An emergency radiobioassay method for 226Ra in human urine samples

A new radioanalytical method was developed for rapid determination of (226)Ra in human urine samples. The method is based on organic removal and decolourisation of a urine sample by a polymeric (acrylic ester) solid phase sorbent material followed by extraction and preconcentration of (226)Ra in an organic solvent using a dispersive liquid-liquid microextraction technique. Radiometric measurement of (226)Ra was carried out using a liquid scintillation counting instrument. The minimum detectable activity for the method (0.15 Bq l(-1)) is lower than the required sensitivity of 0.2 Bq l(-1) for (226)Ra in human urine samples as defined in the requirements for radiation emergency bioassay techniques for the public and first responders based on the dose threshold for possible medical attention recommended by the International Commission on Radiological Protection (ICRP). The accuracy (expressed as relative bias, B(r)) and repeatability of the method (expressed as relative precision, S(B)) evaluated at the reference level (2 Bq l(-1)) were found to be -4.5 and 2.6 %, respectively. The sample turnaround time was <5 h for a single urine sample and <20 h for a batch of six urine samples. With the fast sample turnaround time combined with the potential to carry out the analysis in a field deployable mobile laboratory, the newly developed method can be used for emergency radiobioassay of (226)Ra in human urine samples following a radiological or nuclear accident.     

An improved SRC method based on virtual samples for face recognition

The sparse representation classifier (SRC) performs classification by evaluating which class leads to the minimum representation error. However, in real world, the number of available training samples is limited due to noise interference, training samples cannot accurately represent the test sample linearly. Therefore, in this paper, we first produce virtual samples by exploiting original training samples at the aim of increasing the number of training samples. Then, we take the intra-class difference as data representation of partial noise, and utilize the intra-class differences and training samples simultaneously to represent the test sample in a linear way according to the theory of SRC algorithm. Using weighted score level fusion, the respective representation scores of the virtual samples and the original training samples are fused together to obtain the final classification results. The experimental results on multiple face databases show that our proposed method has a very satisfactory classification performance.     

Rapid determination of 226Ra in urine samples

A new radiochemical separation method has been developed for rapid analysis of (226)Ra in urine samples. In this method, radium is separated from urine matrix using cation and anion exchange column chromatography. A (224)Ra tracer is added, together with its parent in the (228)Th standard, for chemical recovery correction. After separation, the sample is precipitated with hydrous titanium oxide and then prepared for counting by creating a thin-layer counting source using BaSO(4) micro-precipitation. The radium isotopes are then counted by alpha spectrometry. Replicate spike and blank samples were analysed for validation of the procedure. The detection limit was determined to be 0.22 Bq l(-1) with 4 h of counting for 20 ml of urine sample. Using this method, the results can be reported within an 8 h turn-around time. This method is suitable for quick dose assessment of (226)Ra exposure following a radiation emergency.     

An improved method for the determination of saturationcharacteristics of switched reluctance motors

Experimental determination of magnetization characteristics of switched reluctance motors (SRMs) is quite important in their accurate performance prediction. Over the last decade, various experimental procedures have been used to obtain these characteristics. Every evolved new method has its own limitations and constraints. This paper describes an improved, simple and cost effective experimental procedure and an equally simple post-experimental data processing to obtain the flux-linkage-current curves at varying rotor positions of the SRM. The experimental results on a 4 kW, four-phase, 8/6 pole SRMs show the effectiveness of the method and the results compare well with the previously results compare well with the previously published results of similar and higher rating SRM's     

Low-level (PPB) determination of cisplatin in cleaning validation (rinse water) samples. I. An atomic absorption spectrophotometric method

Suitable analytical methods are required for quantitative determination of trace levels of ingredients in samples obtained for purposes of cleaning validation. We describe below an atomic absorption method for the quantitation of cisplatin, an antineoplastic agent, in aqueous samples. Cisplatin was reacted with diethyldithiocarbamic acid (DDTC), sodium salt, to yield a platinum-DDTC (Pt-DDTC) complex. The Pt-DDTC chelate was extracted into methylene chloride, the extract was mixed with acetonitrile, and the platinum content was then determined using a Zeeman atomic absorption (AA) spectrophotometer. The extraction conditions and AA experimental conditions were set up such that the detection level could be extended to 0.5 ng/ml. Reproducible results were obtained at a quantitative working standard concentration of 5 PPB. The absorbance response was found to be a linear function of cisplatin concentration in the region between 0.5 PPB and 20 PPB, which is about 10% to 400% of the target analyte concentration of 5 PPB. The target analyte concentration was set at 5 PPB such that it was at least 10 times the detection limit of about 0.5 PPB.     

