Avoiding biased estimates of dose when nothing is known about the time of intake

A common problem in internal dosimetry occurs in routine monitoring, when it is required to estimate an intake from a measurement made at the end of a monitoring interval, and the time of intake is unknown. ICRP suggests that it should be assumed that the intake occurred in the middle of the monitoring period. However, it has been shown that this will, in the long-term, lead to biased estimates of a worker's intake and dose. In order to overcome this biasing, the United States Department of Energy (USDOE) recommends a different method based on calculating the intakes for all possible intake times in the interval and then taking an arithmetic average. In a recent paper, it has been shown that both the ICRP and USDOE methods were biased and that the only unbiased estimator of the true intake was obtained by assuming a constant chronic intake throughout the monitoring interval. In all of the analyses carried out to date on this 'Constant Chronic' method, it was assumed that the measurements were exact. In this paper, the effects of assuming either normally or log-normally distributed measurement errors are explored, and the effect on the bias of the intake estimate is investigated.     

光码盘测电机转速精度分析

本文根据光码盘测速的基本原理，对电机转速进行了测量；并根据测量结果分析讨论了其测速误差，指出了该方法的实用价值。     

低温流体输送过程中采用贴壁式温度传感器测温时的传热分析

低温流体的输送广泛采用发泡绝热管道和真空绝热管道,采用贴壁式热电阻温度传感器测量管内流体温度时,影响测量精度的因素很多。运用一维稳态径向传热模型和热阻网络分析了发泡绝热结构和真空绝热结构下的热阻组成及热平衡关系,得到了温度传感器所测的温度与管道流体温度以及外界环境温度之间的计算关系式,并定量分析了接触热阻和真空度对输送液氮管道的温度传感器所测温度的影响。     

Preparation and evaluation of an experimental luting glass ionomer cement to be used in dentistry

The aim of this paper is to compare the fluoride-releasing and mechanical properties of an experimental luting glass ionomer cement, which has a modified composition and a commercial luting cement. The experimental powder was obtained by sol–gel process and then, it was used to prepare the experimental cements. The properties of cement pastes, such as setting time and working time, microhardness and diametral tensile strength were determined. Fluoride release from GICs was evaluated at time intervals of 1, 7, 14, 21 and 28 days in deionized water. Atomic force microscopy (AFM) analyses showed that the surface of the experimental cements is more homogeneous than commercial GICs. The mechanical properties and the measure of liberation of fluoride of the two cements were influenced by ratio powder:liquid and chemical composition of the precursor powders. Experimental cements released less fluoride than commercial cements. However, this liberation was more constant during the analyzed period. Thus, the results obtained in this study indicated that the composition of the experimental powder modified by the niobium can lead the formation of the polysalt matrix with good mechanical properties. In other words, we can say that experimental powder offered considerable promise for exploitation in dental field.     

On the normalization method in two-dimensional correlation spectra when concentration is used as a perturbation parameter

Data pretreatment is of importance in two-dimensional (2D) correlation analysis when composition is used as a perturbation parameter. For composition-oriented studies, different normalization methods based on both external parameters (i.e., concentration) and internal parameters (i.e., absorbance from individual components) have been compared. It was found that when there is no overlapping between absorption bands of interest, no normalization is needed for data pretreatment. When overlapped bands must be used for 2D correlation analysis, the mean-centered normalization method could be used to obtain correct signs in synchronous spectra for a transformation process in the specific form of A-->kC. The intensity of the 2D spectrum, however, may not accurately reflect quantitative information of the overall extent of spectral intensity variation observed during experiments.     

Estimated collective effective dose to the population from X-ray and nuclear medicine examinations in Finland

The collective effective doses to the population from X-ray and nuclear medicine (NM) examinations in Finland in 2008 and 2009, respectively, were estimated. The estimated collective effective dose per inhabitant was 0.45 mSv from X-ray examinations and 0.03 mSv from NM examinations. The collective effective doses per inhabitant have not changed substantially during the last 10 y. However, proportional dose due to CT examinations has increased from 50 % in 2005 to 58 % in 2009 of the total collective effective dose from all X-ray examinations and proportional dose of PET examinations from 7 to 13 % of the total collective effective dose from NM examinations. The collective effective dose from conventional plain radiography was over 20 % higher when estimated using the new (ICRP 103) tissue weighting factors than that obtained using the old (ICRP 60) tissue weighting factors.     

