foi conduzido na mesorregião oeste de Minas Gerais, na primavera de 2010, em um galpão comercial com sistema de aquecimento constituído de duas fornalhas de aquecimento indireto do ar, durante os primeiros 14 dias de vida das aves. Os dados foram registrados em intervalos de cinco minutos, no período das 8 às 10 horas. As variáveis foram avaliadas por semivariograma ajustado pelo método da máxima verossimilhança restrita (REML), testando-se os modelos esférico e exponencial. Os mapas de krigagem foram produzidos baseados no melhor método de ajuste do semivariograma. As técnicas da geoestatística possibilitaram caracterizar a variabilidade da t bs e ITGU, permitindo a observação da dependência espacial. Além disso, com a utilização da geoestatística e dos mapas de distribuição, pode-se identificar falhas no sistema de aquecimento, em regiões do galpão que poderiam vir a prejudicar o desenvolvimento dos pintinhos. Abstract in english The air dry-bulb temperature (t db),as well as the black globe humidity index (BGHI), exert great influence on the development of broiler chickens during their heating phase. Therefore, the aim of this study was to analyze the structure and the magnitude of the t db and BGHI spatial variability, usi [...] ng geostatistics tools such as semivariogram analysis and also producing kriging maps. The experiment was conducted in the west mesoregion of the states of Minas Gerais in 2010, in a commercial broiler house with heating system consisting of two furnaces that heat the air indirectly, in the firsts 14 days of the birds' life. The data were registered at intervals of five minutes in the period from 8 a.m. to 10 a.m. The variables were evaluated by variograms fitted by residual maximum likelihood (REML) testing the Spherical and Exponential models. Kriging maps were generated based on the best model used to fit the variogram. It was possible to characterize the variability of the t db and BGHI, which allowed observing the spatial dependence by using geostatistics techniques. In addition, the use of geostatistics and distribution maps made possible to identify problems in the heating system in regions inside the broiler house that may harm the development of chicks.

Patrícia F., Ponciano; Tadayuki, Yanagi Junior; Gabriel A. E S., Ferraz; João D., Scalon; Leonardo, Schiassi.

2013-06-01

310

Journal selection and indexing for Index Medicus and Chinese periodicals indexed in Index Medicus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Index Medicus / MEDLINE / PubMed published by U.S. National Library of Medicine (NLM) is the most important and commonly used biomedical literature retrieval system in the world. According to the "List of Journals Indexed in Index Medicus (2004)", 4 098 journals are indexed for Index Medicus, including 70 journals from mainland China and Hong Kong and 9 journals from Taiwan. Journal of Chinese Integrative Medicine established in May, 2003 is indexed in Index Medicus in 2004. This article outl...

Zhou, Qing-hui

2005-01-01

311

Calculation of conversion coefficients Hp(3)/K air using the PENELOPE Monte Carlo code and comparison with MCNP calculation results  

International Nuclear Information System (INIS)

The authors report calculations performed using the MNCP and PENELOPE codes to determine the Hp(3)/K air conversion coefficient which allows the Hp(3) dose equivalent to be determined from the measured value of the kerma in the air. They report the definition of the phantom, a 20 cm diameter and 20 cm high cylinder which is considered as representative of a head. Calculations are performed for an energy range corresponding to interventional radiology or cardiology (20 keV-110 keV). Results obtained with both codes are compared

312

Index and Indexing Assessment: Criteria and Standards  

Directory of Open Access Journals (Sweden)

Full Text Available Indexing is one of the most important methods of content representation where by assigning descriptors to the documents, their subject content are made known. Since index and indexing are remarkably significant in information retrieval, its quality and evaluation and provision of criteria and standards had always been the mainstay of researchers in this field. Given the fact that Indexing is a complex process, offering definitions, principles and methods could be step towards optimal use of the information. The present study, while offering a capsule definition of index, will investigate the indexing evaluation criteria and would follow it up with a definition of indexing. Finally a number of standards in the field of indexing are presented and would make its conclusions.

Hassan Ashrafi

2007-10-01

313

Index and Indexing Assessment: Criteria and Standards  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Indexing is one of the most important methods of content representation where by assigning descriptors to the documents, their subject content are made known. Since index and indexing are remarkably significant in information retrieval, its quality and evaluation and provision of criteria and standards had always been the mainstay of researchers in this field. Given the fact that Indexing is a complex process, offering definitions, principles and methods could be step towards optimal use of t...

Hassan Ashrafi; Zahra Kazempour

2007-01-01

314

Refractive Index of Sodium Iodide  

Energy Technology Data Exchange (ETDEWEB)

The refractive index of sodium iodide, an important scintillator material that is widely used for radiation detection, is based on a single measurement made by Spangenberg at one wavelength using the index-matching liquid immersion method (Z. Kristallogr., 57, 494-534 (1923)). In the present paper, we present new results for the refractive index of sodium iodide as measured by the minimum deviation technique at six wavelengths between 436 nm (n=1.839 0.002) and 633 nm (n=1.786 0.002). These 6 measurements can be fit to a Sellmeier model, resulting in a 2 of 1.02, indicating a good fit to the data. In addition, we report on ellipsometry measurements, which suggest that the near-surface region of the air sensitive NaI crystal seriously degrades, even in a moisture-free environment, resulting in a significantly lower value of the refractive index near the surface. First-principles theoretical calculations of the NaI refractive index that agree with the measured values within 0.025-0.045 are also presented and discussed.

Jellison Jr, Gerald Earle [ORNL; Boatner, Lynn A [ORNL; Ramey, Joanne Oxendine [ORNL; Kolopus, James A [ORNL; Ramey, Lucas A [ORNL; Singh, David J [ORNL

2012-01-01

315

Refractive index of sodium iodide  

Science.gov (United States)

The refractive index of sodium iodide, an important scintillator material that is widely used for radiation detection, is based on a single measurement made by Spangenberg at one wavelength using the index-matching liquid immersion method (Z. Kristallogr. 57, 494 (1923)). In the present paper, we present new results for the refractive index of sodium iodide as measured by the minimum deviation technique at six wavelengths between 436 nm (n = 1.839 ± 0.002) and 633 nm (n = 1.786 ± 0.002). These six measurements can be fit to a Sellmeier model, resulting in a ?2 of 1.02, indicating a good fit to the data. In addition, we report on ellipsometry measurements, which suggest that the near-surface region of the air sensitive NaI crystal seriously degrades, even in a moisture-free environment, resulting in a significantly lower value of the refractive index near the surface. First-principles theoretical calculations of the NaI refractive index that agree with the measured values within 0.025-0.045 are also presented and discussed.

Jellison, G. E.; Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Ramey, L. A.; Singh, D. J.

2012-02-01

316

Air quality indices : a review  

International Nuclear Information System (INIS)

Pollution Probe presents some background information that will help in the development of a national Air Quality Index (AQI) in Canada. This report examines the issues that should be addressed in revising the national Index of the Quality of Air (IQUA) or creating a new national Air Quality Index. The IQUA was devised in 1976 and provides Canadians with real-time information on the state of community air quality by including major pollutants and their synergies. It is currently being used for air quality management plans and air quality alert systems. At the same time that the IQUA was devised, the United States Environmental Protection Agency (US EPA) produced a parallel air quality index known as the Pollution Standard Index (PSI) which incorporated 5 criteria pollutants (particulate matter, sulphur dioxide, carbon monoxide, nitrogen oxide and ground level ozone) for which national health-based standards were devised. In 1999, the US EPA renamed their index the Air Quality Index (AQI) and made revisions to the primary health-based national ambient air quality standards for ground-level ozone and particulate matter. Separate values for PM2.5 and PM10 were incorporated and mandatory reporting was required for metropolitan areas with populations of 350,000 or more. Similarly, the IQUA has undergone major developments that affect the validity of the index, including: rejection by the Working Group on Air Quality Objectives and Guidelines of the previous maximum desirabluidelines of the previous maximum desirable and maximum acceptable air quality criteria, recognition that standards for many of the contaminants are outdated, developing more sensitive instrumentation for real-time monitoring of contaminants. This report also describes the use of the national short term Air Quality Index by provincial, territorial and local authorities in Canada. Pollution Probe recommends setting up a mechanism to review and revise IQUA on a regular basis that would incorporate governments, the medical profession, special public interest groups, as well as environmental and industrial interest groups. It also recommends that new ways should be developed to facilitate a comparison between IQUA and AQI readings with those for AQI in the United States, especially in border communities. 7 tabs

317

Air Cannon  

Science.gov (United States)

In this activity, learners create air cannons out of everyday materials. Learners use their air cannons to investigate air as a force and air pressure. The activity page includes a fun how-to video for learners and educators.

