bluuebunny/crossref_metadata_2025 huggingface dataset:
Overload traffic management for sensor networks
Authors: Wan Chieh-Yih , Eisenman Shane B. , Campbell Andrew T. , Crowcroft Jon
Published: October 2007

There is a critical need for new thinking regarding overload traffic management in sensor networks. It has now become clear that experimental sensor networks (e.g., mote networks) and their applications commonly experience periods of persistent congestion and high packet loss, and in some cases even congestion collapse. This significantly impacts application fidelity measured at the physical sinks, even under light to moderate traffic loads, and is a direct product of the
funneling effect
; that is, the many-to-one multihop traffic pattern that characterizes sensor network communications. Existing congestion control schemes are effective at mitigating congestion through rate control and packet drop mechanisms, but do so at the cost of significantly reducing application fidelity measured at the sinks. To address this problem we propose to exploit the availability of a small number of all wireless, multiradio
virtual sinks
that can be randomly distributed or selectively placed across the sensor field. Virtual sinks are capable of siphoning off data events from regions of the sensor field that are beginning to show signs of high traffic load. In this paper, we present the design, implementation, and evaluation of
Siphon
, a set of fully distributed algorithms that support virtual sink discovery and selection, congestion detection, and traffic redirection in sensor networks. Siphon is based on a Stargate implementation of virtual sinks that uses a separate longer range radio network (based on IEEE 802.11) to siphon events to one or more physical sinks, and a short-range mote radio to interact with the sensor field at siphon points. Results from analysis, simulation and an experimental 48 Mica2 mote testbed show that virtual sinks can scale mote networks by effectively managing growing traffic demands while minimizing any negative impact on application fidelity. Additionally, we show the scheme is competitive with respect to energy consumption compared to a network composed of only motes.
A canonical seed assignment model for key predistribution in wireless sensor networks
Authors: Tague Patrick , Poovendran Radha
Published: October 2007

A promising solution for trust establishment in wireless sensor networks is the assignment of cryptographic seeds (keys, secrets, etc.) to sensor nodes prior to network deployment, known as
key predistribution
. In this article, we propose a canonical seed assignment model for key predistribution characterizing seed assignment in terms of the probability distribution describing the number of nodes receiving each seed and the algorithm for seed assignment. In addition, we present a sampling framework for seed assignment algorithms in the canonical model. We propose a probabilistic
k
-connectivity model for randomly deployed secure networks using spatial statistics and geometric random graph theory. We analyze key predistribution schemes in the canonical model in terms of network connectivity and resilience to node capture. The analytical results can be used to determine the average or worst-case connectivity or resilience to node capture for a key predistribution scheme. Furthermore, we demonstrate the design of new key predistribution schemes and the inclusion of existing schemes in the canonical model. Finally, we present a general approach to analyze the addition of nodes to an existing secure network and derive results for a well-known scheme.
The self-protection problem in wireless sensor networks
Authors: Wang Dan , Zhang Qian , Liu Jiangchuan
Published: October 2007

Wireless sensor networks have recently been suggested for many surveillance applications, such as object monitoring, path protection, or area coverage. Since the sensors themselves are important and critical objects in the network, a natural question is whether they need certain level of protection, so as to resist the attacks targeting on them directly. If this is necessary, then who should provide this protection, and how it can be done?

We refer to the above problem as
self-protection
, as we believe the sensors themselves are the best (and often the only) candidates to provide such protection. In this article, we for the first time present a formal study on the self-protection problems in wireless sensor networks. We show that, if we simply focus on enhancing the quality of field or object covering, the sensors might not necessarily be self-protected, which in turn makes the system extremely vulnerable. We then investigate different forms of self-protections, and show that the problems are generally NP-complete. We develop efficient approximation algorithms for centrally controlled sensors. We further extend the algorithms to fully distributed implementation, and introduce a smart sleep-scheduling algorithm that minimizes the energy consumption.
Localization using boundary sensors
Authors: Zheng Yunhui , Brady David J. , Agarwal Pankaj K.
Published: October 2007

We consider sensors, such as fibers, lasers, and pyroelectric motion detectors, that fire when objects cross a boundary. A moving object can be localized by analyzing sequences of boundary crossings. We consider the number of distinct sequences and object positions that can be achieved using boundary sensors in one- and two-dimensional spaces. For 1D systems we use representations of sensor sequences on graphs to derive limits on the number of object locations that can be monitored by a given sensor population and sequence length. For 2D systems we show that in certain circumstances the ratio of the number of unique sensor sequences to the number of unique object paths is exponential in the sequence length and we argue that the probability of unique identification is high for sufficiently large sequences. We also prove the triangle grid can track an object with error limited to a small neighborhood.
Reconfiguration methods for mobile sensor networks
Authors: Kansal Aman , Kaiser William , Pottie Gregory , Srivastava Mani , Sukhatme Gaurav
Published: October 2007

