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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

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)

5

Kerma determination in air on mamma by thermoluminescence; Determinacion de Kerma en aire en mama por termoluminiscencia  

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In this work the experimental results of the entrance exposition are shown and Kerma in air [mGy] in mamma obtained by irradiation of accreditation phantom of American College of Radiology (ACR). The irradiations were realized in a conventional mammography equipment of Hospital Juarez in Mexico; the technique used during the irradiations was of automatic exposition; the thickness for the phantom ACR obtained by the technique were of 4.2 and 4.5 cm; the kilo voltage pick was of 24 kV{sub p}, the time and the milli amperage per second variable. The measuring of Kerma in air was obtained with thermoluminescent dosemeters of solid state, of nano particles of zirconium dioxide prepared by the precipitation method. The dosemeters were homogenized previously in low energies of X-rays that are those used for mammography. The thermoluminescent dosemeters of ZrO{sub 2} were calibrated by means of an ionization chamber for different expositions. The calibration curve is reported for the exposition and Kerma in air against thermoluminescent intensity obtained by reading of thermoluminescent dosemeters of ZrO{sub 2}, as well as the technique employee for the Kerma determination in air and entrance exposition in mamma. (Author)

Palacios P, L. L.; Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico)], e-mail: lpalaciop@ipn.mx

2009-10-15

6

Corrections to air kerma rate measurements of 137Cs environmental sources for free space conditions  

International Nuclear Information System (INIS)

Air kerma rate measurements between 2 m and 4 m from a set of 137Cs reference environmental sources (with both stainless steel and brass encapsulation) have been made at NPL using a calibrated Reuter-Stokes high pressure ionisation chamber. Monte Carlo techniques are used to calculate the air kerma rate components over a similar range of distances from these sources. The calculated air kerma values are compared with measurements and the deviation of the data from the inverse square law is investigated. Corrections to the measurement data are then derived to obtain the air kerma rate in free space at 2.5 m from each source. (author)

7

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

8

Evaluation of entrance surface air kerma in pediatric chest radiography  

Science.gov (United States)

The objective of this study was to evaluate the entrance surface air kerma in pediatric chest radiography. An evaluation of 301 radiographical examinations in anterior-posterior (AP) and posterior-anterior (PA) (166 examinations) and lateral (LAT) (135 examinations) projections was performed. The analyses were performed on patients grouped by age; the groups included ages 0-1 y, 1-5 y, 5-10 y, and 10-15 y. The entrance surface air kerma was determined with DoseCal software (Radiological Protection Center of Saint George's Hospital, London) and thermoluminescent dosimeters. Two different exposure techniques were compared. The doses received by patients who had undergone LAT examinations were 40% higher, on average, those in AP/PA examinations because of the difference in tube voltage. A large high-dose “tail” was observed for children up to 5 y old. An increase in tube potential and corresponding decrease in current lead to a significant dose reduction. The difference between the average dose values for different age ranges was not practically observed, implying that the exposure techniques are still not optimal. Exposure doses received using the higher tube voltage and lower current-time product correspond to the international diagnostic reference levels.

Porto, L.; Lunelli, N.; Paschuk, S.; Oliveira, A.; Ferreira, J. L.; Schelin, H.; Miguel, C.; Denyak, V.; Kmiecik, C.; Tilly, J.; Khoury, H.

2014-11-01

9

The air-kerma rate constant of 192Ir.  

Science.gov (United States)

The air-kerma rate constant gamma delta (and its precursors), as one of the basic radiation characteristics of 192Ir, was determined by many authors. Analysis of accessible data on this quantity led us to the conclusion that published data strongly disagree. That is the reason we calculated this quantity on the basis of our and many other authors' gamma-ray spectral data and the latest data for mass energy-transfer coefficients for air. In this way, a value was obtained for gamma delta of 30.0 +/- 0.9 a Gy m2 s-1 Bq-1 for an unshielded 192Ir source and 27.8 +/- 0.9 a Gy m2s -1Bq-1 for a standard packaged radioactive source taking into account attenuation of gamma rays in the platinum source wall. PMID:8416220

Ninkovi?, M M; Rai?evì?, J J

1993-01-01

10

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

International Nuclear Information System (INIS)

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

11

Calculation on free-in-air kermas and effective dose equivalents from radioisotopes deposited on soil  

International Nuclear Information System (INIS)

Free-in-air fluxes, kermas and effective dose equivalents in anthropomorphic phantoms as source energies are calculated by an adjoint Monte Carlo code for gamma emitters in the soil. Fluxes and kermas are given for various heights above the ground. 5 refs., 4 figs., 5 tabs. (Author)

12

X-rays spectrum and air Kerma during a mammography study; Espectro de los rayos X y Kerma en aire durante un estudio mamografico  

Energy Technology Data Exchange (ETDEWEB)

In this calculation series was modeled the source of electrons, the target and the filter. Using thermoluminescent dosemeters of ZrO{sub 2}+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 +{sub -} 0.03 m G, while the other obtained by the calculations was of 0.96 +{sub -} 0.06 mGy, to compare both do not exist significant differences. (author)

Ramirez G, J. [Instituto Nacional de Estadistica Geografia e Informatica, Av. Heroes de Nacozari Sur 2301, Fracc. Jardines del Parque, 20276 Aguascalientes (Mexico); Hernandez V, R.; Hernandez D, V. M.; Vega C, H. R. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)], e-mail: fermineutron@yahoo.com

2009-10-15

13

Corrections to air kerma rate measurements of 125I brachytherapy sources to free space conditions  

International Nuclear Information System (INIS)

Air kerma rate measurements have been made between 40 cm and 100 cm from one of a set of 125I reference sources within the facilities of Amersham International plc. Monte Carlo techniques have been used to calculate the air kerma rate components over the same range of distances from this source. After comparing the calculated data with measurements, the compliance of the data with the inverse square law was investigated, and corrections were derived to obtain the air kerma rate at 1 m in free space from each source. Simulations of the experimental setup with an isotropic monoenergetic point source close to the effective energy of 125I were found to reproduce the air kerma rate measurements reasonably accurately, and indicated that the contribution due to scattered photons was significant. The overall correction (which is defined as the product of individual corrections for chamber size effect, air attenuation and radiation scatter) required to the inverse square law to obtain the air kerma rate at 1 m in free space was found to be 0.981, 0.984 and 0.980, respectively, for air kerma rate measurements at 40 cm, 60 cm and 100 cm from the 125I reference source. The total uncertainty in these corrections was estimated to be 0.88% at the 1? level. (author)

14

Comparison of the air kerma standards of the NRC and the BIPM 60Co ? rays  

International Nuclear Information System (INIS)

A comparison of the standards for air kerma of the National Research Council of Canada and of the Bureau International des Poids et Mesures has been carried out in 60Co gamma radiation. The results show that the NRC and the BIPM standards for air kerma are in agreement, yielding a ratio of 1.0020 for the calibration factors of the transfer chambers, the difference from unity being within the combined standard uncertainty of 0.0031. (authors)

15

Factor kerma decrease for interactions X and gamma rays with air, water, polyethylene and plexiglass  

International Nuclear Information System (INIS)

KERMA decrease caused by secondary particle energy loss in air, water, polyethylene and plexiglass in 0.5 MeV to 10 MeV region of X and gamma-photons, is presented in this paper. The calculations of KERMA factor decrease are made for Compton, photo effects and pair production effects by incident X and gamma rays, in the mentioned energy interval. (author)

16

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

17

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 192}Ir brachytherapy sources. In 2004, the National Physical Laboratory (NPL) commissioned a primary standard for the realization of RAKR of HDR {sup 192}Ir brachytherapy sources. This has meant that it is now possible to calibrate ionization chambers directly traceable to an air kerma standard using an {sup 192}Ir 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, .K{sub R} (ICRU 1985 ICRU Report No 38 (Washington, DC: ICRU); ICRU 1997 ICRU Report No 58 (Bethesda, MD: ICRU)), or air kerma strength, S{sub K} (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 {sup 192}Ir 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 [Medical Physics, Royal Marsden Hospital, Fulham Road, London SW3 6JJ (United Kingdom); Sander, T; Nutbrown, R F [Acoustics and Ionising Radiation, National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW (United Kingdom); Locks, S M [Regional Medical Physics Department, NCCC block, Freeman Hospital, Newcastle upon Tyne, NE7 7DN (United Kingdom); Lee, C D [Medical Physics Department, Clatterbridge Centre for Oncology, Clatterbridge Road, Bebington, Wirral, Merseyside, CH63 4JY (United Kingdom); Aird, E G A [Medical Physics Department, Mt Vernon Hospital, Rickmansworth Road, Northwood, HA6 2RN (United Kingdom); Flynn, A, E-mail: Margaret.Bidmead@rmh.nhs.u [Medical Physics, Cookridge Hospital, Hospital Lane, Cookridge, Leeds, LS16 6QB (United Kingdom)

2010-06-07

18

Reference air kerma and kerma-area product as estimators of peak skin dose for fluoroscopically guided interventions  

International Nuclear Information System (INIS)

Purpose: To determine more accurate regression formulas for estimating peak skin dose (PSD) from reference air kerma (RAK) or kerma-area product (KAP). Methods: After grouping of the data from 21 procedures into 13 clinically similar groups, assessments were made of optimal clustering using the Bayesian information criterion to obtain the optimal linear regressions of (log-transformed) PSD vs RAK, PSD vs KAP, and PSD vs RAK and KAP. Results: Three clusters of clinical groups were optimal in regression of PSD vs RAK, seven clusters of clinical groups were optimal in regression of PSD vs KAP, and six clusters of clinical groups were optimal in regression of PSD vs RAK and KAP. Prediction of PSD using both RAK and KAP is significantly better than prediction of PSD with either RAK or KAP alone. The regression of PSD vs RAK provided better predictions of PSD than the regression of PSD vs KAP. The partial-pooling (clustered) method yields smaller mean squared errors compared with the complete-pooling method.Conclusion: PSD distributions for interventional radiology procedures are log-normal. Estimates of PSD derived from RAK and KAP jointly are most accurate, followed closely by estimates derived from RAK alone. Estimates of PSD derived from KAP alone are the least accurate. Using a stochastic search approach, it is possible to cluster together certain dissimilar types of procedures to minimize the total error sum of squares.

19

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)

20

Air kerma and absorbed dose on the torso of a patient during a mammography study  

International Nuclear Information System (INIS)

Two dosimetric magnitudes, due to the dispersed radiation, have been determined during a mammography study. The magnitudes that were determined are the kerma at the entrance of the torso and the absorbed dose by the torso. This determination was made in a paraffin phantom and with thermoluminescent dosemeters. One of the important parameters in the radiological protection of a patient to which is practiced a mammography is the value of the media glandular dose. However, during the taking of the X-ray a radiation portion that impacts on the mammary gland it is dispersed toward the patient's torso. In this work thermoluminescent dosemeters of ZrO2 has been used to determine the kerma at the entrance of the torso like the absorbed dose. The dosemeters was placed on the surface of the torso phantom while to the mamma phantom was made the mammography. As mamma phantom was used glucose serum to 5%. Of the obtained results we find that 3% of the air kerma at the entrance of the mamma it corresponds at the air kerma that receives the torso and 3.2% of the media glandular dose it is the absorbed dose of the same one. Another important result is the percentage value of the air kerma on the entrance of the thyroid area during a mammography, due to the dispersed radiation, it is 4% of the kerma at the entrance of the mamma. The air kerma at the entrance of the thyroid is of 0.41 ±0.07 mGy, 10% of this value corresponds to the absorbed dose by the thyroid. Therefore, ibsorbed dose by the thyroid. Therefore, it is observed that the media glandular dose and the air kerma at the entrance of the mamma they influence on the dispersed radiation toward the torso. Also, the superior part of the torso has less attenuation capacity to the dispersed radiation that those located in the inferior part. Therefore, the thyroid receives the major quantity of air kerma at the entrance. (Author)

 
 
 
 
21

Comparative study of Brazilian and North American unshielded primary air kerma of radiological equipment  

International Nuclear Information System (INIS)

The philosophy of shield design in diagnostic radiology has changed in recent years, due to the more restrictive dose limits to workers and public adopted in various countries. According to report 147 of the National Council of Radiation Protection and Measurements (NCRP 147, 2004), the structural shielding design is based on the quantity of unshielded primary air kerma, measured at the distance of one meter. Due to the fact that air kerma presents a strong dependent on the workload and output of the x-ray tube, NCRP 147 provides reference values for these parameters, all of them based on North-American clinical routine. The present work surveyed Brazilian values of workload, patient workflow and X-ray tube output, in order to estimate the unshielded primary air kerma at one meter for different diagnostic modalities

22

Air kerma rate estimation by means of in-situ gamma spectrometry: A Bayesian approach  

International Nuclear Information System (INIS)

Full text: Bayesian inference is used to determine the Air Kerma Rate based on a set of in situ environmental gamma spectra measurements performed with a NaI(Tl) scintillation detector. A natural advantage of such approach is the possibility to quantify uncertainty not only in the Air Kerma Rate estimation but also for the gamma spectra which is unfolded within the procedure. The measurements were performed using a 3'' x 3'' NaI(Tl) scintillation detector. The response matrices of such detection system were calculated using a Monte Carlo code. For the calculations of the spectra as well as the Air Kerma Rate the WinBugs program was used. WinBugs is a dedicated software for Bayesian inference using Monte Carlo Markov chain methods (MCMC). The results of such calculations are shown and compared with other non-Bayesian approachs such as the Scofield-Gold iterative method and the Maximum Entropy Method

23

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

International Nuclear Information System (INIS)

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%.

24

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

International Nuclear Information System (INIS)

The 252Cf neutron air kerma strength conversion factor (SKN/mCf) is a parameter needed to convert the radionuclide mass (?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 252Cf brachytherapy sources (Pt/Ir-10%, 316L stainless steel, nitinol, and Zircaloy-2) on SKN/mCf was calculated and results were fit to linear equations. Only for substantial encapsulation thicknesses, did SKN/mCf 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 252Cf neutron interactions. Neutron kerma and energy spectra results calculated herein using MCNP were compared with results of Colvett et al. and Rivard et al

25

X-Rays spectrum and air kerma during a mammography study;Espectro de los rayos X y kerma en aire durante un estudio mamografico  

Energy Technology Data Exchange (ETDEWEB)

The X-rays spectrum produced in a mammography has been calculated by means of Monte Carlo methods. In this calculation series it is modeled the electrons source, the target and the filter. The spectra were calculated for an energy of the electrons of 28 keV and for targets of W, Mo and Rh. The calculations extended to analyze the effect that produces the filters inclusion in the spectra; the spectra of W-A1, Rh-Rh, Mo-Mo, Mo-Rh and Mo-Be were calculated this way. Using thermoluminescent dosemeters of ZrO{sub 2}+PTFE the air kerma was measured in five points located on a phantom made with acrylic and water when it is was exposed to a X-rays beam produced by electrons of 24 keV and 10 m A of current that it produces a mammography. The values of the air kerma on the entrance surface of the phantom were compared with the calculated values by means of Monte Carlo methods. The calculated spectra present a continuous component and another discreet and its form is similar to the reported spectra in the literature. The filters inclusion allows the elimination of the low energy photons that do not have utility in the obtaining of the mammography image and only they contribute to deposit a dose in the mamma. The values of the measured air kerma indicate that the five points receive the same air kerma approximately, what means that the beam is homogeneous, of the Monte Carlo calculations we find that the center receives a bigger dose which implies that the beam is not uniform, the explanation on this fact it is attributed to that a simple model was used in the calculations, nevertheless, the average of the air kerma measured on the entrance surface of the phantom was of 0.96 +- 0.03 m G, while the obtained by means of the calculations was of 0.96 +- 0.06 mGy, when comparing both significant differences do not exist. (Author)

Ramirez G, J. [Instituto Nacional de Estadistica Geografia e Informatica, Direccion General de Innovacion y Tecnologia de Informacion, Av. Heroes de Nacozari Sur No. 2301, Fracc. Jardines del Parque, 20276 Aguascalientes (Mexico); Hernandez V, R.; Chacon R, A.; Vega C, H. R., E-mail: ramirezgonzalezjaime@yahoo.com.m [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

2009-10-15

26

? GONIO: an orientation detector and environmental ? air kerma ratemeter  

International Nuclear Information System (INIS)

The aim of the ?-gonio is to guide a vehicle in order to find out a lost gamma source or to determine a remote area contaminated by ?-emitting pieces following a nuclear accident. It is essentially made of an aluminium sphere (diameter: 10 cm) with 6 detectors located inside, 1 cm deep from the sphere surface. The detectors are placed on 3 orthogonal diameters. The detector counting rates are processed by a software set on a microprocessor giving by cycles the orientation of the ?-source in terms of azimuth and elevation angles, the kerma rate at the sphere centre and the effective energy of the ?-beam incident on the sphere. The physical and mathematical concepts used to develop the instrument are described

27

Variation of the air kerma rate from natural radionuclides in the ground due to the change of source configurations  

International Nuclear Information System (INIS)

It is well known that the source configuration is an essential factor to change the kerma rate in air from natural radionuclides in soil and artificial structures. For example, the kerma rate increases in tunnels or concrete buildings surrounded by source, while the kerma rate decreases on a water body like a river which does not contain radionuclides. However, the features of the change in kerma rate due to source configurations have not been thoroughly investigated. In this study, the kerma rates due to natural radionuclides were calculated using Monte Carlo simulation for different source configurations. The considered terrain was 1) spherical caves in the ground, 2) cylindrical tunnels in the ground, 3) slab-shaped hollows in the ground, 4) two pieces of semi-infinite plain ground which joints at divers angles, 5) rectangular cuts in the ground, and 6) parallel rivers. The natural radionuclides of the U-238 series, Th-232 series, and K-40 were assumed to distribute uniformly in the ground at some typical concentration ratios. The calculated kerma rates were normalized to the value for infinite plain ground geometry. The kerma rate changes according to the solid angle viewing the soil containing radionuclides. Generally, the kerma rate is proportional to the solid angle viewing the soil, but the normalized kerma rate never exceeds two even though the solid angle viewing source is 4p. One a river the kerma rate deceases as the position gets close to the middle, but the decreasing tendency is slower that the decrease of the solid angle viewing the source. Basically, the kerma rates at 1 m on the ground were calculated, but the tendency of change in kerma rate due to height was also discussed for some cases. (author)

28

Air kerma strength characterization of a GZP6 Cobalt-60 brachytherapy source  

Science.gov (United States)

Background Task group number 40 (TG-40) of the American Association of Physicists in Medicine (AAPM) has recommended calibration of any brachytherapy source before its clinical use. GZP6 afterloading brachytherapy unit is a 60Co high dose rate (HDR) system recently being used in some of the Iranian radiotherapy centers. Aim In this study air kerma strength (AKS) of 60Co source number three of this unit was estimated by Monte Carlo simulation and in air measurements. Materials and methods Simulation was performed by employing the MCNP-4C Monte Carlo code. Self-absorption of the source core and its capsule were taken into account when calculating air kerma strength. In-air measurements were performed according to the multiple distance method; where a specially designed jig and a 0.6 cm3 Farmer type ionization chamber were used for the measurements. Monte Carlo simulation, in air measurement and GZP6 treatment planning results were compared for primary air kerma strength (as for November 8th 2005). Results Monte Carlo calculated and in air measured air kerma strength were respectively equal to 17240.01 ?Gym2 h?1 and 16991.83 ?Gym2 h?1. The value provided by the GZP6 treatment planning system (TPS) was “15355 ?Gym2 h?1”. Conclusion The calculated and measured AKS values are in good agreement. Calculated-TPS and measured-TPS AKS values are also in agreement within the uncertainties related to our calculation, measurements and those certified by the GZP6 manufacturer. Considering the uncertainties, the TPS value for AKS is validated by our calculations and measurements, however, it is incorporated with a large uncertainty. PMID:24376948

Toossi, Mohammad Taghi Bahreyni; Ghorbani, Mahdi; Mowlavi, Ali Asghar; Taheri, Mojtaba; Layegh, Mohsen; Makhdoumi, Yasha; Meigooni, Ali Soleimani

2010-01-01

29

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

Science.gov (United States)

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. PMID:15798826

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

2004-01-01

30

Determination of calibration factors in terms of air kerma and absorbed dose to water in the 60Co ? rays  

International Nuclear Information System (INIS)

The method of calibration of an instrument, as performed at the BIPM in the 60Co field in terms of air kerma or absorbed dose to water, is described in detail. The influence of various parameters which can affect the calibration factor is analyzed. The uncertainty is of order 0.3% and 0.5% for calibration factors in terms of air kerma and of absorbed dose to water, respectively. (author). 14 refs, 10 figs, 3 tabs

31

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)

32

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

33

X-Rays spectrum and air kerma during a mammography study  

International Nuclear Information System (INIS)

The X-rays spectrum produced in a mammography has been calculated by means of Monte Carlo methods. In this calculation series it is modeled the electrons source, the target and the filter. The spectra were calculated for an energy of the electrons of 28 keV and for targets of W, Mo and Rh. The calculations extended to analyze the effect that produces the filters inclusion in the spectra; the spectra of W-A1, Rh-Rh, Mo-Mo, Mo-Rh and Mo-Be were calculated this way. 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 is was exposed to a X-rays beam produced by electrons of 24 keV and 10 m A of current that it produces a mammography. The values of the air kerma on the entrance surface of the phantom were compared with the calculated values by means of Monte Carlo methods. The calculated spectra present a continuous component and another discreet and its form is similar to the reported spectra in the literature. The filters inclusion allows the elimination of the low energy photons that do not have utility in the obtaining of the mammography image and only they contribute to deposit a dose in the mamma. The values of the measured air kerma indicate that the five points receive the same air kerma approximately, what means that the beam is homogeneous, of the Monte Carlo calculations we find that the center receives a bigger dose which implies that the beam is not unifor which implies that the beam is not uniform, the explanation on this fact it is attributed to that a simple model was used in the calculations, nevertheless, the average of the air kerma measured on the entrance surface of the phantom was of 0.96 ± 0.03 m G, while the obtained by means of the calculations was of 0.96 ± 0.06 mGy, when comparing both significant differences do not exist. (Author)

34

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

35

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

36

Air-kerma strength determination of a miniature x-ray source for brachytherapy applications  

Science.gov (United States)

A miniature x-ray source has been developed by Xoft Inc. for high dose-rate brachytherapy treatments. The source is contained in a 5.4 mm diameter water-cooling catheter. The source voltage can be adjusted from 40 kV to 50 kV and the beam current is adjustable up to 300 muA. Electrons are accelerated toward a tungsten-coated anode to produce a lightly-filtered bremsstrahlung photon spectrum. The sources were initially used for early-stage breast cancer treatment using a balloon applicator. More recently, Xoft Inc. has developed vaginal and surface applicators. The miniature x-ray sources have been characterized using a modification of the American Association of Physicists in Medicine Task Group No. 43 formalism normally used for radioactive brachytherapy sources. Primary measurements of air kerma were performed using free-air ionization chambers at the University of Wisconsin (UW) and the National Institute of Standards and Technology (NIST). The measurements at UW were used to calibrate a well-type ionization chamber for clinical verification of source strength. Accurate knowledge of the emitted photon spectrum was necessary to calculate the corrections required to determine air-kerma strength, defined in vacuo. Theoretical predictions of the photon spectrum were calculated using three separate Monte Carlo codes: MCNP5, EGSnrc, and PENELOPE. Each code used different implementations of the underlying radiological physics. Benchmark studies were performed to investigate these differences in detail. The most important variation among the codes was found to be the calculation of fluorescence photon production following electron-induced vacancies in the L shell of tungsten atoms. The low-energy tungsten L-shell fluorescence photons have little clinical significance at the treatment distance, but could have a large impact on air-kerma measurements. Calculated photon spectra were compared to spectra measured with high-purity germanium spectroscopy systems at both UW and NIST. The effects of escaped germanium fluorescence photons and Compton-scattered photons were taken into account for the UW measurements. The photon spectrum calculated using the PENELOPE Monte Carlo code had the best agreement with the spectrum measured at NIST. Corrections were applied to the free-air chamber measurements to arrive at an air-kerma strength determination for the miniature x-ray sources.

