bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilizing Wave Rotor Technology to Enhance the Turbo Compression in Power and Refrigeration Cycles
Authors: Akbari Pezhman , Kharazi Amir A. , Mu¨ller Norbert
Published: May 2008

The objective of this paper is to review and suggest wave-rotor applications in power generation and refrigeration systems. The emphasis is on recent investigations performed by the authors for a microturbine (30 kW) and a novel enhancement of a state-of-the-art water (R718) compression refrigeration cycle. The results of thermodynamic analyses performed for the small gas turbine topped with a 4-port wave rotor show that engine overall efficiency and specific work may increase by up to about 33% without changing the compressor. Expecting similar advantages, it is suggested to use wave rotors in novel R718 compression refrigeration systems. This also introduces a new concept of a condensing wave-rotor that employs pressurized water to both (1) additional rise the pressure of the vapor and (2) desuperheat and condense it, all in one dynamic process. Adding the condensing wave-rotor to the refrigeration cycle allows for a lower pressure ratio of the compressor, which is crucial for the R718 chiller technology. Some structural and economic advantages of the proposed system are mentioned.
Waste as a Renewable Source of Energy: Current and Future Practices
Authors: Millrath Karsten , Themelis Nickolas J.
Published: May 2008

Municipal Solid Waste (MSW) has been recognized by several states as a renewable source of energy. Worldwide, about 130 million tons of MSW are combusted annually in waste-to-energy facilities that produce electricity and steam for district heating and also recover metals for recycling. While being linked to environmental pollution prior to the implementation of Maximum Available Control Technology (MACT) regulations, Waste-to-Energy (WTE) was recently named one of the cleanest sources of energy by the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE). However, the WTE industry often faces resistance and preconceptions based on past experience rather than current performance. Due to economic considerations that do not include environmental benefits, most of the U.S. MSW still ends up in landfills despite the fact that for every ton of MSW landfilled greenhouse gas emissions increase by at least 1.2 tons of carbon dioxide. While implemented research and development strategies focused on emissions, there is still a tremendous need for more efficient yet durable combustion technologies including flue gas recirculation and oxygen enrichment, environmentally and economically competitive reuse options for WTE residues, and also public education. The importance of WTE in the universal effort for sustainable development and its need for research and development resources has led to the formation of the Waste-to-Energy Research and Technology Council. Its principal goal is to improve the economic and environmental performance of technologies that can be used to recover materials and energy from solid wastes. This paper provides an overview of the current worldwide WTE practices, predominant technologies, and current research for advancing WTE as a renewable source of energy in the U.S. and elsewhere.
Application of Finite Volume Method for Solid Mechanics
Authors: Fowler Bryce L. , Yee Raymond K.
Published: May 2008

Polymers constitute a large class of nearly incompressible solid materials (i.e., Poisson’s Ratio near 0.5). These materials are often used as passive vibration isolators. Accurately modeling vibration isolators made of nearly incompressible materials has been extremely difficult with standard finite element analysis. This paper provides an alternative to the specialized finite element formulations currently used to model incompressible materials. The finite volume methodology of computational fluid dynamics is employed in this paper to solve the Hooke’s Law equations in solid mechanics. Test cases have been performed to evaluate the performance of finite volume method applied to solid mechanics problems. The formulation has been coded in Matlab for practical use. Based on the preliminary test case results, the finite volume formulation compares favorably to finite element method.
Characterization of Highway Traffic Noise Generated by Rigid Pavement Contraction Joints
Authors: Ellis Lawrin , Niezrecki Christopher , Bloomquist David
Published: May 2008

Contraction joints in rigid (concrete) pavements are required to permit expansion of each monolithic section of roadway. At higher speeds, the major source of highway noise is attributed to vehicle tire/roadway interaction. Current concerns about limiting the impact of highway traffic noise, has forced transportation agencies to consider strategies to control noise generated by tire/roadway interaction. Within this work the difference in noise generated by 1/4 versus 3/8-inch joint widths is conducted. The study focuses on passenger vehicles including a sedan and a light duty van/truck. Both vehicle in-cabin and roadside noise levels are measured for vehicle speeds of 50, 60, and 70 miles per hour. For the sedan, the minimum and maximum observed in-cabin differences were determined to be 1.08 and 1.82 dB(A), respectively. Minimum and maximum observed roadside differences are 1.19 and 2.58 dB(A), respectively. Van tests resulted in minimum and maximum observed in-cabin differences of 0.60 and 1.09 dB(A) and minimum and maximum observed roadside differences of 1.05 and 3.18 dB(A), respectively. This paper contains details of reference standards, test methods, and the results obtained.
An Acquisition and Distribution System for Situational Awareness
Authors: Green William E. , Oh Paul Y. , Yoon Seunghyun
Published: May 2008