Children's Museum of Houston

2010-01-01

318

Air Pollution  

Science.gov (United States)

Air pollution is a mixture of solid particles and gases in the air. Car emissions, chemicals from factories, dust, pollen and ... Ozone, a gas, is a major part of air pollution in cities. When ozone forms air pollution, ...

319

Journal selection and indexing for Index Medicus and Chinese periodicals indexed in Index Medicus  

Directory of Open Access Journals (Sweden)

Full Text Available Index Medicus / MEDLINE / PubMed published by U.S. National Library of Medicine (NLM is the most important and commonly used biomedical literature retrieval system in the world. According to the "List of Journals Indexed in Index Medicus (2004", 4 098 journals are indexed for Index Medicus, including 70 journals from mainland China and Hong Kong and 9 journals from Taiwan. Journal of Chinese Integrative Medicine established in May, 2003 is indexed in Index Medicus in 2004. This article outlines the critical elements of journal selection for Index Medicus/MEDLINE and the journal selection process for indexing at NLM, and introduces some measures for the Journal of Chinese Integrative Medicine being indexed in Index Medicus / MEDLINE.

ZHOU Qing-Hui

2005-01-01

320

Refractive index of plant cell walls  

Science.gov (United States)

Air was replaced with media of higher refractive indices by vacuum infiltration in leaves of cucumber, blackeye pea, tomato, and string bean plants, and reflectance of noninfiltrated and infiltrated leaves was spectrophotometrically measured. Infiltrated leaves reflected less light than noninfiltrated leaves over the 500-2500-nm wavelength interval because cell wall-air interfaces were partly eliminated. Minimal reflectance should occur when the average refractive index of plant cell walls was matched by the infiltrating fluid. Although refractive indices that resulted in minimal reflectance differed among the four plant genera, an average value of 1.425 approximates the refractive index of plant cell walls for the four plant genera.

Gausman, H. W.; Allen, W. A.; Escobar, D. E.

1974-01-01

 
 
 
 
321

Lobby index in networks  

CERN Document Server

We propose a new node centrality measure in networks, the lobby index, which is inspired by Hirsch's h-index. It is shown that in scale free networks the l-index has power tail with exponent square of the exponent of the degree distribution one. Properties of the l-index and extensions are discussed.

Korn, A; Telcs, A

2008-01-01

322

ZZ DLC-14 AIR, Group Constant Library of Secondary Gamma Transport in Air for ANISN Calculation  

International Nuclear Information System (INIS)

1 - Nature of physical problem solved: Format: ANISN, DOT, MORSE (FIDO format); Number of groups: 22 neutron / 18 gamma-ray; Nuclides: air; Origin: ENDF/B for neutron cross sections, DLC-4/HPIC for gamma-ray and DLC-12/POPLIB for secondary gamma-ray production. Weighting spectrum: 1/E for neutron cross sections. The basic idea behind the distribution of this ANISN input data is to allow potential users to repeat the ANISN calculations reported in ref. (1). It is felt that it will be more economical to repeat the calculations rather than to distribute the results of the Straker-Gritzner (1) calculations. However, the cross section part of the data can actually be used in DOT or MORSE or any transport code which will accept input cross section in the FIDO format. 2 - Method of solution: The sample input data for ANISN are for a P5, S16 calculation of the transport of neutrons and secondary gamma-rays from a 12.2 to 15 MeV point neutron source in an infinite air medium. The source is actually uniformly distributed in the first interval (500 cm radius) of a spherical medium of air with radius 3005 meters. The problem is set up for calculating various 'detector responses' by means of the 'activity' option available with ANISN. This is accomplished by providing a cross section table for a 'material' which has detector responses in certain table positions. Then the inclusion of appropriate input data for 22$ and 23$ arrays causes the group fluxes to be multiplied by the grou group fluxes to be multiplied by the group response function values to give the desired answer. The neutron detector responses calculated by this sample problem are Henderson tissue dose, Snyder-Neufeld dose, tissue kerma, and air kerma. The gamma-ray response functions calculated are Henderson tissue dose and air kerma. The neutron cross sections were first reduced from point data from ENDF/B to a 104 fine group structure with a modified version of CSP, assuming a 1/E weighting factor. The gamma-ray data were reduced from point data from DLC-4/HPIC to an 18 group structure using MUG. The POPOP-4 code was used to convert secondary gamma-ray production data from DLC-12/POPLIB to neutron-to-gamma-ray group transfer cross sections. The coupled set (104 neutron, 18 gamma-ray groups) was then collapsed to 22 neutron and 18 gamma-ray groups with ANISN, using as the weighting function the spectrum from a spatially uniform source of 14 MeV neutrons in an infinite air medium with a density of 1.11 mg/cc. The resulting data are coupled macroscopic multigroup, P5 expansion cross sections for air punched on cards and suitable for input to the ANISN code

323

Air Abrasion  

Science.gov (United States)

... delivered directly to your desktop! more... What Is Air Abrasion? Article Chapters What Is Air Abrasion? What Happens? The Pros and Cons Will I Feel Anything? Is Air Abrasion for Everyone? print full article print this ...

324

Dow Jones Internet Indexes  

Science.gov (United States)

Dow Jones Indexes has created the Dow Jones Internet Index (DJII) to bring "an ordered perspective" to "the seeming chaos of Internet stocks." The new index includes companies that generate a minimum of 50 percent of their revenues from the Internet. Complete documentation of DJII components, data, historical values, and news are provided on-site.

325

Equity index construction.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this article, the author detail the historic background behind the science of constructing a country or global index. He argues that the industry has largely developed from practitioners rather than academia. He shows how a country index is related to the market portfolio of the capital market pricing model and details the trade-offs that modern index constructors have to make.

Broby, D.

2011-01-01

326

Making air quality indices comparable - assessment of 10 years of air pollutant levels in western Europe.  

Science.gov (United States)

To address the incomparability of the large number of existing air quality indices, we propose a new normalization method that is suited to directly compare air quality indices based on the common European World Health Organization (WHO) air quality guidelines for NO2, O3, and PM10. Using this method, we compared three air quality indices based on the European guidelines, related them to another air quality index based on the relative risk concept, and used them to assess the air quality and its trends in northwest central Europe. The average air quality in the area of investigation is below the recommended European guidelines. The majority of index values exceeding this threshold are caused by PM10, which is also, in most cases, responsible for the degrading trends in air quality. Eleven out of 29 stations tested showed significant trends, of which eight indicated trends towards better air quality. PMID:24670211

Lokys, Hanna Leona; Junk, Jürgen; Krein, Andreas

2015-02-01

327

Precoder Index Modulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Index modulation, where information bits are conveyed through antenna indices (spatial modulation) and subcarrier indices (subcarrier index modulation) in addition to information bits conveyed through conventional modulation symbols, is getting increased research attention. In this paper, we introduce {\\em precoder index modulation}, where information bits are conveyed through the choice of a precoder matrix at the transmitter from a set of pre-determined pseudo-random phase...

Narasimhan, T. Lakshmi; Chockalingam, A.

2014-01-01

328

Simulation of Iodine-125 seeds photon spectra in the air by using the Monte Carlo method  

International Nuclear Information System (INIS)

Viewing the characteristics of the construction of I-125 seed sources, the low energy of the I-125 photons spectra and the large anisotropy of these photons energy fluence, this paper presents a study of those parameters and their influence on the dose calculations during the sources implant, and also the results of the simulation by using the EGS4 Monte Carlo code for the IMC.6711 I-125 seed photon model, produced by the Amersham Healthcare and Instituto de Pesquisas Energeticas da Comissao Nacional de Energia Nuclear. The intensity of the kerma in the air has been calculated based on the photon fluencies for distances ranging from the source surface to 5 cm in air

329

Compressed Air  

Science.gov (United States)

This website includes an animation which demonstrates a basic overview of compressed air for use in machines. Objective: Describe the different tools that can be used with compressed air. You can find the animation under the heading "Automation Technology."

2012-12-12

330

The Users of Indexes.  

