Use Of Correction Factors Research Articles

Equivalence testing of filter-based, beta-attenuation, TEOM, and light-scattering devices for measurement of PM10 concentration in animal houses

Emissions of particulate matter (PM) from poultry and pig houses may contribute significantly to ambient concentrations. Yet, our knowledge on the accuracy and comparability of samplers available for measuring the high PM10 concentrations (>100μgm–3) in the inside air directly upstream of the ventilation exhausts of these buildings is very limited. The aim of this study was to provide insight into this matter for five candidate samplers: a filter-based cyclone sampler (CYS), the Thermo Scientific FH 62 I-R beta-attenuation sampler (BAS), the Thermo Scientific Tapered Element Oscillating Microbalance, model 1400ab (TEOM), the TSI DustTrak model 8520 (DT), and the GRIMM Portable Aerosol Spectrometer model 1.109 (PAS). Equivalence tests were carried out following European Standard EN 12341 using two devices for each candidate sampler (CAS) and four filter-based low-volume reference samplers (RES). Measurements were performed inside three major animal housings (a fattening pig house, a laying hen house, and a broiler house) and inside an office room. Our key results and conclusions are: (1) neither one of the five CASs, nor the RES itself, met the EN 12341 requirement for comparability between devices of the same sampler type. Using a less strict boundary for this aspect – in concert with performing duplicate sampling – may be appropriate. (2) The CYS met the EN 12341 accuracy requirements in pigs and layers, but overestimated the RES concentration in broilers. The BAS, TEOM, and DT underestimated, and the PAS overestimated, RES concentrations in a systematic manner. The use of correction factors seems to be a promising method to calibrate measured values to RES concentrations. (3) The BAS, TEOM, DT, and PAS started to show scattered regression after 432–500h of sampling, which stresses the need for shortened time intervals between full services. In conclusion, some of the samplers tested could be regarded acceptable when appropriate measures (such as duplicate sampling, correction factors, and more frequent servicing) are applied.

Constituents of the Essential Oil of Euphorbia hebecarpa

The Euphorbiaceae is a large family of flowering plants including 300 genera and over 5000 species. Euphorbia is the largest genus in this plant family with about 2000 species [1]. The Iranian Flora consists of 70 species of Euphorbia, including 17 endemics, and the popular Persian name of the species is “Farfion” [2]. Euphorbia hebecarpa Boiss., endemic to Iran, is a perennial plant distributed mainly in the Zagros Mountains [3]. Latex of some species of Euphorbia has traditionally been used in the treatment of skin diseases, gonorrhea, migraines, intestinal parasites, and warts [4]. Phytochemical investigation of the genus revealed that many of its components are highly bioactive [5–7]. Diterpenoids are found in the majority of the genus with many different core frameworks such as jatrophanes, lathyranes, tiglianes, ingenanes, and myrsinols [8–13]. In addition, some Euphorbia species are known to possess significant anticancer [14, 15], antitumor [16, 17], antimicrobial [17, 18], and antioxidant [19, 20] activities. To the best of our knowledge, there is no published report on the composition of E. hebecarpa essential oil. However, cytotoxic and antimicrobial activities of the extracts of the plant have been reported [21]. The present work studies the chemical composition of the essential oil from the aerial parts of E. hebecarpa for the first time. The plant material was collected during the flowering stage from Baft, the Kiskan area, Kerman Province, Iran in June 2012. A voucher specimen (No. 1136) has been deposited in the Herbarium of the Department of Microbiology, Kerman Branch, Islamic Azad University, Kerman, Iran. The air-dried aerial parts of the plant (100 g) were crushed and subjected to hydrodistillation for 3 h using a Clevenger-type apparatus. The clear yellowish oil was isolated in a yield of 0.2% (w/w). The constituents of the oil were analyzed by GC and GC-MS. GC analysis of the volatile components was carried out using a Hewlett-Packard 6890 instrument coupled to a flame ionization detector (FID). Compounds were separated on an HP-5 capillary column (30 m 0.25 mm, film thickness 0.25 m). The column temperature was kept at 60 C for 3 min and programmed to 220 C at a rate of 5 C/min. Injector and detector temperatures were 270 C, and the flow rate of helium as carrier gas was 1 mL/min. The percentage composition of the individual components was computed from the GC-FID peak areas without the use of correction factors. GC-MS analysis was performed using an Agilent 5975C mass spectrometer coupled to an Agilent 7890A gas chromatograph equipped with an HP-5MS capillary column (30 m 0.25 mm, film thickness 0.25 m). The carrier gas was helium, and the chromatographic conditions were as above. The spectrometer was scanned over the 40–400 amu range with an ionization voltage of 70 eV and an ionization current of 150 A. Retention indices were determined using the retention times of n-alkanes, injected after the essential oil under the same chromatographic conditions. The chemical compounds, which were identified on the basis of their mass spectral characteristics and retention indices [22], are listed in Table 1. As is shown, 28 components were identified in the essential oil, representing 97.6% of the total oil. The main constituents were -bisabolol (31.2%), cis-cadin-4-en-7-ol (20.1%), trans-piperitol (8.6%), cis-p-menth2-en-1-ol (6.4%), and trans-p-menth-2-en-1-ol (6.2%). Oxygenated sesquiterpenes (59.3%) were the most abundant components in the oil. The essential oil of E. teheranica Boiss., endemic to Iran, was also rich in oxygenated sesquiterpenes, and elemol (57.5%) has been reported as the main constituent of the oil [23].

