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Effectiveness of landmark analysis for establishing locality in p2p networks
Locality to other nodes on a peer-to-peer overlay network can be established by means of a set of landmarks shared among the participating nodes. Each node independently collects a set of latency measures to landmark nodes, which are used as a multi-dimensional feature vector. Each peer node uses the feature vector to generate a unique scalar index which is correlated to its topological locality. A popular dimensionality reduction technique is the space filling Hilbert’s curve, as it possesses good locality
preserving properties. However, there exists little comparison between Hilbert’s curve and other techniques for dimensionality reduction. This work carries out a quantitative analysis of their properties. Linear and non-linear techniques for scaling the landmark vectors to a single dimension are investigated. Hilbert’s curve, Sammon’s mapping and Principal Component Analysis
have been used to generate a 1d space with locality preserving properties. This work provides empirical evidence to support the use of Hilbert’s curve in the context of locality preservation when generating peer identifiers by means of landmark vector analysis. A comparative analysis is carried out with an artificial 2d network model and with a realistic network topology model
with a typical power-law distribution of node connectivity in the Internet. Nearest neighbour analysis confirms Hilbert’s curve to be very effective in both artificial and realistic network topologies. Nevertheless, the results in the realistic network model show that there is scope for improvements and better techniques to preserve locality information are required
Coherent transport in extremely underdoped Nd1.2Ba1.8Cu3Oz nanostructures
Proximity-effect and resistance magneto-fluctuations measurements in
submicron Nd1.2Ba1.8Cu3Oz (NBCO) nano-loops are reported to investigate
coherent charge transport in the non-superconducting state. We find an
unexpected inhibition of cooper pair transport, and a destruction of the
induced superconductivity, by lowering the temperature from 6K to 250mK. This
effect is accompanied by a significant change in the conductance-voltage
characteristics and in the zero bias conductance response to the magnetic field
pointing to the activation of a strong pair breaking mechanism at lower
temperature. The data are discussed in the framework of mesoscopic effects
specific to superconducting nanostructures, proximity effect and high
temperature superconductivity.Comment: to appear on new journal of Physic
SoK: Cryptographically Protected Database Search
Protected database search systems cryptographically isolate the roles of
reading from, writing to, and administering the database. This separation
limits unnecessary administrator access and protects data in the case of system
breaches. Since protected search was introduced in 2000, the area has grown
rapidly; systems are offered by academia, start-ups, and established companies.
However, there is no best protected search system or set of techniques.
Design of such systems is a balancing act between security, functionality,
performance, and usability. This challenge is made more difficult by ongoing
database specialization, as some users will want the functionality of SQL,
NoSQL, or NewSQL databases. This database evolution will continue, and the
protected search community should be able to quickly provide functionality
consistent with newly invented databases.
At the same time, the community must accurately and clearly characterize the
tradeoffs between different approaches. To address these challenges, we provide
the following contributions:
1) An identification of the important primitive operations across database
paradigms. We find there are a small number of base operations that can be used
and combined to support a large number of database paradigms.
2) An evaluation of the current state of protected search systems in
implementing these base operations. This evaluation describes the main
approaches and tradeoffs for each base operation. Furthermore, it puts
protected search in the context of unprotected search, identifying key gaps in
functionality.
3) An analysis of attacks against protected search for different base
queries.
4) A roadmap and tools for transforming a protected search system into a
protected database, including an open-source performance evaluation platform
and initial user opinions of protected search.Comment: 20 pages, to appear to IEEE Security and Privac
Slow wave resonance in periodic stacks of anisotropic layers
We consider transmission band edge resonance in periodic layered structures
involving birefringent layers. Previously we have shown that the presence of
birefringent layers with misaligned in-plane anisotropy can dramatically
enhance the performance of the photonic-crystal Fabry-Perot resonator. It
allows to reduce its size by an order of magnitude without compromising on its
performance. The key characteristic of the enhanced photonic-crystal cavity is
that its Bloch dispersion relation displays a degenerate photonic band edge,
rather than only regular ones. This can be realized in specially arranged
stacks of misaligned anisotropic layers. On the down side, the presence of
birefringent layers results in the Fabry-Perot resonance being coupled only
with one (elliptic) polarization component of the incident wave, while the
other polarization component is reflected back to space. In this paper we show
how a small modification of the periodic layered array can solve the above
fundamental problem and provide a perfect impedance match regardless of the
incident wave polarization, while preserving the giant transmission resonance,
characteristic of a degenerate photonic band edge. Both features are of
critical importance for a variety of practical applications, including
antennas, light amplification, optical and microwave filters, etc.Comment: To be submitted to Phys. Rev.
Operation of a LAr-TPC equipped with a multilayer LEM charge readout
A novel detector for the ionization signal in a single phase LAr-TPC, based
on the adoption of a multilayer Large Electron Multiplier (LEM) replacing the
traditional anodic wire arrays, has been experimented in the ICARINO test
facility at the INFN Laboratories in Legnaro. Cosmic muon tracks were detected
allowing the measurement of energy deposition and a first determination of the
signal to noise ratio. The analysis of the recorded events demonstrated the 3D
reconstruction capability of ionizing events in this device in liquid Argon,
collecting a fraction of about 90% of the ionization signal with signal to
noise ratio similar to that measured with more traditional wire chambersComment: 9 pages, 7 Figure
Magnetoresistive biosensors with on-chip pulsed excitation and magnetic correlated double sampling.
Giant magnetoresistive (GMR) sensors have been shown to be among the most sensitive biosensors reported. While high-density and scalable sensor arrays are desirable for achieving multiplex detection, scalability remains challenging because of long data acquisition time using conventional readout methods. In this paper, we present a scalable magnetoresistive biosensor array with an on-chip magnetic field generator and a high-speed data acquisition method. The on-chip field generators enable magnetic correlated double sampling (MCDS) and global chopper stabilization to suppress 1/f noise and offset. A measurement with the proposed system takes only 20 ms, approximately 50× faster than conventional frequency domain analysis. A corresponding time domain temperature correction technique is also presented and shown to be able to remove temperature dependence from the measured signal without extra measurements or reference sensors. Measurements demonstrate detection of magnetic nanoparticles (MNPs) at a signal level as low as 6.92 ppm. The small form factor enables the proposed platform to be portable as well as having high sensitivity and rapid readout, desirable features for next generation diagnostic systems, especially in point-of-care (POC) settings
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