bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation and Optimization of Tribocontacts and Lubrication Systems of Internal Combustion Engines for Various Types of Lubricant
Authors: Sivrikova S. , Rojdestvensky J. , Petrov I. , Popova S.
Published: November 2008

Quality, reliability and fuel efficiency of internal combustion engines (ICE) substantially depend upon optimum choice of lubrication system and tribocontact design and a lubricant liquid. This paper describes a quasistatic method of analysis of ICE lubrication systems for Newtonian and non-Newtonian oils. The method allows for both transient and steady-state conditions.
Wear Characteristics of Polymer Tapes in ATM Tape-Scraper Tribosystem in Sand Dust Environment
Authors: Wu Tonghai , Diao Dongfeng , Yoshida Kazushi
Published: November 2008

The tape-scraper tribosystem of ATM (Auto Teller Machine) was used to study the wear properties of polymer tapes of PEN (polyethylene-2, 6-naphthalenedicarboxylate) and PI (polyimide) sliding against polymer scraper of POM (polyoxymethylene) in the clean air environment and in the simulated environment of sand dust with the natural sand from the desert. As main results, the mean wear rate of the PEN tape in the sand storm environment was about 500 times of that in the clean environment and the mean wear rate of the PI tape in the sand storm environment was about 1700 times of that in the clean environment. The PI tape exhibited higher abrasive resistance than the PEN tape. The bill substrate increased the abrasive resistance of polymer tapes. The micro wear mechanism examination showed the plastic flow and the broken of fibers for PEN tape and block fracture due to brittle nature for PI tape.
Analysis of Particulates Extracted From J52P408 Oil Filters
Authors: Humphrey Gary R.
Published: November 2008

Traditionally, rotrode atomic emission spectroscopy (RAES) is the technology and methodology of choice used in DoD to monitor the wear occurring in oil system components of jet engines. Eight microns is the maximum size of particles that AES can resolve into their elemental composition.[1] The Joint Oil Analysis Program Technical Support Center (JOAP-TSC) has developed an automated technology and methodology to analyze debris extracted from jet engine oil filter elements. The method is termed filter debris analysis (FDA) and particle size is not an issue in FDA. The J52 engine was experiencing catastrophic failures where the root cause was linked to the failure of the 4 1/2 bearing assembly. RAES was not successful in detecting the onset of the failure of the 4 1/2 bearing assembly. FDA was employed in an attempt to detect 4 1/2 bearing failure in the J52 engine. The J52 engineering group has reported that FDA and RAES together are 90% effective in detecting 4 1/2 bearing failure. JOAP-TSC data indicates that the FDA technique is 95% or better in detecting 4 1/2 bearing failure.
From Lab to Field: New High Performance Water Lubricated Bearings
Authors: Orndorff R. , Foster L. , Sheppert R.
Published: November 2008

Recent independent lab testing and field trials have verified significant wear and friction reductions are possible with a new family of polymer alloy bearings. Advanced water-lubricated bearings with projected pressures in the range of 3448 to 6895 kPa (500 to 1,000 psi) are possible with length-to-diameter (L/D) ratios as low as 0.2 without end leakage. Much higher pressures are made possible by dimensionally controlling the “stiffness” (shape factor) of the rubber/plastic alloy bearing.
Application of Hydromechatronics for Studying the Motion Accuracy of the Working Parts of Technological Machines
Authors: Vekteris Vladas , Jurevichius Mindaugas
Published: November 2008

Hydromechatronic Programmable Load Equipment is used for workload simulation while testing technological machines to determine their dynamic characteristics. The structure and principles of operation of the created equipment are described and equations of balances of the hydrostatic bearings of the slider and boring bar and equations of motion of the boring bar have been formed in the article. Analytical and graphical dependences of motion of the slider and boring bar have been determined after entering digital data into the computer.
Friction and Wear of Diamond-Like Carbon Coatings Lubricated With Biodegradable Oils
Authors: Van Acker K. , Vercammen K. , Vanhulsel A. , Barriga J. , Arnsek A. , Kalin M.
Published: November 2008

The tribological behaviour of coated machine components lubricated with a biodegradable saturated ester and unsaturated ester oil has been studied. Different diamond-like carbon-based coatings (DLC) were selected as low friction coatings: pure DLC, Si-doped, Ti-doped and W-doped DLC. The performance of the studied ester oils has been compared with sunflower oil and mineral oil lubrication as reference. The oils were all additivated in the same way with conventional anti-wear (AW) and extreme pressure (EP) additives. Different tests have been performed: disc on disc, ball on disc and block on ring tests give an overview of the influence of different sliding modes. The effect of the lubricant on a coated system compared to the use of the coated system without lubrication is clear for the wear, but less obvious for the friction. It was found that DLC/DLC contacts lubricated with biodegradable lubricants show similar friction as steel/steel contacts. The effect of the different types of base oil is independent of the coating type. Additive activity which was clear in steel/steel contacts was not obvious in DLC/DLC contacts.
Adhesion in the Contact of a Spherical Indenter With a Layered Medium
Authors: Sergici Asri Onur , Adams George G. , Mu¨ftu¨ Sinan
Published: November 2008

