bluuebunny/crossref_metadata_2025 huggingface dataset:
Moisture diffusivity and response time in fine forest fuels
Authors: Anderson Hal E.
Published: July 2008

Fine forest fuels, such as grasses, hardwood leaves, and conifer needles, vary greatly in response times and mean moisture diffusion coefficients when exposed to desorption and adsorption conditions. Results are reported for tests made with recently dead and weathered dead fine forest fuels and small woody samples. Test conditions were 26.7 °C (80°F) with changes in relative humidity from 90 to 20% and back, in an environmental chamber. Moisture diffusivities of fine forest fuels were found to be smaller than diffusivities of woody samples. The diffusivities of the foliage and grass fuels tested ranged from near 1.0 × 10−10 to 1.0 × 10−8 cm2/s, whereas the woody fuels ranged from 1.5 × 10−7 to3.0 × 10−5 cm2/s. Weathered fine fuels had faster response times and higher diffusivities than recently cast materials. Adsorption response times were longer and diffusivities lower than for fuels in desorption. Response times of various recently dead fine fuels ranged from 0.2 to 37 h and weathered fuels from 0.5 to 10 h. Therefore, specific fuel types need to be tested to assign more precise response times. Under the drying conditions of 26.7 °C and 20% relative humidity, fine forest fuels had lower diffusivities and longer response times than anticipated in the United States National Fire Danger Rating System. As a result, predicted fire danger during or after a weather change may be overestimated because fuels are responding more slowly than anticipated. Equations are presented for making first estimates of response time and (or) diffusivity if certain physical properties are known: surface area-to-volume ratio, packing ratio, and bed depth.
Staurosporine aglycone bilaterally regulates ERK1/2 phosphorylation in rat pulmonary arterial smooth muscle cells
Authors: Zhang Jianing , Tang Xiaobo , Lu Changlian , Guo Lei , Zhang Shuang , Chu Xiaojie , Zhu Daling
Published: July 2008

Staurosporine, a protein kinase C (PKC) inhibitor, has been reported to regulate the phosphorylation of ERK1/2 in several cell lines. It is still unknown, however, whether its derivative staurosporine aglycone (SA) has the same effect on ERK1/2 activation. In this study, we investigated the effect of SA on ERK1/2 activity in rat pulmonary arteries and pulmonary arterial smooth muscle cells (PASMCs). The pulmonary arteries and PASMCs were treated with SA at different time points and concentrations, and the activation of ERK1/2 was analyzed by Western blotting. The results showed that SA at nanomolar concentrations suppressed ERK1/2 phosphorylation through the PKC pathway alone, but SA at 30 µmol/L for 2 h enhanced the phosphorylation of ERK1/2. The activation of ERK1/2 was inhibited by the MAPK/ERK kinase inhibitor PD98059 or the protein kinase A (PKA) activator isoproterenol. Together, these results suggest that SA has a strong dual regulating effect on ERK1/2 through the PKC and (or) PKA pathways in rat PASMCs.
CONFORMAL KILLING-YANO TENSOR AND KERR-NUT-DE SITTER SPACETIME UNIQUENESS
Authors: YASUI YUKINORI
Published: July 2008

This paper gives a brief review of recent results on higher dimensional black hole solutions. It is shown that the D-dimensional Kerr-NUT-de Sitter spacetime constructed by Chen-Lü-Pope is the only spacetime admitting a rank-2 conformal Killing-Yano tensor with a certain symmetry.
BLACK HOLE FORMATION VIA TACHYON CONDENSATION
Authors: SUYAMA TAKAO
Published: July 2008

We investigate a possibility for a black hole to be created during closed string tachyon condensation. For the case of a bulk closed string tachyon, we find classical solutions of a low energy effective theory which has a black hole in the space-time. On the other hand, for the case of a localized closed string tachyon, a black hole, if created, would be of the string size and it would quickly evaporate.
EXACT SOLUTIONS AND THE ATTRACTOR MECHANISM IN NON-BPS BLACK HOLES
Authors: HOTTA KYOSUKE
Published: July 2008

We analyze the attractor mechanism for the D0-D4 black hole solution in the four-dimensional [Formula: see text] supergravity. Our analyses are based on new exact solutions, which show explicitly the attractor mechanism for the extremal non-BPS black holes. Our solutions take into account the moduli as general complex fields, while in almost all the non-BPS solutions obtained by previous authors, the moduli fields are restricted to be purely imaginary.
PREPOTENTIALS IN TORIC AdS4 COMPACTIFICATIONS
Authors: LEE SANGMIN
Published: July 2008

We address the question of determining the prepotential of the gauged supergravity resulting from a compactification of M-theory on AdS 4 × Y7. We make a concrete proposal for the prepotential in the case of toric Sasaki-Einstein Y7. Comparison with direct Kaluza-Klein computations show that the proposal is correct in certain cases, but requires modification in general.
A SECRET SYMMETRY OF AdS/CFT S-MATRIX
Authors: MATSUMOTO TAKUYA , MORIYAMA SANEFUMI , TORRIELLI ALESSANDRO
Published: July 2008