Davis, Stephen D.

37

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

38

Proposed specification for a primary standard of air kerma for 60Co, 137Cs and 192Ir ?-ray sources  

International Nuclear Information System (INIS)

The three cavity chambers, the mean response of which constitutes the primary standard of air kerma for 60Co and 137Cs ?-rays in the United Kingdom, have been in continuous, almost daily, use at the National Physical Laboratory (NPL) since 1956. These chambers were initially designed for use with 2 MV X-rays at therapy level air kerma rates. However since 1978 they have also been used for protection level air kerma rates, initially, with X-rays generated at 1 MV and 2 MV and more recently with 60Co and 137Cs ?-rays. They have been used for therapy level air kerma calibrations with 60Co ?-rays since 1997 following the demise of the NPL 2 MV Van de Graaff generator. This report describes the proposals for a new primary standard and the methods that will be used to give a better performance than the present standard when used with air kerma rates from as high as 1 Gy min-1 down to 10 mGy hr-1. The design will also seek to ensure that the standard will be capable of providing traceable calibration for 192Ir high dose rate brachytherapy sources. (author)

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.

Foundation, Wgbh E.

2011-03-21

40

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

 
 
 
 
41

Changes to the National Physical Laboratory primary standards for x-ray exposure and air kerma  

Energy Technology Data Exchange (ETDEWEB)

With effect from 1 January 1992 the U.K. National Physical Laboratory (NPL) will be adopting a number of revised correction factors for the three UK national primary standards for x-ray exposure and air kerma: the 50 kV free air chamber, the 300 kV free air chamber and the 2 MV graphite cavity ionization chambers. The changes arise for two reasons: the decision to adopt revised values for physical data recommended by the Comite Consultatif pour les Etalons de Mesure des Rayonnements Ionisants (CCEMRI) of the International Bureau of Weights and Measures (BIPM), and recent Monte Carlo calculations of some of the correction factors for one of the NPL primary standards, the 2 MV cavity chambers, using data consistent with CCEMRI recommendations. A table summarizes the effects of these changes on calibration factors of secondary standards. (Author).

Moretti, C.J. (National Physical Lab., Teddington (United Kingdom). Div. of Radiation Science and Accoustics)

1992-05-01

42

Changes to the National Physical Laboratory primary standards for x-ray exposure and air kerma  

International Nuclear Information System (INIS)

With effect from 1 January 1992 the U.K. National Physical Laboratory (NPL) will be adopting a number of revised correction factors for the three UK national primary standards for x-ray exposure and air kerma: the 50 kV free air chamber, the 300 kV free air chamber and the 2 MV graphite cavity ionization chambers. The changes arise for two reasons: i) the decision to adopt revised values for physical data recommended by the Comite Consultatif pour les Etalons de Mesure des Rayonnements Ionisants (CCEMRI) of the International Bureau of Weights and Measures (BIPM) and ii) recent Monte Carlo calculations of some of the correction factors for one of the NPL primary standards, the 2 MV cavity chambers, using data consistent with CCEMRI recommendations. A table summarizes the effects of these changes on calibration factors of secondary standards. (Author)

43

Energy required to produce an ion pair in gas in the function of the measurement of kerma in air  

International Nuclear Information System (INIS)

Average energy for producing an ion pair, mean W, was defined. So is its dependence on type of particles, relative partial pressure of the steam and relative humidity. Measurement methods were outlined. Energy W for different gases was presented in a Table, with an accent on the air. For the air, as the most interesting gas, the most recent determined value was given. Relationship between W, exposition X and air kerma K was explained (author)

44

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)

45

Gonio: an orientation detector and environmental gamma air kerma rate meter  

International Nuclear Information System (INIS)

The purpose of the ? Gonio instrument is to guide a vehicle to find a lost ? source, or for measurements following a nuclear accident. This instrument is essentially an aluminium sphere, of 10 cm diameter, in which are situated six detectors at 1 cm depth from its surface. These detectors are installed on three orthogonal diameters. The count rates detected by the detectors are treated by an algorithm, implemented in a microprocessor, which displays by cycles: (i) the orientation of the ? source in terms of azimuth and elevation angles, (ii) the air kerma rate at the location of the centre of the sphere, and (iii) the effective energy of the ? beam incident to the sphere. The paper describes the physical and mathematical concepts used to design and to construct the instrument, and the test results obtained with the instrument exposed to various ? energies in order to verify the accuracy of the displayed readings. This instrument could also be used for ? monitoring of installations. (Author)

46

Entrance surface air kerma to patients during chest computed radiography in the United Republic of Tanzania  

International Nuclear Information System (INIS)

Computed radiography (CR) has the potential to improve the image quality through its image processing capabilities as well as reducing patient doses. However, during transition period from analogue to digital modality, there can be a tendency to maintain the exposure parameters that are used in film-screen imaging. This tendency can lead to higher patient doses than is necessary. Such transition is currently taking place in Tanzania and 5 CR facilities are in clinical use. The main objective of this study was to determine the entrance surface air kerma (ESAK) during chest computed radiography of adult patients so as to monitor patient doses during this transition. A previously applied method was used to determine ESAK to 20 adult patients at each facility. The x-ray tube output for each tube potential in clinical use was measured using model 6000-528, 30 cm3 ionization chamber and Model 4000 M+-SI both manufactured by Fluke Biomedical, New York. The energy response of this dosimetry system as stated by manufacturer is 7% over 50-150 kVp range. From the x-ray output and recorded patient exposure parameters, the incident air kerma values (IAKs) were calculated. The ESAK values (ESAKs) were then derived on basis of IAKs and backscatter factor. The ESAKs obtained at 3 facilities as part of ongoing study are presented. The results show that the mean ESAKs at two hospitals were higher than the national average value of 300 ?Gy for 400 film-screen system and abov0 ?Gy for 400 film-screen system and above the recommended diagnostic reference level of 300 ?Gy. This suggests the need to train the radiology personnel towards optimized practice

47

The ratios of effective dose to entrance skin dose to the air kerma for some medical sources  

Energy Technology Data Exchange (ETDEWEB)

Results are presented for the ratios of the effective dose to skin entrance dose and to air kerma for broad beams of radiation expected to be encountered by medical workers. These workers are monitored by the Personal Radiation Monitoring Service (PRMS) using thermoluminescent dosimeters worn at the front of the body to provide estimates of the entrance skin dose. Factors are given for converting estimates of entrance skin dose to effective dose as defined by the International Commission on Radiological Protection (ICRP 1991) for beams incident on the body by one of three modes-from the front of the subject, from the back of the subject or by rotation around the subject. Additional tables are also given to calculate effective dose for these beams from a measurement of air kerma free-in-air 4 figs., 9 tabs.

Wise, K.N. [Australian Radiation Laboratory, Yallambie, VIC (Australia)

1998-03-01

48

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.)

49

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)

50

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

51

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

52

Revised correction factor for the UK national primary standard for air kerma for 137Cs and 60Co gamma-rays  

International Nuclear Information System (INIS)

From 1 May 2009 the United Kingdom National Physical Laboratory (NPL) has changed its air kerma standards for Cs-137 and Co-60 ?-rays. Adoption of the new correction factors results in an increase in the NPL air kerma standard by ? 1% for both Cs-137 and Co-60 ?-rays. All NPL secondary standard calibrations issued after 1 May 2009 contain the revised correction factor. (authors)

53

SHORT COMMUNICATION: Revised correction factor for the UK national primary standard for air kerma for 137Cs and 60Co gamma-rays  

Science.gov (United States)

From 1 May 2009 the United Kingdom National Physical Laboratory (NPL) has changed its air kerma standards for Cs-137 and Co-60 ?-rays. Adoption of the new correction factors results in an increase in the NPL air kerma standard by ~1% for both Cs-137 and Co-60 ?-rays. All NPL secondary standard calibrations issued after 1 May 2009 contain the revised correction factor.

Pearce, Julia; Bass, Graham; Duane, Simon; Nutbrown, Rebecca; Shipley, David

2009-10-01

54

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 to offer traceable calibration of the hospital well ionization chambers. (author)

55

Calculation of conversion factor of Kerma in the air for ambient dose equivalent in radiotherapy  

International Nuclear Information System (INIS)

This work aims to estimate the average conversion factor of Kerma in air to H * (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 cm2, 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)

56

Evaluation of the entrance surface air kerma in mammographic examinations in Rio de Janeiro, Brazil.  

Science.gov (United States)

The aim of this work was to evaluate the distribution of the entrance surface air kerma (ESAK) and the average glandular dose (D(G)) in four mammography facilities located in the city of Rio de Janeiro. The ESAK values were estimated from the X-ray tube output rate (mGy/mAs) parameters. The image quality was evaluated by the radiologists in each clinic. The ESAK values obtained for a breast thickness of 45 mm were 5.58 mGy in Clinic A, 10.07 mGy in Clinic B, 13.89 mGy in Clinic C and 7.21 mGy in Clinic D. For D(G), it can be seen that, for the same compressed breast thickness (50 mm), the value varied from 0.20 to 3.60 mGy, with a mean value of 1.50 mGy for all the clinics. In image quality evaluation, Clinic D was the only one that presented a very low acceptability for quality criteria and inadequacies in relation to specks, masses and optical density. PMID:19287013

Oliveira, L C G; Dias, T K; Lopes, R T; Kodlulovich, S

2009-02-01

57

Patient investigation of average glandular dose and incident air kerma for digital mammography.  

Science.gov (United States)

Our aim in this study was to investigate the incident air kerma (IAK) and average glandular dose (AGD) for polymethylmethacrylate (PMMA) phantoms and patient breasts for each thickness by use of digital mammography units, and to determine the correlation between phantom and patient measurements. An additional aim was to calculate the numerical value of the diagnostic reference level (DRL) for digital mammography in Japan based on the AGD from patient measurements. Patient-based IAK and AGD values were calculated for 300 patients who underwent mammographic examinations at three institutions. On examination of a 40-mm PMMA phantom, the IAK and the AGD were 7.89 and 1.84 mGy, respectively. The mean patient breast thickness was 37.6 mm, and the mean IAK and the AGD calculated from actual patient data for breast thicknesses between 40 mm and 50 mm were 8.91 and 2.08 mGy, respectively. Approximately 20 % of the 300 patients had IAK >10 mGy. The distributions of patient-based IAK and AGD values were higher than the IAK and AGD values for the PMMA phantom. The patient dose with use of the PMMA phantom can be underestimated. The DRL was calculated from patient-based AGDs of the regular breast thickness as 2.0 mGy in Japan. PMID:24234736

Kawaguchi, Ai; Matsunaga, Yuta; Otsuka, Tomoko; Suzuki, Shoichi

2014-01-01

58

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

59

Ozone - Current Air Quality Index  

Science.gov (United States)

... 11/04/14: Updated AirNow materials in Spanish- Ozone and Your health and Guide to Air Quality for Ozone 10/15/14: Mexico City joins AirNow. 9/ ... more announcements Air Quality Basics Air Quality Index | Ozone | Particle Pollution | UV | Smoke from fires | What You ...

60

Conversion of Airborne Gamma ray Spectra to Ground Level Air Kerma Rates  

DEFF Research Database (Denmark)

A new method for relating airborne gamma-ray spectra to dose rates and kerma rates at ground level is presented. Dependent on flying altitude 50 m to 125 m the method gives correct results for gamma energies above 250 keV respective 350 keV. At lower energies the method underestimate the dose or kerma rates; by having a large fraction of the ground level gamma-rays at energies below 350 keV special care should be taken at an interpretation of the results.

Bargholz, Kim; Korsbech, Uffe C C

1997-01-01

 
 
 
 
61

Study and determination of the national dosimetric standards in terms of air kerma for X-rays radiation fields of low and medium-energies; Etude et realisation des references dosimetriques nationales en termes de kerma dans l'air pour les faisceaux de rayons X de basses et moyennes energies  

Energy Technology Data Exchange (ETDEWEB)

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)

Ksouri, W

2008-12-15

62

Distribution of kerma rate in the air inside of hemodynamic room for typical projections of interventionist cardiology procedures  

International Nuclear Information System (INIS)

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)

63

Measurement of conversion coefficients between air Kerma and personal dose equivalent and backscatter factors for diagnostic X-ray beams  

International Nuclear Information System (INIS)

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 cm3 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 133 Ba, 241 Am and 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)

64

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 192}Ir 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 {sup 192}Ir source. Measurements were made with 2 types of chamber. Firstly measurements were made with a 100 cm{sup 3} spherical graphite transfer chamber and then measurements were repeated using a 1.79 cm{sup 3} cylindrical cavity chamber which is one of a set of 3 chambers which form the primary standard for {sup 60}Co and {sup 137}Cs 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 {sup 192}Ir 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 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)

Nutbrown, R.; Sander, T

2000-07-01

65

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

International Nuclear Information System (INIS)

An indirect comparison of the standards for air kerma of the National Institute of Standards and Technology (NIST), USA, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co and 137Cs radiation protection-level beams of the BIPM in September 2011. The comparison results, based on the calibration coefficient for two transfer standards and expressed as a ratio of the NIST and the BIPM standards for air kerma, are 1.0023 with a combined standard uncertainty of 3.2 * 10-3 in 60Co, and 0.9990 with a combined standard uncertainty of 3.5 * 10-3 in 137Cs. The result in the 60Co beam for radiation protection agrees within the uncertainties with the result of the comparison carried out at the same time in the CIS Bio 60Co beam for radiotherapy-level air kerma. (authors)

66

Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air  

International Nuclear Information System (INIS)

Purpose: For a given radionuclide, there are several photon spectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for 192Ir, 125I, and 103Pd on the final estimations of kerma and dose. Methods: For 192Ir, 125I, and 103Pd, the authors considered from two to five published spectra. Spherical sources approximating common brachytherapy sources were assessed. Kerma and dose results from GEANT4, MCNP5, and PENELOPE-2008 were compared for water and air. The dosimetric influence of 192Ir, 125I, and 103Pd spectral choice was determined. Results: For the spectra considered, there were no statistically significant differences between kerma or dose results based on Monte Carlo code choice when using the same spectrum. Water-kerma differences of about 2%, 2%, and 0.7% were observed due to spectrum choice for 192Ir, 125I, and 103Pd, respectively (independent of radial distance), when accounting for photon yield per Bq. Similar differences were observed for air-kerma rate. However, their ratio (as used in the dose-rate constant) did not significantly change when the various photon spectra were selected because the differences compensated each other when dividing dose rate by air-kerma strength. Conclusions: Given the sr-kerma strength. Conclusions: Given the standardization of radionuclide data available from the National Nuclear Data Center (NNDC) and the rigorous infrastructure for performing and maintaining the data set evaluations, NNDC spectra are suggested for brachytherapy simulations in medical physics applications.

67

Evaluation of the air kerma rates values of x radiation systems used in calibration of measurement instruments in radiodiagnosis  

International Nuclear Information System (INIS)

In this work it was made the evaluation of the air kerma rates values obtained during the calibration of instruments used in diagnostic radiology measurements at the Calibration Laboratory of IPEN, as well as its variation according to the ambient conditions. This evaluation is part of the quality control programme of the reference instruments used in this type of calibration. The measurements carried out from August of 2003 to April of 2004 were analyzed for the Medicor X radiation system and from January to May of 2005 for the Seifert/Pantak X radiation system. Monitor chambers were added in the field in order to correct any possible variations in the electric beam that could cause an alteration in the primary beam for both X radiation systems. After the positioning of the monitor chambers a maximum decrease of 6.9 % for 90 kV in the primary beam was verified. After that the air kerma rates values presented a maximum variation of 8 %. The ambient conditions (temperature, pressure and humidity) control was made using appropriate calibrated instruments for each case. (author)

68

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

International Nuclear Information System (INIS)

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. (authors)

69

Key comparison BIPM.RI(I)-K1 of the air-kerma standards of the PTB, Germany and the BIPM in 60Co gamma radiation  

International Nuclear Information System (INIS)

A direct comparison of the standards for air kerma of the Physikalisch-Technische Bundesanstalt (PTB), Germany and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in March 2014. The comparison result, evaluated as a ratio of the PTB and the BIPM standards for air kerma, is 1.0036 with a combined standard uncertainty of 1.7 * 10-3. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. (authors)

70

Key comparison BIPM.RI(I)-K5 of the air-kerma standards of the PTB, Germany and the BIPM in 137Cs gamma radiation  

International Nuclear Information System (INIS)

A direct comparison of the standards for air kerma of the Physikalisch-Technische Bundesanstalt (PTB), Germany and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation beam of the BIPM in March 2014. The comparison result, evaluated as a ratio of the PTB and the BIPM standards for air kerma, is 1.0024 with a combined standard uncertainty of 2.7 * 10-3. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. (authors)

71

Conversion coefficients from air-kerma to ambient dose equivalent for the International Standards Organisation's wide, narrow and low series of reference filtered X-radiations  

International Nuclear Information System (INIS)

This report provides conversion coefficients from air-kerma to ambient dose equivalent for the International Standards Organisation's Wide, Narrow and Low Series of reference filtered X-radiations. The validity of the theoretical spectra used in the calculations is tested by detailed comparison with experimental results. Also, sensitivity analyses are performed to demonstrate the effect of tolerances in tube potential and filtration on the measured values of mean energy, first half-value layer and air-kerma rate. The theoretical spectral distributions of all members of the series are included within this report. (author)

72

The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays  

Energy Technology Data Exchange (ETDEWEB)

This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100-250 kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison results showed a satisfactory agreement in the measurements which were within the combined expanded uncertainties (k=2)

Lee, J.-H. E-mail: jhlee@iner.gov.tw; Kotler, L.H.; Bueermann, Ludwig; Hwang, W.-S.; Chiu, J.-H.; Wang, C.-F

2005-01-01

73

The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays  

International Nuclear Information System (INIS)

This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100-250 kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison results showed a satisfactory agreement in the measurements which were within the combined expanded uncertainties (k=2)

74

Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air  

Energy Technology Data Exchange (ETDEWEB)

Purpose: For a given radionuclide, there are several photon spectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for {sup 192}Ir, {sup 125}I, and {sup 103}Pd on the final estimations of kerma and dose. Methods: For {sup 192}Ir, {sup 125}I, and {sup 103}Pd, the authors considered from two to five published spectra. Spherical sources approximating common brachytherapy sources were assessed. Kerma and dose results from GEANT4, MCNP5, and PENELOPE-2008 were compared for water and air. The dosimetric influence of {sup 192}Ir, {sup 125}I, and {sup 103}Pd spectral choice was determined. Results: For the spectra considered, there were no statistically significant differences between kerma or dose results based on Monte Carlo code choice when using the same spectrum. Water-kerma differences of about 2%, 2%, and 0.7% were observed due to spectrum choice for {sup 192}Ir, {sup 125}I, and {sup 103}Pd, respectively (independent of radial distance), when accounting for photon yield per Bq. Similar differences were observed for air-kerma rate. However, their ratio (as used in the dose-rate constant) did not significantly change when the various photon spectra were selected because the differences compensated each other when dividing dose rate by air-kerma strength. Conclusions: Given the standardization of radionuclide data available from the National Nuclear Data Center (NNDC) and the rigorous infrastructure for performing and maintaining the data set evaluations, NNDC spectra are suggested for brachytherapy simulations in medical physics applications.

Rivard, Mark J.; Granero, Domingo; Perez-Calatayud, Jose; Ballester, Facundo [Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States); Department of Radiation Oncology, ERESA, Hospital General Universitario, E-46014 Valencia (Spain); Department of Radiation Oncology, La Fe University Hospital, E-46009 Valencia (Spain); Department of Atomic, Molecular, and Nuclear Physics, University of Valencia, E-46100 Burjassot, Spain and IFIC, CSIC-University of Valencia, E-46100 Burjassot (Spain)

2010-02-15

75

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

76

Comparison of the air-kerma standards of the BEV 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 BEV and the BIPM in the low-energy x-ray range. The results at the different radiation qualities show the standards to be in reasonable agreement with respect to the combined relative standard uncertainty of the comparison of 2.4 x 10-3. (authors)

77

Comparison of the air-kerma standards of the OMH and the BIPM in the medium-energy X-ray range  

International Nuclear Information System (INIS)

An indirect comparison has been made between the air-kerma standards of the OMH and the BIPM in the medium-energy x-ray range. The results show the standards to be in agreement within the stated uncertainty, although there is evidence of a slight difference in the result at the 100 kV radiation quality. (authors)

78

COOMET regional comparison of national measurement standards of air kerma for 137Cs ? radiation at protection level  

International Nuclear Information System (INIS)

Results are presented of the COOMET supplementary comparison of the national measurement standards for air kerma in 137Cs ? radiation at protection level (?10 mGy/h). Ten National Metrology Institutes from the COOMET organization and the International Atomic Energy Agency participated in this COOMET project no. 445. The PTB acted as pilot laboratory. Two of the participants, the SMU (Slovakia) and the NSC-'IM' (Ukraine) participated in the measurements but did not submit a valid report of results. The comparison reference value (CRV) was obtained as the mean result of the PTB and the VNIIM, both of which had previously taken part in the key comparison BIPM-RI(I)-K5. The degree of equivalence with the CRV was evaluated. The results were consistent within the relative standard uncertainties of the comparison ranging from 0.28% to 1.3% and deviated from the CRV by less than 1%. (authors)

79

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)

80

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

 
 
 
 
81

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

82

LNE-LNHB air-kerma and absorbed dose to water primary standards for low dose-rate 125I brachytherapy sources  

Science.gov (United States)

The devices and methods applied for the LNE-LNHB primary standards in terms of reference air-kerma and absorbed dose to water for low dose-rate brachytherapy sources are described. Both standards are based on ionometric measurements, using a circular-shaped free-in-air ionization chamber, and Monte Carlo calculated conversion factors. Results for an IBt Bebig 125I source are presented and used here to assess the dose-rate constant. Uncertainties of 1.5% and 1.6% (with k = 1) were found for the air-kerma rate and the absorbed dose to water rate estimated with the new primary standards. Good agreement was found between our values and the AAPM published dose-rate constants. Comparisons with other primary standards are in progress.

Aubineau-Lanièce, I.; Chauvenet, B.; Cutarella, D.; Gouriou, J.; Plagnard, J.; Aviles Lucas, P.