Motion may be used in sensor networks to change the network configuration for improving the sensing performance. We consider the problem of controlling motion in a distributed manner for a mobile sensor network for a specific form of motion capability. Mobility itself may have a high resource overhead, hence we exploit
motility
, a constrained form of mobility, which has very low overheads but provides significant reconfiguration potential. We present an architecture that allows each node in the network to learn the medium and phenomenon characteristics. We describe a quantitative metric for sensing performance that is concretely tied to real sensor and medium characteristics, rather than assuming an abstract range based model. The problem of determining the desirable network configuration is expressed as an optimization of this metric. We present a distributed optimization algorithm which computes a desirable network configuration, and adapts it to environmental changes. The relationship of the proposed algorithm to simulated annealing and incremental subgradient descent based methods is discussed. A key property of our algorithm is that convergence to a desirable configuration can be proved even though no global coordination is involved. A network protocol to implement this algorithm is discussed, followed by simulations and experiments on a laboratory test bed.
Performance tuning with instruction-level cost derived from call-stack sampling
Authors: Dunlavey Michael
Published: October 2007

Except for program-counter histogramming, most modern profiling tools summarize at the level of entire functions or basic blocks, with or without additional information such as calling context or call graphs. This paper explicates the value of information about the cost of specific instructions, relative to summaries that do not include it. A good source of this information is time-random sampling of the call stack. To get the diagnostic benefit of instruction costs it is not necessary to measure them with high precision or efficiency. In fact, manual sampling suffices quite well, when it can be used. Other benefits of call stack sampling are that it can be used with unmodified software and libraries, and it is easily confined to the time intervals of interest. As with other profiling techniques, it can be employed repeatedly to remove all significant performance problems in single-thread programs.
A calculus for java's reference objects
Authors: Gabay Yarom , Kfoury Assaf J.
Published: October 2007

Java's Reference objects provide the programmer with limited control over the process of memory management. Although reference objects are often helpful, they introduce nondeterminism into program evaluation and lead to ambiguous program outcome. In this paper we present a calculus to formally reason about Java's Reference objects. We model multiple levels of reference objects in a single calculus and apply a different garbage collection policy to each one of them. Accordingly, weak references are given the semantics of eager collection and soft references are given the semantics of lazy collection. In addition, we constrain garbage collection with the scarcity of two resources: time and space. We demonstrate the viability of our calculus by modeling a Java program which addresses a commonly-encountered caching problem. Using our model, we reason about the program's evaluation and interaction with the garbage collector.
Unsupervised pattern mining from symbolic temporal data
Authors: Mörchen Fabian
Published: October 2007

We present a unifying view of temporal concepts and data models in order to categorize existing approaches for unsupervised pattern mining from symbolic temporal data. In particular we distinguish time point-based methods and interval-based methods as well as univariate and multivariate methods. The mining paradigms and the robustness of many proposed approaches are compared to aid the selection of the appropriate method for a given problem. For time points, sequential pattern mining algorithms can be used to express equality and order of time points with gaps in multivariate data. For univariate data and limited gaps suffix tree methods are more efficient. Recently, efficient algorithms have been proposed to mine the more general concept of partial order from time points. For time interval data with precise start and end points the relations of Allen can be used to formulate patterns. The recently proposed Time Series Knowledge Representation is more robust on noisy data and offers an alternative semantic that avoids ambiguity and is more expressive. For both pattern languages efficient mining algorithms have been proposed.
5th international workshop on knowledge discovery in inductive databases (KDID'06)
Authors: Džeroski Sašo , Struyf Jan
Published: October 2007

This report presents a review of the 5th International Workshop on Knowledge Discovery in Inductive Databases (KDID'06), which was organized by the authors and held in Berlin, Germany, on September 18, 2006, in conjunction with ECML/PKDD'06, the 17th European Conference on Machine Learning and the 10th European Conference on Principles and Practice of Knowledge Discovery in Databases. The goal of the workshop was to bring together the researchers that are interested in the area of inductive databases, inductive queries, constraint-based data mining, and data mining query languages.
Introduction to the special issue on data mining for health informatics
Authors: Ng Raymond T. , Pei Jian
Published: October 2007

One of the holy grails of medical research in the next decade is what is often called "personalized" medicine. The goal is to individualize therapy and treatment options, and even prevention strategies. This movement is fueled by the rapid advances made in high-throughput biotechnologies. Prime examples include SNP (Single Nucleotide Polymorphisms) chips and CGH (Comparative Genomic Hybridization) arrays for DNA profiling, oligonucleotide arrays for mRNA expression, and advanced mass spectrometry for peptide/protein and metabolite quantitation.
Enabling more sophisticated gene expression analysis for understanding diseases and optimizing treatments
Authors: Soh Donny , Dong Difeng , Guo Yike , Wong Limsoon
Published: October 2007

We survey the progress in the analysis of gene expression data for the purposes of disease subtype diagnosis, new subtype discovery, and understanding of diseases and treatment responses. We find existing works fall short on several issues: these works provide little information on the interplay between selected genes; the collection of pathways that can be used, evaluated, and ranked against the observed expression data is limited; and a comprehensive set of rules for reasoning about relevant molecular events has not been compiled and formalized. We thus envision an advanced integrated framework, and are developing a system based on it, to provide biologically inspired solutions. It comprises: (i) automated analysis and extraction of information from biomedical texts; (ii) targeted construction of known pathways; and (iii) direct hypothesis generation based on logical reasoning on, and tests for, consistencies and inconsistencies of observed data against known pathways.
Novel approaches for small biomolecule classification and structural similarity search
Authors: Karakoc Emre , Cherkasov Artem , Sahinalp S. Cenk
Published: October 2007

Structural similarity search among small molecules is a standard tool used in molecular classification and in-silico drug discovery. The effectiveness of this general approach depends on how well the following problems are addressed. The notion of similarity should be chosen for providing the highest level of discrimination of compounds with respect to the bioactivity of interest. The data structure for performing search should be very efficient as the molecular databases of interest include several millions of compounds.

