6,445 research outputs found
High Speed Lunar Navigation for Crewed and Remotely Piloted Vehicles
Increased navigation speed is desirable for lunar rovers, whether autonomous, crewed or remotely operated, but is hampered by the low gravity, high contrast lighting and rough terrain. We describe lidar based navigation system deployed on NASA's K10 autonomous rover and to increase the terrain hazard situational awareness of the Lunar Electric Rover crew
Potential diagnostic and prognostic values of detecting promoter hypermethylation in the serum of patients with gastric cancer
While there is no reliable serum biomarker for the diagnosis and monitoring of patients with gastric cancer, we tested the potential diagnostic and prognostic values of detecting methylation changes in the serum of gastric cancer patients. DNA was extracted from the pretherapeutic serum of 60 patients with confirmed gastric adenocarcinoma and 22 age-matched noncancer controls. Promoter hypermethylation in 10 tumour-related genes (APC, E-cadherin, GSTP1, hMLH1, MGMT, p15, p16, SOCS1, TIMP3 and TGF-beta RII) was determined by quantitative methylation-specific PCR (MethyLight). Preferential methylation in the serum DNA of gastric cancer patients was noted in APC (17%), E-cadherin (13%), hMLH1 (41%) and TIMP3 (17%) genes. Moreover, patients with stages III/IV diseases tended to have higher concentrations of methylated APC (P=0.08), TIMP3 (P=0.005) and hMLH1 (P=0.03) in the serum. In all, 33 cancers (55%) had methylation detected in the serum in at least one of these four markers, while three normal subjects had methylation detected in the serum (specificity 86%). The combined use of APC and E-cadherin methylation markers identified a subgroup of cancer patients with worse prognosis (median survival 3.3 vs 16.1 months, P=0.006). These results suggest that the detection of DNA methylation in the serum may carry both diagnostic and therapeutic values in gastric cancer patients
Understanding the Relationship between Solar Coronal Abundances and F10.7 cm Radio Emission
Sun-as-a-star coronal plasma composition, derived from full-Sun spectra, and
the F10.7 radio flux (2.8 GHz) have been shown to be highly correlated (r =
0.88) during solar cycle 24. However, this correlation becomes nonlinear during
increased solar magnetic activity. Here, we use co-temporal, high spatial
resolution, multi-wavelength images of the Sun to investigate the underlying
causes of the non-linearity between coronal composition (FIP bias) and F10.7
solar index correlation. Using the Karl G. Jansky Very Large Array (JVLA),
Hinode/EIS (EUV Imaging Spectrometer), and the Solar Dynamic Observatory (SDO),
we observed a small active region, AR 12759, throughout the solar atmosphere
from the photosphere to the corona. Results of this study show that the
magnetic field strength (flux density) in active regions plays an important
role in the variability of coronal abundances, and it is likely the main
contributing factor to this non-linearity during increased solar activity.
Coronal abundances above cool sunspots are lower than in dispersed magnetic
plage regions. Strong magnetic concentrations are associated with stronger
F10.7 cm gyroresonance emission. Considering that as the solar cycle moves from
minimum to maximum, the size of sunspots and their field strength increase with
gyroresonance component, the distinctly different tendencies of radio emission
and coronal abundances in the vicinity of sunspots is the likely cause of
saturation of Sun-as-a-star coronal abundances during solar maximum, while the
F10.7 index remains well correlated with the sunspot number and other magnetic
field proxies.Comment: 15 pages, 5 figures, 2 tables, accepted for publication in The
Astrophysical Journa
Synthesis, structure and dioxygen reactivity of a bis(µ-iodo)dicopper(I) complex supported by the [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine ligand
The air-sensitive bis(µ-iodo)dicopper(I) complex 1 supported by [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine (L) has been prepared by treating copper(I) iodide with L in anhydrous THF. Compound 1 crystallizes as a dimer in space group C2/c. Each copper(I) center has distorted tetrahedral N2I2 coordination geometry with Cu–N(pyridyl) distances 2.061(3) and 2.063(3) Å, Cu–I distances 2.6162(5) and 2.7817(5) and a CuCu distance of 2.9086(8) Å. Complex 1 is rapidly oxidized by dioxygen in CH2Cl2 with a 1 : 1 stoichiometry giving the bis(µ-iodo)peroxodicopper(II) complex [Cu(L)(µ-I)]2O2 (2). The reaction of 1 with dioxygen has been characterized by UV-vis, mass spectrometry, EPR and Cu K-edge X-ray absorption spectroscopy at low temperature (193 K) and above. The mass spectrometry and low temperature EPR measurements suggested an equilibrium between the bis(µ-iodo)peroxodicopper(II) complex 2 and its dimer, namely, the tetranuclear (peroxodicopper(II))2 complex [Cu(L)(µ-I)]4O4 (2). Complex 2 undergoes an effective oxo-transfer reaction converting PPh3 into OPPh3 under anaerobic conditions. At sufficiently high concentration of PPh3, the oxygen atom transfer from 2 to PPh3 was followed by the formation of [Cu(PPh3)3I]. The dioxygen reactivity of 1 was compared with that known for other halo(amine)copper(I) dimers
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