bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms behind the puzzle: microtubule–microfilament cross-talk in pavement cell formationThis review is one of a selection of papers published in the Special Issue on Plant Cell Biology.
Authors: Kotzer A.M. , Wasteneys G.O.
Published: July 2006

Recent studies are revealing plausible mechanisms that help explain how the two major cytoskeletal systems of plant cells interact to co-ordinate morphogenesis in diffusely expanding cells. In this article, we focus on the development of pavement cells typically found in the leaf epidermis, and highlight work that provides insights into the mechanisms that generate their complex morphology. Pavement cells interdigitate with adjacent cells, forming narrow neck regions interspersed with lobe-like projections. Earlier analysis demonstrated that distinct banding of cortical microtubules and associated accumulation of cell wall material was responsible for maintaining the neck regions during expansion. More recently, it has been determined that patches of fine actin microfilaments regulate the formation of lobing regions. This zonation into microtubule-rich bands and actin patches is coordinated by the activity of Rops, small GTPases that control a wide range of signalling pathways including ones that remodel both actin microfilament and microtubule arrays. Moreover, the formation of microtubule bands and actin patches seems to be self-reinforcing. Loss of microtubule polymers by drug treatment or mutation broadens actin patch formation, apparently by enhancing Rop interactions with a positive regulator of actin polymerization. Thus, cross-talk between microtubule and actin microfilament networks is essential for coordinating and reinforcing pavement cell morphogenesis.
Masterminds or minions? Cysteine proteinases in plant programmed cell deathThis review is one of a selection of papers published in the Special Issue on Plant Cell Biology.
Authors: Trobacher Christopher P. , Senatore Adriano , Greenwood John S.
Published: July 2006

Cysteine proteinases are ubiquitously involved in programmed cell death (PCD) in multicellular organisms. In animals, one group of cysteine proteinases, the cysteine-dependent aspartate-specific proteinases (caspases), are involved in a proteolytic signalling cascade that controls apoptosis, the most studied form of PCD. The enzymes act as both masterminds and executioners in apoptotic cell death. In plants, members of the metacaspase family, as well as those of the papain-like and legumain families, of cysteine proteinases have all been implicated in PCD. These enzymes often belong to sizeable gene families, with Arabidopsis having 9 metacaspase, 32 papain-like, and 4 legumain genes. This redundancy has made it difficult to ascertain the functional importance of any particular enzyme in plant PCD, as many are often expressed in a given tissue undergoing PCD. As yet, mechanisms similar to the apoptotic caspase cascade in animals have not been uncovered in plants and, indeed, may not exist. Are the various cysteine proteinases, so often implicated in plant PCD, merely acting as minions in the process? This review will outline reports of cysteine proteinases associated with plant PCD, discuss problems in determining the function of specific proteases, and suggest avenues for determining how these enzymes might be regulated and how PCD pathways upstream of protease expression and activation might operate.
Coupled landscape-lake evolution in High Arctic Canada
Authors: Hove Patrick Van , Belzile Claude , Gibson John AE , Vincent Warwick F
Published: July 2006

We profiled five ice-covered lakes and two ice-covered fiords of Ellesmere Island at the northern limit of High Arctic Canada to examine their environmental characteristics, and to evaluate the long-term limnological consequences of changes in their surrounding landscape through time (landscape evolution). All of the ecosystems showed strong patterns of thermal, chemical, and biological stratification with subsurface temperature maxima from 0.75 to 12.15 °C; conductivities up to 98.1 mS cm1 (twice that of seawater) in some bottom waters; pronounced gradients in nitrogen, phosphorus, pH, dissolved inorganic and organic carbon, manganese, iron, and oxygen; and stratified photo synthetic communities. These ecosystems form an inferred chronosequence that reflects different steps of landscape evolution including marine embayments open to the sea, inlets blocked by thick sea ice (Disraeli Fiord, Taconite Inlet), perennially ice-capped, saline lakes isolated from the sea by isostatic uplift (Lakes A, C1, C2), and isolated lakes that lose their ice cover in summer. The latter are subject to entrainment of saline water into their upper water column by wind-induced mixing (Lake Romulus; Lake A in 2000), or complete flushing of their basins by dilute snowmelt (Lake C3 and Char Lake, which lies 650 km to the south of the Ellesmere lakes region). This chronosequence illustrates how changes in geomorphology and other landscape properties may influence the limnology of coastal, high-latitude lakes, and it provides a framework to explore the potential impacts of climate change.
New, biostratigraphically significant ammonites from the Jurassic Fernie Formation, southern Canadian Rocky Mountains
Authors: Hall Russell L
Published: July 2006

