bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping QTL for grain yield, yield components, and spike features in a doubled haploid population of bread wheat
Authors: Heidari Bahram , Sayed-Tabatabaei Badraldin Ebrahim , Saeidi Ghodratollah , Kearsey Michael , Suenaga Kazuhiro
Published: June 2011

A doubled haploid (DH) population derived from a cross between the Japanese cultivar ‘Fukuho-kumogi’ and the Israeli wheat line ‘Oligoculm’ was used to map genome regions involved in the expression of grain yield, yield components, and spike features in wheat (Triticum aestivum L). A total of 371 markers (RAPD, SSR, RFLP, AFLP, and two morphological traits) were used to construct the linkage map that covered 4190 cM of wheat genome including 28 linkage groups. The results of composite interval mapping for all studied traits showed that some of the quantitative trait loci (QTL) were stable over experiments conducted in 2004 and 2005. The major QTL located in the Hair–Xpsp2999 interval on chromosome 1A controlled the expression of grains/spike (R2= 12.9% in 2004 and 22.4% in 2005), grain weight/spike (R2= 21.4% in 2004 and 15.8% in 2005), and spike number (R2= 15.6% in 2004 and 5.4% in 2005). The QTL for grain yield located on chromosomes 6A, 6B, and 6D totally accounted for 27.2% and 31.7% of total variation in this trait in 2004 and 2005, respectively. Alleles inherited from ‘Oligoculm’ increased the length of spikes and had decreasing effects on spike number. According to the data obtained in 2005, locus Xgwm261 was associated with a highly significant spike length QTL (R2= 42.33%) and also the major QTL for spikelet compactness (R2= 26.1%).
A comparison of small-area estimation techniques to estimate selected stand attributes using LiDAR-derived auxiliary variables
Authors: Goerndt Michael E. , Monleon Vicente J. , Temesgen Hailemariam
Published: June 2011

One of the challenges often faced in forestry is the estimation of forest attributes for smaller areas of interest within a larger population. Small-area estimation (SAE) is a set of techniques well suited to estimation of forest attributes for small areas in which the existing sample size is small and auxiliary information is available. Selected SAE methods were compared for estimating a variety of forest attributes for small areas using ground data and light detection and ranging (LiDAR) derived auxiliary information. The small areas of interest consisted of delineated stands within a larger forested population. Four different estimation methods were compared for predicting forest density (number of trees/ha), quadratic mean diameter (cm), basal area (m2/ha), top height (m), and cubic stem volume (m3/ha). The precision and bias of the estimation methods (synthetic prediction (SP), multiple linear regression based composite prediction (CP), empirical best linear unbiased prediction (EBLUP) via Fay–Herriot models, and most similar neighbor (MSN) imputation) are documented. For the indirect estimators, MSN was superior to SP in terms of both precision and bias for all attributes. For the composite estimators, EBLUP was generally superior to direct estimation (DE) and CP, with the exception of forest density.
Modelled impact of Norway spruce logging residue extraction on biodiversity in Sweden
Authors: Dahlberg Anders , Thor Göran , Allmér Johan , Jonsell Mats , Jonsson Mattias , Ranius Thomas
Published: June 2011

Logging residues are increasingly being extracted for bioenergy purposes. This study estimates how extraction of fine woody debris (FWD) may affect the overall habitat availability for 577 species of wood- and bark-inhabiting basidiomycetes, beetles, and lichens in Sweden using Norway spruce ( Picea abies (L.) Karst.) as their primary substrate. We combined modeling of (i) the amount of various types of woody debris available throughout a forest rotation in managed forests with (ii) a classification of each species’ associations with different types of wood. In three different regions, we compared a scenario with no logging residue extraction with three different levels of extraction. Our results suggest that the extraction may cause a 35%–45% reduction in aboveground FWD and a more than 20% decline in the potential amount of substrate for about 50% of the species (affecting basidiomycetes and beetles more than lichens). The intensified forestry during the last century has, however, steadily increased the production of FWD. Furthermore, no red-listed species is primarily associated with logging residues of Norway spruce. Therefore, the current situation in Sweden with extraction of 70% of Norway spruce FWD on 50% of the clearcuts probably constitutes a minor contribution to the regional extinction risks.
Estimating the effect of poplar resistance on the performance of the woolly poplar aphid, Phloeomyzus passerinii, in various experimental conditions
Authors: Pointeau Sophie , Sallé Aurélien , Lesieur Vincent , Bankhead-Dronnet Stéphanie , Bonnaffoux Matthieu , Lieutier François
Published: June 2011

The woolly poplar aphid, Phloeomyzus passerinii (Signoret) (Sternorrhyncha: Aphididae), causes the most damage to poplars in southern Europe and the Near East as outbreaks can lead to massive mortality in mature stands. Previous studies, conducted on poplar cuttings or young trees, showed that resistance varied depending on the poplar genotype. However, these results did not indicate how aphid populations were affected by tree resistance and were only partially confirmed by field observations. This study investigated the effect on aphid settlement and performance of poplar genotypes belonging to Populus × canadensis Moench, Populus × interamericana Brockh., Populus nigra L., Populus deltoides Bartram ex Marshall, and Populus trichocarpa Torr. & A. Gray ex Hook. using a single aphid clone. The study was conducted under three experimental conditions: (i) unrooted cuttings, (ii) potted cuttings, and (iii) mature trees. The aphid settlement rate, the larval development rate, and the fecundity were affected by the poplar genotype, highlighting the antixenotic and antibiotic properties involved in tree resistance to P. passerinii. The laboratory results for aphid performance and settlement rate on unrooted cuttings were transposable to both potted cuttings and mature trees. Laboratory studies could, therefore, provide useful information for identifying the parameters involved in resistance mechanisms.
Genetic analysis of Eucalyptus globulus diameter, straightness, branch size, and forking in Western Australia
Authors: Callister A.N. , England N. , Collins S.
Published: June 2011

