The most comprehensive search for organics in the Martian soil was performed by the Viking Landers. Martian soil was subjected to a thermal volatilization process to vaporize and break organic ...molecules, and the resultant gases and volatiles were analyzed by gas chromatography‐mass spectrometry. Only water at 0.1–1.0 wt% was detected, with traces of chloromethane at 15 ppb, at Viking landing site 1, and water at 0.05–1.0 wt% and carbon dioxide at 50–700 ppm, with traces of dichloromethane at 0.04–40 ppb, at Viking landing site 2. These chlorohydrocarbons were considered to be terrestrial contaminants, although they had not been detected at those levels in the blank runs. Recently, perchlorate was discovered in the Martian Arctic soil by the Phoenix Lander. Here we show that when Mars‐like soils from the Atacama Desert containing 32 ± 6 ppm of organic carbon are mixed with 1 wt% magnesium perchlorate and heated, nearly all the organics present are decomposed to water and carbon dioxide, but a small amount is chlorinated, forming 1.6 ppm of chloromethane and 0.02 ppm of dichloromethane at 500°C. A chemical kinetics model was developed to predict the degree of oxidation and chlorination of organics in the Viking oven. Reinterpretation of the Viking results therefore suggests ≤0.1% perchlorate and 1.5–6.5 ppm organic carbon at landing site 1 and ≤0.1% perchlorate and 0.7–2.6 ppm organic carbon at landing site 2. The detection of organics on Mars is important to assess locations for future experiments to detect life itself.
Establishing the presence and state of organic matter, including its possible biosignatures, in martian materials has been an elusive quest, despite limited reports of the existence of organic matter ...on Mars. We report the in situ detection of organic matter preserved in lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. Diverse pyrolysis products, including thiophenic, aromatic, and aliphatic compounds released at high temperatures (500° to 820°C), were directly detected by evolved gas analysis. Thiophenes were also observed by gas chromatography–mass spectrometry. Their presence suggests that sulfurization aided organic matter preservation. At least 50 nanomoles of organic carbon persists, probably as macromolecules containing 5% carbon as organic sulfur molecules.
The generation of temperature gradients on nanoparticles heated externally by a magnetic field is crucially important in magnetic hyperthermia therapy. But the intrinsic low heating power of magnetic ...nanoparticles, at the conditions allowed for human use, is a limitation that restricts the general implementation of the technique. A promising alternative is local intracellular hyperthermia, whereby cell death (by apoptosis, necroptosis, or other mechanisms) is attained by small amounts of heat generated at thermosensitive intracellular sites. However, the few experiments conducted on the temperature determination of magnetic nanoparticles have found temperature increments that are much higher than the theoretical predictions, thus supporting the local hyperthermia hypothesis. Reliable intracellular temperature measurements are needed to get an accurate picture and resolve the discrepancy. In this paper, we report the real-time variation of the local temperature on γ-Fe2O3 magnetic nanoheaters using a Sm3+/Eu3+ ratiometric luminescent thermometer located on its surface during exposure to an external alternating magnetic field. We measure maximum temperature increments of 8 °C on the surface of the nanoheaters without any appreciable temperature increase on the cell membrane. Even with magnetic fields whose frequency and intensity are still well within health safety limits, these local temperature increments are sufficient to produce a small but noticeable cell death, which is enhanced considerably as the magnetic field intensity is increased to the maximum level tolerated for human use, consequently demonstrating the feasibility of local hyperthermia.
The Sample Analysis at Mars on the Curiosity rover analyzed the major volatile content of four eolian samples at three locations in Gale crater. The Rocknest sample was taken from an inactive sand ...shadow with a significant component of dust‐sized grains, while Gobabeb and Ogunquit Beach samples were taken from different locations in the Bagnold Dune field and had dust‐free, fine sand sized grains. All eolian samples possessed more oxychlorine, carbon, and nitrate relative to sedimentary materials in Gale crater. Evolved CO2 above 450 °C was consistent with ~0.7 and ~0.4 wt. % carbonate in the Bagnold Dunes and Rocknest materials, respectively, with a regional source inside Gale crater. The fine‐grained phase of Rocknest was enriched in adsorbed water and perhaps in Fe sulfate and Fe nitrate/nitrite compared to coarser Bagnold materials and was estimated to contain up to ~0.1 wt. % of organic carbon.
