bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of medicarpin and maackiain in the response of red clover leaves to Helminthosporium carbonum, Stemphylium botryosum, and S. sarcinaeforme
Authors: Duczek Lorne J. , Higgins Verna J.
Published: September 2008

Helminthosporium carbonum, a corn pathogen, and Stemphylium botryosum, an alfalfa pathogen, are both nonpathogenic on red clover (Trifolium pratense L.), while S. sarcinaeforme is a foliar pathogen on red clover. In clover leaves challenged with H. carbonum, medicarpin and maackiain were the only inhibitory compounds found in diffusates or in leaf tissue in a concentration sufficient to account for the inhibition of this fungus. Helminthosporium carbonum was inhibited by and could not degrade medicaipin and (or) maackiain in vitro. Both S. botryosum and S. sarcinaeforme were only slightly inhibited by these compounds in mycelial growth bioassays, and both fungi degraded medicarpin and (or) maackiain in vitro and some evidence was obtained that degradation occurred in vivo. In contrast with the relatively high amounts of medicarpin and maackiain that accumulated in leaves challenged with H. carbonum, relatively low amounts accumulated in leaves challenged with either S. botryosum or S. sarcinaeforme. The evidence suggests that the resistance of clover to H. carbonum can be accounted for by these phytoalexins; however, differences in relation to accumulation of, inhibition by, and breakdown of medicarpin and (or) maackiain were not enough to explain the difference in pathogenicity of S. botryosum and S. sarcinaeforme on red clover.
Effect of treatment with the phytoalexins medicarpin and maackiain on fungal growth in vitro and in vivo
Authors: Duczek Lorne J. , Higgins Verna J.
Published: September 2008

The effect of medicarpin (3-hydroxy-9-methoxypterocarpan) and maackiain (3-hydroxy-8,9-methylenedioxypterocarpan). phytoalexins from red clover, on germ tube growth, oxygen uptake, and pathogenicity of Helminthosporium carbonum, Stemphylium botryosum, and S. sarcinaeforme was examined. Germ tube growth of all three fungi was inhibited by as little as 10 μg/ml of these compounds and oxygen uptake by H. carbonum and S. botryosum, but not by S. sarcinaeforme, was reduced by higher concentrations (about 60 μg/ml) of these phytoalexins. Medicaipin and maackiain added to inoculum drops prevented H. carbonum from infecting its host plant, corn. This protective effect was probably caused by the failure of H. carbonum to form appressoria in the presence of the phytoalexins. No protective action of the phytoalexins was noted when either S. botryosum or S. sarcinaeforme was used on their host plants, alfalfa and clover, respectively. Inoculation of red clover leaves with the nonpathogen H. carbonum before inoculation with the pathogen S. sarcinaeforme had no effect on symptom development, nor was there any evidence of increased susceptibility to H. carbonum if either S. sarcinaeforme or S. botryosum was added at the time of inoculation. The results are discussed in relation to the role of these phytoalexins in disease resistance of red clover.
Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. I. Variation potentials and putative action potentials in intact plants
Authors: Sambeek Jerome W. Van , Pickard Barbara G.
Published: September 2008

Damaging representative plants from five angiosperm families by heating or crushing a small portion of a single leaf results in an electrical change which may spread throughout the shoot. In Mimosa, similar changes have previously been identified as variation potentials.Except in one of the five plants, a variation potential is often accompanied by brief fluctuations which may propagate either basipetally or acropetally and which have many of the properties of action potentials.The spread of a variation potential as described in Mimosa is due to the concommitant spread of a chemical substance in the transpiration stream. In this paper, it is shown that the spread of the purported variation potential is compatible with movement of material in the transpiration stream. In the next paper causation by a substance or group of substances, at present called Ricca's factor, is demonstrated.
Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. III. Measurements of CO2 and H2O flux
Authors: Sambeek Jerome W. Van , Pickard Barbara G.
Published: September 2008

By using intact plants from five angiosperm families, shifts in CO2 and H2O exchange have been demonstrated to follow the arrival of a variation potential in unharmed leaves shortly after adjacent leaves are damaged.Whether in the light or dark, the first change is a brief burst of CO2, which may well be due to a sudden breakdown of bicarbonate dissolved in the extracellular solution.In the dark, a rise in metabolic CO2 output becomes evident during the decay of the initial burst, and the output remains elevated for at least several hours.In the light, a biphasic drop in both transpiration and net CO2 uptake is underway before the initial CO2 burst has subsided. Since the decrease in CO2 uptake is larger than the increase in output in the dark, it must be due in part to decreased net photosynthetic CO2 fixation. It is plausible but as yet unproven that the biphasic photosynthetic change is a consequence of the biphasic closure of the stomata. In any case, curtailment of both transpiration and net photosynthesis, like the enhancement of dark metabolism, persists for a number of hours.
Studies on lichen-dominated systems. XIX. The postfire recovery sequence of black spruce – lichen woodland in the Abitau Lake Region, N.W.T.
Authors: Maikawa E. , Kershaw K. A.
Published: September 2008

