2,990 research outputs found
Stationary Entangled Radiation from Micromechanical Motion
Mechanical systems facilitate the development of a new generation of hybrid
quantum technology comprising electrical, optical, atomic and acoustic degrees
of freedom. Entanglement is the essential resource that defines this new
paradigm of quantum enabled devices. Continuous variable (CV) entangled fields,
known as Einstein-Podolsky-Rosen (EPR) states, are spatially separated two-mode
squeezed states that can be used to implement quantum teleportation and quantum
communication. In the optical domain, EPR states are typically generated using
nondegenerate optical amplifiers and at microwave frequencies Josephson
circuits can serve as a nonlinear medium. It is an outstanding goal to
deterministically generate and distribute entangled states with a mechanical
oscillator. Here we observe stationary emission of path-entangled microwave
radiation from a parametrically driven 30 micrometer long silicon nanostring
oscillator, squeezing the joint field operators of two thermal modes by
3.40(37) dB below the vacuum level. This mechanical system correlates up to 50
photons/s/Hz giving rise to a quantum discord that is robust with respect to
microwave noise. Such generalized quantum correlations of separable states are
important for quantum enhanced detection and provide direct evidence for the
non-classical nature of the mechanical oscillator without directly measuring
its state. This noninvasive measurement scheme allows to infer information
about otherwise inaccessible objects with potential implications in sensing,
open system dynamics and fundamental tests of quantum gravity. In the near
future, similar on-chip devices can be used to entangle subsystems on vastly
different energy scales such as microwave and optical photons.Comment: 13 pages, 5 figure
The amplifier effect: how Pin1 empowers mutant p53
Mutation of p53 occurs in 15 to 20% of all breast cancers, and with higher frequency in estrogen-receptor negative and high-grade tumors. Certain p53 mutations contribute to malignant transformation not only through loss of wild-type p53 but also through a gain of function of specific p53 mutations. How these hotspot mutations turn p53 from a tumor suppressor into an oncogene had until now remained incompletely understood. In an elegant paper published in the July 12 issue of Cancer Cell, Girardini and colleagues show how Pin1-mediated prolylisomerization, a regulatory mechanism intended by evolution to support p53's function as a guardian of the genome, can go haywire and accelerate malignant transformation when p53 carries a dominant-negative mutation
Digital terrain modelling using triangulated irregular networks (poster)
Many marine scientists and users of the sea consider knowledge of the sea bottom as basic data, a mere context to carry out research or deploy activities. Some disciplines do need more accurate bathymetric data than others, depending on depth values being background information or crucial information for their research or activities. In bathymetry, the representation of the sea bottom surface is the main objective and hence, this discipline will try to render the sea bottom relief as accurate as possible. The latest bathymetric sounding equipment that is available nowadays, especially the multibeam echosounder, yield a very dense bottom sampling. When compared to the common singlebeam echosounder, an enormous amount of data is produced that needs to be processed in a correct and fast way. Grid-overlay (by local linear or more sophisticated interpolation and attributing values to individual grid cells) is not an option here as this method uses an interpolation of the measured values and hence will either cause accuracy loss or generate a still larger amount of data. A triangular irregular network (TIN for short), especially the Delaunay triangulation (Dt), does respect the actual measurements and will not generate new data. In literature, a number of algorithms have been developed that determine the Dt of a set of points (vertices) given in the plane.A performant divide-and-conquer algorithm for Delaunay triangulations was implemented to triangulate large quantities of data in minimum time. Comparison with other implemented algorithms demonstrates its excellent performance.In some cases, it will be necessary to adapt the terrain model. Theoretical terrain models (for instance design models for marine contractors) require manual interventions, while new surveys partially overlapping old data will have to replace the latter. Therefore, the incremental algorithm has been adapted to allow insertion of individual points. When eliminating individual vertices, the hole thus created has to be retriangulated. Vertices belonging to a triangulation that is (partially) covered by a new surveyed area can be eliminated and using a very keen adaptation of the divide-and-conquer principle, the overlapping triangulations can be stitched together. This is a novel technique with the big advantage of quickly and seamlessly joining two large triangulations, without the need for retriangulation of the entire area.Part of the immense amount of data generated by a multibeam echosounder will unavoidably be redundant. An important issue therefore will be: filtering these data, keeping those points that still assure an optimal accuracy. This accuracy can be expressed as a function of the topography or as a function of the volume. For the latter, not the height difference determines whether or not a vertex is allowed in the triangulation, the criterion is rather the change in volume caused by this one vertex. For marine contractors, it is mainly the latter that is important. A hybrid model would be most adequate