Science.gov (United States)

Problems of indexing and index use lie at the heart of information use. They determine maximum possible use of information systems and sources, affect communication with users, influence the use of retrieved documents, and should form a more important field of research than past history indicates. Previous research provides some clues to user…

Beal, Christina

331

A new supersymmetric index  

International Nuclear Information System (INIS)

Witten's index has been an effective tool in addressing questions of supersymmetry breaking. It is natural to ask if there are other 'index-like' objects which can be computed exactly and provide further insight into the structure of supersymmetric theories. In this work such an index is reported. The index is related to the geometry of the vacua and satisfies an exact differential equation as a function of ?. For integrable theories the index can also be computed thermodynamically by using the exact S-matrix. The equivalence of these two results implies a highly non-trivial equivalence of a set of coupled integral equations with these differential equations, among them Painleve III and the affine Toda equations. 56 refs

332

In-air calibration of an HDR 192Ir brachytherapy source using therapy ion chambers.  

Science.gov (United States)

The Gammamed Plus 192Ir high dose rate brachytherapy sources were calibrated using the therapy level ionization chambers (0.1 and 0.6 cc) and the well-type chamber. The aim of the present study was to assess the accuracy and suitability of use of the therapy level chambers for in-air calibration of brachytherapy sources in routine clinical practice. In a calibration procedure using therapy ion chambers, the air kerma was measured at several distances from the source in a specially designed jig. The room scatter correction factor was determined by superimposition method based on the inverse square law. Various other correction factors were applied on measured air kerma values at multiple distances and mean value was taken to determine the air kerma strength of the source. The results from four sources, the overall mean deviation between measured and quoted source strength by manufacturers was found -2.04% (N = 18) for well-type chamber. The mean deviation for the 0.6 cc chamber with buildup cap was found -1.48 % (N = 19) and without buildup cap was 0.11% (N = 22). The mean deviation for the 0.1 cc chamber was found -0.24% (N = 27). Result shows that probably the excess ionization in case of 0.6 cc therapy ion chamber without buildup cap was estimated about 2.74% and 1.99% at 10 and 20 cm from the source respectively. Scattered radiation measured by the 0.1 cc and 0.6 cc chamber at 10 cm measurement distance was about 1.1% and 0.33% of the primary radiation respectively. The study concludes that the results obtained with therapy level ionization chambers were extremely reproducible and in good agreement with the results of the well-type ionization chamber and source supplier quoted value. The calibration procedure with therapy ionization chambers is equally competent and suitable for routine calibration of the brachytherapy sources. PMID:17998656

Patel, Narayan Prasad; Majumdar, Bishnu; Vijiyan, V; Hota, Pradeep K

2005-01-01

333

Fundamental data on environmental gamma-ray fields in the air due to sources in the ground  

International Nuclear Information System (INIS)

This report documents the extensive results of calculations of gamma-ray fields due to sources distributed in the ground. Air kerma per unit source density at 12 heights up to 300 m above the ground was calculated using a Monte Carlo method for monoenergetic plane sources in and on the ground and for natural radionuclides uniformly distributed in the ground. In case of plane sources, calculations were performed for 18 photon energies from 10 keV to 5 MeV and for 22 source depths expressed in mass per unit area ranging from 0 to 200 g/cm2. For natural nuclides, the whole lines compiled in a recent nuclear data file were taken into account. With respect to kerma in air and fluence of primary photon, the whole calculated results are shown in this report. For double-differential gamma-ray fields, several heights and source depths were selected to demonstrate the features. The calculated data for different soil compositions in energy range up to 100 keV were also shown to give the measure of the effect of soil compositions. (author)

334

Concurrency Control for Adaptive Indexing  

CERN Document Server

Adaptive indexing initializes and optimizes indexes incrementally, as a side effect of query processing. The goal is to achieve the benefits of indexes while hiding or minimizing the costs of index creation. However, index-optimizing side effects seem to turn read-only queries into update transactions that might, for example, create lock contention. This paper studies concurrency control in the context of adaptive indexing. We show that the design and implementation of adaptive indexing rigorously separates index structures from index contents; this relaxes the constraints and requirements during adaptive indexing compared to those of traditional index updates. Our design adapts to the fact that an adaptive index is refined continuously, and exploits any concurrency opportunities in a dynamic way. A detailed experimental analysis demonstrates that (a) adaptive indexing maintains its adaptive properties even when running concurrent queries, (b) adaptive indexing can exploit the opportunity for parallelism due ...

Graefe, Goetz; Idreos, Stratos; Kuno, Harumi; Manegold, Stefan

2012-01-01

335

A Ventilation Index for Tropical Cyclones  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An important environmental control of both tropical cyclone intensity and genesis is vertical wind shear. One hypothesized pathway by which vertical shear affects tropical cyclones is midlevel ventilation—or the flux of low-entropy air into the center of the tropical cyclone. Based on a theoretical framework, a ventilation index is introduced that is equal to the environmental vertical wind shear multiplied by the nondimensional midlevel entropy deficit divided by the potential intensity. T...

Tang, Brian; Emanuel, Kerry Andrew

2012-01-01

336

Measuring environmental quality. An index of pollution  

International Nuclear Information System (INIS)

This paper develops an index of pollution based on the epidemiological dose-response function associated with each pollutant, and the welfare losses due to exposure to pollution. The probability of damage is translated into welfare losses, which provides the common metric required for aggregation. Isopollution surfaces may then be used to compare environmental quality over time and space. An Air Pollution Index (API) is computed using 1997 data for the criteria pollutants under the Clean Air Act (CAA). The results are compared with the EPA's Pollutant Standards Index (PSI). Two significant differences emerge: unlike the PSI, the API facilitates a detailed ranking of regions by air quality and API values may contradict PSI results. Some regions with PSI values of 100-200 are considered less polluted under the proposed methodology than those with PSI values between 50 and 100. The key reason for the difference is that PSI values are determined entirely by the gas with the highest relative concentration whereas the API value is based on the ambient concentrations of all pollutants. 14 refs

337

A new supersymmetric index  

International Nuclear Information System (INIS)

We show that Tr(-1)FF e-?H is an index for N = 2 supersymmetric theories in two dimensions, in the sense that it is independent of almost all deformations of the theory. This index is related to the geometry of the vacua (Berry's curvature) and satisfies an exact differential equation as a function of ?. For integrable theories we can also compute the index thermodynamically, using the exact S-matrix. The equivalence of these two results implies a highly non-trivial equivalence of a set of coupled integral equations with these differential equations, among them Painleve III and the affine Toda equations. (orig.)

338

Practical Hydrogen Loading of Air Silica Fibres  

DEFF Research Database (Denmark)

A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown.

SØrensen, Henrik Rokkjær; Jensen, Jesper Bevensee

2005-01-01

339

Gradient index metamaterials.  

Science.gov (United States)

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a range of microwave frequencies. The gradient index metamaterial may prove an advantageous alternative approach to the development of gradient index lenses and similar optics, especially at higher frequencies. In particular, the gradient index metamaterial we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated. PMID:15903607

Smith, D R; Mock, J J; Starr, A F; Schurig, D

2005-03-01

340

CAD Centre - Index Searcher  

Science.gov (United States)

A searchable index of the CAD Centre, a postgraduate teaching and research unit in design manufacture and engineering management, with research focused on design methods and computer support of the design process for engineering applications.

2007-10-11

 
 
 
 
341

The Index of Refraction  

Science.gov (United States)

In this media-rich lesson plan, students explore the refraction of light at the boundary between materials: they learn about the refractive indices of various materials and measure the index of refraction of plastic or gelatin.

Foundation, Wgbh E.

2011-10-25

342

The Oswestry Disability Index.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

STUDY DESIGN: The Oswestry Disability Index (ODI) has become one of the principal condition-specific outcome measures used in the management of spinal disorders. This review is based on publications using the ODI identified from the authors' personal databases, the Science Citation Index, and hand searches of Spine and current textbooks of spinal disorders. OBJECTIVES: To review the versions of this instrument, document methods by which it has been validated, collate data from scores found in...

Fairbank, Jc; Pynsent, Pb

2000-01-01

343

Open access citation index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Conclusions of the breakout session "Open access citation index". What’s wrong with the Science Citation Index? Because of it’s power it has some pernicious side effects: A relatively small group of people decides which journals are to be included. There are somewhere between 24.000 (Harnad) and 40.000 (Garfield) journals. 7.000 or 8.000 are included in SCI.

Gue?don, Jean-claude

2004-01-01

344

Monitoring of Air Polution by Using Fuzzy Logic  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Air Quality Index is a simple and generalized way to describe the air quality in China, Hong Kong, Malaysia and now in India. Indian Air Quality Index (IND-AQI) is mainly a health related index with the descriptor words: “Good (0- 100)”, “Moderate (101-200 )”, “Poor (201-300)”, “Very Poor (301-400)”, “Severe (401-500)”. State Environment Protection Agency (SEPA ) is responsible for measuring the level of air pollution in China . In China the AQI is based on the level o...