Eucalyptus globulus Labill. is increasingly considered for supply of solid-wood products such as sawlogs, yet genetic studies of solid-wood traits have been lacking. We estimated genetic parameters of growth and form traits that affect log value in full-sib families from two advanced-generation breeding populations on eight sites in Western Australia. Mean single-site heritability was 0.11 ± 0.01 for diameter at breast height (DBH), 0.28 ± 0.05 for stem straightness, 0.09 ± 0.02 for branch thickness, and 0.05 ± 0.02 for forking incidence. Dominance effects were significant (p < 0.05) at four sites for DBH and branch thickness and at three sites (one population) for straightness. Mean intersite additive genetic correlations were 0.76 ± 0.06 for DBH (n = 7), 0.75 ± 0.11 for stem straightness (n = 7), and 0.58 ± 0.07 for branch thickness (n = 4). Mean intersite dominance genetic correlations were 0.90 ± 0.04 for DBH (n = 7), 0.26 ± 0.27 (n = 4) for straightness, and 0.68 ± 0.11 for branch thickness (n = 3). Additive genetic correlations between DBH and straightness ranged from –0.71 ± 0.23 to 0.33 ± 0.19 with an average of –0.18 ± 0.12 (n = 8). Genetic correlations between DBH and branch thickness were mostly weak although straightness was generally associated with thinner branches (mean additive correlation 0.44 ± 0.15, n = 6). We conclude that prospects appear favourable for improving the solid-wood value of E. globulus by selection and breeding.
Stiffness of Douglas-fir lumber: effects of wood properties and genetics
Authors: Vikram Vikas , Cherry Marilyn L. , Briggs David , Cress Daniel W. , Evans Robert , Howe Glenn T.
Published: June 2011

Because stiffness (modulus of elasticity (MOE)) is important for structural wood products, breeders and silviculturists seek to efficiently measure and improve this trait. We studied MOE in a 25-year-old progeny test of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) using field-based tools (ST300 and HM200) to measure stress wave MOE of standing trees and logs. We measured density, static bending MOE, and transverse vibration MOE on 2 × 4s, and density, SilviScan MOE, and SilviScan microfibril angle on small clearwood samples. Bending MOE had moderate to strong phenotypic and genetic correlations with stress wave MOE of trees and logs, transverse vibration MOE of 2 × 4s, and the densities of 2 × 4s and basal wood discs but was weakly correlated with the numbers and sizes of knots. The best lumber grade had the highest bending stiffness and smallest edge knots. Bending stiffness had a strong positive correlation with the density of small clearwood samples and a moderate negative correlation with microfibril angle. Compared with microfibril angle and edge knots, path analyses indicated that density had the strongest direct effect on bending MOE. We recommend that breeders measure and select for stress wave velocity to improve bending stiffness in Douglas-fir. Genetic gains can be increased by including wood density, but genetic selection for fewer or smaller knots will be ineffective.
Efficacy of tree defense physiology varies with bark beetle population density: a basis for positive feedback in eruptive species
Authors: Boone Celia K. , Aukema Brian H. , Bohlmann Jörg , Carroll Allan L. , Raffa Kenneth F.
Published: June 2011

We evaluated the ability of constitutive and inducible defenses to protect trees and restrict herbivore reproduction across the endemic, incipient (i.e., transitory), and eruptive phases of a native bark beetle species. Host defenses were major constraints when mountain pine beetle (Dendroctonus ponderosae Hopkins) populations were low, but inconsequential after stand-level densities surpassed a critical threshold. We annually examined all lodgepole pines (Pinus contorta Douglas var. latifolia) in six 12–18 ha stands for 3–6 years for beetle attack and establishment as beetle densities progressed through various population phases. We also assayed a suite of tree physiological and chemical attributes and related them to subsequent attacks during that year. Rapidly inducible defenses appeared more important than constitutive defenses, and total monoterpenes were more important than particular constituents. Trees that exude more resin and accumulate higher monoterpene concentrations in response to simulated attack largely escaped natural attacks when populations were low. In stands where beetles had reached incipient densities, these defenses were ineffective. Larger diameter trees had more pronounced defenses than smaller diameter trees. As populations increased, beetles selected increasingly larger, more resource-rich trees, despite their better defenses. When populations were too low for cooperative attack, beetles exploited trees weakened by lower-stem insects. Behavioral plasticity allows beetles to persist at endemic levels until conditions shift, after which positive feedbacks predominate.
Growth performance, windthrow, and insects: meta-analyses of parameters influencing performance of mixed-species stands in boreal and northern temperate biomes
Authors: Griess Verena C. , Knoke Thomas
Published: June 2011