In this paper we summarize the recent applications of
k
-nearest-neighbor search method for small molecule classification. The
k
-nn classification of small molecules is based on selecting the most relevant set of chemical descriptors which are then compared under standard Minkowski distance

L
p

. Here we describe how to computationally design the optimal
weighted
Minkowski distance

wL
p

for maximizing the discrimination between active and inactive compounds wrt bioactivities of interest.
k
-nn classification requires fast similarity search for predicting bioactivity of a new molecule. We then focus on construction of pruning based
k
-nn search data structures for any

wL
p

distance that minimizes similarity search time.

The accuracy achieved by
k
-nn classifier is better than the alternative LDA and MLR approaches and is comparable to the ANN methods. In terms of running time,
k
-nn classifier is considerably faster than the ANN approach especially when large data sets are used. Furthermore,
k
-nn classifier is capable of quantification of the level of bioactivity rather than returning a binary decision and can bring more insight to the nature of the activity via eliminating unrelated descriptors of the compounds with respect to the activity in question.
Drug exposure side effects from mining pregnancy data
Authors: Chen Yu , Pedersen Lars Henning , Chu Wesley W. , Olsen Jorn
Published: October 2007

This paper presents an interdisciplinary collaborative research project between the Epidemiology Department and the Computer Science Department for using data mining technique to analyze data from pregnant women. Specifically, the authors use association rule mining approach to derive possible side effects due to exposure to multiple drugs at different duration of the pregnancy. The derived temporal sequential rules discover new information that would not be detected by the traditional analysis method that is currently used in pharmaco-epidemiology.
Automatic
in vivo
microscopy video mining for leukocytes
Authors: Zhang Chengcui , Chen Wei-Bang , Yang Lin , Chen Xin , Johnstone John K.
Published: October 2007

Biological videos are very different from conventional videos. Automatic spatiotemporal mining of moving cells from in vivo microscopy videos is extremely difficult because of the severe noises, camera/subject movements, deformations, and strong dependencies on microscopy operators. In this paper, we present an automatic spatiotemporal mining system of rolling and adherent leukocytes for intravital videos. The magnitude of leukocyte adhesion and decrease in rolling velocity are common interests in inflammation response studies. Currently, there is no existing system which is perfect for such purposes. Several approaches have been proposed for tracking leukocytes. However, these approaches can either only track leukocytes that roll along the centerline of the blood vessel, or can only handle leukocytes with fixed morphologies. In addition, the camera/subject movement is a severe problem which occurs frequently while analyzing
in vivo
microscopy videos. In this paper, we proposed a new method for automatic recognition of non-adherent and adherent leukocytes. The proposed method includes three steps: (1) camera/subject movement alignment; (2) moving leukocytes detection; (3) adherent leukocytes detection. The experimental results demonstrate the effectiveness of the proposed method.
Interview with Simon Funk
Authors: Piatetsky Gregory
Published: October 2007

Interview with Simon Funk -- a Netflix prize leader, an outstanding hacker, and an original thinker.
Deterministic high-speed root-hashing automaton matching coprocessor for embedded network processor
Authors: Tseng Kuo-Kun , Lin Ying-Dar , Lee Tsern-Huei , Lai Yuan-Cheng
Published: October 2007

While string matching plays an important role in deep packet inspection applications, its software algorithms are insufficient to meet the demands of high-speed performance. Accordingly, we were motivated to propose fast and deterministic performance root-hashing automaton matching (RHAM) coprocessor for embedded network processor. Although automaton algorithms are robust with deterministic matching time, there is still plenty of room for improvement of their average-case performance. The proposed RHAM employs novel root-hashing technique to accelerate automaton matching. In our experiment, RHAM is implemented in a prevalent automaton algorithm, Aho-Corasick (AC) which is often used in many packet inspection applications. Compared to the original AC, RHAM only requires extra vector size in 48 Kbytes for root-hashing, and has about 900% and 420% outperformance for 20,000 URLs and 10,000 virus patterns respectively. Implementaion of RHAM FPGA can perform at the rate of 12.6 Gbps with the pattern amount in 34,215 bytes. This is superior to all previous matching hardware in terms of throughput and pattern set.
Mapping streaming architectures on reconfigurable platforms
Authors: Bellas Nikolaos , Chai Sek M. , Dwyer Malcolm , Linzmeier Dan
Published: October 2007

