2,498 research outputs found
New Topflavor Models with Seesaw Mechanism
New class of models are constructed in which the third family quarks, but not
leptons, experience a new SU(2) or U(1) gauge force. Anomaly cancellation
enforces the introduction of spectator quarks so that the top and bottom masses
are naturally generated via a seesaw mechanism. We find the new contributions
to the (S,T,U) parameters and Zbb vertex to be generically small. We further
analyze how the reasonable flavor mixing pattern can be generated to ensure the
top-seesaw mechanism and sufficiently suppress the flavor-changing effects for
light quarks. Collider signatures for the light Higgs boson and top quark are
also discussed.Comment: To match the version in Rapid Communication of PRD, RevTex 5p
Self-induced charge currents in electromagnetic materials, photon effective rest mass and some related topics
The contribution of self-induced charge currents of metamaterial media to
photon effective rest mass is discussed in detail in the present paper. We
concern ourselves with two kinds of photon effective rest mass, i.e., the
frequency-dependent and frequency-independent effective rest mass. Based on
these two definitions, we calculate the photon effective rest mass in the
left-handed medium and the 2TDLM media, the latter of which is described by the
so-called two time derivative Lorentz material (2TDLM) model. Additionally, we
concentrate primarily on the torque, which is caused by the interaction between
self-induced charge currents in dilute plasma (e.g., the secondary cosmic rays)
and interstellar magnetic fields (ambient cosmic magnetic vector potentials),
acting on the torsion balance of the rotating torsion balance experiment.Comment: 11 pages, Late
Gravitational Analogues, Geometric Effects and Gravitomagnetic Charge
This essay discusses some geometric effects associated with gravitomagnetic
fields and gravitomagnetic charge as well as the gravity theory of the latter.
Gravitomagnetic charge is the duality of gravitoelectric charge (mass) and is
therefore also termed the dual mass which represents the topological property
of gravitation. The field equation of gravitomagnetic matter is suggested and a
static spherically symmetric solution of this equation is offered. A possible
explanation of the anomalous acceleration acting on Pioneer spacecrafts are
briefly proposed.Comment: 9 pages,0 figures, Late
Production and decay of the neutral top-pion in high energy colliders
We study the production and decay of the neutral top-pion
predicted by topcolor-assisted technicolor(TC2) theory. Our results show that,
except the dominant decay modes , and , the
can also decay into and modes. It can
be significantly produced at high energy collider(LC) experiments
via the processes and . We further calculate the production cross sections of the
processes and . We find that the signatures of the neutral top-pion
can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.
Nonlinear optical diode effect in a magnetic Weyl semimetal
Weyl semimetals have emerged as a promising quantum material system to
discover novel electrical and optical phenomena, due to their combination of
nontrivial quantum geometry and strong symmetry breaking. One crucial class of
such novel transport phenomena is the diode effect, which is of great interest
for both fundamental physics and modern technologies. In the electrical regime,
giant electrical diode effect (the nonreciprocal transport) has been observed
in Weyl systems. In the optical regime, novel optical diode effects have been
theoretically considered but never probed experimentally. Here, we report the
observation of the nonlinear optical diode effect (NODE) in the magnetic Weyl
semimetal CeAlSi, where the magnetic state of CeAlSi introduces a pronounced
directionality in the nonlinear optical second-harmonic generation (SHG). By
physically reversing the beam path, we show that the measured SHG intensity can
change by at least a factor of six between forward and backward propagation
over a wide bandwidth exceeding 250 meV. Supported by density-functional theory
calculations, we establish the linearly dispersive bands emerging from Weyl
nodes as the origin of the extreme bandwidth. Intriguingly, the NODE
directionality is directly controlled by the direction of magnetization. By
utilizing the electronically conductive semimetallic nature of CeAlSi, we
demonstrate current-induced magnetization switching and thus electrical control
of the NODE in a mesoscopic spintronic device structure with current densities
as small as 5 kA/cm. Our results advance ongoing research to identify novel
