bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of shape on the perception of material reflectance
Authors: Vangorp Peter , Laurijssen Jurgen , Dutré Philip
Published: September 2007

Visual observation is our principal source of information in determining the nature of objects, including shape, material or roughness. The physiological and cognitive processes that resolve visual input into an estimate of the material of an object are influenced by the illumination and the shape of the object. This affects our ability to select materials by observing them on a point-lit sphere, as is common in current 3D modeling applications.

In this paper we present an exploratory psychophysical experiment to study various influences on material discrimination in a realistic setting. The resulting data set is analyzed using a wide range of statistical techniques. Analysis of variance is used to estimate the magnitude of the influence of geometry, and fitted psychometric functions produce significantly diverse material discrimination thresholds across different shapes and materials.

Suggested improvements to traditional material pickers include direct visualization on the target object, environment illumination, and the use of discrimination thresholds as a step size for parameter adjustments.
Mesh puppetry
Authors: Shi Xiaohan , Zhou Kun , Tong Yiying , Desbrun Mathieu , Bao Hujun , Guo Baining
Published: September 2007

We present
mesh puppetry
, a variational framework for detail-preserving mesh manipulation through a set of high-level, intuitive, and interactive design tools. Our approach builds upon traditional rigging by optimizing skeleton position and vertex weights in an integrated manner. New poses and animations are created by specifying a few desired constraints on vertex positions, balance of the character, length and rigidity preservation, joint limits, and/or self-collision avoidance. Our algorithm then adjusts the skeleton and solves for the deformed mesh simultaneously through a novel cascading optimization procedure, allowing realtime manipulation of meshes with 50
K
+ vertices for fast design of pleasing and realistic poses. We demonstrate the potential of our framework through an interactive deformation platform and various applications such as deformation transfer and motion retargeting.
Gradient domain editing of deforming mesh sequences
Authors: Xu Weiwei , Zhou Kun , Yu Yizhou , Tan Qifeng , Peng Qunsheng , Guo Baining
Published: September 2007

Many graphics applications, including computer games and 3D animated films, make heavy use of deforming mesh sequences. In this paper, we generalize gradient domain editing to deforming mesh sequences. Our framework is keyframe based. Given sparse and irregularly distributed constraints at unevenly spaced keyframes, our solution first adjusts the meshes at the keyframes to satisfy these constraints, and then smoothly propagate the constraints and deformations at keyframes to the whole sequence to generate new deforming mesh sequence. To achieve convenient keyframe editing, we have developed an efficient alternating least-squares method. It harnesses the power of subspace deformation and two-pass linear methods to achieve high-quality deformations. We have also developed an effective algorithm to define boundary conditions for all frames using handle trajectory editing. Our deforming mesh editing framework has been successfully applied to a number of editing scenarios with increasing complexity, including footprint editing, path editing, temporal filtering, handle-based deformation mixing, and spacetime morphing.
PCU
Authors: Hasselgren Jon , Akenine-Möller Thomas
Published: September 2007

Culling techniques have always been a central part of computer graphics, but graphics hardware still lack efficient and flexible support for culling. To improve the situation, we introduce the programmable culling unit, which is as flexible as the fragment program unit and capable of quickly culling entire blocks of fragments. Furthermore, it is very easy for the developer to use the PCU as culling programs can be automatically derived from fragment programs containing a discard instruction. Our PCU can be integrated into an existing fragment program unit with a modest hardware overhead of only about 10%. Using the PCU, we have observed shader speedups between 1.4 and 2.1 for relevant scenes.
Wave particles
Authors: Yuksel Cem , House Donald H. , Keyser John
Published: September 2007

We present a new method for the real-time simulation of fluid surface waves and their interactions with floating objects. The method is based on the new concept of wave particles, which offers a simple, fast, and unconditionally stable approach to wave simulation. We show how graphics hardware can be used to convert wave particles to a height field surface, which is warped horizontally to account for local wave-induced flow. The method is appropriate for most fluid simulation situations that do not involve significant global flow. It is demonstrated to work well in constrained areas, including wave reflections off of boundaries, and in unconstrained areas, such as an ocean surface. Interactions with floating objects are easily integrated by including wave forces on the objects and wave generation due to object motion. Theoretical foundations and implementation details are provided, and experiments demonstrate that we achieve plausible realism. Timing studies show that the method is scalable to allow simulation of wave interaction with several hundreds of objects at real-time rates.
Factored time-lapse video
Authors: Sunkavalli Kalyan , Matusik Wojciech , Pfister Hanspeter , Rusinkiewicz Szymon
Published: September 2007

We describe a method for converting time-lapse photography captured with outdoor cameras into
Factored Time-Lapse Video
(FTLV): a video in which time appears to move faster (i.e., lapsing) and where data at each pixel has been factored into shadow, illumination, and reflectance components. The factorization allows a user to easily relight the scene, recover a portion of the scene geometry (normals), and to perform advanced image editing operations. Our method is easy to implement, robust, and provides a compact representation with good reconstruction characteristics. We show results using several publicly available time-lapse sequences.
SIMBICON
Authors: Yin KangKang , Loken Kevin , van de Panne Michiel
Published: September 2007

