bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of red alder seed sources in France
Authors: Hibbs David E. , Bouvarel Luc , Cros Eric Teissier Du
Published: September 2007

We report on a series of 7- and 8-year-old genetic trials of red alder (Alnusrubra Bong.) planted in France as an initial exploration of its growth potential and genetic needs. Red alder is native to the Pacific Northwest coast of North America. Seed for the French plantings was collected in four Pacific Northwest river drainages (Santiam, Nisqually, Nooksack, and Hoh), which cover a wide latitudinal and elevational range.Of the four sites at which the red alder seed was planted, the best growth was observed at Rouvray in northwestern France, a site with deep sandy soil and adequate summer precipitation. Growth here was above average for red alder in its native habitat. Poor soil drainage at the other three test sites resulted in much poorer performance. Trees from Santiam River seed sources were generally the poorest performers at all test sites; the source river(s) for the best performing trees, however, varied by test site. Comparing performance of trees from the same source drainage, elevation of seed collection location correlated at best only weakly with growth; the level of nonsys-tematic variation was high. Regression on principal components derived from seed collection location environmental variables indicated that the best growth performance was associated with seed sources from warmer areas with low moisture demands. In general, this combination of climate conditions exists in low-elevation coastal areas; in this study, all seed collection locations fitting this description were in northwestern Washington state.
Sapwood–heartwood proportion related to tree diameter, age, and growth rate in Piceaabies
Authors: Sellin Arne
Published: September 2007

The relationships of sapwood radial width and transverse area to tree diameter, age, and growth rate were investigated in Piceaabies (L.) Karst. A total of 125 trees growing with (suppressed trees) and without (dominant trees) competition for light were sampled. Both sapwood and heartwood amounts showed an increase with diameter at the stem base, with the heartwood portion increasing more rapidly. In young trees sapwood prevails both in terms of diameter and transverse area. After trees have reached a certain age, the width of the sapwood band remains more or less constant (on average 7.8 cm for dominant and 2.0 cm for suppressed trees), and the heartwood amount exceeds that of sapwood. The percentage of heartwood in suppressed trees is substantially greater than in dominant trees of the same age. Sapwood amount is closely correlated with the tree diameter, but not with age. Tree age controls the number of rings in sapwood, while the sapwood width depends on the tree's radial growth rate as well.
Paclobutrazol protects black spruce seedlings against predisposition to gray mold induced by high temperature and drought
Authors: Zhang P.G. , Sutton J.C. , Fletcher R.A.
Published: September 2007

Effects of paclobutrazol on the ability of high temperature and drought to predispose black spruce (Piceamariana (Mill.) B.S.R) seedlings to infection and sporulation of Botrytiscinerea Pers.:Fr. were examined. Paclobutrazol was applied as a soil drench at doses of 0, 20, and 40 mg/seedling pair on the first and third days of 2- and 4-week periods before the seedlings were subjected to darkness at 35 and 45 °C, or to drought, for various periods and inoculated with the pathogen. The paclobutrazol treatments markedly reduced sporulation incidence and the number of spores produced by the pathogen on needles of seedlings subjected to the environmental stresses for periods that marginally or moderately exceeded those needed for predisposition to B. cinerea. Sporulation in needles of paclobutrazol-treated seedlings increased substantially only when the stress treatments were relatively prolonged. The activity of paclobutrazol in suppressing effects of environmental predisposition of the seedlings to infection and sporulation of B. cinerea was considered to be mediated through stress protection as opposed to fungicidal action of the triazole.
Influence of simulated acid rain on the flowering dogwood (Cornusflorida) leaf surface
Authors: Brown Daniel A. , Windham Mark T. , Anderson Robert L. , Trigiano Robert N.
Published: September 2007

Acidic rainfall has the potential to influence anthracnose incidence and severity in flowering dogwood (Cornusflorida L.) of the eastern United States. One-year-old, nursery-grown flowering dogwood seedlings were exposed to 1 cm of simulated rain 10 times over a 42-day period in 1990. Simulated rains were composed of a mixture of salts typical of ambient rainfall in the eastern United States and pH was adjusted to 5.5, 4.5, 3.5, and 2.5 with sulfuric and nitric acids. Samples were cut from the leaf tip, margin, and midvein of rain-treated trees and prepared for scanning electron microscopy. Cuticular cracking, desiccation, and erosion of trichome surfaces was observed in response to acid rain treatment. Increased degradation of dogwood trichomes was observed with decreasing pH for all samples. Cuticular erosion due to acid rain has the potential to predispose dogwoods in the eastern United States to anthracnose caused by Disculadestructiva sp.nov. (Red.) and an unnamed Discula sp.
Global radiation within subarctic open forest canopies
Authors: Lafleur Peter M. , Mantha Blair K.
Published: September 2007

