bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation between leaf biomass and annual ring sapwood of Norway spruce according to needle age-class
Authors: Dvorak Vitezslav , Oplustilova Magda , Janous Dalibor
Published: June 2008

The relationship between leaf biomass and sapwood area was investigated in a 35-year-old Norway spruce (Piceaabies (L.) Karst.) stand in mountainous conditions. Fifteen trees were destructively sampled to determine the needle biomass in several needle age-classes and whorls and the corresponding sapwood areas at the whorl branch bases and in stems at breast height. Leaf biomass/sapwood area ratio and specific leaf biomass (g•mm−2) were calculated for different needle age-classes and also for different positions in the vertical profile of the crown. The leaf biomass/sapwood area ratios were described by linear regression with a high coefficient of determination. Specific leaf biomass analysed in whorl branches was highest in the upper whorls but was decreasing downward through the profile; remained stable in the middle crown layer; and decreased again in the lower crown parts. Specific leaf biomass assessments for stems showed the largest and most increasing values in the youngest three needle age-classes followed by a decreasing trend of the specific leaf biomass in older needle age-classes. The mean values of specific leaf biomass were 1.08 g•mm−2 for branches and 1.02 g•mm−2 for stems. The results of our study are consistent with the "pipe model theory."
Développement d'un modèle de type arbre appliqué à la croissance des peuplements feuillus irréguliers du sud de la Belgique
Authors: Lejeune P.
Published: June 2008

A model predicting circumference growth of individual trees has been developed for mixed irregular stands dominated by Fagussilvatica L. in southeastern Belgium. This model integrates simultaneously tree, stand, and growing site characteristics without considering distances between individual trees. It has a determination coefficient of 40.1% and a residual standard deviation of 0.45 cm/year. Forest mensuration variables considered in the model are circumference, tree social position represented by the total basal area of trees greater than the subject tree, stand basal area, and some index of stand structure corresponding to the ratio of the variance over the mean circumference. The site component is essentially expressed by the length of the growing period. The low accuracy obtained for individual tree growth is relative because the results are used mainly after individual trees have been distributed into size classes. We have been able to show that the introduction of crown description in the model can increase its accuracy. But this modification requires a submodel describing crown changes over time.
Effects of wind velocity and slope on flame properties
Authors: Weise David R. , Biging Gregory S.
Published: June 2008

The combined effects of wind velocity and percent slope on flame length and angle were measured in an open-topped, tilting wind tunnel by burning fuel beds composed of vertical birch sticks and aspen excelsior. Mean flame length ranged from 0.08 to 1.69 m; 0.25 m was the maximum observed flame length for most backing fires. Flame angle ranged from −46° to 50°. Observed flame angle and length data were compared with predictions from several models applicable to fires on a horizontal surface. Two equations based on the Froude number underestimated flame angle for most wind and slope combinations; however, the data support theory that flame angle is a function of the square root of the Froude number. Discrepancies between data and predictions were attributed to measurement difficulties and slope effects. An equation based on Byram's convection number accounted for nearly half of the observed variation in flame angle (R2 = 0.46). Byram's original equation relating fireline intensity to flame length overestimated flame length. New parameter estimates were derived from the data. Testing of observed fire behavior under a wider range of conditions and at field scale is recommended.
Variation in canopy gap formation among developmental stages of northern hardwood stands
Authors: Dahir Sally E. , Lorimer Craig G.
Published: June 2008

Trends in gap dynamics among pole, mature, and old-growth northern hardwood stands were investigated on eight sites in the Porcupine Mountains of western upper Michigan. Recent gaps (created between 1981 and 1992) were identified using permanent plot records of tree mortality, while older gaps (1940–1981) were identified using stand reconstruction techniques. Although canopy gaps were somewhat more numerous in pole and mature stands, gaps were <25% as large as those in old-growth stands because of smaller gap-maker size, and the proportion of stand area turned over in gaps was only about half as large. Gap makers in younger stands generally had mean relative diameters (ratio of gap-maker DBH to mean DBH of canopy trees) <1.0 and were disproportionately from minor species such as eastern hophornbeam (Ostryavirginiana (Mill.) K. Koch). Gap makers in old-growth stands had mean relative diameters >1.5 and were predominantly from the dominant canopy species. Even in old-growth forests, most gaps were small (mean 44 m2) and created by single trees. Based on the identity of the tallest gap tree in each gap, nearly all shade-tolerant and midtolerant species have been successful in capturing gaps, but gap capture rates for some species were significantly different from their relative density in the upper canopy. The tallest gap trees of shade-tolerant species were often formerly overtopped trees, averaging more than 60% of the mean canopy height and having mean ages of 65–149 years. Canopy turnover times, based on gap formation rates over a 50-year period, were estimated to average 128 years for old-growth stands dominated by sugar maple (Acersaccharum Marsh.) and 192 years for old-growth stands dominated by hemlock (Tsugacanadensis (L.) Carrière). While these estimates of turnover time are substantially shorter than maximum tree ages observed on these sites, they agree closely with independent data on mean canopy residence time for trees that die at the average gap-maker size of 51 cm DBH. The data support previous hypothetical explanations of the apparent discrepancy between canopy turnover times of <130 years for hardwood species and the frequent occurrence of trees exceeding 250 years of age.
Duff weight and depth in a high elevation Pinuscontorta Dougl. forest
Authors: Woodard P. M. , Martin R. E.
Published: June 2008