In times of disaster acquiring aerial images is challenging. Runways may be crippled thus denying conventional aircraft in the area from taking off. Also the time required to schedule a satellite fly-by may delay first response efforts. Man backpackable aerial robots can be carried close to the disaster site and flown to capture aerial images. This paper integrates mechatronics, intelligent sensing, and mechanism synthesis in a teleoperable kite-mounted camera. Rapidly deployable, transportable by foot, easy to fly and affordable, our system can quickly acquire, process and distribute aerial images. Images mosaicing edge detection, 3D reconstruction and geo-referencing resulting from images acquired by our aerial platform are also presented.
cAMP-Dependent Signaling as a Core Component of the Mammalian Circadian Pacemaker
Authors: O'Neill John S. , Maywood Elizabeth S. , Chesham Johanna E. , Takahashi Joseph S. , Hastings Michael H.
Published: May 2008

The mammalian circadian clockwork is modeled as transcriptional and posttranslational feedback loops, whereby circadian genes are periodically suppressed by their protein products. We show that adenosine 3′,5′-monophosphate (cAMP) signaling constitutes an additional, bona fide component of the oscillatory network. cAMP signaling is rhythmic and sustains the transcriptional loop of the suprachiasmatic nucleus, determining canonical pacemaker properties of amplitude, phase, and period. This role is general and is evident in peripheral mammalian tissues and cell lines, which reveals an unanticipated point of circadian regulation in mammals qualitatively different from the existing transcriptional feedback model. We propose that daily activation of cAMP signaling, driven by the transcriptional oscillator, in turn sustains progression of transcriptional rhythms. In this way, clock output constitutes an input to subsequent cycles.
Termination Factor Rho and Its Cofactors NusA and NusG Silence Foreign DNA in
E. coli
Authors: Cardinale Christopher J. , Washburn Robert S. , Tadigotla Vasisht R. , Brown Lewis M. , Gottesman Max E. , Nudler Evgeny
Published: May 2008

Transcription of the bacterial genome by the RNA polymerase must terminate at specific points. Transcription can be terminated by Rho factor, an essential protein in enterobacteria. We used the antibiotic bicyclomycin, which inhibits Rho, to assess its role on a genome-wide scale. Rho is revealed as a global regulator of gene expression that matches
Escherichia coli
transcription to translational needs. We also found that genes in
E. coli
that are most repressed by Rho are prophages and other horizontally acquired portions of the genome. Elimination of these foreign DNA elements increases resistance to bicyclomycin. Although
rho
remains essential, such reduced-genome bacteria no longer require Rho cofactors NusA and NusG. Deletion of the cryptic
rac
prophage in wild-type
E. coli
increases bicyclomycin resistance and permits deletion of
nusG
. Thus, Rho termination, supported by NusA and NusG, is required to suppress the toxic activity of foreign genes.
Surface Tension Transport of Prey by Feeding Shorebirds: The Capillary Ratchet
Authors: Prakash Manu , Quéré David , Bush John W. M.
Published: May 2008

The variability of bird beak morphology reflects diverse foraging strategies. One such feeding mechanism in shorebirds involves surface tension–induced transport of prey in millimetric droplets: By repeatedly opening and closing its beak in a tweezering motion, the bird moves the drop from the tip of its beak to its mouth in a stepwise ratcheting fashion. We have analyzed the subtle physical mechanism responsible for drop transport and demonstrated experimentally that the beak geometry and the dynamics of tweezering may be tuned to optimize transport efficiency. We also highlight the critical dependence of the capillary ratchet on the beak's wetting properties, thus making clear the vulnerability of capillary feeders to surface pollutants.
Mars North Polar Deposits: Stratigraphy, Age, and Geodynamical Response
Authors: Phillips Roger J. , Zuber Maria T. , Smrekar Suzanne E. , Mellon Michael T. , Head James W. , Tanaka Kenneth L. , Putzig Nathaniel E. , Milkovich Sarah M. , Campbell Bruce A. , Plaut Jeffrey J. , Safaeinili Ali , Seu Roberto , Biccari Daniela , Carter Lynn M. , Picardi Giovanni , Orosei Roberto , Mohit P. Surdas , Heggy Essam , Zurek Richard W. , Egan Anthony F. , Giacomoni Emanuele , Russo Federica , Cutigni Marco , Pettinelli Elena , Holt John W. , Leuschen Carl J. , Marinangeli Lucia
Published: May 2008

The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed â¼100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements.
An Eccentric Binary Millisecond Pulsar in the Galactic Plane
Authors: Champion David J. , Ransom Scott M. , Lazarus Patrick , Camilo Fernando , Bassa Cees , Kaspi Victoria M. , Nice David J. , Freire Paulo C. C. , Stairs Ingrid H. , van Leeuwen Joeri , Stappers Ben W. , Cordes James M. , Hessels Jason W. T. , Lorimer Duncan R. , Arzoumanian Zaven , Backer Don C. , Bhat N. D. Ramesh , Chatterjee Shami , Cognard Ismaël , Deneva Julia S. , Faucher-Giguère Claude-André , Gaensler Bryan M. , Han JinLin , Jenet Fredrick A. , Kasian Laura , Kondratiev Vlad I. , Kramer Michael , Lazio Joseph , McLaughlin Maura A. , Venkataraman Arun , Vlemmings Wouter
Published: May 2008

Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (
e
= 0.44) 95-day orbit around a solar mass (

\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{M}_{{\odot}}\) \end{document}

) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 ± 0.04

\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{M}_{{\odot}}\) \end{document}

, an unusually high value.
Genetic susceptibility to occupational exposures
Authors: Christiani D C , Mehta A J , Yu C-L
Published: May 2008

Because of their high prevalence in the general population, genetic variants that determine susceptibility to environmental exposures may contribute greatly to the development of occupational diseases in the setting of specific exposures occurring in the workplace. Studies investigating genetic susceptibilities in the workplace may: (1) provide mechanistic insight into the aetiology of disease, in particular the determination of environmentally responsive genes; (2) identify susceptible subpopulations with respect to exposure; and (3) provide valuable input in setting occupational exposure limits by taking genetic susceptibility into account. Polymorphisms in theNAT2and theHLA-DPB1Glu69genes provide classic examples of how genetic susceptibility markers have a clear role in identifying disease risk in bladder cancer and chronic beryllium disease, respectively. For diseases with more complex and multifactorial aetiology such as occupational asthma and chronic airways disease, susceptibility studies for selected genetic polymorphisms provide additional insight into the biological mechanisms of disease. Even when polymorphisms for genetic susceptibility have a clear role in identifying disease risk, the value of wide scale genetic screening in occupational settings remains limited due to primarily ethical and social concerns. Thus, large scale genetic screening in the workplace is not currently recommended.
DWARFING OF WHEAT AND BARLEY BY THE BARLEY STRIPE-MOSAIC (FALSE STRIPE) VIRUS
Authors: Hagborg W. A. F.
Published: May 2008

Intensive studies were made during the past three years on the effect of barley stripe-mosaic (false stripe) on wheat and barley. The identity of this disease with the disease described and named by I. L. Conners in 1925 and reported by H. H. McKinney to be of virus origin in 1951 was established. Under both greenhouse and field conditions, infection caused chlorosis and necrosis accompanied by a marked loss of vigor. Large and statistically significant reductions in the height of crop, the yield, the kernel weight, and the grade of wheat resulted from the early inoculation of field plots, but not from late inoculation. The yield of wheat was reduced by 75% and of barley by 64%. The possibility that this disease has been a factor in the unthriftiness of certain fields of wheat is discussed.
AEROBIOLOGICAL STUDIES OF FUNGI AND BACTERIA OVER THE ATLANTIC OCEAN
Authors: Pady S. M. , Kelly C. D.
Published: May 2008

Two trips were made from Montreal, Que., to London, England, in June and August, 1951, and samples of bacteria and fungi were obtained throughout the flight using quantitative and qualitative methods. Three sampling methods were used, employing the McGill G.E. and slit samplers and a filter. Plates were used, supplemented by silicone slides in the slit sampler. Bacteria varied from 0.0 to 0.05 per cu. ft. in polar air and 0.03-0.9 per cu. ft. for tropical air over the ocean in June. Fungi in polar air ranged from 0.1 to 0.9 per cu. ft. and from 0.2 to 9.0 per cu. ft. in tropical air in June. There was very little difference in the June, and August flights as far as viable organisms were concerned. Fungus spores showed striking differences in air masses. Polar air over the ocean had a maximum of 3.9 per cu. ft. in August whereas tropical air had a maximum of 15.1 per cu. ft. in June. Over land in August a maximum of 361.4 fungus spores per cu. ft. was obtained in tropical air over eastern Canada. Cladosporium was the commonest fungus, with Alternaria, Pullularia, yeasts, Penicillium, Botrytis, and Stemphylium most numerous among 27 types. Of the 4991 colonies the above occurred as 82.3, 2.6, 2.3, 2.1, 1.6, 1.5, and 1.1% of the total. Micrococci, Sarcina, Gram negative rods, Gram positive pleomorphic rods, and aerobic sporeformers occurred as 41.4, 4.3, 20.4, and 33.2% in June and 13.2, 20.7, 37.0, and 29.0% of the total in August.
CHROMOSOME INTERCHANGE BY MISDIVISION IN TRITICUM
Authors: Morrison J. W.
Published: May 2008

An interchanged chromosome and also a telocentric chromosome arose in the progeny of a monosomic wheat plant. The telocentric was recognized by its morphology and the interchange was inferred from quadrivalent and trivalent chromosome associations. Since the interchange affects one of the same chromosomes as the misdivision which gave the telocentric, the interchange is assumed to result from the fusion of two telocentrics from nonhomologous chromosomes.
COMBINED EFFECTS OF GIBBERELLIN AND 2,4-D ON DORMANT SEEDS OF STINKWEED (THLASPI ARVENSE L.)
Authors: Corns William G.
Published: May 2008