With the emergence of micro- and nano-technology, the contact mechanics of MEMS & NEMS devices and components is becoming more important. The motivation for this work is to gain a better understanding of the role of coatings and thin films on micro- and nano-scale contact phenomena, and to understand the interactions of measurement devices, such as an Atomic Force Microscope (AFM), with layered media. The frictionless contact between a rigid spherical indenter and an elastic layered medium is the subject of this research. This configuration can be viewed as either a single asperity contact or as a building block of a multi-asperity rough surface contact model. As the scale decreases to the nano level, adhesion becomes an important issue in this contact problem. The presence of adhesion affects the relationships among the applied force, the penetration of the indenter and the size of the contact area. This axisymmetric problem includes the effect of adhesion using the Maugis model. This model spans the range of the Tabor parameter between the JKR and DMT regions. Key parameters have been identified which are the elastic moduli ratio of the layer and the substrate, the Poisson’s ratios, the dimensionless contact radius, the dimensionless layer thickness, and the adhesion parameter λ.
Evaluation of the Stress Situation of Coated Tribosystems With Contact Mechanics Simulation
Authors: Gold P. W. , Loos J. , Klaas H.
Published: November 2008

For the realization of environmental compatible tribosystems within the special research centre SFB 442 PVD coated systems are developed, which improve the tribological characteristics together in interaction with compatible lubricants. For the evaluation of coated substrate systems employed in tribosystems, it is significant to characterize the mechanical stress collective within the systems by means of their mechanical properties. Subject of the presented investigations is an analysis about the properties of the systems that have significant effects on the system stress collective. Differences to the well-known surface stress of solid materials are pointed out and mathematical models for the description are developed to describe the influence of coated substrates. The aim of these investigations is to draw a connection between these stresses occurring in tribosystems (e.g. industrial applications bearings) and the loads applied in test methods e.g. microindentation (Rockwell Hardness Tests) and nanoindentation. To evaluate the stresses applied in real tribosystems the theory of micro contact mechanics of Greenwood and Williamson is used and is found to be appropriate. Since, only with this connection it is possible to consult the results gained in the coating test methods for the evaluation of a coated system. Essential aid in here is the simulation of the mechanical surface stresses by means of FEM (finite element method). At this point it is possible to take the anisotropic and inhomogeneous material properties of the coating material and the substrate into account.
Scuffing Initiation, Scuffing Propagation and Pitting of a Four-Ball Tribosystem Lubricated With Mineral and Synthetic Oils
Authors: Tuszynski Waldemar , Piekoszewski Witold , Szczerek Marian
Published: November 2008

The research aimed at finding an effect of various base oils on the scuffing initiation, scuffing propagation and pitting. The following base oils were tested: mineral oil, synthetic hydrocarbon oil (polyalphaolefins), synthetic non-hydrocarbon oils (polyol ester, polyglycol) and highly refined mineral one known as a white oil. The tests were performed in two different four-ball testers. One was used to investigate scuffing at pure sliding friction. The second instrument was employed to test pitting at rolling movement. To avoid an effect of the oil viscosity, base oils having similar viscosities ν100 (3,8 – 5,5 mm2 s−1) were compared. In this group the highest load causing the scuffing initiation is given by the polyglycol, and the lowest one — by polyalphaolefins and white oil. The scuffing propagation is similar for all the oils. The best resistance to pitting is given by the mineral oil, and the worst — by the white oil.
Friction-Topography Correlations During Nanotribological Fatigue Testing of Bulk Polystyrene
Authors: Bender Jonathan W. , Gibbs Chris W.
Published: November 2008

Scanning probe microscopy nanotribological experiments on thick polystyrene films have been performed that support the hypothesis that crazing is the mechanism of ‘bundle’ formation. In these fatigue studies, surface patterning appears abruptly at a critical friction, and can either occur spontaneously or be triggered by surface imperfections. After pattern initiation, progressive scanning smoothly increases surface roughness. Friction histograms of these in situ patterned surfaces reveal two distinct friction regions that are statistically correlated with the topography. Using a topography-friction cross-correlation function, high friction was found to coincide with topographic troughs. This supports crazing as the mechanism of deformation, in which surface fracture at troughs leads to fibril formation, consistent with the observation of higher energy dissipation.
Estimation of Polymer Coating Scratch Tensile Strength by Nano-Indentation, Micro-Scratch Testing, and Finite Element Modeling
Authors: Ovaert Timothy C. , Kim B. R.
Published: November 2008

In a previous paper, polymer coating viscoelastic/plastic properties were determined using nanoindentation and the finite element method. In this work, the individual layers, once characterized, were assembled into a multi-layered structure and subject to micro-scratch tests. These tests determined a critical scratch indentation load for the layered structure, as designated by the first appearance during scratching of visible surface layer tensile cracks. Scratch tests were carried out for three different conical scratch tip radii. The top-layer tensile strength of the layered structures was then estimated, utilizing the individual layer properties, the top layer friction coefficients, the micro-scratch test critical loads, and a finite element scratch model, for each scratch tip radius. The values of the top layer scratch tensile strengths were in good agreement for each of the three tip radii, as anticipated. The top-layer scratch tensile strengths may be utilized for further analysis and comparison of differences in gloss retention after gloss reduction experiments. The method may be used as a basis for coating selection, comparison, and performance testing in scratch-resistant polymer coating applications.
A Two-Dimensional Adaptive Elasto-Plastic Contact Model of Rough Surfaces
Authors: Liu Tianxiang , Liu Geng , Xie Qin
Published: November 2008