Measurements of global solar radiation were made at six sites with varying architecture within a subarctic open forest near Churchill, Manitoba. Below-canopy radiation was determined from a network of nine sensors and the mean was compared with global radiation above the canopy. The ratio of below- to above-canopy radiation, R, ranged from 0.52 to 0.7 for the six sites. This range falls within the range of observations from other subarctic sites. At all sites, R was smaller for clear than for overcast skies; however, the differences were not statistically significant. The data from this study were combined with data from the literature in order to develop predictive equations for solar radiation at the floor of subarctic forests, based on easily derived forest parameters. Linear relationships were found between R and canopy closure (r2 = 0.76) and between R and tree height (r2 = 0.88).
Allozyme variation of Faguscrenata in northeastern Japan
Authors: Takahashi Makoto , Tsumura Yoshihiko , Nakamura Tohru , Uchida Koji , Ohba Kihachiro
Published: September 2007

Genetic variation of Faguscrenata Blume was investigated in 14 populations of the Hokkaido and Honshu regions of northeastern Japan. Within populations, averages for the proportion of polymorphic loci (95% criterion), the number of alleles per locus, the effective number of alleles per locus, the expected average heterozygosity, and the observed average heterozygosity were 58.2, 2.63, 1.34, 20.2, and 16.0%, respectively. The relative magnitude of gene differentiation and the average genetic distance among populations were 0.014 and 0.002, respectively. The inbreeding coefficient averaged 0.036. Overall, we detected 24 rare alleles (less than 5% of the allele frequency). The genetic composition of Honshu and Hokkaido populations was essentially the same, except for the five rare alleles absent in Hokkaido populations. These results indicate that Hokkaido populations may have experienced a partial bottleneck in the process of seed dissemination from Honshu.
Nuclear DNA content of commercially important Eucalyptus species and hybrids
Authors: Grattapaglia D. , Bradshaw Jr. H.D.
Published: September 2007

This paper reports the nuclear DNA content estimates obtained by flow cytometry for a group of twelve Eucalyptus species and five fast-growing hybrids that includes those most widely planted throughout the world. Estimates of nuclear (2C) DNA content for the species surveyed ranged from 0.77 pg/2C for Eucalyptuscitriodora Hook. (subgenus Corymbia) to 1.47 pg/2C for Eucalyptussaligna Smith (subgenus Symphyomyrtus). This range corresponds to a haploid genome size range of 370–700 megabase pairs. The average physical equivalent of a 1 cM distance could be as low as 200 kilobase pairs in Eucalyptus, an attractive feature for positional cloning efforts in woody plants. The closer the species were in phylogenetic relationship the more similar were their nuclear DNA content values. All the interspecific hybrids surveyed displayed a nuclear DNA content in the expected intermediate range between the respective parental species, with the exception of one originating from Rio Claro, Brazil, whose exact parentage is unknown. No evidence of polyploidy was observed in any of the hybrids. The flow cytometry procedure employed in this study is an efficient method for investigating ploidy levels of high yielding hybrids of Eucalyptus.
Heterogeneous selfing rates and dominance effects in estimating heritabilities from open-pollinated progeny
Authors: Borralho N.M.G.
Published: September 2007

Estimates of heritability from open-pollinated progeny trials were generally biased by heterogeneous selfing across families and by the presence of dominance, even when the intraclass correlation between sibs was adjusted for the average number of full- and half-sibs and for relatedness among the parents in the population. For high levels of selfing, with a constant selfing rate and inbreeding depression across families, dominance causes a downward bias in the heritabilities. Where rates of selfing and inbreeding depression varied, heritability was overestimated. However, except for low heritabilities, bias was of little practical importance, providing the correct coefficient of relationship among open-pollinated progeny was used.
Blood and gill responses to HCl infusions in the Pacific hagfish (Eptatretus stoutii)
Authors: Parks Scott K. , Tresguerres Martin , Goss Greg G.
Published: September 2007

Pacific hagfish ( Eptatretus stoutii (Lockington, 1878)) were serially infused with HCl (6000 µmol·kg–1) every 6 h over a 24 h period to explore branchial acid secretion mechanisms. Blood pH recovered from a value ~2 pH units below that of resting pH. This pH regulatory mechanism was activated by 6 h and persisted over the 24 h time course. Western-blot analysis revealed an increased abundance (~2.3×) of NHE2-like immunoreactivity (NHE2 L-IR) in whole gill fractions from HCl-infused fish compared with control NaCl-infused fish. Membrane fractions isolated from the gills of HCl-infused fish also showed an increased abundance (~1.8×). Immunohistochemistry results demonstrated a significant redistribution of NHE2 L-IR to the apical region in HCl-infused fish. V-H+-ATPase abundance did not significantly increase in HCl-infused fish, while levels of Na+/K+-ATPase expression were unchanged. Immunohistochemistry of these transporters did not show any changes in cellular localization. We propose that the Pacific hagfish overcomes a metabolic acidosis via an increased synthesis of an NHE-like protein and an increased density of the transporter at the apical region of the mitochondria-rich cells of the gill.
In the mating system of the bat Saccopteryx bilineata, bioacoustic constraints impede male eavesdropping on female echolocation calls for their surveillance
Authors: Hoffmann F.F. , Hejduk J. , Caspers B. , Siemers B.M. , Voigt C.C.
Published: September 2007

