97 research outputs found
Long hold times in a two-junction electron trap
The hold time of a single-electron trap is shown to increase
significantly due to suppression of environmentally assisted tunneling events.
Using two rf-tight radiation shields instead of a single one, we demonstrate
increase of by a factor exceeding , up to about 10 hours, for a
trap with only two superconductor (S) -- normal-metal (N) tunnel junctions and
an on-chip resistor (R-SNS structure). In the normal state, the improved
shielding made it possible to observe 100 s, which is in reasonable
agreement with the quantum-leakage-limited level expected for the two-electron
cotunneling process.Comment: 4 pages, 3 figure
Single-electron current sources: towards a refined definition of ampere
Controlling electrons at the level of elementary charge has been
demonstrated experimentally already in the 1980's. Ever since, producing an
electrical current , or its integer multiple, at a drive frequency has
been in a focus of research for metrological purposes. In this review we first
discuss the generic physical phenomena and technical constraints that influence
charge transport. We then present the broad variety of proposed realizations.
Some of them have already proven experimentally to nearly fulfill the demanding
needs, in terms of transfer errors and transfer rate, of quantum metrology of
electrical quantities, whereas some others are currently "just" wild ideas,
still often potentially competitive if technical constraints can be lifted. We
also discuss the important issues of read-out of single-electron events and
potential error correction schemes based on them. Finally, we give an account
of the status of single-electron current sources in the bigger framework of
electric quantum standards and of the future international SI system of units,
and briefly discuss the applications and uses of single-electron devices
outside the metrological context.Comment: 55 pages, 38 figures; (v2) fixed typos and misformatted references,
reworded the section on AC pump
Photon assisted tunneling as an origin of the Dynes density of states
We show that the effect of a high-temperature environment in current
transport through a normal metal-insulator-superconductor tunnel junction can
be described by an effective density of states (DOS) in the superconductor. In
the limit of a resistive low-ohmic environment, this DOS reduces into the
well-known Dynes form. Our theoretical result is supported by experiments in
engineered environments. We apply our findings to improve the performance of a
single-electron turnstile, a potential candidate for a metrological current
source.Comment: 4+3 pages, 4 figures; updated to the published version, includes
EPAPS supplementary materia
Vanishing quasiparticle density in a hybrid Al/Cu/Al single-electron transistor
The achievable fidelity of many nanoelectronic devices based on
superconducting aluminum is limited by either the density of residual
nonequilibrium quasiparticles n_qp or the density of quasiparticle states in
the gap, characterized by Dynes parameter \gamma. We infer upper bounds n_qp <
0.033 um^-3 and \gamma < 1.6*10^-7 from transport measurements performed on
Al/AlOx/Cu single-electron transistors, improving previous results by an order
of magnitude. Owing to efficient microwave shielding and quasiparticle
relaxation, typical number of quasiparticles in the superconducting leads is
zero.Comment: 5 pages, 3 figures; updated to revised version that was accepted for
publication, contains data from a reference sample without qp trap
Driving a low critical current Josephson junction array with a mode-locked laser
Data for article "Driving a low critical current Josephson junction array with a mode-locked laser"
New Evaluation of T- T<sub>2000</sub> from 0.02Â K to 1Â K by Independent Thermodynamic Methods
Mars Science Laboratory relative humidity observations : Initial results
The authors would like to express their gratitude to the MSL and REMS instrument teams in making this wonderful Mars mission come true. AriâMatti Harri and Hannu Savijarvi are thankful for the Finnish Academy grants 132825 and 131723.Peer reviewedPublisher PD
Cyclin A as a marker for prognosis and chemotherapy response in advanced breast cancer
We wanted to study cyclin A as a marker for prognosis and chemotherapy response. A total of 283 women with metastatic breast cancer were initially enrolled in a randomised multicentre trial comparing docetaxel to sequential methotrexate-fluorouracil (MF) in advanced breast cancer after anthracycline failure. Paraffin-embedded blocks of the primary tumour were available for 96 patients (34%). The proportion of cells expressing cyclin A was determined by immunohistochemistry using a mouse monoclonal antibody to human cyclin A. Response evaluation was performed according to WHO recommendations. The median cyclin A positivity of tumour cells was 14.5% (range 1.2â45.0). Cyclin A correlated statistically significantly to all other tested proliferation markers (mitotic count, histological grade and Ki-67). A high cyclin A correlated significantly to a shorter time to first relapse, risk ratio (RR) 1.94 (95% CI 1.24â3.03) and survival from diagnosis, RR 2.49 (95% CI 1.45â4.29), cutoff point for high/low proliferation group 10.5%. Cyclin A did not correlate to chemotherapy response or survival after anthracycline, docetaxel or MF therapy. Of all tumour biological factors tested (mitotic count, histological grade and Ki-67), cyclin A seemed to have the strongest prognostic value. Cyclin A is a good marker for tumour proliferation and prognosis in breast cancer. In the present study, cyclin A did not predict chemotherapy response
A high proliferation rate measured by cyclin A predicts a favourable chemotherapy response in soft tissue sarcoma patients
A small but not insignificant number of patients experience a prolonged survival after treatment of metastatic soft tissue sarcoma. This must be weighed against the majority of the patients who benefit little from the therapy, but nevertheless experience its side-effects. It would therefore be of utmost importance to be able to screen for those patients who respond to the treatment. Since proliferating cells are more sensitive to chemotherapy than non-proliferative cells, we measured the proliferation rate of the primary tumour of 55 soft tissue sarcoma patients with locally advanced or metastatic disease by determining the flow cytometric S phase fraction and immunohistochemical Ki-67 and cyclin A scores. S phase fraction or Ki-67 score did not predict chemotherapy response or progression-free survival. A high cyclin A score, however, correlated with a better chemotherapy response (P = 0.02) and longer progression-free survival time (P = 0.04). Our results suggest that a high cyclin A score predicts chemotherapy sensitivity. © 1999 Cancer Research Campaig
Pressure observations by the curiosity rover : Initial results
The authors would like to express their gratitude to the MSL and REMS instrument teams in making this wonderful Mars mission come true. Ari-Matti Harri and Hannu Savijarvi are thankful for the Finnish Academy grants 132825 and 131723.Peer reviewedPublisher PD
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