When contact problems are solved by numerical approaches, the surface profile is usually described by a series of discrete nodes with the same intervals along the coordinate axis. An adaptive-surface-based elasto-plastic asperity contact model is presented in this paper. Such a model is developed in order to reduce the computing time by removing the surface nodes that have little influence on the contact behavior of rough surfaces. The removed nodes are determined by setting a threshold. Thus, the contact problems can be described by fewer surface nodes but have similar results to the ones of the original surface. The adaptive asperity contact model is solved by using the element-free Galerkin-finite element (EFG-FE) coupling method because of its flexibility in domain descritization and versatility in node arrangements. The effects of different thresholds on the contact pressure distributions, real contact area, and the elasto-plastic stress fields in the contacting bodies are investigated and discussed. The results show that the computational time will dramatically reduce to about 50% when the relative error is about 5%.
The Effect of Diesel Engine Oil Contamination on Friction and Wear
Authors: Ramkumar P. , Wang L. , Harvey T. J. , Wood R. J. K. , Nelson K. , Yamaguchi E. , Harrison J. J. , Powrie H. E. G.
Published: November 2008

The aim of this work is to better understand the relationship between the wear of sliding tribo-couples and contamination such as soot, sulphuric acid, moisture and oxidation levels to simulate the influence of contamination in model diesel engine oils using electrostatic condition monitoring.
Intelligent Modeling of Contact Mechanics and Friction Dynamics
Authors: Marumo R.
Published: November 2008

This paper considers the investigations into adhesion, contact mechanics metal erosion effects, wear and tare as a result of the effects of frictional forces. Mechanical components rely on friction for the transformation and delivery of energy from point A to point B. This requires the knowledge of combined energies as well as their associated dynamic models and ancillary parameters. Adhesion, contact, friction and wear are major problems limiting both the fabrication yield and lifetime of any devices. Since it is the area of real contact, which determines the sliding friction, adhesion interaction may strongly affect the friction force even when no adhesion can be detected in a pull-off experiment. Therefore a good scientific dynamic modelling of friction forces is a prerequisite for the understanding and monitoring of friction adverse effect on mechanical systems for good maintenance purposes.
Modeling of Acoustic Wave Propagation HAMR Media
Authors: Peng Wei , Hsia Yiao-Tee , Hohlfeld Julius
Published: November 2008

In multi-layered solids, an acoustic wave is partially reflected and partially transmitted at boundaries, which renders a too complex wave pattern to be predicted with analytical models. A Finite Element Method (FEM) based numerical model is developed to predict the acoustic wave propagation in multi-layered solids, where an ANSYS acoustic fluid element is adopted to solve this problem. The model is applied to study the pump-probe transient reflectivity measurements on Heat Assisted Magnetic Recording (HAMR) media, where the thermo-elastic waves are isolated and then subtracted from the composite reflectivity change measurement. As a result, the reflectivity change caused by the thermal decay is separated from the thermo-elastic waves, allowing a more accurate prediction and measurement of the thermal properties of HAMR media.
Relating Friction in CMP to Topography Evolution
Authors: Xie Xiaolin , Boning Duane
Published: November 2008

Die-scale models of chemical-mechanical polishing (CMP) have been previously reported for a number of different CMP processes used in integrated circuit manufacturing, including oxide, dual material shallow trench isolation, and dual material copper damascene processes. These models can dynamically predict the evolution of surface topography (e.g., local feature step heights, film thickness nonuniformity across the different pattern density regions of the chip, dishing, and erosion) for any time point during CMP. This topography evolution information can be applied to better understand the basis for observed friction and wear in the CMP process. In this work, we explore models of the macroscopic frictional force based on the surface topography. CMP endpoint measurements, such as those from motor current traces, enable verification of model predictions relating friction to CMP surface topography evolution, for different types of CMP processes and patterned chips.
Investigation of Cavitation Phenomenon in an Oscillatory Oil Squeeze Film
Authors: Wang Wen , Zhang Zhiming , Chen Xiaoyang , Sun Meili , Sun D. C.
Published: November 2008

For the journal bearing under dynamic loading or under large external excitation condition, the oil film will not be a simple form as normal divided into continue oil film area and cavitation area. Because of squeeze effect, the boundary of oil film changes dynamically and oil film pressure shows more complex. As reviewed in [1], also there are some “cavitation algorithms” [2,3] developed, the oil film performance under dynamic loading remains unclear. For the research on nonlinear analysis of rotor-bearing system, one of the important work is to obtain oil film performance model under large external excitation. In order to investigate cavitation phenomenon, especially how cavitation changing and how much tensile stress oil films can support, a parallel-plate oscillatory squeeze film test-rig was built where a high-speed CCD was used to capture the development of cavitation, and synchronously the oil film pressure and the oscillatory displacement were measured [4]. A new cavitation model also was proposed [1]. In this paper, the new model will be validated with the experimental data. Some phenomenon also was investigated theoretically with new model.
What Causes Low Friction? — What Causes High Friction?
Authors: Zhu Y. Elaine , Granick Steve
Published: November 2008

