bluuebunny/crossref_metadata_2025_split huggingface dataset:
Autograft versus allograft with or without demineralized bone matrix in posterolateral lumbar fusion in rabbits
Authors: Urrutia Julio , Thumm Nicolas , Apablaza Daniel , Pizarro Felipe , Zylberberg Alejandro , Quezada Felipe 
Published: June 2008

ObjectPosterolateral spinal fusions are performed to treat different spinal disorders. Autograft continues to be the gold standard; it is, however, associated with donor site morbidity and limited sources. Allograft has been used, but has been reported to result in lower fusion rates. Demineralized bone matrix (DBM) has also been used and reportedly increases the fusion rate in a variety of critical defect models. Different forms of DBM are available, not all have been independently studied. To evaluate the effect of a xenogenic DBM added to allograft on the fusion rate of posterolateral lumbar spine arthrodesis the authors designed an experimental study comparing posterolateral fusion rate using autograft, allograft, and allograft plus a xenogenic DBM in a validated animal model.MethodsA bilateral, 1-level (L4–5) intertransverse process fusion was performed in 45 male New Zealand rabbits. Iliac crest bone graft was harvested bilaterally from each rabbit. The rabbits were randomly assigned to 3 groups: Group I, Autograft, 15 rabbits; Group II, Allograft, 15 rabbits; and Group III, Allograft plus DBM in a paste form (Dynagraft). The animals were killed 8 weeks after surgery. Fusion was assessed radiographically and by manual palpation by 2 independent observers. The results were analyzed using the Fisher exact test and chi-square test.ResultsThe fusion rate was 46.6% (7 of 15 rabbits) in the autograft group, 33.3% (5 of 15 rabbits) in the allograft group, and 33.3% (5 of 15 rabbits) in the allograft plus DBM group (p > 0.05).ConclusionsAutograft produced a higher fusion rate than allograft in this spinal fusion rabbit model, but the difference was not statistically significant. Allograft plus xenogenic DBM showed the same fusion rate as allograft alone.
Influence of thread design on pedicle screw fixation
Authors: Krenn Michael Hannes , Piotrowski Wolfgang Peter , Penzkofer Rainer , Augat Peter 
Published: June 2008

ObjectThe authors conducted a study to determine the thread properties that provide optimal screw fixation in cancellous bone, when screws of the same external screw diameter are used.MethodsThree compliance engineering–certified screws in clinical use, all of the same external diameter and length, were compared in an axial pullout experiment with respect to advantageous thread properties. As test material, standardized Sawbone blocks with 3 different densities (0.12, 0.16, and 0.32 g/cm3) were used.ResultsScrew thread Type 1, whose flank overlap area (FOA; 261 mm2) results from narrowing the conical core in the thread area, showed significantly better holding strength than the other types. Screw thread Type 2 (FOA 326 mm2) with a conical but thicker core and a smaller thread pitch was found to be the only one without increase of pull-out forces when test materials density changed from 0.12 to 0.16 g/cm3. A screw tested as control, with a constant (cylindrical) core diameter (Type 3; FOA 206 mm2), had the same thread pitch as Type 1 but without the compressive effect on the surrounding bur hole wall material. Nevertheless, it showed higher pullout forces in the 0.16-g/cm3material than screw Type 2.ConclusionsBy reducing the core diameter of a screw toward the tip, while maintaining a constant nominal (external) diameter, one achieves frictional connection due to compression of surrounding material. In addition, the FOA is increased, which, in summary, leads to better fixation, as shown by screw Type 1.
Construction of probability distributions in high dimension using the maximum entropy principle: Applications to stochastic processes, random fields and random matrices
Authors: Soize Christian 
Published: July 2008