Physics-based simulation and control of biped locomotion is difficult because bipeds are unstable, underactuated, high-dimensional dynamical systems. We develop a simple control strategy that can be used to generate a large variety of gaits and styles in real-time, including walking in all directions (forwards, backwards, sideways, turning), running, skipping, and hopping. Controllers can be authored using a small number of parameters, or their construction can be informed by motion capture data. The controllers are applied to 2D and 3D physically-simulated character models. Their robustness is demonstrated with respect to pushes in all directions, unexpected steps and slopes, and unexpected variations in kinematic and dynamic parameters. Direct transitions between controllers are demonstrated as well as parameterized control of changes in direction and speed. Feedback-error learning is applied to learn predictive torque models, which allows for the low-gain control that typifies many natural motions as well as producing smoother simulated motion.
Removing propagation redundant constraints in redundant modeling
Authors: Choi C. W. , Lee J. H.M. , Stuckey P. J.
Published: September 2007

A widely adopted approach to solving constraint satisfaction problems combines systematic tree search with various degrees of constraint propagation for pruning the search space. One common technique to improve the execution efficiency is to add redundant constraints, which are constraints logically implied by others in the problem model. However, some redundant constraints are
propagation redundant
and hence do not contribute additional propagation information to the constraint solver. Redundant constraints arise naturally in the process of redundant modeling where two models of the same problem are connected and combined through channeling constraints. In this paper, we give general theorems for proving propagation redundancy of one constraint with respect to channeling constraints and constraints in the other model. We illustrate, on problems from CSPlib (http://www.csplib.org), how detecting and removing propagation redundant constraints in redundant modeling can speed up search by several order of magnitudes.
Modeling the IT value paradox
Authors: Thatcher Matt E. , Pingry David E.
Published: September 2007

Assessing the value of IT investments has stumped managers and academics for years. If viewed as a commodity input, however, IT should be measured in the context in which the investment takes place.
Theoretical and practical complexity of modeling methods
Authors: Erickson John , Siau Keng
Published: September 2007

Highlighting the importance of taking into account typical usage when estimating the complexity of a systems development method.
Designing large-scale supply chain linear programs in spreadsheets
Authors: LeBlanc Larry J. , Galbreth Michael R.
Published: September 2007

Developing techniques to create a complete supply chain model across an entire product line.
Unintended invitation
Authors: Sipior Janice C. , Ward Burke T.
Published: September 2007

Unauthorized users risk civil and criminal liability; Wi-Fi network providers risk system intrusion and disruption.
Corporate governance of IT
Authors: Raghupathi W. "RP"
Published: September 2007

Boards of directors are beginning to look beyond the accounting roots of IT governance toward the risk of legal liability and harm to product brand and corporate reputation.
Accessibility research at the Czech Technical University
Authors: Sporka Adam J. , Míkovec Zdeněk , Klíma Martin , Slavík Pavel
Published: September 2007

The HCI at the CTU has a long tradition of research of interaction methods for people with difficulties, especially for the users with vision impairments. As of June 2007, our HCI group counts 4 faculty members and 4 PhD students; however, numerous BSc and MSc students of the CTU are also involved in the research by direct appointment or through their coursework in the HCI-related subjects and thesis projects.
From the chair
Authors: Sipior Janice C. , Lending Diane , Amoroso Donald L. , Shayo Conrad , Vowels Susan A.
Published: September 2007

Welcome to the new academic year! I hope you had an enjoyable summer.

Please join me in congratulating the members of the ACM-SIGMIS CPR (Computer Personnel Research) 2007 Conference Committee for organizing a successful conference. This year's conference was held at the Hyatt Regency in St. Louis, Missouri, USA from April 19 - 21, 2007, http://www.sigmis.org/conferences.html. The SIGMIS CPR 2007 Conference Proceedings are available in the ACM Digital Library at: http://portal.acm.org/dl.cfm.

I would like to thank the members of the 2007 Conference Committee for all their hard work in making this conference a success:

Conference Co-Chairs:
Fred Niederman, St. Louis University Mary Sumner, Southern Illinois University Edwardsville

Program Co-Chairs:
Diane Lending, James Madison University Chelley Vician, Michigan Tech University

Local Arrangements:
Jo Ellen Moore, Southern Illinois University Edwardsville Susan Yager, Southern Illinois University Edwardsville

Treasurer:
Donald Amoroso, Appalachian State University

Publicity:
Anne Powell, Southern Illinois University Edwardsville Sandra Newton, University of South Florida

.

