Obtaining carbon isotopic information for organic carbon from Martian sediments has long been a goal of planetary science, as it has the potential to elucidate the origin of such carbon and aspects ...of Martian carbon cycling. Carbon isotopic values (δ
C
) of the methane released during pyrolysis of 24 powder samples at Gale crater, Mars, show a high degree of variation (-137 ± 8‰ to +22 ± 10‰) when measured by the tunable laser spectrometer portion of the Sample Analysis at Mars instrument suite during evolved gas analysis. Included in these data are 10 measured δ
C values less than -70‰ found for six different sampling locations, all potentially associated with a possible paleosurface. There are multiple plausible explanations for the anomalously depleted
C observed in evolved methane, but no single explanation can be accepted without further research. Three possible explanations are the photolysis of biological methane released from the subsurface, photoreduction of atmospheric CO
, and deposition of cosmic dust during passage through a galactic molecular cloud. All three of these scenarios are unconventional, unlike processes common on Earth.
Digital Spatial Profiling (DSP) is a method for highly multiplex spatial profiling of proteins or RNAs suitable for use on formalin-fixed, paraffin-embedded (FFPE) samples. The approach relies on (1) ...multiplexed readout of proteins or RNAs using oligonucleotide tags; (2) oligonucleotide tags attached to affinity reagents (antibodies or RNA probes) through a photocleavable (PC) linker; and (3) photocleaving light projected onto the tissue sample to release PC oligonucleotides in any spatial pattern across a region of interest (ROI) covering 1 to ~5,000 cells. DSP is capable of single-cell sensitivity within an ROI using the antibody readout, with RNA detection feasible down to ~600 individual mRNA transcripts. We show spatial profiling of up to 44 proteins and 96 genes (928 RNA probes) in lymphoid, colorectal tumor and autoimmune tissues by using the nCounter system and 1,412 genes (4,998 RNA probes) by using next-generation sequencing (NGS). DSP may be used to profile not only proteins and RNAs in biobanked samples but also immune markers in patient samples, with potential prognostic and predictive potential for clinical decision-making.
Raman spectroscopy is a powerful technique for the study of materials chemistry and nanostructure. This nondestructive technique is highly sensitive to molecular and crystal lattice vibrations, which ...allow for a comprehensive study of the vibrational modes of molecules incorporated in photovoltaic perovskite materials. In this study, we apply Raman spectroscopy to study FAPbX3 (X = Cl, Br, I) and FA x MA1–x PbI3 (FA stands for formamidinium; MA for methylammonium) metal halide perovskite single crystals and discuss the necessary conditions to obtain reliable data. We establish a correlation between perovskite composition and their unique Raman intensities/spectral shapes. In particular, we show that tuning of the halide content results in a spectral shift of the organic features of the Raman spectrum due to changes in the strength of hydrogen bonding, while tuning of the organic cation is related more to changes in peak intensity. Moreover, the effect of temperature on the vibrational modes corresponding to NCN bending, NH2 torsion, and NH2 wagging were studied. This enables the impact of the organic composition in FA x MA1–x PbI3 on the phase transition temperature of the material to be determined. Furthermore, we establish links between Raman spectroscopy and other conventional measurement techniques such as X-ray diffraction (XRD) and differential scanning calorimetry (DSC). This study provides insight into the interpretation of the Raman spectra of FA-based perovskites, which furthers understanding of the properties of these materials in relation to their full exploitation in solar cells.
The Sample Analysis at Mars instrument stepped combustion experiment on a Yellowknife Bay mudstone at Gale crater, Mars revealed the presence of organic carbon of Martian and meteoritic origins. The ...combustion experiment was designed to access refractory organic carbon in Mars surface sediments by heating samples in the presence of oxygen to combust carbon to CO
2
. Four steps were performed, two at low temperatures (less than ∼550 °C) and two at high temperatures (up to ∼870 °C). More than 950 μg C/g was released at low temperatures (with an isotopic composition of δ
13
C = +1.5 ± 3.8‰) representing a minimum of 431 μg C/g indigenous organic and inorganic Martian carbon components. Above 550 °C, 273 ± 30 μg C/g was evolved as CO
2
and CO (with estimated δ
13
C = −32.9‰ to −10.1‰ for organic carbon). The source of high temperature organic carbon cannot be definitively confirmed by isotopic composition, which is consistent with macromolecular organic carbon of igneous origin, meteoritic infall, or diagenetically altered biomass, or a combination of these. If from allochthonous deposition, organic carbon could have supported both prebiotic organic chemistry and heterotrophic metabolism at Gale crater, Mars, at ∼3.5 Ga.