Hardware accelerators, used as application-specific extensions to the computational capabilities of a system, are efficient mechanisms to enhance the performance and reduce the power dissipation in a System On Chip (SoC). These accelerators execute on the computationally critical part of the application, and offload computations from the scalar processors. In this paper, we present a design automation tool that generates accelerators based on a given application kernel. The accelerators are processing streaming data, and support a programming model which can naturally express a large number of embedded applications, and which results in efficient and fast hardware implementations. We demonstrate the applicability of the tool for architectural space exploration for a number of media applications, with results on area, throughput, and clock speeds.
Improving instruction level parallelism through reconfigurable units in superscalar processors
Authors: Suri Tameesh
Published: October 2007

With reducing feature sizes, more transistors can be integrated on the chip. The increased transistor budget can be utilized to improve the instruction level parallelism (ILP) exploited from the processor. However, the transistors cannot be used to arbitrarily increase the processor width and size in the hope of exploiting better ILP. In this paper, we propose an architecture where the superscalar datapath is tightly coupled with a reconfigurable unit (RFU). The reconfiguration unit is configured to execute the traces of dynamic instructions that are frequently executed. To address the data dependency issues between the instructions in the superscalar and the RFU, we propose to execute the trace on the RFU with predicted values. When the trace instructions reach the issue queue in the superscalar, the predictions are validated. In this technique, performance improvement is obtained for correct prediction, whereas no performance degradation is incurred for mispredictions. With this architecture, we observe an average instructions per cycle (IPC) improvement of about 11% over the simulated SPEC 2000 benchmarks, using a very small last value data value predictor.
Architectural
contesting
Authors: Najaf-abadi Hashem H. , Rotenberg Eric
Published: October 2007

Previous studies have proposed techniques to dynamically change the architecture of a processor to better suit the characteristics of the workload at hand. However, all such approaches are prone to a fundamental trade-off between the architectural diversity they can provide and the latency of architectural change, their fixed-configuration performance and the complexity of finding the best architectural configuration for the workload at hand. In this study we argue that the full potential of dynamic architectural customization can only be achieved by diminishing the effect of the degree of available architectural diversity on the aforementioned performance factors.

The performance of a statically designed processing core in a heterogeneous multi-core system is independent of the architectural diversity available. In addition, it is apparent that concurrent execution of code on differently architected cores automatically reveals which architecture is more suitable for the characteristics of a particular workload.

We therefore propose architectural contesting; the redundant execution of code on a number of differently architected processors (each customized for a different set of workload characteristics) in a leader follower arrangement, such that the leader and follower cores continuously shift roles as one core or the other becomes more favorable for new code phases. In this manner effective execution is naturally transferred from one static architecture to the other with little latency.

In this study, we show that the contesting of only processor width can yield an average speedup of 7.5% and up to 12.5% in integer SPEC benchmarks.
Internet nuggets
Authors: Thorson Mark
Published: October 2007

This column consists of selected traffic from the
comp.arch
newsgroup, a forum for discussion of computer architecture on the Internet---an international computer network.

As always, the opinions expressed in this column are the personal views of the authors, and do not necessarily represent the institutions to which they are affiliated.

Text which sets the context of a message appears underlined or in italics; this is usually text the author has quoted from earlier messages. The code-like expressions below the authors' names are their addresses on Internet.
Development of Low Melting Ionic Liquids using Eutectic Mixtures of Imidazolium and Pyrazolium Ionic Liquids
Authors: Dunstan T Don J. , Caja Josip
Published: October 2007

Phase diagram of the binary ionic liquid 1-ethyl-3- methylimidazolium hexafluorophosphate ([emim][PF6]) - 1- ethyl-2-methylpyrazolium hexafluorophosphate ([empz][PF6]), was determined. The binary system shows a eutectic at 23oC, (which is 38oC below the melting point of the lower melting salt [emim][PF6]), and at the molar composition [emim][PF6]: [empz][PF6] ≈ 47:53. Therefore using the eutectic method a low melting ionic liquid was formed with single salts that contain only small alkyl groups on the cations. At ambient temperature the ionic conductivity of the eutectic mixture is comparable to that of a low melting single salt such as, 1-n-butyl-3- methylimidazolium hexafluorophosphate ([bmim][PF6]), but at higher temperature (e.g. 90oC) the conductivity of the eutectic mixture is 20% higher. This method allows the preparation of purer ionic liquids since the two single salts can be purified by recrystallization, before they are mixed to form the binary system which is a liquid at ambient temperature. Hence the ionic liquids produced by the eutectic method have the potential for finding wider range of applications compared with low melting ionic liquids (single salts) containing longer alkyl groups prepared by the conventional method.
Fulleride Based Ionic Liquids
Authors: Del Sesto Rico E. , Corley Cynthia A. , Dudis Douglas S. , Yeates Alan T. , Wilkes John S.
Published: October 2007

A room temperature fulleride-based ionic liquid has been developed and characterized. Utilizing the trihexyl (tetradecyl) phosphonium cation, the ionic liquid [PC6C6C6C14]3 [C60]Cl was synthesized, and distinctly shows spectroscopic characteristics of the [C60]2- anion. The glass transition of the ionic liquid occurs well below room temperature at -56 {degree sign} C, but it still retains an extremely high viscosity at room temperature. Attempts were made to obtain the pure fulleride salt [PR4]3[C60], but nearly always results in the binary fulleride-chloride salt.
What Makes an Ionic Liquid a Liquid? The Impact of Structure on Ionic Liquid Properties
Authors: Henderson Wesley A. , Trulove P. C. , De Long Hugh C. , Young Victor
Published: October 2007

