1,122 research outputs found
Effect of the shot-noise on a Coulomb blockaded single Josephson junction
We have investigated how the Coulomb blockade of a mesoscopic Josephson
junction in a high-impedance environment is suppressed by shot noise from an
adjacent junction. The presented theoretical analysis is an extension of the
phase correlation theory for the case of a non-Gaussian noise. Asymmetry of the
non-Gaussian noise should result in the shift of the conductance minimum from
zero voltage and the ratchet effect (nonzero current at zero voltage), which
have been experimentally observed. The analysis demonstrates that a Coulomb
blockaded tunnel junction in a high impedance environment can be used as an
effective noise detector.Comment: 4 pages, 1 figure; figure and typos corrected, added reference
A Flexible Privacy-preserving Framework for Singular Value Decomposition under Internet of Things Environment
The singular value decomposition (SVD) is a widely used matrix factorization
tool which underlies plenty of useful applications, e.g. recommendation system,
abnormal detection and data compression. Under the environment of emerging
Internet of Things (IoT), there would be an increasing demand for data analysis
to better human's lives and create new economic growth points. Moreover, due to
the large scope of IoT, most of the data analysis work should be done in the
network edge, i.e. handled by fog computing. However, the devices which provide
fog computing may not be trustable while the data privacy is often the
significant concern of the IoT application users. Thus, when performing SVD for
data analysis purpose, the privacy of user data should be preserved. Based on
the above reasons, in this paper, we propose a privacy-preserving fog computing
framework for SVD computation. The security and performance analysis shows the
practicability of the proposed framework. Furthermore, since different
applications may utilize the result of SVD operation in different ways, three
applications with different objectives are introduced to show how the framework
could flexibly achieve the purposes of different applications, which indicates
the flexibility of the design.Comment: 24 pages, 4 figure
Observation of shot-noise-induced asymmetry in the Coulomb blockaded Josephson junction
We have investigated the influence of shot noise on the IV-curves of a single
mesoscopic Josephson junction. We observe a linear enhancement of zero-bias
conductance of the Josephson junction with increasing shot noise power.
Moreover, the IV-curves become increasingly asymmetric. Our analysis on the
asymmetry shows that the Coulomb blockade of Cooper pairs is strongly
influenced by the non-Gaussian character of the shot noise.Comment: 4 pages, 5 figures, RevTE
Anisotropy and oblique total transmission at a planar negative-index interface
We show that a class of negative index (n) materials has interesting
anisotropic optical properties, manifest in the effective refraction index that
can be positive, negative, or purely imaginary under different incidence
conditions. With dispersion taken into account, reflection at a planar
negative-index interface exhibits frequency selective total oblique
transmission that is distinct from the Brewster effect.
Finite-difference-time-domain simulation of realistic negative-n structures
confirms the analytic results based on effective indices.Comment: to appear in Phys. Rev.
The Design and Validation of the Quantum Mechanics Conceptual Survey
The Quantum Mechanics Conceptual Survey (QMCS) is a 12-question survey of
students' conceptual understanding of quantum mechanics. It is intended to be
used to measure the relative effectiveness of different instructional methods
in modern physics courses. In this paper we describe the design and validation
of the survey, a process that included observations of students, a review of
previous literature and textbooks and syllabi, faculty and student interviews,
and statistical analysis. We also discuss issues in the development of specific
questions, which may be useful both for instructors who wish to use the QMCS in
their classes and for researchers who wish to conduct further research of
student understanding of quantum mechanics. The QMCS has been most thoroughly
tested in, and is most appropriate for assessment of (as a posttest only),
sophomore-level modern physics courses. We also describe testing with students
in junior quantum courses and graduate quantum courses, from which we conclude
that the QMCS may be appropriate for assessing junior quantum courses, but is
not appropriate for assessing graduate courses. One surprising result of our
faculty interviews is a lack of faculty consensus on what topics should be
taught in modern physics, which has made designing a test that is valued by a