The postfire recovery sequence in spruce woodland growing on drumlins in the Abitau–Dunvegan Lakes area of the Northwest Territories is described. Four phases are recognized: year 1 to year 20, the Polytrichum phase dominated by P. piliferum, with Lecidea granulosa and L. uliginosa as associated species; year 21 to about year 60, the Cladonia phase dominated by Cladonia stellaris and C. uncialis; year 61 to about year 130, the spruce–Stereocaulon phase with Stereocaulon paschale forming an almost pure lichen ground cover; after year 130, the canopy closes and the lichen cover disappears and is replaced by a moss cover forming the final phase, spruce–moss woodland. These phases are confirmed by component analysis.The existence of spruce–Stereocaulon woodland in the area is thus dependent on cyclic burning. In the absence of fire the spruce canopy would close and the lichen cover would largely disappear. This event is rare in the area with a rebum cycle of about 100 years. Fire is thus an important vector in the maintenance of this extensive barren-ground caribou winter range.
Effects of nuclear restorer genes on the cytochrome content of corn pollen mitochondria
Authors: Watrud L. S. , Laughnan J. R. , Gabay S. J. , Koeppe D. E.
Published: September 2008

Mitochondria were isolated from mature pollen grains of corn (Zea mays L.) having normal (N) or restored Texas male-sterile (TRf) cytoplasm. Comparison of the cytochrome content of the two sources by low-temperature difference spectroscopy indicates that inbred lines carrying nuclear restorer genes and T cytoplasm have an increased cytochrome oxidase content. A lower cytochrome oxidase concentration was found in mitochondria isolated from anthers of nonrestored Texas (cms-T) male-sterile cytoplasm corn than from those isolated from nonexserted anthers of N or TRf plants. Mitochondria in nonsporogenous tissue of cms-T anthers collected just before the time of anthesis of N plants had fewer well defined cristae than mitochondria in comparable anther tissue of N or TRf plants.
Investigations of the marine algae of Nova Scotia. XII. The flora of Pomquet Harbour
Authors: Bird C. J. , Edelstein T. , McLachlan J.
Published: September 2008

The benthic algal flora of Pomquet Harbour, a sheltered embayment of the lower Gulf of St. Lawrence, was observed over 10 years. Thirty-nine taxa of Chlorophyceae, 32 of Rhodophyceae, 44 of Phaeophyceae, 5 of Xanthophyceae, and 1 taxon of Chrysophyceae are recorded, and data on time of occurrence, reproduction, and hosts are given. Five species, Stichococcus bacillaris, Ulothrix subflaccida, Vaucheria arcassonensis, V. compacta, and V. coronata, are reported as new to Nova Scotia.
Negative turgor pressure in plant cells: fact or fallacy?
Authors: Tyree M. T.
Published: September 2008

Several papers purporting to demonstrate negative turgor pressure in plant cells under extreme water stress are reviewed. A reanalysis of the published data suggests the reports are fallacious.
Apical dominance in the rhizome of Agropyron repens: the influence of water stress on bud activity
Authors: McIntyre Gordon I.
Published: September 2008

Experiments conducted under both field and growth-chamber conditions showed that buds on the rhizome of Agropyron repens L. Beauv. could be released from inhibition by a localized reduction of water stress, e.g. by enclosing the rhizomes in moist vermiculite. This response was obtained even at low N levels, a fact which may be due partly to the relatively low N requirement of buds developing as rhizomes as compared with those developing as shoots. The induced growth of the lateral buds was correlated with a reduction or complete inhibition of apical growth of the parent rhizome or with its transition from rhizome to shoot development. Continuous root removal reduced the bud response to high humidity in N-deficient plants but had relatively little effect at a higher N level. In water-stressed rhizomes the apparent increase of bud inhibition with distance from the apex, a characteristic feature of apical dominance, was correlated with the water content of the rhizome, which was greatest at the apex and decreased basipetally. It is postulated that this gradient of decreasing rhizome water content may be causally related to the increasing inhibition of bud activity.
Primary production of epiphytic algae in a marsh pond
Authors: Hooper Nina M. , Robinson G. G. C.
Published: September 2008

The use of artificial substrates for the estimation of epiphytic algal production was evaluated. The primary productivity of epiphytic algae in a marsh pond (Crescent Pond, Delta Marsh, Manitoba) was estimated using a cellulose acetate substrate. Annual production, based on 14C uptake was 26.8 g C m−2 of pond surface area. Production m−2 colonizable surface area was greatest on Scirpus acutus (32.3 g C m−2 year−1), while Potamogeton pectinatus was the most significant substrate in overall pond production (1700 kg C year−1). The organic C content of the epiphytic community was related to rates of productivity.
Effect of NaCl on cold hardiness of Malus spp. and Syringa vulgaris
Authors: Sucoff Edward , Hong Sung Gak
Published: September 2008

In early winter, NaCl was applied to branch surfaces of Malus sp. cv. Radiant and Syringa vulgaris L. growing in gardens and along salted highways. Hardiness of twigs collected from November to February was determined by damage to xylem, cambium, and bud apical meristems after exposure to test temperatures between 4 and −45 °C. In January and February, twigs receiving NaCl either from controlled applications or from highway deicing salts lost hardiness while NaCl-free twigs remained hardy. In both locations the loss in hardiness corresponded in time and amount to the increase in twig Cl and Na.
Morphology and distribution of resting sporangia of Olpidium brassicae in tobacco roots
Authors: Hiruki C. , Alderson P. G.
Published: September 2008