How the structure of the ions determines the thermal properties of a salt remains poorly understood. Here the crystal structures of different imidazolium salts with bis (trifluoromethanesulfonyl)-imide anions have been compared with their Raman spectra to determine how the conformation of the anions changes with temperature and cation structure. This information provides clarity to the widely varying thermal properties of salts with only minor cation structural modifications.
Ordered Structure in Room Temperature Molten Salts Containing Aliphatic Quaternary Ammonium Ions
Authors: Mizuhata Minoru , Maekawa Masanori , Deki Shigehito
Published: October 2007

The small angle x-ray scattering (SAXS) and wide angle x-ray scattering (WAXS) is measured for RTMS containing aliphatic quaternary ammonium cation and bis(trifluoromethyl sulfonyl) imide anion. For the system containing trimethylammonium aliphatic quaternary ammonium cation; [N111n]+, it is shown that a new peak at low q-value is confirmed above n=5. It is suggested that this new peak is of the local ordering structure formed by van der Waals force between alkyl chains of ammonium cations. The other room temperature molten salts such as [Nnnnn]+(n-5-6), [N1123]+, N- methyl-n-propyl piperidium cation [PP13]+ and N-methyl-n-propyl pyrrolidinium cation [P13]+ having the same anion; TFSI- were also used. The layer spacing (d) of this ordering structure is decrease with increase of the temperature.
Preparation of Functionally Graded Aluminum Nitride-Oxide Coatings Using a Precursor Derived from a Chloroaluminate Ionic Liquid
Authors: Carter Michael T. , Evenson Carl , Schutte Erick
Published: October 2007

Room temperature ionic liquids (RTILs), also called ambient temperature molten salts, have been demonstrated to be potentially useful for a wide variety of chemical and electrochemical functions, ranging from power source electrolytes to alternative solvents for chemical synthesis. We will report on recent work on a materials application of RTILs in which a functionally graded, corrosion-resistant coating for the interior of hot ferrous metal pipes was prepared using precursors derived from an ambient temperature chloroaluminate melt.
Physicochemical Properties of Molten KF-K2NbF7-Nb2O5 System
Authors: Kubikova Blanka , Cibulkova Jarmila , Danek Vladimir , Gaune-Escard Marcelle
Published: October 2007

Molten KF-K2NbF7-Nb2O5 system has been determined from the point of phase equilibria, density, viscosity and surface tension. In spite of narrow investigated concentration region, system has been studied only up to 20 mol % of the Nb2O5; in the system oxofluoroniobate compounds are formed. These have influence on the physicochemical properties.
Dependence of Oxygen Reduction Reaction on Temperature in (Li/Na/La)CO3
Authors: Mitsushima Shigenori , Okuno Shinya , Kamiya Nobuyuki , Ota Kenichiro
Published: October 2007

In order to reduce the overpotential of the oxygen reduction reaction (ORR) for molten carbonate fuel cell, the effect of the La addition, which reduces NiO solubility by its basicity, has been investigated in Li/Na eutectic carbonate with a gold ring meniscus electrode. The ORR was enhanced with the La addition, especially at the lower temperature and higher carbon dioxide partial pressure region. The ORR would be the mixed diffusion control of the superoxide and the percarbonate. The ratio of the percarbonate path increased with the decrease of temperature, and La would enhance the percarbonate path.
Screening and Properties of New Materials for MCFC Application
Authors: Albin Valérie , Goux Aurélie , Belair Sarah , Lair Virginie , Ringuedé Armelle , Cassir Michel
Published: October 2007

A synthetic screening is given on interesting materials, dopants and protective coatings allowing a better control of the corrosion in MCFC systems and the optimization of their lifetime. After outlining the interest of MCFC systems with respect to other fuel cell devices, an analysis of the recent literature is given on electrolyte, cathode, anode and interconnection plate materials.
Electrochemical Reduction of Tantalum Compounds in Ambient Temperature Melts
Authors: Furukawa Yuki , Morimitsu Masatsugu , Matsunaga Morio
Published: October 2007

Electrodeposition of tantalum metal was investigated in BMP- TFSI ambient temperature melts, as well as electrochemistry of tantalum pentachloride. No tantalum compound deposits from the melt containing TaCl5. The addition of LiF forms the tantalum compounds on the tungsten electrode by potentiostatic method. From the BMP-TFSI melts containing TaCl5, LiF and BMPBr, tantalum metal could deposit at 353K, although the surface of deposits was rough and contained the impurities such as chlorides and fluorides.
Electrochemical Studies of Magnesium Deposition in Ionic Liquids
Authors: Cheek Graham T. , O'Grady William , El Abedin Sherif Z. , Moustafa E. M. , Endres Frank
Published: October 2007