2012-10-01

83

LNE-LNHB air-kerma and absorbed dose to water primary standards for low dose-rate 125I brachytherapy sources  

International Nuclear Information System (INIS)

The devices and methods applied for the LNE-LNHB primary standards in terms of reference air-kerma and absorbed dose to water for low dose-rate brachytherapy sources are described. Both standards are based on ionimetric measurements, using a circular-shaped free-in-air ionization chamber, and Monte Carlo calculated conversion factors. Results for an IBt Bebig 125I source are presented and used here to assess the dose-rate constant. Uncertainties of 1.5% and 1.6% (with k = 1) were found for the air-kerma rate and the absorbed dose to water rate estimated with the new primary standards. Good agreement was found between our values and the AAPM published dose-rate constants. Comparisons with other primary standards are in progress. (authors)

84

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)

85

Determining the Photon Air Kerma Backscatter Factor Profiles for the ISO and ICRU Recommended Slab Phantoms: Comparison Between LiF Measurements and Monte Carlo Calculations  

International Nuclear Information System (INIS)

Following the ICRU and ISO documents concerned with the calibration of photon personal dosemeters on slab phantoms, the ENEA Institute for Radiation Protection performed a series of studies aimed at adopting suitable routine procedures. The reference ISO and ICRU slab phantoms for calibrating dosemeters in terms of Hp (10,?) and Hp (0.07,?) have therefore been acquired. A slab phantom should in principle allow the simultaneous calibration of several dosemeters for the whole body. On the other hand, besides the inhomogeneity of the incident beam, it has to be taken into account that the phantom itself is responsible for a spatial dependence of the air kerma backscatter factor along its front face, implying a limitation of the practical calibration area. The results of Monte Carlo homogeneity area calculations are summarised, and validated using ionisation chamber independent mapping, and of a series of TL measurements of the same air kerma backscatter factor profiles are described. (author)

86

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

International Nuclear Information System (INIS)

Direct comparisons of the standards for air kerma of the Glowny Urzad Miar (GUM, Poland) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the 60Co and 137Cs radiation beams of the BIPM in 2006. The results, expressed as ratios of the GUM and the BIPM standards for air kerma, are 1.0023 with a combined standard uncertainty of 2.4 * 10-3 in 60Co, and 0.9995 with a combined standard uncertainty of 2.9 * 10-3 in 137Cs. The result in 60Co agrees with the direct comparison carried out in 1996 when the new correction factors adopted by the GUM and the BIPM in 2007 and 2009 are applied for the present comparison. (authors)

87

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

88

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the PTB, Germany 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 PTB, Germany and the BIPM in the low-energy X-ray range. The results show the standards to be in agreement at the level of the standard uncertainty of the comparison of 2.1 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. (authors)

89

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

International Nuclear Information System (INIS)

A key comparison has been made between the air-kerma standards of the PTB, Germany 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 5.0 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. (authors)

90

COOMET regional comparison of national measurement standards of air kerma for 137Cs ? radiation at protection level  

Science.gov (United States)

Results are presented of the COOMET supplementary comparison of the national measurement standards for air kerma in 137Cs ? radiation at protection level (~10 mGy/h). Ten National Metrology Institutes from the COOMET organization and the International Atomic Energy Agency participated in this COOMET project no. 445. The PTB acted as pilot laboratory. Two of the participants, the SMU (Slovakia) and the NSC-'IM' (Ukraine) participated in the measurements but did not submit a valid report of results. The comparison reference value (CRV) was obtained as the mean result of the PTB and the VNIIM, both of which had previously taken part in the key comparison BIPM-RI(I)-K5. The degree of equivalence with the CRV was evaluated. The results were consistent within the relative standard uncertainties of the comparison ranging from 0.28% to 1.3% and deviated from the CRV by less than 1%. 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).

Büermann, L.; Oborin, A. V.; Milevsky, V. S.; Walwyn Salas, G.; Sukhishvili, S.; Ginga, I.; Ivanov, R.; Gudelis, A.; Gomola, I.

2014-01-01

91

KEY COMPARISON: Final report of the SIM 60Co air-kerma comparison SIM.RI(I)-K1  

Science.gov (United States)

Transfer chambers were used to compare the standards for 60Co air kerma maintained by seven laboratories. Six of the laboratories are members of the Sistema Interamericano de Metrología (SIM) regional metrology organization while the seventh is the International Atomic Energy Agency (IAEA) laboratory in Vienna. The National Research Council (NRC) acted as the pilot laboratory for the comparison. Because of the participation of laboratories holding primary standards, the comparison results could be linked to the key comparison reference value maintained by the Bureau International des Poids et Mesures (BIPM). The results for all laboratories were within the expanded uncertainty (two standard deviations) of the reference value. The estimated relative standard uncertainty of the comparison between any pair of laboratories ranged from 0.5% to 1.0%. The largest discrepancy between any two laboratories was 1.0%. 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 Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Ross, C. K.; Shortt, K. R.; Saravi, M.; Meghzifene, A.; Tovar, V. M.; Barbosa, R. A.; da Silva, C. N.; Carrizales, L.; Seltzer, S. M.

2008-01-01

92

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...

93

Evaluation of entrance skin air kerma in digital and conventional pediatric chest examinations performed in Parana-Brazil  

International Nuclear Information System (INIS)

Full text: In pediatric radiology it is important to evaluate patient exposure due to the high sensitivity of his/her tissue and his/her relatively longer life expectancy, which may increase the chance of radiogenic cancer development. Special attention is necessary when digital systems are used since a high dosage level for the patient may go unnoticed because the resulting image is not overexposed. The purpose of this work is to evaluate the Entrance Skin Air Kerma (ESAK) in pediatric patients submitted to digital and conventional chest examinations performed in the State of Parana, located in the Southern region of Brazil. The survey was performed in two hospitals, one located in Curitiba, the Capital of the State (A) and the other in the city of Cascavel (B). Hospital A uses a conventional image system and Hospital B uses a CR digital system. The study group consisted of 50 patients (from 2 days to six years of age) undergoing chest PA/AP examinations. At the time of the examination, the exposure parameters (kV, mAs, focal-film distance, etc) and the gender, height, weight and age of the patient were recorded. To evaluate the Entrance Skin Air Kerma (ESAK), two TLD-100 dosimeters were packaged in a polyethylene case, heat sealed and placed on the surface of each patient. The TLDs were calibrated the Metrology Laboratory of Ionizing Radiation of the Federal University of Pernambuco. The TLDs were processed on a Victoreen readout system model 2800M. The results showed that the kilovoltage values used in Hospital A are in the range of 46 to 65 kV with the average value of 51,7 kV, while the ones in Hospital B are in the range of 65 to 80 kV. On the other hand, even though hospital B uses the CR system, the mAs used for the chest exams are 4 times higher than the ones used in Hospital A. For Hospital A, the mean ESAK value was 0.044 mGy (min: 0.08 and max 0.146 mGy), and for Hospital B the mean ESAK value was 0.368 mGy (min: 0.021 and max 1.21mGy). The results made it clear that the pediatric chest images produced with the digital system are not optimized and the doses are very high when compared with the film system. It is possible to conclude that the introduction of advanced technologies in the radiographic clinics not necessary represents a reduction of the patient dose. Reduction of patient dose requires optimization of the whole imaging chain, and this includes the information for the technicians. (author)

94

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

95

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

96

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. 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

97

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

98

Comparison of the air-kerma standards of the NPL and the BIPM in the low and medium-energy X-ray ranges  

International Nuclear Information System (INIS)

The air-kerma standards of the NPL and the BIPM have been compared in the low- and medium-energy x-ray ranges. The results for the low-energy comparison show the standards to be in agreement at the level of one standard uncertainty. At medium energies a slight trend with radiation quality is evident, with agreement at the level of one standard uncertainty for 100 kV rising to over two standard uncertainties for 250 kV. In relation to previous comparisons, the good stability of the standards over a period of twenty years is demonstrated. (authors)

99

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

100

Kerma in the air at entry surface in thorax pediatric examinations at public hospital in Parana, Brazil; Kerma no ar na superficie de entrada em exames pediatricos de torax em hospital publico no Parana, Brasil  

Energy Technology Data Exchange (ETDEWEB)

This work consisted in the evaluation of the entrance skin air kerma (ESAK) in pediatric chest x-ray examinations. A study of 186 exams in anterior-posterior, posterior-anterior and lateral projections was carried out for patients with ages ranging from 0 to 15 years. The ESAK was measured with the DoseCal software and Li-Fl thermoluminescent dosimeters. The results were compared with measurements done recently at the same place and with the reference dose values established by the European Community. It was observed that the optimization of the technique and the routine changes suggested in the previous study were not maintained. The charge (mAs) and the ESAK values found in the present study were much higher than the previous one, and the voltage (kVp) values found was lower. The results suggest that the implementation of the Quality Assurance Program could adequate these parameters to the established levels and keep the pediatric examinations more uniform. (author)

Santos, Amanda; Porto, Lorena; Bunick, Ana; Paschuk, Sergei; Denyak, Valeriy, E-mail: schelin@utfpr.edu.b [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Schelin, Hugo; Tilly, Joao, E-mail: joao.tilly@derax.com.b [DERAX Desenvolvimento Radiologico, Curitiba, PR (Brazil); Khoury, Helen, E-mail: hjkhoury@gmail.co [Universidade Federal de Pernambuco (DOIN/UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear. Grupo de Dosimetria e Instrumentacao Nuclear; Ferreira, Jose [Universidade Estadual do Oeste do Parana (UNIOESTE), Cascavel, PR (Brazil)

2011-07-01

 
 
 
 
101

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

102

Evaluation of Wall Correction Factor of INER's Air-Kerma Primary Standard Chamber and Dose Variation by Source Displacement for HDR 192Ir Brachytherapy  

Science.gov (United States)

The aim of the present study was to estimate the wall effect of the self-made spherical graphite-walled cavity chamber with the Monte Carlo method for establishing the air-kerma primary standard of high-dose-rate (HDR) 192Ir brachytherapy sources at the Institute of Nuclear Energy Research (INER, Taiwan). The Monte Carlo method established in this paper was also employed to respectively simulate wall correction factors of the 192Ir air-kerma standard chambers used at the National Institute of Standards and Technology (NIST, USA) and the National Physical Laboratory (NPL, UK) for comparisons and verification. The chamber wall correction calculation results will be incorporated into INER's HDR 192Ir primary standard in the future. For the brachytherapy treatment in the esophagus or in the bronchi, the position of the isotope may have displacement in the cavity. Thus the delivered dose would differ from the prescribed dose in the treatment plan. We also tried assessing dose distribution due to the position displacement of HDR 192Ir brachytherapy source in a phantom with a central cavity by the Monte Carlo method. The calculated results could offer a clinical reference for the brachytherapy within the human organs with cavity. PMID:24222907

Lee, J. H.; Wang, J. N.; Huang, T. T.; Su, S. H.; Chang, B. J.; Su, C. H.; Hsu, S. M.

2013-01-01

103

Computational tool kit for evaluating air kerma with the purpose of radiation protection of hospital inpatients: proposal of a simple experimental evaluation method  

International Nuclear Information System (INIS)

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 Active Sheet was utilized to develop a computational toolkit with exposure measurements 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 x 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. (author)

104

Estimation of mean-glandular dose from monitoring breast entrance skin air kerma using a high sensitivity metal oxide semiconductor field effect transistor (MOSFET) dosimeter system in mammography  

Energy Technology Data Exchange (ETDEWEB)

Estimation of mean-glandular dose (MGD) has been investigated in recent years due to the potential risks of radiation-induced carcinogenesis associated with the mammographic examination for diagnostic radiology. In this study, a new technique for immediate readout of breast entrance skin air kerma (BESAK) using high sensitivity MOSFET dosimeter after mammographic projection was introduced and a formula for the prediction of tube output with exposure records was developed. A series of appropriate conversion factors was applied to the MGD determination from the BESAK. The study results showed that signal response of the high sensitivity MOSFET exhibited excellent linearity within mammographic dose ranges, and that the energy dependence was less than 3% for each anode/filter combination at the tube potentials 25-30 kV. Good agreement was observed between the BESAK and the tube exposure output measurement for breasts thicker than 30 mm. In addition, the air kerma estimated from our prediction formula provided sufficient accuracy for thinner breasts. The average MGD from 120 Asian females was 1.5 mGy, comparable to other studies. Our results suggest that the high sensitivity MOSFET dosimeter system is a good candidate for immediately readout of BESAK after mammographic procedures.

Dong, S.L.; Chu, T.C.; Lee, J.S.; Lan, G.Y.; Wu, T.H.; Yeh, Y.H.; Hwang, J.J. E-mail: jjhwang@ym.edu.tw

2002-12-01

105

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 60}Co and {sup 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 {sup 60}Co of 9.9 x 10{sup -3} with a combined standard uncertainty of 1.8 x 10{sup -3}, and in {sup 137}Cs of 6.4 x 10{sup -3} with a combined standard uncertainty of 2.8 x 10{sup -3}. The earlier comparisons in {sup 60}Co {gamma} rays made in 1971 (direct) and 1989 (indirect) resulted in an agreement of the two standards within 2 x 10{sup -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, k{sub wall} and k{sub pn}, for the PTB standards, which were calculated using Monte Carlo methods. (authors)

Allisy-Roberts, P.J.; Burns, D.T. [Bureau International des Poids et Mesures (BIPM), 92 - Sevres (France); Buermann, L.; Kramer, H.M. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

2005-11-15

106

The index of microbial air contamination.  

Science.gov (United States)

The standard index of microbial air contamination (IMA) for the measurement of microbial air contamination in environments at risk is described. The method quantifies the microbial flow directly related to the contamination of surfaces coming from microbes that reach critical points by falling on to them. The index of microbial air contamination is based on the count of the microbial fallout on to Petri dishes left open to the air according to the 1/1/1 scheme (for 1h, 1m from the floor, at least 1m away from walls or any obstacle). Classes of contamination and maximum acceptable levels have been established. The index of microbial air contamination has been tested in many different places: in hospitals, in food industries, in art galleries, aboard the MIR space station and also in the open air. It has proved to be a reliable and useful tool for monitoring the microbial surface contamination settling from the air in any environment. PMID:11170755

Pasquarella, C; Pitzurra, O; Savino, A

2000-12-01

107

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)

108

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

Energy Technology Data Exchange (ETDEWEB)

Mammography aims to achieve a high image quality associated with a dose in the patient as low as feasible. Values of average glandular dose, D{sub G}, can be obtained by means of two dosimetric methods: one based on the measurement of incident air kerma, K{sub i}, 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 (K{sub i}) and average glandular dose (D{sub G}) 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 D{sub G} determined from K{sub i} and also with the values of K{sub i} and D{sub G} 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 K{sub i} values ranged around 7.9% between the methods of action. The result of the values of D{sub G} ranged around 14.7% between the two methods of action. It is observed that the estimate of D{sub G} by the software is higher than the values measured with the dosimetric phantom. (author)

Coutinho, Celia M.C.; Almeida, Claudio D. de, E-mail: celia@ird.gov.b, E-mail: claudio@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Peixoto, Joao E., E-mail: joao.e.peixoto@uol.com.b [Instituto Nacional de Cancer (INCa/RJ), Rio de Janeiro, RJ (Brazil); Lopes, Ricardo T., E-mail: ricardo@lin.ufrj.b [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

2009-07-01

109

KERMA ratios in pediatric CT dosimetry  

Energy Technology Data Exchange (ETDEWEB)

Patient organ doses may be estimated from CTDI values. More accurate estimates may be obtained by measuring KERMA (Kinetic Energy Released in Matter) in anthropomorphic phantoms and referencing these values to free-in-air X-ray intensity. To measure KERMA ratios (R{sub K}) in pediatric phantoms at CT. CT scans produce an air KERMA K in a phantom and an air KERMA K{sub CT} at isocenter. KERMA ratios (R{sub K}) are defined as (K/K{sub CT}), measured using TLD chips in phantoms representing newborns to 10-year-olds. R{sub K} in the newborn is approximately constant. For the other phantoms, there is a peak R{sub K} value in the neck. The median R{sub K} values for the GE scanner at 120 kV were 0.92, 0.83, 0.77 and 0.76 for newborns, 1-year-olds, 5-year-olds and 10-year-olds, respectively. Organ R{sub K} values were 0.91 {+-} 0.04, 0.84 {+-} 0.07, 0.74 {+-} 0.09 and 0.72 {+-} 0.10 in newborns, 1-year-olds, 5-year-olds and 10-year-olds, respectively. At 120 kV, a Siemens Sensation 16 scanner had R{sub K} values 5% higher than those of the GE LightSpeed Ultra. KERMA ratios may be combined with air KERMA measurements at the isocenter to estimate organ doses in pediatric CT patients. (orig.)

Huda, Walter [Medical University of South Carolina (MUSC), Department of Radiology and Radiological Science, Charleston, SC (United States); Ogden, Kent M.; Lavallee, Robert L.; Roskopf, Marsha L.; Scalzetti, Ernest M. [SUNY Upstate Medical University, Department of Radiology, Syracuse, NY (United States)

2012-05-15

110

Intercomparison of the UK and Swiss primary standards of X ray exposure and air kerma for 50 kV X rays  

International Nuclear Information System (INIS)

A parallel plate free air ionization chamber and a separate air attenuation correction chamber have been constructed jointly by the Swiss Federal Office of Metrology (OFM) and the United Kingdom National Physical Laboratory (NPL) for use as the Swiss National Primary Standard for exposure and air kerma for X rays generated at voltages between 8 and 50 kV. The designs of both chambers, based on the NPL standard, are outline and the modifications made to improve the ease of construction and the stability of the electrode systems are highlighted. The results of the dimensional metrology and the correction factors applied to both chambers are given, together with an outline of the methods used to determine them. The two standards have been intercompared at NPL at a number of X ray qualities. As the NPL standard has been compared with the free air chamber held at the Bureau international des poids et mesures, comparison data for the OFM chamber have been derived from the NPL intercomparison and are also given in the paper. (author). 5 refs, 3 figs, 2 tabs

111

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)

112

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 “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.

113

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.

114

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

115

Effect of Air Outlet Angle on Air Distribution Performance Index  

Directory of Open Access Journals (Sweden)

Full Text Available       In this paper a numerical study of velocity and temperature distribution in air conditioned space have been made. The computational model consists of the non-isothermal 3-D turbulent with (k-? model. The numerical study is made to conduct air distribution in a room air-conditioned space with real interior dimensions (6×4×3m and to analyze the effect of changing angle of grille vanes on the flow pattern, velocity, and temperature distribution in the room under a set of different condition, and under a supply air temperature of 16?C to examine the final result on air distribution performance index (ADPI.The results show a significant effect within the change of supply air angle, the maximum air distribution performance index (ADPI is 52% when air change per hour (ACH is equal to 10 at 16?C inlet temperature with angle ( 15? down, and the minimum value of (ADPI is 20% when ACH is equal to 15 at 16?C inlet temperature and angle ( degree. 

Isbeyeh W. Maid

2013-05-01

116

Air quality complex index estimation of air pollution situations  

International Nuclear Information System (INIS)

To improve the regional system for assessment and management of the ambient air quality in the North-East Estonian region of oil shale mining and processing, as well as natural areas, the corresponding Air Quality Complex Index (AQI) has been elaborated. This method enables to generalize a large number of measured numerical values of concentrations of pollutants in case of multicomponential pollution fields and makes the results more easily understandable. The AQI is suitable for the real-time monitoring as well as for prediction of air quality values and pollution situations by calculated data. (author)

117

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

118

Study of the spatial variation of the air kerma backscatter factor on the standard ISO phantom, with a Co-60 irradiator  

International Nuclear Information System (INIS)

Personal dosimeters should be calibrated on the surface of the ISO water phantom. For this purpose dose values should present a uniform distribution over the calibration area of diameter dF. To determine the boundary of the uniform dose area, two complementary approaches are purposed: the experimental and the numerical simulation. This article presents the results of Monte Carlo calculations and experimental determinations of the spatial variation of the air kerma backscatter factor on the ISO water phantom surface performed for the Co-60 gamma radiation quality. The experimental B values on the center of the phantom surface was 1.04 and dF was 30 cm. However, the experimental determination of the variation of B along the axis of the phantom is a very consuming time process and is very sensitive to the positioning of the ionisation chamber. The methodology advanced in this work allows the knowledge of values of B along the apothem and diagonal axis using only one experimental value the B value on the center of the phantom and taking into account the relative variation of B from the simulation results. (author)

119

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

120

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

International Nuclear Information System (INIS)

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)

 
 
 
 
121

Comparison of mammography radiation dose values obtained from direct incident air kerma measurements with values from measured X-ray spectral data  

International Nuclear Information System (INIS)

The application of X-rays and ionising radiations for diagnostic radiology requires that the procedure is justified and optimised and that the exposure to the patient is kept as low as possible, without compromising image information. X-ray mammography is considered to be the most sensitive technique currently available for early detection of breast cancer. The magnitude of the absorbed radiation dose to the breast from mammography X-ray beams forms an important part of the quality control of the mammographic examination since it gives an indication of the performance of the mammographic imaging system as well as an estimated risk to the patient. In this work mean glandular dose (MGD) values were obtained at various tube potentials and tube loadings (TL) using direct measurements of the incident air kerma (ESAK) at the surface of a standard breast phantom and also from spectral measurements acquired with a solid-state detector. Comparisons of the MGD values thus derived are presented and the relationship between MGD, phantom thickness, image quality and tube operating parameters is discussed

122

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)

123

Modelling the contribution of individual radionuclides to the total gamma air kerma rate for the sediments of the Ribble Estuary, NW England  

International Nuclear Information System (INIS)

The aim of this study was to test the performance of a published dose-rate model, investigate the contribution of individual radionuclides to the total gamma air kerma rate (GAKR) and derive external doses to man in the Ribble Estuary, NW England. GAKRs were measured and sediment cores were collected in order to determine radionuclide specific activities with depth. The latter values were used as input data for the external dose-rate model. The model has a slight tendency to over-predict the GAKR, but, on average, the model predictions fall within ±26% of the measured value. Improvements, in the present case, might be made by accounting for core shortening and variations in soil density in the input data. The model predicted that, for exposed intertidal mud sites, a range of GAKRs between 0.011 and 0.022 ?Gy h-1 was attributable to Springfields discharges alone. The contribution due to 234mPa and 234Th ranged between 20 and 60%. An excess GAKR (GAKR arising from anthropogenic emissions alone) of 0.139-0.150 ?Gy ?Gy h-1, used in conjunction with relevant habit-survey data (for a potential critical group) and conversion factors, yielded a dose to man of 0.029-0.031 mSv year-1. (author)

124

Comparison of mammography radiation dose values obtained from direct incident air kerma measurements with values from measured X-ray spectral data  

Energy Technology Data Exchange (ETDEWEB)

The application of X-rays and ionising radiations for diagnostic radiology requires that the procedure is justified and optimised and that the exposure to the patient is kept as low as possible, without compromising image information. X-ray mammography is considered to be the most sensitive technique currently available for early detection of breast cancer. The magnitude of the absorbed radiation dose to the breast from mammography X-ray beams forms an important part of the quality control of the mammographic examination since it gives an indication of the performance of the mammographic imaging system as well as an estimated risk to the patient. In this work mean glandular dose (MGD) values were obtained at various tube potentials and tube loadings (TL) using direct measurements of the incident air kerma (ESAK) at the surface of a standard breast phantom and also from spectral measurements acquired with a solid-state detector. Comparisons of the MGD values thus derived are presented and the relationship between MGD, phantom thickness, image quality and tube operating parameters is discussed.

Assiamah, M. [Health Physics Service/Schonland Research Institute for Nuclear Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg (South Africa); Nam, T.L. [Health Physics Service/Schonland Research Institute for Nuclear Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg (South Africa)]. E-mail: nam@schonlan.src.wits.ac.za; Keddy, R.J. [Health Physics Service/Schonland Research Institute for Nuclear Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg (South Africa)

2005-04-01

125

Comparison of mammography radiation dose values obtained from direct incident air kerma measurements with values from measured X-ray spectral data.  