The design of tribological interfaces is often motivated by a quest to minimize friction and wear. Among the many strategic design principles that have been developed to this end, the simple idea of decoupling frictional force from normal load is especially attractive. Recent work from this laboratory demonstrates that under certain conditions, it is possible to reduce this coupling significantly with the result that the friction coefficient appears to be very low. However, the materials design requirements to achieve this end are rather stringent. Furthermore, modern methods enable one under some conditions to measure directly the structure and motions of lubricants during tribological sliding.
The Effect of Lubricant Viscosity-Temperature Characteristics on the Performance of Plain Journal Bearings
Authors: Dmochowski Waldemar M. , Webster Martin N.
Published: November 2008

Experimental and analytical results of bearing friction loss, operating temperature, and oil gap thickness are presented comparing performance characteristics of bearings operating with the different lubricants. The lubricants were blended using a variety of mineral and synthetic base stocks to achieve a range of viscosity-temperature characteristics. The results show that the test bearings running with higher viscosity index (VI) lubricants generated slightly lower bearing surface temperatures than those generated using a low VI lubricant. The high VI lubricant also reduced the total power losses by up to 10%. These gains are achieved with little or no change in the minimum oil film thickness.
Multibody Rolling Bearing Calculations: Computer Program BEAST
Authors: Ioannides E. , Stacke L.-E. , Fritzson D. , Nakhimovski I.
Published: November 2008

The need for rapid development of high efficiency jet engines and other mechanical systems has forced the pace of development of simulation tools so that the detailed behavior of the rolling element bearings can be simulated. This includes modeling of the motions, the exchanged forces, and heat between all the bearing components, i.e. rings, cage and rolling elements. The computer program BEAST is a multi-body computer program with sophisticated and robust modeling of the tribological contacts in the bearing where the exchange of forces between the bearing components takes place.
Selfish Genetic Elements Promote Polyandry in a Fly
Authors: Price T. A. R. , Hodgson D. J. , Lewis Z. , Hurst G. D. D. , Wedell N.
Published: November 2008

It is unknown why females mate with multiple males when mating is frequently costly and a single copulation often provides enough sperm to fertilize all a female's eggs. One possibility is that remating increases the fitness of offspring, because fertilization success is biased toward the sperm of high-fitness males. We show that female
Drosophila pseudoobscura
evolved increased remating rates when exposed to the risk of mating with males carrying a deleterious sex ratio–distorting gene that also reduces sperm competitive ability. Because selfish genetic elements that reduce sperm competitive ability are generally associated with low genetic fitness, they may represent a common driver of the evolution of polyandry.
Association of Monoclonal Expansion of Epstein-Barr Virus-Negative CD158a
+
NK Cells Secreting Large Amounts of Gamma Interferon with Hemophagocytic Lymphohistiocytosis
Authors: López-Álvarez María R. , Martínez-Sánchez María V. , Salgado-Cecilia María G. , Campillo José A. , Heine-Suñer Damian , Villar-Permuy Florentina , Fuster José L. , Bas Águeda , Gil-Herrera Juana , Muro Manuel , García-Alonso Ana M. , Álvarez-López María R. , Minguela Alfredo
Published: November 2008

We report the first case of hemophagocytic lymphohistiocytosis (HLH) induced by the monoclonal expansion of Epstein-Barr virus (EBV)-negative NK cells. Consanguinity of the patient's parents made it necessary to discard familial HLH in the patient and her sister with identical HLA markers and demonstrate that no cause other than the expansion of NK cells, which secrete high levels of gamma interferon, was inducing HLH in this patient.
Fibrin glue versus sutures for attaching the conjunctival autograft in pterygium surgery: a prospective observer masked clinical trial
Authors: Srinivasan S , Dollin M , McAllum P , Berger Y , Rootman D S , Slomovic A R
Published: November 2008

Aims:

To compare the degree of conjunctival autograft inflammation, subconjunctival haemorrhage (SCH) and graft stability following the use of sutures or fibrin glue (FG) during pterygium surgery.

Methods:

Prospective, observer masked, clinical trial. 40 eyes of 40 patients undergoing primary pterygium surgery with conjunctival autograft were allocated into two groups. Group 1 (n = 20) had FG (Tisseel) for attaching the conjunctival autograft, whereas group 2 (n = 20) had sutures. Standardised digital slit-lamp photographs were taken at 1 week, 1 month and 3 months postoperatively. Sutures were masked using commercially available photo-editing software. Two masked observers objectively graded the digital photographs for degree of inflammation, SCH and graft stability.

Results:

34 of the 40 patients completed the study. When using FG, the degree of inflammation was significantly less than with sutures at 1 month (p = 0.019) and 3 months (p = 0.001) postoperatively. No significant difference was found for inflammation at 1 week postoperatively (p = 0.518). Conjunctival grafts secured with FG were as stable as those secured with sutures (p = 0.258, p = 0.076 and p = 0.624, at 1 week, 1 month and 3 months, respectively). No significant difference was found in degree of postoperative SCH between the groups (p = 0.417, p = 1 and p = 1, at 1 week, 1 month and 3 months, respectively).