We find a new quantum Yangian symmetry of AdS/CFT S-matrix, which does not have the original Lie algebra 𝔰𝔲(2|2) analogue, and persue the origin of this symmetry in exceptional superalgebra 𝔡(2, 1; ε) , which recovers 𝔰𝔲(2|2) when the paramater ε taken to zero.
DOMAIN WALL SOLITONS AND HOPF ALGEBRAIC TRANSLATIONAL SYMMETRIES IN NONCOMMUTATIVE FIELD THEORIES
Authors: SASAI YUYA , SASAKURA NAOKI
Published: July 2008

Domain wall solitons are the simplest topological objects in field theories. The conventional translational symmetry in a field theory is the generator of a one-parameter family of domain wall solutions, and induces a massless moduli field which propagates along a domain wall. We study similar issues in braided noncommutative field theories possessing Hopf algebraic translational symmetries. As a concrete example, we discuss a domain wall soliton in the scalar braided noncommutative field theory in Lie-algebraic noncommutative spacetime, which has a Hopf algebraic translational symmetry. We construct explicitly a one-parameter family of solutions in perturbation of the noncommutativity parameter. We then find the massless moduli field which propagates on the domain wall soliton. This work is based on arXiv:0711.3059.
PERTURBATIVE VACUA FROM IIB MATRIX MODEL
Authors: KAWAI HIKARU , SATO MATSUO
Published: July 2008

It has not been clarified whether a matrix model can describe various vacua of string theory. In this talk, we show that the IIB matrix model includes type IIA string theory1. In the naive large N limit of the IIB matrix model, configurations consisting of simultaneously diagonalizable matrices form a moduli space, although the unique vacuum would be determined by complicated dynamics. This moduli space should correspond to a part of perturbatively stable vacua of string theory. Actually, one point on the moduli space represents type IIA string theory. Instead of integrating over the moduli space in the path-integral, we can consider each of the simultaneously diagonalizable configurations as a background and set the fluctuations of the diagonal elements to zero. Such procedure is known as quenching in the context of the large N reduced models. By quenching the diagonal elements of the matrices to an appropriate configuration, we show that the quenched IIB matrix model is equivalent to the two-dimensional large N [Formula: see text] super Yang-Mills theory on a cylinder. This theory is nothing but matrix string theory and is known to be equivalent to type IIA string theory. As a result, we find the manner to take the large N limit in the IIB matrix model.
LARGE EDDY SIMULATION OF SEDIMENT-LADEN TURBULENT FLOW IN AN OPEN CHANNEL
Authors: WAN ZHANHONG , SUN ZHILIN , YOU ZHENJIANG , ZHANG QIYAN
Published: July 2008

Sediment transport in fully developed turbulent open channel flow has been investigated using large eddy simulation (LES) of the incompressible Navier–Stokes equations. The scalar transport equation of the sediments concentration, which is based on the continuous-phase approach, is adopted. The settling process is taken into account with a modified settling velocity appearing in the sediment concentration equation. A Smagorinsky model allowing for the interaction between the fluid flow and the suspended sediment is used to simulate the unresolved, subgrid scale terms. The LES results are compared with the experimental data, and good general agreement is achieved.
INFLUENCE OF BOTH ELECTRIC AND MAGNETIC FIELDS ON THE BOUND POLARON IN AN ANISOTROPIC QUANTUM DOT
Authors: CHEN SHI-HUA , XIAO JING-LIN
Published: July 2008

The binding energy of a bound polaron in an anisotropic quantum dot (QD) subject to electric and magnetic fields along the growth axis has been investigated by using a variational method of Pekar type, taking into account the electron-bulk LO-phonon interaction. The results show that the binding energy decreases with increasing electric field strength and increases with increasing confinement strengths in the lateral and the longitudinal direction, the magnetic field strength, and the Coulomb potential.
TRANSPORT IN A CLEAN GRAPHENE SHEET AT FINITE TEMPERATURE AND FREQUENCY
Authors: PERES N. M. R. , STAUBER T.
Published: July 2008

We calculate the conductivity of a clean graphene sheet at finite temperatures starting from the tight-binding model. We obtain a finite value for the dc-conductivity at zero temperature. For finite temperature, the spontaneous electron-hole creation, responsible for the finite conductivity at zero temperature, is washed out and the dc-conductivity yields zero. Our results are in agreement with calculations based on the field-theoretical model for graphene.
A CRITERION FOR EXISTENCE OF A POSITIVE SOLUTION OF A NONLINEAR ELLIPTIC SYSTEM
Authors: VELIN J.
Published: July 2008

In this paper, we give necessary and sufficient conditions for existence of bounded and positive solutions of a nonlinear elliptic system arising from potential type problems.
Deep-crust strike-slip earthquake faulting in southern Italy aided by high fluid pressure: insights from rheological analysis
Authors: Boncio Paolo
Published: July 2008