Jurassic ammonites described here for the first time come from numerous localities in the Fernie Formation in the Foothills and Front Ranges of the Rocky Mountains of north- and south-eastern British Columbia and central- and south-western Alberta, and provide useful new age data for several members of the formation. The occurrence of Orthodactylites sp. in the uppermost beds of the Red Deer Member indicates this unit extends upwards into the basal Toarcian, which will be helpful in the search for carbon-isotope excursions associated with the early Toarcian anoxic event. The presence of Hettangian and lower Pliensbachian strata in outcrop of the Gordondale Member is confirmed. Diversity of the ammonite fauna in the Grey Beds is enlarged by the presence of ? Kepplerites  ? Cadomites and Choffatia spp. These faunas also provide biostratigraphic constraints for carbon- and oxygen-isotope trends and UPb ages recently recorded from the Highwood Member and Grey Beds exposed in Bighorn Creek and its eastern tributary, and in Fording River. The first occurrence of Zemistephanus richardsoni from cratonic rocks, recorded here, suggests close proximity of the allochthonous terranes Wrangellia and Stikinia, the only other areas from which this species is known, to the northwest North American craton by early Bajocian time. One new species, Cardioceras (Subvertebriceras) ferniensis, is described.
Age constraints for Paleoproterozoic glaciation in the Lake Superior Region: detrital zircon and hydrothermal xenotime ages for the Chocolay Group, Marquette Range Supergroup
Authors: Vallini Daniela A , Cannon William F , Schulz Klaus J
Published: July 2006

A geochronological study of the Chocolay Group at the base of the Paleoproterozoic Marquette Range Supergroup in Michigan, Lake Superior Region, is attempted for the first time. Age data from detrital zircon grains and hydrothermal xenotime from the basal glaciogenic formation, the Enchantment Lake Formation, and the stratigraphically higher Sturgeon Quartzite and its equivalent, the Sunday Quartzite, provide maximum and minimum age constraints for the Chocolay Group. The youngest detrital zircon population in the Enchantment Lake Formation is 2317 ± 6 Ma; in the Sturgeon Quartzite, it is 2306 ± 9 Ma, and in the Sunday Quartzite, it is 2647 ± 5 Ma. The oldest hydrothermal xenotime age in the Enchantment Lake Formation is 2133 ± 11 Ma; in the Sturgeon Quartzite, it is 2115 ± 5 Ma, and in the Sunday Quartzite, it is 2207 ± 5 Ma. The radiometric age data in this study implies the depositional age of the Chocolay Group is constrained to ~2.32.2 Ga, which proves its correlation with part of the Huronian Supergroup in the Lake Huron Region, Ontario, and reveals the unconformity that separates the Chocolay Group from the overlying Menominee Group is up to 325 million years in duration. The source(s) of the ~ 2.3 Ga detrital zircon populations in the Enchantment Lake Formation and Sturgeon Quartzite remains an enigma because no known rock units of this age are known in the Michigan area. It is speculated that once widespread volcano-sedimentary cover sequences in Michigan were removed or concealed prior to Chocolay Group deposition. The hydrothermal xenotime ages probably reflect basinal hydrothermal fluid flow associated with the period of extension, involving rifting and major dyke formation, that affected the North American provinces between 2.2 and 2.1 Ga.
Translating restoration scenarios into habitat conditions: an initial step in evaluating recovery strategies for Chinook salmon (Oncorhynchus tshawytscha)
Authors: Bartz Krista K , Lagueux Kerry M , Scheuerell Mark D , Beechie Tim , Haas Andrew D , Ruckelshaus Mary H
Published: July 2006

One of the challenges associated with recovering imperiled species, such as Chinook salmon (Oncorhynchus tshawytscha), is identifying a set of actions that will ensure species' persistence. Here we evaluate the effects of alternative land use scenarios on habitat conditions potentially important to Chinook salmon. We first summarize the alternative scenarios as target levels for certain land use characteristics. We then use the target levels to estimate changes in current habitat conditions. The scenarios we explore indicate considerable potential to improve both the quality and quantity of salmon habitat through protection and restoration. Results from this analysis constitute the habitat inputs to a population model linking changes in habitat to salmon population status. By transparently documenting the approach we use to translate land use actions into changes in salmon habitat conditions, we provide decision makers with a clear basis for choosing strategies to recover salmon.
Comparisons between hatchery and wild steelhead trout (Oncorhynchus mykiss) smolts: physiology and habitat use
Authors: Hill Megan S , Zydlewski Gayle Barbin , Gale William L
Published: July 2006

Hatchery steelhead trout (Oncorhynchus mykiss) smolts, progeny of a newly founded native origin broodstock, were released into Abernathy Creek, Washington, in 2003 and 2004. After release, saltwater tolerance, gill Na+,K+-ATPase activity, and habitat use were compared. A subsample of hatchery and wild steelhead trout were implanted with 23 mm passive integrated transponder (PIT) tags each year. PIT-tagged migrants were used for physiological comparisons. Hatchery fish were significantly larger than wild fish. Hatchery migrants expressed significantly lower levels of gill Na+,K+-ATPase activity than wild migrants. After a 24 h seawater challenge, hatchery migrants had significantly higher plasma osmolality and [Na+] than wild migrants. Microhabitat use of PIT-tagged hatchery and wild individuals in a control (wild fish only) and effect (hatchery and wild fish) site were compared before and after the introduction of hatchery fish. No difference was detected in hatchery and wild smolt habitat use. Wild fish did not change their habitat use after the introduction of hatchery fish. Although hatchery and wild fish differed in smolt physiology, differences in short-term use of freshwater habitat were not detected, and hatchery fish did not appear to displace wild fish.
Synthesis and characterization of a series of 3-methyl-3-{3-[1-methyl-3-aryl-2-triazenyl]propyl}-1-aryl-1-triazenes and related compounds
Authors: Clarke Jeff D , Moser Shasta L , Vaughan Keith
Published: July 2006