Variation in duff depth and weight was studied on two adjacent different aged subalpine stands in eastern Washington, U.S.A. In a 105-year-old Pinuscontorta Dougl. stand, the duff depth averaged 5.46 cm as compared with 4.57 cm for a 305-year-old stand of the same habitat type. The difference between the means was not significant. The greatest duff depth (46 cm) in the younger stand was almost twice that of the older stand (26 cm), due principally to the time since last disturbance by fire. A correlation of duff depth (D; centimetres) to weight (W; tonnes per hectare) produced the equation W = 7.26 + 13.27 D which had r2 = 0.849 and SE = 7.06.
Interacting environmental factors associated with the incidence of Hypoxylon canker on trembling aspen
Authors: Bruck Robert I. , Manion Paul D.
Published: June 2008

Twenty-three natural stands of trembling aspen (Populustremuloides Michx.) were surveyed for incidence of a canker caused by Hypoxylonmammatum (Wahl.) Miller. Canker incidence ranged from 0 to 70%. Horizonal soil samples were analyzed for their chemical and physical properties, and aspen leaf lamina tissue was analyzed for nutrient concentrations. A model accounting for 92% of the variation in canker incidence was constructed, utilizing 56 measured parameters, through the use of simple- and multi-correlation statistical analyses. Highly significant negative correlations were observed between canker frequency and each of aspen cover density, soil moisture, abundance of soil mottles, soil consistence, exchangeable soil Mn, Ca, and Na, and aspen tissue concentrations of Mn, Ca, and Na. Positive correlations were observed between canker incidence and each of soil temperature, soil depth, bulk density, rooting depth, and soil fractions over 2 and 10 mm. The association between exchangeable soil nutrients and aspen tissue concentrations was highly significant (p = 0.01). It is concluded that physical and chemical parameters of the soil which related most directly to moisture comprise a system of variables which are highly related to Hypoxylon canker incidence in trembling aspen.
The role of temperate zone forests in the global carbon cycle
Authors: Armentano Thomas V. , Ralston C. W.
Published: June 2008

Recent growth and harvest trends in commercial timberlands of the temperate zone suggest that these forests have been serving as a net sink for about 1.0 × 109 to 1.2 × 109 t of carbon annually over the past 3 decades. This is 20 to 60% of the annual carbon release from combustion of fossil fuels over the period, indicating that recovery transients in temperate zone forests apparently have been partially dampening the increase in atmospheric CO2 caused by fossil fuel combustion and tropical forest reduction. Net forest growth is occurring throughout the temperate zone with principal carbon sinks found in North America and in Siberia. Timber inventories for North America show an excess of growth over harvest equivalent to over 5 × 1015 g of C since the 1950. Limited data suggest that in Siberia there is a large stock of slowly growing conifers that are underexploited, forming a sink equivalent to that of North America. Reafforestation in western Europe has expanded forest area by 5% since World War II. Similar recovery may now be occurring in temperate Asia. Problems of data reliability, particularly for the U.S.S.R., and the limited basis for estimating carbon balance in entire forests, suggest a severalfold uncertainty in the carbon sink estimates.
Fungicide drenches affect ectomycorrhizal development of container-grown Pinuspalustris seedlings
Authors: Pawuk William H. , Ruehle John L. , Marx Donald H.
Published: June 2008

Results with Pinuspalustris Mill, seedlings grown in pine bark with and without Pisolithustinctorius ((Pers.) Coker and Couch) inoculum and drenched with seven fungicides showed that ectomycorrhizal development by P. tinctorius was completely inhibited by Terraclor, reduced by Captan and Dexon, not affected by Mertect and Truban, and stimulated by Benlate and Banrot. In the noninfested medium, ectomycorrhizal formation by airborne fungi (mostly by Thelephoraterrestris Ehr.) was greater on seedlings drenched with Benlate, Mertect, and Dexon than on the control. Terraclor and Truban reduced T. terrestris ectomycorrhizal development. Generally, fresh top and root weights were not affected by fungicide treatment. Stem diameters of seedlings treated with Captan, Dexon, Mertect, and Truban, and the control were larger in the noninfested medium than in the medium with P. tinctorius.
Effects of nitrogen and phosphorus fertilization on Douglas-fir nursery growth and survival after outplanting
Authors: Driessche R. van den
Published: June 2008