Stand structure is a key attribute of forest ecosystems. Mixed-tree plantations are widely felt to be the appropriate option for providing a broad range of goods and environmental services and to reduce susceptibility to natural hazards. However, the debate continues whether mixed plantations can achieve greater financial return than monocultures can. In this study, mixed-species stands of conifers and hardwood species were analyzed in consideration of economically relevant factors. Growth performance and resistance to hazards and pests are widely noted in the literature and are of general economic interest. Thus meta-analyses of relevant studies were conducted to test the following hypotheses: (1) mixing tree species has no significant influence on growth performance or resistance against hazards and pests and, if refuted, (2) mixing tree species causes mainly negative effects on growth performance and resistance against hazards and pests. However, a positive impact of mixing tree species was proven for resistance against windthrow and pests. The meta-analysis on growth performance just as well indicates a positive effect of mixing tree species. Overall, these positive results underscore the need for a large number of additional studies to examine different silvicultural systems to develop optimal management prescriptions to benefit from positive interactions.
Ethanol synthesis by anoxic root segments from five cedar species relates to their habitat attributes but not their known differences in vulnerability to Phytophthora lateralis root disease
Authors: Kelsey Rick G. , Joseph Gladwin , McWilliams Michael G.
Published: June 2011

Ethanol synthesis by anoxic root segments from Port Orford cedar (Chamaecyparis lawsoniana (A. Murray bis) Parl.); yellow cedar (Chamaecyparis nootkatensis (D. Don) Spach); Atlantic white cedar (Chamaecyparis thyoides (L.) Britton, Sterns & Poggenb.); western redcedar (Thuja plicata Donn ex D. Don), and incense cedar (Calocedrus decurrens (Torr.) Florin ) was compared to determine whether the amounts that they produced during flooding could contribute the known greater vulnerability of Port Orford cedar to infection by Phytophthora lateralis Tucker & Milbrat. Roots were incubated in water at 5, 15, 25, and 35 °C for 14 days with periodic sampling. After 12 h of anoxic stress, Atlantic white cedar and yellow cedar roots produced equal quantities of ethanol that were about two times more than produced by the other three species, which did not differ from one another. The roots remained anoxic for 14 days, with ethanol concentrations increasing 6 to 11 times depending on the species. After 14 days, Atlantic white cedar remained the highest ethanol producer at two to three times more than the other species, whereas incense cedar yields were the lowest. Yellow cedar, western redcedar, and Port Orford cedar had intermediate levels of ethanol. The similarity in responses of Port Orford cedar to the other species is strong evidence that ethanol is not an important contributor to its known greater vulnerability to P. lateralis infection. In general, root incubation temperature affected ethanol synthesis similarly for all species. Increases in temperature from 5 to 15 °C or 15 to 25 °C doubled the ethanol yields at 12 h. Literature ratings of anaerobic tolerance for these cedars were compared with ratings based on their ethanol yields after 12 h or 14 days of anoxia. The latter rating appears to more closely correspond with the cedars associations to wet, mesic environments and their likelihood of experiencing anoxia via flooding.
Ecological and biological information improves inferred paternity in a white spruce breeding orchard
Authors: Doerksen T.K. , Deslauriers M. , Beaulieu J.
Published: June 2011

Biological, ecological, and genetic marker information was used to predict paternal (nF= 104) siring success for offspring (nO= 522) sampled over two years from two mother clones. Distance alone was predictive of siring success, whereas fecundity and a provenance indicator variable captured additional, but not all, remaining variation. Using additional nongenetic measures to predict siring success increased individual probabilities of paternity over a genetic-only model. Reproductive success of males was highly skewed, and not all successful males were consistently successful over years. Overall rate of selfing was 14% in the surviving (56%–63%) seedlings. The estimated number of (unsampled) sires outside of the seed orchard was highly variable, resulting in unassigned seed orchard fathers for 6% of the sampled progeny. Some benefits and limitations of using full-likelihood paternity analyses are discussed.
Integration of bioenergy strategies into forest management scenarios for Crown land in New Brunswick, Canada
Authors: Carle Jean-François , MacLean David A. , Erdle Thom A. , Roy Roger J.
Published: June 2011

About 70% (110 PJ) of energy used in New Brunswick is sourced from fossil fuels, and its high cost and uncertain long-term supply have renewed interest in bioenergy production. To evaluate opportunities for sourcing bioenergy from the forest, we integrated bioenergy and timber production into a forest estate model and evaluated joint production scenarios for 3.3 million hectares of Crown land in New Brunswick over a 100-year horizon. Scenarios included maximizing timber or bioenergy production under three timing preferences (expressed as discount rates) and various combinations of harvest residues, pulpwood biomass, and willow ( Salix spp.) plantations. Under scenarios that allocated 66% of harvest residues and 30% of pulpwood to bioenergy production, maximizing discounted (8%) timber or bioenergy, respectively, generated average timber harvests of 6.51 and 6.26 Mm3·year–1 and bioenergy outputs equivalent to 30% and 32% of provincial fossil fuel consumption. Introducing 40 000 ha of willow plantations under the maximize bioenergy scenario yielded bioenergy equivalent to 41% of provincial fossil fuel consumption while maintaining the timber harvest at 6.21 Mm3·year–1. Our study demonstrates a framework for integrating bioenergy and timber production in forest management design and quantifies the significant potential for obtaining both bioenergy and timber from the forest.
Seasonal shift in the climate responses ofPinus sibirica,Pinus sylvestris, andLarix sibiricatrees from semi-arid, north-central Mongolia
Authors: De Grandpré Louis , Tardif Jacques C. , Hessl Amy , Pederson Neil , Conciatori France , Green Timothy R. , Oyunsanaa Byambasuren , Baatarbileg Nachin
Published: June 2011