At night, bats utter loud echolocation calls at high repetition rates that may reveal the location and current behaviour of callers to eavesdropping bats. Given the strong attenuation of echolocation calls, we predicted that territorial males of a harem-polygynous species ought to forage at close distance to females to survey their movements by social eavesdropping. We estimated a maximum detection distance of 38 m for echolocation calls of Saccopteryx bilineata (Temminck, 1838) (Chiroptera; Emballonuridae) broadcasted within the forest under the sound transmission conditions of our study site and for an assumed signal detection threshold of 20 dB SPL (50 m for a threshold of 0 dB SPL). We then simultaneously radio-tracked the nocturnal movements of eight male–female pairs that each rested in the same harem territory during the day and measured the distances at which dyads foraged. Male–female pairs foraged at a median distance of 139 m. In the case of 90% of simultaneous bearings, males foraged at distances that prevented eavesdropping on 44 kHz echolocation calls (>38 m; 87% of radio fixes >50 m). Males and females of the same daytime territory roosted, on average, 226 ± 194 m apart from each other at night. Thus, males were most likely unaware of where females foraged as a result of the strong attenuation of female echolocation calls. In general, such acoustic constraints on social eavesdropping may promote extra-harem group paternities, female choice, and sperm competition in bats, and may therefore present an important selective force in the evolution of bat mating systems.
A new sex dimorphism in the Harderian gland of the frog Rana esculenta
Authors: Serino Ismene , Izzo Gaia , Ferrara Diana , d’Istria Michela , Minucci Sergio
Published: September 2007

The Harderian gland (Hg), the only gland found in the orbit of the frog Rana esculenta L., 1758, probably plays a role in orbital lubrication. The secretory activity of the Hg is seasonal, showing the highest activity in summer. There is little information on Hg gene expression; previously, we identified a mRNA named harderin, whose deduced protein has no homology with other proteins. Differential expression of the harderin transcript between the sexes expressed during the annual cycle implies sexual dimorphism. RT–PCR (reverse transcription – polymerase chain reaction) analysis, revealed that harderin is expressed during the entire year in the Hg of both sexes. It shows a higher level of expression in the female glands than that of male glands. Two peaks of expression, in February and in June, were observed in the female glands, while only the February peak was observed in those of males. These observations were supported by in situ hybridization. Experiments involving gonadectomy and (or) hormonal replacement therapy showed a significant decrease in harderin in the Hg of females; this effect is prevented by estradiol (testosterone had no effect), while ICI (antiestrogen) counteracts the hormonal prevention, suggesting that this sexual dimorphism is under estradiol control. The constant expression of harderin mRNA during the year suggests a probable constitutive role for this molecule.
Influence of historical events and contemporary estuarine circulation on the genetic structure of the banded killifish (Fundulus diaphanus) in the St. Lawrence River (Quebec, Canada)
Authors: Rey O. , Turgeon J.
Published: September 2007

Eight microsatellite markers were used to examine the historical and contemporary factors influencing the distribution of genetic variation within and among populations of Fundulus diaphanus (Lesueur, 1817) in the St. Lawrence River. Our results show that the contemporary hydrodynamics of the river affect levels of diversity and differentiation in this species. Genetic diversity increased towards downstream sites and levelled off at the upstream end of the tidal section, in the vicinity of Lake St-Pierre outlet. Likewise, differentiation and isolation-by-distance were most pronounced in the upstream, strictly fluvial section of the river. Surprisingly, however, we did not detect any significant intershore differentiation in this riparian fish species. Historical influence was also clearly detected and transcended the contemporary pattern, as revealed by an extremely strong isolation-by-distance pattern along the entire river stretch. This pattern likely results from the historical, postglacial secondary contact between two glacial races, as indicated by the clinal variation of constrasting allele size frequency distributions along the river and the significantly greater values of differentiation indices considering mutational information.
Cytochrome-b haplotypes suggest an undescribed Peromyscus species from the Yukon
Authors: Lucid M.K. , Cook J.A.
Published: September 2007