Science.gov (United States)

The application of X-rays and ionising radiations for diagnostic radiology requires that the procedure is justified and optimised and that the exposure to the patient is kept as low as possible, without compromising image information. X-ray mammography is considered to be the most sensitive technique currently available for early detection of breast cancer. The magnitude of the absorbed radiation dose to the breast from mammography X-ray beams forms an important part of the quality control of the mammographic examination since it gives an indication of the performance of the mammographic imaging system as well as an estimated risk to the patient. In this work mean glandular dose (MGD) values were obtained at various tube potentials and tube loadings (TL) using direct measurements of the incident air kerma (ESAK) at the surface of a standard breast phantom and also from spectral measurements acquired with a solid-state detector. Comparisons of the MGD values thus derived are presented and the relationship between MGD, phantom thickness, image quality and tube operating parameters is discussed. PMID:15701409

Assiamah, M; Nam, T L; Keddy, R J

2005-04-01

126

Air kerma to personal dose equivalent conversion factors for ICRU and ISO recommended slab phantoms for photons from 20 keV to 1 MeV  

International Nuclear Information System (INIS)

The present report summarizes the studies carried out at ENEA-AMB-PRO-IRP (Institute for Radiation Protection) that were addressed to the determination of air kerma to personal dose equivalent conversion coefficients for two practical phantoms as proposed by ICRU (International Commission for Radiation Units and Measurements) and by ISO (International Standard Organization) for photon personal dosimeters' calibration procedure. The analyses, developed using the MCNP Monte Carlo code, were mainly aimed at establishing which of the two proposed phantoms better approximates the ICRU theoretical one. Furthermore a complete tabulation of the conversion coefficients is supplied for monoenergetic photon beams from 20 keV to 1 MeV as well as for the two ISO X-ray reference series Wide Spectrum and Narrow Spectrum. The study has been performed in the framework of the CEC Contract F13P-CT92-0064 'The Measurement of the Spectral and Angular Distribution of External Radiations in Workplace and Implications for Personal Dosimetry

127

From reference air-kerma-rate to nominal absorbed dose-rate to water Paradigm shift in photon brachytherapy: ISO new work item proposal  

International Nuclear Information System (INIS)

Full text: Over decades, photon radiation brachytherapy (BT) has proven worldwide as an essential modality of high precision radiation oncology for certain primary tumor sites. The dosimetric uncertainty of photon brachytherapy, however, is currently much larger than in external beam radiotherapy due to several factors including: calibration to the reference air-kerma-rate K.R K.R (or air-kerma strength), dose calculation model, dosimetric functions and dose measurement complexity, besides the geometrical dose uncertainties in high dose-gradient BT-fields. In addition, many photon sources are applied with quite different dosimetric properties requiring much skill from the medical physicist. This work proposes increased accuracy of brachytherapy through improvements in source calibration and clinical dosimetry methodology. Currently, BT-photon sources are calibrated free in air, at 100 cm distance, and in terms of K.R. By calibrating BT-photon sources directly to the TG-43U1 reference point at 1 cm in water, to be named the nominal absorbed dose-rate to water, D.w,1, the number of calibration steps in the traceability chain is reduced from 6 to 4, thus reducing the expanded uncertainty in dose delivery for patient treatment. With a target combined uncertainty of ucue.w,1 primary standards, whi/sup>w,1 primary standards, which will soon become available for high energy and low energy, high and low dose-rate BT-photon sources. This is a paradigm shift that requires: international consensus, metrologic work and guidance. Thus, there is a need for an ISO standard based on and extending the AAPM TG-43U1 formalism. Taking into account the results and conclusions of the AAPM 2010 discussions, a draft for an ISO new work item proposal on Clinical dosimetry - Photon radiation sources for brachytherapy will be presented. This standardization project could be launched within ISO TC 85/SC 2/WG 22, in continuation of ISO 21439 (2009) for beta radiation sources. Clear terms and definitions are basic requirements for this standard. It is proposed that BT-photon radiation qualities need to be reclassified as: high-energy >100 keV, medium energy 40 keV to 100 keV, and low energy photons .w,1-recalibrated special transfer standards like well-type ionization-chambers) and as fast, direct reading dosemeter with high spatial and temporal resolution as required for detailed acceptance tests of BT-sources, -software, -planning, and -verification. This ISO-standard will provide guidance for clinical BT-dosimetry in terms of absorbed dose to water and for estimating the uncertainty of this new quantity. Most standardized procedures can be given by referring to AAPM-reports and ESTRO-documents. General quality assurance issues, radiation protection and safety issues are outside the scope. Recommendations will be prepared to replace the K.R K.R by D.w,1 as basic dosimetric quantity, to become consistent with external beam radiotherapy and to reduce the dosimetric uncertainty in brachytherapy

128

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)

129

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.

130

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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 dados 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.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 measurements 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

2012-04-01

131

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

132

Final report on APMP.RI(I)-K1: APMP/TCRI key comparison report of measurement of air kerma for 60Co gamma-rays  

International Nuclear Information System (INIS)

The APMP.RI(I)-K1 key comparison of the measurement standards of air kerma for 60Co gamma-rays was undertaken by the APMP/TCRI Dosimetry Working Group between 2004 and 2006, coordinated by the Korean Research Institute of Standards and Science (KRISS). In total, 10 institutes took part in the comparison, among which 7 were APMP member laboratories. Three Farmer-type commercial cavity chambers were used as transfer chambers and circulated among the participants. All the participants carried out their measurements according to the guidelines for the comparison established by the KRISS with the cooperation of the ARPANSA. For each transfer chamber, an NMI calibration coefficient was obtained and a ratio derived by dividing by the average result from the linking laboratories, ARPANSA and NMIJ. The APMP comparison reference value for each chamber was calculated as the mean of the NMI-determined calibration coefficients divided by the average result from the linking laboratories. The results showed that the maximum difference between the APMP linked ratio of a participating NMI and the APMP reference value was 1.76 %. The measured ratios of the calibration coefficient NMI, BIPM R between the participating NMI and the BIPM via the link laboratories for the transfer chambers were obtained. The maximum expanded uncertainty of NMI, BIPM R for any participating laboratory was 2.0 %. The degree of equivalence of each participating laboratory with respect to the key coming laboratory with respect to the key comparison reference value was also evaluated. The expanded uncertainty of the difference between the results ranged from 0.5 % to 1.2 %. The pair-wise degree of equivalence between each pair of laboratories was also obtained and the largest difference of the expanded uncertainty of the difference for any pair-wise degree of equivalence was within the expanded uncertainty of the measurement for the pair of laboratories. (authors)

133

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 ... the AirNow PDF page to learn more. Publications Air Quality Index - A Guide to Air Quality and Your ...

134

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

135

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

136

Comparison of factors given in ICRU Report 23 and IAEA TRS 277 for converting from exposure/air kerma to absorbed dose to water for medium energy X-rays  

International Nuclear Information System (INIS)

New values of the factors required to convert the reading of an ionization chamber calibrated in terms of air kerma (or exposure) to absorbed dose to water for medium energy X-rays were given in a Code of Practice published by the IAEA in 1987. These factors differ by a maximum of 12.5% at 0.15 mm Cu HVL from those given in ICRU Report 23. This paper discusses the difference between the ICRU and IAEA conversion factors and forms the basis of the recommendation of the IPSM low and medium energy X-ray dosimetry working party, that dosimetry in the U.K. should continue to be based on ICRU Report 23 and therefore on the current HPA Code of Practice. (author)

137

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

138

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

139

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.

140

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

 
 
 
 
141

Hold your breath: A new index of air quality  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 and shows a significant influence of determinants such as energy efficiency, industrial production, electricity produced from coal sources, and urba...

Buehn, Andreas; Farzanegan, Mohammad Reza

2012-01-01

142

Air pollution forecast in cities by an air pollution index highly correlated with meteorological variables  

International Nuclear Information System (INIS)

There are many different air pollution indexes which represent the global urban air pollution situation. The daily index studied here is also highly correlated with meteorological variables and this index is capable of identifying those variables that significantly affect the air pollution. The index is connected with attention levels of NO2, CO and O3 concentrations. The attention levels are fixed by a law proposed by the Italian Ministries of Health and Environment. The relation of that index with some meteorological variables is analysed by the linear multiple partial correlation statistical method. Florence, Milan and Vicence were selected to show the correlation among the air pollution index and the daily thermic excursion, the previous day's air pollution index and the wind speed. During the January-March period the correlation coefficient reaches 0.85 at Milan. The deterministic methods of forecasting air pollution concentrations show very high evaluation errors and are applied on limited areas around the observation stations, as opposed to the whole urban areas. The global air pollution, instead of the concentrations at specific observation stations, allows the evaluation of the level of the sanitary risk regarding the whole urban population. (Author)

143

Air Quality Index of an Industrial District of Jharkhand, India  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with the assessment of air quality status of the study area by means of NAAQS Dependant air quality index (AQI. It was performed by combining various pollutant concentrations in a specific mathematical equation to get a single number for air quality. Air quality was monitored at thirty one monitoring locations which are covering entire Jharia Coalfield. Monitoring was done to assess the concentration of various particulate (suspended particulate matter, respirable particulate matter and fine particulate matter and gaseous pollutants (oxides of sulphur, nitrogen and carbon. As per AQI based on prevailing air quality standard, location A7 (Kusunda registered high AQI followed by Bastacola (A17, Lodna (A30, Bank More (A6 and Sijua (A10. These locations were close to opencast mining area as well as receiving vehicular dust resuspension. Only one location i.e., A23 (BIT-Sindri comes under moderate pollution status.

Bhawna Dubey*1

2014-06-01

144

Neutron KERMA factors of human tissues  

International Nuclear Information System (INIS)

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 (au)

145

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

146

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

147

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

148

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

International Nuclear Information System (INIS)

An indirect comparison has been made between the air erma standards of the PTB 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 stated standard uncertainty, although the result for the 100 kV radiation quality differs significantly from that for the other qualities. (authors)

149

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

150

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)

151

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

152

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  

Energy Technology Data Exchange (ETDEWEB)

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 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)

Vijayam, M.; Shigwan, J.B.; Dixit, B.S.; Shaha, V.V.; Misra, S.C. [Radiation Standards and Instrumentation Division, Bhabha Atomic Research Centre, Mumbai (India)

2000-05-01

153

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)

154

Secondary charged particle spectra and kerma calculations  

International Nuclear Information System (INIS)

The calculation of kerma factors from known cross sections is not as simple as is often implied. The kerma factors are strongly influenced by the reaction mechanism assumed. An important example of this dependence on the reaction mechanism is the contribution of the 12C(n,n')3? reaction to the total kerma in carbon. First, a short review will be given of the ENDF/B-V carbon cross sections which were used in the calculation of carbon kerma factors. Using the reaction channels implied in the ENDF/B-V evaluation, the contribution of various reactions to the total kerma factors in carbon will be given. A detailed analysis of the reaction mechanisms which could contribute to the (n,n')3? reaction in carbon has been carried out. First their contribution to kerma, independent of cross section, will be calculated and then the initial spectra of alpha particles produced by the various reaction mechanisms will be given. A discussion of possible ways of experimentally distinguishing the reaction mechanisms will be made by comparing their different initial spectra and their variation in kerma with neutron energy. Finally, the event-size spectra for tissue-equivalent proportional counters will be presented, giving only the contributions from the (n,n')3? reaction and its various possible reaction channels. 3 refs., 11 figs., 4 tabs

155

Status of JENDL KERMA/PKA file  

International Nuclear Information System (INIS)

The JENDL KERMA/PKA file is one of the special purpose files of JENDL, giving the cross section data for neutron radiation damage studies. Two codes, PKAR and KERMA, have been developed to generate the file by processing the composite spectra of emitted neutron and charged particles with the effective single particle emission model. The calculated results for iron generally agree with those of the Monte Carlo method which is based on the exciton and evaporation models for PKA spectra and with those calculated by Howerton et al. for KERMA factors. Future scope of the file generation is also described. (author)

156

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

157

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.

158

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

Science.gov (United States)

...Public Reporting of Daily Air Quality—Air Quality Index (AQI...sub-areas of your MSA. d. Causes for unusual AQI values...However, if a significant air quality problem exists...the AQI Relate to Air Pollution Levels? For...

2010-07-01

159

[Variation characteristics and influencing factors of air pollution index in China].  

Science.gov (United States)

Based on the daily air pollution index (API), primary pollutant, air quality level and status of 42 cities in China during 2001-2010, the characteristics of air quality were analyzed. The results showed that the atmosphere was significantly influenced by consumption of coal. The primary pollutant was PM10, and the air quality status was excellent (0 index correlated linearly with precipitation, wind speed and temperature inversion; The distribution of weather conditions, which was affected by the terrain, also could influence the air quality; In addition, the human activities had both positive and negative functions on the urban air quality. PMID:22946179

Li, Xiao-Fei; Zhang, Ming-Jun; Wang, Sheng-Jie; Zhao, Ai-Fang; Ma, Qian

2012-06-01

160

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

Science.gov (United States)

... a. The reporting area(s) (the MSA or... Maroon. 1 1 Specific colors can be found...Reporting of Daily Air Quality—Air Quality Index... f. The pollutant specific sensitive groups...index values for sub-areas of your MSA....

2010-07-01

 
 
 
 
161

Laminar burning velocity and explosion index of LPG-air and propane-air mixtures  

Energy Technology Data Exchange (ETDEWEB)

The determination of burning velocity is very important for the calculations used in hazardous waste explosion protection and fuel tank venting, which has a direct impact on environmental protection. The scope of the present study encompass an extensive study to map the variations of the laminar burning velocity and the explosion index of LPG-air and propane-air mixtures over wide ranges of equivalence ratio ({phi} = 0.7-2.2) and initial temperature (Ti = 295-400 K) and pressure (P{sub I} = 50-400 kPa). For this purpose a cylindrical combustion bomb was developed. The burning velocity was determined using different models depending on the pressure history (P-t) of the central ignition combustion process at the minimum ignition energy. The data obtained for the laminar burning velocity is correlated to S{sub L} = S{sub L0}(T/T{sub O}){sup {alpha}}(P/P{sub O}){sup {beta}} where S{sub L0} is the burning velocity at NPT, {alpha} and {beta} are the temperature and pressure exponents respectively. The value of {beta} is observed to slightly vary with the equivalence ratio for both fuels. However, propane exhibits higher pressure dependency than that of LPG. The maximum laminar burning velocity found for propane is nearly 455 mm/s at {phi} = 1.1, while that for LPG is nearly 432 mm/s at 4.5% fuel percent ({phi}{approx} 1.5). The maximum explosion index, commonly called the 'explosion severity parameter', is calculated from the determined laminar burning velocity and is found to be 93 bar m/s for propane, and nearly 88 bar m/s for LPG. 53 refs., 20 figs., 5 tabs.

A.S. Huzayyin; H.A. Moneib; M.S. Shehatta; A.M.A. Attia [Benha University, Benha (Egypt). High Institute of Technology]. ali_maattia@yahoo.com

2008-01-15

162

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

163

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

164

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

165

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)

166

Refractometer for Tracking Changes in the Refractive Index of Air Near 780 nm  

CERN Document Server

A new system, consisting of a double channel Fabry Perot etalon and laser diodes emitting around 780 nm is described and proposed to be used for air refractive index measurements. The principle of this refractometer is based on frequency measurements between optical laser sources. It permits quasi-instantaneous measurement with a resolution better than and uncertainty in the range. Some preliminary results on the stability of this system and the measurements of the refractive index of air with this apparatus are presented. The first measurements of the index of air at 780 nm are, within an experimental uncertainty of the order of, in agreement with the predicted values by the so-called revised Edl\\'en equations. This result is to the best of our knowledge the first to extend to the near infra-red the validity of the revised Edl\\'en equation derived for the wavelength range 350- 650 nm.

Khélifa, N E; Xu, J; Juncar, P; Himbert, M

1998-01-01

167

Suppression of Air Refractive Index Variations in High-Resolution Interferometry  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of the refractive index of air has proven to be a major problem on the road to improvement of the uncertainty in interferometric displacement measurements. We propose an approach with two counter-measuring interferometers acting as a combination of tracking refractometer and a displacement interferometer referencing the wavelength of the laser source to a mechanical standard made of a material with ultra-low thermal expansion. This technique combines length measurement within a specified range with measurement of the refractive index fluctuations in one axis. Errors caused by different position of the interferometer laser beam and air sensors are thus eliminated. The method has been experimentally tested in comparison with the indirect measurement of the refractive index of air in a thermal controlled environment. Over a 1 K temperature range an agreement on the level of 5 × 10?8 has been achieved.

Zden?k Buchta

2011-08-01

168

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

169

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

170

Kerma measurements in polyenergetic neutron fields  

International Nuclear Information System (INIS)

Absorbed dose was measured as a function of neutron energy with a small spherical proportional counter (PC) irradiated in the pulsed-beam broad energy spectrum neutron fields of the Physikalisch-Technische Bundesanstalt (PTB) that were produced with the p + Be reaction and extended to 20 MeV neutron energy. Time-of-flight (TOF) discrimination methods augmented the traditional microdosimetric pulse height (PH) analysis and yielded absorbed dose as a function of lineal energy y and neutron TOF. Below 0.7 keV.?m-1 lineal energy, unfolding procedures greatly improve the time resolution, e.g. from 225 ns full width at half maximum (FWHM) to 65 ns FWHM at 1.2 keV.?m-1. The overall time resolution from unfolded TOF spectra is approximately 30 ns FWHM. The absorbed dose was normalised to neutron spectral fluence and, on the assumption that kerma is numerically equal to absorbed dose, yielded relative neutron-fluence-to-kerma conversion coefficients as a function of energy that are in good agreement with values from previous work. (author)

171

Kerma factors in interaction of neutrons with boron carbide  

International Nuclear Information System (INIS)

Heat generation in neutron interactions with boron carbide B10; B11 and 12C is calculated. Kerma-factors (kerma-kinetic energy released in materials) were calculated for neutron energies between 10-4 eV and 15 MeV. No major simplifying assumptions are introduced, and the accuracy of the calculated kerma-factors depends only on availability and accuracy of the basic nuclear data. The ENDF/B-4 data and recent experimental information are used for the calculation of kerma-factors. Plots of these kerma-factors are presented in units of eVxb/atom and wtxsec/(cmxn) as a function of neutron energy

172

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

173

Forecasting of Air Quality Index in Delhi Using Neural Network Based on Principal Component Analysis  

Science.gov (United States)

Forecasting of the air quality index (AQI) is one of the topics of air quality research today as it is useful to assess the effects of air pollutants on human health in urban areas. It has been learned in the last decade that airborne pollution has been a serious and will be a major problem in Delhi in the next few years. The air quality index is a number, based on the comprehensive effect of concentrations of major air pollutants, used by Government agencies to characterize the quality of the air at different locations, which is also used for local and regional air quality management in many metro cities of the world. Thus, the main objective of the present study is to forecast the daily AQI through a neural network based on principal component analysis (PCA). The AQI of criteria air pollutants has been forecasted using the previous day's AQI and meteorological variables, which have been found to be nearly same for weekends and weekdays. The principal components of a neural network based on PCA (PCA-neural network) have been computed using a correlation matrix of input data. The evaluation of the PCA-neural network model has been made by comparing its results with the results of the neural network and observed values during 2000-2006 in four different seasons through statistical parameters, which reveal that the PCA-neural network is performing better than the neural network in all of the four seasons.

Kumar, Anikender; Goyal, P.

2013-04-01

174

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 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)

175

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

176

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 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 g of this stations are described. 4 figs, 2 tables. (J.U)

177

Simultaneous measurements of radar reflectivity and refractive index spectra in clear air convection.  

Science.gov (United States)

Simultaneous measurements of radar reflectivity and radio refractive index at several altitudes in clear air convection have been made. The experimental data were compared with the theoretical relationship which relates the reflectivity to the refractivity spectrum. The agreement between the measurements and the theory is excellent and shows that the radar returns in clear air are the result of, and can be quantitatively described as being from, fine-scale refractivity fluctuations due to turbulent mixing. Further, the data give strong support to the -5/3 spectral decay of the refractivity spectrum in the inertial subrange.

Konrad, T. G.; Robison, F. L.

1972-01-01

178

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 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)

179

Refractometer for tracking changes in the refractive index of air near 780 nm.  

Science.gov (United States)

A new system, consisting of a double-channel Fabry-Perot etalon and laser diodes emitting around 780 nm, is described and proposed for use for measuring air-refractive index. The principle of this refractometer is based on frequency measurements between optical laser sources. It permits quasi-instantaneous measurement with a resolution of better than 10(-9) and uncertainty in the 10(-8) range. Some preliminary results on the stability of this system and the measurements of the refractive index of air with this apparatus are presented. The first measurements of the index of air at 780 nm are, within an experimental uncertainty of the order of 2 x 10(-8), in agreement with the predicted values by the so-called revised Edlén equations. This result is, to the best of our knowledge, the first to extend to the near IR the validity of the revised Edlén equation derived for the wavelength range of 350-650 nm. PMID:18268572

Khélifa, N; Fang, H; Xu, J; Juncar, P; Himbert, M

1998-01-01

180

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)

 
 
 
 
181

Effect of the relative optical air mass and the clearness index on solar erythemal UV irradiance.  

Science.gov (United States)

This paper analyses the effects of the clearness index (Kt) and the relative optical air mass (mr) on erythemal UV irradiance (UVER). The UVER measurements were made in Valencia (Spain) from 6:00 am to 6:00 pm between June 2003 and December 2012 and (140,000 data points). Firstly, two models were used to calculate values for the erythemal ultraviolet irradiance clearness index (KtUVER) as a function of the global irradiance clearness index (Kt). Secondly, a potential regression model to measure the KtUVER as a function of the relative optical air mass was studied. The coefficients of this regression were evaluated for clear and cloudy days, as well as for days with high and low ozone levels. Thirdly, an analysis was made of the relationship between the two effects in the experimental database, with it being found that the highest degree of agreement, or the joint highest frequencies, are located in the optical mass range mr?[1.0, 1.2] and the clearness index range of Kt?[0.8, 1.0]. This is useful for establishing the ranges of parameters where models are more efficient. Simple equations have been tested that can provide additional information for the engineering projects concerning thermal installations. Fourthly, a high dispersion of radiation data was observed for intermediate values of the clearness for UV and UVER. PMID:24911276

Moreno, J C; Serrano, M A; Cañada, J; Gurrea, G; Utrillas, M P

2014-09-01

182

Refractive index of air: 3. The roles of CO2, H2O, and refractivity virials.  

Science.gov (United States)

The author's recent studies of the refractive index of air are extended, and several assumptions made therein are further examined. It is shown that the alternative dispersion equations for CO2, which are due to Edlen [Metrologia 2, 71 (1966)] and Old et al. [J. Opt. Soc. Am. 61, 89 (1971)] result in differences of less than 2 x 10(-9) in the phase refractive index and less than 3 x 10(-9) in the group refractive index for current and predicted concentrations of CO2. However, because the dispersion equation given by Old et al. is consistent with experimental data in the near infrared, it is preferable to the equation used by Edlen, which is valid only in the ultraviolet and the visible. The classical measurement by Barrell and Sears [Philos. Trans. R. Soc. London Ser. A 238, 1 (1939)] on the refractivity of moist air is shown to have some procedural errors in addition to the one discussed by Birch and Downs [Metrologia 30, 155 (1993)]. It is shown that for normal atmospheric conditions the higher refractivity virial coefficients related to the Lorentz-Lorenz relation are adequately incorporated into the empirically determined first refractivity virial. As a guide to users the practical limits to the calculation of the refractive index of the atmosphere that result from the uncertainties in the measurement of the various atmospheric parameters are summarized. PMID:12003222

Ciddor, Philip E

2002-04-20

183

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

184

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

185

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

Energy Technology Data Exchange (ETDEWEB)

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.