A 5N × 5P factorial fertilizer experiment was conducted on Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seed beds at Campbell River nursery on northern Vancouver Island. Nutrient concentrations were measured in soil and seedlings. After 2 years of growth, trees were lifted from each treatment in mid-November and again in mid-February for storage. All were planted out in April and grown for 2 years. Seedling dry weight and height in the nursery were significantly affected by N fertilizer treatment, but not by P fertilizer, although seedling tissue P concentrations were low (0.09-0.17%) and available soil P was significantly increased by treatment. Largest seedlings resulted from application of 50-75 kg N/ha during the 1st year of growth and 100-150 kg N/ha during the 2nd year. Seedling dry weight was correlated with tissue N concentration (r = 0.73-0.75) and greatest dry weight was associated with a 1-0 shoot N or a 2-0 foliar N concentration of 2%. Survival and height 2 years after planting out were significantly affected by N fertilizer treatment in the nursery, and the nursery treatments resulting in largest seedlings yielded the highest survival and height. However the N concentration of 2-0 seedlings was not closely correlated with survival or height, and shoot dry weight was the most useful nursery measurement for predicting these values (r = 0.49). Fertilization did not affect cold hardiness and hardiness of trees was essentially the same at both lifting dates. Survival at 2 years after planting was unaffected by lifting date.
Environmental and physiological control of water flux through Pinuscontorta
Authors: Running Steven W.
Published: June 2008

This study reports measurements of leaf conductance, leaf water potential, temperature, humidity, and radiation collected on a stand of Pinuscontorta Dougl. ex Loud, lodgepole pine throughout a growing season at the Fraser Experimental Forest in central Colorado, U.S.A. The daily range of leaf conductances decreased 10-fold from June through August. A high correlation (R2 = 0.75) was found between predawn leaf water potential and morning maximum leaf conductance. Low atmospheric humidity significantly decreased midday leaf conductance. A comparison with humidity responses published for other conifers showed good agreement with this study. Seasonal change in total soil–plant resistance to water flux was nonlinearly correlated (R2 = 0.99) with change in predawn leaf water potential, an indirect measure of soil water potential.
Biomass and net annual primary production regressions for Populusgrandidentata on three sites in northern lower Michigan
Authors: Koerper Greg J. , Richardson Curtis J.
Published: June 2008

Dimension analysis techniques were used in the harvest of 31 largetooth aspen (Populusgrandidentata Michx.) from three mature stands (55 ± 7 years) representing a wide range of soil quality and clonal variation among aspen in northern lower Michigan, U.S.A. Regression equations were derived to predict component biomass and net annual production from tree dbh. Evaluation by analysis of covariance indicated significant differences (P < 0.05) in regression models among the sites.Total aboveground biomass of P. grandidentata was 171 565, 128 765, and 38 530 kg/ha at the good, intermediate, and poor soil sites where largetooth aspen constituted 81.5, 79.0, and 48.3% of the stand basal area, respectively. Corresponding aboveground net annual production values were 11 038, 7259, and 2925 kg/ha. Component percentages of total biomass were generally similar among sites, except for leaves. Variations in production percentages showed a production per unit leaf weight gradient parallel to the site quality gradient (i.e., poor site production per unit leaf weight was 33% less than the good site value). The errors inherent in the substitution of regressions derived from data from other sites were examined. Total biomass estimates ranged from −27 to +40% of accepted values. Errors for individual components ranged from −33 to +51%. Total aboveground biomass estimates from regressions for the combined data from all sites were acceptable within a standard error of the mean on the good and intermediate sites and with an allowance of 19% error on the poor site.
Rooting greenwood tip cuttings of several Populus clones hydroponically (hydroponic rooting of Populus cuttings)
Authors: Phipps Howard M. , Hansen Edward A. , Tolsted David N.
Published: June 2008

Greenwood cuttings of several Populus clones were successfully rooted with a relatively simple hydroponic method. Indolebutyric acid and naphthaleneacetic acid at concentrations of 500 to 5000 ppm applied as a quick dip to the cutting bases, a complete nutrient solution at 20 to 40% of full strength, and a solution temperature between 27 and 30 °C generally produced the best rooting performance of most clones. Cuttings propagated by the hydroponic procedure rooted faster and generally outgrew those produced by a standard method after being transplanted to pots and grown in the greenhouse.
Electrical resistance measurements to detect Dutch elm disease prior to symptom expression
Authors: Blanchard Robert O. , Carter Jonathan K.
Published: June 2008

Greenhouse-grown elm seedlings inoculated with Ceratocystisulmi developed visible symptoms of Dutch elm disease within 14 to 23 days. Mean electrical resistance measurements were used to detect alterations within host xylem tissue up to 6 days prior to symptom expression in populations of trees. Criteria are given for prediction of the disease in individual trees from 2 to 12 days prior to symptom expression.
Fire frequency reduced two ordersof magnitude in the Bitterroot Canyons, Montana
Authors: McCune Bruce
Published: June 2008

The fire cycle in low-elevation mesic coniferous forests of the Bitterroot Canyons, Montana, has changed from about 60 years before European settlement to about 7500 years between 1910 and 1980. The decreased fire frequency may be responsible for increased severity of western spruce bud worm outbreaks (Choristoneuraoccidentalis Freeman).
Contribution of mycorrhizae and soil fungi to nutrient cycling in a Douglas-fir ecosystem
Authors: Fogel Robert , Hunt Gary
Published: June 2008