Peromyscus maniculatus (Wagner, 1845) and Peromyscus keeni Merriam, 1897 are two species of deer mouse currently recognized in the Yukon. Phylogenetic analyses (Kimura two-parameter and maximum parsimony) of cytochrome-b sequences (560 base pairs) from deer mouse specimens (n = 4) collected near Haines Junction, Yukon, resulted in a monophyletic clade genetically distant from the two currently recognized species. We suggest that the Haines Junction specimens may represent a previously undescribed peromyscine species. Peromyscus arcticus is an available name.
Fidelity to calving areas in moose (Alces alces) in the absence of natural predators
Authors: Tremblay J.-P. , Solberg E.J. , Sæther B.-E. , Heim M.
Published: September 2007

We used long-term monitoring (1991–2005) data from a moose ( Alces alces (L., 1758)) population (i) to determine if moose cows are faithful to their calving sites and (ii) to examine the effect of previous recruitment success on calving-site fidelity. We generated null hypotheses from the distances between calving sites used by other individuals inside the home range of each cow. The calving sites used in successive years by individual cows were closer together (2.1 ± 0.2 km) than were calving sites used by other cows within their home range (3.9 ± 0.1 km; n = 30 cows, 148 sites). The former is similar to distances reported from areas where natural predators are present but females successfully weaned their calf or calves. We did not detect any effects of previous recruitment success, but the distances to the next calving sites of the only two cows that did not wean their calves (3.8 and 3.4 km) are analogous to values reported for cows that have lost their calf or calves to predators. Our data support the theory that fidelity to areas where parturition has been successful could be an evolutionary trade-off between reproductive success and risk of predation to maximize fitness. On an ecological scale, moose cows apparently perceived anthropogenic disturbances as a potential risk, influencing their choice of calving sites and ultimately their fidelity.
LOCALIZATION ON A QUANTUM GRAPH WITH A RANDOM POTENTIAL ON THE EDGES
Authors: EXNER PAVEL , HELM MARIO , STOLLMANN PETER
Published: September 2007

We prove spectral and dynamical localization on a cubic-lattice quantum graph with a random potential. We use multiscale analysis and show how to obtain the necessary estimates in analogy to the well-studied case of random Schrödinger operators.
PATH INTEGRALS ON A COMPACT MANIFOLD WITH NON-NEGATIVE CURVATURE
Authors: LIM ADRIAN P. C.
Published: September 2007

A typical path integral on a manifold, M is an informal expression of the form [Formula: see text] where H(M) is a Hilbert manifold of paths with energy E(σ) < ∞, f is a real-valued function on H(M), [Formula: see text] is a "Lebesgue measure" and Z is a normalization constant. For a compact Riemannian manifold M, we wish to interpret [Formula: see text] as a Riemannian "volume form" over H(M), equipped with its natural G1 metric. Given an equally spaced partition, [Formula: see text] of [0, τ], let [Formula: see text] be the finite dimensional Riemannian submanifold of H(M) consisting of piecewise geodesic paths adapted to [Formula: see text]. Under certain curvature restrictions on M, it is shown that [Formula: see text] where [Formula: see text] is a "normalization" constant, E : H(M) → [0,∞) is the energy functional, [Formula: see text] is the Riemannian volume measure on [Formula: see text], ν is Wiener measure on continuous paths in M, and ρ is a certain density determined by the curvature tensor of M.
DISTRIBUTION OF LOCALIZATION CENTERS IN SOME DISCRETE RANDOM SYSTEMS
Authors: NAKANO FUMIHIKO
Published: September 2007

As a supplement of our previous work [10], we consider the localized region of the random Schrödinger operators on l2(Zd) and study the point process composed of their eigenvalues and corresponding localization centers. For the Anderson model we show that, this point process in the natural scaling limit converges in distribution to the Poisson process on the product space of energy and space. In other models with suitable Wegner-type bounds, we can at least show that limiting point processes are infinitely divisible.
CONSTANT ELASTICITY OF VARIANCE IN RANDOM TIME: A NEW STOCHASTIC VOLATILITY MODEL WITH PATH DEPENDENCE AND LEVERAGE EFFECT
Authors: OSTROVSKY DMITRY
Published: September 2007

An arbitrage-free CEV economy driven by Brownian motion in independent, continuous random time is introduced. European options are priced by the no-arbitrage principle as conditional averages of their classical CEV values over the CEV-modified random time to maturity. A novel representation of the classical CEV price is used to investigate the asymptotics of the average implied volatility. It is shown that the average implied volatility of the at-the-money call option is lower and of deep out-of-the-money call options, under appropriate sufficient conditions, greater than the implied CEV volatilities. Unlike in the classical CEV model, the shape of the out-of-the-money tail can be both downward and upward sloping depending on the tails of random time. The model is implemented in limit lognormal time. Its multiscaling law is shown to imply a term structure of implied volatility that is qualitatively more sensitive to changes in the time to maturity than is the classical CEV model.
THE EQUITY PREMIUM PUZZLE AND EMOTIONAL ASSET PRICING
Authors: GÜRTLER MARC , HARTMANN NORA
Published: September 2007