A series of diazonium salts has been coupled to both secondary nitrogen atoms of the bis-secondary amine, N,N′-dimethyl-1,3-propanediamine (MeNHCH2CH2CH2NHMe), to afford the new bistriazene series, the 3-methyl-3-{3-[1-methyl-3-aryl-2-triazenyl]propyl}-1-aryl-1-triazenes (9). These compounds have been fully characterized by IR and NMR spectroscopy, with supporting data from elemental analysis and high-resolution mass spectrometry. A limited number of model compounds in the N,N-dimethyl-N-{3-[1-methyl-3-aryl-2-triazenyl]propyl}amine series (10) have been synthesized to aid in the interpretation of the NMR spectra of the bistriazenes (9). A series of related compounds, the 3-ethyl-3-{(E)-4-[1-ethyl-3-aryl-2-triazenyl]-2-butenyl}-1-aryl-1-triazenes (11), have been synthesized by diazonium coupling with the bis-secondary amine N,N′-diethyl-2-butene-1,4-diamine (15), and the diazonium coupling reaction with trans-N,N′-dimethycyclohexane-1,2-diamine (19) has been used to prepare another related series of bistriazenes, the 3-methyl-3-{2-[1-methyl-3-aryl-2-triazenyl]cyclohexyl}-1-aryl-1-triazenes (12). The 1H NMR spectra of these compounds are complex because of the presence of two chiral centres in the cyclohexanediamine moiety; the diastereotopic protons of the methylene groups in the cyclohexane ring are clearly distinguished in the 500 MHz spectra of these compounds.Key words: triazene, bistriazene, synthesis, nuclear magnetic resonance, propanediamine, 1,4-diamino-2-butene, cyclohexanediamine.
Welfare effects of forestry best management practices in the United States
Authors: Sun Changyou
Published: July 2006

State forestry best management practice (BMP) programs have been widely developed and implemented to prevent nonpoint source water pollution in the past three decades. The unanswered question is how forestry BMPs have affected the welfare positions of consumers, mills, loggers, and forest landowners. A Muth-type equilibrium displacement model was constructed to examine welfare changes of these stakeholders. The model considered a two-stage vertical production system with variable proportion production technology and imperfect market structure. Industrial mills experienced little welfare loss from forestry BMP regulation. Consumers had the largest absolute welfare loss, and loggers had the largest relative welfare loss in the base scenario. The supply elasticity of harvesting services had the greatest impact on the relative incidence of welfare losses between landowners and loggers, and in the long run their welfare losses were comparable. These results may help to improve future state forestry BMP guidelines and design incentive systems for increasing implementation rates.
Age-independent difference equations for modelling tree and stand growth
Authors: Tomé José , Tomé Margarida , Barreiro Susana , Paulo Joana Amaral
Published: July 2006

Modelling growth of trees or stands when age is not available is often necessary. This is the case in national forest inventories or when age is not a main determinant of growth (e.g., trees growing in uneven-aged stands). Even if age is not known, functions used to model growth should follow the required pattern, with a maximum and a slow decline after the maximum is attained. There are some empirical functions with these properties; however, direct modelling with difference equations derived from the so-called theoretical growth functions has not been used for this purpose, as they are age dependent. This paper presents a methodology to formulate growth functions as age-independent difference equations. These can be used when age is not available or is not relevant. The proposed equations have the advantage of allowing the direct modelling of yield instead of growth. If the parameters are expressed as a function of site variables, the equations are invariant for projection length and therefore can be used when data is not equally spaced in time, as is the case of most data sets. The methodology is applied to the Lundqvist and Richards growth functions, the most commonly used in growth and yield modelling. The use of the age-independent growth functions is illustrated by using two case studies in Portugal: dominant height growth of eucalyptus (Eucalyptus globulus Labill.) plantations and individual tree growth in diameter at breast height in sparse cork oak (Quercus suber L.) stands.
Ten-year effect of dolomitic lime on the nutrition, crown vigor, and growth of sugar maple
Authors: Moore Jean-David , Ouimet Rock
Published: July 2006