The allocation of biomass and nutrients (N, P, K, Ca, Mg) was measured from August 1976 to September 1978 in a young, second-growth Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand in the Oregon Coast Range. Tree biomass comprised 78–79% of the total standing crop of organic matter with the remainder allocated as follows: soil organic matter, 17%; forest floor, 4%; and fungi, 2%. Bole biomass accounted for 64–66% of the total tree standing crop; the remainder was apportioned among: nonmycorrhizal roots, 17–18%; branches, 7–8%; mycorrhizae, 6%; and foliage, 4%. Nutrient stocks in aboveground tree components exceeded those in belowground components by one to nine times. For all nutrients except Ca, roots and mycorrhizae contained larger stocks than either the forest floor or fungi; amounts of Ca in the forest floor and in fungi were twice those in roots and mycorrhizae. Return of organic matter to the soil by fine roots and mycorrhizae ranged from 84 to 78% of total tree return. About 73% of total net primary production was invested in growth and maintenance of roots and mycorrhizae. Return of N, P, and K to the soil by mycorrhizae comprised 83–87% of total tree return and 25–51% of Ca and Mg return. Return by mycorrhizae of N, P, and K was four to five times greater than that of roots, nearly equal for Ca, and three times less for Mg.
Effects of heavy metals on radicle growth of selected woody species germinated on filter paper, mineral and organic soil substrates
Authors: Patterson III William A. , Olson John J.
Published: June 2008

Copper, nickel, and cobalt solutions were added to a variety of substrates to test the effects of these metals on the germination and radicle elongation of two deciduous and five coniferous woody species native to eastern North America. For species grown on filter paper, germination was little affected by metal concentrations of up to 100 ppm. Filter-paper tests showed that radicle elongation was reduced by 25% at concentrations that ranged from 1 to 5 ppm for Betulapapyrifera Marsh, to as much as 50 to 100 ppm for Pinusstrobus L. Concentrations causing similar effects on mineral and organic soil substrates were, respectively, 10 and 100 times greater than those for filter paper. For all species, toxicity followed the pattern Ni > Cu > Co for filter paper and [Formula: see text] for mineral and organic soils. Deciduous species were more readily damaged by these metals than were coniferous species.
Root development of container-reared, nursery-grown, and naturally regenerated pine seedlings
Authors: Nichols T. J. , Alm A. A.
Published: June 2008

Root systems of 6- to 10-year-old red pine (Pinusresinosa Ait.) and jack pine (Pinusbanksiana Lamb.) trees reared in various containers were excavated from four different sites and studied. Nursery-grown and naturally regenerated trees of similar age and stem size growing on the same sites were used for comparison. Root cross-sectional area (RCSA) taken 5 cm from the stem, a measurement found to be highly correlated (r = 0.94) with root weight (In–In transformation), was used to describe root system size. The average RCSA's of jack pine reared in paper pots, book planters, and nonribbed styroblock-2 containers were smaller than those of naturally regenerated seedlings, but the differences were not statistically significant. Jack pine and red pine reared in Ontario tubes had significantly larger RCSA's than nursery-grown trees. There were some differences in radial distribution of horizontal roots, and the apportionment between horizontal and vertical root components differed between some of the seedling types.
Time-related changes in specific gravity and moisture content of spruce budworm killed balsam fir
Authors: Barnes Douglas P. , Sinclair Steven A.
Published: June 2008

The variation in specific gravity and moisture content of healthy balsam fir (Abiesbalsamea (L.) Mill.) and balsam fir killed by the spruce budworm (Choristoneurafumiferana Clem.) in northern Minnesota has been investigated. Disks were removed at 100-in. (254-cm) intervals along the merchantable boles of 31 healthy trees, 16 trees dead 6 months, 42 trees dead 12months, and 18 trees dead 22 months. Knot-free wedges were cut from the disks and separated into inner and outer sections for specific gravity and moisture content determinations. Outer and inner sections' specific gravity averages for healthy (control) balsam fir varied within tree, decreasing then increasing with height. This trend was not apparent for the outer section specific gravity averages in the dead tree categories. Average specific gravities for the four tree categories were not significantly different even 22 months after death. Tree categories' average moisture content rapidly decreased with time after death, and significant differences were detected within months of tree death. Significant outer section moisture losses occurred within 6 months after death, while significant inner section losses developed after 12 or more months.
Dye-layer density analysis identifies new Douglas-fir beetle attacks
Authors: Hall P. M. , McLean J. A. , Murtha P. A.
Published: June 2008

Two study plots containing Douglas-fir, Pseudotsugamenziesii (Mirb.) Franco, newly infested by the Douglas-fir beetle, Dendroctonuspseudotsugae Hopk., were photographed with large scale (1:1100) color infrared film on 29 July 1979 approximately 3 months after insect attack. Significant differences were found between cyan dye-layer densities, and the green/red and red/infrared ratios of the images of the successfully attacked and healthy trees. Discriminant analysis clearly separated the two image groups with 52 of 53 healthy trees and 9 of 15 successfully attacked trees being correctly classified. It is concluded that trees which have been successfully attacked by beetles can be detected on color infrared air photos approximately 3 months after initial attack while the trees still support visually green, healthy appearing foliage.
APPROXIMATING THE MEAN SPEEDUP IN TRACE MONOIDS
Authors: BERTONI ALBERTO , RADICIONI ROBERTO
Published: June 2008