Conclusion:

This is the first prospective clinical trial confirming that conjunctival grafts secured with FG during pterygium surgery not only are as stable as those secured with sutures, but also produce significantly less inflammation.
After-school interventions to increase physical activity among youth: Table 1
Authors: Pate R R , O’Neill J R
Published: November 2008

Most children and adolescents do not meet the recommended 60 minutes or more of moderate to vigorous physical activity per day. One attractive approach to increasing physical activity in young people is providing activity through structured after-school programmes. This paper provides a review of the scientific literature on the effects of after-school programmes on physical activity in children and adolescents. After-school physical activity interventions provided mixed results; some increased children’s physical activity, others did not. Although after-school programmes have the potential to help children and adolescents engage in regular, enjoyable physical activity, the research on these programmes is limited and, in some cases, methodologically weak. Additional, well-controlled studies are needed to identify the components of after-school programmes that promote physical activity and to determine the level of activity that can be attained when children and adolescents participate in these programmes.
Les phytolithes chez le genre Dactylis tétraploïde
Authors: Guignard Gaétan
Published: November 2008

Silica bodies were observed in populations belonging to four tetraploid taxa of the genus Dactylis. Twelve characters were used to describe those elements, which allow some comparisons to be made between populations growing wild and those growing in experimental plots. They also show the taxonomic importance of the silica bodies. This new approach leads to both a confirmation and a better understanding of the morphological affinities previously observed among the different taxa.
Zoospore ultrastructure of Zygorhizidium affluens and Z. planktonicum, two chytrids parasitizing the diatom Asterionella formosa
Authors: Beakes Gordon W. , Canter Hilda M. , Jaworski George H. M.
Published: November 2008

The fine structure of zoospores of two Zygorhizidium species pathogenic on the freshwater planktonic diatom Asterionella formosa Hassall, are described. Zygorhizidium affluens Canter and Z. planktonicum Canter have monocentric operculate sporangia and zoospores which have single lipid globules to which the cell nucleus and single mitochondrion are closely adpressed. Several features place Z. affluens in the Chytridiales sensu Barr. These include having its kinetosome and nonfunctional centrioles not closely associated with the nucleus and having a ribosome-rich core region delimited by endoplasmic reticulum. However, there are no cytoplasmic microtubules or membranous rumposome complex in this species. In contrast, zoospores of Z. planktonicum have dispersed or loosely aggregated ribosomes and a rumposome complex. The zoospores of this species appear to belong to the same morphological subtype as the pathogenic genus Synchytrium, which has also been placed in the Chytridiales. Zygorhizidium planktonicum zoospores possess a number of vesicle types apparently unique to this species and have a nonfunctional centriole which is constructed of a ring of singlet microtubules and is often completely disassociated from the kinetosome. Both species contain "peripheral vesicle" systems which are probably involved in regulating internal water potential. From this study it seems unlikely that the two species are closely related, although they have been placed in the same genus.
Some effects of nitrate versus ammonium nutrition on the nutrient fluxes in Pinus sylvestris seedlings. Effects of mycorrhizal infection
Authors: Boxman Andries W. , Roelofs Jan G. M.
Published: November 2008

As a result of the high deposition of ammonium compounds in The Netherlands the forest trees are under a severe nitrogen stress. Effects of increasing amounts of ammonium on the major nutrient fluxes by Scots pine seedlings have been studied. In addition, the effect of mycorrhization of the roots has been taken into account. With nitrate-N nutrition only, the seedlings accumulate calcium, magnesium, potassium, and protons. When a low ammonium concentration is present, the seedlings lose their cations. When the medium is depleted of ammonium, a reuptake of the cations occurs. In the presence of a high ammonium concentration (based on field studies) a continuous loss of cations from the roots takes place. The reverse has been found for phosphate uptake. Ammonium stimulates phosphate accumulation. It is shown that ammonium inhibits the unidirectional influx rate of 86Rb, while concurrently stimulating the unidirectional efflux rate. Mycorrhization of the roots has a beneficial effect on the nutrient fluxes. With nitrate-N nutrition mycorrhizal seedlings accumulate more nitrate, calcium, magnesium, and protons than nonmycorrhizal seedlings. With high ammonium-N nutrition mycorrhizal seedlings lose fewer cations than nonmycorrhizal seedlings. In conclusion, the ecological significance of ammonium deposition on forest stands is discussed.
A linear plasmid in Tilletia controversa, a fungal pathogen of wheat
Authors: Kim W. K. , McNabb S. A. , Klassen G. R.
Published: November 2008

A linear 7.4-kilobase plasmid designated pTCT was isolated from mycelium of Tilletia controversa Kühn, the causal agent of dwarf bunt of wheat. Linearity was determined by construction of a physical map using eight restriction enzymes and by both 5′ and 3′ exonuclease digestion. pTCT is not homologous to ribosomal genes, nor is it homologous to any sequences in the total DNA of sporidia of Ustilago hordei (isolates 965 and 966) or urediosporelings of Puccinia graminis f.sp. tritici (race C36(48)).
Gibberellins and sorghum development
Authors: Rood Stewart B. , Bruns Darla M. , Smienk Susan J.
Published: November 2008