Dr. Gopal Upadhyaya,; Mr. Nilesh Dashore

2010-01-01

345

Hydrophytometeorological indexes of Virginia type tobacco  

Directory of Open Access Journals (Sweden)

Full Text Available The field trial of Virginia type tobacco (Hevesi-9 was set in irrigation conditions, in the vicinity of Brzi Brod village, Nišava River's valley, on the alluvium soil type. Water consumption for evapotranspiration, at the irrigated variant and the control one, was calculated for each month and the whole vegetation period, by making the balance between water consumption from the soil layer to 2m under the ground, total precipitation amount in the vegetation and water added by irrigation. Hydro-phyto-meteorological indexes of Virginia type tobacco were calculated in regard to air temperature, relative air humidity, air humidity deficiency, sunshine duration and global radiation. Among the six meteorological elements (the above mentioned five and wind speed analyzed in the studied period, the highest level of correlation with tobacco ETP was shown by air temperature (r=0.88, so the use of hydro-phytotermic index could be recommended for calculation of potential evapotranspiration in irrigation practice.

Aksi? Miroljub

2008-01-01

346

Index of Refraction  

Science.gov (United States)

Refraction is an important behavior of light that can be used to explain the operation of lenses, prisms, and optical fiber, as well as natural phenomena such as rainbows and mirages. The index of refraction, or refractive index, is defined as the ratio of the speed of light in a vacuum to the speed of light in a material. The index of refraction is an important property of optical materials and one that can be easily measured in the laboratory.This lesson begins with a video that introduces the concept of refraction. Students learn firsthand how when a wave of light travels from one medium to another, the change in the wave's speed leads to a change in its wavelength and the bending of the wave. Next, students investigate index of refraction through an interactive media asset, research, and a class discussion. Following a video about the index of refraction and Snell's law, students work in groups to conduct their own laboratory experiment to measure the index of refraction of gelatin (or plastic).Note: This is the first of two optics lesson plans. You may want to follow this lesson with the Fiber Optics Lesson Plan.

2012-05-24

347

Hot Air  

Science.gov (United States)

In this activity, learners set up an experiment to investigate the effects of hot air on the path of a laser beam. They observe the wandering position of the laser beam spot on the wall after the light travels through hot air rising from the candle flame. Learners produce a table of observations from both the Cool Air and Hot Air experiments, and answer questions using evidence from their experiment. Apply what learners discover in this experiment to real-life by discussing why stars "twinkle."

Observatory, The U.

2011-01-01

348

The Quilt Index  

Science.gov (United States)

With the goal of creating a single, comprehensive index to American quilts, the Quilt Index builds on the work of 4 state quilt documentation and digitization projects: the Michigan Quilt Project, Kentucky Quilt Project, Illinois Quilt Research Project, and Quilts of Tennessee (more information about these projects is at the site). Currently almost 900 quilt images and pieces of information are searchable in the Quilt Index. The project has established standards for data elements to be collected, and forms to facilitate the addition of quilt documentation from other states. Quilts dating from 1800 to 1999 can be searched by pattern name, quilter's name, location made, date, and collection or documentation project. Searches by pattern name (baby blocks, ocean waves, wedding ring) are possible, but the interface is quite picky about singular and plural. Several ways to browse are also available, such as by collection, period, and style/technique, or choose "view the entire index" to display 887 quilts and records. The Quilt Index is hosted by MATRIX, the humanities technology center at Michigan State University that also hosts H-Net, Humanities and Social Sciences OnLine.

349

Clean Air Kids: Air Quality  

Science.gov (United States)

This resource for younger students is part of a series of information sheets about the atmosphere, climate, and the environment. It offers information about the cause and effects of air pollution, both past and present, and an explanation about deadly smog and the advent of clean air acts. It also provides information about indoor pollution and the dangers of smoking. Two special sections tell why clean air is improtant to human health and the nature and origin of pollutants.

350

UV Index estimation from global radiation and total ozone observations in Azores  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The UV Index (UVI) is a public-oriented meteorological kind of information about the damaging ultraviolet radiation at the ground (Vaniceck et al., 1999). Its use begins to be so popular as temperatures highs, wind chill, fire risk index, air quality index and other meteorological indexes and parameters. A UVI scale was already defined by WHO (WHO, 2002) in order to provide a correspondence between UVI levels and protective measures to avoid damaging effects on humans. However, UVI is usually...

Carvalho, Fernanda; Henriques, Diamantino; Fialho, Paulo

2007-01-01

351

Air Pollution  

Science.gov (United States)

Students are introduced to the concept of air quality by investigating the composition, properties, atmospheric layers and everyday importance of air. They explore the sources and effects of visible and invisible air pollution. By learning some fundamental meteorology concepts (air pressure, barometers, prediction, convection currents, temperature inversions), students learn the impact of weather on air pollution control and prevention. Looking at models and maps, they explore the consequences of pollutant transport via weather and water cycles. Students are introduced to acids, bases and pH, and the environmental problem of acid rain, including how engineers address this type of pollution. Using simple models, they study the greenhouse effect, the impact of increased greenhouse gases on the planet's protective ozone layer and the global warming theory. Students explore the causes and effects of the Earth's ozone holes through an interactive simulation. Students identify the types and sources of indoor air pollutants in their school and home, evaluating actions that can be taken to reduce and prevent poor indoor air quality. By building and observing a few simple models of pollutant recovery methods, students explore the modern industrial technologies designed by engineers to clean up and prevent air pollution.

Integrated Teaching and Learning Program,

352

ResearchIndex  

Science.gov (United States)

Sponsored by the NEC Research Institute, ResearchIndex was created to improve the dissemination, functionality, usability, and efficiency of online scientific literature by demonstrating and providing "algorithms, techniques, and software that can be used in other digital libraries." The current demonstration database indexes over 150,000 computer science articles containing over 2 million citations. Searchable by keyword only, database returns feature several options. Users can review a list of citations to a given paper with links to the full text articles (Postscript or .pdf format), view related articles, and sign up to have new citations for selected articles emailed to them. In the future, users should also be able to review a dynamically created and continuously updated bibliography. Additional resources at the site include a collection of papers about citation indexing, digital libraries, Web analysis, and neural networks. Users may also submit papers to the database and subscribe to be notified when additional databases become available at the site.

353

Internet Corruption Perception Index  

Science.gov (United States)

The Internet Corruption Perception Index is provided by Transparency International and Goettingen University, Germany. The goal of the site to "rank countries by the extent of corruption in public administration." The ranking can then be used to help assess country risks. The Internet Corruption Perception Index is published annually and is based on "surveys undertaken by Gallup International, the World Competitiveness Yearbook, assessments by Political & Economic Risk Consultancy in Hong Kong, DRI/McGraw Hill Global Risk Service, Political Risk Services in Syracuse, USA, and data gathered from internet sources directly." The index for 1997 covers 52 countries, including both developed and developing countries. Recently added to the site is the report on the bribery propensity of leading exporting nations; this section investigates the "propensity to pay bribes for the acquisition of contracts in international trade." At the site, visitors can provide their own input on a country's bribery propensity.

1997-01-01

354

A new supersymmetric index  

Energy Technology Data Exchange (ETDEWEB)

We show that Tr(-1)[sup F]F e[sup -[beta]H] is an index for N = 2 supersymmetric theories in two dimensions, in the sense that it is independent of almost all deformations of the theory. This index is related to the geometry of the vacua (Berry's curvature) and satisfies an exact differential equation as a function of [beta]. For integrable theories we can also compute the index thermodynamically, using the exact S-matrix. The equivalence of these two results implies a highly non-trivial equivalence of a set of coupled integral equations with these differential equations, among them Painleve III and the affine Toda equations. (orig.).