Traces can be viewed as parallel processes and the "mean speedup" of a trace monoid has been introduced as a measure of "intrinsic parallelism" of the monoid. We study the problem of computing the mean speedup under two conditions: uniform distribution on the words of given length and uniform distribution on the traces of given height. In the first case, we give an approximability result showing a probabilistic fully polynomial time approximation scheme, while, in the second case, we prove that the problem is NP-hard to approximate within n1-c for every ∊ > 0, unless NP = coR. A further consequence is the hardness of the problem of generating traces of a given height uniformly at random.
NON-CONSTRUCTIVE METHODS FOR FINITE PROBABILISTIC AUTOMATA
Authors: FREIVALDS RŪSIŅŠ
Published: June 2008

Size (the number of states) of finite probabilistic automata with an isolated cut-point can be exponentially smaller than the size of any equivalent finite deterministic automaton. However, the proof is non-constructive. The result is presented in two versions. The first version depends on Artin's Conjecture (1927) in Number Theory. The second version does not depend on conjectures not proved but the numerical estimates are worse. In both versions the method of the proof does not allow an explicit description of the languages used. Since our finite probabilistic automata are reversible, these results imply a similar result for quantum finite automata.
STATE COMPLEXITY OF UNION AND INTERSECTION OF FINITE LANGUAGES
Authors: HAN YO-SUB , SALOMAA KAI
Published: June 2008

We investigate the state complexity of union and intersection for finite languages. Note that the problem of obtaining the tight bounds for both operations was open. First we compute upper bounds using structural properties of minimal deterministic finite-state automata for finite languages. Then, we show that the upper bounds are tight if we have a variable sized alphabet that can depend on the size of input deterministic finite-state automata. In addition, we prove that the upper bounds are unreachable for any fixed sized alphabet.
CONJUNCTIVE GRAMMARS GENERATE NON-REGULAR UNARY LANGUAGES
Authors: JEŻ ARTUR
Published: June 2008

Conjunctive grammars, introduced by Okhotin, extend context-free grammars by an additional operation of intersection in the body of any production of the grammar. Several theorems and algorithms for context-free grammars generalize to the conjunctive case. Okhotin posed nine open problems concerning those grammars. One of them was a question, whether a conjunctive grammars over a unary alphabet generate only regular languages. We give a negative answer, contrary to the conjectured positive one, by constructing a conjunctive grammar for the language {a4n : n ∈ ℕ}. We also generalize this result: for every set of natural numbers L we show that {an : n ∈ L} is a conjunctive unary language, whenever the set of representations in base-k system of elements of L is regular, for arbitrary k.
AVOIDING APPROXIMATE SQUARES
Authors: OCHEM PASCAL , RAMPERSAD NARAD , SHALLIT JEFFREY
Published: June 2008

As is well-known, Axel Thue constructed an infinite word over a 3-letter alphabet that contains no squares, that is, no nonempty subwords of the form xx. In this paper we consider a variation on this problem, where we try to avoid approximate squares, that is, subwords of the form xx' where |x| = |x'| and x and x' are "nearly" identical.
ON THE IMPLICATION OF MULTIVALUED DEPENDENCIES IN PARTIAL DATABASE RELATIONS
Authors: LINK SEBASTIAN
Published: June 2008

The implication of multivalued dependencies (MVDs) in relational databases has originally and independently been defined in the context of some fixed finite universe by Delobel, Fagin, and Zaniolo. Biskup observed that the original axiomatisation for MVD implication does not reflect the fact that the complementation rule is merely a means to achieve database normalisation. He proposed two alternative ways to overcome this deficiency: i) an axiomatisation that does represent the role of the complementation rule adequately, and ii) a notion of MVD implication in which the underlying universe of attributes is left undetermined together with an axiomatisation of this notion.

In this paper we investigate multivalued dependencies with null values (NMVDs) as defined and axiomatised by Lien. We show that Lien's axiomatisation does not adequately reflect the role of the complementation rule, and extend Biskup's findings for MVDs in total database relations to NMVDs in partial database relations. Moreover, a correspondence between (minimal) axiomatisations in fixed universes that do reflect the property of complementation and (minimal) axiomatisations in undetermined universes is shown.
THE BENFORD-NEWCOMB DISTRIBUTION AND UNAMBIGUOUS CONTEXT-FREE LANGUAGES
Authors: RAVIKUMAR BALA
Published: June 2008

For a string w ∈ {0,1, 2,…, d-1}*, let vald(w) denote the integer whose base d representation is the string w and let MSDd(x) denote the most significant or the leading digit of a positive integer x when x is written as a base d integer. Hirvensalo and Karhumäki [9] studied the problem of computing the leading digit in the ternary representation of 2x ans showed that this problem has a polynomial time algorithm. In [16], some applications are presented for the problem of computing the leading digit of AB for given inputs A and B. In this paper, we study this problem from a formal language point of view. Formally, we consider the language Lb,d,j = {w|w ∈ {0,1, 2,…, d-1}*, 1 ≤ j ≤ 9, MSDb(dvalb(w))) = j} (and some related classes of languages) and address the question of whether this and some related languages are context-free. Standard pumping lemma proofs seem to be very difficult for these languages. We present a unified and simple combinatorial technique that shows that these languages are not unambiguous context-free languages. The Benford-Newcomb distribution plays a central role in our proofs.
TISSUE-LIKE P SYSTEMS WITH DYNAMICALLY EMERGING REQUESTS
Authors: CSUHAJ-VARJÚ ERZSÉBET , PĂUN GHEORGHE , VASZIL GYÖRGY
Published: June 2008