Concentrations of 50 and 500 p.p.m. gibberellin were used alone and in combination with 2,4-D sodium salt solutions ranging from 0.00001 to 8000 p.p.m. acid equivalent, in Petri dishes, with dormant seeds of stinkweed (Thlaspi arvense L.), to determine the effects of these treatments or of subtoxic amounts of 2,4-D alone, on germination and growth. About 90% germination within 2 weeks was induced by the 50 p.p.m. gibberellin and was not augmented by the very dilute concentrations of 2,4-D. Complete germination occurred within only 8 days with 500 p.p.m. gibberellin alone. Strengths greater than approximately 0.02 p.p.m. of 2,4-D retarded shoot elongation and concentrations greater than about 0.5 p.p.m. of 2,4-D progressively reduced germination associated with either 50 or 500 p.p.m. gibberellin. Concentrations of 2,4-D higher than approximately 200 p.p.m. prevented both concentrations of gibberellin from causing any true germination. Beyond 200 p.p.m. of 2,4-D there was still, however, a broad range within which gibberellin was able to cause a definite initial phase of the germination process characterized simply by rupture of the seed coat without protrusion of root and stem. This response could not be prevented by 2,4-D at concentrations lower than 4000 p.p.m. in counteraction with 50 p.p.m. gibberellin, or at dosage lower than about 7000 p.p.m. in association with 500 p.p.m. gibberellin. Potential practical significance of the work is considered.
EFFECTS OF KINETIN AND BENZIMIDAZOLE ON THE GROWTH OF ETIOLATED PEA STEMS AND BARLEY COLEOPTILES
Authors: Forsyth F. R. , Samborski D. J.
Published: May 2008

Optimum growth of etiolated pea stem sections was obtained in a basal solution of 3-indoleacetic acid, cobalt chloride, and sucrose. The final length of pea stem sections was increased when sucrose was added 2, 4, or 6 hours after 3-indoleacetic acid and cobalt were added to the test solution. Benzimidazole at 100 to 200 p.p.m. and kinetin at 1 p.p.m. added to the basal solution inhibited growth of etiolated pea stem sections. Growth.of the pea stem sections was inhibited when they were treated for 4 hours with kinetin plus 3-indoleacetic acid, then transferred to the basal solution for 14 hours. There was no growth inhibition when pea stem sections were treated for 4 hours with kinetin alone, followed by 14 hours on the basal solution. Similar results with kinetin were obtained when barley coleoptiles were used and 2,4-dichlorophenoxyacetic acid was the growth-promoting substance. Ether and hot water extracts of pea stem tissue pretreated with kinetin and 3-indoleacetic acid did not appear to contain a growth inhibitor.
MICROFUNGI: VI. PIRICAUDA BUBÁK
Authors: Hughes S. J.
Published: May 2008

The type species of Piricauda is illustrated and redescribed from the type collection.
DESCRIPTIONS OF NEW SPECIES OF RHIZOCTONIA
Authors: Saksena H. K. , Vaartaja O.
Published: May 2008

Four new species and one variety are added to the form-genus Rhizoctonia from the study of over 60 isolates obtained from forest nurseries in Saskatchewan and Manitoba; these are Rhizoctonia dichotoma, R. endophytica, R. endophytica var. filicata, R. globularis, and R. hiemalis. They are chiefly characterized by chlamydospores in chains produced singly and in sporodochia. The chlamydospore characters were consistent within the species, and are therefore considered of dependable diagnostic value. The sporodochia, however, exhibited considerable variability in character and size depending largely on the substrate, and are of little use for taxonomic purposes.
STUDIES ON FUSARIUM WILT OF BANANAS: VI. VARIABILITY AND THE CULTIVAR CONCEPT IN FUSARIUM OXYSPORUM f. CUBENSE
Authors: Waite B. H. , Stover R. H.
Published: May 2008

The range in cultural variability of Fusarium oxysporum f. cubense on potato dextrose agar was studied. Several hundred isolates obtained from diseased varieties of Musa were categorized into four morphological groupings or cultivars. These were termed 'Sporodochial', 'Ropy', 'Cottony Alba', and 'Slimy Pionnotal'. The morphological cultivar 'Sporodochial' was further divided physiologically into 'Odoratum' and 'Inodoratum' cultivars. Clones producing sporodochia were the parental forms from which all other cultural types could arise by mutation. Mutants did not revert to their parental types. A system is proposed for cataloguing clones of plant pathogenic Fusarium species. Based on morphological characters, the catalog is intended to serve as a collection of data which provides also for the categorizing of cultivars.
THE REGULATION OF NITROGEN LOSS FROM MAIZE ENDOSPERM
Authors: Oaks Ann
Published: May 2008