Estimation of regression coefficients subject to exact linear restrictions when some observations are missing and quadratic error balanced loss function is used

This article considers a linear regression model when a set of exact linear restrictions binding the coefficients is available and some observations on the study variable are missing. Estimators for the vectors of regression coefficients are presented and their superiority properties with respect to the criteria of the variance covariance matrix and the risk under balanced loss functions are analyzed.     

Gamma activity and radiation dose in concrete building blocks used for construction of dwellings in Jos, Nigeria

Radioactivity concentrations of concrete building block samples made and used in Jos, Nigeria, were determined using a gamma ray spectrometry method. The mean values of the radioactivity concentrations were calculated as 66, 126 and 589 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The radium equivalent activities ranged between 131 and 712 Bq kg(-1), with six of the samples exceeding the UNSCEAR reported maximum permissible level of 370 Bq kg(-1). The mean radium equivalent activity (292 Bq kg(-1)) is higher than the values available in the literature for some countries by factors ranging between 2 and 5, a situation that can be traced to the practice of sourcing sand aggregates from mining sites. The indoor annual effective dose for a dwelling of dimension 3.6 x 3.6 x 3.0 m(3) was calculated as 0.81 mSv.     

Determination of the position of the center of a laser beam when the dynamic range of the matrix receiver is exceeded

The effect of saturation of the matrix receiver when determining the coordinates of the center of a laser beam by the weighting method is considered. The dependence of the measurement accuracy on the dimensions of the beam and the number of saturated pixels in the photoreceiver matrix is investigated. Numerical modeling of the output signal is carried out. The model calculations are compared with experimental results.     

LISREL: an Alternative to MANOVA and Principal Components in Designed Experiments when the Response is Multidimensional

In designed industrial experiments, the response is often multidimensional. There may be different responses and/or responses of equal kind that are correlated. The usual analysis is by a separate ANOVA (Analysis of Variance) for each response or by MANOVA (Multivariate Analysis of Variance) of all responses simultaneously. However, ANOVA/MANOVA techniques do not fully address the multivariate situation. In this paper, MANOVA, principal components analysis, and LISREL (Linear Structural Relationship), are applied to the results of an experiment concerning high‐precision breathing apparatus to be used by firefighters. The experimental design is a 2^5?1_V, having seven response measurements and five replicates. We address both establishing a cause–effect relation, and the estimation of the impact size. The multivariate techniques strongly reduce the number of tests to be performed. MANOVA and LISREL provide standard errors of every parameter of interest. The LISREL model is very flexible in model building and parameter testing, and it gives enhanced insight into the experimental results. Its use in industrial experiments has not been fully exploited; one possible explanation is that such experiments often have too few runs. Copyright © 2005 John Wiley & Sons, Ltd.     

Determination of absorbed dose in the vicinity of a neutron source

A computational method is presented that transfers the spectral neutron fluence from the measuring position to a reference point in a biological sample. The method is applied to the determination of the absorbed dose in adult blood irradiated with monoenergetic neutrons of 0.035 and 14.8 MeV.     

Examination of ionic liquids and their interaction with molecules, when used as stationary phases in gas chromatography.