Daily Suspended Sediment Load Estimation by Meta-heuristic Optimization Approaches and Fuzzy-C-Means Clustering Method

Accurate Suspended Sediment Load (SSL) estimation is very important for water resources quantity and quality studies. In this regard, Sediment Rating Curve (SRC) is a common regression model in predicting SSL of discharge. Studies in this field have shown that the data log-transformation in SRC model causing a bias which underestimates SSL prediction. In this study, using data from the daily flow discharge and suspended sediment discharge of Karaj Dam watershed at Siera station, a 30–year period (1981 to 2011), SRC equation derived, and then, using meta-heuristic algorithms (genetic algorithm and particle swarm optimization algorithm) it was calibrated again. Before modeling to increase the generalization power of the models, using fuzzy clustering method, the data were clustered and then by doing data sampling, they were classified into two homogeneous groups (calibration and test data set). The results show that meta-heuristic algorithms are appropriate methods for optimizing coefficients of SRC model and their results are much more favorable than those of the conventional SRC models or SRC models corrected by correction factors. In this relation, the sediment rating curve models calibrated with meta-heuristic algorithms, by reducing the RMSE of the test data set of 3718.87 ton/day (in the initial SRC model) to 2615/119 ton/day (in the calibrated models by meta-heuristic algorithms) increased the accuracy of suspended sediment load estimation at a rate of 1103.68 ton/day. However, the SRC model corrected by FAO factor decreased the efficiency of initial SRC model by increasing the RMSE of the test data set to 4128/73 ton/day. Using meta-heuristic algorithms in calibrating SRC models also prevents data log-transformation and use of correction factors and increases the accuracy of results. Keywords: Fuzzy-C-Means Clustering, Genetic and PSO Algorithms, Karaj Dam, Sediment Rating Curve, Suspended Sediment Load

Control-point-placement method for the aerodynamic correction of the vortex- and the doublet-lattice methods

The use of correction factors to improve the accuracy of the aerodynamic influence coefficient (AIC) matrices produced by the vortex-lattice and the doublet-lattice methods has been an engineering practice in the field of aeroelasticity. In order to account for either viscous or transonic flow effects not considered in the linearized formulation of such methods, the most frequent correction techniques have been to pre-multiply or to post-multiply the AIC matrices by diagonal matrices comprising semi-empirical weighting factors. This paper proposes a different correction approach: the control-point-placement method (CPPM), based on the idea of displacing the control point of each panel – the point where the boundary condition of flow tangency must be satisfied. Both the vortex- and the doublet-lattice methods have been developed with the singularities placed at the quarter-chord line of the panels and the control points at three quarters of their mean chords. With the calculation of modified control point positions, the CPPM intrinsically changes the mutual aerodynamic influence between the panels and allows the lifting surface methods to predict steady-state pressure distributions that match or approximate with minimum error those derived from wind tunnel measurements or higher-fidelity CFD solutions. Different approaches to extend the aerodynamic correction for application at non-zero reduced frequencies in the doublet-lattice method are then studied. Results are presented that are in acceptable agreement with benchmark wind tunnel data and comparisons are made between the proposed methodology and the traditional diagonal matrix corrections.