In a base-poor northern hardwood stand in Quebec, subjected to high acid deposition, sugar maple (Acer saccharum Marsh.) nutrition, growth, and crown vigor were evaluated 10 years after application of 0–50 t·ha–1 of CaMg(CO3)2 in 1994. One decade after treatment, foliar calcium and magnesium concentrations of sugar maple were still higher for treated than for control trees. The analysis of foliar nutrient indices showed that liming improved the nutrition of nitrogen and calcium, but caused imbalance of phosphorus, potassium, and magnesium. In 2004, crown dieback was much lower for limed trees (0.5%–4.5%) as compared to unlimed trees (23.7%). When compared with crown dieback before treatment, dieback of limed trees generally had decreased by 2004, while dieback of untreated maple trees increased over the 1994–2004 period. In 2004, basal area increment for limed trees was nearly double that of unlimed trees. However, no difference was detectable among trees limed at different rates. Midterm efficacy of liming in this study was demonstrated by the improvement of sugar maple calcium nutrition, crown vigor, and stem growth 10 years following treatment. This confirms the potential of liming to limit damage caused by acid deposition in base-poor and declining northern hardwood stands.
SNIAFL
Authors: Zhao Wei , Zhang Lu , Liu Yin , Sun Jiasu , Yang Fuqing
Published: July 2006

To facilitate software maintenance and evolution, a helpful step is to locate features concerned in a particular maintenance task. In the literature, both dynamic and interactive approaches have been proposed for feature location. In this article, we present a static and noninteractive method for achieving this objective. The main idea of our approach is to use information retrieval (IR) technology to reveal the basic connections between features and computational units in the source code. Due to the imprecision of retrieved connections, we use a static representation of the source code named BRCG (branch-reserving call graph) to further recover both relevant and specific computational units for each feature. A premise of our approach is that programmers should use meaningful names as identifiers. We also performed an experimental study based on two real-world software systems to evaluate our approach. According to experimental results, our approach is quite effective in acquiring the relevant and specific computational units for most features.
Dual Flow Nets
Authors: Varea Mauricio , Al-Hashimi Bashir M. , CortéS Luis A. , Eles Petru , Peng Zebo
Published: July 2006

This paper addresses the interrelation between control and data flow in embedded system models through a new design representation, called Dual Flow Net (DFN). A modeling formalism with a very close-fitting control and data flow is achieved by this representation, as a consequence of enhancing its underlying Petri net structure. The work presented in this paper does not only tackle the modeling side in embedded systems design, but also the validation of embedded system models through formal methods. Various introductory examples illustrate the applicability of the DFN principles, whereas the capability of the model to with complex designs is demonstrated through the design and verification of a real-life Ethernet coprocessor.
Predicate abstraction for reachability analysis of hybrid systems
Authors: Alur Rajeev , Dang Thao , Ivančić Franjo
Published: July 2006

Embedded systems are increasingly finding their way into a growing range of physical devices. These embedded systems often consist of a collection of software threads interacting concurrently with each other and with a physical, continuous environment. While continuous dynamics have been well studied in control theory, and discrete and distributed systems have been investigated in computer science, the combination of the two complexities leads us to the recent research on
hybrid systems
. This paper addresses the formal analysis of such hybrid systems. Predicate abstraction has emerged to be a powerful technique for extracting finite-state models from infinite-state discrete programs. This paper presents algorithms and tools for reachability analysis of hybrid systems by combining the notion of predicate abstraction with recent techniques for approximating the set of reachable states of linear systems using polyhedra. Given a hybrid system and a set of predicates, we consider the finite discrete quotient whose states correspond to all possible truth assignments to the input predicates. The tool performs an on-the-fly exploration of the abstract system. We present the basic techniques for guided search in the abstract state-space, optimizations of these techniques, implementation of these in our verifier, and case studies demonstrating the promise of the approach. We also address the completeness of our abstraction-based verification strategy by showing that predicate abstraction of hybrid systems can be used to prove bounded safety.
Efficient remote profiling for resource-constrained devices
Authors: Nagpurkar Priya , Mousa Hussam , Krintz Chandra , Sherwood Timothy
Published: July 2006

The widespread use of ubiquitous, mobile, and continuously connected computing agents has inspired software developers to change the way they test, debug, and optimize software. Users now play an active role in the software evolution cycle by dynamically providing valuable feedback about the execution of a program to developers. Software developers can use this information to isolate bugs in, maintain, and improve the performance of a wide-range of diverse and complex embedded device applications. The collection of such feedback poses a major challenge to systems researchers since it must be performed without degrading a user's experience with, or consuming the severely restricted resources of the mobile device. At the same time, the resource constraints of embedded devices prohibit the use of extant software profiling solutions. To achieve efficient remote profiling of embedded devices, we couple two efficient hardware/software program monitoring techniques: Hybrid Profiling Support(HPS) and Phase-Aware Sampling. HPS efficiently inserts profiling instructions into an executing program using a novel extension to Dynamic-Instruction Stream Editing(DISE). Phase-aware sampling exploits the recurring behavior of programs to identify key opportunities during execution in order to collect profile information (i.e. sample). Our prior work on phase-aware sampling required code duplication to toggle sampling. By guiding low-overhead, hardware-supported sampling according to program phase behavior via HPS, our system is able to collect highly accurate profiles transparently. We evaluate our system assuming a general purpose configuration as well as a popular handheld device configuration. We measure the accuracy and overhead of our techniques and quantify the overhead in terms of computation, communication, and power consumption. We compare our system to random and periodic sampling for a number of widely used performance profile types. Our results indicate that our system significantly reduces the overhead of sampling while maintaining high accuracy.
The application of model checking for securing e-commerce transactions
Authors: Anderson Bonnie Brinton , Hansen James V. , Lowry Paul Benjamin , Summers Scott L.
Published: July 2006