I present the results of a crustal rheological analysis of the Potenza 1990 and Molise 2002 (southern Italy) deep foci (10–25 km) strike–slip earthquake sequences (
M
max
=5.7) located in the upper half of the middle crust. The analysis consists of geotherms and two-mechanism (brittle frictional v. ductile plastic flow) strength envelopes. Strength envelopes are calculated along a sub-vertical E–W-striking inherited crustal-scale fault zone reactivated under a strike–slip tectonic regime. The effects of high pore-fluid pressure (
Pf
) and strain rate increase due to afterslip processes during the co-seismic and early post-seismic phases are evaluated. The results are compared with the depth-distribution of seismicity. Under long-term strain rates, the rheology predicts a brittle layer in the upper part of the middle crust embedded by two plastic horizons: the base of the carbonates and the Verrucano layer (above) and the lower part of middle crust (below). The best rheological model for the observed seismicity is that considering high
Pf
in the middle crust (λ≥0.65). Brittle faulting aided by high
Pf
in the middle crust is in agreement with the focal depths and magnitudes of the main shocks. The upward and downward widening of the brittle layer in the middle crust, due to the increased strain rate in the co-seismic and early post-seismic phases (afterslip), agrees with the width of the aftershock zones. The weak ductile layer at the base of the carbonates (and possibly within the Verrucano) appears to have an important role in delimiting the seismogenic faulting upwards and probably played a role in defining a seal to fluid up-flow along the fault zone.
The distribution of faults and fractures and their importance in accommodating extensional strain at Kimmeridge Bay, Dorset, UK
Authors: Putz-Perrier Martin W. , Sanderson David J.
Published: July 2008

The spatial distribution of extensional strain in interbedded mudstones and carbonates from around Kimmeridge Bay in southern England is examined using a variety of line samples. Normal faults and tensile fractures (veins) from the same deformation event show displacements ranging over 6 orders of magnitude. The relative contribution of these structures to the overall extension varies, with large faults (>10 m heave) accommodating about 65%, smaller faults (1–10 m heave) about 25% and veins less than 10% of the overall extension. The heterogeneity of fracture density and strain can be quantified from cumulative plots by applying a non-parametric method based on Kuiper's test. Both the degree and statistical significance of strain heterogeneity can be determined and are shown to be scale-dependent. Thin veins accommodate a fairly constant background strain across the region, whilst thick veins and small faults take up localized higher strains in damage zones around larger faults. Fault-strain is relatively homogenously distributed across the region. The faults and veins do not share the same scaling relationship. Thus, this study shows that it is not possible to simply extrapolate fracture frequencies and strain from fault scale to vein scale, and that the heterogeneity of extensional strain is scale dependent.
An empirical investigation of software reuse benefits in a large telecom product
Authors: Mohagheghi Parastoo , Conradi Reidar
Published: July 2008

Background
. This article describes a case study on the benefits of software reuse in a large telecom product. The reused components were developed in-house and shared in a product-family approach.
Methods
. Quantitative data mined from company repositories are combined with other quantitative data and qualitative observations.
Results
. We observed significantly lower fault density and less modified code between successive releases of the reused components. Reuse and standardization of software architecture and processes allowed easier transfer of development when organizational changes happened.
Conclusions
. The study adds to the evidence of quality benefits of large-scale reuse programs and explores organizational motivations and outcomes.
Repair localization for query answering from inconsistent databases
Authors: Eiter Thomas , Fink Michael , Greco Gianluigi , Lembo Domenico
Published: July 2008

Query answering from inconsistent databases amounts to finding “meaningful” answers to queries posed over database instances that do not satisfy integrity constraints specified over their schema. A declarative approach to this problem relies on the notion of repair, that is, a database that satisfies integrity constraints and is obtained from the original inconsistent database by “minimally” adding and/or deleting tuples. Consistent answers to a user query are those answers that are in the evaluation of the query over each repair. Motivated by the fact that computing consistent answers from inconsistent databases is in general intractable, the present paper investigates techniques that allow to localize the difficult part of the computation on a small fragment of the database at hand, called “affected” part. Based on a number of localization results, an approach to query answering from inconsistent data is presented, in which the query is evaluated over each of the repairs of the affected part only, augmented with the part that is not affected. Single query results are then suitably recombined. For some relevant settings, techniques are also discussed to factorize repairs into components that can be processed independently of one another, thereby guaranteeing exponential gain w.r.t. the basic approach, which is not based on localization. The effectiveness of the results is demonstrated for consistent query answering over expressive schemas, based on logic programming specifications as proposed in the literature.
On computing temporal aggregates with range predicates
Authors: Zhang Donghui , Markowetz Alexander , Tsotras Vassilis J. , Gunopulos Dimitrios , Seeger Bernhard
Published: July 2008

