784 research outputs found
Topologically Protected Transport in Engineered Mechanical Systems
Mechanical vibrations are being harnessed for a variety of purposes and at many length scales, from the macroscopic world down to the nanoscale. The considerable design freedom in mechanical structures allows to engineer new functionalities. In recent years, this has been exploited to generate setups that offer topologically protected transport of vibrational waves, both in the solid state and in fluids. Borrowing concepts from electronic physics and being cross-fertilized by concurrent studies for cold atoms and electromagnetic waves, this field of topological transport in engineered mechanical systems offers a rich variety of phenomena and platforms. In this review, we provide a unifying overview of the various ideas employed in this area, summarize the different approaches and experimental implementations, and comment on the challenges as well as the prospects
Snowflake phononic topological insulator at the nanoscale
We show how the snowflake phononic crystal structure, which recently has been realized experimentally, can be turned into a topological insulator for mechanical waves. This idea, based purely on simple geometrical modifications, could be readily implemented on the nanoscale
Optimal Computation of Avoided Words
The deviation of the observed frequency of a word from its expected
frequency in a given sequence is used to determine whether or not the word
is avoided. This concept is particularly useful in DNA linguistic analysis. The
value of the standard deviation of , denoted by , effectively
characterises the extent of a word by its edge contrast in the context in which
it occurs. A word of length is a -avoided word in if
, for a given threshold . Notice that such a word
may be completely absent from . Hence computing all such words na\"{\i}vely
can be a very time-consuming procedure, in particular for large . In this
article, we propose an -time and -space algorithm to compute all
-avoided words of length in a given sequence of length over a
fixed-sized alphabet. We also present a time-optimal -time and
-space algorithm to compute all -avoided words (of any
length) in a sequence of length over an alphabet of size .
Furthermore, we provide a tight asymptotic upper bound for the number of
-avoided words and the expected length of the longest one. We make
available an open-source implementation of our algorithm. Experimental results,
using both real and synthetic data, show the efficiency of our implementation
Violation of Bell inequalities by photons more than 10 km apart
A Franson-type test of Bell inequalities by photons 10.9 km apart is
presented. Energy-time entangled photon-pairs are measured using two-channel
analyzers, leading to a violation of the inequalities by 16 standard deviations
without subtracting accidental coincidences. Subtracting them, a 2-photon
interference visibility of 95.5% is observed, demonstrating that distances up
to 10 km have no significant effect on entanglement. This sets quantum
cryptography with photon pairs as a practical competitor to the schemes based
on weak pulses.Comment: 4 pages, REVTeX, 2 postscript figures include
In response to: Anatomy of 18F-GE180, a failed radioligand for the TSPO protein
Purpose!#!Pulmonary hypertension (PH) is characterized by a progressive remodelling of the pulmonary vasculature resulting in right heart failure and eventually death. The serotonin transporter (SERT) may be involved in the pathogenesis of PH in patients with chronic-obstructive pulmonary disease (COPD). This study investigated for the first time the SERT in vivo availability in the lungs of patients with COPD and PH (COPD+PH).!##!Methods!#!SERT availability was assessed using SERT-selective [!##!Results!#![!##!Conclusion!#!By applying
Flipping quantum coins
Coin flipping is a cryptographic primitive in which two distrustful parties
wish to generate a random bit in order to choose between two alternatives. This
task is impossible to realize when it relies solely on the asynchronous
exchange of classical bits: one dishonest player has complete control over the
final outcome. It is only when coin flipping is supplemented with quantum
communication that this problem can be alleviated, although partial bias
remains. Unfortunately, practical systems are subject to loss of quantum data,
which restores complete or nearly complete bias in previous protocols. We
report herein on the first implementation of a quantum coin-flipping protocol
that is impervious to loss. Moreover, in the presence of unavoidable
experimental noise, we propose to use this protocol sequentially to implement
many coin flips, which guarantees that a cheater unwillingly reveals
asymptotically, through an increased error rate, how many outcomes have been
fixed. Hence, we demonstrate for the first time the possibility of flipping
coins in a realistic setting. Flipping quantum coins thereby joins quantum key
distribution as one of the few currently practical applications of quantum
communication. We anticipate our findings to be useful for various
cryptographic protocols and other applications, such as an online casino, in
which a possibly unlimited number of coin flips has to be performed and where
each player is free to decide at any time whether to continue playing or not.Comment: 17 pages, 3 figure
Surface passivation of silicon solar cells using industrially relevant Al2O3 deposition techniques
The next generation of industrial silicon solar cells aims at efficiencies of 20% and above. To achieve this goal using ever-thinner silicon wafers, a highly effective surface passivation of the cell front and rear is required. In the past, finding a suitable dielectric layer providing a high-quality rear passivation has been a major challenge. Aluminium oxide (Al2O3) grown by atomic layer deposition (ALD) has only recently turned out to be a nearly perfect candidate for such a dielectric. However, conventional ALD is limited to deposition rates well below 2nm/min, which is incompatible with industrial solar cell production. This paper assesses the passivation quality provided by three different industrially relevant techniques for the deposition of Al2O3 layers, namely high-rate spatial ALD, plasma-enhanced chemical vapour deposition (PECVD) and reactive sputtering
Advances in the Surface Passivation of Silicon Solar Cells
AbstractThe surface passivation properties of aluminium oxide (Al2O3) on crystalline Si are compared with the traditional passivation system of silicon nitride (SiNx). It is shown that Al2O3 has fundamental advantages over SiNx when applied to the rear of p-type silicon solar cells as well as to the p+ emitter of n-type silicon solar cells. Special emphasis is paid to the transfer of Al2O3 into industrial solar cell production. We compare different Al2O3 deposition techniques suitable for mass production such as ultrafast spatial atomic layer deposition, inline plasma-enhanced chemical vapour deposition and reactive sputtering. Finally, we review the most recent cell results with Al2O3 passivation and give a brief outlook on the future prospects of Al2O3 in silicon solar cell production
A proposed mechanisms for the transient suppression of bacterial luminescence by hydrogen peroxide
It has been shown previously that bacterial luminescence is reversibly suppressed in vivo and in vitro by both X-rays and hydrogen peroxide. The data presented here show that the mechanisms for this phenomenon is based on the transient oxidation of reduced flavin mononucleotide.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33997/1/0000269.pd
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