The recipients of the fourth annual Magid Igbaria Outstanding Conference Paper of the Year Award are Tim Klaus of Texas A&M University, Stephen Wingreen of Southeastern University, and J. Ellis Blanton of University of South Florida for their paper, "Examining User Resistance and Management Strategies in Enterprise Systems Implementations." Congratulations to all of you!.

Please consider submitting your research to next year's CPR 2008. The submission deadline is October 15, 2007. Everyone is welcome! For information about next year's CPR 2008 Conference, please check our website at: http://www.acm.org/sigmis.

Also, please continue to consider Data Base as an outlet for your research. The new online submission system is available at the Data Base website at: http://the-database.org.

Finally, please mark your calendar now for the Seventh Annual ACM-SIGMIS Reception:

Where:
International Conference on Information Systems (ICIS2007) Fairmont The Queen Elizabeth Hotel, Montreal, Canada

When:
5:30 to 7:00 pm -- Saturday, December 8, 2007

Who:
All ACM-SIGMIS members and their invited guests are welcome!

.

We appreciate your continued support of SIGMIS. We welcome any ideas or suggestions to improve SIGMIS. Please feel free to contact any one of us.
Future IS research in net-enabled organizations
Authors: Watson Richard T. , Straub Detmar W.
Published: September 2007

This essay explores the interplay of network technology and the stakeholder viewpoint to argue that the information systems (IS) discipline is now in its third era of networking, and rapidly moving toward a fourth era. The first era, sans significant networks, concentrated on increasing employee productivity. The introduction of private networks ushered in a second era and brought in interorganizational systems that permitted interaction between and among businesses and governments. The third era is built on public networks, which enable firms to interact electronically with individual customers and investors, and to interact in new ways with governments. The fourth era, yet to arrive, will be built on high functionality, mobile devices that support real-time access and stakeholder locatability. Each era results in an order of magnitude increase in the potential impact of information systems on organizational performance because it can address the objectives of one or more additional groups of stakeholders.

Net-enabled organizations (NEOs) are the key evolutionary development of the third era. These organizations require insights into how to organize, architect, and implement the entire range of their electronic connections in the next several decades, and IS researchers are uniquely positioned to deliver on this vision.
Evil twins
Authors: Hansen Jacob Gorm , Christiansen Eske , Jul Eric
Published: September 2007

Traditional high performance computing systems require extensive management and suffer from security and configuration problems. This paper presents two generations of a cluster-management system that aims at making clusters as secure and self-managing as possible. The goal of the system is minimality: All nodes in a cluster are configured with a minimal software base consisting of a virtual machine monitor and a remote bootstrapping mechanism, and customers then buy access using a simple pre-paid token scheme. All necessary application software, including the operating system, is provided by the customer as a full virtual machine, and boot-strapped or migrated into the cluster.

We have explored two different models for cluster control. The first, a decentralized push model ("Evil Man"
1
), requires direct network access to cluster nodes, each of which is running a truly minimal control plane implementation consisting of only a few hundred lines of C code. In the second, a centralized pull model ("Evil Twin"), nodes may be running behind NATs or firewalls, and are controlled by a centralized web service. A specially developed cache invalidation protocol is used for telling nodes when to reload their workload description from the centralized service.
The mechanics of in-kernel synchronization for a scalable microkernel
Authors: Uhlig Volkmar
Published: September 2007

Systems with minimal kernels address the problem of ever-increasing system software complexity by strict separation of resource permission management and resource policies into different trust domains. Lately, such system structure has found wide attention in the research community and industry in the form of hypervisors and virtual machines.

With an increasing number of processors, these systems face a scalability problem. The separation eliminates semantic information about the expected parallelism for individual resources, such as memory pages or processors. Hence, the kernel is unable to optimize its synchronization primitives on a case-by-case basis---a precondition for a scalable, yet well-performing system.

In this paper we present an adaptive synchronization scheme, one of the core building block for scalable microkernels. Herewith, unprivileged components (like virtual machines) can express the degree of concurrency at the granularity of individual resources. The kernel can safely adapt and optimize its internal synchronization regime on a case-by-case basis as we show exemplary for inter-process communication and the memory management subsystem of an L4 microkernel.
An automatic PCB layout design system
Authors: Kulkarni K. G.
Published: September 2007

The paper describes an automatic PCB layout design system featuring software aids for component placement and automated routing of interconnections, implemented on a minicomputer system with the necessary graphical interaction provided by a commercial interactive graphics system. The system is being used extensively to design layouts for double sided PCBs.
Instructional computing
Authors: Thomas David B.
Published: September 2007

The current state of instructional computing art is the focus of a recently released book titled
Instructional Computing in University: The Second Decade
. Edited by Julian Feldman and Charles Mosmann, this slim volume contains papers and discussion reports from an invitational conference celebrating ten years of instructional computing at the University of California at Irvine. The conference planners invited a single paper in each of four areas of instructional computing---
instructional interface, delivery mechanism, organization
, and
cost
---hoping to survey the state of the art in the discipline. Each paper was the focus of a "workshop" and concluding paper. Thus, the volume serves as a proceedings of the conference.
Parallel task scheduling on multicore platforms
Authors: Anderson James H. , Calandrino John M.
Published: September 2007