Maize embryos were grown on agar until the roots were 2–3 cm long, and then were transferred to a nutrient salt solution. The loss of nitrogen from the endosperm was apparent 12 hours after the transfer. When a synthetic mixture of 15 L-amino acids, known to be released by the endosperm, was also included in the medium, the loss of total and alcohol-insoluble nitrogen was delayed for approximately 40 hours. With the omission of leucine, valine, isoleucine, or arginine from the amino acid mixture, this inhibition was still observed. However, when the three branch-chain amino acids were omitted together, or when proline was left out, loss of nitrogen from the endosperm was similar to that observed in the basal medium. These additions and omissions did not significantly affect the loss of dry matter from the endosperm, or the gain in dry matter and alcohol-insoluble nitrogen of the embryo. These results suggest that the degradation of storage protein in the endosperm is a process regulated by the demands of the embryo for amino acids.
Cyclic erosion–instability relationships: Lake Erie north shore bluffs
Authors: Quigley R. M. , Gelinas P. J. , Bou W. T. , Packer R. W.
Published: May 2008

The 27–45 m high bluffs along the north shore of Lake Erie in Ontario are retreating inland at a 150 year average rate of 0.5 to 3.0 m/year. The retreat mechanisms and rates are cyclic and consist of complex interrelationships of toe erosion by wave attack, cliff steepening, sheet sloughing, and landsliding associated with softening in response to changes in effective stress. Four cyclic failure types are presented.1. Slowly retreating (0.6 m/year) unvegetated cliff fronts of 27 m height and nearly constant profile associated with low energy wave attack (0.5 kW/m) at the toe and cyclic sheet sloughing caused by desiccation and wetting at monthly intervals. Landsliding very rare and surficial.2. Cliffs of 34 m height retreating at intermediate rates (1.4 m/year) showing cyclic changes in profile in response to major, cyclic landslides. Retreat mechanisms involve toe erosion by intermediate energy wave attack (1.0 kW/m) and large toe failures at 10–20 year intervals in response to softening and changes in effective stress.3. Cliffs of 42 m height retreating at 2.8 m/year showing cyclic changes in profile in response to major, high velocity, cyclic landslides that deposit offshore fans of slide debris that provide erosion protection but no counterbalancing moment protection. Toe sands play a significant role, enabling undercutting by high energy wave attack (~2 kW/m). Size and frequency of landslides too variable to quantify at present.4. Cliffs of 38–45 m height retreating at 2.0 m/year in response to toe erosion under high energy wave attack (2 kW/m). Thick water bearing surface sands cause sloughing and shallow failure of the upper slopes at 1.5 year intervals above near vertical wave cut toe cliffs. Huge, deep seated failures may develop during periods of cyclic low water level at roughly estimated intervals of 30 years.
Stabilité interne des murs en terre armée
Authors: Chapuis Robert P.
Published: May 2008

The methods currently available to check the internal stability of reinforced earth retaining walls are reviewed and compared with two groups of experimental results obtained by model tests. The results do not agree with the theoretical predictions which generally underestimate the mechanical properties of this reinforced earth. After a reexamination of the mechanical behaviour of reinforced earth retaining walls, a new design method is suggested. It makes use of a cohesion term to represent the soil–ties interaction, and takes into consideration that reinforced earth is a composite material. This new method is in agreement with experimental results and shows the influence of such parameters as the length and spacing of the ties.
Use of residual strength for stability analyses of embankment foundations containing preexisting failure surfaces
Authors: Insley A. E. , Chatterji P. K. , Smith L. B.
Published: May 2008

Three case histories are described which involve the construction of major bridge approach fills on heavily overconsolidated clay or clay shale foundations, in which the residual strength of the foundation materials governed the design. The case histories are well documented by both field and laboratory observations.The difficulties of detecting thin preexisting failure planes in overconsolidated foundation materials are described. The case histories demonstrate that for such foundation conditions, and where major structures are involved, unusually thorough sampling, field instrumentation and laboratory testing programs are justified, and can provide the required data to permit a reliable stability analysis.
Comparison of slope stability methods of analysis
Authors: Fredlund D. G. , Krahn J.
Published: May 2008

The paper compares six methods of slices commonly used for slope stability analysis. The factor of safety equations are written in the same form, recognizing whether moment and (or) force equilibrium is explicitly satisfied. The normal force equation is of the same form for all methods with the exception of the ordinary method. The method of handling the interslice forces differentiates the normal force equations.A new derivation for the Morgenstern–Price method is presented and is called the 'best-fit regression' solution. It involves the independent solution of the force and moment equilibrium factors of safety for various values of λ. The best-fit regression solution gives the same factor of safety as the 'Newton–Raphson' solution. The best-fit regression solution is readily comprehended, giving a complete understanding of the variation of the factor of safety with λ.
A method of estimating surface settlement above tunnels constructed in soft ground
Authors: Rowe R. K. , Lo K. Y. , Kack G. J.
Published: May 2008