Model checking is an effective component for performing online transactions that build customer trust and confidence.
Copyrighting standards
Authors: Samuelson Pamela
Published: July 2006

Should standards be eligible for copyright protection?
Security through legality
Authors: Bono Stephen , Rubin Aviel , Stubblefield Adam , Green Matthew
Published: July 2006

The law alone won't prevent an unauthorized visit or even a deliberate attack. Security depends on being able to think like an attacker.
Automatic complex schema matching across Web query interfaces
Authors: He Bin , Chang Kevin Chen-Chuan
Published: July 2006

To enable information integration, schema matching is a critical step for discovering semantic correspondences of attributes across heterogeneous sources. While complex matchings are common, because of their far more complex search space, most existing techniques focus on simple 1:1 matchings. To tackle this challenge, this article takes a conceptually novel approach by viewing schema matching as
correlation mining
, for our task of matching Web query interfaces to integrate the myriad databases on the Internet. On this “deep Web ” query interfaces generally form
complex matchings
between attribute groups (e.g., {author} corresponds to {first name, last name} in the Books domain). We observe that the co-occurrences patterns across query interfaces often reveal such complex semantic relationships:
grouping attributes
(e.g., {first name, last name}) tend to be co-present in query interfaces and thus positively correlated. In contrast,
synonym attributes
are negatively correlated because they rarely co-occur. This insight enables us to discover complex matchings by a correlation mining approach. In particular, we develop the DCM framework, which consists of
data preprocessing
,
dual mining
of positive and negative correlations, and finally
matching construction
. We evaluate the DCM framework on manually extracted interfaces and the results show good accuracy for discovering complex matchings. Further, to automate the entire matching process, we incorporate automatic techniques for interface extraction. Executing the DCM framework on automatically extracted interfaces, we find that the inevitable errors in automatic interface extraction may significantly affect the matching result. To make the DCM framework robust against such “noisy” schemas, we integrate it with a novel “ensemble” approach, which creates an ensemble of DCM matchers, by randomizing the schema data into many
trials
and aggregating their ranked results by taking majority voting. As a principled basis, we provide analytic justification of the robustness of the ensemble approach. Empirically, our experiments show that the “ensemblization” indeed significantly boosts the matching accuracy, over automatically extracted and thus noisy schema data. By employing the DCM framework with the ensemble approach, we thus complete an automatic process of matchings Web query interfaces.
A taxonomy of Data Grids for distributed data sharing, management, and processing
Authors: Venugopal Srikumar , Buyya Rajkumar , Ramamohanarao Kotagiri
Published: July 2006

Data Grids have been adopted as the next generation platform by many scientific communities that need to share, access, transport, process, and manage large data collections distributed worldwide. They combine high-end computing technologies with high-performance networking and wide-area storage management techniques. In this article, we discuss the key concepts behind Data Grids and compare them with other data sharing and distribution paradigms such as content delivery networks, peer-to-peer networks, and distributed databases. We then provide comprehensive taxonomies that cover various aspects of architecture, data transportation, data replication and resource allocation, and scheduling. Finally, we map the proposed taxonomy to various Data Grid systems not only to validate the taxonomy but also to identify areas for future exploration.
Algorithm 851
Authors: Hager William W. , Zhang Hongchao
Published: July 2006

Recently, a new nonlinear conjugate gradient scheme was developed which satisfies the descent condition
g
T

k

d

k

≤ −7/8 ‖
g

k

‖
2
and which is globally convergent whenever the line search fulfills the Wolfe conditions. This article studies the convergence behavior of the algorithm; extensive numerical tests and comparisons with other methods for large-scale unconstrained optimization are given.
Algorithm 852
Authors: Granvilliers Laurent , Benhamou Frédéric
Published: July 2006

RealPaver is an interval software for modeling and solving nonlinear systems. Reliable approximations of continuous or discrete solution sets are computed using Cartesian products of intervals. Systems are given by sets of equations or inequality constraints over integer and real variables. Moreover, they may have different natures, being square or nonsquare, sparse or dense, linear, polynomial, or involving transcendental functions.The modeling language permits stating constraint models and tuning parameters of solving algorithms which efficiently combine interval methods and constraint satisfaction techniques. Several consistency techniques (box, hull, and 3B) are implemented. The distribution includes C sources, executables for different machine architectures, documentation, and benchmarks. The portability is ensured by the GNU C compiler.
CAVA
Authors: Ceze Luis , Strauss Karin , Tuck James , Torrellas Josep , Renau Jose
Published: July 2006