AbstractThe construction of probabilistic models in computational mechanics requires the effective construction of probability distributions of random variables in high dimension. This paper deals with the effective construction of the probability distribution in high dimension of a vector‐valued random variable using the maximum entropy principle. The integrals in high dimension are then calculated in constructing the stationary solution of an Itô stochastic differential equation associated with its invariant measure. A random generator of independent realizations is explicitly constructed in this paper. Three fundamental applications are presented. The first one is a new formulation of the stochastic inverse problem related to the construction of the probability distribution in high dimension of an unknown non‐stationary random time series (random accelerograms) for which the velocity response spectrum is given. The second one is also a new formulation related to the construction of the probability distribution of positive‐definite band random matrices. Finally, we present an extension of the theory when the support of the probability distribution is not all the space but is any part of the space. The third application is then a new formulation related to the construction of the probability distribution of the Karhunen–Loeve expansion of non‐Gaussian positive‐valued random fields. Copyright © 2008 John Wiley & Sons, Ltd.
Implicit boundary method for analysis using uniform B‐spline basis and structured grid
Authors: Burla Ravi K. , Kumar Ashok V. 
Published: July 2008

AbstractSeveral analysis techniques such as extended finite element method (X‐FEM) have been developed recently, which use structured grid for the analysis. Implicit boundary method uses implicit equations of the boundary to apply boundary conditions in X‐FEM framework using structured grids. Solution structures for test and trial functions are constructed using implicit equations such that the boundary conditions are satisfied even if there are no nodes on the boundary. In this paper, this method is applied for analysis using uniform B‐spline basis defined over a structured grid. Solution structures that are C1 or C2 continuous throughout the analysis domain can be constructed using B‐spline basis functions. As a structured grid does not conform to the geometry of the analysis domain, the boundaries of the analysis domain are defined independently using equations of the boundary curves/surfaces. Compared with conforming mesh, it is easier to generate structured grids that overlap the geometry and the elements in the grid are regular shaped and undistorted. Numerical examples are presented to demonstrate the performance of these B‐spline elements. The results are compared with analytical solutions as well as with traditional finite element solutions. Convergence studies for several examples show that B‐spline elements provide accurate solutions with fewer elements and nodes compared with traditional FEM. They also provide continuous stress and strain in the analysis domain, thus eliminating the need for smoothing stress/strain results. Copyright © 2008 John Wiley & Sons, Ltd.
FE/FMBE coupling to model fluid–structure interaction
Authors: Schneider S. 
Published: July 2008

AbstractIn this paper, a finite element (FE)/fast multipole boundary element (FMBE)‐coupling method is presented for modeling fluid–structure interaction problems numerically. Vibrating structures are assumed to consist of elastic or sound absorbing materials. An FE method (FEM) is used for this part of the solution. This structural sub‐domain is embedded in a homogeneous fluid. The case where the boundary of the structural sub‐domain has a very complex geometry is of special interest. In this case, the BE method (BEM) is a more suitable numerical tool than FEM to account for the sound propagation in the homogeneous fluid. The efficiency of the BEM is increased by using FMBEM. The BE‐surface mesh required is directly generated by the FE‐mesh used to discretize the structural sub‐domain and the absorbing material. This FE/FMBE‐coupling method makes it possible to predict the effects of arbitrarily shaped absorbing materials and vibrating structures on the sound field in the surrounding fluid numerically. The coupling method proposed is used to study the acoustic behavior of the lining of an anechoic chamber and that of an entire anechoic chamber in the low‐frequency range. The numerical results obtained are compared with the experimental data. Copyright © 2008 John Wiley & Sons, Ltd.
Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion
Authors: Deshpande Aniruddha S , Khomane Ramdas B , Vaidya Bhalchandra K , Joshi Renuka M , Harle Arti S , Kulkarni Bhaskar D 
Published: July 2008

Abstract
Sulfur nanoparticles were synthesized from hazardous H2S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe3+–malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 andn-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5–15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.
Scanned Probe Oxidation onp-GaAs(100) Surface with an Atomic Force Microscopy
Authors: Jian Sheng-Rui , Juang Jenh-Yih 
Published: July 2008