Since the equity premium as well as the risk-free rate puzzle question the concepts central to financial and economic modeling, we apply behavioral decision theory to asset pricing in view of solving these puzzles. US stock market data for the period 1960–2003 and German stock market data for the period 1977–2003 show that emotional investors who act in accordance to Bell's [6] disappointment theory — a special case of prospect theory — and additionally administer mental accounts demand a high equity premium. Furthermore, these investors reason a low risk-free rate. However, Barberis et al. [5] already showed that limited rational investors demand a high equity premium. But as opposed to them, our approach additionally supports dividend smoothing.
A GENERAL FRAMEWORK FOR HIGH YIELD BOND INVESTMENT
Authors: KORN RALF , KOVILYANSKAYA HELEN
Published: September 2007

We present a general framework for considering investment in defaultable securities which — as special cases — includes both the firm value and the intensity based approach to credit risky bonds. In this framework, we construct a dynamically evolving portfolio of high-yield bonds where whenever a bond defaults it is replaced by another high yield bond. The properties of this portfolio and in particular the evolution of its face value are investigated. The modeling potential of our framework is demonstrated via examples of bond portfolios admitting extreme properties such as an unbounded face value process.
OPTIMAL PORTFOLIO CONSTRUCTION UNDER PARTIAL INFORMATION FOR A BALANCED FUND
Authors: KEEL SIMON , HERZOG FLORIAN , GEERING HANS P. , SCHUMANN LORENZ M.
Published: September 2007

The model parameters in optimal asset allocation problems are often assumed to be deterministic. This is not a realistic assumption since most parameters are not known exactly and therefore have to be estimated. We consider investment opportunities which are modeled as local geometric Brownian motions whose drift terms may be stochastic and not necessarily measurable. The drift terms of the risky assets are assumed to be affine functions of some arbitrary factors. These factors themselves may be stochastic processes. They are modeled to have a mean-reverting behavior. We consider two types of factors, namely observable and unobservable ones. The closed-form solution of the general problem is derived. The investor is assumed to have either constant relative risk aversion (CRRA) or constant absolute risk aversion (CARA). The optimal asset allocation under partial information is derived by transforming the problem into a full-information problem, where the solution is well known. The analytical result is empirically tested in a real-world application. In our case, we consider the optimal management of a balanced fund mandate. The unobservable risk factors are estimated with a Kalman filter. We compare the results of the partial-information strategy with the corresponding full-information strategy. We find that using a partial-information approach yields much better results in terms of Sharpe ratios than the full-information approach.
A COMPARISON OF SOME UNIVARIATE MODELS FOR VALUE-AT-RISK AND EXPECTED SHORTFALL
Authors: MARINELLI CARLO , D'ADDONA STEFANO , RACHEV SVETLOZAR T.
Published: September 2007

We compare in a backtesting study the performance of univariate models for Value-at-Risk (VaR) and expected shortfall based on stable laws and on extreme value theory (EVT). Analyzing these different approaches, we test whether the sum–stability assumption or the max–stability assumption, that respectively imply α–stable laws and Generalized Extreme Value (GEV) distributions, is more suitable for risk management based on VaR and expected shortfall. Our numerical results indicate that α–stable models tend to outperform pure EVT-based methods (especially those obtained by the so-called block maxima method) in the estimation of Value-at-Risk, while a peaks-over-threshold method turns out to be preferable for the estimation of expected shortfall. We also find empirical evidence that some simple semiparametric EVT-based methods perform well in the estimation of VaR.
TESTING WEAK-FORM MARKET EFFICIENCY IN EMERGING MARKET: EVIDENCE FROM BOTSWANA STOCK EXCHANGE
Authors: MOLLAH A. SABUR
Published: September 2007

Market efficiency is an area of enormous interest in financial literature. Numerous researchers conducted empirical studies in testing weak-form market efficiency in several stock markets and employed various techniques but the empirical evidence is controversial. Triangulation econometric approach is employed to assess the predictability of daily return series of Botswana Stock Exchange (BSE) and to test the null hypothesis of random walk model. The empirical results reject the null hypothesis of random walk model for the daily return series of BSE for the period of 1989–2005 and evidenced serial autocorrelation of return series, which clearly indicate predictability and volatility of security prices of Botswana market. However, the empirical evidence of both non-parametric (Kolmogrov–Smirnov: normality test and run test) and parametric test (Auto-correlation test, Auto-regressive model, ARIMA model) reject the hypothesis of random walk model and indeed violate the notion of weak-form market efficiency.
A MAXIMAL PREDICTABILITY PORTFOLIO MODEL: ALGORITHM AND PERFORMANCE EVALUATION
Authors: YAMAMOTO REI , ISHII DAISUKE , KONNO HIROSHI
Published: September 2007