Hashimoto, M.; Tate, E.; Watarai, J.; Sasaki, M

2006-10-15

186

ZZ VITAMIN-J/KERMA, Gas Production Cross-Sections, Neutron and Gamma Kerma in FOURACES Format  

International Nuclear Information System (INIS)

1 - Description of program or function: Format: ANISN; Number of groups: 175 neutron plus 38 photon energy groups; Nuclides: H-1, D-2, T-3, Li-6, Li-7, Be-9, B-10, B-11, C, O-16, Al-27, Si, Ti, V, Cr, Mn-55, Fe, Ni, Cu, Zr, Nb-93, Mo, Ba-134, Ba-135, Ba-136, Ba-137, Ba-138, W-182, W-183, W-184, W-186, Pb, Bi-209, He-3, He-4, N-14, Mg, P-31, S, Ca, Co-59, In, Sn, Ta-181, Re Origin: EFF-1, DLC-99 (HUGO) data library; Weighting spectrum: Maxwellian plus 1/E plus fission spectrum plus fusion peak. Library of gas production cross sections, neutron kerma factors and photon kerma factors in FOURACES format according to GEFF-1 specifications. Kerma factors have been calculated for temperatures 300 K and 800 K. 2 - Method of solution: For the gas production cross sections, the lump reactions 203 and 207 included in EFF-1 had been assumed as the basic of the computation. The neutronics kerma factors have been calculated with the module KERMA of THEMIS. The photonic kerma factors have been calculated with the module GROUPG of THEMIS, starting from the DLC-99 (HUGO) data library of gamma interactions

187

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

188

Air quality trends and potential health effects - Development of an aggregate risk index  

Science.gov (United States)

The "Provence Alpes Côte d'Azur" (PACA) region, in the South East of France, is one of Europe's regions most influenced by the atmospheric pollution. During the last 15 years, the industrial emissions decrease caused an evolution of the atmospheric pollution nature. Nowadays, atmospheric pollution is more and more influenced by the road traffic, the dominating pollution source in urban zones for the PACA region. Combined with this intense road traffic, the strong hot season of the Mediterranean climate contributes to the region bad air quality; it is known to be one of the worse in Europe. The recognized air pollution effects over public health include increased risk of hospital admissions and mortality by respiratory or cardiovascular diseases. The combination of these serious pollution related health hazards with senior and children vulnerabilities leads to serious sanitary concerns. Over the 1990-2005 period, we obtained, using the non-parametric Mann-Kendall test from annual mortality dataset (CépiDC), decreasing trends for Asthma (-5.00% year -1), Cardiovascular (-0.73% year -1), Ischemic (-0.69% year -1) and cerebrovascular diseases (-3.10% year -1). However, for "Other heart diseases" (+0.10% year -1) and "Respiratory" (+0.10% year -1) an increase was observed. The development of an adequate tool to understand impacts of pollution levels is of utmost importance. Different pollutants have different health endpoints, information may be lost through the use of a single index consequently, in this study we present the modified formula of air quality index, based on Cairncross's concept the Aggregate Risk Index (ARI). ARI is based on the relative risk of the well-established increased daily mortality, or morbidity, enabling an assessment of additive effects of short-term exposure to the main air pollutants: PM 2.5, PM 10, SO 2, O 3 and NO 2 in order to account for the reality of the multiple exposures impacts of chemical agents. The ARI, developed per pathology, takes into account the possible adverse effects associated with the coexistence of all pollutants. This index will enable to communicate the health risks associated, from modelled or monitored pollutant concentrations, to the general population. The second step will consist in the construction of a prediction model of this sanitary index.

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

2011-02-01

189

Indexed  

CERN Document Server

Jessica Hagy is a different kind of thinker. She has an astonishing talent for visualizing relationships, capturing in pictures what is difficult for most of us to express in words. At indexed.blogspot.com, she posts charts, graphs, and Venn diagrams drawn on index cards that reveal in a simple and intuitive way the large and small truths of modern life. Praised throughout the blogosphere as “brilliant,” “incredibly creative,” and “comic genius,” Jessica turns her incisive, deadpan sense of humor on everything from office politics to relationships to religion. With new material along with some of Jessica’s greatest hits, this utterly unique book will thrill readers who demand humor that makes them both laugh and think.

Hagy, Jessica

2008-01-01

190

Air etalon facilitated simultaneous measurement of group refractive index and thickness using spectral interferometry.  

Science.gov (United States)

A simple method based on air etalons of a transparent cavity is proposed to simultaneously measure the group refractive index and thickness of a transparent optical plate by spectral domain low coherence interferometry. In this method, only a single beam path is needed in contrast to the two beam paths, the reference and sample arms, of the conventional Michelson interferometer. An empty cavity is first constructed in the beam path by two glass plates. Then the transparent plate under test is inserted into the cavity, so that two air gaps are formed in the cavity. A beam of light of low coherence length is then transmitted through the cavity in the normal direction. Measurements of the reflected waves by the air gaps before and after the sample plate is put into the cavity allow us to determine the group refractive index (ng) and thickness (d) of the sample simultaneously. The relative precision of the results for d and ng are both approximately 7×10-4. PMID:25402915

Zhang, Ke; Tao, Li; Cheng, Wenkai; Liu, Jianhua; Chen, Zhongping

2014-11-01

191

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

192

Compressed Air Energy Storage System Control and Performance Assessment Using Energy Harvested Index  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper a new concept for control and performance assessment of compressed air energy storage (CAES systems in a hybrid energy system is introduced. The proposed criterion, based on the concept of energy harvest index (HEI, measures the capability of a storage system to capture renewable energy. The overall efficiency of the CAES system and optimum control and design from the technical and economic point of view is presented. A possible application of this idea is an isolated community with significant wind energy resource. A case study reveals the usefulness of the proposed criterion in design, control and implementation of a small CAES system in a hybrid power system (HPM for an isolated community. Energy harvested index and its effectiveness in increasing the wind penetration rate in the total energy production is discussed.

Hanif SedighNejad

2014-01-01

193

Estimation of the refractive index structure characteristic of air from coherent Doppler wind lidar data.  

Science.gov (United States)

A technique is proposed for estimating the refractive index structure characteristic of air from data of a coherent Doppler wind lidar. The proposed technique is tested in atmospheric experiments. Time profiles of the structure characteristic in the atmospheric surface layer are obtained and compared with the time profiles of the dissipation rate of the kinetic energy of turbulence obtained from the same lidar data. It is shown in this way that coherent lidars can be used for investigating not only wind turbulence, but also temperature turbulence. PMID:25078167

Banakh, V A; Smalikho, I N; Rahm, S

2014-08-01

194

Competency Index for Air Conditioning and Refrigeration Programs in Missouri. A Crosswalk of Selected Instructional Materials against Missouri's Competency Profile.  

Science.gov (United States)

This index was developed to help air conditioning and refrigeration instructors in Missouri use existing instructional materials and keep track of student progress on the VAMS system. The list was compiled by a committee of instructors who selected appropriate references and identified areas that pertained to Missouri competencies. The index lists…

Missouri Univ., Columbia. Instructional Materials Lab.

195

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

196

Feed-Forward Artificial Neural Network Model for Air Pollutant Index Prediction in the Southern Region of Peninsular Malaysia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper describes the application of principal component analysis (PCA) and artificial neural network (ANN) to predict the air pollutant index (API) within the seven selected Malaysian air monitoring stations in the southern region of Peninsular Malaysia based on seven years database (2005-2011). Feed-forward ANN was used as a prediction method. The feed-forward ANN analysis demonstr...

Azman Azid; Hafizan Juahir; Mohd Talib Latif; Sharifuddin Mohd. Zain,; Mohamad Romizan Osman

2013-01-01

197

Air Combat Training: Good Stick Index Validation. Final Report for Period 3 April 1978-1 April 1979.  

Science.gov (United States)

A study was conducted to investigate and statistically validate a performance measuring system (the Good Stick Index) in the Tactical Air Command Combat Engagement Simulator I (TAC ACES I) Air Combat Maneuvering (ACM) training program. The study utilized a twelve-week sample of eighty-nine student pilots to statistically validate the Good Stick…

Moore, Samuel B.; And Others

198

Evaluation and file making of PKA, KERMA and DPA data  

International Nuclear Information System (INIS)

The formulas to calculate PKA spectrum, KERMA factor and DPA cross section are summarized as well as modeling effect on PKA spectrum. Enhancement of the higher energy neutron emission due to pre-equilibrium process hardens the spectrum of PKA recoiled by neutron but inversely the anisotropy of secondary neutron makes it softer. As a whole, pre-equilibrium process affects on softening the PKA spectrum and increases by a few ten percent DPA cross section due to inelastic scattering. For (n, 2n) reaction, significance of two particle emission is shown in case of the iron PKA spectrum. A scope of PKA and KERMA related data file is also presented. (author)

199

Fundamental relationships between linear energy transfer, absorbed dose, kerma, and exposure. Application to changes of mediums  

International Nuclear Information System (INIS)

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)

200

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

 
 
 
 
201

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.

202

Energy measurement and analysis for the filtered X ray reference radiation of low kerma series and narrow spectrum series  

International Nuclear Information System (INIS)

A HPGe spectrometer was used to measure the established filtered X ray reference radiation of low kerma series and narrow spectrum series. A monte carlo model of measurement system was developed with the responses matrix for 6 keV - 305 keV simulated by energy interval of 1 keV and the fluence spectra was calculated by unfolding method. To verify the measuring and unfolding method, the mean energy, the first second half-value layers and the energy resolution of the spectra were calculated from the fluence spectra and compared with the values given in GB/T 12162, the deviation was about less than 5%. The conversion coefficients from the air kerma to the ICRU operational quantities Hp(10), Hp (0.07), and H* (10) were calculated using monoenergetic conversion coefficients at zero angle of incidence, which agreed well with the values given in GB/T 12162. (authors)

203

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 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

204

Air cavity-based Fabry-Perot interferometer sensor fabricated using a sawing technique for refractive index measurement  

Science.gov (United States)

We have demonstrated a refractive index sensor based on a fiber optic Fabry-Perot (FP) interferometer with an open air cavity fabricated using a one-step mechanical sawing technique. The sensor head consists of a short FP cavity near the fiber patch cord tip, which was assembled by joining a ceramic ferrule and a single-mode fiber together. Owing to the open air cavity in the sensor head, various liquid samples with different refractive index can fill in-line air cavity, which makes the device usable as a refractometer. Moreover, due to the sensor head encircled with the robust ceramic ferrule, the device is attractive for sensing measurement in harsh environments. The sensor was tested in different refractive index solutions. The experimental result shows that the attenuation peak wavelength of the sensor is shifted toward a shorter wavelength with increasing refractive index, and the refractive index sensitivity is ˜92.5 nm/refractive index unit (RIU) and 73.75 dB/RIU. The proposed sensor can be used as an in-line refractometer for many potential applications in the sensing field.

Jung, Eun Joo; Lee, Woo-Jin; Kim, Myoung Jin; Hwang, Sung Hwan; Rho, Byung Sup

2014-01-01

205

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

206

Exploring EKC, trends of growth patterns and air pollutants concentration level in Malaysia: A Nemerow Index Approach  

Science.gov (United States)

The present study examines an Environmental Kuznets Curve (EKC) hypothesis by analyzing annual data of air pollutants concentartion and per capita GDP as economic indicator over the (1996-2010) period in Malaysia. Nemerow Index Approach (I) used to generate a measures of air pollution. The results show that ambient air quality indicators supports the EKC hypothesis which stated that pollution levels increase as a country develops, but begin to decrease as rising incomes pass beyond a turning poin. Also, the I result is justifying that most pollutants are showing value less than 1.

Bekhet, Hussain A.; >Tahira Yasmin,

2013-06-01

207

Exploring EKC, trends of growth patterns and air pollutants concentration level in Malaysia: A Nemerow Index Approach  

International Nuclear Information System (INIS)

The present study examines an Environmental Kuznets Curve (EKC) hypothesis by analyzing annual data of air pollutants concentartion and per capita GDP as economic indicator over the (1996–2010) period in Malaysia. Nemerow Index Approach (I) used to generate a measures of air pollution. The results show that ambient air quality indicators supports the EKC hypothesis which stated that pollution levels increase as a country develops, but begin to decrease as rising incomes pass beyond a turning poin. Also, the I result is justifying that most pollutants are showing value less than 1.

208

Crustal Strain Observation Using a Two-Color Interferometer with Accurate Correction of Refractive Index of Air  

Directory of Open Access Journals (Sweden)

Full Text Available A highly accurate two-color interferometer with automatic correction of the refractive index of air was developed for crustal strain observation. The two-color interferometer, which can measure a geometrical distance of approximately 70 m, with a relative resolution of 2 × 10?9, clearly detected a change in strain due to earth tides in spite of optical measurement in air. Moreover, a large strain quake due to an earthquake could be observed without disturbing the measurement. We demonstrated the advantages of the two-color interferometer in air for geodetic observation.

Souichi Telada

2014-07-01

209

Instructor's Index to U.S. Navy and Air Force Materials for Teaching Basic Electricity. Final Report, No. 29.  

Science.gov (United States)

The purpose of this index is to identify U.S. Navy and U.S. Air Force transparencies, films, and manuals which can be used by schools and colleges to teach basic electricity. Materials are classified according to 39 major categories including Electron Theory, Batteries and Battery Connections, D.C. Series Circuits, Network Theorems,…

Stoller, Alan

210

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

211

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

212

Time-resolved 3D visualization of air injection in a liquid-saturated refractive-index-matched porous medium  

Science.gov (United States)

The main goal of this work is to implement and validate a visualization method with a given temporal/spatial resolution to obtain the dynamic three-dimensional (3D) structure of an air plume injected into a deformable liquid-saturated porous medium. The air plume develops via continuous air injection through an orifice at the bottom of a loose packing of crushed silica grains. The packing is saturated by a glycerin-water solution having the same refractive index and placed in a rectangular glass container. By using high-speed image acquisition through laser scanning, the dynamic air plume is recorded by sequential tomographic imaging. Due to the overlap between adjacent laser sheets and the light reflection, air bubbles are multiply exposed in the imaging along the scanning direction. Four image processing methods are presented for the removal of these redundant pixels arising from multiple exposure. The respective results are discussed by comparing the reconstructed air plume volume with the injected one and by evaluating the morphological consistency of the obtained air plume. After processing, a 3D dynamic air flow pattern can be obtained, allowing a quantitative analysis of the air flow dynamics on pore-scale. In the present experimental configuration, the temporal resolution is 0.1 s and the spatial resolution is 0.17 mm in plane and about 1 mm out of plane of the laser sheet.

Kong, Xiang-Zhao; Holzner, Markus; Stauffer, Fritz; Kinzelbach, Wolfgang

2011-06-01

213

Calibration of kerma-area product meters with a patient dose calibrator  

International Nuclear Information System (INIS)

Full text: Kerma-area product (KAP) meters are used for monitoring patient exposure during x-ray imaging. These field meters are used attached to clinical x-ray system and their calibration should be performed in the same position. Internationally uncertainty < 7% (confidence level 95%) is recommended for KAP measurements. The use of a proper calibration method is important to achieve appropriate measurement accuracy and comparable results. IAEA introduces three options for calibrations of field KAP meters: (1) calibration of the field KAP meter in laboratory (2) field calibration with a air kerma meter as a reference meter (3) field calibration with a KAP meter as a reference meter. In this study the use of novel large patient dose calibrator (PDC) meter as a reference KAP meter is studied. Comparison to the other calibration methods and to use of a conventional type of KAP meter as a reference instrument is made. The use of reference KAP meter was introduced by Toroi et al. as a tandem calibration method. The main drawback to the method is the uncertainty produced by pronounced energy dependence of the response of conventional type of KAP meters. PDC meter type has studied to have lower energy dependence and decreased uncertainty in tandem method is expected when using this type of KAP meter as a reference instrument. Calibrations of reference meters are made at the secondary standard laboratory of STUK with IEC standard radiation qualities. They are recommended andiation qualities. They are recommended and widely used for calibrations of dosimeters in x-ray imaging. As these radiation qualities do not cover the whole range of clinically used radiation qualities, interpolations, and in some cases also extrapolations, of calibration coefficient is needed. In this study the effect of interpolation from standard to clinical radiation qualities on measurement uncertainty is under specific interest. The calibration of PDC meter in SSDL laboratory is also performed with different field sizes and positions. Uniformity of the response is studied and the effects on field calibrations and uncertainties are valuated. Calibrated reference meters are used for calibrations of field KAP meters in clinical x-ray equipments. Special attention will be made on the achieved accuracy. One of the advantage of the tandem calibration method is that the reference KAP value is measured in the same way as the field KAP meter is measuring it (as a surface integral of air kerma). If the reference value is based on air kerma measured in the centre of the x-ray field, the method itself may have some field size dependence. The field size dependence of the methods was studied by Toroi et al. but the comparison was limited by the small size of reference KAP meter. In this study the field size dependence study was extended to larger field sizes. As a conclusion specific uncertainty budget is given for the field KAP meter calibration made with a PDC meter as a reference meter

214

Ordinal time series analysis for Air Quality Index (AQI) in San Bernardino County  

Science.gov (United States)

Ambient pollutant, especially ground level ozone that causes respiratory diseases, has been a great concern in Southern California. U.S. Environmental Protection Agency provides the Air Quality Index (AQI) as a tool to assist the public of health warnings. AQI for ozone is currently divided into six states depending on the level of public health concern. In statistical point of view AQI can be characterized as nonstationary ordinal-valued time series. The purpose of this study is to implement statistical models for short-term forecasting of AQI. This thesis presents a generalized linear type modeling to handle the autocorrelated ordinal time series. The model is applied with four different link functions: identity, logit, probit, and complementary log-log and their forecast performance are compared. Random time-varying covariates include past AQI state, various meteorological processes, and periodic component. Data used in this study are AQI for ozone from five monitoring stations in San Bernardino County, CA for 2004 to 2006. For the purpose of evaluating the performance of one-day-ahead forecast, the 2007 data from the same place are used. The meteorological data are from the nearby Barstow city in San Bernardino County. The portmanteau test is used to test error autocorrelations. The partial likelihood ratio test, Akaike information criterion (AIC), and Bayesian information criterion (BIC) are used to measure the goodness of fit and compare the models. The results show the model well captures the nonstationarity in ozone process and remove the nonstationarity in residuals. Both logit and probit models correctly forecast about 85% of the observed AQI.

Chitakasempornkul, Kessinee

215

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

216

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)

217

A Satellite-Based Multi-Pollutant Index of Global Air Quality  

Science.gov (United States)

Air pollution is a major health hazard that is responsible formillions of annual excess deaths worldwide. Simpleindicators are useful for comparative studies and to asses strends over time. The development of global indicators hasbeen impeded by the lack of ground-based observations in vast regions of the world. Recognition is growing of the need for amultipollutant approach to air quality to better represent human exposure. Here we introduce the prospect of amultipollutant air quality indicator based on observations from satellite remote sensing.

Cooper, Mathew J.; Martin, Randall V.; vanDonkelaar, Aaron; Lamsal, Lok; Brauer, Michael; Brook, Jeffrey R.

2012-01-01

218

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

219

MACK, Fluence to Kerma Generator from ENDF/B  

International Nuclear Information System (INIS)

ution 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

220

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

Energy Technology Data Exchange (ETDEWEB)

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 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.

NONE

2005-05-15

 
 
 
 
221

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

222

Assessment of skin entrance kerma in the United States: the Nationwide Evaluation of X Ray Trends (NEXT)  

Energy Technology Data Exchange (ETDEWEB)

The Nationwide Evaluation of X ray Trends (NEXT) is an annual survey programme to estimate national skin entrance air kerma, free-in-air, for representative diagnostic X ray examinations, conducted in the United States between the federal government's Food and Drug Administration (FDA) and various state and local governments through the coordinating agency, the conference of Radiation Control Program Directors (CRCPD). NEXT began in 1973 and in 1983 underwent a major change; limiting the annual survey to one examination, using standard attenuation phantoms for the measurement of exposure, empirically evaluating film processing, and the collection of comprehensive technical data such as tube potential, half-value layer (HVL), type of film, screen, grid, and optical density of the resulting phantom radiograph. Surveys have been performed for chest radiography (1984 and 1986), abdomen and lumbosacral spine (1987 and 1989), mammography (1985 and 1988), computerised tomography (CT) (1990), and fluoroscopy (1991). (author).

Rueter, F.G.; Conway, B.J.; McCrohan, J.L.; Slayton, R.J.; Suleiman, O.H. (Food and Drug Administration, Rockville, MD (United States))

1992-01-01

223

Partial kerma factor data for nitrogen and oxygen for fast neutrons  

International Nuclear Information System (INIS)

The kerma for fast neutrons consists of partial kerma contributions from events such as (n,n), (n,n'), (n,p), (n,alpha) and other (n, charged particle) reactions. Improved fast neutron partial kerma values for (n,p) and (m,alpha) events for nitrogen and oxygen are evaluated using the available data on the break up of (n,p) and (n, alpha) cross sections corresponding to the ground and the various excited states of the residual nucleus in each of these two reactions. (author)

224

Lichen sensitivity to the air pollution and index of poleotolerance (I. P. )  

Energy Technology Data Exchange (ETDEWEB)

The influence of air pollution on the presence of lichens in the urban environment in Russia investigated. The basis for these studies concerns the reaction of each individual species to the polluted environment as well as the associated regularities of different species.

Trass, H.

1973-01-01

225

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

Science.gov (United States)

...Relate to Air Pollution Levels? For each pollutant, the AQI transforms ambient concentrations to a scale from 0 to 500. The AQI...U.S. Environmental Protection Agency, research Triangle Park, NC. EPA-454/B-02-002, November 2002) can...

2010-07-01

226

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

227

Applicability of the Environmental Relative Moldiness Index for Quantification of Residential Mold Contamination in an Air Pollution Health Effects Study  

Science.gov (United States)

The Near-Road Exposures and Effects of Urban Air Pollutants Study (NEXUS) investigated the impact of exposure to traffic-related air pollution on the respiratory health of asthmatic children in Detroit, Michigan. Since indoor mold exposure may also contribute to asthma, floor dust samples were collected in participants homes (n = 112) to assess mold contamination using the Environmental Relative Moldiness Index (ERMI). The repeatability of the ERMI over time, as well as ERMI differences between rooms and dust collection methods, was evaluated for insights into the application of the ERMI metric. ERMI values for the standard settled floor dust samples had a mean ± standard deviation of 14.5 ± 7.9, indicating high levels of mold contamination. ERMI values for samples collected from the same home 1 to 7 months apart (n = 52) were consistent and without systematic bias. ERMI values for separate bedroom and living room samples were highly correlated (r = 0.69, n = 66). Vacuum bag dust ERMI values were lower than for floor dust but correlated (r = 0.58, n = 28). These results support the use of the ERMI to evaluate residential mold exposure as a confounder in air pollution health effects studies.

Kamal, Ali; Vesper, Stephen; Batterman, Stuart; Godwin, Christopher; Chavez-Camarena, Marina; Norris, Gary

2014-01-01

228

Experimental determination of kerma factors at E/sub n/ approx. = 15 MeV  

Energy Technology Data Exchange (ETDEWEB)

Experimental values for the kerma per unit fluence at the neutron energy, E/sub n/ = 15 MeV, have been determined for graphite, Mg, and Fe. Ion chambers of small size with walls of these materials were employed, and were filled with a variety of gases--N/sub 2/, CO/sub 2/, Ne, Ar, Kr, and Xe. A calibrated neutron source was employed, allowing a straightforward determination of the kerma per unit fluence.