We propose a scheduling method for real-time systems implemented on multicore platforms that encourages certain groups of tasks to be scheduled together while ensuring real-time constraints. This method can be applied to encourage tasks that share a common working set to be executed in parallel, which makes more effective use of shared caches.
Non-uniform program analysis & repeatable execution constraints
Authors: Anantaraman Aravindh , Rotenberg Eric
Published: September 2007

The objective of this paper is to enable easy, tight, and safe timing analysis of contemporary complex processors. We exploit the fact that out-of-order processors can be analyzed via simulation in the absence of variable control-flow. In our first technique, Non-Uniform Program Analysis (NUPA), program segments with a single flow of control are analyzed on a complex pipeline via simulation and segments with multiple flows of control are analyzed on a simple pipeline via conventional static analysis. A reconfigurable pipeline with dual complex/simple modes mirrors the hybrid analysis. Our second technique, Repeatable Execution Constraints for out-of-ORDER (RECORDER), defines constraints that guarantee a single input-independent execution time on an out-of-order pipeline for program segments with multiple flows of control. Thus, execution time can be derived via simulation with arbitrary inputs.
Adaptive web service composition
Authors: Lins Fernando Antônio Aires , dos Santos Júnior José Carlos , Rosa Nelson Souto
Published: September 2007

Web services have played an important role in the development of distributed systems. In particular, the possibility of composing already implemented web services in order to provide a new functionality is an interesting approach for building distributed applications and business processes. The possibility of dynamically composing web services is also apparent. Current approaches address to this point, but they do not adopt established specifications, like WS-BPEL, as they usually propose modifications in the rules of business process specifications by imposing more difficulties to implement the system. This paper proposes a policy-driven approach for enabling web service adaptability through a semantic modification in the invocation primitive of WS-BPEL, whilst mantains its syntax unaffected. Hence, programmers may define dynamic web service compositions without changing the source code. The approach has been applied to a loan approval system in order to illustrate it.
Superhack
Authors: Wing Michael
Published: September 2007

Sunil has a photographic memory. He closes his eyes and imagines code in his mind, and he edits by moving, inserting, and deleting the text mentally, until it looks just right. Then he types it in from top to bottom and it usually runs right the first time. Sunil has read many books of algorithms and patterns over the years. He can flick to a page, conjure it in his mind, and type what he needs.
CAESAR
Authors: Giudici Francesco
Published: September 2007

VANETs are networks where hosts are vehicles equipped with wireless transmission devices able to communicate without the need of any infrastructure. In this kind of network, routing algorithms are
position aware
, that is, they use geographical information to deliver packets, as in [1] and [2]. Each node periodically sends a broadcast packet, called
beacon
, which contains its unique identifier and its current location coordinates, obtained through a positioning service (e.g. GPS system). Every node receiving the beacon collects ids and coordinates of its neighbors (nodes in radio range) in its neighbor table. When a source node, let us say
S
, needs to communicate with a destination node, called
D
, it first retrieves
D
's location using a
location service
. Then
S
forwards packets to the neighbor that has smallest distance to
D
. This local strategy will be repeated by intermediate forwarding nodes until packets reach destination
D
. These algorithms are very efficient, but need a well-organized location service. Goal of this work is proposing a novel mechanism for this kind of service.
Interference-aware fast path adaptation in wireless mesh networks
Authors: Navda Vishnu , Das Samir , Ganguly Samrat
Published: September 2007

Existing multihop wireless routing protocols are incapable of reacting quickly to transient degradation of link quality rendering them unsuitable for supporting real-time applications such as streaming/interactive voice and video. This limitation in the sensitivity of the routing protocols to link quality is difficult to overcome due to the following reasons. All link quality metrics used in routing, such as ETX [1, 2] require active probing. Too frequent probing results in high overhead and can interfere with the actual traffic. Further, a time window of 5 to 10 seconds is required to gather enough probe samples to allow reasonable confidence in the statistics and avoid load sensitivity. Additional latency is also incurred in propagating routing updates.
Ethane
Authors: Casado Martin , Freedman Michael J. , Pettit Justin , Luo Jianying , McKeown Nick , Shenker Scott
Published: September 2007

This paper presents Ethane, a new network architecture for the enterprise. Ethane allows managers to define a single network-wide fine-grain policy, and then enforces it directly. Ethane couples extremely simple flow-based Ethernet switches with a centralized controller that manages the admittance and routing of flows. While radical, this design is backwards-compatible with existing hosts and switches.