Cecotti, S. (International School for Advanced Studies, SISSA-ISAS, Trieste (Italy) INFN, Trieste (Italy)); Fendley, P. (Dept. of Physics, Boston Univ., MA (United States)); Intriligator, K.; Vafa, C. (Lyman Lab. of Physics, Harvard Univ., Cambridge, MA (United States))

1992-11-09

355

Sustainability index for Taipei  

International Nuclear Information System (INIS)

Sustainability indicators are an effective means of determining whether a city is moving towards sustainable development (SD). After considering the characteristics of Taipei, Taiwan, discussions with experts, scholars and government departments and an exhaustive literature review, this study selected 51 sustainability indicators corresponding to the socio-economic characteristic of Taipei City. Such indicators should be regarded as a basis for assessing SD in Taipei City. The 51 indicators are classified into economic, social, environmental and institutional dimensions. Furthermore, statistical data is adopted to identify the trend of SD from 1994 to 2004. Moreover, the sustainability index is calculated for the four dimensions and for Taipei as a whole. Analysis results demonstrate that social and environmental indicators are moving towards SD, while economic and institutional dimensions are performing relatively poorly. However, since 2002, the economic sustainability index has gradually moved towards SD. Overall, the Taipei sustainability index indicates a gradual trend towards sustainable development during the past 11 years

356

Introduction of a Cooling-Fan Efficiency Index  

DEFF Research Database (Denmark)

In a warm environment, air movement with elevated velocity is a well-known cooling strategy. The local air movement is typically generated by cooling fans (e.g., ceiling fan, table fans, etc.). Appearance, power input, and price are the main parameters considered today when purchasing cooling fans, while cooling capacity and efficiency of energy use are unknown. To address this knowledge gap, this paper introduces the cooling-fan efficiency (CFE) index, defined as the ratio between the cooling effect (measured with a thermal manikin) generated by the device and its power consumption. The index was determined for a ceiling fan, a desk fan, standing fan, and a tower fan in a real office at three room air temperatures and at different fan speed levels. The results reveal that the index is sensitive enough to identify differences in the performance of the cooling devices. A standard method for testing fan cooling effect and an index for determining fan efficiency, such as the CFE index proposed in this study, need to be developed. The cooling fans generate a nonuniform velocity field around occupants, which cannot be described with a single air-velociry value. Therefore, it is not clear how to apply in practice the recommended elevated velocities in warm environments presented in the present standards. The standards need to be revised.

Schiavon, S.; Melikov, Arsen Krikor

2009-01-01

357

A compact wide range radioisotope calibrator with digital display using an air-equivalent re-entrant chamber  

International Nuclear Information System (INIS)

This instrument combines a 400 cm3 re-entrant air-equivalent chamber and a measuring part comprising a MOSFET electrometer, a V to F converter and a variable time-base. Activities in the range of 100 kBq-40 GBq of ?-emitters (30 keV-2 MeV) in various configurations, can be measured within 2 s with a chamber polarizing voltage of only 60 V. The precision is +- 1% (1?) down to an activity of 4 MBq (approximately equal to 100 ?Ci) of 137Cs. By setting the air-kerma or exposure rate constant or the radionuclide, an overall accuracy of +-5% can be achieved. (author)

358

Variation of transmittance spectra of porous antireflection coatings with index profile  

International Nuclear Information System (INIS)

Transmittance spectra were calculated for single-layer coatings with the homogeneous refractive index, index profiles that increase monotonically with distance into the coating, and index profiles that rise in discrete steps. The calculations predict that large transmittance at tuned wavelengths can be obtained using any of these coating designs and known, porous silica coating materials. The spectral bandwidth of transmittance maxima increases when the index profile is altered from homogeneous to any profile whose index increases monotonically with thickness in the coating. Bandwidth is greatest for the linear-ramp coating whose index rises linearly from that of air to that of the substrate

359

Neural computing thermal comfort index for HVAC systems  

International Nuclear Information System (INIS)

The primary purpose of a heating, ventilating and air conditioning (HVAC) system within a building is to make occupants comfortable. Without real time determination of human thermal comfort, it is not feasible for the HVAC system to yield controlled conditions of the air for human comfort all the time. This paper presents a practical approach to determine human thermal comfort quantitatively via neural computing. The neural network model allows real time determination of the thermal comfort index, where it is not practical to compute the conventional predicted mean vote (PMV) index itself in real time. The feed forward neural network model is proposed as an explicit function of the relation of the PMV index to accessible variables, i.e. the air temperature, wet bulb temperature, globe temperature, air velocity, clothing insulation and human activity. An experiment in an air conditioned office room was done to demonstrate the effectiveness of the proposed methodology. The results show good agreement between the thermal comfort index calculated from the neural network model in real time and those calculated from the conventional PMV model

360

Comparing the Palmer Drought Index and the Standardized Precipitation Index for Zagreb-Gric Observatory  

Science.gov (United States)

Conventional Palmer Drought Index (PDSI) and recent Standardized Precipitation Index (SPI) are compared for Zagreb-Gric weather station. Historical time series of PDSI and SPI are compared. For that purpose monthly precipitation, air temperature and air humidity data for Zagreb-Gric Observatory and period 1862-2010 are used. The results indicate that SPI is simpler for interpretation than PDI. On the other side, lack of temperature within SPI, make impossible use of it on climate change applications. Further development of both indices is required. Possible applications of them in irrigation scheduling system is considered as well for drought risk assessment. In addition, a comparison of PDSI and SPI for the periods from 1 to 24 months indicate the best agreement between PDSI and SPI for the periods from 6 to 12 months.

Pandzic, Kreso

2014-05-01

 
 
 
 
361

About Air Toxics  

Science.gov (United States)

... Air Toxics Web site About Air Toxics About Air Toxics What are toxic air pollutants? What are ... more information, see Mobile Source Air Toxics . Indoor air -- EPA, in close cooperation with other Federal agencies ...

362

Indexing Theory and Retrieval Effectiveness.  

Science.gov (United States)

Describes recent attempts to make explicit connections between the indexing process and the use of the index or information retrieval system, particularly the utility-theoretic and automatic indexing models of William Cooper and Stephen Harter. Theory and performance, information storage and retrieval, search stage feedback, and indexing are also…

Robertson, Stephen E.

1978-01-01

363

Fiber optic refractive index monitor  

Science.gov (United States)

A sensor for measuring the change in refractive index of a liquid uses the lowest critical angle of a normal fiber optic to achieve sensitivity when the index of the liquid is significantly less than the index of the fiber core. Another embodiment uses a liquid filled core to ensure that its index is approximately the same as the liquid being measured.

Weiss, Jonathan David (Albuquerque, NM)

2002-01-01

364

$Local^{3}$ Index Theorem  

CERN Document Server

$Local^{3}$ Index Theorem means $Local(Local(Local \\;Index \\; Theorem)))$. $Local \\; Index \\; Theorem$ is the Connes-Moscovici local index theorem \\cite{Connes-Moscovici1}, \\cite{Connes-Moscovici2}. The second "Local" refers to the cyclic homology localised to a certain separable subring of the ground algebra, while the last one refers to Alexander-Spanier type cyclic homology. The Connes-Moscovici work is based on the operator $R(A) = \\mathbf{P} - \\mathbf{e}$ associated to the elliptic pseudo-differential operator $A$ on the smooth manifold $M$, where $\\mathbf{P}$, $\\mathbf{e}$ are idempotents, see \\cite{Connes-Moscovici1}, Pg. 353. The operator $R(A)$ has two main merits: it is a smoothing operator and its distributional kernel is situated in an arbitrarily small neighbourhood of the diagonal in $M \\times M$. The operator $R(A)$ has also two setbacks: -i) it is not an idempotent (and therefore it does not have a genuine Connes-Chern character); -ii) even if it were an idempotent, its Connes-Chern character ...

Teleman, Nicolae

2011-01-01

365

Glycemic Index Values Database  

Science.gov (United States)

NCI has developed a listing of Glycemic Index (GI) values for individual foods. Food codes from the USDA Continuing Survey of Food Intakes of Individuals (CSFII) are used as a reference. This file provides GI values for those foods consumed by adults and queried on the DHQ or other FFQs used at NCI.

366

On indexed actions  

CERN Document Server

We present some laws relating the $\\Cat$-indexed categories of left, right and bi-actions: by defining $(A\\comp M)x = Mx^{Ax}$ one gets a biclosed monoidal action of $\\Set^{X\\op}$ on $(\\Set^X)\\op$, while $\\B X$ and $\\Cat/X$ act (partially) on their opposites by exponentials; both the inclusions $(\\B X,\\B X)\\to (\\Set^{X\\op},\\Set^X) \\to (\\Cat/X,\\Cat/X)$ preserve the (cartesian) monoidal structures and the actions, and the same holds for substitutions along functors. These strong morphisms of strong indexed monoidal actions have in fact a wider range of applications; in particular, replacing $\\Set$ with any (co)complete symmetric monoidal closed category $\\V$, we consider the pair of indexed categories $(\\V_0^{X\\op},\\V_0^X ; X\\in\\Cat)$ with the pair of biclosed indexed monoidal actions of each one on the opposite of the other one and its formal relationships with biactions and constant actions. Some of the resulting laws also hold in a fragment of biclosed bicategory (with an object supporting a symmetric monoid...