The surface of resting sporangia, observed with the scanning electron microscope, was smooth and had well defined symmetry consisting of pentamer and hexamer facets. The number of facets was relative to the size of a resting sporangium. The resting sporangia formed regular ridges which appeared in optical section as stellar points. Resting sporangia were present in root hairs, epidermal cells, and cortex tissue but not in vascular tissue of infected roots.
Leaf anatomy and water relations of Eucalyptus camaldulensis and E. globulus seedlings
Authors: Pereira J. S. , Kozlowski T. T.
Published: September 2008

Leaf anatomy and water relations of juvenile leaves varied between Eucalyptus camaldulensis and E. globulus seedlings. Eucalyptus camaldulensis had three or four pairs of opposite and horizontal lower leaves. Above these, the leaves were alternate, pendant, and nearly vertical. Eucalyptus globulus leaves were opposite and sessile. Stomata were more numerous but smaller in E. camaldulensis (amphistomatous) than in E. globulus (hypostamatous). In both species waxes were more abundant on the abaxial than on the adaxial leaf surface. Waxes of E. camaldulensis consisted of plates arranged perpendicular to the leaf surfaces; those of E. globulus were rodlets branching at right angles. In pot experiments (with a restricted soil volume) transpiration rates of the two species varied and depended on how they were expressed. When the soil was well watered, transpiration rate per seedling or per unit of the abaxial leaf surface area was higher in E. camaldulensis than in E. globulus. As the soil in the pots dried, plant water stress increased faster in E. camaldulensis than in E. globulus. During the first 2 weeks dry weight increment of shoots and roots was greater in E. globulus than in E. camaldulensis. Thereafter, growth of roots and shoots accelerated in E. camaldulensis and surpassed that of E. globulus. After a few weeks root growth of both species declined, reflecting the limitation of pot size. The pot experiments were misleading in suggesting that E. globulus was more drought resistant than E. camaldulensis. The higher transpiration rate and extensive rooting of E. camaldulensis in the restricted volume of soil in the pots induced greater water deficits than developed in E. globulus. When plants of both species were grown in long plastic tubes (with an unrestricted soil volume) water stress did not develop faster in E. camaldulensis than in E. globulus. The tube experiments showed that a major factor in greater drought avoidance of E. camaldulensis over E. globulus was capacity of the former to produce a deep and ramifying root system that could absorb water from deep soil layers after the surface soil dried. This advantage of E. camaldulensis over E. globulus was obscured in the pot experiments.
Microflora of heat-damaged rapeseed
Authors: Mills J. T. , Bollen G. J.
Published: September 2008

Microfloral components present on two sound lots (1 and 2) and three sample grade, heat-damaged lots (3 to 5) of stored Canadian rapeseed (Brassica campestris L. and B. napus L.) were determined with and without surface disinfection. Lots 1 and 2 were from a granary and a warehouse, respectively, and lots 3 to 5 were from primary elevators. Seed in lots 4, 5, and 3 showed progressively increased effects of heat damage as shown by the crush test. Sound lots 1 and 2 had mainly Alternaria and Cladosporium spp. with traces of Eurotium amstelodami, E. repens, and Penicillium spp. Lot 4 seed had low–medium levels of Alternaria alternata, Absidia ramosa, E. amstelodami, and Mucor pusillus. Lot 5 had high levels of E. amstelodami and low levels of Talaromyces thermophilus but A. alternata and M. pusillus were largely absent. Lot 3 had deeper-seated E. amstelodami, T. thermophilus, and Penicillium spp. than lots 4 and 5. Eurotium amstelodami was the predominant storage fungus in the heat-damaged lots. During the early stages of heating, E. amstelodami was often accompanied by the primary sugar fungi M. pusillus and A. ramosa, and after severe heating, by T. thermophilus. The thermal death point was between 50 and 60 °C for moist seed and between 80 and 90 °C for dry seed after 30-min exposure. With the exception of E. amstelodami, heat resistance of the fungal flora did not exceed that of the seed.
A contribution towards elucidating the life history of Palmaria palmate (=Rhodymenia palmata)
Authors: Meer J. P. van der
Published: September 2008

Palmaria palmata from a region of the Atlantic coast of Canada has been examined cytologically. Plants bearing tetrasporangia were found to be diploid with meiosis occurring in the tetrasporangia. Spermatangial plants and sporelings growing from tetraspores were haploid. The haploid chromosome number appears to be 22–23.
Diploidy, polyploidy, and agamospermy among species of Eupatorium (Compositae)
Authors: Sullivan Victoria I.
Published: September 2008

Diploids of eight species of Eupatorium, triploids of three species, and tetraploids of four species are reported here for the first time. Meiosisin microsporocytes of triploids and tetraploids either failed to occur resulting in failure of pollen production or less frequently resulted in either incomplete chromosomal pairing or complete asynapsis; the latter two events lead to the production of grossly malformed, abortive pollen with unevenly deposited walls. Megasporogenesis examined in two polyploid plants led to the formation of eight-nucleate, unreduced embryo sacs which formed endosperm and embryos without pollination, indicating that the sporophytes develop asexually through agamospermy. Evidence is given that this may be a facultative characteristic. Megasporogenesis, studied in diploids of four species, produced normal embryo sacs with no indication of agamospermous development. Diploid plants of 11 of 12 species were tested and found to be self-incompatible.Since diploids could readily be distinguished from polyploids by pollen production (diploids produced normal pollen, polyploids produced none or malformed pollen), distributions of a large number of diploid, triploid, and tetraploid individuals could be determined from examining anthers of herbarium specimens. Distribution maps were made using these data as well as those from chromosome counts. Diploid members of species having both diploid, triploid, and (or) tetraploid members consistently had smaller distributional ranges than polyploids of the same species.
Effect of Curvularia lunata phytotoxin on membrane permeability of corn roots
Authors: Vianello A. , Macrì F. , Passera C.
Published: September 2008