In light of a significant increase in the warming trend observed in recent decades in semi-arid Mongolia, tree-ring attributes and anomalies were analysed to detect potential changes in the growth–climate relationship. In a moisture-limited environment, an increase in temperature could cause a shift in the seasonal response of trees to climate. Chronologies were developed for the dominant tree species (Larix sibirica Ledeb., Pinus sibirica Du Tour, and Pinus sylvestris L.) from north-central Mongolia. In addition to annual ring width, both earlywood and latewood width were measured, and tree-ring anomalies such as false rings and light rings were systematically identified. Earlywood width was mainly associated with precipitation in the year prior to ring formation and early growing season conditions. Temperature was associated with current year growth and mainly influenced latewood development. False rings were good indicators of early summer droughts, whereas light rings were mainly associated with a cold end of summer. A seasonal shift in the significance of monthly climate variables was observed in recent decades. This displacement presumably resulted from changes in the timing and duration of the growing season. Tree growth starts earlier in spring and is now affected by late summer to early autumn climate conditions.
Native forest pathogens facilitate persistence of Douglas-fir in old-growth forests of northwestern California
Authors: Hawkins Ashley E. , Henkel Terry W.
Published: June 2011

Forest pathogens and insects can accelerate tree mortality, increase stand structural heterogeneity, and alter tree community composition. In northern California, the canopy trees Abies concolor var. lowiana (Gord. & Glend.) Lemmon (white fir) and Pseudotsuga menziesii var. menziesii (Mirbel) Franco (Douglas-fir) co-occur but vary in shade tolerance and regenerative abilities following disturbance. Field observations suggested that mortality and turnover of white fir exceeded that of Douglas-fir and that native pathogens may be important drivers in the absence of fire. Pathogens and bark beetles were sampled in old-growth white fir – Douglas-fir stands in northwestern California to assess their contribution to tree mortality, gap formation, and regeneration. We determined abundances and size class distributions of canopy trees, presence of pathogens and bark beetles, and causes of tree mortality. We sampled canopy gaps and closed-canopy forests for overstory species composition, cause of mortality of gap-maker trees, and regeneration of white fir and Douglas-fir. Root-rot fungi accounted for significantly higher mortality and gap formation in white fir than in Douglas-fir. Relative seedling–sapling density of Douglas-fir was higher in pathogen-induced canopy gaps than in closed-canopy forest. In the absence of fire, native forest pathogens enable regeneration and persistence of Douglas-fir by enhancing mortality of white fir, resulting in canopy gap formation.
ELECTRON SPIN RESONANCE INVESTIGATION OF FREE RADICALS PRODUCED IN PULVERIZED NON-IRRADIATED SUGAR
Authors: THAMAPHAT K. , LIMSUWAN P. , SMITH S. M.
Published: June 2011

An electron spin resonance (ESR) study of the effects of pulverization on non-irradiated crystalline sugar was performed. It indicated that the crystalline sugar before being ground did not give any ESR signal but an ESR signal was found in pulverized sugar. These results implied that free radicals were produced by pulverization. Moreover, the free radical density increased as the particle size decreased. From high-performance liquid chromatography analysis and the ESR spectrum of non-irradiated powdered sucrose, it can be inferred that the pulverization-induced free radical in sugar is a sucrose radical. Recently, many researchers have reported that sugar irradiated with 60 Co γ-rays at different doses produced stable sucrose radicals. This may imply that the process of sucrose radical formation by mechanical stress is similar to that for irradiation.
ADJOINT SYMMETRY CONSTRAINTS AND INTEGRABLE COUPLING SYSTEM OF MULTICOMPONENT KN EQUATIONS
Authors: YU FA-JUN
Published: June 2011

A soliton hierarchy of multicomponent KN equations is generated from an arbitrary order matrix spectral problem, along with its bi-Hamiltonian formulation. Adjoint symmetry constraints are presented to manipulate binary nonlinearization for the associated arbitrary order matrix spectral problem. Finally, a class of integrable coupling systems of the multicomponent KN soliton equation hierarchy is obtained using Ma's method associated with enlarging spectral problems [W. X. Ma, Phys. Lett. A316, 72–76 (2003)].
IMPLEMENTING AN n-QUBIT FREDKIN GATE WITH SUPERCONDUCTING QUANTUM-INTERFERENCE DEVICES IN CAVITY QED
Authors: ZHENG ANSHOU , CHENG YONGJIN , LIU JIBIN , WANG XICHENG , ZHENG YUAN
Published: June 2011

An alternative scheme is proposed in this paper to realize an n-qubit Fredkin gate with superconducting quantum-interference device (SQUID) in cavity QED. The multiqubit logical gate is essentially accomplished by a sequence of operations on only two SQUIDs in a large-detuned cavity. In the scheme, the two logical states of a qubit are presented by the two lowest states of a SQUID and the cavity is always in vacuum state so that the limit on the cavity is not serious.
ENTANGLEMENT OF A TWO-LEVEL ATOM INTERACTING WITH A NEW STRUCTURE OF A GENERALIZED NONLINEAR STARK SHIFT VIA Ξ CONFIGURATION
Authors: KHALIL E. M. , AHMED M. M. A. , OBADA A.-S. F.
Published: June 2011