The electrochemical deposition of magnesium has been investigated in the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm BF4), 1-butyl-3-methylpyrrolidinium triflate (BMP TfO), and 1-butyl-3-methylpyrrolidinium bis (trifluorosulfonyl)amide (BMP Tf2N). The electrochemical window of the imidazolium ionic liquid was found to be insufficient for reduction of magnesium triflate, whereas the BMP systems can be used for the reduction of several magnesium salts. Studies of the reduction of other magnesium salts were carried out in nonaqueous solvents such as propylene carbonate for comparison with the work in ionic liquids.
Fabrication of Porous Metal Surfaces from a ZnCl2-1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid
Authors: Tai Chia-Cheng , Lin Yi-Wen , Yeh Fu-Hwa , Huang Jiang-Feng , Sun I-Wen
Published: October 2007

This work describes the fabrication of porous some metal films by electrochemical formation and electrochemical dealloying of Zn alloys in a ZnCl2-EMIC ionic liquid, without using hazardous acids or bases. The effects of the amounts of deposited zinc, deposition potential, current, and temperature on the pore structure are described. It is worth to note that in this process, the zinc(II) species in the IL was consumed during the electrodeposition step but was recovered during the electrochemical dealloying step, making the IL re-usable.
The Bis((trifluoromethyl)sulfonyl)imide-Based Room Temperature Ionic Liquids Used for Several Electrochemical Applications
Authors: Deng Ming-Jay , Su Chung-Jui , Hsu Sodio C.N. , Chen Po-Yu
Published: October 2007

Two room temperature ionic liquids based on the bis ((trifluoromethyl)sulfonyl)-imide anion (TFSI anion), the tributylmethylammonium-TFSI (Bu3MeN-TFSI) and the butylmethylpyrrolidinium-TFSI (BuMePy-TFSI), have been prepared for the electrochemical study of Li+/Li redox couple, the electrodeposition of Mn, Zn-Mn alloys and Cu-Mn alloys, and the extraction of Cu(II) ions from aqueous solutions, respectively. The best coulombic efficiency of Li+/Li couple is 97%. Mn(II), Zn(II) and Cu(I) species were introduced into the Bu3MeN-TFSI or BuMePy-TFSI by the anodic dissolution of the respective metallic electrodes. Coatings containing Mn, Zn, Cu, Zn-Mn or Cu-Mn can be obtained by controlled-potential electrolysis. The current efficiencies of Mn electrodeposition in either ionic liquid approach 100%. The Zn-Mn and Cu-Mn alloy deposits obtained in this study were compact and adherent. The surface morphology of these deposits depended on the Mn/Zn and Mn/Cu ratio, respectively. The BuMePy-TFSI ionic liquid containing N,N,N',N'-tetrakis-(2-pyridin-2-yl-ethyl)- butane-1,4-diamine (N4Py2) exhibits good ability of extracting Cu(II) ions from aqueous solution. The electrochemical study revealed that both Cu(I) and Cu(II) can form strong coordinated compounds with N4Py2 because the redox potentials of Cu(II)/Cu(I) and Cu(I)/Cu(0) couples shift to much more negative values, respectively.
Electrodeposition of Molybdenum in LiTFSI-CsTFSI Melt at 150ºC
Authors: Gao Bingliang , Nohira Toshiyuki , Hagiwara R.
Published: October 2007

Electrodepostion of molybdenum was studied in the eutectic LiTFSI-CsTFSI (0.07: 0.93 in mole fraction, m.p., 112ºC) melt at 150ºC. MoCl5 was selected as molybdenum ion sources. Metallic molybdenum was electrodeposited on nickel substrate. Quality of the deposits was improved by using galvanostatic electrolysis and pulsed current electrolysis.
Electrorefining of Silicon in Molten Calcium Chloride
Authors: Kongstein Ole E. , Wollan Camilla , Sultana Saima , Haarberg Geir Martin
Published: October 2007

Molten salt electrorefining can in principle be used to purify silicon in a simple and inexpensive way. In the present work a melt containing calcium chloride, sodium chloride and calcium oxide at 850 {degree sign}C was used in electrochemical studies. The results indicate that the concept of silicon electrorefining in the melt mentioned above is possible.
Formation of Ni-Zr Alloys in Molten Fluorides
Authors: Groult Henri , Barhoun Abdeslam , El Ghallali Houda , Lantelme Frederic , Borensztajn Stephan
Published: October 2007

The electrochemical behavior of Zr4+ was investigated in LiF-NaF between 923 and 1123 K. With an inert tungsten or molybdenum electrode, a well-defined oxydo-reduction wave was observed during cyclic voltammetry experiments. The reduction of Zr4+ is a single four-electron step and quasi-reversible, and the process is diffusion-controlled. Chronopotentiometry was used to measure the diffusion coefficient of Zr4+ ions. For instance, a value 1.54 × 10-5 cm2 s-1 was found at of at 979 K. The reduction of Zr4+ ions was also studied using nickel electrode. In that case, Ni- Zr alloys were formed as pointed out on cyclic voltammograms which exhibit several characteristic peaks. SEM and EDX analyses have revealed the presence of a multi-layered Ni-Zr alloy deposited film on Ni electrode. At -1.65 V vs Ni/Ni2+, three successive layers were pointed out, corresponding to three different Ni-Zr alloy compositions.
Electrodeposition of Tungsten, Molybdenum and Double Carbides of Tungsten (Molybdenum) and Nickel (Cobalt) from Low-Temperature Halide-Oxide Melts
Authors: Kushkhov Hasbi B. , Adamokova Marina N. N.
Published: October 2007