Corn roots exposed to the Curvularia lunata phytotoxin show a decreased ability to absorb and to retain rubidium, sulphate, and leucine compared with control roots. The phytotoxin also decreased the amount of the amino acid incorporation into protein, whereas respiration was only slightly affected. The effect on active transport was more pronounced and rapid than loss of ions and inhibition of protein synthesis. The data suggest that the phytotoxin causes a general plasma membrane derangement similar to that caused by other phytotoxins, which results in a depression of the active transport, reflected in an inhibition of precursors of proteins and in a loss of ions. The toxin is to be regarded as a specific membrane poison.
A survey of the presence of glutamate synthase in plant cell suspension cultures
Authors: Dougall Donald K. , Bloch Jeff
Published: September 2008

Evidence was sought for the presence of glutamate synthase (EC 2.6.1.53) in extracts from suspension cultures of six higher plant species not previously examined. The level of glutamate synthase measured was above the level of glutamic dehydrogenase (EC 1.4.1.2, 1.4.1.4) in extracts of soybean, parsley, okra, and cotton. Glutamate synthase was detectable but less than glutamic dehydrogenase in extracts of sugarcane. Glutamate synthase was not detected in extracts of peanut. Evidence for two glutamate synthases, each specific for one pyridine nucleotide, was obtained with cultures of carrot. Glutamate synthase has now been detected in eight and possibly nine species representing four and possibly five families of higher plants.
Comparison of two criteria for internal stability of granular soil
Authors: Li Maoxin , Fannin R. Jonathan
Published: September 2008

Internal instability describes the loss of soil particles as a result of seepage. Two criteria are commonly used to determine the potential for such instability within a granular soil that is subject to seepage flow. The criteria are similar, in that they both require an evaluation of the slope of the grain-size distribution curve. However, the manner in which the evaluation is made yields a subtle difference between the respective methods. Comparison of the methods reveals that the difference can have implications for evaluation of broadly graded soils, and guidance is suggested for their use with greater confidence in engineering practice.
Quantification of the effects of structure on the compression of a stiff clay
Authors: Gasparre A. , Coop M. R.
Published: September 2008

A detailed analysis was made of the compression behaviour of London Clay from oedometer tests, investigating the effects of the clay structure through comparisons between the behaviour of the intact soil and that of the same soil in a reconstituted state. The normalizing parameters commonly used in the literature to analyze the effects of structure on the compression behaviour of clays were found not to represent accurately the real behaviour of those clays that have a gradual yield in compression and require very high stresses to reach and cross the intrinsic compression line. For these soils, it is often difficult to identify a clear yield stress and the effects arising from the structure of the intact material may be concealed by the effects arising from the sample depth and the curvature of the intrinsic compression line at high stresses. A new normalizing parameter is introduced that refers the compression of the natural soil to the intrinsic swelling behaviour and the intrinsic compression line of the material. This was found to better represent the enhanced resistance of the intact material in compression while not requiring numerous loading and unloading stages in the oedometer tests as required by other methods.
Bearing capacity of soils for crawler cranes
Authors: Liu Xiteng , Chan Dave H. , Gerbrandt Brian
Published: September 2008

Few studies have been carried out on the bearing capacity of soils for crawler cranes. Directly applying the bearing capacity equations used for shallow foundations to cranes often leads to conservative design. The total settlement is of less concern for cranes than for buildings, and cranes can normally tolerate larger differential settlements. Computer simulation and field studies have been carried out to study the allowable bearing capacity of soils for cranes. Equations modified from the traditional method to calculate the bearing capacity for shallow foundations have been proposed. In general, it was found that the bearing capacity for crawler cranes could be increased by as much as 50% from that for foundations. This depends on the soil type, crane, and mat configuration. A design procedure in evaluating foundation support for crawler cranes is also proposed.
Comparison of shear strength of sand backfills measured in small-scale and large-scale direct shear tests
Authors: Bareither Christopher A. , Benson Craig H. , Edil Tuncer B.
Published: September 2008

Direct shear tests were conducted on 30 sand backfill materials having gravel contents ranging from 0% to 30% in a 64 mm square small-scale direct shear (SSDS) box and a 305 mm square large-scale direct shear (LSDS) box. The objectives were to compare the shearing behavior of a broad range of natural sand backfill materials tested in SSDS and LSDS and to determine if the same friction angle (φ′) is obtained in SSDS and LSDS when the natural backfill material contains gravel. Triaxial compression (TC) tests were also conducted on four of the backfill materials for comparison with the SSDS and LSDS tests. Specimens tested in SSDS and TC included only material passing the No. 4 sieve (P4). Test specimens in LSDS included the P4 material as well as material retained on the No. 4 sieve (R4), to a maximum particle diameter of 25.4 mm. Friction angles corresponding to peak strength (φ′) measured in SSDS and LSDS differed by no more than 4° for a given sand backfill, and in most cases were within 2°. The friction angles also were unaffected by removal of the R4 material. Repeatability tests showed that statistically similar failure envelopes (p-value = 0.98) are obtained in SSDS and LSDS, and that highly repeatable friction angles (φ′) are obtained using the SSDS (φ′ ± 0.25°) and the LSDS (φ′ ± 0.45°) methods. No statistically significant difference was found among the failure envelopes measured in SSDS, LSDS, and TC, suggesting that φ′ for clean sand backfill with less than 30% gravel can be measured with similar accuracy using any of the three test methods.
STATIONARY STATES OF NONLINEAR DIRAC EQUATIONS WITH GENERAL POTENTIALS
Authors: DING YANHENG , WEI JUNCHENG
Published: September 2008

