bluuebunny/crossref_metadata_2025 huggingface dataset:
A tag-based approach for the design and composition of information processing applications
Authors: Bouillet Eric , Feblowitz Mark , Liu Zhen , Ranganathan Anand , Riabov Anton
Published: October 2008

In the realm of component-based software systems, pursuers of the holy grail of automated application composition face many significant challenges. In this paper we argue that, while the general problem of automated composition in response to high-level goal statements is indeed very difficult to solve, we can realize composition in a restricted context, supporting varying degrees of manual to automated assembly for specific types of applications. We propose a novel paradigm for composition in flow-based information processing systems, where application design and component development are facilitated by the pervasive use of faceted, tag-based descriptions of processing goals, of component capabilities, and of structural patterns of families of application. The facets and tags represent different dimensions of both data and processing, where each facet is modeled as a finite set of tags that are defined in a controlled folksonomy. All data flowing through the system, as well as the functional capabilities of components are described using tags. A customized AI planner is used to automatically build an application, in the form of a flow of components, given a high-level goal specification in the form of a set of tags. End-users use an automatically populated faceted search and navigation mechanism to construct these high-level goals. We also propose a novel software engineering methodology to design and develop a set of reusable, well-described components that can be assembled into a variety of applications. With examples from a case study in the Financial Services domain, we demonstrate that composition using a faceted, tag-based application design is not only possible, but also extremely useful in helping end-users create situational applications from a wide variety of available components.
Designed as designer
Authors: Gabriel Richard P.
Published: October 2008

Conceptual integrity arises not (simply) from one mind or from a small number of agreeing resonant minds, but from sometimes hidden co-authors and the thing designed itself.
Removing exponential backoff from TCP
Authors: Mondal Amit , Kuzmanovic Aleksandar
Published: October 2008

The well-accepted wisdom is that TCP's exponential backoff mechanism, introduced by Jacobson 20 years ago, is essential for preserving the stability of the Internet. In this paper, we show that removing exponential backoff from TCP altogether can be done without inducing any stability side-effects. We introduce the implicit packet conservation principle and show that as long as the endpoints uphold this principle, they can only improve their end-to-end performance relative to the exponential backoff case. By conducting large-scale simulations, modeling, and network experiments in Emulab and the Internet using a kernel-level FreeBSD TCP implementation, realistic traffic distributions, and complex network topologies, we demonstrate that TCP's binary exponential backoff mechanism can be safely removed. Moreover, we show that insuitability of TCP's exponential backoff is fundamental, i.e., independent from the currently-dominant Internet traffic properties or bottleneck capacities. Surprisingly, our results indicate that a path to incrementally deploying the change does exist.
A day at the root of the internet
Authors: Castro Sebastian , Wessels Duane , Fomenkov Marina , Claffy Kimberly
Published: October 2008

We analyzed the largest simultaneous collection of full-payload packet traces from a core component of the global Internet infrastructure ever made available to academic researchers. Our dataset consists of three large samples of global DNS traffic collected during three annual "Day in the Life of the Internet" (DITL) experiments in January 2006, January 2007, and March 2008. Building on our previous comparison of DITL 2006 and DITL 2007 DNS datasets [28], we venture to extract historical trends, comparisons with other data sources, and interpretations, including traffic growth, usage patterns, impact of anycast distribution, and persistent problems in the root nameserver system that reflect ominously on the global Internet. Most notably, the data consistently reveals an extraordinary amount of DNS pollution -- an estimated 98% of the traffic at the root servers should not be there at all. Unfortunately, there is no clear path to reducing the pollution, so root server operators, and those who finance them, must perpetually overprovision to handle this pollution. Our study presents the most complete characterization to date of traffic reaching the roots, and while the study does not adequately fulfill the "Day in the Life of the Internet" vision, it does succeed at unequivocally demonstrating that the infrastructure on which we are all now betting our professional, personal, and political lives deserves a closer and more scientific look.
UFO
Authors: Zhu Yaping , Bavier Andy , Feamster Nick , Rangarajan Sampath , Rexford Jennifer
Published: October 2008

Conventional wisdom has held that routing protocols cannot achieve both scalability and high availability. Despite scaling relatively well, today's Internet routing system does not react quickly to changing network conditions (e.g., link failures or excessive congestion). Overlay networks, on the other hand, can respond quickly to changing network conditions, but their reliance on aggressive probing does not scale to large topologies. The paper presents a layered routing architecture called UFO (Underlay Fused with Overlays), which achieves the best of both worlds by having the "underlay" provide explicit notification about network conditions to help improve the efficiency and scalability of routing overlays.
Promoting tolerance for delay tolerant network research
Authors: Crowcroft Jon , Yoneki Eiko , Hui Pan , Henderson Tristan
Published: October 2008

So what is all this DTN research about anyway? Sceptics ask: "Why are there no DTN applications?", or "Why is DTN performance so miserable?" This article attempts to address some of these complaints. We present suggestions of expectations for applications, and metrics for performance, which suggest a more tolerant view of research in the area.
Some comments on hourglasses
Authors: Aguiar Rui L.
Published: October 2008

