Ultrafast Laser Filament-induced Fluorescence Spectroscopy of Uranyl Fluoride.

Uranyl fluoride (UO2F2) is a compound which forms in the reaction between water and uranium hexafluoride, a uranium containing gas widely used for uranium enrichment. Uranyl fluoride exhibits negligible natural background in atmosphere; as a result, its observation implies the presence and active operation of nearby enrichment facilities and could be used as a tracer for treaty verification technologies. Additionally, detection of UO2F2 has a potential application in guiding remediation efforts around enrichment facilities. Laser-induced fluorescence (LIF) has been proposed in the past as a viable technique for the detection and tracking of UO2F2. We demonstrate that ultrafast laser filamentation coupled with LIF extends the capabilities of standard LIF to enable remote detection of UO2F2. An intense femtosecond laser pulse propagated in air collapses into a plasma channel, referred to as a laser filament, allowing for the extended delivery of laser energy. We first investigate the luminescence of UO2F2 excited by the second harmonic of an ultrafast Ti:sapphire laser and subsequently excite it using the conical emission that accompanies ultrafast laser filamentation in air. We measure the decay rates spanning 4.3-5.6 × 104 s-1 and discuss the characteristics of the luminescence for both ultrafast- and filament-excitation. Larger decay rates than those observed using standard LIF are caused by a saturated component of prompt decay from annihilation of dense excited states upon excitation with an ultrafast source. The reproducibility of such decay rates for the given range of incident laser intensities 1.0-1.6 × 1011 W cm-2 is promising for the application of this technique in remote sensing.

Unraveling the mystery of "tech red" - a volatile technetium oxide.

We show that a Tc2O5 molecular species is the likely identity of an unknown volatile oxide which has remained uncharacterized for 50+ years. Exploration of this molecule's absorption spectra and intermolecular self-interactions provides a close match to experimental data and an explanation for volatility and resistance to crystallization.

Plutonium segregation in glassy aerodynamic fallout from a nuclear weapon test.

This study combines electron microscopy equipped with energy dispersive spectroscopy to probe major element composition and autoradiography to map plutonium in order to examine the spatial relationships between plutonium and fallout composition in aerodynamic glassy fallout from a nuclear weapon test. A sample set of 48 individual fallout specimens were interrogated to reveal that the significant chemical heterogeneity of this sample set could be described compositionally with a relatively small number of compositional endmembers. Furthermore, high concentrations of plutonium were never associated with several endmember compositions and concentrated with the so-called mafic glass endmember. This result suggests that it is the physical characteristics of the compositional endmembers and not the chemical characteristics of the individual component elements that govern the un-burnt plutonium distribution with respect to major element composition in fallout.

Behavior of heptavalent technetium in sulfuric acid under α-irradiation: structural determination of technetium sulfate complexes by X-ray absorption spectroscopy and first principles calculations.

The effect of α-radiolysis on the behavior of heptavalent technetium has been investigated in 13 and 18 M H2SO4. Irradiation experiments were performed using α-particles ((4)He(2+), E = 68 MeV) generated by the ARRONAX cyclotron. UV-visible and X-ray absorption fine structure spectroscopic studies indicate that Tc(VII) is reduced to Tc(V) under α-irradiation. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements are consistent with the presence of mononuclear technetium sulfate complexes. Experimental results and density functional calculations show the formation of [TcO(HSO4)3(H2O)(OH)](-) and/or [TcO(HSO4)3(H2O)2] and [Tc(HSO4)3(SO4)(H2O)] and/or [Tc(HSO4)3(SO4)(OH)](-) for 13 and 18 M H2SO4, respectively.

[Efficacy of the newest ultrasonographic techniques in intraoperative neurosurgical diagnosis]. / Skutecznosc najnowoczesniejszych technik ultrasonograficznych w sródoperacyjnej diagnostyce neurochirurgicznej.

The contemporary neurosurgery requires efficient methods of intraoperative image guidance. Among some expensive techniques the rather cheap intraoperative ultrasound has been widely accepted in the last decade. The aim of the study is to estimate the efficacy of this technique in the intraoperative evaluation of the different kinds of brain lesions. The authors illustrate it with some ultrasonic images presented in comparison to the images obtained from the preoperative CT or angiography. B-mode ultrasound has proven to be extremely useful for localizing subcortical rather than deep-seated brain tumours, cysts, abscesses as well as intraparenchymal haematomas. The advantages were particularly evident when searching for tumours that were not visible on brain surface. Its use for guidance in cyst or abscess aspiration, as well as usefulness in tumor vascularization estimations (using Power Doppler mode) is outlined. Ultrasound B-mode Color or Power Doppler sonography with high resolution probes offers new possibilities of intraoperative control of neurovascular procedures--either in the localization of small arterio-venous malformations (AVMs) and feeders estimation or for the evaluation of proper clip application in the aneurysm surgery.

[Acute post-traumatic epidural hematoma: report of 4 non-surgically treated cases]. / Ostry pourazowy krwiak nadtwardówkowy--opis czterech przypadków leczonych zachowawczo.

The authors present four cases of acute epidural hematoma (three supratentorial and one in the posterior fossa), in which non-operative treatment was performed. The conditions to undertake this treatment were: good clinical and neurological state of the patients on admission (GCS equal or more than 14), absence or mild focal symptoms and possibility to observe the patients and to perform CT follow-up. All patients had a good recovery. The authors discuss these cases and present the review of the literature concerning the problem.