The problem of a two-level atom interacting with single mode cavity field is considered, however, the optical cavity is filled with new structure of a generalized nonlinear Stark shift via Ξ configuration. One starts with a three-level trapped atom interacting with the quantized field of center of mass motion thus a Hamiltonian for one-phonon process with nonlinearities is derived. Through the elimination of the intermediate level by using the adiabatic elimination method, we generate a new structure of effective Hamiltonian for a two-level atom with a nonlinear Stark shift. The temporal evolution of the atomic inversion is studied, we introduce that in the presence of the Stark shift parameter the atom leaves in a maximal entangled sate. We use the von Neuman entropy to measure the degree of entanglement between the atom and the field. After adding the nonlinear Stark shift the system never reaches the pure state. Also we study the Q-function for obtaining more information in phase space for this system. These aspects are sensitive to changes in the Stark shift parameter. The results shows that the effect of the nonlinearity in the Stark shift changes the quasiperiod of the field entropy and hence the entanglement between the particle and the field.
TWO ENLARGED LOOP ALGEBRAS FOR OBTAINING NEW INTEGRABLE HIERARCHIES
Authors: ZHANG YUFENG , TAM HONWAH , JIANG WEI
Published: June 2011

Taking a loop algebra [Formula: see text] we obtain an integrable soliton hierarchy which is similar to the well-known Kaup–Newell (KN) hierarchy, but it is not. We call it a modified KN (mKN) hierarchy. Then two new enlarged loop algebras of the loop algebra [Formula: see text] are established, respectively, which are used to establish isospectral problems. Thus, two various types of integrable soliton-equation hierarchies along with multi-component potential functions are obtained. Their Hamiltonian structures are also obtained by the variational identity. The second hierarchy is integrable couplings of the mKN hierarchy. This paper provides a clue for generating loop algebras, specially, gives an approach for producing new integrable systems. If we obtain a new soliton hierarchy, we could deduce its symmetries, conserved laws, Darboux transformations, soliton solutions and so on. Hence, the way presented in the paper is an important aspect to obtain new integrable systems in soliton theory.
EFFECT OF THE ROTATION ON PLANE VIBRATIONS IN A TRANSVERSELY ISOTROPIC INFINITE HOLLOW CYLINDER
Authors: MAHMOUD S. R. , ABD-ALLA A. M. , AL-SHEHRI N. A.
Published: June 2011

In the present paper, a technique is presented for obtaining estimates for the natural frequencies of axisymmetric vibration for transversely isotropic material. The wave propagation of harmonic waves in hollow cylinder of transversely isotropic materials subjected to certain boundary conditions is studied. The two-dimensional equations of elastodynamic are solved in terms of displacement by using the technique of variables separation. The natural frequency of the plane vibrations in the case of harmonic vibrations has been obtained. The natural frequencies are calculated numerically and the effects of rotation is discussed. The numerical results obtained have been illustrated graphically to understand the behavior of natural frequency versus the ratio h. Comparisons are made with the result in the absence of rotation.
FIRST-PRINCIPLES STUDY OF STRUCTURAL AND ELECTRONIC PROPERTIES OF ALKALI METAL CHALCOGENIDES: M2CH[M: LI, NA, K, RB; CH: O, S, SE, TE]
Authors: ALAY-E-ABBAS S. M. , SABIR N. , SAEED Y. , SHAUKAT A.
Published: June 2011

Ground-state structural properties of alkali metal selenides and tellurides (M2X) [M: Li, Na, K, Rb; X: Se, Te] have been studied in the framework of density functional theory for the first time using local density approximation, Perdew–Burke–Ernzerhof generalized gradient approximation (GGA) and Wu–Cohen (WC) GGA parameterization schemes. Also structural properties of alkali metal oxides and sulfides (M2X) [M: Li, Na, K, Rb; X: O, S] have been reinvestigated using WC GGA. Electronic band structures of alkali metal chalcogenide compounds have been calculated using the aforementioned schemes as well as the modified GGA proposed by Engel and Vosko. The calculated structural parameters for all 16 materials have been compared with earlier theoretical and experimental results, and certain trends are discussed. Furthermore, electronic density of states for these compounds has also been presented herein and behavior in electronic properties analyzed. Li, K and Rb chalcogenides have been found to have indirect bandgap, whereas Na chalcogenides appear to have direct bandgap.
MODIFICATION OF A CHARGED-BOSE-GAS MODEL FOR OBSERVED ROOM-TEMPERATURE SUPERCONDUCTIVITY IN NARROW CHANNELS THROUGH FILMS OF OXIDIZED ATACTIC POLYPROPYLENE
Authors: EAGLES D. M.
Published: June 2011

