1,725 research outputs found
First Abundance Measurement of Organic Molecules in the Atmosphere of HH 212 Protostellar Disk
HH 212 is one of the well-studied protostellar systems, showing the first
vertically resolved disk with a warm atmosphere around the central protostar.
Here we report a detection of 9 organic molecules (including newly detected
ketene, formic acid, deuterated acetonitrile, methyl formate, and ethanol) in
the disk atmosphere, confirming that the disk atmosphere is, for HH 212, the
chemically rich component, identified before at a lower resolution as a
"hot-corino". More importantly, we report the first systematic survey and
abundance measurement of organic molecules in the disk atmosphere within
40 au of the central protostar. The relative abundances of these molecules are
similar to those in the hot corinos around other protostars and in Comet
Lovejoy. These molecules can be either (i) originally formed on icy grains and
then desorbed into gas phase or (ii) quickly formed in the gas phase using
simpler species ejected from the dust mantles. The abundances and spatial
distributions of the molecules provide strong constraints on models of their
formation and transport in star formation. These molecules are expected to form
even more complex organic molecules needed for life and deeper observations are
needed to find them.Comment: 12 pages, 4 figure
Solely economic mitigation strategy suggests upward revision of nationally determined contributions
The use of equity principles to review the nationally determined contributions (NDCs) is critical to facilitating more ambitious climate actions. However, disagreement over the equity principles persists. We instead treat emission reduction as a solely economic behavior motivated by avoiding future economic damage from climate change. Assuming no international cooperation, we provide a solely economic mitigation pathway to review national climate pledges until 2100. Using the value in 2030 to review the NDCs, we find that the NDCs of China, the USA, and the EU are 1.5, 1.4, and 0.9 respective GtCO2eq lower than their solely economic emission levels, whereas India commits 3.8 GtCO2eq more than its solely economic emission level. We also propose an equal-effort cooperation scenario toward 2°C where each country reduces emissions by 28% of their solely economic levels in 2030. Through exploration of the economic trade-offs, our results suggest that more ambitious NDCs are urgently needed
Natural liquid organic hydrogen carrier with low dehydrogenation energy: A first principles study
Liquid organic hydrogen carriers (LOHCs) represent a promising approach for
hydrogen storage due to their favorable properties including stability and
compatibility with the existing infrastructure. However, fossil-based LOHC
molecules are not green or sustainable. Here we examined the possibility of
using norbelladine and trisphaeridine, two typical structures of Amaryllidaceae
alkaloids, as the LOHCs from the sustainable and renewable sources of natural
products. Our first principles thermodynamics calculations reveal low
reversibility for the reaction of norbelladine to/from perhydro-norbelladine
because of the existence of stabler isomers of perhydro-norbelladine. On the
other hand, trisphaeridine is found promising due to its high hydrogen storage
capacity (5.9 wt\%) and favorable energetics. Dehydrogenation of
perhydro-trisphaeridine has an average standard enthalpy change of 54
KJ/mol-H, similar to that of perhydro-\textit{N}-ethylcarbazole, a typical
LOHC known for its low dehydrogenation enthalpy. This work is a first
exploration of Amaryllidaceae alkaloids for hydrogen storage and the results
demonstrate, more generally, the potential of bio-based molecules as a new
sustainable resource for future large-scale hydrogen storage
Centrality, system size and energy dependences of charged-particle pseudo-rapidity distribution
Utilizing the three-fireball picture within the quark combination model, we
study systematically the charged particle pseudorapidity distributions in both
Au+Au and Cu+Cu collision systems as a function of collision centrality and
energy, 19.6, 62.4, 130 and 200 GeV, in full pseudorapidity
range. We find that: (i)the contribution from leading particles to
distributions increases with the decrease of the collision
centrality and energy respectively; (ii)the number of the leading particles is
almost independent of the collision energy, but it does depend on the nucleon
participants ; (iii)if Cu+Cu and Au+Au collisions at the same
collision energy are selected to have the same , the resulting of
charged particle distributions are nearly identical, both in the
mid-rapidity particle density and the width of the distribution. This is true
for both 62.4 GeV and 200 GeV data. (iv)the limiting fragmentation phenomenon
is reproduced. (iiv) we predict the total multiplicity and pseudorapidity
distribution for the charged particles in Pb+Pb collisions at TeV. Finally, we give a qualitative analysis of the
and as function of
and from RHIC to LHC.Comment: 12 pages, 8 figure
Transcutaneous electrical nerve stimulation in the treatment of patients with poststroke urinary incontinence
Male germline recombination of a conditional allele by the widely used Dermo1â cre (Twist2â cre) transgene
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138422/1/dvg23048_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138422/2/dvg23048.pd
The role of cellular oxidative stress in regulating glycolysis energy metabolism in hepatoma cells
<p>Abstract</p> <p>Background</p> <p>The Warburg effect has been found in a wide spectrum of human cancers, however the underlying mechanisms are still unclear. This study aims to explore the role of cellular oxidative stress in relation to glycolysis and the Warburg effect in hepatoma cells.</p> <p>Methods</p> <p>Various cell lines combining environmental hypoxia was used as an in vitro model to mimic tumor microenvironment in vivo. Superoxide dismutases (SOD) and xanthine oxidase (XO) gene transfection were used to produce various cellular redox levels. 2',7'-dichlorofluorescin (DCF) fluorescence and ESR spectrum were used to detect cellular reactive oxygen species (ROS).</p> <p>Results</p> <p>We found that endogenous or exogenous interference with the cellular oxidative stress can sensitively regulate glycolysis and the Warburg effect in hepatoma cells. Hepatoma cells displayed a high level of free radicals compared to immortalized normal hepatocyte cells. Increasing the level of ROS stress in hepatoma cells can directly upregulate HIF-1 and activate glycolysis without requirement of a hypoxic condition. This explains the mechanism whereby aerobic glycolysis, i.e. the Warburg effect arises. Either endogenously upregulating SOD or exogenously administration with antioxidant can, through downregulating ROS level, effectively regulate energy pathways in hepatoma cells and can inhibit the growth of tumor cells and xenograft tumors.</p> <p>Conclusion</p> <p>This study suggests that the Warburg effect was related to an inherently high level of cellular ROS and HIF-1. Hepatoma cells adaptation to hypoxia for survival and rapid growth exploits oxidative stress ectopically activated glycolysis to compensate the energy supply. This specific mechanism in which tumor cells through cellular oxidative stress activate glycolysis to meet their energy metabolism requirement could be exploited to selectively kill tumor cells.</p
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