A technique suitable for the analysis of lined tunnels constructed in soft soil is described. This technique permits consideration of the soil-lining interaction, lining weight, and plastic failure within the soil. Particular attention is given to the simulation of loss of ground including the annular void created by the difference between the tunnelling machine and lining diameters. The analysis is used in a parametric study to identify potentially significant factors affecting the prediction of surface settlement due to tunnel construction. Consideration is given to the effects of elastic modulus; the distance between the tunnel and the underlying rigid base stratum; plastic failure; initial stresses; ground loss (including the annular void); and the injection of clay grout into the tailpiece void. The results of this analysis indicate that elastic anisotropy, ground loss, and clay grout injection are all important factors that are not usually considered in analyses. In particular, a parameter called the gap is defined in the paper and is used in an attempt to incorporate practical tunnelling experience into the calculation of surface settlement. Furthermore, it is shown that in predicting surface settlements underestimation of the true elastic modulus below the tunnel may decrease the predicted surface settlement and lead to overestimation of the invert heave. Underestimation of the modulus above the tunnel may also decrease the predicted surface settlement for situations where there is limited ground loss and extensive plastic failure.
Cone penetration testing in deltaic soils
Authors: Campanella R. G. , Robertson P. K. , Gillespie D.
Published: May 2008

A multichannel electric cone penetrometer was used to perform a variety of in situ tests in saturated deltaic deposits.Factors affecting the tip bearing, friction sleeve stress, and pore-water pressures and their interpretation are studied and discussed. Pore pressure measurements were essential to evaluate the in situ test results. The effect of rate of penetration is discussed and the concept of effective bearing introduced as an attempt to interpret cone bearing in undrained or partially drained soil. Field values of consolidation characteristics from pore pressure decay are compared with traditional laboratory consolidation test results on undisturbed samples.The advantages of continuous electric cone logging to evaluate soil stratigraphy are demonstrated. Field and laboratory test results are presented from a test site where stabilization was used to reduce liquefaction potential of hydraulically placed sand and silt. The importance of pore pressure measurements is demonstrated along with examples and recommendations for the location of the porous element.Keywords: static cone penetration testing, in situ testing, pore pressures, consolidation, stratigraphy, liquefaction.
Geotechnical engineering beyond soil mechanics—a case study
Authors: Morgenstern N. R. , Fair A. E. , McRoberts E. C.
Published: May 2008

Geotechnical engineering embraces soil mechanics, rock mechanics, and engineering geology. In practice it employs a wide variety of techniques ranging from site mapping and characterization to advanced theoretical analysis and performance monitoring. This paper draws on the development of the Alberta oil sands as a case study to illustrate the breadth of application of geotechnical engineering in large-scale resource developments.A description of the resource base and common extractive procedures used in the Alberta oil sands is given. The geological setting and geotechnical characterization of the Athabasca deposit are summarized. Detailed discussions are presented on geotechnical contributions to surface mining and slope stability, waste handling and tailings dam construction, and in situ recovery processes. The substantial opportunities for geotechnical engineering to contribute to both safe and economical operations in the extractive industries are emphasized. Key words: oil sands, mining, slope stability, monitoring, dredging, shear strength, tailings dam, overburden, liquefaction, pore pressures, geotechnical engineering.
Field measurements of the behavior of inclined footings on a natural slope
Authors: Clark J. I. , McKeown S. , Crawford C. B.
Published: May 2008

Full-scale field testing for the bearing capacity and stability of inclined footings with anchors was carried out on a colluvial slope near the east portal of the Rogers Pass tunnel in British Columbia. The 35° natural slope was composed of granular material with an angle of shearing resistance [Formula: see text]. A series of small footings (area 1.14 m2) was loaded with anchor loads only and one large footing (area 2.66 m2) was loaded with both anchor and vertical loads up to 2100 kN. Bearing capacity coefficients were back calculated and compared with coefficients from bearing capacity theories. Elastic and deformation moduli were calculated from load–displacement curves during loading and unloading and creep rates were observed at intervals during the tests. Key words: inclined footings, instrumentation, bearing capacity factors, soil anchors, natural slopes, colluvial soils, soil creep, deformation modulus, elastic modulus.
Effect of surfactants on the mechanical properties of a kaolinite in relation to the solid – liquid contact angles
Authors: Fleureau Jean-Marie , Wignyodarsono Legowo , Zerhouni Moulay-Idriss
Published: May 2008

A laboratory test program was undertaken to assess the effects of various ionic surfactants on the mechanical and hydric properties of a kaolinite. The tests showed that surfactants, particularly the cationic species, significantly modified the properties of the unsaturated clay (water absorption rate, absorbed water quantity, suction, swelling, etc.); however, the behaviour of the saturated soil was hardly changed. These results were correlated with measurements of the wettability characteristics of thin plates of consolidated clay. An original method, based on the concept of unit work of dewetting, was used to measure the solid – liquid – gas contact angle of the porous and rugose substrate. In the case of the kaolinite mixed with the cationic surfactant, the contact angle reaches 90° (instead of the 49° for the reference system), corresponding to a significant decrease in the soil suction. Such a decrease can explain the results obtained during infiltration and swelling tests. Key words: surfactants, wettability, unsaturated clays, suction.
Coal ash as structural fill, with special reference to Ontario experience
Authors: Toth P. S. , Chan H. T. , Cragg C. B.
Published: May 2008