We have implemented Ethane in both hardware and software, supporting both wired and wireless hosts. Our operational Ethane network has supported over 300 hosts for the past four months in a large university network, and this deployment experience has significantly affected Ethane's design.
Automating cross-layer diagnosis of enterprise wireless networks
Authors: Cheng Yu-Chung , Afanasyev Mikhail , Verkaik Patrick , Benkö Péter , Chiang Jennifer , Snoeren Alex C. , Savage Stefan , Voelker Geoffrey M.
Published: September 2007

Modern enterprise networks are of sufficient complexity that even
simple
faults can be difficult to diagnose - let alone transient outages or service degradations. Nowhere is this problem more apparent than in the 802.11-based wireless access networks now ubiquitous in the enterprise. In addition to the myriad complexities of the wired network, wireless networks face the additional challenges of shared spectrum, user mobility and authentication management. Not surprisingly, few organizations have the expertise, data or tools to decompose the underlying problems and interactions responsible for transient outages or performance degradations. In this paper, we present a set of modeling techniques for automatically characterizing the source of such problems. In particular, we focus on data transfer delays unique to 802.11 networks - media access dynamics and mobility management latency. Through a combination of measurement, inference and modeling we reconstruct sources of delay - from the physical layer to the transport - layer as well as the interactions among them. We demonstrate our approach using comprehensive traces of wireless activity in the UCSD Computer Science building.
Revealing skype traffic
Authors: Bonfiglio Dario , Mellia Marco , Meo Michela , Rossi Dario , Tofanelli Paolo
Published: September 2007

Skype is a very popular VoIP software which has recently attracted the attention of the research community and network operators. Following a closed source and proprietary design, Skype protocols and algorithms are unknown. Moreover, strong encryption mechanisms are adopted by Skype, making it very difficult to even glimpse its presence from a traffic aggregate. In this paper, we propose a framework based on two complementary techniques to reveal Skypetraffic in real time. The first approach, based on Pearson'sChi-Square test and agnostic to VoIP-related trafficcharacteristics, is used to detect Skype's fingerprint from the packet framing structure, exploiting the randomness introduced at the bit level by the encryption process. Conversely, the second approach is based on a stochastic characterization of Skype traffic in terms of packet arrival rate and packet length, which are used as features of a decision process based on Naive Bayesian Classifiers.In order to assess the effectiveness of the above techniques, we develop an off-line cross-checking heuristic based on deep-packet inspection and flow correlation, which is interesting per se. This heuristic allows us to quantify the amount of false negatives and false positives gathered by means of the two proposed approaches: results obtained from measurements in different networks show that the technique is very effective in identifying Skype traffic. While both Bayesian classifier and packet inspection techniques are commonly used, the idea of leveraging on randomness to reveal traffic is novel. We adopt this to identify Skype traffic, but the same methodology can be applied to other classification problems as well.
Reconciling performance and programmability in networking systems
Authors: Mudigonda Jayaram , Vin Harrick M. , Keckler Stephen W.
Published: September 2007

Challenges in addressing the memory bottleneck have made it difficult to design a packet processing platform that simultaneously achieves both ease-of-programming and high performance. Today's commercial processors support two architectural mechanisms - namely, hardware multithreading and caching - to overcome the memory bottleneck. The configurations of these mechanisms (e.g., cache capacity, number of threads per processor core) are fixed at processor-design time. The relative effectiveness of these mechanisms, however, varies significantly with application, traffic, and system characteristics. Thus, programmers often struggle to achieve high performance from a processor that is not well-suited to a particular deployment.

To address this challenge, we first make a case for, and then develop a malleable processor architecture that facilitates the dynamic reconfiguration of cache capacity and number of threads to best-suit the needs of each deployment. We then present an algorithm that can determine the optimal thread-cache balance at run-time. The combination of these two allows us to simultaneously achieve the goals of ease-of-programming and high performance. We demonstrate that our processor outperforms a processor similar to Intel's IXP2800 - a state-of-the-art commercial Network Processor - in about 89% of the deployments we consider. Further, in about 30% of the deployments our platform improves the throughput by as much as 300%.
Supercharging planetlab
Authors: Turner Jonathan S. , Crowley Patrick , DeHart John , Freestone Amy , Heller Brandon , Kuhns Fred , Kumar Sailesh , Lockwood John , Lu Jing , Wilson Michael , Wiseman Charles , Zar David
Published: September 2007

In recent years, overlay networks have become an important vehicle for delivering Internet applications. Overlay network nodes are typically implemented using general purpose servers or clusters. We investigate the performance benefits of more integrated architectures, combining general-purpose servers with high performance Network Processor (NP) subsystems. We focus on PlanetLab as our experimental context and report on the design and evaluation of an experimental PlanetLab platform capable of much higher levels of performance than typical system configurations. To make it easier for users to port applications, the system supports a fast path/slow path application structure that facilitates the mapping of the most performance-critical parts of an application onto an NP subsystem, while allowing the more complex control and exception-handling to be implemented within the programmer-friendly environment provided by conventional servers. We report on implementations of two sample applications, an IPv4 router, and a forwarding application for the Internet Indirection Infrastructure. We demonstrate an 80x improvement in packet processing rates and comparable reductions in latency.
Can internet video-on-demand be profitable?
Authors: Huang Cheng , Li Jin , Ross Keith W.
Published: September 2007

Video-on-demand in the Internet has become an immensely popular service in recent years. But due to its high bandwidth requirements and popularity, it is also a costly service to provide. We consider the design and potential benefits of peer-assisted video-on-demand, in which participating peers assist the server in delivering VoD content. The assistance is done in such a way that it provides the same user quality experience as pure client-server distribution. We focus on the single-video approach, whereby a peer only redistributes a video that it is currently watching.