Modern superscalar processors often suffer long stalls because of load misses in on-chip L2 caches. To address this problem, we propose hiding L2 misses with Checkpoint-Assisted VAlue prediction (CAVA). On an L2 cache miss, a predicted value is returned to the processor. When the missing load finally reaches the head of the ROB, the processor checkpoints its state, retires the load, and speculatively uses the predicted value and continues execution. When the value in memory arrives at the L2 cache, it is compared to the predicted value. If the prediction was correct, speculation has succeeded and execution continues; otherwise, execution is rolled back and restarted from the checkpoint. CAVA uses fast checkpointing, speculative buffering, and a modest-sized value prediction structure that has about 50% accuracy. Compared to an aggressive superscalar processor, CAVA speeds up execution by up to 1.45 for SPECint applications and 1.58 for SPECfp applications, with a geometric mean of 1.14 for SPECint and 1.34 for SPECfp applications. We also evaluate an implementation of Runahead execution---a previously proposed scheme that does not perform value prediction and discards all work done between checkpoint and data reception from memory. Runahead execution speeds up execution by a geometric mean of 1.07 for SPECint and 1.18 for SPECfp applications, compared to the same baseline.
Thermal issues in disk drive design
Authors: Gurumurthi Sudhanva , Sivasubramaniam Anand
Published: July 2006

The importance of pushing the performance envelope of disk drives continues to grow in the enterprise storage market. One of the most fundamental factors impacting disk drive design is heat dissipation, since it directly affects drive reliability. Until now, drive manufacturers have continued to meet the 40% annual growth target of the internal data-rates (IDR) by increasing RPMs and shrinking platter sizes, both of which have counteracting effects on the heat dissipation within a drive. In this article, we shall show that we are getting to a point where it is going to be very difficult to stay on this roadmap. We first present detailed models that capture the close relationships between capacity, performance, and thermal characteristics over time. Using these models, we quantify the drop-off in IDR growth rates over the next decade if we are to adhere to the thermal design envelope. We motivate the need for continued improvements in IDR by showing that the response times of real workloads can be improved by 30--60% with a 10K increase in the RPM for disks used in their respective storage systems. We then present two dynamic thermal management (DTM) techniques that can be used to buy back some of this IDR loss. The first DTM technique exploits the thermal slack between what the drive was intended to support and the currently lower operating temperature to ramp up the RPM. The second DTM technique assumes that the drive is only designed for average case operation and dynamically throttles its activities to remain within the thermal envelope.
Trust in videoconferencing
Authors: Bekkering Ernst , Shim J.P.
Published: July 2006

People associate poor eye contact with deception. This perception may have hurt large-scale adoption of videoconferencing technology.
Principles of problem solving
Authors: Wegner Peter , Goldin Dina
Published: July 2006

Changed paradigms of human thought are needed to adapt modes of computer problem solving and truth to evolving computational technology.
Enterprise transformation
Authors: Rouse William B. , Baba Marietta L.
Published: July 2006

Fundamental enterprise changes begin by looking at the challenges from technical, behavioral, and social perspectives.
Computing machine-efficient polynomial approximations
Authors: Brisebarre Nicolas , Muller Jean-Michel , Tisserand Arnaud
Published: July 2006

Polynomial approximations are almost always used when implementing functions on a computing system. In most cases, the polynomial that best approximates (for a given distance and in a given interval) a function has coefficients that are not exactly representable with a finite number of bits. And yet, the polynomial approximations that are actually implemented do have coefficients that are represented with a finite---and sometimes small---number of bits. This is due to the finiteness of the floating-point representations (for software implementations), and to the need to have small, hence fast and/or inexpensive, multipliers (for hardware implementations). We then have to consider polynomial approximations for which the degree-
i
coefficient has at most
m

i

fractional bits; in other words, it is a rational number with denominator 2

m

i

. We provide a general and efficient method for finding the best polynomial approximation under this constraint. Moreover, our method also applies if some other constraints (such as requiring some coefficients to be equal to some predefined constants or minimizing relative error instead of absolute error) are required.
Error bounds from extra-precise iterative refinement
Authors: Demmel James , Hida Yozo , Kahan William , Li Xiaoye S. , Mukherjee Sonil , Riedy E. Jason
Published: July 2006