Abstract
Locally anodic oxidation has been performed to fabricate the nanoscale oxide structures onp-GaAs(100) surface, by using an atomic force microscopy (AFM) with the conventional and carbon nanotube (CNT)-attached probes. The results can be utilized to fabricate the oxide nanodots under ambient conditions in noncontact mode. To investigate the conversion of GaAs to oxides, micro-Auger analysis was employed to analyze the chemical compositions. The growth kinetics and the associated mechanism of the oxide nanodots were studied under DC voltages. With the CNT-attached probe the initial growth rate of oxide nanodots is in the order of ~300 nm/s, which is ~15 times larger than that obtained by using the conventional one. The oxide nanodots cease to grow practically as the electric field strength is reduced to the threshold value of ~2 × 107 V cm−1. In addition, results indicate that the height of oxide nanodots is significantly enhanced with an AC voltage for both types of probes. The influence of the AC voltages on controlling the dynamics of the AFM-induced nanooxidation is discussed.
Characteristics of High α‐Linolenic Acid Accumulation in Seed Oils
Authors: Rao Suryadevara , Abdel‐Reheem Mohammed , Bhella Resham , McCracken Charles , Hildebrand David 
Published: July 2008

AbstractModern diets are often deficient in ω‐3 fatty acids and additional dietary sources of ω‐3 fatty acids are useful. In order to investigate the molecular basis of the high accumulation of the ω‐3 fatty acid, α‐linolenic acid (18:3), in three different plants, flax (Linum usitatissimum), Dracocephalum moldavica, and Perilla frutescens ω‐3 desaturase activity, transcript levels, and 18:3 in‐vivo synthesis were examined. The 18:3 content was found to be higher at the later developmental stage of D. moldavica (68%) compared with P. frutescens (59%) and flax (45%) cotyledons. The 18:3 and 18:2 contents in both PC and TAG were determined during various stages of seed development for all three plants in addition to soybean (Glycine max). Northern blot analysis data of three different stages of D. moldavica, flax, and P. frutescens compared with moderately low 18:3 producers, soybean (Glycine max), and Arabidopsis thaliana and Brassica napus, (8–10% 18:3) at a stage of zygotic embryo development of high triglyceride synthesis showed that ω‐3 desaturase mRNA levels were higher in all three high 18:3 producers, flax, D. moldavica and P. frutescens. This indicates that the high level of α‐linolenic acid in TAG may be largely controlled by the level of ω‐3 desaturase gene expression. However, the PC versus TAG fatty acid composition data suggested that along with ω‐3 desaturase other enzymes also play a role in 18:3 accumulation in TAG, and the high accumulators have a selective transfer of α‐linolenic acid into TAG.
Thehobo-related elements in themelanogasterspecies group
Authors: DE FREITAS ORTIZ MAURO , SILVA LORETO ELGION LUCIO 
Published: July 2008

SummaryThehobo-related sequences (hRSs) were considered as degenerate and inactive elements until recently, when one mobilizable copy was described. Using this sequence as the initial seed to search for homologous sequences in 12 availableDrosophilagenomes, in addition to searching for these sequences by PCR and Southern blot in nine other species, we found homologous sequences in every species of theDrosophila melanogasterspecies subgroup. Some evidence suggests that these non-autonomous sequences were kept mobilizable for at least 0·4 million years. Also, some very short sequences with miniature inverted-repeat transposable element (MITE) characteristics were found among thesehRSs. ThesehRSs and their ‘MITE-like’ counterparts could provide a good example of the steps proposed in models that describe the MITEs origin.
Spontaneous mutations in diploidSaccharomyces cerevisiae: another thousand cell generations
Authors: HALL DAVID W. , MAHMOUDIZAD ROD , HURD ANDREW W. , JOSEPH SARAH B. 
Published: July 2008

SummaryPreviously we performed a 1012-generation mutation accumulation (MA) study in yeast and found that a surprisingly large proportion of fitness-altering mutations were beneficial. To verify this result and assess the impact of sampling error in our previous study, we have continued the MA experiment for an additional 1050 cell generations and re-estimated mutation parameters. After correcting for biases due to selection, we estimate that 13% of the mutations accumulated during this study are beneficial. We conclude that the high proportions of beneficial mutations observed in this and our previous study cannot be explained by sampling error. We also estimate the genome-wide mutation rate to be 13·7×10−5mutations per haploid genome per cell generation and the absolute value of the average heterozygous effect of a mutation to be 7·3%.
Does RNA interference influence meiotic crossing over inDrosophila melanogaster?
Authors: CROSS ERIC W. , SIMMONS MICHAEL J. 
Published: July 2008