We study tissue-like P systems which use string objects and communicate by introducing communication symbols in the strings. We prove that these systems are computationally complete and moreover, they are computationally efficient in the sense that NP-complete problems can be solved in this framework in polynomial time.
EXACT SOLUTIONS OF THE SCHRÖDINGER EQUATION FOR A NEW RING-SHAPED NONHARMONIC OSCILLATOR POTENTIAL
Authors: CHENG YAN-FU , DAI TONG-QING
Published: June 2008

The bound state solutions of the Schrödinger equation with a new ring-shaped nonharmonic potential are presented using exactly the Nikiforov–Uvarov method. It is found that the solutions of the angular wave function can be expressed by Jacobi polynomial and radial wave functions are given by the generalized Laguerre polynomials. We also discuss the special case for α = 0 and β = 0 respectively.
MIRROR WORLD WITH BROKEN MIRROR PARITY, E6 UNIFICATION AND COSMOLOGY
Authors: DAS C. R. , LAPERASHVILI L. V.
Published: June 2008

In the present paper we develop a concept of parallel ordinary (O) and mirror (M) worlds. We have shown that in the case of a broken mirror parity (MP), the evolutions of fine structure constants in the O- and M-worlds are not identical. It is assumed that E6-unification inspired by superstring theory restores the broken MP at the scale ~ 1018 GeV , what unavoidably leads to the different E6-breakdowns at this scale: E6 → SO (10) × U (1)Z — in the O-world, and E′6 → SU (6)′ × SU (2)′Z — in the M-world. Considering only asymptotically free theories, we have presented the running of all the inverse gauge constants [Formula: see text] in the one-loop approximation. Then a "quintessence" scenario suggested in Refs. 56–61 is discussed for our model of accelerating universe. Such a scenario is related with an axion ("acceleron") of a new gauge group SU (2)′Z which has a coupling constant gZ extremely growing at the scale ΛZ ~ 10-3 eV .
SUBLEADING TERMS IN ASYMPTOTIC PASSARINO–VELTMAN FUNCTIONS
Authors: BECCARIA M. , GOUNARIS G. J. , LAYSSAC J. , RENARD F. M.
Published: June 2008

We write explicit and self-contained asymptotic expressions for the tensorial B, C and D Passarino–Veltman functions. These include quadratic and linear logarithmic terms, as well as subleading constant terms. Only mass-suppressed [Formula: see text] contributions are neglected. We discuss the usefulness of such expressions, particularly for studying one-loop effects in 2-to-2 body processes at high energy.
SINGLET FERMION DARK MATTER AND ELECTROWEAK BARYOGENESIS WITH RADIATIVE NEUTRINO MASS
Authors: BABU K. S. , MA ERNEST
Published: June 2008

The model of radiative neutrino mass with dark matter proposed by one of us is extended to include a real singlet scalar field. There are then two important new consequences. One is the realistic possibility of having the lightest neutral singlet fermion (instead of the lightest neutral component of the dark scalar doublet) as the dark matter of the universe. The other is a modification of the effective Higgs potential of the Standard Model, consistent with electroweak baryogenesis.
ANTICIPATING A NEW GOLDEN AGE
Authors: WILCZEK FRANK
Published: June 2008

The standard model of fundamental interactions is remarkably successful, but it leaves an unfinished agenda. Several major questions seem ripe for exploration in the near future. I anticipate that the coming decade will be a Golden Age of discovery in fundamental physics.
PERTURBATIVE QCD AT HIGH ENERGY COLLIDERS
Authors: GONSALVES RICHARD J.
Published: June 2008

Selected applications of perturbative Quantum chromodynamics (QCD) to predictions of the Standard Model for processes at high energy colliders are reviewed with emphasis on past successes and future problems.
RELATIVISTIC QUANTUM MECHANICS OF THREE-PARTICLE SYSTEMS
Authors: FUDA MICHAEL G.
Published: June 2008

A brief review of the Bakamjian–Thomas method for constructing Poincaré invariant models of few-particle systems is presented. An application of the method to a simple model of the coupled N – πN – ππN system is outlined. This three-particle model contains vertex interactions as well as renormalization contributions.
PARTICLE PHYSICS IN THE SKY: THE CURRENT STATUS OF INFLATION
Authors: KINNEY WILLIAM H.
Published: June 2008

I discuss the current status of inflationary cosmology in light of the recent WMAP 3-year data release. The basic predictions of inflation are all supported by the data. Inflation also makes predictions which are have not been well tested by current data but can be by future experiments, most notably a deviation from a scale-invariant power spectrum and the production of primordial gravitational waves. A scale-invariant spectrum is disfavored by current data, but not conclusively. Tensor modes are currently poorly constrained, and slow-roll inflation does not make an unambiguous prediction of the expected amplitude of primordial gravitational waves. A tensor/scalar ratio of r ≃ 0.01 is within reach of near-future measurements.
A COMPUTATIONAL MODEL FOR LESION DYNAMICS IN MULTIPLE SCLEROSIS OF THE BRAIN
Authors: MOHAN T. R. KRISHNA , SEN SURAJIT , RAMANATHAN MURALI
Published: June 2008

Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system (CNS) that is characterized by lesions with inflammatory cells, axons with the insulating myelin sheath damaged, and axonal loss. The causes of MS are not known and there is as yet no cure. The purpose of this research was to evaluate a physically motivated network model for lesion formation in the brain. The parsimonious network model contained two elements: (i) a spatially spreading pathological process causing cell damage and death leading to neuro-degeneration and, (ii) generation of alarm signals by the damaged cells that lead to activation of programmed death of cells surrounding the lesions in an attempt to contain the spatial spread of the pathologic process. Simulation results with a range of network geometries indicated that the model was capable of describing lesion progression and arrest. The modeling results also demonstrated dynamical complexity with sensitivity to initial conditions.
FEYNCHOIS: A FEYNMAN DIAGRAM GENERATOR
Authors: CHOI CHUL-WOO , GONSALVES RICHARD J.
Published: June 2008

A Feynman diagram generator, named FeynChois, is described. It provides the user with a full GUI (Graphical User Interface) environment which enables the generation diagrams automatically with several mouse operations. The diagram generator is built on an Application Programming Interface (API) called ViewableBeans which provides a framework for programming graphically representable objects. We also present a means for describing Feynman rules in a computer friendly manner using the XML (Extensible Markup Language) format.
Provably good moving least squares
Authors: Kolluri Ravikrishna
Published: June 2008

We analyze a
moving least squares
(MLS) interpolation scheme for reconstructing a surface from point cloud data. The input is a sufficiently dense set of sample points that lie near a closed surface
F
with approximate surface normals. The output is a reconstructed surface passing near the sample points. For each sample point
s
in the input, we define a linear
point function
that represents the local shape of the surface near
s
. These point functions are combined by a weighted average, yielding a three-dimensional function
I
. The reconstructed surface is implicitly defined as the zero set of
I
.

We prove that the function
I
is a good approximation to the signed distance function of the sampled surface
F
and that the reconstructed surface is geometrically close to and isotopic to
F
. Our sampling requirements are derived from the
local feature size
function used in Delaunay-based surface reconstruction algorithms. Our analysis can handle noisy data provided the amount of noise in the input dataset is small compared to the feature size of
F
.
Primal-dual approach for directed vertex connectivity augmentation and generalizations
Authors: Végh László A. , Benczúr András A.
Published: June 2008

In their seminal paper, Frank and Jordán [1995] show that a large class of optimization problems, including certain directed graph augmentation, fall into the class of covering supermodular functions over pairs of sets. They also give an algorithm for such problems, however, it relies on the ellipsoid method. Prior to our result, combinatorial algorithms existed only for the 0--1 valued problem. Our key result is a combinatorial algorithm for the general problem that includes directed vertex or
S
−
T
connectivity augmentation. The algorithm is based on Benczúr's previous algorithm for the 0--1 valued case [Benczúr 2003].

Our algorithm uses a primal-dual scheme for finding covers of partially ordered sets that satisfy natural abstract properties as in Frank and Jordán. For an initial (possibly greedy) cover, the algorithm searches for witnesses for the necessity of each element in the cover. If no two (weighted) witnesses have a common cover, the solution is optimal. As long as this is not the case, the witnesses are gradually exchanged for smaller ones. Each witness change defines an appropriate change in the solution; these changes are finally unwound in a shortest-path manner to obtain a solution of size one less.
Embeddings of negative-type metrics and an improved approximation to generalized sparsest cut
Authors: Chawla Shuchi , Gupta Anupam , Räcke Harald
Published: June 2008

In this article, we study metrics of
negative type
, which are metrics (
V
, d) such that √d is an Euclidean metric; these metrics are thus also known as ℓ
2
-squared metrics. We show how to embed
n
-point negative-type metrics into Euclidean space ℓ
2
with distortion
D
=
O
(log
3/4
n
). This embedding result, in turn, implies an
O
(log
3/4
k
)-approximation algorithm for the Sparsest Cut problem with nonuniform demands. Another corollary we obtain is that
n
-point subsets of ℓ
1
embed into ℓ
2
with distortion
O
(log
3/4
n
).
Limitations of cross-monotonic cost-sharing schemes
Authors: Immorlica Nicole , Mahdian Mohammad , Mirrokni Vahab S.
Published: June 2008