The purpose of this paper is to show that an algorithm recently proposed by authors can in fact solve a maximal predictability portfolio (MPP) optimization problem, which is a hard nonconvex fractional programming optimization. Also, we will compare MPP with standard mean-variance portfolio (MVP) and show that MPP outperforms MVP and index. We believe that this paper is of interest to researchers and practitioners in the field of portfolio optimization.
Autonomous authoring tools for hypertext
Authors: Truran Mark , Goulding James , Ashman Helen
Published: September 2007

Autonomous authoring tools are routinely used to expedite the translation of large document collections into functioning hypertexts. They are also used to add hyperlinks to pre-existing hypertext structures. In this survey we describe a taxonomy of autonomous hypertext authoring tools. The classification of any given system is determined by the type and nature of the document analysis it performs.
Software design patterns for TinyOS
Authors: Gay David , Levis Philip , Culler David
Published: September 2007

We present design patterns used by software components in the TinyOS sensor network operating system. They differ significantly from traditional software design patterns because of the constraints of sensor networks and to TinyOS's focus on static allocation and whole-program composition. We describe how nesC has evolved to support these design patterns by including a few simple language primitives and optimizations.
Automated reduction of the memory footprint of the Linux kernel
Authors: Chanet Dominique , De Sutter Bjorn , De Bus Bruno , Van Put Ludo , De Bosschere Koen
Published: September 2007

The limited built-in configurability of Linux can lead to expensive code size overhead when it is used in the embedded market. To overcome this problem, we propose the application of link-time compaction and specialization techniques that exploit the
a priori
known, fixed runtime environment of many embedded systems. In experimental setups based on the ARM XScale and i386 platforms, the proposed techniques are able to reduce the kernel memory footprint with over 16%. We also show how relatively simple additions to existing binary rewriters can implement the proposed techniques for a complex, very unconventional program, such as the Linux kernel. We note that even after specialization, a lot of seemingly unnecessary code remains in the kernel and propose to reduce the footprint of this code by applying code-compression techniques. This technique, combined with the previous ones, reduces the memory footprint with over 23% for the i386 platform and 28% for the ARM platform. Finally, we pinpoint an important code size growth problem when compaction and compression techniques are combined on the ARM platform.
Static strands
Authors: Sassone Peter G. , Wills D. Scott , Loh Gabriel H.
Published: September 2007

Modern embedded processors are designed to maximize execution efficiency—the amount of performance achieved per unit of energy dissipated while meeting minimum performance levels. To increase this efficiency, we propose utilizing
static strands
, dependence chains without fan-out, which are exposed by a compiler pass. These dependent instructions are resequenced to be sequential and annotated to communicate their location to the hardware. Importantly, this modified application is binary compatible and functionally identical to the original, allowing transparent execution on a baseline processor. However, these static strands can be easily collapsed and optimized by simple processor modifications, significantly reducing the workload energy. Results show that over 30% of MediaBench and Spec2000int dynamic instructions can be collapsed, reducing issue logic energy by 20%, bypass energy 19%, and register file energy 14%. In addition, by increasing the effective capactity of pipeline resources by almost a third, average IPC can be improved up to 15%. This performance gain can then be traded in for a lower clock frequency to maintain a basline level of performance, further reducing energy.
Accurate and fast system-level power modeling
Authors: Varma Ankush , Jacob Bruce , Debes Eric , Kozintsev Igor , Klein Paul
Published: September 2007

Accurate and fast system modeling is central to the rapid design space exploration needed for embedded-system design. With fast, complex SoCs playing a central role in such systems, system designers have come to require MIPS-range simulation speeds and near-cycle accuracy. The sophisticated simulation frameworks that have been developed for high-speed system performance modeling do not address power consumption, although it is a key design constraint. In this paper, we define a simulation-based methodology for extending system performance-modeling frameworks to also include power modeling. We demonstrate the use of this methodology with a case study of a real, complex embedded system, comprising the Intel XScale®g embedded microprocessor, its WMMX™ SIMD coprocessor, L1 caches, SDRAM and the on-board address and data buses. We describe detailed power models for each of these components and validate them against physical measurements from hardware, demonstrating that such frameworks enable designers to model both power and performance at high speeds without sacrificing accuracy. Our results indicate that the power estimates obtained are accurate within 5% of physical measurements from hardware, while simulation speeds consistently exceed a million instructions per second (MIPS).
Energy efficient DVS schedule for fixed-priority real-time systems
Authors: Quan Gang , Hu Xiaobo Sharon
Published: September 2007

