4,725 research outputs found
Efficient mining of discriminative molecular fragments
Frequent pattern discovery in structured data is receiving
an increasing attention in many application areas of sciences. However, the computational complexity and the large amount of data to be explored often make the sequential algorithms unsuitable. In this context high performance distributed computing becomes a very interesting and promising approach. In this paper we present a parallel formulation of the frequent subgraph mining problem to discover interesting patterns in molecular compounds. The application is characterized by a highly irregular tree-structured computation. No estimation is available for task workloads, which show a power-law distribution in a wide range. The proposed approach allows dynamic resource aggregation and provides fault and latency tolerance. These features make the distributed application suitable for multi-domain heterogeneous environments, such as computational Grids. The distributed application has been evaluated on the well known National Cancer Institute’s HIV-screening dataset
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Distributed mining of molecular fragments
In real world applications sequential algorithms of
data mining and data exploration are often unsuitable for
datasets with enormous size, high-dimensionality and complex
data structure. Grid computing promises unprecedented
opportunities for unlimited computing and storage resources. In this context there is the necessity to develop
high performance distributed data mining algorithms.
However, the computational complexity of the problem and
the large amount of data to be explored often make the design of large scale applications particularly challenging. In this paper we present the first distributed formulation of a frequent subgraph mining algorithm for discriminative fragments of molecular compounds. Two distributed approaches have been developed and compared on the well known National Cancer Institute’s HIV-screening dataset. We present experimental results on a small-scale computing environment
Quantum Brownian motion at strong dissipation probed by superconducting tunnel junctions
We have studied the temporal evolution of a quantum system subjected to
strong dissipation at ultra-low temperatures where the system-bath interaction
represents the leading energy scale. In this regime, theory predicts the time
evolution of the system to follow a generalization of the classical
Smoluchowski description, the quantum Smoluchowski equation, thus, exhibiting
quantum Brownian motion characteristics. For this purpose, we have investigated
the phase dynamics of a superconducting tunnel junction in the presence of high
damping. We performed current-biased measurements on the small-capacitance
Josephson junction of a scanning tunneling microscope placed in a low impedance
environment at milli-Kelvin temperatures. We can describe our experimental
findings by a quantum diffusion model with high accuracy in agreement with
theoretical predications based on the quantum Smoluchowski equation. In this
way we experimentally demonstrate that quantum systems subjected to strong
dissipation follow quasi-classical dynamics with significant quantum effects as
the leading corrections.Comment: 5 pages, 4 figure
Structure formation in sugar containing pectin gels – Influence of tartaric acid content (pH) and cooling rate on the gelation of high-methoxylated pectin
The aim of the study was the application of a recently published method, using structuring parameters calculated from dG′/dt, for the characterisation of the pectin sugar acid gelation process. The influence of cooling rate and pH on structure formation of HM pectin gels containing 65 wt.% sucrose were investigated. The results show that the structure formation process as well as the properties of the final gels strongly depended on both parameters. With increasing cooling rates from 0.5 to 1.0 K/min the initial structuring temperature slightly decreased and the maximum structuring velocity increased. The lower the cooling rates, the firmer and more elastic were the final gels. With increasing acid content (decreasing pH from 2.5–2.0) the initial structuring temperatures were nearly constant. The final gel properties varied visibly but not systematically. Gels with the lowest and highest pH were less elastic and weaker compared to those with medium acid concentrations
Off-nadir antenna bias correction using Amazon rain sigma(0) data
The radar response from the Amazon rain forest was studied to determine the suitability of this region for use as a standard target to calibrate a scatterometer like that proposed for the National Oceanic Satellite System (NOSS). Backscattering observations made by the SEASAT Scatterometer System (SASS) showed the Amazon rain forest to be a homogeneous, azimuthally-isotropic, radar target which was insensitive to polarization. The variation with angle of incidence was adequately modeled as scattering coefficient (dB) = a theta b with typical values for the incidence-angle coefficient from 0.07 to 0.15 dB/deg. A small diurnal effect occurs, with measurements at sunrise being 0.5 dB to 1 dB higher than the rest of the day. Maximum-likelihood estimation algorithms presented here permit determination of relative bias and true pointing angle for each beam. Specific implementation of these algorithms for the proposed NOSS scatterometer system is also discussed
Minimal qubit tomography
We present, and analyze thoroughly, a highly symmetric and efficient scheme
for the determination of a single-qubit state, such as the polarization
properties of photons emitted by a single-photon source. In our scheme there
are only four measured probabilities, just enough for the determination of the
three parameters that specify the qubit state, whereas the standard procedure
would measure six probabilities.Comment: 14 pages, 10 figures; final versio
Development of optical diaphragm deflection sensors
The objective of this project was to develop high-temperature pressure sensors using non-metallic components and optical sensing methods. The sensors are to operate over a temperature range from room temperature approx. 20C to 540C, to respond to internal pressure up to 690 kPa, to respond to external pressure up to 690 kPa, and to withstand external overpressure of 2070 kPa. Project tasks include evaluating sensing techniques and sensor systems. These efforts include materials and sensing method selection, sensor design, sensor fabrication, and sensor testing. Sensors are tested as a function of temperature, pressure, overpressure, and vibration. The project results show that high-temperature pressure sensors based on glass components and optical sensing methods are feasible. The microbend optical diaphragm deflection sensor exhibits the required sensitivity and stability for use as a pressure sensor with temperature compensation. for the microbend sensor, the 95% confidence level deviation of input pressure from the pressure calculated from the overall temperature-compensated calibration equation is 3.7% of full scale. The limitations of the sensors evaluated are primarily due to the restricted temperature range of suitable commercially available optical fibers and the problems associated with glass-to-metal pressure sealing over the entire testing temperature range
07181 Abstracts Collection -- Parallel Universes and Local Patterns
From 1 May 2007 to 4 May 2007 the Dagstuhl Seminar 07181 ``Parallel
Universes and Local Patterns\u27\u27
was held in the International Conference and Research Center (IBFI),
Schloss Dagstuhl. During the seminar, several participants
presented their current research, and ongoing work and open problems
were discussed. Abstracts of the presentations given during the
seminar as well as abstracts of seminar results and ideas are put
together in this paper. The first section describes the seminar
topics and goals in general. Links to extended abstracts or full
papers are provided, if available
Codes for Key Generation in Quantum Cryptography
As an alternative to the usual key generation by two-way communication in
schemes for quantum cryptography, we consider codes for key generation by
one-way communication. We study codes that could be applied to the raw key
sequences that are ideally obtained in recently proposed scenarios for quantum
key distribution, which can be regarded as communication through symmetric
four-letter channels.Comment: IJQI format, 13 pages, 1 tabl
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