We investigated the processes of electrochemical deposition of metallic tungsten and molybdenum, carbides of molybdenum and tungsten by methods of cyclic voltammetry, electrolyses from halide-oxide melts at temperature 550 {degree sign}C. Conditions of joint electroreduction of fluoride complexes of tungsten and molybdenum, carbon dioxide and ions of nickel and cobalt in halide-oxide melts are found at temperature 550 {degree sign}C. Optimum conditions of obtaining of metallic tungsten and molybdenum, carbides of tungsten (molybdenum), double carbides tungsten with nickel (cobalt) from halide-oxide melts are determined.
Study of Causes of Film Formation on the Electrolyte Surface during Niobium Electrorefining
Authors: Polovov Ilya B. , Chernyshov Mikhail V. V. , Rebrin Oleg I. I. , Volkovich Vladimir A. , Shtutsa Mikhail G. G. , Griffiths Trevor R. R.
Published: October 2007

Formation of a conducting film on the surface of fused electrolyte during electrorefining of niobium in chloride melts was investigated. It was found that this film has metallic nature and is formed as a result of disproportionation of niobium(III) ions at a liquid-gas interface. Decreasing temperature gradient along the heated part of the electrolyser can be used to limit the influence of the disproportionation onto film formation. The metal film formation on solid ceramics can be used for creation of conducting layers on various oxide materials.
Codeposition of Silver with Tungsten Carbide in Tungstate Melts
Authors: Malyshev Victor , Gab Angelina , Gaune-Escard Marcelle
Published: October 2007

Diffusion controlled one-electron reversible electroreduction of silver in tungstate melts was established by voltammetric and potentiometric methods, and Ag+ ions effect on electrodeposition of tungsten carbide coatings was studied.
Study of Chlorine-Oxygen Exchange Reaction in NaCl-2CsCl
Authors: Osipenko Alexander , Mayorshin Alexander
Published: October 2007

Formal equilibrium constant for reaction of oxide ion formation and coefficient of oxide ion activity was determined in molten NaCl-2CsCl and at temperature range 823-923K using oxygen sensor and different partial pressure of chlorine and oxygen.
Behaviour of Rare Earth Elements in Molten Salts in Relation to Pyrochemical Reprocessing of Spent Nuclear Fuels
Authors: Volkovich Vladimir A. , Vasin Boris D. D. , Griffiths Trevor R. R. , Polovov Ilya B. , Medvedev Evgenii O. O. , Yakimov Sergei M. M.
Published: October 2007

The kinetics of chlorination of lanthanide oxides (by Cl2 and HCl) and precipitation of lanthanide phosphates was studied by in situ electronic absorption spectroscopy in 3LiCl-2KCl and NaCl-KCl melts at 400-750 oC. Products of the chlorination are the corresponding hexachlorospecies, LnCl63-, and the rate of chlorination increases with increasing temperature. Composition of the precipitated phosphates depends on the melt composition and 1.5-5 fold excess of phosphate, depending on the nature of lanthanide, is needed for the complete removal of the lanthanides from the melt. Over three hours are required for completing the reaction of phosphate precipitation.
Modulation of human cardiovascular outward rectifying chloride channel by intra- and extracellular ATP
Authors: Liu Gong Xin , Vepa Sanjay , Artman Michael , Coetzee William A.
Published: October 2007

The macroscopic volume-regulated anion current (VRAC) is regulated by both intracellular and extracellular ATP, which has important implications in signaling and regulation of cellular excitability. The outwardly rectifying Cl− channel (ORCC) is a major contributor to the VRAC. This study investigated the effects of intracellular and extracellular ATP on the ORCCs expressed in the human cardiovascular system. With inside-out single-channel patch-clamp techniques, ORCCs were recorded from myocytes isolated from human atrium and septal ventricle and from primary cells originating from human coronary artery endothelium and human coronary artery smooth muscle. ORCCs from all of these tissues had similar biophysical properties, i.e., they were outwardly rectifying in symmetrical Cl− solutions, exhibited a slope conductance of ∼90–100 pS at positive potentials and ∼22 pS at negative potentials, and had a high open probability that was independent of voltage or time. The presence of ATP at the cytosolic face of the membrane increased the number of patches that contained functional ORCC but had no effect on gating. In contrast, “extracellular” ATP (in pipette solution) had no effect on the proportion of patches in which ORCC was detected but strongly reduced the open probability by increasing the closed dwell time. The potency order for nucleotides to affect gating was ATPγS > ATP = UTP > ADP > AMP, which suggests that a negatively charged phosphate group is involved in ORCC block. Our findings are consistent with a role of ORCC in the human cardiovasculature (atrium, ventricle, and coronary arteries). Regulation of ORCC by extracellular ATP suggests that this channel may have an important role in maintaining electrical activity and membrane potential under conditions in which extracellular ATP levels are elevated, such as with ATP release from nerve endings or during pathophysiological conditions.
L-type Ca2+ channel mutations and T-wave alternans: a model study
Authors: Zhu Zheng I. , Clancy Colleen E.
Published: October 2007