Variations in Arterial Blood Pressure after Kidney Transplantation
The course of hypertension within the first 2 months after kidney transplantation was correlated with renal function, plasma renin activity (PRA), and the daily maintenance dose of prednisone in 18 homograft recipients. During acute rejection blood pressure (BP) closely correlated with PRA. Patients with normal homograft function showed an increase in BP early after transplantation which in most returned to normal 3-8 weeks later. In the latter group no correlation could be found between the level of BP and PRA, however the BP correlated closely with the dose of prednisone. These observations suggest that during acute rejection the increase in BP may at least partly be mediated by a renal pressor mechanism, whereas with normal renal function the high dose of glucocorticoids may play an important role in the development of hypertension.</jats:p
Manifestation of the Hofstadter butterfly in far-infrared absorption
The far-infrared absorption of a two-dimensional electron gas with a
square-lattice modulation in a perpendicular constant magnetic field is
calculated self-consistently within the Hartree approximation. For strong
modulation and short period we obtain intra- and intersubband magnetoplasmon
modes reflecting the subbands of the Hofstadter butterfly in two or more Landau
bands. The character of the absorption and the correlation of the peaks to the
number of flux quanta through each unit cell of the periodic potential depends
strongly on the location of the chemical potential with respect to the
subbands, or what is the same, on the density of electrons in the system.Comment: RevTeX file + 4 postscript figures, to be published Phys. Rev. B
Rapid Com
Is diversity good?
Prominent ethical and policy issues such as affirmative action and female
enrollment in science and engineering revolve around the idea that diversity is
good. However, even though diversity is an ambiguous concept, a precise
definition is seldom provided. We show that diversity may be construed as a
factual description, a craving for symmetry, an intrinsic good, an instrumental
good, a symptom, or a side effect. These acceptions differ vastly in their
nature and properties. The first one cannot lead to any action and the second
one is mistaken. Diversity as intrinsic good is a mere opinion, which cannot be
concretely applied; moreover, the most commonly invoked forms of diversity
(sexual and racial) are not intrinsically good. On the other hand, diversity as
instrumental good can be evaluated empirically and can give rise to policies,
but these may be very weak. Finally, symptoms and side effects are not actually
about diversity. We consider the example of female enrollment in science and
engineering, interpreting the various arguments found in the literature in
light of this polysemy.
Keywords: ethics, policy, higher education, female students, minority
students, affirmative actionComment: 7 page
SecureKeeper: confidential zooKeeper using intel SGX
Cloud computing, while ubiquitous, still suffers from trust issues, especially for applications managing sensitive data. Third-party coordination services such as ZooKeeper and Consul are fundamental building blocks for cloud applications, but are exposed to potentially sensitive application data. Recently, hardware trust mechanisms such as Intel's Software Guard Extensions (SGX) offer trusted execution environments to shield application data from untrusted software, including the privileged Operating System (OS) and hypervisors. Such hardware support suggests new options for securing third-party coordination services. We describe SecureKeeper, an enhanced version of the ZooKeeper coordination service that uses SGX to preserve the confidentiality and basic integrity of ZooKeeper-managed data. SecureKeeper uses multiple small enclaves to ensure that (i) user-provided data in ZooKeeper is always kept encrypted while not residing inside an enclave, and (ii) essential processing steps that demand plaintext access can still be performed securely. SecureKeeper limits the required changes to the ZooKeeper code base and relies on Java's native code support for accessing enclaves. With an overhead of 11%, the performance of SecureKeeper with SGX is comparable to ZooKeeper with secure communication, while providing much stronger security guarantees with a minimal trusted code base of a few thousand lines of code
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