SummaryMutations in the RNA interference (RNAi) genesaubergine(aub),homelessandpiwiwere tested for effects on the frequency, distribution and coincidence of meiotic crossovers in the long arm of the X chromosome. Some increases in crossover frequency were seen in these tests, but they may have been due to a maternal effect of the balancer chromosomes that were used to maintain the RNAi mutations in stocks rather than to the RNAi mutations themselves. These same balancers produced strong zygotic interchromosomal effects when tested separately. Mutations inaubandpiwidid not affect the frequency of crossing over in the centric heterochromatin of chromosome II; nor did a balancer chromosome III.
Intestinal helminths in a population of children from the Kashmir valley, India
Authors: Wani S.A. , Ahmad F. , Zargar S.A. , Dar P.A. , Dar Z.A. , Jan T.R. 
Published: July 2008

AbstractIn any geographical area, surveys of the prevalence of intestinal helminths are necessary to suggest appropriate control measures. The aim of this study was to determine the prevalence of intestinal helminth infections in children of the Kashmir valley and to identify the risk factors. Stool samples were collected from 2256 children from rural as well as urban areas of the Kashmir valley. The samples were examined by simple smear and zinc sulphate concentration methods. Intensity of the infection was quantified by Stoll's egg-counting technique. Infection by at least one intestinal helminth was found in 71.18% of the sampled population. The prevalence of Ascaris lumbricoides was highest (68.30%), followed by Trichuris trichiura (27.92%), Enterobius vermicularis (12.67%) and Taenia saginata (4.60%). Light (57.1%) to moderate (42.8%) intensity of infection was observed for A. lumbricoides, while the majority of the infected children (92.3%) harboured a light intensity of infection for T. trichiura. The age group, rural or urban residence, type of water source, boiled or unboiled water, type of defecation site, level of personal hygiene and maternal education were associated with helminth infection. Adequate control measures are urgently needed to combat the high prevalence of intestinal helminths and risk factors in the children of Kashmir valley.
The genus Fuscidea ( Fuscideaceae, lichenized Ascomycota) in North America
Authors: FRYDAY Alan M. 
Published: July 2008

Abstract:The species of the genus Fuscidea occurring in North America are revised. Two new species, Fuscidea appalachensis Fryday and F. texana Fryday, are described from eastern North America and southern Texas, respectively. Three new combinations are also made in Fuscidea: Lecidea aleutica Degel. is shown to be a distinct species and not a synonym of Fuscidea lowensis (H. Magn.) R. Anderson &amp; Hertel as previously suggested and is here recognized as F. aleutica (Degel.) Fryday; non-sorediate, apotheciate specimens from eastern North America previously referred to F. recensa (Stirt.) Hertel, V. Wirth &amp; Vězda are recognized as Fuscidea recensa var. arcuatula (Arnold) Fryday; and Fuscidea scrupulosa (Eckf.) Fryday is shown to be the correct name for Fuscidea subreagens (H. Magn.) Oberholl. &amp; V. Wirth. Fuscidea subfilamentosa (Zahlbr.) Brako is shown to be a member of the Lecidea hypnorum group and the new combination Lecidea subfilamentosa (Zahlbr.) Fryday is made, and Lecidea gyrodes H. Magn., described from Tennessee, is shown to be a synonym of F. recensa var. arcuatula. Fuscidea cyathoides (Ach.) V. Wirth &amp; Vězda, F. kochiana (Hepp) V. Wirth &amp; Vězda and F. lightfootii (Sm.) Coppins &amp; P. James are considered not to have been correctly reported from North America.
Studies on Phyllopsora ( Ramalinaceae) in Peru
Authors: TIMDAL Einar 
Published: July 2008