Sorghum (Sorghum bicolor (L.) Moench) hybrids adapted for grain (cv. Northrup King X8102) or forage production (cv. Pride PF70) were grown in field trials at Lethbridge, Alta., Canada, and shoot cylinders containing the apical meristems were harvested at various developmental stages for analyses of endogenous gibberellin-like (GA-like) substances. Extracts were purified and chromatographed on sequential SiO2 partition columns and C18 reversed-phase high-performance liquid chromatography, and GA-like substances were detected and quantified by the cv. Tan-ginbozu dwarf rice microdroop assay. Concentrations of GA-like substances in the shoots were higher during vegetative growth than during shoot elongation or panicle elongation and the pattern of declining concentration of GA-like substances was observed for both hybrids over both field seasons. The qualitative distribution of GA-like substances was generally similar across hybrids and developmental stages, with a GA19-like substance accounting for about 60% of the total GA-like activity (GA19 is a native GA of sorghum). The exogenous application of GA3 promoted height growth and inhibited tillering, with maximal effects occurring when application was early, during rapid vegetative growth. Applications of GA3 subsequent to panicle initiation promoted panicle elongation but did not alter the time of anthesis. These results on endogenous GA concentration and response to exogenous GA3 application suggest a role for endogenous GAs in the control of shoot growth and development in sorghum.
Chrysophycean stomatocysts from the postglacial sediments of a High Arctic lake
Authors: Duff Katharine E. , Smol John P.
Published: November 2008

Twenty-six chrysophycean stomatocyst morphotypes were described from the postglacial sediments of a small, rock basin lake near Baird Inlet, Ellesmere Island. Scanning electron and light microscopy were used to classify the stomatocysts, following the guidelines of the International Statospore Working Group. None of the stomatocysts could be related with certainty to the chrysophyte species that produced them, but sufficient morphological detail is present in most of the stomatocysts to allow for taxonomic differentiation. A stratigraphic analysis of the dominant stomatocyst morphotypes revealed that chrysophyte species composition changed most markedly during the lake's early development but then remained relatively constant. This study demonstrated that chrysophycean stomatocysts provide useful paleoecological information in High Arctic lakes, but further taxonomic and ecological research is required to fully exploit these microfossils.
Spiromastix grisea sp.nov. and its relationship to other Onygenaceae with helical appendages
Authors: Currah R. S. , Locquin-Linard M.
Published: November 2008

Spiromastix grisea sp.nov. is described and illustrated based on cultures obtained from gazelle dung collected in central Sahara, Africa. Spiromastix grisea is similar to the type of Spiromastix, S. warcupii, in having thick-walled helical appendages, a loose, meshlike peridium of thin-walled hyphae, and minute, oblate ascospores. The new species differs from the type in having greyish brown rather than yellow brown ascomata, longer helical appendages, and larger ascospores, which are punctate only in the equatorial zone. The species of Spiromastix can be distinguished from other genera in the Onygenaceae with helical appendages (Ajellomyces, Apinisia, Kuehniella, and Shanorella) on the basis of differences in morphology of peridial hyphae, ascospores, and appendages. The species of Spiromastix lack anamorphs..
Gibberellins and heterosis in poplar
Authors: Bate Nicholas J. , Rood Stewart B. , Blake Terence J.
Published: November 2008

To investigate the possible involvement of gibberellins (GAs) in heterosis of hybrid poplar, six poplar clones were studied, including two Populus deltoides clones and two interspecific hybrid clones (P. ×euramericana = P. deltoides × P. nigra) originating from crosses with each of the P. deltoides clones. In field conditions in Ontario, Canada, the interspecific hybrids were consistently taller and had greater shoot dry weights than their parental P. deltoides clones. Shoot dry weights and heights were highly correlated across the six clones, as clonal rankings for these parameters were identical. Endogenous GA-like substances were extracted, purified, chromatographed on silica gel partition columns, and quantified by the cv. Tan-ginbozu dwarf rice bioassay. Bioactive peaks were further chromatographed on reversed-phase C18 HPLC and again bio-assayed. Statistically significant differences in concentrations of total GA-like substances were observed. With one exception, the rankings for the concentrations of GA-like substances and those of GA1-like plus GA19-like substances were similar to the rankings for height growth. Gibberellins A1 and A19 have been identified from the tissue of hybrid poplar by capillary gas chromatography – selected ion monitoring (GC–SIM), and GA1 was also identified by GC–SIM in this tissue. In three of four comparisons, interspecific hybrids contained significantly higher concentrations of GA-like activity than their corresponding parental clones. Thus, a correlation was observed between the concentration of endogenous GA-like activity and hybrid vigor for height growth and shoot dry weight in poplar.
Effects of phenolics on growth of Fusarium oxysporum f.sp. radicis-lycopersici in vitro
Authors: Kasenberg Todd R. , Traquair James A.
Published: November 2008

Crown and root rot of tomato, caused by Fusarium oxysporum f.sp. radicis-lycopersici, is amenable to allelopathic biocontrol by intercropping host plants with lettuce or dandelion (tribe Lactuceae). Inhibition of growth of the pathogen by phenolic compounds may be part of the allelopathic biocontrol mechanism. In repeated tests in vitro with caffeic acid, ferulic acid, and catechol, the growth of F. oxysporum f.sp. radicis-lycopersici was inhibited. Catechol and 0.04 M ferulic acid were toxic to the fungus, while 0.02 M caffeic acid and 0.01 M ferulic acid reduced growth.
Anatomical changes induced by triazoles in wheat seedlings
Authors: Gao J. , Hofstra G. , Fletcher R. A.
Published: November 2008

