547 research outputs found
Anomalous melting behavior of solid hydrogen at high pressures
Hydrogen is the most abundant element in the universe, and its properties
under conditions of high temperature and pressure are crucial to understand the
interior of of large gaseous planets and other astrophysical bodies. At ultra
high pressures solid hydrogen has been predicted to transform into a quantum
fluid, because of its high zero point motion. Here we report first principles
two phase coexistence and Z method determinations of the melting line of solid
hydrogen in a pressure range spanning from 30 to 600 GPa. Our results suggest
that the melting line of solid hydrogen, as derived from classical molecular
dynamics simulations, reaches a minimum of 367 K at about 430 GPa, at higher
pressures the melting line of the atomics Cs IV phase regain a positive slope.
In view of the possible importance of quantum effects in hydrogen at such low
temperatures, we also determined the melting temperature of the atomic CsIV
phase at pressures of 400, 500, 600 GPa, employing Feynman path integral
simulations. These result in a downward shift of the classical melting line by
about 100 K, and hint at a possible secondary maximum in the melting line in
the region between 500 and 600 GPa, testifying to the importance of quantum
effects in this system. Combined, our results imply that the stability field of
the zero temperature quantum liquid phase, if it exists at all, would only
occur at higher pressures than previously thought.Comment: Submitted to JC
Immigrant assimilation and BMI and waist size: A longitudinal examination among hispanic and chinese participants in the multi‐ethnic study of atherosclerosis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99611/1/oby20104.pd
Large effective magnetic fields from chiral phonons in rare-earth halides
Time-reversal symmetry (TRS) is pivotal for materials optical, magnetic,
topological, and transport properties. Chiral phonons, characterized by atoms
rotating unidirectionally around their equilibrium positions, generate dynamic
lattice structures that break TRS. Here we report that coherent chiral phonons,
driven by circularly polarized terahertz light pulses, can polarize the
paramagnetic spins in CeF3 like a quasi-static magnetic field on the order of 1
Tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found
the transient magnetization is only excited by pulses resonant with phonons,
proportional to the angular momentum of the phonons, and growing with magnetic
susceptibility at cryogenic temperatures, as expected from the spin-phonon
coupling model. The time-dependent effective magnetic field quantitatively
agrees with that calculated from phonon dynamics. Our results may open a new
route to directly investigate mode-specific spin-phonon interaction in
ultrafast magnetism, energy-efficient spintronics, and non-equilibrium phases
of matter with broken TRS
RHYTHM: An Open Source Imaging Toolkit for Cardiac Panoramic Optical Mapping
Fluorescence optical imaging techniques have revolutionized the field of cardiac electrophysiology and advanced our understanding of complex electrical activities such as arrhythmias. However, traditional monocular optical mapping systems, despite having high spatial resolution, are restricted to a two-dimensional (2D) field of view. Consequently, tracking complex three-dimensional (3D) electrical waves such as during ventricular fibrillation is challenging as the waves rapidly move in and out of the field of view. This problem has been solved by panoramic imaging which uses multiple cameras to measure the electrical activity from the entire epicardial surface. However, the diverse engineering skill set and substantial resource cost required to design and implement this solution have made it largely inaccessible to the biomedical research community at large. To address this barrier to entry, we present an open source toolkit for building panoramic optical mapping systems which includes the 3D printing of perfusion and imaging hardware, as well as software for data processing and analysis. In this paper, we describe the toolkit and demonstrate it on different mammalian hearts: mouse, rat, and rabbit
Anti-tumor activity and mechanistic characterization of APE1/Ref-1 inhibitors in bladder cancer
Bladder cancer is the ninth most common cause of cancer-related deaths worldwide. Although cisplatin is used routinely in treating bladder cancer, refractory disease remains lethal for many patients. The recent addition of immunotherapy has improved patient outcomes; however, a large cohort of patients does not respond to these treatments. Therefore, identification of innovative molecular targets for bladder cancer is crucial. Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional protein involved in both DNA repair and activation of transcription factors through reduction-oxidation (redox) regulation. High APE1/Ref-1 expression is associated with shorter patient survival time in many cancer types. In this study, we found high APE1/Ref-1 expression in human bladder cancer tissue relative to benign urothelium. Inhibition of APE1/Ref-1 redox signaling using APE1/Ref-1-specific inhibitors attenuates bladder cancer cell proliferation in monolayer, in three-dimensional cultures, and in vivo. This inhibition corresponds with an increase in apoptosis and decreased transcriptional activity of NF-κB and STAT3, transcription factors known to be regulated by APE1/Ref-1, resulting in decreased expression of downstream effectors survivin and Cyclin D1 in vitro and in vivo. We also demonstrate that in vitro treatment of bladder cancer cells with APE1/Ref-1 redox inhibitors in combination with standard-of-care chemotherapy cisplatin is more effective than cisplatin alone at inhibiting cell proliferation. Collectively, our data demonstrate that APE1/Ref-1 is a viable drug target for the treatment of bladder cancer, provide a mechanism of APE1/Ref-1 action in bladder cancer cells, and support the use of novel redox-selective APE1/Ref-1 inhibitors in clinical studies. SIGNIFICANCE: This work identifies a critical mechanism for APE1/Ref-1 in bladder cancer growth and provides compelling preclinical data using selective redox activity inhibitors of APE1/Ref-1 in vitro and in vivo
Quasi-molecular and atomic phases of dense solid hydrogen
The high-pressure phases of solid hydrogen are of fundamental interest and
relevant to the interior of giant planets; however, knowledge of these phases
is far from complete. Particle swarm optimization (PSO) techniques were applied
to a structural search, yielding hitherto unexpected high-pressure phases of
solid hydrogen at pressures up to 5 TPa. An exotic quasi-molecular mC24
structure (space group C2/c, stable at 0.47-0.59 TPa) with two types of
intramolecular bonds was predicted, providing a deeper understanding of
molecular dissociation in solid hydrogen, which has been a mystery for decades.
We further predicted the existence of two atomic phases: (i) the oC12 structure
(space group Cmcm, stable at > 2.1 TPa), consisting of planar H3 clusters, and
(ii) the cI16 structure, previously observed in lithium and sodium, stable
above 3.5 TPa upon consideration of the zero-point energy. This work clearly
revised the known zero-temperature and high-pressure (>0.47 TPa) phase diagram
for solid hydrogen and has implications for the constituent structures of giant
planets.Comment: accepted in The Journal of Physical Chemistr
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