2,551 research outputs found
Influence of the lattice topography on a three-dimensional, controllable Brownian motor
We study the influence of the lattice topography and the coupling between
motion in different directions, for a three-dimensional Brownian motor based on
cold atoms in a double optical lattice. Due to controllable relative spatial
phases between the lattices, our Brownian motor can induce drifts in arbitrary
directions. Since the lattices couple the different directions, the relation
between the phase shifts and the directionality of the induced drift is non
trivial. Here is therefore this relation investigated experimentally by
systematically varying the relative spatial phase in two dimensions, while
monitoring the vertically induced drift and the temperature. A relative spatial
phase range of 2pi x 2pi is covered. We show that a drift, controllable both in
speed and direction, can be achieved, by varying the phase both parallel and
perpendicular to the direction of the measured induced drift. The experimental
results are qualitatively reproduced by numerical simulations of a simplified,
classical model of the system
A nonadiabatic semi-classical method for dynamics of atoms in optical lattices
We develop a semi-classical method to simulate the motion of atoms in a
dissipative optical lattice. Our method treats the internal states of the atom
quantum mechanically, including all nonadiabatic couplings, while position and
momentum are treated as classical variables. We test our method in the
one-dimensional case. Excellent agreement with fully quantum mechanical
simulations is found. Our results are much more accurate than those of earlier
semi-classical methods based on the adiabatic approximation.Comment: 7 pages, 5 figures, submitted to European Physical Journal
Experimental measurement of efficiency and transport coherence of a cold atom Brownian motor in optical lattices
The rectification of noise into directed movement or useful energy is
utilized by many different systems. The peculiar nature of the energy source
and conceptual differences between such Brownian motor systems makes a
characterization of the performance far from straightforward. In this work,
where the Brownian motor consists of atoms interacting with dissipative optical
lattices, we adopt existing theory and present experimental measurements for
both the efficiency and the transport coherence. We achieve up to 0.3% for the
efficiency and 0.01 for the P\'eclet number
CONSUMER PROTECTION—EXPLORING PRIVATE CAUSES OF ACTION FOR VICTIMS OF DATA BREACHES
Data breaches are becoming a norm in modern life. Every year it seems that bigger and bigger attacks are launched, and more and more individuals are harmed. The law has responded by increasing states’ ability to prosecute cybercriminals. A glaring hole exists in this protection though. The state is largely an unharmed party. The real harm is done to individual citizens affected by the breaches. Their data is compromised, their identities are stolen, and their livelihoods are placed at risk. This Article will analyze the issue and propose a solution for increased consumer protection in addition to the current criminal punishments
Consumer Protection—Exploring Private Causes of Action for Victims of Data Breaches
Data breaches are becoming a norm in modern life. Every year it seems that bigger and bigger attacks are launched, and more and more individuals are harmed. The law has responded by increasing states’ ability to prosecute cybercriminals. A glaring hole exists in this protection though. The state is largely an unharmed party. The real harm is done to individual citizens affected by the breaches. Their data is compromised, their identities are stolen, and their livelihoods are placed at risk. This Article will analyze the issue and propose a solution for increased consumer protection in addition to the current criminal punishments
Van der Waals Density Functional for General Geometries
A scheme within density functional theory is proposed that provides a
practical way to generalize to unrestricted geometries the method applied with
some success to layered geometries [H. Rydberg, et al., Phys. Rev. Lett. 91,
126402 (2003)]. It includes van der Waals forces in a seamless fashion. By
expansion to second order in a carefully chosen quantity contained in the long
range part of the correlation functional, the nonlocal correlations are
expressed in terms of a density-density interaction formula. It contains a
relatively simple parametrized kernel, with parameters determined by the local
density and its gradient. The proposed functional is applied to rare gas and
benzene dimers, where it is shown to give a realistic description.Comment: 4 pages, 4 figure
Laser control for the optimal evolution of pure quantum states
Starting from an initial pure quantum state, we present a strategy for
reaching a target state corresponding to the extremum (maximum or minimum) of a
given observable. We show that a sequence of pulses of moderate intensity,
applied at times when the average of the observable reaches its local or global
extremum, constitutes a strategy transferable to different control issues.