Using a nine-month trace from a client-server VoD deployment for MSN Video, we assess what the 95 percentile server bandwidth costs would have been if a peer-assisted employment had been instead used. We show that peer-assistance can dramatically reduce server bandwidth costs, particularly if peers prefetch content when there is spare upload capacity in the system. We consider the impact of peer-assisted VoD on the cross-traffic among ISPs. Although this traffic is significant, if care is taken to localize the P2P traffic within the ISPs, we can eliminate the ISP cross traffic while still achieving important reductions in server bandwidth. We also develop a simple analytical model which captures many of the critical features of peer-assisted VoD, including its operational modes.
Achieving convergence-free routing using failure-carrying packets
Authors: Lakshminarayanan Karthik , Caesar Matthew , Rangan Murali , Anderson Tom , Shenker Scott , Stoica Ion
Published: September 2007

Current distributed routing paradigms (such as link-state, distance-vector, and path-vector) involve a convergence process consisting of an iterative exploration of intermediate routes triggered by certain events such as link failures. The convergence process increases router load, introduces outages and transient loops, and slows reaction to failures. We propose a new routing paradigm where the goal is not to reduce the convergence times but rather to eliminate the convergence process completely. To this end, we propose a technique called Failure-Carrying Packets (FCP) that allows data packets to autonomously discover a working path without requiring completely up-to-date state in routers. Our simulations, performed using real-world failure traces and Rocketfuel topologies, show that: (a) the overhead of FCP is very low, (b) unlike traditional link-state routing (such as OSPF), FCP can provide both low loss-rate as well as low control overhead, (c) compared to prior work in backup path pre-computations, FCP provides better routing guarantees under failures despite maintaining lesser state at the routers.
Portcullis
Authors: Parno Bryan , Wendlandt Dan , Shi Elaine , Perrig Adrian , Maggs Bruce , Hu Yih-Chun
Published: September 2007

Systems using capabilities to provide preferential service to selected flows have been proposed as a defense against large-scale network denial-of-service attacks. While these systems offer strong protection for established network flows, the Denial-of-Capability (DoC) attack, which prevents new capability-setup packets from reaching the destination, limits the value of these systems.

Portcullis mitigates DoC attacks by allocating scarce link bandwidth for connection establishment packets based onper-computationfairness. We prove that a legitimate sender can establish a capability with high probability regardless of an attacker's resources or strategy and that no system can improve on our guarantee. We simulate full and partial deployments of Portcullis on an Internet-scale topology to confirm our theoretical results and demonstrate the substantial benefits of using per-computation fairness.
Orbis
Authors: Mahadevan Priya , Hubble Calvin , Krioukov Dmitri , Huffaker Bradley , Vahdat Amin
Published: September 2007

Researchers involved in designing network services and protocols rely on results from simulation and emulation environments to understand their application performance and scalability. To better understand the behavior of these applications and predict their performance when deployed on the actual Internet, the generated topologies must closely match real network characteristics, not just in terms of graph structure (node interconnectivity) but also with respect to various node and link annotations. Relevant annotations include link latencies, AS membership and whether a router is a peering or internal router. Finally, it should be possible to rescale a given topology to a variety of sizes while still maintaining its essential characteristics.

In this paper, we propose techniques to generate annotated, Internet router graphs of different sizes based on existing observations of Internet characteristics. We find that our generated graphs match a variety of graph properties of observed topologies for a range of target graph sizes. While the best available data of Internet topology currently remains imperfect, the quality of our generated topologies will improve with the fidelity of available measurement techniques or next generation architectures that make Internet structure more transparent.
Structured streams
Authors: Ford Bryan
Published: September 2007

Internet applications currently have a choice between stream and datagram transport abstractions. Datagrams efficiently support small transactions and streams are suited for long-running conversations, but neither abstraction adequately supports applications like HTTP that exhibit a
mixture
of transaction sizes, or applications like FTP and SIP that use multiple transport instances.
Structured Stream Transport
(SST) enhances the traditional stream abstraction with a hierarchical
hereditary structure
, allowing applications to create lightweight
child streams
from any existing stream. Unlike TCP streams, these lightweight streams incur neither 3-way handshaking delays on startup nor TIME-WAIT periods on close. Each stream offers independent data transfer and flow control, allowing different transactions to proceed in parallel without head-of-line blocking, but all streams share one congestion control context. SST supports both reliable and best-effort delivery in a way that semantically unifies datagrams with streams and solves the classic "large datagram" problem, where a datagram's loss probability increases exponentially with fragment count. Finally, an application can prioritize its streams relative to each other and adjust priorities dynamically through out-of-band signaling. A user-space prototype shows that SST is TCP-friendly to within 2%, and performs comparably to a user-space TCP and to within 10% of kernel TCP on a WiFi network.
Understanding and mitigating the impact of RF interference on 802.11 networks
Authors: Gummadi Ramakrishna , Wetherall David , Greenstein Ben , Seshan Srinivasan
Published: September 2007