A number of mutations have been linked to diseases for which the underlying mechanisms are poorly understood. An example is Timothy Syndrome (TS), a multisystem disorder that includes severe cardiac arrhythmias. Here we employ theoretical simulations to examine the effects of a TS mutation in the L-type Ca2+ channel on cardiac dynamics over multiple scales, from a gene mutation to protein, cell, tissue, and finally the ECG, to connect a defective Ca2+ channel to arrhythmia susceptibility. Our results indicate that 1) the TS mutation disrupts the rate-dependent dynamics in a single cardiac cell and promotes the development of alternans; 2) in coupled tissue, concordant alternans is observed at slower heart rates in mutant tissue than in normal tissue and, once initiated, rapidly degenerates into discordant alternans and conduction block; and 3) the ECG computed from mutant-simulated tissue exhibits prolonged QT intervals at physiological rates and with small increases in pacing rate, T-wave alternans, and alternating T-wave inversion. At the cellular level, enhanced Ca2+ influx due to the TS mutation causes electrical instabilities. In tissue, the interplay between faulty Ca2+ influx and steep action potential duration restitution causes arrhythmogenic discordant alternans. The prolongation of action potentials causes spatial dispersion of the Na+ channel excitability, leading to inhomogeneous conduction velocity and large action potential spatial gradients. Our model simulations are consistent with the ECG patterns from TS patients, which suggest that the TS mutation is sufficient to cause the clinical phenotype and allows for the revelation of the complex interactions of currents underlying it.
Microalbuminuria in Type 2 diabetes indicates impaired microvascular vasomotion and perfusion
Authors: Schmiedel Ole , Schroeter Matthias L. , Harvey John N.
Published: October 2007

Vascular oscillation (vasomotion) occurs in the microcirculation and is thought to be a significant contributor to tissue perfusion. Our aims were to assess the relationship of vasomotion to perfusion in the cutaneous microcirculation of diabetic patients, to determine the influence on it of endothelium-dependent and nonendothelium-dependent vasodilatory stimuli, and to assess the relationship to perfusion and vasomotion of various biochemical markers of vascular function (HbA1c, LDL- and HDL-cholesterol, triglycerides, insulin resistance, high sensitive C-reactive protein, L- and E-selectin, soluble ICAM, von Willebrand factor) and microalbuminuria. Perfusion and vasomotion (spectral density at low and very low frequencies) were measured by laser-Doppler flowmetry after local heat and iontophoresis of ACh and sodium nitroprusside. Perfusion responses to all stimuli were impaired in patients with Type 2 diabetes (heat: F = 28.0, P < 0.001; ACh: F = 7.11, P = 0.003; sodium nitroprusside: F = 4.0, P = 0.028). Responses to endothelium-dependent stimuli were further impaired in microalbuminuric patients (heat: P = 0.035; ACh: P = 0.034). Vasomotion responses at low frequencies after endothelium-dependent stimuli were impaired in diabetic patients compared with that shown in controls (heat: F = 5.62, P = 0.002; ACh: F = 4.32, P = 0.015). Multivariate modeling showed microalbuminuria to be the only consistent predictor of perfusion and vasomotion responses. The results suggest that microalbuminuria in Type 2 diabetes reflects a generalized disturbance of microvascular function related to endothelium-dependent mechanisms.
The visceral pericardium: macromolecular structure and contribution to passive mechanical properties of the left ventricle
Authors: Jöbsis Paul D. , Ashikaga Hiroshi , Wen Han , Rothstein Emily C. , Horvath Keith A. , McVeigh Elliot R. , Balaban Robert S.
Published: October 2007

Much attention has been focused on the passive mechanical properties of the myocardium, which determines left ventricular (LV) diastolic mechanics, but the significance of the visceral pericardium (VP) has not been extensively studied. A unique en face three-dimensional volumetric view of the porcine VP was obtained using two-photon excitation fluorescence to detect elastin and backscattered second harmonic generation to detect collagen, in addition to standard light microscopy with histological staining. Below a layer of mesothelial cells, collagen and elastin fibers, extending several millimeters, form several distinct layers. The configuration of the collagen and elastin layers as well as the location of the VP at the epicardium providing a geometric advantage led to the hypothesis that VP mechanical properties play a role in the residual stress and passive stiffness of the heart. The removal of the VP by blunt dissection from porcine LV slices changed the opening angle from 53.3 ± 10.3 to 27.3 ± 5.7° (means ± SD, P < 0.05, n = 4). In four porcine hearts where the VP was surgically disrupted, a significant decrease in opening angle was found (35.5 ± 4.0°) as well as a rightward shift in the ex vivo pressure-volume relationship before and after disruption and a decrease in LV passive stiffness at lower LV volumes ( P < 0.05). These data demonstrate the significant and previously unreported role that the VP plays in the residual stress and passive stiffness of the heart. Alterations in this layer may occur in various disease states that effect diastolic function.