Pisani, Claudio

2012-01-01

367

Miller Indexes Examples Animation  

Science.gov (United States)

This 3-D animation is a visualization of the Miller indices (Miller indexes) showing approximately 24 various possible planes. The 3 intercepts are shown along with the plane notation. This would be useful for understanding reciprocal lattice vectors, specifically in crystallographic studies for electrical engineering.

2009-07-22

368

Infinitesimal index: cohomology computations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this note several computations of equivariant cohomology groups are performed. For the compactly supported equivariant cohomology, the notion of infinitesimal index developed in arXiv:1003.3525, allows to describe these groups in terms of certain spaces of distributions arising in the theory of splines. The new version contains a large number of improvements.

Concini, Corrado; Procesi, Claudio; Vergne, Michele

2010-01-01

369

GeoIndex  

Science.gov (United States)

GeoIndex, povided by the Datasurge Company, is a search engine specially geared towards geo-environmental professionals. Specific database topics include geotechnical, environmental, hydrogeology, geology, mining, and petroleum. The website is searched via phrases entered by the user. Searches can be narrowed by entering multiple phrases and limiting the search to one of the four key areas: Companies, Associations, Education, and Government.

370

Recommended concentration limits of indoor air pollution indicators for requirement of acceptable indoor air quality  

Directory of Open Access Journals (Sweden)

Full Text Available Object and goals of indoor air pollution control with ventilation may influence improvement of indoor air quality, building energy consumption and even carbon emissions. Indicators of indoor air pollution caused by occupants-related sources and building-related sources were chosen based on sources emitting characteristics, pollutants composition, indicator choosing principles and indoor air pollution situation in China. Then the recommended concentration limits of indicators were given for unadapted and adapted persons according to logarithmic index evaluation method, combined with percentage of dissatisfaction and joint effect of indoor air pollution caused by these two kinds of sources.

Wang J., Zhang X.

2010-07-01

371

New share index to track progress of environmental industry  

International Nuclear Information System (INIS)

This article discusses the work of the environmental finance house Imax Capital in persuading investors to invest in environmental industries. The development of the ET-50 Index by Impax Capital Asset Management to track progress of the environmental industry is reported, and the categories of the ET-50 including alternative energy generators and equipment providers, air and water pollution control, soil and site remediation, recycling and waste management, and environmental engineering and consulting are considered. The performance of the ET-50 Index, and the work of Impax and RER in the development of a dedicated renewable energy share index by are discussed

372

Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources  

Energy Technology Data Exchange (ETDEWEB)

Purpose: Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring the air kerma strength of {sup 125}I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for {sup 125}I selectSeed{sup TM} brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level.Results: Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber.Conclusions: Variations of the altitude and changes in the weather conditions may produce significant density corrections, and that effect should be taken into account. This effect is chamber-dependent, indicating that a specific calibration is necessary for each particular chamber. To our knowledge, this correction has not been considered so far for SourceCheck ionization chambers, but its magnitude cannot be neglected in clinical practice. The atmospheric pressure and temperature at which the chamber was calibrated need to be taken into account, and they should be reported in the calibration certificate. In addition, each institution should analyze the particular response of its SourceCheck ionization chamber and compute the adequate correction factors. In the absence of a suitable pressure chamber, a possibility for this assessment is to take measurements at different altitudes, spanning a wide enough air density range.

Tornero-López, Ana M.; Guirado, Damián; Ruiz-Arrebola, Samuel [Servicio de Radiofísica y Protección Radiológica, Hospital Universitario San Cecilio, E-18012 Granada (Spain); Perez-Calatayud, Jose [Servicio de Radioterapia, Unidad de Radiofísica, Hospital Universitario y Politécnico La Fe, E-46026 Valencia (Spain); Simancas, Fernando; Lallena, Antonio M. [Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Gazdic-Santic, Maja [Department of Medical Physics and Radiation Safety, Clinical Centre of Sarajevo University, 71000 Sarajevo (Bosnia and Herzegovina)

2013-12-15

373

[Seedling index of Salvia miltiorrhiza and its simulation model].  

Science.gov (United States)

Through the correlation analysis on the quantitative traits and their ratios of Salvia miltiorrhiza seedlings and seedling quality, a series of representative indices reflecting the seedling quality of the plant species were determined, and the seedling index suitable to the S. miltiorrhiza seedlings was ascertained by correlation degree analysis. Meanwhile, based on the relationships between the seedling index and the air temperature, solar radiation and air humidity, a simulation model for the seedling index of S. miltiorrhiza was established. The experimental data of different test plots and planting dates were used to validate the model. The results showed that the root diameter, stem diameter, crown dry mass, root dry mass, and plant dry mass had significant positive relationships with the other traits, and could be used as the indicators of the seedling's health. The seedling index of S. miltiorrhiza could be calculated by (stem diameter/root diameter + root dry mass/crown dry mass) x plant dry mass. The stem diameter, root dry mass, crown dry mass and plant dry mass had higher correlations with the seedling index, and thus, the seedling index determined by these indicators could better reflect the seedling's quality. The coefficient of determination (R2) between the predicted and measured values based on 1:1 line was 0.95, and the root mean squared error (RMSE) was 0.15, indicating that the model established in this study could precisely reflect the quantitative relationships between the seedling index of S. miltiorrhiza and the environmental factors. PMID:23359940

Huang, Shu-Hua; Xu, Fu-Li; Wang, Wei-Ling; Du, Jun-Bo; Ru, Mei; Wang, Jing; Cao, Xian-Yan

2012-10-01

374

Conformity index: A review  

International Nuclear Information System (INIS)

We present a critical analysis of the conformity indices described in the literature and an evaluation of their field of application. Three-dimensional conformal radiotherapy, with or without intensity modulation, is based on medical imaging techniques, three-dimensional dosimetry software, compression accessories, and verification procedures. It consists of delineating target volumes and critical healthy tissues to select the best combination of beams. This approach allows better adaptation of the isodose to the tumor volume, while limiting irradiation of healthy tissues. Tools must be developed to evaluate the quality of proposed treatment plans. Dosimetry software provides the dose distribution in each CT section and dose-volume histograms without really indicating the degree of conformity. The conformity index is a complementary tool that attributes a score to a treatment plan or that can compare several treatment plans for the same patient. The future of conformal index in everyday practice therefore remains unclear

375

Film Literature Index  

Science.gov (United States)

This very ambitious project from Indiana University was funded by the National Endowment for the Humanities, and it continues to be updated on a regular basis. The Film Literature Index (FLI) annually indexes 150 film and television periodicals from 30 countries in their entirety, along with 200 other periodicals selectively for articles on film and television. The FLI database can be searched by subject headings, names, production titles, or by corporate names. Visitors can browse around, or perform advanced searches as their needs require. More information about the project can be found in the "About FLI" section, which can be accessed at the top of the homepage. Here visitors can learn about the history of the FLI, and also read about various papers and presentations that document the creation of the FLI Online site.

376

New Economy Index  

Science.gov (United States)

The New Economy Index is a series of indicators that are "gathered from existing public and private data, to illustrate fundamental structural changes in the US economy, to show what those changes mean in the lives of working Americans, and to measure the nation's progress in several key foundation areas for future economic growth." The data in this excellent resource are divided into three sections. What's New About the New Economy includes thirteen indications that show the uniqueness and structure of the new technology-based and innovation-based economy. The second section considers the ways in which the New Economy will affect the lives of American workers. Finally, the third section, Foundations for Future Growth, projects the future growth of technology in the US. The site also includes information about the data sources, endnotes, and several side articles. Although the New Economy Index was created in 1998, the information is still valid and useful.

377

Degree Sequence Index Strategy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We introduce a procedure, called the Degree Sequence Index Strategy (DSI), by which to bound graph invariants by certain indices in the ordered degree sequence. As an illustration of the DSI strategy, we show how it can be used to give new upper and lower bounds on the $k$-independence and the $k$-domination numbers. These include, among other things, a double generalization of the annihilation number, a recently introduced upper bound on the independence number. Next, we us...

