25 research outputs found
On the back reaction of gravitational and particle emission and absorption from straight thick cosmic strings: A toy model
The emission and absorption of gravitational waves and massless particles of
an infinitely long straight cosmic string with finite thickness are studied. It
is shown in a general term that the back reaction of the emission and
absorption {\em always} makes the symmetry axis of the string singular. The
singularity is a scalar singularity and cannot be removed.Comment: To appear in Gen. Relativ. Gra
Hertz-to-terahertz dielectric response of nanoconfined water molecules
Broad-band dielectric spectroscopy, heat capacity measurements and molecular
dynamic simulations are applied to study excitations of interacting electric
dipoles spatially arranged in a network with an inter-dipole distance of 5-10
A. The dipoles with magnitude of 1.85 Debye are represented by single H2O
molecules located in voids (0.5 nm size) formed by ions of the crystal lattice
of cordierite. We discover emergence of nontrivial disordered paraelectric
phase of dipolar system with signs of phase transition below 3 K.Comment: 3 pages, 4 figure
Triclosan Disrupts SKN-1/Nrf2- Mediated Oxidative Stress Response in C. elegans and Human Mesenchymal Stem Cells
Triclosan (TCS), an antimicrobial chemical with potential endocrine-disrupting properties, may pose a risk to early embryonic development and cellular homeostasis during adulthood. Here, we show that TCS induces toxicity in both the nematode C. elegans and human mesenchymal stem cells (hMSCs) by disrupting the SKN-1/Nrf2-mediated oxidative stress response. Specifically, TCS exposure affected C. elegans survival and hMSC proliferation in a dose-dependent manner. Cellular analysis showed that TCS inhibited the nuclear localization of SKN-1/Nrf2 and the expression of its target genes, which were associated with oxidative stress response. Notably, TCS-induced toxicity was significantly reduced
by either antioxidant treatment or constitutive SKN-1/Nrf2 activation. As Nrf2 is strongly associated with aging and chemoresistance, these findings will provide a novel approach to the identification of therapeutic targets and disease treatment
Evidence of electronic phase separation in the strongly correlated semiconductor YbB12
The studies of high-quality single-domain crystals of YbB12 were carried out
by the precise x-ray diffraction technique in combination with the low
temperature polarized THz - infrared spectroscopy and accurate magnetotransport
measurements. It has been shown for the first time that this archetypal
strongly correlated system with a metal-insulator transition to a mysterious
dielectric ground state with a metal Fermi surface (Science 362, 65-69 (2018)
and ibid 362, 32-33 (2018)) is actually a heterogeneous compound in the regime
of electronic phase separation. Changes in the configuration of the discovered
dynamic charge stripes are investigated upon cooling, as a result, a conclusion
is drawn in favor of a crossover between different patterns of the filamentary
electronic structure penetrating the semiconducting matrix of YbB12. We argue
that the discovery of stripes in YbB12 is fundamental, elucidating the nature
of exotic dielectric state in Kondo insulators.Comment: 12 pages including 4 figure
High Quality Graphene Using Boudouard Reaction
Following the game changing high pressure CO HiPco process that established the first facile route toward large scale production of single walled carbon nanotubes, CO synthesis of cm sized graphene crystals of ultra high purity grown during tens of minutes is proposed. The Boudouard reaction serves for the first time to produce individual monolayer structures on the surface of a metal catalyst, thereby providing a chemical vapor deposition technique free from molecular and atomic hydrogen as well as vacuum conditions. This approach facilitates inhibition of the graphene nucleation from the CO CO2 mixture and maintains a high growth rate of graphene seeds reaching large scale monocrystals. Unique features of the Boudouard reaction coupled with CO driven catalyst engineering ensure not only suppression of the second layer growth but also provide a simple and reliable technique for surface cleaning. Aside from being a novel carbon source, carbon monoxide ensures peculiar modification of catalyst and in general opens avenues for breakthrough graphene catalyst composite productio
Single-particle and collective excitations of polar water molecules confined in nano-pores within a cordierite crystal lattice
Dielectric ordering of water molecules arranged in a dipolar lattice
Despite the apparent simplicity of a H2O molecule, the mutual ferroelectric ordering of the molecules is unresolved. Here, the authors realize a macroscopic ferroelectric phase transition in a network of dipole-dipole coupled water molecules located in nanopores of gemstone