14,142 research outputs found
Localization in an Inhomogeneous Quantum Wire
We study interaction-induced localization of electrons in an inhomogeneous
quasi-one-dimensional system--a wire with two regions, one at low density and
the other high. Quantum Monte Carlo techniques are used to treat the strong
Coulomb interactions in the low density region, where localization of electrons
occurs. The nature of the transition from high to low density depends on the
density gradient--if it is steep, a barrier develops between the two regions,
causing Coulomb blockade effects. Ferromagnetic spin polarization does not
appear for any parameters studied. The picture emerging here is in good
agreement with measurements of tunneling between two wires.Comment: 4 pages; 2 new figures, substantial revisions and clarification
Properties of a coupled two species atom-heteronuclear molecule condensate
We study the coherent association of a two-species atomic condensate into a
condensate of heteronuclear diatomic molecules, using both a semiclassical
treatment and a quantum mechanical approach. The differences and connections
between the two approaches are examined. We show that, in this coupled
nonlinear atom-molecule system, the population difference between the two
atomic species plays a significant role in the ground-state stability
properties as well as in coherent population oscillation dynamics.Comment: 7 pages, 4 figure
Energy average formula of photon gas rederived by using the generalized Hermann-Feynman theorem
By virtue of the generalized Hermann-Feynmam theorem and the method of
characteristics we rederive energy average formula of photon gas, this is
another useful application of the theorem.Comment: 2 page
The Equation of State and Quark Number Susceptibility in Hard-Dense-Loop Approximation
Based on the method proposed in [ H. S. Zong, W. M. Sun, Phys. Rev. \textbf{D
78}, 054001 (2008)], we calculate the equation of state (EOS) of QCD at zero
temperature and finite quark chemical potential under the hard-dense-loop (HDL)
approximation. A comparison between the EOS under HDL approximation and the
cold, perturbative EOS of QCD proposed by Fraga, Pisarski and Schaffner-Bielich
is made. It is found that the pressure under HDL approximation is generally
smaller than the perturbative result. In addition, we also calculate the quark
number susceptibility (QNS) at finite temperature and finite chemical potential
under hard-thermal/dense-loop (HTL/HDL) approximation and compare our results
with the corresponding ones in the previous literature.Comment: 12 pages, 3 figure
Generalized Haldane Equation and Fluctuation Theorem in the Steady State Cycle Kinetics of Single Enzymes
Enyzme kinetics are cyclic. We study a Markov renewal process model of
single-enzyme turnover in nonequilibrium steady-state (NESS) with sustained
concentrations for substrates and products. We show that the forward and
backward cycle times have idential non-exponential distributions:
\QQ_+(t)=\QQ_-(t). This equation generalizes the Haldane relation in
reversible enzyme kinetics. In terms of the probabilities for the forward
() and backward () cycles, is shown to be the
chemical driving force of the NESS, . More interestingly, the moment
generating function of the stochastic number of substrate cycle ,
follows the fluctuation theorem in the form of
Kurchan-Lebowitz-Spohn-type symmetry. When $\lambda$ = $\Delta\mu/k_BT$, we
obtain the Jarzynski-Hatano-Sasa-type equality:
1 for all , where is the fluctuating chemical work
done for sustaining the NESS. This theory suggests possible methods to
experimentally determine the nonequilibrium driving force {\it in situ} from
turnover data via single-molecule enzymology.Comment: 4 pages, 3 figure
Targeting tauopathy with engineered tau-degrading intrabodies
BACKGROUND: The accumulation of pathological tau is the main component of neurofibrillary tangles and other tau aggregates in several neurodegenerative diseases, referred to as tauopathies. Recently, immunotherapeutic approaches targeting tau have been demonstrated to be beneficial in decreasing tauopathy in animal models. We previously found that passive immunotherapy with anti-tau antibody to human tau or expression of an anti-tau secreted single-chain variable fragment (scFv) in the central nervous system of a mouse model of tauopathy decreased but did not remove all tau-associated pathology. Although these and other studies demonstrate that conventional immunotherapeutic approaches targeting tau can influence tau pathogenesis, the majority of pathological tau remains in the cytosol of cells, not typically accessible to an extracellular antibody. Therefore, we reasoned targeting intracellular tau might be more efficacious in preventing or decreasing tauopathy.
METHODS: By utilizing our anti-tau scFv, we generated anti-tau intrabodies for the expression in the cytosol of neurons. To enhance the degradation capacity of conventional intrabodies, we engineered chimeric anti-tau intrabodies fused to ubiquitin harboring distinct mutations that shuttle intracellular tau for either the proteasome or lysosomal mediated degradation. To evaluate the efficacy in delaying or eliminating tauopathy, we expressed our tau degrading intrabodies or controls in human tau transgenic mice by adeno-associated virus prior to overt tau pathology and after tau deposition.
RESULTS: Our results demonstrate, the expression of chimeric anti-tau intrabodies significantly reduce tau protein levels in primary neuronal cultures expression human tau relative to a non-modified anti-tau intrabody. We found the expression of engineered tau-degrading intrabodies destined for proteasomal-mediated degradation are more effective in delaying or eliminating tauopathy than a conventional intrabody in aged human tau transgenic mice.
CONCLUSION: This study, harnesses the strength of intrabodies that are amendable for targeting specific domains or modifications with the cell-intrinsic mechanisms that regulate protein degradation providing a new immunotherapeutic approach with potentially improved efficacy
Plaquette valence bond state in spin-1/2 J1-J2 XY model on square lattice
We studied the ground state phase diagram of spin-1/2 J1-J2 XY model on the
square lattice with first- J1 and second-neighbor J2 antiferromagnetic
interactions using both iDMRG and DMRG approaches. We show that a plaquette
valence bond phase is realized in an intermediate region 0.50 <= J2/J1 <= 0.54
between a N\'eel magnetic ordered phase at J2/J1 < 0.50 and a stripy magnetic
ordered phase at J2/J1 >= 0.54. The plaquette valence bond phase is
characterized by finite dimer orders in both the horizontal and vertical
directions. Contrary to the spin-1/2 J1-J2 Heisenberg model, we do not find
numerical evidence for a quantum spin liquid phase in the J1-J2 XY model.Comment: 7 pages, 5 figure
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