We study the impact on 802.11 networks of RF interference from devices such as Zigbee and cordless phones that increasingly crowd the 2.4GHz ISM band, and from devices such as wireless camera jammers and non-compliant 802.11 devices that seek to disrupt 802.11 operation. Our experiments show that commodity 802.11 equipment is surprisingly vulnerable to certain patterns of weak or narrow-band interference. This enables us to disrupt a link with an interfering signal whose power is 1000 times weaker than the victim's 802.11 signals, or to shut down a multiple AP, multiple channel managed network at a location with a single radio interferer. We identify several factors that lead to these vulnerabilities, ranging from MAC layer driver implementation strategies to PHY layer radio frequency implementation strategies. Our results further show that these factors are not overcome by simply changing 802.11 operational parameters (such as CCA threshold, rate and packet size) with the exception of frequency shifts. This leads us to explore rapid channel hopping as a strategy to withstand RF interference. We prototype a channel hopping design using PRISM NICs, and find that it can sustain throughput at levels of RF interference well above that needed to disrupt unmodified links, and at a reasonable cost in terms of switching overheads.
What matters when introducing new information technology
Authors: Brown Susan A. , Chervany Norman L. , Reinicke Bryan A.
Published: September 2007

Focusing on the right issues at the right time increases the likelihood of success.
Autonomous programmable biomolecular devices using self-assembled DNA nanostructures
Authors: Reif John H. , LaBean Thomas H.
Published: September 2007

Surveying recent developments in bio-DNA computing.
Shape cliques
Authors: Bernecky Robert
Published: September 2007

We introduce shape cliques, a simple way to organize a subset of the arrays appearing in an array-language-based application into sets of identically shaped arrays - shape cliques - and show how a compiler can analyze an application to infer membership in those cliques. We describe an algorithm for performing shape clique inference (SCI), and demonstrate that shape cliques can improve the performance of generated code, by permitting extension of an optimization for removal of run-time checks, and by extending the set of arrays to which optimizations, such as Index Vector Elimination (IVE), can be applied. Implementation of SCI in the APEX APL compiler permitted removal of 25% of run-time checks remaining on 156 benchmarks remaining after other compiler optimizations had eliminated 72% of the 1251 checks present in the original code. In the SAC compiler, IVE using SCI produced typical speedups of 2-14X on benchmarks operating on arrays of non-fixed rank and shape, compared to the operation of IVE in a non-SCI environment. Shape clique inference data can be exploited to allow certain other optimizations, such as loop fusion and withloop folding, to be performed on arrays of statically unknown shape and rank, with the potential for significant reductions in execution time.
Generating APL printouts with a2ps
Authors: de Almeida Pedro
Published: September 2007

Printing APL dialects is, quite often, a frustrating task, for there is no simple method to convert the code itself into suitable output, for instance, PostScript or Portable Document Format. Generally speaking, printing of APL has relied on the interpreter itself, or perhaps converting the workspaces using an automatic transliteration scheme. In this article, I introduce a practical solution to the problem of printing APL dialects which does not require the use of the interpreter nor transliteration of workspaces provided a "source" file is available. After a typesetting solution described elsewhere [de Almeida, APL Quote Quad 34(2) (2004) 28] I implement a less complex, direct printing approach using a Type 1 (or outline) APL font, an encoding vector, and Gnu's a2ps, a program which converts files or standard input to PostScript, and I further provide an illustration of conversion of APL "source" into PostScript, ready for printout (or for visualization on the screen) using Morgan Stanley's A+ dialect.
Structure and Function of the Cell Surface (Tethered) Mucins
Authors: Hattrup Christine L. , Gendler Sandra J.
Published: September 2007

Cell surface mucins are large transmembrane glycoproteins involved in diverse functions ranging from shielding the airway epithelium against pathogenic infection to regulating cellular signaling and transcription. Although hampered by the relatively recent characterization of cell surface mucins and the difficulties inherent in working with molecules of their size, numerous studies have placed the tethered mucins in the thick of normal and diseased lung physiology. This review focuses on the three best-characterized cell surface mucins expressed in the respiratory tract: MUC1, MUC4, and MUC16.
Cystathionine-β-synthase gene transfer and 3-deazaadenosine ameliorate inflammatory response in endothelial cells
Authors: Sen Utpal , Tyagi Neetu , Kumar Munish , Moshal Karni S. , Rodriguez Walter E. , Tyagi Suresh C.
Published: September 2007