Plain Language Summary
Wind‐driven processes have been the dominant force shaping the landscape on Mars for the last 3 billion years. Sands from a Martian dune field were analyzed and compared to other deposits with smaller, dust‐sized grains. Samples were heated to release gases and determine their composition, revealing that sandy and dusty samples contained more carbon than rock samples. Sand and dust contained more nitrogen and chlorine bearing molecules made in the atmosphere and grain surfaces, either because they are sitting on the surface accumulating them or because nitrogen and chlorine were removed from rocks in the past by water or other processes. Dusty samples had similar compositions to sandy samples and also contained phases associated only with the small dust grains, including adsorbed water. Dust appeared to contain simple organic carbon molecules, perhaps due to atmospheric and surface processes acting to break down more complex organic molecules in rocks. Sand appeared to contain more inorganic carbon in the form of carbonate, even though the rocks nearby do not contain carbonate. Because sand can only travel a limited distance, this suggests that carbonate is present in rocks somewhere in Gale crater that we have not explored yet.
Key Points
Eolian materials generally possessed more O2, CO2, and NO than sedimentary materials in Gale crater
The presence of CO2 that evolved at temperatures greater than 450 degrees Celsius is consistent with the presence of carbonate in the eolian materials
Differences in evolved gases between dust‐bearing and dust‐free eolian materials suggest that dust on Mars is enriched in volatiles
Abstract Cornea, lens and eye models are analyzed and compared to experimental findings to assess properties and eventually unveil optical design principles involved in the structure and function of ...the optical system of the eye. Models and data often show good match but also some paradoxes. The optical design seems to correspond to a wide angle lens. Compared to conventional optical systems, the eye presents a poor optical quality on axis, but a relatively good quality off-axis, thus yielding higher homogeneity for a wide visual field. This seems the result of an intriguing combination of the symmetry design principle with a total lack of rotational symmetry, decentrations and misalignments of the optical surfaces.
The nitrate/(per)chlorate relationship on Mars Stern, Jennifer C.; Sutter, Brad; Jackson, W. Andrew ...
Geophysical research letters,
28 March 2017, Letnik:
44, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Nitrate was recently detected in Gale Crater sediments on Mars at abundances up to ~600 mg/kg, confirming predictions of its presence at abundances consistent with models based on impact‐generated ...nitrate and other sources of fixed nitrogen. Terrestrial Mars analogs, Mars meteorites, and other solar system materials help establish a context for interpreting in situ nitrate measurements on Mars, particularly in relation to other cooccuring salts. We compare the relative abundance of nitrates to oxychlorine (chlorate and/or perchlorate, hereafter (per)chlorate) salts on Mars and Earth. The nitrate/(per)chlorate ratio on Mars is < 1, significantly lower than on Earth (nitrate/(per)chlorate > 103), suggesting not only the absence of biological activity but also different (per)chlorate formation mechanisms on Mars than on Earth.
Key Points
Nitrate and perchlorate on Mars behave as they do in environments dominated by abiotic processes on Earth
The nitrate/perchlorate ratio is vastly lower on Mars than on Earth due to high Martian perchlorate abundance, suggesting unique processes
The nitrate/perchlorate ratio in Hesperian rocks could be compared to younger materials to detect ongoing production of either species
A single scoop of the Rocknest aeolian deposit was sieved (< 150 µm), and four separate sample portions, each with a mass of ~50 mg, were delivered to individual cups inside the Sample Analysis at ...Mars (SAM) instrument by the Mars Science Laboratory rover's sample acquisition system. The samples were analyzed separately by the SAM pyrolysis evolved gas and gas chromatograph mass spectrometer analysis modes. Several chlorinated hydrocarbons including chloromethane, dichloromethane, trichloromethane, a chloromethylpropene, and chlorobenzene were identified by SAM above background levels with abundances of ~0.01 to 2.3 nmol. The evolution of the chloromethanes observed during pyrolysis is coincident with the increase in O2 released from the Rocknest sample and the decomposition of a product of N‐methyl‐N‐(tert‐butyldimethylsilyl)‐trifluoroacetamide (MTBSTFA), a chemical whose vapors were released from a derivatization cup inside SAM. The best candidate for the oxychlorine compounds in Rocknest is a hydrated calcium perchlorate (Ca(ClO4)2·nH2O), based on the temperature release of O2 that correlates with the release of the chlorinated hydrocarbons measured by SAM, although other chlorine‐bearing phases are being considered. Laboratory analog experiments suggest that the reaction of Martian chlorine from perchlorate decomposition with terrestrial organic carbon from MTBSTFA during pyrolysis can explain the presence of three chloromethanes and a chloromethylpropene detected by SAM. Chlorobenzene may be attributed to reactions of Martian chlorine released during pyrolysis with terrestrial benzene or toluene derived from 2,6‐diphenylphenylene oxide (Tenax) on the SAM hydrocarbon trap. At this time we do not have definitive evidence to support a nonterrestrial carbon source for these chlorinated hydrocarbons, nor do we exclude the possibility that future SAM analyses will reveal the presence of organic compounds native to the Martian regolith.
