L. A. Finney

Bio: L. A. Finney is an academic researcher from University of Michigan. The author has contributed to research in topics: Laser & Ultrashort pulse. The author has an hindex of 4, co-authored 15 publications receiving 66 citations.

Ultrafast Laser Filament-induced Fluorescence Spectroscopy of Uranyl Fluoride.

Abstract: 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.

Single-shot, multi-signature remote detection of uranium by filament-induced breakdown spectroscopy

Abstract: Filament-induced breakdown spectroscopy (FIBS) is an attractive remote detection approach that is potentially applicable to nuclear materials such as uranium (U). Simultaneous detection of atomic U and U monoxide features is demonstrated in a single laser shot with detection probabilities of 52.2% and 39.0%, respectively, and with a 1% false-alarm probability. It is shown that a nearly 100% detection probability can be reached with 1% false-alarm probability in ≲1 second when using an 80 Hz laser and data acquisition system. Atomic U and uranium oxide (UO) signal features are identifiable in the remote measurement with comparable signal-to-background ratios, suggesting that, despite being broader than the U I emission line, the UO band is also suitable for remote detection of U by FIBS.

Remote Detection of Uranium Using Self-Focusing Intense Femtosecond Laser Pulses

Abstract: Optical measurement techniques can address certain important challenges associated with nuclear safety and security. Detection of uranium over long distances presents one such challenge that is difficult to realize with traditional ionizing radiation detection, but may benefit from the use of techniques based on intense femtosecond laser pulses. When a high-power laser pulse propagates in air, it experiences collapse and confinement into filaments over an extended distance even without external focusing. In our experiments, we varied the initial pulse chirp to optimize the emission signal from the laser-produced uranium plasma at an extended distance. While the ablation efficiency of filaments formed by self-focusing is known to be significantly lower when compared to filaments produced by external focusing, we show that filaments formed by self-focusing can still generate luminous spectroscopic signatures of uranium detectable within seconds over a 10-m range. The intensity of uranium emission varies periodically with laser chirp, which is attributed to the interplay among self-focusing, defocusing, and multi-filament fragmentation along the beam propagation axis. Grouping of multi-filaments incident on target is found to be correlated with the uranium emission intensity. The results show promise towards long-range detection, advancing the diagnostics and analytical capabilities in ultrafast laser-based spectroscopy of high-Z elements.

CD4+ T cell help creates memory CD8+ T cells with innate and help-independent recall capacities

Abstract: CD4+ T cell help is required for the generation of CD8+ cytotoxic T lymphocyte (CTL) memory. Here, we use genome-wide analyses to show how CD4+ T cell help delivered during priming promotes memory differentiation of CTLs. Help signals enhance IL-15-dependent maintenance of central memory T (TCM) cells. More importantly, help signals regulate the size and function of the effector memory T (TEM) cell pool. Helped TEM cells produce Granzyme B and IFNγ upon antigen-independent, innate-like recall by IL-12 and IL-18. In addition, helped memory CTLs express the effector program characteristic of helped primary CTLs upon recall with MHC class I-restricted antigens, likely due to epigenetic imprinting and sustained mRNA expression of effector genes. Our data thus indicate that during priming, CD4+ T cell help optimizes CTL memory by creating TEM cells with innate and help-independent antigen-specific recall capacities.

Correlations among oligonucleotide repeats, nucleotide substitutions, and insertion–deletion mutations in chloroplast genomes of plant family Malvaceae

Abstract: The co‐occurrence of mutational events including substitutions and insertions–deletions (InDels) with oligonucleotide repeats has previously been reported for a limited number of prokaryotic, eukaryotic, and organelle genomes. In this study, the correlations among these mutational events in chloroplast genomes of species in the eudicot family Malvaceae were investigated. This study also reported chloroplast genome sequences of Hibiscus mutabilis, Malva parviflora, and Malvastrum coromandelianum. These three genomes and 16 other publicly available chloroplast genomes from 12 genera of Malvaceae were used to calculate the correlation coefficients among the mutational events at family, subfamily, and genus levels. In these comparisons, chloroplast genomes were pairwise aligned to record the substitutions and the InDels in mutually exclusive, 250 nucleotide long bins. Taking one among the two genomes as a reference, the coordinate positions of oligonucleotide repeats in the reference genome were recorded. The extent of correlations among repeats, substitutions, and InDels was calculated and categorized as follows: very weak (0.1–0.19), weak (0.20–0.29), moderate (0.30–0.39), and strong (0.4–0.69). The extent of correlations ranged 0.201–0.6 between “InDels and single‐nucleotide polymorphism (SNP)”, 0.182–0.513 between “InDels and repeat” and 0.055–0.403 between “SNPs and repeats”. At family‐ and subfamily‐level comparisons, 88%–96% of the repeats showed co‐occurrence with SNPs, whereas at the genus level, 23%–86% of the repeats co‐occurred with SNPs in same bins. Our findings support the previous hypothesis suggesting the use of oligonucleotide repeats as a proxy for finding the mutational hotspots.

Additive manufacturing for electrochemical labs: An overview and tutorial note on the production of cells, electrodes and accessories

Abstract: Additive Manufacturing (AM) is an ever-growing part of modern scientific research due to its ability to create complex features, low wastage, ever-decreasing cost of entry and rapid prototyping capabilities. Up to this point, the use of AM in electrochemical research has focused around two of the main components of the experimental setup: the working electrode, and the electrochemical cell. In this paper we highlight how researchers have utilised AM in the literature and offer our own insights into how this technology can be exploited to benefit all areas of electrochemical research. For the development of electrodes, much of the literature utilises commercially available conductive PLA filaments in conjunction with FFF printing, with only a few groups expanding into the development of their own bespoke conductive materials. AM offers huge advantages in the production of electrochemical cells, allowing users to produce bespoke designs to fit their experimental needs, rapidly producing these at low cost and easily modifying the design to improve performance. However, the use of AM in electrochemical laboratories should not stop there. We present basic designs of electrodes, cells and even accessories that can benefit all electrochemical researchers (new and experienced) in their quest for reproducible and reliable results. These designs are offered free of charge, are available to download from the Supporting Information and can be easily modified to meet any users’ specific needs. As such, we feel AM should be a staple of every laboratory and hope this work inspires people to think about all the ways that AM can benefit their research environments.

Identifying the determinants of emotion regulation choice: a systematic review with meta-analysis

Abstract: Day-to-day life is inundated with attempts to control emotions and a wealth of research has examined what strategies people use and how effective these strategies are. However, until more recently,...