We establish the existence of stationary states for the following nonlinear Dirac equation [Formula: see text] with real matrix potential M(x) and superlinearity g(x,|u|)u both without periodicity assumptions, via variational methods.
IN VITROTRANSPLANTATION OF GENETICALLY MODIFIED CELLS TO THE TENDON SURFACE
Authors: Couvreur Paulus J. J. , Zhao Chunfeng , Murphy Stephen , Amadio Peter C.
Published: September 2008

The objective of this paper was to study in vitro transfection of tendon cells and adherence of transfected cells to different tendon surfaces. Achilles tendon fibroblasts from 2-month-old New Zealand white rabbits were cultured to confluence, after which the cells were transfected by an adenovirus carrying either the β-galactosidase reporter gene or the green fluorescent protein (GFP) gene at multiplicities of infection (MOIs) of 50, 100, or 500. Two days later, the cells were transplanted onto the surfaces of rabbit Achilles, peroneus brevis, flexor profundus, and extensor longus tendons. The tendons were assessed by X-gal staining after 9 days, and by GFP fluorescence at 7, 14, and 21 days. Twenty percent to 50% of the treated cells stained for β-galactosidase at an MOI of 500. The GFP-labeled cells showed nearly 100% fluorescence at an MOI of 50. No positive cells were visible in the control group. The β-galactosidase and GFP-expressing cells remained viable for as long as 3 weeks. It is possible to introduce foreign genes into rabbit tendon cells, transplant the cells onto tendon surfaces, and maintain viability of the cell/tendon construct for several weeks.
MOMENT ARMS OF THE ARM MUSCLES AT THE GLENOHUMERAL JOINT USING THE TENDON EXCURSION METHOD
Authors: Itoi Eiji , Lee Seok-Beom , Berglund Lawrence J. , Schultz Fredrick M. , Neale Patricia G. , An Kai-Nan
Published: September 2008

Muscle moment arm defines the function of the muscle. To date, moment arms of the arm muscles at the glenohumeral joint using the tendon excursion method have not been reported. As the functions of these muscles at the shoulder joint are controversial, this study was undertaken to determine the moment arms of the long and short heads of the biceps (LHB, SHB), the coracobrachialis, and the long head of the triceps muscles. The moment arms were determined in 10 cadaveric shoulders by measuring the tendon excursion when the arm was rotated by 1 radian (57.3°) in 22 different motions. The LHB was a flexor, horizontal flexor, and abductor. The SHB and coracobrachialis were flexors, horizontal flexors, and adductors. The long head of the triceps was an extensor and adductor. Arm rotation significantly affected the function of the LHB only: it was an internal rotator in flexion and an external rotator in abduction. This study clarifies the individual function of the arm muscles at the glenohumeral joint.
VESSELPLASTY: A NOVEL CONCEPT OF PERCUTANEOUS TREATMENT FOR STABILIZATION AND HEIGHT RESTORATION OF VERTEBRAL COMPRESSION FRACTURES
Authors: Darwono Bambang
Published: September 2008

Objective: Vertebroplasty, kyphoplasty, VEX-3000, SKy bone expander, arcuplasty, and OptiMesh systems are methods of percutaneous osteoplasty (molding of the bone) to treat symptomatic vertebral compression fractures (VCFs) by injection of bone filler materials (BFMs) such as polymethyl methacrylate (PMMA), other kinds of bone cement, and bone grafts (autografts/allografts) or different kinds of osteoinductive/osteoconductive materials. A common risk in performing the abovementioned techniques is leakage of BFMs. The purpose of this technical consideration of vesselplasty was to review the theory, the surgical technique for stabilization and restoration of the height of VCFs, and the prevention of leakage, using a novel bone filler container (BFC) system. Methods: This novel concept of BFC highlights the Vessel-X™ system (A-Spine Holding, Taipei, Taiwan) as an evolution of the percutaneous osteoplasty technique to stabilize and restore VCFs and to prevent leakage risk. Instead of previously creating a void inside the vertebral body to be filled with BFMs, this system allows the delivery of a nonstretchable BFC into the vertebral body in deflated configuration, to be inflated by injecting viscous BFMs into the BFC, then left as an implant and acting as a vertebral body expander. The volume of the injected BFMs is controlled by a controllable cement delivery (CCD) injector system. The pressure inside the BFC is created by the resistance of the polyethylene terephthalate (PET) container, which is related to the number of layers (one or two layers), the pore size (100 μm), and the container size itself. The optimum pressure needed to lift the endplate is the amount of pressure required to counteract the resistance of the surrounding bone density (fresh or old fractures, young or elderly patients) and the large bending moment due to kyphotic deformity of the spine. The pressure is also related to the amount of BFMs to be injected into a certain size of the BFC. When the pressure is higher than the surrounding bone resistance, BFMs start to penetrate, interdigitate, and stabilize the BFC to the surrounding bone. Conclusions: The vesselplasty technique using the novel concept of BFC allows stabilization and restoration of VCF height, with the added advantages of controlling the volume of the injected BFMs, the pressure inside the BFC, and the leakage risk of BFMs as well as creating a gradual stiffness of BFMs inside the bone from the periphery to the central area.
ULTRASONOGRAPHY AS A DIAGNOSTIC MODALITY OF TIBIAL STRESS FRACTURES
Authors: Farkash Uri , Naftal Javier , Deranze Estela , Blankstein Alexander
Published: September 2008