Sample thickness and quantitative concentration measurements in Br K-edge XANES spectroscopy of organic materials.

While XANES spectroscopy is an established tool for quantitative information on chemical structure and speciation, elemental concentrations are generally quantified by other methods. The edge step in XANES spectra represents the absolute amount of the measured element in the sample, but matrix effects and sample thickness complicate the extraction of accurate concentrations from XANES measurements, particularly at hard X-ray energies where the X-ray beam penetrates deeply into the sample. The present study demonstrates a method of quantifying concentration with a detection limit approaching 1 mg kg(-1) using information routinely collected in the course of a hard X-ray XANES experiment. The XANES normalization procedure unambiguously separates the signal of the absorber from any source of background. The effects of sample thickness on edge steps at the bromine K-edge were assessed and an empirical correction factor for use with samples of variable mass developed.

Shallow-tunnelling correction factor for use with Wigner-Eyring transition-state theory.

We obtain a shallow-tunnelling correction factor for use with Wigner-Eyring transition-state theory (TST). Our starting point is quantum transition state theory (QTST), which approximates the accurate quantum rate as the instantaneous flux through a delocalised transition-state ensemble of ring-polymers. Expanding the ring-polymer potential to second order gives the well-known Wigner tunnelling-factor which diverges at the cross-over temperature between deep and shallow tunnelling. Here, we show how to remove this divergence by integrating numerically over the two softest ring-polymer normal modes. This results in a modified Wigner correction factor involving a one-dimensional integral evaluated along a straight line on the potential energy surface. Comparisons with accurate quantum calculations indicate that the newly derived correction factor gives realistic estimates of quantum rate coefficients in the shallow-tunnelling regime.

Uniform versus Nonuniform Axial Power Distribution in Rod Bundle CHF Experiments

Rod bundle experiments with axially uniform and nonuniform heat fluxes are examined to explore the potential limitations of using uniform rod bundle CHF data for CHF correlation development of light water reactors with nonuniform axial power distribution (APD). The case of upstream burnout is presented as an example of unique phenomena associated with nonuniform rod bundle CHF experiments. It is a result from combined effect of axial nonuniform power shape and different interchannel mixing mechanisms. In addition, several key parameters are investigated with respect to their potential impacts on the thermal-hydraulic behaviors between rod bundles with uniform and nonuniform APDs. This type of misrepresentation cannot be amended or compensated through the use of correction factors due to the lack of critical information in the uniform rod bundle CHF testing as well as the fundamental difference in the underlining driving mechanisms. Other potential issues involved with the use of uniform rod bundle CHF data for nonuniform APD system applications also present strong evidence concerning the limitations and inadequacy of using uniform rod bundle CHF data for the correlation, prediction, and design limit calculation for safety analysis.