Reasons have been found for thinking that the minimum diameter of channels of a given length to support superconductivity through films of oxidized atactic polypropylene (OAPP) at room temperature is considerably larger than that found in a model for Bose condensation in an array of nanofilaments [D. M. Eagles, Philos. Mag.85, 1931 (2005)] used previously. This model was introduced to interpret experimental results dating from 1988 on OAPP. The channels are thought to be of larger diameter than believed before because, for an N–S–N system where the superconductor consists of an array of single-walled carbon nanotubes, the resistance, for good contacts, is RQ/2N, where N is the number of nanotubes and RQ = 12.9 k Ω [see e.g., M. Ferrier et al., Solid State Commun.131, 615 (2004)]. We assume this would be 2RQ/N for a triplet superconductor with all spins in the same direction and no orbital degeneracy, which may be the case for nanofilaments in OAPP. Hence one may infer a minimum number of filaments for a given resistance. In the present model, the E(K) curve for the bosons is taken to be of a Bogoliubov form, but with a less steep initial linear term in the dispersion at Tc than the one at low T. This form is different from the simple linear plus quadratic dispersion, with a steeper initial slope, used in my 2005 paper. A combination of theory and experimental data has been used to find approximate constraints on parameters appearing in the theory.
SPIN SPLITTING PROPERTIES IN GaSb Γ AND L/X-VALLEYS
Authors: WANG W. , ZHANG M. H.
Published: June 2011

The band structures of GaSb in the Γ-valley as well as L/X-valley are excellently reproduced with sp3d5s* nearest-neighbor tight-binding model. The electron spin splitting energy and the spin–orbit interaction coefficients in the Γ, L and X multi-valleys are calculated. In the Γ-valley, the results obtained are in good agreement with experimental report. We then further extend our calculations to the GaSb L- and X-valleys. We also present the results of the top three valence bands in the Γ-valley. Due to the small band offset and large difference of the density of states between Γ- and L-valleys, it is shown that even at zero electric field, there is still an explicit electron population in the L-valley. These results are important to the realization of spintronic device and the investigation of spin dynamics far away from equilibrium.
TRANSPORT AND SPECTRA IN THE HALF-FILLED HUBBARD MODEL: A DYNAMICAL MEAN FIELD STUDY
Authors: BARMAN H. , VIDHYADHIRAJA N. S.
Published: June 2011

We present an improved numerical implementation of the iterated perturbation theory, for use as an impurity solver for lattice models within dynamical mean field theory (DMFT). We demonstrate higher resolution of spectral and transport features and a reduced computational expense. Using this implementation, we study the issues of scaling and universality in spectral and transport properties of the particle-hole symmetric Hubbard model within DMFT. We re-examine experimental results for pressure-dependent resistivity in Selenium doped NiS2and thermal hysteresis on V2O3and find qualitative agreement. A systematic study of spectral weight transfer in optical conductivity is carried out.
SURVIVAL PROBABILITY (HEAT CONTENT) AND THE LOWEST EIGENVALUE OF DIRICHLET LAPLACIAN
Authors: KALINAY PAVOL , ŠAMAJ LADISLAV , TRAVĚNEC IGOR
Published: June 2011

We study the survival probability of a particle diffusing in a two-dimensional domain, bounded by a smooth absorbing boundary. The short-time expansion of this quantity depends on the geometric characteristics of the boundary, whilst its long-time asymptotics is governed by the lowest eigenvalue of the Dirichlet Laplacian defined on the domain. We present a simple algorithm for calculation of the short-time expansion for an arbitrary "star-shaped" domain. The coefficients are expressed in terms of powers of boundary curvature, integrated around the circumference of the domain. Based on this expansion, we look for a Padé interpolation between the short-time and the long-time behavior of the survival probability, i.e., between geometric characteristics of the boundary and the lowest eigenvalue of the Dirichlet Laplacian.
General Expressions for Ellipsoidal-Valley Quantum Transport in Arbitrary Growth Direction: Non-Equilibrium Green's Function
Authors: Chen Chun-Nan , Su Wei-Long , Lee Meng-En , Jen Jen-Yi , Li Yiming
Published: June 2011

A theoretical method for the calculation of quantum transport in an ellipsoidal valley is presented. This method is developed using a non-equilibrium Green's function framework. Importantly, it is instructive that k

z
is separated into two parts so that the wrong figure shape of the transmission coefficients does not exist. The L-electron effect on AlAs–GaAs–AlAs double barrier structures oriented in the [001], [111], and [110] growth directions is explored using the proposed method.
Estimation of Fermi Level Changes Caused by Changes in Ambient Conditions around Organic Semiconductors by Seebeck Effect Measurement
Authors: Suemori Kouji , Yamamoto Ryuuto , Kamata Toshihide
Published: June 2011

By using the Seebeck effect measurement, we investigated changes in the Fermi level of pentacene caused by changes in ambient conditions. Since, measurement of Seebeck voltage is not accompanied with current flow, this measurement is not affected by contact resistance of devices. Thus, we can measure Fermi level change caused by ambient change without influence of contact resistance.
Effects of Phase-Separation Direction of Monomers on Polymer Wall Formation and Electrooptical Properties of Flexible Smectic Liquid Crystal Cell
Authors: Lee Ji-Hoon , Yoon Tae-Hoon
Published: June 2011