Computing temporal aggregates is an important but costly operation for applications that maintain time-evolving data (data warehouses, temporal databases, etc.) Due to the large volume of such data, performance improvements for temporal aggregate queries are critical. Previous approaches have aggregate predicates that involve only the time dimension. In this article we examine techniques to compute temporal aggregates that include key-range predicates as well (
range-temporal aggregates
). In particular we concentrate on the SUM aggregate, while COUNT is a special case. To handle arbitrary key ranges, previous methods would need to keep a separate index for every possible key range. We propose an approach based on a new index structure called the
Multiversion SB-Tree
, which incorporates features from both the SB-Tree and the Multiversion B+--tree, to handle arbitrary key-range temporal aggregate queries. We analyze the performance of our approach and present experimental results that show its efficiency. Furthermore, we address a novel and practical variation called
functional
range-temporal aggregates. Here, the value of any record is a function over time. The meaning of aggregates is altered such that the contribution of a record to the aggregate result is proportional to the size of the intersection between the record's time interval and the query time interval. Both analytical and experimental results show the efficiency of our result.
Optimal branch-decomposition of planar graphs in
O
(
n
3
) Time
Authors: Gu Qian-Ping , Tamaki Hisao
Published: July 2008

We give an
O
(
n
3
) time algorithm for constructing a minimum-width branch-decomposition of a given planar graph with
n
vertices. This is achieved through a refinement to the previously best known algorithm of Seymour and Thomas, which runs in
O
(
n
4
) time.
Improved algorithms for the minmax-regret 1-center and 1-median problems
Authors: Yu Hung-I. , Lin Tzu-Chin , Wang Biing-Feng
Published: July 2008

In this article, efficient algorithms are presented for the minmax-regret 1-center and 1-median problems on a general graph and a tree with uncertain vertex weights. For the minmax-regret 1-center problem on a general graph, we improve the previous upper bound from
O
(
mn
2
log
n
) to
O
(
mn
log
n
). For the problem on a tree, we improve the upper bound from
O
(
n
2
) to
O
(
n
log
2
n
). For the minmax-regret 1-median problem on a general graph, we improve the upper bound from
O
(
mn
2
log
n
) to
O
(
mn
2
+
n
3
log
n
). For the problem on a tree, we improve the upper bound from
O
(
n
log
2
n
) to
O
(
n
log
n
).
COVER STORYChanging energy use through design
Authors: Pierce James , Roedl David
Published: July 2008

Editors' Note: We are delighted to present Eli Blevis' Sustainably Ours forum as the cover story for this issue
TIMELINESTag clouds and the case for vernacular visualization
Authors: Viégas Fernanda B. , Wattenberg Martin
Published: July 2008

Most HCI history articles trace digital developments back to the 1980s, 1960s, or earlier. Information visualization is moving so rapidly that it's great to have a look back and glance forward on tag clouds, just over a decade old in digital form, from leading visualization researchers Fernanda Viégas and Martin Wattenberg. ---Jonathan Grudin
The truth about tech recycling
Authors: Greiner Lynn
Published: July 2008

The awkward thing about getting new tech toys is the fact that there's usually an old tech toy left over, suddenly unloved and unwanted. Over time drawers are filled with old cell phones and MP3 players, piles of old computers linger in our closets, or the obsolete electronics end up in the trash.
Is the power of web search diminishing?
Authors: Treese Win
Published: July 2008

Back in the early days of the World Wide Web, many sites tried to organize the information that was starting to be available on the Internet. At the time, most were taking a "naive library" approach. That is, they were attempting to collect websites and Web pages into categories and sub-categories---an Internet hierarchy of information.
Patently false?
Authors: Rowell Laurie
Published: July 2008

A lawsuit now in federal appeals court may spell the end for software patents
Counter braids
Authors: Lu Yi , Montanari Andrea , Prabhakar Balaji , Dharmapurikar Sarang , Kabbani Abdul
Published: July 2008

Fine-grained network measurement requires routers and switches to update large arrays of counters at very high link speed (e.g. 40 Gbps). A naive algorithm needs an infeasible amount of SRAM to store both the counters and a flow-to-counter association rule, so that arriving packets can update corresponding counters at link speed. This has made accurate per-flow measurement complex and expensive, and motivated approximate methods that detect and measure only the large flows.

This paper revisits the problem of accurate per-flow measurement. We present a counter architecture, called Counter Braids, inspired by sparse random graph codes. In a nutshell, Counter Braids "compresses while counting". It solves the central problems (counter space and flow-to-counter association) of per-flow measurement by "braiding" a hierarchy of counters with random graphs. Braiding results in drastic space reduction by sharing counters among flows; and using random graphs generated on-the-fly with hash functions avoids the storage of flow-to-counter association.

The Counter Braids architecture is optimal (albeit with a complex decoder) as it achieves the maximum compression rate asymptotically. For implementation, we present a low-complexity message passing decoding algorithm, which can recover flow sizes with essentially zero error. Evaluation on Internet traces demonstrates that almost all flow sizes are recovered exactly with only a few bits of counter space per flow.
HMTT
Authors: Bao Yungang , Chen Mingyu , Ruan Yuan , Liu Li , Fan Jianping , Yuan Qingbo , Song Bo , Xu Jianwei
Published: July 2008

Memory trace analysis is an important technology for architecture research, system software (i.e., OS, compiler) optimization, and application performance improvements. Many approaches have been used to track memory trace, such as simulation, binary instrumentation and hardware snooping. However, they usually have limitations of time, accuracy and capacity.

