Gas-phase ion association provides increased selectivity and sensitivity for measuring perchlorate by mass spectrometry

Perchlorate (ClO4-) competitively inhibits the uptake of iodide by the thyroid gland. Trace quantities of perchlorate are being increasingly detected in food and environmental samples. There is great concern that perchlorate contamination may be far more widespread than believed until now. Increasingly sensitive and unambiguous methods are needed for measuring perchlorate. We report here an ion chromatography-ion association-electrospray ionization-mass spectrometry (IC/IA-ESI-MS) method of substantially greater selectivity and sensitivity than other available single-stage MS approaches. A long chain dipositive cationic agent (D2+) is added postcolumn in low concentration. This ion associates with perchlorate, even in the gas phase. Perchlorate is, thus, detected as DClO4+ in the positive ion mode at an m/z value between 300 and 400 (depending on the choice of D2+). This results in much better S/N and selectivity, as compared to detecting 35ClO4- at m/z 99, where H34SO4- also responds. We show results for various dicationic agents which vary in their selectivity and affinity for ClO4-, typically being at least 1 order of magnitude more selective for ClO4- over HSO4-. For a 100-microL injected standard, limits of detection (LOD, S/N = 3) are as good as 25 ng/L on a single quadrupole mass spectrometer. Calibration for concentrations up to 100 microg/L displays an r2 value of > or =0.9993. We show applicability to various real samples. A number of the studied reagents are suitable for such applications.     

Advances in Switched-Mode Power Conversion Part I

A new concept in the design of switched-mode power conversion circuitry is presented. Because of its extreme simplicity, flexibility, and efficiency, it has the potential to replace some conventional electrical power processing methods currently in use. A thorough discussion of the background, development, and operation of the ?uk converter and several of its extensions is included. The coupled-inductor technique further improves efficiency and reduces size and weight. The basic converter and its extensions to two-quadrant and four-quadrant operation are attractive for many applications, i.e., solar (dc) to utility line (ac) power conversion, variable speed dc or ac motor drives, switching power supplies, uninterruptible power supplies, and many others.     

Buss-Durkee assessment and validation with violent versus nonviolent chronic alcohol abusers.

26 male 27–47 yr old chronic alcohol abusers who had been violent while intoxicated and 25 male 34–52 yr old nonviolent alcohol abusers were administered the Buss-Durkee Hostility-Guilt Inventory. All Ss were Caucasians with a reported daily intake of ethanol of 227 ml?±?89 ml for at least the last 5 yrs. Violence was documented by police records and by patient and family reports. Violent drinkers scored significantly higher than controls on the Total Hostility score and on subscales measuring Assault, Irritability, Verbal Hostility, Indirect Hostility, and Resentment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two Algorithms for Determining the Most Reliable Path of a Network

This paper presents two algorithms for determining the most reliable paths of a communication network, taking into account both the reliabilities of nodes and links. A network is modeled by a linear graph. The first algorithm adapts a node labeling scheme; second is based on the shortest-path matrix algorithm. Both algorithms can be applied to oriented and nonoriented nonsymetric networks. The numerical examples confirm that both algorithms efficiently handle networks with hundreds of nodes and edges. The total amount of computation, expressed by the number of multiplications and comparisons, increases in the labeling procedure with the square of the number of nodes, and in the matrix method with the cube of the number of nodes.     

Failure analysis of the combat jet aircraft rudder shaft

This paper analyzes failure causes of the combat jet aircraft rudder shaft (RS) which occurred during the flight mission. A finite element method (FEM), utilized to determine the stress state of the RS subjected to hinge moment ultimate load, resulted in the high stress concentration sites around the rivet holes. The longitudinal crack was initiated from the corrosion pit in the zone of the rivet hole, where the fatigue beach marks were observed. The inner surface of the RS was heavily corroded. Moreover, pitting corrosion has destroyed approximately 50% of the wall thickness. Based on the presented results it was concluded that the failure of the RS had a character of fatigue combined with heavy corrosion. Therefore, it is recommended that the RS should be redesigned; the material changed into more corrosion resistant one and the maintenance procedure changed in order to avoid future similar failures.     

A timely detection of a coated board streak defect in subsampling conditions using monochrome vision system

This paper presents a study of an important improvement in an already installed monochrome vision system for detection of defects during coated board manufacture. This improvement allows the inspection system to detect targeted defect in subsampling conditions (i.e. Nyquist theorem is not satisfied). This improvement is accomplished entirely in the image processing software without the need for additional changes in the vision hardware. Processing software is optimized for SIMD instruction set requiring no improvement in the processing hardware. Results obtained by the use of this improved algorithm provide real time detection of the targeted defect that in turns enables elimination of the waist coated board.     

Development of new models for the estimation of deformation moduli in rock masses based on in situ measurements

Bulletin of Engineering Geology and the Environment - Knowledge of the deformation properties of the rock mass is essential for the stress–strain analysis of structures such as dams, tunnels,...