Fly ash and bottom ash obtained from coal-fired electric power generating stations can be used as alternatives to natural materials for the construction of structural fills. The engineering properties of coal ash pertinent to its use in structural fills are discussed. Four case studies of coal ash structural fills are presented. The performance of these fills was monitored during and after construction. These cases demonstrate that the physical behavior of fly ash is similar to that of silt and that it can be handled with similar methods. Groundwater monitoring data from existing fly ash fills are presented to show the impact that ash leachate migrating into the groundwater regime has on water quality. Results of long-term corrosion studies are presented to show that metals buried in ash, used in such structures as culverts, cable ducts, guard rails and streetlights, are not adversely affected. Ash leachate was found not to be detrimental to good-quality concrete structures. Key words: fly ash, fill, compaction, leachate, corrosion, concrete.
Mining subsidence in Lethbridge, Alberta
Authors: Sladen J. A. , Joshi R. C.
Published: May 2008

Coal mining in Lethbridge began in 1872 and continued until 1965. Workings were by underground room and pillar techniques on a single near-horizontal seam. Parts of the city, and particularly the recently developed or soon to be developed areas, to the north and west of the city, are underlain by mine workings. This has necessitated comprehensive geotechnical investigations to evaluate potential subsidence hazards and to enable guidelines for construction precautions to be developed. Because of the relatively uniform conditions throughout the area, the borehole data accumulated during these investigations illustrate well some aspects of the process of mining subsidence above abandoned workings. Another interesting aspect of the Lethbridge case history is the phenomenon of soil cracking that occurs around the edge of worked seams. Even though calculated potential tensile strains are small, it appears that they can be concentrated to form thin cracks in the very stiff, unsaturated overburden soils. These cracks can subsequently be exploited by surface erosion processes and result in voids or soft zones, which are a potential hazard to construction. Key words: mining subsidence, void migration, soil cracking, development guidelines.
Polysaccharide nano crystal reinforced nanocomposites
Authors: Dufresne Alain
Published: May 2008

There are numerous examples of animals or plants that synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by nano sized crystalline domains. Cellulose and chitin are classical examples of these reinforcing elements, which occur as whisker-like microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, and whose axial physical properties therefore approach those of perfect crystals. During the last decade we have attempted to mimic biocomposites by blending cellulose or chitin whiskers from different sources with polymer matrices. Aqueous suspensions of such nano crystals can be prepared by acid hydrolysis of the substrate. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspensoid by subsequent vigorous mechanical shearing action. The resulting nano crystals occur as rod-like particles or whiskers, whose dimensions depend on the nature of the substrate. They are typically a few hundred nm long and between 5 and 20 nm in diameter. Starch can also be used as a source for the production of nano crystals. The constitutive nano crystals appear as platelet-like nano particles with a length ranging between 20 and 40 nm, a width ranging between 15 and 30 nm, and a thickness ranging between 5 and 7 nm. Since the first announcement of using cellulose whiskers as a reinforcing phase, they have been used extensively as model fillers in several kinds of polymeric matrices, including synthetic and natural ones. Casting mixtures of polysaccharide nano crystals and lattices led to the production of nano composite materials with drastically enhanced mechanical properties, especially at T > Tg of the matrix, by virtue of the formation of a whiskers network, even when the whisker volume fraction was only a few percent. The formation of this rigid network, resulting from strong interactions between whiskers, was assumed to be governed by a percolation mechanism. This hydrogen-bonded network induced a thermal stabilization of the composite up to 500 K, the temperature at which polysaccharides start to decompose. Any factors that perturb the formation of this percolating network directly affect the reinforcing effect of polysaccharide nano crystals. In addition to some practical applications, the study of these nano composite materials can help researchers understand such physical properties as the geometric and mechanical percolation effect.Key words: nano composites, polysaccharide, polymer, cellulose, nano crystal.
Occurrence of poly(hydroxyalkanoate) in the gut homogenate of a phylogenetically higher termite: Macrotermes carbonarius
Authors: Sudesh Kumar , Tay Bee-Yong , Lee Chow-Yang
Published: May 2008

Gas chromatography analysis of a phylogenetically higher termite-gut homogenate detected the presence of trace amounts of poly(3-hydroxybutyrate) (PHB), a prokaryotic storage material. In addition, the gut homogenate smear, stained with Nile blue A, also suggested the presence of PHB-like granules. Chloroform extracts of both soldier and worker classes of this termite were obtained for further spectroscopic analysis. FTIR, 1H NMR, and 2D 1H-1H NMR analyses confirmed the presence of PHB in both the chloroform extracts. This showed for the first time the occurrence of bacteria capable of accumulating PHB in the termite gut. The results indicated that the physiological environment in the termite gut is suitable for the colonization by PHB-producing bacteria and is probably rich in organic carbon sources, which can be readily assimilated and stored as PHB.Key words: Macrotermes carbonarius, poly(hydroxyalkanoate), PHB, termite
Thiolysis of poly(3-hydroxybutyrate) — A novel biochemical reaction
Authors: Uchino K , Saito T
Published: May 2008

