Intercomparison of Small Unmanned Aircraft System (sUAS) Measurements for Atmospheric Science During the LAPSE-RATE Campaign

Small unmanned aircraft systems (sUAS) are rapidly transforming atmospheric research. With the advancement of the development and application of these systems, improving knowledge of best practices for accurate measurement is critical for achieving scientific goals. We present results from an intercomparison of atmospheric measurement data from the Lower Atmospheric Process Studies at Elevation—a Remotely piloted Aircraft Team Experiment (LAPSE-RATE) field campaign. We evaluate a total of 38 individual sUAS with 23 unique sensor and platform configurations using a meteorological tower for reference measurements. We assess precision, bias, and time response of sUAS measurements of temperature, humidity, pressure, wind speed, and wind direction. Most sUAS measurements show broad agreement with the reference, particularly temperature and wind speed, with mean value differences of 1.6 ± 2.6 °C and 0.22 ± 0.59 m/s for all sUAS, respectively. sUAS platform and sensor configurations were found to contribute significantly to measurement accuracy. Sensor configurations, which included proper aspiration and radiation shielding of sensors, were found to provide the most accurate thermodynamic measurements (temperature and relative humidity), whereas sonic anemometers on multirotor platforms provided the most accurate wind measurements (horizontal speed and direction). We contribute both a characterization and assessment of sUAS for measuring atmospheric parameters, and identify important challenges and opportunities for improving scientific measurements with sUAS

Identification of diagnostic serum protein profiles of glioblastoma patients

Diagnosis of a glioblastoma (GBM) is triggered by the onset of symptoms and is based on cerebral imaging and histological examination. Serum-based biomarkers may support detection of GBM. Here, we explored serum protein concentrations of GBM patients and used data mining to explore profiles of biomarkers and determine whether these are associated with the clinical status of the patients. Gene and protein expression data for astrocytoma and GBM were used to identify secreted proteins differently expressed in tumors and in normal brain tissues. Tumor expression and serum concentrations of 14 candidate proteins were analyzed for 23 GBM patients and nine healthy subjects. Data-mining methods involving all 14 proteins were used as an initial evaluation step to find clinically informative profiles. Data mining identified a serum protein profile formed by BMP2, HSP70, and CXCL10 that enabled correct assignment to the GBM group with specificity and sensitivity of 89 and 96%, respectively (p < 0.0001, Fischer’s exact test). Survival for more than 15 months after tumor resection was associated with a profile formed by TSP1, HSP70, and IGFBP3, enabling correct assignment in all cases (p < 0.0001, Fischer’s exact test). No correlation was found with tumor size or age of the patient. This study shows that robust serum profiles for GBM may be identified by data mining on the basis of a relatively small study cohort. Profiles of more than one biomarker enable more specific assignment to the GBM and survival group than those based on single proteins, confirming earlier attempts to correlate single markers with cancer. These conceptual findings will be a basis for validation in a larger sample size

Quantitative comparison of the heteroatom effects in the methoxide attachment to pyrylium and thiopyrylium cations. Thermodynamics of the isomerization of pyrans and thiopyrans

The complete set of kinetic and equilibrium constants for the methoxide attachment to a series of 2,6-di-tert-butyl-4-arylpyrylium cations (aryl = XC6H4 with X = p-NO2, m-Cl, p-Cl, H, p-Me, p-OMe, p-NMe2) has been obtained in MeOH at 25°C. These data complement those previously obtained by studying the methoxide attachment to the corresponding thiopyrylium cations. In both series the reaction involves the kinetically controlled formation of both the corresponding 2H and 4H adducts which equilibrate to form only the thermodynamically more stable 2H adduct. The observed kinetic patterns show that the rate-determining step is the combination of the nucleophile with the cation to give the adducts. Moreover, the experimental data indicate that the Leffler-Hammond postulate cannot give information on the position of the transition state along the reaction coordinate. Both kinetic and equilibrium constants for the formation of the 2H and 4H adducts are correlated with the σ+ constants. The obtained ρ values show, for the pyrylium series, a greater sensitivity to the substituent effects with respect to the corresponding thiopyrylium series. From the equilibrium data we estimate that, in contrast with quantum mechanical calculations, the unsubstituted 2H-pyran is at least 4.6 kcal/mol more stable than the corresponding 4H isomer. © 1986 American Chemical Society

Rates and equilibria of the reaction of 2,4,6-triphenylthiopyrylium ion with piperidine and morpholine in Me2SO. An unusual proton transfer to a nitrogen base

The complete set of kinetic and equilibrium constants of the reaction of 2,4,6-triphenylthiopyrylium ion (1) with piperidine and morpholine has been obtained in Me2SO at 25°C. The reaction involves the formation of both the corresponding 2H- and 4H-thiopyrans, which equilibrate to form only the more stable 2H adduct. The kinetic data are consistent with a two-step process wherein the proton transfer from the protonated 2H- and 4H-thiopyran intermediates to the amine is the rate-controlling step. The thermodynamically favored proton transfer to the neutral adducts by the solvated proton shows a rate below the diffusion limit, whereas the observed Brønsted coefficient would indicate a diffusion-controlled process. This behavior is discussed in terms of the Eigen mechanism. The factors affecting the nucleophilic addition are discussed, and a comparison is made with the previously reported reaction of 1 with primary amines. © 1984 American Chemical Society

Steric effects on rates and equilibria of a cation-anion combination reaction: The methoxide attachment to 4-substituted 2,6-di-tert-butylpyrylium cations

The kinetic and equilibrium constants for the reaction of 2,6-di-tert-butyl-4-R-pyrylium cations (R = H, Me, t-Bu, Et3C, Ph) with methoxide ion, to yield the corresponding 2H and 4H adducts, have been determined in MeOH at 25°C. The reaction involves the kinetically controlled formation of the 4H adduct only when R = H or Me, whereas in the other cases a mixture of both the ZH and 4H adducts is formed. The 2H adducts are the thermodynamically favored products, though in the case of the methyl-substituted cation a comparable amount of the anhydro base is also formed. The rate constants for the formation of the 4H adducts follow a regular trend showing a low sensitivity to steric effects, whereas the corresponding equilibrium constants are not affected by steric interactions until a certain value of the steric hindrance of the γ-substituent is reached. Above this value steric effects are greater on equilibria than on rates. These observations are interpreted in terms of an ion pair-like transition state in which the nucleophile specifically interacts with the electrophilic center. © 1988 American Chemical Society