Essential oil composition of Reseda lutea from Iran

The genus Reseda is one of the herbs in the Resedaceae family [1]. In Iran, this genus is represented by 10 species, including Reseda lutea L. [1]. R. lutea, known as yellow mignonette or wild mignonette, has economic importance. It has been used as a medicinal plant, in salads, in the carpet and rug industry as a source of natural dye, in animal husbandry as a grazing plant and stock food source, in honey production, in combating erosion, and as a primary succession plant [2, 3]. On the other hand, the species is regarded as a weed in some parts of the world, especially in cultivated areas [4]. Sener et al. also reported that the extract of R. lutea possesses pharmacological activities against insects, brine shrimp, nematodes, and microorganisms [5]. Likewise, Nakhatov et al. isolated some alkaloids from the epigeal parts of R. lutea [6]. In this study, due to its economic importance and wide distribution in Iran, the essential oil composition of R. lutea was investigated for the first time. The essential oil components obtained from the aerial part of R. lutea are listed in Table 1, where the percentage and Kovats indices of the components are given. As shown in Table 1, analysis of the aerial parts oil of R. lutea resulted in the identification of 42 constituents, representing 95.6% of the oil. The main constituents of the oil were benzonitrile (17.9%), (Z)-phytol (13.0%), n-heptacosane (7.5%) -ionone (6.2%), hexahydrofarnesyl acetone (5.1%), and palmitic acid (4.6%). The aerial parts of R. lutea were collected during the flowering stage in the Alamut region, province of Qazvin, Iran, in May 2010. Voucher specimens (No. 8273) have been deposited at the Herbarium of the Research Institute of Forests and Rangelands (TARI), Tehran, Iran. The aerial parts (133.0 g) of the plant were subjected to hydrodistillation using a Clevenger-type apparatus and extracted by diethyl ether for 3 hrs. After decanting, drying over anhydrous sodium sulfate, and evaporating of the solvent, the corresponding yellow colored oil was recovered in a yield of 0.05% w/w. GC-FID analysis was performed on a Shimadzu 15A gas chromatograph equipped with a split/splitless (ratio 1:30) injector (250 C) and a flame ionization detector (250 C). Nitrogen was used as the carrier gas (1 mL/min), together with a DB-5 capillary column (50 m 0.2 mm, film thickness 0.32 m). The column was kept at 60 C for 3 min and then heated to 220 C with a 5 C/min rate and kept constant at 220 C for 5 min. Relative percentage amounts were calculated from the peak area using a Shimadzu C-R4A chromatopac data processor without the use of correction factors. GC-MS analysis was performed using a HewlettPackard 5973 with an HP-5MS column (30 m 0.25 mm, film thickness 0.25 m). The column temperature was kept at 60 C for 3 min and programmed to 220 C at a rate of 5 C/min and kept constant at 220 C for 5 min. The flow rate of helium as carrier gas was 1 mL/min. MS were taken at 70 eV, mass range 30 to 350 amu, and scan time 2 scans/sec. The compounds were identified by comparison of the Kovats indexonan HP-5MS column with those reported in [7] and the NIST library, and by comparison of their mass spectra with either the Wiley library or with published mass spectra [7–9]. The Kovats indices for all the components were determined according to the Van Den Dool method using n-alkanes as standards [10].

SU-E-I-07: The Effect of Different Beam Filters On the KV CBCT Image Dose Response Curves of NanoDot OSL Dosimeters

Purpose: To evaluate the effect of different beam filters on the dose response curves of nanoDot OSL dosimeters at kV CBCT energy. Methods: The InLight™ OSL dosimetry system (Landauer,Inc., Glenwood, IL, USA) consisting of nanoDot dosimeters and MicroStar reader was calibrated using the X-ray Volume Imager (XVI) mounted on the Elekta Synergy (Elekta, Crawley, UK) linac and the On Board Imager(OBI) mounted on the Varian True Beam (Varian Medical systems, Palo Alto, CA) linac. Doses ranged between 0 and 12 cGy were delivered to nanoDot OSLDs on 5 cm thick PMMA slab using 120kVp F0(no filter) and F1(Bowtie filter)XVI CBCT beams, 125 kVp half fan (HF) and full fan (FF) OBI beams. Dose points were correlated to absolute air kerma levels measured in air using the 0.6 cc Farmer ionization chamber and converted to dose in water at the phantom surface according to AAPM TG61. Results: Dose response curves for all imaging settings were linear. The dose response curves for the 120 kVp F0 and F1 VXI CBCT beams differed by 8 to 9 %. The dose response curves for the 125 kVp FF and HF OBI CBCT beams also differed by 7 to 8 %. These results suggest that nanoDot dosimeters are sensitive not only to differences in kVp of the beam but also to differences in spectra resulted from the use of different filters. Conclusion: Dose response curves of nanoDot OSLDs for photon beams of same kVp but filtered with different filters are different. Hence,the use of correction factors (based solely on differences in the response of the OSLDs at different kVps) to allow the reading of the MicroStar reader to be converted from one set of reference condition to another is not sufficient to ensure accurate estimation of measured doses.It is important to create dose response curve at every irradiation setting. This project is funded, in part, under a grant with the Pennsylvania Department of Health. The Department specifically declaims responsibility for any analyses, interpretations or conclusions

TU‐C‐108‐03: Beyond the Alfonso Formalism for Small Field Dosimetry: A New Metric, New Detectors, Or Both?