Tibial stress fractures (SFs) are a common orthopedic problem during military basic training. Bone scan is considered the gold standard for diagnosing this condition. Several case reports have described sonographic features of stress fractures. This is a prospective, double-blind study to compare diagnostic ultrasound (US) examination with isotope bone scan in diagnosing SF. Thirty-one soldiers who were referred to the nuclear medicine service for a bone scan to rule out tibial SF participated in this study. The SF lesions of the lower extremities were classified according to the classification criteria introduced by Zwas et al.20 US examination was performed on the same day. Areas of cortical thickening and other pathologies like bone surface irregularity and bone discontinuity were recorded. Each examination was graded as either normal or suggestive of representing a SF. Thirty of 62 tibiae were diagnosed as having SF according to bone scan, whereas US examination suggested SF in 35 tibiae. US examination was positive in 20 of 30 tibiae with SF (67% sensitivity, 53% specificity). Although US correctly diagnosed SF in 20 tibiae, bone scan remains the chosen imaging modality to detect SF in soldiers. US was not found to be a reliable modality to diagnose SF.
EFFECT OF CYCLIC PRECONDITIONING ON THE FAILURE LOAD, STRENGTH, AND STIFFNESS OF MULTIPLE RAT TENDONS AND LIGAMENTS
Authors: Teramoto Atsushi , Su Wei-Ren , Luo Zong-Ping
Published: September 2008

Purpose: Ligaments and tendons are frequently injured structures in sports activities. It has been well known that stretching before activities largely warms up muscles and prevents athletes from getting injuries. Recent studies have suggested that the tendon might also benefit from such preconditioning stretching; however, it is unclear whether the same benefit exists for all ligament and tendon structures. We hypothesized that the effect of preconditioning on mechanical strength is dependent on the type of ligament or tendon. Methods: Twenty-six anterior cruciate ligaments (ACLs), 22 medial collateral ligaments (MCLs), 20 patellar tendons (PTs), and 18 Achilles tendons (ATs) from euthanized mature Sprague-Dawley rats were used. The specimens in the control group were tested for load to failure without preconditioning. In the preconditioning group, 150 sinusoid cyclic stretchings were performed; the specimens were then consecutively loaded to ultimate failure. Results: Preconditioning significantly increased the mechanical strengths of the MCL, PT, and AT (p = 0.04, p = 0.006, and p = 0.002, respectively); however, it did not affect that of the ACL. There were no significant differences among the mechanical strengths of MCL, PT, and AT in the preconditioning group. Conclusion: Preconditioning significantly enhanced all ligament and tendon structures, except for the ACL. The results suggest that optimal preconditioning exists, but depends on the specific ligament or tendon. Different preconditioning strategies may be needed for different ligament and tendon structures in order to gain maximal protection from injuries.
EMERGENT SOCIAL RATIONALITY IN A PEER-TO-PEER SYSTEM
Authors: MARCOZZI ANDREA , HALES DAVID
Published: September 2008

Many peer-to-peer (P2P) applications require that nodes behave altruistically in order to perform tasks collectively. Here we examine a class of simple protocols that aim to self-organize P2P networks into clusters of altruistic nodes that help each other to complete jobs requiring diverse skills. We introduce a variant (called ResourceWorld) of an existing model (called SkillWorld) and compare results obtained in extensive (ten billion interactions) simulation experiments. It was found that for both model variants altruistic behavior was selected when certain cost/benefit constraints were met. Specifically, ResourceWorld selects for altruism only when the collective benefit of an action is at least as high as the individual cost. This gives a minimal method for realizing so-called "social rationality," where nodes select behaviors for the good of the collective even though actions are based on individual greedy utility maximization. Interestingly, the SkillWorld model evidences a kind of superaltruism in which nodes are prepared to cooperate even when the cost is higher than the benefit.
SLOWER IS FASTER: FOSTERING CONSENSUS FORMATION BY HETEROGENEOUS INERTIA
Authors: STARK HANS-ULRICH , TESSONE CLAUDIO J. , SCHWEITZER FRANK
Published: September 2008