Although elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) are associated with increased inflammation and vascular remodeling, the mechanism of Hcy-mediated inflammation and vascular remodeling is unclear. The matrix metalloproteinases (MMPs) and adhesion molecules play an important role in vascular remodeling. We hypothesized that HHcy induces inflammation by increasing adhesion molecules and matrix protein expression. Endothelial cells were supplemented with high methionine, and Hcy accumulation was measured by HPLC. Nitric oxide (NO) bioavailability was detected by a NO probe. The protein expression was measured by Western blot analysis. MMP-9 activity was detected by gelatin-gel zymography. We demonstrated that methionine supplement promoted upregulation of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) through increased Hcy accumulation. In addition, increased synthesis of collagen type-1 was also observed. MMP-9 gene expression and protein activity were increased in methionine supplement groups. 3-Deazaadenosine (DZA), an adenosine analogue, prevented high methionine-induced ICAM-1 and VCAM-1 expression and collagen type-1 synthesis. Transfection of endothelial cells with cystathionine-β-synthase (CBS) gene construct, which converts Hcy to cystathionine, reduced Hcy accumulation in high methionine-fed cells. CBS gene transfection reduced the inflammatory response, as evident by attenuated ICAM-1 and VCAM-1 expression. Furthermore, collagen type-1 expression and MMP-9 activity were dramatically attenuated with CBS gene transfection. These results suggested that methionine supplement increased Hcy accumulation, which was associated with inflammatory response and matrix remodeling such as collagen type-1 synthesis and MMP-9 activity. However, in vitro DZA and CBS gene therapy successfully treated the HHcy-induced inflammatory reaction in the methionine metabolism pathway.
Polyphenolic compounds fromArtemisia dracunculus L.inhibit PEPCK gene expression and gluconeogenesis in an H4IIE hepatoma cell line
Authors: Govorko Dmitry , Logendra Sithes , Wang Yanxin , Esposito Debora , Komarnytsky Slavko , Ribnicky David , Poulev Alexander , Wang Zhong , Cefalu William T. , Raskin Ilya
Published: September 2007

An ethanolic extract of Russian tarragon, Artemisia dracunculus L., with antihyperglycemic activity in animal models was reported to decrease phospho enolpyruvate carboxykinase (PEPCK) mRNA expression in STZ-induced diabetic rats. A quantitative polymerase chain reaction (qPCR) assay was developed for the bioactivity-guided purification of the compounds within the extract that decrease PEPCK expression. The assay was based on the inhibition of dexamethasone-stimulated PEPCK upregulation in an H4IIE hepatoma cell line. Two polyphenolic compounds that inhibited PEPCK mRNA levels were isolated and identified as 6-demethoxycapillarisin and 2′,4′-dihydroxy-4-methoxydihydrochalcone with IC50values of 43 and 61 μM, respectively. The phosphoinositide-3 kinase (PI3K) inhibitor LY-294002 showed that 6-demethoxycapillarisin exerts its effect through the activation of the PI3K pathway, similarly to insulin. The effect of 2′,4′-dihydroxy-4-methoxydihydrochalcone is not regulated by PI3K and dependent on activation of AMPK pathway. These results indicate that the isolated compounds may be responsible for much of the glucose-lowering activity of the Artemisia dracunculus extract.
Protein kinase G-mediated stimulation of basal Leydig cell steroidogenesis
Authors: Andric Silvana A. , Janjic Marija M. , Stojkov Natasa J. , Kostic Tatjana S.
Published: September 2007

The androgen-secreting Leydig cells produce cGMP, but the pathways responsible for generation and actions of this intracellular messenger have been incompletely characterized in these cells. Here, we show the presence of mRNA transcripts for the membrane-bound and soluble guanylyl cyclases (sGC), the cGMP-specific phosphodiesterase 5, and the cGMP-dependent protein kinase I (PKG I) and PKG II in purified rat Leydig cells from adult animals. Stimulation of both guanylyl cyclases and inhibition of phosphodiesterase 5 in vitro were accompanied by elevations in cGMP and androgen production, whereas inhibition of sGC and PKG led to a decrease in steroidogenesis. The stimulatory action of cGMP on steroidogenesis was preserved in cells with inhibited cAMP-dependent protein kinases. Experiments with exogenously added substrates revealed the dependence of cGMP-induced progesterone and androgen synthesis on cholesterol but not on 22-OH cholesterol, pregnenolone, progesterone, and Δ4-androstenedione. Treatment with nitric oxide donor increased phosphorylation of the steroidogenic acute regulatory protein (StAR). In contrast, inhibition of sGC and PKG, but not protein kinase A, significantly reduced StAR phosphorylation. These results suggest that cGMP contributes to the control of basal steroidogenesis in Leydig cells through the PKG-dependent modification of the StAR protein.