Purpose: The Alfonso et al formalism recommends the use of correction factors to report point‐doses under small field conditions. This work considers whether the requirement for small field point‐dose correction factors may be eliminated via (i) an extension of the Alfonso formalism based upon a new integral dose metric and/or (ii) novel mass‐density‐compensation‐based detector design strategies. Methods: We have developed a mathematical definition of dose area product (DAP) for small detectors used to integrate dose inside and outside the boundaries of a radiation field. Here we test the resulting theorem of ‘inter‐detector DAP invariance’ directly using Monte Carlo (MC) simulations and indirectly using linac experiments. Additionally, MC simulations are used to explore the possibility of mass‐density‐based compensation for a series of hypothetical, spherical detectors (of diameter 0.1 cm and 0.2 cm). Cavities of greater than unit mass‐density are modified using shells of less than unit mass‐density and vice‐versa. A similar MC‐based methodology is used to investigate the potential of modifying the designs of two real radiotherapy detectors: PTW PinPoint 31006 and PTW Diamond 60003. Results: The results demonstrate that the application of conventional (detector‐specific) large‐field calibration factors leads to accurate measurement of the dose area product (integral dose) when small dosimeters are used to integrate dose over enough positions. The simulations of modified detectors also indicate that, if a detector cavity is small enough, it should also be possible to use mass‐density‐compensation to manipulate the small to large field detector response ratio so that it matches that obtained for a “point‐like” water‐structure (under a variety of irradiation conditions). Conclusion: This work presents two novel methods by which the requirement for small‐field point‐dose correction factors may be reduced or eliminated: (i) an integral‐dose‐based reformulation of the Alfonso formulation and (ii) a detector re‐design strategy based upon mass‐density compensation.

Essential oil composition of Anchusa italica from Iran

The family Boraginaceae consists of about 100 genera and 2000 species distributed in the temperate zone, especially in the Mediterranean and tropical regions [1]. Five species of the genus Anchusa (Boraginaceae) are found in Iran [2]. The Borage plants are one of the most important folk medicine plants in Iran. They are of value in treating common cold symptoms, depression and stress, and are anti-inflammatory and antibacterial [3, 4]. Anchusa italica Retz. plants, named “Gav zaban” in Persian, grows in the mountains of some provinces of Iran. The people of that area use the leaves and flowers of A. italica specifically to treat flu symptoms. The anti-influenza activity of alcoholic and aqueous extracts of A. italica has been investigated in a previous report [3]. The findings of this study indicated that A. italica exhibited activity against the influenza virus. In other research, a qualitative phytochemical analysis of 55 Iranian plants, especially A. italica, has been performed for the presence of alkaloids, tannins, saponins, and flavonoids [4]. The results showed the existence of alkaloids, saponins, and flavonoids. The extract of A. italica plant has also been used as an emollient. Likewise, poly[3-(3,4-dihydroxyphenyl)glyceric acid] from A. italica roots has been reported [5]. The lipids and lipophilic components of seeds of three Boraginaceae species, including A. italica, have also been studied [6]. The seed oil of A. italica contains significant quantities of -6 and -3-octadecatrionic acids. In this study, the essential oil composition of A. italica from Iran was investigated for the first time. The essential oil constituents from the aerial part of A. italica are listed in Table 1, in which the percentages and Kovats indices of the components are given. As shown in Table 1, the oil of the aerial parts of A. italica consist of 34 compounds, representing 91.4% of the oil. The main constituents of the oil were diisobutyl phthalate (14.6%), dibutyl phthalate (9.0%), and hexahydrofarnesylacetone (8.1%). The aerial parts of A. italica were collected during the flowering stage in the Alamut region, Province of Qazvin, Iran, in May 2010. Voucher specimens (No. 88274) have been deposited at the Herbarium of the Research Institute of Forests and Rangelands (TARI), Tehran, Iran. The aerial parts (150.0 g) of A. italica were subjected to water distillation using a Clevenger-type apparatus and extracted by diethyl ether for 3 h. After decanting, drying over anhydrous sodium sulfate, and evaporating the solvent, we recovered the corresponding yellowish colored oil in a yield of 0.02% w/w. GC-FID analysis was performed on a Shimadzu 15A gas chromatograph with a split/splitless (ratio 1:30), injector (250 C) and a flame ionization detector (250 C); nitrogen was used as the carrier gas (1 mL/min). A DB-5 capillary column (50 m 0.2 mm, film thickness 0.32 m) was used. The column was kept at 60 C for 3 min, then heated to 220 C with a 5 C/min rate and kept constant at 220 C for 5 min. Relative percentage amounts were calculated from the peak area using a Shimadzu C-R4A chromatopac data processor without the use of correction factors. GC-MS analysis was performed using a Hewlett-Packard 5973 with an HP-5MS column (30 m 0.25 mm, film thickness 0.25 m). The column temperature was kept at 60 C for 3 min and programmed to 220 C at a rate of 5 C/min and kept constant at 220 C for 5 min. The flow rate of helium as carrier gas was 1 mL/min. MS were taken at 70 eV, mass range 30 to 350 amu, and scan time 2 scans/sec.