We investigate an extension of the voter model in which voters are equipped with an individual inertia to change their opinion. This inertia depends on the persistence time of a voter's current opinion (ageing). We focus on the case of only two different inertia values: zero if a voter just changed toward a new opinion, and ν otherwise. We are interested in the average time to reach consensus, i.e. the state in which all voters have adopted the same opinion. Adding inertia to the system means to slow down the dynamics at the voter's level, which should presumably lead to slower consensus formation. As an unexpected outcome of our inertial voter dynamics, there is a parameter region of ν where an increasing inertia leads to faster consensus formation. These results rest on the heterogeneity of voters which evolves through the described ageing. In a control setting of homogeneous inertia values, we only find monotonously increasing consensus times. In this paper, we present dynamical equations for the mean field case which allow for analytical insight into the observed slower-is-faster effect.
EMERGENT COMMUNITY STRUCTURE IN SOCIAL TAGGING SYSTEMS
Authors: CATTUTO CIRO , BALDASSARRI ANDREA , SERVEDIO VITO D. P. , LORETO VITTORIO
Published: September 2008

A distributed classification paradigm known as collaborative tagging has been widely adopted in new Web applications designed to manage and share online resources. Users of these applications organize resources (Web pages, digital photographs, academic papers) by associating with them freely chosen text labels, or tags. Here we leverage the social aspects of collaborative tagging and introduce a notion of resource distance based on the collective tagging activity of users. We collect data from a popular system and perform experiments showing that our definition of distance can be used to build a weighted network of resources with a detectable community structure. We show that this community structure clearly exposes the semantic relations among resources. The communities of resources that we observe are a genuinely emergent feature, resulting from the uncoordinated activity of a large number of users, and their detection paves the way for mapping emergent semantics in social tagging systems.
FROM CROWD DYNAMICS TO CROWD SAFETY: A VIDEO-BASED ANALYSIS
Authors: JOHANSSON ANDERS , HELBING DIRK , AL-ABIDEEN HABIB Z. , AL-BOSTA SALIM
Published: September 2008

The study of crowd dynamics is interesting because of the various self-organization phenomena resulting from the interactions of many pedestrians, which may improve or obstruct their flow. Besides formation of lanes of uniform walking direction and oscillations at bottlenecks at moderate densities, it was recently discovered that stop-and-go waves [D. Helbing et al., Phys. Rev. Lett.97 (2006) 168001] and a phenomenon called "crowd turbulence" can occur at high pedestrian densities [D. Helbing et al., Phys. Rev. E75 (2007) 046109]. Although the behavior of pedestrian crowds under extreme conditions is decisive for the safety of crowds during the access to or egress from mass events as well as for situations of emergency evacuation, there is still a lack of empirical studies of extreme crowding. Therefore, this paper discusses how one may study high-density conditions based on suitable video data. This is illustrated at the example of pilgrim flows entering the previous Jamarat Bridge in Mina, 5 kilometers from the Holy Mosque in Makkah, Saudi-Arabia. Our results reveal previously unexpected pattern formation phenomena and show that the average individual speed does not go to zero even at local densities of 10 persons per square meter. Since the maximum density and flow are different from measurements in other countries, this has implications for the capacity assessment and dimensioning of facilities for mass events. When conditions become congested, the flow drops significantly, which can cause stop-and-go waves and a further increase of the density until critical crowd conditions are reached. Then, "crowd turbulence" sets in, which may trigger crowd disasters. For this reason, it is important to operate pedestrian facilities sufficiently below their maximum capacity and to take measures to improve crowd safety, some of which are discussed in the end.
CHEMICAL ORGANIZATIONS IN A TOY MODEL OF THE POLITICAL SYSTEM
Authors: DITTRICH PETER , WINTER LARS
Published: September 2008

Because sociology is seeking mechanisms for explaining social phenomena, we discuss in this paper whether and how the metaphor of a chemical reaction network can be employed as a formal mechanism to describe social and political systems. A reaction network is a quite general concept that allows one to model a variety of dynamical systems. Furthermore, a set of powerful tools can infer potential dynamical properties from the network structure. Using a toy model of the political system inspired by Luhmann, we demonstrate how chemical organization theory can be applied and can give insight into the structure and dynamics of the resulting model. We show how chemical organization theory allows one to identify an overlapping hierarchy of important subsystems in these networks. Simulations reveal how this hierarchy constrains the potential dynamical behavior of the model.
TWO-DIMENSIONAL VORTEX SHEETS FOR THE NONISENTROPIC EULER EQUATIONS: LINEAR STABILITY
Authors: MORANDO ALESSANDRO , TREBESCHI PAOLA
Published: September 2008

We study the linear stability of contact discontinuities for the nonisentropic compressible Euler equations in two space dimensions. Assuming the jump of the tangential velocity across the discontinuity surface is sufficiently large, we derive a suitable energy estimate for the linearized boundary value problem. The found estimate extends to nonisentropic compressible flows the main result of Coulombel–Secchi for the isentropic Euler equations. Compared with this latter case, when the jump of the tangential velocity of the unperturbed flow attains a certain critical value in the region of weak stability, here an additional loss of regularity appears; this is related to the presence of a double root of the Lopatinskii determinant associated to the problem.
THE LIFESPAN OF SOLUTIONS OF EXTERIOR RADIAL QUASILINEAR CAUCHY–NEUMANN PROBLEMS
Authors: GODIN PAUL
Published: September 2008

We consider smooth solutions of radial exterior Cauchy–Neumann problems with small initial data for radial quasilinear wave equations in three space dimensions, when the size of the initial data tends to 0. We obtain rather precise information on the lifespan, analogous with well known Cauchy problem results of Hörmander and John.
THE VLASOV–POISSON EQUATIONS AS THE SEMICLASSICAL LIMIT OF THE SCHRÖDINGER–POISSON EQUATIONS: A NUMERICAL STUDY
Authors: JIN SHI , LIAO XIAOMEI , YANG XU
Published: September 2008