An inverse method for material parameters determination of titanium samples under tensile loading

Different approaches used for the simulation of woven reinforcement forming are investigated. Especially several methods based on finite element approximation are presented. Some are based on continuous modelling, while others, called discrete or mesoscopic approaches, model the components of the fabric. A semi discrete finite element made of woven unit cells under biaxial tension and in-plane shear is detailed. In continuous approaches, the difficulty lies in the necessity to take the strong specificity of the fibrous material into account. The yarn directions must be strictly followed during the large strains of the fabric. This is the main goal of the non-orthogonal model and of the hypoelastic constitutive model based on the yarn rotation presented in this paper. In the case of discrete and semi-discrete approaches the directions of the yarns are “naturally” followed because the yarns are modeled. Explicitly, however, modeling each component at the mesoscopic scale can lead to high numerical cost.     

Membrane optode for mercury(II) determination in aqueous samples

A color changeable optode for Hg(II) was prepared by the immobilization of a dye 4-(2-pyridylazo)resorcinol (PAR) and a liquid ion-exchanger trioctylmethylammonium chloride (Aliquat-336) in the tri-(2-ethylhexyl) phosphate plasticized cellulose triacetate matrix. Hg(II) and CH₃Hg⁺ from aqueous samples could be quantitatively preconcentrated in this transparent optode producing a distinct color change (λ_max = 520 nm) within 5 min equilibration time in bicarbonate aqueous medium or 30 min in natural water. Whereas optode sample without Aliquat-336 did not change its color corresponding to Hg–PAR complex on equilibrium with the same aqueous solution containing Hg(II) ions. The uptake of Hg(II) was found to be pH dependant with a maximum (>90%) at a pH 7.5. The uptake of ions like Cu(II), Fe(II), Zn(II) and Pb(II) was negligible in the optode where as the uptake of Cd(II) and Zn(II) ions was 10–15% at pH 7.5. The optode developed in the present work was studied for its analytical application for Hg(II) in the aqueous samples by spectrophotometry, radiotracer (²⁰³Hg), Energy Dispersive X-ray Fluorescence (EDXRF) analyses and Instrumental Neutron Activation Analysis (INAA). The minimum amount of Hg(II) required to produce detectable response by spectrophotometry, INAA and EDXRF were found to be 5.5, 1 and 12 μg, respectively. This optode showed a linear increase in the absorbance at λ_max = 520 nm over a concentration range of 0.22–1.32 μg/mL of Hg(II) ions in aqueous solution for 5 min. The preconcentration of Hg(II) from large volume of aqueous solution was used to extend the lower limit of concentration range that can be quantified by the spectrophotometry of optode. It was observed that preconcentration of 11 μg Hg(II) in 100 mL (0.11 μg/mL) in aqueous samples gives a distinct color change and absorbance above 3σ of the blank absorbance. The optode developed in the present work was found to be reusable.     

An improved method for the determination of the extinction coefficient of thin film materials

The determination of the extinction coefficient of a material deposited in thin film form is generally made from Wolter's formula using $\text{(R ? R′)}\text{T}$.To avoid the measurement of R′, we have derived an analogous formula involving only R and T in the term $\text{(1 ? R ? T)}\text{T}$. Moreover this new expression can be used in oblique incidence.     

Solid phase extraction method for selective determination of Pb(II) in water samples using 4-(4-methoxybenzylidenimine) thiophenole

A sensitive and selective extractive preconcentration procedure for the determination of traces of lead in water samples has been developed. An alumina-sodium dodecyl sulfate (SDS) coated modified with 4-(4-methoxybenzylidenimine) thiophenole (MBITP) was used for preconcentration and determination of Pb(II) by flame atomic absorption spectrometry. Lead was adsorbed quantitatively on modified column due to its complexation with MBITP and quantitatively eluted using 5 mL 1 mol L(-1) nitric acid in acetone. The effects of parameters such as pH, amount of solid phase, amount of MBITP, flow rate, type and concentration of eluting agent were examined. The effect of interfering ions on the determination of Pb(II) was also investigated. The response of proposed method is linear in the concentration range 0.05-1.2 microg mL(-1) of Pb(II). The limit of detections (3S.D.(b)/m, n=4) and relative standard deviations (n=11) are 1.6 ng mL(-1) and 0.9%, respectively. The presented procedure was successfully applied for determination of lead content in real samples such as river, spring, waste and drinking water.     

An improved multigrid method for Euler equations

A new full approximation storage multigrid method has been developed for Euler equations. Instead of the usual approach of using frozen τ (the relative truncation error between fine and coarse grid levels), the relative truncation error is distributed over coarse grids based on the solution of a set of model equations at every time step. This allows for more number of sweeps at coarse grid level. As a result, the present multigrid method is able to accelerate the solution at much faster rate than the conventional multigrid method. A first order Steger and Warming flux vector splitting strategy has been used here for solving Euler equations as well as the model equations for τ. Results are presented to demonstrate the ability of the present multigrid method.     