Caro, Yair; Pepper, Ryan

2012-01-01

378

Potential vorticity index  

Science.gov (United States)

Based on the European Center For Medium Range Weather Forecasting (ECMWF) First Global Atmospheric Research Program Global Experiment (FGGE) IIIb data set in the 1978 to 1979 winter, a potential vorticity (PV) index was defined as a measure of the zonally averaged, mid-latitude PV gradient on the 300 K isentropic surface in the Northern Hemisphere. The evolution of that index and its relation to teleconnection patterns of 500 mb geopotential height anomaly are studied. The results of the temporal and spatial variation of blocking and cyclogenesis in the 1978 to 1979 winter and its relation to global and local PV gradients were obtained. Complex empirical orthogonal function (EOF) analyses were performed, using the same FGGE data set for the 1978 to 1979 winter, for a representative high latitude band and mid latitude band geopotential height anomalies at 500 mb, phi sub h, phi sub m, and PV gradient at 300 K, delta(Q), at each longitude for the three month period. The focus of current research is the following: (1) to perform Fourier analyses for the first three EOF's of phi sub h, phi sub m, and delta(Q) at given latitude bands, and to find the dominant wavenumbers and frequencies which are responsible for these EOF's; (2) to compare the results from EOF and Fourier analyses which will be used to explore the relations of blocking and cyclogensis with local and global PV gradients; and (3) to study the time dependence of the local PV gradients and relate it to the PV index vacillation cycles observed in the PV index cycle.

Barcilon, Albert; Weng, Hengyi

1991-01-01

379

SCARF SOCIAL FUNCTIONING INDEX  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several instruments measuring social functioning have been developed in the last four decades, as a result of the increasing interest in community care of the chronic mentally ill. SCARF Social Functioning Index (SSFI) was developed to meet the pressing need for an instrument which was easy to administer and which could be used by all mental health professionals. The SSFI comprises four main sections: self concern, occupational role, role in the family and other social roles. Each section has...

Padmavathi, R.; Thara, R.; Srinivasan, Latha; Kumar, Shuba

1995-01-01

380

Indexical Hybrid Tense Logic  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we explore the logic of now, yesterday, today and tomorrow by combining the semantic approach to indexicality pioneered by Hans Kamp [9] and refined by David Kaplan [10] with hybrid tense logic. We first introduce a special now nominal (our @now corresponds to Kamp’s original now operator N) and prove completeness results for both logical and contextual validity. We then add propositional constants to handle yesterday, today and tomorrow; our system correctly treats sentences ...

Jørgensen, Klaus Frovin; Blackburn, Patrick Rowan

2012-01-01

 
 
 
 
381

Air Pollution and Cardiovascular System  

Directory of Open Access Journals (Sweden)

Full Text Available Air pollution is one of the environmental problems that threaten the public health. The air is a gas mixture. Air pollution is defined as the existence in the amount of pollutants harmful to humans and other organisms in the atmosphere as a result of the natural or human activity thereby changing to the gas rates in the air. The negative effects of pollution-causing particles on the health are closely related to the chemical structure of particles, whether causing a fibrotic reaction, whether having an amorphous shape and the aerodynamic diameters of particles. The particles larger than 10 microns in aerodynamic diameter can not reach up to the alveoli, and can be removed by mucociliary system. If the particles are smaller than 10 microns, these particles can reach to the alveoli, and are closely associated with the cardiovascular mortality and morbidity. The concentration of these particles (PM10 is used as an indicator of pollution, and creates the basis for air quality index. Air pollution has several negative effects such as blood pressure changes, atherosclerosis, endothelial dysfunction, autonomic dysfunction, inflammation, oxidative stress etc. In this review, the effects of air pollution on the cardiovascular system will be examined, and the importance of this issue will be emphasized. [TAF Prev Med Bull 2011; 10(1.000: 97-106

Ejder Kardesoglu

2011-02-01

382

A proteome quality index.  

Science.gov (United States)

We present the Proteome Quality Index (PQI; http://pqi-list.org), a much-needed resource for users of bacterial and eukaryotic proteomes. Completely sequenced genomes for which there is an available set of protein sequences (the proteome) are given a one- to five-star rating supported by 11 different metrics of quality. The database indexes over 3000 proteomes at the time of writing and is provided via a website for browsing, filtering and downloading. Previous to this work, there was no systematic way to account for the large variability in quality of the thousands of proteomes, and this is likely to have profoundly influenced the outcome of many published studies, in particular large-scale comparative analyses. The lack of a measure of proteome quality is likely due to the difficulty in producing one, a problem that we have approached by integrating multiple metrics. The continued development and improvement of the index will require the contribution of additional metrics by us and by others; the PQI provides a useful point of reference for the scientific community, but it is only the first step towards a 'standard' for the field. PMID:25339269

Zaucha, Jan; Stahlhacke, Jonathan; Oates, Matt E; Thurlby, Natalie; Rackham, Owen J L; Fang, Hai; Smithers, Ben; Gough, Julian

2015-01-01

383

NASA: Beginner's Guide to Aerodynamics - Aerodynamics Index  

Science.gov (United States)

This web page contains an index of all topics available from NASA's Beginner's Guide to Aerodynamics site. Resources include lesson plans, activities, and interactive simulations for grades 3-12 relating to fundamentals of aerodynamics and the forces acting on airborne objects. The scope of content is extensive and includes specific topics such as thrust, lift, drag, relative velocity, air pressure and density, trajectory, and terminal velocity. Resources are also organized by grade level. These resources, available cost-free, were developed by scientists and teacher workshop participants at NASA's Glenn Learning Research Center.

2008-12-16

384

Determining the Thickness and Refractive Index of a Mirror  

Science.gov (United States)

When a laser beam reflects from a back surface glass mirror and falls on a screen, a pattern of discrete bright spots is created by partial reflection and refraction of the light at the air-glass interface and reflection at the mirror surface (Fig. 1). This paper explains how this phenomenon can be used to determine the refractive index and the…

Uysal, Ahmet

2010-01-01

385

Variación espacial de la exposición a contaminación atmosférica en la ciudad de Valencia y su relación con un índice de privación / The spatial distribution of population exposure to outdoor air pollution in Valencia (Spain) and its association with a privation index  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Objetivo: Evaluar la variación espacial de la exposición a dióxido de nitrógeno (NO2) en la ciudad de Valencia y su relación con la privación socioeconómica y la edad. Métodos: La población por sección censal (SC) procede del Instituto Nacional de Estadística. Los niveles de NO2 se midieron en 100 p [...] untos del área de estudio, mediante captadores pasivos, en tres campañas entre 2002 y 2004. Se utilizó regresión por usos del suelo (LUR) para obtener el mapa de los niveles de NO2. Las predicciones del LUR se compararon con las proporcionadas por: a) el captador más cercano de la red de vigilancia, b) el captador pasivo más cercano, c) el conjunto de captadores en un entorno y d) kriging. Se asignaron niveles de contaminación para cada SC. Se analizó la relación entre los niveles de NO2, un índice de privación con cinco categorías y la edad (>65 años). Resultados: El modelo LUR resultó el método más preciso. Más del 99% de la población superó los niveles de seguridad propuestos por la Organización Mundial de la Salud. Se encontró una relación inversa entre los niveles de NO2 y el índice de privación (? = -2,01?g/m³ en el quintil de mayor privación respecto al de menor, IC95%: -3,07 a -0,95), y una relación directa con la edad (? = 0,12?g/m³ por incremento en unidad porcentual de población >65 años, IC95%: 0,08 a 0,16). Conclusiones: El método permitió obtener mapas de contaminación y describir la relación entre niveles de NO2 y características sociodemográficas. Abstract in english Objective: To evaluate spatial variation in exposure to nitrogen dioxide (NO2) air pollution in the city of Valencia, Spain, and its association with socioeconomic deprivation and age. Methods: Census tract population data were obtained from the National Statistics Institute of Spain. Outdoor NO2 wa [...] s monitored in 100 sites in the study area, through the use of passive samplers, in three campaigns between 2002 and April 2004. Land use regression (LUR) was used to obtain a map of NO2 levels. The LUR predictions were compared with the NO2 level obtained by: a) the nearest sampler of the monitoring network, b) the nearest passive sampler, c) the mean distance-weighted levels of the samplers in the neighborhood, and d) the NO2 level obtained by using Kriging. For each census tract, the NO2 levels were obtained. The association of NO2 air pollution exposure with population age (>65 years) and the 5-category deprivation index was analyzed. Results: The LUR models showed less error than the other prediction methods. The safety levels proposed by the World Health Organization were exceeded in more than 99% of the population. An inverse relationship was found between NO2 levels and the deprivation index (? = -2.01?g/m³ in the most deprived quintile compared with lower deprivation, 95%CI: -3.07; -0.95) and a direct relationship was found with age (? = 0.12?g/m³ per unit increase in percentage of the population > 65 years, 95%CI: 0.08; 0.16). Conclusions: The method allowed pollution maps to be obtained and the association between NO2 levels and sociodemographic characteristics to be described.