We examined the effects of the phase-separation direction of monomers on the polymer wall formation and the electrooptical properties of a chiral smectic C liquid crystal. Monomers are more clearly phase-separated when polymer walls are formed in the layer normal direction rather than in the layer parallel direction. The anisotropic phase-separation property of monomers is considered to be related to the layered structure of the smectic liquid crystal. The tilt angle and contrast ratio of the cell with the layer-normal polymer walls are larger than those of the cell with the layer-parallel polymer walls.
Uncooled InAsSb Photoconductors with Long Wavelength
Authors: Gao Yu Zhu , Gong Xiu Ying , Wu Guang Hui , Feng Yan Bin , Makino Takamitsu , Kan Hirofumi
Published: June 2011

High-sensitivity uncooled InAsSb photoconductors with long wavelength were successfully fabricated. The detectors are based on InAsSb epilayers with the thickness of 100 µm grown on InAs substrates by melt epitaxy (ME). Si optical lenses were set on the photoconductors without any antireflective coatings. At room temperature, the peak detectivity D
λp
* (6.5 µm, 1200) reaches 5.3 ×109 cm Hz1/2 W-1 for InAsSb immersion photoconductors. The detectivity D
* at the wavelength of 8 µm is 1.5 ×108 cm Hz1/2 W-1, and that at 9 µm is 1.0 ×107 cm Hz1/2 W-1. The excellent performance of the detectors indicates the potential applications for infrared (IR) detection and imaging at room temperature.
Analytical Investigation of an All-Optical T-Type Flip-Flop Using a Semiconductor Optical Amplifier Mach–Zehnder Interferometer with Push–Pull Configuration
Authors: Shimizu Satoshi , Uenohara Hiroyuki
Published: June 2011

To achieve an optical regenerator for a differential phase-shift keying signal based on a semiconductor optical amplifier Mach–Zehnder interferometer (SOA-MZI), we need an all-optical T-type flip-flop (T-FF) for encoding. We propose an all-optical T-FF consisting of an SOA-MZI with push–pull configuration and a feedback mirror to overcome the speed limitation of the previously proposed counter-faced configuration. Numerical simulation reveals its possibility of stable operation in 10 Gbps with a 27 - 1 pseudo random binary sequence (PRBS) signal even by using a conventional SOA with a slow carrier recovery of 100 ps, and the possibility of 40 Gbps operation is also investigated.
Kinetics Study on Initial Growth Stage in Vapor Deposition of Organic Thin Film Using Quartz Crystal Microbalance
Authors: Ito Takaya , Onoda Shinya , Kino Masaaki , Hagihara Kiyoshi , Kubono Atsushi
Published: June 2011

The deposition behavior of stearic acid evaporated in vacuum was observed using a quartz crystal microbalance technique, and the time evolution curves of the amount of admolecules in the initial growth were compared with a theoretical curve calculated using a rate equation proposed on the basis of physisorption. From the results, it was demonstrated that the proposed rate equation for the early stage of film formation well described the experimental results and the growth kinetics of organic thin films was dependent on the substrate temperature. Basic parameters for thin-film growth, such as the mean stay time on the substrate of deposited molecules, can be estimated from the fitting of the theoretical equation to the experimental results at each substrate temperature. It should be noted that the basic parameters were sensitive to a small change in substrate temperature.
Current–Voltage Characteristics of Discharge with Water–Ceramic Electrode
Authors: Deguchi Mikio , Niki Toru
Published: June 2011

Current–voltage characteristics of discharge with a water–ceramic electrode were measured under various conditions. The existence of the incandescent ceramic component in the discharge gap reduces the discharge voltage and sustains the discharge in a low current range. Discharge voltage reduction is more notable in the case that the water is positively biased. The closer to the water surface the incandescent ceramic component is positioned, the more notable its effects become. These effects can be attributed to the thermoelectronic emission from the incandescent ceramic component and the intense irradiation onto the water surface from it.
Authorization recycling in hierarchical RBAC systems
Authors: Wei Qiang , Crampton Jason , Beznosov Konstantin , Ripeanu Matei
Published: June 2011

As distributed applications increase in size and complexity, traditional authorization architectures based on a dedicated authorization server become increasingly fragile because this decision point represents a single point of failure and a performance bottleneck. Authorization caching, which enables the reuse of previous authorization decisions, is one technique that has been used to address these challenges.

This article introduces and evaluates the mechanisms for authorization “recycling” in RBAC enterprise systems. The algorithms that support these mechanisms allow making precise and approximate authorization decisions, thereby masking possible failures of the authorization server and reducing its load. We evaluate these algorithms analytically as well as using simulation and a prototype implementation. Our evaluation results demonstrate that authorization recycling can improve the performance of distributed-access control mechanisms.
Relations among privacy notions
Authors: Bohli Jens-Matthias , Pashalidis Andreas
Published: June 2011

This article presents a hierarchy of privacy notions that covers multiple anonymity and unlinkability variants. The underlying definitions, which are based on the idea of indistinguishability between two worlds, provide new insights into the relation between, and the fundamental structure of, different privacy notions. We furthermore place previous privacy definitions concerning group signature, anonymous communication, and secret voting systems in the context of our hierarchy; this renders these traditionally disconnected notions comparable.
Robust and efficient authentication of video stream broadcasting
Authors: Oligeri Gabriele , Chessa Stefano , Pietro Roberto Di , Giunta Gaetano
Published: June 2011