Stable room-temperature ionic liquids (RTILs) have been used as novel reaction solvents. They can solubilize complex polar molecules such as cyclodextrins and glycopeptides. Their wetting ability and viscosity allow them to be coated onto fused silica capillaries. Thus, 1-butyl-3-methylimidazolium hexafluorophosphate and the analogous chloride salt can be used as stationary phases for gas chromatography (GC). Using inverse GC, one can examine the nature of these ionic liquids via their interactions with a variety of compounds. The Rohrschneider-McReynolds constants were determined for both ionic liquids and a popular commercial polysiloxane stationary phase. Ionic liquid stationary phases seem to have a dual nature. They appear to act as a low-polarity stationary phase to nonpolar compounds. However, molecules with strong proton donor groups, in particular, are tenaciously retained. The nature of the anion can have a significant effect on both the solubilizing ability and the selectivity of ionic liquid stationary phases. It appears that the unusual properties of ionic liquids could make them beneficial in many areas of separation science.     

Induction of chromosome aberrations is non-linear within the low dose region and depends on dose rate

The low dose region was evaluated for meristem cells of spring barley. A study of the cytogenetic damage in the low dose range was carried out to determine the genuine shape of the dose curve. The relationship between the frequency of aberrant cells and the absorbed dose is shown to be non-linear with a site at low doses within which the cytogenetic damage exceeds the control level significantly and does not depend on dose value. Within the tested exposure region, the aberrant cell frequency is found to decrease with increasing dose rate, but the shape of the dose curve remained invariable. The piecewise linear model fits the experimental data much better than the linear one.     

Determination of parameters used to prevent ignition of stored materials and to protect against explosions in food industries

There are always risks associated with silos when the stored material has been characterized as prone to self-ignition or explosion. Further research focused on the characterization of agricultural materials stored in silos is needed due to the lack of data found in the literature. The aim of this study was to determine the ignitability and explosive parameters of several agricultural products commonly stored in silos in order to assess the risk of ignition and dust explosion. Minimum Ignition Temperature, with dust forming a cloud and deposited in a layer, Lower Explosive Limit, Minimum Ignition Energy, Maximum Explosion Pressure and Maximum Explosion Pressure Rise were determined for seven agricultural materials: icing sugar, maize, wheat and barley grain dust, alfalfa, bread-making wheat and soybean dust. Following characterization, these were found to be prone to producing self-ignition when stored in silos under certain conditions.     

Estimation of uncertainties on dose calculations of the 99mTc-MDP-injected patients in nuclear medicine

The internal exposures of the patients in nuclear medicine can be calculated based on the equations and data in ICRP Publications 53 and 80. Physical and biological parameters are used for the calculation, and both include uncertainties. Physical parameters can be considered as more precise than biological parameters, so that uncertainties originated from biological parameters are more important. Absorbed fractions (AFs) have been calculated by Monte-Carlo method using medical internal radiation dose (MIRD)-type mathematical phantoms. They depend on the shapes and sizes of the phantoms used in simulations. For estimating shape- and size-related uncertainties, AFs of pairs of source regions and target tissues of the patient-injected 99mTc-MDP were calculated by using EGS4 codes and a voxel phantom of Japanese male. By simply resizing the voxels of the phantom, the dependencies of size for AFs were calculated, and the uncertainties caused by the cumulated activities in source regions were also estimated by assuming these parameters distributions as Gaussian.     

Study to observe the applicability of the adsorption isotherms used for the adsorption of medicine organics onto activated carbon

In the present study, the activated carbon was prepared by chemically activating polymer waste under the influence of potassium hydroxide (KOH). The pore properties including the Brunauer–Emmett–Teller (BET) surface area, the volume of the pore, its size distribution, and average diameter were also characterized herein. The present study also evaluated the ability of the activated carbon to remove naproxen sodium, tannic acid, and caffeine from aqueous solutions through a process of adsorption. The equilibrium isotherms employed for the adsorption of drug organics onto the activated carbon were measured experimentally. The obtained results were analyzed by employing the Redlich–Peterson, Dubinin–Redushkevich, Temkin, Frumkin, Halsey, and Henderson equations by using a linearized correlation coefficient and statistically at varied temperatures. The models and the isotherm constants were evaluated based on the changes in the temperature. Among all, the Redlich–Peterson equation was determined to best represent the equilibrium data for the adsorption of naproxen sodium, and caffeine onto the activated carbon.