Energy consumption has become an increasingly important consideration in designing many real-time embedded systems. Variable voltage processors, if used properly, can dramatically reduce such system energy consumption. In this paper, we present a technique to determine voltage settings for a variable voltage processor that utilizes a fixed-priority assignment to schedule jobs. By exploiting more efficiently the processor slack time, our approach can be more effective in reducing the execution speed for real-time tasks when necessary. Our approach also produces the minimum constant voltage needed to feasibly schedule the entire job set. With both randomly generated and practical examples, our heuristic approach can achieve the dynamic energy reduction very close to the theoretically optimal one (within 2%) with much less computation cost.
Energy optimal speed control of a producer--consumer device pair
Authors: Rao Ravishankar , Vrudhula Sarma
Published: September 2007

We propose a modular approach for minimizing the total energy consumed by a pair of generic communicating devices (producer--consumer scenario) by jointly controlling their speed profiles. Each device (like a CPU, or disk drive) is assumed to have a controllable variable called its speed (e.g., a CPU's clock frequency, a disk drive's spindle motor speed) that affects its power consumption and performance (e.g., throughput, data transfer rate). The device and task models we analyzed were inspired by applications like CD recording (hard drive to CD drive data transfer) and data processing (disk drive to CPU data transfer). The proposed solution can be used for any pair of devices with convex (for continuous speed sets) or W-convex (a discrete version of a convex function for discrete speed sets) power--speed relationships. For discrete speed sets, the method operates directly on the power--speed values and does not require an analytical relationship between power and speed. The key to solving the two-device optimization problem was the observation that it could be split into two single device parametric optimization problems, where the parameters correspond to the common task that both the devices must execute. The following divide-and-conquer approach is proposed: [divide] the optimal speed policy and energy consumption of each device is derived as an analytical function of its task parameters; [conquer] the optimal values of these parameters are found by minimizing the sum of the parameterized energy functions and plugged back into the parameterized speed profiles. The main advantage of this approach is that each device can be characterized independently and this allows system designers to mix and match manufacturer-supplied device energy curves to evaluate and optimize different application scenarios. We demonstrate our approach using three device characterization examples (for a CD drive, hard drive, and a CPU) and two application scenarios (CD recording, MD5 checksum computation).
Power macromodeling of MPSoC message passing primitives
Authors: Loghi Mirko , Benini Luca , Poncino Massimo
Published: September 2007

Estimating the energy consumption of software in multiprocessor systems-on-chip (MPSoCs) is crucial for enabling quick evaluations of both software and hardware optimizations. However, high-level estimations should be applicable at software level, possibly constructing effective power models depending on parameters that can be extracted directly from the application characteristics. We propose a methodology for accurate analysis of power consumption of message-passing primitives in a MPSoC, and, in particular, an energy model which, in spite of its simplicity, allows to model the traffic-dependent nature of energy consumption through the use of a single, abstract parameter, namely, the size of the message exchanged.
Power management in energy harvesting sensor networks
Authors: Kansal Aman , Hsu Jason , Zahedi Sadaf , Srivastava Mani B.
Published: September 2007

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
Common defects in initialization of pseudorandom number generators
Authors: Matsumoto Makoto , Wada Isaku , Kuramoto Ai , Ashihara Hyo
Published: September 2007

We demonstrate that a majority of modern random number generators, such as the newest version of rand.c, ranlux, and combined multiple recursive generators, have some manifest correlations in their outputs if the initial state is filled up using another linear recurrence with similar modulus. Among 58 available generators in the GNU scientific library, 40 show such defects. This is not because of the recursion, but because of carelessly chosen initialization schemes in the implementations. A good initialization scheme eliminates this phenomenon.
Multistep-ahead neural-network predictors for network traffic reduction in distributed interactive applications
Authors: Mccoy Aaron , Ward Tomas , Mcloone Seamus , Delaney Declan
Published: September 2007

Predictive contract mechanisms such as dead reckoning are widely employed to support scalable remote entity modeling in distributed interactive applications (DIAs). By employing a form of controlled inconsistency, a reduction in network traffic is achieved. However, by relying on the distribution of instantaneous derivative information, dead reckoning trades remote extrapolation accuracy for low computational complexity and ease-of-implementation. In this article, we present a novel extension of dead reckoning, termed neuro-reckoning, that seeks to replace the use of instantaneous velocity information with predictive velocity information in order to improve the accuracy of entity position extrapolation at remote hosts. Under our proposed neuro-reckoning approach, each controlling host employs a bank of neural network predictors trained to estimate future changes in entity velocity up to and including some maximum prediction horizon. The effect of each estimated change in velocity on the current entity position is simulated to produce an estimate for the likely position of the entity over some short time-span. Upon detecting an error threshold violation, the controlling host transmits a predictive velocity vector that extrapolates through the estimated position, as opposed to transmitting the instantaneous velocity vector. Such an approach succeeds in reducing the spatial error associated with remote extrapolation of entity state. Consequently, a further reduction in network traffic can be achieved. Simulation results conducted using several human users in a highly interactive DIA indicate significant potential for improved scalability when compared to the use of IEEE DIS standard dead reckoning. Our proposed neuro-reckoning framework exhibits low computational resource overhead for real-time use and can be seamlessly integrated into many existing dead reckoning mechanisms.
Discrete-time heavy-tailed chains, and their properties in modeling network traffic
Authors: Hernández José Alberto , Phillips Iain W. , Aracil Javier
Published: September 2007