The hourglass concept has been undisputable ruler of networking visions on the last years. As network evolution is now a hot topic, this article aims to reflect on this concept, highlighting its current shortcomings, and suggesting its evolution.
Improving accessibility in an automated question-answering system
Authors: Quarteroni Silvia
Published: October 2008

We address the problem of accessibility in information retrieval by introducing a Question Answering system able to filter answers based on their reading difficulty. The reading level estimation technique is applicable to any domain and is potentially adjustable to any user category.
The use of mobile phones by older adults
Authors: Hassan Hazrina , Md Nasir Mohd Hairul Nizam
Published: October 2008

Mobile phone has become essential parts of personal and business life. The recent growth of mobile phone usage is an observable fact that crosses all age and gender boundaries. It can potentially play a significant role in assisting older people in many ways especially in terms of maintaining social relationship, providing sense of safety and accessibility. However, older people seem to be a neglected user group in the design of mobile phone devices and services. Hence, this paper attempts to report the issues which are related with the design of mobile devices and services for older people aged 56 years old and over in Malaysia. The findings may serve as a reference to mobile device manufacturers and service providers when designing mobile devices and services for older Malaysians. This research uses a survey instrument to gather data from older peoples across all the states in Malaysia with the total of 176 older peoples responded. The questionnaires were mainly distributed to older persons who use mobile phones independently in their daily routines
Co-designing the failure analysis and monitoring of large-scale systems
Authors: Chandra Abhishek , Prinja Rohini , Jain Sourabh , Zhang ZhiLi
Published: October 2008

Large-scale distributed systems provide the backbone for numerous distributed applications and online services. These systems span over a multitude of computing nodes located at different geographical locations connected together via wide-area networks and overlays. A major concern with such systems is their susceptibility to failures leading to downtime of services and hence high monetary/business costs. In this paper, we argue that to understand failures in such a system, we need to co-design monitoring system with the failure analysis system. Unlike existing monitoring systems which are not designed specifically for failure analysis, we advocate a new way to design a monitoring system with the goal of uncovering causes of failures. Similarly the failure analysis techniques themselves need to go beyond simple statistical analysis of failure events in isolation to serve as an effective tool. Towards this end, we provide a discussion of some guiding principles for the co-design of monitoring and failure analysis systems for planetary scale systems.
Automatic request categorization in internet services
Authors: Sharma Abhishek B. , Bhagwan Ranjita , Choudhury Monojit , Golubchik Leana , Govindan Ramesh , Voelker Geoffrey M.
Published: October 2008

Modeling system performance and workload characteristics has become essential for efficiently provisioning Internet services and for accurately predicting future resource requirements on anticipated workloads. The accuracy of these models benefits substantially by differentiating among categories of requests based on their resource usage characteristics. However, categorizing requests and their resource demands often requires significantly more monitoring infrastructure. In this paper, we describe a method to automatically differentiate and categorize requests without requiring sophisticated monitoring techniques. Using machine learning, our method requires only aggregate measures such as total number of requests and the total CPU and network demands, and does not assume prior knowledge of request categories or their individual resource demands. We explore the feasibility of our method on the .Net PetShop 4.0 benchmark application, and show that it works well while being lightweight, generic, and easily deployable.
Long range mutual information
Authors: Fonseca Nahur , Crovella Mark , Salamatian Kavé
Published: October 2008

Network traffic modeling generally views traffic as a superposition of flows that creates a timeseries of volume counts (e.g. of bytes or packets). What is omitted from this view of traffic is the contents of packets. Packet contents (e.g. header fields) contain considerable information that can be useful in many applications such as change and anomaly detection, and router performance evaluation. The goal of this paper is to draw attention to the problem of modeling traffic with respect to the contents of packets. In this regard, we identify a new phenomenon: long range mutual information (LRMI), which means that the dependence of the contents of a pair of packets decays as a power of the lag between them. We demonstrate that although LRMI is hard to measure, and hard to model using the mathematical tools at hand, its effects are easy to identify in real traffic, and it may have a considerable impact on a number of applications. We believe that work in modeling this phenomenon will open doors to new kinds of traffic models, and new advances in a number of applications.
DRAM is plenty fast for wirespeed statistics counting
Authors: Lin Bill , Xu Jun (Jim)
Published: October 2008

Per-flow network measurement at Internet backbone links requires the efficient maintanence of large arrays of statistics counters at very high speeds (e.g. 40 Gb/s). The prevailing view is that SRAM is too expensive for implementing large counter arrays, but DRAM is too slow for providing wirespeed updates. This view is the main premise of a number of hybrid SRAM/DRAM architectural proposals [2, 3, 4, 5] that still require substantial amounts of SRAM for large arrays. In this paper, we present a contrarian view that modern commodity DRAM architectures, driven by aggressive performance roadmaps for consumer applications (e.g. video games), have advanced architecture features that can be exploited to make DRAM solutions practical. We describe two such schemes that can harness the performance of these DRAM offerings by enabling the interleaving of counter updates to multiple memory banks. These counter schemes are the first to support arbitrary increments and decrements for either integer or floating point number representations at wirespeed. We believe our preliminary success with the use of DRAM schemes for wirespeed statistics counting opens the possibilities for broader research opportunities to generalize the proposed ideas for other network measurement functions.
Pictures from the Skype
Authors: Rossi Dario , Valenti Silvio , Veglia Paolo , Bonfiglio Dario , Mellia Marco , Meo Michela
Published: October 2008

This paper focuses on the characterization and classification of Skype traffic, a nowadays very popular and fashionable VoIP application. Building over previous work, we develop a software tool which can be used to examine the evolution of Skype call classification in an interactive fashion. The demonstrator software focuses on the main aspects of Skype traffic characterization and presents the traffic patterns Skype generates during a call or while idle. In addition, the demonstrator shows the evolution of the internal indexes the Skype classifiers use.

