A Detrital Zircon Test of Large-Scale Terrane Displacement Along the Arctic Margin of North America

Detrital zircon U-Pb geochronology is one of the most common methods used to constrain the provenance of ancient sedimentary systems. Yet, its efficacy for precisely constraining paleogeographic reconstructions is often complicated by geological, analytical, and statistical uncertainties. To test the utility of this technique for reconstructing complex, margin-parallel terrane displacements, we compiled new and previously published U-Pb detrital zircon data (n = 7924; 70 samples) from Neoproterozoic–Cambrian marine sandstone-bearing units across the Porcupine shear zone of northern Yukon and Alaska, which separates the North Slope subterrane of Arctic Alaska from northwestern Laurentia (Yukon block). Contrasting tectonic models for the North Slope subterrane indicate it originated either near its current position as an autochthonous continuation of the Yukon block or from a position adjacent to the northeastern Laurentian margin prior to \u3e1000 km of Paleozoic–Mesozoic translation. Our statistical results demonstrate that zircon U-Pb age distributions from the North Slope subterrane are consistently distinct from the Yukon block, thereby supporting a model of continent-scale strike-slip displacement along the Arctic margin of North America. Further examination of this dataset highlights important pitfalls associated with common methodological approaches using small sample sizes and reveals challenges in relying solely on detrital zircon age spectra for testing models of terranes displaced along the same continental margin from which they originated. Nevertheless, large-n detrital zircon datasets interpreted within a robust geologic framework can be effective for evaluating translation across complex tectonic boundaries

Time-resolved enzymatic determination of glucose using a fluorescent europium probe for hydrogen peroxide

An enzymatic assay for glucose based on the use of the fluorescent probe for hydrogen peroxide, europium(III) tetracycline (EuTc), is described. The weakly fluorescent EuTc and enzymatically generated H2O2 form a strongly fluorescent complex (EuTc–H2O2) whose fluorescence decay profile is significantly different. Since the decay time of EuTc–H2O2 is in the microseconds time domain, fluorescence can be detected in the time-resolved mode, thus enabling substantial reduction of background fluorescence. The scheme represents the first H2O2-based time-resolved fluorescence assay for glucose not requiring the presence of a peroxidase. The time-resolved assay (with a delay time of 60 mgrs and using endpoint detection) enables glucose to be determined at levels as low as 2.2 mgrmol L–1, with a dynamic range of 2.2–100 mgrmol L–1. The method also was adapted to a kinetic assay in order to cover higher glucose levels (mmol L–1 range). The latter was validated by analyzing spiked serum samples and gave a good linear relationship for glucose levels from 2.5 to 55.5 mmol L–1. Noteworthy features of the assay include easy accessibility of the probe, large Stokesrsquo shift, a line-like fluorescence peaking at 616 nm, stability towards oxygen, a working pH of approximately 7, and its suitability for both kinetic and endpoint determination

Intravenous NPA for the treatment of infarcting myocardium early: InTIME-II, a double-blind comparison on of single-bolus lanoteplase vs accelerated alteplase for the treatment of patients with acute myocardial infarction

Aims to compare the efficacy and safety of lanoteplase, a single-bolus thrombolytic drug derived from alteplase tissue plasminogen activator, with the established accelerated alteplase regimen in patients presenting within 6 h of onset of ST elevation acute myocardial infarction. Methods and Results 15 078 patients were recruited from 855 hospitals worldwide and randomized in a 2:1 ratio to receive either lanoteplase 120 KU. kg-1 as a single intravenous bolus, or up to 100 mg accelerated alteplase given over 90 min. The primary end-point was all-cause mortality at 30 days and the hypothesis was that the two treatments would be equivalent. By 30 days, 6.61% of alteplase-treated patients and 6.75% lanoteplase-treated patients had died (relative risk 1.02). Total stroke occurred in 1.53% alteplase- and 1.87% lanoteplase-treated patients (ns); haemorrhagic stroke rates were 0.64% alteplase and 1.12% lanoteplase (P=0.004). The net clinical deficit of 30-day death or non-fatal disabling stroke was 7.0% and 7.2%, respectively. By 6 months, 8.8% of alteplase-treated patients and 8.7% of lanoteplase-treated patients had died. Conclusion Single-bolus weight-adjusted lanoteplase is an effective thrombolytic agent, equivalent to alteplase in terms of its impact on survival and with a comparable risk-benefit profile. The single-bolus regimen should shorten symptoms to treatment times and be especially convenient for emergency department or out-of-hospital administration. (C) 2000 The European Society of Cardiology