Analyzing geological materials under martian conditions using laser-induced breakdown spectroscopy : plasma fundamentals, sample classification, and trace element quanitification

Laser-induced breakdown spectroscopy (LIBS) is an emission spectroscopy analysis technique that continues to be developed for the study of solids, liquids and gases. Geological applications for LIBS are a particularly exciting area of research, in part due to the capabilities of the technique to quickly and simultaneously detect nearly all major, minor and trace elements on unprepared samples either in a laboratory setting or in situ. A significant advancement in LIBS research is the recent deployment of ChemCam to the surface of Mars at Gale crater onboard the Mars Science Laboratory (MSL) rover, Curiosity. ChemCam consists of a LIBS instrument and a high resolution micro-imager (RMI) and is the first extraterrestrial application for LIBS. While the state of LIBS research is rapidly developing, there are still many aspects of the techniques that warrant additional study. In this work, I have primarily focused on avenues of investigation that are most applicable to ChemCam. To encompass the range of LIBS research and applications with respect to geological materials, I have compiled a body of work that explores aspects of the fundamentals of LIBS plasma temperature as a function of distance, sample classification based on a spectral matching technique called Partial Least Square-Discriminant Analysis, and the quantification of several trace elements (Li, Rb, Sr, and Rb) using ChemCam spectra. Trace element abundances and implications for geological processes on Mars for the first 100 sols of martian rocks and soils analyzed by ChemCam are also discussed

Deep Spectral CNN for Laser Induced Breakdown Spectroscopy

This work proposes a spectral convolutional neural network (CNN) operating on laser induced breakdown spectroscopy (LIBS) signals to learn to (1) disentangle spectral signals from the sources of sensor uncertainty (i.e., pre-process) and (2) get qualitative and quantitative measures of chemical content of a sample given a spectral signal (i.e., calibrate). Once the spectral CNN is trained, it can accomplish either task through a single feed-forward pass, with real-time benefits and without any additional side information requirements including dark current, system response, temperature and detector-to-target range. Our experiments demonstrate that the proposed method outperforms the existing approaches used by the Mars Science Lab for pre-processing and calibration for remote sensing observations from the Mars rover, 'Curiosity'

Analysis of organic compounds in Mars soil analog samples using SuperCam-Raman of Mars2020

One of the main objectives of the Perseverance rover is to find signs of ancient life in the Martian surface, seeking biosignatures and signs of past habitable conditions. This could be achieved with the finding of organic compounds related to life. Raman spectroscopy is among the techniques that the rover is capable of performing, which is able to detect and discern organic molecules. Perseverance carries in its payload two instruments that are able to use this technique, SuperCam for remote sensing and SHERLOC for proximity measurements. SuperCam is a long-distance instrument capable of performing several techniques (Raman, LIBS, luminescence, VISIR, microphone) in order to assess the chemical and molecular composition of rocks (mineral phases and organic molecules) from a distance up to 7 m. Therefore, it could detect organics, or traces of them, from a distance before the rover gets closer.In this work, a set of Mars soil analog samples were analyzed using the Flying Model-Body Unit / Engineering Qualification Model-Mast Unit (FM-BU/EQM-MU) setup of SuperCam. Specifically, the samples were prepared in the laboratory by adsorbing adenosine 5"-monophosphate, L-glutamic acid, L-phenylalanine, and phthalic acid with different known concentrations (5 wt%, 1 wt% and 0.1 wt%) on the clay mineral montmorillonite doped with 1 wt% of Mg-perchlorate. The preparation and characterization of those samples can be found in literature [1]. The analyses were carried out at a 2 m distance from the targets, with a laser spot size of around 300 µm at that distance. SuperCam showed excellent results for the pure compounds, before adsorption on the clay mineral. At 5 wt% concentration, the Raman signals of the organics were barely visible and at 1 wt% they were no longer visible. This fact means that if the laser of SuperCam hits an organic "hotspot" in a rock from a distance, it will be able to detect it as long as it has a concentration around 5 wt% or greater in the analyzed area, allowing SHERLOC to do further contact analysis afterwards. In addition, the SuperCam results were compared with those obtained with a commercial laboratory instrument (Renishaw inVia), obtaining the same main signals and only missing some minor secondary bands.[1] T. Fornaro, J. R. Brucato, G. Poggiali, M. A. Corazzi, M. Biczysko, M. Jaber, D. I. Foustoukos, R. M. Hazen, A. Steele, UV irradiation and Near Infrared characterization of laboratory Mars soil analog samples, Frontiers in Astronomy and Space Sciences, 2020, 7, 1-2

Decision Making about Surgery for Early-Stage Breast Cancer

Practice variation in breast cancer surgery has raised concerns about the quality of treatment decisions. We sought to evaluate the quality of decisions about surgery for early stage breast cancer by measuring patient knowledge, concordance between goals and treatments, and involvement in decisions

The SuperCam Remote Sensing Instrument Suite for Mars 2020

International audienceThe Mars 2020 rover, essentially a structural twin of MSL, is being built to a) characterize the geology and history of a new landing site on Mars, b) find and characterize ancient habitable environments, c) cache samples for eventual return to Earth, and d) demonstrate in-situ production of oxygen needed for human exploration. Remote-sensing instrumentation is needed to support the first three of these goals [1]. The SuperCam instrument meets these needs with a range of instrumentation including the highest-resolution remote imaging on the rover, two different techniques for determining mineralogy , and one technique to provide elemental compositions. All of these techniques are co-boresighted, providing rapid comprehensive characterization. In addition, for targets within 7 meters of the rover the laser shock waves brush away the dust, providing cleaner surfaces for analysis. SuperCam will use an advanced version of the AEGIS robotic target selection software

Observations of Rocks in Jezero Landing Site: SuperCam/LIBS technique overview of results from the first six months of operations.