We present the design and testing of an algorithm for iterative refinement of the solution of linear equations where the residual is computed with extra precision. This algorithm was originally proposed in 1948 and analyzed in the 1960s as a means to compute very accurate solutions to all but the most ill-conditioned linear systems. However, two obstacles have until now prevented its adoption in standard subroutine libraries like LAPACK: (1) There was no standard way to access the higher precision arithmetic needed to compute residuals, and (2) it was unclear how to compute a reliable error bound for the computed solution. The completion of the new BLAS Technical Forum Standard has essentially removed the first obstacle. To overcome the second obstacle, we show how the application of iterative refinement can be used to compute an error bound in any norm at small cost and use this to compute both an error bound in the usual infinity norm, and a componentwise relative error bound.We report extensive test results on over 6.2 million matrices of dimensions 5, 10, 100, and 1000. As long as a normwise (componentwise) condition number computed by the algorithm is less than 1/max{10,√n}εw, the computed normwise (componentwise) error bound is at most 2 max{10,√n} · εw, and indeed bounds the true error. Here,nis the matrix dimension and εw= 2-24is the working precision. Residuals were computed in double precision (53 bits of precision). In other words, the algorithm always computed a tiny error at negligible extra cost for most linear systems. For worse conditioned problems (which we can detect using condition estimation), we obtained small correct error bounds in over 90% of cases.
Algorithm 854
Authors: Benner Peter , Kressner Daniel
Published: July 2006

This article describes Fortran 77 subroutines for computing eigenvalues and invariant subspaces of Hamiltonian and skew-Hamiltonian matrices. The implemented algorithms are based on orthogonal symplectic decompositions, implying numerical backward stability as well as symmetry preservation for the computed eigenvalues. These algorithms are supplemented with balancing and block algorithms which can lead to considerable accuracy and performance improvements. As a by-product, an efficient implementation for computing symplectic QR decompositions is provided. We demonstrate the usefulness of the subroutines for several, practically relevant examples.
Evaluation of spatial displays for navigation without sight
Authors: Marston James R. , Loomis Jack M. , Klatzky Roberta L. , Golledge Reginald G. , Smith Ethan L.
Published: July 2006

We report on two route guidance tasks using a highly accurate GPS receiver. Eight participants who were visually impaired or blind traveled two routes, one on a city sidewalk, and one in a city park. We tested and compared two types of spatial output devices that give route guidance information. One output display used a hand-held pointer, using a standard Talking Signs receiver that integrated the GPS signal information with the Talking Signs® signal information. This device gave travel instructions and on-course confirmation when pointed in the proper direction. The other spatial display used auditory virtual reality that presented the audible spatial information (waypoint direction and distance) through small air-tubes inserted into the ear. Travel times, distance, and errors were recorded. In addition, we tested users' ability to find precise locations, such as the intersections of small paths and a bus stop pole. Various subjective ratings were collected about blind participants' needs and perception of the various display and output options that they used. All subjects completed the tasks with both output displays, found all the waypoints and locations, and rated the two displays highly. The virtual sound display produced superior times overall and received slightly higher favorable ratings.
Haptic discrimination of force direction and the influence of visual information
Authors: Barbagli Federico , Salisbury Ken , Ho Cristy , Spence Charles , Tan Hong Z.
Published: July 2006

Despite a wealth of literature on discrimination thresholds for displacement, force magnitude, stiffness, and viscosity, there is currently a lack of data on our ability to discriminate force directions. Such data are needed in designing haptic rendering algorithms where force direction, as well as force magnitude, are used to encode information such as surface topography. Given that haptic information is typically presented in addition to visual information in a data perceptualization system, it is also important to investigate the extent to which the congruency of visual information affects force-direction discrimination. In this article, the authors report an experiment on the discrimination threshold of force directions under the three display conditions of haptics alone (H), haptics plus congruent vision (HVcong), and haptics plus incongruent vision (HVincong). Average force-direction discrimination thresholds were found to be 18.4°, 25.6°, and 31.9° for the HVcong, H and HVincong conditions, respectively. The results show that the congruency of visual information significantly affected haptic discrimination of force directions, and that the force-direction discrimination thresholds did not seem to depend on the reference force direction. The implications of the results for designing haptic virtual environments, especially when the numbers of sensors and actuators in a haptic display do not match, are discussed.
Fast median and bilateral filtering
Authors: Weiss Ben
Published: July 2006

Median filtering is a cornerstone of modern image processing and is used extensively in smoothing and de-noising applications. The fastest commercial implementations (e.g. in Adobe® Photoshop® CS2) exhibit
O(r)
runtime in the radius of the filter, which limits their usefulness in realtime or resolution-independent contexts. We introduce a CPU-based, vectorizable
O
(log
r
) algorithm for median filtering, to our knowledge the most efficient yet developed. Our algorithm extends to images of any bit-depth, and can also be adapted to perform bilateral filtering. On 8-bit data our median filter outperforms Photoshop's implementation by up to a factor of fifty.
A compact factored representation of heterogeneous subsurface scattering
Authors: Peers Pieter , vom Berge Karl , Matusik Wojciech , Ramamoorthi Ravi , Lawrence Jason , Rusinkiewicz Szymon , Dutré Philip
Published: July 2006