In this paper we propose a platform independent memory trace monitoring system, which is able to track virtual memory reference trace of full systems (including OS, VMMs, libraries, and applications). The system adopts a DIMM-snooping mechanism that uses hardware boards plugged in DIMM slots to snoop. There are several advantages in this approach, such as fast, complete, undistorted, and portable. Three key techniques are proposed to address the system design challenges with this mechanism: (1) To keep up with memory speeds, the DDR protocol state machine is simplified, and large FIFOs are added between the state machine and the trace transmitting logic to handle burst memory accesses; (2) To reconstruct physical-tovirtual mapping and distinguish one process' address space from others, an OS kernel module, which collects page table information, and a synchronization mechanism, which synchronizes the page table information with the memory race, are developed; (3) To dump massive trace data, we employ a straightforward method to compress the trace and use Gigabit Ethernet and RAID to send and receive the compressed trace.

We present our implementation of an initial monitoring system, named HMTT (Hyper Memory Trace Tracker). Using HMTT, we have observed that burst bandwidth utilization is much larger than average bandwidth utilization, by up to 5X in desktop applications. We have also confirmed that the stream memory accesses of many applications contribute even more than 40% of L2 Cache misses and OS virtual memory management may decrease stream accesses in view of memory controller (or L2 Cache), by up to 30.2%. Moreover, we have evaluated OS impact on memory performance in real systems. The evaluations and case studies show the feasibility and effectiveness of our proposed monitoring mechanism and techniques.
Disk scrubbing versus intra-disk redundancy for high-reliability raid storage systems
Authors: Iliadis Ilias , Haas Robert , Hu Xiao-Yu , Eleftheriou Evangelos
Published: July 2008

Two schemes proposed to cope with unrecoverable or latent media errors and enhance the reliability of RAID systems are examined. The first scheme is the established, widely used disk scrubbing scheme, which operates by periodically accessing disk drives to detect media-related unrecoverable errors. These errors are subsequently corrected by rebuilding the sectors affected. The second scheme is the recently proposed intradisk redundancy scheme which uses a further level of redundancy inside each disk, in addition to the RAID redundancy across multiple disks. Analytic results are obtained assuming Poisson arrivals of random I/O requests. Our results demonstrate that the reliability improvement due to disk scrubbing depends on the scrubbing frequency and the workload of the system, and may not reach the reliability level achieved by a simple IPC-based intra-disk redundancy scheme, which is insensitive to the workload. In fact, the IPC-based intra-disk redundancy scheme achieves essentially the same reliability as that of a system operating without unrecoverable sector errors. For heavy workloads, the reliability achieved by the scrubbing scheme can be orders of magnitude less than that of the intra-disk redundancy scheme.
DARC
Authors: Traeger Avishay , Deras Ivan , Zadok Erez
Published: July 2008

OSprof is a versatile, portable, and efficient profiling methodology based on the analysis of latency distributions. Although OSprof has offers several unique benefits and has been used to uncover several interesting performance problems, the latency distributions that it provides must be analyzed manually. These latency distributions are presented as histograms and contain distinct groups of data, called peaks, that characterize the overall behavior of the running code. By automating the analysis process, we make it easier to take advantage of OSprof's unique features.

We have developed the Dynamic Analysis of Root Causes system (DARC), which finds root cause paths in a running program's call-graph using runtime latency analysis. A root cause path is a call-path that starts at a given function and includes the largest latency contributors to a given peak. These paths are the main causes for the high-level behavior that is represented as a peak in an OSprof histogram. DARC performs PID and call-path filtering to reduce overheads and perturbations, and can handle recursive and indirect calls. DARC can analyze preemptive behavior and asynchronous call-paths, and can also resume its analysis from a previous state, which is useful when analyzing short-running programs or specific phases of a program's execution.

We present DARC and show its usefulness by analyzing behaviors that were observed in several interesting scenarios. We also show that DARC has negligible elapsed time overheads for normal use cases.
Analysis of bittorrent-like protocols for on-demand stored media streaming
Authors: Parvez Nadim , Williamson Carey , Mahanti Anirban , Carlsson Niklas
Published: July 2008

This paper develops analytic models that characterize the behavior of on-demand stored media content delivery using BitTorrent-like protocols. The models capture the effects of different piece selection policies, including Rarest-First and two variants of In-Order. Our models provide insight into transient and steady-state system behavior, and help explain the sluggishness of the system with strict In-Order streaming. We use the models to compare different retrieval policies across a wide range of system parameters, including peer arrival rate, upload/download bandwidth, and seed residence time. We also provide quantitative results on the startup delays and retrieval times for streaming media delivery. Our results provide insights into the optimal design of peer-to-peer networks for on-demand media streaming.
Fully decentralized emulation of best-effort and processor sharing queues
Authors: Stanojevi Rade , Shorten Robert
Published: July 2008