After describing the classification process and the demonstrator software, we use the tool to demonstrate the feasibility of online Skype traffic identification, considering both accuracy and computational costs. Experimental results show that few seconds of observation are enough to allow the classifier engines to correctly identify the presence of Skype flows. Moreover, results indicate that the classification engine can cope with multi-Gbps links in real-time using common off-the-shelf hardware.
New perspectives on network calculus
Authors: Jiang Xiaoyue
Published: October 2008

Originated in communications engineering and theoretically rooted in idempotent analysis, the theory of network calculus (NetCal) presents an elegant methodology for offering performance guarantees in deterministic queuing systems. In this research we developed two new formulations of Net-Cal, each of which bears some unique insights. A fuzzy formulation maps NetCal's (min,+) convolution operator to the addition of fuzzy numbers. A conjugate perspective based on the notion of Legendre transform leads to a new NetCal formulation to be termed as CT-NetCal, which possesses some distinct advantages in modeling, computation and interpretation.
Is fair resource sharing responsible for spreading long delays?
Authors: Jelenković Predrag R. , Kang Xiaozhu
Published: October 2008

We show that mixing the statistically long jobs (subexponential) and short ones (exponentially bounded) using processor sharing service discipline causes long (subexponential) delays for all types of jobs in the system. Since processor sharing represents a baseline fair scheduling discipline used in designing Web servers, as well as the basic model of TCP bandwidth sharing, our finding suggests that even though fairness possesses many desirable attributes, it causes unnecessarily long delays for statistically short jobs. Hence, fairness comes with a price.

We further quantify the preceding result when the long jobs follow the widely observed power law distribution x
-α
, α > 0, where we discover the criticality of the
lognormal
distribution for the delay characteristics of the lighter jobs. Specifically, we find that when the shorter jobs are heavier than
lognormal
, the sojourn time
V
and the service time distribution
B
of the shorter jobs are tail equivalent P[
V
>
x
] ~ P[
B
> (1 - ρ)
x
]. However, if P[
B
>
x
] is lighter than
lognormal
, the preceding tail equivalence does not hold.

Furthermore, when the shorter jobs
B
have much lighter tails
e

-λ
x
β

, λ > 0, β > 0, we show that the distribution of the delay
V
for these jobs satisfy, as
x
→ ∞, -log P[
V
>
x
] ~
c
(
x
log
x
) β / β+1, where
c
is explicitly computable. Note that β = 1 and β = 2 represent the exponential and Gaussian cases with the corresponding delay distributions approximately of the form
e

-√
x
log
x

and
e

-(
x
log
x
)
2/3

, respectively. Our results are different from the existing ones in the literature that focused on the delays which are of the same form (tail equivalent) as the jobs size distribution.
Analysis of size interval task assignment policies
Authors: Bachmat Eitan , Sarfati Hagit
Published: October 2008

We analyze the performance of Size Interval task assignment (SITA) scheduling policies, for multi-host scheduling in a non-preemptive environment. We establish a general duality theory for the performance analysis of SITA policies. When the job size distribution is Bounded Pareto and the range of job sizes tends to infinity. we determine asymptotically optimal cutoff values and provide asymptotic formulas for average waiting time and slowdown. In the case of inhomogeneous hosts we determine their optimal ordering. We also consider TAGS policies. We provide a general formula that describes their load handling capabilities and examine their performance when the job size distribution is Bounded Pareto.
O2S2
Authors: Raj Himanshu , Schwan Karsten
Published: October 2008

Object based storage devices (OSDs) elevate the level of abstraction presented to clients, thereby permitting them to offer methods for managing, sharing, and securing information that go beyond those offered by block-based stores. The Object-Oriented Storage System (O2S2) architecture presented and evaluated in this paper provides object-based storage in a virtualized environment. This service provides a virtual object-based storage device (vOSD) to virtual machines. The use of vOSDs permits the service provider, i.e., the
vOSD storage domain
, to offer to guest virtual machines new methods for resource management and consolidation Methods demonstrated in this paper include improved support for access control and for heterogeneity of storage devices. A prototype PVFS-based O2S2 implementation demonstrates that its enhanced services can be provided at low cost, enabled in part by the efficient utilization of otherwise idle storage domain resources.
LAST
Authors: Lee Sungjin , Shin Dongkun , Kim Young-Jin , Kim Jihong
Published: October 2008