Key Points
Perchlorates and chlorinated hydrocarbons detected by SAM at Rocknest
Chlorohydrocarbons produced from terrestrial organic carbon and Martian chlorine
No definitive evidence of Martian organic carbon at Rocknest
Purpose
The term “pachychoroid” refers to a newly described phenotype in which functional and structural choroidal changes are thought to play a key pathogenic role in a spectrum of related retinal ...disorders. A more detailed understanding of how the choroid is involved within this spectrum and a better knowledge of the most relevant clinical signs of the pachychoroid phenotype are important to differentiate these disorders from other retinal conditions. Our objectives are to provide a literature review of pachychoroid and the commonalities that may be present across pathologies included in the spectrum, and to provide details on the examination, monitoring, and management of these disorders.
Methods
We searched the PubMed web platform to identify relevant studies using the following keywords: pachychoroid, pachychoroid pigment epitheliopathy, pachychoroid neovasculopathy, aneurysmal type 1 neovascularization, focal choroidal excavation, peripapillary pachychoroid syndrome, vasculopathy pachysclera, pachychoroid geographic atrophy, and pachydrusen. We selected 157 publications and identified the most important features related to pachychoroid.
Results
The presence of hypertrophic or congested vessels in the choroid, not thickened choroid per se, under an area of reduced or absent choriocapillaris in the posterior pole seems to be the most salient feature of pachychoroid. However, other qualitative/quantitative features are needed to differentiate the uncomplicated pachychoroid from the pathological pachychoroid clinical spectrum, which may be associated with exudation, neovascularization, and/or retinal pigment epithelium and photoreceptor atrophy.
Conclusions
The most salient feature of pachychoroid appears to be the presence of large vessels under an area of reduced or absent choriocapillaris. Knowledge of the features and pathogenesis of the different disorders in the pachychoroid spectrum may assist in the management of patients.
The purpose of this paper is to record and analyze induced gamma-band activity (GBA) (30-60 Hz) in cerebral motor areas during imaginary movement and to compare it quantitatively with activity ...recorded in the same areas during actual movement using a simplified electroencephalogram (EEG). Brain activity (basal activity, imaginary motor task and actual motor task) is obtained from 12 healthy volunteer subjects using an EEG (Cz channel). GBA is analyzed using the mean power spectral density (PSD) value. Event-related synchronization (ERS) is calculated from the PSD values of the basal GBA (GBAb), the GBA of the imaginary movement (GBAim) and the GBA of the actual movement (GBAac). The mean GBAim and GBAac values for the right and left hands are significantly higher than the GBAb value (p = 0.007). No significant difference is detected between mean GBA values during the imaginary and actual movement (p = 0.242). The mean ERS values for the imaginary movement (ERSimM (%) = 23.52) and for the actual movement (ERSacM = 27.47) do not present any significant difference (p = 0.117). We demonstrated that ERS could provide a useful way of indirectly checking the function of neuronal motor circuits activated by voluntary movement, both imaginary and actual. These results, as a proof of concept, could be applied to physiology studies, brain-computer interfaces, and diagnosis of cognitive or motor pathologies.
Glioblastoma is an aggressive and fast‐growing brain tumor with poor prognosis. Predicting the expected survival of patients with glioblastoma is a key task for efficient treatment and surgery ...planning. Survival predictions could be enhanced by means of a radiomic system. However, these systems demand high numbers of multicontrast images, the acquisitions of which are time consuming, giving rise to patient discomfort and low healthcare system efficiency. Synthetic MRI could favor deployment of radiomic systems in the clinic by allowing practitioners not only to reduce acquisition time, but also to retrospectively complete databases or to replace artifacted images. In this work we analyze the replacement of an actually acquired MR weighted image by a synthesized version to predict survival of glioblastoma patients with a radiomic system. Each synthesized version was realistically generated from two acquired images with a deep learning synthetic MRI approach based on a convolutional neural network. Specifically, two weighted images were considered for the replacement one at a time, a T2w and a FLAIR, which were synthesized from the pairs T1w and FLAIR, and T1w and T2w, respectively. Furthermore, a radiomic system for survival prediction, which can classify patients into two groups (survival >480 days and
≤ 480 days), was built. Results show that the radiomic system fed with the synthesized image achieves similar performance compared with using the acquired one, and better performance than a model that does not include this image. Hence, our results confirm that synthetic MRI does add to glioblastoma survival prediction within a radiomics‐based approach.
Glioblastoma is a common brain tumor, with poor prognosis. Radiomic systems (RSs) may improve patient care as an aid to predict survival and personalize treatments. Synthetic MRI favors deployment of RSs by reducing acquisition time and curating databases. Whether an RS can reliably work on synthesized images needs verification. We found that an RS fed with a set of images of which one is synthesized performs similarly to one fed with acquired images, and better than one that ignores the synthesized image.
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