Control of large distributed cloud-based services is a challenging problem. The Distributed Rate Limiting (DRL) paradigm was recently proposed as a mechanism for tackling this problem. The heuristic nature of existing DRL solutions makes their behavior unpredictable and analytically untractable. In this paper we treat the DRL problem in a mathematical framework and propose two novel DRL algorithms that exhibit good and predictable performance. The first algorithm Cloud Control with Constant Probabilities (C3P) solves the DRL problem in best effort environments, emulating the behavior of a single best-effort queue in a fully distributed manner. The second problem we approach is the DRL in processor sharing environments. Our algorithm, Distributed Deficit Round Robin (D2R2), parameterized by parameter α, converges to a state that is, at most,
O
(1/α) away from the exact emulation of centralized processor sharing queue. The convergence and stability properties are fully analyzed for both C3P and D2R2. Analytical results are validated empirically through a number of representative packet level simulations. The closed-form nature of our results allows simple design rules which, together with extremely low communication overhead, makes the presented algorithms practical and easy to deploy.
Revisiting stochastic loss networks
Authors: Jung Kyomin , Lu Yingdong , Shah Devavrat , Sharma Mayank , Squillante Mark S.
Published: July 2008

This paper considers structural and algorithmic problems in stochastic loss networks. The very popular Erlang approximation can be shown to provide relatively poor performance estimates, especially for loss networks in the critically loaded regime. This paper proposes a novel algorithm for estimating the stationary loss probabilities in stochastic loss networks based on structural properties of the exact stationary distribution, which is shown to always converge, exponentially fast, to the asymptotically exact results. Using a variational characterization of the stationary distribution, an alternative proof is provided for an important result due to Kelly, which is simpler and may be of interest in its own right. This paper also determines structural properties of the inverse Erlang function characterizing the region of capacities that ensures offered traffic is served within a set of loss probabilities. Numerical experiments investigate various issues of both theoretical and practical interest.
Efficient mart-aided modeling for microarchitecture design space exploration and performance prediction
Authors: Li Bin , Peng Lu , Ramadass Balachandran
Published: July 2008

Computer architects usually evaluate new designs by cycle-accurate processor simulation. This approach provides detailed insight into processor performance, power consumption and complexity. However, only configurations in a subspace can be simulated in practice due to long simulation time and limited resource, leading to suboptimal conclusions which might not be applied in a larger design space. In this paper, we propose an automated performance prediction approach which employs state-of-the-art techniques from experiment design, machine learning and data mining. Our method not only produces highly accurate estimations for unsampled points in the design space, but also provides interpretation tools that help investigators to understand performance bottlenecks. According to our experiments, by sampling only 0.02% of the full design space with about 15 millions points, the median percentage errors, based on 5000 independent test points, range from 0.32% to 3.12% in 12 benchmarks. Even for the worst-case performance, the percentage errors are within 7% for 10 out of 12 benchmarks. In addition, the proposed model can also help architects to find important design parameters and performance bottlenecks.
Modeling directionality in wireless networks
Authors: Anderson Eric W. , Phillips Caleb T. , Bauer Kevin S. , Grunwald Dirk C. , Sicker Douglas C.
Published: July 2008

The physical-layer models commonly used in current networking research only minimally address the interaction of directional antennas and radio propagation. This paper compares the models found in popular simulation tools with measurements taken across a variety of links in multiple environments. We find that the effects of antenna direction are significantly different from the models used by the common wireless network simulators. We propose a parametric model which better captures the effects of different propagation environments on directional antenna systems. We believe that adopting this model will allow more realistic simulation of protocols relying on directional antennas, supporting better design and more valid assessment of those protocols.
Clock offset estimation using collaborative one-way transit time
Authors: Mota-Garcia Edmar , Hasimoto-Beltran Rogelio
Published: July 2008

We propose a new collaborative clock offset estimation scheme between two nodes in the Internet using independent one-way offset estimations. Our proposal (different than current schemes in the literature) is intended to provide a fast and accurate clock offset estimation in approximately [Round-Trip Time (RTT)+40]ms. The scheme sends a group of 5 probes in the the forward and reverse paths, and models the One-way Transit Time (OTT) by a Gamma distribution (with parameters adapted to actual path condition) to estimate the minimum distribution value (or long-term minimum OTT value). End nodes exchange their corresponding minimum distribution values to get an improved final clock offset estimate, which takes into account the network path asymmetries. We show that our scheme provides a faster clock offset estimation with lower RMSE and superior stability than NTP and current NTP-like state of the art methodologies in the literature.
An integrated model of traffic, geography and economy in the internet
Authors: Holme Petter , Karlin Josh , Forrest Stephanie
Published: July 2008

Modeling Internet growth is important both for understanding the current network and to predict and improve its future. To date, Internet models have typically attempted to explain a subset of the following characteristics: network structure, traffic flow, geography, and economy. In this paper we present a discrete, agent-based model, that integrates all of them. We show that the model generates networks with topologies, dynamics, and more speculatively spatial distributions that are similar to the Internet.
You must be joking...
Authors: Faloutsos Michalis
Published: July 2008

The goal of this column this time was to address major scientific issues and propose novel scientific methods for doing the same thing under different names. However, it turned out to be too complicated as it required mastery of the english alphabet. Then, I had an epiphany (greek word): Why propose something new, when you can complain about something that already exists? I think I am turning into an angry old man prematurely.
Ethics considered harmful
Authors: Froelich Peter
Published: July 2008