Development of a cloud point extraction-spectrofluorimetric method for trace copper(II) determination in water samples and parenteral solutions

A simple and efficient cloud point extraction-spectrofluorimetric method for the determination of copper(II) in different samples has been proposed. The procedure is based on the oxidation of thiamine with copper(II) to form highly fluorescent thiochrome, its extraction to Triton X-114 micelles and spectrofluorimetric determination. The variables affecting the analytical performance were studied and optimized. The calibration graphs using the preconcentration system for copper were linear over the range 1.0-250 ng ml-1 with limit of detection of 0.29 ng ml-1. Relative standard deviation for five replicate determinations of copper at 100 ng ml-1 concentration level was 2.12%. Average recoveries between 94 and 105% were obtained for spiked samples. The method has been applied to water samples and parenteral solutions and the amounts of copper found are very similar to those obtained by a standard method.     

An improved image processing method for assessing multiple cracking development in Strain Hardening Cementitious Composites (SHCC)

Strain Hardening Cementitious Composites (SHCC) exhibit tension-hardening behavior accompanied by the formation of multiple cracks. To study the multiple cracking process, cracks are identified from digital images. As conventional image processing technique based on a single threshold of gray intensity cannot accurately determine the width of both fine and wide cracks, a new double-threshold algorithm is developed and its accuracy is verified by comparing with direct measurement under the microscope. Then, an additional algorithm for removing the noises and isolating individual crack regions is introduced. With the improved image processing method applied to a large number of sequential images, detailed information on the development of crack number and width is acquired. The average value and deviation of crack width at a given strain can be calculated to facilitate durability design. Also, with the stress-crack width relation obtained for various cracks, the fiber distribution among cracked sections can be estimated.     

Modified carbon paste electrode for potentiometric determination of diquat dibromide pesticide in water and urine samples

A carbon paste electrode for diquat dibromide (Dq.2Br) was prepared and fully characterized in terms of composition, usable pH range, response time and temperature. The electrode was applied to the potentiometric determination of diquat ions in water and urine samples with average recoveries of 97.5-104.0% and relative standard deviations of 0.30-4.73%. The electrode is based on the ion pair, namely, diquat-phosphotungstate dissolved in 2-nitrophenyloctyl ether (2-NPOE) as pasting liquid with 1.0% Na-TPB as an additive. The modified electrode showed a near-Nernstian slope of 30.8 mV over the concentration range of 3.8 × 10^− 6to 1.0 × 10^− 3 M with the limit of detection 9.0 × 10^− 7 over the pH range 4.5-9.5. The electrode exhibits good selectivity for Dq cations with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The proposed potentiometric method offers the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.     

高效液相色谱法测定头孢拉定制剂方法的改进

目的:改进头孢拉定制剂含量测定方法。方法:高效液相色谱条件:以Shim—Pack CLC—ODS(250mm×4.6mm)为色谱柱;柱温为35℃;流动相为水—甲醇—3.86％醋酸钠溶液-4％醋酸溶液(1364:500:30:6);流速为0.8mL·min~(-1);检测波长为254nm。结果:头孢拉定峰形良好,分离度和柱效满足药典要求,保留时间由原来的21.32min缩短至8.06min,提高了分析速度,含量测定结果与中国药典无显著差异。结论:该方法快速、准确、能更好地适用于常规检验工作和大批量生产时的质量控制。     

An improved compounding method for calculating stress-intensity factors

The compounding methods for calculating stress-intensity factors for complex geometrical configurations are reexamined. It is shown that techniques which were developed specifically for problems involving localized loads, e.g. a pin-loaded hole with a crack at its edge, can also be used when the loading is remote from the crack. When these techniques are used for cracks at unloaded holes, and for cracks in stiffened sheets, the compounding equations are as simple as those derived previously. However, fewer additional calculations are now needed and numerical tests show that there is no loss of accuracy. These advantages make the new procedures preferable to those used in the earlier compounding method.     

一种改进的机器人手眼系统标定方法

针对机器人手眼系统标定中空间坐标值参考点获取的困难,提出了一种改进的不需要已知坐标值参考点的机器人手眼系统标定方法.该方法的优点是在摄像机内参数标定中考虑了径向畸变,保证了标定精度.在外参数标定中,根据机器人自身运动特性提出了一种简便求取平移矩阵的方法.     

An improved lumped capacitance method for dielectric measurement

An improved lumped capacitance method for dielectric measurement in the broad microwave frequency range is proposed, with which many disadvantages occurring in the previous lumped capacitance method can be avoided. It is an easier and more convenient method for the dielectric measurement of ferroelectrics. Experiments have confirmed the feasibility of the method in the low microwave frequency range.