Goldberg, E.; Slaughter, D.R.; Howell, R.H.

1978-04-05

229

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)

230

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

Science.gov (United States)

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. PMID:6888353

Awschalom, M; Rosenberg, I; Mravca, A

1983-01-01

231

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

232

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

Energy Technology Data Exchange (ETDEWEB)

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.

Awschalom, M.; Rosenberg, I.; Mravca, A.

1983-07-01

233

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

234

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.

235

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

236

174 Reduction in Allergic Rhinitis Index by Decreasing Aero-Allergens and Malodor Causing Volatile Organic Compounds by Luna Air Purifiers Using Photo-Catalytic Oxidation (PCO) Technology  

Science.gov (United States)

Background The quality of the environment within buildings is a topic of major importance for public health. Breathing pure and clean air allows us to think more clearly, sleep more soundly, and stay healthier. Studies show that we receive 56% of our energy from the air we breathe, more than from water and food combined. On average we breathe 37 pounds of air a day. It has been established that the use of negative ions in a purification system is an effective means of eradicating aeroallergens in room air. Methods The wall-mount, Inducts and Mobile Sanifier air purification units of Luna are designed to sanitize air, to kill surface mold, bacteria, and viruses in areas up to 26,000 cubic feet. Samples were collected from the clinic rooms to analyze the VOC concentrations using the Luna air purifiers to detect the efficiency in reducing the VOCs in the indoor air. We analyzed the aroallergens and VOCs prevalent in the indoor air in the clinics at the Coulter Animal Hospital, Amarillo, Texas. The data were correlated to the inhalant allergy index before and after running air purifiers that use PCO technology. Results Samples from the clinic rooms to analyze the VOC concentrations using the Luna air purifiers to detect the efficiency in reducing the VOCs in the indoor air. The SKC Pocket Pump and thermal desorption tubes were used to obtain the samples from the indoor air. Pumps were set on 200 mL/min as air flow to estimate the concentration of Acetic acid, Isobutyric acid, Butyric acid, Isovaleric acid, Valeric acid, Hexanoic acid, Phenol, p-cresol, 4-ethyl, 2-amino, Indole, and Skatole. All desorption tube samples were analyzed using a Markes UNITY and Markes Ultra automated thermal desorber (ATD) and a Varian 3800/Saturn 2000 GC with a MS. Slides with double sticky tape were exposed to room air stained with 2% safranin and were observed using a BX-40 Olympus microscope with DP-70 and Image Pro Plus software. Conclusions The data were correlated with the aeroallergen index and the frequency of inhalant allergy cases that showed reduction in allergic rhinitis index on using air purifiers.

Ghosh, Nabarun; Aguaiza, Cristina; Guzman, Alicia; Chudasama, Jay; Bennert, Jeff; Das, A. B.

2012-01-01

237

Neutron kerma factors for magnesium and aluminium measured with low-pressure proportional counters  

International Nuclear Information System (INIS)

Low-pressure proportional counters enable the simultaneous determination of neutron absorbed dose in the detector wall material and of ionisation yield spectra. In well defined neutron fields the kerma to fluence ratio (kerma factor) can be evaluated from the absorbed dose results. To date this type of investigation has been performed mainly with the compound tissue-equivalent material A-150 plastic. The determination of elemental kerma factors with the proportional counter method is applicable to those materials which enable the construction of electrically conductive chamber walls. In the present investigation, kerma factor measurements with aluminium- and magnesium-walled proportional counters were performed at neutron energies of 13.9, 15.0, 17.0 and 19.0 MeV. The gas-to-wall absorbed dose conversion factors were assessed making use of the measured ionisation yield spectra. Up to 17 MeV neutron energy the measured kerma factors are in good agreement with values calculated by Caswell et al and Dimbylow. At 19.0 MeV the measured results are significantly higher than those of Caswell et al but are in good agreement with those of Dimbylow. (author)

238

Atomic data required in accurate measurements of kerma for neutrons with low pressure proportional counters  

International Nuclear Information System (INIS)

The accuracy achievable in neutron dosimetry for radiation therapy critically depends on the knowledge of the kerma factors for the tissue components and the detector materials. Gas filled cavity chambers allow to achieve relatively accurate measurements of kerma for the chamber wall material. Ionisation chambers and proportional counters measure with high precision the charge from ionisation produced in the gas by the charged particles released in neutron interactions with the wall and with the gas. However, the overall uncertainty of the kerma measurement depends on the quality of the basic physical data required in the application of the cavity chamber principles, in particular, W-values, stopping powers and stopping power ratios for the charged particles released and their energy dependence. The paper summarizes the experience gained in evaluating atomic data to be used in cavity chamber principles for neutron kerma measurements with tissue-equivalent and non hydrogenous proportional counters. Proportional counters with walls made of A-150 TE plastic, graphite, Al, Mg, Fe, Zr and ZrO have been used to measure neutron kerma factors by several groups. Different mixtures such as methane based TE gas, propane based TE gas or CO2 were used as counting gases. It is shown that the spectral information provided by the proportional counters can be used to assess quantities such as the gas-to-wall absorbed dose conversion factor. An attempt is made to assess the factor. An attempt is made to assess the uncertainties in kerma measurements due to the uncertainties of basic atomic data. (author). 40 refs, 12 figs, 5 tabs

239

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

240

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

 
 
 
 
241

A radiation exposure index for CT  

International Nuclear Information System (INIS)

The purpose of this study is to define an Exposure Index for CT (EICT) and to estimate the magnitude of the EICT 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 (EICT) is defined as the average Air Kerma that would be incident on an extended 360 deg. detector array completely surrounding the patient. For an axial scan of a uniform cylindrical phantom, EICT can be approximated as T x [(CTDIair)/4] x [?deg./360 deg.] where T is the fractional transmission through the cylinder, CTDIair 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 CTDIair can be estimated from the weighted CTDI (CTDIw) 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 CTDIair/CTDIw were 1.42±0.12 in 16-cm dosimetry phantom and 2.82±0.37 in 32-cm phantom. Values of b ranged from 30.18 (R = 61 cm and r =8 cm) to 85.38 (R = 55 cm and r=20 cm). For an adult head CT examination, EICT was estimated to be?70 ?Gy at a CTDIvol of 75 mGy (16 cm), and for an adult abdominal CT examination, EICT was estimated to be?11 ?Gy at a CTDIvol of 25 mGy (32 cm). For an abdomen CT examination in a 5-y-old child, EICT was estimated to be ?21 ?Gy at a CTDIvol of 20 mGy (16 cm). The EICT 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 EICT 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. (authors)

242

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

243

Status and evaluation methods of JENDL fusion file and JENDL PKA/KERMA file  

International Nuclear Information System (INIS)

The status of evaluated nuclear data in the JENDL fusion file and PKA/KERMA file is presented. The JENDL fusion file was prepared in order to improve the quality of the JENDL-3.1 data especially on the double-differential cross sections (DDXs) of secondary neutrons and gamma-ray production cross sections, and to provide DDXs of secondary charged particles (p, d, t, 3He and ?-particle) for the calculation of PKA and KERMA factors. The JENDL fusion file contains evaluated data of 26 elements ranging from Li to Bi. The data in JENDL fusion file reproduce the measured data on neutron and charged-particle DDXs and also on gamma-ray production cross sections. Recoil spectra in PKA/KERMA file were calculated from secondary neutron and charged-particle DDXs contained in the fusion file with two-body reaction kinematics. The data in the JENDL fusion file and PKA/KERMA file were compiled in ENDF-6 format with an MF=6 option to store the DDX data. (orig.)

244

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)

245

Calculations of Kerma Due to Fast Neutrons in Tissue-Like Materials  

International Nuclear Information System (INIS)

Dosimetry of neutrons in the presence of gamma radiation is frequently carried out by comparing measurements with various ionization chambers having similar gamma response but a greatly different neutron response. To achieve accuracy, reliable data for the conversion of neutron fluence to kerma is needed. Calculations of kerma due to elastic scattering processes of fast neutrons in tissue have been published in the NCRP report 1961 (NBS Handbook 75). These calculations were based on the assumption of isotropic scattering of neutrons. In the ICRU report 10e, 1962-(NBS Handbook 88) calculations by one of us (FSW) included considerations of non-isotropic scattering to the extent permitted by the available data. Recently, revisions of elastic scattering cross-section data and much more extensive angular distribution data have become available and it is thus possible to revise the previous calculations and make a more accurate statement. The kerma for unit fluence of neutrons in the energy range 0.1 to 10.0 M e V for pure hydrogen, carbon, nitrogen, and oxygen is presented. Compared with the data in the ICRU report, the data for hydrogen are unchanged. Below 3-MeV neutron energy , the data for C, N, and O are basically similar with changes only in the fine structure. At about 8 MeV the average kerma in each case becomes less than previously calculated by a factor of approx. 0.3 for N, 0.7 for O, and 0.6 for C. This information has been transferred to computer data cards sobeen transferred to computer data cards so that the effect of any type of neutron spectrum or any tissue-like material can be rapidly calculated. Curves of kerma versus neutron energy are presented for tissues of the composition of the 1CRP ''standard man'', water, and bone. The data for standard man are similar to those presented previously, up to 3-MeV neutron energy, and at higher energies they gradually diverge to a factor of 0.94 at 8 MeV. Curves of kerma versus neutron energy are also given, together with ratios of these values of kerma to those in standard man, for the materials commonly encountered in dosimetry, namely: acetylene, ethylene, tissue-equivalent gas (Rossi), tissue-equivalent plastic (Rossi), carbon dioxide, and argon. (author)

246

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

247

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

248

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 S.

2012-04-01

249

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.

250

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

International Nuclear Information System (INIS)

ications 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

251

Importance of the neutrons kerma coefficient in the planning of Brachytherapy treatments with Cf-252 sources  

International Nuclear Information System (INIS)

t the average value of the neutrons kerma coefficient for the 4 wicked tumors is from 6% to 7% smaller that the average value for the soft tissue in the interval energy of interest for therapy with fast neutrons with En > 1 MeV. These results have a special importance during the planning process of brachytherapy treatments with sources of 252Cf, to optimize and to individualize the patients treatments. (Author)

252

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

Energy Technology Data Exchange (ETDEWEB)

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/sup -5/ to 20. MeV for the composite materials and from 1.30 x 10/sup -9/ to 20. MeV for the isotopes and elements.

Howerton, R.J.

1986-01-01

253

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

254

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

International Nuclear Information System (INIS)

The effective atomic number, Zeff, the effective electron density, Nel, 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 Zeff and Nel is due to the variations in the dominance of different interaction processes in different energy regions. The maximum values of Zeff and Nel are found in the low-energy range, where photoelectric absorption is the main interaction process. The minimum values of Zeff and Nel are found at intermediate energies, typically 0.05 MeV eff is equal to the mean atomic number of the bio-molecule. Wherever possible, the calculations are compared with experimental results. A comparison is also made with the single values of the Zeff and Nel provided by the program XMuDat. It is also observed that carbohydrates have a larger 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. (note)

255

Kerma coefficients for neutron scattering on 12C and 16O at 96 MeV  

International Nuclear Information System (INIS)

Recently, many new applications of fast neutrons are emerging or under development, like dose effects due to cosmic ray neutrons for airplane crew, fast neutron cancer therapy, studies of electronics failure induced by cosmic ray neutrons and accelerator-driven incineration of nuclear waste and energy production technologies. In radiation treatment, the kerma (Kinetic energy release in matter) coefficient, which describes the average energy transferred from neutrons to charged particles, is widely used. The kerma coefficient can be calculated from microscopic nuclear data. Nuclear data above 20 MeV are rather scarce, and more complete nuclear data libraries are needed in order to improve the understanding of the processes occurring on a cellular level. About half the dose in human tissue due to fast neutrons comes from proton recoils in neutron-proton (np) scattering, 10-15% from nuclear recoils due to elastic and inelastic neutron scattering and the remaining 35-40% from neutron-induced emission of light ions. Experimental data on elastic and inelastic neutron scattering at 96 MeV from 12C and 16O have been obtained recently at The Svedberg Laboratory in Uppsala (Sweden)). These data are shown to be relevant for the determination of nuclear recoil kerma coefficients from elastic and inelastic neutron scattering at intermediate energies. (authors)

256

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.

Gerward, Leif

2008-01-01

257

Particulate Matter Concentrations and the Air Quality Index in the Central Part of Tehran City, Tehran, Iran  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background and Aim: The association between particulate matter (PM) and cardiovascular diseases (CVD) was shown in the mid-1990 through several epidemiological studies. Increased hospital admissions of patients with cardiovascular and respiratory problems in days when, due to high concentrations of PM, air pollution is high, bears witness to this. In this study we measured concentrations of the PM fractions in the air in the central part of Tehran city, Tehran, Iran Methods and Materials: The...

Mesdaghinia, A. R.; Yunesian, M.; Nabizadeh, R.; Nadafi, K.; Leili, M.; Sh. Nazmara

2009-01-01

258

QSPR study on the octanol/air partition coefficient of polybrominated diphenyl ethers by using molecular distance-edge vector index  

Science.gov (United States)

Background The quantitative structure property relationship (QSPR) for octanol/air partition coefficient (KOA) of polybrominated diphenyl ethers (PBDEs) was investigated. Molecular distance-edge vector (MDEV) index was used as the structural descriptor of PBDEs. The quantitative relationship between the MDEV index and the lgKOA of PBDEs was modeled by multivariate linear regression (MLR) and artificial neural network (ANN) respectively. Leave one out cross validation and external validation was carried out to assess the predictive ability of the developed models. The investigated 22 PBDEs were randomly split into two groups: Group I, which comprises 16 PBDEs, and Group II, which comprises 6 PBDEs. Results The MLR model and the ANN model for predicting the KOA of PBDEs were established. For the MLR model, the prediction root mean square relative error (RMSRE) of leave one out cross validation and external validation is 2.82 and 2.95, respectively. For the L-ANN model, the prediction RMSRE of leave one out cross validation and external validation is 2.55 and 2.69, respectively. Conclusion The developed MLR and ANN model are practicable and easy-to-use for predicting the KOA of PBDEs. The MDEV index of PBDEs is shown to be quantitatively related to the KOA of PBDEs. MLR and ANN are both practicable for modeling the quantitative relationship between the MDEV index and the KOA of PBDEs. The prediction accuracy of the ANN model is slightly higher than that of the MLR model. The obtained ANN model shoud be a more promising model for studying the octanol/air partition behavior of PBDEs. PMID:24959199

2014-01-01

259

Air temperature thresholds to evaluate snow melting at the surface of Alpine glaciers by T-index models: the case study of Forni Glacier (Italy)  

Science.gov (United States)

The glacier melt conditions (i.e.: null surface temperature and positive energy budget) can be assessed by analyzing meteorological and energy data acquired by a supraglacial Automatic Weather Station (AWS). In the case this latter is not present the assessment of actual melting conditions and the evaluation of the melt amount is 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 273.15 K. In this paper, to detect the most indicative threshold witnessing melt conditions in the April-June period, we have analyzed air temperature data recorded from 2006 to 2012 by a supraglacial AWS set up at 2631 m a.s.l. on the ablation tongue of the Forni Glacier (Italian Alps), and by a weather station located outside the studied glacier (at Bormio, a village at 1225 m a.s.l.). Moreover we have evaluated the glacier energy budget and the Snow Water Equivalent (SWE) values during this time-frame. Then the snow ablation amount was estimated both from the surface energy balance (from supraglacial AWS data) and from T-index method (from Bormio data, applying the mean tropospheric lapse rate and varying the air temperature threshold) and the results were compared. We found that the mean tropospheric lapse rate permits a good and reliable reconstruction of glacier air temperatures and the major uncertainty in the computation of snow melt is driven by the choice of an appropriate temperature threshold. From our study using a 5.0 K lower threshold value (with respect to the largely applied 273.15 K) permits the most reliable reconstruction of glacier melt.

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

2014-03-01

260

A design of brachytherapy source calibration template for air kerma rate/activity measurement  

International Nuclear Information System (INIS)

This simple template can be used for the purpose of calibration of brachytherapy source, if the department does not have the calibration-track stand. One can design this template in the hospital itself as per the requirement, availability and facility, and the expenses also will be less. It is fully made up of a very thin 0.75 mm thickness of paper cardboard and this is the speciality. Currently this template is being utilized for accurate and easy calibration purposes

 
 
 
 
261

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

262

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.

263

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

264

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)

265

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.)

266

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

267

Air  

Science.gov (United States)

... not clogged with snow or other things. Radon Radon is a cancer-causing, radioactive gas. It is natural and comes from the earth. ... natural breakdown of uranium in soil, rock, and water and gets into the air you breathe. Radon can be found all over the U.S. It ...

268

Obtención de un índice de riesgo de erosión eólica y su aplicación en la provincia de Buenos Aires, Argentina / Erosion risk index attainment and its application in the Buenos Aires province, Argentina  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish En este trabajo se propone un índice climático para estimar el riesgo de ocurrencia de erosión eólica basado en las leyes físicas que cuantifican el efecto de la agresión del medio (turbulencia atmosférica) sobre la resistencia del sistema (textura del suelo). Este indicador es obtenido en función d [...] e observaciones meteorológicas estándar a partir de un modelo que incluye la alteración del perfil vertical del viento ocasionada por la presencia de partículas de suelo en el aire y es expresado en términos de la probabilidad de que la potencia del viento supere las condiciones umbrales para el comienzo del proceso. Si bien el índice fue obtenido para suelo seco y desnudo, la metodología permite avanzar hacia un modelo de evaluación de riesgo más general, si se determinan previamente los valores de velocidad de fricción umbral que corresponden a distintas condiciones que afectan la resistencia del suelo tales como la humedad del suelo, el contenido de materia orgánica, cobertura y uso de la tierra. Este modelo ha sido utilizado para evaluar la distribución espacial del riesgo de erosión eólica en la Provincia de Buenos Aires, Argentina. Abstract in english This paper proposes a climatic index to estimate the wind erosion risk based upon physical laws that quantify the effect of environment's aggression (atmospheric turbulence) on system resistance (soil texture). This index is obtained as a function of standard meteorological observations including th [...] e alteration of the wind profile produced by the presence of soil particles in the air and it is expressed in terms of the probability for the wind power to exceed the threshold conditions. Although this index was obtained for dry and bare soil, it may mean an advance towards a more general model for risk evaluation if other factors intervening in soil resistance, such as soil humidity, organic material content, land cover and use are included. This model has been used to evaluate the spatial distribution of the wind erosion risk in Buenos Aires Province, Argentina.

Susana, Goldberg; Gabriel, Weiss.

2004-12-01

269

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

270

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

271

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

272

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

273

Measurement of the structure coefficient of refractive index fluctuations in a turbulent premixed butane-air flame by means of a laser-based interferometer technique  

Science.gov (United States)

With a view to measuring the structure coefficient of refractive index fluctuations in a turbulent premixed butane-air flame, a thin laser beam is sent into the flame perpendicular to the flow direction. The laser beam generally undergoes fluctuations of direction, phase, and amplitude. Only the random deflections of the laser beam may be taken into account. After having traversed the flame, the perturbed laser beam enters into an interferometric system. Materials and experimental procedure are described. In the unperturbed interference pattern, the zones only sensitive to fluctuations of the angle-of-arrival of the laser beam are detected. From the random displacements of the central bright fringe, the structure coefficient of refractive index fluctuations in the flame is measured. To prove that the method of measurement is satisfactory, the result obtained is applied for computing the power spectral density of the angle-of-arrival of the laser beam from the formula of correlations of the laser beam deflection angles which we have demonstrated in previous works. This computed power spectral density is compared to that measured from the effective position of the detector. A good agreement is observed between the two results.

Ngo Nyobe, Elisabeth; Pemha, Elkana; Hona, Jacques; Bilong, Jean; Lamara, Maurice

2014-08-01

274

A distributed air index based on maximum boundary rectangle over grid-cells for wireless non-flat spatial data broadcast.  

Science.gov (United States)

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. PMID:24940864

Im, Seokjin; Choi, JinTak

2014-01-01

275

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

276

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.

M Azizifar

2012-05-01

277

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

278

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

Science.gov (United States)

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.

Morin, J.; Arnoud, J. C.; David, J.; Zyromski, P.

1998-02-01

279

Development of the JENDL special purpose data file for PKA spectra, DPA cross sections and kerma factors  

International Nuclear Information System (INIS)

Method of calculation of the neutron-induced primary knock-on atom spectra, atom displacement cross sections and kerma factors is presented based on the nuclear data from the evaluated data file of ENDF/B-5 format, supplementing the emitted charged particle spectra from nuclear cross section calculation code. Approximate and compact formulas of DPA cross section and kerma factor were derived for the reaction sum involving multi-particle emissions. The formulas are valid for medium and heavy mass nuclei. Examples of calculation on iron are given for neutron energies up to 40 MeV. Comparison was made with the kerma factor calculated by Howerton and Caswell et al. below 20 MeV and the DPA cross section with RADHEAT-V4 and TENJIN-2 code below 15 MeV. It is shown that the high energy kerma factor is governed by the charged particle emission, while the high energy DPA cross section is mainly determined from neutron optical potential. (author)

280

Neutron spectra and neutron kerma derived from activation and fission detector measurements in a d + T neutron therapy beam  

International Nuclear Information System (INIS)

Neutron spectra at different positions in a phantom have been derived from activation foil and fission counter measurements for the collimated beam of the Amsterdam d + T fast-neutron therapy facility. The spectra show that the fraction of lower-energy neutrons increases with increasing depth in the phantom as well as with increasing distance from the central axis of the beam. Calculation of the ratios of kerma values in tissue and tissue-equivalent (TE) plastic and of Wsub(N) values for the spectra at five positions in the phantom, showed that the variations in these quantities are less than 0.5%. Kerma values have been derived from the neutron spectra and from the fission counter measurements separately. These neutron kerma values were compared with the neutron absorbed dose values derived from combined TE ionisation chamber and GM counter measurements. The dose values have been obtained applying recommendations given in the European protocol for neutron dosimetry for external beam therapy. At 50 mm and 100 mm depth along the central axis of the beam in the phantom, the agreement between the three methods was within 2%. In the penumbra region a maximum difference of about 7% has been observed between the three methods. The contribution from thermal neutrons to the total kerma is less than 1% in the beam as well as in the penumbra. (author)

 
 
 
 
281

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

282

Evaluation of skin entry kerma in radiological examinations at the Hospital de Clinicas, Parana, Brazil  

International Nuclear Information System (INIS)

This paper evaluates the skin entry dose of pediatric and adults patients when submitted to radiological examinations at the Hospital de Clinicas do Parana, Brazil, as part integrate of the data assessment of International Atomic Energy Agency (IAEA) for Latin America. It was performed measurements of dose for evaluation of skin entry kerma in pediatric patients in thorax AP/PA examinations, adults of thorax in AP/PA, cranio caudal mammography and median lateral and patients of computerized tomography in examination of head, thorax and abdomen. The obtained data demonstrate the necessity of verification of diagnostic analysis standards. The great value amplitudes demonstrate the incompatibility of examination executions with those recommended by the literature. The dose values presented partially inside the range recommended and the other over the expected for the due examination when compared with the literature

283

Process of PKA/KERMA file for FENDL from JENDL fusion file  

International Nuclear Information System (INIS)

The project of JENDL PKA/KERMA File is introduced as a file for radiation damage calculations in the incident neutron energy range below 50 MeV. The code ESPERANT using an effective single particle emission approximation (ESPEA) was developed for nucleus except light mass elements as a processing method from an evaluated nuclear data file. The code SCINFUL/DDX is used for light mass nuclides. As a trial task of ESPERANT usage, PKA file for the FENDL project in the energy range below 20 MeV was processed from the JENDL Fusion File. The processed PKA file was compared with results of Monte-Carlo calculation by MCEXCITON and calculated results from ENDF/B-IV. The results of three methods gave similar trends. It was concluded that the processing method with ESPEA was applicable to produce PKA File. (author)

284

Evaluation of Kerma rate in the skin entrance in interventional procedures guided by fluoroscopy  

International Nuclear Information System (INIS)

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

285

Spectral neutron fluence and tissue kerma in collimated neutron beams from Be + d  

International Nuclear Information System (INIS)

The neutron production of the Be - d reaction was studied for deuteron energies from 9.4 MeV to 13.3 MeV. Time-of-flight techniques and an NE 213 scintillator detector were used to determine the number, energy and angular distribution of the neutrons emitted from a thick Be target between 00 and 400 to the direction of the incident deuteron beam. By means of a Monte Carlo code the scattering of neutrons was calculated for different liner materials of a collimator. The influence of the neutron collimator on neutron fluence and standard tissue kerma at a distance of 80 cm from the Be target was evaluated

286

HUMAN USE INDEX (FUTURE)  

Science.gov (United States)

Human land uses may have major impacts on ecosystems, affecting biodiversity, habitat, air and water quality. The human use index (also known as U-index) is the percentage of human land use in an area, including agriculture, urban and suburban development, and mining. Low values ...

