High resolution X-ray spectra of the time evolution of emission from metastable electronic states of highly charged Ni-like ions.

Abstract: Metastable levels of highly charged ions that can only decay via highly forbidden transitions can have a significant effect on the properties of high temperature plasmas. For example, the highly forbidden 3d 10 J = 0 - 3d 9 4 s ( 5 2 , 1 2 ) J = 3 magnetic octupole (M3) transition in nickel-like ions can result in a large metastable population of its upper level which can then be ionized by electrons of energies below the ground state ionization potential. We present a method to study metastable electronic states in highly charged ions that decay by x-ray emission in electron beam ion traps (EBIT). The time evolution of the emission intensity can be used to study the parameters of ionization balance dynamics and the lifetime of metastable states. The temporal and energy resolution of a new transition-edge sensor microcalorimeter array enables these studies at the National Institute of Standards and Technology EBIT. Graphical abstract: NOMAD calculated time evolution of the ratio of the Ni-like and Co-like lines in Nd at varying electron densities compared with measured ratios.

Trapped ion chain thermometry and mass spectrometry through imaging.

We demonstrate a spatial-imaging thermometry technique for ions in a one-dimensional Coulomb crystal by relating their imaged spatial extent along the linear radiofrequency ion trap axis to normal modes of vibration of coupled oscillators in a harmonic potential. We also use the thermal spatial spread of "bright" ions in the case of a two-species mixed chain to measure the center-of-mass resonance frequency of the entire chain and infer the molecular composition of the co-trapped "dark" ions. These non-destructive techniques create new possibilities for better understanding of sympathetic cooling in mixed-ion chains, improving few-ion mass spectrometry, and trapped-ion thermometry without requiring a scan of Doppler cooling parameters.

Evaluation of eight anti-rubella virus immunoglobulin g immunoassays that report results in international units per milliliter.

An evaluation of anti-rubella virus immunoglobulin G (IgG) immunoassays that report in international units per milliliter (IU/ml) was performed to determine their analytical performance and the degree of correlation of the test results. A total of 321 samples were characterized based on results from a hemagglutination inhibition assay. The 48 negative and 273 positive samples were used to determine the sensitivity and specificity of the assays. When equivocal results were interpreted as reactive, the sensitivity of the immunoassays ranged from 98.9 to 99.9% and the specificity ranged from 77.1 to 95.8%. All assays had positive and negative delta values of less than 2. A significant difference between the mean results of all assays was demonstrated by analysis of variance. However, post hoc analysis showed there was good correlation in the mean results expressed in IU/ml between some of the assays. Our results show the level of standardization between anti-rubella virus IgG immunoassays reporting results expressed as IU/ml has improved since a previous study in 1992, but further improvement is required.

Evaluation of three immunoassays used for detection of anti-rubella virus immunoglobulin M antibodies.

Three automated assays (Abbott AxSYM, Bayer ADVIA Centaur, and bioMerieux VIDAS) used for the detection of rubella virus-specific immunoglobulin M were evaluated. A total of 57 samples from individuals with evidence of infection with rubella virus were used to estimate sensitivity, and 220 samples from blood donors and individuals attending an antenatal clinic who had no evidence of recent infection were used to estimate specificity. Seroconversion panels comprising an additional 31 samples from four individuals were used to determine clinical sensitivity. Samples containing potentially cross-reacting substances were also tested. The sensitivities of the three assays ranged from 84.2 to 96.5%, and the specificities ranged from 96.8 to 99.9%. The Abbott AxSYM assay detected more reactive samples than the other two assays when a panel of 57 positive samples was tested. Bayer ADVIA Centaur detected more reactive samples in the seroconversion panels than the other two assays. All three assays evaluated reported a reactive result in 1 or more of the 48 samples containing potentially cross-reacting analytes. The assays demonstrated comparable performance in testing of a well-characterized panel of samples.

Control of calcium entry in human fibroblasts by frequency-dependent electrical stimulation.

Modulation of intracellular calcium ion concentration ((Ca2+)i) could be used to control cellular and molecular responses that are important in cell and tissue engineering. Electrical stimulation (ES) has been used to activate plasma membrane ion channels including Ca2+channels, and to induce changes in (Ca2+)i. Strong direct current (dc) ES depolarizes the membrane electrical potential (MEP) and, thereby, causes rapid increases in (Ca2+)i. Electrocoupling mechanisms that could control (Ca2+)i increases induced by modes of ES other than dc have not been elucidated, however. Here we report that 30 min of continuous exposure to a 1 or 10 Hz, 2 V/cm ES induces an (Ca2+)i increase by approximately 6-fold (baseline 25 nM) in human fibroblasts in culture. In contrast, a 100 Hz, 2 V/cm ES causes no significant (Ca2+)i increase. Either depletion of Ca2+from the extracellular medium or incubation of cells with verapamil inhibits the (Ca2+)i increase, indicating that Ca2+ influx through verapamil-sensitive Ca2+channels is required for the (Ca2+)i increase induced by oscillatory ES. More intense ES by a 1 Hz or a dc 10 V/cm electric field causes a rapid 20 to 25-fold (Ca2+)i increase. We hypothesize that selective, partial activation of Ca2+channels is likely to mediate Ca2+influx. These results suggest that optimal ES could be used to control Ca2+entry and, thereby, regulate cellular calcium homeostasis without adversely affecting cell viability.