majority of physics faculty more difficult than expected.Comment: Submitted to Physical Review Special Topics: Physics Education
Researc
Repulsive Casimir Force in Chiral Metamaterials
We demonstrate theoretically that one can obtain repulsive Casimir forces and
stable nanolevitations by using chiral metamaterials. By extending the Lifshitz
theory to treat chiral metamaterials, we find that a repulsive force and a
minimum of the interaction energy exist for strong chirality, under realistic
frequency dependencies and correct limiting values (for zero and infinite
frequencies) of the permittivity, permeability, and chiral coefficients.Comment: 4 pages, 4 figures, letter. submitted to Phys. Rev. Let
Non-malleable encryption: simpler, shorter, stronger
In a seminal paper, Dolev et al. [15] introduced the notion of non-malleable encryption (NM-CPA). This notion is very intriguing since it suffices for many applications of chosen-ciphertext secure encryption (IND-CCA), and, yet, can be generically built from semantically secure (IND-CPA) encryption, as was shown in the seminal works by Pass et al. [29] and by Choi et al. [9], the latter of which provided a black-box construction. In this paper we investigate three questions related to NM-CPA security: 1. Can the rate of the construction by Choi et al. of NM-CPA from IND-CPA be improved? 2. Is it possible to achieve multi-bit NM-CPA security more efficiently from a single-bit NM-CPA scheme than from IND-CPA? 3. Is there a notion stronger than NM-CPA that has natural applications and can be achieved from IND-CPA security? We answer all three questions in the positive. First, we improve the rate in the scheme of Choi et al. by a factor O(λ), where λ is the security parameter. Still, encrypting a message of size O(λ) would require ciphertext and keys of size O(λ2) times that of the IND-CPA scheme, even in our improved scheme. Therefore, we show a more efficient domain extension technique for building a λ-bit NM-CPA scheme from a single-bit NM-CPA scheme with keys and ciphertext of size O(λ) times that of the NM-CPA one-bit scheme. To achieve our goal, we define and construct a novel type of continuous non-malleable code (NMC), called secret-state NMC, as we show that standard continuous NMCs are not enough for the natural “encode-then-encrypt-bit-by-bit” approach to work. Finally, we introduce a new security notion for public-key encryption that we dub non-malleability under (chosen-ciphertext) self-destruct attacks (NM-SDA). After showing that NM-SDA is a strict strengthening of NM-CPA and allows for more applications, we nevertheless show that both of our results—(faster) construction from IND-CPA and domain extension from one-bit scheme—also hold for our stronger NM-SDA security. In particular, the notions of IND-CPA, NM-CPA, and NM-SDA security are all equivalent, lying (plausibly, strictly?) below IND-CCA securit
Extended preservation and effect of nitric oxide production in liver transplantation
Liver transplantation (Ltx) has become a routine procedure for patients with end-stage liver disease. Despite ongoing progress on short- and long-term graft survival, primary dysfunction (PDF) remains a major problem. PDF is significantly associated with the duration of cold ischemia- and, possibly, with reperfusion-related injury. Nitric oxide (NO) has many physiological functions and plays an important role in modulating tissue injury. However, the mechanism of NO action in ischemia/reperfusion injury after Ltx is thus far unknown. In this study we investigated the role of inducable NO synthase (iNOS) in the liver after preservation with UW solution using the orthotopic Ltx model in the rat. Male Brown Norway rats were used for the Ltx procedure. After donor hepatectomy, livers were stored on ice-cold UW solution for 24 or 40 h and subsequently transplanted. A control group consisted of rats with Ltx after less than 1 h storage. Posttransplant blood samples were taken at 48 h to determine standard parameters for liver injury (aspartate transaminase, lactate dehydrogenase). Liver biopsies were obtained for detection of expression of iNOS (western blot) 24 and 48 h posttransplant. We observed that a preservation time of 24 h in UW solution presents no problem for graft survival after Ltx in rats with some brain function and in healthy animals. After 40 h preservation, liver damage is obvious and graft survival reduced, indicating the limits of cold storage may be within reach. With longer preservation times, more NOs was detected in liver tissue. This finding suggests that NO has a role in ischemia/reperfusion-related injury. Current intervention with NOS inhibitors will reveal whether NO has a negative or a positive effect on graft survival after Ltx.</p
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