Many translucent materials exhibit heterogeneous subsurface scattering, which arises from complex internal structures. The acquisition and representation of these scattering functions is a complex problem that has been only partially addressed in previous techniques. Unlike homogeneous materials, the spatial component of heterogeneous subsurface scattering can vary arbitrarily over surface locations. Storing the spatial component without compression leads to impractically large datasets. In this paper, we address the problem of acquiring and compactly representing the spatial component of heterogeneous subsurface scattering functions. We propose a material model based on matrix factorization that can be mapped onto arbitrary geometry, and, due to its compact form, can be incorporated into most visualization systems with little overhead. We present results of several real-world datasets that are acquired using a projector and a digital camera.
Flash matting
Authors: Sun Jian , Li Yin , Kang Sing Bing , Shum Heung-Yeung
Published: July 2006

In this paper, we propose a novel approach to extract mattes using a pair of flash/no-flash images. Our approach, which we call
flash matting
, was inspired by the simple observation that the most noticeable difference between the flash and no-flash images is the foreground object if the background scene is sufficiently distant. We apply a new matting algorithm called
joint Bayesian flash matting
to robustly recover the matte from flash/no-flash images, even for scenes in which the foreground and the background are similar or the background is complex. Experimental results involving a variety of complex indoors and outdoors scenes show that it is easy to extract high-quality mattes using an off-the-shelf, flash-equipped camera. We also describe extensions to flash matting for handling more general scenes.
AutoCollage
Authors: Rother Carsten , Bordeaux Lucas , Hamadi Youssef , Blake Andrew
Published: July 2006

The paper defines an automatic procedure for constructing a visually appealing collage from a collection of input images. The aim is that the resulting collage should be representative of the collection, summarising its main themes. It is also assembled largely seamlessly, using graph-cut, Poisson blending of alpha-masks, to hide the joins between input images. This paper makes several new contributions. Firstly, we show how energy terms can be included that: encourage the selection of a representative set of images; that are sensitive to particular object classes; that encourage a spatially efficient and seamless layout. Secondly the resulting optimization poses a search problem that, on the face of it, is computationally in-feasible. Rather than attempt an expensive, integrated optimization procedure, we have developed a sequence of optimization steps, from static ranking of images, through region of interest optimization, optimal packing by constraint satisfaction, and lastly graph-cut alpha-expansion. To illustrate the power of AutoCollage, we have used it to create collages of many home photo sets; we also conducted a user study in which AutoCollage outperformed competitive methods.
Photographing long scenes with multi-viewpoint panoramas
Authors: Agarwala Aseem , Agrawala Maneesh , Cohen Michael , Salesin David , Szeliski Richard
Published: July 2006

We present a system for producing multi-viewpoint panoramas of long, roughly planar scenes, such as the facades of buildings along a city street, from a relatively sparse set of photographs captured with a handheld still camera that is moved along the scene. Our work is a significant departure from previous methods for creating multi-viewpoint panoramas, which composite thin vertical strips from a video sequence captured by a translating video camera, in that the resulting panoramas are composed of relatively large regions of ordinary perspective. In our system, the only user input required beyond capturing the photographs themselves is to identify the dominant plane of the photographed scene; our system then computes a panorama automatically using Markov Random Field optimization. Users may exert additional control over the appearance of the result by drawing rough strokes that indicate various high-level goals. We demonstrate the results of our system on several scenes, including urban streets, a river bank, and a grocery store aisle.
Interaction capture and synthesis
Authors: Kry Paul G. , Pai Dinesh K.
Published: July 2006

Modifying motion capture to satisfy the constraints of new animation is difficult when contact is involved, and a critical problem for animation of hands. The compliance with which a character makes contact also reveals important aspects of the movement's purpose. We present a new technique called
interaction capture
, for capturing these contact phenomena. We capture contact forces at the same time as motion, at a high rate, and use both to estimate a nominal reference trajectory and joint compliance. Unlike traditional methods, our method estimates joint compliance without the need for motorized perturbation devices. New interactions can then be synthesized by physically based simulation. We describe a novel position-based linear complementarity problem formulation that includes friction, breaking contact, and the compliant coupling between contacts at different fingers. The technique is validated using data from previous work and our own perturbation-based estimates.
Projection defocus analysis for scene capture and image display
Authors: Zhang Li , Nayar Shree
Published: July 2006

In order to produce bright images, projectors have large apertures and hence narrow depths of field. In this paper, we present methods for robust scene capture and enhanced image display based on projection defocus analysis. We model a projector's defocus using a linear system. This model is used to develop a novel temporal defocus analysis method to recover depth at each camera pixel by estimating the parameters of its projection defocus kemel in frequency domain. Compared to most depth recovery methods, our approach is more accurate near depth discontinuities. Furthermore, by using a coaxial projector-camera system, we ensure that depth is computed at all camera pixels, without any missing parts. We show that the recovered scene geometry can be used for refocus synthesis and for depth-based image composition. Using the same projector defocus model and estimation technique, we also propose a defocus compensation method that filters a projection image in a spatially-varying, depth-dependent manner to minimize its defocus blur after it is projected onto the scene. This method effectively increases the depth of field of a projector without modifying its optics. Finally, we present an algorithm that exploits projector defocus to reduce the strong pixelation artifacts produced by digital projectors, while preserving the quality of the projected image. We have experimentally verified each of our methods using real scenes.