As flash memory technologies quickly improve, NAND flash memory-based storage devices are becoming a viable alternative as a secondary storage solution for general-purpose computing systems such as personal computers and enterprise server systems. Most existing flash translation layer (FTL) schemes are, however, ill-suited for such systems because they were optimized for storage write patterns of embedded systems only. In this paper, we propose a new flash management technique called LAST which is optimized for access characteristics of general-purpose computing systems. By exploiting the locality of storage access patterns, LAST reduces the garbage collection overhead significantly, thus increasing the I/O performance of flash-based storage devices. Our experimental results show that the proposed technique reduces the garbage collection overhead by 54% over the existing flash memory management techniques.
Comparative evaluation of overlap strategies with study of I/O overlap in MPI-IO
Authors: Patrick Christina M. , Son SeungWoo , Kandemir Mahmut
Published: October 2008

Many scientific applications use parallel I/O to meet the low latency and high bandwidth I/O requirement. Among many available parallel I/O operations, collective I/O is one of the most popular methods when the storage layouts and access patterns of data do not match. The implementation of collective I/O typically involves disk I/O operations followed by interprocessor communications. Also, in many I/O-intensive applications, parallel I/O operations are usually followed by parallel computations. This paper presents a comparative study of different overlap strategies in parallel applications. We have experimented with four different overlap strategies 1) Overlapping I/O and communication; 2) Overlapping I/O and computation; 3) Overlapping computation and communication; and 4) Overlapping I/O, communication, and computation. All experiments have been conducted on a Linux Cluster and the performance results obtained are very encouraging. On an average, we have enhanced the performance of a generic collective read call by 38%, the MxM benchmark by 26%, and the FFT benchmark by 34%.
Personalization and choice behavior
Authors: Ho Shuk Ying , Davern Michael J. , Tam Kar Yan
Published: October 2008

Online merchants use personalization technologies to gain knowledge of an individual customer and then generate preference-matched web content for the customer. Among the various types of personalization technologies, this research focuses on personalization engines that generate preference-matched content based on a customer's prior transactions. Extant research in this area has focused on how to maximize knowledge mined from transaction logs to generate content that is highly similar to the customer's past revealed preferences. However, it remains an empirical question as to whether the content closely matched with previous transactions is most likely to influence choice behavior. In this study, we postulate that the content closely matched with previous transactions may not be the most influential in biasing a customer. In the consideration and choice process, an individual's personality traits play a pivotal role in moderating the effect of personalized content. Drawing on research in marketing, we examine three key personality traits: need for cognition; variety seeking, and need for uniqueness; and explore their effects on choice behavior in the context of transaction-driven personalization. Research hypotheses are tested with over 2,000 pre-selected subjects in an online experiment based on a ringtone download website. We find that individual personality traits moderate content consideration and choice. Theoretical and practical implications of the findings are discussed.
An empirical investigation of habitual usage and past usage on technology acceptance evaluations and continuance intention
Authors: Wu Mei-Chun , Kuo Feng-Yang
Published: October 2008

Although much research has examined information technology (IT) usage that involves deliberate evaluation and decision-making, we know less about automatic use that occurs spontaneously with little conscious effort. In this study we have investigated this issue by studying how habitual usage and past usage may influence the predicting power of perceived ease of use (PEOU) and perceived usefulness (PU) on intention. Using 232 cross-sectional responses from subjects who have continuously used the Google search engine, the results show that as individuals get into the habit of continuously using a system, the predicting power of PU and PEOU on intention is diluted by the addition of either habitual usage or past usage. This indicates that the stronger the habitual use of the Google search engine, the less conscious planning is involved, and the relationship between subjects' evaluations of PU/PEOU and their intention to use weakens. Furthermore, our study shows that past usage, often employed as a proxy of habitual usage, demonstrates a similar effect but differs in the predicting power from habitual usage. This result suggests that researchers may employ habitual usage for studies of post-adoption phenomenon concerning continuous information system usage.
Usability in multiple monitor displays
Authors: Truemper Jacob M. , Sheng Hong , Hilgers Michael G. , Hall Richard H. , Kalliny Morris , Tandon Basanta
Published: October 2008

An experimental study was conducted to examine the impact of multiple monitors on user performance and multitasking. Forty-three participants were assigned to two groups - a multi-monitor group and a singlemonitor group - to carry out a series of tasks. Both quantitative and qualitative data were collected and analyzed. Results indicated that those who used the multi-monitor display were more inclined to multitask and scored higher on performance measures than those using the single monitor. Interviews from the participants validated the quantitative results and provided additional insights on usability issues of multi-monitor displays.
Thar's gold in them thar constructs
Authors: Barki Henri
Published: October 2008

Conceptualization and measurement of constructs provide many opportunities for contributing to information systems research and practice by providing a better understanding and explanation of interesting and important phenomena. To assist researchers in such endeavors, this paper describes four approaches to construct conceptualization and illustrates them with examples from past research. The paper also suggests directions for future research by identifying examples of constructs that stand to benefit from the application of the four approaches.
Analysis of Silicon Dioxde Nanowires Synthesized via Rapid Thermal Annealing of Pt-coated Si Substrates
Authors: Lai Yi-Sheng , Wang Jyh-Liang , Liou Sz-Chian
Published: October 2008