nonlinear optical/transport phenomena in magnetic topological materials. The
NODE also provides a way to measure the phase of nonlinear optical
susceptibilities and further opens new pathways for the unidirectional
manipulation of light such as electrically controlled optical isolators.Comment: 28 pages, 12 figure
Epigenetic modification of histone 3 at lysine 9 in sheep zygotes and its relationship with DNA methylation
<p>Abstract</p> <p>Background</p> <p>Previous studies indicated that, unlike mouse zygotes, sheep zygotes lacked the paternal DNA demethylation event. Another epigenetic mark, histone modification, especially at lysine 9 of histone 3 (H3K9), has been suggested to be mechanically linked to DNA methylation. In mouse zygotes, the absence of methylated H3K9 from the paternal pronucleus has been thought to attribute to the paternal DNA demethylation.</p> <p>Results</p> <p>By using the immunofluorescence staining approach, we show that, despite the difference in DNA methylation, modification of H3K9 is similar between the sheep and mouse zygotes. In both species, H3K9 is hyperacetylated or hypomethylated in paternal pronucleus relative to maternal pronucleus. In fact, sheep zygotes can also undergo paternal DNA demethylation, although to a less extent than the mouse. Further examinations of individual zygotes by double immunostaining revealed that, the paternal levels of DNA methylation were not closely associated with that of H3K9 acetylation or tri-methylation. Treatment of either 5-azacytidine or Trichostatin A did not induce a significant decrease of paternal DNA methylation levels.</p> <p>Conclusion</p> <p>Our results suggest that in sheep lower DNA demethylation of paternal genomes is not due to the H3K9 modification and the methylated DNA sustaining in paternal pronucleus does not come from DNA <it>de novo </it>methylation.</p
Viral integration drives multifocal HCC during the occult HBV infection
© 2019 The Author(s). Background & Aims: Although the prognosis of patients with occult hepatitis B virus (HBV) infection (OBI) is usually benign, a small portion may undergo cirrhosis and subsequently hepatocellular carcinoma (HCC). We studied the mechanism of life-long Integration of virus DNA into OBI host's genome, of which may induce hepatocyte transformation. Methods: We applied HBV capture sequencing on single cells from an OBI patient who, developed multiple HCC tumors and underwent liver resection in May 2013 at Tongji Hospital in China. Despite with the undetectable virus DNA in serum, we determined the pattern of viral integration in tumor cells and adjacent non-tumor cells and obtained the details of the viral arrangement in host genome, and furthermore the HBV integrated region in cancer genome. Results: HBV captured sequencing of tissues and individual cells revealed that samples from multiple tumors shared two viral integration sites that could affect three host genes, including CSMD2 on chr1 and MED30/EXT1 on chr8. Whole genome sequencing further indicated one hybrid chromosome formed by HBV integrations between chr1 and chr8 that was shared by multiple tumors. Additional 50 poorly differentiated liver tumors and the paired adjacent non-tumors were evaluated and functional studies suggested up-regulated EXT1 expression promoted HCC growth. We further observed that the most somatic mutations within the tumor cell genome were common among the multiple tumors, suggesting that HBV associated, multifocal HCC is monoclonal in origin. Conclusion: Through analyzing the HBV integration sites in multifocal HCC, our data suggested that the tumor cells were monoclonal in origin and formed in the absence of active viral replication, whereas the affected host genes may subsequently contribute to carcinogenesis
Maximal Violation of Bell's Inequalities for Continuous Variable Systems
We generalize Bell's inequalities to biparty systems with continuous quantum
variables. This is achieved by introducing the Bell operator in perfect analogy
to the usual spin-1/2 systems. It is then demonstrated that two-mode squeezed
vacuum states display quantum nonlocality by using the generalized Bell
operator. In particular, the original Einstein-Podolsky-Rosen entangled states,
which are the limiting case of the two-mode squeezed vacuum states, can
maximally violate Bell's inequality due to Clauser, Horne, Shimony and Holt.
The experimental aspect of our scheme and nonlocality of arbitrary biparticle
entangled pure states of continuous variables are briefly considered.Comment: RevTEX, 4 pages, no figure. An important note was adde
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