On-board the Perseverance rover, the SuperCam instrument is being used as a remote-sensing facility to analyze rocks and soils targets. SuperCam is a suite of five coaligned techniques: just like ChemCam (onboard MSL/Curiosity rover on Mars since 2012), it uses the Laser Induced Breakdown Spectroscopy (LIBS) technique to determine the elementary composition of the targets, but it also uses Raman (for the first time in planetary science) and visible-infrared (VISIR - for the first time in situ) spectroscopic methods in order to access some mineralogical and structural information. A microphone gives access to some physical parameters of the sampled rocks (such as hardness) as well as to some atmospheric parameters (wind direction). These chemical and mineralogical analyses are contextualized thanks to a color remote micro-imager (RMI). In this study, we focus mainly on the LIBS results obtained so far

Surveillance of Sentinel Node-Positive Melanoma Patients with Reasons for Exclusion from MSLT-II:Multi-Institutional Propensity Score Matched Analysis

BACKGROUND: In sentinel lymph node (SLN)-positive melanoma, two randomized trials demonstrated equivalent melanoma-specific survival with nodal surveillance vs completion lymph node dissection (CLND). Patients with microsatellites, extranodal extension (ENE) in the SLN, or >3 positive SLNs constitute a high-risk group largely excluded from the randomized trials, for whom appropriate management remains unknown. STUDY DESIGN: SLN-positive patients with any of the three high-risk features were identified from an international cohort. CLND patients were matched 1:1 with surveillance patients using propensity scores. Risk of any-site recurrence, SLN-basin-only recurrence, and melanoma-specific mortality were compared. RESULTS: Among 1,154 SLN-positive patients, 166 had ENE, microsatellites, and/or >3 positive SLN. At 18.5 months median follow-up, 49% had recurrence (vs 26% in patients without high-risk features, p 3 positive SLN constitute a high-risk group with a 2-fold greater recurrence risk. For those managed with nodal surveillance, SLN-basin recurrences were more frequent, but all-site recurrence and melanoma-specific mortality were comparable to patients treated with CLND. Most recurrences were outside the SLN-basin, supporting use of nodal surveillance for SLN-positive patients with microsatellites, ENE, and/ or >3 positive SLN

Active surveillance of patients who have sentinel node positive melanoma:An international, multi-institution evaluation of adoption and early outcomes after the Multicenter Selective Lymphadenectomy trial II (MSLT-2)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/168248/1/cncr33483.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168248/2/cncr33483_am.pd

The Supercam Instrument Suite on the NASA Mars 2020 Rover: Body Unit and Combined System Tests

The SuperCam instrument suite provides the Mars 2020 rover, Perseverance, with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and infrared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam’s body unit (BU) and testing of the integrated instrument. The BU, mounted inside the rover body, receives light from the MU via a 5.8 m optical fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245–340 and 385–465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer containing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535–853 nm (105–7070 cm−1 Raman shift relative to the 532 nm green laser beam) with 12 cm−1 full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars. Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spectroscopy are shown, demonstrating clear mineral identification with both techniques. Luminescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these subsystems as well

The association between genetic variants in hMLH1 and hMSH2 and the development of sporadic colorectal cancer in the Danish population

<p>Abstract</p> <p>Background</p> <p>Mutations in the mismatch repair genes <it>hMLH1 </it>and <it>hMSH2 </it>predispose to hereditary non-polyposis colorectal cancer (HNPCC). Genetic screening of more than 350 Danish patients with colorectal cancer (CRC) has led to the identification of several new genetic variants (e.g. missense, silent and non-coding) in <it>hMLH1 </it>and <it>hMSH2</it>. The aim of the present study was to investigate the frequency of these variants in <it>hMLH1 </it>and <it>hMSH2 </it>in Danish patients with sporadic colorectal cancer and in the healthy background population. The purpose was to reveal if any of the common variants lead to increased susceptibility to colorectal cancer.</p> <p>Methods</p> <p>Associations between genetic variants in <it>hMLH1 </it>and <it>hMSH2 </it>and sporadic colorectal cancer were evaluated using a case-cohort design. The genotyping was performed on DNA isolated from blood from the 380 cases with sporadic colorectal cancer and a sub-cohort of 770 individuals. The DNA samples were analyzed using Single Base Extension (SBE) Tag-arrays. A Bonferroni corrected Fisher exact test was used to test for association between the genotypes of each variant and colorectal cancer. Linkage disequilibrium (LD) was investigated using HaploView (v3.31).</p> <p>Results</p> <p>Heterozygous and homozygous changes were detected in 13 of 35 analyzed variants. Two variants showed a borderline association with colorectal cancer, whereas the remaining variants demonstrated no association. Furthermore, the genomic regions covering <it>hMLH1 </it>and <it>hMSH2 </it>displayed high linkage disequilibrium in the Danish population. Twenty-two variants were neither detected in the cases with sporadic colorectal cancer nor in the sub-cohort. Some of these rare variants have been classified either as pathogenic mutations or as neutral variants in other populations and some are unclassified Danish variants.</p> <p>Conclusion</p> <p>None of the variants in <it>hMLH1 </it>and <it>hMSH2 </it>analyzed in the present study were highly associated with colorectal cancer in the Danish population. High linkage disequilibrium in the genomic regions covering <it>hMLH1 </it>and <it>hMSH2</it>, indicate that common genetic variants in the two genes in general are not involved in the development of sporadic colorectal cancer. Nevertheless, some of the rare unclassified variants in <it>hMLH1 </it>and <it>hMSH2 </it>might be involved in the development of colorectal cancer in the families where they were originally identified.</p