A fast approach to grow SiO2 nanowires by rapid thermal annealing (RTA) is demonstrated in the study. The material characteristics of SiO2 nanowires were investigated by field emission scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field (HAADF) image, and energy-filtered TEM (EFTEM). The SiO2 nanowire shows amorphous structures after annealing at 900oC. The HAADF image shows the wire tip is predominantly composed of Pt. Besides, the elemental mapping of EFTEM reveals that the wire consists of Si and O. It is suggested that a high SiO2 growth rate of more than 1 μ/min can be achieved by RTA.
Effect of Silica on the Arsenic Electro-Removal from Underground Water
Authors: Montero-Ocampo Cecilia , Maldonado Araceli
Published: October 2008

Silica poses serious problems in the arsenic (As) electro-removal (EC) process with iron electrodes from underground water (GW). It has been shown that silica prevents the effective arsenic electro-removal from GW containing ~120 µg L-1 of As and 106 mg L-1 of SiO2. A procedure is proposed to reduce such interference by addition of a silica-adsorption inhibitor (SAI) compound to the GW. The effect of the current density applied between 1.5 and 12 mA cm-2 on the arsenic removal efficiency by EC process with and without addition of the SAI compound to GW was investigated. The results showed that without SAI compound the As electro-removal from GW achieved an efficiency lower than 13% at a process current density of 3 mA cm-2, while adding the SAI compound to GW the As electro-removal efficiency increases up to > 67% at 3 mA cm-2, and up to 92% at 6 mA cm-2.
Analysis of Subzero Start-Up for Polymer Electrolyte Fuel Cells
Authors: Chen Jixin , Wang Yun
Published: October 2008

This paper investigates the heat and water transport in a fuel cell during startup in subzero environment. Followed by the work of Wang [1], we further evaluate the key parameters that govern the startup of fuel cells with no external heating by considering the range of the relevant factors for a typical fuel cell. Specifically, these key parameters include characteristic times scales of cell warm up , membrane hydration in the catalyst layer , ice buildup , and ice melting , and the ratio of the two important time constants . The results give the ranges of these parameters and therefore are important for material and property selection in fuel cell design for better cold-start characteristics.
Electrochemical Synthesis of 2,2-dinitropropanol
Authors: Lister Tedd E. , Fox Robert
Published: October 2008

Bench-scale electrochemical synthesis of 2,2-dinitropropanol (DNPOH) was performed to evaluate scale-up potential. The synthesis scheme employs a reversible chemical mediator Fe(CN)6-3/-4 couple to perform oxidative nitration of nitroethane using the anode of the electrochemical cell as the oxidant source. The flow-cell based system operated in a continuous fashion with the intermediate product (1,1-dinitroethanate K-salt) precipitated and removed from reaction, and starting materials (nitroethane and potassium nitrate) added as consumed in the reaction. The intermediate product was condensed with formaldehyde to produce DNPOH. A discussion of the waste reduction over the chemical route is presented.
Electrolytic Looping for Through Crack Interruption During Functional Cr+3 Electroplating
Authors: Lozano Morales Alonso , Inman Maria , Taylor E. Jennings
Published: October 2008

Hexavalent chromium plating has been used for many years to provide hard, durable coatings with excellent wear and corrosion resistance properties. However, hexavalent chromium baths have come under increasing scrutiny due to the toxic nature of the bath, effects on the environment, and workers' health. Chromium can also be electroplated using a trivalent chromium bath, but coatings plated using this bath with conventional DC processes typically cannot achieve the required mechanical properties or coating thickness, and are primarily used for decorative applications. In this paper, we present work on an electrolytic looping electrodeposition process that produces functional trivalent chromium coatings with equivalent performance characteristics to those normally associated with hexavalent chromium.
Electrochromic Windows based on Electrodeposited PProDOT-Me2 and V2O5-TiO2 Films with PMMA Gel Electrolytes
Authors: Kim Sooyeun , Taya Minoru , Xu Chunye
Published: October 2008

An all-solid-state electrochromic window (ECW) based on an electrodeposited PProDOT-Me2 and V2O5-TiO2 film with PMMA gel electrolyte that has high conductivity has been fabricated. The ECW has been found to have high contrast, rapid switching speed, long-term electrochemical stability and open-circuit memory. Reversible color change between blue and colorless was observed when an appropriate small potential was repeatedly applied to the ECW. Reversible color change between blue and colorless with 150,000 cycling was also observed.
On Three-Dimensional Magnetic Field Effects during Metal Deposition in Cuboid Cells
Authors: Mutschke Gerd , Cierpka Christian , Weier Tom , Eckert Kerstin , Mühlenhoff Sascha , Bund Andreas
Published: October 2008

In electrochemical reactions, Lorentz forces due to external homogeneous magnetic fields may lead to increased mass transfer as additional convection is forced (MHD effect). A careful analysis shows that often a three-dimensional modeling of this effect is necessary. We present numerical simulations of copper electrolysis in cuboid cells under the influence of homogeneous magnetic fields of vertical direction in the limiting current regime. The Lorentz force is found to drive horizontal counter-rotation which is stronger than the natural convection. Experimental results confirm the numerical findings.
Self-organization of Copper Secondary Nodules by the Second Micro-MHD Effect
Authors: Aogaki Ryoichi , Morimoto Ryoichi , Sugiyama Atsushi
Published: October 2008