The triazoles triadimefon and S-3307, applied as seed treatments at two concentrations each (0.1 and 1.0, and 0.001 and 0.01 g active ingredient/kg of seed, respectively), increased epicuticular wax and reduced the length but increased the width and thickness of wheat leaves (Triticum aestivum L. cv. Glenlea). Mesophyll cells of treated leaves were thicker than those of controls and there were more layers of cells around the median and lateral vascular bundles of leaves treated with the higher concentration of S-3307. The length of epidermal cells was reduced and the width was increased by both triazoles; the depth of epidermal cells was increased by the higher concentration of triadimefon only. S-3307 increased the number of vascular bundles, whereas triadimefon at the higher concentration increased their diameter. Both concentrations of S-3307 reduced the length of trichomes. The two triazoles increased chloroplast size along both the long and short axes. Compared with those of controls, the stomata in the triadimefon-treated leaves were constricted and sunken, whereas in S-3307 treated leaves the subsidiary cells were wider. The effects of the triazoles observed in this study may account in part for several plant growth regulatory activities reported earlier, including growth retardation, stimulation of chlorophyll synthesis, and protection against injury from water stress.
Les successions secondaires sur sites mésiques dans le Haut-Saint-Laurent, Québec, Canada
Authors: Brisson Jacques , Bergeron Yves , Bouchard André
Published: November 2008

Secondary succession on mesic sites was studied in 10 forest stands in the Haut-Saint-Laurent region, using diameter-class distribution and dendrochronological analysis. Size-class ordination allowed the determination of two seral successions associated with forest communities of clear-cut or abandoned field origin. Forest cutting favors vegetative resprouting of Tilia americana, Ostrya virgininiana, and Prunus serotina rather than seed invasion of species from neighbouring communities. Fraxinus americana, Betula populifolia, and Ulmus americana colonize abandoned fields. Whatever the nature of the disturbance, strong regeneration and high shade tolerance leads to the eventual dominance of the sugar maple and to what appears to be succession convergence. However, a situation where the sugar maple is replaced by the American beech is an old community raises questions concerning the stability of the so-called climax maple forest.
Infection of Easter lily leaves from conidia of Botrytis elliptica
Authors: Doss Robert P. , Christian James K. , Chastagner Gary A.
Published: November 2008

Light and scanning electron microscopy were used to study infection of leaves of Easter lily (Lilium longiflorum Thunb.) inoculated with conidia of Botrytis elliptica (Berk.) Cooke. At 20 °C in a saturated atmosphere, germination of conidia occurred within 2–3 h after inoculation, and over 90% of the conidia had germinated after 5 h. Structures recognizable under the light microscope as appressoria began forming between 8 and 16 h after inoculation, and within 24 h, 70% of the germ tubes had formed appressoria. Most appressoria formed on the stomatal apparatus. Degeneration of the cell wall at the site of appressorium formation was noted. Upon inoculation with drops containing large numbers (105/mL) of conidia, hyphae were visible inside the leaf as early as 16 h after inoculation, and degeneration of the leaf cuticle and disruption of the underlying tissue were observed. Application of filter-sterilized germination fluid also caused damage. With low spore numbers (1–10 spores per 5-μL inoculation drop), infection occurred principally after penetration via guard cells or entry through the stomatal aperture; fungal hyphae were visible inside the leaf as early as 24 h after inoculation.
Ectomycorrhiza synthesis between isolated roots of Eucalyptus pilularis and Pisolithus tinctorius
Authors: Bailey S. R. , Peterson R. L.
Published: November 2008

Callus cultures were established from epicotyl–hypocotyl explants of Eucalyptus pilularis seedlings. Roots formed on these cultures were excised and placed in divided petri plates. The apical portion of each root was placed on filter paper overlying modified Bonner–Deverian medium, while the basal portion was placed on Bonner–Deverian medium containing carbohydrates. Plugs of Pisolithus tinctorius mycelium were placed adjacent to the apical portion of each root. After 10–14 days, approximately 40% of all root tips formed a mantle and Hartig net typical of ectomycorrhizas.
Space–Time Correlation and Its Effects on Methods for Detecting Aquatic Ecological Change
Authors: Millard Steven P. , Yearsley John R. , Lettenmaier Dennis P.
Published: November 2008

The analysis of variance (ANOVA) is commonly used to analyze observations collected from aquatic monitoring programs designed to detect ecological change. ANOVA assumes that the deviations of the observations from their true means (the errors) are uncorrelated in space and time. Aquatic monitoring data often violate this assumption. The results of Monte Carlo simulations using simulated data generated from both statistically and mechanistically based models show that the presence of either spatially or temporally correlated errors can significantly affect the outcome of ANOVA tests. In practice, spatial correlation is more likely to be a problem than is temporal correlation, given typical monitoring frequencies. The effects of spatial correlation can be minimized through judicious use of control station pairing in the monitoring design. However, when insufficient flexibility exists in the monitoring design, alternate models, such as multivariate time series analysis, or multivariate analysis of variance, must be used in place of ANOVA.
EXPERIMENTAL ANALYSIS OF THE EFFECTS OF AGENT SYNCHRONIZATION IN ASYNCHRONOUS SEARCH ALGORITHMS
Authors: MUSCALAGIU IONEL , VIDAL JOSE M. , CRETU VLADIMIR , POPA HORIA EMIL , PANOIU MANUELA
Published: November 2008

