41 research outputs found
Charge Transport in Voltage-Biased Superconducting Single-Electron Transistors
Charge is transported through superconducting SSS single-electron transistors
at finite bias voltages by a combination of coherent Cooper-pair tunneling and
quasiparticle tunneling. At low transport voltages the effect of an ``odd''
quasiparticle in the island leads to a -periodic dependence of the current
on the gate charge. We evaluate the characteristic in the framework of a
model which accounts for these effects as well as for the influence of the
electromagnetic environment. The good agreement between our model calculation
and experimental results demonstrates the importance of coherent Cooper-pair
tunneling and parity effects.Comment: RevTeX, 12 pages, 4 figure
Quantum phase transitions in superconducting arrays under external magnetic fields
We study the zero-temperature phase transitions of two-dimensional
superconducting arrays with both the self- and the junction capacitances in the
presence of external magnetic fields. We consider two kinds of excitations from
the Mott insulating phase: charge-dipole excitations and single-charge
excitations, and apply the second-order perturbation theory to find their
energies. The resulting phase boundaries are found to depend strongly on the
magnetic frustration, which measures the commensurate-incommensurate effects.
Comparison of the obtained values with those in recent experiment suggests the
possibility that the superconductor-insulator transition observed in experiment
may not be of the Berezinskii-Kosterlitz-Thouless type. The system is also
transformed to a classical three-dimensional XY model with the magnetic field
in the time-direction; this allows the analogy to bulk superconductors,
revealing the nature of the phase transitions.Comment: 9 pages including 7 figures, to appear in Phys. Rev.
Josephson-phase qubit without tunneling
We show that a complete set of one-bit gates can be realized by coupling the
two logical states of a phase qubit to a third level (at higher energy) using
microwave pulses. Thus, one can achieve coherent control without invoking any
tunneling between the qubit levels. We propose two implementations, using
rf-SQUIDs and d-wave Josephson junctions.Comment: REVTeX4, 4pp., 6 EPS figure files; N.B.: "Alec" is my first, and
"Maassen van den Brink" my family name. v2: gate universality fleshed out,
small fix in d-wave decoherence para, discussion expanded, two Refs. added.
v3: some more Refs., a molecular example, and a few minor fixes; final, to
appear in PRB Rapid
Three-Dimensional Cell Culture Systems in Pediatric and Adult Brain Tumor Precision Medicine
Primary brain tumors often possess a high intra- and intertumoral heterogeneity, which fosters insufficient treatment response for high-grade neoplasms, leading to a dismal prognosis. Recent years have seen the emergence of patient-specific three-dimensional in vitro models, including organoids. They can mimic primary parenteral tumors more closely in their histological, transcriptional, and mutational characteristics, thus approximating their intratumoral heterogeneity better. These models have been established for entities including glioblastoma and medulloblastoma. They have proven themselves to be reliable platforms for studying tumor generation, tumor–TME interactions, and prediction of patient-specific responses to establish treatment regimens and new personalized therapeutics. In this review, we outline current 3D cell culture models for adult and pediatric brain tumors, explore their current limitations, and summarize their applications in precision oncology