In copper electrodeposition under a magnetic field parallel to an electrode surface, at the initial stage, 3D nucleation is suppressed, yielding a flat surface (the first micro-MHD effect). However, after long-term deposition with proton adsorption, characteristic secondary nodules emerge from 2D nucleation, which is called the second micro-MHD effect. From the instability analysis of non-equilibrium fluctuations, at the initial stage, the 2D nuclei are self-organized at a negative overpotential of the double layer, whereas for the secondary nodule formation, a positive overpotential of the double layer is required. Therefore, it is concluded that the adsorption of proton changes the polarity of the double layer overpotential from negative to positive, the secondary nodules are self-organized.
Investigation of the Electrochemical Behavior of Ethyl Caffeate at Glassy Carbon Electrode
Authors: Liang Yan , He Ping , Yu Tingting , Yang Dingming , Jiang Qiying , Zeng Qingyou , Du Licheng , Dong Faqin
Published: October 2008

In this paper, cyclic voltammetry were utilized to study the electrochemical behavior of ethyl caffeate at glassy carbon electrode. It was shown that the shape of electrochemical redox peak and the corresponding peak current in acetic acid/sodium acetate buffer are well-defined and high, respectively. The electrochemical behavior of ethyl caffeate at glassy carbon electrode was found to have a good reversibility, and the electron transfer number n was calculated to be 2 and the diffusion coefficient D0 is 2.4×10-6 cm2 s-1. The redox peak potential of ethyl caffeate was linearly correlative with the pH value of acetic acid/sodium acetate buffer, indicating the numbers of electron transfer and proton were equal. From the experiment data, it was observed that the redox peak current is rectilinear to ethyl caffeate concentration in the range of 4.0×10-7 mol L-1 to 7.2×10-6 mol L-1 (r = 0.9994, n = 8). The detection limit was 1.0×10-7 mol L-1, and the relative standard deviation was 2.0% (n = 11) at the 2.0×10-6 mol L-1 level.
The Impedance of an Electrode Coated by a Film of Distributed Local Thickness and its Relationship with Constant Phase Elements (CPE)
Authors: Cattarin Sandro , Comisso Nicola , Musiani Marco , Tribollet B.
Published: October 2008

The impedance of a rectangular electrode coated by a resistive film of distributed local thickness is calculated, taking into account both linear and non linear thickness profiles. The local film capacity of each surface element is assumed to be inversely proportional to local film thickness and different cases for film resistance are considered. The effect of film resistivity, electrolyte resistance, electrode roughness and thickness range are illustrated. Experimental model systems are obtained by anodizing niobium or tantalum rectangular sheets. The impedance of the coated electrode, measured at a potential close to the lowest anodization potential, shows a minimum in the plot of the ohmic resistance corrected phase angle vs. frequency, and cannot be accurately modeled by a CPE.
Impedance Data Masquerading as Unusual Circuit Elements: Instrumentation Artifacts
Authors: Vanýsek Petr
Published: October 2008

Inherent part of any impedance measurement is interpretation of the data and making physical sense of the investigated system. The impedance response is just a snapshot of the whole system, capturing some of its properties, but neglecting or obscuring others. The method of explaining the impedance data typically relies on finding an adequate equivalent circuit and inferring from it some physical properties. In practice it is often seen that an element, which is unusual in electrochemistry, or in physical world for that matter, can be encountered. Thus, for example, sometimes an inductive element is observed. In some of such cases this can be explained by electrode roughening, pitting or by nucleation. In some cases, this explanation is not sufficient.
Frontiers in Application of Impedance Diagnostics to H2-Fed Polymer Electrolyte Fuel Cells
Authors: Mathias Mark , Baker Daniel , Zhang Junliang , Liu Yuxiu , Gu Wenbin
Published: October 2008

Polymer Electrolyte Fuel Cell (PEFC) cathode cost and durability are currently limiting the commercialization of PEFCs for automotive application. Impedance diagnostics are just beginning to be used for characterizing proton conductivity within the cathode catalyst layer, but techniques have not yet been established for characterizing the O2 reduction reaction (ORR) kinetics and O2 transport resistance. In an operating fuel cell, we show here that slow Pt oxide kinetics can give rise to the large low frequency inductive response observed in the cathode impedance response at frequencies of less than 10 mHz. Understanding and accounting for this response is foundational to eventually being able to use impedance methods to characterize cathode kinetics and O2 transport limitations.
Insulin is required for amino acid stimulation of dual pathways for translational control in skeletal muscle in the late-gestation ovine fetus
Authors: Brown Laura D. , Rozance Paul J. , Barry James S. , Friedman Jacob E. , Hay William W.
Published: October 2008