Among them, post-pulse molecular alignment and orientation are presented as
examples. The robustness of such strategies with respect to experimentally
relevant parameters is also examined.Comment: 16 pages, 9 figure
Reaching optimally oriented molecular states by laser kicks
We present a strategy for post-pulse orientation aiming both at efficiency
and maximal duration within a rotational period. We first identify the
optimally oriented states which fulfill both requirements. We show that a
sequence of half-cycle pulses of moderate intensity can be devised for reaching
these target states.Comment: 4 pages, 3 figure
Identification of genes coding for B cell antigens of Mycoplasma mycoides subsp. mycoides Small Colony (MmmSC) by using phage display
<p>Abstract</p> <p>Background</p> <p>Contagious bovine pleuropneumonia (CBPP) is a mycoplasmal disease caused by <it>Mycoplasma mycoides </it>subsp. <it>mycoides </it>SC (<it>Mmm</it>SC). Since the disease is a serious problem that can affect cattle production in parts of Africa, there is a need for an effective and economical vaccine. Identifying which of the causative agent's proteins trigger potentially protective immune responses is an important step towards developing a subunit vaccine. Accordingly, the purpose of this study was to determine whether phage display combined with bioinformatics could be used to narrow the search for genes that code for potentially immunogenic proteins of <it>Mmm</it>SC. Since the production of IgG2 and IgA are associated with a Th<sub>1 </sub>cellular immune response which is implicated in protection against CBPP, antigens which elicit these immunoglobulin subclasses may be useful in developing a subunit vaccine.</p> <p>Results</p> <p>A filamentous phage library displaying a repertoire of peptides expressed by fragments of the genome of <it>MmmSC </it>was constructed. It was subjected to selection using antibodies from naturally- and experimentally-infected cattle. Mycoplasmal genes were identified by matching the nucleotide sequences of DNA from immunoselected phage particles with the mycoplasmal genome. This allowed a catalogue of genes coding for the proteins that elicited an immune response to be compiled. Using this method together with computer algorithms designed to score parameters that influence surface accessibility and hence potential antigenicity, five genes (<it>abc, gapN, glpO, lppB </it>and <it>ptsG</it>) were chosen to be expressed in <it>Escherichia coli</it>. After appropriate site-directed mutagenesis, polypeptides representing portions of each of these proteins were tested for immunoreactivity. Of these five, polypeptides representing expression products of <it>abc </it>and <it>lppB </it>were recognised on immunoblots by sera obtained from cattle during a natural outbreak of the disease.</p> <p>Conclusion</p> <p>Since phage display physically couples phenotype with genotype, it was used to compile a list of sequences that code for <it>Mmm</it>SC proteins bearing epitopes which were recognised by antibodies in the serum of infected animals. Together with the appropriate bioinformatic analyses, this approach provided several potentially useful vaccine or diagnostic leads. The phage display step empirically identified sequences by their interaction with antibodies which accordingly reduced the number of ORFs that had to be expressed for testing. This is a particular advantage when working with <it>Mmm</it>SC since the mycoplasmal codon for tryptophan needs to be mutated to prevent it from being translated as a stop in <it>E. coli</it>.</p
Electrically switchable entanglement channel in van der Waals magnets
Two-dimensional layered van der Waals (vdW) magnets demonstrate their potential to allow the study
of both fundamental and applied physics due to their remarkable electronic properties. However, the connection of vdW magnets to spintronics and quantum information science is not clear. In particular, it
remains elusive whether there are interesting magnetic phenomena belonging only to vdW magnets but
absent in widely studied crystalline magnets. Here, we consider the quantum correlations of magnons
in a layered vdW magnet and identify an entanglement channel of magnons across the magnetic layers,
which can be effectively tuned and even deterministically switched on and off by both magnetic and electric means. This is a unique feature of vdW magnets, in which the underlying physics is well understood
in terms of the competing roles of exchange and anisotropy fields that contribute to magnon excitation.
Furthermore, we show that such a tunable entanglement channel can mediate the electrically controllable
entanglement of two distant qubits, which also provides a protocol to indirectly measure the entanglement of magnons. Our findings provide an avenue to electrically manipulate qubits and further open up
opportunities to utilize vdW magnets for quantum information scienc
- …