The particular statistical properties found in network measurements, namely self-similarity and long-range dependence, cannot be ignored in modeling network and Internet traffic. Thus, despite their mathematical tractability, traditional Markov models are not appropriate for this purpose, since their memoryless nature contradicts the burstiness of transmitted packets. However, it is desirable to find a similarly tractable model which is, at the same time, rigorous at capturing the features of network traffic.

This work presents
discrete-time heavy-tailed chains
, a tractable approach to characterize network traffic as a superposition of discrete-time “on/off” sources. This is a particular case of the generic “on/off” heavy-tailed model, thus shows the same statistical features as the former, particularly self-similarity and long-range dependence, when the number of aggregated sources approaches infinity.

The model is then applicable to characterize a number of discrete-time communication systems, for instance, ATM and optical packet switching, to further derive meaningful performance metrics such as average burst duration and the number of active sources in a random instant.
Inverse transformed density rejection for unbounded monotone densities
Authors: Hörmann Wolfgang , Leydold Josef , Derflinger Gerhard
Published: September 2007

A new algorithm for sampling from largely arbitrary monotone, unbounded densities is presented. The user has to provide a program to evaluate the density and its derivative and the location of the pole. Then the setup of the new algorithm constructs different hat functions for the pole region and tail region, respectively. For the pole region a new method is developed that uses a transformed density rejection hat function of the inverse density. As the order of the pole is calculated in the setup, conditions that guarantee correctness of the constructed hat functions are provided. Numerical experiments indicate that the new algorithm works correctly and moderately fast for many different unbounded densities.
A framework for locally convergent random-search algorithms for discrete optimization via simulation
Authors: Hong L. Jeff , Nelson Barry L.
Published: September 2007

The goal of this article is to provide a general framework for locally convergent random-search algorithms for stochastic optimization problems when the objective function is embedded in a stochastic simulation and the decision variables are integer ordered. The framework guarantees desirable asymptotic properties, including almost-sure convergence and known rate of convergence, for any algorithms that conform to its mild conditions. Within this framework, algorithm designers can incorporate sophisticated search schemes and complicated statistical procedures to design new algorithms.
Recovering traceability links in software artifact management systems using information retrieval methods
Authors: Lucia Andrea De , Fasano Fausto , Oliveto Rocco , Tortora Genoveffa
Published: September 2007

The main drawback of existing software artifact management systems is the lack of automatic or semi-automatic traceability link generation and maintenance. We have improved an artifact management system with a traceability recovery tool based on Latent Semantic Indexing (LSI), an information retrieval technique. We have assessed LSI to identify strengths and limitations of using information retrieval techniques for traceability recovery and devised the need for an incremental approach. The method and the tool have been evaluated during the development of seventeen software projects involving about 150 students. We observed that although tools based on information retrieval provide a useful support for the identification of traceability links during software development, they are still far to support a complete semi-automatic recovery of all links. The results of our experience have also shown that such tools can help to identify quality problems in the textual description of traced artifacts.
Web accessibility for individuals with cognitive deficits
Authors: Sevilla Javier , Herrera Gerardo , Martínez Bibiana , Alcantud Francisco
Published: September 2007

Tim Berners-Lee claimed in 2001 that “the power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect”. A considerable amount of work has been done to make the web accessible to those with sensory or motor disability, with an increasing number of government and enterprise intranet webs being “accessible”, and also with some consortiums and groups seriously approaching this commitment. Some authors, such as Harrysson, have already highlighted the need for a cognitively accessible web. However, in spite of good intentions, there has been little work to date that has tackled this task. At least until now, the existing WAI and NI4 recommendations about cognitive disability are extremely difficult (if not impossible) to test, as they are only general recommendations. This article explains an alternative Web that has been constructed and tested on a sample of participants with cognitive disabilities (N = 20) with positive results encouraging us to dedicate more effort to fine tune their requirements regarding specific cognitive deficits and automating the process of creating and testing cognitively accessible web content. This alternative web implies the use of a simplified web browser and an adequate web design. Discussion of the need to have several levels of cognitive accessibility, equivalent (although not identical) content for this collective and the need for testable protocols of accessibility that support these people's needs is also included. This article finishes with conclusions about the potential impact of accessible pages in the daily life of people suffering from cognitive deficits, outlining the features to be considered within a user profile specification that support cognitive difficulties and with reflections about the suitability of Semantic Web Technologies for future developments in this field.