During late gestation, amino acids and insulin promote skeletal muscle protein synthesis. However, the independent effects of amino acids and insulin on the regulation of mRNA translation initiation in the fetus are relatively unknown. The purpose of this study was to determine whether acute amino acid infusion in the late-gestation ovine fetus, with and without a simultaneous increase in fetal insulin concentration, activates translation initiation pathway(s) in skeletal muscle. Fetuses received saline (C), mixed amino acid infusion plus somatostatin infusion to suppress amino acid-stimulated fetal insulin secretion (AA+S), mixed amino acid infusion with concomitant physiological increase in fetal insulin (AA), or high-dose insulin infusion with euglycemia and euaminoacidemia (HI). After a 2-h infusion period, fetal skeletal muscle was harvested under in vivo steady-state conditions and frozen for quantification of proteins both upstream and downstream of mammalian target of rapamycin (mTOR). In the AA group, we found a threefold increase in ribosomal protein S6 kinase (p70S6k) and Erk1/2 phosphorylation; however, blocking the physiological rise in insulin with somatostatin in the AA+S group prevented this increase. In the HI group, Akt, Erk1/2, p70S6k, and ribosomal protein S6 were highly phosphorylated and 4E-binding protein 1 (4E-BP1) associated with eukaryotic initiation factor (eIF)4E decreased by 30%. These data show that insulin is a significant regulator of intermediates involved in translation initiation in ovine fetal skeletal muscle. Furthermore, the effect of amino acids is dependent on a concomitant increase in fetal insulin concentrations, because amino acid infusion upregulates p70S6kand Erk only when amino acid-stimulated increase in insulin occurs.
LPS and proinflammatory cytokines decrease lipin-1 in mouse adipose tissue and 3T3-L1 adipocytes
Authors: Lu Biao , Lu Yang , Moser Arthur H. , Shigenaga Judy K. , Grunfeld Carl , Feingold Kenneth R.
Published: October 2008

Infection and inflammation affect adipose triglyceride metabolism, resulting in increased plasma free fatty acid (FFA) and VLDL levels during the acute-phase response. Lipin-1, a multifunctional protein, plays a critical role in adipose differentiation, mitochondrial oxidation, and triglyceride synthesis. Here, we examined whether LPS [a Toll-like receptor (TLR)-4 activator], zymosan (a TLR-2 activator), and proinflammatory cytokines regulate lipin-1 in adipose tissue. LPS administration caused a marked decrease in the levels of lipin-1 mRNA and protein in adipose tissue. The decrease in lipin-1 mRNA levels occurred rapidly and lasted for at least 24 h. In contrast, lipin-2 and -3 mRNA levels did not change, suggesting specific repression of lipin-1. Zymosan similarly decreased lipin-1 mRNA without affecting lipin-2 or lipin-3 mRNA levels. To determine the pathways by which LPS repressed lipin-1, we examined the effect of proinflammatory cytokines on cultured adipocytes. In 3T3-L1 adipocytes, TNF-α, IL-1β, and IFN-γ, but not LPS or IL-6, caused a decrease in lipin-1 mRNA levels. Furthermore, TNF-α and IL-1β administration also decreased mRNA levels of lipin-1 in adipose tissue in mice. Importantly, the LPS-induced decrease in lipin-1 mRNA levels was significantly but not totally blunted in TNF-α/IL-1 receptor-null mice compared with controls, suggesting key roles for TNF-α/IL-1β and other cytokines in mediating LPS-induced repression of lipin-1. Together, our results demonstrate that expression of lipin-1, one of the essential triglyceride synthetic enzymes, was suppressed by LPS, zymosan, and proinflammatory cytokines in mouse adipose tissue and in cultured 3T3-L1 adipocytes, which could contribute to a decrease in the utilization of FFA to synthesize triglycerides in adipose tissue, thus promoting the release of FFA into the circulation.
Channel regulation of glucose sensing in the pancreatic β-cell
Authors: Hiriart Marcia , Aguilar-Bryan Lydia
Published: October 2008

Mammalian β-cells are acutely and chronically regulated by sensing surrounding glucose levels that determine the rate at which insulin is secreted, to maintain euglycemia. Experimental research in vitro and in vivo has shown that, when these cells are exposed to adverse conditions like long periods of hypoglycemia or hyperglycemia, their capability to sense glucose is decreased. Understanding the normal physiology and identifying the main players along this route becomes paramount. In this review, we have taken on the task of looking at the role that ion channels play in the regulation of this process, delineating the different families, and describing the signaling that parallels the glucose sensing process that results in insulin release.
β-Glycosphingolipids improve glucose intolerance and hepatic steatosis of the Cohen diabetic rat
Authors: Zigmond Ehud , Zangen Sarah W. , Pappo Orit , Sklair-Levy Miriam , Lalazar Gadi , Zolotaryova Lydia , Raz Itamar , Ilan Yaron
Published: October 2008

A link between altered levels of various gangliosides and the development of insulin resistance was described in transgenic mice. Naturally occurring glycosphingolipids were shown to exert immunomodulatory effects in a natural killer T (NKT) cell-dependent manner. This study examined whether glycosphingolipid-induced modulation of the immune system may reduce pancreatic and liver steatosis and stimulate insulin secretion in the Cohen diabetes-sensitive (CDS) rat, a lean model of non-insulin-resistant, nutritionally induced diabetes. Four groups of CDS rats fed a diabetogenic diet were treated with daily intraperitoneal injections of glycosphingolipids β-glucosylceramide, β-lactosylceramide, a combination of both (IGL), or vehicle (PBS) for up to 45 days. Immune modulation was assessed by fluorescence-activated cell sorting analysis of intrahepatic and intrasplenic lymphocytes. Steatosis was assessed by MRI imaging and histological examination of liver and pancreas, Blood glucose and plasma insulin concentrations were assessed during an oral glucose tolerance test. Administration of glycosphingolipids, particularly IGL, increased intrahepatic trapping of CD8 T and NKT lymphocytes. Pancreatic and liver histology were markedly improved and steatosis was reduced in all treated groups compared with vehicle-treated rats. Insulin secretion was restored after glycosphingolipid treatment, resulting in improved glucose tolerance. The immunomodulatory effect of β-glycosphingolipids improved the β-cell function of the hyperglycemic CDS rat. Thus our results suggest a role for the immune system in the pathogenesis of diabetes in this model.
Urea and NaCl regulate UT-A1 urea transporter in opposing directions via TonEBP pathway during osmotic diuresis
Authors: Kim Yu-Mi , Kim Wan-Young , Lee Hyun-Wook , Kim Jin , Kwon H. Moo , Klein Janet D. , Sands Jeff M. , Kim Dongun
Published: October 2008