Warum die rheumatoide Arthritis den Kardiologen braucht

Rheumatoid arthritis (RA) is associated with a shortened life expectancy. Most premature deaths are caused by cardiovascular (CV) events; therefore it is of importance to consider the increased CV risk when treating RA patients. Traditional CV risk factors cannot fully explain the increased risk but the common understanding is that inflammation significantly contributes to the excess risk observed. Without the use of correction factors commonly used risk calculators underestimate the true CV risk in RA patients. Methotrexate and TNF inhibitors appear to be beneficial with regard to the CV risk. To date there are only few recommendations for interventions in the CV system of RA patients which go beyond those formulated for the general population. The present manuscript summarizes the published evidence concerning the increased CV risk in RA patients.

Ferrite content measurements in S32101 lean duplex stainless steel and its welded joints

Due to their mechanical and plastic properties as well as unique corrosion resistance, two-phase lean duplex steels are increasingly popular in industrial applications e.g. for building waterside fixtures, ships, pipelines or containers. A critical factor of welded joints made of such steels is the balance between austenite and ferrite; the latter being measured by a special device called ferritoscope. The article contains the results of tests focused on measurements of ferrite content in S32101 lean duplex steel and its welded joints. The text also presents the impact of such factors as test sample thickness or shape and condition of measurement surface etc. on test results. In addition, this paper discusses the use of correction factors, describes problems arising during measurements of ferrite in welded joints and presents manners of the elimination of the latter. The conducted tests revealed that MAG method welding parameters affect the content of ferrite in butt welded joints produced with S32101 lean duplex steel.

On the Fabric of the Human Body

With the publication of De Humani Corporis Fabrica in 1543, Andreas Vesalius bestowed some of the greatest advancements of anatomic understanding since the time of Galen, correcting major misconceptions, eg, the notion that the great vessels originated in the liver. It took nearly 1500 years for this evolution in anatomic thinking to transpire. It is simultaneously humbling and invigorating to note that nearly 500 years later the study of anatomy is just as lively and full of evolutionary change. In this issue of Circulation , Kajstura and colleagues1 definitively dispatch the dogma of the heart as a terminally differentiated organ, a concept formulated a mere 40 years earlier, and in so doing completely recalibrate our understanding of cellular homeostasis in the healthy and diseased heart. Article see p 1869 In 1973, Radovan Zak2 of the University of Chicago stated unequivocally, “The adult heart enlarges only by enlargement of its component muscle cells. Division of ventricular muscle cells in mammals is not activated after cardiac injury.” This conclusion was largely consistent with work by Linzbach3 in 1960; however, in this earlier comprehensive histological analysis, there was a suggestion that under certain circumstances the number of cardiac muscle fibers might increase. The Anversa laboratory began suggesting the possibility of cardiomyocyte proliferation in 1980,4 and by 1992, the group began to document clear evidence for replication of cardiac muscle cells in response to physiological stress and myocardial injury in both experimental models5–8 and humans.9,10 These early works included such bold statements as “the recognition of factors controlling myocyte proliferation may provide a new approach for regeneration of damaged and lost myocardium, a phenomenon considered impossible for several decades.” Although some recognized the power and implications of these observations, the Pfeffers' call for open-mindedness …

Poster - Thur Eve - 46: The upcoming international code of practice for small static photon field dosimetry.