We report new measurements of atmospheric methane by the Curiosity rover’s Tunable Laser Spectrometer that is part of the Sample Analysis at Mars suite (TLS-SAM), finding nondetections during two ...daytime measurements of average value 0.05 ± 0.22 ppbv (95% confidence interval CI). These are in marked contrast with nighttime background levels of 0.52 ± 0.10 (95% CI) from four measurements taken during the same season of northern summer. This large day-night difference suggests that methane accumulates while contained near the surface at night, but drops below TLS-SAM detection limits during the day, consistent with the daytime nondetection by instruments on board the ExoMars Trace Gas Orbiter. With no evidence for methane production by the rover itself, we propose that the source is one of planetary micro-seepage. Dynamical modeling indicates that such methane release is contained within the collapsed planetary boundary layer (PBL) at night due to a combination of nocturnal inversion and convergent downslope flow winds that confine the methane inside the crater close to the point where it is released. The methane abundance is then diluted during the day through increased vertical mixing associated with a higher altitude PBL and divergent upslope flow that advects methane out of the crater region. We also report detection of a large spike of methane in June 2019 with a mean
in situ
value over a two-hour ingest of 20.5 ± 4 ppbv (95% CI). If near-surface production is occurring widely across Mars, it must be accompanied by a fast methane destruction or sequestration mechanism, or both.
Chronic kidney disease (CKD) is a major risk factor for coronary artery disease (CAD). As well as their high prevalence of traditional CAD risk factors, such as diabetes and hypertension, persons ...with CKD are also exposed to other nontraditional, uremia-related cardiovascular disease risk factors, including inflammation, oxidative stress, and abnormal calcium-phosphorus metabolism. CKD and end-stage kidney disease not only increase the risk of CAD, but they also modify its clinical presentation and cardinal symptoms. Management of CAD is complicated in CKD patients, due to their likelihood of comorbid conditions and potential for side effects during interventions. This summary of the Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference on CAD and CKD (including end-stage kidney disease and transplant recipients) seeks to improve understanding of the epidemiology, pathophysiology, diagnosis, and treatment of CAD in CKD and to identify knowledge gaps, areas of controversy, and priorities for research.
Mars methane detection and variability at Gale crater Webster, Christopher R.; Mahaffy, Paul R.; Atreya, Sushil K. ...
Science (American Association for the Advancement of Science),
01/2015, Letnik:
347, Številka:
6220
Journal Article
Recenzirano
Odprti dostop
Reports of plumes or patches of methane in the martian atmosphere that vary over monthly time scales have defied explanation to date. From in situ measurements made over a 20-month period by the ...tunable laser spectrometer of the Sample Analysis at Mars instrument suite on Curiosity at Gale crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 parts per billion by volume (ppbv) at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet degradation of accreted interplanetary dust particles or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period (where 1 sol is a martian day), we observed elevated levels of methane of 7.2 ± 2.1 ppbv (95% CI), implying that Mars is episodically producing methane from an additional unknown source.
Natural orifice endoscopic surgery can enable incisionless approaches, but a major challenge is the lack of small and dexterous instrumentation. Surgical robots have the potential to meet this need ...yet often disrupt the clinical workflow. Hand-held robots that combine thin manipulators and endoscopes have the potential to address this by integrating seamlessly into the clinical workflow and enhancing dexterity. As a case study illustrating the potential of this approach, we describe a hand-held robotic system that passes two concentric tube manipulators through a 5 mm port in a rigid endoscope for transurethral laser prostate surgery. This system is intended to catalyze the use of a clinically superior, yet rarely attempted, procedure for benign prostatic hyperplasia. This paper describes system design and experiments to evaluate the surgeon’s functional workspace and accuracy using the robot. Phantom and cadaver experiments demonstrate successful completion of the target procedure via prostate lobe resection.
The quadrupole mass spectrometer of the Sample Analysis at Mars (SAM) instrument on Curiosity rover has made the first high‐precision measurement of the nonradiogenic argon isotope ratio in the ...atmosphere of Mars. The resulting value of 36Ar/38Ar = 4.2 ± 0.1 is highly significant for it provides excellent evidence that “Mars” meteorites are indeed of Martian origin, and it points to a significant loss of argon of at least 50% and perhaps as high as 85–95% from the atmosphere of Mars in the past 4 billion years. Taken together with the isotopic fractionations in N, C, H, and O measured by SAM, these results imply a substantial loss of atmosphere from Mars in the posthydrodynamic escape phase.
Key Points
First high‐precision measurement of primordial argon isotopes in Martian air
This measurement definitively ties the“martian” meteorites to Mars”
Requires massive loss of Martian atmosphere after the hydrodynamic escape phase
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