In our previous studies of varying osmotic diuresis, UT-A1 urea transporter increased when urine and inner medullary (IM) interstitial urea concentration decreased. The purposes of this study were to examine 1) whether IM interstitial tonicity changes with different urine urea concentrations during osmotic dieresis and 2) whether the same result occurs even if the total urinary solute is decreased. Rats were fed a 4% high-salt diet (HSD) or a 5% high-urea diet (HUD) for 2 wk and compared with the control rats fed a regular diet containing 1% NaCl. The urine urea concentration decreased in HSD but increased in HUD. In the IM, UT-A1 and UT-A3 urea transporters, CLC-K1 chloride channel, and tonicity-enhanced binding protein (TonEBP) transcription factor were all increased in HSD and decreased in HUD. Next, rats were fed an 8% low-protein diet (LPD) or a 0.4% low-salt diet (LSD) to decrease the total urinary solute. Urine urea concentration significantly decreased in LPD but significantly increased in LSD. Rats fed the LPD had increased UT-A1 and UT-A3 in the IM base but decreased in the IM tip, resulting in impaired urine concentrating ability. The LSD rats had decreased UT-A1 and UT-A3 in both portions of the IM. CLC-K1 and TonEBP were unchanged by LPD or LSD. We conclude that changes in CLC-K1, UT-A1, UT-A3, and TonEBP play important roles in the renal response to osmotic diuresis in an attempt to minimize changes in plasma osmolality and maintain water homeostasis.
Substitution of Brown Norway chromosome 16 preserves cardiac function with aging in a salt-sensitive Dahl consomic rat
Authors: Kriegel A. J. , Greene A. S.
Published: October 2008

Determination of the genetic factors that control the progression of left ventricular hypertrophy (LVH) to heart failure has been difficult despite extensive study in animal models. Here we have characterized a consomic rat model of LVH resulting from the introgression of chromosome 16 from the normotensive Brown Norway (BN) rat onto the genetic background of the Dahl salt-sensitive (SS/Mcwi) rat by marker assisted breeding. The SS-16BN/Mcwi consomic rats are normotensive but display LVH equivalent to the hypertensive SS/Mcwi rats at early ages. In this study we tracked the development of LVH by echocardiography and analyzed changes in cardiac function and morphology with aging in the SS-16BN/Mcwi, SS/Mcwi, and BN to determine if the consomic SS-16BN/Mcwi was a model of hypertrophic cardiomyopathy (HCM). Aging SS-16BN/Mcwi rats showed no evidence of heart failure or impaired cardiac function upon extensive analysis of left ventricle function by echocardiography and pressure-volume relationships, while their parental SS/Mcwi experienced deterioration in function between 18 and 36 wk of age. In addition aging SS-16BN/Mcwi did not exhibit tissue remodeling common to pathological hypertrophy and HCM such as increased fibrosis and reduced capillary density in the myocardium. In fact, SS-16BN/Mcwi were better protected from developing LV fibrosis with age than either the hypertensive SS/Mcwi or normotensive BN parental strains. This suggests that a gene or genes on chromosome 16 may be involved with both blood pressure regulation and preservation of cardiac function with aging.
Electrical Properties of Self‐Assembled Nano‐Schottky Diodes
Authors: Ruffino F. , Canino A. , Grimaldi M. G. , Giannazzo F. , Roccaforte F. , Raineri V.
Published: October 2008

A bottom‐up methodology to fabricate a nanostructured material by Au nanoclusters on 6H‐SiC surface is illustrated. Furthermore, a methodology to control its structural properties by thermal‐induced self‐organization of the Au nanoclusters is demonstrated. To this aim, the self‐organization kinetic mechanisms of Au nanoclusters on SiC surface were experimentally studied by scanning electron microscopy, atomic force microscopy, Rutherford backscattering spectrometry and theoretically modelled by a ripening process. The fabricated nanostructured materials were used to probe, by local conductive atomic force microscopy analyses, the electrical properties of nano‐Schottky contact Au nanocluster/SiC. Strong efforts were dedicated to correlate the structural and electrical characteristics: the main observation was the Schottky barrier height dependence of the nano‐Schottky contact on the cluster size. Such behavior was interpreted considering the physics of few electron quantum dots merged with the concepts of ballistic transport and thermoionic emission finding a satisfying agreement between the theoretical prediction and the experimental data. The fabricated Au nanocluster/SiC nanocontact is suggested as a prototype of nano‐Schottky diode integrable in complex nanoelectronic circuits.