The increased use of small photon fields in stereotactic and intensity-modulated radiotherapy has raised the need for standardizing the dosimetry of such fields using procedures consistent with those for conventional radiotherapy. An international working group, established by the IAEA in collaboration with AAPM and IPEM, is finalising a Code of Practice for the dosimetry of small static photon fields. Procedures for reference dosimetry in nonstandard machine specific reference (msr) fields are provided following the formalism of Alfonso et al. (Med. Phys. 35: 5179; 2008). Reference dosimetry using ionization chambers in machines that cannot establish a conventional 10 cm × 10 cm reference field is based on either a direct calibration in the msr field traceable to primary standards, a calibration in a reference field and a generic correction factor or the product of a correction factor for a virtual reference field and a correction factor for the difference between the msr and virtual fields. For the latter method, procedures are provided for determining the beam quality in non-reference conditions. For the measurement of field output factors in small fields, procedures for connecting large field measurements using ionization chambers to small field measurements using high-resolution detectors such as diodes, diamond, liquid ion chambers, organic scintillators and radiochromic film are given. The Code of Practice also presents consensus data on correction factors for use in conjunction with measured, detector-specific output factors. Further research to determine missing data according to the proposed framework will be strongly encouraged by publication of this document.

Small field diode correction factors derived using an air core fibre optic scintillation dosimeter and EBT2 film

There is no commercially available real-time dosimeter that can accurately measure output factors for field sizes down to 4 mm without the use of correction factors. Silicon diode detectors are commonly used but are not dosimetrically water equivalent, resulting in energy dependence and fluence perturbation. In contrast, plastic scintillators are nearly dosimetrically water equivalent. A fibre optic dosimeter (FOD) with a 0.8 mm3 plastic scintillator coupled to an air core light guide was used to measure the output factors for Novalis/BrainLab stereotactic cones of diameter 4–30 mm and Novalis MLC fields of width 5–100 mm. The FOD data matched the output factors measured by a 0.125 cm3 Semiflex ion chamber for the MLC fields above 30 mm and those measured with the EBT2 radiochromic film for the cones and MLC fields below 30 mm. Relative detector readings were obtained with four diode types (IBA SFD, EFD, PFD, PTW 60012) for the same fields. Empirical diode correction factors were determined by taking the ratio of FOD output factors to diode relative detector readings. The diodes were found to over-respond by 3%–16% for the smallest field. There was good agreement between different diodes of the same model number.

Quantification of Ligand PET Studies using a Reference Region with a Displaceable Fraction: Application to Occupancy Studies with [11C]-DASB as an Example

This paper aims to build novel methodology for the use of a reference region with specific binding for the quantification of brain studies with radioligands and positron emission tomography (PET). In particular: (1) we introduce a definition of binding potential BP(D)=DVR-1 where DVR is the volume of distribution relative to a reference tissue that contains ligand in specifically bound form, (2) we validate a numerical methodology, rank-shaping regularization of exponential spectral analysis (RS-ESA), for the calculation of BP(D) that can cope with a reference region with specific bound ligand, (3) we demonstrate the use of RS-ESA for the accurate estimation of drug occupancies with the use of correction factors to account for the specific binding in the reference. [(11)C]-DASB with cerebellum as a reference was chosen as an example to validate the methodology. Two data sets were used; four normal subjects scanned after infusion of citalopram or placebo and further six test-retest data sets. In the drug occupancy study, the use of RS-ESA with cerebellar input plus corrections produced estimates of occupancy very close the ones obtained with plasma input. Test-retest results demonstrated a tight linear relationship between BP(D) calculated either with plasma or with a reference input and high reproducibility.