An enzyme involved in the degradation of poly(3-hydroxybutyrate) (PHB), PhaZa1 from Ralstonia eutropha H16, catalyzes the thiolysis of PHB with coenzyme A. The properties of this novel reaction were investigated in vitro. The active center’s cysteine residue was point-mutated to prepare C183S and C183A. The wild type and the two mutants were compared in terms of hydrolytic and thiolytic activity. C183S was as active as the wild type in the hydrolysis, but less active in the thiolysis, of PHB. The cysteine residue was important for the thiolysis of PHB, which may be why it has been conserved in almost all PhaZa1 homologs in various bacteria.Key words: PHB, thiolysis, PHB depolymerase
Graft copolymers containing poly(3-hydroxyalkanoates) — A review on their synthesis, properties, and applications
Authors: Nguyen Sophie
Published: May 2008

The use of the poly(3-hydroxyalkanoates) in copolymer synthesis has received much interest, as the microbial polyester segments can bring interesting properties, such as biodegradability and biocompatibility. The synthesis, properties, and applications of graft copolymers containing poly(3-hydroxyalkanoates) as main chain or branches are reviewed here, with emphasis on the different preparation methods, which fit into the three main synthesis strategies of graft copolymers: “grafting onto”, “grafting from”, and “grafting through” or macromonomer methods.Key words: poly(3-hydroxyalkanoates), graft copolymer, synthesis, properties, applications.
Direct analysis of analyte–laden chromatographic stationary phase by induction–heating electrothermal vaporizer with inductively coupled plasma atomic emission spectroscopy
Authors: Lam Rebecca , Salin Eric D
Published: May 2008

We describe the inductively heated electrothermal vaporization of 8-hydroxyquinolate complexes of Cd, Pb, and Zn adsorbed onto C18-bonded silica gel with inductively coupled plasma atomic emission spectroscopic detection. The metal complexes were adsorbed onto the chromatographic stationary phase using a solid-phase extraction procedure. Instead of eluting the complexes from the stationary phase, the solid phase was directly vaporized into the plasma. Absolute detection limits for this method ranged from 0.3 to 3 µg.Key words: 8-hydroxyquinoline, silica gel, induction heating electrothermal vaporization, inductively coupled plasma atomic emission spectroscopy.
Decaying exponential feeding of nonanoic acid for the production of medium-chain-length poly(3-hydroxyalkanoates) by Pseudomonas putida KT2440
Authors: Maclean Heather , Sun Zhiyong , Ramsay Juliana , Ramsay Bruce
Published: May 2008

Decaying exponential feeding strategies for the production of medium-chain-length poly(3-hydroxyalkanoates) by Pseudomonas putida KT2440 have been developed as a method of delaying oxygen limitation that is typically responsible for the termination of high cell density aerobic fermentations. Two feeding strategies were evaluated to control the biomass generation rate and consequently control the oxygen uptake rate of the cells. A linear decaying strategy allowed the production of 90 g L–1 dry biomass containing 65% PHA in 31 h with a cumulative productivity of 1.9 g L–1 h–1, while a quadratic decaying exponential feeding rate followed by a constant feeding rate produced 109 g L–1 of dry biomass containing 63% PHA. The latter methodology improved the cumulative PHA productivity to 2.3 g L–1 h–1, which is the highest MCL-PHA productivity ever reported. Analysis of the relationship between the final biomass concentration and the associated maximum cell generation rate (which is directly related to the maximum oxygen transfer rate) indicated that higher biomass levels could be attained by decreasing the substrate feeding rate at high biomass concentrations.Key words: MCL-PHA, high cell density, decaying exponential feeding, oxygen limitation.
Decomposition of indwelling EMG signals
Authors: Nawab S. Hamid , Wotiz Robert P. , De Luca Carlo J.
Published: May 2008

Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probability classifier adapted from the original precision decomposition system (PD I) of LeFever and De Luca ( 25 , 26 ), an artificial intelligence approach has been used to develop a multiclassifier system (PD II) for addressing some of the experimentally identified problem situations. On a database of indwelling EMG signals reflecting such conditions, the fully automatic PD II system is found to achieve a decomposition accuracy of 86.0% despite the fact that its results include low-amplitude action potential trains that are not decomposable at all via systems such as PD I. Accuracy was established by comparing the decompositions of indwelling EMG signals obtained from two sensors. At the end of the automatic PD II decomposition procedure, the accuracy may be enhanced to nearly 100% via an interactive editor, a particularly significant fact for the previously indecomposable trains.
Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae
Authors: Cronin Neil J. , Peltonen Jussi , Ishikawa Masaki , Komi Paavo V. , Avela Janne , Sinkjaer Thomas , Voigt Michael
Published: May 2008

The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8°; 250°/s) were applied to the triceps surae at different moment levels (0–100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because short-latency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required.