Pardon the title, but I wanted to both grab your attention and get straight to the point (which naturally brings my own ethics in choosing the title into question). To clarify: I am referring to textbooks and courses on computer ethics, not to the field of ethics as taught to philosophy majors. I am also speaking only for myself, not for anyone else.
Sustainability & HeartTech
Authors: Muller Logan
Published: July 2008

First, thank you Flo and Joe for this initiative. I would love to make contact with more people interested and active in the use, place, impact and potential of computing in our society.
Web accessibility on campus
Authors: Jewett Tom
Published: July 2008

A number of universities have long-established and highly-regarded research programs in adaptation of information technology (IT) for disabled persons. Some universities have also instituted successful programs to apply accessible IT in various areas of their campuses. But it is safe to claim that no 23-campus university system, with 450,000 students and 46,000 faculty and staff, has ever before attempted to make its entire IT presence---web, instructional materials, and procurement---fully accessible within five years. Since February 2007, the California State University (CSU) system has been doing exactly that, through its ground-breaking Accessible Technology Initiative (ATI).
Oxytocin alleviates the neuroendocrine and cytokine response to bacterial endotoxin in healthy men
Authors: Clodi Martin , Vila Greisa , Geyeregger René , Riedl Michaela , Stulnig Thomas M. , Struck Joachim , Luger Thomas A. , Luger Anton
Published: July 2008

Oxytocin is a hormone and neurotransmitter found to have anti-inflammatory functions in rodents. Here we used experimental bacterial endotoxinemia to examine the role of exogenous oxytocin administration on innate immune responses in humans. Ten healthy men received, in a randomized, placebo-controlled, crossover design, placebo, oxytocin, LPS, and LPS + oxytocin. Oxytocin treatment resulted in a transient or prolonged reduction of endotoxin-induced increases in plasma ACTH, cortisol, procalcitonin, TNF-α, IL-1 receptor antagonist, IL-4, IL-6, macrophage inflammatory protein-1α, macrophage inflammatory protein-1β, monocyte chemoattractant protein-1 (MCP-1), interferon-inducible protein 10, and VEGF. In vitro, oxytocin had no impact on LPS effects in releasing TNF-α, IL-6, and MCP-1 in monocytes and peripheral blood mononuclear cells from healthy human donors. In summary, oxytocin decreases the neuroendocrine and cytokine activation caused by bacterial endotoxin in men, possibly due to the pharmacological modulation of the cholinergic anti-inflammatory pathway. Oxytocin might be a candidate for the therapy of inflammatory diseases and conditions associated with high cytokine and VEGF levels.
Prolonged hyperphagia with high-fat feeding contributes to exacerbated weight gain in rats with adult-onset obesity
Authors: Judge M. K. , Zhang J. , Tümer N. , Carter C. , Daniels M. J. , Scarpace P. J.
Published: July 2008

Leptin-resistant rats, when given a high-fat (HF) diet, have a delayed normalization of caloric intake and greater weight gain than those on a chow diet. Because aged, obese rats are leptin resistant, these data predict that they will also have a delayed normalization of caloric intake and exacerbated weight gain when provided a HF diet. To investigate this hypothesis, along with the consequences of a HF diet on voluntary wheel running, we compared various ages of rats on a HF or chow diet. HF-fed young rats spontaneously divided into diet-induced obese and diet-resistant rats. However, all aged rats were susceptible to the weight-gaining effects of HF feeding. Rate of initial weight gain was proportional to age, and peak caloric intake on the HF diet and the days required to normalize caloric intake to basal levels increased with age. Responsiveness to peripheral leptin before HF feeding revealed a dose-response decrease in food intake and body weight in the young but no responses in the aged to even the highest dose, 0.5 mg/day. In addition, both age and HF feeding decreased the tendency for wheel running, suggesting the propensity for inactivity with age and HF feeding may contribute to age-related obesity and accelerate the rate of diet-induced obesity. These results demonstrate that aged rats are more susceptible to the detrimental effects of a HF diet.
Neuromusculoskeletal Torque-Generation Process Has a Large Destabilizing Effect on the Control Mechanism of Quiet Standing
Authors: Masani Kei , Vette Albert H. , Kawashima Noritaka , Popovic Milos R.
Published: July 2008