287

HUMAN USE INDEX  

Science.gov (United States)

Human land uses may have major impacts on ecosystems, affecting biodiversity, habitat, air and water quality. The human use index (also known as U-index) is the percentage of human land use in an area, including agriculture, urban and suburban development, and mining. Low values ...

288

Uncertainty of kerma factors in neutron dosimetry at Esub(n) = 14.5 MeV  

International Nuclear Information System (INIS)

Assuming that the dominant part of the uncertainty in the kerma ratio is due to the kerma factors of Carbon and Oxygen, it is concluded that the uncertainty in tissue-equivalent ion chamber or calorimeter measurements of absorbed dose in tissue results from calculation of the kerma factors alone before other component uncertainties are considered. In the case of carbon the following conclusions are made: 1) In the reaction 12C(n,n'3?) the energy partition between n' and 3? should be investigated. 2) The uncertainties in the elastic scattering data should be reduced. 3) The uncertainties in the total cross section data should be reduced. In the case of oxygen it is concluded that the elastic scattering data should be accurately measured to allow application of the sum rule in order to extract cross-sections of three and more particle decay reactions such as 16O(n,n'?) and 16O(n,n'p). Also, the energy partition between the n' and the charged particles in these reactions should be studied. (U.K.)

289

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)

290

Use of an index to reflect the aggregate burden of long-term exposure to criteria air pollutants in the United States.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Air pollution control in the United States for five common pollutants--particulate matter, ground-level ozone, sulfur dioxide, nitrogen dioxide, and carbon monoxide--is based partly on the attainment of ambient air quality standards that represent a level of air pollution regarded as safe. Regulatory and health agencies often focus on whether standards for short periods are attained; the number of days that standards are exceeded is used to track progress. Efforts to explain air pollution to ...

Kyle, Amy D.; Woodruff, Tracey J.; Buffler, Patricia A.; Davis, Devra L.

2002-01-01

291

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

292

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

Energy Technology Data Exchange (ETDEWEB)

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.

Goodman, L.J.; Coyne, J.J.

1980-04-01

293

Hydrocarbons and Air Pollution: An Annotated Bibliography. Part I., Categories A to E and Part II., Categories F to M and Indexes.  

Science.gov (United States)

This two-part bibliography represents an effort to collect, condense, and organize the literature on the hydrocarbons in relation to air pollution. The approximately 2,300 documents abstracted are all included in the information storage and retrieval system of the National Air Pollution Control Administration's (NAPCA) Air Pollution Technical…

National Air Pollution Control Administration (DHEW), Raleigh, NC.

294

Relationship between Arterial Inflow Rate and Venous Filling Index of the Lower Extremities Assessed by Air Plethysmography in Subjects with or without Axial Reflux in the Great Saphenous Vein  

Science.gov (United States)

Objective: To evaluate the relationship between arterial inflow rate (AIR) and venous filling index (VFI) in limbs with or without varicose veins, assessed by air plethysmography (APG). Materials and Methods: A total of 142 patients (142 limbs) visiting our clinic with leg complaints, but without arterial and venous disease, were defined as the normal group (NG), and 65 patients (65 limbs) with leg varices were defined as the varicose vein group (VG). Both groups underwent duplex ultrasonography and APG to identify venous reflux and measure hemodynamic parameters, respectively. Examinations were performed at the first visit in the NG and before and one month after treatment in the VG. Results: A strong correlation between resting AIR and VFI was found in the NG (r = 0.72) and postoperative VG (r = 0.71). Twenty-two and three limbs in the NG and postoperative VG, respectively, had a VFI over 2.0 mL/s because of the high AIR. In the VG, AIR tended to decrease after treatment (P >0.01). Conclusions: High leg AIR lead to high VFI measured by APG. AIR and VFI should be measured at the same session to assess venous hemodynamic changes after varicose vein treatment when residual venous reflux cannot be diagnosed with duplex ultrasonography. PMID:25298834

2014-01-01

295

The tree BVOC index  

International Nuclear Information System (INIS)

Urban trees can produce a number of benefits, among them improved air quality. Biogenic volatile organic compounds (BVOCs) emitted by some species are ozone precursors. Modifying future tree planting to favor lower-emitting species can reduce these emissions and aid air management districts in meeting federally mandated emissions reductions for these compounds. Changes in BVOC emissions are calculated as the result of transitioning to a lower-emitting species mix in future planting. A simplified method for calculating the emissions reduction and a Tree BVOC index based on the calculated reduction is described. An example illustrates the use of the index as a tool for implementation and monitoring of a tree program designed to reduce BVOC emissions as a control measure being developed as part of the State Implementation Plan (SIP) for the Sacramento Federal Nonattainment Area. - Highlights: ? A Tree BVOC index based on reduced emissions from low emitting trees is described. ? An example illustrates use of the index as an implementation and monitoring tool. ? This index could be useful for including urban trees in air quality mitigation plans. - A tree BVOC index is presented that calculates reduced BVOC emissions from planting lower-emitting urban tree species that has potential application for SIP compliance.

296

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

297

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

298

Verification of KERMA factor for beryllium at neutron energy of 14.2 MeV based on charged-particle measurement  

International Nuclear Information System (INIS)

In previous direct measurements of nuclear heating for beryllium induced with DT neutrons, it was pointed out that the calculation with JENDL-3.2 underestimated the measured one by 25%. However, reasons of the discrepancy have not been understood clearly. Recently, we measured the ?-particle emission double-differential cross section for beryllium and found that the evaluation of the 9Be(n,2n + 2?) reaction in nuclear data libraries have some problems. We examined KERMA factors for beryllium deduced with three latest nuclear data libraries: JENDL-3.3, ENDF/B-VII.0 and JEFF-3.1. The partial KERMA factors for 9Be(n,2n + 2?) reaction channel at incident neutron energy of 14.2 MeV deduced from these libraries were compared with a new partial KERMA factor calculated based on our experimental model. The partial KERMA factor from JENDL-3.3 was smaller by 20% than our experiment-based one. The reason of the discrepancy in the previous nuclear heating measurement comes from the smaller partial KERMA factor in JENDL-3.3, which is caused by significant underestimation of higher energy part of the ?-particle emission DDX at forward emission angles

299

Patient-specific kerma-area product as an exposure estimator in computed tomography: The concept and typical values  

International Nuclear Information System (INIS)

The concept of the patient-specific kerma-area product (PSKAP) as an exposure estimator in computed tomography (CT) was suggested, but no detailed information on how to evaluate this quantity in practice was given. We extend the idea by proposing (i) a rigorous definition of PSKAP, and (ii) a method for its evaluation by a CT scanner. To demonstrate the performance of the method, we used the Siemens Somatom Open CT scanner to obtain PSKAP values (here denoted as PPSKA) for the standard CT dosimetry head phantom

300

Determination of mass attenuation coefficients, effective atomic numbers, effective electron numbers and kermas for Earth and Martian soils  

Science.gov (United States)

Total mass attenuation coefficients, effective atomic numbers, effective electron numbers and kerma values for Earth and Martian soils are calculated in the energy range from 1 keV to 100 GeV. The values of mass attenuation and absorption coefficients used in calculations are taken from the WinXCOM program and correct data base. Contributions of different scatterings on the total mass attenuation coefficients of the soils are presented. In addition, the obtained results for Martian soils are compared with the results for Earth soils. The similarities of Earth and Martian soils are also investigated.

Un, A.; Sahin, Y.

2012-10-01

 
 
 
 
301

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

International Nuclear Information System (INIS)

In recent years the IAEA and the American Association of Physicists in Medicine (AAPM) have published external beam dosimetry protocols that are based on the use of an ionization chamber calibrated in terms of absorbed dose to water, ND,w, in a standards laboratory's reference quality beam. Since the publication of these protocols many comparisons, theoretical as well as experimental, between ND,w based and between ND,w and the former NK based protocols, have been published. The comparisons of the basic data included in the various IAEA and AAPM protocols show differences within about 1%, except for the case of plane-parallel chambers with an ND,w calibration, which in electron beams reaches up to a 2% difference. Differences sometimes larger than these upper values have, however, been reported in some of the published experimental studies. The paper provides a comprehensive review of the intercomparisons of the different protocols by various authors and discusses the reasons for the discrepancies between them. (author)

302

Ionization chamber correction factors influence on accuracy of air kerma determination in 300 kV X radiation beam  

International Nuclear Information System (INIS)

Importance of ionization chamber correction factors determination for the purpose of radiotherapy dose in 300 kV X radiation beam determination is pointed out in this paper. Therapy dose determined by using correction factors differs from determined without factors for 1.3%. (author)

303

Integral test of KERMA data for SS304 stainless steel in the D-T fusion neutron environment  

International Nuclear Information System (INIS)

The KERMA (Kinetic Energy Release Material) data play the fundamental role for estimating nuclear heating in the structural components of fusion reactors. The data are produced from the large body of nuclear data relevant to reaction channels associated with the kinetic energy release. Both contributions by neutron and gamma-ray should be addressed to arrived at the final heating products. Extensive efforts have been devoted to the neutron and ?-ray transport profile in many materials, resulting in the validation of cross section data. However, the experimental verification of KERMA data, which is a highly integrated product of neutron and ?-ray, has been limited from the lack of available experimental data. Through the JAERI/USDOE collaborative program on fusion neutronics, novel experimental technique for the direct nuclear heating due to 14 MeV neutrons has been developed based on a micro calorimetric system. The technique demonstrated excellent capability for detecting the temperature rise due to nuclear heating and pertinent verification for the calculation data and methods. This paper deals with the most recent experimental endeavor for the direct nuclear heating measurement in SS-304 stainless steel assembly, where appreciably large amounts of slow neutron and associated secondary ?-rays dominated the field. The nuclear heating up to 200 mm depth in the SS-304 assembly were derived from detected temperature rise employing large SS-304 block type probe materials

304

Air Quality Guide for Ozone  

Science.gov (United States)

... Code: State : National Summary Air Quality Guide for Ozone You may have seen the Air Quality Index ... limit outdoor exertion. What You Should Know About Ozone and Your Health Ozone in the air we ...

305

Detection and estimation trends linked to air quality and mortality on French Riviera over the 1990-2005 period to develop a prediction model of an aggregate risk index  

Science.gov (United States)

There is a profound relation between human health and well being from the one side and air pollution levels from the other. Air quality in South of France and more specifically in Nice, is known to be bad, especially in summer. The main objectives are to establish correlations between air pollution, exposure of people and reactivity of these people to this aggression, to validate a risk index built from air quality and pollen data in the area of Nice and to construct a prediction model of this sanitary index. The spatial extent of the experiment will be mainly the territory of "Alpes Maritimes". All the tasks are performed in collaboration with the "Heath-Environment Network" of the "Centre Hospitalier Universitaire" of Nice. The development of an adequate tool for observation (health index and/or indices per pathology) to understand impacts of pollution levels in an area is of utmost importance. These indexes should take into account the possible adverse effects associated with the coexistence of all the pollutants and environmental parameters. This tool must be able to inform the citizens about the levels of pollution in an adequate and understandable way but also to be used by relevant authorities to take a series of predetermined measures to protect the health of the population. This paper describes the first step to construct a prediction model of this sanitary index with a confidence interval 99% (and 95%): detection and estimation trends observed in concentrations of pollutants, emissions and mortality over the 1990-2005 period in the "Alpes Maritimes" area. The non-parametric Mann-Kendall test has been developed for detecting and estimating monotonic trends in the time series and applied in our study at annual values of pollutants air concentrations. An important objective of many environmental monitoring programs is to detect changes or trends in pollution levels over time. Over the period 1990-2005, concerning the emissions of the main pollutants, we obtained significant decreasing trends. Between 1994 and 2005, from the SO2 concentrations, decreasing trends of 1.2 %.year-1 (urban stations) and of 5.4 %.year-1 (traffic stations) were calculated. Over the same period, we obtained a decreasing trend of 1.3 %.year-1 for the NO2 concentrations (urban stations) and of 3.1 %.year-1 for the traffic stations. In addition, a decreasing trend of 0.5 %.year-1 was calculated for the suburban stations over the 1998-2005 period. Globally, the concentration of the major pollutants showed a clear downward trend and those main reductions have reflected the reduction policy of the emissions over twenty years. By considering the ozone mean values in urban areas over the 1997-2005 period, an increasing of 3.0 %.year-1 was obtained with annual averages and 3.9 %.year-1 with median values. Over the 1990-2005 period, we obtained significant decreasing trends concerning the "ischemic heart diseases" (- 1.20 %.year-1) and "asthma" (- 4.03 %.year-1) categories. No significant sex-related difference was identified for these groups. An annual change rate of + 0.31 %.year-1 for the "airway diseases" and of + 2.50%.year-1 for the "unknown causes" were identified. For these categories, we noted a sex-related difference. In fact, we obtained for males a decreasing trend contrary to females.

Sicard, P.; Mangin, A.; Hebel, P.; Lesne, O.; Malléa, P.

2009-04-01

306

Recoil proton, alpha particle, and heavy ion impacts on microdosimetry and RBE of fast neutrons: analysis of kerma spectra calculated by Monte Carlo simulation  

International Nuclear Information System (INIS)

Fast neutrons (FN) have a higher radio-biological effectiveness (RBE) compared with photons, however the mechanism of this increase remains a controversial issue. RBE variations are seen among various FN facilities and at the same facility when different tissue depths or thicknesses of hardening filters are used. These variations lead to uncertainties in dose reporting as well as in the comparisons of clinical results. Besides radiobiology and microdosimetry, another powerful method for the characterization of FN beams is the calculation of total proton and heavy ion kerma spectra. FLUKA and MCNP Monte Carlo code were used to simulate these kerma spectra following a set of microdosimetry measurements performed at the National Accelerator Centre. The calculated spectra confirmed major classical statements: RBE increase is linked to both slow energy protons and alpha particles yielded by (n,?) reactions on carbon and oxygen nuclei. The slow energy protons are produced by neutrons having an energy between 10 keV and 10 MeV, while the alpha particles are produced by neutrons having an energy between 10 keV and 15 MeV. Looking at the heavy ion kerma from <15 MeV and the proton kerma from neutrons <10 MeV, it is possible to anticipate y* and RBE trends. (author)

307

Evaluation of skin entry kerma in radiological examinations at the Hospital de Clinicas, Parana, Brazil; Avaliacao de kerma de entrada na pele em exames radiologicos no Hospital de Clinicas do Parana, Brasil  

Energy Technology Data Exchange (ETDEWEB)

This paper evaluates the skin entry dose of pediatric and adults patients when submitted to radiological examinations at the Hospital de Clinicas do Parana, Brazil, as part integrate of the data assessment of International Atomic Energy Agency (IAEA) for Latin America. It was performed measurements of dose for evaluation of skin entry kerma in pediatric patients in thorax AP/PA examinations, adults of thorax in AP/PA, cranio caudal mammography and median lateral and patients of computerized tomography in examination of head, thorax and abdomen. The obtained data demonstrate the necessity of verification of diagnostic analysis standards. The great value amplitudes demonstrate the incompatibility of examination executions with those recommended by the literature. The dose values presented partially inside the range recommended and the other over the expected for the due examination when compared with the literature

Porto, Lorena E.; Schelin, Hugo R.; Santos, Amanda C. dos; Bunick, Ana Paula; Paschuk, Sergei; Denyak, Valeriy [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Tilly Junior, Joao G. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Hospital de Clinicas; Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE/DEN), Recife, PE (Brazil). Dept. de Energia Nuclear

2011-10-26

308

Immigration Index  

Science.gov (United States)

Striving to become the "immigration resource directory on the net," the Immigration Index is a newly launched Website dedicated to news and information about immigration worldwide. Along with breaking headlines from a variety of news sources about immigration-related issues such as asylum, migration, trafficking and women, and much more, the site contains a fully annotated collection of links to immigration materials all around the World Wide Web. Only a month old, some of the categories in the Index's hierarchy still need some filling in. In time, however, the Immigration Index promises to become an invaluable resource for interested parties.

309

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

310

The tree BVOC index.  

Science.gov (United States)

Urban trees can produce a number of benefits, among them improved air quality. Biogenic volatile organic compounds (BVOCs) emitted by some species are ozone precursors. Modifying future tree planting to favor lower-emitting species can reduce these emissions and aid air management districts in meeting federally mandated emissions reductions for these compounds. Changes in BVOC emissions are calculated as the result of transitioning to a lower-emitting species mix in future planting. A simplified method for calculating the emissions reduction and a Tree BVOC index based on the calculated reduction is described. An example illustrates the use of the index as a tool for implementation and monitoring of a tree program designed to reduce BVOC emissions as a control measure being developed as part of the State Implementation Plan (SIP) for the Sacramento Federal Nonattainment Area. PMID:21435760

Simpson, J R; McPherson, E G

2011-01-01

311

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)

312

Index Morganagus  

Science.gov (United States)

Developed by Eric Lease Morgan, a Systems Librarian for the North Carolina State University Libraries, the eponymous Index Morganagus is a full-text index that collects, organizes, and disseminates articles from over 80 library-related electronic serials. Each electronic serial in the browseable list of indexed titles links to its corresponding Website. The search engine for the index supports Boolean operators and truncation, as well as phrase, compound, and case-sensitive searching. Advanced users have the option to control other query variables--such as number of results allowed or output format--through the manipulation of radio buttons. Extensive help is available online. Mr. Morgan has created a valuable resource for researchers, library students, librarians, and information professionals.

313

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

314

Energy dependence of kerma of thermoluminescent glass dosemeters for photons with energy till 6 MeV  

International Nuclear Information System (INIS)

Experimentally determined is energy dependence of ICG dosemeters (individual control by means of glasses) in the photon energy range from 1 to 6 MeV. The ICG dosemeters of 4x15x15 mm3 dimensions in standard filters compensating energy dependence in the photon energy range from 0.03 to 1.25 MeV. To irradiate the dosemeters the following photon sources were used: 1.38 and 2.76 MeV 24Na source; Pu-?-? 16N neutron source with 4.45 MeV gamma radiation and 6.13 MeV 16N source. Energy dependence of the dosemeters was determined by the kerma which, in turn, was determined by experimentally measured depth absorption doses in a medium equivalent to a detector. It has been established, that ICG energy dependence within the investigated energy range increases, but not more than by 20 %

315

Determination of mass attenuation coefficients, effective atomic numbers, effective electron numbers and kermas for Earth and Martian soils  

International Nuclear Information System (INIS)

Highlights: ? The present work have been expected to be lead to extraterrestrial research. ? Our work have thrown light on the radiation physics and the applications. ? The data which are used to shielding application are not available in the literature. - Abstract: Total mass attenuation coefficients, effective atomic numbers, effective electron numbers and kerma values for Earth and Martian soils are calculated in the energy range from 1 keV to 100 GeV. The values of mass attenuation and absorption coefficients used in calculations are taken from the WinXCOM program and correct data base. Contributions of different scatterings on the total mass attenuation coefficients of the soils are presented. In addition, the obtained results for Martian soils are compared with the results for Earth soils. The similarities of Earth and Martian soils are also investigated.

316

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

317

Estimation of electron-loss and photon-scattering corrections for parallel-plate free-air chambers  

International Nuclear Information System (INIS)

Parallel-plate free-air ionization chambers are used for X-ray air-kerma rate standards at the National Metrology Institute of Japan (NMIJ), AIST. The electron-loss and photon-scattering correction factors are needed for the evaluation of air-kerma rate from measured current. The electron-loss correction factor (Ke) is a correction of the charge loss by giving energy to the electrode part without the high-speed electron stopping in the air area where the charges are collected. The scattering correction factor (Ksc) is for a correction of extra charges produced by scattered photons generated after an incidence photon is interactive. The electron-loss and photon-scattering correction factors for 3 different size parallel-plate free-air chambers are estimated by the EGS4 code. One chamber is used to get primary standards for absolute measurements of air kerma in beams of medium-energy X-rays and the other two are used for the same purpose in beams of low-energy X-rays. These correction factors are calculated for mono-energetic photons. It is found that electron-loss and photon-scattering correction factors depend on the chamber size, and the latter especially changes greatly depending on the size. The Ke and Ksc value for medium- and low-energy X-ray fields at AIST are estimated by averaging the energy deposition contributions over the X-ray spectrum. (author)

318

Evidence for evanescent waves at interfaces in a high-index prism/liquid-crystal-Au-NPs/glass/air structure and effects of relative concentration of gold nanoparticles, wavelength, polarization, and incident angle of the laser beam  

Science.gov (United States)

Incorporation of relatively small concentrations of gold nanoparticles (Au NPs) in a polymer-dispersed liquid crystal (PDLC) is known to lower the operating threshold voltage and increase optical transmission through the device.ootnotetextA. Hinojosa and S. C. Sharma, Applied Physics Letters, 97, 081114 (2010) In order to understand whether there is an interplay between the localized surface plasmon resonance at Au-NPs-dielectric interfaces and the electro-optical properties of PDLC devices, we have investigated propagation of light through a high-index prism/liquid-crystal-Au-NPs/glass/air structure by using Kretschmann geometry as functions of concentration of Au NPs in the liquid crystal, and the wavelength, polarization, and angle of incidence of the laser beam. We will discuss to what extent the results of these experiments support an interplay between the localized surface plasmon resonance at NPs/dielectric interfaces and optical propagation through the above-described structure.

Tiwari, Kunal; Singh, Ankit; Sharma, Suresh

2011-10-01

319

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

320

Molecules | Indexing &  

...Sciences Societies Sports Sustainability Symmetry Systems Technologies Toxics Toxins Vaccines Veterinary Sciences Viruses Water Volume Author Section Issue Article Type all Addendum Article Book Review Case Report Comment Commentary Communication Concept Paper Correction Creative Discussion Editorial Essay Letter New Book Received Opinion Project Report Reply Retraction Review Short Note Technical Note Special Issue Page Molecules Molecules Home About this journal Indexing & Abstracting Instructions for Authors Publication Fees Sections Special ...Directory of Open Access Journals EMBASE (Elsevier) Energy & Power Source (EBSCO) FSTA - Food Science and Technology Abstracts (IFIS) INSPEC (IET) Journal Citation Report (Thomson Reuters) MEDLINE (NLM) Polymer Library (Smithers Rapra) PubMed (NLM) Reaxys - former Crossfire Beilstein (Elsevier) SCIE - Science Citation Index Expanded (Thomson Reuters) SciSearch (Thomson Reuters) Scopus (Elsevier) Web of Science (Thomson Reuters) Full-text Archives CLOCKSS (Digital Archive ...