Marisa, Estarlich; Carmen, Iñiguez; Ana, Esplugues; Enrique, Mantilla; Òscar, Zurriaga; Andreu, Nolasco; Ferran, Ballester.

2013-04-01

386

Variación espacial de la exposición a contaminación atmosférica en la ciudad de Valencia y su relación con un índice de privación / The spatial distribution of population exposure to outdoor air pollution in Valencia (Spain) and its association with a privation index  

Scientific Electronic Library Online (English)

Full Text Available SciELO Public Health | Language: Spanish Abstract in spanish Objetivo: Evaluar la variación espacial de la exposición a dióxido de nitrógeno (NO2) en la ciudad de Valencia y su relación con la privación socioeconómica y la edad. Métodos: La población por sección censal (SC) procede del Instituto Nacional de Estadística. Los niveles de NO2 se midieron en 100 p [...] untos del área de estudio, mediante captadores pasivos, en tres campañas entre 2002 y 2004. Se utilizó regresión por usos del suelo (LUR) para obtener el mapa de los niveles de NO2. Las predicciones del LUR se compararon con las proporcionadas por: a) el captador más cercano de la red de vigilancia, b) el captador pasivo más cercano, c) el conjunto de captadores en un entorno y d) kriging. Se asignaron niveles de contaminación para cada SC. Se analizó la relación entre los niveles de NO2, un índice de privación con cinco categorías y la edad (>65 años). Resultados: El modelo LUR resultó el método más preciso. Más del 99% de la población superó los niveles de seguridad propuestos por la Organización Mundial de la Salud. Se encontró una relación inversa entre los niveles de NO2 y el índice de privación (? = -2,01?g/m³ en el quintil de mayor privación respecto al de menor, IC95%: -3,07 a -0,95), y una relación directa con la edad (? = 0,12?g/m³ por incremento en unidad porcentual de población >65 años, IC95%: 0,08 a 0,16). Conclusiones: El método permitió obtener mapas de contaminación y describir la relación entre niveles de NO2 y características sociodemográficas. Abstract in english Objective: To evaluate spatial variation in exposure to nitrogen dioxide (NO2) air pollution in the city of Valencia, Spain, and its association with socioeconomic deprivation and age. Methods: Census tract population data were obtained from the National Statistics Institute of Spain. Outdoor NO2 wa [...] s monitored in 100 sites in the study area, through the use of passive samplers, in three campaigns between 2002 and April 2004. Land use regression (LUR) was used to obtain a map of NO2 levels. The LUR predictions were compared with the NO2 level obtained by: a) the nearest sampler of the monitoring network, b) the nearest passive sampler, c) the mean distance-weighted levels of the samplers in the neighborhood, and d) the NO2 level obtained by using Kriging. For each census tract, the NO2 levels were obtained. The association of NO2 air pollution exposure with population age (>65 years) and the 5-category deprivation index was analyzed. Results: The LUR models showed less error than the other prediction methods. The safety levels proposed by the World Health Organization were exceeded in more than 99% of the population. An inverse relationship was found between NO2 levels and the deprivation index (? = -2.01?g/m³ in the most deprived quintile compared with lower deprivation, 95%CI: -3.07; -0.95) and a direct relationship was found with age (? = 0.12?g/m³ per unit increase in percentage of the population > 65 years, 95%CI: 0.08; 0.16). Conclusions: The method allowed pollution maps to be obtained and the association between NO2 levels and sociodemographic characteristics to be described.

Marisa, Estarlich; Carmen, Iñiguez; Ana, Esplugues; Enrique, Mantilla; Òscar, Zurriaga; Andreu, Nolasco; Ferran, Ballester.

2013-04-01

387

Variación espacial de la exposición a contaminación atmosférica en la ciudad de Valencia y su relación con un índice de privación The spatial distribution of population exposure to outdoor air pollution in Valencia (Spain and its association with a privation index  

Directory of Open Access Journals (Sweden)

Full Text Available Objetivo: Evaluar la variación espacial de la exposición a dióxido de nitrógeno (NO2 en la ciudad de Valencia y su relación con la privación socioeconómica y la edad. Métodos: La población por sección censal (SC procede del Instituto Nacional de Estadística. Los niveles de NO2 se midieron en 100 puntos del área de estudio, mediante captadores pasivos, en tres campañas entre 2002 y 2004. Se utilizó regresión por usos del suelo (LUR para obtener el mapa de los niveles de NO2. Las predicciones del LUR se compararon con las proporcionadas por: a el captador más cercano de la red de vigilancia, b el captador pasivo más cercano, c el conjunto de captadores en un entorno y d kriging. Se asignaron niveles de contaminación para cada SC. Se analizó la relación entre los niveles de NO2, un índice de privación con cinco categorías y la edad (>65 años. Resultados: El modelo LUR resultó el método más preciso. Más del 99% de la población superó los niveles de seguridad propuestos por la Organización Mundial de la Salud. Se encontró una relación inversa entre los niveles de NO2 y el índice de privación (? = -2,01?g/m³ en el quintil de mayor privación respecto al de menor, IC95%: -3,07 a -0,95, y una relación directa con la edad (? = 0,12?g/m³ por incremento en unidad porcentual de población >65 años, IC95%: 0,08 a 0,16. Conclusiones: El método permitió obtener mapas de contaminación y describir la relación entre niveles de NO2 y características sociodemográficas.Objective: To evaluate spatial variation in exposure to nitrogen dioxide (NO2 air pollution in the city of Valencia, Spain, and its association with socioeconomic deprivation and age. Methods: Census tract population data were obtained from the National Statistics Institute of Spain. Outdoor NO2 was monitored in 100 sites in the study area, through the use of passive samplers, in three campaigns between 2002 and April 2004. Land use regression (LUR was used to obtain a map of NO2 levels. The LUR predictions were compared with the NO2 level obtained by: a the nearest sampler of the monitoring network, b the nearest passive sampler, c the mean distance-weighted levels of the samplers in the neighborhood, and d the NO2 level obtained by using Kriging. For each census tract, the NO2 levels were obtained. The association of NO2 air pollution exposure with population age (>65 years and the 5-category deprivation index was analyzed. Results: The LUR models showed less error than the other prediction methods. The safety levels proposed by the World Health Organization were exceeded in more than 99% of the population. An inverse relationship was found between NO2 levels and the deprivation index (? = -2.01?g/m³ in the most deprived quintile compared with lower deprivation, 95%CI: -3.07; -0.95 and a direct relationship was found with age (? = 0.12?g/m³ per unit increase in percentage of the population > 65 years, 95%CI: 0.08; 0.16. Conclusions: The method allowed pollution maps to be obtained and the association between NO2 levels and sociodemographic characteristics to be described.

Marisa Estarlich

2013-04-01

388

Air surveillance  

Energy Technology Data Exchange (ETDEWEB)

This section of the 1994 Hanford Site Environmental Report summarizes the air surveillance and monitoring programs currently in operation at that Hanford Site. Atmospheric releases of pollutants from Hanford to the surrounding region are a potential source of human exposure. For that reason, both radioactive and nonradioactive materials in air are monitored at a number of locations. The influence of Hanford emissions on local radionuclide concentrations was evaluated by comparing concentrations measured at distant locations within the region to concentrations measured at the Site perimeter. This section discusses sample collection, analytical methods, and the results of the Hanford air surveillance program. A complete listing of all analytical results summarized in this section is reported separately by Bisping (1995).

Patton, G.W.

1995-06-01

389

Healthy Air at Work  

Science.gov (United States)

... for ENews Home > Healthy Air > At Work Healthy Air at Work Employees should be safe while on ... air in the workplace threatens workers' lives. Healthy Air at Work Healthy air quality is an important ...

390

Indoor Air Quality  

Science.gov (United States)

... Associations > Charters > Mid-Atlantic > Air Quality Indoor Air Quality Poor indoor air quality can cause or contribute ... to find safer substitutes. Why does Indoor Air Quality matter? The air quality of our indoor environments ...