SU-E-T-172: Output Factors of a Cyberknife System : Comparison Between Measurements and Monte Carlo Calculations

Purpose: Small photon beams used in radiotherapy are characterised by high dose gradients and a lack of lateral electron equilibrium. Thus, the measurement of output factors (OF) of these beams is problematic and OF measurements with different detectors for similar irradiation conditions can lead to a deviation up to 30% (Derreumaux et al., 2010). The aim of this study is to accurately determine the OF of a Cyberknife system thanks to measurements and Monte Carlo data. Methods: OF were measured on a Cyberknife for the 5, 7.5, 10, 20 and 60 mm diameter field sizes using active detectors (high resolution diodes (IBA SFD, PTW 60016, PTW 60017, Sun Nuclear EDGE), PTW 31014 Pinpoint chamber and PTW 60003 natural diamond) and passive dosemeters (EBT2 radiochromic films and TLD micro‐cubes). Correction factors for diodes (EDGE, PTW 60016, PTW 60017) and for the PTW 31014 chamber were calculated thanks to a recent methodology based on Monte Carlo data (Francescon et al., 2008 and 2009). The Cyberknife used in this study was modelled with Penelope and MCNPXMonte Carlo codes in order to determine the “true” OF. Results: For the smallest field size, a deviation of nearly 20% was observed between the values of the OF measured with the different detectors. The agreement between the passive dosemeters was better than 2%. After correction for diodes and for the chamber, the OF obtained with these active detectors agreed within 2% with the passive OF measurements. Conclusions: This study is encouraging concerning the determination of the output factors of the Cyberknife system. For the active detectors, the use of correction factors improves the accuracy in the OF measurements. The results obtained with the passive dosemeters in this study as well as in another study performed on a Novalis system (Bassinet et al., 2011) are promising.

A new method to compare vehicle emissions measured by remote sensing and laboratory testing: High-emitters and potential implications for emission inventories

A new method is presented which is designed to investigate whether laboratory test data used in the development of vehicle emission models adequately reflects emission distributions, and in particular the influence of high-emitting vehicles. The method includes the computation of a ‘high-emitter’ or ‘emission distribution’ correction factor for use in emission inventories. In order to make a valid comparison we control for a number of factors such as vehicle technology, measurement technique and driving conditions and use a variable called ‘Pollution Index’ (g/kg). Our investigation into one vehicle class has shown that laboratory and remote sensing data are substantially different for CO, HC and NO x emissions, both in terms of their distributions as well as in their mean and 99-percentile values. Given that the remote sensing data has larger mean values for these pollutants, the analysis suggests that high-emitting vehicles may not be adequately captured in the laboratory test data. The paper presents two different methods for the computation of weighted correction factors for use in emission inventories based on laboratory test data: one using mean values for six ‘power bins’ and one using multivariate regression functions. The computed correction factors are substantial leading to an increase for laboratory-based emission factors with a factor of 1.7–1.9 for CO, 1.3–1.6 for HC and 1.4–1.7 for NO x (actual value depending on the method). However, it also clear that there are points that require further examination before these correction factors should be applied. One important step will be to include a comparison with other types of validation studies such as tunnel studies and near-road air quality assessments to examine if these correction factors are confirmed. If so, we would recommend using the correction factors in emission inventories for motor vehicles.

Direct and indirect strain measurement during low cycle fatigue of metals at elevated temperature

Current testing practices in low cycle fatigue (LCF) determinations at elevated temperature recommend the use of side-contacting extensometers or other direct methods for the measurement of strain. In many cases (e.g., when an environmental chamber surrounds the test specimen) this is not possible and resort must be had to indirect methods, which require a correction factor depending on the cyclic stress– strain response of the material. By mounting direct and indirect extensometers on the specimen and grip assembly of the testing machine, direct comparisons were made on the output strain signals during LCF tests on alloys 316, Nimonic 90 and IN718 at temperatures in the range 600 – 900°C. Agreement for plastic strain range was in general good, the remote method however requiring an independent value of the elastic modulus for determination of total strain range. Typical uncertainties in these values are discussed. All comparisons were made under continuous cycling conditions and a correction factor for use under creep-fatigue conditions is suggested.