 
 
 
 
321

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

322

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

323

Evaluated cross section libraries and kerma factors for neutrons up to 100 MeV on 16O and 14N  

International Nuclear Information System (INIS)

We present evaluations of the interaction of 20 to 100 MeV neutrons 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. The evaluated data libraries are available as electronic files

324

Development of improved free-air ionisation chamber as absolute dosimetry standard for low-energy X rays in INER  

International Nuclear Information System (INIS)

The National Radiation Standard Laboratory of the Inst. of Nuclear Energy Research (INER) designed and constructed an improved Attix style free-air ionisation chamber (FAC) for low-energy X-ray measurements. Clinically, X rays in this energy range are used in mammography radiology. This chamber is also used to perform air-kerma measurements. The original Attix two-sectional design was redesigned by INER using the piston design. The correction factors were determined experimentally for volume estimation, ion recombination and air attenuation. The aperture transmission, wall transmission, electron loss and photon scatter correction factors were determined using Monte Carlo calculations. INER established the Bureau International des Poids et Mesures (BIPM) X-ray beam code and performed a comparison of secondary standard air-kerma calibration factors for 10-50 kV low- energy X rays to verify the experimental accuracy and measurement consistency of the improved chamber. The INER-NMIJ/National Inst. of Advanced Industrial Science and Technology (AIST) experimental results comparison using a transfer chamber yielded a difference <1.0% at the 95% confidence level in calibration factors. The overall uncertainty for the X-ray measurement in terms of air kerma was <0.6% at the 95% confidence level. These results indicated that the improved FAC is capable of serving as a primary standard as well as a trace standard in low-energy X-ray calibration services in Taiwan and even forming a basis for the future mammography X-ray air-kerma primary standard. (authors)

325

A QUANTITATIVE EVALUATION OF THE POLLUTANT STANDARDS INDEX  

Science.gov (United States)

The U.S. Environmental Protection Agency has recommended a daily air pollution index for use by State and local air pollution control agencies--the Pollutant Standards Index (PSI). The new index makes use of segmented linear functions which convert measured concentrations of each...

326

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

327

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

328

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

329

Cavity's theory of Bragg-Gray applied to ionization free-air chamber  

Energy Technology Data Exchange (ETDEWEB)

Ionization's chambers are kinds of dosimeters more useful to measurements such as required in radiotherapy. Are detectors of non pulse type (mean effect) and gaseous, calibrate in Kerma, unit Gray (Gy).The objective of this work is to relate the physical theory existing and the construction shape of the primary standard, that is the ionization of free-air chamber with variable volume, manufactured by Victoreen Instruments, used to measure magnitude air Kerma performed by the 'Laboratorio Nacional de Metrologia das Radiacoes Ionizantes' from Instituto de Radioprotecao e Dosimetria - LNMRI-IRD. For in such a way, will be done an evaluation of the chamber capability, and the sensibility of radiations of low energy, range from 20 kV to 80 kV, in the qualities of mammography not attenuate, mammography attenuate, diagnostic, therapy e protection through the construction's acquaintance, dimensions of pieces components and operational tests. Concerning the chamber's construction, the mechanical set consists of two cylinders of aluminium concentrically that moves axially between itself, objectifying the variation of internal volume (variable volume). The practical application of the Bragg-Gray cavity's theory can be applied to the chamber, where the reasons of the absorbed dose in different means to the same fluency is equal to the reason of stopping powers of two means. >From the definition of Kerma we can obtain the adsorbed dose and existing particles in (CPE), the absorbed dose is equal to the Kerma's collision. (author)

Silva, J.L.D.F.; Cardoso, R.S.; Peixoto, J.G.P. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)]. E-mail: joseluiz@ird.gov.br; ricardo@ird.gov.br; guilherm@ird.gov.br

2007-07-01

330

Design and preliminary test of a free-air ionization chamber for low-energy X-ray  

International Nuclear Information System (INIS)

A free-air ionization chamber in low-energy X-ray has been designed and manufactured at the National Institute of Metrology (NIM, China) according to the definition of air-kerma. The results of a preliminary test show that the leakage current of ionization chamber is around 2 x 10-15A, and the correction factor of ion recombination for the ionization chamber is also obtained. The free-air ionization chamber is suitable for the primary standard in low-energy X-rays. (authors)

331

Design and preliminary test of a free-air ionization chamber for low-energy X-ray  

Science.gov (United States)

A free-air ionization chamber in low-energy X-ray has been designed and manufactured at the National Institute of Metrology (NIM, China) according to the defination of air-kerma. The results of a preliminary test show that the leakage current of ionization chamber is around 2×10-15A, and the correction factor of ion recombination for the ionization chamber is also obtained. The free-air ionization chamber is suitable for the primary standard in low-energy X-rays.

Wu, Jin-Jie; Yang, Yuan-Di; Wang, Pei-Wei; Chen, Jing; Liu, Jia-Cheng

2011-06-01

332

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

333

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

334

Determining Weight for Multicriteria Indexes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper discusses methods determining weight for each criterion used in the development of an index representing social indicators. Examples to show computing for weights are also given. Data for percent of household in all districts in the country, obtained from 1991 census, of that owned defined facilities such as car, radio, television, telephone, washing machine, and air-condition are used as example how such weights were computed

Abdul Aziz Jemain

2004-01-01

335

Determining Weight for Multicriteria Indexes  

Directory of Open Access Journals (Sweden)

Full Text Available This paper discusses methods determining weight for each criterion used in the development of an index representing social indicators. Examples to show computing for weights are also given. Data for percent of household in all districts in the country, obtained from 1991 census, of that owned defined facilities such as car, radio, television, telephone, washing machine, and air-condition are used as example how such weights were computed

Abdul Aziz Jemain

2004-06-01

336

Kitap ?ndeksleri / Book Indexing  

Directory of Open Access Journals (Sweden)

Full Text Available This article is a review of Book Indexes from a variety of points, which are in fact the oldest indexes used in the world. They are different than journal indexes and database indexes which are ongoing projects. Book indexes, on the other hand, are unique in their own frameworks, as each one is a completed and finished unit. Construction of book indexes, types of indexes (according to subject headings and proper names, synthesis and analytic methods; and formats of indexes (indented and run-in formats are described. There is a list of important conventions relating to book indexes at the end of the article

Meral Alaku?

2006-04-01

337

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

338

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.

339

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

340

UV (Ultraviolet) Index  

Science.gov (United States)

... Protection Agency Search Search Contact Us SunWise UV Index Check your UV Index Tip: If your ZIP ... factors affect the level of UV radiation? UV Index Forecast The forecast map shows contour lines of ...

 
 
 
 
341

Index Funds Online  

Science.gov (United States)

Matthew Roberts recently released Index Funds Online in response to the lack of index investment fund information on the Internet. Site features include the market performance newsletter Indexing Quarterly, background and definitional information on major US Indexes such as the S&P 500, and a library of new and interesting financial Websites, articles, and book reviews. Links to current index performance figures are also provided as well as a simple site search system and index fund discussion board.

342

Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam  

Science.gov (United States)

We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

Groetz, J.-E.; Ounoughi, N.; Mavon, C.; Belafrites, A.; Fromm, M.

2014-08-01

343

Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam.  

Science.gov (United States)

We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™ and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays. PMID:25173259

Groetz, J-E; Ounoughi, N; Mavon, C; Belafrites, A; Fromm, M

2014-08-01

344

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

345

Monte Carlo simulation for electron-loss and photon-scattering corrections for parallel-plate free-air chambers  

International Nuclear Information System (INIS)

The parallel-plate free-air ionization chambers are used for X-rays air-kerma rate standards at National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST). The electron loss and scattering correction factors are needed for the evaluation of air-kerma rate from measured current. The electron loss correction factor (Ke) is a correction of the charge loss by giving energy to the electrode part without a high-speed electron stopping in the air area where the charges are collected. The scattering correction factor (Ksc) is for a correction of extra charges produced by scattered photon generated after an incidence photon is interactive. The electron-loss and photon-scattering correction factor for 3 different size parallel-plate free-air chambers are estimated by the EGS4 code. One is used as primary standards for absolute measurements of air kerma in beams of medium-energy X-rays and two are of low-energy X-rays. These correction factors are calculated for mono-energetic photons. It is obtained that electron-loss and photon-scattering correction factors depend on the chamber size, and especially, the photon-scattering correction value changes greatly depending on the size. The Ke and Ksc value for medium- and low-energy X-ray fields at AIST are estimated by averaging the energy deposition contributions over the X-ray spectrum. The overall uncertainty of the electron loss overall uncertainty of the electron loss or scattering correction factor is evaluated to be 0.14%. (author)

346

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)

347

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

348

Lobby index in networks  

Science.gov (United States)

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 with exponent ? the distribution of the l-index has power tail with exponent ?(?+1). Properties of the l-index and extensions are discussed.

Korn, A.; Schubert, A.; Telcs, A.

2009-06-01

349

Assessment of corrective factors for the LNHB reference measurement in terms of Kr air for iodine 125  

International Nuclear Information System (INIS)

The LNHB (Laboratoire National Henri Becquerel) is currently developing a new primary reference for low dose rate curietherapy with iodine 125 in terms of reference kerma in air. This includes an innovative sensor: an ionization chamber with a toroidal air wall. The authors present Monte Carlo calculations performed for the determination of corrective factors to be applied to come down to reference conditions or to correct possible measurement errors. Calculations have been performed for the specific geometries of BEBIG sources which are used for ophthalmic and prostatic curietherapy treatments

350

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

351

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

International Nuclear Information System (INIS)

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 125I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for 125I selectSeedTM 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

352

How indexes have changed  

International Nuclear Information System (INIS)

The accompanying table compares refinery construction and operating wages monthly for the years 1990 and 1991. The Nelson-Farrar refinery construction cost indexes are inflation indexes, while the operating indexes incorporate a productivity which shows improvement with experience and the increasing size of operations. The refinery construction wage indexes in the table show a steady advance over the 2-year period. Common labor indexes moved up faster than skilled indexes. Refinery operating wages showed a steady increase, while productivities averaged higher near the end of the period. Net result is that labor costs remained steady for the period

353

77 FR 37859 - Approval and Promulgation of Air Quality Implementation Plans; Utah; Revisions to UAC Rule 401...  

Science.gov (United States)

...regulations.gov index. Although listed in the index, some information...National Ambient Air Quality Standards...Air Strippers and Soil Venting Projects...Emissions from Soil Aeration Projects...National Ambient Air Quality Standards...

2012-06-25

354

Windchill Temperature (WCT) Index  

Science.gov (United States)

... Windchill brochure in PDF format. The NWS Windchill Temperature (WCT) index uses advances in science, technology, and ... calculating the dangers from winter winds and freezing temperatures. The index: Calculates wind speed at an average ...

355

Kaiser's Systematic Indexing.  

Science.gov (United States)

Describes a system of subject indexing developed by Julius Kaiser (1868-1927) which is based on "concretes" and "processes" to govern the form of subject headings and subdivisions. Elements of amplification, guides for the subject index, and criticism of Kaiser's systematic indexing are noted. Five sources are given. (EJS)

Rodriguez, Robert D.

1984-01-01

356

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, ... a gas, is a major part of air pollution in cities. When ozone forms air pollution, it's ...

357

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 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

358

Transport of initial radiations in air over ground  

International Nuclear Information System (INIS)

A time-dependent system of classification is normally used to divide the ionizing radiation from a nuclear explosion into two groups: initial and residual. The initial radiation is the ionizing radiation emitted within the first minute following the detonation of the weapon, and the residual radiation is the ionizing radiation emitted later. Transport calculations for the prompt and delayed radiations were performed separately and then combined at fixed ground locations to obtain the total neutron and gamma-ray fluence, together with their energy and angular distributions. Modeling of the air-over-ground transport for the delayed radiation is a more difficult task. For example, such complex effects as the rapid early-time decay of the fission products, the rise of the fireball, and the blast-enhanced transport of the delayed radiation must be considered. The blast wave from the explosion enhances the transport of the delayed radiations by removing most of the air between the fireball and the shock front. This work uses transport modeling procedures and source term data developed in studies by Science Applications International Corporation (SAIC). In their studies, the delayed neutron and gamma-ray fluences were estimated by means of a one-dimensional ANISN calculation that takes into account the air density profile at a fixed location on the ground at discrete time intervals after the explosion. The effects of ground scattering were then computed separately by means og were then computed separately by means of the VCS code. These transport modeling procedures were verified by applying them to weapon tests where time dependent gamma-ray measurements were made as a function of ground range. Many of the calculations and comparisons of this work involve the use of dosimetric parameter called kerma. Kerma equals the total kinetic energy of all the charged particles liberated by neutrons and gamma rays in a small volume of a given material divided by the mass of the material in that volume element

359

Rapid doubling of Alzheimer’s amyloid-?40 and 42 levels in brains of mice exposed to a nickel nanoparticle model of air pollution [v1; ref status: indexed, http://f1000r.es/T5Rxeo  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Over 20 genetic risk factors have been confirmed to associate with elevated risk for Alzheimer’s disease (AD, but the identification of environmental and/or acquired risk factors has been more elusive. At present, recognized acquired risks for AD include traumatic brain injury, hypercholesterolemia, obesity, hypertension, and type 2 diabetes. Methods: Based on reports associating various inhalants with AD pathology, we investigated the possibility that air pollution might contribute to AD risk by exposing wild-type mice to a standard air pollution modeling system employing nickel nanoparticle-enriched atmosphere for 3 hr. Results: Mice exposed to air pollution showed 72-129% increases in brain levels of both amyloid-? peptides A?40 and A?42, as well as A?42/40 (p <0.01. Conclusions: These effects on elevation of brain A? exceed those associated with trisomy 21, a known risk for early onset AD pathology, raising the possibility that clinical importance might be attached. Further work is required to establish the molecular and physiological basis for these phenomena. The rapid, dramatic effect, if verified, would suggest that inhalant exposures should be evaluated for their possible roles in contributing to the environmental risk for common forms of AD.

Soong Ho Kim

2012-12-01

360

Eco-Index  

Science.gov (United States)

Eco-Index, a project of the Rainforest Alliance, is "a searchable almanac of current and past conservation projects in Mesoamerica, with project descriptions, goals, achievements, lessons learned, and more." With current, well-presented features covering a range of biodiversity conservation issues, Eco-Index offers an excellent way for conservation researchers and practitioners to keep abreast of activity in their field. Users are encouraged to add their own project descriptions to the Eco-Index database. Available in English or Spanish.

 
 
 
 
361

Human Development Index Data  

Science.gov (United States)

This data set traces the varying patterns of national progress in recent decades, documenting impressive long-term Human Development Index (HDI) gains even in most low-income countries. The data set also includes three innovative new measurements: the Inequality-adjusted Human Development Index (IHDI), the Gender Inequality Index (GII) and the Multidimensional Poverty Index (MPI). The data set is available in both CSV and SDMX file formats and contains more than 100 indicators that measure quality of life for all UN member states.

Nations, United

362

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)

Findings of a recent ORNL review, and of other reviews, which have been discussed at the Late Effects Workshop on Dosimetry of Atomic Bomb Survivors, 29th Annual Meeting of the Radiation Research Society, Minneapolis, Minnesota, 31 May 1981, and the Symposium on Reevaluations of Dosimetric Factors, Hiroshima and Nagasaki, US Department of Energy, Germantown, Maryland, 5 and 6 September 1981, have clearly established a need to revise the dosimetry for the A-bomb survivors. This effort will involve several divisions at ORNL, several other national laboratories, and several consulting firms. One of the main tasks of the Health and Safety Research Division at ORNL is to provide revised estimates of various organ-dose parameters related to a survivor's neutron and gamma-ray exposures. The objectives of the work summarized in this report were: (a) to better define the elemental composition of various skeletal components of ICRP-1975 Reference Man, and (b) to investigate photon and neutron fluence-to-kerma conversion factors for various total-body and organ-tissue components of ICRP-1975 Reference man as revised here. Scaled down mathematical descriptions of the volumes and shapes of the total body and internal organs of Reference Man will be used, of course, in the organ-dose calculations for A-bomb survivors

363

Definitions and Methodological Issues Regarding Airline Network Concentration Indexes  

Directory of Open Access Journals (Sweden)

Full Text Available This work aims to develop a review of recent articles regarding concentration of airline networks. Here I discuss the main concentration indexes proposed by recent papers and balance its advantages and disadvantages, with the aim of highlighting the effect that indexes have on the direction of air transportation policies.[Paper in Portuguese

Leandro Capitani

2009-01-01

364

Calculation of conversion coefficients Hp(3)/K air using the PENELOPE Monte Carlo code and comparison with MCNP calculation results; Calcul des coefficients de conversion H{sub p}(3)lK{sub air} au moyen du code de monte-carlo penelope et comparaison avec les resultats de calculs MCNP  

Energy Technology Data Exchange (ETDEWEB)

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

Daures, J.; Gouriou, J.; Bordy, J.M. [CEA Saclay, LIST, Laboratoire National Henri Becquerel (LNE-LNHB), 91 - Gif-sur-Yvette (France)

2010-07-01

365

Comparison of measured and calculated air-transported radiation from a fast unshielded nuclear reactor. Technical report  

Energy Technology Data Exchange (ETDEWEB)

Neutron and gamma-ray spectra have been measured at various distances up to 1100 metres from the fast-neutron reactor of the U.S. Army Pulse Radiation Division (Materiel Testing Directorate, Aberdeen Proving Ground, Md.) The spectra were obtained at a height of two metres above the air-ground interface and are compared to previous measurements performed by two other research laboratories, and also to the results of theoretical predictions based on two-dimensional discrete-ordinates transport theory. Integral quantities such as partial and total radiation kermas are generally in good agreement, however the theoretical calculations tend to predict somewhat softer neutron spectra than are observed experimentally.

Robitaille, H.A.; Hoffarth, B.E.

1980-12-01

366

EMMSE Media Index.  

Science.gov (United States)

This index provides a topical taxonomy of media which have been selected for their relevance in the teaching of materials science and engineering. The index is keyed to a matrix which matches topical and/or class material with six classifications of media: print, 16mm film, super 8 film, slide/tape, videotape, and other (including interactive…

Hewitt, Clifford A., Comp.; McKinstry, Herbert A., Comp.

367

Consumer Price Index  

Science.gov (United States)

According to the Consumer Price Index for March 2000, the Consumer Price Index for All Urban Consumers (CPI-U) rose 0.8 percent in March. This is a 3.7 percent increase since March 1999. After seasonal adjustments, the CPI-U rose 0.7 percent, after a 0.5 percent increase in February 2000.

368

Gradient index retroreflector  

Science.gov (United States)

A retroreflector is formed of a graded index lens with a reflective coating at one end. The lens has a length of an odd multiple of a quarter period thereof. Hexagonally shaped graded index lenses may be closely packed in an array to form a retroreflecting surface.

Layne, Clyde B. (Livermore, CA)

1988-01-01

369

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

370

Sensitivity of coefficients for converting entrance surface dose and kerma-area product to effective dose and energy imparted to the patient  

International Nuclear Information System (INIS)

We investigate the sensitivity of the conversions from entrance surface dose (ESD) or kerma-area product (KAP) to effective dose (E) or to energy imparted to the patient (?) to the likely variations in tube potential, field size, patient size and sex which occur in clinical work. As part of a factorial design study for chest and lumbar spine examinations, the tube potentials were varied to be ±10% of the typical values for the examinations while field sizes and the positions of the field centres were varied to be representative of values drawn from measurements on patient images. Variation over sex and patient size was based on anthropomorphic phantoms representing males and females of ages 15 years (small adult) and 21 years (reference adult). All the conversion coefficients were estimated using a mathematical phantom programmed with the Monte Carlo code EGS4 for all factor combinations and analysed statistically to derive factor effects. In general, the factors studied behaved independently in the sense that interaction of the physical factors generally gave no more than a 5% variation in a conversion coefficient. Taken together, variation of patient size, sex, field size and field position can lead to significant variation of E/KAP by up to a factor of 2, of E/ESD by up to a factor of 3, of ?/KAP by a factor of 1.3 and of ?/ESD by up to a factor of 2. While KAP is preferred to determine ?, the results show no strong preference of KAP over ESD in determining E.nce of KAP over ESD in determining E. The mean absorbed dose D-bar in the patient obtained by dividing ? (determined using KAP) by the patient's mass was found to be the most robust measure of E. (author)

371

A gradient index metamaterial  

CERN Document Server

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult to achieve with existing materials. 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 broad range of frequencies. The gradient index metamaterial represents an alternative approach to the development of gradient index lenses and similar optics that may be advantageous, especially at higher frequencies. In particular, the gradient index material we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated.

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

2004-01-01

372

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

373

Eccentric connectivity index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The eccentric connectivity index $\\xi^c$ is a novel distance--based molecular structure descriptor that was recently used for mathematical modeling of biological activities of diverse nature. It is defined as $\\xi^c (G) = \\sum_{v \\in V (G)} deg (v) \\cdot \\epsilon (v)$\\,, where $deg (v)$ and $\\epsilon (v)$ denote the vertex degree and eccentricity of $v$\\,, respectively. We survey some mathematical properties of this index and furthermore support the use of eccentric connecti...

Ilic?, Aleksandar

2011-01-01

374

Calculating a Biodiversity Index  

Science.gov (United States)

In this Biodiversity Counts activity, students learn how scientists calculate a biodiversity index using a page from the phone book as their data source. The printable five-page PDF handout includes a series of inquiry-based questions to get students thinking about what they already know about biodiversity and how living and non-living things are connected, step-by-step directions for calculating a biodiversity index, and a worksheet that includes brainstorming questions and areas for recording answers.

375

Indexing Moving Points  

DEFF Research Database (Denmark)

We propose three indexing schemes for storing a set S of N points in the plane, each moving along a linear trajectory, so that any query of the following form can be answered quickly: Given a rectangle R and a real value t, report all K points of S that lie inside R at time t. We first present an indexing structure that, for any given constant >0, uses O(N/B) disk blocks and answers a query in O((N/B)1/2+ +K/B) I/Os, where B is the block size. It can also report all the points of S that lie inside R during a given time interval. A point can be inserted or deleted, or the trajectory of a point can be changed, in O(logB2 N) I/Os. Next, we present a general approach that improves the query time if the queries arrive in chronological order, by allowing the index to evolve over time. We obtain a tradeoff between the query time and the number of times the index needs to be updated as the points move. We also describe an indexing scheme in which the number of I/Os required to answer a query depends monotonically on the difference between the query time stamp t and the current time. Finally, we develop an efficient indexing scheme to answer approximate nearest-neighbor queries among moving points.

Agarwal, Pankaj K.; Arge, Lars Allan

2003-01-01

376

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

377

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

378

40 CFR Appendix D to Part 58 - Network Design Criteria for Ambient Air Quality Monitoring  

Science.gov (United States)

...redevelopment, and soil disturbance; and heavily...potentially poor air quality. Similarly, monitors...Manual. Office of Air Quality Planning and Standards...Criteria for Ambient Air Quality Monitoring 4.4Sulfur...Population Weighted Emissions Index. (a) The...

2010-07-01

379

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.

380

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