A cost-sharing scheme is a set of rules defining how to share the cost of a service (often computed by solving a combinatorial optimization problem) amongs serviced customers. A cost-sharing scheme is cross-monotonic if it satisfies the property that everyone is better off when the set of people who receive the service expands. In this article, we develop a novel technique for proving upper bounds on the
budget-balance factor
of cross-monotonic cost-sharing schemes or the worst-case ratio of recovered cost to total cost. We apply this technique to games defined, based on several combinatorial optimization problems, including the problems of edge cover, vertex cover, set cover, and metric facility location and, in each case, derive tight or nearly-tight bounds. In particular, we show that for the facility location game, there is no cross-monotonic cost-sharing scheme that recovers more than a third of the total cost. This result, together with a recent 1/3-budget-balanced cross-monotonic cost-sharing scheme of Pál and Tardos [2003] closes the gap for the facility location game. For the vertex cover and set cover games, we show that no cross-monotonic cost-sharing scheme can recover more than a
O
(
n
−1/3
) and
O
(1/
n
) fraction of the total cost, respectively. Finally, we study the implications of our results on the existence of group-strategyproof mechanisms. We show that every group-strategyproof mechanism corresponds to a cost-sharing scheme that satisfies a condition weaker than cross-monotonicity. Using this, we prove that group-strategyproof mechanisms satisfying additional properties give rise to cross-monotonic cost-sharing schemes and therefore our upper bounds hold.
Formulating and implementing profiling over adaptive ranges
Authors: Mysore Shashidhar , Agrawal Banit , Neuber Rodolfo , Sherwood Timothy , Shrivastava Nisheeth , Suri Subhash
Published: June 2008

Modern computer systems are called on to deal with billions of events every second, whether they are executed instructions, accessed memory locations, or forwarded packets. This presents a serious challenge to those who seek to quantify, analyze, or optimize such systems, because important trends and behaviors may easily be lost in a sea of data. We present range-adaptive profiling (RAP) as a new and general-purpose profiling method capable of
hierarchically
efficiently classifying streams of data in hardware. Through the use of RAP, events in an input stream are dynamically classified into increasingly precise categories, based on the frequency with which they occur. The more important a class, or range of events, the more precisely it is quantified. Despite the dynamic nature of our technique, we build upon tight theoretic bounds covering both worst-case error, as well as the required memory. In the limit, it is known that error and the memory bounds can be
independent
of the stream size and grow only linearly with the level of precision desired. Significantly, we expose the critical constants in these algorithms and through careful engineering, algorithm redesign, and use of heuristics, we show how a high-performance profile system can be implemented for range-adaptive profiling. RAP can be used on various profiles, such as PCs, load values, and memory addresses, and has a broad range of uses, from hot-region profiling to quantifying cache miss value locality. We propose two methods of implementation of RAP, one in software and the other with specialized hardware, for which we also describe our prototype FPGA implementation. We show that with just 8KB of memory, range profiles can be gathered with an average accuracy of 98%.
Versatility of extended subwords and the matrix register file
Authors: Shahbahrami Asadollah , Juurlink Ben , Vassiliadis Stamatis
Published: June 2008

Extended subwords and the matrix register file (MRF) are two micro architectural techniques that address some of the limitations of existing SIMD architectures. Extended subwords are wider than the data stored in memory. Specifically, for every byte of data stored in memory, there are four extra bits in the media register file. This avoids the need for data-type conversion instructions. The MRF is a register file organization that provides both conventional row-wise, as well as column-wise, access to the register file. In other words, it allows to view the register file as a matrix in which corresponding subwords in different registers corresponds to a column of the matrix. It was introduced to accelerate matrix transposition which is a very common operation in multimedia applications. In this paper, we show that the MRF is very versatile, since it can also be used for other permutations than matrix transposition. Specifically, it is shown how it can be used to provide efficient access to strided data, as is needed in, e.g., color space conversion. Furthermore, it is shown that special-purpose instructions (SPIs), such as the sum-of-absolute differences (SAD) instruction, have limited usefulness when extended subwords and a few general SIMD instructions that we propose are supported, for the following reasons. First, when extended subwords are supported, the SAD instruction provides only a relatively small performance improvement. Second, the SAD instruction processes 8-bit subwords only, which is not sufficient for quarter-pixel resolution nor for cost functions used in image and video retrieval. Results obtained by extending the SimpleScalar toolset show that the proposed techniques provide a speedup of up to 3.00 over the MMX architecture. The results also show that using, at most, 13 extra media registers yields an additional performance improvement ranging from 1.38 to 1.57.
Efficient hardware code generation for FPGAs
Authors: Guo Zhi , Najjar Walid , Buyukkurt Betul
Published: June 2008

The wider acceptance of FPGAs as a computing device requires a higher level of programming abstraction. ROCCC is an optimizing C to HDL compiler. We describe the code generation approach in ROCCC. The smart buffer is a component that reuses input data between adjacent iterations. It significantly improves the performance of the circuit and simplifies loop control. The ROCCC-generated datapath can execute one loop iteration per clock cycle when there is no loop dependency or there is only scalar recurrence variable dependency. ROCCC's approach to supporting while-loops operating on scalars makes the compiler able to move scalar iterative computation into hardware.
How RNA Unfolds and Refolds
Authors: Li Pan T.X. , Vieregg Jeffrey , Tinoco Ignacio
Published: June 2008

Understanding how RNA folds and what causes it to unfold has become more important as knowledge of the diverse functions of RNA has increased. Here we review the contributions of single-molecule experiments to providing answers to questions such as: How much energy is required to unfold a secondary or tertiary structure? How fast is the process? How do helicases unwind double helices? Are the unwinding activities of RNA-dependent RNA polymerases and of ribosomes different from other helicases? We discuss the use of optical tweezers to monitor the unfolding activities of helicases, polymerases, and ribosomes, and to apply force to unfold RNAs directly. We also review the applications of fluorescence and fluorescence resonance energy transfer to measure RNA dynamics.