The asynchronous searching techniques are characterized by the fact that each agent instantiates its variables in a concurrent way. Then, it sends the values of its variables to other agents directly connected to it by using messages. These asynchronous techniques have different behaviors in the case of delays in sending messages. This article presents the opportunity for synchronizing the execution of agents in the case of asynchronous techniques. It investigates and compares the behaviors of several asynchronous techniques in two cases: agents process the received messages asynchronously (the real situation) and the synchronous case, when a synchronization of the execution of agents is done, i.e. the agents perform a computing cycle in which they process a message from a message queue. After that, the synchronization is done by waiting for the other agents to finalize the processing of their messages. The experiments show that the synchronization of the agents execution leads to lower costs in searching for solutions. A solution for synchronizing the agents execution is suggested for the analyzed asynchronous techniques.
INTELLIGENT POSITIONING AND OPTIMAL DIVERSITY SCHEMES FOR MOBILE AGENTS IN UBIQUITOUS NETWORKS
Authors: KIM PORA , CHANG SEKCHIN
Published: November 2008

A lot of schemes have been proposed for the establishment of u-city. Especially, most of the schemes are based on ubiquitous networks. In this paper, it is assumed that the ubiquitous networks include some mobile agents. Therefore, an intelligent positioning scheme is proposed for the efficient positioning of the mobile agents in the ubiquitous networks. The approach consists of location detection and location tracking. Furthermore, an optimal diversity technique is presented in this paper to improve the positioning performance. Simulation results indicate that using the suggested algorithms, the excellent detection and tracking performance can be achieved in ubiquitous networks for u-city.
VERIFICATION OF THE MOBILE AGENT NETWORK SIMULATOR — A TOOL FOR SIMULATING MULTI-AGENT SYSTEMS
Authors: KUSEK MARIO , JURASOVIC KRESIMIR , JEZIC GORDAN
Published: November 2008

This paper deals with the verification of a multi-agent system simulator. Agents in the simulator are based on the Mobile Agent Network (MAN) formal model. It describes a shared plan representing a process which allows team formation according to task complexity and the characteristics of the distributed environment where these tasks should be performed. In order to verify the simulation results, we compared them with performance characteristics of a real multi-agent system, called the Multi-Agent Remote Maintenance Shell (MA–RMS). MA–RMS is organized as a team-oriented knowledge based system responsible for distributed software management. The results are compared and analyzed for various testing scenarios which differ with respect to network bandwidth as well as task and network complexity.
DNA damage after long-term repetitive hyperbaric oxygen exposure
Authors: Gröger Michael , Öter Sükrü , Simkova Vladislava , Bolten Markus , Koch Andreas , Warninghoff Volker , Georgieff Michael , Muth Claus-Martin , Speit Günter , Radermacher Peter
Published: November 2008

A single exposure to hyperbaric oxygen (HBO), i.e., pure oxygen breathing at supra-atmospheric pressures, causes oxidative DNA damage in humans in vivo as well as in isolated lymphocytes of human volunteers. These DNA lesions, however, are rapidly repaired, and an adaptive protection is triggered against further oxidative stress caused by HBO exposure. Therefore, we tested the hypothesis that long-term repetitive exposure to HBO would modify the degree of DNA damage. Combat swimmers and underwater demolition team divers were investigated because their diving practice comprises repetitive long-term exposure to HBO over years. Nondiving volunteers with and without endurance training served as controls. In addition to the measurement of DNA damage in peripheral blood (comet assay), blood antioxidant enzyme activities, and the ratio of oxidized and reduced glutathione content, we assessed the DNA damage and superoxide anion radical (O2•−) production induced by a single ex vivo HBO exposure of isolated lymphocytes. All parameters of oxidative stress and antioxidative capacity in vivo were comparable in the four different groups. Exposure to HBO increased both the level of DNA damage and O2•− production in lymphocytes, and this response was significantly more pronounced in the cells obtained from the combat swimmers than in all the other groups. However, in all groups, DNA damage was completely removed within 1 h. We conclude that, at least in healthy volunteers with endurance training, long-term repetitive exposure to HBO does not modify the basal blood antioxidant capacity or the basal level of DNA strand breaks. The increased ex vivo HBO-related DNA damage in isolated lymphocytes from these subjects, however, may reflect enhanced susceptibility to oxidative DNA damage.
Low‐Temperature Preparation of Amorphous‐Shell/ Nanocrystalline‐Core Nanostructured TiO2 Electrodes for Flexible Dye‐Sensitized Solar Cells
Authors: Zhang Dongshe , Hu Hengyao , Li Laifeng , Shi Donglu
Published: November 2008

An amorphous shell/nanocrystalline core nanostructured TiO2 electrode was prepared at low temperature, in which the mixture of TiO2 powder and TiCl4 aqueous solution was used as the paste for coating a film and in this film amorphous TiO2 resulted from direct hydrolysis of TiCl4 at 100∘C sintering was produced to connect the particles forming a thick crack‐free uniform nanostructured TiO2 film (12 μm), and on which a photoelectrochemical solar cell‐based was fabricated, generating a short‐circuit photocurrent density of 13.58 mA/cm2, an open‐circuit voltage of 0.647 V, and an overall 4.48% light‐to‐electricity conversion efficiency under 1 sun illumination.