The delay of the sensory-motor feedback loop is a destabilizing factor within the neural control mechanism of quiet standing. The purposes of this study were 1) to experimentally identify the neuromusculoskeletal torque-generation process during standing posture and 2) to investigate the effect of the delay induced by this system on the control mechanism of balance during quiet standing. Ten healthy adults participated in this study. The ankle torque, ankle angle, and electromyograms from the right lower leg muscles were measured. A ground-fixed support device was used to support the subject at his/her knees, without changing the natural ankle angle during quiet standing. Each subject was asked to mimic the ankle torque fluctuation by exerting voluntary ankle extension while keeping the supported standing posture. Using the rectified soleus electromyogram as the input and the ankle torque as the output, a critically damped, second-order system (twitch contraction time of 0.152 ± 0.027 s) successfully described the dynamics of the torque-generation process. According to the performed Bode analysis, the phase delay induced by this torque-generation process in the frequency region of spontaneous body sway during quiet standing was considerably large, corresponding to an effective time delay of about 200 to 380 ms. We compared the stability of the balance control system with and without the torque-generation process and demonstrated that a much smaller number of gain combinations can stabilize the model with the torque-generation process than without it. We concluded that the phase delay induced by the torque-generation process is a more destabilizing factor in the control mechanism of quiet standing than previously assumed, which restricts the control strategies that can stabilize the entire system.
Reach Adaptation: What Determines Whether We Learn an Internal Model of the Tool or Adapt the Model of Our Arm?
Authors: Kluzik JoAnn , Diedrichsen Jörn , Shadmehr Reza , Bastian Amy J.
Published: July 2008

We make errors when learning to use a new tool. However, the cause of error may be ambiguous: is it because we misestimated properties of the tool or of our own arm? We considered a well-studied adaptation task in which people made goal-directed reaching movements while holding the handle of a robotic arm. The robot produced viscous forces that perturbed reach trajectories. As reaching improved with practice, did people recalibrate an internal model of their arm, or did they build an internal model of the novel tool (robot), or both? What factors influenced how the brain solved this credit assignment problem? To investigate these questions, we compared transfer of adaptation between three conditions: catch trials in which robot forces were turned off unannounced, robot-null trials in which subjects were told that forces were turned off, and free-space trials in which subjects still held the handle but watched as it was detached from the robot. Transfer to free space was 40% of that observed in unannounced catch trials. We next hypothesized that transfer to free space might increase if the training field changed gradually, rather than abruptly. Indeed, this method increased transfer to free space from 40 to 60%. Therefore although practice with a novel tool resulted in formation of an internal model of the tool, it also appeared to produce a transient change in the internal model of the subject's arm. Gradual changes in the tool's dynamics increased the extent to which the nervous system recalibrated the model of the subject's own arm.
Random Volumetric MRI Trajectories via Genetic Algorithms
Authors: Curtis Andrew Thomas , Anand Christopher Kumar
Published: July 2008

A pseudorandom, velocity‐insensitive, volumetric k‐space sampling trajectory is designed for use with balanced steady‐state magnetic resonance imaging. Individual arcs are designed independently and do not fit together in the way that multishot spiral, radial or echo‐planar trajectories do. Previously, it was shown that second‐order cone optimization problems can be defined for each arc independent of the others, that nulling of zeroth and higher moments can be encoded as constraints, and that individual arcs can be optimized in seconds. For use in steady‐state imaging, sampling duty cycles are predicted to exceed 95 percent. Using such pseudorandom trajectories, aliasing caused by under‐sampling manifests itself as incoherent noise. In this paper, a genetic algorithm (GA) is formulated and numerically evaluated. A large set of arcs is designed using previous methods, and the GA choses particular fit subsets of a given size, corresponding to a desired acquisition time. Numerical simulations of 1 second acquisitions show good detail and acceptable noise for large‐volume imaging with 32 coils.
Passive Frequency Selective Surface Array as a Diffuser for Destroying Millimeter Wave Coherence
Authors: Islam Saiful , Stiens Johan , Poesen Gert , Jaeger Irina , Vounckx Roger
Published: July 2008

This paper presents the design, construction, and testing of grounded frequency selective surface (FSS) array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter). The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT), fabricated by etching technique, and characterized theS-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.
Pro‐ and Anti‐Inflammatory Cytokines Release in Mice Injected withCrotalus durissus terrificusVenom
Authors: Hernández Cruz A. , Garcia-Jimenez S. , Zucatelli Mendonça R. , Petricevich V. L.
Published: July 2008

The effects ofCrotalus durissus terrificusvenom (Cdt) were analyzed with respect to the susceptibility and the inflammatory mediators in an experimental model of severe envenomation. BALB/c female mice injected intraperitoneally presented sensibility to Cdt, with changes in specific signs, blood biochemical and inflammatory mediators. The venom induced reduction of glucose and urea levels and an increment of creatinine levels in serum from mice. Significant differences were observed in the time‐course of mediator levels in sera from mice injected with Cdt. The maximum levels of IL‐6, NO, IL‐5, TNF, IL‐4 and IL‐10 were observed 15 min, 30 min, 1, 2 and 4 hours post‐injection, respectively. No difference was observed for levels of IFN‐γ. Taken together, these data indicate that the envenomation by Cdt is regulated both pro‐ and anti‐inflammatory cytokine responses at time‐dependent manner. In serum from mice injected with Cdt at the two first hours revealed of pro‐inflammatory dominance. However, with an increment of time an increase of anti‐inflammatory cytokines was observed and the balance toward to anti‐inflammatory dominance. In conclusion, the observation that Cdt affects the production of pro‐ and anti‐inflammatory cytokines provides further evidence for the role played by Cdt in modulating pro/anti‐inflammatory cytokine balance.