In this paper, we numerically study the semiclassical limit of the Schrödinger–Poisson equations as a selection principle for the weak solution of the Vlasov–Poisson in one space dimension. Our numerical results show that this limit gives the weak solution that agrees with the zero diffusion limit of the Fokker–Planck equation. We also numerically justify the multivalued solution given by a moment system of the Vlasov–Poisson equations as the semiclassical limit of the Schrödinger–Poisson equations.
A FOURTH ORDER DIFFERENCE SCHEME FOR THE MAXWELL EQUATIONS ON YEE GRID
Authors: FATHY ALY , WANG CHENG , WILSON JOSHUA , YANG SONGNAN
Published: September 2008

The Maxwell equations are solved by a long-stencil fourth order finite difference method over a Yee grid, in which different physical variables are located at staggered mesh points. A careful treatment of the numerical values near the boundary is introduced, which in turn leads to a "symmetric image" formula at the "ghost" grid points. Such a symmetric formula assures the stability of the boundary extrapolation. In turn, the fourth order discrete curl operator for the electric and magnetic vectors gives a complete set of eigenvalues in the purely imaginary axis. To advance the dynamic equations, the four-stage Runge–Kutta method is utilized, which results in a full fourth order accuracy in both time and space. A stability constraint for the time step is formulated at both the theoretical and numerical levels, using an argument of stability domain. An accuracy check is presented to verify the fourth order precision, using a comparison between exact solution and numerical solutions at a fixed final time. In addition, some numerical simulations of a loss-less rectangular cavity are also carried out and the frequency is measured precisely.
Genetic, Individual, and Group Facilitation of Disease Resistance in Insect Societies
Authors: Wilson-Rich Noah , Spivak Marla , Fefferman Nina H. , Starks Philip T.
Published: September 2008

In this review, we provide a current reference on disease resistance in insect societies. We start with the genetics of immunity in the context of behavioral and physiological processes and scale up levels of biological organization until we reach populations. A significant component of this review focuses on Apis mellifera and its role as a model system for studies on social immunity. We additionally review the models that have been applied to disease transmission in social insects and elucidate areas for future study in the field of social immunity.
Biology of Subterranean Termites: Insights from Molecular Studies ofReticulitermesandCoptotermes
Authors: Vargo Edward L. , Husseneder Claudia
Published: September 2008

Molecular genetic techniques have made contributions to studies on subterranean termites at all levels of biological organization. Most of this work has focused on Reticulitermes and Coptotermes, two ecologically and economically important genera. DNA sequence data have significantly improved our understanding of the systematics and taxonomy of these genera. Techniques of molecular biology have provided important new insights into the process of caste differentiation. Population genetic markers, primarily microsatellites, have furthered our understanding of the life history, population biology, community ecology, and invasion biology of subterranean termites. Recent results on the behavioral ecology of subterranean termites reveal a picture different from long-held views, especially those concerning colony breeding structures and foraging ranges. As additional molecular tools and genomic resources become available, and as more subterranean termite researchers incorporate molecular techniques into their approaches, we can expect accelerating advances in all aspects of the biology of this group.
Monogamy and the Battle of the Sexes
Authors: Hosken D.J. , Stockley P. , Tregenza T. , Wedell N.
Published: September 2008

Sexual conflict has been suggested to be important in the evolution of reproductive traits, with much recent theoretical and empirical evidence emphasizing its role in generating sexually antagonistic coevolution in the context of promiscuous mating. Here we shift attention to the role of sexual conflict in a monogamous mating context. Conflicts can arise, for example, when males are successful in imposing monandry at a cost to female fitness, or when females impose monogyny on males. Conflict over remating can also generate monogamy. For example, when males invest heavily in attempting to impose female monandry, the cost of their investment may prevent them from securing additional mates. We emphasize that sexual conflicts need not always generate sexually antagonistic coevolution, and that it is important to consider whether mating decisions are controlled primarily by males or females. Finally, we briefly discuss approaches to distinguish between conflict and classical modes of sexual selection, as this highlights difficulties associated with deciding whether monogamy is enforced by one sex or the other. We suggest that documenting the current fitness consequences of mate choice and mating patterns provides insight into the relative importance of classic and conflict modes of selection.
Imitation, Empathy, and Mirror Neurons
Authors: Iacoboni Marco
Published: September 2008

There is a convergence between cognitive models of imitation, constructs derived from social psychology studies on mimicry and empathy, and recent empirical findings from the neurosciences. The ideomotor framework of human actions assumes a common representational format for action and perception that facilitates imitation. Furthermore, the associative sequence learning model of imitation proposes that experience-based Hebbian learning forms links between sensory processing of the actions of others and motor plans. Social psychology studies have demonstrated that imitation and mimicry are pervasive, automatic, and facilitate empathy. Neuroscience investigations have demonstrated physiological mechanisms of mirroring at single-cell and neural-system levels that support the cognitive and social psychology constructs. Why were these neural mechanisms selected, and what is their adaptive advantage? Neural mirroring solves the “problem of other minds” (how we can access and understand the minds of others) and makes intersubjectivity possible, thus facilitating social behavior.