We present a novel video stream authentication scheme which combines signature amortization by means of hash chains and an advanced watermarking technique. We propose a new hash chain construction, the Duplex Hash Chain, which allows us to achieve bit-by-bit authentication that is robust to low bit error rates. This construction is well suited for wireless broadcast communications characterized by low packet losses such as in satellite networks. Moreover, neither hardware upgrades nor specific end-user equipment are needed to enjoy the authentication services. The computation overhead experienced on the receiver only sums to two hashes per block of pictures and one digital signature verification for the whole received stream. This overhead introduces a provably negligible decrease in video quality. A thorough analysis of the proposed solution is provided in conjunction with extensive simulations.
Cross-application data provenance and policy enforcement
Authors: Demsky Brian
Published: June 2011

We present a new technique that can trace data provenance and enforce data access policies across multiple applications and machines. We have developed Garm, a tool that uses binary rewriting to implement this technique on arbitrary binaries. Users can use Garm to attach access policies to data and Garm enforces the policy on all accesses to the data (and any derived data) across all applications and executions. Garm uses static analysis to generate optimized instrumentation that traces the provenance of an application's state and the policies that apply to this state. Garm monitors the interactions of the application with the underlying operating system to enforce policies. Conceptually, Garm combines trusted computing support from the underlying operating system with a stream cipher to ensure that data protected by an access policy cannot be accessed outside of Garm's policy enforcement mechanisms. We have evaluated Garm with several common Linux applications. We found that Garm can successfully trace the provenance of data across executions of multiple applications and enforce data access policies on the application's executions.
Practical defenses against pollution attacks in wireless network coding
Authors: Dong Jing , Curtmola Reza , Nita-Rotaru Cristina
Published: June 2011

Recent studies have shown that network coding can provide significant benefits to network protocols, such as increased throughput, reduced network congestion, higher reliability, and lower power consumption. The core principle of network coding is that intermediate nodes actively mix input packets to produce output packets. This mixing subjects network coding systems to a severe security threat, known as a
pollution attack
, where attacker nodes inject corrupted packets into the network. Corrupted packets propagate in an epidemic manner, depleting network resources and significantly decreasing throughput. Pollution attacks are particularly dangerous in wireless networks, where attackers can easily inject packets or compromise devices due to the increased network vulnerability.

In this article, we address pollution attacks against network coding systems in wireless mesh networks. We demonstrate that previous solutions are impractical in wireless networks, incurring an unacceptable high degradation of throughput. We propose a lightweight scheme, DART, that uses time-based authentication in combination with random linear transformations to defend against pollution attacks. We further improve system performance and propose EDART, which enhances DART with an optimistic forwarding scheme. We also propose efficient attacker identification schemes for both DART and EDART that enable quick attacker isolation and the selection of attacker-free paths, achieving additional performance improvement. A detailed security analysis shows that the probability of a polluted packet passing our verification procedure is very low (less than 0.002% in typical settings). Performance results using the well-known MORE protocol and realistic link quality measurements from the Roofnet experimental testbed show that our schemes improve system performance over 20 times compared with previous solutions.
Nexus authorization logic (NAL)
Authors: Schneider Fred B. , Walsh Kevin , Sirer Emin Gün
Published: June 2011

Nexus Authorization Logic (NAL) provides a principled basis for specifying and reasoning about credentials and authorization policies. It extends prior access control logics that are based on “says” and “speaks for” operators. NAL enables authorization of access requests to depend on (i) the source or pedigree of the requester, (ii) the outcome of any mechanized analysis of the requester, or (iii) the use of trusted software to encapsulate or modify the requester. To illustrate the convenience and expressive power of this approach to authorization, a suite of document-viewer applications was implemented to run on the Nexus operating system. One of the viewers enforces policies that concern the integrity of excerpts that a document contains; another viewer enforces confidentiality policies specified by labels tagging blocks of text.
Access control via belnap logic
Authors: Bruns Glenn , Huth Michael
Published: June 2011

Access control to IT systems increasingly relies on the ability to compose policies. Hence there is benefit in any framework for policy composition that is intuitive, formal (and so “analyzable” and “implementable”), expressive, independent of specific application domains, and yet able to be extended to create domain-specific instances. Here we develop such a framework based on Belnap logic. An access-control policy is interpreted as a
four-valued
predicate that maps access requests to either
grant
,
deny
,
conflict
, or
unspecified
-- the four values of the Belnap bilattice. We define an expressive access-control policy language PBel, having composition operators based on the operators of Belnap logic. Natural orderings on policies are obtained by lifting the truth and information orderings of the Belnap bilattice. These orderings lead to a query language in which policy analyses, for example, conflict freedom, can be specified. Policy analysis is supported through a reduction of the validity of policy queries to the validity of propositional formulas on predicates over access requests. We evaluate our approach through firewall policy and RBAC policy examples, and discuss domain-specific and generic extensions of our policy language.
Lightweight RFID authentication with forward and backward security
Authors: Burmester Mike , Munilla Jorge
Published: June 2011

We propose a lightweight RFID authentication protocol that supports forward and backward security. The only cryptographic mechanism that this protocol uses is a pseudorandom number generator (PRNG) that is shared with the backend Server. Authentication is achieved by exchanging a few numbers (3 or 5) drawn from the PRNG. The lookup time is constant, and the protocol can be easily adapted to prevent online man-in-the-middle relay attacks. Security is proven in the UC security framework.