11,450 research outputs found
Persistent currents in mesoscopic rings and boundary conformal field theory
A tight-binding model of electron dynamics in mesoscopic normal rings is
studied using boundary conformal field theory. The partition function is
calculated in the low energy limit and the persistent current generated as a
function of an external magnetic flux threading the ring is found. We study the
cases where there are defects and electron-electron interactions separately.
The same temperature scaling for the persistent current is found in each case,
and the functional form can be fitted, with a high degree of accuracy, to
experimental data.Comment: 6 pages, 4 enclosed postscript figure
Continuous Monitoring of Rabi Oscillations in a Josephson Flux Qubit
Under resonant irradiation, a quantum system can undergo coherent (Rabi)
oscillations in time. We report evidence for such oscillations in a
_continuously_ observed three-Josephson-junction flux qubit, coupled to a
high-quality tank circuit tuned to the Rabi frequency. In addition to
simplicity, this method of_Rabi spectroscopy_ enabled a long coherence time of
about 2.5 microseconds, corresponding to an effective qubit quality factor
\~7000.Comment: REVTeX4, 4pp., 4 EPS figure files. v3: changed title, fixed typos;
final, to appear in PR
Quantum eigenstate tomography with qubit tunneling spectroscopy
Measurement of the energy eigenvalues (spectrum) of a multi-qubit system has
recently become possible by qubit tunneling spectroscopy (QTS). In the standard
QTS experiments, an incoherent probe qubit is strongly coupled to one of the
qubits of the system in such a way that its incoherent tunneling rate provides
information about the energy eigenvalues of the original (source) system. In
this paper, we generalize QTS by coupling the probe qubit to many source
qubits. We show that by properly choosing the couplings, one can perform
projective measurements of the source system energy eigenstates in an arbitrary
basis, thus performing quantum eigenstate tomography. As a practical example of
a limited tomography, we apply our scheme to probe the eigenstates of a kink in
a frustrated transverse Ising chain.Comment: 8 pages, 4 figure
Algorithmic approach to adiabatic quantum optimization
It is believed that the presence of anticrossings with exponentially small
gaps between the lowest two energy levels of the system Hamiltonian, can render
adiabatic quantum optimization inefficient. Here, we present a simple adiabatic
quantum algorithm designed to eliminate exponentially small gaps caused by
anticrossings between eigenstates that correspond with the local and global
minima of the problem Hamiltonian. In each iteration of the algorithm,
information is gathered about the local minima that are reached after passing
the anticrossing non-adiabatically. This information is then used to penalize
pathways to the corresponding local minima, by adjusting the initial
Hamiltonian. This is repeated for multiple clusters of local minima as needed.
We generate 64-qubit random instances of the maximum independent set problem,
skewed to be extremely hard, with between 10^5 and 10^6 highly-degenerate local
minima. Using quantum Monte Carlo simulations, it is found that the algorithm
can trivially solve all the instances in ~10 iterations.Comment: 7 pages, 3 figure
Low-frequency characterization of quantum tunneling in flux qubits
We propose to investigate flux qubits by the impedance measurement technique
(IMT), currently used to determine the current--phase relation in Josephson
junctions. We analyze in detail the case of a high-quality tank circuit coupled
to a persistent-current qubit, to which IMT was successfully applied in the
classical regime. It is shown that low-frequency IMT can give considerable
information about the level anticrossing, in particular the value of the
tunneling amplitude. An interesting difference exists between applying the ac
bias directly to the tank and indirectly via the qubit. In the latter case, a
convenient way to find the degeneracy point in situ is described. Our design
only involves existing technology, and its noise tolerance is quantitatively
estimated to be realistic.Comment: 6 pages, 11 figures, to appear in Phys.Rev.
Antiinflammatory and Antinociceptive of Hydro Alcoholic Tanacetum balsamita L. Extract
The use of herbs to treat disease is accompanied with the history of human life. This research is aimed to study the anti-inflammatory and antinociceptive effects of hydroalcoholic extract of aerial parts of "Tanacetum balsamita balsamita". In the experimental studies 144 male mice are used. In the inflammatory test, animals were divided into six groups: Control, positive control (receiving Dexamethason at dose of 15mg/kg), and four experimental groups receiving Tanacetum balsamita balsamita hydroalcoholic extract at doses of 25, 50, 100 and 200mg/kg. Xylene was used to induce inflammation. Formalin was used to study the nociceptive effects. Animals were divided into six groups: control group, positive control group (receiving morphine) and four experimental groups receiving Tanacetum balsamita balsamita (Tb.) hydroalcoholic extract at doses of 25, 50, 100 and 200mg/kg. I.p. injection of drugs or normal saline was performed 30 minutes before test. The data were analyzed by using one way Variance analysis and Tukey post-test. Aerial parts of Tanacetum balsamita balsamita hydroalcoholic extract decreased significantly inflammatory at dose of 200mg/kg (P<0/001) and caused a significant decrease and alleviated the nociception in both first and second phases at doses of 200mg/kg (p<0/001) and 100mg/kg (P<0/05). Tanacetum balsamita balsamita extract has the anti-inflammatory and anti-nociceptive effects which seems to be related with flavonoids especially Quercetin
Inhibitory Effect of Bunium persicum Boiss Essential Oil on Castor-Oil Induced Diarrhea
Abstract:
Background & Aims: Bunium persicum Boiss. Belongs to Apiaceae family and its fruit contains high level of essential oils used as native medicinal plant in traditional medicine.
Methods: The essential oil of Bunium persicum (EOBP) was extracted by Clevenger apparatus using hydrodistillation. Lethal dose, 50% (LD50) was calculated based on Lorke’s method. Effects of EOBP (20-80 mg/kg) on upper gastrointestinal transit and on castor oil-induced diarrhea were investigated in adult Wistar rats weighting 200-220 g of either sex.
Results: The LD50 was determined as 375 mg/kg. Abnormal behavioural activities included lethargy, weakness, recumbence, and slow and shallow respiration. EOBP (20 mg/kg) showed inhibitory effects more than atropine where high doses (40 mg/kg) had same inhibition in contrast with atropine. EOBP inhibited intestinal motility more than atropine at lower doses. EOBP inhibitory effect was enhanced with atropine insignificantly. The EOBP (20 and 80 mg/kg) also caused a dose-dependent decrease of diarrheal parameters and markedly protected rats against castor oil-induced diarrhea. The maximal effect of the EOBP was similar to loperamide, one of the most efficacious and widely employed antidiarrheal drugs at the present time.
Conclusion: These primary data indicated that the plant may contain some biologically active constituents that may reveal antimotility and antidiarrheal effects and support the popular therapeutic use of Bunium persicum in traditional medicine for gastrointestinal disorders.
Keywords: Motility, Castor-oil, Medicinal plants, Bunium persicum, Diarrh
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