Abstract:Twenty species of Phyllopsora are recognized in Peru, 8 of which are described as new: P. atrocarpa, P. brakoae, P. glaucescens, P. labriformis, P. lacerata, P. lividocarpa, P. nigrocincta, and P. soralifera. Four new combinations are proposed: Phyllopsora cinchonarum (Fée) Timdal, P. glaucella (Vain.) Timdal, P. leucophyllina (Nyl.) Timdal, and for an extra-Peruvian species, P. sorediata (Aptroot &amp; Sparrius) Timdal. The genera Squamacidia and Triclinum are synonymized with Phyllopsora and sorediate species are included in the genus for the first time. Phyllopsora chodatinica, P. swinscowii, and the acid deficient chemotype of P. furfuracea are new to the neotropics and P. cuyabensis, P. glaucella and P. leucophyllina are new to Peru. A key to the Peruvian species is provided.
Nutrient availability at different altitudes in a tropical montane forest in Ecuador
Authors: Soethe Nathalie , Lehmann Johannes , Engels Christof 
Published: July 2008

AbstractWe measured macronutrient concentrations in soils and leaves of trees, shrubs and herbs at 1900, 2400 and 3000 m in an Ecuadorian tropical montane forest. Foliar N, P, S and K concentrations in trees were highest at 1900 m (21.7, 2.2, 1.9 and 10.0 mg g−1). At 2400 and 3000 m, foliar concentrations of N, P, S and K were similar to nutrient concentrations in tropical trees with apparent nutrient deficiency, as presented in literature. Unlike foliar nutrient concentrations, the amounts of plant-available nutrients in mineral soil were not affected by altitude or increased significantly with increasing altitude. High C:N ratios (25:1 at 2400 m and 34:1 at 3000 m) and C:P ratios (605:1 at 2400 m and 620:1 at 3000 m) in the soil organic layer suggested slow mineralization of plant litter and thus, a low availability of N and P at high altitudes. Foliar N:P ratios were significantly higher at 2400 m (11.3:1) than at 3000 m (8.3:1), indicating that at high altitudes, N supply was more critical than P supply. In conclusion, the access of plants to several nutrients, most likely N, P, S and K, decreased markedly with increasing altitude in this tropical montane forest.
Above-ground biomass and productivity in a rain forest of eastern South America
Authors: Chave Jérôme , Olivier Jean , Bongers Frans , Châtelet Patrick , Forget Pierre-Michel , van der Meer Peter , Norden Natalia , Riéra Bernard , Charles-Dominique Pierre 
Published: July 2008

AbstractThe dynamics of tropical forest woody plants was studied at the Nouragues Field Station, central French Guiana. Stem density, basal area, above-ground biomass and above-ground net primary productivity, including the contribution of litterfall, were estimated from two large permanent census plots of 12 and 10 ha, established on contrasting soil types, and censused twice, first in 1992–1994, then again in 2000–2002. Mean stem density was 512 stems ha−1 and basal area, 30 m2 ha−1. Stem mortality rate ranged between 1.51% and 2.06% y−1. In both plots, stem density decreased over the study period. Using a correlation between wood density and wood hardness directly measured by a Pilodyn wood tester, we found that the mean wood density was 0.63 g cm−3, 12% smaller than the mean of wood density estimated from the literature values for the species occurring in our plot. Above-ground biomass ranged from 356 to 398 Mg ha−1 (oven-dry mass), and it increased over the census period. Leaf biomass was 6.47 Mg ha−1. Our total estimate of aboveground net primary productivity was 8.81 MgC ha−1 y−1 (in carbon units), not accounting for loss to herbivory, branchfalls, or biogenic volatile organic compounds, which may altogether account for an additional 1 MgC ha−1 y−1. Coarse wood productivity (stem growth plus recruitment) contributed to 4.16 MgC ha−1 y−1. Litterfall contributed to 4.65 MgC ha−1 y−1 with 3.16 MgC ha−1 y−1 due to leaves, 1.10 MgC ha−1 y−1 to twigs, and 0.39 MgC ha−1 y−1 to fruits and flowers. The increase in above-ground biomass for both trees and lianas is consistent with the hypothesis of a shift in the functioning of Amazonian rain forests driven by environmental changes, although alternative hypotheses such as a recovery from past disturbances cannot be ruled out at our site, as suggested by the observed decrease in stem density.