1,357 research outputs found
Tuning a magnetic Feshbach resonance with spatially modulated laser light
We theoretically investigate the control of a magnetic Feshbach resonance
using a bound-to-bound molecular transition driven by spatially modulated laser
light. Due to the spatially periodic coupling between the ground and excited
molecular states, there exists a band structure of bound states, which can
uniquely be characterized by some extra bumps in radio-frequency spectroscopy.
With the increasing of coupling strength, the series of bound states will cross
zero energy and directly result in a number of scattering resonances, whose
position and width can be conveniently tuned by the coupling strength of the
laser light and the applied magnetic field (i.e., the detuning of the ground
molecular state). In the presence of the modulated laser light, universal
two-body bound states near zero-energy threshold still exist. However, compared
with the case without modulation, the regime for such universal states is
usually small. An unified formula which embodies the influence of the modulated
coupling on the resonance width is given. The spatially modulated coupling also
implies a local spatially varying interaction between atoms. Our work proposes
a practical way of optically controlling interatomic interactions with high
spatial resolution and negligible atomic loss.Comment: 9pages, 5figur
Observation of Landau level-like quantizations at 77 K along a strained-induced graphene ridge
Recent studies show that the electronic structures of graphene can be
modified by strain and it was predicted that strain in graphene can induce
peaks in the local density of states (LDOS) mimicking Landau levels (LLs)
generated in the presence of a large magnetic field. Here we report scanning
tunnelling spectroscopy (STS) observation of nine strain-induced peaks in LDOS
at 77 K along a graphene ridge created when the graphene layer was cleaved from
a sample of highly oriented pyrolytic graphite (HOPG). The energies of these
peaks follow the progression of LLs of massless 'Dirac fermions' (DFs) in a
magnetic field of 230 T. The results presented here suggest a possible route to
realize zero-field quantum Hall-like effects at 77 K
Life fingerprints of nuclear reactions in the body of animals
Nuclear reactions are a very important natural phenomenon in the universe. On the earth, cosmic rays constantly cause nuclear reactions. High energy beams created by medical devices also induce nuclear reactions in the human body. The biological role of these nuclear reactions is unknown. Here we show that the in vivo biological systems are exquisite and sophisticated by nature in influence on nuclear reactions and in resistance to radical damage in the body of live animals. In this study, photonuclear reactions in the body of live or dead animals were induced with 50-MeV irradiation. Tissue nuclear reactions were detected by positron emission tomography (PET) imaging of the induced beta+ activity. We found the unique tissue "fingerprints" of beta+ (the tremendous difference in beta+ activities and tissue distribution patterns among the individuals) are imprinted in all live animals. Within any individual, the tissue "fingerprints" of 15O and 11C are also very different. When the animal dies, the tissue "fingerprints" are lost. The biochemical, rather than physical, mechanisms could play a critical role in the phenomenon of tissue "fingerprints". Radiolytic radical attack caused millions-fold increases in 15O and 11C activities via different biochemical mechanisms, i.e. radical-mediated hydroxylation and peroxidation respectively, and more importantly the bio-molecular functions (such as the chemical reactivity and the solvent accessibility to radicals). In practice biologically for example, radical attack can therefore be imaged in vivo in live animals and humans using PET for life science research, disease prevention, and personalized radiation therapy based on an individual's bio-molecular response to ionizing radiation
Quantum Transports in Two-Dimensions with Long Range Hopping: Shielding, Localization and the Extended Isolated State
We investigate the effects of disorder and shielding on quantum transports in
a two dimensional system with all-to-all long range hopping. In the weak
disorder, cooperative shielding manifests itself as perfect conducting channels
identical to those of the short range model, as if the long range hopping does
not exist. With increasing disorder, the average and fluctuation of conductance
are larger than those in the short range model, since the shielding is
effectively broken and therefore long range hopping starts to take effect. Over
several orders of disorder strength (until times of nearest
hopping), although the wavefunctions are not fully extended, they are also
robustly prevented from being completely localized into a single site. Each
wavefunction has several localization centers around the whole sample, thus
leading to a fractal dimension remarkably smaller than 2 and also remarkably
larger than 0, exhibiting a hybrid feature of localization and delocalization.
The size scaling shows that for sufficiently large size and disorder strength,
the conductance tends to saturate to a fixed value with the scaling function
, which is also a marginal phase between the typical metal
() and insulating phase (). The all-to-all coupling expels
one isolated but extended state far out of the band, whose transport is
extremely robust against disorder due to absence of backscattering. The bond
current picture of this isolated state shows a quantum version of short circuit
through long hopping.Comment: 15 pages, 8 figure
Cyclic Universe with Quintom matter in Loop Quantum Cosmology
In this paper, we study the possibility of model building of cyclic universe
with Quintom matter in the framework of Loop Quantum Cosmology. After a general
demonstration, we provide two examples, one with double-fluid and another
double-scalar field, to show how such a scenario is obtained. Analytical and
numerical calculations are both presented in the paper.Comment: 11 pages, 2 figure
Biphenyl-3,3′-dicarbÂoxyÂlic acid
The asymmetric unit of the title compound, C14H10O4, contains one half molÂecule, the complete molÂecule being generated by a twofold axis. The two benzene rings form a dihedral angle of 43.11 (5)°. InterÂmolecular O—H⋯O hydrogen bonds link the molÂecules into one-dimensional zigzag chains. These chains are further connected into two-dimensional supraÂmolecular layers by weak π–π stacking interÂactions between neighbouring benzene rings, with centroid–centroid distances of 3.7648 (8) Å
One-Pot Hydrothermal Synthesis, Characterization, and Desulfurization Performance of ZnFe 2
ZnFe2O4/AC composites were prepared by the one-pot hydrothermal method using the activated carbon (AC) as a carrier. The synthesis conditions were optimized by a single-factor experiment. The structural, textural, and surface properties of the adsorbent have been comprehensively characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The SO2 removal capacities of the composites were investigated via testing the adsorption capacity at the self-made desulfurization equipment. The results show that the adsorption capacity of ZnFe2O4/AC composites is much higher than that of the AC and ZnFe2O4 samples, respectively. The composite overcomes the disadvantages of the traditional sintering, showing a very high desulfurization performance. The breakthrough time was 147 min, and the sulfur adsorption capacity could reach 23.67% in the desulfurization performance test
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